,trancrib]'s ,note ,text emphasis is display$ z ,italic & ,bold4 ,:ole & fractional p>ts are display$ z #h-a_/b4 ,al?\gh 9 g5]al1 subscripts are d5ot$ 4 ,! =mulae = ! m9]als are pres5t$ z ,k#b,o,al#b,o#cf,si,o#b 7,or?oclase7 :]e ! numb] foll[+ ! elem5t w\ld normally be subscript$4 ,! ,cambridge ,manuals ( ,sci5ce & ,lit]ature ,,! ,,natural ,,hi/ory ,,( ,,clay ,,cambridge ,,univ]sity ,,press ,london3 ,,fett] ,,lane1 ,e4,c4 ,c4 ,f4 ,,clay1 ,manag] ,illu/ration ,ed9burgh3 #ajj1 ,,pr9ces ,,/reet ,london3 ,,william ,,wesley ,,& ,,son1 #bh1 ,,essex ,,/reet1 ,,/r& ,b]l93 ,a4 ,,a%] ,,& ,,co4 ,leipzig3 ,f4 ,a4 ,,brockhaus ,new ,york3 ,g4 ,p4 ,,putnam',s ,,sons ,bombay & ,calcutta3 ,,macmillan ,,& ,,co41 ,ltd4 ,all rights res]v$ ,illu/ration ,,! ,,natural ,,hi/ory ,,( ,,clay ,,by ,,alfr$ ,b4 ,,se>le ,cantor ,lectur] on ,brickmak+1 ,au?or ( ,briti% ,clays1 ,%ales & ,s&s2 ,! ,claywork]'s ,h&book1 etc41 etc4 ,cambridge3 at ! ,univ]sity ,press ,new ,york3 ,g4 ,p4 ,putnam's ,sons #aiab ,cambridge3 ,,pr9t$ ,,by ,,john ,,clay1 ,m4,a4 ,,at ,,! ,,univ]sity ,,press ,) ! exception ( ! coat ( arms at ! foot1 ! design on ! title page is a reproduction ( "o us$ by ! e>lie/ kn[n ,cambridge pr9t]1 ,john ,sib]*1 #aeba ,,preface ,bo? z raw mat]ials & 9 ! =m ( pott]y1 bricks1 tiles1 t]ra-cotta & _m o!r articles ( use & ornam5t1 clays are among/ ! mo/ important rock products4 ,yet ! orig9 ( ! sub/ances we "k z 'clay1' ! processes occurr+ 9 its =mation & ! causes ( "s ( ! mo/ important ( its *>act]i/ics are ( su* a nature t x is rem>kable t its use %\ld h become s ext5d$ 9 ! arts & sci5ces1 :ile we "k s little ( its prop]ties :5 9 a pure /ate4 ,9 ! foll[+ pages an attempt has be5 made to /ate 9 a simple =m an outl9e ( our pres5t k ( ! subject & to indicate ! problems :i* /ill lie be=e u4 ,! exp]im5tal solution ( ^! problems is r5d]$ peculi>ly difficult by ! in]tness ( ! mat]ials at ord9>y temp]atures & ! ease ) :i* ! clay molecule appe>s to break d[n into its con/itu5t oxides at temp]atures approa*+ r$ heat or z soon z x beg9s to react ) alkal9e or basic mat]ials4 ,ano!r s]i\s difficulty is ! highly complex nature ( t prop]ty kn[n z 'pla/icity' to :i* _m clays owe _! *ief value4 ,= _m ye>s ?is has be5 reg>d$ z an elem5t>y prop]ty su* z h>dness1 cohesion or col\r1 b x is n[ kn[n to be ( s elusive a nature z almo/ to defy measurem5t ) any degree ( accuracy4 ,! ?or\ghness ) :i* ! me?ods ( physical *emi/ry h be5 appli$ to geological & m9]alogical problems dur+ rec5t ye>s has be5 ( v great assi/ance to ! /ud5t ( clay problems1 z w be se5 on /udy+ "s ( ! works m5tion$ 9 ! %ort bibliography at ! end ( ! pres5t volume4 ,:5 ! pr9ciples ( hydrolysis1 ionization1 mass reaction & reactional velocity h be5 appli$ 9 /ill fur!r detail to ! /udy ( clays1 our k ( _! natural hi/ory w increase ev5 m rapidly ?an x has done dur+ ! pa/ few ye>s4 ,no indu/ry ex]cises s great a fasc9ation ov] ^? engag$ 9 x z d ! v>i\s bran*es ( claywork+2 no o!r sub/ance (f]s s _m problems ( su* absorb+ int]e/ to ! arti/1 ! craftsman1 ! geologi/1 ! *emi/ & ! g5]al /ud5t ( nature1 :il/ ! diff]5ces 9 legal op9ion z to ! nature ( clay c\ld !mselves occupy a volume f> l>g] ?an ! pres5t "o4 ,a4 ,b4 ,s4 ,! ,:ite ,build+1 ,%effield4 ,novemb] #aiaa4 ,,cont5ts ,,*ap4 ,,page ,table ( clay rocks viii ,i ,introduction4 ,! *emical & physical prop]ties ( clays #a ,,ii ,clay & associat$ rocks #dh ,,iii ,! orig9s ( clays #gj ,,iv ,! modes ( accumulation ( clays #hd ,v ,"s clays ( comm]cial importance #ajc ,,vi ,clay-sub/ance3 !oretical & actual #ace ,bibliography #afh ,index #agj ,,li/ ,,( ,,illu/rations ,,fig4 #a ,qu>tz cry/als #i #b ,pyrite #ad #c ,m>casite #ad #d ,illu/rat+ ! /ructure ( a 'clay crumb' #bd #e ,*>t %[+ rates ( dry+ #bg #f ,seg] ,cones indicat+ a temp]ature ( #abej ,c4 #cd #g ,ludwig's ,*>t #cf #h ,coal ,measures sequ5ce 9 ,nor? ,/af=d%ire #ee #i ,lias clay be+ work$ = ! manufacture ( h&-made s&-fac$ ro(+ tiles #eh #aj ,ox=d clay ne> ,pet]bor\gh #fj #aa ,cliffs ( ,b\ld] clay at ,filey ly+ on ,calc>e\s ,crag #ff #ab ,*9a clay pit belong+ to ! ,nor? ,cornwall ,*9a ,clay ,co4 #gb #ac ,or?oclase ,felsp> #ge #ad ,illu/rat+ ! successive deposition ( diff]5t /rata #ij #ae ,lacu/r9e clay at ,skipsea #ib #af ,clay at ,no/el1 %[+ ,m>9e ,b& #id #ag ,kaol9ite & ,mica #aje #ah ,m9+ be/ ,pott]'s clay 9 ,devon%ire #aaa ,,! ,,*ief ,,clay ,,rocks 7arrang$ geologically7 ---------------------------------------- ---------------- ,rec5t 7alluvial clay1 silt1 brick e>?s1 b\ld] clay7 ---------------------------------------- ---------------- ,t]ti>y ,plioc5e ,mioc5e 7brick e>?s1 ball clays1 ,oligoc5e co>se pott]y clays7 ,eoc5e ---------------------------------------- ---------------- ,cretace\s 7cem5t clays1 brick clays7 ---------------------------------------- ---------------- ,second>y ,oolitic 7brick & tile clays7 ---------------------------------------- ---------------- ,triassic 7brick1 tile & t]ra-cotta clays7 ---------------------------------------- ---------------- ,p]mian 7brick1 tile & fl[]-pot clays7 ---------------------------------------- ---------------- ,c>bonif]\s 7brick clays1 fireclays1 gani/]7 ---------------------------------------- ---------------- ,prim>y ,devonian ,silurian ,ordovician 7clay s*i/s1 slates & clay %ales7 ,cambrian ,pre-,cambrian ---------------------------------------- ---------------- ,igne\s ,rocks occur on sev]al horizons 7*9a clays & kaol9s7 ---------------------------------------- ---------------- 7,9 ! above ,table only ! clay-be>+ /rata are m5tion$4 ,! =mations nam$ consi/ *iefly ( o!r rocks 9 :i* ! clays =m /rata ( v>iable ?ickness47 ,,*apt] ,i ,,introduction4 ,,! ,,*emical ,,& ,,physical ,,prop]ties ,,( ,,clay ,! *ief uses ( clay h be5 recogniz$ s9ce ! e>lie/ p]iods ( civilization2 ! anci5t ,assyrian & ,egyptian records conta9 num]\s ref]5ces to ! employm5t ( clay = ! manufacture ( bricks & = full+ or :it5+ clo?4 ,clays are di/ribut$ s widely & 9 _m cases are s readily accessible t _! exi/5ce & "s ( _! *>act]i/ics are kn[n 9 entirely unciviliz$ regions4 ,! use ( c]ta9 :ite clays z a food1 or at any rate z a means ( /av+ (f hung]1 is common among "s tribes ( v primitive peoples4 ,! m important uses ( clays = build+ & o!r purposes are naturally conf9$ to ! m civiliz$ nations4 ,! t]m clay 7,a4,s4 cloeg2 ,wel% clai2 ,dut* kley7 al?\gh us$ 9 a sci5tific s5se to include a v>iety ( argillace\s e>?s 7,fr4 argile clay7 us$ 9 ! manufacture ( bricks1 tiles1 pott]y & c]amic products 7,gr4 k]amos pott]'s e>?7 g5]ally1 is really a ^w ( popul> orig9 & use4 ,consequ5tly1 x is necess>y to be> 9 m9d1 :5 consid]+ geological or o!r problems ( a sci5tific nature1 t ?is t]m has be5 incorporat$ into sci5tific t]m9ology & t its use 9 ?is connection n infrequ5tly leads to confusion4 ,9 %ort1 :il/ almo/ e diction>y includes "o or m def9itions ( clay1 & mo/ text-books on geology1 m9]alogy1 & alli$ sci5ces ei!r attempt a def9ition or assume ! read]'s k ( "o1 !re is no entirely satisfactory limitation 9 reg>d to ! sub/ances :i* may or may n be includ$ "u ! t]m4 ,clay is a popul> t]m = a v>iety ( sub/ances ( v v>i$ orig9s1 ( great dissimil>ity 9 _! composition & 9 _m ( _! *emical & physical prop]ties1 & diff]+ greatly 9 almo/ e conceivable respect4 ,x is commonly suppos$ t all clays are pla/ic1 b "s ( ! pure/ *9a clays are almo/ devoid ( ?is prop]ty & "s ( ! mo/ impure e>?s us$ = brickmak+ possess x 9 a /rik+ degree4 ,%ales1 on ! "o h&--:il/ cle>ly a v>iety ( clay--are h>d & rock-l1 requir+ to be r$uc$ to p[d] & v ?or\ghly mix$ ) wat] be=e !y become pla/ic2 _m impure surface deposits1 on ! o!r h&1 are s highly pla/ic z to necessitate ! addition ( o!r 7s&y7 mat]ials be=e !y c be us$ = ! manufacture ( bricks & tiles4 ,attempts h be5 made to include 9 ! t]m clay 'all m9]als capable ( becom+ pla/ic :5 moi/5$ or mix$ ) a suitable quantity ( wat]1' b ?is def9ition is s wide z to be almo/ impracticable1 & leads to ! inclusion ( _m sub/ances :i* h no real connection ) clays4 ,! limitation ( ! use ( ! ^w 'clay' to ! pla/ic or pot5tially pla/ic mat]ials ( any s+le geological epo* is also impracticable1 = clays appe> to h be5 deposit$ 9 almo/ e geological p]iod1 ?\gh !re is "s diff]5ce ( op9ion z to ! "t ( ! =mation ( c]ta9 clays kn[n z kaol9s4 ,clay is n infrequ5tly t]m$ a m9]al1 b ?is does n apply at all accurately to ! _m v>ieties ( e>?s kn[n z 'common clays1' :i*1 toge!r ) ! 'b\ld] clays1' conta9 _m m9]als & s _c1 z a :ole1 be includ$ "u ?is t]m4 ,:atev] may be ! legal significance ( ! t]m 'm9]al'--:i* has an important economic be>+ on acc\nt ( m9]als be+ tax$ or 'res]v$' 9 "s in/ances :]e non-m9]als 7includ+ brick clay7 are exempt--!re c be no d\bt t1 sci5tifically1 clay is n a m9]al b a rock4 ,:atev] m9]al 7if any7 may give ! *ief *>act]i/ic prop]ty to ! clays z a class mu/ be designat$ by a special title1 = ! g5]al t]m 'clay' w n s]ve = ?is purpose4 ,geologically1 ! clays are s$im5t>y rocks1 "s be+ unalt]$1 :il/ o!rs--! slates--are notably metamorphos$ & c seldom be us$ = ! purposes = :i* clays are employ$4 ,mo/ clays may be reg>d$ z a mixture ( qu>tz gra9s1 undecompos$ rock dbris & v>i\s decomposition products ( rocks2 if ! la/-nam$ consi/s *iefly ( c]ta9 hydr\s alum9o-silicates1 !y may be t]m$ 'clay sub/ance' 7see ,*apt] ,,vi4 ,! imp]fections ( ?is /atem5t z a def9ition are obvi\s :5 x is rememb]$ t x may include a mixture ( f9e s& & clay conta9+ only #cj p] c5t4 ( ! latt] sub/ance4 ,x is1 at ! pres5t "t1 q impossible to con/ruct an accurate def9ition ( ! t]m 'clay4' ,! mo/ satisfactory hi!rto publi%$ def9es 'clay' z 'a solid rock compos$ ma9ly ( hydro-alum9o-silicates or alum9o-silicic acids1 b (t5 conta9+ l>ge proportions ( o!r mat]ials2 ! :ole possess+ ! prop]ty ( becom+ pla/ic :5 treat$ ) wat]1 & ( h>d5+ to a /one-l mass :5 heat$ to r$ness4' ,f :at has already be5 writt51 x w be und]/ood t !re is no su* entity z a /&>d clay1 = ! v>ieties are almo/ endless1 & ! diff]5ces betwe5 !m are sometimes s slight z to be sc>cely di/+ui%able4 ,a fur!r consid]ation ( ?is bran* ( ! subject may1 h[ev]1 conv5i5tly be def]r$ to a subsequ5t *apt]4 ,! be/-kn[n clays are ! surface clays1 loams & m>ls1 ! %ales & o!r sub-surface clays1 & ! pott]y & *9a clays4 ,! values ( ^! diff]5t mat]ials v>y enorm\sly1 "s be+ almo/ wor?less :il/ o!rs are highly valu$4 ,! surface clays are *iefly us$ = ! manufacture ( bricks & tiles 7?\gh "s are q unsuitable = ?is purpose7 & =m ! soil employ$ 9 agriculture 9 _m di/ricts4 ,! sub-surface clays & %ales are h>d]1 & usually require me*anical treatm5t be=e !y c be us$ = brick & t]ra-cotta manufacture1 or = ! production ( refractory & sanit>y articles4 ,! pott]y & *9a clays are usually m free f accessory con/itu5ts1 & are reg>d$ z ! 'pure/' clays on ! m>ket1 ?\gh a consid]able am\nt ( latitude mu/ be all[$ 9 int]pret+ ! t]m 'pure4' ,*9a clays are by no means pure 9 ! /ate 9 :i* !y occur1 & require c>eful treatm5t be=e !y c be sold4 ,fur!r in=mation ) reg>d to ! *>act]i/ics ( c]ta9 clays w be f\nd 9 ,*apt] ,v4 ,! ,*emical ,prop]ties ( ,clay4 ,! *ief con/itu5ts ( all clays are alum9a & silica1 ! latt] be+ always 9 excess ( ! =m]4 ,^! two oxides are1 app>5tly1 comb9$ to =m a hydro-alum9o-silicate or alum9o-silicic acid correspond+ to ! =mula ,h#d;,al#b,si#b,o#ia1 b _m clays conta9 a mu* l>g] proportion ( silica ?an is requir$ to =m ?is comp\nd1 & o!r alum9o-silicates also occur 9 !m 9 v>y+ proportions 7see ,*apt]s ,v & ,,vi74 ,all clays may1 app>5tly1 be reg>d$ z consi/+ ( a mixture ( "o or m hydr\s alum9o-silicates ) free silica & o!r non-pla/ic m9]als or rock granules1 & _! *emical prop]ties are l>gely dep5d5t on ! nature & proportion ( ^! accessory +r$i5ts4 ,! pure/ =ms ( clay 7*9a clays & ball clays7 approximate to ! =mula above-m5tion$1 b o!rs diff] widely f x1 z w be se5 f ! analyses on p4 #af4 ,! *emical prop]ties ( pure clay are describ$ m fully 9 ,*apt] ,,vi4 ,footnote #a3 ,?is =mula is commonly writt5 ,al#b,o#ccb,si,o#bb;,h#b,o1 b al?\gh ?is is a conv5i5t arrangem5t1 x mu/ n be und]/ood to mean t clays conta9 wat] 9 a /ate ( comb9ation simil> to t 9 su* sub/ances z wa%+ soda--,na#b;,,co#cbd;,h#b,o1 or z9c sulphate cry/als--,zn,s,o#dg;,h#b,o 7see ,*apt] ,,vi74 ,tak+ *9a clay1 :i* has be5 c>efully purifi$ by levigation1 z repres5tative ( ! composition ( a 'pure' clay1 x w be f\nd t ! *ief impurities 9 clays are 7a7 /ones1 gravel & s&--removable by wa%+ or sift+2 7b7 felsp>1 mica & o!r silicates & free silica--:i* _c be completely remov$ )\t affect+ ! clay & 7c7 lime1 magnesia1 iron1 pota% & soda comp\nds1 toge!r ) m9ute quantities ( o!r oxides1 all ( :i* appe> to be s closely connect$ ) ! clay z to be incapable ( removal f x by any me*anical me?ods ( purification4 ,to give a detail$ description ( ! effect ( ea* ( ! impurities j ref]r$ to w\ld necessitate a mu* l>g] volume ?an ! pres5t1 b a few brief notes on ! m important ones are ess5tial to a fur!r consid]ation ( ! natural hi/ory ( clay4 ,/ones1 gravel & s& are mo/ noticeable 9 ! b\ld] clays1 b !y occur 9 clays ( mo/ geological ages1 ?\gh 9 v v>y+ proportions4 ,sometimes ! /ones are s l>ge t !y may be readily pick$ out by h&2 9 any case ! /ones1 gravel & mo/ ( ! s& may be remov$ by mix+ ! mat]ial ) a suffici5t quantity ( wat] & pass+ ! 'slip' ?r\gh a f9e sieve1 or by all[+ x to rema9 /ation>y = a few mom5ts & !n all[+ ! sup]natant liquid to run (f into a settl+ tank4 ,"s clays conta9 s& gra9s :i* are s f9e t !y _c be remov$ 9 ?is mann] & ! clay mu/ !n be wa%$ out by a /ream ( wat] ) a velocity n exce$+ #b ft4 p] h\r4 ,ev5 !n1 ! clay s remov$ may be f\nd to conta9 m9ute gra9s ( silt1 mu* ( :i* may be remov$ by a s]ies ( s$im5tations = v>i\s p]iods1 ?\gh a mat]ial p]fectly free f non-pla/ic granules may be unatta9able4 ,mo/ ( ! s& f\nd associat$ ) clays is 9 ! =m ( fragm5ts ( qu>tz cry/als 7fig4 #a71 ?\gh x may be compos$ ( irregul> p>ticles ( o!r m9]als or ( amorph\s silica4 ,felsp>1 mica & o!r adv5titi\s silicates occur 9 _m natural clays 9 s f9e a /ate ( division t _! removal w\ld be unremun]ative4 ,9 addition to ?is !y act z fluxes :5 ! clays are heat$ 9 kilns1 b9d+ ! less fusible p>ticles toge!r & =m+ a f> /rong] mass ?an w\ld o!rwise be produc$4 ,consequ5tly1 !y are valuable con/itu5ts 9 clays us$ = ! manufacture ( articles 9 :i* /r5g? or imp]vi\sness is important4 ,if ^! m9]als are pres5t 9 ! =m ( p>ticles :i* are suffici5tly l>ge to be remov$ by elutriation 9 ! mann] describ$ on ! previ\s page1 ! purification ( ! clay is n difficult4 ,usually1 h[ev]1 ! mo/ c>eful treatm5t fails to remove all ^! m9]als2 _! pres5ce may !n be detect$ by microscopical exam9ation & by *emical analysis4 ,= mo/ ( ! purposes = :i* clays are us$1 small proportions ( ^! silicates are unimportant1 b :]e clays ( a highly refractory nature are requir$2 & = mo/ ( ! purposes = :i* *9a clays 7kaol9s7 are employ$1 !y mu/ n be pres5t to ! ext5t ( m ?an #e p] c5t41 small] proportions be+ pref]able4 ,illu/ration3 ,fig4 #a4 ,qu>tz cry/als1 natural size4 7,f ,mi]s' ,m9]alogy by p]mission ( ,macmillan ,co47 ,oxides1 sulphides1 sulphates & c>bonates ( v>i\s metals =m ! ?ird class ( impurities 9 clays4 ,( ^!1 ! mo/ important are calcium oxide 7lime71 calcium c>bonate 7*alk & lime/one71 calcium sulphate 7gypsum & sel5ite71 ! correspond+ magnesia1 magnesium c>bonate1 & sulphate1 ! v>i\s iron oxides1 f]r\s c>bonate & iron sulphides 7pyrite & m>casite7 7p4 #ac74 ,pota% & soda comp\nds are commonly pres5t z con/itu5ts ( ! felsp>1 mica1 or o!r silicates pres5t1 & ne$ no fur!r description1 ?\gh small proportions ( soluble salts--*iefly sodium1 potassium1 calcium & magnesium sulphates--occur 9 mo/ clays & may cause a :ite scum on bricks & t]ra-cotta made f !m4 ,lime & magnesia comp\nds may occur z silicates 7v>ieties ( felsp>1 mica1 etc471 b _! mo/ important occurr5ce is z *alk or lime/one4 ,*alk is a con/ant con/itu5t ( malms#b & ( _m m>ls1 b ! latt] may conta9 lime/one p>ticles4 ,lime/one occurs 9 _m m>ls & to a small] ext5t 9 o!r clays4 ,9 ! b\ld] clays x frequ5tly =ms a l>ge portion ( ! /ony mat]ial4 ,if ! gra9s are v small 7z 9 *alk71 ! lime comp\nds act z a flux1 r$uc+ ! heat-resi/+ p[] ( ! clay & increas+ ! am\nt ( vitrification2 !y produce 9 extreme cases a slag-l mass :5 ! clay is int5sely heat$4 ,if1 on ! contr>y1 ! gra9s are l>g] 7z frequ5tly occurs ) lime/one71 !y are conv]t$ into lime or magnesia :5 ! clay is 'burn$' 9 a kiln1 & ! lime1 on exposure to wea!r1 absorbs moi/ure 7i4e4 slakes71 swells1 & may dis9tegrate ! articles made f ! clay4 ,lime/one 7except :5 9 a v f9ely divid$ /ate7 is almo/ inv>iably objectionable 9 clays1 b *alk is frequ5tly a valuable con/itu5t4 ,footnote #b3 ,a malm is a natural mixture ( clay & *alk 7p4 #fh74 ,*alk is add$ to clay 9 ! manufacture ( malm-bricks to produce a m pleas+ col\r ?an w\ld be obta9$ f ! clay alone1 to r$uce ! %r9kage ( ! clay to conv5i5t limits &1 less frequ5tly1 to =m a m vitrifiable mat]ial4 ,*alk1 on heat+1 comb9es ) iron oxide & clay1 =m+ a :ite silicate1 s t "s clays :i* w\ld1 alone1 =m a r$ brick1 w1 if mix$ ) *alk1 =m a :ite "o4 ,lime comp\nds h ! s]i\s objection ( act+ z v rapid & p[]ful fluxes1 s t :5 clays conta9+ !m are heat$ suffici5tly to />t p>tial fusion1 a v slight additional rise 9 temp]ature may easily r$uce ! :ole to a %apeless1 slag-l mass4 ,magnesia comp\nds act mu* m sl[ly 9 ?is respect & s are less h>mful4 ,gypsum--a calcium sulphate--occurs naturally 9 _m sub-surface clays1 (t5 9 well-def9$ cry/all9e masses4 ,x r$uces ! heat-resi/+ p[] ( ! clays conta9+ x & may1 "u "s conditions1 rise to ! surface ( ! articles made f ! clay1 9 ! =m ( a :ite effloresc5ce or scum1 su* z is se5 on "s brick walls4 ,iron comp\nds are highly important because !y ex]cise a p[]ful influ5ce on ! col\r ( ! burn$ clays4 ,! r$ oxide 7f]ric oxide7 is ! mo/ useful =m 9 burn$ clay1 b 9 ! raw mat]ial f]r\s oxide & f]r\s c>bonate may also occur1 ?\gh !y are conv]t$ into ! r$ oxide on heat+4 ,! r$ iron oxide1 :i* is closely relat$ to 'iron ru/1' occurs 9 s f9ely divid$ a /ate t its p>ticles appe> to be almo/ z small z ^? ( ! f9e/ clays4 ,h5ce attempts to improve ! col\r ( t]ra-cotta & bricks by ! addition ( comm]cial 'iron oxide' are seldom satisfactory1 ! f9e/ mat]ial obta9able be+ f> co>s] ?an t occurr+ 9 clays4 ,x is a curi\s fact t r$ iron oxide does n appe> to =m any comp\nd ) ! o!r con/itu5ts ( clay "u ord9>y conditions ( fir+1 & al?\gh a 'base' & capable ( r$uc+ ! heat-resi/+ p[] ( clays1 x does n appe> to d s z long z ! conditions 9 ! kiln are suffici5tly oxidiz+4 ,x is ?is :i* enables r$ bricks & o!r articles to be obta9$ ) rem>kable uni=mity ( col\r comb9$ ) great physical /r5g?4 ,9 a r$uc+ atmosph]e1 on ! contr>y1 f]r\s oxide readily =ms & attacks ! clay1 =m+ a d>k grey vitre\s mass4 ,if ! iron p>ticles are sep>at$ f ea* o!r !y w1 on r$uction1 =m small slag-l spots1 b if !y are 9 an extremely f9e /ate ( division & well di/ribut$1 ! brick or o!r article w become slightly glossy & ( an uni=m black-grey t9t4 ,! fam\s ,/af=d%ire 'blue' bricks owe _! col\r to ?is *>act]i/ic2 !y are n really 'blue' 9 col\r4 ,! effect ( *alk on ! col\r ( r$-burn+ clays has already be5 m5tion$4 ,iron pyrite 7fig4 #b7 & m>casite 7fig4 #c7--;bo? ( :i* are =ms ( iron sulphide--occur 9 _m clays1 p>ticul>ly ^? ( ! ,coal ,measures4 ,mundic is ano!r =m ( pyrites :i* resembles roots or twigs1 b :5 brok5 %[ a brassy fracture4 ,:5 9 pieces ( obs]vable size ! pyrite may be readily di/+ui%$ by its resemblance to poli%$ brass & ! m>casite by its t9-:ite metallic lu/re & bo? by _! *>act]i/ic cubic1 root-l & sph]ical =ms2 ! latt] only %[ a brass-l %e5 :5 brok54 ,ev5 :5 only a small proportion ( mundic1 pyrite or m>casite is pres5t1 x is highly objectionable = sev]al reasons4 ,9 ! fir/ place1 half ! sulphur pres5t is giv5 (f at a d>k r$ heat & is liable to cause tr\blesome defects on ! goods4 ,secondly1 because ! rema9+ sulphur & iron are n readily oxidiz$1 s t !re is a great t5d5cy to =m slag-spots ( f]r\s silicate1 ow+ to ! iron attack+ ! clay at ! same mom5t z x p>ts ) its rema9+ sulphur4 ,= ?is reason1 clays conta9+ any iron sulphide seldom burn r$1 b =m products ( a buff col\r ) black spots scatt]$ irregul>ly ov] _! surface & ?r\gh\t ! mass--an appe>ance readily obs]vable on mo/ h>d-fir$ firebricks4 ,if *alcopyrite 7copp]-iron sulphide7 is pres5t ! spots may be bright gre5 9 col\r4 ,illu/ration3 ,fig4 #b4 ,pyrite4 ,illu/ration3 ,fig4 #c4 ,m>casite4 ,slightly magnifi$4 7,f ,mi]s' ,m9]alogy by p]mission ( ,macmillan ,co47 ,c>bon1 ei!r free or z hydroc>bons 7*iefly vegetable matt]7 or 9 o!r =ms1 is a con/itu5t ( mo/ clays1 ?\gh seldom report$ 9 analyses4 ,its pres5ce ex]cises an important influ5ce 9 sev]al respects4 ,on heat+ ! clay1 ) an ample supply ( air1 ! c>bonace\s matt] may di/il (f 7z %ale oil71 b m usually x decomposes & burns out leav+ pores 9 ! mat]ial4 ,if ! air-supply is insuffici5t & ! heat+ is s rapid & int5se t vitrification comm5ces be=e ! c>bon is all burn$ away1 ! pores become fill$ ) ! fus$ +r$i5ts ( ! clay1 air c no long] rea* ! c>bon p>ticles & a black 'core' or he>t is produc$4 ,"u peculi>ly disadvantage\s conditions ! mat]ial may also swell greatly4 ,?is is a s]i\s defect 9 _m classes ( clay us$ = brickmak+1 & its causes & prev5tion h be5 exhau/ively /udi$ by ,orton & ,griffi?s 7#a7c b1 beyond ! brief summ>y giv5 above1 ^! are beyond ! scope ( ! pres5t "w4 ,wat] is an ess5tial con/itu5t ( all unburn$ clays1 ?\gh ! proportion 9 :i* x occurs v>ies )9 su* wide limits t no def9ite /&>d c be /at$4 ,?is wat] is f\nd 9 two conditions3 7a7 z moi/ure or me*anically mix$ ) ! clay p>ticles & 7b7 9 a /ate ( *emical comb9ation4 ,footnote #c3 ,ref]5ces to orig9al pap]s1 etc4 w be f\nd 9 ! app5dix4 ,,analyses ,,( ,,typical ,,clays ,! samples 7 all dri$ at #aje ,c4 ---------------------------------------- ------------------------- ,clay ,*9a ,ball ,fireclay ,brick ,b\ld] ,m>l ,clay ,clay ,clay ,clay ---------------------------------------- ------------------------- ,locality ,cornwall ,dorset,york%ire,midl&s ,lancs4,suffolk ---------------------------------------- ------------------------- ,ultimate ,analysis3 ,silica #dga #dia #fhi #egg #fcg #dcg ,alum9a #cia #ccg #aic #bdc #bjd #aee ,f]ric oxide #f #ab #aj #ej #cj #eb ,titanium oxide -- #b #ah #a #b -- ,lime #d #h #i #cg #dc #afc ,magnesia #b #c #c #be #bg #ba ,pota% & ,soda #c #be #i #bh #bi #g ,c>bon #bf #dc #ah #af #d #af ,wat] #ic #gg #dh #bj #bb #bd ,o!r ,matt] #d #b #c #c #b #abe ---------------------------------------- ------------------------- ,total #ajjj #ajjj #ajjj #ajjj #ajjj #ajjj ---------------------------------------- ------------------------- ,proximate ,analysis3 ,gravel & ,s& -- #hd #df #bba #bca #ib ,silt -- #dh #ij #ca #hd #afj ,felsp>- & mica- du/ #eb #aed #ajc #bdc #ahe #hi ,silica-du/ #ca #dj #chj #ca #abf #bj ,free calcium c>bonate -- -- -- #ba #b #bhd ,free iron oxide & pyrites #d #i #g #db #af #ci ',true clay' #iac #ffe #cgd #daa #cef #caf ---------------------------------------- ------------------------- ,total #ajjj #ajjj #ajjj #ajjj #ajjj #ajjj ---------------------------------------- ------------------------- ,= o!r analyses ! books 9 ! ,bibliography at ! end ( ! pres5t volume %\ld be consult$1 p>ticul>ly ,no4 #b1 i4e4 ,briti% ,clays1 ,%ales & ,s&s4 ,! am\nt ( me*anically mix$ wat] w naturally v>y ) ! conditions to :i* ! clay has be5 subject$2 x w be greate/ 9 wet situations & w dim9i% z ! clay is all[$ to dry4 ,! 'comb9$ wat]1' on ! contr>y1 appe>s to be a function ( ! true clay pres5t 9 ! mat]ial1 & rea*es its highe/ proportions 9 ! *9a clays & kaol9s1 :i* conta9 approximately #ac p] c5t4 ,on heat+ a clay to #aje ,c4 ! moi/ure or me*anically mix$ wat] is evaporat$1 b ! comb9$ wat] rema9s unaffect$#d until ! temp]ature is rais$ to m ?an #fjj ,c41 :5 x is driv5 (f & ! clay is conv]t$ into a h>d /one-l mass ) prop]ties entirely diff]5t f ^? x previ\sly possess$ 7see ,*apt] ,,vi74 ,footnote #d3 ,/rictly1 !re is a slight loss at l[] temp]atures1 b x is too small to be important4 ,! ,physical ,*>act]s ( ,clays4 ,! physical *>act]s ( clays are ( f> m int]e/ & importance ?an _! *emical ones1 ?\gh ! two are naturally connect$ 9 _m ways1 & j z ! *emical composition ( clays is a subject ( extreme complexity s is a /udy ( _m ( _! physical prop]ties4 ,h5ce only a few ( ! m important *>act]i/ics c be m5tion$ "h3 = fur!r details ! read] mu/ consult a l>g] treatise 7#b74 ,clays are mod]ately s(t1 solid bodies1 p>ticul>ly :5 moi/5$1 & c usually be cut ) a knife1 ?\gh "s indurat$ clays & %ales are almo/ z h>d z felsp>4 ,_! app>5t specific gravity v>ies greatly1 "s clays be+ mu* m por\s ?an o!rs1 b ! true specific gravity is usually betwe5 #be & #bfe2 x is simil> to t ( qu>tz & slightly l[] ?an t ( felsp> & mica4 ,_m clays appe> to be devoid ( /ructure1 b ^? obta9$ f a consid]able dep? bel[ ! surface are frequ5tly lam9at$ & h a /ructure n unlike t ( mica4 ,?is w be discuss$ lat]4 ,exam9$ "u a microscope1 clays are se5 to consi/ ( gra9s ( a v>iety ( sizes1 ! l>ge/ ( :i* w usually be f\nd to be compos$ ( adv5titi\s mat]ials su* z s&1 qu>tz1 felsp>1 mica1 *alk & lime/one4 ,! smalle/ p>ticles--to :i* clays owe _! *ief *>act]i/ics--are s m9ute z to make any exam9ation ( _! %ape v difficult1 b !y are usually compos$ ( m9ute cry/all9e plates toge!r ) a mu* l>g] proportion ( app>5tly amorph\s mat]ial4 ,! exact nature ( bo? ! cry/als & ! amorph\s mat]ial is /ill unkn[n 9 spite ( _m inve/igations2 9 ! pur] clays bo? =ms ( sub/ance appe> to h ! same *emical composition1 viz4 t ( kaol9ite 7,h#d;,al#b,si#b,o#i71 :i* ! cry/all9e portion closely resembles4 ,clays emit a *>act]i/ic yet indef9able od\r :5 moi/2 ! cause ( ?is is v imp]fectly und]/ood1 ?\gh x is n improbably due to decompos+ organic matt]1 z ?is occurs 9 mo/ clays4 ,! col\rs ( fre%ly-dug clays are extremely v>i$ & range f an almo/ pure :ite ?r\gh all %ades ( yell[1 r$ & br[n to black4 ,! pr$om9at+ col\rs are grey or greyi% br[n & a peculi> yell[ *>act]i/ic ( "s surface clays4 ,! natural col\r ( a clay is no crit]ion z to its purity1 = "s ( ! d>ke/ ball clays produce p]fectly :ite w>e on burn+1 :il/ "s ( ! pal] clays are useless to ! pott] on acc\nt ( ! int5sity ( _! col\r :5 !y come out ( ! kiln4 ,! col\r ( raw clays is l>gely due to ! c>bonace\s matt] !y conta91 & z ?is burns away 9 ! kiln1 ! f9al col\r ( ! w>e be>s no relation :atev] to t ( ! orig9al clay4 ,! col\r ( burn$ w>e dep5ds ^u ! iron comp\nds 9 ! clay--^! produc+ buff1 r$1 br[n or black 7usually t]m$ 'blue'7 articles--on ! pres5ce ( f9ely divid$ calcium c>bonate 7*alk7 :i* c de/roy ! col\r+ p[] ( iron comp\nds & produce :ite w>e1 & on ! treatm5t ! clay has receiv$ 9 ! kiln4 ,a clay :i* is :ite :5 und]fir$ w usually d>k5 9 col\r if heat$ to vitrification1 & "o :i* burns r$ 9 an oxidiz+ atmosph]e may turn blue-grey or black "u r$uc+ conditions4 ,! ext5t to :i* ! c>bonace\s matt] is burn$ out also det]m9es ! col\r ( ! fir$ w>e4 ,! pres5ce ( adv5titi\s m9]als 9 ! clay may also affect its col\r1 p>ticul>ly :5 fir$4 ,! mo/ obvi\s feature 9 a piece ( moi/ clay is its pla/icity#e or ability to alt] its %ape :5 knead$ or put "u slight pressure & to reta9 its new %ape aft] ! pressure has be5 remov$4 ,x is ?is prop]ty :i* enables ! production ( ornam5ts1 vessels ( v>i\s k9ds1 & ! _m o!r articles :i* are ! result ( ! application ( modell+ tools1 ( m\ld+ or ( ! action ( a pott]'s :eel4 ,s long z clay conta9s a suitable proportion ( moi/ure x is pla/ic & may be made into articles ( any desir$ %ape1 b if ! am\nt ( moi/ure 9 x is r$uc$ or remov$ completely1 ! mat]ial is no long] pla/ic4 ,x may become s1 h[ev]1 on add+ a fur!r suitable quantity ( wat] & mix+1 provid$ t x has n be5 excessively heat$4 ,if1 9 ! removal ( ! moi/ure1 ! clay has be5 heat$ to #fjj ,c4 or m1 x loses its p[] ( becom+ pla/ic & is conv]t$ into a mat]ial m closely resembl+ /one4 ,footnote #e3 ,a pla/ic sub/ance is "o ) ! *>act]i/ics ( 'a fluid ( s great a viscosity t x does n lose its %ape "u ! influ5ce ( gravitation4' ,! causes ( pla/icity appe> to be some:at num]\s1 ?\gh !re is no g5]ally accept$ explanation ( ?is rem>kable quality :i* di/+ui%es clays f mo/ o!r sub/ances4 ,x is true t wet s&1 soap1 wax1 lead & "s o!r mat]ials possess a c]ta9 am\nt ( pla/icity1 b n to any?+ l ! same ext5t z clay4 ,s f> z clays are conc]n$1 _! pla/icity appe>s to be connect$ ) ! pres5ce ( comb9$ wat] z well z ( me*anically mix$ wat]1 = if ei!r ( ^! are remov$1 pla/icity--bo? actual & pot5tial--is de/roy$4 ,! "p play$ by wat] is n1 h[ev]1 completely kn[n1 = ! _m !ories :i* h be5 advanc$ only cov] "s ( ! conditions & facts4 ,a numb] ( obs]v]s agree t ! molecul> con/itution ( clay is peculi> & t x is to ?is t pla/icity is due4 ,yet ! curi\s fact t ! pure/ clays--! kaol9s--are rem>kably defici5t 9 pla/icity %[s t molecul> con/itution is n1 alone1 suffici5t4 ,o!rs hold t ! rem>kably small size ( clay p>ticles enables !m to pack toge!r m closely ?an d p>ticles ( o!r mat]ials & to reta9 ar\nd !m a film ( wat] :i* acts p>tly z a lubricant1 facilitat+ ! *ange ( %ape ( ! mass :5 "u pressure1 & p>tly z an adhesive1 caus+ ! p>ticles to adh]e to ea* o!r :5 ! pressure is remov$4 ,zs*okke has laid mu* emphasis on ! importance ( molecul> attraction betwe5 clay & wat] z a cause ( pla/icity1 & has sugge/$ t ! absorption ( ! wat] effects a *ange 9 ! surfaces ( ! clay p>ticles1 giv+ !m a gelat9\s nature & enabl+ !m to *ange _! =m & yet keep 9 close contact4 ,! fact t mica1 fluorsp> & qu>tz1 :5 9 a suffici5tly f9ely divid$ /ate1 are also slightly pla/ic1 appe>s to be oppos$ to ! molecul> con/itution !ory4 ,smallness ( gra9 und\bt$ly has an influ5ce on ! pla/icity ( clay1 co>se-gra9$ clays be+ notably less pla/ic ?an o!rs4 ,daubre po9t$ out t felsp>1 :5 gr\nd ) wat]1 develops pla/icity to a small ext5t1 & ,ols*ewsky c>ri$ ?is obs]vation fur!r & has sugge/$ t clays owe _! pla/icity to prolong$ contact ) wat] dur+ _! removal f _! place ( =mation & previ\s to or dur+ _! deposition4 ,a fur!r confirmation ( ?is !ory is due to ,mellor 7#c7 :o %[$ t on heat+ *9a clay ) wat] "u v consid]able pressure its pla/icity 0 increas$ & t felsp> & "s o!r non-pla/ic mat]ials develop$ pla/icity "u ^! conditions4 ,johnson & ,blake 7#ba7 suppos$ t pla/icity is due to ! clay be+ compos$ ( extremely m9ute plates 'bun*$ toge!r1' a view :i* 0 also held by ,bi$]mann & ,h]zfield1 ,le ,*ateli] & o!rs4 ,ols*ewsky enl>g$ ?is !ory by sugge/+ t ! pla/icity ( c]ta9 clays is dep5d5t on ! l>ge surface & ! int]lock+ ( irregul> p>ticles ) ! plates j m5tion$4 ,^! !ories ( int]lock+ are1 h[ev]1 incomplete1 because ! t5sile /r5g? ( clays %\ld accurately repres5t ! pla/icity if int]lock+ 7 ! sole cause4 ,zs*okke has %[n t t5sile /r5g? is only "o factor :i* mu/ be det]m9$ 9 any attempt to measure pla/icity4 ,e4 ,h4 ,l4 ,s*w>z 7#ce7 has sugge/$ t _m clays are compos$ ( small globul> masses ( plates s arrang$ z to =m an op5 network 7fig4 #d7 :i* is suffici5tly /rong n to be de/roy$ by pressure4 ,9 ! pres5ce ( wat] & mu* rubb+ ! plates are sep>at$ & are made to lie flat on ea* o!r1 !reby giv+ a pla/ic & imp]meable mass4 ,if ?is is really ! case x w\ld expla9 ! porosity & l>ge surface ( "s clays & might acc\nt = _! adsorptive p[]4 ,illu/ration3 ,fig4 #d4 ,illu/rat+ ! /ructure ( a 'clay crumb4' 7,aft] ,s*w>z47 ,a !ory :i* 0 fir/ promulgat$ 9 #ahej by ,way 7#d71 b :i* has only receiv$ detail$ att5tion dur+ ! la/ few ye>s1 attributes pla/icity to ! pres5ce ( colloid sub/ances 9 clay or to ! fact t clay p>ticles possess physical *>act]s analog\s to ^? ( glue & o!r colloids4 ,^! colloid sub/ances h a submicroscopic or micellian /ructure2 !y are web-l1 por\s & absorb wat] eag]ly4 ,?is wat] may be remov$ by dry+1 only to be re-absorb$ on cool+1 b if ! heat+ temp]ature is excessive ! /ructure ( ! colloids is de/roy$4 ,?is colloid !ory expla9s _m ( ! facts not$ by e>li] inve/igators su* z ,aron1 ,bis*(1 ,seg]1 ,ols*ewsky1 etc41 b x is n entirely satisfactory1 ?\gh ,rohl& 7#e7--to :om ! pres5t prom95ce ( ?is !ory 9 ,europe is l>gely due--p]si/5tly ma9ta9s ! contr>y4 ,"o great objection is ! fact t no *>act]i/ic inorganic colloid sub/ance has be5 isolat$ f pure clay4 ,x is possible t "s ( ! s-call$ 'colloidal' prop]ties ( clay may be due to ! smallness ( its p>ticles & to _! great porosity1 z sugge/$ by ,ols*ewsky4 ,despite ! pres5t impossibility ( produc+ a pla/ic mat]ial f artificially prep>$ colloidal hydro-alum9o-silicates ( ! same ultimate composition z clay1 & ! fact t ! addition ( colloidal sub/ances does n necess>ily increase ! true pla/icity ( clay1 x _c be d5i$ t ! pres5ce ( colloids has an important influ5ce on x4 ,! addition ( />*es1 glue1 gums & simil> sub/ances :il/ app>5tly increas+ ! pla/icity ( clay does n d s 9 reality4 ,! addition ( #a p] c5t4 ( tann91 on ! contr>y1 has be5 f\nd by ,ries 7#f7 to increase bo? pla/icity & b9d+ p[]4 ,pla/icity appe>s to be compos$ ( a numb] ( *>act]i/ics s t x is sc>cely likely t any s+le cause c be assign$ to x4 ,on ! contr>y1 a /udy ( ! b9d+ p[]1 t5sile /r5g?1 ext5sibility1 adsorption1 texture & molecul> con/itution ( clays sugge/s v /rongly t all ^! prop]ties are involv$ 9 ! production ( pla/icity & t x is due to ! *emical z well z ! physical nature ( clay4 ,no clay is entirely colloidal--or x w\ld be ela/ic & n pla/ic--b all appe> to conta9 bo? colloidal & non-colloidal 7includ+ plate-l7 p>ticles1 & x is n improbable t mat]ials 9 bo? ^! /ates are requir$1 ! colloidal matt] act+ z a cem5t4 ,ries 7#f7 has1 9 fact1 po9t$ out t colloids alone lack cohesiv5ess & solidity1 & a f9e m9]al aggregate is necess>y to *ange !m into a pla/ic mass resembl+ clay4 ,! relative proportions ( ! colloidal mat]ial & ! sizes ( ! non-pla/ic gra9s w ex]cise an important influ5ce on all ! physical *>act]i/ics m5tion$ above1 & !re=e on ! pla/icity4 ,! mann] 9 :i* slightly pla/ic clays become highly pla/ic 9 nature is by no means c]ta9ly kn[n4 ,x has long be5 und]/ood t ! increase ( pla/icity is due to *anges und]gone by ! clay dur+ transportation4 ,! mo/ illum9at+ sugge/ion is t made by ,a*eson 9 #aijb1 :o conclud$ t x is due to impurities 9 ! wat] us$ 9 transport+ ! clay or rema9+ 9 contact ) x dur+ & aft] its deposition4 ,^! impurities may be consid]$ z d]iv$ f ! wa%+s ( =e/s1 & aft] _m exp]im5ts ) plant extracts ,a*eson believ$ ! mo/ important sub/ance 9 ?is connection to be tann9 or gallo-tannic acid1 a dilute solution ( :i* he f\nd increas$ ! pla/icity ( *9a clay by #cjj p] c5t4 ,f ?is he fur!r argu$ t ! use ( *opp$ /raw by ! ,israelites 9 ,egypt 9 ! manufacture ( bricks 0 unconsci\sly bas$ on ! tann9 cont5t ( ! /raw increas+ ! pla/icity ( ! mat]ial4 ,illu/ration3 ,fig4 #e4 ,*>t %[+ rates ( dry+4 7,aft] ,ble9+]47 ,beadle has /at$ t #b p] c5t4 ( dissolv$ cellulose w increase ! pla/icity ( *9a clay & make x equal to t ( ord9>y clay4 ,pla/icity is dim9i%$ by heat+ clays1 & :il/ mu* ( x may be recov]$ if ! temp]ature has n ris5 above #djj ,c4 x _c be completely re/or$4 ,moreov]1 a clay :i* has once be5 heat$ to a temp]ature above #ajj ,c4 dries 9 a some:at diff]5t mann] to a raw clay4 ,?is is well %[n 9 fig4 #e 9 :i* are summ>iz$ ! results obta9$ by ,a4 ,v4 ,ble9+] on a sample ( ball clay f ,dorset be=e heat+ & aft] portions ( x _h be5 heat$ = #af h\rs to #bjj1 #bej1 #cjj1 #cej & #djj ,c4 respectively4 ,x is n impossible t if subject$ to ! influ5ce ( wat] = a suffici5tly long "t ! :ole ( ! pla/icity ( a heat$ clay may be re/or$1 provid+ t ! temp]ature has n be5 suffici5t to cause a de/ruction ( ! clay molecule1 b z ?is resumption requires a c]ta9 am\nt ( "t1 ,ble9+] has propos$ to use ! r$uction 9 pla/icity effect$ by ! heat+ to enable excessively pla/ic clays to be work$ )\t ! necessity ( add+ non-pla/ic mat]ial to !m4 ,if any de/ruction ( ! clay-molecules has occurr$1 ! pla/icity ( t portion ( ! clay c nev] be re/or$4 ,! b9d+ p[] ( clays is a *>act]i/ic closely connect$ ) pla/icity & occasionally confus$ ) x4 ,all pla/ic clays h ! p[] ( rema9+ pla/ic :5 mix$ ) mat]ials su* z s&1 brick-du/ 7'grog'7 & o!r mat]ials :i* are q devoid ( pla/icity4 ,! ext5t to :i* a clay c ?us b9d o!r mat]ials toge!r into a pla/ic mass dep5ds1 app>5tly1 on ! pla/icity ( ! clay itself & on ! size & nature ( ! p>ticles ( ! add$ mat]ial2 ! m pla/ic ! clay ! l>g] w be ! am\nt ( mat]ial x c ?us 'b9d1' & ! f9] ! latt] ! m easily w x =m a /rong mat]ial :5 mix$ ) a pla/ic clay4 ,rohl& 7#e7 has %[n t ! b9d+ p[] ( clay is n alone due to its cohesion1 b t x is closely associat$ ) ! colloidal nature ( pla/ic clays3 'fat' clays be+ ^? :i* are highly colloidal1 highly pla/ic & possess+ great b9d+ p[]1 :il/ 'lean' clays are ^? defici5t 9 ^! *>act]i/ics4 ,! fact t1 z a g5]al rule1 ! d>k col\r$ clays possess ! mo/ b9d+ p[]1 confirms ?is sugge/ion1 z ! d>k col\r is l>gely due to organic mat]ials1 probably 9 a colloidal /ate4 ,! %r9kage :i* all clays und]go on dry+ & :5 heat$ is ano!r important *>act]i/ic4 ,x is due to ! fact t z wat] is remov$ ! solid p>ticles approa* clos] to ea* o!r1 ! volume ( ! :ole mass be+ !reby r$uc$4 ,9 a wet piece ( clay ea* p>ticle is surr\nd$ by a film ( wat]1 ! ?ickness ( :i* dep5ds on ! nature ( ! clay4 ,z ?is wat] evaporates f ! surface ( ! clay its place is tak5 by wat] f ! int]ior :i* rises to ! surface by capill>y attraction4 ,s long z !re is any wat] betwe5 ! p>ticles ( clay !re w be %r9kage :5 ?is wat] is remov$1 b a /age is ev5tually rea*$ :5 ! p>ticles ( clay are 9 contact ) ea* o!r & no m %r9kage c occur4 ,t ?is cessation ( %r9kage may take place be=e all ! wat] has be5 remov$ f ! clay is easily und]/ood :5 x is rememb]$ t :il/ ! clay p>ticles may be 9 contact1 yet !re are /ill places 7pores7 :]e ! contact is incomplete1 & 9 ^! pores wat] may be reta9$4 ,! am\nt ( %r9kage clays und]go on dry+ dep5ds p>tly on ! proportion ( wat] add$ to !m & p>tly on ! sizes ( ! diff]5t p>ticles ( clay1 s&1 etc4 pres5t4 ,an av]age r$uction 9 volume ( #ab to #ch p] c5t4 may be reg>d$ z normal1 b co>se loams may %r9k only #a p] c5t4 & v f9ely gr\nd1 highly pla/ic ball clays may %r9k z mu* z #ej p] c5t41 ?\gh ?is is unusual4 ,z all coagulat$ colloids1 :i* h absorb$ wat]1 %r9k on dry+1 ?is behavi\r ( clay appe>s to confirm ! view z to its p>tially colloidal nature held by "s inve/igators4 ,:5 a piece ( dry clay is heat$ suffici5tly a fur!r %r9kage 7te*nically kn[n z kiln %r9kage7 occurs4 ,?is beg9s some:at bel[ a r$ heat & increases 9 r\gh proportion to ! temp]ature & ! duration ( ! heat+4 ,prolong$ heat+ at a l[] temp]ature w effect ! same am\nt ( %r9kage z a %ort exposure to a high] temp]ature1 b ?\gh ! great] "p ( ! %r9kage occurs 9 a comp>atively %ort "t1 cont9u$ heat+ w be accompani$ by a fur!r r$uction 9 volume4 ,?is is due to ! fact t clays h no def9ite melt+ po9t1 b und]go p>tial fusion at all temp]atures above #iej ,c4 or1 9 "s cases1 at ev5 l[] ones4 ,z a portion ( ! mat]ial fuses1 x fills up ! pores 9 ! mass & attacks ! unfus$ mat]ial1 ?is process be+ cont9u$ until ei!r ! heat+ is /opp$ or ! :ole mat]ial is r$uc$ to a visc\s slag4 ,! r$uction 9 ! volume ( comm]cial articles made ( clay & plac$ 9 kilns v>ies greatly4 ,) bricks1 t]ra-cotta & pott]y x mu/ n1 usually1 exce$ #dj p] c5t4 or ! w>p+ & crack+ :i* occur w be s great z to make ! articles useless4 ,! f95ess ( ! p>ticles ex]cises an important influ5ce on ! kiln %r9kage ( a clay1 & ! latt] is frequ5tly r$uc$ 9 comm]cial claywork+ by add+ burn$ clay gr\nd to a co>se p[d] to ! pla/ic clay be=e x is us$4 ,s& is sometimes add$ = ! same purpose1 ?\gh its m frequ5t use is to r$uce ! %r9kage 9 dry+4 ,qu>tz & o!r =ms ( free silica exp& on heat+1 s t clays conta9+ !m 9 l>ge quantities %r9k v slightly or may ev5 exp&4 ,z clays %r9k equally 9 all directions x is usual to /ate ! contraction 9 l9e> in/ead ( volume =m4 ,?us in/ead ( /at+ t a c]ta9 clay :5 m\ld$ into bricks1 dri$ & burn$1 %r9ks #ah p] c5t4 by volume1 x is cu/om>y to /ate t x %r9ks #c_/d 94 p] 7l9e>7 foot4 ,= _m purposes1 x is suffici5t to reg>d ! l9e> %r9kage z "o-?ird ! volume-%r9kage1 b ?is is n /rictly accurate4 ,! fusibility ( clays is a *>act]i/ic :i* has be5 v imp]fectly /udi$4 ,mo/ claywork]s & inve/igators employ ! t]m 'fusibility' 9 a special s5se :i* is apt to be mislead+4 ,ow+ to ! extremely high temp]atures to :i* refractory clays c be heat$ )\t ev5 los+ _! %ape1 x is almo/ impossible to fuse !m completely4 ,9 addition to ?is1 clays are n p]fectly homog5e\s mat]ials & "s ( _! con/itu5ts melt at l[] temp]atures ?an o!rs4 ,= ?is reason a clay may %[ signs ( fusion at #aajj ,c41 b x may be heat$ = "s h\rs at #ahjj ,c4 & yet n be completely melt$6 ,consequ5tly no s+le 'fus+ po9t' c be /at$4 ,9 practice1 a sugge/ion made _m ye>s ago by ,seg] 7#g7 is us$2 ! clay to be te/$ is made into a small tetrah$ron 7fig4 #f71 heat$ sl[ly until x b5ds ov] & ! po9t ( ! te/-piece is almo/ on a level ) ! base4 ,! temp]ature at :i* ?is occurs is t]m$ ! 'fus+ po9t' ?\gh x really only indicates ! heat-treatm5t :i* is suffici5t to s(t5 ! mat]ial suffici5tly to cause x to b5d 9 ! mann] describ$4 ,9 spite ( ! app>5t crud5ess ( ! te/ ?is 's(t5+ po9t' appe>s to be fairly con/ant = mo/ refractory clays4 ,! b5d+ ( a te/-piece 9 ?is mann] is ! result ( ! action ( all fluxes#f 9 ! clay1 & z ?is dep5ds on ! size ( gra9 & ! duration ( ! heat+ above incipi5t fusion & does n give a direct measure ( temp]ature1 nor is ! s(t5+ effect "u "o rate ( rise 9 temp]ature ! same z t at ano!r rate4 ,nev]!less a /udy ( ! behavi\r ( v>i\s clays heat$ simultane\sly is valuable & ! me?od =ms a conv5i5t means ( comp>+ diff]5t mat]ials4 ,footnote #f3 ,= flux+ mat]ials see p4 #h4 ,! temp]ature may be measur$ by means ( a pyromet]1 b = ! reason j /at$ x is m conv5i5t & 9 "s respects m accurate to use /&>d mixtures kn[n z ,seg] ,cones 7fig4 #f71 & to /ate ! s(t5+ po9t 9 t]ms ( ! 'cone' :i* behaves l ! clay be+ te/$4 ,a m$ium fireclay w n s(t5 bel[ ,seg] ,cone #bf 7#afej ,c47 & a really good "o w h a s(t5+ po9t ( cone #cd or #ce 7#agej to #ahjj ,c474 ,illu/ration3 ,fig4 #f4 ,seg] ,cones indicat+ a temp]ature ( #abej ,c4 ,! refractor9ess ( a clay1 or its resi/ance to high temp]atures1 is an important requirem5t 9 bricks requir$ = furnace l9+s1 9 crucibles1 gas retorts & o!r articles us$ 9 ! metallurgical & o!r indu/ries4 ,! t]m is mu* abus$ & is frequ5tly und]/ood to mean resi/ance to ! cutt+ action ( flue gases & flame1 ! corrosive action ( slags1 & ! /ra9s set up by ! repeat$ *anges 9 temp]ature4 ,?is is un=tunate1 = ! t]m refractor9ess has a p]fectly def9ite mean+ & %\ld be employ$ exclusively to d5ote t a giv5 clay is capable ( reta9+ its %ape at a giv5 temp]ature or "u giv5 conditions :5 heat$ alone & )\t be+ subject$ to any pressure4 ,9 ,great ,brita9 !re is no (ficially recogniz$ /&>d ( m9imum refractor9ess#g1 b :]e "o is requir$ ! sugge/$ m9imum ( ,seg] ,cone #bf 7#afej ,c47 made by ,e4 ,cram] 7#h7 is usually employ$4 ,?is is ! recogniz$ m9imum 9 ,g]many = fireclays1 & ?\gh objections may be urg$ aga9/ ! use ( ,seg] ,cones z a /&>d1 equally =cible ones may be br\ght aga9/ mak+ a temp]ature-scale ! basis ( measurem5t4 ,"u pres5t circum/ances1 h[ev]1 x is necess>y to adopt "o or o!r ( ^!4 ,footnote #g3 ,see ,refractory ,clays1 ,*apt] ,v4 ,v>i\s attempts h be5 made to asc]ta9 ! relation%ip 7if any7 betwe5 ! refractor9ess ( clays & _! *emical composition4 ,if att5tion is conf9$ /rictly to ! m refractory clays1 "s k9d ( relation%ip does appe> to exi/4 ,?us ,ri*t] f\nd t ! refractor9ess ( clay is influ5c$ by c]ta9 oxides 9 ! foll[+ ord]3 magnesia1 lime1 f]r\s oxide1 soda & pota%1 b ?is only applies to clays conta9+ less ?an #c p] c5t4 ( all ^! oxides4 ,cram]1 9 #ahie1 f\nd t free silica also int]f]$ ) ! action ( ^! oxides & m rec5tly ,ludwig 7#i7 has devis$ a *>t 7fig4 #g71 on ! upright sides ( :i* are plott$ ! equival5ts ( ! lime1 magnesia & alkalies1 :il/ ! silica equival5ts are plott$ on ! horizontal base4 ,9 ea* case ! 'molecul> =mula' ( ! clay is calculat$ f its p]c5tage composition1 & ?is '=mula' is r$uc$ s z to h "o 'molecule' ( alum9a1 !reby fix+ ! alum9a z a con/ant & r$uc+ ! numb] ( v>iables to two--! metallic oxides & ! silica4 ,un=tunately ,ludwig's *>t is only applicable to ! m refractory clays & _c be reli$ ^u ev5 = ^!1 ?\gh x is extremely useful = comp>+ clays f id5tical or simil> geological =mations4 ,illu/ration3 ,fig4 #g4 ,ludwig's ,*>t4 ,attempts to express ! refractor9ess ( clays by means ( =mulae prov+ abortive1 !re only rema9s ! direct te/ ( heat+ a clay "u def9ite conditions 9 ! mann] previ\sly describ$4 ,vitrification is closely connect$ ) ! fusibility & refractor9ess ( clays1 &1 z a t]m1 indicates ! am\nt ( fusion :i* has occurr$ "u c]ta9 conditions ( heat+4 ,z already m5tion$1 all clays1 on be+ subject$ to a high temp]ature1 und]go p>tial fusion1 ! m p[]ful bases attack+ ! f9e/ p>ticles ( clay & silica1 =m+ molt5 silicates1 & !n sl[ly attack+ ! m refractory portion2 ?is sl[ fusion & solution cont9ues until ! :ole ( ! mat]ial is melt$4 ,if ! heat+ is /opp$ be=e ! fusion has begun1 ! clay w be por\s & comp>atively s(t1 b z m & m mat]ial fuses1 ! mass 7on cool+7 becomes h>d] & less por\s1 z ! fus$ mat]ial occupies ! pores & sets to a d5se1 firm glassy mass4 ,! am\nt ( vitrification1 or p>tial fusion1 :i* occurs is1 !re=e1 ( great importance 9 "s indu/ries1 z by /opp+ x at an appropriate /age articles ( any desir$ degree ( porosity1 transluc5cy or /r5g? may be obta9$4 ,?us = common bricks1 only suffici5t vitrification is p]mitt$ to b9d ! p>ticles firmly toge!r1 b 9 eng9e]+ bricks--:]e mu* great] /r5g? is requir$--! vitrification is m complete4 ,porcela9 & e>!nw>e may be simil>ly di/+ui%$4 ,! ext5t to :i* a giv5 clay w vitrify dep5ds on ! am\nt ( flux+ mat]ial 7metallic comp\nds1 & oxides o!r ?an f]ric oxide & alum9a7 x conta9s1 on ! smallness ( its p>ticles & on ! duration & int5sity ( ! heat+4 ,clays conta9+ alkalies & lime comp\nds vitrify ) great rapidity :5 once ! necess>y temp]ature has be5 rea*$1 s t unless great c>e is ex]cis$ ! action w proce$ too f> & ! goods w be w>p$ & twi/$ or may ev5 =m a r\gh slag4 ,refractory clays1 on ! contr>y1 vitrify m sl[ly & at mu* high] temp]atures s t accid5tal ov]heat+s ( !m are f> less common4 ,! diff]5ce betwe5 ! temp]ature at :i* s9t]+ or vitrification occurs & t at :i* ! clay melts completely--usually t]m$ ! 'vitrification range'--v>ies ) ! nature ( ! clay4 ,9 "s cases ! clay melts z soon z vitrification becomes noticeable1 9 o!rs ! vitrification occurs at a dull r$ heat1 b ! mat]ial does n lose its %ape until aft] a prolong$ heat+ at ! highe/ temp]ature ( a firebrick kiln or te/+ furnace4 ,calc>e\s clays h ! melt+ & s9t]+ po9ts close toge!r1 s t x is almo/ impossible to produce vitrifi$ & imp]vi\s w>e f !m1 z !y lose _! %ape too readily4 ,if1 h[ev]1 ! diff]5ce betwe5 ! s9t]+ & fus+ temp]atures c be enl>g$--t is1 if ! vitrification range c be ext5d$--m imp]vi\s w>e c be made4 ,! easie/ means ( ext5d+ ! vitrification range consi/s 9 regulat+ ! proportion ( l>ge & small p>ticles4 ,! =m] increase & ! latt] dim9i% ! range4 ,basic comp\nds & fluxes cause a l[]+ ( ! melt+-po9t & a %ort5+ ( ! vitrification range4 ,! porosity ( raw clay is usually ( small importance1 b ! porosity ( fir$ clay or w>e is (t5 a s]i\s factor 9 det]m9+ ! suitability ( c]ta9 articles = _! int5d$ purposes4 ,9 its natural /ate1 clay does n readily absorb mu* wat]2 on ! contr>y x becomes pa/y & imp]vi\s unless x is di/urb$ & its texture de/roy$1 :5 x may be mix$ ) wat] to =m a pa/e or1 ) m wat]1 a ?9 'cream' or 'slurry4' ,:5 heat$ mod]ately1 clay =ms a por\s mat]ial &1 unless ! heat+ is excessive1 x w absorb ab\t "o-eigh? ( its weight ( wat]4 ,fur!r heat+ at a high] temp]ature r$uces its porosity--! m easily fus$ mat]ial fill+ "s ( ! pores--until a /age is rea*$ :5 ! mat]ial is completely vitrifi$ & is no long] por\s4 ,porosity may ?us be reg>d$ z ! opposite ( vitrification2 por\s goods be+ relatively light & s(t :il/ vitrifi$ ones are d5se & h>d4 ,= "s purposes1 porosity is an important *>act]i/ic3 = example1 build+ bricks :i* are mod]ately por\s are pref]able to ^? :i* are vitrifi$4 ,! manufacture ( por\s blocks = ! con/ruction ( light1 s\nd-pro( p>titions1 etc4 has increas$ rapidly ( late4 ,!y are made by add+ sawdu/ or o!r combu/ible mat]ial to ! clay4 ,! add$ sub/ances burn out on fir+ ! goods 9 a kiln4 ,clays :i* are por\s c be dri$ m readily & ) less risk ( crack+ ?an ^? :i* are m d5se4 ,= ?is reason1 "s claywork]s mix non-pla/ic mat]ial su* z s& or burn$ clay ) _! raw mat]ial4 ,! imp]meability ( pla/ic clay to wat] is a *>act]i/ic :i* is important = _m purposes4 ,! absorptive p[] ( clays is closely relat$ to _! porosity s f> z pure wat] is conc]n$1 b if ! wat] conta9s c]ta9 salts 9 solution a selective absorption occurs1 ! bases be+ reta9$ by ! clay 9 su* a mann] t !y _c be remov$ by wa%+4 ,! selective action is kn[n z adsorption & is mo/ noticeable 9 highly pla/ic clays4 ,b\rry 7#aj7 has %[n t ! slightly pla/ic *9a clays only ex]cise a small p[] ( adsorb+ calcium c>bonate f solution1 b highly pla/ic clays may adsorb #bj p] c5t4 ( x4 ,! alkal9e *lorides & sulphates d n appe> to be adsorb$ 9 ?is mann]1 b ! c>bonates are readily remov$ f solution4 ,all calcium & magnesium comp\nds appe> to be adsorb$1 ?\gh 9 v>iable quantities1 ! reaction be+ complicat$ :5 sev]al soluble salts are pres5t4 ,ries 7#f7 has f\nd t gallo-tannic acid is adsorb$ readily & increases ! pla/icity ( clay4 ,a%ley 7#aa7 has endeav\r$ to measure ! pla/icity ( clays by det]m9+ _! adsorption capacity = v>i\s anil9e dyes1 b 8 untimely decease prev5t$ ! inve/igation be+ complet$4 ,!re is reason to suppose t ! relation betwe5 adsorption & pla/icity is extremely close 9 _m clays & t ! =m] may1 to an important ext5t1 be us$ z a measure ( ! latt]4 ,9 "s clays1 h[ev]1 ?is relation%ip does n exi/4 ,s& & burn$ clay only %[ fa9t adsorption ph5om5a2 felsp> %[s !m to a slight & almo/ negligible ext5t & mo/ ( ! o!r non-pla/ic +r$i5ts ( clays are non-adsorptive4 ,selective adsorption be+ an important *>act]i/ic ( colloidal sub/ances1 ! possession ( ?is p[] by pla/ic clays supports ! claim t pla/icity is due1 at lea/ 9 "p1 to ! pres5ce ( colloids4 ,! addition ( small quantities ( a solution ( c]ta9 sub/ances to a /iff clay pa/e usually r$uces its /iffness1 & 9 "s cases turns x into a liquid4 ,! alkalies are p>ticul>ly p[]ful 9 ?is respect & _! action may be /rik+ly illu/rat$ by mix+ a few drops ( cau/ic soda ) a /iff clay pa/e4 ,9 a few mom5ts ! mixture w be suffici5tly liquid to p\r readily1 b x may be r5d]$ q /iff aga9 by add+ suffici5t acid to neutralize ! alkali previ\sly us$4 ,web] 7#ab7 has utiliz$ ?is *>act]i/ic to great advantage 9 ! production ( sanit>y w>e & crucibles = glass-mak+ by a process ( ca/+ :i* he has pat5t$4 ,! effect ( add+ wat] to a dry clay is curi\s4 ,at fir/ ! p>ticles 9 contact ) ! wat] become /icky & pla/ic1 & if ! proportion ( wat] add$ is suitable & ! mix+ is suffici5tly ?or\gh a pla/ic mass w be produc$1 ! *>act]i/ics ( :i* w dep5d on ! nature ( ! clay us$4 ,?is process ( mix+ clay ) a limit$ am\nt ( wat] is kn[n z 'temp]+4' ,! proportion ( wat] requir$ to make a pa/e ( suitable consi/5cy = modell+ appe>s to be con/ant = ea* clay4 ,if1 h[ev]1 a l>g] proportion ( wat] is add$ ! p>ticles ( clay w be sep>at$ s widely f ea* o!r t !y lose _! cohesion1 & in/ead ( a pla/ic mass1 ! mat]ial w =m a liquid ( cream-l consi/5cy4 ,if a piece ( /iff clay pa/e is susp5d$ 9 a l>ge volume ( wat] )\t /irr+1 dis9tegration w /ill occur 7?\gh a mu* long] "t w be requir$7 & ! clay w be deposit$ z a s$im5t at ! bottom ( ! vessel4 ,! lean] ! clay or ! l>g] ! proportion ( non-pla/ic mat]ial x conta9s1 ! m rapidly w ?is dis9tegration take place4 ,a highly pla/ic clay w become almo/ imp]vi\s & w reta9 its %ape indef9itely4 ,if a mixture ( clay & wat] 9 ! =m ( a cream or slurry be all[$ to re/1 ! l>g] & less pla/ic p>ticles w settle1 b _m ( ! p>ticles ( true clay w rema9 susp5d$ = sev]al h\rs & "s ( !m = sev]al days4 ,"s p>ticles ( clay are s small t x is d\btful if !y w\ld ev] settle completely unless "s coagulant 7 add$1 & z !y readily pass ?r\gh all ord9>y filt]+ m$ia x is extremely difficult to collect !m 9 a pure /ate4 ,^! turbid susp5sions ( clay may be rapidly cle>$ by ! addition ( sodium *loride :i* increases ! surface t5sion ( ! solution4 ,! f9e p>ticles behave 9 ! same way z colloidal sub/ances1 i4e4 z if !y possess$ an electro/atic *>ge4 ,h5ce ! addition ( a salt 7electrolyte71 ^: ions annul ! opposite *>ges ( ! electric d\ble lay] assum$ by ,helmholtz to be pres5t1 enables ! p>ticles to coagulate 9 accordance ) ! ord9>y laws ( surface t5sion 7#ad74 ,exposure to ! action ( air & fro/ has a m>k$ effect on _m clays4 ,:5 fre%ly dug ^! may be h>d & difficult to cru%1 b aft] exposure !y break up readily into small fragm5ts4 ,clays diff] greatly 9 ! ext5t to :i* !y are affect$ by exposure2 "s are completely dis9tegrat$ by /&+ #dh h\rs 9 ! op5 air1 :il/ o!rs are sc>cely affect$ by exposure 9 bleak places ?r\gh sev]al ye>s ( /orm1 sun%9e & fro/4 ,usually1 h[ev]1 ! effect ( a c\ple ( nights exposure to h>d fro/ w produce a m>k$ dis9tegration ( ! mat]ial4 ,?is process ( exposure is kn[n z 'wea!r+' & its effects are s important t x is employ$ :5ev] possible = clays requir+ to be cru%$ be=e use4 ,all clays are r5d]$ m workable by exposure1 b "s ( !m are damag$ by ! oxidation ( "s impurities 7e4g4 pyrites7 9 !m1 ?\gh 9 o!r clays ?is v oxidation1 if foll[$ by ! lea*+ action ( ra91 effects an important purification ( ! mat]ial4 ,wea!r+ appe>s to h no effect on ! *emical composition ( ! p>ticles ( true clay 9 ! mat]ial1 ?\gh x may decompose ! impurities pres5t4 ,on ! clay itself its action is l>gely physical & consi/s *iefly 9 sep>at+ ! p>ticles slightly f ea* o!r1 !reby enabl+ wat] to p5etrate ! mat]ial m readily & facilitat+ ! production ( a pla/ic pa/e4 ,! dis9tegrat+ action ( ! wea!r on "s 'clays' is s complete t !y require no cru%+ b c be conv]t$ into a homog5e\s pa/e by simply knead+ !m ) a suitable proportion ( wat]4 ,x is possible t on exposure to ! heat ( ! sun's rays--p>ticul>ly 9 tropical climates--"s *emical decomposition ( ! clay may occur1 b comp>$ ) ! purely physical action ( wea!r+ ! am\nt ( su* *emical decomposition mu/ be relatively unimportant 9 mo/ cases4 ,x may1 h[ev]1 acc\nt = ! pres5ce ( free silica & free alum9a 9 "s clays4 ,! action ( ! wea!r on rocks1 result+ 9 ! =mation ( clays1 is describ$ 9 ,*apt] ,,iii4 ,heat effects rem>kable *anges 9 ! physical "* ( clays2 ! mo/ important ( ^! h already be5 not$4 ,at a g5tle heat1 ! clay is dri$ & reta9s mo/ ( its p[] ( becom+ pla/ic :5 moi/5$2 v little1 if any1 decomposition occurs4 ,at a high] temp]ature x loses its 'comb9$ wat]1' ! clay molecule app>5tly dissociat+1 & a h>d /ony mass--consi/+ ( p>ticles ( free silica & free alum9a cem5t$ toge!r by ! m easily fusible impurities pres5t--is =m$4 ,if ! heat+ is cont9u$ ! h>dness ( ! mat]ial is increas$ ow+ to m molt5 silicate hav+ be5 produc$ f ! impurities pres5t1 & on cool+1 its t5sile /r5g? & resi/ance to cru%+ w be f\nd to be enorm\sly great] ?an ^? ( ! orig9al clay4 ,all pot5tial pla/icity is de/roy$ by heat+ to #gjj ,c4 & no me?od ( re/or+ x has yet be5 devis$4 ,z clays are abundant1 ?is is n a s]i\s disadvantage = ! specially desir$ *>act]i/ics ( bricks1 t]ra-cotta1 pott]y & porcela9 are all su* z to be incompatible ) pla/icity4 ,! latt] is extremely valuable 9 ! %ap+ ( ! w>es m5tion$1 b aft] ! manufacture is complet$1 ! de/ruction ( ! pla/icity is an ess5tial feature ( _! usefulness4 ,if ! heat+ is v prolong$ or is repeat$ sev]al times1 clays *ange o!r ( _! physical *>act]s & become brittle & liable to crack "u sudd5 *anges ( temp]ature4 ,?is is p>tly due to ! fur!r fusion 7vitrification7 :i* occurs & p>tly to ! =mation ( cry/all9e silicates1 notably ,sillimanite 7#ac74 ,! ext5t to :i* clays are ord9>ily heat$ & ! conditions "u :i* !y are cool$ d n usually induce ! =mation ( cry/als2 ! object ( ! claywork] be+ to produce a homog5e\s mass1 ! p>ticles ( :i* are securely held toge!r4 ,! result is t burn$ clay products are usually compos$ ( amorph\s p>ticles cem5t$ by a glass-l mat]ial =m$ by ! fusion ( "s ( ! m9]al +r$i5ts ( ! orig9al sub/ance4 ,! silicates =m$ are1 !re=e1 9 a condition ( solid1 sup]-cool$ solution 9 :i* ! t5d5cy to cry/allize is re/ra9$ by viscosity4 ,on rais+ ! temp]ature ( fir+ or on prolong+ ! heat+ at ! previ\s maximum temp]ature ! viscosity ( ! fus$ portion is dim9i%$ & cry/allization may !n occur4 ,! facility ) :i* cry/allization occurs v>ies greatly ) ! composition ( ! fus$ mat]ial1 ^? silicates :i* are ri* 9 lime & magnesia cry/alliz+ m readily ?an ^? conta9+ pota% or soda4 ,vogt has /at$ t small quantities ( alum9a promote ! =mation ( a glassy /ructure1 & ,morozewicz has %[n t a l>ge excess ( ?is sub/ance mu/ be pres5t if cry/allization is to occur4 ,! /udy ( ! reactions :i* occur :5 clays are heat$ is1 h[ev]1 extremely complex1 n only on acc\nt ( ! v>iety ( sub/ances pres5t1 b also on acc\nt ( ! high temp]atures at :i* x is necess>y to "w1 s t = a fur!r consid]ation ( x ! read] %\ld consult special treatises on ! fusion ( silicates4 ,?is subject has n[ become an important bran* ( physical *emi/ry4 ,,*apt] ,,ii ,,clay ,,& ,,associat$ ,,rocks ,clay1 z already m5tion$1 is geologically a rock & n a m9]al1 & belongs to ! important gr\p ( s$im5t>y rocks :i* h be5 d]iv$ f ! igne\s or prim>y ones by processes ( wea!r+1 susp5sion 9 wat] & subsequ5t deposition or s$im5tation4 ,:atev] may be ! prim>y orig9 ( clay1 its *ief occurr5ce is 9 geological =mations :i* h und\bt$ly be5 =m$ by aque\s action4 ,! mat]ials result+ f ! exposure ( prim>y rocks to ! action ( ! elem5ts h be5 c>ri$ away by wat]--(t5 = long di/ances--& aft] und]go+ v>i\s purifications h be5 deposit$ :]e ! spe$ ( ! wat] has be5 suffici5tly r$uc$4 ,9 "s cases !y h aga9 be5 transport$ & re-deposit$ & n infrequ5tly clay deposits are f\nd :i* %[ signs ( subsequ5t imm]sion at consid]able dep?s & h e appe>ance ( hav+ be5 subject$ to enorm\s pressures & possibly to high temp]atures4 ,"s clays h only be5 c>ri$ by small /reams & = %ort di/ances2 ^! are seldom highly pla/ic & resemble ! lean *9a clays & kaol9s4 ,o!rs h be5 c>ri$ by rapidly mov+ riv]s & h be5 dis*>g$ into lakes or into ! sea2 !y h ?us und]gone a process ( gradual purification by elutriation1 ! s& & o!r heavi] p>ticles be+ fir/ deposit$ & ! f> small] p>ticles ( clay be+ c>ri$ a great] di/ance t[>ds ! c5tre ( ! lake or ! quiet] portions ( ! ocean4 ,! nature ( su* deposits w1 naturally1 diff] greatly f ea* o!r1 ! mat]ials at fir/ associat$ ) ! clay1 or becom+ mix$ ) x at a lat] /age1 ex]cis+ an important influ5ce on its texture1 composition & prop]ties4 ,if ! transport+ /ream fl[s ?r\gh valleys ^: sides are =m$ ( lime/one1 *alk1 s&/one or o!r mat]ials1 ^! w become mix$ ) ! clay1 & to s great an ext5t has ! mix+ occurr$ t v few clays occur 9 a /ate ev5 approximat+ to purity4 ,! majority ( clays are contam9at$ ) iron oxide1 lime comp\nds & free silica 9 su* a f9e /ate ( division t x is impossible to purify !m completely )\t de/roy+ ! nature ( ! clay4 ,9 addition to ?is x mu/ be rememb]$ t ! l& is cont9ually ris+ or s9k+ ow+ to int]nal *anges 9 ! int]ior ( ! e>?1 & t ^! subt]ranean *anges br+ ab\t tilt+1 fold+1 ov]turn+ & o!r second>y *anges1 :i*1 lat]1 cause a fre% set ( mat]ials to be mix$ ) ! clays4 ,fur!r ?an ?is1 ! action ( ! wea!r1 ( riv]s & ( ! sea nev] ceases1 s t a process ( re-mix+ & re-sort+ ( mat]ials is cont9u\sly tak+ place1 & has be5 do+ s = c\ntless ages4 ,x is1 !re=e1 a legitimate cause = wond] t su* enorm\s deposits ( clays ( s uni=m a "* %\ld occur ?r\gh\t ! l5g? & bread? ( ,europe1 & practically ?r\gh\t ! _w4 ,= al?\gh ! composition ( _m ( ^! b$s is ( a mo/ highly complex nature1 ! g5]al prop]ties su* z pla/icity1 behavi\r on heat+1 etc41 rema9 rem>kably con/ant ov] l>ge areas ( c\ntry1 & ! clays ( ea* geological =mation are s mu* alike 9 diff]5t p>ts ( ! _w z to be readily recogniz$ by anyone famili> ) ! mat]ial ( ! same =mations 9 ?is c\ntry4 ,consid]able diff]5ces und\bt$ly exi/1 b ^! are insignificant 9 comp>ison ) ! va/ly diff]5t circum/ances "u :i* ! deposits 7 accumulat$4 ,leav+ ! consid]ation ( ! modes ( =mation ( ! v>i\s clay deposits to lat] *apt]s 7,,iii & ,,iv71 x is conv5i5t "h to enum]ate "s ( ! *ief *>act]i/ics ( ! diff]5t clay deposits & _! associat$ rocks4 ,9 ?is connection x is n propos$ to ent] into m9ute details1 b r to indicate 9 broad outl9e ! *ief *>act]i/ics ( ! clays f ! diff]5t deposits4 ,?is g5]al view is ! m necess>y z clay occurs 9 ea* ma9 geological division ( ! s$im5t>y rocks & 9 almo/ e sub-division 9 v>i\s p>ts ( ! _w4 ,! ,precambrian1 ,cambrian1 ,silurian & ,devonian 'clays' are *iefly 9 ! =m ( %ales or slates1 ! latt] be+ clays :i* h und]gone a metamorphic *ange2 ! latt] result$ 9 ! production ( a h>d & p>tially cry/all9e mat]ial ) b little pot5tial pla/icity & !re=e ( small importance = ! ord9>y purposes ( clay work+4 ,slates are di/+ui%$ f %ales by _! splitt+ into ?9 leaves :i* are n 9 ! plane ( orig9al deposition1 b are due to ! deposit$ mat]ial be+ subject$ to great lat]al pressure4 ,! re-arrangem5t ( ! p>ticles ?us produc$ has imp>t$ to ! mat]ial a cleavage q indep5d5t ( ! orig9al lam9ation4 ,! %ales 9 ^! =mations are occasionally s(t & friable & are !n t]m$ m>ls1 b ?is "n is mislead+ z !y conta9 no appreciable proportion ( f9ely divid$ calcium c>bonate z d ! true m>ls#h4 ,footnote #h3 ,read]s desir+ m detail$ in=mation on ! occurr5ce ( ! clays m5tion$ 9 ?is *apt] %\ld ref] to ! au?or's ,briti% ,clays 7,no4 #b 9 ,bibliography74 ,! clays 9 ! ,c>bonif]\s ,lime/one are n1 z a :ole1 ( mu* importance1 b ! occurr5ce 9 ?is =mation ( pockets ( :ite refractory clays 9 ,/af=d%ire1 ,nor? ,wales 7,mold7 & ,d]by%ire is int]e/+1 especially z ^! are us$ = ! manufacture ( firebricks & furnace l9+s4 ,^! clays are highly silici\s & 9 composition are int]m$iate betwe5 ! ,york%ire fireclays & gani/]4 ,_! orig9 is unc]ta91 b x is g5]ally consid]$ t !y h be5 produc$ by ! action ( ! wea!r & /reams on ! %ales & grits ( ! ,coal ,measures :i* =m]ly occupi$ ! high] gr\nd ar\nd !m1 ?\gh ,maw 7#af7 /ates t 'x is sc>cely op5 to "q t !y are ! remnants ( ! suba]ial dissolution ( ! lime/one' 7see ',fireclays1' ,*apt] ,v74 ,9 ! ,upp] ,c>bonif]\s ,sy/em ! clays are highly important because ( _! g5]al refractory nature1 ?\gh !y diff] greatly 9 ?is respect1 "s r$-burn+ %ales ( ?is =mation hav+ no great] p[] to resi/ heat ?an h "s ( ! surface clays4 ,^? ( ! ,coal ,measures are ( two ma9 k9ds--%ales1 or lam9at$ rocks :i* readily split along ! planes ( deposition1 & un/ratifi$ und]clays4 ,! %ales usually occur above ! seams ( coal & are ei!r ( lacu/r9e or m>9e orig91 diff]5ces 9 _! fossils & li?ological "* support+ "o orig9 = "s deposits & ! o!r = ! rema9d]4 ,"s ( !m are fairly uni=m 9 composition1 b o!rs v>y s greatly 9 _! physical *>act]s1 t !y are divid$ by m9]s into 'b9ds' or relatively pure %ales1 'rock-b9ds1' or s&y %ales1 & s&/ones4 ,!y also v>y greatly 9 ?ickness 9 diff]5t localities1 & :il/ !y =m ! ma9 feature 9 "s di/ricts1 9 o!rs !y are replac$ by s&/ones4 ,! und]clays are s call$ f _! usually ly+ b5ea? ! coal seams4 ,!y are n noticeably /ratifi$ & v>y greatly 9 "* f s(t unctu\s mat]ials to h>d1 s&y rocks4 ,9 composition !y v>y enorm\sly1 ! p]c5tage ( silica rang+ f #ej p] c5t41 or less1 to z high z #ig p] c5t4 ,! mode ( =mation ( ! und]clays is n c]ta9ly kn[n4 ,!y d n appe> to be soils or ( t]re/rial orig91 b accord+ to ,arb] 7#bd7 correspond closely to ! black oozes ( m>9e & semi-m>9e e/u>9e deposits ( tropical swamps1 or to ! muds surr\nd+ ! /umps ( trees 9 ! buri$ =e/s ( our coa/-l9es4 ,!y ?us appe> to be q di/9ct f ! %ales above !m1 bo? 9 orig9 & physical *>act]s4 ,! m silici\s portions1 kn[n z ,gani/]#i1 possess comp>atively few ( ! *>act]i/ics ( clay ?\gh us$1 l all ! m refractory clays ( ! ,coal ,measures1 = all purposes = :i* fireclay is employ$4 ,! t]m fireclay is1 9 fact1 frequ5tly appli$ to all ! refractory deposits 9 ! ,coal ,measures1 )\t mu* reg>d to _! composition 7see ,*apt] ,v74 ,footnote #i3 ,! ,d9as rock us$ 9 ! ,vale ( ,nea? 7,wales7 is an ev5 m silici\s mat]ial f\nd 9 ! ,mill/one ,grit imm$iately bel[ ! ,coal ,measures4 ,x is l>gely employ$ = firebricks4 ,valuable ,coal ,measure clays occur 9 enorm\s quantities 9 ,nor?umb]l&1 ,durham1 ,york%ire1 ,nott+ham%ire1 ,d]by%ire1 ,/af=d%ire1 ne> ,/\rbridge1 9 ,w>wick%ire1 ,%rop%ire1 ,nor? & ,s\? ,wales & ,s\? ,we/ ,scotl&4 ,9 ,irel&1 on ! contr>y1 ! ,coal ,measure clays are ( little value except 9 ! neighb\rhood ( ,coal ,isl&1 co4 ,tyrone4 ,! position ( ! ',sagg] ,m>ls' ( ,nor? ,/af=d%ire 7,keele ,s]ies & ,etruria ,m>ls71 relative to ! ',f>ewell ,rock' or ,mill/one ,grit1 is %[n 9 fig4 #h 9 :i* ! horizontal l9es repres5t coal-seams & iron/one ve9s4 ,illu/ration3 --------------------- ,keele ,s]ies --------------------- ,newca/le --------------------- ,coal ,etruria ,m>ls ,top ,r$ ,m9e --------------------- ,gubb9 ,iron/one --------------------- --------------------- ,kn[les ,coal ,burnwood ,iron/one --------------------- --------------------- ,mossfield ,coal --------------------- #e ft4 ,coal --------------------- ,h>d m9e ,coal --------------------- ,cock%ead ,coal --------------------- ,crabtree ,coal --------------------- ,mill/one ,grit --------------------- ,fig4 #h4 ,coal ,measures sequ5ce 9 ,nor? ,/af=d%ire4 ,! dissimil>ities 9 ! fossils ( ! ,coal ,measure clays & %ales 9 ! ,nor!rn & ,s\!rn ,hemisph]es sugge/ t !re is a consid]able diff]5ce 9 _! =mation1 b ! numb] ( clays & %ales :i* h be5 exam9$ is too small = any accurate conclusion to be drawn4 ,= _m indu/rial purposes1 p>ticul>ly = ! manufacture ( refractory goods1 ! clays & %ales ( ! ,c>bonif]\s ,sy/em are highly important4 ,! less valuable burn to a r$di% col\r1 (t5 spoil$ ) _m grey spots ( f]r\s silicate d]iv$ f ! pyrites 9 ! clay1 b ! pur] v>ieties burn to a delicate primrose or pale buff t9t & are among/ ! mo/ heat-resi/+ mat]ials kn[n4 ,! ,coal ,measure clays ( ,york%ire are p>ticul>ly e/eem$ = _! refractory prop]ties2 = ! manufacture ( glaz$ bricks & = blocks = ar*itectural purposes some:at ambigu\sly t]m$ 'glaz$ t]ra-cotta4' ,! inf]ior qualities are l>gely us$ = ! manufacture ( r$ eng9e]+ bricks1 "s ( !m compet+ successfully ) ! m widely kn[n 'blue bricks' ( ,/af=d%ire4 ,! ,coal ,measure clays ( ,%rop%ire are not$ = ! manufacture ( r$ ro(+ tiles1 especially 9 ! neighb\rhood ( ,broseley4 ,agriculturally1 ! ,coal ,measure clays are usually poor1 b are occasionally ( good quality4 ,! %ales produce heavy1 cold clays & ! yell[ subsoil produces soils ( a light1 hungry "* s t ! two %\ld1 if possible1 be mix$ toge!r4 ,p]mian clays are ( little value except = ! manufacture ( r$ build+ bricks4 ,! ,nott+ham%ire ,p]mian clays make excell5t ro(+ tiles1 fl[] pots & r$ bricks4 ,agriculturally1 ! ,p]mian clays are a free work+ loam yield+ l>ge crops ( mo/ ( ! ord9>y f>m products4 ,triassic clays are ( great importance 9 ! ,midl&s1 ^? upp] portions ( !m kn[n z ! ,keup] ,m>ls be+ mu* us$ = ! manufacture ( bricks4 ,!y are specially kn[n among/ claywork]s z ! mat]ial f :i* ! ,midl& r$ bricks ( ,nott+ham%ire & ,leice/]%ire & ! ,som]set%ire tiles are prep>$4 ,jurassic clays are an important gr\p1 ( m>9e orig91 occurr+ 9 close association ) lime/one4 ,= ?is reason !y =m a valuable s\rce ( mat]ial = ! manufacture ( ,portl& cem5t1 b are ( less value to ! brick & tile manufactur]4 ,! ,jurassic ,sy/em conta9s s l>ge a v>iety ( clays1 ( su* widely diff]5t ages & *>act]i/ics1 t no g5]al description ( !m c be giv5 9 ! pres5t volume4 ,illu/ration3 ,fig4 #i4 ,lias clay be+ work$ = ! manufacture ( h&-made s&-fac$ ro(+ tiles4 7,by c\rtesy ( ,messrs ,webb ,bros4 ,ltd41 ,*elt5ham47 ,! ',lias clays'--! l[e/ ( ! ,jurassic =mation--are *iefly d>k1 bitum9\s %ales1 includ+ ! 'alum %ales1' & are (t5 s]i\sly contam9at$ ) pyrites & iron/one4 ,:5 c>efully select$ !y may be us$ to advantage 9 ! production ( mo/ r$ articles su* z bricks1 tiles1 *imney pots1 etc4 ,!y %r9k less 9 ! kiln ?an d mo/ clays1 & are easily fusible on acc\nt ( ! lime !y conta91 b on ! :ole ?is =mation is ( great value = ! manufacture ( ! articles j m5tion$4 ,agriculturally1 ! ,lias clays are laid d[n = grass1 b ! light] soils are useful = arable purposes4 ,! ',oolitic clays1' :i* are also ,jurassic1 usually conta9 lime/one 9 ! =m ( nodules1 b are nev]!less important4 ,!y =m a broad belt above ! ,lias f ,dorset to ,york%ire1 & include ! blue clays ( ! ,purbeck b$s1 /iff blue bitum9\s ,kim]idge clays1 ! irregul>1 s&y ,coral ,rag clays1 ! fam\s ,ox=d clay 7f :i* ! ,pet]bor\gh & ,fletton bricks are made71 ! ,kellaways blue clay1 & ! ,full]'s ,e>? deposits4 ,! ',kim]idge clays' are d>k1 /iff lam9at$ clays1 closely resembl+ gault1 & are mu* us$ 9 ! ,we/ & ,midl&s = brickmak+4 ,a well-kn[n deposit ( ?is "* has long be5 us$ at ,pick]+ 9 ,york%ire1 b ! mo/ typical deposits are 9 ,hunt+don%ire4 ,! ,kim]idge clays conta9 a bitum9\s %ale1 or ,sapropelic ,coal1 :i* evolves a *>act]i/ic od\r on burn+4 ,agriculturally1 ! ,kim]idge clays resemble gault & are difficult to "w z arable l&1 ?\gh !y =m fir/-rate pa/urage4 ,illu/ration3 ,fig4 #aj4 ,ox=d clay ne> ,pet]bor\gh4 7,by c\rtesy ( ,messrs ,ru/on1 ,proctor ,co4 ,ltd47 ,! ',ox=d clays' are valuable = brickmak+ :5 _! use is und]/ood1 b to ! un9itiat$ !y are v tr\blesome4 ,_! col\r is d>k blue or grey & !y are usually /iff or some:at %aly 9 texture ) lay]s ( v>iable composition4 ,! closely associat$ ,cornbra% 7lime/one7 is a s\rce ( tr\ble unless great c>e is tak5 9 ! selection ( ! mat]ial4 ',ox=d clays' are n infrequ5tly trav]s$ by seams ( poor coal or by oil-%ales4 ,agriculturally1 ,ox=d clay is difficult to "w &1 :ile mu* ( x is valuable1 l>ge portions are poor & cold4 ,:5 well expos$ to fro/ x is made mu* light]1 b ev5 !n is n v suitable = :eat & autumn s[n crops4 ,! ',kellaway blue clays' are (t5 includ$ 9 ! ,ox=d clays1 ?\gh !y =m irregul> b&s above !m & are ( fre%-wat] orig91 :il/ ! ,ox=d clays are m>9e deposits4 ,!y are *iefly us$ comm]cially = dome/ic firebricks ne> ,oundle & ,/am=d4 ,cretace\s clays occur1 z _! "n implies1 9 association ) *alk4 ,! *ief clay 9 ?is ,sy/em is ! gault1 a /iff1 black1 calc>e\s clay ( m>9e orig9 *iefly us$ = brickmak+4 ,:5 us$ alone1 gault burns to a r$di% col\r1 due to ! iron pres5t1 b if1 z is m usual1 x is mix$ ) *alk1 x burns p]fectly :ite4 ,"s gaults conta9 suffici5t *alk to r5d] ! addition ( a fur!r quantity unnecess>y4 ,agriculturally1 ! ,cretace\s clays =m good arable soil :]e !y are n too expos$1 b !y suff] f dr\ght4 ,! ',weald5 clay' is a /iff yell[i% grey or blue clay ext5sively us$ = brickmak+ 9 ,k5t1 ,sussex & ,surrey4 ,x has be5 subdivid$ by geologi/s into a numb] ( o!r clays1 su* z ! ,wadhur/1 ,fairlight1 etc41 b ! diff]5ces betwe5 !m lie m 9 ! fossils occurr+ 9 !m ?an 9 ! *>act]s ( ! clays !mselves4 ,!y are usually contam9at$ ) iron/one1 gypsum & "s lime/one4 ,agriculturally1 ! ,weald5 clay produces /iff1 yell[i% soils ( a wet & poor "*1 b sometimes loams ( a highly productive nature occur4 ,! ,t]ti>y clays include all ^? deposit$ aft] ! ,*alk & previ\s to ! close ( ! ,glacial p]iod4 ,!y are usually mix$ ) s& & gravel1 & ?\gh ! deposits are (t5 ?9 & irregul> !y are ! mo/ g5]ally important ( all clays4 ,!y v>y greatly 9 "*2 "s1 l ! ,london clay1 be+ almo/ useless unless mix$ ) o!r mat]ials1 :il/ o!rs l ! ball clays ( ,devon%ire & ,dorset are among/ ! pure/ & mo/ valuable ( ! pla/ic clays4 ,! ,t]ti>y clays are divid$ by geologi/s into ,plioc5e1 ,mioc5e & ,eoc5e =mations2 ( ^! ! fir/ are comm]cially unimportant & ! second d n exi/ 9 ,great ,brita94 ,at "o "t ! ,bovey ,tracey clays 7 consid]$ to be ,mioc5e1 b !y h rec5tly be5 class$ z ,oligoc5e by ,clem5t ,reid4 ,agriculturally1 ! mo/ important ( ! ,t]ti>y =mations is ! ,eoc5e1 p>ticul>ly ne> ,london1 ?\gh x is mu* cov]$ by s& or gravel4 ,! ,london clay1 :i* produces a heavy br[n soil1 is ( slight value1 ?\gh :5 prop]ly dra9$ x produces good crops ( :eat1 beans1 & cabbages & o!r m>ket-g>d5 produce4 ,= ?is purpose x is greatly improv$ by ! addition ( lime & ( t[n manure4 ,! ,s\? ,hamp%ire ,eoc5e b$s ( clay are cold1 wet & ( small agricultural value4 ,! ,eoc5e clays are compos$ ( a v>iety ( clays1 _m ( :i* are only di/+ui%able by ! diff]5t fossils !y conta94 ,! mo/ important are ! ,read+ clays1 ! ,london clay & ! ,bag%ot clays4 ,! ,read+ clays ext5d ov] a consid]able area 9 ! ,s\? ( ,engl& & are mo/ valuable ne> ! t[n f :i* !y d]ive _! "n4 ,! be/ qualities are mottl$ 9 a *>act]i/ic mann] & are p>ticul>ly suitable = ! manufacture ( ro(+ tiles & small t]ra-cotta--an indu/ry = :i* ,read+ is fam\s4 ,! ,london clay is always a trea*]\s mat]ial & is be/ avoid$ 9 ! manufacture ( bricks & o!r articles except "u highly skill$ te*nical advice4 ,! ,bag%ot clays 9 ,dorset%ire are fam\s = ! ball & pipe clays %ipp$ f ,poole1 :il/ at ,bovey ,tracey & 9 sev]al p>ts ( ,devon%ire equally valuable ball clays are f\nd & are %ipp$ f ,teignm\?4 ,^! ball clays are ( v>iable composition & col\r & require c>eful selection & te/+4 ,!y are closely associat$ ) s&s1 b ! l[] b$s ( clay are rem>kably /iff1 pla/ic & :ite-burn+4 ,! col\r ( ! raw clay v>ies f a pale yell[ to a d>k br[n or ev5 to black1 b ?is is little or no crit]ion ( ! col\r ( goods made !refrom1 z ! col\r is due to c>bonace\s matt]s1 #d p] c5t4 or m c>bon be+ usually pres5t4 ,! 'blue' & 'black' ball clays are ! mo/ valu$ by pott]s1 b ! quality is usually asc]ta9$ by a burn+ te/4 ,! value ( ^! ball clays bo? 9 ,devon%ire & ,dorset is due to _! comp>ative fre$om f iron & alkalies & to _! rem>kable unctu\sness & pla/icity4 ,!y are1 !re=e1 l>gely us$ 9 ! manufacture ( all k9ds ( e>!nw>e ( :i* !y =m ! f\ndation mat]ial4 ,9 composition1 ball clays appe> to consi/ *iefly ( a hydro-alum9o-silicate correspond+ to ! =mula ,h#d;,al#b,si#b,o#i1 & 9 ?is !y v closely resemble ! *9a clays 7kaol9s74 ,! latt] are1 h[ev]1 b slightly pla/ic :il/ ! ball clays are among/ ! mo/ pla/ic clays kn[n4 ,! *9a clays are also mu* m refractory ?an ! ball clays ow+ to ! some:at l>g] proportion ( alkalies 9 ! latt]4 ,pipe clays are an inf]ior quality ( ball clay2 !y conta9 r m iron & alkalies & consid]ably m silica4 ,= ?is reason !y c only be us$ = *eap] w>es :]e col\r is ( less importance & :]e _! excessive contraction c be neutraliz$ by ! addition ( o!r sub/ances su* z fl9t4 ,! ,b\ld] clays occur 9 a blanket-l cov]+ ( ,drift :i* lies ov] ! great] "p ( ,nor!rn & ,c5tral ,engl&1 & ov] a consid]able portion ( ,scotl& & ,irel&4 ,!y are a product ( ! ,ice ,age &1 :il/ v>y+ greatly 9 "*1 may usually be di/+ui%$ by ! occurr5ce 9 !m ( r\nd$ /ones & gravel1 "s ( ! =m] be>+ cle> indications ( glacial action4 ,! b\ld] clays are l>gely us$ = ! manufacture ( build+ bricks1 b ! /rata 9 :i* !y occur are s irregul> t v c>eful sup]vision ( ! digg+ is necess>y4 ,9 "s localities ^! clays =m b$s #ab ft4 or m 9 ?ickness & relatively free f gravel2 9 o!r di/ricts ! clay is int]sp]s$ ) l5ticul> deposits ( gravel or s& 7commonly kn[n z 'pockets'71 & if ^! are mix$ ) ! clay consid]able difficulty 9 manufacture may be exp]i5c$4 ,! total ?ickness ( ! drift deposits is (t5 v great1 z 9 ! cliffs at ,filey 7fig4 #aa7 :i* are #bjj ft4 high4 ,illu/ration3 ,fig4 #aa4 ,cliffs ( ,b\ld] clay at ,filey ly+ on ,calc>e\s ,crag4 ,! b\ld] clays--consid]$ ap>t f ! /ones1 gravel & s&y mat]ials occurr+ ) !m--are usually r$-burn+1 /iff & v pla/ic1 b ! gravel1 s& & cru%$ /ones mix$ ) !m 9 ! =mation ( ! mat]ial usually r5d] !m ( m$ium pla/icity4 ,by c>eful wa%+1 mo/ b\ld] clays may be purifi$ suffici5tly to enable co>se br[n pott]y to be made f !m4 ,clean deposits ( suffici5t size to be work$ )\t any purification are occasionally f\nd4 ,usually1 h[ev]1 ! b\ld] clay =mation is some:at trea*]\s z x is difficult to asc]ta9 its nature2 boreholes are apt to be q mislead+ z ! =mation is s irregul> 9 "*4 ,agriculturally1 drift or b\ld] clays are poor soils1 b by judici\s managem5t & c>eful mix+ !y may be made m f]tile4 ,:]e x conta9s *alk--z 9 ,norfolk & ,suffolk--b\ld] drift =ms an excell5t arable soil4 ,plei/oc5e or ,rec5t clays are among/ ! mo/ important brickmak+ mat]ials 9 ! ,s\? ( ,engl&4 ,!y are ( rem>kably v>i$ "*1 hav+ be5 d]iv$ f a numb] ( o!r =mations4 ,usually ! deposits are some:at %all[ & irregul> 9 =m1 b b$s ( consid]able ?ickness occur 9 "s localities4 ,agriculturally1 !y are ( consid]able importance4 ,mo/ ( ! brick e>?s us$ 9 ! s\?-ea/ ( ,engl& are ( ,rec5t =mation1 ^? ( ! ,?ames ,valley be+ ( special importance 9 ?is connection1 p>ticul>ly :]e !y are associat$ ) *alk2 ?us =m+ natural m>ls or enabl+ artificial m>ls to be produc$4 ,! brick e>?s--9 ! s5se 9 :i* ?is t]m is us$ 9 ! s\?--comprise ?ree important types ( clay3 7a7 ,pla/ic clays n p>ticul>ly diff]5tiat$ f ^? already describ$1 7b7 ,loams or s&y clays :i* are suffici5tly pla/ic = satisfactory use1 h ! advantage ( %r9k+ b slightly 9 dry+1 & are l>gely us$ 9 ! manufacture ( r$ fac+ bricks & z light soils1 & 7c7 ,m>ls or calc>e\s clays1 us$ = ! production ( light col\r$ or :ite bricks1 ! *alk !y conta9 comb9+ ) any iron comp\nds pres5t &1 at ! same "t1 r$uc+ ! contractility ( ! clay4 ,on burn+1 !y =m a cem5t :i* b9ds ! p>ticles into a /rong mass4 ,^! are ! 'true m>ls' or 'malms' compos$ ( clay & *alk & mu/ n be confus$ ) ! s-call$ m>ls ( ,/af=d%ire & else:]e :i* are almo/ free f lime comp\nds4 ,!re is1 at pres5t1 no def9ition ( 'm>l' :i* is q satisfactory2 a mak] ( ,london /ock bricks und]/&+ by ?is t]m a clay conta9+ at lea/ #aj p] c5t4 ( *alk2 a mak] ( :ite ,suffolk bricks a mat]ial conta9+ at lea/ twice ?is am\nt2 an agriculturali/ any soil1 n obvi\sly s&y1 :i* w make 8 clay l& less /icky2 & _m geologi/s any friable argillace\s e>?s4 ,a g5]al cons5sus ( op9ion is1 h[ev]1 be+ gradually rea*$ t ! t]m 'm>l' %\ld be limit$1 z f> z possible1 to clays conta9+ calcium c>bonate 9 a f9ely divid$ /ate4 ,alluvial deposits--:i* are also ( ,rec5t =mation1 ?\gh /ill ( suffici5t age = skeletons ( mammo?s to be f\nd 9 !m--are ( s v>iable a nature z to r5d] any brief1 g5]al description impossible4 ,_m ( !m are s contam9at$ ) s& & cru%$ lime/one z to be useless = manufactur+ purposes & ( small value agriculturally1 b o!rs are important 9 bo? ^! respects4 ,fur!r details ( ! occurr5ce ( clays 9 ! v>i\s =mations describ$ w be f\nd 9 ! ,maps & ,memoirs ( ! ,geological ,survey & 9 ! au?or's ,briti% ,clays 7#b74 ,,*apt] ,,iii ,,! ,,orig9s ,,( ,,clays ,! t]ms 'prim>y' & 'residual' are appli$ to ^? clays :i* are f\nd ov]ly+ or 9 close association ) ! rocks f :i* !y h be5 d]iv$1 & di/+ui% !m f ! 'second>y' or 'transport$' clays :i* h be5 c>ri$ "s di/ance away f _! place ( orig94 ,residual clays may be =m$ by ! simple removal ( o!r mat]ials1 ! clay rema9+ beh9d1 z 9 ! decomposition ( "s argillace\s lime/ones1 9 :i* ! calc>e\s matt] has be5 remov$ by solution :il/ ! clay is unaffect$4 ,su* a clay is n a prim>y "o z x has probably be5 d]iv$ f "s di/ant s\rce &1 hav+ be5 deposit$ along ) ! lime/one ooze1 has =m$ an intimate mixture f :i* ! lime/one has1 at a lat] geological epo*1 be5 remov$ 9 ! mann] indicat$4 ,residual clays are seldom pure1 be+ (t5 ri* 9 iron comp\nds1 ?\gh ! :ite clays ( ,/af=d%ire & ,d]by%ire are highly refractory4 ,x is seldom necess>y to di/+ui% residual clays f o!r second>y or transport$ ones 7,*apt]s ,,ii & ,,iv74 ,prim>y clays1 on ! contr>y1 h be5 d]iv$ f rocks :i* h und]gone *emical decomposition1 "o ( ! products be+ clay4 ,! mo/ important prim>y clays are ! kaol9s1 :i* are d]iv$ f ! decomposition ( felsp>1 b o!r prim>y clays d]iv$ f o!r m9]als are kn[n1 ?\gh less frequ5tly m5tion$4 ,! kaol9s are prim>y clays#aj =m$ by ! decomposition ( felsp> & occur 9 _m p>ts ( ! _w4 ,9 ,great ,brita9 ! mo/ important are ! *9a clays f\nd 9 ,devon & ,cornwall1 :i* occur 9 association ) ! granite f :i* !y h be5 =m$4 ,! kaol9s 9 ,g]many are1 app>5tly1 ( simil> orig91 ?\gh "s are d]iv$ f porphyry & n f granite2 !y are ! *ief mat]ial us$ 9 ! manufacture ( ,dresd51 ,meiss51 ,b]l9 & o!r porcela9s4 ,! ,fr5* kaol9s f ,/ ,yrieux & ,lim\s9 are said by ,grang] 7#ag7 to be d]iv$ f gneiss amphibole4 ,! ,am]ican kaol9s h1 accord+ to ,ries 7#f71 be5 *iefly =m$ f ! wea!r+ ( pegmatite ve9s1 b ! orig9 ( "s important deposits 9 ,texas & ,indiana has n yet be5 fully expla9$4 ,footnote #aj3 ,"s kaol9s 9 c5tral ,europe appe> to h be5 transport$ & ( second>y orig94 ,illu/ration3 ,fig4 #ab4 ,*9a clay pit belong+ to ! ,nor? ,cornwall ,*9a ,clay ,co4 7,by c\rtesy ( ,w4 ,h4 ,pat*ell ,esq47 ,! correspond+ mat]ial us$ by ! ,*9ese = ! manufacture ( porcela9 be>s a "n :i* is really t ( ! place f :5ce x 0 orig9ally obta9$2 ! t]m ,kao-l+ indicates m]ely a high ridge4 ,accord+ to ,ri*?(5 7#ah7 ! rock f :i* ,*9ese porcela9 is made is n a true kaol91 b is alli$ to ! jades4 ,! t]m 'kaol9' is !re=e a misnom] :5 appli$ to :ite-burn+1 prim>y clays g5]ally1 b its use has become s firmly e/abli%$ z to r5d] x p]man5t4 ,kaol9s are seldom f\nd 9 a suffici5tly pure /ate to be us$ direct1 b mu/ be fre$ f l>ge am\nts ( undecompos$ rock1 qu>tz1 mica1 etc41 by a process ( wa%+ & s$im5tation4 ,:5 purifi$ 9 ?is mann]1 ! be/ qualities ( *9a clay yield1 on analysis1 alum9a1 silica & wat] 9 ! proportions indicat$ by ! =mula ,h#d;,al#b,si#b,o#i toge!r ) ab\t #e p] c5t4 ( mica & o!r impurities4 ,"s high class comm]cial kaol9s conta9 ov] #cj p] c5t4 ( mica & #aj p] c5t4 ( qu>tz4 ,! *ief con/itu5ts ( rocks :i* take "p 9 ! production ( kaol9s appe> to be ! felsp>s1 b ! natural processes by :i* ^! felsp>s are decompos$ are by no means p]fectly und]/ood4 ,"s kaol9s appe> to h be5 =m$ by wea!r+ & o!rs by suba]ial action4 ,?us ,coll9s 7#ai7 has /at$ v emphatically t ! kaol9ization ( ,corni% felsp> has be5 *iefly effect$ by fluor9e & o!r sub/ances ris+ f bel[ & n by c>bonic acid & wat] act+ f above4 ,ries 7#f7 & o!r ,am]ican obs]v]s are equally conv9c$ t c]ta9 kaol9s !y h exam9$ are ! result ( 'wea!r+4' ,g]man & ,fr5* inve/igators are divid$ 9 _! op9ions1 & ,fu*s has f\nd t ! ,passau 7,saxony7 kaol9 is d]iv$ f a special m9]al1 n unlike a soda-lime felsp> defici5t 9 silica1 to :i* he has giv5 ! "n 'porcela9 sp>4' ,! felsp>s =m a class ( m9]als ^: *ief *>act]i/ic is ! comb9ation ( an alkal9e or alkal9e-e>? base ) silica & alum9a4 ,or?oclase 7,k#b,o,al#b,o#cf,si,o#b7--! *ief potassium felsp>--is typical ( ! :ole class4 ,:5 treat$ ) wat] "u suitable conditions1 ! felsp> appe>s to become hydrolys$ & "s ( ! wat] ent]s into comb9ation1 ! pota% be+ remov$ by solution4 ,attempts to effect ?is decomposition artificially h prov$ abortive ?\gh sev]al inve/igators appe> to h effect$ x to a limit$ ext5t by electrolysis or by heat+ "u great pressure 7#c74 ,! effect on felsp>s ( wat]s conta9+ c>bon dioxide 9 solution has be5 /udi$ by ,=s*amm]1 ,vogt1 & o!rs1 & !y h conclud$ t kaol9ization may occur ) ?is ag5t ?\gh x does n appe> to be ! *ief cause 9 ! =mation ( ,corni% *9a clays4 ,illu/ration3 ,fig4 #ac4 ,or?oclase ,felsp>1 natural size4 7,f ,mi]s' ,m9]alogy by p]mission ( ,macmillan ,co47 ,! probable effect ( fluoric vap\rs has be5 /udi$ by ,coll9s 7#ai7 :o confirm$ von ,bu*'s obs]vation t fluorides 7p>ticul>ly lepidolite & t\rmal9e7 are con/antly associat$ ) *9a clay2 he f\nd by direct exp]im5t t felsp> is decompos$ by hydr(luoric acid at ! ord9>y temp]ature )\t ! o!r con/itu5ts ( ! granite 9 :i* x occurs be+ affect$4 ,?is !ory is confirm$ by ! great dep?s ( ! kaol9 deposits 9 ,cornwall & 9 ,zettlitz 7,bohemia7 :i* appe> to be too great to r5d] satisfactory any !ory ( simple wea!r+ ?\gh kaol9s 9 o!r localities1 especially 9 ,am]ica1 appe> to be l>gely ! result ( wea!r+4 ,accord+ to ,hickl+ 7#cf7 ! product ( ! action ( hydr(luoric acid 'has n ! remote/ resemblance to *9a clay4' ,kaol91 :5 c>efully fre$ f its impurities1 z f> z ?is is possible1 is peculi>ly resi/ant to ! action ( wat]4 ,?is resi/ance may be due to its highly complex con/itution1 z ! simpl] hydro-alum9o-silicates1 su* z collyrite1 %[ an acid reaction :5 gr\nd ) wat]4 ,rohl& 7#e71 !re=e1 sugge/s t kaol9ization is effect$ by wat] fir/ hydrolys+ ! felsp> & =m+ colloidal silica & sodium or potassium hydroxides :i* are remov$ :il/ ! complex alum9o-silicate rema9s 9 ! =m ( kaol94 ,hickl+ 7#cf71 on ! contr>y1 believes t ! action ( ! wea!r on felsp> produces second>y muscovite--a =m ( mica--& t ?is is1 lat]1 conv]t$ into kaol9ite or *9a clay 7fig4 #ag1 p4 #aje74 ,! v>i\s !ories :i* h be5 prop\nd$ may be summ>iz$ into ?ree ma9 classes1 & :il/ x is probable t any "o ( !m1 or any "o comb9ation1 may be true = a p>ticul> kaol91 yet ! :ole process ( kaol9ization is s complex & ! conditions "u :i* x has occurr$ appe> to be s div]se t x is d\btful if any simple !ory c be devis$ :i* w satisfactorily meet all cases4 7a7 ,! decomposition ( ! granite1 & p>ticul>ly ( ! felsp> )9 x1 may be ascrib$ to purely *emical reactions 9 :i* ! *ief ag5ts are wat] & c>bon dioxide4 7b7 ,o!r sub/ances--possibly ( an organic nature & d]iv$ f ! soil--may h play$ an important "p4 7c7 ,wet /eam & hot solutions ( fluor9e1 boron or sulphur comp\nds may h effect$ ! decomposition4 ,! rec5t progress made 9 ! application ( ! laws ( physical *emi/ry to geological problems is cont9ually ?r[+ fre% light on ?is int]e/+ subject4 ,?us1 /udies ( ! dissociation pressures & transition po9ts betwe5 ! anhydr\s & ! hydr\s /ates ( v>i\s sub/ances & ! effect ( wat] z a p[]ful ag5t ( decomposition 7hydrolysis7 h %[n t hydration is a *>act]i/ic result ( decompositions occurr+ 9 ! upp] portions ( ! e>?'s cru/ & n 9 ! l[] ones1 & t x is usually *eck$1 or ev5 rev]s$1 :5 ! sub/ance is "u great pressure4 ,at great dep?s kaol9s & o!r complex hydr\s silicates give place to anhydr\s ones su* z muscovite1 &alusite & /aurolite4 ,!re is1 !re=e1 good reason to believe t ! kaol9ization ( ,corni% felsp> has occurr$ at only mod]ate dep?s f ! surface & t x has be5 *iefly produc$ by ! action ( wat] conta9+ acid gases 9 solution4 ,! acid 9 ! wat] may h be5 absorb$ f ! atmosph]e1 or x may be due to vap\rs ris+ f bel[ ?r\gh ! felspa?ic mat]ial4 ,9 ,great ,brita91 *9a clay occurs 9 ! =m ( p[d]y p>ticles app>5tly amorph\s1 b conta9+ "s cry/als1 scatt]$ ?r\gh a mass ( h>d] rock1 ! :ole be+ kn[n z *9a clay rock or 'c>clazite4' ,! s(t] portions ( ?is *9a clay rock are kn[n z 'gr[an' & ! *9a clay 9 x repres5ts only a small proportion ( ! :ole mat]ial4 ,! f9] p>ticles ( clay & o!r mat]ials are remov$ by treatm5t ) wat]1 :]eby "o-?ird to "o-eigh? ( ! mat]ial is sep>at$4 ,?is small proportion is !n subject$ to fur!r wa%+ & s$im5tation 9 ord] to obta9 ! *9a clay 9 a /ate ( comm]cial purity4 ,x w ?us be und]/ood t ! ,corni% *9a clays are n 'deposits' 9 ! usual acceptation ( t t]m1 ! s(t gr[an f :i* !y are obta9$ be+ almo/ inv>iably ! result ( decomposition 9 situ ( "s species ( felsp> 9 dis9tegrat$ granite4 ,! comm]cial kaol9s ( ,france1 ,g]many1 ,am]ica & ,*9a v closely resemble ! ,corni% *9a clays 9 composition1 b :5 us$ 9 ! manufacture ( porcela9 !y create diff]5ces 9 ! f9i%$ mat]ial :i* are cle>ly noticeable1 ?\gh microscopical exam9ation & *emical analysis1 at pres5t1 fail to di/+ui% betwe5 !m 9 ! raw /ate on acc\nt ( _! great resi/ance to ord9>y *emical & physical =ces4 ,9 addition to ! break+ up ( felspa?ic rocks ) ! =mation ( *9a clay or kaol9 7kaol9ization71 o!r decompositions :i* occur may result 9 ! =mation ( clays1 & an exam9ation ( a consid]able numb] ( clays by ,j4 ,m4 van ,bemmel5 7#bf7 has l$ him to suppose t sev]al diff]5t clay-=m+ =ces h be5 at "w 9 ! production ( clays4 ,he classifies ^! "u f\r heads3 7#a7 ,kaol9ization1 or ! decomposition ( felspa?ic & simil> rocks by ! action ( telluric wat] conta9+ active gases 9 solution4 7#b7 ,ord9>y wea!r+ 9 :i* ! action is l>gely me*anical1 b is accompani$ by "s hydrolysis ow+ to ! impurities conta9$ 9 ! wat] :i* is an ess5tial factor4 7#c7 ,lat]itic action--or simple decomposition by heat--:i* occurs *iefly "u tropical conditions1 b may also occur 9 temp]ate climates1 & has = its ma9 product a mixture ( free silica & alum9a1 ! latt] be+ 9 ! =m ( 7amorph\s7 'lat]ite4' ,x may n improbably be a result ( ! decomposition ( ! clay molecule simil> to t :i* occurs :5 *9a clay is heat$1 z !re is no temp]ature bel[ :i* x c be said t *9a clay does n decompose into free silica & alum9a 7#bi74 7#d7 ,second>y reactions 9 :i* ! products ( "o ( ! reactions previ\sly describ$ may und]go fur!r *anges1 z ! conv]sion ( amorph\s clayite into cry/all9e kaol9ite1 or amorph\s lat]ite into cry/all9e hydr>gillite4 ,wea!r+4 ,! action ( ! =ces conv5i5tly class$ "u ! t]m wea!r+ are ( two ma9 k9ds3 7a7 ,! me*anical gr9d+ ( s&/one1 qu>tzite1 lime/one1 & o!r rocks1 causes an addition ( adv5titi\s mat]ial to clay1 ! proportions be+ sometimes s l>ge z to r5d] x necess>y to t]m ! mat]ial an argillace\s s&1 r ?an a s&y clay4 ,"s ( ^! gra9s ( m9]al matt] are s m9ute & s resi/ant to ! ord9>y *emical reag5ts z to make x extremely difficult to di/+ui% !m f clay4 7b7 ,! *emical decomposition due to ! action ( v dilute solutions4 ,by ?is means simple silicates are decompos$ ) ! =mation ( colloidal silica :i* may ei!r rema9 9 solution or may be deposit$ 9 a coagulat$ =m4 ,at ! same "t1 "s alum9o-silicates w be simil>ly decompos$ into colloidal alum9o-silicic acids or clays4 ,! ultimate results ( ! action ( ord9>y wea!r+ on silicate rocks are1 !re=e1 s&s & clays1 ! latt] be+ 9 "s ways q di/9ct 9 _! orig9 & physical prop]ties f ! *9a clays4 ,accord+ to ,j4 ,m4 van ,bemmel5 7#bf7 su* clays also conta9 an alum9o-silicate soluble 9 boil+ hydro*loric acid foll[$ by cau/ic soda1 :]eas pure *9a clays are unaffect$ by ?is treatm5t4 ,! v>iety ( silicates & o!r m9]als :i*--9 a p>tially decompos$ condition--g to =m 'clays' is s great t ! complete sep>ation ( ! smalle/ p>ticles ( !m f ^? ( ! true clay pres5t has nev] be5 accompli%$ & our k ( ! m9]alogical con/itution ( _m ( ! be/ kn[n clays is f> f complete4 ,x is highly probable t ! action ( wat] does n cease ) ! =mation ( clay1 b t x sl[ly effects an increase 9 ! pla/icity ( ! clay4 ,!re ?us appe> to be at lea/ ?ree k9ds ( prim>y clay1 viz43 ,kaol9ic or *9a clays :i* are *iefly d]iv$ f felsp> & c be isolat$ 9 a relatively pure /ate4 ,!y are highly refractory1 b only slightly pla/ic4 ,epig5ic or colloidal clays d]iv$ f kaol9ic clays1 z a second>y product1 or directly f felsp>1 mica1 augite & o!r alum9o-silicates by 'wea!r+4' ,!y are usually less refractory & mu* m pla/ic ?an ! *9a clays & conta9 a l>ge p]c5tage ( impurities--sometimes 9 ! =m ( free silica 7s&7 or ( metallic oxides1 c>bonates1 sulphides1 sulphates1 silicates1 or o!r comp\nds4 ,_m s-call$ second>y clays su* z pipe clays1 ball clays & fireclays may be ( ?is type1 ?\gh _! orig9 is difficult to trace ow+ to _! subsequ5t transportation & deposition4 ,lat]itic or highly alum9\s clays1 ( a highly refractory "*1 b l[ pla/icity4 ,!y are usually some:at ri* 9 iron oxide :i* mat]ially affects _! pla/icity4 ,unlike ! *9a clays1 pure lat]itic clays are completely decompos$ by hydro*loric acid4 ,bauxite & "s ( ! highly alum9\s clays ( ! ,coal ,measures appe> to be ( ?is type4 ,un=tunately ^! diff]5t types ( clay are extremely difficult to di/+ui% & 9 _m in/ances !y h become mix$ ) ea* o!r & ) o!r mat]ials dur+ ! actions to be describ$ 9 ! next *apt]1 t x is (t5 almo/ impossible to decide :e!r ! true clay 9 a giv5 specim5 possess$ its *>act]i/ics ab initio or :e!r x has ga9$ !m s9ce ! "t :5 x ceas$ to be a prim>y clay4 ,second>y clays are ^? :i* h be5 produc$ by ! action ( ! wea!r & o!r natural =ces on prim>y clays1 ! *anges effect$ be+ ( a physical r ?an a *emical nature 7see ,*apt] ,,iv74 ,! ess5tial con/itu5t ( second>y clays has n be5 positively id5tifi$4 ,9 s f> z x has be5 isolat$ x diff]s f ! true clay 9 ! prim>y clays 9 sev]al important respects1 & until its nature has be5 m fully inve/igat$ great caution mu/ be ex]cis$ 9 assign+ a def9ite "n to x4 ,= _m purposes ! t]m pel9ite 7p4 #adi7 is conv5i5t1 be+ analog\s to ! correspond+ "o us$ = mat]ial 9 *9a clays 7clayite1 p4 #ajg74 ,^! t]ms are purely provisional & mu/ be disc>d$ :5 ! true m9]alogical id5tities ( ! sub/ances !y repres5t h be5 e/abli%$4 ,,*apt] ,,iv ,,! ,,modes ,,( ,,accumulation ,,( ,,clays ,f :atev] s\rces clays may h be5 orig9ally d]iv$1 ! mann] 9 :i* !y h be5 accumulat$ 9 _! pres5t positions is a factor ( great importance bo? 9 reg>d to _! *emical & physical *>act]s & _! suitability = v>i\s purposes4 ,z expla9$ 9 ,*apt] ,,iii1 ! *9a clays or kaol9s may usually be reg>d$ z prim>y clays d]iv$ f granitic or o!r felspa?ic or felsitic rocks by *emical decomposition4 ,su* clays are f\nd ne> to _! place ( orig91 are usually obta9able 9 a comp>atively pure /ate & are g5]ally defici5t 9 pla/icity4 ,!y may occur 9 b$s ( small or great dep?1 b ^! are n 'accumulations' 9 ! ord9>y mean+ ( t t]m4 ,residual clays 7p4 #gj7 also =m a di/9ct class1 z unlike ! majority ( argillace\s mat]ials !y are left beh9d :5 o!r sub/ances are remov$1 usually by "s process ( solution4 ,9 _m cases1 h[ev]1 ! residual clays are really second>y 9 "*1 hav+ be5 transport$ f _! place ( orig91 toge!r ) lime/one or o!r m9]als1 ! mixture deposit$ & subject$ to pressure & possibly to heat1 :]eby a rock-l mass is =m$4 ,?is mass has !n be5 subject$ to ! solv5t action ( wat] conta9+ c>bon dioxide or o!r sub/ances :i* dissolve out ! bulk ( ! associat$ m9]als & leave ! residual clay beh9d4 ,! *ief ag5ts 9 ! transport & accumulation ( clays are ! air1 9 ! =m ( w9d2 wat]1 9 ! =m ( ra91 /reams1 riv]s1 floods1 lakes & seas1 or 9 ! =m ( ice & sn[ z 9 glaci]s & avalan*es2 e>?-movem5ts su* z ! *anges wr\ght by volcanoes1 e>?quakes & ! less cle>ly m>k$ ris+ & fall+ ( v>i\s portions ( ! e>?'s cru/ :i* result 9 fold$1 twi/$1 %e>$1 crack$1 incl9$1 lam9at$ & o!r /rata4 ,^! ag5ts h fir/ mov$ ! clay f its orig9al site & h lat] deposit$ x ) o!r mat]ials 9 ! =m ( /rata ( widely v>y+ area & ?ickness1 "s 'clay' b$s be+ sev]al hundr$ feet 9 dep? & occupy+ _m squ>e miles 9 area1 :il/ o!rs are 9 ! =m ( ?9 've9s' only a few in*es ?ick or 9 'pockets' ( small area & dep?4 ,^! deposits h 9 _m places be5 displac$ by subsequ5t e>?-movem5ts & h be5 ov]la9 by o!r deposits s z to r5d] !m q inaccessible4 ,o!rs h be5 cov]$ by deposits sev]al miles ?ick2 b ! great] "p ( ! cov]+ has s9ce be5 remov$ by glacial or o!r =ces1 s t clays ( practically all geological ages may be f\nd )9 ! relatively small area ( ,great ,brita94 ,! ,transportation ( ,clays4 ,by ! action ( w9d or ra91 or ( ra9 foll[+ fro/1 ! f9] ( p>ticles clay are remov$ f _! prim>y site & z ! ra9 drops collect into /reamlets1 ^! unite to =m /reams & riv]s & ! clay ) its associat$ m9]als is c>ri$ along by ! wat]4 ,z x travels ov] o!r rocks or ?r\gh valleys compos$ ( s&/one1 lime/one & o!r mat]ials1 "s ( ^! sub/ances are dislodg$1 brok5 into fragm5ts ( v>i\s sizes & ) ! clay are c>ri$ /ill fur!r4 ,9 _! j\rney ^! mat]ials rub aga9/ ea* o!r & aga9/ ! banks & b$ ( ! /ream1 !reby und]go+ a prolong$ process ( gr9d+ :]eby ! s(t] rocks are r$uc$ to v f9e s& & silt :i* becomes1 9 "t1 v intimately mix$ ) ! clay4 ,if ! velocity ( ! /ream 7 suffici5tly great1 ! mix$ mat]ials--d]iv$ f z _m s\rces z !re are rocks ( ! di/ricts ?r\gh :i* !y h pass$--w\ld be dis*>g$ into a lake or into ! sea4 ,"h ! velocity ( ! wat] w\ld be s greatly r$uc$ t ! mat]ials w\ld gradually settle1 ! l>ge/ & heavie/ fragm5ts be+ fir/ deposit$ & ! f9] ones at a great] di/ance4 ,) mo/ /reams & riv]s1 h[ev]1 ! velocity ( ! wat] is v v>iable1 & a c]ta9 am\nt ( deposition !re=e occurs along ! c\rse1 ! heavi] p>ticles only travell+ a %ort di/ance1 :il/ ! f9] ones are readily transport$4 ,if ! velocity ( ! /ream increases1 ^! f9] p>ticles 7:i* include ! clay7 may become mix$ ) o!r p>ticles ( v>i\s sizes & ! mat]ials ?us und]go a s]ies ( mix+s & p>tial sort+s until !y are dis*>g$ at ! riv] m\? or are left along its sides by a gradual s9k+ ( ! wat] level4 ,! clay w be c>ri$ ! :ole c\rse ( ! riv]1 unless x is deposit$ at "s place :]e ! velocity ( ! wat] is r$uc$ suffici5tly to p]mit x to settle4 ,if floods arise1 ! area affect$ by ! wat] w be increas$4 ,! alluvial clays h1 app>5tly1 be5 =m$ by ov]fl[+ /reams & riv]s1 ! mat]ial 9 susp5sion 9 ! wat] be+ deposit$ z ! rate ( fl[ dim9i%$4 ,su* alluvial deposits conta9 a v>iety ( m9]als--usually 9 a v f9ely divid$ /ate--clay1 lime/one-du/ or *alk1 & s& be+ ^? mo/ usually f\nd4 ,riv]-deposit$ clays1 i4e41 ^? :i* h accumulat$ along ! banks1 are *>act]iz$ by _! irregul>ity 9 ?ickness1 _! v>iable composition & ! ext5t to :i* v>i\s mat]ials are mix$ toge!r4 ,?is r5d]s !m difficult to "w & greatly increases ! risks ( manufacture z ! :ole "* ( a fluviatile clay may *ange completely 9 ! c\rse ( a few y>ds4 ,accord+ to ! di/ricts trav]s$ by ! wat]1 ! ext5t to :i* ! mat]ials h be5 deposit$ & re-transport$ & ! fre% mat]ials introduc$ by e>?-movem5ts1 riv]-deposit$ clays may be 7a7 pla/ic & suffici5tly pure to be classifi$ z 'clays1' 7b7 m>ls or clays conta9+ lime/one-du/ or *alk ?or\ghly mix$ ) ! clay1 & 7c7 loams or clays conta9+ s mu* s& t !y may be di/+ui%$ by ! t\* f ! clays 9 class 7a74 ,int]m$iate to ^! well-def9$ classes !re are num]\s mixtures be>+ comp\nd names su* z s&y loams1 s&y m>ls1 argillace\s lime/one1 calc>e\s s&s1 & calc>e\s ar5ace\s clays1 to :i* no def9ite *>act]i/ics c be assign$4 ,to "s ext5t a transportation ( clays & associat$ mat]ials occurs 9 lakes1 b ! *ief processes !re are ( ! nature ( s$im5tation accompani$ by "s am\nt ( sep>ation4 ,on ! %ores ( lakes1 & to a mu* l>g] ext5t on ! sea coa/s1 ext5sive erosion foll[$ by transportation occurs cont9u\sly1 enorm\s quantities ( l& be+ annually remov$ & deposit$ 9 "s portion ( ! ocean b$4 ,! erosion ( cliffs & ! correspond+ =mation ( s& & pebbles are too well kn[n to ne$ fur!r description4 ,x %\ld1 h[ev]1 be notic$ t ! clay p>ticles1 be+ mu* f9]1 are c>ri$ s f> away f ! %ore t only pebbles & s& rema9 to =m ! bea*es1 ! f9] p>ticles =m+ 'ocean ooze4' ,! action ( ! sea 9 ! transport ( rock-mat]ials is m int5se ?an t ( riv]s1 ! coa/s be+ worn away by repeat$ bl[s f ! waves & ! pebbles & s& gra9s ! latt] conta94 ,! ocean curr5ts c>ry ! mat]ials dislodg$ by ! waves & transport !m1 sometimes to enorm\s di/ances1 usually all[+ a consid]able am\nt ( sep>ation to take place dur+ ! transit4 ,9 ?is way !y act 9 a simil> mann] to riv]s & /reams4 ,glaci]s may be reg>d$ z riv]s ( ice :i* erode _! banks & b$ 9 a mann] simil> to1 b m rapidly ?an1 /reams ( wat]4 ,ow+ to _! mu* great] viscosity1 glaci]s are able to c>ry l>ge b\ld]s z well z gravel1 s& & clay1 s t ! mat]ials transport$ by !m are f> m complex 9 composition & size ?an are ^? c>ri$ by fl[+ wat]4 ,illu/ration3 ,fig4 #ad4 ,illu/rat+ ! successive deposition ( diff]5t /rata4 ,sep>ation & ,s$im5tation4 ,! clay & o!r p>ticles hav+ be5 plac$ 9 susp5sion 9 wat] by "o or m ( ! natural =ces already m5tion$1 !y soon und]go a process ( sort+ or sep>ation1 previ\s to _! deposition4 ,! p[] ( wat] = c>ry+ matt] 9 susp5sion dep5ds l>gely on its velocity1 & :5 ?is is r$uc$1 z :5 a riv] dis*>ges into a lake or sea1 ! l>g] & d5s] p>ticles at once comm5ce to settle1 ! small] ones rema9+ long] 9 susp5sion1 ?\gh if ! velocity ( ! wat] is r$uc$ suffici5tly all ! p>ticles w be deposit$4 ,h5ce1 ! deposits 9 lakes 7lacu/r9e7 & at ! m\?s ( riv]s 7e/u>9e7 increase m or less regul>ly 9 f95ess accord+ to _! di/ance f ! po9t at :i* ! wat] ent]s1 ! gravel & /ones be+ deposit$ fir/1 !n ! co>se s&1 next ! f9] s& & f9ally ! silt & clay 7fig4 #ad74 ,if cross-curr5ts are pres5t1 ! deposits w1 naturally1 be made m irregul>1 & 9 "s cases v>iations 9 ! fl[ ( ! transport+ wat] may cause ! co>s] p>ticles to be c>ri$ fur!r ?an usual s t !y may cov] "s ( ! f9] deposits previ\sly =m$2 b z ! clay & silt p>ticles are s mu* f9] ?an s& & gravel !y usually travel s f> be=e settl+ t _! deposits are v uni=m if ! area ov] :i* !y are spread is suffici5tly l>ge4 ,lake-deposit$ clays are = ?is reason m uni=m ?an e/u>9e b$s1 :il/ b$s deposit$ at consid]able dep?s 9 ! sea & at a great di/ance f l& are /ill m uni=m4 ,a lacu/r9e clay is usually m p]si/5t & uni=m ?an fluviatile b$s ?\gh sometimes difficult to di/+ui% f ! latt]4 ,"s ( ! mo/ valuable clay deposits are ( lacu/r9e =mation2 _! comp>ative purity & great uni=mity enabl+ w>e ( excell5t col\r & texture to be produc$ )\t mu* difficulty4 ,?us ! ,read+ mottl$ clays ( ! ,hamp%ire bas91 on ! outskirts ( ! ,london bas9 & 9 ,nor!rn ,france are well kn[n = ! admirable r$ bricks1 tiles & t]ra-cotta produc$ f !m4 ,/ill pur] clays deposit$ at ,bovey ,hea?field 9 ,devon%ire are also ( lacu/r9e orig91 ?\gh !y diff] 9 _m respects f ! ord9>y lake-deposit$ clays & are ( unusual ?ickness = deposits =m$ 9 ?is mann]4 ,illu/ration3 ,fig4 #ae4 ,lacu/r9e clay at ,skipsea4 7,by c\rtesy ( ,t4 ,%epp>d ,esq47 ,! great] purity ( lacu/r9e clays1 z comp>$ ) fluviatile ones1 is attribut$ to ! mu* l>g] area ov] :i* ! deposit is spread1--enabl+ v>iations 9 ! deposits to be mu* less noticeable ?an :5 a small] area is cov]$--& to ! v small velocity ( ! wat] 9 lakes1 :]eby all ! co>s] p>ticles are deposit$ a consid]able di/ance away f ! clays & silts4 ,ries 7#f7 has po9t$ out t _m 7,am]ican7 lake-clays are ( glacial orig91 hav+ be5 laid 9 bas9s or holl[s along ! m>g9 ( ! ice-%eet or 9 valleys :i* h be5 damm$ by an accumulation ( drift across !m4 ,su* clay b$s are usually surface deposits ( v>iable ?ickness & frequ5tly impure4 ,l all lacu/r9e deposits !y %[ 7?\gh 9 a m m>k$ degree ?an 9 ! old] & l>g] lakes7 alt]nate lay]s ( s& & clay1 ?\gh ! =m] are usually too ?9 to be noticeable except = _! action 9 enabl+ ! deposit$ mat]ial to be easily split along ! l9es ( b$d+4 ,e/u>9e deposits p>take ( ! nature ( bo? fluviatile & m>9e b$s1 accord+ to _! position relative to ! riv] f :i* !y orig9ate4 ,!y are usually unc]ta9 9 "* & are (t5 irregul> 9 composition ow+ to ! v>iations 9 ! fl[ ( ! wat]4 ,! ,e/u>9e clays ( ,great ,brita9--) ! possible exception ( ! ,jurassic deposits 9 ,nor?ampton%ire & ,l9coln%ire--are ( m9or importance1 b 9 "s c\ntries !y =m a valuable s\rce ( clay4 ,illu/ration3 ,fig4 #af4 ,clay at ,no/el1 %[+ ,m>9e ,b&4 7,by c\rtesy ( ,t4 ,%epp>d ,esq47 ,m>9e clays are1 z _! "n implies1 ^? deposit$ f sea wat]4 ,!y are frequ5tly f\nd at a consid]able di/ance f ! %ores ( ! ocean 9 :i* !y 7 laid d[n1 & subsequ5t ris+s & fall+s ( ! surface ( ! e>? h s alt]$ ! areas occupi$ by sea wat]1 t a l>ge numb] ( m>9e deposits n[ =m dry l&4 ,?\gh usually ( enorm\s size & ( g5]ally p]si/5t "*1 m>9e clay deposits v>y consid]ably 9 ! composition ( ! mat]ial at diff]5t dep?s1 z well z 9 diff]5t areas4 ,?is is only to be expect$ f ! mann] ( _! deposition1 f ! v>i$ s\rces ( ! mat]ial & f ! num]\s riv]- & ocean-curr5ts tak+ "p 9 _! =mation4 ,= ?is reason x is g5]ally necess>y to mix toge!r portions ( ! deposit drawn f v>i\s dep?s 9 ord] to secure a great] uni=mity ?an w\ld be obta9$ if a l>g] area 7 to be work$ to a small] dep?4 ,! ,ox=d clay :i* ext5ds f ! c5tre ( ,engl& to ! c5tre ( ,france is a typical m>9e clay4 ,at ! bottom ( all oceans at ! pres5t day is a deposit1 ( unkn[n ?ickness1 ( r$ calc>e\s clay or ooze :i* is /eadily increas+ 9 am\nt & is !reby =m+ a fre% m>9e deposit1 ?\gh at pres5t its inaccessibility deprives x ( all economic value4 ,x is important n to ov]look ! enorm\s "p play$ by v>iations 9 ! level ( ! l& relative to t ( ! ocean 9 pa/ ages4 ,= in/ance1 !re is abundant evid5ce to %[ t practically ! :ole ( ,great ,brita9 has be5 repeat$ly subm]g$ to great dep?s & has be5 rais$ to heights f> great] ?an its pres5t av]age4 ,^! (t-repeat$ ris+s & settl+s h caus$ great *anges 9 ! nature ( ! deposit$ mat]ials s t 9 ! ,coal ,measures1 = example1 !re are deposits ( obvi\sly fre%-wat] orig9 s&wi*$ 9 betwe5 o!rs und\bt$ly m>9e4 ,x c readily be und]/ood1 z /at$ by ,arb] 7#bd71 t if1 at a giv5 p]iod1 ! dry l& dur+ ! =mation ( ! ,coal ,measures gradually subsid$1 x w\ld fir/ be cov]$ ) cle> wat]1 :il/ f ^? portions ( ! area :i* occupi$ ! high] gr\nd ! riv]s & /reams cont9u$ to p\r into _! e/u>y a l>ge am\nt ( fre%-wat] mat]ial4 ,lat]1 a /age w\ld be rea*$ :5 mud ( m>9e orig9 invad$ ! area & cov]$ ! previ\s deposits4 ,:51 aft] an indef9itely long p]iod1 ! gr\nd aga9 rose1 fre%-wat] deposits might aga9 =m1 & ?is alt]nation ( m>9e & fluviatile deposits appe>s to h be5 repeat$ ) great frequ5cy dur+ ! ,c>bonif]\s p]iod4 ,9 ! ,l[] ,coal ,measures ( ,york%ire & ,lanca%ire1 ,/opes & ,watson 7#bc7 h %[n t ! %ales =m+ ! ro( ( ! ,upp] ,foot ,coal 7 d]iv$ f drift$ s$im5ts ( m>9e orig94 ,precipitat$ ,clays4 ,if ! pla/icity ( "s clays is really due to ! colloidal nature ( _! p>ticles1 x is obvi\s t !y mu/ h be5 =m$ by a process ( coagulation or precipitation at a di/ance f ! site ( ! m9]als f :i* !y h be5 d]iv$4 ,accord+ to ! 'colloid !ory1' felsp> & o!r alum9o-silicates are decompos$ by 'wea!r+1' ! *ief effect ( :i* is ! =mation 7by hydrolysis7 ( a colloidal solution ( 'clay4' ,?is app>5tly cle> solution fl[s along 9 ! =m ( a small /reamlet1 jo9s o!r /reamlets & cont9ues its j\rney4 ,s long z x is q neutral or conta9s free alkali ! solution w rema9 practically cle>1 b z soon z acids ent] ! /ream1 or are =m$ 9 x by ! decomposition ( organic matt]1 a coagulation ( ! colloidal matt] w comm5ce & ! am\nt ( 'clay' ?us ?r[n out ( solution w dep5d on ! am\nt ( su* free acid4 ,if ! coagulation or precipitation occurs 9 /ill wat]1 ! 'clay' w be deposit$ almo/ imm$iately1 o!rwise x w be c>ri$ =w>d until x rea*es a place :]e x c be deposit$ 9 ! mann] already describ$4 ,su* precipitat$ clays ne$ n necess>ily be pure1 z o!r sub/ances may be pres5t 9 colloidal =m & may be coagulat$ at ! same "t z ! clay4 ,9 addition to ^!1 ! admixture ( s& & o!r m9]als pres5t 9 susp5sion 9 ! solution may become mix$ ) ! p>ticles dur+ coagulation & be deposit$ ) !m4 ,clays =m$ 9 ?is mann] are extremely difficult to id5tify on acc\nt ( ! highly complex nature ( ! reactions occurr+ 9 _! vic9ity bo? dur+ & subsequ5t to _! =mation4 ,re-,deposit$ ,clays4 ,al?\gh _m clays & o!r mat]ials h be5 transport$ & accumulat$ 9 ! mann] describ$1 ! majority ( ^? n[ available h be5 subject$ to repeat$ transportation & deposition1 ow+ to ! frequ5t & enorm\s *anges 9 ! relative levels ( l& & wat] dur+ ! v>i\s geological epo*s4 ,s f> z c be asc]ta9$1 x is dur+ ^! *anges ( position & ! recurr5t exposure to air & to wat] conta9+ v>i\s sub/ances 9 solution1 toge!r ) ! almo/ incessant gr9d+ :i* took place dur+ ! transportation & deposition1 t mo/ second>y clays became pla/ic4 ,if ?is is ! case1 x expla9s ! impossibility ( increas+ ! pla/icity ( clay by artificial means1 at any rate on a l>ge scale4 ,! simple/ ( ! ag5ts ( re-deposition are ra9-/orms & floods :i*1 =m+ sudd5ly1 may cause ! wat] ( a /ream or riv] to fl[ ) unwont$ velocity & s c>ry away previ\sly =m$ deposits ( v>i\s k9ds4 ,clays transport$ 9 ?is way are t]m$ by ,ries 7#f7 colluvial clays1 ! t]m 'diluvial' is g5]ally employ$ 9 ?is c\ntry4 ,if ^! are d]iv$ f a prim>y clay :i* has n travell$ f> s9ce x left ! orig9al granite f :i* x 0 =m$1 !y w usually be :ite-burn+ & ( only slight pla/icity1 b if ! flood affects mat]ials :i* h already be5 re-deposit$ sev]al times1 ! colluvial clays may be ( almo/ any imag9able composition4 ,floods ( a diff]5t "*--due to ! subsid5ce ( ! l& s t x is p>tially cov]$ ) lake- or sea-wat]1 :i* beats on its %ores & erodes x 9 ! mann] already describ$--are also important factors 9 ! transportation ( clays4 ,s f> z clays are conc]n$1 ! action ( ! sea is bo? erosive & depository1 ?\gh ! s$im5tation 9 x be+ t ( ! pelagic ooze at great dep?s ! clayey mat]ial is q inaccessible4 ,"u c]ta9 conditions1 h[ev]1 ! sea may erode l& 9 "o area & may return ! transport$ mat]ial to ! l& 9 ano!r area4 ,! diluvial clay-silt kn[n z w>p 9 ! valley ( ! ,humb] is ( ?is "*4 ,q ap>t f ! action ( wat]1 h[ev]1 mu* d5udation1 transportation & re-deposition ( clays & associat$ mat]ials has be5 due to ! action ( ice 9 ! =m ( glaci]s1 ?\gh ^! d n appe> to h _h mu* effect 9 increas+ ! pla/icity ( ! clays conc]n$4 ,glacially deposit$ clays are *>act]is$ by _! het]og5e\s composition1 "s ( !m conta9+ f> m s& ?an true clay1 :il/ yet reta9+ a suffici5t am\nt ( pla/icity to enable !m to be us$ = r5d]+ embankm5ts imp]vi\s & = ! manufacture ( common bricks1 &1 occasionally1 ( co>se pott]y2 o!rs conta9 s mu* s& z to be useless = ^! purposes4 ,mo/ glacial deposits conta9 a consid]able proportion ( /ones & gravel :i* mu/ be remov$ be=e ! clay c be us$4 ,! l>ge proportion ( adv5titi\s matt] is due 9 great "p to ! mu* great] erosive =ce & c>ry+ p[] ( ice z comp>$ ) wat]1 result+ 9 mu* l>g] pieces ( mat]ial be+ c>ri$1 & z ! :ole ( ! ice-borne mat]ial is deposit$ almo/ simultane\sly :5 ! glaci] melts1 only a v small am\nt ( sep>ation ( ! mat]ial into diff]5t grades takes place4 ,! comp>ative fre$om f co>se s& ( "s glacial clays %[s t "s sort+ does occur1 b x is v limit$ 9 ext5t z comp>$ ) t wr\ght 9 mat]ials :i* h be5 exclusively transport$ by wat]4 ,= ! manufacture ( bricks1 tiles & co>se pott]y 9 ,york%ire1 ,lanca%ire & "s ( ! m nor!rn c\nties ( ,great ,brita91 glacially deposit$ clays are ( great importance 9 spite ( _! irregul> composition4 ,!y are frequ5tly t]m$ 'b\ld] clays' or 'drift clays' 7p4 #fe71 b 9 us+ ^! or any o!r t]ms = clays transport$ by glacial action x is important t !y %\ld n be und]/ood to ref] to ! :ole ( ! deposit$ matt]4 ,l>ge 'pockets' ( co>se s& & gravel frequ5tly occur 9 deposits ( ?is "* & ve9s ( ! same mat]ials are by no means uncommon4 ,! cu/om ( "s geologi/s ( ref]r+ to ! :ole ( a glacial deposit z 'b\ld] clay' has1 9 a numb] ( cases1 l$ to s]i\s f9ancial loss to claywork]s :o h errone\sly assum$ t1 because "s 'b\ld] clays' are us$ = brick & tile manufacture1 all deposits be>+ a simil> title w\ld be equally suitable4 ,?is difficulty w\ld l>gely be avoid$ if1 z is n[ increas+ly ! case1 ! t]m 'drift' or 'glacial deposit' 7 us$ = ! deposits z a :ole1 ! t]m 'b\ld] clay' be+ re/rict$ to ! pla/ic portions & n includ+ pockets ( s&1 gravel & o!r non-pla/ic mat]ials4 ,b\ld] clays--us+ ?is t]m 9 ! limit$ s5se j m5tion$--consi/ ( v>iable quantities ( s& & clay1 /ones & gravel be+ g5]ally associat$ ) !m4 ,! /ones may usually be remov$ by c>eful pick+1 & ! gravel by means ( a 'clay clean]' :i* =ces ! pla/ic mat]ial ?r\gh ap]tures too small to all[ ! gravel to pass4 ,! pla/ic mat]ial s sep>at$ is f> f be+ a pure clay & may conta9 almo/ half its weight ( s&1 ! great] "p ( :i* is readily sep>at$ by wa%+ ! mat]ial4 ,b\ld] clays1 :5 fre$ f /ones & gravel1 are suffici5tly pla/ic to meet ! ne$s ( mo/ us]s1 )\t be+ s highly pla/ic & contractile z to necessitate admixture ) s& or simil> mat]ial4 ,"s b\ld] clays conta9 lime/one 9 ! =m ( gravel or z a co>se p[d] produc$ by ! cru%+ ( l>g] fragm5ts4 ,^! are less suitable = manufactur+ purposes z ! lime produc$ :5 ! articles are burn$ 9 ! kilns is liable to swell & to dis9tegrate !m on exposure4 ,ow+ to _! orig9 & ! nature ( ! impurities !y conta91 b\ld] clays are nev] pure & :5 burn$ are irregul> 9 col\r & some:at fusible unless subject$ to "s process ( purification4 ,,*apt] ,v ,,"s ,,clays ,,( ,,comm]cial ,,importance ,al?\gh clays occur 9 deposits ( almo/ all geological p]iods1 _m ( !m are ( little or no comm]cial value4 ,?is may be due to _! situation or to _! composition & o!r *>act]i/ics4 ,?us1 a ,coal ,measure clay is ord9>ily q inaccessible1 & to s9k a %aft specially to obta9 x may be an unpr(itable und]tak+2 if1 h[ev]1 a %aft is sunk = coal ! clays 9 ! neighb\rhood ( ! coal seams are r5d]$ accessible &1 usually1 a c]ta9 am\nt ( su* clays is br\ght to ! surface 9 ord] to remove x out ( ! way ( ! coal m9]s4 ,aga91 a clay deposit may be s f> remov$ f human habitations z to make x practically valueless1 b if1 = any reason1 ! population ( ! di/rict 9 :i* ! clay is situat$ gr[s suffici5tly1 ! clay may become ( consid]able value4 ,x n infrequ5tly happ5s1 !re=e1 t ! comm]cial importance ( a clay deposit is "o :i* fluctuates consid]ably1 yet1 9 spite ( ?is fact1 !re are c]ta9 k9ds ( clay :i* are ne>ly always ( "s comm]cial value4 ,! mo/ important ( ^! are ! kaol9s 7*9a clays71 ! pott]y & /onew>e clays1 ! refractory clays 7fireclays71 ! brick & t]ra-cotta clays & %ales1 & ! clays us$ 9 ! manufacture ( ,portl& cem5t4 ,! orig9 & mann] 9 :i* ^! clays h be5 accumulat$ h be5 describ$ 9 ! previ\s *apt]s2 x n[ rema9s to indicate _! *>act]i/ics f ! po9t ( view ( _! comm]cial value4 ,comm]cial *9a clays & kaol9s 9 ! ,unit$ ,k+dom are n simple natural products b1 9 ! /ate 9 :i* !y are sold comm]cially1 h all be5 subject$ to a c>eful treatm5t ) wat]1 foll[$ by a process ( s$im5tation :]eby ! bulk ( ! impurities h be5 remov$4 ,accord+ to ! ext5t to :i* ?is treatm5t has be5 c>ri$ out1 !y w conta9 #aj p] c5t4 or m mica & qu>tz1 ) little or no t\rmal9e1 felsp> & undecompos$ granite4 ,9 "s p>ts ( ,europe & ,am]ica1 kaol9s are f\nd 9 a /ate ( suffici5t purity to ne$ no treatm5t ( ?is k9d unless !y are to be us$ = ! v highe/ class ( w>es4 ,illu/ration3 ,magnifi$ #bbj ,diamet]s ,magnifi$ #ibj ,diamet]s ,magnifi$ #bbj ,diamet]s ,magnifi$ #bbj ,diamet]s ,cry/als ( ,kaol9ite ,magnifi$ #ibj ,diamet]s ,cry/als ( ,second>y ,muscovite4 ,fig4 #ag4 ,kaol9ite & ,mica4 7,aft] ,g4 ,hickl+ 7#cf747 ,mica is usually ! *ief impurity z its p>ticles are s small & _! d5sity resembles t ( ! purifi$ *9a clay m closely ?an d ! o!r m9]als4 ,9 comm]ce ! t]m *9a clay is almo/ inv>iably us$ to d5ote ! wa%$ mat]ial obta9$ f ! '*9a clay rock1' b at ! pits ! ^w 'clay' is us$ indiscrim9ately = ! c>clazite 7p4 #gh7 & = ! mat]ial obta9$ f x4 ,z ! t]m 'kaol9' is us$ indiff]5tly abroad = ! crude 'deposit' & = ! purifi$ comm]cial article1 x %\ld be und]/ood t ! foll[+ in=mation relates solely to ! sub/ance z usually sold & n to ! crude mat]ial4 ,comm]cial *9a clay or kaol9 is a s(t :ite or fa9tly yell[i% sub/ance1 easily r$uc$ to an extremely f9e p[d]1 :i* :5 mix$ ) twice its weight ( wat] w pass completely ?r\gh a ,no4 #bjj sieve4 ,its specific gravity is #bfe1 b ! m9ut5ess & nature ( its smalle/ p>ticles & _! "* are su* t x w rema9 9 susp5sion 9 wat] = sev]al days2 x ?us appe>s to possess colloidal prop]ties1 at any rate s f> z ! small] p>ticles are conc]n$4 ,x is almo/ infusible1 b %[s signs ( s(t5+ at #ahhj ,c4 7,seg] ,cone #ci7 or at a some:at l[] temp]ature1 accord+ to ! proportion ( impurities pres5t4 ,:5 heat$ ) silica or ) v>i\s metallic oxides x fuses m readily ow+ to ! =mation ( silicates4 ,*9a clays & kaol9s are n appreciably affect$ by dilute acids1 b "s specim5s are p>tially decompos$ by boil+ conc5trat$ hydro*loric acid 7#bf7 & all are decompos$ by boil+ sulphuric acid1 ! alum9a be+ dissolv$ & ! silica lib]at$ 9 a =m easily soluble 9 solutions ( cau/ic soda or pota%4 ,?is has l$ to ! conclusion t "s kaol9s may h be5 produc$ by wea!r+1 z ! bulk ( true kaol9itic clays 7su* z ,corni% *9a clay7 is n affect$ by boil+ hydro*loric acid 7p4 #ha74 ,ow+ to ! exceptional m9ut5ess ( its p>ticles1 x is extremely difficult to asc]ta9 :e!r pure *9a clay or kaol9 is cry/all9e or amorph\s4 ,johnson & ,blake 7#ba7 f\nd t all ! specim5s !y exam9$ 'consi/$ l>gely ( hexagonal plates' & t 9 mo/ kaol9s '^! plates are abundant--evid5tly con/itut+ ! bulk ( ! sub/ance4' ,?is obs]vation is contr>y to ! exp]i5ce ( mo/ inve/igators1 ! majority ( :om h f\nd ! bulk ( ! mat]ial to be amorph\s & sponge-l1 b a small portion ( x to consi/ ( hexagonal or rhombic cry/als4 ,mellor 7#bb7 has propos$ ! "n clayite = ?is amorph\s mat]ial1 ! cry/all9e portion be+ t]m$ kaol9ite z sugge/$ by ,johnson & ,blake4 ,bo? kaol9ite 7cry/all9e7 & clayite 7amorph\s7 yield ! same results on analysis & correspond v closely to ! =mula ,h#d;,al#b,si#b,o#i or ,al#b,o#cb,si,o#bb;,h#b,o1 s t x is mo/ probable t !y are ! same sub/ance 9 diff]5t physical /ates4 ,accord+ to ,hickl+ 7#cf7 ! g5]al impression t ! p>ticles ( *9a clay are amorph\s is due to ! use ( microscopes ( insuffici5t p[]4 ,) an improv$ in/rum5t1 ,hickl+ claims to h id5tifi$ ! 'amorph\s' portion ( *9a clay ) cry/all9e kaol9ite1 ! clay p>ticles 7fig4 #ag7 be+ 9 ! =m ( irregul>1 curv$1 hexagonal prisms or 9 isolat$ plates4 ,! =m] %[ /rong transv]se cleavages4 ,! index ( refraction & t ( d\ble refraction agree ) ^? ( ,anglesea kaol9ite cry/als1 z does ! specific gravity4 ,9 spite ( _! great purity1 comm]cial *9a clays & kaol9s are almo/ devoid ( pla/icity1 nor c ?is prop]ty be greatly increas$ by any artificial treatm5t4 ,?is has l$ to ! conclusion t pla/icity is n an ess5tial *>act]i/ic ( ! clayite or kaol9ite molecules1 b is due to physical causes n %[n by any inve/igation ( ! *emical composition ( ! mat]ial4 ,9 addition to ! specially purifi$ kaol9s j describ$1 alkal9e kaol9s1 silice\s kaol9s & f]rug9\s kaol9s are obta9$ f less pure rocks & d n und]go s ?or\gh a treatm5t ) wat]4 ,"s ( ^! v>ieties are n improbably d]iv$ f transport$ kaol9s1 z !y occur 9 ,t]ti>y /rata1 & s be> "s resemblance to ! :ite fireclays on ! ,c>bonif]\s lime/one ( ,/af=d%ire1 ,d]by%ire & ,nor? ,wales1 ?\gh ! latt] are f> m pla/ic4 ,to be ( value1 a *9a clay or kaol9 mu/ be z :ite z possible & mu/ be free f m ?an an insignificant p]c5tage ( metallic oxides :i* w produce a col\r :5 ! clay is heat$ to bright r$ness4 ,if ! mat]ial is to be us$ 9 ! manufacture ( pap]1 pa9t or ultra-m>9e1 ^! col\r-produc+ oxides are ( less importance provid+ t ! clay is suffici5tly :ite 9 its comm]cial /ate4 ,! manufactur] ( *9a-w>e & porcela9 requires *9a clay or kaol9 :i*1 9 addition to ! =ego+ *>act]i/ics1 %all be highly refractory4 ,x mu/1 !re=e1 be free f m ?an ab\t #b p] c5t4 ( lime1 magnesia1 soda1 pota%1 titanic acid & o!r fluxes4 ,x is a mi/ake to suppose t all :ite clays ( slight pla/icity are *9a clays or kaol9s4 ,"s pipe clays h ^! *>act]i/ics1 b !y conta9 s l>ge a proportion ( impurities z to be useless = ! purposes = :i* *9a clay is employ$ & are consequ5tly ( small value4 ,us]s ( *9a clays & kaol9s g5]ally f9d x necess>y to c>ry out a l5g?y s]ies ( te/s be=e accept+ mat]ial f a new s\rce1 z su* a mat]ial may possess *>act]i/ics n readily %[n by ord9>y me?ods ( analysis1 b :i* are suffici5tly active to make x useless = c]ta9 purposes 7see p4 #adc74 ,pott]y clays are1 z _! "n implies1 ^? us$ 9 ! manufacture ( pott]y1 & comprise ! *9a clays already m5tion$ 7p4 #ajd71 ! ball clays & ! less pure clays us$ 9 ! manufacture ( co>se r$ w>e1 fl[] pots1 etc4 ,! *9a clays 7p4 #ajd7 are n us$ alone 9 pott]y manufacture z !y lack pla/icity & cohesion4 ,9 ! production ( *9a-w>e or porcela9 !y are mix$ ) a flux+ mat]ial su* z ,corni% /one1 pegmatite1 or felsp>1 toge!r ) qu>tz or bone a%4 ,?us1 ,engli% *9a w>e is produc$ f a mixture ( approximately equal p>ts ( bone a%1 *9a clay & ,corni% /one1 :il/ felspa?ic or h>d porcela9 is made f a mixture ( kaol91 felsp> & qu>tz1 a little *alk be+ sometimes add$4 ,! ball clays 7p4 #fd7 =m ! basis ( mo/ ord9>y pott]y1 ?\gh "s *9a clay is usually add$ 9 ord] to produce a :it] w>e4 ,fl9t is add$ to r$uce ! %r9kage--:i* w\ld o!rwise be inconv5i5tly great--& ! /r5g? ( ! f9i%$ w>e is increas$1 its texture is r5d]$ clos] & its capability ( emitt+ a r++ s\nd :5 /ruck are produc$ by ! inclusion ( ,corni% /one or felsp> 9 ! mixture4 ,small quantities ( cobalt oxide are also add$ to improve ! :it5ess 9 ! bett] classes ( w>e4 ,illu/ration3 ,fig4 #ah4 ,m9+ be/ ,pott]'s clay 9 ,devon%ire4 7,photo by ,mr ,g4 ,bi%op47 ,! ball clays are *>act]is$ by _! rem>kably high pla/icity1 _! f9e texture & _! fre$om f grit4 ,!y are by no means s pure z ! *9a clays1 & unless c>efully select$ c only be us$ = common w>e4 ,! bett] qualities burn to a vitrifi$ mass ( a light br[ni% t9t1 b :5 mix$ ) ! o!r mat]ials us$ 9 e>!nw>e manufacture !y %\ld produce a p]fectly :ite w>e4 ,! inf]ior qualities are us$ = /onew>e1 dra9 pipes1 etc4 ,x %\ld be not$ t ! t]m 'ball clay' is us$ = clays ( widely diff]+ *>act]i/ics ?\gh all obta9$ f "o geological =mation2 :5 ord]+ x is necess>y to /ate ! purpose = :i* ! clay is requir$ or an entirely unsuitable mat]ial may be suppli$4 ,= ! same reason1 great c>e is ne$$ 9 any endeav\r to sell a ball clay f an hi!rto unwork$ deposit4 ,co>se pott]y clays#aa are usually f\nd ne> ! surface & :il/ !y may be d]iv$ f any geological =mation1 ^? mo/ us$ 9 ,engl& are ( ,triassic or ,p]mian orig91 ?\gh "s small pott]ies use mat]ial ( o!r p]iods1 includ+ alluvial or surface clays4 ,^! clays are closely alli$ to ^? us$ = brickmak+1 b are some:at f9] 9 texture & m pla/ic4 ,9 "s cases !y are prep>$ f brick clays by treat+ ! latt] 9 a wa%-mill1 ! co>s] p>ticles be+ !n remov$1 :il/ ! f9] ones1 9 ! /ate ( a slip or slurry1 are run into a settl+ tank & are !re deposit$4 ,footnote #aa3 ,co>se pott]y has be5 def9$ z t made f natural clay )\t ! addition ( any mat]ial o!r ?an s& & wat]4 ,! pres5ce ( a consid]able proportion ( iron oxide results 9 ! =mation ( r$ w>e1 :i* is necess>ily ( a por\s nature1 z ! fluxes 9 ! clay are su* t !y w n p]mit ( its be+ heat$ to complete vitrification )\t loss ( %ape4 ,to r5d] x imp]vi\s ! w>e is cov]$ ) a glaze1 usually produc+ r$1 br[n or black w>e 7,rock+ham w>e74 ,! /onew>e or dra9-pipe clays1 are ! mo/ important ( ! vitrifiable clays & owe _! value to ! fact t !y c be readily us$ = ! manufacture ( imp]vi\s w>e )\t ! necessity ( employ+ a glaze4 ,!y are1 !re=e1 us$ 9 ! manufacture ( vessels = hold+ corrosive liquids su* z acids & o!r *emicals1 = sanit>y appliances1 sew]age pipes & 9 _m o!r in/ances :]e an imp]vi\s mat]ial is requir$4 ,ow+ to ! lime1 magnesia1 pota% & soda !y conta91 ! /onew>e clays und]go p>tial fusion at a mu* l[] temp]ature ?an is requir$ by "s ( ! pur] clays4 ,! fus$ portion fills ! pores or int]/ices ( ! mat]ial1 mak+--:5 cold--a w>e ( great /r5g? & imp]meability4 ,! *ief difficulty exp]i5c$ 9 ! manufacture ( /onew>e is ! liability ( ! articles to twi/ & w>p :5 heat$4 ,= ?is reason x is necess>y to burn !m v c>efully & to select ! clays ) circumspection4 ,"s clays are q unsuitable = ?is bran* ( pott]y manufacture because ( ! practical impossibility ( produc+ w>e :i* is correct 9 %ape & is free f w>p+4 ,:at is requir$ are clays 9 :i* ! p>tial fusion w comm5ce at a mod]ate temp]ature & w cont9ue until all ! pores are fill$ ) ! fus$ mat]ial )\t ! rema9+ +r$i5ts be+ attack$ or corrod$ suffici5tly to cause ! w>e to lose its %ape4 ,z ! temp]ature inside a pott]'s kiln is cont9ually ris+1 ! great t5d5cy is = ! production ( fus$ mat]ial to take place at an ev]-increas+ rate1 s t ! dang] ( w>p+ becomes great] z ! fir+ ne>s completion4 ,"s clays comm5ce to vitrify at a mod]ate temp]ature & c be heat$ ?r\gh a long range ( temp]ature be=e an appreciable am\nt ( w>p+ occurs2 su* clays are said to possess a 'long range ( vitrification' 7p4 #ch74 ,9 o!r clays ! diff]5ce betwe5 ! temp]ature at :i* vitrification comm5ces & t at :i* loss ( %ape occurs is only a few degrees2 su* clays are useless = ! manufacture ( /onew>e1 z _! vitrification range is too %ort4 ,x is !re=e ess5tial t1 = ! manufacture ( /onew>e1 a clay %\ld conta9 a l>ge proportion ( refractory mat]ial :i* w =m a 'skeleton1' ! int]/ices ( :i* w be fill$ by ! m fusible silicates produc$ by ! fir+4 ,x is g5]ally f\nd t ( all ! fluxes pres5t 9 vitrifiable clays1 soda & pota% comp\nds--! s-call$ 'alkalies'--& all lime comp\nds are ! mo/ detrim5tal1 z 9 association ) clay !y =m a mat]ial ) a v %ort range ( vitrification4 ,magnesia1 on ! contr>y1 accompanies a long vitrification range4 ,! clays us$ 9 ,great ,brita9 = ! manufacture ( ! be/ /onew>e are ! ,devon%ire & ,dorset ball clays1 ! upp] portions ( ^! deposits be+ us$ = ?is purpose z !y are some:at less pure ?an ! l[] portions us$ 9 ! manufacture ( :ite w>e4 ,= co>s] grades ( /onew>e1 clays ( o!r geological =mations are employ$1 especially :]e ! f9i%$ w>e may be col\r$1 z ! purity ( ! clay is ( less importance4 ,provid+ a clay has a suffici5tly long vitrification range1 a suitable col\r :5 burn$1 & t x is capable ( be+ readily =m$ into ! desir$ %apes1 its composition & orig9 are ( small importance to ! /onew>e manufactur]4 ,9 actual practice1 h[ev]1 ! numb] ( s\rces ( good /onew>e clay is di/9ctly limit$1 & _m manufactur]s are ?us compell$ to add suitable fluxes to refractory clays 9 ord] to meet "s ( _! cu/om]s' requirem5ts4 ,= ?is purpose a mixture ( fireclay ) f9ely p[d]$ felsp> or ,corni% /one is us$4 ,*alk--:i* is a *eap] & m p[]ful flux--or p[d]$ glass _c be us$ z ! range ( vitrification ( ! mixture w\ld be too %ort4 ,"s manufactur]s take ! opposite c\rse & add fireclay1 fl9t1 or o!r refractory mat]ial to a readily fusible clay4 ,?is is satisfactory if ! latt] clay is relatively l[ 9 lime & owes its fusibility to pota%1 soda or magnesia 9 ! =m ( mica or felsp>4 ,! mica & felsp> gra9s ent] s sl[ly into comb9ation ) ! clay t a long range ( vitrification occurs1 :]eas ) lime1 or ) "s o!r soda & pota% comp\nds1 ! comb9ation occurs ) great rapidity & ! %ape ( ! w>e is spoil$4 ,! refractory clays are commonly kn[n z fireclays on acc\nt ( _! resi/ance to heat4 ,! *9a clays & kaol9s are also refractory1 b are too exp5sive & are n suffici5tly pla/ic to be us$ comm]cially 9 ! same mann] z fireclays1 except to a v limit$ ext5t1 ?\gh bricks h be5 made = _m ye>s f ! inf]ior portions ( *9a clay rock at ,tregon+ ,hill 9 ,cornwall4 ,! geological occurr5ce ( ! fireclays ( ! ,coal ,measures has already be5 describ$ on p4 #ec4 ,9 addition1 !re are ! refractory clays occurr+ 9 pockets or depressions 9 ! ,m\nta9 ,lime/one ( ,nor? ,wales1 ,/af=d%ire1 ,d]by%ire & ,irel&1 :i* consi/ ( silice\s clays & s&s1 ! insoluble residue ( ! local dissolution ( ! lime/one1 int]mix$ ) ! dbris ( ! ov]ly+ ,mill/one ,grit 7see p4 #ed74 ,^! clays & s&s c be mix$ to produce bricks ( rem>kably l[ %r9kage1 b ! pockets are only l>ge en\gh to enable comp>atively small works to be erect$ & ! clays are s irregul> bo? 9 composition & di/ribution z to r5d] _! use some:at speculative4 ,a ?ird type ( refractory clay--t]m$ fl9t clay--is us$ 9 l>ge quantities 9 ! ,unit$ ,/ates1 b is seldom f\nd 9 ,great ,brita94 ,:5 moi/5$1 fl9t clays d n s(t51 b rema9 h>d & fl9t-l ) a smoo? %ell-l fracture4 ,= use !y are gr\nd extremely f9e1 b ev5 !n !y develop little pla/icity4 ,!y are consid]$ by ,ries 7#f7 to h be5 =m$ by solution & re-precipitation ( ! clay subsequ5t to its prim>y =mation1 9 a mann] simil> to fl9t4 ,!y are some:at ri* 9 alum9a & _m conta9 cry/als ( phol]ite 7,al#b,o#cb,si,o#bc;,h#b,o74 ,! ,coal ,measure fireclays 7p4 #ec7--:i* are by f> ! mo/ important--are divid$ into two sections by ! coal seams1 ^? above ! coal be+ %aly & fissile 9 /ructure :il/ ^? bel[ 7und]clays7 are )\t any di/9ct lam9ation4 ,bo? ^! clays may be equally refractory1 b ! und]clays are ^? to :i* ! t]m fireclay is usually appli$4 ,! l[e/ portions are usually m silici\s & 9 "s areas are s ri* 9 silica z to be m appropriately t]m$ silica rock or gani/]4 ,fireclays may1 9 fact1 be look$ ^u z a special t]m = ! grey clays ( ! ,coal ,measures1 int]/ratifi$ ) & g5]ally 9 close proximity to ! seams ( coal4 ,!y are kn[n locally z clun*es & und]clays & 7 at "o "t suppos$ to repres5t ! soil t produc$ ! vegetation f :i* ! coal 0 =m$1 b are n[ consid]$ by _m au?orities to be ( e/u>9e orig94 ,x is important to notice t :il/ ! coals almo/ inv>iably occur 9 association ) und]clays1 "s fireclays are f\nd at a consid]able di/ance f coal4 ,! fireclays ( ! ,coal ,measures h a composition v>y+ )9 comp>atively wide limits ev5 9 contigu\s /rata2 ^? *iefly us$ hav+ an av]age ( #bj to #cj p] c5t4 ( alum9a & #ej to #gj p] c5t4 ( silica4 ,!y appe> to consi/ ( a mixture ( clay & qu>tz ) a small proportion ( o!r m9]als1 b 9 "s ( !m a portion ( ! clay is replac$ by halloysite--ano!r hydro-alum9o-silicate ) ! =mula ,h#f;,al#b,si#b,o#aj or ,al#b,o#c4b,si,o#b4c;,h#b,o4 ,_! grey col\r is l>gely due to vegetable 7c>bonace\s7 matt] & to iron comp\nds4 ,! latt]--usually 9 ! =m ( pyrites--is detrim5tal to ! quality ( ! goods z x =ms a readily fusible slag4 ,unlike ! iron 9 r$-burn+ clays x c seldom be completely oxidiz$ & s r5d]$ h>mless4 ,! fireclays mu/ !re=e be c>efully select$ by ! m9]s4 ,on ! ,cont95t1 & to a mu* small] ext5t 9 ,great ,brita91 refractory articles are made f mixtures ( grog or burn$ fireclay ) j suffici5t raw clay to =m a mass ( ! requir$ /r5g?4 ,= ?is purpose a highly pla/ic1 refractory clay is requir$ & ! ,t]ti>y ball clays ( ,devon & ,dorset 7p4 #fd7 are p>ticul>ly suitable4 ,! mo/ important *>act]i/ics ( a fireclay are t x %all be able to resi/ any temp]ature to :i* x may be expos$ & t ! articles into :i* x is made %all n be affect$ by rapid *anges 9 temp]ature4 ,o!r *>act]i/ics ( importance 9 "s indu/ries are ! resi/ance to corrosive action ( slags & vap\rs1 to cutt+ & abrasion by du/ 9 flue-gases or by ! implem5ts us$ 9 clean+ ! fires4 ,= ^? purposes x is necess>y t a fireclay %\ld possess high infusibility 7p4 #cb71 a l[ burn+ %r9kage 7p4 #bi7 & a high degree ( refractor9ess 7p4 #cd71 & be=e x is us$ ^! *>act]i/ics %\ld be asc]ta9$ by means ( def9ite te/s1 z !y _c be det]m9$ by inspection ( a sample or f a /udy ( its *emical analysis4 ,sev]al grades ( fireclay h long be5 recogniz$ on ! ,cont95t & 9 ! ,unit$ ,/ates ( ,am]ica1 b ! rec5t ,specification ( ! ,in/itution ( ,gas ,eng9e]s is ! only (ficial recognition 9 ,great ,brita9 ( def9ite grades4 ,?is specification def9es z ,no4 #a grade a fireclay :i* %[s no signs ( fusion :5 heat$ to #afgj ,c4 or ,cone #cj at ! rate ( #aj ,c4 p] m9ute1 & z ,no4 #b grade fireclay ^? :i* %[ no signs ( fusion :5 simil>ly heat$ to #aehj ,c4 or ,cone #bf4 ,x is reg>d$ z a sign ( fusion if a te/ piece ) %>p angles loses its angul>ity aft] heat+ to a pr$et]m9$ temp]ature 7see p4 #ce74 ,x is cu/om>y to reg>d z 'fireclay' all clays :i*1 :5 =m$ into ! %ape ( a ,seg] ,cone 7fig4 #f7 d n b5d on heat+ sl[ly until a temp]ature ( #aehj ,c4 7,cone #bf7 is rea*$4 ,any clays compris$ )9 ?is def9ition & yet n suffici5tly refractory to be ( ! ,no4 #b grade j m5tion$ may be reg>d$ z ,no4 #c grade fireclays4 ,_m ( ! la/ nam$ are well suit$ = ! manufacture ( blocks = dome/ic fireplaces1 = glaz$ bricks & = firebricks n int5d$ to resi/ furnace temp]atures4 ,to resi/ sudd5 *anges 9 temp]ature ! mat]ial mu/ be v por\s--! article be+ capable ( absorb+ at lea/ "o-six? ( its volume ( wat]4 ,= ?is reason x is cu/om>y to mix fireclays ) a l>ge proportion ( non-pla/ic mat]ial ( a some:at co>se texture1 ! sub/ance mo/ g5]ally employ$ be+ fireclay :i* has be5 previ\sly burn$ & !n cru%$4 ,?is mat]ial is kn[n z grog or *amotte & has ! advantage ov] o!r sub/ances ( n affect+ ! composition ( ! fireclay to :i* x is add$1 :il/ greatly increas+ its te*nical usefulness4 ,! addition ( grog also r$uces ! %r9kage ( ! clay dur+ dry+ & ensures a s\nd] article be+ produc$4 ,! mo/ s]i\s impurities 9 refractory clays are lime1 magnesia1 soda1 pota% & titanium & _! comp\nds z !y l[] ! refractor9ess ( ! mat]ial4 ,iron1 9 ! /ate ( f]ric oxide is ( less importance1 b pyrites & all f]r\s comp\nds are p>ticul>ly objectionable4 ,pyritic & calc>e\s nodules may1 to a l>ge ext5t1 be remov$ by pick+1 & by ?r[+ away lumps 9 :i* !y are se5 to occur4 ,!re is1 at pres5t1 no o!r means ( remov+ !m4 ,fireclays may be gr\nd directly !y come f ! m9e1 b x is usually bett] to expose !m to ! action ( ! wea!r z ?is effects v>i\s *emical & physical *anges )9 ! mat]ial1 :i* improves its quality z well z r$uces ! p[] requir$ to cru% x4 ,to take full advantage ( ! refractory qualities ( a clay x is necess>y to select x ) skill1 prep>e & m\ld x ) c>e1 to burn x sl[ly & /eadily1 to f9i% ! heat+ at a suffici5tly high temp]ature & to cool ! w>e sl[ly4 ,rapidly heat$ fireclay is seldom s resi/ant to heat "u comm]cial conditions z t :i* has be5 m /eadily fir$4 ,rapid or irregul> heat+ causes an irregul> =mation & di/ribution ( ! fus$ mat]ial dur+ ! process ( vitrification 7p4 #cg7 & s produces goods :i* are too t5d] to be durable4 ,x is1 !re=e1 necess>y to ex]cise great c>e 9 ! fir+4 ,%ales are rocks :i* h be5 subject$ to consid]able pressure subsequ5t to _! deposition & are1 consequ5tly1 lam9at$ & m readily split 9 "o direction ?an 9 o!rs4 ,"s %ales are almo/ entirely compos$ ( silica or calc>e\s matt]1 b _m o!rs are ri* 9 clay1 ! t]m ref]r+ to physical /ructure & n to *emical composition4 ,! clay-%ales occur *iefly 9 ! ,silurian & ,c>bonif]\s =mations1 ! latt] be+ m g5]ally us$ by claywork]s4 ,clay-%ales are valu$ accord+ to 7a7 ! proportion ( oil :i* c be di/ill$ f !m1 ^? ri* 9 ?is respect be+ t]m$ oil %ales2 7b7 ! col\r :5 burn$1 z 9 brickmak+ & t]ra-cotta %ales2 7c7 ! refractor9ess1 z 9 fireclay %ales & 7d7 ! facility ) :i* !y are decompos$ on exposure or on heat+ & =m sulphuric acid z 9 alum %ales4 ,oil %ales conta9 s mu* c>bonace\s matt] t on di/illation at a l[ r$ heat !y yield comm]cially remun]ative quantities ( a crude oil t]m$ %ale t>4 ,9 composition !y are int]m$iate betwe5 cannel coal & a purely m9]al %ale4 ,to be ( value !y %\ld n yield less ?an #cj gallons ( crude oil p] ton ( %ale1 ) ammonia & illum9at+ gas z by-products4 ,!y are ( ,silurian1 ,c>bonif]\s or ,oolitic orig91 ! ,kim]idge %ale associat$ ) ! la/-nam$ be+ v valuable 9 ?is respect4 ,! mo/ important oil %ales occur 9 ,scotl&4 ,! fireclay %ales h already be5 describ$ on pages #ec & #aaf4 ,! brickmak+ %ales are ^? :i* are suffici5tly ri* 9 clay to =m a pla/ic pa/e :5 gr\nd & mix$ ) wat]4 ,!y c be made into bricks ( excell5t col\r & great /r5g?1 b = ?is purpose require ! use ( p[]ful cru%+ & mix+ ma*9]y4 ,!y are usually conv]t$ into a /iff pa/e ( only mod]ate pla/icity & are !n m\ld$ by ma*9]y 9 specially design$ presses1 ?\gh "s firebricks are made f cru%$ %ale mix$ into a s(t pa/e ) wat] & aft]w>ds m\ld$ by h&4 ,"s %ales1 su* z ! knotts at ,fletton ne> ,pet]bor\gh are n made into a pa/e1 ! moi/ p[d]$ %ale be+ press$ into bricks by v p[]ful ma*9]y4 ,brickmak+ %ales may be f\nd 9 any ( ! old] geological =mations1 ?\gh !y occur *iefly 9 ! ,silurian1 ,p]mian1 ,c>bonif]\s & ,jurassic sy/ems4 ,! pur] %ales ( ! ,coal ,measures burn to an agreeable cream or buff col\r1 ! less pure ones & ^? ( ! o!r =mations m5tion$ produce articles ( a brick-r$ or blue-grey col\r4 ,:]e ! %ales are ( exceptionally f9e gra9 & _! col\r :5 burn$ is v uni=m & ( a pleas+ t9t !y are kn[n z t]ra-cotta %ales1 ! r$ t]ra-cottas be+ *iefly made f ^? occurr+ 9 ,wales & ! buff ones f ! l[] grade fireclays ( ! ,coal ,measures4 ,alum %ales are *>act]is$ by a high proportion ( pyrites1 :i*1 on roa/+1 =m f]r\s sulphate & sulphuric acid4 ,! latt] comb9es ) ! alum9a 9 ! %ale & :5 ! roa/$ ore is extract$ ) wat] a solution ( iron sulphate & alum9ium sulphate is obta9$4 ,f ?is solution 7aft] p>tial evaporation7 alum cry/als are obta9$ by ! addition ( potassium or ammonium sulphate4 ,! *ief alum %ales are ^? ( ! ,silurian =mation 9 ,scotl& & ,sc&9avia4 ,! ,liassic %ales ( ,:itby 7 at "o "t an equally important s\rce ( alum4 ,dur+ rec5t ye>s a l>ge am\nt ( alum has be5 obta9$ f o!r s\rces or has be5 made f ! l[] grade ,dorset & ,devon%ire ball clays by calc9+ !m & !n treat+ !m ) sulphuric acid4 ,^! clays be+ almo/ free f iron comp\nds yield a mu* pur] alum at a l[] co/4 ,brick clays are ^? :i* are n suitable--ei!r f nature or situation--= ! manufacture ( pott]y or porcela9 & yet possess suffici5t pla/icity to enable !m to be made into bricks4 ,! t]m is us$ some:at loosely1 & geologi/s n infrequ5tly apply x to clays :i* are q unsuitable = brickmak+ on acc\nt ( excessive %r9kage & ! abs5ce ( any suitable non-pla/ic m$ium4 ,l>ge portions ( ! ',london clay' are ( ?is nature & c only be reg>d$ z ( use to brick- & ro(+-tile-manufactur]s :5 ! associat$ ,bag%ot s&s are readily accessible4 ,simil>ly1 "s ( ! v t\gh surface clays ( ! ,nor!rn & ,midl& c\nties are equally valueless1 ?\gh designat$ 'brick clays' 9 num]\s geological & o!r reports4 ,x is1 !re=e1 necess>y to rememb] t1 z ord9>ily us$1 ! t]m 'brick clay' m]ely indicates a mat]ial :i* appe>s at fir/ sight to be suitable = brickmak+1 b t m detail$ inve/igations are necess>y be=e x c be asc]ta9$ :e!r a mat]ial s designat$ is actually suitable = ! purpose4 ,x is also important to obs]ve t local indu/rial conditions may be su* t a valuable clay may be us$ = brickmak+ because !re is a dem& = bricks1 b n = ! o!r articles = :i* ! clay is equally suitable4 ,= in/ance1 a consid]able numb] ( h\ses 9 ,nor?umb]l& & ,durham 7 built ( firebricks at a "t :5 x 0 m pr(itable to sell ^! articles = dome/ic build+s ?an = furnaces4 ,9 _m ways ! bricks us$ = int]nal /ructural "w =m ! simple/ & mo/ easily manufactur$ ( all articles made f clay4 ,! col\r ( ! f9i%$ product is ( m9or importance & s long z a brick ( reasonably accurate %ape & ( suffici5t /r5g? is produc$ at a *eap rate1 little else is expect$4 ,impurities--unless 9 excessively l>ge proportions--are ( small importance &1 inde$1 s& may almo/ be consid]$ an ess5tial con/itu5t ( a mat]ial to be us$ = mak+ ord9>y bricks4 ,x is1 !re=e1 possible to utilize = ?is purpose "s mat]ials conta9+ s little 'clay' z to make !m sc>cely fit to be includ$ 9 ?is t]m4 ,s long z ! adv5titi\s mat]ials consi/ *iefly ( silica & *alk & ! mixture is suffici5tly pla/ic to make /rong bricks1 x may be us$ satisfactorily 9 spite ( its l[ cont5t ( clay1 b if ! s-call$ 'brick clay' conta9s lime/one1 ei!r 9 l>ge gra9s or nodules1 x w be liable to bur/ ! bricks or to produce unsightly 'bl[-holes' on _! surfaces4 ,if too mu* s& or o!r non-pla/ic mat]ial is pres5t1 ! result+ bricks w be too weak to be satisfactory4 ,no brick clay c be reg>d$ z 'safe' if x conta9s nodules ( lime/one--unless ^! c be remov$ dur+ ! prep>ation ( ! mat]ial--or if ! result+ bricks w n %[ a cru%+ /r5g? ( at lea/ #he tons p] squ>e foot4 ,! introduction ( ma*9]y 9 place ( h&-m\ld+ & ( kilns in/ead ( clamps has greatly rais$ ! /&>d ( /r5g?1 accuracy 9 %ape & uni=mity 9 col\r 9 _m di/ricts1 & _m build]s 9 ! ,midl&s n[ expect to sort out f ! 'common bricks' pur*as$1 a suffici5t numb] ( sup]ior quality to furni% all ! 'fac+ bricks' !y require4 ,ap>t f ?is1 & 9 di/ricts :]e build+s are fac$ ) /one or ) bricks ( a sup]ior quality1 ! '/ock' or 'common brick' may be made f almo/ any clay :i* w be> dry+ & heat+ to r$ness )\t %r9k+ excessively or crack+4 ,a l9e> %r9kage ( #a 94 p] foot 7 #h-a_/b p] c5t47 may be reg>d$ z ! maximum ) mo/ mat]ials us$ = brickmak+4 ,clays :i* %r9k m ?an ?is mu/ h a suitable quantity ( grog1 s&1 *alk1 a%es or o!r suitable non-pla/ic mat]ial add$4 ,if ! clay conta9s mu* f]ric oxide x w produce r$ or br[n bricks accord+ to ! temp]ature rea*$ 9 ! kiln1 b if mu* *alk is also pres5t 7or is add$ purposely7 a comb9$ lime-iron-silicate is produc$ & ! bricks w be :ite 9 col\r4 ,if only a small p]c5tage ( f]ric oxide is pres5t a clay w produce buff bricks1 :i* w be spott$ ) m9ute black specks or l>g] masses ( a greyi% black slag if pyrites are also pres5t or if f]r\s silicate has be5 produc$ by ! r$uction ( ! iron comp\nds & _! subsequ5t comb9ation ) silica4 ,fur!r in=mation on brick e>?s w be f\nd on page #fg4 ,a description ( ! processes us$ 9 ! manufacture ( bricks be+ outside ! scope ( ! pres5t "w1 ! read] requir+ in=mation on ?is subject %\ld consult ,mod]n ,brickmak+ 7#be7 or "s simil> treatise4 ,ro(+ tiles require clays ( f9] texture ?an ^? :i* may be made into bricks4 ,/ones1 if pres5t1 mu/ be remov$ by wa%+ or o!r treatm5t1 z x is seldom t !y c be cru%$ to a suffici5tly f9e p[d]1 unless only r\gh "w is requir$4 ,if suffici5tly f9e1 ! clay us$ = ro(+ tiles may be precisely ! same z t us$ = bricks & is treat$ 9 a simil> mann]4 ,x mu/1 h[ev]1 be ( su* a nature t x w n w>p or twi/ dur+ ! burn+2 x mu/1 !re=e1 h a long range ( vitrification 7p4 #ch74 ,t]ra-cotta is an ,italian t]m signify+ bak$ e>?1 b its mean+ is n[ limit$ to ^? articles made ( clay :i* are n class$ z pott]y1 su* z /atues1 l>ge vases1 pill>s1 etc41 modell$ "w us$ 9 ar*itecture1 or = ext]nal decoration4 ,al?\gh ! di/9ction _c be rigidly ma9ta9$1 articles made ( clay may be r\ghly divid$ into 7a7 ,pott]y 7fai5ce7 & porcela9 7glaz$71 7b7 ,t]ra-cotta 7unglaz$71 7c7 ,bricks & unglaz$ tiles devoid ( decoration4 ,9 ?is s5se1 t]ra-cotta occupies an int]m$iate position betwe5 pott]y & bricks1 b no satisfactory def9ition has yet be5 f\nd = x4 ,?us1 bricks ) a modell$ or m\ld$ ornam5t are1 /rictly1 t]ra-cotta1 yet are n s nam$1 & "s pott]y is unglaz$ & yet is nev] class$ z t]ra-cotta1 :il/ glaz$ bricks are nev] reg>d$ z pott]y4 ,aga9 dur+ ! pa/ few ye>s1 :at is t]m$ 'glaz$ t]ra-cotta' has be5 l>gely us$ = ar*itectural purposes1 yet ?is is really 'fai5ce4' ,al?\gh ?is ov]lapp+ ( t]ms may appe> confus+ to ! read]1 x does n cause any appreciable am\nt ( inconv5i5ce to ! manufactur]s or us]s1 z x is n difficult = a practical claywork] to decide 9 :i* ( ! ?ree classes m5tion$ a giv5 article %\ld be plac$4 ,p>tly on acc\nt ( ! less] weight1 b *iefly 9 ord] to r$uce ! t5d5cy to crack & to facilitate dry+ & burn+1 t]ra-cotta articles are usually made holl[4 ,x is necess>y t clays us$ 9 ! manufacture ( t]ra-cotta %\ld be ( s f9e a texture t ! f9e/ modell+ c be execut$4 ,su* clays occur naturally 9 sev]al geological =mations1 & "s may be prep>$ f co>s] mat]ials by c>eful wa%+1 :]eby ! l>g] gra9s ( s&1 /ones1 etc41 are remov$4 ,"s %ales1 :5 f9ely gr\nd1 make excell5t clays = ar*itectural t]ra-cotta1 portions ( all ! bett] kn[n fireclay deposits be+ us$ = ?is purpose4 ,x is1 h[ev]1 necess>y to use only ^? %ales :i* are naturally ( f9e texture1 z me*anical gr9d+ _c effect a suffici5t sub-division ( ! p>ticles ( "s ( ! co>s] %ales4 ,! f9] ,triassic 'm>ls' are also admirable = t]ra-cotta "w1 ! mo/ fam\s deposit be+ ! ,etruria ,m>l ,s]ies 9 ! ,upp] ,coal ,measures ne> ,ruabon4 ,! mo/ important *>act]i/ics requir$ 9 t]ra-cotta clays are 7a7 f9e texture1 or at any rate ! ability to yield a f9e1 d5se surface1 7b7 small %r9kage ) little t5d5cy to twi/1 w>p or crack 9 fir+1 7c7 pleas+ & uni=m col\r :5 fir$1 & 7d7 a suffici5t proportion ( fluxes to make x resi/ant to wea!r )\t giv+ a glossy appe>ance to ! f9i%$ product4 ,9 l>ge pieces ( t]ra-cotta "s irregul>ity ( %ape is almo/ unavoidable1 b1 if c>e is tak5 9 ! selection & manipulation ( ! mat]ial1 ?is ne$ n be unsightly4 ,! durability ( t]ra-cotta is l>gely dep5d5t on ! nature ( ! surface4 ,! mo/ suitable clays1 :5 fir$1 h a ?9 'sk9' ( vitrifi$ mat]ial :i* is v resi/ant to climatic influ5ces1 & s long z ?is rema9s intact ! w>e w cont9ue 9 p]fect condition4 ,if ?is 'sk9' is remov$1 ra9 w p5etrate ! mat]ial & "u ! influ5ce ( fro/ may cause rapid dis9tegration4 ,9 ! manufacture ( v l>ge pieces ( t]ra-cotta a co>se1 por\s clay is us$ = ! f\ndation & int]ior1 & ?is is cov]$ ) ! f9] clay4 ,by ?is means a great] resi/ance to *anges 9 temp]ature is secur$1 ! dry+ & ! burn+ ( ! mat]ial 9 ! kiln are facilitat$ & ! risks ( damage 9 manufacture are mat]ially r$uc$4 ,cem5t clays are ^? us$ 9 ! manufacture ( ,portl& cem5t & ( s-call$ natural cem5ts4 ,!y are l>gely ( an alluvial "* & are ( two *ief classes3 7a7 ^? :i* conta9 *alk or lime/one du/ & clay 9 proportions suitable = ! manufacture ( cem5t & 7b7 ^? to :i* *alk or gr\nd lime/one mu/ be add$4 ,!y v>y 9 composition f argillace\s lime/ones conta9+ only a small proportion ( clay to almo/ pure clays4 ,! manufacture ( ,portl& cem5t has assum$ a great importance & ow+ to ! l>ge am\nt ( inve/igations made 9 connection ) x1 x may be said to repres5t ! *ief cem5t made f argillace\s mat]ials1 ! o!rs be+ conv5i5t ?\gh crude modifications ( x4 ,! ess5tial con/itu5ts are calcium c>bonate 7introduc$ 9 ! =m ( *alk or p[d]$ lime/one7 & clay1 ! composition ( ! naturally occurr+ mat]ials be+ modifi$ by ! addition ( a suitable proportion ( "o or o!r ( ^! +r$i5ts4 ,! mat]ial is !n heat$ until x und]goes p>tial fusion & a 'cl9k]' is =m$4 ,?is cl9k]1 :5 gr\nd1 =ms ! cem5t4 ,9 ,k5t1 ! ,m$way mud is mix$ ) *alk2 9 ,sussex1 a mixture ( gault clay & *alk is employ$2 9 ! ,midl&s & ,s\? ,wales1 ,liassic %ales & lime/one are us$2 9 ,nor?umb]l& a mixture ( ,k5ti% *alk & a local clay is pref]r$1 & 9 ,cambridge%ire a special m>l ly+ betwe5 ! ,*alk & ! ,gre5s& is f\nd to be admirable = ! purpose because x conta9s ! +r$i5ts 9 almo/ exactly ! requir$ proportions4 ,= cem5t manufacture1 clays %\ld be z free z possible f mat]ial :i*1 9 slip =m1 w n pass ?r\gh a ,no4 #ajj sieve1 z co>se s& & o!r rock dbris are practically in]t4 ,! proportion ( alum9a & iron %\ld be ab\t "o-?ird1 b n m ?an "o-half1 t ( ! silica1 & 9 c\ntries :]e ! proportion ( magnesia 9 a cem5t is limit$ by /&>d specifications1 x w be f\nd undesirable to use clays conta9+ m ?an #c p] c5t4 ( magnesia & alkalies4 ,:il/ calc>e\s clays usually prove ! mo/ conv5i5t 9 ! manufacture ( cem5t1 x is by no means ess5tial to use !m1 & :]e a clay almo/ free f lime occurs 9 conv5i5t proximity to a suitable *alk or lime/one deposit an excell5t cem5t may usually be manufactur$4 ,! 'clays' f :i* ! s-call$ 'natural' or ',roman cem5ts' are made by simple calc9ation & cru%+1 usually fuse at a l[] temp]ature ?an d ! mixtures us$ = ,portl& cem5t1 & unless _! composition is accurately adju/$ !y yield a product ( su* v>iable quality z to be unsuitable = high class "w4 ,full]'s e>? is a t]m us$ to indicate any e>?y mat]ial :i* c be employ$ = full+ or degreas+ wool & blea*+ oil4 ,true full]'s e>? is obta9$ *iefly f ! neighb\rhood ( ,reigate1 ,surrey1 ,woburn ,s&s1 ,b$=d%ire & f bel[ ! ,oolite =mation ne> ,ba?1 b ow+ to ! sc>city ( ! mat]ial & ! irregul>ity ( its behavi\r1 *9a clay is n[ l>gely us$ = ! same purpose4 ,true full]'s e>? is mu* m fusible ?an ! :ite clays usually sub/itut$ = x1 & :5 mix$ ) wat] x does n =m a pla/ic pa/e b falls to p[d]4 ,z ! *ief requirem5t ( ! full] is ! grease-absorb+ p[] ( ! mat]ial !re is no objection to ! sub/itution ( o!r e>?s ( equal effici5cy4 ,full]'s e>? does n appe> to be a true clay1 ?\gh its con/itution & m9]alogical composition are by no means cle>ly kn[n4 ,t4 ,j4 ,port] consid]s t x is *iefly compos$ ( montmorillonite 7,al#b,o#cd,si,o#b;,h#b,o71 anauxite1 7#b;,al#b,o#ci,si,o#bf;,h#b,o71 & *alk ) "s colloidal silica & a little qu>tz4 ,x !re=e appe>s to resemble ! less pure kaol9s1 b to conta9 little or no true clay1 ?\gh 9 _m respects x behaves 9 a mann] simil> to a kaol9 ( unusually l[ pla/icity4 ,o!r clays ( comm]cial importance1 ) fur!r details ( ! ones j m5tion$1 are describ$ 9 ! au?or's ,briti% ,clays1 ,%ales & ,s&s 7#b74 ,,*apt] ,,vi ,,clay ,,sub/ance3 ,,!oretical ,,& ,,actual ,hav+ indicat$ ! orig91 modes ( accumulation & g5]al *>act]i/ics ( ! num]\s mat]ials kn[n z 'clay1' x n[ rema9s to asc]ta9 :at sub/ance1 if any1 is conta9$ 9 all ( !m & may be reg>d$ z _! ess5tial con/itu5t1 to :i* _! prop]ties are l>gely due4 ,j z ! value ( an ore is dep5d5t to a v l>ge ext5t on ! proportion ( ! desir$ metal :i* x conta9s1 & j z coal is l>gely1 ?\gh n entirely1 e/eem$ 9 proportion to ! p]c5tage ( c>bon & hydrog5 9 x1 s !re may be an ess5tial sub/ance 9 clays to :i* !y owe ! mo/ important ( _! *>act]i/ics4 ,! proportion ( metal 9 an ore or ( hydroc>bon 9 a coal c be asc]ta9$ )\t s]i\s difficulty by "s means ( analysis1 b ) clay ! difficulties are s great t1 to "s ext5t at lea/1 !y mu/ be reg>d$ z be+1 = ! pres5t1 insurm\ntable4 ,?is is 9 no small measure due to ! g5]al recognition ( all m9]als or rocks :i* become pla/ic :5 knead$ ) wat] z 'clays' )\t mu* reg>d be+ paid to _! composition4 ,consequ5tly mat]ials ( ! mo/ div]se nature 9 o!r respects are t]m$ clays if !y are kn[n to become pla/ic "u c]ta9 conditions4 ,!re is1 9 fact1 at ! pres5t "t1 no g5]ally accept$ def9ition ( clay :i* di/+ui%es x f mixtures ( clay & s& or o!r f9e m9]al p>ticles4 ,! usual geological def9itions are s broad z to include _m mixtures conta9+ consid]ably less ?an half _! weight ( true clay or !y avoid ! composition ( ! mat]ial altoge!r & describe x z a f9ely divid$ product ( ! decomposition ( rocks4 ,_m attempts h be5 made to avoid ?is un=tunate position1 :i* is alike unsatisfactory to ! geologi/1 ! m9]alogi/ & ! *emi/ z well z to ! l>ge numb] ( p engag$ 9 ! pur*ase & use ( v>i\s clays2 &1 :il/ ! end s\ght has n be5 rea*$ z completely z is desirable1 great progress has be5 made & mu* has be5 accompli%$ dur+ ! la/ tw5ty ye>s4 ,"o ( ! e>lie/ attempts to asc]ta9 :e!r !re is an ess5tial con/itu5t ( all clays 0 made by ,seg] 7#g7 :o us$ two me?ods ( sep>at+ "s ( ! +r$i5ts ( natural clays f ! rema9+ con/itu5ts4 ,! fir/ ( ^! me?ods consi/s 9 an application ( ! inve/igations ( ,s*ulze1 ,s*loes+ & ,s*o5e on soils1 viz4 ! removal ( ! f9e/ p>ticles by elutriation2 ! second is an ext5sion ( ! me?od ( ,=s*amm] & ,fres5ius1 viz4 ! treatm5t ( ! mat]ial ) sulphuric acid4 ,to ! product conta9+ ! clay :5 ei!r ( ^! me?ods is us$ ,seg] gave ! "n clay sub/ance1 b ! mat]ial s sep>at$ is by no means pure clay4 ,! t]m clay sub/ance mu/1 !re=e1 be conf9$ to ! crude product conta9+ ! clay toge!r ) su* o!r impurities z are 9 ! =m ( extremely small p>ticles or are soluble 9 sulphuric acid4 ,x has n yet be5 f\nd possible to isolate pure clay f ord9>y clays1 s t 9 inve/igat+ ! nature ( :at ,seg] 0 endeav\r+ to produce :5 he obta9$ ! crude clay sub/ance1 indirect me?ods are necess>y4 ,x has long be5 kn[n t if a sample ( 'clay'--us+ ?is ^w 9 ! broade/ s5se--is rubb$ 9 a consid]able quantity ( wat] s z to =m a ?9 slip or slurry1 x may readily be divid$ into a numb] ( fractions ea* ( :i* w consi/ ( gra9s ( diff]5t sizes4 ,?is sep>ation may be effect$ by means ( a s]ies ( sieves ?r\gh :i* ! slurry is p\r$1 or ! slurry may be caus$ to fl[ at a s]ies ( diff]5t spe$s1 ! mat]ial left beh9d at ea* rate ( spe$ be+ kept sep>ate2 or1 f9ally1 ! slurry may be all[$ to /& = a few seconds & may !n be c>efully decant$ into ano!r vessel 9 :i* x may rema9 at re/ = a some:at long] p]iod1 ^! times ( re/+ & decantation1 if repeat$1 provid+ a s]ies ( fractions ! mat]ials 9 :i* are m or less diff]5t 9 _! nature4 ',clays' conta9+ a consid]able proportion ( co>se mat]ial are mo/ conv5i5tly sep>at$ into a s]ies ( fractions by means ( sieves1 :]eby !y are divid$ into 7i7 /ones1 7ii7 gravel1 7iii7 co>se s&1 7iv7 m$ium s&1 7v7 f9e s& & 7vi7 a slurry consi/+ ( su* small p>ticles t !y c no long] be sep>at$ by sift+4 ,if ! residues on ! sieves are c>efully wa%$ free f any adh]+ f9e mat]ial & are !n dri$1 !y w be f\nd on exam9ation to be q di/9ct f any?+ def9able z clay4 ,!y may consi/ ( a consid]able v>iety ( m9]als or may be almo/ entirely compos$ ( qu>tz1 b ) ! possible exception ( "s %ales ( great h>dness1 !y are und\bt$ly n clay4 ,?is simple process !re=e s]ves to remove a proportion ( mat]ial :i* 9 ! case ( "s 'clays' is v l>ge b 9 o!rs is insignificant2 ?us #dj p] c5t4 ( s&-l mat]ial may be remov$ f "s brick-clays :il/ a ball clay us$ = ! manufacture ( /onew>e or pott]y may pass completely ?r\gh a sieve hav+ #bjj me%es p] l9e> in*4 ,! mat]ial :i* passes ?r\gh ! f9e/ sieve employ$ w conta9 all ! true clay 9 ! mat]ial2 t is to say1 ! co>s] portion w1 z already m5tion$1 be devoid ( ! ord9>y *>act]i/ics ( clay4 ,at ! same "t1 ?is v f9e mat]ial w seldom consi/ exclusively ( clay1 b w usually conta9 a consid]able proportion ( silt1 extremely f9e m9]al p>ticles &1 9 ! case ( calc>e\s clays1 a notable proportion ( calcium c>bonate 9 ! =m ( *alk or lime/one p>ticles4 ,only 9 ! case ( ! pure/ clays w ! mat]ial n[ "u consid]ation consi/ entirely ( clay1 s t x mu/ be aga9 sep>at$ into its con/itu5ts4 ,?is is be/ accompli%$1 z fir/ sugge/$ by ,s*o5e1 by expos+ ! mat]ial to ! action ( a /ream ( wat] ( def9ite spe$4 ,h4 ,seg] 7#g7 inve/igat$ ?is me?od v ?or\ghly & 8 recomm5dations z to ! mann] 9 :i* ?is sep>ation by elutriation %\ld be c>ri$ out rema9 9 use at ! pres5t "t4 ,briefly1 all mat]ial suffici5tly f9e to be c>ri$ away by a /ream ( wat] fl[+ at ! rate ( #jdc 94 p] m9ute 0 f\nd by ,seg] to include ! :ole ( ! clay 9 ! samples he exam9$1 b1 z 0 lat] po9t$ out by ,bis*(1 x is n correct to t]m ! :ole ( ?is mat]ial 'clay sub/ance1' z :5 exam9$ "u ! microscope1 x conta9s mat]ial :i* is cle>ly n clay4 ,processes ( decantation ( ! f9e/ mat]ial obta9$ aft] elutriation /ill fail to sep>ate all ! non-clay mat]ial1 & ,vogt has f\nd t :5 ! mat]ial has be5 all[$ to /& 9 susp5sion = n9e days "s p>ticles ( mica are /ill associat$ ) ! clay4 ,x w\ld ?us appe> t no process ( me*anical sep>ation w s]ve = a complete purification ( a clay2 inde$1 !re are good reasons = suppos+ t extremely f9e p>ticles ( qu>tz & mica r5d] physical *>act]i/ics an unc]ta9 means ( accurately di/+ui%+ clays f o!r rock du/4 ,:5 *emical me?ods ( inve/igation are employ$ ! problem is n mat]ially alt]$1 nor is its solution fully atta9$4 ,x is1 ( c\rse1 obvi\s t any *emical me?od %\ld be appli$ to ! product obta9$ by treat+ ! raw mat]ial me*anically z above describ$1 = to d o!rwise is to create ne$less confusion4 ,yet by f> ! great] numb] ( publi%$ analyses ( 'clays' report ! ultimate composition ( ! :ole mat]ial1 no attempt be+ made to %[ h[ mu* ( ! v>i\s con/itu5ts is 9 ! =m ( s&1 /ones or o!r co>se p>ticles ( an entirely non-argillace\s "*4 ,if ! p>ticles ( a 'clay' :i* are suffici5tly small to be c>ri$ away by a /ream ( wat] ) a velocity ( only #jdc 94 p] m9ute are analys$1 x w be f\nd t _! composition w v>y accord+ to ! orig9 ( ! clay & ! subsequ5t treatm5t to :i* x has be5 subject$ dur+ its transport & deposition4 ,if ! clay is fairly free f calc>e\s mat]ial & is ( a :ite-burn+ nature x may be f\nd to h a composition l *9a clays4 ,r$-burn+ clays1 on ! contr>y1 w v>y greatly 9 composition1 s t x becomes difficult to f9d any close analogy betwe5 ^! k9ds ( clay4 ,?is diff]5ce is p>tly due to ! extremely f9e /ate ( division 9 :i* f]ric oxide occurs 9 clays1 ! p>ticles ( ?is mat]ial correspond+ 9 m9ut5ess to ^? ( ! pure/ clays & s be+ insep>able by any me*anical process4 ,9 #ahgf ,h4 ,seg] 7#g7 publi%$ :at he t]m$ a me?od ( 'rational analysis1' :i* consi/$ 9 treat+ ! clay ) boil+ sulphuric acid foll[$ by a treatm5t ) cau/ic soda4 ,he f\nd t ! pur] *9a clays 7kaol9s7 & ball clays 7 made soluble by ?is means & t felsp>1 mica & qu>tz 7 to a l>ge ext5t unaffect$4 ,lat] inve/igators h f\nd t ?is me?od is only applicable to a limit$ ext5t & t its indications are only reliable :5 appli$ to ! clays j nam$1 b ! pr9ciple introduc$ by ,seg] has prov$ invaluable 9 increas+ our k ( ! composition ( clays4 ,by means ( ?is s-call$ rational analysis ,seg] f\nd t ! pur] clays yield$ results ( rem>kable simil>ity & uni=mity1 ! mat]ial ent]+ into solution hav+ a composition agree+ v closely ) ! =mula ,al#b,o#cb,si,o#bb;,h#b,o :i* is g5]ally recogniz$ z t ( ! *ief con/itu5t or con/itu5ts ( *9a clay 7kaol97 & ! pur] ball clays4 ,?is crude sub/ance1 obta9able f a l>ge numb] ( clays by ! treatm5t j describ$1 0 nam$ clay sub/ance by ,seg]1 :o reg>d$ x z ! ess5tial con/itu5t ( all clays4 ,r$-burn+ clays :5 simil>ly treat$ d n yield s uni=m a product1 & ! f]ric oxide ent]+ into solution makes ! results v discordant4 ,moreov]1 ev5 ) ! *9a clays or kaol9s a small proportion ( alkalies1 lime & o!r oxides ent] into solution & a numb] ( m9]als analog\s to clay1 b q di/9ct f x1 are also decompos$ & dissolv$4 ,= ^! reasons ! 'rational analysis' has be5 f\nd insuffici5t2 x is n[ consid]$ necess>y to make an analysis ( ! portion r5d]$ soluble by treatm5t ) sulphuric acid 9 ord] to asc]ta9 :at o!r +r$i5ts x may conta9 9 addition to ! true clay pres5t4 ,z ! *9a clays 7kaol9s7 & ball clays on v c>eful elutriation all yield a product ( ! same ultimate composition1 viz4 #ci p] c5t4 ( alum9a1 #df p] c5t4 ( silica1 #ac p] c5t4 ( wat]1 & #b p] c5t4 ( o!r oxides1 !y are g5]ally reg>d$ z consi/+ ( practically pure clay ) a v>iable am\nt ( impurities4 ,_m ye>s ago ,fres5ius sugge/$ t ^! non-clayey con/itu5ts ( clays %\ld be calculat$ into ! m9]als to :i* !y appe>$ likely to correspond s z to obta9 a result simil> to t obta9$ by ,seg] )\t ! disadvantages ( ! treatm5t ) sulphuric acid & z supplem5t>y to su* treatm5t 9 ! case ( r$-burn+ & "s o!r clays4 ,m rec5t inve/igators h f\nd t if a c>eful microscopic exam9ation ( ! clay is made ! results ( e/imat+ ! composition f ! proportion ( ! diff]5t m9]als recognizable "u ! microscope & by calculation f ! analysis ( ! mat]ial agree v closely & are1 z ,bis*( 7#bh7 &1 m rec5tly1 ,mellor h po9t$ out1 m reliable ?an ! 'rational analysis' 9 ! case ( impure clays4 ,if c>e is tak5 to make a microscopical exam9ation id5tify+ ! *ief impurities pres5t ! calculation f ! analysis may usually be accept$ z suffici5tly accurate1 b x is v unsatisfactory to assume1 z "s *emi/s d1 t ! alkalies & lime 9 ! clay are all 9 ! =m ( felsp> & t ! silica rema9+ 9 excess ( t requir$ to comb9e ) ! alkalies1 lime & alum9a is free qu>tz4 ,"s clays are almo/ de/itute ( felsp> b comp>atively ri* 9 mica1 :il/ o!rs are ! rev]se1 s t "s means ( id5tify+ ! extrane\s m9]als is ess5tial4 ,:5 ?is is n us$1 ! curi\s result is obta9$ t ,g]man *emi/s calculate ! alkalies1 etc4 to felsp> :il/ ! ,fr5* *emi/s1 foll[+ ,vogt1 calculate !m to mica2 ,engli% c]amic *emi/s appe> undecid$ z to :i* c\rse to foll[1 & "s ( !m occasionally report notable am\nts ( felsp> 9 clays q de/itute ( ?is m9]al6 ,a /atem5t ( ! composition ( a 'clay' bas$ on a me*anical sep>ation ( ! co>s] +r$i5ts foll[$ by an analysis ( ! f9] ones & a calculation ( ! probable con/itu5ts ( ! latt]1 z already describ$1 is kn[n z a proximate analysis 9 ord] to di/+ui% x f an ultimate analysis :i* /ates ! composition ( ! :ole mat]ial 9 t]ms ( its ultimate oxides4 ,a proximate analysis !re=e %[s ! v>i\s mat]ials ent]+ into ! composition ( ! clay 9 ! foll[+ or simil> t]ms3 ,/ones p] c5t4 ,gravel ,co>se s& ,m$ium s& ,f9e s& ,silt ,felsp> or mica du/ ,silica du/ ',true clay#ab' ,moi/ure ,c>bon ,o!r volatile matt] ,footnote #ab3 ,9 analytical reports a note %\ld be app5d$ /at+ t ! figure "u ?is t]m %[s ! proportion ( ! ne>e/ approximation to true clay at pres5t atta9able4 ,= "s purposes x is necess>y to %[ ! proportion ( calcium1 iron & o!r comp\nds z 9 an ord9>y ultimate analysis4 ,a comp>ison ( ! =ego+ ) an ultimate or 'ord9>y' analysis ( a clay 7p4 #af7 w %[ at once ! advantage ( ! =m] 9 increas+ our k ( ! ess5tial con/itu5t ( all clays1 if su* a sub/ance really exi/s4 ,its absolute exi/5ce is by no means prov$1 =1 z w h be5 notic$1 its composition is l>gely bas$ on assumption ev5 9 ! mo/ ?or\gh inve/igations1 p>ticul>ly ( ! admitt$ly less pure clays4 ,9 ! pur] clays ! problem is mu* simpl] & 9 _! case an answ] ( at lea/ approximate accuracy c be giv5 to ! "q ',:at is clay8' ,ev5 ) ^! pur] clays x is n suffici5t to /udy an analysis %[+ ! total am\nt ( ! silica1 alum9a & o!r oxides pres5t2 x is /ill necess>y to effect "s k9d ( sep>ation into ! v>i\s m9]als ( :i* !y are compos$4 ,:51 h[ev]1 ! accessory m9]als d n exce$ #e p] c5t4 ( ! total +r$i5ts _! influ5ce is less important & ! nature & *>act]i/ics ( ! 'clay sub/ance' itself c be m accurately /udi$4 ,by c>eful treatm5t ( well select$ *9a clays1 = example1 x is possible to obta9 a mat]ial correspond+ to ! =mula ,al#b,o#cb,si,o#bb;,h#b,o )9 a total error ( #a p] c5t41 ! small am\nt ( impurity be+1 z f> z c be asc]ta9$1 compos$ ( mica4 ,s pure a specim5 ( clay is f\nd on microscopical exam9ation to consi/ ( m9ute irregul> gra9s ( no def9ite =m1 toge!r ) a few cry/als ( ! same composition & id5tifiable z ! m9]al 'kaol9ite' 7p4 #ajg74 ,?is 'amorph\s' mat]ial1 :i* appe>s to be ! *ief con/itu5t ( all *9a clays & kaol9s1 has be5 t]m$ clayite by ,mellor 7#bb74 ,johnson & ,blake1 ,aron & o!r obs]v]s h /at$ t ! majority ( ! p>ticles 9 *9a clays & kaol9s are cry/all9e 9 =m4 ,ow+ to _! extreme smallness x is exce$+ly difficult to prove t !y are n s1 ?\gh = all ord9>y purposes !y may be reg>d$ z amorph\s1 ! proportion ( obvi\sly cry/all9e matt] pres5t 9 ,briti% *9a clay ( ! highe/ qualities be+ s small z to be negligible4 ,hickl+ 7#cf71 us+ an exceptionally p[]ful microscope1 claims to h id5tifi$ ?is 'amorph\s' sub/ance 9 *9a clay z 'worn & fragm5tal cry/als ( kaol9ite1' & rec5tly ,mellor & ,holdcr(t & ,rieke h %[n t ! app>5tly amorph\s mat]ial %[s ! same endo- & exo!rmal reactions z cry/all9e kaol9ite4 ,s f> z *9a clays or kaol9s are conc]n$1 kaol9ite or an amorph\s sub/ance ( ! same composition appe>s to be id5tical ) ! 'ideal clay' or 'true clay' ^: *>act]s h s long be5 s\ght4 ,?is t]m--clayite--is v conv5i5t :5 conf9$ to *9a clays & kaol9s1 b x is sc>cely legitimate to apply x1 z has be5 sugge/$1 to mat]ial 9 o!r clays until x has be5 isolat$ 9 a suffici5tly pure =m to enable its prop]ties to be accurately /udi$4 ,?is re/riction is ! m necess>y z 9 "o v important respect clayite obta9$ f *9a clay & "s kaol9s diff]s noticeably f ! ne>e/ approa* to x obta9able f ! m pla/ic clays3 namely1 9 its v l[ pla/icity4 ,?is may be expla9$ by ! fact t x is only obta9able 9 a reasonably pure =m 9 clays ( a prim>y "*1 :il/ ! pla/ic clays h usually be5 transport$ ov] consid]able areas & h be5 subject$ to a v>iety ( treatm5ts :i* h _h a m>k$ effect on _! physical "*4 ,moreov]1 ! fact t ! pure/ 'clay' :i* c be isolat$ f pla/ic clays appe>s to be amorph\s & to "s ext5t colloidal greatly increases ! difficulty ( obta9+ x 9 a pure /ate1 especially z no liquid is kn[n :i* w dissolve x )\t decompos+ x4 ,! fact t x is n an elem5t>y sub/ance1 b a complex comp\nd ( silica1 alum9a & ! elem5ts ( wat]1 also increases ! intricacy ( ! problem1 = ^! sub/ances occur 9 o!r comb9ations 9 a v>iety ( o!r m9]als :i* are cle>ly di/9ct f clay4 ,ev] s9ce ! publication ( ,seg]'s memorable pap]s 7#g71 & to a small ext5t be=e t "t1 x has be5 g5]ally und]/ood t *9a clay or kaol9 repres5t$ ! true ess5tial con/itu5t ( clays1 b sev]al inve/igators h be5 s imbu$ ) ! idea t all true clay sub/ance mu/ h a cry/all9e =m t !y h frequ5tly us$ ! t]m 'kaol9ite' to include ! 'amorph\s' sub/ance 9 pla/ic clays4 ,?is is un=tunate z x is by no means prov$ t ! latt] is id5tical ) kaol9ite1 & a di/9ctive t]m w\ld be ( value 9 prev5t+ confusion4 ,o!r inve/igators h us$ ! ^w 'kaol9' ) equal fre5ess1 s t :il/ x orig9ally ref]r$ to mat]ial f a p>ticul> hill or ridge 9 ,*9a#ac x has n[ ent]$ into g5]al use = all clays ^: composition approximates to t ( *9a clay 7p4 #af7 9 :i* ! pla/icity is n well develop$4 ,?us1 9 spite ( ! diff]5ce 9 orig9 betwe5 _m ,g]man & ,fr5* kaol9s & ! *9a clays ( ,cornwall1 x is ! cu/om 9 ,europe g5]ally to t]m all ^! mat]ials 'kaol94' ,yet !y are v diff]5t 9 _m respects f ! mat]ial orig9ally import$ f ,*9a4 ,footnote #ac3 ,kao-l+ is ,*9ese = a high ridge or hill4 ,z ! ess5tial clay sub/ance has n yet be5 isolat$ 9 a pure =m f ! mo/ widely spread pla/ic clays1 b is l>gely hypo!tical z f> z !y are conc]n$1 ! au?or pref]s ! t]m pel9ite#ad :5 ref]r+ to t portion ( any pla/ic clays or mixtures ( clays ) o!r m9]als :i* may be reg>d$ z be+ ! con/itu5t to :i* ! argillace\s portion ( ! mat]ial owes its *ief prop]ties4 ,9 *9a clay & kaol9 ! 'true clay' is id5tical ) clayite--or ev5 ) kaol9ite 7p4 #ajh7--;& !re is great probability t ?is id5tity also holds 9 ! case ( ! m pla/ic clays ( o!r geological =mations1 b until x is e/abli%$ x appe>s wise/ to di/+ui% ! hypo!tical or ideal clay common to all clays 7if !re is su* a sub/ance7 by diff]5t t]ms accord+ to ! ext5t to :i* its composition & *>act]s ( ! mat]ials mo/ closely resembl+ x are exp]im5tally kn[n4 ,footnote #ad3 ,f ! ,greek3 pl9os made ( clay4 ,! sub/ances mo/ resembl+ ?is 'ideal clay' :i* h1 up to ! pres5t be5 isolat$1 are3 7a7 ,kaol9ite4 ,f\nd 9 a cry/all9e =m 9 *9a clays & kaol9s 7p4 #ajg74 7b7 ,clayite4 ,a mat]ial ( ! same *emical composition z kaol9ite1 b ^: cry/all9e nature 7if x be cry/all9e7 has n be5 id5tifi$--*iefly obta9$ f *9a clays & kaol9s4 7c7 ,pel9ite4 ,a mat]ial simil> to clayite1 b diff]+ f x 9 be+ highly pla/ic &1 to "s ext5t1 ( a colloidal nature--obta9$ f pla/ic clays4 7d7 ,lat]ite4 ,a mat]ial resembl+ clayite 9 physical appe>ance1 b conta9+ free alum9a & free silica 7p4 #hj74 7e7 ,clay ,sub/ance4 ,a g5]al t]m indicat+ any ( ! =ego+ or a mixture ( !m2 x is also appli$ 7unwisely7 to ! mat]ial obta9$ :5 a natural clay is fre$ f its co>s] impurities by elutriation 7p4 #g74 ,! ,*ief ,*>act]i/ics ( ',true ,clay' f ,diff]5t ,s\rces4 ,9 s f> z x c be isolat$ true clay appe>s to be an amorph\s1 or practically amorph\s1 mat]ial :i* may "u suitable conditions cry/allize into rhombic plates ( kaol9ite4 ,! p>ticles ( :i* x is compos$ are extremely small1 be+ always less ?an #jjjjd 94 9 diamet]4 ,!y adsorb dyes f solutions & %[ o!r prop]ties *>act]i/ic ( colloid sub/ances ?\gh 9 a v v>iable degree1 "s clays appe>+ to conta9 a mu* l>g] proportion ( colloidal matt] ?an d o!rs4 ,to "s ext5t ! p[] ( adsorption ( salts & col\r+ matt]s appe>s to be connect$ ) ! pla/icity 7p4 #da7 ( ! mat]ial1 b ?is latt] prop]ty v>ies s greatly 9 clayite or pel9ite f diff]5t s\rces z to make any g5]alization impossible4 ,true clay sub/ance appe>s to be q :ite1 any col\r pres5t be+ almo/ inv>iably traceable to f]ric comp\nds or to c>bonace\s matt]4 ,! latt] is ( small importance to pott]s z x burns away 9 ! kiln4 ,! specific gravity ( clay sub/ance is #bfe accord+ to ,he*t1 ! l[] figures sometimes report$ be+ too l[4 ,its h>dness is usually less ?an t ( talc--! s(te/ sub/ance on ,mohs' scale--b "s %ales are s indurat$ z to scrat* qu>tz4 ,x is q insoluble 9 wat] & 9 dilute solutions ( acids or alkalies1 b is decompos$ by hydr(luoric acid & by conc5trat$ sulphuric acid :5 heat$1 alum9a ent]+ into solution & silica be+ precipitat$ 9 a colloidal condition4 ,x absorbs wat] easily until a def9ite /ate ( saturation has be5 rea*$1 aft] :i* x becomes imp]vi\s unless ! proportion ( wat] is s l>ge & ! "t ( exposure s great t ! mat]ial falls to an irregul> mass :i* may be conv]t$ into a slurry ( uni=m consi/5cy by g5tly /irr+ x4 ,) a mod]ate am\nt ( wat]1 pel9ite develops suffici5t pla/icity to enable x to be modell$ ) facility1 b clayite & "s specim5s ( pel9ite are some:at defici5t 9 ?is respect4 ,! pel9itic p>ticles usually possess ! capacity to reta9 _! pla/icity aft] be+ mix$ ) consid]able proportions ( s& or o!r non-pla/ic mat]ial & are !n said to possess a high b9d+ p[] 7p4 #bh74 ,if a l>ge proportion ( wat] is add$ to a sample ( clayite or pel9ite & ! mixture is /irr$ into a slurry x w be f\nd to rema9 turbid = a consid]able "t & w n become p]fectly cle> ev5 aft] ! lapse ( sev]al days4 ,its p[] ( rema9+ 9 susp5sion is mu* influ5c$ by ! pres5ce ( ev5 small am\nts ( soluble salts 9 ei!r ! wat] or ! clay sub/ance1 its precipitation be+ ha/5$ by ! addition ( su* salts z cause a p>tial coagulation ( ! colloidal matt] pres5t4 ,"s specim5s ( clayite & pel9ite reta9 _! susp5sibility ev5 9 ! pres5ce ( salts1 b ?is is only true ( a v limit$ proportion ( ! sub/ance4 ,9 mo/ cases ! pres5ce ( soluble salts causes ! l>g] p>ticles to s9k some:at rapidly & to c>ry ! f9] p>ticles ) !m4 ,! rate at :i* a slip or 'cream' made ( elutriat$ clay & wat] w fl[ ?r\gh a small orifice is dep5d5t on ! viscosity ( ! liquid & ?is 9 turn dep5ds on ! am\nt ( colloidal mat]ial pres5t1 i4e4 on h[ mu* ( ! clay 7pel9ite7 is 9 a colloidal =m4 ,its viscosity is greatly affect$ by ! addition or pres5ce ( small quantities ( acid or alkali or ( acidic or basic salts4 ,acids increase ! viscosity2 alkalies & basic salts1 on ! contr>y1 make ! slip m fluid4 ,neutral salts behave 9 diff]5t ways accord+ to ! conc5tration ( ! solution & to ! am\nt ( clay 7pel9ite7 pres5t 9 ! slip4 ,if ! slip conta9s s little wat] z to be 9 ! =m ( a ?9 pa/e1 neutral salts usually h b a small action1 b :5 ! slip conta9s only a small proportion ( clay 7pel9ite7 ! pres5ce ( neutral salts w t5d to cause ! precipitation ( ! clay4 ,9 ?is way salts act 9 two q diff]5t directions accord+ to ! conc5tration ( ! slip4 ,on dry+ a pa/e made ( clay & wat] ! volume gradually dim9i%es until ! great] "p ( ! wat] has be5 remov$2 aft] ?is ! rema9d] ( ! wat] may be driv5 (f )\t any fur!r r$uction 9 volume ( ! mat]ial4 ,?is is ano!r *>act]i/ic common to colloidal sub/ances su* z gelat94 ,! mat]ial :5 dry+ atta9s a lea!ry consi/5cy :i* is at a maximum at ! mom5t :5 ! %r9kage is ab\t to cease2 on fur!r dry+ ! mat]ial becomes h>d] & m closely resembles /one4 ,provid+ t wet clay is n heat$ to a temp]ature high] ?an t ( boil+ wat] x appe>s to und]go no *emical *ange & on cool+ x w aga9 take up wat]#ae & be re/or$ to its orig9al condition except 9 s f> z its colloidal nature may h be5 affect$ by ! heat+4 ,if1 h[ev]1 ! temp]ature is rais$ to ab\t #ejj ,c4 a decomposition ( ! mat]ial comm5ces & wat] is evolv$4 ,?is wat]--:i* is commonly t]m$ 'comb9$ wat]'--is app>5tly an ess5tial "p ( ! clay-molecule & :5 once x has be5 remov$ ! mo/ important *>act]i/ics ( ! clay are de/roy$ & _c be re/or$4 ,! reactions :i* occur :5 clay is heat$ are complex & are r5d]$ /ill m difficult to /udy by ! app>5t polym]ization ( ! alum9a =m$4 ,mellor & ,holdcr(t 7#bi7 h rec5tly inve/igat$ ! heat reactions ( ! pure/ *9a clay obta9able & confirm ,le ,*ateli]'s view 7#aj7 t on heat+ to temp]atures above #ejj ,c4 clay sub/ance decomposes into free silica1 free alum9a & wat]1 ! two =m] und]go+ a p>tial re-comb9ation ) =mation ( sillimanite 7,al#b,o#c,si,o#b7 if a temp]ature ( #abjj ,c4 is rea*$4 ,mellor & ,holdcr(t po9t out t !re is no critical po9t ( decomposition = clay sub/ance obta9$ f *9a clay1 z x appe>s to lose wat] at all temp]atures1 ?\gh its decomposition proce$s at s sl[ a rate bel[ #djj ,c4 z to be sc>cely appreciable4 ,footnote #ae3 ,"s clays are highly hygroscopic & absorb moi/ure readily f ! atmosph]e4 ,accord+ to ,seg] 7#g7 ?is hygroscopicity di/+ui%es true clay f silt & du/4 ,aft] ! :ole ( ! 'comb9$ wat]' has be5 driv5 (f1 if ! temp]ature cont9ues to rise1 x is f\nd t at a temp]ature ( #ijj ,c4 an evolution ( heat occurs4 ,?is exo!rmal po9t1 toge!r ) ! endo!rmal "o occurr+ at ! temp]ature at :i* ! decomposition ( ! clay seems to be mo/ rapid1 has be5 f\nd by ,le ,*ateli]1 confirm$ by ,mellor & ,holdcr(t1 to be *>act]i/ic ( clay sub/ance d]iv$ f kaol9 & *9a clay1 & ! two la/-nam$ inve/igators /ate t x s]ves z a means ( di/+ui%+ kaol9ite or clayite f o!r alum9o-silicates ( simil> composition4 ,^! !rmal reactions h n1 z yet1 be5 fully /udi$ 9 connection ) pla/ic clays2 ) *9a clay1 z already not$1 !y probably indicate a polym]ization ( ! alum9a set free by ! decomposition ( ! clay sub/ance1 z pure alum9a f a v>iety ( s\rces has be5 f\nd by ,mellor & ,holdcr(t to behave simil>ly4 ,on /ill fur!r rais+ ! temp]ature ( pure clay 7pel9ite or clayite7 no fur!r reactions ( importance occur1 ! mat]ial be+ practically infusible4 ,if1 h[ev]1 any silica1 lime1 magnesia1 alkalies1 iron oxide or o!r mat]ial capable ( comb9+ ) ! alum9a & silica is pres5t z impurities 9 ! clay sub/ance1 comb9ation beg9s at temp]atures above #ijj ,c4 ,?is causes a r$uction ( ! heat-resi/+ p[] ( ! mat]ial2 ! silicates & alum9o-silicates produc$ fuse & beg9 to react on ! rema9+ silica & alum9a1 fir/ =m+ an imp]meable mass 9 place ( ! por\s "o produc$ ) pure clay sub/ance1 & gradually1 z ! mat]ial loses its %ape1 produc+ a molt5 slag if ! 'clay' is suffici5tly impure4 ,z ord9>y clays are nev] q free f metallic comp\nds o!r ?an alum9a1 ?is =mation ( a fus$ portion--te*nically kn[n z vitrification 7p4 #cg7--occurs at temp]atures dep5d+ on ! nature ( ! mat]ials pres5t1 s t a wide range ( products is obta9$1 ! s]ies comm5c+ ) ! entirely unfus$ pure clay 7*9a clay71 pass+ ?r\gh ! slightly vitrifi$ fireclays1 ! m completely vitrifi$ ball clays to ! vitrifiable /onew>e clays & end+ ) mat]ials s ri* 9 easily fusible matt] z sc>cely to be wor?y ( ! "n ( clays4 ,! con/itution ( ! clay molecule is a subject :i* has attract$ ! att5tion ( _m inve/igators & is be+ closely /udi$ at ! pres5t "t4 ,x is a subject ( peculi> difficulty ow+ to ! in]tness ( clay sub/ance at all b high temp]atures1 & to ! complexity ( reactions :i* take place z soon z any reag5t is br\ght into active connection ) x4 ,)\t ent]+ into details reg>d+ ! v>i\s graphic =mulae :i* h be5 sugge/$1 x is suffici5t to /ate t ! "o :i* is mo/ probably correct1 z f> z pres5t k goes1 is ,mellor's & ,holdcr(t's re-arrangem5t ( ,gro?'s =mula 7#cj7 ,,ho _/,o,si,o ,al#b_/ ,o _/ _/ ,,ho_/ _/ ,o,si,o_/ _/ ,,ho ,,oh :i* on removal ( ! hydroxyl gr\ps might be expect$ to give ! anhydride ,o _/,o,si,o ,al#b_/ _/_/ _/ ,o_/_/ ,o,si,o_/ ?\gh 9 practice ?is sub/ance--if =m$ at all--appe>s to be in/antly split up into ,al#b,o#c & ,si,o#b4 ,by reg>d+ ! alum9ium z a nucleus1 z above1 & "s alum9ium silicates z hypo!tical alum9o-silicic acids1 z sugge/$ by ,ulff]s1 ,s*>iz]1 ,morozewicz 7#bi7 & o!rs1 clay sub/ance may be conv5i5tly consid]$1 along ) analog\s sub/ances1 z =m+ a special gr\p q di/9ct f ! ord9>y silicates4 ,9 ?is way ,mellor & ,holdcr(t 7#bi7 consid] t clay sub/ance is n a hydrat$ alum9ium silicate--z is usually /at$ 9 ! text-books--b an alum9o-silicic acid1 ! salts ( :i* are ! zeolites & relat$ comp\nds4 ,f ?is hypo!sis x naturally foll[s t clay sub/ance is analog\s to colloidal silica :i* has be5 =m$ by ! decomposition ( a silicate by means ( wat] & an acid4 ,if ?is view be correct1 pure clay sub/ance or true clay is a tetra-basic alum9o-silicic acid ,h#d;,al#b,si,o#i or ,al#b,si#b,o#e7j;,h#d74 ,t its acid prop]ties are n readily recognizable at ord9>y temp]atures is due to its in]tness2 at high] temp]atures its p[] ( comb9ation ) lime1 soda pota% & o!r bases is well recogniz$1 ?\gh ! reactions :i* occur are (t5 complicat$ by decompositions & molecul> re-arrangem5ts :i* occur 9 consequ5ce ( ! elevat$ temp]ature4 ,!re are a numb] ( m9]als :i* closely resemble clayite or pure clay sub/ance 9 composition1 ! *ief diff]5ce be+ 9 ! proportion ( wat] !y evolve on be+ heat$4 ,?us ,rectorite ,h#b;,al#b,si#b,o#h1 ,kaol9ite ,h#d;,al#b,si#b,o#i1 ,halloysite ,h#f;,al#b,si#b,o#aj & ,newtonite ,h#aj;,al#b,si#b,o#ab4 ,9 ! cry/all9e =m ^! m9]als may be di/+ui%$ f ea* o!r by means ( ! microscope1 b z ! *ief mat]ials ( :i* clays are compos$ appe>s to be amorph\s x is impossible to asc]ta9 ) c]ta9ty :e!r a giv5 specim5 ( clay sub/ance is compos$ ( a mixture ( ^! analog\s m9]als 9 an amorph\s =m or :e!r x consi/s entirely ( clayite1 i4e4 ! clay sub/ance obta9$ f *9a clay4 ,z already /at$1 ! !rmal reactions :i* occur on heat+ clayite appe> to be *>act]i/ic ( kaol9ite :il/ halloysite is completely decompos$ at a temp]ature some:at bel[ #bjj ,c42 b ! n improbable pres5ce ( two or m ( ^! alum9o-silicic acids 9 clays ( second>y or mult>y orig9 makes x almo/ impossible to det]m9e :e!r clayite is an ess5tial con/itu5t ( all clays or :e!r ! pure/ clay sub/ance 7pel9ite7 obta9$ f "s ( ! m pla/ic clays does n possess a diff]5t *emical composition z well z diff]5t physical prop]ties4 ,! view t clays may be reg>d$ z impure v>ieties ( clayite is consid]$ errone\s by sev]al inve/igators = v>i\s reasons4 ,= in/ance1 felsp> is r>ely f\nd 9 *9a clays1 b is a common con/itu5t ( second>y 7pla/ic7 clays4 ,j4 ,m4 van ,bemmel5 7#bf71 :o has f\nd t ! alum9a-silica ratio ( clays produc$ by wea!r+ is always high] ?an t 9 clays ( ! *9a clay type produc$ by hypog5ic action4 ,9 a numb] ( clays exam9$ he f\nd t a portion 0 soluble 9 boil+ hydro*loric acid :]eas clayite is sc>cely affect$ by ?is treatm5t4 ,he also f\nd a v>y+ proportion ( alum9o-silicate insoluble 9 hydro*loric acid b dissolv$ on treatm5t ) boil+ sulphuric acid & subsequ5tly ) cau/ic soda solution2 ?is latt] he consid]s to be true clayite4 ,un=tunately1 8 results 7 obta9$ by treat+ ! crude clay ) acid1 in/ead ( fir/ remov+ su* non-pla/ic mat]ials z c be sep>at$ by wa%+1 s t all t !y %[ is t "s clays conta9 alum9o-silicates ( a nature di/9ct f clayite 9 addition to any clayite :i* may be f\nd 9 !m4 ,! fact t all clays :5 heat$ to #gjj or #hjj ,c4 readily react ) lime-wat] to =m ! same calcium silicates & alum9ates indicates s close a resemblance betwe5 ! clay sub/ance obta9able f diff]5t s\rces z to con/itute /rong evid5ce ( ! id5tity ( ?is sub/ance ) clayite or ) mat]ials s analog\s to x z to be indi/+ui%able f x "u pres5t conditions4 ,9 all probability1 ! pla/ic clays h be5 d]iv$ f a some:at great] v>iety ( m9]als ?an ! prim>y clays 7p4 #ga7 & "u conditions ( decomposition :i* diff] 9 details1 ?\gh broadly ( ! same nature z ^? produc+ *9a clays4 ,! pres5ce ( colloidal matt] sugge/s a m vigor\s action--or ev5 a precipitation f solution--in/ead ( ! sl[] reactions :i* result 9 ! =mation ( ! kaol9ite cry/als4 ,! mu* small] p>ticles pres5t 9 pla/ic clays also indicate a m complete gr9d+ dur+ ! transportation ( ! mat]ial or "s =m ( precipitation4 ,if1 z ,hickl+ sugge/s1 all clays are direct products ( ! decomposition ( mica1 ! fact t sev]al v>ieties ( mica are kn[n & t ! conditions "u :i* ^! decompose mu/ v>y consid]ably1 af=d a good1 if incomplete1 explanation ( "s ( ! widely div]se *>act]i/ics obs]v$ 9 diff]5t clays4 ,not)/&+ ! great complexities ( ! :ole subject & ! app>5tly contradictory evid5ce conc]n+ "s clays1 !re is a wide-spread feel+ t :atev] may be ! m9]al f :i* a giv5 clay has be5 d]iv$1 ! true clay sub/ance1 :i* is its ess5tial con/itu5t1 w\ld 7if x c\ld be isolat$ 9 a pure /ate7 prove to be ( ! same composition z kaol9ite obta9able f *9a clay ( exceptional purity4 ,! pure/ clay sub/ances 7pel9ite7 yet obta9$ f "s ( ! mo/ pla/ic clays are1 h[ev]1 s impure z to make any detail$ inve/igation ( _! composition by pres5t me?ods abortive4 ,! me?ods ( syn!sis :i* h prov$ s successful 9 organic *emi/ry h hi!rto yield$ few intelligible results ) clays1 on acc\nt ( ! complexity ( ! accessory reactions :i* occur4 ,! ,diff]5ce betwe5 ,pure ,clay ,sub/ance & ,ord9>y ,clays4 ,! prop]ties & *>act]i/ics ( true clay are v s]i\sly modifi$ by o!r mat]ials :i* may be associat$ ) x4 ,?is may be p]ceiv$ by comp>+ ! prop]ties ( clays m5tion$ 9 ,*apt] ,i ) ^? ( v>i\s =ms ( true clay j giv54 ,moreov]1 z true clay nev] occurs 9 a p]fectly pure /ate 9 nature1 ! prop]ties ( clays mu/ be l>gely dep5d5t on ! accessory +r$i5ts4 ,silica1 = example1 :5 alone is a highly refractory mat]ial1 b 9 ! pres5ce ( true clay x r$uces ! refractor9ess ( ! latt]4 ,lime has a simil> effect ?\gh its *emical action on ! clay is entirely diff]5t4 ,a v small proportion ( "s sub/ances--notably ! oxides ( sodium & potassium--w greatly alt] ! behavi\r ( true clay :5 heat$ & w produce an imp]vi\s mass 9 place ( a por\s "o4 ,= ^! reasons1 x is necess>y 9 /udy+ clays to pay att5tion to bo? _! physical & *emical prop]ties & to sep>ate ! mat]ial into fractions s t ea* ( ^! may be /udi$ sep>ately & _! individual z well z _! collective *>act]i/ics asc]ta9$4 ,failure to d ?is has be5 ! cause ( mu* obscurity & confusion 9 inve/igations on c]ta9 clays compos$ ( a consid]able proportion ( non-argillace\s mat]ial :i* ought to h be5 sep>at$ be=e any attempt 0 made to /udy ! true clay pres5t4 ,!re is1 !re=e1 a consid]able diff]5ce betwe5 a natural clay & ! pure clay sub/ance !oretically obta9able f x2 ?is diff]5ce be+ mo/ m>k$ 9 ! case ( l[-grade brick clays ( glacial orig91 :i* may conta9 #ej p] c5t4 or m ( adv5titi\s mat]ials4 ,if us$ 9 a natural /ate !y w\ld be f\nd to be valueless on acc\nt ( _! impurities giv+ !m *>act]i/ics ( a highly undesirable "*1 :]eas ! true clay 9 !m is f\nd--9 s f> z x c be sep>at$--to be> a close resemblance to t obta9$ f a high grade1 pla/ic1 pott]y clay4 ,un=tunately1 x is1 at pres5t1 impossible to isolate ?is clay sub/ance 9 any?+ approa*+ a pure =m1 & _m clays are )\t comm]cial value because ( comp>atively small proportions ( impurities :i* _c be sep>at$ f ! clay sub/ance )\t de/roy+ ! latt]4 ,classification ( ,clays4 ,ow+ to ! widely diff]+ sub/ances f :i* clays c1 app>5tly1 be =m$ & ! peculi> difficulties :i* are exp]i5c$ 9 inve/igat+ ! nature ( clay sub/ance f diff]5t s\rces1 x is by no means easy to devise a s*eme ( classification ( clays1 ?\gh _m ( ^! h be5 attempt$ by diff]5t sci5ti/s4 ,! classification adopt$ by geologi/s is bas$ on ! fossil rema9s & on ! /ratigraphical position ( clays relative to o!r rocks1 z describ$ 9 ,*apt] ,,ii4 ,?is is ( great value = "s purposes1 b ! composition ( ! sub/ances t]m$ 'clay' by geologi/s diff]s s greatly1 ev5 :5 only "o =mation is consid]$1 z to make _! classification ( little or no use :]e ! value or wor?lessness ( ! mat]ial dep5ds ^u its composition4 ,?us ! s-call$ ,ox=d clay ranges f a h>d silici\s %ale to a comp>atively pure clay2 "s portions ( x are s contam9at$ ) calc>e\s & f]rug9\s matt] z to make ! mat]ial q useless = ! pott] or claywork]4 ,a geological classification ( clays is *iefly ( value z indicat+ probable orig9s1 impurities & c]ta9 physical prop]ties2 b ! limits ( composition & g5]al *>act]i/ics are s wide z to make x ( v limit$ usefulness4 ,! classification ( clays on a basis ( *emical composition is r5d]$ ( comp>atively little value by ! l>ge numb] ( clays :i* occupy ill-def9$ bord]s betwe5 ! m cle>ly m>k$ classes4 ,moreov]1 attempts to pr$ict ! value & uses ( clays f _! *emical composition are g5]ally s mislead+ z to be worse ?an useless1 unless a k ( "s ( ! physical *>act]s ( ! clays is available4 ,x is1 ( c\rse1 possible to diff]5tiate "s clays f o!rs by _! composition1 b n ) suffici5t accuracy to p]mit ( def9ite & accurate classification4 ,a classification bas$ exclusively on ! composition ( clays is equally unsatisfactory = o!r reasons1 ! *ief ( :i* is ! plac+ toge!r ( clays ( widely diff]+ physical "*1 & ! sep>ation ( clays capable ( be+ us$ = a p>ticul> purpose4 ,to "s ext5t ! latt] objection may be disreg>d$1 ?\gh x is ( great importance 9 consid]+ ! comm]cial value ( a clay4 ,classification bas$ on ! uses ( clays ( diff]5t k9ds has be5 sugge/$ by sev]al em95t c]ami/s1 b is obvi\sly unsatisfactory1 p>ticul>ly z x is by no means uncommon to use mixtures ( clays & o!r m9]als = "s purposes4 ,?us /onew>e clays mu/ be vitrifiable "u conditions :i* may be def9$ ) suffici5t accuracy1 b _m manufactur]s ( /onew>e d n use clays :i* are naturally vitrifiable2 !y employ a mixture ( refractory clay & o!r m9]als to obta9 ! mat]ial !y require4 ,a classification bas$ on ! orig9 ( clays reg>d$ f ! petrological po9t ( view (f]s "s advantages1 b is too cumb]some = ord9>y purposes & suff]s f ! disadvantage t ! orig9 ( "s important clays is by no means cle>ly kn[n4 ,! au?or pref]s a modification ( ,grimsley's & ,gr\t's classification 7#ca7 z foll[s3 ,i4 ,prim>y clays4 7a7 ,clays produc$ by 'wea!r+' silicates--z "s kaol9s4 7b7 ,clays produc$ by lat]itic action--v ri* 9 alum9a1 "s ( :i* is app>5tly 9 a free /ate4 7c7 ,clays produc$ by telluric wat] conta9+ active gases 7hypog5ically =m$ clays7--z ,corni% *9a clay4 ,,ii4 ,second>y clays4 7d7 ,refractory#af second>y clays--z fireclays & "s pipe clays4 7e7 ,pale-burn+ non-refractory clays--z pott]y clays1 ball clays & "s %ales4 7f7 ,vitrifiable clays--z /onew>e clays1 pav+ brick clays4 7g7 ,r$-burn+ & non-refractory clays--z brick & t]ra-cotta clays & %ales4 7h7 ,calc>e\s clays or m>ls1 includ+ all clays conta9+ m ?an #e p] c5t4 ( calcium c>bonate4 ,,iii4 ,residual clays4 7i7 ,clays :i* h be5 =m$ by "o ( ! =ego+ actions & h be5 deposit$ along ) calc>e\s or o!r matt] b1 on ! latt] be+ remov$ by subsequ5t solution1 ! clay has rema9$ beh9d--z ! :ite clays ( ! ,d]by%ire hills4 ,footnote #af3 ,a refractory clay is "o :i* does n s(t5 suffici5tly to comm5ce los+ its %ape at any temp]ature bel[ t ne$$ to b5d ,seg] ,cone #bf 7approximately #afjj;,c47 7see p4 #aaf74 ,"s fur!r sub-division is necess>y = special purposes1 p>ticul>ly 9 sections e1 f & h1 b to include fur!r details w\ld only obscure ! g5]al s*eme4 ,"s clays w1 app>5tly1 be capable ( classification 9 m ?an "o section1 ?us a vitrifiable clay may owe its *>act]i/ic to a high proportion ( calcium c>bonate & s be capable ( inclusion z a calc>e\s clay4 ,broadly speak+1 h[ev]1 if ! clay is te/$ z to its inclusion 9 ea* section ( ! s*eme 9 turn x w be f\nd t its highe/ value w be 9 ! section :i* is ne>e/ to ! fir/ 9 :i* ! clay c legitimately be plac$4 ,f a consid]ation ( a classification su* z ! =ego+1 toge!r ) a detail$ /udy ( ! physical & *emical prop]ties ( ! mat]ial z a :ole1 & also ( ! v>i\s portions into :i* x may be divid$--p>ticul>ly t :i* has be5 isolat$ by me*anical me?ods ( purification & sep>ation--x is n difficult to ga9 a fairly accurate idea ( ! nature ( any clay4 ,al?\gh ! pres5t /ate ( k does n p]mit !m to be classifi$ ) su* detail z is ! case ) plants1 animals1 or simple *emical comp\nds1 ! /udy ( clays & ! alli$ mat]ials has a fasc9ation peculi>ly its own1 n ! lea/ int]e/+ features ( :i* are ^? prop]ties ( ! clay aft] x has be5 made into articles ( use or ornam5t4 ,^! are1 h[ev]1 beyond ! scope ( :at is commonly und]/ood by ! t]m '! natural hi/ory ( clay4' ,,bibliography ,a complete bibliography ( clay w\ld occupy sev]al volumes4 ,! foll[+ li/ only includes ! m accessible ( ! works quot$ 9 ! text4 #a4 ,second ,report ( ! ,committee on ,te*nical ,inve/igation--,rle ( ,iron 9 ,burn+ ,clays4 ,orton & ,griffi?4 ,indianapolis4 #aije4 #b4 ,briti% ,clays1 ,%ales & ,s&s4 ,alfr$ ,b4 ,se>le4 ,*>les ,griff9 & ,co4 ,ltd4 ,london4 #aiaa4 #c4 ,transactions ( ! ,engli% ,c]amic ,society4 v4 p4 #gb4 ,hughes & ,h>b]4 ,longton1 ,/affs4 #aije4 #d4 ,royal ,agricultural ,society's ,j\rnal4 ,,xi4 #e4 ,die ,tone4 ,p4 ,rohl&4 ,h>tleb5's ,v]lag4 ,vi5na4 #aiji4 #f4 ,clays3 _! ,occurr5ce1 ,prop]ties & ,uses4 ,h4 ,ries4 ,*apman & ,hall4 ,london4 #aijh4 #g4 ,gesammelte ,s*rift54 ,h4 ,seg]4 ,ton9du/rie ,zeitung ,v]lag4 ,b]l94 #aijh4 #h4 ,ton9du/rie ,zeitung4 #aijb4 p4 #ajfd4 #i4 ,ton9du/rie ,zeitung4 #aijd4 p4 #ggc4 #aj4 ,treatise on ,c]amic ,indu/ries4 ,e4 ,b\rry 7,revis$ translation by ,a4 ,b4 ,se>le74 ,scott1 ,gre5wood & ,son4 ,london4 #aiaa4 #aa4 ,! ,colloid ,matt] ( ,clay4 ,h4 ,e4 ,a%ley4 ,u4,s4,a4 ,geological ,survey ,bullet9 #chh4 ,wa%+ton4 #aiji4 #ab4 ,spre*saal4 #aije4 p4 #abc4 #ac4 ,action ( ,heat on ,refractory ,mat]ials4 ,j4 ,w4 ,mellor & ,f4 ,j4 ,au/54 ,trans4 ,eng4 ,c]4 ,soc4 ,,vi4 ,hughes & ,h>b]4 ,longton1 ,/affs4 #aijf4 #ad4 ,wi$]mann's ,annal54 ,,vii4 p4 #ccg4 #ae4 ,geological ,contemporaneity4 #ahfb4 #af4 ,geological ,magaz9e4 ,,iv4 pp4 #bda1 #bii4 #ag4 ,la ,cramique indu/rielle4 ,a4 ,grang]4 ,gau?i] ,frres4 ,p>is4 #aije4 #ah4 ,am]ican ,j\rnal ( ,sci5ce4 #ahga4 p4 #ahj4 #ai4 ,! ,h5sb>r[ ,di/rict4 ,j4 ,h4 ,coll9s4 ,geological ,survey4 #ahgh4 #bj4 ,monographs ( ! ,u4,s4,a4 ,geological ,survey4 ,,xxviii4 ,c4 ,r4 van ,hise4 #ahig4 #ba4 ,on ,kaol9ite & ,phol]ite4 ,am]ican ,j\rnal ( ,sci5ce4 ,,xliii4 #ahfg4 #bb4 ,! ,nom5clature ( ,clays4 ,j4 ,w4 ,mellor4 ,eng4 ,c]4 ,soc4 ,,viii4 ,hughes & ,h>b]4 ,longton1 ,/affs4 #aijh4 #bc4 ,on ! pres5t di/ribution ( ,coal ,balls4 ,m4 ,c4 ,/opes & ,d4 ,m4 ,s4 ,watson4 ,phil4 ,trans4 ,royal ,society4 ,b4 ,vol4 ,,cc4 #aijh4 #bd4 ,natural ,hi/ory ( ,coal4 ,e4 ,a4 ,n4 ,arb]4 ,cambridge ,univ]sity ,press4 #aiaa4 #be4 ,mod]n ,brickmak+4 ,a4 ,b4 ,se>le4 ,scott1 ,gre5wood & ,son4 ,london4 #aiaa4 #bf4 ,die v]s*i$5e ,art5 d] ,v]witt]ung4 ,j4 ,m4 van ,bemmel54 ,zeits4 angew&te ,*emie4 ,,lxvi4 ,leopold ,voss ,v]lag4 ,hamburg4 #aiaj4 #bg4 ,pyrometris*e ,beleu*tung4 ,c>l ,bis*(4 ,ton9du/rie ,zeitung4 #ahgg4 #bh4 ,die feu]fe/e ,tone4 ,c>l ,bis*(4 ,qu&t & ,ha5dl]4 ,leipzig4 #aijd4 #bi4 ,! ,*emical ,con/itution ( ! ,kaol9ite ,molecule4 ,trans4 ,eng4 ,c]4 ,soc4 ,x4 ,hughes & ,h>b]4 ,longton1 ,/affs4 #aiaa4 #cj4 ,tabell>is*e ,ueb]si*t d] ,m9]ali54 ,p4 ,gro?4 ,brunswick4 #ahih4 #ca4 ,we/ ,virg9ia ,geological ,survey4 ,,iii4 #aijf4 #cb4 ,memoirs ( ! ,geological ,survey4 ,london4 #cc4 ,! ,publications ( ,/an=d's ,geographical ,in/itute4 ,london4 #cd4 ,h&bu* d] gesam4 ,tonw>59du/rie4 ,b4 ,k]l4 ,v]lag d] ,ton9du/rie ,zeitung4 #aiaj4 #ce4 ,causal ,geology4 ,e4 ,h4 ,l4 ,s*w>z4 ,blackie & ,sons1 ,ltd4 #aiaj4 #cf4 ,*9a ,clay3 its nature & orig94 ,g4 ,hickl+4 ,trans4 ,in/4 ,m9+ ,eng9e]s4 #aijh4 ,,index ,absorption1 #dj1 #aea ,absorptive p[] ( clays1 #dj ,accumulation ( clays1 #hd ,acid-pro( w>e1 #aac ,acids1 effect (1 #ajf1 #aea1 #aeb ,adsorption1 #dj1 #aej ,agriculture1 clays 91 #e1 #ef1 #eg1 #ei1 #fa1 #fb1 #fc1 #fg ,air1 #dc1 #he ,alkalies 9 clay1 #ch1 #aae1 #acc1 #adb1 #adc1 #aee ,alluvial deposits1 #fh1 #hg1 #aab1 #acb ,alum clays & %ales1 #eg1 #abc1 #abd ,alum manufacture1 clays =1 #abd ,alum9a1 #f ,alum9a1 free1 #hj1 #hb1 #aed ,alum9a-silica ratio1 #acc1 #aei ,alum9o-silicic acid1 #f1 #gf1 #ha1 #aah1 #aee1 #aeg ,alum9\s clays1 #hb1 #aag ',amorph\s' clay1 #ajg1 #adf ,analyses ( clays1 #af1 #ada1 #add ,anauxite1 #acd ,ar*itectural w>e1 #abi1 #acj ,argillace\s e>?s1 #a ,argillace\s lime/one1 #hh1 #acb ,associat$ rocks1 #dh ,bag%ot clays & s&s1 #fd1 #abe ,ball clays1 #f1 #ai1 #bh1 #fb1 #fd1 #hb1 #aaj1 #aae1 #aai1 #abe1 #ach1 #ada1 #aef1 #aff ,b5d+ ( clay1 #cc ,bibliography1 #afh ,b9d+ p[]1 #bh1 #aea ,b9ds1 #ec ,bitum9\s %ales1 #eg1 #ei ,black spots1 #ad1 #abh ,black w>e1 #aac ,blea*+ oil1 #acd ,blue bricks1 #ac1 #ef ,bone-a%1 #aaj ,b\ld] clays1 #c1 #g1 #aj1 #fe1 #aja ,bovey ,tracey clay1 #fb ,brick clays1 e>?s & %ales1 #a1 #b1 #e1 #aj1 #aa1 #ab1 #ac1 #ca1 #cg1 #dj1 #df1 #ef1 #eg1 #ei1 #fa1 #fc1 #fe1 #fg1 #fh1 #ia1 #ajj1 #aja1 #ajd1 #aab1 #aag1 #abc1 #abe1 #abi1 #ach1 #afb1 #aff ,brittl5ess1 #df ,br[n w>e1 #aac ,buff bricks1 #abh ,burn$ clay1 #bh1 #ca1 #da1 #aai1 #aba ,calc>e\s clays1 #ch1 #fa1 #fh1 #hh1 #acc1 #aci1 #aff ,calc>e\s s&s1 #hh ,calcium1 see ,lime comp\nds ,cambrian clays1 #ea ,c>bon 9 clay1 #ae1 #aai1 #add ,c>bonates 9 clay1 #aj1 #hb ,c>bonif]\s clays & %ales1 #eb1 #abd ,c>bonif]\s lime/one1 #eb1 #ajh ,c>clazite1 #gh1 #ajf ,cellulose 9 clays1 #bg ,cem5t clays1 #eg1 #ajd1 #aca ,*alcopyrite1 #ad ,*alk1 #aj1 #aa1 #fa1 #fg1 #fh1 #hh1 #aaf1 #abg1 #abh1 #acb1 #acd1 #aci ,*amotte1 #aba ,*emical prop]ties ( clay1 #f ,*9a clay rock1 #gh1 #ajf1 #aaf ,*9a clays1 #b1 #e1 #f1 #g1 #i1 #bb1 #bg1 #dj1 #di1 #fd1 #ga1 #ge1 #gh1 #hb1 #hd1 #ajd1 #aaj1 #aaf1 #ada1 #adf1 #adg1 #adh1 #aef1 #afe ,*9a-w>e1 #aji1 #aaj ,*9ese clay1 #gc ,classification ( clays1 #afc ,clay molecule1 #aef ,clay-%ales1 #abb ,clay sub/ance1 #ace et seq4 ,clay sub/ance1 def9$1 #aej ,clayite1 #hc1 #ajg1 #adg1 #adi ,cl9k]1 #acb ,clun*es1 #aah ,coagulat$ clays1 #ig ,coagulation1 #dc1 #aeb ,coal ,measure clays & %ales1 #ec1 #if1 #ajc1 #aag1 #abd1 #acj ,co>se pott]y1 #aab ,cobalt1 #aaj ,colloid !ory1 #ig ,colloidal prop]ties ( clay1 #be1 #ha1 #hb1 #ig1 #ajf1 #adg1 #aej1 #aeb ,colloidal silica1 #ha1 #acd1 #aeg ,colloids1 #bd1 #da1 #dc1 #gf1 #afj ,colluvial clays1 #ii ,col\rs ( burn$ w>e1 #ai1 #abc1 #aca ,col\rs ( clays & %ales1 #ai1 #ei1 #aae1 #aai1 #abd1 #abf ,comb9$ wat]1 #de1 #aed ,common clays1 #c ,composition ( clays1 #d1 #f1 #af1 #bc1 #ce1 #dd1 #ajg1 #aag1 #aah1 #acc1 #acd1 #add1 #aef1 #afd ,composition ( clays 7burn$71 #df ,corni% /one1 #aaj1 #aaf ,crack$ w>e1 #df1 #abg1 #acj1 #aca ',cream1' #ci1 #dc1 #aeb ,cretace\s clays1 #fa ',crumb' ( clay1 #bd ,cru%+ clay1 #de ',cry/all9e' clay1 #ajg1 #adf1 #adh ,cry/als 9 clay-w>e1 #df ,decantation1 #aci ,decomposition ( clay1 #aed ,def9itions ( clay1 #b-e1 #abj1 #ace1 #adi1 #aej ,de-greas+ wool1 #acd ,deposition ( clays1 #di1 #ea1 #ij1 #ii ,devonian clays1 #ea ,diluvial clays1 #ii ,d9as rock1 #ed ,dis9tegration1 #ajb ,di/ribution ( clays1 #a ,dra9-pipe clays1 #aab1 #aac ,drift1 #fe1 #aja ,drift clays1 #aja ,dry+ clays1 #bg1 #abg1 #aec ,durability1 #aca ,dyes1 #da1 #aej ,e>? movem5ts1 #he1 #if ,e>!nw>e1 #cg1 #aab ,e>?s = bricks1 see ,brick clays ,electrolytes1 #dc ,elutriation1 #h1 #acg1 #adj ,eoc5e clays1 #fc ,epig5ic clays1 #hb ,erosion1 #hi1 #ii1 #ajj ,e/u>9e clays1 #ij1 #ic1 #aah ,etruria m>ls1 #ee1 #acj ,expansion1 #cb ,exposure1 #dc ,fai5ce1 #abi ,f>ewell ,rock1 #ed ,fat clays1 #bi ,felsp>1 #g1 #h1 #da1 #gd1 #ajd1 #aaj1 #aaf1 #ada1 #add1 #aei ,f]ric & ,f]r\s comp\nds1 #ab1 #aba1 see ,iron ,f9e clays1 #aab ,f95ess1 see ,texture ,firebricks1 #ad1 #ed1 #fa1 #aaf ,fireclay1 #cc1 #ce1 #eb1 #ed1 #hb1 #ajd1 #ajh1 #aaf1 #abc1 #aef1 #aff ,fissile clays1 #aag ,fl9t1 #aaj1 #aaf ,fl9t clays1 #aag ,floods1 #he1 #hg1 #ii ,fl[]-pot clays1 #eg1 #aaj ,fluoric vap\rs1 #ge1 #gg1 #afe ,fluviatile clays1 #hh1 #ib ,fluxes1 #h1 #aa1 #ch1 #ci1 #aae1 #aaf1 #aca ,food-clays1 #a ,=mation ( clays1 #dh1 #gj ,=mula ( clay1 #aef ,free alum9a1 #hj1 #aed ,free silica1 #g1 #hj1 #aed1 #afa ,fro/1 #dc1 #hf ,full]'s e>?1 #ei1 #acc ,full+ clo?1 #a1 #acc ,fusibility1 #cb1 #eh1 #aac1 #aaf ,fusible clays1 #aaf ,fus+ po9t1 #cb ,fusion1 #dg1 #aac1 #abj1 #acb1 #aee ,gani/]1 #eb1 #ed1 #aah ,gault1 #fa1 #acb ,geological classification1 #afc ,geological nature ( clay1 #d1 #ej ,glacial clays1 #fe1 #ajj1 #afb ,glaci]s1 #he1 #hi1 #ajj ,glass1 #aaf ,glassy /ructure1 #dg ,glaz$ bricks1 #aai ,glaz$ pott]y1 #abi ,glaz$ t]ra-cotta1 #ef1 #abi ,grades ( fireclay1 #abj ,gravel1 #g1 #fb1 #fe1 #hi1 #ajj1 #aja1 #ajb1 #ach1 #add ,gre5 col\r1 #ad ,gre5s&1 #acc ,gr9d+1 #hj1 #aba ,grit1 #aab1 see also ,mill/one ,grit ,grog1 #bh1 #ca1 #da1 #aai1 #aba ,gr[an1 #gh ,gypsum1 #aj1 #ab1 #fb ,halloysite1 #aah1 #aeh ,h>dness1 #de ,heat1 effects (1 #bh1 #cg1 #ci1 #de1 #hj1 #abb1 #adf1 #aec1 #aed1 #aeh1 #aei ,hydr>gillite1 #hj ,hydro-alum9o-silicates1 #f ,hydroc>bons 9 clay1 #ae ,hydrolysis1 #gh1 #ig ,hygroscopic clays1 #aec ,hypog5ic clays1 #afe ,ice-action1 #he1 #ajj ,ideal clay1 #adf ,imp]meability1 #dj1 #aac ,imp]vi\s articles1 #aac1 #aee ,impurities 9 clays1 #g1 #di1 #hb1 #ajb1 #ajd1 #aji1 #aba1 #abf1 #adb1 #adc1 #aee1 #afb1 #afc ,ions1 #dc ,indurat$ clays1 #ah ,infusibility1 #ajf1 #aai1 see ,refractor9ess ,iron comp\nds1 #g1 #aj1 #ab1 #ac1 #bj1 #fb1 #aab1 #aai1 #aba1 #abh1 #acc1 #ada1 #ade1 #afd ,iron/one1 #fb ,irregul>ity 9 %ape1 #aca ,jurassic clays & %ales1 #eg1 #abd ,kao-l+1 #adh ,kaol9ite1 #ai1 #hj1 #aje1 #ajg1 #adf1 #adi1 #aeh ,kaol9ization1 #gf1 #gg1 #gi ,kaol9s1 #i1 #ba1 #di1 #fd1 #ga1 #gc1 #gf1 #gi1 #hb1 #hd1 #ajd1 #aaf1 #ada1 #adf1 #adg1 #adh1 #afe ,keele s]ies1 #ee ,kellaways clay1 #ei1 #fa ,keup] m>ls1 #eg ,kiln %r9kage1 #cj ,kim]idge clays1 #ei ,knotts1 #abd ,lacu/r9e clays1 #ij1 #ia ,lake-deposit$ clays1 #he1 #hh1 #ia ,lakes1 #he1 #hh ,lam9at$ clays1 #ec1 #aag1 #abb ,lat]ite1 #hj1 #adi ,lat]itic action1 #hj1 #afe ,lat]itic clays1 #hb ,lean clays1 #bi ,liassic clays & %ales1 #eg1 #abe1 #acb ,lime1 #g1 #aj1 #ajb1 #aei ,lime comp\nds1 #aj1 #aa1 #ch1 #da1 #dg1 #aac1 #aae1 #aaf1 #aba1 #abg1 #aci1 #adb1 #adc1 #ade1 #aee1 #aeg1 #afb1 #afd ,lime/one1 #aj1 #aa1 #eb1 #ei1 #fa1 #fb1 #hh1 #ajb1 #aag1 #abg1 #acb1 #aci ,lime tr\bles1 #aa ,loam1 #eg1 #fg1 #hh ,london clay1 #fb1 #fc1 #abe ,ludwig's *>t1 #ce ,magnesium comp\nds1 #g1 #aj1 #aa1 #da1 #dg1 #aac1 #aae1 #aaf1 #aba1 #acc1 #aee ,malm-bricks1 #aa ,malms1 #aj1 #fh ,m>casite1 #aj1 #ac ,m>9e clays1 #fa1 #ic ,m>ls1 #aj1 #ea1 #ed1 #ee1 #eg1 #fg1 #fh1 #hh1 #acj1 #acb1 #aff ,me*anical analysis1 #acg ,m$way mud1 #acb ,melt+ po9t1 #ca1 #cb ,mica1 #g1 #h1 #gf1 #ajd1 #aje1 #aaf1 #adj1 #ada1 #add1 #afj ,microscopical exam9ation1 #ah1 #aje1 #adc1 #aeh ,mill/one grit1 #ed1 #ee1 #aag ,m9]al nature ( clay1 #c ,m9]als resembl+ clay1 #aeh ,m9+ ball clay1 #aaa ,modell+ clays1 #acj ,moi/ure1 #ae1 #add ,molecul> attraction1 #bb ,molecul> con/itution ( clay1 #ba1 #aef ,montmorillonite1 #acd ,mundic1 #ac ,muscovite1 #aje ,newtonite1 #aeh ,nodules1 #aba1 #abg ,non-pla/ic mat]ial1 #dc1 #aba1 #aea ,non-refractory clays1 #aff ,occurr5ce ( clays1 #dh1 #aaf ,ocean curr5ts1 action (1 #hi ,od\r ( clay1 #ai ,oil1 blea*+1 #acd ,oil %ales1 #fa1 #abb1 #abc ,oolite clays1 #ei1 #acd ,ooze1 #ie1 #ii ,organic matt]1 #ai1 #aai ,orig9s ( clays1 #dh1 #ga1 #afj1 #afe ,ox=d clay1 #ei1 #ie1 #afd ,oxides 9 clay1 #aj1 #hb ,pa9t1 clays =1 #aji ,pap]1 clays =1 #aji ,p>ticles1 nature (1 #ah1 #ca1 #ajf1 #ajg1 #aej ,pav+ brick clays1 #aff ,pelagic ooze1 #ie1 #ii ,pel9ite1 #hc1 #adh1 #adi ,p]mian clays & %ales1 #eg1 #aab1 #abd ,phol]ite1 #aag ,physical *>act]s ( clays1 #ag ,pick+ clay1 #aba ,pipe clays1 #fd1 #fe1 #hb1 #aji1 #aff ,plant-extracts 9 clays1 #bf ,pla/ic clays1 #b1 #dc1 #fe1 #fg1 #hb1 #hh1 #ajb1 #aab1 #abc1 #adg1 #adh1 #afj ,pla/icity1 #bj-bg1 #da1 #df1 #ig1 #ih1 #ii1 #ajh1 #aji1 #aab1 #aag1 #abc1 #abe1 #abg1 #aea1 #afj ,plei/oc5e clays1 #fg ,pockets1 #fe1 #he1 #aja1 #aaf1 #aff ,porcela91 #cg1 #df1 #gc1 #aji1 #aaj1 #abe1 #abi ,pores 9 clay1 #cj1 #aad ,porosity1 #cj1 #ci1 #aba1 #aca1 #aee ,portl& cem5t1 #aca ,pota% comp\nds1 #g1 #aj1 #aac1 #aae1 #aaf1 #aba1 #aeg1 see ,alkalies ,pott]y clays1 #a1 #e1 #ca1 #df1 #ff1 #ajj1 #aja1 #ajd1 #aaj1 #aab1 #aad1 #abe1 #abi1 #afb1 #aff ,precambrian clays1 #ea ,precipitat$ clays1 #ig1 #aeb ,prim>y clays1 #gj1 #ga1 #hd1 #afe ,proximate analysis1 #af1 #add ,purbeck clays1 #ei ,pure clays1 #e1 #f1 #g1 #adb1 #aee1 #aef ,purification ( clay1 #g1 #ff1 #gh1 #ajd1 #aac1 #abh1 #adj ,pyrites1 #aj1 #ac1 #dd1 #ef1 #eg1 #aai1 #abd1 #abh ,qu>tz1 #h1 #ajd1 #aaj1 #aah1 #adj1 #ada1 #adc ,ra91 #dd1 #he1 #hf ,rational analysis1 #ada ,read+ clays1 #fc ,rec5t clays1 #fg ,rectorite1 #aeh ,re-deposit$ clays1 #ih ,r$ bricks1 #ab ,r$ burn+ clays1 #ada1 #adb1 #aff ,r$ iron oxide1 #ab ,r$ w>e1 #aac ,r$uction 9 volume1 #cj ,refractor9ess1 #cd1 #aai1 #abj1 #abc1 #aee ,refractory articles1 #e1 #aai ,refractory clays1 #i1 #cb1 #cc1 #ce1 #ch1 #eb1 #fe1 #hb1 #ajd1 #aaf1 #afe1 #aff ,residual clays1 #gj1 #hd1 #aff ,resi/ance to abrasion1 #aai ,resi/ance to corrosion1 #aai ,resi/ance to cru%+1 #df ,resi/ance to cutt+1 #aai ,resi/ance to temp]ature1 see ,refractor9ess ,resi/ance to wea!r+1 #gf ,r++ s\nd1 #aaj ,riv]-deposit$ clays1 #hh ,riv]s1 #he1 #hg ,rock b9ds1 #ec ,rock+ham1 #aac ,rock-l clays1 #b ,rocks associat$ ) clay1 #dh ,roman cem5ts1 #acc ,ro(+ tiles1 #eg1 #fc1 #abf1 #abh ,sagg] m>ls1 #ed ,s&1 #g1 #ca1 #da1 #fb1 #hb1 #hi1 #ajj1 #aja1 #aag1 #acc1 #ach1 #add ,s&/ones1 #ec ,s&y clays1 #fh ,s&y loams1 #hh ,s&y m>ls1 #hh ,sanit>y articles1 #e1 #aac ,sawdu/1 #dj ,scum1 #aj ,sea1 action (1 #he1 #hi1 #ii ,sea-deposit$ clays1 #ic ,second>y clays1 #gj1 #hb1 #hc1 #aff ,s$im5t>y rocks1 #dh ,s$im5tation ( clay1 #dc1 #hh1 #ij1 #ajd ,seg] cones1 #cc1 #cd ,selection ( clay1 #abb ,sel5ite1 #aj ,sep>ation ( clays1 #ij1 #ade ,settl+1 #dc ,sew]age pipes1 #aac ,%ale oil1 #ae1 #fa ,%ale t>1 #abc ,%ales1 #b1 #e1 #ea1 #eb1 #ec1 #eg1 #fa1 #if1 #ajd1 #abb1 #acj1 #acb1 #ach1 #aea1 #afb1 #aff ,%r9kage1 #aa1 #bi1 #eh1 #fh1 #ajb1 #aaj1 #aag1 #aai1 #aba1 #abg1 #aca1 #aec ,sift+1 #g1 #ach ,silica1 #f1 #g1 #hj1 #aed1 #aee1 #afa ,silica rock1 #aah ,silicates1 #h1 #hb ,silice\s clays1 #aag ,sillimanite1 #df1 #aed ,silt1 #ij1 #ia1 #ii1 #aci1 #add ,silurian clays & %ales1 #ea1 #abd ,s9t]+1 #ch ,size ( p>ticles1 #ah1 #ba1 #ca1 #ajf1 #ajg1 #aej ',skeleton1' #aae ',sk9' on w>e1 #aca ,slag 9 bricks1 etc41 #aa1 #ac1 #aai1 #aee ,slates1 #ea ,slurry1 #ci1 #dc1 #aeb ,sn[1 #he ,soda comp\nds1 #g1 #aj1 #aac1 #aae1 #aaf1 #aba1 #aeg1 see ,alkalies ,s(t5+ po9t1 #cc ,soil1 see ,agriculture ,solubility ( clay1 #aea1 #aei ,soluble salts1 #aj ,sort+1 #ij ,s\rces ( clays1 #he ,specification ( fire clays1 #abj ,specific gravity1 #ah1 #ajf1 #aea ,/af=d%ire bricks1 #ac1 #ef ,/&>d clay1 #d ,/one1 ,corni%1 #aaj1 #aaf ,/onew>e clays1 #ajd1 #aab1 #aac1 #aef1 #afe1 #aff ,/ones1 #g1 #fe1 #ajj1 #ajb1 #abh1 #ach1 #add ,/reams1 #he1 #hf ,/r5g?1 #bc1 #de1 #aac ,sub-surface clays1 #e ,sulphates 9 clay1 #aj1 #ab1 #hb ,sulphides 9 clay1 #aj1 #hb ,sulphuric acid1 #abd ,sunlight1 #de ,surface clays1 #b1 #e1 #eb1 #aab ,susp5sion ( clay1 #dc1 #ij1 #adj1 #aeb ,swell+1 #ae1 #ajb ,tann9 9 clay1 #be1 #bf1 #da ,telluric wat]1 #afe ,temp]ature1 resi/ance to1 #aai1 #abj ,t5sile /r5g?1 #bc1 #de ,t]ra-cotta clays & %ales1 #e1 #aj1 #ab1 #ca1 #df1 #ef1 #fc1 #ia1 #ajd1 #abc1 #abd1 #abi1 #aff ,t]ti>y clays1 #fb ,texture1 #aab1 #acj ,!rmal reactions1 #adf1 #aed1 #aeh ,tiles1 #a1 #e1 #eg1 #ia1 #aja1 #abi ,titanium comp\nds1 #aba ,t\rmal9e1 #gf1 #ajd ,transportation ( clays1 #di1 #hf1 #ih1 #ii1 #ajj ,transport$ clays1 #gj ,triassic clays1 #eg1 #aab1 #acj ,true clay1 #add1 #adf1 #adi1 #aej1 #afj ,twi/$ w>e1 #aad1 #abi1 #aca ,types ( clay1 #hb ,ultimate analysis1 #af1 #add ,ultra-m>9e1 clays =1 #aji ,und]clays1 #ec1 #aag1 #aah ,uses ( clay1 #a1 #afe ,valuation ( clay1 #ajc1 #aji1 #abc1 #abf1 #afb1 #afe ,vegetable matt]1 #ae1 #aai ,ve9s1 #he ,viscosity1 #aeb ,v]ifiable clays1 #aac1 #aef1 #aff ,vitrification1 #ae1 #bj1 #cg1 #aab1 #aac1 #aad1 #aef ,vitrification range1 #ch1 #aad1 #aae1 #aaf1 #abi ,volcanoes1 #he ,w>p1 #ii ,w>p$ w>e1 #aad1 #abi1 #aca ,wa%+1 #g1 #gi ,wat]1 effect (1 #gd1 #gf1 #ha1 #he1 #hf1 #aea ,wat] 9 clays1 #ae1 #ag1 #bi1 #ci1 #de1 #aed ,weald5 clay1 #fb ,wea!r+1 #dd1 #gd1 #gf1 #gi1 #hj1 #ig1 #ajg1 #afe ,:ite bricks1 #fh1 #abh ,:ite clays1 #gj1 #aff ,w9d1 #hf ,zeolites1 #aeg ,,cambridge3 ,,pr9t$ ,,by ,,john ,,clay1 ,m4,a4 ,,at ,,! ,,univ]sity ,,press