,transcrib] ,note ,text emphasis d5ot$ by ,italics & ,bold4 ,,! ,,anci5t ,,volcanoes ,,( ,,great ,,brita9 ,illu/ration ,,! ,,anci5t ,,volcanoes ,,( ,,great ,,brita9 ,,by ,,sir ,,ar*ibald ,,geikie1 ,f4,r4,s4 ,d4,c4,l4 ,oxf41 ,d4 ,sc4 ,camb41 ,dubl42 ,,ll4,d4 ,/4 ,&41 ,ed9b4 ,,director-,,g5]al ,,( ,,! ,,geological ,,survey ,,( ,,great ,,brita9 ,,& ,,irel&2 ,,correspond5t ,,( ,,! ,,in/itute ,,( ,,france2 ,,( ,,! ,,academies ,,( ,,b]l91 ,,vi5na1 ,,muni*1 ,,tur91 ,,belgium1 ,,/ockholm1 ,g,,tt+51 ,,new ,,york2 ,,( ,,! ,,imp]ial ,,m9]alogical ,,society ,,& ,,society ,,( ,,naturali/s1 ,,/4 ,,pet]sburg2 ,,natural ,,hi/ory ,,society1 ,,mosc[2 ,,sci5tific ,,society1 ,,*ri/iania2 ,,am]ican ,,philosophical ,,society2 ,,( ,,! ,,geological ,,societies ,,( ,,london1 ,,france1 ,,belgium1 ,,/ockholm1 ,,etc4 ,,) ,,sev5 ,,maps ,,& ,,num]\s ,,illu/rations ,,9 ,,two ,,volumes ,,vol4 ,i ,london ,,macmillan ,,& ,,co41 ,limit$4 ,,new ,,york3 ,,! ,,macmillan ,,company4 #ahig ,all rights res]v$ ,,to ,m4 ,f]d9& ,f\qu ,,memb] ,,( ,,! ,,in/itute ,,pr(essor ,,( ,,! ,,natural ,,hi/ory ,,( ,,inorganic ,,bodies ,,9 ,,! ,,coll,,ge ,,de ,,france ,,& ,m4 ,augu/e ,mi*el-,lvy ,,memb] ,,( ,,! ,,in/itute ,,director ,,( ,,! ,,geological ,,survey ,,( ,,france ,,di/+ui%$ ,,repres5tatives ,,( ,,t ,,fr5* ,,s*ool ,,( ,,geology ,,:i* ,,by ,,! ,,h&s ,,( ,,desm>e/ ,,f\nd$ ,,! ,,/udy ,,( ,,anci5t ,,volcanoes ,,& ,,has ,,s9ce ,,done ,,s ,,mu* ,,to ,,promote ,,its ,,progress ,,^! ,,volumes ,,are ,,inscrib$ ,,) ,,! ,,highe/ ,,admiration ,,& ,,e/eem ,,preface ,9 no dep>tm5t ( sci5ce is ! sl[ & *equ]$ progress ( inve/igation m conspicu\s ?an 9 t bran* ( ,geology :i* treats ( volcanoes4 ,al?\gh f ! e>lie/ dawn ( hi/ory1 m5 _h be5 famili> ) ! /up5d\s ev5ts ( volcanic eruptions1 !y 7 s+ul>ly sl[ 9 recogniz+ ^! ph5om5a z def9ite & important p>ts ( ! natural hi/ory ( ! e>?4 ,ev5 )9 ! pres5t c5tury1 ! dom9ant geological s*ool 9 ,europe taught t volcanoes 7 m]e accid5ts1 due to ! combu/ion ( subt]ranean b$s ( coal casually set on fire by lightn+1 or by ! decomposition ( pyrites4 ,burn+ m\nta9s1 z !y 7 call$1 7 believ$ to be only local & =tuit\s appe>ances1 dep5d+ on ! position ( ! coal-fields1 & hav+ no ess5tial connection ) ! int]nal /ructure & pa/ condition ( our planet4 ,s long z su* fanta/ic conceptions prevail$1 x 0 impossible t any solid progress c\ld be made 9 ?is bran* ( sci5ce4 ,a ju/] appreciation ( ! nature ( ! e>?'s int]ior 0 ne$$ be=e m5 c\ld recognize t volcanic action _h once be5 vigor\s & prolong$ 9 _m c\ntries1 :]e no rema9s ( volcanoes c n[ be se54 ,to ,france1 :i* has l$ ! way 9 s _m dep>tm5ts ( human inquiry1 belongs ! m]it ( hav+ laid ! f\ndations ( ! sy/ematic /udy ( anci5t volcanoes4 ,h] gr\ps ( ,puys furni%$ ! e>lie/ inspiration 9 ?is subject1 & h ev] s9ce be5 classic gr\nd to :i* ! geological pilgrim has made 8 way f all p>ts ( ! _w4 ,z f> back z ! ye> #ageb1 ,guett>d recognis$ t ^! m>vell\s hills 7 volcanic cones t _h p\r$ =? /reams ( lava4 ,b x 0 res]v$ = ,desm>e/ twelve ye>s lat] to exam9e ! "q 9 detail1 & to e/abli% ! inve/igation ( =m] volcanic action ^u a broad & firm basis ( c>eful obs]vation & sagaci\s inf]5ce4 ,8 me?od ( rese>* 0 z well conceiv$ z ! region ( ,auv]gne 0 admirably fitt$ to be ! field ( exploration4 ,he soon discov]$ t ! volcanoes ( ,c5tral ,france 7 n all ( "o age1 b _h made _! appe>ance 9 a long s]ies1 :]e( ! individual memb]s became less p]fect & di/9ct 9 proportion to _! antiquity4 ,beg9n+ ) ! cones1 crat]s1 & lava-/reams :i* /& out s fre% t !y might almo/ be suppos$ to h be5 erupt$ only a few g5]ations ago1 ,desm>e/ trac$ ! volcanic s]ies backw>d 9 "t1 ?r\gh successive /ages ( ! decay & degradation wr\ght ^u !m by ! influ5ce ( ! atmosph]e1 ra9 & runn+ wat]4 ,he 0 ?us able1 z x 71 to wat* ! gradual oblit]ation ( ! cones1 ! removal ( ! a%es & scori1 & ! erosion ( ! lava-/reams1 until he c\ld po9t to m]e isolat$ remnants ( lava1 p]*$ ^u ! hills1 & ov]look+ ! valleys :i* _h be5 excavat$ ?r\gh !m4 ,he %[$ h[ e /ep 9 ?is process ( d5udation c\ld be illu/rat$ by examples ( its occurr5ce 9 ,auv]gne1 & h[1 9 ?is way1 ! v>i\s eruptions c\ld be gr\p$ accord+ to _! place 9 ! *ronological sequ5ce4 ,to ?is illu/ri\s ,fr5*man geology is ?us indebt$1 n only = ! f\ndation ( ! sci5tific /udy ( =m] volcanic action1 b = ! fir/ c>efully work$ out example ( ! pot5cy ( subrial erosion 9 ! excavation ( valleys & ! trans=mation ( ! sc5]y ( ! l&4 ,:ile ^! fruitful rese>*es 7 9 progress 9 ,france1 o!rs ( h>dly less mom5t 7 advanc+ 9 ,scotl&4 ,!re likewise ,nature _h provid$ ample mat]ial to arre/ ! att5tion ( all :o c>$ to make !mselves acqua9t$ ) ! pa/ hi/ory ( our globe4 ,hutton1 z a "p ( 8 immortal ,!ory ( ! ,e>?1 _h conceiv$ ! idea t mu* molt5 mat]ial _h be5 inject$ f bel[ into ! t]re/rial cru/1 & he _h f\nd _m pro(s ( su* intrusion among ! rocks alike ( ! ,l[l&s & ,highl&s ( 8 native c\ntry4 ,8 obs]vations1 confirm$ & ext5d$ by ,playfair & ,hall1 & subsequ5tly by ,maccullo*1 op5$ up ! inve/igation ( ! subt]ranean phases ( anci5t volcanic action4 ,"u ! influ5ce ( ^! great pione]s1 volcanic geology w\ld h made /eady & p]haps rapid progress 9 ! lat] decades ( la/ c5tury1 & ! e>li] ye>s ( ! pres5t1 b = ! !oretical views un=tunately adopt$ by ,w]n]4 ,t illu/ri\s tea*]1 to :om volcanoes seem$ to be a blot on ! sy/em ( nature :i* he _h devis$1 did all 9 8 p[] to depreciate _! importance4 ,adopt+ ! old & absurd notion t !y 7 caus$ by ! combu/ion ( coal "u gr\nd1 he lab\r$ to %[ t !y 7 m]e mod]n accid5ts1 & _h no connection ) 8 univ]sal =mations4 ,he proclaim$1 z an obvi\s axiom 9 sci5ce1 t ! basalts1 s widely spread ov] ,c5tral & ,we/]n ,europe1 & :i* ! obs]vations ( ,desm>e/ _h %[n to m>k ! sites ( old volcanoes1 7 really *emical precipitates f a primeval univ]sal ocean4 ,yet he _h actually be=e him 9 ,saxony examples ( basalt hills :i* entirely disprove 8 ass]tions4 ,=tunately = ! progress ( natural k1 ,w]n] dislik$ ! manual lab\r ( p5man%ip4 ,consequ5tly he wrote little4 ,b 8 wide range ( acquirem5t1 n 9 m9]alogy only1 8 precision ( /atem5t1 8 absolute c]ta9ty ab\t ! tru? ( 8 own op9ions1 & 8 h>dly disguis$ contempt = op9ions t diff]$ f !m1 comb9$ ) 8 en?usiasm1 eloqu5ce & p]sonal *>m1 fir$ 8 pupils ) emulation ( 8 zeal & turn$ !m into v]itable propag&i/s4 ,misl$ z to ! /ructure ( ! c\ntry 9 :i* _! ma/] taught1 & undiscipl9$ to inve/igate nature ) an imp>tial m9d1 !y travell$ into o!r l&s = ! purpose ( apply+ !re ! artificial sy/em :i* !y _h le>nt at ,freib]g4 ,! me?odical b cumbr\s t]m9ology 9 :i* ,w]n] _h tra9$ !m 0 translat$ by !m into _! own languages1 :]e x look$ /ill m unc\? ?an 9 its native ,g]man4 ,besides imbib+ _! tea*]'s sy/em1 !y acquir$ & ev5 improv$ ^u 8 some:at disda9ful mann] t[>ds all conclusions diff]5t f ^? ( ! ,saxon ,m9+ ,s*ool4 ,su* 0 ! _s 9 :i* ! pupils ( ,w]n] proce$$ to set ! geognosy ( ,europe to rights4 ,! views1 ann\nc$ by ,desm>e/1 t v>i\s rocks1 f> remov$ f any active volcano1 7 yet ( volcanic orig91 _h be5 sl[ly ga9+ gr\nd :5 ! militant /ud5ts f ,saxony spread !mselves ov] ! ,cont95t4 ,^! views1 h[ev]1 be+ irreconcilable ) ! t5ets enunciat$ f ! ,freib]g ,*air1 7 n[ ei!r ignor$ or contemptu\sly reject$4 ,w]n]'s disciples lov$ to call !mselves by _! tea*]'s t]m geogno/s1 & claim$ t !y conf9$ !mselves to ! /rict inve/igation ( fact ) reg>d to ! /ructure ( ! e>?1 9 app>5t unconsci\sness t _! t]m9ology & me?ods 7 f\nd$ on baseless assumptions & almo/ pu]ile hypo!ses4 ,) su* elem5ts ready = controv]sy1 x 0 no wond] t be=e long a battle arose ov] ! orig9 ( basalt & ! "p play$ by volcanoes 9 ! pa/ hi/ory ( ! globe4 ,! disciples ( ,w]n]1 *ampions ( a univ]sal ocean & ! deposition ( ev]y?+ f wat]1 7 dubb$ ,neptuni/s1 :ile _! oppon5ts1 equally /ubborn 9 def5ce ( ! pot5cy ( volcanic fire1 7 kn[n z ,vulcani/s or ,plutoni/s4 ,= m ?an a g5]ation ?is futile w>f>e 0 wag$ ) extraord9>y bitt]ness--dogmatism & au?ority do+ _! be/ to /op ! progress ( imp>tial obs]vation & hone/ op9ion4 ,"o ( ! mo/ notable incid5ts 9 ! campaign is to be f\nd 9 ! way 9 :i* ! tide ( battle 0 at la/ turn$ aga9/ ! ,w]n]ians4 ,cuvi] tells u t :5 "s ( ! ard5t uphold]s ( ! ,freib]g fai? came to consult ,desm>e/1 ! old man1 :o took no "p 9 ! fray1 w\ld only answ]1 ,g & see4 ,he felt t 9 8 memoir & maps he _h demon/rat$ ! tru? ( 8 conclusions1 & t an unprejudic$ obs]v] _h only to visit ,auv]gne to be conv9c$4 ,by a curi\s irony ( fate x 0 f t v ,auv]gne t ! light broke :i* f9ally *as$ away ! ,w]n]ian d>kness1 & x 0 by two ( ,w]n]'s mo/ di/+ui%$ disciples t ! reaction 0 begun4 ,daubuisson1 a fav\rite pupil ( ! ,freib]g pr(essor1 _h writt5 & publi%$ at ,p>is 9 #ahjc a volume on ! ,basalts ( ,saxony1 conceiv$ 9 ! true ,w]n]ian _s1 & treat+ ^! rocks1 z he _h be5 taught to reg>d !n1 z *emical precipitates f a =m] univ]sal ocean4 ,9 ! foll[+ ye> ! "y & accompli%$ ,fr5*man w5t to ,auv]gne & ! ,viv>ais t he might see ) 8 own eyes ! alleg$ pro(s ( ! volcanic orig9 ( basalt4 ,greatly no d\bt to 8 own surprise1 he f\nd ^! pro(s to be irrefragable4 ,) praisewor?y frankness he lo/ no "t 9 publicly ann\nc+ 8 recantation ( ! ,w]n]ian doctr9e on ! subject1 & ev] aft]w>ds he did good s]vice 9 mak+ ! cause ( tru? & progress prevail4 ,/ill m s5sational 0 ! conv]sion ( a yet m illu/ri\s prophet ( ! ,freib]g s*ool--! great ,leopold von ,bu*4 ,he too _h be5 educat$ 9 ! /ricte/ ,w]n]ian fai?4 ,b ev5tually1 aft] a j\rney to ,italy1 he made 8 way to ,auv]gne 9 #ahjb1 & !re1 9 pres5ce ( ! a/oni%+ volcanic records ( t region1 ! scales seem to h fall5 f 8 eyes also4 ,) evid5t reluctance he began to d\bt 8 ma/]'s tea*+ 9 reg>d to basalt & volcanoes4 ,he w5t into raptures ov] ! cle> pres5tation ( volcanic ph5om5a to be f\nd 9 ,c5tral ,france1 trac$ ea* detail among ! puys1 z 9 ! exam9ation ( a s]ies ( va/ models1 & rem>k$ t :ile we may inf] :at takes place at ,vesuvius1 we c actually see :at has transpir$ at ! ,puy de ,p>i\4 ,) ! en?usiasm ( a conv]t he ru%$ into ! discussion ( ! ph5om5a1 b someh[ omitt$ to make any m5tion ( ,desm>e/1 :o _h taught ! tru? s _m ye>s be=e4 ,impress$ by ! example ( su* m5 z ,daubuisson & ,von ,bu*1 ! ,w]n]ian disciples gradually slack5$ 9 zeal = _! ma/]'s t5ets4 ,!y clung to _! errors long] p]haps 9 ,scotl& ?an any:]e else out ( ,g]many--a s+ul> p>adox only explicable by ano!r p]sonal influ5ce4 ,jameson1 tra9$ at ,freib]g1 c>ri$ !nce to ! ,univ]sity ( ,ed9burgh ! mo/ implicit acceptance ( ! t5ets ( ! ,saxon s*ool1 & cont9u$ to ma9ta9 ! aque\s orig9 ( basalt = _m ye>s aft] ! notion _h be5 ab&on$ by "s ( 8 mo/ di/+ui%$ contempor>ies4 ,b ! error1 ?\gh x di$ h>d1 0 confess$ at la/ ev5 by ,jameson4 ,aft] ! close ( ?is protract$ & animat$ controv]sy ! /udy ( =m] volcanic action resum$ its place among ! accept$ subjects ( geological rese>*4 ,f ! peculi>ly fav\rable /ructure ( ! c\ntry1 ,brita9 has be5 enabl$ to make _m important contributions to ! inve/igation ( ! subject4 ,de la ,be*e1 ,mur*ison & ,s$gwick l$ ! way 9 recogniz+1 ev5 among ! mo/ anci5t /ratifi$ =mations ( ,engl& & ,wales1 ! records ( contemporane\s volcanoes & ( _! subt]ranean intrusions4 ,scrope ?rew himself ) ard\r into ! /udy ( ! volcanoes ( ,italy & ( ,c5tral ,france4 ,macl>5 made kn[n ! /ructure ( "s ( ! volcanic gr\ps ( ! l[l&s ( ,scotl&4 ,ramsay1 ,selwyn1 & ,jukes1 foll[+ ^! pione]s1 7 ! fir/ to map out a ,palozoic volcanic region 9 ample detail4 ,sorby1 apply+ to ! /udy ( rocks ! me?od ( microscopic exam9ation by ?9 slices1 devis$ by ,william ,nicol ( ,ed9burgh = ! /udy ( fossil plants1 op5$ up a new & va/ field 9 ! doma9 ( obs]vational geology1 & furni%$ ! geologi/ ) a key to solve _m ( ! problems ( volcanism4 ,?us1 alike f ! /ratigraphical & petrographical sides1 ! igne\s rocks ( ?is c\ntry h receiv$ con/antly increas+ att5tion4 ,! pres5t "w is int5d$ to (f] a summ>y ( :at has n[ be5 asc]ta9$ reg>d+ ! =m] volcanoes ( ! ,briti% ,isles4 ,! subject has occupi$ mu* ( my "t & ?\ght all ?r\gh life4 ,born among ! crags t m>k ! sites ( "s ( ^! volcanoes1 ,i 0 l$ 9 my boyhood to int]e/ myself 9 _! /ructure & hi/ory4 ,! fasc9ation :i* !y !n ex]cis$ has la/$ till n[1 impell+ me to make myself acqua9t$ ) ! volcanic records all ov] our isl&s1 & to travel into ! volcanic regions ( ,europe & ,we/]n ,am]ica = ! purpose ( ga9+ cle>] conceptions ( ! ph5om5a4 ,f "t to "t dur+ a p]iod ( almo/ =ty ye>s ,i h communicat$ *iefly to ! ,geological ,society ( ,london & ! ,royal ,society ( ,ed9burgh ! results ( my rese>*es4 ,z mat]ials accumulat$1 ! desire arose to comb9e !m into a g5]al n>rative ( ! :ole progress ( volcanic action f ! remote/ geological p]iods d[n to ! "t :5 ! late/ eruptions ceas$4 ,an opportunity ( p>tially putt+ ?is design into execution occurr$ :51 z ,presid5t ( ! ,geological ,society1 ! duty devolv$ ^u me ( giv+ ! ,annual ,addresses 9 #ahia & #ahib4 ,)9 ! limits p]missible to su* essays1 x 0 n possible to pres5t m ?an a full summ>y ( ! subject4 ,s9ce t "t ,i h cont9u$ my rese>*es 9 ! field1 especially among ! ,t]ti>y volcanic areas1 & h n[ exp&$ ! two ,addresses by ! incorporation ( a l>ge am\nt ( new matt] & ( portions ( my publi%$ pap]s4 ,9 ! onw>d m>* ( sci5ce a book :i* is abrea/ ( our k to-day beg9s to be left beh9d to-morr[4 ,nev]!less x may s]ve a useful purpose if x does no m ?an make a def9ite pres5tation ( ! condition ( t k at a p>ticul> "t4 ,su* a /atem5t becomes a k9d ( l&m>k by :i* subsequ5t progress may be measur$4 ,x may also be ( s]vice 9 indicat+ ! gaps t h to be fill$ up1 & ! fields :]e fre% rese>* may mo/ hopefully be und]tak54 ,i h to ?ank ! ,c\ncils ( ! ,royal ,society ( ,ed9burgh & ! ,geological ,society = _! p]mission to use a numb] ( ! illu/rations :i* h accompani$ my pap]s publi%$ 9 _! ,transactions & ,j\rnal4 ,to ,colonel ,evans & ,miss ,?om ( ,canna ,i am indebt$ = ! photographs :i* !y h k9dly tak5 = me4 ,to ^? ( my colleagues 9 ! ,geological ,survey :o h furni%$ me ) in=mation my be/ ?anks are due4 ,_! contributions are ackn[l$g$ :]e !y h be5 made use ( 9 ! text4 ,! illu/rations ( ^! volumes are *iefly f my own note-books & sket*-books4 ,b besides ! photographs j ref]r$ to1 ,i h avail$ myself ( a s]ies tak5 by ,mr4 ,rob]t ,lunn = ! ,geological ,survey among ! volcanic di/ricts ( ,c5tral ,scotl&4 ,geological ,survey ,(fice1 #bh ,j]myn ,/reet1 ,london1 #a/ ,janu>y #ahig4 ,,cont5ts ,,book ,i ,,g5]al ,,pr9ciples ,,& ,,me?ods ,,( ,,inve/igation ,,*apt] ,i ,,page ,e>lie/ ,k ( ,volcanoes--,_! ,influ5ce on ,my?ology & ,sup]/ition--,"p tak5 by ,volcanic ,rocks 9 ,sc5]y--,progress ( ! ,d5udation ( ,volcanoes--,value ( ! ,records ( =m] ,volcanoes z illu/rat+ ,mod]n ,volcanic ,action--,fav\rable ,position ( ,brita9 = ! ,/udy ( ?is ,subject #a ,,*apt] ,,ii ,! ,nature & ,causes ( ,volcanic ,action--,mod]n ,volcanoes #aj ,,*apt] ,,iii ,anci5t ,volcanoes3 ,pro(s ( _! exi/5ce d]iv$ f ! ,nature ( ! ,rocks erupt$ f ! ,e>?'s ,int]ior4 ,a4 ,mat]ials erupt$ at ! ,surface--,extrusive ,s]ies4 i4 ,lavas1 _! ,g5]al ,*>act]s4 ,volcanic ,cycles4 ii4 ,agglom]ates1 ,breccias & ,tuffs #ad ,,*apt] ,,iv ,mat]ials erupt$ at ! ,surface--,extrusive ,s]ies--cont9u$4 iii4 ,types ( old ,volcanoes--#a4 ,! ,vesuvian ,type2 #b4 ,! ,plateau or ,fissure ,type2 #c4 ,! ,puy ,type4 iv4 ,det]m9ation ( ! relative ,geological ,dates ( ,anci5t ,volcanoes4 v4 ,h[ ! ,physical ,geography associat$ ) ,anci5t ,volcanoes is asc]ta9$ #ci ,,*apt] ,v ,und]gr\nd ,phases ( ,volcanic ,action4 ,b4 ,mat]ials inject$ or consolidat$ b5ea? ! ,surface--,intrusive ,s]ies3 ,i4 ,v5ts ( ,eruption--i4 ,necks ( ,fragm5t>y ,mat]ials2 ii4 ,necks ( ,lava-=m ,mat]ials2 iii4 ,di/ribution ( ,v5ts 9 relation to ,geological ,/ructure-,l9es2 iv4 ,metamorphism 9 & ar\nd ,volcanic ,cones1 ,solfat>ic ,action2 v4 ,inw>d ,dip ( ,rocks t[>ds ,necks2 vi4 ,influ5ce ( contemporane\s ,d5udation ^u ,volcanic ,cones2 vii4 ,/ages 9 ! ,hi/ory ( old ,volcanic ,v5ts #eb ,,*apt] ,,vi ,und]gr\nd ,phases ( ,volcanic ,action--cont9u$4 ,,ii4 ,subt]ranean ,movem5ts ( ! ,magma3 i4 ,dykes & ,ve9s2 ii4 ,sills & ,laccolites2 iii4 ,bosses 7,/ocks1 ,culots71 ,conditions t gov]n ! ,intrusion ( ,molt5 ,rock )9 ! ,t]re/rial ,cru/ #gg ,,*apt] ,,vii ,influ5ce ( ,volcanic ,rocks on ! ,sc5]y ( ! ,l&--,effects ( ,d5udation #ajj ,,book ,,ii ,,volcanic ,,action ,,9 ,,pre-,,cambrian ,,"t ,,*apt] ,,viii ,pre-,cambrian ,volcanoes ,! ,beg9n+s ( ,geological ,hi/ory--,difficulties 9 fix+ on a g5]ally applicable ,t]m9ology--i4 ,! ,lewisian 7,ar*an7 ,gneiss2 ii4 ,! ,dalradian or ,y\ng] ,s*i/s ( ,scotl&2 iii4 ,! ,gneisses & ,s*i/s ( ,anglesey2 iv4 ,! ,uriconian ,volcanoes2 v4 ,! ,malv]n ,volcano2 vi4 ,! ,*>nwood ,=e/ ,volcano #aji ,,book ,,iii ,,! ,,cambrian ,,volcanoes ,,*apt] ,,ix ,*>act]i/ics ( ! ,cambrian ,sy/em 9 ,brita9 ,! ,physical ,geography ( ! ,cambrian ,p]iod--,! ,pione]s ( ,palozoic ,geology 9 ,brita9--,"w ( ! ,geological ,survey 9 ,wales--,subdivisions ( ! ,cambrian ,sy/em 9 ,brita9 #aci ,,*apt] ,x ,! ,cambrian ,volcanoes ( ,s\? ,wales #ade ,,*apt] ,,xi ,! ,cambrian ,volcanoes ( ,nor? ,wales1 ! ,malv]n ,hills & ,w>wick%ire #aei ,,book ,,iv ,,! ,,silurian ,,volcanoes ,,*apt] ,,xii ,*>act]s ( ! ,silurian ,sy/em 9 ,brita94 ,! ,ar5ig ,volcanoes ,! ,l& & ,sea ( ,silurian "t--,classification ( ! ,silurian ,sy/em--,g5]al ,petrography ( ! ,silurian ,volcanic ,rocks--,i4 ,! ,eruptions ( ,ar5ig ,age #agc ,,*apt] ,,xiii ,! ,eruptions ( ,ll&eilo & ,bala ,age i4 ,! ,buil? ,volcano--ii4 ,! ,volcanoes ( ,pembroke%ire--iii4 ,! ,ca]n>von%ire ,volcanoes ( ! ,bala ,p]iod--iv4 ,! ,volcanic ,di/rict ( ! ,b]wyn ,hills--v4 ,! ,volcanoes ( ,anglesey--vi4 ,! ,volcanoes ( ! ,lake ,di/rict2 ,ar5ig to close ( ,bala ,p]iod--vii4 ,upp] ,silurian 787 ,volcanoes ( ,gl\ce/]%ire #bjb ,,*apt] ,,xiv ,! ,silurian ,volcanoes ( ,irel& #bci ,,book ,v ,,! ,,volcanoes ,,( ,,devonian ,,& ,,old ,,r$ ,,s&/one ,,"t ,,*apt] ,,xv ,! ,devonian ,volcanoes #beg ,,*apt] ,,xvi ,! ,volcanoes ( ! ,old ,r$ ,s&/one ,geological ,revolutions at ! close ( ! ,silurian ,p]iod ,physical ,geography ( ! ,old ,r$ ,s&/one--,old ,lake-bas9s1 _! ,flora & ,fauna--,abundance ( ,volcanoes--,hi/ory ( ,inve/igation 9 ! ,subject #bfc ,,*apt] ,,xvii ,di/ribution ( ! ,volcanic ,c5tres 9 ! ,l[] ,old ,r$ ,s&/one--,*>act]s ( ! ,mat]ials ,erupt$ by ! ,volcanoes #bga ,,*apt] ,,xviii ,/ructure & ,arrangem5t ( ! ,l[] ,old ,r$ ,s&/one ,volcanic ,rocks 9 ! ,field #bha ,,*apt] ,,xix ,volcanoes ( ! ,l[] ,old ,r$ ,s&/one ( ,lake ,cal$onia ,description ( ! sev]al ,volcanic ,di/ricts3 ,lake ,cal$onia1 its ,*a9s ( ,volcanoes--,! ,nor!rn ,*a93 ,montrose ,gr\p--,o*il & ,sidlaw ,hills--! ,arran & ,cantyre ,c5tre--! ,ul/] ,c5tre #bid ,,*apt] ,,xx ,volcanoes ( ! ,l[] ,old ,r$ ,s&/one ( ,lake ,cal$onia--cont9u$ ,! ,s\!rn ,*a9--,! ,p5tl& ,volcano--,! ,bigg> ,c5tre--,! ,duneaton ,c5tre--,! ,ayr%ire ,volcanoes #cag ,,*apt] ,,xxi ,volcanoes ( ! ,l[] ,old ,r$ ,s&/one ( ! ,*eviot ,hills1 ,lorne1 ,lake ,orcadie & ,kill>ney #ccf ,,*apt] ,,xxii ,volcanoes ( ! ,upp] ,old ,r$ ,s&/one--,! ,s\?-,we/ ( ,irel&1 ! ,nor? ( ,scotl& #cdh ,,book ,,vi ,,! ,,c>bonif]\s ,,volcanoes ,,*apt] ,,xxiii ,! ,c>bonif]\s ,sy/em ( ,brita9 & its ,volcanic ,records ,geography & ,sc5]y ( ! ,c>bonif]\s ,p]iod--,range ( ,volcanic ,eruptions dur+ t "t--,i4 ,! ,c>bonif]\s ,volcanoes ( ,scotl&--,di/ribution1 ,arrangem5t & ,local ,*>act]s ( ! ,c>bonif]\s ,sy/em 9 ,scotl&--,sket* ( ! ,"w ( previ\s ,obs]v]s 9 ?is ,subject #cee ,,*apt] ,,xxiv ,c>bonif]\s ,volcanic ,plateaux ( ,scotl& ,i4 ,! ,plateau-type re/rict$ to ,scotl&--i4 ,di/ribution 9 ! ,diff]5t ,areas ( ,eruption--ii4 ,nature ( ! ,mat]ials ,erupt$ #cfg ,,*apt] ,,xxv ,geological ,/ructure ( ! ,c>bonif]\s ,volcanic ,plateaux ( ,scotl& #a4 ,b$d$ ,lavas & ,tuffs2 ,upp] ,limits & ,orig9al ,areas & ,slopes ( ! ,plateaux2 #b4 ,v5ts2 ,necks ( ,agglom]ate & ,tuff2 ,necks ( ,massive ,rock2 ,composite ,necks2 #c4 ,dykes & ,sills2 #d4 ,close ( ! ,plateau-eruptions #chc ,,*apt] ,,xxvi ,! ,c>bonif]\s ,puys ( ,scotl& i4 ,g5]al ,"* & ,di/ribution ( ! ,puys2 ii4 ,nature ( ! ,mat]ials ,erupt$--,lavas ,eject$ at ! ,surface--,intrusive ,%eets--,necks & ,dykes--,tuffs #dad ,,*apt] ,,xxvii ,geological ,/ructure ( ! ,c>bonif]\s ,puys ( ,scotl& #a4 ,v5ts3 ,relation ( ! ,necks to ! ,rocks ?r\gh :i* !y rise--,evid5ce ( ! probable ,subrial ,"* ( "s ( ! ,cones or ,puys ( ,tuff--,entombm5t ( ! ,volcanic ,cones & _! ,relation to ! ,sup]ficial ,ejections4 #b4 ,b$d$ ,tuffs & ,lavas--,effects ( ,subsequ5t ,dislocations4 #c4 ,sills1 ,bosses1 & ,dykes #dbd ,,*apt] ,,xxviii ,illu/rative ,examples ( ! ,c>bonif]\s ,puys ( ,scotl& ,! ,bas9 ( ! ,fir? ( ,=?--,nor? ,ayr%ire--,liddesdale #dfb ,,li/ ,,( ,,illu/rations ,,fig4 ,,page #a4 ,vesicul> /ructure1 ,lava f ,asc5sion ,isl&1 slightly less ?an natural size #ae #b4 ,elongation & bran*+ ( /eam-vesicles 9 a lava1 ,kiln9ian1 ,isle ( ,mull1 a little less ?an natural size #ag #c4 ,microlites ( ! ,pit*/one ( ,arran 7magnifi$ #gj diamet]s7 #ai #d4 ,p]litic /ructure 9 ,felsitic ,glass1 ,isle ( ,mull 7magnifi$7 #ai #e4 ,sph]ulitic /ructure 7magnifi$7 #ai #f4 ,micropegmatitic or ,granophyric /ructure 9 ,granophyre1 ,mull 7magnifi$7 #bj #g4 ,ophitic /ructure 9 ,dol]ite1 ,gortacloghan1 ,co4 ,d]ry 7magnifi$7 #bj #h4 ,v>iolitic or orbicul> /ructure1 ,napoleonite1 ,corsica 7nat4 size7 #bb #i4 ,fl[-/ructure 9 ,rhyolite1 ,antrim1 slightly r$uc$ #bc #aj4 ,lumpy1 irregul> tra*ytic lava-/reams 7,c>bonif]\s71 ,ea/ ,l9ton1 ,hadd+ton%ire #bd #aa4 ,view at ! entrance ( ! ,sv9(jord1 ,f>oe ,isl&s1 illu/rat+ ! t]rac$ =ms assum$ by basic lavas #be #ab4 ,sack-l or pill[-=m /ructure ( basic lavas 7,l[] ,silurian71 ,b5nan ,head1 ,ballantrae1 ,ayr%ire #bf #ac4 ,alt]nations ( co>s] & f9] ,tuff #cd #ad4 ,alt]nations ( ,tuff ) non-volcanic s$im5t #ce #ae4 ,eject$ block ( basalt :i* has fall5 among ,c>bonif]\s %ales & lime/ones1 %ore1 ,pettycur1 ,fife #cg #af4 ,effects ( d5udation on a ,vesuvian cone #dj #ag4 ,section to illu/rate ! /ructure ( ! ,plateau type #dc #ah4 ,diagram illu/rat+ ! /ructure & d5udation ( ,puys #de #ai4 ,section illu/rat+ subm>9e eruptions2 alt]nations ( lavas & tuffs ) lime/ones & %ales full ( m>9e organisms #dh #bj4 ,diagram illu/rat+ volcanic eruptions on a riv]-pla9 #di #ba4 ,diagram illu/rat+ volcanic eruptions on a l&-surface #ej #bb4 ,gr\nd-plans ( "s volcanic v5ts f ! ,c>bonif]\s di/ricts ( ,scotl& #ee #bc4 ,view ( an old volcanic ,neck 7,! ,knock1 ,l>gs1 ,ayr%ire1 a v5t ( ,l[] ,c>bonif]\s age7 #ef #bd4 ,section ( neck ( agglom]ate1 ris+ ?r\gh s&/ones & %ales #eh #be4 ,neck fill$ ) /ratifi$ tuff #fd #bf4 ,section ( neck ( agglom]ate ) plug ( lava #fe #bg4 ,section ( agglom]ate neck ) dykes & ve9s #ff #bh4 ,section ( neck fill$ ) massive rock #fh #bi4 ,successive %ift+s ( v5ts giv+ rise to d\ble or triple cones #gj #cj4 ,section to %[ ! connection ( a neck ) a cone & surr\nd+ b$d$ tuffs #ga #ca4 ,diagram illu/rat+ ! gradual em]g5ce ( buri$ volcanic cones ?r\gh ! influ5ce ( prolong$ d5udation #ge #cb4 ,dyke1 ,ve91 & ,sill #hj #cc4 ,section ( ,sill or ,intrusive ,%eet #hc #cd4 ,ideal section ( ?ree ,laccolites4 7,aft] ,mr4 ,gilb]t7 #hf #ce4 ,diagram illu/rat+ ! /ratigraphical relations ( ! pre-,cambrian & ,cambrian rocks ( ! ,nor?-we/ ,highl&s ( ,scotl& #aab #cf4 ,map ( a portion ( ! ,lewisian gneiss ( ,ross-%ire #aah #cg4 ,section %[+ ! position ( sills 9 ! mica-s*i/ s]ies betwe5 ,lo* ,tay & ,amulree #abd #ch4 ,sket* ( cru%$ basic igne\s rock among ! s*i/s1 ,e4 side ( ,por?-tywyn-mawr1 ,e4 side ( ,holyhead ,/raits #abh #ci4 ,section across ! ,uriconian s]ies ( ,ca] ,c>adoc #acb #dj4 ,map ( ! volcanic di/rict ( ,/4 ,david's #adf #da4 ,section %[+ ! int]/ratification ( tuff & conglom]ate above ,l[] ,mill1 ,/4 ,david's #aed #db4 ,basic dyke trav]s+ qu>tz-porphyry & conv]t$ into a k9d ( slate by cleavage4 ,we/ side ( ,llyn ,pad>n #afb #dc4 ,section ( well-cleav$ tuff1 grit & breccia pass+ up into rudely-cleav$ conglom]ate & well-b$d$ cleav$ f9e conglom]ate & grit4 ,ea/ side ( ,llyn ,pad>n #afc #dd4 ,section ( ,clegyr on ! nor?-ea/ side ( ,llyn ,pad>n1 ne> ! l[] end #afd #de4 ,section across ! ,cambrian =mations ( ! ,malv]n ,hills1 %[+ ! position ( ! int]calat$ igne\s rocks4 ,aft] ,phillips #agj #df4 ,section across ,rhobell ,fawr #agh #dg4 ,section at ! ,slate ,qu>ry1 ,p5rhyn ,gwyn1 nor? slopes ( ,cad] ,idris #ahj #dh4 ,sket*-section across ,cad] ,idris #ahb #di4 ,section across ! ,moelwyn ,range #ahe #ej4 ,section across ! anticl9e ( ,corndon #aij #ea4 ,/ructure 9 f9ely-amygdaloidal diabase lava1 s\? ( m\? ( ,/9*> ,riv]1 ,ayr%ire #aic #eb4 ,view ( ,knockdolian ,hill f ! ea/ #aid #ec4 ,section across ! ,l[] ,silurian volcanic s]ies 9 ! s\? ( ,ayr%ire 7,b4 ,n4 ,pea*7 #aig #ed4 ,section ( "p ( ! ,ar5ig volcanic gr\p1 /ream s\? ( ,b5nane ,head1 ,ayr%ire #aih #ee4 ,fl[-/ructure 9 ! l[e/ felsite on ! track f ,llanb]is to ! top ( ,sn[don #baa #ef4 ,section ( ,sn[don #bab #eg4 ,section across ! ,b]wyn ,hills4 7,r$uc$ f ,horizontal ,section1 ,geol4 ,surv4 ,%eet #ce7 #bai #eh4 ,section ( ! /rata on ! %ore at ,por? ,w51 we/ ( ,amlw* #bbc #ei4 ,section ( int]calat$ black %ale 9 ! volcanic s]ies at ,por? yr hw*1 s\? ( ,c>mel ,po9t1 ,anglesey #bbd #fj4 ,gre5 slates ov]la9 ) volcanic breccia1 ,c>mel ,po9t #bbd #fa4 ,blue %ale or slate pass+ into volcanic breccia ea/ ( ,por? ,padrig1 ne> ,c>mel ,po9t #bbe #fb4 ,section ( felsites 9 ! ,coni/on ,lime/one gr\p1 we/ ( ,/ockdale #bcb #fc4 ,f9e tuff ) co>s] b&s ne> ,quayfoot ,qu>ries1 ,borr[dale #bcd #fd4 ,diagram ( ! g5]al relations ( ! diff]5t gr\ps ( rock 9 ! ,l[] ,silurian volcanic di/rict along ! we/]n %ore ( ,l\gh ,mask #bec #fe4 ,ve9s & ne/s ( s&/one due to ! wa%+ ( s& into fissures & cavities ( an ,old ,r$ ,s&/one lava4 ,turnb]ry ,po9t1 ,ayr%ire #bhc #ff4 ,gr\nd-plan ( reticulat$ cracks 9 ! upp] surface ( an ,old ,r$ ,s&/one lava fill$ 9 ) s&/one4 ,r$ ,head1 ,=f>%ire #bhd #fg4 ,section across ! volcanic s]ies ( ,=f>%ire #bhf #fh4 ,section across two necks above ,tillic\ltry1 ,o*il ,hills #bhh #fi4 ,section ( ! granite core betwe5 ,m]rick & ,corscr9e #bij #gj4 ,section across ! ?ree ,dirr+ton ,laws1 ,b]wick%ire #bia #ga4 ,section ( ,papa ,/\r1 ,%etl&s1 %[+ sill ( sph]ulitic felsite trav]s+ ,old ,r$ ,s&/one & b$d$ porphyrites 7,messrs4 ,pea* & ,horne7 #bib #gb4 ,section across ,nor?mav9e1 f ,okrea ,head to ,skea ,ness1 ,%etl&1 %[+ dykes & connect$ sill ( granite & felsite 7,messrs4 ,pea* & ,horne7 #bib #gc4 ,section at ! edge ( "o ( ! bays ( ,l[] ,old ,r$ ,s&/one along ! nor!rn m>g9 ( ,lake ,cal$onia1 ne> ,o*t]tyre #bie #gd4 ,craig ,be9n-nan-,eun 7#bjfg feet71 ea/ ( ,uam ,v>1 ,braes ( ,d\ne4 ,old ,r$ ,conglom]ate1 ) ! truncat$ ends ( ! /rata look+ across into ! ,highl&s2 mora9es ( ,corry ,bea* 9 ! =egr\nd #bif #ge4 ,section %[+ ! top ( ! volcanic s]ies at ! foot ( ! precipice ( ! ,r$ ,head1 ,=f>%ire #cjj #gf4 ,&esite ) s&/one ve9+s & ov]ly+ conglom]ate4 ,todhead1 s\? ( ,cat]l9e1 coa/ ( ,k9c>d9e%ire #cjc #gg4 ,section across ! ,b\nd>y-fault ( ! ,highl&s at ,gl5 ,turrit1 ,p]?%ire #cje #gh4 ,section across ! *a9 ( ! ,sidlaw ,hills ne> ,kilsp9die #cjf #gi4 ,section across ! ,ea/]n ,o*il ,hills f ne> ,newburgh to ne> ,au*t]mu*ty #cjg #hj4 ,g5]aliz$ section across ! he>t ( ! ,o*il ,hills f ,dunn+ on ! nor? to ! ,fife coal-field ne> ,sal9e on ! s\? #cjh #ha4 ,diagram ( ! volcanic s]ies ( ! ,we/]n ,o*il ,hills #cji #hb4 ,view ( ,cnoc ,g>bh1 ,s\!nd1 ,campbelt[n4 ,a volcanic neck ( ,l[] ,old ,r$ ,s&/one age1 ab\t #djj y>ds wide 9 its long] diamet] #cab #hc4 ,section ( volcanic s]ies on bea*1 ,s\!nd1 ,campbelt[n #cac #hd4 ,section ( ! base ( ! volcanic s]ies1 ,recla91 five miles s\? ( ,pom]oy #caf #he4 ,section ( %ales & breccias at ,crossna ,*apel1 nor?-ea/ ( ,boyle #caf #hf4 ,section across ! nor? end ( ! ,p5tl& ,hills1 f ,w>klaw ,hill to ,p5tl& ,ma9s4 ,l5g? ab\t five miles #cah #hg4 ,view ( ! lava-esc>pm5ts ( ,w>klaw ,hill1 ,p5tl& *a91 f ! nor?-we/ #cai #hh4 ,section across ! ,p5tl& ,hills ?r\gh ,nor? ,black ,hill & ,scald ,law4 ,l5g? ab\t ?ree miles #cbb #hi4 ,section f ! valley ( ! ,gutt]=d ,burn ?r\gh ,gre5 ,law & ,braid ,law to ,eight-,mile ,burn #cbb #ij4 ,section across ! nor? end ( ! ,p5tl& ,hills1 & ! s\!rn edge ( ! ,braid ,hill v5t4 ,l5g? ab\t two miles #cbd #ia4 ,section across ! nor!rn end ( ! ,bigg> volcanic gr\p1 f ,fadd5 ,hill to beyond ,m5dick ,hill #cbf #ib4 ,section across ! s\!rn "p ( ! ,bigg> volcanic gr\p f ,cov+ton to ,cult] #cbh #ic4 ,section f ,?ank]ton ,moor across ,t9to to ,lam+ton #cbh #id4 ,section across ! ,duneaton volcanic di/rict f ! head ( ! ,duneaton ,wat] to ,kirklea ,hill #ccj #ie4 ,cav]n\s spaces 9 &esite1 fill$ 9 ) s&/one1 ,john o' ,groats ,port1 ,turnb]ry1 ,ayr%ire #ccc #if4 ,section ( &esites1 ,turnb]ry ,ca/le1 ,ayr%ire #ccd #ig4 ,l5ticul> =m ( a brecciat$ &esite 7%[n 9 ,fig4 #if71 ,turnb]ry1 ,ayr%ire #ccd #ih4 ,section across ! volcanic area ( ,/4 ,abb's ,head 7aft] ,pr(4 ,j4 ,geikie7 #cci #ii4 ,view ( t]rac$ &esite hills re/+ on massive conglom]ate1 s\? ( ,oban #cda #ajj4 ,section ( lava-esc>pm5t at ,be9n ,lora1 nor? side ( m\? ( ,lo* ,etive1 ,argyll%ire #cdb #aja4 ,section across ,/ra?bogie1 bel[ ,rhyme1 %[+ ! position ( ! volcanic b& #cdd #ajb4 ,view ( ,knockfe]9a1 ,lim]ick1 f ! nor?-ea/--a volcanic neck ( ,upp] ,old ,r$ ,s&/one age #cdi #ajc4 ,section ( ! volcanic zone 9 ! ,upp] ,old ,r$ ,s&/one1 ,cam ( ,hoy1 ,orkney #cea #ajd4 ,section ( ! volcanic zone 9 ! ,upp] ,old ,r$ ,s&/one at ,black ,ness1 ,rackwick1 ,hoy #cea #aje4 ,section across ! volcanic b& & its associat$ necks1 ,hoy1 ,orkney #ceb #ajf4 ,gr\nd-plan ( volcanic neck pi]c+ ! ,cai?ness ,flag/one s]ies on ! bea* ne> ,john o' ,groat's ,h\se #cec #ajg4 ,view ( ! esc>pm5t ( ! ,clyde ,plateau 9 ! ,little ,cumbrae1 f ! s\?-we/ #cfh #ajh4 ,view ( ! edge ( ! ,volcanic ,plateau s\? ( ,campbelt[n1 ,argyll%ire #cgj #aji4 ,view ( ,nor? ,b]wick ,law f ! ea/1 a phonolite neck m>k+ "o ( ! *ief v5ts ( ! ,g>leton ,plateau4 7,f a photograph7 #cga #aaj4 ,! ,bass ,rock1 a tra*ytic neck belong+ to ! ,g>leton plateau1 f ! %ore at ,canty ,bay #cgb #aaa4 ,cor/on ,hill--a fragm5t ( ! ,midlo?ian ,plateau1 se5 f ! nor? #cgc #aab4 ,view ( ,ar?ur ,seat f ,calton ,hill to ! nor? #cgd #aac4 ,view ( ,arkleton ,fell1 "p ( ! ,solway ,plateau1 f ! s\?-we/ #cgf #aad4 ,v]tical sections ( ! esc>pm5t ( ! ,clyde plateau f nor?-ea/ to s\?-we/ #chd #aae4 ,section ( ,craiglockh>t ,hill1 ,ed9burgh #chg #aaf4 ,section ( ! bottom ( ! ,midlo?ian ,plateau1 ,l9nh\se ,wat] above ,mid-,cald] ,oilworks #chg #aag4 ,section ( ! top ( ! ,midlo?ian ,plateau 9 ! ,murie/on ,wat] #chh #aah4 ,section ( ,calton ,hill1 ,ed9burgh #chi #aai4 ,cliff ( tuff & agglom]ate1 ea/ side ( ,oxroad ,bay1 a little ea/ f ,tantallon ,ca/le1 ,ea/ ,lo?ian #cia #abj4 ,section across "p ( ! ,clyde ,plateau to ! we/ ( ,b[l+ 7r$uc$ f ,%eet #f ( ! ,horizontal ,sections ( ! ,geological ,survey ( ,scotl&7 #cib #aba4 ,diagram illu/rat+ ! ?9n+ away s\?w>ds ( ! lavas ( ! ,clyde ,plateau betwe5 ,l>gs & ,ardrossan4 ,l5g? ab\t #aj miles #cic #abb4 ,diagram illu/rat+ ! ?9n+ away ea/w>ds ( ! lavas ( ! ,clyde ,plateau 9 ! ,f9try ,hills4 ,l5g? ab\t #ab miles #cid #abc4 ,view ( ! two necks ,dumgoyn & ,dumfoyn1 ,/irl+%ire1 tak5 f ! s\? #cie #abd4 ,gr\nd-plan ( ,plateau-v5ts ne> ,/ra?blane1 ,/irl+%ire1 on ! scale ( #f in*es to a mile #cie #abe4 ,gr\nd-plans ( d\ble & triple necks 9 ! ,plateau s]ies1 on ! scale ( #f in*es to a mile #cif #abf4 ,gr\nd-plan ( tuff-neck1 %ore ea/ ( ,dunb> #cih #abg4 ,section across ! v5ts ,dumgoyn & ,dumfoyn1 & ! edge ( ! ,clyde plateau above ,/ra?blane1 ,/irl+%ire #djj #abh4 ,section ?r\gh ! l>ge v5t ( ! ,campsie ,hills #djj #abi4 ,diagrammatic section across ! c5tral v5t ( ! ,clyde plateau 9 ,r5frew%ire #djj #acj4 ,section across ,s\!rn ,b]wick%ire1 to %[ ! relation ( ! volcanic plateau to ! v5ts ly+ s\? f x #dja #aca4 ,section ( s\? end ( ,dumbuck ,hill4 ,ea/ ( ,dumb>ton #djc #acb4 ,section across ! ,ea/ ,lo?ian plateau1 to %[ ! relative position ( "o ( ! necks #djc #acc4 ,view ( ,trapra9 ,law f ! s\?1 a phonolite neck ( ! ,g>leton ,plateau #dje #acd4 ,ve9s & dykes trav]s+ ! agglom]ate & tuff ( ! great ,r5frew%ire v5t #djh #ace4 ,! ,yell[ ,man1 a dyke 9 volcanic tuff & conglom]ate on ! %ore a little ea/ ( ,nor? ,b]wick #dji #acf4 ,tra*ytic sills1 ,knockvadie1 ,kilpatrick ,hills #daj #acg4 ,section across ! edge ( ! ,clyde plateau1 s\?-ea/ ( ,bei? #daa #ach4 ,section across ! upp] "p ( ! ,clyde plateau at ,kilbirnie1 ,ayr%ire #daa #aci4 ,section across ! upp] surface ( ! ,clyde volcanic plateau1 ,burnhead1 nor?-we/ ( ,kilsy? #dab #adj4 ,section across ! upp] surface ( ! ,clyde volcanic plateau at ,campsie #dab #ada4 ,section across we/]n edge ( ! ,g>lton plateau #dab #adb4 ,section across ! ,solway plateau #dac #adc4 ,section ( volcanic v5t at ,ea/ ,grange1 ,p]?%ire coal-field1 con/ruct$ by ,mr4 ,b4 ,n4 ,pea* f ! rocks expos$ 9 a railway-cutt+1 & f plans ( iron/one- & coal-pits #dbf #add4 ,view ( ! ,b9n ( ,burntisl&--a volcanic neck ( agglom]ate #dbh #ade4 ,view ( "p ( ! cliffs ( v]tical agglom]ate1 ,b9n ( ,burntisl& #dca #adf4 ,diagram ( buri$ volcanic cone ne> ,dalry1 ,ayr%ire4 ,con/ruct$ f in=mation obta9$ 9 m9+ op]ations #dcd #adg4 ,diagram to illu/rate h[ ,volcanic ,necks may be conceal$ & expos$ #dcd #adh4 ,section across ! ,sal9e ,hills1 ,fife #dce #adi4 ,section across ! ,b9n ( ,burntisl&1 9 an ea/ & we/ direction #dcf #aej4 ,section 9 old qu>ry1 we/ ( ,we/] ,o*iltree1 ,l9li?g[%ire4 ,calcif]\s ,s&/one s]ies #dcg #aea4 ,eject$ volcanic block 9 ,c>bonif]\s /rata1 ,burntisl& #dch #aeb4 ,view ( volcanic agglom]ate becom+ f9] above ea/ end ( ,k+swood ,craig1 two miles ea/ f ,burntisl& #dci #aec4 ,alt]nations ( basalt & tuff1 ) %ale1 etc41 ( ,k+swood ,craig1 ,burntisl& #dda #aed4 ,section ( ! upp] surface ( a diabase 7leck/one7 %eet1 ,skolie ,burn1 s\?-ea/ ( ,ba?gate #ddc #aee4 ,section across ! volcanic ridge ( ! ,l9li?g[ & ,ba?gate ,hills1 %[+ ! int]calation ( lime/ones t m>k important /ratigraphical horizons #ddd #aef4 ,section 9 ,w>dlaw ,qu>ry1 ,l9li?g[%ire #dde #aeg4 ,section f ,l9li?g[ ,lo* to ! ,fir? ( ,=? #ddf #aeh4 ,section across ! ,campsie ,fells illu/rat+ ! contra/ betwe5 ! sills bel[ & above ! plateau-lavas #ddg #aei4 ,section %[+ ! position ( ! basic sills 9 relation to ! volcanic s]ies at ,burntisl&1 ,fife #ddh #afj4 ,sills betwe5 %ales & s&/ones1 ,h\nd ,po9t1 ,l9li?g[%ire #ddi #afa4 ,section ( ,sill1 ,cramond ,railway1 ,b>nton1 ne> ,ed9burgh #dej #afb4 ,intrusive dol]ite %eet enclos+ & s5d+ ?reads into portions ( %ale1 ,salisbury ,crags1 ,ed9burgh #deb #afc4 ,intrusive %eet invad+ lime/one & %ale1 ,dodhead ,qu>ry1 ne> ,burntisl& #deb #afd4 ,sph]oidal wea!r+ ( dol]ite sill1 qu>ry ea/ ( ,nor? ,que5sf]ry1 ,fife4 #dee #afe4 ,two ?9 sills ( :ite trap inject$ into black c>bonace\s %ale ov]ly+ ! ,hurlet ,lime/one1 ,hillh\se ,qu>ry1 ,l9li?g[ #def #aff4 ,dyke cutt+ ! agglom]ate ( a neck4 ,b9n ( ,burntisl& #deg #afg4 ,boss ( diabase cutt+ ! ,burdieh\se ,lime/one & s5d+ sills & ve9s into ! ov]ly+ %ales4 ,railway cutt+1 ,we/ ,qu>ry1 ,ea/ ,cald]1 ,midlo?ian #deh #afh4 ,side ( column> basalt-dyke 9 ! same agglom]ate z 9 ,fig4 #aff #dei #afi4 ,dyke ris+ ?r\gh ! ,hurlet ,lime/one & its ov]ly+ %ales4 ,silv]m9e ,qu>ry1 ,l9li?g[%ire #dfj #agj4 ,junction ( amygdaloidal basalt ) %ales & lime/one1 %ore1 half a mile ea/ f ,k+horn1 ,fife #dfd #aga4 ,column> basalt1 ,pettycur1 ,k+horn1 ,fife #dfi #agb4 ,section across ! ,fife b& ( ,sills #dgc #agc4 ,section across ! upp] volcanic b& ( nor? ,ayr%ire4 ,l5g? ab\t f\r miles #dgd #agd4 ,section %[+ ! connection ( ! two volcanic b&s 9 ,liddesdale #dgf #age4 ,diagram to %[ ! position ( a mass ( ,upp] ,old ,r$ ,s&/one :i* has fall5 into ! great v5t ne> ,tudhope ,hill1 ea/ ( ,mosspaul #dgf ,,maps ,i4 ,g5]al map ( ! ,volcanic di/ricts ( ! ,briti% ,isles--,at ! end ( ! volume ,,ii4 ,map ( ! ,cambrian & ,silurian volcanic region ( ,nor? ,wales ,to face p4 #bef ,,iii4 ,map ( ! ,old ,r$ ,s&/one volcanic region ( ,lake ,cal$onia 9 ,c5tral ,scotl& & ,nor? ,irel& ,to face p4 #ccd ,,iv4 ,map ( ! ,c>bonif]\s volcanic di/ricts ( ,scotl& ,to face p4 #dgf ,,book ,i ,,g5]al ,,pr9ciples ,,& ,,me?ods ,,( ,,inve/igation ,,*apt] ,i ,e>lie/ ,k ( ,volcanoes--,_! ,influ5ce on ,my?ology & ,sup]/ition--,"p tak5 by ,volcanic ,rocks 9 ,sc5]y--,progress ( ! ,d5udation ( ,volcanoes--,value ( ! ,records ( =m] ,volcanoes z illu/rat+ ,mod]n ,volcanic ,action--,fav\rable ,position ( ,brita9 = ! ,/udy ( ?is ,subject4 ,among ! influ5ces :i* affect$ ! infancy ( mank9d1 ! mo/ pot5t 7 ^? ( environm5t4 ,:atev] 9 out] nature /imulat$ or repress$ c\rage1 inv5tiv5ess1 endurance1 :atev] t5d$ to h>d5 or to weak5 ! bodily faculties1 :atev] appeal$ to ! imag9ation or excit$ ! fancy1 became a p[]ful factor 9 human developm5t4 ,?us1 9 ! dawn ( civilization1 ! frequ5t recurr5ce ( e>?quakes & volcanic eruptions ?r\gh\t ! bas9 ( ! ,m$it]ranean c\ld n b h a m>k$ effect on ! peoples t dwelt by ! bord]s ( t sea4 ,:ile e "p ( ! region 0 f "t to "t %ak5 by und]gr\nd commotion1 !re 7 c]ta9 places t became specially notewor?y = ! wond] & t]ror ( _! cata/rophes4 ,:51 aft] successive convulsions1 va/ cl\ds ( black smoke rose f a m\nta9 & ov]spread ! sky1 :5 ! brightness ( noon 0 rapidly replac$ by ! d>kness ( midnight1 :5 ! air grew ?ick ) /ifl+ du/ & a ra9 ( /ones & a%es fell f x on all ! surr\nd+ c\ntry1 :5 /reams ( :at look$ l liquid fire p\r$ =? & desolat$ g>d5s1 v9ey>ds1 fields & villages--!n did m5 feel sure t ! gods 7 angry4 ,! contra/ betwe5 ! peacefulness & beauty ( ! ord9>y l&scape & ! hide\s w>f>e ( ! elem5ts at ^! times ( volcanic fury c\ld n b p[]fully impress ! imag9ation & give a col\r to e>ly human conceptions ( nature & religion4 ,x 0 n only 9 "o limit$ di/rict t ^! manife/ations ( und]gr\nd convulsion %[$ !mselves4 ,! isl&s ( ! gean _h _! volcanoes1 & ! ,greeks :o dwelt among !m wat*$ _! gl[+ fires by night & _! cl\ds ( /eam by day1 culm9at+ n[ & !n 9 a /up5d\s explosion1 l t :i*1 9 prehi/oric "t1 de/roy$ ! isl& ( ,santor94 ,z ! isl&]s voyag$ ea/w>d !y w\ld see1 on ! coa/ ( ,asia ,m9or1 ! black bri/l+ lavas ( ! ,burnt ,c\ntry1 p]haps ev5 !n fl[+ f _! rugg$ heaps ( c9d]s4 ,or :51 m adv5tur\sly /ill1 !y sail$ we/w>d into ! ,tyrrh5ian wat]s1 !y beheld ! sn[y cone ( ,etna1 ) its d>k canopy ( smoke & ! lurid nocturnal gleam ( its fires2 :ile f "t to "t !y witness$ !re on a /ill m /up5d\s scale ! horrors ( a great volcanic eruption4 ,f all sides1 !re=e1 ! e>ly ,greek voyag]s w\ld c>ry back to ! "m-c\ntry m>vell\s tales ( convulsion & disa/]4 ,!y w\ld tell h[ ! sky rapidly d>k5$ ev5 9 ! blaze ( mid-day1 h[ ! l& 0 smo!r$ ) du/ & /ones1 h[ ov] ! sea !re spread su* a cov]+ ( a%es t ! o>sm5 c\ld h>dly drive _! vessels onw>d1 h[ r$-hot /ones1 :irl+ high ov]head1 ra9$ d[n on sails & deck1 & cru%$ or burnt :atev] !y fell ^u1 & h[1 z ! e>? %ook & ! sea rose 9 sudd5 waves & ! m\nta9 gave =? an appall+ d9 ( con/ant explosion1 x v]ily seem$ t ! end ( ! _w _h come4 ,to ! actual horrors ( su* sc5es !re c\ld h>dly fail to be add$ ! usual embelli%m5ts ( travell]s' tales4 ,?us1 9 ! end1 ! volcanoes ( ! ,m$it]ranean bas9 came to play a n unimportant "p 9 ,hell5ic my?ology4 ,!y seem$ to /& up z ev]la/+ memorials ( ! victory ( ,zeus ov] ! giants & mon/]s ( an e>li] "t4 ,& z ! lively ,greek beheld ,m\nt ,etna 9 eruption1 8 imag9ation readily pictur$ ! imprison$ ,titan buri$ "u ! burn+ roots ( ! m\nta91 brea?+ =? fire & smoke1 & convuls+ ! c\ntry f> & ne>1 z he turn$ himself on 8 uneasy pallet4 ,:5 9 lat] c5turies ! sci5tific _s began to displace ! popul> & my?ological int]pretation ( natural ph5om5a1 ! exi/5ce ( volcanoes & _! extraord9>y ph5om5a (f]$ a fruitful field = speculation & conjecture4 ,z m5 j\rney$ outw>d f ! ,m$it]ranean cradle ( civilization1 !y met ) volcanic manife/ations 9 _m o!r p>ts ( ! _w4 ,:5 !y ev5tually p5etrat$ into ! ,f> ,ea/1 !y enc\nt]$ volcanoes on a colossal scale & 9 a/oni%+ abundance4 ,:5 !y _h discov]$ ! ,new ,_w !y le>nt t1 9 t hemisph]e also1 burn+ m\nta9s 7 num]\s & ( gigantic dim5sions4 ,gradually x 0 asc]ta9$ t va/ l9es ( volcanic activity encircle ! globe4 ,by sl[ degrees ! volcano 0 recogniz$ to be z normal a "p ( ! me*anism ( our planet z ! riv]s t fl[ on ! t]re/rial surface4 ,& n[ at la/ m5 devote !mselves to ! task ( critically wat*+ ! op]ations ( volcanoes ) z mu* en?usiasm z !y display 9 ! inve/igation ( any o!r dep>tm5t ( nature4 ,!y feel t _! k ( ! e>? ext5ds to little beyond its m]e out] sk91 & t ! my/]y :i* /ill hangs ov] ! va/ int]ior ( ! planet c only1 if ev]1 be dispell$ by ! pati5t /udy ( ^! v5ts ( communication betwe5 ! int]ior & ! surface4 ,if1 h[ev]1 we desire to =m "s adequate idea ( ! "p :i* volcanic action has play$ 9 ! pa/ hi/ory ( ! e>?1 we %\ld be misl$ 7 we to conf9e our att5tion to ! ph5om5a ( ! eruptions ( ! pres5t day4 ,an att5tive exam9ation ( any mod]n volcano w conv9ce u t ( "s ( ! mo/ />tl+ features ( an eruption no endur+ memorial rema9s4 ,! convulsive e>?quakes t accompany a great volcanic p>oxysm1 unless :]e !y actually fissure ! gr\nd1 leave little or no trace beh9d !m4 ,lam5tably de/ructive z !y are to human life & prop]ty1 ! havoc :i* !y "w is mo/ly sup]ficial4 ,9 a ye> or two ! ru9s h be5 cle>$ away1 ! e>?-falls h be5 heal$ ov]1 ! pro/rat$ trees h be5 remov$1 &1 save 9 ! memories & *ronicles ( ! inhabitants1 no record ( ! cata/rophe may survive4 ,! cl\ds ( du/ & %[]s ( a%es :i* de/roy$ ! crops & cru%$ 9 ! ro(s ( h\ses soon disappe> f ! air1 & ! cov]+ :i* !y leave ov] ! surface ( a di/rict gradually m+les ) ! soil4 ,vegetation ev5tually rega9s its place1 & ! l&scape becomes aga9 z smil+ z be=e4 ,ev5 :]e ! mat]ials ?r[n out f ! crat] accumulate 9 mu* great] mass1 :]e ?ick deposits ( a%es or solid %eets ( lava bury ! old l&-surface1 ! look ( b>r5 desolation1 ?\gh 9 "s cases x may endure = long c5turies1 may 9 o!rs vani% 9 a few ye>s4 ,! surface-features ( ! di/rict are alt]$ inde$1 b ! new topography soon ceases to look new4 ,ano!r g5]ation ( inhabitants loses recollection ( ! old l&m>ks1 & c h>dly realize t :at has become s famili> to itself diff]s s mu* f :at 0 famili> to its fa!rs4 ,b ev5 :5 ! volcanic cov]+1 ?us ?r[n a?w>t a wide tract ( c\ntry1 has be5 conceal$ "u a new gr[? ( soil & vegetation1 x /ill rema9s a prey to ! ceaseless processes ( decay & degradation :i* ev]y:]e affect ! surface ( ! l&4 ,no feature ( a mod]n volcano is m impressive ?an ! lesson :i* x conveys ( ! reality & pot5cy ( ?is cont9ual wa/e4 ,! nor!rn slopes ( ,vesuvius1 = example1 are tr5*$ ) deep rav9es1 :i* 9 ! c\rse ( c5turies h be5 dug out ( ! lavas & tuffs ( ,monte ,somma by ra9 & melt$ sn[4 ,ye> by ye> ^! *asms are gr[+ deep] & wid]1 :ile ! ridges betwe5 !m are becom+ n>r[]4 ,9 "s cases1 inde$1 ! int]v5+ ridges h be5 r$uc$ to %>p cre/s :i* are split up & l[]$ by ! unceas+ influ5ce ( ! wea!r4 ,! slopes ( su* a volcanic cone h be5 aptly comp>$ to a half-op5$ umbrella4 ,x requires little ef=t ( imag9ation to picture a "t1 by no means remote 9 a geological s5se1 :51 unless r5ovat$ by ! effects ( fre% eruptions1 ! cone w h be5 s levell$ ) ! surr\nd+ c\ntry t ! peasants ( ! future w trail _! v9es & build _! cots ov] ! site ( ! old volcano1 9 happy ignorance ( :at has be5 ! hi/ory ( ! gr\nd b5ea? _! feet4 ,:at is "h pr$ict$ z probable or c]ta9 9 ! future has und\bt$ly happ5$ aga9 & aga9 9 ! pa/4 ,ov] _m di/ricts ( ,europe & ,we/]n ,am]ica ext9ct volcanoes may be se5 9 e /age ( decay4 ,! y\nge/ may /ill %[1 p]fect & b>e ( vegetation1 _! cones & _! crat]s1 ) ! /reams ( lava t escap$ f !m4 ,^? ( old] date h be5 worn d[n into m]e l[ r\nd$ hills1 or ! :ole cone has be5 cle>$ away1 & !re is only left ! h>d core ( mat]ial t solidifi$ 9 ! funnel bel[ ! surface4 ,! lava-%eets h be5 cut ?r\gh by /reams1 & n[ rema9 9 m]e scatt]$ pat*es capp+ deta*$ hills1 :i* only a tra9$ eye c recognize z relics ( a once cont9u\s level %eet ( solid rock4 ,by ?is resi/less degradation1 a volcanic di/rict is /ep by /ep /ripp$ ( e trace ( its orig9al surface4 ,all t ! eruptions did to *ange ! face ( ! l&scape may be entirely oblit]at$4 ,cones & crat]s1 a%es & lavas1 may be gradually effac$4 ,& yet en\gh may be left to enable a geologi/ to make sure t volcanic action 0 once rife !re4 ,z ! volcano m>ks a *annel ( direct communication betwe5 ! int]ior ( ! e>? & ! atmosph]e outside1 !re are subt]ranean z well z sup]ficial manife/ations ( its activity1 & :ile ! latt] are remov$ by d5udation1 ! =m] are "o by "o br\ght into light4 ,! progress ( d5udation is a process ( dissection1 :]eby e detail 9 ! /ructure ( a volcano is successively cut d[n & laid b>e4 ,b = ?is process1 our k ( ! me*anism & hi/ory ( volcanic action w\ld be mu* less full & def9ite ?an happily x is4 ,9 active volcanoes ! int]nal & subt]ranean /ructure c only be conjectur$2 9 ^? ( anci5t date1 :i* h be5 deeply erod$1 ?is und]gr\nd /ructure is op5 to ! close/ exam9ation4 ,by ga!r+ toge!r evid5ce ( ?is nature ov] ! surface ( ! globe1 we le>n t abundantly z /ill active volcanoes are di/ribut$ on t surface1 !y =m b a small fraction ( ! total numb] ( v5ts :i* h at v>i\s times be5 9 eruption4 ,9 ,italy1 = example1 :ile ,vesuvius is active on ! ma9l&1 & ,etna1 ,/romboli & ,volcano display _! vig\r among ! isl&s1 !re are scores ( old volcanoes t h be5 sil5t & cold ev] s9ce ! beg9n+ ( hi/ory1 yet %[ by _! cones ( c9d]s & /reams ( bri/l+ lava t !y 7 en]getic en\gh 9 _! day4 ,b ! ,italian volcanic region is only "o ( _m to be f\nd on ! ,european ,cont95t4 ,if we travel ea/w>d into ,hung>y1 or nor?w>d into ! ,eifel1 or into ! he>t ( ,france1 we enc\nt] abundant cones & crat]s1 _m ( !m s fre% t1 ?\gh !re is no hi/orical record ( _! activity1 !y look z if !y _h be5 9 eruption only a few g5]ations ago4 ,b :5 ! geologi/ beg9s to se>* among rocks ( /ill old] date ?an ^! comp>atively rec5t volcanic memorials1 he meets ) abundant relics ( f> e>li] eruptions4 ,& z he arranges ! *ronicles ( ! e>?'s hi/ory1 he discov]s t ea* section ( ! long cycle ( geological ages has pres]v$ its records ( =m] volcanoes4 ,9 a rese>* ( ?is k9d he c be/ realize h[ mu* he owes to ! process ( d5udation4 ,! volcanic rema9s ( =m] geological p]iods h 9 mo/ cases be5 buri$ "u y\ng] deposits1 & h sunk sometimes ?\s&s ( feet bel[ ! level ( ! sea4 ,!y h be5 dislocat$ & upheav$ aga9 dur+ successive commotions ( ! t]re/rial cru/1 & h at la/ be5 reveal$ by ! gradual removal ( ! pile ( mat]ial "u :i* !y _h la94 ,h5ce we le>n t ! active volcanoes ( ! pres5t "t1 :i* really embrace b a small "p ( ! volcanic hi/ory ( our planet1 are ! desc5dants ( a long l9e ( ance/ors4 ,_! di/ribution & activity %\ld be consid]$ n m]ely f ! evid5ce !y !mselves supply1 b 9 ! light d]iv$ f a /udy ( t ance/ry4 ,x is only :5 we take ?is broad view ( ! subject t we c be 9 a position to =m "s adequate conception ( ! nature & hi/ory ( volcanoes 9 ! geological evolution ( ! globe4 ,9 ?is rese>* x is obvi\s t ! pres5tly active volcano mu/ be ! basis & />t+-po9t ( inquiry4 ,at t *annel ( communication betwe5 ! unkn[n inside & ! famili> outside ( our globe1 we c wat* :at takes place 9 times ( quiesc5ce or ( activity4 ,we c !re /udy ea* successive phase ( an eruption1 measure temp]atures1 photograph pass+ ph5om5a1 collect gases & vap\rs1 regi/] ! fall ( a%es or ! fl[ ( lavas1 & ga!r a va/ body ( facts reg>d+ ! mat]ials t are eject$ f ! int]ior1 & ! mann] ( _! emission4 ,indisp5sable z ?is in=mation is = ! compreh5sion ( volcanic action1 x obvi\sly af=ds aft] all b a sup]ficial glimpse ( t action4 ,we _c see beyond ! bottom ( ! crat]4 ,we _c tell any?+ ab\t ! subt]ranean ducts1 or h[ ! molt5 & fragm5tal mat]ials behave 9 !m4 ,all ! und]gr\nd me*anism ( volcanoes is necess>ily hidd5 f our eyes4 ,b mu* ( ?is conceal$ /ructure has be5 reveal$ 9 ! case ( anci5t volcanic masses1 :i* h be5 buri$ & aft]w>ds uprais$ & laid b>e by d5udation4 ,9 yet ano!r important aspect mod]n volcanoes d n p]mit u to obta9 full k ( ! subject4 ,! t]re/rial v5ts1 f :i* we d]ive our in=mation1 by no means repres5t all ! exi/+ po9ts ( direct connection betwe5 ! int]ior & ! ext]ior ( ! planet4 ,we "k t "s volcanic eruptions occur "u ! sea1 & d\btless va/ numb]s m take place !re ( :i* we "k no?+4 ,b ! conditions "u :i* ^! subm>9e dis*>ges are effect$1 ! behavi\r ( ! outfl[+ lava "u a body ( oceanic wat]1 & ! "p play$ by fragm5t>y mat]ials 9 ! explosions1 c only be surmis$4 ,n[ & !n a subm>9e volcano pu%es its summit above ! sea-level1 & all[s its op]ations to be se51 b 9 s do+ x becomes practically a t]re/rial volcano1 & ! peculi> subm>9e ph5om5a are /ill effectually conceal$ f obs]vation4 ,! volcanic records ( =m] geological p]iods1 h[ev]1 are 9 l>ge measure ^? ( eruptions "u ! sea4 ,9 /udy+ !m we are p]mitt$1 z x 71 to explore ! sea-bottom4 ,we c trace h[ %eets ( coral & groves ( cr9oids 7 buri$ "u %[]s ( a%es & /ones1 & h[ ! ooze & silt ( ! sea-floor 7 ov]spread ) /reams ( lava4 ,we are ?us1 9 "s degree1 enabl$ to realize :at mu/ n[ happ5 ov] _m p>ts ( ! b$ ( ! exi/+ ocean4 ,! geologi/ :o und]takes an inve/igation into ! hi/ory ( volcanic action )9 ! area ( ! ,briti% ,isles dur+ pa/ "t1 ) a view to ! bett] compreh5sion ( ?is dep>tm5t ( t]re/rial physics1 f9ds himself 9 a situation ( peculi> advantage4 ,probably no region on ! face ( ! globe is bett] fitt$ ?an ^! isl&s to furni% a l>ge & v>i$ body ( evid5ce reg>d+ ! progress ( volcanic en]gy 9 =m] ages4 ,?is special fitness may be trac$ to f\r causes--#a/1 ,! rem>kable complet5ess ( ! geological record 9 ,brita92 #bnd1 ,! geographical position ( ! region on ! oceanic bord] ( a cont95t2 #crd1 ,! s+ul>ly ample developm5t to be f\nd !re ( volcanic rocks belong+ to a long succession ( geological ages2 & #d?1 ,! ext5t to :i* ?is full *ronicle ( volcanic activity has be5 laid b>e by d5udation4 #a4 ,9 ! fir/ place1 ! geological record ( ,brita9 is s+ul>ly complete4 ,x has (t5 be5 rem>k$ h[ l>gely all ! great p]iods ( geological "t are repres5t$ )9 ! n>r[ conf9es ( ^! isl&s4 ,! gaps 9 ! *ronicle are comp>atively few1 & = ! mo/ "p are n ( great mom5t4 ,?anks to ! re/rict$ area ( ! c\ntry & to ! l>ge numb] ( obs]v]s1 ?is rem>kably full record ( geological hi/ory has be5 /udi$ ) a m9ute c>e :i* has h>dly be5 equall$ 9 any o!r c\ntry4 ,! detail$ succession ( all ! =mations has be5 s fully det]m9$ 9 ,brita9 t ! v names fir/ appli$ "h to !m & to _! subdivisions h 9 l>ge measure pass$ into ! famili> language ( geology all ov] ! globe4 ,e def9ite plat=m 9 ! /ratigraphical s]ies has be5 m or less fully work$ out4 ,a basis has ?us be5 laid = ref]r+ ea* incid5t 9 ! geological hi/ory ( ! region to its prop] relative date4 #b4 ,9 ! second place1 ! geographical position ( ,brita9 gives x a notable advantage 9 reg>d to ! manife/ations ( volcanic en]gy4 ,ris+ f ! m>g9 ( a great ocean-bas9 & ext5d+ along ! edge ( a cont95t1 ^! isl&s h la9 on t critical bord]-zone ( ! t]re/rial surface1 :]e volcanic action is apt to be mo/ vigor\s & cont9u\s4 ,x has long be5 rem>k$ t volcanoes are g5]ally plac$ n f> f ! sea4 ,f ! e>lie/ geological p]iods ! site ( ,brita91 ev5 :5 subm]g$ bel[ ! sea1 has nev] la9 f> f ! l& :i* suppli$ ! va/ accumulations ( s$im5t t w5t to =m ! ,palozoic & lat] =mations1 :ile1 on ! o!r h&1 x frequ5tly =m$ "p ( ! l& ( =m] geological p]iods4 ,x 0 ?us mo/ fav\rably situat$ z a !atre = bo? t]re/rial & subm>9e volcanic activity4 #c4 ,9 ! ?ird place1 ?is advantage\s geographical position is f\nd to h be5 att5d$ ) an altoge!r rem>kable abundance & p]si/5ce ( volcanic eruptions4 ,no tract ( equal size yet kn[n on ! face ( ! globe furni%es s ample a record ( volcanic activity f ! e>lie/ geological p]iods d[n into ,t]ti>y "t4 ,e degree ( en]gy may be signaliz$ 9 t record1 f colossal eruptions :i* pil$ up ?\s&s ( feet ( rock d[n to ! feeble/ dis*>ge ( du/ & /ones4 ,e kn[n type ( volcano is repres5t$--great c5tral cones l ,etna or ,vesuvius1 scatt]$ gr\ps ( small cones l ! puys ( ,france1 & fissure- or dyke-eruptions l ^? ( rec5t times 9 ,icel&4 ,moreov]1 ! accurate mann] 9 :i* ! /ratigraphy ( ! c\ntry has be5 e/abli%$ p]mits ea* successive era 9 ! long volcanic hi/ory to be precisely det]m9$1 & all[s u to foll[ ! :ole progress ( t hi/ory /age by /age1 f ! beg9n+ to ! end4 ,^! *>act]i/ics may be in/ructively repres5t$ on a map1 su* z t :i* accompanies ! pres5t volume 7,map ,i474 ,! read] w !re obs]ve h[ repeat$ly volcanic eruptions h tak5 place1 n m]ely )9 ! g5]al area ( ! ,briti% ,isles1 b ev5 )9 ! same limit$ region ( t area4 ,! broad midl& valley ( ,scotl& has be5 especially ! !atre = _! display4 ,f ! e>ly "p ( ! ,l[] ,silurian p]iod1 ?r\gh ! ages ( ! ,old ,r$ ,s&/one1 ,c>bonif]\s & ,p]mian sy/ems1 hundr$s ( volcanic v5ts 7 active 9 t region1 :ile 9 long subsequ5t "t !re came ! fissure-eruptions ( ! ,t]ti>y s]ies4 #d4 ,9 ! f\r? place1 ! geological revolutions ( successive ages h made ?is long volcanic *ronicle fully accessible to obs]vation4 ,_h ! lavas & a%es ( "o p]iod rema9$ buri$ "u ! s$im5t>y accumulations ( ! next1 _! /ory w\ld h be5 lo/ to u4 ,we %\ld only h be5 able to deciph] ! late/ records :i* might happ5 to lie on ! surface4 ,=tunately = ! progress ( geology1 ! endless vicissitudes ( a cont95tal bord] h br\ght up ! v olde/ rocks once m to ! surface4 ,all ! lat] =mations ( ! e>?'s cru/ h likewise be5 uprais$ & expos$ to d5udation dur+ long cycles ( "t4 ,9 ?is mann]1 ! rocky framework ( ! c\ntry has be5 laid b>e1 & ea* successive *apt] ( its geological hi/ory may be satisfactorily deciph]$4 ,! s+ul>ly complete volcanic *ronicle1 aft] be+ entomb$ "u y\ng] deposits1 has be5 brok5 up & rais$ once m into view4 ,! active v5ts ( =m] p]iods h be5 dissect$1 subm>9e /reams ( lava h be5 uncov]$1 %eets ( a%es t fell ov] ! sea-bottom h be5 laid b>e4 ,! progress ( d5udation is specially fav\r$ 9 su* a v>iable & moi/ climate z t ( ,brita91 & ?us by ! co-op]ation ( und]gr\nd & meteoric causes ! m>vell\s volcanic records ( ?is c\ntry h be5 laid op5 9 m9ute/ detail4 ,!re is yet ano!r respect 9 :i* ! volcanic geology ( ,brita9 possesses a special value4 ,popul> imag9ation has long be5 prone to see signs ( volcanic action 9 ! m prom95t rocky features ( l&scape4 ,a bold crag1 a deep & precipit\s rav9e1 a *asm 9 ! side ( a m\nta91 h be5 unhesitat+ly set d[n z pro( ( volcanic di/urbance4 ,_m a cauldron-%ap$ recess1 l ! corries ( ,scotl& or ! cwms ( ,wales1 has be5 cit$ z an actual crat]1 ) its encircl+ walls /ill /&+ almo/ complete4 ,! relics ( =m] volcanoes 9 ?is c\ntry furni% ample pro(s to dispel ^! common misconceptions4 ,!y %[ t n a s+le crat] any:]e rema9s1 save :]e x has be5 buri$ "u lava2 t no trace ( ! orig9al cones has surviv$1 except 9 a few d\btful cases :]e !y may h be5 pres]v$ "u subsequ5t accumulations ( mat]ial2 t 9 ! rugg$ tracts1 :]e volcanic action has be5 ?\ght to h be5 mo/ rife1 !re may be n a ve/ige ( x1 :ile1 on ! o!r h&1 :]e ! un$ucat$ eye w\ld nev] suspect ! pres5ce ( any remnant ( volcanic en]gy1 lavas & a%es may ab\nd4 ,we are ?us pres5t$ ) "s ( ! mo/ impressive contra/s 9 geological hi/ory1 :ile1 at ! same "t1 ?is mom5t\s lesson is borne 9 ^u ! m9d1 t ! exi/+ inequalities 9 ! configuration ( a l&scape are g5]ally due f> less to ! influ5ce ( subt]ranean =ce ?an to ! action ( ! sup]ficial ag5ts :i* are ceaselessly c>v+ ! face ( ! l&4 ,^? rocks :i* f _! h>dness or /ructure are be/ able to )/& t de/ruction rise into prom95ce1 :ile ! s(t] mat]ial ar\nd !m is worn away4 ,volcanic rocks are no exception to ?is rule1 z ! geological /ructure ( ,brita9 amply proves4 ,9 ! foll[+ *apt]s1 =m+ ,book ,i4 ( ?is "w1 ,i propose to beg9 by (f]+ "s g5]al rem>ks reg>d+ ! nature & causes ( volcanic action1 s f> z ^! are kn[n to u4 ,i %all !n proce$ to consid] ! "* ( ! evid5ce t may be expect$ to be met ) respect+ ! =m] preval5ce ( t action at any p>ticul> locality :]e volcanic di/urbances h long s9ce ceas$4 ,! mo/ tell+ evid5ce ( old volcanoes is naturally to be f\nd 9 ! mat]ials :i* !y h left beh9d !m1 & ! read]'s att5tion w be ask$ to ! special *>act]i/ics ( ^! mat]ials1 9 s f> z !y give evid5ce ( =m] volcanic activity4 ,z has be5 already rem>k$1 _m ( ! mo/ prom95t ph5om5a ( a mod]n volcano are only ( transi5t importance4 ,! e>?quakes & tremors1 & ! con/ant dis5gagem5t ( /eam & gases1 t play s conspicu\s a "p 9 an eruption1 may leave no s5sible record beh9d !m4 ,b ev5 ! cones ( a%es & lava1 :i* are pil$ up into m\nta9\s masses1 h no true p]man5ce3 !y are liable to ceaseless erosion by ! meteoric ag5cies ( wa/e1 & e /age 9 _! degradation may be trac$4 ,9 successive examples we c foll[ !m z !y are cut d[n to ! v core1 until 9 ! end !y are entirely effac$4 ,we may well1 !re=e1 ask at ! outset by :at m endur+ records we may hope to detect ! traces ( =m] volcanic action4 ,! foll[+ introductory *apt]s w be devot$ to an attempt to answ] ?is "q4 ,i %all try to %[ ! nature & relative importance ( ! records ( anci5t volcanoes2 h[ ^! records1 g5]ally s fragm5t>y1 may be piec$ toge!r s z to be made to furni% ! hi/ory :i* !y conta92 h[ _! relative *ronology may be e/abli%$2 h[ _! te/imony may be supplem5t$ 9 su* wise t ! position ( long vani%$ seas1 l&s1 riv]s1 & lakes may be asc]ta9$2 & h[1 aft] ages ( geological revolution1 volcanic rocks t h la9 long buri$ "u ! surface n[ influ5ce ! sc5]y ( ! regions :]e !y h once m be5 expos$ to view4 ,f ?is gr\ndwork ( asc]ta9$ fact & reasonable inf]5ce1 we %all ent] 9 ,book ,,ii4 ^u ! /ory ( ! old volcanoes ( ! ,briti% ,isles4 ,x is usual to treat geological hi/ory 9 *ronological ord]1 beg9n+ ) ! e>lie/ ages4 ,& ?is me?od1 z on ! :ole ! mo/ conv5i5t1 w be adopt$ 9 ! pres5t "w4 ,at ! same "t1 ! plan s p]si/5tly foll[$ by ,lyell1 ( work+ backw>d f ! pres5t into ! pa/1 has "s di/9ct advantages4 ,! volcanic records ( ! lat] ages are mu* simpl] & cle>] ?an ^? ( old] times1 & ! /ud5t may1 9 "s respects1 pr(itably /udy ! hi/ory ( ! ,t]ti>y eruptions be=e he proce$s to make himself acqua9t$ ) ! scanti] *ronicles ( ! eruptions ( ! ,palozoic p]iods4 ,b z ,i wi% to foll[ ! gradual evolution ( volcanic ph5om5a1 & to %[ h[ volcanic en]gy has v>i$1 wax+ & wan+ ?r\gh successive va/ int]vals ( "t1 ,i w adh]e to ! *ronological sequ5ce4 ,,*apt] ,,ii ,! ,nature & ,causes ( ,volcanic ,action--,mod]n ,volcanoes4 ,a volcano is a conical or dome-%ap$ hill or m\nta91 consi/+ ( mat]ials :i* h be5 erupt$ f an orifice lead+ d[n f ! surface into ! heat$ int]ior ( ! e>?4 ,among mod]n & rec5t volcanoes ?ree types may be recogniz$4 ,9 ! fir/ & mo/ famili> ( ^!1 ! lavas & a%es eject$ f ! c5tral v5t h ga!r$ ar\nd x by successive eruptions1 until !y h built up a c5tral cone l ^? ( ,etna & ,vesuvius4 ,z ?is cone gr[s 9 height & diamet]1 lat]al or p>asitic cones are =m$ on its flanks1 & may become !mselves ! *ief actively erupt+ v5ts4 ,?is type ( volcano1 :i* has be5 s long well kn[n f its ,m$it]ranean examples1 0 until rec5tly believ$ by geologi/s to be ! normal1 or inde$ ! only1 phase ( volcanic en]gy on ! face ( ! e>?4 ,a modification ( ?is type is to be f\nd 9 a few regions :]e fragm5t>y dis*>ges are small 9 am\nt & :]e ! eruptions are almo/ :olly conf9$ to ! emission ( tol]ably liquid lava4 ,a va/ dome ) g5tly slop+ declivities may 9 ?is way be =m$1 z 9 ! ,s&wi* ,isl&s & 9 c]ta9 p>ts ( ,icel&4 ,! second type ( volcano is at ! pres5t day ext5sively develop$ only 9 ,icel&1 b 9 ,t]ti>y "t x appe>s to h _h a wide range ov] ! globe1 = /up5d\s memorials ( x are pres]v$ 9 ,nor?-,we/]n ,europe1 9 ,we/]n ,am]ica1 & 9 ,india4 ,x is di/+ui%$ by ! =mation ( num]\s p>allel fissures f :i* ! lava gu%es =?1 ei!r ) or )\t ! =mation ( small c9d]-cones along ! l9es ( ! *asms4 ,! ?ird type is di/+ui%$ by ! =mation ( gr\ps ( c9d]-cones or lava-domes1 :i* f _! admirable developm5t 9 ,c5tral ,france h receiv$ ! "n ( ,puys4 ,f ^! v5ts consid]able /reams ( lava h sometimes be5 dis*>g$4 ,)\t ent]+ "h into a detail$ inquiry reg>d+ ! nature & causes ( ,volcanic ,action1 we may ) advantage consid] briefly ! two ma9 factors on :i* ?is action appe>s to dep5d4 #a4 ,mu* unc]ta9ty /ill exi/s z to ! condition & composition ( ! e>?'s int]ior4 ,! wide di/ribution ( volcanoes ov] ! globe1 toge!r ) ! g5]al simil>ity ( mat]ials br\ght by !m up to ! surface1 =m]ly l$ to ! belief t our planet consi/s ( a c5tral mass ( molt5 rock enclos$ )9 a comp>atively ?9 solid cru/4 ,physical argum5ts1 h[ev]1 h s9ce demon/rat$ t ! e>?1 ) su* a /ructure1 w\ld h und]gone great tidal de=mation1 b t 9 actual fact x has a great] rigidity ?an if x 7 made ( solid glass or /eel4 ,f all ! evid5ce obta9able x is c]ta9 t ! temp]ature ( ! e>?'s int]ior mu/ be high4 ,! rate ( increase ( ?is temp]ature d[nw>d f ! surface diff]s f place to place2 b an increase is always obs]v$4 ,at a dep? ( a few miles1 e kn[n sub/ance mu/ be mu* hott] ?an its melt+ po9t at ! surface4 ,b at ! great pressures )9 ! e>?1 actual liquefaction is no d\bt prev5t$1 & ! nucleus rema9s solid1 ?\gh at a temp]ature at :i*1 b = ! pressure1 x w\ld be l s mu* molt5 iron4 ,any cause :i* w dim9i% ! pressure may all[ ! int5sely hot mat]ial )9 ! globe to pass into ! liquid /ate4 ,!re is "o kn[n cause :i* w br+ ab\t ?is result4 ,! d[nw>d increm5t ( temp]ature proves t our planet is cont9ually los+ heat4 ,z ! out] cru/ is comp>atively cool1 & does n become s5sibly hott] by ! uprise ( heat f )91 ! hot nucleus mu/ cool fa/] ?an ! cru/ is do+4 ,n[ cool+ involves contraction4 ,! hot int]ior is contract+ fa/] ?an ! cool] %ell :i* encloses x1 & t %ell is ?us =c$ to subside4 ,9 its desc5t x has to adju/ itself to a con/antly dim9i%+ diamet]4 ,x c d s only by plication or by rupture4 ,:5 ! t]re/rial cru/1 "u ! /ra9 ( contraction1 is compress$ into folds1 ! relief ?us obta9$ is n di/ribut$ uni=mly ov] ! :ole surface ( ! planet4 ,f an e>ly geological p]iod x appe>s to h foll[$ c]ta9 l9es4 ,h[ ^! came to be at fir/ det]m9$ we _c tell4 ,b x is c]ta9 t !y h s]v$ aga9 & aga91 dur+ successive p]iods ( t]re/rial readju/m5t4 ,^! l9es ( relief co9cide1 on ! :ole1 ) ! axes ( our cont95ts4 ,! l&-areas ( ! globe may be reg>d$ z ow+ _! exi/5ce above sea-level to ?is result ( t]re/rial contraction4 ,! cru/ und]nea? !m has be5 repeat$ly wr9kl$1 fractur$ & ?ru/ upw>d by ! va/ oceanic subsid5ce ar\nd !m4 ,! long m\nta9-*a9s are ?us1 s to speak1 ! cre/s ( ! waves into :i* ! cru/ has f "t to "t be5 ?r[n4 ,aga91 ! great l9es ( fracture 9 ! cru/ ( ! e>? probably lie 9 l>ge measure )9 ! l&-areas1 or at lea/ p>allel ) _! axes & close to _! bord]s4 ,:]e ! disposition ( ! *ief ruptures & ( ! pr$om9ant plications c be exam9$1 ^! lead+ /ructural features are f\nd to be1 on ! :ole1 co9cid5t4 ,9 ! ,briti% ,isl&s1 = in/ance1 ! preval5t tr5d ( ! axes ( fold+ f e>ly ,palozoic to ,t]ti>y "t has be5 f s\?-we/ to nor?-ea/4 ,h[ pr(\ndly ?is direction ( e>?-movem5t has affect$ ! /ructure ( ! region is %[n by any ord9>y map1 9 ! long hill-ranges ( ! l& & 9 ! long inlets ( ! sea4 ,a geological map makes ! dep5d5ce ( ! sc5]y ^u ! build+ ( ! rocks /ill m /rik+4 ,n only h ^! rocks be5 plicat$ into endless fold+s1 ! axes ( :i* trav]se ! ,briti% ,isl&s ) a nor?-ea/]ly tr5d3 !y h likewise be5 dislocat$ by _m gigantic ruptures1 :i* t5d on ! :ole to foll[ ! same direction4 ,! l9e ( ! ,great ,gl51 ! s\!rn front ( ! ,highl&s1 & ! nor!rn b\nd>y ( ! ,s\!rn ,upl&s ( ,scotl&1 are conspicu\s examples ( ! position & effect ( "s ( ! great] fractures 9 ! /ructure ( ?is c\ntry4 ,! ridg+ up ( any "p ( ! t]re/rial cru/ w af=d "s relief f pressure to ! p>ts ( ! int]ior imm$iately und]nea?4 ,if1 z is probable1 ! mat]ial ( ! e>?'s int]ior is at ! melt+ po9t prop] = ! pressure at ea* dep?1 !n any dim9ution ( ! pressure may all[ ! int5sely heat$ sub/ance to pass into ! liquid /ate4 ,x w\ld be along ! l9es ( t]re/rial uplift t ?is relief w\ld be giv54 ,x is !re t active volcanoes are f\nd4 ,! molt5 mat]ial is =c$ upw>d "u ^! uprais$ ridges by ! subsid5ce ( ! surr\nd+ regions4 ,& :]e by rupture ( ! cru/ ?is mat]ial c make its way to ! surface1 we may conceive t x w be eject$ z lava or z /ones & a%es4 ,view$ 9 a broad way1 su* appe>s to be ! me*anism involv$ 9 ! =mation & di/ribution ( volcanoes ov] ! surface ( ! e>?4 ,b obvi\sly ?is explanation only c>ries u s f> 9 ! elucidation ( volcanic action4 ,if ! molt5 magma fl[$ out m]ely 9 virtue ( ! influ5ce ( t]re/rial contraction1 x might d s = ! mo/ "p tranquilly1 ?\gh x w\ld probably be affect$ by occasional sudd5 snaps1 z ! cru/ yield$ to accumulations ( pressure4 ,human exp]i5ce has no record ( ! actual elevation ( a m\nta9-*a94 ,we may believe t if su* an ev5t 7 to happ5 sudd5ly or rapidly1 x w\ld be att5d$ ) gigantic cata/rophes ov] ! surface ( ! globe4 ,we c h>dly conceive :at w\ld be ! scale ( a volcanic eruption att5d+ ^u s colossal a di/urbance ( ! t]re/rial cru/4 ,b ! eruptions :i* h tak5 place )9 ! memory ( man h be5 ! accompanim5ts ( no su* di/urbance4 ,al?\gh !y h be5 _m 9 numb] & sometimes p[]ful 9 effect1 !y h seldom be5 att5d$ ) any m>k$ displacem5t ( ! surr\nd+ p>ts ( ! t]re/rial cru/4 ,contraction is1 ( c\rse1 cont9u\sly & regul>ly 9 progress1 & we may suppose t ! consequ5t subsid5ce1 ?\gh x results 9 int]mitt5t wr9kl+ & uplift+ ( ! t]re/rial ridges1 may also be m or less p]si/5t 9 ! regions ly+ outside ^! ridges4 ,!re w ?us be a con/ant pressure ( ! molt5 magma into ! roots ( volcanoes1 & a p]si/5t t5d5cy = ! magma to issue at ! surface at e available r5t or orifice4 ,! en]gy & duration ( outfl[1 if !y dep5d$ :olly ^u ! effects ( contraction1 w\ld ?us v>y ) ! rate ( subsid5ce ( ! s9k+ areas1 probably assum+ g5]ally a feeble developm5t1 b sometimes bur/+ into f\nta9s ( molt5 rock hundr$s ( feet 9 height1 l ^? obs]v$ f "t to "t 9 ,hawaii4 #b4 ,! actual ph5om5a ( volcanic eruptions1 h[ev]1 %[ t a s\rce ( explosive en]gy is almo/ always associat$ ) !m1 & t :ile ! transf]5ce ( ! subt]ranean molt5 magma t[>ds ! volcanic v5ts may be ref]r$ to ! results ( t]re/rial contraction1 ! viol5t dis*>ge ( mat]ials f ^? v5ts mu/ be assign$ to "s k9d ( en]gy /or$ up 9 ! sub/ance ( ! e>?'s int]ior4 ,! deep-seat$ magma f :i* lavas asc5d conta9s v>i\s vap\rs & gases :i*1 "u ! enorm\s pressure )9 & b5ea? ! t]re/rial cru/1 are absorb$ or dissolv$ 9 x4 ,s great is ! t5sion ( ^! gase\s con/itu5ts1 t :5 f any cause ! pressure on ! magma is sudd5ly reliev$1 !y are lib]at$ ) explosive viol5ce4 ,a volcanic p>oxysm is ?us imm$iately ! effect ( ! rapid escape ( ^! imprison$ gases & vap\rs4 ,) su* en]gy does ! explosion sometimes take place1 t ! asc5d+ column ( molt5 lava is bl[n into ! f9e/ impalpable du/1 :i* may load ! air ar\nd a volcano = _m days be=e x falls to ! gr\nd1 or may be borne 9 ! upp] regions ( ! atmosph]e r\nd ! globe4 ,! proportion ( dissolv$ gases v>ies 9 diff]5t lavas1 :ile ! lavas !mselves diff] 9 ! degree ( _! liquidity4 ,"s fl[ out tranquilly l molt5 iron1 o!rs issue 9 a pa/y condition & rapidly congeal into scori & cl9k]s4 ,?us )9 ! magma itself ! am\nt ( explosive en]gy is f> f be+ always ! same4 ,x is to ! co-op]ation ( ^! two causes--t]re/rial contraction & its effects on ! "o h&1 & ! t5sion ( absorb$ gases & vap\rs ! o!r--t ! ph5om5a ( volcanoes appe> to be ma9ly due4 ,!re is no reason to believe t mod]n volcanoes diff] 9 any ess5tial respect f ^? ( pa/ ages 9 ! e>?'s hi/ory4 ,x might1 inde$1 h be5 anticipat$ t ! g5]al en]gy ( ! planet w\ld manife/ itself 9 f> m /up5d\s volcanic eruptions 9 e>ly times ?an ^? ( ! mod]n p]iod4 ,b !re is c]ta9ly no geological evid5ce 9 fav\r ( su* a diff]5ce4 ,"o ( ! objects ( ! pres5t "w is to trace ! cont9uity ( volcanic ph5om5a back to ! v e>lie/ epo*s1 & to %[ t1 s f> z ! geological records g1 ! int]ior ( ! planet has react$ on its ext]ior 9 ! same way & ) ! same results4 ,we may n[ proce$ to inquire h[ f> volcanoes leave beh9d !m evid5ce ( _! exi/5ce4 ,i %all devote ! next two or ?ree *apt]s to a consid]ation ( ! pro(s ( volcanic action furni%$ by ! v nature ( ! mat]ials br\ght up f ! int]ior ( ! e>?1 by ! arrangem5t ( ^! mat]ials at ! surface1 by ! exi/5ce ( ! actual funnels or ducts f :i* !y 7 dis*>g$ above gr\nd1 & by ! disposition ( ! masses ( rock :i*1 at v>i\s dep?s bel[ ! surface1 h be5 inject$ into & h solidifi$ )9 ! t]re/rial cru/4 ,,*apt] ,,iii ,anci5t ,volcanoes3 ,pro(s ( _! exi/5ce d]iv$ f ! ,nature ( ! ,rocks erupt$ f ! ,e>?'s ,int]ior4 ,a4 ,mat]ials erupt$ at ! ,surface--,extrusive ,s]ies4 i4 ,lavas1 _! ,g5]al ,*>act]s4 ,volcanic ,cycles4 ii4 ,volcanic ,agglom]ates1 ,breccias & ,tuffs4 ,! mat]ials br\ght by volcanic action f ! e>?'s int]ior h c]ta9 common *>act]s :i* di/+ui% !m f o!r con/itu5ts ( ! t]re/rial cru/4 ,h5ce ! occurr5ce ( ^! mat]ials on any "p ( ! e>?'s surface af=ds conv9c+ pro(s ( =m] volcanic eruptions1 ev5 :]e all outw>d trace ( actual volcanoes may h be5 effac$ f ! topographical features ( ! gr\nd4 ,volcanic products may be class$ 9 two divisions--#a/1 ,^? :i* h be5 eject$ at ! surface ( ! e>?1 or ! ,extrusive s]ies2 & #bnd1 ,^? :i* h be5 inject$ into ! t]re/rial cru/ at a great] or less di/ance bel[ ! surface1 & :i* are kn[n z ! ,intrusive s]ies4 ,extrusive rocks may be fur!r classifi$ 9 two great gr\ps--7i47 ,! ,lavas1 or ^? :i* h be5 p\r$ out 9 a molt5 condition at ! surface2 & 7ii47 ,! ,fragm5tal ,mat]ials1 includ+ all k9ds ( pyrocla/ic detritus dis*>g$ f volcanic v5ts4 ,tak+ fir/ ! ,extrusive volcanic rocks1 we may 9 ! pres5t *apt] consid] ^? *>act]s 9 !m :i* are ( mo/ practical value 9 ! inve/igation ( ! volcanic ph5om5a ( =m] geological p]iods4 i4 ,,lavas ,! t]m ,lava is a conv5i5t & compreh5sive designation = all ^? volcanic products :i* h fl[$ out 9 a molt5 condition4 ,!y diff] f ea* o!r 9 composition & /ructure1 b _! v>iations are compris$ )9 tol]ably def9ite limits4 ,z reg>ds _! composition !y are commonly class$ 9 ?ree divisions--#a/1 ,! ,acid lavas1 9 :i* ! proportion ( silicic acid ranges f a little bel[ #gj p] c5t upw>ds2 #bnd1 ,! ,int]m$iate lavas1 :]e9 ! p]c5tage ( silica may v>y f #ee to ne> #gj2 & #crd1 ,! ,basic lavas1 :]e ! acid con/itu5t ranges f #ee p] c5t d[nw>ds4 ,sometimes ! mo/ basic k9ds are di/+ui%$ z a f\r? gr\p "u ! "n ( ,ultrabasic1 9 :i* ! p]c5tage ( silica may fall bel[ #dj4 ,! /ructures ( lavas1 h[ev]1 furni% _! mo/ easily appreciat$ *>act]i/ics4 ,f\r ( ^! /ructures des]ve m p>ticul> att5tion3 #a/1 ,cellul>1 vesicul> or pumice\s /ructure2 #bnd1 ,! pres5ce ( glass1 or "s result ( ! devitrification ( an orig9al glass2 #crd1 ,fl[-/ructure2 & #d?1 ,! arrangem5t ( ! rocks 9 %eets or b$s1 ) column> & o!r /ructures4 ,illu/ration3 ,fig4 #a4--,vesicul> /ructure1 ,lava f ,asc5sion ,isl&1 slightly less ?an natural size4 #a4 ,! ,,cellul>1 ,,vesicul>1 ,,scoriace\s or ,,pumice\s ,,/ructure ( volcanic rocks 7,fig4 #a7 c\ld only h aris5 9 molt5 masses f ! expansion ( imprison$ vap\rs or gases1 & is ?us ( crucial importance 9 decid+ ! once liquid condition ( ! rocks :i* display x4 ,! vesicles may be ( microscopic m9ut5ess1 b are g5]ally q visible to ! nak$ eye1 & are (t5 l>ge & conspicu\s4 ,sometimes ^! cavities h be5 subsequ5tly fill$ up ) calcite1 qu>tz1 agate1 zeolites or o!r m9]al deposition4 ,z ! k]nels ?us produc$ are frequ5tly flatt5$ or almond-%ap$ 7amygdales71 ow+ to elongation ( ! /eam-holes by movem5t ( ! lava be=e its consolidation1 ! rocks conta9+ !m are said to be amygdaloidal4 ,?is /ructure1 ?\gh em95tly *>act]i/ic ( sup]ficial lavas1 is n always by itself suffici5t to di/+ui% !m f ! intrusive rocks4 ,examples w be giv5 9 lat] *apt]s :]e dykes1 sills & o!r masses ( inject$ igne\s mat]ial are conspicu\sly cellul> 9 "s p>ts4 ,b1 9 su* cases1 ! cavities are g5]ally comp>atively small1 usually sph]ical or approximately s1 tol]ably uni=m 9 size & di/ribution1 &1 especially :5 !y occur 9 dykes1 di/ribut$ m p>ticul>ly along c]ta9 l9es or b&s1 sometimes ) consid]able regul>ity 7see ,figs4 #ij1 #ia1 & #bcf74 ,among ! sup]ficial lavas1 h[ev]1 su* regul>ity is r>ely to be se54 ,n[ & !n1 inde$1 a lava1 :i* is n on ! :ole cellul>1 may be f\nd to h r[s ( vesicles arrang$ p>allel to its "u or upp] surface1 or x may h acquir$ a peculi> b&$ /ructure f ! arrangem5t ( its vesicles 9 p>allel lay]s along ! direction ( fl[4 ,! la/-nam$ peculi>ity is widely di/ribut$ among ! ,t]ti>y lavas ( ,nor?-,we/]n ,europe1 & gives to _! wea!r$ surfaces a deceptive resemblance to tuffs or o!r /ratifi$ rocks 7see ,figs4 #bfj1 #caj & #caa74 ,x w be m p>ticul>ly ref]r$ to a few pages fur!r on4 ,9 g5]al1 h[ev]1 we may say t ! /eam-cavities ( lavas are q irregul> 9 size1 %ape & di/ribution1 sometimes increas+ to su* relative proportions z to occupy mo/ ( ! bulk ( ! rock1 & 9 o!r places disappe>+1 s z to leave ! lava tol]ably compact4 ,:5 a lava pres5ts an irregul>ly vesicul> "*1 l t ( ! slags ( an iron-furnace1 x is said to be slaggy4 ,:5 its upp] surface is rugg$ & full ( /eam-vesicles ( all sizes up to l>ge cav]n\s spaces1 x is said to be scoriace\s1 & fragm5ts ( su* a rock eject$ f a volcanic v5t are spok5 ( z scori4 ,att5tion to ! flatt5+ ( ! /eam-vesicles 9 cellul> lavas1 :i* has j be5 allud$ to z ! result ( ! onw>d movem5t ( ! /ill molt5 mass1 may %[1 by ! tr5d & gr\p+ ( ^! elongat$ cavities1 ! probable direction ( ! fl[ ( ! lava be=e x came to re/4 ,sometimes ! vesicles h be5 drawn out & flatt5$ to su* a degree t ! rock has acquir$ 9 consequ5ce a fissile /ructure4 ,9 o!r in/ances1 ! vesicles h be5 orig9ally =m$ z long p>allel & ev5 bran*+ tubes1 l ! burr[s ( ,annelids or ! bor+s ( ,t]$o4 ,"s rem>kable examples ( ?is exceptional /ructure h be5 obta9$ f ! ,t]ti>y plateau-basalts ( ! ,we/]n ,isles1 ( :i* an example is repres5t$ 9 ,fig4 #b4 ,9 _m cases ! vesicles ext5d ?r\gh ! :ole ?ickness ( a lava4 ,frequ5tly !y may be f\nd mo/ develop$ t[>ds ! top & bottom2 ! c5tral portion ( ! %eet be+ compact1 :ile ! top & bottom are rugg$1 cav]n\s or scoriace\s4 ,?\gh orig9ally ! vesicles & cav]n\s spaces1 bl[n op5 by ! expansion ( ! vap\rs dissolv$ 9 molt5 lava1 rema9$ empty on ! consolidation ( ! rock1 !y h g5]ally be5 subsequ5tly fill$ up by ! deposit )9 !m ( m9]al sub/ances c>ri$ 9 aque\s solution4 ,! m9]als ?us introduc$ are su* z might h be5 d]iv$ f ! removal ( _! con/itu5t +r$i5ts by ! solv5t action ( wat] on ! surr\nd+ rock4 ,& z amygdaloids are g5]ally m decay$ ?an ! non-vesicul> lavas1 x has be5 g5]ally believ$ t ! ab/raction ( m9]al mat]ial & its re-deposit )9 ! /eam-vesicles h be5 due to ! influ5ce ( meteoric wat]1 :i* at atmosph]ic temp]atures & pressures has sl[ly p]colat$ f ! surface ?r\gh ! cellul> lava1 long aft] ! latt] _h consolidat$ & cool$1 & ev5 aft] volcanic en]gy at ! locality _h entirely ceas$4 ,illu/ration3 ,fig4 #b4--;,elongation & bran*+ ( /eam-vesicles 9 a lava1 ,kiln9ian1 ,isle ( ,mull1 a little less ?an natural size4 ,examples1 h[ev]1 are n[ accumulat+ :i* c]ta9ly prove t1 9 "s cases1 ! vesicles 7 fill$ up dur+ ! volcanic p]iod4 ,among ! ,t]ti>y basalt-plateaux ( ! ,inn] ,hebrides1 = in/ance1 x c be %[n t ! lavas 7 already amygdaloidal be=e ! protrusion ( ! gabbros & granophyres :i* m>k lat] /ages ( ! same cont9u\s volcanic hi/ory1 & ev5 be=e ! outp\r+ ( mu* ( ! basalt ( ^! plateaux4 ,n improbably ! m9]al secretions 7 l>gely due to ! influ5ce ( hot volcanic vap\rs dur+ ! eruption ( ! basalts4 ,?is subject w be aga9 ref]r$ to 9 ! description ( ! ,t]ti>y volcanic s]ies4 ,vesicul> /ructure is m commonly & p]fectly develop$ among ! lavas :i* are basic & int]m$iate 9 composition ?an among ^? :i* are acid4 ,:ile ! exi/5ce ( a highly vesicul> or scoriace\s /ructure may g5]ally be tak5 z pro( t ! rock display+ x fl[$ out at ! surface z a lava1 o!r evid5ce po9t+ to ! same conclusion may (t5 be ga!r$ f ! rocks ) :i* ! suppos$ lava is associat$4 ,:]e1 = example1 a scoriace\s lava is cov]$ ) /ratifi$ deposits :i* conta9 pieces ( t lava1 we may be confid5t t ! rock is an int]/ratifi$ or contemporane\s %eet4 ,x has be5 erupt$ aft] ! deposition ( ! /rata on :i* x re/s1 & be=e t ( ! /rata :i* cov] x & conta9 pieces ( x4 ,9 su* a case1 ! geological date ( ! eruption c\ld be precisely def9$4 ,illu/rations ( ?is reason+ w be giv5 9 ,*apt] iv41 & 9 ! acc\nt ( ! volcanic s]ies ( ,c>bonif]\s age 9 ,c5tral ,scotl&1 :]e a basic lava c sometimes be prov$ to be a true fl[ & n an intrusive sill by ! fact t portions ( its upp] slaggy surface are enclos$ 9 ov]ly+ s&/one1 %ale or lime/one4 #b4 ,! pres5ce ( ,,glass1 or ( "s result ( ! devitrification ( an orig9al glass1 is an indication t ! rock :i* exhibits x has once be5 9 a /ate ( fusion4 ,ev5 :]e no trace ( ! orig9al vitre\s condition may rema91 /ages 9 its devitrification1 t is1 9 its conv]sion into a /ony or li?oid condition1 may be traceable4 ,?us :at are call$ sph]ulitic & p]litic /ructures 7:i* w be imm$iately describ$71 ei!r visible to ! nak$ eye or only obs]vable ) ! aid ( ! microscope1 af=d evid5ce ( ! consolidation & conv]sion ( a glassy into a li?oid sub/ance4 ,/rik+ evid5ce ( ! =m] glassy1 & !re=e molt51 condition ( _m rocks n[ li?oid is to be ga9$ by ! exam9ation ( ?9 slices ( !m "u ! microscope4 ,n only are ve/iges ( ! orig9al glass recognizable1 b ! :ole progress ( devitrification may be foll[$ into a cry/all9e /ructure4 ,! primitive cry/allites or microlites ( diff]5t m9]als may be se5 to h gr\p$ !mselves toge!r into m or less p]fect cry/als1 :ile scatt]$ cry/als ( e>li] consolidation h be5 p>tially dissolv$ 9 & corrod$ by ! molt5 glass4 ,^! & o!r *>act]i/ics ( once fus$ rocks h to a consid]able ext5t be5 imitat$ artificially by ,,mm4 ,f\qu & ,mi*el ,lvy1 :o h fus$ ! con/itu5t m9]als 9 ! prop] proportions4 ,s9ce traces ( glass or ( its repres5tative devitrifi$ /ructures are s abundantly discov]able 9 lavas1 we may inf] ! orig9al condition ( mo/ lavas to h be5 vitre\s4 ,:]e1 = in/ance1 ! out] selvages ( a basic dyke or sill are coat$ ) a lay] ( black glass :i* rapidly passes into a f9e-gra9$ cry/all9e basalt1 & !n aga9 into a m l>gely cry/all9e or dol]itic texture 9 ! c5tre1 !re c be no hesitation 9 believ+ t glassy coat+ to be due to ! sudd5 *ill+ & consolidation ( ! lava inject$ betwe5 ! cool rocks t enclose x4 ,! "p t solidifi$ fir/ may be reg>d$ z probably repres5t+ ! condition ( ! :ole body ( lava at ! "t ( intrusion4 ,! li?oid or cry/all9e portion betwe5 ! two vitre\s out] lay]s %[s ! condition :i* ! molt5 rock f9ally assum$ z x cool$ m sl[ly4 ,"s lavas1 su* z obsidians & pit*/ones1 h consolidat$ 9 ! glassy =m4 ,m usually1 h[ev]1 a li?oid /ructure has be5 develop$1 ! orig9al glass be+ only discov]able by ! microscope1 & (t5 n ev5 by its aid4 ,two v>ieties ( devitrification may be obs]v$ among lavas1 :i*1 ?\gh n m>k$ (f f ea* o!r by any %>p l9es1 are on ! :ole di/9ctive ( ! two great gr\ps ( acid & basic rocks4 7#a7 ,among ! acid rocks1 :at is call$ ! ,felsitic type ( devitrification is *>act]i/ic4 ,?us1 obsidians pass by int]m$iate /ages f a cle> transp>5t or transluc5t glass into a dull fl9ty or horny mass4 ,:5 ?9 slices ( ^! transitional =ms are exam9$ "u ! microscope1 m9ute hairs & fibres or tri*ites1 :i* may be obs]v$ ev5 9 ! mo/ p]fectly glassy rocks1 are se5 to increase 9 numb] until !y entirely take ! place ( ! glass4 ,microlites ( def9ite m9]als may likewise be obs]v$1 toge!r ) indef9ite granules1 & ! rock f9ally becomes a rhyolite1 felsite or alli$ v>iety 7,fig4 #c74 ,illu/ration3 ,fig4 #c4--,microlites ( ! ,pit*/one ( ,arran 7magnifi$ #gj diamet]s74 ,at ! same "t x %\ld be obs]v$ t1 ev5 9 ! vitre\s condition ( a lava1 def9ite cry/als ( an e>ly consolidation 7 g5]ally already pres5t4 ,felsp>s & qu>tz1 usually 9 l>ge porphyritic =ms1 may be se5 9 ! glass1 (t5 s corrod$ z to indicate t !y 7 9 c\rse ( be+ dissolv$ 9 ! magma at ! "t ( ! cool+ & solidification ( ! mass4 ,9 obsidians & pit*/ones su* relics ( an e>li] or d]iv$ s]ies ( cry/alliz$ m9]als may (t5 be recogniz$1 :ile 9 felsites & qu>tz-porphyries !y are equally prom95t4 ,:]e l>ge disp]s$ cry/als =m a prom95t *>act]i/ic 9 a rock !y give rise to :at is t]m$ ! ,porphyritic /ructure4 ,illu/ration3 ,fig4 #d4--,p]litic /ructure 9 ,felsitic ,glass1 ,isle ( ,mull 7magnifi$74 ,illu/ration3 ,fig4 #e4--,sph]ulitic /ructure 7magnifi$74 ,accompany+ ! passage ( glass into /one1 v>i\s /ructures make _! appe>ance1 sometimes di/9ctly visible to ! nak$ eye1 at o!r times only p]ceptible ) ! aid ( ! microscope4 ,"o ( ^! /ructures1 kn[n z ,p]litic 7,fig4 #d71 consi/s 9 ! =mation ( m9ute curv$ or /raight cracks betwe5 :i* ! vitre\s or felsitic sub/ance1 dur+ its contraction 9 cool+1 assum$ a f9ely globul> =m4 ,ano!r /ructure1 t]m$ ,sph]ulitic 7,fig4 #e71 %[s ! developm5t ( globules or sph]ules :i* may range f gra9s ( microscopic m9ut5ess up to balls two in*es or m 9 diamet]4 ,^! n infrequ5tly pres5t a well-=m$ int]nal fibr\s radiation1 :i* gives a black cross betwe5 cross$ ,nicol prisms4 ,sph]ulites are m especially develop$ along ! m>g9s ( intrusive rocks1 & may be f\nd 9 dykes1 sills & bosses 7see ,figs4 #cge & #cgg74 ,:]e ! inject$ mass is n ?ick x may be sph]ulitic to ! v c5tre1 z c be se5 among ! felsitic & granophyric dykes ( ,skye4 ,"s felsitic lavas possess a peculi> nodul> /ructure1 :i* 0 develop$ dur+ ! process ( consolidation4 ,s m>k$ does ?is arrangem5t sometimes become t ! rocks :i* display x h actually be5 mi/ak5 = conglom]ates4 ,x is well exhibit$ among ! ,l[] ,silurian lavas ( ,sn[don1 ! ,upp] ,silurian lavas ( ,d+le1 & ! ,l[] ,old ,r$ ,s&/one lavas ne> ,kill>ney4 ,illu/ration3 ,fig4 #f4--,micropegmatitic or ,granophyric /ructure 9 ,granophyre1 ,mull 7magnifi$74 ,illu/ration3 ,fig4 #g4--,ophitic /ructure 9 ,dol]ite1 ,gortacloghan1 ,co4 ,d]ry 7magnifi$74 ,a m>k$ /ructure among "s intrusive rocks1 especially ( an acid composition1 is t call$ ,micropegmatitic or ,granophyric4 ,x consi/s 9 a m9ute int]gr[? ( two compon5t m9]als1 especially qu>tz & felsp>1 & is m especially *>act]i/ic ( c]ta9 granitic or granitoid rocks :i* h consolidat$ at "s di/ance f ! surface & occur z bosses1 sills & dykes4 ,x is also met )1 h[ev]1 9 "s basic sills4 ,examples ( all ^! & o!r /ructures w occur 9 ! c\rse ( ! foll[+ description ( ,briti% volcanic rocks4 7#b7 ,! second type ( devitrification1 conspicu\s 9 rocks ( m basic composition1 is m>k$ by a m complete developm5t ( cry/allization4 ,among basic1 z among acid rocks1 !re are pro(s ( ! consolidation ( def9ite m9]als at m ?an "o p]iod4 ,:]e ! molt5 mat]ial has sudd5ly cool$ into a black glass1 porphyritic felsp>s or o!r m9]als are (t5 to be se5 :i* 7 already float+ 9 ! magma 9 its molt5 condition4 ,dur+ devitrification1 h[ev]1 o!r felsp>s ( a lat] p]iod ( g5]ation made _! appe>ance1 b !y are g5]ally di/+ui%able f _! pr$ecessors4 ,probably mo/ basic & int]m$iate rocks1 :5 p\r$ out at ! surface z lavas1 7 no long] m]e vitre\s mat]ial1 b _h already advanc$ to v>i\s /ages ( progress t[>ds a /ony condition4 ,^! /ages are /ill to "s ext5t traceable by ! aid ( ! microscope4 ,microlites ( ! compon5t m9]als are fir/ develop$1 :i*1 if ! process ( aggregation is n arre/$1 build up m or less p]fect cry/als or cry/all9e gra9s ( ! m9]als4 ,ev5tually ! glass may be s completely devitrifi$ by ! developm5t ( its con/itu5t m9]als z to be :olly us$ up1 ! rock !n becom+ entirely cry/all9e1 or to survive only 9 scanty int]/itial spaces4 ,9 ! family ( ! basalts & dol]ites ! gradual transition f a true glass into a holocry/all9e comp\nd may be foll[$ ) admirable cle>ness4 ,! compon5t m9]als h sometimes cry/alliz$ 9 _! own di/9ct cry/allographic =ms 7idiomorphic72 9 o!r cases1 ?\gh ?or\ghly cry/all9e1 !y h assum$ ext]nally diff]5t irregul> %apes1 fitt+ into ea* o!r )\t _! ,prop] geometric b\nd>ies 7allotriomorphic74 ,a specially *>act]i/ic feature ( _m basic rocks is ! pres5ce ( :at is t]m$ an ,ophitic /ructure 7,fig4 #g74 ,?us ! compon5t cry/als ( pyrox5e occur z l>ge plates sep>at$ & p5etrat$ by small ne$les & cry/als ( felsp>4 ,! portions ( pyrox5e1 divid$ by ! enclos$ felsp>1 are se5 "u ! microscope to be 9 optical cont9uity1 & to h cry/alliz$ r\nd ! already =m$ felsp>4 ,?is /ructure is nev] f\nd 9 metamorphic cry/all9e rocks4 ,x has be5 reproduc$ artificially f fusion by ,messrs4 ,f\qu & ,mi*el ,lvy4 ,! "n ,v>iolitic is appli$ to ano!r /ructure ( basic rocks 7,fig4 #h71 9 :i*1 especially t[>ds ! m>g9 ( eruptive masses1 abundant sph]oidal aggregates h be5 develop$ f ! size ( a millet-se$ to t ( a walnut1 imb$d$ 9 a f9e-gra9$ or compact gre5i% matrix into :i* ! k]nels seem to %ade (f4 ,^! k]nels consi/ ( silicates arrang$ ei!r radially or 9 conc5tric zones4 #c4 ,fl[-/ructure is an arrangem5t ( ! cry/als1 vesicles1 sph]ulites1 or devitrification-/reaks 9 b&s or l9es1 :i* sweep r\nd any enclos$ object1 su* z a porphyritic cry/al or deta*$ sph]ulite1 & repres5t ! curv+ fl[ ( a mobile or visc\s mass4 ,admirable examples ( ?is /ructure may (t5 be obs]v$ 9 old lavas1 z well z 9 dykes & sills1 ! /reaky l9es ( fl[ be+ m>k$ z di/9ctly z ! l9es ( foam t curve r\nd ! b\ld]s project+ f ! surface ( a m\nta9-brook4 ,fl[-/ructure is mo/ p]fectly develop$ among ! obsidians1 rhyolites1 felsites & o!r acid rocks1 ( :i* x may be said to be a frequ5tly conspicu\s "* 7,fig4 #i74 ,9 ^! rocks x is reveal$ by ! p>allel arrangem5t ( ! m9ute hair-l bodies & cry/als1 or by alt]nate lay]s ( glassy & li?oid mat]ial4 ,! /reaky l9es ?us develop$ are sometimes almo/ z ?9 & p>allel z ! leaves ( a book4 ,b !y g5]ally %[ int]ruptions & curvatures1 & may be se5 to b5d r\nd l>g] enclos$ cry/als1 or to ga!r into eddy-l curves1 9 su* a mann] z vividly to portray ! fl[ ( a visc\s sub/ance4 ,^! l9es repres5t on a m9ute scale ! same fl[-/ructure :i* may be trac$ 9 l>ge %eets among ! lavas4 ,! porphyritic cry/als & ! sph]ulites are also drawn out 9 r[s 9 ! same g5]al direction4 ,sometimes1 inde$1 ! sph]ulites h be5 s symmetrically gr\p$ 9 p>allel r[s t !y appe> z rod-l aggregates :i* ext5d along ! m>g9 ( a dyke4 ,illu/ration3 ,fig4 #h4--,v>iolitic or ,orbicul> /ructure1 ,napoleonite1 ,corsica 7nat4 size74 ,among lavas ( m basic composition fl[-/ructure is n s (t5 well display$4 ,x mo/ frequ5tly %[s itself by ! ori5tation ( porphyritic felsp>s or ( l9es ( /eam-vesicles4 ,occasionally1 h[ev]1 %eets ( basalt may be f\nd 9 :i* a di/9ct /reak9ess has be5 develop$ ow+ to v>iations 9 ! diff]5tiation ( ! orig9al molt5 magma4 ,a rem>kable & widespread occurr5ce ( su* a /ructure is met ) among ! ,t]ti>y basalt-plateaux ( ! ,inn] ,hebrides & ! ,f>oe ,isl&s4 ,9 ! l[] p>ts ( ^! ?ick accumulations ( successive lava-%eets1 a b&$ "* is s m>k$ z to give ! rocks ! aspect ( truly /ratifi$ deposits4 ,! obs]v]1 inde$1 c h>dly undeceive himself z to _! real nature until he exam9es !m closely4 ,z a full description ( ?is /ructure w be giv5 9 a lat] *apt]1 x may suffice to /ate "h t ! b&+ arises f two causes4 ,9 "s cellul> lavas1 ! vesicles are arrang$ 9 lay]s :i* lie p>allel ) ! upp] & "u surfaces ( ! %eets4 ,^! lay]s ei!r project z ribs or rec$e into depressions along ! outcrop1 & ?us imp>t a di/9ctly /ratifi$ aspect to ! rock4 ,m frequ5tly1 h[ev]1 ! b&$ /ructure is produc$ by ! alt]nation ( diff]5t v>ieties ( texture1 & ev5 ( composition1 9 ! same %eet ( basalt4 ,l5ticul> seams ( oliv9e-basalt may be f\nd int]calat$ 9 a m l>gely cry/all9e dol]ite4 ,^! diff]5ces appe> to po9t to consid]able v>iations 9 ! con/itution ( ! magma f :i* ! lavas issu$--v>iations :i* already exi/$ be=e ! dis*>ge ( ^! lavas1 & :i* %[$ !mselves 9 ! successive outfl[ ( basaltic & dol]itic mat]ial dur+ ! eruption ( :at 0 really1 z reg>ds its appe>ance at ! surface1 "o cont9u\s /ream ( molt5 rock4 ,x is impossible to acc\nt = su* v>iations 9 ! same %eet ( lava by any process ( diff]5tiation 9 ! melt$ mat]ial dur+ its outfl[ & cool+4 ,analog\s v>iations occur among ! basic sills & bosses ( ! ,t]ti>y volcanic s]ies ( ,brita94 ,^!1 z w be m fully discuss$ 9 lat] *apt]s1 indicate a consid]able am\nt ( het]og5eity 9 ! deep-seat$ magma f :i* ! intrusive %eets & bosses 7 suppli$ 7see vol4 ii4 pp4 #cbi1 #cdb74 ,illu/ration3 ,fig4 #i4--;,fl[-/ructure 9 ,rhyolite1 ,antrim1 slightly r$uc$4 ,x is a common error to assume t fl[-/ructure is a di/9ctive "* ( lavas t h fl[$ out at ! surface4 ,9 reality "s ( ! mo/ p]fect examples ( ! /ructure occur 9 dykes & sills1 bo? among acid & basic rocks4 ,innum]able in/ances might be quot$ f ! ,briti% ,isles 9 support ( ?is /atem5t4 ,al?\gh1 9 ! va/ majority ( cases1 ! pres5ce ( fl[-/ructure may be confid5tly assum$ to indicate a =m] molt5 condition ( ! rock 9 :i* x occurs1 x is n an absolutely reliable te/ = an igne\s rock4 ,exp]im5t has %[n t "u enorm\s pressure ev5 solid metals may be made to fl[ into cavities prep>$ = _! reception4 ,"u ! va/ compression to :i* ! e>?'s cru/ is subject$ dur+ t]re/rial contraction1 ! mo/ obdurate rocks are cru%$ into fragm5ts v>y+ f l>ge blocks to ! f9e/ p[d]4 ,?is comm9ut$ mat]ial is driv5 along 9 ! direction ( ?ru/1 & :5 x comes to re/ pres5ts a /reak9ess1 ) curv+ l9es ( fl[ r\nd ! l>g] fragm5ts1 closely simulat+ ! /ructure ( _m rhyolites & obsidians4 ,x is only by att5tion to ! local surr\nd+s t su* deceptive resemblances c be assign$ to _! true cause4 ,illu/ration3 ,fig4 #aj4--,lumpy1 irregul> tra*ytic ,lava-/reams 7,c>bonif]\s71 ,ea/ ,l9ton1 ,hadd+ton%ire4 #d4 ,! ,,disposition ,,( ,,lavas ,,9 ,,%eets ,,or ,,b$s is ! result ( successive outfl[s ( molt5 rock4 ,su* %eets may range f only a y>d or two to sev]al hundr$ feet 9 ?ickness4 ,z a rule1 ?\gh ) _m exceptions1 ! basic lavas1 su* z ! basalts1 appe> 9 ?9n] b$s ?an ! acid =ms4 ,?is diff]5ce is well br\ght out if we comp>e1 = in/ance1 ! massive rhyolites or felsites ( ,nor? ,wales ) ! ?9 %eets ( basalt 9 ,antrim & ! ,inn] ,hebrides4 ,! regul>ity ( ! b$d$ "* is likewise m def9ite among ! basic ?an among ! acid rocks1 & ?is contra/ also is /rik+ly illu/rat$ by ! two s]ies ( rocks j ref]r$ to4 ,! rhyolites & felsites1 sometimes also ! tra*ytes & &esites1 assume lumpy1 irregul> =ms1 & "s little c>e may be requir$ to trace _! upp] & "u surfaces1 & to asc]ta9 t !y really d =m cont9u\s %eets1 ?\gh v>y+ mu* 9 ?ickness f place to place 7,fig4 #aj74 ,l mod]n acid lavas1 !y seem to h fl[$ out 9 a pa/y condition1 & to h be5 heap$ up r\nd ! v5ts 9 ! =m ( domes1 or ) an irregul> hummocky or m\nd$ surface4 ,! basalts1 & dol]ites1 & sometimes ! &esites1 h issu$ 9 a m fluid condition1 & h spread out 9 %eets ( m uni=m ?ickness1 z may be in/ructively se5 9 ! sea-cliffs ( ,antrim1 ,mull1 ,skye1 & ! ,f>oe ,isl&s1 :]e ! horizontal or g5tly-incl9$ fl[s ( basalt lie ^u ea* o!r 9 ev5 p>allel b$s traceable = consid]able di/ances along ! face ( ! precipices 7,figs4 #aa1 #bfe1 & #bhf74 ,! &esites ( ! ,old ,r$ ,s&/one 7,figs4 #ii1 #ajj7 & ,c>bonif]\s s]ies 7,figs4 #ajg1 #ajh1 #aaa1 #aab1 #aac1 #abc7 9 ,scotl& likewise =m t]rac$ hills4 ,! l5g? ( a lava-/ream may v>y )9 wide limits4 ,sometimes an outfl[ ( lava has n rea*$ ! base ( ! cone f ! side ( :i* x issu$1 l ! obsidian /ream on ! flanks ( ! little cone ( ! isl& ( ,volcano4 ,9 o!r cases1 ! molt5 rock has fl[$ = =ty or fifty miles1 l ! copi\s ,icel&ic lava-floods ( #aghc4 ,9 ! basalt-plateaux ( ! ,inn] ,hebrides a s+le %eet may sometimes be trac$ = sev]al miles4 ,illu/ration3 ,fig4 #aa4--,view at ! entrance ( ! ,sv9(jord1 ,f>oe ,isl&s1 illu/rat+ ! t]rac$ =ms assum$ by basic lavas4 ,! isl& on ! left is ,bor1 t 9 ! c5tre ,vid]1 & t on ! "r ,sv94 ,"s lavas1 m especially among ! basic s]ies1 assume 9 cool+ a ,column> /ructure1 ( :i* two types may be notic$4 ,9 "o ( ^! ! columns pass ) regul>ity & p>allelism f ! top to ! bottom ( a b$ 7,figs4 #aga1 #bbe74 ,! basalt 9 :i* ,f+al's ,cave1 9 ! isle ( ,/affa1 has be5 holl[$ out may be tak5 z a *>act]i/ic example 7,fig4 #bff;a74 ,n infrequ5tly ! columns are curv$1 z at ! well-kn[n ,clam-%ell ,cave ( ,/affa4 ,9 ! o!r type1 ! columns or prisms are n p]si/5t1 b die out into ea* o!r & h a wavy1 irregul> %ape1 some:at l prisms ( />*4 ,^! two types may occur 9 successive %eets ( basalt1 or may ev5 pass into ea* o!r4 ,at ,/affa ! regul>ly column> b$ is imm$iately ov]la9 ) "o ( ! />*-l "*4 ,! column> /ructure 9 ei!r case is a contraction ph5om5on1 produc$ dur+ ! cool+ & %r9k+ ( ! lava4 ,b x is difficult to say :at special conditions 9 ! lava 7 requir$ = its production1 or :y x %\ld sometimes h assum$ ! regul>1 at o!rs ! irregul> =m4 ,x may be f\nd n only 9 sup]ficial lavas b 9 equal p]fection 9 "s dykes & intrusive sills or injections1 z among ! ,t]ti>y volcanic rocks ( ! isl& ( ,canna 7,figs4 #cjg & #cjh74 ,! precipitation ( a lava-/ream into a lake or ! sea may cause ! out] cru/ ( ! rock to break up ) viol5ce1 s t ! /ill molt5 mat]ial inside may ru% into ! wat]4 ,"s basic lavas on fl[+ into wat] or into a wat]y silt h assum$ a rem>kable sph]oidal sack-l or pill[-l /ructure1 ! sph]oids be+ sometimes press$ into %apes l piles ( sacks4 ,a good in/ance ( ?is /ructure occurs 9 a basalt at ,acica/ello 9 ,sicily4#a ,a simil> appe>ance w be describ$ 9 a lat] *apt] z peculi>ly *>act]i/ic ( c]ta9 ,l[] ,silurian lavas associat$ ) radiol>ian *]ts 9 ,brita9 & 9 o!r c\ntries 7,fig4 #ab74 ,footnote #a3 ,see ,pr(4 ,g4 ,platania 9 ,dr4 ,john/on-,lavis' ,s\? ,italian ,volcanoes1 ,naples 7#ahia71 p4 #da & plate xii4 ,illu/ration3 ,fig4 #ab4--,sack-l or pill[-=m /ructure ( basic lavas 7,l[] ,silurian71 ,b5nan ,head1 ,ballantrae1 ,ayr%ire4 ,x probably seldom happ5s t a solit>y %eet ( lava occurs among non-volcanic s$im5t>y /rata1 ) no o!r indication ar\nd x ( =m] volcanic activity4 ,su* an isolat$ record does n seem to h be5 met ) 9 ! rem>kably ample volcanic regi/] ( ! ,briti% ,isles4 ,! outp\r+ ( molt5 rock has g5]ally be5 accompani$ ) ! ejection ( fragm5t>y mat]ials4 ,h5ce among ! memorials ( volcanic eruptions1 :ile int]calat$ lavas are g5]ally associat$ ) %eets ( tuff1 b&s ( tuff may n infrequ5tly be enc\nt]$ 9 a s$im5t>y s]ies )\t any lava4 ,in/ances 9 illu/ration ( ^! /atem5ts may be cull$ f ! ,briti% ,palozoic =mations back ev5 into ! ,cambrian sy/em4 ,a *>act]i/ic feature ( "s int]e/ 9 connection ) ! fl[ ( lava is ! effect produc$ by x on ! und]ly+ rocks4 ,if ^! are n firmly compact$ !y may be pl\gh$ up or ev5 dislocat$4 ,?us ! tuffs ( ! ,velay h sometimes be5 plicat$1 inv]t$1 & fractur$ by ! movem5t ( a fl[+ curr5t ( basalt4#b ,! great heat ( ! lava has frequ5tly induc$ consid]able alt]ation ^u ! und]ly+ rocks4 ,induration is ! mo/ common result1 (t5 accompani$ ) a r$d5+ ( ! alt]$ sub/ance4 ,occasionally a beautifully prismatic /ructure has be5 develop$ 9 ! s(t mat]ial imm$iately b5ea? a basalt1 z 9 f]rug9\s clay ne> ! village ( ,esplot 9 ! ,velay1 9 :i* ! close-set columns are #ej c5timetres long & #d to #e c5timetres 9 diamet]4#c ,*anges ( ?is nature1 h[ev]1 are m frequ5t among sills ?an among sup]ficial lavas4 ,_m examples ( !m may be ga!r$ f ! ,scotti% ,c>bonif]\s di/ricts4 ,footnote #b3 ,m4 ,b\le1 ,bull4 ,c>t4 ,gol4 ,france1 ,no4 #bh1 tom4 iv4 7#ahib71 p4 #bce4 ,footnote #c3 ,m4 ,b\le4 ,op4 cit4 p4 #bcd4 ,v>iations ( /ructure 9 s+le lava-%eets4--,f :at has be5 said above 9 reg>d to c]ta9 k9ds ( fl[-/ructure among basic rocks1 x w be evid5t t "s consid]able range ( *emical1 b m p>ticul>ly ( m9]alogical1 composition may be sometimes obs]v$ ev5 )9 ! same %eet ( lava4 ,su* diff]5ces1 x is true1 are m frequ5t among intrusive rocks1 especially ?ick sills & l>ge bosses4 ,b !y h be5 met ) 9 s _m in/ances among sup]ficial lavas z to %[ t !y are ! results ( "s g5]al law1 :i* probably has a wide application among ! surface-products ( volcanic action4 ,scrope express$ ! op9ion t 9 ! focus ( a volcano !re may be a k9d ( filtration ( ! con/itu5ts ( a molt5 mass1 ! heavi] m9]als s9k+ ?r\gh ! light]1 s t ! upp] portions ( ! mass w become m felspa?ic & ! l[] p>ts m augitic & f]rug9\s4#d ,footnote #d3 ,volcanoes1 p4 #abe4 ,leopold von ,bu* f\nd t 9 "s ( ! highly glassy lavas ( ! ,can>y ,isl&s ! felsp> increases t[>ds ! bottom ( ! mass1 becom+ s abundant z almo/ to exclude ! matrix1 & giv+ rise to a comp\nd t might be mi/ak5 = a primitive rock4#e ,footnote #e3 ,description ,physique des ,isles ,can>ies 7#ahcf71 p4 #aij4 ,d>w9 obs]v$ t 9 a grey basalt fill+ up ! holl[ ( an old crat] 9 ,james ,isl&1 "o ( ! ,galapagos gr\p1 ! felsp> cry/als became mu* m abundant 9 ! l[] scoriace\s "p1 & he discuss$ ! "q ( ! desc5t ( cry/als by virtue ( _! specific gravity ?r\gh a /ill molt5 lava4#f ,footnote #f3 ,geological ,obs]vations on ,volcanic ,isl&s 7#ahdd71 p4 #aag4 ,mr4 ,cl>5ce ,k+ dur+ a visit to ,hawaii f\nd t 9 e case :]e he broke newly-congeal$ /reamlets ( lava1 ! bottom ( ! fl[ 0 ?ickly cr[d$ ) tricl9ic felsp>s & augites1 :ile ! :ole upp] "p ( ! /ream 0 ( ne>ly pure isotropic & acid glass4#g ,?is subject w be aga9 ref]r$ to :5 we come to discuss ! *>act]s ( intrusive sills & bosses1 = x is among !m t ! mo/ m>k$ petrographical v>iations may be obs]v$4 ,examples w be cit$ bo? f ! intrusive & extrusive volcanic gr\ps ( ,brita94 ,footnote #g3 ,u4,s4 ,geol4 ,exploration ( ! ,=tie? ,p>allel1 vol4 i4 7#ahgh71 p4 #gaf4 ,volcanic cycles4--,closely relat$ to ! problem ( ! range ( /ructure & composition 9 a s+le mass ( lava is ano!r problem pres5t$ by ! rem>kable sequ5ce ( diff]5t types ( lava :i* are erupt$ )9 a giv5 di/rict dur+ a s+le volcanic p]iod4 ,ne>ly ?irty ye>s ago ,b>on von ,ri*?(5 drew att5tion to ! sequ5ce ( volcanic mat]ials erupt$ )9 ! same geographical area4 ,he %[$1 m especially f obs]vations 9 ,we/]n ,am]ica1 t a def9ite ord] ( appe>ance 9 ! successive species ( lava c\ld be e/abli%$1 ! e>lie/ eruptions consi/+ ( mat]ials ( an int]m$iate or av]age composition1 & ^? ( subsequ5t outfl[s becom+ on ! :ole progressively m acid1 b f9i%+ by an abrupt transition to a basic type4 ,8 sequ5ce 0 z foll[s3 #a4 ,propylite2 #b4 ,&esite2 #c4 ,tra*yte2 #d4 ,rhyolite2 #e4 ,basalt4#h ,?is g5]alisation has be5 f\nd to hold good ov] wide regions ( ! ,old ,_w z well z ! ,new4 ,x is n1 h[ev]1 ( univ]sal application4#i ,examples are n uncommon ( an actual alt]nation ( acid & basic lavas f ! same1 or at lea/ f adjac5t v5ts4 ,su* an alt]nation occurs among ! ,t]ti>y eruptions ( ,c5tral ,france & among ^? ( ,old ,r$ ,s&/one age 9 ,scotl&4 ,footnote #h3 ,trans4 ,acad4 ,cali=nia1 #ahfh4 ,pr(4 ,idd+s' ,j\rn4 ,geol41 vol4 i4 7#ahic71 p4 #fjf4 ,footnote #i3 ,see ,pr(4 ,brgg]1 ,die ,eruptivge/e9e des ,kri/ianiagebietes1 "p ii4 7#ahie71 p4 #age2 ,zeits*4 ,kry/4 und ,m9]al1 vol4 xvi4 7#ahij7 p4 #hc4 ,?is au?or w\ld1 f ?is po9t ( view1 draw a di/9ction betwe5 rocks :i* h consolidat$ deep )9 ! e>? & ^? :i* h fl[$ out at ! surface1 s9ce he ?9ks t we are n ju/ifi$ 9 apply+ our exp]i5ce ( ! ord] ( sequ5ce 9 ! "o s]ies to ! o!r4 ,yet !re c be no d\bt t 9 _m old volcanic di/ricts ! masses t may be presum$ to h consolidat$ at a great dep? h be5 9 unbrok5 connection ) masses t rea*$ ! surface4 ,^! latt]1 z ,pr(4 ,idd+s has urg$1 furni% a mu* l>g] body ( evid5ce ?an ! intrusive %eets & bosses4 ,! range ( v>iation 9 ! nature ( ! eruptive rocks dur+ ! :ole ( a volcanic p]iod 9 any di/rict may be t]m$ a volcanic cycle4 ,9 ,brita91 :]e ! records ( _m volcanic p]iods h be5 pres]v$1 a numb] ( su* cycles may be /udi$4 ,9 ?is way ! evolution ( ! subt]ranean magma dur+ "o geological age may be comp>$ ) t ( ano!r4 ,x w be "o ( ! objects ( ! foll[+ *apt]s to trace out ?is evolution 9 ea* p]iod :]e ! requisite mat]ials = ! purpose are available4 ,we %all f9d t back to ,ar*an "t a numb] ( di/9ct cycles may be obs]v$1 diff]+ 9 _m respects f ea* o!r1 b agree+ 9 ! g5]al ord] ( developm5t ( ! successive eruptions4 ,leav+ ^! ,briti% examples = future consid]ation1 x may be useful to cite "h a few f ! l>ge s]ies n[ collect$ f ! ,european cont95t & ,nor? ,am]ica4#aj ,footnote #aj3 ,pr(4 ,m4 ,b]tr& 9 a sugge/ive pap] publi%$ 9 #ahhh dealt ) ! g5]al ord] ( appe>ance ( eruptive rocks 9 diff]5t prov9ces ( ,europe4 ,b ! mat]ials !n at 8 comm& probably did n w>rant him 9 (f]+ m ?an a sket* ( ! subject1 ,bull4 ,soc4 ,geol41 ,france1 xvi4 p4 #egc4 ,9 ! same volume !re is a pap] by ,m4 ,le ,v]ri]1 :o ann\nces 8 op9ion t ! eruption ( ! basic rocks takes place 9 times ( t]re/rial calm1 :ile t ( ! acid rocks occurs 9 p]iods ( great di/urbance1 op4 cit4 p4 #dih4 ,comp>e also ,pr(4 ,brgg]1 ,die ,eruptivge/e9e des ,kri/ianiagebietes1 ii4 p4 #afi4 ,among ! old] rocks ( ! ,european cont95t1 ,pr(4 ,brgg] has %[n t 9 ! ,*ri/iania di/rict ! eruptive rocks :i* trav]se ! ,cambrian & ,silurian =mations began ) ! outbur/ ( basic mat]ial su* z melaphyre1 augite-porphyrite1 & gabbro-diabase1 hav+ f ab\t #dd to ab\t #eb p] c5t ( silica4 ,^! 7 foll[$ by rocks ) a silica-p]c5tage rang+ f ab\t #ej to #fa1 includ+ "s *>act]i/ic ,norwegian rocks1 l ! rhomb5-porphyry4 ,! acidity cont9u$ to increase1 = 9 ! next s]ies ( eruptions ! silica-p]c5tage rose to betwe5 #fj & #fg1 ! *>act]i/ic rock be+ a qu>tz-sy5ite4 ,!n came deep-seat$ protrusions ( highly acid rocks1 v>ieties ( granite1 conta9+ f #fh to #ge p] c5t ( silica4 ,! y\nge/ eruptive masses 9 ! di/rict %[ a complete *ange ( "*4 ,!y are basic dykes 7prot]obase1 diabase1 etc474#aa ,footnote #aa3 ,eruptivge/4 ,kri/ianiageb41 #ahie4 ,! same au?or in/itutes a comp>ison betwe5 ! po/-,silurian eruptive s]ies ( ,*ri/iania & t ( ! ,triassic sy/em 9 ! ,tyrol1 & believes t ! two cycles closely agree4#ab ,footnote #ab3 ,op4 cit4 ,he supposes 9 ea* case ! pre-exi/5ce ( a p>5t magma f :i* ! eruptive s]ies />t$ & :i* _h a silica-p]c5tage ( ab\t #fd or #fe4 ,9 ?is difficult subject x is ( ! utmo/ importance to accumulate fact be=e proce$+ to speculation4 ,dur+ ,t]ti>y "t 9 ,c5tral ,france m ?an "o cycle may be made out 9 di/9ct di/ricts4 ,?us 9 ! ,velay1 dur+ ! ,mioc5e ,p]iod1 volcanic activity began ) ! outp\r+ ( basalts1 foll[$ successively by tra*ytes1 labradorites & augitic &esites1 phonolites & basalts4 ,! ,plioc5e eruptions %[$ a rev]sion to ! int]m$iate types ( augitic &esites & tra*ytes1 foll[$ by abundant basalts1 :i* cont9u$ to be p\r$ =? 9 ,plei/oc5e "t4#ac ,footnote #ac3 ,m4 ,b\le1 ,description ,gologique du ,velay1 ,bull4 ,c>te4 ,gol4 ,france1 #ahib4 ,?is au?or draws special att5tion to ! evid5ce = ! alt]nation ( basic & m acid mat]ial 9 ! ,t]ti>y eruptions ( ,c5tral ,france4 ,fur!r nor?1 9 ,auv]gne1 :]e ! eruptions come d[n to a lat] p]iod1 ! volcanic sequ5ce appe>s to h be5 fir/ a some:at acid gr\p ( lavas 7tra*ytes or domites71 foll[$ by a s]ies ( basalts1 !n by &esites & labradorites1 ! late/ outfl[s aga9 consi/+ ( basalts4#ad ,footnote #ad3 ,m4 ,mi*el ,lvy1 ,bull4 ,soc4 ,gol4 ,france1 #ahij1 p4 #gjd4 ,n less /rik+ is ! succession ( lavas 9 ! ,yell[/one region1 z describ$ by ,mr4 ,idd+s4 ,! fir/ eruptions consi/$ ( &esites4 ,^! 7 foll[$ by abundant dis*>ges ( basalt1 succe$$ by lat] outfl[s ( &esite1 & ( basalt l t previ\sly erupt$4 ,aft] a p]iod ( ext5sive erosion1 occupy+ a prolong$ int]val ( "t1 volcanic en]gy 0 r5ew$ by ! eruption ( a va/ flood ( rhyolite1 aft] :i* came a feebl] outfl[ ( basalt t br\ght ! cycle to a close1 ?\gh geys]s & fum>oles %[ t ! volcanic fires are n yet entirely ext+ui%$ bel[4#ae ,footnote #ae3 ,j\rnal ( ,geology1 ,*icago1 i4 7#ahic7 p4 #fjf4 ,see also ?is au?or's excell5t monograph on ,electric ,peak & ,sepul*re ,m\nta91 #ab? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey 7#ahij-ia71 & ,mr4 ,h4 ,w4 ,turn] on ,! ,succession ( ,t]ti>y ,volcanic ,rocks 9 ! ,si]ra ,nevada ( ,nor? ,am]ica1 #ad? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey 7#ahib-ic71 p4 #dic4 ,b n only is !re evid5ce ( a rem>kable evolution or succession or erupt$ mat]ial )9 ! volcanic cycle ( a s+le geological p]iod4 ,"o ( ! objects ( ! pres5t "w is to br+ =w>d pro(s t su* cycles h succe$$ ea* o!r aga9 & aga91 at widely sep>at$ int]vals1 )9 ! same region4 ,aft] ! completion ( a cycle & ! relapse ( volcanic en]gy into repose1 !re has be5 a r5ewal ( ! previ\s condition ( ! subt]ranean magma1 giv+ rise ultimately to a simil> succession ( erupt$ mat]ials4 ,if we are at a loss to acc\nt = ! *anges 9 ! sequ5ce ( lavas dur+ a s+le volcanic cycle1 our difficulties are increas$ :5 we f9d t 9 "s way ! magma is re/or$ ea* "t to some:at ! same initial condition4 ,analogies may be trac$ betwe5 ! diff]5tiation :i* has tak5 place )9 a plutonic intrusive boss or sill & ! sequ5ce ( lavas 9 volcanic cycles4 ,x c be %[n t ?\gh ! orig9al magma t suppli$ ! intrusive mass may be suppos$ to h _h a fairly uni=m composition deep d[n 9 its res]voir1 diff]5tiation set 9 long be=e ! intrusive mass consolidat$1 ! m basic con/itu5ts travell+ outw>ds to ! m>g9 & leav+ ! c5tral p>ts m acid4 ,if "s su* process takes place )9 a lava-res]voir1 x may acc\nt = a sequ5ce ( v>iations 9 composition4 ,b ?is w\ld n meet all ! difficulties ( ! case1 nor expla9 ! det]m9+ cause ( ! sep>ation ( ! con/itu5ts )9 ! res]voir ( molt5 rock1 :e!r aris+ f temp]ature1 specific gravity1 or o!r influ5ce4 ,?is subject w be fur!r consid]$ 9 connection ) intrusive ,bosses4 ,ano!r fact :i* may be reg>d$ z n[ well e/abli%$ is ! p]si/5ce ( composition & /ructure 9 ! lavas ( all ages4 ,not)/&+ ! (t-repeat$ cycles 9 ! "* ( ! magma1 ! mat]ials erupt$ to ! surface1 :e!r acid or basic1 h reta9$ ) wond]ful uni=mity ! same fundam5tal *>act]i/ics4 ,no "p ( ! contribution ( ,briti% geology to ! elucidation ( ! hi/ory ( volcanic action is ( m importance ?an ! evid5ce :i* x furni%es = ?is p]si/5t sam5ess ( ! subt]ranean magma4 ,an artificial l9e has sometimes be5 drawn betwe5 ! volcanic products ( ,t]ti>y "t & ^? ( e>li] ages4 ,b a c>eful /udy ( ! eruptive rocks ( ,brita9 %[s t no su* l9e ( division is bas$ ^u any fundam5tal diff]5ces4 ,! lavas ( ,palozoic "t h ( c\rse be5 f> long] expos$ to alt]ations ( e k9d ?an ^? ( ! ,t]ti>y p]iods1 & c]ta9 sup]ficial di/9ctions may be made betwe5 !m4 ,b :5 ^! accid5tal diff]5ces are elim9at$1 we f9d t ! olde/ kn[n lavas exhibit ! same types ( /ructure & composition t are famili> 9 ^? ( ,t]ti>y & rec5t volcanoes4 ,_m illu/rations ( ?is /atem5t w be furni%$ 9 lat] *apt]s4 ,z a p>ticul>ly /rik+ in/ance1 ,i may cite "h ! mo/ anci5t & mo/ mod]n lavas ( ! ,gr& ,caon ( ! ,colorado4 ,mr4 ,walcott & ,mr4 ,idd+s h %[n t 9 ! ,l[] ,cambrian1 or possibly pre-,cambrian1 =mations ( t great gorge1 c]ta9 basic lavas 7 contemporane\sly int]/ratifi$1 :i*1 9 spite ( _! va/ antiquity1 are only slightly diff]5t f ! mod]n basalts t h be5 p\r$ ov] ! surr\nd+ plateau4#af ,footnote #af3 #ad? ,annual ,report ,u4,s4 ,geol4 ,survey 7#ahib-ic74 ,! *ief lavas f\nd 9 ,brita94--,( ! lavas :i* h be5 p\r$ out at ! surface )9 ! region ( ! ,briti% ,isles1 ! foll[+ v>ieties are ( mo/ frequ5t occurr5ce4 ,9 ! acid s]ies are ,rhyolites & ,felsites1 b ! vitre\s =ms are probably all intrusive4 ,! int]m$iate s]ies is repres5t$ by ,tra*ytes & ,&esites 7,porphyrites71 :i* range f a glassy to a holocry/all9e /ructure4 ,! basic s]ies includes ,dol]ites1 ,diabases1 ,basalts1 ,limburgites 7or ,magma-basalts1 conta9+ little or no felsp>71 & ,picrites or o!r v>ieties ( ,p]idotites4 ,! intrusive rocks display a great] v>iety ( composition & /ructure4 ii4 ,,volcanic ,,agglom]ates1 ,,breccias ,,& ,,tuffs ,! co>s] fragm5t>y mat]ials ?r[n f volcanic v5ts are kn[n z ,agglom]ates :]e !y %[ no def9ite arrangem5t1 & especially :]e !y actually fill up ! old funnels ( dis*>ge4 ,:5 !y h accumulat$ 9 %eets or /rata ( angul> detritus outside an active v5t !y are t]m$ ,breccias1 or if _! compon5t /ones h be5 wat]-worn1 ,conglom]ates4 ,! f9] eject$ mat]ials may be compreh5d$ "u ! g5]al "n ( ,tuffs4 ,al?\gh ^! v>i\s =ms ( pyrocla/ic detritus consi/ z a rule ( ?or\ghly volcanic mat]ial1 !y may include fragm5ts ( non-volcanic rocks4 ,?is is especially ! case among ^? :i* repres5t ! e>lie/ explosions ( a volcano4 ,! fir/ ef=ts to e/abli% an eruptive v5t lead to ! %att]+ ( ! t]re/rial cru/1 & ! consequ5t dis*>ge ( abundant debris ( t cru/4 ,! breccias or agglom]ates ?us produc$ may conta91 inde$1 little or no truly volcanic mat]ial1 b may be made up ( fragm5ts ( granite1 gneiss1 s&/one1 lime/one1 %ale1 or :atev] may happ5 to be ! rocks ?r\gh :i* ! eruptive orifice has be5 drill$4 ,if ! fir/ explosions exhau/$ ! en]gy ( ! v5t1 x may happ5 t ! only dis*>ges f x consi/$ m]ely ( non-volcanic debris4 ,examples ( ?is k9d h be5 cit$ f v>i\s old volcanic di/ricts4 ,a /rik+ case occurs at ,sepul*re ,m\nta9 9 ! ,yell[/one ,p>k1 :]e ! l[] breccias1 ! product ( ! e>lie/ explosions ( ! ,electric ,peak volcano1 & atta9+ a ?ickness ( #ejj feet1 are full ( pieces ( ! ,ar*an rocks :i* und]lie ! y\ng] =mations ( t di/rict4#ag ,^! non-volcanic /ones d n occur among ! breccias high] up4 ,obvi\sly1 h[ev]1 ?\gh mo/ abundant at fir/1 pieces ( ! und]ly+ rocks may reappe> 9 subsequ5t dis*>ges1 :]ev] by ! en]gy ( explosion1 fragm5ts are brok5 f ! walls ( a volcanic *imney & hurl$ out ( ! crat]4 ,illu/rations ( ^! features w be giv5 9 ! acc\nt ( ! ,briti% ,c>bonif]\s1 ,p]mian & ,t]ti>y volcanic rocks4 ,footnote #ag3 ,pr(4 ,j4 ,p4 ,idd+s1 #ab? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey 7#ahij-ia71 p4 #fcd4 ,x w be obvi\s t :]e ! compon5t mat]ials ( su* fragm5t>y accumulations consi/ entirely ( non-volcanic rocks1 great caution mu/ be ex]cis$ 9 attribut+ !m to volcanic ag5cy4 ,two s\rces ( error 9 su* cases may "h be po9t$ out4 ,9 ! fir/ place1 :]e angul> detritus has be5 precipitat$ into /ill wat]1 z1 = in/ance1 f a crag or rocky declivity into a lake1 a v co>se & tumultu\s k9d ( breccia may be =m$4 ,x is conceivable t1 9 c\rse ( "t1 su* a breccia may be buri$ "u ord9>y s$im5ts1 & may !reby be pres]v$1 :ile all trace ( its p>5t precipice may h disappe>$4 ,! breccia might resemble "s true volcanic agglom]ates1 b ! resemblance w\ld be entirely deceptive4 ,9 ! second place1 notice mu/ be tak5 ( ! frequ5t results ( movem5ts )9 ! t]re/rial cru/1 :]eby rocks h n only be5 ruptur$ b1 z already po9t$ out1 h be5 cru%$ into fragm5ts4 ,9 ?is way1 important masses ( breccia or conglom]ate h be5 =m$1 sometimes runn+ = a numb] ( miles & atta9+ a bread? ( sev]al hundr$ feet4 ,! /ones1 (t5 9 huge blocks1 h be5 d]iv$ f ! surr\nd+ rocks1 & :ile sometimes angul>1 are sometimes well-r\nd$4 ,!y are imb$d$ 9 a f9] matrix ( ! same mat]ial1 & may be scatt]$ promiscu\sly ?r\gh ! mass1 9 su* a way z to pres5t ! close/ resemblance to true volcanic breccia4 ,:]e ! cru%$ mat]ial has includ$ anci5t igne\s rocks x might deceive ev5 an exp]i5c$ geologi/4 ,inde$1 "s rocks :i* h be5 mapp$ & describ$ z volcanic tuffs or agglom]ates are n[ kn[n to be only examples ( cru%-conglom]ates4#ah ,footnote #ah3 ,= an acc\nt ( cru%-conglom]ates1 see ,mr4 ,lamplugh's pap] on ^? ( ! ,isle ( ,man1 ,qu>t4 ,j\rn4 ,geol4 ,soc41 li4 7#ahie71 p4 #efc4 ,mr4 ,m',h5ry has po9t$ to probable cases ( mi/ake ( ?is k9d 9 ,irel&1 ,nature1 #e? ,m>* #ahif4 ,a4 ,geikie1 ,geol4 ,mag4 ,novemb] #ahif4 ,n only h va/ quantities ( detritus ( non-volcanic rocks be5 %ot =? f volcanic v5ts1 b sometimes enorm\s solid masses ( rock h be5 br\ght up by asc5d+ lavas or h be5 eject$ by explosive vap\rs4 ,e visitor to ! puys ( ,auv]gne w rememb] ! great cliff-l prom95ce ( granite & mica-s*i/ :i*1 z describ$ long ago by ,scrope1 has be5 c>ri$ up by ! tra*yte ( ! ,puy ,*op9e1 & =ms "o ( ! summits ( ! dome 7,fig4 #cdd74 ,! same ph5om5on is obs]vable at ! ,puy de ,mont*>1 :]e l>ge blocks ( granite h be5 transport$ f ! und]ly+ plat=m4 ,abi* has describ$ "s rem>kable examples 9 ! region ( ,erz]\m4 ,! huge crat] ( ,pal&okn1 #ifhg feet above ! sea conta9s1 9 cliff-l projections f its walls z well z scatt]$ ov] its unev5 bottom1 great masses ( m>moris$ lime/one & alaba/]1 associat$ ) pieces ( ! gre5 *loritic s*i/s1 s]p5t9es & gabbros ( ! und]ly+ non-volcanic plat=m4 ,^! rocks1 :i* =m an integral "p ( ! /ructure ( ! crat]1 h be5 c>ri$ up by masses ( tra*ydol]itic1 &esitic & qu>tz-tra*ytic lavas4#ai ,examples w be giv5 9 a lat] *apt] %[+ h[ gigantic blocks ( mica-s*i/ & o!r rocks h be5 c>ri$ _m hundr$ feet upw>ds & buri$ among %eets ( lava or masses ( agglom]ates dur+ ! ,t]ti>y volcanic p]iod 9 ,brita9 7,fig4 #bfb74 ,footnote #ai3 ,abi*1 ,geologie des ,arm5is*5 ,ho*l&es 7,"p ii41 we/]n half71 #ahhb1 p4 #gf4 ,9 ! va/ majority ( cases1 ! fragm5t>y sub/ances eject$ by anci5t volcanic explosions1 l ^? ( ! pres5t day1 h consi/$ :olly or ma9ly ( mat]ial :i* exi/$ 9 a molt5 condition )9 ! e>?1 & :i* has be5 viol5tly expell$ to ! surface4 ,su* eject$ detritus v>ies f ! f9e/ impalpable du/ or p[d] up to huge masses ( solid rock4 ,^! v>i\s mat]ials may come f m ?an "o s\rce4 ,:]e a volcanic orifice is bl[n out ?r\gh already solidifi$ lavas belong+ to previ\s eruptions1 ! fragm5ts ( ^! lavas may accumulate )9 or ar\nd ! v5t1 & be gradually consolidat$ into agglom]ate or breccia4 ,aga91 explosions )9 ! funnel may break up lava-cru/s t h !re =m$ ov] ! cool+ upp] surface ( ! column ( molt5 rock4 ,or ! upris+ lava 9 ! *imney may be spurt$ out 9 lumps ( slag & bombs1 or may be viol5tly bl[n out 9 ! =m ( m9ute lapilli1 or ( extremely f9e du/ & a%es4 ,al?\gh 9 !ory ^! sev]al v>ieties ( orig9 may be discrim9at$1 x is h>dly possible always to di/+ui% !m among ! products ( anci5t volcanic action4 ,9 ! great majority ( cases old tuffs1 hav+ be5 orig9ally deposit$ 9 wat]1 h und]gone a good deal ( decomposition1 & su* e>ly alt]ation has be5 aggravat$ by ! subsequ5t influ5ce ( p]colat+ meteoric wat]4 ,:]e dis9tegration has n proce$$ too f>1 ! f9] p>ticles ( tuffs may be se5 to consi/ ( m9ute angul> pieces ( alt]$ glass1 or ( microlites or cry/als1 or ( "s vitre\s or semi-vitre\s sub/ance1 9 :i* su* microlites & cry/als are enclos$4 ,x has already be5 /at$ t ! occurr5ce ( glass1 or ( any sub/ance :i* has result$ f ! devitrification ( glass1 may be tak5 z good evid5ce ( =m] volcanic activity4 ,mo/ commonly1 especially 9 ! case ( tuffs ( high antiquity1 l ^? associat$ ) ! ,palozoic =mations1 ! fre% glassy & microlitic con/itu5ts1 s conspicu\s 9 mod]n volcanic a%es1 are h>dly to be recognis$4 ,! f9] du/ :i* no d\bt conta9$ ^! *>act]i/ic sub/ances has g5]ally pass$ into dull1 e>?y1 granul>1 or /ructureless mat]ial1 ?\gh "h & !re1 among basic tuffs1 rema9+ z palagonite4 ,9 ! mid/ ( ?is decay$ matrix1 ! lapilli ( disrupt$ lavas may endure1 b x may be difficult or impossible to decide :e!r !y 7 d]iv$ f ! break+ up ( old] lavas by explosion1 or f ! bl[+ out ( ! lava-cru/s )9 ! funnel4 ,! cellul> /ructure1 :i* we h se5 to be a m>k$ly volcanic peculi>ity among ! lavas1 is n less s 9 _! fragm5ts among ! agglom]ates1 breccias & tuffs2 inde$ x may be said to be em95tly *>act]i/ic ( !m4 ,! vesicles 9 ! lapilli1 bombs1 & blocks are sometimes ( l>ge size1 z 9 masses ( eject$ slag1 b !y range d[n to microscopic m9ut5ess4 ,! lapilli ( _m old tuffs are sometimes s cr[d$ ) su* m9ute pores1 z to %[ t !y 7 orig9ally true pumice4 ,! composition ( tuffs mu/ obvi\sly dep5d ^u t ( ! lavas f :i* !y 7 d]iv$4 ,b _! frequ5tly decay$ condition makes x less easy1 9 _! case1 to draw def9ite b\nd>y-l9es betwe5 v>ieties4 ,9 a gr\p ( acid lavas1 ! tuffs may be expect$ to be also acid1 :ile among int]m$iate or basic lavas1 ! tuffs w g5]ally be f\nd to correspond4 ,!re are1 h[ev]1 exceptions to ?is g5]al rule4 ,z w be aft]w>ds describ$ 9 detail1 abundant felsitic tuffs may be se5 among ! &esitic lavas ( ,l[] ,old ,r$ ,s&/one age 9 ,scotl&1 & rhyolitic tuffs occur also among ! ,t]ti>y basalts ( ,antrim4 ,z a rule1 basic & int]m$iate tuffs1 l ! lavas f :i* !y h be5 d]iv$1 are r m prone to decomposition ?an ! acid v>ieties4 ,"o ( _! mo/ *>act]i/ic features is ! pres5ce 9 !m ( lapilli ( a m9utely vesicul> pumice1 :i* w be m p>ticul>ly describ$ 9 connection ) volcanic necks1 ( :i* x is a *>act]i/ic con/itu5t4 ,occasional deta*$ cry/als ( volcanic m9]als1 ei!r entire or brok51 may be detect$ 9 !m1 ?\gh p]haps less frequ5tly ?an 9 ! agglom]ates4 ,! e>?y matrix is g5]ally gre5i% 9 col\r1 v>y+ into %ades ( brick-r$1 purple & br[n4 ,! acid tuffs are1 on ! :ole1 pal] 9 col\r ?an ! o!rs1 sometimes inde$ !y are :ite or pale grey1 b graduate into tones ( hmatitic r$ or br[n1 ! v>y+ f]rug9\s t9ts be+ indicative ( /ages 9 ! oxidation ( ! iron-be>+ con/itu5t m9]als4 ,small r\nd$ lapilli or angul> fragm5ts ( felsite or rhyolite may be notic$ among !m1 sometimes exhibit+ ! mo/ p]fect fl[-/ructure4 ,z typical examples ( su* tuffs1 ,i may ref] to ^? ( ! ,p5tl& ,hills1 ne> ,ed9burgh1 & ^? t lie betwe5 ! two gr\ps ( basalt 9 ,antrim4 ,illu/ration3 ,fig4 #ac4--;,alt]nations ( co>s] & f9] ,tuff4 ,?r[n out promiscu\sly f active v5ts1 ! mat]ials t =m tuffs arrange !mselves1 on ! :ole1 accord+ to relative size ov] ! surface on :i* !y come to re/1 ! l>ge/ be+ g5]ally gr\p$ ne>e/ to ! focus ( dis*>ge1 & ! f9e/ ext5d+ f>!/ f x4 ,z ! volcanoes ( :i* records h be5 pres]v$ among ! geological =mations 7 *iefly subaque\s1 ! fragm5t>y sub/ances1 z !y fell into wat]1 w\ld naturally be to "s ext5t spread out by ! action ( curr5ts or waves4 ,!y w\ld ?us t5d to take a m or less di/9ctly /ratifi$ arrangem5t4 ,moreov]1 z dur+ an eruption !re might be successive p>oxysms ( viol5ce 9 ! dis*>ges1 co>s] & f9] detritus w\ld successively fall ov] ! same spot4 ,9 ?is way1 rapid alt]nations ( texture w\ld arise 7,fig4 #ac74 ,a little exp]i5ce w enable ! obs]v] to di/+ui% betwe5 su* truly volcanic v>iations & ^? ( ord9>y s$im5tation1 :]e1 = in/ance1 lay]s ( gravel & s& repeat$ly alt]nate4 ,besides ! volcanic nature ( ! fragm5ts & _! non-wat]-worn =ms1 he w notice t "h & !re ! l>g] blocks may be plac$ on end--a position ! rev]se ( t usual 9 ! disposal ( aque\s s$im5ts1 b "o :i* is n infrequ5tly assum$ by eject$ /ones1 ev5 :5 !y fall ?r\gh "s little dep? ( wat]4 ,fur!r1 ! occurr5ce ( l>ge pieces ( lava1 scatt]$ at r&om ?r\gh deposits ( f9e tuff1 w\ld lead him to recognize ! tumultu\s dis*>ges ( a volcanic focus1 r ?an ! sort+ & sift+ action ( mov+ wat]4 ,admirable illu/rations ( ^! v>i\s *>act]i/ics may be ga!r$ 9 endless numb] f ! ,palozoic volcanic *ronicles ( ,brita94 ,i may especially cite ! bas9 ( ! ,fir? ( ,=? z a classical region = ! /udy ( ,c>bonif]\s examples4 ,illu/ration3 ,fig4 #ad4--;,alt]nations ( ,tuff 7t1 t17 ) non-volcanic s$im5t 7l1 l74 ,:5 ! conditions ( mod]n volcanic eruptions are consid]$1 x w be se5 t :]e eject$ a%es & /ones fall into wat]1 !y w !re m+le ) any ord9>y s$im5t t may be 9 c\rse ( deposition at ! "t4 ,!re w ?us be a bl5d+ ( volcanic & non-volcanic detritus1 & ! transition betwe5 ! two may be s ins5sible t no h>d l9e ( dem>cation c be drawn4 ,su* int]m+l+ has cont9ually tak5 place dur+ pa/ ages4 ,"o ( ! fir/ lessons le>nt by ! geologi/1 :o beg9s ! /udy ( anci5t volcanic records1 is ! necessity ( recogniz+ ?is gradation ( mat]ial1 & likewise ! frequ5tly recurr+ alt]nations ( true tuff ) %ale1 s&/one1 lime/one or o!r entirely non-volcanic detritus 7,fig4 #ad74 ,he soon p]ceives t su* facts z ^! furni% him ) "s ( ! mo/ /rik+ pro(s ( ! reality & progress ( =m] eruptions4 ,! int]m+l+ ( mu* ord9>y detritus ) ! volcanic mat]ial may be reg>d$ z indicative ei!r ( comp>atively feeble activity1 or at lea/ ( consid]able di/ance f ! focus ( dis*>ge4 ,x is sometimes possible to trace su* int]mixtures ?r\gh gradually augm5t+ proportions ( volcanic du/ & /ones1 until ! deposit becomes :olly volcanic 9 composition1 & s co>se 9 texture z to indicate ! proximity ( ! eruptive v5t4 ,on ! o!r h&1 ! gradual decrease ( ! volcanic ejections c be foll[$ 9 ! upw>d sequ5ce ( a s]ies ( /ratifi$ deposits1 until ! :ole mat]ial becomes entirely non-volcanic4 ,! occurr5ce ( ?9 p>t+s ( tuff betwe5 ord9>y s$im5t>y /rata po9ts to occasional int]mitt5t eruptions ( a%es or /ones1 ! vig\r & duration ( ea* eruptive int]val be+ r\ghly indicat$ by ! ?ickness & co>s5ess ( ! volcanic detritus4 ,! pauses 9 ! volcanic activity all[$ ! deposit ( ord9>y s$im5t to proce$ un*eck$4 ,! nature ( su* non-volcanic int]calations gives a clue to ! physical conditions ( s$im5tation at ! "t1 :ile _! ?ickness af=ds "s indication ( ! relative duration ( ! p]iods ( volcanic repose4 ,a little reflection w conv9ce ! obs]v] t 9 su* a section z t repres5t$ 9 ,fig4 #ad ! volcanic int]calations mu/ be reg>d$ z a m]e local accid5t4 ,evid5tly ! normal conditions ( s$im5tation at ! "t ^! /rata 7 accumulat$ are indicat$ by ! lime/one b&s 7l1 l74 ,_h !re be5 no volcanic eruptions1 a cont9u\s mass ( lime/one w\ld h be5 deposit$1 b ?is cont9uity 0 f "t to "t int]rupt$ by ! explosions t gave rise to ! int]calat$ b&s ( tuff 7t1 t74 ,! application ( ^! rules ( geological evid5ce w be be/ und]/ood f actual examples ( _! use4 ,_m illu/rations ( !m w be subsequ5tly giv51 m especially f ! volcanic records ( ! ,c>bonif]\s p]iod4 ,"o ( ! mo/ int]e/+ peculi>ities ( int]/ratifi$ tuffs is ! n infrequ5t occurr5ce ( ! rema9s ( plants & animals imb$d$ 9 !m4 ,su* rema9s w\ld h be5 entomb$ 9 ! ord9>y s$im5t _h !re be5 no volcanic eruptions1 & _! pres5ce 9 ! tuffs is ano!r conv9c+ pro( ( contemporane\s volcanic action dur+ ! deposition ( a s$im5t>y s]ies4 ,b !y may be made to furni% mu* m in=mation z to ! *ronology ( ! eruptions & ! physical geography ( ! localities :]e ! volcanoes 7 active1 z w be set =? f>!r on4 ,tuffs1 z already rem>k$1 frequ5tly occur )\t any accompanim5t ( lava1 al?\gh lavas seldom appe> )\t "s tuff4 ,we ?us le>n t 9 ! pa/1 z at pres5t1 dis*>ges ( fragm5t>y mat]ials alone 7 m common ?an ! outfl[ ( lava by itself4 ,! relative proportions ( ! lavas & tuffs 9 a volcanic s]ies v>y indef9itely4 ,9 ! ,t]ti>y basalt-plateaux ( ,brita91 ! lavas succe$ ea* o!r1 %eet above %eet1 = hundr$s ( feet1 ) few & trifl+ fragm5tal int]calations4 ,among ! ,c>bonif]\s volcanic ejections1 on ! o!r h&1 _m solit>y or successive b&s ( tuff may be obs]v$ )\t any visible %eets ( lava4 ,view$ broadly1 h[ev]1 9 _! g5]al di/ribution dur+ geological "t1 ! two great gr\ps ( volcanic mat]ial may be reg>d$ z hav+ g5]ally appe>$ toge!r4 ,9 all ! great volcanic s]ies1 f ! base ( ! ,palozoic sy/ems up to ! ,t]ti>y plateaux1 lavas & tuffs are f\nd associat$1 mu* z !y are among ! ejections ( mod]n volcanoes4 ,!y (t5 alt]nate1 & ?us furni% evid5ce z to oscillations ( en]gy at ! eruptive v5ts4 ,n[ & !n1 by ! explosions f a volcano at ! pres5t day1 a s+le /one may be eject$ at su* an angle & ) su* =ce z to fall to ! gr\nd at a long di/ance f ! v5t4 ,9 l mann]1 among ! volcanic records ( =m] p]iods1 we may occasionally come ^u a s+le block ( lava imb$d$ among tuffs or ev5 9 non-volcanic /rata4 ,:]e su* a /one has fall5 ^u s(t s$im5t1 x c be se5 to h sunk into x1 press+ d[n ! lay]s b5ea? x1 & hav+ ! subsequ5tly deposit$ lay]s heap$ ov] x4 ,an eject$ block ( ?is nature is repres5t$ among ! tuffs %[n 9 ,fig4 #ac4 ,ano!r in/ance f a gr\p ( non-volcanic s$im5ts is giv5 9 ,fig4 #ae1 & is select$ f a numb] ( illu/rations ( ?is int]e/+ feature :i* h be5 obs]v$ among ! ,l[] ,c>bonif]\s =mations ( ! bas9 ( ! ,fir? ( ,=?4 ,a solit>y block1 imb$d$ 9 a s]ies ( /rata1 w\ld n1 ( c\rse1 by itself af=d a demon/ration ( volcanic activity4 ,!re are v>i\s ways 9 :i* su* /ones may be transport$ & dropp$ ov] a muddy wat]-bottom4 ,!y may1 = example1 be float$ (f atta*$ to sea-we$s1 or wrapp$ r\nd by ! roots ( trees4 ,b :]e a block ( basalt or o!r volcanic rock has obvi\sly desc5d$ ) su* =ce z to cru% d[n ! deposits on :i* x fell1 & :5 lavas & tuffs are kn[n to exi/ 9 ! vic9ity1 !re c be little hesitation 9 reg>d+ su* a block z hav+ be5 eject$ f a neighb\r+ v5t1 ei!r dur+ an explosion ( exceptional viol5ce or ) an unusually l[ angle ( projection4 ,illu/ration3 ,fig4 #ae4--;,eject$ block ( ,basalt :i* has fall5 among ,c>bonif]\s %ales & lime/ones1 %ore1 ,pettycur1 ,fife4 ,9 conclusion1 ref]5ce may conv5i5tly be made "h to ano!r v>iety ( fragm5tal volcanic mat]ials :i* _c always be satisfactorily di/+ui%$ f true tuffs1 al?\gh aris+ f a ?or\ghly non-volcanic ag5cy4 ,:]e a mass ( lava has be5 expos$ to d5udation1 z1 = in/ance1 :5 a volcanic isl& has be5 =m$ 9 a lake or 9 ! sea1 ! detritus worn away f x may be spread out l any o!r k9d ( s$im5t4 ,?\gh d]iv$ f ! degradation ( lava1 su* a me*anical deposit is n prop]ly a tuff1 nor c x ev5 be includ$ among /rictly volcanic =mations4 ,x may be call$ a volcanic conglom]ate1 rhyolitic conglom]ate1 diabase s&/one1 felsitic %ale1 or by any o!r "n t w adequately d5ote its composition & texture4 ,b x may n af=d pro( ( /rictly contemporane\s volcanic activity4 ,all t we are entitl$ to inf] f su* a deposit is t1 at ! "t :5 x 0 laid d[n1 volcanic rocks ( a c]ta9 k9d 7 expos$ at ! surface & 7 und]go+ degradation4 ,b ! date ( _! orig9al eruption may h be5 long previ\s to t ( ! =mation ( ! detrital deposit f _! wa/e4 ,nev]!less1 x is sometimes possible to make sure t ! conglom]ate or s&/one1 ?\gh :olly due to ! me*anical de/ruction ( already erupt$ lavas1 0 9 a g5]al s5se contemporane\s ) ! volcanoes t gave =? ^! lavas4 ,! detrital =mation may be trac$ p]haps up to ! lavas f :i* x 0 d]iv$1 & may be f\nd to be int]calat$ 9 ! same s$im5t>y s]ies ) :i* !y are associat$4 ,or x may conta9 l>ge bombs & slags1 su* z mo/ probably came ei!r directly f explosions or f ! wa%+ d[n ( c9d]-cones or o!r contemporane\sly exi/+ volcanic heaps4 ,examples ( su* int]calat$ conglom]ates w be giv5 f ! ,l[] ,old ,r$ ,s&/one ( ,c5tral ,scotl& & f ! ,t]ti>y volcanic plateaux ( ! ,inn] ,hebrides4 ,,*apt] ,,iv ,mat]ials erupt$ at ! ,surface--,extrusive ,s]ies--cont9u$4 iii4 ,types ( old ,volcanoes--#a4 ,! ,vesuvian ,type2 #b4 ,! ,plateau or ,fissure ,type2 #c4 ,! ,puy ,type4 iv4 ,det]m9ation ( ! relative ,geological ,dates ( anci5t ,volcanoes4 v4 ,h[ ! ,physical ,geography associat$ ) anci5t ,volcanoes is asc]ta9$4 ,hav+ n[ tak5 note ( ! v>i\s mat]ials eject$ to ! surface f volcanic orifices1 we may pass to ! consid]ation ( ^! orifices !mselves1 ) ! view ( asc]ta9+ "u :at v>i\s conditions volcanic action has tak5 place 9 ! geological pa/4 ,we h se5 t mod]n & n long ext9ct volcanoes may be gr\p$ into ?ree types1 & a /udy ( ! records ( anci5t volcanoes %[s t ! same types may be recogniz$ 9 ! eruptions ( =m] ages4 ,! foll[+ *apt]s w supply _m illu/rations ( ea* type f ! geological hi/ory ( ! ,briti% ,isles4 ,9 deal+ ) ^! illu/rations1 h[ev]1 we mu/ ev] be> 9 m9d ! all-p[]ful influ5ce ( d5udation4 ,we ought n to expect to meet ) ! orig9al =ms ( ! volcanoes4 ,"s little reflection & exp]i5ce may be requir$ be=e we c realize "u :at aspect we may hope to recognize anci5t & mu*-d5ud$ volcanoes4 ,x may !re=e be ( advantage to consid] "h1 9 a broad way1 :i* ( ! orig9al *>act]s are mo/ p]man5t1 & %\ld be look$ = z mem5toes ( anci5t volcanoes aft] long ages ( d5udation4 iii4 ,,types ,,( ,,old ,,volcanoes ,! ?ree =ms ( anci5t volcanoes n[ to be discuss$ are--#a/1 ! ,vesuvian type2 #bnd1 ! ,plateau or ,fissure type2 & #crd1 ! ,puy type4 #a4 ,! ,vesuvian ,type4--,9 ?is k9d ( volcano1 lavas & fragm5tal ejections are dis*>g$ f a c5tral v5t1 :i* is gradually built up by successive eruptions ( ^! mat]ials4 ,z ! cone increases 9 size1 p>asitic cones appe> on its sides1 & 9 ! en]gy & complet5ess ( _! ph5om5a become true volcanoes1 almo/ rivall+ _! p>5t m\nta94 ,/reams ( lava desc5d ^u ! l[] gr\nds1 :ile %[]s ( du/ & a%es are spread f> & wide ov] ! surr\nd+ c\ntry4 ,if a transv]se section c\ld be made ( a mod]n ,vesuvian cone1 ! volcanic pile w\ld be f\nd to consi/ ( alt]nations ( lavas & tuffs1 ?icke/ at ! c5tre1 & ?9n+ away 9 all directions4 ,at "s di/ance f ! crat]1 ^! volcanic mat]ials might be se5 to include lay]s ( soil & rema9s ( l&-vegetation1 m>k+ pauses betwe5 ! eruptions1 dur+ :i* soil accumulat$ & plants sprang up ^u x4 ,:]e ! lavas & a%es _h made _! way into %eets ( fre% wat] or into ! sea1 !y w\ld probably be f\nd int]/ratifi$ ) lay]s ( ord9>y s$im5t conta9+ rema9s ( ! animal or vegetable life ( ! "t4 ,illu/ration3 ,fig4 #af4--;,effects ( d5udation on a ,vesuvian cone4 ,conceive n[ ! effects ( prolong$ d5udation ^u su* a pile ( volcanic rocks4 ,! cone w ev5tually be worn d[n1 ! crat] w disappe>1 & ! only relics ( ! eruptive orifice may be ! top ( ! c5tral lava-column & ( any fragm5tal mat]ials t solidifi$ )9 ! v5t 7,fig4 #af74 ,! wa/e w1 on ! :ole1 be great] at ! cone ?an on ! m level areas beyond4 ,x might1 9 c\rse ( "t1 rea* ! orig9al surface ( ! gr\nd on :i* ! volcano built up its heap ( eject$ mat]ial4 ,! c5tral lava-plug might ?us be left z an isolat$ em95ce ris+ f a plat=m ( old] non-volcanic rocks1 & ! di/ance betwe5 x & ! dw9dl+ %eets ( lava & tuff :i* came out ( x w\ld !n be cont9ually increas$ z _! outcrop rec$$ "u con/ant degradation4 ,?is piece ( volcanic hi/ory is diagrammatically illu/rat$ 9 ,fig4 #af4 ,! orig9al =ms ( ! c5tral volcano & ( its p>asitic cones are sugge/$ by ! dott$ l9es 9 ! upp] half ( ! ,figure4 ,all ?is upp] portion has be5 remov$ by d5udation1 & ! pres5t surface ( ! gr\nd is %[n by ! upp]mo/ cont9u\s l9e4 ,! g5]al /ructure ( ! volcanic pile is indicat$ und]nea? t l9e--! l5ticul> %eets ( lava & tuff 7l1 l71 ! dykes 7d1 d71 & ! lavas 7p1 p7 & agglom]ates 7a1 a7 ( ! c5tral v5t & ( ! subord9ate cones4 ,! wa/e1 ?\gh greate/ on ! high] gr\nd ( ! great cone1 w\ld n /op !re4 ,x w\ld ext5d ov] ! flatt] area ar\nd ! volcano4 ,/reams fl[+ ov] ! pla9 w\ld cut _! way d[n ?r\gh ! lavas & tuffs1 erod+ rav9es 9 !m1 & leav+ !m 9 deta*$ & ev] dim9i%+ outli]s on ! cre/s ( ! int]v5+ ridges4 ,we c easily picture a "t :5 ! la/ ( ^! relics w\ld h be5 worn away1 & :5 e ve/ige ( ! volcanic ejections w\ld h be5 remov$1 save ! lava-column m>k+ ! site ( ! =m] v5t4 ,e /age 9 ?is process ( effacem5t may be recogniz$ 9 actual progress among ! ext9ct volcanoes ( ! e>?'s surface4 ,probably n[h]e may ! ph5om5a be m conv5i5tly & impressively /udi$ ?an among ! volcanic di/ricts ( ,c5tral ,france4 ,on ! "o h&1 we meet !re ) c9d]-cones s p]fect t x is h>d to believe !m to h be5 sil5t ev] s9ce ! beg9n+s ( hi/ory4 ,on ! o!r h&1 we see solit>y cones ( agglom]ate or ( lava1 :i* h be5 left isolat$1 :ile _! once ov]ly+ & encircl+ %eets ( eject$ mat]ial h be5 s ext5sively worn away z to rema9 m]ely 9 scatt]$ pat*es capp+ ! neighb\r+ hills4 ,valleys _m hundr$s ( feet 9 dep? h be5 cut by ! riv]s ?r\gh ! volcanic %eets & ! und]ly+ ,t]ti>y /rata & granite s9ce ! old] eruptions ceas$4 ,& yet ^! eruptions belong to a p]iod :i*1 9 a geological s5se1 is q rec5t4 ,x is n difficult to contemplate a future "t1 geologically n v remote1 :5 9 ! valley ( ! ,loire n a trace w rema9 ( ! wond]fully v>i$ & int]e/+ volcanic *ronicle ( t di/rict1 save ! plugs t w m>k ! positions ( ! =m] active v5ts4 ,9 ! ,briti% ,isl&s1 anci5t volcanoes ( ! ,vesuvian type are well repres5t$ among ! ,palozoic sy/ems ( /rata4 ,_! pres]vation has be5 l>gely due to ! fact t !y made _! appe>ance 9 areas t 7 und]go+ sl[ subsid5ce4 ,_! piles ( erupt$ lava & a%es 7 *iefly heap$ up ov] ! sea-floor1 & 7 buri$ "u ! s&1 silt & ooze t ga!r$ !re4 ,?us cov]$ up1 !y 7 protect$ f d5udation4 ,x is only 9 mu* lat] geological ages t1 ow+ to upheaval1 gradual degradation ( ! surface1 & removal ( _! ov]ly+ cov] ( /ratifi$ =mations1 !y h at la/ be5 expos$ to wa/e4 ,! process ( dis9t]m5t may be obs]v$ 9 _m diff]5t /ages ( progress4 ,9 "s localities1 only ! tops ( ! %eets ( lava & tuff h begun to %[ !mselves2 9 o!rs1 ev]y?+ is gone except ! inde/ructible lava-plug4 ,^! inequalities ( d5udation arise n only f v>iations 9 ! durability ( volcanic rocks1 b /ill m f ! relative position ( ^! rocks 9 ! t]re/rial cru/1 & ! geological p]iod at :i*1 9 ! c\rse ( ! g5]al l[]+ ( ! surface1 !y h be5 laid b>e4 ,n only are volcanic rocks ( _m diff]5t ages1 & lie1 !re=e1 on _m successive plat=ms )9 ! cru/ ( ! e>?3 _! places h be5 /ill fur!r dep5d5t ^u *anges 9 ! arrangem5t ( t cru/4 ,fracture1 upheaval1 depression1 curvature1 uncon=mable deposition ( /rata1 h contribut$ to protect "s portions1 :ile leav+ o!rs expos$ to attack4 ,h5ce x happ5s t ! volcanic record v>ies greatly 9 its fulness ( detail f "o geological sy/em or "o di/rict to ano!r4 ,"s *apt]s h be5 record$ ) ! mo/ surpris+ m9ut5ess1 s t ! ev5ts :i* !y reveal c be realiz$ z vividly z ^? ( a mod]n volcano4 ,o!rs1 aga91 are meagre & fragm5t>y1 because ! *ronicle is /ill = ! mo/ "p buri$ und]gr\nd1 or because x has be5 s long expos$ at ! surface t only fragm5ts ( x n[ rema9 !re4 ,9 ! descriptions :i* w subsequ5tly be giv5 ( anci5t ,briti% volcanoes ( ! ,vesuvian type1 x w be %[n t at _m successive p]iods dur+ ,palozoic "t1 & at _m di/9ct c5tres1 lavas & tuffs h be5 pil$ up to a dep? ( frequ5tly m ?an #ejjj feet--t is to say1 high] ?an ! height ( ,vesuvius4 ,sometimes ! v5t f :i* ^! mat]ials 7 eject$ c be recogniz$4 ,9 o!r places1 x is /ill buri$ "u lat] =mations1 or has be5 s d5ud$ z to be repres5t$ n[ m]ely by ! column ( molt5 or fragm5tal rock t f9ally solidifi$ 9 x4 ,examples w be quot$ ( su* anci5t v5ts1 measur+ n less ?an two miles 9 diamet]1 ) subsidi>y necks on _! flanks1 l ! p>asitic cones on ,etna4 ,i %all %[ t :ile ! eject$ volcanic products h accumulat$ 9 greate/ dep? close to ! v5t t dis*>g$ !m1 !y die away z !y rec$e f x1 sometimes s rapidly t a volcanic pile :i* is #gjjj feet ?ick ar\nd its s\rce may entirely ?9 out & disappe> 9 a di/ance ( n m ?an t5 or twelve miles4 ,i %all po9t out h[1 z ! lavas & tuffs are foll[$ outw>ds f _! c5tre1 !y n only get ?9n]1 b are increas+ly int]/ratifi$ among ! s$im5t>y deposits ) :i* !y 7 coeval1 & t 9 ?is way _! limits1 _! age1 & ! geographical conditions "u :i* !y 7 accumulat$ c be satisfactorily fix$4 ,z illu/rations ( ! ,vesuvian type 9 ! volcanic hi/ory ( ,brita91 ,i may ref] to ! great ,l[] ,silurian volcanoes ( ,cad] ,idris1 ,ar5ig1 ,sn[don & ! ,lake ,di/rict1 & to ! ,old ,r$ ,s&/one volcanoes ( ,c5tral ,scotl&4 #b4 ,! ,plateau or ,fissure type is1 among mod]n volcanoes1 be/ develop$ 9 ,icel&1 z w be m fully detail$ 9 ,*apt] xl4 ,9 t isl&1 dur+ a volcanic eruption1 ! gr\nd is r5t op5 into long p>allel fissures1 only a few feet or y>ds 9 wid?1 b traceable sometimes = _m miles1 & desc5d+ to an unkn[n dep? into ! int]ior4 ,f ^! fissures lava issues--9 "s cases fl[+ out tranquilly 9 broad /reams f ei!r side1 9 o!r cases issu+ ) ! dis*>ge ( slags & blocks ( lava :i* are pil$ up into small cones set closely toge!r along ! l9e ( ! r5t4 ,x 0 f a fissure ( ?is k9d t ! great eruption ( #aghc took place--! mo/ /up5d\s outp\r+ ( lava )9 hi/oric "t4 ,by successive dis*>ges ( lava f fissures1 or f v5ts op5+ on l9es ( fissure1 wide pla9s may be cov]$ ) a floor ( rock hundr$s or ?\s&s ( feet 9 ?ickness1 made up ( horizontal b$s4 ,! orig9al topography1 :i* might h be5 undulat+ & v>i$1 is completely buri$ "u a va/ level lava-des]t4 ,! riv]s :i* dra9$ ! c\ntry be=e ! beg9n+ ( ! volcanic hi/ory w h _! *annels fill$ up1 & w be driv5 to seek new c\rses across ! lava-fields4 ,aga9 & aga91 z fre% eruptions take place1 ^! /reams w be compell$ to %ift _! l9e ( fl[1 ea* riv]-b$ be+ 9 turn seal$ up 9 lava1 ) all its gravels1 silts & drift-wood4 ,b ! ra9 w cont9ue to fall1 & ! dra9age to seek its way seaw>d4 ,:5 ! la/ eruption ceases1 & ! riv]s are at l5g? left undi/urb$ at _! task ( erosion1 !y w c>ve t lava-floor into deep gorges or op5 valleys4 ,:]e !y fl[ betwe5 ! lavas & ! slopes aga9/ :i* ^! end$1 !y w cut back ! volcanic pile1 until 9 c\rse ( "t ! lavas w pres5t a bold mural esc>pm5t to ! l& t once =m$ _! limit4 ,! volcanic pla9 w become a plateau1 end+ (f 9 ?is v]tical wall & deeply tr5*$ by ! /reams t w9d across x4 ,& if ! d5udation is cont9u$ long en\gh1 ! plateau w be r$uc$ to deta*$ hills1 sep>at$ by deep & wide valleys4 ,illu/ration3 ,fig4 #ag4--,section to illu/rate ! /ructure ( ! ,plateau type4 ,?is geological hi/ory is illu/rat$ by ! diagram 9 ,fig4 #ag4 ,! /ippl$ gr\nd und]nea? 7x1 x7 repres5ts ! orig9al undulat+ surface ( ! c\ntry on :i* ! plateau eruptions 7 p\r$ out4 ,! lavas ( ^! eruptions are %[n by ! horizontal l9es to h entirely buri$ ! heights & holl[s ( ! old l&1 & to h ris5 up to ! upp] dott$ l9e1 :i* may be tak5 to m>k ! limit rea*$ by ! accumulation ( volcanic mat]ial4 ,! d>k l9es 7d1 d7 :i* come up ?r\gh ! b$d$ lavas indicate ! dykes ) _! connect$ v5ts4 ,d5udation has s9ce /ripp$ (f ! upp] "p ( ! volcanic s]ies d[n to ! upp]mo/ cont9u\s black l9e :i* repres5ts ! exi/+ surface ( ! gr\nd4 ,! level %eets ( lava h be5 deeply tr5*$1 & 9 "o in/ance ! valley has n only be5 cut ?r\gh ! volcanic pile1 b has be5 p>tly erod$ out ( ! old] rocks bel[4 ,to ! "r & left1 ! lavas end (f abruptly 9 great esc>pm5ts4 ,! succession ( ev5ts "h depict$ has occurr$ m ?an once 9 ,brita94 ,! ,plateau type is *iefly develop$ 9 ?is c\ntry among ! great ,t]ti>y basalt di/ricts ( ,antrim & ! ,inn] ,hebrides1 :i* reappe> 9 ! ,f>oe ,isl&s1 & aga9 /ill f>!r nor? 9 ,icel&4 ,b x also occurs among ! volcanic rocks ( ! ,old ,r$ ,s&/one & ,c>bonif]\s p]iods4 ,z comp>$ ) ! o!r volcanic types1 t ( ! ,plateaux is di/+ui%$ by ! wide ext5t ( surface :i* its rocks cov]1 by ! great prepond]ance ( lavas ov] tuffs1 & by ! regul>ity & p]si/5ce ( ! individual %eets ( rock4 ,9 ,brita91 ! plateau-lavas are ev5 /ill (t5 approximately horizontal1 & lie pil$ on ea* o!r 9 tol]ably regul> b$s to a ?ickness ( #ajjj1 & 9 "o place to m ?an #cjjj feet4 ,!y =m wide level or g5tly undulat+ tablel&s1 :i* rise 9 bold esc>pm5ts f ! surr\nd+ c\ntry & h be5 deeply c>v$ into valleys4 ,! sides ( _! cliffs & slopes are m>k$ by p>allel l9es ( t]race1 aris+ f ! outcrop ( successive %eets ( lava 7,figs4 #aa1 #bfe74 ,) ! ,t]ti>y basalt-plateaux are connect$ ?\s&s ( dykes1 t foll[ ea* o!r along ne>ly p>allel l9es 9 a g5]al nor?-we/]ly direction1 & m>k ! position ( fissures up :i* ! molt5 lava asc5d$4 ,occasional necks ( agglom]ate or basalt indicate ! sites ( "s ( ! eruptive v5ts4 ,! ,c>bonif]\s volcanic plateaux h be5 m ext5sively d5ud$ ?an ^? ( ,t]ti>y age1 s t a l>ge numb] ( _! v5ts h be5 laid b>e4 ,9 g5]al ^! v5ts are ( comp>atively small size1 ?\gh l>g] ?an ^? ( ! ,c>bonif]\s ,puys4 ,9 "s di/ricts1 abundant dykes trav]se ! rocks on :i* ! plateaux re/1 ?\gh ! fissures seem to h be5 less num]\s ?an 9 ,t]ti>y "t4 #c4 ,! ,puy type1 z be=e rem>k$1 takes its "n f ! well-kn[n puys1 or volcanic cones1 ( ,c5tral ,france4 ,volcanoes ( ?is type =m conical hills1 g5]ally ( small size1 consi/+ usually ( fragm5tal mat]ials1 sometimes ( lava4 ,:]e a cone is p>tially effac$ by a second1 & ev5 by a ?ird1 successive slight %ift+s ( ! v5t are to be inf]r$ 7see ,figs4 #bi & #bad74 ,9 _m cases1 no lava has issu$ f su* cones1 nor 7 ! a%es & c9d]s disp]s$ f> f ! v5t4 ,h5ce1 9 ! progress ( d5udation1 cones ( ?is k9d are easily effac$4 ,f ! uni=mity ( composition ( _! mat]ials1 ! simplicity & regul>ity ( _! =ms1 & _! small size1 x may be inf]r$ t _m ( ^! cones 7 ! products ( s+le eruptions4 ,!y may conceivably h be5 ?r[n up 9 a few days1 or ev5 9 a s+le day4 ,! hi/ory ( ,monte ,nuovo1 9 ! ,bay ( ,naples1 :i* 0 =m$ )9 tw5ty-f\r h\rs 9 ! ye> #aech1 is a memorable example ( ! rapidity ) :i* a cone m ?an #djj feet high may be ?r[n up at "s di/ance f a c5tral v5t4 ,! smalle/ indep5d5t volcanoes are includ$ 9 ! ,puy type4 ,9 _m in/ances ! diamet] ( ! funnel has n exce$$ a few y>ds2 ! l>ge/ examples ( ! type seldom exce$ #ajjj feet 9 wid?4 ,:]e lavas h be5 dis*>g$1 z well z a%es & /ones1 a m vigor\s activity is indicat$ ?an :]e m]ely cones ( tuff 7 =m$4 ,! lavas may come f m ?an "o side ( a cone1 & may fl[ 9 opposite directions = a di/ance ( sev]al miles4 ,x is obs]vable t consid]able /reams ( lava h issu$ f ! base ( a c9d]-cone )\t di/urb+ x4 ,! molt5 rock has f\nd a passage betwe5 ! loose mat]ials & ! surface on :i* !y re/1#bj ?\gh1 9 "s cases1 ! cone may h be5 ?r[n up aft] ! emission ( ! lava4 ,footnote #bj3 ,m4 ,b\le1 ,bull4 ,c>te ,gol4 ,france1 ,no4 #bh1 tome iv4 p4 #bcb4 ,9 ! hi/ory ( a puy !re is commonly a fir/ dis*>ge ( fragm5t>y mat]ial2 !n lava may fl[ out1 foll[$ by a f9al dis*>ge ( loose /ones & a%es4 ,h5ce ! products ( su* a v5t gr\p !mselves into ?ree lay]s--two ( breccia sep>at$ by an int]v5+ %eet ( lava4#ba ,footnote #ba3 ,m4 ,b\le1 ,bull4 ,c>te ,gol4 ,france1 ,no4 #bh1 tome iv4 ,great *anges are wr\ght on puys & _! connect$ lavas & tuffs dur+ ! progress ( d5udation4 ,! cones are ev5tually de/roy$1 & only a /ump ( agglom]ate or lava is left to m>k its place4 ,! connection ( a lava-/ream ) its p>5t v5t may likewise be effac$1 & ! lava itself may be r$uc$ to m]ely a few sep>ate pat*es1 p]haps capp+ a ridge1 :ile ! surr\nd+ gr\nd has be5 holl[$ into valleys4 ,if ! wa/e cont9ues long en\gh1 ev5 ^! outli]s w disappe>1 & no?+ b ! neck or /ump ( ! little volcano w rema94 ,illu/ration3 ,fig4 #ah4--;,diagram illu/rat+ ! /ructure & d5udation ( ,puys4 ,! accompany+ diagram 7,fig4 #ah7 may help to make ^! *anges m intelligible4 ,! upp] dott$ l9es %[ ! orig9al =ms ( ?ree puys ) ! cov]+ ( loose mat]ials dis*>g$ by !m ov] ! surr\nd+ gr\nd4 ,! l[] %ad$ portion repres5ts ! surface z left by d5udation1 & a section ( ! ?ree v5ts b5ea? t surface4 ,! :ole ( ! cones & crat]s has "h be5 swept away1 & only ! volcanic neck is 9 ea* case left4 ,9 ! v5t to ! "r1 ! mat]ial t fills x up is a co>se agglom]ate1 :i* projects z a r\nd$ dome above ! surr\nd+ c\ntry4 ,! c5tral pipe is fill$ ) fragm5t>y mat]ials1 ?r\gh :i* molt5 rock has ris51 giv+ (f dykes & ve9s4 ,9 ! v5t to ! left h&1 only lava is se5 to occupy ! orifice1 repres5t+ ! column ( molt5 rock :i* solidifi$ !re & br\ght ! activity ( ?is little volcano to an end4 ,x w be obs]v$ t 9 ea* ( ^! volcanic hills ! pres5t outl9es are v f> f be+ ^? ( ! orig9al volcano1 & t ! em95ce projects because ( its great] resi/ance to ! =ces ( d5udation t h n only remov$ ! sup]ficial volcanic mat]ial1 b h made "s progress 9 l[]+ ! level ( ! gr\nd on :i* t mat]ial 0 accumulat$4 ,! typical area = ! /udy ( ,puys is ! extraord9>ily int]e/+ volcanic region ( ,c5tral ,france4 ,!re ! volcanic cones are clu/]$ 9 irregul> gr\ps1 sometimes s close z to be t\*+ ea* o!r2 else:]e sep>at$ by int]vals ( sev]al miles4 ,!y may be trac$ 9 all /ages ( decay1 f ! mo/ p]fect cones & crat]s to ! isolat$ em95ce t m>ks ! site ( a once active *imney4 ,_! lavas1 too1 may be se5 z deta*$ fragm5ts ( plateaux1 _m hundr$ feet above ! valleys t h be5 excavat$ s9ce !y fl[$4#bb ,footnote #bb3 ,see ,desm>e/'s classic map & 8 pap]s 9 ,mem4 ,acad4 ,roy4 ,sci5ces1 ,p>is1 #aggd1 #aggi2 ,j\rn4 de ,physique1 #aggi2 ,scrope's ,geology ( ,c5tral ,france1 #ahbg1 & ,ext9ct ,volcanoes ( ,c5tral ,france1 #aheh2 ,lecoq's poques ,gologiques de l',auv]gne1 #ahfg2 ,m4 ,mi*el ,lvy1 ,bull4 ,soc4 ,gol4 ,france1 #ahij1 p4 #fhh2 ,m4 ,b\le1 ,bull4 ,c>te ,gol4 ,france1 ,no4 #bh1 tome iv4 #ahib4 ,ano!r well-kn[n region ( mod]n ,puys is t ( ! ,eifel1 :]e ! cones & crat]s are (t5 s fre% t x is difficult to believe !m to be prehi/oric4#bc ,"o ( ! mo/ rem>kable d5ud$ puy-regions 9 ,europe cov]s a wide t]ritory 9 ! ,swabian ,alps ( ,wrtemb]g4 ,no few] ?an #abe d5ud$ necks fill$ ) tuff1 agglom]ate & basalt h !re be5 mapp$ & describ$4 ,!y are ( high] antiquity ?an ! ,upp] ,mioc5e /rata1 & h ?us probably be5 expos$ to prolong$ d5udation4 ,9 ext]nal aspect & int]nal /ructure !y pres5t ! close/ p>allel to ! ,c>bonif]\s & ,p]mian necks ( ,brita9 describ$ 9 ,books ,,vi4 & ,,vii4 ( ! pres5t "w4#bd ,among ! ,palozoic volcanoes ( ,brita9 _m admirable illu/rations ( ! ,puy type are to be f\nd4 ,_! cones are almo/ always entirely gone1 ?\gh traces ( !m occasionally appe>4 ,! necks t %[ ! position ( ! v5ts are 9 "s di/ricts cr[d$ toge!r z ?ickly z ^? ( ,auv]gne4 ,dur+ ! ,c>bonif]\s & ,p]mian p]iods 9 ,c5tral ,scotl&1 clu/]s ( su* little volcanoes mu/ h ris5 among %all[ lagoons & inl& %eets ( wat]1 ca/+ out _! a%es & p\r+ =? _! little /reams ( lava ov] ! wat]-bottom ar\nd !m & !n dy+ out4 ,z ^! eruptions took place 9 a region t 0 gradually subsid+1 ! cones & _! eject$ a%es & lavas 7 "o by "o subm]g$1 ! loos] mat]ials be+ wa%$ d[n & spread out among ! silt1 s& or mud1 & envelop+ ! rema9s ( any plants or animals t might be /rewn ov] ! floor ( ! lake or sea4 ,h5ce ! ,puys ( ,palozoic "t 9 ,brita9 h be5 pres]v$ ) extraord9>y fulness ( detail4 ,!y h be5 dissect$ by d5udation1 bo? among ! hills ( ! int]ior & along ! m>g9 ( ! sea4 ,_! /ructure c ?us be 9 "s respects made out ev5 m satisfactorily ?an t ( ! mu* y\ng] & m p]fect cones ( ,c5tral ,france4 ,footnote #bc3 ,! ,eifel di/rict has be5 fully describ$ by ,hibb]t1 ,von ,de*51 & o!r writ]s4 ,von ,de*5's little h&books to ! ,eifel & ,sieb5gebirge are useful guides4 ,footnote #bd3 ,^! ,wrtemb]g v5ts h be5 elaborately describ$ & discuss$ by ,pr(essor ,w4 ,branco ( ,tb+5 9 8 ,s*wab5s #abe ,vulkan-,embryon5 und d]5 tuff]flte ,ausbru*srhr51 das grs/e ,gebiet *emalig] ,ma>e auf d] ,erde1 ,/uttg>t1 #ahid4 iv4 ,,det]m9ation ,,( ,,! ,,relative ,,geological ,,dates ,,( ,,anci5t ,,volcanoes ,9 !mselves1 accumulations ( volcanic mat]ials d n furni% any exact or reliable evid5ce ( ! geological p]iod 9 :i* !y 7 erupt$4 ,! lavas ( ! e>ly ,palozoic ages may1 inde$1 on c>eful exam9ation1 be di/+ui%$ f ^? ( ,t]ti>y date1 b1 z we h se51 ! diff]5ce is r due to ! effects ( age & gradual alt]ation ?an to any inh]5t fundam5tal di/9ction betwe5 !m4 ,9 all ess5tial p>ticul>s ( composition & int]nal /ructure1 ! lavas ( ! ,cambrian or ,silurian p]iod resemble ^? ( ,t]ti>y & mod]n volcanoes4 ,! igne\s magmas :i* supply volcanic v5ts ?us appe> to h be5 v mu* :at !y are n[ f e>ly geological epo*s4 ,at lea/ no important diff]5ce1 accord+ to relative age1 has yet be5 satisfactorily e/abli%$ among !m4 ,b al?\gh ! rocks !mselves af=d no precise or tru/wor?y clue to _! date1 yet :]e !y h be5 int]calat$ contemporane\sly among fossilif]\s /ratifi$ =mations1 ( :i* ! geological horizon c be det]m9$ f includ$ organic rema9s1 x is easy to assign !m to _! exact place 9 geological *ronology4 ,a det]m9ation ( ?is k9d is only an application ( ! g5]al pr9ciple on :i* ! sequ5ce ( ! geological record is def9$4 ,a few illu/rations w suffice to make ?is po9t q obvi\s4 ,among ! volcanic tuffs 9 ! upp] "p ( ,sn[don v>i\s fossils occur1 :i* are id5tical ) ^? f\nd 9 ! well-kn[n ,bala ,lime/one4 ,z ! accept$ read+ ( su* evid5ce1 we conclude t ^! tuffs mu/ !re=e be ( ! same geological age z t lime/one4 ,n[ ! position ( ?is seam ( rock has be5 well e/abli%$ z a def9ite horizon 9 ! s]ies ( ,l[] ,silurian =mations4 ,& we consequ5tly )\t hesitation place ! eruptions ( ! ,sn[don volcano on t same plat=m1 & speak ( !m z belong+ to ! ,bala division ( ! ,l[] ,silurian p]iod4 ,aga91 9 ,we/ ,lo?ian ! tuffs & lavas eject$ f _m scatt]$ puys 7 int]/ratifi$ among %ales & lime/ones 9 :i* ! *>act]i/ic fossils ( ! ,c>bonif]\s ,lime/one are abundant4 ,!re _c1 !re=e1 be any d\bt t ^! eruptions 7 mu* y\ng] ?an ^? ( ,sn[don1 & t !y took place at ! "t :5 ! ,c>bonif]\s ,lime/one 0 be+ deposit$4 ,we ?us speak ( !m z belong+ to volcanoes :i* 7 active 9 t e>ly "p ( ! ,c>bonif]\s p]iod to :i* ! ?ick ,m\nta9 ,lime/one ( ,irel& & ,d]by%ire belongs4 ,z yet ano!r illu/ration ( ! det]m9ation ( geological age1 an example f ! plateau-type ( eruption may be giv54 ,! great basalt-plateaux ( ,antrim & ! ,inn] ,hebrides are built up ( lavas t lie uncon=mably on ! ,*alk4 ,!y are ?us prov$ to be lat] ?an ! ,cretace\s sy/em1 & ?is d$uction w\ld hold true ev5 if no organic rema9s 7 f\nd associat$ ) ! volcanic rocks4 ,b "h & !re1 int]calat$ betwe5 ! basalts1 lie lay]s ( %ale1 lime/one & tuff conta9+ well-pres]v$ rema9s ( plants :i* are recognizable z old] ,t]ti>y =ms ( vegetation4 ,?is fossil evid5ce def9itely places ! date ( ! eruptions 9 old] ,t]ti>y "t4 ,x is cle> t1 proce$+ on ?is basis ( reason+1 we may arrange ! successive volcanic eruptions ( any giv5 di/rict1 make out _! ord] ( sequ5ce 9 "t1 & ?us obta9 mat]ials = a consecutive hi/ory ( !m4 ,or1 proce$+ f t di/rict into o!r regions1 we may comp>e its volcanic ph5om5a ) !irs1 det]m9e ! relative dates ( _! respective eruptions1 & 9 ?is way compile a wid] hi/ory ( volcanic action 9 pa/ "t4 ,x is on ^! pr9ciples t ! g5]al & detail$ *ronology ( ! volcanic rocks ( ! ,briti% ,isles has be5 work$ out1 & t ! foll[+ *apt]s h be5 arrang$4 v4 ,,h[ ,,! ,,physical ,,geography ,,associat$ ,,) ,,anci5t ,,volcanoes ,,is ,,asc]ta9$ ,:ile ! mat]ials erupt$ f old volcanic v5ts tell pla9ly en\gh _! subt]ranean orig91 !y may leave u q 9 ! d>k z to ! conditions "u :i* !y 7 ?r[n out at ! surface4 ,yet a c>eful exam9ation ( ! /rata associat$ ) !m may ?r[ mu* light on ! circum/ances 9 :i* ! eruptions took place4 ,_m ( ! results ( su* exam9ation w be giv5 9 subsequ5t *apt]s4 ,i w "h submit illu/rations ( h[ f\r diff]5t phases ( physical geography dur+ =m] volcanic eruptions may be satisfactorily det]m9$4 ,illu/ration3 ,fig4 #ai4--,section illu/rat+ subm>9e eruptions2 alt]nations ( lavas & tuffs ) lime/ones & %ales full ( m>9e organisms4 #a4 ,subm>9e ,eruptions4--,z by f> ! l>ge/ accessible "p ( ! cru/ ( ! e>? consi/s ( old m>9e s$im5ts1 x is natural t ! volcanic records pres]v$ 9 t cru/ %\ld be ma9ly ^? ( subm>9e eruptions4 ,t _m lavas dur+ ! geological pa/ 7 p\r$ out ^u ! sea-bottom is pla9ly %[n by ! ?ick b$s ( m>9e organisms :i* !y h ov]spread & :i* lie above !m 7,fig4 #ai74 ,9 ,c5tral ,scotl&1 = example1 %eets ( basalt h fl[$ ov] a sea-bottom on :i* ?ick groves ( cr9oids1 bun*es ( coral & cr[ds ( sea-%ells 7 liv+4 ,n less /rik+ is ! evid5ce suppli$ by b&s ( tuff4 ,ar\nd ,lim]ick1 = in/ance1 ! ?ick ,c>bonif]\s ,lime/one is int]rupt$ by _m ?9 lay]s ( tuff m>k+ int]vals :5 %[]s ( volcanic du/ fell ov] ! sea-bottom1 kill+ (f ! organisms t liv$ !re4 ,b ! lime/one t ov]lies ^! volcanic int]calations is aga9 cr[d$ ) fossils1 prov+ t ! cr9oids1 corals & %ells once m spread ov] ! place & fl\ri%$ z abundantly z ev] above ! tuff4 ,! accompany+ diagram 7,fig4 #ai7 illu/rates ^! /atem5ts4 ,at ! bottom a ?ick mass ( lime/one 7l7 full ( cr9oids1 corals1 bra*iopods & o!r m>9e organisms be>s witness to a long "t ( repose1 :5 ! cle> sea-wat] teem$ ) life4 ,at la/ a volcanic explosion took place1 :i* ?rew out ! fir/ seam ( tuff 7t74 ,b ?is 0 only a transi5t int]ruption1 = ! accumulation ( calc>e\s s$im5t 0 imm$iately resum$1 & ! next b& ( lime/one 0 laid d[n4 ,!reaft] a m prolong$ or vigor\s eruption eject$ a l>g] mass ( du/ & /ones1 :i* fell ov] ! bottom & prev5t$ ! cont9uation ( ! lime/one4 ,b t ! sea /ill ab\nd$ 9 life is %[n by ! num]\s organisms imb$d$ 9 ! second /ratifi$ b& ( tuff4 ,at la/ an access ( volcanic vig\r gave v5t to a /ream ( slaggy lava1 :i* roll$ ov] ! sea-bottom & solidifi$ 9 ! ?ick %eet ( amydaloidal basalt m>k$ ,b4 ,?is outfl[ 0 foll[$ by a fur!r dis*>ge ( a%es & /ones1 :i*1 f _! abs5ce ( /ratification1 may be suppos$ to h be5 ! result ( a s+le explosion1 or at lea/ to h fall5 too rapidly = ! m>9e curr5ts to re>range !m 9 lay]s4 ,:5 ! wat] cle>$1 ! abundant sea-creatures return$1 & f _! cr[d$ rema9s lime/one once m ga!r$ ov] ! bottom4 ,yet ! volcanic hi/ory _h n !n rea*$ its close1 = aga9 !re came a dis*>ge ( a%es1 foll[$ by ! outp\r+ ( a second lava1 :i* consolidat$ z a %eet ( column> basalt 7,b'74 ,x is n necess>y1 9 ord] to prove ! eruptions to h be5 subm>9e1 t organic rema9s %\ld be f\nd 9 ! tuffs or betwe5 !m4 ,if ! volcanic ejections are int]calat$ among /rata :i* else:]e c be prov$ to be m>9e1 _! dis*>ge mu/ obvi\sly h tak5 place "u ! sea4 ,! v5t t dis*>g$ !m may h rais$ its head above ! sea-level1 b its lavas & tuffs 7 spread out ov] ! adjo9+ sea-floor4 #b4 ,lacu/r9e ,eruptions4--,! same l9e ( evid5ce furni%es pro( t "s volcanoes arose 9 inl& %eets ( wat]4 ,if _! products are int]/ratifi$ among s&/ones1 gravels & %ell-m>ls1 :]e9 ! rema9s ( l&-plants1 insects & lacu/r9e %ells1 are pres]v$1 we may be confid5t t ! eruptions took place 9 or ne> to "s lake-bas94 ,! old] lavas & tuffs ( ,c5tral ,france supply an in/ructive example ( su* an association4 ,9 ,brita91 ! abundant & ext5sive outp\r+ ( lavas & tuffs dur+ ! "t ( ! ,l[] ,old ,r$ ,s&/one probably occurr$ 9 l>ge lakes4 ,among ! s$im5ts ( ^! bodies ( wat]1 int]/ratifi$ betwe5 ! volcanic %eets1 rema9s ( l&-plants are abundant1 toge!r )1 "h & !re1 ^? ( myriapods wa%$ d[n f ! woodl&s1 & ( _m =ms ( ganoid fi%es4 ,illu/ration3 ,fig4 #bj4--;,diagram illu/rat+ volcanic eruptions on a riv]-pla94 #c4 ,fluviatile ,eruptions4--,volcanoes h sometimes aris5 on riv]-pla9s or on ! edges ( valleys & gorges1 & h p\r$ out _! lavas & dis*>g$ _! a%es ov] ! *annels or alluvial l&s ( ! /reams4 ,volcanic mat]ials1 usurp+ ! wat]-*annels1 bury or are int]/ratifi$ ) fluviatile s& or %+le1 conta9+ p]haps rema9s ( ! vegetation or animal life ( ! surr\nd+ l&4 ,!re may ?us be a con/ant %ift+ ( ! riv]-c\rses1 & a consequ5t deposit ( fluviatile s$im5t at _m successive levels among ! lavas & tuffs4 ,9 ,fig4 #bj "s ( ^! *anges are indicat$ 9 a s]ies ( b$d$ lavas 7l74 ,! l[] "p ( ! diagram %[s ! dy+ out ( a b$ ( riv] gravel 7g7 aga9/ ! slop+ end ( a lava-/ream1 & ! seal+ up ( ?is int]calation by a fre% outp\r+ ( lava4 ,high] up 9 ! diagram a section is %[n ( a gully or rav9e :i* has be5 cut out ( ! lavas by a /ream1 & has become *ok$ up ) wat]-worn detritus4 ,subsequ5t outfl[s ( lava h roll$ ov] ?is *annel & seal$ x up4 ,examples ( su* int]calations ( lava ) old riv] deposits1 & ( ! bury+ ( wat]-c\rses1 w be cit$ 9 ! acc\nt ( ! ,t]ti>y volcanic plateaux ( ,brita9 9 ,*apt] xxxviii4 #d4 ,t]re/rial ,eruptions4--,t volcanoes 9 =m] times broke out on l& z well z 9 wat] may readily be expect$4 ,b x is obvi\s t ! pro(s ( a t]re/rial orig9 may n be always easy to obta91 = e l&-surface is expos$ to d5udation2 & ?us ! relics ( ! eruptions ( "o age may be effac$ by ! w9ds1 ra9s1 fro/s & riv]s ( ! next4 ,9 assign+ any volcanic gr\p to a t]re/rial orig91 we may be guid$ p>tly by negative evid5ce1 su* z ! abs5ce ( all trace ( m>9e organisms 9 any ( ! s$im5t>y lay]s associat$ ) ! gr\p4 ,b su* evid5ce /&+ by itself w\ld n be satisfactory or suffici5t4 ,if1 h[ev]1 betwe5 ! %eets ( lava !re occur occasional depressions1 fill$ ) h>d5$ s$im5t full ( l&-plants1 ) possibly traces ( insects & o!r t]re/rial organisms1 we may ) "s confid5ce inf] t ^! silt$-up holl[s repres5t pools or lakes t ga!r$ on ! surface ( ! lava-%eets1 & into :i* ! vegetation ( ! surr\nd+ gr\nd 0 bl[n or wa%$4 ,ra9 fall+ on ! rugg$ surface ( a lava-field w\ld naturally ga!r into pools & lakes1 z ! bottoms ( ! holl[s became puddl$ by ! gradual decay ( ! rock & ! wa%+ ( f9e silt into ! crevices ( ! lava4 ,illu/ration3 ,fig4 #ba4--;,diagram illu/rat+ volcanic eruptions on a l&-surface4 ,aga91 x may be expect$ t prolong$ exposure to ! air w\ld give rise to dis9tegration ( ! lava & to ! consequ5t =mation ( soil4 ,t]re/rial vegetation w\ld naturally spr+ up on su* soil2 trees might take root ^u x4 ,h5ce1 if ano!r lava-flood delug$ ! surface1 ! soil & its vegetable mantle w\ld be entomb$ "u ! molt5 rock4 ,^! geological *anges are repres5t$ diagrammatically 9 ,fig4 #ba4 ,two holl[s among ! lavas are !re %[n to h be5 fill$ ) silt1 includ+ successive lay]s ( vegetation n[ conv]t$ into coal4 ,"o ( ! soils 7s7 is m>k$ betwe5 ! lavas1 & ! *>r$ /ump ( a tree ) its roots /ill 9 ano!r lay] ( soil high] up is se5 to h be5 engulph$ 9 ! ov]ly+ %eet ( melt$ rock4 ,admirable illu/rations ( ?is succession ( ev5ts are to be enc\nt]$ among ! great ,t]ti>y basaltic plateaux :i* cov] s l>ge an area 9 ! nor?-we/ ( ,europe4 ,n only has no trace ( any m>9e organism be5 f\nd among _! int]/ratifi$ s$im5t>y lay]s1 b !y h yield$ a t]re/rial flora :i* is pres]v$ 9 holl[s betwe5 ! successive %eets ( basalt4 ,a full acc\nt ( ^! rocks w be giv5 9 ,book ,,viii4 ,,*apt] ,v ,und]gr\nd ,phases ( ,volcanic ,action4 ,b4 ,mat]ials inject$ or consolidat$ b5ea? ! ,surface--,intrusive ,s]ies3 ,i4 ,v5ts ( ,eruption--i4 ,necks ( ,fragm5t>y ,mat]ials2 ii4 ,necks ( ,lava-=m ,mat]ials2 iii4 ,di/ribution ( ,v5ts 9 relation to ,geological ,/ructure-,l9es2 iv4 ,metamorphism 9 & ar\nd ,volcanic ,cones1 ,solfat>ic ,action2 v4 ,inw>d ,dip ( ,rocks t[>ds ,necks2 vi4 ,influ5ce ( contemporane\s ,d5udation ^u ,volcanic ,cones2 vii4 ,/ages 9 ! ,hi/ory ( old ,volcanic ,v5ts4 ,9 our pr(\nd ignorance ( ! nature ( ! e>?'s int]ior1 we "k z yet no?+ c]ta9 reg>d+ ! condition & di/ribution !re ( ^? molt5 mat]ials :i* =m ! prime visible s\rce ( volcanic en]gy4 ,by ! /udy ( volcanoes & _! products we le>n t ! fus$ sub/ances are n ev]y:]e precisely ! same & d n rema9 absolutely uni=m1 ev5 9 ! same volcanic region4 ,b 9 :at mann] & f :at causes ^! v>iations arise is /ill unkn[n4 ,we are fur!r aw>e t ! molt5 magma1 "u a c5tre ( volcanic di/urbance1 manife/s f "t to "t en]getic movem5ts :i* culm9ate 9 eruptions at ! surface4 ,b :at may be ! excit+ cause ( ^! movem5ts1 to :at dep? !y desc5d1 & ov] :at ext5t ( sup]ficies !y spread1 are matt]s reg>d+ :i* no?+ bett] ?an conjecture c z yet be (f]$4 ,x is true t1 9 "s cases1 a magma ( fairly uni=m composition has be5 erupt$ ov] a va/ tract ( ! e>?'s surface1 & mu/ h _h a correspond+ly wide ext5t )9 ! t]re/rial cru/4 ,?us 9 ! case ( ! old] ,t]ti>y volcanic eruptions ( ,nor?-,we/]n ,europe1 basalt ( practically ! same composition 0 dis*>g$ f ?\s&s ( fissures & v5ts di/ribut$ f ! s\? ( ,antrim nor?w>d beyond ! ,inn] ,hebrides1 ?r\gh ! *a9 ( ! ,f>oe ,isl&s & ov] ! :ole bread? ( ,icel&4 ,"u ! ,briti% ,isles alone1 ! subt]ranean res]voirs ( molt5 lavas mu/ h be5 at lea/ #dj1jjj squ>e miles 9 unit$ area4 ,if !y /ret*$ cont9u\sly nor?w>ds bel[ ! ,f>oe ,isl&s & ,icel&1 z is highly probable1 t is1 = #fjj miles fur!r1 _! total ext5t may h be5 comp>able to su* a region z ,sc&9avia4 ,0 ?is va/ und]gr\nd body ( lava "p ( a univ]sal liquid mass )9 ! globe1 or 0 x r ( ! nature ( "o or m lakes or l>ge vesicles )9 ! cru/8 ,we c only (f] speculation = answ]4 ,on ! o!r h&1 !re seems to be good pro( t 9 "s di/ricts1 bo? n[ & 9 =m] geological p]iods1 su* diff]5ces exi/ betwe5 ! mat]ials eject$ f v5ts n f> di/ant f ea* o!r z to %[ ! exi/5ce ( m limit$ di/9ct res]voirs ( liquid rock und]nea?4 ,"s ( ! que/ions "h ask$ w be fur!r dealt ) 9 lat] pages 9 connection ) su* geological evid5ce z c be produc$ reg>d+ !m4 ,b x w be f\nd t at e /ep 9 ! endeav\r to asc]ta9 ! orig9 ( volcanic ph5om5a difficulties pres5t !mselves :i* are n[ & may long rema9 insoluble4 ,i4 ,v5ts ( ,eruption ,x is a g5]al belief t ! fir/ /age 9 ! =mation ( a volcano ( ! ,vesuvian type by ! ef=ts ( subt]ranean en]gy is ! r5d+ ( ! t]re/rial cru/ 9 a l9e ( fissure4 ,"s ( ! mo/ rem>kable gr\ps ( active volcanoes on ! face ( ! globe are c]ta9ly plac$ 9 r[s1 z if !y _h ris5 along "s su* great r5ts4 ,! actual fissure1 h[ev]1 is n !re se51 & its exi/5ce is only a matt] ( probable inf]5ce4 ,und\bt$ly ! effect ( successive eruptions mu/ be to conceal ! fissure1 ev5 if x ev] reveal$ itself at ! surface4 ,:at is suppos$ to h m>k$ ! initial /ep 9 ! =mation ( a great volcano is occasionally repeat$ 9 ! subsequ5t hi/ory ( ! m\nta94 ,dur+ ! convulsive %ocks t prec$e & accompany an eruption1 ! sides ( ! cone1 & ev5 sometimes "p ( ! gr\nd beyond1 are r5t op51 occasionally = a di/ance ( sev]al miles1 & on ! fissures ?us =m$ m9or volcanoes are built up4 ,x is 9 ,icel&1 z already /at$1 t ! ph5om5a ( fissures are be/ display$4 ,!re ! great des]ts ( lava are f "t to "t dislocat$ by new l9es ( r5t1 :i* asc5d up to ! surface & /ret* = horizontal di/ances ( _m miles4 ,f ^! long n>r[ *asms lava fl[s out to ei!r side2 :ile cones ( slag & scori usually =m ^u !m4 ,?is int]e/+ eruptive phase w be m fully describ$ 9 ! *apt]s deal+ ) ! ,t]ti>y volcanic rocks ( ,brita94 ,!re c be no d\bt1 h[ev]1 t 9 a va/ numb] ( volcanic v5ts ( all geological p]iods no trace c be discov]$ ( _! connection ) any fissure 9 ! e>?'s cru/4 ,su* fissures may inde$ exi/ und]nea?1 & may h s]v$ z passages = ! asc5t ( lava to )9 a great] or less di/ance f ! surface4 ,b x is c]ta9 t volcanic en]gy has ! p[] ( bl[+ out an op5+ = itself ?r\gh ! upp] "p ( ! cru/ )\t ! exi/5ce ( any visible fissure !re4 ,:at may be ! limits ( dep? at :i* ?is mode ( communication ) ! out] air is possible we d n yet "k4 ,!y mu/ obvi\sly v>y greatly accord+ to ! /ructure ( ! t]re/rial cru/ on ! "o h&1 & ! am\nt & p]si/5ce ( volcanic en]gy on ! o!r4 ,we may suppose t :]e a fissure t]m9ates upw>d "u a great dep? ( ov]ly+ rock1 ! int]nal magma may rise up to ! end ( ! r5t1 & ev5 be inject$ lat]ally into ! surr\nd+ p>ts ( ! cru/1 b may be unable to complete ! =mation ( a volcano by op5+ a passage to ! surface4 ,b :]e ! ?ickness ( rock above ! end ( ! fissure is n too great1 ! expansive en]gy ( ! vap\rs absorb$ 9 ! magma may ov]come ! resi/ance ( t cov]1 & bl[ out an orifice by :i* ! volcanic mat]ials c rea* ! surface4 ,9 ! =mation ( new cones )9 ! hi/oric p]iod at a di/ance f any c5tral volcano1 ! exi/5ce ( an op5 fissure at ! surface has n be5 g5]ally obs]v$4 ,:51 = example1 ,monte ,nuovo 0 =m$1 x rose close to ! %ore among fields & g>d5s1 b )\t ! appe>ance ( any r5t f :i* its mat]ials 7 dis*>g$4 ,t 9 innum]able in/ances dur+ ! geological pa/1 simil> v5ts h be5 op5$ )\t ! aid ( fissures t rea*$ ! surface1 w be made cle> f ! evid5ce to be drawn f ! volcanic hi/ory ( ! ,briti% ,isles4 ,s abundant1 inde$1 are ^! in/ances t !y may be tak5 z prov+ t1 at lea/ 9 ! ,puy type ( volcanoes1 ! actual v5ts h g5]ally be5 bl[n out by explosions r ?an by ! asc5t ( fissures to ! op5 air4 ,9 cases :]e1 z 9 ,icel&1 fissures op5 at ! surface & dis*>ge lava !re1 ! *annel ( asc5t is ! op5 space betwe5 ! sev]$ walls ( ! r5t4 ,)9 ?is space ! lava w ev5tually cool & solidify z a dyke4 ,x is obvi\s t a comp>atively small am\nt ( d5udation w suffice to remove all trace ( ! connection ( su* a dyke ) ! /ream ( lava t issu$ f x4 ,among ! ?\s&s ( dykes belong+ to ! ,t]ti>y p]iod 9 ! ,briti% ,isl&s1 x is probable t _m may h s]v$ z l9es ( escape = ! basalt at ! surface4 ,b x is n[ app>5tly impossible to di/+ui% betwe5 ^? :i* _h su* a communication ) ! out] air & ^? t end$ upw>d )9 ! cru/ ( ! e>?4 ,! /ructure ( dykes w be subsequ5tly discuss$ among ! subt]ranean intrusions ( volcanic mat]ial4 ,9 an ord9>y volcanic orifice ! gr\nd-plan is usually irregul>ly circul> or elliptical4 ,if t portion ( ! cru/ ( ! e>? ?r\gh :i* ! v5t is drill$ %\ld be ( uni=m /ructure1 & w\ld ?us yield equally to ! effects ( ! volcanic en]gy1 we might anticipate t ! asc5t & explosion ( successive globul> masses ( highly heat$ vap\rs w\ld give rise to a cyl9drical pipe4 ,b 9 tru? ! rocks ( ! t]re/rial cru/ v>y greatly 9 /ructure2 :ile ! direction & =ce ( volcanic explosions are liable to *ange4 ,h5ce consid]able irregul>ities ( gr\nd-plan are to be look$ = among v5ts4 ,"s ( ^! irregul>ities are depict$ 9 ,fig4 #bb1 :i* repres5ts ! gr\nd plan ( "s v5ts f ! ,c>bonif]\s volcanic di/ricts ( ,scotl&4 ,!y are all drawn on ! same scale4 ,o!r examples w be cit$ 9 lat] *apt]s f ! same & o!r p>ts ( ! ,briti% ,isles4 ,"s ( ! mo/ m>k$ dep>tures f ! normal & simple type ( v5t occur :]e two orifices h be5 op5$ close to ea* o!r1 or :]e ! same v5t has %ift$ its position 7,figs4 #bi1 #abe1 #bje1 & #bad74 ,curi\sly irregul> or elongat$ =ms may ?us arise 9 ! resultant necks n[ visible at ! surface4 ,_m /rik+ examples ( ^! features may be se5 among ! ,c>bonif]\s & ,p]mian volcanoes to be aft]w>ds describ$4 ,occasionally :]e an op5 fissure has s]v$ z a v5t x has giv5 rise to a long dyke-l mass 7,no4 #a 9 ,fig4 #bb74 ,illu/ration3 ,fig4 #bb4--;,gr\nd-plans ( "s ,volcanic v5ts f ! ,c>bonif]\s di/ricts ( ,scotl&4 #a4 ,l9hope ,burn1 ne> ,mosspaul1 ,roxburgh%ire2 ! %ad$ p>ts are intrusions ( tra*ytic mat]ial4 #b4 ,hazelside ,hill1 two miles ,w4 f ,newca/leton1 ,roxburgh%ire4 #c4 ,/4 ,magdal5's1 ,l9li?g[4 #d4 ,s\?-we/ side ( ,coom's ,fell 7see ,fig4 #agd74 #e4 ,neck on ,greatmoor1 ,roxburgh%ire4 #f4 ,pe/] ,hill1 ,t>ras ,wat]4 #g4 ,head ( ,r\t+ ,burn1 ,s4,e4 side ( ,h>tsg>? ,fell1 ,liddesdale4 #h4 ,h>tsg>? ,fl[1 ,liddesdale4 ,! size ( a volcanic v5t may v>y indef9itely f a diamet] ( n m ?an a y>d or two up to "o or two or m miles4 ,z a rule1 ! small] ! v5ts ! m num]\sly are !y cr[d$ toge!r4 ,9 ! case ( l>ge c5tral volcanoes l ,etna1 :]e _m subsidi>y v5ts1 "s ( !m =m+ n inconsid]able hills1 may spr+ up along ! sides ( ! p>5t cone1 d5udation w ultimately remove all ! mat]ial t 0 heap$ up on ! surface1 & leave ! /umps or necks ( ! p>asitic v5ts 9 gr\ps ar\nd ! c5tral funnel4 ,ea* volcanic *imney1 by :i* vap\rs1 a%es or lava are dis*>g$ at ! surface1 may be conceiv$ to desc5d 9 a m or less ne>ly v]tical direction until x rea*es ! surface ( ! lava :5ce ! eruptions proce$4 ,aft] ! cessation ( volcanic activity1 ?is pipe w be left fill$ up ) ! la/ mat]ial dis*>g$1 :i* w usually take ! =m ( a rudely cyl9drical column rea*+ f ! bottom ( ! crat] d[n to ! lava-res]voir4 ,x w be obvi\s t no matt] h[ great may be ! d5udation ( ! volcano1 or h[ ext5sive may be ! removal ( ! v>i\s mat]ials dis*>g$ ov] ! surr\nd+ gr\nd1 ! pipe or funnel ) its column ( solid rock mu/ /ill rema94 ,no am\nt ( wa/e ( ! surface ( ! l& c efface t column4 ,successively l[] & yet l[] levels may be laid b>e 9 x1 b ! column itself goes /ill fur!r d[n4 ,x w cont9ue to make its appe>ance at ! surface until its roots are laid b>e 9 ! lava ( ! subt]ranean magma4 ,h5ce1 ( all ! relics ( volcanic action1 ! fill$-up *imney ( ! eruptive v5t is ! mo/ endur+4 ,save :]e x may h be5 ( ! less deep-seat$ nature ( a hornito ^u a lava-/ream1 we may reg>d x z practically p]man5t4 ,! full mean+ ( ^! /atem5ts w be be/ und]/ood f a consid]ation ( ! num]\s illu/rations to be aft]w>ds giv54 ,! /umps ( volcanic columns ( ?is nature1 aft] prolong$ d5udation1 g5]ally project above ! surr\nd+ gr\nd z r\nd$ or conical em95ces kn[n z ,necks 7,fig4 #bc4 ,see also ,figs4 #eb1 #hb1 #ajb1 #aji1 #abc1 #acc1 #add1 #agh1 #aib1 #aie1 #bjc1 #bjd1 #bji1 #bid1 #bih1 #cjf & #caj74 ,_! outl9es1 h[ev]1 v>y ) ! nature ( _! compon5t mat]ials4 ,! s(t] rocks1 su* z tuffs & agglom]ates1 are apt to assume ! =m ( smoo? domes or cones1 :ile ! h>d] & especially ! cry/all9e rocks rise into irregul>1 craggy hills4 ,occasionally1 inde$1 x may happ5 t a neck makes no prom95ce on ! surface ( ! gr\nd1 & its exi/5ce may only be discov]able by a c>eful exam9ation ( ! geological /ructure ( ! locality4 ,n[ & !n an old v5t w be f\nd n to =m a hill1 b to s9k into a holl[4 ,su* v>iations1 h[ev]1 h little or no ref]5ce to orig9al volcanic cont\rs 9 ! hi/ory ( ! localities :i* display !m4 ,!y arise ma9ly f ! diff]+ h>dness & /ructure ( ! mat]ials t h fill$ ! v5ts1 & ! consequ5t div]sity 9 ! am\nt ( resi/ance :i* !y h (f]$ to ! progress ( d5udation4 ,illu/ration3 ,fig4 #bc4--,view ( an old volcanic ,neck 7,! ,knock1 ,l>gs1 ,ayr%ire1 a v5t ( ,l[] ,c>bonif]\s age74 ,! mat]ials n[ f\nd 9 volcanic funnels are ( two k9ds3 #a/1 ,fragm5t>y1 d]iv$ f volcanic explosions2 & #bnd1 ,lava-=m1 aris+ f ! asc5t & consolidation ( molt5 rock )9 ! funnel4 i4 ,necks ( ,fragm5t>y ,mat]ials ,by f> ! mo/ satisfactory evid5ce ( a =m] volcanic orifice is furni%$ by a neck ( fragm5t>y mat]ials4 ,:]e bosses ( cry/all9e rock rise to ! surface & assume ! outw>d =m ( necks1 we _c always be c]ta9 t !y may n h be5 produc$ by subt]ranean intrusions t nev] effect$ any connection ) ! surface4 ,9 o!r words1 su* bosses may n m>k volcanic orifices at all1 ?\gh !y may h be5 "p ( ! und]gr\nd protrusions ( volcanoes 9 _! neighb\rhood4 ,b :]e ! *imney has be5 fill$ ) debris1 !re c be no d\bt t x truly m>ks ! site ( a once active volcano4 ,! fragm5t>y mat]ial is an eloqu5t memorial ( ! volcanic explosions t drill$ ! v5t1 kept x op51 & f9ally fill$ x up4 ,^! explosions c\ld n h tak5 place unless ! ela/ic vap\rs :i* caus$ !m _h f\nd an escape f ! pressure "u :i* !y lay )9 ! cru/ ( ! e>?4 ,n[ & !n1 inde$1 :]e ! outp\r+ ( lava or "s o!r cause has left cav]n\s spaces )9 ! cru/1 !re may conceivably be "s feeble explosion !re1 & "s trifl+ accumulation ( fragm5t>y mat]ials4 ,b we may reg>d x z practically c]ta9 t ! mass ( tumultu\s detritus n[ f\nd 9 volcanic necks c\ld n h be5 =m$ unless :]e a free passage _h be5 op5$ f ! molt5 magma und]nea? to ! out] surface ( ! planet4 ,consid]able div]sity may be obs]v$ 9 ! nature & arrangem5t ( ! fragm5t>y mat]ials 9 volcanic necks4 ,! *ief v>ieties may be arrang$ 9 f\r gr\ps3 7#a7 ,necks ( non-volcanic detritus2 7#b7 ,necks ( volcanic agglom]ate or tuff2 7#c7 ,necks ( agglom]ate or tuff ) a c5tral plug ( lava2 & 7#d7 ,necks ( agglom]ate or tuff ) ve9s1 dykes or "s lat]al irregul> mass ( lava4 7#a7 ,necks ( non-volcanic ,detritus4--,dur+ ! fir/ convulsive ef=ts ( a volcanic focus to f9d a v5t at ! surface1 ! explosions t ev5tually =m ! orifice d s by bl[+ out 9 fragm5ts ! solid rocks ( ! ext]ior ( ! t]re/rial cru/4 ,( ! detritus ?us produc$1 %ot up ! funnel & dis*>g$ into ! air1 "p may ga!r r\nd ! m\? ( ! op5+ & build up !re a cone ) an enclos$ crat]1 :ile "p w fall back into ! *imney1 ei!r to accumulate !re1 %\ld ! explosions cease1 or to be ?r[n out aga91 %\ld !y cont9ue4 ,9 ! feeble/ or mo/ transi5t k9ds ( volcanic en]gy1 ! explosive vap\rs may escape )\t any accompany+ asc5t ( ! molt5 magma to ! surface1 & ev5 )\t any s5sible dis*>ge ( volcanic a%es f t magma4 ,9 su* cases1 z ,i h already po9t$ out1 ! detritus ( ! non-volcanic rocks1 :atev] !y may be1 ?r\gh :i* volcanic en]gy has made an op5+1 accumulate 9 ! pipe & ev5tually consolidate !re4 ,examples ( ?is nature w be adduc$ 9 lat] *apt]s f ! volcanic di/ricts ( ,brita94 ,:]e only non-volcanic mat]ials fill up a v5t we may reasonably inf] t ! eruptions 7 comp>atively feeble1 nev] advanc+ beyond ! initial /age :5 ela/ic vap\rs made _! escape ) explosive viol5ce1 b did n lead to ! outfl[ ( lava or ! dis*>ge ( a%es4 ,9 ! great majority ( necks1 h[ev]1 traces ( ! e>lie/ eruptions h be5 de/roy$ by subsequ5t explosions1 & ! uprise ( ?or\ghly volcanic fragm5ts4 ,yet ev5 among ^! fragm5ts1 occasional blocks may be detect$ :i* h be5 deta*$ f ! rocks =m+ ! walls ( ! funnel4 ,! g5]al "n ( ,agglom]ate1 z already /at$1 is giv5 to all accumulations ( co>se1 usually un/ratifi$1 detritus 9 volcanic funnels1 irrespective ( ! li?ological nature ( ! mat]ials4 ,= fur!r & m precise designation1 :5 an agglom]ate is ma9ly made up ( fragm5ts ( "o p>ticul> rock1 ! "n ( t rock may be prefix$ z s&/one-agglom]ate1 granite-agglom]ate1 basalt-agglom]ate1 tra*yte-agglom]ate4 ,volcanic agglom]ate is a useful g5]al t]m t may include all ! co>s] detritus eject$ by volcanic action4 ,:]e volcanic explosions h be5 ( suffici5t viol5ce or long cont9uance1 ! upp] "p ( ! funnel may be left empty1 & on ! cessation ( volcanic activity1 may be fill$ ) wat] & become a lake4 ,! eject$ detritus left r\nd ! edge ( ! orifice sometimes h>dly =ms any wall1 ! crat]-bottom be+ b little bel[ ! level ( ! surr\nd+ gr\nd4 ,explosion-lakes are n infrequ5t 9 ,c5tral ,france & ! ,eifel 7,ma>e74 ,a m gigantic illu/ration is af=d$ by ! p]fectly circul> crat] ( ,coon ,butte 9 ,arizona1 ab\t #djjj feet 9 diamet] & #fjj feet deep4 ,x has be5 bl[n out 9 lime/one1 ! debris ( :i* =ms a ramp>t #bjj feet high ar\nd x4 ,examples w aft]w>ds be cit$ f ! ,t]ti>y volcanic plateaux ( ,nor?-,we/]n ,europe4 ,v5ts may also be =m$ by an engulphm5t or subsid5ce ( ! mat]ial1 l t :i* has tak5 place at ! great lava cauldron ( ,hawaii1 /ill an active volcano4 ,! picturesque ,crat] ,lake ( ,oregon is an admirable in/ance ( ?is /ructure4 7#b7 ,necks ( ,agglom]ate or ,tuff4--,9 ! va/ majority ( cases1 ! explosions t cle> out a funnel ?r\gh ! rocks ( ! upp] "p ( ! cru/ d n end by m]ely bl[+ out ^! rocks 9 fragm5ts4 ,! ela/ic vap\rs t escape f ! molt5 lava und]nea? are usually foll[$ by an uprise ( ! lava )9 ! pipe4 ,reliev$ f ! enorm\s pressure "u :i* x _h be=e la91 ! lava z x asc5ds is kept 9 ebullition1 or may be torn into bombs :i* are s5t :irl+ up into ! air1 or may ev5 be bl[n into ! f9e/ du/ by ! sudd5 expansion ( ! imprison$ /eam4 ,if its asc5t is arre/$ )9 ! v5t1 & a cru/ is =m$ on ! upp] surface ( ! lava-column1 ?is congeal$ cru/ may be disrupt$ & ?r[n out 9 scatt]$ pieces by successive explosions1 b may re-=m aga9 & aga94 ,illu/ration3 ,fig4 #bd4--,section ( neck ( agglom]ate1 ris+ ?r\gh s&/ones & %ales4 ,9 _m v5ts1 bo? 9 rec5t & 9 anci5t times1 volcanic progress has nev] advanc$ beyond ?is e>ly /age ( ! ejection ( /ones & du/4 ,! column ( lava1 ?\gh ris+ ne> en\gh to ! surface to supply by its ebullition abundant pyrocla/ic detritus1 co>se & f9e1 has n fl[$ out above gr\nd1 nor ev5 asc5d$ to ! top ( ! funnel4 ,x may h =m$1 at ! surface1 cones ( /ones & c9d]s ) enclos$ crat]s4 ,b !reaft] ! eruptions h ceas$4 ,! v5ts1 fill$ up ) ! fragm5t>y eject$ mat]ial1 h giv5 passage only to hot vap\rs & gases4 ,z ^! gradually ceas$1 ! volcanoes h become f9ally ext9ct4 ,d5udation has attack$ _! sides & cre/s4 ,if subm]g$ 9 ! sea or a lake1 ! cones h be5 wa%$ d[n1 & _! mat]ials h be5 /rewn ov] ! bottom ( ! wat]4 ,if /&+ on ! l&1 !y h be5 gradually levell$1 until p]haps only ! project+ knob or neck ( solidifi$ rubbi% 9 ea* funnel has rema9$ to m>k its site4 ,! buri$ column ( compact$ fragm5t>y mat]ial w survive z ! only memorial ( ! eruptions 7,fig4 #bd4 ,= views ( necks =m$ ( agglom]ate or tuff see ,figs4 #bc1 #hb1 #ajb1 #abc1 #add1 #agh1 #aib1 #bjc1 #bjd1 #bji1 #baj1 #bab1 #baf74 ,! volcanic agglom]ates ( su* v5ts sometimes include1 among _! non-volcanic mat]ials1 pieces ( rock :i* be> evid5ce ( hav+ be5 subject$ to consid]able heat 7see vol4 ii4 p4 #gh74 ,c>bonace\s %ales1 = in/ance1 h _h _! volatile con/itu5ts driv5 (f1 lime/ones h be5 conv]t$ into m>ble1 & a g5]al induration or bak+ may be p]ceptible4 ,9 o!r cases1 h[ev]1 ! fragm5ts exhibit no s5sible alt]ation4 ,fossilif]\s lime/ones & %ales (t5 reta9 _! organic rema9s s un*ang$ t specim5s tak5 out ( ! agglom]ate _c be di/+ui%$ f ^? ga!r$ f ! /rata ly+ 9 situ outside4 ,"s /ones h evid5tly be5 d]iv$ f a deep] "p ( ! *imney1 :]e !y h be5 expos$ to a high] temp]ature ?an o!rs1 or !y may h be5 la9 long] )9 ! influ5ce ( hot asc5d+ vap\rs4 ,! volcanic mat]ials 9 agglom]ate range 9 size f ! f9e/ du/ to blocks sev]al y>ds 9 l5g?1 ) occasionally ev5 mu* l>g] masses4 ,! proportions ( du/ to /ones v>y indef9itely1 ! f9] mat]ial sometimes m]ely fill+ 9 ! int]/ices betwe5 ! /ones1 at o!r times =m+ a consid]able "p ( ! :ole mass4 ,! /ones ( an agglom]ate may be angul> or subangul>1 b are m usually some:at r\nd$4 ,_m ( !m are obvi\sly pieces t h be5 brok5 f already solid rock & h _h _! edges r\nd$ by attrition1 probably by knock+ aga9/ ea* o!r & ! walls ( ! *imney z !y 7 hurl$ up & fell back aga94 ,_! frequ5tly angul> %apes negative ! supposition t !y c\ld h be5 produc$ by ! dis*>ge ( spurts ( /ill liquid lava4 ,z already /at$1 !y h probably be5 9 l>ge measure d]iv$ f ! viol5t disruption ( ! solidifi$ cake or cru/ on ! top ( ! column ( lava 9 ! pipe4 ,_m ( !m may h be5 brok5 (f f ! lay] ( congeal$ lava t p>tially coat$ ! r\gh walls ( ! funnel aft] successive uprises ( ! molt5 mat]ial4 ,among !m may be obs]v$ _m l>ge & small blocks t appe> to h be5 d]iv$ f ! disruption ( true lava-/reams1 z if b$s ( lava _h be5 pi]c$ 9 ! =mation ( ! v5t1 or z if ^? t congeal$ on ! slopes ( ! cone _h be5 brok5 up by subsequ5t explosions4 ,^! fragm5ts ( lava are sometimes /rongly amygdaloidal4 ,a *>act]i/ic feature1 inde$1 ( ! blocks ( volcanic mat]ial 9 ! agglom]ates is _! frequ5t cellul> /ructure4 ,_m ( !m may be describ$ z r\gh slags or scori4 ,^! h g5]ally come f ! spongy cru/ or upp] "p ( ! lava :]e ! imprison$ /eam1 reliev$ f pressure1 is able to exp& & ga!r into vesicles4 ,less frequ5tly evid5ce is obta9able t ! blocks 7 p>tially or :olly molt5 at ! "t ( expulsion4 ,sometimes1 = example1 a mass :i* pres5ts on "o side su* a brok5 face z to indicate t x came f already solidifi$ mat]ial1 w %[ on ! o!r t its /eam-vesicles h be5 pull$ out 9 su* a way z to con=m to ! r\nd$ surface ( ! block4 ,?is elongation c\ld only take place 9 lava t 0 n yet :olly consolidat$4 ,x seems to indicate t su* blocks 7 d]iv$ f a ?9 h>d5$ cru/ ly+ ^u /ill molt5 mat]ial1 & t !y c>ri$ up p>ts ( t mat]ial ) !m4 ,z ea* /one w5t :irl+ up ! funnel into ! op5 air1 its melt$ "p w\ld be drawn r\nd ! gyrat+ mass1 & w\ld rapidly cool !re4 ,9 o!r cases1 we enc\nt] true volcanic bombs1 t is1 r\nd$ or bomb-%ap$ blocks ( lava1 ) _! vesicles elongat$ all r\nd !m & con=m+ to _! sph]ical %ape4 ,sometimes su* blocks are s+ul>ly vesicul> 9 ! c5tre1 ) a m close-gra9$ cru/ on ! outside4 ,_! rapid c5trifugal motion dur+ flight w\ld all[ ( ! great] expansion ( ! dissolv$ /eam 9 ! c5tral "p ( ea* mass1 :ile ! out] p>ts w\ld be quickly *ill$1 & w\ld assume a m compact texture4 ,bombs ( ?is k9d are met ) among anci5t volcanic products1 &1 l ^? ( mod]n volcanoes1 h obvi\sly be5 produc$ by ! ejection ( spurts or gobbets ( lava f ! surface ( a mass 9 a /ate ( viol5t ebullition4 ,occasionally !y are holl[ inside1 ! rotation 9 ^! cases hav+ probably be5 exceptionally rapid4 ,pass+ f ! l>g] blocks to ! small] fragm5ts1 we notice ! great abundance ( nut-l subangul> or r\nd$ pieces ( lava 9 ! agglom]ates4 ,^! include lumps ( f9e gra9 n specially vesicul>1 & probably d]iv$ f ! disruption ( solidifi$ rock4 ,b 9 _m agglom]ates1 especially ^? associat$ ) ! outp\r+ ( basalts or o!r basic lavas 7z ^? ( ,c>bonif]\s & ,t]ti>y age describ$ 9 lat] *apt]s71 !y comprise also va/ numb]s ( v f9ely cellul> mat]ial or pumice4 ,^! pumice\s lapilli h be5 already allud$ to z +r$i5ts ( ! /ratifi$ tuffs4 ,b !y are /ill m *>act]i/ic ( ! necks1 & rea* !re a l>g] size1 rang+ f ! f9e/ gra9s up to lumps z l>ge z a h5's egg1 or ev5 l>g]4 ,! peculi> di/9ctions ( ?is eject$ pumice are ! extreme m9ut5ess ( its vesicles1 _! rem>kable abundance1 _! preval5t sph]ical =ms1 & ! ?9ness ( ! walls :i* sep>ate !m4 ,9 ^! respects !y pres5t a m>k$ contra/ to ! l>ge irregul>ly-%ap$ /eam-cavities ( ! outfl[+ lavas1 or ev5 ( ! scori 9 ! agglom]ates4 ,?is *>act]i/ic m9utely vesicul> pumice is basic 9 composition4 ,:]e n too mu* decay$1 x may be recogniz$ z a basic glass4 ,?us among ! rem>kable agglom]ates :i* fill up ! ,plioc5e or ,plei/oc5e v5ts ( ! ,velay1 ! fragm5ts consi/ ( a d>k v basic glass1 :i* encloses su* a multitude ( m9ute /eam-cavities t1 :5 se5 "u ! microscope1 !y are f\nd to be sep>at$ f ea* o!r by walls s ?9 t ! slice looks l a patt]n ( delicate lace4#be ,9 necks ( e>li] date1 su* z ^? ( old] ,t]ti>y1 & /ill m ( ,palozoic1 "t1 ! glass has g5]ally be5 alt]$ into "s palagonitic mat]ial4 ,footnote #be3 ,m4 ,b\le1 ,bull4 ,c>t4 ,gol4 ,france1 ,no4 #bh1 tome iv4 7#ahib7 p4 #aic4 ,?is f9ely pumice\s sub/ance appe>s to be peculi> to ! v5ts & to ! deposits ( tuff imm$iately d]iv$ f !m4 ,x is n f\nd1 s f> z ,i "k1 among any ( ! sup]ficial lavas1 &1 ( c\rse1 w\ld n be look$ = among intrusive rocks4 ,x 0 evid5tly a special product ( ! volcanic *imney1 z di/+ui%$ f ! mass ( ! magma bel[4 ,we may p]haps reg>ds x z 9 "s way due to a process ( quiet simm]+ )9 ! v5t1 :5 ! cont9ual passage ( asc5d+ vap\rs kept ! molt5 lava !re 9 ebullition1 & gave x its special fro?y or f9ely pumice\s "*4 ,! compact$ du/1 s& or gravelly detritus f\nd 9 necks1 & compris$ "u ! g5]al "n ( ,tuff1 consi/s p>tly ( ! f9] p>ticles produc$ dur+ ! viol5t disruption ( already solidifi$ rocks1 p>tly ( ! detritus aris+ f ! friction & impact ( /ones asc5d+ & desc5d+ above an active v5t dur+ times ( eruption1 & p>tly ( ! extremely light du/ or a% into :i* molt5 lava may be bl[n by viol5t volcanic explosions4 ,9 old volcanic necks1 :]e ! rocks h long be5 subject$ to ! influ5ce ( p]colat+ meteoric wat]1 x is n p]haps possible to discrim9ate1 except 9 a r\gh way1 ! products f ^! ?ree s\rces4 ,! m m9utely comm9ut$ mat]ial has g5]ally und]gone consid]able alt]ation1 s t "u ! microscope x seldom reveals any di/9ctive /ructures4 ,"h & !re 9 a slide1 traces may occasionally be detect$ ( loose volcanic microlites1 ?\gh m usually ^! c only be f\nd 9 lapilli ( alt]$ glass or f9ely pumice\s lava4 ,! composition ( ! detritus 9 a neck ( agglom]ate or tuff has almo/ always a close relation to t ( any lavas :i* may h be5 emitt$ f t v5t4 ,if ! lavas h be5 ( an acid "*1 su* z rhyolites1 felsites or obsidians1 ! pyrocla/ic mat]ials w almo/ always be f\nd to be also acid4 ,:]e1 on ! o!r h&1 ! lavas h be5 int]m$iate or basic1 s also w be ! tuffs & agglom]ates4 ,occasionally1 h[ev]1 z has already be5 po9t$ out1 f ! same or closely adjo9+ v5ts lavas ( v diff]5t *emical composition h be5 successively erupt$4 ,felsites or rhyolites h alt]nat$ ) diabases1 basalts or &esites4 ,9 su* cases1 a comm+l+ ( acid & basic detritus may be obs]v$1 z1 = example1 among ! volcanoes ( ! ,old ,r$ ,s&/one4 ,x has ev5 happ5$ sometimes t su* a mixture ( mat]ial has tak5 place :5 only "o class ( lavas has be5 p\r$ out at ! surface1 z 9 ! agglom]ates t fill v5ts among ! basalts ( ! ,inn] ,hebrides4 ,b we may be sure t1 ?\gh n dis*>g$ at ! surface1 ! lavas ( :i* pieces are f\nd 9 ! tuffs mu/ h ris5 high en\gh 9 ! v5ts to be actually bl[n out 9 a fragm5t>y =m4 ,! occurr5ce ( felsitic fragm5ts among ! o!rwise basic agglom]ates ( ,mull & ,skye w be describ$ 9 subsequ5t pages1 likewise ! int]calation ( rhyolitic detritus betwe5 ! basalts ( ,antrim4 ,a simil> association occurs among ! mod]n v5ts ( ,icel&4 ,among ! cont5ts ( ! tuffs & agglom]ates t occupy old volcanic v5ts1 "s are occasionally to be obs]v$ ( :i* ! s\rce is n easily conjectur$4 ,deta*$ cry/als ( v>i\s m9]als sometimes occur abundantly :i* 7 c]ta9ly n =m$ 9 situ1 b mu/ h be5 eject$ z loose lapilli ) ! o!r volcanic detritus4 ,:]e ^! cry/als belong to m9]als t ent] into ! composition ( ! lavas ( ! di/rict 9 :i* !y are f\nd1 !y may be reg>d$ z hav+ probably be5 d]iv$ f ! explosion ( su* lavas 9 ! v5ts1 ! molt5 magma be+ bl[n into du/1 & its already =m$ cry/als be+ lib]at$ & expell$ z sep>ate gra9s4 ,b x seems to be extremely r>e to f9d any neighb\r+ lava 9 :i* ! m9]als 9 "q are s l>gely & s p]fectly cry/alliz$ z !y are 9 ^! loose cry/als ( ! neck4 ,! beautifully complete cry/als ( augite f\nd 9 ! old tuffs ( ,vesuvius & on ! flanks ( ,/romboli may be p>allel$ among ,palozoic tuffs & agglom]ates 9 ,brita94 ,?us ! necks belong+ to ! ,ar5ig & ,ll&eilo volcanoes ( s\!rn ,scotl& are sometimes cr[d$ ) augite1 v>y+ f m9ute se$-l gra9s up to p]fectly =m$ cry/als z l>ge z hazel nuts4 ,! conditions "u :i* su* well-%ap$ idiomorphic m9]als 7 =m$ 7 probably diff]5t f ^? t gov]n$ ! cool+ & consolidation ( ! ord9>y lavas4 ,b besides ! m9]als t may be claim$ z belong+ to ! volcanic s]ies ( a di/rict1 o!rs occur n infrequ5tly 9 "s tuff-necks1 ! orig9 ( :i* is extremely puzzl+4 ,su* are ! l>ge felsp>s1 micas1 g>nets & ! v>i\s gems t h be5 obta9$ f necks4 ,! l>ge size ( "s ( ^! cry/als & _! frequ5tly p]fect cry/allographic =ms negative ! idea t !y c1 z a rule1 be d]iv$ f ! de/ruction ( any kn[n rocks1 ?\gh !y may sometimes be conceivably ! residue left aft] ! solution ( ! o!r con/itu5ts ( a rock by ! und]gr\nd magma1 l ! l>ge residual felsp>s enclos$ 9 "s dykes4 ,! cry/als 9 "q1 h[ev]1 seem r to po9t to "s *emical processes /ill unkn[n1 :i*1 9 ! dep?s ( a volcanic focus1 "u conditions ( pressure & temp]ature :i* we may speculate ab\t b c p]haps h>dly ev] imitate 9 our laboratories1 lead to ! elaboration ( ! diamond1 g>net1 sahlite1 sm>agdite1 zircon & o!r m9]als4#bf ,examples ( su* =eign or deep-seat$ cry/als w be describ$ f ! probably ,p]mian necks ( ,c5tral ,scotl&4 ,footnote #bf3 ,= li/s ( ! m9]als f\nd 9 ! diamond-be>+ necks ( ,kimb]ley1 see ,m4 ,b\tan 9 ,frmy's ,encyclopdie ,*imique 7#ahhf71 vol4 ii4 p4 #afh2 ,dr4 ,m4 ,bau]'s ,edel/e9kunde 7#ahie71 p4 #bbc4 ,:atsoev] may be ! s\rce & nature ( ! fragm5t>y mat]ials t fill old volcanic v5ts1 !y pres5t1 z a g5]al rule1 no def9ite arrangem5t 9 ! necks4 ,blocks ( all sizes are scatt]$ promiscu\sly ?r\gh ! agglom]ate1 j z !y fell back into ! *imney & came to re/ !re4 ,! l>g] masses are plac$ at all angles1 or /& on end1 & are sometimes especially conspicu\s 9 ! c5tre ( a neck1 ?\gh m usually disp]s$ ?r\gh ! :ole4 ,su* a ?or\ghly tumultu\s accumulation is precisely :at might be expect$ :]e explosions h tak5 place 9 /ill liquid & 9 already consolidat$ lavas1 & :]e ! mat]ials1 viol5tly dis*>g$ to ! surface1 h fall5 back & come f9ally to re/ 9 ! *imney ( ! volcano4 ,nev]!less1 ?is abs5ce ( arrangem5t sometimes gives place to a /ratification :i* becomes m di/9ct 9 proportion z ! mat]ial ( ! v5t passes f co>se agglom]ate into f9e tuff4 ,x is possible t ! exi/5ce & developm5t ( ?is /ructure dep5d on ! dep? at :i* ! mat]ials accumulate 9 ! funnel4 ,we may conceive1 = in/ance1 t 9 ! l[] p>ts ( ! *imney1 ! /ones & du/1 tumultu\sly fall+ & reb\nd+ f projections ( ! rugg$ walls1 w h>dly be likely to %[ mu* trace ( arrangem5t1 ?\gh ev5 !re1 if ! explosions cont9ue to keep an op5 ?\gh dim9i%+ passage 9 ! v5t1 alt]nations ( co>s] & f9] lay]s1 m>k+ v>y+ phases ( eruptivity1 may be =m$ 9 ! gradually height5+ pile ( agglom]ate4 ,rude indications ( "s su* alt]nations may sometimes be detect$ 9 :at are o!rwise q un/ratifi$ necks4 ,9 ! upp] "p ( a volcanic funnel1 h[ev]1 close to & ev5 )9 ! crat]1 ! conditions are n s unfav\rable to ! production ( a /ratifi$ arrangem5t4 ,z ! pipe is fill$ up1 & ! activity ( eruption less5s1 explosions may occur only f ! v middle ( ! orifice4 ,! debris t falls back into ! v5t w ga!r mo/ ?ickly r\nd ! walls1 :5ce x w slide d[n to ! c5tral1 /ill eruptive hole4 ,x w ?us assume a /ratifi$ arrangem5t1 ! successive lay]s ly+ at ! /eepe/ angles ( repose1 or f #cj to #ce1 & dipp+ d[n 9 an inv]t$ conical disposition t[>ds ! c5tre4 ,if ! process %\ld cont9ue long en\gh1 ! crat] itself may be p>tially or completely fill$ up ) detritus 7,fig4 #be74 ,( ?is gradual infill+ ( a volcanic *imney ) /ratifi$ agglom]ate & tuff1 examples belong+ to diff]5t geological p]iods w be cit$ 9 subsequ5t *apt]s4 ,i may "h especially allude to "o ( ! mo/ rec5tly obs]v$ & be/ m>k$ illu/rations1 :i* occurs on ! we/ side ( ,/rom1 9 ! ,f>oe ,isl&s 7see ,figs4 #caj1 #caa1 #cab74 ,a neck has !re be5 fill$ up ) co>se agglom]ate1 :i* is rudely /ratifi$1 ! lay]s dipp+ /eeply into ! c5tre1 :]e ! tumultu\s assemblage ( l>ge blocks no d\bt po9ts to ! f9al *ok+ up ( ! dim9i%$ orifice ( explosion4 ,! walls ( ! neck are ne>ly v]tical1 & consi/ ( ! b$d$ basaltic lavas ?r\gh :i* ! v5t has be5 op5$4 ,!y t]m9ate upw>d 9 a conical expansion1 evid5tly ! old crat]1 :i* has subsequ5tly be5 fill$ up by ! inroads ( sev]al lava-/reams f adjac5t v5ts4 ,x is "h manife/ t ! b$d$ agglom]ate belongs to ! upp]mo/ "p ( ! volcanic funnel4 ,illu/ration3 ,fig4 #be4--,neck fill$ ) /ratifi$ tuff4 ,a4 gr\nd plan2 ,b4 transv]se section4 ,:]e v5ts h be5 fill$ up ) tuff r ?an ) agglom]ate1 ! /ratifi$ /ructure is be/ develop$4 ,alt]nations ( co>s] & f9] detritus give rise to m or less def9ite lay]s1 :i*1 ?\gh incon/ant & irregul>1 s]ve to imp>t a di/9ctly /ratifi$ "* to ! mass4 ,:]e !re has be5 no subsequ5t di/urbance )9 a v5t1 ^! lay]s %[ ! same inw>d dip t[>ds ! c5tre j ref]r$ to1 at ! ord9>y angles ( repose4 ,n[ & !n1 :]e a neck ) ?is /ructure has be5 laid b>e on a bea*1 its d5ud$ cross-section pres5ts a s]ies ( conc5tric r+s ( /rata f ! walls t[>ds ! c5tre4 ,good illu/rations ( ^! features are suppli$ by ! probably ,p]mian necks ( ea/]n ,fife 7,figs4 #be ,a & #bag74bg ,footnote #bg3 ,see also ! sections ( v5ts on ! we/ coa/ ( ,/rom ,f>oes1 above ref]r$ to4 ,x has frequ5tly happ5$1 h[ev]1 t1 ow+ to subsid5ce ( ! mat]ials fill+ up ! v5ts or to lat] volcanic di/urbances1 ! compact$ tuffs h be5 brok5 up & ?r[n into v>i\s positions1 l>ge masses be+ ev5 plac$ on end4 ,among ! ,c>bonif]\s & ,p]mian necks ( ,c5tral ,scotl& su* dislocat$ & v]tical tuffs are ( common occurr5ce 7see ,figs4 #ade1 #bah74 ,if1 z is probable1 we are ju/ifi$ 9 reg>d+ ! /ratifi$ p>ts ( necks z indicative ( ! upp]mo/ p>ts ( volcanic funnels1 n f> f ! surface1 ! importance ( ?is inf]5ce w be be/ und]/ood :5 ! ,c>bonif]\s & ,p]mian volcanoes are describ$4 7#c7 ,necks ) a c5tral ,lava-plug4--,"s v5ts ( agglom]ate or tuff are pi]c$ by a plug ( lava1 z may be in/ructively se5 9 _m ( ! ,c>bonif]\s & ,p]mian necks ( ! c5tre & s\? ( ,scotl& 7,fig4 #bf2 comp>e also ,figs4 #adh1 #agd1 #bjg1 & #bbf74 ,:]e ?is /ructure %[s itself1 ! contra/ 9 h>dness & durability betwe5 ! m de/ructible fragm5t>y mat]ial & ! solid resi/+ lava leads to a topographical di/9ction 9 ! out] =ms ( necks4 ,! smoo? declivities ( ! friable tuffs are cr[n$ or int]rupt$ by m craggy features1 :i* m>k ! position ( ! h>d] intrusive rock4 ,illu/ration3 ,fig4 #bf4--,section ( neck ( agglom]ate 7a a7 ) plug ( lava 7b74 ,! plug1 l ! pipe up :i* x has ris51 is 9 g5]al irregul>ly circul> 9 gr\nd-plan4 ,x may be conceiv$ to be a column ( rock1 desc5d+ to an unkn[n dep? into ! int]ior1 ) a cas+ ( pyrocla/ic debris surr\nd+ x4 ,x may v>y consid]ably 9 ! proportion :i* its cross-section be>s to t ( ! surr\nd+ fragm5tal mat]ial4 ,sometimes x does n occupy m ?an a small "p ( ! :ole1 (t5 appe>+ 9 ! c5tre4 ,9 o!r cases1 x m ?an equals all ! re/ ( ! mat]ial 9 ! v5t1 :ile in/ances may be not$ :]e only occasional pat*es ( tuff or agglom]ate are visible betwe5 ! lava-plug & ! wall ( ! pipe4 ,f ^! we naturally pass to ! second type ( v5t1 :]e no fragm5t>y mat]ial is to be se51 b :]e ! *imney is n[ entirely fill$ ) "s massive once-molt5 rock4 ,a neck ) a lava-plug probably conta9s ! records ( two /ages 9 volcanic progress1 ! fir/ ( :i*1 indicat$ by ! tuff or agglom]ate1 0 conf9$ to ! dis*>ge ( fragm5t>y mat]ials2 :ile ! second1 %[n by ! lava-plug1 belong$ to ! "t :51 aft] ! e>li] explosions1 lava asc5d$ 9 ! v5t & solidifi$ !re1 ?us br++ ! eruptions f t p>ticul> orifice to an end4 ,:]e a small c5tral column ( lava rises ?r\gh ! tuff1 we may suppose t ! funnel _h be5 ma9ly *ok$ up by ! accumulation 9 x ( eject$ detritus1 :i* 0 compact$ to a solid mass adh]+ to ! wall ( ! funnel1 b leav+ a c5tral orifice to be kept op5 by ! gradually wan+ en]gy ( ! volcano4 ,by a f9al ef=t t impell$ molt5 rock up t duct & all[$ x to consolidate !re1 ! op]ations ( ! v5t 7 br\ght to a close4 ,:]e1 on ! o!r h&1 only occasional /rips ( tuff or agglom]ate are to be f\nd betwe5 ! lava-plug & ! wall ( ! pipe1 ! la/ uprise ( lava may be suppos$ to h be5 prec$$ by m vigor\s explosions :i* cle>$ ! ?roat ( ! volcano1 driv+ out ! accumulat$ detritus & leav+ only scatt]$ pat*es adh]+ to ! sides ( ! funnel4 ,!re is1 no d\bt1 "s d[nw>d limit to ! production ( fragm5t>y mat]ial1 & if we c\ld lay b>e successive levels 9 ! *imney ( a volcano we %\ld f9d ! agglom]ate ev5tually replac$ entirely by lava4 ,! mat]ials ( ! lava-plugs v>y widely 9 composition4 ,sometimes !y are rem>kably basic1 & pres5t rocks ( ! picrite or limburgite type2 9 o!r cases !y are ?or\ghly acid rocks su* z felsite & granophyre4 ,_m int]m$iate v>ieties may be f\nd betwe5 ^! extremes4 ,x is notewor?y t1 9 di/ricts :]e ! lavas erupt$ to ! surface h be5 &esitic or basaltic1 ! mat]ial :i* has f9ally solidifi$ 9 ! v5ts is (t5 m acid 9 composition1 tra*ytic rocks be+ specially frequ5t4 ,illu/ration3 ,fig4 #bg4--,section ( agglom]ate neck 7a a7 ) dykes & ve9s 7b b74 7#d7 ,necks ) ,dykes1 ,ve9s1 or irregul> intrusions ( ,lava4--,:ile ! pres5ce ( a c5tral plug ( lava 9 a neck ( fragm5tal mat]ial may indicate t ! v5t 0 /ill to "s ext5t op51 !re is ano!r /ructure :i* seems to po9t to ! asc5t ( lava aft] ! funnel has be5 *ok$ up4 ,num]\s in/ances h be5 obs]v$ :]e lava has be5 =c$ upw>d ?r\gh r5ts 9 a mass ( tuff or agglom]ate1 & has solidifi$ !re 9 ! =m ( dykes or ve9s 7,fig4 #bg74 ,illu/rations ( ?is /ructure ab\nd among ! ,c>bonif]\s & ,p]mian necks ( ,brita94 ,"h1 aga91 ?\gh on a less m>k$ scale1 ! contra/ 9 ! am\nt & "* ( ! wea!r+ ( ! two gr\ps ( rock gives rise to correspond+ topographical features1 :i* are especially obs]vable 9 cliffs & coa/-sections1 :]e ! dykes & ve9s project out ( ! tuffs z d>k prom95t walls 7,figs4 #ace1 #adi1 #aff1 #afh1 #bai1 #bba1 #bbb74 ,^! intrusive injections are g5]ally irregul> 9 _! =ms1 ! lava hav+ evid5tly be5 driv5 ?r\gh a mass ( mat]ial :i*1 n hav+ yet consolidat$ suffici5tly to acquire a jo9t$ /ructure1 af=d$ few dom9ant l9es ( division along :i* x c\ld asc5d4 ,n[ & !n1 h[ev]1 %>ply def9$ dykes or ve9s1 :i* at a di/ance look l d>k ribbons1 may be se5 runn+ v]tically or at a high angle1 & ) a /raight or wavy c\rse1 ?r\gh ! f9e compact$ tuff ( a v5t4 ,frequ5tly ! inject$ mat]ial has f\nd its readie/ l9e ( asc5t along ! walls ( ! funnel1 betwe5 ! tuff & ! surr\nd+ rocks4 ,occasionally x has made its way into r5ts 9 ^! rocks1 z well z into ! body ( ! neck4 ,x is wor?y ( rem>k 9 pass+ t complete consolidation ( ! fragm5t>y mat]ial does n appe> to be always requisite 9 ord] to all[ ( ! =mation ( su* fissures z are ne$$ = ! production ( dykes4 ,a s+ul>ly int]e/+ illu/ration ( ?is fact may be se5 on ! nor!rn cre/ ( ! out] crat] ( ! ,puy ,p>i\ 9 ,auv]gne4 ,a dyke ( &esite #h or #aj feet broad may !re be trac$ runn+ = a di/ance ( ab\t #cjj y>ds ?r\gh ! loose mat]ial ( ! cone4 ,! rock is highly vesicul>1 & ! vesicles h be5 elongat$ 9 ! direction ( ! c\rse ( ! dyke s z to imp>t a some:at fissile /ructure to ! mass4 ,!re c be little d\bt t ! dykes & ve9s :i* trav]se necks ( agglom]ate belong to "o ( ! clos+ phases 9 ! hi/ory ( ! v5ts 9 :i* !y occur4 ,!y c\ld only h be5 inject$ aft] ! pipes _h be5 s *ok$ up t explosions _h almo/ or entirely ceas$1 & eruptions _h consequ5tly become ne>ly or q impossible4 ,!y %[1 h[ev]1 t volcanic en]gy /ill cont9u$ to manife/ itself by impell+ ! molt5 magma into ^! ext9ct funnels1 :ile at ! same "t x may h be5 actively dis*>g+ mat]ials f o!r /ill op5 v5ts 9 ! same neighb\rhood4 ,) reg>d to ! composition ( ^! dykes & ve9s1 x may be rem>k$ t 9 a di/rict ( acid lavas !y may be expect$ to be felsitic or rhyolitic1 sometimes granophyric4 ,:]e1 on ! o!r h&1 ! lavas p\r$ out at ! surface h be5 int]m$iate or basic1 ! ve9s 9 ! necks may be &esites1 basalts or o!r /ill m basic comp\nds4 ,b x is obs]vable1 z 9 ! case ( ! lava-plugs1 t ! injections into ! necks may be mu* m acid ?an any ( ! sup]ficial lavas4 ,! adv5t ( acid mat]ial 9 ! lat] "p ( a volcano's hi/ory has be5 already allud$ to1 & _m examples ( x w be giv5 9 ?is "w4 ,aft] all explosions & eruptions h ceas$1 heat$ vap\rs may /ill = a long p]iod cont9ue to make _! way upw>d ?r\gh ! loose spongy detritus fill+ up ! v5t4 ,! asc5t ( su* vap\rs1 & m p>ticul>ly ( /eam1 may induce consid]able metamorphism ( ! agglom]ate1 z is m p>ticul>ly notic$ at p4 #ga4 ii4 ,necks ( ,lava-=m ,mat]ial ,! second type ( neck is t 9 :i* ! volcanic pipe has be5 entirely fill$ up ) "s massive or cry/all9e rock4 ,z already rem>k$1 x is n always possible to be c]ta9 t bosses ( rock1 hav+ ! ext]nal =m ( necks ( ?is k9d1 m>k ! sites ( actual volcanic orifices4 ,eruptive mat]ial t has nev] rea*$ ! surface1 b has be5 inject$ into ! cru/ ( ! e>?1 has sometimes solidifi$ !re 9 =ms :i*1 :5 subsequ5tly expos$ by d5udation1 pres5t a deceptive resemblance to true volcanic necks4 ,ea* example mu/ be exam9$ by itself1 & its probable orig9 mu/ be det]m9$ by a consid]ation ( all ! circum/ances connect$ ) x4 ,:]e o!r evid5ce exi/s ( volcanic activity1 su*1 = in/ance1 z ! pres5ce ( b$d$ tuffs or int]calat$ %eets ( lava1 ! occurr5ce ( neck-l em95ces or bosses ( felsite1 &esite1 dol]ite1 basalt or o!r eruptive rock1 w\ld furni% a presumption t ^! m>k$ ! sites ( "s ( ! active v5ts ( ! p]iod to :i* ! tuffs & lavas belong$4 ,if a neck-l em95ce ( ?is k9d 7 f\nd to possess a circul> or elliptical gr\nd-plan1 & to desc5d v]tically l a huge pill> into ! cru/ ( ! e>?2 if ! surr\nd+ rocks 7 b5t d[n t[>ds x & alt]$ 9 ! mann] :i* ,i %all aft]w>ds describe 9 detail2 if1 moreov]1 ! mat]ial compos+ ! em95ce 7 asc]ta9$ to be closely relat$ petrographically to "s p>ts ( ! surr\nd+ volcanic s]ies1 x might ) "s confid5ce be set d[n z m>k+ ! place ( "o ( ! active v5ts f :i* t s]ies 0 eject$4 ,! *ief contra/ 9 ext]nal =m betwe5 ?is type ( neck & t =m$ ( fragm5t>y mat]ial arises f diff]5ces 9 ! relative durability ( _! compon5t sub/ance4 ,! v>i\s k9ds ( lava-=m rock f\nd 9 necks are1 z a :ole1 mu* h>d] & m inde/ructible ?an agglom]ates & tuffs4 ,consequ5tly bosses ( !m are apt to /& out m prom95tly4 ,!y m\nt into high] po9ts1 pres5t /eep] declivities1 & are sc>p$ into m rugg$ crags4 ,b ess5tially !y are *>act]iz$ by simil> conical outl9es1 & by ris+ 9 ! same solit>y & abrupt way f l[] gr\nd ar\nd !m 7see ,figs4 #aji1 #acc1 & #aie1 #bid74 ,illu/ration3 ,fig4 #bh4--,section ( neck fill$ ) massive rock4 ,v>i\s jo9t-/ructures may be obs]v$ 9 ^! necks4 ,9 "s cases !re is a t5d5cy to sep>ate into jo9ts p>allel to ! b\nd+ walls1 & occasionally ?is arrangem5t goes s f> t ! rock has acquir$ a fissile /ructure z if x 7 compos$ ( v]tical /rata4 ,9 o!r in/ances1 ! rock %[s a column> /ructure1 ! columns div]g+ f ! out] m>g91 or curv+ inw>ds1 or display+ v>i\s irregul> gr\p+s4 ,m usually1 h[ev]1 ?is jo9t+ is s indef9ite t no satisfactory connection c be trac$ betwe5 x & ! walls ( ! orifice 9 :i* ! rock has solidifi$4 ,"s ( ! mo/ rem>kable examples ( necks ev] figur$ & describ$ are ^? to :i* att5tion 0 call$ by ,capta9 ,dutton z display$ 9 ! ,zuni plateau ( ,new ,mexico1 :]e1 amid wide d5ud$ %eets ( basalt1 num]\s prom95t crags m>k ! sites ( eruptive v5ts4 ,! basalt ( ^! em95ces is column>1 ! columns /&+ or ly+ 9 all sorts ( attitudes1 & 9 mo/ cases curv$4#bh ,9 ! ,upp] ,velay1 9 ,c5tral ,france1 num]\s conspicu\s domes & cones ( phonolite rise amid/ ! mu*-worn basalt-plateau ( t region 7,fig4 #cde74 ,_m in/ances w be cit$ 9 lat] *apt]s f ! ,briti% ,isles4 ,footnote #bh3 ,u4,s4 ,geol4 ,survey1 #f? ,annual ,report1 #ahhd-he1 p4 #agb4 iii4 ,di/ribution ( ,v5ts 9 ,relation to ,geological ,/ructure-l9es ,:]e ! positions ( true volcanic necks c be accurately det]m9$1 x is int]e/+ to /udy _! di/ribution & _! relation to ! ma9 l9es ( geological /ructure ar\nd !m4 ,sometimes a di/9ct l9e> arrangem5t c be detect$ 9 _! gr\p+4 ,^? ( ! ,l[] ,old ,r$ ,s&/one ( ,c5tral ,scotl&1 = in/ance1 c be foll[$ 9 l9es = di/ances ( _m miles 7,map ,no4 ,,iii74 ,yet :5 we try to trace ! connection ( su* an arrangem5t ) any kn[n great l9es ( dislocation 9 ! t]re/rial cru/1 we c seldom e/abli% x satisfactorily4 ,9 ! case ( ! ,scotti% ,old ,r$ ,s&/one j cit$1 x is obvi\s t ! v5ts 7 op5$ along a broad belt ( subsid5ce betwe5 ! m\nta9s ( cry/all9e s*i/ on ! nor?1 & ^? ( convolut$ ,silurian /rata on ! s\?1 ei!r m>g9 ( t belt be+ subsequ5tly1 if n !n1 def9$ by l9es ( p[]ful fault4 ,no v5ts h ris5 along ^! faults1 nor has any relation be5 detect$ betwe5 ! sites ( ! volcanic foci & dislocations 9 ! area ( anci5t depression4 ,inde$1 x may be ass]t$ ( ! v5ts ( ,brita9 t !y are usually entirely indep5d5t ( any faults t trav]se at lea/ ! upp] visible "p ( ! e>?'s cru/4 ,!y sometimes rise close to su* l9es ( fracture )\t t\*+ !m1 b !y are equally well develop$ :]e no fractures are to be f\nd4 ,n[ & !n "o ( !m may be obs]v$ ris+ along a l9e ( fault1 b su* a co9cid5ce c\ld h>dly fail occasionally to happ54 ,f ! evid5ce 9 ! ,briti% ,isles1 x is q c]ta9 t if volcanic v5ts h1 z is possible1 ris5 pref]ably along l9es ( fissure 9 ! t]re/rial cru/1 ^! l9es are seldom ^? ( ! visible sup]ficial faults1 b mu/ lie mu* deep]1 & are n g5]ally prolong$ upw>d to ! surface4 ,! frequ5t recurr5ce ( volcanic outbur/s at successive geological p]iods f ! same or adjac5t v5ts seems to po9t to ! exi/5ce ( l9es or po9ts ( weakness deep d[n 9 ! cru/1 )9 rea* ( ! int]nal molt5 magma1 b f> b5ea? ! horizon ( ! /ratifi$ =mations at ! surface1 ) _! m sup]ficial displacem5ts4 ,:ile sometimes runn+ 9 l9es1 old volcanic v5ts ( ! ,vesuvian & ,puy types (t5 occur also 9 scatt]$ gr\ps4 ,two or ?ree may be f\nd toge!r )9 an area ( a few hundr$ y>ds4 ,!n may come an int]val :]e none1 or possibly only a solit>y individual1 may appe>4 ,& beyond t space may rise ano!r sporadic gr\p4 ,^! features are well exhibit$ by ! ,c>bonif]\s & ,p]mian s]ies ( ,scotl&1 to ! acc\nt ( :i* ! read] is ref]r$4 ,a l>ge neck may h a numb] ( small] ones plac$ ar\nd x1 j z a mod]n ,vesuvian cone has small] p>asitic cones ^u its flanks4 ,an in/ructive example ( ?is arrangem5t is to be se5 at ! great v5t ( ! ,braid ,hills belong+ to ! ,l[] ,old ,r$ ,s&/one & describ$ 9 ,*apt] xx4 ,o!r in/ances may be cit$ f ! ,c>bonif]\s & ,p]mian volcanic s]ies 7see ,figs4 #ij1 #adh1 #bac74 ,n infrequ5tly ! irregul>ities 9 ! gr\nd-plan ( a neck1 z already rem>k$1 may be acc\nt$ = on ! supposition t !y m>k ! site ( m ?an "o v5t4 ,sometimes1 inde$1 x is possible to demon/rate ! exi/5ce ( two or ev5 m v5ts :i* h be5 successively op5$ ne>ly on ! same spot4 ,! fir/ orifice hav+ become *ok$ up1 ano!r has brok5 out a little to "o side1 :i* 9 turn ceas+ to be effective f ! same or "s o!r cause1 has be5 succe$$ by a ?ird 7,fig4 #bi74 ,! ?ree cones & crat]s ( ! little isl& ( ,volcanello supply a s+ul>ly p]fect rec5t in/ance ( ?is /ructure 7,fig4 #bad74 ,"h ! funnel has twice %ift$ its position1 ea* cone becom+ successively small] & p>tially effac+ t :i* prec$$ x4 ,9 ,auv]gne1 ! ,puy de ,p>i\ has long be5 celebrat$ z an example ( a fre% c9d]-cone p>tially effac+ an e>li] "o4 ,9 ! mu* d5ud$ ,palozoic volcanic tracts ( ,brita91 :]e ! cones h long s9ce disappe>$ & only ! /umps ( ! volcanic cyl9d]s are left1 _m illu/rations occur ( a simil> displacem5t ( ! funnel1 especially among ! volcanoes ( ! ,c>bonif]\s sy/em4 ,among ! irregul>ities ( necks t may indicate a connection ) l9es ( fissure1 ref]5ce may be made "h to dykes or dyke-l masses ( agglom]ate :i* are sometimes to be se5 among ! volcanic di/ricts ( ,brita94 ,9 ^! cases ! fragm5t>y mat]ials1 in/ead ( ly+ 9 a m or less cyl9drical pipe1 appe> to fill up a long fissure4 ,we may suppose t ! explosions :i* produc$ !m did actually occur 9 fissures in/ead ( 9 ord9>y v5ts4 ,! rem>kable ,icel&ic fissures ) _! long r[s ( c9d] cones are d\btless1 at lea/ 9 _! upp] p>ts1 l>gely fill$ up ) slag & scori4 ,"s illu/rations ( ?is /ructure w be giv5 9 ! acc\nt ( ! ,c>bonif]\s volcanic rocks ( ,scotl& 7see ,no4 #a 9 ,fig4 #bb74 ,illu/ration3 ,fig4 #bi4--,successive %ift+s ( v5ts giv+ rise to d\ble or triple cones4 ,a1 gr\nd-plan2 ,b1 v]tical section4 ,!re is yet ano!r consid]ation 9 reg>d to ! =m & size ( necks :i* des]ves att5tion4 ,:]e ! actual m>g9 ( a neck & its l9e ( v]tical junction ) ! rocks ?r\gh :i* x has be5 drill$ c be se51 !re is no room = dispute z to ! diamet] ( ! orig9al funnel1 :i* mu/ h be5 t ( ! actual neck4 ,b 9 _m cases x is impossible to obs]ve ! b\nd>y2 n m]ely because ( sup]ficial soil or drift1 b occasionally because ! volcanic detritus ext5ds beyond ! actual limits ( ! funnel4 ,9 su* cases ! necks h reta9$ "s portion ( ! orig9al volcanic cone :i* accumulat$ on ! surface ar\nd ! eruptive v5t4 ,x may ev5 *ance t :at appe>s to be a l>ge neck w\ld be consid]ably r$uc$ 9 diamet]1 & might be %[n to include m ?an "o pipe if all ?is out] cas+ c\ld be remov$ f x4 ,9 ,fig4 #cj1 = example1 a section is giv5 ( a neck 7n7 f :i* on ! "r-h& side all ! cone & surr\nd+ tuffs 7t7 h be5 remov$ by d5udation1 ! orig9al =m ( ! volcano be+ sugge/$ by ! dott$ l9es4 ,on ! left side1 h[ev]1 ! tuffs :i* 7 int]/ratifi$ ) ! contemporane\s s$im5ts are /ill connect$ ) ! neck1 d5udation n hav+ yet sev]$ !m f x4 ,! ov]ly+ /rata 7l1 l7 :i* orig9ally ov]spread ! ext9ct volcano h be5 b5t into an anticl9e1 & ! neck ( ! v5t has ?us be5 laid b>e by ! removal ( ! cre/ ( ! ar*4 ,illu/ration3 ,fig4 #cj4--,section to %[ ! connection ( a neck ) a cone & surr\nd+ b$d$ tuffs4 ,! in/ances :]e a /ructure ( ?is k9d is conceal$ are probably few] 9 numb] 9 proportion to _! antiquity4 ,b among ,t]ti>y cones !y may p]haps n be s r>e4 ,! possibility ( _! occurr5ce %\ld be kept 9 view dur+ ! inve/igation ( ext9ct volcanoes4 ,! t]m ,neck ought n prop]ly to be appli$ to su* degrad$ volcanic cones4 ,! true neck /ill rema9s pres]v$ 9 ! inside ( !m4 ,z illu/rative ( ! /ructure "h ref]r$ to1 ,i may cite ! example ( ! ,sal9e ,hill 7,fig4 #adh7 & ( ,l>go ,law 7,fig4 #bbf71 bo? 9 ,fife4 iv4 ,metamorphism 9 & ar\nd ,volcanic ,v5ts--,solfat>ic ,action ,! prolong$ asc5t ( hot vap\rs1 /ones1 du/ & lava1 9 ! funnel ( a volcano mu/ necess>ily affect ! rocks ?r\gh :i* ! funnel has be5 driv54 ,we may !re=e expect "s signs ( alt]ation 9 ! mat]ial =m+ ! walls ( a volcanic neck4 ,! nature ( ! metamorphism w no d\bt dep5d1 9 ! fir/ place1 on ! "* & duration ( ! ag5ts produc+ x1 & 9 ! second1 on ! susceptibility ( ! rocks to und]go *ange4 ,m]e heat w indurate rocks1 bak+ s&/one1 = in/ance1 into qu>tzite1 & %ales into porcellanite4 ,b !re w almo/ inv>iably be causes ( alt]ation o!r ?an m]e high temp]ature4 ,wat]-vap\r1 = in/ance1 has probably always be5 "o ( ! mo/ abundant & mo/ p[]ful ( !m4 ,! copi\s evolution ( /eam f volcanoes is "o ( _! mo/ *>act]i/ic features at ! pres5t day1 & t x 0 equally s 9 pa/ "t seems to be put beyond "q by ! con/antly recurr+ vesicul> /ructure 9 anci5t lavas & 9 ! lapilli & eject$ blocks ( old agglom]ates & tuffs4 ,direct exp]im5t has demon/rat$1 9 ! h&s ( v>i\s skilful obs]v]s1 f ! "t ( ,sir ,james ,hall to t ( ,pr(essor ,daubre1 h[ p[]fully rocks are act$ ^u :5 expos$ to sup]heat$ vap\r ( wat] "u great pressure4 ,b ! /eam ( volcanoes (t5 conta9s o!r vap\rs or m9]aliz+ ag5ts dissolv$ 9 x1 :i* increase its metamorphic influ5ce4 ,! m9]al acids1 = in/ance1 mu/ ex]t a p[]ful effect 9 corrod+ mo/ m9]als & rocks4 ,at ! ,solfat>a ( ,naples & at o!r volcanic orifices 9 diff]5t p>ts ( ,italy1 consid]able alt]ation is se5 to be due to ?is cause4 ,be>+ ^! well-kn[n facts 9 m9d1 we may be prep>$ to f9d v>i\s pro(s ( metamorphism ar\nd & )9 old volcanic v5ts4 ,! surr\nd+ rocks are g5]ally mu* h>d5$ imm$iately contigu\s to a neck1 :e!r its mat]ials be fragm5tal or massive4 ,s&/ones1 = example1 are (t5 m>k$ly blea*$1 acquire ! vitre\s lu/re & texture ( qu>tzite1 lose _! usual fissility1 break irregul>ly into angul> blocks1 & on an expos$ surface project above ! level ( ! unalt]$ p>ts beyond4 ,%ales are bak$ into a k9d ( porcela9-l sub/ance4 ,coal-seams are entirely de/roy$ = economic purposes1 hav+ be5 burnt into a k9d ( c9d] or fus$ into a bli/]$ slag-l mass4 ,lime/ones likewise lose _! usual blui%-grey t9t1 become :ite & h>d1 & assume ! sacc>oid texture ( m>ble4 ,! di/ance to :i* ?is metamorphism ext5ds f ! wall is1 among ! expos$ necks 9 ,brita91 small] ?an might be anticipat$4 ,?us ,i h seldom be5 able to trace x among ^? ( ,c>bonif]\s or ,p]mian age = m ?an #ae or #bj y>ds 9 ord9>y ar5ace\s & argillace\s /rata1 ev5 :]e e detail ( a neck & its surr\nd+s has be5 laid b>e 9 plan ^u a bea*4 ,! alt]ation seems to rea* fur!/ 9 c>bonace\s seams1 su* z coals4 ,x is evid5t t ! elem5t ( "t mu/ ent] into ! "q ( ! am\nt ( metamorphism produc$ 9 ! t]re/rial cru/ imm$iately surr\nd+ a volcanic pipe4 ,a volcano1 ( :i* ! eruptions beg9 & end )9 an int]val ( a few days or h\rs1 _c be expect$ to h _h mu* metamorphic influ5ce on ! rocks ?r\gh :i* its v5t 0 op5$4 ,on ! o!r h&1 ar\nd a funnel :i* s]v$ = _m c5turies z a *annel = ! escape ( hot vap\rs1 a%es or lava to ! surface1 !re c\ld h>dly fail to be a consid]able am\nt ( alt]ation4 ,! abs5ce or comp>atively slight developm5t ( metamorphism at ! ,c>bonif]\s & ,p]mian necks ( ,scotl& may p]haps be reg>d$ z "s indication t ^! volcanoes 7 g5]ally %ort-liv$4 ,on ! o!r h&1 m ext5sive alt]ation may be tak5 z po9t+ to a long] cont9uance ( eruptive vig\r4 ,! same causes :i* h induc$ metamorphism 9 ! rocks surr\nd+ a volcanic v5t might obvi\sly effect x also among ! fragm5t>y mat]ials by :i* ! v5t may h be5 fill$ up4 ,:5 ! eruptions ceas$ & ! funnel 0 left *ok$ ) volcanic debris1 hot vap\rs & gases w\ld no d\bt /ill cont9ue = a "t to f9d _! way upw>d ?r\gh ! loose or p>tially compact$ mass4 ,9 _! asc5t !y w\ld p]meate ?is mat]ial1 & 9 ! end produce 9 x a s]ies ( *anges simil> to1 & possibly ev5 m pron\nc$ ?an1 ^? traceable 9 ! walls ( ! v5t4 ,in/ances ( ?is k9d ( metamorphism w be cit$ 9 ! foll[+ *apt]s 7see 9 p>ticul> p4 #djd74 v4 ,inw>d ,dip ( ,docks t[>ds ,necks ,"o conclud+ obs]vation requires to be made reg>d+ ! relation ( old volcanic necks to ! rocks :i* imm$iately surr\nd !m4 ,:]e a v5t has be5 op5$ ?r\gh massive rocks1 su* z granite1 felsite1 &esite or basalt1 x is g5]ally difficult or impossible to det]m9e :e!r !re has be5 any displacem5t ( ^! rocks1 beyond ! disruption ( !m caus$ by ! explosions t blew out ! orifice4 ,b :]e ! pipe has be5 drill$ ?r\gh /ratifi$ rocks1 especially :5 ^! /ill lie ne>ly flat1 ! planes ( /ratification usually supply a ready te/ & measure ( any su* movem5t4 ,inve/igation ( ! volcanic rocks ( ,brita9 has %[n me t :]e any displacem5t c be detect$ at a neck1 x is almo/ inv>iably 9 a d[nw>d direction4 ,! /rata imm$iately ar\nd ! v5t t5d to dip t[>ds x1 :atev] may be _! preval5t incl9ation 9 ! gr\nd beyond 7,fig4 #bd74 ,?is is ! rev]se ( ! position :i* might h be5 expect$4 ,x is s frequ5t1 h[ev]1 t x appe>s to indicate a g5]al t5d5cy to subsid5ce at ! sites ( volcanic v5ts4 ,aft] copi\s eruptions1 l>ge cav]n\s spaces may conceivably be left at ! roots ( volcanoes1 & ! mat]ials t h fill$ ! v5ts1 los+ support und]nea?1 w t5d to gravitate d[nw>ds1 & if firmly weld$ to _! surr\nd+ walls may drag ^! irregul>ly d[n ) !m4 ,examples ( su* sagg+ /ructures are abundantly to be se5 among ! dissect$ v5ts ( ! ,c>bonif]\s & ,p]mian volcanic s]ies ( ,scotl&4 vi4 ,influ5ce ( ,contemporane\s ,d5udation ^u ,volcanic ,cones ,x mu/ be rememb]$ t =m] v5ts1 except ^? ( ! lat] geological p]iods1 are reveal$ at ! surface n[ only aft] ext5sive d5udation4 ,z a rule1 ! volcanoes t =m$ !m appe>$ & cont9u$ 9 eruption dur+ p]iods ( g5]al subsid5ce1 & 7 "o by "o subm]g$ & buri$ b5ea? subaque\s deposits4 ,we c conceive t1 :ile a volcanic cone 0 s9k+ "u wat]1 x might be s]i\sly alt]$ 9 =m & height by waves & curr5ts4 ,if x consi/$ ( loose a%es & /ones1 x might be entirely levell$1 & its mat]ial might be /rewn ov] ! floor ( ! sea or lake 9 :i* x /ood4 ,b1 z has be5 already po9t$ out1 ! de/ruction ( ! cone w\ld /ill leave ! *ok$-up pipe or funnel f :i* ! mat]ials ( t cone _h be5 eject$4 ,?\gh1 dur+ ! subsid5ce1 e outw>d ve/ige ( ! actual volcano might disappe>1 yet ! agglom]ate or lava t solidifi$ 9 ! funnel und]nea? w\ld rema94 ,& if ^! mat]ials _h ris5 "s way )9 ! cone or crat]1 or if !y rea*$ at lea/ a high] level 9 ! funnel ?an ! surr\nd+ wat]-bottom or l&-surface1 ! de/ruction ( ! cone might leave a project+ knob or neck to be surr\nd$ & cov]$ by ! accumulat+ s$im5ts ( ! "t4 ,x is ?us evid5t t ! levell+ ( a cone ( loose a%es dur+ gradual subsid5ce1 & ! deposition ( a contempor>y s]ies ( s$im5t>y deposits1 might give rise to a true neck1 :i* w\ld be coeval ) ! geological p]iod ( ! volcano itself4 ,9 practice x is extremely difficult to decide h[ f> any n[ visible neck may h be5 r$uc$ to ! condition ( a m]e /ump or core ( a volcano be=e be+ buri$ "u ! /ratifi$ accumulations ( its "t4 ,9 e case ! exi/5ce ( ! neck is a pro( ( d5udation1 & p]haps1 9 mo/ cases1 ! *ief am\nt ( t d5udation is to be ascrib$ n to ! era ( ! orig9al volcano1 b to ! comp>atively rec5t int]val t has elaps$ s9ce1 9 ! progress ( degradation1 ! volcanic rocks1 aft] be+ long buri$ )9 ! cru/1 7 once m laid b>e by ! cont9u\s wa/e & l[]+ ( ! level ( ! l&4 vii4 ,/ages 9 ! ,hi/ory ( old ,volcanic ,v5ts ,let u n[ try to foll[ ! successive /ages 9 ! hi/ory ( a volcano aft] its fires _h q burnt out1 & :51 sl[ly s9k+ 9 ! wat]s ( ! sea or lake :]e9 x _h bur/ =?1 x 0 buri$ "u an ev]-gr[+ accumulation ( s$im5t>y mat]ial4 ,! s&1 mud1 calc>e\s ooze1 %ell-banks1 or :atev] may h be5 ! s$im5t t 0 ga!r+ !re1 gradually crept ov] ! subm]g$ cone or neck1 & w\ld no d\bt be m or less mix$ ) any volcanic detritus :i* waves or curr5ts c\ld /ir up4 ,if ! cone escap$ be+ levell$1 or if x left a project+ neck1 ?is subaque\s feature w\ld be entomb$ & pres]v$ b5ea? ^! detrital deposits4 ,hundr$s or ?\s&s ( feet ( /rata might be laid d[n ov] ! site ( ! volcano1 :i* w\ld !n rema9 hidd5 & pres]v$ = an indef9ite p]iod1 until 9 ! c\rse ( geological revolutions x might once aga9 be br\ght to ! surface4 ,^! successive *anges involve no !ory or supposition4 ,!y mu/ obvi\sly h tak5 place aga9 & aga9 9 pa/ "t4 ,t !y actually did occur is demon/rat$ by _m examples 9 ! ,briti% ,isles4 ,i ne$ only ref] "h to ! int]e/+ cases br\ght to light by m9+ op]ations 9 ! ,dairy coal-fields ( ,ayr%ire1 :i* are m fully describ$ 9 ,*apt] xxvii4 7p4 #dcc74 ,9 t di/rict a numb] ( cones ( tuff1 "o ( :i* is #gjj feet 9 height1 h be5 met ) 9 ! c\rse ( bor+ & m9+ = iron/one & coal4 ,! well-kn[n m9]al seams ( ! coal-field c be foll[$ up to & ov] ^! hidd5 hills ( volcanic tuff :i* 9 ! progress ( d5udation h n yet be5 laid b>e 7,fig4 #adf74 ,! subsid5ce :i* c>ri$ d[n ! wat]-bottom & all[$ ! volcanic v5ts to be entomb$ 9 s$im5t>y deposits may h be5 9 mo/ cases tol]ably equable1 s t at any giv5 po9t ^! deposits w\ld be s5sibly horizontal4 ,b subsequ5t t]re/rial di/urbances might s]i\sly affect ?is regul>ity4 ,! s$im5t>y =mations1 pil$ above ea* o!r to a great dep?1 & acquir+ solidity by compression1 might be ?r[n into folds1 dislocat$1 upheav$ or depress$4 ,! buri$ volcanic funnels w\ld1 ( c\rse1 %>e 9 ! effects ( ^! di/urbances1 & ev5tually might be s squeez$ & brok5 z to be ) difficulty recognizable4 ,x is possible t "s ( ! extreme /ages ( su* subt]ranean commotions are reveal$ among ! ,dalradian rocks ( ,scotl&4 ,c]ta9 gre5 s*i/s :i* 7 evid5tly orig9ally s$im5ts1 & probably tuffs1 are associat$ ) num]\s sills & bosses ( eruptive mat]ial4 ,! way 9 :i* ^! v>i\s rocks are gr\p$ toge!r /rik+ly sugge/s a s]ies ( volcanic products1 "s ( ! cru%$ bosses recall+ ! =ms ( true necks 9 y\ng] =mations4 ,b !y h be5 s enorm\sly compress$ & %e>$ t ! v lavas :i* orig9ally 7 massive amorph\s cry/all9e rocks h pass$ into fissile hornbl5de-s*i/s4 ,illu/ration3 ,fig4 #ca4--;,diagram illu/rat+ ! gradual em]g5ce ( buri$ volcanic cones ?r\gh ! influ5ce ( prolong$ d5udation4 ,among ! ,palozoic sy/ems ( ,brita91 h[ev]1 :]e consid]able fracture & displacem5t h tak5 place1 examples ( successive /ages 9 ! reappe>ance ( buri$ volcanic cones & necks may be ga!r$ 9 abundance4 ,z an illu/rative diagram ( ! process ( revelation by ! gradual d5udation ( an upheav$ tract ( c\ntry1 ,fig4 #ca may be ref]r$ to 7comp>e also ,fig4 #adg74 ,"h ?ree volcanic v5ts are repres5t$ 9 diff]5t /ages ( re-em]g5ce4 ,9 ! fir/ 7,a7 we see a cone & funnel :i*1 aft] hav+ be5 buri$ "u s$im5t>y deposits 7s1 s17 h be5 tilt$ up by subt]ranean movem5ts4 ,! ov]ly+ /rata h be5 br\ght )9 ! influ5ce ( d5udation1 & _! expos$ basset edges along ! pres5t surface ( ! l& 7g1 g7 be> witness to ! loss :i* !y h suff]$4 ,already1 9 ! progress ( degradation1 a portion ( ! volcanic mat]ials :i*1 eject$ f t v5t1 7 int]/ratifi$ ) ! contemporane\s s$im5ts ( ! surr\nd+ sea-floor1 has be5 expos$ at t4 ,a geologi/ com+ to t volcanic int]calation w\ld be sure t x po9t$ to ! exi/5ce ( "s volcanic v5t 9 ! neighb\rhood1 b )\t fur!r evid5ce he w\ld be unable to tell :e!r x lay to "r or left1 :e!r x 0 n[ at ! surface or lay /ill buri$ "u cov] ( ! /ratifi$ deposits :i* 7 laid d[n ^u x4 ,9 ! second or c5tral example 7,b7 we h a pipe & cone :i* h be5 simil>ly di/urb$4 ,b 9 ?is case d5udation has proce$$ s f> z to reveal ! cone & ev5 to cut away a portion ( x1 z %[n by ! dott$ l9es to ! "r h&4 ,ow+1 h[ev]1 to ! g5]al incl9ation ( ! rocks t[>ds ! left1 t side ( ! cone1 toge!r ) ! tuffs or lavas connect$ ) x1 /ill lies buri$ & protect$ "u cov] ( ! s$im5t>y =mations 7s1 s74 ,! ?ird example 7,c7 %[s a mu* m advanc$ /age ( de/ruction4 ,"h ! :ole ( ! cone has be5 worn away4 ,all ! lavas & tuffs :i* 7 eject$ f x t[>ds ! "r h likewise disappe>$1 & /rata old] ?an ! eruptions ( ?is v5t n[ come to ! surface !re4 ,to ! left1 h[ev]1 a little portion ( its lavas /ill rema9s at l1 ?\gh all ! int]v5+ volcanic mat]ial has be5 remov$4 ,t solit>y fragm5t ( ! outp\r+s ( ?is volcano once ext5d$ fur!r to ! left h&1 b ! occurr5ce ( ! l>ge dislocation 7f7 has c>ri$ ?is ext5sion = d[n bel[ ! surface4 ,! v5t 9 ?is in/ance1 ow+ to its position1 has suff]$ m f d5udation ?an ! o!r two4 ,yet1 judg$ by ! size ( its neck1 x 0 probably l>g] ?an ei!r ( !m1 & ?rew out a m ext5sive pile ( volcanic mat]ial4 ,its funnel has be5 fill$ ) agglom]ate 7a71 ?r\gh :i* a c5tral plug ( lava 7p7 has asc5d$1 & into :i* dykes or ve9s 7d1 d71 ! la/ ef=ts ( eruption1 h be5 inject$4 ,?is diagram w s]ve to illu/rate ! fact already s (t5 insi/$ on1 t al?\gh d5udation may entirely remove a volcanic cone1 & also all ! lavas & tuffs :i* issu$ f x1 ! actual fill$-up pipe _c be s effac$1 b is practically p]man5t4 ,,*apt] ,,vi ,und]gr\nd ,phases ( ,volcanic ,action--cont9u$4 ,,ii4 ,subt]ranean ,movem5ts ( ! ,magma3 i4 ,dykes & ,ve9s2 ii4 ,sills & ,laccolites2 iii4 ,bosses 7,/ocks1 ,culots7--,conditions t gov]n ! ,intrusion ( ,molt5 ,rock )9 ! ,t]re/rial ,cru/4 ,,ii4 ,subt]ranean ,movem5ts ( ! ,magma ,9 ! =ego+ pages att5tion has be5 m specially direct$ to ^? aspects ( volcanic en]gy :i* reveal !mselves above gr\nd & 9 eruptive v5ts4 ,we h n[ to consid] ! v>i\s ways 9 :i* ! molt5 magma is inject$ into ! cru/ ( ! e>?4 ,su* injection mu/ obvi\sly take place dur+ ! expulsion ( volcanic mat]ials to ! surface4 ,if ! explosive viol5ce ( an eruption1 or ! concomitant movem5ts ( ! e>?'s cru/1 %\ld lead to ruptures among ! subt]ranean rocks1 ! molt5 magma w be =c$ into ^! r5ts4 ,x is evid5t t ?is may happ5 ei!r ) or )\t any dis*>ge ( lava at ! surface4 ,x may be ei!r entirely a plutonic1 t is1 a deep-seat$ ph5om5on1 or x may be "p ( a truly volcanic s]ies ( ev5ts4 ,x is cle> t1 by ! /udy ( old volcanoes t h _h _! /ructure laid b>e by d5udation1 we may hope to obta9 fre% light 9 reg>d to "s ( ! m deeply-seat$ features ( volcanic en]gy1 :i* 9 a mod]n volcano are entirely conceal$ f view4 ,a little reflection w conv9ce u t ! conditions = consolidation )9 ! cru/ are s diff]5t f ^? at ! surface t we may expect !m to make !mselves visible 9 ! int]nal *>act]s ( ! rocks4 ,an ess5tial di/9ction betwe5 und]gr\nd propulsions ( molt5 rock & sup]ficial outfl[s ( ! same mat]ial lies 9 ! fact t :ile ! latt] are free to take any %ape :i* ! =m & slope ( ! gr\nd may p]mit1 ! subt]ranean injections1 l metal p\r$ into a m\ld1 are always b\nd$ by ! walls ( ! ap]ture into :i* !y are ?ru/4 ,accord+1 !re=e1 to ! %ape ( ?is ap]ture a conv5i5t classification ( su* intrusions may be made4 ,:]e ! molt5 mat]ial has ris5 up v]tical fissures or irregul> cracks1 x has solidifi$ z ,dykes & ,ve9s4 ,:]e x has be5 ?ru/ betwe5 ! divisional planes ei!r ( /ratifi$ or un/ratifi$ rocks1 s z to =m b$s1 ^! are conv5i5tly kn[n z ,sills1 ,laccolites or ,intrusive ,%eets4 ,:]e x has tak5 ! =m ( l>ge cyl9drical masses1 :i*1 asc5d+ ?r\gh ! cru/1 appe> at ! surface 9 r\nd$1 elliptical or irregul>ly-%ap$ em95ces1 ^! are call$ ,bosses 7,/ocks1 ,culots74 ,fur!r contra/s betwe5 ! sup]ficial & subt]ranean consolidation ( molt5 mat]ial are to be f\nd 9 ! respective textures & m9ute /ructures ( ! rocks4 ,! deep-seat$ intrusions are commonly *>act]iz$ by a g5]al & m>k$ly great] co>s5ess ( cry/allization ?an is possess$ by lavas p\r$ out at ! surface4 ,?is diff]5ce ( texture1 obvi\sly 9 great measure ! result ( sl[] cool+1 %[s itself 9 acid1 int]m$iate1 & basic magmas4 ,a lava :i* at ! surface has cool$ z a f9e-gra9$1 compact black basalt1 9 :i* nei!r ) ! nak$ eye nor ) ! l5s c ! con/itu5t m9]als be di/9ctly det]m9$1 may conceivably be repres5t$ at ! roots ( its p>5t volcano by a co>se-textur$ gabbro1 9 :i* ! felsp>s & pyrox5es may h gr[n into cry/als or cry/all9e aggregates an in* or m 9 l5g?4 ,mr4 ,idd+s has po9t$ out t ! v>i\s porphyrites :i* =m ! dykes & sills ( ,electric ,peak are connect$ ) a c5tral boss ( co>sely cry/all9e diorite4#bi ,examples ( ! same relation f diff]5t volcanic c5tres 9 ,brita9 w be cit$ 9 lat] *apt]s4 ,footnote #bi3 #ab? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey 7#ahij-ia71 p4 #eie4 ,?is great] co>s5ess ( texture is %[n by microscopic exam9ation to be accompani$ by o!r notable diff]5ces4 ,9 p>ticul>1 ! glassy residuum1 or its devitrifi$ repres5tatives1 :i* may be s frequ5tly detect$ among ! cry/als ( outfl[+ lavas1 is less (t5 traceable 9 ! body ( subt]ranean intrusive rocks1 ?\gh x may sometimes be notic$ at _! out] m>g9s :]e !y h be5 rapidly *ill$ by contact ) ! cool upp] "p ( ! cru/ into :i* !y h be5 impell$4 ,v>i\s m9]als1 ! con/itu5ts ( :i* exi/ 9 ! orig9al magma1 b :i* may be h>dly or n all recognisable 9 ! sup]ficial lavas1 h _h leisure to cry/allize out 9 ! deep-seat$ intrusions & appe> sometimes among ! compon5ts ( ! g5]al body ( ! rock1 or z well-t]m9at$ cry/als 9 its drusy cavities4 ,consid]able ?\gh ! v>iations may be betwe5 ! petrographical *>act]s ( ! intrusive & extrusive rocks ( a giv5 di/rict & ( ! same eruptive p]iod1 !y appe> g5]ally to lie )9 su* limits z to sugge/ a g5etic relation betwe5 ! :ole s]ies4 ,conditions ( temp]ature & pressure1 & ! ret5tion or escape ( ! absorb$ vap\rs :i* play s l>ge a "p 9 volcanic activity1 mu/ ex]cise great influ5ce on ! cry/allization ( con/itu5t m9]als1 & on ! consolidation & ultimate texture ( ! rocks4 ,sl[ cool+ "u great pressure & ) ! m9]aliz+ vap\rs /ill l>gely reta9$ seems to be pre-em95tly fav\rable = ! production ( a holocry/all9e texture 9 deep-seat$ portions ( ! magma1 :ile rapid cool+ "u m]ely atmosph]ic pressure & ) a cont9u\s dis5gagem5t ( vap\rs1 appe>s to be requir$ = ! f9] gra91 m glassy /ructure1 & m vesicul> "* ( lavas p\r$ out at ! surface4 ,besides ^! diff]5ces1 h[ev]1 !re is evid5ce ( a migration ( ! con/itu5t m9]als 9 ! body ( l>ge intrusive masses be=e consolidation4 ,9 p>ticul>1 ! heavi] & m basic con/itu5ts travel t[>ds ! cool+ m>g91 leav+ ! c5tral portions m acid4 ,?is subject w be m fully consid]$ 9 connection ) ! int]nal con/itution ( ,bosses1 & "s ,briti% examples w !n be cit$4 ,ref]5ce1 h[ev]1 may "h be made to "o ( ! mo/ exhau/ive & in/ructive /udies ( ! relations ( ! subt]ranean & sup]ficial erupt$ rocks ( an old volcano1 :i* w be f\nd 9 ! monograph by ,mr4 ,idd+s on ,electric ,peak & ,sepul*re ,m\nta9 9 ! ,yell[/one ,p>k ( ,we/]n ,am]ica4 ,f ! data !re obta9able he draws ! d$uction t "o p>5t magma1 reta9+ ! same *emical composition1 may result 9 ! ultimate production ( rocks /rik+ly diff]5t f ea* o!r 9 /ructure & m9]alogical con/itution1 yet *emically id5tical4 ,electric ,peak includes ! c5tral funnel fill$ up ) co>sely cry/all9e diorite1 & hav+ a connect$ s]ies ( sills & dykes ( v>i\s porphyrites4 ,sepul*re ,m\nta91 sep>at$ f its neighb\r+ em95ce by a fault ( #djjj feet1 displays "s ( ! sup]ficial dis*>ges f ! v5t--co>se breccias ) &esite-lavas4 ,^! rocks are n *emically di/+ui%able f ! intrusive s]ies1 b ! lavas are1 on ! :ole1 m glassy1 :ile ! mat]ials ( ! bosses1 sills & dykes are m cry/all9e4 ,! latt] display mu* m visible qu>tz & biotite4#cj ,footnote #cj3 #ab? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey1 #ahij-ia4 ,z already /at$1 ! eruptions ( ?is volcanic c5tre became progressively m acid1 & ?is *ange appe>s to be exhibit$ by ! extrusive lavas z well z by ! intrusive rocks4 ,by practice 9 ! field1 supplem5t$ by inve/igation ) ! aid ( ! microscope1 a geologi/ acquires a p[] ( discrim9at+ ) fair accuracy1 ev5 9 h& specim5s1 ! sup]ficial f ! subt]ranean igne\s rocks ( an old volcanic di/rict4 ,d5udation1 :ile lay+ b>e ! und]gr\nd me*anism ( an anci5t volcano1 has n always reveal$ ! evid5ce ( ! actual /ructural relations ( ! rocks1 or has fir/ expos$ & !n de/roy$ x4 ,sometimes a mass ( eruptive rock has be5 worn d[n & left 9 su* an isolat$ condition t its connection ) ! re/ ( ! volcanic network _c be det]m9$4 ,s f> z its position goes1 x might p]haps be ei!r a remnant ( a lava-/ream or ! project+ "p ( "s deep]-seat$ protrusion4 ,b its texture & int]nal /ructure w (t5 enable a confid5t op9ion to be express$ reg>d+ ! true relations ( su* a solit>y mass4 i4 ,dykes & ,ve9s ,= ! /udy ( ^! manife/ations ( volcanic en]gy1 ! ,briti% ,isles may be reg>d$ z a typical region4 ,x 0 !nce t ! ^w dyke pass$ into geological lit]ature4 ,?\s&s ( examples ( bo? dykes & ve9s may be se5 f ! ,out] ,hebrides s\?w>ds across ! l5g? & bread? ( ! s\!rn half ( ,scotl&1 f> into ! nor? ( ,engl& & t[>ds ! c5tre ( ,irel&4 ,!y may be f\nd cutt+ ! cre/s ( ! m\nta9s & ext5d+ z reefs bel[ ! level ( ! sea4 ,!y are ?us expos$ 9 e conceivable div]g5ce ( position & 9 endless v>ieties ( enclos+ rock4 ,moreov]1 !y c be %[n to repres5t a va/ range ( geological "t4 ,"o sy/em ( !m belongs to "s remote "p ( ! ,ar*an p]iods1 ano!r is z "y z ! old] ,t]ti>y ages4 ,illu/ration3 ,fig4 #cb4--;,dyke1 ,ve9 & ,sill4 ,! dyke 7d7 rises along a small fault among s&/ones1 %ales1 & iron/ones 7%71 & gives (f a ve9 7v7 & an intrusive %eet or sill 7b74 ,full details reg>d+ ^! int]e/+ relics ( volcanic activity w be giv5 9 lat] *apt]s1 especially 9 ,*apt]s xxxiv4 & xxxv4 ,x may suffice "h to note t ea* ( ! ?ree types ( old volcanoes above describ$ has1 9 ,brita91 its accompanim5t ( dykes & ve9s4 ,! plateaux1 h[ev]1 pres5t by f> ! mo/ abundant & v>i$ developm5t ( !m4 ,! dykes ( ?is s]ies are *>act]iz$ n only by _! prodigi\s numb]s 9 & ar\nd "s ( ! plateaux1 b by ! long di/ances to :i* !y may be trac$ beyond ^! limits4 ,!y are *iefly f\nd 9 connection ) ! ,t]ti>y basalt-plateaux1 ?\gh ! ,c>bonif]\s &esite-plateaux pres5t a feebl] display ( !m4 ,! ,t]ti>y dykes are pre-em95tly di/+ui%$ by _! p]si/5t rectil9e> l9es1 sometimes = di/ances ( _m miles1 & _! g5]al nor?-we/]ly direction4 ,!y =m a va/ sy/em ext5d+ ov] an area ( "s #dj1jjj squ>e miles4 ,?r\gh\t t wide region _! p]si/5ce ( direction & ( petrographical *>act]s po9t to ! =m] exi/5ce ( "o or m res]voirs ( an &esitic & basaltic magma und]nea? ! nor!rn half ( ,brita91 & to ! rupture ( ! cru/ ov]ly+ ?is subt]ranean res]voir by ?\s&s ( p>allel fissures4 ,!y ?us con/itute p]haps ! mo/ a/oni%+ feature 9 ! volcanic hi/ory ( ,t]ti>y "t4 ,! dykes & ve9s connect$ ) ! puys are ma9ly to be f\nd at or close to ! v5ts4 ,n infrequ5tly !y trav]se ! agglom]ates ( ! necks1 & are sometimes to be trac$ to a c5tral pipe or core ( basalt4 ,! l>g] cones are likewise int]sect$ ) simil> v]tical1 incl9$ or tortu\sly irregul> walls ( intrud$ lava4 ,occasionally a radiate arrangem5t may be obs]v$ 9 su* cases1 l t noticeable at "s mod]n volcanoes1 ! dykes div]g+ f ! eruptive c5tre4 ,_m dykes exi/ reg>d+ :i* !re is no evid5ce to connect !m ) any actual volcanic rocks4 ,!y h be5 inject$ into fissures1 b :e!r ?is took place dur+ volcanic p>oxysms1 or ow+ to "s subt]ranean movem5ts :i* nev] culm9at$ 9 any eruption1 _c be decid$4 ,! "q ( ! age ( dykes1 l t ( intrusive masses ( all k9ds1 is (t5 difficult or impossible to decide4 ,a dyke mu/ ( c\rse be y\ng] ?an ! rocks :i* x trav]ses1 & a limit to its antiquity is ?us easily fix$4 ,b we _c always affirm t because a dyke /ops %ort ( a p>ticul> rock1 or s]ies ( rocks1 x is old] ?an ^!4 ,! ,hett ,dyke1 9 ! nor? ( ,engl&1 rises ?r\gh ! ,coal-measures1 b /ops at ! ,magnesian ,lime/one2 yet ?is cessation does n necess>ily imply t ! dyke 0 9 place be=e ! deposition ( t lime/one4 ,! /ructure may h aris5 f ! dyke-fissure hav+ end$ at ! bottom ( ! lime/one4 ,:]e dykes rise up to ! base ( an uncon=mable =mation )\t 9 any s+le case ent]+ x1 & :]e fragm5ts ( !m are enclos$ 9 t =mation1 !y mu/ be ( high] antiquity1 & mu/ h be5 laid b>e by ext5sive d5udation be=e ! uncon=mable /rata 7 deposit$ ^u !m4 ,! great sy/em ( dykes 9 ! ,lewisian ,gneiss ( ! nor?-we/ ( ,scotl& is 9 ?is way prov$ to be mu* m anci5t ?an ! ,torridon ,s&/ones "u :i* x passes 7,figs4 #ce1 #cf74 ,:]e two dykes cross ea* o!r1 x is sometimes n difficult to decide ^u _! relative antiquity4 ,9 intrusive rocks1 ! f9e/-gra9$ p>ts are ^? :i* lie ne>e/ ! out] m>g91 :]e ! molt5 mat]ial 0 rapidly *ill$ by com+ 9 contact ) cool surfaces ( rock4 ,su* *ill$ m>g9s ( clos] gra9 are common *>act]i/ics ( dykes4 ,:]ev] a dyke c>ries its *ill$ m>g9 across ano!r dyke1 x mu/ be ! y\ng] ( ! two1 & :]ev] su* a m>g9 is int]rupt$ by ano!r dyke1 x mu/ belong to ! old]4 ,z a rule1 ! uprise ( molt5 mat]ial 9 a fissure has s effectually seal$ x up t 9 ! subsequ5t di/urbances ( ! t]re/rial cru/ ! fissure has n be5 reop5$1 ?\gh o!rs may h be5 produc$ ne> x1 or across x4 ,sometimes1 h[ev]1 ! enorm\s t5sion to :i* ! cru/ 0 expos$ op5$ ! fissure once m1 sometimes ev5 splitt+ a dyke along its c5tre1 & a new asc5t ( molt5 rock took place )9 ! r5t4 ,h5ce d\ble or treble or comp\nd dykes h be5 produc$4 ,! second or lat] infill+s are g5]ally some:at diff]5t f ! orig9al dyke4 ,occasionally1 inde$1 !y pres5t a /rong contra/ to x4 ,?us1 among ! dykes ( ,skye examples occur :]e ! c5tre is occupi$ by an acid granophyre1 :ile ! sides are occupi$ by dykes ( basalt4 ,in/ances ( ?is comp\nd type ( dyke w be giv5 9 ! acc\nt ( ! ,t]ti>y volcanic rocks ( ,brita94 ,x is obvi\s t 9 a wide fissure ! c5tral portion may rema9 molt5 = "s "t aft] ! sides h consolidat$4 ,if ! fissure s]v$ z a *annel = ! asc5t ( lava to ! surface1 x is conceivable t ! c5tral /ill fluid "p might be driv5 out & be replac$ by o!r mat]ial f bel[1 & t ?is lat] mat]ial might diff] consid]ably 9 composition f t :i* fir/ fill$ ! op5+4 ,su*1 accord+ to ,mr4 ,idd+s1 has be5 ! probable hi/ory ( "s ( ! dykes at ! old volcano ( ,electric ,peak4#ca ,b we c h>dly suppose t ?is explanation ( comp\nd dykes c h any wide application4 ,x c\ld only hold good ( broad fissures hav+ an outlet1 & is probably inadmissible 9 ! case ( ! num]\s comp\nd dykes n m ?an #aj or #ae feet 9 diamet]1 :]e ! sev]al b&s ( rock are %>ply m>k$ (f f ea* o!r4 ,! abrupt dem>cation ( ! mat]ials 9 ^! dykes1 _! clos] texture along _! mutual b\nd>ies1 ! indications ( solution ( ! old] p>ts ( ! gr\p by ! y\ng]1 & ( injection ( ! latt] into ! =m]1 %[ t !y belong to sep>ate & unconnect$ intrusions4 ,^! que/ions w be aga9 ref]r$ to 9 ! acc\nt ( ! ,briti% ,t]ti>y dykes 7,*apt] xxxv4 vol4 ii4 p4 #aei74 ,footnote #ca3 #ab? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey 7#ahij-ia71 p4 #ehg4 ,ano!r k9d ( comp\nd dyke has aris5 f ! mann] 9 :i* ! orig9al fissure has be5 produc$4 ,:ile1 9 g5]al1 ! dislocation has tak5 ! =m ( a s+le rectil9e> r5t1 :i* on op5+ has left two clean-cut walls1 cases occur :]e ! rupture has foll[$ sev]al p>allel l9es1 & ! magma on ris+ into ! r5ts appe>s z two or m v]tical %eets or dykes1 sep>at$ by int]v5+ p>titions ( ! surr\nd+ rock4 ,examples ( ?is /ructure are n infrequ5t among ! ,t]ti>y dykes ( ,scotl&4 ,"o ( ^! may be notic$ ris+ ?r\gh ! cliffs ( ,lewisian gneiss on ! ea/ coa/ ( ! isl& ( ,lewis1 s\? ( ,/orn[ay4 ,"o ( ! mo/ extraord9>y in/ances ( ! same /ructure yet obs]v$ is t describ$ by ,pr(essor ,a4 ,c4 ,lawson f ! ,laur5tian rocks at ! m\? ( ,:ite ,gravel ,riv]1 on ! ,n4,e4 coa/ ( ,lake ,sup]ior4 ,9 a bread? ( only ab\t #ad feet no less ?an #bh v]tically intrusive %eets or dykes ( diabase1 f #a in* to #f in*es broad1 rise ?r\gh ! granite1 :i* is ?us split into #bg ?9 %eets4 ,! diabase und\bt$ly cuts ! granite1 "s ( ! %eets actually ana/omos+ & s5d+ ve9s into ! old] rock4#cb ,footnote #cb3 ,am]ican ,geologi/ 7#ahid71 p4 #bic4 ,f ! evid5ce suppli$ by ! mod]n eruptions ( ,icel&1 x is evid5t t gap+ fissures1 :i* are fill$ by asc5d+ lava & !reby conv]t$ into dykes1 9 _m in/ances s]ve z *annels by :i* molt5 rock escapes to ! surface4 ,x w\ld be int]e/+ if any te/ c\ld be discov]$ :]eby ^? dykes c\ld be di/+ui%$ :i* _h ev] e/abli%$ a connection ) ! out] air4 ,if ! lava cont9u$ to asc5d 9 ! fissures1 & to p\r out 9 sup]ficial /reams = a long "t1 ! rocks on ei!r side w\ld be likely to und]go consid]ably m metamorphism ?an :]e !re 0 only "o rapid injection ( ! magma1 :i* w\ld soon cool4 ,possibly 9 ! mu* great] alt]ation ( ! same rocks by "s dykes ?an by o!rs1 a sign ( su* a connection ) ! surface may survive4 ,?is subject w be aga9 ref]r$ to 9 ! acc\nt ( ! ,t]ti>y dykes ( ,brita9 9 ,book ,,viii41 :]e ! :ole ( ! ph5om5a ( ?is phase ( volcanic action w be fully discuss$ 7see vol4 ii4 p4 #afc74 ii4 ,sills & ,laccolites ,! ^w sill1 d]iv$ f a rem>kable %eet ( eruptive rock 9 ! nor? ( ,engl&1 kn[n z ! ,great ,:9 ,sill 7,*apt] xxix471 is n[ appli$ z a conv5i5t g5]al t]m to masses ( intrusive mat]ial1 :i* h be5 inject$ betwe5 su* divisional planes z ^? ( /ratification1 & :i* n[ appe> z %eets or b$s 7,fig4 #cc74 ,^! masses are likewise call$ ,intrusive ,%eets1 & :]e ! inject$ mat]ial has accumulat$ 9 l>ge bli/]-l expansions1 ^! are kn[n z ,laccolites 7,fig4 #cd74 ,illu/ration3 ,fig4 #cc4--,section ( ,sill or ,intrusive ,%eet4 ,sills v>y f only an in* or two up to #ejj feet or m 9 ?ickness4 ,ly+1 z !y frequ5tly d1 p>allel ) /rata above & bel[ !m1 !y resemble 9 "s respects true lava-%eets erupt$ contemporane\sly ) ! s]ies ( s$im5ts among :i* !y are int]calat$4 ,&1 inde$1 cases occur 9 :i* x is h>dly possible to decide :e!r to reg>d a giv5 mass z a sill or z a sup]ficial lava4 ,9 g5]al1 h[ev]1 sills exhibit ! co>s] texture above ref]r$ to z specially *>act]i/ic ( subt]ranean eruptive masses4 ,moreov] !y are usually1 ?\gh n always1 free f ! vesicul> & amygdaloidal /ructures ( true surface-lavas4 ,_! "u & upp] surfaces1 unlike ! m scoriace\s p>ts ( lavas1 are commonly mu* clos] 9 gra9 ?an ! g5]al body ( ! mass2 9 o!r words1 !y possess *ill$ bord]s1 ! result ( m rapid consolidation by contact ) cool] rock4 ,aga91 in/ead ( con=m+ to ! /ratification ( ! =mations among :i* !y lie1 z truly int]/ratifi$ lavas d1 !y may be se5 to break across ! b$d+ & pursue _! c\rse on a high] or l[] plat=m4 ,! /rata t ov]lie !m1 in/ead ( enclos+ pieces ( !m & wrapp+ r\nd irregul>ities on _! surface1 z 9 ! case ( contemporane\sly erupt$ lava-%eets1 are usually indurat$1 sometimes ev5 consid]ably alt]$1 :ile 9 _m cases !y are invad$ by ve9s f ! eruptive %eet1 or portions ( !m are involv$ 9 x1 & are !n mu* h>d5$ or metamorphos$4 ,! petrographical "* ( ! sills 9 a volcanic di/rict dep5ds prim>ily on ! con/itution ( ! p>5t magma1 :5ce bo? !y & ! outfl[+ lavas h issu$4 ,:]e ! lavas are rhyolites or felsites ! sills are acid1 :]e basalts h be5 erupt$ ! sills are basic1 ?\gh !re has (t5 be5 a t5d5cy t[>ds ! appe>ance ( m acid mat]ial1 su* z tra*yte4 ,z we h se51 consid]able diff]5ces 9 petrographical *>act]s may arise betwe5 ! intrusive & extrusive (f%oots f ! same p>5t magma dur+ ! c\rse ( a volcanic cycle4 ,?is "q w be m appropriately discuss$ toge!r ) ! lead+ *>act]s ( ,bosses4 ,betwe5 ! upp] & "u surface ( a ?ick sill consid]able petrographical v>iation may sometimes be obs]v$1 especially :]e ! rock is ( basic con/itution4 ,diff]5ces bo? ( texture & ev5 to "s ext5t ( composition c be detect$4 ,sometimes :at h be5 call$ segregation ve9s trav]se ! mass1 consi/+ ( ! same m9]als z ! g5]al body ( ! rock1 b 9 l>g] cry/als & 9 some:at diff]5t proportions4 ,t ^! ve9s belong to ! p]iod ( orig9al consolidation appe>s to be %[n by ! abs5ce ( f9e-gra9$1 *ill$ m>g9s1 & by ! way 9 :i* ! compon5t cry/als ( ! ve9s are int]lock$ ) ^? ( ! body ( ! rock4 ,o!r ve9s ( f9] gra9 & m acid composition probably belong to a lat] phase ( consolidation1 :51 aft] ! sep>ation & cry/allization ( ! m basic m9]als1 ! m acid "m liquor t rema9$ 01 9 consequ5ce ( t]re/rial movem5ts1 inject$ into cracks 9 ! n[ solidifi$1 ?\gh /ill highly heat$1 rock4 ,examples ( ^! features w be cit$ f v>i\s geological =mations 9 ! foll[+ *apt]s4 ,ref]5ce has already be5 made to ! diff]5ce occasionally p]ceptible betwe5 ! con/itution ( ! upp] & t ( ! "u portions ( sup]ficial lavas4 ,a simil> v>iation is sometimes /rongly m>k$ among sills1 especially ^? ( a basic "*1 ! felsp>s rema9+ mo/ abundant above1 :ile ! oliv9es & augites prepond]ate bel[4 ,mr4 ,idd+s has obs]v$ "s excell5t illu/rations ( ?is "* 9 ! great s]ies ( sills connect$ ) ! volcanic pipe ( ,electric ,peak 9 ! ,yell[/one c\ntry4#cc ,"s examples ( ! same /ructure w subsequ5tly be cit$ f ! ,c>bonif]\s volcanic s]ies ( ,c5tral ,scotl&4 ,footnote #cc3 ,electric ,peak & ,sepul*re ,m\nta91 #ab? ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey 7#ahij-ia71 p4 #ehd4 ,! greate/ extreme ( diff]5ce :i* ,i h obs]v$ 9 ! petrographical *>act]s ( any gr\p ( sills is t display$ by ! ,t]ti>y gabbros ( ,skye4 ,^! rocks occur z %eets int]pos$ among ! b$d$ basalts1 & inject$ betwe5 ea* o!r 9 su* a mann] z to =m ?ick piles ( rudely /ratifi$ sills4 ,!y possess a rem>kable b&$ /ructure1 due to ! aggregation ( _! compon5t m9]als 9 di/9ct lay]s1 "s ( :i* are d>k 9 col\r1 f ! abundance ( _! iron-ore1 pyrox5e & oliv9e2 :ile o!rs are light-col\r$1 f ! pr$om9ance ( _! felsp>4 ,f ! mann] 9 :i* ! compon5t m9]als ( "o b& int]lace ) ^? ( ! contigu\s b&s1 x is q c]ta9 t ! /ructure is n due to successive injections ( mat]ial among already consolidat$ rocks1 b belongs to ! orig9al conditions ( expulsion ( ! gabbro z a :ole4 ,x seems to indicate t ! magma :i* suppli$ ! sills 0 at ! "t ( its extrusion het]og5e\s 9 composition1 & t ! b&+ arises f ! simultane\s or rapidly successive protrusion ( diff]5t portions ( ?is v>i\sly-con/itut$ magma4 ,! details ( ! /ructure w be describ$ 9 ! g5]al acc\nt to be giv5 ( ! ,t]ti>y volcanic rocks 7,*apt]s xliii4 & xliv474 ,besides su* visible diff]5ces 9 ! composition ( sills1 o!rs mu* less obtrusive may occasionally be detect$ ) ! aid ( microscopic or *emical rese>*4 ,! out] p>ts ( "s sills are ?us discov]$ to be m basic or m acid ?an ! inn] portions4 ,or evid5ce may be obta9$ po9t+ to ! probable melt+ d[n ( surr\nd+ rocks by ! erupt$ magma1 ) a consequ5t local *ange 9 ! *emical & m9]alogical con/itution ( ! mass4 ,9 reg>d to _! position 9 ! geological /ructure ( an old volcanic di/rict ,i may "h rem>k t sills1 seldom entirely abs5t1 are m especially develop$ ei!r among ! rocks ?r\gh :i* ! volcano has driv5 its v5t1 or ab\t ! base ( ! erupt$ lavas & tuffs4 ,_m illu/rations ( ?is di/ribution w be describ$ f ! v>i\s volcanic areas ( ,brita9 belong+ to ,palozoic & ,t]ti>y "t4 ,at ! base ( ! great ,cambrian & ,l[] ,silurian volcanic s]ies ( ,m]ione?%ire1 sills are admirably develop$1 :ile among ! basaltic eruptions :i* clos$ ! long volcanic record 9 ! nor? ( ,irel& & ! ,inn] ,hebrides1 !y play a notable "p4 ,f ! frequ5t place :i* sills take at ! base ( a volcanic s]ies1 x may be inf]r$ t !y g5]ally belong to a late phase 9 ! hi/ory ( an eruptive episode or cycle1 :5 ! orifices ( dis*>ge _h become *ok$ up1 & :5 ! volcanic en]gy f\nd an easi] passage lat]ally betwe5 ! /rata und]nea? ! volcanic pile or betwe5 ! %eets ( t pile itself1 ?an upw>d ?r\gh ! ev]-increas+ ?ickness ( eject$ mat]ial4 ,:ile !re is an obvi\s relation betwe5 mo/ sills & "s eruptive c5tre 9 _! neighb\rhood1 cases occur 9 :i* no trace ( any contemporane\s volcano c be f\nd1 b :]e ! intrusive %eet rema9s z ! sole evid5ce ( ! movem5ts ( ! subt]ranean magma4 ,! ,great ,:9 ,sill1 "o ( ! mo/ ext5sive intrusive %eets 9 ! ,briti% ,isles1 is an in/ance ( ?is k9d4 ,?\gh ?is l>ge mass ( inject$ mat]ial c be trac$ = a di/ance ( ab\t #hj miles1 & ?\gh ! /rata b5ea? & above x are well expos$ 9 innum]able sections1 no evid5ce has yet be5 detect$ to %[ t x 0 connect$ ) any v5t t =m$ a volcano at ! surface 7see vol4 ii4 p4 #b74 ,! abs5ce ( ?is evid5ce may1 ( c\rse1 arise f ! failure ( d5udation to uncov] ! site ( ! v5t1 :i* may possibly /ill rema9 buri$ "u ! ,c>bonif]\s /rata t ov]lie ! sill t[>ds ! s\?-ea/4 ,b x may be due to ! non-exi/5ce ( any su* v5t4 ,we c q conceive t volcanic en]gy %\ld sometimes h fail$ to complete ! =mation ( an actual volcano4 ,aid$ by subt]ranean movem5ts1 x might h be5 pot5t en\gh to disrupt ! l[] p>ts ( ! t]re/rial cru/1 to propel ! molt5 magma into fissures1 ev5 to inject x = _m miles betwe5 ! planes ( /ratification1 :i* w\ld be l9es ( lea/ resi/ance1 & yet 9 default ( available r5ts1 might h be5 unable to =ce its way ?r\gh ! upp] lay]s & s rea* ! surface4 ,examples ( su* incomplet$ volcanoes are p]haps to be recogniz$ among solit>y sills1 :i* n infrequ5tly pres5t !mselves 9 ! geological /ructure ( ,brita94 ,b ! positive decision ( ?is "q is almo/ always fru/rat$ by ! imp]fection ( ! evid5ce1 & ! consequ5t possibility t a connect$ v5t may /ill lie conceal$ "u ov]ly+ /rata4 ,besides ! m usual intrusions ( molt5 mat]ial 9 ! =m ( %eets ( :i* ! v]tical ?ickness be>s b a small proportion to ! horizontal ext5t1 !re occur also l>ge & ?ick cakes ( intrud$ mat]ial 9 :i* ! v]tical ?ickness may approa*1 or p]haps ev5 surpass1 ! horizontal diamet]4 ,^! dome-%ap$ or irregul> expansions =m a connect+ l9k betwe5 ord9>y sills & ! bosses to be subsequ5tly describ$4 ,!y h receiv$ ! "n ( ,laccolites f ,mr4 ,g4 ,k4 ,gilb]t1 :o work$ out ?is peculi> type ( /ructure 9 ! case ( ! ,h5ry ,m\nta9s 9 s\!rn ,utah#cd 7,fig4 #cd74 ,! same type has s9ce be5 f\nd di/ribut$ ov] ,arizona & ,colorado1 & x has be5 recogniz$ z ess5tially t ( _m eruptive masses or bosses 9 all p>ts ( ! _w4 ,footnote #cd3 ,geology ( ! ,h5ry ,m\nta9s1 ,u4,s4 ,geog4 & ,geol4 ,survey ( ! ,rocky ,m\nta9 ,region1 #ahgg4 ,= a review ( ! :ole subject ( laccolites 9 ,we/]n ,am]ica see a pap] by ,mr4 ,:itman ,cross1 9 ! #ad? ,annual ,report ( ! ,director ( ! ,u4,s4 ,geological ,survey1 #ahib-ic 7pub4 #ahie71 p4 #aeg4 ,illu/ration3 ,fig4 #cd4--;,ideal section ( ?ree ,laccolites4 7,aft] ,mr4 ,gilb]t47 ,9 ,we/]n ,am]ica1 ow+ 9 l>ge measure to ! previ\sly undi/urb$ condition ( ! s$im5t>y =mations1 ! relations ( ! inject$ igne\s mat]ial to ^! =mations c be satisfactorily asc]ta9$4 ,! geological /ructure ( ! v>i\s isolat$ laccolites ?us cle>ly pres5t$1 helps to expla9 ! /ructure ( o!r intrusive bodies :i*1 hav+ be5 inject$ among plicat$ & dislocat$ rocks1 d n s readily admit ( int]pretation4 ,9 ,colorado1 ,utah & ,arizona ! eruptive magma1 usually a porphyrite1 diorite or qu>tz-porphyry1 has ris5 9 "o or m pipes1 & has !n intrud$ itself lat]ally betwe5 ! planes ( ! s$im5t>y =mations :i*1 ov] ! c5tre ( intrusion1 h be5 pu%$ upw>d into a va/ dome-%ap$ or bli/]-l elevation4 ,! horizon on :i* ?is lat]al & v]tical expansion ( ! intrud$ mat]ial took place w\ld seem to h la9 sev]al ?\s& feet bel[ ! surface4 ,x ranges f ! ,cambrian to ! ,t]ti>y =mations4 ,subsequ5t d5udation has cut d[n ! uprais$ mantle ( s$im5t>y lay]s1 & has reveal$ m or less ( ! igne\s rock und]nea?1 :i* is ?us all[$ to protrude & to be affect$ by atmosph]ic erosion4 ,9 ?is way1 wide pla9s ( horizontal or g5tly undulat+ ,second>y & ,t]ti>y /rata h be5 div]sifi$ by ! appe>ance ( cones1 deta*$ or 9 gr\ps1 :i* h become m peak$ & v>i$ 9 outl9e 9 proportion z _! orig9al s$im5t>y cov]+ has be5 remov$ f !m4 ,! l>ge/ ( ! laccolitic masses 9 ! ,h5ry ,m\nta9s is ab\t #gjjj feet deep & ab\t #d miles 9 diamet]4 ,less ?an "o-half ( ! cov] ( ov]>*+ /rata has be5 remov$1 & d5udation has cut deeply into ! rema9+ "p4 ,t ! type ( /ructure1 s well exhibit$ among ! ,h5ry ,m\nta9s1 has n be5 m abundantly recogniz$ else:]e probably arises f ! fact n t x is r>e1 b t ! conditions = its developm5t are seldom s fav\rable z 9 ,we/]n ,am]ica4 ,obvi\sly :]e /ratifi$ rocks h be5 mu* di/urb$1 !y cease to furni% def9ite or regul> plat=ms = ! reception ( eruptive mat]ial1 & to af=d conv5i5t datum-l9es = e/imat+ :at 0 probably ! %ape ( ! intrud$ magma4 ,we may believe t ! effect ( ! propulsion ( eruptive mat]ial is usually to upheave ! ov]ly+ cru/1 & ?us to give rise to a laccolitic =m ( intrusion4 ,! upheaval relatively to ! surr\nd+ c\ntry w be apt to be practically p]man5t1 ! intrud$ body ( rock be+ weld$ to ! surr\nd+ =mations1 & =m+ 9 ?is way a solid & resi/+ core directly unit$ by pipes or funnels ) ! great magma-res]voir und]nea?4 ,on ! o!r h&1 :]e ! molt5 rock1 in/ead ( consolidat+ und]gr\nd1 has be5 copi\sly dis*>g$ at ! surface1 its emission mu/ t5d t[>ds ! production ( cav]n\s spaces )9 ! cru/4 ,! fall+ 9 ( ! ro(s ( su* cav]ns w give rise to %ocks ( e>?quakes4 ,subsequ5t upris+s ( ! magma may fill ^! spaces up1 & :5 ! rock has solidifi$ 9 ! =m ( laccolites or bosses1 x may effectually put an end !re to fur!r eruptions4 ,"s contact metamorphism may be obs]v$ along ! upp] & "u surfaces ( l>ge sills4 ,! rocks ov] ! ,am]ican laccolites h sometimes be5 highly alt]$4 ,b z ! *ange is ! same 9 k9d z t att5dant ^u ,bosses1 ?\gh g5]ally less 9 degree1 x w be consid]$ ) ^! intrusive masses4 ,! problems 9 t]re/rial physics sugge/$ by ! intrusion ( su* ?ick & p]si/5t masses ( eruptive mat]ial z ^? :i* =m sills & laccolites w likewise be discuss$ 9 connection ) ! me*anism ( ! rema9+ intrusive masses :i* h n[ to be describ$4 iii4 ,bosses 7,/ocks1 ,culots7 ,! t]m ,boss has be5 appli$ to masses ( intrusive rock :i* =m at ! surface r\nd$1 craggy or v>i\sly-%ap$ em95ces1 hav+ a circul>1 elliptical or irregul> gr\nd-plan1 & desc5d+ into ! t]re/rial cru/ ) v]tical or /eeply-incl9$ sides 7,fig4 #bh74 ,sometimes !y c be se5 to h pu%$ ! surr\nd+ rocks aside4 ,9 o!r places !y seem to occupy ! place ( ^! rocks ?r\gh :i*1 z x 71 an op5+ has be5 pun*$ = ! reception ( ! intrusive mat]ial4 ,occasionally1 m especially 9 ! case ( l>ge bosses1 l ^? 9 :i* granite s frequ5tly appe>s1 ! eruptive mass may be obs]v$ to rise "h & !re 9 deta*$ knobs ?r\gh ! surr\nd+ rocks1 or to enclose pat*es ( ^!1 9 su* a mann] z to indicate t ! l>ge body ( eruptive mat]ial t]m9ates upw>d 9 a v irregul> surface1 ( :i* only ! m prom95t p>ts project ?r\gh ! cake ( ov]ly+ rocks4 ,9 true bosses1 unlike sills or laccolites1 we d n get to any bottom on :i* ! eruptive mat]ial re/s4 ,laccolites1 inde$1 may be reg>d$ z int]m$iate betwe5 ! typical sill & ! typical boss4 ,! diff]5ce betwe5 a laccolite & a boss lies 9 ! fact t ! body ( ! laccolite does n desc5d into an unkn[n dep? 9 ! cru/1 b lies ^u a plat=m on :i* x has accumulat$1 ! magma hav+ asc5d$ by "o or m ducts1 :i* g5]ally be> b a small proportion 9 area to ! mass ( ! laccolite4 ,! boss1 on ! o!r h&1 is n kn[n to lie on any horizon1 nor to proce$ f small] ducts und]nea?1 b plunges z a great pill> or irregul> mass1 :i* may frequ5tly be notic$ to wid5 d[nw>ds into ! cru/4 ,!re c be no d\bt1 h[ev]1 t _m masses ( eruptive rock1 :i*1 accord+ to ! def9ition "h giv51 %\ld be call$ bosses1 w\ld be f\nd to be truly laccolites if _! /ructure bel[ gr\nd c\ld be asc]ta9$4 ,x is obvi\s t our failure to f9d any plat=m on :i* ! body ( a boss lies1 may arise m]ely f d5udation hav+ be5 z yet insuffici5t to lay su* a plat=m b>e4 ,x is h>dly probable t a boss sev]al miles 9 diamet] %\ld desc5d z a column ( t magnitude to ! magma-res]voir f :i* its mat]ial came4 ,m probably x has be5 suppli$ ?r\gh "o or m small] ducts4 ,! l>ge boss n[ visible at ! surface may ?us be really a laccolitic expansion on "o or m horizons4 ,m4 ,mi*el ,lvy lays /ress on ! g5]al wid5+ ( granitic bosses z !y desc5d into ! cru/4#ce ,:ile 8 obs]vations are support$ by _m illu/rations f all p>ts ( ! globe1 & are probably true ( ! deep]-seat$ masses ( granite1 x is no less true t num]\s examples h be5 met ) :]e a granite boss is %>ply m>k$ (f f ! rocks :i* x has invad$ & on :i* x may be se5 to lie4 ,ap>t f ! cases :]e granite seems to =m "p ( a va/ int]nal1 once molt5 mass1 into :i* its encircl+ gneisses seem to graduate1 !re are o!rs 9 :i* ?is rock1 z n[ visible1 has be5 inject$ into ! cru/ z a boss or z a laccolite4 ,in/ances w be describ$ 9 lat] *apt]s :]e su* bosses h ris5 ?r\gh ,cambrian1 ,silurian1 ,devonian & ,c>bonif]\s =mations4 ,x may be said t betwe5 su* granitic intrusions & volcanic op]ations no connection c be trac$4 ,b reasons w be br\ght =w>d 9 lat] *apt]s to reg>d "s ( ! granitic bosses z p>ts ( ! me*anism ( ,palozoic volcanoes4 ,x w also be %[n t among ! intrusive rocks ( ! ,t]ti>y volcanic s]ies ( ,brita9 !re occur bosses ( truly granophyric & granitic mat]ial4 ,h5ce1 ?\gh ma9ly :at is call$ a plutonic rock1 granite has made its appe>ance among ! subt]ranean protrusions ( volcanoes4 ,footnote #ce3 ,m4 ,mi*el ,lvy1 ,bull4 ,c>te ,gol4 ,france1 ,no4 #ce1 tome v4 7#ahic71 p4 #cb4 ,! view /at$ 9 ! text is also t adopt$ by ,pr(4 ,brgg] ) ref]5ce to ! granite ( ! ,*ri/iania di/rict4 ,die ,eruptivge/e9e des ,kri/ianiagebietes4 ,x is no d\bt true t _m intrusive masses1 :i* mu/ be includ$ "u ! g5]al "n ( bosses1 h probably _h no connection :atev] ) volcanic action prop]ly s call$4 ,!y are plutonic injections1 t is1 portions ( ! subt]ranean magma :i* h be5 intrud$ into ! t]re/rial cru/ dur+ its p]iods ( di/urbance1 & h n be5 accompani$ ) any sup]ficial dis*>ges1 :i* are ess5tial 9 truly volcanic en]gy4 ,x has be5 propos$ to draw a di/9ction betwe5 su* deep-seat$ intrusions & ^? :i* repres5t volcanic funnels4#cf ,if ?is 7 always practicable x w\ld c]ta9ly be desirable4 ,b ! di/9ction is n "o t c 9 e case be satisfactorily drawn4 ,ev5 9 reg>d to granitic bosses1 :i* may g5]ally be assum$ to be plutonic 9 orig91 ! ,briti% examples j ref]r$ to h 9 all likelihood be5 connect$ ) und\bt$ volcanic outbur/s4 ,)\t1 !re=e1 attempt+ "h to sep>ate ! obvi\sly volcanic necks ( eruptive mat]ial f ! probably plutonic bosses1 ,i propose to describe briefly ! g5]al *>act]s ( bosses consid]$ z a gr\p ( intrusive rocks1 toge!r ) ! ph5om5a :i* accompany !m1 & ! conditions "u :i* !y may h be5 inject$4 ,footnote #cf3 ,m4 ,mi*el ,lvy1 ,bull4 ,c>te ,gol4 ,france1 ,no4 #ce1 tome v4 7#ahic74 ,bosses1 :e!r ( plutonic or volcanic orig91 are frequ5tly n m]ely s+le masses ( eruptive rock1 b are accompani$ ) a sy/em ( dykes & ve9s1 "s ( :i* c be trac$ directly into ! p>5t-mass1 :ile o!rs trav]se x z well z ! surr\nd+ rocks4 ,h5ce ! hi/ory ( a boss may be consid]ably m complex ?an ! ext]nal =m ( ! mass might sugge/4 ,! petrographical *>act]s ( bosses l9k !m ) ! o!r und]gr\nd injections ( igne\s mat]ial1 m especially ) sills & laccolites4 ,inde$1 on m]e li?ological gr\nds no satisfactory l9e c\ld be drawn betwe5 ^! v>i\s =ms ( intrusive rocks4 ,! l>g] ! mass ! m co>sely cry/all9e x may be expect$ to be4 ,b ! :ole range ( /ructure1 texture & composition1 f ^? ( ! n>r[e/ ve9 to ^? ( ! wide/ boss1 con/itutes "o connect$ s]ies ( gradations4 ,acid1 int]m$iate & basic rocks are abundantly display$ among ! bosses4 ,huge masses ( granite1 granophyre1 qu>tz-porphyry1 felsite or rhyolite1 repres5t ! acid s]ies4 ,int]m$iate v>ieties consi/ ( tra*yte1 phonolite1 diorite1 &esite or o!r rock4 ,! basic bosses include v>ieties ( gabbro1 dol]ite1 basalt1 picrite1 & o!r comp\nds4 ,9 a boss ( l>ge size1 a consid]able range ( texture1 composition & /ructure may (t5 be obs]v$4 ,! rock is g5]ally mu* co>s] 9 gra9 ?an t ( ?9 sills or dykes4 ,sometimes x exhibits a f9] texture along ! m>g9 ?an 9 ! c5tre1 ?\gh ?is v>iation is n usually s m>k$ z 9 sills & dykes4 ,! rapidly-*ill$ & !re=e m close-textur$ selvage seems to h be5 develop$ mu* m fully 9 small ?an 9 l>ge masses ( eruptive mat]ial4 ,! latt]1 cool+ m sl[ly1 all[$ ev5 _! m>g9al p>ts to reta9 _! heat1 & sometimes p]haps ev5 _! molt5 condition1 long] ?an small injections4 ,"s influ5ce mu/ also h be5 ex]cis$ by ! temp]ature ( ! rocks into :i* ! eruptive mat]ial 0 intrud$4 ,:]e ?is temp]ature 0 high1 z 9 deep-seat$ p>ts ( ! cru/1 x w\ld all[ ! intrusive magma to cool m sl[ly1 & ?us to assume a m co>sely cry/all9e condition4 ,! abs5ce ( a close gra9 r\nd ! m>g9s ( granitic bosses may be due to ?is cause4 ,b a mu* m important di/9ction may be trac$ betwe5 ! c5tral & m>g9al p>ts ( "s l>ge bosses & ?ick sills4 ,i h already allud$ to ! fact t :ile ! middle ( a l>ge intrusive mass may be decid$ly acid1 tak+ ev5 ! =m ( granite1 ! out] bord]s are sometimes f\nd to be mu* m basic1 pass+ into su* a rock z gabbro1 or ev5 into "s ultra-basic comp\nd4 ,betwe5 ^! extremes ( composition no %>p division is sometimes discov]able1 su* z might h be5 expect$ _h ! "o rock be5 intrud$ into ! o!r4 ,! diff]5ces graduate s ins5sibly into ea* o!r z to sugge/ t orig9ally ! :ole mass ( ! rock =m$ "o cont9u\s body ( eruptive mat]ial4 ,x is possible t 9 "s cases ! magma itself 0 het]og5e\s at ! "t ( intrusion4#cg ,b ! frequ5cy ( ! di/ribution ( ! basic +r$i5ts t[>ds ! out] m>g91 & ! acid t[>ds ! c5tre1 po9ts r to a process ( diff]5tiation among ! con/itu5ts ( ! boss be=e consolidation4 ,9 "s in/ances ! diff]5tiation w\ld appe> to h tak5 place be=e cry/allization to any great ext5t _h set 91 because ! m9]als ultimately develop$ 9 ! c5tral p>ts diff] f ^? at ! sides4 ,9 o!r cases1 ! transf]5ce ( mat]ial w\ld seem to h be5 9 progress aft] ! compon5t m9]als _h cry/alliz$ out ( ! magma1 = !y are ! same ?r\gh\t ! :ole intrusive mass1 b diff] 9 relative proportions f c5tre to circumf]5ce4#ch ,footnote #cg3 ,! ,t]ti>y gabbros ( ! ,inn] ,hebrides h already be5 cit$1 & w be m fully describ$ 9 a lat] *apt] z exhibit+ ! het]og5e\sness ( an eruptive magma4 ,footnote #ch3 ,see ,messrs4 ,dakyns & ,teall1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlviii4 7#ahib71 p4 #ajd2 ,pr(4 ,brgg]1 op4 cit4 #a4 7#ahid71 p4 #ae2 ,mr4 ,a4 ,h>k]1 op4 cit4 p4 #cbj2 ,pr(4 ,idd+s1 ,j\rn4 ,geol4 ,*icago1 i4 7#ahic71 p4 #hcc2 ,bull4 ,phil4 ,soc4 ,wa%+ton1 ii4 7#ahij71 p4 #aia2 #ahib1 p4 #hi4 ,z illu/rations ( ^! features ,i may cite two good examples1 "o f ,scotl& & "o f ,engl&4 ,! mass ( ,g>abol ,hill1 9 ! ,lo* ,lomond di/rict1 consi/s ma9ly ( granite1 occupy+ an area ( ab\t #ab squ>e miles4 ,messrs4 ,dakyns & ,teall h %[n t :ile ! c5tral portions consi/ ( granite1 ! s\?-ea/]n m>g9 af=ds a rem>kable s]ies ( int]m$iate rocks1 su* z hornbl5de-biotite-granite1 tonalite 7qu>tz-mica-diorite71 diorite & augite-diorite1 :i* lead u outw>ds into highly basic comp\nds1 includ+ wehrlites 7oliv9e-diallage rocks71 picrites 7oliv9e-augite rocks71 s]p5t9e 7possibly repres5t+ dunites1 saxonites1 & lh]zolites71 & a peculi> rock consi/+ ess5tially ( en/atite1 diallage1 br[n hornbl5de & biotite4 ,! au?ors reg>d ! :ole ( ^! widely diff]5t rocks z ! products ( "o orig9al magma1 ! m basic m>g9al area hav+ consolidat$ fir/ z p]idotites1 foll[$ by diorites1 tonalites & granites 9 ! ord] ( increas+ acidity4 ,! mo/ acid rock 9 ! :ole s]ies consi/s ( felsp> & qu>tz1 is almo/ devoid ( f]ro-magnesian m9]als1 & occurs 9 n>r[ ve9s 9 ! granite & tonalite4 ,x indicates t aft] ! segregation & consolidation ( ! :ole boss1 ruptures occurr$ :i* 7 fill$ 9 by ! asc5t ( ! v late/ & mo/ acid rema9+ portion ( /ill fluid magma4#ci ,footnote #ci3 ,messrs4 ,dakyns & ,teall1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlviii4 7#ahib71 p4 #ajd4 ,! case ( ,c>rock ,fell 9 ,cumb]l& has be5 describ$ by ,mr4 ,a4 ,h>k]1 :o has asc]ta9$ t ! gabbro ( ?is boss has 9 its c5tral portions a specific gravity ( less ?an #bhe & a silica-p]c5tage sometimes z high z #eidf1 :il/ its m>g9al zone gives a specific gravity above #bie & a silica-p]c5tage z l[ z #cbej4 ,! migration ( ! heavy iron ores t[>ds ! m>g9 is readily app>5t to ! nak$ eye1 & is well e/abli%$ by *emical analysis1 ! oxides ( iron am\nt+ 9 ! c5tre to #fbd 7,fe#b,o#c #cfj1 ,fe,o #bfd71 & at ! m>g9 to #beed 7,fe#b,o#c #hdd1 ,fe,o #agaj74dj ,nei!r 9 ?is in/ance nor 9 t ( ,g>abol ,hill has any evid5ce be5 notic$ :i* w\ld sugge/ t ! basic & acid rocks belong to diff]5t p]iods ( intrusion4 ,!y pass s ins5sibly into ea* o!r z to =m 9 ea* case "o graduat$ mass4 ,footnote #dj3 ,mr4 ,a4 ,h>k]1 op4 cit4 p4 #cbj4 ,f ^! & o!r examples :i* h be5 obs]v$1 x is difficult to escape ! conclusion t ! diff]5ces betwe5 ! basic m>g9 & ! acid c5tre are due to "s process ( segregation or diff]5tiation :ile ! mass 0 /ill 9 a liquid condition1 & its con/itu5ts c\ld pass f "o "p ( ! boss to ano!r4 ,accord+ to ,pr(essor ,brgg]1 x may be /at$ z a g5]al law t diff]5tiation sets 9 dur+ consolidation1 & is det]m9$ by1 & dep5d5t on1 ! laws ( cry/allization 9 a magma1 9 s f> z ! comp\nds :i*1 on giv5 conditions1 w\ld fir/ cry/allize out1 diffuse !mselves t[>ds ! cool+ m>g9 s z to produce 9 ! contact-/ratum a peculi> *emical composition 9 ! /ill liquid mat]ial be=e cry/allization takes place4#da ,footnote #da3 ,?is g5]al conclusion is /at$ by ,pr(essor ,brgg] f 8 inve/igation ( ! rocks ( ,gran1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 l4 7#ahid71 p4 #cf4 ,if dur+ ! process ( diff]5tiation1 & be=e consolidation1 injections ( ! magma occur1 !y may be expect$ to diff] 9 "* accord+ to ! portion ( ! magma f :i* !y are d]iv$4 ,pr(essor ,brgg] believes t among ! basic eruptive rocks ( ,gran 9 ! ,*ri/iania di/rict1 "o & ! same magma has 9 ! bosses solidifi$ z oliv9e-gabbro-diabases1 & 9 ! dykes z camptonites1 bo/onites1 pyrox5ites1 hornbl5dites1 & m acid augite-diorites4#db ,footnote #db3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 l4 7#ahid71 p4 #ce4 ,v>i\s op9ions h be5 prop\nd$ z to ! cause or causes ( ?is s-call$ diff]5tiation1 b none ( !m are entirely satisfactory4 ,we mu/ await ! results ( fur!r exploration 9 ! field & ( cont9u$ rese>* 9 ! laboratory4 ,:at appe>s to h tak5 place )9 a subt]ranean molt5 magma :i* has be5 propell$ into ! e>?'s cru/ z a boss or laccolite1 ) or )\t a connect$ sy/em ( dykes1 may possibly be made to ?r[ "s light on ! rem>kable *anges 9 ! *>act]s ( lavas successively erupt$ f ! same v5t dur+ ! cont9uance ( a volcanic cycle4 ,:e!r or n any su* process ( diff]5tiation c be prov$ to take place )9 a subt]ranean volcanic res]voir1 ! sequ5ce ( erupt$ lavas be>s a curi\s resemblance to ! ord] 9 :i* ! con/itu5ts ( "s l>ge bosses succe$ ea* o!r f m>g9 to c5tre4 ,! e>lie/ lavas may be ( an int]m$iate or ev5 basic "*1 b !y g5]ally t5d to become m acid4 ,nev]!less alt]nations ( basic & acid lavas :i* h be5 not$ 9 v>i\s di/ricts w\ld seem to %[ t if !re be a process ( diff]5tiation 9 ! magma-bas9s1 x is n regul> & cont9u\s1 b liable to int]ruption & r5ewal4 ,! return to basic eruptions1 :i* s (t5 m>ks ! close ( a volcanic cycle1 is likewise n easily explicable on ! supposition ( cont9u\s diff]5tiation4 ,:]e no s5sible evid5ce ( diff]5tiation is traceable 9 ! g5]al body ( a l>ge intrusive mass1 indications t "s su* process has !re be5 9 progress are p]haps suppli$ by ! m acid dykes or ve9s1 & ! s-call$ segregation ve9s1 :i* h be5 already allud$ to z trav]s+ l>ge intrusive masses4 ,?\gh ^! portions diff] to a great] or less ext5t 9 texture & composition f ! ma9 sub/ance ( ! boss1 ! diff]5ces are n su* z to prev5t u f reg>d+ !m z really p>ts ( ! same p>5t magma4 ,! ve9s1 :i* are m acid ?an ! rock t !y trav]se1 may be reg>d$ z hav+ emanat$ f "s c5tral or deep]-seat$ "p ( a boss1 :i* /ill rema9$ fluid aft] ! m>g9al or upp] portion _h consolidat$ suffici5tly f> to be capable ( be+ r5t op5 dur+ subt]ranean di/urbance4 ,b t ! mass1 ?\gh coh]5t en\gh to be fissur$1 /ill rema9$ at a high temp]ature1 may be inf]r$ f ! g5]al abs5ce ( *ill$ edges to ^! ve9s4 ,! evid5ce ( diff]5tiation suppli$ by segregation ve9s has be5 ref]r$ to 9 ! case ( ,sills4 ,! /udy ( ! petrographical v>iations 9 ! con/itution ( l>ge eruptive bosses has a tw(old int]e/ = ! geologi/4 ,9 ! fir/ place1 x af=ds him mat]ial = an inve/igation ( ! *anges :i* a volcanic magma und]goes dur+ its eruption & consolidation1 & !reby provides him ) "s data = an elucidation ( ! cause ( ! sequ5ce ( erupt$ products dur+ a volcanic cycle4 ,9 ! second place1 x yields to him "s int]e/+ analogies ) ! /ructures ( anci5t gneisses1 & ?us helps t[>ds ! compreh5sion ( ! orig9 & hi/ory ( ^! pr(\ndly difficult b deeply fasc9at+ rocks4 ,bosses1 l sills1 occur 9 ! mid/ ( volcanic %eets1 & also z solit>y protrusions4 ,:]e !y rise amid/ int]/ratifi$ lavas & tuffs !y may (t5 be recogniz$ z occupy+ ! position ( volcanic v5ts4 ,!y are !n necks1 & _! *>act]s 9 ?is connection h already be5 giv54 ,:]e1 h[ev]1 z s frequ5tly happ5s1 !y appe> among rocks 9 :i* no trace ( any contemporane\s volcanic mat]ial is to be detect$1 _! relation to =m] volcanic activity rema9s unc]ta94 ,( ?is d\btful nature "s ( ! mo/ notable examples are suppli$ by ! great granitic bosses :i* occur s frequ5tly among ! old] ,palozoic rocks ( ,brita94 ,! age ( ^! c sometimes be approximately fix$1 & is !n f\nd to correspond m or less closely ) "s volcanic episode4 ,?us ! granite-bosses ( ,gall[ay1 9 ! s\? ( ,scotl&1 disrupt ,upp] ,silurian /rata1 b are old] ?an ! ,upp] ,old ,s&/one4 ,h5ce !y probably belong to ! p]iod ( ! ,l[] ,old ,r$ ,s&/one1 :i* 0 em95tly *>act]iz$ by ! vig\r & long cont9uance ( its volcanoes4 ,! granite ( ,arran & ( ! ,m\rne ,m\nta9s c be %[n by "o l9e ( reason+ to be y\ng] ?an surr\nd+ ,c>bonif]\s =mations1 by o!r argum5ts to be probably lat] ?an ! ,p]mian p]iod1 & by a review ( ! :ole evid5ce to =m almo/ c]ta9ly "p ( ! volcanic hi/ory ( ,t]ti>y "t4 ,b ev5 :]e x c be %[n t ! uprise ( a huge boss ( eruptive mat]ial 0 geologically contemporane\s ) en]getic volcanic action1 ?is co9cid5ce may n w>rant ! conclusion t ! boss !re=e m>ks "o ( ! volcanic c5tres ( activity4 ,ea* example mu/ be judg$ by itself4 ,!re h1 d\btless1 be5 _m cases ( ! intrusion ( molt5 mat]ial 9 bosses1 z well z 9 sills1 )\t ! e/abli%m5t ( any connection ) ! surface4 ,su* incomplet$ volcanoes h be5 reveal$ by d5udation aft] ! removal ( a great ?ickness ( sup]9cumb5t rock4 ,! evid5ce :i* w\ld h decid$ ! "q to :at ext5t any ( !m became true volcanic v5ts has ?us be5 de/roy$4 ,we c only reason t5tatively f a c>eful collation ( all ! facts t are n[ recov]able4 ,illu/rations ( ?is k9d ( reason+ w be fully giv5 9 subsequ5t *apt]s4 ,x has be5 suppos$ t a te/ = ! discrim9ation ( a subt]ranean protrusion f a true volcanic *imney may be f\nd 9 ! condition ( ! surr\nd+ rocks1 :i* 9 ! case ( ! prolong$ fl[ ( molt5 matt] up a v5t w\ld be likely to und]go f> m metamorphism ?an w\ld be ! case 9 ! injection ( a s+le eruptive mass4#dc ,b1 z has be5 already po9t$ out1 no special or excessive metamorphism ( ! encircl+ rocks is noticeable ar\nd _m v5ts4 ,!re is c]ta9ly no m alt]ation contigu\s to num]\s true necks ?an ar\nd bosses1 :i* !re is no reason to suppose ev] communicat$ directly ) ! surface1 & :i* 7 probably ! result ( a s+le intrusion4 ,we mu/ always rememb] t ! d5udation :i* has reveal$ ^! bosses has g5]ally remov$ ! evid5ce ( _! upw>d t]m9ation & ( _! possible connection ) any volcanic ejections4 ,_m ( !m may m>k ! sites ( true v5ts f :i* only s+le eruptions took place4 ,! op5+ ( a volcanic v5t does n necess>ily imply a prolong$ asc5t ( volcanic mat]ial4 ,9 a va/ numb] ( cases ! orig9al eruption 0 ! fir/ & la/ ef=t ( ! volcano1 s t 9 su* circum/ances !re seems no m reason = mu* alt]ation ( ! walls ( ! *imney ?an = ! metamorphism ( ! rocks r\nd a boss1 laccolite1 sill or dyke4 ,footnote #dc3 ,see1 = example1 ,mr4 ,h>k]1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 l4 7#ahid71 p4 #cbi4 ,! metamorphism produc$ by intrusions ( molt5 mat]ial ^u ! rocks ) :i* !y h come 9 contact has long be5 /udi$4 ,its am\nt v>ies s greatly 9 diff]5t cases t ! conditions on :i* x has specially dep5d$ are n easily det]m9$4 ,?ree factors h obvi\sly be5 ( great importance--fir/1 ! bulk ( ! intrud$ mat]ial2 secondly1 ! *emical composition & li?ological texture & /ructure ( ! rocks affect$2 & ?irdly1 ! con/itution & temp]ature ( ! invad+ magma4 #a4 ,x is cle> t a huge boss ( eruptive mat]ial w be likely to effect mu* m alt]ation ( ! surr\nd+ rocks ?an a small boss1 sill or dyke4 ,its initial temp]ature w probably be high] at ! "t ( its assum+ its f9al place ?an t ( ! same mat]ial aft] x has f\nd its way into ! n>r[] space ( a ?9 sill or dyke4 ,x w likewise take mu* long] to cool4 ,h5ce ! influ5ce ( its heat & its vap\rs w cont9ue to act long aft] ^? ( ! dyke or sill h ceas$ to manife/ !mselves4 #b4 ,x is equally evid5t t mu* ( ! resultant metamorphism w dep5d on ! susceptibility ( ! rocks to *ange4 ,an obdurate mat]ial su* z pure qu>tz-s&1 = example1 w resi/ fur!r alt]ation ?an m]e h>d5+ into qu>tzite4 ,%ales & mud/ones may be indurat$ into *]ty sub/ances ( v>i\s textures4 ,lime/ones & dolomites1 on ! o!r h&1 may become entirely cry/all9e1 & may ev5 h new m9]als1 su* z g>net1 tremolite1 pyrox5e1 etc41 develop$ 9 !m4 ,h5ce 9 comp>+ ! am\nt ( metamorphism att5dant on two sep>ate bosses we mu/ always take into acc\nt ! nature ( ! rocks 9 :i* x has be5 induc$4 #c4 ,b p]haps ! mo/ effective cause ( v>iation 9 ! nature & am\nt ( contact metamorphism has be5 ! con/itution ( ! eruptive magma4 ,a broad di/9ction may be drawn betwe5 ! alt]ation produc$ by basic & by acid rocks4 ,! intrusion ( basic mat]ial has (t5 produc$ s+ul>ly little *ange1 ev5 :5 ! eruptive mass has be5 ( consid]able size4 ,! greate/ am\nt ( alt]ation is to be f\nd :]e ! basic boss has caught up & envelop$ portions ( ! surr\nd+ rocks4 ,?us :]e ! gabbro ( ,c>rock ,fell has invad$ ! basic ,l[] ,silurian lavas ( ! ,lake ,di/rict1 ! envelop$ portions ( ! latt] %[ consid]able modification4 ,_! gr\ndmass becomes d>k] & m lu/r\s1 ! felsp>s assume a cle>] appe>ance & lose "s ( _! conspicu\s inclusions1 ! pyrox5ic con/itu5ts are conv]t$ into pale amphibole1 & ! glassy base disappe>s4 ,at ! actual l9e ( contact ! felsp>s ( ! lavas h become dis5gag$ f _! orig9al matrix1 :i* seems to h be5 dissolv$ & absorb$ 9 ! gabbro-magma4 ,br[n mica has be5 exceptionally develop$ 9 ! alt]$ lava4 ,at ! same "t1 a *ange is noticeable 9 ! "* ( ! gabbro itself ne> ! contact4 ,br[n mica is !re to be se51 ?\gh n a con/itu5t ( ! rock else:]e4 ,! eruptive mat]ial has incorporat$ ! basic gr\ndmass ( ! lavas1 leav+ ! felsp>s undissolv$4#dd ,footnote #dd3 ,mr4 ,h>k]1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 l4 7#ahid71 p4 #cca4 ,mu* m s]i\s are ! *anges produc$ by intrusions ( acid mat]ial1 ?\gh "h aga9 ! metamorphism v>ies )9 wide limits1 be+ sometimes h>dly p]ceptible1 & 9 o!r cases advanc+ s f> z to conv]t m]e s$im5t>y mat]ial into ?or\ghly cry/all9e rocks4 ,small sills & dykes ( felsite & granophyre may produce v slight *ange ev5 ^u %ales & lime/ones1 z may be se5 among ! eruptive rocks ( ,skye & ,raasay4 ,l>ge bosses ( granophyre1 & /ill m ( granite1 h be5 accompani$ ) ! mo/ ext5sive metamorphism4 ,r\nd ^! eruptive masses e gradation may be trac$ among s&y & argillace\s s$im5ts1 until !y pass into cry/all9e mica-s*i/s1 :i* d n appe> to be di/+ui%able f rocks ( ,ar*an age4 ,admirable examples ( ?is extreme alt]ation may be obs]v$ ar\nd ! great granite bosses ( ,gall[ay4#de ,aga91 among calc>e\s rocks a transition may be trac$ f dull grey ord9>y fossilif]\s lime/ones & dolomites into pure :ite cry/all9e m>bles1 full ( cry/als ( tremolite1 zoisite1 g>net & o!r m9]als4 ,! alt]ation ( ! fossilif]\s ,cambrian lime/ones ( ,/ra? 9 ,skye by ! intrusive bosses ( ,t]ti>y granite well illu/rates ?is *ange4#df ,footnote #de3 ,see ,explanation to ,%eet #i ( ! ,geological ,survey ( ,scotl&1 p4 #bb2 ,pr(4 ,bonney & ,mr4 ,allport1 ,proc4 ,roy4 ,soc4 xvi4 7#ahhi72 ,miss ,g>d9]1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvi4 7#ahij71 p4 #efi4 ,footnote #df3 ,maccullo*1 ,trans4 ,geol4 ,soc4 vol4 iii4 7#ahaf71 p4 #a2 ,description ( ! ,we/]n ,isles1 vol4 i4 p4 #cbb4 ,see also ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xiv4 7#aheg71 p4 #a2 & vol4 xliv4 7#ahhh71 p4 #fb4 ,)\t ent]+ fur!r "h into ! wide subject ( contact metamorphism1 to :i* a l>ge lit]ature has n[ be5 devot$1 we may note ! effects :i* h be5 produc$ 9 ! eruptive mat]ial itself by its contact ) ! surr\nd+ rocks4 ,n only h ^! rocks be5 alt]$1 b v consid]able modifications h likewise tak5 place 9 ! active ag5t ( ! *ange4 ,sometimes ! alt]ation ( ! invad+ mat]ial has be5 effect$ )\t any s5sible absorption ( ! m9]al con/itu5ts ( ! rocks invad$4 ,?is appe>s to be ! case 9 ^? in/ances :]e %eets ( basalt1 intrud$ among coals or highly c>bonace\s %ales1 h lo/ _! compact cry/all9e "* & h become m]e clays4 ,9 ! coal-fields ( ,brita91 :]e _m examples ( ?is *ange h be5 not$1 ! igne\s mat]ial is kn[n z :ite trap4 ,! iron oxides h be5 9 great "p remov$1 or1 toge!r ) ! lime ( ! compon5t m9]als1 h be5 conv]t$ into c>bonates4 ,traces ( ! orig9al felsp> cry/als may /ill be detect$1 b ! gr\ndmass has be5 *ang$ into a dull1 e>?y1 friable & decompos$ sub/ance4 ,ne>ly always1 h[ev]1 ! alt]ation ( ! intrusive magma has result$ f ! incorporation ( portions ( ! surr\nd+ rocks4 ,ref]5ce has be5 made above to ! alt]ation ( ! ,c>rock ,fell gabbro by ! absorption ( "s ( ! basic lavas ar\nd x4 ,b /ill m rem>kable is ! *ange produc$ 9 "s acid rocks by ! incorporation ( basic mat]ial into _! sub/ance4 ,pr(essor ,sollas has describ$ 9 great detail a rem>kable in/ance ( ?is effect 9 ! probably ,t]ti>y eruptive rocks ( ! ,c>l+=d di/rict 9 ! nor?-ea/ ( ,irel&4 ,he has asc]ta9$ t ! eruptive gabbro ( t di/rict is old] ?an ! granite1 = x is trav]s$ by granophyre dykes :i* enclose pieces ( x4 ,! granophyre dykes1 on ! o!r h&1 (t5 %[ a li?oidal or *ill$ m>g91 :i* is n visible 9 ! gabbro4 ,he believes t ! gabbro is n only old] ?an ! acid protrusions1 b 0 already completely solid1 trav]s$ by contraction-jo9ts1 & probably fractur$ by e>?-movem5ts1 be=e ! injection ( ! granophyric mat]ial1 :i* at ! "t ( its intrusion 0 9 a /ate ( extreme fluidity1 = x has f\nd its way into ! m9ute/ cracks & crevices4 ,he has especially /udi$ ! alt]ation produc$ by ! granophyre ^u ! enclos$ pieces ( basic rock4 ,! diallage1 isolat$ f ! o!r con/itu5ts ( ! gabbro1 may commonly be se5 to h brok5 up into num]\s granules1 l ! augite gra9s ( basalt1 :ile 9 "s cases biotite & hornbl5de h be5 develop$ ) ! concomitant excretion ( magnetite4 ,! acid rock itself has und]gone consid]able modification ow+ to ! incorporation ( basic mat]ial into its sub/ance4 ,pr(essor ,sollas di/+ui%es ! foll[+ v>ieties ( ! rock3--,biotite-granophyre1 biotite-amphibole-granophyre1 augite-granophyre1 diallage-amphibole-augite-granophyre4#dg ,footnote #dg3 ,trans4 ,roy4 ,iri% ,acad4 xxx4 7#ahid71 "p xii4 p4 #dgg4 ,simil> ph5om5a h be5 describ$ by ,mr4 ,h>k] z occurr+ :]e granophyre has invad$ ! gabbro ( ,c>rock ,fell4#dh ,! same obs]v] has m rec5tly detect$ "s int]e/+ examples furni%$ by injections ( ,t]ti>y granophyre 9 ! agglom]ates ( ,skye4 ,! acid rock is r\ghly e/imat$ by him to h tak5 up ab\t "o-f\r? ( its bulk ( gabbro fragm5ts4 ,he has inve/igat$ ! m9ute /ructure ( ! rock ?us con/itut$1 & has be5 able to recognize ! augite ( ! orig9al gabbro1 9 v>i\s /ages ( alt]ation & completely isolat$1 ! o!r m9]als hav+ be5 dissolv$ 9 ! acid magma4#di ,footnote #dh3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 li4 7#ahie71 p4 #ahc4 ,footnote #di3 ,op4 cit4 lii4 ,! metamorphism produc$ ^u fragm5ts ( diff]5t k9ds ( =eign mat]ial enclos$ )9 v>i\s igne\s rocks has 9 rec5t ye>s be5 /udi$ 9 great detail by ,pr(essor ,lacroix--,les ,enclaves des ,ro*es ,volcaniques1 ,macon1 #ahic4 ,x is n easy to compreh5d ! conditions "u :i* l>ge masses ( molt5 mat]ial h be5 inject$ into ! cru/ ( ! e>?4 ,! two ma9 factors 9 volcanic action--t]re/rial contraction & ! en]gy ( ! vap\rs 9 ! magma--h no d\bt play$ ! *ief "p 9 ! process4 ,b ! relative %>e ( ea* & ! way 9 :i* ! enorm\s load ( ov]ly+ rock has be5 ov]come are n readily intelligible4 ,let u fir/ consid] = a mom5t ! pressure ( ! sup]9cumb5t cru/ "u :i* ! injection 9 _m cases took place4 ,! ,:9 ,sill ( ,engl& may s]ve z a good illu/ration ( ! difficulties ( ! problem4 ,?is notable mass ( intrusive rock has be5 =c$ betwe5 ! /ratification planes ( ! ,c>bonif]\s ,lime/one s]ies 9 "o1 or sometimes m ?an "o1 %eet4 ,x /ret*es = a horizontal di/ance ( n less ?an #hj miles ) an av]age ?ickness ( betwe5 #hj & #ajj feet4 ,f ! area ov] :i* x c be trac$ its total ext5t und]gr\nd mu/ be at lea/ #djj squ>e miles 7see ,*apt] xxix474 ,9 any s+le section ! ,:9 ,sill might be suppos$ to be a truly int]/ratifi$ %eet1 s ev5ly does x seem to be int]calat$ betwe5 ! s$im5t>y /rata4 ,b "h & !re x div]ges upw>d or d[nw>d 9 su* a way z to prove x to be really a va/ inject$ %eet4 ,! age ( ! injection _c be precisely fix$4 ,x mu/ be lat] ?an ! ,c>bonif]\s ,lime/one4 ,!re is no trace ( any /ratigraphical break 9 ! ,c>bonif]\s sy/em ( ! region trav]s$ by ! sill4 ,if ! injection took place dur+ ! ,c>bonif]\s p]iod1 x does n appe> to h be5 att5d$ ) any local di/urbance1 su* z we might suppose w\ld h be5 likely to accompany ! extravasation ( s enorm\s a mass ( igne\s mat]ial4 ,if ! date ( injection be assign$ to ! next volcanic episode 9 ! geological hi/ory ( ,brita9--t ( ! ,p]mian p]iod--x w foll[ t ! ,:9 ,sill 0 intrud$ into its pres5t position "u ! sup]9cumb5t weight ( ! :ole ( ! ,c>bonif]\s sy/em high] ?an ! plat=m foll[$ by ! inject$ rock4 ,! ov]ly+ body ( /rata w\ld ?us exce$ #ejjj feet 9 ?ickness1 or 9 r\nd numb]s w\ld am\nt at lea/ to an ,engli% mile4 ,! pressure ( ?is mass ( sup]9cumb5t mat]ial1 at ! dep? at :i* ! inject$ magma 0 =c$ betwe5 ! /rata1 mu/ h be5 s gigantic t x is difficult to believe t ! en]gy ( ! magma w\ld h be5 able to a*ieve ( itself s /up5d\s a task z ! =mation ( ! ,great ,:9 ,sill4 ,! volume ( inject$ mat]ial is likewise des]v+ ( special att5tion4 ,_m sills exce$ #cjj or #djj feet 9 ?ickness2 & "s laccolites mu/ enorm\sly surpass ^! limits4 ,! intrusion ( s va/ a body ( new mat]ial into ! t]re/rial cru/ w necessitate ei!r a correspond+ elevation ( t "p ( ! cru/ ov]ly+ ! inject$ magma or a subsid5ce ( t "p und]ly+ x1 or "s comb9ation ( bo? movem5ts4 ,x is conceivable t1 :]e ! body ( protrud$ magma 0 l>ge & ! ?ickness ( ov]ly+ cru/ 0 small1 ! expansive =ce ( ! vap\rs "u high t5sion 9 ! molt5 rock may h suffic$ = ! uplift4 ,?is result w be mo/ likely to be effect$ ar\nd a volcanic *imney :]e ! magma has ! lea/ am\nt ( ov]ly+ load1 & enc\nt]s t relief f pressure :i* enables x to become a p[]ful ag5t 9 t]re/rial physics4 ,b 9 ! case ( ! l>g] bodies ( inject$ rock1 especially :]e !y d n seem to h be5 accompani$ by ! op5+ ( any volcanic v5ts1 ! propulsion ( ! igne\s mat]ial into ! cru/ has probably be5 effect$ z a consequ5ce ( di/urbance ( ! t]re/rial cru/4 ,:5 ! /ra9 ( contraction leads to ! pu%+ upw>d ( ! t]re/rial areas int]v5+ betwe5 wide regions ( subsid5ce1 ev5 ?\gh ! diff]5tial movem5t may be slight1 ! isogeo!rms und]go de=mation4 ,! int5sely hot nucleus is squeez$ upw>d1 & if 9 ! process ( compression ruptures take place 9 ! cru/1 & cavities 9 x are consequ5tly op5$1 ! magma w at once be =c$ into !m4 ,su* ruptures may be expect$ to take place along l9es ( weakness4 ,rocks w split along _! /ratification-planes1 & ! t5d5cy to sep>ation along ^! l9es may be aid$ by ! read9ess ( ! en]getic magma to f9d its way into & to enl>ge e available op5+4 ,h5ce we may expect t1 besides v]tical fractures1 lead+ to ! production ( dykes & bosses1 !re w (t5 be horizontal ?ru/s & ruptures1 :i* w give rise to ! =mation ( sills4 ,!re is /ill ano!r feature ( t]re/rial contraction :i* may help u to foll[ ! behavi\r ( ! magma )9 ! cru/4 ,plication ( ! cru/ is "o ( ! mo/ *>act]i/ic results ( ! contract+ /ra94 ,:]e a great s]ies ( s$im5t>y =mations has be5 viol5tly compress$ s t its compon5t /rata h be5 ?r[n into rapid folds & squeez$ into a v]tical position1 ! portion ( ! cru/ ?us treat$ may possibly be on ! :ole /r5g!n$ aga9/ ! uprise ( molt5 mat]ial ?r\gh x4 ,b ! fold+ is (t5 accompani$ ) dislocation4 ,n only are ! rocks ?r[n into endless plications1 b portions ( !m are ruptur$ & ev5 driv5 horizontally ov] o!r p>ts4 ,su* greatly di/urb$ areas ( ! cru/ are n infrequ5tly f\nd to h be5 pl5tifully inject$ ) igne\s rocks 9 ! =m ( dykes1 ve9s1 sills1 laccolites & bosses4 ,! elevation ( a m\nta9-*a9 is kn[n to be accompani$ ) a dim9ution ( d5sity 9 ! cru/ und]nea?4 ,mr4 ,o4 ,fi%] has sugge/$ t along su* l9es ( t]re/rial uplift !re may be a d\ble bulge 9 ! cru/1 "o portion ris+ to =m ! upheav$ l& & ! o!r s9k+ d[n into ! hot nucleus4 ,if ! light] desc5d+ cru/ 7 !re melt$ x might =m a magma ready to be p\r$ out z lava on ! op5+ ( any v5t4 ,! lava ?us eject$ w\ld be ( ! light] k9ds4 ,x has be5 rem>k$ z c]ta9ly a curi\s fact t ! lavas :i* issue f high m\nta9 ranges are g5]ally mu* m acid ?an ! heavy basic lavas :i* are s *>act]i/ic ( volcanoes close to ! level ( ! sea4 ,b ev5 :]e no actual m\nta9-*a9 is =m$1 !re are g5tle undulations ( ! cru/ :i* no d\bt also affect ! isogeo!rms4 ,if any s]ies ( di/urbances %\ld give rise to a d\ble sy/em ( su* undulations1 "o cross+ ! o!r1 !re w\ld be limit$ dome-%ap$ elevations at ! int]sections ( ^! waves1 & if at ! same "t actual rupture ( ! cru/ %\ld take place1 ! magma might f9d its way upw>d "u su* domes & give rise to ! =mation ( laccolitic intrusions4 ,cessation ( ! e>?-movem5ts might all[ ! intrud$ mat]ial sl[ly to solidify )\t ev] mak+ an op5+ to ! surface & =m+ a volcano4 ,d\btless _m sills1 laccolites & bosses repres5t su* e>ly or arre/$ /ages 9 volcanic hi/ory4 ,propell$ into ! cru/ at a high temp]ature1 & end[$ ) great en]gy f ! t5sion ( its absorb$ vap\rs & gases1 ! magma w avail itself ( e r5t :i* may be op5$ 9 ! surr\nd+ cru/1 & :]e x has succe$$ 9 rea*+ ! surface1 its own explosive viol5ce may enable x to rupture ! cru/ /ill fur!r1 & op5 = itself _m new passages4 ,?us an eruptive laccolite or boss is (t5 fr+$ ) ve9s1 dykes & sills :i* proce$ f its mass into ! rocks ar\nd4 ,! "q h[ f> an asc5d+ mass ( magma c melt d[n its walls is "o to :i* no def9ite answ] c yet be giv54 ,rec5t obs]vations %[ t :]e ! diff]5ce 9 ! silica p]c5tage betwe5 ! magma & ! rock attack$ is great1 !re may be consid]able dissolution ( mat]ial f ?is cause4 ,allusion has already be5 made to ,mr4 ,h>k]'s computation t "s ( ! acid granophyres ( ,skye h melt$ d[n ab\t a f\r? ( _! bulk ( ! basic gabbros4 ,if su* a reaction %\ld take place betwe5 ! magma ( a boss1 sill or laccolite & ! rocks among :i* x has be5 intrud$1 great *anges might result 9 ! composition ( ! intrud$ rock4 ,we are n yet1 h[ev]1 9 possession ( evid5ce to indicate t absorption ( ?is k9d really takes place on an ext5sive scale )9 ! e>?'s cru/4 ,if x did occur to a l>ge ext5t1 we %\ld expect mu* great] v>ieties 9 ! composition ( eruptive rocks ?an usually occur1 & also "s obs]vable relation betwe5 ! composition ( ! igne\s mat]ial & t ( ! rocks into :i* x has be5 inject$4 ,b en\gh is n yet kn[n ( ?is subject to w>rant any decid$ op9ion reg>d+ x4 ,,*apt] ,,vii ,influ5ce ( ,volcanic ,rocks on ! ,sc5]y ( ! ,l&--,effects ( ,d5udation4 ,z consid]able popul> misappreh5sion exi/s respect+ ! "p :i* volcanism has play$ 9 ! evolution ( ! exi/+ topography ( ! e>?'s surface1 & z ! ,briti% ,isles1 f _! v>i$ geological /ructure1 (f] special facilities = ! discussion ( ?is subject1 x may n be out ( place to devote a f9al section ( ! pres5t ,introduction to a consid]ation ( ! real topographical influ5ce ( volcanic action4 ,) mod]n1 & especially ) active1 volcanoes we ne$ n "h conc]n ourselves4 ,_! topographical =ms are well kn[n1 & give rise to no difficulty4 ,! l(ty cones ( ! ,vesuvian type1 ) _! widespread lavas & a%es1 _! va/ crat]s & _! abundant p>asitic volcanoes2 ! cr[d$1 b g5]ally dim9utive1 cones & domes ( ! puy type1 s well display$ 9 ,auv]gne1 ! ,eifel & ! ,bay ( ,naples2 & ! va/ lava des]ts ( ! plateaux1 s *>act]i/ically develop$ 9 ,icel& & ,we/]n ,am]ica1 illu/rate ! v>i\s ways 9 :i* volcanic en]gy directly *anges ! cont\rs ( a t]re/rial surface4 ,b ! circum/ances are alt]$ :5 we deal ) ! topographical influ5ce ( long ext9ct volcanoes4 ,o!r ag5cies !n come into play1 & "s caution may be ne$$ 9 ! ef=t to dis5tangle ! elem5ts ( ! complicat$ problem1 & to assign to ea* contribut+ cause its own prop] effect4 ,ref]5ce has already be5 made to ! cont9u\s d5udation ( volcanic hills f ! "t t !y are fir/ erupt$4 ,b ! comp>ative rapidity ( ! wa/e & ! rem>kable topographical *anges :i* x involves c h>dly be adequately realiz$ )\t ! inspection ( an actual example4 ,a visit to ! back ( ,monte ,somma1 already allud$ to1 w tea* ! obs]v]1 f> m vividly ?an books c d1 h[ a volcanic cone is affect$ by daily meteoric *anges4 ,! sides ( su* a cone may rema9 tol]ably uni=m slopes s long z !y are always be+ r5ew$ by deposits f fre% eruptions4 ,b :5 ! volcanic activity ceases1 & ! declivities und]go no su* rep>ation1 !y are rapidly *annell$ by ! desc5t ( ra9-wat]1 until ! furr[s gr[ by degrees wide & deep rav9es1 ) only n>r[ & cont9ually-dim9i%+ cre/s betwe5 !m4 ,if un*eck$ by any fre% dis*>ge ( volcanic mat]ial1 ! degradation w at la/ h remov$ ! :ole cone4 ,x is ?us obvi\s t purely volcanic topography1 t is1 ! t]re/rial sc5]y due directly to ! eruption ( mat]ials f )9 ! e>?1 c nev] become 9 a geological s5se v old4 ,x c only endure s long z x is cont9ually r5ew$ by fre% eruptions1 or :]e x is c>ri$ d[n by subsid5ce "u wat] & is !re buri$ "u a cov] ( protect+ s$im5ts4 ,:51 !re=e1 we meet ) volcanic rocks ( anci5t date expos$ at ! surface1 we may be q c]ta9 t _! pres5t cont\rs are n ^? ( ! orig9al volcano1 b h be5 br\ght ab\t by ! processes ( d5udation4 ,x is true t1 9 ! g5]al erosion ( ! surface ( ! l&1 volcanic rocks ( anci5t date sometimes rise into wond]fully craggy heights1 includ+1 p]haps1 cones & deep crat]-l holl[s1 :i* to popul> imag9ation betok5 cont\rs left by n[ ext+ui%$ volcanic fires4 ,examples ( su* sc5]y are famili> 9 v>i\s p>ts ( ,brita92 b ! resemblance to rec5t volcanic topography is deceptive4 ,!re are1 inde$1 a few hills :]e9 ! progress ( d5udation seems n z yet to h entirely remov$ ! lavas & tuffs t ga!r$ r\nd ! orig9al v5ts4 ,"s ( ! tuff-cones ( ea/]n ,fife1 = example1 pres5t cases ( ?is k9d4 ,aga91 ! great granophyre domes & cones ( ! ,t]ti>y volcanic s]ies ( ! ,inn] ,hebrides1 ?\gh !y h und\bt$ly be5 ext5sively d5ud$1 may possibly reta9 cont\rs t d n greatly diff] f ^? :i* ^! protrud$ bosses orig9ally assum$ "u ! mass ( rock :i* has be5 remov$ f !m4 ,nev]!less1 putt+ su* d\btful exceptions aside1 we may confid5tly affirm t hills compos$ ( anci5t volcanic mat]ial give no clue to ! =ms ( ! orig9al volcanoes4 ,x c h>dly be too (t5 repeat$ t ! fundam5tal law 9 ! univ]sal decay & sculpture ( ! l& is t ! wa/e is proportion$ to ! resi/ance (f]$ to x3 ! s(t] rocks are worn d[n ) comp>ative rapidity1 :ile ! h>d] v>ieties are left project+ above !m4 ,z a g5]al rule1 volcanic rocks are m durable ?an ^? among :i* !y are int]/ratifi$1 & h5ce project above !m1 b ?is is n always ! case4 ,no univ]sal rule c1 inde$1 be laid d[n ) reg>d to ! relative durability ( any rocks4 ,:ile1 !re=e1 topographic cont\rs af=d a valuable indication ( ! nature & disposition ( ! rocks bel[ ! surface1 !y _c be reli$ ^u z 9 all circum/ances an infallible guide 9 ?is respect4 ,no bett] pro( c be (f]$ ( ! caution t is ne$$ 9 trac+ su* cont\rs back to _! orig9 ?an is furni%$ by ! old volcanic rocks ( ,brita94 ,^! eruptive masses1 consi/+ usually ( durable mat]ials & rang+ ?r\gh a va/ cycle ( geological "t1 usually rise into prom95t features & ?us support ! g5]al law4 ,b !y include also _m easily erod$ memb]s1 :i*1 in/ead ( =m+ em95ces1 are worn into holl[s4 ,!y include1 9 %ort1 e type ( sc5]y1 f featureless pla9s & roll+ l[l&s to craggy & spiry m\nta9s4 ,! fir/ po9t1 !n1 :i* is e/abli%$ 9 an inve/igation ( ! topographical influ5ce ( old volcanic rocks is t _! prevail+ prom95ce arises f relative durability amid/ univ]sal degradation4 ,:5 we proce$ fur!r to inquire :y !y v>y s mu* f ea* o!r 9 diff]5t places1 & h[ _! complicat$ details ( feature h be5 elaborat$1 we soon le>n t su* local peculi>ities h aris5 ma9ly f v>iations 9 ! int]nal /ructure & gr\p+ ( ! rocks !mselves4 ,"h aga9 ! g5]al law ( sculpture comes into play4 ,! local features h dep5d$ ^u ! comp>ative resi/ance (f]$ to ! sculptur+ ag5ts by ! diff]5t portions ( a volcanic s]ies4 ,ea* di/9ct v>iety ( rock possesses its own *>act]i/ic int]nal /ructure4 ,! l9es along :i* atmosph]ic dis9tegration w mo/ effectually c>ry on its c>v+ "w are ?us already trac$ 9 ! v sub/ance & ar*itecture ( ! rock itself4 ,ea* rock consequ5tly yields 9 its own way to ! processes ( dis9tegration1 & ?us contributes its own di/9ctive %>e to topographical feature4 ,among ! massive rocks abundant examples ( su* special types ( wea!r+ may be cit$1 f ! acid & basic s]ies1 & f sup]ficial lavas z well z f intrusive bosses & sills4 ,acid bosses1 su* z ^? ( granite1 granophyre & qu>tz-porphyry1 t5d to wea!r into blocks & f9ally into s&1 & z ?is t5d5cy is some:at uni=mly di/ribut$ ?r\gh ! rocks1 !y are apt to assume r\nd$1 dome-%ap$ or conical =ms :i*1 at a di/ance1 may seem to h smoo? declivities1 b on exam9ation are g5]ally f\nd to be cov]$ ) a sl[ly-desc5d+ %eet ( dis9tegrat$ blocks & debris 7,fig4 #cdf74 ,:5 less prone to decay1 & especially :]e trav]s$ by a /rongly-def9$ sy/em ( v]tical jo9ts1 !y may %oot up into t[]-l heights1 ) prom95t spires & obelisks4 ,basic bosses1 :5 _! mat]ials decay some:at rapidly1 give rise to analog\s topographical =ms1 ?\gh ! m f]tile soils :i* !y produce g5]ally lead to _! be+ clo!d ) vegetation4 ,:]e !y consi/ ( an obdurate rock1 mu* jo9t$ & fissur$1 l ! gabbro ( ! ,inn] ,hebrides1 !y =m exce$+ly rugg$ m\nta9s1 t]m9at+ upw>d 9 s]rat$ cre/s & gr\ps ( aiguilles 7,figs4 #cca1 #ccc74 ,acid lavas t h be5 sup]ficially erupt$ wea!r into irregul>ly craggy hills1 l ! flanks ( ,sn[don4 ,^? ( int]m$iate composition1 :]e !y h accumulat$ 9 ?ick masses1 are apt to wea!r into conical =ms1 z may be se5 among ! ,*eviot1 ,p5tl& & ,g>leton ,hills 7,figs4 #aji1 #aaj1 #acc72 b :]e !y h be5 p\r$ out 9 successive ?9 %eets !y h built up undulat+ plateaux ) t]rac$ sides1 z among ! ,ayr%ire & ,campsie ,fells & ! hills ( ,lorne 7,figs4 #ii1 #ajg74 ,basic lavas h issu$ 9 comp>atively ?9 %eets1 frequ5tly column> or slaggy1 =m+ flat-topp$ hills & t]rac$ esc>pm5ts1 su* z are typically develop$ among ! ,t]ti>y basalt-plateaux ( ! ,inn] ,hebrides & ! ,f>oe ,isl&s 7,figs4 #aa1 #bfe1 #bhc1 #bhd1 #bhf74 ,"o ( ! mo/ frequ5t causes ( local peculi>ities ( topography among old volcanic rocks is ! int]calation ( v di/9ct v>ieties ( mat]ial 9 ! same volcanic s]ies4 ,:]e1 = in/ance1 lavas & tuffs alt]nate1 great inequalities ( surface may be produc$4 ,! tuffs1 be+ g5]ally m friable1 decay fa/] & give rise to holl[s1 :ile ! lavas1 be+ m durable1 project 9 bold ridges or rise into mural esc>pm5ts 7,fig4 #bfe74 ,aga91 :]e dykes wea!r m readily ?an ! rocks :i* !y trav]se1 !y orig9ate deep n>r[ clefts1 :ile :]e !y wea!r m sl[ly ?an ! rocks ar\nd !m1 !y project z d>k ribs4 ,?us 9 ,skye "s dykes :i* rise ?r\gh ! obdurate gabbro are m>k$ by *asms :i* rea* up ev5 to ! highe/ cre/s ( ! m\nta9s 7,fig4 #ccc71 :ile ( ^? :i* run 9 ! pale crumbl+ granophyre1 "s /& up z black walls t c be foll[$ ) ! eye across ! ridges ev5 f a long di/ance4 ,_m fur!r illu/rations ( ^! pr9ciples might be cit$ "h f ! old volcanic di/ricts ( ,brita94 ,b !y w pres5t !mselves successively 9 lat] *apt]s4 ,= my pres5t purpose x is en\gh to %[ t ! sc5]y ( ^! di/ricts is n directly due to volcanic action1 b is ! imm$iate result ( d5udation act+ ^u volcanic rocks1 modifi$ & direct$ by _! geological /ructure4 ,x may1 h[ev]1 be useful1 9 conclud+ ! discussion ( ?is subject1 to cite "s typical volcanic regions 9 ! ,briti% ,isles z illu/rations ( ! relations betwe5 geology & topography1 :i*1 besides impress+ ! ma9 lesson "h en=c$1 may s]ve also to %[ "s ( ! /rik+ contra/s :i* geology reveals betwe5 ! pres5t & =m] conditions ( ! surface ( ! globe4 ,among ^! contra/s none are m s+ul> ?an ^? (f]$ by tracts :]e volcanic action has once be5 rife1 & :]e ! picture ( anci5t geography pres5t$ 9 ! rocks diff]s s widely f ! sc5]y ( ! same places to-day z to appeal vividly to ! imag9ation4 ,! fir/ di/rict to :i* ,i may ref] :]e anci5t volcanic rocks are well develop$ is t ( ,devon%ire4 ,! /ory ( ! ,devonian volcanoes w be told 9 "s detail 9 lat] *apt]s1 :5 x w be %[n t ! eruptions 7 aga9 & aga9 r5ew$ dur+ a long c\rse ( ages4 ,yet1 abundant z ! int]calat$ lavas & tuffs are1 !y c h>dly be said to h _h any m>k$ effect on ! sc5]y1 ?\gh "h & !re a h>d] or l>g] mass ( diabase rises into a prom95t knoll or isolat$ hill4 ,:5 ! am\nt ( volcanic mat]ial 9 ?is region is consid]$1 we may feel "s surprise at ! trifl+ influ5ce :i* x has ex]t$ 9 ! g5]al d5udation ( ! surface4 ,to "o :o w&]s ov] ! ri* *ampaign ( s\!rn ,devon%ire1 & surveys f "s high] prom95ce ! undulat+ tree-cr[n$ ridges t slope d[n into or*>d-fill$ holl[s1 & ! gre5 upl&s t sweep 9 successive waves ( v]dure to ! di/ant blue tors ( ,d>tmoor1 ! sc5e appe>s z a type ( all t is mo/ peaceful1 v>i$ & f]tile 9 ,engli% l&scape4 ,9 ! trim luxuriance t meets ! eye on e side1 ! h& ( man is app>5t1 ?\gh f _m a po9t ( vantage no s\nd may be he>d = a "t to %[ t he himself is any:]e ne> u4 ,yet ev] & anon f ! deep lanes1 hidd5 out ( sight "u _! canopy ( foliage1 !re w come ! creak ( ! groan+ waggon & ! crack ( ! waggon]'s :ip1 z evid5ce t !re are roads & human traffic ?r\gh ?is bosky sil5t c\ntry4 ,amid s mu* quiet beauty1 :]e e feature seems to be eloqu5t ( long g5]ations ( undi/urb$ repose1 x mu/ surely /ir ! imag9ation to be told t und]nea? ^! or*>ds1 mead[s & woodl&s lie ! m\ld]+ remnants ( once active & long-liv$ volcanoes4 ,yet we h only to desc5d into "o ( ! deep lanes to f9d ! crumbl+ lavas & a%es ( ! old eruptions4 ,! l&scape has1 9 tru?1 be5 c>v$ out ( ^! volcanic rocks1 & _! decomposition has furni%$ ! ri* loam t n\ri%es s luxuriant a vegetation4 ,n less impressive is ! contra/ pres5t$ betwe5 ! pres5t & =m] condition ( ! broad pa/oral upl&s ( ! s\? ( ,scotl&4 ,n[h]e 9 ! ,briti% ,isl&s c ! feel+ ( m]e lonel9ess be m p]fectly exp]i5c$ ?an among ^! elevat$ tracts ( b>e moorl&4 ,!y h no?+ ( ! gr&eur ( outl9e peculi> to m\nta9 tracts4 ,sometimes1 = miles ar\nd "o ( _! conspicu\s summits1 we may see no project+ knob or p9nacle4 ,! rocks h be5 g5tly r\nd$ (f into broad featureless hills1 :i* s9k into w9d+ valleys1 ea* ) its ?read ( /reamlet & its f>ms along ! bottom1 & its scatt]$ remnants ( bir*-wood or ald]-copse along its slopes & d+les4 ,across miles ( hea?y pa/ure & moorl&1 on ! summits ( ?is great tablel&1 we may p]*ance see no sign ( man or 8 h&iwork1 ?\gh ! bleat+ ( ! %eep & ! f>-(f b>k+ ( ! collie tell t we are "h )9 ! quiet doma9 ( ! s\?-c\ntry %eph]d4 ,9 ?is pa/oral t]ritory1 also1 ?\gh !y h>dly affect ! sc5]y1 volcanic rocks come to ! surface :]e ! fold+s ( ! e>?'s cru/ h br\ght up ! olde/ =mations4 ,_! appe>ance ext5ds ov] s wide an area z to %[ t a l>ge "p ( ^! upl&s lies on a deeply-buri$ volcanic floor4 ,a :ole s]ies ( subm>9e volcanoes1 ext5d+ ov] an area ( _m hundr$s ( squ>e miles1 & /ill 9 great "p ov]la9 ) ! accumulat$ s&s & silts ( ! sea-bottom1 n[ h>d5$ into /one1 und]lies ^! quiet hills & lonely valleys4 ,a contra/ ( ano!r type meets u 9 ! broad midl& valley ( ,scotl&4 ,ar\nd ! city ( ,ed9burgh1 = in/ance1 ! l&scape is div]sifi$ by _m hills & crags :i* %[ :]e h>d] rocks project f amid/ ! s$im5ts ( ! ,c>bonif]\s sy/em4 ,on "s ( ^! crags ! =ts ( ! e>ly races1 ! t[]s ( ,celt & ,saxon1 & ! feudal ca/les ( ! middle ages 7 successively plant$1 & r\nd _! base clu/]$ = protection ! cots ( ! peasants & ! e>lie/ home/eads ( ! future city4 ,b5ea? ^! crags _m ( ! mo/ notable ev5ts 9 ! /ormy annals ( ! c\ntry 7 transact$4 ,"u _! %ad[1 & n )\t inspiration f _! local =m & col\r1 lit]ature1 art & sci5ce h aris5 & fl\ri%$4 ,n[h]e1 9 %ort1 )9 ! compass ( ! ,briti% ,isles has ! political & intellectual progress ( ! p be5 m pla9ly affect$ by ! environm5t ?an 9 ?is c5tral di/rict ( ,scotl&4 ,:5 n[ we inquire into ! orig9 & hi/ory ( ! topography :i* has s influ5c$ ! population ar\nd x1 we f9d t its prom95ces are relics ( anci5t volcanoes4 ,! feudal t[]s are bas$ on sills & dykes & necks4 ,! fields & g>d5s1 monum5ts & roadways1 ov]lie %eets ( lava or b$s ( volcanic a%es4 ,n only is e conspicu\s em95ce imm$iately ar\nd ( volcanic orig91 b ev5 ! ranges ( blue hills t close 9 ! di/ant view to s\? & nor? & ea/ & we/ are ma9ly built up ( lavas & tuffs4 ,! eruptions ( :i* ^! heights are memorials belong to a va/ range ( geological ages1 ! late/ ( !m hav+ pass$ away long be=e ! adv5t ( man4 ,b !y h left _! traces deeply engrav5 9 ! rocky framework ( ! l&scape4 ,:ile human hi/ory1 /ormy or peaceful1 has be5 sl[ly evolv+ itself dur+ ! progress ( ! c5turies 9 ^! f]tile l[l&s1 ! crags & heights h rema9$ z memorials ( an e>li] hi/ory :5 ,c5tral ,scotl& cont9u$ = _m ages to be ! !atre ( vigor\s volcanic activity4 ,z a f9al illu/ration ( ! influ5ce ( volcanic rocks 9 sc5]y1 & ( ! contra/ betwe5 _! orig9 & _! pres5t condition1 ,i may cite ! m prom95t gr\ps ( hills 9 ! ,inn] ,hebrides4 ,9 ! s+ul>ly v>i$ l&scapes ( t region ?ree di/9ct types ( topography attract ! eye ( ! travell]4 ,^! are be/ comb9$ & mo/ fully develop$ 9 ! isl& ( ,skye4 ,?r\gh\t ! nor!rn half ( t picturesque isl&1 ! gr\nd rises into a roll+ tablel&1 deeply p5etrat$ by arms ( ! sea1 into :i* x slopes 9 gre5 declivities1 :ile along its out] bord]s x plunges 9 ranges ( precipice into ! ,atlantic4 ,ev]y:]e1 alike on ! cliffs & ! inl& slopes1 long p>allel l9es ( rock-t]race meet ! eye4 ,^! m\nt "o above ano!r f ! %ores up to ! flat tops ( ! highe/ hills1 pres5t+ level or g5tly-incl9$ b>s ( d>k crag t rise above slopes ( debris1 gre5 sw>d & brack54 ,x is ^! p>allel1 %>ply-def9$ b>s ( rock1 ) _! int]v5+ /rips ( v]dure1 t give its di/9ctive "* to ! sc5]y ( nor!rn ,skye4 ,on hillside aft] hillside & 9 valley aft] valley1 !y reappe> ) ! same almo/ artificial monotony4 ,& f> beyond ! limits ( ,skye !y are repeat$ 9 "o isl& aft] ano!r1 all d[n ! *a9 ( ! ,inn] ,hebrides4 ,9 /rik+ contra/ to ?is sc5]y1 & abruptly b\nd+ x on ! s\?1 rise ! ,r$ ,hills ( ,skye--a s+ul> gr\p ( connect$ cones4 ,alike 9 =m & 9 col\r1 ^! hills /& ap>t f ev]y?+ ar\nd !m4 ,! v]dure ( ! nor!rn t]rac$ tablel& "h entirely disappe>s4 ,! slopes are %eets ( angul> debris1--huge blocks ( nak$ /one & trails ( s&1 amid/ :i* h>dly any vegetation f9ds a foot+4 ,! decay ( ! rock gives x a pale yell[i%-grey hue1 :i* aft] ra9 deep5s into russet1 s t 9 fav\rable lights ^! /range cones gleam ) a w>m gl[ z if !y1 9 "s special way1 c\ld cat* & reflect ! radiance ( ! sky4 ,imm$iately to ! we/ ( ^! pale smoo?-slop$ cones1 ! d>k mass ( ! ,cuill9 ,hills completes ! int]ruption ( ! nor!rn tablel&4 ,9 almo/ e topographical feature ^! hills pres5t a contra/ to ! o!r two k9ds ( sc5]y4 ,_! =ms are m rugg$ ?an ^? ( any o!r hill-gr\p 9 ,brita9 7,fig4 #cca74 ,e declivity among !m is an irregul> pile ( crags1 e cre/ is not*$ l a saw1 e peak is %>p5$ into a p9nacle4 ,in/ead ( be+ buri$ "u va/ %eets ( _! own debris1 ^! hills %[ ev]y:]e _! nak$ rock1 :i* seems to brave ! elem5ts z few o!r rocks c d4 ,unlike ! pale ,r$ ,hills1 !y are d>k1 almo/ black 9 tone1 ?\gh :5 canopi$ ) cl\d !y assume a hue ( deepe/ violet4 ,ea* ( ^! ?ree di/9ct types ( topography owes its exi/5ce to ! way 9 :i* a special k9d ( volcanic rock yields to ! influ5ces ( d5udation4 ,! t]rac$ tablel& ( ! nor? is built up ( hundr$s ( %eets ( basaltic lava1 ea* ( ! long level l$ges ( br[n rock m>k+ ! outcrop ( "o or m ( ^! once molt5 /reams4 ,! black rugg$ mass ( ! ,cuill9 ,hills consi/s ( a va/ protrud$ body ( eruptive mat]ial1 :i*1 9 ! =m ( endless sills & bosses ( gabbro & dol]ite1 has invad$ ! basalt-plateau1 & has n[ be5 reveal$ by ! gradual removal ( ! portion ( t plateau :i* x uprais$4 ,! pale cones & domes ( ! ,r$ ,hills m>k ! place ( "o ( ! la/ protrusions 9 ! volcanic hi/ory ( ,brita9--t ( l>ge masses ( an acid magma1 :i* broke ?r\gh ! basalt-plateau & also disrupt$ ! e>li] gabbro4 ,9 no "p ( ,nor?-,we/]n ,europe has volcanic activity left m v>i$ & abundant records ( its op]ations ?an 9 ^! ?ree contigu\s tracts ( ,skye4 ,x is int]e/+ !re=e to note ! /rik+ contra/ betwe5 ! =m] & ! pres5t l&scapes ( ! region4 ,! lavas ( ! basaltic tablel& crumble into a ri* loam1 t 9 ! mild moi/ climate ( ! ,hebrides supports a gre5] v]dure ?an any ( ! o!r rocks ar\nd w yield4 ,! upl&s h accord+ly become pa/ure-gr\nds = h]ds ( %eep & cattle4 ,! /rips ( l[l& along ! valleys & 9 ! recesses ( ! coa/-l9e furni% ! *ief tracts ( arable l& 9 ! isl&1 & are ?us ! ma9 c5tres ( ! cr(t] population4 ,! bays & creeks ( ! mu*-ind5t$ %ores =m natural h>b\rs1 :i* 9 =m] days attract$ ! ,norse sea-rov]s1 & suppli$ !m ) sites = _! settlem5ts4 ,norse names /ill l+] on headl& & inlet1 b ! _s ( adv5ture has pass$ away1 & a few poor fi%+-boats1 "h & !re drawn up on ! bea*1 are usually ! only tok5 t ! isl&]s make any attempt to ga!r ! h>ve/ ( ! sea4 ,! m\nta9 gr\ps :i* s abruptly b\nd ! basalt-plateau on ! s\?1 & pres5t 9 _! topographical features su* di/9ctive sc5]y1 comprise a region too l(ty1 too rugg$ & too b>r5 = human occupation4 ,! black ,cuill9s & ! pale ,r$ ,hills are solitudes left to ! few wild creatures t h n yet be5 ext]m9at$4 ,! corries are ! home ( ! r$ de]4 ,! gabbro cliffs are haunts ( ! eagle & ! rav54 ,:]e pat*es ( soil h ga!r$ 9 ! crannies ( ! gabbro1 alp9e plants f9d _! home4 ,9 ! *asms left by ! decay ( ! dykes betwe5 ! v]tical walls ( _! fissures1 ! w9t] sn[s l+] into summ]1 & conceal ) _! ?ick drifts ! m\ld]+ surface ( ! once molt5 rock b5ea? !m4 ,on e side & at e turn a mute appeal is made to ! imag9ation by ! /range contra/s betwe5 ! quiet re/fulness ( to-day1 :5 ! sculpture-tools ( nature are ea* busily c>v+ ! features ( ! l&scape1 & ! tumult ( ! "t :5 ! rocks1 n[ s sil5t1 7 erupt$4 99 99 99 99 99 ,! g5]al discussion ( ! subject ( ,volcanism 9 ?is ,introduction w1 ,i hope1 h prep>$ ! read] :o has no special geological tra9+ = ent]+ ^u ! m detail$ descriptions 9 ! re/ ( ?is treatise4 ,z already /at$1 ! *ronological ord] ( arrangem5t w be foll[$4 ,beg9n+ ) ! records ( ! e>lie/ ages1 we %all foll[ ! /ory ( volcanic action d[n to ! end ( ! late/ eruptions4 ,ea* great geological sy/em w be tak5 z a :ole1 repres5t+ a long p]iod ( "t1 & its volcanic evolution w be trac$ f ! beg9n+ ( ! p]iod to ! close4 ,"s v>iety ( treatm5t is necess>ily entail$ by ! wide range 9 ! nature & am\nt ( ! evid5ce = ! volcanic hi/ory ( diff]5t ages4 ,b :]e practicable1 an outl9e w fir/ be giv5 ( :at c be ga!r$ respect+ ! physical geography ( ea* geological p]iod 9 ,brita94 ,9 ! description :i* w !n foll[ ( ! volcanic ph5om5a1 an acc\nt ( ! g5]al *>act]s ( ! erupt$ rocks w prec$e ! m detail$ n>rative ( ! hi/ory ( ! volcanic eruptions 9 ! sev]al regions :]e !y took place4 ,ref]5ces to ! publi%$ lit]ature ( ea* =mation w be giv5 9 ! fir/ "p ( ea* section1 or w be introduc$ 9 subsequ5t pages1 z may be f\nd mo/ conv5i5t4 ,,book ,,ii ,,volcanic ,,action ,,9 ,,pre-,,cambrian ,,"t ,,*apt] ,,viii ,,pre-,,cambrian ,,volcanoes ,! ,beg9n+s ( ,geological ,hi/ory--,difficulties 9 fix+ on a g5]ally-applicable ,t]m9ology--i4 ,! ,lewisian 7,ar*an7 ,gneiss2 ii4 ,! ,dalradian or ,y\ng] ,s*i/s ( ,scotl&2 iii4 ,! ,gneisses & ,s*i/s ( ,anglesey2 iv4 ,! ,uriconian ,volcanoes2 v4 ,! ,malv]n ,volcano2 vi4 ,! ,*>nwood ,=e/ ,volcano4 ,! e>ly geological hi/ory ( ?is globe1 l ! e>ly hi/ory ( mank9d1 mu/ be drawn f records at once scanty & h>dly deciph]able4 ,expos$ to ! long s]ies ( revolutions :i* ! surface ( ! planet has und]gone1 ^! records1 nev] p]haps complete at ! fir/1 h be5 9 l>ge measure oblit]at$4 ,ev5 :]e !y /ill exi/1 _! mean+ is (t5 s d\btful t1 9 try+ to int]pret x1 we f9d little solid foot+1 & feel ourselves to be grop+1 z x 71 9 ! dimness ( my?ological leg5d1 r ?an work+ 9 ! light ( tru/wor?y & intelligible *ronicles4 ,^! primeval records h be5 m p>ticul>ly ! objects ( s$ul\s /udy dur+ ! la/ tw5ty ye>s all ov] ,europe & 9 ,nor? ,am]ica4 ,a c]ta9 am\nt ( progress 9 _! deciph]m5t has be5 made4 ,b ! problems !y /ill pres5t = solution are num]\s & obscure4 ,=tunately1 ) _m ( ^! problems ! subject ( ! pres5t treatise is n imm$iately connect$4 ,we ne$ only conc]n ourselves ) ^? :i* are relat$ to ! hi/ory ( primeval volcanic activity4 ,to ! e>lie/ & lea/ def9ite division ( ! geological annals v>i\s names h be5 appli$4 ,"s writ]s1 believ+ t ?is p]iod prec$$ ! fir/ appe>ance ( plants or animals ^u ! globe1 h nam$ x ,azoic--! lifeless age ( geological hi/ory4 ,b ! abs5ce ( any hi!rto detect$ trace ( organic exi/5ce among ! olde/ kn[n rocks _c be held to prove t ^! rocks 7 =m$ be=e ! adv5t ( liv+ ?+s on ! surface ( ! e>?4 ,! *ance discov]y ( a s+le fossil1 :i* might at any mom5t be made1 w\ld %[ ! "n ,azoic to be a misnom]4 ,o!r geologi/s1 believ+ t1 z a matt] ( fact1 organic /ructures ( l[ types d actually occur 9 !m1 h call$ ^! old rocks ,eozoic1 to d5ote t !y 7 deposit$ dur+ ! dawn ( life ^u our planet4 ,b ! suppos$ organisms h n be5 ev]y:]e accept$ z evid5ce ( =m] life4 ,by _m able obs]v]s !y are reg>d$ z m]e m9]al aggregates4 ,ano!r t]m1 ,ar*an1 has be5 propos$ = ! primeval ages ( geological hi/ory1 :i* are record$ 9 rocks t c>ry u z f> z may ev] be possible t[>ds ! beg9n+s ( t hi/ory4 ,9 *oos+ "s g5]al t]m to include ! olde/ kn[n p>ts ( ! e>?'s cru/1 geologi/s are apt unconsci\sly to assume t ! rocks ?us class$ toge!r repres5t a def9ite section ( geological "t1 comp>able1 = in/ance1 to t d5ot$ by "o ( ! ,palozoic sy/ems4 ,yet x is obvi\s t1 "u "o ( ^! g5]al t]ms ( conv5i5t classification1 a mo/ multif>i\s s]ies ( rocks may be includ$1 repres5t+ n "o b possibly _m1 & widely sep>at$1 p]iods ( geological hi/ory4 ,9 _m c\ntries ! olde/ s$im5t>y accumulations1 :e!r fossilif]\s or n1 are und]la9 by a s]ies ( cry/all9e rocks1 :i* consi/ 9 great "p ( co>se massive gneisses & o!r s*i/s4 ,all ov] ! _w ^! rocks pres5t a s+ul> sam5ess ( /ructure & composition4 ,:at might be f\nd bel[ !m no man c say4 ,!y are 9 ea* c\ntry ! olde/ rocks ( :i* any?+ is yet kn[n1 & :atsoev] may be our !ory ( _! orig91 we mu/1 at lea/ = ! pres5t1 />t f !m z ! fundam5tal plat=m ( ! t]re/rial cru/4 ,b ?\gh cry/all9e rocks ( ?is p]si/5t "* are widely di/ribut$1 bo? 9 ! ,old ,_w & 9 ! ,new1 !y 9 !mselves furni% no means ( det]m9+ _! precise geological age4 ,no me?od has yet be5 devis$ :]eby ! olde/ gneiss ( "o c\ntry c be %[n to be ! true /ratigraphical equival5t ( ! olde/ gneiss ( ano!r4 ,palontology is "h ( no avail1 & ,petrology has n yet provid$ u ) su* a g5etic s*eme z w enable u to make use ( m9]als & rock-/ructures1 z we d ( fossils1 9 ! det]m9ation ( geological horizons4 ,all t c be positively affirm$ reg>d+ ! /ratigraphical relations ( ! rocks 9 "q is t !y are va/ly m anci5t ?an ! olde/ s$im5t>y & fossilif]\s =mations 9 ea* c\ntry :]e !y are f\nd4 ,! ,lewisian gneiss ( ! nor?-we/ ( ,scotl&1 ! ,urgneiss ( ,c5tral ,europe1 & ! ,laur5tian gneiss ( ,canada occupy simil> /ratigraphical positions1 & pres5t a close resemblance 9 li?ological *>act]s4 ,we may conv5i5tly class !m "u "o common "n to d5ote ?is g5]al relation%ip4 ,b we h1 z yet1 no means ( det]m9+ h[ f> !y belong to "o cont9u\s p]iod ( geological hi/ory4 ,!y may really be ( va/ly diff]5t degrees ( antiquity4 ,f ! v nature ( ! case1 any "n by :i* we may *oose to designate su* anci5t rocks _c possess ! precise /ratigraphical value ( ! t]ms appli$ to ! fossilif]\s =mations4 ,yet ! conv5i5ce ( possess+ su* a g5]al descriptive epi!t is obvi\s4 ,until mu* m k ( ! subject has be5 ga9$1 any t]m9ology :i* may be propos$ mu/ be reg>d$ z m or less provisional4 ,! compreh5sive t]m pre-,cambrian may be usefully adopt$ z a g5]al designation = all rocks old] ?an ! base ( ! ,cambrian sy/em1 irrespective ( _! nature & orig94 ,already x is well kn[n t "u ?is t]m a va/ s]ies ( rocks1 igne\s & s$im5t>y1 is includ$4 ,9 "s regions sev]al successive =mations1 or sy/ems ( =mations1 may be recogniz$ 9 ?is s]ies4 ,b until "s me?od has be5 devis$ = det]m9+ ! /ratigraphical relations ( ^! =mations 9 diff]5t regions1 x w\ld seem safe/ n to attempt to introduce g5]al names = univ]sal adoption1 b to let ! sequ5ce ( rocks 9 ea* di/9ct geological prov9ce be express$ by a local t]m9ology4 ,?is caution is m especially desirable 9 ! case ( s$im5t>y deposits4 ,we may surmise z to ! equival5ce ( ! rocks call$ ,huronian1 ,torridonian & ,longmyndian1 b :il/ s mu* is m]e conjecture1 x is c]ta9ly injudici\s to transf] ! local names ( "o prov9ce to ! rocks ( ano!r4 ,! only relaxation ( ?is g5]al precaution :i* ,i ?9k may at pres5t be made is ! adoption ( a common "n = ! olde/ type ( gneisses4 ,! t]m ,ar*an has be5 appli$ to ^! rocks1 & if x is us$ simply to express a common petrographical type1 occupy+ ! l[e/ horizon 9 ! /ratigraphical s]ies ( a c\ntry1 x has obvi\s advantages4 ,b ,i w\ld /ill reta9 ! local names z subord9ate t]ms to m>k ! local *>act]i/ics ( ! ,ar*an rocks ( ea* prov9ce4 ,?us ! ,laur5tian rocks ( ,canada & ! ,lewisian rocks ( ,scotl& are widely-sep>at$ repres5tatives ( ! peculi> /ratigraphical s]ies :i* is kn[n z ,ar*an4 ,! pre-,cambrian rocks ( ,brita9 include sev]al di/9ct sy/ems or gr\ps4 ,h[ f> ^? ( ev5 "o "p ( ?is comp>atively limit$ region are ! prop] equival5ts ( ^? ( ano!r & di/ant "p is a problem /ill unsolv$4 ,h5ce ea* di/9ct area1 ) its own type ( rocks1 w "h be treat$ by itself4 ,! foll[+ rock-types w be describ$3 ,i4 ,! ,lewisian 7,ar*an7 ,gneiss2 ,,ii4 ,! ,y\ng] 7,dalradian7 ,s*i/s ( ,scotl&2 ,,iii4 ,! ,gneisses & ,s*i/s ( ,anglesey2 ,,iv4 ,! ,uriconian ,gr\p2 ,v4 ,! ,malv]n ,gr\p2 ,,vi4 ,! ,*>nwood ,=e/ ,gr\p 7see ,map ,i474 i4 ,,! ,,lewisian 7,,ar*a,n7 ,,gneiss ,! ,briti% ,isles are s+ul>ly =tunate 9 possess+ an admirable developm5t ( pre-,cambrian rocks4 ,^! anci5t masses rise up 9 v>i\s p>ts ( ! isl&s1 b ! region :]e !y are mo/ ext5sively display$1 & :]e _! /ratigraphical position & sequ5ce are mo/ cle>ly %[n1 lies 9 ! nor?-we/ ( ,scotl&4#ej ,9 t t]ritory !y =m ! :ole *a9 ( ! ,out] ,hebrides1 & likewise ext5d z an irregul> selvage along ! we/]n m>g9 ( ! c\nties ( ,su!rl& & ,ross4 ,! l[e/ kn[n plat=m ( ! fossilif]\s =mations has !re be5 discov]$ & has be5 trac$ = a di/ance ( m ?an #ajj miles4 ,f ?is def9ite horizon1 ! high antiquity ( all t lies bel[ x is impressively demon/rat$4 ,! accompany+ diagram 7,fig4 #ce7 w expla9 ! g5]al relations ( ! v>i\s geological =mations ( ! region4 ,footnote #ej3 ,^! rocks h be5 ! subject ( mu* discussion1 b geologi/s are n[ agre$ z to _! succession & /ructure4 ,a full summ>y ( ! lit]ature ( ! controv]sy reg>d+ !m w be f\nd 9 ! ,qu>t]ly ,j\rnal ( ! ,geological ,society1 vol4 xliv4 7#ahhh71 p4 #cgh4 ,9 c]ta9 d>k %ales 7b7 :i* occupy a well-def9$ & readily-traceable position among ! rocks ( ,su!rl& & ,ross1 num]\s specim5s ( ! trilobite g5us ,ol5ellus1 toge!r ) o!r fossils1 h be5 f\nd4 ,by common cons5t among geologi/s1 ! zone ( rock 9 :i* ?is g5us appe>s is tak5 z ! l[e/ /age ( ! ,cambrian sy/em4 ,9 ,brita9 x m>ks ! olde/ kn[n gr\p ( fossilif]\s /rata--! plat=m on :i* ! :ole ( ! ,palozoic sy/ems re/4 ,illu/ration3 ,fig4 #ce4--;,diagram illu/rat+ ! /ratigraphical relations ( ! pre-,cambrian & ,cambrian rocks ( ! ,nor?-we/ ,highl&s ( ,scotl&4 c1 ,durness ,lime/ones1 ) ,upp] ,cambrian & p]haps ,l[] ,silurian fossils1 #aejj feet1 top n[h]e se54 b1 ,s]pulite grit & fucoid %ales1 #gj to #hj feet1 conta9+ ! ,ol5ellus-zone4 a1 ,qu>tzite1 ) abundant annelid tubes1 ab\t #fjj feet4 ,,ii4 ,r$ ,s&/ones & ,conglom]ates1 sometimes #hjjj feet or m 7,torridonian74 ,i4 ,gneiss ) dykes1 etc4 7,lewisian74 ,f ! def9ite geological epo* indicat$ by ?is plat=m1 we c g backw>d into pre-,cambrian "t1 & realize 9 "s measure h[ prodigi\s mu/ be ! antiquity ( ! successive gr\ps ( rock :i* em]ge f b5ea? ! base ( ! ,palozoic sy/ems4 ,n[h]e is ?is antiquity m impressively proclaim$ ?an 9 ! nor?-we/ ( ,scotl&4 ,f bel[ ! ,ol5ellus-zone ) its und]ly+ %eets ( qu>tzite 7a71 a ?ick gr\p ( dull r$ s&/ones & conglom]ates 7,,ii47 rises into a s]ies ( deta*$ conical or pyramidal m\nta9s1 :i* =m "o ( ! mo/ *>act]i/ic features 9 ! sc5]y ( t region4 ,z ?is detrital =mation is well develop$ ar\nd ,lo* ,torridon1 x has be5 t]m$ ,torridonian4 ,x atta9s a ?ickness ( at lea/ #hjjj or #aj1jjj feet1 & is traceable all ! way f ! extreme nor!rn headl&s ( ,su!rl& to ! s\!rn cliffs ( ! isl& ( ,rum4 ,9 judg+ ( ! *ronological significance ( ! geological /ructure ( ! nor?-we/ ( ,scotl&1 we are fir/ impress$ by ! /ratigraphical break betwe5 ! base ( ! ,cambrian sy/em & ! ,torridonian deposits bel[4 ,?is break is s complete t "h & !re ! ?ick int]v5+ mass ( s&/ones & conglom]ates has be5 ne>ly or :olly remov$ by d5udation be=e ! l[e/ ,cambrian /rata 7 laid d[n4 ,su* a discordance m>ks ! passage ( a protract$ int]val ( "t4 ,aga91 :5 ! composition ( ! ,torridonian rocks is consid]$1 fur!r /rik+ evid5ce is obta9$ ( ! lapse ( long p]iods4 ,! s&/ones1 conglom]ates & %ales ( ?is pre-,cambrian sy/em pres5t no evid5ce ( cataclysmal action4 ,on ! contr>y1 !y be> te/imony t !y 7 accumulat$ mu* 9 ! same way & at ! same rate z ! subsequ5t ,palozoic sy/ems4 ,9 t primeval p]iod1 z n[1 s& & silt 7 spread out "u lakes & seas1 7 ripple-m>k$ by ! agitation ( ! wat]1 & 7 gradually buri$ "u o!r lay]s ( simil> s$im5t4 ,! accumulation ( #aj1jjj feet ( su* gradually-assort$ detritus mu/ h dem&$ a long s]ies ( ages4 ,"h1 !n1 9 ! int]nal /ructure ( ! ,torridonian rocks1 !re is pro( t 9 pass+ across !m1 f _! summit to _! base1 we make ano!r va/ /ride backw>d into ! e>ly pa/ ( geological hi/ory4 ,b :5 att5tion is direct$ to ! relations ( ! ,torridonian /rata to ! rocks b5ea? !m1 a /ill m /rik+ pro( ( an enorm\sly protract$ p]iod ( "t is obta9$4 ,betwe5 ! two s]ies ( =mations lies "o ( ! mo/ m>k$ /ratigraphical breaks 9 ! geological /ructure ( ! ,briti% ,isles4 ,!re is absolutely no?+ 9 common betwe5 !m1 save t ! conglom]ates & s&/ones h be5 l>gely made out ( ! wa/e ( ! und]ly+ gneiss4 ,! d5udation ( ! cry/all9e rocks be=e ! deposition ( any ( ! ,torridonian s$im5ts mu/ h be5 prolong$ & gigantic4 ,! m1 inde$1 we /udy ! gneiss1 ! m d we feel impress$ by ! evid5ce = ! lapse ( a va/ int]val ( "t1 "h unrecord$ 9 rock1 betwe5 ! la/ t]re/rial movem5ts indicat$ by ! gneiss & ! e>lie/ ( ! ,torridonian s$im5ts4 ,9 ?is mann]1 reason+ backw>d f ! horizon ( ! ,ol5ellus-zone1 we are enabl$ to =m "s conception ( ! va/ness ( ! antiquity ( ! fundam5tal rocks ( ! ,nor?-we/ ,highl&s4 ,! nature & orig9 ( ^! rocks acquire a special int]e/ f a consid]ation ( _! age4 ,!y conta9 ! *ronicles ( ! v beg9n+s ( geological hi/ory1 9 s f> z ?is hi/ory is conta9$ 9 ! cru/ ( ! e>?4 ,no "p ( ! geological record is s obscure z ?is e>lie/ *apt]1 b we ne$ n "h ent] fur!r into its difficulties ?an may be necess>y = ! purpose ( und]/&+ :at light x c be made to ?r[ on ! e>lie/ manife/ations ( volcanic action4 ,"u ! t]m ,lewisian ,gneiss 7,i4 9 ,fig4 #ce7 a s]ies ( rocks is compris$ :i* diff] f ea* o!r 9 composition1 /ructure & age1 ?\gh mo/ ( !m possess su* cry/all9e & g5]ally foliat$ *>act]s z may be conv5i5tly includ$ "u ! designation ( gneiss4 ,! complexity ( ^! anci5t cry/all9e masses 0 n recogniz$ at ! "t :5 ,mur*ison call$ !m ! ,fundam5tal or ,lewisian gneiss4 ,x is only s9ce ! ,geological ,survey began to /udy & map !m 9 full detail t _! true nature & hi/ory h begun to be und]/ood4#ea ,footnote #ea3 ,see ! ,report ( ?is ,survey "w by ,messrs4 ,pea*1 ,horne1 ,gunn1 ,cl\gh1 ,cadell & ,h9xman1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xliv4 7#ahhh71 pp4 #cgh-dda2 & ,annual ,reports ( ,director-,g5]al ( ! ,geological ,survey 9 ! ,report ( ,! ,sci5ce & ,art ,dep>tm5t = #ahid1 p4 #bgi1 & #ahie1 p4 #ag ( repr9t4 ,! g5]al area ( ! gneiss is %[n 9 ,map ,i4 ,! rese>*es ( ! ,survey h %[n ! s-call$ ,lewisian gneiss to comprise ! foll[+ five gr\ps ( rock3 #a4 ,a gr\p ( v>i\s m or less b&$ & foliat$ rocks :i* =m toge!r ! olde/ & *ief "p ( ! gneiss 7,fundam5tal complex72 #b4 ,highly basic dykes cutt+ ! fir/ gr\p2 #c4 ,dykes & sills ( dol]ite1 epidiorite & hornbl5de-s*i/2 #d4 ,a few dykes ( peculi> composition2 #e4 ,gneissose granite & pegmatite4 ,! fir/ ( ^! gr\ps1 =m+ ! ma9 body ( ! gneiss1 has be5 critically /udi$ on ! ma9l& f ,cape ,wra? to ,skye4 ,b its developm5t 9 ! ,out] ,hebrides has n yet be5 work$ out1 al?\gh ! "n ,lewisian 0 actually tak5 f t *a9 ( isl&s4 ,s f> z at pres5t kn[n1 h[ev]1 ! gneiss ( ! ,hebrides repeats ! ess5tial *>act]s ( t ( ! ma9l&4 ,mr4 ,teall1 z ! result ( a c>eful inve/igation 9 ! field & ) ! microscope1 has asc]ta9$ t on ! ma9l& betwe5 ,skye & ,cape ,wra? ! rocks ( ! fundam5tal complex are ess5tially compos$ ( oliv9e1 hyp]/h5e1 augite 7includ+ diallage71 hornbl5de1 biotite1 plagioclase1 or?oclase1 microcl9e & qu>tz4 ,he has fur!r obs]v$ t ^! m9]als are associat$ toge!r 9 ! same mann] z 9 p]idotites1 gabbros1 diorites & granites4 ,treat+ ! rocks 9 accordance ) _! composition & p>tly ) _! /ructure1 b exclud+ !oretical consid]ations1 he has arrang$ !m 9 ! foll[+ five subdivisions3-- #a4 ,rocks compos$ ( f]ro-magnesian m9]als1 )\t felsp> or qu>tz--,pyrox5ites1 ,hornbl5dites4 #b4 ,rocks 9 :i* pyrox5es are ! dom9at+ f]ro-magnesian con/itu5ts1 felsp> always be+ pres5t1 sometimes qu>tz3 ,a1 ,)\t qu>tz1 ,hyp]/h5e-augite-rocks 7pyrox5e granulites2 rocks ( ! ,baltimore-gabbro type7 & augite-rocks 7gabbros72 ,b1 ,) qu>tz1 ,augite-gneiss4 #c4 ,rocks 9 :i* hornbl5de is ! preval5t f]ro-magnesian con/itu5t3 ,a1 ,)\t qu>tz1 or conta9+ x only 9 small quantity2 rocks basic 9 composition3 7a7 massive or only slightly foliat$ 7,amphibolites1 z epidote-amphibolite1 zoisite-amphibolite1 g>net-amphibolite72 7b7 foliat$ 7,hornbl5de-s*i/74 ,b1 ,) qu>tz2 rocks int]m$iate or acid 9 composition3 7a7 ) compact hornbl5de & a granul> /ructure 7,hornbl5de-gneiss prop]72 7b7 ) hornbl5de occurr+ 9 fibr\s or o!r aggregates2 7c7 ) compact hornbl5de & a m or less granulitic /ructure 7,granulitic hornbl5de-gneiss74 #d4 ,rocks 9 :i* biotite is ! pr$om9ant f]ro-magnesian con/itu5t2 felsp> & qu>tz bo? pres5t3 7a7 ,biotite occurr+ z indep5d5t plates or 9 aggregates ( two or ?ree l>ge individuals 7,biotite-gneiss72 7b7 ,biotite occurr+ 9 aggregates ( num]\s small individuals 7r>e type72 7c7 ,biotite occurr+ z indep5d5t plates 9 a granulitic /ructure4 #e4 ,rocks 9 :i* muscovite & biotite are pres5t1 toge!r ) felsp> & qu>tz--,muscovite-biotite-gneiss4 ,^!1 ?\gh n =m+ a well-def9$ natural gr\p1 are plac$ toge!r = purposes ( description4 ,!y are all foliat$1 "s hav+ ! aspect ( mica-s*i/s1 o!rs be+ typical aug5-gneisses1 or light grey gneisses ) abundant oligoclase & inclusions ( microlitic epidote4 ,! rocks ( ea* ( ^! types are usually re/rict$ to relatively small areas1 & !y succe$ ea* o!r ) mu* irregul>ity all ! way f ,skye to ,cape ,wra?4 ,_! *emical & m9]alogical composition proves !m to h decid$ aff9ities ) ! plutonic igne\s masses ( ! e>?'s cru/4 ,! only exceptions to ?is preval5t igne\s type occur 9 ! di/ricts ( ,gairlo* & ,lo* ,c>ron1 :]e ! gneiss appe>s to be associat$ ) a gr\p ( mica-s*i/s1 graphitic-s*i/s1 qu>tzites & silice\s granulites1 lime/ones1 dolomites1 *lorite-s*i/s & o!r s*i/s4 ,t ^! are alt]$ s$im5t>y =mations c h>dly be d\bt$4 ,:at _! precise relations to ! fundam5tal complex ( ! gneiss may be has n yet be5 satisfactorily det]m9$4 ,!y are c]ta9ly f> old] ?an ! ,torridon s&/one :i* cov]s !m uncon=mably4 ,possibly !y may repres5t a s$im5t>y =mation /ill m anci5t ?an ! gneiss4 ,save ^! obscure relics ( a pre-,torridonian sy/em ( /rata1 ! gneiss nev] pres5ts any /ructure :i* sugge/s ! alt]ation ( cla/ic con/itu5ts4 ,ev]y:]e its m9]al composition po9ts to a connection ) ! subt]ranean intrusions ( diff]5t igne\s magmas1 :ile ! mann] 9 :i* its diff]5t rock-gr\ps are associat$ toge!r1 & ! int]nal /ructure ( "s ( !m1 /ill fur!r l9k x ) ph5om5a :i* w be describ$ 9 succe$+ *apt]s z p>ts ( ! records ( volcanic action4 ,an int]e/+ feature ( ! fundam5tal complex1 z be>+ on ! orig9 ( ! gneiss1 is to be f\nd 9 ! occurr5ce ( bosses & b&s :i* are ei!r non-foliat$ or foliat$ only 9 a slight degree4 ,^! comp>atively /ructureless portions pres5t mu* ( ! "* ( bosses or sills ( true eruptive rocks4 ,!y occur 9 v>i\s p>ts ( ,su!rl& & ,ross4 ,_! ext]nal m>g9s are n well def9$1 & !y pass ins5sibly into ! ord9>y gneiss1 ! d>k basic massive rocks %ad+ (f into co>se basic gneisses1 & ! pegmatites ( qu>tz & felsp> :i* trav]se !m m]g+ into b&s ( grey qu>tzose gneiss4 ,s f>1 !re=e1 z pres5t k goes1 ! ma9 body or fundam5tal complex ( ! ,lewisian gneiss 9 ! ,nor?-we/ ,highl&s ( ,scotl& consi/s ( :at may h be5 orig9ally a mass ( v>i\s eruptive rocks4 ,x has subsequ5tly und]gone a succession ( de=mations f enorm\s /resses )9 ! t]re/rial cru/1 :i* h be5 inve/igat$ ) great c>e by ! ,geological ,survey4 ,b x pres5ts /ructures :i*1 9 spite ( ! abundant pro(s ( great me*anical de=mation1 are yet1 ,i v5ture to ?9k1 orig9al1 or at lea/ belong to ! "t ( igne\s protrusion be=e de=mation took place4 ,! alt]nation ( rocks ( diff]5t petrographical con/itution sugge/s a succession ( extravasations ( eruptive mat]ials1 ?\gh x may n be always possible n[ to det]m9e ! ord] 9 :i* ^! foll[$ ea* o!r4 ,9 ! feebly foliat$ or massive b&s & bosses !re is a p>allel arrangem5t ( _! con/itu5t m9]als or ( f9e & co>se cry/all9e lay]s :i* recalls sometimes v /rik+ly ! fl[-/ructure ( rhyolites & o!r lavas4 ,?is resemblance 0 /rongly insi/$ on by ,p\lett ,scrope1 :o believ$ t ! lam9> /ructure ( su* rocks z gneiss & mica-s*i/ 0 be/ expla9$ by ! supposition ( ! fl[ ( a granitic magma "u great pressure )9 ! e>?'s cru/4#eb ,footnote #eb3 ,volcanoes1 pp4 #adj1 #bhc1 #bii4 ,! conviction t ^! p>allel /ructures d1 9 "s cases1 really repres5t traces ( movem5ts 9 ! orig9al unconsolidat$ igne\s masses1 n yet :olly effac$ by lat] me*anical /resses1 has be5 greatly /r5g!n$ 9 my m9d by a rec5t /udy ( ! /ructures ( v>i\s eruptive bosses1 especially ^? ( gabbro 9 ! ,t]ti>y volcanic s]ies ( ! ,inn] ,hebrides4 ,! b&$ /ructure1 ! sep>ation ( ! con/itu5t m9]als into di/9ct lay]s or zones1 ! alt]nation ( m>k$ly basic ) m acid lay]s1 & ! puck]+ & plication ( ^? b&s1 c be se5 z p]fectly among ! ,t]ti>y gabbro bosses ( ,skye z 9 ! ,lewisian gneiss 7see ,figs4 #ccf & #ccg74 ,x _c be cont5d$ t su* /ructures 9 ! gabbro are due to any subsequ5t t]re/rial di/urbance & consequ5t de=mation4 ,!y mu/ be accept$ z "p ( ! orig9al /ructure ( ! molt5 magma4#ec ,x seems to me1 !re=e1 highly probable t ! p>allel b&+ 9 ! uncru%$ cores ( ! ,lewisian gneiss reveals to u "s ( ! movem5ts ( ! orig9al magma at ! "t ( its extrusion & be=e x und]w5t ^? great me*anical /resses :i* h s l>gely contribut$ to ! production ( _m ( its mo/ *>act]i/ic /ructures4 ,footnote #ec3 ,see ,a4 ,geikie & ,j4 ,j4 ,h4 ,teall1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 #a4 7#ahid71 p4 #fde4 ,:ile ! mat]ial ( ! olde/ gneiss pres5ts _m aff9ities to plutonic rocks ( mu* y\ng] date1 a wide region ( m]e speculation op5s out :5 we try to picture ! conditions "u :i* ?is mat]ial 0 accumulat$4 ,"s geologi/s h boldly advanc$ ! doctr9e t ! ,ar*an gneisses repres5t ! e>lie/ cru/ t consolidat$ ^u ! surface ( ! globe4 ,b ^! rocks (f] no po9ts ( resemblance to ! ord9>y aspect ( sup]ficial volcanic ejections4 ,on ! contr>y1 ! co>sely-cry/all9e condition ev5 ( ^? portions ( ! gneiss :i* seem mo/ ne>ly to repres5t orig9al /ructure1 ! abs5ce ( any?+ l scori or fragm5tal b&s ( any k9d1 & ! resemblances :i* may be trac$ betwe5 p>ts ( ! gneiss & intrusive bosses ( igne\s rock compel u to seek ! ne>e/ analogies to ! orig9al gneiss 9 deep-seat$ masses ( eruptive mat]ial4 ,x is difficult to conceive t any rocks approa*+ 9 "* to ! gabbros1 picrites1 granulites & o!r co>sely-cry/all9e portions ( ! old gneiss c\ld h consolidat$ at or ne> ! surface4 ,:5 ! l>g] area ( gneiss =m+ ! *a9 ( ! ,out] ,hebrides is /udi$1 we may obta9 additional in=mation reg>d+ ! probable orig9 & ! e>lie/ /ructures ( ! fundam5tal complex ( ! ,lewisian gneiss4 ,9 p>ticul>1 we may look = "s unfoliat$ cores ( a m acid "*1 & p]haps = evid5ce :i* w %[ t bo? acid & basic mat]ials 7 successively protrud$4 ,we may ev5 ent]ta9 a fa9t hope t "s trace may be discov]$ ( sup]ficial or truly volcanic products connect$ ) ! bosses :i* recall ^? ( lat] date & obvi\sly eruptive nature4 ,b up to ! pres5t "t no indication ( any su* sup]ficial accompanim5ts has be5 detect$4 ,if any portions ( ! old gneiss repres5t ! deep] p>ts ( columns ( molt5 rock t fl[$ out at ! surface z lava1 ) dis*>ges ( fragm5t>y mat]ials1 all ?is sup]9cumb5t mat]ial1 at lea/ 9 ! regions :i* h be5 /udi$ 9 detail1 _h disappe>$ entirely be=e ! deposition ( ! v olde/ "p ( ! ,torridonian rocks1 unless "s trace ( x may rema9 among ! pebbles ( ! ,torridonian conglom]ates1 to :i* ref]5ce w be imm$iately made4 ,s f>1 !n1 z ! evid5ce n[ available all[s a conclusion to be drawn1 ! ,lewisian gneiss reveals to u a primeval gr\p ( eruptive rocks pres5t+ a /rong resemblance to "s :i* 9 lat] =mations are connect$1 z und]gr\nd cont9uations1 ) b$d$ lavas & tuffs t 7 erupt$ at ! surface2 & al?\gh no pro( has yet be5 obta9$ ( true volcanic ejections associat$ ) ! fundam5tal complex1 ! rocks seem to be mo/ readily und]/ood if we reg>d !m z hav+ consolidat$ f igne\s fusion at "s dep?1 & we may plausibly inf] t !y may h be5 actually connect$ ) ! dis*>ge ( volcanic mat]ials at ! surface4 ,! graphite-s*i/s1 mica-s*i/s1 & lime/ones ( ! ,gairlo* & ,lo* ,c>ron may ?us be surviv+ fragm5ts ( ! /ratifi$ cru/ into :i* ^! deep-seat$ masses 7 intrud$1 & ?r\gh :i* any volcanic eruptions t 7 connect$ ) !m _h to make _! way4 ,! limit$ areas occupi$ by ! sev]al v>ieties ( rock 9 ! fundam5tal complex sugge/s ! successive protrusion ( diff]5t magmas1 or ( diff]5t portions f "o gradually *ang+ magma4 ,mr4 ,teall has asc]ta9$ t :5ev] 9 ?is s]ies ( rocks ! relative ages ( two petrographical types c be cle>ly asc]ta9$1 ! m basic is old] ?an ! m acid4 ,b besides all ! complexity aris+ f orig9al div]sity ( area1 /ructure & composition among ! successive intrusions1 a fur!r intricacy has be5 produc$ by ! subsequ5t t]re/rial di/urbances1 :i* on a gigantic scale affect$ ! nor?-we/ ( ,europe aft] ! =mation ( ! fundam5tal complex ( ! old gneiss1 b long be=e ! ,torridonian p]iod4 ,by a s]ies ( t]re/rial /resses t came z precursors ( ^? :i* 9 lat] geological times work$ su* great *anges among ! rocks ( ! ,scotti% ,highl&s1 ! orig9al bosses & %eets ( ! gneiss 7 compress$1 plicat$1 fractur$ & roll$ out1 acquir+ 9 ?is process a crumpl$1 foliat$ /ructure4 ,:e!r or n ^! di/urbances 7 accompani$ by any manife/ations ( sup]ficial volcanic action has n yet be5 det]m9$4 ,b we "k t !y 7 foll[$ by a succession ( dyke-eruptions1 to :i*1 = ext5t & v>iety1 !re is no p>allel 9 ! geological /ructure ( ,brita91 save 9 ! rem>kable assemblage ( dykes belong+ to ! ,t]ti>y volcanic p]iod#ed 7,fig4 #cf74 ,footnote #ed3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xliv4 7#ahhh71 p4 #chi et seq4 ,illu/ration3 ,walk] ,b\tall sc4 ,fig4 #cf4--,map ( a portion ( ! ,lewisian gneiss ( ,ross-%ire4 ,tak5 f ,%eet #ajg ( ! ,geological ,survey ( ,scotl& on ! scale ( "o in* to a mile4 ,! :ite gr\nd 7,a7 m>ks ! g5]al body ( ! ,lewisian gneiss4 ,?is is trav]s$ by dykes ( dol]ite 7,b71 :i* are cut by lat] dykes ( highly basic mat]ial 7p]idotite1 picrite1 etc41 ,p74 ,! gneiss & its sy/em ( dykes is ov]la9 uncon=mably by ! ne>ly horizontal ,torridon ,s&/one 7t71 :i* is inject$ by %eets ( oligoclase-porphyry 7,f74 ,= ! production ( ^! dykes a s]ies ( fissures 0 fir/ op5$ ?r\gh ! fundam5tal complex ( ! gneiss1 hav+ a g5]al tr5d f ,e4,s4,e4 to ,w4,n4,w41 runn+ 9 p>allel l9es = _m miles1 & s close toge!r 9 "s places t fifte5 or tw5ty ( !m occurr$ )9 a horizontal space ( "o mile4 ,! fissures 7 probably n all =m$ at ! same "t2 at all ev5ts1 ! molt5 mat]ials t rose 9 !m exhibit di/9ct evid5ce ( a succession ( upwell+s f ! igne\s magma bel[4 ,consid]$ simply f ! petrographical po9t ( view1 ! mat]ials t h fill$ ! fissures h be5 arrang$ by ,mr4 ,teall 9 ! foll[+ gr\ps3 #a4 ,ultrabasic dykes1 sometimes massive 7p]idotites71 sometimes foliat$ 7talcose s*i/s conta9+ c>bonates & sometimes g$rite72 #b4 ,basic dykes :i* :]e massive take ! =ms ( dol]ite & epidiorite1 & :]e foliat$ appe> z hornbl5de-s*i/1 ! same dyke (t5 pres5t+ ! ?ree conditions ( dol]ite1 epidiorite & hornbl5de-s*i/2 #c4 ,dykes ( peculi> composition1 compris+ microcl9e-mica rocks & biotite-diorite ) macro-poikilitic plagioclase2 #d4 ,granites & gneissose granites 7biotite-granite ) microcl9e72 #e4 ,pegmatites 7microcl9e-qu>tz rocks ) a v>iable am\nt ( oligoclase or albite74#ee ,footnote #ee3 ,annual ,report ( ,geological ,survey = #ahie1 p4 #ah ( repr9t4 ,di/9ct evid5ce ( a succession ( eruptions c be made out among ^! rocks4 ,by f> ! l>ge/ proportion ( ! dykes consi/s ( basic mat]ials4 ,! olde/ & mo/ abundant ( !m are ( plagioclase-augite rocks1 :i*1 :]e uncru%$1 diff] 9 no ess5tial feature ( /ructure or composition f ! dol]ites & basalts ( m mod]n p]iods1 ?\gh !y h be5 pl5tifully *ang$ into epidiorite & hornbl5de-s*i/4#ef ,!y pres5t1 too1 mo/ ( ! broad features t *>act]ize ! dykes ( lat] times--! c5tral m co>sely-cry/all9e portion1 ! m>g9al b& ( f9] gra91 pass+ occasionally into :at 0 probably a basic glass1 & ! transv]se jo9t+4 ,!y belong to m ?an "o p]iod ( emission1 = !y cross ea* o!r4 ,!y v>y 9 wid? up to ne>ly #bjj feet1 & sometimes run ) s+ul> p]si/5ce completely across ! :ole bread? ( ! /rip ( gneiss 9 ! we/ ( ,su!rl& & ,ross4 ,doz5s ( dykes h be5 foll[$ by ! ,geological ,survey = di/ances ( t5 or twelve miles4 ,footnote #ef3 ,see ,mr4 ,teall1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xli4 7#ahhe71 p4 #acc4 ,lat] 9 "t1 & mu* less abundant1 are c]ta9 highly basic dykes--p]idotites ) s*i/ose modifications--:i* cut across ! dol]ites 9 a m ne>ly ea/-&-we/ direction4 ,!re are likewise occasional dykes ( peculi> composition1 :i*1 z above /at$1 h be5 di/+ui%$ by ,mr4 ,teall z microcl9e-mica rocks & biotite-diorite4 ,la/ ( all comes a gr\p ( ?or\ghly acid rocks--v>ieties ( granite & pegmatite--:i* =m intrusive %eets & dykes4 ,! granites conta9 biotite ) microcl9e1 & are sometimes gneissose4 ,! pegmatites are microcl9e-qu>tz rocks ) a v>iable am\nt ( oligoclase or albite4 ,^! dykes co9cide 9 direction ) ! basalts & dol]ites1 b !y are apt to run toge!r into belts ( granite & pegmatite1 sometimes #aejj feet broad4 ,up to ! pres5t "t no evid5ce has be5 f\nd ( any sup]ficial outp\r+ ( mat]ial 9 connection ) ?is rem>kable s]ies ( dykes 9 ! ,lewisian gneiss4 ,t !y may h be5 concomitant ) true volcanic eruptions may be plausibly inf]r$ f ! close analogy :i*1 9 spite ( _! antiquity & ! metamorphism !y h und]gone1 !y /ill pres5t to ! sy/em ( dykes t =ms a "p ( ! great ,t]ti>y volcanic s]ies ( ,antrim & ! ,inn] ,hebrides4 ,! close-set fissures runn+ 9 a ,w4,n4,w direction1 ! abundant uprise into ^! fissures ( basic igne\s rocks1 foll[$ by a lat] & m feeble extravasation ( acid mat]ial1 are features :i* 9 a s+ul> mann] anticipate ! volcanic ph5om5a ( ,t]ti>y "t4 ,!re c be no "q z to ! high antiquity ( ^! dykes4 ,!y 7 already 9 place be=e ! adv5t ( ^? extraord9>y v]tical l9es ( %e>+ :i* h s greatly affect$ bo? ! gneiss & ! dykes2 & ^! movem5ts1 9 turn1 _h long be5 accompli%$ be=e ! ,torridon ,s&/one 0 laid d[n1 = ! dykes1 ) _! abundant de=mation1 run up to & pass b5ea? ! s&/one :i* buries !m & all ! rocks ) :i* !y are associat$4 ,?\gh lat] ?an ! orig9al fundam5tal complex1 ! dykes h become s integral & ess5tial a "p ( ! gneiss z x n[ exi/s t !y mu/ be unhesitat+ly gr\p$ ) x4 ,) s wide an ext5sion ( ! subt]ranean relics ( volcanic en]gy1 x is surely n too mu* to hope t some:]e !re may h be5 pres]v$1 & may /ill be discov]$1 pro(s t ^! eruptive rocks op5$ a connection ) ! surface1 & t we may ?us recognize ve/iges ( ! sup]ficial products ( actual ,ar*an volcanoes4 ,among ! pebbles 9 ! conglom]ates ( ! ,torridon ,s&/one !re occur1 inde$1 fragm5ts ( felsites :i* possess great int]e/ f ! p]fection ) :i* !y reta9 "s ( ! *>act]i/ic features ( y\ng] lavas4 ,mr4 ,teall has describ$ _! m9ute /ructure4 ,!y are d>k1 purpli%1 compact rocks1 consi/+ ( a sph]ulitic micropegmatitic1 micropoikilitic or microcry/all9e gr\ndmass1 9 :i* are imb$d$ porphyritic cry/als or cry/al-gr\ps ( felsp>1 (t5 oligoclase4 ,^! sph]ulitic rocks occasionally %[ traces ( p]litic /ructure4 ,!y be> a /rik+ resemblance to "s ( ! ,uriconian felsites ( ,%rop%ire1 pebbles f :i* occur 9 ! ,longmynd rocks4#eg ,^! fragm5ts sugge/ ! exi/5ce ( volcanic mat]ials at ! surface :5 ! ,torridon ,s&/one 0 deposit$4 ,possibly !y may repres5t "s vani%$ ,lewisian lavas4 ,b ! "t betwe5 ! uprise ( ! dykes & ! =mation ( ! ,torridonian s]ies 0 va/ en\gh = ! adv5t ( _m successive volcanic episodes4 ,! pebbles may !re=e be ! relics ( eruptions t took place long aft] ! p]iod ( ! dykes4 ,footnote #eg3 ,annual ,report ( ,geological ,survey = #ahie1 p4 #ba ( repr9t4 ,among ! ,torridonian /rata no und\bt$ trace ( any contemporane\s volcanic eruptions has be5 met )4#eh ,! only relics ( volcanic rocks 9 ?is enorm\s accumulation ( s$im5ts are ! pebbles j ref]r$ to1 :i* may be ref]able to a "t long ant]ior to ! v olde/ p>ts ( ! ,torridonian s]ies4 ,footnote #eh3 ,! suppos$ tuff ref]r$ to 9 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlviii4 7#ahib71 p4 #afh1 is probably n ( truly volcanic orig94 ,t ,ar*an "t witness$ volcanic eruptions on a consid]able scale1 & ) great v>iety ( petrographical mat]ial1 has rec5tly be5 %[n 9 detail by ,mr4 ,otto ,nord5skjld f a /udy ( ! rocks ( ,sml& 9 ,sw$54 ,he has describ$ a s]ies ( acid outbur/s1 includ+ masses ( rhyolite & dacite1 toge!r ) agglom]ates & tuffs1 likewise basic eruptions1 ) dioritic rocks1 augite-porphyrite & breccia4 ,he ref]s ^! rocks to ! same age z mo/ ( ! ,sc&9avian gneisses1 & rem>ks t ?\gh !y h und]gone mu* me*anical de=mation & metamorphism1 !y h yet "h & !re reta9$ "s ( _! di/9ctive volcanic /ructures1 su* z ! sph]ulitic4#ei ,:5 ! l>ge area ( ,lewisian gneiss =m+ ! *a9 ( ! ,out] ,hebrides is inve/igat$ x may possibly supply examples ( a simil> s]ies ( anci5t volcanic masses4 ,footnote #ei3 b] ,ar*is*e ,ergussge/e9e aus ,sml&1 ,sv]iges ,geol4 ,und]skn1 ,no4 #ace 7#ahid74 ii4 ,,! ,,dalradian ,,or ,,y\ng] ,,s*i/s ,,( ,,scotl& ,we n[ come to "o ( ! great gaps 9 ! geological record4 ,! ,lewisian gneiss af=ds u glimpses ( probable volcanic activity at ! v beg9n+ ( geological hi/ory4 ,an enorm\s lapse ( "t1 app>5tly unrepres5t$ 9 ,brita9 by any geological record1 mu/ be m>k$ by ! uncon=mability betwe5 ! gneiss & ! ,torridon ,s&/one4 ,ano!r prodigi\s int]val is und\bt$ly %[n by ! ,torridonian s]ies4 ,nei!r ?is ?ick accumulation ( s$im5t nor ! ,cambrian =mations1 :i* to a dep? ( "s #bjjj feet ov]lie ! ,torridon ,s&/one1 h yield$ any evid5ce ( true sup]ficial eruptions1 ?\gh !y are trav]s$ by num]\s dykes1 sills & bosses4 ,! age ( ^! intrusive masses _c be precisely fix$2 a l>ge proportion ( !m is c]ta9ly old] ?an ! great t]re/rial displacem5ts & concurr5t metamorphism ( ! ,nor?-,we/ ,highl&s4 ,:ile f ! ,lewisian gneiss upw>d to ! highe/ visible ,cambrian plat=m 9 ,su!rl&1 no ve/ige ( contemporane\s volcanic rocks is to be se51 ! cont9uity ( ! geological record is abruptly brok5 at ! top ( ! ,durness ,lime/one4 ,by a s]ies ( ! mo/ /up5d\s dislocations1 ! rocks ( ! t]re/rial cru/ h !re be5 displac$ to su* a degree t portions h be5 ?ru/ we/w>d = a horizontal di/ance ( sometimes z mu* z t5 miles1 :ile !y h be5 s cru%$ & %e>$ z to h (t5 lo/ entirely _! orig9al /ructures1 & to h pass$ into ! cry/all9e & foliat$ condition ( s*i/s4 ,portions ( ! floor ( ,lewisian gneiss1 & l>ge masses ( ! ,torridon ,s&/one1 :i* _h be5 buri$ "u ! ,cambrian s$im5ts1 h be5 torn up & driv5 ov] ! ,durness ,lime/one & qu>tzite4 ,?\gh mu* c>e has be5 be/[$ by ! (fic]s ( ! ,geological ,survey on ! inve/igation ( ! complicat$ mass ( mat]ial :i*1 pu%$ ov] ! ,cambrian /rata1 =ms ! m\nta9\s gr\nd t lies to ! ea/ ( a l9e drawn f ,lo* ,eribol1 9 ! nor? ( ,su!rl&1 to ! s\?-ea/ ( ,skye1 "s unc]ta9ty /ill exi/s z to ! age & hi/ory ( ! rocks ( t region4 ,= ! purposes ( ?is "w1 !re=e1 ! re/ ( ! c\ntry ea/w>ds to ! l9e ( ! ,great ,gl5--t rem>kable valley :i* cuts ,scotl& 9 two--may be left out ( acc\nt4 ,to ! ea/ ( ! ,great ,gl5 ! ,scotti% ,highl&s display a va/ succession ( cry/all9e s*i/s1 ! true /ratigraphical relations ( :i* to ! ,lewisian gneiss h /ill to be det]m9$1 b :i*1 tak5 z a :ole1 no "o n[ s]i\sly d\bts mu/ be greatly y\ng] ?an t anci5t rock4 ,mur*ison fir/ sugge/$ t ! qu>tzites & lime/ones f\nd 9 ?is new] s]ies are ! equival5ts ( ^? ( ! ,nor?-,we/4 ,?is id5tification may yet be %[n to be correct1 b mu/ be reg>d$ z /ill unprov$4 ,traces ( fossils 7annelid-pipes7 h be5 f\nd 9 "s ( ! qu>tzites1 b !y af=d little or no help 9 det]m9+ ! horizons ( ! rocks4 ,9 ,donegal1 :]e simil> qu>tzites1 lime/ones & s*i/s are well develop$1 obscure indications ( organic rema9s 7corals & graptolites7 h likewise be5 detect$1 b !y also fail to supply any satisfactory basis = /ratigraphical comp>ison4 ,ess5tially ! s*i/s ( ! ,scotti% ,highl&s ea/ ( ! ,great ,gl5 consi/ ( alt]$ s$im5t>y rocks4 ,besides qu>tzites & lime/ones1 !re occur ?ick masses ( clay-slate & o!r slates & s*i/s1 ) b&s ( graphitic s*i/1 greywacke1 pebbly grit1 qu>tzite1 b\ld]-b$s & conglom]ates4 ,among rocks t h be5 s di/urb$ & foliat$ x is necess>ily difficult to det]m9e ! true ord] ( succession4 ,9 ! ,c5tral ,highl&s1 h[ev]1 a c]ta9 def9ite sequ5ce has be5 f\nd to cont9ue z f> z ! gr\nd has yet be5 mapp$4 ,7 ! rocks always sev]ely contort$1 brok5 & plac$ at high angles1 ?is sequ5ce might be deceptive1 & leave /ill unc]ta9 ! orig9al ord] ( deposition ( ! :ole s]ies4 ,b ov] _m squ>e miles ! angles ( incl9ation are l[1 & ! successive b&s may be trac$ f hill to hill1 across /ra? & gl51 =m+ esc>pm5ts along ! slopes & outli]s on ! summits1 precisely z g5tly-undulat+ b$s ( s&/one & lime/one may be se5 to d 9 ! dales ( ,york%ire4 ,x is difficult to resi/ ! belief1 ?\gh x may1 p]haps1 be premature to conclude1 t ?is obvi\s & p]si/5t ord] ( succession really m>ks ! orig9al sequ5ce ( deposition4 ,9 ,donegal also a def9ite arrangem5t ( ! rock-gr\ps has be5 asc]ta9$ :i*1 :5 foll[$ across ! c\ntry1 gives ! key to its geological /ructure4#fj ,footnote #fj3 ,geol4 ,survey ,memoirs3 ,geology ( ,n4,w4 ,donegal1 #ahia4 ,9 ! ord] ( succession :i* has be5 recogniz$ dur+ ! progress ( ! ,geological ,survey ?r\gh ! ,c5tral & ,s\!rn ,highl&s1 x is h>d 9 _m places to det]m9e :e!r ! sequ5ce t c be recogniz$ is 9 an upw>d or d[nw>d direction4 ,two b&s ( lime/one1 :i* appe> to reta9 _! relative positions across ,scotl& = a di/ance ( "s #bcj miles1 may af=d a solution ( ?is difficulty1 & if1 z is probable1 !y are to be id5tifi$ ) ! simil> lime/ones ( ,donegal1 ,mayo & ,galway1 _! assi/ance w ?us be available across a tract ( m ?an #djj miles4 ,:at is reg>d$ z ! l[] zone ( lime/one is p>ticul>ly well se5 ab\t ,lo* ,tay2 :at is believ$ to be ! upp] is typically display$ 9 ! he>t ( ,p]?%ire1 ab\t ,blair-,a?ol4 ,f "u ! ,lo* ,tay ,lime/one a great ?ickness ( mica-s*i/s1 gre5 s*i/s1 s*i/ose grits & conglom]ates1 slates & greywackes1 em]ges up to ! bord] ( ! ,highl&s4 ,above t calc>e\s b& ?ick masses ( mica-s*i/ & s]icite-s*i/ are succe$$ by a well-m>k$ zone ( qu>tzite1 :i* =ms ! m\nta9s ( ,b5-y-,glo & ,s*ihallion1 & /ret*es s\?-we/w>d across ,argyll%ire into ,islay & ,jura4 ,! second or ,blair-,a?ol ,lime/one lies next to ?is qu>tzite4 ,if ! lime/ones are id5tical ) ^? ( ,donegal1 ,mayo & ,galway1 ! qu>tzites may d\btless be also reg>d$ z cont9u$ 9 ^? ( ! same ,iri% c\nties1 :]e !y =m "s ( ! mo/ conspicu\s features 9 ! sc5]y1 s9ce !y rise into su* conspicu\s m\nta9s z ,erigal1 ,slieve ,league1 ,neph91 & ! twelve ,b9s ( ,connem>a4 ,! age ( ?is va/ sy/em ( alt]$ rocks has /ill to be det]m9$4 ,x is possible t !y may include "s p>ts ( ! ,torridonian s]ies1 or ev5 "h & !re a w$ge ( ! ,lewisian gneiss driv5 into position by gigantic disruptions1 l ^? ( ! ,nor?-,we/ ,highl&s4 ,b !re c be no d\bt t ! s*i/s1 qu>tzites & lime/ones =m an assemblage ( metamorphos$ s$im5t>y /rata :i* diff]s mu* 9 v>iety ( petrographical "*1 z well z 9 ?ickness1 f ! ,torridonian s&/one1 & :i* has n be5 id5tifi$ z ! equival5t ( any kn[n ,palozoic sy/em or gr\p ( =mations 9 ,brita94 ,x may conceivably embrace ! ,cambrian s]ies ( ! ,nor?-,we/ ,highl&s1 & also ! s$im5t>y deposits t succe$$ ! ,durness ,lime/one1 ( :i* no recognizable ve/ige rema9s 9 ,su!rl& or ,ross4 ,t ! metamorphic rocks ea/ ( ! l9e ( ! ,great ,gl5 are at lea/ old] ?an ! ,ar5ig =mation ( ! ,l[] ,silurian sy/em may be inf]r$ f an int]e/+ discov]y rec5tly made by ! (fic]s ( ! ,geological ,survey4 ,a n>r[ /rip ( rocks has be5 f\nd :i*1 f _! rem>kable petrographical *>act]s1 _! ord] ( sequ5ce & _! scanty fossil cont5ts 7,radiol>ia71 are ) "s confid5ce id5tifi$ ) a peculi> assemblage ( rocks on ! ,ar5ig horizon ( ! ,silurian sy/em 9 ! ,s\!rn ,upl&s ( ,scotl&1 to :i* full] ref]5ce w be made 9 ,*apt] xii4 ,?is /rip or w$ge ( probably ,l[] ,silurian /rata int]v5es betwe5 ! ,highl& s*i/s & ! ,old ,r$ ,s&/one 9 ,k9c>d9e%ire1 ,=f>%ire & ,dumb>ton%ire4 ,x has be5 recogniz$ also1 occupy+ a simil> position1 9 ,tyrone 9 ,irel&4 ,! s*i/s 9 "s places reta9 _! foliat$ "* up to ! abrupt l9e ( junction ) ! presumably ,l[] ,silurian /rata1 :ile 9 o!r di/ricts1 z at ,ab]foyle1 !y h be5 s little affect$ t x is h>dly possible to draw a l9e betwe5 ! ,highl& rocks & ^? ( ?is bord]-zone1 :i* inde$ are !re p]haps m metamorphos$ ?an ! ,highl& grits to ! nor? ( !m4 ,! metamorphism ( ! s*i/s may h be5 ma9ly effect$ be=e ! f9al di/urbances t w$g$ 9 ?is /rip ( ,silurian /rata along ! ,highl& bord]1 ?\gh "s am\nt ( cru%+ & s*i/-mak+ seems to h accompani$ ^! di/urbances4 ,no trace ( any simil> /rip ( ,palozoic rocks has ev] be5 detect$ among ! folds ( ! s*i/s fur!r into ! ,highl&s4 ,b "s ( ! ,highl& rocks 9 ! region ( ,lo* ,awe lose _! metamorphos$ "*1 & pass into s$im5t>y /rata :i*1 s f> z petrographical *>act]s are conc]n$1 might well be ,palozoic4 ,until "s clue is f\nd to ! age ( ! ,y\ng] or ,ea/]n s*i/s1 qu>tzites & lime/ones ( ! ,highl&s1 x is desirable to h "s %ort conv5i5t adjective to di/+ui% !m4 ,z a provisional t]m = !m ,i h propos$ ! t]m ,dalradian1 f ,dalriada1 ! "n ( ! old ,celtic k+dom ( ! nor? ( ,irel& & s\?-we/ ( ,scotl&4#fa ,footnote #fa3 ,presid5tial ,address to ,geological ,society1 #ahia1 p4 #ci4 ,! special feature = :i* ?is ,dalradian s]ies is cit$ 9 ! pres5t volume is ! evid5ce x furni%es ( p[]ful & ext5sive volcanic action4 ,9 a s]ies ( rocks s greatly dislocat$1 crumpl$ & metamorphos$1 we _c look = ! usual cle> pro(s ( contemporane\s eruptions4 ,nev]!less all ov] ! ,scotti% ,highl&s1 f ! f> coa/ ( ,ab]de5%ire to ! ,mull ( ,cantyre1 & across ! we/ ( ,irel& f ! headl&s ( ,donegal into ,galway1 !re occurs abundant evid5ce ( ! exi/5ce ( rocks :i*1 ?\gh n[ =m+ an integral "p ( ! s*i/s1 c be p>allel$ ) masses ( und\bt$ly volcanic orig94 ,illu/ration3 ,fig4 #cg4--,section %[+ ! position ( ,sills 9 ! mica-s*i/ s]ies betwe5 ,lo* ,tay & ,amulree4 a1 ,mica-s*i/2 b1 b1 ,sills4 ,int]calat$ 9 ! va/ pile ( alt]$ s$im5ts lie num]\s %eets ( epidiorite & hornbl5de-s*i/1 :i* 7 erupt$ z molt5 mat]ials1 n improbably z v>ieties ( diabase-lava4 ,mo/ ( ^! %eets are d\btless intrusive sills1 = !y c be obs]v$ to break across f "o horizon to ano!r4 ,b "s ( !m may possibly be contemporane\s lava-/reams4 ,a %eet may sometimes be foll[$ = _m miles1 occupy+ ! same /ratigraphical plat=m4 ,?us a b& ( sills may be trac$ f ! coa/ ( ,banff%ire to ne> ,b5 ,l$i1 a di/ance ( m ?an #ajj miles4 ,among ! hornbl5dic sills ( ?is b& "s occur on a numb] ( horizons betwe5 ! gr\p ( ,b5 ,voirli* grits & ! ,b5-y-,glo qu>tzite4 ,"o ( ! mo/ m>k$ ( ^! is a %eet1 sometimes #bjj feet ?ick1 :i* und]lies ! ,lo* ,tay ,lime/one4 ,ano!r int]e/+ gr\p 9 ! same great b& has be5 mapp$ by ! ,geological ,survey on ! hills betwe5 ,lo* ,tay & ,amulree1 "s ( !m be+ traceable = sev]al miles among ! mica-s*i/s ) :i* !y alt]nate 7,fig4 #cg74 ,9 ,argyll%ire also1 betwe5 ,lo* ,t>b]t & ,lo* ,awe1 & along ! ea/]n coa/s ( ! isl&s ( ,islay & ,jura1 an abundant s]ies ( %eets ( epidiorite1 amphibolite & hornbl5de-s*i/ runs ) ! preval5t /rike ( ! s*i/s1 grits & lime/ones ( t region4 ,simil> rocks reappe> 9 a l position 9 ,donegal1 :]e1 z 9 ,scotl&1 ! frequ5cy ( ! occurr5ce ( ^! eruptive rocks on ! horizons ( ! lime/ones is wor?y ( rem>k4 ,! p]si/5ce1 numb] & aggregate ?ickness ( ! sills 9 ?is great b& m>k x out z ! mo/ ext5sive s]ies ( intrusive %eets 9 ! ,briti% ,isles4 ,9 addition to ! sills !re occur also bosses ( simil> mat]ial1 :i* 9 _! =m & _! obvi\s relation to ! %eets recall ! /ructure ( volcanic necks4 ,!y consi/ ( hornbl5dic rocks1 l ! sills1 b are usually tol]ably massive1 & %[ mu* less trace ( sup]9duc$ foliation4 ,besides ! obvi\sly eruptive masses !re is ano!r abundant gr\p ( rocks :i*1 ,i believe1 furni%es important evid5ce z to contemporane\s volcanic action dur+ ! accumulation ( ! ,dalradian s]ies4 ,?r\gh\t ! ,c5tral & ,s\?-,we/]n ,highl&s c]ta9 zones ( gre5 s*i/ h long occupi$ ! att5tion ( ! (fic]s ( ! ,geological ,survey4 ,!y occur m especially on two horizons betwe5 ! ,lo* ,tay ,lime/one & a mu* l[] s]ies ( grits & f9e conglom]ates1 :i* run ?r\gh ! ,trossa*s & =m ! craggy ridges ( ,b5 ,l$i1 ,b5 ,voirli* & o!r m\nta9s ne> ! ,highl& bord]4 ,9 ! l[] gr\p ( gre5 s*i/s1 ?ick hornbl5dic sills beg9 to make _! appe>ance1 increas+ 9 numb] upw>ds4 ,! upp] gr\p ( gre5 s*i/s lies betwe5 two b&s ( g>netif]\s mica-s*i/1 above ! high] ( :i* comes ! ,lo* ,tay ,lime/one4 ,! peculi> gre5i% t9t & correspond+ m9]al con/itu5ts ( ^! s*i/s1 h[ev]1 are likewise f\nd diffus$ ?r\gh high] p>ts ( ! s]ies4 ,s mu* d ! gre5 s*i/s v>y 9 /ructure & composition t no s+le def9ition ( !m is always applicable4 ,at "o extreme are dull gre5 *lorite-s*i/s1 pass+ into a pot/one1 :i*1 l t ( ,trondhjem1 c be cut into blocks = ar*itectural purposes4#fb ,at ! o!r extreme lie grits & qu>tzites1 ) a slight admixture ( ! same gre5i%-col\r$ con/itu5t4 ,betwe5 ^! limits almo/ e /age may be met )1 ! proportion ( *lorite or hornbl5de & ( granul> or pebbly qu>tz v>y+ cont9ually1 n only v]tically1 b ev5 9 ! ext5sion ( ! same b$4 ,! qu>tz-pebbles are sometimes opalesc5t1 & occasionally l>g] ?an peas4 ,an av]age specim5 f "o ( ! zones ( gre5 s*i/s is f\nd1 on clos] exam9ation1 to be a ?or\ghly s*i/ose rock1 compos$ ( a matrix ( granul> qu>tz1 ?r\gh :i* acicul> hornbl5de & biotite cry/als1 or act9olite & *lorite1 are rang$ along ! planes ( foliation4 ,footnote #fb3 ,f su* a rock1 :i* crosses ! upp] "p ( ,lo* ,fyne1 ! ,duke ( ,argyll's resid5ce at ,inv]>ay has be5 built4 ,t ^! rocks are ess5tially ( detrital orig9 admits ( no d\bt4 ,!y diff]1 h[ev]1 f ! o!r s$im5t>y memb]s ( ! ,dalradian s]ies 9 ! p]si/5ce & abundance ( ! magnesian silicates diffus$ ?r\gh !m4 ,! idea :i* !y sugge/$ to my m9d "s ye>s ago 0 t ! gre5 col\r+-matt] repres5ts f9e basic volcanic du/1 :i* 0 %[]$ out dur+ ! accumulation ( ord9>y qu>tzose1 argillace\s & calc>e\s s$im5ts1 & t1 "u ! influ5ce ( ! metamorphism :i* has s greatly affect$ all ! rocks ( ! region1 ! orig9al pyrox5es & felsp>s suff]$ ! usual conv]sion into hornbl5des1 *lorites & micas4 ,?is view has occurr$ also to my colleagues on ! ,survey1 & is n[ g5]ally adopt$ by !m4 ,n only are ^! gre5 s*i/s traceable all ?r\gh ! ,c5tral & ,s\?-,we/]n ,highl&s1 rocks ( simil> "*1 & n improbably on ! same horizons1 reappe> 9 ! nor?-we/ ( ,irel&1 & run !nce s\?-we/w>d z f> z ! ,dalradian rocks ext5d4 ,if we are ju/ifi$ 9 reg>d+ !m z metamorphos$ tuffs & a%y s$im5ts1 !y m>k a widespread & long-cont9u$ volcanic p]iod dur+ ! "t :5 ! lat] half ( ! ,dalradian s]ies 0 deposit$4 ,besides ! ext5sive developm5t ( basic sills :i*1 ?\gh probably 9 great "p lat] ?an ! gre5 s*i/s1 may belong to ! same prolong$ p]iod ( subt]ranean activity1 num]\s acid protrusions are to be obs]v$ 9 ! ,dalradian s]ies ( ,scotl& & ,irel&4 ,t ^! masses 7 erupt$ at sev]al widely-sep>at$ int]vals is well %[n by _! relation to ! s*i/s among :i* !y occur4 ,"s ( ! great bosses & sills ( granite 7 und\bt$ly inject$ be=e ! metamorphism ( ! s*i/s 0 complet$1 = !y h %>$ 9 ! foliation ( ! region4 ,o!rs h c]ta9ly appe>$ aft] ! metamorphism 0 complete1 = !y %[ no trace ( hav+ suff]$ f its effects4 ,?us "s ( ! va/ tracts ( new] granite 9 ! ,grampian *a91 :i* cov] _m squ>e miles ( gr\nd1 mu/ be among ! newe/ rocks ( t area4 ,!y h rec5tly be5 f\nd by ,mr4 ,g4 ,b>r[1 ( ! ,geological ,survey1 to s5d ve9s into ! belt ( probably ,l[] ,silurian /rata :i* flanks ! ,highl& s*i/s4 ,!y are ?us lat] ?an ! ,ar5ig p]iod4 ,n impossibly !y may be ref]able to ! great granite intrusions :i* =m$ s /rik+ a feature 9 ! hi/ory ( ! ,l[] ,old ,r$ ,s&/one4 iii4 ,,! ,,gneisses ,,& ,,s*i/s ,,( ,,anglesey ,9 ! isl& ( ,anglesey an int]e/+ s]ies ( s*i/s & qu>tzites pres5ts _m po9ts ( resemblance to ! ,dalradian or y\ng] s*i/s ( ! ,highl&s4 ,at pres5t ! geologi/ possesses no means ( det]m9+ :e!r ^! ,wel% rocks are ! equival5ts ( ! ,scotti% 9 /ratigraphical position1 b _! rem>kable simil>ity ju/ifies a brief allusion to !m 9 ?is place4 ,mu* controv]sy has aris5 reg>d+ ! geology ( ,anglesey1 b into ?is dispute x is n necess>y = my pres5t purpose to ent]4#fc ,i w cont5t myself ) express+ :at seems to me1 aft] sev]al trav]ses1 to be ! geological /ructure ( ! gr\nd4 ,footnote #fc3 ,! lit]ature ( ,anglesey geology is n[ some:at volum9\s1 b ,i may ref] to ! foll[+ z ! *ief au?orities4 ,! isl& is mapp$ 9 ,%eet #gh ( ! ,geological ,survey ( ,engl& & ,wales1 & its /ructure is illu/rat$ 9 ,horizontal ,sections1 ,%eet #dj4 ,a full acc\nt ( its v>i\s =mations & ( _! relations to ea* o!r is giv5 9 vol4 iii4 ( ! ,memoirs ( ! ,geological ,survey1 ,! ,geology ( ,nor? ,wales1 by ,sir ,a4 ,c4 ,ramsay1 #bnd edit4 #ahha4 ,! subject has be5 discuss$ by ,pr(essor ,hughes1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxxiv4 7#ahgh7 p4 #acg1 xxxv4 7#ahgi7 p4 #fhb1 xxxvi4 7#ahhj7 p4 #bcg1 xxxviii4 7#ahhb7 p4 #af2 ,brit4 ,assoc4 ,rep4 7#ahha7 pp4 #fdc1 #fdd2 ,proc4 ,camb4 ,phil4 ,soc4 vol4 iii4 pp4 #fg1 #hi1 #cda2 by ,pr(essor ,bonney1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxv4 7#ahgi7 pp4 #cjj1 #cba2 ,geol4 ,mag4 7#ahhj7 p4 #abe2 by ,dr4 ,h4 ,hicks1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxxiv4 7#ahgh7 p4 #adg1 xxxv4 7#ahgi7 p4 #bie2 ,geol4 ,mag4 7#ahgi7 pp4 #dcc1 #ebh 7#ahic7 p4 #edh2 by ,dr4 ,c4 ,callaway1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxxvii4 7#ahha7 p4 #baj1 xl4 7#ahhd7 p4 #efg2 & by ! ,rev4 ,j4 ,f4 ,blake1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xliv4 7#ahhh7 p4 #dfc4 ,fur!r ref]5ces to ! "w ( ^! obs]v]s 9 ,anglesey are giv5 9 ,*apt] xiii4 p4 #bbj et seq4 ,! ,pre-,cambrian areas ( ,anglesey are %[n 9 ,map ,,ii4 ,!re are two gr\ps ( rocks 9 ,anglesey to :i* a pre-,cambrian age may ) probability be assign$4 ,9 ! he>t ( ! isl& lies a core ( gneiss :i*1 if petrographical *>act]s may be tak5 z a guide1 mu/ c]ta9ly be look$ ^u z ,ar*an4 ,9 visit+ t di/rict ) my colleague ,mr4 ,teall ,i 0 mu* a/oni%$ to f9d !re s /rik+ a c\nt]p>t to portions ( ! ,lewisian gneiss ( ! nor?-we/ ( ,su!rl& & ,ross4 ,! v ext]nal features ( ! gr\nd recall ! peculi> hummocky surface :i* s p]si/5tly *>act]izes ! areas ( ?is rock ?r\gh\t ! nor?-we/ ( ,scotl&4 ,if ! geologi/ c\ld be sudd5ly transport$ f ! r\nd$ rocky knolls ( ,su!rl&1 ,ross-%ire or ! ,hebrides to ^? 9 ! middle ( ,anglesey1 s\? ( ,llan]*ym$d1 he w\ld h>dly be aw>e ( ! *ange1 save 9 ! great] v]dure ( ! holl[s1 :i* has result$ f a m advanc$ /ate ( decomposition ( ! rocks at ! surface1 z well z f a bett] climate & agriculture4 ,:5 we exam9e ^! rocky hummocks 9 detail we f9d !m to consi/ ( co>se gneisses1 ! foliation ( :i* has a preval5t dip to ,n4,n4,w4 ,"s portions ab\nd 9 d>k hornbl5de & g>nets1 o!rs are ri* 9 br[n mica1 ! folia be+ co>sely cry/all9e & rudely b&$1 z 9 ! m massive gneisses ( ,su!rl&4 ,abundant ve9s ( co>se pegmatite may "h & !re be se51 ) p9ki% & :ite felsp>s & milky qu>tz4 ,occasionally ! gneiss is trav]s$ by b&s ( a d>k gre5i%-grey rock1 :i* rem9d "o ( ! dykes ( ! nor?-we/ ( ,scotl&4 ,!re are o!r rocks1 "s ( !m probably intrusive & ( lat] date1 to be se5 9 ! same area2 b !y require m detail$ /udy ?an !y h yet receiv$4 ,! relation ( ?is core ( gneiss & its associat$ rocks to ! second gr\p ( pre-,cambrian rocks has n hi!rto be5 satisfactorily asc]ta9$4 ,! core may conceivably be an eruptive boss 9 t gr\p1 & may h acquir$ its foliation dur+ ! movem5ts t produc$ ! foliation ( ! surr\nd+ s*i/s4 ,b x seems m probable t ! gneiss is mu* old] ?an ^! s*i/s1 ?\gh x w\ld und\bt$ly p>ticipate 9 ! effects ( ! me*anical movem5ts :i* gave rise to _! de=mation1 cleavage & foliation4 ,! second gr\p ( rocks occupies a l>ge area 9 ! we/ & 9 ! c5tre & s\? ( ,anglesey4 ,! s*i/s ( :i* x consi/s are obvi\sly 9 ! ma9 a cla/ic s]ies4 ,"o ( _! mo/ conspicu\s memb]s is qu>tzite1 :i*1 besides occurr+ sporadically all ov] ! isl&1 =ms ! prom95t mass ( ,holyhead ,m\nta94 ,!re are likewise flaggy *loritic s*i/s1 gre5 & purple phyllites or slates1 & b&s ( grit1 :ile p>ts ( ! s-call$ grey gneiss consi/ ( pebbly s&/ones t h acquir$ a cry/all9e /ructure4 ,t "s ord] ( sequ5ce among ^! v>i\s /rata may yet be work$ out is n impossible1 b ! task w be "o ( no ord9>y difficulty1 = ! plications & fractures are num]\s1 & mu* ( ! surface ( ! gr\nd is obscur$ by ! spread ( ,palozoic =mations & sup]ficial deposits4 ,^! ,anglesey s*i/s are s obvi\sly an alt]$ s$im5t>y s]ies t x is n surpris+ t !y %\ld h be5 reg>d$ z metamorphos$ ,cambrian /rata4 ,all t c be positively affirm$ reg>d+ _! age is t !y are n only old] ?an ! l[e/ fossilif]\s rocks ar\nd !m--t is1 ?an ,ar5ig or ev5 ,tremadoc /rata--b t !y _h already acquir$ _! pres5t metamorphic "* be=e ^! /rata 7 laid d[n uncon=mably ^u !m4 ,!re is no actual pro( t !y include no alt]$ ,cambrian rocks4 ,b :5 we consid] _! di/9ctly cry/all9e /ructure1 & ! abs5ce ( su* a /ructure f any portion ( ! ,cambrian areas ( ! ma9l&2 :51 moreov]1 we reflect t ! metamorphism :i* has affect$ !m is ( ! regional type1 & c h>dly h be5 re/rict$ to m]ely ! limit$ area ( ,anglesey2 we mu/ agree ) ^? obs]v]s :o1 9 spite ( ! abs5ce ( positive pro( ( _! true geological horizon1 h reg>d$ ^! rocks z ( mu* high] antiquity ?an ! ,cambrian /rata ( ! neighb\rhood4 ,no "o famili> ) ! ,dalradian rocks ( ,scotl& & ,irel& c fail to be /ruck ) ! close resemblance :i* ^! y\ng] ,anglesey s*i/s be> to !m1 d[n ev5 into ! m9ute/ details4 ,petrographically !y are precisely ! c\nt]p>ts ( ! qu>tzites & s*i/s ( ,p]?%ire & ,donegal1 & a fur!r connection may be e/abli%$ ( a palontological k9d4 ,! upp] "p ( ! ,holyhead qu>tzite 0 f\nd by ,mr4 ,b4 ,n4 ,pea* & myself 9 ! autumn ( ! ye> #ahij to be at "o place cr[d$ ) annelid-pipes1 & ,i subsequ5tly f\nd ! same to be ! case ) "s ( ! flaggy qu>tzites ne> ! ,s\? ,/ack4 ,illu/ration3 ,fig4 #ch4--,sket* ( cru%$ basic igne\s rock among ! s*i/s1 ,e4 side ( ,por?-tywyn-mawr1 ,e4 side ( ,holyhead ,/raits4 ,= ! purpose ( ! inquiry :i* =ms ! !me ( ?is "w1 ! feature ( greate/ int]e/ ab\t ^! y\ng] s*i/s ( ,anglesey is ! association ( igne\s rocks ) !m4 ,!y include b&s ( d>k basic mat]ial1 ! less cru%$ p>ts ( :i* resemble ! diabases ( lat] =mations1 :ile ! %e>$ portions pass into epidiorites & true hornbl5de-s*i/s4 ,z 9 o!r regions :]e eruptive rocks h be5 cru%$ d[n & *ang$ into ! s*i/ose modification1 x is frequ5tly possible to see gr\ps ( uncru%$ cores r\nd :i*1 "u sev]e me*anical /resses1 ! rock has und]gone ?is conv]sion4 ,l9es ( movem5t ?r\gh ! body ( ! rock may be detect$ by b&s ( s*i/1 ! gradation f ! solid core to ! hornbl5de-s*i/ be+ q gradual4 ,! accompany+ figure 7,fig4 #ch7 repres5ts a portion ( "o ( ^! cru%$ basic igne\s rocks on ! ea/ side ( ,holyhead ,/raits4 ,z 9 ! ,dalradian s]ies ( ! ,highl&s1 _m1 p]haps mo/1 ( ^! igne\s b&s are probably intrusive sills1 b o!rs may be int]calat$ contemporane\s %eets4 ,!y occur across ! :ole bread? ( ! isl& f ! ,m5ai ,/rait to ! %ores ( ,holyhead4 ,besides ^! und\bt$ly igne\s rocks1 ! gre5 *loritic slates ( ,anglesey des]ve notice4 ,!y are well-b$d$ /rata1 consi/+ ( alt]nations ( foliat$ f9e grit or s&/one1 ) lay]s m l>gely made up ( s*i/ose *lorite4 ,! gritty b&s sometimes conta9 pebbles ( blue qu>tz1 & evid5tly repres5t orig9al lay]s ( s&y s$im5t1 b ) an admixture ( *loritic mat]ial4 ,! mann] 9 :i* ?is gre5 *loritic con/itu5t is diffus$ ?r\gh ! :ole succession ( /rata1 & likewise aggregat$ into b&s ) comp>atively little qu>tzose s$im5t1 rem9ds "o ( ! gre5 s*i/s ( ! ,c5tral ,highl&s & ,donegal1 & sugge/s a simil> explanation4 ,tak5 9 connection ) ! associat$ basic igne\s rocks1 ^! *loritic s*i/s seem to me to repres5t a ?ick gr\p ( volcanic tuffs & int]/ratifi$ s&y & clayey lay]s4 ,if ?is inf]5ce is well f\nd$1 & if we are ju/ifi$ 9 gr\p+ ^! ,anglesey rocks ) ! ,dalradian s*i/s ( ,scotl& & ,irel&1 a /rik+ picture is pres5t$ to ! m9d ( ! wide ext5t & p]si/5t activity ( ! volcanoes ( t primeval p]iod 9 ,brita94#fd ,footnote #fd3 ,mr4 ,e4 ,gre5ly1 late ( ! ,geological ,survey ( ,scotl&1 has rec5tly e/abli%$ himself on ! ,m5ai ,/rait = ! purpose ( work+ out 9 detail ! geological /ructure ( ?is int]e/+ & complicat$ region4 ,we may !re=e hope t "s ( ! /ill unsolv$ problems pres5t$ by ! rocks ( ,anglesey w be=e long be satisfactorily expla9$4 iv4 ,,! ,,uriconian ,,volcanoes ,along ! ea/]n bord]s ( ,wales a ridge ( anci5t rocks1 mu* brok5 by faults & pres5t+ sev]al /rik+ uncon=mabilities1 has long be5 classic gr\nd 9 geology f ! descriptions & illu/rations ( ,mur*ison's ,silurian ,sy/em4#fe ,! ma9 outl9es ( ! /ructure ( t di/rict1 fir/ admirably work$ out by ?is great pione]1 7 del9eat$ on ! maps & sections ( ! ,geological ,survey1 :]e9 x 0 %[n t 9 ! ,longmynd an enorm\sly ?ick gr\p ( /ratifi$ rocks1 :i*1 ?\gh unfossilif]\s1 7 ref]r$ to ! ,cambrian sy/em1 rose 9 ! v he>t ( ! c\ntry2 t to ! ea/ ( ^! rocks lay /rata ( ,c>adoc or ,bala age2 t by a great hiatus 9 ! /ratigraphy ! ,upp] ,silurian s]ies transgressively wrapp$ r\nd ev]y?+ bel[ x2 t yet aga9 ! ,coal-measures crept ov] all ^! v>i\s ,palozoic =mations1 foll[$ once m uncon=mably by ,p]mian & ,triassic deposits4#ff ,besides all ?is evid5ce ( extraord9>y & repeat$ t]re/rial movem5t1 x 0 f\nd t ! region 0 trav]s$ by "s ( ! mo/ p[]ful dislocations 9 ?is c\ntry1 :ile to complete ! picture ( di/urbance1 _m protrusions ( igne\s rocks 7 recogniz$4 ,footnote #fe3 ,see especially *ap4 xix4 vol4 i4 p4 #bbe4 ,footnote #ff3 ,! area is embrac$ 9 ,%eet #fa ( ! ,geological ,survey1 & is illu/rat$ by ,nos4 #cc & #cf ( ! %eets ( ,horizontal ,sections4 ,9 ! e>ly editions ( ! ,survey maps ! felspa?ic traps & ! gre5/ones ( ! ,wrek9 di/rict 7 di/+ui%$ by sep>ate col\rs1 b un=tunately ?is useful & s f> correct discrim9ation 0 giv5 up 9 subsequ5t editions1 :]e all ! acid & basic rocks are m]g$ into "o4 ,9 a t]ritory s complicat$1 ?\gh x _h be5 s$ul\sly & skilfully explor$1 !re c\ld h>dly fail to rema9 features ( /ructure :i* _h escap$ ! notice ( ! fir/ obs]v]s4 ,9 p>ticul>1 ! igne\s rocks _h be5 dealt ) only 9 a g5]al way1 & !y consequ5tly (f]$ a fav\rable field = m detail$ /udy2 :ile by a m se>*+ exam9ation ( "s ( ! rocks = fossils1 important corrections ( ! e>li] "w might yet be made4 ,a notable /ep t[>ds a revision ( ! receiv$ op9ions reg>d+ ! igne\s rocks ( ?is region 0 tak5 by ,mr4 ,allport1 :o %[$ t ! s-call$ gre5/one includ$ masses ( devitrifi$ sph]ulitic pit*/ones & p]lites1 toge!r ) indurat$ volcanic breccias1 agglom]ates & a%es4#fg ,subsequ5tly ,pr(essor ,bonney describ$ m fully ! petrographical *>act]s ( ! ,wrek9 igne\s rocks1 confirm+ & ext5d+ ! obs]vations ( ,mr4 ,allport4#fh ,footnote #fg3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxiii4 7#ahgg7 p4 #ddi4 ,footnote #fh3 ,op4 cit4 vol4 xxxv4 7#ahgi7 p4 #ffb2 vol4 xxxviii4 7#ahhb7 p4 #abd4 ,b ! correction ( ! preval5t error z to ! geological age ( ^! rocks 0 due to ,dr4 ,callaway1 :o1 aft] sp5d+ mu* "t & lab\r 9 asc]ta9+1 by a c>eful se>* = fossils1 ! position ( ! sup]9cumb5t rocks 7:]e9 he discov]$ ,cambrian organisms71 & 9 a detail$ inve/igation ( ! /ructure & relation%ips ( ! igne\s masses !mselves1 0 l$ to reg>d !m z "p ( an anci5t pre-,cambrian ridge2 & he propos$ = ! volcanic gr\p ! "n ( ,uriconian1 f ! "n ( ! =m] ,roman t[n :i* /ood n f> to ! we/ ( !m4#fi ,he has %[n h[ ess5tially volcanic ?is anci5t s]ies ( rocks is1 h[ seldom !y pres5t any cle>ly-m>k$ evid5ce ( /ratification1 & h[ small is ! proportion ( s$im5t>y mat]ial associat$ ) !m4#gj ,footnote #fi3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxx4 7#ahgd7 p4 #aif1 xxxiv4 7#ahgh7 p4 #ged1 xxxv4 7#ahgi7 p4 #fdc1 xlii4 7#ahhf7 p4 #dha4 ,= a criticism ( ,dr4 ,callaway's views z to ! ord] ( succession among ! rocks ( ?is di/rict1 see ,pr(4 ,blake1 op4 cit4 vol4 xlvi4 7#ahij7 p4 #chf1 & ,dr4 ,callaway's reply1 vol4 xlvii4 7#ahia7 p4 #aji4 ,footnote #gj3 ,op4 cit4 vol4 xlvii4 7#ahia7 p4 #abc4 ,subsequ5tly ,pr(essor ,lapwor?1 by 8 discov]y ( ! ,ol5ellus-fauna1 m>k+ ! l[e/ kn[n fossilif]\s ,cambrian zone 9 ! ,wrek9 di/rict1 & 8 recognition ( ,cambrian fossils "u ! ,coal-measures ( ,w>wick%ire1 suppli$ valuable evid5ce = ! discussion ( ! geological position ( ! old] rocks ( ! ,midl&s4 ,he has mapp$ 9 m9ute detail ! rocks ( ! ,wrek91 & has exhau/$ all ! evid5ce t is at pres5t obta9able on ! subject4 ,b un=tunately ! publication ( 8 rese>*es is /ill delay$4#ga ,footnote #ga3 ,geol4 ,mag4 7#ahhb7 p4 #efc1 7#ahhf7 p4 #cai1 7#ahhg7 p4 #gh1 7#ahhh7 p4 #dhd2 & a jo9t pap] ) ,mr4 ,w4 ,w4 ,watts on ! ,geology ( ,s\? ,%rop%ire1 ,proc4 ,geol4 ,assoc4 vol4 xiii4 7#ahid7 pp4 #cjb1 #cce4 ,x is n[ recogniz$ t ! core ( ! anci5t ridge1 ext5d+ f ne> ,well+ton ?r\gh ! ,wrek91 ,ca] ,c>adoc & o!r hills1 until x s9ks b5ea? ! ,upp] ,silurian =mations1 is =m$ ( igne\s rocks t consi/ p>tly ( lavas1 p>tly ( volcanic breccias & f9e tuffs4 ,! lavas are ?or\ghly acid rocks ( ! felsitic or rhyolitic type4 ,"o ( !m1 ab\t #ajj feet ?ick1 :i* =ms a prom95t feature on ! flanks & cre/ ( ,ca] ,c>adoc1 %[s abundant f9ely-b&$ fl[-/ructure1 (t5 curv$ or on end1 :ile its bottom & upp] p>ts are /rongly amygdaloidal1 ! cavities be+ occasionally pull$ out 9 ! direction ( fl[ & l9$ ) qu>tz or *alc$ony4 ,"s ( ! deta*$ areas ( eruptive rocks %[ ! beautiful sph]ulitic & p]litic /ructures fir/ notic$ 9 ?is region by ,mr4 ,allport4 ,m rec5tly ! /ructures ( ^! acid rocks h be5 describ$ by ,mr4 ,f4 ,rutley4#gb ,footnote #gb3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia7 p4 #edj4 ,mr4 ,rutley m p>ticul>ly describes ^? ( ,c>adoc ,hill4 ,! breccias & tuffs appe> to consi/ ma9ly ( felsitic mat]ial4 ,9 ! co>s] v>ieties1 fragm5ts ( f9ely-b&$ felsite may be notic$1 :ile ! f9] k9ds pass into a k9d ( horn/one 7hllefl9ta71 :i* 9 h&-specim5s c\ld h>dly be di/+ui%$ f close-gra9$ felsite4 ,9 "s places1 ^! pyrocla/ic rocks are well /ratifi$1 b else:]e no satisfactory b$d+ c be recogniz$ 9 !m4 ,v>i\s o!r rocks1 :i* are probably intrusive1 occur 9 ! ridge4 ,at ei!r end ( ! ,wrek9 !re is a mass ( p9k microgranite1 :ile at ,ca] ,c>adoc num]\s %eets ( gre5/one1 int]calat$ 9 ! f9e tuffs1 sweep across ! hill4 ,mr4 ,rutley has publi%$ an acc\nt ( ^! basic rocks1 :i* he classes z melaphyres1 or alt]$ =ms ( basalt or &esite4#gc ,t at lea/ "s ( !m are intrusive is manife/ by ! way 9 :i* !y ramify ?r\gh ! surr\nd+ /rata4 ,b o!rs are s /rongly amygdaloidal & slaggy t !y may possibly be true int]b$d$ lavas1 ?\gh !re may be "s hesitation 9 admitt+ t su* basic outfl[s c\ld be erupt$ 9 ! mid/ ( ?or\ghly acid ejections4#gd ,leav+ ^! d\btful fl[s out ( acc\nt1 we h "h a gr\p ( und\bt$ volcanic rocks repres5t$ by acid lavas & pyrocla/ic mat]ials1 by intrusive bosses ( acid rocks1 & by y\ng] basic sills4 ,! g5]al li?ological *>act]s ( ^! masses & ! sequ5ce ( _! appe>ance ?us /rongly resemble ^? ( subsequ5t ,palozoic volcanic episodes4 ,footnote #gc3 ,op4 cit4 p4 #ecd4 ,footnote #gd3 ,?is difficulty1 h[ev]1 ne$ n be 9 itself insup]able1 z is evid5t f ! rem>kable alt]nation ( basic & acid lavas & tuffs 9 ! ,cambrian volcanic gr\p ( ,/4 ,david's & 9 ! ,old ,r$ ,s&/one s]ies ( ! ,p5tl& ,hills4 ,! geological age ( ?is volcanic gr\p is a "q ( mu* int]e/ & importance 9 reg>d to ! hi/ory ( volcanism 9 ?is c\ntry4 ,an inf]ior limit to ! antiquity ( ! gr\p c at once be fix$ by ! fact t1 z orig9ally po9t$ out by ,dr4 ,callaway1 ! qu>tzite :i* ov]lies ! volcanic rocks passes "u a lime/one conta9+ ,cambrian fossils 9 :i* ,pr(essor ,lapwor? has s9ce recogniz$ ,ol5ellus1 ,p>adoxides & o!r ,l[] ,cambrian =ms4 ,! eruptions1 !re=e1 mu/ be at lea/ z old z ! e>li] "p ( ! ,cambrian p]iod4 ,b x is affirm$ t ! qu>tzite re/s ) a complete uncon=mability on ! volcanic rocks4 ,if ?is be s1 !n ! epo* ( eruption mu/ be %ift$ mu* f>!r back4 ,illu/ration3 ,fig4 #ci4--,section across ! ,uriconian s]ies ( ,ca] ,c>adoc4 ,s#c1 ,upp] ,silurian2 ,s#b1 ,bala gr\p2 ,s#a1 ,ar5ig gr\p2 ,c1 ,cambrian2 ,l1 ,longmyndian2 u1 ,uriconian2 f f1 faults4 ,! evid5ce adduc$ 9 fav\r ( ?is great break appe>s to me to be ?reefold4 ,9 ! fir/ place1 ! qu>tzite conta9s fragm5ts ( ! volcanic rocks4 ,i d n ?9k mu* /ress c be laid on ?is fact4 ,:5 ,i visit$ ! gr\nd1 :at /ruck me mo/ 9 ! composition ( ! qu>tzite 0 its s+ul>ly pure qu>tzose "*1 & ! comp>ative sc>city ( felsite-pebbles 9 x4 ,any deposit laid d[n con=mably ^u ! top ( ! breccias & tuffs might obvi\sly conta9 "s ( ^! mat]ials1 :ile1 if laid d[n uncon=mably1 x might reasonably be expect$ to be full ( !m4 ,9 ! second place1 ?is qu>tzite is alleg$ to pass transgressively across ! edges ( successive %eets ( ! volcanic gr\p1 & ?us to h a q discordant dip & /rike4 ,i fail$ to f9d satisfactory evid5ce ( ?is uncon=mability 9 ! nor!rn "p ( ! di/rict4 ,b 9 ! ,ca] ,c>adoc area ! qu>tzite does appe> to /eal across ! outcrops ( ! old] rocks1 :i* plunge at ne>ly "r angles 9 an opposite direction4 ,9 ! ?ird place1 ! felsitic volcanic gr\p is believ$ by ,pr(essor ,lapwor? to pass upw>ds into ! ,longmynd rocks4 ,obvi\sly1 if ?is gr\p lies at ! v bottom ( ! va/ ,longmynd s]ies1 ! discordance betwe5 x & ! qu>tzite mu/ be enorm\s1 & ! date ( ! volcanic eruptions mu/ be plac$ va/ly f>!r back 9 geological antiquity4 ,?\gh ! evid5ce does n seem to me to am\nt to cle> pro(1 ,i am dispos$1 9 ! meantime1 to accept x z af=d+ ! mo/ probable solution ( ! difficulties pres5t$ by ! /ructure ( ! gr\nd4 ,! sequ5ce ( ! rocks ar\nd ,ca] ,c>adoc is p>tly conceal$ by surface accumulations1 b if ^! c\ld be cle>$ away ! /ructure ( ! gr\nd w\ld be1 accord+ to ,messrs4 ,lapwor? & ,watts1 z %[n 9 ,fig4 #ci4ge ,footnote #ge3 ,proc4 ,geol4 ,assoc4 vol4 xiii4 7#ahid71 pp4 #cad1 #cae4 ,if1 !n1 ?is volcanic gr\p und]lies ! :ole ( ! ,longmynd s]ies1 & if1 z x n[ appe>s1 t s]ies is old] ?an ! ,ol5ellus-zone ( ! ,l[] ,cambrian rocks1 we c h>dly include ! volcanic rocks ( ! ,wrek9 & ,ca] ,c>adoc 9 ! ,cambrian sy/em4 ,!y mu/ belong to a /ill old] geological =mation1 & ,i ?9k we _c d bett] ?an adopt = !m ,dr4 ,callaway's "n1 ,uriconian4 ,!re are /ill1 h[ev]1 _m problems to be solv$ be=e ! geological hi/ory ( t region is completely und]/ood4 ,! rocks ( ! ,longmynd mu/ be m fully work$ out4 ,x is improbable t /rata :i* look s likely to yield fossils %\ld = ev] prove b>r54 ,! l[] half at lea/ may be hopefully se>*$1 al?\gh ! upp] massive r$di% s&/ones & conglom]ates (f] less prospect ( success4 ,on ! we/ side ( ! ,longmynd1 above ,pontesbury1 !re occurs a small area ( volcanic rocks l ^? ( ! ,wrek9 di/rict1 includ+ a well-m>k$ nodul> felsite & f9e tuffs4 ,^! rocks h be5 reg>d$ by ,dr4 ,callaway z ano!r axis ( ! ,uriconian s]ies4 ,x is v difficult1 h[ev]1 by any comb9ation ( geological /ructures1 to br+ up a portion ( ! v bottom ( ! ,longmynd s]ies & place x app>5tly at ! top4 ,?is is a feat :i* a detail$ /udy ( ! region1 & ! detection ( uncon=mabilities 9 ! ,longmynd1 may possibly accompli%4 ,9 ! meantime1 h[ev]1 ,i w\ld v5ture to sugge/ :e!r x is n m probable t we h "h a deta*$ area ( mu* y\ng] volcanic rocks1 l ^? :i*1 9 v>i\s di/ricts1 may be includ$ 9 ! ,cambrian sy/em1 & :i* w be ref]r$ to 9 "s detail 9 subsequ5t pages4 ,v4 ,,! ,,malv]n ,,volcano ,reg>d+ ! age & orig9 ( ! olde/ rocks ( ! ,malv]n ,hills "s controv]sy has aris51 & no g5]al agreem5t has yet be5 rea*$4#gf ,x is cle> t ! core ( cry/all9e rocks :i* is ov]la9 uncon=mably by ! ,hollybu% ,s&/one mu/ be old] ?an ! ,upp] ,cambrian rocks4 ,!re is no good evid5ce ( any /ratigraphical break 9 ! ,cambrian sy/em ( ,engl& or ,wales1 & x may be reasonably inf]r$ t ! break se5 at ! base ( ! ,hollybu% ,s&/ones indicates t ! rocks und]nea? t horizon are pre-,cambrian4 ,"s portions ( ^! c]ta9ly v anci5t rocks are gneisses or s*i/s2 o!rs h be5 describ$ z felsites1 & h be5 reg>d$ z pass+ into s*i/s1 & z ! orig9al mat]ial f :i* portions ( ! foliat$ s]ies ( ! range h be5 produc$ by me*anical de=mation4 ,n improbably ! :ole s]ies ( rocks is ( igne\s orig91 b has be5 subsequ5tly r5d]$ m or less s*i/ose4 ,footnote #gf3 ,!re is no room "h = a full bibliography ( ! geological lit]ature devot$ to ?is locality4 ,9 ! monograph by ,j4 ,phillips 9 vol4 ii4 "p i4 ( ! ,memoirs ( ! ,geological ,survey1 a li/ ( writ+s is giv5 up to ! "t ( its publication 9 #ahdh4 ,s9ce t ye> _m additional pap]s h appe>$4 ,i may especially ref] to ,h4 ,b4 ,holl1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xxi4 7#ahfe7 p4 #gb2 ,j4 ,h4 ,tim9s1 op4 cit4 xxii4 7#ahfg72 ,mr4 ,f4 ,rutley1 op4 cit4 xliii4 7#ahhg7 p4 #dha2 ,dr4 ,callaway1 op4 cit4 xliii4 7#ahhg7 p4 #ebe1 xlv4 7#ahhi7 p4 #dge1 xlix4 7#ahic7 p4 #cih2 ,pr(4 ,gre51 op4 cit4 li4 7#ahie7 p4 #a2 ,mr4 ,h4 ,d4 ,acl&1 ,geol4 ,mag4 #ahid1 p4 #dh4 ,!re is "o area :]e ! rocks h escap$ metamorphism1 & :]e !y pres5t "s ( ! well-kn[n features ( anci5t volcanic mat]ials4 ,?is tract 0 fir/ indicat$ by ,dr4 ,h4 ,b4 ,holl z "o occupi$ by alt]$ primordial rocks & po/-primordial trap4 ,its evid5tly igne\s mat]ials h be5 exam9$ & describ$ by diff]5t obs]v]s1 among :om ,dr4 ,callaway has contribut$ "s detail$ pap]s on ! subject4 ,m rec5tly ,pr(essor ,gre51 :o _h ! advantage ( sections expos$ 9 ! excavations = ! con/ruction ( a res]voir = supply+ wat] to ,great ,malv]n1 came to ! conclusion t ! rocks consi/ ma9ly ( felsites1 hav+ _m ( ! *>act]s ( rhyolites4 ,) ^! are associat$ felsitic tuffs1 :ile b&s ( dol]ite1 probably intrusive1 =m likewise "p ( ! s]ies4 ,s f> z ! some:at meagre evid5ce all[s an op9ion to be =m$1 !re appe>s to be an alt]nation ( felsites1 lavas & tuffs plac$ 9 a m or less v]tical position1 /rik+ 9 a nor!rly direction1 & trav]s$ by sev]al %eets ( intrusive dol]ite4 ,no junction has be5 f\nd betwe5 ^! unfoliat$ volcanic rocks & ! s*i/s t =m ! core ( ! range4 ,judg+ m]ely f _! pres5t relative condition1 "o w\ld naturally inf] t ! volcanic rocks mu/ be ! y\ng] ( ! two gr\ps4 ,b1 z ,pr(essor ,gre5 has po9t$ out1 x is conceivable t ! latt] may h locally escap$ cru%+1 & yet be ( ! same age z ! felsites & epidiorites ( ! neighb\r+ ,ragg$/one ,hill1 :i* h be5 9 "p consid]ably affect$ by me*anical movem5ts4#gg ,footnote #gg3 ,op4 cit4 p4 #g4 ,! metamorphism ( ! igne\s rocks ( ! ,malv]n ,hills into s*i/s has be5 especially inve/igat$ by ,dr4 ,callaway4 ,= our pres5t inquiry x is p]haps suffici5t to take note t 9 ! he>t ( ! ,malv]n ,hills !re lies a remnant ( a volcanic di/rict1 probably ( pre-,cambrian age1 ! rocks ( :i* _h be5 rais$ up into a v]tical position s z to =m islets or reefs 9 ! sea 9 :i* ! ,upp] ,cambrian /rata 7,hollybu% ,s&/one & ,upp] ,l+ula %ales7 7 deposit$4 ,until "s m precise evid5ce is obta9$ z to ! geological age ( ^! rocks x may be conv5i5t to place !m provisionally ) ! volcanic ,uriconian s]ies4 vi4 ,,! ,,*>nwood ,,=e/ ,,volcano ,9 ! he>t ( ,engl& ! great ,triassic pla9 is div]sifi$ by ! uprise ?r\gh x ( ! peaks & cre/s ( an old ,triassic l&-surface1 :i* are embrac$ 9 ! di/rict kn[n z ,*>nwood ,=e/4 ,^! scatt]$ em95ces consi/ ( mat]ials n only imm5sely old] ?an ! ,trias1 b once d\btless buri$ "u ?\s&s ( feet ( ,palozoic /rata4 ,!y _h be5 laid b>e by d5udation & c>v$ into picturesque crags & p9nacles be=e ! ,new ,r$ ,s&/one 0 deposit$ ar\nd & above !m4 ,to ^! ve/iges ( an e>ly ,mesozoic l&1 /ill half buri$ among ,triassic /rata1 a peculi> int]e/ atta*es f ! obvi\sly high antiquity ( _! rocks & _! uprise 9 ! v c5tre ( ! isl&4 ,v>i\s op9ions h be5 express$ z to ! age ( _! compon5t rocks4 ,:5 !y 7 mapp$ by ! ,geological ,survey !y 7 recogniz$ to be z old z any gr\p ( rocks !n kn[n1 & !y 7 accord+ly plac$ 9 ! ,cambrian sy/em4 ,m rec5t rese>* has sugge/$ t !y may be /ill m anci5t1 & may be reg>d$ z pre-,cambrian4 ,! rocks ( ,*>nwood ,=e/ h be5 ! subject ( an exhau/ive rese>* by ! ,rev4 ,e4 ,hill & ,pr(essor ,bonney1 to :om mo/ ( our k reg>d+ !m is due4 ,^! obs]v]s fir/ po9t$ out ! truly volcanic nature ( ! co>se cla/ic rocks ( ! di/rict4 ,!y h trac$ _! relations 9 ! field1 & h likewise describ$ _! /ructure & composition z %[n by ! microscope4 ,subsequ5tly ! di/rict has be5 re-mapp$ on ! scale ( six in*es to a mile by ,mr4 ,fox ,/rangways = ! ,geological ,survey1 :ile ,mr4 ,w4 ,w4 ,watts1 ano!r memb] ( ! ,survey1 has /udi$ ! petrography ( ! gr\nd1 & has trac$ ! b\nd>ies ( ! sev]al rock-gr\ps s f> z ^! c be det]m9$4 ,confirm+ g5]ally ! /ratigraphical arrangem5t sket*$ by ,messrs4 ,hill & ,bonney1 ,mr4 ,watts has propos$ ! foll[+ classification ( ! rocks3--#gh #g4 ,groby & ,s)l& slates4 #f4 ,hang+ ,rocks conglom]ate & ,! ,br& s]ies4 ,bradgate qu>tzite4 #e4 ,woodh\se b$s 7a%y grits74 #d4 ,slate-agglom]ate ( ,roecliffe4 ,! ,maplewell s]ies 7volcanic tuffs & agglom]ates74 #c4 ,horn/one b$s ( ,beacon ,hill4 #b4 ,felsitic agglom]ate ( ,b5scliffe4 #a4 ,qu>tzose1 felspa?ic & felsitic grits4 ,! ,blackbrook s]ies4 ,footnote #gh3 ,annual ,report ( ,director-,g5]al ( ! ,geological ,survey1 9 ! ,report ( ,sci5ce & ,art ,dep>tm5t = #ahie4 ,"u any computation or measurem5t1 ! total ?ickness ( detrital mat]ial 9 ?is s]ies ( =mations mu/ am\nt to sev]al ?\s& feet4 ,! *ief int]e/ c5tres 9 ! middle s]ies1 :i* consi/s l>gely ( fragm5tal volcanic rocks1 ) int]calations ( slate & grit4 ,z 0 fir/ %[n by ,mr4 ,hill & ,pr(essor ,bonney1 ^! volcanic mat]ials v>y f exce$+ly co>se agglom]ates to f9e1 a%y or felspa?ic slates4 ,9 mo/ cases di/9ct b$d+ c be recogniz$ 9 !m1 b m p>ticul>ly 9 ! f9e-gra9$ mat]ial4 ,yet ev5 among ! massive agglom]ates a t5d5cy may be se5 t[>ds an ori5tation ( ! blocks ) _! long axes p>allel4 ,t ?is arrangem5t is n entirely due to ! effects ( cleavage may be inf]r$ f ! _m exceptions to x1 :i* w\ld h>dly h occurr$ _h su* p[]ful cleavage affect$ ! :ole di/rict1 z w\ld be ne$$ to re>range ! l>ge blocks 9 ! agglom]ates4 ,besides1 ! co>s] p>ts (t5 int]calate ) f9e felspa?ic grits1 :i* di/9ctly m>k ! /ratification ( ! :ole4 ,! rem>kably co>se breccia ( ,b5scliffe is ma9ly made up ( blocks ( qu>tz-porphyry1 felsite or rhyolite1 ) slate fragm5ts4 ,! ,roecliffe agglom]ate1 ano!r extraord9>ily co>se rock1 consi/s ( slate fragm5ts imb$d$ 9 an &esitic matrix1 "s ( ! blocks ( slate be+ six feet long4 ,! f9] tuffs h be5 asc]ta9$ to consi/ ( felsitic or &esitic detritus1 sometimes =m+ exce$+ly compact fl9ty rocks or horn/ones4 ,9 ?is ?ick accumulation ( detrital rocks we are pres5t$ ) a s]ies ( alt]nations ( co>s] & f9] pyrocla/ic mat]ial1 int]/ratifi$ among gre51 grey & purple slates & grits1 :i* probably repres5t ! non-volcanic s$im5ts ( ! "t ( eruption4 ,! succession ( /rata be>s witness to a long s]ies ( eruptions ( v>y+ int5sity1 b culm9at+ at two di/9ct p]iods 9 ! dis*>ge ( huge blocks ( rock 7,b5scliffe & ,roecliffe agglom]ates74 ,aft] "s se>* ,i h be5 unable to detect a s+le vesicul> fragm5t among ! /ones 9 ! breccias & tuffs1 & ,messrs4 ,hill & ,bonney 7 n m successful4 ,n a trace ( any?+ 9 ! lea/ degree scoriace\s is any:]e to be f\nd4 ,! pa/e 9 :i* ! blocks lie consi/s ( su* f9e mat]ial z w\ld result f ! trituration ( felsite & slate4 ,x conta9s _m brok5 cry/als ( felsp>1 ) gra9s ( cle> qu>tz4 ,a gradation c be trac$ f ! co>s] into ! f9] b&s ( volcanic & non-volcanic mat]ial1 f9e slates be+ also int]leav$ ) highly-felspa?ic p>t+s ( grit4 ,hav+ look$ ) "s c>e = a trace ( a true volcanic neck 9 ! di/rict1 ,i h n se5 any?+ t c\ld be unhesitat+ly s designat$4 ,ev5 9 ! nor?-we/]n "p ( ! di/rict1 :]e ! breccias are co>se/1 & !re is lea/ trace ( ord9>y s$im5ts1 "s signs ( b$d+ c usually be detect$ 9 ! position ( ! imb$d$ /ones & ! p>t+s ( f9] tuff4 ,bo? ! co>s] & f9] detritus sugge/ ! k9d ( mat]ial dis*>g$ f v5ts be=e ! uprise ( any lava4 ,! entire abs5ce ( scoriace\s fragm5ts is notewor?y1 & ! abundance ( slate blocks r po9ts to ! e>ly eruptions ( a volcanic focus4 ,possibly1 :ile ! *ief c5tre ( eruption lay t[>ds ! nor?-we/1 num]\s v5ts may h be5 op5$ all ov] ! di/rict1 dis*>g+ abundant %[]s ( du/ & /ones1 b seldom or nev] culm9at+ 9 ! actual outp\r+ ( lava4 ,no indubitable lava-%eet has1 9 my judgm5t1 be5 yet recogniz$ 9 ,*>nwood ,=e/4 ,v>i\s op9ions h be5 express$ z to "s ( ! m compact close-gra9$ rocks1 & ev5 ! v]dicts ( ! same obs]v]s h v>i$ f "t to "t1 ! rocks once consid]$ z felsites be+ aft]w>ds reg>d$ z tuffs1 & subsequ5tly plac$ ) ! felsites or &esites aft] all4 ,x is n necess>y = my pres5t purpose to ent] into ^! que/ions1 :i* are r ( local int]e/4 ,i w only say t1 9 my op9ion1 ! rocks ( ,%>pley1 ,peld>1 & ,b>don ,hill are massive rocks1 z !y h f9ally be5 class$ by ,messrs4 ,hill & ,bonney4 ,b ,i _c look ^u !m z lavas1 at lea/ ,i h se5 no evid5ce to lead me to believe t !y 7 ev] erupt$ at ! surface4 ,i h fully consid]$ ! argum5ts ( ,mr4 ,hill & ,pr(essor ,bonney on ?is po9t4#gi ,!re c1 ,i ?9k1 be no d\bt ( ! close association ( ^! felsitic rocks & ! breccias1 b ! /ructure ( ! rocks 9 ! field seems to me to be decid$ly 9 fav\r ( ! view express$ above4 ,! microscope af=ds no assi/ance 9 ! "q4#hj ,! d\btful rocks seem to me r to be intrusive masses :i* h be5 protrud$ into ! volcanic s$im5t>y s]ies among :i* !y rise4 ,!y are acid1 f9e-gra9$1 porphyritic rocks1 :i* w\ld =m]ly h be5 includ$ "u ! g5]al "n ( felsites or qu>tz-porphyries4 ,_! co>se porphyritic p>ts rapidly pass into close-gra9$ felsitic mat]ial4 ,_m ( ! blocks 9 ! breccias are precisely l p>ts ( ^! rocks4 ,x might h5ce be ass]t$ t ^! fragm5tal deposits are lat] ?an ! eruptive bosses4 ,at lea/ x is obvi\s t rocks ( ! same type z ^? ( ,%>pley1 ,peld>1 & ,b>don ,hill mu/ h be5 disrupt$ to produce ! co>se breccias4 ,footnote #gi3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia71 pp4 #hj-hh4 ,footnote #hj3 ,see ,messrs4 ,hill & ,bonney1 op4 cit4 xxxiv4 7#ahgh71 p4 #baa4 ,lat] eruptive rocks1 consi/+ ( masses ( sy5ite & granite1 ) /ill y\ng] dykes ( dol]ite1 &esite1 diorite & felsite1 h successively made _! appe>ance1 & add to ! div]sity ( ! igne\s ph5om5a ( ?is di/rict4 ,! "q ( ! age ( ?is isolat$ volcanic s]ies is "o ( mu* int]e/1 b ( great p]plexity4 ,?\gh a resemblance may be admitt$ to exi/ betwe5 "s ( ! slates & p>ts ( ! ,cambrian sy/em ( ,nor? ,wales1 ! diff]5ce betwe5 ! ,*>nwood rocks & ! und\bt$ ,cambrian s]ies ( ,w>wick%ire1 only ?irte5 miles to ! s\?-we/1 is su* z to indicate t ! =m] are probably old] ?an ! latt]4 ,:ile ! ,*>nwood rocks h be5 int5sely cleav$ & cru%$1 ^? ( ,w>wick%ire h und]gone no su* *ange4 ,! argillace\s /rata 9 ! "o region h be5 conv]t$ into slates1 9 ! o!r !y rema9 m]e %ales4 ,?\gh cleavage is sometimes irregul>ly develop$1 its rapid disappe>ance 9 s %ort a di/ance z ! int]val betwe5 ,*>nwood ,=e/ & ,nuneaton seems mo/ explicable if we suppose t ! rocks at ! m ea/]ly locality 7 cleav$ be=e ^? t[>ds ! we/ 7 deposit$4 ,if ?is inf]5ce be well gr\nd$ ! pre-,cambrian age ( ! ,*>nwood volcanoes w\ld be e/abli%$4 ,b ! argum5t is n conclusive4 ,no fossils ( any k9d h yet be5 f\nd 9 any ( ! old rocks ( ,*>nwood4#ha ,m]ely li?ological resemblances or diff]5ces are all t c be us$ z a guide to ! geological age ( ^! masses4 ,mr4 ,watts has sugge/$ t possibly ! qu>tzite ( ,bradgate 7,no4 #f ( ! ,*>nwood gr\ps7 may be ! equival5t ( ! qu>tzite :i* 9 ,%rop%ire & ,w>wick%ire =ms ! base ( ! s$im5t>y ,cambrian =mations4 ,if t correlation c\ld be e/abli%$1 ! volcanic s]ies bel[ ! qu>tzite 9 ,*>nwood might be reg>d$ z repres5t+ ! ,uriconian volcanic s]ies ( ,%rop%ire4 ,footnote #ha3 ,s9ce ?is page 0 9 type1 ,pr(essor ,lapwor? has f\nd a worm-burr[ l[ d[n 9 ! ,br& ,s]ies1 & "o or two additional examples h s9ce be5 obta9$ by ,mr4 ,j4 ,rhodes ( ! ,geological ,survey4 ,^! are ! fir/ und\bt$ organisms f ! ,*>nwood ,=e/ rocks4 ,mr4 ,watts1 ,geol4 ,mag4 #ahif1 p4 #dhg4 ,,book ,,iii ,,! ,,cambrian ,,volcanoes ,,*apt] ,,ix ,,*>act]i/ics ,,( ,,! ,,cambrian ,,sy/em ,,9 ,,brita9 ,! ,physical ,geography ( ! ,cambrian ,p]iod--,! ,pione]s ( ,palozoic ,geology 9 ,brita9--,"w ( ! ,geological ,survey 9 ,wales--,subdivisions ( ! ,cambrian ,sy/em 9 ,brita94 ,9 leav+ ! inve/igation ( ! pre-,cambrian rocks & ent]+ ^u t ( ! ,palozoic sy/ems1 t is1 ! great s]ies ( s$im5t>y =mations :i* include ! e>lie/ records ( organiz$ life ^u ! surface ( ! globe1 ! geologi/ feels mu* z ! hi/orian :51 quitt+ ! doma9 ( leg5d & tradition1 he c tread firmly 9 ! region ( docum5t>y evid5ce4 ,f ! bottom ( ! ,cambrian sy/em upw>d ?r\gh ! long s]ies ( geological =mations1 ! *ronicle1 ?\gh (t5 sadly incomplete1 is usually cle> & legible4 ,z we foll[ ! l[e/ fossilif]\s /rata across a t]ritory1 we recognize t !y be> witness to ! same processes ( d5udation & deposition :i* h be5 go+ on un9t]rupt$ly on ! face ( ! globe ev] s9ce4 ,! b$s ( conglom]ate repres5t ! gravels & %+les ( old coa/-l9es & riv]-b$s4 ,! s&/ones recall ! famili> features ( s&y sea-bottoms n f> f l&4 ,! %ales be> witness to ! fall ( f9e s$im5t 9 /ill] wat]1 su* z n[ takes place 9 ! deep] p>ts ( seas & lakes4 ,not)/&+ _! va/ antiquity1 ! /rata !mselves exhibit no exceptional peculi>ities ( orig94 ,!y seem to be j su* famili> deposits z are ga!r+ "u fitt+ conditions at ! pres5t "t4 ,"s writ]s h speculat$ on ! f> great] int5sity ( all geological activities 9 ! e>ly times ( ! planet's hi/ory4 ,b if we may int]pret ! record ( ! /ratifi$ =mations by ! ph5om5a ( to-day1 !re is = ^! speculations no confirmation 9 ! s$im5tation ( ! olde/ /ratifi$ deposits4 ,x is ( c\rse q intelligible1 if n probable1 t _m geological =ces may h be5 m vigor\s 9 primeval times ?an !y aft]w>ds became4 ,b ( ! gigantic tides1 prodigi\s d5udation & viol5t huddl+ toge!r ( ! wa/e ( ! e>?'s surface1 :i* h be5 po/ulat$ = ! e>ly ,palozoic ages1 !re is assur$ly n[h]e any indication among ! /ratifi$ =mations4 ,9 ^? va/ ord]ly repositories1 lay] succe$s lay] among ?9ly-lam9at$ %ales1 z g5tly & equably z ! f9e silt ( ea* tide s9ks to-day ov] ! floor ( a %elt]$ e/u>y4 ,at ! primeval p]iod ( :i* ^! s$im5ts are ! memorial1 ! wat]s rec$$ f flat %ores & left tracts ( mud b>e to ! sky1 precisely z !y d /ill4 ,!n z n[1 ! sun %one & dri$ su* mud-flats1 cov]+ _! surfaces ) a network ( cracks2 ! ra9 fell 9 heavy drops1 t left _! impr9ts on ! dry+ mud2 & ! next tide rose s g5tly z to ov]fl[ ^! records ( sun%9e & %[] )\t effac+ !m1 b spread+ ov] !m a fre% film ( s$im5t1 to be succe$$ by o!r sl[ly-accumulat+ lay]s1 "u :i* !y h la9 pres]v$ dur+ ! long cycles ( geological hi/ory4 ,t organiz$ creatures _h already appe>$ ^u ! e>?'s surface be=e ! beg9n+ ( ! ,cambrian p]iod _c be d\bt$4 ,! animal rema9s 9 ! l[e/ ,cambrian /rata are f> f be+ ! simple =ms :i* might be expect$ to indicate ! fir/ />t ( animal life ^u ! surface ( ! e>?4 ,on ! contr>y1 ?\gh !y are comp>atively scanty 9 types1 & (t5 r>e or abs5t ?r\gh\t a ?ick mass ( s$im5t>y deposits1 !y %[ beyond dispute t1 :5 !y fl\ri%$1 inv]tebrate life _h already rea*$ su* a /age ( advancem5t & diff]5tiation t v>i\s lead+ types _h appe>$ :i* h desc5d$1 9 "s cases ) g5]ic id5tity1 d[n to our own day4 ,!re mu/ h be5 a long p$igree to ^! organisms ( ! olde/ kn[n fossilif]\s rocks4 ,& some:]e on ! e>?'s surface we may yet hope to f9d ! rema9s ( _! prog5itors 9 pre-,cambrian deposits4 ,! rese>*es ( _m explor]s 9 ,europe & ,nor? ,am]ica h br\ght to light an int]e/+ s]ies ( organic rema9s f ! ,cambrian sy/em4 ,( ! plants ( ! "t h>dly any traces h surviv$1 save "s m>k+s :i* h be5 ref]r$ to sea-we$s4 ,! e>lie/ kn[n sponges & corals occur 9 ?is sy/em1 likewise ! ance/ors ( ! graptolites1 :i* play$ s prom95t a "p 9 ! life ( ! next or ,silurian p]iod4 ,!re 7 already repres5tatives ( cr9oids & />-fi%es1 besides examples ( ! ext9ct gr\p ( cy/ideans4 ,sea-worms crawl$ ov] ! muddy & s&y sea-bottom1 = !y h left _! trails & burr[s 9 ! h>d5$ s$im5ts4 ,molluscs _h by ?is "t appe>$ 9 _! f\r great divisions ( ,bra*iopods1 ,lamellibran*s1 ,ga/]opods & ,cephalopods1 ?\gh ! =ms yet discov]$ among ,cambrian rocks are comp>atively few4 ,! mo/ abundant & *>act]i/ic inhabitants ( ! ,cambrian seas 7 ! trilobites1 ( :i* _m g5]a h be5 dis9t]r$ f ! /rata4 ,9 ! l[e/ fossilif]\s ,cambrian gr\p ! trilobitic g5us ,ol5ellus1 already ref]r$ to1 is ! *>act]i/ic =m4 ,high] up ,p>adoxides is pr$om9ant1 :ile t[>ds ! top ( ! sy/em ! mo/ *>act]i/ic g5us is ,ol5us4 ,f ! organic rema9s :i* h be5 pres]v$1 we may legitimately inf] ! exi/5ce ( o!rs :i* h entirely disappe>$4 ,!re seems no reason to d\bt t ! lead+ grades ( inv]tebrate life :i* are want+ 9 ! kn[n ,cambrian fauna 7 really repres5t$ 9 ! ,cambrian seas4 ,! *ance discov]y ( a b& ( lime/one may any day entirely alt] our k z to ! relative proportions ( ! sev]al divisions ( ! animal k+dom 9 ! e>lie/ ,palozoic rocks4 ,s& is r adv]se to ! pres]vation ( a v>i$ repres5tation ( ! organisms ( ! ov]ly+ sea-wat]4 ,mud is g5]ally fav\rable1 b calc>e\s accumulations are greatly m s1 & !y usually consi/ almo/ entirely ( organic rema9s4 ,?us 9 ! ,cambrian s]ies ( ! nor?-we/ ( ,scotl& ! qu>tzites t =m ! l[] gr\p1 ?\gh sometimes cr[d$ ) worm-burr[s1 conta9 h>dly any o!r sign ( organisms4 ,! ov]ly+ %ales1 besides _! abundant worm-ca/+s1 h yield$ p]fect specim5s ( ,ol5ellus & o!r fossils4 ,b 9 ! upp]mo/ gr\p1 consi/+ ( lime/ones1 e p>ticle ( ! s$im5t appe>s to h pass$ ?r\gh ! inte/9es ( worms1 & z x ga!r$ on ! sea-bottom x enclos$ & has pres]v$ a v>i$ & abundant assemblage ( organisms1 includ+ trilobites1 ga/]opods & a numb] ( cephalopods4 ,:ile 9 ! ,cambrian rocks ( ,europe calc>e\s b&s are comp>atively r>e1 9 ^? ( ,nor? ,am]ica !y are n infrequ5t4 ,h5ce x is l>gely f ,am]ican deposits t our k ( ! ,cambrian fauna has be5 d]iv$4 ,n a ve/ige ( any v]tebrate organism has yet be5 detect$ among ! e>li] ,palozoic s$im5ts4 ,s f> z we "k1 !re 7 no fi%es 9 ! ,cambrian seas4 ,! highe/ organisms !n exi/+ 7 *amb]$ %ells1 a once abundant & s+ul>ly v>i$ class1 ( :i* ! liv+ ,nautilus is n[ ! sole repres5tative4 ,9 try+ to realize ! g5]al geographical conditions ( ,cambrian "t1 ! geologi/ f9ds himself entirely )\t any evid5ce z to ! "* ( ! t]re/rial vegetation4 ,we c h>dly d\bt t ! l& 0 clo!d ) plants1 probably includ+ lycopods & f]ns1 possibly ev5 cycads & conif]s4 ,b no rema9s ( ?is flora h yet be5 recov]$4 ,nor h any traces ( l&-animals be5 detect$4 ,all t we yet "k ( ! life ( ! p]iod has be5 glean$ f m>9e s$im5ts1 :i* %[ t ! inv]tebrate population by :i* ! sea 0 !n t5ant$ embrac$ "s ( ! lead+ types ( /ructure t h surviv$ ?r\gh all ! long vi/a ( geological "t d[n to our own day4 ,"s ( ! %ore-l9es ( ! ,cambrian wat]s may /ill be trac$1 & x is possible to say :]e ! l& ( ! "t /ood & :]e lay ! sea4 ,9 ! ,briti% area ! l>ge/ relic ( ,cambrian l& is f\nd 9 ! f> nor?-we/ ( ,scotl&4 ,=m$ p>tly ( ! ,lewisian ,gneiss & p>tly ( ! ,torridon ,s&/one1 x takes 9 ! :ole *a9 ( ! ,out] ,hebrides & likewise "p ( ! pres5t we/]n seabo>d ( ,su!rl& & ,ross4 ,along ! m>g9 ( t nor!rn l& ! :ite s& 0 laid d[n :i* n[ gleams 9 %eets ( sn[-l qu>tzite on mo/ ( ! high] m\nta9s f ,cape ,wra? to ,skye4 ,! sea lay to ! ea/ &1 s f> z we "k1 may h /ret*$ across ! re/ ( ,scotl&1 & ! nor? & c5tre ( ,engl&4 ,ano!r ve/ige ( ! l& ( ?is anci5t era occurs 9 ,anglesey4 ,!re1 & likewise ov] scatt]$ tracts 9 ! ,midl&s1 & 9 ! s\?-we/ ( ,engl&1 ! geologi/ seems to descry ! la/ relics ( islets t rose out ( ! ,cambrian sea1 & are n[ surr\nd$ ) its h>d5$ s$im5ts4 ,:ile su* 0 ! g5]al aspect ( ! region ( ! ,briti% ,isles dur+ ,cambrian "t1 volcanic action manife/$ itself at v>i\s localities ov] ! area1 break+ out on ! sea-bottom1 & p\r+ =? %eets ( lava & %[]s ( a%es1 :i* m+l$ ) ! s& & silt t 7 settl+ !re at ! "t4 ,9 ! nor!rn or ,scotti% tract no trace ( ?is subt]ranean activity has be5 f\nd2 b 9 ! ,engli% ,midl&s & ov] mu* ( ,wales abundant evid5ce has be5 obta9$ to %[ t 9 ^? di/ricts ! ,cambrian p]iod 0 m>k$ by frequ5t & prolong$ eruptions4 ,z its "n d5otes1 ! ,cambrian sy/em is typically develop$ 9 ,wales4 ,x 0 !re t ,s$gwick fir/ work$ out ! /ratigraphical relations ( its anci5t s$im5ts1 & t ,mur*ison demon/rat$ ! succession ( organic rema9s conta9$ 9 !m1 apply+ to !m ! pr9ciples ( classification laid d[n by ,william ,smi? 9 reg>d to ! ,second>y =mations4 ,x 0 !re too t "s ( ! e>lie/ & mo/ memorable a*ievem5ts 7 made 9 ! inve/igation ( anci5t volcanic rocks4 ,s$gwick & ,mur*ison1 besides ! admirable "w :i* !y accompli%$ 9 e/abli%+ ! /ratigraphy ( ! old] ,palozoic =mations1 cle>ly recogniz$ t among ^! =mations !re 7 pres]v$ ! records ( contemporane\s subm>9e eruptions4 ,s$gwick %[$ t ! m\nta9\s masses ( eruptive rock 9 ,nor? ,wales 7 really lavas & a%es1 :i* _h be5 dis*>g$ ov] ! sea-floor at ! "t :5 ! anci5t s$im5ts ( t region 7 deposit$1 :ile ,mur*ison e/abli%$ ! same fact by num]\s obs]vations 9 ! ea/ & s\? ( ,wales1 & 9 ! bord]+ ,engli% c\nties4 ,de la ,be*e _h f\nd simil> evid5ce among ! grauwacke rocks ( ,devon%ire4#hb ,footnote #hb3 ,= e>ly rese>*es on ! old] ,palozoic volcanic rocks ( ,brita91 see ,s$gwick1 ,proc4 ,geol4 ,soc4 vols4 ii4 7#ahch7 pp4 #fgh1 #fgi1 iii4 7#ahda7 p4 #edh1 iv4 7#ahdc7 p4 #bae2 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 i4 7#ahde7 pp4 #h-ag1 iii4 7#ahdg7 p4 #acd4 ,mur*ison1 ,proc4 ,geol4 ,soc4 vol4 ii4 7#ahcc-cd7 p4 #he2 ,silurian ,sy/em 7#ahci7 pp4 #bbe1 #beh1 #bfh1 #bhg1 #cag1 #cbd1 #dja2 ,siluria1 #d? edit4 7#ahfg7 p4 #gf et seq4 ,de la ,be*e1 ,mem4 ,geol4 ,survey1 vol4 i4 7#ahdf7 pp4 #bi-cf4 ,a4 ,c4 ,ramsay 9 ! ,maps & ,horizontal ,sections ( ,wales publi%$ by ! ,geological ,survey2 also ,descriptive ,catalogue ( ! ,rock-,specim5s 9 ! ,museum ( ,practical ,geology1 #a/ edit4 7#aheh71 #bnd edit4 7#ahei71 #crd edit4 7#ahfb72 ,! ,geology ( ,nor? ,wales1 =m+ vol4 iii4 ( ,memoirs ( ! ,geological ,survey1 #a/ edit4 7#ahff71 #bnd edit4 7#ahha74 ,foll[+ 9 ! track ?us op5$ up by ^! great ma/]s1 ! (fic]s ( ! ,geological ,survey 7 enabl$ to unravel1 z _h nev] be=e be5 attempt$1 ! complicat$ /ructure ( ! old volcanic regions ( ,wales4 ,at ! outset ( ! foll[+ discussion ,i wi% to express my admiration ( ! lab\rs ( ! e>ly pione]s :o ?us laid = u ! f\ndation ( our k ( volcanic action 9 ! ,palozoic p]iods4 ,to ,de la ,be*e & 8 associates 9 ! ,survey a special measure ( gratitude is due f all :o h foll[$ 9 _! /eps & pr(it$ by _! "w4 ,:5 we consid] ! condition ( geological sci5ce1 & especially ( ! dep>tm5t ( petrography1 9 ?is c\ntry at ! "t :5 ^! e>ly & detail$ inve/igations 7 c>ri$ on1 :5 we rememb] ! imp]fection ( mu* ( ! topography on ! old "o-in* ,ordnance maps 7:i* 7 ! only maps !n available71 :5 we call to m9d ! rugg$ & l(ty nature ( ! gr\nd :]e "s ( ! mo/ complicat$ geological /ructures are display$1 we mu/ admit t at ! p]iod :5 ^! maps & sections 7 produc$ !y c\ld n h be5 bett] done2 nay1 t z 9 "s important respects !y 7 di/9ctly 9 advance ( _! "t1 _! publication m>k$ an era 9 ! progress ( /ructural1 & especially ( volcanic1 geology4 ,! sep>ation ( lavas & tuffs ov] hundr$s ( squ>e miles 9 a m\nta9\s region1 ! discrim9ation ( intrusive %eets & eruptive bosses1 ! det]m9ation ( successive /ratigraphical zones ( volcanic activity among "s ( ! olde/ fossilif]\s =mations1 7 a*ievem5ts :i* w ev] place ! names ( ,ramsay1 ,selwyn1 ,jukes & _! associates high 9 ! b$e-roll ( geological sci5ce4 ,no "o ev] ?9ks n[ ( mak+ a geological excursion into ,wales )\t c>ry+ ) him ! %eets ( ! ,geological ,survey map4 ,^! =m 8 guide & h&book1 & furni% him ) ! basis ( in=mation f :i* he />ts 9 8 own rese>*es4 ,b sci5ce does n /& /ill4 ,! mo/ p]fect geological map t c be made to-day w be capable ( improvem5t ?irty or =ty ye>s h5ce4 ,! maps ( ! ,geological ,survey are no exception to ?is rule4 ,9 criticiz+ & correct+ !m1 h[ev]1 let u judge !m n by ! /&>d ( k :i* we h n[ rea*$1 b by t ( ! "t :5 !y 7 prep>$4 ,x is easy to criticize2 x is n s easy to recognize h[ mu* we owe to ! v "w :i* we pron\nce to be imp]fect4 ,! anci5t volcanoes ( ,wales1 ?anks ma9ly to ! admirable lab\rs ( my =m] fri5d & *ief1 ,sir ,&rew ,c4 ,ramsay1 h tak5 a famili> place 9 geological lit]ature4 ,b a good deal has be5 le>nt reg>d+ !m s9ce he mapp$ & wrote4 ,! volcanic hi/ory1 z he view$ x1 began 9 ! ,ar5ig p]iod4 ,! progress ( subsequ5t inquiry1 h[ev]1 has %[n t !re are volcanic rocks 9 ,wales ( mu* old] date4 ,i %all %[ t ! ,cambrian p]iod1 bo? 9 ,s\? & ,nor? ,wales1 0 em95tly volcanic4 ,mu* controv]sy hav+ aris5 z to ! respective limits & nom5clature ( ! old] ,palozoic rocks1 let me /ate1 at ! outset ( ! inquiry into ! volcanic eruptions ( ,cambrian "t1 t "u ! t]m ,cambrian ,i class all ! kn[n ,palozoic rocks :i* lie bel[ ! bottom ( :at is t]m$ ! ,ar5ig gr\p4 ,x 0 ma9ta9$ by ,sir ,&rew ,ramsay & 8 colleagues on ! ,geological ,survey t on ! ma9l& ( ,wales no base is ev] f\nd to ! ,cambrian sy/em4 ,m rec5tly c]ta9 conglom]ates h be5 fix$ ^u z ! true ,cambrian base1 bo? 9 ,s\? & ,nor? ,wales1 & endeav\rs h be5 made to trace an uncon=mability at t l9e1 all rocks bel[ x be+ treat$ z pre-,cambrian4 ,b conglom]ates d n necess>ily m>k a /ratigraphical discordance1 & 9 ,s\? ,wales !re is no trace ( any uncon=mability betwe5 ! /rata above & bel[ ! suppos$ l9e ( break4#hc ,pr(essor ,bonney has %[n t 9 ,nor? ,wales sev]al zones ( conglom]ate h be5 errone\sly id5tifi$ z ! suppos$ basal plat=m ( ! ,cambrian s]ies1 & m rec5tly ,mr4 ,blake has po9t$ out t "s ( ^! conglom]ates are unque/ionably ,l[] ,silurian4 ,footnote #hc3 ,see a discussion ( ?is subject 9 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxix4 7#ahhc71 p4 #cje4 ,my own exam9ation s f> confirms ! conclusions arriv$ at by ^! obs]v]s4 ,l my pr$ecessors 9 ! ,geological ,survey1 h[ev]1 ,i h be5 unable to detect any:]e 9 ,ca]n>von%ire or ,m]ione?%ire a base to ! ,cambrian sy/em1 & ,i am compell$ to agree ) !m 9 reg>d+ z ,cambrian 7p>tly ev5 z ,l[] ,silurian7 all ! rocks f ,bangor to ,llanllyfni1 :i* h m rec5tly be5 class$ z pre-,cambrian4 ,b ?\gh ?us support+ _! g5]al /ratigraphy1 ,i am b\nd to ackn[l$ge t !y fail$ to recognize ! exi/5ce ( a great volcanic s]ies bel[ ! ,ar5ig horizon4 ,! exi/5ce ( ?is s]ies1 notic$ by ,s$gwick1 0 fir/ def9itely /at$ by ,pr(essor ,hughes1#hd & 8 /atem5ts h be5 confirm$ & ext5d$ by subsequ5t obs]v]s1 notably by ,pr(essor ,bonney & ,mr4 ,blake4 ,! ,cambrian p]iod is ?us prov$ to h be5 p]haps ev5 m cont9u\sly volcanic ?an ! ,l[] ,silurian p]iod 0 9 ,wales4 ,footnote #hd3 ,proc4 ,camb4 ,phil4 ,soc4 vol4 iii4 7#ahgg71 p4 #hi4 ,! ,cambrian volcanic areas ( ,nor? ,wales are repres5t$ 9 ,map ,,ii4 ,! foll[+ table %[s ! subdivisions ( ! ,cambrian sy/em n[ recogniz$ 9 ,brita93-- ---------------------------------------- ----------------------------- ,wales4 7,rang+ up to ,we/]n ,engl&4 ,n4,w4 ,scotl&4 #ab1jjj feet 7,ab\t #cjjj feet47 7,ab\t #bjjj feet47 or m47 ---------------------------------------- ----------------------------- ,upp] or ,ol5us ,zones4 ,tremadoc ,slates ,%9eton ,%ales ,lime/ones1 ab\t #aejj ,l+ula ,flags 7,dictyograptus feet ?ick1 divisible 7,l+ulella1 or ,dictyonema1 into sev5 gr\ps ,ol5us1 etc474 ,ol5us1 etc474 7,ar*ocya?us1 ,maclurea1 ,ophileta1 ,middle or ,p>adoxides ,zones4 ,mur*isonia1 ,m5evian gr\p ,conglom]ates & ,or?oc]as1 7,p>adoxides74 lime/ones 7,comley71 & va/ quantities ( 7,comley71 ) annelid ca/+s74 ,p>adoxides1 etc4 ,l[] or ,ol5ellus ,zones4 ,h>le* & ,?9 qu>tzite ,%ales 7fucoid b$s71 ,llanb]is pass+ up into ) ,ol5ellus1 gr\p ) gre5 flags1 grits1 ,salt]ella1 etc4 basem5t volcanic %ales ,qu>tzites ) annelid rocks2 bottom n & s&/one burr[s4 ,! base ( se54 7,comley ,s&/one71 ! s]ies lies conta9+ uncon=mably on ,ol5ellus4 pre-,cambrian rocks4 ---------------------------------------- ----------------------------- ,,*apt] ,x ,,! ,,cambrian ,,volcanoes ,,( ,,s\? ,,wales ,9 ! s\!rn "p ( ! ,pr9cipality ( ,wales a rem>kably v>i$ display ( ,briti% ,cambrian volcanic rocks has be5 pres]v$4 ,! di/rict ar\nd ,/4 ,david's has ! di/9ction ( be+ ! fir/ 9 :i* volcanic rocks ( su* high antiquity 7 recogniz$4 ,z f> back z ! ye> #ahdb1 ,ramsay f\nd t felspa?ic volcanic a% 0 associat$ ) o!r pro(s ( igne\s action1 & ?is fact 0 record$ by him on ! publi%$ ,horizontal ,sections ( ! ,geological ,survey4 ,un=tunately he aft]w>ds came to reg>d ! rocks z alt]$ ,cambrian1 ?us foll[+ c]ta9 hypo!tical views :i*1 z w be fur!r allud$ to 9 ! sequel1 he _h adopt$ 9 explanation ( ! ph5om5a 9 ,ca]n>von%ire & 9 ,anglesey4 ,! volcanic nature ( ^! anci5t mat]ials 0 subsequ5tly r$iscov]$ by ,dr4 ,hicks1 :o has devot$ mu* "t & lab\r to _! /udy4 ,di/+ui%+ ! volcanic s]ies ( ,/4 ,david's by ! "n ,pebidian1 he has cont5d$ t x =ms a pre-,cambrian sy/em sep>at$ by an uncon=mability f ! base ( ! ,cambrian =mations4 ,he likewise endeav\r$ to %[ t an old] sy/em ( rhyolitic lavas1 felsitic breccias & hllefl9tas c\ld be di/+ui%$1 :i* he t]m$ ,arvonian2 & m anci5t /ill1 a core ( granitoid or gneissic rocks1 :i* he sep>at$ "u ! "n ( ,dimetian4 ,my own inve/igation ( ! gr\nd ?or\ghly conv9c$ me t !re are no pre-,cambrian rocks at ,/4 ,david's2 t ! ,arvonian & ,dimetian s]ies are m]ely intrusive rocks 7qu>tz-porphyry1 granite1 etc47 :i* h invad$ ! volcanic s]ies2 & t ! ,pebidian1 in/ead ( be+ a pre-,cambrian =mation on :i* ! ,cambrian base re/s uncon=mably1 is a gr\p ( volcanic rocks into :i* ! ,cambrian /rata pass d[n con=mably1 & :i* 9 ! ,/4 ,david's di/rict con/itutes ! l[e/ gr\p ( ! ,cambrian sy/em4#he ,footnote #he3 ,= ,dr4 ,hicks' views1 see especially 8 pap]s 9 ! ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxxi4 xxxiii4 xxxiv4 xl4 ,my criticism ( !m w be f\nd 9 op4 cit4 vol4 xxxix4 7#ahhc71 subsequ5tly 9 ! ma9 confirm$ by ,pr(4 ,lloyd ,morgan1 op4 cit4 xlvi4 p4 #bda4 ,see also ,pr(4 ,blake1 op4 cit4 xl4 7#ahhd74 ,dr4 ,hicks 9 8 m rec5t pap]s has m]ely reit]at$ 8 previ\sly publi%$ op9ions4 ,illu/ration3 ,walk] ,b\tall sc4 ,fig4 #dj4--,map ( ! volcanic di/rict ( ,/4 ,david's4 ,! volcanic geology ( ,/4 ,david's possesses a special int]e/ inasmu* z x embraces a tol]ably full developm5t ( v>i\s features :i* *>act]ize ! volcanic gr\ps ( lat] ,palozoic sy/ems4 ,?\gh ! rocks are *iefly tuffs1 !y include also %eets ( lava1 z well z sills1 dykes & bosses4 ,!y %[ a rem>kable range 9 *emical composition f q basic to highly acid mat]ials4 ,!y pres5t ! ample/ pro(s ( hav+ be5 erupt$ & spread out ov] ! sea-bottom1 & !y likewise af=d cle> evid5ce ( alt]nation ) ! ord9>y non-volcanic s$im5t ( ! "t to :i* !y belong4 ,9 ^! respects !y are p>ticul>ly notewor?y1 = !y prove t 9 ! e>lie/ ,palozoic ages ! ess5tial features ( volcanic action 7 already z well develop$ z 9 any subsequ5t epo* ( geological hi/ory4 ,! volcanic gr\p ( ,/4 ,david's atta9s a visible ?ickness ( ab\t #ahjj feet4 ,its upp] "p graduates upw>d into purple & gre5 ,l[] ,cambrian s&/ones4 ,! base ( ! gr\p is n se5 ow+ to ! plicat$ /ructure ( ! di/rict4 ,h5ce ! total ?ickness ( volcanic mat]ial _c be det]m9$1 nei!r c we tell on :at x re/s1 :e!r on a /ill l[] s$im5t>y s]ies or on "s plat=m ( pre-,cambrian rocks4 ,! /ructure ( ! gr\p1 not)/&+ all t has be5 writt5 ab\t x1 has nev] yet be5 adequately work$ out4 ,! un=tunate & b>r5 controv]sy ab\t suppos$ pre-,cambrian rocks at ,/4 ,david's has t5d$ to obscure ! real importance ( ^! rocks z ! olde/ well-pres]v$ record ( volcanic action 9 ,brita94 ,!y des]ve to be c>efully survey$ on maps ( a l>ge scale1 9 ! same detail$ mann] z has be5 s successfully appli$ to ! elucidation ( y\ng] volcanic tracts4 ,until su* detail$ inve/igation is made1 any acc\nt ( !m :i* is giv5 c be little m ?an a g5]al outl9e ( ! subject4 ,! foll[+ description is ! result ( my exam9ation ( ! gr\nd 9 company ) my colleague ,mr4 ,b4 ,n4 ,pea*1 & aft]w>ds ) ! late ,mr4 ,w4 ,topley4#hf ,a few additional obs]vations1 f ! subsequ5t exploration ( ,pr(essor ,lloyd ,morgan1#hg are incorporat$ 9 ! n>rative4 ,footnote #hf3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxix4 7#ahhc71 p4 #bid et seq4 ,:ile ! ess5tial p>ts ( ! inve/igation are giv5 9 ! foll[+ pages1 ,i w\ld ref] ! read] to ?is pap] = details n transf]r$ to ! pres5t volume4 ,footnote #hg3 ,op4 cit4 vol4 xlvi4 7#ahij71 p4 #bda4 ,! geologi/ :o traces ^! ,/4 ,david's rocks 9 ! field _c fail to be /ruck ) _! g5]al resemblance to volcanic masses ( lat] ,palozoic date4 ,_m ( ! lavas & tuffs are 9 outw>d *>act]s q indi/+ui%able f ^? ( ! ,l[] ,old ,r$ ,s&/one & ,c>bonif]\s sy/ems ( ,brita94 ,s _m po9ts ( detail may be obs]v$ to be common to ! ,palozoic eruptive rocks all ov] ! c\ntry f ! ,cambrian to ! ,p]mian p]iods z to indicate t volcanic ph5om5a mu/ h recurr$ "u mu* ! same conditions ?r\gh\t ,palozoic "t4 ,by f> ! l>g] "p ( ! ,cambrian volcanic gr\p ( ,/4 ,david's consi/s ( b$d$ tuffs1 ?\gh a few lavas are int]/ratifi$ 9 x1 p>ticul>ly t[>ds ! top4 ,! :ole has subsequ5tly be5 invad$ by acid protrusions1 & la/ly by basic dykes4 #a4 ,b$d$ ,tuffs & ,lavas4--,! tuffs1 :i* are ! pr$om9ant memb]s ( ! volcanic gr\p1 pres5t _m v>ieties ( col\r1 f d>k purple1 ?r\gh t9ts ( brick-r$ & lilac1 to pale p9k1 yell[ & creamy :ite1 b n unfrequ5tly assume v>i\s %ades ( dull gre54 ,!y v>y likewise 9 texture f some:at co>se breccias or agglom]ates1 ?r\gh _m gradations1 into f9e silky s*i/s 9 :i* ! tufface\s "* is almo/ lo/4 ,g5]ally !y are di/9ctly granul>1 pres5t+ to ! nak$ eye abundant angul> & subangul> lapilli1 among :i* brok5 cry/als ( a :ite1 some:at kaol9iz$1 felsp> & fragm5ts ( f9e-gra9$ felsite are (t5 conspicu\s4 ,! great] "p ( ! tuffs1 p>ticul>ly ! purple1 r$ & d>k-gre5 v>ieties1 :i* con/itute s l>ge a proportion ( ! :ole1 has be5 d]iv$ f ! explosion ( basic rocks simil> 9 "* to ! diabases n[ f\nd associat$ ) !m4 ,on ! o!r h&1 ! pal] v>ieties1 bo? 9 ! =m ( f9e tuffs & ( breccias1 h probably result$ ma9ly f ! de/ruction ( m silice\s lavas1 probably felsites 7rhyolites7 or o!r acid rocks4 ,t _m ( ! tuffs are due to ! de/ruction ( diabase-lavas may be surmis$ f _! close g5]al ext]nal resemblance to ^! rocks1 & f ! way 9 :i* !y are associat$ ) ! contemporane\s %eets ( diabase4 ,"s ( ! dull d>k-purple tuffs might almo/ at fir/ sight be mi/ak5 = truly eruptive rocks4 ,! analyses ( two typical examples ( ^! basic tuffs 7,nos4 ,i4 & ,,ii471 & "o 7,no4 ,,iii47 ( an int]m$iate v>iety conta9+ an admixture ( acid fragm5ts1 are giv5 9 ! subjo9$ table4 ---------------------------------------- ------------- ,i4 ,,ii4 ,,iii4 ---------------------------------------- ------------- ,si,o#b #eabe #dhaa #faed ,al#b,o#c #bjda #accj #afcj ,fe#b,o#c #cjb #cgj #ddj ,fe,o #cia #haj #cff ,mn,o #jba #adc #jcb ,ca,o #dec #hdh #cjh ,mg,o #gbb #iea #bii ,k#b,o #bic #aeg #afb ,na#b,o #ahb #aif #bha ,h#b,o & ,loss on ,ignition4 #ejb #dba #bii ,total4 #ajjcb #ajjcg #iiga ,specific ,gravity4 #bhd #bib 444 ---------------------------------------- ------------- ,i4 ,purpli%-r$ %aly tuff f bel[ oliv9e-diabase1 ,crag ,rhosson4 ,analysis by ,mr4 ,j4 ,s4 ,grant ,wilson4 ,,ii4 ,dull purple & gre5 tuff f ! l[e/ gr\p ( tuffs betwe5 ,p5-ma5-melyn & ,p5-y-foel4 ,analysis by ,mr4 ,wilson4 ,,iii4 ,gre5i% %aly f9ely granul> tuff1 f road-side1 nor? ( ,bo>d ,s*ools1 ,/4 ,david's4 ,analysis by ,pr(4 ,a4 ,r5>d ( ,gh5t4 ,al?\gh ! majority ( ! tuffs are m or less basic1 !y frequ5tly conta9 evid5ce 9 ! =m ( small felsitic lapilli t acid lavas 7 pres5t 9 ! eruptive v5ts1 :ile ! pale tuffs %[ t at ! "t ( _! dis*>ge x 0 ^! acid lavas & n ! diabases t 7 bl[n out by ! explosions4 ,app5d$ are ?ree analyses ( ! acid tuffs 7,nos4 ,,iv4 ,v4 & ,,vi474 ---------------------------------------- ------------- ,,iv4 ,v4 ,,vi4 ---------------------------------------- ------------- ,si,o#b #hjei #gcdb #gbfc ,al#b,o#c #aabi #abji #afbc ,fe#b,o#c #jbh #jia #bgj ,fe,o #ada #cac #jdh ,mn,o trace #jbe 444 ,ca,o #jeb #bid #jah ,mg,o #jie #aab #acf ,k#b,o #bih #afg #cce ,na#b,o #jgb #chh #jae ,h#b,o & ,loss on ,ignition #aif #abh #cjj ,total4 #ajjgj #ajjfi #ajjab ,specific ,gravity4 #bee #bgd 444 ---------------------------------------- ------------- ,,iv4 ,gre5i% felsitic breccia1 ,clegyr ,hill2 angul> fragm5ts ( v>i\s felsites 9 a gre5i% base4 ,analysis by ,mr4 ,j4 ,s4 ,grant ,wilson4 ,v4 ,grey granul> felsitic tuff1 ,bridge ov] ,allan ,riv] nor? f ,/4 ,david's ,bo>d ,s*ools4 ,analysis by ,mr4 ,wilson4 ,,vi4 ,pale p9ki%-:ite1 f9ely s*i/ose tuff--a *>act]i/ic sample ( ! ,por?-lisky s*i/s4 ,analysis by ,pr(4 ,r5>d4 ,_m v>ieties ( texture c be trac$ among ! tuffs1 f co>se breccias or agglom]ates1 ) blocks a y>d or m 9 l5g?1 to f9e s*i/ose mud/ones or s]icitic s*i/s4 ,"o ( ! mo/ rem>kable ( ! f9] k9ds1 f\nd ne> ,p5-y-foel1 is ext]nally dirty-gre51 compact & tol]ably homog5e\s1 b ) di/9ct evid5ce ( its cla/ic "*4 ,"u ! microscope x is f\nd to be compos$ ma9ly ( lapilli ( a peculi> rock1 :i* is *>act]iz$ by ! abundance & fre%ness ( its plagioclase 7an unusual feature 9 ! volcanic gr\p ( ,/4 ,david's72 by ! l>ge1 well-def9$ cry/als 7"o ( :i* measur$ #jjbb in* by #jjabe in*7 ( augite2 by l>ge cry/als replac$ by gre5 decomposition-products1 b hav+ ! ext]nal =m ( oliv9e2 by ! abs5ce or scant9ess ( any base or gr\ndmass2 &1 9 _m ( ! lapilli1 by ! abundance ( sph]ical cells1 ei!r empty or fill$ up z amygdales ) decomposition-products4 ,^! sph]ical vap\r-vesicles1 s *>act]i/ic ( ! basic or palagonitic lapilli 9 _m ,palozoic volcanic v5ts1 7 f\nd 9 "o fragm5t1 :]e !y 7 p>ticul>ly abundant1 to range f a m9imum ( #jjjjh in* to a maximum ( #jjjcc in*1 ) a mean ( ab\t #jjjah4 ,! rock f :i* ^! lapilli h be5 d]iv$ comes ne>e/ to "o ( ! diabases f ! same "p ( ! di/rict 7:i* w aft]w>ds be ref]r$ to71 b %[s a clos] approa* to basalt rocks4 ,ano!r int]e/+ tuff is t ( :i* ! analysis 7,no4 ,,ii47 has be5 giv54 ,x occurs n f> f ! horizon ( ! rock j describ$4 ,"u a l[ p[]1 x is se5 to be compos$ ma9ly ( fragm5ts ( diabase l ! rocks ( ,rhosson & ,clegyr ,foig4 ,^! fragm5ts are subangul>1 or irregul> 9 %ape1 & v>y consid]ably 9 size4 ,!y are sometimes f9ely cellul>--! cavities1 z 9 ! case j ref]r$ to1 be+ sph]ical4 ,! plagioclase cry/als 9 ! diabase-lapilli are ev]y:]e conspicu\s2 s also is ! augite1 :i* occurs 9 l>g] =ms ?an 9 ! rock ( ,rhosson or ,clegyr ,foig4 ,next 9 abundance to ^! basic fragm5ts are r\nd$ or subangul> pieces ( felsite4 ,^! wea!r out 9 conspicu\s grey r\gh projections on ! expos$ face ( ! rock2 "u ! microscope !y are se5 to consi/ ( f9e granul> felsite1 :i* %[s a gr\ndmass rema9+ d>k betwe5 cross$ nicols1 b ) lum9\s po9ts & filam5ts1 & an occasional sph]ulite giv+ ! usual cross 9 pol>iz$ light4 ,lapilli ( an old] tuff may "h & !re be detect$4 ,a few angul> & subangul> gra9s ( qu>tz are scatt]$ ?r\gh ! rock4 ,! lapilli are b\nd toge!r by a f9ely-granul> dirty-gre5 sub/ance4 ,z a typical illu/ration ( ! m9ute /ructure ( ! felsitic tuffs1 ,i may ref] to ! rock ,no4 ,v4 ( ! =ego+ analyses4 ,x is compos$ ma9ly ( fragm5ts ( v>i\s felsites1 _m ( :i* %[ good fl[-/ructure4 ,l>ge1 & usually brok51 cry/als ( or?oclase are disp]s$ among ! o!r +r$i5ts4 ,"h & !re a fragm5t ( diabase may be detect$2 b ,i c\ld f9d no trace ( pieces ( ! peculi> microcry/all9e sph]ulitic qu>tz-porphyries ( ,/4 ,david's4 ,!re is b little t c\ld be call$ matrix cem5t+ ! lapilli toge!r4 ,! pres5ce ( fragm5ts ( diabase may possibly r$uce ! proportion ( silica & increase t ( magnesia1 z comp>$ ) :at w\ld o!rwise h be5 pres5t 9 ! rock4 ,"s ( ! tuffs appe> to h be5 a k9d ( volcanic mud4 ,a specim5 ( ?is nature collect$ f ! road-side section1 nor? ( ! ,bo>d ,s*ool1 pres5ts a f9ely-granul> pa/e enclos+ abundant angul> & subangul> lapilli ( diabase1 a small] proportion ( felsite 7sometimes display+ p]fect fl[-/ructure71 brok5 plagioclase cry/als1 & a gre5i% micace\s m9]al :i* has be5 subsequ5tly develop$ out ( ! matrix betwe5 ! lapilli4 ,?\gh !y lie 9 ! s$im5t>y s]ies above ! ma9 volcanic gr\p1 ,i may ref] "h to c]ta9 ?9 b&s ( tuff at ,ca/ell1 on acc\nt ( _! int]e/ 9 relation to ! true ,cambrian age ( ! volcanic gr\p4 ,!y are n q s fre% z ! tuff t occurs 9 ?ick] masses1 b _! volcanic orig9 is readily obs]vable4 ,"o b& appe>s to be made up ( ! debris ( "s basic rock1 l ! diabase ( ! di/rict1 ?r\gh :i* deta*$ plagioclase cry/als are scatt]$4 ,! lapilli are subangul>2 & ar\nd _! bord] a granul> deposit ( hmatite has tak5 place1 giv+ a r$ col\r to ! rock4 ,ano!r b& pres5ts small angul> lapilli1 almo/ entirely compos$ ( a sub/ance :i* to ! nak$ eye1 or ) a l5s1 is dull1 :ite & clay-l1 easily scrat*$1 & slightly unctu\s to ! t\*4 ,"u ! microscope1 ) a l[ p[]1 x becomes pale greyi%-gre5 & transp>5t1 & is se5 to consi/ 9 l>ge "p ( alt]$ felsp> cry/als1 p>tially kaol9iz$ & p>tially *ang$ into :ite mica & calcite4 ,^! scatt]$ cry/als are true volcanic lapilli1 & h n be5 d]iv$ f ! me*anical wa/e ( any pre-exi/+ volcanic rock4 ,9 ! tuffs int]/ratifi$ ) ! conglom]ate1 at ! qu>ry above ,por?-clais1 ?\gh mu* decompos$1 cry/als ( plagioclase c likewise /ill be trac$4 ,^! /rata are also true tuffs1 & n m]e detritus due to me*anical degradation 7see ,fig4 #da74 ,! g5]al result ( ! /udy ( ! microscopic /ructure ( ! ,cambrian tuffs ( ,/4 ,david's may be briefly summ$ up z foll[s3-- #a4 ,^! pyrocla/ic deposits are almo/ :olly compos$ ( fragm5ts ( eruptive rocks1 sometimes r\nd$1 b usually angul> or subangul>4 ,9 ! m granul> v>ieties v little matrix is pres5t2 x consi/s ( f9e debris ( ! same mat]ials4 ,no deta*$ microlites h be5 not$1 su* z are common among mod]n volcanic a%es2 b !re are abundant eject$ cry/als4 ,9 ^! respects ! ,cambrian tuffs resemble ^? ( ! o!r ,palozoic sy/ems4 ,a m+l+ ( gra9s ( qu>tz-s& may indicate ! int]mixture ( ord9>y ) volcanic s$im5t4 #b4 ,!y may be divid$ into two gr\ps--"o compos$ ma9ly ( fragm5ts ( diabase or o!r simil> basic rocks1 ! o!r ( felsite4 ,! =m] gr\p has d\btless be5 d]iv$ f ! explosion ( su* rocks z ! diabase-%eets ( ! di/rict4 ,! felsitic tuffs h n be5 obs]v$ to conta9 any fragm5ts ( ! microcry/all9e qu>tz-porphyries ( ,/4 ,david's4 ,!y h be5 d]iv$ f true f9e-gra9$ felsites or rhyolites4 ,!re are v>i\s int]m$iate v>ieties ( tuff1 due to ! m+l+ 9 v>i\s proportions ( ! two k9ds ( debris4 #c4 ,!y are m>k$ by ! pres5ce ( "s *>act]i/ic features ( ! volcanic v5ts ( lat] ,palozoic "t1 & 9 p>ticul> by pres5t+ ! foll[+ peculi>ities3 7a7 lapilli ( a m9utely-cellul> pumice ) sph]ical cells2 7b7 lapilli ) well-develop$ fl[-/ructure2 7c7 lapilli consi/+ ( a pale gre5 s]p5t9\s sub/ance resembl+ alt]$ palagonite & probably orig9ally glass2 7d7 lapilli d]iv$ f ! de/ruction ( old] tuffs2 & 7e7 lapilli consi/+ ( eject$ cry/als1 especially ( felsp>s1 sometimes entire1 (t5 brok54 #d4 ,!y frequ5tly %[ t !y h und]gone metamorphism1 by ! developm5t ( a pale gre5i% micace\s m9]al betwe5 ! lapilli1 ! *ange advanc+ until ! f9e tuffs occasionally pass into f9e silky s*i/s4 ,9 my /udy ( ! ,/4 ,david's di/rict1 ,i 0 unable to obs]ve any evid5ce t ! basic & silice\s tuffs *>act]ize two di/9ct p]iods ( volcanicity4 ,f ! =ego+ analyses x appe>s t "s ( ! olde/ visible tuffs :i* are se5 betwe5 ,p5-ma5-melyn & ,p5-y-foel conta9 only #dhaa p] c5t ( silica2 :ile a specim5 f ,por?-lisky yield$ #gbfc p] c5t ( t +r$i5t4 ,specim5s tak5 ev5 f adjac5t b$s %[ great diff]5ces 9 ! p]c5tage ( silica1 z may be se5 9 ! analyses ,nos4 ,,iii4 & ,v4 ,?is alt]nation ( basic & silice\s fragm5tal mat]ials has its p>allel 9 ! neighb\r+ eruptive rocks1 "s ( :i* are oliv9e-diabases conta9+ only #de p] c5t ( silica1 :ile o!rs are highly silice\s qu>tz-porphyries4 ,b all ! silice\s eruptive rocks1 s f> z ,i h be5 able to discov]1 are intrusive1 & belong1 ,i believe1 to a lat] p]iod ?an t ( ! volcanic gr\p2 9 no s+le in/ance d !y appe> to me to be true sup]ficial lava-fl[s4 ,on ! o!r h&1 ! basic eruptive rocks occur bo? z contemporane\s %eets & z intrusive masses4 ,! pres5ce ( bo? silice\s & basic lavas 9 ! ,cambrian volcanic res]voirs1 h[ev]1 is prov$ by ! "* ( ! tuffs4 ,x w\ld appe> f ! evid5ce at pres5t kn[n1 t :ile ! basic lavas 7 mo/ abundant 9 ! v5ts dur+ ! volcanic p]iod record$ by ! rocks ( ,/4 ,david's1 furni%+ ! mat]ial = mo/ ( ! fragm5tal eruptions1 & issu+ 9 occasional sup]ficial /reams ( molt5 rock1 ! silice\s lavas did n fl[ =? at ! surface1 ?\gh _! debris 0 copi\sly dis*>g$ 9 ! =m ( du/ & lapilli4 ,! rise ( bo? basic & acid lavas at diff]5t p]iods 9 ! same or adjo9+ v5ts1 s famili> 9 rec5t volcanic ph5om5a1 ?us appe>s to h also *>act]iz$ "s ( ! olde/ examples ( volcanic action4 ,an int]e/+ p>allel may be trac$ betwe5 ! succession ( ev5ts at ,/4 ,david's & t :i* occurr$ 9 ! volcanic gr\p ( ! ,l[] ,old ,r$ ,s&/one ( ! ,p5tl& ,hills1 ne> ,ed9burgh1 ( :i* a detail$ acc\nt w be giv5 9 ,*apt] xx4 ( ?is volume4 ,x is also wor?y ( rem>k t 9 ! late/ ( ! volcanic episodes 9 ,briti% geology a rem>kable simil>ity to ! ,/4 ,david's volcanic gr\p may be obs]v$4 ,"s ( ! old] ,t]ti>y agglom]ates are full ( pieces ( acid rocks 7felsites1 rhyolites or granophyres71 :ile ! lavas p\r$ out at ! surface 7 ma9ly basalts4 ,9 ! volcanic gr\p ( ,/4 ,david's ! tuffs conta9 evid5ce t ord9>y s$im5tation 0 n entirely int]rupt$ by ! volcanic dis*>ges4 ,?us1 9 ! ,allan valley1 we/ f ! ,ca!dral1 "o ( ! s*i/ose tuffs is full ( well-r\nd$ pebbles ( :ite qu>tz4 ,occasional %aly b&s indicate ! deposit ( mud ) ! tuffs4 ,exclud+ ! granites & porphyries 7:i* are describ$ at p4 #aee71 two k9ds ( eruptive rocks are associat$ ) ! volcanic gr\p4 ,"o ( ^! is c]ta9ly intrusive & ( late date1 viz4 dykes & ve9s ( diabase1 to be aft]w>ds ref]r$ to4 ,! o!r k9d occurs 9 long p>allel %eets1 "s ( :i*1 if n all1 are true contemporane\s lava-/reams1 erupt$ at int]vals dur+ ! accumulation ( ! volcanic gr\p4 ,!y =m prom95t crags to ! we/ ( ,/4 ,david's1 su* z ,clegyr ,foig1 ,rhosson1 & ! rocky gr\nd ris+ f ! ea/]n %ores ( ,ramsey ,s\nd4 ,_! dip & /rike co9cide ) ^? ( ! tuffs above & bel[ !m4 ,x is possible t "s ( ^! %eets may be intrusive sills int]calat$ along ! b$d+ ( ! tuffs2 & 9 "o or two cases ,i h obs]v$ indications ( :at1 on fur!r & m c>eful exploration1 may prove to be disruption across ! b$d+4 ,b x is ! int]b$d$ %eets t possess ! *ief int]e/ z sup]ficial lava-/reams ( su* v5]able antiquity4 ,!y pres5t _m ( ! ord9>y features ( true lava-fl[s4 ,9 p>ticul> a slaggy /ructure may be detect$ at ! bottom ( a %eet1 ! vesicles be+ "h & !re l5g!n$ 9 ! direction ( fl[4 ,"s ( ! %eets are 9 "p amygdaloidal4 ,! alt]nation ( ^! %eets ) tuffs1 evid5tly d]iv$ f lavas ( simil> "*1 is ano!r argum5t 9 fav\r ( _! contemporane\s date4 ,"o ( ! be/ localities = /udy+ ^! features lies betwe5 ,clegyr ,foig & ! coa/1 we/ ( ,rhosson4 ,! eruptive rocks ?ick5 t[>ds ! s\?-we/1 z if ! ma9 v5ts _h la9 9 t direction4 ,!re are d\btless intrusive z well z contemporane\sly int]b$d$ masses 9 ! r\gh gr\nd betwe5 ,p5-ma5-melyn & ,treg9nis4 ,to sep>ate ^! out w\ld be a mo/ int]e/+ & beautiful piece ( mapp+ = any compet5t geologi/ 9 possession ( a good map on a suffici5tly l>ge scale4 ,! int]b$d$ lavas1 s f> z ,i h _h an opportunity ( /udy+ !m1 appe> to pres5t rem>kable uni=mity ( petrographical *>act]s4 ,megascopically !y are dull1 f9e-gra9$ to compact1 sp>+ly porphyritic1 rang+ 9 col\r f an epidote-gre5 to dull blacki%-gre5 & d>k *ocolate-br[n4 ,"s ( !m are f9ely porphyritic f ! pres5ce ( small gli/5+ surfaces :i* pres5t ! col\r & metallic lu/re ( hmatite & yield its *>act]i/ic /reak4 ,obvi\sly basic rocks1 !y pres5t1 z ,i h said1 a close ext]nal resemblance to _m ( ! lavas ( ! ,l[] ,old ,r$ ,s&/one & ,c>bonif]\s di/ricts ( ,scotl&4 ,f _! *emical composition & microscopic /ructure !y may be mo/ appropriately rang$ among ! diabases4 ,! analyses ( two ( ! mo/ conspicu\s diabases ( ?is class 9 ! di/rict1 ^? ( ,rhosson 7,,vii47 & ,clegyr ,foig 7,,viii471 by ,mr4 ,j4 ,s4 ,grant ,wilson1 are %[n 9 ! foll[+ table3-- ---------------------------------------- ------ ,,vii4 ,,viii4 ---------------------------------------- ------ ,si,o#b #deib #dech ,al#b ,o#c #ahaf #affb ,fe#b ,o#c #aah #djf ,fe,o #ibg #hfc ,mn,o #jai #jad ,ca,o #gai #hai ,mg,o #ajjg #ida ,k#b,o #agh #jga ,na#b,o #bab #bbj ,h#b,o & ,loss on ,ignition4 #dbb #dcd ,insoluble ,residue4 #jjd #jjh ,total4 #ajjad #iigf ,specific ,gravity4 #bif #b4ii ---------------------------------------- ------ ,! two rocks "h analyz$1 likewise t f ! crag s\? ( ,ca/ell & t f ! cliffs at ! s\!rn end ( ! promontory betwe5 ,ramsey ,s\nd & ,p5-y-foel1 %[ "u ! microscope a g5]al simil>ity ( composition & /ructure4 ,!y pres5t a v>iable quantity ( a base1 :i* "u a objective is resolv$ into ill-def9$ coalesc5t globulites & fibre-l bodies1 t rema9 d>k :5 rotat$ betwe5 cross$ nicols4 ,9 "s v>ieties1 z 9 "p ( ,rhosson ,crag1 ! base is ne>ly lo/ 9 ! cr[d ( cry/all9e con/itu5ts2 9 o!rs1 z 9 ! crag s\? ( ,ca/ell1 x =ms a l>ge "p ( ! :ole mass1 & may be se5 9 di/9ct spaces free f any cry/all9e p>ticles4 ,?r\gh ?is base are diffus$1 9 va/ numb]s1 irregul>ly-%ap$ gra9s ( augite1 seldom %[+ idiomorphic =ms4 ,^! gra9s1 or granules1 may p]haps av]age ab\t #jjjc in* 9 diamet]4 ,plagioclase is g5]ally h>dly to be recogniz$1 ?\gh "h & !re a cry/al ) *>act]i/ic tw9n+ may be detect$ 9 ! base4 ,magnetite occurs abundantly--its m9ute octah$ra1 ) _! peculi> col\r & lu/re1 be+ app>5t ) reflect$ light on ! fre%] specim5s1 ?\gh apt to be lo/ z diffus$ f]rug9\s blot*es 9 ! m decompos$ v>ieties4 ,b p]haps ! mo/ rem>kable +r$i5t is oliv9e4 ,r$ hmatitic cry/als are visible1 ev5 to ! nak$ eye1 disp]s$ ?r\gh ! gr\ndmass ( ! rocks4 ,) a l5s ^! may be obs]v$ to be or?orhombic 9 =m1 & to be evid5tly pseudomorphs aft] "s m9]al :i* has be5 conv]t$ *iefly into hmatite4 ,su* r$ pseudomorphs are common 9 ,c>bonif]\s & ,old ,r$ ,s&/one lavas1 :]e 9 "s cases !y appe> to be aft] hornbl5de1 & 9 o!rs aft] augite1 b occasionally are sugge/ive ( oliv9e1 ?\gh ) no trace ( ! orig9al sub/ance ( t m9]al4 ,9 ! lava associat$ ) ! tuffs at ! s\? end ( ! promontory betwe5 ,ramsey ,s\nd & ,p5-y-foel1 h[ev]1 c]ta9 l>ge1 well-develop$ pseudomorphs are und\bt$ly aft] oliv9e4 ,!y h ! *>act]i/ic cont\r ( t m9]al & its peculi> transv]se curv$ & irregul> fractures4 ,! av]age l5g? ( ^! pseudomorphs 0 f\nd1 f ! measurem5t ( six examples1 to be #jjbc in*1 ! l>ge/ be+ #jjcd1 & ! smalle/ #jjad4 ,se5 by transmitt$ light !y pres5t a /ructureless pale-gre5 mat]ial ne>ly in]t 9 pol>iz$ light1 r\nd ! bord]s & across fissures 9 :i* an opaque sub/ance has be5 develop$1 z s]p5t9e & magnetite h be5 gr\p$ 9 ! famili> alt]ation ( oliv9e4 ,! opaque mat]ial is bright brick-r$ 9 reflect$ light1 & is evid5tly n[ *iefly oxidiz$ into hmatite4 ,e /age may be trac$1 f or?orhombic =ms ) ! incipi5t developm5t ( transv]se fissures fill$ ) iron-oxide1 to o!rs ( di/ort$ %apes 9 :i* ! f]rug9\s matt] occupies ! :ole1 or ne>ly ! :ole1 ( ! m\ld ( ! orig9al cry/al4 ,! rocks n[ describ$ diff] f ! ,palozoic &esites or porphyrites1 ) :i* ,i am acqua9t$1 9 _! m basic composition1 9 ! less abundance ( _! microscopic base1 9 ! comp>atively inconspicu\s developm5t ( _! felsp>s ( lat] consolidation1 9 ! abs5ce ( l>ge porphyritic felsp>s ( e>li] consolidation1 9 ! extraord9>y prom95ce ( ! granul> augite1 & 9 ! pres5ce ( oliv9e4 ,9 composition & /ructure !y are ess5tially =ms ( oliv9e-diabase4 ,illu/ration3 ,fig4 #da4--,section %[+ ! int]/ratification ( tuff & conglom]ate above ,l[] ,mill1 ,/4 ,david's4 ,above ! volcanic gr\p ( ,/4 ,david's lies a b& ( qu>tz-conglom]ate :i* has be5 tak5 by ,dr4 ,hicks to m>k ! base ( ! ,cambrian sy/em4 ,?is rock1 ?\gh ma9ly compos$ ( qu>tz & qu>tzite1 conta9s fragm5ts ( ! und]ly+ volcanic rocks4 ,b t x does n m>k any decid$ break 9 ! s$im5tation1 mu* less ! viol5t uncon=mability & va/ int]val ( "t :i* x has be5 errone\sly suppos$ to d1 is well illu/rat$ by ! occurr5ce ( b&s ( tuff1 z well z diffus$ volcanic du/1 9 ! conglom]ate & also 9 ! gre5 & r$ %ales & s&/ones :i* con=mably ov]lie x4 ,an example ( ?is int]calation ( volcanic mat]ial is repres5t$ 9 ,fig4 #da4 ,on ! left side v]tical lay]s ( f9e r$di% tuff 7a7 are succe$$ by a b& ( qu>tz conglom]ate 7b7 ( ! usual "*4 ,p>allel to ?is conglom]ate comes a b&1 ab\t six in*es ?ick1 ( f9e tuff 7c71 foll[$ by a%y s&/one 7d71 :i* graduates into conglom]ate 7e74 ,no m complete evid5ce c\ld be desir$ ( ! p]fect inosculation ( ! conglom]ate ) ! volcanic gr\p4 ,on ! coa/ at ,nun's ,*apel simil> evid5ce pres5ts itself4 ,! conglom]ate !re conta9s "s ?9 seams ( tuff1 & is int]calat$ betwe5 a s]ies ( dull gre5 agglom]ates & tuffs & "s gre5i% %ales & s&/ones ) lay]s ( tuff4 ,n less /rik+ is ! evid5ce ( ! contemporane\s eruption ( f9e volcanic du/ 9 ! ov]ly+ %ales & s&/ones4#hh ,"s ( ! r$ %ales are full ( ?is mat]ial1 :i* "h & !re is ga!r$ into ! ?9 seams or ribs ( :i* ! microscopic *>act]s h already be5 describ$4 ,?is diffus$ volcanic detritus m>ks1 no d\bt1 ! enfeebl$ dis*>ges ( f9e du/ t[>ds ! close ( ! volcanic episode 9 ! ,l[] ,cambrian p]iod at ,/4 ,david's4 ,x w\ld be difficult to f9d an in/ance ( a m p]fect transition f a s]ies ( ?or\ghly volcanic masses into a s]ies ( ord9>y me*anical s$im5ts4 ,footnote #hh3 ,^! are a portion ( ,dr4 ,hicks' ,ca]fai gr\p 9 ! ,l[] ,cambrian s]ies4 ,!y h yield$ ,l[] ,cambrian fossils4 #b4 ,intrusive ,granite & ,qu>tz-,porphyry4--,! he>t ( ! volcanic gr\p is pi]c$ by a mass ( granite :i* also cuts ! conglom]ate & ov]ly+ %ales & s&/ones on ! ea/ side4 ,! age ( ?is intrusive boss _c be m def9itely fix$ ?an by say+ t x mu/ be lat] ?an ! volcanic gr\p4 ,?is rock has be5 ! subject ( a rem>kable am\nt ( description1 & has be5 dignifi$ by be+ actually elevat$ into a di/9ct ,ar*an =mation compos$ ( highly cry/all9e gneissic rocks1 ) b&s ( lime/one1 hornbl5de1 *lorite1 & micace\s s*i/s4#hi ,into ?is some:at dre>y *apt] ( ,engli% geological lit]ature x is =tunately n necess>y to ent] "h4 ,i w only say t ! rock is unque/ionably a granite1 ) no ess5tial diff]5ces f _m o!r bosses reg>d+ :i* !re has be5 no controv]sy4 ,x is a holocry/all9e rock ) a ?or\ghly granitic texture1 & compos$ ( ! ord9>y m9]als ( granite--qu>tz1 or?oclase & plagioclase1 among :i* a gre5 *loritic m9]al1 m or less pl5tiful1 probably repres5ts orig9al hornbl5de1 biotite or augite4 ,sometimes ! qu>tz & felsp> 9 ! body ( ! rock %[ a micropegmatitic arrangem5t1 & ! same /ructure occurs 9 ve9s t trav]se x4 ,?is /ructure gives ! rock "s resemblance to ! ,t]ti>y granites & granophyres ( ,irel& & ,scotl&4 ,footnote #hi3 ,see ! pap]s cit$ on p4 #ade & my discussion ( ! relations ( ?is granite 9 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxix42 also ,pr(4 ,lloyd ,morgan1 op4 cit4 vol4 xlvi4 7#ahij74 ,?is granite has und]gone a good deal ( decomposition1 = its felsp>s are turbid1 & its orig9al f]ro-magnesian con/itu5ts are always replac$ by gre5 *loritic aggregates1 :ile epidote is also pres5t4 ,! rock t5ds to become f9] 9 gra9 t[>ds ! m>g91 & !n sometimes assumes a m decid$ly pegmatitic /ructure1 l graphic granite4 ,at ! nor!rn end ( ! granite ridge1 a gradation c be trac$ f ! ord9>y texture ?r\gh increas+ly f9e-gra9$ v>ieties until we pass into a microcry/all9e sph]ulitic porphyry4 ,aft] a c>eful exam9ation ( ! gr\nd ,i satisfi$ myself t ! sph]ulitic qu>tz-porphyries1 :i* =m a conspicu\s feature 9 ! geology ( ,/4 ,david's1 are really (f%oots f ?is granitic core4#ij ,footnote #ij3 ,^! apophyses f ! granite con/itute ! ,arvonian =mation ( ,dr4 ,hicks' pre-,cambrian s]ies ( ,/4 ,david's4 ,^! sph]ulitic rocks h be5 fully describ$4#ia ,!y consi/ ( a base compos$ ( a microcry/all9e aggregate ( qu>tz & or?oclase1 :i* is di/ribut$ betwe5 ! sph]ulites4 ,^! h be5 develop$ 9 rem>kable beauty & p]fection4 ,:ile ! microcry/all9e /ructure is ev]y:]e recognizable1 ! sph]ulites occasionally disappe>4 ,b _! abs5ce is m]ely local1 & !y may be f\nd bo? 9 l>ge dykes & n>r[ ve9s4 ,a fur!r porphyritic /ructure is giv5 to ! rocks by ! pres5ce 9 !m ( abundant qu>tz1 :i* takes ! =m ( conspicu\s r\nd$ blebs or worn cry/als sometimes di/9ctly dihexih$ral1 b ) some:at blunt$ angles4 ,porphyritic plagioclase is also common4 ,fl[-/ructure is occasionally traceable4 ,"s p>ts ( ^! rocks :]e ! porphyritic elem5ts are locally abs5t might be cursorily class$ z felsites2 b !y all possess a microcry/all9e & n a felsitic base4 ,!y _c be conf\nd$ ) ! true felsites ( :i* fragm5ts occur 9 ! tuffs4 ,footnote #ia3 ,see1 = example1 ,j4 ,davies1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxiv4 p4 #afd1 xxxv4 p4 #bjc2 also ! pap] already ref]r$ to1 op4 cit4 xxxix4 p4 #cae2 & ,mr4 ,teall's ,briti% ,petrography1 p4 #ccd4 ,9 addition to ! p>allelism t may be trac$ betwe5 ! e>lie/ ,palozoic agglom]ates & ^? ( ! y\nge/ volcanic s]ies ( ,brita91 a close analogy may also be notic$ betwe5 ! acid intrusive rocks ( ! two widely-sep>at$ p]iods4 ,9 bo? cases we h a granitic core s5d+ out apophyses :i* assume a sph]ulitic /ructure & trav]se e>li] volcanic products ( ! di/rict4 ,^! sph]ulitic qu>tz-porphyries ( ,/4 ,david's occur z bosses1 dykes 7elvans7 or ve9s1 cutt+ ?r\gh all horizons ( ! volcanic gr\p1 & 9 "o case app>5tly1 if n actually1 rea*+ ! qu>tz conglom]ate4 ,"o ( ! be/ exposures ( ?is intrusive "* may be se5 9 ! cliff bel[ ,nun's ,*apel1 :]e ! elvan runs along ! face ( ! cliff ?r\gh ! upp]mo/ zone ( ! volcanic gr\p1 cutt+ ! /rata some:at irregul>ly4 ,app>5tly 9 connection ) ?is dyke1 a network ( intrusions ( decompos$ qu>tz-porphyry may be obs]v$ 9 ! %ales along ! face ( ! cliff imm$iately bel[ ,nun's ,*apel4 ,on ! :ole1 ! intrud$ mat]ial has =c$ its way along ! b$d+-planes ( ! %ales1 b has also brok5 across !m1 s5d+ out f+]-l bran*es4 #c4 ,diabase ,dykes & ,sills4--,! late/ rocks ( ! ,/4 ,david's di/rict are dykes & intrusive %eets ( diabase1 :i* trav]se all ! o!r =mations4 ,! dykes are specially abundant 9 ! granite4 ,"o or two may be detect$ 9 almo/ e artificial op5+ :i* has be5 made 9 t rock2 :ile on ! coa/-section !y are "h & !re pr(usely abundant4 ,!y are likewise frequ5t 9 ! qu>tz-porphyries1 & occur also 9 ! volcanic gr\p z well z 9 ! s&/ones & %ales above ! conglom]ate1 b become few] 9 numb] z !y rec$e f ! granite c5tre4#ib ,footnote #ib3 ,! occurr5ce ( ^! dykes is p>allel$ by t ( ! simil> intrusions 9 ! qu>tz-felsite ( ,llyn ,pad>n to be aft]w>ds describ$4 ,9 ext]nal *>act]s1 ! rock compos+ ^! dykes & %eets may be describ$ z usually a dull dirty-gre5 or yell[i%-br[n mass1 to :i* ! old "n ( wacke might appropriately be giv54 ,x exhibits ! texture & mode ( wea!r+ ( ! m di/9ctly cry/all9e memb]s ( ! basalt family4 ,x is occasionally amygdaloidal or cellul>1 ! k]nels or cavities be+ arrang$ p>allel ) ! sides ( ! dyke4 ,"h & !re a rudely prismatic /ructure ext5ds betwe5 ! walls4 ,! microscopic /ructure ( ?is rock has be5 describ$ by ,pr(essor ,judd1 ,mr4 ,davies & ,mr4 ,tawney4 ,x is a diabase1 b m alli$ 9 /ructure to true basalt ?an ! oliv9e-diabase ( ! volcanic gr\p4 ,x especially diff]s f ! old] rock 9 ! abundance & fre%ness ( its felsp>s1 9 ! comp>ative sc>city ( its augite1 & 9 ! abs5ce ( oliv9e4 ,! magnesian silicates are v g5]ally replac$ by gre5 decomposition-products diffus$ ?r\gh ! mass4 ,an occasional cry/al ( hornbl5de1 recognizable by its cleavages & di*roism1 may be detect$4 ,"s ( ! diabase dykes pres5t excell5t examples ( fl[-/ructure4 ,a beautiful in/ance occurs 9 a dyke t cuts ! %ales1 9 a small cove to ! ea/ ( ,nun's ,*apel4 ,! %ale & eruptive rock are 9 contact2 & ! small acicul> prisms ( felsp>1 besides rang+ !mselves 9 l9e p>allel to ! side ( ! dyke1 /ream r\nd ! l>g] felsp> cry/als4 ,"s ( ! dykes or ve9s are only ?ree in*es broad4 ,!y s5d out f+]s1 & sometimes break abruptly across f "o l9e to ano!r4 ,!y appe> g5]ally to h foll[$ ! l9es ( jo9t 9 ! granite1 z ,mr4 ,tawney has obs]v$2#ic consequ5tly !y mu/ be po/]ior to ! developm5t ( ! sy/em ( jo9t+ 9 t rock4 ,footnote #ic3 ,proc4 ,nat4 ,hi/4 ,soc4 ,bri/ol1 vol4 ii4 "p ii4 7#ahgi71 p4 #aae4 ,besides ! abundant dykes1 !re has be5 a m limit$ extrusion ( ! same mat]ial 9 %eets p>allel 7or approximately s7 to ! b$d+ ( ! s&/ones & %ales4 ,^! %eets are well display$ at ,/4 ,john's ,po9t1 :]e evid5ce ( _! be+ intrusive1 & n truly b$d$1 may be se5 along ! f9e cliffs :i* h be5 cut by ! waves on ?is "p ( ! coa/-l9e4 ,! s$im5t>y s]ies :i* ov]lies ! volcanic gr\p ( ,/4 ,david's1 & conta9s ! fossils ( ! l[] "p ( ! ,cambrian sy/em1 gradually loses all trace ( volcanic mat]ial1 z its memb]s are foll[$ upw>d 9 /ratigraphical ord]4#id ,we ?us le>n t ! eruptions ( ?is di/rict came to an end 9 an e>ly "p ( ! ,cambrian p]iod4 ,b z we %all see 9 ! foll[+ pages1 volcanic activity 0 subsequ5tly r5ew$ at no great di/ance 9 ! next or ,silurian p]iod4 ,footnote #id3 ,dr4 ,hicks has not$ ! occurr5ce ( volcanic tuff 9 ! ,l[] ,l+ula ,flags ( ,por?-y-,rhaw1 a little to ! ea/ ( ,/4 ,david's 7,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xx4 #ahfd1 p4 #bdj74 ,?is int]calation is m>k$ z a dyke 9 ! ,,ms4 notes ( ,sir ,a4 ,c4 ,ramsay on a copy ( ! ,geological ,survey map ( ! di/rict4 ,,*apt] ,,xi ,,! ,,cambrian ,,volcanoes ,,( ,,nor? ,,wales1 ,,! ,,malv]n ,,hills ,,& ,,w>wick%ire ,,nor? ,,wales ,! ,cambrian volcanic rocks 9 ! nor!rn "p ( ! ,wel% ,pr9cipality h _! ma9 developm5t 9 ,ca]n>von%ire4 ,s\?w>ds f t tract1 ?\gh ! ,l[] ,cambrian /rata =m a va/ pile ( s$im5t>y mat]ial 9 ! ,h>le* anticl9e1 :i* is e/imat$ by ! ,geological ,survey to be f #fjjj to #gjjj feet ?ick1 !y h yield$ no trace ( any contemporane\s volcanic rocks4#ie ,! purple slates t rise along ! c5tre ( ! anticl9e dip bel[ ! grits & conglom]ates on ei!r side )\t disclos+ a glimpse ( ! base ( ! sy/em4 ,?is enorm\s accumulation ( s$im5t>y deposits seems to dim9i% 9 ?ickness z x is trac$ nor?w>ds1 = t[>ds ! ,m5ai ,/rait x does n rea* m ?an a f\r? "p ( ! dep? :i* x is said to display 9 ! ,h>le* anticl9e4#if ,9 ! ,pass ( ,llanb]is ! s]ies ( grits t ov]lies ! purple slates is e/imat$ to be ab\t #acjj feet ?ick4#ig ,?is gradual ?9n+ away ( ! ,cambrian s]ies t[>ds ! nor? 01 9 ! op9ion ( ,sir ,&rew ,ramsay1 accompani$ by an increas+ metamorphism ( ! l[] portions ( ! sy/em4 ,9 8 view1 ! long ridge ( qu>tz-porphyry :i* crosses ! l[] end ( ,llyn ,pad>n repres5ts ! result ( ! extreme alt]ation ( ! /ratifi$ rocks4 ,he believ$ t he c\ld trace an ins5sible passage f ! slates1 grits & conglom]ates into ! porphyry1 & he 0 l$ to ! conviction t ! solid porphyry itself is no?+ b ! result ( ! alt]ation ( ! /ratifi$ masses c>ri$ a /age fur!r ?an ! /age ( porcellanite1 into ! condition ( t k9d ( absolute fusion t 9 _m o!r regions seems to h result$ 9 ! =mation ( granites1 sy5ites & o!r rocks1 commonly call$ intrusive4#ih ,c]ta9 /ructural l9es 9 ! qu>tz-porphyry he look$ ^u z indicat+ traces ( /ratification 9 a rock1 ! orig9al felspa?ic & qu>tzose mat]ial ( :i* has be5 metamorphos$ into true porphyry4#ii ,9 con=mity ) ^! ideas1 ! rem>kable felspa?ic /rata :i* lie ne>e/ ! porphyry 7 reg>d$ z metamorphos$ ,cambrian rocks1 & :]e simil> rocks reappe> ov] a l>ge area ne> ,bangor !y 7 col\r$ on ! map ) ! same t9t & lett]+ z 7 us$ = ! s-call$ alt]$ ,cambrian ( ,anglesey4 ,footnote #ie3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 ,geology ( ,nor? ,wales1 p4 #ba4 ,x is possible t ?is ?ickness has be5 some:at ov]e/imat$4 ,dr4 ,hicks 7,geol4 ,mag4 #ahhj1 p4 #eai7 has ref]r$ to c]ta9 highly felsitic rocks1 = ! mo/ "p a metamorphic s]ies ( s*i/s1 alt]nat+ ) h>d] felsitic b&s1 probably orig9ally felsitic a%es1 ly+ at ! bottom ( ! :ole pile1 & he has claim$ !m z pre-,cambrian4 ,b ,i h n f\nd any evid5ce ( su* rocks1 nor any trace ( igne\s mat]ials save dykes & sills1 acid & basic1 su* z are indicat$ on ! ,survey map4 ,footnote #if3 ,ibid4 p4 #bd4 ,footnote #ig3 ,ibid4 p4 #agc4 ,footnote #ih3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #agc4 ,footnote #ii3 ,ibid4 p4 #agd4 ,no "o :o has exam9$ ?is ,ca]n>von%ire gr\nd c h fail$ to f9d ! sections :i* d\btless l$ my pr$ecessor to =m ! convictions to :i* he gave expression 9 ! passages ,i h j quot$4 ,x is easy to see h[ ^! sections1 :]e9 x is c]ta9ly difficult to draw a %>p l9e betwe5 ! igne\s rock & ! cla/ic mat]ials d]iv$ f x1 w\ld be welcom$ z appe>+ to (f] confirmation ( ! ideas conc]n+ metamorphism :i* 7 !n 9 vogue4 ,!re _c1 h[ev]1 be any d\bt t my fri5d 0 mi/ak5 9 8 int]pretation ( ! /ructure ( t "p ( ! c\ntry4 ,x is to me a subject ( ke5 regret t 9 8 lat] ye>s1 :5 ! subject 0 reviv$1 he 0 no long] able to re-exam9e ?is gr\nd himself1 = no "o w\ld h confess$ m frankly 8 error1 & done m ample ju/ice to ^? :o1 com+ aft] him1 h be5 able 9 "s p>ts to correct 8 "w4 ,! qu>tz-porphyry1 felsite or rhyolite ( ,llyn ,pad>n1 z well z t ( ,ll&e9iol51 is n a metamorphic b an eruptive rock1 z has be5 demon/rat$ by ,pr(essors ,hughes & ,bonney4 ,!re is no true passage ( ! s$im5t>y rocks into x2 on ! contr>y1 ! conglom]ates :i* abut aga9/ x are 9 great "p made out ( its fragm5ts1 s t x 0 already 9 exi/5ce be=e ^! ,cambrian /rata 7 deposit$ ^u x4 ,^! conclusions mu/ be reg>d$ z :olly indisputable4 ,b mo/ ( ! critics ( ! "w ( ! ,geological ,survey h proce$$ to c]ta9 fur!r d$uctions4 ,!y h ma9ta9$ t ! pres5ce ( fragm5ts ( ! porphyry 9 ! ov]ly+ conglom]ate m>ks an uncon=mability betwe5 ! two rocks1 t ! conglom]ate %[s ! base ( ! ,cambrian sy/em1 & t ! porphyry is !re=e pre-,cambrian4 ,^! ass]tions & inf]5ces d n seem to me to be w>rant$4 ,!y h1 9 my judgm5t1 be5 disprov$ by ,mr4 ,blake1#ajj :o %[s t !re is no break 9 ! ,cambrian s]ies1 t ! v>i\s porphyries & _! accompanim5ts are p>ts ( t s]ies1 & t !re is no c]ta9 pro( ( ! exi/5ce ( any pre-,cambrian rocks 9 ! :ole di/rict4#aja ,footnote #ajj3 ,9 an excell5t memoir read be=e ! ,geological ,society 9 #ahhh1 ) ! ma9 conclusions ( :i* ,i agree4 ,footnote #aja3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xliv4 p4 #bga4 ,= subsequ5t pap]s by ,mr4 ,blake1 see op4 cit4 vols4 xlviii4 7#ahib7 p4 #bdc1 xlix4 7#ahic7 p4 #dda4 ,t ! igne\s rocks ( ! ,llyn ,pad>n area m>k a volcanic p]iod has be5 recogniz$ by mo/ writ]s s9ce ,pr(essor ,bonney po9t$ out ! fl[-/ructure ( ! qu>tz-porphyry1 & o!r pro(s ( active volcanic eruptions h be5 trac$ by him1 z well z by ,pr(essor ,hughes & ,mr4 ,blake1 9 ! /ratifi$ rocks :i* /ret* nor?-ea/w>ds to ,bangor4 ,! ext5t & p]si/5ce ( ^! anci5t volcanic ph5om5a1 & _! probable connection ) ! rem>kable nor?w>d att5uation ( ! ,cambrian s$im5t>y rocks1 des]ve special att5tion4 ,x is g5]ally agre$ t ! rocks v>i\sly t]m$ qu>tz-porphyries1 felsites or rhyolites =m ! olde/ memb]s ( ?is volcanic s]ies4#ajb ,!y come to ! surface 9 two long ridges1 "o runn+ f ,ca]n>von to ne> ,bangor1 ! o!r f ,llanllyfni to ,ann's ,*apel1 at ! m\? ( ,nant ,francon 7,map4 ,,ii474 ,:e!r ! mat]ials ( ^! two ridges are p>ts ( "o orig9ally cont9u\s %eet or gr\p ( %eets1 or1 if diff]5t protrusions1 :e!r !y belong to ! same geological horizon1 or :e!r1 z ,mr4 ,blake believes1 !y are di/9ct masses1 sep>at$ by a consid]able ?ickness ( detrital mat]ial1 _c 9 ! pres5t /ate ( our k be positively decid$4 ,x seems to me probable t !y are connect$ und]gr\nd1 z a cont9u\s plat=m b5ea? ! ov]ly+ pyrocla/ic mat]ials4 ,footnote #ajb3 ,:e!r ! granitic rock ( ,twt ,hill1 ,ca]n>von1 is connect$ ) ! porphyry or belongs to an old] eruption is immat]ial = my pres5t purpose4 ,^! acid rocks h be5 reg>d$ by "s obs]v]s z intrusive %eets1 by o!rs z lava-/reams t 7 p\r$ out at ! surface4 ,if acc\nt be tak5 simply ( _! petrographical *>act]s1 !y f9d _! ne>e/ analogies among ! intrusive qu>tz-porphyries ( old] geological p]iods4 ,! pres5ce ( fl[-/ructure 9 !m has be5 ?\ght to indicate t !y 7 sup]ficial /reams4 ,b ?is /ructure may be f\nd 9 dykes & intrusive %eets z p]fectly z 9 lava-fl[s1 s t x _c by itself be tak5 z pro( ( a surface-dis*>ge ( lava4 ,x mu/ be confess$ t1 bo? 9 ! ma9 mass ( qu>tz-porphyry & 9 ! abundant fragm5ts ( x 9 ! ov]ly+ conglom]ates & breccias1 !re is an abs5ce ( su* scori=m portions z "o w\ld naturally look = 9 a sup]ficial lava-/ream2#ajc :ile1 on ! o!r h&1 ! rock g5]ally pres5ts ! tol]ably uni=m fl9ty texture s famili> 9 intrusive %eets ( simil> mat]ial4#ajd ,my own impression is t ^! igne\s masses 7 probably erupt$ to ! surface z long banks :i* rose above ! waves2 t !y 7 ?us expos$ to prolong$ subrial & m>9e d5udation2 t by ?is means any upp] m cellul> portions ( ! lava :i* may h exi/$ 7 brok5 up & p\nd$ d[n into detritus1 & ?us t :at is n[ visible is a "p ( ! eruptive rock :i* orig9ally lay at "s dep? )9 its body4 ,?is view is confirm$ by a /udy ( o!r lavas :i* are f\nd on diff]5t plat=ms 9 ! detrital deposits t ov]lie ! ,llyn ,pad>n qu>tz-porphyry4 ,footnote #ajc3 ,b ! ,llyn ,pad>n rock1 l _m acid lavas1 may nev] h possess$ a vesicul> /ructure 9 any portion ( its mass4 ,! %eets ( felsite :i* occur among ! ov]ly+ tuffs are n cellul>1 b pres5t ! close/ resemblance to ! ma9 mass bel[4 ,footnote #ajd3 ,mr4 ,blake br\ght =w>d ! evid5ce ( a section on ! nor? or "u side ( ! ,llyn ,pad>n ridge to %[ t ! rock has !re be5 intrud$ into ! ,cambrian /rata 7,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xliv4 7#ahhh71 p4 #bhc74 ,b ! rock suppos$ by him to be alt]$ slate has be5 %[n to be intrusive gre5/one 7,miss ,rais91 op4 cit4 vol4 xlvii4 7#ahia71 p4 #ccf74 ,t ! mat]ial ( ea* ( ! two ma9 ridges is ! result ( m ?an "o eruption has be5 inf]r$ f ! suppos$ int]calation ( b&s ( slate & ( breccia 9 ! rock4#aje ,consid]able li?ological diff]5ces may be detect$ 9 ea* mass1 b !y are n great] ?an may be obs]v$ 9 s+le sills & bosses4 ,9 "s p>ts ( ! ,llyn ,pad>n porphyry a di/9ct nodul> /ructure appe>s :i* %ades (f into b&s & l5ticul> /reaks1 rem9d+ "o ( ! *>act]s ( "s ( ! ,bala rhyolites4 ,o!r portions are m>k$ly brecciat$1 ! sep>at$ fragm5ts be+ surr\nd$ 9 a matrix ( ! rock1 :i* %[s fl[-/ructure sweep+ pa/ !m4 ,on ,moel ,gronw angul> fragm5ts ( a d>k p9ki% t9t are scatt]$ ?r\gh ! g5]al mass4 ,aga91 "s p>ts are cr[d$ ) qu>tz-gra9s1 :ile o!rs are comp>atively free ( ^!1 & occasionally a sph]ulitic /ructure has be5 obs]v$4#ajf ,footnote #aje3 ,see = example1 ,pr(4 ,bonney1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxv4 7#ahgi71 p4 #cab2 ,mr4 ,blake1 op4 cit4 vol4 xliv4 7#ahhh71 pp4 #bgg1 #bhg4 ,b "s at lea/ ( ! suppos$ slates1 z /at$ 9 a previ\s footnote1 h be5 s9ce %[n to be dykes4 ,footnote #ajf3 ,mr4 ,blake1 ibid4 p4 #bgg4 ,! microscopic /ructure ( ?is anci5t eruptive rock has be5 /udi$ by ,pr(essor ,bonney1 :o f\nd t ! g5]al type 0 a compact dull grey felsite1 ) porphyritic cry/als ( felsp> & gra9s ( qu>tz1 closely resembl+ "s mod]n rhyolites4 ,?\gh unable to detect any actual glass 9 ! base1 he _h no d\bt t ! rock 0 orig9ally vitre\s1 & he f\nd abundant & fre% examples ( ! mo/ p]fect fl[-/ructure4#ajg ,footnote #ajg3 ,op4 cit4 vol4 xxxv4 p4 #cab4 ,illu/ration3 ,fig4 #db4--;,basic dyke trav]s+ qu>tz-porphyry & conv]t$ into a k9d ( slate by cleavage4 ,we/ side ( ,llyn ,pad>n4 p p1 qu>tz-porphyry2 d d1 dyke & connect$ ve9s4 ,ref]5ce may be made "h to ! rem>kable influ5ce ( ! int5se cleavage ( ! di/rict ^u ?is rock4#ajh ,along its s\!rn m>g91 :]e x has be5 expos$ to pressure f ! s\?-ea/1 ! qu>tz-porphyry has be5 s cru%$ t x passes "h & !re into a f9e unctu\s slate or almo/ a s*i/4 ,n[h]e c ?is *ange be m cle>ly se5 ?an on ! slopes ( ,mynydd y ,cilgwyn4 ,! cleavage planes /rike ab\t ,n4 #dj ,e41 ) an incl9ation to dip t[>ds ! ,n4,w4 ,)9 a space ( a few y>ds a s]ies ( specim5s may be collect$ %[+ at "o end an ord9>y or only slightly-%e>$ qu>tz-porphyry ) abundant qu>tz-blebs1 & at ! o!r a f9e gre5i% s]icitic slate or phyllite1 :]e9 ! qu>tz has be5 almo/ entirely cru%$ d[n4 ,l9es ( %e>+ may be detect$ across ! bread? ( ! porphyry ridge1 ea* ( !m co9cid+ ) ! preval5t tr5d ( ! cleavage4 ,sometimes also c]ta9 basic dykes1 :i* trav]se ! porphyry 9 "s numb]s1 h und]gone consid]able de=mation f ! same cause4 ,_! ?9n] portions are s well cleav$ t !y h be5 mi/ak5 = includ$ b&s ( gre5 slate 7,fig4 #db74 ,b ^! cleav$ bran*es may sometimes be trac$ into a ?ick] & m solid dyke1 ^: uncru%$ cores /ill pres]ve ! orig9al "* ( ! rock & prove x to be eruptive4 ,footnote #ajh3 ,! second>y planes due to cleavage mu/ n be conf\nd$ ) ! orig9al fl[-/ructure4 ,illu/ration3 ,fig4 #dc4--,section ( well-cleav$ tuff1 grit & breccia pass+ up into rudely-cleav$ conglom]ate & well-b$d$ cleav$ f9e conglom]ate & grit4 ,ea/ side ( ,llyn ,pad>n4 ,! rocks :i* succe$ ! porphyry 9 ! ,valley ( ,llanb]is are ( great int]e/1 = !y conta9 abundant pro( ( contemporane\s volcanic activity1 & !y %[ t1 s f> f !re be+ any m>k$ hiatus "h1 !re is evid5ce ( ! p]si/5ce ( eruptions ev5 into ! "t ( ! ,llanb]is ,slates4#aji ,consid]able misappreh5sion has aris5 f ! attempt to make "o ( ! conglom]ates ! base ( ! ,cambrian s]ies1 & ! real significance ( ! volcanic detrital /rata 9 association ) x 0 consequ5tly miss$4 ,! conglom]ate does n lie on "o def9ite horizon4 ,9 tru?1 !re are sev]al zones ( conglom]ate1 ea* ) "s diff]5ce ( composition1 ?ickness or ext5t4#aaj ,^! may be well /udi$ bo? on ! s\? & ! nor? side ( ! porphyry ridge at ! l[] end ( ,llyn ,pad>n4 ,!y are int]calat$ among f9e tuffs1 grits1 volcanic breccias & purple slates1 sometimes full ( f9e a%y mat]ial4 ,on ! s\?-ea/ side ( ! ridge1 :]e ! rocks h suff]$ int5se cleavage1 !y assume a fissile unctu\s "*1 & !n resemble p>ts ( ! cleav$ ,cambrian tuffs at ,/4 ,david's4 ,b on ! nor?-we/ side1 :]e !y h 9 l>ge measure escap$ ! effects ( ! cleavage-movem5ts1 _! orig9al /ructures are well pres]v$4 ,footnote #aji3 ,! sections 9 ! ,vale ( ,llanb]is on ei!r side ( ,llyn ,pad>n h be5 aga9 & aga9 describ$ & f\ght ov]4 ,"s ( ! pap]s are cit$ 9 ! foll[+ pages1 b x w\ld be impossible 9 ?is volume to f9d room = a full discussion ( ! diff]5ces ( op9ion4 ,:at is /at$ 9 ! text is ! result ( my own /udy ( ! rocks on ! gr\nd1 c\pl$ ) a c>eful consid]ation ( ! "w ( o!r obs]v]s4 ,footnote #aaj3 ,i c f9d no evid5ce ( uncon=mability b5ea? any ( ! conglom]ates4 ,! section describ$ by ,pr(essor ,gre51 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xli4 7#ahhe71 p4 #gd1 m]ely %[s ! diff]5ce betwe5 ! effects ( cleavage on ! f9e tuffs & ! m massive resi/+ conglom]ate :i* ov]lies !m4 ,?is section is repres5t$ 9 ,fig4 #dc4 ,at fir/ sight ! conglom]ate appe>s to be ly+ on ! v]tical edges ( an old] gr\p ( slates1 b any "o acqua9t$ ) cleavage c trace ?is /ructure f ! tuffs into ! conglom]ate & resum+ its c\rse aga9 9 ! f9] s$im5ts above4 ,! :ole s]ies ( deposits 9 ! section is cont9u\s & con=mable4 ,! section on ! slate railway has deceiv$ ,mr4 ,blake z well z ,pr(essor ,gre5 7,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlix4 7#ahic71 p4 #dde74 ,! correct int]pretation is giv5 by ,pr(essor ,bonney & ,miss ,rais9 7op4 cit4 vol4 l4 p4 #eib74 ,"o ( ! fir/ features ( ^! detrital deposits to arre/ att5tion is ! am\nt & v>iety ( ! fragm5ts ( igne\s rocks 9 !m4 ,"s ( ! conglom]ates1 ?\gh enclos+ pebbles ( qu>tz1 qu>tzite1 granite & o!r rocks n f\nd 9 situ 9 ! imm$iate di/rict1 are ma9ly compos$ ( ! debris ( ! qu>tz-porphyry ( ! ridge4 ,inde$1 ?is latt] mat]ial appe>s to h contribut$ a l>ge proportion ( ! detritus ( :i* ! g5]al body ( /rata "h is made up4 ,b !re are to be notic$ among ! cont5ts ( ! conglom]ates & breccias pieces ( _m volcanic rocks n to be f\nd on ! porphyry ridge4 ,among ^!1 besides felsites %[+ sometimes beautiful fl[-/ructure 7rhyolites7 & v>i\s qu>tz-porphyries1 !re occur abundant fragm5ts ( less acid lavas 7&esites7 & pieces ( old] tuffs4 ,"s ( ! fragm5tal rocks are gre5 9 col\r1 probably f ! abundance ( f9e basic volcanic du/ 9 !m4 ,c]ta9 b&s are full ( l>ge angul> pieces ( %ale1 simil> 9 "* to ! ,cambrian slates1 & d\btless due to ! disruption ( pre-exi/+ ,cambrian /rata by volcanic explosions4 ,x is cle> t f v5ts 9 ?is neighb\rhood !re cont9u$ to be an abundant dis*>ge ( du/ & v>i\s &esitic & o!r lapilli1 :i*1 fall+ on ! sea-floor1 m+l$ !re ) ! ord9>y me*anical s$im5t t 0 be+ deposit$ at ! "t4#aaa ,footnote #aaa3 ,on ! composition ( ! conglom]ates or breccias1 see ,pr(essor ,bonney & ,miss ,rais91 ,qu>t4 ,j\r4 ,geol4 ,soc4 vol4 l4 7#ahid71 p4 #eih4 ,illu/ration3 ,fig4 #dd4--,section ( ,clegyr on ! nor?-ea/ side ( ,llyn ,pad>n1 ne> ! l[] end4 ,b we h evid5ce t1 dur+ ! p]iod :5 ^! %[]s ( volcanic detritus 7 ?r[n out1 /reams ( lava1 ?\gh on a greatly dim9i%$ scale1 cont9u$ to be p\r$ =?4 ,! hill ( ,clegyr 7,fig4 #dd71 ne> ! l[] end ( ,llyn ,pad>n1 on ! nor?-ea/ side1 consi/s ma9ly ( cleav$ tuffs 7t7 & slates ) conglom]ates 7c71 ov]ly+ ! qu>tz-porphyry 7p74 ,ne> ! summit a b& ( felsite is int]calat$ 9 ^! rocks4 ,/ill m /rik+ are ! sections on ! s\?-we/ side ( ! lake4#aab ,/>t+ f ! porphyry ( ! ridge1 we cross a zone ( conglom]ate & grit l>gely compos$ ( ! debris ( ! porphyry1 until we rea* a b& ( felsite or qu>tz-porphyry1 :i* at its ea/]n end is ab\t t5 feet ?ick1 :ile x seems to increase 9 dim5sions we/w>ds4#aac ,9 ! c5tre ! rock is d>k purpli%-r$1 exce$+ly compact or fl9ty1 spr9kl$ ) a v>iable proportion ( qu>tz-blebs & felsp> cry/als4 ,t[>ds its s\!rn or upp] edge 7= ! rocks1 ?\gh ne>ly v]tical1 dip s\?w>ds7 x has be5 cleav$ into a v>iety ( purple slate1 & w\ld !re at once be class$ among ! ord9>y slates ( ! neighb\rhood4 ,b ! fissile "* is m]ely a m>g9al /ructure :i* ! rock %>es ) ! highly-cleav$ tuffs t foll[ x4 ,trac$ we/w>ds1 ?is b$ is f\nd to enclose a core ( qu>tzif]\s porphyry1 :i*1 ?\gh x has escap$ f ! mo/ complete results ( cru%+1 is nev]!less cleav$ along its m>g9 z well z p>tially 9 its int]ior4 ,x w\ld n be possible to di/+ui% p>ts ( ?is int]calat$ less cru%$ core f portions ( ! porphyry ( ! ma9 ridge4 ,! diff]5ce ( col\r does n c\nt = mu*1 = ev5 9 ?is core ! purple t9t gives place to gre5i% grey1 & :at 9 ! c5tre at ! ea/ end is a solid d>k purpli%-r$ felsite passes we/w>d into a gre5i% slate1 l t already notic$ on ,mynydd y ,cilgwyn4 ,footnote #aab3 ,= v>i\s read+s ( ^! sections1 comp>e ,mr4 ,blake 7,qu>t4 ,j\r4 ,geol4 ,soc4 vol4 xlix4 7#ahic71 p4 #dej7 ) ,pr(essor ,bonney & ,miss ,rais9 7op4 cit4 vol4 l4 7#ahid71 p4 #eha74 ,footnote #aac3 ,see ,pr(essor ,bonney & ,miss ,rais91 op4 cit4 p4 #eic et seq4 ,! microscopical exam9ation ( ?is rock %[s x to be a true felsite ( ! rhyolitic type1 :i* 9 ! c5tral uncleav$ "p exhibits a wavy fl[-/ructure l t f\nd 9 ! qu>tz-porphyry ( ! ridge4 ,s int5se has be5 ! cleavage 9 its upp] "p t ! orig9al /ructure ( ! rock is !re effac$4 ,! imm$iately ov]ly+ tuffs1 :i* are likewise s ?or\ghly cleav$ t x is n easy to draw a %>p & cont9u\s l9e betwe5 !m & ! int]calat$ lava1 precisely resemble ^? f\nd bel[ ! conglom]ate on ! opposite side ( ! lake4 ,!y include b&s ( co>se volcanic breccia z well z f9e compact mat]ial1 %[+ ! v>y+ int5sity ( ! volcanic dis*>ges4 ,_! includ$ /ones consi/ ( v>i\s felsites1 &esites & slates4#aad ,footnote #aad3 ,i see no reason to d\bt t ! less acid igne\s fragm5ts 7 eject$ dur+ ! clos+ phases ( volcanic action1 ev5 ?\gh no su* rocks h be5 f\nd at ! surface 9 situ4 ,we mu/ rememb] h[ frequ5tly mixtures ( acid & basic mat]ials are to be f\nd 9 ! same cont9u\s s]ies ( volcanic ejections & ev5 9 ! same v5t1 ( :i* illu/ration w be giv5 9 subsequ5t pages4 ,nor %\ld we =get :at a m]e fragm5t ( a volcanic gr\p is expos$ at ! surface 9 ! ,llanb]is di/rict4 ,see ,pr(essor ,bonney & ,miss ,rais91 op4 cit4 p4 #eif1 footnote4 ,! ?9 %eet ( int]/ratifi$ qu>tz-porphyry "h describ$ is n ! only "o to be f\nd 9 ! section4 ,o!rs ?9n] & m int5sely cleav$ lie among ! tuffs high] up4 ,!y h be5 %e>$ into m]e pale unct\s slates1 b ! rema9s ( _! qu>tz-blebs may /ill be detect$ 9 !m4 ,! tuffs1 ) _! int]/ratifi$ b&s ( porphyry1 become m & m m+l$ ) ord9>y argillace\s & s&y s$im5t z !y are foll[$ 9 upw>d succession4 ,among !m occur b&s ( grit & f9e conglom]ate conta9+ pebbles ( porphyry & pieces ( slate4 ,"s ( ^! grits are ma9ly compos$ ( :ite felsp>1 felsite & cle> gra9s ( qu>tz1 evid5tly d]iv$ f ! dis9tegration ( a rock l ! porphyry ( ! ma9 ridge4 ,z ! ord9>y s$im5t ( ! ,llanb]is gr\p sets 91 ! tuffs are re/rict$ to ?9n] & m widely-sep>at$ b&s4 ,"s ?9 lay]s ( felspa?ic breccia1 se5 among ! slates close to ! ,glyn ,p]is ,hotel1 probably m>k ! la/ dis*>ges ( ! sl[ly-expir+ v5ts ( ?is region4 ,"h1 z at ,/4 ,david's1 f ! mo/ anci5t ( our volcanic records1 /rik+ evid5ce is furni%$ ( ! gradual ext9ction ( volcanic action4 ,?r\gh _m hundr$s ( feet ( /rata :i* n[ sup]v5e1 repres5t+ ! clos+ ages ( ! ,cambrian & ! e>li] ages ( ! ,silurian p]iod1 no trace ( volcanic mat]ial has be5 f\nd 9 ?is di/rict until we rea* ! ,bala lavas & agglom]ates ( ,sn[don & ! ,pass ( ,llanb]is4 ,9 ! neighb\rhood ( ,bangor ano!r area ( simil> rocks wraps r\nd ! nor!rn end ( ! we/]n porphyry ridge4 ,! ,geological ,survey map1 9 con=mity ) ! ideas t gov]n$ its repres5tation ( ! old] rocks ( ,anglesey & ,ca]n>von1 col\rs ^! z alt]$ ,cambrian4 ,t ?is error %\ld h be5 made1 or1 :5 made1 %\ld n h be5 spe$ily correct$1 is all ! m surpris+ :5 we consid] ! ?or\gh ma/]y :i* ! surveyors _h acquir$ ( ! aspects & ! int]pretation ( anci5t volcanic rocks 9 ,wales1 & :51 moreov]1 we rememb] t z f> back z #ahdc1 long be=e ! ,survey ( ,ca]n>von%ire 0 publi%$1 ,s$gwick _h po9t$ out ! true volcanic nature ( ! rocks4 ,t great pione] recogniz$ ! pres5ce ( trappean conglom]ates & trappean %ales 7,s*aal/e97 among ^! deposits at ,bangor2 b he c\ld n sep>ate !m f ! ,cambrian s]ies ( ! re/ ( ,wales4#aae ,& 9 8 section he repres5ts !m z undulat+ t[>ds ! ea/ & pass+ "u ! great mass ( ! ,ca]n>von%ire slates & porphyries4 ,footnote #aae3 ,proc4 ,geol4 ,soc4 vol4 iv4 p4 #bab2 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 iii4 7#ahdg71 p4 #acf4 ,?is int]pretation1 :i* ,i believe to be ess5tially accurate1 0 modifi$ by ,pr(essor ,hughes1 :o1 fix+ on a conglom]ate z ! base ( ! ,cambrian sy/em1 reg>d$ all ! rocks bel[ x1 or :at he t]m$ 8 ,bangor gr\p1 z pre-,cambrian4#aaf ,he has be5 foll[$ 9 ?is view by subsequ5t writ]s2#aag b ,mr4 ,blake has argu$ t "h1 z 9 ! ,llanb]is di/rict1 !re is no evid5ce to sep>ate ! volcanic detrital deposits above ! porphyry f ! ,cambrian sy/em4#aah ,footnote #aaf3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxiv4 7#ahgh71 p4 #acg4 ,footnote #aag3 ,pr(4 ,bonney1 op4 cit4 vol4 xxxv4 7#ahgi71 p4 #caf2 ,dr4 ,hicks1 ibid4 p4 #bif4 ,footnote #aah3 ,op4 cit4 vol4 xliv4 7#ahhh71 p4 #bgh4 ,a little s\?w>d f ,bangor ! qu>tz-porphyry is ov]la9 by a mo/ int]e/+ gr\p ( fragm5tal rocks1 ! ,bangor gr\p ( ,pr(essor ,hughes4 ,l>gely ( volcanic orig91 !y mu/ be "s hundr$s ( feet ?ick1 & pass "u ! d>k %ales & grits ( ! ,l[] ,silurian 7,ar5ig7 s]ies4 ,"s ( ! mo/ p]si/5t b&s among !m are conglom]ates1 :i* diff] f ea* o!r 9 composition1 b mo/ ( :i* consi/ l>gely ( fragm5ts ( v>i\s igne\s rocks4 ,"s ( ! co>s] masses might be t]m$ agglom]ates1 = !y %[ little or no trace ( b$d+1 & are ess5tially made up ( blocks ( volcanic mat]ial4 ,!re are abundant b$s ( grit1 sometimes pebbly or f9ely conglom]atic1 alt]nat+ ) tuffs & ) b&s ( m ord9>y s$im5t4 ,c\rses ( purple %ale & s&/one1 gre5 %ale & d>k grey s&y %ale occasionally occur to m>k pauses 9 ! volcanic explosions4 ,p]haps ! mo/ /rik+ feature 9 ! pyrocla/ic mat]ials is ! great abundance ( v f9e compact pale tuffs 7hllefl9tas ( "s writ]s71 sometimes ?9ly lam9at$1 sometimes occurr+ 9 ribbon-l b&s1 ea* ( :i* pres5ts int]nally a close-gra9$1 almo/ felsitic or fl9ty texture4#aai ,footnote #aai3 ,! occurr5ce ( fl9ty or *]ty deposits1 9 association ) volcanic rocks ( ,l[] ,silurian age1 is well e/abli%$ 9 ,brita91 & w be m p>ticul>ly ref]r$ to 9 ! sequel4 ,a cursory exam9ation ( ! cont5ts ( ! conglom]ates1 breccias & grits %[s !m to consi/ l>gely ( diff]5t felsites1 ) fragm5ts ( m basic lavas4 ,"s ( ^! might obvi\sly h be5 d]iv$ f ! rock ( ! porphyry ridge1 b1 z at ,llyn ,pad>n1 !re is a f> great] v>iety ( mat]ial ?an c be f\nd 9 t ridge4 ,"s ( ! fragm5ts %[ p]fect fl[-/ructure4 ,pr(essor ,bonney has describ$ ! microscopic *>act]s ( "s ( ^! fragm5ts1 & has especially rem>k$ ^u _! glassy "*4 ,among ! slides prep>$ f specim5s collect$ by myself1 besides ! abundant fragm5ts ( felsite 7rhyolite71 !re are also num]\s pieces ( diff]5t &esitic lavas & f9e tuffs1 z well z gra9s ( qu>tz & felsp>1 & sometimes a good deal ( granul> iron-ore4 ,t a l>ge proportion ( ! mat]ial ( ! s-call$ ,bangor b$s 0 directly d]iv$ f volcanic explosions c h>dly be d\bt$4 ,!re appe>s to h be5 a prolong$ succession ( eruptions1 v>y+ 9 int5sity1 & some:at also 9 ! nature z well z 9 ! relative f95ess ( ! mat]ial dis*>g$4 ,on ! "o h&1 co>se massive agglom]ates 7 probably accumulat$ n f> f ! active v5ts1 z ! result ( m viol5t or transi5t explosions2 on ! o!r h&1 exce$+ly f9e & well-/ratifi$ tuffs1 :i* atta9 a great ?ickness1 s]ve to indicate a phase ( eruptivity m>k$ by ! long-cont9u$ dis*>ge ( f9e volcanic du/4 ,ord9>y s$im5t 0 d\btless drift$ ov] ! sea-bottom 9 ?is di/rict dur+ ! volcanic episode1 b ! comp>ative infrequ5ce ( di/9ct int]/ratifications ( %ale or s&/one may be tak5 to imply t z a rule ! pauses betwe5 ! eruptions 7 n long en\gh to all[ any consid]able accumulation ( s& or mud to take place4 ,no satisfactory pro( has yet be5 obta9$ ( any int]/ratifi$ lavas among ! tuffs ( ! ,bangor di/rict4 ,"s rocks1 inde$1 c be se5 on ! road betwe5 ! ,george ,hotel & ,h5drew51 :i*1 if !re 7 bett] exposures1 might possibly furni% ! requir$ pro(2 b at pres5t little c be made ( !m1 = _! relations to ! surr\nd+ rocks are ev]y:]e conceal$4 ,f :at ,i h n[ adduc$1 x is obvi\s t :ile bo? felsitic & &esitic lavas exi/$ )9 ! volcanic foci1 & 7 eject$ 9 fragm5ts to =m ! tuffs & breccias1 ! lavas p\r$ out at ! surface dur+ ! ,cambrian p]iod 9 ,ca]n>von%ire 7 ma9ly1 if n entirely1 felsites 7rhyolites7 9 :i* ! *ief porphyritic con/itu5t 0 qu>tz4 ,^! lavas ?us /& entirely by !mselves 9 ! volcanic hi/ory ( ,wales4 ,?\gh felsites ( v>i\s types 7 aft]w>ds p\r$ out1 no?+ ( ! same qu>tzif]\s k9d1 s f> z we yet "k1 ev] aga9 appe>$4 ,fur!r s\?1 9 ,m]ione?%ire1 z w be %[n 9 ,*apt] xii41 ! ,cambrian volcanic eruptions appe> to h be5 on ! :ole less acid1 & to h begun ) ! outp\r+ ( &esitic lavas4 ,i h n[ to consid] ! relation ( ! volcanic gr\p ( ,bangor to ! /rata :i* ov]lie x4 ,! geological horizon ( ^! /rata is n1 p]haps1 v def9itely fix$4 ,x may be ,ar5ig1 possibly ev5 old]4 ,b = my pres5t purpose x w be suffici5t to consid] ! /rata 9 "q z ly+ at ! bottom ( ! ,l[] ,silurian s]ies4 ,pr(essors ,hughes & ,bonney h tak5 z _! base a m>k$ b imp]si/5t b& ( conglom]ate4 ,mr4 ,blake1 h[ev]1 has m rec5tly %[n t1 z ?is b& is succe$$ by tuffs l ^? bel[ x1 x _c be claim$ z m>k+ ! upp] limit ( ! volcanic gr\p4 ,he !re=e classes x 9 t gr\p & traces :at he ?9ks is an ov]lap or uncon=mability at ! bottom ( ! ,l[] ,silurian /rata to ! ea/4 ,mr4 ,b4 ,n4 ,pea*1 :o accompani$ me 9 an exam9ation ( ?is gr\nd1 agre$ ) me 9 confirm+ ,mr4 ,blake's obs]vation z to ! position ( ! conglom]ate1 :i* is und\bt$ly ov]la9 by ! same fl9ty felsitic tuffs z are f\nd bel[ x4 ,b we 7 unable to trace any uncon=mability4 ,accord+ to ! num]\s obs]vations :i* we made1 !re does n seem to be any discordance 9 /rike or dip betwe5 ! fl9ty tuffs & ! ov]ly+ %ales & grits4 ,! two gr\ps ( rock appe>$ to u to be con=mable & to pass into ea* o!r1 z at ,llyn ,pad>n4#abj ,footnote #abj3 ,see ,mr4 ,blake on ?is po9t1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlviii4 7#ahib71 p4 #beb1 note4 ,i reta9 ! op9ion express$ above4 ,an uncon=mable junction "h w\ld1 9 "s respects1 h be5 welcome1 = x w\ld at once h acc\nt$ = ! sup]position ( ,l[] ,silurian /rata directly ^u ! ,cambrian volcanic s]ies1 & = ! disappe>ance ( ! ,llanb]is slates & grits :i* =m s conspicu\s a feature above ! tuffs & conglom]ates at ,llyn ,pad>n4 ,9 ! abs5ce ( su* a /ructure we mu/ accept ! ord] ( succession z app>5tly unbrok51 & rely on "s su* explanation z 0 propos$ by ,sir ,&rew ,ramsay to acc\nt = ! ov]lap ( ! ,ar5ig rocks on ev]y?+ old] ?an !mselves z !y are trac$ nor?w>ds4#aba ,b ?is explanation w n entirely remove ! difficulties ( ! case4 ,! inosculation ( ! volcanic gr\p ( ,bangor ) ! base ( ! ,l[] ,silurian s]ies _c be acc\nt$ = by any su* ov]lap2 x seems only explicable on ! supposition t ! volcanic activity1 :i* ceas$ 9 ! ,llyn ,pad>n di/rict ab\t ! "t t ! ,llanb]is ,slates 7 deposit$1 0 cont9u$ 9 ! ,bangor area until ,ar5ig "t1 or 0 !n r5ew$4 ,! ?ick volcanic gr\p ( ,bangor w\ld ?us be ! /ratigraphical equival5t n only ( ! ?9 volcanic gr\p ( ,llyn ,pad>n1 b ( ! ov]ly+ mass ( /rata up to ! ,ar5ig rocks4 ,9 confirmation ( ?is view1 ,i %all %[ 9 a lat] *apt] t volcanic action seems to h be5 prolong$ 9 ,anglesey to a /ill lat] geological p]iod1 t x appe>$ dur+ ! deposition ( ! ,ar5ig /rata1 & t x atta9$ a great developm5t ?r\gh\t ! "t ( ! ,bala gr\p4 ,t a s]ies ( volcanic rocks1 ) associat$ *]ty /rata1 may be ! /ratigraphical equival5t ( a great ?ickness ( ord9>y s$im5ts 9 o!r di/ricts w be dwelt ^u 9 ! description ( ! ,l[] ,silurian volcanic geology ( ! ,s\!rn ,upl&s ( ,scotl&4#abb ,footnote #aba3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #beb4 ,footnote #abb3 ,a gr\p ( *]ts & mud/ones n m ?an #fj or #gj feet ?ick appe> 9 t region to be /ratigraphically equival5t to ! great dep? ( s$im5t>y mat]ial :i* else:]e con/itutes ! ,upp] ,ar5ig & ,l[] & ,middle ,ll&eilo =mations4 ,see ,annual ,report ( ! ,geological ,survey = #ahie1 p4 #bg ( repr9t4 ,9 ! areas ( ,nor? ,wales :i* h n[ be5 describ$1 volcanic action appe>s to h begun & end$ )9 ! limits ( ! ,cambrian p]iod4 ,s\?w>ds1 9 ! di/rict ( ,dolgelly1 ano!r di/9ct &1 9 "s respects1 v diff]5t developm5t ( ,cambrian volcanic activity may be recogniz$4 ,9 t di/rict !re is evid5ce t ! volcanoes :i* di/+ui%$ ! e>li] "p ( ! ,silurian p]iod _h already begun _! eruptions dur+ ,cambrian "t4 ,z _! records1 h[ev]1 are intimately l9k$ ) ^? ( ,silurian age1 an acc\nt ( !m is def]r$ to ! next *apt]4 ,,! ,,malv]n ,,hills ,al?\gh ! *ief surviv+ records ( ,cambrian volcanic action 9 ,brita9 are f\nd 9 ,wales1 !re is no evid5ce t ! volcanoes ( ! p]iod lay *iefly 9 t region4 ,x is c]ta9ly a sugge/ive fact t1 9 ! few di/ricts :]e ,cambrian /rata appe> f "u y\ng] =mations 9 ,engl&1 !y are g5]ally accompani$ ) igne\s rocks1 ?\gh ! age ( ! latt] may be old] or lat] ?an ! ,cambrian p]iod4 ,if ! olde/ ,palozoic rocks c\ld be uncov]$ ov] ! ,engli% c\nties1 a m abundant developm5t ( volcanic mat]ials might be laid b>e ?an is n[ to be se5 9 ,wales4 ,tak+1 h[ev]1 ! extremely limit$ exposures ( ,cambrian /rata1 we f9d two tracts t specially des]ve att5tion4 ,ref]5ce has already be5 made to ! anci5t eruptive rocks ( ! ,malv]n ,hills1 ! antiquity ( :i* is prov$ by ! position ( ! ,cambrian fossilif]\s /rata t ov]lie !m4 ,b ^! /rata !mselves include c]ta9 igne\s rocks :i* po9t to a recrudesc5ce ( eruptive en]gy 9 a f> lat] geological p]iod4 ,ne>ly half a c5tury has pass$ away s9ce ,john ,phillips m5tion$ ! int]calation ( igne\s rocks 9 ! s]ies ( /rata :i* is n[ class$ z ,upp] ,cambrian 9 ! ,malv]n ,hills4 ,s9ce t date h>dly any?+ has be5 add$ to ! in=mation :i* he collect$4 ,! exi/5ce ( a gr\p ( rocks ( su* high antiquity1 ass]t$ to be ( truly volcanic orig91 & ! precise horizon ( :i* c\ld be fix$ by ! /ratigraphical aid ( organic rema9s1 seems to h almo/ dropp$ out ( sight4 ,phillips not$ ! occurr5ce ( :at he reg>d$ z truly volcanic mat]ials 9 ! ,hollybu% ,s&/one & ! ov]ly+ d>k 7,l+ula7 %ales1 & he cle>ly recogniz$ t a wide diff]5ce ( age sep>at$ !m f ! f> m anci5t igne\s rocks ( ! c5tral core ( ! *a94 ,! ,hollybu% ,s&/ones 7 obs]v$ by him to h (t5 a trappean aspect & to be trav]s$ ) felspa?ic dykes4 ,he f\nd ! ov]ly+ black %ales to include lay]s ( trappean a%y s&/one4 ,b x 0 at ! top ( ^! %ales t he obta9$ :at he reg>d$ z ! mo/ conspicu\s evid5ce ( contemporane\s volcanic action4 ,he !re enc\nt]$ a zone ( int]pos$ trap rocks v>y+ up to #ej feet 9 ?ickness1 consi/+ ( porphyritic & gre5/one masses1 :i*1 erupt$ f bel[1 h fl[$ 9 limit$ /reams ov] ! surface ( ! black %ales4 ,he recogniz$ amygdaloidal & prismatic /ructures among !m4#abc ,! position ( ^! eruptive rocks is %[n 9 ,fig4 #de4 ,footnote #abc3 ,mem4 ,geol4 ,survey1 vol4 ii4 "p i4 pp4 #eb1 #ee2 also ,horizontal ,sections ( ! ,geol4 ,survey1 ,%eet #ac1 ,no4 #h1 & ,%eet #ae4 ,ref]5ce to ! igne\s rocks ( ?is area w be f\nd 9 ! rem>kable essay by ,de la ,be*e 9 vol4 i4 ( ! ,mem4 ,geol4 ,surv4 pp4 #cd1 #ch4 ,illu/ration3 ,fig4 #de4--,section across ! ,cambrian =mations ( ! ,malv]n ,hills1 %[+ ! position ( ! int]calat$ igne\s rocks 7p p74 ,aft] ,phillips4 ,^! rocks 7 aft]w>ds obs]v$ & describ$ by ,dr4 ,holl1 :o f\nd :at he consid]$ to be f\r true lava %eets int]/ratifi$ 9 ! ,hollybu% ,s&/ones4 ,he not$ ! int]calation ( num]\s b$s ( volcanic a%1 grit & lava 9 ! black %ales4#abd ,footnote #abd3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxi4 7#ahfe71 pp4 #hg-ia4 ,s f> z ,i am aw>e1 no m rec5t acc\nt ( ^! rocks has be5 publi%$4 ,_! true /ratigraphical & petrographical relations require to be m precisely det]m9$4 ,if !y are really contemporane\s lavas1 !y po9t to volcanic eruptions at ! "t :5 ! middle division ( ! ,cambrian sy/em 0 be+ deposit$4 ,if1 on ! o!r h&1 !y %\ld prove to be intrusive1 !y w\ld indicate probable volcanic activity 9 ?is "p ( ,engl& at "s "t lat] ?an ! middle ( ! ,cambrian p]iod4 ,,w>wick%ire ,"s fifty miles to ! nor?-ea/ ( ! ,malv]n ,hills1 9 ! he>t ( ! ri* ,midl&s1 & among ! coal-fields & ! ,new ,r$ ,s&/one to :i* ^! ,midl&s owe s mu* ( _! manufactur+ indu/ry & _! agricultural f]tility1 ano!r little tract ( ,cambrian rocks rises to ! surface on ! ea/ side ( ! ,w>wick%ire coal-field betwe5 ,nuneaton & ,a!r/one4 ,s unobtrusively d ^! anci5t /rata take _! place among _! y\ng] pe]s1 t _! v5]able antiquity 0 = a long "t undetect$4#abe ,!y 7 actually reg>d$ z p>ts ( ! ,c>bonif]\s s]ies1 :i* at fir/ sight !y seem to und]lie con=mably4 ,x 0 n until #ahhb t ! mi/ake 0 correct$ by ,pr(essor ,lapwor?1 :o prov$ ! rocks to be ,cambrian by f9d+ und\bt$ ,upp] ,cambrian fossils 9 !m4#abf ,subsequ5t inve/igation enabl$ him to "w out ! detail$ sequ5ce ( ^! /rata4 ,he f\nd t ! suppos$ ,mill/one ,grit is a ?ick-b$d$ qu>tzite p]haps #ajjj feet 9 ?ickness1 & resembl+ ! well-kn[n qu>tzites ( ! ,lickey & ,ca] ,c>adoc4 ,! ,coal-%ales prov$ to be a s]ies 7possibly #bjjj feet ?ick7 ( purple1 gre51 grey & black %ales1 :i* f _! fossils c\ld be p>allel$ ) ! d>k %ales ( ! ,upp] ,cambrian s]ies ( ! ,malv]n ,hills4#abg ,^! %ales are imm$iately ov]la9 by ! ,coal-measures4 ,footnote #abe3 ,_! antiquity 0 recogniz$ by ,yates z f> back z #ahbe 7,trans4 ,geol4 ,soc4 #bnd s]ies1 vol4 ii4 p4 #bfa74 ,!y _h be5 conf\nd$ ) ,mill/one ,grit & ,coal-%ale by ,conybe>e & ,phillips1 & ?is mi/ake 0 adopt$ on ! maps & memoirs ( ! ,geological ,survey4 ,footnote #abf3 ,geol4 ,mag4 7#ahhb71 p4 #efc4 ,footnote #abg3 ,op4 cit4 7#ahhf71 p4 #cai4 ,= our pres5t inquiry1 h[ev]1 ! *ief feature ( int]e/ 9 ^! discov]ies is ! recognition ( a gr\p ( volcanic rocks und]nea? ! qu>tzite4 ,?is gr\p 0 nam$ ! ,caldecote ,volcanic ,rocks by ,pr(essor ,lapwor?1 :o fir/ recogniz$ its nature & relations4 ,its rocks h be5 /udi$ by ,mr4 ,t4 ,h4 ,wall]#abh & ,mr4 ,f4 ,rutley1#abi & h be5 trac$ ^u a revis$ edition ( ! ,geological ,survey map by ,mr4 ,a4 ,/rahan4#acj ,!y consi/ ( a ?9 s]ies ( well-/ratifi$ tuffs app>5tly d]iv$ f &esitic lavas4 ,_! base is n se5 ow+ to ! fault :i* br+s d[n ! ,new ,r$ ,s&/one aga9/ !m4 ,!y are surm\nt$ by ! qu>tzite1 :i* at its base is conglom]atic & conta9s blocks ( ! tuff4 ,a mass ( qu>tz-felsite is possibly intrusive 9 ^! /rata1 & is associat$ ) a diabase-porphyrite4 ,9 ^! rocks1 b /ill m 9 ! %ales :i* ov]lie !m1 num]\s sills ( diorite & diabase occur4 ,! total ?ickness ( rocks f ! l[e/ visible "p ( ! ,caldecote volcanic s]ies to ! base ( ! ,coal-measures is probably betwe5 #bjjj & #cjjj feet4 ,footnote #abh3 ,op4 cit4 p4 #cbc4 ,footnote #abi3 ,op4 cit4 p4 #eeg4 ,footnote #acj3 ,geol4 ,mag4 7#ahhf71 p4 #edj4 ,9 ?is pap] full ref]5ces w be f\nd to ! previ\s pap]s on ! geology ( ! di/rict4 ,jukes _h recogniz$ t ! rocks bel[ ! coal-be>+ /rata 7 old] ?an ! ,upp] ,silurian1 p]haps old] ?an any ,silurian1 ,mem4 ,geol4 ,survey1 ,s\? ,/af=d%ire ,coal-field 7#ahei71 p4 #acd4 ,!re c be no d\bt z to ! geological position ( ! d>k fossilif]\s %ales & _! und]ly+ qu>tzite4 ,! fact t ! basem5t conglom]ate ( ! qu>tzite is p>tly made up ( ! und]ly+ volcanic s]ies may possibly m>k a wide diff]5ce ( age betwe5 !m1 & may indicate t ! eruption ( ! tuffs took place long be=e ,upp] ,cambrian "t4 ,on ! o!r h&1 ! tuffs h ! same /rike & angle ( dip ) ! qu>tzite1 & z ,pr(essor ,lapwor? admits1 ! break betwe5 !m may n be ( great mom5t4 ,x is at lea/ c]ta9 t ! intrusive sills ( ! di/rict are lat] ?an ! tuffs1 & lat] also ?an ! s$im5t>y ,cambrian gr\ps4 ,,book ,,iv ,,! ,,silurian ,,volcanoes ,,*apt] ,,xii ,,*>act]s ,,( ,,! ,,silurian ,,sy/em ,,9 ,,brita94 ,,! ,,ar5ig ,,volcanoes ,! ,l& & ,sea ( ,silurian "t--,classification ( ! ,silurian ,sy/em--,g5]al ,petrography ( ! ,silurian ,volcanic ,rocks--,i4 ,! ,eruptions ( ,ar5ig ,age4 ,! next great geological p]iod1 to :i* ,mur*ison gave ! "n ( ,silurian1 has 9 ,brita9 a full] record ?an ! p]iod :i* prec$$ x4 ,! rocks t tell its hi/ory are m v>i$ 9 orig9 & /ructure4 ,!y are display$ at ! surface ov] a f> wid] area1 &1 :at gives !m special int]e/ & value1 !y conta9 a mu* l>g] assemblage ( organic rema9s4 ,= ! imm$iate subject ( ! pres5t volume1 !y h likewise ! additional attraction t !y include a s+ul>ly complete & widespread volcanic *ronicle4 ,!y display 9 _m admirable sections ! pil$-up lavas & tuffs ( scores ( volcanoes1 scatt]$ all ov] ! ?ree k+doms1 f ! headl&s ( ,k]ry to ! hills ( ,lamm]muir4 ,!y ?us enable u to =m a tru] conception ( :at ! e>ly ,palozoic volcanoes 7 ?an is possible f ! m limit$ evid5ce furni%$ by ! ,cambrian sy/em4 ,at ! beg9n+ ( ! ,silurian p]iod mo/ ( ! area ( ! ,briti% ,isles lay "u ! sea4 ,b if we may judge f ! s$im5t>y /rata :i* repres5t ! floor ( t sea1 ! wat]1 dur+ mo/ ( ! "t1 0 ( no great dep?4 ,!re is evid5ce1 inde$1 t dur+ a "p ( ! p]iod ! sea 0 deep en\gh to admit ( ! accumulation ( wide tracts ( radiol>ian ooze1 ) b little admixture ( me*anical s$im5t4 ,b1 = ! mo/ "p1 s& & mud 7 drift$ f neighb\r+ l&s1 ! m important ( :i* probably lay to ! nor?1 ov] :at are n[ ! ,highl&s ( ,scotl& & ! nor? & nor?-we/ di/ricts ( ,irel&4 ,no g5]al *ange 9 topography or 9 physical conditions took place at ! close ( ,cambrian "t4 ,! old] era glid$ ins5sibly into ! new]1 unm>k$ by any su* cata/rophe z 0 once suppos$ to h int]v5$ at ! end ( ea* great geological p]iod4 ,!re are traces1 inde$1 ( slight local di/urbances1 b ^! only make ! g5]al gradual transition m m>k$4 ,( ! vegetation :i* cov]$ ! ,silurian l&s h>dly any?+ is kn[n4 ,traces ( lycopods & f]ns h be5 detect$1 & ^! probably =m$ ! *ief con/itu5ts 9 :at mu/ h be5 r a sombre & monoton\s flora4 ,! "* ( ! t]re/rial fauna is /ill hidd5 f u1 ?\gh we d "k t insects w+$ _! way ?r\gh ^? gre5 fl[]less =e/s1 & t scorpions likewise h>b\r$ !re4 ,t ^! primeval ara*noids 7 air-brea!rs is %[n by _! brea?+ /igmata2 & f ! fact t !y possess$ a well-develop$ poison-gl& & /+1 we may believe t !re 7 already liv+ at ! same "t o!r l&-animals1 possibly ( high] grade1 on :i* !y prey$4 ,b ( ^! ance/ral types no actual relics h yet be5 discov]$4 ,x is ! life ( ! sea-floor t has ma9ly be5 *ronicl$ among ! s$im5t>y =mations4 ,tak+ ! ,silurian sy/em z a :ole1 we f9d x to be ! repository ( a rem>kably v>i$ assemblage ( organisms4 ,among ! simpl] =ms1 ,radiol>ia des]ve especial notice1 f _! wide range 9 space & "t1 & ! comp>ative inde/ructibility ( ! highly-silice\s1 f9e-gra9$1 fl9ty /rata1 :i* h pres]v$ !m 9 abundance & h a wide di/ribution ov] ! ,briti% ,isles4 ,! ,graptolites1 s specially *>act]i/ic ( ! sy/em1 range entirely ?r\gh x1 & by _! successive diff]5ces ( specific & g5]ic =ms1 furni% a basis = ! division ( ! :ole s]ies ( rocks into m or less def9ite /ratigraphical zones4 ,h>dly less important = purposes ( correlation are ! ,trilobites :i* 9 ! ,silurian p]iod rea*$ ! culm9ation ( _! developm5t 9 reg>d to numb] ( species & g5]a4 ,^! int]e/+ ext9ct types ( cru/acean life mu/ h sw>m$ ov] "s p>ts ( ! sea-bottom1 = _! rema9s ab\nd 9 its h>d5$ silts4 ,! ,bra*iopods are likewise num]\sly repres5t$ among ,silurian /rata2 & s9ce ! v]tical range ( ! species is g5]ally n great1 !y s]ve z useful guides 9 fix+ /ratigraphical horizons4 ,lamellibran*s1 ,ga/]opods1 & ,cephalopods become increas+ly num]\s & v>i$ z we foll[ ! succession ( /rata f ! base to ! summit ( ! ,silurian sy/em4 ,t !re 7 fi%es also 9 ! ,silurian seas is prov$ by ! occurr5ce ( _! rema9s1 m p>ticul>ly 9 ! high] =mations4 ,f ! organic rema9s :i* h be5 pres]v$ 9 ! rocks1 x may be inf]r$ t ! animal life ( ! globe became m v>i$ 9 ,silurian "t2 high] types made _! appe>ance1 until v]tebrates took ! place ( pre-em95ce :i* !y h ev] s9ce ma9ta9$4 ,! volcanic activity t _h m>k$ ! passage ( ,cambrian "t 9 ,brita9 0 prolong$ into ! ,silurian p]iod4 ,9 ,nor? ,wales1 inde$1 x is cle> t ?\gh ! eruptions began 9 ! e>li] era ( geological hi/ory !y cont9u$ to be comp>atively feeble until !y broke out into full activity 9 ! succe$+ epo*4 ,!re is no hiatus or ess5tial diff]5ce betwe5 ! volcanic ph5om5a1 any m ?an !re is betwe5 ! s$im5t>y deposits1 ( ! two p]iods4 ,al?\gh x may be only ow+ to ! fact t ! ,silurian =mations come mu* m ext5sively to ! surface ( ! l& ?an ! und]ly+ ,cambrian are p]mitt$ to d1 yet x is at lea/ notewor?y t ! relics ( ,silurian volcanoes are spread ov] a f> wid] area ( ! ,briti% ,isles ?an ^? ( ! e>li] p]iod4 ,?r\gh\t a l>ge "p ( ,wales !y =m "s ( ! mo/ prom95t m\nta9s1 su* z ,cad] ,idris1 ! ,arans1 ,ar5ig ,fawr1 ,moel ,wyn1 ,moel ,siabod1 & ,sn[don4 ,!y rise into ! picturesque hill-gr\ps ( ! ,lake ,di/rict1 !y appe> at _m deta*$ places ?r\gh\t ! s\? ( ,scotl&1 & =m conspicu\s em95ces 9 ,c>rick4 ,9 ,irel& !y ab\nd all d[n ! ea/ side ( ! isl&1 & ev5 reappe> on ! f> we/]n headl&s ( ! ,d+le coa/-l9e4 ,to ! same pione]s1 by :om ! f\ndations ( our k ( ! ,cambrian volcanoes 7 laid1 we are indebt$ = ! fir/ broad outl9es ( ! hi/ory ( volcanic action 9 ,silurian "t4 ,! writ+s ( ,s$gwick & ,mur*ison1 b /ill m ! detail$ mapp+ ( ,de la ,be*e1 ,ramsay1 ,selwyn1 ,jukes1 & ! o!r memb]s ( ! ,geological ,survey1 h giv5 to ! ,silurian volcanic rocks ( ,wales a classic int]e/ 9 ! hi/ory ( geology4 ,to ^! lab\rs fur!r ref]5ce w be made 9 subsequ5t pages4#aca ,footnote #aca3 ,= ref]5ces to ! old] lit]ature see ante1 p4 #adb4 ,! am\nt ( mat]ial be+ s ample = ! compilation ( a record ( volcanic action 9 ,brita9 dur+ ,silurian "t1 x w be desirable to arrange x 9 /ratigraphical ord]4 ,= ?is purpose invaluable assi/ance is af=d$ by ! evid5ce ( organic rema9s1 :]eby ! :ole ,silurian sy/em has be5 subdivid$ into sections1 ea* *>act]iz$ ?r\gh\t ! :ole region by c]ta9 di/9ctive fossils4 ,! foll[+ tabul> /atem5t exhibits ! *ief /ratigraphical divisions ( ! sy/em1 & ! %ort black l9es 9 x m>k ! positions ( sep>ate volcanic plat=ms 9 ea* ( ! ?ree k+doms3-- ---------------------------------------- ---------------------------- ,engl& ,wales ,scotl&,irel& ---------------------------------------- ---------------------------- ,ludl[ ,gr\p 444 444 444 444 ,upp] ,silurian ,w5lock ,gr\p 444 444 444 --- ,ll&ov]y ,gr\p 8 444 444 444 ,bala & ,c>adoc ,gr\p --- --- --- --- ,l[] ,silurian ,ll&eilo ,gr\p --- --- --- --- ,ar5ig ,gr\p --- --- --- --- ---------------------------------------- ---------------------------- ,x w be mo/ conv5i5t1 foll[+ ! comb9$ /ratigraphical & geographical arrangem5t ( ?is table1 to discuss fir/ ! volcanic hi/ory ( ! ,l[] ,silurian p]iod z record$ 9 ea* ( ! ?ree k+doms1 & !n t ( ! ,upp] ,silurian4 ,i4 ,,! ,,eruptions ,,( ,,ar5ig ,,age i4 ,,m]ione?%ire ,plac+ ! upp] limit ( ! ,cambrian sy/em at ! top ( ! ,tremadoc gr\p1 we pass into ! records ( ano!r s]ies ( volcanic eruptions :i* m>k$ v>i\s epo*s dur+ ! ,silurian p]iod ov] ! area ( ! ,briti% ,isles4 ,! e>lie/ ( ^! volcanic episodes has left its memorials 9 "s ( ! mo/ impressive sc5]y ( ,nor? ,wales4 ,to ! picturesque =ms sculptur$ out ( ! lavas & a%es ( t e>ly "t1 we owe ! noble range ( cliffs & peaks t sweeps 9 a va/ semicircle ?r\gh ! heights ( ,cad] ,idris1 ,aran ,mawddwy1 ,ar5ig1 & ,moel ,wyn4 ,to ! ea/ o!r volcanic masses1 p]haps 9 "p coeval ) ^!1 rise f amid/ y\ng] =mations 9 ! gr\ps ( ! ,b]wyn & ,breidd5 ,hills1 & ! long ridges ( ! ,%elve & ,corndon c\ntry4 ,f> to ! s\?1 traces ( ,silurian volcanoes are met ) ne> ,buil?1 :ile /ill m remote are ! %eets ( lava & tuff int]/ratifi$ among ! ,l[] ,silurian rocks ( ,pembroke%ire1 & ^? :i* ext5d into ,skom] ,isl&4 ,! mo/ important ( ^! di/ricts is unque/ionably t ( ,m]ione?%ire4 ,9 ?is area1 z 0 po9t$ out 9 ! la/ *apt]1 ! eruptions c]ta9ly began be=e ! close ( ! ,cambrian p]iod1 = traces ( !m occur 9 ! ,tremadoc & ,l+ula ,flag gr\ps4 ,b bel[ ^! /rata1 9 ! va/ pile ( grits & conglom]ates ( ! ,h>le* anticl9e1 !re does n appe> to be any trace ( contemporane\s volcanic action4 ,at ! "t :5 ! ,geological ,survey maps ( ?is region 7 prep>$1 ! ,cambrian & ,l[] ,silurian rocks _h n be5 subdivid$ into ! v>i\s palontological gr\ps :i* are n[ recogniz$4 ,nor _h any attempt be5 made to sep>ate ! v>i\s k9ds ( contemporane\s igne\s masses f ea* o!r & f ! tuffs 9 s ext5sive & complicat$ a m\nta9-region4 ,! task und]tak5 by ! ,survey 0 beset ) difficulties1 "s ( :i* geologi/s1 furni%$ ) ! advantages ( a lat] "t1 c h>dly p]haps realize4 ,! imp]fections ( ! mapp+ 7 long ago recogniz$ by ! orig9al surveyors1 & v>i\s corrections ( !m 7 made f "t to "t4 ,fir/ ( all1 ! volcanic rocks1 :i* orig9ally _h be5 all mass$ "u "o col\r1 7 trac$ out sep>ately on ! gr\nd1 accord+ to _! /ructure & mode ( orig91 & 7 di/+ui%$ f ea* o!r on ! maps4#acb ,subsequ5tly divisional l9es 7 foll[$ out betwe5 "s ( ! l>g] /ratigraphical gr\ps1 ! maps & sections 7 /ill fur!r modifi$1 & ! results 7 summ$ up 9 ! volume on ! ,geology ( ,nor? ,wales4#acc ,b %ort ( actually resurvey+ ! :ole ( t rugg$ tract1 x 0 impossible to br+ ! maps abrea/ ( ! onw>d m>* ( sci5ce4 ,!y consequ5tly rema91 z a :ole1 v mu* z !y 7 "s ?irty or =ty ye>s ago4 ,footnote #acb3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #ie1 note4 ,footnote #acc3 ,"s ( ! modifications introduc$ are1 ,i ?9k1 to be regrett$1 = ! e>li] editions ( ! maps & sections are 9 c]ta9 respects m accurate ?an ! lat]4 ,on ?is po9t ,i concur ) ! criticism made by ,messrs4 ,cole & ,j5n+s1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlv4 7#ahhi71 p4 #dcf4 ,sir ,&rew ,ramsay1 9 8 great ,monograph on ! geology ( ,nor? ,wales1 has describ$ ! ,m]ione?%ire volcanic di/rict 9 consid]able detail4 ,he seems f9ally to h come to ! conclusion t ! eruptions ( t area 7 includ$ )9 ! ,ar5ig p]iod4#acd ,he %[s1 inde$1 t on ,rhobell ,fawr ! eject$ mat]ials lie directly on di/urb$ ,l+ula ,flags )\t ! int]v5tion ( ! ,tremadoc gr\p1 :i* is nev]!less pres5t 9 full developm5t 9 ! ne> neighb\rhood4#ace ,& 9 try+ to acc\nt = ?is rem>kable fact he evid5tly _h 9 8 m9d ! possibility t volcanic eruptions _h tak5 place long be=e z well z aft] ! beg9n+ ( ! deposition ( ! ,ar5ig grit & slates4#acf ,he seems ev5tually1 h[ev]1 to h look$ on ! ,rhobell ,fawr sections z exceptional & possibly to be acc\nt$ = by "s local di/urbance & intrusion ( eruptive rock4#acg ,he cle>ly recogniz$ t !re 7 two great epo*s ( volcanic activity dur+ ! ,silurian p]iod 9 ,wales1 "o belong+ to ! "t ( ! ,ar5ig1 ! o!r to t ( ! ,bala rocks1 & he po9t$ out t ! records ( ^! two p]iods are sep>at$ by a ?ick accumulation ( s$im5t>y /rata :i*1 be+ free f int]/ratifications ( contemporane\s igne\s rocks1 may be tak5 to indicate a long int]val ( quiesc5ce among ! subt]ranean =ces4#ach ,footnote #acd3 ,mem4 ,geol4 ,survey1 vol4 iii4 #bnd ed41 p4 #if4 ,footnote #ace3 ,! a%es & agglom]ates ( ,rhobell ,fawr c be se5 9 v>i\s places to re/ on ! highe/ memb]s ( ! ,l+ula ,flags4 ,see ,messrs4 ,cole & ,holl&1 ,geol4 ,mag4 7#ahij71 p4 #dea4 ,footnote #acf3 ,op4 cit4 p4 #gb4 ,footnote #acg3 ,he 0 dispos$ to reg>d ,rhobell ,fawr z "o ( ! great c5tres ( eruption ( ! di/rict4 ,see ,memoir ( ,a4 ,c4 ,ramsay1 p4 #ha1 & ,geology ( ,nor? ,wales1 #bnd edit4 p4 #ih4 ,footnote #ach3 ,op4 cit4 pp4 #ga1 #if1 #aje4 ,! l[] limit ( ! ,ar5ig rocks has be5 fix$ at a b& or b&s ( grit or conglom]ate 7,g>? grit7 :i* c be foll[$ ) "s slight int]ruptions all r\nd ! great dome ( ,cambrian /rata f ,llanegr9 on ! s\? to ! %ore at ,criccie? on ! nor?4 ,! volcanic gr\p d\btless lies1 g5]ally speak+1 above t basem5t plat=m4 ,b1 besides ! sections at ,rhobell ,fawr j ref]r$ to1 :]e ! volcanic mat]ials lie on ! ,l+ula ,flags1 ! same relation may1 ,i ?9k1 be obs]v$ on ! nor? flank ( ,cad] ,idris4 ,messrs4 ,cole1 ,j5n+s1 & ,holl& h come to ! conclusion t ! eruptions began at a r e>li] date ?an t assign$ to !m 9 ! ,survey ,memoirs1 & my own exam9ation ( ! gr\nd l$ me to accept _! conclusion4#aci ,i inf]r$ t ! e>lie/ dis*>ges 9 ! s\!rn "p ( ! region took place 9 ,cambrian "t1 at or possibly be=e ! close ( ! deposition ( ! ,l+ula ,flags1 & t int]mitt5t outbur/s occurr$ at _m int]vals dur+ ! "t :5 ! ,tremadoc & ,ar5ig rocks 7 deposit$4 ,footnote #aci3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlv4 7#ahhi71 p4 #dcf2 ,geol4 ,mag4 7#ahij71 p4 #ddg4 ,pres4 ,address ,geol4 ,soc4 #ahij1 p4 #ajg4 ,important confirmation ( ?is view ( ! ,cambrian age ( ! e>li] volcanic eruptions ( ! ,cad] ,idris region has rec5tly be5 obta9$ by ,messrs4 ,p4 ,lake & ,s4 ,h4 ,reynolds :o1 9 ! gr\nd int]v5+ betwe5 ! l[] slopes ( ,cad] ,idris & ,dolgelly1 h asc]ta9$ ! exi/5ce ( a m>k$ b& ( &esitic lava traceable = "s di/ance 9 ! upp] ,l+ula ,flags4 ,!y h also obs]v$ a high] volcanic gr\p repos+ ^u ! ,tremadoc /rata at ! top ( ! ,cambrian sy/em1 & consi/+ ( rhyolite ) rhyolite-tuffs4#adj ,footnote #adj3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 lii4 7#ahif71 p4 #eaa4 ,"s ( ! mo/ /up5d\s memorials ( ! e>li] eruptions are to be se5 9 ! huge m\nta9 mass ( ,rhobell ,fawr 7#bdjc feet74 ,!y consi/ ma9ly ( agglom]ates & tuffs1 "o ( ! mo/ rem>kable v>ieties ( :i* is di/+ui%$ by its abundant scatt]$ cry/als ( hornbl5de & ( augite4 ,! fragm5ts ( rock includ$ 9 ^! rocks are scori & lumps ( v>i\s lavas1 especially basaltic & tra*ytic &esites4 ,! tuffs become f9] t[>ds ! top ( ! m\nta9 :]e !y are int]leav$ ) grits4 ,among ! pyrocla/ic mat]ials occasional lavas 7basaltic &esites7 occur :i* may be contemporane\s /reams1 b mo/ ( ! lava-=m rocks appe> to be intrusive4 ,!y include dol]ites 7augite-aphanites71 basaltic &esites1 & tra*ytic &esites4#ada ,footnote #ada3 ,pr(4 ,cole1 ,geol4 ,mag4 7#ahic71 p4 #ccg4 ,illu/ration3 ,fig4 #df4--,section across ,rhobell ,fawr4#adb ,l ,l1 ,l+ula flags2 t1 tuffs & a%y slates2 s1 slates & grits2 ,f ,f1 ,ar5ig volcanic s]ies2 ,d1 dol]ite4 ,footnote #adb3 ,aft] ,messrs4 ,cole & ,holl&1 ,geol4 ,mag4 7#ahij71 p4 #dej4 ,! mat]ials f ! ,rhobell ,fawr volcano are cle>ly di/+ui%able f ^? ( ! ,ar5ig volcanoes 9 ! neighb\rhood4 ,! latt] beg9 to make _! appe>ance among ! black slates at ! base ( ! nor!rn declivities ( ,cad] ,idris1 & ext5d upw>d ?r\gh t m\nta9 into ! c\ntry beyond4 ,an upp] limit to ?is volcanic gr\p is n easily traceable2 p>tly1 no d\bt1 f ! gradual cessation ( ! eruptions & p>tly f ! want ( any m>k$ & p]si/5t /ratigraphical horizon ne> ! top ( ! gr\p4 ,sir ,&rew ,ramsay1 inde$1 ref]s to ! well-kn[n b& ( pisolitic iron-ore z ly+ at or ne> to ! top ( ! ,ar5ig rocks4#adc ,!re c be no d\bt1 h[ev]1 t ! volcanic int]calations cont9ue f> above t horizon 9 ! s\!rn "p ( ! di/rict4 ,footnote #adc3 ,mem4 ,geol4 ,survey1 vol4 iii4 #bnd edit4 pp4 #bdi1 #bej4 ,9 spite ( ! ext5t to :i* ! volcanic masses ( ! ,ar5ig p]iod h be5 cov]$ by lat] ,palozoic =mations1 x is /ill possible to fix approximately ! nor!rn1 we/]n1 & s\!rn limits ( ! di/rict ov] :i* ! a%es & lavas 7 di/ribut$4 ,^! mat]ials die out z !y are trac$ s\?w>ds f ,cad] ,idris & nor?-we/w>ds f ,tremadoc4#add ,! greate/ diamet] ( gr\nd across :i* !y are n[ cont9u\sly traceable is ab\t tw5ty-eight miles4 ,!y atta9 _! greate/ ?ickness1 upw>ds ( #ejjj feet1 9 ,aran ,mawddwy1 :i* rises f _! mo/ ea/]ly esc>pm5t4 ,we may !re=e inf] t ! ma9 v5t or v5ts lay some:]e 9 t direction4 ,! noble range ( precipices fac+ we/w>ds %[s h[ greatly ! limits ( ! volcanic rocks h be5 r$uc$ by d5udation4 ,!re c be little d\bt t at lea/ ! f9] tuffs ext5d$ we/w>ds z f> z a l9e drawn f ,tremadoc to ,llanegr9--t is1 "s fifte5 miles or m beyond ! cliffs ( ,aran ,mawddwy1 ?us /ret*+ across mu* ( ! site ( :at is n[ ! great ,h>le* anticl9e4 ,footnote #add3 ,op4 cit4 p4 #if4 ,?is compact1 well-def9$ volcanic area1 9 spite ( ! faults :i* trav]se x & ! di/urb$ positions into :i* its rocks h be5 ?r[n1 is1 9 _m respects1 "o ( ! simple/ & mo/ easily /udi$ among ! ,palozoic =mations ( ?is c\ntry4 ,its ma9 features h be5 del9eat$ on ! maps ( ! ,geological ,survey & h be5 describ$ 9 ,sir ,&rew ,ramsay's monograph4 ,b ^! publications _c be reg>d$ z m ?an a fir/ broad1 ?\gh ma/]ly1 outl9e ( ! :ole subject4 ,!re is an ample field = fur!r & m m9ute rese>* :]e91 ) ! l>g] & bett] ,ordnance maps n[ available1 & ) ! advantage ( ! num]\s mod]n petrographical aids1 a m exhau/ive acc\nt may be giv5 ( ! di/rict4 ,! :ole volcanic succession f base to summit is laid b>e 9 innum]able magnific5t natural sections along ranges ( hills = a di/ance ( "s =ty miles1 & a c>eful /udy & re-mapp+ ( x c\ld n fail to add greatly to our k ( ! e>ly hi/ory ( volcanic action4#ade ,footnote #ade3 ,! excell5t pap]s ( ,pr(essor ,cole1 ,mr4 ,j5n+s1 ,mr4 ,holl&1 ,mr4 ,g4 ,j4 ,williams1 ,mr4 ,p4 ,lake & ,mr4 ,s4 ,h4 ,reynolds are illu/rations ( h[ ! publi%$ "w ( ! ,geological ,survey may be modifi$ & elaborat$4 ,accord+ to ! obs]vations ( ! ,geological ,survey1 ! ,ar5ig volcanic rocks ( ,m]ione?%ire naturally arrange !mselves 9 ?ree great b&s1 ea* ( :i* is describ$ z tol]ably p]si/5t ?r\gh\t ! :ole di/rict3--#a/1 a l[] s]ies ( a%es & conglom]ates1 sometimes #ccjj feet ?ick 7,aran ,mawddwy72 #bnd1 a middle gr\p ( fel/ones & porphyries1 consi/+ p>tly ( true contemporane\s lava-/reams & p>tly ( intrusive %eets1 & rea*+ a ?ickness ( #aejj feet2 #crd1 an upp] s]ies ( fragm5tal deposits l t b5ea?1 ! extreme ?ickness ( :i* is #hjj feet 7,ar5ig m\nta974 ,a re-mapp+ ( ! gr\nd on ! six-in* maps w\ld1 no d\bt1 %[ _m local dep>tures f ?is g5]al s*eme4 ,! pyrocla/ic memb]s ( ?is volcanic s]ies pres5t _m features ( int]e/ bo? to ! field-geologi/ & ! petrograph]2 b !y h z yet be5 only p>tially /udi$4 ,at ! s\!rn end ( ! di/rict x is rem>kable to :at a l>ge ext5t ! e>lie/ eruptions mu/ h be5 m]e gase\s explosions1 ) ! dis*>ge ( comp>atively little volcanic mat]ial4 ,_m ( ! tuffs t are int]/ratifi$ ) black slates 78 ,l+ula ,flags7 at ! foot ( ! long nor!rn slope ( ,cad] ,idris1 consi/ ma9ly ( black-slate fragm5ts l ! slate und]nea?1 ) a v>iable proportion ( grey volcanic du/4 ,illu/ration3 ,fig4 #dg4--,section at ! ,slate ,qu>ry1 ,p5rhyn ,gwyn1 nor? slopes ( ,cad] ,idris4 ,! accompany+ section 7,fig4 #dg7 repres5ts ! arrangem5t ( ! rocks expos$ at ! ,slate ,qu>ry ( ,p5rhyn ,gwyn4 ,ab\t #ej feet ( black slate 7a7 are !re se51 ! b$d+ 9 :i* dips ,s4 at #bj1 :ile ! cleavage is incl9$ t[>ds ,s4,w4 at a slightly high] angle4 ,! next #bj feet ( slate 7b7 are di/+ui%$ by _m int]calations ( slate-tuff or breccia1 v>y+ f less ?an an in* to ?ree feet 9 ?ickness4 ,an intrusive %eet ( &esite 7c71 :i* v>ies f two or ?ree to t5 feet 9 ?ickness1 & is /rongly cellul> 9 ! c5tre1 int]rupts ! slates & h>d5s !m4 ,above ?is sill ! indurat$ slate & tuff 7d71 conta9+ abundant felsp> cry/als1 pass "u a fl9ty porphyritic felsite 7e7 or exce$+ly f9e tuff1 enclos+ a b& ( granul> tuff4 ,beyond ?is b& ! black slates ) _! seams ( tuff cont9ue up ! hill & include a %eet ( slaggy felsitic lava #h or #aj feet ?ick4 ,?is section1 af=d+ z x does ! fir/ glimpse ( ! volcanic hi/ory ( ,cad] ,idris1 indicates a cont9u$ s]ies ( feeble gase\s dis*>ges1 probably f "o or m small v5ts1 :]eby ! black clay on ! sea-floor 0 bl[n out1 ! fragm5ts fall+ back aga9 to be cov]$ up "u a gradual accumulation ( simil> d>k mud4 ,by degrees1 z ! vig\r ( eruption increas$1 lava-du/ & deta*$ felsp> cry/als 7 eject$1 & ev5tually lava rose to ! surface & fl[$ ov] ! sea-bottom 9 ?9 %eets4 ,b else:]e1 & likewise at a lat] p]iod 9 ?is same s\!rn "p ( ! di/rict1 ! fragm5tal dis*>ges consi/$ ma9ly ( volcanic mat]ial4 ,sir ,&rew ,ramsay has describ$ ! co>se conglom]ates compos$ ( subangul> & r\nd$ blocks ( diff]5t porphyries1 sometimes #bj in*es 9 diamet]1 emb$d$ 9 a f9e matrix ( simil> mat]ials4 ,! true nature ( ! compon5t fragm5ts 9 ^! rocks has /ill to be work$ out4 ,messrs4 ,cole & ,j5n+s h notic$ t ! grey volcanic du/ ( ! old] slate-tuff ( ,cad] ,idris is se5 "u ! microscope to ab\nd 9 p>ticles ( scoriace\s &esite-glass1 n[ conv]t$ into a gre5 palagonite4#adf ,_! inve/igations %[ t :ile ! same k9ds ( volcanic rocks cont9ue to be met ) f ! bottom to ! top1 nev]!less !re is an increase 9 ! acid "* ( ! lapilli z ! section is trac$ upw>ds4 ,"s ( ! fragm5ts consi/ ( col\rless devitrifi$ glass1 ) pieces ( pumice1 z if d]iv$ f ! break+ up ( previ\sly-=m$ tuffs4 ,o!rs resemble qu>tz-&esites1 rhyolites1 or tra*ytes1 :ile 9 at lea/ "o in/ance1 some:at l[ d[n 9 ! section1 qu>tz-gra9s ) intrud$ mat]ial po9t to ! exi/5ce ( "s fairly acid & vitre\s lava4#adg ,on ! s\? side ( ,llyn ,cau1 t is t[>ds ! top ( ! volcanic gr\p1 ,i f\nd a co>se agglom]ate ) blocks ( felsitic lavas1 sometimes ?ree feet across 7see ,fig4 #dh74 ,?is gradual increase ( acidity 9 ! lapilli ( ! tuffs f9ds an int]e/+ confirmation 9 ! contemporane\s lava-%eets to :i* ,i %all aft]w>ds allude4 ,footnote #adf3 ,qu>t4 ,j\rn4 ,geol4 ,soc41 vol4 xlv4 7#ahhi71 p4 #dbd2 ,geol4 ,mag4 7#ahij71 p4 #ddg4 ,footnote #adg3 ,op4 cit4 p4 #dbi4 ,a tuff ly+ bel[ ! iron/one ne> ,cross ,foxes1 ea/ ( ,dolgelly1 likewise conta9s fragm5ts ( tra*ytic lavas4 ,"o ( ! mo/ noticeable features 9 ! tuffs ( ?is volcanic gr\p is ! great abundance ( entire & brok5 cry/als disp]s$ ?r\gh !m4 ,^! cry/als h c]ta9ly n be5 =m$ 9 situ1 b 7 dis*>g$ f ! v5ts z "p ( ! volcanic du/4 ,!y usually consi/ ( felsp> :i*1 at lea/ 9 ! s\!rn portion ( ! di/rict1 appe>s g5]ally to be plagioclase4 ,frequ5t ref]5ce to ^! cry/als z evid5ce ( volcanic explosions may be f\nd 9 ! publications ( ! ,survey4 ,n[h]e c !y be bett] se5 ?an 9 ! black slate-tuffs ( ,cad] ,idris4 ,!y are !re :ite1 m or less kaol9iz$1 & z !y lie disp]s$ ?r\gh ! black base1 !y give ! rock a deceptive resemblance to "s d>k porphyry4 ,! l>ge cry/als ( hornbl5de & augite abundantly scatt]$ ?r\gh mu* ( ! tuff ( ,rhobell ,fawr h be5 already ref]r$ to4 ,9 ! c5tral p>ts ( ! di/rict ?ick b&s ( a%es 7 mapp$ by ! ,survey1 & describ$ z consi/+ almo/ :olly ( volcanic mat]ials1 b conta9+ occasional ?9 b&s ( slate :i* suffice to m>k pauses 9 ! eruptions1 :5 ord9>y s$im5t 0 /rewn ov] ! sea-bottom4 ,9 ! ,cad] ,idris gr\nd1 on ! o!r h&1 int]/ratifications ( non-volcanic mat]ial are ( su* frequ5t recurr5ce z to %[ t !re1 in/ead ( con/ant & vigor\s dis*>ges accumulat+ a va/ pile ( a%es1 ! eruptions foll[$ ea* o!r aft] int]vals ( suffici5t duration to all[ ( ! usual d>k s$im5t spread+ = a dep? ( _m feet ov] ! sea-bottom4 ,"o ( ! mo/ int]e/+ deposits ( ^! int]ludes ( quiesc5ce is t ( ! pisolitic iron/one & its accompany+ /rata on ! nor? front ( ,cad] ,idris 7i 9 ,fig4 #dh74 ,a co>se pumice\s conglom]ate ) l>ge slag-l blocks ( &esite & o!r rocks1 se5 ne> ,llyn-y-,gadr1 passes upw>d into a f9e blui% grit & %ale1 among :i* lies ! b$ ( pisolitic 7or r oolitic7 iron/one :i* is s widely diffus$ ov] ,nor? ,wales4 ,! f9ely-oolitic /ructure ( ?is b& is obvi\sly orig9al1 b ! sub/ance 0 probably deposit$ z c>bonate ( lime "u quiet conditions ( precipitation4 ,! pres5ce ( num]\s small ,l+ul 9 ! rock %[s t molluscan life fl\ri%$ on ! spot at ! "t4 ,! iron exi/s 9 ! ore ma9ly z magnetite1 ! orig9al calcite or aragonite hav+ be5 fir/ replac$ by c>bonate ( iron1 :i* 0 subsequ5tly brok5 up s z to leave a residue ( m9ute cubes ( magnetite4#adh ,footnote #adh3 ,messrs4 ,cole & ,j5n+s1 op4 cit4 p4 #dbf4 ,above ! iron/one "s m blue & black %ale & grit pass "u a co>se volcanic conglom]ate l t bel[1 ly+ at ! base ( ! high precipice ( ,cad] ,idris4 ,h5ce ?is int]calat$ gr\p ( s$im5t>y /rata m>ks a pause 9 ! dis*>ge ( a%es & lavas1 dur+ :i* ! peculi> conditions ( s$im5tation indicat$ by ! iron/one spread ov] at lea/ ! s\!rn "p ( ! volcanic area4 ,"s few miles to ! ea/1 :]e ! iron/one has be5 excavat$ ne> ,cross ,foxes1 ! b& is aga9 f\nd ly+ among tuffs & grits full ( volcanic lapilli4 ,betwe5 a l[] & an upp] b& ( tuff 9 ! ,ar5ig volcanic gr\p ! ,maps & ,memoirs ( ! ,geological ,survey di/+ui% a c5tral zone ( felspa?ic porphyry1 :i* atta9s a maximum ?ickness ( #aejj feet 7see ,fig4 #dh74 ,f ,sir ,&rew ,ramsay's descriptions1 x is cle> t he recogniz$ 9 ?is zone bo? intrusive & extrusive %eets1 & t ! latt]1 :]e ?icke/1 7 n to be reg>d$ z "o mighty lava-fl[1 b r z ! result ( successive outp\r+s1 ) occasional int]vals m>k$ by ! int]calation ( b&s ( slate or ( tuff4 ,to a c]ta9 ext5t ! intrud$ %eets are sep>at$ on ! map f ! contemporane\s lavas2 b ?is has be5 done only 9 a broad & sket*y way4 ,"o ( ! mo/ important1 & at ! same "t mo/ difficult1 tasks yet to be accompli%$ 9 ?is di/rict is ! sep>ation ( ! rocks :i* 7 probably p\r$ out at ! surface f ^? t 7 inject$ und]nea? x4 ,my own trav]ses ( ! gr\nd h conv9c$ me t good evid5ce ( sup]ficial outfl[s may be f\nd 9 tracts :i* h be5 mapp$ z entirely intrusive2 :ile1 on ! o!r h&1 "s ( ! s-call$ lavas may m probably be ( ! nature ( sills4 ,illu/ration3 ,fig4 #dh4--,sket*-section across ,cad] ,idris4 /1 slates & tuffs & a%y slates2 s1 slates & grits2 i1 iron/one2 b1 volcanic breccias2 a1 slaggy &esitic & m basic lavas2 e1 microgranite or eurite2 f1 felsites2 d1 gre5/one 7dol]ites1 diabases1 etc474 ,! petrography ( ! rocks1 moreov]1 /ill requires mu* /udy4 ,among ! s-call$ felspa?ic porphyries ( ! ,survey maps a consid]able v>iety ( texture1 /ructure & composition w d\btless be detect$4 ,9 ! ,descriptive ,catalogue ( ,rock-,specim5s 9 ! ,museum ( ,practical ,geology 7#crd edit41 #ahfb7 ! rocks t =m ! lava-/reams ( ,ll&eilo age1 9 ,m]ione?%ire1 are nam$ fel/one1 felsp>-porphyry1 fel/one-porphyry1 felspa?ic-porphyry1 & calc>e\s amygdaloid4 ,! mo/ int]e/+ feature :i* my own slight p]sonal acqua9tance ) ! region has br\ght be=e me is ! cle> evid5ce ( a succession f comp>atively basic lavas 9 ! l[] "p ( ! gr\p to mu* m acid masses 9 ! high] "p4 ,9 ! ,survey map num]\s %eets ( intrusive gre5/one are %[n trav]s+ ! ,l+ula ,flags1 ,tremadoc slates1 & l[] "p ( ! volcanic gr\p along ! nor!rn slopes ( ,cad] ,idris4 ,! true intrusive nature ( mu* ( ?is mat]ial is cle>ly e/abli%$ by transgressive l9es ( junction & by contact-metamorphism1 z well z by ! di/9ctive cry/all9e texture ( ! rocks !mselves4 ,b ! surveyors 7 evid5tly puzzl$ by "s p>ts ( ! gr\nd4 ,sir ,&rew ,ramsay speaks ( ! great mass ( problematical vesicul> & sometimes calc>e\s rock :i* is 9 places almo/ a%y-look+4 ,aft] sev]al oscillations ( op9ion1 he seems to h come f9ally to ! conclusion t ?is vesicul> mat]ial1 :i* occurs also 9 ! upp] "p ( ! m\nta91 passes into1 & _c be sep>at$ f1 ! und\bt$ intrusive gre5/ones4#adi ,footnote #adi3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #cf2 see also pp4 #ca1 #cb4 ,! true solution ( ! difficulty w be f\nd1 ,i believe1 9 ! recognition ( a gr\p ( scoriace\s lavas among ^! gre5/ones4 ,! pres5ce ( a cellul> /ructure might n be suffici5t to demon/rate t ! rocks 9 :i* x appe>s are true lava-b$s1 = su* a /ructure is f> f unkn[n bo? among dykes & sills4 ,b 9 ! pres5t case !re is o!r corroborative te/imony t "s ( ^! ,cad] ,idris amygdaloids 7 really p\r$ out at ! surface4 ,bel[ ,llyn-y-,gadr--! d>k t>n at ! foot ( ! va/ wall ( ,cad] ,idris--! b$s ( co>se volcanic conglom]ate 7b 9 ,fig4 #dh71 to :i* ,i h already allud$1 are l>gely compos$ ( blocks ( ! vesicul> gre5/ones on :i* !y lie4 ,^! gre5/ones1 moreov]1 h _m ( ! mo/ /rik+ *>act]i/ics ( true lavas 7a 9 ,fig4 #dh74 ,!y are extraord9>ily cellul>2 _! upp] surfaces sometimes pres5t a mass ( bomb-l slags ) fl[-/ructure1 & ! vesicles are n infrequ5tly arrang$ 9 r[s & b&s along ! dip-planes4 ,a microscopic exam9ation ( two slides cut f ^! rocks %[s !m to be ( a tra*ytic or &esitic type1 ) porphyritic cry/als ( a kaol9iz$ felsp> emb$d$ 9 a microlitic gr\ndmass4 ,! rocks are mu* impregnat$ ) calcite1 :i* fills _! vesicles & ramifies ?r\gh _! mass4 ,a few miles to ! ea/ "s rem>kable felsitic rocks take ! place ( ^! vesicul> lavas imm$iately bel[ ! pisolitic iron ore4 ,i h n det]m9$ satisfactorily _! relations to ! surr\nd+ rocks1 & 9 p>ticul> am unc]ta9 :e!r !y are int]b$d$ lavas or intrusive %eets4 ,dr4 ,f4 ,h4 ,hat* f\nd t _! microscopic *>act]s %[ a close resemblance to ! soda-felsites describ$ by him f ! ,bala s]ies ( ! s\?-ea/ ( ,irel&4 ,! slopes ( ,cad] ,idris are p>tly obscur$ ) debris1 f above :i* rises ! great precipit\s face =m$ by ! esc>pm5t ( porphyry1 "h intrusively int]pos$ among ! ,ar5ig volcanic rocks4 ,?is enorm\s sill w be ref]r$ to a little fur!r on 9 connection ) ! o!r intrusive %eets ( ! region4 ,! rem>kably cellul> rock :i* =ms ! peak ( ,cad] ,idris is col\r$ on ! ,survey map z an intrusive sill ( gre5/one1 :i* 9 ! ,memoir is said to alt] ! contigu\s slates & to appe> to cut across !m diagonally4 ,i am dispos$1 h[ev]1 to ?9k t ^! appe>ances ( intrusion are deceptive4 ,on ! s\!rn declivity ( ! m\nta9 ?is rock pres5ts "o ( ! mo/ curi\s /ructures to be se5 9 ! :ole di/rict4 ,its surface displays a mass ( sph]oidal or pill[-%ap$ blocks aggregat$ toge!r1 ea* hav+ a t5d5cy to divide int]nally into prisms :i* div]ge f ! outside t[>ds ! c5tre4#aej ,"s portions are extremely slaggy1 & r\nd ^! m solid portions f9ely cry/all9e p>ts are drawn1 sugge/ive r ( free motion at ! surface ?an ( ! conditions "u :i* a subt]ranean sill mu/ be =m$4 ,! idea occurr$ to me on ! gr\nd t :ile ! b& ( rock m>k$ z gre5/one on ! map is probably1 9 ! ma91 an int]/ratifi$ lava1 !re may nev]!less be basic intrusions along its c\rse1 z 9 ! l[] "p ( ! m\nta94 ,! m9ute /ructure ( ?is amygdaloid1 z reveal$ by ! microscope1 %[s x to be an epidiorite :]e9 ! hornbl5de1 p>amorphic aft] augite1 has be5 aga9 p>tially alt]$ along ! m>g9s into *lorite4 ,footnote #aej3 ,?is peculi> /ructure ( ! m basic ,ar5ig lavas1 :]e ! rock looks z if built up ( irregul>ly-sph]oidal1 sack-l or pill[-%ap$ blocks1 w be aga9 ref]r$ to 9 connection ) ! ,ar5ig 7& ,ll&eilo7 lavas ( ,scotl& & ,irel&4 ,x appe>s to be widely di/ribut$1 & especially 9 connection ) ! occurr5ce ( radiol>ian *]ts4 ,! black slate above ! ,cad] ,idris amygdaloid w\ld1 9 a simil> position 9 ,scotl&1 be associat$ ) su* *]ts1 b ^! h n yet be5 notic$ at ?is locality4 ,) ! sph]oidal int]nally-radiat+ prismatic /ructure ( ! ,cad] ,idris rock1 comp>e t ( ! lava at ,acica/ello already notic$ on p4 #bf4 ,! highe/ lavas ( ,cad] ,idris1 =m+ ! ridge to ! s\? ( ,llyn ,cau1 are sep>at$ f ! amygdaloid j describ$ by a ?ick zone ( black slate ) ?9 a%y int]calations1 beyond :i* comes ! co>se volcanic agglom]ate already ref]r$ to z conta9+ blocks ( felsite a y>d or m 9 diamet]4 ,^! lavas are true felsites1 sometimes beautifully sph]ulitic & exhibit+ abundant fl[-/ructure1 l "s ( ! felsites ( ! next or ,bala volcanic p]iod4#aea ,! petrography ( ^! rocks /ill rema9s to be work$ out4 ,footnote #aea3 ,messrs4 ,cole & ,j5n+s1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlv4 7#ahhi71 p4 #dcj4 ,f ! exam9ation ( slices prep>$ f a few ( ! felsites ( ! ,dolgelly di/rict1 ,dr4 ,hat* obs]v$ a /rik+ diff]5ce betwe5 _! *>act]s & ^? ( ! ,cambrian felsites ( ,ca]n>von%ire4 ,! porphyritic con/itu5t is n[ no long] qu>tz1 b felsp> 7plagioclase71 & ! rocks belong1 n to ! rhyolitic1 b r to ! less acid tra*ytes1 p]haps ev5 to ! &esites4 ,! volcanic s]ies ( ,cad] ,idris sweeps nor?w>d ?r\gh ! *a9 ( ,aran & ,ar5ig1 & !n curves we/w>d ?r\gh ! gr\p ( ,manod & ,moelwyn1 beyond :i* x rapidly dies out4 ,9 its c\rse ( ab\t #de miles x und]goes consid]able v>iation1 z may be se5 by comp>+ a section ?r\gh ,moelwyn ) t ?r\gh ,cad] ,idris already giv54 ,accord+ to ! rese>*es ( ,mr4 ,j5n+s & ,mr4 ,williams1#aeb ! ma9 mass ( volcanic mat]ial 9 ! nor!rn "p ( ! region consi/s ( fragm5t>y rocks v>y+ 9 texture f agglom]ates into f9e tuffs1 b %[+ "s diff]5ces 9 ! succession ( b$s 9 diff]5t localities4 ,footnote #aeb3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia71 p4 #cfh4 ,! ,tremadoc gr\p ( /rata cle>ly und]lies ! volcanic s]ies ( ^! m nor!rly tracts4 ,b x conta9s1 s f> z appe>s1 no int]calation ( volcanic mat]ial4 ,! inf]5ce may ?us be drawn t ! eruptions began 9 ! ,cad] ,idris di/rict1 & did n ext5d into t ( ,manod & ,moelwyn until aft] ! beg9n+ ( ! ,ar5ig p]iod4 ,above ! ,tremadoc gr\p lies ! well-m>k$ & p]si/5t b&1 ab\t #ac feet ?ick1 kn[n z ! ,g>? grit1 :i* has be5 already ref]r$ to z a conv5i5t base-l9e to ! ,ar5ig gr\p4 ,illu/ration3 ,fig4 #di4--,section across ! ,moelwyn ,range4#aec #a1 ,tremadoc ,gr\p2 #b1 ,g>? or ,ar5ig grit 7base ( ,ar5ig gr\p72 #c1 ,ar5ig slates1 etc42 #ca1 ,l[] slate b&2 #cb1 ,middle slate b&2 #cc1 ,upp] slate b&2 #da1 ,l[] agglom]ate2 #db1 ,middle agglom]ate2 #dc1 ,upp] agglom]ate2 #e1 ,ll&eilo gr\p2 ,g1 ,granite boss ( ,moel tan y ,grisiau4 ,footnote #aec3 ,aft] ,messrs4 ,j5n+s & ,williams1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia71 p4 #cga1 & ,horizont4 ,sect4 ,geol4 ,surv4 ,%eet #bh4 ,9 ?is nor!rn di/rict1 among ! s$im5ts :i* ov]lie ! ,g>? grit1 lay]s ( f9e tuff beg9 to make _! appe>ance1 :i* nor? ( ,cwm ,or?9 ?ick5 out into a consid]able mass betwe5 ! grit & ! l[e/ ( ! great agglom]ates4 ,^! tuffs1 :i* m>k ! beg9n+ ( ! volcanic eruptions ( ! di/rict1 are foll[$ by a b& ( slate :i* 9 "s places has yield$ a ,l+ula1 ,or?is ,c>ausii1 & a ,tetragraptus1 & po9ts to an int]val ( quiesc5ce 9 ! volcanic hi/ory4 ,we n[ ent] ^u an enorm\s ?ickness ( agglom]ates & tuffs sep>at$ by sev]al b&s ( slate4 ,tak+ advantage ( ! slaty int]calations1 ,messrs4 ,j5n+s & ,williams h divid$ ?is great accumulation ( fragm5t>y volcanic mat]ial into ?ree b$s 7,fig4 #di74 ,! matrix ( ! agglom]ates is compact & pale1 s z to resemble & to h be5 call$ fel/one1 b %[+ its fragm5t>y nature on wea!r$ surfaces4 ,! blocks imb$d$ 9 ?is pa/e range up to sometimes z mu* z #aa feet 9 l5g? by #d feet 9 wid?4 ,_! m9ute petrographical *>act]s h n be5 /udi$1 b ! blocks are /at$ to consi/ = ! mo/ "p ( slaty & s*i/ose fragm5ts mix$ ) r\nd$ pebbles ( f9e-gra9$ 'fel/one4' ,!y are heap$ toge!r z 9 true agglom]ates4 ,9 ! upp] agglom]ate1 fragm5ts ( cleav$ slate conta9+ ,l+ula h be5 obs]v$4 ,! "n ( fel/one is re/rict$ by ,messrs4 ,j5n+s & ,williams to c]ta9 f9e-gra9$ v>ieties ( rock1 ( :i* a ?9 b& lies at ! base ( ! l[] agglom]ate1 :ile ano!r ( consid]ably great] importance occurs 9 ! middle ( ! upp] agglom]ate4 ,^! b&s consi/ ( a f9e compact gre5i% base1 & wea!r ) a dull :ite cru/2 sometimes1 z 9 ! ?ick] %eet1 a column> /ructure %[s itself4 ,:e!r ^! rocks are to be reg>d$ z lavas or sills1 or ev5 z f9] v>ieties ( tuff1 is a "q t awaits fur!r inquiry4 ,b x is cle>1 f ! inve/igation ( ! two obs]v]s j cit$1 t ! pyrocla/ic con/itu5ts mu/ va/ly prepond]ate 9 ! volcanic s]ies ov] ! nor!rn "p ( ! region4 ,all ^! rocks1 :e!r co>se or f9e-gra9$1 appe> to be r acid 9 composition1 & no evid5ce has yet be5 obta9$ ( a sequ5ce among !m f a m basic to a m acid s]ies1 z 9 ,cad] ,idris4 ,! highe/ agglom]ate b$ ( ! ,manod & ,moelwyn area is cov]$ by slates :i* conta9 ,ll&eilo graptolites4 ,9 ?is way1 by means ( palontological evid5ce1 ! upw>d & d[nw>d limits ( ! ,ar5ig volcanic s]ies 9 ?is "p ( ,wales are def9itely fix$4 ,h>dly any in=mation has yet be5 obta9$ z to ! situation & "* ( ! v5ts f :i* ! lavas & a%es ( ,m]ione?%ire 7 dis*>g$4 ,9 ! c\rse ( ! mapp+ ( ! gr\nd1 ! ,geological ,survey recogniz$ t1 z ! greate/ bulk ( erupt$ mat]ial lies 9 ! ea/]n & s\?-ea/]n p>ts ( ! region1 ! *ief c5tres ( emission 7 to be look$ = 9 t qu>t]1 & t possibly "s ( ! intrusive masses :i* break ?r\gh ! rocks we/ ( ! great esc>pm5t may m>k ! site ( v5ts1 su* z ,tyddyn-rhiw1 ,gelli-llwyd-fawr1 ,y-,foel-ddu1 ,rhobell ,fawr1 & c]ta9 bosses ne> ,ar5ig4#aed ,! di/ribution ( ! volcanic mat]ials indicates t !re 7 c]ta9ly m ?an "o active crat]4 ,:ile ! s\?w>d ?ick5+ ( ! :ole volcanic gr\p po9ts to "s specially vigor\s volcano 9 t qu>t]1 ! notable ?9n+ away ( ! upp] tuffs s\?w>d & _! great dep? ab\t ,ar5ig sugge/ _! hav+ come f "s v5t 9 ?is neighb\rhood4 ,on ! o!r h&1 ! l[] tuffs are abs5t at ,ar5ig1 :ile on ,aran ,mawddwy1 only n9e miles to ! s\?1 !y rea* a dep? ( #cjjj feet4 ,/ill f>!r to ! s\? ^! volcanic ejections become m & m divid$ by int]calat$ b&s ( ord9>y s$im5t4 ,"o ( ! mo/ important volcanoes ( ! region evid5tly rose some:]e 9 ! neighb\rhood ( :at is n[ ,aran ,mawddwy4 ,!re seems reason to surmise t ! sites ( ! *ief v5ts n[ lie to ! ea/ & s\? ( ! great esc>pm5t1 buri$ "u ! ?ick s$im5t>y =mations :i* cov] all t region4 ,footnote #aed3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #ih2 see also pp4 #dd1 #ed1 #eh1 #ga4 ,if we are ju/ifi$1 on /ratigraphical & petrographical gr\nds1 9 connect+ ! l[e/ volcanic rocks ( ! ,b]wyn range ) ^? ( ,m]ione?%ire1 we may speculate on ! exi/5ce ( a gr\p ( subm>9e v5ts1 com+ into eruption at successive int]vals1 f "s epo* dur+ ! p]iod ( ! ,l+ula ,flags up to t ( ! ,bala rocks1 & cov]+ ) lavas & a%es a space ( sea-bottom at lea/ =ty miles f ea/ to we/ by m ?an tw5ty miles f nor? to s\?1 or r\ghly1 an area ( "s #hjj squ>e miles4#aee ,footnote #aee3 ,! ,b]wyn ,hills1 h[ev]1 w be describ$ 9 lat] pages z a di/9ct volcanic di/rict4 ,besides ! mat]ials eject$ to ! surface1 ! anci5t volcanic region ( ,m]ione?%ire 0 m>k$ by ! intrusion ( a va/ am\nt ( igne\s rock betwe5 & across ! b$d+-planes ( ! /rata deep und]gr\nd4 ,"o ( ! mo/ prom95t features ( ! ,geological ,survey map is ! great numb] ( sills repres5t$ z runn+ ) ! g5]al /rike ( ! /rata1 especially betwe5 ! top ( ! ,h>le* grits & ! base ( ! volcanic s]ies4 ,on ! nor? side ( ! valley ( ! ,mawdda*1 betwe5 ,b>m\? & ,rhaiadr ,mawdda*1 9 a di/ance ( twelve miles ! ,survey mapp$ m ?an #aej intrusions v>y+ f a few y>ds to ne>ly a mile 9 l5g?4#aef ,?is zone ( sills is equally m>k$ on ! s\? side ( ! valley4 ,x may be trac$ all r\nd ! ,h>le* anticl9e until x dies out1 z ! b$d$ masses also d1 t[>ds ,t[yn on ! s\? & ab\t ,tremadoc on ! nor?4 ,footnote #aef3 ,mem4 ,geol4 ,surv4 vol4 iii4 p4 #bf4 ,! pres5ce ( su* a zone ( intrusive %eets at ! base ( an anci5t volcanic s]ies is a *>act]i/ic feature 9 ! geology ( ,brita94 ,x is met ) aga9 & aga9 among ! ,palozoic sy/ems1 & appe>s on a /rik+ scale 9 association ) ! ,t]ti>y basaltic plateaux ( ,antrim & ! ,inn] ,hebrides4 ,b n[h]e1 p]haps1 is x m /rongly develop$ ?an b5ea? ! ,ar5ig gr\p ( lavas & tuffs 9 ,nor? ,wales4 ,abundant z are ! protrusions m>k$ on ! ,geological ,survey map1 !y fall %ort ( ! actual numb] to be met ) on ! gr\nd4 ,inde$1 to repres5t !m z !y really are w\ld require labori\s survey+ & ! use ( maps on a f> l>g] scale ?an "o in* to a mile4 ,! va/ majority ( ^! sills are basic rocks1 or1 9 ! old & conv5i5t t]m9ology1 gre5/ones4 ,^? ( ! ,cad] ,idris di/rict h be5 exam9$ by ,messrs4 ,cole & ,j5n+s1 :o f\nd t1 not)/&+ ! consid]able alt]ation ev]y:]e %[n by ! abundant epidote & calcite1 ! co>s] v>ieties may be recogniz$ z hav+ orig9ally be5 dol]ites approa*+ gabbro1 ) a well-develop$ ophitic "*1 ! g5]al range ( /ructure be+ f dol]ites )\t oliv9e & aphanites to &esitic rocks ) an orig9ally glassy matrix4#aeg ,dr4 ,hat* confirm$ ?is diagnosis f slides prep>$ f my specim5s4 ,! ophitic /ructure is usually *>act]i/ic & well pres]v$1 9 spite ( ! alt]ation indicat$ by epidote1 *lorite1 uralite1 & leucox5e4 ,footnote #aeg3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlv4 7#ahhi71 p4 #dcb4 ,t ?is zone ( gre5/one sills belongs to ! p]iod ( ! ,m]ione?%ire volcanoes may be reasonably conclud$4 ,! way 9 :i* !y foll[ ! l9e ( ! great esc>pm5t1 _! almo/ entire abs5ce f ! ,cambrian dome to ! we/1 _! cessation z ! ov]ly+ lavas & tuffs die out lat]ally1 & _! sc>city above ! l[] "p ( ! volcanic gr\p1 seem to indicate _! close relation%ip to t gr\p4 ,moreov]1 t !y mu/ h be5 z a :ole lat] ?an ! ma9 "p ( ! lavas & tuffs may be inf]r$ f _! position4 ,! molt5 mat]ial ( :i* !y 7 =m$ c\ld h>dly h =c$ its way betwe5 & across ! /rata unless egress to ! surface _h be5 imp$$ by "s ?ick ov]ly+ mass4 ,! gre5/ones may !re=e be reg>d$ z lat]al emanations f funnels ( m basic lava t[>ds ! close ( ! volcanic p]iod4 ,possibly "s at lea/ ( ! highly slaggy & vesicul> b&s to :i* ,i h ref]r$ may repres5t portions ( ?is mat]ial1 :i* actually fl[$ out z /reams ( lava at ! surface4 ,b !re is likewise evid5ce ( ext5sive intrusion ( m silice\s rocks4 ,on ! ,geological ,survey map1 besides ! num]\s gre5/ones1 v>i\s %eets ( felspa?ic porphyry are repres5t$ z runn+ ) ! g5]al /rike ( ! region1 b "h & !re break+ across x4 ,"o ( ! mo/ rem>kable ( ^! acid sills is t :i*1 9 ! noble precipice ( ,cad] ,idris1 has a ?ickness ( ab\t #aejj feet & a l5g? ( ?ree or f\r miles4 ,x is %[n on ! map to be transgressive across o!r rocks1 &1 z se5 on ! gr\nd1 x ma9ta9s ! uni=mity ( texture :i* is *>act]i/ic r ( %eets t h solidifi$ und]nea? ?an ( ^? :i* h congeal$ ) comp>ative rapidity at ! surface4 ,on a fre% fracture ! rock pres5ts a pale blui%-grey t9t1 becom+ yell[i% or br[ni% z ! result ( wea!r+4 ,its texture is f9ely granul>1 ) occasional dissem9at$ felsp>s4 ,"u ! microscope a section ( x 0 f\nd by ,dr4 ,hat* to exhibit ! *>act]i/ic /ructure ( a microgranite1 a confus$ holocry/all9e aggregate ( qu>tz & felsp>1 ) a few porphyritic felsp>s4 ,messrs4 ,cole & ,j5n+s h propos$ to revive = ?is rock ,daubuisson's "n ,eurite4#aeh ,footnote #aeh3 ,mr4 ,h>k] speaks ( ! rock z a granophyre4 ,a simil> rock occurs at a l[] horizon among ! ,l+ula ,flags at ,gelli-llwyd-fawr1 two miles s\?-we/ ( ,dolgelly1#aei & mu* microgranite has be5 inject$ along ! slopes above ,tyddyn-mawr4 ,footnote #aei3 ,messrs4 ,cole & ,j5n+s1 op4 cit4 p4 #dce4 ,! *ronological relation ( ^! acid %eets & bosses to ! m basic intrusions has n yet be5 def9itely det]m9$4 ,t "s ( !m may h solidifi$ 9 v5ts & may h be5 directly connect$ ) ! protrusion ( ! lat] or m highly silice\s lavas is n at all improbable4 ,o!rs aga9 w\ld seem to belong to a mu* lat] geological p]iod ?an ! ,ar5ig volcanoes4 ,9 ?is late s]ies ! well-kn[n boss ( ,tan-y-grisiau ne> ,fe/9iog %\ld probably be includ$4 ,?is mass ( eruptive mat]ial 0 mapp$ by ! ,geological ,survey z intrusive sy5ite4 ,x has be5 m rec5tly exam9$ & describ$ by ,messrs4 ,j5n+s & ,williams z a granitite4#afj ,^! obs]v]s h notic$ n only t x intrusively trav]ses & alt]s ! ,tremadoc gr\p1 b t its intrusion appe>s to h tak5 place subsequ5t to ! cleavage :i* affects ! ,ll&eilo z well z old] =mations4 ,?is granitic boss has ?us probably no connection ) ! ,ar5ig volcanoes1 b belongs to a lat] p]iod 9 ! volcanic hi/ory ( ! ,pr9cipality4 ,footnote #afj3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia71 p4 #cgi4 ,! rem>kable sc>city ( dykes 9 ! volcanic di/ricts ( ,wales has be5 notic$ by m ?an "o obs]v]4 ,among ! intrusive gre5/ones ( ,m]ione?%ire "s occasionally assume ! dyke =m1 & ?r\gh ! agglom]ates & tuffs ( ,rhobell ,fawr dykes ( oliv9e-diabase h work$ _! way4 ,9 ! ,fe/9iog di/rict v>i\s alt]$ &esitic dykes h be5 not$4 ,b !re has be5 no widespread fissur+ ( ! gr\nd & uprise ( lava 9 ! r5ts1 su* z may be se5 9 ! ,ar*an gneiss1 & 9 ! lat] ,palozoic1 b /ill m 9 ! ,t]ti>y volcanic regions4 ,?is feature becomes all ! m notable :5 x is view$ 9 connection ) ! great developm5t ( sills1 & ! evid5ce !reby af=d$ ( widespread & extremely vigor\s subt]ranean volcanic action4 ,9 ! ,m]ione?%ire region !re c]ta9ly 0 a long p]iod ( quiesc5ce betwe5 ! close ( ! ,ar5ig & ! beg9n+ ( ! ,bala eruptions4 ,moreov]1 no evid5ce has yet be5 f\nd t active v5ts ev] aga9 appe>$ 9 t di/rict1 ! subt]ranean en]gy at its next outbur/ hav+ brok5 out f>!r to ! ea/ & nor?4 ,9 ,anglesey1 h[ev]1 :]e1 z ,i %all po9t out1 !re is pro( ( contemporane\s tuffs among ! ,ar5ig rocks1 x is possible t a cont9u\s record ( volcanic action may yet be trac$ f ,ar5ig well onw>d into ,bala "t4 ii4 ,,%rop%ire ,ab\t #ce miles to ! s\?-ea/ ( ! great volcanic range ( ,m]ione?%ire a small tract ( ,ar5ig rocks rises f amid/ y\ng] =mations1 & =ms ! picturesque c\ntry betwe5 ,*ur* ,/oke & ,pontesbury4 ,mur*ison 9 8 excell5t acc\nt ( ?is di/rict cle>ly recogniz$ ! pres5ce ( bo? intrusive & int]/ratifi$ igne\s rocks4#afa ,! gr\nd has 9 rec5t ye>s be5 m c>efully work$ ov] by ,mr4 ,g4 ,h4 ,morton#afb & ,pr(essor ,lapwor?4#afc ,footnote #afa3 ,silurian ,sy/em 7#ahci71 *ap4 xix42 ,siluria1 #d? edit4 7#ahfg71 pp4 #bf1 #di4 ,footnote #afb3 ,proc4 ,liv]pool ,geol4 ,soc4 x4 7#ahed71 p4 #fb4 ,footnote #afc3 ,geol4 ,mag4 7#ahhg71 p4 #gh4 ,at ! top ( ! ,ar5ig gr\p ( ?is di/rict lies a zone ( well-/ratifi$ &esitic tuff & breccia 7,/apeley ,a%71 ) frequ5t int]calations ( %ales1 & occasionally fossilif]\s4#afd ,!re is ?us satisfactory pro( ( contemporane\s eruptions at int]vals dur+ ! accumulation ( ! lat] ,ar5ig s$im5ts4 ,t !re 7 also outfl[s ( lava is %[n by ! pres5ce ( %eets ( augite- & hyp]/h5e-&esite4 ,^! volcanic int]calations =m m>k$ ridges1 hav+ a g5]al nor!rly tr5d4 ,!y are fold$ ov] ! broad laccolitic ridge ( ,corndon1 on ! ea/ side ( :i* !y are ?r[n into a syncl9al tr\gh1 s t successive p>allel outcrops ( !m are expos$4 ,accord+ to ! mapp+ ( ! ,geological ,survey !y are ?icke/ t[>ds ! we/1 & become m split up ) int]calat$ s$im5ts z !y range ea/w>d4 ,footnote #afd3 ,pr(4 ,lapwor? & ,mr4 ,w4 ,w4 ,watts1 ,proc4 ,geol4 ,assoc4 xiii4 7#ahid71 pp4 #cag1 #ccg4 ,volcanic eruptions 9 ?is ,%rop%ire region cont9u$ f ! ,ar5ig into ! ,bala p]iod4 ,!y are m>k$ among ! ,ll&eilo /rata by occasional tuffs & by two massive b$s ( volcanic grit1 describ$ by ,mur*ison1#afe b !y appe> to h be5 r less vigor\s 9 ! int]val repres5t$ by ?is subdivision ( ! ,silurian sy/em4 ,^? ( ,bala "t gave =? abundant dis*>ges ( a%1 ( :i* ! l[e/ accumulation1 locally kn[n z ! ,hagley ,a%1 consi/s ( &esitic detritus4 ,occasional lay]s ( tuff are int]calat$ 9 ! ov]ly+ ,hagley ,%ales1 above :i* comes an important b& call$ ! ,:itt]y ,a%1 consi/+ ( &esitic & rhyolitic breccias & conglom]ates1 f9e a%es ) curi\s sph]ulitic or pisolitic /ructures1 & b&s ( %ale (t5 fossilif]\s4#aff ,x is evid5t t ! eruptions ( ! ,%elve di/rict came f indep5d5t v5ts 9 t neighb\rhood1 & nev] rea*$ ! importance ( ! great volcanoes ( ,ar5ig age 9 ,montgom]y%ire or ( ,bala age 9 ,ca]n>von%ire4 ,footnote #afe3 ,silurian ,sy/em1 p4 #bbi4 ,footnote #aff3 ,messrs4 ,lapwor? & ,watts1 op4 cit4 p4 #cah4 ,illu/ration3 ,fig4 #ej4--,section across ! anticl9e ( ,corndon4#afg ,a1 ,ar5ig flags & %ales2 ,b1 &esites & tuffs2 ,c1 intrusive dol]ite4 ,footnote #afg3 ,aft] ,pr(4 ,lapwor? & ,mr4 ,watts1 op4 cit4 p4 #cdb4 ,num]\s dykes & sills trav]se ! rocks ( ?is di/rict4 ,!y consi/ *iefly ( hyp]/h5e-dol]ite4 ,!y appe> to belong to a mu* lat] p]iod ?an ! int]/ratifi$ volcanic s]ies2 at lea/ "s ( !m are f\nd alt]+ ! ,p5tam]us lime/ones1 & ^! mu/ be lat] ?an ! ,ll&ov]y rocks4#afh ,! mo/ important sill is t :i* =ms ,corndon1 ! c5tral igne\s mass ( ! di/rict4 ,?is body ( dol]ite 0 asc]ta9$ by ,mr4 ,watts n to be a boss b a laccolite1 :i* w$ges out bo? t[>ds ! nor?-we/ & s\?-ea/1 z %[n 9 ,fig4 #ej4 ,footnote #afh3 ,op4 cit4 p4 #cci4 ,six miles to ! nor? ( ! ,%elve & ,corndon di/rict ! ,breidd5 ,hills rise on ! bord] ( ,%rop%ire & ,montgom]y%ire1 & include a mass ( volcanic mat]ial belong+ to a di/9ct area ( eruption4 ,9 ! ridge t ext5ds = ab\t ?ree & a half miles ?r\gh ,moel-y-golfa & ,middlet[n ,hill1 a syncl9al tr\gh ( volcanic rocks lies ^u %ales1 :i* f _! fossils h be5 plac$ 9 ! ,bala gr\p4 ,! volcanic s]ies appe>s to exce$ #ajjj feet 9 ?ickness4 ,! l[e/ "p ( x on ,moel-y-golfa consi/s ( &esitic lavas ab\t #djj feet ?ick1 foll[$ by tuffs & volcanic conglom]ates4 ,! lavas resemble "s ( ! porphyrites ( ! ,old ,r$ ,s&/one1 & conta9 two =ms ( pyrox5e--"o rhombic1 probably en/atite1 & ! o!r monocl9ic augite4 ,!re are likewise consid]able masses ( intrusive rock1 :i* are v>ieties ( diabase or dol]ite4#afi ,footnote #afi3 ,see ,mr4 ,w4 ,w4 ,watts on ! ,igne\s & ,associat$ ,rocks ( ! ,breidd5 ,hills1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xli4 7#ahhe71 p4 #ecb4 iii4 ,,scotl& ,f ! c5tre ( ,engl& we mu/ 9 imag9ation transport ourselves into ! ,s\!rn ,upl&s ( ,scotl&1 :]e a widely di/ribut$ s]ies ( ,silurian volcanic rocks has be5 pres]v$4 ,x 01 until rec5tly1 suppos$ t ! ,silurian sy/em nor? ( ! ,twe$ conta9s no contemporane\sly erupt$ volcanic rocks4 ,yet1 z f> back z ! ye> #ahfj1 ,i po9t$ to ! abundant exi/5ce ( volcanic detritus 9 ^! /rata ?r\gh\t ! s\!rn c\nties z a probable indication ( volcanic activity at ! "t & 9 ! area )9 :i* ! /rata 7 deposit$4#agj ,"s ye>s lat]1 :5 ! microscope _h be5 introduc$ z an aid to field-geology1 ,i slic$ "s ( ! ,silurian s$im5ts ( t region & f\nd !m1 p>ticul>ly c]ta9 %ales & grits ( ,m(fatdale1 to conta9 a l>ge admixture ( p]fectly fre% unworn felsp> cry/als1 :i* ,i felt tol]ably c]ta9 _h be5 suppli$ by volcanic explosions4 ,z no trace1 h[ev]1 _h !n be5 detect$ ( an int]calat$ volcanic gr\p 9 any "p ( ! ,silurian s]ies ( ! s\? ( ,scotl&1 ,i us$ at t "t to speculate on ! possibility ( ! volcanic detritus hav+ be5 w9d-borne f ! volcanoes ( ! ,lake ,di/rict4 ,i _h at t "t no suspicion t its s\rce 0 r to be s\ght "u my feet4 ,! pres5ce ( volcanic rocks und]nea? ! upl&s ( ! s\? ( ,scotl& w\ld h be5 a welcome explanation ( ! frequ5t felspa?ic composition ( _m ( ! ,silurian greywackes & %ales ( t region1 & p>ticul>ly ! abundance ( &esitic & felsitic fragm5ts 9 !m4 ,footnote #agj3 ,trans4 ,roy4 ,soc4 ,ed94 xxii4 7#ahfj71 p4 #fcf4 ,x _h be5 long kn[n t ! ,scotti% ,silurian =mations1 besides hav+ und]gone ext5sive plication1 h also be5 inject$ by protrusions ( igne\s mat]ial ( v>i\s k9ds4 ,! intrusive "* ( _m ( ^! is s obvi\s t a simil> orig9 0 attribut$ ev5 to ^? bosses :i* c\ld n be prov$ to be intrusive4 ,rec5t "w ( ! ,geological ,survey1 h[ev]1 & m especially ! num]\s & c>eful trav]ses ( my fri5d & colleague ,mr4 ,pea*1 h reveal$ ! unlook$-= & important fact t a l>ge numb] ( ^! suppos$ intrusions are really portions ( a volcanic gr\p br\ght up on ! cre/s ( anticl9al folds1 & laid b>e by d5udation4 ,?is gr\p c be trac$ = at lea/ #ajj miles f nor?-ea/ to s\?-we/ ov] a belt ( c\ntry sometimes #cj miles broad4 ,its orig9al limits _c be asc]ta9$1 b !y obvi\sly exce$$ ^? )9 :i* ! rocks c n[ be se54 ,nev]!less ! pres5t b\nd>ies embrace an area ( ne>ly #bjjj squ>e miles4 ,?is ,palozoic volcanic region is ?us "o ( ! mo/ ext5sive 9 ! ,briti% ,isles4 ,ow+1 h[ev]1 to ! con/ant plication ( ! /rata1 & ! wide space :i* ! ov]ly+ s$im5t>y deposits are ?us made to cov]1 ! volcanic gr\p only comes occasionally into view1 & ?us occupies b a m]e fraction ( ! sup]ficial ext5t ( ! region ov] :i* its scatt]$ outcrops appe>4 ,^! exposures1 sometimes only a few squ>e y>ds 9 ext5t1 may always be look$ = :]e ! anticl9al folds br+ up a suffici5tly l[ portion ( ! ,silurian sy/em2 !y prove t a va/ volcanic floor und]lies ! visible ,l[] ,silurian grits & %ales ov] ! l5g? & bread? ( ! ,s\!rn ,upl&s ( ,scotl&4 ,)\t anticipat+ details :i* w prop]ly appe> 9 ! (ficial ,memoirs ( ! ,geological ,survey1 ,i may briefly indicate ! visible b\nd>ies ( ! volcanic gr\p1 & ref] to "s ( ! localities :]e x may be/ be se54 ,! mo/ ea/]ly po9ts :]e x has be5 recogniz$ by ,mr4 ,pea* /& on ! cre/s ( "s %>p anticl9al folds ne> ,/4 ,m>y's ,lo* & ne> ,leadburn & ,w9k/one 9 ,peebles%ire4 ,f>!r we/w>ds x appe>s at _m places along ! nor!rn bord] ( ! ,silurian t]ritory1 z at ,romanno ,bridge1 ,wrae1 ,kilbu*o1 ,cult] ,wat] & ,ab+ton1 ! l5g? & bread? ( ea* exposure dep5d+ p>tly on ! bread? ( ! anticl9e & p>tly on ! dep? to :i* x has be5 cut d[n by d5udation4 ,ne> ,sanquh> ! volcanic s]ies op5s out = a bread? ( m ?an a mile1 & is se5 at int]vals across ! wild moorl&s ( ,c>rick1 until f ! ,/9*> valley x wid5s out seaw>d & occupies mu* ( ! coa/-l9e ( ,ayr%ire betwe5 ,girvan & ! m\? ( ,lo* ,ryan4 ,x probably rises aga9 along a fold ne> ,portpatrick1 & x is se5 at v>i\s po9ts along ! s\!rn bord]s ( ! ,silurian upl&s1 z ne> ,ca/le-,d\glas1 at ,gl5kiln1 ,bell ,craig ne> ,m(fat1 & ! head ( ,ettrickdale4 ,! be/ sections are ^? expos$ along ! coa/ to ! nor? & s\? ( ,ballantrae4 ,:5 t gr\nd 0 fir/ exam9$ by ! ,geological ,survey1 ! hypo!tical views 9 reg>d to metamorphism already ref]r$ to 7 9 full asc5dant1 & ! rocks 7 mapp$ on ! same g5]al pr9ciples z ^? :i* _h be5 foll[$ 9 ,wales4 ,pr(essor ,bonney1 h[ev]1 a few ye>s lat] recogniz$ ! true igne\s nature ( _m ( ! rocks4 ,he f\nd among !m porphyrite lavas & agglom]ates :i* he reg>d$ z ( ,old ,r$ ,s&/one age1 likewise intrusive s]p5t9es & gabbros4#aga ,footnote #aga3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxiv4 7#ahgh71 p4 #gfi4 ,! volcanic rocks ( ?is wide di/rict include bo? lavas & _! pyrocla/ic accompanim5ts1 z well z intrusive sills & bosses ( v>i\s mat]ials4 ,!y h rec5tly be5 /udi$ by ,mr4 ,j4 ,j4 ,h4 ,teall1 & full descriptions ( !m by him w appe> 9 a =?com+ volume ( ! ,memoirs ( ! ,geological ,survey4 ,he has asc]ta9$ t ?\gh g5]ally m or less decompos$1 ! lavas w\ld be class$ by ,g]man petrograph]s z diabases & diabase-porphyrites4 ,! =m] are compact d>k-gre5 non-porphyritic rocks1 (t5 conta9+ num]\s small sph]ical amygdales2 :ile ! latt] are m>k$ly porphyritic1 enclos+ l>ge ph5ocry/s ( m or less alt]$ plagioclase1 (t5 measur+ half an in* across4 ,^! two gr\ps ( rock are connect$ by transitional v>ieties4 ,!y 7 probably1 9 ! fir/ in/ance1 compos$ ( plagioclase1 augite1 iron-ores1 & a v>iable quantity ( imp]fectly cry/alliz$ int]/itial matt]4 ,"s ( ^! rocks closely resemble 9 outw>d appe>ance ! &esites 7porphyrites7 ( ! ,old ,r$ ,s&/one ( ! di/rict n _m miles to ! nor?1 t is1 f9e purpli%-r$ rocks ) a compact base ?r\gh :i* porphyritic felsp>s are abundantly scatt]$4 ,occasionally !y are m>k$ly slaggy1 & %[ ev5 a ropy surface1 :ile ! breccias associat$ ) !m conta9 blocks ( simil> slag4 ,illu/ration3 ,fig4 #ea4--,/ructure 9 f9ely-amygdaloidal diabase lava1 s\? ( m\? ( ,/9*> ,riv]1 ,ayr%ire4 ,! f9e dots & circles m>k ! l9es ( amygdales4 ,b ! mo/ *>act]i/ic ext]nal feature ( ^! lavas is _! t5d5cy to assume irregul>ly-elliptical1 sack-l or pill[-%ap$ =ms4 ,on a wea!r$ face !y sometimes look l a pile ( p>tially-fill$ sacks heap$ on ea* o!r1 ! prom95ces ( "o project+ into correspond+ holl[s 9 ! next4 ,! g5]al aspect ( ?is /ructure is %[n 9 ,fig4 #ab1 :i* repres5ts a face ( rock ab\t eight feet high & six feet broad4 ,! rocks exhibit+ ?is peculi>ity are usually f9ely amygdaloidal1 & x may be obs]v$ t ! vesicles are gr\p$ 9 l9es p>allel to ! out] surface ( ! pill[-l block 9 :i* !y occur4 ,! diagram 9 ,fig4 #ea repres5ts 9 gr\nd-plan a surface ab\t twelve feet squ>e on ! %ore imm$iately to ! s\? ( ! m\? ( ! ,riv] ,/9*>4 ,9 ! he>t ( ! sph]oids enclos$ fragm5ts ( o!r lavas are sometimes obs]vable4 ,?is s+ul> /ructure has already 7p4 #ahd7 be5 ref]r$ to z /rik+ly display$ 9 a rock at ! top ( ,cad] ,idris4 ,x is f\nd 9 d>k basic lavas probably ( ,ar5ig age1 :i* w be aft]w>ds ref]r$ to z occurr+ along ! s\!rn flanks ( ! ,scotti% ,highl&s & also 9 ! nor? ( ,irel&4 ,x has be5 obs]v$ by ,mr4 ,teall among ! rocks ( ! ,liz>d1 & has be5 describ$ z occurr+ 9 ,saxony & ,cali=nia4#agb ,9 ^! diff]5t localities x is associat$ ) jasp]s & *]ts1 "s ( :i* conta9 abundant ,radiol>ia4 ,! same /ructure has be5 f\nd among ! v>iolitic diabases ( ,mont ,g5vre1#agc & likewise 9 "s mod]n lavas1 z 9 t ( ,acica/ello already ref]r$ to 7ante1 p4 #bf74 ,footnote #agb3 ,mr4 ,j4 ,j4 ,h4 ,teall1 ,roy4 ,geol4 ,soc4 ,cornwall1 #ahid1 p4 #c4 ,mr4 ,l4 ,ransome1 ,bull4 ,dep>t4 ,geol4 ,univ]sity ( ,cali=nia1 vol4 i4 p4 #ajf4 ,footnote #agc3 ,messrs4 ,cole & ,gregory1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvi4 7#ahij71 p4 #caa4 ,illu/ration3 ,fig4 #eb4--,view ( ,knockdolian ,hill f ! ea/4 ,! volcanic agglom]ates & breccias1 9 ! s\?-we/ ( ,ayr%ire1 atta9 a great developm5t 9 sev]al c5tres probably at or ne> ! orig9al volcanic v5ts4 ,!y pres5t sev]al di/9ct petrographical types4 ,! rem>kable neck-l hill ( ,knockdolian 9 ! ,/9*> ,valley is made ( a co>se breccia compos$ ma9ly ( angul> pieces ( dull greyi%-gre5 f9e-gra9$ diabase4 ,! breccias & agglom]ates ( ,b5nane ,head 9 "s p>ts consi/ l>gely ( brok5-up %ales1 fl9ty mud/one1 black radiol>ian fl9t or *]t1 & abundant fragm5ts ( &esites & felsites4 ,9 o!r p>ts ! volcanic mat]ial pr$om9ates1 includ+ angul> & subangul> fragm5ts ( v>i\s some:at basic lavas1 lumps ( vesicul> slag & pieces ( pumice4 ,"h & !re mu* calcite is diffus$ ?r\gh ! matrix 9 /r+s1 ve9s & pat*es1 :i* enclose ! lapilli4 ,! agglom]ate nor? ( ,l5dalfoot possesses a gre5i%1 some:at s]p5t9\s matrix1 ?r\gh :i* imm5se numb]s ( tabul> felsp> cry/als are scatt]$4 ,simil> cry/als also occur abundantly 9 emb$d$ blocks ( "o ( ! purpli% diabase-porphyrites1 :i* occurs 9 mass on ! %ore & inl&1 & closely resembles ! rock ( ,c>ne?y 9 ! ,old ,r$ ,s&/one volcanic s]ies ( ! ,p5tl& ,hills4 ,yet ano!r & v di/9ct type ( agglom]ate is to be se5 on ! ,ma9s ,hill s\?-ea/ ( ,ballantrae4 ,x is a co>se rock1 enclos+ blocks up to a y>d or m 9 diamet]1 ( a f9e compact purpli% porphyrite1 ) l>ge cry/als ( plagioclase & small] ones ( augite4 ,9 "s places imm5se numb]s ( ! small lapilli 9 ! matrix consi/ ( an extremely f9e vesicul> pumice4 ,small p]fect & l>g] brok5 cry/als ( augite are likewise abundant 9 "s ( ! gre5i%1 m basic p>ts ( ! mass4 ,^! gre5i% s]p5t9\s p>ts & ! num]\s augite cry/als po9t to ! explosion ( "s tol]ably basic pyrox5ic lava4 ,a simil> d>k gre51 almo/ black1 rock1 ) augite cry/als1 :i* sometimes measure a qu>t] ( an in* 9 diamet]1 occurs ne> ,sanquh> 9 ,ni?sdale4 ,x pres5ts a close resemblance to ! agglom]ate ( ,rhobell ,fawr1 already allud$ to4 ,s f> z ^! ,scotti% agglom]ates h yet be5 microscopically exam9$1 !y h be5 f\nd to be compos$ ( cry/als1 cry/al-fragm5ts1 & lapilli d]iv$ p>tly f lavas simil> to ^? above describ$1 & p>tly f felsitic & o!r rocks :i* h n yet be5 obs]v$ "h 9 ! =m ( lavas4 ,! f9] tuffs %[ likewise a consid]able range ( composition4 ,accord+ to ,mr4 ,pea*'s obs]vations along ! s\?-ea/]n p>ts ( ! volcanic area1 ! eject$ mat]ials h consi/$ l>gely ( f9e du/ 7probably 9 great measure felsitic71 :i* t[>ds ! nor?-ea/ is gradually int]leav$ ) ord9>y s$im5t till ! a%y "* disappe>s4 ,z ,i h already rem>k$1 !re is reason to believe t ! ov]ly+ greywackes & %ales d]iv$ "p ( _! mat]ial ei!r directly f volcanic explosions or f ! attrition ( banks ( lavas & tuffs expos$ to d5udation4 ,b besides ! int]/ratifi$ lavas & fragm5tal rocks !re occur num]\s intrusive masses :i* are s intimately associat$ ) ! volcanic s]ies t !y may ) little hesitation be reg>d$ z =m+ "p ( x4 ,!y consi/ ( v>i\s gabbros & s]p5t9es1 :i* are especially develop$ :]e ! volcanic s]ies comes out 9 greate/ =ce 9 ! s\?-we/ ( ,ayr%ire4 ,!y also include m acid intrusions :i*1 z 9 ! case ( ! rock ( ,byne ,hill1 ne> ,girvan1 ev5 assume ! *>act]s ( granite4 ,! dy+ out ( ! volcanic mat]ial t[>ds ! nor?-ea/ probably indicates t ! v5ts ( ! p]iod lay r 9 ! c5tral or s\?-we/]n p>ts ( ! di/rict4 ,un=tunately1 ! limit$ ext5t ( ! exposures ( ! rocks makes x a hopeless task to se>* = traces ( ^! v5ts ov] by f> ! l>ge/ "p ( ! area4 ,!re are two localities1 h[ev]1 :]e ! se>* may be made ) bett] prospect ( success4 ,"o ( ^! is a tract to ! nor? ( ,sanquh> 9 ,ni?sdale1 :i* /ill requires to be /udi$ 9 detail ) ref]5ce to ! sequ5ce & /ructure ( its volcanic rocks4 ,! o!r area is t s\?-we/]n "p ( ,ayr%ire :i* has be5 already cit$ z display+ s l>ge a developm5t ( ! volcanic s]ies4 ,"h ! coa/-sections reveal ! int]calation ( fossilif]\s b&s :i* %[ ! true /ratigraphical horizons ( ! lavas & tuffs4 ,"u ,b5nane ,head1 ,pr(essor ,lapwor? "s ye>s ago f\nd1 9 c]ta9 h>d5$ black %ales1 a gr\p ( graptolites :i* m>k an und\bt$ ,ar5ig plat=m4#agd ,rec5tly ! gr\nd has be5 c>efully re-exam9$ by ,messrs ,pea* & ,horne1 :o h detect$ a numb] ( o!r fossilif]\s zones :i* confirm & ext5d previ\s obs]vations4 ,!y h also be5 able to unravel ! complicat$ /ructure ( ! volcanic s]ies1 & to repres5t x on ! #f-;in* maps ( ! ,geological ,survey1 ( :i* a r$uction on ! scale ( #a in* to a mile is n[ 9 c\rse ( prep>ation4 ,! foll[+ tabul> summ>y1 tak5 p>tly f notes made by myself dur+ a s]ies ( trav]ses ( ! gr\nd ) ,mr4 ,pea* :5 ! revision 0 begun1 & p>tly f memor&a suppli$ by t geologi/ himself1 may suffice z a g5]al outl9e ( ! volcanic hi/ory ( ?is exce$+ly int]e/+ & important region4 ,footnote #agd3 ,geol4 ,mag4 #ahhi1 p4 #bb4 ,ll&ov]y4 ,p5tam]us grit4 ,conglom]ate 7,mullo* ,hill74 ,c>adoc4 ,%ales1 s&/ones1 grits1 etc4 7,ardmillan1 ,balclet*ie74 ,?ick conglom]ate 7,byne ,hill1 ,b5nane1 etc474 ,?ick fossilif]\s lime/one 7,/9*>1 ,girvan74 7,on ?is horizon come ! p]litic felsites & soda-felsites ( ,w9k/one & ,wrae47 ,s&/one 7,or?is conf9is7 pass+ d[n into ?ick conglom]ate4 ,uncon=mability4 ,upp] ,ll&eilo4 ,gre5 mud/ones1 grits & greywackes4 ,?9 b& ( d>k mud/one ) ,upp] ,ll&eilo graptolites4 ,ar5ig & ,l[] & ,middle ,ll&eilo4 ,gr\p ( ,radiol>ian *]ts 7ab\t #gj feet7 ) alt]nat+ tuffs4 ,tuff or volcanic conglom]ate1 ) occasional lava-fl[s4 ,black %ale 7#aj feet7 ) ,ar5ig graptolites4 ,volcanic breccias ar\nd local c5tres 7,knockdolian1 etc474 ,?ick gr\p ( porphyrite & diabase lavas4 ,r$ fl9ty mud/ones ) ,ar5ig graptolites4 ,porphyrites1 etc4 ,f9e tuffs1 etc41 ) ,l[] ,ar5ig fossils4 ,diabase lavas1 etc4 7base n se574 ,x w be notic$ f ?is table t ! bottom ( ! volcanic s]ies is n rea*$1 s t no e/imate c be =m$ ( its full ?ickness1 nor on :at geological plat=m x beg9s4 ,possibly its visible portions repres5t m]ely ! clos+ sc5es ( a long volcanic hi/ory1 :i*1 ov] ! area ( ! s\? ( ,scotl&1 ext5d$ into ,cambrian "t1 l ! contempor>y s]ies ( ,cad] ,idris4 ,among ! l[e/ lavas !re are int]/ratifi$ c\rses ( f9e tuffs1 fl9ty %ales & ?9 lime/ones1 :i* sometimes fill 9 ! holl[s betwe5 ! pill[-l blocks above ref]r$ to4 ,among ! *>act]i/ic ,l[] ,ar5ig graptolites ( ^! int]calat$ lay]s are ,tetragraptus bryonoides1 ,t4 fruticosus1 ,t4 quadribra*iatus1 & ,t4 ,headi toge!r ) ,c>yoc>is ,wrightii4 ,consid]able v>iation is to be se5 9 ! developm5t ( ! upp] "p ( ! volcanic s]ies4 ,9 "s places ! lavas asc5d almo/ to ! top2 9 o!rs1 ?ick masses ( breccia or agglom]ate take _! place4 ,^! fragm5t>y mat]ials are locally develop$ r\nd p>ticul> c5tres1 :i* probably lie ne> ! sites ( active v5ts :5ce l>ge quantities ( pyrocla/ic mat]ial 7 dis*>g$4 ,"o ( ! volcanic c5tres mu/ h be5 situat$ close to ! position ( ,knockdolian ,hill already ref]r$ to4 ,! exce$+ly co>se breccia ( t em95ce is rudely /ratifi$ 9 alt]nations ( co>s] & f9] mat]ial1 :i* 0 probably to "s ext5t assort$ "u wat] ar\nd ! c9d]-cone t dis*>g$ x4 ,! date ( ! explosions ( ?is hill has be5 asc]ta9$ by ,mr4 ,pea* f ! int]calation ( black %ales conta9+ ,ar5ig graptolites among ! breccias4 ,ano!r v5t lay some:]e 9 ! imm$iate neighb\rhood ( ! ,ma9s ,hill agglom]ate1 if n actually on "p ( ! site ( t rock4 ,?\gh probably n m ?an a mile f ! ,knockdolian volcano1 & belong+ to ! same epo* ( eruption1 ?is v5t1 to judge f ! peculi>ities ( its eject$ mat]ial1 mu/ h be5 q di/9ct 9 its s\rce4 ,a ?ird v5t lay some:]e 9 ! imm$iate vic9ity ( ,b5nane ,head1 & ?rew out ! extraord9>y masses ( agglom]ate & ! %eets ( lava se5 on ! coa/ at t locality4 ,a f\r? may be trac$ by its sep>ate gr\p ( f9e tuffs on ! coa/ ?ree miles s\? ( ,ballantrae4 ,illu/ration3 ,fig4 #ec4--,section across ! ,l[] ,silurian volcanic s]ies 9 ! s\? ( ,ayr%ire 7,b4 ,n4 ,pea*74 ,b1 ,int]/ratifi$ lavas 9 ,ar5ig gr\p2 t1 tuffs2 r1 radol>ian *]ts2 b#b1 ,ll&eilo gr\p2 b#c ,c>adoc gr\p4 1 ,s]p5t9e4 ,g1 ,gabbro4 ,a feature ( s+ul> int]e/ 9 ! mat]ial erupt$ f ^! v>i\s c5tres ( activity consi/s 9 ! evid5ce t ! explosions occurr$ at int]vals dur+ ! deposition ( ! ,l[] ,silurian =mations1 & t ^! =mations 7 successively disrupt$ by subm>9e explosions4 ,mr4 ,pea* has f\nd1 = example1 abundant pieces ( ! peculi> & easily recogniz$ radiol>ian *]ts imb$d$ 9 ! volcanic s]ies4 ,t ^! *]ts 7 deposit$ contemporane\sly ) ! volcanic eruptions is prov$ by _! int]calation among ! breccias4 ,yet among ^! v breccias lie abundant fragm5ts ( *]t :i* mu/ h already solidifi$ be=e disruption4 ,x is ?us evid5t t ?is silice\s ooze n only accumulat$ b set into solid /one on ! sea-floor1 betwe5 p]iods ( volcanic outbur/1 & t su* an occurr5ce took place sev]al times 9 succession ov] ! same area4 ,^! facts d]ive fur!r int]e/ f ! organic orig9 ( ! *]t4 ,x is n[ "s ye>s s9ce ,mr4 ,pea* & 8 colleagues obs]v$ t betwe5 ! ,gl5kiln ,%ale ) its ,upp] ,ll&eilo graptolites & ! top ( ! volcanic gr\p 9 ! c5tral "p ( ! ,silurian upl&s1 alt]nations ( gre51 grey or r$ %aly mud/ones & fl9ty greywackes are int]leav$ ) f9e tuffs1 & are specially m>k$ by ! occurr5ce 9 !m ( nodules & b&s ( black1 grey & r$di% *]t4 ,?is latt] sub/ance1 on be+ submitt$ to ,dr4 ,h9de1 0 f\nd by him to yield tw5ty-?ree new species ( ,radiol>ia belong+ to twelve g5]a1 ( :i* half are new4 ,x ?us appe>s t dur+ ! volcanic activity !re mu/ h be5 int]vals ( su* quiesc5ce1 & su* sl[1 tranquil s$im5tation 9 cle>1 p]haps mod]ately deep wat]1 t a true radiol>ian ooze ga!r$ ov] ! sea-bottom4#age ,footnote #age3 ,ann4 ,mag4 ,nat4 ,hi/4 7#ahij71 #f? s]4 vi4 p4 #dj4 ,t ! deposition ( ?is ooze probably occupi$ a prolong$ lapse ( "t seems cle>ly indicat$ by ! evid5ce ( ! fossils t occur bel[ & above ! *]ts4 ,! graptolites und]nea? indicate a horizon 9 ! ,middle ,ar5ig gr\p1 ^? ov]ly+ ! *]ts are unmi/akably ,upp] ,ll&eilo4 ,?us ! great dep? ( /rata :i* else:]e con/itute ! ,upp] ,ar5ig & ,l[] & ,middle ,ll&eilo subdivisions is "h repres5t$ by only "s #fj or #gj feet ( radiol>ian *]ts4 ,^! f9e silice\s1 organic s$im5ts probably accumulat$ ) extreme sl[ness 9 a sea ( "s dep? & ov] a "p ( ! sea-floor :i* lay outside ! area ( ! transport & deposit ( ! l&-d]iv$ s$im5t ( ! "t4#agf ,footnote #agf3 ,annual ,report ( ! ,geol4 ,surv4 = #ahie1 p4 #bg ( repr9t4 ,illu/ration3 ,fig4 #ed4--,section ( "p ( ! ,ar5ig volcanic gr\p1 /ream s\? ( ,b5nane ,head1 ,ayr%ire4 ,z an illu/ration ( "s ( ! *>act]i/ic features 9 ! succession ( deposits 9 ! volcanic s]ies ( ! s\?-we/ ( ,ayr%ire1 ! accompany+ section 7,fig4 #ed7 is ins]t$4 ,9 desc5d+ ord] we come fir/ ^u a gr\p ( greywackes & grey %att]y mud/ones 7a71 foll[$ by grey-gre5 & d>k b&$ *]ts1 conta9+ ,radiol>ia & mu* plicat$4 ,next comes a gr\p ( d>k-grey1 black & r$ *]ts1 ) num]\s p>t+s & ?9 b&s ( tuff & volcanic conglom]ate 7c74 ,! silice\s b&s 7 c]ta9ly deposit$ dur+ ! volcanic eruptions1 & !y are m\ld$ r\nd ! rugose1 slaggy upp] surface ( ! b& ( lavas 7d7 on :i* !y directly lie4 ,^! lavas h ! sack-l or pill[ /ructure already describ$1 & !y enclose lumps ( *]t conta9+ ,radiol>ia4 ,a few y>ds to ! we/ ( ! l9e ( section b&s ( nodul> tuff are int]pos$ betwe5 ! top ( ! lavas & ! ov]ly+ *]ts1 ) :i* also !y are int]/ratifi$4 ,^! tuffs conta9 blocks ( lava six in*es or m 9 diamet]4 ,bel[ ! belt ( lavas come black *]ts & %ales 7e7 succe$$ bel[ by volcanic breccias & tuffs 7f7 alt]nat+ ) %ales 9 ?9 incon/ant c\rses4 ,^! co>se detrital rocks are ?or\ghly volcanic 9 orig91 & !y conta9 fragm5ts ( ! black *]ts :i* lie /ill l[] 9 ! s]ies4 ,! :ole dep? ( /rata repres5t$ 9 ?is section does n am\nt to mu* m ?an #ajj feet4 ,:ile 9 "s p>ts ( ! ,ayr%ire di/rict ! co>se breccias t accumulat$ ar\nd _! p>5t v5ts =m mo/ ( ! upp] "p ( ! volcanic s]ies1 9 o!rs ! lavas are succe$$ by f9e tuffs :i* are int]calat$ among ! ord9>y s$im5ts1 & %[ a gradual decl9e & cessation ( volcanic en]gy4 ,s\? ( ,ballantrae1 = example1 ! lavas occupy m ?an two miles ( coa/1 9 :i* space !y display h>dly any int]calations ( s$im5t>y mat]ial1 ?\gh !y %[ m or less di/9ctly t !y consi/ ( _m sep>ate fl[s4 ,:]e !y at la/ end1 b&s ( nodul> & f9e tuff make _! appe>ance1 toge!r ) b&s ( a%y %ale & ! *>act]i/ic zone ( ! r$ radiol>ian *]ts or fl9ts4 ,above ^!1 9 con=mable sequ5ce1 come b&s ( black %ale1 conta9+ abundant ,upp] ,ll&eilo graptolites1 ov]la9 by gre5i% or olive-col\r$ %aly mud/ones1 :i* pass upw>d into a ?ick ov]ly+ gr\p ( greywackes4 ,9 ?is section ! alt]nation ( f9e pyrocla/ic ) ord9>y s$im5t %[s t ! volcanic eruptions 9 ! s\!rn "p ( ! ,ballantrae di/rict came to an end by a sl[ly-less5+ s]ies ( explosions4 ,! a%y mat]ial gradually dies out1 & does n reappe> all ?r\gh ! ?ick gr\p ( s&y & muddy s$im5ts :i* "h ov]lies ! volcanic s]ies4 ,we ?us le>n f ! evid5ce ( ! ,ayr%ire sections t volcanic action 0 9 full vig\r 9 ! s\?-we/ ( ,scotl& dur+ ! ,ar5ig p]iod1 b gradually di$ out be=e ! end ( ! ,ll&eilo p]iod4 ,! rocks 9 :i* ?is volcanic hi/ory is *ronicl$ h be5 v greatly di/urb$ & plicat$1 s t ?\gh f _! frequ5tly v]tical position !y might be ?\ght to atta9 a va/ dep?1 !y v possibly d n exce$ #ejj feet 9 ?ickness4 ,z ! volcanic s]ies is foll[$ nor?-ea/w>ds x exhibits a gradual dim9ution 9 ext5t & v>iety1 b ?is may be at lea/ p>tly due to ! mu* less dep? ( x expos$ on ! cre/s ( ! n>r[ anticl9es t br+ x to ! surface4 ,!re is evid5ce 9 t region t ! eruptions did n ev]y:]e t]m9ate 9 ! ,ll&eilo p]iod1 b 7 9 "s di/ricts prolong$ into ! age ( ! ,bala rocks4 ,?us 9 ! neighb\rhood ( ,sanquh> volcanic breccias1 tuffs & lavas h be5 f\nd by ,messrs4 ,pea* & ,horne int]calat$ 9 /rata app>5tly belong+ to ! ,bala gr\p4 ,aga91 9 ! di/rict ( ,h>tfell1 a mod]ately co>se volcanic agglom]ate occurs 9 ! he>t ( ! s-call$ b>r5 mud/ones ( ! ,h>tfell black-%ale gr\p1 :i*1 f its graptolites1 is plac$ on ! horizon ( ! ,bala rocks4 ,at ,w9k/one1 ,hamilton ,hill1 & ,wrae 9 ,peebles%ire1 p]litic felsites & soda-felsites h be5 detect$ by ,messrs4 ,pea* & ,horne & det]m9$ by ,mr4 ,teall4 ,!y are associat$ ) ! ,bala lime/one1 :i* 9 "s ( its conglom]atic b&s conta9s pebbles ( felsite4 ,! intrusive rocks :i* accompany ! ,l[] ,silurian volcanic s]ies ( ! s\? ( ,scotl& are be/ display$ 9 ! s\?-we/ ( ,ayr%ire1 betwe5 ,girvan & ,ballantrae1 :]e !y appe> to be on ! :ole lat] ?an at lea/ ! great mass ( ! int]/ratifi$ lavas & tuffs4 ,! mo/ abundant rocks & ! e>lie/ to be inject$ are complex basic masses :i* include s]p5t9e1 oliv9e-en/atite rock1 troctolite1 gabbro & o!r comp\nds1 all :i* may be diff]5t modifications ( ! same orig9al basic magma4 ,!y d n %[ a f9] texture :]e !y respectively meet1 nor any o!r symptom ( hav+ be5 subsequ5tly intrud$ into ea* o!r1 ?\gh !y d exhibit su* /ructures along _! l9es ( contact ) ! surr\nd+ rocks1 into :i* !y are intrusive4 ,^! m basic masses h subsequ5tly be5 invad$ by irregul> bosses & dyke-l protrusions1 :i*1 :5 small1 are f9e-gra9$ dol]ites1 b :5 9 l>g] bodies take ! =m ( gabbro1 sometimes exhibit+ a m9]al b&+ & foliat$ /ructure4 ,^! b&$ v>ieties mu* resemble ! b&$ ,t]ti>y gabbros ( ,skye & "s p>ts ( ! ,lewisian gneiss4 ,at ! ,byne ,hill1 ne> ,girvan1 a l>ge intrusive boss or ridge displays on its out] m>g9 a f9e-gra9$ texture1 :]e x comes 9 contact ) ! s]p5t9e4 ,fur!r inw>ds x becomes a f9e dol]ite1 pass+ into gabbro & increas+ 9 co>s5ess ( gra9 z well z 9 acidity ( composition1 ?r\gh /ages ( :at 9 ! field w\ld be call$ diorite & qu>tz-diorite1 into a c5tral granitic rock1 :]e( milky or blue qu>tz =ms ! prom95t con/itu5t4 ,! intrusive rocks ( ?is di/rict h g5]ally be5 inject$ p>allel to ! /ratification-planes1 & take on ! :ole ! =m ( sills4 ,"s "t aft] ! close ( ! volcanic episode 9 ! ,silurian p]iod ( ! s\? ( ,scotl&1 ! rocks 7 locally subject$ to consid]able di/urbance & elevation1 :]eby p>ts ( ! volcanic s]ies 7 expos$ to ext5sive d5udation4 ,h5ce ! ov]ly+ uncon=mable ,c>adoc conglom]ates are 9 "s places l>gely made up ( ! detritus ( ! volcanic rocks4 ,x is int]e/+ to f9d ?is evid5ce ( wa/e dur+ ! v next /age ( ! ,silurian p]iod1 = x af=ds good evid5ce t ! ext5sive %eets ( intrusive mat]ial c\ld n h _h any l>ge am\nt ( ov]ly+ /rata re/+ ^u !m at ! "t ( _! injection4 ,pieces ( ^! intrusive rocks1 su* z ! s]p5t9e1 occur abundantly 9 ! ,c>adoc conglom]ates1 "s ( :i* inde$ are almo/ :olly compos$ ( _! detritus4 ,probably ! total ?ickness ( ! ov]ly+ cov] ( rock "u :i* ! sills 7 inject$ did n am\nt to z mu* z #bjj or #cjj feet4 ,yet we see t among ! sills 7 co>se gabbros & granitoid rocks4 ,we may !re=e inf] t = ! injection ( su* intrusive masses1 great dep? & enorm\s sup]9cumb5t pressure are possibly n always necess>y4 ,dur+ ! progress ( ! ,geological ,survey along ! s\!rn bord]s ( ! ,highl&s1 a rem>kable gr\p ( rocks has be5 obs]v$1 int]v5+ z a n>r[ int]rupt$ /rip betwe5 ! s*i/ose masses to ! nor? & ! great b\nd>y-fault :i* br+s ! ,old ,r$ ,s&/one 9 v]tical /rata aga9/ !m4 ,betwe5 ,corta*y 9 ,=f>%ire & ,/onehav5 on ! ea/ coa/1 ^! rocks h be5 mapp$ by ,mr4 ,g4 ,b>r[1 :o has c>efully work$ out _! relations4 ,!y appe> aga9 betwe5 ,call&] & ,lo* ,lomond1 :]e _! ext5t & /ructure h be5 mapp$ by ,mr4 ,c4 ,t4 ,cl\gh4 ,= ! purpose ( our pres5t inquiry two *ief features ( int]e/ are pres5t$ by ^! rocks4 ,!y include a gr\p ( s$im5t>y /rata among :i* occur b&s ( jasp] or *]t conta9+ radiol>ia1 & "o ( _! mo/ conspicu\s memb]s is a s]ies ( volcanic rocks consi/+ *iefly ( dol]ites & basalts1 "s ( :i* h be5 mu* cru%$ & cleav$1 b 9 :i* vesicul> /ructures c /ill occasionally be recogniz$4 ,! /rik+ resemblance ( bo? ! aque\s & igne\s memb]s ( ?is m>g9al /rip ( rocks along ! ,highl& bord] to ! ,ar5ig *]ts & _! accompany+ lavas 9 ! s\? ( ,scotl&1 ! rem>kable association ( ! same k9ds ( mat]ial 9 ! same ord] ( sequ5ce1 ! occurr5ce ( radiol>ia 9 ! silice\s b&s 9 bo? regions1 furni% /rong presumptive evid5ce t a /rip ( ,ar5ig rocks has be5 w$g$ 9 aga9/ ! ,highl& s*i/s4 ,9 _m respects1 ^! dull gre5 diabasic lavas ( ! ,highl& bord] resemble ^? ( ! ,ayr%ire coa/4 ,9 p>ticul>1 ! same peculi> sack-l or pill[-%ap$ masses are conspicu\s 9 ! ,=f>%ire rav9es4 ,z 9 ,ayr%ire1 igne\s mat]ials und]lie ! *]ts :i* are d\bl$ ov] & repeat$ by _m successive folds4 ,un=tunately1 x is only a n>r[ /rip ( ^! probably ,ar5ig lavas t has be5 pres]v$1 & no trace has be5 detect$ ( tuffs1 agglom]ates or necks4 ,if1 h[ev]1 we may reg>d ! rocks z truly ( ,ar5ig age1 !y furni% int]e/+ additional pro( ( ! wide ext5t ( ! e>lie/ ,silurian volcanoes4 ,! di/ance betwe5 ! la/ ,ar5ig volcanic outcrop 9 ! ,s\!rn upl&s & ! b& ( simil> lavas along ! m>g9 ( ! ,highl&s is ab\t #ej miles4 ,if ! volcanic ejections 7 cont9u\s across ! int]v5+ tract1 ! total area ov] :i* ! lavas & tuffs ( ! ,ar5ig volcanoes 7 di/ribut$ mu/ be increas$ by at lea/ #fjjj squ>e miles 9 ,scotl&4 ,b x is 9 ! nor? ( ,irel& t ?is nor!rn ext5sion ( :at may probably be reg>d$ z an ,ar5ig s]ies ( volcanic rocks atta9s its greate/ developm5t4 ,( ?is ,iri% prolongation a brief acc\nt is giv5 9 ,*apt] xiv41 :]e ! :ole ( ! ,silurian volcanic rocks ( ! isl& are discuss$4 ,,*apt] ,,xiii ,,! ,,eruptions ,,( ,,ll&eilo ,,& ,,bala ,,age i4 ,! ,buil? ,volcano--ii4 ,! ,volcanoes ( ,pembroke%ire--iii4 ,! ,ca]n>von%ire ,volcanoes ( ! ,bala ,p]iod--iv4 ,! ,volcanic ,di/rict ( ! ,b]wyn ,hills--v4 ,! ,volcanoes ( ,anglesey--vi4 ,! ,volcanoes ( ! ,lake ,di/rict2 ,ar5ig to close ( ,bala ,p]iod--vii4 ,upp] ,silurian 787 volcanoes ( ,gl\ce/]%ire4 ,! /ratigraphical subdivisions ( geology are necess>ily m or less arbitr>y4 ,! sequ5ce 9 ! s$im5t>y deposits ( "o region always diff]s 9 "s degree f t ( adjo9+ regions4 ,9 draw+ up a table ( /ratigraphical equival5ts = sep>ate c\ntries1 we mu/ be cont5t to accept a g5]al p>allelism1 )\t insi/+ on too close an id5tity 9 ei!r ! "* ( ! /rata or ! gr\p+ ( _! organic rema9s4 ,we ne$ especially to gu>d aga9/ ! assumption t ! limit assign$ to a geological =mation 9 any c\ntry m>ks a *ronological epo* :i* w practically agree ) t d5ot$ by ! limit fix$ = ! same =mation 9 ano!r c\ntry4 ,! desirability ( caution 9 ?is respect is well %[n by ! vagu5ess ( ! horizons betwe5 ! sev]al subdivisions ( ! ,l[] ,silurian sy/em4 ,s long z ! areas ( comp>ison are ne> ea* o!r1 no great error may p]haps be committ$ if _! /ratigraphical equival5ts are tak5 to h be5 9 a broad geological s5se contempor>y4 ,b 9 proportion z ! elem5t ( di/ance comes 91 !re ent]s ) x ! elem5t ( unc]ta9ty4 ,ev5 )9 s limit$ a region z ! ,briti% ,isles1 ?is difficulty makes itself /rongly felt4 ,?us1 9 ! typical regions ( ,wales1 ! sev]al subdivisions ( ! ,l[] ,silurian /rata are tol]ably well m>k$1 bo? by li?ological nature & by fossils4 ,b z !y are foll[$ into o!r p>ts ( ! c\ntry1 !y assume new features1 sometimes increas+ sometimes dim9i%+ 9 ?ickness1 *ang+ _! s$im5t>y "*1 & alt]+ ! association or range ( _! organisms4 ,! subdivisions into :i* ! geologi/ gr\ps !m may ?us be vaguely def9$ by limits :i*1 9 diff]5t p>ts ( ! region1 may be f> f repres5t+ ! same p]iods ( "t4 ,h5ce1 9 try+ to asc]ta9 h[ f> ! volcanic eruptions ( "o area dur+ ! ,silurian p]iod may h be5 contempor>y ) ^? ( ano!r area1 we mu/ be cont5t to all[ a wide m>g9 = error4 ,x is h>dly possible to adh]e /rictly to ! /ratigraphical arrangem5t1 = ! geological record %[s t 9 ! volcanic di/ricts ! s$im5t>y =mations by :i* ! *ronology might h be5 work$ out are n infrequ5tly abs5t or obscure4 ,x w be m conv5i5t to treat ! re/ ( ! ,l[] ,silurian =mations z ! records ( "o long & tol]able def9ite section ( geological "t1 )\t attempt+ 9 ea* case to di/+ui% betwe5 ! eruptions ( ! successive includ$ p]iods1 s long z ! actual volcanic sequ5ce is di/9ctly kept 9 view4 ,i w !re=e take ! hi/ory ( ea* di/rict 9 turn & foll[ its *anges f ! close ( ! ,ar5ig p]iod to ! end ( ,upp] ,silurian "t4 ,! /ages 9 ! volcanic evolution ( ea* tract w ?us be cle>ly se54 ,above ! ,ar5ig gr\p ) its volum9\s volcanic records comes ! great gr\p ( s$im5ts kn[n z ! ,ll&eilo =mation1 9 :i* also !re are pro(s ( contemporane\s volcanic activity ov] v>i\s p>ts ( ! sea-floor )9 ! site ( ,brita94 ,we h se5 t 9 ! s\? ( ,scotl& ! eruptions ( ,ar5ig "t 7 probably cont9u$ into ! p]iod ( ! ,ll&eilo rocks1 or ev5 /ill lat] into t ( ! ,bala gr\p4 ,b x is 9 ,wales t ! hi/ory ( ! ,ll&eilo volcanoes is mo/ fully pres]v$4 ,a s]ies ( deta*$ areas ( volcanic rocks1 int]calat$ among ! ,ll&eilo s$im5ts1 may be foll[$ = ne>ly #ajj miles1 f ! nor!rn end ( ! ,breidd5 ,hills 9 ,montgom]y%ire1 by ,%elve1 ,buil?1 ,llanwrtyd & ,llangadock1 to ! m\? ( ! ,taf riv]4 ,b "s #ce miles fur!r we/ ano!r gr\p ( lavas & tuffs appe>s on ! coa/ ( ,pembroke%ire1 f ,ab]eiddy ,bay to beyond ,fi%gu>d4 ,! want ( cont9uity 9 ^! scatt]$ outcrops is no d\bt p>tly due to concealm5t by geological /ructure4 ,b f ! comp>ative ?9ness ( ! volcanic accumulations & _! app>5t ?9n+ out along ! /rike x may be inf]r$ t no l>ge ,ll&eilo volcano exi/$ 9 ,wales4 ,!re w\ld r seem to h be5 a long l9e ( m9or v5ts :i* 9 ! s\?-ea/ "p ( ! area appe> to h only dis*>g$ a%es4 ,c]ta9ly1 if we may judge f _! visible relics1 ^! eruptions nev] rivall$ ! magnitude ( ! dis*>ges f ! ,ar5ig volcanoes t prec$$1 or ! ,bala volcanoes t foll[$ !m4 i4 ,,! ,,volcano ,,( ,,buil? ,,& ,,its ,,neighb\rs ,s f> z ! available evid5ce goes1 ! mo/ important volcanic c5tre d[n ! ea/]n side ( ,wales dur+ ! ,ll&eilo p]iod 0 "o :i* lay n f> f ! c5tre ( ! long l9e ( v5ts j ref]r$ to4 ,its visible rema9s =m an isolat$ tract ( hilly gr\nd1 "s sev5 miles long1 & f\r or five miles broad1 imm$iately nor? f ! t[n ( ,buil?4 ,?is area is almo/ entirely surr\nd$ by uncon=mable ,upp] ,silurian /rata1 s t its total ext5t is n se51 & may be mu* m consid]able ?an ! area n[ laid b>e by d5udation4 ,! volcanic rocks ( ,buil? 7 fir/ describ$ 9 ! ,silurian ,sy/em4 ,mur*ison cle>ly recogniz$ t !y includ$ "s :i* 7 evolv$ f volcanic ap]tures dur+ ! subm>9e accumulation ( ! ,l[] ,silurian rocks1 & also unb$d$ volcanic masses :i* _h be5 intrud$ subsequ5tly1 dismemb]+ & alt]+ all ! /rata ) :i* !y came 9 contact4#agg ,^! igne\s rocks 7 mapp$ 9 "s detail by ! ,geological ,survey1 & _! g5]al relations 7 express$ 9 l9es ( horizontal section4#agh ,!y 7 likewise describ$ by ,ramsay 9 ! ,catalogue ( ! ,rock-specim5s 9 ! ,j]myn ,/reet ,museum1 specim5s ( !m be+ display$ 9 t collection4#agi ,! tuffs & lavas 7 di/+ui%$1 & likewise ! intrusive gre5/ones4 ,b no attempt 0 made t[>ds petrographical detail4 ,footnote #agg3 ,silurian ,sy/em1 #ahci1 p4 #ccj4 ,! occurr5ce ( trappean a% ) fossils 9 ! ,buil? di/rict 0 notic$ by ,de la ,be*e1 ,mem4 ,geol4 ,surv4 vol4 i4 7#ahdf71 p4 #ca4 ,footnote #agh3 ,see ,%eet #ef ( ! "o-in* map & ,%eets #e & #f ( ! ,horizontal ,sections4 ,footnote #agi3 ,catalogue ( ,rock ,specim5s1 #crd edit4 #ahfb1 p4 #cf et seq4 ,?is int]e/+ di/rict has rec5tly be5 /udi$ by ,mr4 ,h5ry ,woods1#ahj :o has gr\p$ ! igne\s rocks 9 probable ord] ( appe>ance1 z foll[s3--#a/1 ,&esites2 #bnd1 ,&esitic a%2 #crd1 ,rhyolites2 #d?1 ,diabase-porphyrite2 & #e?1 ,diabase4 ,footnote #ahj3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 l4 7#ahid71 p4 #eff4 ,"s ( ! &esites are describ$ z intrusive 9 ! ,ll&eilo /rata4 ,! a% 9 its l[] "p conta9s num]\s well-r\nd$ pebbles ( &esite1 usually five or six in*es 9 diamet]1 b sometimes hav+ a l5g? ( two feet4 ,x conta9s fossils 7,or?is calligramma1 ,leptna s]icea1 ,s]pulites disp>1 etc471 & z x is ov]la9 ) %ales conta9+ ,ogygia ,bu*ii1 x may be reg>d$ z probably ( ,l[] ,ll&eilo age4 ,! rhyolites are feebly repres5t$1 & "s ( !m may possibly be intrusive4 ,among !m a nodul> v>iety has be5 notic$1 ! nodules be+ solid ?r\gh\t1 v>y+ up to two in*es 9 diamet]1 & =m$ ( microcry/all9e qu>tz & felsp>1 ) no trace ( any radial or conc5tric int]nal arrangem5t4 ,! diabase-porphyrite1 ! mo/ conspicu\s rock ( ! di/rict1 is intrusive 9 ! &esites & a%es1 & occurs 9 f\r sep>ate masses or sills4 ,! diabases are all intrusive & ( lat] date ?an any ( ! o!r igne\s rocks1 & z !y trav]se also ! ,ll&eilo %ales1 !y are probably consid]ably lat] ?an ! previ\s eruptions4 ,b z !y d n ent] ! surr\nd+ ,ll&ov]y & ,w5lock /rata1 !y are reg>d$ by ,mr4 ,woods z ( int]m$iate age betwe5 ! "t ( ! ,ll&eilo & t ( ! ,upp] ,silurian =mations4 ,ab\t n9e miles 9 a we/-s\?-we/]ly direction f ! s\!rn extremity ( ! ,buil? volcanic area1 ano!r mu* small] exposure ( igne\s rocks has be5 mapp$ by ! ,geological ,survey at ! village ( ,llanwrtyd4 ,?is tract is only ab\t ?ree miles long & half a mile broad4 ,! volcanic rocks are repres5t$ z consi/+ ( ?ree or m b&s ( felspa?ic trap int]/ratifi$ 9 ! ,l[] ,silurian /rata1 & fold$ into an anticl9e along ! ridge ( ,ca] ,cwm4 ,no publi%$ l9e ( section runs across ?is gr\nd1 & ! b& ( rock does n appe> to h be5 describ$4#aha ,footnote #aha3 ,! locality is ref]r$ to by ,de la ,be*e1 ,mem4 ,geol4 ,surv4 vol4 i4 p4 #ca1 & by ,ramsay 9 ! ,descriptive ,catalogue ( ,rock-specim5s 9 ! ,museum ( ,practical ,geology1 #crd edit4 p4 #ch1 b no specim5s f x are 9 ! collection4 ,sev5te5 miles to ! s\?-we/ a /ill feebl] display ( int]calat$ volcanic mat]ial occurs 9 ! ,ll&eilo =mation ne> ! village ( ,llangadock4 ,! ,geological ,survey map repres5ts "o or m b&s ( a% associat$ ) lime/one1 & ?r[n into a succession ( folds4 ,9 ! ,horizontal ,section 7,%eet ,,iii4 ,section #c7 a b&1 #ajj to #bjj feet ?ick1 ( trappean a% ) fossils is %[n among ! %ales1 lime/ones & grits1 & 9 ! ,catalogue ( ,rock-specim5s ! same rock is ref]r$ to z brecciat$ a% 9 connection ) specim5s ( x 9 ! ,museum1 :i* are describ$ z n purely a%y1 b conta9+ _m slate-fragm5ts & brok5 felsp>-cry/als toge!r ) organic rema9s4#ahb ,footnote #ahb3 ,op4 cit4 p4 #ch4 ,ab\t tw5ty-f\r miles /ill fur!r 9 ! same s\?-we/]ly direction1 two pat*es ( a% are %[n ^u ! ,survey map1 ne> ! m\? ( ! riv] ,taf4 ,no description ( ^! rocks is giv54#ahc ,footnote #ahc3 ,"o ( ! pat*es 0 %[n by ,j4 ,phillips 9 ,horizontal ,section1 ,%eet ,,iii4 ,section #f1 z a felspa?ic trap1 ne> :i* ! %ales are blea*$4 ,! map1 h[ev]1 0 subsequ5tly alt]$1 s z to make ! igne\s rocks pyrocla/ic4 ii4 ,,! ,,volcanoes ,,( ,,pembroke%ire ,9 nor?-we/]n ,pembroke%ire1 ! obs]vations ( ,mur*ison1 ,de la ,be*e & ,ramsay %[$ ! exi/5ce ( an important volcanic di/rict1 :]e num]\s igne\s b&s are int]/ratifi$ among ! ,l[] ,silurian rocks1 ov] an area ext5d+ f ,/4 ,david's ,head = ?irty miles to ! ea/w>d4#ahd ,on ! maps ( ! ,geological ,survey1 lavas1 tuffs1 sills & bosses 7 discrim9at$1 b no description ( ^! rocks 0 publi%$4 ,s9ce ! publication ( ! ,survey map v little has yet be5 add$ to our in=mation on ! subject4 ,footnote #ahd3 ,see ,silurian ,sy/em1 p4 #dja2 ,%eet #dj ( ! ,geological ,survey ,map2 ,memoir ( ,a4 ,c4 ,ramsay1 p4 #bcb et seq42 ,de la ,be*e1 ,trans4 ,geol4 ,soc4 #bnd s]ies1 vol4 ii4 "p i4 7#ahbf71 p4 #c4 ,!re appe> to h be5 at lea/ ?ree pr9cipal gr\ps ( v5ts4 ,"o may be indicat$ by ! b&s ( felspa?ic trap :i* h be5 mapp$ z ext5d+ f ne> ,/4 ,lawr5ce = f\rte5 miles to ! ea/4 ,ano!r mu/ h exi/$ 9 ! neighb\rhood ( ,fi%gu>d4 ,a ?ird is %[n to h la9 betwe5 ,ab]eiddy ,bay & ,ma?ry1 by ! abundant b&s ( lava & tuff & intrusive sills !re to be se54 ,( ^! areas ! only "o :i* has yet be5 exam9$ & describ$ 9 "s detail is t ( ,fi%gu>d1 ( :i* an acc\nt has rec5tly be5 publi%$ by ,mr4 ,c[p] ,re$4#ahe ,?is obs]v] has %[n t ! eruptions began !re dur+ ! deposition ( ! ,l[] ,ll&eilo rocks1 & cont9u$ int]mitt5tly into ! ,bala p]iod4 ,! e>lie/ consi/$ ( felsites & tuffs int]calat$ betwe5 ,l[] ,ll&eilo black slates conta9+ ,didymograptus ,mur*isoni1 ! tuffs !mselves be+ sometimes fossilif]\s4 ,a second great volcanic belt1 compos$ ( felsitic lavas1 breccias & tuffs1 lies at ! base ( ! ,upp] ,ll&eilo /rata & %[s ! maximum ( volcanic en]gy4 ,! breccias are p>tly co>se agglom]ates1 :i* probably repres5t1 or lie n f> f1 "s ( ! eruptive v5ts ( ! "t4 ,a high] b& ( lavas & breccias appe>s to be ref]able to ! ,bala =mation4 ,! :ole volcanic s]ies is /at$ to ?9 out t[>ds ! s\?-we/1 s t ! *ief focus ( eruption probably lay some:]e 9 ! neighb\rhood ( ,fi%gu>d4 ,footnote #ahe3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 li4 7#ahie71 p4 #adi4 ,! lavas may all be includ$ "u ! g5]al t]m felsite4 ,_! specific gravity ranges f #bfj to #bgf1 & _! silica p]c5tage f #fh to #gb4 ,mr4 ,c[p] ,re$ obs]v$ among !m ?ree conspicu\s types ( /ructure4 ,"s are *>act]iz$ by a di/9ct arrangem5t 9 f9e light & d>k b&s :i* rapidly alt]nate1 & are sometimes ?r[n into folds & convolutions4 ,a second /ructure1 obs]v$ only at "o locality1 consi/s 9 ! developm5t ( pale grey or :iti% ovate nodules1 ab\t half an in* 9 l5g?1 ) a cle> qu>tz-gra9 9 _! c5tre1 or else holl[4 ,! ?ird type is %[n by ! appe>ance ( p]litic /ructure on ! wea!r$ surface4#ahf ,footnote #ahf3 ,mr4 ,c[p] ,re$ ent]s into a detail$ acc\nt ( ! microscopic /ructures & *emical composition ( ^! rocks4 ,!y h r a high p]c5tage ( alum9a1 pota% & soda1 & are obvi\sly ak9 to ! k]atophyres ( o!r di/ricts4 ,! tuffs & breccias are *iefly develop$ at ! base & top ( ea* volcanic gr\p4 ,"s ( !m conta9 highly vesicul> fragm5ts1 z well z pieces ( slate & brok5 cry/als ( qu>tz & felsp>4 ,a *>act]i/ic feature ( ?is volcanic di/rict is ! occurr5ce 9 x ( sills & irregul>ly-intrud$ masses ( gre5/one4 ,"u t "n are compris$ basalts1 dol]ites1 &esitic dol]ites ) ta*ylitic modifications1 z well z diabases & gabbros4#ahg ,"s ( ^! rocks exhibit a v>iolitic /ructure4 ,z reg>ds age1 "s ( ! intrusions appe> to h tak5 place be=e ! tilt+1 cleavage & fault+ ( ! /rata4 ,!y h n be5 notic$ 9 ! surr\nd+ ,upp] ,silurian /rata1 & we may p]haps inf] t "h1 z at ,buil?1 !y are ( ,l[] ,silurian date4 ,mr4 ,c[p] ,re$1 h[ev]1 is incl9$ to reg>d ! l>ge ,/rumble ,head masses z lat] ?an ! tilt+ & fold+ ( ! rocks4#ahh ,footnote #ahg3 ,mr4 ,c[p] ,re$1 op4 cit4 p4 #ahj4 ,footnote #ahh3 ,op4 cit4 p4 #aic4 ,a few miles to ! s\?-we/ ( ! ,fi%gu>d di/rict1 on ! coa/ ( ,ab]eiddy ,bay1 good sections h be5 laid b>e ( ! volcanic rocks ( ?is region4 ,dr4 ,hicks has %[n t ! b&s ( tuff !re display$ are int]calat$ among ! black slates ( ! ,l[] ,ll&eilo gr\p1 & t !re 0 probably a r5ewal ( volcanic activity dur+ ! deposition ( ! upp] gr\p4#ahi ,b ! volcanic hi/ory ( ?is area /ill rema9s to be prop]ly inve/igat$4 ,footnote #ahi3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xxxi4 7#ahge71 p4 #agg4 ,9 s\!rn ,pembroke%ire two conspicu\s b&s ( eruptive rocks h long be5 kn[n & describ$4 ,_! g5]al *>act]s & di/ribution 7 sket*$ by ,de la ,be*e1#aij & fur!r details 7 aft]w>ds add$ by ,mur*ison4#aia ,z trac$ by ! (fic]s ( ! ,geological ,survey1 !y 7 repres5t$ z consi/+ ( gre5/one1 sy5ite & granite4 ,! m nor!rly b& 0 %[n to run 9 a ne>ly ea/ & we/ l9e f ,lawr5ny to ! ,/ack ,rock1 we/ ( ,talb5ny1 a di/ance ( ab\t f\rte5 miles4 ,! second b&1 plac$ a %ort way f>!r s\?1 /ret*es 9 ! same g5]al l9e1 f ,mil=d ,hav5 at ,dall ,road into ,skom] ,isl&1 a di/ance ( ab\t sev5 miles4 ,footnote #aij3 ,trans4 ,geol4 ,soc41 #bnd s]4 vol4 ii4 7#ahbc71 p4 #f et seq4 ,footnote #aia3 ,silurian ,sy/em1 p4 #dja et seq4 ,! relations ( ^! rocks to ! surr\nd+ =mations & _! geological age h be5 v>i\sly int]pret$4 ,de la ,be*e reg>d$ ! diff]5t masses z intrusive1 & probably lat] ?an ev5 ! adjo9+ ,coal-measures4#aib ,mur*ison1 on ! o!r h&1 consid]$ ! b$d$ eruptive rocks ( ,skom] ,isl& to be und\bt$ly lavas contemporane\s ) ! /rata among :i* !y are int]calat$4#aic ,footnote #aib3 ,mem4 ,geol4 ,survey1 vol4 i4 p4 #bca4 ,footnote #aic3 ,silurian ,sy/em1 p4 #djd4 ,! rocks h be5 /udi$ petrographically by v>i\s obs]v]s4 ,mr4 ,rutley gave a full description ( ! rem>kable nodul> & b&$ felsites ( ,skom] ,isl&4#aid ,mr4 ,teall has also notic$ ^! rocks1 likewise a magnific5t s]ies ( basic lava-fl[s 9 ! same isl&1 & a numb] ( porphyrites4 ,! basic lavas seem$ to him to conta9 too mu* felsp> & too little oliv9e to be reg>d$ z p]fectly typical oliv9e-basalts1 & he f\nd !m to lie sometimes 9 v ?9 & highly vesicul> %eets4 ,! porphyrites he plac$ on ! bord]-l9e betwe5 basic & int]m$iate rocks4#aie ,footnote #aid3 ,! ,felsitic ,lavas ( ,engl& & ,wales1 ,mem4 ,geol4 ,survey 7#ahhe71 pp4 #af1 #ah4 ,footnote #aie3 ,briti% ,petrography1 pp4 #bbd1 #bhd1 #ccf4 ,m rec5tly ?is s\!rn di/rict ( ,pembroke%ire has be5 exam9$ by ,messrs4 ,f4 ,t4 ,h[>d & ,e4 ,w4 ,small1 :o h obta9$ fur!r evid5ce ( ! int]b$d$ "* ( ! igne\s s]ies4 ,bel[ an upp] basalt !y h not$ ! occurr5ce ( b&s ( felsitic conglom]ate1 s&/one1 %ale & breccia ly+ ^u & obvi\sly d]iv$ f a b&$ sph]ulitic felsite1 bel[ :i* comes a l[] gr\p ( basalts4 ,! age ( ?is int]e/+ alt]ation ( basic & acid eruptions has n be5 precisely det]m9$1 b is conjectur$ to be t ( ! ,bala or ,ll&ov]y rocks4#aif ,footnote #aif3 ,rep4 ,brit4 ,assoc4 #ahic1 p4 #gff2 ,geol4 ,mag4 #ahif1 p4 #dha4 iii4 ,,! ,,ca]n>von%ire ,,volcanoes ,,( ,,! ,,bala ,,p]iod ,ow+ to ! effects p>tly ( plication & p>tly ( d5udation1 ! rocks ( ! next volcanic episode 9 ,wales1 t ( ! ,bala p]iod1 occupy a less compact & def9$ area ?an ^? ( ! ,ar5ig gr\p 9 ,m]ione?%ire4 ,f ! latt] !y are sep>at$1 z we h se51 by a consid]able dep? ( /rata1#aig :5ce we may inf]1 ) ! ,geological ,survey1 t ! eruptions ( ,ar5ig1 ! ,arans & ,cad] ,idris 7 succe$$ by a long p]iod ( repose1 ! ,ll&eilo outbreaks describ$ 9 ! =ego+ pages n hav+ ext5d$ app>5tly into ,nor? ,wales4 ,:5 ! next outbreaks took place1 ! v5ts are f\nd to h %ift$ nor?w>ds into ,ca]n>von%ire1 :]e !y fix$ !mselves along a l9e n mu* to ! ea/ ( :]e ! ,cambrian porphyries & tuffs n[ appe> at ! surface4 ,! lavas & a%es t 7 ?r[n out f ^! v5ts =m ! highe/ & mo/ picturesque m\nta9s ( ,nor? ,wales1 culm9at+ 9 ! noble cone ( ,sn[don4 ,!y /ret* nor?w>ds to ,diganwy1 beyond ,conway1 & s\?w>ds1 at lea/ z f> z ! neighb\rhood ( ,criccie?4 ,!y die out nor?-ea/w>ds beyond ,bala ,lake1 & !re c be b little d\bt t !y ?9 out also ea/w>ds "u ! ,upp] ,bala rocks4 ,! lavas & tuffs t rise up on a simil> horizon among ! ,bala rocks ( ! ,b]wyn ,hills evid5tly came n f ! ,sn[donian v5ts1 b f ano!r m9or volcanic c5tre "s miles to ! ea/1 :ile /ill m remote lay ! v5ts ( ! ,breidd5 ,hills & ! %eets ( &esitic tuff t probably spread f !m ov] ! gr\nd ea/ ( ,*irbury 7,map ,,ii474 ,footnote #aig3 ,e/imat$ at f #fjjj to #gjjj feet1 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #aca4 ,! ,ca]n>von%ire volcanic gr\p ext5ds f nor? to s\? = fully ?irty miles1 ) an extreme bread? ( ab\t fifte5 miles2 :ile1 if we include ! rocks ( ! ,lleyn p59sula1 ! area w be prolong$ "s tw5ty miles f>!r to ! s\?-we/4 ,! g5]al /ratigraphical horizon ( ?is volcanic gr\p has be5 well det]m9$ by ! c>eful mapp+ ( ,ramsay1 ,selwyn & ,jukes on ! maps ( ! ,geological ,survey4 ,^! obs]v]s br\ght =w>d ample evid5ce to %[ t ! lavas & tuffs 7 erupt$ dur+ ! deposition ( ! ,bala /rata ( ! ,l[] ,silurian s]ies1 t ! ,bala ,lime/one is 9 places full ( a%y mat]ial1 & t ?is well-m>k$ fossilif]\s b& passes lat]ally into /ratifi$ volcanic tuffs conta9+ ! same species ( fossils4#aih ,b ! progress ( /ratigraphical geology1 & ! increas+ value f\nd to atta* to organic rema9s z m>k+ ev5 m9or /ratigraphical horizons1 give u reason to believe t a r5ew$ & /ill m detail$ /udy ( ! ,bala rocks ( ,nor? ,wales w\ld probably furni% data = m precisely def9+ ! plat=ms ( successive eruptions1 & w\ld ?us fill 9 ! details ( ! broad sket* :i* ,sir ,&rew ,ramsay & 8 associates s admirably trac$4 ,besides ! ,bala ,lime/one !re may be o!r li?ological horizons :i*1 l ! ,g>? grit & ! pisolitic iron-ore ( ! ,ar5ig gr\p1 might be capable ( be+ foll[$ among ! cwms & cre/s z well z ! op5] valleys ( ,ca]n>von%ire4 ,until "s su* detail$ mapp+ is accompli%$1 we _c safely advance mu* beyond ! po9t :]e ! /ratigraphy 0 left by ! ,survey4 ,footnote #aih3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 pp4 #abf1 #abh1 #aca1 #aci1 etc4 ,f ! ,survey maps & sections x is n difficult to foll[ ! g5]al volcanic succession1 & to p]ceive t ! erupt$ mat]ials mu/ altoge!r be sev]al ?\s& feet 9 ?ickness f ! l[e/ lavas 9 ! nor? to ! highe/ on ! cre/ ( ,sn[don4 ,9 t m\nta9 ! total mass ( volcanic mat]ial is set d[n z #cajj feet4 ,b ?is includes only ! high] "p ( ! :ole volcanic gr\p4 ,bel[ x come ! lavas ( ,y ,glyd]-,fa*1 :i*1 accord+ to ! ,survey measurem5ts1 are ab\t #aejj feet ?ick1 :ile /ill l[] lie ! anci5t c\les ( ,c>n$d ,dafydd & ^? t run nor? f ! v5t ( ,y-foel-frs1 :i* mu/ rea* a unit$ ?ickness ( _m hundr$ feet4 ,we c ?us h>dly put ! total dep? ( volcanic mat]ial at a maximum ( less ?an #fjjj to #hjjj feet4 ,! pile is1 ( c\rse1 ?icke/ r\nd ! v5ts ( dis*>ge1 s t no measurem5t1 h[ev] c>efully made at "o locality1 w\ld be f\nd to hold good = m ?an a %ort di/ance4 ,?\gh little is said 9 ! ,survey ,memoir ( ! v5ts f :i* ?is va/ am\nt ( volcanic mat]ial 0 erupt$1 ! probable positions ( a numb] ( ^! orifices may be inf]r$ f ! maps4 ,f ! %ore we/ ( ,conway a s]ies ( rem>kable em95ces may be trac$ s\?-we/w>ds = a di/ance ( ne>ly =ty miles into ! p59sula ( ,lleyn4 ,at ! nor!rn extremity ( ?is l9e /&s ! prom95t boss ( ,p5ma5-mawr1 :ile s\?w>d beyond ! l>ge mass ( ,y-foel-frs1 ) ! small] knobs we/ ( ,nant ,francon1 & ! great dome ( ,mynydd-mawr1 ! eye ranges z f> z ! /rik+ gr\p ( puy-l cones t rise f ! sea ar\nd ,yr ,eifl & ,nev94 ,"s ( ^! hills1 p>ticul>ly ,y-foel-frs1 7 recogniz$ by ! ,survey z v5ts4#aii ,b ! fir/ connect$ acc\nt ( !m & ( _! probable relation to ! volcanic di/rict 9 :i* !y occur has be5 giv5 by ,mr4 ,h>k] 9 8 exce$+ly able essay on ,! ,bala ,volcanic ,s]ies ( ,ca]n>von%ire1#bjj--! mo/ important contribution to ! volcanic hi/ory ( ,wales :i* has be5 made s9ce ! publications ( ! ,geological ,survey appe>$4 ,i %all ref] to ^! v5ts m specially 9 ! sequel4 ,i allude to !m "h = ! purpose ( %[+ at ! outset ! m>vell\s complet5ess ( ! volcanic records ( ,ca]n>von%ire4 ,s great has be5 ! d5udation ( ! region t ! pile ( lavas & tuffs :i* accumulat$ imm$iately ar\nd & above ^! orifices has be5 swept away4 ,no trace ( any portion ( t pile has surviv$ to ! we/ ( ! l9e ( bosses2 :ile to ! ea/1 ow+ to curvature & subsequ5t d5udation1 ! rocks h be5 dissect$ f top to bottom1 until almo/ e phase ( ! volcanic activity is reveal$4 ,footnote #aii3 ,op4 cit4 pp4 #acg1 #bbj4 ,footnote #bjj3 ,?is 0 ! ,s$gwick ,prize ,essay = #ahhh1 & 0 publi%$ 9 #ahhi4 ,! volcanic products dis*>g$ f ^! v5ts consi/ ( a succession ( lava-/reams sep>at$ by b&s ( slate1 tuff1 conglom]ate & breccia4 ,^! fragm5tal int]calations1 :i* v>y f a few y>ds to _m hundr$ feet 9 ?ickness1 are important n only z m>k+ pauses 9 ! emission ( lava or 9 ! activity ( ! volcanoes1 b z af=d+ a means ( trac+ ! sev]al lavas to _! respective v5ts4 ,ess5tially1 h[ev]1 ! volcanic mat]ials consi/ ( lava-fl[s1 ! int]calations ( fragm5t>y mat]ials1 ?\gh num]\s1 be+ comp>atively ?94 ,! ?icke/ accumulation ( tuffs is t =m+ mu* ( ! upp] "p ( ,sn[don4 ,x is set d[n by my pr$ecessor at #abjj feet 9 ?ickness1 b ,i %\ld be incl9$ to r$uce ?is e/imate4 ,i %all h occasion to %[ t ! summit & upp] %\ld]s ( ,sn[don are capp$ ) &esites int]/ratifi$ among ! tuffs4 ,sir ,&rew ,ramsay has ref]r$ ) ju/ice to ! difficulty ( always discrim9at+ 9 ! field betwe5 ! f9e tuffs & "s ( ! lavas4#bja ,yet ,i am compell$ to admit t1 if ! gr\nd 7 to be re-mapp$ n[1 ! area repres5t$ z cov]$ by fragm5tal rocks w\ld be consid]ably re/rict$4 ,mr4 ,h>k] is und\bt$ly correct :5 he rem>ks t1 tak5 z a :ole1 ! ,bala volcanic s]ies ( ,ca]n>von%ire is r rem>kable = ! paucity ( g5u9e a%es & agglom]ates4#bjb ,footnote #bja3 ,op4 cit4 p4 #adh4 ,footnote #bjb3 ,bala ,volcanic ,rocks1 p4 #be4 ,! lavas ( ! ,bala volcanic gr\p1 l ^? ( ! ,ar5ig s]ies1 7 mapp$ by ! ,survey z porphyries1 fel/ones1 or felspa?ic traps4 ,!y 7 %[n to be acid-lavas1 hav+ (t5 a well-develop$ fl[-/ructure comp>able ) t ( obsidian & pit*/one1 & to consi/ ( successive %eets t 7 p\r$ out ov] ! sea-floor4 ,_! petrography has subsequ5tly be5 /udi$ m 9 detail by _m obs]v]s1 among :om ,i ne$ only cite ,pr(essor ,bonney1 ,pr(essor ,cole1 ,mr4 ,rutley1 ,mr4 ,teall1 & ,miss ,rais92 ! mo/ important rec5t additions to our k ( ?is subject hav+ be5 made by ,mr4 ,h>k] 9 ! ,essay to :i* ,i h j ref]r$4 ,! great majority ( ^! lavas are ?or\ghly acid rocks1 & pres5t close analogies ( composition & /ructure to mod]n rhyolites1 ?\gh ,i pref] to reta9 = !m ! old "n ( felsites4 ,_! silica-p]c5tage ranges f #ge to m ?an #hj4 ,to ! nak$ eye !y are ext]nally pale greyi%1 or ev5 :ite1 b :5 brok5 into bel[ ! ?ick decompos$ & decol\r$ cru/1 !y are blui%-grey to d>k iron-grey1 or ev5 black4 ,!y break ) a spl9t]y or almo/ con*oidal fracture1 & %[ on a fre% surface an exce$+ly f9e-gra9$1 tol]ably uni=m texture1 ) m9ute scatt]$ felsp>s4 ,"o ( _! mo/ /rik+ features is ! frequ5cy & rem>kable developm5t ( _! fl[-/ructure4 ,n m]ely z a microscopic "*1 b on su* a scale z to be visible at a little di/ance on ! face ( a cliff or crag1 ?is /ructure may be foll[$ = "s way along ! crops ( p>ticul> fl[s4 ,! d>k] & light] b&s ( devitrification1 ) _! l5ticul> =ms1 rude p>allelism & twi/$ curvature1 h be5 comp>$ to ! /ructure ( mica-s*i/ & gneiss4 ,"o aspect ( ?is /ructure1 h[ev]1 appe>s to h escap$ obs]vation1 or1 at lea/1 has attract$ less notice ?an x seems to me to des]ve4 ,9 _m cases x is n difficult to detect1 f ! mann] 9 :i* ! l5ticles & /rips ( ! fl[-/ructure h be5 curl$ ov] & pu%$ onw>d1 :at 0 ! direction 9 :i* ! lava 0 mov+ :ile /ill a visc\s mass4 ,by mak+ a suffici5t numb] ( obs]vations ( ?is direction1 x might 9 "s places be possible to asc]ta9 ! qu>t] f :i* ! sev]al fl[s proce$$4 ,z an illu/ration1 ,i w\ld ref] to "o ( ! basem5t-felsites ( ,sn[don1 :i* =ms a l9e ( picturesque crags on ! slope fac+ ,llanb]is4 ,! lay]s ( v>i\sly-devitrifi$ matt] curl & fold ov] ea* o!r1 & h be5 roll$ into balls1 or h be5 brok5 up & enclos$ "o )9 ! o!r 7,fig4 #ee74 ,! g5]al pu% indicat$ by !m po9ts to a movem5t f ! we/w>d4 ,turn+ r\nd f ! crags1 & look+ t[>ds ! we/1 we see be=e u on ! o!r side ( ! deep vale ( ,llyn ,cwellyn1 at a di/ance ( little m ?an ?ree miles1 ! great dome-%ap$ ,mynydd-mawr1 :i*1 !re is e reason to believe1 m>ks "o ( ! orifices ( eruption4 ,x might 9 ?is way be practicable to obta9 in=mation reg>d+ ev5 "s ( ! v5ts t /ill lie deeply buri$ "u volcanic or s$im5t>y rocks4 ,t ^! felsites 7 p\r$ =? 9 a glassy condition may be inf]r$ f ! occurr5ce ( ! m9ute p]litic & sph]ulitic =ms s *>act]i/ic ( ! devitrification ( once vitre\s rocks4 ,mr4 ,rutley 0 ! fir/ :o call$ att5tion to ?is int]e/+ pro( ( ! close resemblance betwe5 ,palozoic felsites & mod]n obsidians1 & o!r obs]v]s h s9ce confirm$ & ext5d$ 8 obs]vations4#bjc ,footnote #bjc3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxv4 7#ahgi71 p4 #ejh4 ,illu/ration3 ,fig4 #ee4--;,fl[-/ructure 9 ! l[e/ felsite on ! track f ,llanb]is to ! top ( ,sn[don4 ,l5g? ab\t #d feet1 height #b feet4 ,ano!r rem>kable aspect ( ! felsites is t nodul> /ructure s (t5 to be se5 among !m1 & reg>d+ ! orig9 ( :i* s mu* has already be5 writt54 ,i agree ) ,pr(essor ,cole & ,mr4 ,h>k] 9 look+ ^u ! nodules z d]iv$ f orig9al sph]ulites by a process ( alt]ation1 ( :i* almo/ e successive /age may be trac$ until ! orig9al sub/ance ( ! rock has be5 conv]t$ into a fl9ty or agate-l mat]ial4 ,if ?is be ! true explanation ( ! /ructure1 "s ( ! orig9al lavas mu/ h exhibit$ p]litic & sph]ulitic =ms on a gigantic scale4 ,!re c1 ,i ?9k1 be little d\bt t ?is peculi> /ructure 0 v g5]ally misund]/ood by ! e>li] obs]v]s1 :o naturally look$ ^u x z ( cla/ic orig91 & :o !re=e believ$ t l>ge b$s ( rock consi/$ ( volcanic conglom]ate1 :i* we %\ld n[ map z nodul> felsite 7pyrom]ide74#bjd ,footnote #bjd3 ,ano!r s\rce ( error may probably be trac$ 9 ! occasional brecciat$ /ructure ( ! felsites1 :i* has be5 mi/ak5 = true volcanic breccia1 b :i* c be trac$ disappe>+ into ! solid rock4 ,sometimes ?is /ructure has result$ f ! break+ up ( ! l5ticles ( fl[1 sometimes f lat] cru%+4 ,:ile by f> ! l>g] proportion ( ! ,ca]n>von%ire lavas consi/s ( ?or\ghly acid rocks1 ! olde/ outfl[s are mu* less acid ?an ^? erupt$ at ! height ( ! volcanic activity1 :5 ! rocks ( ,sn[don 7 p\r$ =?4#bje ,b t[>ds ! close ( ! p]iod !re 0 app>5tly a fall+ (f 9 ! acidity ( ! magma1 = at ! top ( ! gr\p ! &esitic lavas to :i* ,i h already allud$ are enc\nt]$4 ,sir ,&rew ,ramsay has %[n ! exi/5ce ( an upp] fel/one or felspa?ic porphyry1 almo/ entirely remov$ by d5udation1 b ( :i* outli]s occur on ,crib-go*1 ,lliw$d1 & o!r cre/s ar\nd ,sn[don1 & likewise on ,moel ,hebog4#bjf ,mr4 ,h>k] alludes to ^! remnants1 & speaks ( !m z less acid ?an ! old] lavas1 b he gives no details z to _! /ructure & composition4#bjg ,9 an exam9ation ( ,sn[don ,i 0 surpris$ to f9d t ! summit ( ! m\nta91 in/ead ( consi/+ ( b$d$ a%es z hi!rto repres5t$1 is =m$ ( a gr\p ( lava-%eets hav+ a total ?ickness ( p]haps f #ajj to #aej feet 7#f 9 ,fig4 #ef74 ,! apex ( ,yr ,wyddfa1 ! peak ( ,sn[don1 consi/s ( fossilif]\s %ale ly+ on a dull grey rock t wea!rs ) elongat$ vesicles1 some:at l a cleav$ amygdaloid1 b a good deal decompos$4 ,a ?9 slice ( ?is latt] rock %[s "u ! microscope irregul> gra9s & microlites ( felsp>1 ) a few grams ( qu>tz1 ! :ole mu* %e>$ & calcifi$4 ,bel[ ?is b$ comes a felsite1 or devitrifi$ obsidian1 %[+ 9 places good sph]ulitic /ructure1 & foll[$ by a grey amygdaloid4 ,! latt] is a m>k$ly cellul> rock1 &1 ?\gh r decay$1 %[s "u ! microscope a microlitic felspa?ic gr\ndmass1 ?r\gh :i* granules ( magnetite are disp]s$4 ,footnote #bje3 ,mr4 ,h>k]1 op4 cit4 p4 #abg4 ,footnote #bjf3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 pp4 #ada1 #add1 #ade1 #adg1 #afa4 ,footnote #bjg3 ,bala ,volcanic ,s]ies1 pp4 #aj1 #bc1 #abe4 ,he ref]s also to lavas occupy+ a simil> position at ,nant ,gwynant & ,moel ,hebog2 b he adds t he _h n _h an opportunity ( /udy+ !m4 ,illu/ration3 ,fig4 #ef4--,section ( ,sn[don4#bjh #a4 ,grits & slates2 #b4 ,felsite ) good fl[-/ructure2 #c4 ,volcanic tuffs2 #d4 ,felsite2 #e4 ,tuffs ) %eets ( felsite & &esite2 #f4 ,gr\p ( &esitic lavas on summit ( ,sn[don2 #g4 ,intrusive gre5/ones4 ,footnote #bjh3 ,aft] ! ,geological ,survey ,section 7,horizont4 ,sect4 ,%eet #bh71 slightly modifi$4 ,und]nea? ?is upp] gr\p ( lavas lie ! tuffs = :i* ,sn[don has be5 s long celebrat$4 ,b1 z ,i h already /at$1 !re does n appe> to me to be su* a cont9u\s ?ickness ( fragm5tal mat]ial z has be5 suppos$4 ,!re _c1 ,i ?9k1 be any d\bt t n only at ! top1 b at _m horizons ?r\gh\t ?is suppos$ ?ick accumulation ( tuff1 "s ( ! b$s ( rock are really lava-fl[s4 ,"s ( ^! lavas h suff]$ consid]ably f ! cleavage :i* has affect$ ! :ole ( ! rocks ( ! m\nta91 :ile ! results ( c5turies ( atmosph]ic dis9tegration1 s active 9 t high expos$ locality1 h /ill fur!r contribut$ to alt] !m4 ,!y consequ5tly pres5t on _! wea!r$ faces a resemblance to ! pyrocla/ic rocks among :i* !y lie4 ,:]e1 h[ev]1 ! lavas are ?ick] & m massive1 & h resi/$ cleavage bett]1 "s ( !m appe> z cellul> dull grey &esites or tra*ytes1 :ile a few are felsites4 ,_m in/ructive sections ( su* b&s among ! true tuffs may be se5 on ! ea/]n precipices ( ,sn[don above ,glas-lyn4 ,x ?us appe>s t ! late/ lavas :i* fl[$ f ! ,sn[donian v5t 71 on ! :ole1 decid$ly m basic ?an ! ma9 body ( felsites t imm$iately prec$$ !m4 ,!y occur also 9 ?9n] %eets1 & are f> m abundantly accompani$ ) a%es4 ,at ! same "t x is des]v+ ( special notice t among ^! less acid outfl[s !re are int]calat$ %eets ( felsite1 & t "s ( ^! /ill reta9 ! sph]ulitic /ructure =m$ by ! devitrification ( an orig9al volcanic glass4 ,f> to ! s\?-we/1 9 ! promontory ( ,lleyn1 ano!r gr\p ( volcanic rocks exi/s :i* may h be5 9 a g5]al s5se contemporane\s ) ^? ( ! ,sn[don region1 b :i* 7 c]ta9ly erupt$ f indep5d5t v5ts4 ,mr4 ,h>k] has describ$ !m z qu>tzless pyrox5e-&esites1 sometimes m>k$ly cellul>1 & ?\gh _! geological relations are r obscure1 he reg>ds !m z lava-fl[s int]b$d$ among /rata ( ,bala age & occurr+ bel[ ! *ief rhyolites ( ! di/rict4 ,if ?is be _! true position1 !y indicate ! outfl[ ( mu* less highly silice\s lavas be=e ! eruption ( ! acid felsites4 ,9 ! ,sn[don area any su* int]m$iate rocks :i* may h be5 p\r$ out be=e ! "t ( ! felsitic outfl[s h be5 buri$ "u ^!4 ,! tuffs ( ! ,bala s]ies 9 ,ca]n>von%ire h n receiv$ ! same att5tion z ! lavas4 ,"o ( ! fir/ results ( a m c>eful /udy ( !m w probably be a modification ( ! publi%$ maps by a r$uction ( ! area ov] :i* ^! rocks h be5 repres5t$4 ,!y range f co>se volcanic breccias to exce$+ly f9e compact$ volcanic du/1 :i* _c easily be di/+ui%$1 ei!r 9 ! field or "u ! microscope1 f ! f9] cru%$ =ms ( felsite4 ,among ! olde/ tuffs pieces ( d>k blue %ale z well z ( felsite may be recogniz$1 po9t+ to ! explosions by :i* ! v5ts 7 drill$ ?r\gh ! old] ,silurian s$im5ts already deposit$ & consolidat$4 ,sometimes1 inde$1 !y recall ! d>k slate-tuffs ( ,cad] ,idris1 l :i* !y are pl5tifully spr9kl$ ) kaol9iz$ felsp> cry/als4 ,! b$s ( volcanic breccia int]calat$ betwe5 ! l[] felsites ( ,sn[don include magnific5t examples ( ! accumulation ( co>se volcanic detritus4 ,! blocks ( v>i\s felsites 9 !m are (t5 a y>d or m 9 diamet]4 ,among ! felsite fragm5ts small] scatt]$ pieces ( &esitic rocks may be f\nd4 ,?is mixture ( m basic mat]ials appe>s to increase upw>ds1 ! highe/ a%es conta9+ detritus ( &esitic lavas l ^? :i* occur among !m z fl[s4 ,! tuffs 9 ! upp] "p ( ,sn[don are well-b$d$ deposits made up p>tly ( volcanic detritus & p>tly ( ord9>y muddy s$im5t4#bji ,lay]s ( blue %ale or slate int]/ratifi$ among !m indicate t ! enfeebl$ volcanic activity m>k$ by ! f9e tuffs pass$ occasionally into a /ate ( quiesc5ce4 ,z is well kn[n1 num]\s fossils *>act]i/ic ( ! ,bala rocks occur 9 ^! tuffs4 ,! volcanic dis*>ges are ?us prov$ to h be5 subm>9e & to h occurr$ dur+ ,bala "t4 ,footnote #bji3 ,see ! int]e/+ acc\nt ( ^! tuffs giv5 by ,sir ,a4 ,ramsay1 ,mem4 ,geol4 ,survey1 vol4 iii4 #bnd edit4 p4 #adb4 ,i h already allud$ to "s ( ! probable v5ts f :i* ! lavas & tuffs 7 dis*>g$1 & to _! position along a l9e drawn f ,p5ma5-mawr into ! p59sula ( ,lleyn4 ,x w be obs]v$ t !y lie outside ! area ( ! b$d$ volcanic rocks & rise ?r\gh p>ts ( ! ,silurian sy/em old] ?an ^! rocks4 ,! l>ge/ & mo/ important ( !m is unque/ionably t =m$ by ,y-foel-frs & its neighb\r+ heights4 ,z mapp$ by ! ,geological ,survey1 ?is mass ( igne\s rock is irregul>ly elliptical1 measures ab\t six squ>e miles 9 area1 & consi/s ma9ly ( intrusive fel/one-porphyry pass+ into hornbl5dic gre5/one4#baj ,mr4 ,h>k]1 h[ev]1 has made an important correction ( ?is petrography1 by %[+ t a l>ge "p ( ! area consi/s ( augitic granophyre1 :ile ! s-call$ gre5/one is p>tly diabase & p>tly &esitic a%es & agglom]ates4 ,he sugge/s t an old] v5t has "h be5 de/roy$ by a lat] & l>g] protrusion ( igne\s matt]4#baa ,?is high & some:at inaccessible tract ( gr\nd is /ill 9 ne$ ( detail$ mapp+ & clos] /udy1 = und\bt$ly x is ! mo/ important volcanic v5t n[ visible 9 ,nor? ,wales4 ,my =m] colleague 9 ! ,geological ,survey1 ,mr4 ,e4 ,gre5ly1 sp5t a week ^u x "s ye>s ago1 & k9dly suppli$ me ) ! foll[+ notes ( 8 obs]vations3--,! c5tral & l>ge/ area ( ! neck is ma9ly occupi$ ) diabases & &esites1 :ile ! a%es & agglom]ates1 :i* are intimately connect$ ) !m1 seem to run z a belt or r+ r\nd !m1 & to occur 9 "o or m pat*es 9 ! mid/ ( !m4 ,portions ( gre5 amygdaloid run ?r\gh ! pyrocla/ic masses4 ,outside ! r+ ( agglom]ate & a%es an int]rupt$ bord] ( felsite c be trac$1 :i* may be presum$ to be old] ?an !y1 = a block ( x 0 obs]v$ 9 !m4 ,! granophyre1 on ! o!r h&1 :i* is int]pos$ betwe5 ! fragm5tal masses & ! surr\nd+ rocks on ! we/]n wall ( ! v5t1 seems to be ( lat] date4 ,dykes or small bosses ( diabase1 l ! mat]ial ( ! sills1 pi]ce bo? ! agglom]ates & ! rocks ( ! c5tre4#bab ,footnote #baj3 ,mem4 ,geol4 ,survey1 vol4 iii4 #bnd edit4 pp4 #acg1 #aci4 ,footnote #baa3 ,bala ,volcanic ,s]ies1 pp4 #da1 #ga1 #gb1 #abc4 ,footnote #bab3 ,mr4 ,gre5ly has made a sket* map ( ?is int]e/+ locality4 ,z he has n[ e/abli%$ 8 home 9 ,nor? ,wales1 ,i tru/ he may f9d an opportunity ( return+ to ,y-foel-frs & complet+ 8 inve/igations4 ,no agglom]ate appe>s to h be5 notic$ by any obs]v] among ! o!r suppos$ v5ts along ! l9e t runs s\?-we/w>ds f ,p5ma5-mawr1 to ! promontory ( ,lleyn4 ,^! bosses are rudely circul> 9 gr\nd-plan & rise v]tically out ( ! ,l[] ,silurian or ,cambrian /rata1 or p>take m ( ! nature ( l5ticul> %eets or laccolites :i* h be5 ?ru/ betwe5 ! planes ( b$d+4 ,!re is usually an obs]vable alt]ation ( ! surr\nd+ rocks along ! l9e ( contact4 ,! mat]ial ( ^! bosses is sometimes ?or\ghly acid1 z is ! granophyre ( ,y-foel-frs1 ! microgranite ( ,mynydd-mawr ) its riebeckite cry/als1 ! augite-granite-porphyry ( ,clynog-fawr1 & ! granophyric & rhyolitic qu>tz-porphyries ( ! ,rivals4 ,9 o!r cases ! rock is ( an int]m$iate grade1 z 9 ! en/atite-diorite ( ,p5ma5-mawr1 ! pyrox5e-&esite ( ,c>n ,boduan1 & ! qu>tz-augite-sy5ite ( ,llanfogl54#bac ,a few bosses ( /ill m basic mat]ial occur 9 ! ,s>n di/rict1 includ+ hornbl5de-diabase & hornbl5de-picrite4 ,sometimes bo? ! acid & ! m basic rocks are f\nd 9 ! same boss1 z 9 ! l>ge mass ( ,y-foel-frs4 ,footnote #bac3 ,! geological relations & petrographical *>act]s ( ^! v>i\s rocks are giv5 by ,mr4 ,h>k] 9 ! f\r? & fif? sections ( 8 ,essay4 ,x mu/ be confess$ t !re is no absolute pro( t any ( ^! masses m>k ! actual sites ( eruptive v5ts1 except probably ! boss ( ,y-foel-frs4 ,"s ( !m may h be5 intrud$ )\t e/abli%+ any outlet to ! surface4#bad ,b t a few ( !m really repres5t orifices f :i* ! ,bala volcanic gr\p 0 erupt$ may be plausibly inf]r$ f _! neck-l =m1 f _! positions ) ref]5ce to ! volcanic di/rict1 f ! obvi\s ?ick5+ ( ! lavas & tuffs 9 ! direction ( ^! bosses1 & f ! petrographical relation t exi/s betwe5 _! compon5t mat]ials & rocks t 7 dis*>g$ at ! surface4 ,?is la/-nam$ feature has be5 well po9t$ out by ,mr4 ,h>k]1 :o has e/abli%$1 by a /udy ( microscopic slides1 a gradation f ! granophyric mat]ial ( ! bosses into /ructures greatly resembl+ ^? ( ! b$d$ felsites1 & likewise a close simil>ity betwe5 ! int]m$iate rocks ( ! o!r bosses & ! &esites :i* h else:]e be5 p\r$ out at ! surface4#bae ,b p]haps ! mo/ impressive evid5ce z to ! sites ( ! *ief c5tres ( eruption is suppli$ by ! lavas & tuffs !mselves z !y ?ick5 9 c]ta9 directions & ?9 away 9 o!rs4 ,?is feature ( _! di/ribution has be5 well express$ 9 ! maps & sections ( ! ,survey1 & has be5 cle>ly summ>iz$ by ,mr4 ,h>k]4#baf ,! olde/ lavas n[ visible lie at ! nor!rn end ( ! di/rict1 & ! v5ts f :i* !y proce$$ may1 ) consid]able probability1 be plac$ some:]e 9 ! tract :i* includes ! *a9 ( bosses ( ,p5ma5-mawr1 ,y-foel-frs1 & ,y ,drosgl4 ,! *ief c5tre ( eruption no d\bt lay some:]e 9 ! ,sn[don tract1 :]e ! lavas & tuffs atta9 _! greate/ ?ickness1 & :5ce !y ?9 away 9 all directions4 ,! ,mynydd-mawr boss may be presum$ to h be5 "o ( ! ma9 v5ts4 ,b !re 7 n improbably o!rs1 n[ conceal$ "u ! deep cov] ( _! own ejections4 ,footnote #bad3 ,mr4 ,h>k] speaks ( "s ( !m z laccolites4 ,footnote #bae3 ,op4 cit4 pp4 #eg1 #gb4 ,footnote #baf3 ,see especially pp4 #i1 #abj et seq41 & fig4 #f ( 8 ,essay4 ,m dilig5t se>*1 ) a special eye to ! discov]y ( su* v5ts1 might inde$ be rew>d$1 ev5 9 ! mid/ ( ! volcanic di/rict itself4 ,to ! nor?-ea/ ( ,capel ,curig1 = example1 !re is a prom95t knob ( agglom]ate1#bag :i* ,i visit$ ) ,mr4 ,b4 ,n4 ,pea*1 & :i* we reg>d$ z probably m>k+ "o ( ! m9or v5ts4 ,! mat]ial ( ?is em95ce has a base :i* by itself w\ld probably be reg>d$ by ! field-geologi/ z a felsite4 ,b ?r\gh ?is compact matrix are disp]s$ abundant /ones ( all sizes up to six in*es or m 9 diamet]4 ,!y are mo/ly subangul> or some:at r\nd$-(f at ! edges1 & g5]ally m>k$ly cellul>4 ,among !m may be obs]v$ pieces ( tra*yte1 felsite1 & a rock t is probably a devitrifi$ pit*/one or obsidian4 ,! vesicles 9 ^! /ones are sometimes l9$ ) an acicul> zeolite4 ,traces ( rude b$d+ c be detect$1 dipp+ at high angles4 ,on ! nor?-ea/ side ( ! hill f9] agglom]ate is se5 to alt]nate ) a%y grits & grey %ales1 :i*1 dipp+ ,e4,n4,e4 at #bj-cj1 pass "u a gr\p ( felsites1 "o at lea/ ( :i* reta9s a v f9e p]litic /ructure & evid5tly fl[$ z a true glass4 ,"s ( ^! lavas are full ( enclos$ pieces ( v>i\s fl9ty cellul> & porphyritic felsites & &esites or tra*ytes1 l ! /ones :i* occur abundantly 9 ! agglom]ate4 ,! connection ( ^! b$d$ lavas & tuffs ) ! agglom]ate-neck seems obvi\s4 ,footnote #bag3 ,?is rock is ref]r$ to 9 ! ,geological ,survey ,memoir z a %ort ?ick b& ( conglom]atic a%1 :i* /rikes nor?w>ds ab\t half a mile & !n disappe>s 7p4 #acd74 ,! ,ca]n>von%ire volcanic area furni%es ano!r admirable example ( ! intrusion ( basic sills z a f9al phase ( eruptivity4 ,^! masses h be5 c>efully sep>at$ out on ! maps ( ! ,geological ,survey1 :i* pres5t a /rik+ picture ( _! di/ribution & _! relation to ! o!r igne\s rocks4 ,an exam9ation ( ! maps %[s at once t ! basic %eets t5d to lie p>allel ) ! b$d+ along c]ta9 horizons4 ,9 ! s\!rn & we/]n portions ( ! area !y h =c$ !mselves among ! ,l[] ,silurian s$im5t>y /rata t und]lie ! ,bala volcanic gr\p--a position analog\s to t tak5 by ! correspond+ sills ( ! ,ar5ig s]ies4 ,b !y likewise invade ! volcanic gr\p itself4 ,along ! ea/]n bord]s ( ! di/rict !y ab\nd1 especially 9 ! high] p>ts ( ! volcanic pile1 :]e !y h be5 inject$ betwe5 ! fl[s1 & h subsequ5tly p>ticipat$ 9 ! abundant plication ( ! rocks betwe5 ! m\nta9s & ! l9e ( ! ,riv] ,conway4 ,! curvatures into :i* ! rocks ( ! region h be5 ?r[n1 & ! consequ5t bread? ( c\ntry ov] :i* ! volcanic %eets c n[ be exam9$1 furni% a mu* bett] field ?an ,m]ione?%ire = ! attempt to trace ! probable c5tre or c5tres f :i* ! basic magma ( ! sills 0 protrud$4 ,a /udy ( ! ,survey maps soon leads to a conviction t ! intrusions 7 n connect$1 except p]haps to a trifl+ ext5t1 ) ! great l9e ( we/]n v5ts4 ,x is rem>kable t ! old] /rata :i* em]ge f "u ! volcanic gr\p on its we/]n outcrop are1 on ! :ole1 s+ul>ly free f sills1 ?\gh "s conspicu\s examples are %[n opposite to ,mynydd-mawr1 :ile a few m occur fur!r nor? along ! same l9e4 ,_! l5ticul> =ms1 _! %ort outcrops1 & _! appe>ance on diff]5t horizons at widely sep>at$ po9ts seem to indicate t ! sills probably proce$$ f _m di/9ct subt]ranean pipes4 ,_! great] abundance along ! ea/]n "p ( ! di/rict may be tak5 to indicate t ! ducts lay = ! mo/ "p consid]ably to ! ea/w>d ( ! l9e ( we/]n v5ts4 ,!y may h ris5 9 m9or funnels1 l t ( ,capel ,curig4 ,x is notewor?y t s abundant an extravasation ( basic mat]ial %\ld h tak5 place )\t ! =mation ( num]\s dykes4 ,we h "h a repetition ( ! ph5om5a t di/+ui%$ ! prec$+ ,ar5ig volcanic p]iod 9 ,m]ione?%ire1 & x w be rememb]$ t ! ,ll&eilo eruptions ( ,buil? 7 likewise foll[$ by ! injection ( l>ge bodies ( basic rock4 ,z an enorm\s am\nt ( igne\s magma may ?us be impell$ into ! ,e>?'s cru/ )\t ! =mation ( dykes1 x is evid5t t ! conditions = ! production ( sills mu/ be 9 "s important respects diff]5t f ^? requir$ = dykes4 ,no evid5ce has yet be5 obta9$ t any "o ( ^! sills e/abli%$ a connection ) ! surface4 ,n a trace c be f\nd ( ! outp\r+ ( any su* basic lava-/reams1 nor h fragm5ts ( su* mat]ials be5 met ) 9 any ( ! tuffs4 ,on ! o!r h&1 !re is abundant pro( ( ! usual contact-metamorphism4 ,?\gh ! sills con=m on ! :ole to ! b$d+1 !y frequ5tly break across x4 ,!y swell into ?ick irregul> masses1 & ?9 out rapidly4 ,9 %ort1 !y behave z true intrusive %eets1 & n z b$d$ lavas4 ,9 reg>d to _! int]nal "*1 !y %[ ! cu/om>y uni=mity ( texture ?r\gh\t ea* mass4 ,!y are mapp$ "u ! g5]al "n ( gre5/ones by ! ,geological ,survey1 & are describ$ 9 ! ,memoir z hornbl5dic4#bah ,! m precise mod]n me?ods ( exam9ation1 h[ev]1 prove !m to be true diabases1 9 :i* ! felsp> has1 z a rule1 consolidat$ be=e ! augite1 giv+ z a result ! v>i\s types ( diabasic /ructure4#bai ,footnote #bah3 ,op4 cit4 p4 #aef4 ,footnote #bai3 ,mr4 ,h>k]1 ,bala ,volcanic ,s]ies1 p4 #hc4 ,! date ( ! intrusion ( ^! basic sills c be fix$ by ! same process ( reason+ z 0 appli$ to ^? ( ! ,ar5ig volcanic gr\p4 ,_! connection ) ! o!r igne\s rocks ( ,ca]n>von%ire is s obvi\s t !y mu/ be includ$ z "p ( ! volcanic hi/ory ( ! ,bala p]iod4 ,b !y cle>ly belong to a late /age1 p]haps ! v late/ /age1 ( t hi/ory4 ,!y probably c\ld n h be5 inject$ into _! pres5t positions1 unless a consid]able mass ( rocky mat]ial _h ov]la9 !m4 ,"s ( !m are c]ta9ly y\ng] ?an ! tuffs ( ,sn[don & ,moel ,hebog1 :i* belong to a late "p ( ! volcanic p]iod4 ,on ! o!r h&1 !y _h be5 intrud$ be=e ! curvature & compression ( ! region1 = !y %>e 9 ! fold+s & cleavage ( ! rocks among :i* !y lie4 ,! t]re/rial movem5ts t produc$ ?is di/urbance h be5 prov$ to h occurr$ aft] ! "t :5 ! upp]mo/ ,bala rocks 7 deposit$1 & be=e t ( ! accumulation ( ! ,upp] ,silurian =mations4#bbj ,! epo* ( intrusion is ?us n>r[$ d[n to "s "p ( ! ,upp] ,bala p]iod4 ,) ?is subt]ranean manife/ation1 volcanic action 9 ?is "p ( ! c\ntry f9ally di$ out4 ,footnote #bbj3 ,mem4 ,geol4 ,sur4 vol4 iii4 #bnd edit4 p4 #cbf4 ,see also ,mr4 ,h>k]'s ,bala ,volcanic ,s]ies1 p4 #gf4 iv4 ,,! ,,volcanic ,,c5tre ,,( ,,! ,,b]wyn ,,hills ,among ! ?ick gr\p ( s$im5t>y =mations :i* ov]lies ! great volcanic ridge ( ! ,arans & ,ar5ig1 & undulates ea/w>ds across ! ,bala ,valley1 occasional ?9 int]calations ( tuff po9t to ! exi/5ce ( ano!r c5tre ( volcanic activity :i* lay some:]e 9 ! region ( ! ,b]wyn ,hills4 ,! /ructure ( ?is gr\nd1 fir/ indicat$ by ,s$gwick1 0 inve/igat$ 9 detail by ,j4 ,b4 ,jukes & 8 colleagues1 ^: "w 0 embodi$ 9 ! ,maps1 ,sections & ,memoirs ( ! ,geological ,survey4#bba ,! di/+ui%+ *>act]i/ics ( ! volcanic rocks ( ?is di/rict are ! occurr5ce ( bo? lavas & tuffs z comp>atively ?9 solit>y b&s 9 ! mid/ ( ! ord9>y s$im5ts1 & ! p]si/5ce ( ^! b&s = a di/ance ( sometimes m ?an #bd miles4 ,! position ( ! v5t or v5ts f :i* ?is ext5sive outp\r+ ( volcanic mat]ial took place has n be5 reveal$4 ,z ! b&s t5d to ?9 away ea/w>ds1 x may be surmis$ t ! *ief focus ( eruption lay r t[>ds ! we/1 p]haps "u ! tr\gh ( ,upp] ,silurian /rata some:]e 9 ! neighb\rhood ( ,ll&d]fel4 ,!re 0 probably ano!r 9 ! ,hirnant di/rict4 ,footnote #bba3 ,see ,%eet #gd ( ! "o-in* map2 ,%eets #cb1 #ce1 #cg & #ch ( ! ,horizontal ,sections2 & *apt] xxxi4 ( ! ,memoir on ! ,geology ( ,nor? ,wales4 ,! mapp+ ( ! (fic]s ( ! ,survey %[$ t 9 ! ,b]wyn ,hills !re are repres5tatives ( bo? ! great volcanic p]iods ( ,nor? ,wales4 ,a l[] s]ies ( fel/ones & gre5/ones probably belongs to ! old] p]iod1 :i* began t[>ds ! end ( ,cambrian "t & la/$ 9 "s di/ricts ev5 into ! "t ( ! ,ll&eilo =mation4 ,an upp] gr\p ( tuffs1 ly+ among ! ,bala rocks1 is evid5tly equival5t1 on ! :ole1 to ! mu* ?ick] volcanic s]ies ( ! ,sn[don region4 ,! l[e/ visible volcanic rocks occur among ! hills to ! nor?-we/ ( ,llanrhaiadr yn ,mo*nant4 ,!y are describ$ z consi/+ ( fel/one ( a pale gre5i%-grey col\r & compact texture1 l ^? ( ,ar5ig1 & a%es di/9ctly int]/ratifi$ ) ! slates4 ,no exact petrographical exam9ation ( ^! rocks has yet be5 made4 ,f ! acc\nt giv5 9 ! ,survey ,memoir !re appe>s to be "h a gr\p ( lavas & tuffs int]calat$ 9 ,ll&eilo p]haps p>tly 9 ,upp] ,ar5ig1 /rata :i* =m ! brok5 dome ( ! ,b]wyn anticl9e4 ,! lavas are repres5t$ z ly+ on f\r or five plat=ms1 a s+le b& rea*+ a ?ickness ( #cjj feet & sep>at$ f ! next b& by sometimes #ajjj or #aejj feet ( non-volcanic s$im5t4 ,^! l[] lavas1 accord+ to ! measurem5ts ( ,jukes1 are ov]la9 by m ?an #djjj feet ( s$im5t>y /rata be=e ! upp] or ,bala volcanic s]ies is rea*$4 ,?ree successive a%-b$s con/itute ?is upp] s]ies4 ,( ^! ! l[e/ b&1 ab\t #ej or #fj feet ?ick1 0 nam$ a gre5/one a% 9 contradi/9ction to a fel/one a%1 & 0 n traceable = m ?an a %ort di/ance4 ,above x1 aft] an int]v5+ ?ickness ( sev]al hundr$ feet ( s$im5t>y /rata1 comes a second & mu* m cont9u\s b& ( tuff1 kn[n z ! ,l[] a%-b$1 ab\t #ajj feet ?ick on ! we/ front ( ! ,b]wyn range4 ,/ill high]1 aft] an int]val ( ab\t #aejj feet ( slates1 lies ! ,upp] a%-b$1 :i* on ! same l9e ( section has a ?ickness ( ab\t #bjj feet4 ,?is is ! mo/ p]si/5t ( all ! volcanic horizons1 = x c be foll[$ cont9u\sly r\nd ! :ole range ( ! ,b]wyns until x is ov]la9 by ! ,c>bonif]\s ,lime/one ne> ,selattyn1 a di/ance ( n less ?an tw5ty-f\r miles4 ,! same b&1 b mu* m feebly develop$1 has be5 trac$ ?r\gh ! fault$ c\ntry on bo? sides ( ,bala ,lake1 :]e x =m$ a useful plat=m 9 ! inve/igation ( ! complicat$ geological /ructure ( t area4 ,along ! nor? side ( ! ,b]wyn ,hills ano!r ?9 b& ( tuff lies f #aej to #bjj feet /ill high] up 9 ! s]ies1 & has be5 trac$ = a di/ance ( ab\t twelve miles4 ,! ,bala lime/one comes 9 ab\t #hjj or #ajjj feet above ! ,upp] a%-b$4 ,illu/ration3 ,fig4 #eg4--,section across ! ,b]wyn ,hills4 7,r$uc$ f ,horizontal ,section1 ,geol4 ,surv41 ,%eet #ce74 ,l1 ,ll&eilo ,flags2 ,b1 ,bala gr\p2 ,b ,l1 ,bala ,lime/one2 t t1 volcanic tuffs2 ,d1 intrusive gre5/ones4 ,besides ! rocks n[ enum]at$1 ! ,survey maps %[ ! int]calation ( f\r or five %eets ( gre5/one1 :i* are repres5t$ z foll[+ ) m>k$ regul>ity ! /rike ( ! /rata4 ,until ^! %eets h be5 m precisely exam9$ x is impossible to decide reg>d+ _! true petrographical "*1 or to det]m9e :e!r !y are sills1 or int]/ratifi$ lavas1 or include rocks ( bo? ^! types4 ,v4 ,,! ,,volcanoes ,,( ,,anglesey ,we n[ turn to ano!r "p ( ! c\ntry1 ab\t :i* mu* has be5 writt5 & ke5 controv]sy has aris54 ,9 ! c5tre ( ,anglesey1 among ! rocks gr\p$ toge!r by ! ,geological ,survey z alt]$ ,cambrian1 !re occur masses ( breccia1 ! probable volcanic orig9 ( :i* 01 s f> z ,i "k1 fir/ sugge/$ by ,pr(essor ,hughes4#bbb ,dr4 ,callaway reg>ds !m z pre-,cambrian1#bbc :ile ,pr(essor ,blake places !m 9 8 ,monian sy/em4#bbd ,:5 ,i w5t ov] !m "s ye>s ago1 ,i accept$ ! view t !y are volcanic agglom]ates4#bbe ,subsequ5t exam9ation1 h[ev]1 has conv9c$ me t not)/&+ _! rem>kable resemblance to true agglom]ates !y are n really ( volcanic orig91 b are ess5tially cru%-conglom]ates1 l ^? 9 ! ,isle ( ,man1 s well describ$ by ,mr4 ,lamplugh4#bbf ,footnote #bbb3 ,proc4 ,camb4 ,phil4 ,soc4 vol4 iii4 7#ahhj71 p4 #cdg4 ,footnote #bbc3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 ,footnote #bbd3 ,op4 cit4 ,footnote #bbe3 ,presid5tial ,address ,geol4 ,soc4 vol4 xlvii4 7#ahia71 p4 #acj4 ,footnote #bbf3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 li4 7#ahie71 p4 #efc4 ,see ,geol4 ,mag4 #ahif1 p4 #dha4 ,b ?\gh _! pres5t co>se1 agglom]ate-l /ructure is1 ,i ?9k1 entirely due to ! me*anical cru%+ ( ! rocks 9 situ & n to volcanic explosions1 x does n foll[ t ! rocks :i* h be5 brok5 up d n conta9 evid5ce ( volcanic action contemporane\s ) _! orig9al =mation4 ,obvi\sly1 pyrocla/ic mat]ials may be subject$ to de=mation & disruption z well z any o!r compon5ts ( ! e>?'s cru/1 & may be equally conv]t$ into cru%-conglom]ates4 ,& 9 ,anglesey x c1 ,i ?9k1 be %[n t "s ( ! rocks :i* h be5 brok5 up 7 orig9ally tuffs & volcanic breccias4 ,?r\gh\t ,anglesey ! /ratifi$ rocks pres5t evid5ce ( hav+ und]gone v great compression1 de=mation & rupture4 ,?us at ,llan]*ym$d ?ick-b$d$ ,l[] ,silurian grits1 ) _! int]calations ( %ale1 h be5 brok5 up by num]\s small faults1 & h be5 pu%$ ov] ea* o!r 9 l>ge irregul> blocks1 ! %ales be+ n[ p9*$ out1 & n[ press$ up into ! int]/ices betwe5 ! dislocat$ h>d] & m resi/+ grits4 ,?is condition ( rupture may be reg>d$ z "o ( ! /ages t[>ds ! =mation ( a conglom]ate by ! cru%+ toge!r ( rocks 9 situ4 ,a few miles fur!r s\? at ! beg9n+ ( ! railway cutt+s ( ,llangefni1 gre51 r$ & purple slates & grits appe> 9 a r m cru%$ /ate1 & imm$iately beyond ^! /rata come ! co>se breccias4 ,nei!r 9 _! composition nor 9 _! /ructural condition d ^! ,llangefni /rata appe> to be m>k$ (f f ! und\bt$ ,l[] ,silurian rocks z p>ts ( a diff]5t sy/em4 ,! railway cutt+s at ,llangefni reveal a s]ies ( rocks :i* appe> to h be5 orig9ally %ales1 ) ?9 b&s ( silice\s grit4 ,! argillace\s portions ( ?is s]ies are n[ gre5 & phyllitic1 & rem9d "o ( ! f9] p>ts ( "s basic tuffs among ! old] ,palozoic sy/ems4 ,!y include1 h[ev]1 pale fl9ty b&s1 su* z might h be5 d]iv$ f f9e felsitic du/4 ,! grits are = ! mo/ "p f9e-gra9$ & highly silice\s1 b !y include also co>s] v>ieties ) cle> qu>tz-gra9s4 ,! enorm\s de=mation :i* ^! /rata h und]gone is at once app>5t4 ,!y seem to h be5 plicat$1 ruptur$ & ?ru/ ov] ea* o!r1 ! h>d] p>ts surviv+ longe/1 b be+ ev5tually brok5 into small fragm5ts4 ,e /age may be trac$ f a recognizable b& ( grit d[n to ! r\nd$ or elliptical pebbles ( ! same mat]ial entirely isolat$ 9 ?is phyllitic matrix ( cru%$ %ale4 ,b :ile ! volcanic orig9 ( ^! co>sely-fragm5tal masses _c be ma9ta9$1 !re is else:]e evid5ce t ! old] ,palozoic rocks ( ,anglesey include relics ( contemporane\s volcanic eruptions4 ,sev5 miles to ! s\?-ea/ ( ,holyhead1 9 ! basal ,l[] ,silurian conglom]ates :i*1 z be=e ref]r$ to1 ,mr4 ,selwyn f\nd ly+ uncon=mably on ! gre5 s*i/s1 !re occur abundant fragm5ts ( volcanic rocks1 besides ! preval5t detritus ( ! s*i/s ( ! neighb\rhood4 ,"s ( ! b&s h some:at ! "* ( volcanic breccias or tuffs1 & !y %[ an evid5t resemblance to portions ( ! ,bangor gr\p & ! rocks ( ,llyn ,pad>n1 ?\gh !y are d\btless ( mu* lat] age4 ,t ^! volcanic fragm5ts 7 n d]iv$ f ! wa/e ( rocks ( a mu* e>li] p]iod is made tol]ably c]ta9 by ! int]calation ( true tuffs among ! black %ales high] up 9 ! ord] ( succession4 ,"h1 !n1 we h evid5ce ( contemporane\s volcanic action 9 ! v basem5t ,l[] ,silurian /rata ( ,anglesey1 :i* by _! fossil cont5ts are %[n to be on ! horizon ( ! l[e/ ,ar5ig or ev5 ,tremadoc gr\p4 ,b /ill fur!r & full] evid5ce ( ,silurian volcanism is to be obta9$ by an exam9ation ( ! nor!rn coa/-l9e4 ,i h already ref]r$ to ! elliptical fault :i* is m>k$ on ! ,geological ,survey map z runn+ f ! nor?-we/]n headl& to ! ea/]n coa/ beyond ,amlw*4 ,! necessity = ins]t+ ?is fault1 ap>t f any actual visible trace ( its occurr5ce1 arose :5 ! conclusion 0 arriv$ at t ! rocks ( ! extreme nor? ( ,anglesey 7 ess5tially alt]$ ,cambrian /rata4#bbg ,= imm$iately to ! s\? ( ^! rocks black %ales1 obvi\sly ,silurian1 7 se5 to dip to ! nor?--a /ructure :i* c\ld only be acc\nt$ = by a dislocation lett+ !m d[n into t position4 ,! same necessity = a fault has ( c\rse be5 felt by all writ]s :o h subsequ5tly treat$ ! nor!rn area z pre-,cambrian4 ,b x is des]v+ ( notice t 9 ! orig9al mapp+ ( ! ,survey no cont9u\s abrupt hiatus is %[n by ! l9e :i* 0 aft]w>ds m>k$ z a cont9u\s l9e ( fault4 ,on ! contr>y1 on "o ( ! field-maps 91 ,i believe1 ,mr4 ,selwyn's h&writ+ ! rem>k occurs3--,! gradual passage f ! black %ale to ! upp] gre5 gritty slates ( ,llanfe*ell is be/ se5 at ,bo!dd1 on road f ,llanfae?lu to ,llyn-llygeirian4#bbh ,footnote #bbg3 ,i h fully consid]$ ! evid5ce adduc$ by ,dr4 ,callaway & ,pr(essor ,blake1 & h exam9$ ! gr\nd1 & c come to no o!r conclusion ?an t /at$ 9 ! text4 ,b see ,mr4 ,blake's rem>ks1 ,geol4 ,mag4 #ahia1 p4 #dhc4 ,footnote #bbh3 ,!re is no cont9u\s section n[ visible at ?is place1 b ! two gr\ps ( rock c be trac$ to )9 a few feet ( ea* o!r1 bo? incl9$ z usual 9 ! same direction1 & ! black %ales appe>+ to pass "u ! o!rs4 ,x is no "p ( my aim to disprove ! exi/5ce ( faults along ! l9e ref]r$ to4 ,^! may q well exi/2 b !re is assur$ly no "o gigantic displacem5t1 su* z ! !ory ,i am combat+ w\ld require2 :ile any faults :i* d occur _c be greatly diff]5t f ! o!rs ( ! di/rict1 & d n prev5t ! true relations ( ! rocks f be+ discov]able4 ,:]e ! suppos$ elliptical fault rea*es ! %ore at ,c>mel ,po9t1 ! two gr\ps ( rock seem to me to foll[ ea* o!r 9 unbrok5 sequ5ce4#bbi ,! black slates1 :i* are admitt$ly ,l[] ,silurian1 dip und]nea? a breccia & gre5i% 7,amlw*7 slates4 ,n only s1 b b&s ( simil> black slates occur high] up1 int]/ratifi$ ) & %ad+-(f into tuffs & gre5i% slates4 ,fur!r1 b&s ( co>se volcanic breccia occur among ! black slates s\? ( ! suppos$ break4 ,^!1 9 accordance ) ! exig5cies ( !ory1 are repres5t$ z sep>at$ by a network ( faults f ! black slates amid :i* !y lie4 ,b good evid5ce may be f\nd t !y are truly int]b$d$ 9 ^! slates4 ,9 %ort1 ! :ole ( ! rocks 9 t "p ( ,anglesey =m "o great s]ies1 consi/+ p>tly ( black slates1 p>tly ( gre5i% slates1 ) abundant int]calations ( volcanic detritus4 ,! age ( ! base ( ?is s]ies is moreov] det]m9$ by ! occurr5ce ( ,bala fossils 9 a b& ( lime/one ne> ,c>mel ,po9t4 ,footnote #bbi3 ,i _c admit t !re is any evid5ce ( a ?ru/-plane "h4 ,to ins]t "o is m]ely to modify field-evid5ce to suit !ory4 ,see ,geol4 ,mag4 #ahia1 p4 #dhc4 ,! rocks :i* ext5d ea/w>d along ! coa/ f ! nor?-we/]n headl& ( ,anglesey are m>k$ on ! ,survey map z gre51 grey & purple slates ) conglom]atic & silice\s b$s4 ,! truly volcanic nature ( a consid]able proportion ( ^! /rata has be5 cle>ly /at$ by ,mr4 ,blake4#bcj ,z !y dip 9 a g5]al nor!rly direction1 high] portions ( ! s]ies pres5t !mselves z f> z ! mo/ nor!rn projection ( ! isl& ne> ,por? ,w5 7,fig4 #eh74 ,!y h be5 greatly crumpl$ & cru%$1 s t ! slates pass into phyllites4 ,!y include "s ?ick seams ( blue lime/one & :ite qu>tzite1 also c\rses ( black %ale conta9+ ,l[] ,silurian graptolites4 ,among _! upp]mo/ /rata sev]al 7probably ,bala7 fossils1 includ+ ,or?is ,bailyana1 h be5 obta9$ by ,pr(essor ,hughes4 ,x has be5 suppos$ t ! high] b&s ( black %ale may also h be5 br\ght into _! pres5t positions by faults1 & t !y d n really belong to ! s]ies ( /rata among :i* !y lie4 ,b ?is sugge/ion is completely disprov$ by ! coa/-sections1 :i* exhibit _m ?9 int]/ratifi$ leaves ( black %ale1 sometimes less ?an an in* ?ick4 ,^! & ! a%y lay]s conta9+ ! ,or?is & o!r fossils =m an integral "p ( ! s-call$ ,amlw* slates4#bca ,footnote #bcj3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xliv4 7#ahhh71 p4 #eag4 ,see 8 fur!r rem>ks 9 ,geol4 ,mag4 #ahia1 p4 #dhc4 ,footnote #bca3 ,! ,amlw* slates exhibit on a great scale ! puck]+ t po9ts to int5se compression4 ,?is gn>l$ /ructure1 z ,pr(4 ,hughes call$ x1 has be5 illu/rat$ by ,mr4 ,h>k]1 ,briti% ,assoc4 ,report 7#ahhe71 pp4 #hci1 #hdj4 ,z evid5ce ( ! regul> int]calation ( ! black %ales & tuffs 9 ?is s$im5t>y s]ies1 a portion ( ! coa/ section at ,por? ,w5 is "h giv5 7,fig4 #eh74 ,! l[e/ memb] 7#a7 ( ! s]ies is a :ite qu>tzite mu* jumbl$ 9 its b$d+1 b yet di/9ctly int]/ratifi$ ) ! o!r s$im5ts1 & conta9+ int]calat$ c\rses ( gre5 tuff & highly c>bonace\s %ale4 ,m>k+s l worm-pipes are "h & !re to be se54 ,! next gr\p ( /rata 7#b7 consi/s ( black %ale foll[$ by yell[ conglom]atic s&/one & pebbly tuffs4 ,! %ales enclose r\nd$ & angul> fragm5ts ( qu>tzite4 ,! s&/one passes upw>d into p9ki% & yell[i% conglom]ate 7#c71 ) an abundant lu/r\s phyllitic matrix1 :i* :5 free f pebbles closely resembles "s ( ! tuffs ( ,llyn ,pad>n4 ,! next b& 7#d7 is "o ( yell[1 s&y1 felspa?ic grit1 qu>tz-conglom]ate & f9e tuffs1 ) leaves ( d>k %ale t[>ds ! base4 ,x 0 9 ! l[] "p ( ?is b& t ! ,or?is above m5tion$ 0 f\nd4 ,! black %ales conta9 m>k+s :i* are probably graptolites4 ,r$di% qu>tzite & qu>tz-conglom]ate 7#e7 next succe$4 ,^! /rata h ! same phyllitic base j notic$4 ,! highe/ gr\p "h %[n is "o ( black1 yell[ & gre5 %ales mix$ ) pat*es & b&s ( volcanic breccia & tuff1 ! :ole be+ greatly di/urb$1 cleavage & b$d+ seem+ z x 7 to be /ruggl+ = ! ma/]y4 ,^! la/ /rata look z if !y 7 ab\t to pass up v]tically into ! ord9>y d>k ,l[] ,silurian %ales or slates4 ,illu/ration3 ,fig4 #eh4--,section ( ! /rata on ! %ore at ,por? ,w51 we/ ( ,amlw*4 ,!re c be no d\bt reg>d+ ! s]i\s am\nt ( cru%+ :i* ! rocks ( ?is coa/-l9e h und]gone4 ,"s ( ! b&s might ev5 be describ$ z cru%-conglom]ates4 ,yet ! int]calation ( seams ( black %ale & lime/one1 & ! occurr5ce ( ! exactly simil> b ?ick] gr\p ( black %ales at ,por? ,prydd1 :i* are admitt$ to be ,l[] ,silurian1 unite ! :ole s]ies ( /rata z p>ts ( "o =mation4 ,x ?us appe>s t ! area col\r$ alt]$ ,cambrian on ! ,survey map1 & reg>d$ z pre-,cambrian by "s lat] obs]v]s1 is prov$ by ! evid5ce ( fossils at its base1 t[>ds its c5tre & at its top1 to belong to ! ,l[] ,silurian s]ies1 probably to ! ,bala division4 ,t ?is 0 ! geological horizon ( "p at lea/ ( ! area 0 recogniz$ by ,sir ,a4 ,ramsay1 ?\gh he confess$ himself unable precisely to det]m9e on ! nor? coa/ ( ,anglesey h[ mu* ( ! /rata are ( ,silurian & h[ mu* ( ,cambrian age4#bcb ,pr(essor ,hughes 0 ! fir/ to sugge/ t ! :ole ( ^! rocks %\ld be ref]r$ to ! ,bala gr\p4#bcc ,footnote #bcb3 ,mem4 ,geol4 ,surv4 vol4 iii4 #bnd edit4 p4 #bdb4 ,footnote #bcc3 ,proc4 ,camb4 ,phil4 ,soc4 vol4 iii4 7#ahhj71 pp4 #cda-cdh4 ,illu/ration3 ,fig4 #ei4--,section ( int]calat$ black %ale 9 ! volcanic s]ies at ,por? yr hw*1 s\? ( ,c>mel ,po9t4 ,illu/ration3 ,fig4 #fj4--;,gre5 slates ov]la9 ) volcanic breccia1 ,c>mel ,po9t1 ,anglesey4 ,i h dwelt on ! det]m9ation ( ! true geological age ( ! rocks ( ! nor? ( ,anglesey because ( ! div]sity ( op9ion respect+ !m1 & because ( _! great int]e/ 9 reg>d to ! hi/ory ( volcanic action 9 ,wales4 ,^! rocks conta9 a record ( volcanic eruptions1 probably contemporane\s on ! :ole ) ^? ( ! ,bala p]iod 9 ,ca]n>von%ire1 yet indep5d5t ( !m & belong+ to a diff]5t type ( volcanic en]gy4 ,"s ( ! v5ts probably lay 9 ! nor?-we/]n "p ( ,anglesey4 ,! mat]ials eject$ f !m 71 s f> z we "k1 entirely ( a fragm5t>y k9d4 ,va/ quantities ( detritus1 l>gely 9 ! =m ( f9e du/1 7 ?r[n out2 b no trace has yet be5 f\nd ( ! outfl[ ( any lava4 ,! l[] "p ( ?is volcanic s]ies consi/s ( b$d$ breccias :i* are sometimes rem>kably co>se4 ,_! includ$ /ones1 rang+ up to six in*es or m 9 diamet]1 are usually m or less angul>1 & consi/ ma9ly ( v>i\s felsites4 ,lay]s ( m r\nd$ pebbles occasionally occur1 :ile ! b$d+ is /ill fur!r indicat$ by f9] & co>s] b&s1 & ev5 by int]calations ( f9e tuffs & a%y %ales4 ,t[>ds _! upp] limits "s ( ^! volcanic b&s %ade (f into pale grey or gre5i% a%y %ale1 foll[$ by black s&y %ale ( ! usual k9d4 ,! relation ( ! peculi> gre5i% %ale ( ! ,amlw* type to ^! tuffs & breccias is well %[n ea/ ( ,c>mel ,po9t4 ,?is %ale is int]leav$ ) tuff & conta9s frequ5t repetitions ( f9] or co>s] volcanic breccia1 z well z occasional seams ( black %ale4 ,an illu/ration ( ?is /ructure is giv5 9 ,fig4 #ei1 :]e "s yell[ decompos+ breccias 7#a71 cut by a fault 7f71 are ov]la9 by ab\t #dj or #ej feet ( black %ale 7#b71 above :i* lies a fl9ty felsitic rock 7#c7 t appe>s to run 9 b&s or dykes ?r\gh ! agglom]ate4 ,at ,c>mel ,po9t 7,fig4 #fj7 a simil> /ructure may be obs]v$ to t at ,llyn ,pad>n already ref]r$ to 7p4 #afc74 ,! cleavage1 :i* is well develop$ 9 ! gre5 slates 7a71 is mu* m fa9tly m>k$ 9 ! ov]ly+ breccia 7b71 b ! b$d+ c /ill be detect$ 9 bo? rocks runn+ p>allel to _! mutual b\nd>y-l9e4 ,beyond ,por? ,padrig1 :i* lies ea/ f ,c>mel ,po9t1 ! section may be se5 :i* is %[n 9 ,fig4 #fa4 ,"h ! blue or lead-col\r$ %ale or slate 7a7 m>k$ z ,silurian on ! ,geological ,survey map passes up into a mass ( f9e yell[i% felsitic tuff & breccia 7b74 ,! %ale at ! junction int]calates 9 ?9 leaves ) ! tuff4 ,illu/ration3 ,fig4 #fa4--;,blue %ale or slate pass+ into volcanic breccia ea/ ( ,por? ,padrig1 ne> ,c>mel ,po9t1 ,anglesey4 ,! breccias s\? ( ,c>mel ,po9t1 ?\gh !y are *iefly made up ( felsitic detritus1 sometimes %[ a prepond]ance ( fragm5ts ( %ale4 ,!y v>y also rapidly 9 texture & composition4 ,^! v>iations may indicate t ! v5t or v5ts f :i* _! mat]ials 7 d]iv$ /ood some:]e 9 ! ne> neighb\rhood1 if inde$ !y are n to be recogniz$ 9 "s ( ! boss-l em95ces t rise above ! %ore4 ,at ! same "t1 ! enorm\s am\nt ( cru%+ & %e>+ :i* ! rocks ( ?is region h und]gone has d\btless introduc$ cru%-conglom]ates into ! /ructure ( ! gr\nd4 ,& "s pati5t lab\r may be requir$ be=e ! nature & orig9 ( ! diff]5t fragm5tal masses are det]m9$4 ,c]ta9 rem>kably co>se1 tumultu\s breccias1 expos$ on ! coa/ at ,mynyddwylfa & ,cemmaes1 7 =m]ly reg>d$ by me z volcanic agglom]ates4 ,b m rec5t exam9ation has satisfi$ me t ^!1 l ! breccias at ,llangefni1 are n ( volcanic orig9 b are cru%-conglom]ates4#bcd ,footnote #bcd3 ,presid5tial ,address1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 p4 #acd2 ,rep4 ,brit4 ,assoc4 #ahif1 ,section ,c2 ,geol4 ,mag4 #ahif1 p4 #dha4 ,:ile ! l[] breccias are sometimes tol]ably co>se1 ! volcanic detritus becomes mu* f9] 9 ! high] p>ts ( ! ,amlw* slates4 ,above ! lime/ones & black %ales ( ,cemmaes volcanic breccias & a%es1 ) lime/one1 qu>tzite1 conglom]ate & ?9 seams ( black %ale1 cont9ue to ! extreme nor!rn headl&s4 ,! am\nt ( f9e volcanic detritus di/ribut$ ?r\gh ^! /rata is v great4 ,we c cle>ly make out t :ile ord9>y s$im5tation 0 9 progress1 an almo/ con/ant b v>iable dis*>ge ( fragm5tal mat]ials took place f ! v5ts 9 ! neighb\rhood4 ,sometimes a special p>oxysm ( explosion w\ld give rise to a di/9ct b& ( breccia or ( tuff1 b ev5 :]e1 dur+ a "t ( comp>ative quiesc5ce1 ! ord9>y s& or mud pr$om9at$1 x 0 g5]ally m+l$ ) m or less volcanic du/4 ,"s b&s ( conglom]ate 9 ?is gr\p ( /rata des]ve p>ticul> notice4 ,! mo/ conspicu\s ( ^!1 already ref]r$ to z se5 at ,por? ,w51 is made up ( qu>tz & qu>tzite blocks1 emb$d$ 9 a r$di% matrix l>gely compos$ ( a%y mat]ial1 & recall+ ! r$ spott$ tuffs ( ,llyn ,pad>n4 ,! occurr5ce ( /rong conglom]ates ne> ! top ( a volcanic s]ies has be5 not$ at ,/4 ,david's1 ,llyn ,pad>n & ,bangor4 ,9 none ( ^! localities1 z ,i h tri$ to %[1 d ! conglom]ates m>k an uncon=mability or s]i\s break betwe5 two widely-sep>at$ gr\ps ( rock4 ,! ,anglesey section entirely supports ?is view1 = ! conglom]ates are !re m]ely int]calations 9 a cont9u\s sequ5ce ( deposits2 !y are succe$$ by tuffs & %ales l ^? :i* und]lie !m4 ,! int]position ( su* co>se mat]ials1 h[ev]1 may und\bt$ly indicate local di/urbance1 connect$1 p]haps1 9 ?is & ! o!r localities1 ) t]re/rial readju/m5ts consequ5t ^u ! wan+ ( volcanic en]gy4 ,! detail$ geological /ructure ( ,anglesey is /ill f> f be+ completely und]/ood4 ,besides ! s]i\s cru%+ "h ref]r$ to1 !re is reason to suspect t consid]able plication1 p]haps ev5 inv]sion1 ( ! /rata has tak5 place1 & t1 by d5udation1 deta*$ portions ( "s ( ! high] gr\ps h be5 left 9 diff]5t p>ts ( ! isl&4 ,! occurr5ce ( ,upp] ,silurian fossils 9 sev]al localities adds to ! p]plexity ( ! problem by indicat+ t1 among ! folds & h>dly di/+ui%able f ! old] slates1 portions ( ,upp] ,silurian =mations may h be5 caught & pres]v$4 ,^! difficulties1 moreov]1 involve 9 "s obscurity ! clos+ phases ( volcanic activity 9 ,wales2 = until !y are1 to "s ext5t at lea/1 remov$1 we %all be left 9 d\bt :e!r ! v5ts 9 ! nor? ( ,anglesey1 :i* 7 9 eruption probably dur+ ,bala "t1 7 ! la/ ( ! long succession ( ,wel% volcanoes4 ,if ! black %ales ( ,p>ys ,m\nta9 are really ref]able to ! horizon ( ! ,mayhill ,s&/one1 ! two great igne\s b&s betwe5 :i* !y lie w\ld seem to m>k an outbreak ( volcanic en]gy dur+ ,upp] ,silurian "t4 ,no o!r indications1 h[ev]1 ( eruptions ( t age hav+ be5 met ) 9 ,great ,brita9 7?\gh !y occur 9 ! s\?-we/ ( ,irel& & possibly 9 ,gl\ce/]%ire71 m c>eful inve/igation is requir$ be=e su* a position c be safely assign$ to any rocks 9 ,anglesey4 ,putt+ ^! d\btful rocks aside = ! pres5t1 we may1 9 conclusion1 contra/ ! type ( eruption 9 ,anglesey ) t ( ! great ,sn[donian region4 ,:ile ! ,ca]n>von%ire volcanoes 7 p\r+ =? _! volumes ( felsitic lava1 & pil+ !m up = ?\s&s ( feet on ! sea-floor1 ! nor!rn ,anglesey v5ts1 n m ?an "s five-&-tw5ty miles away1 ?rew out only /ones & du/1 b cont9u$ _! int]mitt5t explosions until !y _h /rewn ! sea-bottom ) detritus to a dep? ( _m hundr$ feet4 ,!re is yet ano!r feature ( int]e/ 9 ?is indep5d5t gr\p ( subm>9e v5ts 9 ,anglesey4 ,_! op]ations appe> to h begun be=e ! e>lie/ eruptions ( ! ,bala volcanoes 9 ,ca]n>von%ire4 ,_! fir/ beg9n+s may1 inde$1 h be5 coeval ) ! explosions t produc$ ! old] ,ar5ig tuffs ( ,m]ione?%ire2 _! late/ dis*>ges 7 possibly ! la/ manife/ations ( volcanic en]gy 9 ,wales4 ,!y seem ?us to bridge ov] ! va/ int]val f ,tremadoc to ,upp] ,bala1 possibly ev5 to ,upp] ,silurian "t4 ,b we may1 p]haps1 connect !m ) ! /ill e>li] p]iod ( ,cambrian volcanism4 ,i h ref]r$ to ! evid5ce :i* appe>s to %[ t ! v5ts :5ce ! lavas & tuffs ( ,moel ,trefan & ,llyn ,pad>n 7 erupt$ gradually mov$ nor?w>ds1 & cont9u$ 9 eruption until aft] ! beg9n+ ( ! deposition ( ! black slates t are g5]ally reg>d$ z ,ar5ig4 ,! ,anglesey tuffs & breccias may ?us be look$ ^u z evid5ce ( a /ill fur!r %ift+ ( ! active orifices nor?w>d4 ,9 ?is view1 :ile ! ,aran & ,cad] ,idris volcanoes broke out 9 ,upp] ,cambrian & cont9u$ ?r\gh ,ar5ig "t1 & ! ,sn[donian gr\p 0 conf9$ to ,bala "t1 a l9e ( v5ts op5$ to ! nor?-we/ 9 ! ,cambrian p]iod be=e ! epo* ( ! ,llanb]is slates1 &1 dy+ out 9 ! s\?1 cont9u$ to manife/ a m9or degree ( en]gy1 frequ5tly dis*>g+ fragm5tal mat]ials1 b no lava1 ov] ! sea-bottom1 until1 t[>ds ! close ( ! ,bala p]iod1 possibly ev5 9 ,upp] ,silurian "t1 !y f9ally became ext9ct4 vi4 ,,! ,,volcanoes ,,( ,,! ,,lake ,,di/rict 7,,ar5ig ,,to ,,close ,,( ,,bala ,,p]iod7 ,f ! "t ( ! appe>ance ( ,s$gwick's classic lett]s to ,wordswor?1 no volcanic area ( ,brita9 has probably be5 s well kn[n 9 a g5]al s5se to ! ord9>y travell+ public z ! di/rict ( ! ,engli% ,lakes4 ,_m geologi/s h s9ce !n visit$ ! gr\nd1 & n a few ( !m h publi%$ additions to our k respect+ :at is n[ kn[n z ! ,borr[dale ,volcanic ,s]ies4 ,! mo/ elaborate & detail$ acc\nt ( any "p ( x is t giv5 by ! late ,mr4 ,j4 ,c4 ,w>d 9 ! ,geological ,survey ,memoirs1 :]e9 he embodi$ ! results ( 8 m9ute inve/igation & mapp+ ( ! nor!rn portion ( ! di/rict4#bce ,notices ( ! petrography ( "s ( ! m int]e/+ rocks h subsequ5tly be5 publi%$ by ,mr4 ,rutley1 ,pr(essor ,bonney1 ,mr4 ,h>k]1 ,mr4 ,m>r1 ,mr4 ,hut*+s & o!rs4 ,b up to ! pres5t "t no complete memoir on ! volcanic geology ( ! ,lake ,di/rict z a :ole has appe>$4 ,! %eets ( ! ,geological ,survey map pres5t a graphic view ( ! g5]al di/ribution ( ! rocks1 b s rapid has ! progress ( c]ta9 bran*es ( geology be5 s9ce ^! %eets 7 publi%$1 t ! map is ev5 n[ susceptible ( consid]able improvem5t4 ,footnote #bce3 ,%eet #aja ,s4 ,e4 ( ! ,geological ,survey ( ,engl& & ,wales & ,explanation illu/rat+ ! same2 & pap]s by him 9 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxxi4 xxxii4 7#ahge-gf74 ,see also ,messrs4 ,avel9e & ,hughes1 ,mem4 ,geol4 ,survey1 ,%eet #ih ,n4,e4 7,k5dal1 ,s$b]gh1 etc474 ,9 e/imat+ ! area ov] :i* ! volcanic rocks ( ! ,lake ,di/rict are spread1 geologi/s are apt to consid] only ! tract :i* lies to ! s\? ( ,keswick & /ret*es s\?w>d to a l9e drawn f ! ,duddon ,s&s to ,%ap4 ,b x c easily be %[n t ?is area falls f> %ort ( ! ext5t ( t :]e9 ! rocks c /ill be trac$1 & yet fur!r %ort ( t ov] :i* ! lavas & a%es orig9ally spread4 ,=1 9 ! fir/ place1 ! volcanic gr\p c be foll[$ r\nd ! ea/]n end ( ! m\nta9-gr\p :i* culm9ates 9 ,skiddaw1 & along ! nor!rn base ( ^! heights to ,cock]m\?1 ?\gh only a n>r[ fr+e ( x em]ges f und]nea? ! ,c>bonif]\s s]ies4 ,x is ?us manife/ t ! volcanic rocks once /ret*$ completely across ,skiddaw & its neighb\rs1 & t !y ext5d nor?w>ds bel[ ! ,:itehav5 ,coal-field4 ,b1 9 ! next place1 f> beyond ^! limits1 volcanic rocks1 :i* !re c be little d\bt 7 orig9ally cont9u\s ) ^? ( ! ,lakes1 em]ge f b5ea? ! base ( ! ,cross ,fell esc>pm5t1#bcf & /ill fur!r to ! ea/ a prolongation ( ! same gr\p rises = a brief space to ! surface f "u ! great lime/one %eets ( ,upp] ,teesdale4 ,betwe5 ! nor?-we/]n & s\?-ea/]n limits )9 :i* ! rocks c n[ be se5 !re int]v5es a di/ance ( "s #aa miles1 :ile ! extreme l5g? ( ! tract f s\?-we/ to nor?-ea/ is ab\t #ej miles4 ,ev5 if we take ^! figures z m>k+ ! approximate b\nd>ies ( ! region cov]$ by ! volcanic ejections1 x _c be less ?an #eej squ>e miles4 ,b ?is is probably mu* less ?an ! orig9al area4 ,footnote #bcf3 ,= an acc\nt ( ! ,cross ,fell inli] ( ,silurian rocks see ! pap] by ,pr(essor ,ni*olson & ,mr4 ,m>r1 ) ! petrographical app5dix by ,mr4 ,h>k]4 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia71 pp4 #ejj1 #eab4 ,! ?ickness ( ! accumulat$ volcanic mat]ials is proportionate to ! l>ge tract ( c\ntry ov] :i* !y h be5 spread4 ,f v>i\s causes1 x is difficult to arrive satisfactorily at any precise /atem5t on ?is "q4 ,9 a volcanic s]ies b$d+ is apt to be obscure :]e1 z 9 ! pres5t case1 !re are no int]/ratifi$ b&s ( ord9>y s$im5t>y /rata to m>k x (f4 ,x t5ds1 moreov]1 to v>y consid]ably & rapidly )9 %ort di/ances1 n only f subsequ5t unequal movem5ts ( subsid5ce or elevation1 b f ! v conditions ( orig9al accumulation4 ,mr4 ,w>d consid]$ t ! maximum ?ickness ( ! volcanic gr\p ( ! ,lake ,di/rict might be tak5 to range f #ab1jjj to #ae1jjj feet4#bcg ,pr(essors ,h>kness & ,ni*olson1 on ! o!r h&1 gave ! av]age ?ickness z n m ?an #ejjj feet4#bch ,my own impression is t ! tru? is to be f\nd some:]e betwe5 ^! two e/imates1 & t ! maximum ?ickness probably does n exce$ #hjjj or #ijjj feet4 ,9 any case !re _c1 ,i ?9k1 be mu* d\bt t we h "h ! ?icke/ accumulation ( volcanic mat]ial1 belong+ to a s+le geological p]iod1 any:]e kn[n to exi/ 9 ,brita94 ,footnote #bcg3 ,w>d1 op4 cit4 p4 #df4 ,footnote #bch3 ,brit4 ,assoc4 7#ahgj7 ,sectional ,reports1 p4 #gd4 ,! geological age ( ?is rem>kable volcanic episode is =tunately fix$ by def9ite palontological horizons bo? bel[ & above4 ,! base ( ! volcanic gr\p re/s ^u & is int]/ratifi$ ) ! upp] "p ( ! ,skiddaw ,slate1#bci :i* f ! evid5ce ( its fossils is p>allel$ ) ! ,ar5ig rocks ( ,wales4 ,! highe/ memb]s ( ! gr\p are int]/ratifi$ ) ! ,coni/on ,lime/one1 :i*1 f its abundant fauna1 c )\t hesitation be plac$ on ! same plat=m z ! ,bala ,lime/one ( ,wales1 & is imm$iately foll[$ by ! ,upp] ,silurian s]ies4 ,?us ! volcanic hi/ory comprises ! geological int]val t elaps$ betwe5 ! lat] "p ( ! ,ar5ig p]iod & ! close ( ! ,bala p]iod4 ,x beg9s probably n s f> back z t ( ! ,ar5ig gr\p ( ,m]ione?%ire1 & its t]m9ation 0 p]haps co9cid5t ) ! dy+ out ( ! ,sn[donian volcanoes4 ,b x conta9s no record ( a great break or int]val ( quiesc5ce l t :i* sep>at$ ! ,ar5ig f ! ,bala eruptions 9 ,wales4 ,footnote #bci3 ,mr4 ,dakyns has express$ 8 belief t ! volcanic gr\p lies uncon=mably on ! ,skiddaw ,slate 7,geol4 ,mag4 #ahfi1 pp4 #ef1 #aaf71 & ,pr(essor ,ni*olson has =m$ ! same op9ion 7op4 cit4 pp4 #aje1 #afg2 ,proc4 ,geol4 ,assoc4 vol4 iii4 p4 #ajf74 ,mr4 ,good*ild1 h[ev]1 has %[n t 9 ! ,cross ,fell inli] ! olde/ tuffs are int]/ratifi$ ) ! ,skiddaw ,slates 7,proc4 ,geol4 ,assoc4 vol4 xi4 7#ahhi71 p4 #bfa74 ,mr4 ,w>d 9 mapp+ ! di/rict ins]t$ a complex s]ies ( faults along ! junction-l9e betwe5 ! volcanic s]ies & ! ,skiddaw ,slates4 ,:5 ,i w5t ov] ! gr\nd ) him "s ye>s be=e 8 dea? ,i discuss$ ?is b\nd>y-l9e ) him & c\ld n adopt 8 view t x 0 s dislocat$4 ,m rec5t re-exam9ation has confirm$ me 9 my diss5t4 ,a l>ge numb] ( ! faults ins]t$ on ! ,geological ,survey map to sep>ate ! ,skiddaw ,slates f ! ,borr[dale volcanic s]ies _c be prov$1 & probably d n exi/4 ,o!rs may be ( ! nature ( ?ru/-planes4 ,b see ,mr4 ,w>d's explanation ( 8 views1 op4 cit4 p4 #dh4 ,! mat]ials t =m ?is enorm\s volcanic pile consi/ entirely ( lavas & a%es4 ,no int]calations ( ord9>y s$im5t>y mat]ial h be5 met ) 9 x1 save at ! bottom & at ! top4 ,! l[] lavas1 well se5 among ! hills to ! s\? ( ,keswick1 7 %[n by ,mr4 ,w>d to be int]m$iate betwe5 felsites & dol]ites 9 reg>d to _! silica p]c5tage1 & he propos$ = !m ! "n ( felsi-dol]ites4 ,!y are compris$ 9 ! gr\p ( ! &esites or porphyrites4 ,f ! analyses publi%$ by ,mr4 ,w>d1 ! am\nt ( silica appe>s to range up to ab\t #fj p] c5t4#bdj ,!y are usually close-gra9$1 dull d>k-grey to black rocks1 break+1 :]e fre%1 ) a spl9t]y or con*oidal fracture1 %[+ a few m9ute /riat$ felsp>s1 apt to wea!r ) a pale-br[n or yell[i%-grey cru/1 & sometimes /rongly vesicul> or amygdaloidal4 ,!y pres5t _m ext]nal resemblances to "s ( ! porphyrites or alt]$ &esites ( ! ,l[] ,old ,r$ ,s&/one ( ,scotl&4 ,a microscopic exam9ation ( specim5s collect$ by ,dr4 ,hat* & myself f ! hills to ! s\? ( ,keswick %[$ ! rocks to be true &esites1 compos$ ( a multitude ( sl5d] la?s 7sometimes l>ge porphyritic cry/als7 ( felsp> ) a br[ni% glassy gr\ndmass1 & ) "s *loritic mat]ial probably repres5t+ augite1 b ) no trace ( qu>tz4#bda ,footnote #bdj3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxxi4 7#ahge7 p4 #djh1 vol4 xxxii4 7#ahgf7 p4 #bd4 ,geology ( ,nor!rn ,"p ( ,lake ,di/rict 7,mem4 ,geol4 ,survey71 p4 #bb4 ,9 a subsequ5t pap] ! m basic lavas ( ,eycott ,hill are comp>$ ) dol]ites 7,mon?ly ,microscopical ,j\rn4 #ahgg1 p4 #bdf74 ,footnote #bda3 ,^! rocks 7 mapp$ z tuffs by ,mr4 ,w>d4 ,_! microscopic *>act]s h be5 describ$ by ,messrs4 ,h>k] & ,m>r1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia71 p4 #bib2 by ,mr4 ,h>k]1 op4 cit4 p4 #eag2 & by ,mr4 ,w4 ,m4 ,hut*+s1 ,geol4 ,mag4 #ahia1 p4 #ecg2 #ahib1 pp4 #bbg1 #edj4 ,ano!r type ( &esite has be5 f\nd by ,mr4 ,hut*+s to occur abundantly at ,h>t] ,fell1 ,m>dale1 betwe5 ! ,nan ,bield ,pass & ,high ,/reet1 & 9 ! cliffs on ! "r side ( ! ,k5tm]e ,valley4 ,x consi/s ( rocks mo/ly ( a grey-gre5 or grey-blue col\r ) res9\s lu/re & extremely spl9t]y fracture4 ,!y are augite-&esites ( a mu* m vitre\s nature ?an ! dom9ant type ( lavas ( ! ,lake ,di/rict4 ,_! gr\ndmass "u ! microscope is se5 to h orig9ally v>i$ f a :olly glassy base to an intimate mixture ( glass & exce$+ly m9ute felsp>-microlites4 ,?is gr\ndmass is p]meat$ ) *lorite 9 m9ute flakelets1 & encloses num]\s porphyritic %>ply-def9$ felsp>-cry/als1 toge!r ) *lorite-pseudomorphs aft] augite4#bdb ,gradations f ^! rocks to ! ord9>y m co>se-gra9$ &esites may be obs]v$4 ,footnote #bdb3 ,mr4 ,hut*+s1 ,geol4 ,mag4 #ahia1 p4 #eci4 ,?is obs]v] describes a qu>tz-&esite or dacite f ne> ,dunmail ,raise4 ,"s ( ! &esites appe> to h a tra*ytic facies1 :]e ! felsp>s ( ! gr\ndmass consi/ l>gely ( untw9n$ la?s & appe> to be ma9ly or?oclase4#bdc ,footnote #bdc3 ,op4 cit4 p4 #edc4 ,among ! lavas ( ! ,lake ,di/rict !re occur _m :i* are decid$ly m basic ?an ! &esites1 & :i* %\ld r be class$ among ! dol]ites & basalts1 ?\gh !y d n appe> to conta9 oliv9e4 ,^! rocks occur at ,eycott ,hill1 above ,eas$ale ,t>n1 ,sc>f ,gap ,pass1 ,dale ,head1 ,high ,scawdell1 ,seatoll] ,fell & o!r places4 ,analyses ( ^? f ,eycott ,hill 7 publi%$ by ,mr4 ,w>d1 & _! silica p]c5tage 0 %[n to range f #ea to #ecc4bdd ,! microscopic *>act]s ( ! gr\p h be5 m rec5tly det]m9$ by ,mr4 ,hut*+s#bde & ,messrs4 ,h>k] & ,m>r4#bdf ,footnote #bdd3 ,mon?ly ,microscopical ,j\rnal1 #ahgg1 p4 #bdf4 ,footnote #bde3 ,geol4 ,mag4 #ahia1 p4 #ech4 ,footnote #bdf3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlix4 7#ahic71 p4 #chi4 ,mr4 ,h>k]1 op4 cit4 vol4 xlvii4 7#ahia74 ,! &esitic & m basic lavas are p>ticul>ly develop$ 9 ! l[] & c5tral "p ( ! volcanic gr\p4 ,!y rise into ranges ( craggy hills above ! ,skiddaw ,slates1 & =m1 ) _! accompany+ tuffs1 ! mo/ rugg$ & l(ty gr\nd 9 ! ,lake ,di/rict4 ,!y ext5d ev5 to ! s\!rn m>g9 ( ! volcanic area at "o locality to ! s\?-we/ ( ,coni/on1 :]e !y may be se5 ) _! *>act]i/ic vesicul> /ructure =m+ a succession ( di/9ct fl[s or b$s1 /rik+ at ! ,coni/on ,lime/one :i* lies ^u !m ) a decid$1 ?\gh probably v local1 uncon=mability4#bdg ,"o ( ! fl[s f ?is locality 0 f\nd by ,dr4 ,hat*1 "u ! microscope1 to belong to ! m basic s]ies4 ,x approa*es a basalt1 conta9+ porphyritic cry/als ( fre% augite in/ead ( ! usual felsp>s1 & %[+ a gr\ndmass ( felsp> microlites ) "s granules ( augite & disp]s$ magnetite4 ,?is local increase ( basic composition is int]e/+ z occurr+ t[>ds ! top ( ! volcanic gr\p4 ,a porphyritic & some:at vesicul> &esite1 ) l>ge cry/als ( /riat$ felsp> 9 a d>k almo/ isotropic gr\ndmass1 occurs "u ! ,coni/on ,lime/one ne> ,/ockdale4 ,footnote #bdg3 ,?is uncon=mability has be5 describ$ & discuss$ by v>i\s obs]v]s4 ,! g5]al impression has be51 ,i ?9k1 t ! break is only ( local importance4 ,mr4 ,avel9e1 h[ev]1 believ$ x to be mu* m s]i\s1 & he reg>d$ ! volcanic rocks :i* 7 eject$ dur+ ! deposition ( ! ,coni/on ,lime/one s]ies z mu* lat] 9 date ?an ^? ( ! ,borr[dale gr\p4 ,see ,mem4 ,geol4 ,survey1 ,explanation to ,%eet #ih ,n4,e4 #bnd edit4 p4 #h 7#ahhh74 ,mr4 ,w>d 0 mu* impress$ ) ! widespread metamorphism :i* he believ$ all ! volcanic rocks ( ?is region _h und]gone1 & z a consequ5ce ( :i* arose ! difficulty he f\nd 9 discrim9at+ betwe5 close-gra9$ lavas & f9e tuffs4 ,!re is1 ( c\rse1 a g5]al induration ( ! rocks1 :ile cleavage has widely1 & sometimes v s]i\sly1 affect$ !m4 ,!re is also local metamorphism r\nd su* bosses z ! ,%ap granite1 b ! evid5ce ( any g5]al & s]i\s metamorphism ( ! :ole area does n seem to me to be conv9c+4#bdh ,footnote #bdh3 ,! metamorphism ( all ! rocks1 aque\s & igne\s1 ar\nd ! ,%ap granite has be5 well work$ out by ,messrs4 ,h>k] & ,m>r1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia7 p4 #bff1 xlix4 7#ahic7 p4 #cei4 ,) reg>d to ! orig9al /ructure & subsequ5t alt]ation ( "s ( ! &esitic lavas1 an int]e/+ section has rec5tly be5 cut along ! road up ,borr[dale a little s\? ( ! ,b[d] ,/one4 ,sev]al b&s ( co>se amygdaloidal lava may !re be se5 int]/ratifi$ among tuffs4 ,! calcite amygdales 9 ^! rocks are arrang$ p>allel to ! b$d+ & !re=e 9 ! planes ( fl[1 :ile ^? l9$ ) *lorite are m usually de=m$ p>allel to ! direction ( ! cleavage4 ,?is diff]5ce sugge/s t be=e ! cleavage took place1 n improbably dur+ ! volcanic p]iod1 ! rocks _h be5 trav]s$ by heat$ wat] produc+ int]nal alt]ation & re>rangem5ts1 9 virtue ( :i* ! vesicles along c]ta9 pa?s ( p]meation 7 fill$ up ) calcite1 s z !n to (f] "s resi/ance to ! cleavage1 :ile ^? :i* rema9$ empty1 or :i* _h be5 m]ely l9$ ) infiltrat$ sub/ance1 7 flatt5$ & pull$ out ( %ape4 ,messrs4 ,h>k] & ,m>r h %[n t ! amygdaloidal k]nels _h already be5 introduc$ into ! cellul> lavas be=e ! intrusion ( ! ,%ap granite4 ,9 ! acc\nt to be giv5 ( ! ,t]ti>y plateau-basalts 7,*apt] xxxvi47 evid5ce w be adduc$ t ?is fill+ up ( ! /eam-cavities ( lava may take place dur+ a volcanic p]iod1 & t x is probably connect$ ) ! passage ( heat$ vap\rs or wat] ?r\gh ! rocks4 ,?\gh acid lavas are n :olly abs5t f ! c5tral & l[] p>ts ( ! volcanic gr\p1 x is at ! top t _! *ief developm5t appe>s to occur4 ,^! rocks may be gr\p$ toge!r z felsites or rhyolites4 ,!y probably play a mu* l>g] "p 9 ! /ructure ( ! s\!rn "p ( ! volcanic area ?an ! publi%$ maps w\ld sugge/1 & a detail$ survey & petrographical /udy ( !m w\ld well rew>d ! ne$ful lab\r4#bdi ,a f9e s]ies ( felsites is int]b$d$ 9 ! l[] "p ( ! ,coni/on ,lime/one1 & spreads out und]nea? x along ! s\!rn m>g9 ( ! volcanic di/rict f ! ,%ap granite s\?-we/w>d = "s miles#bej 7,fig4 #fb74 ,betwe5 ! valleys ( ! ,spr9t & ,k5t ^! felsites 7:i* f>!r ea/ are said to be #gjj feet ?ick7 may be se5 int]pos$ betwe5 ! lime/one & ! fossilif]\s calc>e\s %ales bel[ x1 :ile f und]nea? ! latt] o!r %eets rise up into ! range ( hills beh9d4 ,footnote #bdi3 ,see ,mr4 ,f4 ,rutley1 ,! ,felsitic ,lavas ( ,engl& & ,wales1 ,mem4 ,geol4 ,surv4 #ahhe1 pp4 #ab-ae2 also ! description ( ,messrs4 ,h>k] & ,m>r1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia71 p4 #cja4 ,footnote #bej3 ,un=tunately ^! acid lavas are n di/+ui%$ f ! o!rs 9 ! ,geological ,survey maps4 ,illu/ration3 ,fig4 #fb4--,section ( felsites on ! ,coni/on ,lime/one gr\p1 we/ ( ,/ockdale4 a1 ,felsites m or less cleav$2 b1 ,calc>e\s %ales ) fossils1 mu* cleav$2 c1 ,cleav$ felsite2 d1 ,coni/on ,lime/one2 e1 ,/ockdale ,%ales 7) graptolites74 ,^! acid lavas are g5]ally grey1 cream-col\r$1 or p9k1 ) a :ite wea!r$ cru/4 ,_! texture :5 fre% is fl9ty or horny1 or at lea/ extremely f9e-gra9$ & compact4 ,!y are seldom m>k$ly porphyritic4 ,!y frequ5tly display good fl[-/ructure1 & sometimes split up readily along ! planes ( fl[4 ,occasionally ! fl[-l9es on ! out] cru/ h brok5 up 9 ! movem5t ( ! rock1 giv+ rise to irregul> fragm5ts :i* h be5 c>ri$ =w>d4 ,%ort1 extremely irregul>1 bran*+ ve9s ( a f9e *]ty felsitic sub/ance1 :i* occasionally %[s a well-m>k$ fl[-/ructure p>allel to ! walls1 trav]se c]ta9 p>ts ( a d>k-grey felsite1 ne> ,brock/ones1 betwe5 ! valleys ( ! ,k5t & ,spr9t4#bea ,occasionally a di/9ct nodul> /ructure may be obs]v$ 9 ^! acid lavas1 sometimes m9ute1 l an oolite1 9 o!r p>ts1 z on ,great ,y>lside1 pres5t+ l>ge r\nd$ balls4 ,?is nodul> /ructure is n conf9$ to ! lava-fl[s1 b has be5 detect$ by ,messrs4 ,h>k] & ,m>r 9 :at appe>s to be an intrusive rock ne> ,%ap ,wells4 ,! microscopic *>act]s ( "s ( ! ,lake ,di/rict rhyolites 7 describ$ by ,mr4 ,rutley1 :o f\nd !m to exhibit beautiful p]litic & sph]ulitic /ructures4#beb ,t su* rocks z ^! 7 p\r$ out 9 a vitre\s condition1 l obsidian or pit*/one1 _c be d\bt$4 ,*emical analysis %[s t ! ,lake ,di/rict rhyolites agree exactly ) ^? ( ,nor? ,wales 9 _! composition4 ,!y conta9 ab\t #gf p] c5t ( silica4#bec ,footnote #bea3 ,comp>e ! /ructure describ$ by ,mr4 ,h>k] f ! ,cross ,fell inli]1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia71 p4 #eah4 ,footnote #beb3 ,geology ( ,k5dal1 etc41 ,mem4 ,geol4 ,survey1 ,%eet #ih ,n4,e4 #bnd edit4 p4 #i4 ,footnote #bec3 ,messrs4 ,h>k] & ,m>r1 op4 cit4 p4 #cjb4 ,! rhyolitic lavas h be5 s]i\sly affect$ by ! g5]al cleavage ( ! region4 ,9 "s places !y h be5 s int5sely cleav$ z to become a k9d ( fissile slate1 & !re seems good reason to believe t 9 ?is alt]$ condition !y h (t5 be5 mi/ak5 = tuffs4 ,:]e !y assume a nodul> /ructure1 ! nodules h sometimes be5 flatt5$ & elongat$ 9 ! direction ( ! preval5t cleavage4 ,! abundance & p]si/5ce ( ?or\ghly acid lavas along ! s\!rn edge ( ! volcanic area :]e ! y\nge/ outfl[s are f\nd1 is a fact ( mu* int]e/ & importance 9 ! hi/ory ( ! eruptions ( ?is region4 ,x h>monizes ) ! obs]vations made 9 ,wales1 :]e 9 ! ,ar5ig1 & less di/9ctly 9 ! ,bala gr\p1 a m>k$ increase 9 acidity is noticeable 9 ! lat] volcanic products4 ,at ! same "t1 z above m5tion$1 !re is evid5ce also ( ! dis*>ge ( m basic mat]ials t[>ds ! close ( ! eruptions1 & ev5 ( ! outfl[ ( a lava approa*+ 9 "* to basalt4 ,accord+ to ! ,geological ,survey maps1 by f> ! l>ge/ "p ( ! volcanic di/rict consi/s ( pyrocla/ic mat]ials4 ,:5 my lam5t$ fri5d1 ! late ,mr4 ,w>d1 0 engag$ 9 mapp+ ! nor!rn "p ( ! di/rict1 :i* he did ) s mu* en?usiasm1 ,i _h an opportunity ( go+ ov] "s ( ! gr\nd ) him1 & ( le>n+ f him 8 ideas z to ! nature & di/ribution ( ! rocks & ! g5]al /ructure ( ! region4 ,i rememb] ! difficulty ,i _h 9 recogniz+ z tuff mu* ( :at he _h mapp$ z su*1 & ,i felt t _h ,i be5 myself requir$1 )\t 8 exp]i5ce ( ! gr\nd1 to map ! rocks1 ,i %\ld probably h greatly enl>g$ ! area col\r$ z lava1 ) a correspond+ r$uction ( t col\r$ z tuff4 ,a rec5t visit to ! di/rict has reviv$ ^! d\bts4 ,x is q true1 z ,mr4 ,w>d ma9ta9s1 t :]e ! f9]-gra9$ tuffs h und]gone "s degree ( induration or metamorphism1 !y c h>dly1 by any te/ 9 ! field1 be di/+ui%$ f compact lavas4 ,he 0 himself q aw>e ( ! objections t might be made to 8 mapp+1#bed b ! conclusions he rea*$ _h be5 d$uc$ only aft] ye>s ( unremitt+ /udy 9 ! field & ) ! microscope1 & 9 ! light ( exp]i5ce ga9$ 9 o!r volcanic regions4 ,nev]!less ,i ?9k t he has some:at exagg]at$ ! am\nt ( fragm5tal mat]ial 9 ! nor!rn "p ( ! ,lake ,di/rict1 & t ! mapp+1 s consi/5tly & ably c>ri$ out by him1 & foll[$ by ^? memb]s ( ! ,survey :o mapp$ ! re/ ( ! gr\nd1 l$ to simil> ov]-repres5tation !re4 ,"s portions ( ! s-call$ tuffs ( ! ,keswick region are und\bt$ly &esites2 o!r p>ts 9 ! s\!rn tracts include int]calat$ b&s ( felsite z well z &esite4 ,footnote #bed3 ,he says3 ,i %all be v mu* surpris$ if my mapp+ ( _m p>ts ( ! di/rict be n sev]ely criticiz$ & f\nd fault ) by ^? :o exam9e only "o small area & d n take into consid]ation all ! facts ga!r$ toge!r1 dur+ ! c\rse ( sev]al ye>s1 f e m\nta9 flank & summit 7op4 cit4 p4 #be74 ,mr4 ,hut*+s has express$ 8 agreem5t ) ! op9ions /at$ 9 ! text4 ,he likewise co9cides 9 ! belief t !re are _m ( ^! ,lake ,di/rict volcanic rocks1 reg>d+ :i* x is impossible to decide :e!r !y are lavas or a%es 7,geol4 ,mag4 #ahia1 p4 #edd74 ,b ev5 ) ?is limitation1 ! pyrocla/ic mat]ial 9 ! ,lake ,di/rict is und\bt$ly v great 9 am\nt4 ,x v>ies 9 texture f co>se breccia or agglom]ate1 ) blocks measur+ sev]al y>ds across1 to ! mo/ impalpable compact$ volcanic du/4 ,9 ! l[] p>ts ( ! gr\p "s ( ! tuffs ab\nd 9 blocks & *ips ( ,skiddaw ,slate4 ,"s good examples ( ?is k9d may be se5 9 ,borr[dale1 bel[ ,falcon ,crag & at ! ,quayfoot qu>ries4 ,:]e ! tuff is l>gely made up ( fragm5ts ( d>k blue slate1 x mu* resembles ! slate-tuffs ( ,cad] ,idris4 ,"s ( ! pieces ( slate are six or eight in*es long & are n[ plac$ p>allel to ! cleavage ( ! rock4 ,among ! slate debris1 h[ev]1 felsp> cry/als & felsitic fragm5ts may be obs]v$4 ,b&s ( co>s] & f9] gre5 tuff %[ v cle>ly ! b$d+ 9 spite ( ! m>k$ cleavage 7,fig4 #fc74 ,illu/ration3 ,fig4 #fc4--;,f9e tuff ) co>s] b&s ne> ,quayfoot qu>ries1 ,borr[dale4 ,! highly-incl9$ f9e l9es %[ ! cleavage4 ,! m g5tly dipp+ b&s & l9es m>k ! b$d+4 ,b ?r\gh\t ! :ole volcanic gr\p ! mat]ial ( ! tuff is *iefly ( ?or\ghly volcanic orig91 & its di/ribution appe>s to agree on ! :ole ) t ( ! b$d$ lavas4 ,9 ! old] portions ( ! gr\p x is probably ma9ly d]iv$ f &esitic rocks1 ?\gh ) an occasional int]m+l+ ( felsitic or rhyolitic detritus1 :ile 9 ! high] p>ts _m ( ! tuffs are m>k$ly rhyolitic4 ,among ! lapilli m9ute cry/als ( felsp>1 brok5 or entire1 may be detect$ ) ! microscope4 ,"s ( ! eject$ a% mu/ h be5 an exce$+ly f9e du/4 ,compact$ lay]s ( su* mat]ial =m b&s ( gre5 slates1 :i* may occasionally be se5 to consi/ ( alt]nations ( co>s] & f9] detritus1 n[ & !n false-b$d$4 ,su* tuffs br+ vividly be=e ! m9d ! int]mitt5t explosions1 v>y+ a little 9 int5sity1 by :i* s mu* ( ! fabric ( ! ,lake m\nta9s 0 built up4 ,breccias ( v>y+ co>s5ess are likewise abundant1 compos$ ( fragm5ts ( &esite & old] tuffs 9 ! c5tral & l[] p>ts ( ! volcanic gr\p1 & ma9ly ( felsitic or rhyolitic detritus 9 ! upp] p>ts4 ,"s ( ^! rocks1 :]e9 ! blocks measure sev]al y>ds across1 are probably n f> f ! eruptive v5ts1 z at ,s\rmilk ,gill & bel[ ,honi/] ,pass4 ,g5]ally ! /ones are angul>1 b occasionally m or less r\nd$4 ,/ratification c g5]ally be detect$ among ^! fragm5tal rocks1 b x is apt to be conceal$ or effac$ by ! cleavage1 :ile x is fur!r obscur$ by t widespread induration on :i* ,mr4 ,w>d has laid s mu* /ress4 ,! extreme /ate ( comm9ution ( ! volcanic du/ t w5t to =m ! tuffs has probably caus$ !m to be m liable to metamorphism ?an ! lavas4#bee ,footnote #bee3 ,! microscopic & *emical *>act]s ( ! ,a%-,slates ( ! ,lake ,di/rict h be5 inve/igat$ by ,mr4 ,hut*+s1 ,geol4 ,mag4 #ahib1 pp4 #aee1 #bah4 ,little has yet be5 done 9 id5tify+ any ( ! v5ts f :i* ! va/ mass ( volcanic mat]ial 9 ! ,lake ,di/rict 0 eject$4 ,mr4 ,w>d believ$ t ! diabase boss =m+ ! ,ca/le ,head ( ,keswick m>ks ! site ( "o ( ! ma9 volcanic c5tres ( ?is p>ticul> di/rict1#bef :5ce ! great lava %eets to ! s\?w>d fl[$ out4 ,!re are obvi\sly two gr\ps ( bosses on ! nor!rn side ( ! di/rict1 "s ( :i* may possibly m>k ! position ( v5ts4 ,a few ( !m are occupi$ by m basic1 o!rs by m acid rocks4 ,x is n necess>y to suppose t ! &esitic lavas asc5d$ only f ! =m] & ! felsites f ! latt]4 ,:ile ! felsites on ! :ole are y\ng] ?an ! m basic lavas1 !y may h be5 erupt$ f v5ts :i* _h previ\sly emitt$ &esites1 s t ! pres5t plug may repres5t only ! lat] & m acid protrusions4 ,footnote #bef3 ,op4 cit4 p4 #gj4 ,besides ! boss ( ,ca/le ,head !re are num]\s small] basic intrusions f>!r d[n ! ,d]w5t ,valley on ei!r side ( ,bass5?waite ,lake4 ,among ^! are ! highly basic rocks =m+ ! picrite on ! ea/ side ( ! ,da% ,beck & ! dykes on ,bass5?waite ,common4 ,all ^! bosses1 sills1 & dykes rise ?r\gh ! ,skiddaw ,slates1 b !re is no positive pro( t !y belong to ! ,l[] ,silurian volcanic s]ies2 !y may possibly be mu* lat]4 ,! mo/ important & mo/ int]e/+ ( all ! intrusive masses ( basic mat]ial is t :i* con/itutes a l>ge "p ( ! em95ce t culm9ates 9 ,c>rock ,fell4 ,! rem>kable v>iations 9 ! composition ( ?is mass h be5 already ref]r$ to4 ,mr4 ,h>k] has %[n t :ile ! c5tre ( ! mass is a qu>tz-gabbro1 x becomes progressively m basic t[>ds ! m>g94 ,?r\gh ! gabbro a mass ( granophyre has subsequ5tly made its way1 & along ! l9e ( junction has incorporat$ into its own sub/ance s mu* ( ! basic rock z to und]go a m>k$ modification 9 its /ructure & composition4 ,:e!r ^! intrud$ bodies ( basic & acid mat]ial h asc5d$ 9 "o ( ! old volcanic funnels & h be5 inject$ lat]ally 9 laccolitic fa%ion has n be5 asc]ta9$4 ,mr4 ,h>k]1 inde$1 is r incl9$ to ref] ! intrusions to a "t n only lat] ?an ! ,borr[dale volcanoes1 b lat] ev5 ?an ! t]re/rial movem5ts t subsequ5tly affect$ ! di/rict & gave ! rocks _! pres5t cleav$ & fault$ /ructures4 ,besides ! gabbro & granophyre ( ?is locality1 igne\s activity has manife/$ itself 9 ! uprise ( num]\s lat] dykes & ve9s1 int]m$iate to basic 9 composition4 ,"s ( ^! are glassy 7ta*ylyte7 & sph]ulitic or v>iolitic4#beg ,footnote #beg3 ,mr4 ,h>k]1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 l4 7#ahid7 p4 #cab1 li4 7#ahie7 p4 #abe4 ,geol4 ,mag4 #ahid1 p4 #eea4 ,?r\gh\t ! ,lake ,di/rict a consid]able numb] ( bosses ( m acid rocks rise ?r\gh ! ,skiddaw ,slates1 & likewise ?r\gh ! volcanic gr\p ev5 up to its highe/ memb]s4 ,"s ( ^! bosses may possibly indicate ! site ( volcanic v5ts4 ,two ( !m1 :i* =m conspicu\s features on ei!r side ( ! ,vale ( ,/4 ,john1 consi/ ( microgranite1 & rise l great plugs ?r\gh ! ,skiddaw ,slates1 z well z ?r\gh ! base ( ! volcanic gr\p4 ,! view ( ! m ea/]n hill1 z se5 f ! we/1 is at once sugge/ive ( a neck4 ,^! masses measure r\ghly ab\t a squ>e mile ea*4 ,) ! acid intrusions may possibly be associat$ "s ( ! o!r masses ( granophyre1 microgranite & granite 7felsite1 fel/one1 qu>tz-felsite1 sy5itic granite1 qu>tz-sy5ite1 elvanite71 :i* h long attract$ att5tion 9 ?is region4 ,! l>ge/ ( ^! intrusions is ! tract ( granite :i* /ret*es f ,eskdale d[n to ne> ! sea-coa/ z a belt ab\t elev5 miles long & f "o to ?ree miles broad4 ,ano!r l>ge mass is ! granophyre or sy5ite ( ,enn]dale4 ,num]\s o!r intrusions ( small] dim5sions h be5 mapp$4 ,to :at ext5t any ( ^! eruptive masses 7 associat$ ) ! volcanic ph5om5a rema9s /ill to be work$ out4 ,!re seems to be little d\bt t a numb] ( !m mu/ belong to a mu* lat] p]iod4 ,mr4 ,h>k] has express$ 8 belief t ! intrusion ( "s ( ^! igne\s rocks 0 intimately associat$ ) ! po/-,silurian t]re/rial movem5ts ( :i* cleavage is "o ( ! memorials4#beh ,! ,skiddaw granite1 ?\gh x does n t\* any "p ( ! volcanic gr\p1 b is conf9$ to ! und]ly+ ,skiddaw ,slates1 0 erupt$ aft] ! cleavage ( ! di/rict1 :i* affects ! volcanic z well z ! s$im5t>y s]ies4 ,9 o!r in/ances also1 z 9 t ( ,c>rock ,fell1 ! intrusion seems to h be5 lat] ?an ! di/urbances ( ! cru/4#bei ,! am\nt ( metamorphism ar\nd "s ( ! bosses ( granite is consid]able4 ,t ( ! ,skiddaw region has be5 well describ$ by ,j4 ,c4 ,w>d1#bfj :ile t ( ! volcanic gr\p by ! ,%ap granite has be5 c>efully work$ out by ,mr4 ,h>k] & ,mr4 ,m>r4#bfa ,footnote #beh3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 li4 7#ahie71 p4 #add4 ,footnote #bei3 ,op4 cit4 p4 #abf4 ,footnote #bfj3 ,geology ( ,nor!rn ,"p ( ! ,engli% ,lake ,di/rict1 ,mem4 ,geol4 ,surv4 #ahgf1 *ap4 iii4 ,! metamorphism ar\nd ! diorites & dol]ites1 & ! granophyres & felsites1 is describ$ 9 ! same *apt]4 ,footnote #bfa3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia7 p4 #bff1 xlix4 7#ahic7 p4 #cei4 ,! ,%ap granite comes ?r\gh ! v highe/ memb] ( ! volcanic s]ies1 & ev5 alt]s ! ,upp] ,silurian /rata4 ,x mu/ ?us be ( mu* y\ng] date ?an ! volcanic hi/ory ( ! ,lake ,di/rict4 ,x pres5ts "s features 9 common ) ! granite bosses ( ! s\? ( ,scotl&4 ,l ^!1 x is lat] ?an ,upp] ,silurian & old] ?an ,l[] ,c>bonif]\s or ,upp] ,old ,r$ ,s&/one "t4 ,its protrusion may ?us h be5 coeval ) ! great volcanic eruptions ( ! p]iod ( ! ,l[] ,old ,r$ ,s&/one4 ,x w accord+ly be aga9 ref]r$ to 9 a lat] *apt]4 ,x mu/ be confess$ t none ( ! l>ge bosses ( massive rocks1 :e!r diabases1 gabbros1 felsites1 granophyres1 or granites1 appe> to af=d any satisfactory pro( ( ! position ( ! v5ts :i* suppli$ ! lavas & tuffs ( ! ,lake ,di/rict4 ,nor c su* a decid$ accumulation ( ! volcanic mat]ials 9 c]ta9 directions be e/abli%$ z to indicate ! qu>t]s :]e ! c5tres ( eruption %\ld be s\ght4 ,on ! contr>y1 ! confus$ comm+l+ ( mat]ials1 & ! comp>ative %ortness ( ! outcrop ( ! sev]al %eets :i* h be5 trac$1 r sugge/ t if any "o great c5tral volcano exi/$1 its site mu/ lie outside ( ! pres5t volcanic di/rict1 or m probably1 t _m scatt]$ v5ts ?rew out _! lavas & a%es ov] no v wide area1 b ne> en\gh to ea* o!r to all[ _! eject$ mat]ials to meet & m+le4 ,! sc5e may h be5 r ( ! type ( ! ,phlegran fields ?an ( ,etna & ,vesuvius4 ,if ?is surmise be true1 we may expect yet to recognize little necks scatt]$ ov] ! volcanic di/rict & m>k+ ! positions ( "s ( ^! vani%$ cones4 ,:at appe>s to h be5 "o ( ^! small v5ts /&s ne> ,grange at ! m\? ( ,borr[dale1 :]e ,i came ^u x 9 #ahij4 ,9 ! little ,comb ,beck1 ! ,skiddaw ,slates are pi]c$ by a mass ( extremely co>se agglom]ate1 =m+ a rudely-circul> boss4 ,! slates are greatly di/urb$ along ! edges ( ! boss1 s mu* s1 inde$1 t x is 9 "s places difficult to draw a l9e betwe5 !m & ! mat]ial ( ! agglom]ate4 ,t mat]ial is made up ( angul> blocks1 v>y+ 9 size up to ?ree feet long1 /uck 9 e position & angle 9 an int5sely-indurat$ matrix =m$ app>5tly ( comm9ut$ debris l ! /ones4 ,! blocks consi/ ( a f9ely-/ratifi$ %ale1 :i* is n[ h>d5$ into a k9d ( horn/one1 ) "s felsitic fragm5ts4 ,i c\ld see no slags or bombs ( any k9d4 ,!re is no trace ( cleavage among ! blocks1 nor is ! matrix itself s5sibly cleav$4 ,i believe ?is to be a small volcanic neck & n a cru%-conglom]ate4 ,x has be5 bl[n ?r\gh ! ,skiddaw ,slates1 & is n[ fill$ up ) ! debris ( ^! slates4 ,its =mation seems to h tak5 place be=e ! cleavage ( ! /rata1 & its firm position & great induration enabl$ x to resi/ ! cleavage :i* has s p[]fully affect$ ! slates & _m memb]s ( ! volcanic gr\p4 ,x 0 ! op9ion ( my pr$ecessor1 ,sir ,&rew ,ramsay1 & likewise ( ,mr4 ,w>d1 t ! ,cumbrian volcanic action 0 ma9ly subrial4 ,?is op9ion 0 f\nd$ *iefly on ! fact t1 save at ! bottom & top ( ! s]ies1 !re is no evid5ce ( any int]/ratifi$ s$im5t ( non-volcanic k9d4 ,! abs5ce ( su* int]/ratification may und\bt$ly furni% a presumption 9 fav\r ( ?is view1 b1 ( c\rse1 x is by no means a pro(4 ,bett] evid5ce is furni%$ by ! uncon=mability already m5tion$ betwe5 ! ,coni/on ,lime/one & ! lavas on :i* x lies4 ,besides angul> pieces ( lava1 probably d]iv$ f direct volcanic explosion1 ?is lime/one conta9s fragm5ts ( amygdaloidal &esite1 & also roll$ cry/als ( /riat$ felsp>4#bfb ,^! +r$i5ts seem to indicate t "s "p ( ! volcanic gr\p 0 above wat] :5 ! ,coni/on ,lime/one 0 deposit$4 ,footnote #bfb3 ,messrs4 ,h>k] & ,m>r1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia71 p4 #caj4 ,! abs5ce ( int]/ratifications ( ord9>y non-volcanic s$im5t 9 ! ,borr[dale gr\p might conceivably arise f ! eruptions foll[+ ea* o!r s cont9u\sly on ! sea-floor1 & at s great a di/ance f l& t no deposition ( s& or mud f ! outside c\ld s5sibly affect ! accumulation ( volcanic mat]ial4 ,c]ta9ly "s miles to ! ea/ at ! ,cross ,fell inli]1 z already m5tion$1 !re is evid5ce ( ! alt]nation ( tuffs ) ! s&y & muddy s$im5t ( ! sea-bottom4 ,"h1 at ! out] conf9es ( ! volcanic di/rict1 ! eject$ mat]ials evid5tly fell on ! sea-floor1 m+l$ !re ) ord9>y s$im5t1 & enclos$ ! same organic rema9s4 ,! well-def9$ /ratification ( _m ( ! f9e tuffs is r sugge/ive to my m9d ( subaque\s ?an ( subrial accumulation4 ,at ! same "t1 !re seems no reason :y1 "h & !re at lea/1 ! volcanic cones %\ld n h ris5 above ! wat]1 ?\gh _! mat]ials w\ld be wa%$ d[n & spread out by ! waves4 ,"o ( ! mo/ m>k$ po9ts ( contra/ betwe5 ! ,cumbrian & ! ,wel% volcanic di/ricts is to be f\nd 9 ! great paucity ( sills 9 ! =m] region4 ,a few %eets ( diorite & diabase h be5 mapp$1 especially 9 ! l[] p>ts ( ! volcanic gr\p & 9 ! und]ly+ ,skiddaw ,slates4 ,on ! o!r h&1 dykes are 9 "s p>ts ( ! di/rict n unfrequ5t1 & c]ta9ly play a mu* m prom95t "p "h ?an !y d 9 ! ,wel% volcanic di/ricts4 ,! majority ( !m consi/ ( felsites1 qu>tz-porphyries1 diorites1 & mica-traps4 ,b !re is reason to suspect t :]e !y are cr[d$ toge!r ne> ! granite1 z ar\nd ,%ap ,fells1 !y ought to be connect$ ) ! uprise ( ! po/-,silurian granitic magma r ?an ) ! hi/ory ( ! volcanic gr\p4#bfc ,if ?is s]ies ( dykes be elim9at$1 !re rema9 comp>atively few t c ) any confid5ce be associat$ ) ! eruption ( ! ,borr[dale rocks4 ,footnote #bfc3 ,= a description ( ! dykes ar\nd ! ,%ap granite see ! pap] by ,messrs4 ,h>k] & ,m>r1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlvii4 7#ahia71 p4 #bhe4 vii4 ,,upp] ,,silurian 787 ,,volcanoes ,,( ,,gl\ce/]%ire ,a rem>kable gr\p ( igne\s mat]ials has long be5 kn[n to rise among ! ,silurian rocks ( ! ,tortwor? di/rict at ! nor? end ( ! ,bri/ol coal-field4 ,!y 7 believ$ to be aque\s deposits 9 ! ,w]n]ian s5se by ,weav]4#bfd ,mur*ison reg>d$ !m z intrusive %eets2#bfe ,phillips look$ on !m z p>tly intrusive & p>tly int]/ratifi$4#bff ,!y consi/ l>gely ( co>sely-amygdaloidal basalts1 "s ( :i* h be5 microscopically exam9$4#bfg ,b _! field-relations z well z _! petrography h n yet be5 adequately det]m9$4 ,!y are repres5t$ on ! ,geological ,survey ,map z =m+ a numb] ( p>allel b&s 9 /rata class$ z ,upp] ,ll&ov]y4 ,if1 z seems probable1 "s ( !m are really int]/ratifi$1 !y =m ! y\nge/ gr\p ( ,silurian volcanic rocks 9 ,engl&1 ,scotl&1 or ,wales4 ,footnote #bfd3 ,trans4 ,geol4 ,soc4 #bnd s]4 vol4 i4 7#ahai71 pp4 #cbd-ccd4 ,footnote #bfe3 ,silurian ,sy/em 7#ahci71 p4 #deg4 ,footnote #bff3 ,mem4 ,geol4 ,surv4 vol4 ii4 "p i4 7#ahdh71 p4 #aid4 ,footnote #bfg3 ,geology ( ,ea/ ,som]set1 etc41 9 ,mem4 ,geol4 ,surv4 7#ahgf71 p4 #baj2 descriptions by ,mr4 ,f4 ,rutley4 ,,*apt] ,,xiv ,,! ,,silurian ,,volcanoes ,,( ,,irel& ,abundant z are ! volcanic records ( ! ,silurian p]iod 9 ,engl&1 ,wales & ,scotl&1 ! description ( !m w\ld be incomplete )\t an acc\nt ( ^? ( ,irel&4 ,! eruptions ( ,ar5ig1 ,ll&eilo & ,bala "t1 :i* we h foll[$ f ! s\? ( ,ca]m>!n%ire to ! bord]s ( ! ,scotti% ,highl&s1 _h _! c\nt]p>ts all d[n ! ea/ ( ,irel&4 ,! ,iri% regi/] ( !m1 h[ev]1 supplies "s details :i* are less cle>ly pres]v$ 9 ! si/] isl&4 ,b ! mo/ di/9ctive feature ( ! ,silurian volcanic hi/ory 9 ,irel& is ! pres]vation ( memorials ( eruptions dur+ ! ,upp] ,silurian p]iod4 ,9 no "p ( ,great ,brita9 has any unque/ionable trace be5 f\nd ( volcanic activity dur+ t "p ( ! geological record1 ! la/ eruptions ( :i* ! age is kn[n be+ ^? ( ! ,bala rocks4 ,b 9 ! s\?-we/ ( ,irel& !re is evid5ce t = a "t active v5ts appe>$ ov] ! sea-floor on :i* ! e>li] deposits ( ,upp] ,silurian "t 7 laid d[n4 ,i4 ,! ,l[] ,silurian ,s]ies i4 ,eruptions probably ( ,ar5ig ,age ,x is 9 t "p ( ,irel& :i* lies ea/ ( a l9e drawn f ,/rabane to ,dung>van ,h>b\r t ! records ( ,l[] ,silurian volcanic activity are to be f\nd4 ,9 ! nor? ! developm5t ( volcanic rocks resembles t 9 ,scotl&1 9 ! s\? x corresponds r ) ! volcanic di/ricts ( ,wales4 ,! ,iri% ,silurian volcanic rocks h be5 trac$ ) m or less detail on ! maps ( ! ,geological ,survey4 ,s9ce ^! maps 7 publi%$1 h[ev]1 great advances h be5 made 9 ! /udy ( ! petrography ( volcanic rocks1 z well z 9 ! art ( trac+ _! /ructure ^u maps4 ,mu*1 !re=e1 n[ rema9s to be done to br+ our k ( ! old] volcanic hi/ory ( ,irel& abrea/ ( t ( ! re/ ( ! ,briti% ,isles4 ,9 ! foll[+ summ>y ,i h _h to rely ma9ly on my own trav]ses ( ! gr\nd1 guid$ by ! maps & memoirs ( ! ,survey1 & ) ! p]sonal assi/ance ( "s ( my colleagues4 ,! rem>kable zone ( cru%$ *]ts1 igne\s rocks & s&/ones1 probably ( ,l[] ,silurian age1 :i* ,i h ref]r$ to 7p4 #bja7 z w$g$ 9 betwe5 ! s*i/s & ! ,old ,r$ ,s&/one along ! s\!rn m>g9 ( ! ,highl&s ( ,scotl&1 reappe>s 9 ,irel&4 ,x occupies an area 9 ! ,c\nty ,tyrone1 ab\t #bd miles long & ab\t #i miles broad at ! broade/ "p1 b disappe>+ t[>ds ! nor?-ea/ & s\?-we/4#bfh ,ly+ betwe5 ! ,palozoic =mations on ! s\? & ! s*i/s on ! nor?1 x occupies a simil> position to ! ,scotti% belt1 b pres5ts a mu* broad] area1 & ?us af=ds great] facilities = exam9+ ! rocks4 ,x pres5ts ! same indef9ite or fault$ b\nd>ies z 9 ,scotl&1 s t its relations to ! rocks along its flanks h n be5 satisfactorily det]m9$4 ,t ! rocks ( ?is area are old] ?an ! ,silurian /rata to ! s\? ( !m seems to be e/abli%$ by ! occurr5ce ( fragm5ts ( !m 9 ^! /rata1 & t !y are y\ng] ?an ! s*i/s may be inf]r$ f _! non-foliat$ "*4 ,b !y h und\bt$ly und]gone consid]able cru%+ by p[]ful t]re/rial movem5ts :i* h plac$ !m 9 _! pres5t position4 ,footnote #bfh3 ,?is area 0 mapp$ by ,mr4 ,j4 ,nolan = ! ,geological ,survey1 & 0 describ$ by him 9 ! ,geol4 ,mag4 = #ahgi4 ,i visit$ x 9 company ) my colleagues1 ,mr4 ,b4 ,n4 ,pea* & ,mr4 ,a4 ,m',h5ry1 9 #ahij & aga9 9 #ahid4 ,my fir/ conclusion 0 t ! volcanic rocks %\ld be reg>d$ z "p ( ! s*i/ose s]ies ly+ to ! nor? ( !m 7,pres4 ,address ,geol4 ,soc4 #ahia1 p4 #gg74 ,b on ! second visit1 aft] hav+ /udi$ ! rocks ( ! bord] ( ! ,scotti% ,highl&s1 ,i =m$ ! op9ion /at$ 9 ! text4 ,! special feature ( int]e/ 9 ?is ,iri% area is ! rem>kable developm5t ( volcanic mat]ials :i* is !re to be se51 spread+ ov] a f> wid] area ?an 9 ,scotl&4 ,! rocks include lavas associat$ ) tuffs & agglom]ates1 likewise a v>i$ s]ies ( intrusive masses4 ,! lavas are *iefly dull gre5i%1 f9e-gra9$ rocks1 hav+ ! g5]al "* ( diabases & porphyrites4 ,!y are sometimes q slaggy1 & :]e ! amygdaloidal k]nels rema91 ^! are usually ( calcite4 ,"u ! microscope1 ! diabases %[ 9 "s p>ts t _! la?-%ap$ felsp>s1 & ! augite :i* ^! p5etrate1 are tol]ably fre%1 :ile 9 o!r p>ts fibr\s *lorite1 granul> epidote & ve9s ( calcite be> witness to ! metamorphism :i* !y h und]gone4 ,"o ( ! mo/ conspicu\s features 9 "s ( ^! lavas is ! occurr5ce ( ! same sack-l or pill[-%ap$ /ructure :i* has be5 already ref]r$ to z s m>k$ among ! ,ar5ig lavas ( ,scotl&4 ,?\gh ! vesicles ( ^! rocks are (t5 q uncru%$1 %[+ t !re has be5 no g5]al subsequ5t de=mation ( ! :ole mass1 !re occur local tracts :]e evid5ce ( consid]able movem5t may be notic$4 ,?us close to a mass ( gneiss1 & else:]e along _! m>g91 ! lavas are apt to be mu* jo9t$ & brok5 ) num]\s l9es ( %e>1 along :i* ! cru%$ mat]ial assumes m or less ( a s*i/ose /ructure4 ,yet 9 ! solid cores betwe5 ^! b&s ( cru%+ ! orig9al =ms ( ! vesicles are reta9$4 ,^! gre5i% lavas are occasionally int]leav$ ) grey fl9ty mud/ones1 *]ts & r$ jasp]s1 :i* are m p>ticul>ly develop$ imm$iately above4 ,9 li?ological "*1 & 9 _! relation to ! diabases1 ^! silice\s b&s be> ! close/ resemblance to ^? ( ,ar5ig age 9 ,scotl&4 ,b no recognizable ,radiol>ia h yet be5 detect$ 9 !m4 ,besides ! m basic lavas1 !re occur also1 b less abundantly1 platy felsitic rocks :i* h suff]$ mu* f %e>+1 & consequ5tly h acquir$ a fissile slaty /ructure4 ,! agglom]ates are made up ( angul>1 subangul> & r\nd$ fragm5ts imb$d$ 9 a matrix ( simil> composition4 ,?is matrix has 9 places become q s*i/ose1 & !n closely resembles "s p>ts ( ! gre5 s*i/s ( ! ,scotti% ,highl&s4 ,( ! inclos$ /ones ! great majority consi/ ( v>i\s felsites1 :i*1 wea!r+ ) a ?ick :ite opaque cru/1 are int]nally close-gra9$1 dull-grey or ev5 black1 sometimes %[+ fl[-/ructure1 & ( all sizes up to eight in*es 9 diamet] or m4 ,!re are also fragm5ts ( ! basic lavas1 & likewise pieces ( *]t & jasp]4 ,on _m ( ! rocky hummocks no di/9ct b$d+ c be made out 9 ! agglom]ate1 b 9 o!rs ! rock is tol]ably well /ratifi$4 ,! tuffs are f9e silky s*i/ose rocks1 & seem to h be5 l>gely d]iv$ f basic lavas4 ,!y h suff]$ m ?an any ( ! o!r rocks f me*anical de=mation1 = !y pass into gre5 *loritic s*i/s4 ,"s portions ( !m are n unlike ! slaty tuffs ( ,llyn ,pad>n 9 ,ca]n>von%ire4 ,accompany+ ! fragm5tal volcanic rocks1 "s ord9>y s$im5t>y int]calations are to be f\nd--r$ %ales & pebbly qu>tzites1 t seem to h escap$ mu* cru%+4 ,! true ord] ( succession 9 ! volcanic s]ies has n yet be5 det]m9$4 ,b app>5tly above ?is s]ies come "s d>k %ales1 su* z might yield graptolites1 pale grits & occasional lime/ones4 ,lat] ?an ! lavas & ! pyrocla/ic mat]ial are v>i\s intrusive masses1 :i* 9 b&s & bosses =m num]\s craggy hills ?r\gh\t ! area4 ,s f> z ,i h be5 able to obs]ve1 ^! rocks include two gr\ps4 ,( ^! ! old] consi/s ( basic injections1 su* z gabbros & alli$ rocks1 "s ( :i* rem9d me ( ! s-call$ hyp]/h5e-rock ( ,l5dalfoot1 9 ,ayr%ire4 ,! co>s] v>ieties1 z at ,c>rickmore or ,t]mon rock1 are sometimes trav]s$ by f9e-gra9$ ve9s f an in* to sev]al feet 9 bread?4 ,portions ( ! slaggy diabases may be obs]v$ inclos$ 9 ^! intrusive masses4 ,! y\ng] gr\p is ( m acid composition 7granite1 qu>tz-porphyry1 etc471 & s5ds ve9s into ! old]4 ii4 ,eruptions ( ,ll&eilo & ,bala ,age ,into ! ea/ ( ,irel& ! ,l[] ,silurian rocks are prolong$ f ,scotl&1 f ! ,lake ,di/rict & f ,wales4 ,?\gh greatly conceal$ "u y\ng] =mations across ! bread? ( ! isl&1 & occasionally int]rupt$ by :at are reg>d$ z old] /rata ( ,cambrian age1 !y nev]!less occupy by mu* ! l>g] "p ( ! m>itime c\nties f ,belfa/ ,l\gh to ! s\!rn coa/-l9e ( ,wat]=d1 ev5 z f> z ,dung>van ,h>b\r4 ,) ! same li?ological types ( s$im5t>y deposits z 9 o!r p>ts ( ! ,unit$ ,k+dom1 !y c>ry ) !m "h also _! *>act]i/ic records ( contemporane\s volcanic action4 ,?\gh n[h]e pil$ into su* magnific5t m\nta9-masses z 9 ,we/morel& & ,nor? ,wales1 ^! records become increas+ly abundant & int]e/+ z !y are trac$ s\?w>ds1 until !y are abruptly t]m9at$ by ! coa/-l9e along ! s\? ( ! c\nties ( ,wex=d & ,wat]=d4 ,:ile mu* rema9s to be done1 bo? 9 ! field & 9 ! laboratory & microscope-room1 be=e our acqua9tance ) ! ,iri% ,silurian volcanic rocks is z complete z our k ( _! equival5ts 9 o!r portions ( ! ,unit$ ,k+dom1 a s]i\s prelim9>y difficulty mu/ be recogniz$ 9 ! fact t ! sev]al geological horizons ( ^! rocks h only be5 approximately fix$4 ,great difficulty 0 exp]i5c$ by ! ,geological ,survey 9 draw+ any satisfactory l9e betwe5 ! ,ll&eilo & ,bala =mations4 ,?is arose n s mu* f defici5cy ( fossil evid5ce z f ! way 9 :i* ! fossils ( ea* gr\p seem$ to occur 9 alt]nat+ b&s 9 :at 7 reg>d$ z a cont9u\s s]ies ( /rata4 ,inde$1 9 "s localities x almo/ appe>$ z if ! occurr5ce ( "o or o!r facies ( fossils dep5d$ ma9ly on li?ological *>act]s indicative ( orig9al conditions ( deposit1 = ! ,ll&eilo =ms recurr$ :]e black %ales set 91 :ile ,bala =ms made _! reappe>ance :]e calc>e\s & gritty /rata pr$om9at$4#bfi ,m rec5t "w among ! ,silurian =mations 9 ,engl& & ,scotl&1 h[ev]1 indicates t ! p>allel repetition ( ! two types ( fossils is due to rapid & con/ant plication ( ! rocks1 :]eby ! two =mations1 nei!r ( !m1 p]haps1 ( great ?ickness1 h be5 fold$ ) ea* o!r 9 su* a way t )\t ! evid5ce ( an e/abli%$ sequ5ce ( fossils1 or ! aid ( cont9u\s sections1 x becomes extremely difficult to make out ! /ratigraphical ord] 9 any di/rict4 ,:5 ! gr\nd is attack$ anew 9 detail1 ) ! assi/ance ( su* palontological & li?ological horizons z h p]mitt$ ! complicat$ /ructure ( ! s\!rn upl&s ( ,scotl& to be unravell$1 we may be enabl$ to tabulate ! successive phases ( ! volcanic hi/ory ( ! region 9 a way :i* is = ! pres5t impossible4 ,we h z yet no palontological evid5ce t 9 ! ,silurian region ( ! ea/ ( ,irel&1 :i* ext5ds f ,belfa/ ,l\gh to ! s\? coa/ ( ,c\nty ,wat]=d1 any ( ! anticl9al folds br+ up to ! surface a portion ( ! ,l[] ,ar5ig =mation1 ?\gh possibly "s ( ! l[e/ visible /rata may be ( ,upp] ,ar5ig age4 ,a consid]able "p ( ! region mu/ be ref]r$ to ! ,ll&ov]y & o!r ,upp] ,silurian =mations1 b ! precise limits ( ! two divisions ( ! ,silurian sy/em h n yet be5 det]m9$1 except = ! region nor? ( ,dubl91 :i* has rec5tly be5 re-exam9$ = ! ,geological ,survey by ,mr4 ,f4 ,w4 ,egan & ,mr4 ,a4 ,m',h5ry4 ,footnote #bfi3 ,jukes 0 dispos$ to reg>d ! two faunas z ess5tially coeval1 b inhabit+ diff]5t k9ds ( sea-bottom4 ,see 8 note1 ,explanation ( ,%eets #afg1 #afh1 #agh1 #agi1 p4 #cj4 ,^! obs]v]s h asc]ta9$ t1 z 9 ,s\!rn ,scotl&1 by f> ! l>g] "p ( ! ,silurian region ( ! nor?-ea/ ( ,irel& is occupi$ by /rata belong+ to ! upp] division ( ! sy/em4 ,! ,l[] ,silurian =mations1 includ+ ! ,ll&eilo & ,bala gr\ps1 =m a belt v>y+ up to six miles 9 bread?1 :i* /ret*es f ! coa/ ( ,d[n1 betwe5 ! m\? ( ,belfa/ ,l\gh & ,copel& ,isl&1 9 a s\?-we/]ly direction to ne> ! valley ( ! ,%annon 9 ,c\nty ,long=d4 ,s\? ( ?is belt ! ,l[] ,silurian rocks rise to ! surface only "h & !re on ! cre/s ( anticl9al folds1 & x is 9 ^! scatt]$ inli]s t ! volcanic & intrusive rocks are f\nd4 ,s f> z ! available evid5ce goes1 ! volcanic hi/ory ( ?is "p ( ,irel& is entirely to be assign$ to ,l[] ,silurian "t1 & m especially to ! int]val betwe5 ! beg9n+ ( ! ,ll&eilo & ! close ( ! ,bala p]iod4 ,i mu/ = ! pres5t cont5t myself ) ?is g5]al limit ( geological *ronology1 & make no attempt to trace ! relative antiquity ( ! igne\s rocks 9 ! sev]al di/ricts 9 :i* !y are di/ribut$4#bgj ,footnote #bgj3 ,! task ( revis+ ! ,iri% maps & trac+ out ! respective areas ( ,upp] & ,l[] ,silurian rocks ov] ! :ole isl& is n[ 9 progress by ! ,geological ,survey1 ,mr4 ,egan & ,mr4 ,m',h5ry be+ entirely engag$ on x4 ,view+ ! volcanic region ( ,ea/]n ,irel& z a :ole1 we are fir/ /ruck by ! feebl5ess ( ! manife/ations ( eruptivity 9 ! nor?1 & _! increas+ developm5t z we advance s\?w>ds4 ,at ! nor!rn end ( ! ,silurian area 9 ,c\nty ,d[n1 ?9 b&s ( fel/one & a% h be5 mapp$ by ! ,geological ,survey z int]/ratifi$ ) ! highly incl9$ & plicat$ ,silurian rocks4#bga ,z ! latt] are pla9ly a cont9uation ( ! /rata :i* h be5 mapp$ out zone by zone 9 ! s\? ( ,scotl&1 _! igne\s int]calations may be look$ ^u z probably equival5ts ( "s ( ^? 9 ! ,silurian di/ricts ( ,wigton%ire & ,kirkcudbright%ire4 ,b 9 ,c\nty ,d[n no repres5tative has yet be5 detect$ ( ! ,ar5ig & ,ll&eilo volcanic s]ies ( ! s\!rn upl&s ( ,scotl&4 ,nor has m precise petrographical exam9ation confirm$ ! ref]5ce ( any ( ! igne\s rocks 9 ! ,silurian area ( t di/rict to truly contemporane\sly int]calat$ volcanic rocks4 ,all ! eruptive mat]ial appe>s to be ( an intrusive "*4 ,x occurs 9 ! =m ( dykes ( lamprophyre or mica-trap belong+ to ! gr\ps ( m9ettes & k]santites4 ,no?+ def9ite is kn[n ( ! age ( ^! intrusions3 !y are possibly ref]able to ! "t ( ! ,l[] ,old ,r$ ,s&/one4#bgb ,footnote #bga3 ,see ,%eet #di ,geol4 ,survey1 ,irel&1 & ,explanation !reto 7#ahga71 pp4 #af1 #cg1 #ci4 ,! s-call$ a%es ( ! ,explanation are probably p>ts ( dykes :i* h be5 m or less cru%$4 ,footnote #bgb3 ,guide to ! ,collection ( ,rocks & ,fossils belong+ to ! ,geological ,survey ( ,irel&1 by ,messrs4 ,m',h5ry & ,watts1 ,dubl91 #ahie1 p4 #gd4 ,f> 9 ! int]ior sev]al b&s ( felspa?ic a% & massive agglom]ate are %[n on ! ,survey map z runn+ ?r\gh ! c\nties ( ,monaghan & ,cavan4#bgc ,9 "o locality s\? ( ! ,drumcalp9 ,l\ghs a l>ge exposure ( ?is a% is visible3 br[n crumbly b$s1 ) small r\nd$ pebbles1 give place to a massive b$ ( agglom]ate1 ! enclos$ blocks ( :i* are always ( "o species ( fel/one1 sometimes measur+ #aj #ab #ah in*es1 & n always r\nd$4 ,s\? ( ,c>rickatee ,l\gh1 & a few miles f>!r to ! s\?-we/1 ne> ,lackan ,bridge1 consid]able exposures ( ^! rocks occur4 ,"o crag 9 p>ticul> displays a ?ickness ( m ?an #gj feet ( t\gh flaky breccias1 ?ick agglom]ates ) small & l>ge blocks ( fel/one1 & ?9 b$s ( f9e pale gre5 compact grit )\t pebbles1 & a few flags4 ,"o ( ! flaky b$s conta9s num]\s :ite worn cry/als ( felsp>2 ! imb$d$ blocks ( fel/one are ( ! usual k9d--pale compact matrix %[+ d>k oblong pat*es1 vesicul> & amygdaloidal1 ! cavities be+ fill$ ) *lorite4 ,footnote #bgc3 ,%eet #fi ,geol4 ,survey1 ,irel&1 & ,explanation ( ,%eets #fh & #fi1 pp4 #i1 #ac1 #ae4 ,fur!r s\? a m ext5sive area ( igne\s rocks has be5 mapp$ on ! bord]s ( ,l\? & ,mea?1 :]e1 accord+ to ! ,geological ,survey map1 a gr\p ( lavas & tuffs ext5ds = ab\t twelve miles ne> ,slane4#bgd ,o!r b&s ( a% & fel/one h be5 mapp$ 9 ! ,silurian area s\? ( ,drogh$a4 ,?us at ,hillt[n1 we/ f ! racec\rse1 a blui% cry/all9e fel/one1 %[+ 9 places l9es ( visc\s fl[1 is /at$ to be ov]la9 by indurat$ felspa?ic a% & tuff1 fel/one1 & indurat$ %ale 9 alt]nat+ b$s4#bge ,on a rec5t visit to ?is locality ,i f\nd t ! porcellanite or indurat$ %ale is a gre5i%-grey *]t1 full ( ,radiol>ia & f9ely-diffus$ volcanic du/4 ,?is association ( radiol>ian *]t ) contemporane\s volcanic activity is ( mu* int]e/1 z %[+ ! ext5sion ( ! same physical conditions ( ! ,l[] ,silurian sea f ,scotl& into ,irel&4 ,! ,l[] ,ll&eilo age ( ! volcanic int]calations 9 ,c\nty ,mea? is fur!r indicat$ by ! occurr5ce ( ,didymograptus ,mur*isoni 9 grey %ales 9 ! same neighb\rhood ) ! radiol>ian *]ts4 ,9 ! ,l[] ,silurian di/rict ( ,balbriggan num]\s intrusive bosses & sills h be5 mapp$ by ! ,geological ,survey4 ,i h f\nd1 h[ev]1 t among ^! rocks !re occur b&s ( volcanic breccia1 conta9+ abundant angul> fragm5ts ( a m9utely-vesicul> pumice1 & also t "s ( ! diabase-masses display ! pill[-/ructure & amygdaloidal texture4 ,h5ce1 ?\gh mo/ ( ! igne\s rocks are no d\bt intrusive1 !y appe> to include lavas & tuffs ( ,bala age4 ,footnote #bgd3 ,ibid4 ,%eets #ha & #ia4 ,^! rocks are *iefly augitic &esites1 a few are basalts1 & "s seem relat$ to fel/ones4 ,probably _m ( !m are intrusive sills ( unc]ta9 age4 ,! a%es conta9 fragm5ts ( felsite & porphyrite (t5 ( consid]able size 7,guide to ,iri% ,rock-,collection1 p4 #cf74 ,footnote #bge3 ,ibid4 ,%eets #ia & #ib & ,explanation to ^! ,%eets 7#ahga71 p4 #aj2 ,guide to ,iri% ,rock-,collection1 p4 #cf4 ,"s ( ^! lavas are &esites1 o!rs are felsites4 ,mr4 ,m',h5ry has cont5d$ t c]ta9 a%es & agglom]ates1 p>ticul>ly ^? expos$ on ! coa/ at ,portra9e1 opposite ,lambay ,isl&1 are cru%-conglom]ates due to t]re/rial di/urbances1 :i* h affect$ bo? intrusive igne\s rocks & ! s$im5t>y s]ies into :i* ^! h be5 inject$4 ,:5 ! num]\s ,silurian cores ( ! m\nta9-gr\ps 9 ! int]ior ( ,irel& %all h be5 se>*$ = traces ( contemporane\s volcanic action1 x is n improbable t ^! w be f\nd4 ,"o ( ! small] ,silurian inli]s :i* div]sify ! great ,c>bonif]\s pla91 t ( ! ,*air ( ,kild>e1 has long be5 kn[n to h igne\s rocks associat$ ) its abundantly fossilif]\s ,bala lime/one4#bgf ,on rec5tly visit+ ?is locality ,i f\nd t1 besides ! amygdaloidal & porphyritic &esites & basalts describ$ by ,jukes & ,du ,noy]1 ! fossilif]\s conglom]ates conta9 pebbles ( rocks l ^? ( ! ,*air1 toge!r ) worn cry/als ( felsp>1 :ile int]calat$ ) !m are ?9 c\rses ( volcanic tuff4 ,!re is ?us evid5ce "h ( contemporane\s volcanic activity dur+ ! accumulation ( ! ,bala gr\p ( /rata4 ,! limit$ area ov] :i* ! rocks are expos$1 h[ev]1 af=ds m]ely a glimpse ( ?is volcanic c5tre4 ,footnote #bgf3 ,see ,explanation to ,qu>t] ,%eet #ce ,n4,e4 7,%eet #aai ( new] num]ation7 ( ,geol4 ,survey ,irel& 7#aheh71 p4 #af4 7,see note1 p4 #bef47 ,cross+ ov] ! broad belt ( ,c>bonif]\s ,lime/one ?r\gh :i* ! ,liffey fl[s into ,dubl9 ,bay1 we come to ! great cont9u\s tract ( old] ,palozoic rocks :i* /ret*es s\?w>d to ! cliffs ( ,wat]=d4 ,?r\gh ?is tract runs ! huge ridge ( ! ,wickl[ & ,c>l[ granite4 ,on ! we/ side ( ?is intrusive mass1 b&s ( gre5/one-a%1 z well z felspa?ic a%es1 h be5 trac$ among ! ,silurian rocks by ! ,geological ,survey4 ,b x is on ! s\?-ea/ side ( ! granite t ! volcanic int]calations are be/ display$4 ,inde$1 f ,wickl[ ,head to ,dung>van ,h>b\r !re is an almo/ cont9u\s developm5t ( igne\s rocks1 ris+ into rocky em95ces1 tr5*$ into rav9es by ! num]\s /reams1 & laid b>e by ! waves 9 f9e coa/-cliffs4 ,x is 9 ?is s\?-ea/]n region1 compris+ ! c\nties ( ,wickl[1 ,wex=d & ,wat]=d1 t ! ,iri% ,l[] ,silurian igne\s rocks c be/ be /udi$4 ,!re are obvi\sly v>i\s di/9ct c5tres ( eruption 9 ?is long belt ( c\ntry4 ,! ,ra?drum & ,ca/letimon tract =ms "o ( ^!4 ,ano!r ( less size culm9ates 9 ,kilpatrick ,hill1 a few miles to ! s\?w>d4 ,arkl[ ,head m>ks ! position ( a ?ird4 ,! lavas & tuffs :i* set 9 a few miles to ! s\? ( t promontory1 & may be said to ext5d )\t int]ruption to ! s\? coa/1 7 probably ?r[n out by a s]ies ( v5ts :i*1 plac$ along a nor?-ea/ & s\?-we/ l9e1 unit$ _! ejections into "o long subm>9e volcanic bank4 ,!re c be no d\bt t ! mo/ active v5ts lay at ! s\!rn end ( ! belt1 = !re ! volcanic mat]ials are pil$ up 9 ?icke/ mass1 & succe$ ea* o!r ) comp>atively trifl+ int]calations ( ord9>y s$im5t>y mat]ial4 ,"s ( ^! v5ts1 z ,i %all relate 9 ! sequel1 h be5 cut op5 by ! sea along a range ( precipit\s cliffs4 ,! comp>atively feeble "* ( ! volcanic en]gy dur+ ,l[] ,silurian "t ov] ! great] "p ( ! s\?-ea/ ( ,irel& is %[n by ! great contra/ betwe5 ! ?ickness ( ! volcanic int]calations !re & 9 ,wales & ! ,lake c\ntry1 b /ill m /rik+ly by innum]able sections :]e ?9 int]/ratifications ( f9e tuff or volcanic breccia occur among ! ord9>y s$im5t>y /rata1 & are sometimes cr[d$ ) ,bala fossils4 ,"s int]e/+ illu/rations ( ?is feature are to be se5 9 ! ,enniscor?y di/rict1 :]e lay]s ( f9e felsitic tuff1 sometimes less ?an an in* 9 ?ickness1 lie among ! %ales4 ,9 "s ( ! tuffs ! lapilli are fragm5ts ( tra*ytic or &esitic rocks4 ,a /rik+ example ( rapid alt]nations ( pyrocla/ic mat]ial ) ord9>y s$im5t lies f> to ! s\? 9 ,c\nty ,wat]=d1 close to ,dunhill ,bridge1 :]e a gr\p ( f9e volcanic breccias & grits has be5 laid b>e by qu>ry+4#bgg ,^! /rata consi/ ( co>s] & f9] detritus1 enclos+ angul> fragm5ts ( felsites & grey & black %ale4 ,! felsite-lapilli v>y 9 texture1 "s ( !m pres5t+ beautiful fl[-/ructure4 ,! /ones are /uck at r&om ?r\gh ea* b$1 ! l>ge/ be+ (t5 at ! bottom4 ,! b$s ( breccia v>y f a few in*es to a foot or m 9 ?ickness4 ,!re c1 ,i ?9k1 be little d\bt t ea* ( ^! breccia-b&s po9ts to a s+le volcanic explosion1 :]eby felsitic fragm5ts 7 ?r[n out1 m+l$ ) pieces ( ! ,silurian /rata ?r\gh :i* ! v5ts 7 drill$4 ,9 a v]tical ?ickness ( "s fifty feet ( rock !re mu/ ?us be a record ( t5 or twelve su* explosions4 ,footnote #bgg3 ,see ,explanation ( ,%eets #afg1 #afh1 #agh & #agi1 ,geol4 ,surv4 ,irel&1 p4 #ef4 ,ne>] ! active v5ts ! fragm5tal deposits become1 z usual1 co>s] & ?ick]4 ,b ,i h n obs]v$ any ?ick masses ( tuff l ^? ( ,nor? ,wales4 ,s f> z my exam9ation has gone1 ! tuffs are ma9ly felsitic4 ,! s-call$ gre5/one-a% ( ! ,survey maps is c]ta9ly 9 _m cases n a true tuff4 ,?is t]m 0 propos$ by ,jukes = c]ta9 apple-gre5 to olive-br[n flaky fissile rocks only f\nd 9 association ) masses ( gre5/one4#bgh ,"s ye>s ago ,i _h occasion to make a s]ies ( trav]ses 9 ,wickl[ & ,wex=d1 & !n conv9c$ myself t 9 t "p ( ! c\ntry ! gre5/one-a%es 7 probably cru%$ b&s ( basic sills4 ,dr4 ,hat* has prov$ ?is to be _! orig9 f a s]ies ( microscopic slides prep>$ f specim5s collect$ by himself on ! gr\nd4#bgi ,9 o!r cases ! gre5/one-a%es seem to be excessively-cleav$ or %e>$ felsites1 :i* h acquir$ a soapy feel & a dull gre5 col\r2 b !y also d include true tuffs4 ,?us1 9 "o in/ance1 at ,ballyvoyle cross-roads1 9 ! s\? ( ,c\nty ,wat]=d1 a gre5/one-a% is a dull gre5 tuff full ( fragm5ts ( felsp> 7*iefly plagioclase7 & pieces ( d>k &esitic lavas4 ,ano!r example may be f\nd to ! we/ ( ! ,metal ,man1 ne> ,tramore1 :]e ! tuff is full ( fragm5ts ( felsp> & %ale cem5t$ 9 a gre5i%-yell[ mat]ial :i* may be palagonite4 ,footnote #bgh3 ,explanation ( ,%eets #abi1 #acj1 p4 #ac 7#ahfi74 ,footnote #bgi3 ,explanation ( ,%eets #ach1 #aci4 ,! felsites ( ! s\?-ea/ ( ,irel& =m by mu* ! l>ge/ proportion ( ! :ole volcanic s]ies4 ,!y occur z l5ticul> %eets f a few feet to sev]al hundr$ feet 9 ?ickness1 & occasionally traceable = "s miles4 ,on ! :ole1 !y are compact dull grey rocks1 wea!r+ ) a :ite cru/4 ,a geologi/ famili> ) ! contempor>y lavas ( ,nor? ,wales _c fail to be /ruck ) ! abs5ce ( ! co>se fl[-/ructure s (t5 *>act]i/ic ( ! felsites 9 t region4 ,?is /ructure1 inde$1 is n entirely abs5t f ! ,iri% rocks1 b x occurs1 s f>1 at lea/1 z ,i h se51 r z a f9e /reak9ess ?an 9 ! bold l5ticul> b&s s common 9 ,ca]n>von%ire4 ,9 l mann] ! nodul> /ructure1 ?\gh n entirely abs5t1 is r>e4#bhj ,footnote #bhj3 ,9 ,wat]=d nodul> felsites occur ) concretions v>y+ f ! size ( a pea to sev]al in*es 9 diamet]4 ,explanation to ,%eets #afg1 #afh1 #agh & #agi1 p4 #aa4 ,until ^! felsites h be5 subject$ to m detail$ inve/igation1 little c be said z to _! petrography1 & z to ! po9ts ( resemblance or diff]5ce betwe5 !m & ^? ( o!r ,l[] ,silurian di/ricts 9 ! ,unit$ ,k+dom4 ,an important /ep1 h[ev]1 9 ?is direction 0 tak5 by ,dr4 ,hat*1 :o /udi$ !m on ! gr\nd1 9 ! laboratory1 & ) ! microscope4 ,he f\nd t "s ( !m 7 soda-felsites or k]atophyres 7) albite z _! felsp>71 t o!rs 7 pota%-felsites 7) or?oclase z _! felsp>71 :ile a ?ird gr\p conta9$ bo? soda & pota%1 ! la/-nam$ greatly prepond]at+4#bha ,! exi/5ce ( soda-felsites _h n be5 previ\sly detect$ among ,briti% volcanic rocks1 & x rema9s to be se5 h[ f> !y may occur 9 ! l>ge & some:at v>i$ gr\p ( rocks comb9$ "u ! g5]al t]m felsites4 ,dr4 ,hat* believ$ t ^! rocks probably graduate into ! normal or or?oclase felsites2 b x has n yet be5 possible to te/ ?is view on ! gr\nd1 nor to asc]ta9 :e!r !re is any ess5tial diff]5ce betwe5 ! mode ( occurr5ce ( ! two types4 ,footnote #bha3 ,explanation ( ,%eets #ach1 #aci1 p4 #di2 & ,geol4 ,mag4 #ahhi1 p4 #ede4 ,besides ! m abundant felsites1 occasional b&s ( &esite h be5 detect$4 ,v>i\s o!r eruptive rocks occur1 probably 9 mo/ or all cases intrusive4 ,su* are qu>tz-mica-diorites1 qu>tz-diorites1 augite-diorites or prot]obases1 dol]ites1 gabbros1 diabases & epidiorites4#bhb ,footnote #bhb3 ,guide to ,iri% ,rock-,collections1 pp4 #cd1 #ce4 ,i h said t ! *ief !atre ( eruption lay t[>ds ! s\?-we/ end ( ! volcanic belt ( ! s\?-ea/ ( ,irel&4 ,! coa/-l9e ( ,c\nty ,wat]=d1 f ,tramore we/w>d to ,ballyvoyle ,head--a di/ance ( ne>ly fifte5 miles--pres5ts1 p]haps1 ! mo/ wond]ful s]ies ( sections ( volcanic v5ts )9 ! ,briti% ,isl&s4 ,no "o com+ f ! inl& is prep>$ = ei!r ! /rik+ "* ( ! cliff sc5]y or ! extraord9>y geological /ructure !re pres5t$1 = ! c\ntry is1 on ! :ole1 r featureless1 & mu* ( x is smoo!d ov] & obscur$ by a cov]+ ( drift1 ?r\gh :i* occasional knobs ( ! h>d] felsites protrude4 ,! cliffs = mile aft] mile range f #ajj to #aej or #bjj feet 9 height1 & pres5t nak$ v]tical walls ( rock1 tr5*$ by occasional gullies1 ?r\gh :i* a desc5t may be made to ! bea*4 ,?r\gh\t ! :ole di/ance agglom]ates & felsites succe$ ea* o!r 9 bewild]+ confusion1 v>i$ "h & !re by ! int]calation ( ,l[] ,silurian %ales & lime/ones involv$ & pi]c$ by ! igne\s rocks4 ,h>dly any b$d$ volcanic mat]ial is to be recogniz$ f "o end to ! o!r4 ,! sea has laid b>e a succession ( volcanic v5ts plac$ s close to ea* o!r t x w be difficult or impossible to sep>ate !m out4 ,a c>eful /udy & detail$ mapp+ ( ?is m>vell\s coa/-section1 h[ev]1 is a task well wor?y ( ! lab\r ( any "o desir\s ( mak+ himself acqua9t$ ) "s ( ! conditions ( volcanism dur+ old] ,palozoic "t4 ,at ! ea/ end ( ! section1 black %ales conta9+ ,ll&eilo graptolites1 & calc>e\s b&s full ( ,bala fossils1 dip we/w>d bel[ a gr\p ( soda-felsites & felsitic tuffs1 :i* seem to lie q con=mably on ^! /rata4 ,"h1 !n1 we />t ) pro( t ! volcanic eruptions ( ?is locality began dur+ "s "p ( ! ,bala p]iod4 ,b imm$iately to ! we/1 ^! b$d$ igne\s rocks are brok5 ?r\gh by a neck ( co>se agglom]ate /uck full ( *ips & blocks ( %ale1 "s ( !m a foot long1 ) abundant fragm5ts ( scori=m & fl9ty felsites4 ,"s column> dykes ( dol]ite cut ?r\gh ! neck1 & a l>g] intrusion seems to h ris5 up ! same funnel4 ,! b$d$ tuffs appe> aga9 = a %ort di/ance1 b !y are soon replac$ by a tumultu\s mass ( agglom]ate4 ,& f ?is "p ( ! coa/ onw>ds = "s di/ance all is disord]4 ,! agglom]ates are cr[d$ ) blocks ( v>i\s felsites & micro-granites sometimes #ah in*es 9 diamet]1 _m ( !m pres5t+ ! mo/ exquisite /reaky fl[-/ructure4 ,! angul>ity ( ^! /ones & ! abrupt truncation ( _! l9es ( fl[ prove t !y 7 d]iv$ f ! %att]+ ( already consolidat$ rocks4 ,9 o!r places ! eject$ mat]ials consi/ almo/ :olly ( black %ale fragm5ts1 b ) an int]mixture ( felsite-lapilli4 ,x is difficult to convey an adequate idea ( ! way 9 :i* ! agglom]ates are trav]s$ by dykes1 ve9s & bosses ( v>i\s felsites1 & ( h[ ^! break 9 endless confusion ?r\gh ea* o!r4 ,"s ( ! intrusive rocks are compact & amorph\s1 o!rs are vesicul>1 o!rs close-gra9$ & column>4 ,aga9 & aga9 !y pres5t ! mo/ p]fect fl[-/ructure1 & x is noticeable t ! l9es ( fl[ foll[ ! inequalities ( ! walls ( ! fissure up :i* ! rock has asc5d$1 & n only s1 b ev5 ( ! surfaces ( deta*$ blocks ( %ale or felsite :i* h be5 caught up & enclos$ 9 ! /ill mov+ mass4 ,a few ( ^! intrusive rocks 7 exam9$ 9 ?9 slices by ,dr4 ,hat*4 ,mo/ ( !m appe> to be soda-felsites1 b !y include also r decompos$ rocks1 "s ( :i* are probably diorites & qu>tz-diorites4 ,occasionally1 ?or\ghly basic dykes 7dol]ite7 may be obs]v$4 ,9 ! mid/ ( ?is tumultu\s assemblage ( volcanic masses1 repres5t+ ! roots ( a gr\p ( anci5t v5ts1 !re occur occasional int]spaces occupi$ by ord9>y /ratifi$ rocks4 ,9 ! ea/]n "p ( ! section ^! consi/ ma9ly ( black %ale1 sometimes ) calc>e\s b&s1 f :i* a s]ies ( ,bala fossils has be5 obta9$4#bhc ,a v cursory exam9ation suffices to %[ t ^! int]calations d n m>k pauses 9 ! volcanic eruptions4 ,!y are1 9 fact1 portions ( ! m>9e accumulations "u ! sea-floor ?r\gh :i* ! v5ts 7 bl[n2 !y h be5 toss$ ab\t1 cru%$ & invad$ by dykes & ve9s ( felsite4 ,footnote #bhc3 ,b see ! ,geol4 ,survey ,memoir on ,%eets #afg1 #afh1 #agh & #agi1 ,irel& 7#ahfe71 p4 #bh1 = a description ( ! association ( ,bala & ,ll&eilo fossils on t coa/-l9e4 ,b c]ta9 o!r int]calat$ /rips ( /ratifi$ rocks pres5t a special int]e/1 = !y br+ be=e u examples ( volcanic a%es t ga!r$ on ! sea-floor1 b :i* 7 disrupt$ by lat] explosions4 ,?us1 at ! ,knockmahon headl&1 well-b$d$ felspa?ic grits & a%y %ales occur1 ?r[n 9 among ! g5]al mass ( eruptive mat]ial4 ,z ,i h already rem>k$1 x is difficult or impossible to fix ! horizons ( ! /ratifi$ pat*es t are involv$ among ! igne\s ejections ( ?is coa/-section1 save :]e !y conta9 recognizable fossils1 b ! int]calation ( true b$d$ tuffs among !m is a pro( t volcanic action _h be5 9 op]ation !re long be=e ! outbreak ( ! v5ts :i* are n[ laid b>e along ! cliffs4 ,9 ! s\?-ea/ ( ,irel& !re is ! usual association ( acid & basic sills ) ! evid5ce ( a sup]ficial outp\r+ ( lavas & a%es4 ,b ^! intrusive masses play a mu* less impos+ "p ?an 9 ,wales4 ,!y may be reg>d$1 inde$1 z be>+ some:at ! same proportion to ! comp>atively feeble display ( extrusive rocks 9 ?is region t ! abundant & massive %eets ( ,m]ione?%ire & ,ca]n>von%ire d to ! enorm\s piles ( lavas & tuffs :i* ov]lie !m4 ,among ! acid intrusive %eets ! mo/ conspicu\s are ^? mapp$ by ! ,survey z elvans4 ,^! rocks1 z !y occur 9 ,wickl[ & ,wex=d1 h be5 exam9$ by ,dr4 ,hat*1 :o f9ds !m to be micro-granitic 9 /ructure1 occasionally exhibit+ micropegmatitic or granophyric modifications4#bhd ,! true /ratigraphical relations ( ^! rocks h n yet be5 adequately inve/igat$4 ,^? ( !m :i* occur on ! flanks ( ! great granite ridge are n improbably connect$ ) t mass1 & if s are mu* y\ng] ?an ! ,l[] ,silurian volcanoes4#bhe ,footnote #bhd3 ,explanation ( ,%eets #ach & #aci1 p4 #ec4 ,footnote #bhe3 ,! ,le9/] granite is c]ta9ly lat] ?an ! ,l[] ,silurian rocks & old] ?an ! ,c>bonif]\s rocks ( ! s\?-ea/ ( ,irel&4 ,x may belong to ! great epo* ( granite protrusion dur+ ! ,old ,r$ ,s&/one p]iod4 ,! basic sills1 or gre5/ones1 consi/ l>gely ( diabase1 frequ5tly alt]$ into epidiorite2 !y include also v>ieties ( diorite4#bhf ,t !y 7 intrud$ be=e ! plication & cleavage ( ! rocks among :i* !y lie is well %[n by _! cru%$ & %e>$ m>g9s :]e !y are 9 ?ick mass1 & by _! cleav$ & almo/ s*i/ose condition :]e !y are ?9n]4 ,! int5se compression & cru%+ to :i* !y h be5 subject$ are well %[n by ! /ate ( _! compon5t m9]als1 & notably by ! p>amorphism ( ! orig9al augite into hornbl5de4 ,footnote #bhf3 ,dr4 ,hat*1 op4 cit4 p4 #di4 ,! sc>city ( dykes associat$ ) ,silurian volcanic action is z noticeable 9 ! s\?-ea/ ( ,irel& z x is 9 ,wales4 ,i h obs]v$ a consid]able numb]1 inde$1 b !y are conf9$ to ! l9e ( old v5ts on ! ,wat]=d coa/1 &1 b = ! cle> cliff-sections cut by ! sea1 !y w\ld c]ta9ly h escap$ obs]vation1 = !y make no feature on ! gr\nd 9 ! int]ior4 ,!y are sometimes di/9ctly column>1 & v>y f less ?an a foot to _m y>ds 9 wid?4 ,!y trav]se bo? ! agglom]ates & ! intrusive felsites4 ,mo/ ( !m are ( felsite1 sometimes cellul>2 b 9 "s cases !y are dol]ites4 ,!re is obvi\sly no clue to ! dates ( ^! dykes4 ,t "s at lea/ ( ! v5ts along ! s\? coa/ ( ,c\nty ,wat]=d may be va/ly y\ng] ?an ! ,l[] ,silurian rocks ?r\gh :i* !y h =c$ _! way is sugge/$1 if n prov$1 by a section :i* is 9 "s respects ! mo/ extraord9>y ( ! :ole ( ?is rem>kable s]ies4 ,! occurr5ce ( a gr\p ( r$ /rata 0 c>efully not$ by ! late ,mr4 ,du ,noy] at ,ballyd\ane ,bay1 :5 he 0 engag$ 9 c>ry+ on ! ,geological ,survey ( t "p ( ! c\ntry4 ,at fir/ he reg>d$ !m z belong+ to ! ,old ,r$ ,s&/one1 :i* comes on 9 great =ce only a few miles to ! we/2 b he subsequ5tly arriv$ at ! belief t !y are really an integral "p ( ! ,l[] ,silurian rocks ( ! di/rict4 ,pr(essor ,jukes _h previ\sly express$ himself 9 fav\r ( ?is latt] idea1 :i* 0 ?\ght to receive support f ! occurr5ce ( "s r$di% /rata 9 ! ,l[] ,silurian rocks ( ,tagoat1 ,c\nty ,wex=d4#bhg ,footnote #bhg3 ,explanation ( ,%eets #afg1 #afh1 #agh & #agi ( ! ,geological ,survey ( ,irel& 7#ahfe71 pp4 #aj1 #ei4 ,! occurr5ce ( r$ rocks among ,silurian /rata1 :i* are n usually r$1 might q reasonably be look$ = 9 ! neighb\rhood ( ,old ,r$ ,s&/one1 ,p]mian or ,triassic deposits4 ,if ^! deposits once spread ov] ! ,silurian =mations1 a m or less decid$ raddl+ ( ! latt] may h tak5 place4 ,b 9 ! pres5t in/ance1 ?\gh ! ,old ,r$ ,s&/one beg9s n _m miles to ! we/1 no su* explanation ( ! col\r ( ! /rata is possible4 ,! cliffs ( ,ballyd\ane ,bay consi/ ( r$ s&/one1 r$ s&y %ale & conglom]ate4 ,! r$ t9t is ( t dull *ocolate tone s *>act]i/ic ( ! ,l[] ,old ,r$ ,s&/one4 ,! conglom]ates are imm5se accumulations ( anci5t %+le1 consi/+ l>gely ( pieces ( :ite ve9-qu>tz & qu>tzite1 sometimes a foot long & (t5 well wat]-worn4 ,"s ( ! s&y b$s are full ( l>ge scales ( :ite mica1 z if d]iv$ f "s granitic or s*i/ose region at no great di/ance4 ,tak5 z a :ole1 ! /rata are mu* less indurat$ & brok5 ?an ! ,silurian grits & %ales ( ! di/rict2 "s ( !m1 inde$1 wea!r into m]e incoh]5t s& t crumbles "u ! f+]s4 ,!re does n appe> to be any positive pro( t ! r$ rocks are truly b$d$ ) ! ord9>y ,silurian /rata1 ! junctions be+ fault$ or obscur$ by intrusive igne\s masses4 ,n[h]e 9 ! ,briti% ,isl&s1 s f> z ,i am aw>e1 is !re a simil> gr\p ( /rata among ! ,l[] ,silurian rocks4 ,if !y belong to s anci5t a s]ies1 !y %[ t 9 ! s\? ( ,irel&1 dur+ ,l[] ,silurian "t1 !re arose a set ( peculi> physical conditions precisely l ^? t det]m9$ ! accumulation ( ! ,old ,r$ ,s&/one 9 ! same region at a lat] geological p]iod4 ,& 9 t case x is h>dly possible to conceive t ^! conditions c\ld h be5 conf9$ to ! extreme s\? ( ,irel&4 ,we %\ld c]ta9ly expect to meet ) evid5ce ( !m else:]e1 at lea/ 9 ! same ,silurian region4#bhh ,footnote #bhh3 ,! ne>e/ approa* ( any ,silurian gr\p ( /rata to ! "* ( ^! conglom]ates is furni%$ by ! rem>kably co>se conglom]ates1 b\ld]-b$s & pebbly grits ( ! ,bala & ,ll&ov]y s]ies 9 ! region betwe5 ,kill>y ,h>b\r & ,l\gh ,mask1 to :i* fur!r ref]5ce is made 9 a lat] "p ( ?is *apt]4 ,:ile ,i hesitate to express a decid$ op9ion 9 opposition to ! conclusions ( su* exp]i5c$ obs]v]s z ,jukes & ,du ,noy]1 ,i incl9e to believe t ! rocks 9 "q really belong to ! ,old ,r$ ,s&/one4 ,if su* %all f9ally be det]m9$ to be _! geological position1 !y w supply evid5ce t "s at lea/ ( ! volcanic v5ts ( ! coa/-l9e _c be old] ?an ! ,old ,r$ ,s&/one4 ,!y are pi]c$ by masses ( soda-felsite & by a co>se r$ agglom]ate conta9+ abundant pieces ( felsite4 ,^! volcanic rocks belong to ! same type z ^? :i* break ?r\gh ! und\bt$ ,silurian rocks on ei!r side4 ,!y may ?us come to prove a recrudesc5ce ( volcanic en]gy 9 ?is same di/rict at a mu* lat] geological p]iod2 & a new problem w arise to task ! skill ( ! mo/ accompli%$ field-geologi/ & petrograph]--to unravel ! /ructure & hi/ory ( ?is *a9 ( volcanic v5ts1 &1 9 s do+1 to detect & sep>ate ! eruptions ( ,l[] ,silurian "t f ^? ( ! ,l[] ,old ,r$ ,s&/one4 ,9 ! f> we/ ( ,irel&1 ano!r gr\p ( ,l[] ,silurian volcanoes has left its rema9s 9 ! m\nta9\s tract ( c\ntry betwe5 ! we/]n %ores ( ,l\gh ,mask & ,kill>y ,h>b\r4#bhi ,!re appe> to h be5 at lea/ ?ree sep>ate c5tres ( eruption along a l9e /ret*+ 9 a nor?-ea/]ly direction = ab\t #af miles f ! we/]n end ( ,l\gh ,nafooey to ! hamlet ( ,d]r9daffd]y beyond ,t\rmakeady1 :]e ! old] rocks are uncon=mably ov]la9 by ! l[] ,c>bonif]\s /rata4 ,z %[n by ! mapp+ ( ! ,geological ,survey1 ! mo/ nor!rly area1 :i* may be call$ ! ,t\rmakeady c5tre1 has a bread? ( ab\t a mile1 & dies out s\?w>d aft] a c\rse ( ne>ly six miles4 ,ab\t a mile to ! s\?-we/ ( ! la/ visible prolongation ( its rocks1 we enc\nt] a second volcanic c5tre :i* occupies an area ( ab\t a squ>e mile 9 ! valley ( ,gl5saul4 ,! ?ird c5tre /ret*es f ! we/]n %ores ( ,l\gh ,mask across ,l\gh ,nafooey1 :]e x =ms a mass ( high rugg$ gr\nd1 & rea*es a l5g? ( "s six or sev5 miles be=e x f9ally dies out4#bij ,footnote #bhi3 ,?is gr\p 0 plac$ 9 ! ,upp] ,silurian s]ies by ! (fic]s ( ! ,geological ,survey :o mapp$ ! region 7see ,%eets #hd1 #he1 #id & #ie ( ! ,geological ,map ( ,irel& & accompany+ ,explanation71 & on _! te/imony ,i =m]ly ref]r$ to ! volcanic rocks z ( ,upp] ,silurian age4 ,mr4 ,baily1 h[ev]1 _h po9t$ out t ! lime/one associat$ ) ! lavas & agglom]ates conta9s ,bala fossils4 ,yet1 9 spite ( ?is palontological te/imony1 ! fossils 7 consid]$ to be d]ivative1 & ! rocks 7 remov$ f ! s]ies ( =mations to :i* !y w\ld naturally be assign$4 ,a rec5t exam9ation ( ! gr\nd1 9 company ) ,mr4 ,j4 ,r4 ,kilroe ( ! ,geological ,survey1 has satisfi$ me t ! volcanic rocks are int]/ratifi$ ) s$im5t>y deposits ( ,bala age1 & mu/ consequ5tly be gr\p$ ) ! re/ ( ! ,l[] ,silurian s]ies ( ,irel&4 ,! results ( ?is exam9ation are giv5 9 ! text4 ,footnote #bij3 ,^! areas 7 c>efully mapp$ = ! ,survey by ,mr4 ,nolan1 & ! l9es ( division m>k$ by him fairly repres5t ! g5]al di/ribution ( ! rocks4 ,! rocks 9 ea* ( ^! ?ree areas are simil>4 ,"o ( _! di/+ui%+ features is ! int]calation among !m ( a fossilif]\s lime/one & calc>e\s fossilif]\s tuffs1 :i* conta9 well-pres]v$ species ( organisms *>act]i/ic ( ! ,bala division ( ! ,l[] ,silurian rocks4#bia ,!re _c be any "q t ^! organisms 7 liv+ at ! "t ! /rata 9 :i* _! rema9s occur are f\nd4 ,! mo/ delicate p>ts ( ! sculpture on ,illnus ,b[manni & ,or?is elegantula are well pres]v$4 ,nor h ! lime/ones be5 pu%$ into _! pres5t places by volcanic ag5cy1 or by faults 9 ! t]re/rial cru/4 ,!y are n only regul>ly int]calat$ among ! volcanic rocks1 b ! lime/one 9 "s places ab\nds 9 volcanic du/1 :ile above x come calc>e\s tuffs1 also conta9+ ! same fossils4 ,x is ?us cle>ly e/abli%$ t ! volcanic s]ies n[ to be describ$ has its geological age def9itely fix$ z t ( ! ,bala p]iod4 ,footnote #bia3 ,see ! li/ ( fossils z det]m9$ by ,mr4 ,baily 9 ,explanatory ,memoir to accompany ,%eets #gc1 #gd1 #hc & #hd ( ! ,geological ,survey ( ,irel&1 p4 #fh 7#ahgf74 ,! lavas ( ! ,l\gh ,mask region consi/ ( felsites & &esites ) rocks ( probably m basic composition4 ,! felsites are g5]ally qu>tzif]\s porphyries1 :i* occupy a consid]able space 9 ea* ( ! ?ree di/ricts4 ,to :at ext5t !y are intrusive r ?an int]/ratifi$ rema9s = inve/igation4 ,"s ( !m h und\bt$ly invad$ o!r memb]s ( ! volcanic s]ies4 ,b1 on ! o!r h&1 fragm5ts ( simil> qu>tz-porphyries & felsites ab\nd 9 ! int]calat$ b&s ( volcanic breccia4 ,! &esites & m basic lavas are f9ely-cry/all9e or compact1 dull-gre5 to *ocolate-purple rocks1 (t5 resembl+ ! porphyrites ( ! ,old ,r$ ,s&/one4 ,"s ( !m are /rongly vesicul>1 ! cavities be+ fill$ ) calcite on fre% fracture1 ?\gh empty on wea!r$ surfaces4 ,! sack-l or pill[ /ructure1 already ref]r$ to z *>act]i/ic ( _m ,l[] ,silurian lavas1 appe>s conspicu\sly among "s ( ^! rocks4 ,at ,bohaun1 n9e miles s\? f ,we/port1 :]e a prolongation ( ! volcanic s]ies rises to ! surface f "u ! ov]ly+ co>se conglom]ates1 ,i obs]v$ t1 ow+ to ! compression :i* ! rocks h !re und]gone1 ! pill[-%ap$ blocks h be5 squeez$ toge!r into rudely polygonal =ms1 :ile _! vesicles h be5 greatly drawn out 9 ! direction ( t5sion4 ,:]e ! rocks h be5 /ill m %e>$1 ! di/9ct pill[-%ap$ blocks ) _! vesicul> /ructure disappe>1 :ile ! m f9e-gra9$ cru/s t surr\nd !m h be5 brok5 up & appe> z fragm5ts involv$ 9 a matrix ( gre5 s*i/4 ,int]calat$ ) ! lavas are num]\s b&s ( volcanic breccia & f9e tuff4 ,! /ones 9 ^! breccias consi/ *iefly ( v>i\s felsites ) &esites & m basic lavas4 ,b pieces ( jasp]1 *]t1 %ale & grit are n infrequ5t4 ,9 "s places abundant blocks ( black %ale are to be notic$1 probably d]iv$ f ! ,ll&eilo gr\p :i* exi/s bel[1 & :i* has "h & !re be5 ridg$ up to ! surface 9 ! mid/ ( ! volcanic rocks4#bib ,ne> ,%angort ,i notic$ 9 "o ( ^! breccias "o block measur+ #ab feet1 ano!r #bj feet 9 l5g? & #c or #d feet ?ick1 compos$ ( alt]nat+ b&s ( grit & slate4 ,x is int]e/+ to note t ^! /rata _h already und]gone cleavage be=e disruption1 ! b&s ( slate be+ /rongly cleav$ obliquely to ! b$d+4 ,none ( ! ,ll&eilo or o!r rocks 9 ! neighb\rhood display ?is /ructure4 ,! blocks seem to h be5 d]iv$ f "s deep] gr\p ( /rata4 ,!y are laid d[n p>allel ) ! rude b$d+ ( ! breccia 9 :i* !y lie4 ,footnote #bib3 ,9 re-exam9+ ?is region1 ,mr4 ,kilroe has f\nd 9 ! /ream we/ ( ! mona/]y1 ,t\rmakeady1 an uprise ( graptolitic black %ale conta9+ =ms belong+ to ! v l[e/ ,ll&eilo or ,upp] ,ar5ig /rata1 & a simil> b& above ,le5ane1 ,kill>y ,h>b\r4 ,! f9e tuffs & ?9 a%y lime/ones associat$ ) ! ?ick] b& ( lime/one %[ ! r5ewal ( volcanic explosions aft] ! int]val m>k$ by ! calc>e\s deposit :i* is sometimes #bj or #dj feet ?ick4 ,9 _m places ?is lime/one is brecciat$ & mu* m+l$ ) volcanic du/ & lapilli4 ,at ,%angort1 = example1 ! ?ick tol]ably pure lime/one is truncat$ on ! we/ & nor? sides by a co>se agglom]ate probably fill+ a volcanic v5t4 ,a few hundr$ y>ds fur!r nor?1 beyond ! int]rupt+ agglom]ate1 ! lime/one reappe>s on ! same l9e ( /rike1 b is !n f\nd to be nodul> & brecciat$ & mu* m+l$ ) volcanic detritus4 ,x lies among a%y grits & tuffs4 ,illu/ration3 ,fig4 #fd4--;,diagram ( ! g5]al relations ( ! diff]5t gr\ps ( rock 9 ! ,l[] ,silurian volcanic di/rict along ! we/]n %ore ( ,l\gh ,mask4 a1 ,ll&eilo %ales1 *]ts & grits2 b1 ,volcanic breccias2 c1 ,felsites & &esites2 d1 ,tuffs & a%y grits & %ales2 e1 ,lime/one ) ,bala fossils2 f1 ,calc>e\s tuffs & ?9 b&s ( a%y lime/one ) fossils2 g1 ,co>se conglom]ate & grits2 h1 ,w5lock /rata re/+ uncon=mably on ! ,bala rocks & pass+ s\?w>ds f ^! to ov]lie an old] s]ies ( s*i/s2 991 ,fault4 ,! g5]al /ructure ( ! gr\nd occupi$ by ! ,l\gh ,mask volcanic rocks is diagrammatically repres5t$ 9 ,fig4 #fd4 ,! ?ickness ( ! volcanic s]ies mu/ am\nt to _m hundr$ feet1 b x has n be5 precisely det]m9$4 ,! upp]mo/ p>ts ( ! s]ies pass "u a great ?ickness ( co>se conglom]ates & pebbly grits :i* =m ! ridge ( ,=mnamore1 & /ret* !nce we/w>ds along ,kill>y ,h>b\r & ?r\gh ! ,mweelrea m\nta9s4 ,^! /rata are class$ z ! ,upp] ,silurian on ! ,geological ,survey map4 ,s9ce1 h[ev]1 !y con=mably ov]lie rocks conta9+ ,bala fossils1 & 9 ! ,kill>y di/rict include gre5 %ales :i* h yield$ fossils ( ! same age1 !y d\btless belong 9 l>ge "p to ! ,l[] ,silurian division4 ,! rem>kable co>s5ess ( ^! conglom]ates t[>ds ! s\?1 & _! rapid passage into mu* f9] grits & %ales t[>ds ! nor?1 probably indicate t !y 7 =m$ close to ! %ores ( a l& compos$ ( s*i/ose rocks1 qu>tzite & granite1 ( :i* ! m\nta9\s tracts ( ,connem>a are ! la/ relics4 ,a base to ! volcanic s]ies is f\nd 9 ! occasional uprise ( a %ort axis ( ,ll&eilo1 or p]haps ev5 upp] ,ar5ig /rata1 conta9+ b&s ( d>k *]t & black graptolitic %ales4 ,un=tunately ! relations ( ^! und]ly+ rocks to ! volcanic masses are n v cle>1 be+ obscur$ by sup]ficial accumulations & also by fault+4 ,x is ?us h>dly possible to be c]ta9 :e!r !y pass up con=mably into ! base ( ! volcanic s]ies1 or are cov]$ by x uncon=mably4 ,! position ( ?is isolat$ volcanic di/rict 9 ! f> we/ ( ,irel&1 ! abundance1 v>iety & ?ickness ( ! erupt$ mat]ials1 & ! def9ite int]calation ( ^! mat]ials 9 ! ,bala or highe/ division ( ! ,l[] ,silurian s]ies1 acquire a special int]e/ f ! hi/ory ( ! ne>e/ ,silurian volcanic area :i* has n[ to be describ$--t ( ! we/]n %ores ( ! ,d+le promontory4 ,,ii4 ,! ,upp] ,silurian ,s]ies ,! late/ volcanic eruptions ( ,silurian "t yet def9itely kn[n took place dur+ ! accumulation ( ! ,w5lock & ,ludl[ rocks 9 ! f> we/ ( ,irel&4 ,no satisfactory record ( any contemporane\s ph5om5a ( a l k9d has yet be5 met ) 9 any o!r ,upp] ,silurian di/rict 9 ! ,briti% ,isles1 unless at ,tortwor? 9 ,gl\ce/]%ire1 z above describ$4 ,s f> z at pres5t kn[n1 only "o c5tre ( activity has be5 pres]v$4 ,x lies among ! headl&s ( ,k]ry1 :]e ! l& projects fur!/ we/ into ! /ormy ,atlantic4 ,! occurr5ce ( volcanic rocks 9 ?is remote area & _! geological horizon h be5 cle>ly indicat$ on ! maps ( ! ,geological ,survey4 ,m ?an ?irty ye>s1 h[ev]1 h elaps$ s9ce "s ( ! mapp+ 0 done1 & we mu/ !re=e be prep>$ to f9d x1 m especially 9 its petrography1 capable ( modification & improvem5t n[4 ,9 ! c\ntry kn[n z ! ,d+le promontory1 ^! traces ( contemporane\s volcanic rocks are to be obs]v$ at v>i\s localities & on sev]al horizons4 ,to ! ea/1 ne> ,anascaul1 on ! nor!rn %ore ( ,d+le ,bay1 "s tuffs occur 9 :at are believ$ to be ,ll&ov]y /rata4 ,b x is on ! we/]n coa/1 among ! headl&s & coves t lie to ! nor? & s\? ( ,clogh] ,head1 t ! be/ sections are to be se54 ,! succession ( ! rocks 9 ?is locality 0 well work$ out by ,du ,noy]1 & ! ,memoir prep>$ by him1 ) ! g5]al introduction by ,jukes1 is an invaluable guide to ! geologi/ :o w\ld explore ?is some:at inaccessible region4#bic ,! mo/ important correction t w require to be made 9 ! "w arises f a mi/ake z to ! true nature ( c]ta9 rocks :i* 7 describ$ z pisolitic tuffs1 b :i* are nodul> felsites4 ,footnote #bic3 ,%eets #afj & #aga ( ! "o-in* map1 & ,memoir on ,%eets #afj1 #afa1 #aga & #agb4 ,by f> ! mo/ /rik+ geological feature ( ?is s+ul>ly int]e/+ & impressive coa/-l9e is to be f\nd 9 ! int]/ratification ( lavas ) b&s ( tuff among abundantly fossilif]\s /rata :i*1 f _! organic cont5ts1 are unmi/akably ( ! age ( ! ,w5lock gr\p4 ,^! lavas occur 9 a numb] ( %eets1 sep>at$ f ea* o!r by tuffs & o!r fragm5tal deposits4 ,!y ?us po9t to a s]ies ( eruptions ov] a sea-bottom t teem$ ) ,upp] ,silurian life4 ,!y consi/ = ! mo/ "p ( rem>kably f9e typical nodul> felsites4 ,! nodules v>y 9 dim5sions f less ?an a pea to ! size ( a h5's egg4 ,!y are sometimes holl[ & l9$ ) qu>tz-cry/als4 ,!y v>y greatly 9 numb]1 "s p>ts be+ almo/ free f !m & o!rs entirely made up ( !m4 ,! matrix1 :]e a fre% fracture c be obta9$1 is horny 9 texture1 & (t5 exhibits an exce$+ly beautiful & f9e fl[-/ructure4 ,on wea!r$ faces !re may be se5 ?ick p>allel /rips & l5ticles ( fl[-/ructure l ^? ( ! ,sn[don lavas4 ,! upp] portions ( "s ( ! %eets enclose fragm5ts ( =eign rocks4 ,! microscopic exam9ation ( a few slices cut f ^! lavas %[s !m to be true felsites 7rhyolites7 compos$ ( a microcry/all9e aggregate ( qu>tz & felsp>1 ) lay]s & pat*es ( cryptocry/all9e matt]1 & only occasional porphyritic cry/als ( or?oclase & plagioclase4 ,! pyrocla/ic rocks associat$ ) ^! lavas v>y f exce$+ly f9e tuff to co>se agglom]ate4 ,"s ( ! f9] tuffs conta9 pumice\s fragm5ts & pieces ( grey & r$ %ale2 !y pass into f9e a%y s&/ones & %ales1 cr[d$ ) fossils1 & into gravelly breccias made up ( fragm5ts ( diff]5t volcanic rocks4 ,b ! mo/ extraord9>y ( ^! int]calat$ fragm5tal /rata is a breccia or agglom]ate1 ab\t #ae feet ?ick1 :i* lies 9 a ?ick gr\p ( fossilif]\s dull-yell[1 a%y & o*re\s s&/ones4 ,! /ones ( ?is b$ consi/ *iefly ( blocks ( diff]5t felsites1 v>y+ up to ?ree feet 9 l5g?4 ,"s ( !m %[ mo/ p]fect fl[-/ructure2 o!rs are spongy & cellul>1 l lumps ( pumice4 ,! calc>e\s s&/one on ! top ( ! breccia is cr[d$ ) fossils *iefly 9 ! =m ( empty ca/s1 & ! same mat]ial1 /ill full ( bra*iopods1 cr9oids1 corals1 etc41 fills up ! int]/ices among ! blocks d[n to ! bottom ( ! breccia1 :]e simil> fossilif]\s /rata und]lie x4 ,n[h]e has ! volcanic hi/ory ( a portion ( ,palozoic "t be5 m cle>ly & eloqu5tly record$ ?an 9 ?is remote l9e ( cliffs swept by ! gales ( ! ,atlantic4 ,we see t ! ord9>y s$im5tation ( ,upp] ,silurian "t 0 quietly proce$+1 f9e mud & s& be+ deposit$1 & enclos+ ! rema9s ( ! m>9e organisms t sw>m$ ov] ! sea-bottom :5 volcanic eruptions began4 ,fir/ came dis*>ges ( f9e du/ & small /ones1 :i* sometimes fell s lightly z n s]i\sly to di/urb ! fauna on ! sea-floor1 b at o!r times foll[$ s rapidly & cont9u\sly z to mask ! usual s$im5t & =m %eets ( tuff & volcanic gravel4 ,occasionally !re w\ld come m p>oxysmal explosions1 :]eby l>ge blocks ( lava 7 hurl$ =? until !y ga!r$ 9 a ?ick lay] ov] ! bottom4 ,b ! life t teem$ 9 ! sea1 ?\gh tempor>ily de/roy$ or driv5 out1 soon return$4 ,corals1 cr9oids & %ells f\nd _! way back aga91 & f9e s$im5t c>ri$ _! rema9s ) x & fill$ up ! crevices4 ,! eject$ volcanic blocks are ?us enclos$ 9 a highly fossilif]\s matrix4 ,a succession ( lava-/reams1 ( :i* ! /rongly-nodul> %eet ( ,clogh] ,head is ! ?icke/ & mo/ conspicu\s1 m>k ! culm9ation ( ! volcanic en]gy1 & %[ h[ at ?is late "p ( ! ,silurian p]iod felsites t reproduce "s ( ! mo/ /rik+ peculi>ities ( e>li] "t 7 once m p\r$ out at ! surface4 ,a few m dis*>ges ( tuff & ! outfl[ ( a gre5i% fl9ty felsite br\ght ?is s]ies ( eruptions to an end1 & clos$ 9 ,brita9 ! long & v>i$ record ( old] ,palozoic volcanic activity4#bid ,footnote #bid3 ,z ?is %eet is pass+ ?r\gh ! press1 ! int]e/+ pap] by ,messrs4 ,s4 ,h4 ,reynolds & ,c4 ,j4 ,g>d9]1 ,on ! ,kild>e ,inli] has appe>$ 7,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 lii4 p4 #ehg74 ,^! au?ors give petrographical details reg>d+ ! lavas1 :i* !y %[ to be &esites & basalts ( ,bala age1 associat$ ) highly fossilif]\s tuffs4 ,illu/ration ,,to ,,accompany ,,sir ,,ar*ibald ,,geikie',s ,,anci5t ,,volcanoes ,,( ,,brita9 ,map ,,ii ,,map ,,( ,,! ,,silurian ,,volcanic ,,di/ricts ,,( ,,nor? ,,wales ,r$uc$ f ! ,maps ( ! ,geological ,survey4 ,! ,ed9burgh ,geographical ,in/itute -- ,copyright -- ,j4 ,g4 ,b>?olomew4 ,,book ,v ,,! ,,volcanoes ,,( ,,devonian ,,& ,,old ,,r$ ,,s&/one ,,"t ,,*apt] ,,xv ,,! ,,devonian ,,volcanoes ,?r\gh\t ! :ole region ( ! ,briti% ,isles1 :]ev] ! upp]mo/ /rata ( ! ,silurian sy/em c be se5 to graduate into any lat] s]ies ( s$im5t>y deposits1 !y are f\nd to pass up con=mably into an enorm\s accumulation ( r$ s&/ones1 m>ls1 corn/ones1 & conglom]ates1 :i* h long be5 gr\p$ toge!r "u ! "n ( ,old ,r$ ,s&/one4 ,9 ,engl& & ,wales1 9 ,scotl& & 9 ,irel&1 ?is upw>d succession is s well %[n t at fir/ ,briti% geologi/s 7 naturally dispos$ to believe x to repres5t ! normal ord] ( ! geological record4 ,:51 h[ev]1 ,s$gwick & ,mur*ison demon/rat$ t 9 ! c\nties ( ,devon & ,cornwall a v diff]5t gr\p ( /rata conta9$ an abundant assemblage ( organic rema9s1 includ+ types :i* ,lonsdale %[$ to be int]m$iate betwe5 ^? ( ! ,silurian & ! ,c>bonif]\s sy/ems2 :51 moreov]1 ?is palontological facies ( ! s\?-we/ ( ,engl&1 t]m$ by its discov]]s ,devonian1 0 f\nd to be abundantly develop$ on ! ,cont95t1 & to be !re inde$ ! preval5t /ratigraphical type ( ! =mations int]v5+ betwe5 ,silurian & ,c>bonif]\s1 geologi/s began to p]ceive t ! ,old ,r$ ,s&/one mu/ be reg>d$ z ! record ( peculi> local conditions ( s$im5tation1 :ile ! ,devonian type 0 evid5tly ! m usual developm5t ( ! same geological p]iod4 ,f ! remote ,%etl& ,isles1 across ! :ole ( ,scotl& & ,engl&1 d[n to ! nor!rn %ores ( ! ,bri/ol ,*annel1 ! ,old ,r$ ,s&/one ma9ta9s its g5]al *>act]s4 ,n[h]e1 inde$1 are ^! *>act]s m typically develop$ ?an 9 ,s\? ,wales1 :]e _m ?\s&s ( feet ( r$ s$im5ts1 almo/ entirely devoid ( organic rema9s1 em]ge f "u ! esc>pm5ts ( ,c>bonif]\s ,lime/one1 & /ret* into broad upl&s until !y are lo/ at ! top ( ! ,silurian sy/em4 ,b :5 ! geologi/ crosses ! ,bri/ol ,*annel to ! opposite %ores ( ,nor? ,devon1 he enc\nt]s a rem>kably diff]5t assemblage ( rocks4 ,x is true t he has n yet be5 able to detect !re any equival5ts ( ! upp]mo/ ,silurian /rata ( ,glamorgan%ire1 nor does he f9d any conspicu\s b& ( ,c>bonif]\s ,lime/one1 su* z t :i* encircles ! ,wel% ,coal-field4 ,he is ?us unable to />t f a kn[n def9ite horizon 9 ! attempt to "w out ! ord] ( succession1 ei!r 9 an upw>d or d[nw>d direction4 ,li?ological *>act]s likewise af=d him no means ( e/abli%+ any satisfactory p>allelism4 ,z he foll[s ! ,devonian /rata1 h[ev]1 he f9ds !m to disappe> con=mably "u ! ,culm-measures1 :i*1 ?\gh /rangely unlike ! ,c>bonif]\s /rata on ! opposite coa/1 are yet prov$ by _! fossils to belong to ! ,c>bonif]\s sy/em4 ,h5ce ! ,devonian type1 l ! ,old ,r$ ,s&/one1 is prov$ to be imm$iately ant]ior to1 & to graduate into1 ! ,c>bonif]\s rocks4 ,!re is no /ratigraphical *ange 9 ,brita9 s rapid & complete z t f ! ,old ,r$ ,s&/one on ! "o side ( ! ,bri/ol ,*annel to ! ,devonian s]ies on ! o!r4 ,no satisfactory explanation has yet be5 f\nd = ?is sudd5 trans=mation1 :i* /ill rema9s "o ( ! unsolv$ problems 9 ,briti% geology4 ,z ! obs]v] foll[s ! ,devonian assemblage across ! l& to ! s\!rn coa/-l9e1 he is consci\s t its g5]al *>act]s1 bo? li?ological & palontological1 dep>t m & m f ! type ( ! ,old ,r$ ,s&/one1 & approa* m closely to ! common ,devonian facies ( ! ,cont95t4 ,he is =c$ to admit t ! ,old ,r$ ,s&/one1 not)/&+ its ext5sive developm5t 9 ,brita91 mu/ be reg>d$ z an exceptional type ( s$im5tation1 :ile ! ,devonian facies repres5ts t :i* is mo/ widely preval5t1 n only 9 ,europe1 b g5]ally ov] ! _w4 ,! broad e/u>y ( ! ,bri/ol ,*annel un=tunately conceals f view ! tract :i* lies betwe5 ! typical ,old ,r$ ,s&/one ( ,glamorgan%ire & ! typical ,devonian =mations ( ,devon%ire4 ,:e!r ?is int]v5+ space ( "s fifte5 miles 0 occupi$ by a physical b>ri]1 :i* sep>at$ ! respective areas ( deposit ( ^! two types1 or ! circum/ances ( s$im5tation 9 ! "o region m]g$ ins5sibly into ^? ( ! o!r1 mu/ rema9 matt] = speculation4 ,! geographical conditions betok5$ by ! ,old ,r$ ,s&/one w be consid]$ 9 ! next *apt]4 ,!re c be no d\bt t ^? indicat$ by ! ,devonian sy/em 7 m>9e4 ,! organic rema9s s pl5tifully di/ribut$ ?r\gh ! argillace\s & ar5ace\s s$im5ts ( t sy/em1 & s cr[d$ toge!r 9 its lime/ones1 7 obvi\sly d5iz5s ( ! op5 sea4 ,yet ! only tract ( ,brita9 ov] :i* ?is sea c be %[n to h spread 0 ! s\? ( ,engl&4 ,to ! nor? ( t belt1 ! site ( ,brita9 dur+ ,devonian "t appe>s to h be5 p>tly l& & p>tly wide wat]-bas9s 9 :i* ! ,old ,r$ ,s&/one 0 deposit$4 ,9 t half t]re/rial half lacu/r9e t]ritory t /ret*$ nor?w>ds to beyond ! ,%etl& ,isles1 _m volcanoes 7 active1 ( :i* ! *ronicles w be describ$ 9 lat] pages4 ,! mo/ s\!rly ( ^! c5tres ( eruption yet kn[n 0 ! di/rict ( ! ,*eviot ,hills4 ,?r\gh\t ! re/ ( ,engl& & ,wales no trace ( any contempor>y volcanic action has be5 detect$ 9 ! ,old ,r$ ,s&/one4 ,x is true t ov] mo/ ( t region rocks ( ?is age h be5 conceal$ "u y\ng] =mations4 ,yet ?r\gh\t ,wales1 :]e ! ,old ,r$ ,s&/one atta9s s va/ a ?ickness1 & cov]s s wide an area1 x has n yet yield$ a ve/ige ( any contemporane\s volcanic eruptions4 ,b ov] ! sea-floor t cov]$ ! s\? ( ,engl&1 & /ret*$ !nce into ! he>t ( ,europe1 abundant volcanoes h left beh9d !m pro(s ( _! activity4 ,! fir/ geologi/ :o recogniz$ ^! pro(s & trac$ _! ext5t on ! gr\nd appe>s to h be5 ,de la ,be*e1 :o1 by 8 detail$ maps & c>eful description ( ! igne\s rocks ( ,devon%ire1 did s mu* to advance ! /udy ( anci5t volcanic action4 ,?is great pione] n only det]m9$ ! =m] exi/5ce ( ,devonian volcanoes1 b he 0 likewise ! fir/ to detect & map ! volcanic rocks associat$ ) ! ,c>bonif]\s & ,new ,r$ ,s&/one =mations ( ! same region4 ,! broad outl9es trac$ by him among ! volcanic products ( ^! ?ree geological p]iods 9 ! s\?-we/ ( ,engl& /ill rema9 b little *ang$4 ,nor are !y likely to be mu* improv$ until ! gr\nd is resurvey$ on a l>g] & m accurate map1 & ) bett] petrographical equipm5t ?an 7 available 9 8 day4 ,n long aft] ! obs]vations ( ,de la ,be*e came ^? ( ,a4 ,c4 ,godw9-,au/51 :o devot$ mu* "t to a s$ul\s exploration ( ! rocks ( ,s\? ,devon1 & satisfi$ himself t contemporane\s volcanic %eets 7 int]calat$ among ! lime/ones ( t di/rict4 ,! coral lime/ones1 he says1 are 9 _m places sup]9cumb5t on great %eets ( volcanic mat]ials1 ) :i*1 9 "s in/ances1 z at ,nor? ,:ilbor\gh1 !y alt]nate4 ,he po9t$ out t ! int]/ratifi$ volcanic rocks are ( two p]iods1 "o ,devonian & ! o!r ,c>bonif]\s4#bie ,footnote #bie3 ,trans4 ,geol4 ,soc4 #bnd s]4 vol4 vi4 7#ahdb71 pp4 #dfe1 #dgj1 #dgc4 ,9 8 ,geological ,maps ( ,devon & ,cornwall1 :i* are to ! pres5t "t ^? issu$ by ! ,geological ,survey1 ,de la ,be*e made no attempt to discrim9ate betwe5 ! v>ieties ( igne\s rocks1 save t ! basic gre5/ones 7 di/+ui%$ f ! acid bosses ( granite & ! elvans4 ,b 9 8 classic ,report mu* m detail 0 ins]t$1 %[+ t he cle>ly recogniz$ ! exi/5ce bo? ( volcanic a%es & ( lavas1 z well z ( intrusive %eets4 ,at ! outset ( 8 acc\nt ( ! ,grauwacke1 he rem>ks t ! s$im5t>y deposits are accompani$ ) igne\s products1 a portion ( :i* may also be t]m$ s$im5t>y1 inasmu* z x w\ld seem to h be5 deposit$ 9 b$s among contemporane\s rocks ( ! =m] description by ! ag5cy ( wat]1 aft] hav+ be5 eject$ f fissures or crat]s 9 ! %ape ( a%es & c9d]s1 precisely z we may n[ expect w\ld happ5 ) ! a%es & c9d]s eject$ f volcanoes1 p>ticul>ly insul> & littoral volcanoes1 into ! sea4#bif ,aga9 he speaks ( two k9ds ( trappean rocks hav+ probably be5 erupt$1 "o 9 ! /ate ( igne\s fusion1 & ! o!r 9 t ( a%1 dur+ ! "t t ! mud1 n[ =m+ slates1 0 deposit$1 ! mixtures ( volcanic & s$im5t>y mat]ials be+ irregul> f ! irregul> action ( ! respective causes :i* produc$ !m2 s t ?\gh ! "o may h be5 d]iv$ f igne\s action1 & ! o!r f ! ord9>y abrasion ( pre-exi/+ solid rocks1 !y 7 geologically contemporane\s4#big ,he recogniz$ ! orig9 ( ! amygdaloidal v>ieties ( rock1 & by dissolv+ out ! calcite f _! cells %[$ h[ close 0 _! resemblance to mod]n pumice4#bih ,footnote #bif3 ,report on ! ,geology ( ,cornwall1 ,devon & ,we/ ,som]set1 ,mem4 ,geol4 ,survey1 #ahci1 p4 #cg4 ,footnote #big3 ,op4 cit4 p4 #eg4 ,footnote #bih3 ,op4 cit4 pp4 #eg1 #fa4 ,s9ce ^! e>ly rese>*es _m geologi/s h /udi$ ! igne\s rocks ( ,devon%ire4 ,i w\ld especially ref] to ! lab\rs ( ,mr4 ,allport1#bii ! late ,j4 ,a4 ,phillips1#cjj ,mr4 ,rutley1#cja ! late ,mr4 ,*amp]n[ne1#cjb ,mr4 ,w4 ,a4 ,e4 ,us%]1#cjc ,mr4 ,hobson1#cjd & ,g5]al ,m',mahon4#cje ,mr4 ,*amp]n[ne 9 p>ticul> has %[n ! abundance ( volcanic mat]ial among ! rocks ( ,devon%ire1 & ! resemblance :i* 9 ?is respect !y (f] to ! ,devonian sy/em ( ,nor? ,g]many4 ,footnote #bii3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xxxii4 7#ahgf71 p4 #dah4 ,footnote #cjj3 ,op4 cit4 xxxi4 7#ahge7 p4 #cbe1 xxxii4 7#ahgf7 p4 #aee1 xxxiv4 7#ahgh7 p4 #dga4 ,footnote #cja3 ,br5t ,tor1 ,mem4 ,geol4 ,surv4 p4 #ah2 ,qu>t4 ,j\rn4 ,geol4 ,soc4 lii4 7#ahif71 p4 #ff4 ,footnote #cjb3 ,see 9 p>ticul> 8 la/ pap] ,on ! ,a%pr+ton ,volcanic ,s]ies ( ,s\? ,devon1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlv4 7#ahhi71 p4 #cfi4 ,footnote #cjc3 ,?is geologi/ has sp5t _m labori\s ye>s 9 ! inve/igation ( ! geology ( ,devon%ire1 & has publi%$ num]\s pap]s on ! subject1 9 ! ,transactions ( ! ,devon%ire ,association & ( ! ,royal ,cornwall ,geological ,society1 9 ! ,proce$+s ( ! ,som]set%ire ,ar*ological & ,natural ,hi/ory ,society1 & ( ! ,geologi/s' ,association1 9 ! ,geological ,magaz9e1 & ! ,qu>t]ly ,j\rnal ( ! ,geological ,society4 ,ref]5ce may especially be made to 8 ,memoir 9 ! la/ nam$ j\rnal1 vol4 xlvi4 7#ahij71 p4 #dhg4 ,footnote #cjd3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlviii4 7#ahib71 p4 #dif4 ,footnote #cje3 ,op4 cit4 xlix4 7#ahic71 p4 #che4 ,un=tunately ! geological /ructure ( ! ,palozoic rocks ( ! ,s\?-we/ ( ,engl& has be5 complicat$ to an amaz+ ext5t by plication & fracture1 ) concomitant cleavage & metamorphism4 ,h5ce x is a task ( extreme difficulty to trace out ) any c]ta9ty def9ite /ratigraphical horizons1 & to det]m9e ! range ( contemporane\s volcanic action4 ,mr4 ,us%] has %[n ) :at success ?is task may be accompli%$ :5 x is pursu$ on a basis ( m9ute mapp+1 comb9$ ) a s$ul\s collection & det]m9ation ( fossils4#cjf ,b ye>s mu/ necess>ily elapse be=e su* detail$ "w is c>ri$ ov] ! :ole ,devonian region1 & probably n till !n w ! /ory ( ! volcanic hi/ory ( ! rocks be adequately made out4 ,footnote #cjf3 ,see ,memoir cit$ 9 a previ\s note4 ,9 ! meantime1 x has be5 e/abli%$ t :ile !re is a s+ul> abs5ce ( igne\s rocks 9 ,nor? ,devon1 a /rip ( c\ntry ext5d+ f ,newton ,abbot & ,torquay we/w>ds by ,plym\? across ,cornwall to ,p5zance conta9s abundant records ( volcanic action4 ,x has n yet be5 possible to map out1 among :at 7 =m]ly all gr\p$ toge!r z gre5/ones1 ! respective limits ( ! b$d$ lavas & ! tuffs1 to di/+ui% ! true sills1 & to fix on ! position ( ! *ief v5ts ( eruption4 ,s int5se h be5 ! compression & %e>+ ( ! rocks t solid %eets ( diabase h be5 cru%$ into fissile s*i/s1 :i* c h>dly be di/+ui%$ f tuffs4 ,moreov]1 ow+ p]haps 9 l>ge measure to ! mantle ( r$ ,p]mian 7or ,triassic7 /rata1 :i* has be5 /ripp$ (f by d5udation f l>ge tracts ( ?is region once ov]spread by x1 ! ,devonian rocks h be5 deeply raddl$1 or /a9$ r$4 ,b probably "o ( ! ma9 s\rces ( difficulty 9 /udy+ ! petrography ( ! area is to be f\nd 9 ! results ( atmosph]ic wea!r+4 ,devon%ire lies 9 t s\!rn non-glaciat$ /rip ( ,engl&1 :]e ! rocks h be5 und]go+ cont9u\s decay s9ce long be=e ! ,ice ,age4 ,no pl\gh%>e ( ice has !re swept (f ! deep wea!r$ cru/1 s z to leave h>d surfaces ( rock1 fre% & b>e1 "u a protect+ %eet ( b\ld]-clay4 ,x is seldom t a really fre% piece ( any igne\s rock c be procur$ among ! lanes & %all[ pits ( ,devon1 :]e alone1 = ! mo/ "p1 ! mat]ials are expos$4 ,mu*1 !re=e1 rema9s to be done1 bo? 9 ! /ratigraphy & petrography ( ! ,devonian volcanic rocks ( ?is c\ntry4 ,to ! late ,j4 ,a4 ,phillips geology is indebt$ = ! fir/ detail$ *emical & microscopical inve/igation ( ^! rocks4 ,he cle>ly %[$ ! truly volcanic orig9 ( _m ( ! s-call$ gre5/ones4 ,he believ$ t c]ta9 slaty blue elvans1 :i* he f\nd to h a composition id5tical ) t ( alt]$ dol]ites1 might be highly metamorphos$ tuffs1 & t o!rs might h be5 orig9ally %eets ( volcanic mud4 ,aft] /udy+ ! *emical composition & m9ute /ructure ( a l>ge collection ( gre5/ones1 he demon/rat$ t 9 all ess5tial p>ticul>s !y 7 dol]ites1 ?\gh some:at alt]$ f _! orig9al "*4#cjg ,subsequ5tly !y 7 /udi$ by ,dr4 ,hat*1 :o f\nd ! fre%] specim5s g5]ally to possess an ophitic /ructure1 :ile "s are granul>1 o!rs porphyritic4#cjh ,footnote #cjg3 ,see especially ,qu>t4 ,j\rn4 ,geol4 ,soc4 vols4 xxxii4 & xxxiv4 ,footnote #cjh3 ,a few ( ! eruptive rocks ( ,devon%ire h rec5tly be5 /udi$ by ,k4 ,busz4 ,he f9ds mo/ ( 8 specim5s 7*iefly f ! ,torquay di/rict7 to be v>ieties ( diabase1 b describes a palopicrite f ,highweek ne> ,newton ,bu%el1 & a k]santite f ,s\? ,br5t on ! s\?-ea/ edge ( ,d>tmoor 7,neues ,jahrb4 #ahif1 p4 #eg74 ,al?\gh ! rocks h und]gone s mu* cru%+1 solid cores ( !m1 %[+ ! orig9al /ructure1 may be obta9$1 also examples ( ! amygdaloidal1 vesicul> or slaggy "*4 ,!y occur 9 %eets ei!r s+ly or 9 gr\ps1 & appe> g5]ally to be regul>ly int]/ratifi$ 9 ! slates & grits4 ,:ile "s ( ^! int]calations1 especially ! amygdaloidal %eets1 may be true sup]ficial lavas1 x c h>dly be d\bt$ t o!rs are sills1 especially ^? :i* assume ! cry/all9e /ructure & composition ( gabbros1 & %[ an entire abs5ce ( ! vesicul> /ructure4 ,b no "o has yet attempt$ to sep>ate ! two types f ea* o!r4 ,) ^! rocks are associat$ abundant diabase-tuffs 7s*al/e971 frequ5tly m+l$ ) ord9>y non-volcanic detrital matt]1 & %ad+ (f into ! surr\nd+ grits & slates4 ,!re is ?us cle> evid5ce ( ! outp\r+ ( basic lavas & %[]s ( a%es dur+ ! ,devonian p]iod 9 ! s\?-we/ ( ,engl&1 "u conditions analog\s to ^? :i* *>act]iz$ ! deposition ( ! ,devonian sy/em 9 ,nassau & ! ,h>z4 ,! exact range ( ^! eruptions 9 geological "t has /ill to be asc]ta9$4 ,s f> z at pres5t det]m9$1 volcanic activity 0 n awak5$ dur+ ! accumulation ( ! ,l[] ,devonian =mations4 ,x 0 n until ! sporadic coral-reefs & %ell-banks _h gr[n up1 :i* =m ! basem5t lime/ones ( ! ,middle ,devonian gr\p1 t ! fir/ eruptions took place4 ,z ,godw9-,au/51 ,*amp]n[ne & ,mr4 ,us%] h %[n1 "s ( ^! reefs 7 ov]:elm$ ) /reams ( lava or buri$ "u %[]s ( a%es4 ,! volcanic dis*>ges1 h[ev]1 7 peculi>ly local1 probably f _m scatt]$ v5ts1 & nev] on any great scale4 ,"s di/ricts rema9$ little or n at all affect$ by !m1 s t ! gr[? ( lime/one w5t on )\t int]ruption1 or at lea/ ) no s]i\s break4 ,9 o!r areas aga9 ! place ( ! lime/one is tak5 by volcanic mat]ials4 ,! *ief epo* ( ?is volcanic action1 m>k$ by ! ,a%pr+ton ,volcanic ,s]ies1 appe>s to h occurr$ ab\t midway 9 ! ,middle ,devonian p]iod4 ,b 9 c]ta9 di/ricts x ext5d$ into ,upp] ,devonian "t4 ,intrusive sills ( diabase may m>k ! lat] phases ( ! volcanic hi/ory4 ,b ! occurr5ce ( su* sills ev5 9 ! ,upp] ,devonian rocks1 & ! alt]ation ( ! /rata 9 contact ) !m 7spilosite71 po9t to ! cont9uance or r5ewal ( subt]ranean di/urbance ev5 9 ! lat] ,devonian ages1 if n 9 subsequ5t geological "t4 ,t volcanic activity accompani$ ! deposition ( ! ,c>bonif]\s rocks ( ,devon%ire has long be5 well kn[n 7see ,*apt] xxix474 ,,*apt] ,,xvi ,,! ,,volcanoes ,,( ,,! ,,old ,,r$ ,,s&/one ,geological ,revolutions at ! close ( ! ,silurian ,p]iod--,physical ,geography ( ! ,old ,r$ ,s&/one--,old ,lake-bas9s1 _! ,flora & ,fauna--,abundance ( ,volcanoes--,hi/ory ( ,inve/igation 9 ! ,subject4 ,we n[ ent] ^u ! consid]ation ( ! records ( a notable era 9 ! geological evolution ( nor?-we/]n ,europe4 ,up to ! close ( ! ,silurian p]iod ! long hi/ory embodi$ 9 ! rocks pres5ts a con/ant succession ( sl[ly s9k+ sea-floors4 ,wide tracts ( ocean /ret*$ ov] mo/ ( ,europe1 & across ! %ift+ bottom1 s& & mud1 wa%$ f l&s t h long vani%$1 spread 9 an ev]-accumulat+ pile4 ,n[ & !n1 "s t]re/rial movem5t ( m ?an usual pot5cy uprais$ ?is monoton\s sea-b$1 b ! old conditions ( ceaseless wa/e cont9u$1 & fre% %eets ( detritus 7 ?r[n d[n ^u ! brok5-up heaps ( old] s$im5t4 ,all ?r\gh ! va/ cycles ( "t d5ot$ by ^! accumulations ( /rata1 g5]ations ( sea-creatures came & w5t 9 long procession1 leav+ _! relics amid/ ! ooze ( ! bottom4 ,g5]a & families1 once abundant1 gradually di$ out1 & gave place to o!rs1 ! onw>d m>* ( life be+ sl[ b un9t]rupt$4 ,( ! l& ( ! "t or ( ! plants & animals t liv$ on its surface1 h>dly any?+ is kn[n4 ,! *ronicles t h come d[n to u are almo/ :olly records ( ! vicissitudes ( ! ocean-b$4 ,ov] ! c5tre & s\? ( ,europe1 ! m>9e conditions ( ,silurian "t 7 prolong$1 z we h se51 into ! next p]iod1 :5 ! ,devonian =mations 7 deposit$4 ,9 t wide region1 no m>k$ break has be5 trac$ betwe5 ei!r ! s$im5tation or ! animal life ( ! ,silurian & ,devonian p]iods4 ,b 9 ! nor?-we/ ( ,europe a /rik+ dep>ture took place f ! protract$ monotony ( m>9e conditions4 ,by a s]ies ( t]re/rial movem5ts t affect$ ! area ly+ to ! nor? ( ! l9e ( ! ,bri/ol ,*annel1 & ext5d$ n only to ! fur!/ limit ( ! ,briti% ,isles1 b probably z f> z ,norway1 & p]haps ev5 into nor!rn ,russia1 ! previ\s widespread conditions ( m>9e s$im5tation 7 entirely alt]$4 ,in/ead ( ! f9e oceanic silts & s&s ) _! abundant organic rema9s1 & ! ?ick lime/ones ) _! masses ( coral & cr[ds ( cr9oids1 !re 7 n[ laid d[n1 ov] ^! nor!rn regions1 va/ piles ( deep r$ s$im5t1 f :i* traces ( animal life are almo/ :olly abs5t4 ,! %elv+ l& aga9/ :i* ^! f]rug9\s s&s & gravels ga!r$ c /ill 9 "p be recogniz$4 ,z ! obs]v] foll[s its m>g91 notes ! v>y+ local peculi>ities ( its s$im5t1 & detects1 sometimes 9 great abundance1 rema9s ( ! vegetation :i* clo!d x1 ! conviction gr[s 9 8 m9d t ! rem>kable contra/ betwe5 ^! deposits1 kn[n z ! ,old ,r$ ,s&/one1 & ^? ( ! ,silurian & ,devonian sy/ems is n to be acc\nt$ = by any m]e re>rangem5t ( ! sea-bottom1 or r$i/ribution ( ! l& t suppli$ t sea-bottom ) s$im5t4 ,x has long be5 ! g5]al belief among geologi/s t ! subt]ranean movem5ts :i*1 ov] ! great] "p ( ,brita91 br\ght ! deposition ( ! ,upp] ,silurian =mations to a close1 l$ to a total alt]ation ( ! geography ( ! region affect$1 t ! sea-floor 0 elevat$1 & t1 ov] ! uprais$ tract1 l>ge lakes or inl& seas 7 ev5tually =m$1 9 :i* ! peculi> s$im5ts ( ! ,old ,r$ ,s&/one 7 accumulat$4 ,! records ( ?is s]ies ( geographical *anges are too fragm5t>y to enable u to foll[1 except 9 a v g5]al way1 ! sequ5ce ( ev5ts 9 ! trans=mation ( ! ,silurian sea into ! peculi> topographical conditions 9 :i* ! ,old ,r$ ,s&/one 0 laid d[n4 ,:ile !re 0 a widespread elevation ( ! sea-floor1 & ( su* ridges ( insul> l& z may h ris5 above sea-level1 ! upheaval appe>s to h be5 ( a some:at complicat$ k9d1 & to h be5 comb9$ ) _m local subsid5ces4 ,! area ( di/urbance 0 probably ?r[n into a s]ies ( p>allel ridges & tr\ghs1 ! =m] cont9u+ to be pu%$ upw>d1 :ile ! latt] t5d$ to subside4 ,! ridges ?us became l& surfaces1 & _! prolong$ elevation may h m or less comp5sat$ = ! d5udation to :i*1 on _! em]g5ce1 !y 7 necess>ily expos$4 ,! tr\ghs1 on ! o!r h&1 :i* sank d[n1 may 9 _m cases h subsid$ bel[ ! sea4 ,b :]e ! g5]al upheaval ( ! cru/ 0 mo/ pron\nc$1 "s ( ! depressions w\ld be isolat$ above sea-level & become lake-bas9s 9 ! t]re/rial areas4 ,( "s ( ^! wat]-bas9s ! outl9es c /ill 9 "s measure be def9$4 ,! rocks t rose into hills ar\nd !m1 & f :i* _! enorm\s accumulations ( detritus 7 d]iv$1 /ill p>tially survive4 ,we c explore ^! piles ( s$im5t1 & f !m c =m "s idea ( ! condition ( ! wat] 9 ! lakes1 & ! nature ( ! vegetation on ! surr\nd+ l&4 ,! frequ5t occurr5ce & exce$+ co>s5ess ( ! conglom]ates1 :i* appe> on _m successive horizons ?r\gh\t ! deposits ( ^! bas9s1 probably indicate contemporane\s t]re/rial di/urbances4 ,! same causes t l$ to ! wr9kl+ ( ! cru/ into p>allel ridges & tr\ghs no d\bt /ill cont9u$ 9 op]ation4 ,f "t to "t ! ridges1 mu* worn d[n by prolong$ d5udation1 7 pu%$ upw>d1 ei!r by gradual uprise or by m rapid j]ks4 ,! tr\ghs may 9 l mann] h be5 /ill affect$ by _! old t5d5cy to subsid5ce4 ,h5ce1 9 spite ( ! effects ( degradation & deposition1 x is possible t ! ridges may n1 on ! :ole1 h v>i$ mu* 9 height1 nor ! bas9s 9 dep?1 dur+ ! "t :5 ?\s&s ( feet 7 /ripp$ (f ! l& & /rewn 9 detritus ov] ! bottoms ( ! lakes4 ,let u try to realize a little m def9itely ! g5]al aspect ( ! region 9 :i* ! ,old ,r$ ,s&/one wat]-bas9s lay4 ,z ! axes ( ! folds into :i* ! cru/ ( ! e>? 0 ?r[n ran 9 a nor?-ea/ & s\?-we/ direction1 !y gave ?is tr5d to ! lakes & to ! tracts ( l& t sep>at$ !m4 ,^! int]v5+ ridges mu/ 9 "s in/ances h be5 hilly or ev5 m\nta9\s4 ,?us1 ! ,scotti% ,highl&s rose betwe5 two ( ! lakes1 & p\r$ into !m an abundant tribute ( gravel1 s& & silt4 ,! t]re/rial vegetation ( ! "t has be5 p>tially pres]v$4 ,! hills seem to h be5 clo!d ) conif]s1 :ile ! l[] slopes & swamps 7 gre5 ) sigill>i1 lepidod5dra & calamites4 ,"o ( ! mo/ *>act]i/ic plants 0 ,psilophyton1 ( :i* l>ge matt$ %eets 7 drift$ across ! lakes & entomb$ 9 ! silt ( ! bottom4 ,a grass-l vegetation1 ) long l9e> leaves1 seems to h gr[n ?ickly 9 "s ( ! %all[s ( ! lakes4 ,( ! l& animals we h /ill less k ?an ( ! vegetation4 ,d\btless v>i\s =ms ( insect life flitt$ ?r\gh ! woodl&s1 ?\gh no relics ( _! =ms h yet be5 recov]$4 ,b ! rema9s ( myriapods h be5 f\nd 9 ,=f>%ire4#cji ,^! e>ly relics ( ! animal life ( ! l& inhabit$ ! woodl&s1 l our mod]n gally-worms1 & 7 swept d[n into ! lakes1 toge!r ) l>ge quantities ( vegetation4 ,footnote #cji3 ,mr4 ,b4 ,n4 ,pea*1 ,proce$+s ( ,royal ,physical ,society ( ,ed9burgh1 vol4 vii4 7#ahhb74 ,"s ( ! lakes1 especially 9 ! e>li] "p ( _! hi/ory1 ab\nd$ 9 eurypt]id cru/acea4 ,^! animals inhabit$ ! seas 9 ,upp] ,silurian "t1 & appe> to h be5 isolat$ 9 ! wat]-bas9s ( ! ,old ,r$ ,s&/one4 ,c]ta9 species ( ,pt]ygotus1 a ,silurian g5us f\nd also 9 ! ,l[] ,old ,r$ ,s&/one1 rea*$ a l5g? ( six feet4 ,b ! mo/ abundant =ms ( animal life 7 fi%es4 ,^! furni% additional evid5ce 9 fav\r ( ! lacu/r9e nature ( ! wat]s 9 :i* !y liv$4 ,su* *>act]i/ically m>9e =ms z ! %>ks & rays ( ! ,silurian seas 7 replac$ by g5]a ( ,acan?odians1 ,o/racod]ms1 ,dipnoids1 ,teleo/omes1 ,placod]ms1 & ,paloniscids1 :i* ab\nd$ 9 ! m nor!rly wat]s4 ,! di/9ctive outw>d *>act]s ( _m ( ^! e>ly v]tebrates 7 _! bony scales & plates4 ,"s ( !m _h _! heads encas$ 9 an armature ( bone1 ( l>ge size & massive ?ickness4 ,9 sev]al g5]a ! bone 0 coat$ ) a lay] ( glitt]+ enamel4 ,ev5 n[1 aft] ! va/ lapse ( "t s9ce _! day1 ! cuirasses & scale-arm\r ( ^! fi%es keep _! bright %e5 9 ! h>d5$ s& & mud f :i* !y are dis9t]r$4 ,a diff]5ce is obs]vable betwe5 ! faunas ( ! diff]5t wat]-bas9s4 ,ev5 :]e ! same g5us occurs 9 two adjac5t areas1 ! species are (t5 di/9ct4 ,two l>ge lakes1 sep>at$ by ! tract ( ! ,scotti% ,highl&s1 _h ea* its own assemblage ( fi%es1 n a s+le g5us be+ common to ! two bas9s4 ,su* contra/s1 :e!r ! two lakes 7 geologically contemporane\s1 or ! nor!rn arose lat] ?an ! s\!rn1 und\bt$ly indicate long-cont9u$ isolation & ! gradual evolution ( new =ms "u diff]5t conditions ( environm5t4#caj ,footnote #caj3 ,9 my memoir ,on ! ,old ,r$ ,s&/one ( ,we/]n ,europe 7,trans4 ,roy4 ,soc4 ,ed94 vol4 xxviii4 #ahgh71 ,i argu$ = ! probable geological contemporaneity ( ! conglom]ates1 s&/ones & flag/ones on ei!r side ( ! ,grampian *a91 ev5 al?\gh _! organic cont5ts 7 s unlike4 ,! /ratigraphical evid5ce fav\rs ?is view4 ,9 ea* case a ?ick s]ies ( /rata is cov]$ uncon=mably by ,upp] ,old ,r$ ,s&/one1 conta9+ ,holopty*ius nobilissimus & o!r fi%es4 ,! "q _c p]haps be def9itely settl$ by ! data available 9 ,scotl&4 ,x is q possible t ! bas9 on ! nor!rn side ( ! ,grampians1 :i* ,i h t]m$ ,lake ,orcadie1 came into exi/5ce aft] t on ! s\!rn side4 ,b ,i d n ?9k ! diff]5ces 9 _! respective faunas are to be acc\nt$ = simply by lapse ( "t & ! gradual organic evolution 9 progress ov] "o cont9u\s region4 ,! m ! ,old ,r$ ,s&/one is /udi$1 ! m local d its v>i\s fi%-faunas appe> to h be54 ,^! /rongly-m>k$ div]sities appe> to me r to po9t to prolong$ isolation ( ! bas9s f ea* o!r1 z /at$ above4 ,dr4 ,traquair has drawn att5tion to ! rem>kable fact t1 ev5 9 :at appe>s to be "o cont9u\s s]ies ( /rata ( no great ?ickness =m+ ! ,upp] ,old ,r$ ,s&/one ( ! ,moray ,fir? bas91 ! fi%es f\nd ab\t ,nairn are entirely diff]5t f ^? met ) 9 ! re/ ( ! region4 ,su*1 9 brief1 7 ! aspects ( ! physical geography ( ! "t on ! fur!r consid]ation ( :i* we are n[ to ent]4 ,! subt]ranean di/urbances1 s *>act]i/ic ( ! p]iod1 7 accompani$ by a display ( volcanic activity m widespread1 p]haps1 ?an any :i* _h yet tak5 place 9 ! geological hi/ory ( ,brita94 ,nev]!less1 x is wor?y ( rem>k t ?is manife/ation ( und]gr\nd en]gy did n beg9 ) ! comm5cem5t ( ^! displacem5ts ( ! cru/4 ,! e>lie/ eruptions only took place aft] ! geography ( ! region _h be5 completely *ang$2 at lea/ no trace ( !m is to be f\nd 9 ! e>lie/ portions ( ! ,old ,r$ ,s&/one4 ,aft] ! la/ l+]+ ,silurian volcanoes 9 ! we/ ( ,irel& _h di$ out1 a protract$ quiesc5ce ( ! subt]ranean fires ensu$4 ,9 ! late/ ages ( ,silurian "t !re 0 n 9 ,brita91 s f> z at pres5t kn[n1 a s+le volcanic eruption4 ,n until aft] ! inauguration ( ! ,old ,r$ ,s&/one topography1 :5 ! lakes _h tak5 %ape & _h begun to be fill$ ) s$im5t f ! surr\nd+ hills1 did a s]ies ( new volcanoes bur/ into activity ov] ! nor!rn half ( ,brita94 ,ris+ 9 ! mid/ ( ! lakes 9 gr\ps ( sep>ate cones1 ^! v5ts p\r$ out floods ( lava1 toge!r ) cl\ds ( a%es & /ones4 ,_! sites1 ! hi/ory ( _! eruptions1 & ! piles ( mat]ial eject$ by !m1 c /ill be asc]ta9$1 & ,i %all n[ proce$ to give "s acc\nt ( !m4 ,! ?ick mass ( s$im5t>y mat]ial kn[n z ! ,old ,r$ ,s&/one1 ly+ betwe5 ! top ( ! ,silurian & ! base ( ! ,c>bonif]\s sy/em1 has be5 divid$ into two sections1 :i*1 h[ev]1 are ( unequal dim5sions1 & d\btless repres5t v unequal p]iods ( "t4 ,! old] s]ies1 or ,l[] ,old ,r$ ,s&/one1 is by f> ! m important & int]e/+ 9 its ext5t1 ?ickness1 palontological ri*es1 &1 :at specially conc]ns u 9 ! pres5t inquiry1 9 its volcanic records4 ,:]ev] its true base c be se51 ?is s]ies passes d[n con=mably into ,upp] ,silurian /rata4 ,x sometimes rea*es a ?ickness ( #ae1jjj & ev5 #bj1jjj feet4 ,!re is g5]ally a m>k$ break betwe5 its highe/ visible /rata & all y\ng] =mations4 ,ev5 ! upp] division ( ! ,old ,r$ ,s&/one re/s uncon=mably ^u ! l[]4#caa ,su* a hiatus und\bt$ly po9ts to a consid]able lapse ( geological "t1 & to ! adv5t ( important geographical *anges t consid]ably modifi$ ! rem>kable topography ( ! old] "p ( ! p]iod4 ,footnote #caa3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xvi4 7#ahfj71 p4 #cab4 ,9 ,wales no break has actually be5 discov]$ betwe5 ! two divisions ( ! ,old ,r$ ,s&/one1 ?\gh x is suspect$ to exi/ !re also4 ,! y\ng] division or ,upp] ,old ,r$ ,s&/one passes upw>d con=mably into ! base ( ! ,c>bonif]\s sy/em4 ,its r$ & yell[ s&/ones1 conglom]ates & breccias1 cov]+ mu* m re/rict$ areas1 & atta9+ a mu* less ?ickness ?an ^? ( ! l[] division1 indicate ! dim9ution & gradual effacem5t ( ! lakes ( ! old] "t1 & ! ev5tual return ( ! sea to ! tracts f :i* x _h be5 s long exclud$4 ,s va/ an int]val elaps$ betwe5 ! "t record$ 9 ! deposits respectively ( ! two sections ( ! ,old ,r$ ,s&/one t ! *>act]i/ic =ms ( animal life 9 ! e>li] ages _h entirely pass$ away1 & _! places _h be5 tak5 by o!r types :5 ! dim9i%$ lake-bas9s ( ! second p]iod began to be fill$ up4 ,volcanic action also dw9dl$ to su* a degree t 9 contra/ to ! abundant v5ts ( ! old] p]iod1 only "o or two widely scatt]$ gr\ps ( v5ts are kn[n to h exi/$ 9 ! area ( ! ,briti% ,isles dur+ ! lat] p]iod1 & ^!1 aft] a feeble activity1 gave way to a prolong$ volcanic quiesc5ce1 :i* la/$ until ! e>li] ages ( ! succe$+ or ,c>bonif]\s p]iod4 ,al?\gh geologi/s are 9 ! habit ( gr\p+ ! ,old ,r$ ,s&/one & ! ,devonian rocks z equival5t or homotaxial =mations1 deposit$ 9 di/9ct areas "u consid]ably diff]5t conditions ( s$im5tation1 ! attempt to foll[ out ! sequ5ce ( /rata 9 ,devon%ire1 & to trace "s analogy betwe5 ! ,devonian succession & t ( ! ,old ,r$ ,s&/one1 pres5ts _m difficulties = :i* no obvi\s solution sugge/s itself4 ,into ^! problems x is n ne$ful to ent] fur!r ?an 0 done 9 ! la/ *apt]4 ,we may assume t n improbably "s ( ! eruptions n[ to be describ$ 7 coeval ) ^? ( ,devonian "t 9 ! s\?-we/ ( ,engl&1 ?\gh we may hesitate to decide :i* ( !m %\ld be br\ght into p>allelism4 ,z we trace ! %ore-l9es ( ! anci5t bas9s ( ! ,l[] ,old ,r$ ,s&/one1 & walk ov] ! %+le ( _! bea*es1 or z we exam9e ! silt ( _! deep] gulfs1 & exhume ! rema9s ( ! plants t %ad$ _! bord]s1 & ( ! fi%es t sw>m$ 9 _! wat]s1 we gradually le>n t al?\gh ! s$im5ts :i* accumulat$ 9 "s ( ^! bas9s am\nt to _m ?\s& feet 9 ?ickness2 yet f bottom to top !y ab\nd 9 evid5ce ( %all[-wat] conditions ( deposit4 ,! t]re/rial di/urbances above ref]r$ to cont9u$ = a va/ int]val1 & :ile1 z already sugge/$1 ! floors ( ! bas9s sank1 & ! int]v5+ tracts 7 ridg$ up1 z ! results ( "o great movem5t ( ! e>?'s cru/1 ! d5udation ( ! surface ( ! l& contribut$ to ! bas9s su* a con/ant influx ( s$im5t z1 on ! :ole1 comp5sat$ = ! gradual depression ( _! bottoms4 ,we ne$ n suppose t ^! movem5ts ( subsid5ce & upheaval 7 un9t]rupt$ & uni=m4 ,inde$1 ! abundant co>se conglom]ates1 :i* play s prom95t a "p 9 ! mat]ials ?r[n into ! bas9s1 sugge/ t at v>i\s int]vals dur+ ! prolong$ s$im5tation subt]ranean di/urbances 7 specially vigor\s4 ,b ! occurr5ce ( /rong uncon=mabilities among ! deposits ( ! bas9s sets ?is "q at re/1 by prov+ t ! t]re/rial movem5ts 7 s great z sometimes to break up ! floor ( a lake1 & to place its old] s$im5ts on end1 9 :i* position !y 7 cov]$ up & deeply buri$ by ! succe$+ deposits4#cab ,footnote #cab3 ,an uncon=mability ( ?is k9d occurs betwe5 ! s\? end ( ! ,p5tl& ,hills & ,t9to 9 ,lan>k%ire1 & ano!r 9 ,ayr%ire4 ,x is n surpris+ to discov]1 among ^! evid5ces ( great t]re/rial di/urbance1 t ev5tually gr\ps ( volcanoes rose 9 long l9es f ! wat]s ( mo/ ( ! lakes1 & ?rew out enorm\s quantities ( lava & a%es ov] tracts hundr$s ( squ>e miles 9 ext5t4 ,s va/1 inde$1 7 ^! dis*>ges1 across :at is n[ ! ,midl& ,valley ( ,scotl&1 t ! portions ( %eets ( lava & tuff visible at ! surface =m "s ( ! mo/ conspicu\s ranges ( hills 9 t di/rict1 /ret*+ cont9u\sly = #dj or #ej miles & rea*+ heights ( m ?an #bjjj feet above ! sea4 ,expos$ 9 hundr$s ( rav9es & esc>pm5ts1 & dissect$ by ! waves along bo? ! ea/]n & we/]n coa/s ( ! c\ntry1 ^! volcanic records may be /udi$ ) a fulness ( detail :i* _c be f\nd among e>li] ,palozoic =mations4 ,x might h be5 suppos$ t a s]ies ( rocks s well display$ & s full ( int]e/1 w\ld long ere ?is h be5 fully exam9$ & describ$4 ,b !y c h>dly be said to h yet receiv$1 z a :ole1 ! att5tion !y des]ve4 ,)\t enum]at+ all ! writ]s :o1 ea* 9 8 own measure1 h add$ to ! sum ( our k ( ! subject1 ,i may ref] to ! lab\rs ( ,jameson1#cac ,macknight#cad & ,flem+1#cae among ! obs]v]s :o began ! inve/igation4 ,b ( ! e>ly pione]s1 by f> ! mo/ important 9 reg>d to ! igne\s rocks ( ! ,old ,r$ ,s&/one 0 ,ami ,b\4 ,:ile att5d+ ! ,univ]sity ( ,ed9burgh1 :]e he took ! degree ( ,m4,d4 9 ! ye> #ahaf1 he imbib$ f ,jameson a love ( m9]alogy & geognosy1 & = sev]al ye>s sp5t 8 leisure "t 9 p]sonally visit+ _m p>ts ( ,scotl&1 9 ord] to /udy ! geological /ructure ( ! c\ntry4 ,probably 9 #ahbj he publi%$ 9 ,fr5* 8 n[ classic ,essai4#caf ,! value ( ?is "w z an orig9al contribution to ! geology ( ! ,briti% ,isles has probably nev] be5 adequately ackn[l$g$4 ,= ?is want ( due recognition ! au?or himself 0 no d\bt 9 "s measure to blame4 ,he ref]s di/9ctly en\gh to v>i\s previ\s writ]s1 notably to ,jameson & ,maccullo*1 b he m+les ! results ( 8 own p]sonal exam9ations ) !irs 9 su* a way t x is h>dly possible to asc]ta9 :at portions are ! outcome ( 8 own orig9al obs]vations4 ,less cr$it has accord+ly be5 giv5 to him ?an he c\ld fairly h claim$ = solid additions to ! subjects ( :i* he treat$4 ,9 ! lat] ye>s ( 8 life ,i _h opportunities ( le>n+ p]sonally f him h[ ext5sive _h be5 8 e>ly p]egr9ations 9 ,scotl&1 & h[ vivid 7 ! recollections :i*1 aft] ! lapse ( half a c5tury1 he /ill reta9$ ( !m4 ,judg$ simply z a well-ord]$ summ>y ( all ! kn[n facts reg>d+ ! geology ( ,scotl&1 8 ,essai mu/ be reg>d$ z a "w ( v great value4 ,especially important is 8 arrangem5t ( ! volcanic ph5om5a ( ! c\ntry1 :i* /&s f> 9 advance ( any?+ ( ! k9d previ\sly attempt$4 ,"u ! head ( ! ,t]ra9 ,volcanique1 he treats ( ! basaltic =mations1 di/+ui%+ !m z %eets 7nappes1 c\les7 & dykes2 & ( ! felspa?ic or tra*ytic =mations1 :i* he subdivides into phonolites1 tra*ytes1 porphyries 7=m+ m\nta9s & also %eets7 & felspa?ic or tra*ytic dykes4 ,9 ! details suppli$ "u ea* ( ^! sections he gives facts & d$uctions :i* 7 obvi\sly ! result ( 8 own indep5d5t exam9ation ( ! gr\nd1 & he likewise m>%als ! data accumulat$ by ,jameson1 ,maccullo* & o!rs1 9 su* a way z to pres5t a m compreh5sive & def9ite picture ( ! volcanic ph5om5a ( ,scotl& ?an any previ\s writ] _h v5tur$ to give4 ,footnote #cac3 ,memoirs ( ! ,w]n]ian ,society1 vol4 ii4 7#ahaa71 pp4 #agh1 #bag1 #fah2 vol4 iii4 7#ahbj71 p4 #bbj1 #bbe4 ,footnote #cad3 ,op4 cit4 vol4 ii4 pp4 #abc1 #dfa4 ,footnote #cae3 ,op4 cit4 vol4 i4 7#ahjh71 p4 #afb2 vol4 ii4 7#ahaa71 pp4 #ach1 #cci4 ,footnote #caf3 ,essai gologique sur l'cosse 7,p>is2 no date1 b probably ab\t #ahbj74 ,he ackn[l$ges 8 indebt$ness to ,jameson1 ^: demon/rations ( ! geology ( ! ,ed9burgh di/rict he p>tly reproduc$ 9 8 book4 ,jameson's e>ly writ+s 9 ! ,w]n]ian ,memoirs & 9 sep>ate works 7 m]e m9]alogical or geogno/ical descriptions4 ,8 lat] lectures became m valuable b 7 nev] publi%$1 save indirectly 9 s f> z !y influ5c$ ! op9ions ( 8 pupils :o publi%$ writ+s on ! same subjects4 ,see1 = in/ance1 ,hay ,cunn+ham's ,geology ( ! ,lo?ians1 p4 #ei1 footnote4 ,comp>e an article on ,b\1 ,ed9burgh ,review = ,may #ahbc 7vol4 xxxviii4 p4 #dac74 ,! acc\nt :i* ,b\ wrote ( ! ,old ,r$ ,s&/one & its associat$ igne\s rocks m>k$ ! fir/ great =w>d /ep 9 ! inve/igation ( ?is section ( ! geological record4 ,he 0 ! e>lie/ obs]v] to divide :at he calls ! ro*es feldspa?iques et trappennes into gr\ps accord+ to _! geological position & m9]alogical "*1 & to reg>d !m z ( igne\s orig9 & ( ! age1 or ne>ly ( ! age1 ( ! r$ s&/one ( ,c5tral ,scotl&4 ,( lat] writ]s :o h treat$ ( ! volcanic rocks ( ! ,old ,r$ ,s&/one1 my old fri5d ,*>les ,macl>5 des]ves special recognition4 ,8 survey & description ( ! ,p5tl& ,hills embodi$ ! fir/ detail$ & accurate inve/igation ( any portion ( ^! rocks1 & 8 ,geology ( ,fife & ! ,lo?ians may /ill be read ) pleasure & in/ruction4#cag ,b\ _h indicat$ r\ghly on ! little sket*-map accompany+ 8 ,essai ! *ief b&s ( 8 felspa?ic & trappean rocks ( ! ,old ,r$ ,s&/one1 b _! position & limits 7 m precisely def9$ 9 ,maccullo*'s ,geological ,map ( ,scotl&1 :i* 0 publi%$ 9 #ahdj1 five ye>s aft] ! sudd5 & tragic dea? ( its au?or4 ,! obs]v]s :o h m rec5tly /udi$ ^! rocks h be5 *iefly memb]s ( ! ,geological ,survey1 & to "s ( ! m important results obta9$ by !m ,i %all ref] 9 ! sequel4 ,footnote #cag3 ,geology ( ,fife & ! ,lo?ians1 #ahci4 ,m detail$ ref]5ce w be made 9 lat] pages to ?is classic4 ,= _m ye>s ,i h devot$ mu* "t to ! inve/igation ( ! ,old ,r$ ,s&/one & its volcanic rocks4 ,9 ! ye> #ahei ,i asc]ta9$ ! exi/5ce ( ! great hiatus betwe5 ! ,l[] & ,upp] divisions ( ! sy/em4#cah ,a fir/ sket* ( ! volcanic hi/ory ( ! ,old ,r$ ,s&/one 0 giv5 by me 9 #ahfa1cai :i* 0 subsequ5tly enl>g$ & fill$ 9 ) m detail 9 #ahgi4cbj ,b x 0 n until #ahib t ,i publi%$ a some:at detail$ outl9e ( ! :ole subject1 trac+ ! hi/ory ( volcanic action dur+ ! p]iod ( ! ,old ,r$ ,s&/one1 ! di/ribution ( ! volcanoes1 & ! "* ( ! mat]ials erupt$ by !m4#cba ,?is outl9e ,i n[ proce$ to amplify1 fill+ 9 details t 7 necess>ily omitt$ be=e1 ?\gh !re are /ill sev]al di/ricts reg>d+ :i* in=mation is scanty4 ,footnote #cah3 ,on ! ,old ,r$ ,s&/one ( ! ,s\? ( ,scotl&1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xvi4 7#ahfj71 p4 #cab4 ,footnote #cai3 ,on ! ,*ronology ( ! ,trap-,rocks ( ,scotl&1 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxii4 7#ahfa71 p4 #fc4 ,footnote #cbj3 ,article ,geology1 9 ,n9? ,edition ( ! ,encyclopdia ,britannica1 vol4 x4 7#ahgi71 p4 #cdc4 ,repr9t$ 9 my ,text-,book ( ,geology1 ( :i* ! fir/ edition appe>$ 9 #ahhb4 ,footnote #cba3 ,presid5tial ,address to ! ,geological ,society1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlviii4 7#ahib74 ,9 arrang+ ! treatm5t ( ! subject ,i %all divide ! record into two ma9 sections1 ! fir/ & mu* ! m important be+ devot$ to ! ,l[] & ! second to ! ,upp] ,old ,r$ ,s&/one4 ,9 ! fir/ ( ^! divisions x w be conv5i5t to beg9 by tak+ note ( ! di/ribution ( ! v>i\s di/ricts ov] :i* ! geological evid5ce is spread4 ,we may !n proce$ to consid] ! g5]al "* ( ! volcanic rocks & ! mann] 9 :i* !y are arrang$ 9 ! /ratigraphy ( ! c\ntry1 tak+ 9 consecutive ord] 7#a7 ! sup]ficial lavas & tuffs2 7#b7 ! v5ts2 7#c7 ! dykes & sills4 ,f ^! g5]al consid]ations we may pass to ! detail$ hi/ory ( ev5ts 9 ea* ( ! sep>ate volcanic areas1 & ?us obta91 z f> z ! evid5ce at pres5t p]mits1 a broad view ( ! progress ( volcanic action dur+ ! "t ( ! ,l[] ,old ,r$ ,s&/one 9 ,brita94 ,,*apt] ,,xvii ,,di/ribution ,,( ,,! ,,volcanic ,,c5tres ,,9 ,,! ,,l[] ,,old ,,r$ ,,s&/one--,,*>act]s ,,( ,,! ,,mat]ials ,,erupt$ ,,by ,,! ,,volcanoes i4 ,,di/ribution ,,( ,,volcanic ,,c5tres ,! area )9 :i* volcanic rocks belong+ to ! ,l[] ,old ,r$ ,s&/one appe> is "o ( ! mo/ ext5sive regions ov] :i* ! volcanic eruptions ( any geological p]iod c be trac$ 9 ! ,briti% ,isles 7,map ,i474 ,its nor!rn limit rea*es z f> z ! islet ( ,uya 9 ,%etl&1 & its s\!rn appe>s 9 ,engl& 9 ! ,*eviot ,hills--a di/ance ( ab\t #bej miles4 ,b volcanic rocks ( probably correspond+ age occur ev5 z f> to ! s\? z ! hills ne> ,kill>ney4 ,! mo/ ea/]ly m>g9 ( ?is area is def9$ by ! ,nor? ,sea on ! coa/ ( ,b]wick%ire1 & its extreme we/]n b\nd>y ext5ds to ne> ,l\gh ,erne 9 ! nor? ( ,irel&--a di/ance ( "s #bcj miles4 ,if we include ! po/-,silurian bosses & dykes1 l ^? ( ,%ap1 & likewise ! ,devonian volcanic rocks ( ,devon & ,cornwall1 z contemporane\s ) ^? ( ! ,old ,r$ ,s&/one1 ! area ( eruption w be greatly enl>g$4 ,b leav+ ^! out ( acc\nt = ! pres5t1 & conf9+ our att5tion to ! ,l[] ,old ,r$ ,s&/one s]ies1 we f9d t1 )9 ! wide limits ov] :i* ! volcanic rocks are di/ribut$1 a numb] ( di/9ct & (t5 widely sep>at$ c5tres ( eruption may be trac$4 ,tak+ ^! z !y lie f nor? to s\?1 we may specially enum]ate ! foll[+3-- #a4 ,! ,%etl& & ,orkney ,isl&s1 toge!r ) ! bas9 ( ! ,moray ,fir?4 ,?is region includes sev]al di/9ct volcanic gr\ps1 ( :i* ! mo/ nor!rly ext5ds ?r\gh ! c5tre to ! nor?-we/]n headl&s ( ! ma9l& ( ,%etl&1 ano!r lies 9 ! isl& ( ,%ap9%ay1 "o ( ! ,orkneys1 :ile at lea/ two c be recogniz$ on ! s\? side ( ! ,moray ,fir?4 ,to ?is wide region ( ,old ,r$ ,s&/one ,i h giv5 ! g5]al designation ( ,lake ,orcadie4#cbb ,footnote #cbb3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxviii4 7#ahgh71 p4 #ced4 #b4 ,! bas9 ( ,lorne1 on ! we/ ( ! ma9l& ( ,argyll%ire1 ext5d+ f ,lo* ,cr]an to ,lo* ,mel=t & ! hills on ! we/ side ( ,lo* ,awe4 #c4 ,! great c5tral bas9 ( ,scotl&1 :i*1 = ! sake ( di/9ctness1 ,i h call$ ,lake ,cal$onia1#cbc /ret*+ betwe5 ! ,highl&s & ! ,s\!rn ,upl&s1 f ! ea/ coa/ s\?-we/w>ds across ,arran & ! s\? end ( ,cantire into ,irel& z f> z ,l\gh ,erne4 ,num]\s di/9ct volcanic gr\ps occur 9 ?is great bas91 & _! volcanic hi/ory w be discuss$ 9 detail 9 lat] *apt]s 7see ,map ,,iii474 ,footnote #cbc3 ,op4 cit4 #d4 ,! bas9 ( ! ,*eviot ,hills & ,b]wick%ire1 ) ^! hills z ! *ief area1 b includ+ also o!r tracts1 probably indep5d5t1 :i* are cut (f by ! sea along ! ea/]n coa/ ( ,b]wick%ire betwe5 ,/4 ,abb's ,head & ,eyem\?4 #e4 ,! ,kill>ney tract1 includ+ ! hills ly+ ar\nd ,l\gh ,guitane 9 ! ea/ ( ,c\nty ,k]ry4 ,at ! outset we may take note ( a feature 9 ! volcanic hi/ory ( ,brita91 fir/ prom95tly noticeable 9 ! records ( ! ,old ,r$ ,s&/one1 & becom+ increas+ly di/9ct dur+ ! re/ ( ! long sequ5ce ( ,palozoic eruptions1 namely1 ! p]si/5ce ) :i* ! v5ts h be5 op5$ 9 ! valleys & h avoid$ ! high gr\nds4 ,i =m]ly dwelt on ?is relation1 ) ref]5ce to ! ,c>bonif]\s volcanic ph5om5a1#cbd b ! obs]vation may be greatly ext5d$4 ,) reg>d to ! ,old ,r$ ,s&/one ( ,c5tral ,scotl&1 ?\gh ! lavas & tuffs t 7 dis*>g$ ov] ! floor ( ! %eet ( wat] :i* occupi$ t region gradually rose along ! flanks ( ! nor!rn & s\!rn hills1 yet x 0 on ! lake-bottom & n among ! hills t ! orifices ( eruption broke =?4 ,footnote #cbd3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxix4 7#ahgi71 p4 #ded4 ,s f> z ,i am aw>e1 no und\bt$ v5ts ( ! age ( ! ,l[] ,old ,r$ ,s&/one h be5 detect$ among ! high gr\nds ( ! ,highl&s on ! "o h&1 or among ! ,silurian upl&s on ! o!r1 al?\gh a fr+e ( ! lavas may be trac$ "h & !re along ! base ( ! hills4#cbe ,9 "s cases1 d\btless1 ! position ( ! valleys may h be5 det]m9$ by l9es ( fault t might well s]ve z l9es ( relief along :i* volcanic v5ts w\ld be op5$4 ,b 9 _m in/ances x c be prov$ t1 ?\gh ! v5ts h ris5 9 valleys & l[ gr\nds1 !y h n select$ l9es ( fault visible at ! surface1 ev5 :5 ^! exi/$ 9 _! neighb\rhood4 ,any fissures up :i* ! volcanic ejections made _! way mu/ h la9 at great dep?s b5ea? ! =mations t n[ =m ! surface rocks4 ,footnote #cbe3 ,c]ta9 rem>kable necks ( breccia h be5 detect$ by ,mr4 ,j4 ,r4 ,dakyns ris+ ?r\gh ! s*i/s at ! upp] end ( ,lo* ,lomond2 b !re is n suffici5t evid5ce to connect !m ) ! volcanic s]ies ( ! ,l[] ,old ,r$ ,s&/one4 ,"s ( ! y\ng] granite bosses are n improbably to be ref]r$ to ?is volcanic s]ies4 ,! late/ granites ( ! ea/]n ,grampians1 z already /at$1 h lately be5 f\nd by ,mr4 ,b>r[ cutt+ ! b& ( probably ,l[] ,silurian /rata along ! s\!rn bord] ( ! ,highl&s4 ,^? ( ,gall[ay are y\ng] ?an ! ,upp] ,silurian =mations1 :i* !y invade1 & old] ?an ! conglom]ates ( ! ,upp] ,old ,r$ ,s&/one1 :i* conta9 pebbles ( !m4 ,^! eruptive bosses w be fur!r discuss$ 9 ! sequel4 ii4 ,,*>act]s ,,( ,,! ,,mat]ials ,,erupt$ ,,by ,,! ,,volcanoes ,a g5]al summ>y ( ! petrographical *>act]s ( ! igne\s rocks ( ! ,l[] ,old ,r$ ,s&/one may "h f9d a place4 ,fur!r details w be giv5 9 ! acc\nt ( ,lake ,cal$onia1 :i* is ! typical area = !m2 b1 on ! :ole1 ! prevail+ types 9 "o region are f\nd to be repeat$ 9 ! o!rs4 #a4 ,b$d$ ,lavas4--,beg9n+ ) ! lavas :i* 7 p\r$ out at ! surface1 we h to notice a consid]able range ( *emical composition among !m1 al?\gh1 z a rule1 !y are *>act]iz$ by g5]al simil>ity ( ext]nal appe>ance4 ,at ! "o end1 come diabases & o!r anci5t =ms ( basalt or dol]ite1 :]e9 ! silica p]c5tage is bel[ or little above #ej4 ,by f> ! l>ge/ proportion ( ! lavas1 h[ev]1 are porphyrites or alt]$ &esites1 hav+ ab\t #fj p] c5t ( silica4 ,) ^! are associat$ lavas conta9+ m or less un/rip$ felsp> & a some:at high] proportion ( silica1 :i* may be gr\p$ z tra*ytes1 ?\gh no v %>p l9e c be drawn betwe5 !m & ! &esites4 ,9 ! ,p5tl& ,hills1 & "s o!r areas1 or?ophyres fl[$ out alt]nately ) ! m basic lavas1 & 7 associat$ ) felsitic tuffs & breccias4 ,x is notewor?y t ! lava-%eets ( ! ,l[] ,old ,r$ ,s&/one1 if we consid] ! "* ( ! preval5t type1 hold an int]m$iate grade betwe5 ! av]age *emical composition ( ^? ( ,silurian & ( ^? ( lat] ,c>bonif]\s "t4 ,on ! "o h&1 !y r>ely assume ! "* ( ?or\ghly acid rocks1 l ! nodul> rhyolites ( ! ,bala & ,upp] ,silurian s]ies2#cbf on ! o!r h&1 !y seldom include su* basic lavas z ! basalts1 s common among ! puy-eruptions ( ! ,c>bonif]\s sy/em1 & nev]1 s f> z ,i "k1 conta9 v>ieties comp>able to ! ultra-basic comp\nds :i* ,i %all h occasion to allude to z *>act]i/ic ( a p>ticul> volcanic zone 9 t sy/em4 ,footnote #cbf3 ,! only examples kn[n to me are ^? ( ,b5aun ,m & o!r hills 9 ,c\nty ,k]ry4 7a7 ,! ,diabase-lavas are typically develop$ 9 ! *a9 ( ! ,p5tl& ,hills1 :]e !y =m long b&s int]calat$ betwe5 felsitic tuffs--a rem>kable association1 to :i* ,i %all make m detail$ ref]5ce 9 a lat] *apt]4 ,!y range 9 texture f a compact d>k gre5i% base to a dull e>?y amygdaloid4 ,"o ( _! mo/ rem>kable v>ieties is a f9e-gra9$ gre5 porphyry1 ) l>ge flat tabul> cry/als ( plagioclase arrang$ p>allel to ! direction ( fl[ 7,c>ne?y ,hill74 ,mo/ ( !m1 h[ev]1 are m or less amygdaloidal1 & "s ( !m 7,w>klaw ,hill7 /rongly s4 ,! foll[+ analyses1 made 9 ! laboratory ( ! ,royal ,s*ool ( ,m9es "u ! direction ( ,pr(4 ,e4 ,frankl&1 %[ ! *emical composition ( "s ( ! diabases ( ! ,p5tl& ,hills3#cbg-- ,footnote #cbg3 ,= analyses ( "s ,%etl& diabases ( ,old ,r$ ,s&/one age1 see ,mr4 ,r4 ,r4 ,tatlock1 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxxii4 7#ahhg71 p4 #chg4 ---------------------------------------- ----------------------- ,c>ne?y ,buiselaw4 ,w>klaw ,hill4 ,hill#cbh ,sp4 grav4 #bhj4 ,sp4 grav4 #bgg4 ---------------------------------------- ----------------------- ,soluble ,insoluble ,soluble ,insoluble 9 ,h,cl 9 ,h,cl 9 ,h,cl 9 ,h,cl ---------------------------------------- ----------------------- ,si,o#b #eaaf 444 #ebjj 444 #dggg ,al#b,o#c #bbbg #acj #agdf #ebc #acjh ,fe#b,o#c #bid #aec #ghe #gcb #jhd ,fe,o #djb #aad 444 444 444 ,ca,o #efa #bdc #fhj #ghh #djg ,mg,o #cdf #jih #ajf #cfe #jcj ,k#b,o #bdb 444 #aff 444 #aag ,na#b,o #beh 444 #dag 444 #bcj ,h#b,o #cdb 444 #bfh 444 #bdh ,p#b,o#e #jdh #jcb 444 #jab 444 ,,co#b #abh 444 444 #eja 444 ---------------------------------------- ----------------------- ,footnote #cbh3 ,!re 0 a trace ( mangan\s oxide 9 ?is specim54 7b7 ,! ,&esites1 or1 z !y 7 =m]ly call$1 ,porphyrites1 :i* con/itute by f> ! l>ge/ proportion ( ! lavas1 h a *>act]i/ic b limit$ range ( li?ological v>ieties4 ,! prevail+ type pres5ts a close-gra9$1 r dull texture1 & a col\r v>y+ f p9ki% grey1 ?r\gh _m %ades ( gre5 & br[n1 to purpli% r$1 :i* la/ is1 on ! :ole1 ! pr$om9ant hue4 ,m9ute la?-%ap$ felsp>s may frequ5tly be detect$ ) ! nak$ eye on fre% surfaces1 :ile scatt]$ cry/als1 :i* are g5]ally hmatitic pseudomorphs aft] "s pyrox5e1 occasionally aft] hornbl5de or mica1 may (t5 be obs]v$4 ,! usual porphyritic con/itu5ts are plagioclase felsp>s1 occasionally 9 abundant tabul> cry/als measur+ half an in* or m across1 also "o or m pyrox5es 7augite1 en/atite71 & sometimes br[n or black mica4 ,:]e l>ge felsp>-cry/als occur 9 a compact gre5 matrix1 ! rock assumes a resemblance to ! v]de antique ( ! anci5ts4#cbi ,"o ( ! ,*eviot &esites ly+ at ! bottom ( ! s]ies is di/+ui%$ by its l>ge & abundant plates ( black mica4#ccj ,footnote #cbi3 ,an in/ance ( ?is rock occurs 9 ,k9c>d9e%ire1 f :i* ! l>ge flat tw9s ( labradorite h be5 analyz$ by ,dr4 ,h$dle 7,trans4 ,roy4 ,soc4 ,ed94 vol4 xxviii4 7#ahgi71 p4 #beg74 ,footnote #ccj3 ,c4 ,t4 ,cl\gh1 ,! ,*eviot ,hills1 ,mem4 ,geol4 ,survey 7#ahhh71 p4 #ab4 ,! texture ( ! &esites occasionally becomes fa9tly res9\s1 :]e a consid]able proportion ( glass /ill rema9s undevitrifi$1 z 9 ! well-kn[n v>ieties f ! ,*eviot ,hills1 & 9 ano!r pit*/one-l rock f above ,air?rey ,ca/le 9 ! ,o*il ,hills1 ne> ,bridge ( ,allan4 ,x sometimes pres5ts a nodul> or co>sely p]litic "*1 wea!r+ out 9 nut-l balls1 l ! rock ( ,buckham's ,wall ,burn 9 ! ,*eviot ,hills4#cca ,mu* m frequ5t is a well-develop$ amygdaloidal /ructure1 :i* inde$ may be said to be ! mo/ obvi\s *>act]i/ic ( ^! rocks z a :ole4 ,! /eam-vesicles1 n[ fill$ ) agate1 qu>tz1 calcite or zeolite1 v>y 9 size f m]e granules up to l>ge irregul> cavities a foot or m 9 diamet]4 ,:]e ! k]nels are coat$ ) pale-gre5 e>? & lie 9 a d>k br[n matrix1 !y give rise to "s ( ! mo/ beautiful v>ieties ( rock 9 any volcanic s]ies 9 ?is c\ntry1 z may be se5 on ! ,ayr%ire coa/ at ,culzean & ,turnb]ry4 ,"s rocks conta9 ! vesicles only z r>e individuals1 o!rs h !m s cr[d$ toge!r z to =m ! great] "p ( ! cubic cont5ts ( ! mass4 ,:5 ! infiltration-products h wea!r$ out1 "s ( ! amygdaloids pres5t a /rik+ resemblance to rec5t slaggy br[n lavas2 lumps ( !m mu/ h be5 orig9ally light en\gh to float 9 wat]4 ,footnote #cca3 ,ibid4 p4 #aa4 ,my colleague 9 ! ,geological ,survey1 ,mr4 ,j4 ,s4 ,grant ,wilson1 "s ye>s ago made = me a l>ge s]ies ( det]m9ations ( ! specific gravity ( ! volcanic rocks ( ! ,l[] ,old ,r$ ,s&/one ( ,scotl&4 ,he f\nd t ! &esites collect$ f v>i\s di/ricts to illu/rate ! m typical v>ieties ( rock av]ag$ ab\t #bff4 ,he also made a s]ies ( *emical analyses ( a numb] ( ! same rocks f ! ,*eviot ,hills1 :]e !y are well pres]v$4 ,! results are %[n 9 ! foll[+ table3-- ---------------------------------------- ------------------------------- ,scawd,r5nie-,cunrie-,duncan's,:itton,cu ddies' ,cocklaw- ,m- ,law /on /on ,dubs ,hill ,tops foot battle ---------------------------------------- ------------------------------- ,si,o#b #eibi #fbha #fcch #eidd #fjgj #fjeh #fbbi #eihb ,al#b,o#cafcj #afdj #aegg #afae #agih #abbe #agjc #afif ,fe#b,o#c #agg #ee #gc #aje #ff #aja #ic #bj ,fe,o #cgj #cbg #bfe #bhc #beh #dac #bdd #feg ,mn,o #da #ha #jh #cg #bj #ae #ba #ae ,ca,o #dha #ddf #ddd #fgj #gjg #ddj #cib #dgc ,mg,o #cae #afd #ahh #bdf #bbj #bhf #bga #bhd ,k#b,o #dai #cfj #ahh #cah #ceg #bai #aad #bfc ,na#b,o #cdd #cjb #ded #cgj #bie #cfa #cbj #cjd ,h#b,o #chd #djd #dfi #cce #cde 444 #biccb 444 ,h#b,,s#d 444 444 444 444 444 #ee #cg trace ,loss4 444 444 444 444 444 #bae #dha #aih ---------------------------------------- ------------------------------- ,footnote #ccb3 ,?is is ,,co#b4 ,! microscopic /ructure ( ! &esites ( ! ,l[] ,old ,r$ ,s&/one has be5 p>tially inve/igat$1 especially ^? ( ! ,*eviot ,hills1 by ,mr4 ,teall#ccc & by ,dr4 ,pet]s51#ccd :o bo? give *emical analyses ( ! rocks4 ,mu*1 h[ev]1 /ill rema9s to be done be=e our k ( ?is bran* ( ,briti% petrography c be reg>d$ z adequate4 ,! gr\ndmass 9 "s ( ! rocks consi/s ma9ly ( a br[n glass ) a /reaky /ructure 7z 9 ! well-kn[n v>iety ( ,kirk ,ye?olm1 & 9 ! rock1 /ill m l pit*/one1 f ne> ,air?rey ,ca/le 9 ! ,o*il *a972 m usually x has be5 devitrifi$ m or less completely by ! appe>ance ( felspa?ic microlites1 until x pres5ts a confus$ felsp> aggregate4 ,! porphyritic felsp>s are (t5 l>ge1 g5]ally /rip$1 b sometimes includ+ cry/als t %[ no /rip+4 ,!y are frequ5tly f\nd to be full ( inclusions ( ! base1 & ^! sometimes consi/ ( glass4 ,! f]ro-magnesian con/itu5ts are usually r decompos$1 be+ n[ repres5t$ by *loritic pseudomorphs2 b augite1 & p]haps /ill m frequ5tly en/atite1 may be recogniz$1 or its pres5ce may be inf]r$ among !m4 ,! beautiful res9\s or pit*/one-l rock f ne> ,air?rey ,ca/le has be5 f\nd by ,mr4 ,watts to be a glassy hyp]/h5e-augite-&esite1 s9ce among its ph5ocry/s ( plagioclase1 augite & hyp]/h5e bo? occur4 ,magnetite is commonly traceable1 & apatite may be occasionally detect$4 ,z ! result ( decomposition1 calcite1 *lorite & limonite are v g5]ally diffus$ ?r\gh ! rocks4#cce ,footnote #ccc3 ,geol4 ,mag4 = #ahhc1 pp4 #ajj1 #ade1 #beb4 ,footnote #ccd3 ,mikroskopis*e und *emis*e ,unt]su*ung5 am ,en/atit-porphyrit aus d5 ,*eviot ,hills1 ,inaug4 ,diss]t4 ,kiel1 #ahhd4 ,descriptions h also be5 publi%$ ( deta*$ rocks f o!r di/ricts1 su* z ^? by ,pr(4 ,judd & ,mr4 ,durham ( specim5s f ! ,ea/]n ,o*ils1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlii4 7#ahhf71 p4 #dah4 ,footnote #cce3 ,dr4 ,f4 ,h4 ,hat* suppli$ notes on microscopic /ructure :i* are incorporat$ 9 ! text1 toge!r ) p>ticul>s aft]w>ds furni%$ by ,mr4 ,watts4 7c7 ,! lavas :i* may be sep>at$ z ,tra*ytes (f] no di/9ctive features ext]nally by :i* !y may be di/+ui%$ f ! &esites4 ,inde$1 bo? gr\ps ( rocks appe> to be connect$ by int]m$iate v>ieties4 ,9 ! ,*eviot ,hills "s ( ! lavas are f\nd1 on microscopic exam9ation1 to conta9 a l>ge admixture ( un/rip$ porphyritic felsp>s1 :i* c occasionally be recogniz$ z sanid9e 9 ,c>lsbad tw9s4 ,! gr\ndmass is sometimes a br[n glass1 b is usually m or less completely devitrifi$1 portions ( x be+ inclos$ 9 ! l>ge felsp>s4 ,*lorite1 pseudomorphic aft] augite or en/atite1 may be detect$1 & sometimes a br[n mica4 ,a specim5 ( "o ( ^! rocks1 f a locality to ! nor?-we/ ( ,:itton1 ne> ,j$burgh1 0 f\nd by ,mr4 ,j4 ,s4 ,grant ,wilson to h ! foll[+ composition3-- ----------------------- ,n4,w4 ( ,:itton ,hill1 ,j$burgh 7,no4 #aich7 ,sp4 gr4 #bee4 ---------------------- ,si,o#b #fbdd ,al#b,o#c #ahii ,fe#b,o#c #cce ,fe,o #ah ,mn,o #be ,ca,o #ahd ,mg,o #acg ,k#b,o #ejb ,na#b,o #bfe ,h#b,o #bdh ---------------------- ,total4 #ajjai ---------------------- 7d7 ,acid rocks su* z ,felsites & ,rhyolites are r>e among ! lavas p\r$ out at ! surface dur+ ! "t ( ! ,l[] ,old ,r$ ,s&/one4 ,!y occur 9 ! ,p5tl& ,hills1 also ne> ,dolph9ton 9 ! ,bigg> di/rict1 & 9 ! ,o*il ,hills ne> ,au*t]>d]1 associat$ ) ext5sive accumulations ( felsitic tuffs & breccias4 ,!y are usually s mu* decompos$ t x is h>dly possible to procure fre% specim5s ( !m4 ,"s ( !m display beautiful fl[-/ructure4 ,!y appe> to be g5]ally or?oclase-felsites or or?ophyres4 ,dull1 f9e-gra9$ to fl9ty 9 texture1 !y h>dly ev] display free qu>tz1 s t !y c seldom be plac$ among ! typical rhyolites1 ?\gh 9 _! b&$ fl[-/ructure !y (t5 /rongly resemble "s li?oid v>ieties ( ^! rocks1 especially su* v>ieties z t repres5t$ 9 ,fig4 #i4 ,mr4 ,watts1 to :om ,i submitt$1 = microscopic exam9ation1 a numb] ( specim5s f ! ,p5tl& & ,o*il ,hills1 has f\nd !m to consi/ ( a br[n felsitic gr\ndmass 9 :i* are emb$d$ a g5]ation ( small /umpy prisms ( or?oclase & a set ( l>g] ph5ocry/s1 g5]ally consi/+ ( or?oclase & plagioclase 9 equal proportions4 ,br[n mica is usually pres5t & zircons are n uncommon4 ,! rocks1 :5 !y und]go wea!r+1 pass into ! v>ieties =m]ly compris$ "u ! "n clay/one4 ,! only nodul> felsite ( ?is age :i* ,i h met ) is t ( ,l\gh ,guitane among ! ,d+le ,b$s1 ne> ,kill>ney1 to :i* ref]5ce w be made 9 lat] pages4 #b4 ,intrusive ,bosses1 ,sills & ,dykes4--,:ile ! int]b$d$ lava-%eets are ma9ly &esites1 ! intrusive rocks are g5]ally m acid1 & mo/ ( !m may be gr\p$ "u ! conv5i5t head ( felsites4 ,"s intrusive &esites1 & ev5 m basic rocks1 d inde$ occur 9 dykes & sills1 z well z also fill+ v5ts4 ,b ! rule rema9s ( g5]al application ov] ! :ole c\ntry t ! mat]ials :i* h consolidat$ 9 ! volcanic orifices ( ! ,old ,r$ ,s&/one1 or h be5 ?ru/ among ! rocks 9 dykes1 bosses or sills1 are decid$ly acid4 ,9 ?is s]ies ( rocks a great] range ( types may be trac$ ?an among ! extrusive lavas4 ,at ! "o end we f9d true granites or granitites1 z 9 ! intrusive bosses ( ,spango ,wat] & ( ,gall[ay1 :i*1 = reasons :i* ,i w aft]w>ds adduce1 may ) "s probability be assign$ to ! volcanic hi/ory ( ! ,l[] ,old ,r$ ,s&/one p]iod4 ,among ! bosses1 _m ( :i* probably m>k ! positions ( eruptive v5ts1 or?ophyres are especially prom95t4 ,^! rocks frequ5tly conta9 no mica1 b1 on ! o!r h&1 !y sometimes %[ abundant qu>tz 9 _! gr\ndmass4 ,! augite-granitite ( ! ,*eviot ,hills1 s well describ$ by ,mr4 ,teall1 has invad$ ! b$d$ &esites ( t region4#ccf ,a simil> rock has be5 notic$ by my bro!r1 ,pr(4 ,james ,geikie1 associat$ ) ! ,l[] ,old ,r$ ,s&/one volcanic rocks ( ! ea/ ( ,ayr%ire4 ,a rem>kable petrographical v>iety has be5 mapp$ by ,mr4 ,b4 ,n4 ,pea*1 ris+ z a small boss ?r\gh ! l[] "p ( ! great lava-%eets ( ! ,o*il ,hills1 above ,tillic\ltry4 ,x is a granophyric qu>tz-diorite1 :i*1 "u ! microscope1 is se5 to be compos$ ( %ort1 ?ick-set prisms ( plagioclase1 ) abundant granophyric qu>tz1 a pleo*roic hyp]/h5e1 & ne$les ( apatite4 ,sometimes ! pyrox5e is replac$ by gre5 *loritic pseudomorphs4#ccg ,footnote #ccf3 ,geol4 ,mag4 = #ahhc1 pp4 #ajj1 #ade1 #beb2 & ,briti% ,petrography1 pp4 #bgb1 #bgh4 ,footnote #ccg3 ,notes by ,dr4 ,hat*4 ,at ! o!r end ( ! s]ies come ! felsites1 qu>tz-porphyries1 mica-porphyrites1 m9ettes1 vogesites1 horn/ones & clay/ones 7or decay$ felsites71 :i* h a close-gra9$ texture1 (t5 ) porphyritic felsp>s1 qu>tz or black mica1 g5]ally a :iti%1 pale buff1 orange1 p9k or purpli%-grey col\r1 & a specific gravity ( ab\t #bee4cch ,footnote #cch3 ,! intrusive porphyry ( ,l9tra!n 9 ,=f>%ire 7:i* may be y\ng] ?an ! ,old ,r$ ,s&/one7 is a bright r$ rock ) porphyritic felsp>1 qu>tz1 :ite mica & a v s+ul> black mica 7,mr4 ,teall's ,briti% ,petrography1 p4 #bhf74 ,?\gh ,i class ^! rocks z intrusive1 ,i am n prep>$ to ass]t t 9 none ( ! in/ances :]e !y occur z %eets may !y possibly h be5 erupt$ at ! surface z lavas4 ,9 "o or two cases ! evid5ce ei!r way is d\btful1 b z ! great majority ( ! acid rocks c be %[n to be intrusive 9 _! behavi\r1 ,i h pref]r$ to keep !m all 9 ! same category4 ,i am prep>$ to f9d1 h[ev]1 t1 z s va/ an am\nt ( felsitic debris 0 eject$ to =m ! tuffs1 m ( ?is mat]ial may h fl[$ out 9 /reams ( lava ?an is at pres5t recogniz$4 ,! foll[+ table %[s ! *emical composition ( "s acid sills & dykes f ! ,l[] ,old ,r$ ,s&/one1 z det]m9$ 9 ! laboratory ( ,pr(4 ,e4 ,frankl&3#cci-- ,footnote #cci3 ,two analyses ( rhyolites f ,%etl& by ,mr4 ,tatlock w be f\nd 9 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxxii4 7#ahhg71 p4 #chg4 ,_! silica p]c5tage is #gbcb & #gcgj4 ,an analysis ( a qu>tz-felsite f ! ,*eviot ,hills by ,mr4 ,t4 ,wall] is giv5 9 ! ,geological ,survey ,memoir on ! ,*eviot ,hills1 p4 #be4 ,! proportion ( silica 9 ?is rock is #fgi4 ---------------------------------------- ------------------- ,t9to1 ,horn/one4 ,lan>k%ire3 ,torgei? ,horn/one4 ,soluble 9 ,kn[e1 ,braid hydro*loric,insoluble ,p5tl&s ,hills#cdj acid 9 ditto4 ---------------------------------------- ------------------- ,si,o#b #gcia #fdgc #jd #gjbh ,al#b,o#c #adda #agja #aja #abed ,fe#b,o#c #gf #bce #abd #dc ,mn,o #jg #bd 444 444 ,ca,o #aba #dai #ib #ia ,mg,o #dij #ff #eb 444 ,k#b,o #ccf #cbg 444 #cib ,na#b,o #aeg #cge 444 #ehd ,p#b,o#e 444 #bf #af 444 ,h#b,o #ij #bgh 444 #aii ---------------------------------------- ------------------- ,footnote #cdj3 ,?is specim5 also yield$ #jac ( f]r\s oxide1 & #bdb ( c>bon dioxide4 ,! rock ( ,t9to1 :i* may be consid]$ typical ( ! prevail+ acid intrusive rocks ( ! s]ies1 pres5ts sev]al slightly diff]5t v>ieties4 ,dr4 ,hat*1 z ! result ( 8 exam9ation ( a numb] ( microscopic slides prep>$ f specim5s tak5 by me f v>i\s p>ts ( ! hill1 f\nd "s to be m9ettes1 %[+ small isolat$ cry/als ( or?oclase & r>e flakes ( biotite1 sometimes granules ( qu>tz1 imb$d$ 9 a br[n1 f9ely microlitic gr\ndmass ( felsp> p[d]$ ov] ) calcite2 :ile o!r specim5s _h a granul> in/ead ( a microlitic gr\ndmass1 & conta9$ a consid]able am\nt ( qu>tz 9 addition to ! con/itu5ts j m5tion$4 ,a conspicu\s knob on ! s\? side ( ,t9to1 call$ ! ,pap ,craig1 is a mass ( augite-diorite1 :i* has ris5 ?r\gh ! o!r rocks#cda 7see ,fig4 #ic74 ,! sills 9 ! same region %[ /ill fur!r diff]5ces4 ,"s are true felsp>-porphyries1 & qu>tz-porphyries v>y+ 9 ! relative abundance & size ( _! porphyritic or?oclase & qu>tz1 :ile o!rs1 by ! introduction ( hornbl5de or pseudomorphs aft] t m9]al1 pass into vogesites4 ,footnote #cda3 ,?is rock diff]s consid]ably f ! o!r intrusive masses 9 its neighb\rhood4 ,dr4 ,hat* f\nd x to be compos$ *iefly ( la?-%ap$ /rip$ felsp>1 ) "s granul> augite1 magnetite & int]/itial qu>tz4 ,basic sills & bosses are *iefly develop$ among ! ,o*il & ,sidlaw ,hills4 ,!y may g5]ally be class$ z diabases4 ,b sometimes _! pyrox5ic con/itu5t is p>tly hyp]/h5e1 z 9 a co>sely cry/all9e boss ab\t a mile s\? ( ,dunn+1 :i* has be5 det]m9$ by ,mr4 ,watts to consi/ ( augite & hyp]/h5e imb$d$ 9 & occurr+ among/ l>ge plagioclase prisms4 ,"s iron-ore is also pres5t2 ! rock is a hyp]ite4 #c4 ,tuffs & ,agglom]ates4--,! fragm5tal mat]ials1 eject$ f or fill+ up ! v5ts1 v>y f ! f9e/ compact$ du/ up to "s ( ! co>se/ agglom]ates 9 ?is c\ntry4 ,9 g5]al !y consi/ ma9ly ( detritus ( &esite1 & h be5 d]iv$ f ! bl[+ up ( already consolidat$ masses ( t rock4 ,! fragm5ts are usually angul>1 & range f m9ute gra9s up to blocks z l>ge z a cottage4 ,! tuffs are (t5 m or less mix$ ) ord9>y non-volcanic s$im5t1 & z !y are trac$ away f ! c5tres ( eruption !y pass ins5sibly into s&/ones & conglom]ates4 ,b :ile1 z might be expect$1 ! tuffs are mo/ commonly made up ( debris ( ! same k9d ( lavas z ^? t usually =m ! %eets :i* 7 p\r$ out at ! surface1 !y include also b&s ( mat]ial d]iv$ f ! de/ruction ( mu* m acid rocks4 ,?r\gh\t ! *a9 ( ! ,o*il ,hills1 = example1 9 ! mid/ ( ! b$d$ &esite-lavas1 _m ( ! ?9 c\rses ( f9e tuff consi/ l>gely ( felsitic fragm5ts1 ) scatt]$ felsp> cry/als4 ,! mo/ rem>kable examples ( ?is nature1 h[ev]1 are to be met ) at ! great v5t ( ! ,braid ,hills1 9 ! *a9 ( ! ,p5tl& ,hills :i* runs s\?-we/w>d f x1 & 9 ! ,bigg> volcanic di/rict /ill fur!r s\?4 ,^! acid tuffs are g5]ally pale fle%-col\r$ or lilac 9 t9t1 & compact 9 texture1 b1 l ! felsitic lavas f :i* !y 7 d]iv$1 !y are apt to wea!r into yell[ or buff clay/ones4 ,! f9] v>ieties are s compact z to pres5t to ! nak$ eye no di/+ui%able gra9s2 !y might be mi/ak5 = felsites1 & inde$1 except :]e !y conta9 recognizable fragm5ts ( rock or brok5 cry/als ( felsp>1 c h>dly be discrim9at$ f !m4 ,!y consi/ ( an exce$+ly f9e compact$ felsitic du/4 ,"h & !re1 h[ev]1 ! scatt]$ cry/als ( felsp> & small angul> fragm5ts ( felsite1 :i* may be detect$ 9 !m1 increase 9 numb] until !y =m ! :ole ( ! rock1 :i* is !n a brecciat$ tuff or f9e volcanic breccia1 made up ( diff]5t felsites1 among :i*1 ev5 ) ! nak$ eye1 delicate fl[-/ructures may be detect$4 ,9 ^! pale acid tuffs1 fragm5ts ( diff]5t &esites may (t5 be obs]v$1 :i* increase 9 numb] z ! rocks are trac$ away f ! ma9 v5ts ( eruption4 ,at my reque/ my colleague1 ,mr4 ,george ,b>r[1 det]m9$ ! silica p]c5tages 9 a few specim5s :i* ,i select$ z %[+ "s ( ! m *>act]i/ic v>ieties ( ^! tuffs f ! ,braid & ,p5tl& ,hills4 ,8 results are exhibit$ 9 ! foll[+ table3-- ,silica p]c5tage4 #a4 ,qu>ry above ,woodh\selee #fcc #b4 ,s\?-we/ side ( ,ca/lelaw ,hill #gcae #c4 ,qu>ry on road1 mile ,n4,e4 ( ,swan/on 7,braid ,hill v5t7 #gda #d4 ,s\?-we/ side ( ,ca/lelaw ,hill #gej #e4 ,ca/lelaw ,hill #gfjj #f4 ,s\? side ( ,:ite ,hill ,plantation #ijjj ,f ^! analyses x may be inf]r$ t ! av]age am\nt ( silica 9 ! m typical v>ieties is betwe5 #gj & #ge p] c5t4 ,! la/ specim5 9 ! table1 ) its abnormally high p]c5tage ( acid1 mu/ be reg>d$ z an exceptional v>iety1 :]e !re has ei!r be5 an excessive removal ( "s ( ! bases1 or :]e silica has be5 add$ by infiltration4 ,! microscopic exam9ation ( ^! rocks has n add$ mu* to ! in=mation d]ivable f a /udy ( !m 9 ! field4 ,9 _! mo/ close-gra9$ v>ieties1 z above rem>k$1 !y are h>dly to be di/+ui%$ f felsites4 ,b !y g5]ally %[ traces ( ! m9ute detrital p>ticles ( felsite ( :i* !y are ess5tially compos$4 ,! brecciat$ v>ieties exhibit f9ely-/reak$ fl[-/ructure 9 "s ( ! fragm5ts4 ,pieces ( &esite1 gra9s ( qu>tz1 & o!r extrane\s +r$i5ts appe> 9 ^! rocks t[>ds ! s\!rn limits ( ! volcanic area ( ! ,p5tl& ,hills1 :]e ! acid tuffs are associat$ ) & pass lat]ally & v]tically into ord9>y non-volcanic s$im5t>y /rata4 ,fur!r details z to ! "p :i* ^! tuffs play 9 ! volcanic hi/ory ( ! regions :]e9 !y occur w be giv5 9 lat] pages4 ,,*apt] ,,xviii ,,/ructure ,,& ,,arrangem5t ,,( ,,! ,,l[] ,,old ,,r$ ,,s&/one ,,volcanic ,,rocks ,,9 ,,! ,,field ,we h n[ to consid] ! mann] 9 :i* ! v>i\s volcanic products h be5 gr\p$ ar\nd & )9 ! orifices ( dis*>ge4 ,! fir/ feature to arre/ ! eye ( a tra9$ geologi/ :o approa*es !m z !y are display$ 9 "o ( ! ranges ( hills 9 ,c5tral ,scotl& is ! b$d$ aspect ( ! rocks4 ,if1 = example1 he looks ea/w>d f ! head ( ! ,fir? ( ,tay1 he m>ks on ! "r h&1 runn+ = _m miles ?r\gh ! c\nty ( ,fife1 a succession ( p>allel esc>pm5ts1 ( :i* ! /eep fronts face nor?w>ds1 :ile _! long dip-slopes desc5d t[>ds ! s\?4 ,on 8 left h& a simil> b high] s]ies ( esc>pm5ts1 /ret*+ f> ea/w>ds into ,=f>%ire1 ?r\gh ! *a9 ( ! ,sidlaw ,hills1 repeats ! same features1 b 9 opposite directions4 ,if he /&s on ! alluvial pla9 ( ! ,=?1 ne> ,/irl+1 & looks t[>ds ! nor?1 he c trace b> aft] b> ( br[n rock & grassy slope ris+ f base to summit ( ! we/]n end ( ! ,o*il ,hills4 ,if1 aga91 f any height on ! s\!rn outskirts ( ! city ( ,ed9burgh1 he lets 8 eye range along ! nor?-we/]n front ( ! *a9 ( ! ,p5tl& ,hills1 especially t[>ds ev5+1 he c foll[ ! same p>allel b&+ z a conspicu\s feature on ea* successive hill t m\nts above ! pla94 ,or if1 z he trav]ses ! we/ ( ,argyll%ire1 he comes 9 sight ( ! upl&s ( ,lorne1 he at once recognizes ! t]rac$ cont\rs ( ! hills betwe5 ,lo* ,awe & ! we/]n sea1 pres5t+ s /range a contra/ to ! rugg$ & irregul> outl9es ( ! m anci5t s*i/ & granite m\nta9s all ar\nd 7see ,fig4 #ii74 i4 ,,b$d$ ,,lavas ,,& ,,tuffs ,on a ne>] inspection1 ! dom9ant topographical features are f\nd to correspond ) a well-m>k$ /ratification ( ! :ole volcanic s]ies4 ,:]e two %eets ( &esite are sep>at$ by lay]s ( tuff1 s&/one or conglom]ate1 a well-m>k$ holl[ w (t5 be f\nd to indicate ! junction-l9e2 b ev5 :]e ! lavas foll[ ea* o!r )\t su* int]/ratifications1 _! diff]5ces ( texture & consequ5t v>iations 9 mode & am\nt ( wea!r+ usually suffice to m>k !m (f f ea* o!r1 & to indicate _! tr5d along ! surface 9 successive t]races4 ,ev5 :]e ! angles ( incl9ation are high1 ! b$d$ arrangem5t c g5]ally be detect$4 ,x is 9 ! picturesque & in/ructive coa/-sections1 h[ev]1 t ! details ( ?is b$d$ /ructure are mo/ cle>ly display$4 ,on bo? sides ( ! c\ntry1 along ! %ores ( ,ayr%ire on ! we/1 & ^? ( ,k9c>d9e%ire & ,=f>%ire on ! ea/1 ! volcanic gr\p has be5 admirably dissect$ by ! waves4 ,! lava-b$s h be5 cut 9 v]tical section1 s t _! /ructure & _! mode ( sup]position1 "o ov] ano!r1 c be conv5i5tly /udi$1 :ile at ! same "t1 ! upp] surfaces ( _m ( ! fl[s h be5 once m laid b>e z !y exi/$ be=e !y 7 buri$ "u ! s$im5t>y accumulations ( ! wat]s 9 :i* !y 7 erupt$4 ,?\gh di/9ctly b$d$1 ! ,lavas %[ little ( ! regul>ity & p]si/5ce s *>act]i/ic ( ^? ( ,c>bonif]\s & ( ,t]ti>y "t4 ,"s ( !m are n m ?an f f\r to t5 feet ?ick1 & g5]ally1 on ! coa/-cliffs1 !y appe> to be less ?an fifty feet4 ,a cont9u\s gr\p ( %eets c sometimes be trac$ = t5 miles or m f ! probable v5t ( dis*>ge4 ,t _m ( ^! lavas 7 erupt$ 9 a m>k$ly pa/y condition may be inf]r$ f c]ta9 ( _! m prom95t *>act]i/ics4 ,sometimes1 inde$1 !y appe> z tol]ably d5se homog5e\s masses1 break+ ) a k9d ( prismatic jo9t+2 b m frequ5tly !y are /rongly amygdaloidal1 & sometimes s mu* s t1 z already /at$1 ! amygdales =m ! l>g] proportion ( _! bulk4 ,:]e ! second>y infiltration-products h wea!r$ out1 ! r\gh scori=m rock looks z if x might only rec5tly h be5 erupt$4 ,9 a few in/ances ,i h obs]v$ an undulat+ rope-l surface1 :i* rem9d$ me ( well-kn[n ,vesuvian lavas4 ,usually ! top & bottom ( ea* %eet assume a /rik+ly slaggy aspect1 :i* "h & !re is exagg]at$ to su* an ext5t t betwe5 ! m solid & homog5e\s p>ts ( two consecutive fl[s an int]m$iate b& occurs1 t5 or twelve feet ?ick1 made up ( cl9k]-l lumps ( slag1 ! int]spaces be+ fill$ 9 ) h>d5$ s&4 ,9 "s cases ^! agglom]atic lay]s may actually consi/ 9 "p ( eject$ blocks2 b ! way 9 :i* _m ( ! lavas h cool$ 9 rugg$ scoriace\s surfaces is z conspicu\s z on any mod]n c\le4 ,! loos5$ slags1 or ! brok5-up cakes & blocks ( lava1 h sometimes be5 caught up 9 ! /ill mov+1 pa/y curr5t1 :i* has congeal$ ) its vesicles drawn out r\nd ! enclos$ fragm5ts1 giv+ rise to a mass t might be tak5 = a breccia or agglom]ate4 ,n[ & !n we may obs]ve t ! upp] slaggy portion ( a %eet has assum$ a bright r$ col\r f ! oxidation ( its f]rug9\s m9]als2 & f ! contra/ x ?us pres5ts to ! re/ ( ! rock we may p]haps legitimately inf] t ! dis9tegration took place be=e ! outfl[ ( ! next succe$+ lava4 ,if ?is inf]5ce be well f\nd$1 & x is confirm$ by o!r evid5ce :i* w be subsequ5tly adduc$1 x po9ts to ! probable lapse ( consid]able int]vals ( "t betwe5 "s ( ! outfl[s ( lava4 ,illu/ration3 ,fig4 #fe4--,ve9s & ne/s ( s&/one due to ! wa%+ ( s& into fissures & cavities ( an ,old ,r$ ,s&/one lava4 ,turnb]ry ,po9t1 ,ayr%ire4 ,b p]haps ! mo/ s+ul> /ructure display$ by ^! lavas is to be se5 9 ! mann] 9 :i* !y are trav]s$ by & enclose portions ( s&/one4 ,s9ce ,i orig9ally obs]v$ ?is feature on ! ,ayr%ire coa/1 ne> ,turnb]ry ,po9t1 _m ye>s ago1#cdb ,i h repeat$ly met ) x 9 ! v>i\s volcanic di/ricts ( ! ,l[] ,old ,r$ ,s&/one across ! :ole ( ! ,midl& ,valley ( ,scotl&4 ,! fir/ & natural inf]5ce :i* a cursory exam9ation ( x sugge/s is t ! molt5 rock has caught up & c>ri$ along pieces ( already consolidat$ s&/one4 ,b a little fur!r obs]vation w %[ t ! l9es ( /ratification 9 ! s&/one1 ev5 9 :at appe> to be deta*$ fragm5ts1 are m>k$ by a g5]al p>allelism1 & lie 9 ! same g5]al plane ) ! surface ( ! b$ ( lava 9 :i* ! s&y mat]ial is enclos$4 ,9 a v]tical section ! s&/one is se5 to occur sometimes 9 n>r[ dykes ) ev51 p>allel walls1 b m usually 9 irregul> twi/+ & bran*+ ve9s1 or ev5 9 lumps :i*1 ?\gh probably once connect$ ) "s ( ^! ve9s1 n[ appe> z if entirely deta*$ f !m 7,fig4 #fe74 ,frequ5tly1 inde$1 ! nodul> slaggy &esite & ! s&/one are s mix$ up t ! obs]v] may hesitate :e!r to describe ! mass z a s&/one enclos+ balls & blocks ( lava1 or z a scoriace\s lava p]meat$ ) h>d5$ s&4 ,a close connection may be trac$ betwe5 ^! s&/one-inclosures & ! b$s ( s&/one int]/ratifi$ betwe5 ! successive lavas4 ,we c foll[ ! s&y mat]ial d[nw>ds f ^! int]calat$ b$s into ! &esites bel[ !m4 ,on expos$ upp] surfaces ( ! lava1 an intricate reticulation ( s&/one ve9s may be notic$1 9 ea* ( :i* ! /ratification ( ! mat]ial runs across ! ve9s1 %[+ sometimes di/9ct curr5t-b$d+1 b ma9ta9+ a g5]al p>allelism ) ! b$d+ ( ! volcanic %eets & _! fragm5t>y accompanim5ts 7,fig4 #ff74 ,if we c\ld remove ! s&/one-ve9+s & aggregates1 we %\ld f9d ! upp] surfaces ( ^! igne\s masses to pres5t a s+ul>ly fissur$ & slaggy appe>ance1 rem9d+ u ( ! rugg$1 r5t & cl9k]-load$ slopes ( a mod]n visc\s lava1 l "s ( ^? 9 ! ,atrio del ,cavallo on ,vesuvius4 ,!re _c1 !re=e1 be any d\bt t ! s&/one1 s irregul>ly disp]s$ ?r\gh ^! lavas1 0 introduc$ orig9ally z loose s& wa%$ 9 f above s z to fill ! num]\s r5ts & cav]n\s int]spaces ( ! volcanic rock4 ,a m /rik+ pro( ( ! subaque\s "* ( ! eruptions c\ld h>dly be conceiv$4 ,?is int]e/+ feature 9 lavas erupt$ "u wat] is n conf9$ to ! volcanic s]ies ( ! ,old ,r$ ,s&/one4 ,we %all f9d t x is h>dly less di/9ct among ! basic lavas ( ! ,p]mian s]ies bo? 9 ,scotl& & 9 ,devon%ire4 ,footnote #cdb3 ,see ,jukes' ,manual ( ,geology1 #crd edit4 7#ahgb71 ,fig4 #aaa1 p4 #bgf4 ,illu/ration3 ,fig4 #ff4--;,gr\nd-plan ( reticulat$ cracks 9 ! upp] surface ( an ,old ,r$ ,s&/one lava fill$ 9 ) s&/one4 ,r$ ,head1 ,=f>%ire4 ,a rem>kable exception to ! g5]al type ( d>k basic & int]m$iate lavas is furni%$ by ! pale1 decompos+ felsites ( ! ,p5tl& & ,dolph9ton ,hills4 ,^? :i* issue f ! great eruptive c5tre ( ! ,braid ,hills1 alt]nate ) ! &esites & ! diabases1 gradually dim9i%+ l ^! 9 a s\?w>d direction & dy+ out 9 "s six or sev5 miles4 ,beyond ! limits ( ^! lavas1 ano!r simil> ?ick gr\p 0 erupt$ f a sep>ate v5t at ! nor!rn end ( ! ,bigg> di/rict ne> ,dolph9ton4 ,! same occurr5ce has be5 asc]ta9$ also 9 ! area ( ! ,o*il *a94 ,full] ref]5ce w be made to ^! int]e/+ rocks 9 ! descriptions to be aft]w>ds giv5 ( ! /ructure & hi/ory ( ! volcanic areas ( ! ,p5tl& ,hills1 ! ,bigg> c5tre & ! ,o*il ,hills4 ,x is c]ta9ly a notable feature 9 ! volcanism ( ,old ,r$ ,s&/one "t t f ! same1 or f closely adjo9+ v5ts1 lavas %\ld be alt]nately p\r$ =?1 diff]+ s mu* f ea* o!r1 alike 9 *emical composition & petrographical *>act]s1 z &esites & diabases on ! "o h&1 & felsites on ! o!r4 ,additional examples1 f widely diff]5t geological sy/ems1 w be cit$ 9 subsequ5t pages4 ,x w be %[n t ev5 9 ! v late/ volcanic p]iod 9 ,brita91 t ( old] ,t]ti>y "t1 highly basic & m>k$ly acid mat]ials 7 eject$ f ! same c5tres ( eruption4 ,! "p tak5 by ! ,tuffs 9 ! /ructure ( ! gr\nd agrees ) :at might h be5 expect$ 9 ! accompanim5ts ( extremely slaggy & viscid lavas4 ,^! pyrocla/ic int]calations are1 9 mo/ ( ! volcanic di/ricts1 comp>atively insignificant 9 am\nt1 by f> ! l>ge/ proportion ( solid mat]ial eject$ f ! v>i\s v5ts hav+ consi/$ ( /reams ( lava4 ,r\nd or )9 "s ( ! v5ts ! fragm5t>y mat]ials atta9 a rem>kable co>s5ess1 z may be se5 9 ! great agglom]ates ( ,dumyat1 ne> ,/irl+1 ! l>ge/ ( :i* is m ?an #gjj feet ?ick4 ,^! massive accumulations d\btless repres5t a long s]ies ( explosive dis*>ges f ! summit ( ! lava column 9 "o or m adjac5t v5ts4 ,trac$ away f ! orifices ( emission1 ! tuffs rapidly gr[ f9] 9 gra91 less 9 ?ickness1 & m mix$ ) ord9>y detritus1 until !y pass into ord9>y non-volcanic s$im5t or die out betwe5 ! lava-%eets4 ,good sections1 %[+ ! nature & arrangem5t ( ! ?9 int]calations ( &esite-tuff betwe5 ! successive outp\r+s ( lava1 may be exam9$ on ! coa/4 ,?us1 ne> ,turnb]ry ,po9t1 9 ,ayr%ire1 upw>ds ( a doz5 successive fl[s ( lava1 ) _! s&y & a%y int]v5+ lay]s1 are expos$ 9 plan ^u ! bea*1 & p>tly also 9 section along ! cliffs on :i* ! ru9s ( ! hi/oric ca/le ( ,turnb]ry /&4 7,figs4 #ie1 #if1 #ig74 ,aga91 along ! coa/ ( ,=f>%ire1 f ! ,r$ ,head to ,montrose1 ! num]\s %eets ( &esite are sep>at$ by lay]s ( dull purpli% tuff pass+ into conglom]ate1 ) blocks ( porphyrite a y>d or m 9 diamet]4 ,! mo/ rem>kable int]/ratifi$ tuffs 9 ! ,l[] ,old ,r$ ,s&/one are ! felsitic v>ieties4 ,^? :i* proce$ f ! great v5t ( ! ,braid ,hills1 ext5d s\?-we/w>ds = eight or n9e miles1 & _! peculi> mat]ials1 mix$ ) ord9>y s$im5t1 may be trac$ sev]al miles fur!r4 ,!y occur 9 successive %eets1 :i*1 f a maximum ?ickness & numb] at ! nor? end1 gradually ?9 away s\?w>ds1 l ! felsitic lavas :i* !y accompany1 & f ! explosion ( :i* !y no d\bt 7 d]iv$4 ,!y consi/ to a l>ge ext5t ( extremely f9e volcanic du/1 & s9ce !y are g5]ally mu* decompos$1 x is (t51 z already rem>k$1 h>dly possible to di/+ui% betwe5 !m & ! equally decay$ felsites4 ,9 "s p>ts ( ! hills !y pres5t a di/9ct fissile b$d+2 b /ill m satisfactory is ! occasional f9e brecciat$ /ructure :i* !y assume1 :5 !y are se5 to consi/ ( angul> lapilli ( diff]5t felsites4 ,! am\nt ( volcanic mat]ial eject$ f ! m important v5ts 0 mu* great] ?an ! height ( ! pres5t hills w\ld lead u to suppose4 ,! rocks h g5]ally be5 tilt$ into positions mu* m incl9$ ?an ^? :i* !y orig9ally occupi$1 s t to measure _! actual ?ickness we mu/ take a l9e approximately p]p5dicul> to ! dip4 ,9 ?is way we asc]ta9 t ! accumulat$ mass ( lavas & tuffs imm$iately outside ! v5t at ! nor? end ( ! ,p5tl& ,hills mu/ be at lea/ #gjjj feet ?ick1 = ! base ( ! s]ies is conceal$ "u ! uncon=mable ov]lap ( ! ,l[] ,c>bonif]\s ,s&/ones1 :ile ! top is cut (f by a fault :i* br+s d[n ! ,c>bonif]\s =mations aga9/ ! ea/]n flank ( ! hills4 ,probably n less volum9\s is ! pile ( eject$ mat]ial 9 ! ,o*il ,hills1 :]e1 ?\gh ! base ( ! :ole is conceal$ by ! fault :i* ?r[s d[n ! coal-field1 "s #fejj feet ( lavas1 tuffs & conglom]ates c be se54 ,!re 7 ?us1 dur+ ! "t ( ! ,l[] ,old ,r$ ,s&/one1 m ?an "o volcano 9 ,c5tral ,scotl& :i* might be comp>$ 9 bulk ( eject$ mat]ial to ,vesuvius4 ,illu/ration3 ,fig4 #fg4--,section across ! volcanic s]ies ( ,=f>%ire4 a1 conglom]ates1 s&/ones & flag/ones2 b1 %eets ( &esitic lava4 ,t ! eruptions 7 ma9ly subaque\s is indicat$1 z ,i h %[n1 by ! int]calat$ b&s ( s&/one & conglom]ate betwe5 ! successive lavas1 z ^! are trac$ away f ! c5tres ( dis*>ge1 & likewise1 ev5 m impressively1 by ! h>d5$ s& :i* has be5 wa%$ into =m] fissures & crevices 9 ! lava4 ,b t1 9 "s cases1 ! volcanic cones 7 built up above ! surface ( ! lake may be legitimately inf]r$ f ! rem>kable volcanic conglom]ates :i* occur1 m p>ticul>ly 9 ! great *a9 ( ! ,o*il & ,sidlaw ,hills4 ,^! ?ick accumulations ( well-r\nd$ & wat]-worn blocks are int]sp]s$ betwe5 %eets ( &esite1 & are ma9ly made up ( &esite fragm5ts4 ,impressive sections ( !m may be se5 along ! ,k9c>d9e%ire coa/4 ,! conglom]ates are sometimes s rem>kably co>se1 _m ( _! blocks exce$+ two feet 9 diamet]1 & s rudely b$d$1 t x is only by not+ ! position ( oblong b\ld]s t "o c make out ! g5]al direction ( ! /ratification4 ,9 _! smoo? r\nd$ =ms1 ^! blocks resemble ! mat]ials ( /orm-bea*es on an expos$ coa/4 ,! trituration ( ! &esite fragm5ts has giv5 rise to a c]ta9 am\nt ( gre5 pa/e1 :i* firmly wraps r\nd ! /ones1 & reta9s ca/s ( !m aft] !y h dropp$ out4 ,x is fur!r des]v+ ( rem>k t :ile 9 "s di/ricts1 z 9 ! c5tral ,o*ils1 ! mat]ials 7 entirely d]iv$ f ! de/ruction ( volcanic rocks1 9 o!rs a l>ge proportion ( non-volcanic mat]ials is m+l$ ) ! debris ( ! lavas4 ,s\? ( ,/onehav51 = example1 l>ge b\ld]s ( qu>tzite =m a conspicu\s feature 9 ! conglom]ates1 ( :i* 9 places !y make up q half ( ! total con/itu5ts4 ,!re c be little d\bt1 ,i ?9k1 t ! mat]ials ( ^! co>se detrital accumulations 7 ga!r$ toge!r z %+le-bea*es1 & 7 d]iv$ 9 "p f volcanic cones :i* _h ris5 above ! level ( ! lake4 ,!y seem to sugge/ consid]able degradation ( ^! cones by break]-action1 :]eby blocks ( rock a y>d or m 9 diamet] c\ld be r\nd$ & smoo!d4 ,ano!r inf]5ce d$ucible f su* conglom]ates1 & to :i* ,i h already allud$1 is t consid]able int]vals ( "t took place betwe5 "s ( ! eruptions4 ,r\nd ! v5ts1 inde$1 :]e ! successive %eets ( volcanic mat]ial foll[ ea* o!r cont9u\sly1 x is p]haps impossible to =m any def9ite op9ion z to ! relative *ronological value ( ! l9es ( sep>ation betwe5 diff]5t ejections4 ,b :]e "s hundr$s ( feet ( co>se conglom]ate1 *iefly compos$ ( well-r\nd$ &esite blocks1 int]v5e betwe5 two /reams ( lava1 we may conclude t ! int]val betwe5 ! outp\r+ ( ^! /reams mu/ h be5 ( consid]able duration4 ,o!r evid5ce ( a simil> t5d5cy may be recogniz$ 9 ! int]calation ( gr\ps ( v>i$ s$im5t>y accumulations1 su* z ^? :i* 7 deposit$ ov] ! site ( ,ea/]n ,=f>%ire & ,k9c>d9e%ire dur+ ! "t t elaps$ betwe5 two successive floods ( lava4 ,9 ! ,d5 ( ,cant]l&1 = example1 9 ! mid/ ( ! volcanic %eets we f9d int]e/+ evid5ce ( "o ( ^! int]vals ( quiesc5ce1 dur+ :i* lay]s ( f9e olive %ales 7 laid quietly d[n1 :ile mac]at$ vegetation1 drift+ ov] ! lake-bottom1 0 buri$ ) rema9s ( fi%es1 & abundant gally-worms 7,kampec>is1 ,ar*idesmus71 wa%$ f ! neighb\r+ l&4#cdc ,s undi/urb$ 7 ! conditions ( deposition t calc>e\s s$im5t ga!r$ r\nd "s ( ! organisms & encas$ !m 9 lime/one nodules4 ,footnote #cdc3 ,an abundant organism 9 "s ( ^! deposits1 nam$ ,p>ka1 0 fir/ reg>d$ z a plant1 0 aft]w>ds believ$ to be ! egg-packets ( cru/acea1 & is n[ pron\nc$ by compet5t au?orities to belong to an aquatic plant ) creep+ /ems1 l9e> leaves & sessile sporoc>ps4 ,9 "s ( ! di/ricts ! dis*>ges ( volcanic mat]ial 7 s abundant or s cont9u\s t no recognizable deposition ( ord9>y s$im5t has tak5 place betwe5 !m4 ,?us1 at ! nor? end ( ! ,p5tl& ,hills ! rocks are entirely ( volcanic orig91 & ?\gh1 z we trace !m s\?w>ds away f ! c5tre ( eruption1 !y dim9i% 9 ?ickness1 !y include h>dly any int]/ratifi$ s&/ones & conglom]ates until !y f9ally beg9 to die out4 ,! di/ances to :i* ! lavas & tuffs h be5 erupt$ f ! *ief v5ts ( a di/rict v>y up to #ae or #bj miles4 ,^? ( ! ,p5tl& ,hills ext5d f ! ,braid ,hill v5t = #aj miles to ! s\?-we/4 ,^? ( ! ,bigg> c5tre /ret* = ab\t #af miles to ! nor?-ea/4 ,^? ( ! ,o*il ,hills1 :i* probably came f a numb] ( di/9ct v5ts1 c be trac$ = ne>ly #ej miles4 ii4 ,,v5ts ,on ! :ole ! actual v5ts ( ! volcanoes ( ,l[] ,old ,r$ ,s&/one "t are less cle>ly di/+ui%able ?an ^? ( subsequ5t volcanic p]iods4 ,?is defici5cy d\btless arises f ! geological /ructure ( ! di/ricts 9 :i* ! =mation is *iefly develop$4 ,?us1 9 ! great ,midl& ,valley ( ,scotl&1 :]e ! ,old ,r$ ,s&/one cov]s a l>ge "p ( ! surface1 ! v5ts seem to h be5 plac$ along ! c5tral p>ts ( ! long tr\gh r ?an among ! old] rocks on ei!r m>g94 ,h5ce !y are 9 l>ge measure buri$ ei!r "u ! volcanic & s$im5t>y accumulations ( _! own p]iod or "u ,c>bonif]\s /rata4 ,illu/ration3 ,fig4 #fh4--,section across two necks above ,tillic\ltry1 ,o*il ,hills4 #a #a1 ,&esite lavas2 #b #b1 ,tuffs & volcanic conglom]ates2 #c #c1 ,! two necks2 #d #d1 ,dykes ( felsite1 etc42 #e1 ,coal-measures2 f1 ,fault4 ,c]ta9 bosses ( massive rocks ly+ well )9 ! volcanic area may ) "s confid5ce be reg>d$ z ! sites ( eruptive c5tres4 ,!y occur ei!r s+ly or 9 gr\ps1 & may be specially notic$ along ! *a9 ( ! ,o*il & ,sidlaw ,hills4 ,yet x seems to me probable t ^! visible bosses1 ev5 if we are correct 9 reg>d+ !m z m>k+ ! positions ( true v5ts1 d n indicate ! *ief orifices ( dis*>ge4 ,if we consid] _! size & _! di/ribution ) ref]5ce to ! areas ( lava & tuff dis*>g$ at ! surface1 we are r l$ to look ^u !m z subsidi>y v5ts1 ! m important orifices1 f :i* ! ma9 bulk ( ! eruptions took place1 be+ /ill conceal$ "u ! ,c>bonif]\s rocks ( ! ,midl& ,valley4 ,! bosses :i* rise ?r\gh diff]5t portions ( ! volcanic s]ies are obvi\sly n ! olde/ or orig9al v5ts4 ,! great felsitic mass ( ,t9to 9 ,lan>k%ire 7,fig4 #ic71 inde$1 pi]ces /rata :i* lie ne> ! base ( ! ,l[] ,old ,r$ ,s&/one1 b ! small] cone ( ,quo?quan 9 its neighb\rhood appe>s 9 ! mid/ ( ! lavas 7,fig4 #ib74 ,9 ! s\?-we/]n "p ( ! ,o*il *a9 ! bosses or necks are *iefly small 9 size1 seldom exce$+ half a mile 9 diamet]4 ,!y h be5 fill$ sometimes ) cry/all9e1 sometimes ) fragm5tal mat]ials4 ,two ( !m1 conta9+ ! rem>kable granophyric qu>tz-diorite already ref]r$ to1 em]ge f among ! tuffs 9 a l[ "p ( ! s]ies1 imm$iately above ! village ( ,tillic\ltry 9 ,clackmannan 7,fig4 #fh74 ,two or ?ree m1 :i* are occupi$ by or?ophyres & qu>tz-felsites1 pi]ce ! volcanic gr\p a few miles to ! we/ ( ,lo* ,lev54 ,! :ole ( ! visible bosses ( ! ,o*il ,hills may be reg>d$ z "o connect$ gr\p1 subsidi>y to ! ma9 orifices :i* lay r fur!r to ! s\? & we/4 ,m p>ticul> ref]5ce to ?is di/rict w be made 9 ! foll[+ *apt] 7p4 #cjc74 ,v5ts :i* h be5 fill$ up ) agglom]ate1 & :i* ?us furni% ! mo/ obvi\s pro(s ( _! connection ) ! eruptions ( ! volcanic s]ies1 ?\gh n frequ5t1 may be obs]v$ 9 a numb] ( ! volcanic di/ricts4 ,_! fragm5t>y mat]ials g5]ally consi/ ma9ly ( ! detritus ( &esites or diabases l ^? :i* =m ! b$d$ lavas4 ,b :]e m acid lavas h ris5 to ! surface1 fragm5ts ( felsite may occur m or less abundantly4 ,9 ! great v5t ( ! ,braid ,hills ! tuffs & breccias are almo/ :olly acid4 ,non-volcanic mat]ials may (t5 be f\nd 9 ! agglom]ates1 & occasionally ev5 to ! exclusion ( volcanic detritus4 ,?us1 9 ! f> nor? ( ,scotl& sev]al examples occur among ! ,%etl& ,isles ( necks fill$ entirely ) blocks ( ! surr\nd+ flag/ones & s&/ones4 ,su* cases1 z has be5 already po9t$ out1 probably repres5t incomplet$ volcanoes1 :5 ! explosive vap\rs 7 p[]ful en\gh to drill orifices 9 ! cru/ ( ! e>? & eject ! %att]$ debris f !m1 b 7 n suffici5tly vigor\s or la/+ to br+ up any solid or liquid volcanic mat]ial to ! surface4 ,^! ,%etl& examples are fur!r notic$ on p4 #cde4 ,necks ( agglom]ate 9 ! ,l[] ,old ,r$ ,s&/one v>y 9 size f a great orifice measur+ two miles across to little plugs only a few y>ds 9 diamet]4 ,!y may be f\nd 9 limit$ numb]s 9 mo/ ( ! volcanic di/ricts4 ,no examples h be5 obs]v$ ris+ ?r\gh old] rocks ?an ! ,old ,r$ ,s&/one1 all ! kn[n in/ances be+ eruptive ?r\gh "s "p ( ! volcanic s]ies or ( ! s&/ones1 & !re=e n belong+ to ! e>lie/ eruptions4 ,! l>ge/1 & 9 "s respects ! mo/ int]e/+1 v5t 9 ! ,l[] ,old ,r$ ,s&/one1 t ( ! ,braid ,hills ne> ,ed9burgh1 describ$ 9 ,*apt] xx41 cov]s an area ( m ?an two squ>e miles1 & is fill$ ) felsitic breccias & tuffs1 ?r\gh :i* bosses & ve9s ( acid & basic rocks h be5 inject$4 ,x completely truncates ! b$d$ lavas & tuffs ( ! ,p5tl& ,hills1 & n improbably m>ks ! *ief c5tre f :i* ^! rocks 7 erupt$4 ,sev]al small] necks rise a little beyond its s\!rn m>g91 m>k+1 p]haps1 lat]al cones on ! ma9 volcano4 ,9 ! small area ( ,l[] ,old ,r$ ,s&/one ly+ betwe5 ,campbelt[n & ! ,mull ( ,cantyre1 sev]al necks ( agglom]ate occur1 :i* h be5 p>tly dissect$ by ! waves along ! %ore1 ?us reveal+ _! int]nal /ructure & _! relation to ! surr\nd+ conglom]ates4 ,an acc\nt ( !m w be f\nd at p4 #caa4 ,"o ( ! s]ies1 :i* lies back f ! coa/-l9e1 =ms a prom95t r\nd$ hill measur+ ab\t #djj y>ds 9 its longe/ diamet]4 ,its g5]al cont\r is repres5t$ 9 ,fig4 #hb4 ,( ! eruptive bosses ( massive rock outside ! limits ( ! ,old ,r$ ,s&/one :i* may be plausibly ref]r$ to ! volcanic ph5om5a ( ! p]iod1 ?\gh !y _c be prov$ to be actually "p ( !m1 ! mo/ notable are ! bosses ( granite & o!r acid mat]ial :i* rise ?r\gh ! ,silurian /rata ( ! ,s\!rn ,upl&s ( ,scotl&4#cdd ,! l>ge/ are ! well-kn[n masses ( ,gall[ay 7,fig4 #fi71 ) :i* mu/ be gr\p$ ! bosses ne> ,new ,cumnock1 t ( ! ,spango ,wat] 7,fig4 #id71 & ^? ( ,cockburn ,law & ,prie/law 9 ,lamm]muir1 toge!r ) a numb] ( masses ( felsitic mat]ial scatt]$ ov] ! same region1 su* z ! ,dirr+ton ,laws ( ,b]wick%ire 7,fig4 #gj74 ,^! bosses pres5t "s po9ts ( /ructure 9 common ) true v5ts4 ,!y come l great v]tical columns ?r\gh highly-fold$ & puck]$ /rata1 &1 z !y truncate ! ,ll&ov]y & ,w5lock =mations1 !y are c]ta9ly y\ng] ?an ! great] "p ( ! ,upp] ,silurian s]ies4 ,!y mu/ be lat]1 too1 ?an ! *ief plication & cleavage ( ^! /rata2 b !y are old] ?an ! ,upp] ,old ,r$ ,s&/one or basem5t ,c>bonif]\s rocks :i* conta9 pebbles ( !m4 ,_! date ( eruption is ?us n>r[$ to ! int]val betwe5 ! lat] "p ( ! ,upp] ,silurian p]iod & ! beg9n+ ( ! ,upp] ,old ,r$ ,s&/one4 ,i h myself little d\bt t !y are to be associat$ ) ! volcanic epo* we are n[ consid]+1 z x 0 ! only kn[n great episode ( igne\s activity 9 ?is region dur+ ! int]val )9 :i* ! protrusion ( ^! granites mu/ h tak5 place4 ,9 ! ,*eviot ,hills1 inde$1 we h evid5ce ( ! eruption ( a l>ge mass ( augite-granitite ?r\gh ! porphyrite-lavas ( ! ,l[] ,old ,r$ ,s&/one1 ) abundant ve9s project+ f x into !m1 z w be n>rat$ 9 lat] pages4#cde ,footnote #cdd3 ,i sugge/$ ?is possible connection _m ye>s ago 9 ,trans4 ,geol4 ,soc4 ,ed94 vol4 ii4 7#ahgd7 p4 #ba4 ,footnote #cde3 ,! volcanic geology ( ! ,*eviot ,hills is describ$ by ,mr4 ,teall1 ,geol4 ,mag4 = #ahhc1 p4 #ajf2 & by ,mr4 ,cl\gh1 ,mem4 ,geol4 ,survey1 ,geology ( ! ,*eviot ,hills1 ,%eet #ajh ,n4,e41 #ahhh1 p4 #bd4 ,illu/ration3 ,fig4 #fi4--,section ( ! granite core betwe5 ,m]rick & ,corscr9e4 a1 ,silurian greywackes1 grits & %ales2 b1 granite4 ,n improbably _m o!r granite protrusions ?r\gh\t ! ,briti% ,isles are to be ref]r$ to ! volcanic op]ations ( ! ,l[] ,old ,r$ ,s&/one4 ,su* are ^? ( ! ,lake ,di/rict1 notably t ( ,%ap1#cdf ! granites ( ,newry & ,le9/] 9 ! ea/ ( ,irel&1 :i* are lat] ?an ! ,silurian rocks & old] ?an ! ,c>bonif]\s ,lime/one1 & ! y\ng] ,grampian granites1 :i* pi]ce ! presumably ,ar5ig belt along ! ,highl& bord]4 ,:e!r or n ^! granitic protrusions 7 connect$ ) sup]ficial volcanic dis*>ges ( :i* no rema9s h surviv$1 !y seem to indicate ! wide ext5t & rem>kable vig\r ( ! subt]ranean igne\s action ( ?is geological p]iod4 ,footnote #cdf3 ,see ! descriptions ( ! ,%ap granite by ,messrs4 ,m>r & ,h>k]1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlvii4 7#ahia7 p4 #bff1 & xlix4 7#ahic7 p4 #cei4 ,illu/ration3 ,fig4 #gj4--,section across ! ?ree ,dirr+ton ,laws1 ,b]wick%ire4 a1 ,upp] ,silurian /rata2 b1 ,necks probably ( ,l[] ,old ,r$ ,s&/one age2 c1 ,upp] ,old ,r$ ,s&/one ly+ uncon=mably bo? on a & b4 ,view$ z a :ole1 ! mat]ials :i* n[ occupy ! v5ts ( ! volcanic *a9s 9 ! ,l[] ,old ,r$ ,s&/one ( ! ,briti% ,isles are m acid ?an ! lavas erupt$ at ! surface4 ,9 ! ,p5tl& di/rict1 inde$1 & 9 "s o!r areas ?is acid mat]ial 0 eject$ at int]vals 9 abundant dis*>ges ( du/ & lapilli & 9 outfl[s ( felsitic lavas1 :ile betwe5 ^! successive dis*>ges copi\s /reams ( diabasic & &esitic lavas1 ei!r f ! same or f "s closely-adjo9+ v5t1 7 p\r$ out4 ,?r\gh\t ! :ole region1 h[ev]1 z a clos+ phase ( ! volcanic hi/ory1 ! acid magma rose aft] ! outp\r+ ( ! m basic lavas & fill$ su* *imneys ( ! volcanoes z 7 n already block$ ) agglom]ate4 ,x 0 probably aft] ^! pipes 7 plugg$ t ! f9al ef=ts ( volcanic en]gy 7 exp5d$ 9 ! protrusion ( ! acid mat]ial z sills betwe5 ! b$d+-planes ( ! surr\nd+ rocks1 & z dykes & ve9s 9 & ar\nd ! v5ts4 iii4 ,,sills ,,& ,,dykes ,n[h]e ?r\gh\t ! volcanic tracts ( ! ,l[] ,old ,r$ ,s&/one is !re any su* developm5t ( sills z may be se5 b5ea? ! ,silurian volcanic %eets ( ,nor? ,wales4 ,^? :i* occur are mo/ abundant 9 ! ,lan>k%ire di/rict1 to ! nor?-we/ & s\?-we/ ( ,t9to1 & 9 ! s\? ( ,ayr%ire4 ,f ! village ( ,muirkirk to ! gorge ( ! ,clyde1 bel[ ! ,falls1 ! ,upp] ,silurian & ,l[] ,old ,r$ ,s&/one /rata are trav]s$ by num]\s intrusive %eets ( p9k & yell[ felsite1 qu>tz-porphyry1 m9ette1 lamprophyre & alli$ rocks1 :i* are no d\bt to be reg>d$ z "p ( ! volcanic ph5om5a ) :i* we are "h conc]n$4 ,9 ! s\? ( ,ayr%ire1 betwe5 ! villages ( ,dalmell+ton & ,b>r1 !re is a copi\s developm5t ( simil> sills1 especially along "o or m horizons ne> ! base ( ! ,old ,r$ ,s&/one4 ,g>leff9 ,fell1 ,gl5alla ,fell1 ,turg5y & o!r heights are conspicu\s prom95ces =m$ ( ^! rocks2 above ! sills lie ?ick conglom]ates & s&/ones on :i* ! great &esite-%eets re/4 ,9 ! ,p5tl& ,hills1 z w be describ$ 9 ,*apt] xx41 a massive felsitic sill =ms a conspicu\s feature along ! nor? side ( ! *a91 & !re are probably o!rs :i* h n yet be5 sep>at$ f ! felsitic tuffs & or?ophyres :i* !y s mu* resemble4 ,p]haps ! mo/ rem>kable acid sills 9 ! ,old ,r$ ,s&/one ( ,brita9 are ^? :i* occur at ! extreme nor!rn end ( ! region among ! volcanic ph5om5a ( ! ,%etl& ,isles 7,figs4 #ga1 #gb74 ,! l>ge/ ( !m1 consi/+ ma9ly ( granite & felsite1 is believ$ to rea* a l5g? ( #bj & a bread? ( f ?ree to f\r miles4#cdg ,footnote #cdg3 ,messrs4 ,b4 ,n4 ,pea* & ,j4 ,horne1 ,trans4 ,roy4 ,soc4 ,ed94 xxxii4 7#ahhd71 p4 #cei4 ,illu/ration3 ,fig4 #ga4--,section ( ,papa ,/\r1 ,%etl&s1 %[+ sill ( sph]ulitic felsite trav]s+ ,old ,r$ ,s&/one & b$d$ porphyrites 7,messrs4 ,pea* & ,horne74 #a4 ,r$ s&/ones & flag/ones2 #b4 ,purple diabase-porphyrites2 #c4 ,great %eet ( p9k sph]ulitic felsite4 ,illu/ration3 ,fig4 #gb4--,section across ,nor?mav9e1 f ,okrea ,head to ,skea ,ness1 ,%etl&1 %[+ dykes & connect$ sill ( granite & felsite 7,messrs4 ,pea* & ,horne74 #a4 ,s*i/s1 etc42 #b4 ,s]p5t9e2 #c4 ,granite & qu>tz-felsite2 #d4 ,breccia ( s]p5t9e fragm5ts2 #e4 ,b$d$ &esites & tuffs4 f1 ,fault4 ,a gr\p ( sills compos$ ( a bright r$ qu>tz-porphyry has be5 trac$ along ! s\!rn flanks ( ! ,highl&s = upw>ds ( #ah miles4#cdh ,?is rock1 already ref]r$ to z ! ,l9tra!n porphyry1 lies *iefly among ! conglom]ates & s&/ones1 b also int]sects ! lavas1 & may be lat] ?an ! ,old ,r$ ,s&/one 7p4 #bgg74 ,an ext5sion ( x is f\nd ev5 on ! nor? side ( ! b\nd>y fault1 cutt+ ! &esites :i* !re lie uncon=mably on ! s*i/s4 ,footnote #cdh3 ,see ,%eet #ef ( ! ,geological ,survey ( ,scotl&4 ,examples1 h[ev]1 occur ( sills mu* less acid 9 composition4 ,9 ! ,dundee di/rict1 = in/ance1 ! intrusive %eets are &esites & diabases4 ,!y s5d ve9s into & bake ! s&/ones among :i* !y h be5 intrud$1 & are sometimes full ( fragm5ts ( su* indurat$ s&/one1 z may be well se5 on ! nor!rn %ore ( ! ,fir? ( ,tay1 we/ ( ,dundee4 ,a conspicu\s *>act]i/ic ( mo/ ( ! volcanic tracts ( ! ,l[] ,old ,r$ ,s&/one is ! comp>ative sc>city ( contemporane\s dykes4 ,9 ! b& ( acid sills betwe5 ,muirkirk & ! ,clyde1 a consid]able numb] ( dykes h be5 mapp$1 :i* mu/ be reg>d$ z due to ! same s]ies ( movem5ts & protrusions ( ! magma t produc$ ! adjac5t sills4 ,?r\gh\t ! l5g? ( ! ,s\!rn ,upl&s dykes ( felsite1 m9ette1 lamprophyre1 vogesite & o!r v>ieties1 :i* may also be connect$ ) ! volcanic ph5om5a ( ! ,l[] ,old ,r$ ,s&/one1 n infrequ5tly occur among ! ,silurian rocks4 ,on ! ,k9c>d9e%ire coa/1 s\? ( ,b]vie1 a numb] ( dykes ( p9k qu>tz-porphyry trav]se ! conglom]ates & s&/ones4 ,! coa/ s\? ( ,montrose displays "s s+ul>ly picturesque sections1 :]e a porphyry dyke runn+ ?r\gh &esitic lavas & agglom]ates /&s up 9 wall-l & t[]-l projections4 ,on ! %ore at ,g\rdon1 z well z inl&1 intrusive dykes ( s]p5t9e occur4 ,a l9e ( ^!1 possibly along ! same fissure1 has be5 trac$ = m ?an a doz5 ( miles f above ,corta*y ,ca/le to ne> ,bamff4 ,b !re is no evid5ce to connect !m ) ! volcanic ph5om5a ( ! ,old ,r$ ,s&/one4 ,n improbably !y belong to a lat] geological p]iod4 ,"o w\ld expect to meet ) a network ( dykes 9 & ar\nd ! volcanic v5ts2 b ev5 !re !y are usually n conspicu\s ei!r = numb] or size4 ,9 ! great v5t ( ! ,braid ,hills only a few h be5 notic$4 ,9 ! ,o*il ,hills gr\ps ( dykes ( felsite & &esite may be obs]v$1 especially ne> ! necks4 ,!y are fairly num]\s 9 ! neighb\rhood ( ,doll> 7see ,fig4 #fh74 ,"o ( ! mo/ abundant s]ies yet obs]v$ trav]ses ! tract ar\nd ! granite boss ( ! ,*eviot ,hills1 f :i* _m dykes ( granite1 felsite1 qu>tz-porphyry & &esite radiate4 ,?is di/rict w be m fully ref]r$ to 9 ,*apt] xxi4 ,ano!r rem>kable developm5t ( dykes occurs 9 ,%etl& 7,fig4 #gb71 :]e !y consi/ ( granite1 felsite & rhyolite1 & are associat$ ) ! acid sills above ref]r$ to4 ,,*apt] ,,xix ,,volcanoes ,,( ,,! ,,l[] ,,old ,,r$ ,,s&/one ,,( ,,lake ,,cal$onia ,description ( ! sev]al ,volcanic ,di/ricts3 ,lake ,cal$onia1 its ,*a9s ( ,volcanoes--,! ,nor!rn ,*a93 ,montrose ,gr\p1 ,o*il & ,sidlaw ,hills1 ! ,arran & ,cantyre ,c5tre1 ! ,ul/] ,c5tre4 ,i n[ propose to give "s acc\nt ( ea* ( ! di/ricts :i* h be5 sep>ate areas ( volcanic action dur+ ! "t ( ! ,l[] ,old ,r$ ,s&/one1 trac+ its g5]al /ructure1 ! arrangem5t & sequ5ce ( its volcanic rocks & ! hi/ory ( its eruptions4 ,z by f> ! mo/ v>i$ developm5t ( ! ,old ,r$ ,s&/one is to be f\nd 9 ! great ,midl& ,valley ( ,scotl&1 & z x is !re t ! rem>kable volcanic ph5om5a ( ! sy/em h be5 mo/ abundantly display$ & are mo/ cle>ly record$1 ,i %all beg9 my description ( ! volcanic eruptions ( ! ,l[] ,old ,r$ ,s&/one ) a detail$ acc\nt ( ! diff]5t c5tres ( volcanic activity 9 t region4 ,! ph5om5a are s fully display$ !re t a m summ>y treatm5t ( ! subject w suffice = ! o!r regions4 ,"u ! designation ( ,lake ,cal$onia1 z already rem>k$1 ,i include ! :ole ( ! ,midl& ,valley ( ,scotl& betwe5 ! ,highl&s & ! ,s\!rn ,upl&s1 likewise ! cont9uation ( ! same anci5t holl[ by ,arran & ! s\? ( ,cantyre across ! nor? ( ,irel& to ,l\gh ,erne4#cdi ,?r\gh\t mo/ ( ! area ?us def9$1 ! pres5t limits ( ! ,l[] ,old ,r$ ,s&/one are %>ply m>k$ (f by l>ge p>allel faults4 ,on ! nor?-we/ side "o1 or r a p>allel s]ies1 ( su* dislocations runs f ,/onehav5 along ! flank ( ! ,highl& m\nta9s to ! ,clyde1 ?us trav]s+ ! :ole bread? ( ! isl&4 ,on ! s\?-ea/ side ano!r simil> s]ies ( faults1 :i* !re skirts ! edge ( ! ,silurian tablel&1 has ne>ly ! same effect 9 precisely def9+ ! m>g9 ( ! ,old ,r$ ,s&/one4 ,z ?us limit$1 ! tract has a bread? ( ab\t #ej miles 9 ,scotl&1 :ile ! portion ( x n[ visible 9 ! ,briti% ,isles has an extreme l5g? ( ab\t #bhj miles 7,map ,,iii474 ,footnote #cdi3 ,my own inve/igations ( ?is region h be5 cont9u$ ov] an int]val ( =ty ye>s4 ,besides p]sonally trav]s+ e portion ( x1 ,i h mapp$ 9 detail1 = ! ,geological ,survey1 _m hundr$s ( squ>e miles ( its area f ! outskirts ( ,ed9burgh s\?-we/w>ds into ,lan>k%ire1 9 ,ayr%ire1 & 9 ! c\nties ( ,fife1 ,p]? & ,k9ross4 ,! ,geological ,survey maps ( ! volcanic tracts ( ! ,sidlaw ,hills h be5 prep>$ by my bro!r1 ,pr(4 ,james ,geikie1 & ,messrs4 ,h4 ,m4 ,skae & ,d4 ,r4 ,irv9e4 ,! ,we/]n ,o*ils 7 mapp$ *iefly by ,mr4 ,b4 ,n4 ,pea*1 p>tly by ,pr(4 ,j4 ,"y1 ,mr4 ,r4 ,l4 ,jack & myself2 ! ,ea/]n ,o*ils 7 survey$ ma9ly by ,mr4 ,h4 ,h4 ,h[ell2 :ile ! volcanic belt betwe5 ! tracts mapp$ by me 9 ,lan>k%ire & 9 ,ayr%ire 0 *iefly trac$ out by ,mr4 ,pea*4 ,z a rule1 ea* ( ^! geologi/s has describ$ 9 ! ,survey ,memoirs ! portions ( c\ntry survey$ by him4 ,b ?\gh ! b\nd>y-faults det]m9e1 on ! :ole1 ! pres5t limits ( ! tract ( ,old ,r$ ,s&/one1 !y d n necess>ily indicate ! %ore-l9es ( ! %eet ( wat] 9 :i* t great s]ies ( deposits 0 laid d[n4 ,!y po9t to an enorm\s subsid5ce ( ! tract betwe5 !m--a prolong$ & ext5sive sagg+ ( ! /rip ( c\ntry t /ret*es across ! ,midl& ,valley ( ,scotl& into ! nor? ( ,irel&4#cej ,?is d[nw>d movem5t began z f> back z ! close ( ! ,silurian p]iod1 b ! m>g9al fractures & ! disruption & plication ( ! ?ick masses ( s&/one & conglom]ate :i* 7 accumulat$ 9 ! lake *iefly took place aft] ! close ( ! p]iod ( ! ,l[] ,old ,r$ ,s&/one4 ,i ?9k we may reasonably connect ^! movem5ts ) ! g5]al s9k+ ( ! area consequ5t ^u ! enorm\s outp\r+ ( volcanic mat]ials dur+ t p]iod4 ,footnote #cej3 ,9 "s ( ! dislocations along ! ,highl& bord]1 ! ,old ,r$ ,s&/one is b5t back ^u itself1 & ! old] s*i/s are ?us made to recl9e ^u x1 z if !re _h be5 a pu% ov] f ! ,highl& area4 ,along bo? ! nor!rn & s\!rn m>g9s ( ! bas9 !re occur1 on ! f>!r side ( ! b\nd>y faults1 outly+ pat*es ( ,l[] ,old ,r$ ,s&/one t re/ uncon=mably on ! rocks =m+ ! flanks ( ! hills4 ,^! areas possess a peculi> int]e/1 inasmu* z !y reveal "s p>ts ( ! %ore-l9e ( ! lake1 & %[ ! relation betwe5 ! e>li] rocks & ! s$im5ts ( ! ,old ,r$ ,s&/one4 ,we le>n f !m t ! %ore-l9e 0 ind5t$ ) wide bays1 b nev]!less ran 9 a g5]al nor?-ea/]ly direction4 ,x ?us correspond$ 9 tr5d ) ! pres5t ,midl& ,valley1 ) ! axes ( plication among ! s*i/s ( ! ,highl&s z well z among ! ,silurian rocks ( ! ,s\!rn ,upl&s1 & ) ! subsequ5t fault+ & fold+ ( ! ,old ,r$ ,s&/one4 ,illu/ration3 ,fig4 #gc4--,section at ! edge ( "o ( ! bays ( ,l[] ,old ,r$ ,s&/one along ! nor!rn m>g9 ( ,lake ,cal$onia1 ne> ,o*t]tyre4 a1 slates & phyllites2 b1 volcanic conglom]ates2 c1 &esite-lava4 ,i may rem>k 9 pass+ t ! conglom]ates & o!r associat$ mat]ials :i* h be5 pres]v$ 9 ^! bays & holl[s beyond ! l9es ( ! great faults1 ?\gh !y lie uncon=mably on ! rocks b5ea?1 are n ! basem5t portions ( ! ,old ,r$ ,s&/one4 ,on ! contr>y1 :]e _! probable /ratigraphical horizons c be recogniz$ or inf]r$1 !y are f\nd to belong to p>ts ( ! s]ies consid]ably above ! base ( ! :ole4 ,!y po9t to ! gradual s9k+ ( ! bas9 & ! creep+ ( ! wat]s ) _! littoral %+les fur!r & fur!r up ! slopes ( ! hills on ei!r side 7,fig4 #gc74 ,b ?is is n all ! evid5ce t c be adduc$ to %[ t ! limits ( ! lake ext5d$ consid]ably beyond ! l9es ( dislocation betwe5 :i* ! pres5t area ( ,old ,r$ ,s&/one ma9ly lies4 ,no "o c look at ! noble esc>pm5ts ( ! ,braes ( ,d\ne on ! "o side 7,fig4 #gd71 or walk ov] ! upturn$ conglom]ates & &esites :i* flank ! ,lan>k%ire upl&s on ! o!r1 )\t be+ conv9c$ t if ! effects ( ! b\nd>y faults c\ld be undone1 s z to re/ore ! orig9al /ructure ( ! gr\nd1 ! prolongations ( ! rocks1 n[ remov$ by d5udation1 w\ld be f\nd sweep+ f> into ! ,highl&s on ! nor? & into ! ,silurian ,upl&s on ! s\?4 ,illu/ration3 ,fig4 #gd4--;,craig ,be9n nan-,eun 7#bjfg feet71 ea/ ( ,uam ,v>1 ,braes ( ,d\ne4 ,old ,r$ ,conglom]ate1 ) ! truncat$ ends ( ! /rata look+ across into ! ,highl&s2 mora9es ( ,corry ,bea* 9 ! =egr\nd4 ,if ! area ( ,lake ,cal$onia 7 tak5 to be def9$ by ! b\nd>y faults1 x cov]$ a space ( ab\t #aj1jjj squ>e miles4 ,b1 z we "k t x c]ta9ly /ret*$ beyond ! limits m>k$ by ^! faults1 x mu/ h be5 ( /ill great] ext5t4 ,we %all probably n exagg]ate if we reg>d x z some:at l>g] ?an ! pres5t ,lake ,erie1 ! sup]ficies ( :i* is ab\t #iijj squ>e miles4 ,9 ?is long n>r[ bas9 ! rem>kable volcanic hi/ory 0 enact$ ( :i* ,i n[ proce$ to give "s acc\nt4 ,! ,l[] ,old ,r$ ,s&/one ( ,c5tral ,scotl& may be conv5i5tly divid$ into ?ree great gr\ps1 ea* ( :i* m>ks a di/9ct epo* 9 ! hi/ory ( ! bas9 :]e9 !y 7 successively accumulat$4 ,! l[e/ ( ^! gr\ps indicates a "t ( quiet s$im5tation dur+ :i* ! bas9 0 def9$ by plication ( ! t]re/rial cru/1 & :51 by ! same subt]ranean movem5ts1 "s p>ts ( ! floor ( ! lake 7 pu%$ upw>d above wat]1 & 7 !n d5ud$ & buri$4 ,! middle gr\p consi/s l>gely ( volcanic rocks4 ,x po9ts to ! exi/5ce ( l9es ( active volcanic cones situat$ along ! l5g? ( ! lake4 ,! upp]mo/ gr\p records ! ext9ction ( volcanic action & ! gradual oblit]ation ( ! lake1 p>tly by ! p\r+ ( s$im5t into x1 & p>tly no d\bt by ! cont9u$ t]re/rial movem5ts :i* _h orig9ally produc$ ! bas94 ,x is evid5t f ^! records t ?\gh volcanic activity cont9u$ vigor\s = a va/ p]iod ( "t1 x _h entirely ceas$ 9 ,lake ,cal$onia long be=e ! la/ s$im5ts ( ! ,l[] ,old ,r$ ,s&/one 7 laid d[n4 ,! great cones ( ! ,o*il ,hills1 = example1 sank bel[ ! wat]s ( ! lake 9 :i* !y _h long be5 a conspicu\s feature1 & s protract$ 0 ! subsid5ce ( ! lake-bottom t ! site ( ^! volcanoes 0 buri$ "u #hjjj or #ijjj feet ( s&/ones & conglom]ates1 among :i* no trace ( any volcanic eruptions has yet be5 f\nd4 ,! sagg+ ( ! t]re/rial cru/ ov] an area f :i* su* an enorm\s am\nt ( volcanic products _h be5 dis*>g$ w\ld d\btless be a protract$ process4 ,long aft] ! subsid5ce ( ! lake-bottom & ! accumulation ( its ?ick mass ( s$im5ts1 aft] ev5 ! entire effacem5t ( ! topography & ! deposition ( ! ?ick ,c>bonif]\s =mations ov] its site1 ! d[nw>d movem5t %[$ itself 9 ! production ( gigantic nor?-ea/ faults1 & ! s9k+ ( ! ,c>bonif]\s rocks = sev]al ?\s& feet4 ,^! dislocations1 z 0 natural1 h run ?r\gh ! he>t ( "s ( ! volcanic gr\ps1 c>ry+ mu* ( ! evid5ce ( ! anci5t volcanoes out ( sight1 & leav+ u only fragm5ts f :i* to piece toge!r ! records ( a volcanic p]iod :i* is by no means ! lea/ int]e/+ 9 ! geological hi/ory ( ?is c\ntry4 ,conf9+ our att5tion = ! pres5t to ! records ( ! middle or volcanic gr\p1 we f9d evid5ce ( a numb] ( di/9ct clu/]s ( volcanoes rang$ along ! :ole l5g? ( ! bas94 ,! indep5d5ce ( ^! volcanic di/ricts may be inf]r$ f ! foll[+ facts3--#a/1 ,! actual v5ts ( dis*>ge may 9 "s cases be recogniz$2 #bnd1 ,ev5 :]e ^! v5ts h be5 buri$1 we may (t5 obs]ve1 z we approa* _! probable sites1 a m>k$ increase 9 ! ?ickness ( ! volcanic accumulations1 z well z a great developm5t ( agglom]ates & tuffs2 #crd1 ,trac$ 9 opposite directions1 ! volcanic mat]ials are f\nd to ?9 away or ev5 to disappe>4 ,^? f "o c5tre ( dis*>ge may be obs]v$ n[ & !n to ov]lap ^? f ano!r1 b ! two s]ies rema9 di/9ct4 ,reason+ f ^! data & /udy+ ! di/ribution ( ! v>i\s volcanic areas1 we are l$ to recognize ! =m] exi/5ce ( two p>allel *a9s ( v5ts1 runn+ along ! l5g? ( ! lake at a di/ance f ea* o!r ( some:]e ab\t tw5ty miles4 ,!y may be conv5i5tly di/+ui%$ z ! nor!rn & ! s\!rn *a94 ,! nor!rn b& runs f ! coa/-l9e ne> ,/onehav5 s\?-we/w>d ?r\gh ! ,sidlaw & ,o*il ,hills4 ,x is !n abruptly truncat$ by a l>ge fault & by ! uncon=mable sup]position ( ! ,c>bonif]\s =mations4 ,b #fj miles fur!r to ! s\?-we/1 :]e ! ,old ,r$ ,s&/one comes out on ! we/ side ( ! ,fir? ( ,clyde1 a cont9uation ( ! volcanic b& has rec5tly be5 detect$ by ,mr4 ,w4 ,gunn ( ! ,geological ,survey 9 ! ,isl& ( ,arran4 ,tw5ty-five miles /ill fur!r 9 ! same direction a mu* ampl] developm5t ( ! volcanic rocks occurs to ! s\? ( ,campbelt[n 9 ,cantyre4 ,if we cross ! #bb miles ( sea t sep>ate ! ,argyll%ire coa/-sections f ^? ( ,r$ ,bay 9 ,irel&1 we f9d ne> ,cu%5dall a repetition ( ! ,scotti% volcanic conglom]ates1 :ile /ill fur!r along ! same p]si/5t l9e1 "s #ej miles into ! int]ior1 ! hills ( ,tyrone include %eets ( lava precisely l ^? ( ,c5tral ,scotl&4 ,! total l5g? ( ?is nor!rn *a9 ( volcanoes is ?us n mu* less ?an #bej miles1 & z its nor?-ea/]n end is n[ cut (f by ! ,nor? ,sea x mu/ h be5 /ill long]4 ,x ran p>allel to ! nor?-we/]n coa/-l9e ( ! lake1 at a di/ance :i*1 ov] ! site ( ! ,midl& ,valley ( ,scotl&1 seems to h v>i$ f #aj to #bj miles1 b :i* greatly less5$ fur!r to ! s\?-we/4 ,at a di/ance ( "s tw5ty miles to ! s\? ( ! nor!rn belt1 ! second p>allel *a9 ( volcanoes ran 9 a ne>ly /raight l9e1 :i* is n[ traceable f ! s\!rn suburbs ( ,ed9burgh to ! coa/ ( ,ayr%ire1 a di/ance ( ab\t #ge miles1 b z its nor?-ea/]n end is conceal$ by ,c>bonif]\s =mations1 & its s\?-we/]n passes "u ! sea1 its true l5g? is probably consid]ably m4 ,if ! areas :i* pres5t evid5ce ( di/9ct & indep5d5t v5ts are gr\p$ accord+ to _! positions on ^! two l9es1 !y naturally arrange !mselves z 9 ! foll[+ li/3-- ,i4 ,nor!rn ,*a9 ( ,volcanoes #a4 ,! ,montrose ,c5tre4 #b4 ,! ,sidlaw & ,o*il ,gr\p4 #c4 ,! ,arran & ,cantyre ,c5tre4 #d4 ,! ,ul/] ,c5tres4 ,,ii4 ,s\!rn ,*a9 ( ,volcanoes #e4 ,! ,p5tl& ,volcano4 #f4 ,! ,bigg> ,c5tre4 #g4 ,! ,duneaton ,c5tre4 #h4 ,! ,ayr%ire ,gr\p4 ,! di/ribution ( ^! v>i\s volcanic areas w be mo/ easily und]/ood f an exam9ation ( ,map ,,iii4 accompany+ ?is volume4 ,i4 ,,! ,,nor!rn ,,*a9 ,,( ,,volcanoes ,,9 ,,lake ,,cal$onia #a4 ,! ,montrose ,c5tre ,beg9n+ at ! nor?-ea/]n end ( ! area1 we fir/ enc\nt] a s]ies ( volcanic rocks :i* atta9 _! maximum ?ickness 9 ,=f>%ire ar\nd ! t[n ( ,montrose4 ,! ma9 v5ts probably lay some:]e to ! ea/ ( ! pres5t coa/1 "u ! floor ( ! ,nor? ,sea2 at lea/ no cle> indication ( _! exi/5ce ei!r on ! coa/ or inl& has be5 detect$4 ,f ,montrose1 bo? to ! nor?-ea/ & s\?-we/1 ! lavas ?9 away1 becom+ int]calat$ among ! s&/ones1 flag/ones & conglom]ates1 & gradually dy+ out4 ,! total l5g? ( ! volcanic belt is ab\t #ah miles1 t is n9e miles f ! c5tral ?ick mass 9 a nor?-ea/]ly & ! same di/ance 9 a s\?-we/]ly direction4#cea ,! volcanic pile mu/ be sev]al ?\s& feet ?ick1 b ow+ to ! prolongation ( ! great ,o*il anticl9e1 ! lavas roll ov] & d n all[ _! base to be se54 ,! axis ( ! fold mu/ pass out to sea1 ?r\gh ! holl[ on :i* ! t[n ( ,montrose /&s4 ,! volcanic s]ies consi/s ( &esite-%eets ) volcanic conglom]ates4 ,x conta9s little ord9>y tuff1 b ! conglom]ates no d\bt p>tly repres5t eject$ fragm5tal mat]ial1 z well z ! wa/e ( expos$ lavas4 ,a section across ! anticl9al fold f ,=f> to ,panbride1 a little to ! s\?-we/ ( ,montrose1 w\ld reveal ! /ructure %[n 9 ,fig4 #fg4 ,footnote #cea3 ,! s\?-we/]n "p ( ?is area f ,arbroa? to ,john%av5 0 mapp$ = ! ,geological ,survey by ! late ,mr4 ,h4 ,m4 ,skae1 ! nor?-ea/]n "p by ,mr4 ,d4 ,r4 ,irv9e4 ,my acc\nt ( x is ma9ly tak5 f notes made by myself on ! gr\nd prelim9>y to ! comm5cem5t ( ! mapp+ ( ! ,survey4 ,9 ! nor?-ea/]n prolongation ( ! volcanic s]ies f ! ,montrose c5tre1 successively l[] memb]s are expos$ along ! coa/-l9e4 ,b ! lavas are dy+ out 9 t direction1 & sometimes _m hundr$s ( feet ( ord9>y s$im5t int]v5e betwe5 two successive fl[s4 ,x 0 9 "o ( ^! long pauses ne> ! top ( ! :ole pile ( lavas t ! /rata ( ,cant]l& 7 deposit$1 to :i* ref]5ce has already be5 made4 ,s\?-we/ f ,montrose ! ?ick volcanic mass rapidly dim9i%es1 & is prolong$ to ! end only by ?ree or f\r b&s sep>at$ by s&/ones & flag/ones4 ,x is 9 ^! int]calat$ gr\ps ( s$im5t>y mat]ial t ! ,=f>%ire flags occur4 ,n[h]e c ! details ( ! ,old ,r$ ,s&/one volcanic rocks be m conv5i5tly /udi$ ?an along ! coa/-section 9 ?is di/rict f ! ,r$ ,head to ,/onehav54 ,! rocks h n only be5 cut into v]tical cliffs1 b along _m p>ts ( ! %ore !y h be5 also laid b>e 9 gr\nd-plan1 s t a complete dissection ( !m is pres5t$ to ! geologi/4 ,at ! s\? end1 ! top ( ! volcanic s]ies appe>s at ! bold promontory ( ! ,r$ ,head4 ,!re1 at ! base ( ! cliffs ( r$ s&/one1 ! accompany+ section may be se54 ,b5ea? ! r$ false-b$d$ & sometimes pebbly s&/ones 7e71 :i* =m ne>ly ! :ole precipice1 lies a b& ( dull purpli% a%y conglom]ate 7d71 compos$ almo/ :olly ( fragm5ts ( diff]5t &esites1 imb$d$ 9 a pa/e ( ! same comm9ut$ mat]ial4 ,t[>ds ! s\?1 ?is rock rapidly becomes co>s]1 until x passes into a k9d ( agglom]ate1 9 :i* ! &esite blocks are sometimes a y>d or m 9 diamet]4 ,x includes b&s ( s&/one1 :i* increase 9 numb] & ?ickness t[>ds ! nor?1 & sometimes int]v5e und]nea? ! conglom]ate4 ,! l[e/ rocks "h visible are %eets ( &esite or porphyrite 7a71 sep>at$ f ea* o!r by irregul> bright r$ lay]s ( tuface\s s& & agglom]ate4 ,^! lavas are dull purpli%-grey to gre51 "s ( !m be+ tol]ably compact1 o!rs highly amygdaloidal1 ) l>ge /eam-cavities (t5 drawn out 9 ! direction ( fl[4 ,illu/ration3 ,fig4 #ge4--,section %[+ ! top ( ! volcanic s]ies at ! foot ( ! precipice ( ! ,r$ ,head1 ,=f>%ire4 a1 ,top ( slaggy &esite2 b1 co>se volcanic conglom]ate2 c1 ,r$ s&/one2 d1 ,tuff & volcanic conglom]ate2 e1 ,r$ s&/ones4 ,"o ( ! mo/ /rik+ features 9 ! &esites ( ?is coa/ is ! rem>kable mann] 9 :i* !y include ! ve9+s ( pale gre5 & r$ s&/one already describ$ 7see ,figs4 #fe1 #ff74 ,"s ( ! %eets h 9 cool+ crack$ into rude polygons4 ,!y are likewise trav]s$ by l>ge cav]n\s spaces & intricate fissures or /eam-cavities4 ,into all ^! op5+s ! s& has be5 wa%$1 fill+ !m up & solidify+ into well-/ratifi$ s&/one1 ! b$d+ ( :i* is g5]ally p>allel ) t ( ! rocks t enclose x1 ! dip ( ! :ole s]ies ( /rata be+ g5tly seaw>ds4 ,b a /ill m intimate mixture ( ! s& ) ! lava-%eets is to be rem>k$ :]e ^! rocks assume _! mo/ slaggy "*4 ,9 "s ( !m ! upp] "p1 to a dep? ( t5 or twelve feet1 consi/s ( m]e rugg$ lumps ( slag :i*1 :ile ! mass 0 9 motion1 7 probably 9 l>ge measure loose1 & roll$ ov] ea* o!r z !y 7 borne onw>d4 ,! s& has f\nd its way into all ! int]/ices ( ^! cl9k]-b$s1 & n[ b9ds ! :ole mass firmly toge!r4 ,at fir/ sight1 ^! b&s might be tak5 = agglom]ates ( eject$ blocks1 & z already sugge/$1 "s ( ! slags may h be5 ?r[n out z loose pieces1 b a little exam9ation w %[ t 9 ! ma9 ! r\gh scoriace\s lumps are pieces ( ! lava und]nea?4 ,9 ^! in/ances1 also1 x is cle> t ! blocks 7 9 position be=e ! f9e s& 0 sift$ into _! int]spaces1 = ! pale gre5 s&/one is horizontally /ratifi$ ?r\gh its intricate ramifications among ! pile ( d>k cl9k]s4 ,! seaw>d incl9ation ( ! rocks all[s ! succession ( lavas to be se5 z ! coa/ is foll[$ we/w>d into ,lunan ,bay4 ,on ! fur!r side ( t inlet1 aft] pass+ ov] a gr\p ( s&/ones t und]lie ! volcanic s]ies ( ! ,r$ ,head1 ! obs]v] meets ) a second & l[] succession ( lavas :i* 9 ! five miles nor?w>d to ,montrose ,h>b\r are admirably expos$ bo? along coa/-cliffs & on ! bea*4 ,!y resemble ^? ( ! ,r$ ,head1 be+ made up ( alt]nations ( highly vesicul> &esite ) m compact v>ieties1 & %[+ simil> s&/one ve9+s4 ,"h & !re1 z at ,fi%t[n ( ,us>1 ! sea has cut !m d[n into a plat=m f :i* ! h>d] p>ts rise z fanta/ic half-tide /acks4 ,9 "s cases1 ! m durable rock consi/s ( ! slaggy upp] portions ( ! fl[s1 & 9 "o case ?is mat]ial /&s up z a rude pill> twelve feet high1 compos$ ( cl9k]s firmly cem5t$ ) ve9+s ( s&/one4 ,! geologi/ :o w&]s ov] ?is coa/-l9e is arre/$ at e turn by ! m>vell\sly fre% volcanic aspect ( _m ( ! lavas4 ,_! upp] p>ts are s cellul> t if ! calcite1 *alc$ony & o!r infiltrat$ m9]als 7 remov$ f _! vesicles1 !y w\ld be trans=m$ into surfaces ( m]e slag4 ,9 "o respect w\ld _! antiquity /ill be evid5t4 ,^! slaggy b&s are g5]ally a good deal r$d5$1 z if !y _h be5 long expos$ to oxidation be=e be+ cov]$ by ! ov]ly+ %eets ( lava--a feature already cit$1 z probably indicat+ ! lapse ( "s consid]able int]val ( "t betwe5 successive outfl[s4 ,along ?is coa/-section ! abs5ce ( int]calat$ tuffs is soon rem>k$4 ,! volcanic ejections seem to h consi/$ almo/ entirely ( &esitic lavas1 ?\gh x is possible t "h & !re ! v slaggy b&s betwe5 ! m solid p>ts ( ! %eets may include a little pyrocla/ic mat]ial4 ,! l[e/ portion ( ! volcanic gr\p "h visible is rea*$ at ,montrose ,h>b\r1 :]e1 9 ! flag/ones & %ales ( ,f]ryd51 ! late ,rev4 ,hugh ,mit*ell obta9$ "s ( ! fossil-fi%es ( ! =mation4 ,a space ( m ?an ?ree miles n[ int]v5es :]e ! rocks are conceal$ by bl[n s& & o!r sup]ficial accumulations4 ,x is ?r\gh ?is holl[1 z already /at$1 t ! great ,o*il anticl9e runs out to sea4 ,on ! nor? side ( ! ,nor? ,esk ,riv]1 we aga9 come ^u ! same b& ( lavas z to ! s\? ( ,montrose1 b ) a dip to ! nor?-we/4 ,?is incl9ation1 h[ev]1 soon b5ds r\nd m we/]ly1 & ! result ( ! *ange is to expose a sl[ly desc5d+ section all ! way to ! ,highl& fault at ,/onehav54 ,a picturesque l9e ( high inl& cliff1 runn+ nor?w>ds beyond ,/4 ,cyrus1 reveals ) great cle>ness ! b$d$ /ructure ( ! &esites4 ,b z "o moves nor?w>d1 ow+ to ! *ange 9 ! direction ( dip1 "o f9ally passes out ( ?is volcanic belt & beg9s gradually to desc5d into ! ?ick ,k9c>d9e%ire ,old ,r$ ,s&/one4 ,! am\nt ( conglom]ate expos$ along ?is "p ( ! coa/-l9e probably consid]ably surpasses 9 ?ickness any o!r conglom]ate s]ies 9 ! ,l[] ,old ,r$ ,s&/one ( ,brita94 ,?r\gh\t ! enorm\s dep? ( s$im5t>y mat]ial1 ! conglom]ates are well-b$d$1 consi/+ ( a dull gre5 pa/e1 compos$ 9 l>ge degree ( comm9ut$ &esitic debris1 & int]/ratifi$ ) gre5 felspa?ic s&/ones4 ,!y are (t5 rem>kably co>se1 ! pebbles sometimes measur+ ?ree feet 9 l5g?4 ,int]pos$ among !m are "s t5 or twelve b&s1 probably (t5 s+le outfl[s ( &esite1 sometimes compact & porphyritic1 at o!r times highly amygdaloidal4 ,su* is ! succession ( rocks = _m miles along ! %ore2 & z ! incl9ation v>ies f a little nor? ( we/ to we/1 or ev5 we/ by s\?1 ! obs]v] gradually passes ov] a ?ickness ( r m ?an #bjjj feet f ! base ( ! ,/4 ,cyrus &esites to ,g\rdon4 ,9 ?is accumulation ( co>se1 well wat]-worn mat]ial1 ) abundant int]calations ( f9] s&/one & occasional %eets ( lava1 !re is ! record ( prolong$ & p[]ful d5udation ) int]mitt5t volcanic activity4 ,dykes ( a qu>tzif]\s porphyry cut ! conglom]ates1 & at ,g\rdon !y are pi]c$ by ! intrusion ( s]p5t9e above ref]r$ to4 ,! proportion ( &esite fragm5ts 9 ! conglom]ates ( ?is "p ( ! coa/ v>ies1 b is g5]ally mu* l[] ?an t ( ! rocks f ! ,highl&s4 ,?us at ,john%av51 out ( #ajj blocks1 brok5 promiscu\sly f ! conglom]ate1 ,i f\nd t only #h p] c5t 7 ( &esite1 :ile #dd p] c5t 7 ( qu>tzite1 & ! rema9d] consi/$ ( v>i\s qu>tz-porphyries1 granites & s*i/s4 ,x is evid5t1 !re=e1 t "s area ( cry/all9e rocks 0 subject$ to enorm\s wa/e1 & t its detritus 0 /rewn ov] ! floor ( ,lake ,cal$onia1 at ! same "t t f ! ,montrose volcanic v5ts _m /reams ( &esitic lava 7 p\r$ =?4 ,a va/ mass ( co>se conglom]ate int]v5es betwe5 ,g\rdon & ,dunnott>1 & =ms a ne>ly cont9u\s l9e ( precipices :i* 9 "s places rise #bjj feet above ! waves4 ,! b$d+ is ev]y:]e di/9ctly m>k$1 s t !re is no difficulty 9 foll[+ ! succession ( ! /rata1 & e/imat+ _! ?ickness4 ,f ! la/ ( ! lavas at ,g\rdon to ! base ( ! conglom]ates ne> ,/onehav51 !re lies an accumulation ( conglom]ate at lea/ #hjjj feet ?ick4 ,! b\ld]s & pebbles 9 ^! deposits are g5]ally well-r\nd$1 & v>y up to f\r feet or m 9 l5g?4 ,i obs]v$ "o ( qu>tz-porphyry at ,k9neff :i* measur$ sev5 feet long & six feet broad4 ,! proportion ( &esite fragm5ts 9 ^! conglom]ates cont9ues to be small4 ,i asc]ta9$ t 9 ! co>se/ mass at ,k9neff !y numb]$ only #ad p] c5t2 at ,todhead ,po9t1 a mile & a half to ! nor?1 #bj p] c5t1 & at ,cat]l9e1 ?ree qu>t]s ( a mile fur!r 9 ! same direction1 #ba p] c5t4 ,9 ! mid/ ( ?is gigantic accumulation ( ! v co>se/ wat]-worn detritus1 !re are /ill records ( contemporane\s volcanic action4 ,ne> ,k9neff ! beautiful &esite1 ) l>ge tabul> cry/als ( plagioclase1 allud$ to on p4 #bgd1 occurs 9 ! conglom]ate4#ceb ,s\? ( ,cat]l9e two fl[s1 ly+ /ill l[] 9 ! sy/em1 project into ! sea4 ,"o ( ^! pres5ts a section ( mu* int]e/4 ,x %[s a c5tral solid portion1 jo9t$ into rudely prismatic blocks1 ) an indef9ite platy /ructure1 :i* gives x a r\ghly-b$d$ aspect4 ,its upp] t5 or twelve feet are %>ply m>k$ (f by _! slaggy /ructure1 end+ upw>ds 9 a wavy surface l t ( ! ,vesuvian lava ( #aheh4 ,into its fissures1 /eam-cavities & irregul> holl[s1 f9e s& has be5 wa%$ f above1 z at ,r$ ,head1 :ile imm$iately above x comes a co>se conglom]ate ( ! usual "* 7,fig4 #gf74 ,/ill l[] d[n1 b5ea? "s #ijj feet ( rem>kably co>se conglom]ate1 ano!r gr\p ( %eets ( &esite abuts at ,crawton ^u ! coa/1 ) :i*1 at a %ort di/ance inl&1 x runs p>allel = m ?an two miles1 com+ back to ! sea at ,?ornyhive ,bay & at ,maid5kaim4 ,we h !n to pass ov] ab\t #ejjj feet ( simil> conglom]ates1 until1 aft] hav+ cross$ sev]al int]calat$ %eets ( &esite1 we meet ) ! la/ & l[e/ ( ! :ole volcanic s]ies ( ?is region 9 ! =m ( "s b&s ( porphyrite at ! ,bellman's ,head1 ,/onehav54 ,! peculi> geographical conditions t l$ to ! =mation ( ! co>se conglom]ates appe> to h be5 e/abli%$ at ! same "t t ! volcanic eruptions began1 = z we desc5d 9 ! long coa/ section1 we f9d t ! co>se s$im5t & ! int]calat$ lavas cease on ! same g5]al horizon4 ,bel[ t plat=m lie "s #ejjj feet ( r$ s&/ones & r$ %ales1 yet ! base ( ! s]ies is n se51 = ! l[e/ visible /rata h be5 fault$ aga9/ ! s*i/s ( ! ,highl&s4 ,x is ?us obvi\s t m ?an #ejjj feet ( s$im5t _h be5 laid d[n ov] ?is "p ( ! floor ( ,lake ,cal$onia be=e ! fir/ lavas 7 "h erupt$4 ,footnote #ceb3 ,= an analysis ( ! felsp> 9 ?is rock1 see ,pr(4 ,h$dle's pap]1 ,trans4 ,roy4 ,soc4 ,ed94 xxviii4 7#ahgi71 p4 #beg4 ,illu/ration3 ,fig4 #gf4--;,&esite ) s&/one ve9+s & ov]ly+ conglom]ate4 ,todhead1 s\? ( ,cat]l9e1 coa/ ( ,k9c>d9e%ire4 #b4 ,! ,sidlaw & ,o*il ,gr\p ,! volcanoes :i* p\r$ out ! masses ( mat]ial t n[ =m ! *a9 ( ! ,o*il & ,sidlaw ,hills appe> to h be5 among ! mo/ vigor\s 9 ! :ole region ( ,lake ,cal$onia4 ,_! *ief v5ts probably lay t[>ds ! s\?-we/ 9 ! neighb\rhood ( ,/irl+1 :]e ! lavas1 agglom]ates & tuffs dis*>g$ f !m rea* a ?ickness ( n less ?an #fejj feet1 )\t reveal+ _! bottom4 ,f t c5tre ! lavas range cont9u\sly = ne>ly fifty miles to ! nor?-ea/1 until !y rea* ! sea at ,tayport2 b !y are prolong$ on ! nor? side ( ! ,fir? ( ,tay f ,br\ghty ,f]ry to ne> ,arbroa?1 s z to ov]lap ^? ( ! ,montrose gr\p4 ,!y ?us atta9 a total l5g? ( ne>ly sixty miles 9 a nor?-ea/]ly l9e4 ,h[ f> !y /ret*$ s\?-we/ _c n[ be asc]ta9$1 = !y h be5 dislocat$ & buri$ 9 t direction "u ! ,c>bonif]\s =mations ( ! ,midl& ,valley4 ,x w be obs]v$ f ! map 7,no4 ,,iii47 t ! great volcanic ridge ( ! ,o*il ,hills cont9ues unbrok5 = tw5ty-two miles1 f ,/irl+ to ,bridge ( ,e>n4 ,!reaft] x bran*es into two div]g5t portions1 "o ( :i* runs on ?r\gh ! nor? ( ,fife to ! s\!rn promontory ( ! e/u>y ( ! ,tay1 :ile ! o!r1 aft] s9k+ bel[ ! alluvial pla9s ( ! ,e>n & ! ,tay1 m\nts once m into a high ridge ne> ,p]?1 & !nce /ret*es ea/w>d into ,=f>%ire z ! *a9 ( ! ,sidlaw ,hills4 ,?is bifurcation is due to ! op5+ out & d5udation ( ! great anticl9al fold above m5tion$4 ,! rocks 9 ! nor!rn limb dip nor?-we/w>d1 ^? 9 ! s\!rn limb dip s\?-ea/w>d4 ,! l[] memb]s ( ! ,old ,r$ ,s&/one1 und]ly+ ! volcanic s]ies1 ought to be se5 b5ea? !m along ! cre/ ( ! anticl9e4 ,un=tunately1 h[ev]1 p>tly by ! action ( faults along ! b\nd>ies ( ! volcanic b&s1 b *iefly f ! uncon=mable ov]spread ( ,upp] ,old ,r$ ,s&/one & ,l[] ,c>bonif]\s rocks across ! pla9s ( ! ,c>se ( ,g[rie & ( ! ,e>n1 ! l[] p>ts ( ! sy/em are !re conceal$ 7see ,fig4 #gh74 ,z already rem>k$1 ?is important anticl9al fold runs to ! nor?-ea/ across ,=f>%ire1 & passes out to sea nor? ( ,montrose4 ,?r\gh ! ,o*il *a9 ! fold runs obliquely 9 a s\?-we/]ly direction1 until x is truncat$ by ! great fault :i* lets d[n ! ,clackmannan coal-field4 ,! total traceable l5g? ( ?is anticl9e is ?us ab\t sixty miles4 ,x flatt5s d[n t[>ds ! s\?-we/2 consequ5tly ! rocks 9 ! we/]n "p ( ! ,o*il ,hills are s g5tly incl9$ t ! same b&s may be foll[$ w9d+ r\nd ! sides ( ! valleys1 & giv+ to ! /eep declivities ! t]rac$ cont\rs to :i* allusion has already be5 made 7see ,fig4 #fh74 ,ano!r result ( ?is /ructure is t ! base ( ! volcanic s]ies is entirely conceal$ by its high] portions4 ,f an exam9ation ( ! map x w be fur!r obvi\s t ! :ole wide pla9 ( ,/ra?more--t is ! great holl[1 m ?an #hj miles long & ab\t t5 or twelve miles broad1 :i* /ret*es betwe5 ! base ( ! ,highl& m\nta9s & ! nor?-we/]n slopes ( ! ,o*il & ,sidlaw *a9--is und]la9 ) volcanic rocks ( ,l[] ,old ,r$ ,s&/one age4 ,?is pla9 lies on a broad syncl9al fold1 along ! s\?-ea/ side ( :i* ! lavas1 tuffs & conglom]ates ( ! ,o*il & ,sidlaw ,hills dip "u a ?ick accumulation ( r$ s&/one & flag/one4 ,on ! nor?-we/ side simil> lavas & tuffs rise aga9 to ! surface1 bo? on ! s\!rn side ( ! great b\nd>y faults1 & also 9 ! little bays :i* "h & !re survive on ! nor!rn side ( ! dislocations 7,fig4 #gg74 ,i h already allud$ to ^! int]e/+ relics ( ! %ore-l9e ( ,lake ,cal$onia1 & to ! fact t ?\gh !y lie uncon=mably on ! ,highl& s*i/s1 !y d n belong to ! actual basem5t memb]s ( ! ,old ,r$ ,s&/one 7ante1 p4 #bie1 & ,fig4 #gc74 ,we h se5 t bel[ ! bottom ( ! volcanic s]ies a ?ickness ( #ejjj feet ( s&/ones & %ales em]ges on ! ,/onehav5 coa/1 & yet t ev5 !re ! base ( ! :ole sy/em is n visible1 ow+ to ! effect ( ! ,highl& b\nd>y fault4 ,x is ?us evid5t t ov] ! bottom ( ,lake ,cal$onia a v ?ick deposit ( tol]ably f9e s$im5t>y mat]ial 0 spread be=e ! comm5cem5t ( ! ,o*il & ,sidlaw eruptions1--t :5 ! lavas 7 p\r$ out & ! co>se conglom]ates began to be =m$1 ^! mat]ials ov]lapp$ ! old] deposits & gradually encroa*$ ^u ! subsid+ area ( ! ,highl&s4 ,! lavas roll$ across ! floor ( ! lake & ent]$ ! successive bays ( ! nor!rn coa/-l9e1 :]e _! outly+ pat*es may /ill be se54 ,illu/ration3 ,fig4 #gg4--,section across ! ,b\nd>y-fault ( ! ,highl&s at ,gl5 ,turrit1 ,p]?%ire4 s1 ,cry/all9e s*i/s ( ! ,highl&s2 c c1 conglom]ates & s&/ones 7,l[] ,old ,r$ ,s&/one7 ) int]/ratifi$ volcanic rocks 7v v72 f1 fault4 ,f ^! facts x is cle> t to ! actually visible area ( volcanic mat]ial 9 ! ,o*il & ,sidlaw region1 & to ! anticl9al tract :5ce ! &esites h be5 remov$ by d5udation1 we h to add ! area t lies "u ! pla9 ( ,/ra?more1 :i* may be comput$ to be at lea/ #hjj squ>e miles1 mak+ a total ( probably n less ?an #acjj squ>e miles4 ,b x w be rememb]$ t practically only "o side ( ! anticl9al fold is accessible to obs]vation4 ,we _c tell h[ f> 9 a s\!rly direction ! lavas ( ! ,o*il ,hills may ext5d4 ,x is q possible t n a half ( ! total area cov]$ by ! eruptions ( ?is volcanic gr\p is n[ )9 rea*1 ei!r ( obs]vation or ( well-f\nd$ inf]5ce4 ,"o fur!r g5]al *>act]i/ic ( ?is volcanic di/rict w be obvi\s f an inspection ( ! map4 ,:ile ! ?icke/ mass ( lavas & tuffs1 ly+ t[>ds ! s\?-we/1 po9ts to ! exi/5ce ( ! mo/ active v5ts 9 t "p ( ! area1 ! actual positions ( ^! v5ts h n be5 detect$4 ,probably !y lie some:]e to ! s\? ( ! edge ( ! ,o*il *a91 "u ! tract :i* is ov]spread ) ! coal-field4 ,b o!r & possibly m9or orifices ( eruption appe> to h ris5 at irregul> int]vals t[>ds ! nor?-ea/ along ! l5g? ( ! lake4 ,?us !re are num]\s bosses ( felsitic & &esitic rocks among ! c5tral ,o*ils1 "s ( :i* may m>k ! positions ( active v5ts4 ,= "s miles to ! ea/ ( t area an int]val occurs1 m>k$ by ! pres5ce ( only a few small intrusive masses4 ,b z ! broad anticl9e ( ! ,fir? ( ,tay op5s out & all[s ! l[] or pre-volcanic memb]s ( ! ,old ,r$ ,s&/one to approa* ! surface1 ano!r gr\p ( bosses em]ges f ! l[] s&/ones & flag/ones4 ,"s ( ^! cov] a consid]able space at ! surface1 ?\gh a portion ( _! visible area may be due to lat]al extravasation f adjac5t pipes1 ! true dim5sions ( :i* are !reby obscur$4 ,"s ( ! masses are und\bt$ly sills4 ,9 ! case ( ,dundee ,law we probably see bo? ! pipe & ! sill :i* proce$$ f x2 ! prom95t1 well-def9$ hill m>k+ ! =m]1 :ile ! b& ( rock :i* /ret*es f x s\?-we/w>ds to ! %ore belongs to ! latt]4 ,! mat]ial t =ms ! bosses & sills 9 ?is neighb\rhood is g5]ally a d>k compact &esite4 ,! rock ( ,dundee ,law 0 f\nd by ,dr4 ,hat* to %[ "u ! microscope /rip$ la?-%ap$ felsp>s abundantly imb$d$ 9 a f9ely granul> gr\ndmass1 speckl$ ) granules ( magnetite1 b %[+ no unalt]$ f]ro-magnesian con/itu5ts4 ,"h & !re 9 ! same di/rict a solit>y neck may be obs]v$ fill$ ) agglom]ate 7,fig4 #gh74 ,illu/ration3 ,fig4 #gh4--,section across ! *a9 ( ! ,sidlaw ,hills1 ne> ,kilsp9die4 #a4 ,l[] ,old ,r$ ,flag/ones & ,s&/ones2 #b4 ,&esite lavas2 #c4 ,volcanic tuff2 #d4 ,volcanic conglom]ates & s&/ones2 ,n1 ,volcanic neck2 #e4 ,upp] ,old ,r$ ,s&/one "u ,c>se ( ,g[rie1 ly+ uncon=mably on ! l[] division2 f1 ,fault2 d1 ,basic dyke4 ,! v>iations 9 ! /ructure ( ! ,o*il & ,sidlaw volcanic gr\p w be mo/ easily und]/ood f a s]ies ( p>allel sections4 ,beg9n+ on ! nor?-ea/]n or ,sidlaw bran* ( ! volcanic b&1 we f9d ! arrangem5t ( ! rocks to be z is %[n 9 ! accompany+ figure#cec 7,fig4 #gh74 ,z is usually ! case 9 ?is region1 ! base ( ! volcanic s]ies is "h conceal$ by ! fault :i* br+s d[n ! ,upp] ,old ,r$ ,s&/one "u ! alluvial deposits ( ! ,c>se ( ,g[rie4 ,! total ?ickness ( ! s]ies 9 ?is section is ab\t #bejj feet4 ,! rocks consi/ ( successive %eets ( &esite ( ! famili> types1 v>y+ 9 col\r ?r\gh %ades ( blue1 purple & r$1 & 9 texture f a dull compact almo/ felsitic "* to m co>sely cry/all9e v>ieties4 ,!y are (t5 amygdaloidal1 especially 9 ! upp] & l[] portions ( ! individual fl[s4 ,!y are n infrequ5tly sep>at$ f ea* o!r by c\rses ( conglom]ate or a%y s&/one & grit4 ,( ^! int]calations f\r are ( suffici5t ?ickness & p]si/5ce to be mapp$1 & are %[n on ! ,geological ,survey ,%eet #dh4 ,! /ones 9 ! conglom]ates v>y up to blocks two feet 9 diamet]1 & consi/ *iefly ( &esites1 b include also "s p9k felsites & pieces ( gre5i% h>d5$ s&/one4 ,g5]ally !y are m or less well-r\nd$2 b occasionally !y become angul> l ^? ( volcanic agglom]ates4 ,footnote #cec3 ,?is section & ! notes accompany+ x h be5 suppli$ by ,pr(4 ,james ,geikie1 :o mapp$ ! we/]n half ( ! ,sidlaw range = ! ,geological ,survey4 ,! ea/]n half 0 mapp$ by ! late ,mr4 ,h4 ,m4 ,skae4 ,"o ( ! mo/ int]e/+ features 9 ?is section is ! neck :i* at ,ov] ,durdie rises ?r\gh ! volcanic s]ies4 ,oval 9 =m1 x measures #fcj y>ds 9 "o diamet] & #cej 9 ano!r1 & is fill$ ) p9ki% granul> tuff1 full ( &esitic lapilli & blocks4 ,a mu* small] neck ( simil> mat]ial lies ab\t #ajj y>ds fur!r to ! s\?-we/4 ,!re seems no reason to d\bt t ^! necks m>k two ( ! volcanic v5ts belong+ to a late "p ( ! volcanic hi/ory ( ! di/rict4 ,! /ructure ( ! ,sidlaw range is repeat$ among ! hills ( ea/ ,fife on ! s\!rn side ( ! great anticl9al fold4#ced ,?us a section f ne> ,newburgh on ! ,fir? ( ,tay s\?w>d to ne> ,au*t]mu*ty 9 ,/ra!d5 gives ! arrangem5t ( rocks %[n 9 ,fig4 #gi4 ,9 ?is trav]se a ?ick mass ( fragm5tal mat]ial occurs 9 ! high] "p ( ! s]ies ( volcanic rocks4 ,?\gh on ! :ole /ratifi$ & =m+ a gr\p ( conglom]ate-b$s betwe5 ! lavas1 ! mat]ial is 9 places an amorph\s agglom]ate ( volcanic blocks v>y+ 9 size up to two feet 9 diamet]4 ,^! portions %[ abundant angul> & subangul> blocks1 _m ( :i*1 aft] hav+ und]gone "s attrition1 h be5 f9ally brok5 across be=e rea*+ _! pres5t re/+-places4 ,%>ply fractur$ surfaces c be pick$ out ( ! felspa?ic a%y matrix4 ,! /ones are *iefly v>ieties ( &esite1 b !y include also p9k felsites & pieces ( "s old] f9e-gra9$ tuff4 ,footnote #ced3 ,! ea/]n "p ( ! ,o*ils 0 mapp$ = ! ,geological ,survey by ,mr4 ,h4 ,h4 ,h[ell & ,mr4 ,b4 ,n4 ,pea*4 ,illu/ration3 ,fig4 #gi4--,section across ! ,ea/]n ,o*il ,hills f ne> ,newburgh to ne> ,au*t]mu*ty4 #a4 ,l[] ,old ,r$ ,s&/ones & conglom]ates2 #b4 ,&esite lavas2 #c4 ,volcanic conglom]ates2 #d4 ,upp] ,old ,r$ ,s&/one4 ,^! fragm5tal mat]ials =m a local deposit ab\t n9e miles long1 & probably n less ?an #agjj feet ?ick4 ,!y are p>tly int]/ratifi$ ) fl[s ( &esite4 ,?\gh1 f ! r\nd$ =ms ( "s ( ! pebbles1 wave-action may be inf]r$ to h be5 conc]n$ 9 _! accumulation1 !y seem to be ma9ly due to volcanic explosions4 ,no trace1 h[ev]1 has be5 f\nd ( ! v5t f :i* ! eruptions took place4 ,n improbably its site lies some:]e to ! s\? 9 ! area n[ conceal$ "u ! ,upp] ,old ,r$ ,s&/one & ,c>bonif]\s =mations4 ,! l>ge size ( _m ( ! blocks sugge/s t !y d n lie f> f _! p>5t focus ( dis*>ge4 ,x is impossible to tell h[ mu* ( ! volcanic s]ies is "h conceal$ by ! uncon=mable ov]lap ( ! y\ng] =mations4 ,illu/ration3 ,fig4 #hj4--;,g5]aliz$ section across ! he>t ( ! ,o*il ,hills1 f ,dunn+ on ! nor? to ! ,fife ,coal-field ne> ,sal9e on ! s\?4 #a4 ,volcanic tuffs & agglom]ates2 #b4 ,&esite lavas2 #c4 ,l[] ,old ,r$ ,s&/one & conglom]ate2 #d4 ,necks ( felsitic rocks2 #e4 ,upp] ,old ,r$ ,s&/one & ,calcif]\s ,s&/ones2 #f4 ,repres5tative ( ! ,plateau lavas & tuffs ( ! ,l[] ,c>bonif]\s s]ies2 #g4 ,hurlet 7,c>bonif]\s7 ,lime/one2 #h4 ,dol]ite sill2 #i4 ,s&/ones1 %ales & coals ( ! ,c>bonif]\s ,lime/one s]ies2 #aj4 ,neck ( ! ,puy s]ies 7,c>bonif]\s72 f1 ,fault4 ,a section across ! c5tre ( ! ,o*il *a91#cee f ,dunn+ 9 ,/ra!>n to ! ,crook ( ,devon & ! ,fife ,coal-field1 gives ! /ructure :i* is g5]aliz$ 9 ,fig4 #hj4 ,at ! nor? end ! volcanic s]ies is f\nd to be gradually split up into sep>ate lava-%eets until x dips "u ! r$ s&/ones ( ,/ra!>n4 ,trac$ s\?w>ds ! rocks become entirely volcanic4 ,"s ( _! mo/ conspicu\s & int]e/+ memb]s are pale felsitic tuffs1 :i* occupy a consid]able tract ( gr\nd ab\t ,craig ,rossie1 s\?-ea/ ( ,au*t]>d]4 ,z ! dip gradually less5s ! h>d] lavas are able to spread ov] wid] tracts ( gr\nd1 capp+ ! hills & ridges1 :ile und]nea? !m ?ick masses ( tuff & conglom]ate are laid b>e 9 ! valleys4 ,a numb] ( bosses ( or?ophyre rise ?r\gh ^! rocks & are accompani$ by _m ve9s & dykes ( simil> mat]ial4 ,x is n improbable t "s ( ^! bosses1 z already sugge/$1 may repres5t v5ts4 ,!y are especially prom95t among ! hills due s\? ( ,au*t]>d]4 ,"o ( ^! em95ces1 kn[n z ! ,black ,mall]1 is compos$ ( a typical or?oclase-felsite )\t mica4 ,ano!r1 ab\t f\r & a half miles fur!r s\?1 =ms ! conspicu\s summit ( ,b5 ,%ee ov]look+ ,gl5 ,devon1 & consi/s ( a simil> rock ) a *>act]i/ic platy /ructure4 ,footnote #cee3 ,! c5tral portion ( ! ,o*ils 0 mapp$ = ! ,geological ,survey by ,mr4 ,b4 ,n4 ,pea*1 ,pr(4 ,james ,geikie1 ,pr(4 ,j4 ,"y1 ,mr4 ,r4 ,l4 ,jack & myself4 ,no necks ( agglom]ate h be5 obs]v$ 9 ?is "p ( ! *a94 ,x w be se5 f ! section t ! l[e/ visible p>ts ( ! ,o*il volcanic s]ies are "h truncat$ by a fault :i* br+s 9 ! l[] "p ( ! ,c>bonif]\s sy/em4 ,by a curi\s conjuncture1 imm$iately on ! s\? side ( ?is fault1 a b& ( tuff appe>s1 ly+ on ! plat=m ( ! ,c>bonif]\s plateau-lavas1 to be h]eaft] consid]$1 & pass+ bel[ ! well-kn[n ,hurlet seam ( ! ,c>bonif]\s ,lime/one1 :ile ?r\gh ^! /rata rises "o ( ! puys belong+ to ! second phase ( volcanic activity 9 ,c>bonif]\s "t 9 ,scotl&4 ,! be/ sections to %[ ! nature & sequ5ce ( ! volcanic s]ies ( ! ,o*il ,hills are to be obs]v$ at ! we/ end ( ! *a94 ,b z ! :ole succession ( rocks _c conv5i5tly be obta9$ along "o l9e1 x is bett] to make sev]al trav]ses1 />t+ 9 ea* case f a kn[n horizon4 ,9 ?is way1 by means ( ?ree p>allel sections1 we may obta9 ! :ole s]ies ( lavas & tuffs 9 cont9u\s ord]4 ,! fir/ l9e ( section />ts 9 ! l[e/ "p ( ! tuffs repres5t$ at ! bottom ( ! gr\p 9 ,fig4 #hj1 & runs up to ! fir/ ?ick a%y int]calation among ! lavas4 ,foll[+ ?is b$ s\?-we/w>d to ! ,burn ( ,sorr[1 we make f t horizon a second trav]se across ! /rike to ! summit ( ,k+'s ,seat ,hill 7#baaa feet above ! sea71 :]e we meet ) a well-m>k$ lava :i* c be trac$ s\?-we/w>ds1 gradually desc5d+ ! s\!rn esc>pm5t ( ! hills until x rea*es ! b\nd>y fault ne> ! village ( ,m5/rie4 ,/>t+ aga9 f ?is def9ite horizon1 we take a ?ird l9e across ! top ( ,dumyat 7#acgc feet7 to ! pla9 ( ,%]iffmuir1 & !re pass beyond ! volcanic s]ies into ! ov]ly+ r$ s&/ones4 ,arrang$ ?us 9 cont9u\s v]tical sequ5ce ! succession is f\nd to be z repres5t$ 9 ,fig4 #ha4 ,! total ?ickness ( volcanic mat]ial am\nts to m ?an #fejj feet4 ,illu/ration3 ,fig4 #ha4--;,diagram ( ! volcanic s]ies ( ! ,we/]n ,o*il ,hills4 ,! b&s ) v]tical l9es are v>i\s lavas 7a72 ! tuffs & volcanic breccias are %[n by ! dott$ b&s 7b72 ! upp]mo/ portion ( ! section above ! la/ ?ick gr\p ( lavas consi/s ( conglom]ates & s&/ones 7c7 ) a %eet ( lava4 ,9 ?is va/ pile ( volcanic ejections ! lavas are almo/ entirely &esites ( ! usual *>act]s4 ,!y include _m slaggy & amygdaloidal v>ieties1 "s beautiful porphyries ) l>ge tabul> felsp>s1 likewise ! res9\s or glassy v>iety already ref]r$ to z occurr+ above ,air?rey ,ca/le4 ,_! upp] & "u surfaces %[ ! same /ructure z already describ$ 9 ^? ( ! coa/-sections 9 ! ,montrose tract4 ,!y include also m acid lavas1 l ! pale p9k decompos+ felsites ( ! ,p5tl& ,hills4 ,! tuffs & conglom]ates occur on _m plat=ms ?r\gh\t ! succession ( lava-%eets4 ,!y =m ! l[e/ visible "p ( ! :ole volcanic s]ies1 b !y are mo/ abundant t[>ds ! top1 & are be/ display$ at ! we/]n end ( ! hills4 ,9 ,dumyat !y =m a conspicu\s feature4 ,! :ole ( t hill consi/s ( a con/ant alt]nation ( lavas 7*iefly slaggy &esites1 b includ+ also "o felsitic fl[7 ) b&s ( co>se & f9] tuff & volcanic conglom]ate4 ,! greate/ cont9u\s mass ( ?is fragm5tal mat]ial is #fjj or #gjj feet ?ick4 ,f ! extraord9>y size ( its includ$ blocks x obvi\sly mu/ h be5 =m$ ( a%es1 /ones & huge pieces ( lava eject$ f "s v5t 9 ! ne> neighb\rhood4 ,"s ( ! individual blocks 9 ?is mass are z l>ge z a ,highl& cr(t]'s cottage4 ,! upp]mo/ lavas ( ,dumyat dip "u a /ill high] s]ies ( co>se volcanic conglom]ates entirely made up ( &esitic debris & rea*+ a ?ickness ( ab\t #ajjj feet4 ,?is enorm\s accumulation 0 probably due p>tly to ! abrasion ( expos$ cones & lava-ridges1 & p>tly to volcanic dis*>ges ( fragm5t>y mat]ials4 ,yet x is wor?y ( note t ev5 amid/ ^! evid5ces ( ! mo/ vigor\s volcanic activity we h also pro(s ( quiet s$im5tation & traces ( ! fi%es t liv$ 9 ! wat]s ( ! lake4 ,?is p>ticul> zone ( co>se conglom]ate z x ext5ds 9 a s\?-we/]ly direction becomes f9]1 & its upp] "p passes into a *ocolate-col\r$ s&/one :i* has be5 qu>ri$ at ,wolfe's ,hole1 ,we/]ton1 ,bridge ( ,allan1 at a di/ance ( ab\t ?ree miles f :]e ! l9e ( section runs1 :i* is embodi$ 9 ! diagram1 ,fig4 #ha4 ,x 0 f ?is locality t ! specim5s ( ,eucephalaspis1 ,pt]aspis & ,scaphaspis 7 obta9$ :i* 7 describ$ by ,pr(essor ,ray ,lanke/]4#cef ,footnote #cef3 ,palontographical ,society1 vols4 xxi4 7#ahfg7 & xxiii4 7#ahfi74 ,above ! la/-nam$ ?ick gr\p ( co>se volcanic conglom]ates a solit>y %eet ( d>k slaggy &esite may be obs]v$4 ,?is lava is !n ov]la9 by ! great dep? ( *ocolate-col\r$ & r$ s&/ones & m>ls ( ! pla9 ( ,/ra?more 7c 9 ,fig4 #ha74 ,nev]!less a few hundr$ feet up 9 ^! s$im5t>y deposits we meet ) yet "o fur!r ?9 %eet ( lava--! la/ kn[n eruption ( ! long volcanic hi/ory ( ?is di/rict4 ,be=e quitt+ ! ,o*il range ,i may ref] to ! evid5ce !re obta9able z to ! horizontal ext5t ( sep>ate %eets ( lava4 ,! we/]n end ( ?is range af=ds great facilities = foll[+ out individual b$s ( &esite along ! b>e t]rac$ front ( ! great esc>pm5t4 ,?us1 ! easily recognizable porphyrite :i* caps ,k+'s ,seat ,hill1 above ,tillic\ltry 7see ,fig4 #fh71 c be trac$ w9d+ along ! hill-slopes until x desc5ds to ! pla91 & is !n lo/ "u ! great fault1 at ! foot ( ,dumyat--a di/ance ( m ?an six miles4 ,!re is1 !re=e1 no difficulty 9 suppos+ t f ! ,o*il l9e ( v5ts /reams ( lava %\ld h roll$ along ! floor ( ! lake across to ! base ( ! ,highl& slopes1 #aj or #ab miles di/ant4 ,we _c tell1 ( c\rse1 :e!r any buri$ v5ts lie bel[ ! pla9 ( ,/ra?more1 b c]ta9ly no unque/ionable trace ( v5ts has yet be5 f\nd among ! cry/all9e rocks along ! bord]s ( ! ,highl&s4#ceg ,footnote #ceg3 ,allusion has already be5 made to ! possible connection ( ! y\ng] ,highl& granites ) ! volcanic s]ies ( ! nor?-ea/]n "p ( ,lake ,cal$onia2 also to ! occurr5ce ( isolat$ masses ( breccia pi]c+ ! cry/all9e s*i/s ne> ,lo* ,lomond 7ante1 p4 #bgb74 ,ref]5ce has already be5 made to ! comp>ative sc>city ( sills 9 ?is region1 & to ! occurr5ce ( ! acid gr\p ( ,l9tra!n porphyry & ! m basic %eets betwe5 ! ,fir? ( ,tay & ,=f>4 ,?is sc>city no d\bt arises 9 "p f ! ext5t to :i* ! rocks t und]lie ! volcanic s]ies are conceal$4 ,yet x is notewor?y t along ! coa/-section ( ^! rocks ne> ,/onehav5 h>dly any intrusive %eets are to be se54 #c4 ,! ,arran & ,cantyre ,c5tre ,x is un=tunate t ! ,o*il *a9 %\ld be brok5 across & buri$ "u y\ng] =mations at ! v place :]e "s ( ! mo/ int]e/+ v5ts 9 ! :ole area ( ! ,old ,r$ ,s&/one might h be5 look$ =4#ceh ,we h to pass we/w>ds across ! ,fir? ( ,clyde to ! ,isle ( ,arran be=e we aga9 meet ) rocks ( ! same age & "*4 ,footnote #ceh3 ,! ,o*il area is n ! only example ( ! abrupt t]m9ation ( a volcanic b& ne> its c5tre ow+ to faults or ov]laps4 ,! sudd5 disappe>ance ( ! ,p5tl& lavas & tuffs on ! nor!rn side ( ! ,braid ,hills is ano!r /rik+ illu/ration4 ,9 ! c\rse ( ! rec5t "w ( ! ,geological ,survey 9 t isl&1 ,mr4 ,w4 ,gunn has discov]$ t ! ,l[] ,old ,r$ ,s&/one includes "s int]/ratifi$ volcanic rocks on ! nor? side ( ,nor? ,gl5 ,sannox1 & he has suppli$ me ) ! foll[+ notes reg>d+ !m4 ,! area 9 :i* ! volcanic int]calations occur is mu* fault$ & only a "p ( x has be5 mapp$ 9 detail1 b ! position ( ! int]b$d$ igne\s rocks is q cle>4 ,! ,old ,r$ ,s&/one "h consi/s ( ?ree di/9ct memb]s1 ! l[e/ ( :i* is made up ( co>se1 well-r\nd$ conglom]ates1 alt]nat+ ) s&/ones & purple mud/ones4 ,above ?is1 & app>5tly uncon=mable to x1 is a middle s]ies ( light col\r$ conglom]ates & s&/ones1 ! pebbles 9 :i* are ma9ly ( qu>tz4 ,f9ally comes an upp] s]ies ( r$ s&/ones & conglom]ates1 :i* occupy ne>ly ! :ole ( ! coa/ section1 & x is ?is s]ies :i* has g5]ally be5 tak5 z ! typical ,old ,r$ ,s&/one ( ! isl&4 ,! volcanic s]ies is int]calat$ betwe5 ! middle & upp] divisions giv5 above1 & may be se5 9 sev]al places on ! hillside betwe5 ! %eph]d's h\se at ,nor? ,sannox & ,laggan4 ,x consi/s ma9ly ( old lava-b$s ( a dull r$di% or purpli% col\r1 (t5 s(t1 & 9 places mu* decompos$4 ,x seems basic 9 "*4 ,a specim5 f ne> ! ,fall5 ,rocks1 exam9$ by ,mr4 ,teall1 0 f\nd to be too mu* alt]$ = precise det]m9ation1 b 0 probably a basalt orig9ally4 ,^! rocks d n occur on ! coa/4 ,9 ! s\!rn extremity ( ,cantyre "s important relics ( ! volcanic rocks ( ! ,l[] ,old ,r$ ,s&/one h be5 rec5tly detect$ & mapp$ = ! ,geological ,survey by ,mr4 ,r4 ,g4 ,symes4#cei ,?is division ( ! sy/em has be5 asc]ta9$ by him to be ext5sively develop$ to ! s\? ( ,campbelt[n1 & to include "s small b int]e/+ rema9s ( ! volcanic action :i* 0 s m>k$ a feature 9 ! areas ( ,lake ,cal$onia1 ly+ fur!r to ! ea/4 ,to ! /ud5t ( volcanic geology1 inde$1 ?is small tract at ! extreme s\!rn end ( ,argyll%ire has a peculi> int]e/1 = 9 no o!r "p ( ! ,briti% ,isles h ! ph5om5a ( ! eruptive v5ts ( ! ,l[] ,old ,r$ ,s&/one be5 m admirably laid b>e4 ,n only are !re necks 9 ! int]ior l t repres5t$ 9 ,fig4 #hb2 b o!rs h be5 dissect$ by ! waves along ! s\!rn %ore1 & _! relations to ! deposits ( fragm5t>y mat]ial %[]$ ov] ! bottom ( ! lake h be5 m or less cle>ly expos$4 ,footnote #cei3 ,! late ,pr(4 ,james ,nicol publi%$ 9 #aheb an acc\nt ( ! geology ( ! s\!rn portion ( ,cantyre4 ,he gr\p$ all ! igne\s rocks ( ! di/rict z "o s]ies1 :i* he reg>d$ z lat] ?an ! ,coal-=mation & possibly ( ! same age z ^? ( ! nor?-ea/ ( ,irel&4 ,he made no di/9ction betwe5 ! ,l[] ,old ,r$ ,s&/one & ! y\ng] uncon=mable conglom]ates 7,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 viii4 7#aheb71 p4 #djf74 ,illu/ration3 ,fig4 #hb4--,view ( ,cnoc ,g>bh1 ,s\!nd1 ,campbelt[n4 ,a volcanic neck ( ,l[] ,old ,r$ ,s&/one age1 ab\t #djj y>ds wide 9 its long] diamet]4 ,at ,keil ,po9t1 a little to ! ea/ ( ! mo/ s\!rly headl& ( ! ,mull ( ,cantyre1 "s r$di% & purpli% highly felspa?ic s&/ones 7a 9 ,fig4 #hc7 dipp+ t[>ds ! ea/ are f\nd to pass upw>d into co>se volcanic breccias 7b71 :i*1 foll[$ ea/w>ds1 lose almo/ all trace ( /ratification1 & are !n abruptly succe$$ by a neck ( co>se agglom]ate 7c7 measur+ #be y>ds f nor? to s\?1 :]e its limits c be se51 & at lea/ #ab y>ds f we/ to ea/4 ,x is h>dly possible to di/+ui% betwe5 ! breccias to ! we/ & ! agglom]ate ( ! neck1 except by ! rude b$d+ ( ! =m] :i* pass d[n into ! well-b$d$ s&/ones4 ,! agglom]ate is a ?or\ghly volcanic rock4 ,! mat]ials consi/ *iefly ( angul> blocks ( a pale purpli% or lilac highly porphyritic mica-porphyrite1 ) l>ge :ite felsp>s & hexagonal tables ( black mica4 ,^! blocks might sometimes be mi/ak5 = slags f _! cav]n\s1 wea!r$ surfaces1 b ?is r\gh aspect is f\nd on exam9ation to be due to ! decay ( _! felsp>s4 ,illu/ration3 ,fig4 #hc4--,section ( volcanic s]ies on bea*1 ,s\!nd1 ,campbelt[n4 a1 ,f9e r$di% & purpli% highly felspa?ic s&/ones1 l>gely compos$ ( porphyry-debris & pass+ up into co>se breccias2 b1 volcanic breccias1 co>se & only rudely /ratifi$1 =m$ ( blocks ( porphyry1 s&/one f9e tuff & &esite1 toge!r ) wat]-worn qu>tzite pebbles d]iv$ f "s conglom]ate2 c1 co>se un/ratifi$ agglom]ate =m+ a neck4 ,p]haps ! mo/ s+ul> feature among ! cont5ts ( ?is neck is ! numb] ( well-r\nd$ & smoo!d pebbles & b\ld]s ( qu>tzite4 ,^! are disp]s$ at r&om ?r\gh ! mass1 & are (t5 plac$ on end4 ,!re c be no d\bt t !y are wat]-worn /ones1 b ! contra/ ( _! smoo? surfaces & r\nd$ =ms ) ! r\gh angul> blocks ( igne\s mat]ial is s /rik+ z to lead at once to ! conclusion t !y _c h acquir$ _! wat]-worn "* 9 ! deposit :]e !y n[ lie4 ,_! positions & _! occurr5ce ) eject$ volcanic blocks sugge/ t !y too 7 dis*>g$ by volcanic explosions4 ,!y s exactly resemble ! qu>tzite b\ld]s & pebbles 9 ! neighb\r+ ,old ,r$ ,conglom]ates t !re c be little hesitation 9 reg>d+ !m z d]iv$ f ^! conglom]ates4 ,!y seem to me to h come f a l[] "p ( ! ,old ,r$ ,s&/one1 :i* 0 %att]$ by volcanic en]gy ei!r be=e ! conglom]ates 7 firmly consolidat$ or aft]w>ds by su* viol5t explosions z s]v$ to sep>ate ! pebbles f ! matrix ( ! rock4 ,!re occur also 9 ! agglom]ate blocks ( f9e tuff & a%y s&/one sometimes f\r feet long1 & (t5 /uck on end1 %[+ t ! deposits ( e>li] eruptions 7 brok5 up dur+ ! drill+ ( ?is little v5t4 ,a few hundr$ y>ds fur!r ea/ a l>g] neck rises on ! bea*1 imm$iately to ! s\? ( ! old ,celtic *apel ( ,/4 ,columba4 ,x consi/s also ( exce$+ly co>se agglom]ate1 ) &esite blocks ?ree & f\r y>ds 9 diamet]4 ,x is ab\t #abe y>ds broad f ea/ to we/1 on :i* sides x is se5 to be flank$ by co>se volcanic breccias & conglom]ates1 resembl+ 9 composition ! mat]ials ( ! neck1 b %[+ an increas+ly def9ite /ratification z !y are trac$ ea/w>d 9 ! asc5d+ succession ( deposits4 ,foll[+ ! section 9 /ill ! same ea/]ly direction along ! coa/1 we f9d t b&s ( f9e felspa?ic s&/one1 m>k+ probably int]vals ( quiesc5ce1 are aga9 & aga9 succe$$ by co>se brecciat$ conglom]ates ( igne\s mat]ials1 :i* may be inf]r$ to h be5 due to a r5ewal ( viol5t eruptions4 ,by degrees ! evid5ce ( /ratification & ( attrition among ! volcanic mat]ials becomes m pron\nc$ z ! asc5d+ section is foll[$2 blocks ( &esite1 ev5 #ah in*es or two feet 9 diamet]1 assume well-roll$1 r\nd$1 wat]-worn =ms1 l ! pebbles ( qu>tzite associat$ ) !m1 & ev5tually ! /rata return to ! usual aspect ( ! conglom]ates ( ! di/rict4 ,i h nev] se5 any:]e bett] pro(s ( volcanic explosions1 contemporane\s ) a gr\p ( /rata1 & ( ! di/ribution ( volcanic fragm5t>y mat]ial r\nd ! v5ts4 ,a fur!r po9t ( mu* int]e/ is ! additional evid5ce furni%$ by ?is %ore-section ( consid]able wave-action dur+ ! accumulation ( ! co>se conglom]ates4 ,to give to blocks ( porphyrite two feet 9 diamet] a smoo!d & r\nd$ =m mu/ h requir$ ! action ( wat] 9 consid]able agitation4 #d4 ,! ,ul/] ,c5tres ,f ! volcanic breccias & conglom]ates ( ! ,mull ( ,cantyre to ! coa/ ( ,antrim 9 a /raight l9e is a di/ance ( little m ?an tw5ty miles4 ,on a cle> day ! ,old ,r$ ,s&/one ( ,cross ,slieve1 & ! range ( cliffs 9 :i* x abruptly desc5ds to ! sea betwe5 ,cu%5dall & ,cu%5dun1 c be di/9ctly se5 f ! ,argyll%ire %ore4 ,! geologi/ :o passes f ! ,scotti% to ! ,iri% sections _c fail to be impress$ ) ! resemblance ( ! rocks 9 ! two c\ntries1 & ) ! p]si/5ce ( ! types ( conglom]ate 9 ,lake ,cal$onia4 ,a picturesque section has be5 laid b>e betwe5 ! ,coa/gu>d ,/ation s\? ( ,cu%5dall & ,cu%5dun ,bay4#cfj ,at ! s\? side ( ! little inlet ( ,cu%5dall1 a compact dull qu>tz-porphyry is expos$ 9 crags along ! %ore4 ,?is rock ranges 9 col\r f d>k br[n & purple to pale-gre5 & buff4 ,its texture also v>ies1 z well z ! proportion ( its felsp>-cry/als & qu>tz-blebs4 ,"s p>ts h a cav]n\s /ructure1 l t ( an amygdaloid1 ! small globul> cavities be+ fill$ ) gre5 decomposition products4 ,footnote #cfj3 ,= descriptions ( ?is di/rict see ,j4 ,bryce1 ,proc4 ,geol4 ,soc4 i4 7#ahcd7 p4 #cif1 v4 7#ahcg7 p4 #fi2 ,j4 ,kelly1 ,proc4 ,roy4 ,iri% ,acad4 x4 7#ahfh71 p4 #bci4 ,! area is conta9$ 9 ,%eet #ad ( ! ,geological ,survey ( ,irel&1 & 0 mapp$ by ,mr4 ,a4 ,m',h5ry & describ$ by him 9 ! accompany+ ,explanatory ,memoir 7#ahhf71 pp4 #ab1 #be4 ,! /ratigraphical relations ( ?is rock are n q cle>1 b x is c]ta9ly old] ?an ! ,old ,r$ conglom]ates :i* lie to ! nor? ( x1 = ^! are l>gely made up ( its fragm5ts4 ,! matrix ( ^! detrital masses consi/s ma9ly ( ! comm9ut$ debris ( ! porphyry4 ,! pebbles include all ! v>ieties ( t rock1 & are tol]ably well-r\nd$4 ,!re is no di/9ct evid5ce ( volcanic action among ^! conglom]ates4 ,!y resemble1 h[ev]1 _m ( ! conglom]ates 9 ! ,midl& ,valley ( ,scotl&1 :i*1 z 9 ! case ( ^? on ! ,=f>%ire & ,k9c>d9e%ire coa/1 are 9 great "p made ( ! detritus ( &esitic lavas4 ,! ,cu%5dall rocks become co>s] z !y are trac$ nor?w>ds into l[] memb]s ( ! s]ies1 :ile at ! same "t ! proportion ( porphyry-debris 9 _! con/itution dim9i%es1 & mat]ials f ! metamorphic s]ies take its place4 ,?us at ,cu%5dun ! p]c5tage ( qu>tz-pebbles rises to #gj or #hj4 ,^! blocks1 ( all sizes up to two feet or m 9 diamet]1 are admirably r\nd$ & smoo!d1 l ^? 9 ! ,/onehav5 section & ^? among ! conglom]ates at ! s\? end ( ,cantyre4 ,fragm5ts ( ! porphyry1 h[ev]1 /ill cont9ue to appe>1 & ! matrix %[s an admixture ( ! f9] detritus ( t rock4 ,i may rem>k 9 pass+ t no conglom]ates ( ! ,old ,r$ ,s&/one %[ m /rik+ly ?an ^! at ,cu%5dun ! effects ( me*anical cru%+ subsequ5t to deposition & consolidation4 ,9 _m p>ts ( ! rock x is h>dly possible to f9d a r\nd$ block t has n be5 fractur$4 ,"s ( !m1 inde$1 may be se5 cut into half a doz5 slices1 :i* h be5 pu%$ ov] ea* o!r "u ! /ra9 ( /rong lat]al or v]tical pressure4 ,9 ! int]ior ( ! c\ntry1 aft] pass+ ov] ! broad ,t]ti>y basaltic plateau ( ,antrim1 we come ^u a l>ge area ( ,l[] ,old ,r$ ,s&/one 9 ,tyrone4 ,x /ret*es f ,pom]oy to ,lo* ,erne1 a di/ance ( ab\t #cj miles1 & is ab\t #ab miles broad4 ,9 li?ological "* ! /rata ( ?is tract exactly resemble p>ts ( ! deposits ( ,lake ,cal$onia 9 ,c5tral ,scotl&4 ,!y include also a volcanic s]ies :i*1 d[n to ! smalle/ po9ts ( detail1 may be p>allel$ 9 ! si/] isl&4#cfa ,?is int]e/+ we/w>d prolongation ( ! volcanic record consi/s ( a numb] ( outly+ pat*es conf9$ to ! ea/]n "p ( ! di/rict4 ,footnote #cfa3 ,?is area ( ,old ,r$ ,s&/one is repres5t$ on ,%eets #cc1 #cd1 #de & #df ( ! ,geological ,survey ( ,irel&1 & ! igne\s rocks are describ$ 9 ! ,memoirs on ,%eets #cc 7#ahhf1 p4 #ag7 by ,mr4 ,j4 ,r4 ,kilroe1 & #cd 7#ahgh1 p4 #af7 by ,mr4 ,j4 ,nolan4 ,! l>ge/ ( ^! pat*es lies to ! s\? ( ,pom]oy1 :]e x =ms a l9e ( hills ab\t f\r miles long1 & cov]s an area ( "s five squ>e miles4 ,! rocks consi/ ( successive %eets ( &esite-lavas4 ,^!1 z a rule1 are n m>k$ly cellul>1 ?\gh !y include "s *>act]i/ic amygdaloids4 ,a di/+ui%+ feature ( "s ( ! %eets is _! rem>kably well-develop$ fl[-/ructure4 ,?us on ,s5try ,box1 at ! nor?-we/]n end ( ! ridge1 ! fissility result+ f ?is /ructure s p]fectly divides ! rock into p>allel flags t ! mat]ial might easily be mi/ak5 = a b$d$ rock4 ,:]e ?is /ructure has be5 produc$ 9 a cellul> lava1 ! cavities h be5 drawn out & flatt5$ 9 ! direction ( fl[4 ,i h n obs]v$ true tuffs 9 any ( ! sections trav]s$ by me 9 ?is di/rict4 ,b ! conglom]ates furni% abundant evid5ce ( ! contemporane\s outp\r+ ( ! lavas4 ,?us1 9 a brook a little we/ ( ,recla91 five miles s\? ( ,pom]oy1 ! section %[n 9 ,fig4 #hd may be se54 ,at ! base lies a co>se conglom]ate 7a7 l>gely compos$ ( &esite-debris1 ! /ones be+ "h1 z else:]e 9 ! di/rict1 well r\nd$4 ,!n comes a s]ies ( gre5 & r$di% highly-felspa?ic s&/ones 7b71 foll[$ by an exce$+ly co>se conglom]ate 7c71 =m$ ma9ly ( ! debris ( &esites1 especially lumps ( slag4 ,"s ( ! /ones measure #ah in*es 9 diamet]1 & all are well wat]-worn4 ,imm$iately ov] ?is mass ( detritus lies ! l[e/ %eet ( &esite-lava 7d74 ,illu/ration3 ,fig4 #hd4--,section ( ! base ( ! volcanic s]ies1 ,recla91 five miles s\? ( ,pom]oy4 ,"s sections visible 9 ! neighb\rhood ( ,omagh af=d fur!r evid5ce ( volcanic action at ! "t ( ! deposition ( ! ,old ,r$ ,s&/one ( ?is region4 ,at ,f>m ,hill1 a little to ! ea/ ( ! t[n1 felspa?ic s&/ones & breccias enclose angul> & subangul> pieces ( v>i\s &esites1 & occasionally ev5 pieces ( tuff4 ,ne> ^! /rata a decay$ &esite occurs 9 ! b$ ( a /ream1 & a fre%] v>iety is qu>ri$ at ,f>m ,hill4 ,a little fur!r s\? ano!r v>iety ( &esite is expos$ 9 two qu>ries at ,rec>son ,meet+-,h\se--a f9e granul> purpli%-grey rock1 ) abundantly-diffus$ hmatite pseudomorphs1 probably aft] a pyrox5e1 & sometimes /rongly amygdaloidal4 ,illu/ration3 ,fig4 #he4 ,section ( %ales & breccias at ,crossna ,*apel1 nor?-ea/ ( ,boyle4 a a1 ,gre5 & grey %ales2 b b1 gre5 & grey h>d s&/ones & grits1 "s b&s /rongly felspa?ic2 c1 f9e compact felspa?ic breccia1 ) angul> *ips ( diff]5t felsites & &esites1 etc4 ,!re c ?us be no d\bt t ?is region ( ,ul/] includ$ sev]al c5tres ( volcanic activity dur+ ! deposition ( ! r$ s&/ones & conglom]ates1 & t ! lavas & volcanic conglom]ates belong$ to precisely ! same types z ^? ( ! same geological age :i* occur s abundantly 9 ,scotl&4 ,fur!r s\?-we/1 ne> ,boyle1 9 ! c\nty ( ,roscommon1 c]ta9 curi\s felspa?ic breccias 9 ! ,old ,r$ ,s&/one h be5 mapp$ z fel/one4#cfb ,s f> z ,i h be5 able to exam9e !m1 h[ev]1 !y are entirely ( fragm5tal orig94 ,!y conta9 pieces ( &esitic & felsitic rocks1 ) fragm5ts ( devitrifi$ glass1 :i* und\bt$ly po9t to ! occurr5ce ( volcanic eruptions dur+ _! deposition1 ?\gh no tuffs & lavas appe> to crop out 9 ! n>r[ /rip ( ! =mation !re expos$4 ,footnote #cfb3 ,see ,%eet #ff ,geological ,survey ( ,irel&1 & ,explanation to t %eet 7#ahgh71 p4 #ae4 ,! rocks 7 previ\sly describ$ by ,jukes & ,foot1 ,j\rn4 ,roy4 ,geol4 ,soc4 ,irel&1 vol4 i4 7#ahff71 p4 #bdi4 ,! accompany+ section 7,fig4 #he7 may be se5 on ! hills to ! nor?-ea/ ( ,boyle4 ,:]e qu>ri$ on ! road-side to ! nor? ( ,boyle1 ! s]ies ( deposits "h repres5t$ conta9s a b$ ( co>se & exce$+ly compact breccia1 simil> to t j ref]r$ to1 b conta9+ angul> & subangul> fragm5ts six or eight in*es long4 ,! jo9ts ( ^! compact /rata are rem>kably %>p & clean cut1 s t :]e ! fragm5t>y "* is n v di/9ct ! rocks might easily be mi/ak5 on casual inspection = felsites4 ,,*apt] ,,xx ,,volcanoes ,,( ,,! ,,l[] ,,old ,,r$ ,,s&/one ,,( ,,lake ,,cal$onia--cont9u$ ,! ,s\!rn ,*a9--,! ,p5tl& ,volcano--,! ,bigg> ,c5tre--,! ,duneaton ,c5tre--,! ,ayr%ire ,volcanoes4 ,we h n[ to note ! lead+ features ( ! gr\ps ( volcanic rocks di/ribut$ along ! s\!rn l9e ( v5ts already describ$4 ,at lea/ f\r diff]5t c5tres ( eruption may be obs]v$ on t l9e4 ,_! mutual limits are1 on ! :ole1 bett] se5 ?an ^? ( ! nor!rn l9e1 = f ! nor?-ea/]n to ! s\?-we/]n end ( ! volcanic belt ! ,old ,r$ ,s&/one & rocks ( old] date are almo/ cont9u\sly expos$ at ! surface4 ,! encroa*+ areas ( ,c>bonif]\s =mations 9 ,lan>k%ire & ,ayr%ire int]rupt b d n entirely conceal ! volcanic tracts4 ,,ii4 ,,! ,,s\!rn ,,*a9 ,,( ,,volcanoes ,,9 ,,lake ,,cal$onia #e4 ,! ,p5tl& ,volcano ,beg9n+ at ! nor?-ea/ end ( ! l9e we fir/ come ^u ! classic area ( ! ,p5tl& ,hills1 = ! /udy ( :i* ! geologi/ is prep>$ by ! admirable description ( ,*>les ,macl>51#cfc & ! e>li] geogno/ical pap]s ( ,jameson4#cfd ,! area mapp$ 9 detail is repres5t$ 9 ,%eet #cb ( ! ,geological ,survey ( ,scotl&1 publi%$ 9 #ahei1 & describ$ 9 ! ,memoir accompany+ t %eet4 ,footnote #cfc3 ,a ,sket* ( ! ,geology ( ,fife & ! ,lo?ians1 #ahci4 ,! detail$ descriptions 9 ?is "w are accompani$ ) a map & two plates ( sections4 ,9 ! map all ! volcanic rocks are repres5t$ by "o col\r4 ,9 ! sections ! b$d+ ( ! rocks is %[n1 & an indication is giv5 ( ! succession ( _! *ief v>ieties4 ,footnote #cfd3 ,see specially ,mem4 ,w]n]ian ,soc4 vol4 ii42 also ,mac,knight 9 vol4 i4 ,! acc\nt ( ! ,p5tl& ,hills by ,hay ,cunn+ham 9 vol4 vii4 7#ahch7 is cle> b brief4 ,:5 9 ^! e>ly days ,i survey$ ?is gr\nd ,i f\nd x extremely difficult to und]/&4 ,be+ !n myself b a beg9n] 9 geology1 & ! /udy ( old volcanic rocks n hav+ yet advanc$ mu* beyond its elem5t>y /age1 ,i fail$ to dis5tangle ! puzzle4 ,n until aft] m ?an tw5ty ye>s1 l>gely sp5t 9 ! inve/igation ( volcanic rocks else:]e1 _h ,i an opportunity ( resurvey+ ! gr\nd & br++ to its r5ew$ /udy a wid] k ( ! subject4 ,a new edition ( ! map 0 issu$ 9 #ahib1 & ,i %all "h embody 9 my summ>y ! *ief results obta9$ 9 ! c\rse ( ?is revision4 ,! mo/ obvi\s features 9 ! ,p5tl& area are ! m>k$ developm5t ( ! volcanic rocks at ! nor? end ( ! *a91 _! rapid dim9ution & disappe>ance t[>ds ! s\?-we/1 ! abrupt truncation ( ! b$d$ masses by ! l9e ( craggy declivity :i* =ms ! nor!rn t]m9ation ( ! hills1 & la/ly1 ! cont9uation ( ! volcanic s]ies nor?w>d 9 a totally diff]5t =m 9 ! l[] em95ces ( ! ,braid ,hills4 ,! l5g? ( ! :ole volcanic tract is ab\t elev5 miles2 its bread? at ! wide/ nor!rn "p is f\r miles1 b f t maximum x dw9dles s\?w>ds & dies out 9 sev5 miles4 ,its we/]n side is 9 l>ge measure flank$ by ! uncon=mable ov]lap ( ! ,upp] ,old ,r$ ,s&/one & ,l[] ,c>bonif]\s =mations1 ?\gh 9 "s places ! base ( ! volcanic s]ies is se54 ,! ea/]n b\nd>y is *iefly =m$ by a l>ge fault :i* br+s d[n ! ,c>bonif]\s rocks aga9/ ! volcanic ridge4 ,at ! nor!rn end1 ?is ridge plunges uncon=mably "u ! ,upp] ,old ,r$ ,s&/one ( ! s\!rn outskirts ( ,ed9burgh4 ,! b$d$ aspect ( ! truncat$ end ( ! ,p5tl& *a91 z se5 f ! nor?1 has be5 already allud$ to 7p4 #bha74 ,! rocks dip to ! s\?-ea/1 h5ce ! l[] memb]s ( ! s]ies are to be f\nd along ! nor?-we/ side ( ! hills4 ,illu/ration3 ,fig4 #hf4--,section across ! nor? end ( ! ,p5tl& ,hills1 f ,w>klaw ,hill to ,p5tl& ,ma9s4 ,l5g? ab\t five miles4 #a4 ,upp] ,silurian grits & %ales1 n se5 :]e ! l9e ( section crosses2 #b #b4 ,&esites & diabases 9 num]\s int]/ratifi$ %eets2 #b s4 ,int]calat$ s&/ones & conglom]ates2 #c4 ,felsitic tuffs & breccias & or?ophyre %eets2 n1 ,volcanic neck2 #d4 ,l[] ,c>bonif]\s /rata ly+ uncon=mably on & ov]lapp+ ! volcanic s]ies2 #e4 ,calcif]\s ,s&/ones & ,c>bonif]\s ,lime/one s]ies br\ght d[n aga9/ ! volcanic s]ies by a fault 7f74 ,x w be notic$ f ! ,geological ,survey map t ! volcanic rocks ( ! ma9 body ( ! ,p5tl& ,hills are arrang$ 9 alt]nations ( some:at basic & m acid b&s4 ,! mo/ basic %eets are "s amygdaloidal diabases at ! bottom ( ! :ole s]ies :i* make _! appe>ance 9 ,w>klaw ,hill 7,fig4 #hf74 ,! great] numb] ( ! d>k lavas are v>ieties ( &esite1 sometimes tol]ably compact1 sometimes highly cellul> & amygdaloidal4 ,b int]/ratifi$ ) ^! are ?ick %eets ( :at us$ to be call$ clay/one1 a t]m :i* "h compris$ decay$ felsites 7or?ophyres71 & also felsitic tuffs & breccias4 ,! rem>kably acid nature ( "s ( ^! rocks has be5 already po9t$ out4 ,! total ?ickness ( ! volcanic s]ies at ! nor? end ( ! hills is ab\t #gjjj feet1 b z nei!r ! top nor ! bottom is !re visible1 x may be consid]ably great]4 ,at ^! maximum dim5sions ! rocks =m ! high sc>p$ front ( ! ,p5tl& ,hills1 :i* rises into s prom95t a feature 9 ! s\!rn l&scape ( ,ed9burgh4 ,a s]ies ( transv]se sections across ! *a9 f nor? to s\? w illu/rate its /ructure & hi/ory4 ,^! ,i %all "h describe1 res]v+ = subsequ5t consid]ation ! great v5t ( ! ,braid ,hills4 ,a section tak5 ?r\gh ! nor? end ( ! *a91 :]e ! maximum dep? ( volcanic mat]ial is expos$1 pres5ts ! arrangem5t repres5t$ 9 ,fig4 #hf4 ,x w be se5 t ! base ( ! s]ies is "h conceal$ by ! uncon=mable ov]lap ( ! ,l[] ,c>bonif]\s rocks on ! we/ side1 :ile ! top is cut (f by ! great fault :i* on ! ea/ side br+s d[n ! ,midlo?ian ,coal-field4 ,illu/ration3 ,fig4 #hg4--,view ( ! lava-esc>pm5ts ( ,w>klaw ,hill1 ,p5tl& *a91 f ! nor?-we/4 ,! ,l[] ,c>bonif]\s conglom]ates 7#d7 creep ov] ! edge & up ! slopes ( ! volcanic s]ies ( ! ,p5tl& ,hills4 ,!y conta9 abundant pebbles ( ! lavas1 & 7 evid5tly laid d[n along a %ore f :i* ! ,p5tl& rocks rose /eeply into l&4 ,?\gh ! actual base ( ! lavas is n se5 "h1 two miles fur!r to ! s\? highly-incl9$ ,upp] ,silurian %ales & mud/ones are f\nd em]g+ uncon=mably f "u ! volcanic pile1 & simil> /rata probably und]lie ,w>klaw ,hill z indicat$ 9 ! figure4 ,! ,upp] ,silurian /rata pass up into a l[] gr\p ( ! ,l[] ,old ,r$ ,s&/one1 :i* has also be5 cov]$ uncon=mably by ! volcanic s]ies4 ,9 ^! und]ly+ deposits we h evid5ce ( ! pre-volcanic accumulations ( ! lake1 :i* 7 brok5 up & tilt$ at ! beg9n+ ( ! volcanic eruptions4 ,! l[e/ lavas1 consi/+ ( well-m>k$ b$s ( diabase 7#b71 pres5t _! esc>pm5ts to ! nor?-we/ & dip into ! ris+ gr\nd1 z sket*$ 9 ,fig4 #hg4 ,_! *>act]s h be5 already notic$ 9 ! g5]al petrography ( ! ,old ,r$ ,s&/one volcanic rocks4 ,d>k solid compact portions ( !m pass rapidly into co>sely cellul> slag1 especially along ! upp] & "u p>ts ( ! sev]al %eets4 ,no tuff has be5 notic$ betwe5 ^! basic fl[s1 b "h & !re ?9 l5ticul> lay]s ( s&/one1 ly+ 9 holl[s ( ! lava-%eets1 are connect$ ) v]tical or highly-incl9$ ramify+ ve9s ( simil> mat]ial1 ) ! pla9s ( /ratification pass+ across ! bread? ( ! ve9s4 ,^! features are an exact reproduction ( ^? above describ$ 9 ,=f>%ire & ,k9c>d9e%ire4 ,! amygdales consi/ ( *alc$ony1 cry/alliz$ qu>tz & calcite4 ,torduff ,hill1 :i* rises to ! ea/ ( ,w>klaw1 consi/s ( a mass ( co>se volcanic breccia or agglom]ate 7n71 m>k$ly felsitic 9 its mat]ials4 ,x probably =ms a neck m>k+ a small volcanic v5t1 l "s o!rs at ! nor? end ( ! *a9 to be aft]w>ds ref]r$ to4 ,9 ! l[] "p ( ,capelaw ,hill1 ! next em95ce 9 an ea/]ly direction1 b$d$ &esites1 ) an int]calat$ b& ( s&/one & conglom]ate 7#bs71 appe> & pass "u rocks ( s decompos+ a k9d t no good sections ( !m are to be f\nd4 ,! hill is cov]$ ) grass1 b among ! rubbi% ( ! screes pieces ( felsite-l rocks & breccias may be obs]v$4 ,"s ( ^! blocks %[ an alt]nation ( lay]s ( felsitic breccia ) a f9e felsite-l mat]ial :i* may be a tuff4 ,^! rocks1 conspicu\s by ! light col\rs ( _! screes1 alt]nate fur!r up ) o!r d>k &esitic lavas1 & run s\?-we/w>d = ab\t five miles4 ,beyond ,capelaw ,hill1 ^u a b& ( ^! pale rocks1 comes a ?ick gr\p ( %eets ( d>k &esite1 :i* =m ! ma9 mass ( ,all]muir ,hill4 ,!y are well se5 f ! s\? side & likewise f ! nor?1 dipp+ t[>ds ! s\?-ea/ at angles ( f #ce to #dj1 & wea!r+ along ! cre/ ( ! hills into a succession ( sc>s & slopes :i* %[ ! b$d$ "* ( ! lavas4 ,at ,ca]ketton ,hill ano!r b& ( pale mat]ial =ms ! conspicu\s craggy face s famili> 9 ! aspect ( ! ,p5tl& ,hills z se5 f ,ed9burgh4 ,?is b& consi/s ( pale felsitic breccia1 & amorph\s1 compact1 mu*-decay$ rock1 reg>d+ :i* x is difficult to decide :e!r x %\ld be consid]$ z a f9e felsitic tuff1 or z a decompos$ felsite4 ,! b& is bett] se5 :5 trac$ s\?w>ds4 ,! light col\r ( its screes makes x easily foll[$ by ! eye ev5 f a di/ance along ! hill-tops & declivities4 ,on ! next hill to ! s\?-we/1 kn[n z ,ca/lelaw ,hill1 ?is pale b& ( rock is expos$ 9 a few crags & qu>ries1 & its debris1 protrud+ ?r\gh ! scanty h]bage1 slips d[n ! slopes4 ,on its nor? side ! screes display ! same felsitic breccias & compact1 decay$ felsitic rocks1 occasionally %[+ a /ructure l ! fl[-/ructure ( rhyolite4 ,! breccia :i* projects 9 blocks f ! summit ( ! hill has be5 qu>ri$ imm$iately bel[ ! cre/ on ! s\? side1 :]e x ov]lies a ?9 int]calat$ b& ( a dull1 mu*-decompos$ porphyry4 ,! breccias are compos$ almo/ entirely ( ?or\ghly acid rock-fragm5ts1 z may be judg$ f ! p]c5tage ( silica %[n to occur 9 !m4 ,^! fragm5ts v>y f ! f9e/ lapilli up to angul> pieces sev]al in*es long4 ,!y n infrequ5tly display a f9e & extremely beautiful fl[-/ructure4 ,x is ?us q c]ta9 t !re are acid breccias int]calat$ among ! m basic lavas ( ! nor!rn ,p5tl&s1 & t among ! con/itu5ts ( ^! breccias are fragm5ts ( felsite or p]haps ev5 li?oid rhyolite4 ,we may !re=e be prep>$ to f9d t actual outfl[s ( felsitic lava accompani$ ! dis*>ge ( ^! highly-silice\s tuffs4 ,un=tunately ! mann] 9 :i* ! rocks decay & conceal !mselves "u _! own debris makes x difficult to sep>ate ! und\bt$ly fragm5tal b&s f ^? :i* may be true lavas4 ,b an occasional op5+1 & "h & !re a scatt]$ loose block1 s]ve to indicate t ! two gr\ps ( rock c]ta9ly d coexi/ 9 ?is pale b&1 :i* c be foll[$ ?r\gh ! *a9 = upw>ds ( six miles until x is cut (f by ! ea/]n b\nd>y fault4 ,at ! s\?-we/ end ( ,ca/lelaw ,hill1 :]e a qu>ry has be5 op5$ above ! ,kirk ,burn1 blocks ( felsite may be obs]v$ %[+ fl[-/ructure on a l>ge scale4 ,! b&s ( v>i$ devitrification are sometimes a qu>t] ( an in* broad1 & wea!r out 9 light] & d>k] t9ts4 ,"s ( !m h reta9$ _! felsitic texture bett] ?an o!rs1 :i* h become m ?or\ghly kaol9iz$4 ,t ^! are n deceptive lay]s ( diff]5t texture 9 f9e tuffs is made q cle> by "s *>act]i/ic rhyolitic /ructures4 ,! b&s are n q p>allel1 b1 on ! contr>y1 are develop$ l5ticul>ly1 & may be obs]v$ to be occasionally puck]$1 & to be ev5 b5t back & fold$ ov] z 9 ord9>y rhyolites4 ,!re is no contortion to be obs]v$ among ! /ratifi$ tuffs ( ! hills4 ,?is irregul>ity 9 ! lay]s is obvi\sly orig9al1 & c only be due to ! fl[ ( a mov+ lava4 ,on ! ea/ side ( ,ca/lelaw ,hill1 z %[n 9 ,fig4 #hf1 dull r$di% &esites ov]lie ! pale belt ( felsitic rocks4 ,_! l[] b&s are m>k$ by ! pres5ce ( well-=m$ cry/als ( a d>k gre5 mica4 ,_! c5tral & high] portions consi/ ( porphyrites ( ! preval5t type1 bo? compact & vesicul>4 ,^! lavas cont9ue z f> z any rock c be se54 ,beyond ! b\nd>y fault1 ! ,burdieh\se ,lime/one & oil-%ales ( ! ,l[] ,c>bonif]\s s]ies are met )1 incl9$ at high angles aga9/ ! hills4 ,x is impossible to say h[ mu* ( ! volcanic s]ies has "h be5 remov$ f sight by ! dislocation4 ,if n[ we move ?ree miles fur!r to ! s\?-we/ & take a second section across ! ,p5tl& ,hills1 x w be f\nd to expose ! arrangem5t ( rocks repres5t$ 9 ,fig4 #hh4 ,at ! we/]n end ! ,upp] ,old ,r$ ,s&/ones 7#d7 & ,l[] ,c>bonif]\s s]ies 7#e7 are se5 ly+ uncon=mably on ! upturn$ edges ( ! ,upp] ,silurian %ales 7#a74 ,nor? ,black ,hill consi/s ( a l>ge intrusive %eet ( pale felsite 7,f7 t has brok5 ?r\gh ! ,silurian /rata & has 9 places ?ru/ itself betwe5 !m & ! conglom]ates ( ! ,l[] ,old ,r$ ,s&/one :i* lie uncon=mably ^u !m4 ,9 ! neighb\r+ ,logan ,burn1 at ! bottom ( ! ,habbie's ,h[e ,wat]fall1 ! felsite c be se5 inject$ into ! conglom]ate4 ,! felsitic sill ( ,nor? ,black ,hill runs = a mile & a half along ! we/]n base ( ! volcanic s]ies1 & has a bread? ( ab\t half a mile4 ,x is ! only important intrusive mass 9 ! ,p5tl& ,hills4 ,illu/ration3 ,fig4 #hh4--,section across ! ,p5tl& ,hills ?r\gh ,nor? ,black ,hill & ,scald ,law 7l5g? ab\t ?ree miles74 ,to ! s\? ( ! ,silurian %ales t lie aga9/ ! s\!rn flank ( ,nor? ,black ,hill1 pale felsitic tuffs 7#c7 occur1 :i* are a cont9uation ( ^? already ref]r$ to z runn+ s\?w>ds f ,capelaw ,hill4 ,above !m a s]ies ( &esites 7#b71 ) int]calat$ b&s ( tuff1 s&/one & conglom]ate 7#bs71 occupy ! bottom ( ! ,logan valley & "p ( ! slopes on bo? sides4 ,9 ! ?icke/ b& ( tuffs1 :i* is well-expos$ along ! road by ! side ( ! ,loganlee ,res]voir1 a gr\p ( well-b$d$ /rata occurs f less ?an an in* to a foot or m 9 ?ickness4 ,g5]ally !y are pale 9 col\r1 & are made up ( :ite felsitic detritus1 b ) a spr9kl+ ( dull purpli%-r$ fragm5ts1 & occasional l>g] r\nd$ pieces ( diff]5t &esites4 ,"s ( ! rocks might be call$ felspa?ic s&/ones4 ,o!r b&s 9 ! gr\p are d>k purpli%-r$ 9 t9t1 & consi/ ma9ly ( &esitic debris1 ) a du/+ ( :ite felsitic gra9s & fragm5ts4 ,!re w\ld ?us seem to h be5 %[]s bo? ( felsitic & ( &esitic a%es & lapilli4 ,! d>k lavas t ov]lie ! tuffs are likewise well display$ along ! same road-section4 ,!y v>y rapidly f extremely compact homog5e\s d>k blue rocks1 t wea!r ) a gre5i% cru/1 to co>se1 slaggy masses & amygdaloids4 ,illu/ration3 ,fig4 #hi4--,section f ! valley ( ! ,gutt]=d ,burn ?r\gh ,gre5 ,law & ,braid ,law to ,eight-,mile ,burn4 ,^! m basic lavas are a cont9uation ( ^? ( ,all]muir ,hill1 &1 z at t locality1 !y plunge "h also "u ! same b& ( :ite tuffs1 breccias & felsites 7#c71 :i* has be5 ref]r$ to z /ret*+ s\?w>d f ,ca]ketton ,crags4 ,?is b& mu/ "h be at lea/ #ejj feet ?ick4 ,x =ms ,scald ,law 7#ahih feet7 & ! surr\nd+ summits1 & ?us occupies ! highe/ elevations 9 ! ,p5tl& *a94 ,x dips b5ea? ! upp]mo/ gr\p ( &esites1 :i*1 z be=e1 are "h truncat$ by ! ea/]n fault 7f71 ! ,calcif]\s ,s&/ones & ,c>bonif]\s ,lime/one s]ies 7#f7 be+ ?r[n aga9/ !m4 ,a ?ird section 7,fig4 #hi71 tak5 two miles /ill fur!r s\?1 %[s a rem>kable att5uation ( ! volcanic s]ies1 & ! appe>ance ( a ?ick gr\p ( conglom]ates 7#b7 ly+ con=mably bel[ t s]ies1 b re/+ on ! upturn$ edges ( ! upp] ,silurian %ales 7#a74 ,! ?ick ,all]muir porphyrites are "h r$uc$ to a few ?9 b$s 7#c7 int]calat$ among ! conglom]ates & s&/ones1 amid/ :i* ! :ole volcanic s]ies dies out s\?w>d4 ,a detail$ section ( ! rocks expos$ on ! we/]n front ( ,braid ,law %[s ! foll[+ succession3-- ,:ite felsitic rocks ( ,braid ,law 7#d 9 ,fig4 #hi74 ,co>se conglom]ate pass+ d[n into s&/one4 ,ab\t #bj feet visible4 ,d>k &esite1 #d feet4 ,p>t+ ( yell[ felspa?ic grit1 #h or #aj in*es4 ,&esite1 #aj feet4 ,h>d felspa?ic grit1 #f feet4 ,d>k gre5 amygdaloidal &esite1 #b feet4 ,yell[ felspa?ic s&/one & grit1 #b feet4 ,d>k gre5 amygdaloidal &esite1 #f feet4 ,felspa?ic grit & r$ & br[n s&/one1 #d feet4 ,d>k &esite1 p]haps #f or #h feet4 ,great conglom]ate ) alt]nat+ c\rses ( s&/one1 rapidly increas+ 9 ?ickness s\?w>ds4 ,above ^! dw9dl+ repres5tatives ( ! nor!rn &esitic lavas comes ! cont9uation ( ! :ite b& ( tuffs & breccias ( ,ca]ketton & ,scald ,law 7#d71 :i* 9 turn dips "u ! highe/ gr\p ( &esites4 ,! ,c>bonif]\s /rata 7#e7 are br\ght 9 by ! fault 7f74 ,9 little m ?an two miles beyond ?is l9e ( section ! volcanic s]ies disappe>s1 & ! ,old ,r$ ,s&/one = a brief space consi/s only ( s$im5t>y deposits4 ,besides ! rem>kable alt]nation ( basic & acid ejections1 !re is a fur!r notable feature 9 ! geology ( ! ,p5tl& ,hills4 ,?is volcanic c5tre pres5ts u ) "o ( ! mo/ rem>kable v5ts any:]e to be se5 among ! volcanic rocks ( ,brita94 ,! full significance ( ?is feature may be/ be p]ceiv$ if we advance along ! hills f _! s\?-we/]n end4 ,z has n[ be5 made cle>1 ! volcanic mat]ials :i* beg9 ab\t ! l9e ( ! ,nor? ,esk ne> ,c>lops rapidly augm5t 9 ?ickness until1 9 a di/ance ( n m ?an sev5 miles1 !y atta9 a ?ickness ( ab\t #gjjj feet1 & !n =m ! great sc>p$ front ( ! hills t look ov] ,ed9burgh4 ,b at ! base ( t wall _! cont9uity abruptly ceases4 ,! l[] gr\nd1 :i* ext5ds !nce to ! s\!rn suburbs ( ,ed9burgh1 & includes ! gr\p ( ! ,braid ,hills1 is occupi$ by ano!r & m complex gr\p ( rocks 9 :i* ! p>allelism & p]si/5ce s m>k$ 9 ! ,p5tl& *a9 entirely disappe>4 ,?is abrupt truncation ( ! b$d$ lavas & tuffs m>ks approximately ! s\!rn m>g9 ( a l>ge v5t f :i* at lea/ "s1 if n mo/1 ( ^! rocks 7 probably eject$4 ,! size ( ?is v5t _c be precisely asc]ta9$ on acc\nt ( ! uncon=mable ov]spread ( ,l[] ,c>bonif]\s /rata4 ,b t x mu/ h be5 a l>ge & important volcanic orifice may be inf]r$ f ! fact t ! visible area ( ! mat]ials t fill x up measures two miles f nor?-ea/ to s\?-we/1 & a mile & a half f s\?-ea/ to nor?-we/1 ?us includ+ a space ( r m ?an two squ>e miles4 ,its orig9al limits t[>ds ! nor? & s\? c be trac$ by help ( ! b$d$ lavas t p>tially surr\nd x1 b on ! two o!r sides !y are conceal$ by ! y\ng] =mations4 ,we %all probably n ov]-e/imate ! orig9al area ( ! v5t if we /ate x at ab\t f\r squ>e miles4 ,illu/ration3 ,fig4 #ij4--,section across ! nor? end ( ! ,p5tl& ,hills1 & ! s\!rn edge ( ! ,braid ,hill v5t4 ,l5g? ab\t two miles4 #a #a4 ,&esites2 #b4 ,f9e tuffs1 etc41 ( ! ,braid ,hill v5t2 #c #c #c4 ,agglom]ate 9 lat]al necks ) felsitic intrusions 7#d74 ,! mat]ials t n[ fill ?is important orifice consi/ ma9ly ( clay/ones1 l ^? ( ! ,p5tl& s]ies--dull rocks1 meagre to ! t\*1 v>y+ 9 texture f ! r\gh por\s aspect ( a s9t] ?r\gh /ages ( increas+ firmness till !y become almo/ felsitic1 & rang+ 9 col\r f a d>k purple-r$1 ?r\gh %ades ( lilac & yell[1 to ne>ly :ite1 b (t5 /rik+ly mottl$4 ,a m or less lam9> /ructure is (t5 to be obs]v$ among !m1 indicat+ a dip 9 v>i\s directions 7b especially t[>ds ! nor?7 & at consid]able angles4 ,?r\gh\t ?is exce$+ly f9e-gra9$ mat]ial1 l9es ( small lapilli may occasionally be detect$1 also b&s ( breccia1 consi/+ ( brok5-up tuff ( ! same "*1 & ( f9e horn/one & felsite1 ) delicate fl[-/ructure4 ,exhibit+ on ! :ole s little /ructure1 ?is tract may be reg>d$ z consi/+ l>gely ( f9e volcanic du/ d]iv$ f ! explosion ( felsitic or or?ophyric lavas4 ,"s portions inde$ are n improbably compos$ ( decay$ felsites1 l ^? :i* pres5t s _m difficulties to ! geologi/ :o w\ld try to trace _! c\rse among ! o!r lavas & tuffs ( ! ,p5tl& *a94 ,v>i\s ve9s1 dykes & small bosses ( felsite1 &esite & ev5 m basic mat]ial1 su* z f9e dol]ite1 h be5 intrud$ into ! g5]al body ( ! mass4 ,on ! outskirts ( ! ma9 v5t "s subord9ate necks may be obs]v$ 7#c1 #c 9 ,fig4 #ij71 p]haps1 l ,torduff ,hill1 already notic$ 7,fig4 #hf71 m>k+ lat]al eruptions f ! flanks ( ! great cone4 ,?ree ( ^! occur 9 a l9e m ?an half a mile long1 possibly indicat+ a fissure on ! side ( ! old volcano1 runn+ 9 a s\?-we/]ly direction f ! s\!rn edge ( ! v5t4 ,! smalle/ ( !m measures ab\t #ejj feet 9 diamet]2 ! l>ge/ is oblong 9 %ape1 its %ort] diamet] be+ ab\t #ejj feet1 & its long] ab\t #ajjj feet4 ,! mat]ials t fill ^! lat]al v5ts are co>se agglom]ates1 trav]s$ by ve9s & irregul> intrusions ( a f9e horny or fl9ty felsite4 ,f ! acid "* ( mo/ ( ! rocks t n[ fill ! wide v5t ( ! ,braid ,hills x may be inf]r$ t at lea/ ! la/ eruptions f x consi/$ *iefly ( acid tuffs & lavas4 ,! upp] portion ( ! volcanic s]ies be+ ev]y:]e conceal$1 !re are no means left to v]ify ?is inf]5ce f an exam9ation ( ! eject$ mat]ial4 ,x may be rem>k$1 h[ev]1 t ! pale yell[ s&/ones :i* lie on ! ea/ side ( ! fault & are expos$ 9 ! ,lyne ,wat] above ,we/ ,l9ton are 9 great measure compos$ ( f9e felsitic mat]ial4#cfe ,!y c]ta9ly belong to a high] horizon ?an ! mo/ s\!rly lavas ( ! ,p5tl& ,hills1 & if !y h n d]iv$ _! volcanic detritus f ! ,bigg> volcanic area1 x may be assum$ t !y obta9$ x f ! v5t ( ! ,braid ,hills4 ,9 any case !y %[ t aft] ! lavas ( ! s\!rn end ( ! ,p5tl& ,hills 7 buri$1 acid volcanic detritus cont9u$ to be abundantly di/ribut$ ov] ?is "p ( ! floor ( ,lake ,cal$onia4 ,footnote #cfe3 ,explanation to ,%eet #bd ( ! ,geological ,survey ( ,scotl&1 pp4 #aj1 #ab4 #f4 ,! ,bigg> ,c5tre#cff ,footnote #cff3 ,?is area is includ$ 9 ,%eets #bc & #bd ( ! ,geological ,survey ( ,scotl&4 ,x 0 mapp$ & describ$ by myself4 7,explanations ( ,%eets #bc & #bd47 ,v>i\s p>ts ( x h be5 ref]r$ to by e>li] writ]s1 p>ticul>ly ,macl>51 ,geology ( ,fife1 etc41 p4 #agf4 ,ano!r di/9ct gr\p ( volcanoes _h its c5tre ab\t #be miles s\?-we/w>d f ! ,braid v5t1 & on ! same l9e z ^? ( ! ,p5tl& ,hills4 ,9 no "p ( ! bas9 c ! isolation ( ! diff]5t volcanic clu/]s be s impressively obs]v$ z 9 ! area to ! s\?-we/ ( ^! hills4 ,on ! "o h&1 ! lavas & tuffs f ! ,braid v5t die out1 & on ! o!r1 z we foll[ ! conglom]ates s\?-we/w>ds1 a new volcanic s]ies imm$iately makes its appe>ance4 ,! space betwe5 ! la/ extremity ( ! ,p5tl& lavas & ! beg9n+ ( ! ,bigg> s]ies does n exce$ "s #ejj y>ds4 ,x w be rememb]$ t ! l[] half ( ! ,p5tl& volcanic s]ies dies out long be=e x rea*es ! s\!rn end ( ! hills1 & t x is by lavas on ! horizon ( "s ( ! d>k &esites ( ,all]muir ,hill t ! volcanic b& is f9ally prolong$ to its extreme s\!rn limit4 ,! mo/ nor!rly ext5sion ( ! ,bigg> lavas lies some:]e on ! same g5]al plat=m4 ,b :]eas1 at ! nor? end ( ! ,p5tl& *a91 ! volcanic %eets re/ on ! edges ( ! ,upp] ,silurian %ales1 at ! s\? end1 sev]al hundr$ feet ( co>se conglom]ate & s&/one int]v5e betwe5 ! ,silurian %ales & ! porphyrites4 ,s rapidly does ! bulk ( ^! s$im5t>y =mations increase t 9 ! c\rse ( two miles !y mu/ be #cjjj feet 9 ?ickness bel[ ! mo/ nor!rly ( ! ,bigg> lavas j ref]r$ to4 ,b aft] t po9t1 :5 !y cross ! ,lyne ,wat]1 !y beg9 to be m & m int]/ratifi$ ) ?9 %eets ( &esite4 ,^! lavas1 ! beg9n+ ( ! ,bigg> s]ies1 soon numb] n9e or t5 di/9ct b&s1 & s quickly d !y usurp ! place ( ! s$im5t>y mat]ials t 9 a di/ance ( n m ?an twelve miles !y =m1 :]e trav]s$ by ! riv] ,clyde1 ! :ole bread? ( ! visible tract ( ,old ,r$ ,s&/one1 to ! exclusion ( ! conglom]ates4 ,un=tunately1 soon aft] ! lavas make _! appe>ance at ! nor? end !y are 9 great measure ov]lapp$ uncon=mably by ! r$ s&/ones at ! base ( ! ,c>bonif]\s sy/em1 b :]e ! ,m$w9 ,wat] has cut ?r\gh ?is cov]+1 !y c be se5 "h & !re und]nea? on _! s\!rly c\rse4 ,a section ?r\gh ! nor!rn end ( ! ,bigg> s]ies1 :]e ! successive lavas are dy+ out nor?w>ds among ! conglom]ates1 %[s ! /ructure giv5 9 ,fig4 #ia4 ,! s$im5t>y /rata consi/ l>gely ( debris ( &esite1 & ! lavas include d>k r$ or purple &esites & also pale felsites1 bo? hav+ ! same *>act]s z ^? ( ! ,p5tl& ,hills4 ,illu/ration3 ,fig4 #ia4--,section across ! nor!rn end ( ! ,bigg> volcanic gr\p1 f ,fadd5 ,hill to beyond ,m5dick ,hill4 #a4 ,conglom]ates & s&/ones2 #b4 ,lavas1 ! l[e/ be+ an oliv9e-diabase or basalt1 ! ma9 mass be+ &esites2 #c4 ,felsites & tuffs2 #d4 ,upp] ,old ,r$ ,s&/one4 f1 ,fault4 ,9 "o important respect ! volcanic s]ies 9 ! nor!rn "p ( ! ,bigg> area diff]s f t ( ! ,p5tl& ,hills1 = :]eas ! upp]mo/ p>ts ( ! latt] are conceal$ by faults :i* br+ d[n ! ,c>bonif]\s /rata aga9/ ! base ( ! hills1 ! lavas at ! nor? end ( ! ,bigg> di/rict pass con=mably "u a ?ick gr\p ( ,l[] ,old ,r$ conglom]ates & s&/ones4 ,we ?us le>n t "h ! volcanic eruptions ceas$ long be=e ! close ( ! deposition ( ! ,l[] ,old ,r$ ,s&/one4 ,! ov]ly+ s$im5t>y s]ies is dispos$ 9 a long syncl9al tr\gh1 correspond+ 9 direction ) ! g5]al nor?-ea/]ly /rike ( ! volcanic rocks :i* reappe> f "u ! s&/ones & conglom]ates along its s\?-ea/]n bord]1 :]e !y are abruptly truncat$ by ! fault 7f1 ,fig4 #ib71 :i* br+s !m aga9/ ! flanks ( ! ,silurian ,upl&s4 ,x is int]e/+ to note t by ?is dislocation ! lavas ( ! ,l[] ,old ,r$ ,s&/one are plac$ almo/ 9 imm$iate contact ) ^? ( ! ,l[] ,silurian s]ies1 :i* appe> "h on ! cre/s ( num]\s anticl9al folds t are obliquely cut (f by ! fault4 ,!re is yet ano!r feature ( int]e/ 9 ! nor!rn "p ( ! ,bigg> volcanic c5tre4 ,:ile ! l[e/ visible lava is an oliv9e-diabase n unlike p>ts ( ! ,w>klaw gr\p ( ! ,p5tl& ,hills1 ^? :i* occur above x are p>tly &esites & p>tly or?oclase-felsites4 ,! latt] =m1 among ! hills ne> ,dolph9ton1 an important gr\p :i* rea*es its greate/ developm5t 9 ! ,black ,m\nt 7#afhi feet74 ,^! rocks cov] a bread? ( m ?an a mile ( gr\nd1 & probably atta9 a ?ickness ( n less ?an #bjjj feet4 ,!y s closely resemble 9 _! g5]al *>act]s ! correspond+ rocks ( ! ,p5tl& ,hills t a brief description ( !m may suffice4 ,z 9 t *a9 ( hills1 !y are s prone to decomposition t !y are 9 l>ge "p conceal$ "u a cov]+ ( _! own debris & ( h]bage1 ?\gh _! fragm5ts =m abundant screes1 & num]\s project+ knobs ( rock suffice to %[ ! ma9 features ( ! lavas & _! accompanim5ts4 ,! felsites wea!r into pale yell[ & greyi% clay/ones1 b :]e fre%] sections c be procur$ !y (t5 %[ d>k] t9ts ( lilac & purple4 ,!y are close-gra9$1 sometimes fl9ty1 g5]ally porphyritic ) scatt]$ highly-kaol9iz$ :ite felsp>s1 b )\t qu>tz1 (t5 pres5t+ beautiful fl[-/ructure1 & n infrequ5tly %[+ a brecciat$ appe>ance1 :i* 9 ! usual wea!r$ blocks is h>dly to be di/+ui%$ f ! breccia ( int]/ratifi$ tuffs4 ,a locality :]e "s ( ^! features may be satisfactorily exam9$ is a dry rav9e 9 ! f>m ( ,bank1 on ! s\?-ea/ side ( ! ,black ,m\nt4 ,"h ! felsite possesses su* a p]fectly develop$ fl[-/ructure z to split into slabs :i*1 dipp+ ,s4,e4 at ab\t #be1 might deceive ! obs]v] into ! belief t x is a s$im5t>y rock4 ,a fre% fracture %[s ! lam9 ( fl[1 _m ( :i* are z ?9 z %eets ( pap]1 to be lilac 9 col\r1 "s ( ! m decompos$ lay]s assum+ t9ts ( grey4 ,! felsp>s & micas are arrang$ ) _! long axes p>allel to ! l9es ( fl[4 ,! rock is n vesicul>1 b x breaks up "h & !re into ! brecciat$ condition j ref]r$ to4 ,bel[ ! %eet :i* displays ! mo/ p]fect fl[-/ructure1 :at is probably a true volcanic breccia makes its appe>ance4 ,x consi/s ( angul> fragm5ts ( a simil> lilac felsite1 ( all sizes up to pieces two or ?ree in*es 9 l5g?1 cem5t$ 9 a matrix ( ! same mat]ial /a9$ r$di%-br[n4 ,9 ?is breccia ! /ones %[ little or no fl[-/ructure4 ,above ! gr\p ( felsites & felsitic breccias1 grey &esites make _! appe>ance1 l "s ( ^? 9 ! ,p5tl& ,hills4 ,!y are sometimes extraord9>ily vesicul>1 ! vesicles 9 ! body ( ! rock be+ fill$ ) calcite1 agate1 etc4 ,su* lavas mu/ h be5 orig9ally %eets ( r\gh slag4 ,! elongat$ /eam-vesicles h be5 p>tly fill$ up ) micace\s s& & f9e r$ mud t 7 wa%$ into crannies ( ! lava 9 direct communication ) ! ov]ly+ wat]4 ,x is evid5t t 9 ! nor!rn "p ( ! ,bigg> c5tre ! succession ( volcanic ev5ts foll[$ closely ! ord] obs]vable 9 ! ,p5tl& ,hills1 b on a feebl] scale4 ,we may suppose t ! l[] diabases & &esites are ! equival5ts ( ^? ( ,w>klaw & ,all]muir1 t ! felsites & breccias 7 contemporane\s ) ^? ( ,capelaw1 ,ca]ketton & ,ca/lelaw1 & t ! la/ &esites made _! appe>ance toge!r ) ^? :i* =m ! highe/ lavas ( ! ,p5tl& *a94 ,illu/ration3 ,fig4 #ib4--,section across ! s\!rn "p ( ! ,bigg> volcanic gr\p f ,cov+ton to ,cult]4 #a4 ,l[] ,silurian /rata2 #b4 ,l[] ,old ,r$ ,s&/one 7pre-volcanic gr\p72 #c4 ,&esite lavas ) int]calat$ s&/ones & conglom]ates2 #d4 ,felsite neck4 f1 ,! b\nd>y-fault on nor!rn edge ( ,s\!rn ,upl&s4 ,a section across ! s\!rn end ( ! ,bigg> volcanic belt %[s less div]sity ( /ructure 7,fig4 #ib74 ,! lavas 7#c7 are !re f\nd to flatt5 out & to spread uncon=mably ov] ! old] "p ( ! ,l[] ,old ,r$ ,s&/one 7#b71 :i*1 z already /at$1 passes d[n into ! ,upp] ,silurian %ales4 ,a few int]calations ( conglom]ate1 ma9ly made up ( volcanic detritus1 are "h & !re to be detect$ among ^! lavas4 ,b ! *ocolate s&/ones & conglom]ates t lie uncon=mably bel[ !m conta9 no su* detritus1 = !y belong to ! pre-volcanic "p ( ! hi/ory ( ,lake ,cal$onia1 & 7 "h locally uprais$1 p]haps z an accompanim5t ( ! t]re/rial di/urbances t prec$$ or att5d$ ! fir/ outbur/ ( volcanic en]gy4 ,foll[$ s\?-we/w>ds1 ! /ratigraphical break 9 ! ,l[] ,old ,r$ ,s&/one disappe>s1 &1 z w be %[n 9 ! acc\nt ( ! ,duneaton c5tre1 a cont9u\s succession c !re be trac$ f ! ,upp] ,silurian %ales up into ! volcanic s]ies4 ,an int]e/+ feature 9 ?is di/rict is ! felsitic boss ( ,quo?quan already allud$ to 7p4 #bhh7 z ris+ up ?r\gh ! &esites1 & possibly m>k+ "o ( ! v5ts ( ! di/rict4 ,x is "o ( a numb] ( felsitic intrusions 9 ?is neighb\rhood1 ( :i* ! mo/ important is ,t9to4 ,illu/ration3 ,fig4 #ic4--,section f ,?ank]ton ,moor across ,t9to to ,lam+ton4 #a;a4 ,l[] ,silurian2 #a4 ,upp] ,silurian /rata2 #b4 ,l[] ,old ,r$ ,s&/one ) two m>k$ b&s ( conglom]ate2 #c4 ,l[] ,old ,s&/one 7pre-volcanic *ocolate s&/ones72 #d4 ,&esite lavas ) s&/ones1 conglom]ates & tuffs ly+ uncon=mably on ,no4 #c2 #e4 ,felsite sill ( ,t9to ) ! small] sill ( ! ,pap ,craig 7#f74 f1 ,fault b\nd+ ! ,silurian upl&s on ! nor?4 ,a small pat* ( ! uncon=mable ,l[] ,old ,r$ conglom]ate is se5 on ! s\? side ( ! fault4 ,a ?ird section tak5 across ,t9to1 f ,?ank]ton ,moor on ! nor? side to ,lam+ton on ! s\?1 w s]ve fur!r to illu/rate ! great uncon=mability 9 ! ,l[] ,old ,r$ ,s&/one ( ?is di/rict1 & to %[ ! relation ( ! l>ge/ felsitic intrusion to ! surr\nd+ rocks 7,fig4 #ic74 ,! conglom]ates & s&/ones t appe> on ! s\? slopes ( ,t9to lie ne> ! base ( ! ,old ,r$ ,s&/one1 & if we c\ld bore among ! ov]ly+ &esites we %\ld probably meet ) ! ,upp] ,silurian %ales among or con=mably b5ea? ! r$ passage-b$s1 z 9 ! ,lesmahag[ di/rict4 ,! &esitic lavas creep ov] ! upturn$ d5ud$ edges ( ^! /rata & sweep r\nd ! flanks ( ,t9to4 ,?is conspicu\s hill rea*es a height ( #bcce feet above ! sea1 & consi/s ( ! felsitic rocks already describ$ 7p4 #bgh74 ,se5 f _m po9ts ( view x rises z a graceful cone1 di/+ui%$ f all ! o!r em95ces ar\nd x by ! p9ki% col\r ( its screes4 ,9 reality x =ms a cont9u\s ridge :i* runs 9 an ea/ & we/ direction = ab\t five & a half miles1 ) a bread? ( ab\t a mile4 ,"s "p at lea/1 & possibly ! :ole ( ?is oblong mass1 is 9 ! =m ( a sill or laccolite :i* dips t[>ds ! nor?4 ,conglom]ates & s&/ones plunge "u x on ! s\!rn side1 & simil> s&/ones ov]lie x on ! nor?4 ,if !re be a neck 9 ?is mass1 z "o might inf] f ! %ape ( ! hill1 its precise limits are conceal$4 ,! rock does n break ?r\gh ! &esites1 & may belong to an e>li] p]iod ( eruptivity ?an ! lavas imm$iately ar\nd x4 ,!re 7 o!r1 ?\gh small]1 v5ts 9 ! imm$iate neighb\rhood4 ,besides ! cone ( ,quo?quan j ref]r$ to1 ano!r may be m>k$ by ! felsite boss :i* ov]looks ! village ( ,d\glas1 f\r miles to ! s\?-we/ ( ! ,t9to ridge1 :ile a ?ird rises into a l[ r\nd$ hill close to ! village ( ,sym+ton4 ,! lavas spread out aga9 to ! s\?-we/ ( ,t9to 9 a gr\p ( hills1 until !y are int]rupt$ by a fault :i* br+s 9 ! ,d\glas coal-field4#cfg ,?is dislocation abruptly t]m9ates ! ,bigg> volcanic b& 9 a s\?-we/]ly direction1 aft] ext5d+ = a l5g? ( #bf miles1 ) a bread? ( sometimes z mu* z five miles4 ,footnote #cfg3 ,see ,explanation to ,%eet #bc ( ! ,geological ,survey ( ,scotl& 7#ahgc71 p4 #ae4 ,?is gr\nd 0 mapp$ & describ$ by ,mr4 ,b4 ,n4 ,pea*4 #g4 ,! ,duneaton ,c5tre ,among ! high bleak muirl&s on ! conf9es ( ! ?ree c\nties ( ,lan>k1 ,ayr & ,dumfries1 trav]s$ by ! ,duneaton ,wat]1 a di/9ct volcanic area may be trac$4#cfh ,its b\nd>ies1 h[ev]1 _c be satisfactorily fix$4 ,x is ov]spread ) ,c>bonif]\s rocks bo? to ! nor?-ea/ & s\?-we/1 s t its rocks are only visible along a /rip ab\t sev5 miles long & two miles broad4 ,on ! nor?-we/]n side its l[] memb]s are se5 ly+ int]/ratifi$ among ! s&/ones & conglom]ates :i* !nce pass d[n con=mably into ! ,upp] ,silurian s]ies 7,fig4 #id74 ,b al?\gh we ?us get bel[ ! volcanic s]ies we meet ) no v5ts or sills among ! l[] rocks4 ,on ! s\?-ea/ side ! highe/ lavas & tuffs are ov]la9 by "s #ejjj feet ( r$ s&/ones & conglom]ates 7#b1 #c71 :i* completely bury all traces ( ! volcanic hi/ory4 ,footnote #cfh3 ,?is area 0 mapp$ by ,mr4 ,b4 ,n4 ,pea* 9 ,%eet #ae ( ! ,geological ,survey ( ,scotl&1 & is describ$ by him 9 ! accompany+ ,memoir4 ,! volcanic s]ies 9 ?is limit$ di/rict rea*es an e/imat$ ?ickness ( #djjj feet1 built up ( purple & gre5 slaggy &esites1 d>k heavy diabases 7melaphyres7 & tuffs1 ) abundant int]/ratification ( s&/one1 especially t[>ds ! base4 ,"o ( its *ief features ( int]e/ is ! mann] 9 :i* x exhibits1 bett]1 p]haps1 ?an c be f\nd 9 any ( ! o!r volcanic areas1 ! frequ5t & rapid alt]nations ( lavas & tuffs ) s&/one & conglom]ate4 ,9 ?is "p ( ! region ! volcanic dis*>ges 7 obvi\sly frequ5t & int]mitt5t1 :ile at ! same "t ! transport & deposition ( s$im5t 7 cont9u\s4 ,?is s$im5t consi/$ l>gely1 inde$1 ( volcanic detritus mix$ ) ord9>y s& & silt4 ,t ^! conditions ( s$im5tation 7 n :olly inimical to animal life is %[n by ! occasional occurr5ce ( worm-burr[s 9 ! a%y s&/ones4#cfi ,footnote #cfi3 ,memoir on ,%eet #ae ,geol4 ,surv4 ,scotl& 7#ahga71 p4 #bb4 ,illu/ration3 ,fig4 #id4--,section across ! ,duneaton volcanic di/rict f ! head ( ! ,duneaton ,wat] to ,kirklea ,hill4 #a4 ,silurian /rata2 #b4 ,l[] ,old ,r$ ,s&/one & conglom]ate2 #c4 ,co>se conglom]ate2 #d4 ,&esite-lavas2 #e4 ,/ratifi$ tuffs2 #f4 ,spango granite2 #g4 ,upp] ,old ,r$ ,s&/one4 ,! ?ick accumulation ( s&/ones & conglom]ates above ! ma9 mass ( lavas has be5 d]iv$ almo/ :olly f ! wa/e ( ! volcanic rocks 7#c74 ,blocks ( &esite1 well r\nd$ & (t5 f six to twelve in*es 9 diamet]1 may be se5 9 ! rem>kable b& ( co>se conglom]ate :i* runs z a ne>ly cont9u\s ridge f ! ,ni? to ! ,clyde--a di/ance ( m ?an tw5ty miles4 ,no?+ impresses ! geologi/ m1 z he w&]s ov] ?is di/rict1 ?an ! evid5ce ( ! prodigi\s wa/e :i* ! volcanic s]ies und]w5t be=e x 0 f9ally buri$4 ,"s "p ( ! detritus may h be5 suppli$1 inde$1 by occasional dis*>ges ( fragm5tal matt]1 z has already be5 sugge/$ 9 ! case ( ! ,o*il & ,montrose conglom]ates4 ,b ! nature ( ! pebbles 9 ^! masses ( anci5t %+le %[s !m to be n bombs1 b pieces worn away f %eets ( lava4 ,t ! lavas und]lie ^! piles ( detritus & ext5d s\?w>ds ev5 up to ! v edge ( ! ,silurian ,upl&s is %[n by ! rise ( a numb] ( successive b$s f "u ! tr\gh into :i* ! conglom]ate has be5 ?r[n4 ,^! lavas1 h[ev]1 are almo/ imm$iately cut (f by ! great b\nd>y fault 7f7 :i* flanks ! ,silurian t]ritory4 ,t !y are n met ) n[ to ! s\?-ea/ ( ! dislocation1 :]e !y mu/ once h la91 is an evid5ce ( ! great d5udation :i* ! di/rict has und]gone4 ,fig4 #id1 :i* gives a section across ! broade/ "p ( ! area1 f ! edge ( ! ,muirkirk coal-field to ! ,silurian upl&s1 %[s ! g5]al /ructure ( ! gr\nd4 ,no satisfactory evid5ce reg>d+ ! position ( any ( ! v5ts ( ! p]iod has be5 met ) 9 ?is di/rict4 ,! rocks to ! s\? ( ! b\nd>y-fault are old] ?an ! ,old ,r$ ,s&/one1 & z !y mu/ h be5 = "s di/ance ov]spread by ! conglom]ates1 s&/ones & volcanic s]ies1 we might hope to f9d some:]e among !m traces ( necks or bosses4 ,! only mass ( eruptive rock 9 t "p ( ! di/rict is ! tract ( ,spango granite :i* has be5 already ref]r$ to 9 connection ) ! subject ( ! v5ts & granite protrusions ( ,old ,r$ ,s&/one "t4 ,?is mass1 ab\t f\r miles long & two miles broad1 rises ?r\gh ,silurian /rata1 & by means ( ! b\nd>y fault is br\ght aga9/ ! high] gr\p ( conglom]ates & s&/ones4 ,! ,silurian %ales & s&/ones ar\nd ! granite h und]gone contact-metamorphism1 becom+ highly micace\s & s*i/ose4 ,! asc5t ( ?is granite mu/ h tak5 place betwe5 ! upheaval & contortion ( ! ,upp] ,silurian /rata1 & ! deposition ( ! high] p>ts ( ! ,l[] ,old ,r$ ,s&/one ( ?is region4 ,its date might ?us come )9 ! limits ( ! volcanic p]iod4 ,b "o mu/ frankly own t !re is no positive evid5ce to connect its production ) ! volcanic hi/ory4 #h4 ,! ,ayr%ire ,gr\p ( ,v5ts ,! orig9al limits ( ! volcanic di/ricts 9 ! rema9+ portion ( ! ,old ,r$ ,s&/one area on ! ma9l& ( ,scotl&1 f ! valley ( ! ,ni? to ! ,fir? ( ,clyde1 c only be vaguely indicat$4#cgj ,!re is a difficulty 9 asc]ta9+ ! s\?-we/]n t]m9ation ( ! ,duneaton area1 & 9 decid+ :e!r ! lavas & tuffs ( ,cors9cone 9 ,ni?sdale %\ld be assign$ to t di/rict or be plac$ ) ^? fur!r to ! s\?-we/4 ,betwe5 ,cors9cone & ! next visible volcanic rocks ( ! ,l[] ,old ,r$ ,s&/one !re int]v5es a space ( six miles1 along :i*1 ow+ to ! effect ( ! great fault t flanks ! nor?-we/]n m>g9 ( ! ,s\!rn ,upl&s1 ! ,c>bonif]\s ,lime/one & ev5 ! ,coal-measures are br\ght aga9/ ! ,silurian =mations1 e int]m$iate s]ies ( rocks be+ !re cut out4 ,x may !re=e be1 on ! :ole1 bett] to include all ! volcanic rocks on ! left side ( ! ,ni? z "p ( ! ,duneaton s]ies4 ,!re w /ill rema9 a tract ( five miles ( blank int]m$iate gr\nd be=e we ent] ^u ! volcanic rocks ( ,ayr%ire4 ,footnote #cgj3 ,! mapp+ ( ! ,old ,r$ ,s&/one volcanic areas ( ,ayr%ire = ! ,geological ,survey 0 ?us di/ribut$3--,! di/rict ea/ ( ,dalmell+ton 0 survey$ by ,mr4 ,b4 ,n4 ,pea*1 t betwe5 ,dalmell+ton & ,/raiton by ,pr(4 ,james ,geikie1 & all f ! l9e ( ! ,girvan ,valley s\? ( ,/raiton we/w>d to ! sea by myself4 ,! gr\nd is embrac$ 9 ,%eets #h1 #ac & #ad ( ! ,map ( ,scotl&1 & is describ$ 9 accompany+ ,explanations4 ,ow+ to complicat$ faults1 ext5sive uncon=mable ov]laps ( ! ,c>bonif]\s =mations1 & enorm\s d5udation1 ! volcanic tracts ( ,old ,r$ ,s&/one age 9 ,ayr%ire h be5 r$uc$ to m]e scatt]$ pat*es1 ! true relations ( :i* are n always easily discov]able4 ,"o ( ^! isolat$ areas flanks ! ,silurian ,upl&s z a belt f a mile to a mile & a half 9 bread? & ab\t six miles long1 b ) its limits ev]y:]e def9$ by faults4 ,a second mu* m div]sifi$ di/rict ext5ds = ab\t t5 miles to ! s\?-we/ ( ,dalmell+ton4 ,x too =ms a belt1 av]ag+ ab\t f\r miles 9 bread?1 b pres5t+ a s+ul>ly complicat$ geological /ructure4 ,ow+ to faults1 curvatures & d5udation1 ! volcanic rocks h !re be5 isolat$ into a numb] ( deta*$ portions1 betwe5 "s ( :i* ! old] p>ts ( ! ,old ,r$ ,s&/one1 & ev5 ! ,silurian rocks1 h be5 laid b>e1 :ile betwe5 o!rs ! gr\nd is ov]spread ) ,c>bonif]\s /rata4 ,a ?ird unbrok5 area =ms ! ,br[n ,c>rick ,hills1 s\? ( ! t[n ( ,ayr1 & is ( special int]e/ f ! fact t its rocks h be5 expos$ along a range ( sea-cliffs & ( bea*-sections = a di/ance ( ne>ly f\r miles4 ,o!r deta*$ tracts ( volcanic rocks are display$ on ! %ore at ,turnb]ry & ,port ,g>rick1 on ! hills betwe5 ,mo*rum & ! vale ( ! ,girvan1 & on ! l[ gr\nd betwe5 ,dalrymple & ,kirkmi*ael4 ,! isolation ( ^! v>i\s outli]s & sep>at$ di/ricts is probably n entirely due to ! effects ( subsequ5t geological revolutions4 ,m probably "s ( ! areas 7 always indep5d5t ( ea* o!r1 & _! igne\s rocks 7 dis*>g$ f di/9ct volcanic c5tres4 ,we may conjecture t "o ( ^! c5tres lay some:]e 9 ! neighb\rhood ( ,new ,cumnock1 = ! lavas betwe5 t t[n & ,dalmell+ton appe> to dim9i% 9 ?ickness & numb] z !y are trac$ s\?-we/w>d4 ,ano!r v5t1 or m probably a gr\p ( v5ts1 may h /ood on ! site ( ! pres5t hills to ! "r & left ( ! ,girvan ,valley1 s\? ( ! village ( ,/raiton4 ,a ?ird probably rose some:]e betwe5 ,dailly & ,cros%ill1 & p\r$ out ! lavas ( ! ridges betwe5 ,maybole & ! ,dailly coal-field4 ,! important c5tre ( eruption t produc$ ! ?ick & ext5sive lavas ( ! ,br[n ,c>rick ,hills may be conceal$ "u ^! hills1 or may h /ood some:]e to ! we/ ( ,maybole4 ,/ill ano!r v5t1 p]haps n[ "u ! sea1 appe>s to be indicat$ by ! porphyrites ( ! coa/-section betwe5 ,turnb]ry & ,culzean ,bay4 ,ow+ to ! complicat$ /ructure ( ! gr\nd1 sev]al important po9ts 9 ! hi/ory ( ! ,old ,r$ ,s&/one ( ?is region h n be5 e/abli%$ beyond dispute4 ,9 p>ticul>1 ! uncon=mability :i* und\bt$ly exi/s 9 t sy/em 9 ! s\?-we/ ( ,ayr%ire has n be5 trac$ f> en\gh ea/w>ds to det]m9e :e!r x affects ! volcanic belt ea/ ( ,dalmell+ton1 or :e!r ! break took place be=e or aft] ! eruption ( t belt4 ,we/ ( ,dalmell+ton x cle>ly sep>ates a high] gr\p ( s&/ones1 conglom]ates & volcanic rocks f ev]y?+ old] ?an !mselves4 ,! /ructure is simil> to t 9 ! ,p5tl& ,hills1 a m>k$ di/urbance hav+ tak5 place "h z well z !re aft] a consid]able portion ( ! ,l[] ,old ,r$ ,s&/one _h be5 deposit$4 ,^! e>li] /rata 7 uprais$1 & on _! d5ud$ ends ano!r gr\p ( s&/ones & conglom]ates 0 laid d[n1 foll[$ by an ext5sive eruption ( volcanic mat]ials4 ,x is ! upp] uncon=mable s]ies t requires to be consid]$ "h1 z x includes all ! volcanic rocks ( ! ,old ,r$ ,s&/one ly+ to ! we/ ( ! m]idian ( ,dalmell+ton4 ,! position ( ^! rocks on _! und]ly+ conglom]ates is admirably expos$ among ! hills betwe5 ! valleys ( ! ,doon & ! ,girvan1 z well z on ,b5nan ,hill to ! s\? ( ,/raiton4 ,! &esites rise 9 a craggy esc>pm5t cr[n+ long gre5 slopes t m or less conceal ! conglom]ates & s&/ones bel[4 ,along ! coa/-sections ! /ructure ( ! volcanic rocks may be mo/ advantage\sly /udi$4 ,! %ore f ! ,heads ( ,ayr to ,culzean ,ca/le af=ds a f9e s]ies ( exposures1 :]e e feature 9 ! succession ( ! lavas may be obs]v$4 ,/ill m in/ructive1 p]haps1 is ! mile & a half ( bea* betwe5 ,turnb]ry ,bay & ,d\gla/on1 ( :i* ,i %all "h give a cond5s$ acc\nt1 = comp>ison ) ! coa/-sections ( ,k9c>d9e%ire & ,=f>%ire already describ$4 ,! special feature ( ?is "p ( ! ,ayr%ire coa/-l9e is ! numb] ( di/9ct &esite %eets :i* c be discrim9at$ by means ( ! ?9 lay]s ( s&/one & s&y tuff t int]v5e betwe5 !m4 ,9 ! %ort space ( a mile & a half some:]e ab\t ?irty %eets c be recogniz$1 ea* m>k+ a sep>ate outfl[ ( lava4 ,x 0 9 ?is section t ,i fir/ obs]v$ ! s&/one-ve9+s :i* h be5 describ$ 9 previ\s pages1 & n[h]e are !y m cle>ly develop$4 ,almo/ e successive /ream ( &esite has be5 m or less fissur$ 9 cool+1 & its r5ts & irregul> cav]n\s holl[s h be5 fill$ ) f9e s& silt$ 9 f above4 ,! connection may (t5 be obs]v$ betwe5 ^! s&/one p>titions or pat*es & ! b$ ( ! same mat]ial1 :i* ov]spread ! surface ( ! lava at ! "t t ! fissures 7 be+ fill$ up4 ,illu/ration3 ,fig4 #ie4--;,cav]n\s spaces 9 &esite1 fill$ 9 ) s&/one1 ,john o' ,groat's ,port1 ,turnb]ry1 ,ayr%ire4 ,! &esites ( ! ,turnb]ry %ore are ( ! usual d>k purpli%-r$ to gre5 col\rs1 m or less compact 9 ! c5tre & vesicul> t[>ds ! top & bottom4 ,!y display ) great cle>ness ! l>ge empty spaces t 7 apt to be =m$ 9 su* visc\s slaggy lavas z !y mov$ along ! lake-bottom4 ,^! spaces1 aft]w>ds fill$ ) f9e s&1 n[ appe> z irregul> enclosures ( h>d gre5 s&/one emb$d$ 9 ! &esite4 ,! example %[n 9 ,fig4 #ie may be se5 9 "o ( ! lavas at ,john o' ,groat's ,port4 ,illu/ration3 ,fig4 #if4--,section ( &esites1 ,turnb]ry ,ca/le1 ,ayr%ire4 ,f ! arrangem5t ( ! ve9s ( s&/one x is evid5t t irregul>ly div]g5t1 b (t5 m or less /ellate1 fissures op5$ 9 ! lavas z !y cool$4 ,sometimes1 inde$1 ! molt5 rock appe>s to h brok5 up into a %att]$ mass ( fragm5ts1 z mu/ (t5 h happ5$ :5 lavas 7 p\r$ ov] ! lake-floor4 ,:at may be an in/ance ( ?is effect is to be se5 on ! cliff "u ! walls ( ,turnb]ry ,ca/le1 :5ce ! annex$ sket* 7,fig4 #if7 0 tak54 ,! l[] &esite 7a7 is highly amygdaloidal t[>ds ! top1 & is trav]s$ 9 all directions ) irregul> ve9s & ne/s ( s&/one :i* c be trac$ upw>d to ! b$ 7b71 consi/+ ( s&/one1 b s full ( lumps or slags ( amygdaloidal &esite t "o is "h & !re puzzl$ :e!r to reg>d x z a s$im5t>y deposit1 or z ! upp] lay] ( cl9k]s ( a lava-/ream /rewn ) s&4 ,above ?is fragm5t>y lay] lies ano!r b$ ( &esite 7c7 ( a co>sely amygdaloidal /ructure1 :i* encloses pat*es ( ! und]ly+ s&/one4 ,x passes upw>d1 9 a space ( f f\r to six feet1 into a mass ( angul> scoriace\s fragm5ts 7d7 ( all sizes up to blocks #ah in*es 9 l5g? cem5t$ 9 a ve9-/uff ( calcite1 *alc$ony & qu>tz4 ,?is brecciat$ /ructure asc5ds = ab\t #ac or #ad feet1 & is !n succe$$ by a gre5i% compact &esite 7e71 :i* fur!r nor? becomes amygdaloidal & mu* ve9$ ) s&/one1 pass+ into a breccia ( lava fragm5ts & s&/one4 ,illu/ration3 ,fig4 #ig4--,l5ticul> =m ( a brecciat$ &esite 7%[n 9 ,fig4 #if71 ,turnb]ry1 ,ayr%ire4 ,illu/ration3 ,map ,,iii4 ,,map ,,( ,,! ,,volcanic ,,di/ricts ,,( ,,! ,,l[] ,,old ,,r$ ,,s&/one ,,( ,,lake ,,cal$onia ,,9 ,,c5tral ,,scotl& ,,nor? ,,ea/ ,,irel& ,! rem>kable brecciat$ b& 7d7 9 ?is cliff1 ?\gh #ac or #ad feet 9 ! c5tre1 imm$iately ?9s out on ei!r side1 until 9 ! c\rse ( a few y>ds x completely disappe>s & all[s ! lavas c & e to come toge!r1 z %[n 9 ,fig4 #ig4 ,we may suppose t ?is section reveals ! /ructure ( ! t]m9al portion ( a highly visc\s lava :i* 0 %att]$ into fragm5ts z x mov$ along "u wat]4 ,no cle> evid5ce ( ! sites ( any ( ! volcanic v5ts has yet be5 detect$ 9 ! ,old ,r$ ,s&/one ( ,ayr%ire4 ,possibly "s ( ! num]\s felsitic bosses to ! s\?-we/ ( ,dalmell+ton may p>tly m>k _! positions4 ,b ! sills connect$ ) ! volcanic s]ies are well expos$ 9 ! #ab miles ( hilly gr\nd betwe5 ,dalmell+ton & ,b>r4 ,two gr\ps ( intrusive %eets may !re be se54 ,! mo/ num]\s consi/ ( pale or d>k-p9k felsite1 (t5 full ( cry/als ( mica4 ,!y =m prom95t hills1 su* z ,turg5y1 ,knockskae & ,g>leff9 ,fell4 ,! second gr\p comprises v>i\s diabase-%eets :i* h be5 intrud$ ne> ! base ( ! r$ s&/ones & conglom]ates1 ov] a di/ance ( sev5 miles on ! nor? side ( ! ,/9*> ,valley above ,b>r4 ,!y atta9 _! greate/ developm5t on ,j$burgh ,hill1 :]e !y =m a s]ies ( successive sills1 ! l>ge/ ( :i* unite nor?w>ds into "o ?ick mass & die out s\?w>d among ! s&/ones & conglom]ates4 ,,*apt] ,,xxi ,,volcanoes ,,( ,,! ,,l[] ,,old ,,r$ ,,s&/one ,,( ,,! ,,*eviot ,,hills1 ,,lorne1 ,,lake ,,orcadie ,,& ,,kill>ney ,,! ,,*eviot ,,& ,,b]wick%ire ,,di/rict ,9 ! s\?-ea/ ( ,scotl&1 & ext5d+ !nce into ! nor? ( ,engl&1 ! rema9s ( sev]al di/9ct volcanic c5tres ( ! ,l[] ,old ,r$ ,s&/one may /ill be recogniz$4 ,( ^! ! l>ge/ & mo/ int]e/+ =ms ! mass ( ! ,*eviot ,hills2 a second has be5 p>tially dissect$ by ! sea along ! coa/ s\? f ,/4 ,abb's ,head2 :ile possibly relics ( o!rs may survive 9 deta*$ bosses ( eruptive rock :i* rise ?r\gh ! ,silurian =mations ( ,b]wick%ire4 ,! wat]-bas9 9 :i* ^! volcanic gr\ps 7 active 0 nam$ by me ,lake ,*eviot1#cga to di/+ui% x f ! o!r bas9s ( ! same geological p]iod 7,map ,i474 ,footnote #cga3 ,trans4 ,roy4 ,soc4 ,ed94 xxviii4 7#ahgh71 p4 #ced4 ,! volcanic rocks ( ! ,*eviot ,hills1 ?\gh _! limits h be5 r$uc$ by faults1 uncon=mable ov]lap ( y\ng] =mations & sev]e d5udation1 /ill cov] ab\t #bcj squ>e miles ( gr\nd1 & rise to a height ( #bfgf feet above ! sea4 ,z !y h be5 mapp$ 9 detail by ! ,geological ,survey1 bo? on ! ,engli% & ! ,scotti% sides ( ! ,bord]1 _! /ructure is n[ kn[n4#cgb ,no good horizontal section1 h[ev]1 has yet be5 con/ruct$ to %[ ?is /ructure--a defici5cy :i*1 x is hop$1 may be=e long be suppli$4 ,footnote #cgb3 ,! ,geology ( ! ,*eviot ,hills is compris$ 9 ,%eets #ajh ,n4,e41 #aji ,n4,w41 & #aaj ,s4,w4 ( ! ,geological ,survey ( ,engl& & ,wales1 & 9 ,%eets #ag1 #ah & #bf ( ! ,geological ,survey ( ,scotl&4 ,= descriptive acc\nts ! ,memoirs to "s ( ^! ,%eets may be consult$1 p>ticul>ly ,geology ( ! ,*eviot ,hills 7,engli% side71 by ,c4 ,t4 ,cl\gh 7,mem4 ,geol4 ,surv4 #ahhh72 ,geology ( ,ott]burn & ,elsdon1 by ,h4 ,mill] & ,c4 ,t4 ,cl\gh 7,mem4 ,geol4 ,surv4 #ahhg72 ,geology ( ,"p ( ,nor?umb]l& betwe5 ,wool] & ,cold/ream1 by ,w4 ,gunn & ,c4 ,t4 ,cl\gh1 ) ,petrographical ,notes by ,w4 ,w4 ,watts 7,mem4 ,geol4 ,surv4 #ahie74 ,o!r descriptions h be5 publi%$ by ,pr(essor ,james ,geikie1 ,good ,words1 vol4 xvii4 7#ahgf71 repr9t$ 9 ,fragm5ts ( ,e>?-lore 7#ahic71 & by ,pr(4 ,leb\r1 ,outl9es ( ! ,geology ( ,nor?umb]l&1 #bnd edit4 #ahhf4 ,= ! petrography ( ! rocks consult ,mr4 ,j4 ,j4 ,h4 ,teall1 ,geol4 ,mag4 #ahhc1 pp4 #ajj1 #ade1 #beb1 #cdd2 #ahhd1 p4 #bbf2 #ahhe1 p4 #ajf2 ,proc4 ,geol4 ,assoc4 ix4 7#ahhf7 p4 #ege2 & 8 ,briti% ,petrography1 #ahhh2 ,dr4 ,j4 ,pet]s51 ,mikroskopis*e und *emis*e ,unt]su*ung5 am ,en/atit-porphyrit aus d5 ,*eviot ,hills1 ,inaugural ,diss]tation1 ,kiel1 #ahhd4 ,?is volcanic pile1 consi/+ ma9ly ( b$d$ &esites :i* re/ uncon=mably on ! upturn$ edges ( ,w5lock %ales & grits1 pres5ts a mo/ typical display ( ! lavas ( ! ,l[] ,old ,r$ ,s&/one4 ,^! rocks range f vitre\s or res9\s pit*/one-l v>ieties to co>sely porphyritic =ms1 on ! "o h&1 & to highly vesicul> & amygdaloidal k9ds1 on ! o!r4 ,analyses ( "s ( ^! rocks1 & an acc\nt ( _! petrography1 h already be5 giv54 ,! lavas are (t5 sep>at$ by ?9 p>t+s ( tuff1 & _! upp] surfaces %[ ! fissur$ "* ) s&/one infill+s1 s *>act]i/ic among ! lavas ( ,lake ,cal$onia4#cgc ,tuffs =m a v subord9ate "p ( ! :ole volcanic s]ies4 ,"o ( ! mo/ important b&s is a ?ick mass at ! base ( ! s]ies1 ly+ imm$iately on ! highly incl9$ ,silurian %ales4 ,! fragm5ts are g5]ally ( a f9e-gra9$ purple mica-&esite1 (t5 two or ?ree feet & sometimes at lea/ five feet long4 ,= a few feet ne> ! bottom ( ?is mass ( tuff1 pieces ( ,silurian %ale an in* 9 l5g? may be notic$4 ,mr4 ,cl\gh rem>ks t di/9ct b$d+ is n usual among ! tuffs4 ,?\gh no d\bt mo/ ( ! fragm5tal mat]ials really lie int]calat$ betwe5 successive lava-/reams1 yet "s ( ! isolat$ pat*es ( co>se volcanic breccia may m>k ! sites ( eruptive v5ts4 ,"o su* probable neck has be5 mapp$ on ! ,scotti% side betwe5 ,cocklawfoot1 at ! head ( ! ,b[mont ,wat]1 & ,k+'s ,seat1 :ile o!rs may p]haps occur among ! deta*$ pat*es t h be5 obs]v$ on ! ,nor?umbrian side4 ,no ?ick conglom]ates or s&/ones h be5 notic$ 9 ! ,*eviot ,di/rict4 ,! volcanic eruptions appe> to h usually succe$$ ea* o!r )\t ! spread ( any notable am\nt ( ord9>y detritus ov] ! floor ( ! wat]-bas94 ,x is difficult to e/imate ! total ?ickness ( volcanic mat]ial "h pil$ up1 b x probably am\nts to sev]al ?\s& feet4 ,! top ( ! s]ies is n visible1 hav+ be5 p>tly remov$ by d5udation & p>tly buri$ "u ! ,c>bonif]\s =mations4 ,footnote #cgc3 ,cl\gh1 ,geology ( ! ,*eviot ,hills1 p4 #ae4 ,x w ?us be se5 t ! ,*eviot area /&s ap>t f ! o!r volcanic di/ricts ( ! ,l[] ,old ,r$ ,s&/one 9 ! great relative ?ickness ( its accumulat$ lavas1 ! comp>ative ?9ness ( its tuffs1 & ! abs5ce ( ! ?ick int]calations ( co>se conglom]ate s abundantly develop$ among ! volcanic s]ies all ov] ,c5tral ,scotl&4 ,b !re is yet ano!r *>act]i/ic 9 :i* ?is area is pre-em95tly conspicu\s4 ,9 ! he>t ( ! &esites lies a core ( augite-granitite1 ar\nd :i* ^! rocks are trav]s$ ) dykes4 ,?is int]e/+ granitic boss rises into ! highe/ summit ( ! :ole ,*eviot range1 & cov]s an area ( r m ?an #bj squ>e miles4 ,:ile its petrographical *>act]s h be5 describ$ by ,mr4 ,teall1 its b\nd>y has be5 mapp$ by ,mr4 ,cl\gh1 :o f\nd ! l9e difficult to trace1 ow+ p>tly to ! preval5t cov]+ ( peat1 & p>tly to ! jagg$ & irregul> junction caus$ by ! protrusion ( dykes f & into ! boss4 ,he obta9$ evid5ce t ! granite has brok5 ?r\gh ! b$d$ &esites1 & t x is 9 turn trav]s$ by dykes compos$ ( a mat]ial indi/+ui%able f t ( "s ( ! fl[s4 ,he !re=e consid]$ t x is ess5tially ( ! same age z ! re/ ( ! volcanic s]ies1 & n improbably ! deep-seat$ s\rce ( x4#cgd ,mr4 ,teall also1 f a *emical & microscopical exam9ation ( ! rocks1 drew a simil> conclusion4#cge ,footnote #cgd3 ,op4 cit4 p4 #bd4 ,footnote #cge3 ,geol4 ,mag4 #ahhe1 p4 #ajf4 ,! &esites ar\nd ! granite h und]gone contact-metamorphism1 b ! nature & ext5t ( ! *ange h n yet be5 /udi$4 ,!re occur ar\nd ! granite _m dykes ( felsite & qu>tz-felsite1 to ! petrographical "* ( :i* ref]5ce has already be5 made4 ,b ! mo/ abundant & rem>kable dykes ( ! di/rict are ^? ( a r$di% mica-porphyrite1 ( :i* ,mr4 ,cl\gh has mapp$ no few] ?an =ty1 besides ^? 9 ! granitic area4 ,he has call$ att5tion to ! significant mann] 9 :i* all ! dykes ( ! di/rict t5d to po9t 9 a g5]al way to ! great core ( granite1 z if t 7 ! nucleus f :i* !y _h radiat$4#cgf ,footnote #cgf3 ,op4 cit4 pp4 #bf-bh4 ,! c5tral granite ( ! ,*eviot ,hills1 ) its p]iph]al dykes1 has no accompany+ agglom]ates nor any decid$ pro( t x ev] communicat$ ) ! surface4 ,:51 h[ev]1 we consid] its petrographical & *emical con/itution1 its position z a core among ! b$d$ lavas1 & ! intimate way 9 :i* x is l9k$ ) ^! rocks by ! network ( dykes1 we are1 ,i ?9k1 ju/ifi$ 9 accept+ ! inf]5ce t x belongs to ! volcanic s]ies4 ,x possesses "s curi\s & int]e/+ features 9 common ) ! great granophyre bosses ( ,t]ti>y age 9 ! ,inn] ,hebrides4 ,l ^! x has no visible accompanim5t ( sup]ficial dis*>ges4 ,yet x may h asc5d$ by means ( "s c5tral v5t or gr\p ( v5ts :i*1 (f]+ to x a weak "p ( ! cru/1 all[$ x to communicate ) ! surface & give rise to ! outfl[ ( lavas & fragm5tal ejections4 ,9 any case1 x af=ds u a mo/ int]e/+ & in/ructive insight into "o ( ! deep]-seat$ ducts ( a volcanic region1 & ! relation ( a volcanic focus to ! asc5t ( ! granitic magma4 99 99 99 99 99 ,ab\t tw5ty miles to ! nor? ( ! ,*eviot ,hills1 & sep>at$ f !m by ! ,c>bonif]\s & ,upp] ,old ,r$ ,s&/ones :i* spread across ! broad pla9 ( ! ,m]se1 a gr\p ( volcanic rocks has be5 laid op5 9 a s+ul>ly in/ructive mann] along ! coa/ ( ,b]wick%ire1 betwe5 ! village ( ,eyem\? & ! promontory ( ,/4 ,abb's ,head4 ,n only ! actual v5ts1 b ! lavas & tuffs connect$ ) !m1 h !re be5 admirably dissect$ by ! =ces ( d5udation4 ,t ?is volcanic area 0 q di/9ct f t ( ! ,*eviot ,hills may be inf]r$ f its co>se agglom]ates1 & f ! fact t :5 ! rocks are foll[$ inl& 9 a s\?-we/]ly direction1 t is1 t[>ds ! ,*eviot area1 !y are f\nd to dim9i% 9 ?ickness & to disappe> among ! ord9>y s$im5ts4 ,= ! same reason we may reg>d ! area z indep5d5t ( any v5ts :i* may h ris5 fur!r we/ ab\t ,cockburn ,law & ! ,dirr+ton ,laws4 ,un=tunately1 h[ev]1 only a small "p ( ! area comes into view1 ! re/ ( x ly+ b5ea? ! wat]s ( ! ,nor? ,sea4#cgg ,footnote #cgg3 ,?is area lies 9 ,%eet #cd ,geological ,survey ( ,scotl&1 & 0 describ$ by myself 9 ! ,memoir to accompany t ,%eet 7,geology ( ,ea/]n ,b]wick%ire1 #ahfd1 p4 #bj74 ,m rec5tly ! %ore betwe5 ,/4 ,abb's ,head & ,cold+ham has be5 re-mapp$ by ,pr(essor ,james ,geikie :o has also /udi$ ! microscopic "* ( ! rocks1 ,proc4 ,roy4 ,soc4 ,ed94 xiv4 7#ahhg74 ,( ! sev]al v5ts dissect$ along ?is coa/-l9e1 "o may be se5 at ,eyem\?1 fill$ ) a v co>se tumultu\s agglom]ate ( &esite fragm5ts emb$d$ 9 a compact felspa?ic matrix1 ?r\gh :i* are scatt]$ brok5 cry/als ( felsp>1 & imp]fect tabul> cry/als ( black mica4 ,ano!r ( simil> "* is expos$ = m ?an a mile & a half along ! %ore at ,cold+ham4 ,x conta9s blocks1 sometimes m ?an a y>d 9 diamet]1 ( diff]5t v>ieties ( &esite1 &1 z at ,eyem\?1 is mu* invad$ by ve9s & bosses ( intrusive &esite4 ,illu/ration3 ,fig4 #ih4--,section across ! volcanic area ( ,/4 ,abb's ,head 7aft] ,pr(4 ,j4 ,geikie74 #aa4 ,silurian =mations2 #b4 ,l[] ,old ,r$ ,conglom]ate & ,s&/one2 #c #c4 ,%eets ( &esitic lava2 #d4 ,volcanic tuffs1 l>gely compos$ ( scori 9 ! high] p>ts2 #e4 ,volcanic agglom]ate ( neck on %ore2 #f4 ,intrusive &esites4 f1 ,fault4 ,to ! nor? ( ,cold+ham1 a s]ies ( b$d$ volcanic rocks :i* =m ! picturesque headl& ( ,/4 ,abb's ,head1 are1 accord+ to ! e/imate ( ,pr(essor ,james ,geikie1 ab\t #ajjj to #abjj feet ?ick1 b nei!r _! bottom nor _! top is se54 ,! same obs]v] f\nd !m to consi/ ( ?ree gr\ps ( &esite %eets sep>at$ & ov]la9 by b$d$ tuffs4 ,! l[e/ lavas h _! base conceal$ "u ! sea1 & are cov]$ by a ?ick b& ( co>se agglom]atic tuff1 above :i* lies ! second gr\p ( &esites1 ab\t #bej feet ?ick4 ,an int]calation ( v>i\s tuffs f #dj to #ej feet ?ick !n succe$s1 foll[$ by ! ?ird lava-gr\p1 #bej or #cjj feet 9 dep?4 ,! highe/ memb] ( ! s]ies is a mass ( b$d$ tuffs "s #djj feet ?ick4 ,! &esites lie 9 b$s v>y+ f ab\t #ae to ab\t #ej feet or m 9 ?ickness4 ,!y are f9e-gra9$1 purpli%-blue1 or greyi%-blue1 (t5 r$di% rocks1 ( ! usual type4 ,g5]ally r close-gra9$1 !y are n z a rule v porphyritic1 b (t5 highly scoriace\s & amygdaloidal1 especially t[>ds ! top & bottom ( ea* b$4 ,! m slaggy portions are sometimes s fill$ 9 ) f9e tuff t ! rock might be mi/ak5 = "o ( fragm5tal orig94 ,! b$d$ tuffs are usually well /ratifi$ deposits4 ,! mo/ important b& ( !m is t :i* =ms ! highe/ memb] ( ! volcanic s]ies4 ,x consi/s ( successive b$s t v>y f f9e r$ mud/ones up to volcanic breccias ) blocks "o foot or m 9 diamet]4 ,! mat]ials h be5 d]iv$ f ! explosion ( &esitic lavas4 ,mo/ ( ! lapilli are vesicul> or amygdaloidal1 & _m ( !m h evid5tly come f vitre\s scoriace\s lavas4 ,pr(essor ,geikie rem>ks t f _! highly vesicul> "*1 !y might well h float$ 9 wat] at ! "t ( _! ejection--!y are 9 %ort m]e c9d]s4 ,he c\ld detect no trace ( ord9>y s$im5t 9 ! matrix1 ! :ole mat]ial be+ ?or\ghly volcanic 9 orig94 ,! lavas1 tuffs & agglom]ates h be5 abundantly invad$ by intrusive rocks1 *iefly &esites4#cgh ,footnote #cgh3 ,see ,pr(4 ,j4 ,geikie1 op4 cit4 ,! agglom]ates ( ?is ,b]wick%ire coa/ ext5d = a %ort way inl& f ! ,cold+ham & ,eyem\? v5ts1 b ! fragm5tal mat]ial soon becomes f9] & m wat]-roll$1 & assumes a di/9ctly /ratifi$ /ructure1 z x is gradually & increas+ly int]leav$ ) lay]s ( ord9>y s$im5t4 ,h5ce 9 pass+ t[>ds ! s\?-we/1 away f ! coa/-l9e1 we are obvi\sly rec$+ f ! v5ts ( eruption & ent]+ into ! usual non-volcanic deposits ( ! "t4 ,t ^! deposits belong to ! ,l[] ,old ,r$ ,s&/one 0 fir/ asc]ta9$ dur+ ! progress ( ! ,geological ,survey 9 ?is di/rict by ! discov]y ( abundant plant-rema9s 9 ! =m ( l9e> grass-l /rips1 & also pieces ( ,pt]ygotus 9 "s ( ! gre5 %ales int]/ratifi$ among f9e tuffs & a%y s&/ones4#cgi ,be=e ! volcanic detritus disappe>s f ! /rata z !y are foll[$ 9 a s\?-we/]ly direction1 ! :ole s]ies is uncon=mably ov]la9 by ! ,upp] ,old ,r$ ,s&/one4 ,! l[] division ( ! =mation is n aga9 se5 until x rises f "u ! s\!rn m>g9 ( ! pla9 ( ! ,m]se into ! ,*eviot ,hills4 ,footnote #cgi3 ,geology ( ,ea/]n ,b]wick%ire1 ,mem4 ,geol4 ,surv4 ,scotl& 7#ahfd71 pp4 #bf1 #bg1 #eg4 ,ab\t t5 miles to ! s\?-we/ ( ! l>ge ,cold+ham neck ! great boss ( ,cockburn ,law & ,/one%iel ,hill rises out ( ! ,silurian rocks4#chj ,five miles /ill fur!r 9 ! same direction ! gr\p ( ! beautiful cones ( ,dirr+ton 7,fig4 #gj7 ov]looks ! wide ,m]se ( ,b]wick%ire1#cha & six miles to ! nor? ( ^! hills1 9 ! v he>t ( ,lamm]muir1 lies ! solit>y boss ( ! ,prie/law granite4#chb ,to ^! protrusions ( igne\s mat]ial ref]5ce has already be5 made z possible volcanic v5ts connect$ ) ! eruptions ( ! ,l[] ,old ,r$ ,s&/one4 ,z reg>ds _! age !y mu/ c]ta9ly be y\ng] ?an ! ,ll&ov]y rocks :i* !y disrupt1 & old] ?an ! ,upp] ,old ,r$ ,s&/one1 ( :i* ! conglom]ates1 l>gely made f _! debris1 lie on !m uncon=mably4 ,x seems !re=e probable t ^! great bosses may =m a "p ( ! volcanic hi/ory ( ! ,l[] ,old ,r$ ,s&/one p]iod4 ,b no positive pro( has yet be5 obta9$ t any "o ( !m 0 ! site ( an eruptive v5t1 & no trace has be5 detect$ ar\nd !m ( any lavas or tuffs :i* might h proce$$ f !m4 ,footnote #chj3 ,see ,! ,geology ( ,ea/]n ,b]wick%ire 7,%eet #cd71 ,mem4 ,geol4 ,surv4 ,scotl& 7#ahfd71 p4 #bi4 ,footnote #cha3 ,^! hills are *iefly repres5t$ 9 ,%eet #be4 ,b see ,! ,geology ( ,ea/ ,lo?ian1 ,mem4 ,geol4 ,surv4 ,scotl& 7#ahff71 p4 #bf4 ,footnote #chb3 ,geology ( ,ea/ ,lo?ian1 ,mem4 ,geol4 ,surv4 ,scotl&1 p4 #ae1 & au?orities !re cit$4 ,,! ,,lake ,,( ,,lorne ,illu/ration3 ,fig4 #ii4--,view ( t]rac$ &esite hills re/+ on massive conglom]ate1 s\? ( ,oban4 ,! bas9 ( ,lorne has n yet be5 c>efully exam9$ & describ$1 ?\gh v>i\s writ]s h ref]r$ to diff]5t p>ts ( x 7,map ,i474 ,my own obs]vations h be5 too few to enable me to give an adequate acc\nt ( x4 ,! volcanic %eets ( ?is area =m a notable feature 9 ! sc5]y ( ! ,we/ ,highl&s1 = !y are ! mat]ials out ( :i* ! rem>kable t]rac$ hills h be5 c>v$1 :i* /ret* f ,lo* ,mel=t to ,lo* ,cr]an 7,fig4 #ii71 & :i* reappe> 9 picturesque outli]s among ! m\nta9s trav]s$ by ,gl5 ,coe4 ,betwe5 ! anci5t s*i/s t =m ! f\ndation-rocks ( ?is di/rict & ! base ( ! volcanic s]ies1 lies a gr\p ( s$im5t>y /rata :i* 9 ! we/]n "p ( ! di/rict mu/ be #ejj feet ?ick4 ,?is gr\p consi/s ( exce$+ly co>se breccias at ! bottom1 above :i* come massive conglom]ates1 volcanic grits or tuffs1 f9e s&/ones & c\rses ( %ale4 ,:ile ! basem5t-breccias are compos$ ma9ly ( detritus ( ! und]ly+ s*i/s1 includ+ blocks six feet long1 !y pass up into co>se conglom]ates made up almo/ entirely ( fragm5ts ( diff]5t lavas 7&esites1 diabases1 etc471 & m ?an #ajj feet ?ick1 :i* (t5 %[ little or no trace ( /ratification1 b break up into l>ge quadrangul> blocks by means ( jo9ts :i* cut across ! imb$d$ b\ld]s4 ,^! volcanic conglom]ates =m "s ( ! m conspicu\s features ( ! coa/ to ! s\? & nor? ( ,oban1 & are well expos$ 9 ! ,isle ( ,k]r]a4 ,!y (f] _m po9ts ( resemblance to ^? ( ,lake ,cal$onia1 b no c]ta9 pro( has be5 not$ t !y belong to ! ,l[] ,old ,r$ ,s&/one4 ,!y h obvi\sly be5 d]iv$ f lava-%eets t 7 expos$ to /rong break]-action1 :i* at ! same "t transport$ & r\nd$ blocks ( granite1 s*i/ & o!r cry/all9e rocks d]iv$ f ! adjac5t hills4 ,dur+ ! int]vals ( quiet] s$im5tation indicat$ by ! f9e s&/ones & %ales1 volcanic explosions cont9u$1 z may be se5 by ! occurr5ce ( occasional l>ge bombs :i* h fall5 ^u & press$ d[n ! f9e a%y silt t 0 ga!r+ on ! bottom4 ,x w\ld seem f ! *>act]s ( "s ( ! /rata 9 ?is s$im5t>y s]ies t ov] ! area ( deposit portions ( ! %all[] wat]s 7 occasionally laid b>e to ! sun & air4 ,among ! conglom]ates !re lie c]ta9 b&s ( r$di% s&y1 ripple-m>k$1 sun-crack$ & ra9-pitt$ %ales & f9e s&/ones4 ,su* accumulations1 indicative ( ! ultimate exposure ( f9e s$im5t t silt$ up holl[s 9 ! great banks ( co>se %+le1 may be notic$ at ! s\? end ( ! ,isl& ( ,k]r]a1 on at lea/ two horizons :i* are sep>at$ f ea* o!r by ?ick masses ( conglom]ate & f9e felspa?ic grit4 ,we may inf]1 !re=e1 t ! f9e littoral mud1 :i* ga!r$ dur+ pauses 9 ! heap+ up ( ! co>se gravel & %+le1 0 occasionally laid dry4 ,simil> /rata may be obs]v$ beh9d ,oban1 :]e ! alt]nation ( exce$+ly f9e s$im5t & granul> a%y b&s is well exhibit$4 ,illu/ration3 ,fig4 #ajj4--,section ( lava-esc>pm5t at ,be9n ,lora1 nor? side ( m\? ( ,lo* ,etive1 ,argyll%ire4 #a4 ,phyllites2 #b4 ,?ick conglom]ate2 #c4 ,successive %eets ( &esite4 ,b ! explosions t gave rise to ! volcanic mat]ials s l>gely repres5t$ 9 ^! l[] conglom]ates1 7 m]ely prelim9>y to ^? :i* l$ to ! outfl[ ( ! great %eets ( lava t n[ con/itute s l>ge a "p ( ! hills ( ,lorne4 ,9 ! few trav]ses :i* ,i h made across diff]5t p>ts ( ?is di/rict ,i h not$ ! g5]al resemblance ( ! lavas to ^? ( ! ,l[] ,old ,r$ ,s&/one ( ! ,midl& ,valley ( ,scotl&1 _! b$d$ "*1 & ! occurr5ce ( occasional lay]s ( /ratifi$ mat]ial betwe5 !m4 ,! prom95t features ( ^! rocks1 & _! relation to ! volcanic conglom]ates bel[ !m1 & to ! und]ly+ slates & s*i/s are well display$ on ,be9n ,lora at ! m\? ( ,lo* ,etive 7,fig4 #ajj74 ,!re ! black slates ( ! di/rict are uncon=mably cov]$ by ! co>se volcanic conglom]ate1 =m$ *iefly ( blocks ( &esite1 cem5t$ 9 a h>d matrix ( simil> composition4 ,ab\t #aej or #bjj feet ( ?is mat]ial und]lie ! great esc>pm5t ( ! lavas1 :i* "h rise 9 successive b$s to ! top ( ! hill1 #ajjj feet above its base4 ,on ! s\? side ( ,lo* ,etive ! base ( ! volcanic s]ies1 ) its und]ly+ conglom]ate1 may be foll[$ we/w>d to ,oban & !nce s\?w>d to ,lo* ,feo*an4 ,! lavas cov] mo/ ( ! gr\nd f ! we/]n %ore ea/w>ds to ne> ,lo* ,awe4 ,b ?is area is /ill v imp]fectly kn[n4 ,! ,geological ,survey1 h[ev]1 has n[ advanc$ to ?is "p ( ! c\ntry1 s t we %all be=e long be 9 possession ( m detail$ in=mation reg>d+ ! "* & sequ5ce ( its volcanic hi/ory & ! geological age ( ! eruptions4 ,mr4 ,h4 ,kyna/on1 :o has begun ! mapp+ ( ! ea/]n portion ( ! di/rict1 f9ds t !re1 z fur!r we/1 ! bottom ( ! volcanic s]ies is g5]ally a breccia or conglom]ate4 ,he has met ) two lead+ types among ! lavas1 ! m abundant be+ /rongly vesicul>1 ! o!r m compact4 ,he has obs]v$ also num]\s dykes & sills ( intrusive porphyrite1 tr5d+ 9 a g5]al ,n4,n4,e4 & ,s4,s4,w4 direction1 & po9t+ t[>ds ! great granite mass ( ,b5 ,crua*an4#chc ,footnote #chc3 ,ann4 ,report ,geol4 ,surv4 7#ahie71 p4 #bi ( repr9t4 ,mr4 ,r4 ,g4 ,symes has trac$ ! volcanic s]ies to ! nor? & s\? ( ,oban4 ,:ile visit+ ) him "p ( 8 gr\nd1 ,i 0 mu* /ruck ) ! evid5ce ( an intrusive mass at ! base ( ! volcanic s]ies 9 ! ,s\nd ( ,k]r]a4 ,a prom95t feature on ! ea/ side ( ! *annel1 kn[n z ,dun ,uabairti* & #bgj feet high1 consi/s ( &esite :i* appe>s to comb9e bo? a c5tral boss & a sill4 ,! rock breaks ?r\gh ! black slates & ! ov]ly+ conglom]ates & s&/ones1 & has w$g$ itself into ! uncon=mable junction betwe5 ! two =mations4 ,x is beautifully column> on its sea-cov]$ face1 "s ( ! columns be+ #abj feet or m 9 l5g?1 & g5tly curv$4 ,,lake ,,orcadie ,we n[ cross ! :ole bread? ( ! ,scotti% ,highl&s 9 ord] to p]use ! records ( ano!r ( ! great deta*$ wat]-bas9s ( ! ,old ,r$ ,s&/one1 :i* = ! sake ( brevity ( ref]5ce ,i h nam$ & describ$ z ,lake ,orcadie 7,map ,i474 ,?is area has its s\!rn limits along ! base ( ! hills t enclose ! wide ,moray ,fir?4 ,x spreads nor?w>d ov] ! ,orkney & mu* ( ! ,%etl& ,isl&s1 b its b\nd>ies 9 t direction are lo/ "u ! sea4 ,9 ! ext5sive %eet ( wat] :i* spread ov] all t nor!rn region ! peculi> ,cai?ness ,flags1 ) _! associat$ s&/ones & conglom]ates1 7 deposit$ to a total dep? ( #af1jjj feet4 ,a sigill>oid & lycopodiace\s vegetation fl\ri%$ on ! surr\nd+ l&1 toge!r ) f]ns1 ,psilophyton & conif]s4 ,! wat]s teem$ ) fi%es ( :i* _m g5]a & species h n[ be5 describ$4 ,! rema9s ( ^! creatures lie cr[d$ ^u ea* o!r 9 ! flag/ones 9 su* a mann] z to indicate t f "t to "t va/ quantities ( fi% 7 sudd5ly kill$4 ,n impossibly1 ^! de/ructions may h be5 connect$ ) ! volcanic activity :i* has n[ to be describ$4 ,9 ! ye> #ahgh ,i call$ att5tion to ! evid5ce = ! exi/5ce ( contemporane\s volcanic rocks 9 ! ,old ,r$ ,s&/one nor? ( ! range ( ! ,grampians1 & specially not$ ?ree localities :]e ?is evid5ce c\ld be se5--,/ra?bogie1 ,buckie & ,%etl&4#chd ,s9ce t "t ,messrs4 ,b4 ,n4 ,pea* & ,j4 ,horne h add$ a f\r? c5tre 9 ! ,orkney ,isl&s4 ,at pres5t1 !re=e1 we are acqua9t$ ) ! records ( f\r sep>ate gr\ps ( volcanic v5ts 9 ,lake ,orcadie4 ,footnote #chd3 ,trans4 ,roy4 ,soc4 ,ed94 xxviii4 7#ahgh74 ,! s\!rn m>g9 ( ?is wat]-bas9 appe>s to h ind5t$ ! l& ) long fjord-l inlets4 ,"o ( ^! n[ =ms ! vale ( ,/ra?bogie1 :i* runs into ! hills = a di/ance ( fully #bj miles beyond :at seems to h be5 ! g5]al tr5d ( ! coa/-l9e4 ,9 ?is valley ,i f\nd a b$ ( d>k vesicul> diabase int]calat$ among ! r$ s&/ones & high above ! base ( ! =mation1 z expos$ on ! we/ side ( ! valley ne> ,burn ( ,craig4 ,on ! ea/ side a simil> b& has s9ce be5 mapp$ = ! ,geological ,survey by ,mr4 ,l4 ,h9xman :o has trac$ x = "s miles d[n ! ,/ra?4#che ,?is latt] b&1 z %[n 9 ,fig4 #aja1 lies n f> above ! bottom ( ! ,old ,r$ ,s&/one ( ?is di/rict1 & is ?us probably di/9ct f ! ,craig outcrop4 ,!re w\ld ?us appe> to be evid5ce ( two sep>ate outfl[s ( basic lava 9 ?is fjord ( ! ,old ,r$ ,s&/one p]iod4 ,footnote #che3 ,see ,%eet #gf ( ! ,geological ,survey ( ,scotl&4 ,illu/ration3 ,fig4 #aja4--,section across ,/ra?bogie1 bel[ ,rhynie1 %[+ ! position ( ! volcanic b&4 #a4 ,knott$ s*i/s2 #b4 ,diorite intrusive 9 s*i/s2 #c4 ,old ,r$ ,conglom]ate2 #d4 ,volcanic b&2 #e4 ,%ales ) calc>e\s nodules2 #f4 ,s&/ones ( ,rhynie2 #g4 ,%ales & s&/ones4 f1 ,fault4 ,no ve/ige has "h be5 f\nd ( any v5t1 nor is ! lava accompani$ ) tuff4 ,! eruptions took place "s "t aft] ! e>li] s$im5ts ( ! bas9 7 accumulat$1 b ceas$ be=e ! ?ick mass ( upp] s&/ones & %ales 0 deposit$4 ,a section across ! valley gives ! /ructure repres5t$ 9 ! accompany+ diagram 7,fig4 #aja74 ,tw5ty-five miles fur!r nor? a /ill small] &esite b& has be5 detect$ by ,mr4 ,j4 ,grant ,wilson among ! s&/ones & conglom]ates ne> ,buckie4#chf ,x is a truly contemporane\s fl[1 = pebbles ( x occur 9 ! ov]ly+ /rata4 ,b aga9 x =ms only a solit>y b$1 & no trace ( any accompany+ tuff has be5 met )1 nor ( ! v5t f :i* x came4 ,bo? ?is v5t & t ( ,/ra?bogie mu/ h be5 situat$ ne> ! s\!rn coa/-l9e ( ! lake4 ,footnote #chf3 ,see ,%eet #ie ( ! ,geological ,survey ( ,scotl& & ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxviii4 7#ahgh71 p4 #dce4 ,at a di/ance ( "s #ij miles nor?w>d f ^! ,moray ,fir? v5ts ano!r volcanic di/rict lies 9 ! v he>t ( ! ,orkney ,isl&s4#chg ,! lavas :i* 7 !re eject$ occur at ! s\?-ea/]n corn] ( ! isl& ( ,%ap9%ay1 :]e !y are regul>ly b$d$ ) ! flag/ones4 ,!y consi/ ( d>k gre5 oliv9e-diabases ) highly amygdaloidal & vesicul> upp] surfaces4 ,_! ?ickness _c be asc]ta9$1 z _! base is n se51 b !y h be5 cut by ! sea into tr5*es :i* %[ !m to exce$ #cj feet 9 dep?4 ,! position ( ! v5t f :i* !y came has n be5 asc]ta9$4 ,nei!r "h nor 9 ! ,moray ,fir? area d any sills accompany ! int]b$d$ %eets1 & 9 bo? cases ! volcanic action w\ld seem to h be5 ( a feeble & %ort-liv$ "*4 ,footnote #chg3 ,messrs4 ,b4 ,n4 ,pea* & ,j4 ,horne1 ,proc4 ,roy4 ,phys4 ,soc4 ,ed94 vol4 v4 7#ahgi71 p4 #hj4 ,mu* m important 7 ! volcanoes t broke out ne>ly #ajj miles /ill fur!r nor?1 :]e ! ,ma9l& ( ,%etl& n[ lies4 ,i %all nev] =get ! pleasure ) :i* ,i fir/ recogniz$ ! traces ( ^! eruptions1 & f\nd ne> ! mo/ nor!rly limits ( ! ,briti% ,isles pro(s ( volcanic activity 9 ! ,l[] ,old ,r$ ,s&/one4 ,s9ce my obs]vations 7 publi%$1#chh ,mr4 ,pea*1 :o accompani$ me 9 ,%etl&1 has return$ to ! di/rict1 &1 9 conc]t ) 8 colleague ,mr4 ,horne1 has ext5d$ our k ( ! subject4#chi ,! *ief v5t or v5ts lay t[>ds ! we/ & nor?-we/ ( ! ,ma9l& & ,nor? ,mav9e2 o!rs ( a less active & p]si/5t type 7 bl[n out "s #be miles to ! ea/1 :]e ! isl&s ( ,bressay & ,noss n[ /&4 ,9 ! we/]n di/rict /reams ( slaggy &esite & diabase ) %[]s ( f9e tuff & co>se agglom]ate 7 eject$1 until ! total accumulation rea*$ a ?ickness ( n less ?an #ejj feet4 ,! volcanic eruptions took place contemporane\sly ) ! deposition ( ! r$ s&/ones1 = ! lavas & tuffs are int]calat$ 9 ^! /rata4 ,! lavas & volcanic conglom]ates are traceable f ! s\!rn coa/ ( ,papa ,/\r across ,/4 ,magnus' ,bay to ! we/]n headl&s ( ,e%a ,ness1 a di/ance ( m ?an #ad miles4 ,!y h be5 cut by ! ,atlantic into a picturesque range ( cliffs1 :i* exhibit 9 "s places1 z at ! s+ul> sea-/alk ( ,doreholm1 r\gh banks ( &esitic lava ) ! conglom]ate deposit$ aga9/ & ov] !m1 & 9 o!r places1 z along ! cliffs ( ,e%a ,ness1 %eets ( lava ov]ly+ ! conglom]ates4 ,footnote #chh3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxviii4 7#ahgh71 p4 #dah4 ,footnote #chi3 ,ibid4 vol4 xxxii4 7#ahhd71 p4 #cei4 ,no trace ( any v5ts has be5 f\nd 9 ! we/]n & *ief volcanic di/rict1 b 9 ,noss ,s\nd a gr\p ( small necks occurs1 fill$ ) a co>se agglom]ate compos$ ( pieces ( s&/one1 flag/one & %ale4 ,messrs4 ,pea* & ,horne inf] t ^! little orifices nev] dis*>g$ any /reams ( lava4 ,m probably !y 7 op5$ by explosions :i* only gave =? vap\rs & fragm5t>y dis*>ges1 su* z a b& ( tuff :i* is int]calat$ among ! flag/ones 9 _! neighb\rhood4 ,b "o ( ! mo/ /rik+ features ( ! volcanic ph5om5a ( ?is remote region is ! relative size & numb] ( ! sills & dykes :i* "h z else:]e m>k ! late/ phases ( subt]ranean activity4 ,messrs4 ,pea* & ,horne h %[n u t ?ree great %eets ( acid rocks 7granites & sph]ulitic felsites1 to :i* ref]5ce has already be5 made1 p4 #bib7 h be5 inject$ among ! s&/ones & basic lavas1 t abundant ve9s ( granite1 qu>tz-felsite & rhyolite radiate f ^! acid sills1 & t ! late/ phase ( igne\s action 9 ?is region 0 ! intrusion ( a s]ies ( bosses & dykes ( basic rocks 7diabases7 :i* trav]se ! sills4 ,! ,kill>ney ,di/rict ,9 ! s\? ( ,irel& ! ,upp] ,silurian /rata are foll[$ upw>ds con=mably by ! great s]ies ( r$ s&/ones & conglom]ates kn[n z ! ,d+le ,b$s4 ,li?ologically ^! rocks pres5t ! close/ resemblance to ! ,l[] ,old ,r$ ,s&/one ( ,c5tral ,scotl&4 ,!y occupy a simil> /ratigraphical position1 & ?\gh !y h n yield$ any palontological data = comp>ison1 !re c1 ,i ?9k1 be no hesitation 9 class+ !m ) ! ,scotti% ,l[] ,old ,r$ ,s&/one1 & reg>d+ !m z hav+ be5 deposit$ "u simil> geographical conditions4 ,!y (f] "o feature ( special int]e/ = ! purpose ( ! pres5t inquiry1 s9ce !y conta9 a well-m>k$ gr\p ( contemporane\s volcanic rocks1 includ+ nodul> felsites1 l ^? s *>act]i/ic ( ! ,silurian p]iod4 ,! area :]e ?is remote & isolat$ volcanic gr\p is be/ develop$ =ms a range ( high rugg$ gr\nd along ! nor!rn front ( ! hills t /ret* ea/w>d f ! ,lakes ( ,kill>ney4 ,_! g5]al di/ribution is %[n on ,%eets #ahd & #ahe ( ! ,geological ,survey ( ,irel&2#cij ?\gh ,i may aga9 rem>k t petrography has made great /rides dur+ ! ?irty ye>s & m t h pass$ s9ce ^! maps & _! accompany+ ,memoirs 7 publi%$1 & t1 7 ! di/rict to be survey$ n[1 probably a consid]able tract ( gr\nd col\r$ z a% w\ld be m>k$ z felsite4 ,at ! same "t ! exi/5ce ( bo? ^! rocks "h _c be ga9said4 ,footnote #cij3 ,see ! ,memoir 7by ,j4 ,b4 ,jukes & ,g4 ,v4 ,du ,noy]7 on ,%eet #ahd1 p4 #ae4 ,o!r volcanic rocks h be5 mapp$ at ,val5tia ,h>b\r 9 ! ,d+le ,b$s1 b ^! ,i h n _h an opportunity ( p]sonally exam9+4 ,! felsite 0 long ago br\ght into notice by ,dr4 ,haughton1 :o publi%$ an analysis ( x4#cia ,x is also ref]r$ to by ,mr4 ,teall = its sph]ulitic /ructure4#cib ,se5 on ! gr\nd x appe>s z a pale gre5i%-grey close-gra9$ rock1 sometimes exhibit+ fl[-/ructure 9 a rem>kably cle> mann]1 ! lam9 ( devitrification foll[+ ea* o!r 9 wavy l9es1 sometimes twi/$ & delicately puck]$ or frill$1 z 9 "s s*i/s4 ,portions ( ! rock are /rongly nodul>1 ! nodules v>y+ 9 size f less ?an a pea to t ( a h5's egg4 ,footnote #cia3 ,trans4 ,roy4 ,iri% ,acad4 vol4 xxiii4 7#ahei71 p4 #fae4 ,footnote #cib3 ,briti% ,petrography1 p4 #cdi4 ,! close resemblance ( ?is rock to _m ( ! ,l[] ,silurian nodul> felsites ( ,wales _c b /rike ! geologi/4 ,x pres5ts analogies also to ! ,upp] ,silurian felsites ( ,d+le4 ,b its *ief int]e/ arises f ! geological horizon on :i* x occurs4 ,ly+ 9 ! s-call$ ,d+le-,b$s1 :i* may be reg>d$ z ! equival5ts ( ! ,l[] ,old ,r$ ,s&/one ( ,engl& & ,scotl&1 x is1 s f> z my obs]vations g1 ! only example ( su* a nodul> felsite ( lat] date ?an ! ,silurian p]iod4 ,we recognize 9 x a survival1 z x 71 ( ! peculi> ,silurian type ( acid lava1 ! la/ prec$+ eruption ( :i* took place n _m miles to ! we/1 9 ! ,d+le promontory4 ,b else:]e ?is type does n appe> to h surviv$ ! end ( ! ,silurian p]iod4 ,! detrital rocks accompany+ ! felsite1 9 ! di/rict ea/ ( ,kill>ney1 v>y f su* clos$-gra9$ felsitic mat]ial z _c readily be di/+ui%$ f ! felsite itself to unmi/akable felsitic breccias4 ,ev5 9 ! f9e/ p>ts ( !m1 occasional r\nd$ qu>tz-pebbles may be detect$1 :ile "h & !re a r$di% %aly b&1 or a lay] ( f9e pebbly conglom]ate ) qu>tz-pebbles an in* 9 l5g?1 %[s at once ! b$d+ & ! dip4 ,mr4 ,w4 ,w4 ,watts1 :o1 ) ,mr4 ,a4 ,m',h5ry ( ! ,iri% ,/aff ( ! ,geological ,survey1 accompani$ me ov] ?is gr\nd1 f\nd t a microscopic exam9ation ( ! slides :i* 7 prep>$ f ! specim5s we collect$ completely confirm$ ! conclusions rea*$ f inspection ( ! rocks 9 ! field4#cic ,he detect$ among ! angul> gra9s slightly damag$ cry/als ( felsp>1 *iefly or?oclase4 ,_m portions ( ^! felspa?ic grits mu* resemble ! detrital ,cambrian rocks :i* 9 ! ,vale ( ,llanb]is h be5 made out ( ! pale felsite ( t locality4 ,footnote #cic3 ,mr4 ,watts also exam9$ ! microscopic /ructure ( ! felsite ( ,b5aun ,m4 ,he f\nd t ! sph]ulites appe> to h a micropegmatitic /ructure1 ow+ to ! int]gr[? ( qu>tz & felsp>4 ,9 "s p>ts ( ! rock ! sph]ulites1 f #jb to #ja in* 9 diamet]1 are surr\nd$ by exce$+ly m9ute gre5 ne$les1 possibly ( hornbl5de1 :ile inside "s ( !m are small qu>tz-gra9s4 ,l>g] porphyritic felsp>s occur outside ! sph]ulites1 "s be+ ( plagioclase1 b mo/ ( or?oclase4 ,! sph]ulitic /ructure is n s well develop$ ne> ! felsp>s4 ,a few ( ! l>ge nodules are holl[ & l9$ ) cry/als1 :ile "s ( !m %[ a f9ely conc5tric lam9ation l ! successive lay]s ( an agate4 ,,*apt] ,,xxii ,,volcanoes ,,( ,,! ,,upp] ,,old ,,r$ ,,s&/one--,,! ,,s\?-,,we/ ,,( ,,irel&1 ,,! ,,nor? ,,( ,,scotl& ,9 ! nor!rn half ( ,brita91 :]e ! ,old ,r$ ,s&/one is s well display$1 ! two great divisions into :i* ?is s]ies ( s$im5t>y deposits is !re divisible are sep>at$ f ea* o!r by a /rongly m>k$ uncon=mability4 ,! int]val ( "t repres5t$ by ?is break mu/ h be5 ( long duration1 = x witness$ ! effacem5t ( ! old wat]-bas9s1 ! fold+1 fracture1 & elevation ( _! ?ick s$im5t>y & volcanic accumulations1 & ! removal by d5udation (1 9 "s places1 sev]al ?\s& feet ( ^! rocks4 ,! ,upp] ,old ,r$ ,s&/one1 consi/+ s l>gely z x does ( r$ s&/ones & conglom]ates1 indicates ! return or p]si/5ce ( geographical conditions n unlike ^? t m>k$ ! deposition ( ! l[] subdivision4 ,b 9 "o important respect its hi/ory diff]s greatly f t :i* ,i h sket*$ = ! old] "p ( ! sy/em4 ,?\gh ! ,upp] ,old ,r$ ,s&/one is well develop$ across ! s\!rn di/ricts ( ,scotl& f ! ,o*il to ! ,*eviot ,hills1 & appe>s 9 scatt]$ areas ov] s mu* ( ,engl& & ,wales1 no trace has ev] be5 !re detect$ 9 x ( any contemporane\sly erupt$ volcanic rocks4 ,! topographical *anges :i* prec$$ its deposition mu/ h involv$ no inconsid]able am\nt ( subt]ranean di/urbance1 yet ! volcanic en]gy1 :i* _h di$ out s completely long be=e ! close ( ! "t ( ! ,l[] ,old ,r$ ,s&/one1 does n appe> to h be5 rek9dl$ until ! beg9n+ ( ! ,c>bonif]\s p]iod4 ,two widely sep>at$ tracts 9 ! ,briti% ,isles h yield$ traces ( contemporane\s volcanic rocks 9 ! ,upp] ,old ,r$ ,s&/one4 ,"o ( ^! lies 9 ! s\?-we/ ( ,irel&1 ! o!r 9 ! f> nor? ( ,scotl&4 ,,! ,,s\?-,,we/ ,,( ,,irel& ,! ,iri% locality is situat$ a few miles to ! s\? ( ! t[n ( ,lim]ick1 :]e ! ,c>bonif]\s ,lime/one has be5 ?r[n into long folds1 & :]e1 along ! anticl9es1 /rips ( ! und]ly+ r$ s&/ones h be5 br\ght up to ! surface4 ,two su* ridges ( ,upp] ,old ,r$ ,s&/one be>1 ea* on its cre/1 a small b int]e/+ relic ( volcanic activity#cid 7,map ,i474 ,footnote #cid3 ,see ,%eet #aec ( ! ,geological ,survey ( ,irel&1 & ,explanation to t ,%eet 7#ahfa71 by ,messrs4 ,g4 ,h4 ,k9ahan & ,j4 ,o',kelly4 ,! acc\nt ( ! gr\nd above giv5 is f notes :i* ,i made dur+ a p]sonal visit4 ,! m nor!rly ridge rises 9 ! conical em95ce ( ,knockfe]9a to a height ( #idi feet above ! sea4 ,ev5 f a di/ance ! resemblance ( ?is hill 7,fig4 #ajb7 to _m ( ! ,c>bonif]\s necks ( ,scotl& at once attracts ! eye ( ! geologi/4 ,! resemblance is f\nd to hold /ill m closely :5 ! int]nal /ructure ( ! gr\nd is exam9$4 ,! cone consi/s ma9ly ( a co>se agglom]ate1 ) blocks g5]ally some:at r\nd$ & v>y+ 9 size up to two feet 9 l5g?4 ,! mo/ prom95t ( ^!1 on ! l[] ea/]n slopes1 are pieces ( a f9e fl9ty felsite wea!r+ :ite1 b !re also occur fragm5ts ( grit & bak$ %ale4 ,! matrix is dull-gre5 9 col\r1 & among its +r$i5ts are abundant small lapilli ( a f9ely vesicul> &esite or diabase4 ,^! m basic +r$i5ts increase 9 numb] t[>ds ! top ( ! em95ce1 :]e mu* ( ! agglom]ate is almo/ :olly made up ( !m4 ,no m>k$ dip is obs]vable ov] mo/ ( ! hill1 ! rock appe>+ z a tumultu\s agglom]ate1 ?\gh "h & !re1 p>ticul>ly ne> ! top & on ! s\? side1 a rude b$d+ may be detect$ dipp+ outw>ds4 ,on ! we/ side ! agglom]ate is flank$ ) yell[ s&/one bak$ into qu>tzite1 s t ! l9e ( junction !re betwe5 ! two rocks n improbably gives u ! actual wall ( ! v5t4 ,! induration ( ! surr\nd+ s&/ones is a famili> feature among ! ,c>bonif]\s v5ts4 ,"s intrusive d>k fl9ty rock trav]ses ! agglom]ate ne> ! top on ! nor? side4 ,illu/ration3 ,fig4 #ajb4--,view ( ,knockfe]9a1 ,lim]ick1 f ! nor?-ea/--a volcanic neck ( ,upp] ,old ,r$ ,s&/one age4 ,retir+ ea/w>ds f ! cone1 ! obs]v] f9ds evid5ce ( ! int]calation ( tuff among ! surr\nd+ ,upp] ,old ,r$ ,s&/one4 ,at ! ea/ end ( ! village ( ,knockfe]9a a r$ nodul> tuff1 ) r\nd$ pieces ( &esite1 grit & s&/one1 sometimes #ab in*es long1 is se5 to dip "u yell[1 grey & r$ s&/ones & %ales1 :ile o!r %ales & s&/ones und]lie ?is tuff & crop out betwe5 x & ! agglom]ate4 ,!re is ?us evid5ce ( ! int]calation ( volcanic tuff 9 ! ,upp] ,old ,r$ ,s&/one ( ?is di/rict4 ,& !re seems no reason to d\bt t ! tuff 0 eject$ f ! adjo9+ v5t ( ,knockfe]9a4 ,on ! next ridge ( ,old ,r$ ,s&/one1 :i* runs p>allel to t ( ,knockfe]9a at a di/ance ( little m ?an a mile to ! s\?1 ano!r mass ( volcanic mat]ial rises into a prom95ce at ,ball9le5y4 ,on ! nor? side x consi/s ( agglom]ate l t j describ$1 & is flank$ by s&/one bak$ into qu>tzite4 ,"h aga9 we probably see ! edge ( a volcanic funnel4 ,!re may possibly be m ?an "o v5t 9 ?is area4 ,b well-b$d$ tuffs c be obs]v$ to dip away f ! c5tre & to pass "u s&/ones & %ales :i* are full ( f9e a%y mat]ial4 ,gradations c be trac$ f ! tuff into ord9>y s$im5t4 ,9 ?is in/ance1 !re=e1 !re is additional pro( ( contemporane\s volcanic action 9 ! ,upp] ,old ,r$ ,s&/one4 ,!re c be no unc]ta9ty z to ! horizon ( ! /rata 9 :i* ^! records h be5 pres]v$1 = !y dip con=mably "u ! %ales & lime/ones at ! base ( ! ,c>bonif]\s ,lime/one s]ies4 ,!y are said to h yield$ ! *>act]i/ic f]n ,palopt]is ( ,kiltorcan4#cie ,footnote #cie3 ,!re may be "s o!r examples ( ,upp] ,old ,r$ ,s&/one volcanic rocks 9 ,irel& :i* ,i h n yet be5 able p]sonally to exam9e4 ,on ! maps ( ! ,geological ,survey 7,%eet #aih1 & ,explanation1 pp4 #h1 #ag7 contemporane\s rocks ( ?is age are m>k$ z occurr+ at ,cod's ,head & ,dursey ,isl&1 on ! s\? side ( ! m\? ( ! ,k5m>e e/u>y4 ,,! ,,nor? ,,( ,,scotl& ,! only di/rict 9 ,engl& or ,scotl& :]e9 traces ( volcanic action dur+ ! "t ( ! ,upp] ,old ,r$ ,s&/one h be5 obs]v$ lies f> to ! nor? among ! ,orkney ,isl&s1 ne> ! c5tre ( ! scatt]$ outli]s :i* ,i h unit$ z p>ts ( ! deposits ( ,lake ,orcadie#cif 7,map ,i474 ,! ?ick gr\p ( yell[ & r$ s&/ones :i* =m mo/ ( ! high isl& ( ,hoy1 & :i*1 !re c be little d\bt1 are correctly ref]r$ to ! ,upp] ,old ,r$ ,s&/one1 re/ ) a m>k$ uncon=mability on ! edges ( ! ,cai?ness flag/ones 7,fig4 #ajc74 ,at ! base ( ^! pale s&/ones1 & regul>ly int]/ratifi$ ) !m1 lies a b& ( lavas & tuffs :i* c be trac$ f ! base ( ! r\nd$ hills to ! edge ( ! cliffs at ! ,cam1 along ! face ( :i* x runs z a conspicu\s feature1 gradually slop+ to a l[] level1 till x rea*es ! sea4 ,at ! ,cam ( ,hoy x is ab\t #bjj feet ?ick1 & consi/s ( ?ree or m %eets ( &esite4 ,! upp] #ej or #fj feet %[ a /rongly slaggy /ructure1 ! c5tral portion is rudely column>1 & ! l[] "p pres5ts a k9d ( horizontal jo9t+ or b$d+4 ,!re c be no "q t ?is rock is n a sill b a gr\p ( contemporane\s lava-fl[s4 ,b5ea? x1 & ly+ across ! edges ( ! flag/ones bel[1 !re is a zone ( dull-r$1 f9e-gra9$ tuff1 b&$ ) seams ( h>d r$ & yell[ s&/one4 ,?is tuff zone dies out to ! ea/w>d ( ! ,cam4 ,footnote #cif3 ,fir/ notic$ 9 ,geol4 ,mag4 ,febru>y #ahgh2 & ,trans4 ,roy4 ,soc4 ,ed94 xxviii4 7#ahgh71 p4 #daa4 ,illu/ration3 ,fig4 #ajc4--,section ( ! volcanic zone 9 ! ,upp] ,old ,r$ ,s&/one1 ,cam ( ,hoy1 ,orkney4 #a4 ,cai?ness flag/ones2 #b4 ,dull-r$ tuff & b&s ( s&/one2 #c4 ,lava zone 9 ?ree b&s2 #d4 ,yell[ & r$ s&/one4 ,illu/ration3 ,fig4 #ajd4--,section ( ! volcanic zone 9 ! ,upp] ,old ,r$ ,s&/one at ,black ,ness1 ,rackwick1 ,hoy4 ,a few miles s\? ( ! ,cam ! volcanic zone appe>s aga9 z ! plat=m on :i* ! picturesque natural obelisk ( ! ,old ,man ( ,hoy /&s4 ,"h ! lava runs out z a promontory f ! base ( ! cliff1 & on ?is projection ! ,old ,man has be5 left isolat$ f ! ma9 precipice4 ,! cliffs ( ,hoy are trav]s$ by num]\s small faults :i* h %ift$ ! volcanic zone4 ,b on ! great face ( rock beh9d ! ,old ,man !re appe>s to be a second volcanic zone ly+ sev]al hundr$ feet above t j describ$4 ,x is probably ?is upp] zone :i* em]ges f "u ! hills a mile & a half to ! s\? at ,black ,ness 9 ! bay ( ,rackwick4 ,a good section is !re visible1 :i* is repres5t$ 9 ,fig4 #ajd4 ,! ord9>y r$ & yell[ s&/ones 7a7 appe> f "u ! volcanic rocks at ?is locality1 & /ret* s\?w>ds to ! mo/ s\!rly headl& ( ,hoy4 ,! l[e/ volcanic b& 9 ! section is "o ( r$ s&y well-b$d$ tuffs 7b74 ,"s ( ! lay]s are co>se & almo/ agglom]atic1 :ile o!rs are f9e m>ly & s&y1 ) disp]s$ bombs1 blocks & lapilli ( diabase & &esite4 ,h>d ribs ( a s&y tuface\s mat]ial also occur4 ,^! fragm5tal deposits are imm$iately ov]la9 by a d>k-blue rudely prismatic diabase ) slaggy top 7c74 ,x is ab\t #aej feet ?ick at its ?icke/ "p1 b rapidly ?9s away 9 a we/]ly direction4 ,x passes "u a zone ( r$ tuff 7d7 l t bel[1 & above ?is highe/ memb] ( ! volcanic gr\p comes ! great ov]ly+ pile ( yell[ & r$di% s&/one ( ,hoy4 ,foll[$ we/w>d = a %ort di/ance1 ! :ole volcanic zone is f\nd to die out & ! s&/ones bel[ & above x !n come toge!r4 ,! int]e/ ( ?is little volcanic c5tre 9 ,hoy is height5$ by ! fact t ! progress ( d5udation has reveal$ "s ( ! v5ts belong+ to x4 ,on ! l[ gr\nd to ! ea/ ( ! ,cam1 & imm$iately to ! nor? ( ! volcanic esc>pm5t1 ! flag/ones :i* !re em]ge f "u ! base ( ! uncon=mable upp] s&/ones are pi]c$ by ?ree volcanic necks :i* we may ) little hesitation recognize z m>k+ ! sites ( v5ts f :i* ?is s]ies ( lavas & tuffs 0 dis*>g$ 7,fig4 #aje74 ,! l>ge/ ( !m =ms a conspicu\s hill ab\t #dej feet high1 ! smalle/ is only a few y>ds 9 diamet]1 & rises f ! surface ( a flag/one ridge4 ,!y are fill$ ) a co>se1 dull-gre51 volcanic agglom]ate1 made up ( fragm5ts ( ! lavas ) pieces ( h>d5$ yell[ s&/one & flag/one4 ,ar\nd ! *ief v5t ! flag/ones ?r\gh :i* x has be5 op5$ h be5 greatly h>d5$ & bli/]$4 ,! mo/ ea/]ly v5t1 :i* has be5 laid b>e on ! bea* at ,br+1 due ea/ ( ,hoy ,hill1 c be se5 to pi]ce ! flag/ones1 :i*1 al?\gh _! g5]al dip is we/]ly at f #aj to #ae1 yet at _! junction ) ! agglom]ate are b5t 9 t[>ds ! neck1 & are o!rwise mu* jumbl$ & di/urb$4 ,illu/ration3 ,fig4 #aje4--,section across ! volcanic b& & its associat$ necks1 ,hoy1 ,orkney4 #a4 ,cai?ness flag/ones2 #b4 ,volcanic b& ly+ on r$ s&/ones & conglom]ates & dy+ out ea/w>ds2 #c #c4 ,two v5ts betwe5 ! base ( ! hills & ! sea2 _! connection ) ! volcanic b& is %[n by dott$ l9es2 #d4 ,ov]ly+ mass ( ,upp] ,old ,r$ ,s&/one =m+ ! hills ( ,hoy4 ,on ! nor!rn coa/ ( ,cai?ness ,i h describ$ a rem>kable volcanic v5t ab\t #cjj feet 9 diamet]1 :i* rises ?r\gh ! upp]mo/ gr\p ( ! ,cai?ness flag/ones4 ,x is fill$ ) a co>se agglom]ate consi/+ ( a dull-gre5i% diabase pa/e cr[d$ ) blocks ( diabase1 sometimes ?ree feet 9 diamet]1 & o!rs ( r$ s&/one1 flag/one1 lime/one1 gneiss & lumps ( black cleavable augite 7,fig4 #ajf74cig ,! s&/ones ar\nd x pres5t ! usual disrupt$1 indurat$ & jo9t$ "*1 & are trav]s$ by a small diabase dyke close to ! we/]n m>g9 ( ! neck4 ,ano!r simil> neck has s9ce be5 f\nd by ! (fic]s ( ! ,geological ,survey on ! same coa/4 ,t ^! volcanic orifices 7 active ab\t ! same "t ) ^? 9 ! opposite isl& ( ,hoy may be legitimately inf]r$4 ,footnote #cig3 ,see ,trans4 ,roy4 ,soc4 ,ed94 xxviii4 7#ahgh71 p4 #dje2 also p4 #dhb ( ! same volume = an acc\nt ( ! cleavable augite4 ,illu/ration3 ,fig4 #ajf4--;,gr\nd-plan ( volcanic neck pi]c+ ! ,cai?ness ,flag/one s]ies on ! bea* ne> ,john o' ,groat's ,h\se4 ,^! nor!rn volcanoes made _! appe>ance 9 a di/rict :]e dur+ ! prec$+ ,l[] ,old ,r$ ,s&/one p]iod !re _h be5 sev]al widely sep>at$ gr\ps ( active volcanic v5ts4 ,s f> z ! fragm5t>y nature ( ! geological evid5ce p]mits an op9ion to be =m$1 !y seem to h brok5 out at ! beg9n+1 or at lea/ at an e>ly /age1 ( ! deposition ( ! ,upp] ,old ,r$ ,s&/one1 & to h become entirely ext9ct aft] ! lavas ( ,hoy 7 p\r$ =?4 ,no high] plat=m ( volcanic mat]ials has be5 met ) 9 t region4 ,) ^! brief & limit$ ,orcadian explosions ! long record ( ,old ,r$ ,s&/one volcanic activity 9 ! area ( ! ,briti% ,isles comes to an end4#cih ,footnote #cih3 ,!re appe> to be traces ( volcanic eruptions contemporane\s ) ! ,upp] ,old ,r$ ,s&/one ( ,b]wick%ire1 b z !y m]ely =m$ a prelude to ! great volcanic activity ( ,c>bonif]\s "t1 !y are includ$ 9 ! acc\nt ( ! ,c>bonif]\s plateau ( ,b]wick%ire 9 ,*apt]s xxiv4 & xxv4 ,,book ,,vi ,,! ,,c>bonif]\s ,,volcanoes ,,*apt] ,,xxiii ,,! ,,c>bonif]\s ,,sy/em ,,( ,,brita9 ,,& ,,its ,,volcanic ,,records ,geography & ,sc5]y ( ! ,c>bonif]\s ,p]iod--,range ( ,volcanic ,eruptions dur+ t "t--,i4 ,! ,c>bonif]\s ,volcanoes ( ,scotl&--,di/ribution1 ,arrangem5t & ,local ,*>act]s ( ! ,c>bonif]\s ,sy/em 9 ,scotl&--,sket* ( ! ,"w ( previ\s ,obs]v]s 9 ?is ,subject4 ,)9 ! area ( ! ,briti% ,isles1 ! geological record is comp>atively full & cont9u\s f ! base ( ! ,upp] ,old ,r$ ,s&/one to ! top ( ! ,coal-measures4 ,we le>n f x t ! local bas9s ( deposit 9 :i* ! lat] portion ( ! ,old ,r$ ,s&/one 0 accumulat$ sank /eadily 9 a wide g5]al subsid5ce1 t all[$ ! cle> sea ( ! ,c>bonif]\s ,lime/one ultimately to spread = "s #gjj miles f ! we/ coa/ ( ,irel& into ,we/phalia4 ,ov] ! c5tre ( ,engl& ?is ,c>bonif]\s ,m$it]ranean _h a bread? ( at lea/ #aej miles1 gradually %all[+ nor?w>ds 9 ! direction ( l& 9 ,scotl& & ,nor!rn ,irel&4 ,! g5tle s9k+ ( ! floor ( ! bas9 cont9u$ until m ?an #fjjj feet ( s$im5t1 *iefly compos$ ( ! rema9s ( cr9oids1 corals & o!r m>9e organisms1 _h be5 pil$ up 9 ! deep] p>ts4 ,traces ( ! s\!rn m>g9 ( ?is sea1 or at lea/ ( a long insul> ridge t rose out ( its wat]s1 are to be se5 9 ! protub]ances ( old] rocks :i* appe> at int]vals f "u ! ,coal-measures & lat] =mations betwe5 ! bord]s ( ,wales & ! he>t ( ,leice/]%ire1 & ( :i* ! crags ( ,*>nwood ,=e/ are among ! few peaks t /ill rema9 visible4 ,to ! s\? ( ?is ridge1 op5 sea ext5d$ f> s\?w>d & we/w>d ov] ! site ( ! ,m5dip ,hills & ! upl&s ( ,s\? ,wales4 ,! ,c>bonif]\s p]iod1 z *ronicl$ by its s$im5t>y deposits1 0 a "t ( sl[ subm]g5ce & quiet s$im5tation1 t]re/rial & m>9e conditions alt]nat+ along ! m>g9s ( ! s9k+ l&1 accord+ z ! rate ( depression surpass$ or fell %ort ( t ( ! deposition ( s$im5t4 ,!re is no trace ( any g5]al di/urbance among ! /rata1 su* z w\ld be m>k$ by an important & widely ext5d$ uncon=mability4 ,b _m indications may be obs]v$ t ! rate ( subsid5ce did n cont9ue uni=m1 if1 inde$1 ! d[nw>d movem5t 0 n locally arre/$1 & ev5 ex*ang$ = a movem5t 9 ! opposite direction4 ,x is difficult1 = in/ance1 to believe ! anci5t ridge ( ! ,midl&s to h be5 s l(ty t ev5 ! prolong$ subsid5ce requir$ = ! accumulation ( ! :ole ,c>bonif]\s sy/em 0 insuffici5t to c>ry its highe/ cre/s bel[ ! level ( ! coal-jungles4 ,m probably ! depression rea*$ its maximum along c]ta9 l9es or b&s runn+ 9 a g5]al nor?-ea/]ly direction1 ! int]vals betwe5 ^! l9es s9k+ less1 or possibly ev5 und]go+ "s measure ( uplift4 ,"o ( ! subsid+ tracts1 t ( ! wide l[l&s ( ,c5tral ,scotl&1 0 flank$ on ! s\? by a ridge :i*1 :ile its nor?-ea/]n portion 0 buri$ "u ! ,upp] ,old ,r$ ,s&/one & ,l[] ,c>bonif]\s rocks1 rema9$ above wat] t[>ds ! s\?-we/1 & does n appe> to h be5 :olly subm]g$ !re ev5 at ! close ( ! ,c>bonif]\s p]iod4 ,s abundant & v>i$ are ! s$im5t>y =mations ( ,c>bonif]\s "t1 & s fully h !y pres]v$ rema9s ( ! contempor>y plants & animals1 t x is n difficult to realise 9 "s measure ! g5]al aspect ( ! sc5]y ( ! "t1 & ! succession ( *anges :i* x und]w5t f ! beg9n+ to ! end ( ! p]iod4 ,! l& 0 gre5 ) a luxuriant if some:at monoton\s vegetation4 ,l>ge p9e trees fl\ri%$ on ! dri] upl&s4 ,! l[] gr\nds n\ri%$ d5se groves ( cycads or plants alli$ to !m1 :i* rose z slim trees tw5ty or ?irty feet high1 ) long h>d gre5 leaves & catk9s t grew into b]ries4 ,! swamps & wett] l&s bore a rank gr[? ( v>i\s gigantic k9ds ( club-moss1 equisetace\s re$s & f]ns4 ,nor 0 ! hum ( insect-life abs5t f ^! =e/s4 ,ance/ral types ( cockroa*es1 mayflies & beetles liv$ !re4 ,scorpions sw>m$ along ! m>g9s ( ! %all[ wat]s1 = _! rema9s1 wa%$ away ) ! decay$ vegetation among :i* !y h>b\r$1 are n[ f\nd 9 abundance ?r\gh\t _m ( ! d>k %ales4 ,! wat]s 7 haunt$ by num]\s k9ds ( fi% q di/9ct f ^? ( ! ,old ,r$ ,s&/one4 ,9 ! lagoons1 %oals ( small ganoids liv$ on ! cyprids t peopl$ ! bottom1 & !y 7 9 turn prey$ on by l>g] ganoids ) massive armature ( bone4 ,n[ & !n a %>k f ! op5] sea w\ld f9d its way into ^! m inl& wat]s4 ,! highe/ types ( animal life yet kn[n to h exi/$ at ?is "t 7 v>i\s amphibians ( ! ext9ct ord] ( ,labyr9?odonts4 ,! op5 sea1 too1 teem$ ) life4 ,wide tracts ( its floor support$ a ?ick gr[? ( cr9oids ^: jo9t$ /ems1 pil$ ov] ea* o!r g5]ation aft] g5]ation1 grew into masses ( lime/one _m hundr$s ( feet 9 ?ickness4 ,corals ( v>i\s k9ds liv$ s+ly & 9 colonies1 "h & !re ev5 gr[+ into reefs4 ,=am9if]a1 sponges1 sea-ur*9s1 bra*iopods1 ga/]opods1 lamellibran*s & cephalopods1 9 _m g5]a & species1 m+l$ _! rema9s ) ! dead cr9oids & corals to furni% mat]ials = ! wide & ?ick accumulation ( ,c>bonif]\s ,lime/one4 ,look+ broadly at ! hi/ory ( ! ,c>bonif]\s p]iod1 & be>+ 9 m9d ! evid5ce ( prolong$ depression already ref]r$ to1 we c recognize 9 x ?ree great eras4 ,dur+ ! fir/1 ! wide cle> sea ( ! ,c>bonif]\s ,lime/one spread ov] ! c5tre & s\? ( ,brita91 int]rupt$ "h & !re by isl&s t rose f long ridges :]eby ! sea-floor 0 divid$ into sep>ate bas9s4 ,next came a "t ( less5$ depression1 :5 ! sea-bottom 0 ov]spread ) s&1 mud & gravel1 & 0 ev5 9 "p silt$ up1 z has be5 *ronicl$ 9 ! ,mill/one ,grit4 ,! ?ird /age br+s be=e u ! jungles ( ! ,coal-measures1 :5 ! =m] sea-floor became a s]ies ( %all[ lagoons :]e1 z 9 ! mangrove-swamps ( our own "t1 a t]re/rial vegetation sprang up & m+l$ its rema9s ) ^? ( m>9e %ells & fi%es4 ,su* a /ate ( balance among ! geological =ces z is indicat$ by ! /ratigraphy ( ! ,c>bonif]\s sy/em w\ld n prep>e u = ! discov]y ( ! relics ( any s]i\s display ( contempor>y volcanic activity4 ,&1 inde$1 ?r\gh\t ! ,c>bonif]\s rocks ( ,we/]n ,europe !re is = ! mo/ "p little trace ( contemporane\s volcanic eruptions4 ,yet /rik+ evid5ce exi/s t1 along ! we/]n bord]s ( ! cont95tal area1 9 ,france z well z ov] mu* ( ,brita91 :i* _h = s _m previ\s geological ages be5 ! !atre ( subt]ranean activity1 ! old] half ( ,c>bonif]\s "t witness$ an abundant1 ?\gh less /up5d\s & prolong$1 r5ewal ( volcanic en]gy4 ,f ! v comm5cem5t ( ! ,c>bonif]\s p]iod to ! epo* :5 ! ,coal-measures began to be accumulat$1 ! area ( ! ,briti% ,isles cont9u$ to be a sc5e ( active volcanism4 ,9 ! c\rse ( t prolong$ int]val ( geological "t ! v5ts %ift$ _! positions1 & gradually grew less en]getic1 b !re does n appe> to h be5 any protract$ section ( ! int]val :5 ! subt]ranean activity became ev]y:]e entirely quiesc5t4 ,! geologi/ :o traces1 f old] to y\ng] =mations1 ! progress ( "s p]si/5t op]ation ( nature1 obs]ves ! evid5ce gradually to increase 9 am\nt & cle>ness z x is furni%$ by successively lat] p>ts ( ! record4 ,he f9ds t ! old] rocks h g5]ally be5 s dislocat$ & fold$1 & are (t5 s widely cov]$ by y\ng] =mations1 t ! evid5ce :i* !y no d\bt actually conta9 may be difficult to deciph]1 or may be altoge!r conceal$ f view4 ,9 foll[+1 = in/ance1 ! progress ( volcanic action1 he is impress$1 z he passes f ! old] to ! y\ng] ,palozoic *ronicles1 by ! /rik+ contra/ betwe5 ! fulness & legibility ( ! ,c>bonif]\s records & ! comp>ative meagr5ess & obscurity ( ^? ( ! e>li] p]iods4 ,! ,c>bonif]\s rocks h und]gone f> less di/urbance ?an ! ,cambrian & ,silurian =mations2 :ile ov] wide tracts1 :]e _! volcanic *apt]s are fulle/ & mo/ int]e/+1 !y lie at ! surface1 & c ?us be subject$ to ! close/ scrut9y4 ,h5ce ! rema9s ( ! volcanic ph5om5a ( ! lat] ,palozoic p]iods pres5t a curi\sly mod]n aspect1 :5 contra/$ ) ! fragm5t>y & antique look ( ^? ( old] date4 ,! hi/ory ( volcanic action dur+ ! ,c>bonif]\s p]iod 9 ,brita9 is almo/ :olly compris$ 9 ! records ( ! e>li] half ( t p]iod1 t is1 dur+ ! long int]val repres5t$ by ! ,c>bonif]\s ,lime/one s]ies & ! ,mill/one ,grit4 ,x 0 *iefly 9 ! nor!rn "p ( ! region t volcanic activity manife/$ itself4 ,9 ,scotl& !re is ! *ronicle ( a long succession ( eruptions across ! di/rict ( ! c5tral & s\!rn c\nties1 f ! v beg9n+ ( ,c>bonif]\s "t d[n to ! epo* :5 ! ,coal-measures began to be accumulat$4 ,9 ,engl&1 on ! o!r h&1 ! traces ( ,c>bonif]\s volcanoes are conf9$ )9 a limit$ range 9 ! ,c>bonif]\s ,lime/one1 :ile 9 ,irel& !y appe> to be likewise re/rict$ to ! same l[] division ( ! sy/em4 ,dur+ ! :ole ( ! va/ int]val repres5t$ by ! ,coal-measures volcanic en]gy1 s f> z at pres5t kn[n1 0 entirely dormant ov] ! region ( ! ,briti% ,isles4 ,^! g5]al /atem5ts w be m cle>ly grasp$ f ! accompany+ table1 :i* %[s ! v>i\s sections into :i* ! ,c>bonif]\s sy/em ( ,brita9 has be5 divid$1 & also1 by black v]tical l9es1 ! range ( volcanic int]calations 9 ea* ( ! ?ree k+doms4 ---------------------------------------- -------------------------------- ,engl&4 ,scotl&4 ,irel&4 ---------------------------------------- -------------------------------- ,coal-measures4 ,upp] ,r$ ,s&/ones ) ,spirorbis-lime/one4 ,middle or *ief coal-be>+ measures4 ,ganni/] gr\p4 ,mill/one ,grit4 ,grits1 flag/ones & %ales ) ?9 coals4 ,c>bonif]\s ,lime/one4 ,yor$ale gr\p ( %ales & grits ) lime/ones4 ,?ick 7,scaur or ,ma97 ,lime/one ( ,engl&1 ) s&/ones & coals 9 ,scotl&4 ,l[] ,lime/one ,%ale 7,calcif]\s ,s&/ones ( ,scotl&74 ---------------------------------------- -------------------------------- ,su* be+ ! g5]al range 9 "t ( ! ,c>bonif]\s volcanic ph5om5a1 x may be conv5i5t1 9 ?is prelim9>y survey1 to take note ( ! g5]al di/ribution ( ! volcanic di/ricts ov] ! ,briti% ,isles1 z 9 ?is way we may be/ realise ! ext5t & gr\p+ ( ! eruptions1 :i* w !n be consid]$ 9 fur!r detail 7see ,map ,i474 ,n only 7 ! ,c>bonif]\s volcanoes mo/ abundant & p]si/5t 9 ,scotl&1 b !y atta9$ !re a v>iety & developm5t :i* give _! rema9s an altoge!r exceptional int]e/ 9 ! /udy ( volcanic geology4 ,!y 7 di/ribut$ ov] ! wide c5tral valley1 f ! s\? ( ,cantyre to beyond ! m\? ( ! e/u>y ( ! ,=?4 ,on ! s\!rn side ( ! ,silurian ,upl&s1 !y 7 likewise num]\s & active4 ,!re is ?us no consid]able tract ( ,l[] ,c>bonif]\s rocks 9 ,scotl& :i* does n furni% its evid5ce ( contemporane\s volcanic action4 ,al?\gh "s portions ( ! ,scotti% ,c>bonif]\s igne\s rocks run = a %ort di/ance into ,engl&1 x is rem>kable t1 :5 ^! at la/ die out s\?w>ds1 no o!r relics ( contemporane\s volcanic en]gy take _! place4 ,along ! ,p5n9e *a91 f ! ,bord] into ! he>t ( ,engl&1 ?\gh natural sections are abundant1 no trace ( includ$ volcanic rocks appe>s until we rea* ,d]by%ire4 ,! :ole ( t wide int]val ( #aej miles1 s f> z ! pres5t evid5ce goes1 rema9$ dur+ ,c>bonif]\s "t entirely free f any volcanic eruption4 ,b f ! picturesque c\ntry ( ! ,peak s\?w>ds1 ! sea-floor ( ! ,c>bonif]\s ,lime/one1 9 :at is n[ ! he>t ( ,engl&1 0 dott$ ) v5ts :5ce ! %eets ( toad/one 7 eject$1 :i* h s long be5 a famili> feature 9 ,engli% geology4 ,beyond ?is limit$ volcanic di/rict ! ,c>bonif]\s =mations ( ! s\?-we/ ( ,engl& rema91 on ! :ole1 devoid ( contemporane\s volcanic int]calations1 traces ( ,c>bonif]\s volcanic action hav+ be5 recogniz$ only 9 ,we/ ,som]set & ,devon%ire4 ,9 ! ,m5dip di/rict & 9 ! ridges ( lime/one ne> ,we/on-sup]-,m>e b&s ( cellul> lava & tuff h be5 obs]v$4 ,to ! we/ ( ,d>tmoor1 ,br5t ,tor & "s ( ! surr\nd+ igne\s masses may m>k ! positions ( eruptive v5ts dur+ an e>ly "p ( ! ,c>bonif]\s p]iod4 ,at ! s\? end ( ! ,isle ( ,man relics rema9 ( a gr\p ( v5ts among ! ,c>bonif]\s lime/ones4 ,pass+ across to ,irel&1 :]e ^! lime/ones atta9 s great a ?ickness & cov] s l>ge a proportion ( ! surface ( ! isl&1 we se>* 9 va9 = any cont9uation ( ! abundant & v>i$ volcanic ph5om5a ( ,c5tral ,scotl&4 ,s f> z obs]vation has yet gone1 only two widely sep>at$ areas ( ,c>bonif]\s volcanic rocks are kn[n to occur 9 ,irel&4#cii ,"o ( ^! %[s t a little gr\p ( v5ts probably rose f ! floor ( ! ,c>bonif]\s ,lime/one sea1 ne> ,philip/[n1 9 ,k+'s ,c\nty4 ,! o!r lies f> to ! we/ 9 ! ,gold5 ,vale ( ,lim]ick1 :]e a m important s]ies ( v5ts p\r$ out successive /reams ( lava ) %[]s ( a%es1 f an e>ly "p ( ! ,c>bonif]\s p]iod up to ab\t ! beg9n+ ( ! "t ( ! ,coal-measures4 ,footnote #cii3 ,! suppos$ ,c>bonif]\s volcanic rocks ( ,be>hav5 on ! coa/ ( ,cork are notic$ on p4 #di1 vol4 ii4 ,! total area )9 :i* ! volcanic eruptions ( ,c>bonif]\s "t took place 0 ?us less ?an t ov] :i* ! volcanoes ( ! ,l[] ,old ,r$ ,s&/one 7 di/ribut$1 yet !y 7 scatt]$ across ! l>g] "p ( ! site ( ! ,briti% ,isles4 ,f ! v5ts ( ,fife to ^? ( ,lim]ick is a di/ance ( above #cjj miles2 f ! latt] ea/w>d to ^? ( ,devon%ire is an int]val ( #bej miles2 :ile ! space betwe5 ! ,devon%ire volcanoes & ^? ( ,fife is ab\t #djj miles4 ,9 ?is triangul> space volcanic action manife/$ itself at ea* ( ! apices1 to a slight ext5t along ! c5tre ( ! ea/]n side1 b ) mu* ! greate/ vig\r ?r\gh\t ! nor!rn "p ( ! area4 ,s9ce ! volcanic ph5om5a ( ,c>bonif]\s "t are exhibit$ on a mu* m ext5sive scale 9 ,scotl& ?an 9 any o!r region ( ! _w yet /udi$1 x w be desirable to describe t area 9 consid]able detail4 ,! o!r tracts 9 ,brita9 :]e volcanic rocks ( ! same age occur ne$ n be s fully treat$1 except :]e !y help to a bett] compreh5sion ( ! g5]al volcanic hi/ory4 99 99 99 99 99 ,x is 9 ! s\!rn half ( ,scotl& t ! ,c>bonif]\s sy/em is develop$ 7,map ,,iv474 ,a l9e drawn f ,ma*rihani% ,bay1 ne> ! ,mull ( ,cantyre1 nor?-ea/w>d across ,arran & ,bute to ! s\? end ( ,lo* ,lomond1 & !nce ea/w>d by ,bridge ( ,allan1 ,k9ross & ,cup> to ,/4 ,&rews ,bay1 =ms ! nor!rn limit ( ?is sy/em4 ,s\? ( t l9e ,c>bonif]\s volcanic int]calations are to be met ) 9 ne>ly e c\nty across into ! bord]s ( ,nor?umb]l&4 ,t we may foll[ intellig5tly ! rem>kably v>i$ volcanic hi/ory ( ?is region1 x is desirable to beg9 by tak+ note ( ! nature & sequ5ce ( ! s$im5t>y =mations among :i* ! volcanic rocks are int]calat$1 = ^! s]ve to br+ be=e u ! g5]al conditions ( ! geography ( ! p]iod4 ,! subjo9$ table exhibits ! subdivisions into :i* ! ,c>bonif]\s sy/em 9 ,scotl& has be5 gr\p$3-- ,coal-measures4 ,upp] ,r$ ,s&/one gr\p1 ne>ly devoid ( coal-seams4 ,coal-be>+1 :ite1 yell[ & grey s&/ones1 d>k %ales & iron/ones 7,upp] ,coal s]ies74 ,mill/one ,grit4 ,?ick :ite & r$di% s&/ones & grits4 ,c>bonif]\s ,lime/one s]ies4 ,s&/ones1 %ales1 fireclays1 coal-seams1 iron/ones & ?ree seams ( m>9e lime/one1 ( :i* ! upp]mo/ is kn[n z ! ,ca/lec>y seam1 ! second z ! ,calmy or ,ard51 & ! l[e/ z ! ,index 7,l[] ,coal s]ies74 ,b&s ( m>9e lime/one int]calat$ among s&/ones1 %ales & "s coal-seams4 ,a ?ick b& ( lime/one ly+ at or ne> ! bottom ( ! gr\p1 traceable all ov] ,c5tral ,scotl&1 is kn[n z ! ,hurlet or ,ma9 ,lime/one4 ,"s high] & ?9n] seams are call$ ,hosie's 7see ,fig4 #aee74 ,calcif]\s ,s&/ones4#djj ,9 ! bas9 ( ! ,fir? ( ,=?1 bel[ ! ,hurlet ,lime/one1 comes a v>i$ s]ies ( :ite & yell[ s&/ones1 black %ales 7oil-%ales71 cyprid %ales & lime/ones 7,burdieh\se71 & occasional coal-seams 7,h\/on71 hav+ a total dep? ( ab\t #cjjj feet4 ,?is local gr\p ab\nds 9 fossil plants1 entomo/raca & ganoid fi%es4 ,x passes d[n into ! ,cem5t-/one gr\p1 :i*1 h[ev]1 is feebly develop$ 9 ?is di/rict1 unless x is p>tly repres5t$ by ! s&/ones1 %ales1 lime/ones & coals j m5tion$4 ,cem5t-/one gr\p consi/+ ( r$1 blue & gre5 m>ls & %ales1 r$ & grey s&/ones1 & ?9 b&s ( cem5t-/one3 fossils sc>ce4 ,r$di% & grey s&/ones & %ales1 ) occasional plant- rema9s1 pass+ d[n into ! deep r$ 7sometimes yell[7 s&/ones1 r$ m>ls & corn/ones ( ! ,upp] ,old ,r$ ,s&/one4 ,footnote #djj3 ,! ,calcif]\s ,s&/ones are ! /ratigraphical equival5ts ( ! ,lime/one ,%ale & l[] portion ( ! ,c>bonif]\s ,lime/one ( ,engl&4 ,f ?is table ! gradual geographical evolution ( ! ,c>bonif]\s p]iod 9 ,scotl& may be glean$4 ,we obs]ve t at ! beg9n+1 ! conditions "u :i* ! ,old ,r$ ,s&/one _h be5 accumulat$ /ill 9 "p cont9u$4 ,! great lacu/r9e bas9s ( ! ,l[] ,old ,r$ ,s&/one _h inde$ be5 effac$1 & _! sites 7 occupi$ by comp>atively %all[ areas ( fre% or bracki% wat] 9 :i* ! ,upp] ,old ,r$ ,s&/one 0 laid d[n4 ,_! conglom]ates & s&/ones _h be5 uplift$ & fractur$4 ,_! va/ ranges ( volcanic mat]ial1 aft] be+ deeply buri$ "u s$im5t1 _h be5 once m laid b>e1 & ext5d$ z ridges ( l&1 sep>at+ ! pools & lagoons :i* !y suppli$ ) s& & silt4 ,?is s+ul> topography _h n be5 entirely effac$ at ! beg9n+ ( ! ,c>bonif]\s p]iod1 = we f9d t _m ( ! ridges :i* b\nd$ ! bas9s ( ! ,upp] ,old ,r$ ,s&/one rema9$ z l& until !y sank b5ea? ! wat]s 9 :i* ! e>lie/ ,c>bonif]\s /rata accumulat$4 ,?us1 :ile no trace ( an uncon=mability has yet be5 detect$ at ! top ( ! ,upp] ,old ,r$ ,s&/one1 !re is (t5 a /rong ov]lap ( ! succe$+ deposits4 ,at ! s\? end ( ! ,p5tl& ,hills1 = example1 ! ,upp] ,old ,r$ ,s&/one atta9s a ?ickness ( #ajjj feet1 b only ?ree miles fur!r s\? x entirely disappe>s1 toge!r ) all ! ov]ly+ mass ( ,calcif]\s ,s&/ones1 & ! ,c>bonif]\s ,lime/one !n re/s directly on ! ,l[] ,old ,r$ ,s&/one4 ,aga91 at ! nor? end ( ! same *a9 ! upp] division ( ! ,old ,r$ ,s&/one dies out aga9/ ! l[]1 :i* is ev5tually ov]lapp$ by ! ,calcif]\s ,s&/ones4 ,! *ange f ! physical conditions ( ! ,scotti% ,old ,r$ ,s&/one to ^? ( ! ,c>bonif]\s sy/em 0 no d\bt gradual & sl[4 ,! peculi> r$ s&y s$im5t cont9u$ to be laid d[n 9 bas9s t 7 app>5tly be+ gradually wid5$ by access ( wat] f ! op5 sea4 ,yet x w\ld seem t 9 ,scotl& ^! bas9s /ill = a long "t cont9u$ sal9e or1 f "s o!r cause1 unfav\rable to life2 = ! r$1 blue & gre5 %ales or m>ls1 & occasional impure lime/ones or cem5t-/ones & gypse\s lay]s1 :i* 7 deposit$ 9 !m1 are 9 g5]al unfossilif]\s1 ?\gh drift$ plants f ! neighb\r+ l& are "h & !re common en\gh4 ,! s$im5ts ( ^! e>ly ,c>bonif]\s wat]s are met ) all ov] ! s\!rn half ( ,scotl&1 b 9 v unequal developm5t1 & con/itute :at is kn[n z ! ,cem5t-/one ,gr\p4 ,x 0 :ile ^! /rata 7 9 c\rse ( deposition t ! e>lie/ ,c>bonif]\s volcanoes broke into eruption4 ,9 "s localities a ?ickness ( sev]al hundr$ feet ( ! ,cem5t-/one gr\p und]lies ! l[e/ lavas4 ,9 o!r places ! lavas occur 9 & re/ on ! ,upp] ,old ,r$ ,s&/one & h ! ,cem5t-/one gr\p :olly above !m2 :ile 9 yet o!r di/ricts ! volcanic rocks seem entirely to take ! place ( t gr\p4 ,s vigor\s 0 ! e>lie/ display ( volcanic action 9 ,c>bonif]\s times t f ! bord]s ( ,nor?umb]l& to ! upl&s ( ,gall[ay1 & f ! slopes ( ! ,lamm]muirs to ,/irl+%ire & !nce across ! e/u>y ( ! ,clyde to ,cantyre1 innum]able v5ts 7 op5$ & l>ge bodies ( lava & a%es 7 eject$4 ,! ,cem5t-/one gr\p1 save :]e succe$$ by volcanic int]calations1 passes up con=mably into ! l[e/ cr9oidal lime/ones ( ! ,c>bonif]\s ,lime/one s]ies4 ,9 ! bas9 ( ! ,fir? ( ,=?1 h[ev]1 ! cem5t-/ones1 feebly repres5t$ !re1 are ov]la9 by a rem>kable assemblage ( :ite s&/ones1 black c>bonace\s %ales1 or oil-%ales1 cyprid lime/ones1 occasional m>9e lime/ones & ?9 seams ( coal1 ! :ole hav+ a ?ickness ( m ?an #cjjj feet4 ,^! /rata1 unlike ! typical ,cem5t-/one gr\p1 ab\nd 9 fossils bo? vegetable & animal4 ,!y prove t1 ov] ! area ( ! ,=?1 ! insalubri\s bas9s :]e9 ! r$ & gre5 s$im5ts ( ! ,cem5t-/one gr\p 7 laid d[n1 gave place to op5] & cle>] wat] ) occasional access ( ! sea4 ,! peculi> lagoon-conditions :i* fav\r$ ! =mation ( coal 7 ?us develop$ 9 ,c5tral ,scotl& e>li] ?an else:]e 9 ,brita94 ,we %all see 9 lat] pages t ^! conditions 7 accompani$ by a fre% outbreak ( volcanic activity1 9 a phase less vigor\s b m endur+ & ext5sive ?an t ( ! fir/ ,c>bonif]\s eruptions4 ,! ,c>bonif]\s ,lime/one sea ov] ! site ( ! s\!rn half ( ,scotl& appe>s nev] to h rea*$ ! dep? :i* x atta9$ 9 ,engl& & ,irel&4 ,to ! nor? ( x lay ! l& f :i* l>ge quantities ( s& & mud 7 c>ri$ into x1 z %[n by ! deep accumulations ( s&/one & %ale1 :i* f> surpass 9 ?ickness ! few comp>atively ?9 m>9e lime/ones int]calat$ 9 !m4 ,!re is ?us a /rik+ contra/ betwe5 ! ?ick masses ( lime/one 9 c5tral & s\?-we/]n ,engl& & _! dw9dl$ repres5tatives 9 ! nor?4 ,ano!r m>k$ diff]5ce betwe5 ! ,scotti% & ,engli% developm5ts ( ?is =mation is to be notic$ 9 ! abundant pro( t ! comp>atively %all[ wat]s ( ! nor!rn bas9 7 pl5tifully dott$ ov] ) active volcanoes4 ,! eruptions 7 especially vigor\s & prolong$ 9 ! bas9 ( ! ,fir? ( ,=?4 ,!y cont9u$ at int]vals1 ev5 aft] ! peculi> geographical conditions ( ! ,c>bonif]\s ,lime/one _h ceas$4 ,b !y _h di$ out by ! "t ( ! beg9n+ ( ! ,coal-measures4 ,ow+ to ! numb] & v>iety ( ! natural sections1 ! ,c>bonif]\s volcanic rocks ( ,scotl& h be5 ! subject ( num]\s obs]vations & descriptions1 f ! e>ly days ( geology d[n to ! pres5t "t4 ,! m]e enum]ation ( ! titles ( ! v>i\s publications reg>d+ !m w\ld make a long li/4 ,^! rocks =m$ ! subject ( "s ( ,hutton's e>ly obs]vations1 & furni%$ him ) facts f :i* he e/abli%$ ! igne\s orig9 ( :9/one4#dja ,!y suppli$ ,playfair ) num]\s apt illu/rations 9 support ( ,hutton's views1 & he seems to h made himself ?or\ghly famili> ) !m4#djb ,9 ! h&s ( ,sir ,james ,hall !y became ! gr\ndwork ( ^? rem>kable exp]im5ts on ! fusion ( :9/one :i* may be said to h laid ! f\ndation ( exp]im5tal geology4#djc ,9 ! controv]sies ( ! ,neptunian & ,plutonian s*ools ^! rocks 7 frequ5tly appeal$ to by ea* side 9 confirmation ( its dogmas4 ,! appo9tm5t 9 #ahjd ( ,jameson to ! ,*air ( ,natural ,hi/ory 9 ! ,ed9burgh ,univ]sity gave increas$ impetus to ! /udy ( ! igne\s rocks ( ,scotl&4 ,?\gh he did n himself publi% mu* reg>d+ !m1 we "k t he 0 con/antly 9 ! habit ( conduct+ 8 class to ! hills1 rav9es & qu>ries ar\nd ,ed9burgh1 & t ! views :i* he taught 7 imbib$ & ext5d$ by 8 pupils4#djd ,among ! e>ly writ]s ! names ( ,allan1#dje ,t[nson1#djf ,"l ,gre5ock1#djg & ,ami ,b\1#djh des]ve especial m5tion4 ,footnote #dja3 ,hutton's ,!ory ( ! ,e>?1 vol4 i4 p4 #aee et seq4 ,footnote #djb3 ,playfair's ,illu/rations ( ! ,huttonian ,!ory1 #bee et seq4 ,footnote #djc3 ,trans4 ,roy4 ,soc4 ,ed94 7#ahje71 vol4 v4 p4 #dc4 ,footnote #djd3 ,mem4 ,w]n4 ,soc4 ii4 #agh1 #fah2 iii4 #be2 ,ed94 ,phil4 ,j\rn4 i4 #ach1 #ceb2 xv4 #chf4 ,footnote #dje3 ,trans4 ,roy4 ,soc4 ,ed94 7#ahaa71 vi4 p4 #dje4 ,footnote #djf3 ,tracts & ,obs]vations 9 ,natural ,hi/ory & ,physiology1 #hvo1 ,lond4 #agii4 ,footnote #djg3 ,trans4 ,roy4 ,soc4 ,ed94 7#ahcc71 xiii4 pp4 #ci1 #ajg4 ,footnote #djh3 ,essai gologique sur l'cosse4 ,p>is2 no date1 probably #ahbj4 ,! fir/ broad g5]al sket* ( ! ,c>bonif]\s igne\s rocks ( a l>ge di/rict ( ! c\ntry 0 t giv5 by ,hay ,cunn+ham 9 8 valuable essay on ! geology ( ! ,lo?ians4#dji ,he sep>at$ !m into two s]ies1 ! ,felspa?ic1 includ+ porphyry & cl9k/one1 & ! ,augitic or ,trap rocks4 ,to ^! he add$ ,trap-tufa1 :i* he consid]$ to be id5tical 9 orig9 ) mod]n volcanic tuff4 ,x 0 ! eruptive "* ( ! igne\s rocks on :i* he specially dwelt1 %[+ by num]\s sections ! effects :i* ! protrusion ( ! molt5 masses h _h ^u ! surr\nd+ rocks4 ,he did n attempt to sep>ate ! intrusive f ! int]/ratifi$ %eets1 nor to =m a *ronological arrangem5t ( ! :ole4 ,footnote #dji3 ,mem4 ,w]n4 ,soc4 vii4 p4 #a4 ,publi%$ sep>ately1 #ahch4 ,/ill m important 0 ! sket* giv5 by ,macl>51 9 8 classic ,geology ( ,fife & ! ,lo?ians4#daj ,?is au?or cle>ly recogniz$ t _m ( ! igne\s rocks 7 ?r[n out contemporane\sly ) ! /rata among :i* !y n[ lie4 ,he con/antly s\ght = analogies among mod]n volcanic ph5om5a1 & pres5t$ ! ,c>bonif]\s igne\s rocks ( ! ,lo?ians n z s _m petrographical v>ieties1 b z monum5ts ( diff]5t phases ( volcanic action previ\s to ! =mation ( ! ,coal-measures4 ,8 detail$ descriptions ( ,ar?ur ,seat & ! rocks imm$iately ar\nd ,ed9burgh1 :i* alone ! "w 0 orig9ally int5d$ to embrace1 may be cit$ z models ( exact & lum9\s rese>*4 ,! portions ref]r+ to ! re/ ( ! bas9 ( ! ,=? did n pr(ess to be m ?an a m]e sket* ( ! subject4 ,footnote #daj3 ,small #hvo1 ,ed94 #ahch1 fir/ p>tly publi%$ z articles 9 ! ,scotsman newspap]4 ,a second edition1 :i* 0 little m ?an a repr9t ( ! fir/1 appe>$ 9 #ahff4 ,v>i\s pap]s ( m local int]e/1 to "s ( :i* allusion w be made 9 ! sequel1 appe>$ dur+ ! next qu>t] ( a c5tury4 ,b no sy/ematic /udy ( ! volcanic ph5om5a ( any "p ( ,scotl& 0 resum$ until ! ext5sion 9 #ahed ( ! ,geological ,survey to ! nor? ( ! ,twe$ by ,a4 ,c4 ,ramsay4 ,! volcanic rocks ( ! ,lo?ians & ,fife 7 mapp$ by ,mr4 ,h4 ,h4 ,h[ell & myself4 ,! maps ( t di/rict began to be publi%$ 9 ! ye> #ahei1 & ! ,memoirs two ye>s lat]4 ,9 #ahfa1 9 a *ronological gr\p+ ( ! :ole ( ! volcanic ph5om5a ( ,scotl&1 ,i gave an outl9e ( ! ,c>bonif]\s eruptions4#daa ,by degrees ! detail$ mapp+ ( ! ,geological ,survey 0 pu%$ across ! :ole ( ! re/ ( ! s\? ( ,scotl&1 & ! ,c>bonif]\s volcanic rocks ( ea* area 7 !n = ! fir/ "t c>efully trac$ & assign$ to _! v>i\s /ratigraphical horizons4 ,9 ! foll[+ pages ref]5ce w be giv5 to ! m important features ( ! ,survey maps & ,memoirs4 ,9 ! ye> #ahgi1 avail+ myself ( ! l>ge am\nt ( in=mation :i* my own trav]ses & ! "w ( ! ,survey _h enabl$ me to acquire1 ,i publi%$ a ,memoir on ! geology & petrography ( ! volcanic rocks ( ! bas9 ( ! ,fir? ( ,=?2#dab & la/ly1 9 my ,presid5tial ,address to ! ,geological ,society 9 #ahib1 ,i gave a summ>y ( all t _h !n be5 asc]ta9$ on ! subject ( ! volcanic rocks ( ,c>bonif]\s "t 9 ! ,briti% ,isles4#dac ,footnote #daa3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxii4 ,footnote #dab3 ,ibid4 vol4 xxix4 7#ahgi71 p4 #dcg4 ,footnote #dac3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 xlviii4 7#ahib71 p4 #ajd4 ,?is summ>y1 ) additional details & illu/rations1 is embodi$ 9 ! text4 ,two well-m>k$ types ( volcanic accumulations are recognizable 9 ! ,briti% ,isles1 :i* may be conv5i5tly t]m$ ,plateaux & ,puys4 #a4 ,plateaux4--,9 ?is type1 ! volcanic mat]ials 7 dis*>g$ ov] wide tracts ( c\ntry1 s t !y n[ =m broad tablel&s or ranges ( hills1 rea*+ sometimes an ext5t ( _m hundr$s ( squ>e miles & a ?ickness ( m ?an #ajjj feet4 ,plateaux ( ?is "* occur )9 ! ,briti% area only 9 ,scotl&1 :]e !y are ! pr$om9ant phase ( volcanic int]calations 9 ! ,c>bonif]\s sy/em4 ,x is notewor?y t ! ,c>bonif]\s plateaux appe>$ dur+ a well-m>k$ int]val ( geological "t4 ,! e>lie/ examples ( !m date f ! close ( ! ,upp] ,old ,r$ ,s&/one4 ,!y 7 all 9 vigor\s eruption dur+ ! "t ( ! ,calcif]\s ,s&/ones1 b 9 no case did !y survive into t ( ! ,hurlet & lat] lime/ones4 ,!y are ?us em95tly *>act]i/ic ( ! e>lie/ portion ( ! ,c>bonif]\s p]iod4 #b4 ,puys4--,9 ?is type1 ! ejections 7 (t5 conf9$ to ! dis*>ge ( a small am\nt ( fragm5t>y mat]ials f a s+le solit>y v5t1 & ev5 :]e ! v5ts 7 m num]\s & ! outp\r+s ( lava & %[]s ( a% m copi\s1 ! eject$ mat]ial usually cov]$ only a small area r\nd ! c5tres ( eruption4 ,occasionally /reams ( basic lava & accumulations ( tuff 7 pil$ up into long ridges4 ,volcanoes ( ?is "* 7 specially abundant 9 ! bas9 ( ! ,fir? ( ,=?1 & m sp>+ly 9 ,ayr%ire & ,roxburgh%ire4 ,!y =m ! p]si/5t type ?r\gh\t ! re/ ( ! ,briti% ,isles4 ,! ,puys also occupy a well-def9$ /ratigraphical position4 ,!y did n beg9 until "s ( ! volcanic plateaux _h become ext9ct4 ,f ! top ( ! ,cem5t-/one gr\p up into ! ,c>bonif]\s ,lime/one s]ies1 _! lavas & tuffs are met ) on _m plat=ms1 b none occur above t s]ies save 9 ,ayr%ire1 :]e "s ( ! eruptions appe> to h be5 z late z ab\t ! beg9n+ ( ! ,coal-measures4 ,arrang$ 9 tabul> =m ! /ratigraphical & geographical di/ribution ( ! two great volcanic types ( ! ,c>bonif]\s sy/em 9 ,scotl& w be m easily foll[$4 ,i h !re=e drawn up ! accompany+ s*eme3-- ,location ,key3 ,a4 ,ayr%ire & ,r5frew%ire4 ,b4 ,/irl+%ire4 ,c4 ,we/ ,lo?ian4 ,d4 ,midlo?ian4 ,e4 ,ea/ ,lo?ian4 ,f4 ,fife4 ,g4 ,b]wick ,roxburgh%ire4 ---------------------------------------- ------------------------------ ,plateau-type4 ,puy-type4 ---------------------------------------- ------------------- ,a4,b4,d4,e4,g4,a4,b4,c4,d4,e4,f4,g4 ,coal ,measures 444444444444444444444444 ,mill/one ,grit 4444444444 444444444444 ,c>bonif]\s ,lime/one ,s]ies4 ,ca/lec>y ,lime/one 4444444444 444444444444 ,calmy 4444444444 444444444444 ,index 4444444444 44 4444 44 ,hurlet 44444444444444 4444 ,calcif]\s ,s&/one ,s]ies4 ,burdieh\se ,lime/one & ,oil-%ale ,gr\p 44 444444 4444 ,cem5t-/one ,gr\p 44444444 4444 44 ,r$ ,s&/ones pass+ d[n 44444444 44444444444444 into ,upp] ,old ,r$ ,s&/one44444444 44444444444444 ---------------------------------------- ------------------- ,,*apt] ,,xxiv ,,c>bonif]\s ,,volcanic ,,plateaux ,,( ,,scotl& ,i4 ,! ,plateau-type re/rict$ to ,scotl&--i4 ,di/ribution 9 ! ,diff]5t ,areas ( ,eruption--ii4 ,nature ( ! ,mat]ials erupt$4 ,9 ! division ( ! ,plateaux ,i gr\p all ! m copi\s eruptions dur+ ! ,c>bonif]\s p]iod1 :5 ! fragm5t>y mat]ials g5]ally =m$ b a small "p ( ! dis*>ges1 b :5 ! lavas 7 p\r$ out s abundantly & frequ5tly z to =m lava-fields sometimes m ?an #bjjj squ>e miles 9 area1 & to build up piles ( volcanic mat]ial sometimes upw>ds ( #cjjj feet 9 ?ickness4 ,z already rem>k$1 ?is phase ( volcanic action1 especially *>act]i/ic ( ! e>li] "p ( ! ,c>bonif]\s p]iod across ! s\? ( ,scotl&1 b n f\nd else:]e 9 ! same sy/em 9 ,brita91 prec$$ ! type ( ! ,puys4 ,its eruptions ext5d$ f ab\t ! close ( ! ,old ,r$ ,s&/one p]iod ?r\gh t section ( ,c>bonif]\s "t :i* 0 m>k$ by ! deposition ( ! ,calcif]\s ,s&/ones1 b !y entirely ceas$ be=e ! accumulation ( ! ,ma9 or ,hurlet ,lime/one1 at ! base ( ! ,c>bonif]\s ,lime/one ,s]ies ( ,scotl&4 ,its /ratigraphical limits1 h[ev]1 are n ev]y:]e ! same4 ,9 ! ea/]n "p ( ! region1 ! lavas appe> to be int]calat$ )1 & c]ta9ly lie directly ^u1 ! ,upp] ,old ,r$ ,s&/one conta9+ scales ( ,bo?riolepis & o!r *>act]i/ic fi%es1 & !y are cov]$ by ! ,cem5t-/one gr\p ( ! ,calcif]\s ,s&/ones4 ,9 ! we/]n di/rict a consid]able ?ickness ( ,c>bonif]\s /rata sometimes und]lies ! volcanic %eets4 ,on ! o!r h&1 ! type ( ! ,puys1 al?\gh x appe>$ 9 ,fife1 ,l9li?g[%ire & ,midlo?ian dur+ ! "t ( ! ,calcif]\s ,s&/ones1 atta9$ its *ief developm5t dur+ t ( ! ,c>bonif]\s ,lime/one1 & did n f9ally die out 9 ,ayr%ire until ! beg9n+ ( ! deposition ( ! ,coal-measures4 i4 ,,di/ribution ,,( ,,! ,,plateaux ,not)/&+ ! effects ( _m p[]ful faults & ext5sive d5udation1 ! g5]al position ( ! ,plateaux & _! indep5d5ce ( ea* o!r c /ill be trac$4 ,!y are entirely conf9$1 z ,i h said1 to ! s\!rn half ( ,scotl& 7see ,map ,,iv474 ,9 not+ _! situations we are once m br\ght face to face ) ! rem>kable fact1 s /rik+ly manife/$ 9 ! geological hi/ory ( ,brita91 t volcanic action has be5 apt to recur aga9 & aga9 9 or ne> to ! same areas4 ,! ,c>bonif]\s volcanic plateaux 7 p\r$ out f v5ts1 "s ( :i* n impossibly rose among ! ext9ct v5ts ( ! ,old ,r$ ,s&/one4 ,ano!r fact1 to :i* also ,i h already allud$ z p>tially recognizable 9 ! records ( ,old ,r$ ,s&/one volcanism1 n[ becomes increas+ly evid5t--! t5d5cy ( volcanic v5ts to be op5$ along l9es ( valley r ?an ov] tracts ( hill4 ,! v5ts t suppli$ ! mat]ials ( ! l>ge/ ( ! ,c>bonif]\s volcanic plateaux broke =?1 l ! ,old ,r$ ,s&/one volcanoes1 along ! broad ,midl& ,valley ( ,scotl&1 betwe5 ! ridge ( ! ,highl&s on ! nor? & t ( ! ,s\!rn ,upl&s on ! s\?4 ,o!rs appe>$ 9 ! long holl[ betwe5 ! s\!rn side ( ^! upl&s1 & ! ,*eviot ,hills & hills ( ! ,lake ,di/rict4 ,x is n a "q ( ! rise ( volcanic v5ts m]ely along l9es ( fault1 b ov] broad tracts ( l[ gr\nd r ?an on ! surr\nd+ or neighb\r+ heights4 ,x c easily be %[n t ?is di/ribution is n ! result ( bett] pres]vation 9 ! valleys & great] d5udation f ! high] gr\nds1 =1 z has be5 already rem>k$ 9 reg>d to ! volcanoes ( ! ,old ,r$ ,s&/one1 ^! high] gr\nds are s+ul>ly free f traces ( necks :i*1 _h any v5ts ev] exi/$ !re1 w\ld c]ta9ly h rema9$ z memorials ( !m4 ,! foll[+ summ>y ( ! position & ext5t ( ! ,plateaux w af=d "s idea ( _! g5]al *>act]s3-- ,illu/ration3 ,fig4 #ajg4--,view ( ! esc>pm5t ( ! ,clyde ,plateau 9 ! ,little ,cumbrae1 f ! s\?-we/4 #a4 ,! ,clyde ,plateau4--,! *ief plateau rises into "o ( ! mo/ conspicu\s features 9 ! sc5]y ( ,c5tral ,scotl&4 ,beg9n+ at ,/irl+1 x =ms ! tablel& ( ! ,f9try1 ,kilsy?1 ,campsie & ,kilpatrick ,hills1 /ret*+ we/w>ds to ! ,clyde ne> ,dumb>ton4 ,x rises aga9 on ! s\? side ( t riv]1 sweep+ s\?w>ds into ! hilly moorl&s :i* range f ,gre5ock to ,ardrossan1 & spread+ ea/w>ds along ! high wat]%$ betwe5 ,r5frew%ire1 ,ayr%ire1 & ,lan>k%ire to ,gal/on & ,/ra?avon4 ,b x is n conf9$ to ! ma9l&1 = its prolongation c be trac$ d[n ! broad expanse ( ! ,fir? ( ,clyde by ! isl&s ( ,cumbrae to ! s\!rn end ( ,bute1 & !nce by ! ea/ ( ,arran to ,campbelt[n 9 ,cantyre4 ,its visible remnants ?us ext5d = m ?an #ajj miles f nor?-ea/ to s\?-we/1 ) a wid? ( "s ?irty-five miles 9 ! broade/ "p4 ,we %all probably n exagg]ate if we e/imate ! orig9al ext5t ( ?is great volcanic area z n less ?an betwe5 #bjjj & #cjjj squ>e miles4 ,x is 9 ?is tract t ! ph5om5a ( ! plateaux are mo/ admirably display$4 ,ranges ( l(ty esc>pm5ts reveal ! succession ( ! sev]al eruptions1 & ! l[] gr\nd 9 front ( ^! esc>pm5ts pres5ts to u1 z ! result ( /up5d\s d5udation1 _m ( ! v5ts f :i* ! mat]ials ( ! plateau 7 eject$1 :ile 9 ! we/]n portion ( ! area admirable coa/-sections lay b>e to view ! m9ute/ details ( /ructure4#dad ,footnote #dad3 ,?is plateau is repres5t$ 9 ,%eets #ab1 #ba1 #bi1 #cj1 #ca & #ci ( ! ,geological ,survey1 & is describ$ 9 ! accompany+ ,memoirs z f> z publi%$4 ,! ea/]n "p ( ! ,campsie ,hills 0 survey$ by ,mr4 ,b4 ,n4 ,pea*1 ! we/]n "p by ,mr4 ,r4 ,l4 ,jack1 :o also mapp$ ! re/ ( ! plateau to ! ,clyde1 & a portion ( ! high gr\nd ( ,r5frew%ire & ,ayr%ire2 ! re/ ( ! area1 s\? to ,ardrossan1 0 survey$ by myself4 ,! tract f ,/ew>ton to ,/ra?avon 0 survey$ by ,mr4 ,james ,geikie1 ! ,cumbraes & ,bute by ,mr4 ,w4 ,gunn1 & s\!rn ,cantyre by ,mr4 ,r4 ,g4 ,symes4 ,! ,campsie ,hills h be5 p>tly describ$ by ,mr4 ,john ,"y 9 ! fir/ volume ( ! ,transactions ( ! ,glasg[ ,geological ,society4 ,! occurr5ce ( plants 9 ! tuffs ( ! ea/ coa/ ( ,arran 0 discov]$ by ,mr4 ,e4 ,wuns*4 ,! ,campbelt[n igne\s rocks 7 describ$ by ,j4 ,nicol1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 viii4 7#aheb71 p4 #djf4 ,see also ,j4 ,bryce's ,arran & ,clydesdale4 ,x w be se5 f ! map 7,no4 ,,iv471 t ! ,clyde plateau ext5ds 9 a g5]al nor?-ea/ & s\?-we/ direction4 ,x is incl9$ on ! :ole t[>ds ! ea/1 :]e1 :5 n int]rupt$ by faults1 its highe/ lavas & tuffs may be se5 to pass "u ! ,c>bonif]\s ,lime/one s]ies4 ,its greate/ elevations are ?us t[>ds its esc>pm5t1 :i*1 comm5c+ above ! pla9s ( ! ,=? a little to ! we/ ( ,/irl+1 ext5ds z a /rik+ feature to ! ,clyde above ,dumb>ton4 ,on ! s\? side ( ! great e/u>y ! esc>pm5t aga9 /ret*es 9 a noble range ( t]rac$ slopes = _m miles into ,ayr%ire4 ,x is well develop$ 9 ! ,little ,cumbrae ,isl& 7,fig4 #ajg71 & 9 ! s\? ( ,bute1 :]e its successive plat=ms ( lava m\nt 9 t]races & gre5 slopes above ! ,fir?4 ,ev5 z f> z ! s\!rn coa/ ( ,cantyre ! *>act]i/ic plateau sc5]y reappe>s 9 ! outli]s :i* !re cap ! hills & desc5d ! slopes 7,fig4 #ajh74 ,:ile ! esc>pm5t side ( ?is plateau is comp>atively unfault$1 s t ! ord] ( succession ( ! lavas & _! sup]position 9 ! s$im5t>y rocks c be di/9ctly se51 ! ea/]n or dip side is almo/ ev]y:]e dislocat$4 ,innum]able local ruptures h tak5 place1 all[+ ! lime/one s]ies to subside1 & giv+ to ! m>g9 ( ! volcanic area a rem>kably not*$ appe>ance4 ,to ! effects ( ?is fault+ may be attribut$ ! way 9 :i* ! plateau has be5 sep>at$ into deta*$ blocks ) int]v5+ y\ng] /rata4 ,?us a complex s]ies ( dislocations br+s 9 a long /rip ( ,c>bonif]\s ,lime/one :i* ext5ds f ,john/on to ,ardrossan1 :ile ano!r s]ies lets 9 ! lime/one t runs f ,b>rhead to ne> ,dalry4 ,9 ea* ( ^! in/ances1 ! cont9uity ( ! volcanic plateau is int]rupt$4 ,to ! same cause we owe ! occasional reappe>ance ( a portion ( ! plateau beyond ! limits ( ! ma9 mass1 z = in/ance 9 ! deta*$ area :i* occurs 9 ! valley ( ! ,g>nock above ,kilw9n+4 ,illu/ration3 ,fig4 #ajh4--,view ( ! edge ( ! ,volcanic ,plateau s\? ( ,campbelt[n1 ,argyll%ire4 ,! upp]mo/ ( ! ?ree zones is ! volcanic s]ies ) its lava-ridges4 ,! c5tral b& is ! ,upp] ,old ,r$ ,s&/one1 ly+ con=mably b5ea? ! lavas1 ) its corn/one :i* has be5 qu>ri$4 ,! l[e/ b&1 t9t$ d>k1 is ! ,l[] ,old ,r$ ,s&/one1 on :i* ! o!r rocks re/ uncon=mably4 ,d5udation has likewise come into play1 n only 9 r$uc+ ! area ( ! plateau1 b 9 isolat+ portions ( x into outli]s1 ) or )\t ! assi/ance ( faults4 ,! site ( ! ,cumbraes & ,bute 0 no d\bt at "o "t cov]$ ) a cont9u\s %eet ( volcanic mat]ial1 & !re appe>s to be no reason = refus+ to believe t ?is %eet =m$ "p ( t :i* caps ! opposite upl&s ( ,ayr%ire4 ,f ! s\!rn end ( ,bute x is only ab\t sev5 miles across to ! %ore ( ,arran ne> ,corrie1 :]e ! lavas & tuffs reappe>4 ,!y are s poorly repres5t$ !re1 h[ev]1 t we are evid5tly n f> f ! limit ( ! plateau 9 t direction4 ,s va/ has be5 ! d5udation ( ! region t x is n[ impossible to det]m9e :e!r ! volcanic ejections ( ,campbelt[n1 :i* occupy ! same geological plat=m z ^? ( ,arran1 ,bute & ,ayr%ire1 7 also actually cont9u\s ) !m4 ,b z ! di/ance betwe5 ! d5ud$ fragm5ts ( ! volcanic s]ies 9 ,arran & 9 ,cantyre is only ab\t #bj miles x is n improbable t ?is cont9uity exi/$1 & ?us t ! volcanic accumulations rea*$ at lea/ z f> z ! s\!rn end ( ,argyll%ire1 :]e !y n[ slip "u ! sea4 ,illu/ration3 ,fig4 #aji4--,view ( ,nor? ,b]wick ,law f ! ea/1 a tra*yte neck m>k+ "o ( ! *ief v5ts ( ! ,g>leton ,plateau4 7,f a photograph47 ,?is illu/ration & ,figs4 #aai1 #acc & #ace are f photographs tak5 by ,mr4 ,rob]t ,lunn = ! ,geological ,survey4 #b4 ,! ,ea/ ,lo?ian or ,g>leton ,plateau4--,"s #ej miles to ! ea/ ( ! ,clyde volcanic di/rict1 & entirely indep5d5t ( x1 lies ! plateau ( ! ,g>leton ,hills 9 ,ea/ ,lo?ian1 :i*1 z its limits t[>ds ! ea/ & nor? h be5 r$uc$ by d5udation1 & t[>ds ! we/ are hidd5 "u ! ,c>bonif]\s ,lime/one s]ies ( ,hadd+ton1 cov]s n[ an area ( n m ?an ab\t #fj squ>e miles4#dae ,t ! eruptions f ?is area did n ext5d f> to ! nor? is %[n by ! abs5ce ( all trace ( !m among ! ,l[] ,c>bonif]\s rocks ( ,fife4 ,a relic ( !m occurs above ,bor?wick1 9 ,midlo?ian1 ab\t twelve miles to ! s\?-we/ ( ! ne>e/ m>g9 ( ! plateau4 ,! area ov] :i* ! lavas & tuffs 7 dis*>g$ may n h exce$$ #aej squ>e miles4 ,small ?\gh ?is plateau is1 x possesses mu* int]e/ f ! rem>kable v>iety ( petrographical "* 9 its lavas1 f ! size & composition ( its necks1 & f ! picturesque coa/-l9e :]e its details h be5 admirably dissect$ by ! waves4 ,9 _m respects x /&s by itself z an exception to ! g5]al type ( ! o!r plateaux4 ,footnote #dae3 ,?is plateau is repres5t$ 9 ,%eets #cc & #da ( ! ,geological ,survey ( ,scotl&1 & is describ$ 9 ! ,explanation to accompany ,%eet #cc4 ,illu/ration3 ,fig4 #aaj4--,! ,bass ,rock1 a tra*ytic neck belong+ to ! ,g>leton plateau1 f ! %ore at ,canty ,bay4 ,f its proximity to ,ed9burgh ?is volcanic area has be5 (t5 /udi$ & describ$4 ,! memoirs ( ,hay ,cunn+ham & ,macl>5 gave ! fulle/ acc\nt ( x until its /ructure 0 mapp$ by ! ,geological ,survey4 ,its sc5]y diff]s f t ( ! o!r plateaux *iefly 9 ! abs5ce ( ! t]rac$ cont\r :i* 9 !m is s *>act]i/ic4 ,! peculi> lavas ( ! ,g>leton ,hills =m irregul>ly-unev5 gr\nd1 ris+ to n m ?an #fjj feet above ! sea4 ,!y slope gradually d[n to ! coa/1 :]e a succession ( f9e sections ( ! volcanic s]ies has be5 laid b>e = a di/ance ( altoge!r ab\t t5 miles4 ,n[h]e1 inde$1 c ! ph5om5a ( ! plateau-tuffs & _! association ) ! ,c>bonif]\s /rata be s well /udi$ z along ! coa/-l9e f ,nor? ,b]wick to ,dunb>4 ,among ! necks ( ?is plateau di/+ui%$ = _! size1 conspicu\s prom95ce & compon5t mat]ials1 ! mo/ important are ^? t =m ! conical em95ces ( ,nor? ,b]wick ,law 7,fig4 #aji71 ,trapra9 ,law 7,fig4 #acc71 & ! ,bass ,rock 7,fig4 #aaj74 #c4 ,! ,midlo?ian ,plateau4--,on ! same g5]al /ratigraphical horizon z ! o!r volcanic plateaux1 a n>r[ b& ( lavas & tuffs c be foll[$ f ! ea/]n outskirts ( ! city ( ,ed9burgh into ,lan>k%ire1 a di/ance ( ab\t #bc miles4 ,x is n cont9u\sly visible1 (t5 disappe>+ altoge!r1 & v>y+ mu* 9 ?ickness & composition4 ,?is volcanic tract1 :i* may be conv5i5tly t]m$ ! ,midlo?ian ,plateau1 is ! smalle/ & mo/ fragm5t>y ( all ! s]ies4 ,its mo/ ea/]ly outli]s =m ,ar?ur ,seat & ,calton ,hill at ,ed9burgh4#daf ,?ree miles to ! s\?-we/ a ?ird deta*$ portion is kn[n z ,craiglockh>t ,hill4 ,aft] ano!r int]val ( t5 miles1 ! l>ge/ rema9+ fragm5t =ms ! prom95t ridge ( ,cor/on ,hill 7,fig4 #aaa71 :5ce a discont9u\s n>r[ /rip may be trac$ ne>ly z f> z ! ,riv] ,clyde4 ,footnote #daf3 ,i =m]ly class$ ^! em95ces ) ! ,puys1 b ,i am n[ ( op9ion t !y ought r to be reg>d$ z fragm5ts ( a long & some:at n>r[ plateau4 ,_! basic lavas & ov]ly+ %eets ( porphyrite repeat ! usual sequ5ce ( ! plateaux1 :i* is n met ) among ! ,puys4 ,b1 z w be po9t$ out 9 ! sequel1 ,ar?ur ,seat 9 long subsequ5t "t became aga9 ! site ( a volcanic v5t4 ,illu/ration3 ,fig4 #aaa4--;,cor/on ,hill--a fragm5t ( ! ,midlo?ian ,plateau1 se5 f ! nor?4 ,! volcanic rocks =m a cake on ! top1 ! slopes ly+ across ! edges ( ! ,calcif]\s ,s&/ones4 ,! well-kn[n ,ar?ur ,seat & ,calton ,hill h be5 fully describ$ by ,macl>51 & h be5 ! subject ( num]\s obs]vations by o!r geologi/s4#dag ,!y h be5 likewise mapp$ 9 detail on a l>ge scale by ! ,geological ,survey1 & h be5 describ$ 9 ! ,survey ,memoirs4 ,! re/ ( ! plateau to ! s\?-we/ is mu* less famili>4 ,footnote #dag3 ,macl>5's ,geology ( ,fife & ! ,lo?ians1 #ahci1 pp4 #a-fg2 & ,hay ,cunn+ham1 ,mem4 ,w]4 ,soc4 vii4 pp4 #ea-fb4 ,! plateau is repres5t$ 9 ,%eets #bd & #cb ( ! ,geological ,survey1 & ,ar?ur ,seat & ,calton ,hill w be f\nd on ,%eet #b ( ! ,geological ,survey map ( ,ed9burgh%ire on ! scale ( #f in*es to a mile4 ,9 ,fig4 #aab ! great esc>pm5t :i* desc5ds f ! "r t[>ds ! c5tre is ! sill ( ,salisbury ,crags4 ,! long d>k crag 7,long ,r[7 ris+ betwe5 ! two valleys is ! l[e/ ( ! int]/ratifi$ lavas4 ,! slope t rises above x has be5 cut out ( well-b$d$ tuffs1 on :i* lie ! basalts & &esites 9 successive %eets t =m all ! ea/]n or left side ( ! hill4 ,! rocks ar\nd ! summit belong to a mu* lat] p]iod ( volcanic eruption1 & are ref]r$ to 9 ,*apt] xxxi4 ,illu/ration3 ,fig4 #aab4--,view ( ,ar?ur ,seat f ,calton ,hill to ! nor?4 ,! rocks ( ?is plateau are comp>atively limit$ 9 ?ickness1 & h a mu* m re/rict$ v]tical range ?an ^? ( o!r di/ricts4 ,at ,ar?ur ,seat & ,cor/on ,hill !y beg9 above ! cem5t-/ones & cease 9 a l[ "p ( ! great gr\p ( :ite s&/ones & d>k %ales :i* =m ! upp] half ( ! ,calcif]\s ,s&/ones ( ,midlo?ian4 ,!y d n asc5d z high z ! ,burdieh\se ,lime/one1 :i* to ! we/ ( ,cor/on ,hill is se5 to come on above !m4 ,"o ( _! mo/ rem>kable features is ! mann] 9 :i* !y dim9i% to a s+le ?9 b$ & !n die out altoge!r1 reappe>+ aga9 9 a simil> att5uat$ =m on ! same horizon4 ,?is imp]si/5ce is well se5 9 ! s\?-we/]n "p ( ! area1 betwe5 ,butel&1 9 ! p>i% ( ,currie1 & ,crosswood1 9 ! p>i% ( ,mid-,cald]4 ,! l[e/ m basic b& may !re be trac$ at int]vals = _m miles )\t ! ov]ly+ &esitic gr\p4 ,yet t &esites foll[$ ! basalts1 z 9 o!r plateaux1 is well %[n by l>ge remnants ( ^! less basic lavas left 9 ,ar?ur ,seat & ,calton ,hill4 ,on ! extreme s\!rn m>g9 ( ! area also a ?9 b& ( porphyrite ) a gr\p ( ov]ly+ tuffs is se5 above ! r$ s&/ones ne> ,dunsyre4#dah ,! eruptions ov] ! site ( ?is plateau seem to h be5 mu* m local & limit$ ?an 9 ! o!r plateaux4 ,!y appe> to h ga!r$ *iefly ar\nd two c5tres ( activity1 "o ( :i* lay ab\t ! position ( ,ed9burgh1 ! o!r 9 ! neighb\rhood ( ,cor/on ,hill4 ,x is wor?y ( rem>k t ?is tract ( volcanic mat]ial flanks ! mu* old] range ( lavas & tuffs ( ! ,p5tl& ,hills & wraps r\nd ! s\?-we/]n end ( ?is range1 ?us furni%+ ano!r illu/ration ( ! r5ewal ( volcanic activity 9 ! same region dur+ successive geological p]iods4 ,footnote #dah3 ,explanation1 ,geol4 ,surv4 ,scotl&1 ,%eet #bd1 p4 #ac 7#ahfi74 #d4 ,! ,b]wick%ire ,plateau4--,ano!r & entirely disconnect$ area occurs 9 ! broad pla9 or ,m]se ( ! l[] portion ( ! valley ( ! ,twe$4#dai ,! nor!rn limit ( its volcanic tuff occurs 9 ! ,riv] ,:itadd] above ,duns1 :5ce ! erupt$ mat]ials rapidly wid5 & ?ick5 t[>ds ! s\?-we/ by ,/it*ell & ,kelso1 until !y die out aga9/ ! flanks ( ! ,*eviot ,hills4 ,! ea/]n ext5sion ( ! area is lo/ b5ea? ! ,cem5t-/one gr\p :i* cov]s ! ,m]se d[n to ! sea4 ,its we/]n b\nd>y mu/ once h rea*$ f> beyond its pres5t limits1 = ! l[ ,silurian gr\nd 9 t direction is dott$ ov] ) scatt]$ v5ts to a di/ance ( t5 miles or m f ! pres5t outcrop ( ! b$d$ lavas1 ext5sive d5udation hav+ cle>$ away ! erupt$ mat]ials & expos$ ! volcanic pipes ov] _m squ>e miles ( c\ntry4 ,among ! m prom95t ( ^! old v5ts are ! ,eildon ,hills1 ,m9to ,crags & ,rub]s ,law1 z well z _m o!r em95ces famili> 9 ,bord] /ory4 ,footnote #dai3 ,?is plateau is %[n on ,%eets #ag1 #be1 #bf & #cc ( ! ,geological ,survey ,map ( ,scotl&4 ,x 0 *iefly mapp$ by ,pr(4 ,james ,geikie & ,mr4 ,b4 ,n4 ,pea*4 ,! b$d$ volcanic rocks ( ?is area =m a m>k$ feature 9 ! topography & geology ( ! di/rict4 ,!y rise above ! pla9 ( ! ,m]se z a b& ( undulat+ hills1 ( :i* ! em95ce cr[n$ by ,hume ,ca/le1 ab\t #fjj feet above ! sea1 is ! mo/ conspicu\s height4 ,9 ! geological /ructure ( ?is "p ( ,scotl& !y are ma9ly int]pos$ betwe5 ! ,upp] ,old ,r$ ,s&/one & ! base ( ! ,c>bonif]\s sy/em1 :i* !y ?us s]ve to divide f ea* o!r4 ,b _! l[e/ %eets appe> to be 9 "s places int]calat$ 9 ! ,old ,r$ ,s&/one1 s t _! eruption probably began be=e ! beg9n+ ( ! ,c>bonif]\s p]iod4 ,!y =m a b& t curves r\nd ! end ( ! great ,c>bonif]\s tr\gh at ,kelso & skirts ! nor!rn edge ( ! &esites ( ! ,l[] ,old ,r$ ,s&/one 9 ! ,*eviot ,hills4 #e4 ,! ,solway ,plateau4--,! la/ plateau1 t ( ! ,solway bas91 ?\gh its pres5t visible ea/]n limits approa* ^? rea*$ by ! lavas f ! ,b]wick%ire area1 0 q di/9ct1 & _h its *ief v5ts at "s di/ance t[>ds ! s\?-we/4#dbj ,on ! nor?-we/]n flanks ( ! ,*eviot ,hills1 ! ,upp] ,old ,r$ ,s&/one is ov]la9 by ! l[e/ ,c>bonif]\s /rata1 )\t ! int]calation ( any volcanic zone1 s t !re mu/ h be5 "s int]m$iate gr\nd t escap$ be+ flood$ ) lava f ! v5ts ( ! ,m]se on ! "o h&1 & ( ! ,solway on ! o!r4 ,! ,solway lavas =m a mu* ?9n] gr\p ?an ^? ( ,b]wick%ire4 ,f ! wild moorl& betwe5 ! s\rces ( ! ,liddell & ! ,rule ,wat]1 !y run 9 a n>r[ & mu*-fault$ b& s\?-we/w>d across ,eskdale & ! foot ( ,ann&ale1 & are traceable 9 occasional pat*es on ! f>!r side ( ! ,ni? along ! s\!rn flanks ( ,criffel1 ev5 z f> z ,torrorie on ! coa/ ( ,kirkcudbright--a total di/ance ( ab\t #de miles4 ,x is probable t ?is long outcrop pres5ts m]ely ! nor!rn edge ( a volcanic plat=m :i* is ma9ly buri$ "u ! ,c>bonif]\s rocks ( ! ,solway bas94 ,yet x exhibits _m ( ! *ief *>act]s ( ! o!r plateaux1 & ev5 occasionally rivals !m 9 ! dignity ( ! esc>pm5ts :i* m>k its progress ?r\gh ! lonely upl&s betwe5 ! head ( ,liddesdale & ! ,ewes ,wat] 7,figs4 #aac1 #adb74 ,footnote #dbj3 ,= a del9eation ( ! di/ribution & /ructure ( ?is plateau see ,%eets #e1 #f1 #aj1 #aa & #ag ( ! ,geological ,survey ( ,scotl&4 ,9 ! upp] "p ( ,liddesdale1 ,ewesdale & ,t>ras x 0 mapp$ by ,mr4 ,b4 ,n4 ,pea*2 9 l[] ,liddesdale & ,eskdale by ,mr4 ,r4 ,l4 ,jack & ,mr4 ,j4 ,s4 ,grant ,wilson2 f ,langholm to ! ,annan by ,mr4 ,h4 ,skae2 & 9 ,kirkcudbright by ,mr4 ,john ,horne4 ,illu/ration3 ,fig4 #aac4--,view ( ,arkleton ,fell1 "p ( ! ,solway ,plateau1 f ! s\?-we/4 ,! l[] slopes bel[ ! s+le bird1 r\nd to ! left side ( ! sket*1 are on ! ,upp] ,old ,r$ ,s&/one2 ! l9e ( crag bel[ ! two birds m>ks ! volcanic gr\p above :i* lies an outli] ( ! ,calcif]\s ,s&/one s]ies1 =m+ ! upp] "p ( ! hill 7?ree birds74 ,! knobs "u ! f\r birds are bosses ( &esite4 ,! plateaux ( ! ,m]se & ! ,solway illu/rate 9 a /rik+ mann] ! di/ribution ( ! volcanic eruptions along valleys & l[ pla9s4 ,! v5ts f :i* ! lavas & tuffs proce$$ are *iefly to be f\nd on ! l[] gr\nds1 ?\gh ^! b$d$ volcanic rocks rise to a height ( #agab feet 7! ,pikes7 to ! we/ ( ! ,*eviot ,hills4 ,betwe5 ! ,silurian upl&s ( ,selkirk%ire & ,b]wick%ire on ! nor? & ! ridge ( ! ,*eviot ,hills on ! s\?1 ! broad pla9 0 dott$ ) volcanic v5ts & flood$ ) lava1 :ile to ! s\?-we/ ! correspond+ holl[ betwe5 ! upl&s ( ,dumfries & ,gall[ay on ! "o side1 & ^? ( ,cumb]l& on ! o!r1 0 simil>ly ov]spread4 ,! significance ( ^! facts w be m app>5t :5 ! gr\p+ ( ! v5ts has be5 describ$4 ,we %all !n also be bett] able to realize ! validity ( ! inf]5ce t ! pres5t plateaux are m]e fragm5ts ( :at !y orig9ally 71 wide areas hav+ be5 remov$ f ! "o side ( !m by d5udation1 & hav+ be5 conceal$ on ! o!r "u lat] portions ( ! ,c>bonif]\s sy/em4 ,! same two plateaux likewise supply fur!r illu/rations ( ! outfl[ ( simil> volcanic mat]ials 9 ! same locality at widely sep>at$ int]vals ( "t4 ,!y may be trac$ up to & r\nd ! m>g9 ( ! great pile ( &esites ( ,l[] ,old ,r$ ,s&/one age =m+ ! ,*eviot ,hills4 ii4 ,,nature ,,( ,,! ,,mat]ials ,,erupt$ ,! volcanic mat]ials *>act]i/ic ( ! plateau-type ( eruptions consi/ ma9ly ( lavas 9 successive %eets1 b include also v>i\s tuffs 9 frequ5t ?9 c\rses1 & less commonly 9 ?ick local accumulations4 ,! lavas are *iefly &esites 9 ! alt]$ condition ( porphyrites4 ,!y v>y a good deal 9 ! relative proportions ( silica4 ,"s ( !m are decid$ly basic & take ! =m ( dol]ites & oliv9e-basalts4 ,) ^! rocks are occasionally associat$ ultra-basic v>ieties1 :]e ! felsp> almo/ disappe>s & ! mat]ial consi/s ma9ly ( f]ro-magnesian m9]als4 ,! m basic rocks are g5]ally f\nd t[>ds ! bottom ( ! volcanic s]ies1 :]e !y appe> z ! olde/ fl[s4 ,9 ! ,g>leton ,hills lavas ( a mu* m acid nature are met )--true sanid9e-tra*ytes1 :i* ov]lie ! porphyrites & basalts ( ! e>li] eruptions4 ,no adequate inve/igation has yet be5 made ( ! *emical & microscopic *>act]s ( ^! v>i\s rocks1 reg>d$ z a great volcanic s]ies belong+ to a def9ite geological age1 ?\gh _m ( ! individual rocks & ! petrography ( diff]5t di/ricts h be5 m or less fully describ$4 ,i _c "h ent] into mu* detail on ! subject1 b mu/ cont5t myself ) su* a summ>y z w convey "s idea ( ! g5]al composition & /ructure ( ?is v int]e/+ volcanic s]ies4 7a7 ,augite-oliv9e ,rocks 7,picrites & ,limburgites74--,t[>ds ! bottom ( ! plateaux !re are f\nd "h & !re %eets ( ultra-basic mat]ial1 "s ( :i* appe> to be b$d$ ) ! o!r rocks & to h fl[$ out z surface-lavas1 ?\gh x may be impossible to prove t !y are n sills4 ,?us at ,:itelaw ,hill1 on ! s\? side ( ! ,g>leton ,hills1 a d>k heavy rock is f\nd to conta9 h>dly any felsp>1 b to be made up ma9ly ( oliv9e & augite4 ,dr4 ,hat* has publi%$ a description & draw+ ( ?is rock1 toge!r ) ! foll[+ analysis by ,mr4 ,play]3#dba-- ,silica #djb ,titanic oxide #bi ,alum9a #abh ,f]ric oxide #dj ,f]r\s oxide #ajd ,lime #ajd ,magnesia #aai ,pota% #jh ,soda #bg ,loss by ignition #cd ---- ,spec4 grav4 #cjc4 #iie ,footnote #dba3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxxvii4 7#ahic71 p4 #aaf4 7b7 ,dol]ites & ,basalts4#dbb--,^! rocks are f\nd bo? z int]/ratifi$ lavas & z intrusive masses4 ,9 ! =m] condition !y take a conspicu\s place among ! %eets ( ! plateaux1 b especially 9 ! l[] p>ts ( ! s]ies4 ,!y are d>k1 (t5 black1 usually m or less porphyritic1 ) l>ge felsp>s1 frequ5tly also l>ge cry/als ( augite or oliv9e1 & may be describ$ z porphyritic oliv9e-dol]ites & oliv9e-basalts1 m r>ely z oliv9e-free dol]ites & basalts4 ,_! gr\ndmass consi/s ( %ort la?s or microlites ( felsp> 7probably labradorite7 & granules or small cry/als ( augite & magnetite1 ) sometimes a little fibr\s br[n mica4 ,! l>ge porphyritic felsp>s are /rip$ 7probably labradorite71 ! augites are frequ5tly *loritiz$1 & ! oliv9es are g5]ally m or less s]p5t9iz$4 ,b 9 "s cases all ^! m9]als are z fre% z 9 a rec5t basalt4 ,! rocks are sometimes beautifully column>1 z at ,ar?ur ,seat4 ,footnote #dbb3 ,a g5]al classification ( ! :ole s]ies ( ,scotti% ,c>bonif]\s dol]ites & basalts1 includ+ bo? ! plateau & puy examples1 w be giv5 9 ! acc\nt ( ! rocks ( ! puys 9 ,*apt] ,,xxvi4 7p4 #dah74 ,( ^! basic lavas conspicu\s examples may be se5 at ,ar?ur ,seat1 ,calton ,hill & ,craiglockh>t ,hill4 ,! ea/]n "p ( ,ar?ur ,seat1 kn[n z ,:9ny ,hill1 furni%es examples ( oliv9e-dol]ites ( ! ,j$burgh type 7p4 #dah74 ,! beautiful basalt ( ,craiglockh>t ) its l>ge porphyritic oliv9es & augites has af=d$ a di/9ct type ( ,c>bonif]\s basalt 7p4 #dah74 ,! same type occurs on ! ,calton ,hill 9 ! cliff bel[ ! gaol4 ,simil> basic lavas are especially abundant & rem>kable 9 ! ,clyde plateau ne> ,campbelt[n 9 ,argyll%ire1 & at ! s\? end ( ,bute & 9 ! ,cumbraes1 :]e !y are associat$ ) an int]e/+ s]ies ( dykes & sills4 ,b ev5 :]e1 z 9 ! ,g>leton ,hills1 ! lavas are = ! mo/ "p some:at acid 9 composition1 ^? fir/ p\r$ out1 :i* =m ! l[e/ b&1 include "s typical oliv9e-basalts1 ( :i* a *>act]i/ic example occurs at ,kippie ,law at ! base ( ! ,g>leton plateau 7p4 #dah74 ,x has be5 describ$ by ,dr4 ,hat* z exhibit+ "u ! microscope porphyritic cry/als ( felsp> & oliv9e ly+ 9 a gr\ndmass compos$ ( la?-%ap$ felsp>s1 granul> oliv9e & magnetite1 & microlitic augite4 ,! oliv9e1 orig9ally ! mo/ abundant con/itu5t1 has be5 conv]t$ into a fibr\s aggregate ( s]p5t9e4 ,all ! m9]als are m or less idiomorphic1 b especially ! augite1 :i* cr[ds ! gr\ndmass 9 delicately-%ap$ prisms1 mo/ ( :i* are t]m9at$ at bo? ends by faces ( ! hemi-pyramid4 ,! analysis ( ?is rock is giv5 9 ! accompany+ table ( analyses ( ,g>leton basalts4 ,! ,kippie ,law type ( basalt 0 recogniz$ by ,dr4 ,hat* among ! ,geological ,survey collections f o!r di/ricts1 z 9 ! intrusive bosses ( ,neides ,law & ,bon*e/] ne> ,j$burgh1 & f ! ,campsie plateau a mile & a half nor? ( ,l5noxt[n4#dbc ,footnote #dbc3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxxvii4 7#ahic71 pp4 #aag-aai4 ,at ,hailes ,ca/le1 9 ! ,g>leton plateau1 ! l[] basic lavas include ano!r oliv9e-basalt some:at m felspa?ic ?an t j describ$1 & at ,m>kle qu>ry ! rock is /ill m felspa?ic & conta9s ! oliv9e only 9 small sporadic gra9s4 ,! composition ( ^! basic rocks ( ! ,g>leton plateau is %[n 9 ! subjo9$ table ( analyses by ,mr4 ,j4 ,s4 ,grant ,wilson3-- ---------------------------------------- ------------------ ,kippie ,law1 ,hailes ,ca/le1 ,m>kle ,qu>ry1 specific specific specific gravity #bh gravity #bgf gravity #bg ---------------------------------------- ------------------ ,si,o#b #dfja #dijg #died ,al#b,o#c #aiai #aidc #bbbc ,fe#b,o#c #eia #ajeh #iee ,fe,o #fge #bce #aab ,mn,o #jai #jcb #jjh ,ca,o #hfh #ghg #gai ,mg,o #fha #dcf #bhj ,k#b,o #abj #jih #aha ,na#b,o #cbg #cca #def ,h#b,o #cjg #bbf #bdb ,total #ajajh #ajjec #ajacj ---------------------------------------- ------------------ ,oliv9e-dol]ites are m especially develop$ 9 ! di/rict ar\nd ,j$burgh1 :]e !y =m "s ( ! mo/ prom95t bosses1 su* z ,dunian & ,black ,law4 ,!y %[ a sub-ophitic gr\ndmass1 ) inconspicu\s porphyritic cry/als1 among :i* ^? ( oliv9e are m prom95t ?an ! felsp>s 7p4 #dah74 7c7 ,&esites 7,porphyrites74--,^! are ! mo/ abundant lavas ( ! plateaux4 ,!y occur 9 e di/rict1 & usually =m ! ma9 con/itu5ts ( ! pile ( volcanic mat]ial4 ,!y v>y 9 col\r f a pale p9ki% grey1 ?r\gh _m %ades ( r$1 purple1 br[n & yell[1 to sometimes a d>k gre5 or ne>ly black rock4 ,_! texture ranges f almo/ semi-vitre\s1 ?r\gh diff]5t degrees ( compactness1 to op51 cellul>1 slaggy masses4 ,g5]ally ?r\gh _! base porphyritic felsp>s are abundantly dissem9at$1 sometimes 9 l>ge1 flat1 tabul> =ms1 l ^? ( ! ,l[] ,old ,r$ ,s&/one already ref]r$ to4 ,! amygdaloidal k]nels consi/ ( calcite1 zeolites1 *alc$ony or qu>tz4 ,x is f ! amygdaloids on ei!r side ( ! ,clyde t ! f9e examples ( zeolites h be5 *iefly obta9$ = :i* ! s\? ( ,scotl& has long be5 fam$4 ,occasionally1 z at ! s\? end ( ,bute1 ! &esitic lavas display a m>k$ column> /ructure4 ,"u ! microscope ^! rocks pres5t ! usual f9e felt$ aggregate ( felsp> microlites1 ) granules or cry/als ( magnetite & sometimes pyrox5e4 ,! porphyritic felsp>s1 (t5 l>ge & well def9$1 g5]ally conta9 inclusions ( ! gr\ndmass4 ,occasionally "s ( ! l>ge porphyritic con/itu5ts are augite1 or pseudomorphs aft] t m9]al4 ,! alt]ation ( ! rocks has oxidiz$ "s ( ! iron-ore & giv5 rise to ! preval5t purpli% & r$di% t9ts4 7d7 ,tra*ytes4--,"s ( ! mo/ rem>kable lavas to be f\nd 9 any ( ! plateaux are ^? :i* con/itute a l>ge "p ( ! ,g>leton ,hills4 ,!y ov]lie ! l[] &esite & basalt plat=m1 :i* surr\nds !m z a n>r[ belt1 :ile !y occupy ! c5tral & mu* ! l>ge/ "p ( ! area4 ,!y h be5 includ$ among ! porphyrites1 b are pale rocks1 g5]ally ) a yell[i% cru/1 pres5t+ :5 q fre% a grey1 compact1 felsitic base ) l>ge porphyritic cry/als ( un/rip$ felsp>4 ,a numb] ( specim5s select$ z illu/rative ( ! diff]5t v>ieties h be5 analyz$ & ! results are /at$ 9 ! subjo9$ table4#dbd ,! specific gravity ( ! rocks is ab\t #bf4 ,footnote #dbd3 ,! fir/ two analyses are by ,mr4 ,j4 ,s4 ,grant ,wilson1 ! la/ two by ,mr4 ,a4 ,dick jun41 & t f ,hopet\n ,monum5t by ,mr4 ,g4 ,b>r[4 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxxvii4 p4 #abb4 ---------------------------------------- --------------------- ,pepp] ,kae ,hopet\n ,phantassie ,bangley ,craig ,heughs ,monum5t ,qu>ry ---------------------------------------- --------------------- ,si,o#b #fbfa #face #fbej #eiej #ehej ,al#b,o#c #ahag #afhh #ahea #ahbe #baab ,fe#b,o#c #jcb #jda #dci #dha #dfh ,fe,o #dbe #eja #bcd 444 ,mn,o #jba #jbf 444 444 444 ,ca,o #beh #bci #bjj #baj #cgj ,mg,o #jgd #jdd #jfa #jgj #jic ,k#b,o #djb #fab #fca #fcj #ehd ,na#b,o #fdi #ebf #cdd #ejc #cij ,h#b,o #jhj #agj #baj #afj #bjj ,total #ajjai #iihb #iihf #ajjfc #ajjfg ---------------------------------------- --------------------- ,! microscopic *>act]s ( ^! rocks1 z work$ out by ,dr4 ,hat*1 %[ !m to be well-m>k$ & wond]fully fre% sanid9e-tra*ytes4 ,"s ( !m are porphyritic1 ) l>ge cry/als ( p]fectly unalt]$ sanid9e1 sometimes also oligoclase4 ,small b well-=m$ cry/als ( yell[i%-gre5 augite1 9 addition to ! porphyritic felsp>s1 are imb$d$ 9 a f9e gr\ndmass compos$ *iefly ( microlites ( sanid9e1 b ) granules ( augite & magnetite pl5tifully int]sp]s$1 & occasionally prisms ( apatite4 ,!re is a gr\p 9 :i* ! porphyritic felsp>s are sc>ce or abs5t4 ,9 ^! !re is little or no f]ro-magnesian con/itu5t4 ,o!r tra*ytes1 r less basic ?an ! augite-be>+ v>ieties "h ref]r$ to1 occur z bosses 9 ! ,g>leton ,hills di/rict1 & are ref]r$ to 9 ! foll[+ section 7e74#dbe ,footnote #dbe3 ,= full] petrographical details consult ,dr4 ,hat*'s pap] above cit$4 7e7 ,rocks ( ! ,necks4--,9 ! necks connect$ ) ! plateaux o!r types ( massive rock are to be f\nd4 ,among ^! p]haps ! mo/ frequ5t are tra*ytes1 grey to p9k 9 col\r1 b apt to wea!r yell[1 exce$+ly compact1 sp>+ly porphyritic1 & ) a peculi> platy /ructure & waxy lu/re4 ,rocks ( ?is "* also appe> z sills & dykes4 ,o!r v>ieties t occur 9 simil> positions are m basic 9 composition1 includ+ d>k1 co>se1 granul> diabases4 ,9 ! ,j$burgh di/rict ! mo/ frequ5t rocks are beautiful v>ieties ( oliv9e-dol]ite & oliv9e-basalt1 :i* =m mo/ ( ! prom95t hills ( ! neighb\rhood4 ,^! bosses are sometimes associat$ ) agglom]ates z at ,rub]s ,law4 ,9 ! ,g>leton ,hills di/rict1 "s ( ! necks pres5t ano!r petrographical type :i* directly connects !m ) ! rem>kable lavas ( ! high] "p ( t plateau4 ,?us ! rock ( ,trapra9 ,law 0 asc]ta9$ by ,dr4 ,hat* to be a true phonolite4 ,9 its g5]al platy /ructure & sonor\s r+ "u ! hamm] x rem9ds "o ( typical phonolites4 ,"u ! microscope ! rock is f\nd to consi/ ma9ly ( small la?-%ap$ cry/als ( sanid9e arrang$ 9 a m>k$ m9ute fl[-/ructure1 b ) few porphyritic cry/als4 ,x conta9s small cry/als & ophitic pat*es ( a light gre5 soda-augite1 ) practically no magnesia 9 x4 ,a small quantity ( iron-ore & isolat$ granules ( apatite are also pres5t1 toge!r ) pat*es ( nephel9e :i*1 ?\gh g5]ally decompos$ & replac$ ) zeolitic products1 occasionally display six- & f\r-sid$ cry/al-cont\rs4 ,an analysis ( ! ,trapra9 phonolite by ,mr4 ,play] is subjo9$3--#dbf ,silica #efh ,titanic acid #je ,alum9a #aig ,f]ric oxide #bb ,f]r\s oxide #ce ,mangan\s oxide #jb ,lime #bb ,magnesia #jd ,soda #dc ,pota% #ga ,loss by ignition #be ---- ,spec4 grav4 #behh #iid ,footnote #dbf3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxxvii4 p4 #abe4 ,! neck ( ,nor? ,b]wick ,law 0 f\nd by ,dr4 ,hat* to be a tra*yte1 %[+ a plexus ( la?-%ap$ sanid9es t dim9i% 9 size to m9ute microlites1 b ) no porphyritic or f]ro-magnesian con/itu5t4 ,! ,bass ,rock1 ?\gh its geological relations are conceal$ by ! sea1 is 9 all probability ano!r neck ( ?is di/rict4 ,x is likewise a mass ( tra*yte1 compos$ almo/ entirely ( la?-%ap$ cry/als ( sanid9e1 ) no f]ro-magnesian con/itu5t1 b a good deal ( iron ore4 ,x %[s none ( ! l>ge porphyritic felsp>s s *>act]i/ic ( ! ,g>leton ,hills lavas1 b x closely resembles ! non-porphyritic v>ieties1 p>ticul>ly ! lavas ( ,score ,hill1 ,p5craig1 ,lock ,pit ,hill1 & ,craigie ,hill4#dbg ,footnote #dbg3 ,! composition ( ! rocks ( ,nor? ,b]wick ,law & ! ,bass closely resembles t ( ! tra*ytic lavas ( ! plateau4 ,= analyses1 see ,dr4 ,hat*'s ,pap]1 ibid4 pp4 #abc1 #abd4 7f7 ,tuffs4--,! fragm5t>y ejections ( ! plateaux v>y 9 texture f ! f9e/-gra9$ tuffs to co>se agglom]ates4#dbh ,z !y h be5 d]iv$ f ! explosion ( &esite-lavas1 !y consi/ ma9ly ( ! debris ( ^! rocks4 ,!y are (t5 deep r$ 9 col\r1 z = example ^? ( ,dunb>1 b are mo/ frequ5tly gre5i%4 ,!y h a granul> texture1 due to ! small lapilli ( v>i\s porphyrites imb$d$ 9 a f9e du/ ( ! same mat]ial4 ,gra9s ( qu>tz1 frequ5tly to be detect$ ev5 9 ! f9] tuffs1 may ei!r h be5 eject$ f ! volcanic v5ts1 or may h be5 gra9s ( s& 9 ! ord9>y s$im5t ( ! sea-bottom4 ,bo? at ! base & at ! top ( ! plateau-s]ies1 ! tuffs are int]/ratifi$ ) & bl5d into s&/ones & %ales1 s t specim5s may be collect$ %[+ a gradual passage f volcanic into non-volcanic detritus4 ,9 _m ( ! tuffs ( ! necks fragm5ts ( s&/one & o!r /ratifi$ rocks occur1 repres5t+ ! /rata ?r\gh :i* ! v5ts 7 drill$4 ,9 ! tuffs ( ! ,eagle%am di/rict pieces ( grey & p9k granite h be5 met ) :i*1 if !y are portions ( an old granite mass bel[1 mu/ h come f a great dep?4#dbi ,9 ! co>s] tuffs & agglom]ates a l>g] v>iety ( lava-=m rocks is to be f\nd ?an c be se5 among ! b$d$ lavas ( ! ,plateaux4 ,!y include felsites & qu>tz-porphyries1 & m r>ely basic lavas 7diabases1 etc474 ,footnote #dbh3 ,= acc\nts ( ^! rocks1 see ,explanation ( ,%eet #cc ,geol4 ,surv4 ,scot4 p4 #cb2 ,%eet #bb1 pp4 #aa-ad2 ,%eet #ca1 pp4 #ad-ag4 ,footnote #dbi3 ,explanation ( ,%eet #bb ,geol4 ,surv4 ,scot4 p4 #ab4 ,,*apt] ,,xxv ,,geological ,,/ructure ,,( ,,! ,,c>bonif]\s ,,volcanic ,,plateaux ,,( ,,scotl& #a4 ,b$d$ ,lavas & ,tuffs2 ,upp] ,limits & ,orig9al ,areas & ,slopes ( ! ,plateaux2 #b4 ,v5ts2 ,necks ( ,agglom]ate & ,tuff2 ,necks ( ,massive ,rock2 ,composite ,necks2 #c4 ,dykes & ,sills2 #d4 ,close ( ! ,plateau-eruptions4 ,! /ructure ( ! v>i\s plateaux pres5ts a g5]al simil>ity1 ) _m local v>iations4 ,ea* plateau is built up entirely1 or almo/ entirely1 ( %eets ( volcanic mat]ial1 ! int]calations ( ord9>y s$im5t>y lay]s be+1 = ! mo/ "p1 few & unimportant1 & usually occurr+ ei!r t[>ds ! base or ! top ( ! volcanic s]ies1 ?\gh at a few localities int]/ratifications ( %ale & s&/one1 m>k+ pauses 9 ! eruptions1 occur ?r\gh\t t s]ies4 ,! v5ts ( eruption are 9 "s in/ances /ill to be recogniz$ on ! plateaux !mselves4 ,m usually !y occur on ! l[] gr\nd flank+ ! volcanic esc>pm5ts1 :]e !y h be5 laid b>e by d5udation4 ,dykes1 ?\gh seldom abundant1 are associat$ ) ! plateaux1 :ile ! sills :i* may m>k ! late/ manife/ations ( volcanic en]gy1 ?\gh n develop$ on s l>ge a scale z among ! ,cambrian & ,silurian volcanoes1 c nev]!less be di/9ctly recogniz$4 ,x is a "q ( "s int]e/ to det]m9e ! geological date ( ! comm5cem5t ( ! plateau-eruptions by fix+ ! precise /ratigraphical horizon on :i* ! base ( ! volcanic s]ies re/s4 ,i h already ref]r$ to ! fact t ?is base does n always lie on ! same plat=m among ! ,l[] ,c>bonif]\s =mations4 ,9 ,b]wick%ire1 z above m5tion$1 ! e>lie/ eruptions appe> to h tak5 place be=e ! close ( ! ,upp] ,old ,r$ ,s&/one p]iod4 ,^! are ! e>lie/ ( ! :ole s]ies4 ,9 ,cantyre1 ! l[e/ lavas & tuffs come directly ^u ! s&/ones1 m>ls & corn/ones ( ! ,upp] ,old ,r$ ,s&/one4 ,9 ,/irl+%ire1 ,r5frew%ire & ,ayr%ire sev]al hundr$ feet ( ! ,cem5t-/one gr\p are sometimes int]pos$ betwe5 ! bottom ( ! volcanic rocks & ! top ( ! ,old ,r$ ,s&/one4 ,?is div]g5ce d\btless indicates t ! eruptions began e>li] 9 "s di/ricts ?an 9 o!rs4 ,b !re 7 also probably unequal t]re/rial movem5ts prec$+1 & p]haps accompany+1 ! volcanic outbur/s4 ,9 ! case ( ! ,clyde plateau1 = example1 if we exam9e its base 9 ! neighb\rhood ( ,f9try1 we f9d t x lies ^u "s #ejj feet ( ,c>bonif]\s :ite s&/one1 r$ & gre5 m>ls & cem5t-/ones1 :i* re/ on ! ,upp] ,old ,r$ ,s&/one4 ,yet only eight miles to ! ea/w>d1 ?is consid]able mass ( /rata disappe>s1 & ! bottom ( ! lavas comes d[n ^u ! r$ s&/ones4 ,five miles /ill fur!r 9 ! same direction ! volcanic masses likewise die out1 & !n ! ,c>bonif]\s ,lime/one s]ies is f\nd at ,abbey ,craig to lie1 ) sc>cely any repres5tative ( ! ,cem5t-/one gr\p1 on ! ,upp] ,old ,r$ ,s&/one 7,fig4 #aad74 ,aga91 to ! s\?-we/ ( ,f9try1 ! zone ( cem5t-/ones bel[ ! volcanic s]ies cont9ues to v>y consid]ably 9 ?ickness & sometimes almo/ to disappe>1 :ile 9 ,ayr%ire ! lavas lie imm$iately on ! r$ s&/ones4 ,illu/ration3 ,fig4 #aad4--,v]tical sections ( ! esc>pm5t ( ! ,clyde plateau f nor?-ea/ to s\?-we/4 ,i4 ,section at ! ea/ end ( ! ,campsie ,hills1 f\r miles we/ f ,/irl+4 ,,ii4 ,section above ,gl9s1 six miles we/ f ,no4 ,i4 ,,iii4 ,section at ,/ra?blane ,hill1 eight miles fur!r s\?-we/4 ,,iv4 ,section at ,lang ,craig1 ea/ f ,dumb>ton1 eight miles s\?-we/ f ,no4 ,,iii4 ,v4 ,section above ,=t ,matilda1 ,gre5ock1 elev5 miles f ! previ\s section & on ! s\? side ( ! ,clyde4 #a4 ,l[] ,old ,r$ ,s&/one2 #b4 ,upp] ,old ,r$ ,s&/one2 #c4 ,c>bonif]\s %ales1 s&/ones & cem5t-/ones 7! ,ballagan b$s72 #d4 ,?ick :ite s&/one :i* comes 9 above ! ,ballagan b$s2 #e4 ,&esite lava-%eets2 #f4 ,int]/ratifi$ tuffs4 ,! dott$ l9es connect ! base ( ! volcanic s]ies4 ,^! irregul>ities1 n improbably indicative ( inequalities ( subsid5ce & ( deposition1 may h be5 connect$ ) ! subt]ranean di/urbances :i* culm9at$ 9 ! abundant outbreak ( volcanic action4 ,b ?\gh ! volcanic rocks ( ! plateaux may be trac$ ov]lapp+ ! und]ly+ /rata1 no evid5ce has any:]e be5 detect$ ( an uncon=mability betwe5 !m & ! ,l[] ,c>bonif]\s or ,upp] ,old ,r$ ,s&/one s]ies4 #a4 ,,b$d$ ,,lavas ,,& ,,tuffs ,! successive %eets ( lava 9 a plateau usually =m ?9 & widespread b$s :i* are only occasionally sep>at$ by int]calations ( tuff or ( r$ m>l4 ,9 ?is1 z well z 9 o!r respects1 !y pres5t mu* resemblance to ! lavas ( ! ,t]ti>y plateaux ( ,antrim & ! ,inn] ,hebrides4 ,!y are g5]ally m>k$ (f f ea* o!r by ! slaggy upp] & "u portions ( ! successive fl[s1 & ?is /ructure gives a di/9ctly b$d$ aspect to ! esc>pm5ts1 z 9 ! ,campsie & ,l>gs ,hills1 or /ill m conspicu\sly 9 ,little ,cumbrae 7,fig4 #ajg7 & ! s\!rn end ( ,bute4 ,consid]able div]sity ( /ructure may be notic$ among ^! %eets4 ,"s pres5t a compact jo9t$ c5tre pass+ up & d[n into ! slaggy mat]ial j ref]r$ to2 o!rs h assum$ a vesicul> "* ?r\gh\t1 ! vesicles be+ (t5 elongat$ 9 ! direction ( fl[4 ,:]e1 z usually occurs1 ! vesicul> is replac$ by ! amygdaloidal /ructure1 "s ( ! rocks h long be5 fam\s = ! m9]als f\nd 9 _! cavities4 ,! beautiful zeolites ( ! ,kilpatrick & ,r5frew%ire ,hills1 = example1 may be f\nd 9 e l>ge m9]alogical collection 9 ! c\ntry4 ,well-develop$ column> /ructure occasionally appe>s among ! lavas ( ! plateaux1 b *iefly1 s f> z ,i h obs]v$1 9 ! l[] or m basic gr\p1 z 9 ! basalts along ! ea/ side ( ! ,dry ,dam at ,ar?ur ,seat4 ,9 ea* plateau ! lavas may be obs]v$ to ?ick5 9 "o direction1 or m usually t[>ds m ?an "o1 & ?is increase no d\bt indicates 9 :i* qu>t]s ! *ief c5tres ( dis*>ge lay4 ,?us 9 ! ,clyde plateau1 sev]al areas ( maximum developm5t may be detect$4 ,9 ! ,kilpatrick ,hills ! total ?ickness ( lavas & tuffs exce$s #cjjj feet 7,fig4 #abj74 ,above ,l>gs x is m ?an #aejj feet1 rapidly ?9n+ away t[>ds ! s\?4 ,! cont9uation ( ! plateau f> to ! nor?-ea/ 9 ! ,campsie ,fells reveals a ?ickness ( ab\t #ajjj feet ( lavas at ,kilsy?1 :i* become ?ick] fur!r we/1 b ea/w>d rapidly dim9i% 9 collective bulk1 until 9 ab\t twelve or ?irte5 miles !y disappe> altoge!r1 & !n1 z already rem>k$1 ! ,calcif]\s ,s&/one s]ies closes up )\t any volcanic int]calation4 ,9 ! ,solway plateau1 ! lavas atta9 a maximum developm5t ab\t ,birr5sw>k1 :5ce !y dim9i% 9 bulk t[>ds ! nor?-ea/ & s\?-we/4 ,! ,b]wick%ire plateau rea*es its ?icke/ mass ab\t ,/it*ill1 :5ce x rapidly ?9s away t[>ds ! nor?-ea/1 until at a di/ance ( "s twelve miles x disappe>s altoge!r1 ! la/ trace ( x 9 t direction be+ a b& ( tuff :i* dies out 9 ! ,calcif]\s ,s&/ones to ! nor? ( ,duns4 ,9 ! ,midlo?ian ,plateau1 ! developm5t ( ! volcanic s]ies is m irregul> ?an 9 any ( ! o!rs4 ,z already rem>k$1 !re appe> to h be5 at lea/ two *ief c5tres ( dis*>ge 9 ?is region1 "o at ,ed9burgh & "o "s f\rte5 miles to ! s\?-we/4 ,at ! =m]1 ! volcanic mat]ials atta9 9 ,ar?ur ,seat & ,calton ,hill a ?ickness ( ab\t #aajj feet4 ,9 ,craiglockh>t ,hill1 ?ree miles di/ant1 !y are /ill ab\t #fjj feet ?ick4 ,b beyond t em95ce !y cease to be traceable = ab\t eight miles1 ei!r because !y entirely die out1 or because _! dw9dl+ outcrops are conceal$ "u sup]ficial deposits4 ,z we approa* ! s\?-we/]n c5tre ( eruption ar\nd ,cor/on ,hill a new volcanic gr\p beg9s & soon increases 9 bulk4 ,a di/+ui%+ feature ( ! plateaux is f\nd 9 ! diff]5ce betwe5 ! lavas t 7 fir/ erupt$ & ^? :i* foll[$ !m4 ,! e>li] eruptions1 z above rem>k$1 7 g5]ally basic1 sometimes highly s4 ,?us at ,ar?ur ,seat ! ?ick s]ies ( lavas :i* =m ! ea/]n "p ( ! hill h at _! base sev]al %eets ( column> basalt1 ov] :i* come ! &esites t make up ! ma9 mass ( ! erupt$ mat]ial4 ,9 ! ,calton ,hill ! same sequ5ce may be obs]v$4 ,und]nea? ! &esites ( ,campbelt[n comes a well-m>k$ & p]si/5t b& ( oliv9e-dol]ite4 ,/ill m basic are "s portions ( ! e>lie/ lavas ( ! ,g>leton plateau :]e1 z already /at$1 rocks pres5t !mselves compos$ ma9ly ( oliv9e & augite4 ,x is wor?y ( notice t :]e ! lavas ( a plateau dim9i% greatly 9 ?ickness or become imp]si/5t1 ! l[e/ basic gr\p may cont9ue :ile ! ov]ly+ &esites disappe>4 ,?is feature has be5 already m5tion$ z well se5 9 ! ,midlo?ian plateau4 ,! ?ick gr\p ( &esites 9 ,ar?ur ,seat & ,calton ,hill is n to be f\nd 9 ! next volcanic em95ce1 ,craiglockh>t ,hill2 b ! basalts ) _! und]ly+ tuffs cont9ue4 ,9 ! s\?-we/]n tract f ,h>p] ,rig to ,h>e ,law 9 ,lan>k%ire1 ! ?9 lava-b&1 :i* c be f\nd only at int]vals along ! l9e ( outcrop ( ! volcanic s]ies = ab\t n9e miles1 is a dol]ite (t5 highly slaggy 9 /ructure4 ,aga91 at ,corrie 9 ,arran1 ! lavas :i* appe> ^u ! %ore1 app>5tly at ! extreme we/]n limits ( ! ,clyde plateau1 are basic rocks4 ,b :e!r or n ! l[e/ & m basic lavas appe> 9 any plateau1 ! ma9 mass ( ! molt5 mat]ial erupt$ has usually consi/$ ( v>ieties ( &esite4 ,! successive dis*>ges ( ^! int]m$iate lavas h fl[$ out 9 %eets1 "s ( :i* mu/ h be5 little m ?an heaps ( cl9k]s & scori1 :ile o!rs 7 m fluid & roll$ along ) a ropy or slaggy surface4 ,occasionally ! upp] "p ( an &esite %[s ! r$d5$ & decompos$ "* t sugge/s "s degree ( dis9tegration or wea!r+ be=e ! next lava-/ream buri$ x4 ,! int]vals betwe5 successive outfl[s ( ^! lavas are n1 z a rule1 def9$ by any m>k$ breaks or by ! int]calation ( o!r mat]ial4 ,9 g5]al1 ! plateaux are ma9ly built up ( successive %eets ( lava :i* h foll[$ ea* o!r at int]vals suffici5tly %ort to prev5t ! accumulation ( mu* detritus betwe5 !m4 ,?us ! ,campsie ,hills h ! upp] #fjj feet ( _! mass =m$ ( admirably-well-def9$ %eets ( &esite1 sep>at$ sometimes by ?9 p>t+s ( tuff1 b m usually only by ! slaggy vesicul> surfaces betwe5 successive fl[s4 ,:]e ! lavas consi/$ ( tra*ytes !y 7 apt to assume m irregul> =ms4 ,( ?is t5d5cy ! rocks ( ! ,g>leton ,hills supply an excell5t example4 ,z already /at$1 _! lumpy "* gives to ^! hills an outl9e :i* (f]s /rong contra/ to ! ord9>y symmetrical t]rac$ cont\rs ( ! &esitic plateaux4 ,illu/ration3 ,fig4 #aae4--,section ( ,craiglockh>t ,hill1 ,ed9burgh4 #a4 ,r$ s&/ones & clays2 #b4 ,gre5 /ratifi$ tuffs2 #c4 ,column> basalt2 #d4 ,d>k %ales1 iron/ones & s&/ones1 ) plants4 ,illu/ration3 ,fig4 #aaf4--,section ( ! bottom ( ! ,midlo?ian ,plateau1 ,l9nh\se ,wat] above ,mid-,cald] ,oilworks4 #a4 ,%ales & cem5t-/ones2 #b4 ,s&/ones2 #c4 ,highly vesicul> lava2 #d4 ,tuffs & s&/one b&s4 f1 ,fault4 ,al?\gh tuffs play1 on ! :ole1 a comp>atively unimportant "p among ! con/itu5ts ( ! plateaux1 !y atta9 9 a few localities an exceptionally great developm5t1 & ev5 :]e !y occur only z ?9 p>t+s betwe5 ! successive lava-fl[s1 !y are always int]e/+ memorials ( ! volcanic activity ( a di/rict4 ,9 _m portions ( ! plateaux1 ! l[e/ memb]s ( ! volcanic s]ies are tuffs & agglom]ates1 %[+ t ! eruptions (t5 began ) ! dis*>ge ( fragm5t>y mat]ials4 ,?us 9 ! ,midlo?ian plateau at ,ar?ur ,seat1 ?\gh ! l[e/ int]b$d$ volcanic %eet is a dol]ite1 x is imm$iately foll[$ by a s]ies ( b$d$ tuffs1 be=e ! ma9 mass ( ! lavas ( t hill make _! appe>ance4 ,at ,craiglockh>t ,hill1 ?ree miles di/ant 7,fig4 #aae71 ?is l[e/ lava is abs5t1 & a gr\p ( tuffs ab\t #cjj feet ?ick re/s imm$iately on ! r$ ,c>bonif]\s s&/ones & %ales1 & is ov]la9 by %eets ( column> basalt4 ,! scoriace\s bottom ( ! latt] rock may "h & !re be se5 to h cut out p>ts ( ! tuff z x roll$ ov] ! /ill unconsolidat$ mat]ial4 ,9 ! same di/rict1 a few miles fur!r to ! s\?-we/1 "s int]e/+ sections ( ! ,midlo?ian plateau are laid b>e 9 ! /reams :i* desc5d f ! we/]n slopes ( ! ,p5tl& ,hills4 ,i may cite1 9 p>ticul>1 ^? expos$ 9 ! c\rse ( ! ,l9nh\se ,wat]4 ,at ! railway viaduct ne> ! foot ( ,cor/on ,hill1 a good section is display$ ( ! ,cem5t-/one gr\p--?ick r$di%1 purpli%1 & gre5i%-blue m>ly %ales or clays1 ) ?9 ribs & b&s ( cem5t-/one & grey compact cyprid-lime/one1 z well z l5ticul> seams & ?ick] b$s ( grey %aly s&/one1 sometimes full ( ripple-m>ks & sun-cracks4 ,^! /rata1 :i* exactly reproduce ! typical li?ological *>act]s ( ! ,cem5t-/one gr\p ( ,/irl+%ire 7,ballagan ,b$s71 ,ayr%ire & ,b]wick%ire1 are surm\nt$ by a gr\p ( r$di%1 yell[ & br[n s&/ones1 sometimes pebbly & conta9+ a b& ( conglom]ate4 ,among ! /ones 9 ?is b&1 pieces ( ! radiol>ian *]ts ( ! ,l[] ,silurian s]ies ( ! ,s\!rn ,upl&s are conspicu\s1 likewise pieces ( &esite :i* may h come f ! neighb\r+ ,p5tl& ,hills4 ,above ^! /rata lie ! lavas ( ,cor/on ,hill4 ,^! are highly vesicul> 9 "s p>ts1 & include b&s ( tuff :i* are well expos$ fur!r d[n ! same /ream1 imm$iately above ! railway bridge ne> ! ,mid-,cald] oilworks 7,fig4 #aaf74 ,!re ! lavas1 ?\gh mu* decompos$1 %[ a highly vesicul> /ructure ) a rugg$ upp] surface1 9 ! holl[s & ov] ! prom95ces ( :i* f9e flaky & s&y tuffs h be5 deposit$1 :ile ?9 seams ( vesicul> lava are int]calat$ among ^! /rata4 ,illu/ration3 ,fig4 #aag4--,section ( ! top ( ! ,midlo?ian ,plateau 9 ! ,murie/on ,wat]4 ,! upp] "p ( ! same plateau1 z expos$ 9 ! c\rse ( ! ,murie/on ,wat]1 conta9s evid5ce t ! la/ eruptions consi/$ ( tuff4 ,! highly slaggy lava 7#a 9 ,fig4 #aag7 is !re surm\nt$ by a ?ick mass ( grey & gre5i%-:ite well-b$d$ granul> tuff 7#b7 includ+ occasional lumps ( ! basic lava1 & pass+ up into black %ale 7#c74 ,b t ! volcanic eruptions cont9u$ dur+ ! accumulation ( ! %ale is prov$ by ! int]calation ( ?9 p>t+s & ?ick] lay]s ( tuff 9 ! black s$im5t4 ,a %ort way high] up ! ,burdieh\se ,lime/one comes 94 ,! great lava-esc>pm5t ( ! ,kilpatrick ,hills re/s on a cont9u\s b& ( tuff :i* is ?icke/ t[>ds ! we/1 ne> ! gr\p ( v5ts above ,dumb>ton1 :ile x ?9s away ea/w>d & disappe>s 9 ,/ra?blane1 ! lavas !n =m+ ! base ( ! volcanic s]ies4 ,b p]haps ! mo/ rem>kable gr\p ( basal tuffs is t :i* und]lies ! lavas ( ! ,g>leton plateau1 to :i* fur!r ref]5ce w be imm$iately made4 ,ext5sive accumulations ( tuff =m 9 "o or two localities a l>ge proportion ( ! ?ickness ( ! :ole volcanic s]ies ( a plateau4 ,?us 9 ! nor?-ea/]n "p ( ,ayr%ire1 betwe5 ,eagle%am & ! valley ( ! ,irv9e1 ! lavas die out = a space & give place to tuffs4 ,dur+ ! dis*>ge ( ! fragm5t>y mat]ials ov] t gr\nd no lava seems to h fl[$ out = a long p]iod4 ,ord9>y s$im5t1 h[ev]1 m+l$ ) ! volcanic detritus1 & !re 7 ev5 pauses 9 ! eruptions :5 lay]s ( iron/one 7 deposit$1 toge!r ) ?9 impure lime/one t inclos$ %ells ( ,productus giganteus4#dcj ,footnote #dcj3 ,explanation ( ,%eet #bb ,geol4 ,surv4 ,scotl&1 p4 #ab4 ,9 "s ( ! plateaux1 p>ticul>ly )9 ! old] "p ( ! volcanic s]ies1 int]calations ( ord9>y s$im5t among ! tuffs & lavas %[ t eruptions occurr$ only occasionally1 & t dur+ ! long int]vals betwe5 !m ! deposition ( s& & mud w5t on z be=e4 ,?us ! l[] #djj feet ( ! ,campsie ,fells are built up ( slaggy &esites & ?ick b$s ( f9e-gra9$ /ratifi$ tuff1 ) b&s ( r$1 gre5 & grey clays & cem5t-/one & a zone ( :ite s&/one4 ,! ,calton ,hill at ,ed9burgh 7,fig4 #aah7 af=ds an excell5t illu/ration ( ! int]/ratification bo? ( tuffs & ord9>y s$im5ts among ! successive outfl[s ( lava4 ,9 ! total ?ickness ( ab\t #aajj feet ( volcanic mat]ial 9 ?is hill1 at lea/ eight int]vals 9 ! dis*>ge ( ! lavas are m>k$ by ! int]calation ( z _m b&s ( nodul> tuff1 toge!r ) seams ( %ale & s&/one m or less *>g$ ) volcanic detritus4 ,! highe/ lava is imm$iately cov]$ by ! :ite s&/ones & black %ales ( ! ,calcif]\s ,s&/one s]ies4 ,illu/ration3 ,fig4 #aah4--,section ( ,calton ,hill1 ,ed9burgh4 #a4 ,l[] ,c>bonif]\s s&/ones2 #b4 ,basic lava at ! bottom ( ! volcanic s]ies2 #c4 ,tuff (t5 int]/ratifi$ ) s&/ones & %ales2 #d4 ,%eets ( &esite-lava frequ5tly sep>at$ by lay]s ( tuff2 #e4 ,%ale pass+ into tuff2 #f4 ,:ite s&/one & black c>bonace\s %ales ov]ly+ ! volcanic s]ies4 ,! tuffs1 z might be expect$1 are co>se/ 9 texture & ?icke/ 9 mass :]e !y approa* mo/ ne>ly to "s ( ! v5ts ( eruption1 &1 on ! o!r h&1 become f9] z !y rec$e f ^!4 ,z a rule1 !y are di/9ctly /ratifi$1 & consi/ ( lay]s v>y+ 9 ! size ( _! compon5t lapilli4 ,"h & !re1 ne> ! c5tres ( dis*>ge1 ! b$d+ becomes h>dly traceable or disappe>s1 & ! fragm5t>y mat]ials take ! =m ( agglom]ate4 ,9 ! admirable range ( coa/-cliffs :i* ext5d f ,nor? ,b]wick to ,dunb>1 we le>n t above ! r$ s&/ones at ! base ( ! ,c>bonif]\s sy/em1 a ?ick pile ( volcanic a%es 0 accumulat$ by num]\s dis*>ges f v5ts 9 ! imm$iate neighb\rhood4 ,"s ( ! explosions 7 s vigor\s t blocks ( diff]5t lavas1 sometimes a y>d or m 9 l5g?1 7 ?r[n out & heap$ up 9 irregul> m\nds & holl[s4 ,o!rs dis*>g$ exce$+ly f9e du/1 & betwe5 ^! two extremes e degree ( co>s5ess ( mat]ial may be recogniz$4 ,z an illu/ration ( ! rem>kable alt]nation ( co>se & f9e mat]ials1 accord+ to ! v>y+ int5sity ( ! volcanic p>oxysm1 ,fig4 #aai is "h introduc$4 ,x repres5ts a portion ( ! tuff-cliffs ea/ ( ,tantallon ,ca/le1 & %[s at ! bottom f9e well-/ratifi$ tuff1 ov] :i* a %[] ( l>ge blocks ( lava has fall54 ,f9e detritus is se5 to cov] ! deposits ( ?is %[]1 & successive dis*>ges ( l>ge /ones may be notic$ high] up on m or less well-def9$ horizons4 ,! space ov] :i* ?is pyrocla/ic mat]ial c n[ be trac$1 l>ge ?\gh x is1 does n repres5t ! :ole ( ! orig9al area includ$ )9 ! range ( ! dis*>ges ( a% & /ones1 = mu* has be5 remov$ by d5udation4 ,dur+ pauses ( v>i\s l5g? betwe5 ! eruptions1 waves & curr5ts wa%$ d[n ! heaps ( volcanic mat]ial & di/ribut$ ord9>y s$im5t ov] ! bottom ( ! wat]4 ,h5ce1 abundantly int]/ratifi$ 9 "s p>ts ( ! tuff1 seams ( s&/one1 blue & gre5 %ale1 cem5t-/one & lime/one occur4 ,"o ?ick b& ( lime/one may be trac$ f ne> ,tynn+ham ,h\se to ,:itt+hame1 a di/ance ( ab\t f\r miles2 ano!r pat* appe>s ne> ,rockville ,h\se2 & a ?ird at ,rhodes1 ne> ,nor? ,b]wick4 ,no fossils h be5 notic$ 9 ^! lime/ones4 ,! calc>e\s matt]1 toge!r sometimes ) silica1 appe>s to h be5 suppli$1 at lea/ 9 "p1 by spr+s1 :i* may h be5 connect$ ) ! volcanic ph5om5a ( ! di/rict4 ,! ,nor? ,b]wick lime/one1 9 p>ticul>1 has ! peculi> c>i\s wavy /ructure ) m9ute mamillat$ int]/ices s common among s9t]s4 ,x conta9s gra9s ( pyrites1 flakes ( :ite kaol91 :i* probably repres5t decay$ prisms or tufts ( natrolite1 & cavities l9$ ) dog-too? sp>4 ,"s portions give out a /rongly ftid od\r :5 fre%ly brok54 ,aft] ! tuffs ( ! ,g>leton plateau _h accumulat$ to a dep? ( p]haps #bjj feet or m1 lavas began to be p\r$ out4 ,fir/ came basic outfl[s 7oliv9e-basalts ) picrites7 & &esites 7porphyrites71 :i* =m a ?9 b cont9u\s %eet all ov] ! area4 ,^! 7 succe$$ by ! s]ies ( tra*ytes :i* di/+ui% ?is area4 ,al?\gh ! obs]v] rem>ks ! abs5ce !re ( ! usual t]rac$ arrangem5t1 yet f "s po9ts ( view1 p>ticul>ly f ! we/w>d1 a succession ( l[ esc>pm5ts & long] dip-slopes c be detect$ among ! tra*ytes ( ! ,g>leton ,hills1 :ile !re c be no d\bt t1 9 spite ( _! irregul> lumpy cont\rs1 ^! lavas lie z a great cake above ! l[] plat=m ( m basic fl[s 7,fig4 #aj74 ,!re is evid5ce t dur+ ! emission ( ! tra*ytes occasional eruptions ( &esite took place4 ,n ! lea/ /rik+ & int]e/+ feature ( ?is plateau is ! size & di/ribution ( its necks1 to :i* ref]5ce w be made 9 ! sequel4 ,! late/ eruption 9 ! ,g>leton area _h ceas$ & ! cones & lava %eets _h probably be5 buri$ "u s$im5t be=e ! comm5cem5t ( ! deposition ( ! ,hurlet or ?ick ,ma9 ,lime/one ( ! ,c>bonif]\s ,lime/one s]ies :i* lies imm$iately to ! we/ ( ! plateau4 ,! tuffs ( ! plateaux are seldom fossilif]\s1 probably = ! same reason t fossils are sc>ce 9 ! ,cem5t-/one gr\p :i* ! plateau volcanic rocks ov]spread & ) :i* !y are int]/ratifi$4 ,occasional /ems & o!r fragm5ts ( vegetation occur 9 ! plateau-tuffs1 z 9 ^? ( ,nor? ,b]wick1 :]e ,i h f\nd a decay$ conif]\s trunk ?ree feet 9 l5g?4 ,! gre5 tuff at ! base ( ! volcanic gr\p ( ,ar?ur ,seat conta9s abundant mac]at$ plant-rema9s1 toge!r ) scales ( ,rhizodus & o!r fi%es4 ,9 "s places ! plants are repres5t$ by trunks or roots1 :i* appe> to rema9 9 _! positions ( gr[?4 ,a rem>kable in/ance ( ?is nature occurs 9 "s b&s ( tuff 9 ! volcanic gr\p ( ! ea/ coa/ ( ! ,isle ( ,arran1 fir/ br\ght to notice by ,mr4 ,e4 ,wuns*1#dca & ( :i* ! plants h be5 s fully inve/igat$ by ,pr(essor ,williamson4#dcb ,footnote #dca3 ,trans4 ,geol4 ,soc4 ,glasg[1 vol4 ii4 7#ahfg7 p4 #ig4 ,footnote #dcb3 ,phil4 ,trans4 #ahga-ahhc4 ,illu/ration3 ,fig4 #aai4--;,cliff ( tuff & agglom]ate1 ea/ side ( ,oxroad ,bay1 a little ea/ f ,tantallon ,ca/le1 ,ea/ ,lo?ian4 ,plant-rema9s also occasionally occur 9 ! /ratifi$ lay]s int]calat$ among ! lavas & tuffs ( ! plateaux4 ,"s ( ! be/ examples ( _! occurr5ce are to be f\nd 9 ! %ales & tuffs int]/ratifi$ among ! enorm\s pile ( volcanic mat]ial ne> ,b[l+4 ,n only does abundant vegetable debris occur di/ribut$ ?r\gh ! detrital /rata 9 ! volcanic s]ies at t locality1 b x is ev5 aggregat$ into ?9 seams ( coal :i* h be5 exam9$ & describ$ by v>i\s obs]v]s4#dcc ,x may be rem>k$ t ! plant rema9s ?us f\nd int]calat$ 9 ! volcanic s]ies1 especially :5 !y h be5 entomb$ 9 tuff1 h (t5 _h _! int]nal /ructure admirably pres]v$1 ! organic tissues hav+ be5 delicately replac$ by calcite or o!r petrify+ m$ium4 ,! rem>kably p]fect /ructure ( "s ( ^! plants has be5 demon/rat$ by ,pr(essor ,williamson1 especially 9 ! case ( ! ,arran deposit j ref]r$ to4 ,mr4 ,john ,"y has also f\nd ! /ructure well pres]v$ among ! ,sigill>i & ,/igm>i t occur 9 ! /ratifi$ int]calations betwe5 ! lavas ne> ,b[l+4 ,footnote #dcc3 ,see 9 p>ticul> ,j4 ,"y1 ,trans4 ,geol4 ,soc4 ,glasg[1 vol4 iv4 7#ahgd7 p4 #abc4 ,illu/ration3 ,fig4 #abj4--,section across "p ( ! ,clyde ,plateau to ! we/ ( ,b[l+ 7r$uc$ f ,%eet #f ( ! ,horizontal ,sections ( ! ,geological ,survey ( ,scotl&74 #a4 ,ballagan ,b$s2 #b4 ,:ite s&/one2 #c4 ,tuffs1 #fjj feet ?ick1 ) a ?9 %eet ( &esite2 #d4 ,&esite %eets1 #ejj feet2 #e4 ,/ratifi$ tuffs ) ?9 coals1 %ales1 fireclays & plant-rema9s1 #ejj or #fjj feet2 #f #f4 ,a s]ies ( &esite-lavas1 ab\t #aejj feet ?ick1 enclos+ a ?9 coal-seam at 992 #g4 ,/ratifi$ tuffs1 #bjj feet2 #h4 ,%ales ) plants & coaly seams1 #aej feet2 #i4 ,base ( ano!r &esite s]ies1 :i* mu/ be "s hundr$s ( feet ?ick2 #aj & #aa4 ,necks ( agglom]ate4 ,upp] ,limits & ,orig9al ,areas & ,slopes ( ! ,plateaux4--,:]e ! highe/ memb]s ( ! volcanic s]ies c be se5 pass+ con=mably "u ! ov]ly+ ,c>bonif]\s /rata !y are frequ5tly f\nd to be ma9ly compos$ ( f9e tuffs1 ! la/ feeble ef=ts ( ! plateau-volcanoes hav+ consi/$ 9 ! dis*>ge ( %[]s ( a%es4 ,^! mat]ials 7 m+l$ ) a gradually increas+ proportion ( ord9>y me*anical s$im5t1 :i* f9ally ov]spread & buri$ ! volcanic tracts ( gr\nd1 z ^! sl[ly sank 9 ! g5]al subsid5ce ( ! region4 ,! *>act]i/ic corals1 cr9oids & %ells ( ! ,c>bonif]\s ,lime/one beg9 to appe> 9 ^! a%y s$im5ts4 ,!re is ?us an ins5sible passage f volcanic detritus into fossilif]\s %ales & lime/ones4 ,examples ( ?is gradation may be se5 9 _m natural sections along ! flanks ( ! ,ayr%ire plateau f above ,kilbirnie to ,/ra?avon4 ,x is /ill possible to fix 9 "s qu>t]s ! limits beyond :i* nei!r ! lavas nor ! tuffs ext5d$1 & ?us p>tially to map out ! orig9al areas ( ! plateaux4 ,= example1 9 c]ta9 directions ! ,c>bonif]\s =mations c be foll[$ cont9u\sly d[nw>d bel[ ! ,ma9 ,lime/one1 )\t ! int]v5tion ( any volcanic mat]ial1 or ) only a slight int]mixture ( f9e volcanic lapilli1 su* z might h be5 c>ri$ by a /rong w9d f "s neighb\r+ active v5ts4 ,by ?is k9d ( evid5ce & by ! prov$ ?9n+-out ( ! mat]ials ( ! plateau1 we c demon/rate t 9 ! nor? ( ,ayr%ire ! s\!rn limits ( ! great volcanic bank did n pass beyond a l9e drawn f ne> ,ardrossan to ,gal/on4 ,we c %[1 too1 t ! lavas ( ! ,campsie ,fells end$ (f ab\t a mile beyond ,/irl+ be=e !y rea*$ ! l9e ( ! ,o*il heights1 & t ! c\les :i* fl[$ f ! ,solway v5ts did n q jo9 ) ^? f ! ,b]wick%ire volcanoes4 ,illu/ration3 ,fig4 #aba4--;,diagram illu/rat+ ! ?9n+ away s\?w>ds ( ! lavas ( ! ,clyde ,plateau betwe5 ,l>gs & ,ardrossan4 ,l5g? ab\t #aj miles4 #a4 ,upp] ,old ,r$ ,s&/one2 #b4 ,s&/ones1 %ales1 etc41 ) ,ballagan ,b$s2 #c4 ,tuffs2 #d4 ,&esite lavas2 #e4 ,c>bonif]\s ,lime/one s]ies4 ,moreov]1 evid5ce en\gh rema9s to enable u to =m a tol]ably cle> conception ( ! orig9al av]age slopes ( ! surface ( "s ( ! plateaux4 ,?us 9 ! great esc>pm5t above ,l>gs & ! high gr\nd ea/w>d to ,kilbirnie ! volcanic s]ies1 z already /at$1 mu/ be at lea/ #aejj feet ?ick4 ,?is ?ick mass ( lavas & tuffs ?9s away s\?w>ds & probably disappe>s a %ort di/ance s\? f ,ardrossan 9 a space ( ab\t t5 miles 7,fig4 #aba74 ,! orig9al s\?w>d slope ( ! plateau w\ld ?us appe> to h be5 ab\t #a 9 #ce4 ,aga91 ! nor?w>d slope ( ! same plateau may be e/imat$ f obs]vations 9 ! ,campsie ,fells4 ,we h se5 t above ,kilsy? ! total dep? ( ! volcanic %eets is ab\t #ajjj feet1 :ile to ! we/w>d x is mu* ?ick]4 ,f ! top ( ! ,meikle ,b9 7#ahgj feet7 above ,kilsy? nor?-ea/w>ds to ,causewayhead1 :]e ! :ole volcanic s]ies has di$ out1 is a di/ance ( #ab miles1 s t ! slope ( ! surface ( erupt$ mat]ials on ?is side 0 ab\t #a 9 #fc 7,fig4 #abb74 ,judg+ f ! sections expos$ along ! faces ( ! esc>pm5ts1 we may inf] t ! volcanic %eets _h a tol]ably uni=m surface :i* slop$ g5tly away f ! *ief v5ts1 b ) local inequalities accord+ to ! irregul>ities ( ! lava-/reams t 7 heap$ up r\nd ! v5ts & fl[$ outw>d 9 diff]5t directions & to v>i\s di/ances f !m4 ,at ! beg9n+1 ^! flat volcanic domes 7 c]ta9ly subaque\s4 ,:ile !y 7 be+ =m$1 cont9u\s subsid5ce appe>s to h be5 9 progress4 ,b ! great ?ickness ( ! volcanic accumulations1 z 9 ! ,kilpatrick & ,r5frew%ire areas1 & ! paucity ( ord9>y s$im5t>y /rata among !m1 make x n improbable t at lea/ _! high] p>ts rose above ! wat]4 ,:]e ?is 0 ! case !re may h be5 consid]able degradation ( ! lava-banks be=e ^! 7 r$uc$ or 7 by subsid5ce subm]g$ b5ea? ! wat]-level4 ,evid5ce ( ?is wa/e is probably to be recogniz$ 9 ! b&s ( conglom]ate1 occasionally ( consid]able ?ickness1 :i*1 p>ticul>ly 9 "s p>ts ( ,ayr%ire1 int]v5e betwe5 ! top ( ! volcanic gr\p & ! ,hurlet ,lime/one4 ,z ,i %all h occasion to po9t out fur!r on1 !re seems to be "s am\nt ( evid5ce 9 fav\r ( ! view t a consid]able int]val ( "t elaps$ betwe5 ! close ( ! plateau-eruptions & ! date ( t widespread depression :i* l$ to ! deposition ( ! ,hurlet ,lime/one ov] ! :ole ( ,c5tral ,scotl&4 ,if su* an int]val did occur x w\ld include a prolong$ abrasion ( any project+ p>ts ( ! plateaux1 & ! production & deposition ( volcanic conglom]ate4 ,illu/ration3 ,fig4 #abb4--;,diagram illu/rat+ ! ?9n+ away ea/w>ds ( ! lavas ( ! ,clyde ,plateau 9 ! ,f9try ,hills4 ,l5g? ab\t #ab miles4 #a4 ,upp] ,old ,r$ ,s&/one2 #b4 ,:ite s&/one1 blue %ales & cem5t-/ones 7,ballagan ,b$s72 #c4 ,&esite %eet1 ab\t #ajj feet ?ick2 #d4 ,tuffs 7#bej feet71 ) an includ$ b& ( a%y s&/one conta9+ plant-rema9s2 #e4 ,&esite lavas2 #f4 ,c>bonif]\s ,lime/one s]ies1 :i* to ! ea/ lies imm$iately on ! ,upp] ,old ,r$ ,s&/one4 #b4 ,,v5ts ,we h n[ to consid] ! ext]nal =ms1 int]nal cont5ts & di/ribution ( ! v5ts f :i* ! mat]ial ( ! plateaux 0 dis*>g$4 ,9 ! ,c>bonif]\s sy/em ^! int]e/+ relics ( =m] volcanoes are f> m di/9ctly def9$ & bett] pres]v$ ?an 9 old] geological =mations4 ,moreov]1 9 ,scotl&1 !y are laid b>e to great] advantage1 bo? inl& & along ! sea-coa/1 & may inde$ be /udi$ !re z typical illu/rations ( ?is k9d ( geological /ructure4 ,illu/ration3 ,fig4 #abc4--,view ( ! two necks ,dumgoyn & ,dumfoyn1 ,/irl+%ire1 tak5 f ! s\?4 ,^! two necks =m a conspicu\s feature 9 front ( & bel[ ! lava plateau1 a portion ( :i* is %[n on ! "r h&4 ,! gr\nd-plan ( ! same necks is %[n 9 ,fig4 #abd4 ,illu/ration3 ,fig4 #abd4--;,gr\nd-plan ( ,plateau-v5ts ne> ,/ra?blane1 ,/irl+%ire1 on ! scale ( #f in*es to a mile4 ,9 ext]nal =m ! necks connect$ bo? ) ! plateaux & ! puys g5]ally rise f ! surr\nd+ gr\nd z isolat$1 r\nd$1 conical or dome-%ap$ prom95ces1 _! details ( cont\r dep5d+ ma9ly ^u ! mat]ials ( :i* !y consi/4 ,:5 ^! mat]ials are ( agglom]ate1 tuff or o!r readily dis9tegrat$ rock1 ! surface ( ! domes is g5]ally smoo? & grass-cov]$4 ,:]e1 on ! o!r h&1 !y consi/ :olly or 9 "p ( dol]ite1 basalt1 diabase1 &esite1 tra*yte or o!r cry/all9e rock1 !y pres5t m irregul> rocky outl9es4 ,illu/rations ( "s ( ^? v>y+ =ms are giv5 9 ,figs4 #bc & #abc4 ,9 r>e in/ances ! v5t is m>k$ at ! surface n by a hill b by a holl[1 z 9 ! great neck 9 ! he>t ( ! ,campsie ,fells 7,fig4 #abh74 ,illu/ration3 ,fig4 #abe4--;,gr\nd-plans ( d\ble & triple necks 9 ! ,plateau s]ies1 on ! scale ( #f in*es to a mile4 ,a4 ,b>wood ,hill & ,rav5scraig1 ea/ ( ,dumb>ton1 d\ble v5t4 ,b4 ,! ,knock ,hill1 ,l>gs1 ,ayr%ire1 d\ble v5t 7see ,fig4 #bc74 ,c4 ,dumb[ie & ,dumbuck1 ea/ ( ,dumb>ton1 triple v5t4 ,z reg>ds _! gr\nd-plan1 :i* af=ds a cross-section ( ! orig9al volcanic funnel1 ! plateau-v5ts pres5t consid]able v>iety4 ,! simple/ cases are ^? 9 :i* ! =m is approximately circul> or some:at elliptical4 ,"h ! outl9e corresponds to ! cross-section ( a s+le & normal orifice4 ,"s examples ( ?is simple type are giv5 9 ,fig4 #abd1 :i* repres5ts a gr\p ( v5ts on ! edge ( ! ,clyde plateau ne> ,/ra?blane4 ,! two l>g] necks "h %[n are ! same :i* appe> 9 ! view 9 ,fig4 #abc4dcd ,:]e two v5ts h be5 successively op5$ close to ea* o!r1 or :]e ! same v5t has %ift$ its position1 ! gr\nd-plan may be greatly modifi$4 ,9 "s in/ances ! d\ble funnel c be di/9ctly trac$4 ,?us 9 ! conspicu\s ,knock ,hill above ,l>gs 9 ,ayr%ire 7,fig4 #abe1 ,b7 !re are two conjo9$ necks1 & su* appe>s to be also ! /ructure %[n by ! gr\nd-plan ( ! neck ( ,b>wood ,hill & ,rav5's ,craig1 ea/ ( ,dumb>ton 7,fig4 #abe1 ,a74#dce ,b m complex =ms occur :i* po9t to a /ill l>g] numb] ( coalesc+ necks4 ,a gr\p ( hills to ! ea/ ( ,dumb>ton gives ! gr\nd-plan %[n 9 ,c1 ,fig4 #abe1 :]e traces may be detect$ ( ?ree sep>ate v5ts4 ,/ill m irregul> are long n>r[ dyke-l masses ( tuff or agglom]ate :i* h probably ris5 along l9es ( fissure 7,fig4 #bb1 ,no4 #a74 ,! mo/ /rik+ example ( ^!1 h[ev]1 occur 9 association ) ! puys & w be describ$ 9 lat] pages4 ,footnote #dcd3 ,! illu/rations 9 ,figs4 #abd & #abe are tak5 f ! field-maps ( ! ,geological ,survey on ! scale ( #f in*es to a mile4 ,! gr\nd repres5t$ 9 ,fig4 #abd 0 mapp$ by ,mr4 ,r4 ,l4 ,jack4 ,footnote #dce3 ,^! gr\nd-plans are likewise tak5 f ! field-maps ( ! ,geological ,survey4 ,a & ,c 7 mapp$ by ,mr4 ,jack1 ,b by myself4 ,! %ad$ p>ts are intrusive &esites & dol]ites2 ! d>k b>s 9 ,a & ,c be+ dol]ite dykes ( mu* lat] date ?an ! necks4 ,! dott$ portions m>k tuff & agglom]ate4 ,connect$ ) _! gr\nd-plan is ! relative size ( ! plateau-v5ts4 ,on ! :ole !y are l>g] ?an ^? ( ! puy s]ies4 ,! simple circul> or elliptical type pres5ts ! smalle/ necks1 "s ( !m n exce$+ #ajj feet 9 diamet]4 ,! m complex =ms are g5]ally also ( l>g] dim5sions4 ,by mu* ! l>ge/ v5t or connect$ gr\p ( v5ts is t :i* lies among ! upl&s ( ,mi/y ,law 9 ! he>t ( ! ,r5frew%ire "p ( ! ,clyde plateau1 :]e a connect$ mass ( tuff & agglom]ate n[ occupies a space ( ab\t #d miles 9 l5g? by #b miles 9 bread? 7,fig4 #abi74 ,x has n be5 f\nd possible1 h[ev]1 to trace ! b\nd>ies ( ! sep>ate v5ts ( ?is tract1 nor to di/+ui% ! mat]ial ( ! necks f t :i* surr\nds !m4 ,ano!r l>ge mass :i* f its %ape may be conjectur$ to repres5t m ?an "o v5t is ! great tract nor? ( ,melrose1 :i* measures #hhjj by #dbjj feet4#dcf ,footnote #dcf3 ,! foll[+ measurem5ts are1 l ^? 9 ! text1 tak5 f ! field-maps ( ! ,geological ,survey4 ,c>ewood ,rig1 on ! bord]s ( ,roxburgh%ire & ,dumfries%ire1 #gjjj #bdjj feet2 ! great v5t 9 ! middle ( ! ,campsie ,fells1 #ebjj #bfjj2 ,black ,law1 betwe5 ,b$rule & ,j$burgh1 #cdjj #afjj2 ,dumgoyn1 ,/ra?blane1 #bcjj #acjj2 ,rub]s ,law1 #aejj #ajjj2 ,m9to ,hill 7s\?71 #bcjj #afej2 ,m9to ,hill 7nor?71 #aejj #aajj2 ,d\ghnot ,hill1 ,kilpatrick range1 #ajjj #gjj2 f\r ( ! smalle/ agglom]ate v5ts along ! nor!rn esc>pm5t ( ! ,clyde plateau betwe5 ,/ra?blane & ,f9try1 #ejj #dej1 #dej #djj1 #bej #ajj1 #bjj #bjj2 ,pike ,law1 ,arkleton1 ,t>ras ,wat]1 #ejj #ejj2 ,h>wood1 ,/on$ge1 #e miles ,s4,e4 f ,hawick1 #ejj #cjj2 ,arkleton ,burn1 ,dumfries%ire1 #djj #ajj2 ,dalbate ,burn1 #bej #abj4 ,! di/ribution ( ! necks c be/ be und]/ood f ! maps ( ! ,geological ,survey1 :]e !y h be5 c>efully indicat$4 ,z might h be5 expect$1 !y are n f\nd outside ! orig9al limits )9 :i* x may be reasonably inf]r$ t ! lavas & tuffs 7 erupt$4 ,!y occur mo/ abundantly & atta9 _! l>ge/ size 9 & ar\nd ! di/ricts :]e ! plateaux are mo/ ext5sively develop$4 ,no d\bt a l>ge numb] ( !m are conceal$ "u ^! plateaux4 ,a few appe> at ! surface among ! lavas & tuffs1 b by f> ! l>ge/ numb] n[ visible h be5 reveal$ by d5udation1 ! esc>pm5ts hav+ be5 cut back s z to lay b>e ! und]ly+ rocks ?r\gh :i* ! necks rise4 ,?us1 along ! flanks ( ! great esc>pm5t t ext5ds f ne> ,/irl+ by ,f9try & ,/ra?blane to ,dumb>ton1 m ?an two doz5 ( agglom]ate necks may be c\nt$ 9 a di/ance ( ab\t sixte5 miles1 :ile if ! necks ( lava-=m mat]ial are includ$1 ! numb] ( v5ts mu/ be ab\t fifty4 ,n[h]e 9 ,scotl& d su* necks =m a m conspicu\s feature 9 ! sc5]y z well z ! geology ?an !y d betwe5 ,f9try & ,/ra?blane1 :]e1 /&+ out z bold isolat$ hills 9 front ( ! esc>pm5ts1 _! conical & r\nd$ outl9es pres5t a /rik+ contra/ to ! t]rac$ esc>pm5ts beh9d !m4 ,i w\ld especially ref] aga9 to ! two rem>kable cones ( ,dumfoyn & ,dumgoyn above ,/ra?blane 7,figs4 #abc1 #abd1 #abg74 ,along ! we/ front ( ! hills betwe5 ,g\rock & ,ardrossan sev5te5 agglom]ate-v5ts occur 9 a di/ance ( sixte5 miles4 ,9 ,roxburgh%ire a gr\p ( l>ge agglom]ate-necks is dott$ ov] ! ,silurian c\ntry ar\nd ,melrose & ,selkirk#dcg 7see ,fig4 #acj74 ,footnote #dcg3 ,9 ?is region & f>!r s\?w>d1 besides ! plateau-eruptions1 a lat] gr\p ( puys is to be se51 & x is difficult to discrim9ate betwe5 ! necks belong+ to ! two gr\ps4 ,^? :i* lie to ! ea/ are probably connect$ ) ! plateaux1 ^? to ! we/ ) ! puys4 ,! latt] are ref]r$ to on p4 #dge4 ,illu/ration3 ,fig4 #abf4--;,gr\nd-plan ( tuff-neck1 %ore ea/ ( ,dunb>4 ,! surr\nd+ rocks are s&/ones1 :i* are mu* h>d5$ r\nd ! v5t 9 ! zone m>k$ by ! %ort div]g5t l9es4 ,! arr[s m>k ! direction ( dip4 ,see ,geology ( ,ea/ ,lo?ian1 ,mem4 ,geol4 ,survey1 p4 #dd4 ,f ! evid5ce ( ^! necks x is pla9 t ! volcanic mat]ials ( ! plateaux mu/ 9 ea* case h be5 suppli$ n f great c5tral orifices1 b f abundant v5ts /&+ sometimes s+ly1 ) int]v5+ spaces ( sev]al miles1 (t5 9 gr\ps ( f\r or five )9 a s+le squ>e mile4 ,9 ! int]ior ( ! c\ntry1 x is seldom possible to exam9e ! actual junction ( necks ) ! rocks ?r\gh :i* !y rise1 ! b\nd>y-l9e be+ usually obscur$ by debris or h]bage4 ,on ! coa/1 ! v5ts ( ! plateaux h n be5 b>$ by ! sea s fully z 9 ! case ( ! mu* y\ng] s]ies ( ! ea/ ( ,fife to be describ$ 9 lat] pages4 ,b :]e ! ,ea/ ,lo?ian plateau t\*es ! %ore1 ! waves h laid b>e a numb] ( its m9or v5ts1 :i* h ?us be5 dissect$ 9 gr\nd-plan on ! bea*4 ,z an illu/ration ( ^! v5ts an example is giv5 9 ,fig4 #abf1 f ! %ore ea/ ( ,dunb>4 ,"h ! s&/ones1 :i* are incl9$ 9 an ea/]ly direction at #bj to #be1 are pi]c$ by an irregul> mass ( tuff4 ,x is obs]vable t 9 ?is in/ance long tongue-l projections ( ! s&/ones protrude into ! neck2 m frequ5tly ! mat]ial ( a neck s5ds ve9s or dykes into ! surr\nd+ walls4 ,a volcanic *imney w\ld seem to h be5 (t5 mu* %att]$ & fissur$ 9 ! c\rse ( ! volcanic explosions1 & ! fragm5t>y mat]ial has fall5 or be5 inject$ into ! r5ts ?us caus$4 ,z a rule1 ! rocks imm$iately ar\nd ! ,c>bonif]\s necks are m or less indurat$1 z 9 ?is in/ance f ! ,dunb> %ore4 ,! mat]ials :i* h fill$ up ! v5ts connect$ ) ! plateau-eruptions g5]ally consi/ ( 7a7 agglom]ates or tuffs1 b occasionally ( 7b7 "s k9d ( lava1 & frequ5tly 7c7 ( bo? ^! k9ds ( rock comb9$4 7a7 ,necks ( ,agglom]ate or ,tuff4--,^! mat]ials v>y greatly 9 ! nature & relative proportions ( _! con/itu5ts4 ,usually ! includ$ blocks & lapilli are pieces ( &esite1 diabase1 basalt or o!r lava1 l ! rocks ( ! plateaux4 ,b ) ^! occur also fragm5ts probably deta*$ f ! sides ( ! funnels ?r\gh :i* ! explosions took place1 su* z pieces ( greywacke1 s&/one1 lime/one & %ale4 ,consid]able induration may be obs]v$ among ^! non-volcanic +r$i5ts4 ,9 "s cases1 z 9 t ( ! occurr5ce ( pieces ( granite ref]r$ to on p4 #chb1 ! /ones h probably be5 br\ght up f "s consid]able dep?4 ,9 o!rs x is easy to see t ! blocks h slipp$ d[n f "s high] gr\p ( /rata n[ remov$ f ! surr\nd+ surface by d5udation4 ,"s /rik+ illu/rations ( ?is feature w be cit$ f necks ( ! puy-s]ies 9 ! s\? ( ,roxburgh%ire 7p4 #dgf74 ,! lava blocks 9 ! tuffs & agglom]ates are usually r\nd$ or subangul>4 ,pe>-%ap$ blocks1 or flatt5$ discs1 or holl[ sph]ical balls are h>dly ev] to be obs]v$1 ?\gh ,i h notic$ a few examples 9 ! tuffs ( ,dunb>4 ,a frequ5t "* ( ! blocks is t ( r\ghly r\nd$1 highly amygdaloidal pieces ( lava1 ! cellul> /ructure be+ specially develop$ 9 ! int]ior1 & ! cells on ! outside be+ (t5 mu* drawn out r\nd ! circumf]5ce ( ! mass4 ,su* blocks 7 probably torn f ! cav]n\s1 p>tially consolidat$1 or at lea/ r visc\s1 top ( a lava column4 ,mo/ ( ! /ones1 h[ev]1 sugge/ t !y 7 produc$ by ! explosion ( already solidifi$ lava1 & 7 some:at r\nd$ by attrition 9 _! asc5t & desc5t4 ,! v5ts fill$ ) su* mat]ials mu/ h be5 ! sc5e ( prolong$ & int]mitt5t activity2 successive p>oxysms result+ 9 ! cle>+ out ( ! h>d5$ lava column 9 ! ?roat ( ! volcano1 & 9 ! rise ( fre% lava1 ) abundant ejection ( du/ & lapilli4 ,illu/ration3 ,fig4 #abg4--,section across ! v5ts ,dumgoyn & ,dumfoyn1 & ! edge ( ! ,clyde plateau above ,/ra?blane1 ,/irl+%ire4 #a4 ,upp] ,old ,r$ ,s&/one2 #b4 ,%ales1 cem5t-/ones & s&/ones 7,ballagan b$s72 #c4 ,:ite s&/one2 #d4 ,&esite lavas2 #e4 ,agglom]ate 7%[n by ! dott$ portions71 trav]s$ by intrusive diabase4 f1 ,fault4 ,d4 ,late dol]ite dyke4 ,necks =m$ entirely ( agglom]ate are abundant among ! v5ts connect$ ) ! plateaux4 ,z examples ( !m ,i may ref] to ! s]ies already m5tion$ z front+ ! esc>pm5t ( ! ,clyde plateau f ,f9try to ,l>gs4 ,ano!r int]e/+ gr\p rises ?r\gh ! ,silurian & ,old ,r$ ,s&/one rocks to ! we/ ( ! esc>pm5t ( ! ,b]wick%ire plateau1 t ne> ,melrose =m+ "o ( ! l>ge/ 9 ,scotl&4 ,illu/ration3 ,fig4 #abh4--,section ?r\gh ! l>ge v5t ( ! ,campsie ,hills4 #a4 ,&esite lavas2 #b4 ,agglom]ate & tuff2 #c4 ,tra*ytic & &esitic intrusive rocks4 ,illu/ration3 ,fig4 #abi4--;,diagrammatic section across ! c5tral v5t ( ! ,clyde plateau 9 ,r5frew%ire4 #a4 ,&esite lavas2 #b4 ,agglom]ates & f9e tuffs (t5 mu* alt]$2 #c4 ,dykes ( tra*ytic & &esitic rocks2 #d4 ,lat] dykes ( dol]ite & basalt4 ,illu/rations ( ! v>y+ /ructure ( ^! v5ts are giv5 9 ! accompany+ figures4 ,9 ,fig4 #abg1 a section is drawn ?r\gh ! two necks ,dumgoyn & ,dumfoyn1 :i* h already be5 %[n 9 outl9e & 9 gr\nd-plan4 ,! relation ( ^! two v5ts to ! neighb\r+ plateau to ! "r c "h be se54 ,fig4 #abh gives a section tak5 ?r\gh ! great v5t ( ! ,campsie ,hills1 ) ! m9or adjac5t necks ( ,dungoil1 ,b9 ,bairn1 & ! ,meikle ,b94 ,! diagram 9 ,fig4 #abi is meant to convey 9 a g5]al way :at appe>s to be ! /ructure ( ! c5tral v5t ( ! ,r5frew%ire plateaux1 to be aft]w>ds ref]r$ to4 ,b1 z already m5tion$1 ! limits ( ! v>i\s rocks are too mu* obscur$ to all[ an accurate del9eation to be giv5 ( _! areas & relations to ea* o!r4 ,! ,b]wick%ire plateau supplies abundant int]e/+ examples ( tuff necks :i* rise ?r\gh ! ,old ,r$ ,s&/one _m miles di/ant f ! edge ( ! lavas4 ,?is /ructure is %[n 9 ,fig4 #acj4 ,illu/ration3 ,fig4 #acj4--,section across ,s\!rn ,b]wick%ire to %[ ! relation ( ! volcanic plateau to ! v5ts ly+ s\? f x4 #a4 ,upp] ,silurian /rata2 #b4 ,upp] ,old ,r$ ,s&/one2 #c4 ,! volcanic plateau2 #d4 ,agglom]ate & tuff ( ! v5ts2 #e4 ,basalt & dol]ite2 #f4 ,l[] ,c>bonif]\s /rata4 ,indications may occasionally be obs]v$ ( an agglom]ate v5t hav+ be5 fir/ occupi$ by "o k9d ( mat]ial & !n1 aft] be+ 9 great measure cle>$ out by explosions1 hav+ be5 subsequ5tly fill$ up ) ano!r4 ,z an example ( ?is /ructure ,i may cite aga9 ! d\ble neck ( ! ,knock ,hill a little to ! nor? ( ,l>gs1 ( :i* ! outl9e is %[n 9 ,fig4 #bc1 & ! gr\nd-plan 9 ,fig4 #abe1 ,b4 ,?is hill rises f ! r$ s&/one slopes t front ! great ,ayr%ire plateau & =ms a conspicu\s cone ! top ( :i* is r m ?an #gjj feet above ! sea4 ,its summit comm&s a rem>kably ext5sive & int]e/+ panorama ( ! sc5]y ( ! ,clyde1 b to ! geologi/ p]haps ! mo/ /rik+ feature 9 ! l&scape is ! range ( t]rac$ hills beh9d1 m\nt+ up into ! great v5ts ( ! ,r5frew%ire upl&s4 ,on ^! declivities ! successive lava-/reams t h built up ! plateau c be se5 pil$ ov] ea* o!r = a ?ickness ( m ?an #ajjj feet1 & pres5t+ _! esc>pm5ts z p>allel l9es ( br[n crag ) gre5 slopes betwe54 ,! ,knock has _h its upp] "p artificially dress$1 = l9es ( tr5* h be5 cut out ( its rocks by "s e>ly race t conv]t$ ! summit ( ! hill into a /rongly intr5*$ camp4 ,f ! apex ( ! cone ! gr\nd falls rapidly we/w>d into a holl[1 beyond :i* rises a l[] r\nd$ ridge ( simil> mat]ials4 ,x is possible t ?is we/]n ridge may really =m "p ( ! ma9 hill1 b ! grass-cov]$ gr\nd does n af=d suffici5t exposures ( ! rocks to settle ?is po9t4 ,f ! cont\rs ( ! surface1 x may be inf]r$ t !re are two closely adjac5t v5ts1 & t ! we/]n & l[] em95ce is ! old] ( ! two4 ,?is hill or ridge consi/s p>tly ( a co>se agglom]ate1 & p>tly ( ve9s & irregul> protrusions ( a d>k1 compact1 slightly cellul> lava4 ,! /ones 9 ! fragm5tal rock are diff]5t oliv9e-basalts1 or o!r basic lavas1 & s&/ones4 ,! pa/e is r\gh1 loose & granul>4 ,! s&/one fragm5ts are mu* indurat$ & sometimes blea*$4 ,! ,knock itself is =m$ ma9ly ( a rem>kably co>se & /rik+ly volcanic agglom]ate4 ,r\nd ! outside1 & p>ticul>ly on ! s\?-ea/1 ! rock is f9] 9 texture1 compact1 & gravelly1 or l a mud/one1 ) few or no imb$d$ blocks1 dull-gre5 to r$ 9 col\r1 & break+ ) a clean fracture :i* %[s angul> lapilli ( v>i\s basalts or diabases4 ,at ! s\!rn end ( ! neck1 :]e ! surr\nd+ r$ s&/one c be se5 )9 a few feet ( ! tuff1 ! latt] is bright r$ 9 col\r1 & conta9s mu* debris ( r$ s&/one & m>l4 ,possibly ?is f9] tuff1 :i* is traceable z an irregul> b& r\nd ! outside ( ! neck1 may m>k an old] infill+ ( ! v5t ?an ! agglom]ate ( ! c5tre2 b !re is no %>p l9e to be drawn betwe5 ! two1 ?\gh a holl[ c sometimes be trac$ on ! surface :]e !y jo94 ,! agglom]ate ( ?is locality is "o ( ! mo/ *>act]i/ic among ! plateau-necks ( ! ,clyde region4 ,its blocks sometimes measure f two to ?ree feet 9 diamet]4 ,!y consi/ almo/ :olly ( a d>k cry/all9e porphyritic oliv9e-basalt4 ,^! blocks are subangul> 9 =m1 (t5 ) clean-fractur$ surfaces4 ,?\gh occasionally slightly cellul>1 !y are nev] slaggy s f> z ,i c\ld see1 nor are any true scori to be notic$ among !m4 ,! blocks sugge/ t !y 7 d]iv$ f ! disruption ( an already solidifi$ mass ( lava4 ,! agglom]ate is entirely )\t any trace ( /ratification4 ,?r\gh ?is tumultu\s accumulation ( volcanic debris "s irregul> ve9s ( oliv9e-basalt1 sometimes glassy 9 /ructure1 h be5 inject$1 & rea* ne>ly to ! summit ( ! hill4 ,?is intrusive mat]ial resembles g5]ally "s ( ! d>k intrusive masses 9 ! ,dumb>ton%ire necks4 ,l ^!1 x exhibits a t5d5cy to assume a m or less di/9ctly column> /ructure1 its columns hav+ ! same *>act]i/ic wavy sides & irregul> curvature4 ,! intrusive rocks 9 ! two em95ces ( ! ,knock may be p>allel$ among ! /ones 9 ! agglom]ate4 ,! neck on its nor?-ea/]n side rises /eeply f ! r$ s&/ones :i* x pi]ces1 b :i*1 al?\gh !y are mu* jo9t$ & brok51 are n s5sibly indurat$4 ,un=tunately ! actual junction ( ! igne\s & s$im5t>y rocks is conceal$ "u h]bage4 ,z a rule1 ! fragm5tal mat]ials ( ! plateau-necks are q un/ratifi$4 ,_! includ$ blocks1 di/ribut$ irregul>ly ?r\gh ! mass1 h evid5tly und]gone little or no assortm5t aft] !y fell back into ! v5ts4 ,occasionally1 h[ev]1 a m or less di/9ct b$d+ ( ! agglom]ate or tuff may be obs]v$1 ! lay]s hav+ a t5d5cy to dip inw>d into ! c5tre4 ,"o ( ! mo/ conspicu\s examples ( ?is /ructure is to be f\nd 9 ! hill ( ,dumbuck1 to ! ea/ ( ,dumb>ton4 ,?is neck1 :i* =ms s prom95t a feature 9 ! l&scape1 pres5ts a precipit\s face t[>ds ! s\?1 & all[s ! disposition ( its compon5t mat]ials to be !re se54 ,! agglom]ate consi/s ( a succession ( rudely /ratifi$ b$s ( co>s] & f9] detritus1 :i* on bo? sides are incl9$ t[>ds ! c5tre1 :]e a plug ( f9e-gra9$ oliv9e-basalt has ris5 & spread out into a column> %eet above 7,fig4 #aca74 ,9 g5]al =m ?is basalt resembles su* intrusions z t ( ,l>go ,law1 to be aft]w>ds describ$ 7,fig4 #bbf71 :]e :at may h be5 ! holl[ or bottom ( ! crat] is fill$ ) basalt4 ,illu/ration3 ,fig4 #aca4--,section ( s\? end ( ,dumbuck ,hill4 ,ea/ ( ,dumb>ton4 ,illu/ration3 ,fig4 #acb4--,section across ! ,ea/ ,lo?ian plateau to %[ ! relative position ( "o ( ! necks4 #a4 ,l[] ,c>bonif]\s s&/ones & %ales2 #b4 ,r$ & gre5 tuffs ) a seam ( lime/one 7l72 #c4 ,b& ( basic %eets at ! base ( ! lavas2 #d4 ,tra*ytes2 #e4 ,phonolite neck4 7b7 ,necks ( ,&esite1 ,tra*yte1 ,dol]ite1 ,diabase1 or o!r massive ,rock4--,:5 ! v5ts h be5 fill$ by ! uprise ( "s molt5 rock1 x is g5]ally1 z we h se51 ( a m acid "* ?an ! ord9>y lavas ( ! plateaux4 ,frequ5tly x consi/s ( "s v>iety ( tra*yte or &esite1 commonly ( a dull yell[ or grey t9t & waxy lu/re4 ,good examples may be se5 among ! rem>kable gr\p ( necks on ei!r side ( ! valley nor? ( ! village ( ,/ra?blane & 9 ^? above ,b[l+4 ,! ?ree great necks 9 ,ea/ ,lo?ian1 already allud$ to1--,trapra9 ,law 7,figs4 #acb1 #acc71 ,nor? ,b]wick ,law 7,fig4 #aji71 & ! ,bass ,rock 7,fig4 #aaj7--;are masses ( phonolite & tra*yte1 obvi\sly relat$ to ! tra*ytes ( ! adjac5t plateau4 ,a small] b v p]fect in/ance ( a v5t simil>ly fill$ is to be se5 9 ! same neighb\rhood on ! %ore to ! ea/ ( ,nor? ,b]wick ,law4#dch ,footnote #dch3 ,see ,geology ( ,ea/ ,lo?ian1 ,geological ,survey ,memoir1 p4 #dj4 ,examples occur :]e ! funnels ( eruption h be5 f9ally seal$ up by ! rise ( m basic mat]ial1 & ?is has happ5$ ev5 9 a di/rict :]e mo/ ( ! lava-=m necks consi/ ( tra*yte or "s o!r int]m$iate lava4 ,?us1 9 ! ,campsie ,fells1 sev]al su* bosses appe>1 ( :i* ! mo/ conspicu\s =ms ! hill ( ,dungoil 7#acif feet1 ,fig4 #abh74 ,fur!r we/1 among ! ,kilpatrick ,hills1 bosses ( ?is k9d are /ill m num]\s4 ,! gr\p ( bosses ne> ,ancrum & ,j$burgh is ma9ly made up ( oliv9e-dol]ites & oliv9e-basalts 7,fig4 #acj74 ,?is m basic composition ( itself sugge/s t ^! bosses may be connect$ r ) ! puy- ?an ) ! plateau-eruptions4 7c7 ,necks ( ,composite ,"*4--,9 n a few examples1 ! v5ts h be5 fill$ ) agglom]ate :i* has be5 pi]c$ by a plug or ve9s ( lava-=m mat]ial4 ,_m illu/rations ( ?is composite /ructure may be obs]v$ along ! we/ front ( ! great esc>pm5ts f ,f9try to ,ardrossan 7see ,figs4 #abd1 #abe1 #abg & #abh74 ,9 t region ! intrud$ rock is (t5 a dull yell[i% or grey tra*ytic or &esitic mat]ial4 ,oliv9e-basalt is ! *ief rock intrud$ 9 ! v5ts 9 ! ,dumb>ton di/rict4 ,among ! ,roxburgh%ire v5ts1 :]e ! inject$ mat]ial is commonly oliv9e-basalt or dol]ite1 x occasionally happ5s1 z 9 ,rub]s ,law1 t ! uprise ( ! lava has almo/ entirely cle>$ out or conceal$ ! agglom]ate1 & 9 "s ( ! bosses1 :]e no agglom]ate is n[ to be se51 ! basalt may h tak5 its place 7,fig4 #acj74 ,! l>ge/ & mo/ int]e/+ v5ts connect$ ) ?is type ( ,c>bonif]\s volcano1 are ^? :i* occur )9 ! limits ( ! plateaux1 :]e !y are /ill surr\nd$ ) lavas & tuffs t probably came out ( !m4 ,( ^! by f> ! mo/ ext5sive & rem>kable lies among ! high moorl&s ( ,r5frew%ire betwe5 ,l>gs & ,lo*w9no*1 :]e ! gr\nd rises to m ?an #agjj feet above ! sea 7see ,fig4 #abi74 ,?is area1 z already rem>k$1 is un=tunately mu* obscur$ ) drift & peat1 s t ! limits ( its rocks _c be s satisfactorily trac$ z might be desir$4 ,i ?9k x probable t sev]al successive v5ts h "h be5 op5$ close to ea* o!r1 b _! erupt$ a%es probably _c be di/+ui%$4 ,ov] a space measur+ ab\t f\r miles 9 l5g? by two & a half 9 bread?1 ! rocks expos$ at ! surface are f9e tuffs1 breccias & co>se agglom]ates1 l>gely made up ( tra*ytic1 &esitic or felsitic mat]ial1 & pi]c$ by innum]able protrusions ( v>i\s &esitic1 tra*ytic or felsitic rocks 9 bosses & ve9s1 z well z also by dykes ( a m basic k9d1 su* z dol]ites & basalts4 ,"s ( ! tuffs pres5t a curi\sly indurat$ condition2 & !y are frequ5tly mu* decay$ at ! surface4#dci ,ano!r l>ge mass ( tuff & agglom]ate lies a little to ! s\?-we/ ( ! ma9 area4 ,footnote #dci3 ,?is tract ( gr\nd 0 mapp$ = ! ,geological ,survey by ,mr4 ,r4 ,l4 ,jack1 n[ 9 *>ge ( ! ,geological ,survey ( ,que5sl&4 ,see ,%eet #ca1 ,geological ,survey ( ,scotl&4 ,aft] ! explosions ceas$1 by :i* ! v5ts 7 op5$ & ! cones ( debris 7 heap$ up1 heat$ vap\rs w\ld 9 _m cases1 z 9 mod]n volcanoes1 cont9ue = a long :ile to asc5d 9 ! funnels4 ,! exp]im5ts ( ,daubre on ! effects ( wat] & vap\r ^u silicates "u great pressure & at a l[ r$ heat1 h %[n h[ great may be ! li?ological *anges !reby sup]9duc$4 ,x is improbable t :]e a mass ( tuff & lava1 ly+ deep )9 a volcanic v5t1 0 ?or\ghly p]meat$ ) con/antly asc5d+ heat$ vap\rs1 x %\ld escape "s k9d ( *ange4 ,i am incl9$ to attribute to ?is cause ! frequ5t conv]sion ( ! s&/ones r\nd ! walls ( ! v5ts into qu>tzite4 ,! mo/ rem>kable example ( metamorphism )9 a v5t :i* ,i h obs]v$ among ! plateaux1 occurs 9 ! he>t ( ! ,campsie ,fells1 :]e1 in/ead ( =m+ a prom95ce1 ! neck is m>k$ by a great holl[1 measur+ ab\t a mile 9 l5g? & half a mile 9 bread? 7,fig4 #abh74ddj ,x is occupi$ ma9ly by a co>se tumultu\s agglom]ate1 l t ( o!r necks 9 ! same di/rict1 b ) a matrix r m indurat$1 & assum+ 9 c]ta9 p>ts a cry/all9e texture1 s z to be at fir/ sight h>dly di/+ui%able f "s ( ! surr\nd+ &esites4 ,ev5 9 ?is alt]$ condition1 h[ev]1 its includ$ fragm5ts may be recogniz$1 p>ticul>ly blocks ( s&/one :i* h be5 h>d5$ into qu>tzite4 ,num]\s small ve9s ( p9k & yell[ tra*yte trav]se ! agglom]ate1 & are f\nd also cutt+ ! b$d$ &esites t encircle x4 ,footnote #ddj3 ,see ,explanation to ,%eet #ca1 ,geological ,survey ( ,scotl&1 p>4 #ba 7#ahgh74 ,illu/ration3 ,fig4 #acc4--,view ( ,trapra9 ,law f ! s\?1 a phonolite neck ( ! ,g>leton ,plateau4 #c4 ,,dykes ,,& ,,sills ,intrusive masses bo? 9 ! =m ( dykes & ( sills are ( frequ5t occurr5ce 9 connection ) ! ,c>bonif]\s volcanic plateaux4 ,f ! v>iety ( _! compon5t mat]ials x may be inf]r$ t ^! rocks belong to diff]5t ages ( intrusion4 ,dykes4--,! great majority ( ! ,dykes consi/ ( tra*yte or ( &esite1 resembl+ 9 li?ological *>act]s ! mat]ial ( ! necks & d\btless connect$ ) its uprise4 ,!re occur also dykes ( diabase1 basalt or dol]ite4 ,"s ( ! latt]1 especially ^? :i* run = _m miles1 cutt+ e rock 9 ! di/ricts 9 :i* !y occur1 & cross+ l>ge faults )\t deviation1 are c]ta9ly long po/]ior to ! plateau volcanic p]iod4 ,:e!r ! small incon/ant dykes ( m basic composition1 f\nd 9 ! same di/ricts ) ! tra*ytes1 are to be look$ ^u z "p ( ! volcanic ph5om5a ( ! plateaux1 is a "q to :i* at pres5t no def9ite answ] c be giv54 ,i %all h occasion to %[ t 9 ! next volcanic p]iod ! lavas t fl[$ f ! puys are m basic ?an mo/ ( ^? ( ! plateaux1 & t !y are associat$ ) m basic dykes & sills4 ,9 ,roxburgh%ire1 :]e x is s difficult to di/+ui% betwe5 ! d5ud$ v5ts ( ! two p]iods1 ! d>k heavy oliv9e-basalts & dol]ites ( ! bosses may possibly belong r to ! lat] ?an to ! e>li] volcanic episode4 ,& if t be _! true age1 ! dykes ( simil> mat]ial may be connect$ ) !m4 ,at ! same "t x mu/ be rememb]$ t ! e>lie/ eruptions ( ! plateaux 7 m>k$ly basic1 t _m v5ts 9 ! plateaux are pi]c$ by basic intrusions1 & t basic dykes may h be5 associat$ ) ! uprise ( ! same magma4 ,! dykes occur 9 consid]able numb]s & 9 two di/9ct positions1 ?\gh ^! may be closely relat$ to ea* o!r3 #a/1 among ! rocks outside & b5ea? ! plateau-lavas1 or cutt+ ^! lavas2 & #bnd1 9 & ar\nd ! v5ts4 #a4 ,among ! rocks :i* em]ge f "u ! ,c>bonif]\s volcanic plateaux1 dykes are sometimes to be obs]v$ 9 consid]able numb]s4 ,!y may be comp>$ to ! f> m ext5sive s]ies connect$ ) ! ,t]ti>y basalt-plateaux1 l :i* !y may h _h a close relation to ! actual build+ up ( ! successive %eets ( &esite1 tra*yte & basalt t 7 erupt$ at ! surface4 ,!y are p>ticul>ly well develop$ 9 ! ,clyde plateau1 :]e by ext5sive d5udation !y h be5 admirably expos$4 ,i w\ld especially ref] to ^? t trav]se ! tract ( r$ s&/ones :i* und]lie ! volcanic s]ies along ! flanks ( ! great esc>pm5ts f ,f9try to ,/ra?blane & ,dumb>ton1 & betwe5 ,g\rock & ,ardrossan4 ,^! dykes h be5 dissect$ by ! sea along bo? sides ( ! e/u>y ( ! ,clyde & 9 ! isl&s ( ,cumbrae4 ,9 ^! isl&s & 9 ,bute !y h rec5tly be5 mapp$ 9 great detail = ! ,geological ,survey by my colleague1 ,mr4 ,w4 ,gunn1 :o has suppli$ me ) notes ( 8 obs]vations on ! subject1 f :i* ! foll[+ summ>y is compil$4 ,!re are at lea/ f\r di/9ct gr\ps ( intrusive rocks 9 ! ,great] ,cumbrae4 ,! olde/ ( ^! is tra*ytic 9 "*1 & occurs bo? z dykes & %eets1 :i* run g5]ally 9 ! same ,e4,n4,e4 direction4 ,! rock is usually p9ki% 9 col\r1 sometimes grey or purpli%4 ,a specim5 f ! dyke ( ! ,hawk's ,ne/1 nor? ( ,f>l& ,po9t1 analyz$ by ,mr4 ,teall1 0 f\nd to conta9 #aa p] c5t ( alkalies1 pr9cipally pota%1 :ile ! p]c5tages ( lime & iron 7 v l[4 ,sometimes ^! rocks are f9e 9 gra9 ) only a few porphyritic or?oclase cry/als1 ?\gh num]\s small cry/als ( ?is m9]al are f\nd ) ! aid ( ! microscope4 ,^! r$ tra*yte dykes are almo/ conf9$ to ! ,upp] ,old ,r$ ,s&/one1 r>ely ent]+ ! ov]ly+ :ite ,calcif]\s ,s&/ones1 & nev] invad+ ! plateau-lavas4 ,!y are !re=e probably ( e>ly ,c>bonif]\s age4 ,! next gr\p foll[s ! same g5]al direction1 b cle>ly trav]ses ! tra*ytes1 & mu/ !re=e be ( lat] date4 ,! dykes ( ?is gr\p are ! mo/ num]\s ( ! :ole1 ! great] "p ( ! isl& be+ int]sect$ by !m4 ,9 ! nor?-ea/ corn] ab\t #dj ( !m may be c\nt$ 9 half a mile ( coa/-l9e1 "s be+ ( l>ge size4 ,all ( !m :i* c be cle>ly made out are porphyritic oliv9e-basalts ( ! type ( ! ,lion's ,haun* at ,ar?ur's ,seat4 ,!y are g5]ally grey 9 col\r & f9] at ! edges ?an 9 ! c5tre1 :i* is (t5 co>sely porphyritic & amygdaloidal4 ,oliv9e seems always *>act]i/ic1 b has (t5 be5 replac$ by hmatite or calcite4 ,9 ,bute a good _m dykes h be5 mapp$ to ! nor? ( ,kil*attan ,bay resembl+ ?is basalt s]ies ( ,cumbrae1 & runn+ 9 ! same direction4 ,b !y appe> to be all porphyritic &esites4 ,! second gr\p ( dykes1 ?\gh x cuts ! fir/ & is ?us prov$ to be lat] 9 date1 is nev]!less conf9$ )9 ! same /ratigraphical limits4 ,x may ?us belong ne>ly to ! same p]iod ( intrusion4 ,! dykes ( ! ?ird gr\p are dol]ites )\t oliv9e1 & foll[ on ! :ole an ea/ & we/ direction4 ,!y cut bo? ( ! two =ego+ sets ( dykes1 & likewise ! lavas ( ! plateau4 ,!y mu/ ?us belong to a f> lat] p]iod ( intrusion4 ,!y may be connect$ ) o!r dykes & sills on ! ma9l&1 :i* trav]se ! ,coal-measures1 & w\ld ?us be n old] ?an late ,c>bonif]\s or ,p]mian "t4 ,! f\r? gr\p ( dykes int]sects all ! o!rs1 & is probably ( ,t]ti>y age4 ,! preval5t direction ( ^! dykes 9 ! ,cumbraes is ,n4,n4,w4 ,! ,t]ti>y dykes are m fully describ$ 9 ,*apt]s xxxiv4 & xxxv4 ,! great gr\p ( tuffs :i* und]lies ! lavas ( ! ,ea/ ,lo?ian plateau is trav]s$ by num]\s dykes & sills1 ( :i* _m good examples may be se5 9 ! coa/-cliffs ( ,nor? ,b]wick4 ,among ^! rocks are beautiful oliv9e-basalts ) s+ul>ly fre% oliv9e1 z on ! %ore at ,nor? ,b]wick4 ,"s ( !m are /ill m basic1 z 9 ! case ( a limburgite intrusion at ! ,g9 ,head1 ,tantallon ,ca/le4 ,illu/ration3 ,fig4 #acd4--,ve9s & dykes trav]s+ ! agglom]ate & tuff ( ! great ,r5frew%ire v5t4 #b4 ,9 ! necks1 dykes are sometimes abundant1 & !y may be obs]v$ occasionally to trav]se ! surr\nd+ lavas4 ,!y consi/ ( simil> mat]ials to ^? f\nd outside ! plateaux4 ,"s ( ! l>g] necks are int]sect$ by a network ( dykes & ve9s4 ,! great v5t or gr\p ( v5ts among ! upl&s ( ,r5frew%ire1 already describ$ 7,fig4 #abi71 furni%es "s admirable examples ( ?is *>act]i/ic volcanic feature4 ,an illu/ration f t locality =ms ! subject ( ,fig4 #acd4 ,! agglom]ate :i* fills ! l>ge holl[ among ! ,campsie ,hills may be quot$ z ano!r illu/ration 7,fig4 #abh74 ,fur!r in/ances w be f\nd 9 "s ( ! sections giv5 9 prec$+ pages 7see ,figs4 #abd1 #abe1 #abg74 ,! g5]al aspect ( a dyke 9 ! volcanic s]ies is %[n 9 ,fig4 #ace4 ,illu/ration3 ,fig4 #ace4--,! ,yell[ ,man1 a dyke 9 volcanic tuff & conglom]ate on ! %ore a little ea/ ( ,nor? ,b]wick4 ,! ,sills associat$ ) ! plateau-type ( ,c>bonif]\s volcanic action =m a less prom95t feature ?an !y d among ! e>li] ,palozoic =mations or 9 ! puy-type :i* succe$$ !m4 ,!y consi/ 9 g5]al ( %ort l5ticul> %eets ( &esite or tra*yte1 l ! necks & dykes 9 proximity to :i* !y commonly appe>4 ,! be/ area = ! /udy ( !m is ! gr\nd :i* /ret*es out f ! base ( ! great esc>pm5ts ( ! ,campsie1 ,kilpatrick & ,ayr%ire ,hills 7,fig4 #acf71 :]e1 among ! agglom]ate-v5ts & abundant dykes1 intrusive %eets h likewise be5 inject$ betwe5 ! b$d+-planes ( ! r$ s&/ones4 ,b ^! %eets are ( comp>atively trifl+ dim5sions4 ,v few ( !m rea* a mile 9 l5g?1 ! great majority fall+ f> %ort ( t size4 ,9 ! ,cumbraes & 9 ,bute1 ,mr4 ,gunn has obs]v$ t ! tra*ytic1 oliv9e-basalt & dol]ite dykes are apt to pass into intrusive %eets4 ,t ! sills1 z well z ! dykes & bosses ( ! same mat]ial1 are n ( old] date ?an ! lavas ( ! plateaux is prov$ by ! mann] 9 :i* !y pi]ce ^! lavas1 especially t[>ds ! bottom ( ! s]ies4 ,! g5]al abs5ce ( basic sills1 :5 we consid] h[ ?ick a mass ( ^! rocks has sometimes be5 p\r$ out 9 ! plateaux1 is n a little rem>kable4 ,only 9 ! bas9 ( ! ,fir? ( ,=? d we enc\nt] ?ick basic sills ne> ! plateaux1 su*1 = in/ance1 z ,salisbury ,crags at ,ed9burgh4 ,b x is d\btful :e!r !y ought n r to be class$ ) ! sills ( ! puys1 to be aft]w>ds describ$4 ,illu/ration3 ,fig4 #acf4--,tra*ytic sills1 ,knockvadie1 ,kilpatrick ,hills4 #a4 ,upp] ,old ,r$ ,s&/one2 #b4 ,ballagan ,b$s2 #c4 ,tuffs2 #d4 ,lavas ( ! ,plateau2 #e4 ,agglom]ate ( necks2 #f4 ,tra*yte sills2 #g4 ,dol]ite dyke 78 ,t]ti>y74 #d4 ,close ( ! ,plateau-eruptions ,! relative geological date :5 ! eruptions ( ea* plateau ceas$ c =tunately be det]m9$ ) mu* m precision ?an ! "t ( _! beg9n+4 ,! ,hurlet ,lime/one1 s well kn[n z ! l[e/ ?ick calc>e\s seam 9 ! ,c>bonif]\s ,lime/one s]ies1 ( :i* x is g5]ally tak5 z ! base1 c be id5tifi$ ov] ! :ole ( ,c5tral ,scotl&1 & ?us =ms an excell5t /ratigraphical horizon1 f :i* ! upw>d t]m9ation ( ! volcanic %eets und]nea? x c be measur$4 ,:5 ! volcanic episode ( ! plateau-eruptions came to an end1 su* banks or cones z rose above ! level ( ! %all[ sea :i* !n ov]spread ,c5tral ,scotl& 7 br\ght b5ea? ! wat]1 z ,i h already rem>k$1 ei!r by prolong$ d5udation or m probably 9 l>ge "p by ! cont9u$ subsid5ce ( ! region4 ,! d[nw>d movem5t may possibly = a "t h be5 accel]at$1 especially 9 "s di/ricts4 ,?us ! ,hurlet ,lime/one1 ?\gh usually n m ?an five or six feet ?ick1 increases locally to a mu* great] ?ickness4 ,at ,pet]sfield1 ne> ,ba?gate1 = example1 x is betwe5 #gj & #hj feet 9 dep?1 :ile at ,bei?1 9 ,nor? ,ayr%ire1 x increases to #ajj feet 7,fig4 #acg71 :i* is ! ?icke/ mass ( ,c>bonif]\s ,lime/one kn[n to exi/ 9 ,scotl&4 ,at bo? ( ^! localities ! lime/one lies ^u a s]ies ( volcanic rocks1 & we may p]haps inf] t ! subsid5ce advanc$ !re some:at m rapidly or to a great] ext5t1 s z to =m holl[s 9 :i* ! lime/one c\ld ga!r to an abnormal dep?4 ,! wat] w\ld appe> to h become = a "t tol]ably free f me*anical s$im5t4 ,! lime/one is h5ce comp>atively pure1 & is ext5sively qu>ri$ all ov] ! c\ntry = indu/rial purposes4 ,x is a cr9oidal rock1 ab\nd+ 9 _m species ( corals1 bra*iopods1 lamellibran*s1 & ga/]opods1 ) trilobites1 cephalopods1 & fi%es4 ,illu/ration3 ,fig4 #acg4--,section across ! edge ( ! ,clyde plateau1 s\?-ea/ ( ,bei?4 #a4 ,plateau-lavas2 #b4 ,tuffs & volcanic conglom]ates2 #c4 ,hurlet ,lime/one2 #d4 ,coal-be>+ /rata above ! lime/one2 #e4 ,dol]ite dyke4 ,a v>iable ?ickness ( /rata int]v5es betwe5 ! top ( ! volcanic s]ies & ! ,ma9 ,lime/one4 ,sometimes ^! deposits consi/ 9 l>ge measure ( a mixture ( ord9>y s&y & muddy mat]ial ) ! wa%$-d[n tuff ( ! cones1 & probably ) volcanic du/ & lapilli ?r[n out by ! late/ eruptions4 ,?us along ! flank ( ! hills f ,b>rhead to ,/ra?avon1 yell[ & gre5 a%y s&/ones1 grits & conglom]ates are succe$$ by ord9>y s&/ones1 black %ales & iron/ones1 :ile "h & !re true volcanic tuff & conglom]ate make _! appe>ance4#dda ,fur!r we/1 9 ! ,kilbirnie di/rict1 ! lime/one lies directly on ! tuffs t re/ ^u ! &esites 7,figs4 #acg1 #ach74 ,footnote #dda3 ,explanation ( ,%eet #bb1 ,geol4 ,surv4 ,scotl&1 p4 #ab4 ,illu/ration3 ,fig4 #ach4--,section across ! upp] "p ( ! ,clyde plateau at ,kilbirnie1 ,ayr%ire4 #a #a4 ,plateau-lavas2 #b #b4 ,tuffs2 #c #c4 ,hurlet ,lime/one2 #d4 ,black-b& ,iron/one4 f f4 ,faults4 ,b p]haps ! mo/ /rik+ contra/ betwe5 adjac5t localities 9 reg>d to ! di/ance betwe5 ! lime/one & ! top ( ! volcanic s]ies is to be obs]v$ along ! s\!rn front ( ! ,campsie ,fells4 ,9 spite ( ! abundant faults :i* h !re s brok5 up ! regul> sequ5ce ( ! rocks1 we c see t at ,banton & ,burnhead ! lime/one lies almo/ imm$iately on ! volcanic s]ies 7,fig4 #aci74 ,b a little to ! we/w>d1 s&/ones1 conglom]ates1 %ales & ?9 lime/ones beg9 to int]v5e betwe5 ! volcanic s]ies & ! ,hurlet ,lime/one & swell out s rapidly t on ,craigmaddie ,muir & ,s\? ,hill ( ,campsie1 only "s five miles (f1 !y mu/ =m a total ?ickness ( n less ?an f #fjj to #hjj feet ( ord9>y non-volcanic deposits1 *iefly ?ick pebbly s&/ones 7,fig4 #adj74 ,su* local v>iations n improbably s]ve to indicate holl[s on ! flanks ( ! plateaux t 7 fill$ up ) detritus be=e ! depression & cle>+ ( ! wat] t l$ to ! deposition ( ! ,hurlet ,lime/one4 ,illu/ration3 ,fig4 #aci4--,section across ! upp] surface ( ! ,clyde volcanic plateau1 ,burnhead1 nor?-we/ ( ,kilsy?4 #a4 ,lavas ( ! plateau2 #b4 ,tuffs2 #c4 ,hurlet ,lime/one2 #d4 ,hosie's ,lime/one2 f1 ,fault4 ,illu/ration3 ,fig4 #adj4--,section across ! upp] surface ( ! ,clyde volcanic plateau at ,campsie4 #a4 ,%ales1 s&/ones1 cem5t-/ones1 etc4 7,ballagan ,b$s72 #b4 ,lavas ( ! plateau2 #c4 ,?ick :ite s&/one & conglom]ate2 #d4 ,hurlet ,lime/one2 #e4 ,hosie's ,lime/one2 f4 ,fault4 ,illu/ration3 ,fig4 #ada4--,section across we/]n edge ( ! ,g>leton plateau4 #a4 ,tra*yte lavas ( ! plateau2 #b4 ,calcif]\s ,s&/ones2 #c4 ,hurlet ,lime/one4 ,i h already rem>k$ t ! eruptions ( ! plateau p]iod la/$ long] 9 ! we/]n ?an 9 ! ea/]n p>ts ( ! region4 ,9 ! ,g>leton di/rict1 :]e ! peculi> visc\s tra*ytic lavas probably gave rise to a m unev5 surface or m prom95t cones ?an 0 usual among ! &esitic plateaux1 ! eruptions ceas$ "s "t be=e ! deposition ( ! ,hurlet ,lime/one4 ,z ! area sank1 ! successive zones ( ! ,calcif]\s ,s&/ones crept ov] ! flanks ( ! tra*ytes1 until at la/ !y _h completely buri$ ^! rocks be=e ! lime/one spread ov] ! area 7,fig4 #ada74 ,9 consequ5ce1 probably1 ( ! unev5 surface ( ?is plateau1 !re is "h a /rong ov]lap ( ! high] "p ( ! ,calcif]\s ,s&/ones4 ,on ! we/ side ( ! volcanic area !re c h>dly be m ?an "s #bjj feet ( /rata betwe5 ! top ( ! tra*ytic s]ies & ! lime/one1 :ile on ! s\? side !re mu/ be greatly m ?an t ?ickness4 ,?is /ructure probably indicates t ! ,g>leton volcanoes became ext9ct aft] hav+ pil$ up a mass ( tuffs & lavas to su* a height t its summits 7 n subm]g$ until ! area _h subsid$ #hjj or #ajjj feet 9 ! wat]s1 ov] ! floor ( :i* ! ,calcif]\s ,s&/ones 7 laid d[n4 ,h5ce1 9 spite ( ! proximity ( ! lavas to ! lime/one1 !re may h be5 a va/ int]val ( "t betwe5 _! respective epo*s1 z has be5 already sugge/$ ) reg>d to o!r plateaux4 ,?is subject w be aga9 ref]r$ to 9 discuss+ ! relative *ronology ( ! plateaux & puys4 ,9 ! ,b]wick%ire & ,solway di/ricts1 ! ext9ction ( ! plateau-v5ts appe>s to h tak5 place at a /ill e>li] "p ( ! ,c>bonif]\s p]iod1 = !re ! &esites1 :ile !y re/ on ! ,upp] ,old ,r$ ,s&/one1 are cov]$ ) at lea/ ! high] gr\p ( ! ,calcif]\s ,s&/ones 7,fig4 #adb74 ,! equival5t ( ! ,hurlet ,lime/one ( ,c5tral ,scotl& mu/ lie _m hundr$ feet above !m4 ,! subm]g5ce ( ! plateaux1 & _! entombm5t "u ! ?ick ,c>bonif]\s ,lime/one s]ies1 did n m>k ! close ( volcanic activity 9 ,c5tral ,scotl& dur+ ,c>bonif]\s "t4 ,! plateau-type ( eruption ceas$ & 0 n repeat$1 b a new type arose1 to :i* ,i w\ld n[ call ! read]'s att5tion4 ,illu/ration3 ,fig4 #adb4--,section across ! ,solway plateau f ,birr5sw>k to ,kirtlebridge4 #a4 ,upp] ,silurian /rata2 #b4 ,upp] ,old ,r$ ,s&/one2 #c4 ,plateau-lavas2 #d4 ,calcif]\s ,s&/ones & ,c>bonif]\s ,lime/one s]ies2 #e4 ,trias4 ,,*apt] ,,xxvi ,,! ,,c>bonif]\s ,,puys ,,( ,,scotl& i4 ,g5]al ,"* & ,di/ribution ( ! ,puys2 ii4 ,nature ( ! ,mat]ials ,erupt$--,lavas ,eject$ at ! ,surface--,intrusive ,%eets--,necks & ,dykes--,tuffs4 i4 ,,g5]al ,,"* ,,& ,,di/ribution ,aft] ! beg9n+ ( ! ,c>bonif]\s ,lime/one p]iod1 :5 eruptions ( ! plateau-type _h g5]ally ceas$1 volcanic activity %[$ itself ov] ! area ( ! ,briti% ,isles 9 a diff]5t guise bo? z reg>ds ! nature ( its products & ! mann] & scale ( _! dis*>ge4 ,in/ead ( widely ext5d$ lava-%eets & tuffs1 pil$ above ea* o!r sometimes to a ?ickness ( _m hundr$ feet1 & /ret*+ ov] hundr$s ( squ>e miles1 we h n[ to /udy ! records ( ano!r phase ( volcanism1 :]e scatt]$ gr\ps & r[s ( ,puys1 or small volcanic cones1 ?rew out 9 mo/ in/ances m]ely tuffs1 & ^! (t5 only 9 trifl+ quantity1 ?\gh "h & !re _! v5ts also p\r$ =? lavas & gradually pil$ up volcanic ridges :i*1 9 a few cases1 almo/ rivall$ "s ( ! plateaux4 ,! evid5ce = ^! less vigor\s manife/ations ( volcanic activity is furni%$ 7#a7 by lay]s ( tuff & %eets ( basaltic-lavas int]calat$ among ! /rata t 7 be+ deposit$ at ! "t ( ! eruptions1 7#b7 by necks ( tuff1 agglom]ate1 or diff]5t lava-=m rocks t m>k ! positions ( ! orifices ( dis*>ge1 & 7#c7 by sills1 bosses1 & dykes t indicate ! subt]ranean ef=ts ( ! volcanoes4 ,! comp>atively small ?ickness ( ! accumulations usually =m$ by ^! v5ts1 _! extremely local "*1 ! num]\s di/9ct horizons on :i* !y appe>1 & ! intimate way 9 :i* !y m+le & alt]nate ) ! ord9>y ,c>bonif]\s /rata are features :i* at once arre/ ! att5tion ( ! geologi/1 pres5t+1 z !y d1 s /rik+ a contra/ to ^? ( ! plateaux4 ,f ! cle> int]calation ( ^! volcanic mat]ials on successive plat=ms ( ! ,c>bonif]\s sy/em1 ! limits ( geological "t )9 :i* !y 7 erupt$ c be fix$ ) consid]able precision4 ,x may be said t1 9 a broad s5se1 !y co9cid$ ) ! p]iod ( ! ,c>bonif]\s ,lime/one1 & c]ta9ly x 0 dur+ ! deposition ( t =mation t ! eruptions :i* produc$ !m rea*$ _! greate/ vig\r & wide/ ext5t4 ,"h & !re 9 ,scotl& evid5ce may be f\nd t ! phase ( ! ,puys began dur+ t e>li] section ( ,c>bonif]\s "t record$ by ! ,calcif]\s ,s&/ones4 ,?is is m>k$ly ! case 9 ,liddesdale & ! neighb\r+ t]ritory4 ,ov] ! we/]n "p ( ,midlo?ian also1 ! ea/]n portion ( ,we/ ,lo?ian1 & ! s\!rn m>g9 ( ,fife1 abundant traces occur ( puy-eruptions dur+ ! deposition ( ! ,calcif]\s ,s&/ones4 ,else:]e 9 ,c5tral ,scotl& !re is no evid5ce ( ! v5ts hav+ be5 op5$ until aft] ! deposition ( ! ,hurlet ,lime/one1 :i*1 z we h se51 may conv5i5tly be tak5 z ! base ( ! ,scotti% ,c>bonif]\s ,lime/one s]ies4 ,! volcanoes rema9$ active 9 ,we/ ,lo?ian until ne> ! close ( ! "t repres5t$ by t s]ies2 b 9 ,ayr%ire !y cont9u$ 9 eruption until ! beg9n+ ( ! accumulation ( ! ,coal-measures4 ,^! we/]n examples ( ! puy-type are1 s f> z ,i am aw>e1 ! late/ kn[n 9 ,brita94 ,:e!r or n ! e>lie/ puy-eruptions began be=e ! late/ plateau-lavas & tuffs 7 accumulat$ is a "q t _c be readily answ]$4 ,x w be rememb]$ t 9 ! bas9 ( ! ,fir? ( ,=? a ?ickness ( m ?an #cjjj feet ( s$im5t>y /rata1 includ+ ! ,burdieh\se ,lime/one & num]\s oil-%ales z well z ?9 coal-seams1 lies above ! r$ & gre5 m>ls1 %ales1 s&/ones & cem5t-/ones ( ! ,calcif]\s ,s&/one s]ies4 ,?is rem>kable assemblage ( /rata is abs5t 9 ! we/]n p>ts ( ! c\ntry1 :]e ! top ( ! ,clyde volcanic plateau is almo/ imm$iately ov]la9 by ! ,hurlet ,lime/one4 ,if we 7 to judge ( ! sequ5ce ( ev5ts m]ely f ! /ratigraphy1 z express$ 9 su* sections z ,figs4 #acg1 #ach1 #aci & #adj1 we might naturally inf] t z no trace ( any break occurs at ! top ( ! ,clyde plateau1 ! tuffs %ad+ upw>d !re into ! lime/one s]ies1 no important pause 9 s$im5tation took place1 b t ! la/ volcanic eruptions 7 soon succe$$ by ! conditions t l$ to ! deposition ( ! widespread encr9ite-lime/ones4 ,if ?is inf]5ce 7 well f\nd$ x w\ld foll[ t :ile ! plateau-eruptions 9 ! we/ la/$ till ! "t ( ! ,hurlet ,lime/one1 ^? 9 ! ea/ ceas$ long be=e t "t & 7 succe$$ by ! puys ( ,fife & ! ,lo?ians4 ,!re w\ld ?us be an ov]lap ( ! two phases ( volcanic action4 ,i am incl9$ to believe1 h[ev]1 t 9 spite ( ! sup]position ( ! ,hurlet ,lime/one almo/ imm$iately ^u ! volcanic rocks ( ! ,clyde plateau1 & ! abs5ce ( any trace ( a break 9 ! process ( s$im5tation1 a long int]val nev]!less elaps$ betwe5 ! la/ eruptions & ! deposit ( t lime/one4 ,! ,campsie section 7,fig4 #adj7 %[s u h[ rapidly a ?ick mass ( /rata c come 9 along t horizon4 ,! volcanic ridges may h rema9$ p>tly unsubm]g$ = su* "t z 0 requir$ = ! subsid5ce ( ! ,=? bas9 & ! deposit ( ! ?ick ,calcif]\s ,s&/one s]ies !re1 & _! summits may only h f9ally sunk "u ! sea n long be=e ! ,hurlet ,lime/one grew z a cont9u\s floor ( calc>e\s mat]ial ov] ! :ole area ( c5tral ,scotl&4 ,9 ^! circum/ances1 ! puy-eruptions ( t bas9 w\ld be long subsequ5t to ! eruptions ( ! ,clyde plateau1 z !y c]ta9ly 7 to ^? ( ! plateaux ( ,midlo?ian & ! ,g>leton ,hills4 ,9 trac+ ! geographical di/ribution ( ! puy-eruptions we are fir/ impress$ ) ! =ce ( ! evid5ce = _! extremely local & re/rict$ "* 7,map ,,iv474 ,?us 9 ! area ( ! bas9 ( ! ,fir? ( ,=?1 :i* may be reg>d$ z ! typical region 9 ,brita9 = ! /udy ( ?is =m ( ,c>bonif]\s volcano1 traces ( !m are abundant to ! we/ ( ! l9e ( ! ,p5tl& ,hills4 ,to ! ea/ ( t l9e1 h[ev]1 n a ve/ige ( puy-eruptions1 save a few sills ( unc]ta9 relation%ip1 c be detect$1 ?\gh ! same s]ies ( /ratigraphical horizons is well develop$ on bo? sides ( ! ,lo?ian coal-field4 ,aga91 to ! we/w>d ( ! ,=? bas9 ov] ! area ( ,/irl+%ire1 ,lan>k%ire & ,r5frew%ire ly+ to ! nor? ( ! great volcanic plateau1 no record ( puy-eruptions has be5 notic$4 ,imm$iately to ! s\? ( t plateau1 h[ev]1 ^! eruptions 7 num]\s 9 ! nor? ( ,ayr%ire4 ,yet ! re/ ( ! ,c>bonif]\s area 9 t l>ge c\nty has suppli$ no relics ( ^! eruptions save at "o locality--! ,heads ( ,ayr4 ,la/ly1 :ile no trace ( any y\ng] display ( volcanic activity occurs 9 ! ,m]se ( ,b]wick%ire1 ea/ ( ! plateau s]ies ( t di/rict1 ! gr\nd imm$iately to ! we/ ab\nds 9 puys1 & conta9s likewise ext5sive %eets ( tuff & b$s ( basic lavas connect$ ) ^! v5ts4 ,ano!r fact :i* at once attracts notice 9 ,scotl& is ! way 9 :i* ! puy-v5ts h g5]ally avoid$ ! areas ( ! plateaux1 ?\gh !y sometimes approa* !m closely4 ,z a rule1 x is possible to di/+ui% ! tuffs & agglom]ates :i* h fill$ up ^! v5ts f ^? t m>k ! sites ( ! eruptive orifices ( ! plateaux4 ,!re are1 no d\bt1 "s in/ances1 z 9 ,liddesdale1 :]e puys h appe>$ on ! sites ( ! old] lavas1 b ^! are exceptional collocations4#ddb ,on ! o!r h&1 _m examples may be f\nd :]e puys h ris5 9 ! int]space betwe5 ! limits ( ! eruptions ( two plateau-areas4 ,?us ! tract betwe5 ! ,clyde plateau-eruptions on ! we/ & ^? ( ! ,g>leton ,hills on ! ea/ 0 dott$ ov] ) puys4 ,aga91 ! s\!rn m>g9 ( ! ,clyde plateau 9 ,ayr%ire1 f ,dalry to ,gal/on is flank$ ) puys & long %eets ( _! lavas & tuffs4#ddc ,footnote #ddb3 ,a means ( def9itely plac+ "s ( ^! v5ts 9 ! s]ies ( puy-eruptions is /at$ fur!r on1 at p4 #dgf4 ,footnote #ddc3 ,ref]5ce may aga9 be made "h to ! rem>kable simil>ity betwe5 ! ,scotti% ,c>bonif]\s puy-v5ts & ^? ( old] ,t]ti>y "t 9 ! ,swabian ,alps s fully describ$ by ,pr(essor ,branco 9 ! "w already cit$ p4 #df4 ,d5udation 9 t region has b>$ ! cones & expos$ ! /ructure ( ! necks :i*1 d[n to ev5 m9ute details1 repeat ! ph5om5a ( ,c>bonif]\s & ,p]mian "t 9 ,scotl&4 ii4 ,,nature ,,( ,,! ,,mat]ials ,,erupt$ ,a4 ,! ,lava-=m ,rocks ,we h n[ to consid] ! nature ( ! mat]ials erupt$ by ! volcanic activity ( ! puys4 ,! geologi/ :o passes f ! /udy ( ! plateau lavas to ^? ( ! puys at once rem>ks ! preval5t m basic "* ( ! latt]4 ,! great majority ( !m are basalts1 g5]ally oliv9e-be>+1 9 ! v>i\s types embrac$ 9 ! table on ! foll[+ page4 ,! oliv9e-free dol]ites are g5]ally f\nd z intrusive bosses1 sills & dykes4 ,su* m acid rocks z &esites occur only r>ely1 & /ill m seldom are qu>tzif]\s masses met ) 9 "s ( ! bosses4 ,dol]ites & ,basalts4--,! great majority ( ! lava-=m rocks connect$ ) ! puys are basic 9 composition1 & belong to ! family ( ! ,dol]ites & ,basalts4 ,!y graduate1 on ! "o h&1 into ultra-basic rocks su* z limburgite & picrite1 & on ! o!r1 into comp\nds t approa* &esites or tra*ytes 9 composition4 ,a l>ge s]ies ( specim5s f ,c5tral ,scotl& 0 /udi$ a few ye>s ago by ,dr4 ,hat*1 :o propos$ a petrographical classification ( ! rocks1 & arrang$ !m 9 a numb] ( types :i* he nam$ aft] localities :]e !y are well develop$4#ddd ,m rec5tly ! rocks h aga9 be5 subject$ to microscopic inve/igation by my colleague ,mr4 ,watts1 :o1 confirm+ g5]ally ,dr4 ,hat*'s discrim9ations1 has made "s modifications ( !m4 ,he has furni%$ me ) a revis$ classification 7p4 #dah71 bas$ on purely petrographical consid]ations4 ,! dol]itic & basaltic s]ies may be gr\p$ into two divisions1 "o )1 & ! o!r )\t1 oliv9e1 & ea* division may be fur!r sep>at$ into a dol]ite gr\p1 :i* pres5ts an ophitic or sub-ophitic /ructure1 & a basalt-gr\p 9 :i* ! gr\ndmass is made up ( felsp> & granul> augite1 & possesses ! int]s]tal /ructure ( ,ros5bus*1 or consi/s ( idiomorphic augite emb$d$ 9 felsp> sub/ance4 ,! t]m sub-ophitic is employ$ by ,mr4 ,watts to imply t ! augite gra9s are nei!r v l>ge nor v cont9u\s1 optically1 & t !y r>ely conta9 entire felsp>-cry/als imb$d$ 9 !m1 m]ely ! ends ( a gr\p ( ^! cry/als z a rule p5etrat+ into !m4 ,footnote #ddd3 ,?is classification 0 giv5 9 my ,presid5tial ,address to ! ,geological ,society1 #ahib1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xlviii4 p4 #abi4 ,see ,report ( ,geological ,survey = #ahif4 ,transitional =ms occur betwe5 _m ( ! foll[+ types by ! increase or dim9ution 9 ! relative proportions ( ! con/itu5ts4 ,?us x is n easy to draw a l9e betwe5 #b;b & #b;c2 ! latt] aga9 %ades into #b;d & #b;e by ! decrease ( ! felsp>4 ,mr4 ,watts has fur!r obs]v$ t ! rocks conta9+ no oliv9e (f] great] difficulties 9 classification ?an ^? 9 :i* t m9]al is pres5t4 ,! v di/9ction1 he rem>ks1 betwe5 dol]ites & basalts is less m>k$1 ! types are mu* less %>ply di/+ui%$1 & decomposition & mask+ ( ! /ructure are m common4 ,:ile us+ ! t]m ,dol]ite = su* rocks z h a sub-ophitic /ructure1 ,i h ext5d$ x to ^? rocks 9 :i* evid5ce exi/s t a great "p ( ! cry/allization took place "u intratelluric conditions4 ,al?\gh n q holocry/all9e1 ! cry/als ( felsp>1 augite & magnetite are l>ge & ! /ructure co>se-gra9$1 :ile ! gr\ndmass is conf9$ to comp>atively small int]/itial pat*es4 ,9 ^! rocks !re is usually no "o dom9ant porphyritic +r$i5t4 ,i4 ,! ,oliv9e-be>+ ,s]ies #a4 ,oliv9e-,dol]ites #a;a4 ,porphyritic elem5ts inconspicu\s1 oliv9e be+ ! pr9cipal1 & felsp> ( second>y importance2 ,j$burgh ,type4 gr\ndmass sub-ophitic4 #a;b4 ,/rongly porphyritic2 felsp>-ph5ocry/s l>ge2 ,kilsy? ,type4 oliv9e small]2 gr\ndmass sub-ophitic4 #a;c4 ,porphyritic oliv9e1 b n felsp>2 gr\ndmass ,galla/on ,type4 sub-ophitic4 #b4 ,oliv9e-,basalts #b;a4 ,porphyritic oliv9e1 augite & felsp>2 gr\ndmass ,lion's ,haun* ( felsp>-la?s imb$d$ 9 granules ( augite4 ,type4 7,see ,fig4 #bjg47 #b;b4 ,porphyritic oliv9e & augite2 gr\ndmass ( felsp>-la?s imb$d$ 9 granules ( augite4 ,m ,craiglockh>t r>ely ! gr\ndmass is made ( idiomorphic augite ,type4 imb$d$ 9 felsp>-sub/ance4 #b;c4 ,porphyritic oliv9e abundant1 augite mu* less common1 & felsp> v r>e or abs5t2 gr\ndmass ,dalm5y ,type4 ) granul> or idiomorphic augite 7"o ( ! mo/ common types74 #b;d4 ,porphyritic oliv9e m common ?an augite2 gr\ndmass ( granules ( augite set among/ la?-l ,picrite ,type4 felsp>s :i* are mu* few] 9 numb] ?an 9 #b;c4 #b;e4 ,porphyritic oliv9e m common ?an augite2 gr\ndmass ( idiomorphic augite imb$d$ 9 ,limburgite felspa?ic mat]ial :i* is n abundant4 ,type4 #b;f4 ,porphyritic oliv9e & felsp>1 )\t augite2 ,kippie ,law ,type4 gr\ndmass ( granul> or idiomorphic augite1 ) 7,= analysis la?-%ap$ felsp>s4 see p4 #cgi74 ,,ii4 ,! ,non-oliv9e-be>+ ,s]ies #c4 ,oliv9e-free ,dol]ites ,felsp>1 augite1 magnetite 9 co>se-gra9$ aggregate usually ophitic or sub-ophitic2 gr\ndmass n pl5tiful4 #c;a4 ,gr\ndmass abs5t ,ophitic ,type4 #c;b4 ,gr\ndmass micropegmatitic ,ra?o ,type4 #c;c4 ,gr\ndmass an un/riat$ felsp> 7n or?oclase7 & occasionally "s int]/itial alt]$ glass or a ,burntisl& little qu>tz4 ,sill ,type4 #d4 ,dol]itic ,basalts ,felsp>1 augite & magnetite 9 co>se-gra9$ aggregate2 gr\ndmass r m pl5tiful & (t5 9 l>ge pat*es4 #d;a4 ,felsp> & augite1 relat$ sub-ophitically :]e toge!r1 b augite %[+ cry/all9e cont\rs 9 ,b[d5 contact ) ! gr\ndmass2 "s int]/itial qu>tz ,hill ,type4 & un/riat$ felsp>4 #e4 ,basalts ,f9]-gra9$ rocks1 g5]ally ) a porphyritic +r$i5t & mu* scatt]$ int]/itial matt] 9 ! gr\ndmass4 #e;a4 ,porphyritic felsp>1 & occasionally a little augite2 gr\ndmass ( granul> augite1 felsp> ne$les ,b9ny ,craig & magnetite ) "s int]/itial matt]4 ,type4 #e;b4 ,porphyritic felsp>s n conspicu\s & small2 ! rock ma9ly made up ( a me% ( f9e felsp>-la?s set ,?oleiite among/ granul> augite1 magnetite & base4 ,type4 #e;c4 ,simil> to ! la/ b ev5 f9]-gra9$1 & ,crypto- ) ! base 9 a cryptocry/all9e condition4 cry/all9e ,type4 ,tak+ fir/ ! sup]ficial lavas1 ,i "k ( only "o locality :]e picrite occurs 9 su* a position t x may be includ$ among ! surface outfl[s4 ,?is is ! qu>ry ne> ,blackburn1 to ! ea/ ( ,ba?gate1 :]e ,i orig9ally obs]v$ x4#dde ,! rock occurs !re on ! l9e ( ! basalt-fl[s f ! ,ba?gate ,hills1 & ,i mapp$ x z "o ( !m be=e ! microscope reveal$ ! rem>kable composition ( ! mass4 ,i /ill believe x to be a lava l ! leck/one describ$ on p4 #ddc1 ?\gh ! o!r kn[n examples ( ?is rock 9 ! bas9 ( ! ,fir? ( ,=? are intrusive %eets4 ,! rock locally kn[n z leck/one or lake/one has long be5 qu>ri$ = ! purpose ( con/ruct+ ! soles ( bak]s' ov5s1 z x /&s a consid]able temp]ature )\t crack+4 ,its microscopic /ructure is n[ well kn[n4 ,z expos$ 9 ,blackburn qu>ry1 an int]e/+ diff]5ce is obs]vable betwe5 ! l[] & upp] p>ts ( ! %eet4 ,! l[] portion is a picrite1 ) abundant s]p5t9iz$ oliv9e1 l>ge cry/als ( augite1 & a consid]able am\nt ( ores4 ,! upp] portion1 on ! o!r h&1 has plagioclase z its mo/ abundant def9ite m9]al1 ) a m9or quantity ( m9ute prisms ( augite & ( iron-ores1 & scatt]$ cry/als ( oliv9e4 ,"h1 )9 ! compass ( a few y>ds & 9 "o cont9u\s mass ( rock1 we h a transition f a v>iety ( oliv9e-basalt into a picrite4 ,footnote #dde3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxix4 7#ahgi7 p4 #ejf4 ,! great majority ( ! puy lavas belong to ! oliv9e-be>+ s]ies4 ,a few ( !m are dol]ites1 b mo/ are true basalts ( ! ,dalm5y type1 ( :i* typical examples may be se5 at ! ,kirkton qu>ries1 ,ba?gate1 & 9 ! coa/ section betwe5 ,pettycur & ,k+horn4 ,occasionally !y pres5t transitions t[>ds picrite1 z 9 ! %eet ov]ly+ ! l[e/ lime/one at ,kirkton1 & 9 ! l[e/ lava ( ,k+ ,alex&]'s ,crag1 ,burntisl&4 ,^! puy lavas exhibit consid]able v>iety ( /ructure z se5 9 ! field4 ,"s are solid1 compact1 black rocks1 n infrequ5tly column> & wea!r+ into sph]oidal exfoliat+ =ms4 ,o!rs are some:at granul> 9 texture1 acquir+ gre5 & br[n t9ts by wea!r+1 (t5 %[+ amygdaloidal k]nels1 & ev5 pass+ into well-m>k$ amygdaloids4 ,_m ( !m exhibit a slaggy /ructure at _! upp] & "u surfaces 7,figs4 #aec1 #agj1 #aga74 ,^! ext]nal diff]5ces are an index to ! correspond+ v>iations 9 composition & microscopic /ructure enum]at$ 9 ! =ego+ tabul> arrangem5t4 ,z a rule1 ! basic rocks :i* occur intrusively 9 connection ) ! puys1 especially :]e !y =m a consid]able mass1 h assum$ a mu* m co>sely cry/all9e texture ?an ^? ( simil> composition :i* h be5 p\r$ out at ! surface4 ,!y are g5]ally dol]ites r ?an basalts4 ,b ) ?is obvi\s di/9ction1 ! two gr\ps h s mu* 9 common1 t ! geologi/ :o passes f ! /udy ( ! subt]ranean ph5om5a ( ! ,plateaux to t ( ! correspond+ ph5om5a ( ! ,puys is at once impress$ ) ! close relation%ip betwe5 ! mat]ial :i*1 9 ! case ( ! puys1 has consolidat$ above gr\nd1 & t :i* has be5 inject$ bel[4 ,!re is no su* contra/ betwe5 !m1 = example1 z t betwe5 ! basic & int]m$iate lavas ( ! plateaux & ! m acid intrusions associat$ ) !m4 ,by f> ! l>ge/ numb] ( ! basic sills1 bosses & dykes associat$ ) ! puys are some:at co>sely cry/all9e dol]ites )\t oliv9e4 ,!y include1 h[ev]1 oliv9e-dol]ites & basalts1 & ev5 "s extremely basic comp\nds4 ,( ^! la/1 a typical example is suppli$ by ! n[ well-kn[n picrite ( ,in*colm1 9 ! ,fir? ( ,=?1 :i* occurs z an intrusive %eet among ! ,l[] ,c>bonif]\s ,s&/ones4#ddf ,9 rec5t ye>s "o or two o!r picrite-sills h be5 obs]v$ 9 ! same di/rict4 ,an int]e/+ example has be5 describ$ f a railway cutt+ betwe5 ,ed9burgh & ,cramond :]e ! rock invades & alt]s %ales4 ,m detail$ ref]5ce to x w be made 9 ! acc\nt ( ! sills connect$ ) ! puys4 ,ano!r in/ance ( ! occurr5ce ( ?is rock is 9 a railway cutt+ imm$iately to ! we/ ( ,burntisl& :]e x has be5 intrud$ among ! ,calcif]\s ,s&/ones bel[ ! ,burdieh\se ,lime/one4 ,footnote #ddf3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxix4 7#ahgi7 p4 #ejf4 ,teall1 ,briti% ,petrography1 p4 #id4 ,rocks approa*+ limburgite occur among ! sills & bosses :i* pi]ce ! ,c>bonif]\s ,lime/one s]ies ( ,fife betwe5 ,c[d5bea? & ,inv]kei?+4 ,"o ( ^! is f\nd at ,pit&rew1 ne> ,=del ,ca/le4 ,dr4 ,hat* obs]v$ t x consi/s ( num]\s porphyritic cry/als ( oliv9e1 ) a few gra9s ( augite & an occasional small la?-%ap$ cry/al ( felsp> imb$d$ 9 a gr\ndmass :i* is compos$ pr9cipally ( idiomorphic augite microlites1 small cry/als ( a br[n mica1 granules ( magnetite & prisms ( apatite4 ,9 addition1 !re is a consid]able am\nt ( int]/itial matt]1 :i* is p>tly col\rless glass1 & p>tly %[s a slight reaction betwe5 cross$ nicols4 ,ano!r example ( ! same type ( rock occurs z a plug or boss 9 ! tuff-v5t ( ! ,hill ( ,bea?1 & a fur!r display ( ! limburgite type is to be se5 9 ,dune>n ,hill ne> ,burntisl&4 ,al?\gh oliv9e-basalts ( ! ,dalm5y type are mo/ frequ5tly met ) z int]/ratifi$ lavas1 !y also occur z bosses & sills4 ,! typical example f ,dalm5y is itself intrusive4 ,o!r illu/rations are to be f\nd 9 ! ,ca/le ,rock ( ,ed9burgh & 9 ! %eets ne> ,crossgates & ,blairadam 9 ,fife4 ,! pres5ce or abs5ce ( oliv9e1 h[ev]1 may sometimes be a m]e accid5t ( cool+ or o!rwise4 ,i h %[n t 9 ! same mass ( rock at ,blackburn a gradation c be trac$ f a rock l>gely compos$ ( alt]$ oliv9e into "o consi/+ ma9ly ( felsp> ) b little oliv9e1 & ano!r example occurs 9 ! picrite-sill betwe5 ,ed9burgh & ,cramond4 ,dr4 ,/e*] has asc]ta9$ t ! m>g9al portions ( ! sills 9 ! bas9 ( ! ,fir? ( ,=?1 :i* cool$ fir/ & rapidly1 & may be tak51 !re=e1 to indicate ! m9]al composition ( ! rock at ! "t ( extrusion1 are (t5 ri* 9 oliv9e1 :ile t m9]al may be h>dly or n at all disc]nible 9 ! ma9 body ( ! rock4#ddg ,footnote #ddg3 ,dr4 ,/e*]1 ,ts*]mak's ,m9]alog4 ,mit!il4 vol4 ix4 7#ahhg7 p4 #aic4 ,proc4 ,roy4 ,soc4 ,ed94 vol4 xv4 7#ahhh7 p4 #afb4 ,( ! ord9>y & *>act]i/ic dol]ites )\t oliv9e :i* con/itute mo/ ( ! intrusive masses1 ! v>i\s types enum]at$ 9 ! tabul> arrangem5t are abundantly develop$ 9 ,c5tral ,scotl&4 ,?us ! normal ophitic type is display$ by ! upp]mo/ sill ( ! ,burntisl& s]ies1 & by ! rock :i* =ms ! plug ( ! ,b9ns ,hill neck 9 ,l9li?g[%ire4 ,! ,ra?o type is well se5 9 ! l>ge sill at ,ra?o1 likewise 9 ! ext5sive intrusive %eets 9 ! we/ ( ,l9li?g[%ire z at ,muckraw & ,c>ribb]4 ,! ,burntisl& sill type is %[n by ! l[] sills ( ,burntisl& & by "s o!rs 9 ! same region1 especially by t ( ,col9swell1 & by ano!r on ! %ore ea/ f ! ,poorh\se1 ne> ,k+horn4 ,! great boss among ! ,ba?gate ,hills likewise displays x4 ,! ,b[d5 ,hill type occurs 9 well-m>k$ developm5t at ,b[d5 ,hill1 ?ree miles s\?-we/ ( ,l9li?g[1 & 9 ! massive sill at ,/4 ,m>g>et's1 we/ f ,nor? ,que5sf]ry4 ,! non-oliv9e-be>+ basalts are f\nd 9 v>i\s bosses & %eets 9 ! bas9 ( ! ,fir? ( ,=?4 ,?us ! ,b9ny ,craig type occurs 9 ! prom95t & picturesque sill f :i* x is nam$1 likewise among ! intrusive %eets ne> ,kirkcaldy1 9 ,fife4 ,sometimes ! same mass ( rock displays m ?an "o type ( /ructure1 z 9 ! case ( ! great ,galabraes neck among ! ,ba?gate ,hills :]e9 bo? ! ,?oleiite & ,burntisl& sill types may be recogniz$4 ,"s ( ! sills 9 ,we/ ,lo?ian1 z ,i po9t$ out _m ye>s ago1 conta9 bitum5 & give (f a bitum9\s od\r :5 fre%ly brok54 ,!y h be5 inject$ into bitum9\s %ales or coal-seams4#ddh ,footnote #ddh3 ,geol4 ,survey ,memoir on ,geology ( ,ed9burgh 7,%eet #cb1 ,scotl&71 p4 #df4 #b4 ,&esites4--,rocks ref]able to ?is s]ies appe> to h be5 ( r>e occurr5ce among ! puy-eruptions4 ,examples ( !m conta9+ z mu* z #fj p] c5t ( silica occur among ! lavas ( ! ,lim]ick bas94 ,"s ( ! necks & :at may be sills 9 ! same di/rict likewise consi/ ( !m4 #c4 ,tra*ytes & ,qu>tz-be>+ ,rocks4--,acid rocks1 z ,i h already said1 are extremely r>e among ! puy-eruptions4 ,! only important examples kn[n to me are ^? ar\nd ! ,lim]ick bas91 :]e !y rise app>5tly 9 old v5ts & =m conspicu\s r\nd$ or conical hills4 ,^! rocks h be5 exam9$ microscopically by ,mr4 ,w4 ,w4 ,watts4 ,"o ( ! mo/ int]e/+ v>ieties1 :i* occurs at ! ,/&+ ,/one ne> ,oola1 0 f\nd by him to %[ qu>tz enclos+ ophitically ! felsp>s :i*1 ) well-t]m9at$ prisms1 project into x4 ,fur!r we/1 ne> ,knockaunavoh]1 ano!r boss occurs ) conspicu\s qu>tz4 ,^! rocks h mu* 9 common ) tra*ytes b h a :olly cry/all9e /ructure4 ,!y w be describ$ 9 ! acc\nt ( ! ,lim]ick bas94 ,b4 ,tuffs ,! fragm5tal rocks connect$ ) ! puy-eruptions =m a well-m>k$ gr\p1 easily di/+ui%able1 = ! mo/ "p1 f ! tuffs ( ! plateaux4 ,!y v>y f exce$+ly f9e compact$ du/ or volcanic mud1 ?r\gh v>i\s /ages ( increas+ co>s5ess ( texture1 to basalt-conglom]ates & tumultu\s agglom]ates4 ,! fragm5t>y mat]ial f\nd 9 ! necks ( ! puys is g5]ally an agglom]ate ( a dull dirty-gre5 col\r4 ,! matrix ranges f a f9e compact volcanic mud to a ?or\ghly granul> detritus1 & sometimes %[s a sph]oidal conc5tric /ructure 9 wea!r+4 ,9 ?is matrix ! lapilli are di/ribut$ ) great irregul>ity & 9 con/antly v>y+ proportions4 ,!y consi/ 9 l>ge measure ( a pale yell[i%-gre51 sometimes pale grey1 v basic1 f9ely vesicul>1 devitrifi$ glass1 :i* is g5]ally mu* decompos$ & cuts easily ) ! knife4 ,?is highly basic sub/ance is a k9d ( palagonite4 ,s m9ute are its vesicles t "u ! microscope a ?9 slice may pres5t a delicate lace-l network ( connect$ walls1 ! palagonite occupy+ mu* less space ?an ! vesicles4 ,! mat]ial has be5 a f9ely fro!d-up pumice4 ,besides ?is g5]ally di/ribut$ basic pumice1 ! /ones 9 ! agglom]ate ( ! necks likewise include fragm5ts ( old] volcanic grits or tuffs1 blocks ( basalt or diabase1 z well z pieces ( ! ,c>bonif]\s /rata ( ! di/rict1 especially %ale1 s&/one & lime/one4 ,n infrequ5tly also1 !y comprise angul> blocks ( fossil wood4 ,! mat]ials :i* fill ! necks are g5]ally mu* co>s] ?an ^? t =m int]calat$ b$s4 ,b :ile 9 num]\s cases huge blocks ( basalt & l>ge masses ( s&/one1 %ale1 lime/one1 iron/one or o!r /rata may be se5 wrapp$ up 9 a matrix ( co>se basalt-tuff1 9 n a few in/ances ! mat]ial 9 ! necks may be obs]v$ to consi/ ( a tuff q z f9e z t ( ! int]/ratifi$ b&s4 ,su* necks appe> to m>k ! sites ( tuff-cones :]e only f9e a%es & lapilli 7 eject$1 & :]e1 aft] sometimes a brief & feeble p]iod ( activity1 ! orifice became ext9ct4 ,! b$d$ tuffs int]/ratifi$ ) ! ord9>y ,c>bonif]\s /rata d n ess5tially diff] 9 composition f ! mat]ial ( ! necks4 ,!y are basalt- 7diabase-7 tuffs & basalt- 7diabase-7 conglom]ates1 usually dull gre5 9 col\r & granul> 9 texture1 ! lapilli consi/+ 9 great measure ( v>i\s m or less decay$ basalts1 b conta9+ ! same highly vesicul> basic glass or pumice above ref]r$ to4 ,!y are ma9ly to be di/+ui%$ by _! conspicu\s /ratification1 & especially by _! rapid alt]nations ( co>s] & f9] mat]ial1 by ! int]calation ( %ales1 lime/ones1 s&/ones or iron/ones 9 !m1 & by ! ins5sible gradations by :i* !y pass bo? v]tically & lat]ally into ord9>y s$im5ts4 ,occasional l>ge blocks or bombs1 indicat+ "s p>oxysm ( explosion1 may be obs]v$ ev5 among ! f9] tuffs1 %ales & o!r /rata1 :i* r\nd ! sides ( ^! masses h _h _! lay]s b5t d[n by ! fall ( heavy blocks4#ddi ,_m ( ! b$d$ tuffs conta9 fossils1 su* z cr9oids1 corals1 bra*iopods1 fi%-tee? or mac]at$ fragm5ts ( l&-plants4 ,coal-seams also are occasionally int]/ratifi$ among !m4 ,footnote #ddi3 ,ante1 p4 #cf1 & ,figs4 #ae & #aea4 ,see also ,geol4 ,mag4 i4 7#ahfd71 p4 #bb2 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxix4 7#ahgi7 p4 #eae4 ,( ! f9] k9ds1 ! be/ example is furni%$ by a rem>kable gr\p ( gre5 & r$ m>ls :i* lie above a seam ( coal 7,h\/on ,coal7 9 ! ,calcif]\s ,s&/ones ( ,we/ ,lo?ian4#dej ,^! /rata1 :i* diff] mu* f any ( ! rocks ) :i* !y are associat$1 are exce$+ly f9e 9 gra91 dull sage-gre5 & br[ni% or *ocolate-r$ 9 col\r1 n well lam9at$ l ! %ales1 b break+ "u ! influ5ce ( wea!r+ into angul> fragm5ts1 sometimes ) a con*oidal fracture4 ,!y look l indurat$ mud4 ,mr4 ,h4 ,m4 ,cadell1 :o has rec5tly re-exam9$ !m 9 connection ) a revision ( ! ,geological ,survey ,map 7,%eet #cb7 has f\nd !m pass+ into ord9>y granul> tuff4 ,footnote #dej3 ,memoir on ,%eet #cb ,geol4 ,surv4 ,scotl& 7#ahfa71 p4 #db4 ,! /ratigraphical position ( ^! ,h\/on ,m>ls1 z !y are locally call$1 is indicat$ 9 ,fig4 #aee4 ,palagonitic-tuff is ( frequ5t occurr5ce4 ,x is met ) 9 ! ,fir? ( ,=? di/rict1#dea & ,mr4 ,watts has detect$ fragm5ts ( palagonite among ! tuffs ( ! ,lim]ick bas94 ,footnote #dea3 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxix4 7#ahai7 p4 #eae4 ,,*apt] ,,xxvii ,,geological ,,/ructure ,,( ,,! ,,c>bonif]\s ,,puys ,,( ,,scotl& #a4 ,v5ts3 ,relation ( ! ,necks to ! ,rocks ?r\gh :i* !y rise--,evid5ce ( ! probable ,subrial ,"* ( "s ( ! ,cones or ,puys ( ,tuff--,entombm5t ( ! ,volcanic ,cones & _! ,relation to ! ,sup]ficial ,ejections4 #b4 ,b$d$ ,tuffs & ,lavas--,effects ( ,subsequ5t ,dislocations4 #c4 ,sills1 ,bosses & ,dykes4 ,! puy-type ( volcanic hill diff]s widely 9 "o respect f ^? :i* we h hi!rto be5 consid]+4 ,9 ! e>li] epo*s ( volcanism )9 ! ,briti% area1 x is ! masses ( mat]ial dis*>g$ f ! v5t1 r ?an ! v5ts !mselves :i* arre/ att5tion4 ,inde$1 s copi\sly h ^! masses be5 erupt$ t ! v5ts are (t5 buri$1 or _! positions h be5 r5d]$ d\btful1 by ! uprise 9 & ar\nd !m ( sills & bosses ( molt5 rock4 ,b among ! ,c>bonif]\s puys ! v5t is (t5 ! only record t rema9s ( ! volcanic activity4 ,9 "s cases we "k t x nev] eject$ any igne\s mat]ial to ! surface4 ,9 o!rs1 ?\gh x may be fill$ ) volcanic agglom]ate or tuff1 !re is no record ( any %[] ( su* detritus hav+ be5 dis*>g$ f x4 ,9 yet a ?ird class ( examples1 we see t lava rose 9 ! v5t1 b no evid5ce rema9s z to :e!r or n x ev] fl[$ out above gr\nd4 ,o!r cases occur :]e b$s ( lava or ( tuff1 or ( bo? toge!r1 h be5 int]calat$ 9 a gr\p ( /rata1 b ) no trace n[ visible ( ! v5t f :i* !y came4 ,! mo/ complete *ronicle1 pres]v+ at once a record ( ! outfl[ ( lava1 ( ! %[]+ =? ( a%es & bombs1 & ( ! necks t m>k ! v5ts ( eruption1 is only to be f\nd 9 "s ( ! di/ricts4 ,i %all !re=e1 9 ! pres5t in/ance1 rev]se ! ord] ( arrangem5t foll[$ 9 ! previ\s *apt]s1 & treat fir/ ( ! v5ts1 !n ( ! mat]ials emitt$ f !m1 & la/ly ( ! sills & dykes4 i4 ,,v5ts ,a l>ge numb] ( v5ts rise ?r\gh ! ,c>bonif]\s rocks ( ,scotl&4 ,"s ( ^! are n associat$ ) any int]b$d$ volcanic mat]ial1 s t _! geological age _c be m precisely def9$ ?an by say+ t !y mu/ be lat] ?an ! p>ticul> =mations :i* !y pi]ce4 ,"s ( !m1 z ,i %all endeav\r to %[1 are 9 all probability ( ,p]mian age4 ,b _m1 f _! position ) ref]5ce to ! ne>e/ int]calat$ lavas & tuffs1 are to be reg>d$ z almo/ c]ta9ly belong+ to ! ,c>bonif]\s p]iod4 ,^? :i* are imm$iately surr\nd$ by %eets ( lava & tuff1 simil> 9 "* to ! mat]ials 9 ! v5ts !mselves1 may )\t hesitation be connect$ ) ^! %eets z m>k+ ! orifices ( dis*>ge4 ,! v5ts ( ! puys are 9 g5]al mu* less ?an ^? ( ! plateaux4 ,_! smalle/ examples measure only a few y>ds 9 diamet]1 _! l>ge/ seldom mu* exce$ half a mile4#deb ,footnote #deb3 ,! foll[+ measurem5ts ( necks belong+ to ! puy-eruptions 9 diff]5t p>ts ( ,scotl& are tak5 f ! #f-;in* field-maps ( ! ,geological ,survey3--,sal9e ,hill1 ,fife1 #fjjj #djjj feet2 ,b9n ( ,burntisl&1 #cejj #aejj2 ,hill ( ,bea?1 ,fife1 #bijj #aeej2 ,b9ns ,hill1 ,l9li?g[%ire1 #dhjj #bbjj2 ,tor ,hill1 ,ecclesma*an1 ,l9li?g[%ire1 #aijj #ajjj 7,fig4 #aee72 ,great ,moor1 ne> ,maid5 ,pap1 ,roxburgh%ire1 #bfjj #bdjj2 ,t9nis ,hill1 ,liddesdale1 #aejj #ajjj2 ,roan ,fell1 ,liddesdale1 #cjj #bjj2 ,hadsg>? ,burn1 ,liddesdale1 #bej #bjj2 ,dalbate ,burn1 #bej #abj4 ,9 "s cases1 especially 9 ^? ( ! l>g] necks1 x is probable t ! tuff belongs to m ?an "o funnel4 ,?us ! ,b9n ( ,burntisl& almo/ c]ta9ly includes two necks1 a small] "o to ! we/ & a mu* l>g] "o to ! ea/4 ,sal9e ,hill may also conceal m ?an "o v5t4 ,b 9 ! cont9u\s mass ( tuff at ! surface x is at pres5t impossible to det]m9e precisely ! numb] & b\nd>ies ( ! sev]al orifices4 ,! dislocations ( ! ,c>bonif]\s sy/em are probably on ! :ole lat] ?an its volcanic ph5om5a4 ,x is at lea/ c]ta9 t ! lavas & tuffs ( ! puys h be5 ext5sively fault$1 l ! surr\nd+ s$im5t>y /rata1 & ! v5ts seldom %[ any app>5t relation to faults4 ,x may sometimes be obs]v$1 h[ev]1 t ! v5ts are arrang$ 9 l9es sugge/ive ( fissures und]nea?4 ,a rem>kable in/ance ( ! l9e> di/ribution is furni%$ by ! *a9 ( necks :i* ext5ds f ! ,vale ( ! ,twe$ at ,melrose s\?-we/w>ds across ! wat]%$ & d[n ,liddesdale4 ,! mo/ notable "p ( ?is l9e lies among ! upl&s to ! ea/ ( ! ,old ,mosspaul ,inn at ! head ( ! ,ewes ,wat]4 ,a /r+ ( masses ( agglom]ate has !re solidifi$ 9 a fissure among ! ,silurian greywackes & %ales1 runn+ 9 a nor?-ea/]ly direction = sev]al miles4 ,! l>ge/ connect$ mass ( agglom]ate is #dgjj feet long1 & f #cej to #fjj feet broad 7see ,no4 #a 9 ,fig4 #bb74 ,t ?is curi\s v5t1 or connect$ l9e ( v5ts along a great fissure1 belongs to ! puy-eruptions ( ,liddesdale is %[n by ! abundant fragm5ts ( yell[ s&/one & cem5t-/one :i* occur 9 ! agglom]ate4#dec ,footnote #dec3 ,^! facts 7 asc]ta9$ by ,mr4 ,pea* 9 mapp+ ! gr\nd = ! ,geological ,survey4 ,see ,%eet #ag1 ,scotl&4 ,mo/ frequ5tly ! v5ts are di/ribut$ irregul>ly 9 gr\ps4 ,z examples ( ?is arrangem5t ,i may cite ^? ( ! we/ ( ,fife1 ( ,we/ ,lo?ian & ( ! nor? ( ,ayr%ire4 ,a conv5i5t classification ( ! v5ts may be made by divid+ !m into f\r gr\ps accord+ to ! nature ( ! mat]ial t n[ fills !m3 #a/1 ,necks ( non-volcanic debris2 #bnd1 ,necks ( tuff & agglom]ate2 #crd1 ,necks ( simil> mat]ials1 b ) a c5tral plug ( basalt2 #d?1 ,bosses ( basalt or o!r lava1 )\t agglom]ate or tuff4 #a4 ,necks ( ,non-volcanic ,debris4--,9 a few in/ances ! orifices ( eruption h be5 fill$ up entirely ) non-volcanic debris4 ,!y h s]v$ z funnels = ! dis*>ge ( explosive vap\rs only1 )\t ! expulsion ( any solid volcanic mat]ials4 ,at lea/ no trace ( fragm5t>y lavas is met ) 9 !m1 nor are any b$s ( tuff or lava int]calat$ among ! surr\nd+ /rata4 ,"s int]e/+ examples ( ?is k9d 7 laid b>e 9 ! op5 iron/one-work+s ne> ,c>luke 9 ,lan>k%ire4 ,!y 7 circul> 9 gr\nd-plan1 desc5d$ v]tically into ! /rata1 & 7 some:at wid] at ! top ( ! qu>ry ?an at ! bottom4 ,!y 7 fill$ ) angul> pieces ( ,c>bonif]\s s&/one1 %ale1 lime/one1 iron/one & o!r rocks1 ^! mat]ials be+ rudely arrang$ ) a dip t[>ds ! c5tre ( ! neck1 :]e ! blocks 7 l>ge/ 9 size4 ,?\gh no fragm5ts ( igne\s rocks 7 obs]v$ among ! debris1 a few /r+-l ve9s ( :ite trap1 or alt]$ basalt1 7 se5 to trav]se ! agglom]ate "h & !re4 ,! necks & ! /rata surr\nd+ !m 7 highly impregnat$ ) pyrites & sulphate ( lime4#ded ,footnote #ded3 ,pr(4 ,jas4 ,geikie1 ,mem4 ,geol4 ,surv4 ,scotl&1 ,explanation ( ,%eet #bc1 p4 #ci4 ,illu/ration3 ,fig4 #adc4--,section ( volcanic v5t at ,ea/ ,grange1 ,p]?%ire coal-field1 con/ruct$ by ,mr4 ,b4 ,n4 ,pea* f ! rocks expos$ 9 a railway-cutt+1 & f plans ( iron/one- & coal-pits4 #a4 ,?ree feet coal2 #b4 ,ontake coal2 #c4 ,upp] & ,l[] ,black-b& ,iron/ones2 #d4 ,index ,lime/one2 #e4 ,gas ,coal & ,janet ,peat ,coal2 #f4 ,calmy ,lime/one2 #g4 ,neck4 ,a v5t ( ! same nature1 b on a mu* l>g] scale1 has be5 mapp$ by ,mr4 ,pea* 9 ! s\? ( ,p]?%ire1 ne> ,ea/ ,grange1 :]e x rises ?r\gh ! high] coal-be>+ "p ( ! ,c>bonif]\s ,lime/one s]ies 7,fig4 #adc74 ,x has be5 enc\nt]$ 9 ! m9+ ( coal & iron/one1 & its cross-section has be5 asc]ta9$ 9 ! und]gr\nd work+s :i* h be5 c>ri$ up to its m>g94 ,x measures #aejj feet 9 diamet] f ea/ to we/ & #bjjj feet f nor? to s\?4 ,x does n appe> ev] to h emitt$ any a%es or lava4 ,mr4 ,pea* f\nd x fill$ ) d>k s&y crumbl+ clays1 full ( fragm5ts ( s&/one1 %ale & coal4 ,^! s$im5ts are arrang$ 9 lay]s t dip 9 ! same g5]al direction z ! /rata surr\nd+ ! v5t4 ,!y conta9 abundant calc>e\s nodules ( all sizes f t ( a hazel-nut up to concretions #ah feet 9 diamet]4 ,! clays likewise include _m ( ! common %ells & cr9oids ( ! ,c>bonif]\s ,lime/one sea1 & ! same fossils are enclos$ 9 ! nodules4 ,a rem>kable feature 9 ?is v5t is ! occurr5ce ( abundant v]tical r5ts1 :i* h be5 fill$ p>tly ) ! same mat]ial t =ms ! nodules1 & p>tly ) s&/one4 ,! =mation ( ! neck took place aft] ! deposition ( ! ,index ,lime/one1 & probably ab\t ! "t ( ! accumulation ( ! next lime/one1 :i* lies imm$iately to ! we/ some:at high] 9 ! s]ies4 ,x w\ld appe> t ! eruption :i* produc$ ?is funnel gave =? only gase\s explosions1 & occurr$ on ! sea-floor2 t ! l[ crat]-walls 7 wa%$ d[n to su* an ext5t t ! sea ent]$ & c>ri$ "s ( its *>act]i/ic organisms into ! lagoon or ma> )92 fur!r1 t z ! silt ga!r$ inside1 successive subsid5ces occurr$1 :]eby ! s$im5t 0 r5t by cracks into :i* s& & calc>e\s mud 7 wa%$ f above4#dee ,footnote #dee3 ,! v5t is %[n 9 ,%eet #ci1 ,geol4 ,surv4 ,scotl&4 ,_m necks occur :]e9 non-volcanic mat]ials1 ?\gh n =m+ ! :ole ( ! agglom]ate1 make up by f> ! l>g] "p1 ) only a slight admixture ( volcanic tuff betwe5 !m4 ,among ! ,burntisl& necks ( ,fife1 = in/ance1 abundant fragm5ts ( ! well-m>k$ cyprid lime/one & %ale may be obs]v$1 :ile at ,niddry 9 ,l9li?g[%ire blocks sev]al y>ds 9 l5g?1 & consi/+ ( diff]5t lay]s ( %ale & cem5t-/one /ill adh]+ to ea* o!r1 may be se5 imb$d$ at all angles 9 ! tuff4 ,:]e only ! debris ( non-volcanic rocks occupies a v5t1 we may inf] t ! volcanic action 0 limit$ to ! explosion ( /eam1 :]eby ! rocks 7 dislocat$1 & an orifice communicat+ ) ! surface 0 drill$ ?r\gh !m1 & t :ile no true volcanic rock 9 su* a case appe>$1 ! pipe 0 fill$ up to p]haps n f> f ! surface by ! fall+ back ( ! %att]$ detritus4 ,a little great] int5sity or f>!r prolongation ( ! volcanic action w\ld br+ ! column ( lava up ! funnel1 & all[ its upp] "p to be bl[n out z du/ & lapilli2 :ile /ill m vigor\s activity w\ld be m>k$ by ! rise ( ! lava into r5ts ( ! cone or its actual outfl[ at ! surface4 ,e gradation 9 ?is scale ( progress may be detect$ among ! ,c>bonif]\s volcanoes ( ! bas9 ( ! ,fir? ( ,=?4 #b4 ,necks ( ,tuff & ,agglom]ate4--,! majority ( ! necks connect$ ) ! puys consi/ ( tuff or agglom]ate4 ,ext]nally !y g5]ally appe> z smoo? r\nd$ grassy hills t rise disconnect$ f o!r em95ces4 ,9 "s di/ricts _! mat]ials consi/ ( a gre5i% granul> (t5 /ratifi$ tuff1 enclos+ r\nd$ balls ( v>i\s basic lavas & pieces ( s&/one1 %ale1 lime/one or o!r /rata ?r\gh :i* !y h be5 drill$4 ,?is is _! usual "* 9 ! ,=? region4 ,b 9 "s cases1 ! tuff becomes a co>se agglom]ate1 made up p>tly ( l>ge blocks ( basalt & o!r volcanic rocks & p>tly ( ! s$im5t>y /rata ar\nd !m1 ( :i* l>ge masses1 _m cubic y>ds 9 bulk1 may be se54 ,among ! enclos$ fragm5ts x is n unusual to f9d pieces ( old] /ratifi$ tuff4 ,^! resemble 9 g5]al petrographical "* p>ts ( ! tuff among :i* !y are imb$d$4 ,sometimes !y h be5 ,illu/ration3 ,fig4 #add4--,view ( ! ,b9n ( ,burntisl&--a volcanic neck ( agglom]ate4 7,?is illu/ration & ,figs4 #ade1 #aeb1 #aec1 #afd1 #aff & #afh are f photographs tak5 by ,mr4 ,rob]t ,lunn = ! ,geological ,survey47 d]iv$ f previ\s tuffs :i*1 int]/ratifi$ among ! s$im5t>y /rata1 _h be5 brok5 up by ! op5+ ( a new v5t4 ,b probably 9 mo/ cases !y %\ld be reg>d$ z portions ( ! volcanic debris :i*1 hav+ solidifi$ inside ! crat]1 0 bl[n out 9 fragm5ts by subsequ5t explosions4 ,9 a mod]n volcano a consid]able am\nt ( /ratifi$ tuff may be =m$ inside ! crat]4 ,! a%es & /ones ?r[n out dur+ a p]iod ( activity fall n only on ! out] slopes ( ! cone1 b on ! /eep inn] declivities ( ! crat]1 :]e !y arrange !mselves 9 b$s t dip at high angles t[>ds ! crat] bottom4 ,?is feature is well se5 9 "s ( ! ext9ct cones 9 ! ,neapolitan di/rict4 ,9 "s ( ! ,scotti% puys ! tuff is /ratifi$ & has tumbl$ d[n into a highly incl9$ or v]tical position 7,fig4 #ade74 ,z a good illu/ration ( ! v>iety & relative proportions ( ! eject$ blocks 9 ! gre5 tuff ( ! puy-v5ts1 ,i may cite ! foll[+ table ( p]c5tages :i* ,i took _m ye>s ago 9 ! tuff :i* rises ?r\gh ! ,cem5t-/one gr\p on ! bea* at ! ,heads ( ,ayr4 ,diabase & basalt #eg p] c5t4 ,old] tuff #c ,&esite 7probably f ,old ,r$ ,s&/one volcanic s]ies ( ! neighb\rhood7 #ad ,lime/one 7cem5t-/one1 etc47 #bj ,%ale #c ,s&/one #b ,fossil wood #a ---- #ajj ,:ile _m examples might be cit$ :]e no molt5 rock ( any k9d has ris5 9 ! v5ts1 or :]e at lea/ all ! visible mat]ials are ( a fragm5t>y "*1 yet small ve9s & dykes ( basalt h n infrequ5tly be5 inject$ into ! tuff or agglom]ate4 ,^! seldom run f>1 & usually pres5t a m or less tortu\s c\rse4 ,?us1 on ! s\? front ( ! ,b9n ( ,burntisl& 7,figs4 #aff1 #afh7 a numb] ( basalt-dykes1 :i* v>y 9 bread? f five or six feet to sc>cely s _m in*es1 bifurcate & rapidly disappe> 9 ! tuff1 "o ( !m asc5d+ tortu\sly to ne> ! top ( ! cliff4 ,!y at once recall ! appe>ance ( ! well-kn[n dykes 9 ! great crat] wall ( ,somma4 ,?\gh n by any means ! l>ge/ or mo/ p]fect ( ! v5ts 9 ! bas9 ( ! ,fir? ( ,=?1 ! ,b9n ( ,burntisl&1 ( :i* a view is giv5 9 ,fig4 #add1 may be cit$ 9 illu/ration ( _! g5]al *>act]s4 ,x pres5ts 9 detail "s ( ! mo/ /rik+ly volcanic aspects ( sc5]y any:]e to be se5 9 t region4 ,consi/+ ( a dull gre5 granul> volcanic tuff1 x rises abruptly out ( ! ,l[] ,c>bonif]\s =mations to a height ( #fca feet above ! sea4 ,! s\!rn edge ( ?is neck has be5 s ext5sively d5ud$1 t x pres5ts /eep craggy slopes & rugg$ precipices1 :i* desc5d f ! v summit ( ! cone to ! pla9 bel[--a v]tical di/ance ( ne>ly #ejj feet4 ,"h & !re ! action ( atmosph]ic wa/e has holl[$ out huge crat]-l *asms 9 ! crumbl+ tuff4 ,/&+ 9 "o ( ^!1 ! geologi/ c realize :at mu/ h be5 ! aspect ( ! int]ior ( ^! anci5t ,c>bonif]\s volcanic cones4 ,! sc5e at once rem9ds him ( ! crat]-walls ( a mod]n or n long ext9ct volcano4 ,! dull-gre5 rudely /ratifi$ tuff rises ar\nd 9 v]dureless crumbl+ %eets ( nak$ rock1 r\gh5$ by ! innum]able blocks ( lava1 :i* =m s conspicu\s an elem5t 9 ! composition ( ! mass4 ,! ribs or ve9s ( column> basalt run up ! declivities z black %att]$ walls4 ,! fro/s & ra9s ( _m c5turies h re/or$ to ! tuff its orig9al loose gravelly "*4 ,x dis9tegrates rapidly1 & rolls d[n ! slopes 9 long grey l9es ( volcanic s&1 precisely z x no d\bt did at ! "t ( its ejection1 :5 x fell on ! out] & inn] declivities ( ! orig9al cone4 ,"s ( ^! features may be p>tly realiz$ f ,fig4 #ade1 :i* repres5ts a portion ( ! s\? front ( ! hill4 ,sections ( ?is neck are giv5 9 ,figs4 #adi & #aei4 7#c7 ,necks ( ,tuff or ,agglom]ate ) a ,c5tral ,plug ( ,basalt or o!r ,lava4--,x has (t5 happ5$ t1 aft] ! explosions 9 a v5t h begun to decrease 9 vig\r1 or h at la/ ceas$1 lava has ris5 9 ! *imney & f9ally seal$ x up4 ,9 su* cases ! ma9 mass ( ! rock may consi/ ( tuff or agglom]ate1 :i* ! enfeebl$ volcanic activity has be5 unable to expel f ! orifice1 :ile a plug ( basalt1 dol]ite1 or ev5 m basic mat]ial1 ( mu* small] dim5sions1 may h ris5 up ! pipe 9 ! c5tre or t[>ds "o side4 ,b9ns ,hill1 ,we/ ,lo?ian1 ! ,bea? & ,sal9e ,hills ( ,fife1 & ,t9nis ,hill 9 ,liddesdale are good examples ( ?is /ructure4 7,see ,figs4 #bf1 #adh1 #adi & #agd74 7#d7 ,necks ( ,basalt1 ,dol]ite1 etc4--,9 o!r cases no fragm5tal mat]ial is pres5t 9 ! v5t1 or possibly traces ( x may be se5 "h & !re adh]+ to ! walls ( ! funnel1 ! prevail+ rock be+ "s =m ( lava4 ,necks ( ?is k9d are mu* less frequ5t 9 ! puy- ?an 9 ! plateau-type4 ,b examples may be f\nd 9 sev]al di/ricts4 ,! mo/ /rik+ ) :i* ,i am acqua9t$ are ^? :i* =m s picturesque a gr\p ( isolat$ cones ar\nd ! volcanic bas9 ( ,lim]ick1 to be aft]w>ds describ$ 7,figs4 #aie1 #aif74 ,! v5ts !re h be5 fill$ by ! uprise ( mu* m acid rocks ?an ! lavas ( ! bas91 =1 z ,i h already /at$1 !y include ev5 qu>tzif]\s tra*ytes4 ,9 ! bas9 ( ! ,fir? ( ,=? "s prom95t bosses ( basalt probably m>k ! sites ( =m] v5ts1 su* z ,dune>n ,hill 9 ,fife1 ! ,ca/le ,rock ( ,ed9burgh1 & ,galabraes ,hill ne> ,ba?gate4 ,"s /rik+ v5ts :i* occur 9 ! ,j$burgh di/rict1 9 ! debateable l& betwe5 ! plateau s]ies on ! ea/ & ! puy-s]ies on ! we/1 %[ ! ne>ly complete usurpation ( ! funnel by basalt1 b ) portions ( ! tuff /ill rema9+ visible4 ,relation ( ! ,necks to ! ,rocks ?r\gh :i* !y rise4--,a rem>kable feature among ! ,c>bonif]\s & ,p]mian v5ts ( c5tral ,scotl& is pres5t$ by ! effect :i* has be5 produc$ on ! /rata imm$iately surr\nd+ !m4 ,9 ! int]ior ( ! c\ntry ?is effect is (t5 ,illu/ration3 ,fig4 #ade4--,view ( "p ( ! cliffs ( v]tical agglom]ate1 ,b9n ( ,burntisl&4 conceal$ by h]bage1 b :]e ! rocks h be5 laid b>e by ! sea x may be mo/ in/ructively /udi$4 ,9 su* %ore-sections1 a s+ul> *ange ( dip is (t5 obs]vable among ! /rata r\nd ! edge ( a v5t4 ,no matt] :at may be ! normal incl9ation at ! locality1 ! b$s are b5t %>ply d[n t[>ds ! wall ( ! neck1 & are frequ5tly plac$ on end4 ,?is /ructure 7%[n 9 ,figs4 #bd1 #adc1 #adg1 #adh & #adi7 is precisely ! rev]se ( :at might h be5 anticipat$1 & c h>dly be due to upw>d volcanic explosions4 ,x is frequ5tly associat$ ) consid]able metamorphism 9 ! di/urb$ /rata4 ,%ales are conv]t$ into porcellanite or v>i\s jasp]y rocks1 accord+ to _! composition4 ,s&/ones pass into qu>tzite1 ) its *>act]i/ic lu/r\s fracture4 ,x is common to f9d v5ts surr\nd$ ) a r+ ( ?is contact-metamorphism1 :i*1 f ! h>dness & frequ5tly v]tical or highly incl9$ b$d+ ( its /rata1 /&s up prom95tly on ! bea* 7z 9 ,figs4 #abf & #baj71 & s]ves to m>k ! position ( ! necks f a di/ance4 ,i h n be5 able to f9d an altoge!r satisfactory explanation ( ?is inw>d dip ( ! /rata ar\nd v5ts4 ,tak+ x 9 connection ) ! metamorphism1 ,i am incl9$ to believe t x arose aft] ! close ( ! long-cont9u$ volcanic action :i* _h h>d5$ ! rocks ar\nd ! volcanic pipe1 & z ! result ( "s k9d ( subsid5ce )9 ! v5t4 ,! outp\r+ ( s mu* tuff & lava z escap$ f _m ( ! volcanoes w\ld d\btless (t5 be apt to produce cavities und]nea? !m1 & on ! decay ( volcanic en]gy !re might be a t5d5cy 9 ! solid or cav]n\s column fill+ up ! funnel1 to settle d[n by m]e gravitation4 ,s firmly1 h[ev]1 did mu* ( x coh]e to ! sides ( ! pipe1 t if x sank at all1 x c\ld h>dly fail to drag d[n a portion ( ^! sides4 ,s g5]al is ?is evid5ce ( d[nw>d movem5t 9 all ! volcanic di/ricts ( ,scotl& :]e ! necks h be5 adequately expos$1 t ! /ructure may be reg>d$ z normal to ^! volcanic v5ts4 ,x has be5 obs]v$ among ! %ore-sections ( ! volcanoes ( ! ,auckl& di/rict1 ,new ,zeal&4 ,mr4 ,c4 ,heaphy1 9 an int]e/+ pap] ^u t di/rict1 gives a draw+ ( a crat] & lava-/ream abutt+ on ! edge ( a cliff :]e ! /rata b5d d[n t[>ds ! po9t ( eruption1 z 9 ! num]\s cases 9 ,scotl&4#def ,footnote #def3 ,qu>t4 ,j\rn4 ,geol4 ,soc4 #ahfj1 vol4 xvi4 p4 #bde4 ,evid5ce = ! probable subrial ,"* ( "s ( ! ,cones or ,puys ( ,tuff4--,f ! /ratigraphical data furni%$ by ! bas9 ( ! ,fir? ( ,=?1 x is c]ta9 t ?is region1 dur+ a great "p ( ! ,c>bonif]\s p]iod1 exi/$ z a wide %all[ lagoon1 sometimes ov]spread ) sea-wat] deep en\gh to all[ ( ! gr[? ( corals1 cr9oids1 & bra*iopods2 at o!r times1 %oal$ to su* an ext5t ) s& & mud z to be cov]$ ) wide jungles ( a lepidod5droid & calamitoid vegetation4 ,z volcanic action w5t on int]rupt$ly dur+ a va/ section ( t p]iod1 ! v5ts1 ?\gh g5]ally subm>9e1 may occasionally h be5 subrial4 ,inde$1 we may suppose t ! same v5t might beg9 z a subaque\s orifice & cont9ue to eject volcanic mat]ials1 until1 z ^! rose above ! level ( ! wat]1 ! v5t became subrial4 ,an in/ance ( a subm>9e v5t has be5 cit$ f ! ,p]?%ire coal-field 7p4 #dbf74 ,among ! evid5ce :i* may be collect$ to %[ t "s ,c>bonif]\s volcanoes probably rose z insul> cones ( tuff above ! surr\nd+ wat]s1 ! /ructure ( ! tuff 9 _m necks may be cit$1 = x sugge/s subrial r ?an subaque\s /ratification4 ,! way 9 :i* ! /ones1 l>ge & small1 are gr\p$ toge!r 9 l5ticul> seams may be p>allel$ on ! slopes ( _m a mod]n volcano4 ,ano!r indication ( ?is mode ( orig9 is suppli$ by ! traces ( wood to be met ) 9 "s ( ! tuff-necks4 ,! v5ts ( ,fife & ,l9li?g[%ire conta9 ^! traces sometimes 9 great abundance4 ,! specim5s are always angul> fragm5ts1 & are frequ5tly encru/$ ) calcite4#deg ,sometimes !y pres5t ! glossy fracture & cle> ligne\s /ructure %[n by /icks ( well-made wood *>coal4 ,9 a neck at ,/4 ,magdal5's1 ne> ,l9li?g[1 ! wood fragm5ts occur z num]\s black *ips4 ,s f> z c be asc]ta9$ f ! slices already prep>$ = ! microscope1 ! wood is always conif]\s4 ,^! woody fragm5ts seldom occur 9 ! int]/ratifi$ tuffs or 9 ! associat$ /rata :]e ,/igm>ia1 ,lepidod5dron1 etc41 are common4 ,!y are specially *>act]i/ic ( ! necks & adjac5t tuffs4 ,! p>5t trees may h gr[n on ! volcanic cones1 :i* z dry insul> spots w\ld support a diff]5t vegetation f ! club-mosses & re$s ( ! surr\nd+ swamps4 ,z ! fragm5ts occur 9 ! tuffs :i*1 on ! gr\nds already /at$1 may be held to h be5 deposit$ )9 ! crat]1 !y seem to po9t to int]vals ( volcanic quiesc5ce1 :5 ! dormant or ext9ct crat]s 7 fill$ ) a t]re/rial flora1 z ,vesuvius 0 betwe5 ! ye>s #aejj & #afca1 :5 no eruptions took place4 ,"s ( ! cones1 su* z ,sal9e ,hill & ! ,b9n ( ,burntisl&1 may h ris5 sev]al hundr$ feet above ! wat]4 ,clo!d ) d>k p9e woods1 !y w\ld =m a notable feature 9 ! o!rwise monoton\s sc5]y ( c5tral ,scotl& dur+ ! ,c>bonif]\s p]iod4 ,footnote #deg3 ,! l>ge/ ,i h obs]v$ is a portion ( a /em ab\t two feet long & six in*es broad1 9 ! 7,p]mian87 neck bel[ ,/4 ,monan's *ur*4 ,entombm5t ( ! ,volcanic ,cones & _! relation to ! b$d$ ,lavas & ,tuffs4--,f ! facts above detail$1 x is evid5t t 9 mo/ cases ! necks repres5t1 z x 71 ! m]e d5ud$ /umps ( ! volcanoes4 ,z ! puys took _! rise 9 areas :i*1 on ! :ole1 7 und]go+ a movem5t ( subsid5ce1 !y 7 ev5tually subm]g$ & buri$ "u s$im5t>y accumulations4 ,_! loose a%es w\ld be apt to be wa%$ d[n & /rewn ov] ! sea-bottom1 s t only ! l[] & inn] "p ( a cone might rema94 ,we c h>dly hope to discov] any ( ! actual crat]s among ^! volcanic relics4 ,! cones hav+ be5 subm]g$ & buri$ "u _m hundr$ feet ( s$im5t1 _! pres5t position at ! surface is due to subsequ5t elevation & prolong$ d5udation4 ,x is obvi\s t !re mu/ /ill be _m buri$ cones :i* ! progress ( d5udation has n yet rea*$4 ,"s ( ^! h be5 reveal$ 9 ! c\rse ( m9+ op]ations4 ,valuable seams ( coal1 iron/one & oil-%ale 9 ! ,scotti% ,c>bonif]\s ,lime/one & ,calcif]\s ,s&/one s]ies are ext5sively work$1 & 9 ! und]gr\nd op]ations _m illu/rations ( =m] volcanic action h be5 met )4 ,! mo/ rem>kable in/ances ( ! discov]y ( buri$ volcanoes h occurr$ 9 ! ,dalry coal-field 9 ! nor? ( ,ayr%ire4 ,9 "o pit-%aft ab\t a mile & a half to ! s\?-we/ ( ! village ( ,dalry1 a ?ickness ( #aae fa?oms ( tuff 0 pass$ ?r\gh1 & 9 ano!r pit #ij fa?oms ( simil> tuff 7 sunk into be=e ! position ( ! black-b& iron/one ( t m9]al field 0 rea*$ by driv+ levels ?r\gh ! tuff into ! s$im5t>y /rata outside ( x4 ,only a %ort di/ance f ^! ?ick piles ( tuff1 _! place is entirely tak5 up by ! ord9>y s$im5t>y /rata ( ! di/rict4 ,! work+-plans ( ! m9es %[ ! tuff to occur 9 irregul> pat*es & /rips1 betwe5 :i* ! iron/one is workable4 ,f ^! data we p]ceive t ! %afts h 9 "s cases be5 sunk directly ^u ! tops ( puys ( tuff1 :i* 71 9 "o case1 ne>ly #gjj feet1 & 9 ano!r in/ance1 #edj high#deh 7,fig4 #adf74 ,footnote #deh3 ,explanation ( ,%eet #bb1 ,geol4 ,surv4 ( ,scotl&1 p4 #af4 ,illu/ration3 ,fig4 #adf4--;,diagram ( buri$ volcanic cone ne> ,dalry1 ,ayr%ire4 ,con/ruct$ f in=mation obta9$ 9 m9+ op]ations4 #a4 ,hurlet ,lime/one4 #b4 ,clayb& ,iron/one4 #c4 ,black-b& ,iron/one4 #d4 ,bore/one ,coal4 #e4 ,wee ,coal4 #f4 ,highfield ,lime/one4 #g & #h4 ,?9 ,lime/ones4 #i4 ,l9n ,lime/one4 #aj4 ,volcanic neck & cone ( tuff4 ,x is obvi\s t f ! condition ( a completely buri$ & conceal$ cone e /age may be expect$ to occur up to ! deeply worn-d[n neck repres5t+ m]ely ! /ump ( ! volcanic column4 ,! subjo9$ diagram 7,fig4 #adg7 may s]ve to illu/rate ?is process ( gradual re-em]g5ce4 ,illu/ration3 ,fig4 #adg4--;,diagram to illu/rate h[ ,volcanic ,necks may be conceal$ & expos$4 #a1 ,neck1 /ill buri$ "u ! succe$+ s$im5t>y accumulations2 #b1 ,neck uncov]$ & d5ud$4 ,:51 9 ! progress ( d5udation1 a volcanic cone began to %[ itself f "u ! cov] ( remov$ /rata1 x w\ld /ill = a "t ma9ta9 its connection ) ! %eets ( tuff or ( lava :i*1 :5 active1 x _h erupt$4 ,a numb] ( examples ( ?is /ructure may be obs]v$ 9 ! bas9 ( ! ,fir? ( ,=?1 :]e ! degradation ( ! surface has n yet proce$$ s f> z to isolate ! column ( agglom]ate or tuff f ! %eets ( tuff t 7 /rewn ar\nd ! old volcano4 ,9 su* cases1 ! actual limits ( ! v5t are /ill m or less conceal$1 or at lea/ no %>p l9e c be drawn betwe5 ! v5t & its ejections4 ,z an illu/ration ( ?is connection ( a volcanic pipe ) ! mat]ials eject$ f x ov] ! surr\nd+ c\ntry ,i w\ld cite ,sal9e ,hill 9 ! we/ ( ,fife4 ,t em95ce rises to a height ( #aagh feet above ! sea1 out ( a b& ( tuff :i* c be trac$ across ! c\ntry = fully ?ree miles4 ,num]\s sections 9 ! wat]-c\rses %[ t ?is tuff is regul>ly int]b$d$ 9 ! ,c>bonif]\s ,lime/one s]ies1 s t ! relative geological date ( its eruption c be precisely fix$4 ,on ! s\? ( ,sal9e ,hill1 coal & iron/one1 work$ "u ! tuff1 prove t ?is portion ( ! mass belongs to ! g5]al %eet ( loose a%es & du/1 ext5d+ outw>ds f ! orig9al cone ov] ! floor ( ! %eet ( wat] 9 :i* ! ,c>bonif]\s ,lime/one s]ies ( /rata 0 be+ deposit$4 ,b ! c5tral portion ( ! hill is occupi$ by "o or m volcanic pipes4 ,a section across ! em95ce f nor?-we/ to s\?-ea/ w\ld probably %[ ! /ructure repres5t$ 9 ,fig4 #adh4 ,imm$iately to ! ea/ ( ! ,sal9e ,hill lies ano!r em95ce1 kn[n z ! ,knock ,hill1 :i* m>ks ! site ( ano!r eruptive v5t4 ,a coal-seam 7! ,little ,p>rot or ,gas ,coal7 is work$ along its s\!rn base1 & is f\nd to plunge d[n /eeply t[>ds ! volcanic rocks4 ,?is seam1 h[ev]1 is n ! same z t work$ "u ! ,sal9e ,hill1 b lies "s #fjj feet bel[ x4 ,probably ! :ole ( ! ,knock ,hill occupies ! place ( a =m] v5t4 ,illu/ration3 ,fig4 #adh4--,section across ! ,sal9e ,hills1 ,fife4 ,! ?ick p>allel black l9es m>k ! position ( seams ( coal & iron/one1 "s ( :i* are work$ "u ,sal9e ,hill4 ,t1 ,tuff ( ! necks2 t1 ,tuff at a little di/ance f ! cone1 int]/ratifi$ ) ! ord9>y s$im5t>y b$s2 ,b1 ,basalt4 ,! l>g] em95ce is ,sal9e ,hill1 ! l[] is ,knock ,hill4 ,a fur!r /age ( decay & d5udation br+s be=e u ! entire sev]ance ( ! volcanic column f ! mat]ials t 7 eject$ f x4 ,an excell5t example ( ?is isolation ( ! neck 9 ! mid/ ( surr\nd+ masses ( tuff & lava :i* proce$$ f x is pres5t$ by ! ,b9n ( ,burntisl&1 to :i* ,i h already allud$4 ,a section across t em95ce gives ! geological /ructure repres5t$ 9 ,fig4 #adi4 ,! dip ( ! rocks away f ! volcanic pipe at ?is locality has be5 produc$ long aft] ! volcanic ph5om5a _h ceas$4 ,! ar* "h %[n is really ! prolongation & f9al disappe>ance ( ! great anticl9al fold ( :i* ! ,p5tl& ,hills =m ! axis on ! opposite side ( ! ,fir?4 ,b if we re/ore ! rocks to a horizontal1 or approximately horizontal position1 we f9d ! ,b9n ( ,burntisl& ris+ among !m 9 "o or m necks1 :i* d\btless m>k c5tres ( volcanic activity 9 t di/rict4 ,a s]ies ( small] neck-l em95ces runs = two miles we/w>d4 ,/rik+ z ! =ms ( _m ( ! necks are1 & mu* z _! pres5t conical =ms resemble ^? ( active & ext9ct volcanoes1 ! evid5ce ( ext5sive d5udation proves t ^! cont\rs are n ! orig9al outl9es ( ! ,c>bonif]\s v5ts1 b are 9 e case ! result ( prolong$ wa/e4 ,:at we n[ see is a section ( ! volcanic *imney1 & ! conical =m is due to ! way 9 :i* ! mat]ials fill+ ! *imney h yield$ to ! =ces ( d5udation4 ,illu/ration3 ,fig4 #adi4--,section across ! ,b9n ( ,burntisl&1 9 an ,ea/ & ,we/ direction4 #a1 ,s&/ones2 #b1 ,lime/one 7,burdieh\se72 #c1 ,%ales1 etc42 b1 b1 ,int]/ratifi$ basalts2 t t1 ,b$d$ tuff1 etc42 ,t1 ,tuff ( ! great neck ( ,burntisl&2 ,b1 ,basalt ve9s4 ii4 ,,b$d$ ,,tuffs ,,& ,,lavas ,dur+ at lea/ ! e>li] "p ( ! p]iod ( ! puys1 9 "s di/ricts or f c]ta9 v5ts1 su* z ^? ( ,ea/ ,fife1 ,we/]n ,midlo?ian1 ,ea/]n ,l9li?g[%ire1 ,nor!rn ,ayr%ire1 ,heads ( ,ayr & ,l[] ,eskdale1 only f9e tuff seems to h be5 ?r[n out1 :i* we n[ f9d int]calat$ among ! surr\nd+ /rata4 ,^! eruptions1 nei!r s vigor\s nor s long-cont9u$ z ^? ( ! plateaux1 nev] gave =? su* ?ick & widespread %eets ( fragm5t>y mat]ials z ^? associat$ ) ! plateaux 9 ,ea/ ,lo?ian & ! nor?-ea/ ( ,ayr%ire4 ,a s+le dis*>ge ( a%es seems 9 _m cases to h be5 ! sole a*ievem5t ( "o ( ^? little volcanoes2 at lea/ only "o ?9 b& ( tuff may be discov]able to m>k its activity4 ,! tuff ( ^! solit>y b&s is seldom co>se 9 texture4 ,x usually consi/s ( ! ord9>y dull gre5 pa/e1 ) du/ & lapilli ( basic pumice4 ,! local v>iations 9 ! tuffs ( ! puys g5]ally arise ma9ly f diff]5ces 9 ! composition1 size & numb]s ( ! includ$ eject$ blocks4 ,g5]ally ! mo/ abundant /ones are pieces ( diff]5t diabases1 or basalts2 !n come fragm5ts f ! surr\nd+ ,c>bonif]\s /rata1 f old] tuffs & r>ely f rocks ( mu* deep]-seat$ orig94 ,n[ & !n ! eruptions ( tuff h consi/$ ( extremely f9e volcanic du/1 :i*1 m+l+ ) wat]1 took ! =m ( a compact mud/one1 z 9 ! case ( ! ,h\/on ,m>ls 7p4 #dbc71 :i* rem9d "o ( a volcanic mud4 ,b 9 mo/ localities ! dis*>ge ( tuff1 ?\gh = a "t x may h completely obscur$ ! ord9>y contemporane\s s$im5tation1 0 int]mitt5t1 s t 9 ! int]vals betwe5 successive %[]s ( detritus1 ! deposition ( non-volcanic s$im5t w5t on z usual4 ,h5ce x is t b&s ( tuff1 :e!r !y lie among lavas or among s$im5t>y =mations1 are apt to conta9 int]/ratifications ( s&/one1 %ale1 lime/one or o!r detrital deposit1 & to pass ins5sibly into ^!4 ,! extremely g5tle gradation f volcanic into non-volcanic s$im5t1 & ! occasional reappe>ance ( ?9 p>t+s ( tuff br+ vividly be=e ! m9d ! sl[ dy+ out ( volcanic en]gy among ! ,c>bonif]\s lagoons4 ,illu/ration3 ,fig4 #aej4--,section 9 old qu>ry1 we/ ( ,we/] ,o*iltree1 ,l9li?g[%ire4 ,calcif]\s ,s&/one s]ies4 ,! comp>atively quiet "* ( ! volcanic explosions1 & ! contemporane\s undi/urb$ deposition ( s$im5t dur+ ! e>li] "p ( ! puy p]iod1 are exemplifi$ 9 _m sections ?r\gh\t ! areas above enum]at$1 z w be m fully illu/rat$ 9 subsequ5t pages4 ,two typical examples may suffice = ?is g5]al /atem5t ( ! *>act]s ( ! dis*>ges ( tuff 9 ! puy-eruptions4 ,9 ! ,l9li?g[%ire qu>ry repres5t$ 9 ,fig4 #aej1 :]e ab\t t5 feet ( /rata h be5 expos$1 a black %ale 7#a7 ( ! usual c>bonace\s "*1 s common 9 ! ,oil-%ale s]ies ( ?is region1 may be se5 at ! bottom ( ! section4 ,x is cov]$ by a b$ ( nodul> blui%-grey tuff 7#b7 conta9+ black %ale fragm5ts4 ,a second black %ale 7#c7 is succe$$ by a second ?9 b& ( f9e pale yell[i% tuff 7#d74 ,black %ale 7#e7 aga9 sup]v5es1 conta9+ r\nd$ fragm5ts ( tuff1 p]haps eject$ lapilli1 & pass+ up into a lay] ( tuff 7#f74 ,x is evid5t t we h "h a cont9u\s deposit ( black %ale :i* 0 ?ree times int]rupt$ by %[]s ( volcanic du/ & /ones4 ,at ! close ( ! ?ird int]ruption1 ! deposition ( ! %ale 0 r5ew$ & cont9u$1 ) suffici5t sl[ness to p]mit ( ! segregation ( ?9 seams & nodules ( clay iron/one r\nd ! decompos+ organic rema9s ( ! muddy bottom 7#g74 ,a f\r? volcanic int]lude n[ took place1 & ! floor ( ! wat] 0 once m cov]$ ) tuff 7#h74 ,b ! old conditions ( deposit 7 imm$iately aft]w>ds resum$ 7#i72 ! muddy bottom 0 abundantly peopl$ ) o/racod cru/aceans1 :ile _m fi%es1 ^: coprolites h be5 left 9 ! mud1 haunt$ ! locality4 ,at la/1 h[ev]1 a mu* m s]i\s volcanic explosion took place4 ,a co>se agglom]atic tuff 7#aj71 ) blocks sometimes ne>ly ?ree feet 9 diamet]1 0 !n ?r[n out1 & ov]spread ! lagoon4#dei ,footnote #dei3 ,see ,geol4 ,surv4 ,memoir ( ,ed9burgh1 p4 #de4 ,^! tuffs are fur!r describ$ on pp4 #dfe et seq4 ,! second illu/ration may be tak5 f ! admirable coa/-section betwe5 ,burntisl& & ,k+horn1 :]e ! numb] ( int]calations ( tuff is v great4 ,besides ?ick] well-m>k$ b&s1 successive innum]able ?9 lay]s occur !re among ! associat$ zones ( s$im5t>y /rata :i* sep>ate ! %eets ( basalt4 ,! "* ( ^! tuff-seams may be inf]r$ f ! foll[+ details ( less ?an two feet ( rock at ,pettycur ,po9t3-- ,tuff #ae in*4 ,lime/one #jb ,tuff #je ,%ale #jb ,tuff #ja ,%ale & tuff #aj ,%ale #jb ,lime/one #je ,%ale full ( volcanic du/ #ce ,%aly lime/one #ae ,lam9at$ tuface\s lime/one #bj ,lime/one 9 ?9 b&s1 ) ?9 lam9 ( tuff #jh ,granul> tuff #jf ,argillace\s lime/one1 ) diffus$ tuff #ji ,f9e granul> tuff #jg ,argillace\s lime/one1 ) diffus$ tuff #ae ,lam9at$ lime/one #ja ,lime/one1 ) p>t+ ( granul> tuff 9 middle #ji ,tuface\s %ale #bj ,lime/one #jd ,%aly tuff #abe ,lam9at$ lime/one #ja ,tuff #ab ----- #bafe in*es4 ,illu/ration3 ,fig4 #aea4--;,eject$ volcanic block 9 ,c>bonif]\s /rata1 ,burntisl&4 #a4 ,br[n %aly fire-clay ) rootlets1 ab\t five in*es2 #b4 ,impure coal1 five or six in*es1 press$ d[n 9 its upp] lay]s by ! impact & weight ( ! /one2 #c4 ,gre5 crumbl+ a%y fire-clay1 "o foot1 ) its l[] lay]s press$ d[n by ! /one :ile ! upp] lay]s rise ov] x1 %[+ t ! /one fell at ! "t :5 half ?is seam 0 deposit$4 ,! fire-clay passes up into d>k gre5i% & black a%y %ale 7#d7 ab\t six in*es ?ick & conta9+ plant-rema9s4 ,! /one is a pale diabase weigh+ ab\t six or eight p\nds4 ,su* a section z ?is br+s vividly be=e ! m9d a long-cont9u$ int]mitt5t feeble volcanic action dur+ pauses betwe5 successive outbur/s ( lava4 ,9 su* int]vals ( quiesc5ce1 ! ord9>y s$im5t ( ! lagoons accumulat$1 & 0 mix$ up ) ! debris suppli$ by occasional %[]s ( volcanic du/4 ,9 ?is ,fife volcanic s]ies1 ?9 lay]s ( s&/one1 /reak$ ) rema9s ( ! ,c>bonif]\s vegetation2 b$s ( %ale full ( cyprid-cases1 ganoid scales1 & fragm5t>y f]ns2 ?9 b$s ( lime/one1 & b&s ( fire-clay support+ seams ( coal1 are int]leav$ ) /rata ( tuff & %eets ( basalt4 ,n[ & !n a %>p dis*>ge ( l>g] /ones is se5 to h tak5 place1 z 9 ! case ( ! block _m ye>s ago describ$ by me z hav+ fall5 & cru%$ d[n a /ill s(t b$ ( coal 7,fig4 #aea74dfj ,footnote #dfj3 ,geol4 ,mag4 vol4 i4 p4 #bb4 ,?is ,fife coa/-section is giv5 9 full at p4 #dgj4 ,illu/ration3 ,fig4 #aeb4--,view ( volcanic agglom]ate becom+ f9] above4 ,ea/ end ( ,k+swood ,craig1 two miles ea/ f ,burntisl&4 ,! ,fife coa/-section f :i* ^! details are tak5 supplies almo/ endless in/ances ( ! v>y+ *>act]s ( ! pyrocla/ic mat]ials ( ! puy-eruptions4 ,! v same cliff1 bank or reef w %[ at "o po9t an accumulation ( excessively co>se volcanic debris & at ano!r ?9 lam9 ( ! f9e/ du/ & lapilli4 ,^! rapid gradations are illu/rat$ 9 ,fig4 #aeb1 :i* is tak5 f ! ea/ end ( ! ,k+swood ,craig4 ,! l[] "p ( ! declivity is a co>se agglom]ate :i* passes upw>d into f9] tuff4 ,besides ! ?9 p>t+s & ?ick] lay]s ( tuff :i*1 int]calat$ among ! s$im5t>y /rata ( ! ,c>bonif]\s sy/em1 m>k a comp>atively feeble & int]mitt5t volcanic activity1 we meet 9 "s localities ) examples :]e ! puys h pil$ up mu* ?ick] accumulations ( fragm5t>y mat]ial )\t any int]calat$ /reams ( lava1 or int]/ratifi$ s&/one1 %ale or lime/one4 ,?us ! widespread ,h\/on m>ls above describ$ rea* a ?ickness ( "s #bjj feet4 ,! v5ts ( ! ,sal9e ,hills 9 ,fife cov]$ ! sea-floor ) volcanic a%es to a dep? ( sev]al hundr$ feet4 ,9 ! nor? ( ,ayr%ire ! fir/ eruptions ( ! puys h =m$ a cont9u\s b& ( f9e tuff traceable = "s #ae miles1 & 9 places at lea/ #bjj feet ?ick4 ,:]e volcanic en]gy rea*$ its highe/ int5sity dur+ ! "t ( ! puys1 n only tuffs b %eets ( lava 7 emitt$1 :i*1 ga!r+ r\nd ! v5ts1 =m$ cones or long1 connect$ banks & ridges4 ,( ^! !re are f\r conspicu\s examples 9 ,scotl&--! hills ( ! ,burntisl& di/rict1 ! ,ba?gate ,hills1 ! gr\nd betwe5 ,dalry & ,gal/on 9 nor? ,ayr%ire1 & a brok5 tract 9 ,liddesdale4 ,n[h]e 9 ! volcanic hi/ory ( ?is c\ntry h ev5 ! m9ute/ details ( t hi/ory be5 m admirably pres]v$ ?an among ! mat]ials erupt$ f puys 9 ^! respective di/ricts4 ,lava-cones1 answ]+ to solit>y tuff-cones among ! fragm5tal eruptions1 d n appe> to h exi/$1 or1 l "s ( ^? 9 ! great lava-fields ( ,nor!rn ,icel& & ,we/]n ,am]ica1 mu/ h be5 m]e small heaps ( slag & c9d]s at ! top ( ! lava-column1 :i* 7 wa%$ d[n & effac$ dur+ ! subsid5ce & entombm5t ( ! volcanic mat]ials4 ,! lavas nev] occur )\t traces ( fragm5t>y dis*>ges4 ,two successive /reams ( basalt may inde$ be f\nd at a giv5 locality )\t any visible int]calation ( tuff1 b pro(s ( ! eruption ( fragm5tal mat]ial w g5]ally be obs]v$ to occur some:]e 9 ! neighb\rhood1 associat$ ) "o or bo? ( !m1 or ) o!r lavas above or bel[ !m4 ,:]e ! ph5om5a ( ! puys h be5 mo/ typically develop$1 lavas & tuffs succe$ ea* o!r 9 rapid succession1 ) num]\s or occasional int]/ratifications ( ord9>y s$im5t4 ,p]haps ! mo/ complete & int]e/+ example ( ?is association is to be f\nd on ! coa/ betwe5 ,burntisl& & ,kirkcaldy1 :]e1 out ( a total ?ickness ( rock :i* may be comput$ to be betwe5 #aejj & #bjjj feet1 x w probably be a fair e/imate to say t ! igne\s mat]ials con/itute f\r-fif?s1 or f ,illu/ration3 ,fig4 #aec4--;,alt]nations ( basalt & tuff ) %ale1 etc41 ,k+swood ,craig1 ,burntisl&4 #abjj to #afjj feet4 ,! lavas are v>ieties ( basalt rang+ 9 "* f a black compact column> to a dirty gre5 e>?y cellul> or slaggy rock4 ,ea* sep>ate fl[ may be on ! av]age ab\t #bj or #cj feet 9 ?ickness4 ,column> & amorph\s %eets succe$ ea* o!r )\t any int]position ( fragm5t>y mat]ial 7,fig4 #aga74 ,b along ! junctions ( ! sep>ate fl[s lay]s ( r$ clay1 l ! bole betwe5 ! basalts ( ! ,giant's ,causeway1 may frequ5tly be notic$4 ,! *>act]i/ic slaggy aspect ( ! upp] p>ts ( ^! anci5t c\les is sometimes rem>kably /rik+4 ,! full details ( ?is mo/ int]e/+ section w be giv5 9 lat] pages 7p4 #dgj74 ,b "s ( its m *>act]i/ic ext]nal features may be und]/ood f ! views :i* are pres5t$ 9 ,figs4 #aeb1 #aec1 #agj1 #aga4 ,! g5]al b$d$ "* ( ! volcanic s]ies is well %[n 9 ,fig4 #aec1 :i* repres5ts ! alt]nations ( lavas & tuffs 9 ! ,k+swood ,craig two miles to ! ea/ ( ,burntisl&4 ,! h>d] basalts w be se5 to project z bold crags :ile ! tuffs & o!r /ratifi$ deposits betwe5 !m give rise to grassy slopes & holl[s4 ,a ne>] view ( ! alt]nation ( lavas & tuffs ) non-volcanic s$im5t>y deposits is suppli$ 9 ,fig4 #agj1 :i* is tak5 f a "p ( ! ,fife coa/ a little fur!r to ! ea/ ?an ! la/ illu/ration4 ,"h "o ( ! lime/ones ( ! ,c>bonif]\s ,lime/one s]ies is ov]la9 ) %ale & tuff1 :i*1 be+ easily dis9tegrat$1 h be5 cut away by ! waves1 leav+ ! lava above to ov]hang & fall (f 9 blocks4 ,! column> /ructure ( "s ( ! basalts ( ?is coa/ is well br\ght out 9 ,fig4 #aga1 :i* %[s fur!r h[ ! columns sometimes m]ge into an amorph\s "p ( ! same %eet4 ,^! ,fife basalts illu/rate admirably ! peculi>ities ( ! %eets ( lava :i* are int]calat$ among ! ,c>bonif]\s /rata4 ,!y %[ h[ easy x g5]ally is to discrim9ate betwe5 su* %eets & intrusive sills4 ,! true lavas are nev] s l>gely cry/all9e1 nor spread out 9 su* ?ick %eets z ! sills2 !y are frequ5tly slaggy & amygdaloidal1 especially t[>ds ! top & bottom1 ! c5tral portion be+ g5]ally m f9e-gra9$ & sometimes porphyritic4 ,:]e mo/ highly cellul> !y (t5 decompose into a dull1 e>?y1 dirty-gre5 rock4 ,:]e !y =m a ?ick mass !y are usually compos$ ( diff]5t b$s ( v>y+ texture4 ,except ! diff]5ces betwe5 ! m compact c5tre & ! slaggy lay] above & bel[1 ! b$d$ lavas d n pres5t any m>k$ v>iation 9 composition or /ructure )9 ! same %eet4 ,a /rik+ exception to ?is rule1 h[ev]1 is furni%$ by ! ,ba?gate leck/one already describ$4#dfa ,?is mass =ms a cont9uation ( ! great basaltic ridge ( ! ,ba?gate ,hills1 & ?\gh its exact relations to ! surr\nd+ /rata are conceal$1 x appe>s to be an int]b$d$ & n an intrusive %eet4 ,! rem>kable sep>ation ( its con/itu5t m9]als into an upp]1 light] felspa?ic lay]1 & a l[]1 heavi] lay]1 ri* 9 oliv9e1 augite & iron-ores1 is a /ructure :i* might be m naturally expect$ to occur 9 a sill4 ,an in/ance ( its developm5t 9 an und\bt$ sill w be describ$ fur!r on4 ,nev]!less1 if we foll[ ! tr5d ( ! volcanic b& ( ! ,ba?gate ,hills s\?w>d = only two miles beyond ! picrite qu>ry1 we f9d 9 ! ,skolie ,burn a rock 9 _m respects simil>1 & qu>ri$ = ! same purpose ( build+ ov5-soles4 ,?is leck/one is !re se5 to be surm\nt$ by a gr\p ( calc>e\s %ales & ?9 lime/ones4 ,! section laid b>e 9 ! /ream is repres5t$ 9 ,fig4 #aed4 ,imm$iately above ! diabase1 :i* is highly cellul>1 lies a gre5 felspa?ic s&/one or %ale conta9+ deta*$ fragm5ts ( ! amygdaloid toge!r ) ,l+ul & o!r %ells4 ,!re seems no reason to d\bt t ?is is a true int]/ratifi$ lava4#dfb ,footnote #dfa3 ,trans4 ,roy4 ,soc4 ,ed94 xxix4 7#ahgi7 p4 #ejd4 ,footnote #dfb3 ,trans4 ,roy4 ,soc4 ,ed94 xxix4 7#ahgi71 pp4 #eje-ejg4 ,illu/ration3 ,fig4 #aed4--,section ( ! upp] surface ( a diabase 7leck/one7 %eet1 ,skolie ,burn1 s\?-ea/ ( ,ba?gate4 #a4 ,slaggy diabase2 #b4 ,gre5 s&y %ale & %aly s&/one conta9+ ,l+ul1 also pieces ( slag f ! und]ly+ lava1 :i* are completely wrapp$ r\nd 9 ! s$im5t2 #c4 ,yell[ calc>e\s %elly s&/one2 #d4 ,d>k %ale ) ,spirif]1 etc42 #e4 ,b$ ( blue cr9oidal lime/one2 #f4 ,clays & ?9 coal2 #g4 ,black & blue calc>e\s %ales & ?9 lime/ones4 ,:]e ! puys atta9$ _! greate/ developm5t 9 ,scotl&1 !y rose 9 ! %all[ lagoons1 & "h & !re f deep] p>ts ( ! sea-bottom1 until by _! successive dis*>ges ( lavas & tuffs !y gradually built up piles ( mat]ial1 :i*1 9 ! ,l9li?g[ & ,ba?gate di/rict1 may h be5 ne>ly #bjjj feet 9 ?ickness4 ,x mu/ be rememb]$1 h[ev]1 t ! eruptions took place 9 a subsid+ area1 & t ev5 ! ?icke/ volcanic ejections1 if ! d[nw>d movem5t kept pace ) ! volcanic activity1 ne$ n h gr[n into a l(ty volcanic hill4 ,inde$1 l>gely z ! lavas & tuffs bulk 9 ! geology ( "s p>ts ( ,c5tral ,scotl&1 _! eruption does n seem to h s]i\sly int]f]$ ) ! broad] physical *anges t 7 9 progress ov] ! :ole region4 ,?us ! subsid5ce :i* l$ to ! spread ( a m>9e & lime/one-mak+ fauna ov] mu* ( ,c5tral ,scotl& includ$ also ! volcanic di/ricts4 ,! lime/ones1 =m$ ( cr9oids1 corals & o!r m>9e organisms1 ext5d$ ov] ! subm]g$ lavas & tuffs1 & 7 ev5 int]/ratifi$ ) !m4 ,:ile ! volcanic mat]ials are f\nd to replace locally ! ord9>y ,c>bonif]\s s$im5t>y /rata1 x is int]e/+ 9 ?is reg>d to note t1 dur+ pauses 9 ! volcanic activity1 :ile ! subsid5ce d\btless 0 /ill go+ on1 "s gr\ps ( s&/ones1 %ales or lime/ones ext5d$ !mselves across ! volcanic ridges s z to int]pose1 on m ?an "o plat=m1 a mass ( ord9>y s$im5t betwe5 ! lavas or tuffs already erupt$ & ^? ( succe$+ dis*>ges1 & ?us to furni% valuable geological *ronomet]s by :i* to def9e ! /ratigraphical horizons ( ! successive phases ( volcanic en]gy4 ,illu/ration3 ,fig4 #aee4--,section across ! volcanic ridge ( ! ,l9li?g[ & ,ba?gate ,hills1 %[+ ! int]calation ( lime/ones t m>k important /ratigraphical horizons4 #a4 ,h\/on ,coal2 #b4 ,h\/on ,m>ls & tuffs2 #c4 ,int]/ratifi$ %eets ( basic lavas ) occasional tuffs & int]calations ( %ale1 s&/one1 etc42 #d4 ,t>trav5 ,lime/one2 #e4 ,hurlet ,lime/one ) tuffs1 %ales & s&/ones above & bel[2 #f4 ,w>dlaw ,lime/one2 #g4 ,index ,lime/one2 #h4 ,highe/ b& ( tuff--upw>d limit ( ! volcanic s]ies2 #i #i4 ,volcanic necks2 #aj4 ,sill ( basalt2 #aa4 ,lev5seat or ,ca/lec>y ,lime/one2 #ab4 ,mill/one ,grit2 #ac4 ,base ( ,coal-measures2 #ad4 ,?ick dol]itic sill2 #ae4 ,dol]ite dyke 78 ,t]ti>y74 ,! volcanic banks or ridges n improbably em]g$ z islets out ( ! wat]1 & 7 sometimes t5 miles or m 9 l5g?4 ,_! mat]ials 7 suppli$ f _m sep>ate v5ts along _! surface1 b probably nev] atta9$ to any?+ approa*+ ! elevation :i* !y w\ld h rea*$ _h !y be5 p\r$ out ^u a /able plat=m4 ,?is feature 9 ! hi/ory ( ! volcanic ridges is admirably %[n by ! fact j ref]r$ to1 t recognizable /ratigraphical horizons c sometimes be trac$ "r ?r\gh ! he>t ( ! ?icke/ volcanic accumulations4 ,"o ( ! l>ge/ areas ( basalts & tuffs connect$ ) ! puys is t ( ! ,l9li?g[ & ,ba?gate ,hills1 :]e1 z already rem>k$1 a dep? ( "s #bjjj feet ( igne\s rocks has be5 pil$ up4 ,yet sev]al well-kn[n seams ( /one c be trac$ ?r\gh x1 su* z ! ,hurlet ,lime/one & ! ,index ,lime/one 7,fig4 #aee74 ,only at ! nor? end1 :]e ! volcanic mass is ?icke/ & ! surface-exposures ( rock are n cont9u\s1 has x be5 impossible to subdivide ! mass by mapp+ int]calations ( s$im5t>y /rata across x4 ,x w\ld ?us seem t1 ev5 :]e ! ample/ accumulations ga!r$ r\nd ! puys1 !y =m$ l[ flat domes1 r ?an prom95t hills1 :i*1 z subsid5ce w5t on & ! tuff-cones 7 wa%$ d[n1 gradually sank "u wat]1 & 7 buri$ "u ! accumulat+ silt ( ! sea-floor4 ,z a detail$ illu/ration ( ! mann] 9 :i* ! gr[? ( organically-=m$ lime/ones & ! deposit ( ord9>y s$im5t took place concurr5tly ) ! occasional outfl[ ( lava-/reams ov] ! sea-bottom1 ,i may cite ! section pres5t$ 9 ano!r ,l9li?g[%ire qu>ry 7,fig4 #aef74 ,at ! bottom ( ! gr\p ( /rata !re expos$1 a pale amygdaloidal1 some:at alt]$ basalt 7,a7 m>ks ! upp] surface ( "o ( ! subm>9e lavas ( ! p]iod4 ,directly ov] x comes a b$ ( lime/one 7,b7 #ae feet ?ick1 ! l[] lay]s ( :i* are made up ( a d5se gr[? ( ! ?9-/emm$ coral ,li?o/rotion irregul>e4 ,! next /ratum is a b& ( d>k %ale 7,c7 ab\t two feet ?ick1 foll[$ by ab\t ! same ?ickness ( an impure lime/one ) %ale seams 7,d74 ,! conditions = coral & cr9oid gr[? 7 evid5tly n fav\rable1 = ?is argillace\s lime/one 0 ev5tually arre/$ fir/ by ! deposit ( a d>k mud1 n[ to be se5 9 ! =m ( ?ree or f\r in*es ( a black pyrit\s %ale 7,e71 & next by ! inroad ( a l>ge quantity ( d>k s&y mud & drift vegetation1 :i* has be5 pres]v$ z a s&y %ale 7,f71 conta9+ ,calamites1 ,producti1 ganoid scales & o!r traces ( ! life ( ! "t4 ,f9ally1 a great %eet ( lava1 repres5t$ by ! upp]mo/ amygdaloid 7,g71 ov]spread ! area1 & seal$ up ^! records ( ,palozoic hi/ory4#dfc ,footnote #dfc3 ,geol4 ,surv4 ,mem4 ,geology ( ,ed9burgh1 p4 #eh4 ,illu/ration3 ,fig4 #aef4--,section 9 ,w>dlaw ,qu>ry1 ,l9li?g[%ire4 ,among ! ph5om5a associat$ ) ! ,c>bonif]\s volcanoes m5tion may1 9 conclusion1 be made ( ! evid5ce = ! =m] exi/5ce ( !rmal spr+s & sal9e sublimations or incru/ations4 ,among ! plateau-tuffs ( ,nor? ,b]wick1 z has be5 already po9t$ out 7p4 #cij71 a ftid lime/one has be5 qu>ri$1 :i* be>s indications ( hav+ be5 deposit$ by spr+s1 probably 9 connection ) ! volcanic action ( ! di/rict4 ,! l[] lime/ones ( ,ba?gate furni% abundant lam9 ( silica int]leav$ ) calc>e\s matt]1 ! :ole probably due to ! action ( silice\s & calc>e\s spr+s connect$ ) ! active puys ( t di/rict4 ,"s portions ( ! lime/one are full ( cellul> spaces1 l9$ ) *alc$ony4#dfd ,a sal9e wat] has be5 met ) among ! volcanic rocks to ! we/ ( ,l9li?g[1 9 a bore :i* 0 sunk to a dep? ( #cdh feet 9 ^! rocks )\t rea*+ _! bottom4 ,! wat] t rose f ! bore-hole 0 f\nd to conta9 z mu* z #ace gra9s ( *loride ( sodium 9 ! gallon4 ,x is n improbable t ?is salt 0 orig9ally produc$ by incru/ations on ! ,c>bonif]\s lavas imm$iately aft] _! eruption1 z has happ5$ s (t5 9 rec5t times at ,vesuvius1 & t x 0 !n buri$ "u succe$+ %[]s ( tuff & /reams ( lava4#dfe ,footnote #dfd3 ,ibid4 p4 #di1 et seq4 ,footnote #dfe3 ,proc4 ,roy4 ,soc4 ,ed94 vol4 ix4 p4 #cfg4 ,besides *loride ( sodium ! wat] conta9$ also *lorides ( calcium1 magnesium & potassium1 c>bonates ( lime & magnesia1 sulphate ( lime1 & o!r +r$i5ts 9 m9ute proportions4 ,subsequ5t ,dislocation ( ,b$d$ ,lavas & ,tuffs4--,z ! int]/ratifi$ volcanic mat]ials 7 laid d[n 9 %eets at ! surface1 !y necess>ily behave l ! ord9>y s$im5t>y /rata1 & h und]gone ) !m ! v>i\s curvatures & fractures :i* h occurr$ s9ce ,c>bonif]\s times4 ,not)/&+ _! volcanic nature1 !y c be trac$ & mapp$ precisely z if !y _h be5 lime/ones or s&/ones4 ,?is p]fect con=mability ) ! associat$ /ratifi$ rocks is /rik+ly se5 9 ! case ( ! %eets ( lava :i* lie imb$d$ 9 ! he>t ( ! great volcanic ridge ( ,l9li?g[%ire4 ,! ov]ly+ /rata hav+ be5 remov$ f _! surface = "s di/ance1 & ! gr\nd hav+ be5 brok5 by faults1 ^! volcanic rocks might at fir/ be tak5 = irregul> intrusive bosses1 b _! true "* is t %[n 9 ,fig4 #aeg1 :]e by a succession ( faults1 ) a ?r[ 9 ! same direction1 ! upp] basalts ( ,bonnyt\n ,hill are gradually br\ght d[n to ! level ( ! ,fir? ( ,=?4 ,illu/ration3 ,fig4 #aeg4--,section f ,l9li?g[ ,lo* to ! ,fir? ( ,=?4 iii4 ,,sills1 ,,bosses ,,& ,,dykes ,"o ( ! *>act]i/ic features ( ,c5tral ,scotl& is ! great numb]1 & (t5 ! l>ge size & extraord9>y p]si/5ce1 ( ! masses ( eruptive1 m or less basic mat]ial1 :i* h be5 inject$ among ! ,c>bonif]\s /rata4 ,! precise geological age ( ^! intrusions _c1 ( c\rse1 be m exactly def9$ ?an by /at+ t !y are y\ng] ?an ! rocks :i* !y trav]se1 ?\gh 9 _m cases _! association ) ! necks1 lavas & tuffs is su* z to %[ t !y mu/ be reg>d$ z "p ( ! ,c>bonif]\s volcanic ph5om5a4 ,sills4--,) reg>d to ! sills ,i h be5 l$1 = ! foll[+ reasons1 to connect ! great majority ( !m ) ! puys1 ?\gh "s are c]ta9ly ( f> lat] date1 :ile o!rs %\ld possibly be assign$ to ! plateaux4 ,9 ! fir/ place1 ! sills obvi\sly connect$ ) ! plateaux are 9 great measure int]m$iate1 or ev5 some:at acid rocks1 :ile ^? ( ! puy s]ies are mu* m basic4 ,x is h>dly possible1 h[ev]1 9 all cases to decide to :i* s]ies a p>ticul> sill %\ld be assign$4 ,?is difficulty is p>ticul>ly manife/ 9 ! we/]n "p ( ,midlo?ian1 :]e ! plateau ( t di/rict exhibits su* frequ5t int]ruption1 & :]e x (t5 consi/s only ( a s+le basaltic %eet4 ,to ! we/ ( x lie ! abundant puys ) _! lavas & tuffs1 & betwe5 ! two volcanic areas num]\s sills ( dol]ite & diabase make _! appe>ance4 ,9 ! difficulty ( decid+ to :i* s]ies ^! sills %\ld be ref]r$1 x w be conv5i5t to consid] !m ) ^? ( ! puys4 ,illu/ration3 ,fig4 #aeh4--,section across ! ,campsie ,fells illu/rat+ ! contra/ betwe5 ! sills bel[ & above ! plateau-lavas4 #a4 ,upp] ,old ,r$ ,s&/one2 #b4 ,ballagan ,b$s2 #c4 ,tuffs2 #d4 ,lavas ( ! ,campsie di/rict ( ! ,clyde plateau2 #e #e4 ,necks belong+ to ! plateau volcanic s]ies2 #f4 ,tra*ytic sills belong+ to ! plateau2 #g4 ,c>bonif]\s ,lime/one s]ies2 #h4 ,dol]ite sills cutt+ ! ,c>bonif]\s ,lime/one s]ies4 f1 ,fault4 ,a rem>kable illu/ration ( ! contra/ 9 petrographical "* betwe5 ! typical sills ( ! plateaux & ^? ( ! puys is furni%$ by ! *a9 ( ! ,campsie ,fells1 :]e1 on ! nor? side1 among ! ,calcif]\s ,s&/ones :i* em]ge f "u ! &esitic lavas ( ! ,clyde plateau1 _m intrusive %eets & bosses ( tra*ytic mat]ial may be se51 :ile on ! s\!rn side come ! great basic sills :i*1 f ,milngavie by ,kilsy? to ,/irl+1 run 9 ! ,c>bonif]\s ,lime/one s]ies 7,fig4 #aeh74 ,a simil> contra/ may be obs]v$ 9 ,r5frew%ire betwe5 ! tra*ytic sills bel[ ! plateau-lavas s\? ( ,gre5ock & ! basic sills above ^! lavas 9 ! ,c>bonif]\s ,lime/one s]ies ar\nd ,john/one & ,paisley4 ,9 ! second place1 ! m basic sills1 z a rule1 appe> on plat=ms high] 9 /ratigraphical position ?an ! plateaux1 & :]ev] ?is is _! position !re _c be any hesitation 9 decid+ aga9/ _! association ) ! old] phase ( volcanic activity4 ,9 ! ?ird place1 ! basic sills (t5 occur 9 obvi\s connection ) ! v5ts or b$d$ lavas & tuffs ( ! puy s]ies4 ,a conspicu\s example ( ?is dep5d5ce is suppli$ by ! intrusive %eets ( ,burntisl&1 und]ly+ ! basalts & tuffs ( t di/rict 9 ! imm$iate neighb\rhood ( "s ( ! v5ts f :i* ^! b$d$ rocks 7 erupt$ 7,fig4 #aei74 ,9 ! f\r? place1 ev5 :]e no visible v5ts appe> n[ at ! surface ne> ! sills1 ! latt] g5]ally occupy horizons )9 ! /ratigraphical range indicat$ by ! int]b$d$ volcanic rocks4 ,x mu/ be rememb]$ t all ! ,c>bonif]\s v5ts 7 deeply buri$ "u s$im5t>y deposits1 & t l>ge z is ! numb] ( !m :i* has be5 expos$ by d5udation1 x is probably mu* small] ?an ! numb] /ill conceal$ f our view4 ,! sills are to be reg>d$ z deep-seat$ p>ts ( ! volcanic protrusions1 & !y m especially appe> at ! surface :]e ! /rata betwe5 :i* !y 7 inject$ crop out f "u "s ( ! high] memb]s ( ! ,c>bonif]\s sy/em4 ,?us ! rem>kable gr\p ( sills betwe5 ,kilsy? & ,/irl+ 7,fig4 #aeh7 may q possibly be connect$ ) a gr\p ( v5ts ly+ n f> to ! ea/w>d1 b n[ buri$ "u ! high] p>ts ( ! ,c>bonif]\s ,lime/one1 ,mill/one ,grit & ,coal-measures4 ,aga91 ! great s]ies ( sills t gives rise to su* a conspicu\s range ( hills 9 ! nor? & middle ( ,fife may h dep5d$ = its orig9 ^u ! ef=ts ( a l9e ( v5ts runn+ ea/ & we/ ?r\gh ! c5tre ( ! c\nty1 b n[ buri$ "u ! ,coal-measures4 ,"s v5ts1 inde$1 h be5 laid b>e 9 t di/rict1 su* z ! conspicu\s gr\ps ( ! ,sal9e ,hills & ! ,hill ( ,bea?1 b _m m may be conceal$ "u high] ,c>bonif]\s /rata fur!r ea/4 ,illu/ration3 ,fig4 #aei4--,section %[+ ! position ( ! basic sills 9 relation to ! volcanic s]ies at ,burntisl&1 ,fife4 #a4 ,calcif]\s ,s&/one s]ies2 #b4 ,burdieh\se ,lime/one2 #c4 ,s&/ones1 %ales & tuffs2 #d4 ,basalts & tuffs1 ) int]calations ( s&/one1 %ale & lime/one2 #e4 ,agglom]ate ( ! ,b9n ( ,burntisl& neck2 #f4 ,basalt dyke2 #g4 ,dyke & sill2 #h #h #h4 ,?ree sills4 ,9 ! fif? place1 ! mat]ials ( :i* ! sills consi/ l9k !m 9 petrographical "* ) ^? t proce$$ f ! puys4 ,! rocks ( ! intrusive %eets 9 ,we/ ,lo?ian1 ,midlo?ian & ,fife are v mu* :at an exam9ation ( ! b$d$ lavas ( ! puys 9 ! same region w\ld lead u to expect4 ,!re is1 ( c\rse1 ! m>k$ textural diff]5ce betwe5 masses ( molt5 rock :i* h cool$ v sl[ly )9 ! cru/ ( ! e>? & ^? :i* h solidifi$ ) rapidity at ! surface1 ! sills be+ = ! mo/ "p mu* m co>sely cry/all9e ?an ! lavas1 & m uni=m 9 texture ?r\gh\t1 ?\gh g5]ally f9] at ! m>g9s ?an at ! c5tre4 ,!re is likewise ! fur!r contra/ aris+ f diff]5ces 9 ! composition ( ! volcanic magma at widely-sep>at$ p]iods ( its extravasation4 ,at ! "t :5 ! /reams ( basalt fl[$ out f ! puys its con/itution 0 comp>atively basic1 9 "s localities ev5 extremely basic4 ,any sills dat+ f t "t may be expect$ to %[ an equal proportion ( bases4 ,b ^? :i* 7 inject$ at a long subsequ5t /age 9 ! volcanic p]iod may well h be5 consid]ably m acid4 ,9 actual fact ! petrographical range ( ! sills reasonably ref]able to ! puy-eruptions v>ies f picrite or limburgite to dol]ite )\t oliv9e4 ,! great majority ( ^! %eets 9 ! bas9 ( ! ,fir? ( ,=?1 :]e !y are *iefly display$1 are dol]ites 7diabases71 sometimes )1 b m frequ5tly )\t1 oliv9e4 ,!y include all ! m co>sely cry/all9e rocks ( ! region1 ?\gh occasionally !y are ord9>y close-gra9$ basalts4 ,_! texture may be obs]v$ to be> "s relation to _! mass1 s f> at lea/ z t1 :]e !y occur 9 b$s only two or ?ree feet or y>ds 9 ?ickness1 !y are almo/ inv>iably clos]-gra9$4 ,a cellul> or amygdaloidal texture is seldom to be obs]v$ among !m1 & nev] :]e !y are l>gely cry/all9e4 ,?is texture is mo/ (t5 to be f\nd 9 ?9 sills :i* h be5 inject$ among c>bonace\s %ales or coals4 ,^! intrusive %eets are g5]ally f9ely cellul>1 & m or less decay$ 7:ite trap74 ,illu/ration3 ,fig4 #afj4--,sills betwe5 %ales & s&/ones1 ,h\nd ,po9t1 ,l9li?g[%ire4 ,diff]5ces ( texture may (t5 be obs]v$ )9 %ort di/ances 9 ! same sill1 & likewise consid]able v>ieties 9 col\r & composition4 ,! mo/ f9ely cry/all9e portions are1 z usual1 ^? along ! junction ) ! /ratifi$ rocks1 ! mo/ cry/all9e occurr+ 9 ! c5tral p>ts ( ! mass4 ,a dim9ution 9 ! size ( ! cry/all9e con/itu5ts may be trac$ n only at ! base1 b also at ! top ( a %eet1 or at any int]m$iate portion :i* has come 9 contact ) a l>ge mass ( ! surr\nd+ rock4 ,a good illu/ration is suppli$ by ! intrusive %eet at ,h\nd ,po9t 7,fig4 #afj71 to ! ea/ ( ,s\? ,que5sf]ry1 :]e "s lay]s ( %ale h be5 involv$ 9 ! igne\s rock1 :i* becomes rem>kably close-gra9$ along ! junction4#dff ,?is *ange 9 texture & abs5ce ( cellul> /ructure =m a well-m>k$ di/9ction betwe5 ^! %eets & ^? :i* h fl[$ out at ! surface z true lava-/reams4 ,footnote #dff3 ,see ,hay ,cunn+ham's ,essay1 p4 #ff1 & plate ix42 & ,geol4 ,survey ,memoir on ,geology ( ,ed9burgh1 p4 #aad4 ,"s ( ! l>g] dol]itic sills display a some:at co>sely cry/all9e texture 9 _! c5tral portions1 & occasionally pres5t a notable micropegmatitic aggregate1 :i* plays ! "p ( int]/itial sub/ance enclos+ ! o!r m9]als4 ,mr4 ,teall has ref]r$ to ! frequ5t occurr5ce ( ?is /ructure 9 ! co>s] p>ts ( ! ,:9 ,sill ( ! nor? ( ,engl&4#dfg ,x occurs also 9 a m>k$ degree 9 ! ,ra?o sill & 9 "s portions ( ! great dol]itic sill ( :i* ! crags ( ,/irl+ =m a "p4#dfh ,footnote #dfg3 ,briti% ,petrography1 p4 #bjh4 ,footnote #dfh3 ,mr4 ,h4 ,w4 ,monckton4 ,qu>t4 ,j\rnal ,geol4 ,soc4 vol4 li4 7#ahie71 p4 #dhb4 ,b beside ! diff]5ces 9 texture1 ma9ly due to v>y+ rates ( cool+1 ! sills sometimes exhibit /rik+ v>ieties ( composition 9 ! same mass ( rock4 ,^! v>iations are m especially noticeable among ! l>g] sills1 & p>ticul>ly :]e ! mat]ial is mo/ m>k$ly basic4 ,! special type ( diff]5tiation1 s noticeable 9 ! ,ba?gate diabase & picrite mass already allud$ to1 is likewise well exhibit$ 9 an intrusive %eet or gr\p ( %eets1 rec5tly expos$ at ,b>nton1 9 ! cutt+ ( a railway f ,ed9burgh to ,cramond#dfi 7,fig4 #afa74 ,! intrusive nature ( ! sev]al b&s ( igne\s rock :i* occur "h is made q evid5t by ! alt]ation !y h produc$ ^u ! %ales ) :i* !y h come 9 contact4 ,x is ! upp]mo/ & mo/ ext5sive ( ^! sills :i* specially des]ves notice1 = ! diff]5tiation ( its con/itu5ts4 ,x /ret*es along ! cutt+ = sev]al hundr$ y>ds at an angle ( dip ( ab\t #ae4 ,at ! we/]n or upp] "p ( ! mass its actual contact ) ! sup]9cumb5t s$im5t>y /rata is n visible1 b z ! igne\s rock is !re a good deal f9] 9 gra9 ?an else:]e1 its upp] surface _c be _m feet di/ant4 ,! upp] visible portion is a light well-cry/alliz$ dol]ite ) a rudely b$d$ /ructure1 ! planes dipp+ we/w>ds at #ae4 ,ab\t #bj or #cj feet bel[ ! upp] visible t]m9ation ( ! mass1 ! d>k f]ro-magnesian m9]als beg9 rapidly to increase 9 relative proportion to ! pale felsp>1 & ! rock consequ5tly becomes d>k-gre5i% br[n4 ,! *ange is p>ticul>ly noticeable 9 c]ta9 b&s :i* run p>allel ) ! g5]al dip4 ,!re is no def9ite l9e betwe5 ! pale & d>k body ( ! rock1 ! two graduat+ into ea* o!r & ! d>k] "p becom+ deep] 9 col\r1 heavi] & m decompos+1 until x becomes a true typical picrite4 ,ev5 9 ?is ultra-basic portion ! same rude b$d+ or b&+ may be obs]v$4 ,footnote #dfi3 ,?is rock has be5 describ$ by ,mr4 ,j4 ,h5d]son & ,mr4 ,good*ild1 ,trans4 ,geol4 ,soc4 ,ed94 vi4 7#ahic7 pp4 #big1 #cja1 & by ,mr4 ,h4 ,w4 ,monckton1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 l4 7#ahid7 p4 #ci4 ,mr4 ,good*ild recogniz$ ! occurr5ce ( picrite1 & ,mr4 ,monckton has describ$ ! succession ( rocks1 & giv5 a diagram ( !m4 ,illu/ration3 ,fig4 #afa4--,section ( ,sill1 ,cramomd ,railway1 ,b>nton1 ne> ,ed9burgh4 #a4 ,bak$ %ale2 #b4 ,sill ( v felspa?ic dol]ite ab\t1 n9e feet ?ick2 #c4 ,bak$ %ale1 eight in*es2 #d4 ,dol]ite %[+ *ill$ f9e-gra9$ edge & adh]+ firmly to ! %ale bel[2 x rapidly passes up into 7#e7 ,picrite ) :ite felspa?ic ve9s 7#f72 #g4 ,junction ( picrite & dol]ite ) a simil> ve9 along ! l9e ( contact2 #h4 ,l>ge globul> body ( dol]ite enclos+ a mass ( picrite4 ,ve9s 9 :i* felsp> pr$om9ates ov] ! d>k] m9]als trav]se ! rock1 sometimes p>allel ) ! b$d+1 sometimes across x4 ,!y v>y f less ?an an in* to a foot 9 wid?1 sometimes divid+ & enclos+ p>ts ( ! surr\nd+ mass4 ,b t !y are on ! :ole contemporane\s ) ! sill itself1 & n long subsequ5t injections1 is %[n by ! way 9 :i* ! d>k f]ro-magnesian m9]als project f ! picrite into ! ve9s & lock ! two toge!r4 ,b besides ^! injections1 :i* d\btless repres5t ! la/ & m acid portions ( ! magma inject$ into ! basic p>ts be=e ! f9al consolidation ( ! :ole1 !re are to be obs]v$ irregul> concretion>y pat*es1 ( simil> "* to ! ve9s1 di/ribut$ ?r\gh ! picrite4 ,on ! o!r h&1 t[>ds its base ! sill becomes a co>se dol]ite r\nd :i* ! picrite is wrapp$1 & :i* encloses a deta*$ portion ( t rock4 ,x is des]v+ ( note t :ile ! ultra-basic portion desc5ds almo/ to ! v bottom ( ! sill1 ! l[e/ five feet %[ ! same *ange z occurs at ! top ( ! mass4 ,!re ! felsp> rapidly beg9s to pr$om9ate ov] ! d>k] m9]als1 & ! dol]ite into :i* ! rock passes %[s a f9e-gra9$ m>g9 adh]+ firmly to ! %ales on :i* x re/s4 ,?is l[] dol]itic b&1 %[+ z x does ! effect ( *ill+ ^u its "u surface1 may be due to m rapid cool+ & cry/allization1 :ile 9 ! ov]ly+ p>ts ! mass rema9$ suffici5tly mobile to all[ ( a sep>ation ( ! heavi] m9]als f ! felsp>s1 :i* appe> 9 pr$om9ant quantity t[>ds ! top4 ,x mu/ be frankly admitt$1 h[ev]1 t we are /ill v ignorant ( ! causes :i* l$ to ?is sep>ation ( +r$i5ts 9 a few sills1 :ile !y 7 entirely abs5t or non-effici5t 9 mo/ ( !m4 ,! intrusive "* ( ! ,c>bonif]\s sills ( ,c5tral ,scotl& & _! contact-metamorphism h be5 fully describ$1 & "s ( !m h become1 z x 71 h\sehold words 9 geology4#dgj ,expos$ 9 s _m f9e natural sections 9 ! vic9ity ( ,ed9burgh1 !y e>ly attract$ ! notice ( geologi/s1 & furni%$ a battle-gr\nd on :i* _m a conflict took place betwe5 ! ,plutoni/ & ,neptuni/ *ampions at ! beg9n+ ( ! pres5t c5tury4 ,footnote #dgj3 ,see1 = in/ance1 ,macl>5's ,geology ( ,fife & ! ,lo?ians1 #ahci2 ,hay ,cunn+ham's ,essay1 previ\sly cit$2 ,geological ,survey ,memoir on ! ,geology ( ,ed9burgh 7,%eet #cb71 #ahfa2 ,mr4 ,allport1 ,qu>t4 ,j\rn4 ,geol4 ,soc4 vol4 xxx4 7#ahgd7 p4 #eec2 ,teall1 ,briti% ,petrography1 p4 #ahg2 ,e4 ,/e*]1 ,contact]s*e9ung5 an s*ottis*5 ,oliv9diabas51 ,ts*]mak's ,m9]alog4 ,mit!il4 vol4 ix4 7#ahhg7 p4 #ade2 ,proc4 ,roy4 ,soc4 ,ed94 vol4 xv4 7#ahhh7 p4 #afj4 ,z ! sills frequ5tly lie 9 ev5 %eets p]fectly p>allel ) ! b$d+ ( ! /rata betwe5 :i* !y h be5 inject$1 c>e is requir$ 9 "s cases to e/abli% t !y are ( intrusive orig94 ,"o ( ! mo/ obvi\s te/s = ?is purpose is furni%$ by ! alt]ation !y produce among ! /rata ?r\gh :i* !y h made _! way1 :e!r ^! lie above or bel[ !m4 ,! /rata are sometimes crumpl$ up 9 su* a mann] z to indicate consid]able pressure4 ,!y are occasionally brok5 into fragm5ts1 ?\gh ?is may h be5 due r to ! effects ( gase\s explosions ?an to ! actual protrusion ( melt$ rock4 ,b ! mo/ frequ5t *ange sup]9duc$ ^u !m is an induration :i* v>ies greatly 9 am\nt ev5 along ! edge ( ! same intrusive %eet4 ,s&/ones are h>d5$ into qu>tzite1 break+ ) a smoo? cle> gli/5+ fracture4 ,coals are conv]t$ into a s(t sooty sub/ance1 sometimes into an?racite4 ,lime/ones acquire a cry/all9e sac*>oid /ructure4 ,%ales pass g5]ally into a k9d ( porcellanite1 b occasionally exhibit o!r types ( contact-metamorphism4 ,?us bel[ ! ?ick picrite sill at ,b>nton1 ne> ,ed9burgh1 ! %ales h assum$ a f9ely concretion>y /ructure by ! appe>ance 9 !m ( sph]ical pea-l aggregates4 ,ano!r pro( ( intrusion is to be f\nd 9 ! mann] 9 :i* sills cat* up & completely enclose portions ( ! ov]ly+ /rata4 ,! well-kn[n examples on ,salisbury ,crags 7,fig4 #afb7 are p>allel$ by scores ( o!r in/ances 9 diff]5t p>ts ( ! same region4 ,moreov]1 sills d n always rema9 on ! same horizon2 t is1 betwe5 ! same /rata4 ,!y may be obs]v$ to /eal across or break ?r\gh ! b$s1 s z to lie successively betwe5 diff]5t lay]s4 ,no m in/ructive example ( ?is relation on a small scale c\ld be cit$ ?an t ( ! intrusive %eet :i* has be5 laid op5 9 ! ,dodhead ,lime/one ,qu>ry1 ne> ,burntisl&4 ,z %[n 9 ! accompany+ figure 7,fig4 #afc71 ?is rock breaks ?r\gh ! lime/one & !n spreads out among ! ov]ly+ %ales1 across :i* x passes obliquely4 ,illu/ration3 ,fig4 #afb4--;,intrusive dol]ite %eet enclos+ & s5d+ ?reads into portions ( %ale1 ,salisbury ,crags1 ,ed9burgh4 ,among ! l>g] sills ?is transgressive "* is se5 to be sometimes manife/$ on a great scale4 ,?us1 along ! important belt ( intrusive rocks t runs f ,kilsy? to ,/irl+1 ! ,hurlet ,lime/one lies 9 "o place bel[1 9 ano!r above1 ! invad+ mass1 b 9 ! int]v5+ gr\nd has be5 engulph$ 9 x4 ,simil> evid5ce ( ! widely sep>ate horizons occupi$ by diff]5t p>ts ( ! same sill is suppli$ at ,kilsy?1 :]e ! intrusive %eet lies ab\t #gj or #hj fa?oms bel[ ! ,index ,lime/one1 :ile at ,croy1 9 ! same neighb\rhood1 x actually passes above t seam4#dga ,footnote #dga3 ,explanation ( ,%eet #ca1 ,geological ,survey ( ,scotl&1 #dc & #hc4 ,illu/ration3 ,fig4 #afc4--;,intrusive %eet invad+ lime/one & %ale1 ,dodhead ,qu>ry1 ne> ,burntisl&4 ,o!r int]e/+ evid5ce ( ! intrusive nature ( ! ,c>bonif]\s dol]ite sills ( ,c5tral ,scotl& is suppli$ by ! int]nal modifications :i* ! eruptive rock has und]gone by contact ) ! /rata betwe5 :i* x has be5 ?ru/4 ,^! alt]ations1 ?\gh p>tly visible to ! nak$ eye1 are be/ /udi$ 9 ?9 slices ) ! aid ( ! microscope4 ,trac+ ! v>iations ( an intrusive dol]ite outw>ds 9 ! direction ( ! rocks :i* x has invad$1 we p]ceive *ange fir/ 9 ! augite4 ,! l>ge cry/als & k]nels ( t m9]al gr[ small] until !y pass into a granulat$ =m l t *>act]i/ic ( basalts4 ,! l>ge plates & amorph\s pat*es ( titanif]\s iron or magnetite give place to m9ute p>ticles1 :i* t5d to gr\p !mselves into long club-%ap$ bodies4 ,! labradorite cont9ues b little affect$1 except t its prisms1 ?\gh z def9$1 may n be q s l>ge4 ,! int]/itial glassy gr\ndmass rema9s 9 mu* ! same condition & relative am\nt z 9 ! c5tre ( ! rock4 ,along ! l9e ( contact1 :ile ! dol]ite becomes exce$+ly close-gra9$1 its felsp> cry/als are /ill q di/9ct ev5 up to ! v edge4 ,b !y become few] 9 relative numb]1 & /ill small] 9 size1 ?\gh an occasional prism two or ?ree millimetres 9 l5g? may occur4 ,!y reta9 also _! %>pness ( outl9e1 & _! comp>ative fre$om f enclosures ( any k9d4 ,!y t5d to range !mselves p>allel ) ! surface ( ! contact-rock4 ,! augite exi/s z a f9ely granul> pale gre5 sub/ance1 :i* might at fir/ be tak5 = a glass1 b x gives ! *>act]i/ic action ( augite ) pol>iz$ light4 ,x is intimately mix$ ?r\gh ! cle> glass ( ! gr\ndmass1 :i* x f> exce$s 9 quantity4 ,! iron oxides n[ appe> z a f9e granul> du/1 :i* is frequ5tly aggregat$ into elongat$ club-%ap$ objects1 z if r\nd "s inn] pellucid or transluc5t microlite4 ,9 pat*es ?r\gh\t ! field1 h[ev]1 ! oxides take ! =m ( a geometrically p]fect network ( int]lac+ rods4 ,?is beautiful /ructure1 describ$ & figur$ by ,zirkel & o!rs1#dgb is nev] to be se5 9 any ( ! dol]ites1 except close to ! l9e ( contact ) ! surr\nd+ rocks4 ,x occurs also 9 "s ( ! dykes4 ,i h n succe$$ 9 detect+ any microlites 9 ! s&/ones at ! edge ( a dol]ite %eet1 ?\gh ,i h _h _m slices prep>$ = ! purpose4 ,footnote #dgb3 ,mikroskopis*e ,bes*aff5heit d] ,m9]ali5 und ,ge/e9e1 p4 #bgc2 ,vogelsang's ,kry/allit54 ,:]e "o ( ! dol]ite sills has invad$ s&/one1 !re is usually a tol]ably %>p l9e ( dem>cation betwe5 ! two rocks1 ?\gh x is seldom easy to procure a h&-specim5 %[+ ! actual contact1 = ! /one is apt to break along ! junction-l9e4 ,:]e1 h[ev]1 ! rock trav]s$ by ! igne\s mass is argillace\s %ale1 we may f9d a ?or\gh weld+ ( ! two sub/ances into ea* o!r4 ,9 su* cases ! dol]ite at ! actual contact becomes a d>k opaque rock1 :i* 9 ?9 slices "u ! microscope is f\nd to be =m$ ( a mottl$ or curdl$ segregation ( exce$+ly m9ute black gra9s & hairs 9 a cle> glassy matrix1 9 :i* ! augite & felsp> are n individualiz$4 ,b ev5 9 ?is ta*ylyte-l rock p]fectly =m$ & v %>ply def9$ cry/als ( tricl9ic felsp> may be obs]v$ rang+ !mselves z usual p>allel to ! b\nd+ surfaces ( ! rock4 ,^! *>act]s are well se5 9 ! contact ( ! intrusive %eet ( dol]ite ) %ale & s&/one at ,h\nd ,po9t 7,fig4 #afj74 ,ano!r in/ructive example is furni%$ by ! small ?reads :i* proce$ f ! dol]ite ( ,salisbury ,crags1 & trav]se enclos$ fragm5ts ( %ale 7,fig4 #afb74 ,"s ( ^! m9iature dykes are n m ?an "o-eigh? ( an in* 9 diamet]1 & may !re=e easily be includ$1 toge!r ) "p ( ! surr\nd+ rock1 9 ! field ( ! microscope4 ,! dol]ite 9 ^! ramifications assumes an exce$+ly f9e texture4 ,! felsp> is ! only m9]al di/9ctly =m$ into def9ite cry/als4 ,x occurs 9 prisms ( an e>ly consolidation1 sometimes "o-fif? ( an in* long1 & !re=e readily recognizable by ! nak$ eye4 ,^! prisms are p]fectly %ap$1 conta9 abundant tw9 lamell1 & %[ enclosures ( ! iron ( ! base4 ,!y _h be5 already completely =m$ at ! "t ( injection2 = occasionally !y may be obs]v$ project+ beyond ! wall ( ! ve9 into ! adjac5t %ale or s&/one1 & !y h rang$ !mselves p>allel to ! sides ( ! ve94#dgc ,! black gr\nd1 f :i* ^! l>ge well-def9$ cry/als /& out prom95tly1 consi/s ( a devitrifi$ glass1 r5d]$ d>k by ! multitude ( its enclos$ black opaque microlites4 ,^! are v m9ute gra9s & rudely fea!r$ rods1 ) a t5d5cy to gr\p !mselves "h & !re into =ms l portions ( ! rhomboh$ral skeletons ( titanif]\s iron4 ,s ?or\ghly fus$ & liquid has ! dol]ite be5 at ! "t ( its injection1 t little ?reads ( x1 less ?an #a_/ajj ( an in* 9 diamet]1 consi/+ ( ! same d>k base1 ) well-def9$ felsp>s1 may be se5 isolat$ )9 ! surr\nd+ s$im5t>y rock4 ,m9ute gra9s & r\nd$ portions ( ! latt] may also be notic$ 9 ! m>g9al p>ts ( ! dol]ite4 ,footnote #dgc3 ,! infusibility ( ! felsp> 0 well %[n 9 "s exp]im5ts on ! rocks ( ! neighb\rhood ( ,ed9burgh1 made at my reque/ by ,dr4 ,r4 ,s4 ,m>sd51 :o subject$ "s ( ^! rocks to fusion at ! laboratory ( ! ,univ]sity ( ,ed9burgh4 ,microscopic sections 7 prep>$ ( ! products obta9$4 ,! basalt ( ,lion's ,haun* is peculi>ly in/ructive4 ,its l>ge labradorite cry/als h resi/$ ! int5se :ite heat :i*1 cont9u$ = f\r h\rs1 has r$uc$ ! re/ ( ! m9]als to a p]fect glass4 ,we c ?us well und]/& h[ l>ge def9ite cry/als ( felsp> %\ld h surviv$ or appe>$ 9 dykes & ve9s :ile ! rock 0 /ill ?or\ghly liquid4 ,! glass obta9$ f ! ,lion's ,haun* rock is ( a honey-yell[1 & conta9s transluc5t tuft$ microlites4 ,! iron =ms beautiful d5dritic films 9 ! cracks4 ,altoge!r1 ! glass pres5ts a /rong resemblance to ! palagonitic sub/ance s abundant among ! lapilli 9 ! tuffs ( ! v5ts4 ,x is ?us evid5t t specim5s tak5 f ! edge ( an intrusive %eet1 :]e ! rock has rapidly *ill$ & solidifi$1 repres5t to u an e>li] /age 9 ! hi/ory ( ! :ole mass ?an specim5s tak5 f its c5tral portions4 ,9 fact1 a s]ies ( samples collect$ at %ort int]vals f ! out] contact to ! inn] mass %[s1 z x 71 ! successive /ages 9 ! consolidation ( ! molt5 rock4 ,f ! obs]vations j describ$1 x appe>s t ! tricl9ic felsp>s began to assume ! %ape ( l>ge def9ite cry/als be=e any ( ! o!r m9]als4 ,^! felsp>s already exi/$ :5 ! molt5 mass =c$ its way among ! %ales1 = !y c be se5 ly+ ) _! long axes p>allel to ! surface ( %ale1 precisely z1 9 ! well-kn[n fl[-/ructures1 !y behave r\nd a l>ge cry/al emb$d$ 9 ! he>t ( a rock4 ,a few feet f :]e ! consolidation 0 n s rapid1 ! iron oxides h gr\p$ !mselves into incipi5t cry/all9e =ms & skeleton cry/als2 ! felsp> cry/als abundantly occur1 & ! augite has be5 left 9 ! f9ely granul> condition4 ,/ill fur!r t[>ds ! int]ior ( ! mass1 ! normal "* ( ! dol]ite is gradually assum$4#dgd ,footnote #dgd3 ,= a fur!r & m detail$ inve/igation ( ! contact ph5om5a ( ! ,c>bonif]\s dol]itic sills ( ! bas9 ( ! ,fir? ( ,=?1 see ! pap]s by ,dr4 ,/e*]1 quot$ on p4 #dea4 ,illu/ration3 ,fig4 #afd4--,sph]oidal wea!r+ ( dol]ite sill1 qu>ry ea/ ( ,nor? ,que5sf]ry1 ,fife4 ,:]e a sill has be5 inject$ among c>bonace\s %ales & coals x has und]gone great alt]ation along ! contact1 & if ! %eet is only a few in*es or feet ?ick1 ! *ange ext5ds ?r\gh\t its :ole mass4 ,black basalts & dol]ites1 9 su* circum/ances1 pass into a sub/ance l a :ite or pale yell[ clay1 :i* at fir/ might be mi/ak5 = "s b& ( fire-clay int]calat$ among ! o!r s$im5ts4 ,b evid5ce ( actual intrusion may usually be f\nd1 z :]e ! igne\s rock has caught up or brok5 ?r\gh ! adjac5t /rata1 besides alt]+ !m4 ,su* :ite traps1 z !y h be5 call$1 h long be5 famili> 9 ! coal-fields ( ,scotl& & ,c5tral ,engl&4 ,illu/ration3 ,fig4 #afe4--,two ?9 sills ( ,:ite ,trap inject$ into black c>bonace\s %ale ov]ly+ ! ,hurlet ,lime/one1 ,hillh\se ,qu>ry1 ,l9li?g[4 #a4 ,hurlet ,lime/one2 #b4 ,black %ales2 #c #c4 ,two sills ( ,:ite ,trap2 #d4 ,column> ,basalts4 ,z a good illu/ration ( ! behavi\r ( su* ?9 sills among c>bonace\s %ales ,i give "h a section 7,fig4 #afe7 expos$ 9 ! old lime/one qu>ry ( ,hillh\se1 s\? ( ,l9li?g[4 ,at ! bottom lies ! ,hurlet ,lime/one :i* has once be5 ext5sively m9$ at ?is locality4 ,above x comes a gr\p ( black %ales :i* 9 turn are surm\nt$ by a %eet ( beautifully column> basalt4 ,! %ales seem at fir/ sight to include two lay]s ( pale fire-clay1 ea* only a few in*es 9 ?ickness4 ,clos] inspection1 h[ev]1 w %[ t ^! two ?9 int]calations are really sills :i*1 ?\gh on ! :ole p>allel ) ! b$d+ ( ! %ale1 may be se5 to cut across x1 & ev5 at "o place to s5d a f+] into x4 ,! upp] example may also be obs]v$ to dim9i% rapidly 9 ?ickness 9 "o direction4 ,! dim5sions ( ! sills v>y )9 tol]ably wide limits4 ,al?\gh "h & !re ! inject$ mat]ial dw9dles d[n to an in* or less 9 ?ickness1 runn+ away ev5 into ?reads1 x m usually =ms %eets ( consid]able dep?4 ,! rock ( ,salisbury ,crags1 = example1 is fully #aej feet ?ick at its maximum4 ,t ( ,cor/orph9e ,hill is probably ab\t #cej feet4 ,! great %eet :i* runs among ! l[] lime/ones f ,kilsy? by ,d5ny to ,/irl+ has be5 bor$ ?r\gh to a dep? ( #bgf feet1 b z ! bore />t$ on ! rock1 & n 9 ov]ly+ /rata1 "s addition may ne$ to be made to t ?ickness4 ,! sph]oidal wea!r+ s *>act]i/ic ( basic eruptive rocks is n[h]e m *>act]i/ically display$ ?an among ! great dol]itic sills ( ! bas9 ( ! ,fir? ( ,=?4 ,z an illu/ration ( ?is /ructure an example is tak5 "h f ! l>ge %eet at ,nor? ,que5sf]ry 7,fig4 #afd74 ,:ile "o is /ruck ) ! great size & ext5t ( "s ( ! sills connect$ ) ! puys1 z comp>$ ) ! small & local %eets und]nea? ! plateaux1 !re is a fur!r fact reg>d+ !m t ,illu/ration3 ,fig4 #aff4--;,dyke cutt+ ! agglom]ate ( a neck4 ,b9n ( ,burntisl&4 des]ves rem>k--_! caprici\s di/ribution4 ,_! occurr5ce seems to h little or no relation to ! measure ( volcanic en]gy z manife/$ 9 sup]ficial eruptions4 ,?us 9 ! nor? ( ,ayr%ire1 :]e a long b& ( lavas & tuffs1 po9t+ to vigor\s activity1 lies at ! top ( ! ,c>bonif]\s ,lime/one s]ies1 & :]e ! /rata und]nea? x are abundantly expos$ at ! surface1 ! sills occur z ?9 & incon/ant b&s 9 ! c5tral & ea/]n p>ts ( ! di/rict only4 ,! b$d$ lavas & tuffs at ! head ( ! ,slitrig ,wat] h no visible accompanim5t ( sills4 ,on ! o!r h&1 9 ! ,ed9burgh & ,burntisl& di/ricts1 ! sills be> a l>ge proportion to ! am\nt ( b$d$ lavas & tuffs1 :ile 9 ! ,ba?gate & ,l9li?g[ di/rict1 :]e ! sup]ficial eruptions 7 especially vigor\s & prolong$1 ! sills are ( trifl+ ext5t4 ,x w\ld seem f ^! facts t ! ext5t to :i* ! cru/ ( ! e>? r\nd a volcanic orifice is inject$ ) molt5 rock1 9 ! =m ( intrusive %eets betwe5 ! /rata1 does n dep5d ^u ! en]gy ( ! volcano z gaug$ by its sup]ficial outp\r+s1 b on o!r consid]ations n q app>5t4 ,possibly1 ! m effectively volcanic en]gy succe$$ 9 expell+ mat]ials f ! v5t1 ! less opportunity 0 af=d$ = subt]ranean injections4 ,& if ! protrusion ( ! sills took place aft] ! v5ts 7 solidly seal$ up ) agglom]ate or lava1 x w\ld d\btless (t5 be easi] = ! impell$ magma to op5 a way = itself lat]ally betwe5 ! b$d+-planes ( ! /rata ?an v]tically ?r\gh ! ?ick solid cru/4 ,! size & ext5t ( ! sills may ?us be a record ( ! int5sity ( ?is late/ phase ( ! volcanic eruptions4 ,illu/ration3 ,fig4 #afg4--;,boss ( diabase cutt+ ! ,burdieh\se ,lime/one & s5d+ sills & ve9s into ! ov]ly+ %ales4 ,railway cutt+1 ,we/ ,qu>ry1 ,ea/ ,cald]1 ,midlo?ian4 #a4 ,burdieh\se ,lime/one2 #b4 ,%ales2 #c4 ,diabase4 99 99 99 99 99 ,bosses4--,! r\nd$1 oval or irregul>ly %ap$ masses ( igne\s rock includ$ "u ?is head are f\nd 9 "s cases to be only d5ud$ domes ( sills1 z1 = example1 9 ! app>5tly isolat$ pat*es 9 ! oil-%ale di/rict ( ,l9li?g[%ire1 :i* h be5 f\nd to unite "u gr\nd4 7,comp>e ,fig4 #aeg74 ,9 o!r in/ances1 bosses possibly1 or almo/ c]ta9ly1 m>k ! position ( volcanic funnels1 z at ! ,ca/le ,rock ( ,ed9burgh1 ,dune>n ,hill1 ,burntisl&1 & ,galabraes1 ne> ,ba?gate4 ,b _m examples occur :i* c only be reg>d$ z ! expos$ ends ( irregul> bodies ( molt5 mat]ial :i* has be5 protrud$ upw>ds into ! ,illu/ration3 ,fig4 #afh4--,side ( column> basalt-dyke 9 ! same agglom]ate z 9 ,fig4 #aff4 ,c>bonif]\s =mations4 ,! area betwe5 ,ed9burgh & ,l9li?g[ & ! hills ( ! nor? ( ,fife furni% _m examples4 ,! connection betwe5 bosses & intrusive %eets is in/ructively exhibit$ 9 a railway cutt+ to ! we/ ( ,ed9burgh1 :]e ! section %[n 9 ,fig4 #afg may be se54 ,9 ! space ( a few y>ds no few] ?an f\r di/9ct b&s ( diabase trav]se ! %ale1 ?ick5+ rapidly 9 "o direction & unit+ ) a l>ge boss ( m co>sely cry/all9e mat]ial4 ,su* connections mu/ exi/ 9 all sills1 = ! mat]ial inject$ z a %eet betwe5 /ratifi$ =mations _c b be unit$ to "s column1 dyke or irregul> protrusion :i* desc5ds to ! p>5t magma 9 ! int]ior4 ,b x is v r>ely t ! geologi/ is p]mitt$ to see !m4 99 99 99 99 99 ,illu/ration3 ,fig4 #afi4--;,dyke ris+ ?r\gh ! ,hurlet ,lime/one & its ov]ly+ %ales4 ,silv]m9e ,qu>ry1 ,l9li?g[%ire4 ,dykes take a comp>atively unimportant place 9 ! eruptive ph5om5a ( ! puys4 ,!y occur 9 "s numb]s1 b on a small scale1 among ! tuff v5ts1 & !re !y c )\t mu* hesitation be set d[n z "p ( ! ph5om5a ( eruption ?r\gh ^! pipes4 ,! ,b9n ( ,burntisl&1 :i* has be5 s (t5 ref]r$ to 9 ?is ,*apt]1 may aga9 be cit$ z a typical v5t = ! display ( ?is s]ies ( dykes 7,figs4 #adi & #aei74 ,two additional illu/rations f ?is locality are "h giv54 ,9 ,fig4 #aff a dyke ( compact black basalt is se5 on ! "r h& runn+ up ! /eep slopes ( ! agglom]ate4 ,"s ( ^! dykes are di/9ctly column>1 ! columns div]g+ f ! walls on ea* side4 ,:]e ! encas+ agglom]ate has be5 remov$ by ! wea!r1 ! side ( ! dyke pres5ts a reticulat$ network ( prism-ends4 ,a n>r[ basalt-dyke ( ?is "* ne> ! top ( ! ,b9n v5t is repres5t$ 9 ,fig4 #afh4 ,b dykes also occur ap>t f v5ts & )\t any app>5t relation to ^!4 ,!y are sometimes associat$ ) sills & bosses 9 su* a mann] z to sugge/ t ! :ole ( ^! =ms ( inject$ mat]ial belong to "o connect$ s]ies ( intrusions4 ,among ! ,ba?gate ,hills1 = example1 f :i* ,i h already cit$ in/ances ( sills & a boss1 ! section repres5t$ 9 ,fig4 #afi occurs4 ,yet 9 ?is same di/rict !re is a gr\p ( l>ge ea/ & we/ dykes :i* cut all ! o!r rocks includ+ ! b$d$ lavas & tuffs1 & mu/ be ( lat] date ?an ! highe/ "p ( ! ,coal-measures 7,fig4 #aee74 ,x is difficult to asc]ta9 ! age ( ! dykes :i* rise ?r\gh ! ,c>bonif]\s =mations at a di/ance f any int]b$d$ %eets ( lava & tuff1 or f any recognizable v5t4 ,! s\?-ea/ & nor?-we/ dykes1 increas+ 9 numb] z !y g we/w>d1 & atta9+ a prodigi\s developm5t 9 ! great volcanic area ( ,antrim & ! ,inn] ,hebrides1 are probably ( ,t]ti>y date4#dge ,o!rs may possibly be ,p]mian1 :ile a c]ta9 numb] may reasonably be look$ ^u z ,c>bonif]\s4 ,9 petrographical *>act]s ! latt] resemble ! dol]ites & basalts 7diabases7 ( ! f9]-gra9$ sills4 ,footnote #dge3 ,^! are fully describ$ 9 ,*apt]s xxxiv4 & xxxv4 ,,*apt] ,,xxviii ,,illu/rative ,,examples ,,( ,,! ,,c>bonif]\s ,,puys ,,( ,,scotl& ,! ,bas9 ( ! ,fir? ( ,=?--,nor? ,ayr%ire--,liddesdale4 ,?\gh _m ( ! geological details ( ea* ( ! ,scotti% di/ricts ( ,puys h be5 giv5 9 ! =ego+ pages1 x w be ( advantage to describe 9 connect$ sequ5ce ! /ructure & geological hi/ory ( a few typical areas4 ,by f> ! fulle/ & mo/ v>i$ record ( ?is phase ( volcanic activity has be5 pres]v$ 9 ! bas9 ( ! ,fir? ( ,=?2 b ! nor? ( ,ayr%ire & ! di/rict ( ,liddesdale furni% also _m int]e/+ *>act]i/ics4 #a4 ,,bas9 ,,( ,,! ,,fir? ,,( ,,=? ,ref]5ce has already be5 made to ! rem>kable peculi>ity 9 ! developm5t ( ! l[] "p ( ! ,c>bonif]\s sy/em 9 ?is di/rict4#dgf ,else:]e ?r\gh\t ,scotl& ! ,cem5t-/one gr\p & ! plateau lavas are imm$iately ov]la9 by ! ,c>bonif]\s ,lime/one s]ies4 ,b 9 ! bas9 ( ! ,fir? ( ,=? a v>i$ succession ( /rata1 m ?an #cjjj feet 9 ?ickness1 int]v5es betwe5 ! ,cem5t-/ones & ! ,hurlet ,lime/one4 ,! l[] portion ( ?is ?ick mass ( s$im5t may repres5t a "p ( ! ,cem5t-/one gr\p ( o!r di/ricts1 b ev5 if "s d$uction is made on ?is acc\nt !re rema9 _m hundr$ feet ( /ratifi$ deposits1 = :i* !re does n appe> to be any /ratigraphical equival5t else:]e 9 ,scotl&4 ,! di/+ui%+ features ( ?is s]ies ( /rata are ! ?ick zones ( :ite s&/one1 ) occasional b&s ( f9e conglom]ate1 ! abundant seams ( d>k %ale1 (t5 highly c>bonace\s 7oil-%ales71 ! cyprid lime/ones & ! seams ( coal4 ,su* an association ( deposits may indicate a m humid climate & m v>i$ conditions ( d5udation & deposition ?an are pres5t$ by ! typical ,cem5t-/ones4 ,! muddy floor ( ! %all[ wat] mu/1 9 _m places1 h support$ a luxuriant gr[? ( vegetation1 :i* is pres]v$ 9 occasional seams & /reaks ( coal4 ,num]\s epiphytic f]ns grew on ! subrial /ems & bran*es ( ! lycopodiace\s trees4 ,l>ge conif]ae clo!d ! high] gr\nds1 f :i* ! /reams br\ght d[n copi\s supplies ( s$im5t1 & :5ce a flood n[ & !n transport$ huge pro/rate trunks ( p9e4 ,9 ! lagoons animal life ab\nd$4 ,cyprids sw>m$ to su* a degree z to =m by _! accumulat$ rema9s b&s ( lime/one1 :i* 9 ! well-kn[n ,burdieh\se seam sometimes atta9 a ?ickness ( #gj feet4 ,fi%es ( _m g5]a haunt$ ! wat]s1 = _! scales1 bones & coprolites are f\nd 9 pr(usion among ! %ales & lime/ones4 ,footnote #dgf3 ,see ,macl>5's ,geology ( ,fife & ! ,lo?ians1 ! ,memoirs ( ! ,geological ,survey ( ,scotl&1 on ,%eets #ca & #cb1 & my ,memoir1 already cit$1 ,trans4 ,roy4 ,soc4 ,ed94 vol4 xxix4 7#ahgi7 p4 #dcg4 ,:5 ! puys began _! activity1 ?is di/rict 0 gradually dott$ ov] ) little volcanic cones4 ,at ! same "t x 0 affect$ by ! g5]al movem5t ( sl[ subsid5ce :i* embrac$ all ,c5tral ,scotl&4 ,cone aft] cone1 m or less effac$ by ! wat]s :i* clos$ ov] x1 0 c>ri$ d[n & buri$ "u ! gr[+ accumulation ( s$im5t4 ,new v5ts1 h[ev]1 cont9u$ to be op5$ else:]e1 ?r[+ out = a "t _! %[]s ( du/ & /ones1 & !n laps+ into quiesc5ce z !y sank into ! lagoon4 ,two gr\ps ( volcanoes emitt$ /reams ( lava & built up two long volcanic ridges--^? ( ,fife & ,we/ ,lo?ian4 ,! occasional pres5ce ( ! sea ov] ! area is well %[n by ! occurr5ce ( ?9 b&s ( lime/one or %ale1 conta9+ su* fossils z species ( ,or?oc]as1 ,bell]ophon & ,disc9a1 :i* suffice to prove ! /rata to be /ratigraphical equival5ts ( ! ,l[] ,lime/one %ale1 & "p ( ! ,c>bonif]\s ,lime/one ( ,engl& 7,fig4 #agj74 ,yet ! g5]al e/u>9e or fre%wat] "* ( ! accumulations seems satisfactorily e/abli%$1 n only by ! abs5ce ( und\bt$ly m>9e =ms f mo/ ( ! /rata1 b by ! abundance ( cyprids & small ganoids1 ! pr(usion ( vegetable rema9s1 & ! occasional seams ( coal4 ,! portion ( ! ,=? bas9 )9 :i* ! puys are display$ ext5ds f ne> ,lev5 9 ,fife1 on ! nor?1 to ,crosswood ,burn ne> ! bord]s ( ,lan>k%ire1 on ! s\?1 a di/ance ( ab\t #cf miles1 & f ne> ,culross 9 ,fife & ! l9e ( ! ,almond ,riv] betwe5 ,/irl+%ire & ,l9li?g[%ire1 on ! we/1 to ! isl& ( ,in*kei? on ! ea/1 a di/ance ( ab\t #af miles 7,map ,,iv474 ,b ^! limits d n precisely m>k ! orig9al b\nd>ies ( ! eruptions4 ,to ! nor? & s\?1 inde$1 we c trace ! gradual dy+ out ( ! volcanic int]calations1 until we rea* gr\nd ov] :i* no trace ( ei!r lavas or tuffs c be detect$4 ,to ! ea/1 ! wat]s ( ! ,fir? conceal ! geology ( a consid]able area1 ! isl& ( ,in*kei? ) its b$d$ lavas & tuffs %[+ t ^! rocks ext5d "s way f>!r ea/w>ds ?an ! position ( t isl&4 ,b 9 ,midlo?ian !re is no evid5ce t any ( ! puy-eruptions took place to ! ea/ ( ! l9e ( ! ,p5tl& ,hills4 ,on ! we/ side1 ! volcanic rocks dip "u ! ,mill/one ,grit & ,coal-measures1 s t we d n "k h[ f> !y ext5d 9 t direction4 ,b z ! ,c>bonif]\s ,lime/one s]ies1 :5 x rises aga9 to ! surface on ! we/ side ( ! ,/irl+%ire coal-field1 is de/itute ( includ$ lavas & tuffs1 ! we/w>d limit ( ! eruptions _c lie mu* beyond ! l9e ( ! ,riv] ,illu/ration3 ,fig4 #agj4--;,junction ( amygdaloidal basalt ) %ales & lime/one1 ,%ore1 half a mile ea/ f ,k+horn1 ,fife4 7,f a photograph by ,mr4 ,r4 ,lunn47 ,almond4 ,we %all probably be )9 ! m>k if we set d[n ! orig9al area ov] :i* puys broke out & spread abroad _! lavas & tuffs z cov]+ ab\t #cjj squ>e miles ( ! lagoons & jungles ( ,c5tral ,scotl&4 ,i h already %[n t ! range 9 geological "t ( ! puy-eruptions 9 ?is di/rict ext5ds f a l[ horizon among ! ,calcif]\s ,s&/ones ?r\gh ! ,c>bonif]\s ,lime/one s]ies1 up to ne>ly ! level ( ! ,calmy ,lime/one1 :i* lies n f> f ! top ( t s]ies4 ,! v]tical ?ickness ( /rata betwe5 ^! two /ratigraphical limits1 :5 !re are no int]calat$ volcanic rocks1 is probably m ?an #djjj feet4 ,! v5ts f :i* ! volcanic mat]ials 7 eject$1 s f> z !y are n[ to be obs]v$ at ! surface1 may be divid$ into two gr\ps1 "o ly+ to ! nor?1 ! o!r to ! s\? ( ! ,fir? ( ,=?4 ,! nor!rn or ,fife gr\p may be foll[$ ov] an area #ae miles long1 & ab\t ?ree miles broad4 ,"s fifte5 sep>ate v5ts may be recogniz$ 9 x1 di/ribut$ *iefly at ! two ends ( ! belt1 a clu/] ( ab\t six ris+ ar\nd ,burntisl&1 :ile ano!r ( ne>ly z _m appe>s at ,sal9e4 ,! *>act]s ( "s ( ^! necks h be5 already giv5 9 ! =ego+ pages4 ,! s\!rn or ,we/ ,lo?ian gr\p includes ab\t a doz5 v5ts :i* are scatt]$ ov] an area ( "s #fj squ>e miles1 ext5d+ f ! coa/-l9e betwe5 ,borr[/\nness & ,que5sf]ry s\?w>ds to ,ba?gate & ,uphall4 ,9 ?is gr\p ,b9ns ,hill1 a mile long by almo/ half a mile broad1 & ris+ to a height ( ne>ly #cjj feet above ! sea1 =ms ! mo/ prom95t individual4 ,b ! v5ts are g5]ally small] 9 ! s\!rn ?an 9 ! nor!rn gr\p4 ,! mann] 9 :i* ! v5ts h be5 left fill$ ) volcanic mat]ial has be5 describ$ 9 previ\s pages4 ,mo/ ( !m are occupi$ by tuff or agglom]ate4 ,9 _m cases ! neck consi/s entirely ( pyrocla/ic detritus1 z 9 mo/ ( ! v5ts ( ea/]n ,l9li?g[%ire & _m ( ^? 9 ,fife4 ,n infrequ5tly a column ( basalt has ris5 9 ! funnel & solidifi$ !re1 z exemplifi$ by ,b9ns ,hill & ,sal9e ,hill1 or ! basalt has fill$ r5ts 9 ! tuff & n[ appe>s 9 dykes l ^? on ! ,b9n ( ,burntisl& 7,figs4 #adh1 #adi1 #aei1 #aff1 #afh74 ,b x is possible t 9 "s cases v5ts may be repres5t$ by bosses ( basalt or dol]ite1 unaccompani$ by any agglom]ate or tuff4 ,p]haps ! be/ example ( ?is sugge/$ orig9 is suppli$ by ,galabraes ,hill1 :i* rises ?r\gh ! ,hurlet lime/one & ! volcanic s]ies ( ! ,ba?gate ,hills1 ab\t a mile nor?-ea/ f ! t[n ( ,ba?gate4 ,?is em95ce rises to a height ( #idj feet above ! sea1 & consi/s ( a rudely elliptical boss ( basalt1 measur+ #cejj feet 9 its great] & #cjjj feet 9 its m9or axis4 ,x disrupts ! s$im5t>y & volcanic s]ies1 :i* c be trac$ up to x on all sides4 ,"s ( ! small] circul> or elliptical bosses 9 ea/]n ,l9li?g[%ire & we/]n ,fife may p]haps belong to ! same category4 ,b und\bt$ly mo/ ( ! intrusive basalts & dol]ites ( ?is volcanic region are sills4 ,ov] ! great] "p ( ! di/rict1 only f9e tuffs 7 eject$4 ,^! occur z int]/ratifications among ! ord9>y s$im5ts1 & v>y f m]e ?9 p>t+s1 m>k+ ! feeble/ & briefe/ explosions1 up to cont9u\s accumulations sev]al hundr$ feet ?ick4 ,z an example ( ! lea/ vigor\s emission ( tuff ,i may ref] to ! sections already giv5 on pp4 #dcg1 #dch4 ,! ?ick] b&s are well illu/rat$ by t :i* lies "s way above ! ,h\/on ,coal1 betwe5 ,drumcross & ,we/ ,broadlaw 9 ,l9li?g[%ire1 & by ! great mass ( tuff :i* occurs imm$iately bel[ ! ,calmy ,lime/one on ! ,riv] ,avon ne> ,l9li?g[ ,bridge1 & :i* may be #cjj feet ?ick4 ,x is a /rik+ *>act]i/ic ( ! tuffs t !y may be met ) 9 _! solit>y b$s int]calat$ 9 ! mid/ ( ord9>y s$im5ts at a di/ance f any o!r trace ( volcanic activity1 _! p>5t v5ts n be+ visible4 ,i may cite 9 illu/ration an int]e/+ case 9 ! ,swe> ,burn1 ne> ! s\!rn end ( ! volcanic di/rict4 ,a b& ( tuff ab\t t5 feet ?ick lies !re int]calat$ 9 a gr\p ( d>k %ales & ?9 coals4 ,bel[ x !re is a seam ( coal f\r in*es ?ick1 & among ! blue %ales ov]ly+ x is ano!r coal t5 in*es ?ick4 ,! tuff is pale gre51 almo/ :ite 9 col\r1 f9e 9 texture1 l a volcanic mud1 :ile "s ( its compon5t b$s1 "o foot 9 ?ickness1 are made up ( f9e lam9 & are ev5 false-b$d$4 ,we might inf] t ! volcanic v5t lay at "s di/ance1 s t only ! f9e/ du/ fell ov] ! swamps 9 :i* ! coal-vegetation 0 accumulat+1 b = ! pres5ce ( occasional blocks ( basalt "o foot 9 diamet] scatt]$ ?r\gh ! tuff4 ,:5 ! eruptions ceas$1 ! deposition ( ord9>y mud & ! accumulation ( plant-rema9s w5t on z be=e1 & animal life cr[d$ 9 aga9 ov] ! spot1 = betwe5 ! p>t+s ( ! coal above ! tuff1 abundant fragm5ts ( eurypt]ids & scorpions may be f\nd4 ,"o ( ! mo/ ext5sive volcanic dis*>ges ( fragm5t>y mat]ial 0 t :i* produc$ ! ,h\/on m>ls already ref]r$ to4 ,^! /rata appe> to m>k a peculi> phase 9 ! volcanic hi/ory ( ! ,l[] ,c>bonif]\s rocks ( ! ,fir? ( ,=?1 :5 exce$+ly f9e a%1 or p]haps ev5 volcanic mud1 0 erupt$ 9 consid]able quantity4 ,! m>ls atta9 9 "s places a ?ickness ( ne>ly #bjj feet1 & c be trac$ ?r\gh mo/ ( ! ea/]n "p ( ,l9li?g[%ire1 ov] an area ( p]haps m ?an #ej squ>e miles4 ,?is volcanic plat=m1 :i* has be5 foll[$ 9 m9+ = oil-%ale1 is "o ( ! mo/ ext5sive among ! puy-eruptions4 ,! mat]ial1 :i* probably came f "o or m v5ts among ! ,ba?gate ,hills1 is n always ( equal f95ess1 b passes into & ev5 alt]nates ) ord9>y granul> tuff4 ,?us 9 ! ,niddry ,burn1 above ,ecclesma*an1 ! dull sage-gre5 & br[ni% r$ ,h\/on m>ls conta9 a few incon/ant lay]s ( gre5 tuff1 9 :i* may be notic$ pieces ( black %ale & lapilli ( ! usual basic pumice4 ,n f> to ! we/1 beyond ,we/] ,o*iltree1 & ?us probably ne>] to ! active v5ts t eject$ ! du/ & a%es1 ! ,h\/on m>ls are replac$ by or include a b$d$ granul> tuff or basalt-agglom]ate1 :i* lies above ! #b-;feet coal ( ! di/rict4 ,! matrix ( ?is rock is 9 "p a dull gre5 granul> mud/one1 wrapp+ r\nd ! lapilli & eject$ /ones1 :i*1 :5 !y fall out "u ! action ( ! wea!r1 leave ca/s ( _! =ms beh9d !m4 ,! enclos$ fragm5ts v>y 9 size up to blocks ?ree feet 9 diamet]1 & consi/ 9 great measure ( a compact volcanic grit1 compos$ ( a f9e mud mix$ ) m9ute fragm5ts ( black %ale1 gra9s ( s& & flakes ( mica4 ,!re are likewise blocks ( cem5t-/one & %ale4 ,?9 c\rses ( black %ale int]lam9at$ ) ! tuff %[ its b$d+4 ,! ?icke/ & mo/ cont9u\s accumulations ( tuff occur r\nd "s ( ! l>g] tuff cones1 p>ticul>ly r\nd ! ,sal9e ,hills1 & 9 ! ,burntisl& di/rict4 ,9 ! fir/-nam$ area ! copi\s eruptions ( fragm5t>y mat]ial br\ght ! volcanic hi/ory !re to an end2 b ar\nd ,burntisl& !y 7 only ! prelude to a prolong$ & v>i$ s]ies ( dis*>ges4 ,i h already rem>k$ t 9 ! area ( ! puys ( ! ,=?-bas91 :ile ! majority ( ! v5ts 7 tuff-cones1 & emitt$ only fragm5t>y dis*>ges1 !re 7 two well-m>k$ tracts :]e lavas 7 p\r$ out ext5sively & dur+ a long geological int]val4 ,"o ( ^? lies 9 ! s\!rn1 ! o!r 9 ! nor!rn area4 ,! s\!rn or ,l9li?g[%ire lava-ridge =ms n[ :at are kn[n z ! ,ba?gate & ,l9li?g[ ,hills4 ,! lavas ext5d = ab\t #ad miles f nor? to s\?1 dy+ out 9 bo? directions1 :ile _! pres5t visible bread? is ab\t ?ree miles at its wide/ "p4 ,! highe/ summit rea*es a height ( ab\t #ajjj feet above ! sea4 ,! /ructure ( ?is long ridge reveals an int]e/+ record ( volcanic eruptions4 ,x consi/s ma9ly ( %eets ( basalt1 sometimes sep>at$ by lay]s ( tuff 7,fig4 #aee74 ,b on "o or two horizons ! volcanic rocks cease1 & ord9>y s$im5t>y deposits take _! place4 ,z has be5 already /at$1 ! ,ma9 or ,hurlet ,lime/one c be trac$ ?r\gh ! he>t ( ! volcanic masses4 ,?is seam atta9s !re an exceptional ?ickness ( z mu* z #gj to #hj feet1 & is n[h]e m abundantly fossilif]\s4 ,dur+ its deposition !re seems to h be5 a subsid5ce ( ! area1 toge!r ) a cessation ( volcanic activity = a "t4 ,! cr9oids1 corals1 bra*iopods1 bryozoa1 lamellibran*s1 ga/]opods1 cephalopods & fi%es1 :i* sw>m$ 9 ! cle> wat]1 built up a ?ick calc>e\s lay] above ! lavas & tuffs ( ! sea-bottom4 ,among ! s&/ones & %ales t cov] ! lime/one1 b&s ( tuff make _! appe>ance1 indicat+ ! r5ewal ( volcanic activity4 ,^! are imm$iately surm\nt$ by ano!r ?ick pile ( basalt-%eets4 ,subsequ5tly1 dur+ pauses 9 ! eruptions1 :ile ! g5]al subsid5ce cont9u$1 r5ew$ deposits ( s$im5t spread ov] ! subm]g$ volcanic bank4 ,"o ( ! longe/ p]iods ( quiesc5ce 0 t dur+ :i* ! coals & ev5 ! ,index ,lime/one ( ,ba?gate crept nor?w>ds ov] ! sunk5 lavas & tuffs4 ,b ! :ole ( ! ridge does n seem to h disappe>$ at t "t "u wat]1 at lea/ ^! int]calat$ /rata h n be5 trac$ across ! ?ick pile ( volcanic mat]ial ne> ,l9li?g[4 ,dur+ ! f9al p]iod ( eruption1 ! outp\r+ ( lava & dis*>ge ( a%es1 nei!r 9 unit$ ?ickness nor 9 horizontal ext5t1 equall$ ^? :i* _h prec$$ !m4 ,:5 ! volcanoes ceas$ _! activity1 ! area cont9u$ to s9k1 & ov] ! subm]g$ lavas m>9e organisms cr[d$ ! sea-floor1 s z to build up ! ,calmy ,lime/one4 ,aft] t "t volcanic action seems to h become ext9ct 9 ?is region1 = no trace ( any int]calat$ lava or tuff has be5 detect$ ei!r 9 ! ov]ly+ ,mill/one ,grit or 9 ! ,coal-measures4 ,! total ?ickness ( rock 9 ! ,l9li?g[%ire volcanic ridge is ab\t #bbjj feet4 ,x w probably n be an exagg]ation to place ! proportion ( lava & tuff 9 t dep? ( mat]ial at ne>ly #bjjj feet4 ,! nor!rn or ,fife%ire di/rict ov] :i* lavas 7 abundantly erupt$ /ret*es along ! coa/ f ,ab]d\r to ,kirkcaldy & inl& to ne> ,lo*gelly1 z well z seaw>ds to ,in*kei?4 ,x may comprise an area ( ab\t #cj squ>e miles4 ,9 _m respects ?is is ! mo/ important locality 9 ,brita9 = ! /udy ( ,c>bonif]\s volcanic hi/ory4 ,! sea has cut an admirable coa/-section 9 :i* ! /ructures ( ! rocks are laid b>e4 ,! bottom & top ( ! :ole volcanic s]ies c be se54 ,! v5ts & _! relation to ! lavas & tuffs t 7 emitt$ f !m may easily be made out2 :ile ! int]/ratification ( well-kn[n seams ( rock 9 ! ,scotti% ,c>bonif]\s sy/em p]mits ! sequ5ce & *ronology ( ! :ole volcanic s]ies to be trac$ ) great cle>ness4 ,mo/ ( ^! features h already be5 describ$ 9 =ego+ pages1 = ! di/rict is a typical "o = ! /udy ( ,c>bonif]\s volcanic ph5om5a4 ,?us ! gr\p ( v5ts ab\t ,burntisl& has be5 illu/rat$ by ! ,b9n ( ,burntisl& ris+ among ! b$d$ lavas & tuffs4 ,! *>act]s ( ! ,c>bonif]\s basalt-%eets h be5 enum]at$1 toge!r ) _! int]calat$ lay]s ( tuff & bole1 & _! f9e p>t+s ( a%y mat]ial t 0 ?r[n out ov] ! lagoons dur+ ! int]vals betwe5 two outbur/s ( lava4 ,b x may be ( s]vice if ,i ins]t "h a detail$ section ( ! :ole volcanic s]ies z x is display$ along ! coa/-section betwe5 ,burntisl& & ,k+horn4 ,! l[e/ int]calat$ lavas ( t section lie a little above ! horizon ( ! ,burdieh\se ,lime/one1 & are ?us probably r e>li] ?an ^? ( ,l9li?g[%ire4 ,! highe/ rea* up to ! base ( ! ,hurlet ,lime/one4 ,! volcanic en]gy manife/ly di$ out "h long be=e x ceas$ on ! s\? side ( ! ,fir?4 ,yet s vigor\s 0 its activity :ile x cont9u$1 t x pil$ up "o ( ! ?icke/ masses ( volcanic mat]ial any:]e to be se5 among ! puy-eruptions ( ! ,briti% ,isles4 ,! foll[+ tabul> /atem5t ( ! alt]nations ( mat]ial 9 ?is great mass 9 desc5d+ ord]1 0 drawn up by me on ! gr\nd _m ye>s ago1 be=e ! con/ruction ( =tifications & o!r *anges p>tly conceal$ ! rocks4 ,illu/ration3 ,fig4 #aga4--;,column> basalt1 ,pettycur1 ,k+horn1 ,fife4 7,f a photograph tak5 = ! ,geological ,survey by ,mr4 ,r4 ,lunn47 ,section ( ! ,volcanic ,s]ies bel[ ! ,hurlet or ,ma9 ,lime/one on ! ,coa/ ( ,fife1 we/ ( ,k+horn1 9 desc5d+ ord]#dgg ,footnote #dgg3 ,! succession ( rocks 9 ?is int]e/+ coa/-section 0 briefly giv5 by ,dr4 ,p4 ,neill 9 8 translation ( ,daubuisson's ,basalts ( ,saxony1 ,ed9burgh1 #ahad1 note f1 p4 #bae4 ,he 0 secret>y ( ! ,w]n]ian ,society1 & 9 8 enum]ation ! ,w]n]ian t]m9ology is us$ )\t a h9t t any s+le b& 9 ! :ole s]ies is ( volcanic orig94 #ge4 ,r$di% & :ite s&/ones4 #gd4 ,%ale ) h>d ribs ( lime/one & iron/one nodules4 ,fossils abundant4 #gc4 ,lime/one1 cr9oidal1 #h or #i feet4 #gb4 ,blue %ale1 becom+ calc>e\s t[>ds ! top1 :]e %ells are pl5tiful4 #ga4 ,r$di% false-b$d$ s&/ones1 ) b&s ( r$di% & blue %ale4 #gj4 ,basalt 9 two sills sep>at$ by #b or #c feet ( s&/one & %ale4 #fi4 ,d>k fissile s&y %ale1 pass+ up into :ite %aly s&/one1 & includ+ a ?9 p>t+ ( impure coal4 #fh4 ,lime/one 7,hurlet or ,ma9 ,seam7 9 a numb] ( b&s hav+ a unit$ ?ickness ( #be feet4 ,abundant fossils4 #fg4 ,black %ale becom+ calc>e\s at top1 & !n enclos+ abundant ,productus1 etc41 #h or #aj feet4 #ff4 ,r$ & gre5 tuface\s m>l & tuff4 ,ab\t #cj feet4 #fe4 ,basalt1 ! l[] "p /rongly amygdaloidal4 #fd4 ,tuface\s r$ m>l & tuff2 comp>atively co>se bel[1 becom+ f9] above1 #c or #d feet4 #fc4 ,basalt1 e>?y & amygdaloidal1 ) an irregul> bottom involv+ masses ( ! %ales bel[4 #fb4 ,d>k calc>e\s %ale & dull gre5 tuface\s m>ly %ale1 #b or #c feet4 #fa4 ,cr9oidal lime/one 9 sev]al b&s ) a unit$ ?ickness ( #aj feet4 #fj4 ,%ale1 #a foot4 #ei4 ,f9e gre5 s&y tuffs 9 a numb] ( b&s ( v>y+ co>s5ess1 ab\t #f feet4 #eh4 ,d>k %ale ) abundance ( ,aviculopect5 imm$iately "u ! tuffs above1 #a feet4 #eg4 ,s(t1 light1 m>ly %ale ) fragm5t>y plants1 #a feet4 #ef4 ,d>k fissile %ale1 full ( fi%-scales1 plants1 etc41 #c feet4 #ee4 ,basalt1 rudely column>1 d>k f9e-gra9$ 9 c5tre1 becom+ highly amygdaloidal & scoriace\s at bottom & top4 #ed4 ,basalt1 l ! %eet above1 vesicul> at top & bottom1 ) a p>t+ ( r$ clay on top4 #ec4 ,fissile rippl$ s&y %ale1 ) plants1 hav+ a r$ & gre5 m>ly p>t+ at ! top1 #ab or #ad feet4 #eb4 ,basalts2 a gr\p ( b$s1 probably 9 "p sills1 involv+ ?ree b&s ( s&/one or qu>tzite4 #ea4 ,qu>tzite--a h>d :ite alt]$ s&/one1 #b to #c feet4 #ej4 ,basalt1 light gre51 e>?y1 amygdaloidal4 #di4 ,s&/ones & %ales ) plants1 #be feet4 #dh4 ,basalt1 ) a highly amygdaloidal c5tral b&4 ,!re may be sev]al %eets "h4 #dg4 ,gre5 tuface\s %ale & m>l1 #a foot4 #df4 ,basalt1 d>k1 firm & amygdaloidal4 #de4 ,s&/ones & %ales ) plants4 #dd4 ,basalt =m+ we/ side ( ,k+horn ,bay1 & includ+ m ?an "o %eet4 ,! rock is v black1 compact1 irregul>ly column>1 ) ! usual amygdaloidal e>?y b& at ! base1 & =ms ! crag call$ ! ,c>l9ehead ,rocks4 ,an irregul> & incon/ant b& ( dull gre5 tuface\s %ale1 sometimes #b feet ?ick1 s]ves to sep>ate two ( ! basalt-%eets4 ,bel[ x lies a rem>kable scoriace\s almo/ brecciat$ basalt1 :i* has be5 brok5 up on cool+ 9 su* a mann] t at fir/ x might be mi/ak5 = a volcanic conglom]ate4 #dc4 ,basalt1 a compact black solid rock1 ) a vesicul> & amygdaloidal bottom1 ab\t #dj feet4 ,?is %eet runs out into ! promontory ( ,k+horn ,ness4 #db4 ,basalt1 firm1 compact & highly amygdaloidal ?r\gh\t1 #ae feet4 #da4 ,basalt1 e>?y1 amygdaloidal & scoriace\s 9 ! upp] "p1 compact bel[4 #dj4 ,r$ tuface\s m>l1 clay or bole1 a few in*es ?ick4 #ci4 ,basalt3 "o ( ! mo/ compact %eets ( ! :ole s]ies1 ab\t #dj feet4 ,! top is =m$ ( a ?ick zone ( scoriace\s & brecciat$ mat]ial1 ! bottom is s+ul>ly unev5 ow+ to ! v irregul> surface ( ! und]ly+ b$4 #ch4 ,basalt m or less scoriace\s ?r\gh\t1 especially at ! bottom1 ! vesicles be+ drawn out r\nd ! slag-l blocks4 #cg4 ,gre5 tuface\s %ales ) b&s ( f9e gre5 tuff1 #g to #h feet4 ,! l[] b&s consi/ ( a gravelly tuff pass+ up into a f9e volcanic mud/one1 ) scatt]$ lapilli ( basalt an in* or m 9 diamet]4 #cf4 ,basalt1 ) an upp]1 e>?y & highly amygdaloidal portion1 #cj feet4 #ce4 ,tuface\s s&/one & %ale1 #f to #h feet4 #cd4 ,basalt1 9 a ?ick b$1 hav+ an e>?y1 slaggy top & a scoriace\s bottom4 #cc4 ,basalt1 v slaggy bel[ ) a compact c5tre4 #cb4 ,basalt1 l t bel[ x4 #ca4 ,basalt1 firm1 compact1 black rock1 ) a r\gh1 gre5 e>?y b&1 f #f in*es to a foot1 at ! bottom1 & becom+ aga9 v slaggy at ! top4 #cj4 ,gre5 %ale l t bel[ ! und]ly+ lime/one1 a few in*es 9 ?ickness4 #bi4 ,co>se1 gre51 s&y tuface\s lime/one1 av]ag+ #a foot 9 ?ickness4 #bh4 ,black %ale ) plants1 #ab or #ad feet1 becom+ gre5 & tuface\s at ! top4 #bg4 ,basalt--! mo/ /rik+ ( ! :ole section--a f9e compact black oliv9e-be>+ rock1 beautifully column>1 #cj feet4 ,! columns rea* to )9 a foot ( ! bottom ( ! b$ & cease ab\t #aj feet f ! top1 ! upp] portion ( ! b$ be+ massive1 ) vesicles :i* are drawn out p>allel to ! b$d+ ( ! s]ies4 ,! l[e/ "p ( ! b$ is a brok5 brecciat$ b&1 #c or #d in*es ?ick4 7,see ,fig4 #aga47 #bf4 ,black %ale ) fragm5t>y plants1 #c feet4 #be4 ,basalt1 ) pl5tiful oliv9e1 #ab to #af feet4 ,! base is n highly scoriace\s1 b f9ely vesicul>4 ,t[>ds ! top x becomes gre51 e>?y & r\ghly brecciat$4 ,x p>tly cuts out ! tuff und]nea?4 #bd4 ,tuff1 gre51 f9e-gra9$ & well-/ratifi$1 consi/+ *iefly ( f9e volcanic du/1 b becom+ co>s] t[>ds ! top1 :]e x conta9s lapilli & occasional bombs ( highly vesicul> lavas4 #bc4 ,black c>bonace\s %ale1 #c feet2 approa*+ to ! "* ( an impure coal 9 ! l[] "p1 & becom+ m argillace\s above ) "s ?9 nodul> calc>e\s b&s4 #bb4 ,gre5 tuff1 #ab feet1 well /ratifi$ & f9e-gra9$1 ) m9ute lapilli ( highly vesicul> basic lavas2 becomes %aly at ! bottom4 #ba4 ,basalt1 compact1 amygdaloidal1 ) highly vesicul> upp] surface1 #bj feet4 #bj4 ,basalt1 h>d1 black & full ( oliv9e2 an irregul> b$ #c to #f feet ?ick4 #ai4 ,basalt1 dull br[ni%-gre5 to black1 full ( k]nels & /r+s ( calcite1 & %[+ h>d] & s(t] b&s p>allel ) upp] & "u surfaces1 :i* give x a /ratifi$ appe>ance4 #ah4 ,basalt1 "s p>ts irregul>ly compact1 o!rs e>?y & scoriace\s4 ,! di/+ui%+ feature ( ?is b$ is ! abundance ( its enclos$ fragm5ts ( %ale1 iron/one & lime/one1 :i* "h & !re =m half ( its bulk4 ,! r\ghly scoriace\s upp] portion is especially full ( ^! fragm5ts4 ,9 ! iron/one balls coprolites may be detect$1 & occasional pieces ( plant-/ems are emb$d$ 9 ! basalt4 ,?is lava has evid5tly brok5 up & involv$ "s ( ! und]ly+ /rata ov] :i* x fl[$4 ,?is rock ov]hangs ,pettycur ,h>b\r4 #ag4 ,%ales & lime/one b&s m or less tuface\s1 #h to #aj feet1 ) plants1 cyprids1 etc4 ,! int]calation ( f9e p>t+s ( tuff 9 ?is b& has be5 already cit$ on p4 #dch1 z an illu/ration ( ! feeble int]mitt5t "* ( _m ( ! volcanic explosions betwe5 successive outfl[+s ( lava4 ,ow+ to a *ange 9 ! direction ( /rike ! rocks n[ :eel r\nd & = a "t run ne>ly p>allel ) ! coa/-l9e1 :ile !y are p>tly conceal$ by bl[n s& & h]bage4 ,! %ales & lime/ones j m5tion$ are n con/ant1 & are soon lo/1 b ab\t a qu>t] ( a mile we/w>d a b& ( tuff beg9s on ! same horizon or ne> x1 & increases 9 ?ickness t[>ds ! we/1 :]e x is associat$ ) o!r s$im5ts4 ,! %ore ceases to furni% a cont9u\s section1 s t rec\rse mu/ be _h to ! craggy slopes imm$iately to ! nor?1 :]e ! rocks c be exam9$ on a cliff face 7,fig4 #aec74 ,!re ! tuff j ref]r$ to1 toge!r ) "s ov]ly+ b&s ( s&/one1 is se5 to pass "u ! gr\p ( basalts la/ enum]at$4 ,x is a gre51 /ratifi$ rock1 p]haps #fj feet ?ick at its maximum1 b dy+ out rapidly to nor?-we/ & s\?-ea/4 ,x encloses balls ( basalt & subangul> & r\nd$ fragm5ts ( s&/one1 lime/one & %ale4 ,a mass ( co>se volcanic agglom]ate :i* is connect$ ) x & cuts across ! ends ( "s ( ! basalts bel[1 probably m>ks ! position ( ! v5t f :i* ! tuff 0 eject$ 7,fig4 #aeb74 #af4 ,black & grey %ales =m+ a ?9 b& at ! summit ( ,k+ ,alex&]'s ,crag4 #ae4 ,basalt1 d>k compact rock1 ) an upp] & l[] highly scoriace\s & amygdaloidal b&1 #ae feet4 #ad4 ,black %ales1 tuface\s gre5 %ales1 s&/one1 & #f in*es ( coal1 =m+ a gr\p ( /rata ab\t #ab feet ?ick betwe5 two basalts2 plants & cyprids abundant4 7,! coal seam is %[n 9 ,fig4 #aea47 #ac4 ,basalt1 dull1 e>?y & highly amygdaloidal1 ) abundant calcite 9 k]nels & ve9s2 ab\t #ae feet1 b v>y+ 9 ?ickness4 #ab4 ,basalt1 =m+ a well-m>k$ b$ f #ab to #be feet ?ick4 ,x is a compact black oliv9e-be>+ rock1 sp>+ly amygdaloidal1 b %[+ ! usual dull gre51 e>?y scori=m base4 ,! upp] surface is s+ul>ly irregul>1 hav+1 9 fl[+1 brok5 up into l>ge cl9k]-l blocks1 :i* are involv$ 9 ! imm$iately ov]ly+ basalt4 ,! bottom also is v unev51 = ! basalt has 9 "s places cut out ! und]ly+ %ales1 s z to re/ directly ^u ! basalt bel[4 #aa4 ,black %ale1 v>y+ up to #f in*es1 b sometimes entirely remov$ by ! ov]ly+ lava-/ream4 #aj4 ,basalt1 conta9+ l>ge irregul>ly sph]oidal masses ( h>d black f9ely vesicul> mat]ial enclos$ 9 m e>?y & co>sely vesicul> rock4 ,! vesicles are sometimes elongat$ p>allel to ! b$d+1 b h (t5 be5 drawn out r\nd a sph]oid2 "s ( !m measure ne>ly a foot 9 l5g? by #b or #c in*es 9 bread?4 ,! upp] surface is unev5 & co>sely amygdaloidal4 #i4 ,basalt1 h>d black1 ) abundant oliv9e1 & a column> /ructure4 #h4 ,gre5 %ale1 #f in*es to #a foot1 mu* bak$ & involv$ 9 ! ov]ly+ basalt4 #g4 ,basalt1 dull-gre51 e>?y1 amygdaloidal1 v>y+ f #aj to #dj feet 9 ?ickness4 #f4 ,blue %ale1 disappe>+ :]e ! basalt above x unites ) t bel[4 #e4 ,basalt ) oliv9e1 =m+ a ?ick irregul> b$1 :i* 9 "s places is black & compact1 9 o!rs gre51 e>?y & amygdaloidal4 ,! upp] "p is p>ticul>ly cellul>4 #d4 ,s&/ones =m+ a ?ick gr\p ( b$s :i* h long be5 qu>ri$ = build+-/one at ! ,grange & else:]e4 #c4 ,black %ales4 #b4 ,lime/one 7,burdieh\se74 #a4 ,s&/ones1 %ales & ?9 lime/ones =m+ ! /rata at ,burntisl& ?r\gh :i* ! sills ( t di/rict h be5 inject$ 7,fig4 #aei74 ,! ph5om5a ( sills are abundantly develop$ among ! ,c>bonif]\s rocks ( ! bas9 ( ! ,fir? ( ,=?1 & "s ( ! m rem>kable examples 9 ?is di/rict h be5 already cit$4 ,tak+ n[ a g5]al survey ( ?is "p ( ! volcanic hi/ory1 ,i may obs]ve t if ! sills are = a mom5t consid]$ simply z !y appe> at ! surface1 & ap>t f ! geological horizons on :i* !y lie1 !y =m a wide r+ surr\nd+ ! ,falkirk & ,/irl+%ire coal-field4 ,beg9n+ at ! ,abbey ,craig1 ne> ,/irl+1 we may trace ?is r+ z a cont9u\s belt ( high gr\nd f ,/irl+ to ! ,riv] ,c>ron4 ,!nce x splits up into m9or masses 9 diff]5t portions ( ! ,c>bonif]\s sy/em1 & d\btless belong+ to diff]5t p]iods ( volcanic di/urbance1 b yet sweep+ z a :ole across ! nor?-ea/]n "p ( ! ,clyde coal-field1 & !n circl+ r\nd into ,/irl+%ire & ,l9li?g[%ire4 ,!re are no visible masses to fill up ! portion ( ! r+ back to ,abbey ,craig4 ,b ?r\gh ,l9li?g[%ire & ! we/ ( ,ed9burgh%ire a numb] ( intrusive %eets =m an ea/w>d prolongation ( ! r+4 ,l>ge z "s ( ^! %eets are at ! surface1 = !y sometimes exce$ two or ?ree squ>e miles 9 area1 a mu* l>g] portion ( _! mass is g5]ally conceal$ bel[ gr\nd4 ,m9+ op]ations1 = example1 h prov$ t 9 ! s\?-ea/ ( ,l9li?g[%ire areas ( intrusive rock :i* appe> z deta*$ bosses or b&s at ! surface are connect$ und]nea? z portions ( "o cont9u\s sill1 :i* mu/ be sev]al squ>e miles 9 ext5t4 ,illu/ration3 ,fig4 #agb4--,section across ! ,fife b& ( ,sills4 #a4 ,upp] ,old ,r$ ,s&/one2 #b4 ,calcif]\s ,s&/ones2 #c4 ,c>bonif]\s ,lime/one s]ies2 #d4 ,mill/one ,grit2 #e4 ,coal-measures2 #f4 ,dol]ite ,sills4 f1 ,fault4 ,b x is 9 ,fife t ! sills rea* _! greate/ developm5t among ! ,c>bonif]\s rocks ( ,scotl& 7,fig4 #agb74 ,a ne>ly cont9u\s belt ( !m runs f ! ,cult ,hill ne> ,sal9e on ! we/1 to ne> ,/4 ,&rews on ! ea/1 a di/ance ( ab\t #ce miles4 ,?is rem>kable b& is connect$ ) a less ext5sive "o1 :i* ext5ds f ,torryburn on ! we/1 to ne> ,kirkcaldy on ! ea/4 ,9 two di/ricts ( ! ,fife region ( sills1 a connection seems to be traceable betwe5 ! intrusive %eets & volcanic v5ts1 at lea/ gr\ps ( necks are f\nd 9 ! mid/ ( ! sills4 ,"o ( ^! di/ricts is t ( ! ,sal9e ,hills already describ$1 ! o!r is t ( ,burntisl&4 ,9 ! latt] case ! evid5ce is especially /rik+1 = ! v5ts are connect$ above ) b$d$ lavas & tuffs1 :ile bel[ lie ?ree well-m>k$ sills 7,fig4 #aei74 ,x is c]ta9ly wor?y ( rem>k t sills are g5]ally abs5t f ^? areas :]e no traces ( contemporane\s volcanic activity are to be f\nd4 ,no contra/ 9 ?is respect c be /rong] ?an t betwe5 ! gr\nd to ! ea/ & we/ ( ! old axis ( ! ,p5tl& ,hills4 ,9 ! we/]n di/rict1 :]e ! puys are s well display$1 sills ab\nd1 b 9 ! ea/]n tract bo? disappe>4 ,ano!r "q ( importance 9 deal+ ) ! hi/ory ( ^! sills is _! /ratigraphical position4 ,by f> ! l>g] proportion ( !m lies 9 ! ,c>bonif]\s ,lime/one s]ies4 ,?us ! great sill betwe5 ,/irl+ & ,kilsy? keeps among ! l[] p>ts ( t s]ies4 ,on ! same g5]al horizon are ! va/ %eets ( dol]ite :i* /ret* ?r\gh ,fife 9 ! *a9 ( ! ,cult1 ,clei%1 & ,lomond ,hills on ! "o side1 & 9 ! em95ces f ,torryburn to ,k+horn on ! o!r1 ?\gh ! intrusive mat]ial sometimes desc5ds almo/ to ! ,old ,r$ ,s&/one4 ,9 ,l9li?g[%ire & ,ed9burgh%ire1 z well z 9 ! s\? ( ,fife1 ! sills trav]se ! ,calcif]\s ,s&/one gr\ps4 ,if ! horizons ( ! sills furni%$ any reliable clue to _! age1 x might be inf]r$ t ! rocks 7 all intrud$ dur+ ! ,c>bonif]\s p]iod1 & z mo/ ( !m lie b5ea? ! upp] /ratigraphical limit ( ! puy-eruptions1 ! fur!r d$uction might be drawn t !y are connect$ ) ^! eruptions4 ,i h little d\bt t 9 a g5]al s5se bo? conclusions are well-f\nd$4 ,b t !re are exceptions to ! g5]alization mu/ be frankly conc$$4 ,on close exam9ation x w be obs]v$ t ! same intrusive mass sometimes ext5ds f ! l[] into ! upp] p>ts ( ! ,c>bonif]\s gr\ps4 ,?us1 9 ! we/ ( ,l9li?g[%ire1 a l>ge protrusion :i* lies ^u ! ,upp] ,lime/ones1 crosses mo/ ( ! ,mill/one ,grit1 & rea*es up almo/ z high z ! ,coal-measures4 ,aga91 9 ,fife1 to ! ea/ ( ,lo* ,lev51 a spur ( ! great ,lomond sill1 cross+ ! ,c>bonif]\s lime/one1 advances s\?w>d into ! coal-field ( ,k+lassie1 ,9 ,/irl+%ire & ,lan>k%ire num]\s l>ge dol]ite %eets h invad$ ! ,mill/one ,grit & ,coal-measures1 includ+ ev5 ! upp] r$ s&/ones1 :i* =m ! top ( ! ,c>bonif]\s sy/em 9 ?is region4 ,x is ?us obvi\s t if ! puy-eruptions 9 ! bas9 ( ! ,=? ceas$ t[>ds ! close ( ! deposition ( ! ,c>bonif]\s ,lime/one s]ies1 !re mu/ h be5 a subsequ5t injection ( basic lava on a gigantic scale 9 c5tral ,scotl&4 ,i %all recur to ?is subject 9 ,*apt] xxxi4 ,illu/ration3 ,fig4 #agc4--,section across ! ,upp] ,volcanic ,b& ( nor? ,ayr%ire4 ,l5g? ab\t f\r miles4 #a4 ,&esite lavas ( ! ,clyde ,plateau2 #b4 ,tuffs clos+ ! ,plateau volcanic s]ies2 #c4 ,hurlet ,lime/one2 #d4 ,c>bonif]\s ,lime/one s]ies ) coal-seams2 #e4 ,l[] tuff zone ( ! ,upp] volcanic b&2 #f4 ,basic lavas2 #g4 ,upp] tuff zone2 #h4 ,basic sill2 #i4 ,coal-measures4 #b4 ,,nor? ,,( ,,ayr%ire ,9 ?is "p ( ! c\ntry ano!r gr\p ( puys & _! associat$ tuffs & lavas may be trac$ f ne> ,dairy on ! we/1 to ne> ,gal/on on ! ea/ 7,map ,,iv474 ,! l5g? ( ! tract is ab\t sixte5 miles1 :ile its bread? v>ies f ab\t a furlong to ne>ly a mile & a half4 ,i h _h occasion to allude to ?is m>k$ b& ( volcanic mat]ials :i* "h int]v5es betwe5 ! ,c>bonif]\s ,lime/one & ! ,coal-measures1 & f its position appe>s to m>k ! late/ ,c>bonif]\s volcanoes4 ,its compon5t rocks rea* a ?ickness ( sometimes #fjj feet1 & z !y dip s\?w>ds "u ! ,coal-measures1 !y may ext5d = "s di/ance 9 t direction4 ,!y h be5 met ) 9 bor+s sunk ?r\gh ! nor!rn "p ( ! ,irv9e coal-field4 ,ev5 :at ( !m c be se5 at ! surface1 9 spite ( ! effects ( faults & d5udation1 %[s t !y =m "o ( ! mo/ p]si/5t plat=ms ( volcanic rock among ! puy-eruptions ( ,scotl&4 ,:]e be/ develop$ ?is volcanic b& has a zone ( tuff at ! bottom1 a c5tral & mu* ?ick] zone ( b$d$ basalts1 & an upp] gr\p ( tuffs1 on :i* ! ,coal-measures re/ con=mably4 ,a few v5ts1 probably connect$ ) x1 are to be se5 at ! surface betwe5 ,f5wick & ,ardrossan4 ,b o!rs h be5 buri$ "u ! ,c>bonif]\s s$im5t>y rocks1 &1 z already describ$1 h be5 discov]$ 9 ! und]gr\nd work+s = coal & iron/one 7p4 #dcd74 ,^! m9+ op]ations h1 inde$1 reveal$ ! pres5ce ( f> m volcanic mat]ial bel[ gr\nd ?an w\ld be surmiz$ f :at c be se5 at ! surface4 ,"h & !re1 ?9 lay]s ( tuff appe> 9 brook-sections1 indicat+ :at might be conjectur$ to h be5 trifl+ dis*>ges ( volcanic mat]ial4 ,b ! prosecution ( ! iron/one-m9+ has prov$ t1 at ! "t :5 ! seam ( ,black-b& ,iron/one ( t di/rict 0 accumulat$1 ! floor ( ! %all[ sea or lagoon :]e ?is deposition took place 0 dott$ ov] ) cones ( tuff1 9 ! holl[s betwe5 :i* ! f]rug9\s & o!r s$im5ts ga!r$ into lay]s4 ,t seam is 9 "o place ?ick & ( good quality2 yet only a %ort di/ance (f x is f\nd to be s mix$ ) f9e tuff z to be wor?less1 & ev5 to die out altoge!r4#dgh ,footnote #dgh3 ,see ,explanation ( ,%eet #bb1 ,geol4 ,surv4 ( ,scotl&1 p>s4 #bi1 #cc1 #de4 #c4 ,,liddesdale ,a rem>kable developm5t ( puys lies 9 t little-visit$ tract ( c\ntry :i* /ret*es f ! valleys ( ! ,teviot & ,rule ,wat] s\?-we/w>ds across ! high moorl& wat]%$1 & d[n ,liddesdale4 ,?r\gh ?is di/rict a zone ( b$d$ oliv9e-basalts & associat$ tuffs runs 9 a brok5 b& :i*1 ow+ to num]\s faults & ext5sive d5udation1 cov]s n[ only a few scatt]$ pat*es ( ! site ov] :i* x once spread4 ,! geological horizon ( ?is zone lies 9 ! ,calcif]\s ,s&/ones1 _m hundr$ feet above ! position ( ! top ( ! plateau-lavas 7,map ,,iv474 ,s great an am\nt ( mat]ial has be5 "h remov$ by d5udation t n only has ! volcanic zone be5 b>$ away1 b ! v5ts :i* suppli$ its mat]ials h be5 reveal$ 9 ! mo/ rem>kable mann] ov] an area "s tw5ty miles long & eight miles broad4 ,upw>ds ( =ty necks ( agglom]ate may be se5 9 ?is di/rict1 ris+ ?r\gh ! ,silurian1 ,old ,r$ ,s&/one1 & l[e/ ,c>bonif]\s rocks4 ,x fills ! geologi/ ) wond] to meet ) ^? /umps ( old volcanoes f> to ! we/ among ! ,silurian l[l&s1 sometimes fully t5 miles away f ! ne>e/ relic ( ! b$d$ lavas connect$ ) !m4#dgi ,t ^! v5ts1 ?\gh !y rose ?r\gh gr\nd :i* at ! "t ( _! activity 0 cov]$ ) ! volcanic s]ies ( ! plateaux1 d n belong to t s]ies1 b are ( y\ng] date1 has be5 prov$ 9 sev]al cases by ,mr4 ,pea*4 ,he has f\nd t among ! blocks compos+ _! agglom]ates1 pieces ( ! s&/ones1 fossilif]\s lime/ones & %ales ( ! ,cem5t-/one gr\p1 ov]ly+ ! plateau-lavas1 are to be recogniz$4 ,^! v5ts 7 !re=e drill$ ?r\gh "s "p at lea/ ( ! ,calcif]\s ,s&/ones1 :i* are ?us %[n to h ext5d$ across ! tract dott$ ) v5ts4 ,aft] ! volcanic activity ceas$1 fragm5ts ( ^! /rata tumbl$ d[n f ! sides into ! funnels4 ,d5udation has s9ce /ripp$ (f ! ,calcif]\s ,s&/ones1 b ! pieces deta*$ f !m1 & seal$ up at a l[] level 9 ! agglom]ates1 /ill rema94 ,mr4 ,pea*'s obs]vations indicate to h[ consid]able an ext5t sagg+ ( ! walls ( ^! orifices took place1 ) ! precipitation n m]ely ( blocks1 b ( enorm\s masses ( rock1 into ! volcanic *imneys4 ,9 "o in/ance1 betwe5 ,tudhope ,hill & ,anton ,heights1 a long neck1 or p]haps gr\p ( necks1 :i* crosses ! wat]%$1 %[s a mass ( ! r$ s&/one _m acres 9 ext5t1 & l>ge en\gh to be ins]t$ on ! "o-in* map1 :i* has fall5 into ! v5t 7,fig4 #age74 ,footnote #dgi3 ,!y h be5 recogniz$ & mapp$ by ,mr4 ,b4 ,n4 ,pea* = ! ,geological ,survey4 ,see ,%eets #aa & #ag1 ,geol4 ,surv4 ,scotl&4 ,illu/ration3 ,fig4 #agd4--,section %[+ ! connection ( ! two volcanic b&s 9 ,liddesdale4 #a4 ,upp] ,silurian /rata2 #b4 ,upp] ,old ,r$ ,s&/one2 #c4 ,! lavas ( ! ,solway plateau2 #d4 ,agglom]ate neck ) lava plug1 belong+ to ! plateau sy/em2 #e4 ,calcif]\s ,s&/one s]ies2 #f4 ,?ick ,c>bonif]\s ,lime/ones2 #g4 ,tuff1 & #h4 ,lavas1 ( ! upp] volcanic b&1 connect$ ) ! puys2 #i4 ,agglom]ate neck ) lava plug belong+ to ! puy-sy/em2 #aj4 ,basic sill4 ,illu/ration3 ,fig4 #age4--;,diagram to %[ ! position ( a mass ( ,upp] ,old ,r$ ,s&/one :i* has fall5 into ! great v5t ne> ,tudhope ,hill1 ea/ ( ,mosspaul4 #a4 ,upp] ,silurian /rata2 #b4 ,outli] ( ,upp] ,old ,r$ ,s&/one2 #b4 ,l>ge mass ( ?is =mation 9 ! v5t2 #c4 ,agglom]ate ( ! neck ) &esite intrusion 7#d74 ,! mat]ials eject$ f ! ,liddesdale v5ts include bo? basaltic lavas & tuffs4 ,! =m] are sometimes highly vesicul>1 especially along ! upp] p>ts ( ! fl[s4 ,!y are ?icke/ t[>ds ! nor?1 & 9 ,w9dburgh ,hill atta9 a dep? ( at lea/ #cjj or #djj feet4 ,9 t "p ( ! di/rict !y =m ! l[] & ma9 "p ( ! volcanic s]ies1 be+ !re cov]$ by a gr\p ( tuffs4 ,b a few miles s\?w>ds1 n f> to ! we/ ( ,k]%opefoot1 !y die out4 ,! tuffs !n =m ! :ole ( ! volcanic b& :i*1 int]calat$ 9 a well-m>k$ gr\p ( lime/ones1 c be foll[$ across ! moors = "s six miles into ! valley ( ! ,esk1 :]e an int]e/+ section ( !m & ( ! associat$ lime/one & %ales is expos$ 7,fig4 #agd74 ,at ,k]%opefoot1 a high] b& ( basic lava ov]lies ! ,k]%opefoot lime/one1 & c be trac$ 9 scatt]$ pat*es bo? on ! ,scotti% & ,engli% side ( ! ,bord]4 ,,end ,,( ,,vol4 ,i4 ,pr9t$ by ,r4 ,r4 ,cl>k1 ,limit$1 ,ed9burgh4 ,illu/ration3 ,,to ,,accompany ,,sir ,,ar*ibald ,,geikie',s ,,anci5t ,,volcanoes ,,( ,,brita9 ,map ,,iv4 ,,map ,,( ,,! ,,c>bonif]\s ,,volcanoes ,,( ,,scotl& ,engli% ,miles ,,explanation ,,( ,,col\r+ ,basalts & ?9 ,tuffs ,puy ,s]ies ,?ick] ,%eets ( ,tuff ,lavas & ?9 ,tuffs ,plateau ,s]ies ,?ick] ,%eets ( ,tuff ,v5ts fill$ ) ,agglom]ate or ,tuff ,basic ,sills & ,bosses ,int]m$iate & acid ,sills & ,bosses ,! ,ed9burgh ,geographical ,in/itute ,copyright ,j4 ,g4 ,b>?olomew4 ,illu/ration3 ,,map #a ,,map ,,( ,,! ,,volcanic ,,di/ricts ,,( ,,! ,,briti% ,,isles ,,by ,sir ,,ar*ibald ,,geikie1 ,d4,c4,l41 ,f4,r4,s4 ,,by ,,! ,,same ,,au?or4 ,,text-,,book ,,( ,,geology4 ,) ,illu/rations4 ,?ird ,edition4 ,revis$ & ,enl>g$4 ,m$ium #hvo4 #bhs4 ,,class-,,book ,,( ,,geology4 ,illu/rat$ ) woodcuts4 ,second ,edition4 ,cr[n #hvo4 #ds4 #f;d4 ,,elem5t>y ,,lessons ,,9 ,,physical ,,geography4 ,illu/rat$ ) woodcuts & t5 plates4 ,fcap4 #hvo4 #ds4 #f;d4 ,que/ions = ! use ( ,s*ools4 ,fcap4 #hvo4 #as4 #f;d4 ,,physical ,,geography4 ,illu/rat$4 ,pott #hvo4 #as4 ,sci5ce ,prim]s4 ,,! ,,sc5]y ,,( ,,scotl& ,,view$ ,,9 ,,connexion ,,) ,,its ,,physical ,,geology4 ,) a ,geological ,map & ,illu/rations4 ,second ,edition4 ,cr[n #hvo4 #abs4 #f;d4 ,,geology4 ,) ,illu/rations4 ,pott #hvo4 #as4 ,sci5ce ,prim]s4 ,,outl9es ,,( ,,field ,,geology4 ,new & revis$ ,edition4 ,extra ,fcap4 #hvo4 #cs4 #f;d4 ,,geological ,,sket*es ,,at ,,home ,,& ,,abroad4 ,) ,illu/rations4 #hvo4 #ajs4 #f;d4 ,,! ,,tea*+ ,,( ,,geography4 ,sugge/ions reg>d+ pr9ciples & me?ods = ! use ( tea*]s4 ,globe #hvo4 #bs4 ,geographical ,s]ies4 ,,geography ,,( ,,! ,,briti% ,,isles4 ,pott #hvo4 #as4 ,geographical ,s]ies4 99 99 99 99 99 ,box ( ,geological ,specim5s to illu/rate ,geikie's ,prim] ( ,geology4 #ajs4 #f;d4 ,,macmillan ,,& ,,co41 ,ltd41 ,,london4 ,,macmillan ,,& ,,co4',s ,,books ,,= ,,/ud5ts ,,( ,,physical ,,geography1 ,,geology1 ,,& ,,m9]alogy4 ,,physics ,,( ,,! ,,e>?',s ,,cru/4 ,by ,rev4 ,osmond ,fi%]1 ,m4,a41 ,f4,g4,s41 ,hon4 ,fell[ ( ,k+'s ,college1 ,london4 #bnd ,ed41 enl>g$4 #hvo4 #abs4 ,,tables ,,= ,,! ,,det]m9ation ,,( ,,! ,,rock-,,=m+ ,,m9]als4 ,compil$ by ,f4 ,l4 ,loew9son-,less+4 ,trans4 by ,j4 ,w4 ,gregory1 ,b4,sc41 ,f4,g4,s4 ,gloss>y by ,pr(4 ,g4 ,a4 ,j4 ,cole1 ,f4,g4,s4 #hvo4 #ds4 #f;d4 net4 ,,microscopical ,,physiography ,,( ,,! ,,rock-,,mak+ ,,m9]als4 ,by ,h4 ,ros5bus*4 ,trans4 by ,j4 ,p4 ,idd+s4 #hvo4 #bds4 ,,meteorology4 ,by ,t4 ,russell4 #hvo4 #afs4 net4 ,a ,,popul> ,,treatise ,,on ,,! ,,w9ds4 ,by ,w4 ,f]rel1 ,m4,a41 ,memb] ( ! ,am]ican ,national ,academy ( ,sci5ces4 #hvo4 #ags4 net4 ,,economic ,,geology ,,( ,,! ,u4,s4 ,by ,r4 ,s4 ,t>r1 ,b4 ,s4 #hvo4 #afs4 net4 ,,elem5t>y ,,physical ,,geography4 ,by ,r4 ,s4 ,t>r1 ,b4,s4 ,cr[n #hvo4 #gs4 #f;d4 net4 ,,elem5ts ,,( ,,cry/allography1 = ,/ud5ts ( ,*emi/ry1 ,physics1 & ,m9]alogy4 ,by ,g4 ,h4 ,williams1 ,ph4,d4 ,cr[n #hvo4 #fs4 ,,popul> ,,lectures ,,& ,,addresses4 ,by ,"l ,kelv91 ,p4,r4,s41 ,vol4 ,,ii4 ,geology & ,g5]al ,physics4 ,cr[n #hvo4 #gs4 #f;d4 ,,! ,,planet ,,e>?4 ,by ,r4 ,a4 ,gregory1 ,f4,r4,a4,s4 ,cr[n #hvo4 #bs4 ,,physiography4 ,an ,introduction to ! ,/udy ( ,nature4 ,by ! ,"r ,hon4 ,t4 ,h4 ,huxley1 ,f4,r4,s4 ,illu/rat$4 ,cr[n #hvo4 #fs4 ,,%ort ,,/udies ,,9 ,,e>? ,,k4 ,introduction to ,physiography4 ,by ,william ,gee4 ,illu/rat$4 ,globe #hvo4 #hs4 #f;d4 ,,outl9es ,,( ,,physiography--,,! ,,movem5ts ,,( ,,! ,,e>?4 ,by ,j4 ,norman ,locky]1 ,f4,r4,s4 ,illu/rat$4 ,cr[n #hvo4 ,sew$1 #as4 #f;d4 ,,physiography ,,= ,,beg9n]s4 ,by ,a4 ,t4 ,simmons1 ,b4,sc4 ,globe #hvo4 #bs4 #f;d4 ,,macmillan ,,& ,,co4 ,ltd41 ,,london4 99 99 99 99 99 ,transcrib] ,note ,m9or typos correct$4 ,sev]al tables 7 rotat$ s !y w fit 9 ! limits ( ! text =mat4 ,text re>rang$ to avoid split p>agraphs at full page images4