,transcrib]'s note3 ,= ?is text v]sion passages 9 italics are indicat$ by und]scores4 ,small caps h be5 replac$ by ,,all ,,caps & subscripts are d5ot$ z #b4 99 99 99 99 99 ,illu/ration3 cov] ,illu/ration3 ,by p]mission ( ,messrs4 ,*ance ,bros1 & ,co41 ,ltd4 ,a ,,huge ,,lamp ,! m>vell\s arrangem5t ( l5ses & prisms :i* enables ! ligh?\se to s5d out its guid+ fla%es1 ) ! me*anism = turn+ x4 ,made = ,*ilang ,ligh?\se1 ,*9a ,frontispiece ,,m>vels ,,( ,,sci5tific ,,inv5tion ,,an ,,int]e/+ ,,acc\nt ,,9 ,,non-,,te*nical ,,language ,,( ,,! ,,inv5tion ,,( ,,guns1 ,,torp$oes1 ,,subm>9es ,,m9es1 ,,up-,,to-,,date ,,smelt+1 ,,freez+1 ,,col\r ,,photography1 ,,& ,,_m ,,o!r ,,rec5t ,,discov]ies ,,( ,,sci5ce ,,by ,,?omas ,w4 ,,corb9 ,,au?or ,,( ,,eng9e]+ ,,( ,,to-,,day1 ,,me*anical ,,inv5tions ,,( ,,to-,,day1 ,,! ,,romance ,,( ,,subm>9e ,,eng9e]+1 c41 c4 ,,) #cb ,,illu/rations ,,diagrams ,,philadelphia ,j4 ,b4 ,,lipp9cott ,,company ,,london3 ,,seeley1 ,,s]vice ,,co4 ,,ltd4 #aiag ,,cont5ts ,,*apt] ,,page ,i4 ,,digg+ ,,) ,,dynamite #i ,,ii4 ,,measur+ ,,electricity #bb ,,iii4 ,,! ,,fuel ,,( ,,! ,,future #db ,,iv4 ,,"s ,,valuable ,,electrical ,,processes #ee ,v4 ,,ma*9e-,,made ,,cold #fg ,,vi4 ,,sci5tific ,,inv5tions ,,at ,,sea #gh ,,vii4 ,,! ,,gyro-,,compass #ij ,,viii4 ,,torp$oes ,,& ,,subm>9e ,,m9es #ih ,,ix4 ,,gold ,,recov]y #aji ,x4 ,,int5se ,,heat #abc ,,xi4 ,,an ,,artificial ,,coal ,,m9e #acg ,,xii4 ,,! ,,mo/ ,,/rik+ ,,inv5tion ,,( ,,rec5t ,,times #adi ,,xiii4 ,,h[ ,,pictures ,,c ,,be ,,s5t ,,by ,,wire #agf ,,xiv4 ,a ,,wond]ful ,,example ,,( ,,sci5ce ,,& ,,skill #aia ,,xv4 ,,sci5tific ,,te/+ ,,& ,,measur+ #aih ,,xvi4 ,,col\r ,,photography #bab ,,xvii4 ,,h[ ,,sci5ce ,,aids ,,! ,,/rick5 ,,colli] #bbj ,,xviii4 ,,h[ ,,sci5ce ,,helps ,,to ,,keep ,,u ,,well #bca ,,xix4 ,,mod]n ,,artill]y #bcf ,,app5dix #bde ,,index #bdg ,,li/ ,,( ,,illu/rations ,a ,huge ,lamp ,frontispiece ,,fac+ ,,page ,fir/ ,effect ( ! ,dynamite #af ,a ,f9e ,crop #bd ,apple-tree plant$ by ,spade #dh ,ma*9e-made ,ice #gb ,a ,cold ,/ore #hj ,dass5 ,isl& ,ligh?\se #hh ,measur+ ,heat #abh ,! ,telewrit] #ahd ,a ,m9]s' ,rescue ,team #bjh ,pneumatic ,hamm] ,drill #baf ,an ,artificial ,coal ,m9e #bbd ,sectional view ( a #fj-p\nd] ,gun #bcb ,rifles ( diff]5t ,nations #bdj ,,diagrams ,,fig4 ,,page #a4 ,pr9ciple ( ,galvanomet] #cj #b4 ,/r+ ,galvanomet] #ca #c4 ,duddell ,!rmo-,galvanomet] #ci #d4 ,con/ruction ( a ,voltmet] #fd #e4 ,! ,work+ ( a ,refrig]at+ ,ma*9e #gj #f4 ,h]tz's ,ma*9e #aee #g4 ,h]tz ,detector #aef #h4 #i4 #aj4 ,wireless ,waves #aeh #aa4 ,a ,wireless ,ant5na #afd #ab4 ,p\ls5's ,ma*9e #aff #ac4 #ad4 ,h[ ,pictures are s5t by ,wire #agg #ae4 ,message receiv$ by ,telewrit] #ahi ,,m>vels ,,( ,,sci5tific ,,inv5tion ,,*apt] ,i ,,digg+ ,,) ,,dynamite ,mo/ p are afraid ( ! ^w explosion & %udd] ) appreh5sion at ! m5tion ( dynamite4 ,! latt]1 p>ticul>ly1 conjures up visions ( an>*i/s1 bombs1 & all mann] ( wick$ness4 ,yet ! "t seems to be com+ :5 e f>m] w reg>d explosives1 ( ! g5]al type kn[n to ! public z dynamite1 z among 8 mo/ tru/y implem5ts4 ,x is s already 9 "s places4 ,9 ! ,unit$ ,/ates explosives h be5 us$ = ye>s1 ow+ to ! ex]tions ( ! ,du ,pont ,p[d] ,company1 :ile ,messrs ,curtiss' & ,h>vey1 & ,messrs ,nobels1 ! great explosive manufactur]s1 are busy introduc+ !m 9 ,great ,brita94 ,x w p]haps be int]e/+ fir/ ( all to see :at ?is t]ror-/rik+ comp\nd is4 ,"o ess5tial feature is ! h>mless gas :i* con/itutes ! bulk ( our atmosph]e1 nitrog54 ,ord9>ily "o ( ! mo/ lazy1 inactive1 in]t ( sub/ances1 ?is gas w1 "u c]ta9 circum/ances1 ent] into comb9ation ) o!rs1 & :5 x does s x becomes 9 "s cases ! v rev]se ( its usual peaceful1 le?>gic self4 ,x is z if x ent]$ reluctantly into ^! comp\nds & s introduc$ an elem5t ( in/ability into !m4 ,x is l a dissatisfi$ p>tn] 9 a bus9ess1 ready to break up ! :ole comb9ation on v slight provocation4 ,& x mu/ be rememb]$ t an explosive is simply "s *emical comp\nd :i* c *ange sudd5ly into some?+ else ( mu* l>g] volume4 ,wat]1 :5 boil$1 increases to ab\t #afjj times its own volume ( /eam1 & if x 7 possible to br+ ab\t ! *ange sudd5ly wat] w\ld be a fairly p[]ful explosive4 ,coal burnt 9 a fire *anges1 ) oxyg5 f ! atmosph]e1 into c>bonic acid gas1 & ! volume ( t latt] :i* is s produc$ is mu* m ?an t ( ! comb9$ volumes ( ! oxyg5 & coal4 ,:5 ! burn+ takes place 9 a grate or furnace we see no?+ at all l an explosion1 = ! simple reason t ! *ange takes place gradually4 ,t is necess>ily s s9ce ! coal & oxyg5 are only 9 contact at ! surface ( ! =m]4 ,if1 h[ev]1 we gr9d ! coal to a v f9e p[d] & mix x well ) air1 !n ea* f9e p>ticle is 9 contact ) oxyg5 & c burn in/antly4 ,h5ce coal-du/ 9 air is an explosive4 ,x us$ to be ?\ght t colli]y accid5ts 7 due entirely to ! explosion ( me?ane1 a gas :i* is giv5 (f by ! coal1 b x has ( rec5t ye>s dawn$ ^u p t x is ! coal-du/ 9 ! m9e :i* really does ! damage4 ,! explosion ( me?ane /irs up ! du/1 :i* !n explodes4 ,! =m] is comp>atively h>mless1 b x acts z ! trigg] or detonator :i* lets loose ! =ce p5t up 9 ! innoc5t-look+ coal-du/4 ,h5ce ! greate/ ef=ts 9 mod]n colli]ies are b5t t[>ds ridd+ ! work+s ( du/ or else damp+ x or 9 "s o!r way prev5t+ x f be+ /irr$ up into ! dang]\s /ate4 ,s ! ess5tial feature ( any explosive is oxyg5 & some?+ :i* w burn ) x4 ,if x be a solid or liquid ! oxyg5 mu/ be a "p ( ! comb9ation or mixture1 = x _c get air f ! surr\nd+ atmosph]e quickly en\gh to explode2 &1 moreov]1 x is g5]ally necess>y t explosives %\ld "w 9 a conf9$ space away f all contact ) air4 ,s oxyg51 ( necessity1 mu/ be an integral "p ( ! /uff itself4 ,b :5 oxyg5 comb9es ) any?+ x usually cl+s r t5aci\sly to its place 9 ! comp\nd & is n easily di/urb$ quickly1 & t is :]e ! nitrog5 seems to f9d its "p4 ,x supplies ! di/urb+ elem5t 9 :at w\ld o!rwise be a h>moni\s comb9ation1 s t ! oxyg5 & ! burnable sub/ances readily split up & =m a new comb9ation1 ) ! nitrog5 left out4 ,( all ! h>mless ?+s 9 ! _w "o w\ld ?9k t t sweet1 /icky fluid1 glyc]9e1 :i* mo/ ( u h us$ at "o "t or ano!r to lubricate a sore ?roat1 0 ! mo/ h>mless4 ,z x /&s 9 its bottle ^u ! dome/ic m$ic9e %elf1 :o w\ld suspect t x is ! basis ( su* a ?+ z dynamite8 ,su* is ! case1 h[ev]1 = glyc]9e on be+ br\ght into contact ) a mixture ( sulphuric & nitric acids gives bir? to nitro-glyc]9e1 an explosive ( su* s5sitivity1 ( su* a furi\s1 viol5t nature1 t x is nev] all[$ to rema9 long 9 its primitive condition1 b is z quickly z possible *ang$ into some?+ less excitable4 ,glyc]9e is "o ( ^? organic comp\nds :i* is obta9$ f once-liv+ matt]4 ,aris+ z a by-product 9 ! manufacture ( soap1 x consi/s1 z d s _m ( ! organic sub/ances1 ( c>bon & hydrog51 ! atoms ( :i* are peculi>ly arrang$ to =m ! glyc]9e molecule4 ,to ?is ! nitric acid adds oxyg5 & nitrog51 ! sulphuric acid simply /&+ by1 z x 71 & remov+ ! surplus wat] :i* arises dur+ ! process4 ,s :ile glyc]9e is c>bon & hydrog51 nitro-glyc]9e is c>bon1 hydrog51 nitrog5 & oxyg54 ,9 ?is /ate !y =m a compact liquid1 :i* occupies little space4 ,! lea/ ?+ upsets !m1 h[ev]4 ,! c>bon comb9es ) oxyg5 into c>bon dioxide1 commonly call$ c>bonic acid gas1 ! hydrog5 & "s m oxyg5 =m /eam1 :ile ! nitrog5 is left out 9 ! cold1 s to speak4 ,& ! total volume ( ! gases s produc$ is ab\t #fjjj times t ( ! orig9al liquid4 ,x is easy to see t a sub/ance :i* is liable sudd5ly to increase its volume by #fjjj times is an explosive ( no mean ord]4 ,b ! fact t x is liable to make ?is *ange on a comp>atively slight increase 9 temp]ature or aft] a concussion makes x too dang]\s = practical use4 ,x ne$s to be tam$ d[n some:at4 ,?is 0 fir/ done by ! fam\s ,nobel1 :o mix$ x ) a f9e e>? kn[n z kieselguhr1 :]eby its s5sitiv5ess 0 mu* decreas$4 ,?is mixture is dynamite4 ,x w be se5 t ! function ( ! e>? is simply to act z an absorb5t ( ! liquid nitro-glyc]9e1 & sev]al o!r ?+s c be us$ = ! same purpose4 ,moreov]1 !re are n[ _m explosives ( ! dynamite nature b diff]+ f x 9 hav+ an active in/ead ( a passive absorb5t1 s t ! decrease 9 s5sitivity is accompani$ by an increase 9 /r5g?4 ,= example1 gelignite1 :i* is be+ us$ = agricultural purposes 9 ,great ,brita91 consi/s ( nitro-glyc]9e mix$ ) nitro-cotton1 wood-meal & saltpetre4 ,! wood-meal acts z ! absorb5t in/ead ( ! kieselguhr1 :ile ! nitro-cotton is ano!r k9d ( explosive & ! saltpetre1 "o ( ! +r$i5ts 9 ! old gunp[d]1 provides ! necess>y oxyg5 = burn+ up ! wood-meal4 ,nitro-cotton is made 9 mu* ! same way z nitro-glyc]9e1 except t cotton takes ! place ( ! glyc]9e4 ,cotton is almo/ pure cellulose1 ano!r organic sub/ance1 l glyc]9e insomu* z x is compos$ ( c>bon & hydrog51 b1 unlike x1 conta9+ also oxyg54 ,treat$ ) nitric acid x also =ms a comb9ation ( c>bon1 hydrog51 oxyg5 & nitrog51 :i* is call$ nitro-cotton1 nitro-cellulose1 or gun-cotton4 ,x may be ask$1 :y1 if ^! two sub/ances are ?us simil>1 ne$ !y be mix$8 ,! answ] is t al?\gh alike to a c]ta9 degree !y are n exactly ! same1 & ! mod]n manufactur] ( explosives 9 8 /rife aft] p]fection f9ds t = c]ta9 purposes "o is ! be/1 & = o!rs ano!r1 :ile = o!rs aga9 a comb9ation may excel any s+le "o4 ,= "s "w ano!r k9d ( explosive altoge!r is to be pref]r$4 ,?is is bas$ ^u *lorate ( pota%1 a comp\nd v ri* 9 oxyg51 :i* x is prep>$ to give up readily to burn any o!r suitable elem5t :i* may be at h&4 ,a well-kn[n explosive ( ?is class is t kn[n z *$dite1 s9ce x 0 fir/ made at a factory at ,*$de1 9 ,savoy4 ,= ! sake ( simplicity1 h[ev]1 ,i propose 9 ! foll[+ descriptions to ref] to all ^! explosives "u ! common t]m dynamite1 s9ce t w probably convey to ! g5]al public an idea ( _! nature bett] ?an any o!r t]m or t]ms :i* ,i c\ld *oose4 ,s n[ we come to ! great "q1 h[ c ! mod]n f>m] b5efit by ! use ( high explosives su* z ^!8 ,! answ] is1 9 _m ways4 ,let u take ! mo/ obvi\s "o fir/4 ,a f>m] has be5 pl\gh+ 8 l& & gr[+ 8 crops ^u x = ye>s4 ,p]*ance 8 =efa!rs h be5 do+ ! same = g5]ations4 ,e ye>1 = c5turies possibly1 a h>d /eel pl\gh%>e has gone ov] t gr\nd1 turn+ ov] & ov] ! top soil to a dep? ( six to eight in*es4 ,ea* season ! plants1 :atev] !y may be1 gr[ ma9ly 9 t top lay]4 ,!y take ! goodness or n\ri%m5t out ( x & x ev5tually becomes m or less /]ile4 ,by prop]ly rotat+ 8 crops he mitigates ?is to a c]ta9 ext5t1 9 addition to :i* he re/ores to ! l& "s ( its old nitrog5\s con/itu5ts by ! addition ( manure4 ,yet1 d :at he w1 ?is ?9 top lay] is b\nd to become exhau/$4 ,& all ! :ile a few in*es l[] d[n !re is almo/ virg9 soil :i* has sc>cely be5 di/urb$ s9ce ! creation ( ! _w4 ,nay1 m1 t virg9 soil1 ) all its plant food /ill 9 x1 is n only do+ little = its own]1 x is positively do+ him h>m4 ,= e "t 8 pl\gh goes ov] x x t5ds to ram x d[n flat2 e "t a man walks ov] x ! result is ! same2 e horse t passes1 ev]y?+ t happ5s or has happ5$ = c5turies 9 t field1 t5ds to make t soil j bel[ ! rea* ( ! pl\gh%>e a h>d1 imp]vi\s mass1 ?r\gh :i* only ! roots ( ! mo/ /rongly gr[+ plants c f9d a way1 & :i* t5ds to make ! soil above x wet 9 wet wea!r & dry 9 dry wea!r4 ,?us roots h to spread sideways in/ead ( d[nw>ds2 or1 gr[+ d[nw>ds ) difficulty1 ea* plant has to exp5d vital en]gy 9 =c+ its roots ?r\gh ! h>d gr\nd :i* x might bett] employ 9 produc+ fl[]s or fruits4 ,& !re is no natural /orage ( wat]4 ,a %[] dr5*es ! gr\nd4 ,9 "t x dries1 ?r\gh evaporation into ! air1 & !n :5 ! dr\ght comes all is arid z ! ,sah>a4 ,t h>d subsoil is kn[n by ! t]m h>d-pan1 &1 z we h se51 x is produc$ m or less by all t goes on 9 ! field4 ,ev5 worse is ! case--a v frequ5t "o too--:]e9 !re is a natural /ratum ( clay or equally d5se wat]pro( mat]ial ly+ a few feet d[n4 ,beyond ! rea* ( any pl\gh1 ?is h>d /ratum c be brok5 up by ! use ( dynamite4 ,! usual me?od is to drive holes 9 ! gr\nd ab\t fifte5 to tw5ty feet ap>t & ab\t ?ree or f\r feet deep1 "r into ! he>t ( ! h>d lay]4 ,at ! bottom ( ea* hole is plac$ a c>tridge ( dynamite ) a fuse & a detonator4 ,?is latt] is a small tube conta9+ a small quantity ( explosive :i*1 unlike ! dynamite1 c be easily fir$1 & initiates ! detonation ( ! c>tridge4 ,:5 ^! m9iature e>?quakes h tak5 place all ov] a field a v diff]5t /ate ( ?+s prevails4 ,! h>d-pan has be5 brok54 ,! explosive us$ = su* a purpose has a sudd5 %att]+ p[]1 :]eby x pulv]ises ! gr\nd 9 its vic9ity r ?an mak+ a great upheaval at ! surface4 ,! sudd5 %ock makes cracks & fissures 9 all directions1 ?r\gh :i* roots c easily make _! way4 ,moreov]1 x p]mits air to f9d an entrance1 !reby a]at+ ! soil 9 su* a way z to increase its f]tility4 ,! heat1 or else ! *emical products ( ! explosion1 seem to de/roy ! fungus g]ms 9 ! gr\nd4 ,f9ally a natural /orage ( wat] is set up4 ,heavy ra91 in/ead ( dr5*+ ! upp] soil1 simply moi/5s x nicely1 :ile ! surplus wat] desc5ds into ! newly di/urb$ lay]s1 !re to rema9 until ! roots pump x up 9 "t ( dr\ght4 ,x is /at$ t an acre ( hay pumps up out ( ! soil #ejj tons ( wat] p] annum1 s x is easy to see :at an important feature ?is natural wat]-/orage is4 ,f>m]s say t _! crops h d\bl$ 9 value aft] ?us dynamit+ ! subsoil4 ,?is op]ation has be5 spok5 ( z a sub/itute = pl\gh+1 b t may be put d[n to j\rnali/ic lic5ce1 = :ile x truly conveys ! g5]al idea1 x is h>dly correct4 ,! ord9>y pl\gh turns ov] ab\t eight in*es1 ! special subsoil pl\gh rea*es d[n to ab\t eighte5 in*es1 b ! dynamite me?od loos5s ! gr\nd to a dep? ( six or sev5 feet4 ,corn roots if giv5 a *ance w g d[nw>ds f f\r to eight feet4 ,potatoes g d[n ?ree feet1 hops eight to eighte5 feet & v9es tw5ty feet1 s x is easy to see h[ re/rict$ ! plants are :5 _! natural root+ in/9cts are re/ra9$ by a h>d lay] at a dep? ( eighte5 in*es or s4 ,! holes are made by means ( a b> or drill4 ,a great deal dep5ds1 ( c\rse1 ^u ! h>dness ( ! soil4 ,sometimes a /eel b> has to be driv5 9 by a sl$ge-hamm]4 ,at o!rs a po9t$ b> c be pu%$ d[n by h&4 ,9 "s cases x w be f\nd t ! be/ tool to employ is a dirt-aug]1 a tool l a c>p5t]'s aug]1 :i* on be+ turn$ r\nd & r\nd bores its way into ! e>?4 ,h[ev] x may be done1 "o or m c>tridges ( dynamite are l[]$ into ! f9i%$ hole1 "o ( !m be+ fitt$ ) ! necess>y detonator & fuse4 ,!n a little loose e>? or s& is dropp$ into ! hole until x is fill$ to a dep? ( six in*es or s above ! upp]mo/ c>tridge4 ,above t x is q safe to fill ! hole ) e>?1 ramm+ x 9 ) a wood5 ramm]4 ,?is is call$ tamp+1 & x is necess>y 9 ord] to prev5t ! =ce ( ! explosion be+ wa/$ 9 simply bl[+ up ! hole4 ,:at is want$ is t ! explosion %all take place )9 an enclos$ *amb] s t its effect may be felt equally 9 all directions4 ,! holes are g5]ally ab\t an in* & a half or an in* & ?ree-qu>t]s 9 diamet]4 ,!re are two ways ( fir+ ! *>ges4 ,"o is by means ( fuses4 ,! detonator is fa/5$ to "o c>tridge & a l5g? ( fuse is atta*$ to ! detonator1 :i* pass+ up ! hole t]m9ates above ! gr\nd4 ,! fuse is a tube ( cotton fill$ ) gunp[d]1 & x burns at ! rate ( ab\t two feet a m9ute4 ,?us if ?ree feet ( fuse be us$ ! man :o lights x has a m9ute & a half 9 :i* to f9d a place ( safety f fall+ /ones4 ,! o!r way is by electricity4 ,9 ?is case an electric fuse is atta*$ to ! c>tridge & two wires are l$ up ! hole4 ,^! are connect$ to an electrical ma*9e1 :i* causes a curr5t to pass d[n into ! fuse1 :]e1 by heat+ a f9e plat9um wire1 x fires ! detonat+ mat]ial ) :i* x is pack$4 ,?is detonat+ mat]ial 9 turn fires ! dynamite4 ,! advantage ( ! electrical me?od is t tw5ty or ?irty holes be+ simultane\sly connect$ to ! same ma*9e c all be fir$ at once4 ,& n[ let u ?9k ( ano!r k9d ( f>m+1 9 :i* fruit trees are conc]n$4 ,) a l>ge tree ! ne$ ( pl5ty ( und]gr\nd space = its roots w\ld seem to be m important ev5 ?an 9 ! case ( annual plants l :eat4 ,yet we "k v well t ! usual proc$ure is to dig a small hole j ab\t big en\gh to accommodate ! roots ( ! sapl+ :5 x is plant$1 :ile ! gr\nd all r\nd is left undi/urb$4 ,! assumption is t ! tree w1 9 "t1 be able to pu% its roots ?r\gh any?+ :i* is n actually solid rock4 ,s mu* is ?is ! case t "o au?ority has ?\ght fit to w>n tree-gr[]s 9 ?is picturesque fa%ion4 ,:5 plant+ a tree1 he says1 =get :at x is y are do+1 & ?9k t y are ab\t to bury ! bigge/ horse y "k4 ,h[ _m p :5 plant+ any tree dig a hole big en\gh to bury a horse8 ,x is fairly safe to reply1 only ^? :o d x by dynamite4 ,illu/ration3 ,by p]mission ( ,dupont ,p[d] ,co41 ,wilm+ton1 ,delaw>e ,,fir/ ,,effect ,,( ,,! ,,dynamite ,cle>+ a field ( tree /umps by bl[+ !m up ) dynamite4--,see p4 #af ,! me?od ( work+ is to bore a hole ne>ly z deep z ! hole y want to bla/4 ,at ! bottom place a p[]ful *>ge1 f> /rong] ?an y w\ld use = subsoil+1 z j describ$4 ,t w n only bl[ a hole big en\gh = y to put y\r tree 91 b x w loos5 ! gr\nd all ar\nd ! hole = y>ds4 ,! ma9 debris f ! hole w fall back into x1 b t w n matt] mu*1 s9ce1 be+ all loose1 x is an easy matt] to remove z mu* z is necess>y to plant ! "y tree4 ,! advantages are ! same z ^? enum]at$ 9 ! previ\s case--namely1 ! loos5$ gr\nd gives m scope = ! roots--apple-tree roots want tw5ty feet or s--! gr\nd holds moi/ure bett]1 & ! explosion kills ! fungus g]ms4 ,9 addition to ^! !re is ! advantage t to bla/ a hole l ?is is *eap] ?an digg+ x4 ,& t ! advantages are n m]ely !oretical is %[n by ! fact t trees s plant$ actually d gr[ /rong]1 bigg] & quick] ?an precisely simil> ones "u ! same conditions1 b set 9 ! ord9>y way ) a spade4 ,& n only d new trees ?us b5efit2 old trees c be help$ by dynamite4 ,_m an exi/+ or*>d has be5 improv$ by explod+ dynamite at int]vals betwe5 ! r[s ( trees4 ,c>e has to be tak5 to see t ! di/urbance is n s viol5t or s close z to damage ! trees1 b t c be easily arrang$1 & !n ! result is t ! soil all ar\nd ! trees is loos5$1 ! roots are giv5 m fre$om & ! wat]-/or+ prop]ties ( ! gr\nd are greatly improv$4 ,aga91 h[ (t5 a f>m] is tr\bl$ ) a pond or a pat* ( m>%y gr\nd "r 9 ! mid/ ( 8 fields4 ,x is ( no use1 & simply s]ves to make ! field 9 :i* x occurs m difficult to pl\gh & to cultivate--besides be+ s mu* good l& wa/$4 ,n[ ! reason = ! exi/5ce ( t pond or m>% is t und]nea? ! surface !re is an imp]vi\s lay] 9 :i*1 z 9 a bas91 ! wat] c collect4 ,make a hole 9 t & x w no m hold wat] ?an a crack$ jug w4 ,& to make t hole ) dynamite is ! easie/ ?+ 9 ! _w4 ,if ! pond be m]ely a collection ( wat] :i* occurs 9 wet wea!r1 b :i* dries up quickly1 !re simply ne$s to be drill$ a deep hole & a fairly /rong explosion caus$ at ! bottom ( x4 ,h[ deep ! hole mu/ be dep5ds ^u ! =mation ( ! e>? at t po9t1 & h[ l[ d[n is ! /ratum :i*1 be+ wat]pro(1 causes ! wat] to rema94 ,x is t1 ( c\rse1 :i* mu/ be brok5 ?r\gh1 & s ! explosion mu/ be caus$ at a po9t ne> ! "u side ( t lay]4 ,) a little exp]i5ce ! op]ator c judge ! position by ! feel ( ! tool ) :i* he makes ! hole4 ,if ! pond is p]man5t b %all[1 m5 c wade to ab\t ! c5tre1 !re to drill a hole & fire a %ot4 ,if x be p]man5t & deep1 !n ! "w mu/ be done f a raft1 :i*1 h[ev]1 c be easily con/ruct$ = ! purpose4 ,once brok5 ?r\gh1 ! wat] w quickly pass away bel[ ! imp]vi\s /ratum & useless l& w become valuable4 ,! same may be done on a l>g] scale by bla/+ dit*es ) dynamite4 ,?is is 9 _m cases mu* *eap] ?an digg+ !m4 ,a r[ ( holes is put d[n1 or ev5 two or ?ree r[s1 accord+ to ! wid? ( ! propos$ dit*4 ,9 dep? !y are made a little less ?an ! dep? ( ! dit* t is to be4 ,& = a reason :i* w be app>5t !y are put v close toge!r1 say ?ree feet or s ap>t4 ,prep>ations may ?us be made = bla/+ a dit* hundr$s ( feet long & !n all are fir$ toge!r4 ,! e>? is ?r[n up by a mighty upheaval1 a dit* be+ produc$ ( rem>kable regul>ity consid]+ ! means by :i* x is made4 ,! sides1 ( c\rse1 take a nice slope1 ! debris is ?r[n away on bo? sides & spread to a consid]able di/ance1 s t1 giv5 fav\rable conditions & a well-arrang$ explosion1 !re is con/ruct$ a f9i%$ dit* :i* h>dly ne$s t\*+ ) spade or o!r tool4 ,x n be+ feasible to fire a lot ( holes electrically1 ! limit be+ ab\t ?irty1 ! simultane\s explosion ( p]haps hundr$s has to be br\ght ab\t 9 "s o!r mann]1 & usually x is accompli%$ by ! simple device ( putt+ ! holes fairly ne> toge!r & fir+ "o ) a fuse4 ,! commotion set up by ?is "o causes ! ne>e/ ones to g (f1 !y 9 turn detonat+ ^? f>!r on1 ) ! result t explosion foll[s explosion all along ! l9e s rapidly z to be almo/ in/antane\s4 ,a f>m] :o is tr\bl$ by a w9d+ /ream pass+ ?r\gh 8 l&1 cutt+ x up into awkw>d %apes1 c /raight5 x by bla/+ a dit* across a loop 9 ! mann] j describ$4 ,9 ! case ( l[-ly+ l&1 h[ev]1 dit*es are obvi\sly no use1 s9ce wat] w\ld n fl[ away along !m4 ,9 t case ! pr9ciple sugge/$ j n[ = deal+ ) an inconv5i5t pond c sometimes be us$1 = if ! subsoil be bla/$ ?r\gh at sev]al po9ts x is v likely t wat] w f9d a way d[nw>ds by "s means or o!r4 ,& ! li/ ( possible uses is by no means exhau/$ yet4 ,a man op5+ up virg9 l& (t5 f9ds old tree /umps 8 greate/ bo!r4 ,he c dig r\nd !m & !n pull !m out ) a team ( horses1 b by f> ! simpl] way is ) a few well-plac$ dynamite c>tridges1 = !y n only ?r[ up ! /ump = him1 b !y break x up1 %ake ! e>? f x1 & leave x ready = him to c>t away or to burn4 ,b\ld]s1 too1 c be bl[n to pieces f> m easily ?an "o w\ld ?9k4 ,! *>ges may be put und]nea? !m z ) ! tree /umps1 b 9 _m cases t is n necess>y1 all t is ne$$ be+ "s dynamite laid ^u ! top ( ! rock & cov]$ ) a heap ( clay4 ,s sudd5 is ! action ( ! explosive t its %ock w break up ! /one und]nea? x4 ,yet ano!r way1 p]haps ! mo/ effective ( all1 is to drill a hole into ! /one & fire a *>ge inside x4 ,x behoves ! onlook] !n to keep away1 = ! fragm5ts may be ?r[n ?ree or f\r hundr$ feet1 a fair pro( t ! /one w be v ?or\ghly demoli%$4 ,ev5 9 ! digg+ ( wells explosives may be useful4 ,9 t case ! holes are made 9 a circle1 & !y slant d[nw>ds & inw>ds1 s t _! l[] ends t5d to meet4 ,! result ( simultane\sly explod+ ! *>ges 9 ^! holes is to cut out a conical hole a little l>g] 9 size ?an ! r+ & a little deep] ?an ! po9t at :i* ! explosion took place4 ,! bottom ( t hole c be levell$ a little & ! op]ation repeat$1 & s /age by /age ! well w proce$ to gr[ d[nw>ds4 ,! ?\ght t naturally occurs to "o is ?is4 ,all ! op]ations describ$ may be v well1 ! co/ may be l[1 & ! effect good1 b are !y suffici5t to comp5sate = ! risks necess>ily dep5d5t ^u ! use ( explosives8 ,! d\bt impli$ 9 t "q1 natural ?\gh x be1 is bas$ ^u prejudice1 ) :i* we are all m or less afflict$4 ,! art ( mak+ ^! explosive sub/ances has be5 br\ght to su* a pit* t ) reasonable c>e !re is no risk :atev]4 ,! greate/ possible c>e is us$ 9 ! factory to see t all explosives s5t out are :at !y are meant to be1 & t !y c !re=e be reli$ ^u to behave accord+ to programme & n to play any tricks4 ,t is ! fir/ /ep1 & :at ) competition betwe5 mak]s1 ,gov]nm5t inspection1 & se>*+ inquiry into ! slighte/ accid5t1 & ! desire ( ea* mak] to keep up ! cr$it ( 8 "n1 x is safe to say t mod]n explosives may be reli$ ^u to d _! duty fai?fully4 ,! second /ep 9 ! process ( secur+ safety is t ! p[]ful explosive1 ! "o t does ! "w1 is made v ins5sitive1 s t x is really q h>d to explode x4 ,) reasonable c>e1 !n1 x w nev] g (f by accid5t4 ,on ! o!r h&1 ! s5sitive mat]ial1 :i* is easy to let (f1 is 9 v small quantities1 s small t an accid5t ) x w\ld n1 aga9 ) reasonable precautions1 be a s]i\s matt]4 ,fuse1 too1 is v reliable n[adays4 ,! man :o lights ! fuse may be absolutely sure t he w h t "t to get to a place ( safety :i* corresponds to ! l5g? ( fuse :i* he employs4 ,) electrical fir+1 too1 x is q easy to arrange t ! f9al electrical connection %all n be made until all are at a safe di/ance1 s t a premature explosion is impossible4 ,9 _m ( ! cases describ$1 ! %ock takes place almo/ entirely )9 ! e>? & !re is v little debris ?r[n ab\t4 ,inde$ ! only dang] :i* is to be fe>$ ) ^! op]ations is ab\t on a p> ) t :i* e f>m h& runs f ! kick ( a horse4 ,any c>eful1 tru/wor?y man c\ld be q safely taught to d ?is "w1 & ) ! assi/ance ( a lab\r] he c\ld d all t is necess>y4 ,giv5 a fair am\nt ( intellig5ce1 too1 he w\ld take b little tea*+4 ,altoge!r !re is no d\bt t ! use ( explosives is go+ to h a m>k$ effect ^u f>m+ op]ations 9 ! ne> future4 ,,*apt] ,,ii ,,measur+ ,,electricity ,!re are _m p ^: acqua9tance ) electricity consi/s ma9ly 9 pay+ ! electric light bill4 ,to su* ! in/rum5ts :]eby electricity is measur$ w make a specially int]e/+ appeal4 ,curr5t is sold 9 ,great ,brita9 at s mu* p] ,bo>d ( ,trade ,unit4 ,to /ate :at t is ne$s a prelim9>y explanation ( ! o!r units employ$ 9 connection ) electric curr5ts4 ,! public electricity supply 9 any di/rict is ann\nc$ to be s _m volts1 x may be #ajj1 #bjj or p]haps #bcj1 b :atev] x be1 x is always s _m volts4 ,!n ! electrician speaks lightly ( numb]s ( amp]es1 he may ev5 talk ( ! numb] ( watts us$ by ! lamps1 :ile occasionally ! ^w ohm w leak out4 ,among ^! t]ms ! g5]al read] is apt to become completely fog-b\nd4 ,b really !y are q simple if once und]/ood1 &1 z we %all see 9 a mom5t1 !re are "s v rem>kable in/rum5ts = measur+ !m1 "s ( :i* exhibit a delicacy truly a/oni%+4 ,x is well at ! outset to try & dive/ ourselves ( ! idea t !re is any?+ my/]i\s or occult ab\t electricity4 ,x is q true t !re are _m ?+s ab\t x v little und]/ood ev5 by ! mo/ le>n$1 b = ord9>y practical purposes x may be reg>d$ z a fluid1 :i* fl[s along a wire j z wat] fl[s along a pipe4 ,! wire is1 electrically speak+1 a hole ?r\gh ! air or o!r non-conduct+ sub/ance ) :i* x is surr\nd$4 ,a wat]-pipe be+ a hole ?r\gh a b> ( iron1 s ! copp] core ( an electrical wire is1 s f> z ! curr5t is conc]n$1 b a hole ?r\gh ! c5tre ( a tube ( silk1 cotton1 rubb] or :atev] x be4 ,electricity c fl[ ?r\gh c]ta9 solids j z wat] c fl[ ?r\gh empty space4 ,wat] w n fl[ ?r\gh a pipe unless a pressure be appli$ to x some:]e4 ,9 a pipe ! ends ( :i* are at ! same level wat] w lie in]t & motionless4 ,l[] "o end1 h[ev]1 & ! pressure produc$ by gravity--9 o!r words1 ! weight ( ! wat]--w cause x to move4 ,9 l mann] pressure produc$ by ! action ( a pump w make wat] fl[4 ,on ! o!r h&1 :5 x moves x enc\nt]s resi/ance1 ?r\gh ! wat] rubb+ aga9/ ! walls ( ! pipe4 ,simil>ly1 an electrical pressure is necess>y be=e a curr5t ( electricity w fl[4 ,& e conductor (f]s m or less resi/ance to ! fl[ ( curr5t1 ?us oppos+ ! action ( ! pressure4 ,be=e curr5t w fl[ ?r\gh y\r dome/ic gl[-lamps & cause !m to give light !re mu/ be a pressure at "w1 & t pressure is describ$ z s _m volts4 ,a batt]y is really a little automatic electrical pump = produc+ an electrical pressure4 ,& ! volt1 :i* is a legal measure1 j z mu* z a p\nd or a y>d1 is a c]ta9 fraction ( ! pressure produc$ by a c]ta9 batt]y kn[n z ,cl>k's ,cell4 ,x is n necess>y "h to say exactly :at t fraction is1 b x w give a g5]al idea to /ate t ! ord9>y ,leclan*e or dry cell1 su* z is us$ = electric bells1 produces a pressure ( ab\t "o & a half volts4 ,?us we see ! volt is ! electrical c\nt]p>t ( ! t]m p\nd p] squ>e in* :i* is us$ 9 ! case ( wat] pressure4 ,a fl[ ( wat] is measur$ 9 gallons p] m9ute4 ,an electrical curr5t is measur$ 9 c\lombs p] second4 ,?us ! c\lomb is ! electrical c\nt]p>t ( ! gallon4 ,b 9 ?is p>ticul> we diff] slightly 9 our me?ods ( talk+ ( wat] & electricity4 ,gallons p] m9ute or p] h\r is ! inv>iable t]m 9 ! =m] case1 b 9 ! latt] we d n speak ( c\lombs p] second1 al?\gh t is :at we mean1 = we h a special "n = "o c\lomb p] second1 & t same is amp]e4 ,"o amp]e is "o c\lomb p] second1 two amp]es are two c\lombs p] second1 & s on4 ,!re is no recognis$ t]m to d5ote ! resi/ance :i* a wat]-pipe (f]s to ! passage ( wat] ?r\gh x1 b 9 ! simil> case ) electricity !re is a t]m specially inv5t$ = ! purpose1 ! ohm4 ,legally x is ! resi/ance ( a column ( m]cury ( a c]ta9 size & weight4 ,a r\gh idea ( x is giv5 by ! fact t a copp] wire a sixte5? ( an in* ?ick & #djj feet long has a resi/ance ( ab\t "o ohm4 ,! ?ree units--! volt1 amp]e & ohm--are s relat$ t a pressure ( "o volt act+ ^u a circuit ) a resi/ance ( "o ohm w produce a curr5t ( "o amp]e4 ,a curr5t c d "w2 :5 x lights or heats y\r room or drives a tramc> x is do+ "w2 & ! rate at :i* a curr5t does "w is f\nd by multiply+ toge!r ! numb] ( volts & ! numb] ( amp]es4 ,! result is 9 /ill ano!r unit1 ! watt4 ,& #ajjj watts is a kil[att4 ,f9ally1 to cr[n ! :ole /ory1 a kil[att = "o h\r is a ,bo>d ( ,trade unit4 ,s = e unit :i* y pay = 9 ! qu>t]ly bill y h _h a curr5t equal to #ajjj watts = an h\r4 ,to give a concrete example1 if ! pressure ( y\r supply is #bjj volts1 & y take a curr5t ( five amp]es = an h\r1 y w h consum$ "o ,b4,t4,u4 ,p]haps x w give add$ cle>ness to ?is explanation to tabulate ! t]ms z foll[3-- ,volt ,! unit ( pressure1 analog\s to p\nds p] squ>e in* 9 ! case ( wat]4 ,c\lomb ,! measure ( quantity1 analog\s to ! gallon4 ,amp]e ,! measure ( ! /r5g? ( a curr5t1 mean+ "o c\lomb p] second4 ,watt ,! unit d5ot+ ! p[] = "w ( any curr5t4 ,x is ! result ( multiply+ toge!r volts & amp]es4 ,kil[att #ajjj watts4 ,bo>d ( ,trade ,unit ,a curr5t ( "o kil[att fl[+ = "o h\r4 ,illu/ration3 ,by p]mission ( ,dupont ,p[d] ,co4 ,a ,,f9e ,,crop ,cel]y gr[n on soil till$ by dynamite4--,see p4 #bd ,9 practice ! measurem5ts are g5]ally made by means ( ! connection betwe5 electricity & magnetism4 ,a curr5t ( electricity is a magnet4 ,:5ev] a curr5t is fl[+ x is surr\nd$ by a region 9 :i* magnetism c be felt4 ,?is region is call$ ! magnetic field1 & ! /r5g? ( ! field v>ies ) ! /r5g? t is ! numb] ( amp]es 9 ! curr5t4 ,if a wire c>ry+ a curr5t be w\nd up into a coil x is evid5t t ! magnetic field w be m int5se ?an if ! wire be /raight1 = x w be conc5trat$ into a small] area4 ,iron1 ) its peculi> magnetic prop]ties1 if plac$ 9 a magnetic field seems to draw ! magnetic =ces t[>ds itself1 & consequ5tly1 if ! wire be w\nd r\nd a core ( iron1 ! magnetism due to ! curr5t w be l>gely conc5trat$ at ! ends ( ! core4 ,b ! ma9 pr9ciple rema9s--9 any giv5 magnet ! magnetic p[] exhibit$ w be 9 proportion to ! curr5t fl[+4 ,! swit*bo>d at a g5]at+ /ation is always suppli$ ) in/rum5ts call$ ammet]s1 an abbreviation ( amp]emet]s1 = ! purpose ( measur+ ! curr5t pass+ out f ! dynamos4 ,ea* ( ^! consi/s ( a coil ( wire ?r\gh :i* ! curr5t passes4 ,9 "s !re is a piece ( iron ne> by1 :i* is attract$ m or less z ! curr5t v>ies1 ! iron be+ pull$ back by a spr+ & its movem5t aga9/ ! t5sion ( ! spr+ be+ indicat$ by a po9t] on a dial4 ,9 o!rs ! coil itself is free to sw+ 9 ! neighb\rhood ( a p[]ful /eel magnet1 ! int]action betwe5 ! electro-magnet1 or coil1 & ! p]man5t magnet be+ su* t !y approa* ea* o!r or rec$e f ea* o!r z ! curr5t v>ies4 ,a po9t] on a dial records ! movem5ts z be=e4 ,9 yet ano!r k9d ! p]man5t magnet gives way to a second coil1 ! curr5t pass+ ?r\gh bo? 9 succession1 ! result be+ v mu* ! same1 ! two coils attract+ ea* o!r m or less accord+ to ! curr5t4 ,ano!r k9d ( ammet] kn[n z a !rmo-ammet] works on q a diff]5t pr9ciple4 ,x consi/s ( a piece ( f9e plat9um wire :i* is arrang$ z a %unt--t is to say1 a c]ta9 small b def9ite proportion ( ! curr5t to be measur$ passes ?r\gh x4 ,n[1 be+ f9e1 ! curr5t has consid]able difficulty 9 =c+ its way ?r\gh ?is wire & ! en]gy s exp5d$ becomes turn$ into heat 9 ! wire4 ,x is inde$ a mild =m ( :at we see 9 ! filam5t ( an inc&esc5t lamp1 :]e ! en]gy exp5d$ 9 =c+ ! curr5t ?r\gh makes ! filam5t :ite-hot4 ,! same pr9ciple is at "w :5 we rub out a p5cil m>k ) india-rubb]1 :]eby ! rubb] becomes heat$1 z mo/ ( u h obs]v$4 ,! wire1 !n1 is heat$ by ! curr5t pass+ ?r\gh x1 & accord+ly exp&s1 ! am\nt ( expansion =m+ an indication ( ! curr5t pass+4 ,! elongation ( ! wire is made to turn a po9t]4 ,a simple modification makes any ( ^! in/rum5ts into a voltmet]4 ,?is in/rum5t is int5d$ to measure ! =ce or pressure 9 ! curr5t z x leaves ! dynamo4 ,a %ort bran* circuit is con/ruct$1 lead+ f ! positive wire ne> ! dynamo to ! negative wire1 or to ! e>?1 :]e ! pressure is z]o4 ,9 ?is circuit is plac$ ! in/rum5t1 toge!r ) a coil made ( a v long l5g? ( f9e wire s t x has a v great resi/ance4 ,v little curr5t w fl[ ?r\gh ! bran* circuit because ( ! high resi/ance ( ! coil1 b :at !re is w be 9 exact proportion to ! pressure4 ,! voltmet] is !re=e ! same z ! ammet]1 except t its dial is m>k$ = volts in/ead ( = amp]es1 & x has to be provid$ ) ! resi/ance coil4 ,in/rum5ts ( ! ammet] type c also be us$ z ohmmet]s4 ,9 ?is case :at is want$ is to te/ ! resi/ance ( a circuit1 & x is done by apply+ a batt]y1 ! voltage ( :i* is kn[n1 & see+ h[ mu* curr5t fl[s4 ,all ! voltmet]s & ohmmet]s m5tion$ owe _! me?od ( work+ to :at is kn[n z ,ohm's law4 ,"o ( ! greate/ /eps 9 ! developm5t ( electrical sci5ce 0 tak5 :5 ,dr ,ohm put =w>d ! law :i* he _h discov]$ :]eby pressure1 curr5t & resi/ance are relat$4 ,! read] w probably h notic$ f :at has already be5 said ab\t ! units ( measurem5t--! volt1 ! amp]e & ! ohm--t ! curr5t v>ies directly z ! pressure & inv]sely z ! resi/ance4 ,t is ! fam\s & important ,ohm's law & anyone :o has once grasp$ t has gone a long way t[>ds und]/&+ _m ( ! pr9cipal ph5om5a ( electric curr5ts4 ,b ! in/rum5ts s f> ref]r$ to are ( ! big1 clumsy type1 suitable = measur+ l>ge curr5ts & great pressures4 ,!y are l ! great railway weigh-bridges1 :i* weigh a :ole truck-load at a "t & are good en\gh if !y are true to a qu>t] ( a hundr$weight4 ,! in/rum5ts ab\t to be describ$ are m comp>able ) ! delicate balance ( ! *emi/1 :i* c detect ! add$ weight :5 a p5cil m>k is made ^u a piece ( pap]4 ,inde$ beside !m su* a balance is q crude & clumsy4 ,!y may be said to be ! mo/ delicate measur+ in/rum5ts 9 exi/5ce4 ,we w comm5ce ) ! galvanomet]4 ,! simple/ =m ( ?is is a ne$le l t ( a m>9]'s compass v delicately susp5d$ by a ?9 fibre 9 ! neighb\rhood ( a coil ( wire4 ,! magnetic field produc$ by ! curr5t fl[+ 9 ! wire t5ds to turn ! ne$le1 :i* movem5t is resi/$ by its natural t5d5cy to po9t nor? & s\?4 ,?us ! curr5t only turns ! ne$le a c]ta9 di/ance1 :i* di/ance w be 9 proportion to its /r5g?4 ,! deflection ( ! ne$le1 !re=e1 gives u a measure ( ! /r5g? ( ! curr5t4 ,b su* an in/rum5t is n delicate en\gh = ! mo/ ref9$ exp]im5ts1 & ! improv$ =m g5]ally us$ is due to t pr9ce ( inv5tors1 ! late ,"l ,kelv94 ,he orig9ally devis$ x1 x is int]e/+ to note1 n = laboratory exp]im5ts1 b = practical use z a telegraph in/rum5t 9 connection ) ! e>ly ,atlantic cables4 ,be=e describ+ x1 x may %>p5 ! read]'s int]e/ to m5tion a wond]ful exp]im5t :i* 0 made by ,v>ley1 ! fam\s electrician1 on ! fir/ successful ,atlantic cable4 ,he =m$ a m9ute batt]y ( a brass gun-cap1 ) a scrap ( z9c & a s+le drop ( acidulat$ wat]4 ,?is he connect$ up to ! cable4 ,probably !re is n "o read] ( ?is book b w\ld h ?\ght1 if he _h be5 pres5t1 t ! man 0 mad4 ,:at conceivable good c\ld come ( connect+ su* a feeble s\rce ( electrical pressure to ! two ?\s& miles ( wire spann+ ! great ocean2 ! v idea seems fanta/ic 9 ! extreme4 ,yet t t9y batt]y 0 able to make its p[] felt ev5 ov] t great di/ance1 = ! ,?omson ,mirror ,galvanomet] 0 !re to detect x4 ,two ?\s& miles away1 ! galvanomet] felt & 0 op]at$ by ! =ce g5]at$ 9 a batt]y ab\t ! size ( "o ( ! capital lett]s on ?is page4 ,?is wond]ful in/rum5t consi/$ ( a magnet made ( a small fragm5t ( wat*-spr+1 susp5d$ 9 a horizontal position by means ( a ?read ( f9e silk1 close to a coil ( f9e wire4 ,:5 curr5t fl[$ ?r\gh ! coil ! magnetic field caus$ ! wat*-spr+ magnet to sw+ r\nd1 b :5 ! curr5t ceas$ ! untwi/+ ( ! silk br\ght x back to its orig9al position aga94 ,s f> x seems to diff] v little f ! ord9>y galvanomet] previ\sly m5tion$1 b ! /roke ( g5ius 0 9 ! me?od ( read+ x4 ,) a small curr5t ! movem5t ( ! magnet 0 too small to be obs]v$ by ! unaid$ eye1 s x 0 atta*$ to a m9ute mirror made ( "o ( ^? little circles ( glass us$ = cov]+ microscope slides1 silv]$ on ! back4 ,! magnet 0 cem5t$ to ! back ( ?is1 yet bo? 7 s small t toge!r _! weight 0 support$ by a s+le ?read ( cocoon silk4 ,light f a lamp 0 made to fall ^u ?is mirror1 !reby ?r[+ a spot ( light ^u a di/ant scre54 ,?us ! slighte/ movem5t ( ! magnet 0 magnifi$ into a consid]able movem5t ( ! spot ( light4 ,! beam ( light f ! mirror to ! scre5 became1 9 fact1 a long lev] or po9t]1 )\t weight & )\t friction4 ,! task ( wat*+ ! rock+ to & fro ( ! spot ( light 0 f\nd to be too n]ve-rack+ = ! telegraph op]ators1 & s ,"l ,kelv9 improv$ ^u 8 galvanomet] 9 two ways4 ,he fir/ ( all manag$ to give x great] turn+-p[]1 s t1 actuat$ by ! same curr5t1 ! new in/rum5t w\ld "w mu* m /rongly ?an ! old] "o4 ,!n he utilis$ ?is add$ p[] to move a p5 :]eby ! signals 7 record$ automatically ^u a piece ( pap]4 ,! new in/rum5t is kn[n z ! ,siphon ,record]4 ,! add$ p[] 0 obta9$ by turn+ ! in/rum5t inside out1 z x 71 mak+ ! coil ! mov+ "p & ! p]man5t magnet ! fix$ "p4 ,?is enabl$ him to employ a v p[]ful p]man5t magnet 9 place ( ! m9ute "o made ( wat*-spr+4 ,! int]action ( two magnets is ! result ( _! comb9$ /r5g?1 & t ( ! coil be+ limit$ by ! /r5g? ( ! m9ute curr5t ! only way to increase ! comb9$ p[] ( ! two 0 to sub/itute a l>ge p[]ful magnet = ! small magnetis$ wat*-spr+4 ,?is l>ge magnet w\ld1 ( c\rse1 h be5 too heavy to sw+ easily & !re=e ! positions _h to be rev]s$4 ,s n[ we h two types ( galvanomet]1 bo? due orig9ally to ! inv5tions ( ,"l ,kelv94 ,= "s purposes ! ,?omson type 78 "n 0 ,?omson be=e he became ,"l ,kelv97 are /ill us$1 b 9 a slightly elaborat$ =m4 ,its s5sitiv5ess is su* t a curr5t ( a ?\s&? ( a micro-amp]e w move ! spot ( light appreciably4 ,& :5 "o comes to consid] t a micro-amp]e is a million? "p ( an amp]e ?is is p]fectly a/\nd+4 ,b !re is a m wond]ful /ory /ill to come1 ( an in/rum5t :i* c detect a million? ( a micro-amp]e1 or "o million? ( a million? ( an amp]e4 ,x is n g5]ally kn[n t we are all possessors ( an electric g5]ator 9 ! =m ( ! human he>t1 b x is s1 & ,pr(essor ,e9?ov51 ( ,leyd51 wi%+ to inve/igate ^! curr5ts f ! he>t1 f\nd himself 9 ne$ ( a galvanomet] exce$+ 9 s5sitiv5ess any?+ !n kn[n4 ,ev5 ! t9y ne$les or coils ) _! m9ute mirrors h "s weight & s possess 9 an appreciable degree ! prop]ty ( in]tia1 9 virtue ( :i* !y are loa? to />t movem5t &1 hav+ />t$1 are reluctant to /op4 ,?is in]tia1 x is easy to see1 militates aga9/ ! accurate record+ ( rapid v>iations 9 m9ute curr5ts1 s ! en]getic ,pr(essor set ab\t devis+ a new galvanomet] :i* %\ld answ] 8 purpose4 ,?is is kn[n z ! ,/r+ ,galvanomet]4 ,illu/ration3 ,,fig4 #a4-,?is %[s ! pr9ciple ( ?is wond]ful ,galvanomet] inv5t$ by ,"l ,kelv9 9 its late/ =m4 ,curr5t ent]s at a1 passes r\nd ! coils1 z %[n by ! arr[s1 & away at b4 ,a light rod1 c1 is susp5d$ by ! f9e fibre1 d1 s t ! eight little magnets hang 9 ! c5tres ( ! coils--f\r 9 ea*4 ,! curr5t deflects ^! magnets & s turns ! mirror1 m1 at ! bottom ( ! rod4 ,at e are two l>ge magnets :i* give ! little ones ! necess>y t5d5cy to keep at z]o4 ,illu/ration3 ,,fig4 #b4--;,"h we see ! work+ p>ts ( ! ,/r+ ,galvanomet]1 by :i* ! beat+ ( ! he>t c be regi/]$ electrically4 ,! curr5t fl[s d[n ! f9e silv]$ fibre1 betwe5 ! poles1 a & b1 ( a p[]ful magnet4 ,z ! curr5t v>ies1 ! fibre b5ds m or less4 ,! ma9 body ( ! in/rum5t is a l>ge1 p[]ful electro-magnet1 9 %ape l a l>ge pair ( jaws ne>ly %ut4 ,en]gis$ by a /rong curr5t1 ?is magnet produces an exce$+ly /rong magnetic field 9 ! small space betwe5 ! tee? z x 74 ,9 ?is space !re is /ret*$ a f9e ?read ( qu>tz :i* is almo/ p]fectly ela/ic4 ,x is a non-conductor1 h[ev]1 s x is cov]$ ) a f9e coat+ ( silv]4 ,silv] wire is sometimes us$1 b no way has yet be5 f\nd ( draw+ any metallic wire s ?9 z ! qu>tz fibre1 :i* is sometimes z ?9 z two ?\s&?s ( a millimetre1 or ab\t a twelve-?\s&? ( an in*4 ,a hundr$ pages ( ?is book make up a ?ickness ( ab\t an in*1 s t "o leaf is ab\t a fiftie? ( an in*4 ,consequ5tly ! fibre 9 "q c\ld be multipli$ #bdj times be=e x became z /\t z ! pap] on :i* ^! words are pr9t$4 ,! curr5t to be measur$1 !n1 is pass$ ?r\gh ! /ret*$ fibre & ! int]action ( ! magnetic field by :i* ! fibre is !n surr\nd$1 ) ! magnetic field 9 :i* x is imm]s$1 causes x to be deflect$ to "o side4 ,( c\rse ! deflection is exce$+ly small 9 am\nt1 & z x is undesirable to hamp] its movem5ts by ! weight ( a mirror1 no matt] h[ small1 "s o!r means ( read+ ! in/rum5t _h to be devis$4 ,?is is a microscope :i* is fix$ to "o ( ! jaws1 ?r\gh a f9e hole 9 :i* ! movem5ts ( ! fibre c be view$4 ,or :at is (t5 bett] /ill1 a picture ( ! wire c be project$ ?r\gh ! microscope on to a scre5 or on to a mov+ photographic plate or /rip ( photographic pap]4 ,9 ! latt] case a p]man5t record is made ( ! *anges 9 ! fl[+ curr5t4 ,an electric picture c ?us be made ( ! work+ ( a man's he>t4 ,he holds 9 8 h&s two metal h&les or is 9 "s o!r way connect$ to ! two ends ( ! fibre by wires j z ! h&les ( a %ock+ coil are connect$ to ! ends ( ! coil4 ,! fa9t curr5ts caus$ by ! beat+ ( 8 he>t are ?us set d[n 9 ! =m ( a wavy l9e4 ,su* a diagram is call$ a c>diogram1 & x seems t ea* ( u has a p>ticul> =m ( c>diogram peculi> to himself1 s t a man c\ld almo/ be recognis$ & di/+ui%$ f 8 fell[s by ! electrical action ( 8 he>t4 ,! galvanomet] has a ne> relative1 ! electromet]1 ! a/\nd+ delicacy ( :i* r5d]s x equally int]e/+4 ,x is p>ticul>ly valuable 9 c]ta9 important inve/igations z to ! nature & con/ruction ( atoms4 ,! galvanomet]1 x w be rememb]$1 measures m9ute curr5ts2 ! electromet] measures m9ute pressures1 p>ticul>ly ^? ( small electrically *>g$ bodies4 ,e conductor 7& all ?+s are conductors1 m or less7 c be giv5 a *>ge ( electricity4 ,any insulat$ wire1 = example1 if connect$ to a batt]y w become *>g$--curr5t w fl[ into x & !re rema9 /ation>y4 ,& t is :at we mean by a *>ge z oppos$ to a curr5t4 ,air compress$ into a clos$ vessel is a *>ge4 ,air1 h[ev] compress$1 fl[+ along a pipe w\ld be bett] describ$ z a curr5t4 ,imag9e "o ( ^? cyl9d]s us$ = ! conveyance ( gas "u pressure & suppose t we desire to f9d ! pressure ( ! gas ) :i* x is *>g$4 ,we connect a pressure-gauge to x1 & see :at ! f+] ( ! gauge has to say4 ,:at happ5s is t gas f ! cyl9d] fl[s into ! little vessel :i* con/itutes ! gauge & !re records its own pressure4 ,& j ! same applies ) electromet]s4 ,precisely z ! pressure-gauge measures ! pressure ( air or gas 9 "s vessel1 s ! electromet] measures ! electrical pressure 9 a *>g$ body4 ,fur!r1 "s ( ! *>g$ bodies ) :i* ! /ud5t ( physics is mu* conc]n$ are f> small] ?an c be se5 ) ! mo/ p[]ful microscope4 ,h[ wond]fully m9ute & delicate1 !re=e1 mu/ be ! in/rum5t :i* c be influ5c$ by ! t9y *>ge :i* s small a body c c>ry4 ,x w be int]e/+ "h to describe an exp]im5t p]=m$ ) an electromet] by ,pr(essor ,ru!r=d1 by :i* he det]m9$ h[ _m molecules !re are 9 a c5timetre ( gas1 a numb] v important to "k b v difficult to asc]ta91 s9ce molecules are too small to be se54 ,?is numb]1 by ! way1 is kn[n to sci5ce z ,avogadro's ,con/ant4 ,ev]yone has he>d ( radium1 & kn[s t x is 9 a /ate :i* c be/ be describ$ z a long-drawn-out explosion4 ,x is always %oot+ (f t9y p>ticles4 ,night & day1 ye> 9 & ye> out1 x is fir+ (f ^! exce$+ly m9ute projectiles1 ( :i* !re are two k9ds1 "o ( :i* appe>s to be atoms ( helium4 ,"s ye>s ago1 :5 radium 0 be+ mu* talk$ ab\t & ! names ( ,m4 & ,madame ,curie 7 9 ev]yone's m\?1 little toys 7 sold1 ! inv5tion1 ,i believe1 ( ,sir ,william ,crookes1 call$ sp9?>iscopes4 ,ea* ( ^! consi/$ ( a %ort brass tube ) a small l5s 9 "o end4 ,look+ ?r\gh ! l5s 9 a d>k room1 "o c\ld see little spla%es ( light on ! walls ( ! tube4 ,^? spla%es 7 caus$ by a t9y speck ( radium 9 ! middle ( ! tube1 ! helium atoms f :i*1 by bomb>d+ ! inn] surface ( ! tube1 produc$ ! sp>ks4 ,n[ if we c c\nt ^? spla%es we c tell h[ _m atoms ( helium are be+ giv5 (f p] m9ute4 ,& if !n we reckon h[ _m m9utes x takes to accumulate a cubic c5timetre ( helium we c easily reckon h[ _m atoms g to ! cubic c5timetre4 ,b ! difficulty is to c\nt !m4 ,s ! le>n$ ,pr(essor call$ 9 ! aid ( ! electromet]4 ,he c\ld n c\nt all ! atoms %ot (f1 s he put ! piece ( radium at "o end ( a tube & an electromet] at ! o!r4 ,e n[ & !n an atom %ot "r ?r\gh ! tube & out at ! f>!r end4 ,& s9ce ea* ( ^! atoms f radium is *>g$ ) electricity1 ea* z x em]g$ op]at$ ! electromet]4 ,by simply wat*+ ! twit*+ ( ! in/rum5t1 !re=e1 x 0 possible to c\nt h[ _m atoms %ot ?r\gh ! tube--"o atom "o twit*4 ,& f ! size & position ( ! tube x 0 possible to reckon :at proportion ( ! :ole numb] %ot (f w\ld pass t way4 ,! result ( ! exp]im5t %[$ t !re are 9 a cubic c5timetre ( helium a numb] ( atoms repres5t$ by #bef foll[$ by sev5te5 n\ghts4 ,& z helium is "o ( ! few sub/ances 9 :i* ! molecule is =m$ ( b "o atom1 t is also ! numb] ( molecules4 ,& n[ consid] ?is1 please4 ,a cubic c5timetre is ab\t ! size ( a boy's m>ble4 ,t conta9s ! va/ numb] ( molecules j m5tion$4 ,& ! electromet] 0 able to detect ! pres5ce ( ^? "o at a "t4 ,ne$ "o add ano!r ^w z to ! inconceivable delicacy ( ! in/rum5t4 ,9 its simple/ =m ! electromet] is call$ ! electroscope4 ,two /rips ( gold-leaf are susp5d$ by _! ends "u a glass or metal %ade4 ,z !y hang normally !y are 9 close proximity4 ,_! upp] ends are1 9 fact1 9 contact & are atta*$ to a small v]tical conductor4 ,a *>ge imp>t$ to ! small conductor w pass d[n into ! leaves1 & s9ce x w *>ge !m bo? !y w repel ea* o!r s t _! l[] ends w sw+ ap>t4 ,su* an in/rum5t is v delicate1 b because ( ! extreme ?9ness ( ! leaves x is v difficult to read accurately ! am\nt ( _! movem5t & s to det]m9e ! *>ge :i* has be5 giv5 to !m4 ,9 a m rec5t improvem5t1 !re=e1 only "o /rip ( gold-leaf is us$1 ! place ( ! o!r be+ tak5 by a copp] /rip4 ,! :ole ( ! movem5t is ?us 9 ! s+le gold-leaf1 z ! copp] /rip is comp>atively /iff1 & x is possible to arrange = ! movem5t ( ?is "o piece ( gold-leaf to be measur$ by a microscope4 ,! o!r pr9cipal k9d ( electromet] we owe1 z we d ! galvanomet]s1 to ! wond]ful +5uity ( ,"l ,kelv94 ,9 ?is ! mov+ "p is a /rip ( ?9 alum9ium1 :i* is susp5d$ 9 a horizontal position by means1 g5]ally1 ( a f9e qu>tz fibre4 ,s9ce x is necess>y t ?is fibre %\ld be a conductor1 :i* qu>tz is n1 x is electro-plat$ ) silv]4 ,?us a *>ge communicat$ to ! upp] end ( ! fibre1 :]e x is atta*$ to ! case1 passes d[n to ! alum9ium ne$le1 z x is call$4 ,n[ ! ne$le is free to sw+ to & fro1 ) a rotat+ motion1 betwe5 two metal plates c>efully insulat$4 ,ea* plate is cut into f\r quadrants1 ! opposite ones be+ electrically connect$1 :ile all are insulat$ f _! ne>e/ neighb\rs4 ,"o set ( quadrants is *>g$ positively1 & "o set negatively1 by a batt]y1 b ^! *>ges h no effect ^u ! ne$le until x is itself *>g$4 ,z soon z t occurs1 h[ev]1 !y pull x r\nd1 & ! am\nt ( its movem5t indicates ! am\nt ( ! *>ge ^u ! ne$le1 & !re=e ! pressure exi/+ ^u ! *>g$ body to :i* x is connect$4 ,! direction ( its movem5t %[s1 moreov]1 :e!r ! *>ge be positive or negative4 ,a little mirror is atta*$ to ! ne$le1 s t its slighte/ motion is reveal$ by ! movem5t ( a spot ( light1 z 9 ! case ( ! mirror galvanomet]s4 ,in/rum5ts su* z ^! are call$ ,quadrant ,electromet]s4 ,my read]s w rememb]1 too1 ! ,/r+ ,galvanomet] already m5tion$4 ,! same idea has be5 adapt$ to ?is purpose4 ,a f9e fibre is /ret*$ betwe5 two *>g$ conductors :ile ! fibre is itself connect$ to ! body ^: *>ge is be+ measur$4 ,! *>ge :i* x d]ives f ! body causes x to be deflect$1 :i* deflection is measur$ by a microscope4 ,9 all cases ( transmission ( electricity ov] long di/ances = light+ or p[] purposes ! curr5ts are alt]nat+4 ,!y fl[ fir/ "o way & !n ! o!r1 rev]s+ p]haps tw5ty times a second1 or x may be two hundr$1 or ev5 m times 9 t %ort p]iod4 ,"s electric railways are work$ ) alt]nat+ curr5t1 & x is us$ = light+ q z mu* z direct curr5t & is equally satisfactory4 ,9 wireless telegraphy x is ess5tial4 ,9 t case1 h[ev]1 ! rev]sals may take place millions ( times p] second4 ,consequ5tly1 to di/+ui% ! comp>atively sl[ly *ang+ curr5ts ( a frequ5cy or p]iodicity ( a few hundr$s p] second f ^! mu* m rapid ones1 ! latt] are m (t5 spok5 ( z electrical oscillations4 ,& ^! alt]nat+ & oscillat+ curr5ts ne$ to be measur$ j z ! direct curr5ts d4 ,yet 9 _m cases ! same in/rum5ts w n answ]4 ,!re has !re=e gr[n up a class ( wond]ful measur+ in/rum5ts specially design$ = ?is purpose1 by :i* n only does ! /ation eng9e] "k :at 8 alt]nat+ curr5t dynamos are do+1 b ! wireless op]ator c tell :at is happ5+ 9 8 app>atus1 ! inve/igator c probe ! subtleties ( ! curr5ts :i* he is work+ )1 & app>atus = all purposes c be design$ & work$ ) a sy/em & reason :i* w\ld be impossible b = ! possibility ( be+ able to measure ! behavi\r ( ! subtle curr5t "u all conditions4 ,"o tr\ble 9 connection ) measur+ ^! alt]nat+ curr5ts is t !y are v reluctant to pass ?r\gh a coil4 ,"o me?od by :i* ?is difficulty c be ov]come has be5 m5tion$ incid5tally already4 ,i ref] to ! heat+ ( a wire ?r\gh :i* curr5t is pass+4 ,?is is j ! same :e!r ! curr5t be alt]nat+ or direct4 ,"o ( ! simple/ in/rum5ts ( ?is class has be5 appropriat$ by ! ,g]mans1 :o h nam$ x ! ,reiss ,electrical ,!rmomet]1 al?\gh x 0 really inv5t$ ne>ly a c5tury ago by ,sir ,william ,sn[ ,h>ris4 ,x consi/s ( a glass bulb on "o end ( a glass tube4 ,! curr5t is pass$ ?r\gh a f9e wire inside ?is bulb1 & z ! wire becomes heat$ x exp&s ! air inside ! bulb4 ,?is expansion moves a little globule ( m]cury :i* lies 9 ! tube1 & :i* =ms ! po9t] or indicator by :i* ! in/rum5t is read4 ,z ! temp]ature ( ! wire rises ! m]cury is =c$ away f ! bulb1 z ! temp]ature falls x returns4 ,& z ! temp]ature is v>i$ by ! passage ( ! curr5t1 s ! movem5t ( ! m]cury is a measure ( ! curr5t4 ,ano!r way is to employ a ,rectifi]4 ,?is is a conductor :i* has ! peculi> prop]ty ( all[+ curr5t to pass "o way b n ! o!r4 ,x ?us elim9ates e alt]nate curr5t & *anges ! alt]nat+ curr5t into a s]ies ( int]mitt5t curr5ts all 9 ! same direction4 ,rectifi$ curr5t is ?us h>dly describ$ by ! t]m cont9u\s1 b /ill x is cont9u\s curr5t 9 ! s5se t ! fl[ is always 9 ! same direction1 & s x c be measur$ by ! ord9>y cont9u\s curr5t in/rum5ts4 ,! difficulty ab\t x is t !re is "s d\bt z to ! relation betwe5 ! quantity ( rectifi$ curr5t :i* ! galvanomet] regi/]s & ! quantity ( alt]nat+ curr5t1 :i* aft] all is ! quantity :i* is really to be measur$4 ,h[ ! rectification is accompli%$ w be ref]r$ to aga9 9 ! *apt] on ,wireless ,telegraphy4 ,b to return to ! !rmo-galvanomet]s1 z ^? are t]m$ :i* asc]ta9 ! /r5g? ( a curr5t by ! heat :i* x produces1 ! simple little contrivance ( ,sir ,william ,sn[ ,h>ris has m elaborate successors1 ( :i* p]haps ! mo/ int]e/+ are ^? associat$ ) ! "n ( ,mr ,w4 ,duddell1 :o has made ! subject l>gely 8 own4 ,besides _! int]e/ z wond]fully delicate measur+ in/rum5ts1 ^! h an add$ int]e/1 s9ce !y introduce u to ano!r /range ph5om5on 9 electricity4 ,we h j not$ ! fact t electricity causes heat4 ,n[ we %all see ! exact opposite1 9 :i* heat produces electrical pressure & curr5t4 ,& ! feature ( ,mr ,duddell's in/rum5ts is ! way 9 :i* ^! two ?+s are comb9$4 ,by a r\ndab\t b v effective way he rectifies ! curr5t to be measur$1 = he fir/ conv]ts "s ( ! alt]nat+ curr5t into heat & !n conv]ts t heat into cont9u\s curr5t4 ,if two pieces ( dissimil> metals be connect$ toge!r by _! ends1 s z to =m a circuit1 & "o ( ! jo9ts be heat$1 an electrical pressure w be g5]at$ :i* w cause a curr5t to fl[ r\nd ! circuit4 ,! direction 9 :i* x w fl[ w dep5d ^u ! metals employ$4 ,! am\nt ( ! pressure w also dep5d ^u ! metals us$1 comb9$ ) ! temp]ature ( ! junctions4 ,) any giv5 pair ( metals1 h[ev]1 ! =ce1 & !re=e ! volume ( curr5t1 w v>y z ! temp]ature4 ,really x w be ! diff]5ce 9 temp]ature betwe5 ! hot junction & ! cold junction1 b if we s arrange ?+s t ! cold junction %all always rema9 ab\t ! same1 ! curr5t :i* fl[s w v>y z ! temp]ature ( ! hot "o4 ,! volume ( t curr5t w !re=e be a measure ( ! temp]ature4 ,su* an arrangem5t is kn[n z a !rmo-c\ple1 & is becom+ ( great use 9 _m manufactur+ processes z a means ( measur+ temp]atures4 ,9 ! ,duddell ,!rmo-galvanomet]s1 !re=e1 ! alt]nat+ curr5t is fir/ l$ to a heat] consi/+ ( f9e plat9is$ qu>tz fibre or ?9 metal wires4 ,j above ! heat] !re hangs a !rmo-c\ple1 consi/+ ( two little b>s1 "o ( bismu? & ! o!r ( antimony4 ,^! two are connect$ toge!r at _! l[] end1 :]e !y ne>ly t\* ! heat]1 b _! upp] ends are kept a little ap>t1 be+ jo9$1 h[ev]1 by a loop =m$ ( silv] /rip4 ,?is arrangem5t w be q cle> f ! accompany+ sket*1 & x w be obs]v$ t ! loop is s %ap$ t ! :ole ?+ c be easily susp5d$ by a delicate fibre :i* w p]mit x to sw+ easily1 l ! coil 9 a mirror galvanomet]4 ,x is inde$ a sw++ coil ( a galvanomet] =m$ ) a s+le turn in/ead ( ! _m turns usual 9 ! ord9>y in/rum5ts1 & x w be notic$ f ! sket* t !re is a mirror fix$ j above ! top ( ! loop4 ,?is coil1 !n1 ) ! !rmo-c\ple at its l[] extremity1 is hung betwe5 ! ends ( a p[]ful magnet mu* z ! fibre ( ! ,e9?ov5 ,galvanomet] is situat$4 ,! alt]nat+ curr5t to be measur$ comes along ?r\gh ! heat]4 ,! heat] rises 9 temp]ature4 ,t w>ms ! l[] end ( ! !rmo-c\ple4 ,in/antly a /eady1 cont9u\s curr5t beg9s to circulate r\nd ! silv] /rip :i* =ms ! coil1 & t1 act+ j z ! curr5t does 9 ! ord9>y galvanomet]1 causes ! coil to sw+ r\nd m or less1 :i* movem5t is indicat$ by ! spot ( light f ! mirror4 ,a curr5t z small z tw5ty micro-amp]es 7or tw5ty million?s ( an amp]e7 c be measur$ 9 ?is way4 ,mr ,duddell has also p]fect$ a wond]ful in/rum5t call$ an ,oscillograph1 = ! /range purpose ( mak+ actual pictures ( ! rise & fall 9 volume ( curr5t 9 alt]nat+ circuits4 ,illu/ration3 ,,fig4 #c4--,! ,duddell ,!rmo-galvanomet]4 ,9 ?is rem>kable in/rum5t alt]nat+ curr5t ent]s at a1 passes ?r\gh ! f9e wire & leaves at b4 ,9 do+ ?is x heats ! wire1 :i* 9 turn heats ! l[] end ( ! bismu? & antimony b>s4 ,?is g5]ates cont9u\s curr5t1 :i* circulates ?r\gh ! loop ( silv] wire1 c1 :i*1 s9ce x hangs betwe5 ! poles1 d & e1 ( a magnet1 is !reby turn$ m or less4 ,! am\nt ( ! turn+ indicates ! /r5g? ( ! alt]nat+ curr5t4 ,to realise ! almo/ miracul\s delicacy ( ^! wond]ful in/rum5ts we ne$ fir/ ( all to con/ruct a m5tal picture ( :at takes place 9 a circuit ?r\gh :i* alt]nat+ curr5t is pass+4 ,! curr5t beg9s to fl[3 x gradually increases 9 volume until x rea*es its maximum3 !n x beg9s to die away until x becomes nil3 !n x beg9s to gr[ 9 ! opposite direction1 increases to its maximum & dies away once m4 ,t cycle ( ev5ts occurs ov] & ov] aga9 at ! rate x may be ( hundr$s ( times p] second4 ,n[ = ! actual effici5t op]ation ( electrical ma*9]y work+ on alt]nat+ curr5t x is v necess>y to "k exactly h[ ^? *anges take place--d !y occur gradually1 ! curr5t gr[+ & increas+ 9 volume regul>ly & /eadily1 or irregul>ly 9 a jumpy mann]8 ,eng9e]s h a great fancy = sett+ out su* *anges 9 ! =m ( diagrams1 9 :i* case ! alt]nations are repres5t$ by a wavy l9e1 & x is ( mu* importance to obta9 an actual diagram %[+ n :at ! *anges %\ld be accord+ to !ory1 b :at !y really are 9 practice4 ,x is !n possible to see :e!r ! wave-=m ( ! curr5t is :at x ought to be4 ,once aga9 we mu/ turn our ?\ghts back to ! /r+ galvanomet]4 ,9 t case1 x w be rememb]$1 !re is a conduct+ fibre pass+ betwe5 ! ends or poles ( a p[]ful magnet1 ! result ( :i* arrangem5t is t z ! curr5t passes ?r\gh ! fibre x is b5t by ! action ( ! magnetic =ces produc$ ar\nd x4 ,if ! curr5t pass "o way1 d[nw>ds let u say1 ! fibre w be b5t "o way1 :ile if x pass upw>ds x w be b5t ! opposite way4 ,suppose !n t we h two fibres in/ead ( "o1 & t we s5d ! curr5t up "o & d[n ! o!r4 ,"o w be b5t inw>ds & ! o!r outw>ds4 ,!n suppose t we fix a little mirror to ! c5tre ( ! fibres1 "o side ( x be+ atta*$ to "o fibre & ! o!r to ! o!r4 ,z "o fibre advances & ! o!r rec$es ! mirror w be turn$ m or less4 ,consequ5tly1 z ! curr5t fl[+ 9 ! fibres increases or decreases1 or *anges 9 direction1 ! mirror w be slew$ r\nd m or less 9 "o direction or ! o!r4 ,! spot ( light ?r[n by ! mirror w !n dance f side to side ) e v>iation1 & if x be made to fall ^u a rapidly mov+ /rip ( photograph pap] a wavy l9e w be drawn ^u ! pap] :i* w fai?fully repres5t ! *anges 9 ! curr5t4 ,9 its action1 ( c\rse1 x is n unlike an ord9>y mirror galvanomet]1 b its special feature is 9 ! me*anical arrangem5t ( its p>ts :i* enable x to move ) suffici5t rapidity to foll[ ! rapidly succe$+ *anges :i* ne$ to be inve/igat$4 ,x is f> less s5sitive ?an1 say1 a ,?omson ,galvanomet]1 b ! latt] c\ld n respond quickly en\gh = ?is p>ticul> purpose4 ,,*apt] ,,iii ,,! ,,fuel ,,( ,,! ,,future ,we n[ ent] = a :ile ! realm ( organic *emi/ry1 a bran* ( k :i* is ( supreme int]e/1 s9ce x cov]s ! matt]s ( :i* our own bodies are con/ruct$1 ! foods :i* we eat & ! bev]ages :i* we dr9k1 besides a ho/ ( o!r ?+s ( great value to u4 ,al?\gh ! old division ( *emi/ry into inorganic & organic is /ill kept up z a matt] ( conv5i5ce1 ! old b\nd>ies betwe5 ! two h become l>gely oblit]at$4 ,! di/9ction arose f ! fact t !re us$ to be 7& are /ill to a v great ext5t7 a numb] ( highly complex sub/ances ! composition ( :i* is kn[n1 = !y c be analys$1 or tak5 to pieces1 b :i* ! wit ( man has fail$ to put toge!r4 ,consequ5tly ^! sub/ances c\ld only be obta9$ f organic bodies4 ,! liv+ trees1 or animals1 c\ld 9 "s my/]i\s way br+ ^! comb9ations ab\t1 b man c\ld n4 ,! molecules ( ^! sub/ances are mu* m complicat$ ?an ^? ) :i* ! inorganic *emi/ deals4 ,! important +r$i5t 9 !m all is c>bon1 :i* ) hydrog51 nitrog5 & oxyg5 almo/ completes ! li/ ( ! simple elem5ts ( :i* ^! m>vell\s sub/ances are comp\nd$4 ,9 "s cases !re appe> to be hundr$s ( atoms 9 ! molecule4 ,if "o takes a glance at a text-book on organic *emi/ry ! pages are se5 to be spr9kl$ all ov] ) ,c's & ,o's1 ,n's & ,h's1 ) b an occasional symbol = "s o!r elem5t4 ,ano!r feature ( ?is bran* :i* _c fail to /rike ! casual obs]v] is ! que] names :i* _m ( ! sub/ances possess4 ,trime?ylanil9e1 triph5ylme?ane & mononitroph5ol are a few examples :i* happ5 to occur to ! memory1 & !y are by no means ! longe/ or que]e/-s\nd+4 ,ano!r peculi>ity ab\t ^! organic sub/ances is t a numb] ( !m1 ea* q diff]5t f ! o!rs1 c be =m$ ( ! same atoms4 ,c]ta9 atoms ( hydrog51 sulphur & oxyg5 =m sulphuric acid1 & "u :atev] conditions !y comb9e !y nev] =m any?+ else4 ,on ! o!r h&1 !re are sixty-six diff]5t sub/ances all =m$ ( eight ( c>bon1 twelve ( hydrog5 & f\r ( oxyg54 ,?is c only mean t 9 su* cases z ! latt] ! atoms h diff]5t gr\p+s & t :5 gr\p$ 9 "o way !y =m "o ?+1 9 ano!r way "s o!r ?+1 & s on4 ,?is expla9s ! extreme difficulty :i* ! *emi/ f9ds 9 build+ up "s ( ^! organic sub/ances4 ,e n[ & aga9 we are />tl$ by "s em95t man /at+ t ! "t w come :5 we %all be able to make liv+ ?+s1 :5 ! laboratory w turn out liv+ c[s & %eep1 birds & insects1 ev5 man ) a m9d & s\l ( 8 own4 ,yet "o _c b feel t su* m51 no matt] h[ great _! au?ority1 are simply pull+ ! public's leg1 to use a colloquial expression4 ,= !y hopelessly fail to make _m ( ! commone/ ?+s4 ,9 _m cases :]e !y wi% to produce an organic sub/ance !y h to call 9 ! aid ( "s liv+ ?+ to d x = !m1 ev5 if x be b a humble microbe4 ,= ! microbes p]=m wond]ful feats 9 *emi/ry1 f> surpass+ ^? ( ! mo/ em95t m54 ,h5ce ! latt] v s5sibly use ! microbe1 employ x to "w = !m1 j set ?+s 9 ord] & !n /& by :ile ! microbe does ! "w4 ,?us mo/ ?+s c be analys$--t is to say1 tak5 to pieces--:ile _m ?+s c n[ be syn!sis$--t is to say1 built up f _! con/itu5t atoms--b /ill a great _m rema91 & among !m ! mo/ important1 ! syn!sis ( :i* completely baffles man4 ,"o ( ! mo/ useful & widespread sub/ances1 = example1 cellulose1 is1 at pres5t at lea/1 utt]ly beyond u4 ,we d n ev5 "k h[ _m atoms !re are 9 ! cellulose molecule4 ,! molecules may1 = all we "k1 conta9 ?\s&s ( atoms4 ,inde$ _m ( ^! organic matt]s h v l>ge molecules4 ,& ev5 if ! *emi/ 7 able to make all k9ds ( organic matt]1 he w\ld /ill be z f> (f z ev] f mak+ liv+ matt]4 ,indigo us$ to be d]iv$ entirely f plants ( t "n4 ,"o ( ! greate/ triumphs ( ! organic *emi/ 0 :5 he produc$ artificial or syn!tic indigo4 ,b he is z f> (f z ev] f mak+ ! indigo plant4 ,x is claim$ t syn!tic rubb] is exactly ! same z natural rubb]1 al?\gh "s us]s say x is n q ! same4 ,/ill1 if x be s1 x is dead rubb]1 n ! liv+ "p ( ! plant4 ,! "t1 !n1 is inf9itely f> di/ant :5 ! *emi/ w be able to make any?+ ) ! *>act]i/ics ( life--namely1 to gr[ by accretion f )9 & to reproduce its k9d4 ,! mo/ wond]ful product ( ! laboratory is dead4 ,at mo/ x simply resembles some?+ :i* once 0 alive4 ,b t is some:at ( a digression4 ,?is diss]tation on organic *emi/ry 0 simply int5d$ to lead up to ! "q ( liquid fuels1 all ( :i* are organic4 ,9 ! life ( to-day "o ( ! mo/ important ?+s is petroleum4 ,?is is a k9d ( liquid coal4 ,j h[ x 0 =m$ d[n 9 ! dep?s ( ! e>? is n cle>4 ,"o idea is t x is due to ! decomposition ( animal & vegetable matt]4 ,ano!r is t c]ta9 volcanic rocks :i* are kn[n to conta9 c>bide ( iron might1 "u ! influ5ce ( /eam1 h 9 bygone ages giv5 (f petroleum1 or p>aff91 to use ! o!r "n = ! same ?+4 ,9 _m p>ts ( ! _w ^! deposits ( oil are obta9$ by s9k+ wells & pump+ up ! oil4 ,9 o!rs ! liquid gu%es out )\t ! necessity ( pump+ at all4 ,?is is believ$ to be due to ! fact t wat] pressure is at "w4 ,artesian wells1 f :i* ! wat] ru%es ( its own accord1 are q famili>1 & are due to ! fact t "s und]gr\nd res]voir tapp$ by ! well is f$ ?r\gh natural pipes1 really fissures 9 ! rock1 f "s po9t high] ?an ! m\? ( ! well4 ,n[ suppos+ t a res]voir ( oil 7 also 9 communication ) ! upp] _w 9 ! same way1 ! desc5d+ wat] w\ld g to ! bottom1 und]nea? ! light] oil1 & w\ld ?us lift x up1 s t on be+ tapp$ ! oil w\ld ru% out4 ,ano!r s\rce ( m9]al oil is %ale1 su* z is to be f\nd 9 va/ deposits 9 ! s\?-ea/ ( ,scotl&4 ,?is %ale is m9$ mu* z coal is3 x is !n heat$ 9 retorts z coal is heat$ at ! gas-works3 & ! vap\r :i* is giv5 (f1 on be+ cond5s$1 =ms a liquid l crude petroleum4 ,9 all ^! cases ! orig9al oil is a mixture ( a great numb] ( grades diff]+ f ea* o!r 9 v>i\s ways4 ,!y are all hydro-c>bons1 :i* means comp\nds ( c>bon & hydrog51 & !y ext5d f cymog5e 7! molecules ( :i* conta9 f\r atoms ( c>bon & t5 ( hydrog57 to p>aff9 wax1 :i* has some:]e ab\t ?irty-two ( c>bon to sixty-six ( hydrog54 ,= practical purposes _! mo/ important diff]5ce is ! temp]ature at :i* !y boil1 or turn quickly into vap\r4 ,?is =ms ! means by :i* !y are sort$ out4 ,9 a huge /ill1 l a /eam-boil]1 ! crude or mix$ oil is gradually heat$1 & ! gas giv5 (f is l$ to a cool+ vessel :]e x is *ill$ back into liquid4 ,! lighte/ ( all1 cymog5e1 is giv5 (f ev5 at ! freez+-po9t ( wat]4 ,t is l$ into "o *amb] & cond5s$ !re4 ,!n1 z ! temp]ature rises to #ah deg4 ,c41 rhigol5e is giv5 (f3 t is collect$ & cond5s$ 9 ano!r vessel4 ,betwe5 #gj deg4 & #abj deg4 petroleum e!r & petroleum naph?a are produc$1 & !y toge!r con/itute :at is commonly call$ petrol4 ,betwe5 #abj deg4 & #aej deg4 petroleum b5z9e arises4 ,all ! =ego+ tak5 toge!r con/itute ab\t #h to #aj p] c5t4 ( ! :ole crude oil4 ,!n betwe5 #aej deg4 & #cjj deg4 !re comes (f ! great bulk ( ! oil1 ne>ly #hj p] c5t41 ! k]os5e or p>aff9 :i* we burn 9 lamps4 ,above #cjj deg4 !re is obta9$ ano!r oil1 :i* is us$ = lubrication1 also ! invaluable vasel9e1 & f9ally1 :5 ! /ill is all[$ to cool1 !re rema9s a solid residuum kn[n z p>aff9 wax4 ,?is process is kn[n z fractional di/illation1 & x w be notic$ t x consi/s ess5tially 9 collect+ & liquefy+ sep>ately ^? vap\rs :i* are giv5 (f at diff]5t ranges ( temp]ature4 ,= our purpose 9 ?is *apt] we are ma9ly conc]n$ ) ! petrol & ! k]os5e4 ,_m ef=ts h be5 made 9 times gone by to use k]os5e = fir+ ! boil]s ( /eam-eng9es4 ,9 naval vessels a great deal is s us$ at ! pres5t "t4 ,b ! *ief me?od ( employ+ oil = g5]at+ p[] is to use x 9 an int]nal combu/ion-eng9e4 ,^! ma*9es h be5 dealt ) at l5g? 9 ,eng9e]+ ( ,to-day & ,me*anical ,inv5tions ( ,to-day & s mu/ be simply m5tion$ "h4 ,!y consi/ ( two types4 ,9 "o1 :i* is exemplifi$ by ! ord9>y c> or bicycle motor1 ! oil is gasifi$ 9 a vessel call$ a c>burett] or vaporis] & !n l$ into ! cyl9d] ( ! eng9e1 toge!r ) ! necess>y air to enable x to burn4 ,at ! "r mom5t a sp>k ignites ! mixture1 :i* burns sudd5ly1 caus+ a sudd5 expansion1 9 o!r words1 an explosion4 ,?us ! p[] ( ! eng9e is d]iv$ f a succession ( explosions4 ,if ! fuel be petrol x vaporises at ! ord9>y temp]ature ( ! eng9e & ne$s no add$ heat4 ,) k]os5e1 h[ev]1 heat has to be employ$ 9 ! vaporis] to make x turn readily into a gas4 ,! o!r me?od is employ$ 9 eng9es ( ! new ,diesel type1 9 :i* ! cyl9d] ( ! eng9e1 be+ already fill$ ) hot air1 has a jet ( oil spray$ into x4 ,! heat ( ! air causes x to bur/ into flame1 caus+ an expansion :i* drives ! eng9e4 ,an important feature 9 ! latt] type ( eng9e is t ! oil is v completely burnt1 s t v heavy oils c be us$1 oils :i*1 if employ$ 9 an eng9e ( ! o!r k9d1 w\ld *oke up ! cyl9d] ) soot4 ,9 o!r words1 ! range ( oils :i* c be us$ 9 ?is new k9d ( eng9e is mu* wid] ?an is possible 9 ! o!rs4 ,! latt] may be lik5$ to a fa/idi\s man :o is v p>ticul> ab\t 8 food1 :ile ! =m] resembles ! man ( he>ty appetite :o c eat any?+4 ,& j z a man ( ! latt] sort is m easily provid$ = by ! dome/ic au?orities1 s ! ,diesel eng9e makes ! problem ( ! provision ( liquid fuel mu* simpl]4 ,= x mu/ nev] be =gott5 t ! provision ( liquid fuel = ! _w is by no means a simple matt]1 s9ce ! supply is by no means adequate4 ,! output runs into ?\s&s ( millions ( gallons1 & ! :ole _w is be+ se>*$ = new fields ( oil1 & yet x is all swall[$ up z fa/ z x c be produc$1 :ile ! coal m9es d n feel ! competition4 ,a ye> or s ago ! ,unit$ ,/ates & ,russia betwe5 !m 7& !y are ! greate/ produc]s7 obta9$ #e1jjj1jjj1jjj gallons ( oil1 seem+ly an enorm\s quantity4 ,b1 on ! o!r h&1 ,great ,brita9 alone produces ov] #bej1jjj1jjj tons ( coal p] annum4 ,if1 !re=e1 liquid fuel is to displace coal1 z "s p lightly ?9k x is go+ to d1 ! supply w h to be multipli$ _m times4 ,9 ! am\nt ( heat :i* x is capable ( giv+ ! coal ( ,great ,brita9 alone beats ! oil produc$ by ! :ole _w4 ,& ano!r ?+ to be borne 9 m9d is t z ! coal m9] goes d[n to ! seam & sees = himself :at is !re1 :ile ! oil produc] simply /ays at ! surface & draws x up ) a pump1 ! coal man kn[s f> m z to h[ mu* !re is /ill left ?an ! oil man does4 ,we "k t ! coal deposits w la/ = _m ye>s to come1 ev5 if ! production g on increas+1 :]eas ! oil supply may fall (f 9 ! ne> future in/ead ( increas+4 ,& 9 bo? cases we are us+ up capital4 ,coal is n be+ made on ! e>? n[1 at any rate 9 any appreciable quantity4 ,! /age ( ! e>?'s hi/ory fav\rable to ! =mation ( coal measures has long gone by4 ,& ! same probably applies to oil4 ,x is int]e/+ 9 ?is connection to note t coal itself is to a c]ta9 ext5t1 or c be at all ev5ts1 a s\rce ( oil4 ,:5 coal is heat$ 9 ord] to make x give up its gas1 or to turn x into coke1 vap\rs are giv5 (f :i* on cool+ become coal-t>4 ,at "o "t reg>d$ only z a crude sort ( pa9t1 ?is is n[ ! s\rce f :i* _m *emical sub/ances are obta9$1 v>y+ f photographic *emicals to sac*>9e1 a sub/itute = sug>4 ,s valuable are ^! products t !re is a brisk dem& = ! t>1 9 o!r directions ?an ! manufacture ( oils1 b oils ( v>i\s k9ds are also obta9$ f x4 ,! fir/ /ep 9 ! op]ations is fractional di/illation1 aft] ! mann] j describ$ = petroleum4 ,! fir/ fraction is coal-t> naph?a4 ,!n foll[s c>bolic oil1 aft] t heavy or creosote oil1 an?rac5e oil1 & f9ally !re rema9s 9 ! /ill on cool+ a solid residue kn[n z coal-pit*4 ,! naph?a1 on be+ di/ill$ aga91 gives1 among o!r ?+s1 b5z9e1 f :i* ! fam\s anil9e dyes are made1 & :i* is useful 9 _m indu/ries4 ,creosote is l>gely employ$ z a pres]vative = wood1 be+ =c$ into ! timb] "u high pressure1 s t x p5etrates "r into x & t5ds to prev5t rott+1 no matt] h[ wet x may be4 ,railway sleep]s are ?us treat$1 small truck-loads ( !m be+ run into a ca/-iron tunnel :i* is !n seal$ at bo? ends1 :ile ! creosote is =c$ 9 by p[]ful pumps4 ,aft] su* treatm5t !y c lie ne>ly buri$ 9 ! damp balla/ = a long "t )\t any det]ioration4 ,^! coal-t> sub/ances are all v simil> to petroleum & its products1 hydro-c>bons1 comp\nds ( hydrog5 & c>bon 9 v>i\s proportions4 ,_m ( !m c\ld be us$ = fuel4 ,illu/ration3 ,by p]mission ( ,dupont ,p[d] ,co4 ,,apple ,,tree ,,plant$ ,,) ,a ,,spade ,?is apple tree 0 plant$ 9 ! ord9>y way ) a spade4 ,comp>e its size ) t 9 foll[+ illu/ration at p4 #dh4 ,b s9ce !y are bas$ ^u ! supply ( coal1 :i* is itself limit$1 !y _c1 h[ev] !y may be us$1 d m ?an /ave (f ! evil day :5 ! supply w be exhau/$4 ,q diff]5t is x ) alcohol1 :i* x seems likely may be ! fuel ( ! future4 ,"s p w be incl9$ to exclaim ,:at a pity to burn x6 s9ce to _m ! ^w conveys ideas ( ano!r sort altoge!r4 ,!re are _m n[adays1 h[ev]1 :o1 l ! writ]1 h none b a sci5tific int]e/ 9 x4 ,to su* :isky1 = example1 is b impure alcohol1 & x is )\t ! impurities t x may become ( va/ use to ! _w1 !reby possibly repay+ man = "s ( ! h>m :i* 9 ! pa/ x has inflict$ ^u him4 ,alcohol1 aga91 is a hydroc>bon4 ,x is really m correct to speak ( x 9 ! plural1 z alcohols1 s9ce !re is a l>ge gr\p ( sub/ances all ( ! same "n4 ,two ( ^! are ( ! greate/ importance1 me?yl alcohol & e?yl alcohol4 ,! =m] is obta9$ f wood1 h5ce x is sometimes call$ wood _s4 ,wood is /rongly heat$ 9 an iron /ill1 & ! me?yl alcohol is giv5 (f 9 ! =m ( vap\r1 :i* on be+ collect$ & cool$ cond5ses into liquid4 ,x is exce$+ly unpleasant to ! ta/e3 if x 7 ! only k9d !re w\ld be no consumption ( alcohol z a dr9k4 ,! second k9d m5tion$ is obta9$ by ! ag5cy ( g]ms or microbes1 & ! /ory ( its production is s int]e/+ z to dem& a little space4 ,we w comm5ce ) ! malt/]4 ,he p]=ms ! fir/ "p ( ! op]ation4 ,/>t+ ) ord9>y b>ley1 by ! action ( heat1 aid$ by natural gr[?1 he produces ! raw mat]ial on :i* ! brew] may "w4 ,n[ b>ley1 l all gra91 is l>gely made up ( />*1 & al?\gh />* w n make alcohol1 x c be turn$ into sug>1 :i* w4 ,s ! task ( ! malt/] is to comm5ce ! *ange ( ! />* 9 ! gra9 into sug>4 ,fir/ ( all x is soak$ 9 wat] & spread ^u floors & heat$ until x beg9s to spr\t4 ,!re is a little "p 9 ea* gra9 call$ ! endosp]m1 :i* is ! embryonic plant1 & ! />* is really ! food provid$ by nature to n\ri% ! gr[+ endosp]m until su* "t z x %all be /rong en\gh to draw its n\ri%m5t f ! soil4 ,9 ord] t x may n be wa%$ away prematurely1 ! />* is lock$ up by nature 9 closely fa/5$ cells1 &1 moreov]1 x is insoluble1 s t wat] _c c>ry x away4 ,! endosp]m1 h[ev]1 has at its disposal c]ta9 sub/ances kn[n z enzymes 7& x increases its /ore ( ^! z x gr[s71 "o ( :i* is able to dissolve away ! walls ( ! cells1 to unlock ! treasures1 z x 71 :ile ! o!r turns ! insoluble />* into soluble matt]1 9 :i* /ate ! gr[+ organism is able to make use ( x z food4 ,s z ! gra9 spr\ts ^u ! malt/]'s floor ?is process is go+ on--! cells are be+ op5$ & _! cont5ts conv]t$ f />* into soluble matt]s4 ,!n1 :5 ! gr[? has gone f> en\gh1 ! gra9 is transf]r$ to a kiln1 :]e x is subject$ to heat1 by :i* ! gr[? is /opp$4 ,! liv+ "p ( ! gra9 is1 9 fact1 kill$4 ,t is ma9ly to /op ! "y plant f eat+ up ! alt]$ />*1 :i* x w\ld d if all[$ "t1 b :i* ! brew] wants to be kept = 8 own use4 ,! malt/]'s task is n[ f9i%$1 & we come to ! brew]'s4 ,! fir/ ?+ he does ) ! malt is to cru% x betwe5 rolls1 !reby lib]at+ ?or\ghly ^? sub/ances :i* h be5 =m$ f ! />* & :i* he int5ds to turn into sug>4 ,hav+ cru%$ x1 he places x 9 ! ma% tun1 a l>ge tank ( wood or iron1 9 :i* x is mix$ ) wat] & subject$ to heat4 ,:ile 9 ?is vessel ! enzymes become active aga9 & turn ! soluble />*1 or a "p ( x1 into a k9d ( sug>4 ,! liquid drawn (f f ! ma% tun1 conta9+1 ( c\rse1 ! sug>1 is subsequ5tly boil$1 num]\s flav\r+ matt]s 7includ+ hops7 are add$1 & !n x is cool$ aga91 ready = ! f9al process--f]m5tation4 ,?is takes place 9 a l>ge vat or tun & is br\ght ab\t by ! ag5cy ( yea/ :i* is add$ to ! liquid4 ,n[ yea/ is a multitude ( microscopic plants r\nd 9 %ape & ab\t "o ?ree-?\s&? ( an in* 9 diamet]4 ,?\gh s small1 ?is little organism is really q complicat$ 9 its /ructure1 & )9 its little body !re are c>ri$ on complicat$ *emical *anges :i* baffle entirely ! mo/ le>n$ *emi/ to imitate4 ,fur!r1 he has yet to f9d out h[ ! little yea/ plant does x4 ,he n only _c imitate ! process1 he does n "k :at ! process is4 ,^! little organisms multiply ma9ly by ! process ( budd+4 ,a new "o gr[s out ( ! side ( ea* old "o1 rapidly rea*es maturity1 breaks away & comm5ces an indep5d5t exi/5ce4 ,no soon] is x free ?an x 9 turn gives bir? to ano!r4 ,inde$ s great is its hurry to propagate itself t sometimes ! new cell beg9s to ?r[ out a bud be=e x has itself sep>at$ f its p>5t4 ,x is !re=e easy to see t yea/ increases 9 quantity by :at "s call leaps & b\nds1 b :i* ! ma!matically m9d$ "k z geometrical progression4 ,! p>ticul> =m ( sug> ) :i* we are conc]n$ "h is kn[n z dextro-glucose4 ,?is ! yea/ splits up into alcohol & c>bonic acid gas4 ,! latt] bubbles up to ! surface1 & escapes into ! air1 :ile ! alcohol becomes dissolv$ 9 ! wat]y liquid4 ,x is believ$ t ! yea/ p]=ms ?is op]ation n directly1 b by ! production ( c]ta9 enzymes1 :i* 9 _! turn act ^u ! sug>4 ,! liquid s =m$ is be]4 ,b s9ce x is alcohol ) :i* we are conc]n$1 & n be]1 _m details connect$ ) its manufacture h be5 omitt$4 ,en\gh has be5 said1 h[ev]1 to %[ t by comp>atively simple processes gra9 ( all sorts1 9 fact1 any?+ :i* conta9s />*1 & su* ?+s are to be f\nd 9 worldwide pr(usion1 c be turn$ into alcohol4 ,all ! really intricate *emical functions are p]=m$ readily & *eaply by liv+ organisms4 ,all man has to d is to set up ! conditions "u :i* ! organisms c "w4 ,9 ! process j describ$ only a portion ( ! />* 9 ! gra9 is conv]t$ into sug>1 h5ce ! p]c5tage ( alcohol 9 be] is comp>atively small4 ,if all ! />* be conv]t$ a liquid mu* /rong] 9 alcohol is produc$1 & if t be di/ill$1 s z to sep>ate ! _s f ! wat] ) :i* x is mix$1 !re results :isky4 ,br&y1 likewise1 is ! _s di/ill$ f w9e1 rum f molasses1 & s on4 ,9 all ^! famili> bev]ages ! ess5tial feature is ?is same alcohol1 ( ! v>iety kn[n z e?yl alcohol4 ,x w be notic$ t 9 ! mak+ ( be] ! alcohol is actually =m$ 9 wat]4 ,!re is a sug>y wat] :i* "u ! action ( ! yea/ becomes an alcoholic wat]4 ,& ?is indicates a v useful feature ab\t ! liquid :5 us$ = indu/rial purposes4 ,a tank full ( petrol is extremely dang]\s1 s mu* s t ! /orage ( petrol is h$g$ ab\t by all mann] ( precautions4 ,! dang] is t x gives (f an inflammable vap\r & t if x once beg9 to burn !re is practically no possibility ( putt+ x out4 ,be+ light] ?an wat]1 x simply clo!s ) a lay] ( fire any wat] :i* may be ?r[n on to x4 ,! wat] 9 su* circum/ances simply s]ves to spread ! nam+ petrol ab\t & s to make matt]s worse4 ,n[ alcohol1 ) its p>tiality = ! companion%ip ( wat]1 behaves q diff]5tly4 ,true1 x also may give (f an inflammable vap\r1 b if a quantity ( x cat* fire x c be ext+ui%$ 9 ! usual way by a fire-eng9e4 ,! wat] & alcohol imm$iately comb9e--! alcohol becomes dissolv$ 9 ! wat] j z sug> may d1 & z soon z ! p]c5tage ( wat] 9 ! mixture becomes consid]able ! burn+ /ops4 ,x may be t "s read]s w h discov]$ ?is fact = !mselves )\t kn[+ precisely :at x 04 ,x is a common dodge ) amateur photograph]s if !y want to dry a negative quickly to imm]se x 9 me?ylat$ _s4 ,! _s seems to take ! wat] out ( ! film &1 itself dry+ quickly1 leaves ! negative 9 a p]fectly dry condition 9 a few m9utes4 ,n[ aft] us+ _s 9 t way x is useless to put x 9 a _s /ove or lamp4 ,x w n burn4 ,me?ylat$ _s is alcohol1 & ! reason :y x has su* a quick dry+ action is t x & ! wat] 9 ! wet film quickly mix4 ,aft] imm]sion ! film is wet1 n ) wat] m]ely1 b ) a mixture ( a lot ( _s & a little wat]4 ,h5ce ! spe$ ) :i* x evaporates4 ,& ! non-inflammability ( ! mixture is due to ! pres5ce ( ! wat]4 ,me?ylat$ _s only diff]s f ! alcohol 9 alcoholic bev]ages 9 t some?+ is add$ to make x undr9kable4 ,ow+ to ! crav+ = x1 :i* is s widespread1 & ! d\btful effect :i* x has on c]ta9 citiz5s1 mo/ /ates reg>d x z pre-em95tly a subject = taxation1 !reby on ! "o h& br++ 9 a good rev5ue1 & on ! o!r disc\rag+ its too free use4 ,b ^? consid]ations apply only to dr9kable alcohol4 ,t :i* is to be us$ = indu/rial purposes is n 9 any way a legitimate object = taxation4 ,h5ce ! problem arises ( mak+ a =m ( alcohol :i* %all answ] all ! ne$s ( ! indu/ries :i* use x1 & at ! same "t be s repulsive to ! s5ses t no "o c possibly dr9k x4 ,?is result is a*iev$ by add+ "s ( ! me?yl alcohol d]iv$ f ! vap\r giv5 (f by wood :5 heat$4 ,commonly kn[n z wood _s1 ?is is s unpleasant t x r5d]s ! mixture ( no use = dr9k+1 & s x c safely be fre$ f taxation4 ,un=tunately ?is _s has less heat+ value ?an petrol4 ,t means t a giv5 quantity ( ea* liquid w produce m heat 9 ! case ( petrol ?an 9 ! case ( alcohol4 ,inde$ ! diff]5ce is ab\t two to "o4 ,h5ce an eng9e to give out a c]ta9 horse-p[] w\ld ne$ to h its cyl9d]s twice z big if x 7 to use alcohol in/ead ( ! o!r fuel4 ,!re is a c]ta9 comp5sation1 h[ev]1 9 ! fact t alcohol is v easily compressible4 ,9 mod]n int]nal combu/ion-eng9es mu* ( ! effici5cy is due to ! explosive *>ge :i* is drawn into ! cyl9d] be+ compress$ into a small space be=e x is fir$4 ,x 0 ! discov]y ( ! value ( compress+ ! gas :i* made ! gas-eng9e s =midable a rival to ! /eam-eng9e1 & ! wond]ful p]=mances ( ! ,diesel eng9es are due v l>gely to ! fact t ! air is compress$ 9 ! cyl9d] to a v high pressure4 ,! jet ( oil burns 9 highly compress$ air4 ,& because ( ! facility ) :i* alcohol c be compress$ x is said to be m effective z a s\rce ( motive p[] ?an w\ld be expect$ f its comp>atively feeble heat4 ,?us we may sum up ! possibilities ( ! future4 ,coal1 petroleum & _! d]ivatives exi/ 9 limit$ quantities 9 ! _w1 & s f> z we c see ! va/ drafts :i* we are tak+ f !m are n be+ replac$1 inde$ at ?is /age ( ! e>?'s developm5t _c be replac$1 by any m4 ,soon] or lat] we mu/ come to an end ( !m4 ,is x n com=t+1 !re=e1 to "k t !re is ano!r s\rce ( fuel at h&1 inexhau/ible1 s9ce x c be produc$ z ne$$4 ,we h only to set ! sun & ! gr\nd to "w to produce gra91 rice1 potatoes1 or any ( ! myriad sub/ances :i* conta9 />*1 & f t1 by simple & well-kn[n processes1 we c obta9 a *eap1 safe & reliable fuel4 ,inde$ !re seems no?+ b ! ultimate loss ( sunlight1 c\ntless millions ( ye>s h5ce1 :i* c ev] *eck ! supply ( ?is valuable commodity4 ,:at has d\btless1 9 _m cases1 be5 a curse 9 ! pa/ may turn out to be ! great boon ( ! future4 ,,*apt] ,,iv ,,"s ,,valuable ,,electrical ,,processes ,/ud5ts ( t bran* ( sci5ce kn[n z physics are com+ to ! conclusion t electricity plays a mu* m important "p 9 ! univ]se ?an 0 suppos$4 ,!y are l$ to believe t electrical attraction is ! cem5t :i* b9ds toge!r ^? exce$+ly m9ute p>ticles out ( :i* ev]y?+ is built up4 ,:e!r electricity b9ds !m toge!r or n1 x is c]ta9 t electrical action c 9 "s cases sep>ate ^? p>ticles1 & ?is process ( sep>ation provides a means ( c>ry+ on "s v rem>kable & useful indu/rial processes4 ,let u imag9e a vessel fill$ ) wat] to :i* has be5 add$ a little sulphuric acid1 :ile susp5d$ 9 x are two /rips ( plat9um4 ,!re is a space betwe5 ! /rips1 s t :5 _! upp] ends are suitably connect$ to a s\rce ( electric curr5t t curr5t fl[s f "o /rip to ! o!r ?r\gh ! liquid4 ,t is an example ( ! app>atus = c>ry+ out ?is electrical sep>ation 9 its simple/ =m1 & x w facilitate ! fur!r description if ! names ( v>i\s p>ts are enum]at$4 ,! process itself is electrolysis2 ! liquid is ! electrolyte1 :ile ! /rips are ! electrodes4 ,! individual electrodes1 aga91 h special names1 t by :i* ! curr5t ent]s be+ ! anode & t by :i* x leaves ! ca?ode4 ,x is n difficult to rememb] :i* is :i* if we be> 9 m9d t ! curr5t trav]ses !m 9 alphabetical ord]4 ,s9ce1 h[ev]1 x may n be easy = ! g5]al read] to c>ry all ^! t]ms 9 8 m9d1 we w1 :5 x is necess>y to diff]5tiate betwe5 ! two electrodes1 call "o ! 9-electrode & ! o!r ! out-electrode4 ,return+ n[ to our imag9>y app>atus1 let u turn on ! curr5t4 ,at fir/ no?+ seems to be happ5+1 al?\gh suitable in/rum5ts w\ld %[ t curr5t 0 fl[+4 ,soon1 h[ev]1 little bubbles appe> ^u ! electrodes1 & ^! gr[ l>g] & l>g]1 until !y deta* !mselves f ! plat9um to :i* !y h be5 adh]+1 float up to ! surface & bur/4 ,! "q :i* naturally arises is1 ,:at d ^? bubbles consi/ (8 ,are !y air8 ,if we take means to collect ! gases :i* =m$ !m we get an unmi/akable answ]4 ,! bubbles :i* arise f ! 9-electrode are oxyg51 ^? f ! o!r hydrog54 ,if we all[ our app>atus to "w = "s "t1 & collect all ! gas :i* arises1 we %all f9d t !re is twice z mu* hydrog5 z oxyg54 ,we %all also f9d1 z ! process goes on1 t ! quantity ( wat] dim9i%es4 ,p]haps ,i may be all[$ at ?is po9t to rem9d my read]s t wat] is a collection ( m9ute ultra-microscopic p>ticles call$ molecules1 ea* ( :i* is =m$ ( ?ree small] p>ticles /ill call$ atoms4 ,( ! ?ree atoms two are hydrog5 & "o oxyg54 ,wat] !re=e consi/s ( hydrog5 & oxyg51 !re be+ twice z mu* ( ! =m] z !re is ( ! latt]4 ,we see1 !re=e1 t electrolysis gives u hydrog5 & oxyg5 9 exactly ^? proportions 9 :i* !y occur 9 wat]1 & s9ce we also see t z ^! gases appe> ! wat] itself disappe>s1 we are l$ to conclude t ! curr5t is splitt+ up ! wat] into ! gases ( :i* x is =m$4 ,b ! /range ?+ is t ?is w n "w ) pure wat]4 ,we h to add some?+ to x4 ,9 ! case ( our imag9>y exp]im5t x 0 sulphuric acid4 ,:at "p does t play8 ,?is is n fully und]/ood1 b we may be able to =m a m5tal picture ( :at is believ$ to happ5 z foll[s4 ,! 9-electrode is surr\nd$ by a va/ assemblage ( ^! t9y molecules1 mo/ ( !m ^? ( wat]1 b a few ^? ( ! acid4 ,! latt] are m complex 9 _! /ructure ?an ! =m]1 b !y too conta9 hydrog54 ,curr5t fl[s into ! electrode & in/antly hydrog5 atoms f ! acid molecules cr[d r\nd x1 l boatm5 at ! seaside anxi\s to secure a pass5g]4 ,ea* takes on bo>d a quantity ( electricity & ) x d>ts across ! int]v5+ space to ! o!r electrode4 ,arriv$ !re1 x gives up its load &1 its "w done1 rema9s ly+ ^u ! electrode until en\gh o!rs l unto itself h ga!r$ !re to =m a bubble & s escape4 ,^! hydrog5 atoms are ?\ght to be ! craft :i* c>ry ! curr5t ?r\gh ! liquid & enable x to pose1 z x 71 z a conductor ( electricity1 :i* 9 reality x is n4 ,b :]e does ! oxyg5 come f8 ,to f9d ! answ] to t we mu/ add a second *apt] to our /ory4 ,:5 ! hydrog5 boats took on bo>d _! load ( electricity !y left _! =m] associates1 & ^! =?) set ^u neighb\r+ wat] molecules & ) ! audacity ( highwaym5 /ole f !m en\gh hydrog5 atoms to take ! place ( ^? !y _h lo/4 ,?us ! acid molecules became complete once m1 :ile ! sc5e ( ! conflict ne> ! 9-electrode 0 /rewn ) ! rema9s ( ! wat] molecules f :i* ! hydrog5 atoms _h be5 /ol54 ,^! rema9s1 ( c\rse1 w\ld be oxyg51 & !y1 collect+ toge!r on ! electrode1 w\ld ev5tually be 9 numb]s suffici5t to =m bubbles & s escape4 ,?us x may be ! acid :i* really does ! "w1 yet because ( its subsequ5t raid ^u ! wat] x is ! latt] :i* disappe>s1 & x is ! mat]ials ( ! latt] :i* are b\ght to ! surface 9 ! bubbles4 ,& !re we see ! me*anism :]eby1 s x is believ$1 electric curr5t c pass ?r\gh o!rwise non-conduct+ liquids4 ,& ! important po9t1 z f> z practical utility is conc]n$1 is t ! passage ( ! curr5t is accompani$ by a splitt+ up ( some?+ or o!r1 ei!r ! wat] or some?+ 9 x1 ! mat]ials ( :i* are deposit$1 "o on "o electrode & ! o!r on ! o!r4 ,& n[ we c proce$ to ^? useful applications ( electrolysis1 ! commone/ ( :i*1 p]haps1 is electro-plat+4 ,we h se5 h[ electrolysis causes hydrog51 probably out ( ! acid1 to be deposit$ ^u "o electrode4 ,suppose t1 in/ead ( an acid1 we put 9 ! wat] "o ( ^? sub/ances kn[n to *emi/s z a salt1 ! commone/ example ( :i* is ord9>y table salt4 ,?is well-kn[n condim5t is caus$ by ! int]action ( hydro*loric acid & ! metal sodium & w s]ve to illu/rate :at all salts are4 ,all acids are comp\nds ( hydrog5 & some?+ else1 & _! bit+ action is due to ! read9ess ) :i* ! some?+ else evicts ! hydrog5 & takes 9 a metal 9 its place4 ,?us hydro*loric acid1 giv5 ! opportunity1 gets rid ( its hydrog5 & takes 9 sodium1 !reby =m+ *loride ( soda or common salt4 ,ano!r example is ! gold *loride famili> to photograph]s4 ,?is is ! result ( ! action ( c]ta9 acids ^u gold1 :]e9 ! acids ?r[ out _! hydrog5 & take 9 gold in/ead4 ,to sum up1 !n1 a salt is j ! same sort ( ?+ z an acid1 l ! sulphuric acid :i* we us$ 9 our exp]im5t1 except t "s metal has tak5 ! place ( ! hydrog54 ,x is n surpris+1 !n1 to f9d t if we put a salt 9 ! electrolyte in/ead ( an acid we get a simil> result4 ,9 ! "o case hydrog5 is deposit$ ^u ! out-electrode1 9 ! o!r ! metal4 ,9 ! =m] case1 s9ce hydrog5 is a gas1 x =ms bubbles & floats away1 b 9 ! latt] ! solid metal rema9s a ?91 ev5 coat+ ^u ! electrode4 ,t is ! pr9ciple ( electro-plat+4 ,! electrolyte consi/s ( a suitable solution conta9+ a salt ( ! metal to be deposit$1 & x is plac$ 9 an insulat+ vessel or vat4 ,! articles to be plat$ =m ! out-electrode1 s t !y h to be susp5d$ 9 "s conv5i5t way f a metal conductor by conduct+ wires4 ,( c\rse !y are entirely imm]s$ 9 ! liquid4 ,! 9-electrode is sometimes a plate ( plat9um 7! reason t exp5sive metal is us$ be+ t x is unaffect$ by ! *emicals7 or else a plate ( ! metal be+ deposit$4 ,9 ! =m] case1 ! solution becomes weak] z ! "w proce$s1 & m salt has to be add$4 ,9 ! latt]1 h[ev]1 ! /r5g? ( ! solution rema9s un*ang$1 = by an int]e/+ int]*ange ! 9-electrode adds to x j :at x loses by deposition ^u ! o!r "o4 ,! effect is !re=e j z if ! curr5t tore (f p>ticles f ! "o & plac$ !m ^u ! o!r4 ,?is is believ$ to be due to ! ag5cy ( ! oxyg5 :i* 9 ! case ( ! electrolysis ( wat] becomes free1 b :i* 9 ?is case =ms ) ! metal electrode a lay] ( oxide ^u its surface1 ?is oxide be+ !n dissolv$ away by ! liquid4 ,?us z fa/ z ! metal is deposit$ ^u ! out-electrode its place is tak5 by m metal f ! 9-electrode4 ,9 "s processes x is desir$ to deposit metal ^u a non-conduct+ surface1 & x is evid5t t su* _c be us$ z an electrode4 ,nor is x any use to attempt to deposit ^u any?+ except an electrode4 ,! only ?+ to d1 !n1 is to make ! object a conductor by "s means4 ,models 9 clay1 wax & pla/]1 once-liv+ objects l small animals1 fruit1 fl[]s or insects1 c1 h[ev]1 h a p]fect replica made ( !m by electrical deposition1 by ! simple me?od ( coat+ ! surface to be plat$ ) a ?9 lay] ( plumbago4 ,?is sk91 al?\gh extremely ?91 is a suffici5tly good conductor to make ! process possible4 ,process blocks = pr9t+ are copi$ 9 ?is way1 s t a p>ticul>ly delicate example ( ! blockmak]'s art ne$ n be worn d[n by mu* press+1 copies or electros be+ made (f x = actual use 9 ! press4 ,! orig9al block is a plate ( copp] on :i* ! picture is repres5t$ by m9ute depressions & prom95ces4 ,on ?is a lay] ( s(t wax is press$1 s z to obta9 a p]fect b rev]s$ copy4 ,hav+ be5 coat$ ) plumbago1 ?is is !n put into a vat conta9+ a solution ( copp] salts & is us$ z ! out-electrode1 ! o!r be+ a plate ( copp]4 ,:5 ! curr5t is turn$ on ! copp] is ?us deposit$ on ! wax until a ?9 %eet ( copp] is =m$ :i* is an exact b rev]s$ copy ( ! wax1 a direct copy1 t is1 ( ! orig9al block4 ,! back ( ?is ?9 %eet is !n cov]$ ) molt5 lead or type metal to fill up any depressions & to give x suffici5t /r5g?4 ,anyone :o has se5 "o ( ^! half-tone blocks cov]$ ) m9ute depressions s slight t !y c sc>cely be se51 yet s p]fect t a beautiful pr9t c be obta9$ f !m1 w realise ! wond]ful p[] ( ?is electrolytic process1 ! m>vell\s accuracy ) :i* ! orig9al is copi$1 & ! un]r+ way 9 :i* ! electric curr5t c>ries ! p>ticles ( copp] into e "o ( ! myriad recesses 9 ! wax4 ,ano!r specim5 ( ! m>vell\s "w ( ?is sy/em is ! wax cyl9d] ( ! phonograph4 ,! s\nd is produc$ by a ne$le trail+ along a groove ( v>y+ dep? cut 9 ! surface ( ! cyl9d]4 ,?is groove =ms a spiral1 pass+ r\nd & r\nd l ! ?read ( a screw1 & x encircles ! cyl9d] "o hundr$ times 9 e in* ( its l5g?4 ,consequ5tly1 at any po9t "o may take1 !re is b "o "o-hundr$? ( an in* f ! c5tre ( "o turn to ! c5tre ( ! turn on ei!r side ( x4 ,& at its deepe/ ! groove is less ?an "o-?\s&? ( an in* deep4 ,! phonograph itself cuts ! fir/ ma/] record1 z x is t]m$1 & ! problem is to take a numb] ( ca/s (f ?is model ( su* delicacy & accuracy t e v>iation 9 t exce$+ly f9e groove %all be fai?fully reproduc$4 ,su* a task might well be giv5 up z hopeless1 b ) ! help ( electrolysis x is accompli%$ easily & *eaply4 ,to attempt to press any?+ ^u ! surface ( ! ma/] w\ld b smoo? out ! s(t wax & oblit]ate ! groove altoge!r4 ,to apply any?+ s(t5$ by heat+ w\ld be to melt x4 ,b electrolysis1 )\t t5d+ 9 any way to di/ort or damage ! delicately cut surface1 deposits ^u x a surface ( metal f :i* ?\s&s ( ca/s c be made4 ,! g5tle f+]s ( ! electricity ov]lay ! s(t wax ) ! h>d1 /rong metal ) a m9ute p]fection almo/ beyond belief4 ,to comm5ce )1 ! ma/] record is plac$ ^u a sort ( turntable 9 a vacuum & turn$ r\nd 9 ! neighb\rhood ( two /rips ( gold-leaf /rongly electrifi$4 ,by ?is means ! gold is vaporis$ & a p]fect coat+ ( gold is laid ^u ! wax4 ,?is is f> too ?9 to be ( any use1 except to r5d] ! cyl9d] a conductor1 = ! coat+ is s fragile t x is no /rong] ?an ! wax itself4 ,x enables ! cyl9d]1 h[ev]1 to be electro-plat$ ) copp] until x is surr\nd$ by a /rong metallic %ell a sixte5? ( an in* ?ick4 ,x takes ab\t f\r days to deposit ?is ?ickness4 ,! copp] %ell is !n turn$ smoo? 9 a la! & fitt$ tightly into a brass jacket4 ,a little cool+ causes ! wax record to %r9k suffici5tly to free x f ! copp] %ell & all[ x to be lift$ out4 ,a copp] m\ld is ?us =m$ 9 :i* any numb] ( additional records c be ca/4 ,! molt5 wax is simply introduc$ into ! inside1 & all[$ to set2 ! inside is bor$ out 9 a la!1 & !n ) a little cool+ x %r9ks & c be )drawn1 a completely f9i%$ record1 e t9y depression or swell+ 9 ! orig9al ma/] be+ reproduc$ ) an accuracy almo/ incr$ible4 ,ano!r valuable use to :i* ?is process is put is ! purification ( metals4 ,! electro-*emical action works ) un]r+ precision3 x nev] mi/akes an atom ( iron = an atom ( copp]1 = example4 ,pass+ ?r\gh a solution ( copp] salt1 ! curr5t deposits only copp]4 ,= mod]n electrical ma*9]y & app>atus copp] is requir$ ( ! utmo/ possible purity1 = e impurity adds to its electrical resi/ance1 9 o!r words1 dim9i%es its value z a conductor4 ,consequ5tly ?\s&s ( tons ( electrolytic copp]1 z x is t]m$1 are produc$ e ye>4 ,! electrodes us$ are plates ( ord9>y copp]4 ,a coat+ ( pure metal is deposit$ by electrolysis ^u ! out-electrode f ! o!r "o4 ,:5 ! deposit is ?ick en\gh ! out-electrode is tak5 out & ! deposit torn (f x1 ! union betwe5 ! two be+ suffici5tly imp]fect = ?is to be done )\t difficulty4 ,! metal ( :i* ! 9-electrode is made has already be5 purifi$ by o!r processes1 until x conta9s b "o p] c5t4 ( =eign matt]1 & by ?is means ev5 t small p]c5tage is entirely got rid (4 ,! impurities fall to ! bottom ( ! vessel 9 ! =m ( slime1 :i* is p]iodically remov$4 ,& n only is electrolysis ?us un]r+ 9 pick+ out c]ta9 atoms f among a mixture1 b !re is an exact relation betwe5 ! "w done & ! quantity ( curr5t us$4 ,consequ5tly x =ms a v exact me?od ( measur+ curr5ts4 ,! me?od ( measur+ curr5t by ! /r5g? ( ! magnetic field :i* x produces has be5 m5tion$ already1 & su* measurem5ts c be *eck$ by electrolysis4 ,?us ! practical def9ition ( ! amp]e is t curr5t :i* :5 pass$ ?r\gh a solution ( silv] nitrate 9 wat] w deposit silv] at ! rate ( 4#jjaaah gramme p] second4 ,! electric accumulator or second>y batt]y1 "o ( ! mo/ useful appliances1 is ! result ( electrolysis rev]s$4 ,_m l>ge electric-light+ plants h 9 addition to _! g5]at+ ma*9]y a l>ge batt]y ( second>y cells1 :i*1 be+ kept *>g$1 are able to help ! ma*9]y 9 times ( heavy dem&1 or ev5 to supply ! :ole curr5t ne$$ =1 say1 half-an-h\r1 s t ! :ole ( ! ma*9]y c\ld1 9 ! ev5t ( an accid5t1 be %ut d[n = t "t & ! supply ma9ta9$ f ! batt]ies4 ,?is w\ld be suffici5t 9 _m cases = fre% ma*9]y to be br\ght into action or em]g5cy arrangem5ts to be made4 ,x may be t ?is book is be+ read by someone seat$ s]5ely 9 8 arm-*air :ile eng9e]s & workm5 at ! g5]at+ /ation are work+ 9 frantic ha/e to set "r "s sudd5 breakd[n be=e ! batt]ies are run d[n4 ,! batt]ies may h sav$ ! t[n half-an-h\r's d>kness4 ,l>ge telegraph (fices are fitt$ ) second>y batt]ies4 ,_m motori/s owe ! ignition :i* keeps _! eng9es at "w to second>y batt]ies4 ,x is second>y batt]ies :i* keep ! wireless app>atus at "w on a wreck$ vessel aft] ! eng9es h /opp$4 ,inde$ second>y batt]ies are "o ( ! mo/ b5efic5t inv5tions4 ,& if only !y c\ld be made 9 a light] =m ?an is possible at pres5t _! value w\ld be inf9itely increas$4 ,we h se5 h[ ! passage ( curr5t ?r\gh acidulat$ wat] produces hydrog5 & oxyg54 ,if ^? gases be collect$ 9 clos$ vessels ov] ! wat]1 s t !y rema9 9 contact ) ! wat]1 z soon z ! curr5t is /opp$ a rev]se action sets 94 ,! gases t5d to recomb9e ) ! electrolyte & 9 s do+ to give back a curr5t equal to t :i* =m$ !m4 ,fig4 #d %[s ! con/ruction ( :at is call$ a voltamet]1 9 :i* ! gases aris+ f ! electrodes are collect$ 9 little glass vessels plac$ j above !m4 ,su* an app>atus enables u to see easily h[ ! accumulator works4 ,! picture %[s ! batt]y :i* is effect+ ! sep>ation ( ! oxyg5 & hydrog54 ,if t be disconnect$1 & ! wires jo9$1 z %[n by ! dott$ l9e1 a curr5t w fl[ back until ! oxyg5 & hydrog5 h return$ into ! solution aga94 ,! app>atus w1 9 fact1 "w l an ord9>y batt]y1 except t in/ead ( a plate or rod ( z9c a mass ( hydrog5 w =m ! ess5tial "p4 ,an appliance su* z a voltamet] is n ( mu* use = ! practical purpose ( /or+ l>ge quantities ( electrical en]gy1 because ! surfaces ( ! electrodes are s small & ! surfaces :]e liquid & gases are 9 contact are small too4 ,x is cle> t ! l>g] ! electrodes are ! wid] w be ! passage = ! curr5t1 j z a wide road c accommodate m traffic ?an a n>r[ pa?4 ,we may reg>d ! electrodes z l gateways ?r\gh :i* ! curr5t passes4 ,by mak+ !m l>ge1 !re=e1 we enable a l>ge curr5t to pass1 & consequ5tly p]mit electrolysis to take place ) great comp>ative rapidity4 ,illu/ration3 ,,fig4 #d4 ,! plates1 z ! electrodes 9 a second>y batt]y are t]m$1 are g5]ally l>ge metal plates4 ,exp]im5t has %[n t lead is ! be/ = ?is purpose4 ,x has also be5 f\nd t x c be improv$ by mak+ x por\s1 s9ce ! inn] surfaces ( ! pores are s mu* add$ surface ?r\gh :i* curr5t c pass into ! electrolyte4 ,!re are v>i\s ways ( produc+ ?is porosity1 :i* ne$ n tr\ble u "h1 h[ev]4 ,x w suffice = our purpose to und]/& t an ord9>y second>y cell consi/s ( two lead plates1 ) ! l>ge/ possible surface1 imm]s$ 9 a liquid1 g5]ally a dilute solution ( sulphuric acid 9 wat]4 ,to *>ge ! batt]y1 curr5t is s5t to "o plate1 ?r\gh ! liquid to ! o!r plate1 & s away4 ,a ?9 film ( hydrog5 is ?us =m$ ^u ! outgo+ plate1 :ile oxyg5 is =m$ at ! incom+ "o4 ,s9ce ! hydrog5 is spread ov] su* a l>ge area1 x does n accumulate suffici5tly = mu* ( x to rise to ! surface4 ,mo/ ( x rema9s adh]+ to ! plate4 ,! oxyg5 comb9es ) ! lead ( its plate & s is safely /or$ up !re 9 ! =m ( oxide ( lead4 ,?is /orage ( hydrog5 ^u ! "o plate & oxyg5 on ! o!r _c g on indef9itely1 & s z soon z ! limit is rea*$ ! cell is fully *>g$4 ,passage ( fur!r curr5t is !n simply wa/e4 ,! dynamo or prim>y batt]ies :i* are us$ = *>g+ hav+ be5 disconnect$1 ! two plates c be connect$ toge!r ?r\gh lamps1 motors1 or 9 any o!r desir$ way1 & ! curr5t w !n fl[ out aga91 ! opposite way to t 9 :i* x ent]$1 j z a /one ?r[n up 9 ! air returns ! opposite way4 ,! curr5t :i* comes out is1 9 fact1 a sort ( reflex action aris+ f t :i* w5t 91 ! me*anism by :i* x is produc$ be+ ! reabsorption ( ! oxyg5 & hydrog5 into ! electrolyte4 ,:e!r a cell is fully *>g$ or n is asc]ta9$ by weigh+ ! electrolyte1 an op]ation :i* at fir/ sight seems to h no?+ :atev] to d ) ! matt]4 ,x arises f ! diff]5ce 9 weight betwe5 wat] & sulphuric acid1 ! latt] be+ ! heavi]4 ,we h se5 t :ile a little acid mu/ be add$ to wat] be=e x c be electrolys$1 x is ! wat] :i* is ultimately resolv$ into its con/itu5t gases4 ,h5ce ! result ( electrolysis is to increase n ! am\nt1 b ! proportion ( acid4 ,!re=e x increases ! weight ( ! electrolyte4 ,?is weight is asc]ta9$ by means ( a hydromet]1 a glass tube1 /opp$1 & load$ ) "s small %ot at its l[] end4 ,on ! upp] "p is engrav$ a graduat$ scale1 s t ! exact dep? to :i* x s9ks c be easily read4 ,?is dep? w1 ( c\rse1 v>y ) ! specific gravity ( ! liquid1 & s ! dep? record$ by ! scale w be an indication ( ! proportion ( acid1 & t 9 turn w %[ h[ f> ! process ( *>g+ has progress$4 ,accumulators are1 or h be5 hi!rto at any rate1 v tr\blesome ?+s4 ,!y are apt to lose _! p[]4 ,if n prop]ly *>g$ !y are easily damag$4 ,too rapid *>g+ or too rapid dis*>g+1 /&+ = a :ile only p>tly *>g$--all ^! ?+s h a bad effect1 9 extreme cases ev5 de/roy+ !m altoge!r4 ,because ( ! use ( lead !y are t]ribly heavy too1 s mu* s t = traction purposes !y are ( v little use1 = a l>ge am\nt ( ! en]gy /or$ 9 ! accumulators is !n us$ up 9 haul+ !m ab\t4 ,yet :at a field !re is = ! successful accumulator6 ,take ! "o in/ance ( ! electrification ( a railway4 ,if good light & effici5t accumulators 7 to be _h1 no alt]ation at all w\ld be necess>y to ! p]man5t way4 ,! eng9es or motor c>riages w\ld ne$ to g p]iodically to a depot to be re-*>g$1 b t c\ld easily be arrang$4 ,su* ?+s z conductor rails1 ov]head conductors & s on w\ld be ne$less4 ,! _w has !re=e be5 int]e/$ = ye>s 9 ! rum\r t ,t4 ,a4 ,edison 0 engag$ ^u ?is problem1 & at la/ he has produc$ 8 accumulator1 by :i* he has remov$ _m ( ! difficulties1 if n all4 ,in/ead ( a case ( glass or celluloid1 z is usual ) ! old] cells1 8 cells are enclos$ 9 /rong boxes ( nickel /eel4 ,! positive plate consi/s ( nickel tubes fill$ ) alt]nate lay]s ( nickel hydroxide1 :ile ! negative plate is =m$ ( prep>$ oxide ( iron 9 a nickel framework4 ,! electrolyte is a solution ( potassium hydroxide4 ,! *emical action & ! electrical reaction is1 ( c\rse1 on ! same pr9ciple precisely z 9 ! old] cells1 b x is claim$ t ! ,edison cells are fool-pro(--t is to say1 !y _c be damag$ by c>eless h&l+1 & !y appe> to be a little light]4 ,?us ! problem is p>tly solv$1 & ) t z a fre% />t+-po9t someone may soon] or lat] give u a second>y batt]y :i* is light z well z /rong4 ,if any w\ld-be sci5tific inv5tor reads ^! words !re is a sugge/ion = a promis+ l9e ( inve/igation4 ,,*apt] ,v ,,ma*9e-,,made ,,cold ,"o ( ! mo/ rem>kable adaptations ( sci5tific k is ! manufacture ( cold4 ,at fir/ t phrase seems /range1 b x is really q legitimate4 ,!re are ma*9es at "w at ?is mom5t :i* are turn+ out cold z if x 7 any o!r manufactur$ article4 ,x is n t !y manufacture cold wat] or cold air1 x is ! cold itself :i* !y produce4 ,( c\rse1 cold has no real exi/5ce1 s9ce x is simply a negative quantity1 an abs5ce ( heat1 yet its effects are s real t we are 9 ! habit ( talk+ ( x z if x 7 a reality1 & 9 t s5se we c reg>d x z a product ( manufacture4 ,moreov]1 we see 9 ?is a conspicu\s in/ance ( ! int]dep5d5ce ( inv5tion & sci5ce1 = sci5tific pr9ciples 7 fir/ adapt$ to produce cold1 & !n artificial cold 0 employ$ 9 sci5tific inve/igations1 :]eby ! r>e gases ( ! atmosph]e h be5 discov]$1 z we %all see pres5tly4 ,9 ,me*anical ,inv5tions ( ,to-day ,i h dealt ) ! uses :i* c be made ( heat z a motive p[]4 ,"h we h 9 "s s5se a rev]sal ( ! process4 ,9 ! heat-eng9e ! exp5diture ( heat produces motion4 ,9 ! refrig]at+ ma*9e motion produces heat1 on ! face ( x a /range way ( produc+ cold4 ,yet x is by ! production ( heat 9 ! fir/ in/ance t we are ultimately able to obta9 ! cold4 ,"o way to make a ?+ cold is to place x 9 contact ) ice4 ,b t process suff]s f sev]e limitations4 ,9 ! fir/ place1 we may n be able to procure ice :5 we want x4 ,& 9 ! second place1 we may want to produce a temp]ature mu* l[] ?an t ( ice4 ,n[ a ma*9e c produce any degree ( coldness1 almo/ d[n to ! absolute z]o1 ! po9t at :i* a body is absolutely devoid ( any heat :atev]1 ! condition 9 :i* its molecules are absolutely /ill4 ,t po9t is #bgd deg4 ,c4 bel[ freez+-po9t4 ,freez+-po9t on t scale is z]o1 & s ?is absolute z]o is m9us #bgd deg4 ,or1 to put x ano!r way1 freez+-po9t is #bgd deg4 absolute temp]ature4 ,! absolute z]o has nev] be5 rea*$1 & !re is reason to believe t x nev] c be q rea*$1 b by me?ods ab\t to be describ$ a temp]ature )9 a few degrees ( x has be5 atta9$4 ,& all ( ?is c be done )\t any cool+ ag5t cold] ?an wat] at an ord9>y temp]ature4 ,!re are sev]al sy/ems1 b ! "o :i* illu/rates ! pr9ciple mo/ simply is t 9 :i* c>bonic acid gas is ! work+ fluid4 ,?is is a v compressible gas1 & s is well fitt$ = ! purpose4 ,fir/ ( all a pump or compressor compresses x4 ,t has ! effect ( heat+ x4 ,su* we might expect f ! fact t heat is molecul> activity3 :5 by compress+ ! gas we =ce ! molecules clos] toge!r1 !y naturally hit ea* o!r & ! sides ( ! conta9+ vessel h>d] ?an !y did be=e1 & ! increas$ activity is manife/$ z increas$ heat4 ,s ! fir/ effect1 z 0 rem>k$ j n[1 is to produce1 app>5tly1 increas$ heat4 ,b !n ! hot compress$ gas1 by be+ pass$ ?r\gh a coil ( pipe surr\nd$ by cold wat]1 c be robb$ ( t heat4 ,accord+ to ! spe$ at :i* x trav]ses ! coil x w be m or less cool$3 by caus+ x to travel sl[ly x c be br\ght d[n almo/ to ! temp]ature ( ! wat]4 ,s we />t ) ! gas at atmosph]ic pressure & at some:]e ab\t atmosph]ic temp]ature too4 ,?is we conv]t into compress$ gas at a high temp]ature4 ,aft] cool+ x we h compress$ gas at a mod]ate temp]ature4 ,!n1 to complete ! process1 we let ! gas exp& aga94 ,n[ j z compress+ a gas heats x1 lett+ x exp& cools x4 ,if we compress$ x & !n exp&$ x aga9 we %\ld be j z we 7 to comm5ce )4 ,b s9ce1 9 betwe5 ! two op]ations we extract a quantity ( heat by means ( ! cool+ wat]1 we get at ! end a v mu* l[] temp]ature ?an t ) :i* we />t$4 ,we _c cool ! gas )\t compress+ x1 because heat w only fl[ f "o body into ano!r :5 ! second is cool] ?an ! fir/4 ,b by mak+ ! gas hot tempor>ily by compression we enable ! wat] to draw "s heat f x1 & !n1 all[+ x to s9k back to its orig9al /ate1 we get practically ! old temp]ature1 less :at ! wat] has extract$4 ,! pr9ciple is really absurdly simple :5 "o once gets to und]/& x4 ,! application is n s simple z f> z ! design] ( ! ma*9e is conc]n$1 = he has to adju/ ! v>i\s p>ts to exactly ! "r %ape & dim5sions1 s t !y may "w well ) "o ano!r & produce ! desir$ result ) ! m9imum exp5diture ( p[]4 ,to ! obs]v]1 h[ev]1 & to ! us] too1 ! f9i%$ ma*9e is wond]ful 9 its simplicity4 ,! pr9ciple is illu/rat$ diagrammatically 9 ,fig4 #e4 ,9 ! c5tre is ! compressor4 ,its action =ces ! gas along ! pipe to ! "r & d[n into ! cond5s]4 ,z x fl[s d[nw>ds ?r\gh ! coil !re cold wat] ent]s at ! bottom ( ! tank1 fl[s upw>d pa/ ! coil & escapes aga9 at ! top4 ,?us ! coil is kept 9 contact ) cold wat]4 ,pass+ !n ?r\gh ! bottom ( ! tank ! gas travels f "r to left ?r\gh ! regulat+ valve & into an arrangem5t almo/ exactly simil> to ! cond5s] b call$ ! evaporator4 ,"h ! gas exp&s & suff]s a great fall 9 temp]ature4 ,?is cold is communicat$ to liquid circulat+ 9 ! tank :i* =ms a "p ( ! evaporator1 & ?is liquid c be circulat$ ?r\gh pipes into any rooms to be cool$ or ar\nd vessels ( wat] :i* x is desir$ to freeze4 ,?is liquid1 :i* acts z ! c>ri] ( ! cold1 is call$ br9e1 & is wat] to :i* is add$ calcium *loride to keep x f freez+4 ,illu/ration3 ,,fig4 #e4--,?is diagram %[s ! work+ ( ! ,refrig]at+ ,ma*9e4 ,! pump compresses ! gas & drives x ?r\gh ! coil 9 ! cond5s]1 :]e x is cool$ by wat]4 ,x passes !nce ?r\gh ! coil 9 ! evaporator1 :]e x exp&s & cools ! surr\nd+ br9e4 ,n[ ! obs]vant read] may h notic$ t !re is no app>5t reason = ! "n ( ! left-h& vessel4 ,x w be q cle>1 h[ev]1 :5 ,i expla9 t al?\gh ,i h spok5 ( ! work+ fluid all along z gas1 ,i h only done s to avoid br++ 9 too _m explanations at once4 ,x is actually liquid = a good "p ( its j\rney4 ,c>bonic acid gas liquefies at a v mod]ate temp]ature & pressure1 & s :ile x leaves ! compressor z a gas x becomes liquid 9 ! cond5s] & rema9s s until x has pass$ ! regulat+ valve4 ,!n x beg9s to exp& into gas once m1 & 9 t /ate x passes back to ! compressor4 ,!re is a pressure-gauge on ! pipe leav+ ! compressor & ano!r on ! "o ent]+ x4 ,a comp>ison ( ! read+s on ^! two tells h[ ! app>atus is work+4 ,! diff]5ce betwe5 !m indicates h[ mu* compression is be+ giv5 to ! gas4 ,assum+ t ! compressor is work+ at a con/ant spe$1 ?is compression c be regulat$ to a nicety by ! valve3 close x a little & ! compression w increase3 op5 x a little & ! compression w decrease4 ,by ?is means ! degree ( cold produc$ c be v>i$ at w4 ,?is is ! way 9 :i* _m %ips are enabl$ to c>ry c>goes ( froz5 meat4 ,! *amb]s 9 :i* ! meat is /[$ are insulat$--t is to say1 _! walls are made z imp]vi\s z possible to heat4 ,!n ! br9e is c>ri$ into ! *amb]s 9 pipes1 cool+ !m mu* z ! hot-wat] pipes heat an ord9>y public build+4 ,or ano!r me?od is to c>ry ! pipe :i* con/itutes ! evaporator into ! *amb] to be cool$4 ,a ?ird way is to disp5se ) br9e & to bl[ air ?r\gh ! coils ( ! evaporator1 :]eby ! air is made to c>ry away ! cold to :]ev] x is ne$$4 ,ice c be made easily 9 m\lds ( metal or wood ar\nd :i* br9e circulates4 ,if made ( ord9>y wat] ! ice is likely to be cl\dy & opaque1 :i* is q good en\gh = _m purposes4 ,9 cases :]e x is desir$ t x %\ld be cle>1 ! wat] is agitat$ dur+ freez+1 or else di/ill$ wat] is us$4 ,to enable ! blocks to be got out ( ! m\lds x is sometimes arrang$ to circulate w>m br9e = a few mom5ts4 ,ice skat+ r9ks are =m$ by mak+1 fir/1 an insulat+ lay] ( sawdu/1 slag-wool or some?+ ( t sort 7^? by ! way1 be+ ! mat]ials g5]ally us$ = insulat+ cold *amb]s7 und]nea? ! floor4 ,! floor1 too1 is made wat]pro( & !n ^u x is laid z closely z possible a s]ies ( iron pipes4 ,wat] is flood$ on to ! floor until ! pipes are cov]$ to a dep? ( sev]al in*es1 & !n br9e is pump$ ?r\gh ! pipes4 ,9 "t ! wat] freezes1 & s long z ! br9e circulates x rema9s s4 ,b al?\gh ! ,,co#b process describ$ above is ! simple/ illu/ration ( ! pr9ciple1 !re are o!r sy/ems4 ,9 "o v popul> =m ammonia gas is ! work+ fluid4 ,?is is liquefi$ by pressure & cool+ ) wat]1 be+ subsequ5tly exp&$ j z describ$ above4 ,ano!r mu*-us$ sy/em is ! ammonia-absorption process1 9 :i* ! ammonia is n liquefi$1 b :5 "u pressure is absorb$ by wat]1 return+ to gas aga9 :5 ! pressure is releas$4 ,b ! degree ( cold atta9$ 9 ^! comm]cial ma*9es is z no?+ to ! extremely int5se cold g5]at$ on ! same pr9ciples 9 ! liquid-air ma*9e1 :i* is f\nd 9 e well-equipp$ physical laboratory4 ,briefly1 ?is consi/s ( a coil ( _m turns ( small tube enclos$ 9 a small d\ble vessel1 ! space betwe5 ! inn] & out] sk9s ( :i* is pack$ ) insulat+ mat]ial4 ,a compressor pumps air 9 at ! top ( ! coil at a pressure ( f #aej to #bjj atmosph]es4 ,an atmosph]e1 x may be rem>k$1 is a unit (t5 us$ 9 sci5tific matt]s1 mean+ ! normal pressure ( ! atmosph]e1 :i* is1 r\ghly speak+1 #ae lb4 p] squ>e in*4 ,h5ce #bjj atmosph]es is ab\t #cjjj lb4 p] squ>e in*4 ,( c\rse air s highly compress$ z t is hot1 b aft] x has pass$ d[n ! coil & has escap$ f ! valve :i* lib]ates x at ! bottom x is mu* cool]4 ,b t is only ! beg9n+ ( ! op]ation4 ,! exp&$1 & !re=e cool$1 air f9ds its way upw>d ?r\gh ! turns ( ! coil d[n :i* ! foll[+ air is com+4 ,t1 exp&+ 9 its turn1 is cold] /ill1 because ( ! cool+ action ( ! fir/ air1 & s ! process goes on4 ,illu/ration3 ,by p]mission ( ,messrs4 ,j4 & ,e4 ,hall1 ,ltd41 ,london & ,d>t=d ,,ma*9e-,,made ,,ice ,"h we see a huge block ( ice be+ lift$ 7x may be on a hot summ] day7 f ! m\ld 9 :i* x has be5 made ,?is is p]haps easi] to und]/& if we imag9e t ! air comes ?r\gh ! coil 9 gu/s & we notice :at happ5s to ea* succe$+ gu/4 ,! fir/ comes d[n1 exp&s1 cools & asc5ds1 !reby cool+ ! second gu/ z x comes d[n4 ,! second !n1 aft] expansion1 w be cool] ?an ! fir/ 04 ,t 9 its turn w cool ! ?ird1 & s ! ?ird aft] expansion w be cool] ?an ! second4 ,& t w g on1 ea* succe$+ gu/ be+ cool] ?an ! "o be=e4 ,& al?\gh ! fl[ ( air is cont9u\s1 & n 9 gu/s1 ! result is j ! same3 x goes on gett+ cool] & cool] until at la/ ! air comes out 9 its liquid =m4 ,?is liquid collects 9 a little *amb] =m$ at ! bottom ( ! vessel :i* conta9s ! coil & c be drawn (f :5 desir$4 ,air 9 its liquid /ate looks v mu* l wat]4 ,9 fact x is difficult to get *ance obs]v]s to believe t x is n wat]4 ,x boils at a temp]ature f> bel[ ! freez+-po9t ( wat]1 s t liquid air if plac$ 9 a cup made ( ice w boil furi\sly4 ,ice is s mu* ! hott] t x behaves t[>ds liquid air z a v hot fire does to wat]4 ,! feature ( ! above ma*9e1 x w be notic$1 is t no cool+ wat] is requir$1 z 9 ! refrig]at+ ma*9e1 al?\gh ! pr9ciple ( ! two is ! same4 ,! coil is ! cond5s] & ! vessel 9 :i* x is enclos$ is ! evaporator1 & s ! cold air produc$ by ! process 9 ! evaporator cools ! coil ( ! cond5s]4 ,?us x is self-int5sive1 z ! mak]s call x4 ,hydrog5 c be liquefi$ 9 a simil> ma*9e1 except t x ne$s a little prelim9>y cool+ ) liquid air4 ,liquid hydrog5 is ! coole/ ?+ kn[n approa*+ ! region ( absolute z]o4 ,& n[ we c turn to ! wond]ful discov]ies :i* h foll[$ ^u ! manufacture ( liquid air4 ,to make ! /ory complete we ne$ to g back to ! "t ( ,prie/ly & ,cav5di%1 e>ly 9 la/ c5tury4 ,!y inve/igat$ ! atmosph]e & %[$ t x consi/$ ( oxyg5 & nitrog5 9 c]ta9 inv>iable proportions1 ) "u c]ta9 conditions a small proportion ( c>bonic acid4 ,^! facts 7 s well au!nticat$1 & !y seem$ to expla9 ev]y?+ s satisfactorily1 t x 0 q ?\ght almo/ up to ! end ( ! n9ete5? c5tury t !re 0 no?+ m to le>n ab\t ! atmosph]e4 ,nev]!less !re 0 an idea 9 ! m9ds ( "s sci5ti/s t !re mu/ be ano!r gr\p ( elem5ts some:]e1 ! exi/5ce ( :i* 0 !n undiscov]$1 b x 0 nev] dream$ t ^! 7 9 ! air4 ,soon aft] ! weights ( ! atoms _h be5 f\nd a m$ical /ud5t nam$ ,pr\t 9 an anonym\s essay call$ att5tion to ! fact t !re 7 curi\s num]ical relation%ips betwe5 !m4 ,speculation on ! subject w5t on = _m ye>s1 until 9 #ahfe ! great ,russian *emi/ ,m5deleeff publi%$ 8 conclusions4 ,he _h arrang$ ! elem5ts 9 ! =m ( a table 9 ! ord] ( _! atomic weights4 ,! table consi/$ ( twelve r[s ( names =m+ eight v]tical columns1 & ! rem>kable ?+ 0 t all ^? elem5ts :i* fell into any p>ticul> column1 al?\gh _! atomic weights 7 v widely diff]5t1 _h simil> prop]ties4 ,?is enabl$ him to pr$ict ! discov]y ( c]ta9 new elem5ts1 = ! table conta9$ a numb] ( blank spaces4 ,?ree elem5ts h be5 f\nd s9ce1 & _! atomic weights & prop]ties are j su* z to fill ?ree ( ! blank spaces4 ,"o blank space1 x is ?\ght1 may be fill$ "s day by ! gas coronium1 :i* l helium has be5 discov]$ 9 ! sun1 b unlike x has n yet be5 detect$ "h4 ,:5 x is1 !re is ! place 9 ! table :i* x may fill4 ,! table !n comm5c$ ) :at is /ill call$ ,gr\p #a1 b = reasons too complicat$ to expla9 "h x appe>$ z if !re mu/ be a gr\p be=e t1 a gr\p ! *ief *>act]i/ic ( :i* w\ld be ! inactivity ( ! elem5ts includ$ 9 x4 ,^! 7 expect$ to be ( v>i\s atomic weights1 b ^! weights1 x 0 anticipat$1 w\ld s occur 9 ! int]vals betwe5 ! o!rs t !y w\ld all fall into a new column to ! left ( ,gr\p #a4 ,9 ! ye> #ahib ,"l ,rayleigh 0 inve/igat+ ! "q ( ! d5sity ( a numb] ( diff]5t gases1 includ+1 s x happ5$1 nitrog54 ,n[ !re are sev]al ways ( procur+ nitrog54 ,"o is to get x f ! atmosph]e by ridd+ x ( ! oxyg5 ) :i* x is normally mix$4 ,ano!r way is to split up "s comp\nd1 su* z ammonia1 ( :i* x =ms a "p1 9 su* a way z to cat* ! nitrog5 & leave ! o!r elem5ts ) :i* x 0 comb9$ else:]e4 ,"l ,rayleigh tri$ bo? ways1 & he f\nd t ! nitrog5 f ! atmosph]e 0 d5s] ?an t d]iv$ f ammonia4 ,sir ,william ,ramsey !n c>ri$ ! matt] a /ep fur!r4 ,he heat$ atmosph]ic nitrog5 9 ! pres5ce ( magnesium1 "u :i* conditions "s ( ! nitrog5 comb9es ) ! latt] elem5t to =m nitride ( magnesium4 ,t1 x 0 f\nd1 made ! rema9+ nitrog5 d5s] /ill4 ,! explanation !n seem$ obvi\s4 ,suppose we imag9e a mixture ( sawdu/ & iron fil+s3 x w be heavi] ?an an equal quantity ( pure sawdu/4 ,& if we contrive to take away "s ( ! sawdu/ f ! mixture we %all f9d t :at is left is heavi] /ill1 :5 comp>$ ) an equal bulk ( pure sawdu/4 ,= x is cle> t z we take away sawdu/ we !reby increase ! proportion ( ! heavi] iron fil+s & s we make ! mixture heavi]4 ,apply+ a simil> process ( reason+ to ^! discov]ies1 ! conviction grew t ! nitrog5 ( ! air 0 n pure1 b t x _h mix$ ) x a small proportion ( "s o!r gas ( great] d5sity4 ,!y soon succe$$ 9 isolat+ ?is d5s] gas1 to :i* !y gave ! "n ( argon4 ,its atomic weight 0 f\nd1 &1 wond]ful to relate1 x 0 su* t argon fell into a new column to ! left ( ,gr\p #a1 z _h be5 anticipat$4 ,! discov]y ( argon 0 ann\nc$ 9 #ahid4 ,! next ye> ,sir ,william ,ramsey1 inve/igat+ a gas :i* _h be5 discov]$ lock$ up 9 ! int]/ices ( a m9]al call$ clevite1 0 able to /ate t x 0 helium1 ! elem5t :i* _h be5 previ\sly notic$ by ! spectroscope 9 ! sun4 ,l argon1 x 0 f\nd to be extremely inactive1 & its atomic weight turn$ out to be su* t x too fell into ! ,z]o ,gr\p4 ,9 #ahih ,pr(essors ,ramsey & ,trav]s f\nd two m gases 9 ! air1 krypton & neon1 & a little lat] /ill1 !re 0 f\nd mix$ ) ! krypton a fur!r new gas1 x5on4 ,all ( ^! _h _! atomic weights f\nd1 & fell into t new column 9 ! p]iodic table4 ,b :at has all ?is got to d ) liquid air8 ,! two subjects are closely relat$1 = x is by liquid-air ma*9es t ^! r>e gases are n[ obta9$1 & x 0 f liquid air t ! la/ ?ree 7 fir/ discov]$4 ,= air1 z we well "k1 is a mixture ( gases1 & :5 extreme cold & pressure are appli$ ^! gases liquefy1 ea* behav+ accord+ to its own nature4 ,!y d n all liquefy at ! same "t1 nor on be+ reliev$ f ! pressure & heat$ d all evaporate aga9 at ! same temp]ature4 ,al?\gh !y em]ge f ! liquid-air ma*9e 9 ! =m ( a s+le liquid1 x is really a mixture ( liquids1 ea* ) its own boil+-po9t4 ,9 an e>li] *apt] we saw h[ petroleum c be sep>at$ into its v>i\s con/itu5ts1 su* z petrol1 by fractional di/illation1 advantage be+ tak5 ( ! diff]5ce 9 ! boil+-po9t ( ! v>i\s fractions4 ,! boil+-po9t ( a liquid is1 ( c\rse1 ! temp]ature at :i* x turns freely into vap\r1 & j z petroleum :5 heat$ gives (f fir/ cymog5e1 next rhigol5e1 !n petrol1 b5z9e1 k]os5e & s on1 9 ! ord] nam$1 s liquid air1 :5 x is evaporat$1 gives (f its diff]5t con/itu5ts 9 ord]4 ,nitrog51 oxyg51 argon1 helium1 krypton1 neon & x5on c all be sep>at$ ea* f ! o!rs 9 ?is way1 by fractional di/illation4 ,! heat f ! surr\nd+ objects is all[$ to get at ! liquid1 & ! gases are !n giv5 (f 9 ! ord] ( _! boil+-po9ts4 ,& ?us we see h[ ! me*anical production ( cold has assi/$ 9 ! pursuit ( pure sci5ce4 ,! newly-f\nd gases are n ( any great use at pres5t4 ,!y are s inactive t possibly !y nev] w be1 ) "o exception1 & t is neon4 ,if an electric dis*>ge be made to pass ?r\gh a tube fill$ ) ?is gas1 a beautiful gl[ is ! result1 & x is j possible t neon tubes may become ! electric light ( ! future4 ,t is only a pr$iction1 h[ev]1 & a hesitat+ "o at t4 ,! inactive elem5ts may become ( value 9 explosives4 ,we h se5 h[ important nitrog5 is 9 ^! dang]\s sub/ances1 ! *ief feature ( :i* is _! in/ability--_! read9ess1 t is1 to *ange into some?+ else--:i* in/ability is due to ! reluctance ) :i* nitrog5 ent]s into !m4 ,n[ nitrog51 ?\gh inactive1 is mu* less s ?an ^! o!rs1 & if a way %\ld ev] be f\nd ( induc+ !m to ent] into a comp\nd1 t comp\nd w probably be an extremely p[]ful explosive4 ,,*apt] ,,vi ,,sci5tific ,,inv5tions ,,at ,,sea ,! safety ( our fell[-creatures has always be5 a /rong /imulus to our inv5tive faculties4 ,! occurr5ce ( a bad railway accid5t1 &1 r\ghly1 its nature1 c be inf]r$ f ! files ( ! ,pat5t ,(fice1 = su* an ev5t br+s m5's ?\ghts to devis+ ways & means ( prev5t+ a recurr5ce1 & an avalan*e ( su* inv5tions desc5ds ^u ! pat5t dep>tm5t 9 consequ5ce4 ,9 l mann] a p>ticul>ly di/ress+ accid5t to a lifeboat "s ye>s ago br\ght out _m inv5tions = ! improvem5t ( ^? romantic craft4 ,_m ( ! inv5tions :i* arise "u ^! conditions are1 ( c\rse1 utt]ly wor?less1 b "s ( !m come to /ay4 ,x is n surpris+1 !re=e1 :5 we ?9k ( ! almo/ innum]able wrecks :i* happ51 ev5 ) mod]n %ipp+1 t human +5uity has be5 extremely busy 9 devis+ ways = br++ m ( safety & less ( risk into ! lives ( ^? :o g d[n to ! sea 9 %ips4 ,( ^! p]haps none is m fasc9at+ ?an ! mod]n ligh?\se1 ) its tall t[]1 its brightly fla%+ light1 /&+ undi/urb$ 9 ! wilde/ /orm1 quietly & p]si/5tly s5d+ =? its guid+ rays1 no matt] h[ ! elem5ts may be buffet+ x4 ,!re is some?+ specially attractive 9 ?is p]fect embodim5t ( quiet /r5g? & devotion to duty4 ,( c\rse1 its orig9 is v anci5t4 ,"o ( ! e>lie/ inv5tions1 no d\bt1 0 ! bright ?\ght ( a v primitive man :o lit a fire on a hill to s]ve z a guide to "s belat$ fri5ds out 9 _! fi%+ canoes4 ,f "s su* beg9n+ ! mod]n ligh?\se1 a magnific5t product ( ! sci5ce ( civil eng9e]+ & ! sci5ce ( optics1 has aris54 ,( ! difficulties enc\nt]$ 9 ! con/ruction ( ligh?\se t[]s on outly+ rocks mu* has be5 writt54 ,! hi/oric ,eddy/one1 = example1 has q a volum9\s lit]ature ( its own4 ,( ! light itself1 h[ev]1 mu* less is kn[n4 ,x w be int]e/+ fir/ to note ! diff]5t purposes = :i* a light may be requir$1 & !n see h[ ! app>atus ( ! ligh?\se is made to s]ve ^! purposes4 ,!re is ! mak+ light1 p]*$1 if possible1 ^u "s high em95ce1 d]iv+ its "n f ! fact t ! sailor sights x z he is mak+ ! l&4 ,vessels approa*+ ,engl& f ! s\?-we/ by night fir/ see ! light at ! ,liz>d4 ,! transatlantic vessels "k !y are approa*+ l& by cat*+ sight ( ! ,fa/net ,rock light (f ! coa/ ( ,irel&4 ,cape ,race light s]ves 9 ! same way = ^? ab\t to ent] ! ,/ ,lawr5ce & ,naves9k = ! entrance to ,new ,york h>b\r4 ,all su* z ^! h to be ( ! greate/ p[] practicable1 s t !y may be visible n only at ! longe/ possible di/ance1 b also "u unfav\rable conditions1 su* z haze & slight fog4 ,no light1 ( c\rse1 c p5etrate ?ick fog1 b 9 light fog & haze a p[]ful light c be se5 at consid]able di/ances4 ,= ! same reason ^! lights mu/ be high up1 or ! curvature ( ! ocean's surface w limit _! range4 ,a light elevat$ #ajj feet above ! sea-level w be visible ne>ly #af miles away1 b if only #ej feet up x w be invisible at #ac miles4 ,to be se5 #dj miles away x mu/ be z high z #ajjj feet4 ,b !n aga9 height is 9 "s cases a disadvantage1 = sometimes fog hov]s a little di/ance above ! sea1 :ile bel[ x ! air is cle>1 & ! high] a light may be ! m likely is x to h its lant]n imm]s$ 9 a float+ cl\d ( fog4 ,_m read]s famili> ) ! s\? coa/ ( ,brita9 w rememb] t ! light :i* us$ to %[ on ! summit ( ,bea*y ,head is !re no m1 b has be5 replac$ by a t[] at ! foot ( ! cliffs1 ! reason be+ t x may be bel[ ! cl\ds ( fog :i* are preval5t at t po9t4 ,b ! m5tion ( ,bea*y ,head introduces u to ano!r class ( lights1 kn[n z coa/+ lights1 s9ce !y are int5d$ to lead ! m>9] on f po9t to po9t along a coa/4 ,x w be se5 at once t 9 _m cases !y d n ne$ to be visible at su* great di/ances z ! mak+ lights4 ,:5 ! m>9] has sight$ ! ,liz>d1 = example1 he kn[s :]e he is4 ,9 ord] t he may le>n t important fact z soon z possible x is desirable t t light %\ld h ! greate/ possible range1 b hav+ ?us locat$ himself1 :5 he beg9s to feel 8 way along ! ,engli% ,*annel he is guid$ by ! coa/+ lights1 & s long z !y are ( su* range t he w nev] be out ( sight ( "o or two ( !m t w be suffici5t4 ,?us ! ,bea*y ,head light1 9 its pres5t l[ position1 has a suffici5t range = its purpose1 ) ! add$ advantage ( m fre$om f obscuration by fog4 ,?us we see h[ ! local conditions & ! purpose ( ea* p>ticul> light h to be tak5 into consid]ation 9 det]m9+ its position & p[]4 ,! ,eddy/one1 aga91 is an example ( a fur!r class4 ,x simply s]ves to d5ote ! position ( a gr\p ( dang]\s rocks4 ,its function is n s mu* guidance1 al?\gh no d\bt x (t5 s]ves = t1 b = w>n+4 ,! ,liz>d light beckons ! on-com+ %ip to ! safety ( ! ,engli% ,*annel2 ! ,eddy/one w>ns x away f dang]4 ,! latt]1 !re=e1 & simil> lights are w>n+ lights4 ,illu/ration3 ,by p]mission ( ,messrs4 ,j4 & ,e4 ,hall1 ,ltd4 ,a ,,cold ,,/ore ,int]ior ( a cold /ore1 9 :i* meat & p\ltry are kept good & fre% by ! use ( ma*9e-made cold4--,see p4 #fg ,"r at ! entrance to ! ,engli% ,*annel1 t greate/ ( all highways = %ipp+1 !re lie ! ,scilly ,isles4 ,?is gr\p comprises "s few isl&s ( fair size f :i* we draw ^? pl5tiful supplies ( beautiful spr+ fl[]s1 b x also includes a l>ge numb] ( rocky islets :i* h s5t _m a /rong %ip to its doom4 ,on "o ( ! islets1 !re=e1 ! ,bi%op's ,rock1 !re n[ /&s a v p[]ful light :i* exemplifies _m ^: purpose is ! d\ble "o ( welcom+ ! m>9] z he approa*es our %ores & at ! same "t w>n+ him ( a local dang]4 ,su* are bo? mak+ & w>n+ lights4 ,( no less importance1 ?\gh less impressive1 are ! guid+ lights1 :i* guide ! %ips into & out ( h>b\rs & ?r\gh n>r[ *annels4 ,^! are g5]ally arrang$ 9 pairs1 "o ( ! pair be+ a little way beh9d & above ! o!r4 ,?us :5 ! sailor sees !m bo?1 "o exactly ov] ! o!r1 he kn[s he is on ! "r c\rse4 ,sometimes ligh?\ses h subsidi>y lights z well z ! ma9 light1 to m>k a passage betwe5 two dang]s1 or to give w>n+ ( "s dang]4 ,! subsidi>y lights are (t5 col\r$1 & !y are g5]ally sectors %[+ n all r\nd a complete circle1 or ev5 a consid]able portion ( "o1 b j 9 "o c]ta9 direction4 ,!y are g5]ally %[n f a w9d[ 9 ! t[] l[] d[n bel[ ! ma9 light4 ,f9ally1 x is important to rememb] t e light mu/ be di/+ui%able f its neighb\rs4 ,h5ce e "o 9 any giv5 locality has a diff]5t "* f all ! o!rs4 ,?is "* is giv5 to x by means ( fla%es4 ,in/ead ( %[+1 z ! primitive lights did1 a /eady light1 ! mod]n ligh?\se exhibits a s]ies ( fla%es1 ! duration ( :i*1 toge!r ) ! int]vals betwe51 give x its di/9ctive "*4 ,?is fla%+ arrangem5t has a fur!r advantage ov] ! /eady light4 ,ea* fla% c be made m p[]ful ?an a /eady light c\ld be4 ,b ( t m lat]4 ,! actual s\rce ( light v>ies ) circum/ances4 ,! electric arc is1 z we all "k1 a v p[]ful light1 9 fact x c be made ! mo/ p[]ful ( all1 b its light is decid$ly blui%4 ,n[ ! "t :5 a light is mo/ ( all ne$$ is :5 ! wea!r is ?ick4 ,fogs v>y+ f a slight haze to a ?ick pall ( d>kness are ( v common occurr5ce1 & ! ligh?\se light mu/ be able z f> z possible to p5etrate !m4 ,z a matt] ( fact clean fog1 su* z "o gets at sea1 is n by any means opaque4 ,! black fogs ( ! great cities are ano!r matt]1 b !y are n ! sort :i* afflict ! m>9]4 ,on a foggy day 9 ! op5 c\ntry or by ! sea x is (t5 p>ticul>ly light2 inde$ ! light is ( a peculi>ly diffuse nature :i* gives a nice ev5 illum9ation to ev]y?+4 ,?us we see t fog is really transp>5t1 b x diffuses ! light4 ,x does n /op ! light rays1 b simply b5ds !m ab\t & scatt]s !m 9 all directions4 ,?us we c see no?+ ?r\gh ! fog1 yet a flood ( light rea*es u ?r\gh x4 ,9 its effect x is l t cr9kl$ glass :i* is (t5 us$ = p>titions betwe5 rooms1 :i* lets light ?r\gh1 b :i* _c be se5 ?r\gh4 ,we see1 !n1 t ! effect :i* a fog produces is ma9ly to refract ! light rays4 ,ea* little drop ( wat] 7= x mu/ be rememb]$ t fog is myriads ( t9y drops ( liquid2 x is n vap\r7 acts l a m9ute l5s1 & b5ds ! rays :i* pass ?r\gh x4 ,& ! m blue a ray is ! m x is b5t4 ,on ! contr>y1 ! m r$ x is ! less is x b5t4 ,:5 a beam ( light is analys$ 9 ! spectroscope ! r$ rays are b5t lea/ & ! blue rays mo/1 s t ! r$ rays fall at "o end ( ! spectrum & ! blue at ! o!r4 ,n[ we only see a ?+ :5 light rays proce$+ f e "p ( x fall /raight 7or ne>ly s7 ^u our eyes4 ,consequ5tly1 s9ce r$ rays are b5t & scatt]$ by ! fog less ?an blue rays are1 a r$ light w be m easily se5 ?r\gh a fog ?an a blue "o4 ,x might seem f ?is t a r$ glass put 9 front ( a light w\ld make x bett] = ?is purpose1 b t is n ! case1 = ! simple reason t filt]+ ! light ?r\gh r$ glass does n really make x any r$d] ?an x 0 be=e3 x simply makes x look r$d] by extract+ f ! orig9al light all except ! r$4 ,b a s\rce ( light :i* is naturally r$di% is s because x is m pl5tifully end[$ ) r$ rays1 :ile a blui% light l ! electric arc is naturally defici5t 9 r$ rays4 ,consequ5tly we %\ld be incl9$ to expect f !ory t ! electric arc w\ld n be a good light = a ligh?\se1 s9ce x w\ld lack p5etrat+ p[] 9 foggy wea!r4 ,"s read]s may h notic$ !mselves1 9 t[ns :]e electric lights & gas lamps are 9 use ne> ea* o!r1 t ! latt]1 ?\gh relatively feebl] "u normal conditions1 seem to give m light 9 fog4 ,& exp]im5ts %[ t ?is is really ! case4 ,s al?\gh !re are "s ligh?\ses ) electric arc lights1 t :i* is n[ believ$ to be ! be/ is an oil lamp ( special design1 us+ a mantle ( ! ,welsba* type4 ,! oil is /or$ 9 /rong /eel res]voirs into :i* air is pump$ by means ( a pump n unlike ^? us$ to inflate bicycle tyres4 ,by ?is means a pressure is ma9ta9$ ^u ! oil ( ab\t #fe lb4 p] squ>e in*4 ,?is =ces ! oil up a pipe & drives x 9 a jet into a vaporis]1 a tube heat$ f ! outside s t 9 x ! oil is turn$ into gas4 ,?is gas !n rises to ! burn] & heats ! mantle1 j z ! gas does 9 ! ord9>y inc&esc5t gas light4 ,inde$ 9 ! case ( lights on ! ma9l& ne> a t[n ! gas f ! t[n ma9 is (t5 utilis$4 ,b ?is simple arrangem5t = us+ vaporis$ oil1 z w readily be se51 c be employ$ any:]e4 ,a little ( ! gas produc$ is l$ ?r\gh a bran* pipe & burnt to heat ! vaporis]4 ,to />t ! app>atus ! vaporis] is heat$ ) a little me?ylat$ _s4 ,?us ev]y?+ is q self-conta9$ & s simple t !re is little to get out ( ord]4 ,! l>ge/ size ( lamp w give #bdjj c&le-p[]1 ) an exp5diture ( #b-a_/d p9ts ( oil p] h\r1 j common oil1 too1 ( ! k9d us$ ) ord9>y wick lamps4 ,hav+ got a s\rce ( p[]ful light1 ! next ?+ is to collect t light & ?r[ x 9 ! direction requir$4 ,= ! light proce$s f ! lamp 9 all directions 7practically71 & mu* ( x w\ld be entirely wa/$ c\ld x n be collect$ & guid$ 9 ! requir$ direction4 ,! e>lie/ attempt at ?is 0 to use a reflector ( bright poli%$ metal4 ,9 ! mo/ improv$ =m ^! 7 made to t peculi> curve kn[n z a p>abola4 ,?is is a curve obta9$ by cutt+ a cone 9 a c]ta9 way1 :]e=e x is "o ( ! conic sections1 & its p>ticul> appropriat5ess = ?is "w resides 9 ! fact t if a light be plac$ at a c]ta9 po9t kn[n z ! focus all ! div]g+ rays :i* fall ^u ! reflector w be reflect$ 9 ! same direction1 p>allel to ea* o!r4 ,an ord9>y sph]ical mirror w\ld reflect !m ei!r back to ! lamp or 9 div]g+ directions4 ,at any di/ance ! beam f ! p>abolic reflector w be m int5se ?an t f ! sph]ical "o1 s9ce ! rays w be clos] toge!r4 ,b ev5 ) ! p>abolic "o !re is "s diffusion1 = ! simple reason t :]eas ! focus is a ma!matical po9t 7position )\t magnitude7 ! mo/ conc5trat$ =m ( light kn[n has a consid]able magnitude4 ,h5ce ! rays proce$+ f ! c5tre ( ! mantle are reflect$ z p] ! !ory1 b ^? f ! outly+ p>ts ( x are some:at diffus$4 ,?is difficulty _c possibly be ov]come1 & h5ce ev5 9 ! f9e/ examples ( ligh?\se ar*itecture ! fla%es are n q %>p & cle>-cut4 ,!re is a c5tral mom5t1 s to speak :]e9 ! fla% is almo/ bl9d+ 9 its int5sity1 b x is prec$$ by a p]iod ( gr[+ brightness & succe$$ by "o ( decreas+ light4 ,9 ! mod]n app>atus1 h[ev]1 metallic mirrors are entirely disp5s$ )1 _! place be+ tak5 by reflect+ prisms ( glass4 ,! metallic ones _h to be cont9ually rubb$ to keep !m clean1 & ?is soon dull$ _! brightness1 :ile ! glass prisms ne$ only to be wip$ c>efully1 :i* op]ation has little effect ^u _! surface4 ,x may come z a surprise to "s t reflect+ prisms are possible4 ,! idea ( refraction ?r\gh a prism is q famili>4 ,su* =ms ! ess5tial pr9ciple ( ! spectroscope4 ,refraction is expla9$ to e s*ool *ild 9 ord] to acc\nt = ! ra9b[4 ,b reflection by a piece ( ! cle>e/ glass seems a contradiction 9 t]ms almo/4 ,yet x is only a "q ( %ape4 ,9 "s prisms ! light is simply b5t z x passes ?r\gh4 ,9 o!rs x is b5t twice1 s t x leaves ! prism j z if x _h be5 reflect$ (f a mirror4 ,bo? devices are us$ 9 ! ligh?\se4 ,let u see h[ !y are comb9$ s z to p]=m ! "w to be done4 ,take fir/ ( all ! case ( a light ^u an isolat$ rock :]e ! w>n+ is ne$$ equally all r\nd4 ,all t is necess>y "h is to pick up ^? rays :i*1 if left to !mselves1 w\ld fall ^u ! wat] ne> ! foot ( ! t[]1 & ^? :i* w\ld wa/e !mselves skyw>ds1 & !n to ga!r all ! rays into sev]al bundles or beams4 ,we w suppose a simple case 9 :i* ! light is suppos$ to give fla%es at regul> int]vals4 ,we are 9 ! topmo/ room ( ! ligh?\se1 ! lant]n1 z x is call$4 ,9 ! c5tre !re /&s ! murette or p$e/al4 ,9 ?is sev]al columns support a circul> plat=m on ! top ( :i* !re moves :at we might call a turntable1 :i* 9 turn be>s a frame ( gun-metal into :i* are fitt$ a maze ( glass b>s triangul> 9 section & curv$ to =m conc5tric circles4 ,! :ole /ructure1 possibly1 is ( great size4 ,f ! floor to ! plat=m is z high z an ord9>y man4 ,inde$ ar\nd ! turntable !re is a gall]y :i* =ms a ro( ov] our heads1 s t x is only aft] m\nt+ "s iron /eps on to ?is gall]y t we are able to exam9e ! glass "p4 ,z we asc5d we notice t ! walls ( ! *amb] z f> up z ! gall]y are =m$ ( iron plates1 :ile above t !re is a metal framework fill$ 9 ) glass panes1 & above all a dome-%ap$ ro(4 ,hav+ rea*$ ! plat=m we proce$ to exam9e ! glass1 & we f9d t ! metal framework =ms a cage ) f\r sides1 ea* approximately flat1 b really slightly sph]ical4 ,ea* ( ^! sides is call$ a panel4 ,9 ! c5tre ( ea* is a l5s4 ,peep+ ?r\gh ! int]/ices betwe5 ! prisms1 we p]ceive t ! lamp is inside ?is /ructure1 exactly 9 ! c5tre1 s t its light %9es directly ?r\gh ! c5tral l5s or bull's eye4 ,ar\nd ?is bull's-eye are _m circles ( glass b>1 =m+ refract+ prisms4 ,ar\nd ?is aga9 are m b>s 9 ! =m ( segm5ts1 :i* toge!r =m circles1 "s be+ refract+ prisms & o!rs reflect+ prisms4 ,all ! light rays f ! lamp :i* fall on any "o prism are deflect$1 s t !y proce$ approximately 9 ! same direction4 ,^? prisms 9 ! upp] "p lay hold ( ! rays :i* w\ld o!rwise g up into ! sky4 ,^? at ! bottom collect ^? :i* w\ld fall ne> ! foot ( ! t[]4 ,s sc>cely any are lo/4 ,b = ! fact t ! lamp itself is comp>atively l>ge & n a !oretical po9t1 z already expla9$1 ! beam f ?is panel w\ld be p]fectly /raight1 p>allel1 & ( uni=m d5sity ev]y:]e4 ,z x is1 x wid5s slightly z x proce$s1 b1 practically speak+1 we might call x a solid beam ( light4 ,ea* ( ! panels s5ds =? su* a beam1 s t !y /rike out 9 f\r directions f ! c5tral lamp mu* z f\r spokes f ! hub ( a :eel4 ,!n desc5d+ once m to ! floor f :i* we />t$1 we see t among ! columns !re is a l>ge clockwork arrangem5t1 ! purpose ( :i* is to drive r\nd ! turntable & all t x c>ries--9 ! language ( ! ligh?\se eng9e] ! optical app>atus or1 m briefly1 ! app>atus4 ,& z ?is turns ! radiat+ beams ( light sweep r\nd ! horizon & 9 succession /rike into ! eyes ( any m>9] :o may be )9 range4 ,ea* "t a beam /rikes him he sees a fla%4 ,if ! app>atus revolve once a m9ute he w see f\r fla%es e m9ute1 "o f ea* panel4 ,let u consid]1 !n1 ! advantages ( ?is wond]ful me*anism1 ) its cunn+ arrangem5t ( prisms4 ,x is ^! latt]1 ( c\rse1 :i* are ! important ?+4 ,! re/1 ! me*anical portion1 is simply = ! purpose ( hold+ !m & turn+ !m at ! prop] spe$4 ,9 ! fir/ place1 ! contrivance gives u fla%es in/ead ( a /eady light2 x gives ! ligh?\se its "*4 ,!n aga9 x enhances ! brightness ( ! light4 ,in/ead ( %9+ all r\nd1 ! light is conc5trat$ 9 f\r special directions1 & ! light :i* w\ld be wa/$ upw>ds or d[nw>ds is sav$ & br\ght into use4 ,b suppose t ! ligh?\se we are consid]+ be ne> ! %ore1 s t !re is no ne$ = x to ?r[ any light 9 "o--! l&w>d--direction4 ,!n we %\ld see inside ! revolv+ framework ) its prisms a fix$ frame ) reflect+ prisms :i* w\ld cat* any rays go+ f ! lamp 9 ! direction ( ! l& & simply hurl !m1 z x 71 back into ! flame4 ,?us ! int5sity ( ! flame becomes increas$ by ^? rays ?r[n back :i* w\ld else h be5 wa/$4 ,or suppose t ! "* ( ! light is su* t ! fla%es h to be at irregul> int]vals4 ,!n ! framework1 in/ead ( be+ symmetrically f\r-sid$1 w\ld be ( an irregul> %ape4 ,& t br+s u to a beautiful feature ( ! me*anism ( ! app>atus4 ,we h be5 discuss+ a f\r-panel arrangem5t4 ,suppose t we 7 to r$uce x to ?ree4 ,!n1 s9ce all ! light w\ld be conc5trat$ into ?ree beams in/ead ( f\r1 ea* beam w\ld be m int5se4 ,we %\ld !reby h increas$ ! range ( our app>atus )\t any increase 9 ! co/ ( oil--= no?+1 z x 74 ,b to get ! same numb] ( fla%es p] m9ute we %\ld h to drive x r\nd s mu* ! fa/]4 ,b increas$ spe$ means increas$ burd5 on ! keep]s :o h to w9d up ! heavy weights :i* op]ate ! clockwork4 ,s !re is a limit to ! spe$ :i* c be atta9$4 ,b if friction c be almo/ elim9at$ ! app>atus c revolve at a high spe$ )\t ?r[+ undue burd5 ^u ! m54 ,b h[ c friction ?us be got rid (8 ,messrs ,*ance ,bros41 ! great ligh?\se con/ructors1 ( ,birm+ham1 h done x1 almo/ entirely1 by float+ ! app>atus on m]cury4 ,! turntable has on its "u side a l>ge r+ :i* ne>ly fits a ca/-iron tr\gh on ! top ( ! p$e/al4 ,9 ?is tr\gh !re is m]cury1 s t ^u ! liquid metal ! app>atus floats z if ^u a circul> raft4 ,! table ) its l5ses1 prisms & o!r fitt+s may weigh six or sev5 tons1 yet x c be pu%$ r\nd by "o f+]4 ,! v>i\s sizes ( optical app>atus are kn[n z ord]s4 ,"o ( ! fir/ ord] has a focal di/ance ( #ibj millimetres4 ,?is means t !re is t di/ance betwe5 ! c5tre ( ! lamp & ! bull's-eye4 ,!y desc5d by successive /ages d[n to ! six? ord]1 ) a focal di/ance ( #aej millimetres1 :ile ! mo/ important lights are ( an ord] sup]ior ev5 to ! s-call$ fir/1 t]m$ ! hyp]-radial1 ! focal di/ance ( :i* is #accj millimetres4 ,a rec5t example ( a hyp]-radial light is at ! well-kn[n ,cape ,race 9 ,newf\ndl&4 ,x revolves once e #cj seconds1 giv+ a fla% ( #c seconds e #g-a_/b seconds4 ,! optical app>atus weighs sev5 tons4 ,illu/ration3 ,by p]mission ( ,messrs4 ,*ance ,bros4 & ,co41 ,ltd41 ,birm+ham ,,dass5 ,,isl& ,,ligh?\se1 ,,cape ,,( ,,good ,,hope ,?is ligh?\se1 #hj feet high1 is built ( ca/-iron plates1 bolt$ toge!r ,mo/ ligh?\ses are fitt$ ) fog signals ( "s k9d :i* h a di/9ctive "* ! same z ! lights4 ,"s are horns bl[n at int]vals by compress$ air (t5 obta9$ f a special air-pump driv5 by an oil-eng9e4 ,ano!r ?+ is to let (f detonators at /at$ int]vals4 ,b p]haps ! mo/ int]e/+ ( all is ! subm>9e telephone4 ,! tr\ble ) audible signals is t !y are apt to v>y z ! conditions ( ! atmosph]e *ange4 ,=1 /range ?\gh x may appe>1 ! air :i* is ! natural m$ium by :i* s\nds are c>ri$ to our e>s is really a v bad sub/ance = ! purpose4 ,wat] is mu* sup]ior4 ,a swimm] :o c>es to try ! exp]im5t ( ly+ ^u ! wat] ) 8 e>s imm]s$ :ile a fri5d beats a gong "u ! wat] "s di/ance (f w be a/\nd$ at ! result4 ,s _m mod]n %ips are fitt$ ) "u-wat] e>s1 wat]pro( telephone receiv]s1 really4 ,"o is fix$ ea* side ( ! vessel1 ! wires f !m be+ l$ to telephone receiv]s ne> ! bridge4 ,_m ligh?\ses & light%ips 9 l mann] are fitt$ ) "u-wat] bells :i* c be rung at int]vals4 ,! s\nds s convey$ ?r\gh ! wat] are always ! same4 ,atmosph]ic or simil> *anges h no effect ^u !m4 ,&1 moreov]1 ! (fic] c tell :i* side ( 8 %ip ! bell is4 ,if x be on 8 port-side x s\nds l\d] 9 8 port telephone1 & vice v]sa4 ,by turn+ 8 %ip until he he>s !m equally he kn[s t he is po9t+ directly to or f ! bell4 ,?us if ! bell belong to a w>n+ light he c /e] confid5tly "r away f ! dang] ev5 9 ! ?icke/ fog4 ,b sci5ce has n only provid$ ! m>9] ) lights ( m>vell\s p[] & ( /range di/9ctive *>act]s1 & reliable s\nd-signals = foggy wea!r1 x has also f\nd him a reliable compass1 b t is wor?y ( a *apt] to itself4 ,,*apt] ,,vii ,,! ,,gyro-,,compass ,! magnetic compass has be5 = ages ! m>9]'s guide ov] ! trackless wat]s4 ,9 cl\dy wea!r x has be5 8 only means ( kn[+ ! direction 9 :i* 8 craft 0 head+4 ,inde$1 x is n too mu* to say t ! m>itime comm]ce ( ! _w 0 bas$ ^u ! behavi\r ( t little piece ( magnetis$ /eel4 ,x has always1 h[ev]1 be5 subject to c]ta9 faults4 ,to comm5ce )1 x po9ts1 n to ! geographical nor?1 b to ! magnetic pole1 a po9t "s di/ance f ! geographical pole1 & "o1 moreov]1 :i* is n q p]man5t4 ,! fact t ! magnetic pole v>ies its position is impressively %[n by ! fact t a special dep>tm5t at ,gre5wi* ,obs]vatory is cont9ually employ$1 by ! aid ( delicate self-record+ in/rum5ts1 wat*+ & sett+ d[n its fluctuations4 ,& ! premi] obs]vatory ( ! _w1 x %\ld be rememb]$1 exi/s prim>ily1 n 9 ! int]e/s ( pure sci5ce1 b z a dep>tm5t ( ! ,briti% ,admiralty 9 ord] to /udy matt]s ( int]e/ to navigation4 ,?us we h te/imony to ! importance ( ^! little vag>ies on ! "p ( ! magnetic compass4 ,b 9 addition to ^! inh]5t faults !re is a new s\rce ( error 9 ! magnetic compass :i* man has introduc$ himself by mak+ 8 %ips ( iron in/ead ( wood4 ,e %ip ( ! pres5t day is a huge magnet4 ,a piece ( iron left 9 ! same position = a l5g? ( "t becomes pol>is$1 :i* is to say t x acquires ! prop]ties ( a magnet2 & two magnets always ex]t an influ5ce ^u ea* o!r4 ,consequ5tly ! %ip1 aft] ly+ = p]haps a ye> 9 "o position1 dur+ ! p]iod ( build+1 becomes itself magnetic & int]f]es ) its own compass4 ,!n1 aga91 our me?ods ( %ip con/ruction aggravate ?is tr\ble4 ,x is believ$ t e molecule ( iron is itself a m9ute magnet ) a nor? & s\? pole ( its own4 ,^! ly+ 9 confusion 9 ! mass ( unmagnetis$ iron neutralise ea* o!r1 s t ! mass1 tak5 z a :ole1 does n exhibit any magnetic p[]4 ,b if by "s means ! :ole ( ! millions ( millions ( molecules c be set ! same way--) all _! nor? poles 9 "o direction1 & _! s\? poles 9 ! opposite direction--!n !y w all act toge!r4 ,in/ead ( neutralis+ ea* o!r !y w !n help ea* o!r1 & "u ^? conditions ! mass ( iron w possess t peculi> p[] :i* is di/9ctive ( a magnet4 ,s long z a piece ( iron is left 9 ! same position ! magnetism ( ! e>? is ?us act+ ^u ! molecules4 ,j z x t5ds to place ! compass ne$le nor? & s\?1 s x does ) e molecule 9 ! iron mass4 ,& if1 :ile ly+ /ill1 ! iron be hamm]$1 ! %ak+ ( ! molecules due to ! hamm]+ loos5s !m z x 7 & assi/s ! e>?'s p[] 9 pull+ !m into position4 ,"o has only1 !n1 to wat* ! rivet+ up ( a %ip1 & to see ! vigor\s way 9 :i* ! rivet]s wield _! hamm]s1 to realise t :5 ! ?\s&s or ev5 millions ( rivets h all be5 f9i%$ ! mat]ial ( t %ip w h _h ! v be/ possible *ance ( becom+ magnetic4 ,to make matt]s worse /ill1 %ips are (t5 load$ ) great weights ( iron among _! c>go4 ,t1 too1 may affect ! compass4 ,on w>%ips !re are ! heavy guns1 ea* weigh+1 ) its turret1 hundr$s ( tons1 & !y move1 s t _! effect ^u ! compass is n always ! same1 b may v>y f "t to "t4 ,& f9ally "o may m5tion ! electrical ma*9]y 9 a mod]n %ip consi/+ l>gely ( p[]ful magnets4 ,altoge!r1 !n1 x is n surpris+ t ! old magnetic compass is some:at unreliable4 ,x has to be coax$ into do+ its duty4 ,pieces ( iron & magnets h to be dispos$ ab\t x to c\nt]act ^! di/urb+ influ5ces ) :i* x is surr\nd$4 ,be=e a voyage exp]ts h to come on bo>d to adju/ ! compasses1 & ev5 !n !re is reason to believe t ! in/rum5t sometimes plays ! %ip false4 ,x is n to be wond]$ at1 !n1 t ! naval au?orities 9 p>ticul> ?r\gh\t ! _w h welcom$ ! adv5t ( a new compass :i* appe>s to possess none ( ^! drawbacks4 ,x po9ts to ! geographical nor?1 to ! actual pivot1 if "o may s speak1 ^u :i* ! e>? turns4 ,x is non-magnetic1 s t ! pres5ce ( iron or magnets ev5 9 its imm$iate neighb\rhood has little or no effect ^u x4 ,on ! o!r h&1 x has to be driv5 by a curr5t ( electricity1 & x seems j possible t 9 "s great crisis x might fail1 al?\gh e provision is made = alt]native s\rces ( supply 9 case ( "o fail+1 & !re is always ! possibility ( fall+ back ^u ! old magnetic compass %\ld ! new "o g wrong4 ,9 pr9ciple ! improv$ compass is1 l its old] bro!r1 simplicity itself4 ,! latt] is b a small piece ( iron magnetis$2 ! =m] is no?+ m ?an a sp9n+-top4 ,x is r /range t al?\gh ! sp9n+ object has be5 a famili> toy = ye>s1 & t1 moreov]1 its behavi\r has be5 ! subject ( inve/igation by "s v em95t sci5tific m51 x is only ( rec5t ye>s t its pr9ciples h be5 put to practical use4 ,ev]yone is famili> ) ! fact t a r\nd block ( wood w support itself ^u a comp>atively tall peg s long z x is rapidly rotat+4 ,& t is b "o ( ! curi\s ?+s :i* a rotat+ body w d4 ,= example1 imag9e a :eel m\nt$ ^u an axle ! ends ( :i* are support$ inside a r+1 :ile ! r+ aga9 is support$ on pivots betwe5 ! two prongs ( a =k1 ! =k be+ free to swivel r\nd 9 a socket4 ,! :eel is !n free to move 9 any direction4 ,te*nically1 x is said to h ?ree degrees ( fre$om4 ,x c sp9 r\nd1 its axle c turn ov] & ov] ) ! pivot$ r+ inside :i* x is fix$1 :ile x c also sw+ r\nd & r\nd z ! =k turns 9 its socket4 ,assum+ t ! jo9ts are all p]fectly free1 t ! pivots move 9 _! sockets ) p]fect fre$om--:i*1 ( c\rse1 !y d n--!n a :eel s m\nt$ c\ld move 9 any direction "u ! influ5ce ( any =ce t might act ^u x4 ,n[ a :eel s m\nt$ if left alone rema9s 9 precisely ! same position s long z x goes on rotat+4 ,if x be turn+ suffici5tly quickly its t5d5cy to rema9 w be /rong en\gh to ov]come ! friction ( any ord9>ily well-made in/rum5t4 ,consequ5tly a :eel ( t description has be5 us$ to demon/rate ! rotation ( ! e>?1 x rema9+ /ill 7except1 ( c\rse1 = its rotat+ movem5t7 :ile ! e>? has mov$ "u x4 ,c\ld we entirely elim9ate ! effects ( friction t might be us$ z a compass1 = x c\ld be set1 say ) its axle po9t+ nor? & s\?1 at ! comm5cem5t ( ! voyage1 & x w\ld rema9 s despite all ! evolutions ?r\gh :i* ! %ip might g4 ,b !re is a bett] s*eme ev5 ?an t1 bas$ ^u ! peculi> behavi\r ( a revolv+ :eel :5 x has only two degrees ( fre$om4 ,suppose t we disp5se ) ! r+ employ$ 9 ! previ\s arrangem5t1 pivot+ ! ends ( ! axle betwe5 ! prongs ( ! =k4 ,! :eel is !n free to rotate1 & its axle c slew r\nd ?r\gh a complete circle by ! turn+ ( ! =k 9 its socket1 b !re c be no tilt+ ( ! axle4 ,be+ ?us depriv$ ( "o ( its movem5ts ! gyroscope ) ?ree degrees becomes a gyroscope ) two degrees ( fre$om1 & 9 t =m x supplies ! ne$ = an effici5t & reliable compass4 ,! secret ( ! :ole ?+ is ! curi\s fact t a gyroscope ) two degrees ( fre$om exhibits a ke5 desire to place its axis p>allel ) ! axis ( ! e>?4 ,ow+ to ! %ape ( ! e>?1 a device su* z has be5 describ$1 ) its =k /&+ up v]tically1 _c possibly h its axis really p>allel ) t ( ! e>?1 except on ! ,equator4 ,/ill x gets z ne>ly p>allel z possible4 ,to be sci5tifically accurate1 we ought to say t x places x own axis 9 ! same plane z t ( ! e>?4 ,to und]/& ?is we ne$ to realise t all movem5t is relative4 ,9 ord9>y language1 :5 we say a ?+ is /ill we mean t x is /ill 9 relation to ! surface ( ! e>?1 b s9ce ! e>? is mov+ ! /ille/ ?+1 app>5tly1 is really travell+ at enorm\s spe$4 ,sa9t ,paul's ,ca!dral 9 ,london1 or a tall sky-scrap] 9 ,new ,york1 w\ld usually be reg>d$ z supreme in/ances ( immobility4 ,x w\ld be h>d to f9d bett] examples ( /ation>9ess1 z we ord9>ily look at ?+s4 ,ea* /&s1 firm & /rong1 ^u a horizontal base4 ,yet ea* is really turn+ a som]sault e tw5ty-f\r h\rs4 ,! plateau ^u :i* ,/ ,paul's /&s1 ?\gh x seems /ill & motionless b5ea? our feet1 is cont9ually tilt+2 its ea/]n edge is cont9ually go+ d[nw>ds & its we/]n edge upw>ds1 z ! e>? p]=ms its daily sp94 ,x is only a nor? & s\? l9e :i* does n %>e 9 "s degree ?is cont9ual tilt+ action4 ,e plane1 l>ge or small1 s long z x rema9s horizontal1 is be+ tilt$ ?us1 d[n at ! ea/]n edge & up at ! we/]n4 ,& ! plane 9 :i* ! axle ( a gyroscope ) two degrees is free to move is a horizontal plane4 ,ow+ to its be+ held betwe5 ! prongs ( ! =k1 :ile x c sw+ r\nd to po9t nor?1 s\?1 ea/ or we/1 or t[>ds any po9t betwe5 !m1 x _c deviate f ! horizontal plane4 ,!re=e su* axle is always be+ tilt$ by ! motion ( ! e>?1 except :5 x happ5s to be ly+ exactly nor? & s\?4 ,n[ = a reason :i* is too complex to g into "h a gyroscope /rongly objects to hav+ its axle tilt$ 9 ?is mann]4 ,if x be compell$ by sup]ior =ce to submit to tilt+1 x tries to wr5* itself r\nd sideways4 ,anyone :o has a gyroscope top & c>es to try ! exp]im5t w feel ?is action q easily4 ,hold ! sp9n+-top 9 y\r h& & turn x ov] s z to tilt ! axle1 :5 x w1 if y are n c>eful1 twi/ itself out ( y\r grasp4 ,s a gyroscope ( ! k9d we are consid]+1 :5 ! motion ( ! e>? tilts its axis1 turns itself r\nd 9 its socket until at la/ x rea*es ! nor? & s\? position1 :5 ! tilt+1 & !re=e ! twi/+1 ceases4 ,h5ce ! axle ( ! gyroscope if left to itself 7! rotation ( ! :eel be+ ma9ta9$ ! :ile7 w place itself 9 a nor? & s\? direction4 ,&1 moreov]1 x w keep 9 t direction4 ,x w take "s =ce to slew x r\nd into any o!r4 ,& if mov$ into any o!r by "s extrane\s means x w re/ore itself to ! old position aga94 ,h5ce a :eel ?us arrang$ has all ! attributes :i* we ne$ = a m>9]'s compass4 ,b un=tunately !re are me*anical difficulties 9 ! way ( us+ su* a simple contrivance = t purpose4 ,*ief ( all ^! is ! fact t x is n :at eng9e]s call dead-beat4 ,t means t x w n g to ! prop] position & !n rema9 !re q /ill4 ,in/ead1 x w fir/ slightly ov]%oot ! m>k1 :i* be+ foll[$ by ! rev]se action1 x w come back & ov]%oot x j z f> 9 ! opposite direction4 ,in/ead1 !re=e1 ( a /eady po9t+1 always 9 ! same direction precisely1 x w oscillate m or less1 ! exact nor? & s\? l9e be+ ! mean or av]age position1 ! c5tre ( ! oscillations4 ,x w\ld ( c\rse be possible to damp ?is1 to apply a break z x 71 if ! app>atus 7 to rema9 /ation>y4 ,= example1 if ! :ole conc]n 7 imm]s$ 9 wat] ! resi/ance ( ! liquid w\ld re/ra9 any quick movem5t ( ! axle1 yet x w\ld n prev5t x f sl[ly f9d+ its true position4 ,?us ! oscillations w\ld be r$uc$ to su* a small range z to be = practical purposes negligible4 ,b ! drawback to a device ( t k9d1 appli$ to a gyroscope on bo>d %ip1 w\ld be t ! axle w\ld be c>ri$ r\nd to "s ext5t e "t ! %ip turn$4 ,z %e *ang$ direction x w\ld m or less c>ry r\nd ! wat] ) x2 t 9 turn w\ld c>ry ! gyroscope1 & s ! direction ( ! latt] w\ld be = a "t untrue4 ,x w\ld 9 c\rse ( "t rega9 its accuracy1 b 9 ! meantime x w\ld be lead+ ! %ip a/ray4 ,consequ5tly ! application ( ?is1 9 itself wond]fully simple1 idea1 to ?is extremely important purpose 0 accompani$ ) a difficulty :i* 0 = a long "t insup]able4 ,b all 0 ov]come at la/ by ! g5ius ( ,dr ,ans*utz1 ( ,hamburg1 ^: firm 7 ! fir/ to turn out ! practicable article4 ,tak+ advantage ( ano!r movem5t ( ! gyroscope :5 arrang$ z has be5 describ$1 & us+ ! revolv+ :eel itself z a c5trifugal fan1 he 0 able to make ! :eel bl[ air aga9/ itself1 z x 71 :5 9 any position o!r ?an nor? & s\?4 ,?us1 if x deviates t[>ds ! ea/1 ?is jet ( air t5ds to bl[ x back2 if x turns we/w>ds ! jet aga9 comes into op]ation1 t5d+ to br+ ! err+ gyro back to its prop] place2 & s ! t5d5cy to oscillate is *eck$4 ,! f9i%$ in/rum5t z x is in/all$ on ! late/ w>%ips is1 ( c\rse1 q diff]5t 9 detail f ! simple contrivance :i* we h be5 consid]+ s f>1 al?\gh x is ! same precisely 9 pr9ciple4 ,! ess5tial "p is a heavy metal :eel comb9$ ) :i* is an electric motor :i* keeps x rotat+ at a spe$ ( #bj1jjj or s times p] m9ute4 ,! be>+s ( ! :eel are support$ ^u a metal r+ :i* floats ^u ! surface ( a tr\gh ( m]cury4 ,?us friction is br\ght d[n almo/ to ! irr$ucible m9imum4 ,! only place :]e ! :eel & its supports t\* any?+ solid is at "o delicately made pivot :i* s]ves to keep ! float+ me*anism 9 ! c5tre ( ! m]cury bas91 & to prev5t x f rubb+ aga9/ ! side ( x4 ,! curr5t :i* drives ! motor rea*es x ?r\gh ?is pivot & leaves ?r\gh ! m]cury4 ,?us arrang$1 al?\gh ! float+ "p is ( consid]able weight1 a v slight =ce inde$ is en\gh to move x2 :ile1 look+ at x ! o!r way1 we c see t ! %ip might turn rapidly to "r or to left1 c>ry+ r\nd ! m]cury b[l ) x1 )\t turn+ ! float+ "p at all4 ,?us ! gyroscopic action is v free inde$ to ex]cise its function ( keep+ ! contrivance po9t+ always 9 ! "o way4 ,! float has m\nt$ ^u x a compass c>d mu* l t ( ! ord9>y magnetic in/rum5t1 & ! sailor reads x 9 precisely ! same way4 ,to outw>d appe>ance !re is little ess5tial diff]5ce2 9 "o case !re is a magnet "u ! c>d to keep x /ill1 9 ! o!r !re is ! float ) ! revolv+ :eel m\nt$ ^u x4 ,x is cu/om>y to h "o ma/] compass ( ?is k9d on a %ip1 ) an electrical repeat] 9 ea* ( ! /e]+ positions4 ,z ! ma/] turns 9 its cas+ x s5ds a rapid s]ies ( curr5ts to all ! o!rs1 caus+ !m to turn 9 unison ) x4 ,! ma/] is fitt$ 9 "s safe "p ( ! %ip :]e x is lea/ likely to be ! victim ( any accid5tal damage4 ,,*apt] ,,viii ,,torp$oes ,,& ,,subm>9e ,,m9es ,x is sad to ?9k h[ mu* sci5tific skill & le>n+ has1 dur+ ! ,great ,w>1 be5 devot$ to kill+ p4 ,x us$ to be ?\ght t "o day a great sci5tific inv5tion w\ld arise1 ( su* deadly p[] t = ev] aft]w>ds w> w\ld be un?9kable2 its horrors w\ld be su* t all nations w\ld %r9k f x4 ,t prophecy1 h[ev]1 has n be5 fulfill$1 nor are !re any signs ( x4 ,on ! contr>y1 ea* sci5tific a*ievem5t 9 ! realm ( w>f>e is quickly c\nt]$ by ano!r3 s mu* s t ) all our sci5ce 9 ! manufacture ( weapons1 & our skill 9 us+ !m1 w>f>e 9 ! tw5tie? c5tury is if any?+ less deadly 9 proportion to ! numb]s engag$ ?an x us$ to be4 ,!re are1 h[ev]1 two weapons :i* 9 ?is w> h rea*$ a deadly effici5cy :i* !y did n seem to possess be=e1 & to :i* satisfactory antidotes h n yet appe>$4 ,^! two are ! subm>9e m9e & ! torp$o4 ,! latt]1 p>ticul>ly1 _h be5 a dismal failure previ\sly1 b z ! weapon ( ! subm>9e x has n[ e/abli%$ itself4 ,x is1 h[ev]1 only 9 connection ) ! subm>9e t x has a*iev$ any measure ( success1 &1 z !re are /rong indications t v soon ! subm>9e itself w be robb$ ( its t]rors1 x is q likely t ! reign ( ! torp$o w be brief4 ,al?\gh x has only j made itself felt s]i\sly 9 w>f>e1 ! torp$o is a fairly old idea4 ,9 fact we c trace ! g5]al idea ( x back to v anci5t times4 ,! mod]n weapon1 h[ev]1 dates f ! ye> #ahfd1 :5 an ,au/rian inv5tor approa*$ an ,engli% eng9e] nam$ ,:itehead ) a reque/ to take up 8 idea4 ,mr ,:itehead _h at t "t a works at ,fiume1 on ! ,adriatic1 & x 0 really 8 g5ius t develop$ ! crude idea into a practicable inv5tion4 ,?us !re came into exi/5ce ! ,:itehead ,torp$o1 n[ us$ 9 a great _m navies1 & also ! ,s*w>tzkopff1 :i* may be reg>d$ z ! ,g]man v>iety ( ! same ?+4 ,speak+ g5]ally1 x may be describ$ z a small automatic subm>9e boat4 ,ext]nally1 x naturally foll[s some:at ! l9es ( a fi%4 ,d]iv+ its "n f t curi\s fi% :i* is able to give electric %ocks f its sn\t1 x likewise c>ries on its nose t appliance :]eby x gives a %ock1 n electric x is true1 b equally deadly1 to any?+ :i* x may t\*4 ,s9ce no man-made me*anism c approa* ! m>vell\s action ( ! fi%'s f9s & tail1 ! propulsion is a*iev$ by a propell] l t ( a /eamboat1 b ( c\rse on a v small scale4 ,a s+le propell]1 h[ev]1 w\ld t5d to turn ! torp$o ov] & ov] 9 ! wat]1 & s x has two1 "o beh9d ! o!r1 driv5 9 opposite ways1 s t ! turn+ t5d5cy ( "o is neutralis$ by t ( ! o!r4 ,! blades ( ! propell]s are1 h[ev]1 set 9 opposite ways1 s t al?\gh rotat+ 9 diff]5t directions !y bo? pu% ! torp$o along4 ,beh9d ! propell]s1 aga91 !re are rudd]s = /e]+4 ,"o /e]s to "r or left1 z does t ( an ord9>y %ip1 :ile two o!rs are s plac$ t !y c /e] upw>ds & d[nw>ds4 ,s !re we h ! g5]al picture ( ! outside3 a smoo?1 fi%-l body ) a /+ 9 its nose1 propell]s at ! re> to drive x along1 & rudd]s to guide x4 ,inside are v>i\s *amb]s4 ,"o conta9s ! explosive :i* bl[s up :5 ! nose /rikes some?+4 ,?is head1 z x is t]m$1 is deta*able1 s t x c be left (f until x is really requir$ = w>4 ,! peace-head1 :i* is ( ! same size1 %ape & weight z ! w>-head1 is :at ! torp$o c>ries dur+ its e>li] c>e]4 ,) ?is x c be tri$ & te/$ 9 safety1 ! w>-head be+ sub/itut$ :5 ! real bus9ess ( ! torp$o beg9s4 ,ano!r *amb] conta9s ! compress$ air :i* furni%es ! motive p[]4 ,?is also s]ves to give buoyancy4 ,ano!r *amb]1 aga91 conta9s ! eng9es1 beautiful little ?+s ( ! f9e/ workman%ip almo/ exactly l ! f9e/ /eam-eng9e1 b ( c\rse v small 9 comp>ison4 ,9 ! e>ly /ages ! range ( ! torp$o 0 limit$ by ! am\nt ( compress$ air :i* x c\ld c>ry4 ,at fir/ sight !re seems no reason :y any limit %\ld be plac$ ^u ?is1 b 9 practice !re are (t5 limitations 9 eng9e]+ matt]s :i* are n app>5t on ! surface4 ,= example1 to increase ! air *amb] w\ld mean enl>g+ ! :ole torp$o1 call+ = m propulsive p[] & l>g] eng9es1 & ^! l>g] eng9es w\ld call = m air1 ?us defeat+ ! object 9 view4 ,=c+ m air 9 by us+ a high] pressure1 9 a simil> way w\ld necessitate a ?ick] *amb]1 to resi/ ! high] pressure4 ,?is w\ld add weight1 call+ = m buoyancy4 ,?us !re seem$ to be a practical limit beyond :i* x 0 impossible to g4 ,! difficulty 0 ov]come1 h[ev]1 9 a v cunn+ way4 ,:5 ! eng9es h us$ "s ( ! air1 & ! /ore is some:at exhau/$1 *emicals come into action :i* g5]ate heat1 :i* is imp>t$ to ! air :i* is left4 ,?is heat exp&s ! air1 produc+ 9 effect a l>g] supply ( x1 & enabl+ ! torp$o to make a long] j\rney4 ,/e]+ 9 a horizontal direction--t is to say1 to left or "r--is done by a gyroscope4 ,! action ( a rotat+ :eel is discuss$ 9 ! la/ *apt]1 & x is n necess>y "h to say m ?an ?is3 a rotat+ :eel always tries to keep its axle po9t$ 9 ! same direction4 ,j at ! mom5t ( />t+ su* a :eel is set go+ inside ! torp$o1 & its arrangem5t is su* t1 %\ld ! torp$o sw]ve to ! left1 ! gyroscope op]ates ! rudd] & /e]s x back4 ,9 ! same way1 if x t5ds to turn to ! "r1 ! ev]-wat*ful gyroscope br+s x to its true c\rse once m4 ,! effect ( ! gyroscope1 !re=e1 act+ ^u ! rudd]1 is to keep ! torp$o fai?fully to ! direction ^u :i* x is />t$4 ,! up & d[n rudd]s are likewise controll$ q automatically1 b 9 a diff]5t way4 ,_! function1 cle>ly1 is to keep ! ?+ at a c]ta9 uni=m level4 ,)\t su* control a torp$o w\ld be equally likely to jump out ( ! wat] altoge!r1 or to g d[nw>ds v]tically & bury its nose 9 ! mud4 ,! dep? at :i* x is to move is det]m9$ be=eh&1 c]ta9 necess>y adju/m5ts are made1 & ! torp$o !n pursues its ev5 way1 nei!r com+ to ! surface nor driv+ b5ea? its t>get4 ,= ?is purpose !re is fir/ ( all a hydro/atic valve4 ,?is little appliance1 :i* is op5 to ! action ( ! wat]1 responds to *anges 9 pressure4 ,! pressure at any po9t "u wat] is exactly proportional to ! dep?4 ,at t5 feet1 = example1 x is precisely t5 times :at x is at "o foot4 ,s ! hydro/atic valve is adju/$ to set ! rudd]s /raight :5 ! wat]-pressure ^u x is a c]ta9 am\nt4 ,if1 !n1 x dives d[nw>ds ! pressure increases & ! valve op]ates ! rudd]s s z to br+ x upw>ds1 :ile if x rise too high ! decrease ( pressure causes x to be guid$ d[nw>ds4 ,?is action1 h[ev]1 is too sudd5 & viol5t1 s t ) x alone ! torp$o w\ld proce$ by leaps & b\nds4 ,aft] be+ l[ x w\ld come up too sudd5ly1 ov]%oot ! m>k1 only to be /e]$ d[nw>ds aga9 equally sudd5ly4 ,! valve1 !re=e1 is comb9$ ) a p5dulum1 ^: action t5ds to re/ra9 ^! too sudd5 *anges1 ) ! result t "u ! influ5ce ( ! two ?+s comb9$ ! torp$o keeps fairly well to an ev5 c\rse1 only v>y+ upw>ds or d[nw>ds to an ext5t :i* is negligible4 ,f9ally1 !re is an int]e/+ little feature ab\t ! fir+ me*anism :i* m]its a description4 ,! actual fir+ is caus$ by ! driv+ 9 ( a little p9 :i* projects at ! nose ( ! torp$o4 ,suppose t1 9 ! process ( po9t+ ! torp$o & laun*+ x ^u its c\rse1 t p9 7 to be knock$ accid5tally1 an awful disa/] w\ld result4 ,x mu/ be provid$ aga9/1 !re=e1 & ! me?od adopt$ is beautiful 9 its c]ta9ty & simplicity4 ,normally1 ! fir+-p9 is fix$ by a screw s securely t no accid5tal fir+ is possible4 ,!re is1 h[ev]1 a little propell]-l object associat$ ) x1 :i* is driv5 r\nd by ! wat] z ! torp$o is pu%$ ?r\gh x1 & ?is unscrews1 & !reby releases ! p94 ,! little fan has to rotate a c]ta9 numb] ( times be=e ! p9 is releas$1 & x is q impossible = ?is numb] to be accompli%$ be=e ! torp$o has proce$$ to a safe di/ance f ! %ip :i* fires x4 ,on bo>d ! %ip1 !re=e1 & s long z x is ne> ! %ip1 x is q safe1 b by ! "t x rea*es its t>get x is ready to explode4 ,z f> z is kn[n1 ! =ego+ description gives a true g5]al description ( ! torp$oes n[ 9 use4 ,^? ( diff]5t p[]s may v>y 9 detail1 b1 broadly1 !y are z j describ$4 ,!re are o!rs1 h[ev]4 ,! ,br5nan1 = in/ance1 0 once adopt$ & l>gely us$ by ! ,briti% = h>b\r def5ce4 ,?is 0 controll$ f ! %ore by wires4 ,x 0 driv51 s to speak1 ) wire re9s1 & ?us guid$ x c\ld fairly hunt d[n its prey1 turn+ to "r & to left z requir$4 ,( great] sci5tific int]e/1 p]haps1 /ill1 is ! ,armor#a wireless controll$ torp$o4 ,?is is ! inv5tion ( two g5tlem51 ,messrs ,arm/rong & ,orl+1 ^: fir/ syllables comb9e to =m ! title ( ! torp$o4 ,( ?is1 two v int]e/+ features may be m5tion$4 ,fir/ly1 ! wireless control4 ,9 ! *apt] on ,wireless ,telegraphy !re is describ$ ! coh]]1 a simple little app>atus :i* we might describe z a door :i* is op5$ by ! waves :i* travel ?r\gh ! e!r f ! s5d+ app>atus4 ,:5ev] ! key ( ! s5d+ app>atus is depress$ ^! waves travel =?1 & :5 !y fall ^u ! coh]] x op5s4 ,normally1 ! coh]] is %ut1 b :5 act$ ^u by ! incom+ waves x op5s & lets ?r\gh curr5t f a batt]y1 :i* curr5t c be caus$ to p]=m any duty :i* we may wi%4 ,?us1 ignor+ ! int]m$iate /eps1 we get ?is3 :5ev] ! s5d+ key is depress$ curr5t fl[s ?r\gh ! coh]] & p]=ms :atev] duty is set be=e x4 ,& n[ picture to y\rself a too? :eel ) f\r tee?4 ,a cat* normally holds "o ( ! tee?1 b :5 ! cat* is lift$ = a mom5t x lets t too? slip & ! next "o is caught4 ,at e lift+ ( ! cat* ! :eel turns a qu>t] ( a turn4 ,!n imag9e t t cat* is op]at$ by an electro-magnet en]gis$ by ! curr5t :i* passes ?r\gh ! coh]]4 ,we see1 !n1 t e "t ! s5d+ key is depress$ ! :eel turns a qu>t] turn4 ,atta*$ to ! :eel is a little crank :i* turns ) x1 & ! p9 ( ?is crank fits 9 a slot 9 ! end ( a b> l ! till] ( a boat4 ,suppose t1 to comm5ce )1 ! till] is /raight1 s z to /e] ! boat /raight4 ,depress ! key1 ! :eel turns a qu>t] turn & ! till] is set s z to /e] to "o side1 say ! left4 ,ano!r pressure ^u ! key & a second qu>t] turn br+s ! till] /raight aga94 ,yet ano!r pressure1 ano!r qu>t] turn1 & ! till] is /e]+ to ! "r4 ,?us by simply press+ ! key ! correct numb] ( times ! torp$o c be made to travel 9 any desir$ direction4 ,! second +5i\s feature ( ?is weapon is ! means by :i* x is made visible to ! man :o is controll+ x f ! %ore or %ip4 ,probably ! reason :y ^! torp$oes are n us$ m is t ! man :o guides !m is ( necessity himself visible4 ,he has to be po/$ some:]e :]e he c foll[ its c\rse1 or he has no idea h[ to /e] x4 ,consequ5tly1 he w\ld be an object = attack by ! enemy4 ,su* a torp$o w\ld be useless 9 a subm>9e1 = ! subm>9e w\ld ne$ to come to ! surface 9 ord] t ! obs]v] might get a suffici5tly good view to be able to /e] ! torp$o1 & we all "k t :5 ^u ! surface a subm>9e is a v vuln]able craft4 ,b t is by ! way4 ,! po9t is h[ to make ! torp$o v cle>ly visible :ile x is /ill "u wat]4 ,a %ort ma/ might be us$1 b t w\ld be liable to be %ot away4 ,! inv5tor _h a happy inspiration :5 he made x bl[ up a jet ( wat]1 l a :ale does4 ,?is jet is q easy to see1 yet no %ot c de/roy x4 ,compress$ air bl[s up ?is tell-tale jet :i* ! obs]v] c see1 & by its means he c guide ! torp$o at w4 ,a subm>9e m9e may be reg>d$ z a /ation>y torp$o4 ,x consi/s ( a metal case fill$ ) a p[]ful *>ge ( explosive :i* floats h>mlessly 9 ! wat] until "s un=tunate vessel /rikes aga9/ x1 :5 x bl[s up ) suffici5t =ce to make a hole 9 ! /\te/ %ip4 ,!re are two classes ( m9e3 "o :i* is laid 9 peace "t1 to protect h>b\rs & *annels2 & ! o!r1 :i* is laid dur+ actual w>f>e4 ,! =m] are an*or$ 9 a m or less p]man5t way4 ,! s]vices ( div]s are us$ to place !m 9 position4 ,9 "s cases !y float well d[n 9 ! wat]1 out ( ! way ( pass+ %ips1 b come up ne>] ! surface :5 ne$$4 ,?is result is a*iev$ by hav+ an an*or *a9 ( su* a l5g? t :5 fully ext5d$ ! m9e floats a little way "u ! surface1 j high en\gh to be /ruck by a pass+ %ip1 toge!r ) :at is call$ an explosive l9k4 ,! l9k is us$ to loop toge!r two p>ts ( ! *a91 & s1 9 effect1 to r$uce its l5g?4 ,wires pass f ! l9k to ! %ore1 & :5 an electric curr5t is s5t along ^! wires ! l9k bur/s asund]1 lib]ates ! *a91 & ! m9e floats up to ! full l5g? ( its *a94 ,ano!r plan is to let ! m9es float high up always1 b to fire !m1 n by ! t\* ( ! %ip b by electricity f ! %ore4 ,9 ?is way a safe *annel is kept = fri5dly vessels1 :ile an enemy c be de/roy$4 ,necess>ily1 ^? m9es :i* are hurri$ly laid 9 w> "t are v diff]5t f ^!4 ,to be ( mu* use1 a m9e mu/ be conceal$ bel[ ! surface4 ,if x floats ^u ! wat] x w be visible1 & c be avoid$1 or1 at all ev5ts1 easily pick$ up4 ,x is practically impossible to set a float+ object at a c]ta9 dep? 9 ! wat]1 except by an*or+ x to ano!r1 heavi]1 object1 :i* w lie at ! bottom4 ,!re=e m9es h to be an*or$ 9 "s way4 ,b ! sea v>ies 9 dep?1 s t ! l5g? ( ! an*or *a9 mu/ be v>i$1 or else "s ( ! m9es w be on ! surface1 !reby adv]tis+ ! pres5ce ( ! m9e-field1 :ile o!rs w be bel[ ! dep? ( ev5 ! bigge/ %ip4 ,9 w>f>e1 h[ev]1 m9es ne$ to be laid quickly4 ,!re is no "t to s\nd = ! dep? & !n to adju/ ! l5g? ( cable accord+ly4 ,h5ce ! m9e mu/ be s made z to set itself correctly at a pre-det]m9$ dep?4 ,possibly "s read]s may ?9k t su* ?+s might be made to float1 ( !mselves1 at ! "r dep?4 ,x is a fact1 h[ev]1 t a ?+ ei!r floats ^u ! surface ( wat] or falls to ! bottom4 ,wat] is practically incompressible1 s t ! wat] at ! bottom ( ! sea is no heavi] ?an t ne> ! surface4 ,! conditions :i* prevail 9 air & all[ a balloon to float at any desir$ height d n apply4 ,! only ?+1 9 ?is case1 is to h an an*or *a9 or rope ( ! "r l5g?4 ,s let u picture a m9e-lay+ %ip /eam+ along1 probably 9 ! dead ( night1 surreptiti\sly lay+ m9es 9 ! hope t ! enemy w run into !m on ! morr[4 ,along ! deck ( ! %ip are small railway l9es1 & on ^! l9es /& :at appe> to be tra9s ( small trucks1 ea* truck hav+ small :eels to run on1 & ea* be>+ a l>ge r\nd metal ball4 ,z ! %ip travels along1 ! crew1 h&l+ ^! deadly ?+s q freely1 z if !y 7 innoc5t ( any dang]1 propel !m along to ! /]n1 & at regul> int]vals pu% "o ov]bo>d4 ,t is all4 ,! fre$om ) :i* ! m5 h&le !m is n folly1 = !y are !n q h>mless4 ,nor ne$ !y tr\ble ab\t ! l5g? ( rope1 = t adju/s itself4 ,j tumble ! ?+s ov]bo>d1 & 9 due "t !y an*or !mselves at ! "r dep? & set !mselves 9 ! "r condition = bl[+ up any %ip :i* may get among/ !m4 ,! truck-l object ^u :eels is n ! m9e itself3 x is ! s9k] :i* lies at ! bottom ( ! sea4 ,! r\nd ball :i* x be>s is ! m9e1 & ! two are connect$ toge!r by a wire rope4 ,to comm5ce )1 ?is rope is coil$ ^u a drum 9 ! s9k]1 :i* drum is ei!r held tightly or is free to revolve accord+ to ! position ( a cat*4 ,t cat* is held op51 s t ! drum is free1 by a weight at ! end ( a %ort rope4 ,let u assume t t rope is t5 feet long4 ,!n1 :5 ! :ole ?+ is tumbl$ into ! wat]1 ! weight s9ks fir/ t5 feet bel[ ! s9k]1 :i*1 be+ m bulky 9 proportion to its weight1 foll[s d[nw>ds m sl[ly4 ,:ile s9k+1 ! weight is pull+ ^u its rope & hold+ op5 t cat*1 s t ! drum pays out its rope & ! m9e lies s]5ely ^u ! surface4 ,z soon z ! weight t\*es bottom1 h[ev]1 ! pull on ! %ort rope ceases1 ! cat* grips ! drum1 no m rope is paid out1 & ! s9k]1 9 settl+ d[n its la/ t5 feet1 has to drag ! m9e d[n too4 ,?us1 q automatically1 by :at is really a beautifully simple arrangem5t1 ! m9e becomes automatically an*or$ at a dep? bel[ ! surface equal to ! l5g? ( ! %ort rope4 ,by mak+ t rope ! desir$ l5g?1 ! dep? ( ! m9e "u ! wat] c be fix$4 ,!re are v>i\s me?ods ( fir+ ^! m9es1 all ( :i* "w p]=ce by ! concussion ( ! %ip itself4 ,9 "s cases ! sudd5 tilt+ ov] causes an electric contact to be made1 & p]mits a batt]y 9 ! m9e to cause ! explosion4 ,ano!r way is to furni% ! m9e ) project+ horns ( s(t metal1 inside :i* are glass vessels conta9+ *emicals4 ,! %ip1 /rik+ a horn1 b5ds x1 breaks ! glass1 & lib]ates ! *emicals :i* cause ! explosion4 ,9 ! type ( m9e l>gely us$ by ! ,briti% ,navy !re is a project+ arm pivot$ on ! top ( ! m9e & project+ f x horizontally4 ,! m9e itself rolls along ! side ( ! pass+ %ip1 b ! arm simply trails or scrapes along4 ,?us ! m9e turns 9 relation to ! arm1 & a trigg] is !reby releas$1 :i* fires ! m9e4 ,9 ?is1 be x not$1 ! %ip only pulls ! trigg]1 s to speak1 & releases a hamm] :i* does ! "w1 j z ! trigg] ( a gun releases ! hamm]4 ,! motive =ce :i* makes ! hamm] d its "w :5 ! trigg] is pull$ is ! pull on ! an*or rope4 ,t arrangem5t has a virtue :i* is n app>5t at fir/ sight4 ,s9ce x is ! pull on ! an*or rope :i* actually fires ! m9e1 x foll[s t if su* a m9e break away f its moor+s x in/antly becomes h>mless4 ,safety = ! m5 :o lay ! m9es is secur$ 9 sev]al ways4 ,"o is by ! use ( a hydro/atic valve4 ,! fir+ me*anism is lock$ until ! pressure ( wat] releases x1 & t pressure does n exi/ until ! m9e is sev]al feet "u wat]4 ,ano!r way is to seal up ! fir+ me*anism ) a soluble seal made ( "s sub/ance su* z sal-ammoniac4 ,! m9e _c !n explode until x has be5 "u wat] long en\gh = ! seal to be melt$4 ,x n[ rema9s to relate h[ ^! m9es are swept up & remov$1 yet !re is v little really to tell1 = ! process is s exce$+ly simple4 ,s f> z is g5]ally kn[n1 no me?od has be5 f\nd t is sup]ior to ! primitive plan ( dragg+ a rope along betwe5 two %ips s z to cat* ! an*or ropes4 ,! vessels employ$ are usually ( v light draft1 s t !y /& a good *ance ( pass+ ov] ! m9es !mselves1 & ! rope us$ is z long z possible1 s t a m9e1 if explod$ by be+ caught 9 ! loop ( ! rope1 explodes s f> away z to d no h>m4 ,:5 dragg$ to ! surface ! m9es are explod$ f a di/ance by %ots f a small gun1 or ev5 f a rifle4 ,9 ! case ( ^? m9es :i* h horns1 a bl[ f a bullet is en\gh to break ! glass & cause explosion1 & 9 all cases m9es seem soon] or lat] to succumb to a %>p bl[4 ,?us !y are de/roy$1 by _! own action1 at a safe di/ance f ! sweep]s4 ,accid5ts happ51 h[ev]1 & m9e-sweep+ is no job = anyone b ! brave/4 ,x has be5 some:at difficult to cr[d a description ( torp$oes & m9es into ! small space ( "o *apt]1 & s _m details h _h to be omitt$1 b ! above descriptions give ! broad1 g5]al pr9ciples und]ly+ practically all =ms ( ^! t]rible weapons4 ,,*apt] ,,ix ,,gold ,,recov]y ,!re has always be5 some?+ v fasc9at+ ab\t gold4 ,ev5 9 anci5t times x 0 priz$ above all o!r ?+s1 & app>5tly x 0 comp>atively pl5tiful4 ,x is e/imat$1 = example1 t ,k+ ,solomon possess$ ov] ,l#d1jjj1jjj wor? ( x1 :ile ! little gift :i* ! ,que5 ( ,%eba br\ght him 0 ( ! h&some value ( ,l#fjj1jjj1 s t %e too mu/ h be5 pl5tifully suppli$ ) x4 ,probably x 0 m easily come by 9 ^? days1 ow+ to ! ri*ness ( ! primitive deposits1 ! be/ ( :i*1 p]*ance1 h be5 work$ out4 ,9 "o respect gold diff]s f all o!r metals 7) ! s+le exception ( plat9um1 :i* is sc>c] /ill7 9 t x appe>s naturally z gold1 n z ore4 ,! little pieces ( gold lie 9 ! m9e ready to be pick$ out1 & s if ! deposit 9 :i* x occurs be ne> ! surface1 & ! p>ticles be ( any consid]able size1 !y are sure to be f\nd4 ,a savage may be1 & (t5 is1 v anxi\s to secure weapons & tools ( iron1 little kn[+ t ! v gr\nd ^u :i* he /&s is possibly ( iron ore4 ,he covets ! s+le article ( iron1 & 9 "s cases is will+ to give mu* gold = x1 or ivory1 or "s su* treasure1 :ile ?\s&s or millions ( tons ( iron lie at 8 feet1 only he does n recognise x1 nor w\ld he "k h[ to utilise x if he did4 ,= iron1 l all o!r metals except ! two j ref]r$ to1 is f\nd naturally 9 comb9ation ) some?+ else1 g5]ally oxyg51 & ! comb9ation be>s no resemblance at all to ! metal4 ,! r$ ru/ s famili> to u on iron is a comb9ation ( iron & oxyg51 & x is fairly typical ( ! k9d ( /ate 9 :i* iron is f\nd 9 ! e>?4 ,nor w\ld anyone recognise copp] ore1 lead ore1 t9 ore1 or any ( ! ores1 any bett] ?an iron ore4 ,all are difficult to recognise4 ,x is said t ! highe/ complim5t t a ,corni% m9]--! f9e/ metallif]\s m9]s 9 ! _w come f ,cornwall1 or are ! product ( ,corni% influ5ce--! highe/ complim5t t su* a man c pay to ano!r is to say t he kn[s t91 mean+ t he c tell t9 ore :5 he sees x4 ,contra/$ ) ^! o!r metals1 gold is easy to f9d4 ,x does1 x is true1 "u c]ta9 conditions1 =m *emical comp\nds ) o!r ?+s1 z1 = in/ance1 9 gold *loride1 :i* is pres5t 9 sea-wat]1 b x does n oxidise z ! o!rs d1 & s :5 x is 9 ! e>? x is 9 ! bright yell[ gra9s su* z 7if !y be l>ge en\gh7 c easily be recognis$ at sight4 ,& x is (t5 f\nd 9 b$s ( loose gravel1 alluvial deposits1 z !y are t]m$4 ,9 su* cases ! gold is to be _h simply = ! pick+ up4 ,sometimes a lucky f9d occurs 9 ! =m ( a big nugget1 b m (t5 ! metal lies 9 t9y gra9s at long di/ances ap>t1 s t a ton ( gravel has to be sort$ ov] to f9d a paltry ounce or s ( gold4 ,yet s desir$ is x t gold w always fet* its price1 & an ounce to ! ton 7ev5 less7 is sometimes wor? gett+4 ,b 9 ! e>ly hi/ory ( ! _w !re 7 possibly p>ticul>ly g5]\s deposits ) pl5ty ( gold 9 good-siz$ pieces1 & su* w\ld be quickly discov]$ & work$ by primitive man4 ,no d\bt ! *iefta9s ( ^? days took mu*1 if n all1 ( ! gold t _! p f\nd1 & m p[]ful *iefs & k+s w\ld1 9 turn1 ei!r by =ce or 9 trade1 take x f ! weak]1 s t x is n surpris+ to le>n t "s ( ! mighty k+s & pot5tates ( long ago 7 well suppli$ ) gold4 ,yet !re are few ?+s m useless4 ,its value 9 ! fir/ in/ance 0 probably entirely due to its beautiful col\r1 & ! fact t x does n easily t>ni%4 ,= ?is reason1 c\pl$ ) ! fact t x 0 by no means pl5tiful1 m5 lik$ to deck !mselves ) x1 n only add+ to _! beauty by s do+1 b adv]tis+ to _! fell[s ! fact t !y 7 m5 ( weal?1 m5 :o possess$ :at few o!rs _h1 or at all ev5ts possess$ x m abundantly4 ,^! ?ree basic facts ab\t gold1 its beauty1 its fre$om f det]ioration & its comp>ative sc>city1 give x its peculi> /atus among ! commodities ( comm]ce1 9 t = x1 & = x alone1 !re is a cont9u\s & univ]sal dem&4 ,no gold-m9+ company ev] %ut d[n its prop]ties because ( ! fall+ (f 9 ! dem& = gold4 ,no "o ev] _h to hawk gold ab\t to f9d a pur*as]2 x is always saleable4 ,& h5ce its value to humanity z ! great m$ium ( ex*ange4 ,:5 a tailor wants bread1 z has be5 po9t$ out by a great political economi/1 he does n g se>*+ = a bak] :o happ5s to ne$ a coat4 ,if he did1 he might />ve be=e he f\nd "o4 ,in/ead1 he gives 8 coat to anyone :o ne$s "o1 no matt] :at 8 trade may be1 tak+ gold 9 ex*ange4 ,!n he goes ) confid5ce to ! bak]1 kn[+ full well t he1 9 turn1 w be p]fectly ready to give bread 9 ex*ange = gold4 ,t is ! pr9ciple ^u :i* gold1 & 9 a few cases silv]1 has become ! f\ndation ( trade4 ,we use x = ton+ photographs & a few o!r ?+s1 b1 practically speak+1 x is useless /uff1 yet c]ta9 special circum/ances h giv5 x a special function 9 civilis$ society1 & s gov]nm5ts n[ make x up into little flat discs1 putt+ _! own special /amp ^u !m z a gu>antee ( size & quality1 & x is by h&+ ^? little discs ab\t t we c>ry on our trade4 ,or ev5 :]e we use no actual disc1 we pret5d t we d1 & use a piece ( pap] ! value ( :i* we say is s _m discs1 b t value dep5ds entirely ^u ! fact t someone has gu>ante$1 on dem&1 to give s _m discs = x4 ,& ! /range ?+ ab\t x is t al?\gh ?is usefulness ( gold dep5ds ^u its r>ity1 we lose no opportunity ( look+ = new s\rces ( supply1 & s dim9i%+ t r>ity4 ,z has be5 said1 gold is pres5t 9 sea-wat]1 al?\gh no "o kn[s h[ to get x out1 except at a co/ :i* makes x n wor? :ile4 ,b suppose t "s g5ius f\nd a way1 & gold ?us became twice z pl5tiful z x is n[1 ! _w w\ld be no bett] (f4 ,ev]y?+ w\ld co/ twice z mu* z x does n[2 t is all4 ,a p\nd is m]ely s mu* gold4 ,if gold be twice z pl5tiful p w want twice z mu* ( x 9 ex*ange = :at !y h to sell4 ,yet1 all ! same1 ! man :o c\ld solve t problem ( gett+ gold f sea-wat]1 or f any:]e else1 9 fact1 w\ld be hail$ z a b5efactor1 & = a "t at lea/ he w\ld reap a g5]\s h>ve/4 ,ev5 z x is1 sci5ce has done mu* = ! production ( gold4 ,n1 z 9 o!r metals1 9 f9d+ ways = extract+ x f its ores1 =1 /rictly speak+1 x has none1 b 9 f9d+ ways ( cat*+ ! t9y p>ticles ( metal f ! gangue1 z x is call$1 ! rock or e>? 9 :i* !y are emb$d$4 ,! tr\ble is t !y are s small1 s inf9itesimally small1 almo/4 ,!re are two great types ( place :]e gold is f\nd4 ,9 ! alluvial deposits1 ! b$s ( old riv]s1 ! gold is q loose4 ,! convulsions ( ages ago h1 9 _m cases1 elevat$ ^! b$s1 until n[ !y are on ! sides ( m\nta9s4 ,9 su* cases ! loose1 gravelly /uff ( :i* !y are compos$ is wa%$ d[n by a p[]ful /ream ( wat] f a huge hose-pipe t]m9at+ 9 a nozzle call$ a monitor4 ,?is process1 call$ hydraulic+1 br+s d[n ev]y?+ into a pond =m$ at ! foot ( ! hill1 & 9 "s cases a boat or raft is float$ ^u ! pond ) ma*9]y on bo>d = dr$g+ up ! mat]ial4 ,(t5 a p[]ful c5trifugal pump sucks up ! wat] ?r\gh a pipe rea*+ to ! bottom ( ! pond1 br++ gravel & gold ) x4 ,arriv$ 9 ?is way ^u ! raft1 x all goes on to sep>at+ tables1 by :i* ! gold1 be+ heavi]1 is divid$ f ! gravel1 :i* is light]4 ,^! tables w be ref]r$ to aga9 lat]4 ,9 non-alluvial work+s ! gold is emb$d$ 9 rock ( "s k9d1 su* z t call$ qu>tz4 ,?is is h>d1 some:at ( ! nature ( granite1 & be=e ! gold c be lib]at$ x has to be cru%$ to ! lik5ess ( f9e s&1 s t ! t9y gra9s ( gold c be captur$4 ,! qu>tz is f\nd 9 ve9s or lodes1 fissures1 evid5tly1 9 ! orig9al cru/ ( ! e>?1 produc$ probably z ! e>? cool$4 ,^! h be5 gradually fill$ up by hot volcanic /reams ( wat]1 :i* c>ri$ n only ! gold 9 solution b also ! mat]ials ( :i* ! qu>tz is =m$4 ,x us$ to be ?\ght t ! ve9s 7 ! result ( hot liquids =c$ up f bel[ by volcanic action1 ! rock & metal be+ !mselves 9 ! liquid /ate ?r\gh int5se heat4 ,x is n[ m g5]ally held t wat] 0 ! vehicle by :i* ! mat]ials 7 br\ght 91 & ! ve9 =m$4 ,! gold 9 ! alluvial deposits1 too1 is n[ ?\ght to h come !re 9 solution 9 wat]1 & n by ! erosion & wa%+ d[n ( rocks high] up ! orig9al riv]4 ,h[ev] t may be1 & x is ! subject ( discussion among geologi/s & metallurgi/s1 !re ! gold is to-day1 firmly fix$ 9 ! h>d rock1 & ! problem :i* confronts ! metallurgi/ is to get x out ) ! lea/ exp5se4 ,! old hi/oric way ( break+ up ! qu>tz rock is ) :at are call$ /amps1 pe/les & mort>s on a huge scale4 ,!re are a numb] ( v]tical beams ( wood1 ea* %od ) iron1 fix$ 9 a wood5 frame1 s t !y are free to slide up & d[n4 ,runn+ along beh9d ^! /amps is a horizontal %aft ) projections ^u x call$ cams4 ,!re is "o cam = ea* /amp1 & z ! %aft turns sl[ly r\nd ?is projection cat*es "u a projection on ! /amp1 & aft] lift+ x up a %ort di/ance drops x sudd5ly4 ,?us1 z ! ma*9e works1 ! /amps are lift$ & dropp$ 9 rapid succession4 ,! rock is f$ into a box into :i* ! feet ( ! /amps fall1 & ?us x is p\nd$ until x is q small4 ,mean:ile a /ream ( wat] fl[s ?r\gh ! box & c>ries away ! f9ely brok5 p>ticles ?r\gh a k9d ( sieve :i* =ms ! front ( ! box1 & :i* all[s ! f9e1 small pieces to escape1 :ile hold+ back ! l>g] ones & keep+ !m until !y too h be5 cru%$4 ,an av]age /amp w weigh #fjj to #gjj lb41 & ! repeat$ bl[s ( su* a hamm] are en\gh to pulv]ise ! h>de/ rock4 ,ma*9es su* z ^! h be5 employ$ s9ce ! sixte5? c5tury1 at all ev5ts1 & ! improvem5ts ( mod]n times are only z reg>ds details4 ,x may well be wond]$1 !n1 :y su* an old device is /ill 9 use & h[ x comes ab\t t x has n be5 displac$ by some?+ new] & bett]4 ,! answ]1 :i* is an in/ructive "o1 well wor? be>+ 9 m9d by _m inexp]i5c$ inv5tors1 is t x is s simple4 ,x c be %ipp$ 9 comp>atively small p>ts1 & s tak5 *eaply to any outl&i% place4 ,a good deal ( x c be made r\ghly ( wood1 s t if native timb] is available x c be made p>tly at ! m9e1 & c>riage co/s sav$4 ,f9ally1 x is s easy to "w & to und]/& t ! mo/ inexp]i5c$ workman c h&le x1 & !re is s little t c g wrong t ! mo/ c>eless att5dant _c damage x4 ,9 ! bottom ( ! boxes !re is plac$ "s m]cury1 = :i* gold has a curi\s aff9ity4 ,if a p>ticle ( gold once gets into contact ) ! surface ( ! m]cury x w n get away aga9 easily4 ,?us ! m]cury cat*es & holds _m ( ! gold p>ticles :i* are lib]at$ :5 ! rock is brok5 up4 ,z x rea*es ! requir$ f95ess1 !n1 ! cru%$ rock escapes f ! /amp ma*9e & fl[s away 9 ! /ream ( wat]1 & al?\gh mu* gold is caught by ! m]cury1 x is by no means all4 ,! /ream is !re=e direct$ ov] tables =m$ ( copp] %eets coat$ ) m]cury1 s t additional opportunities are giv5 to m]cury to cat* ! gra9s ( gold4 ,moreov]1 ! table1 :i*1 by ! way1 is plac$ at a slight incl9e1 is brok5 at int]vals by little tr\ghs ( m]cury call$ riffles1 :i* assi/ 9 ! deposit+ & cat*+ ( ! metal p>ticles4 ,b ev5 !n all ! gold is n captur$4 ,! cru%$ rock is n[ l s&1 & "s ( ! gra9s /ill conta9 gold1 :i* has n be5 deta*$ by ! cru%+4 ,! gold1 h[ev]1 makes su* gra9s slightly heavi] ?an ! o!rs1 & because ( t !y c be sep>at$4 ,! old way is to use a blanket table1 a table1 t is1 cov]$ ) co>se flannel or baize1 ! hairs ( :i* cat* ^! heavi] p>ticles z ! wat] /ream c>ries !m along1 ! light] p>ticles escap+4 ,! gra9s s caught =m :at are kn[n z conc5trates1 s9ce 9 !m ! gold is conc5trat$4 ,! conc5trates are subsequ5tly treat$ z we %all see lat]4 ,n[ we c see h[ mod]n sci5tific me?ods h supplem5t$ ! old ways4 ,take fir/ ! case ( ! /amp mill or /amp batt]y4 ,9 spite ( t prime virtue ( simplicity :i* has kept x at "w almo/ un*ang$ = c5turies1 x has its weaknesses1 & no d\bt = "s purposes cru%+ mills are bett]4 ,( ^! !re are a great v>iety1 sev]al ( :i* dep5d = _! action ^u c5trifugal =ce1 or1 z x is m correctly t]m$1 c5trifugal t5d5cy4 ,9 ^! cru%+ mills !re is a r+1 g5]ally ( /eel1 inside :i* are susp5d$ "o or m heavy iron roll]s4 ,! %afts :i* c>ry ^! roll]s are atta*$ by _! upp] ends to ! driv+ me*anism on ! top ( ! mill1 & :5 t is set 9 motion ! rolls are c>ri$ r\nd & r\nd inside ! r+4 ,because ( ! c5trifugal t5d5cy1 !y sw+ outw>ds1 press+ heavily aga9/ ! inn] surface ( ! r+4 ,! rock is f$ 9 9 su* a way t ! roll]s1 z !y roll r\nd ! inside ( ! r+1 repeat$ly travel ov] x & cru% x4 ,9 ano!r type ( mill1 call$ ! ball mill1 ! pr9ciple is diff]5t4 ,!re y h a cyl9d] ( /eel :i* turns ^u a horizontal axis4 ,?is cyl9d] is p>tly fill$ ) /eel balls ( v>i\s sizes1 & z ! mill turns1 ! rock1 be+ mix$ ) ^! balls1 is p\nd$ & brok5 up4 ,z ! mill turns ov] & ov] ! balls fall ^u ! pieces ( rock1 ?us produc+ a f9e p[d]4 ,o!r mills1 aga91 are b ref9$ editions ( ! common mort> mill s (t5 se5 :]e build+ op]ations are go+ on1 9 :i* heavy iron roll]s travel ov] ! mat]ial to be cru%$ z x lies 9 a r\nd pan4 ,! blanket table1 too1 gives place at ! mod]n m9e to ! vann]1 ( :i* !re are sev]al v>ieties4 ,ess5tially !y are mu* ! same1 & a description ( two w s]ve to give an idea ( !m all4 ,let u take ! ,record vann]4 ,imag9e a l>ge table =m$ ( wood1 ! upp] surface cov]$ ) l9oleum4 ,x is fix$ on slides s t x c move to & fro endwise4 ,x is giv5 a slight slope 9 ! direction at "r angles to its l5g?--t is to say1 "o edge is a little l[] ?an ! o!r4 ,! mat]ial is f$ on at "o end1 at ! high] edge1 & naturally t5ds to run d[n & (f at ! l[] edge4 ,x is re/ra9$ some:at f do+ ?is by ! pres5ce ( r[s ( riffles or ridges runn+ l5g?wise4 ,nev]!less x does 9 a %ort "t f9d its way (f ! table at ! l[] end4 ,b all ! "t t x is at "w ! table is be+ slidd5 backw>ds & =w>ds on ! slides4 ,by a simple b curi\s me*anism x is arrang$ s t x moves quickly 9 "o direction & sl[ly 9 ! o!r1 ) ! result t ! heavi] p>ticles ( s&--^? :i* conta9 gold--are c>ri$ to ! f>!r end ( ! table4 ,?us1 z has be5 said1 all ! /uff is f$ on to ! high] edge & c>ri$ d[n by ! wat]1 until x falls (f at ! l[] edge1 b dur+ ! j\rney f edge to edge ! peculi> motion ( ! table causes ! diff]5t k9ds ( s& to sep>ate !mselves1 s t ! conc5trates fall (f ne> "o end1 & ! re/ ne> ! o!r end4 ,ano!r int]e/+ example ( +5uity is ! well-kn[n ,frue vann]4 ,9 ?is ! table is a broad1 endless b& ( india-rubb]1 ext5d$ ^u two roll]s1 "o ( :i* is slightly high] ?an ! o!r4 ,! /ream ( wat] & cru%$ ore fl[s on at ! upp] end1 & runs d[n to ! l[]1 ! light] p>ticles be+ c>ri$ d[n & dropp$ (f at ! l[] end1 :ile ! heavi] re/ ^u ! b&4 ,mean:ile ! turn+ ( ! roll]s c>ries ! b& sl[ly along1 s t ! heavi] p>ticles gradually asc5d & are c>ri$ ov] at ! upp] end4 ,to assi/ 9 ! sep>ation1 ! :ole conc]n is giv5 a side-to-side %ak+ motion :ile x is at "w4 ,we h se5 s f> h[ ! ore is cru%$1 & ! co>s] gra9s ( gold got out ( x by ! aid ( m]cury4 ,! mixture ( m]cury & gold is t]m$ amalgam1 & ! process ( extract+ gold by m]cury is call$ amalgamation4 ,! gold is actually dissolv$ 9 ! m]cury1 & s :5 ! amalgam has be5 7z x is p]iodically7 collect$ f ! plant1 x has to be filt]$ & !n evaporat$ 9 a retort4 ,! m]cury vap\r is caught & cond5s$ back into a liquid1 :ile ! gold is left 9 ! retort4 ,9 fact ! amalgam is di/ill$ 9 ord] to sep>ate ! gold & m]cury4 ,b :5 all t is done we /ill h ! conc5trates f ! vann]s1 or :atev] be us$1 to deal )4 ,m]cury is useless ) !m1 = ! gold is cov]$ probably ) a coat+ ( ! o!r sub/ances1 :atev] !y may be1 ) :i* x has be5 associat$1 or else !re is mix$ ) ! gold "s sub/ances :i* make amalgamation impossible1 or at lea/ difficult4 ,(t5 roa/+ is necess>y be=e any?+ m c be done4 ,if ars5ic or sulphur be pres5t1 = example1 !y int]f]e ) ! recov]y ( ! gold1 & roa/+ w disp]se !m4 ,s ! conc5trates are pass$ ?r\gh great furnaces1 9 :i* !y are heat$ 9 contact ) air until ^! objectionable matt]s h be5 oxidis$ or burnt4 ,!n f9ally we come to "s process by :i* ! rema9+ gold is dissolv$ out f its admixtures 9 "s solv5t liquid f :i* x c be subsequ5tly precipitat$4 ,?is is r int]e/+1 because x means t man has adopt$1 to recov] ?is gold f ! ore1 ! v me?od :i* x is believ$ nature employ$ to put x !re4 ,z already said1 ! late/ idea is t ! gold 0 c>ri$ into & deposit$ 9 ! lodes :]e x is n[ to be f\nd by wat]--t ! gold 0 actually dissolv$ 9 wat] at ! "t4 ,b1 ( c\rse1 gold 9 its metallic /ate w n dissolve 9 wat]4 ,salts ( gold1 h[ev] 7! mean+ ( ! t]m salt1 z appli$ to a metal1 has be5 expla9$ e>li]71 w dissolve 9 wat]1 z e photograph] :o makes up 8 own ton+ solution kn[s f exp]i5ce4 ,gold w n dissolve 9 wat]1 b *loride ( gold w4 ,& s ! gold mu/ h be5 c>ri$ to its re/+-place z a salt1 & conv]t$ into ! metallic =m aft] arrival4 ,9 ! same way1 to recov] ^! f9e/ p>ticles ( all1 x has to be conv]t$ back into a salt2 !n t salt mu/ be dissolv$ & dra9$ away f ! o!r /uff2 &1 f9ally1 ! gold mu/ be ?r[n out ( solution aga9 9 "s way4 ,! great example ( ?is op]ation is ! famili> cyanide process4 ,! ^w famili> is appropriate to ?is matt] 9 only "o way1 h[ev]4 ,hold]s ( %>es 9 m9+ companies1 = example1 may he> ab\t x repeat$ly at %>ehold]s' meet+s & 9 prospectuses1 b v few h any cle> idea z to :at x is4 ,s ,i _c be accus$ ( tell+ an (t-told tale if ,i devote a %ort space to its consid]ation4 ,! comb9ation ( "o atom ( c>bon & "o atom ( nitrog5 is call$ cyanog54 ,if cyanog5 be giv5 ! *ance x w take unto itself an atom ( hydrog51 produc+ ! deadly hydrocyanic or prussic acid4 ,alt]natively1 if potassium be br\ght into comb9ation ) x1 !re results potassium cyanide1 :i*1 ) ! assi/ance ( wat] & oxyg51 c dissolve gold4 ,9 apply+ ?is sci5tific fact to ! purpose ( recov]+ gold f ! conc5trates1 ! latt] are plac$ 9 vats ) a weak solution ( ! cyanide 9 wat]4 ,! "t dur+ :i* !y are all[$ to rema9 dep5ds ^u ! size ( ! gold p>ticles4 ,if !y be comp>atively l>ge1 x /&s to reason t x mu/ be long] ?an if !y be small1 = !y w take long] to dissolve4 ,aft] ! prop] "t1 :i* is f\nd by exp]im5t1 ! liquid is drawn (f1 & 9 "s cases ! conc5trates are giv5 a second dose to ensure t ! gold %all be ?or\ghly remov$ & none left undissolv$4 ,if ! mat]ial be+ op]at$ ^u be v f9e1 z x (t5 is1 =m+ :at ! m9+ p call slimes1 !n me*anical /irr]s h to be us$ 9 ! vats to keep ! /uff mov+1 z o!rwise ! cyanide w\ld n get to all ! p>ticles & "s w\ld n be act$ ^u4 ,! liquid1 hav+ be5 ! appropriate "t 9 ! vat1 is drawn (f1 plac$ 9 wood5 tanks or boxes1 & f9e %r$s ( z9c are add$ to x4 ,discs ( %eet z9c are put into a la! & a f9e %av+ tak5 (f !m1 & x is ^! f9e %av+s :i* are us$4 ,n[ z9c1 z we "k f ! fact t x is ! ess5tial "p 9 electric batt]ies1 has v pron\nc$ electrical prop]ties1 & x is believ$ t ^! come into play "h4 ,at all ev5ts ! gold becomes deposit$ ^u ! z9c1 :ile ! z9c itself is to a c]ta9 ext5t eat5 away by ! solution4 ,! result is 7a7 a solution weak] ?an x 0 be=e1 7b7 ! rema9s ( ! %av+s1 & 7c71 at ! bottom ( ! box 9 :i* ?is process takes place1 a d>k mud4 ,t black mud1 on be+ heat$1 produces ! bright metallic gold1 & ! object ( ! :ole op]ation is a*iev$4 ,! solution is !n l$ to ano!r tank1 br\ght up to its prop] /r5g? aga9 & is ready to be us$ once m1 :ile ! rema9s ( ! %av+s are us$ = ! next bat* ( mat]ial to be treat$4 ,9 "s cases ! cru%$ ore /raight f ! cru%+ mill is cyanid$1 9 o!rs x is simply ! rema9s left ov] f ! previ\s amalgamat+ process :i* is ?us treat$4 ,all dep5ds ^u ! nature ( ! mat]ial 9 "q4 ,!re are o!r *emical me?ods besides ! cyanid+1 b x is ! *ief4 ,x has be5 f\nd specially useful ) ! ,johannesburg ores1 & to x ! ,s\? ,african goldfields owe a great deal ( _! success4 ,!re is a m mod]n =m ( x1 al?\gh ! :ole process is q novel1 hav+ be5 introduc$ only 9 ! n9eties ( la/ c5tury4 ,?is developm5t1 x is almo/ we>y+ to repeat1 is electrical4 ,in/ead ( ! z9c %av+s be+ us$ to precipitate ! gold out ( ! solution1 ! process is electrolytic4 ,a lead anode is us$ :ile ! process is c>ri$ on 9 a box ! bottom ( :i* is cov]$ ) m]cury1 :i* =ms ! ca?ode4 ,! precipitat$ gold is ?us amalgamat$1 ! amalgam be+ remov$ at int]vals1 retort$1 & ! gold recov]$4 ,! idea ( recov]+ gold f ! wat]s ( ! sea is c]ta9ly a mo/ attractive "o4 ,to "s1 x is true1 ! sugge/ion may br+ ?\ghts ! rev]se ( pleasant1 = !re h be5 sev]al p>tially successful attempts to delude ! public ) speci\s promises ( va/ divid5ds to be ga!r$ 9 ! =m ( pure gold f ! inexhau/ible sea4 ,/ill1 !re is some?+ 9 x1 & "s day ! dreams may be realis$4 ,! quantity ( gold dissolv$ 9 sea-wat] is s small t 9 #bjj cubic c5timetres x is impossible to detect x1 ev5 by ! mo/ delicate te/s kn[n4 ,! quantity ne$s to be multipli$ ?reefold be=e ! quantity ( gold becomes ev5 detectable1 to say no?+ ( be+ recov]able4 ,a writ] 9 ,cassi]'s ,magaz9e1 a few ye>s ago1 relat$ h[ he _h actually obta9$ gold f ! wat] ( ,long ,isl& ,s\nd4 ,b :]eas he got two doll>s' wor?1 x co/ him ov] #djjj doll>s to d x4 ,no company w ev] be float$ on results su* z t4 ,f ! mud ( a creek ne> ,new ,york1 h[ev]1 he did a little bett]1 = !re t5 doll>s' wor? ( gold only co/ #cgi doll>s4 ,a company promot] w\ld /ill look askance at ev5 t comp>atively successful und]tak+4 ,z usual1 au?orities diff]1 b !re is a cons5sus ( op9ion t 9 e ton ( sea-wat] !re is f "o-half to "o gra9 ( gold1 besides silv] & iod9e4 ,x seems z if ! wat] 7 able to dissolve t am\nt & no m4 ,if1 z has be5 sugge/$ e>li] 9 ?is *apt]1 all ! gold :i* is n[ f\nd 9 m9es & 9 gravel b$s 0 c>ri$ !re 9 wat]1 x is probable t ! sea obta9s its gold f ! same orig9al s\rces1 & t1 j z ! hot ocean ( ages ago c>ri$ its burd5 ( gold 9 solution1 s ! cold] wat] ( to-day has its %>e1 ! cold wat] naturally c>ry+ less ?an ! hot did4 ,x is q likely1 !n1 t1 c\ld we f9d out h[ to rob ! sea ( its preci\s metal1 x c\ld repl5i% its /ore f "s secret ho>d ( its own4 ,b ev5 if x c\ld n1 x w\ld make little diff]5ce to u1 s9ce :at x holds is f> m ?an we c\ld ev] use4 ,put x at half-a-gra9 p] ton3 !re are #dbje million tons 9 e cubic mile ( ocean1 & #cjj million cubic miles ( wat] 9 ! ocean4 ,if all ! gold t man has ev] h&l$ 7 to be dissolv$ 9 ! sea1 no *emi/ w\ld be able to discov] ! fact4 ,on ! o!r h&1 if t half-gra9 p] ton :i* we believe to be 9 ! ocean n[ 7 to be recov]$ we %\ld h ab\t #dj1jjj million tons ( gold1 a prospect :i* is en\gh to make ! political economi/ turn pale ) appreh5sion4 ,:at is requir$ is "s sub/ance :i*1 on be+ add$ to sea-wat]1 w comb9e ) ! gold1 & !n be precipitat$--t is to say1 fall to ! bottom4 ,! precipitate--t :i* falls to ! bottom--w\ld ne$ to be heavy1 s t x w\ld fall quickly & n necessitate ! wat] be+ left /&+ = long p]iods4 ,x w\ld ne$ to be *eap1 too1 or easily recov]able1 s t x c\ld be us$ ov] & ov] aga94 ,&1 f9ally1 x w\ld ne$ to be su* t ! gold1 hav+ be5 captur$ by x1 c\ld be easily obta9$ f x4 ,giv5 su* a precipitant1 ! process ( recov]+ ! gold w\ld be simple & *eap4 ,tanks w\ld be =m$ 9 %elt]$ bays & inlets4 ,at e tide ^! w\ld be fill$1 & :5 full ! precipitant w\ld be add$4 ,! tide fall+1 ! wat] w\ld run out aga9 & leave ! precipitate on ! floor ( ! tanks1 :5ce x c\ld be remov$ by scrap+4 ,simple treatm5t w\ld release ! gold f its p>tn]1 :i* w\ld !n be return$ to ! tanks to act z ! precipitant once m4 ,?us by simple means1 ! tide itself assi/+1 ! gold c\ld be obta9$ f ! sea4 ,& !re is no?+ inh]5tly impossible ab\t ?is sugge/ion4 ,! necess>y precipitant may exi/1 await+ discov]y4 ,a l>ge works op]at+ 9 ?is mann] w\ld produce1 x is e/imat$1 ab\t ?irte5 tons ( gold p] annum4 ,x looks z if x w\ld be a bad day = ! ,r& :5 t discov]y is made4 ,& !re is yet ano!r possibility1 ?\gh less allur+ ?an :at has j be5 describ$4 ,! ,am]ican writ] m5tion$ a little :ile back got a bett] return f ! mud ( a creek ?an f ! wat] itself4 ,9 all probability ?is is due to ! action ( organic matt] c>ri$ d[n by /reams1 or 9 "s o!r way introduc$ into ! wat]s ( ! creek :5ce ! mud 0 obta9$4 ,?is organic matt] w\ld possibly h an effect z a precipitant ^u ! dissolv$ gold1 caus+ x to be ?r[n out ( solution & deposit$ 9 ! mud4 ,?us ! mud ar\nd our %ores1 & p>ticul>ly 9 ! creeks & e/u>ies1 may be pot5tial gold m9es :5ce 9 "t to come we may draw supplies ( ! preci\s metal4 ,! cyanide or "s simil> process may be ne$$ 9 ord] t we may extract ! metal f its enclos+ mud1 b ! "t may n be s v f> di/ant :5 dr$g+ = gold may be a regul> occupation at1 = example1 ! m\?s ( ! ,?ames & ! ,hudson4 ,,*apt] ,x ,,int5se ,,heat ,_m ( ! useful & int]e/+ manufactur+ processes ( to-day are bas$ ^u ! int5se heat :i* sci5ce has taught ! manufactur] h[ to produce4 ,tasks :i* our =efa!rs dream$ (1 b 7 unable to accompli%1 are easy to-day because ( ! facility ) :i* great heat c be g5]at$4 ,! burn+ fi]y furnace sev5 times heat$ is z no?+ to "s ( ! temp]atures :i* are n[ obta9$ 9 ! ord9>y c\rse ( ?+s4 ,! greate/ heat ( all is t ( ! electric arc4 ,two conductors1 g5]ally rods ( c>bon1 are plac$ ) _! ends t\*+1 & ! curr5t is turn$ on s t x passes f "o to ! o!r4 ,!n !y are gradually drawn ap>t4 ,z ! gap wid5s ! curr5t exp]i5ces m & m difficulty 9 pass+ ov] ?is non-conduct+ gap1 & great electrical en]gy has to be employ$ to keep x go+4 ,n[ t wond]ful law ( ! ,cons]vation ( ,en]gy decrees t no en]gy c ev] be lo/4 ,x c only be *ang$ f "o =m into ano!r4 ,!re=e ! en]gy exp5d$ ^u ! arc is n lo/1 b is conv]t$ into heat4 ,x is t heat1 act+ ^u ! small p>ticles ( c>bon :i* are torn (f ! ends ( ! rods1 :i* gives u ! arc light4 ,z a matt] ( fact ne>ly all artificial light 7& natural light too = t matt]#a7 is due to heat4 ,! heat sets ! molecules 9 viol5t agitation1 :i*1 act+ ^u ! corpuscles 9 ! atoms1 sets !m 9 viol5t motion too1 s t light is (t5 ! companion ( heat4 ,"s sub/ances give light m readily ?an o!rs1 "u ! influ5ce ( heat1 & we may reasonably believe t !y are ^? ^: corpuscul> arrangem5ts are su* t !y c be readily accel]at$ by ! molecul> action4 #a ,! gl[-worm is an example ( ! few exceptions4 ,to take a famili> in/ance1 coal-gas is ma9ly me?ane1 "o ( ! _m comb9ations ( c>bon & hydrog51 & :5 x is burnt 9 air ! hydrog5 & oxyg5 comb9e1 lib]at+ heat1 :i* causes ! c>bon lib]at$ at ! same "t to gl[4 ,z ea* me?ane molecule breaks up ! c>bon atoms are ?r[n out1 =m+ solid p>ticles ( c>bon1 & x is !y really :i* give ! light4 ,x is !re=e ! combu/ible gas heat+ ! solid p>ticles ( c>bon :i* =ms ! lum9\s "p ( ! gas flame4 ,! non-lum9\s "p ( ! flame1 ne> ! burn] 7,i am n[ speak+ ( ! old-fa%ion$ burn]71 is ! burn+ gas be=e ! c>bon p>ticles h _h "t to heat up4 ,& ! old gas flame1 z we "k1 is n[ be+ rapidly displac$ by ! inc&esc5t mantle1 ! reason be+ simply t ,von ,welsba* discov]$ h[ c]ta9 r>e m9]als gave a m brilliant light :5 heat$ ?an p>ticles ( c>bon d4 ,9 o!r words1 x is easi] to accel]ate ! motion ( ! corpuscles 9 c]ia1 ?oria & ! o!r +r$i5ts ( ! mantle1 ?an x is ^? ( c>bon4 ,consequ5tly1 !y soon] rea* t degree ( agitation :i* w s5d =? electro-magnetic waves ( ! high frequ5cy necess>y to produce ! s5sation ( light4 ,= ?is reason ! mantle heat$ by gas gives z bright a light z ! c>bon p>ticles 9 ! electric arc1 al?\gh ! latt] are subject$ to a mu* m int5se heat4 ,b ! arc c be1 & (t5 is1 us$ z a s\rce ( heat1 ap>t altoge!r f ! light :i* x gives4 ,9 ,sw$51 = example1 :]e coal is r>e1 b wat]-p[] pl5tiful1 ! p[] ( ! wat]falls is made to smelt iron4 ,h5ce ! wat]falls are sometimes t]m$ ! :ite coal ( t c\ntry4 ,ne$less to say1 x is ! ubiquit\s electricity :i* p]=ms ! *ange f ! =ce ( fall+ wat] into heat4 ,! furnaces are 9 %ape mu* l ^? 9 :i* iron is smelt$ ) coal--namely1 tall *imney-l /ructures at ! bottom ( :i* is ! fire4 ,9 ! arc furnaces !re are1 pass+ 9 ?r\gh ! side1 ne> ! bottom1 a numb] ( electrodes1 & betwe5 ^! a s]ies ( arcs are =m$4 ,coke & iron/one are ?r[n 9 f ! top into ?is region ( int5se heat1 & !re ! iron is lib]at$ f ! oxyg5 ) :i* x is comb9$ 9 ! ore4 ,lib]at$1 x fl[s out ?r\gh a sp\t at "o side ( ! furnace4 ,b ! "q w arise 9 ! read]'s m9d3 ,:y is coke ne$$ 9 an electric furnace8 ,x is = metallurgical reasons4 ,! heat ( ! arc loos5s ! bonds betwe5 ! iron & oxyg51 b x ne$s ! pres5ce ( "s c>bon to tempt ! oxyg5 atoms away4 ,!re=e coke1 z ! mo/ conv5i5t =m ( c>bon1 has to be !re4 ,x is !re1 h[ev]1 9 mu* small] quantity ?an x w\ld be 9 an ord9>y furnace4 ,x is n !re z fuel1 b simply z ! c\nt]-attraction to draw ! oxyg5 atoms away f _! old love4 ,! arc is also us$ = weld+ pieces ( iron toge!r1 = :i* purpose x is em95tly suitable1 s9ce :at is want$ is int5se heat at a p>ticul> po9t4 ,b p]haps ! read] w be wond]+ by ?is "t :at ! heat ( ! arc is4 ,x has be5 repeat$ly ref]r$ to z int5se1 b some?+ m def9ite may be dem&$4 ,9 !ory x is unlimit$4 ,apply m pressure--m volts1 t is--!reby driv+ m curr5t across1 & ! temp]ature w rise4 ,x is only a "q ( mak+ dynamos l>ge en\gh1 & driv+ !m fa/ en\gh1 & any temp]ature is possible4 ,b !re are practical difficulties :i* limit ! degree ( heat4 ,"o is ! melt+-po9t ( ! furnace itself4 ,fire-clay melts at ab\t #agjj deg4 to #ahjj deg4 ,c4 ,s 9 a furnace :i* has to be l9$ ) fire-clay t is ab\t ! limit4 ,9 weld+ two pieces ( iron toge!r1 ! iron1 ( c\rse1 def9es :at ! limit %all be4 ,x ne$s to be heat$ to weld+ heat & no m--t is1 a little %ort ( melt+--s t ! p>ts to be jo9$ are s(t1 &1 ) a little hamm]+1 w jo9 ?or\ghly toge!r4 ,if too mu* heat 7 to be appli$ ! p>ts w\ld melt away4 ,b ! heat ( ! arc c be controll$ by simply v>y+ ! curr5t1 & s ! "r heat c be appli$ at ! "r place1 ?an :i* little m is want$4 ,"o v simple way ( do+ ?is is = ! workman to hold "o ( ! electrodes--a rod ( c>bon suitably insulat$--9 8 h&4 ,! curr5t is l$ to x ?r\gh a flexible wire4 ,! iron itself is made ! o!r electrode by be+ gripp$ 9 a vice :i* is itself insulat$ b connect$ to ! s\rce ( curr5t4 ,?us on br++ ! po9t ( 8 rod ne> to ! "p to be heat$ ! man causes an arc to be creat$ !re4 ,by mov+ ! rod he c move ! arc ab\t1 heat+ "o "p m ?an ano!r1 di/ribut+ 8 heat if he wants to d s ov] a l>g] area1 or keep+ x to a small "o1 j z he wills4 ,on rea*+ ! "r heat ! rod is )drawn1 ! arc de/roy$1 & ! iron c be hamm]$ j z if x _h be5 heat$ 9 a fire4 ,yet ano!r way /ill is kn[n z resi/ance weld+4 ,9 x an enorm\s curr5t at an extremely l[ voltage is us$4 ,! fundam5tal pr9ciple is ! same1 s9ce ! heat is =m$ by =c+ curr5t pa/ a po9t ov] :i* x is reluctant to pass4 ,t po9t ( poor conductivity is ! ends ( ! two b>s to be jo9$4 ,!y are plac$ j t\*+1 b s9ce an imp]fect contact l t always (f]s consid]able resi/ance to ! fl[ ( a curr5t1 ! pass+ curr5t ne$s only to be made l>ge en\gh = great heat to be g5]at$4 ,?is is exce$+ly pretty to wat*4 ,we w suppose t ! article to be op]at$ ^u is ! tyre ( a :eel4 ,! b> ( iron has already be5 b5t by roll]s into ! correct curve & ! two ends are t\*+4 ,br\ght to ! ma*9e1 x is gripp$1 ea* side ( ! junction1 9 ! jaws ( an insulat$ vice & ! curr5t is turn$ on4 ,9 a few seconds ! place :]e ! two ends are j t\*+ beg9s to gl[4 ,rapidly x increases 9 brightness until 9 ab\t half-a-m9ute x is at weld+ heat4 ,!n "o vice1 :i* is movable1 is =c$ along a little by a screw1 s t ! ends are press$ firmly toge!r1 a little judici\s hamm]+ mean:ile help+ to complete ! job4 ,!n ! curr5t is swit*$ (f & ! complete tyre tak5 out ( ! ma*9e4 ,! curr5t us$ has a =ce comp>able ) t :i* op]ates dome/ic electric bells1 b 9 volume x is ?\s&s ( amp]es4 ,alt]nat+ curr5t is us$1 & x is obta9$ f a trans=m] or induction coil4 ,9 su* a case ! prim>y "p ( ! coil is made ( _m turns ( f9e wire1 s t little curr5t passes ?r\gh x1 :ile ! second>y "p is b "o or two turns ( ?ick b>4 ,?us ! voltage g5]at$ 9 ! second>y is v little1 b s9ce ! second>y has an almo/ negligible resi/ance ! curr5t caus$ by t small voltage is enorm\s4 ,su* an arrangem5t is 9 indu/rial realms g5]ally call$ a trans=m]1 ! t]m induction coil be+ employ$ m = ^? ?+s ( a simil> nature int5d$ = ! laboratory4 ,! "o j describ$ is1 moreov]1 a /ep-d[n trans=m]1 s9ce x l[]s ! voltage1 to di/+ui% x f /ep-up trans=m]s1 :i* raise ! voltage4 ,& ! resi/ance pr9ciple is also appli$ 9 ano!r way to l>ge furnaces1 su* z ^? = ref9+ iron4 ,9 ^! ! resi/ance ( ! iron itself is utilis$ to g5]ate ! heat4 ,( c\rse1 x %\ld be well und]/ood1 heat is always g5]at$ 9 ev]y?+ ?r\gh :i* curr5t fl[s4 ,!re is no p]fect conductor1 & s e conductor is m or less heat$ by ! passage ( curr5t ?r\gh x4 ,"s en]gy ne$s to be exp5d$ to drive curr5t1 ev5 along l>ge copp] wires1 & t en]gy mu/ be turn$ into heat 9 ! wires4 ,if ! same volume ( curr5t be =c$ along iron wires ( ! same size1 ! heat w be great]1 s9ce iron is b a poor conductor comp>$ ) copp]1 ! relation be+ ab\t z "o to six4 ,& if ! iron be hot ! resi/ance w be /ill m1 = x /&s to reason t :5 heat$ ! molecules1 be+ f>!r ap>t1 w be ! less easily able to ex*ange corpuscles4 ,we h ! be/ reasons = believ+1 z has be5 sugge/$ already1 t a curr5t ( electricity is b a fl[ ( corpuscles1 & s we are n surpris$ to he> t1 z a g5]al rule1 ! hott] a ?+ is ! less does x conduct electricity4 ,illu/ration3 ,by p]mission ( ,cambridge ,sci5tific ,in/4 ,co41 ,ltd41 ,cambridge1 ,eng4 ,,measur+ ,,heat ,,at ,a ,,di/ance ,?is wond]ful in/rum5t1 ! ,f]y ,radiation ,pyromet]1 al?\gh itself "s di/ance away f ! furnace1 is tell+ ! temp]ature ( its hotte/ "p4 ,s imag9e a circul> tr\gh ( fire-clay or o!r heat-resi/+ mat]ial fill$ ) fragm5ts ( iron1 or1 x may be1 ) iron b>ely above melt+-po9t1 :i* has come f ano!r furnace1 :]e x und]w5t ! previ\s process4 ,circl+ inside or outside ?is tr\gh is an enorm\s coil ( wire ?r\gh :i* curr5ts ( electricity are alt]nat+4 ,t is ! prim>y ( a trans=m]1 & ! second>y is--! iron itself1 9 ! tr\gh4 ,if x be1 z x (t5 is1 9 ! =m ( scrap1 or brok5 pieces1 ! heat w beg9 to %[ itself :]e ! pieces t\* ea* o!r4 ,! curr5ts g5]at$ 9 ! tr\gh1 by ! coil outside1 w1 ( c\rse1 pass f piece to piece & ! po9ts ( contact1 s9ce !y (f] ! greate/ resi/ance1 w %[ signs ( heat4 ,?is w increase until ! pieces beg9 to melt4 ,z ! sep>ate fragm5ts m]ge into ! molt5 mass ! resi/ance w 9 "o way decrease1 = ! imp]fect contacts betwe5 ! pieces w give place to ! p]fect contact ?r\gh\t ! mass ( liquid metal4 ,b = ano!r reason--namely1 ! increase 9 heat--! resi/ance w increase4 ,& all ! :ile ! alt]nations 9 ! prim>y coil w be pump+ curr5ts1 z x 71 r\nd & r\nd ! r+ ( molt5 iron4 ,:e!r ! resi/ance increase or decrease1 ! curr5t w d ! opposite1 s t heat w be g5]at$ :atev] happ5s4 ,= z resi/ance decreases curr5t increases1 & vice v]sa4 ,& ! slighte/ v>iation 9 ! /r5g? ( ! prim>y curr5t w h its effect ^u ! second>y1 & !re=e on ! heat g5]at$4 ,s1 by simply regulat+ ! prim>y curr5t1 ! temp]ature ( ! metal c be controll$ to a nicety4 ,& su* furnaces h ! imm5se advantage t !re is no possibility ( delet]i\s sub/ances 9 ! fuel gett+ into & spoil+ ! metal1 a ?+ :i* may v easily happ5 dur+ ! manufacture ( high-class /eels1 alloys ( iron 9 :i* ! exact quantities1 purity & proportions ( ! +r$i5ts are ( ! utmo/ importance4 ,h5ce ^! induction furnaces1 z !y are call$1 are frequ5tly us$ q ap>t f any "q ( utilis+ wat]-p[]4 ,& !y w probably be us$ /ill m z "t goes on4 ,= "o ?+1 !y may become valuable adjuncts to ! old] =m ( iron & /eel furnaces1 f :i* !y w obta9 _! p[] free1 gratis & = no?+4 ,9 di/ricts su* z ,middlesbr\gh !y c\ld g5]ate m electricity ?an !y h any use =4 ,! ord9>y iron furnaces bel* =? flames :i* are really good useful gas 7c>bon monoxide7 burn+ to wa/e4 ,_m ( ! furnaces are cov]$ 9 at ! top1 & ?is gas is l$ away to heat boil]s = ! /eam-eng9es or to drive l>ge gas-eng9es1 b 9 a l>ge works !re is m ( ?is wa/e gas ?an !y "k :at to d )4 ,n[ t c\ld1 & probably w ere long1 be turn$ into electricity by means ( gas-eng9es & ! curr5t us$ = mak+ /eel 9 induction furnaces4 ,x w probably surprise _m to "k t ^! enorm\s curr5ts :i* c ?us heat great masses ( metal until !y melt are no dang] at all to ! m5 :o "w ) !m4 ,a man might dip an iron rod into ! tr\gh ( metal & he w\ld sc>cely feel ! %ock4 ,& ! same is true ( ! weld+ ma*9e1 :i* c be t\*$ 9 any "p )\t fe>4 ,! reason1 ( c\rse1 is t1 broadly speak+1 x is volume ( curr5t :i* does h>m1 & ! resi/ance ( ! human body is s great t ) ! small voltages us$1 ! volume :i* c pass is negligible4 ,x %\ld be m5tion$1 h[ev]1 t ! volume ( curr5t 9 lightn+ is also small1 b we "k t x is capable ( inflict+ t]rible injury4 ,lightn+1 h[ev]1 is 9 a class by itself4 ,our t]re/rial voltages are baffl$ by an air-gap ( a few in*es1 b lightn+ spr+s across a gap miles wide4 ,its voltage mu/1 !re=e1 am\nt to millions1 & ! ord9>y rules relat+ to e>?ly curr5ts d n apply4 ,b o!r s\rces ( heat besides electricity are at ! disposal ( our manufactur]s n[adays4 ,pre-em95tly !re is ! flame ( "s gas burn+ ) pure oxyg54 ,! oxyhydrog5 jet has be5 kn[n = _m ye>s z ! be/ means ( produc+ ! light = a magic lant]n4 ,su* a jet imp++ ^u a p5cil ( lime causes ! latt] to gl[ ) a dazzl+ :ite light4 ,b ! oxyhydrog5 jet is n[ employ$ 9 _m factories = ! weld+ ( metals4 ,?is is kn[n z fusion weld+1 s9ce ! two p>ts are actually r$uc$ to liquid4 ,! usual way to g ab\t ?is "w is to bevel (f ! ends or edges to be jo9$4 ,suppose1 = in/ance1 t we want$ to weld two pieces ( brass pipe toge!r4 ,we %\ld fir/ file or o!rwise trim ! edges to be jo9$ until :5 put toge!r !y =m a groove practically z deep z ! metal is ?ick4 ,!n ) a /ick ( brass wire 9 ! left h&1 & an oxyhydrog5 bl[pipe 9 ! "r1 we %\ld direct ! flame f ! pipe on to ! metal until1 at "o po9t1 ! sides ( ! groove 7 beg9n+ to melt4 ,!n1 ins]t+ ! po9t ( ! wire into ! groove1 we %\ld melt a little (f x4 ,?us we %\ld "w all r\nd ! jo9t1 melt+ ! sides ( ! groove & fill+ 9 ) melt$ metal f ! wire1 until ! :ole groove _h be5 fill$ up & ! metal add$ _h be5 ?or\ghly amalgamat$ ) t on ei!r side4 ,z a matt] ( fact1 if x 7 brass :i* we 7 work+ on we %\ld probably use ! *eap] ?\gh less pure =m ( hydrog5--coal-gas--s t x w\ld really be oxycoal-gas t we %\ld use & n oxyhydrog54 ,! latt] is us$1 h[ev]1 notably = ! fusion-weld+ ( lead1 or lead-burn+1 z x is t]m$4 ,! bl[pipe is a brass tube ab\t a foot or eighte5 in*es long1 ) two passages 9 x1 "o = ! oxyg5 & ! o!r = ! o!r gas4 ,! gases are br\ght to "o end ( x ?r\gh rubb] pipes1 :ile at ! o!r end !re is a nozzle 9 :i* ! gases m+le & f :i* !y em]ge 9 a f9e jet4 ,! oxyhydrog5 flame has a temp]ature ( ab\t #bjjj deg4 ,c41 hot en\gh to melt fire-clay4 ,t does n matt] 9 ! case ( weld+1 h[ev]1 s9ce ! molt5 metal is v small 9 quantity at any giv5 mom5t1 & is all[$ to cool be=e x c run away4 ,x w\ld be an awkw>d temp]ature to deal )1 nev]!less1 9 a furnace4 ,x seems /range t x does n burn ! nozzle ( ! bl[pipe1 b ! fact t x does n is1 x is believ$1 expla9$ by ! fact t ! expansion ( ! gas1 z soon z x em]ges f ! hole out ( :i* x %oots1 causes a comp>atively cool space j !re1 %ield+ x f ! int5se heat f>!r on4 ,an exce$+ly int]e/+ use ( ! oxyhydrog5 flame is 9 ! manufacture ( artificial rubies4 ,^! /ones are made 9 ,p>is by a v simple means4 ,! necess>y *emicals are prep>$ & gr\nd to an exce$+ly f9e p[d]4 ,?is is !n all[$ to fall ?r\gh an oxyhydrog5 flame4 ,?us !re is no ne$ = a crucible capable ( )/&+ ?is high temp]ature1 s9ce ! melt+ takes place z ! p>ticles are 9 ! act ( fall+4 ,:5 !y rea* ! support prep>$ to cat* !m !y h cool$ some:at4 ,/ones s call$ are real rubies--artificial1 b n %ams4 ,!y possess e prop]ty ( ! ruby f ! m9e4 ,ano!r product ( ! oxyhydrog5 flame is ! qu>tz fibres :i* are us$ = susp5d+ ! ne$les 9 ! f9e/ galvanomet]s4 ,! qu>tz is melt$1 9 ?is case a crucible be+ employ$4 ,an arr[ is !n dipp$ 9 ! liquid qu>tz & imm$iately fir$ into ! air4 ,! ?ick treacly liquid is ?us drawn out into a ?read ( su* f95ess t a microscope is necess>y to f9d x )4 ,hott] ev5 ?an oxyhydrog5 is ! oxyacetyl5e flame1 :i* at its hotte/ po9t rea*es ne>ly #cejj deg4 ,c4 ,! gas1 :i* is ano!r ( ! comb9ations ( c>bon & hydrog5 7its molecules conta9+ two atoms ( ea*71 is easily made by all[+ wat] to come into contact ) calcium c>bide4 ,! latt]1 :i* is ,ca,c#b1 is made by heat+ coke & lime toge!r 9 ! int5se heat ( an electric furnace4 ,?is acc\nts l>gely = ! great heat+ p[] ( acetyl5e1 = s9ce great heat is necess>y to cause ! elem5ts to comb9e great heat is giv5 out by !m :5 !y ultimately sep>ate4 ,"h aga9 is ! cons]vation ( en]gy4 ,! heat en]gy ( ! electric furnace is l>gely exp5d$ 9 =c+ ^! two elem5ts into p>tn]%ip4 ,!y are1 z x 71 giv5 a l>ge am\nt ( capital 9 ! =m ( heat4 ,x ceases to be s5sible heat1 becom+ lat5t 9 ! comp\nd1 b /ill x is !re4 ,s a lump ( calcium c>bide1 ) :i* _m read]s are famili>1 has va/ /ores ( heat lock$ up )9 x4 ,:5 wat] comes into contact ) ! c>bide ! p>tn]%ip is brok51 b ! heat is n lib]at$ !n1 s9ce ano!r p>tn]%ip is =m$1 :i* /ill reta9s ! old heat-capital4 ,! calcium 9 ! c>bide is displac$ by ! hydrog5 f ! wat]1 & s ,c#b;,h#b comes into be+1 :ile ! reject$ calcium consoles itself by ent]+ into comb9ation ) ! equally =sak5 oxyg5 f ! wat]1 =m+ ,ca,o1 :i* is b ano!r "n = lime4 ,!n ! acetyl5e 7,c#b;,h#b7 is mix$ ) oxyg5 9 ! bl[pipe & burnt1 "u :i* conditions ! p5t-up heat1 borr[$ orig9ally f ! electric furnace1 is br\ght into play4 ,) ?is flame ! h>d] metals c be fus$ & weld$4 ,wr\ght iron1 ca/-iron1 /eel 9 all its =ms1 all c be melt$ by ! oxyacetyl5e flame1 almo/ z easily z sn[ by a hot iron4 ,! fusion weld+ ( ^! metals is !n c>ri$ on j z already describ$ = brass4 ,by means ( a special bl[pipe1 :]e9 an excess ( oxyg5 is introduc$ at ! hot po9t1 h>d /eel plates c be cut to pieces almo/ z easily z a groc] cuts *eese4 ,ev5 ?ick1 h>d arm\r-plate c ?us be cut1 almo/ ! only way1 inde$1 9 :i* x c be cut4 ,& = purposes su* z weld+ & cutt+ ?is flame has an int]e/+ & peculi> advantage ov] all o!r k9ds ( heat4 ,:5 a metal is heat$ 9 ! air !re is usually tr\ble f oxidation4 ,! dome/ic pok]1 = example1 aft] x has be5 left to get r$-hot 9 ! fire is se5 to be coat$1 9 ! "p :i* has be5 heat$1 ) scales :i* w flake (f if ! ?+ be /ruck4 ,^? scales are oxide ( iron1 caus$ by ! union ( iron & oxyg5 :5 ! pok] 0 hot4 ,b if ! heat be appli$ by ! oxyacetyl5e flame t w n happ54 ,! oxyg5 & ! c>bon f ! acetyl5e w burn1 & if ! supply ( ! =m] be prop]ly regulat$ x w be entirely us$ up 9 ! process4 ,! hydrog5 f ! acetyl5e is1 /range to say1 unable to unite ) oxyg5 at su* a high temp]ature z t ( ! oxyg5 & c>bon1 s t x passes on beyond ! oxyg5-c>bon flame & ultimately burns on its own acc\nt ) ! oxyg5 f ! atmosph]e 9 a second flame surr\nd+ ! fir/4 ,?us !re is a d\ble flame3 inside1 a little po9t$ cone ( :ite flame1 t is ! oxyg5 & c>bon2 & outside t a blui% flame1 ! hydrog5 & ! atmosph]ic oxyg54 ,! latt] flame =ms a k9d ( jacket entirely envelop+ ! =m]4 ,& s :5 "o melts metal by means ( ! :ite cone ! hydrog5 jacket %ields ! molt5 metal f oxyg5 & prev5ts ! oxidation4 ,only "o :o kn[s ! bo!r caus$ by oxidation :5ev] metals are heat$ c realise ! wond]ful advantage ( ?is4 ,& n[ we c turn to ev5 ano!r s\rce1 also q mod]n1 ( high temp]ature4 ,if ! (t-quot$ man 9 ! /reet 7 ask$ ! two commone/ ?+s on e>? he might possibly "n oxyg5 z "o1 & s f> he w\ld be "r1 b ! *ances are mu* aga9/ 8 nam+ alum9ium z ! second4 ,if he did n1 h[ev]1 he w\ld be wrong4 ,alum9ium & oxyg5 =m alum9a1 ( :i* are con/itut$ ! sapphire1 ! ruby & o!r preci\s /ones1 b alum9a is mo/ commonly f\nd 9 comb9ation ) silica1 or silicon & oxyg54 ,?is comp\nd is call$ silicate ( alum9ium1 & ( x are =m$ clay & _m rocks4 ,! reason :y ! metal alum9ium 0 until rec5tly r>e & exp5sive 0 because ( ! great difficulty ( dis5tangl+ ! metal f ?is r complex comb9ation4 ,& ^! two commone/ elem5ts h1 "u c]ta9 conditions1 a r>e aff9ity = ea* o!r4 ,!y jo9 =ces ) su* en]gy t great heat is giv5 out 9 ! process4 ,?is1 aga91 we may reg>d z an example ( ! cons]vation ( en]gy4 ,heat _h to be us$ up1 app>5tly1 9 sep>at+ ! alum9ium & oxyg5 z !y 7 f\nd toge!r 9 ! natural /ate4 ,& t heat reappe>s :5 !y comb9e toge!r aga94 ,?is is a mo/ useful pr9ciple1 = if heat has disappe>$ any:]e 9 ! c\rse ( "s op]ation1 we "k t 9 all probability1 if we g ab\t x ! "r way1 we c get t heat back aga91 p]haps 9 a m conv5i5t =m4 ,t is s 9 ?is case at all ev5ts4 ,n[ alum9ium w n readily comb9e ) atmosph]ic oxyg51 b x w readily d s ) oxyg5 f ! oxide ( a metal4 ,s if we put into a vessel "s oxide ( iron & "s f9ely p[d]$ alum9ium1 & give x "s heat at "o po9t1 j to set ! process go+1 ! :ole mass w burn ) int5se heat4 ,& :5 ! burn+ is f9i%$ ! crucible w be f\nd to conta9 7#a7 "s molt5 iron1 ! oxide ( iron ) ! oxyg5 gone1 & 7#b7 "s oxide ( alum9ium or alum9a1 9 ! =m :i* we call corundum1 a v h>d sub/ance :i* 9 a p[d]$ =m is us$ = gr9d+ h>d metals4 ,we />t1 y w notice1 ) a pure metal & an oxide4 ,we f9i% ) a pure metal & an oxide1 only ! oxyg5 has *ang$ its qu>t]s1 hav+ pass$ f ! iron to ! alum9ium4 ,& 9 ! c\rse ( ! *ange a va/ am\nt ( p5t-up heat has be5 lib]at$4 ,alum9ium is ?us a fuel1 /range ?\gh x may seem to say s1 j z coal is4 ,coal1 h[ev]1 is will+ to pair (f ) oxyg5 f ! air1 :ile alum9ium1 m fa/idi\s1 w only accept x z p>tn] :5 x c /eal x f ano!r comb9ation4 ,b ! practical result is em95tly satisfactory1 = ! action ( ! alum9ium & iron oxide is to leave u ) a crucible full ( molt5 iron at a v high temp]ature4 ,& ?is c be us$ 9 v>i\s ways4 ,tramway rails1 = example1 c be jo9$ toge!r by x4 ,a m\ld is =m$ ar\nd ! ends ( two rails1 :]e !y butt toge!r1 & into ?is m\ld a quantity ( ! melt$ iron c be p\r$4 ,s hot is x t x p>tially melts ! ends ( ! rails1 & !n1 amalgamat+ ) !m1 x =ms a p]fectly homog5e\s connection betwe5 !m4 ,! same me?od c be appli$ to ! repair ( iron /ructures ( all k9ds4 ,! propell] %aft ( a %ip1 = example1 sometimes breaks on a voyage4 ,su* a cata/rophe is fraught ) ! mo/ s]i\s consequ5ces1 unless x c be quickly repair$4 ,!rmit1 z ?is process is call$1 is p]haps ! only means :]eby1 "u c]ta9 conditions1 ?is c be accompli%$4 ,! extraord9>y heat ( ! metal produc$ 9 ?is way is demon/rat$ by ! fact t if x be p\r$ on to an iron plate an in* ?ick x goes clean ?r\gh x4 ,x melts its way ?r\gh in/antly4 ,b al?\gh su* high temp]atures are at ! comm& ( ! mod]n manufactur]1 !re are "s ?+s--inde$ _m ?+s--:i* /ill baffle him1 ! diamond1 = example4 ,x is true t diamonds ( small size h be5 made1 b l>g] ones h s f> defi$ all ef=ts4 ,"o v int]e/+ fact ab\t ?is may be m5tion$ 9 conclud+ ?is *apt]4 ,sir ,&rew ,noble1 a memb] ( ! great firm ( ,arm/rong1 ,:itwor? ,co41 ( ,elswick1 tri$ ! exp]im5t ( explod+ "s cordite1 a high explosive1 inside a /eel vessel ( enorm\s /r5g?4 ,he ?us produc$ :at is believ$ to be ! highe/ temp]ature ev] produc$ on e>?4 ,x is reckon$ to h be5 #ebjj deg4 ,c41 & ! pressure at ! same "t 01 x is calculat$1 #ej tons p] squ>e in*4 ,8 int5tion 0 n to make diamonds1 b ,sir ,william ,crookes pr$ict$ t diamonds w\ld be ! result4 ,= ! cordite consi/$ ma9ly ( c>bon1 :i*1 z is well kn[n1 is ! mat]ial ( :i* ! diamond is =m$1 & ! comb9ation ( high temp]ature & high pressure is j :at is ne$$1 s x is believ$1 to br+ ! c>bon into ?is p>ticul> =m4 ,& true en\gh1 on ! iron be+ exam9$ aft] ! explosion1 !re 7 se5 t9y diamonds4 ,= l>g] ones ev5 high] temp]atures & great] pressures are1 no d\bt1 necess>y1 & z ! diamond1 l gold1 has a peculi> fasc9ation = mank9d1 s ! ef=ts to manufacture x w cont9ue4 ,9 ye>s to come ! means may be f\nd ( creat+ ^! extreme conditions ( temp]ature & pressure1 & s ano!r ( ! problems ( ! ages w be solv$4 ,illu/ration3 ,by p]mission ( ! ,briti% ,alum9ium ,co ,a ,,/rik+ ,,feature ,,( ,,mod]n ,,alum9ium ,,works ,= ! production ( alum9ium wat] p[] is requir$4 ,wat] is /or$ at a high level & is !n br\ght d[n to ! factory 9 pipes4 ,! illu/ration %[s ! pipe track rec5tly laid d[n = ?is purpose at ,k9lo*lev5 9 ,argyle%ire4 ,! six pipes1 ea* ( :i* is ?irty-n9e in*es 9 diamet]1 run d[n ! hillsides = "o mile & a qu>t] ,,*apt] ,,xi ,,an ,,artificial ,,coal ,,m9e ,^? c\ntries :i* are bless$ ) a pl5tiful supply ( coal are p]iodically %ock$ & sadd5$ by a t]rible calamity--an explosion 9 "o ( ! m9es1 9 :i* (t5 scores ( poor fell[s lose _! lives1 & hundr$s ( wid[s & orphans f9d !mselves )\t a breadw9n]4 ,"o has only to recall t he>t-r5d+ calamity ( ! ,c\rri]es m9es 9 ,france1 :]e ov] a ?\s& lives 7 lo/1 to realise h[ important is ! "q ( ! cause & ! cure ( ! colli]y explosion4 ,x us$ to be ?\ght a settl$ matt] t ^! 7 due to ! accid5tal ignition ( a gas call$1 sci5tifically1 me?ane1 b by ! m9]s fire-damp4 ,?is und\bt$ly does collect 9 _m m9es1 & s9ce x is mu* ! same z ! dome/ic coal-gas 7inde$ me?ane =ms ! bulk ( coal-gas7 x is n surpris+ t ! explosions 7 attribut$ to x4 ,at times %ots 7 fir$1 to bla/ d[n ! coal1 & al?\gh ! greate/ precautions are tak5 to prev5t any accid5t result+1 x seems c]ta9 t explosions h occasionally foll[$ ! fir+ ( %ots4 ,b /ill m dang]\s is ! adv5tur\s m9] :o1 = "s reason1 op5s 8 safety lamp4 ,x is lit = him be=e he ent]s ! work+s1 & lock$ up1 s t1 !oretically1 he _c tamp] ) x2 b x has to be a clev]ly devis$ lock t _c be pick$ 9 "s way1 & ) ! c>elessness born ( long immunity f accid5t ^! are got op5 sometimes1 )1 x may be1 disa/r\s results4 ,ev5 a sp>k /ruck f a m9]'s pick may ignite ! gas2 or a sp>k f "s electrical ma*9e us$ 9 ! m9e4 ,t is "o ( ! reasons :y electrical app>atus is suspect 9 colli]y matt]s & ma*9es work$ by ! less conv5i5t & m co/ly means ( compress$ air are pref]r$4 ,9 "s su* mann] ! fire-damp is ignit$1 & !n !re foll[s ! fi]y bla/1 :i*1 sweep+ ?r\gh ! n>r[ gall]ies & passages :i* con/itute ! work+s1 simply licks up ! life ( ! m5 :om x enc\nt]s4 ,o!rs1 9 byways & %elt]$ corn]s1 escap+ ! burn+ cl\d ( flame1 are poison$ by ! deadly fumes ( c>bon monoxide :i* x leaves :5 its =ce is sp5t4 ,:ile o!rs1 p]*ance ! mo/ un=tunate ( all1 are sav$ = a "t1 b1 be+ imprison$ by falls f ! ro( & walls1 die a l+]+ dea? ( hung] & sl[ suffocation4 ,a colli]y explosion is "o ( ! gha/lie/ ev5ts imag9able1 ! only relief f :i* is ! noble h]oism ) :i* ! survivors1 f ! m9e manag]s to ! humble/ workm51 cr[d r\nd ! pit-m\?1 eag] to risk _! own lives = ! fa9t *ance ( sav+ "s bel[4 ,n infrequ5tly ^! brave volunte]s only %>e ! fate ( ! m5 !y w\ld rescue4 ,n[ all t1 z ,i h said1 us$ to be put d[n to ! effect ( ! fire-damp4 ,b x dawn$ ^u m5's m9ds "s ye>s ago t ! damage seem$ to be out ( proportion to ! p[] ( ! gas4 ,mod]n m9es are well v5tilat$ by l>ge fans1 :i* impel great volumes ( air ?r\gh all ! work+s4 ,! air curr5ts are cunn+ly guid$ by p>titions or brattices1 s t e nook & corn] %all be sc\r$ out by ! pl5tiful draught ( pure fre% air4 ,consequ5tly ! am\nt ( explosive gas :i* c collect 9 any "o place is b small4 ,h[1 !n1 c s small a volume ( gas d s l>ge an am\nt ( damage8 ,c\pl$ ) ?is 0 ! fact t explosions take place 9 fl\r mills1 :]e !re is no gas1 & exp]im5t]s _h f\nd 9 _! laboratories t almo/ any burnable sub/ance1 if gr\nd up f9ely en\gh & bl[n into a cl\d1 w\ld explode4 ,coal-du/ w\ld naturally d ?is4 ,inde$ anyone ?r[+ ! du/ f ! bottom ( ! coal-%ovel ^u a fire w see = himself h[1 quickly su* du/ w burn1 &1 z has be5 po9t$ out 9 an e>li] *apt]1 an explosion is b rapid burn+4 ,s ! blame 0 l>gely transf]r$ f ! %\ld]s ( ! fire-damp to ^? ( ! cl\ds ( coal-du/ :i* collect ?r\gh\t ! work+s ( a m9e4 ,b !n a difficulty arose f ! fact t !re is du/ 9 all m9es1 yet "s di/ricts are q free f explosions4 ,& su* di/ricts are ^? :]e !re is little or no fire-damp4 ,^! two facts seem to be expla9able 9 "o way1 & 9 "o way only4 ,x mu/ be t ! gas fir/ ( all explodes feebly1 & s1 /irr+ up ! du/ ly+ along ! roads & passages1 prep>es ! way = ! p[]ful1 deadly explosion ( coal-du/ :i* foll[s4 ,b t 0 only a guess1 & ! matt] 0 ( su* importance t x ne$$ some?+ m c]ta9 ?an m]e assumption4 ,s ! ,m9+ ,association ( ,great ,brita9 decid$ to h a s]ies ( exp]im5ts :i* %\ld settle once & = all :at "p ! coal-du/ play$ 9 ^! cata/rophes1 & h[ be/ !y c\ld be prev5t$4 ,x 0 at fir/ ?\ght t an old m9e might be utilis$ = ! exp]im5ts1 b !re 0 ! difficulty t su* always become wet aft] "w has ceas$ 9 !m1 & s ! du/ w\ld n behave normally4 ,moreov]1 ! "w w\ld be extremely dang]\s & ! results difficult to obs]ve4 ,!n a culv]t 0 sugge/$ built ( concrete1 p>tly buri$ 9 ! gr\nd1 b t too 0 dismiss$4 ,f9ally x 0 decid$ to make an imitation m9e ( /eel1 us+ old boil] %ells ) ! ends tak5 out4 ,! sum ( ,l#aj1jjj 0 subscrib$ = ! purpose by ! coal-own]s ( ,great ,brita91 & ! great "w 0 c>ri$ out at ,alt(ts1 9 ,york%ire1 close to a colli]y :]e a t]rible disa/] occurr$ 9 #ahhf4 ,"h ! great tube or gall]y 0 built4 ,r\ghly ! %ape ( a lett] ,l1 "o leg is ov] #ajjj feet long1 :ile ! o!r is #bie feet4 ,! long] leg is #g-a_/b feet 9 diamet] & ! %ort] #f feet4 ,at ! end ( ! %ort] "p a l>ge fan is in/all$ :i* c =ce #ej1jjj to #hj1jjj cubic feet ( air p] m9ute ?r\gh ! /ructure1 s produc+ ! conditions ( a well-v5tilat$ m9e4 ,! %ort] l5g? has sev]al %>p turns 9 x = ! purpose ( break+ ! =ce ( ! explosion along t "p1 & s %ield+ ! fan f damage1 :ile a tall *imney is provid$ !re1 s t1 ! door be+ %ut to cut (f ! fan1 ! gases f ! explosion c f9d a h>mless way out4 ,inside ! tube1 %elves are fix$ along ! sides s z to reproduce ! effect ( ! timb]+ 9 a real m9e1 ^u ! beams ( :i* ! du/ f9ds lodgm5t4 ,props 7 put up too1 j z !y w\ld be 9 ! real m9e4 ,ev]y?+1 9 fact1 0 done to make ! place z p]fect a replica z possible ( actual und]gr\nd work+s4 ,& !n1 add$ to ?is huge & co/ly /ructure1 0 an outfit ( sci5tific in/rum5ts wor?y ( ! important inve/igations :i* 7 to be c>ri$ on4 ,to grasp ! purpose & work+ ( ^! we ne$ to rem9d ourselves ( ! aims & int5tions ( ! exp]im5ts4 ,fir/ ( all x 0 desir$ to f9d out h[ v>i\s quantities & qualities ( coal-du/ behav$4 ,! du/ 0 laid along ! floor ( ! tube & along ! %elves4 ,a small gun fir$ at "s po9t 9 ! tube rais$ a cl\d ( ?is du/ j z ! gas explosion 9 ! real m9e w\ld d4 ,!n ano!r gun 0 fir$ to explode ! du/-cl\d4 ,s f> all is q simple & easy4 ,b to d t w\ld be ( no value )\t ! means ( f9d+ out exactly :at result$ f ! explosion4 ,& t is ! function ( ! in/rum5ts4 ,to comm5ce )1 !re is ! great wave or tide ( =ce or pressure :i* surges along ! gall]y imm$iately ! cl\d bur/s into flame4 ,h[ fa/ does t wave travel8 ,h[ long is x aft] ! explosion be=e ! %att]+ effects ( x are felt a hundr$ y>ds away8 ,to solve t problem electrical contact-break]s are fix$ at int]vals ( fifty y>ds along ! gall]y4 ,ea* ( ^! consi/s ( a cyl9d] ) a pi/on inside x some?+ l1 %all we say1 a cycle pump4 ,! pi/on1 held d[n normally by a spr+1 is bl[n upw>ds by ! =ce ( ! explosion4 ,! spr+ is adju/able1 & s x c be arrang$ t ! feeble =ce ( ! gun _c lift ! pi/on1 b ! m p[]ful coal-du/ explosion :i* foll[s c4 ,?us :5 ! explosion takes place ^! contact-break]s are op]at$ 9 succession4 ,! "o ne>e/ ! seat ( ! di/urbance is op]at$ fir/2 next ! "o fifty y>ds f>!r away2 !n ! "o a hundr$ y>ds away1 & s on4 ,! mom5ts :5 !y "w w tell ! spe$ at :i* ! bla/ travels along ! gall]y4 ,b x travels ) great spe$1 & s to measure & record ! exact mom5t :5 ea* contact-break] is mov$ is a matt] ( no little difficulty4 ,electricity1 h[ev]1 makes ?is1 l s _m o!r ?+s1 comp>atively easy4 ,!re is an app>atus us$ 9 a/ronomical obs]vatories call$ a *ronograph1 :i* regi/]s1 )9 a small fraction ( a second1 ! mom5t :5 a /> seems to pass across a wire 9 ! transit circle1 ! telescope by :i* ! positions ( />s are det]m9$ & ! exact "t kept4 ,! obs]v] sits ) 8 eye to ! telescope1 wat*+ ! app>5t movem5t ( ! />4 ,9 8 h& he holds a small pu%1 pressure on :i* by 8 f+]s op]ates a m9ute prick]1 :i* acts ^u a mov+ /rip ( pap]4 ,! pap] travels along ) ! utmo/ /ead9ess & regul>ity1 :ile a clock drives a %>ply po9t$ prick] on to x e two seconds4 ,?us ! clock m>ks out ! pap] into l5g?s1 ea* ( :i* repres5ts two seconds4 ,b ! o!r prick]1 work$ electrically by ! obs]v]'s h&1 also makes its m>k ^u ! pap]1 & s1 :ile ! regul> m>ks indicate int]vals ( two seconds1 ea* irregul> "o m>ks ! "t ( a transit or pass+ ( a /> across ! wire4 ,an exam9ation ( ! /rip subsequ5tly enables ! times ( a transit to be se5 ) great accuracy1 f ! position ( ! correspond+ m>k betwe5 two ( ! regul> m>ks4 ,& ! same pr9ciple 0 appli$ to ! circuit-break]s ( ?is artificial m9e4 ,normally1 curr5t fl[s ?r\gh ! circuit-break]1 b ! lift+ ( ! pi/on breaks ! circuit 7:5ce ! "n ( ! contrivance71 & t break+ ( ! circuit & consequ5t cessation ( ! curr5t op]ates ! *ronograph4 ,by a clev]ly con/ruct$ device1 ! details ( :i* are too complicat$ to set out "h1 ea* circuit-break] 9 turn makes its m>k on ! same /rip1 s t ! di/ances ap>t ( ^! m>ks %[ ! "t tak5 by ! =ce ( ! explosion to travel fifty y>ds4 ,mean:ile ! clock goes on mak+ its regul> m>ks 79 ?is case e half-second71 s t !y =m a scale by :i* ! o!r int]vals c be measur$ v exactly4 ,! *ronograph us$ "h is m accurate ?an t 9 use at ,gre5wi* ,obs]vatory1 ! reason be+ t 9 ?is case ! record+ curr5ts are s5t me*anically by ! contact-break]s op]at$ by ! explosion itself1 :ile 9 ! case ( ! a/ronom] ! human elem5t comes 94 ,to wat* a mov+ speck ( light & to tell exactly :5 x crosses a f9e l9e is by no means easy1 & s to tell ! "t )9 a t5? ( a second1 is ab\t ! limit ( possible accuracy4 ,! in/rum5t we h be5 ref]r+ to1 h[ev]1 c regi/] ! "t :i* a gase\s wave mov+ #cjjj feet p] second takes to travel fifty feet4 ,9 o!r words1 ! circuit-break]s c be op]at$ s fa/ t :5 only a sixtie? ( a second int]v5es betwe5 ! action ( "o & t ( ! next ! *ronograph c duly record ! fact4 ,! records ( ! *ronograph c be made 9 two ways3 "o by a p5 on a piece ( pap] tape1 & ! o!r by a scrat* on a piece ( smok$ pap]4 ,s by t means ! progress ( ! =ce ( ! explosion c be measur$4 ,x is necess>y also to "t ! movem5t ( ! heat ( ! explosion1 = ! two may n travel toge!r1 & ! diff]5ce betwe5 !m may let 9 "s light z to ! nature & behavi\r ( ! explosion4 ,s = ?is second purpose a second set ( circuit-break]s are us$4 ,ea* ( ^! consi/s ( a /rip ( ?9 t9foil /ret*$ across ! gall]y4 ,be+ plac$ edgeways to ! mov+ curr5t ( gas1 ! =ce ( ! explosion has no effect ^u x1 b ! heat in/antly melts x4 ,normally1 curr5t fl[s ?r\gh ! /rip1 & s ! melt+ is signalis$ by ! cessation ( ! curr5t1 :i* ev5t is record$ by ! *ronograph4 ,?us ! spe$s at :i* ! =ce & ! heat ( ! explosion travel are asc]ta9$4 ,ano!r important fact :i* ne$s to be f\nd is ! am\nt ( ! =ce1 or ! pressure1 at diff]5t po9ts4 ,= ?is purpose pressure-gauges c be connect$ to ! gall]y at ! desir$ spots by means ( flexible tubes4 ,?is flexible tube is necess>y 9 ord] t ! vibration ( ! /eel %ell1 due to ! explosion1 %all n be communicat$ to ! in/rum5t4 ,! pressure1 f9d+ its way along ! flexible pipe1 raises a pi/on aga9/ ! =ce ( a spr+1 & ! di/ance to :i* x is rais$ =ms1 ( c\rse1 a measure ( ! pressure inside ! gall]y at ! po9t to :i* ! tube is connect$4 ,! pressure is record$ by ! action ( ! pi/on 9 mov+ a /yle :i* j t\*es aga9/ ! surface ( a mov+ pap]4 ,!re are ?ree /yles 9 all m>k+ ?is pap]4 ,! fir/ is ! "o j m5tion$4 ,! second is held d[n on to ! pap] by an electro-magnet en]gis$ by curr5t fl[+ ?r\gh a f9e wire /ret*$ across ! gall]y j :]e ! explosion orig9ates4 ,?is f9e wire is brok5 at ! mom5t ( ! explosion1 :]eby ! curr5t is cut (f & ! /yle rais$4 ,x !re=e makes its m>k until ! mom5t ! explosion occurs1 & !n leaves (f4 ,! end ( t l9e1 !re=e1 %[s ! "t ( ! explosion4 ,mean:ile ! fir/ /yle is draw+ a /raight l9e1 b z soon z ! pressure beg9s to be felt by ! pressure record] ?is /yle moves & ! l9e slopes upw>d4 ,upw>d x goes z ! pressure increases1 until x has rea*$ its height1 aft] :i* x desc5ds1 until ! /yle is draw+ a /raight l9e once m4 ,?us ! rise & fall ( ! l9e repres5ts ! rise & fall ( ! =ce ( ! explosion4 ,!n comes ! matt] ( "t4 ,h[ soon aft] ! explosion occurr$ did ! pressure beg9 to be felt8 ,h[ long did x take to rea* its maximum & h[ long to die out aga98 ,^! que/ions ne$ answ]s :i* ! app>atus s f> describ$ does n give4 ,true1 ! spe$ ( ! pap] may be kn[n approximately1 b all t ,i h describ$ w occur )9 ! space ( a fraction ( a second1 & x is difficult to tell ! spe$ ( ! pap] ) suffici5t accuracy4 ,!re9 we see ! purpose ( ! ?ird /yle4 ,x is atta*$ electrically to ! t5?-(-a-second "t-m>k]4 ,?is consi/s ( a weight susp5d$ at a height4 ,! =ce ( ! explosion lets x drop4 ,! mom5t x />ts to fall x causes ! /yle to make a m>k on ! pap]4 ,:5 x has fall5 a c]ta9 di/ance ! /yle makes ano!r m>k4 ,& ! di/ance t ! weight falls betwe5 ! mak+ ( ! two m>ks is s adju/$ t ! space betwe5 !m on ! *>t repres5ts exactly a t5? ( a second4 ,?us a scale is =m$ ^u ! *>t by :i* ! o!r times c be measur$4 ,!re is ! l9e t]m9at+ at ! mom5t ( explosion2 ! /raight l9e *ang+ into an up-&-d[n curve1 repres5t+ ! "t & ! v>iation ( ! pressure2 f9ally !re are ! two m>ks repres5t+ a t5? ( a second by :i* ! o!r m>ks record$ ^u ! *>t c be int]pret$4 ,b ! m]e pressure & velocity ( ! explosion =m b a "p ( ! k desir$4 ,h[ ! explosion is =m$1 :e!r or n ! coal-du/ is burnt up entirely1 :e!r1 inde$1 x be ! du/ itself :i* burns or coal-gas giv5 (f by ! du/ "u ! heat ( ! prelim9>y explosion1 :at ! gas is :i* is left by ! explosion at v>i\s /ages--^! are important ?+s to be kn[n1 & !y c only be asc]ta9$ by tak+ samples ( ! gases 9 ! gall]y at diff]5t mom5ts dur+ & aft] ! explosion4 ,to obta9 ^! samples bottles are us$1 b ! "q is h[ to get !m fill$ at j ! "r "t4 ,into ! %ell ( ! gall]y holes are drill$1 & to ^! ! metal bottles or flasks are screw$1 a pipe lead+ f ! m\? ( ea* bottle well 9 t[>ds ! c5tre ( ! gall]y4 ,! end ( ?is tube is clos$ by a cap ( glass above :i* !re /&s pois$ a little hamm]4 ,controll+ ! hamm] is an electrical device call$ a contact-mak]1 s arrang$ t j at ! desir$ mom5t ! hamm] falls1 break+ ! glass1 & admitt+ a sample ( ! gas 9 ! gall]y1 ! bottle & its tube hav+ previ\sly _h ! air exhau/$ f !m1 s t on ! glass be+ brok5 ! gas is suck$ 94 ,at ! same mom5t a weight falls1 atta*$ to ! end ( a cord1 & ?is1 on rea*+ ! end ( its te!r1 closes ! end ( ! tube1 & ! sample is imprison$ until su* "t z ! bottle c be disconnect$ & tak5 away to ! laboratory = its cont5ts to be analys$4 ,! contact-mak]s are ( two k9ds4 ,9 "o ! pressure ( ! explosion raises a pi/on :i* completes a circuit all[+ curr5t to fl[ ?r\gh ! v f9e wire :i* prev5ts ! fall ( ! hamm]4 ,?is f9e wire be+ fus$ by ! curr5t1 ! hamm] falls & does its "w4 ,! o!r k9d1 :i* are us$ :5 ! =ce ( ! explosion is n en\gh to raise a pi/on1 is op]at$ by "o ( ! t9foil circuit-break]s4 ,a magnet1 be+ en]gis$ by curr5t pass+ ?r\gh ! foil1 holds up a curv$ b> ov] two cups ( m]cury4 ,brok5 by ! heat ( ! explosion1 ! foil cuts (f ?is curr5t1 de-en]gises ! magnet1 & all[s ! b> to fall ) its ends 9 ! m]cury4 ,?is completes ano!r circuit1 p]mitt+ curr5t to pass to ! f9e wire1 :]eby ! hamm] is releas$4 ,by connect+ a bottle to a contact-mak] at a di/ance ! sample c be obta9$ at any desir$ p]iod ( ! explosion4 ,if1 = in/ance1 ! sample is to repres5t ! imm$iate products ( combu/ion1 x is plac$ ne> to ! contact-mak]4 ,!n ! sample is drawn 9 practically at ! mom5t ( explosion4 ,if1 on ! o!r h&1 x is ! aft]-damp t is to be sampl$1 !n ! bottle w\ld be connect$ to a contact-mak] a long way f ! seat ( ! explosion1 ) ! result t its glass cap w\ld n be brok5 until "s consid]able "t _h elaps$ aft] ! explosion has pass$ ! bottle4 ,! "t also dur+ :i* ! bottle is draw+ 9 its sample c be adju/$ by v>y+ ! l5g? ( ! cord to :i* ! weight is atta*$4 ,& la/ ( all mu/ be m5tion$ ! employm5t ( a k9ematograph1 capable ( tak+ tw5ty-two photographs p] second1 = obs]v+ ! effects at ! ends ( ! gall]y 7see illu/rations74 ,?us records are obta9$ ( ! =ce & heat ( ! explosion1 its me*anical & !rmal effects ^u ! walls ( ! gall]y1 or1 if x 7 9 a real pit1 ! effects :i* x w\ld h 9 %ak+ & 9 heat+ ! work+s1 & ! m5 lab\r+ 9 !m4 ,?is & ! analysis ( ! gases produc+ & produc$ by ! explosion1 d]iv$ f ! cont5ts ( ! bottles1 give s\nd data ^u :i* c be built up reliable !ories z to ! nature ( colli]y explosions & ! way to prev5t !m1 results :i* c\ld be obta9$ 9 no o!r way4 ,no "o c help be+ /ruck ) ! ?or\ghness & +5uity ( ! means adopt$ to ^! ends1 & x is no exagg]ation to say t x is a spl5did example ( ?or\ghly sci5tific me?ods appli$ to an important indu/rial inve/igation4 ,x w be int]e/+ to conclude ?is acc\nt ) a brief m5tion ( "s ( ! results to :i* ^! pa9/ak+ ef=ts h l$4 ,fir/ 9 importance ! fact is plac$ beyond d\bt t coal-du/1 :i* 9 bulk w only burn sl[ly1 w1 :5 well mix$ ) air1 explode4 ,& no combu/ible gas ne$ be pres5t to aid 9 ! explosion4 ,! du/-rais+ gun1 by bl[+ "s du/ into a cl\d :i* 0 ignit$ by ! second gun1 caus$ an explosion p[]ful en\gh to d all ! damage exp]i5c$ 9 ! mo/ disa/r\s natural explosions4 ,s x is practically c]ta9 t ! function ( ! gas is b t ( ! fir/ gun1 to raise ! cl\d ( du/4 ,a typical exp]im5tal explosion may be briefly describ$4 ,on ! cl\d-rais+ gun be+ fir$ a small cl\d ( du/ 0 driv5 out ( ! ends ( ! gall]y1 ev5 t end at :i* ! fan 0 bl[+ air 94 ,9 o!r words1 ! curr5t ( air 0 *eck$1 ev5 rev]s$1 by ! prelim9>y %ock4 ,?is cl\d 01 ( c\rse1 %[n by ! k9ematograph4 ,!n :5 ! second gun 0 fir$1 & ! real coal-du/ explosion occurr$1 !re 0 fir/ a cl\d ( du/ %ot out l>g] ?an ! o!r "o1 to be foll[$ by a cl\d ( flame #ahj feet long4 ,^! also 7 record$ by ! k9ematograph4 ,! s\nd 0 he>d sev5 miles away4 ,pressures z high z #ib lb4 p] squ>e in* 7 record$1 & ! =ce ( ! bla/ 0 f\nd to travel well ov] #bjjj feet p] second4 ,9 _m cases1 /range to say1 ! effects 7 v slight at ! seat ( ! di/urbance1 ! =ce seem+ to increase z ! wave travell$ along ! gall]y4 ,probably ! du/ _h n "t to burn completely b only p>tially at ! fir/ onset4 ,:]e props or timb]s *eck$ ! fl[ ( ! flam+ gases !re ! damage 0 mo/1 = no d\bt ! eddies caus$ ! air & coal to be p>ticul>ly well mix$ at su* po9ts4 ,an encru/ation ( coke 0 f\nd on ! sides & ! timb]s aft] all 0 ov]1 probably because !re 0 n suffici5t air to burn all ! du/1 & "s 0 only heat$ into coke to be deposit$ on ! ne>e/ surface1 :]e ! t>ry matt]s w\ld make x /ick4 ,f9ally1 ! mo/ important1 p]haps1 ( all1 x 0 demon/rat$ t an admixture ( /one-du/ ) ! coal-du/ made x non-inflammable4 ,if a small zone 7 treat$ 9 ?is way1 /one-du/ be+ m+l$ ) ! o!r1 ! explosion became /ifl$ at t po9t4 ,true1 ! poison\s aft]-damp swept on beyond1 s t m5 !re might h be5 poison$ by x1 b ! /one zone w\ld c]ta9ly save !m f ! direct effects ( ! bla/4 ,if1 h[ev]1 /one-du/ be m+l$ ) coal-du/ all along ! gall]y1 !n no explosion at all w\ld occur1 aga9 prov+ t x is ! coal-du/ :i* does ! damage4 ,9 ! colli]y adjo9+ ! exp]im5tal gall]y ?is plan _h be5 9 use = ye>s4 ,s(t %ale is gr\nd to f9e p[d]1 & is spr9kl$ :]ev] coal-du/ has collect$4 ,x is j /rewn by h&1 giv+ ! work+s ! appe>ance ( hav+ be5 r\ghly :itewa%$4 ,& s9ce t has be5 done !re has be5 no explosion 9 t pit4 ,! exp]im5ts %[$ beyond d\bt t t 0 no *ance occurr5ce4 ,!y %[$ t 9 "s way n ?or\ghly und]/ood ?is addition ( /one-du/ r5d]s ! coal-du/ h>mless4 ,x may be t x m]ely dilutes x4 ,x may be t 9 "s way x takes "s ( ! heat & s prev5ts ! coal p>ticles becom+ hot en\gh4 ,x may be t1 be+ a little heavi]1 x *ecks ! =mation ( ! du/-cl\d4 ,h[ev] t may be1 !re is no d\bt n[ t /one-du/ is ! salvation ( ! m9] s f> z explosions are conc]n$4 ,wat] spr9kl$ ^u ! coal-du/1 by lay+ x & keep+ x f =m+ a cl\d1 has ! same effect1 b x is less conv5i5t1 = ! simple reason t wat] evaporates1 :ile /one-du/ /ays :]e x is put4 ,,*apt] ,,xii ,,! ,,mo/ ,,/rik+ ,,inv5tion ,,( ,,rec5t ,,times ,probably no inv5tion has made su* a s5sation dur+ rec5t ye>s z wireless telegraphy4 ,& s9ce x is ! direct outcome ( ! mo/ ab/ruse1 purely sci5tific inve/igations1 !re c\ld be no m appropriate subject = a place 9 ?is book4 ,= _m ye>s !re has be5 a belief 9 ! exi/5ce ( a my/]i\s some?+ to :i* has be5 giv5 ! "n ( ,! ,e!r4 ,totally diff]5t1 x %\ld be not$1 f ! *emical ( ! same "n1 x is entirely a creature ( ! intellect4 ,none ( our s5ses give u ! slighte/ direct indication ( its exi/5ce4 ,no "o has ei!r se51 felt1 he>d1 smelt or ta/$ x4 ,yet we feel t x mu/ exi/1 = ! simple reason t "s ?+s :i* our s5ses d tell u ( are utt]ly inexplicable )\t x4 ,x 0 orig9ally ?\ght ( 9 connection ) light4 ,/&+ at night ^u ! top ( a hill1 we see ! lights ( a t[n a mile away4 ,h[ is x t ^? di/ant gas or electric lamps affect our eyes8 ,!y are a mile away2 & ! idea t "o object c affect ano!r at a di/ance is "o :i* ! human m9d refuses to accept4 ,we feel compell$ to believe t !re is some?+ 9 contact ) ! s\rce ( light :i* is affect$ fir/1 & ?r\gh :i* ! di/urbance1 :atev] x may be1 is convey$ to our eyes1 ) :i* x mu/ also be 9 contact4 ,we feel t !re mu/ be a some?+ /ret*+ f our eyes to ! di/ant objects1 by :i* ! light is c>ri$4 ,( c\rse ! air fills ! space ref]r$ to1 b t _c be ! c>ri] ( light1 = if we look ?r\gh a glass vessel f :i* ! air has be5 exhau/$ we see di/ant objects undimm$4 ,we also h good reason to believe t ! air belongs specially to our globe1 & does n ext5d upw>ds = m ?an a few miles4 ,consequ5tly x _c be air :i* br+s sunlight & />light4 ,we are =c$ to fall back1 !re=e1 ^u ! belief 9 some?+1 ( :i* we h no o!r k1 :i* mu/ fill all ! vacant spaces 9 ! :ole univ]se1 pass+1 ev51 betwe5 ! p>ticles ( :i* ord9>y matt] is compos$1 rea*+ z f> z ! remote/ />1 able to p5etrate ev]y?+1 & consequ5tly n excludable f ! mo/ p]fect vacuum4 ,x is some?+ s diff]5t f any?+ ( :i* we h any direct k t "o is tempt$ sometimes to d\bt :e!r !re mu/ n be "s o!r explanation ( light4 ,9 ord] to transmit light at ! spe$ at :i* we f9d t x does 9 fact travel1 ! e!r mu/ be m rigid ?an ! h>de/ sub/ance we "k (4 ,_m1 _m ?\s& times m rigid1 inde$4 ,yet x seems to (f] no resi/ance to ! passage ( ! planets ?r\gh x4 ,/ill1 !re is no o!r alt]native1 s f> z m5 c conceive1 & we are compell$1 !re=e1 to believe 9 ! exi/5ce ( ! e!r4 ,! fir/ ?+s discov]$ by ! telescope 7 ! l>g] satellites ( ,jupit]4 ,) t precision = :i* a/ronom]s are not$1 !y soon drew up "t-tables1 %[+ n only ! pa/ movem5ts ( ^! bodies1 b also _! future ones4 ,!y 7 soon puzzl$1 h[ev]1 by ! obvi\s fact t ! moons ( ,jupit] 7 n work+ accord+ to s*$ule1 to use a railway expression4 ,!y got lat] & lat] = a "t1 & !n gradually quick5$ up until !y got too fa/4 ,!n !y sl[$ d[n aga94 ,?is repeat$ itself1 & is go+ on /ill1 ) ?is diff]5ce1 h[ev]1 t ! cause has be5 discov]$ & ! s*$ules am5d$ accord+ly4 ,! solution ( ! puzzle 0 t :5 ! e>? & ! great planet are on ! same side ( ! sun !y are "s #ahf millions ( miles ne>] toge!r ?an :5 !y are on opposite sides ( ! sun4 ,! evolutions ( ! satellites are q regul>1 accord+ to ! a/ronom]s' calculations1 b !y seem$ to ! e>?ly a/ronom]s to v>y1 because ( ! "t :i* light took to trav]se t #ahf millions ( miles4 ,:5 ! two bodies 7 ne>e/ toge!r ! occurr5ces seem$ to happ5 ab\t #ajjj seconds 7#af m9utes7 e>li] ?an :5 !y 7 f>!/ ap>t4 ,consequ5tly x became evid5t t light took #ajjj seconds to travel #ahf million miles1 or t1 9 o!r words1 x mov$ at ! prodigi\s spe$ ( #ahf ?\s& miles p] second4 ,t discov]y 01 ( c\rse1 _m ye>s ago1 b exp]im5ts s9ce h prov$ ! figure m5tion$ to be ab\t "r4 ,x put beyond "q ! fact t ! action ( a di/ant light ^u ! eye 0 n an action at a di/ance1 = su* action1 7 x possible1 w\ld take effect at once4 ,see+ t light pass$ f ! di/ant satellites at a def9ite velocity1 & took a c]ta9 "t to rea* u1 x 0 evid5t t x 01 dur+ t "t1 pass+ ?r\gh a m$ium ( "s sort1 & t m$ium mu/ be ! e!r1 = no alt]native explanation w suffice4 ,s x became recognis$ t light really consi/s ( waves or undulations ( "s sort 9 ! e!r2 t a di/ant1 lum9\s body set ^! waves go+2 t !y travell$ ) a def9ite velocity1 & !n1 /rik+ our eyes1 produc$ ! s5sation kn[n z light4 ,_m ?+s 7 f\nd out ab\t light 9 ! ye>s :i* foll[$ ! discov]y ( its velocity4 ,! l5g?s ( ! waves 7 asc]ta9$--t is to say1 ! di/ance f ! cre/ ( "o to ! cre/ ( ! next4 ,! diff]5t l5g?s 7 sort$ out & f\nd to give rise to diff]5t col\rs1 :ile long] waves1 :i* produc$ no s5sation ( light1 7 f\nd to c>ry heat1 !reby expla9+ h[ ! heat rea*es u f a di/ant fire1 or f ! sun4 ,( ! actual nature ( ! waves1 h[ev]1 little 0 kn[n1 al?\gh !re 0 a vague idea t !y 7 connect$ 9 "s way ) electricity1 at :i* po9t 9 ! /ory !re comes 9 ! fam\s "n ( ,james ,cl]k ,maxwell1 a pr(essor ( ,cambridge ,univ]sity1 :o 9 #ahfd produc$ be=e ! ,royal ,society ! explanation ( ! nature ( ! waves & _! connection ) electricity & magnetism4 ,t 9 itself 0 a wond]ful a*ievem5t1 b f> m wond]ful /ill is ! fact t he truly pr$ict$ ! exi/5ce ( long] waves ?an any !n kn[n1 :i* no "o knew h[ to cause1 or h[ to detect if caus$4 ,t pr$iction has s9ce be5 fulfill$4 ,! long waves h be5 f\nd2 we "k h[ to make !m & h[ to p]ceive _! pres5ce4 ,!y are ! mess5g]s :i* c>ry our wireless messages4 ,! discov]y ( ^!1 at t "t unkn[n waves1 on pap]1 by simply calculat+ & reason+ ab\t !m1 is m m>vell\s ev5 ?an ! feat ( ,adams & ,le ,v]ri] 9 discov]+ a planet on pap] be=e anyone _h se5 x4 ,x e/abli%$ ,maxwell among ! h]oes ( sci5ce = all "t4 ,a magnet acts ^u a piece ( iron "s di/ance away4 ,! pull mu/ be transmitt$ ?r\gh "s k9d ( e!r4 ,a curr5t ( electricity behaves 9 ! same way1 act+ precisely z a magnet1 ) p[] to affect ?+s at a di/ance4 ,aga9 an e!r is necess>y4 ,a dynamo works by mov+ a magnet pa/ a wire :i* x does n t\*1 !reby g5]at+ curr5t 9 x4 ,!re aga9 an e!r is necess>y to transmit ! effect f ! "o to ! o!r4 ,tak+1 !n1 ! kn[n magnetic effects ( an electric curr5t & ! electrify+ effects ( magnets1 he 0 able to %[ t ! same e!r acc\nt$ = all1 & = ! transmission ( light z well1 t1 9 fact1 !re 0 b "o e!r :i* p]=m$ all ^! v>i\s duties4 ,he prov$ f ! kn[n facts ab\t electricity & magnetism t waves su* z he imag9$ w\ld1 9 fact1 move ) ! spe$ ( light4 ,& once kn[+ ! nature ( ! waves1 he ass]t$ t 9 all probability !re 7 o!rs ( :i* m5 _h !n no practical k4 ,maxwell's !ory soon set exp]im5t]s se>*+ = ! means ( produc+ ! long waves :i* he _h pr$ict$ w\ld be f\nd4 ,sev]al au?orities _h be=e !n /at$ _! belief t ! curr5t d]iv$ f a ,leyd5 j> 0 n simply a fl[ 9 "o direction4 ,!y sugge/$1 & gave gr\nds = ! belief1 t ! curr5t surg$ to & fro = "s "t be=e x settl$ d[n2 t x swung to & fro1 inde$1 l a p5dulum4 ,!re may be "s ( my read]s :o are unacqua9t$ ) ?is int]e/+ piece ( electrical app>atus ! ,leyd5 j>4 ,x is a conv5i5t =m ( :at is call$ an electro/atic cond5s]4 ,?is is two conductors1 g5]ally 9 ! =m ( two plates ) an insulator betwe5 !m4 ,9 ! ,leyd5 j> ! insulator is a glass j>1 :ile ! plates are coat+s ( t9foil1 "o inside & ! o!r outside4 ,on connect+ "o coat+ to "o pole ( a batt]y1 & ! o!r to ! o!r pole1 !y become *>g$1 "o positively & ! o!r negatively4 ,"o1 t is1 acquires an excess ( electricity1 :ile ! o!r becomes defici5t to an exactly simil> ext5t4 ,:5 ! two are aft]w>ds connect$ by a wire ! surplus on "o fla%es ?r\gh x to make good ! defici5cy on ! o!r4 ,ru%+ fir/ ( all f positive coat+ to negative1 electrical in]tia causes x to ov]%oot ! m>k & to re*>ge ! j> ) ! *>ges rev]s$4 ,!n curr5t beg9s to fl[ back aga91 do+ ! same sev]al times ov]1 until at la/ equilibrium is e/abli%$4 ,! p[] to absorb & hold a *>ge ( electricity1 :i* is ! *>act]i/ic ( a cond5s]1 is call$ capacity4 ,:at1 !n1 is electrical in]tia8 ,i h already ref]r$ to ! effect :i* ! creation ( a magnetic field ar\nd a curr5t has ^u neighb\r+ conductors4 ,x also has an effect ^u itself4 ,z soon z ! curr5t beg9s to fl[ x builds up ! magnetic field1 & 9 ! process "s ( its en]gy is exhau/$4 ,on ! orig9al curr5t ceas+1 h[ev]1 ! magnetic field collapses back on to ! conductor once m & 9 s do+ re/ores t en]gy4 ,?is occurs :5ev] curr5t fl[s1 b x is specially noticeable 9 long conductors1 l subm>9e cables4 ,9 !m ! batt]y has to act = a consid]able "t be=e any curr5t rea*es ! f>!r end4 ,x is 9 ! meantime employ$ 9 build+ up ! magnetic field ar\nd ! wire4 ,!n :5 ! batt]y has ceas$ to act ! curr5t /ill comes fl[+ out at ! f>!r end--! magnetic field is giv+ back ! en]gy exp5d$ ^u x4 ,?us a curr5t is reluctant to />t fl[+ ?r\gh a conductor1 &1 hav+ />t$1 is dis9cl9$ to /op4 ,?is is call$ inductance1 & x has exactly ! same effect ^u ! curr5t t in]tia has ^u a body4 ,:at in]tia is to a mat]ial body inductance is to an electric curr5t4 ,& la/ly1 ! resi/ance :i* ! conductor (f]s to ! passage ( ! curr5t is precisely analag\s to ! friction ( ! wat] 9 a pipe4 ,s1 we see1 ! capacity ( ! two coat+s ( ! j> & ! inductance :i* occurs 9 ! connect+ wire cause ! curr5t to oscillate to & fro = a :ile :5 ! j> is dis*>g$1 :i* surg+ or oscillation is ultimately /opp$ by ! resi/ance ( ! wire4 ,! two coat+s & ! wire =m :at is call$ an oscillatory circuit4 ,we c n[ resume our /ory4 ,aft] mu* exp]im5t+ ,h]tz1 ( ,c>lsruhe1 discov]$ ! fact t :5 a dis*>ge 0 tak+ place 9 an oscillatory circuit t9y sp>ks pass$ betwe5 ! ends ( a curv$ wire held "s di/ance away4 ,8 app>atus is illu/rat$ 9 ,figs4 #f & #g4 ,! =m]1 :i* is t]m$ n[adays a ,h]tz ,oscillator1 is simply two metal discs almo/ connect$ by a ?ick wire4 ,! wire is brok51 h[ev]1 at ! c5tre1 & ! two halves t]m9ate 9 two metal balls4 ,ea* ball is connect$ to "o t]m9al ( an induction coil4 ,n[ ! curr5t comes f an induction coil 9 a s]ies ( spurts4 ,x is n an alt]nat+ curr5t exactly 7s9ce e alt]nate curr5t is s feeble z to be negligible71 b is practically an int]mitt5t curr5t always 9 ! same direction4 ,?us we may call "o ! positive end ( ! coil & ! o!r ! negative4 ,a %ort curr5t comes along ) e backw>d movem5t ( ! little vibrat+ arm :i* =ms a "p ( ! app>atus4 ,?is break+ ( ! prim>y circuit may take place p]haps fifty times p] second1 s t ! int]mitt5t second>y curr5ts w succe$ ea* o!r at int]vals ( a fiftie? ( a second1 or ev5 less4 ,! bra9 reels at ! attempt to ?9k ( a fiftie? ( a second1 b x is really q a long int]val z ^! ?+s g1 & dur+ t int]val q a lot happ5s4 ,= ! curr5t fir/ ( all *>ges ! two plates z a cond5s]4 ,illu/ration3 ,,fig4 #f4--,! app>atus by :i* ,h]tz made 8 discov]ies1 h5ce call$ ! ,h]tz ,oscillator4 a a are metal plates2 d is ! sp>k-gap betwe5 ! two metal balls2 b is ! batt]y1 & c ! induction coil4 ,:5 !y are z full z !y w hold ! curr5t ov]fl[s1 z x 71 across ! gap betwe5 ! two balls4 ,n[ an air-gap--a gap t is fill$ ) air1 betwe5 two conductors--is a v /rong insulator4 ,b :5 curr5t has once brok5 ?r\gh x x becomes a fairly good conductor4 ,h5ce z soon z ! fir/ sp>k has pass$ betwe5 ! two knobs ! plates become connect$ almo/ z if a wire 7 pass$ f "o to ! o!r4 ,& !re we h q a good oscillatory circuit4 ,!re is capacity at ea* end & a fairly long l5g? ( wire to provide ! inductance4 ,consequ5tly t breakd[n ( ! insulation ( ! air 9 ! sp>k-gap is foll[$ by electrical oscillations :i* take place ) inconceivable rapidity4 ,yet because ( ! resi/ance ( ! sp>k-gap1 :i* is consid]able ev5 aft] x has be5 brok5 ?r\gh1 ! oscillations d n cont9ue = long4 ,!y h di$ away long be=e ! lapse ( a fiftie? ( a second1 :5 ! next impulse comes along f ! coil4 ,9 ! meantime ! air-gap rega9s its insulat+ prop]ties1 & s1 on ! arrival ( ! next impulse1 ! :ole ?+ occurs once m4 ,?us a little tra9 ( oscillations is produc$ = e impulse f ! coil4 ,e tra9 causes a correspond+ di/urbance 9 ! e!r1 & s5ds (f a tra9 ( electro-magnetic waves1 & ^!1 fall+ ^u ! di/ant wire1 g5]ate 9 x a tra9 simil> to t :i* br\ght !m into be+4 ,^! tra9s1 9 ,h]tz' simple app>atus1 manife/$ !mselves 9 ! =m ( m9ute sp>ks leap+ across ! small gap betwe5 ! ends ( ! curv$ wire 7,fig4 #g74 ,illu/ration3 ,,fig4 #g4--;,h]tz ,detector4 ,x 0 ) ?is simple app>atus t ,h]tz discov]$ h[ to detect ! wireless waves4 ,x 0 9 #ahhh t ,h]tz made ?is discov]y ( a way to detect long electric waves4 ,he subject$ ! matt] to _m m exp]im5ts & f\nd t ! waves h _m po9ts 9 common ) light rays4 ,he f\nd t !y 7 reflect$ f c]ta9 surfaces1 j z light is reflect$ f ! surface ( a mirror4 ,he made prisms :i* 7 able to b5d !m z light waves are b5t by a prism ( glass4 ,"s ?+s appe>$ to be transp>5t to !m1 z cle> glass is to light1 :ile o!rs are opaque4 ,x does n foll[ t ! same ?+s :i* reflect light waves reflect electric waves1 & s on4 ,! latt] c pass ?r\gh a brick wall1 = example4 ,b ! same div]g5ce is to be obs]v$ betwe5 light & radiant heat1 ( :i* ! action ( glass is a famili> example4 ,cle> glass w let light ?r\gh almo/ undimm$1 yet we use x = fire-scre5s to %ield u f too mu* radiant heat4 ,! important fact is t all ?ree--light1 radiant heat & ,h]tzian waves--9 addition to travell+ at ! same spe$1 are reflect$1 absorb$ or refract$1 accord+ to precisely ! same pr9ciples4 ,?is is almo/ p]fect te/imony to _! ess5tial id5tity4 ,! diff]5ce betwe5 !m1 z has be5 said already1 is ! di/ance f cre/ to cre/ ( ! waves--! wave-l5g?1 t is4 ,& ! read] w wond] by :at mann] ( means ?is my/]i\s dim5sion c be asc]ta9$4 ,9 spite ( its seem+ my/]y ! me?od is v simple4 ,x is bas$ ^u ! fact t two sets ( simil> waves travell+ at ! same spe$ 9 opposite directions int]f]e ) "o ano!r 9 a peculi> way4 ,suppose t "o set ( waves travel along to a reflector & /rike x v]tically2 !n ano!r set w travel back f ! reflector exactly simil> to ! fir/1 except t _! direction w be opposite4 ,& ! result w be t at c]ta9 int]vals !y w exactly neutralise ea* o!r1 s t at ^? po9ts !re w be no wave-action appreciable at all4 ,^? po9ts :]e no action is to be p]ceiv$ are call$ nodes1 & !y are exactly half a wave-l5g? ap>t4 ,?is w be q easily und]/ood f ! accompany+ diagrams4 ,9 ea* ( ^! diagrams ! set ( waves m>k$ a are suppos$ to be mov+ f left to "r1 :ile ^? d5ot$ by b are reflect$ back & are mov+ f "r to left4 ,x w be notic$ t ea* wavy l9e has a /raight l9e drawn ?r\gh x1 divid+ x into alt]nate cre/s & holl[s1 :i* l9e is kn[n z ! axis ( ! waves4 ,n[ notice t 9 ,fig4 #h !re are po9ts m>k$ x1 :]e ! a waves are j z mu* above ! axis z ! b waves are bel[ x1 & vice v]sa4 ,h5ce at ^? po9ts ! two sets ( waves w neutralise ea* o!r4 ,n[ turn to ! next figure1 :i*1 be x rememb]$1 %[s ! same waves a mom5t lat]1 :5 !y h mov$ a little f>!r on 9 _! respective j\rneys1 & x w be se5 t !re1 too1 are places m>k$ x :]e ! two sets ( waves neutralise ea* o!r4 ,& ! same ) ! ?ird diagram4 ,& f9ally obs]ve t ! places m>k$ x are always ! same 9 all ! diagrams--t is to say1 !y are always ! same di/ance f ! l9e on ! "r-h& side1 :i* d5otes ! reflector4 ,x w be cle>1 too1 t ea* node is half a wave-l5g? f ! next4 ,?us x c be %[n t at e mom5t1 & n m]ely at ! ?ree indicat$ 9 ! diagrams1 ! two sets neutralise ea* o!r at ! nodes1 t ! nodes are always 9 ! same places & half a wave-l5g? ap>t4 ,illu/ration3 ,,figs4 #h1 #i & #aj4--,^! diagrams help u to see h[ ! wireless waves are measur$4 ,! a waves are suppos$ to be mov+ f left to "r & ! b waves f "r to left4 ,at ! po9ts m>k$ x !y neutralise ea* o!r4 ,x is !n easy to discov] ^? po9ts & ! di/ance ap>t ( any two adjac5t ones is half ! wave-l5g?4 ,n4,b4--,9 ,fig4 #aj ! b waves fall exactly on top ( ! a waves4 ,ev]y:]e else1 except at ! nodes1 !re is action m or less en]getic1 b !re is p]petual calm4 ,b h[ c we tell :]e ! nodes are8 ,:5 we recollect t !y are po9ts at :i* no wave-motion at all takes place x is easy to see t we %all at ^? po9ts get no sp>k 9 our detector4 ,s :at ,h]tz did 0 to set 8 oscillator go+ s t x ?rew waves ^u a reflect+ surface & !n move 8 detector to & fro 9 ! neighb\rhood until he f\nd ! nodes4 ,betwe5 ! nodes1 z w be se5 by an inspection ( ! curves once m1 !re are o!r po9ts at :i* ! wave-action w be twice z great z ) ! s+le wave1 & s at ^? po9ts ! response ( ! detector w\ld be especially en]getic4 ,?is mutual action betwe5 an incid5t wave & a reflect$ wave is t]m$ int]f]5ce1 & by x ! wave-l5g?s ( all ! e!real waves h be5 measur$4 ,! plan us$ 9 ! case ( light waves1 al?\gh ! same 9 pr9ciple1 is some:at diff]5t because ( ! extreme %ortness ( ! waves4 ,s ! exp]im5ts ( ,h]tz n only %[$ t long electric waves exi/$1 b t !y 7 9 all ess5tials simil> to light1 & _! wave-l5g?s 7 asc]ta9$4 ,on t basis has be5 built up mod]n wireless telegraphy4 ,x may be int]e/+ to m5tion at ?is po9t a v curi\s1 & 9 a s5se pa!tic1 incid5t4 ,pr(essor ,hughes1 ^: "n is associat$ ) c]ta9 well-kn[n in/rum5ts = ord9>y telegraphy1 n9e ye>s be=e ,h]tz' discov]y notic$ t a microphone 0 affect$ by ! action ( an induction coil "s di/ance away4 ,he himself atta*$ "s importance to ! matt]1 b he all[$ himself to be dissuad$ f foll[+ up ! discov]y by o!r sci5ti/s1 m em95t ?an himself at ! "t1 :o ?\ght t x 0 n a promis+ field = inve/igation4 ,b = ! influ5ce ( ^! fri5ds he w\ld possibly be ! h]o ( ?is /ory 9 place ( ,h]tz4 ,pr(essor ,silvanus ,?omson has said t he too notic$ ! sp>ks produc$ at a di/ance :5 a ,leyd5 j> 0 dis*>g$1 b he makes no claim to prec$5ce ov] ,h]tz1 s9ce1 see+ ! ph5om5on1 he did n p]ceive its real mean+1 :ile ,h]tz1 ?\gh a little lat] 9 "t1 realis$ ! pr(\nd significance ( x4 ,h]tz himself 9 8 acc\nt ( 8 exp]im5ts is g5]\s en\gh to ass]t t1 _h he n discov]$ ! waves :5 he did1 he is q c]ta9 t ,sir ,oliv] ,lodge w\ld h done s4 ,be=e proce$+ to describe ! pr9cipal app>atus us$ 9 ! wireless /ation ,i %\ld l to devote a little space to ! explanation ( a t]m :i* w come up aga9 & aga91 & :i* repres5ts t :i* is responsible1 9 ! ma91 = ! m>vell\s advances :i* ! art ( s5d+ wireless messages has a*iev$ 9 ! la/ few ye>s4 ,i ref] to resonance4 ,x w be a great help if ! read] w try = himself a simple1 inexp5sive little exp]im5t4 ,/ret* a /r+ horizontally across a room & on to x tie two o!r /r+s s t !y hang d[n v]tically a little di/ance ap>t4 ,to ! ends ( ! two /r+s tie "s small objects--a cotton reel on ea* w answ] admirably4 ,!y w ?us =m two p5dulums1 &1 to comm5ce )1 !y %\ld be j ! same l5g?4 ,hav+ rigg$ all ?is up1 give "o p5dulum a good sw+4 ,x w imp>t motion ( a to-&-fro v>iety to ! support+ /r+1 :i* 9 its turn w pass t motion on to ! o!r p5dulum4 ,9 a v %ort "t1 !n1 ! second p5dulum w be vibrat+ l ! fir/4 ,inde$ ! :ole motion ( ! fir/ w %ortly become transf]r$ to ! second1 s t ! second w be sw++ & ! fir/ /ill4 ,!n ! second w re-transf] its en]gy back to ! fir/1 & s !y w g on until ! orig9al en]gy giv5 to ! fir/ p5dulum is exhau/$4 ,! po9t to be obs]v$ is ! quickness ) :i* "o p5dulum responds to ! impulses giv5 x by ! o!r1 & ! ease ) :i* ! en]gy ( ! "o passes to ! o!r4 ,n[ r$uce ! l5g? ( "o p5dulum4 ,on sett+ ! fir/ 9 motion a c]ta9 irregul> spasmodic action is to be obs]v$ 9 ! second1 b x is v diff]5t f ! :ole-he>t$ response 9 ! previ\s in/ance4 ,9 ! =m] case ! second "o respond$ naturally & readily to ! fir/4 ,n[ its response is reluctant 9 ! extreme4 ,x moves some:at because x is =c$ to1 b x is app>5tly unwill+4 ,en]gy has to be impress$ ^u x4 ,!re is no read9ess1 because !re is no sympa?y betwe5 !m4 ,t sympa?y betwe5 ! two equal p5dulums is resonance4 ,! same occurs betwe5 two viol9 or piano /r+s :5 !y are 9 tune4 ,! explanation is t a p5dulum has a c]ta9 natural frequ5cy :i* dep5ds ^u its l5g?4 ,ano!r p5dulum ( ! same l5g?1 arrang$ z j describ$1 !re=e imp>ts impulses to x at j ! frequ5cy :i* is natural to x4 ,consequ5tly ! effect is a cumulative "o1 & x responds quickly4 ,impulses at any o!r frequ5cy t5d m or less to neutralise ea* o!r4 ,9 ! same way a /r+1 ( a c]ta9 l5g? & a c]ta9 t5sion1 has a frequ5cy peculi>ly its own1 & x w respond to ano!r simil> /r+ because ! o!r gives its impulses at its own natural frequ5cy4 ,x is on record t an eng9e 9 a factory happ5$ to run at precisely ! same spe$ z ! natural frequ5cy ( ! build+1 ) ! result t aft] a little "t ! /ructure %ook s mu* t x collaps$4 ,n[ electrical circuits 9 :i* curr5ts oscillate h a natural frequ5cy ( _! own4 ,t frequ5cy dep5ds ^u ! two electrical prop]ties ( ! circuit3 capacity & inductance4 ,& if y want to set up an electrical oscillation 9 any circuit y c be/ d x by giv+ x impulses at int]vals :i* agree ) its natural frequ5cy4 ,sir ,oliv] ,lodge seems to h be5 ! fir/ to appreciate fully ! effects ( resonance 9 wireless telegraphy4 ,x is /range t 9 ,engl& ! "w ( ?is em95t man 9 wireless matt]s is n m fully recognis$4 ,:5 wireless telegraphy rea*$ ! po9t at :i* ! public became int]e/$1 ,m>coni 0 j com+ to ! front & s1 = ev]1 w 8 "n be =emo/ 9 ! public e/imation4 ,inde$ m ?an =emo/1 = 9 ! m9ds ( _m he monopolises ! cr$it = ?is inv5tion4 ,_m p are "u ! impression t he is ! "o & only1 or at any rate ! orig9al1 inv5tor ( wireless telegraphy4 ,n[ ,m>coni has done exce$+ly valuable "w 9 ?is field4 ,moreov]1 he has be5 ! means ( plac+ ! affair on a good comm]cial foot+4 ,b all ! same he is by no means ! orig9al or only inv5tor4 ,:ile admitt+ t he is a rem>kable man1 :o has done wond]s1 x is only common ju/ice to ref] to ! o!rs ^: contributions to ! solution ( ! problem are possibly ( equal value4 ,&1 ( ^!1 few c comp>e ) ,sir ,oliv] ,lodge4 ,b to return to ! "q ( resonance4 ,at fir/ ! di/ances ov] :i* messages c\ld be s5t 7 b small4 ,n[ a m>conigram c be flung across a hemisph]e4 ,at fir/ little c\ld be done by day1 "w _h to be done ma9ly at night4 ,n[ communication passes by day & night alike4 ,yet 9 pr9ciple1 & 9 _m details1 ! in/rum5ts are unalt]$ f :at !y 7 sev]al ye>s ago4 ,! ma9 s\rce ( all ?is improvem5t is ! use ( resonance4 ,to enum]ate broadly ! app>atus us$ = ! dispat* & receipt ( messages ! foll[+ li/ w be useful3-- ,transmitt+ ,end 7#a7 ,an ,ant5na1 consi/+ ( a numb] ( wires rais$ to a consid]able height above ! gr\nd4 7#b7 ,a ,sp>k-gap1 consi/+ ( a s]ies ( metal balls ) gaps betwe5 !m1 ! out] ones be+ connect$ to ! ant5na & to ! induction coil4 7#c7 ,a p[]ful ,induction ,coil ) batt]ies or o!r s\rce ( curr5t to "w x4 7#d7 ,a ,telegraph ,key1 by :i* ! induction coil c be />t$ & /opp$ at w4 ,receiv+ ,end 7#a7 ,an ,ant5na precisely simil> to ! o!r4 7#b7 ,a ,coh]] or o!r oscillation detector4 7#c7 ,a ,receiv+ ,in/rum5t :i* may be a writ+ telegraph in/rum5t1 a telephone1 any ( a numb] ( ord9>y telegraph in/rum5ts1 or a galvanomet]4 ,transmitt+ & s5d+ in/rum5ts are1 ( c\rse1 in/all$ at bo? ends & ei!r ( !m c be connect$ to ! ant5na at w by ! simple movem5t ( a swit*4 ,! ant5na plays ! "p ( "o ( ! metal plates 9 ! ,h]tz oscillator4 ,e>ly exp]im5ts 7 made ) ,h]tz app>atus1 b ! range ( su* a contrivance is v limit$4 ,= "o ?+1 x neglects to take advantage ( ! e>?4 ,x is little realis$ :at an important "p ! e>? plays 9 ! c>ry+ ( wireless messages4 ,a v great /ep 0 tak5 :5 ,m>coni disp5s$ ) "o ( ! plates ( ,h]tz1 & us$ ! e>? in/ead2 :ile ! o!r plate gave place to ! elevat$ wires1 ! mo/ famili> "p ( ! app>atus to mo/ p4 ,! cond5s] is ?us =m$ by ! e>? z "o plate1 ! elevat$ wires z ! o!r1 & ! int]v5+ air z ! insulator4 ,! capacity mu/ be exce$+ly small 9 su* an app>atus1 b x is suffici5t2 :ile ! long l9es ( electrical =ce /ret*+ f ! high ant5na to ! e>? produce waves ( great c>ry+ p[]4 ,la/ly1 :5 ! e>? =ms a "p ( ! cond5s] ! waves cl+ to x1 s t in/ead ( be+ l>gely dissipat$ into space1 !y move along ! surface ( ! e>?4 ,! advantage ( ?is is obvi\s4 ,at fir/ x 0 cu/om>y to place ! sp>k-gap 9 ! wire lead+ f ! ant5na to ! e>?1 z 9 ! accompany+ sket*4 ,lat]1 h[ev]1 x 0 f\nd bett] to place ! coil & sp>k-gap 9 a local circuit 9 :i* ! oscillations are fir/ produc$4 ,^! oscillations pass ?r\gh a coil :i* is int]w\nd ) ano!r "o connect$ to ! ant5na & to e>?1 & ?us ! local oscillations1 z we might call !m1 induce simil> oscillations 9 ! ant5na1 j z ! fluctuations 9 "o "p ( an induction coil induce fluctuations 9 ! o!r4 ,inde$ ! coil 9 ! local circuit & ! "o 9 ! ant5na circuit actually con/itute an induction coil4 ,! advantage ( ?is is t by introduc+ cond5s]s ! capacity ( :i* c be v>i$1 & coils ! inductance ( :i* c be v>i$1 into ! oscillation circuit x becomes possible to tune ! circuits effectively4 ,?us resonance comes into play & ! p[] exp5d$ c be made to produce ! maximum effect4 ,"s attempts h be5 made to displace ! induction coil 9 wireless telegraphy altoge!r by a specially made dynamo4 ,^! ma*9es c produce ei!r alt]nat+ or cont9u\s curr5ts1 9 fact ! alt]nat+ curr5t dynamo is really simpl] ?an ! m famili> cont9u\s-curr5t ma*9e4 ,! difficulty is1 h[ev]1 to run x suffici5tly fa/ to produce suffici5tly rapid alt]nations4 ,nicola ,tesla made an alt]nator 7to give ! alt]nat+ curr5t dynamo its %ort title7 :i* c\ld produce #aejj alt]nations p] second1 :ile ,mr ,w4 ,duddell made "o :i* produc$ #abj1jjj1 b nei!r 0 satisfactory = ! "w 9 "q4 ,c\ld su* a ma*9e be made1 x w\ld be invaluable1 = x w be app>5t t a cont9u\s succession ( waves w\ld be =m$ by x & n a succession ( %ort tra9s ( waves su* z is produc$ by ! induction coil & sp>k-gap4 ,! difficulties are n electrical1 b me*anical4 ,x seems d\btful if a ma*9e w ev] be made to run ) suffici5t rapidity :i* w\ld n knock itself to pieces 9 a v %ort "t4 ,illu/ration3 ,,fig4 #aa4--,! simple/ =m ( wireless ant5na4 ,small alt]nators are us$ sometimes1 h[ev]1 to supply alt]nat+ curr5t to ! prim>y ( an induction coil1 or trans=m]1 z x is m (t5 call$ 9 its l>g] sizes4 ,! int]rupt] is only ne$$ :5 ! prim>y curr5t is cont9u\s--f batt]ies1 = example4 ,alt]nat+ curr5t ne$s no int]rupt]1 & s t bo!r is remov$4 ,! alt]nations ( a hundr$ or s p] second1 :i* are q ! common ?+ ) alt]nators1 are j :at is ne$$ to excite an induction coil4 ,consequ5tly small ma*9es ( ?is k9d are to be f\nd 9 _m /ations4 ,a ,dani% inv5tor1 ,valdem> ,p\ls51 has adopt$ an altoge!r diff]5t me?od ( produc+ electrical oscillations1 :i* me?od is ! di/9ctive feature ( 8 mode ( telegraphy4 ,he takes advantage ( a curi\s effect ( pass+ curr5t betwe5 two rods1 "o ( :i* is c>bon1 s z to =m an arc su* z we see 9 arc lamps4 ,my read]s are already famili> ) ! t]m %unt 9 connection ) electrical matt]s1 & s w p]ceive at once :at is meant :5 a second circuit is said to be arrang$ z a %unt to ! arc4 ,! accompany+ diagram w 9 any case make ! matt] cle>4 ,! curr5t comes along f ! batt]y or cont9u\s-curr5t dynamo to a holl[ rod ( copp] :i*1 to prev5t x be+ melt$1 has cold wat] cont9ually circulat+ inside x4 ,!nce ! curr5t jumps across to a c>bon rod1 =m+ an arc betwe5 ! two rods1 & returns :5ce x came4 ,9 its j\rney x trav]ses ! coils ( an electro-magnet1 ! poles ( :i* are "o ea* side ( ! arc4 ,?is t5ds to bl[ ! arc out1 z a puff ( w9d bl[s out a c&le1 an effect :i* a magnet always has ^u an electric arc4 ,! %unt consi/s ( a wire lead+ f ! copp] to ! c>bon rod ) a cond5s] & an inductance coil ins]t$ 9 x4 ,! latt] coil also =ms "o "p ( t coil by :i* ! oscillations 9 ! local circuit are transf]r$ to ! ant5na4 ,! electrical explanation ( :at happ5s :5 ! curr5t is turn$ on to an arrangem5t l ?is is r too complex to set out "h4 ,x dep5ds ^u a curi\s behavi\r ( ! arc4 ,x is really a conductor1 yet x does n behave z ord9>y conductors d1 & ! result is t ! cont9u\s curr5t fl[+ ?r\gh ! arc is accompani$ by an oscillat+ curr5t 9 ! %unt circuit4 ,& ! important feature ( ! arrangem5t is t ^! oscillations are cont9u\s1 9 "o long tra91 n 9 a succession ( tra9s4 ,! advantage ( ?is has already be5 ref]r$ to4 ,"o o!r feature ( ! app>atus j describ$ %\ld be m5tion$1 s9ce x w seem curi\s to ! g5]al read]4 ,= x to "w prop]ly x is necess>y t ! arc %\ld be enclos$ 9 a *amb] fill$ ) hydrog5 or a hydro-c>bon gas4 ,coal-gas is g5]ally us$4 ,h]tz' orig9al discov]y 0 t small sp>ks c\ld be se5 to pass betwe5 ! ends ( a curv$ wire :5 ! electric waves fell ^u x4 ,su* sp>k detectors1 z !y are call$1 are useful 9 ! laboratory1 b n = practical telegraphy4 ,illu/ration3 ,,fig4 #ab4--;,diagram 7simplifi$7 %[+ h[ ,p\ls5 g5]ates oscillations4 ,curr5t f a dynamo fl[s ?r\gh ! arc1 :]eupon curr5ts oscillate ?r\gh ! cond5s] & coil 7z describ$ 9 ! text74 ,sev]al p seem to h notic$ 9 ye>s gone by t a mass ( loose metal fil+s1 normally a v bad conductor ( electricity1 became a mu* bett] conductor :5 an electrical dis*>ge ( "s sort occurr$ ne> by4 ,! dem& = a wireless receiv] _h n !n aris51 h[ev]1 & s ! discov]ies 7 n foll[$ up4 ,consequ5tly x rema9$ to be r$iscov]$ by ,branly1 ( ,p>is1 9 #ahij4 ,he plac$ "s metal fil+s 9 a glass tube1 ! ends ( :i* he clos$ ) metal plugs4 ,ly+ loosely toge!r ! fil+s w\ld n conduct ! curr5t ( a small batt]y f "o plug to ! o!r1 b :5 a sp>k occurr$ n f> away !y sudd5ly became conductive & all[$ x to pass4 ,sev]al ye>s aft] ?is ,sir ,oliv] ,lodge took up ! idea z a receiv] = wireless messages1 & believ+ t its action 0 due to ! waves caus+ ! fil+s to cl+ toge!r1 he *ri/5$ x ,coh]]4 ,m>coni succe$$ 9 mak+ a v delicate =m ( ?is1 al?\gh work+ on /rictly ! same l9es4 ,! tr\ble ) a coh]] is t :5 once x becomes conductive x rema9s s unless ! fil+s be %ak5 ap>t4 ,lodge !re=e arrang$ = ! tube to be cont9ually /ruck by clockwork or by a me*anism l t ( an electric bell4 ,m>coni effect$ a fur!r improvem5t by mak+ ! curr5t pass+ ?r\gh ! coh]] control ! /rik+ me*anism1 s t ! latt] is normally quiet b adm9i/]s "o or two taps at j ! "r mom5t4 ,sir ,oliv] ,lodge & ,dr ,muirhead devis$ ano!r detector :i*1 ?\gh q diff]5t 9 =m1 is really mu* ! same 9 pr9ciple4 ,a /eel disc ) a %>p knife-l edge is made to rotate above a vessel ( m]cury4 ,! edge j t\*es ! m]cury b no m4 ,on ! top ( ! m]cury !re floats a ?9 lay] ( oil1 a bad conductor4 ,n[ z ! disc revolves x picks up on its edge a film ( oil1 :i* x c>ries d[n into ! m]cury4 ,! film adh]es s tightly t x prev5ts ! mov+ disc f actually t\*+ ! liquid metal4 ,?us1 "u normal conditions1 ! two are electrically insulat$ f ea* o!r by ! film ( oil & no curr5t c pass f m]cury to disc4 ,oscillations1 h[ev]1 caus$ by incom+ electric waves1 are able to break ?r\gh ! oil film & s br+ disc & m]cury into contact1 :]eupon ! curr5t fl[s4 ,! con/ant movem5t ( ! disc re/ores ! oil-film z soon z ! oscillations cease4 ,! reason :y ^! detectors act z !y d is n q und]/ood4 ,"o sugge/$ explanation is t ! oscillat+ curr5ts heat ! p>ticles & s p>tially weld !m toge!r4 ,ano!r is t adjac5t p>ticles become *>g$ z ! plates ( a m9ute cond5s]1 & s are drawn tightly toge!r z ! plates 9 an electro/atic voltmet] are drawn t[>ds ea* o!r4 ,suppos+ t ! orig9al non-conductivity ( ! loose fil+s be due to ! film ( air :i* may surr\nd !m1 ei!r ( ^! ?+s w\ld acc\nt = ! film be+ brok5 or squeez$ out1 result+ 9 bett] contact & improv$ conduct+ p[]4 ,b bo? sugge/ions seem to be contradict$ by ! fact t if ! pieces 9 contact be ( c]ta9 sub/ances ! coh]] works ! opposite way4 ,"u ^? conditions ! conductivity is normally good1 b ! influ5ce ( ! incom+ waves causes x to become bad4 ,9 #ahif ,pr(essor ,ru!r=d1 n[ ( ,man*e/]1 describ$ "s discov]ies :i* he _h made z to ! magnetic effects ( oscillations4 ,a simple little contrivance :i* he _h con/ruct$ 0 op]at$ by ! dis*>ge ( a coil half-a-mile away1 at t "t a great p]=mance4 ,?is detector 0 simply an electro-magnet ) a /eel core in/ead ( ! usual s(t iron core4 ,! reason ! latt] is us$ 9 ! ord9>y magnet is t x loses its magnetism ! mom5t ! curr5t ceases to pass ?r\gh ! coil ) :i* x is surr\nd$1 :ile a /eel core reta9s its magnetism4 ,= mo/ purposes a /eel core w\ld r5d] an electro-magnet useless1 b 9 ?is case x 0 desir$ t ! core %\ld be p]man5tly magnetis$4 ,s a curr5t 0 fir/ pass$ ?r\gh ! coil to magnetise ! core1 & !n ! coil 0 connect$ to a simple =m ( ant5na :ile a sw++ magnet 0 br\ght ne> s t ! magnetic p[] ( ! core w\ld be indicat$ & any *ange made app>5t4 ,! effect ( ! dis*>ge half-a-mile away 0 to demagnetise ! core slightly4 ,?is 0 %[n by ! movem5t ( ! sw++ magnet1 & s ! fir/ magnetic detector 0 f\nd4 ,b "h1 p]haps1 ,i ought to expla9 ! use ( ! ant5na at ! receiv+ /ation--its function at ! s5d+ end has already be5 made cle>4 ,! electro-magnetic waves1 com+ f ! di/ant transmitt]1 /rike ! receiv+ ant5na & 9 s do+ set up 9 x oscillations su* z ^? :i* set !m 9 motion4 ,= e oscillation 9 ! s5d+ ant5na !re w be ano!r1 simil> 9 e respect except t x w be feebl]1 9 ! receiv+ ant5na4 ,& ! oscillations are "h l$ to ! detector1 ( :atev] =m x may be1 & 9 x !y make _! pres5ce felt4 ,9 "s few cases a ,duddell !rmo-galvanomet] has be5 employ$ z ! detector1 9 :i* ! oscillat+ curr5ts report !mselves directly4 ,9 coh]]s ! detector works by caus+ ! oscillat+ curr5ts to control a cont9u\s curr5t f a batt]y & x is ! latt] :i* actually gives ! signal1 b !re are a numb] ( extremely int]e/+ means :i* h be5 inv5t$ to detect ! oscillat+ curr5ts by _! heat+ effect4 ,r4 ,a4 ,fess5d51 = in/ance1 has p]fect$ "o :i* is a m>vel ( delicate workman%ip4 ,he dep5ds ^u ! heat+ ( a wire by ! curr5ts pass+ ?r\gh x4 ,su* heat+ is ! result ( ! electrical =ce act+ aga9/ resi/ance1 & ! difficulty is t if ! resi/ance be great x w almo/ entirely kill ! fa9t oscillat+ =ces 9 ! receiv+ ant5na1 :ile if1 on ! o!r h&1 x be small1 ! rise 9 temp]ature w be inappreciable4 ,s he encloses a f9e ?read ( plat9um 9 a glass bulb f :i* ! air is exhau/$4 ,! plat9um wire is fir/ ( all emb$d$ 9 a wire ( silv]3 ! silv] wire is giv5 a core ( plat9um1 9 fact4 ,!n ! comp\nd wire is drawn d[n until x is s ?9 t ! plat9um core is only "o & a half ?\s&?s ( an in* 9 diamet]4 ,a %ort l5g? ( ?is comp\nd wire is !n b5t into a ,u-%ap$ loop & its ends connect$ to ?ick] wires4 ,f9ally ! bottom ( ! loop is imm]s$ 9 nitric acid1 :i* eats away ! silv] at t po9t & leaves ! b>e plat9um4 ,?us is produc$ a v %ort l5g? 7a few millimetres7 ( exce$+ly ?9 plat9um wire support$ at its ends by comp>atively ?ick wires4 ,be+ s %ort1 ?is wire does n (f] mu* resi/ance1 & consequ5tly does n mat]ially *eck ! oscillations4 ,at ! same "t1 s9ce x is s f9e1 x does (f] "s resi/ance1 & f9ally1 s9ce :at heat is g5]at$ w be 9 an exce$+ly small space1 x w be appreciable !re4 ,a telephone is arrang$ s t its curr5t also passes ?r\gh ! f9e wire1 & e slight v>iation 9 ! temp]ature ( ! plat9um wire1 by v>y+ its resi/ance1 v>ies ! curr5t ?r\gh ! telephone4 ,& exce$+ly slight v>iations c be detect$ by s\nd 9 ! telephone4 ,?us ! oscillations g5]at$ 9 ! ant5na affect ! heat 9 ! wire2 t affects its resi/ance2 & t aga9 affects ! telephone1 :i*1 f9ally1 affects ! e> ( anyone :o is li/5+ to x4 ,x mu/ be und]/ood1 h[ev]1 t ?is is n a wireless telephone1 = ! s\nds he>d are n articulate b m]ely long & %ort s\nds1 repres5t+ ! dots & da%es ( ! ,morse ,code4 ,electrolysis provides u ) ano!r =m ( detector4 ,an exce$+ly small plat9um wire =ms "o electrode & a l>ge lead plate ! o!r1 & bo? are imm]s$ 9 dilute acid4 ,! passage ( curr5t f a local batt]y sets up electrolysis1 & s /ops itself by =m+ a film ( oxyg5 on ! small electrode4 ,?is film1 h[ev]1 is brok5 by ! oscillat+ curr5ts f ! ant5na1 s t z long z !y are com+ ! batt]y curr5t c fl[1 b z soon z !y cease ! batt]y curr5t /ops itself aga94 ,?us ! fl[+ & /opp+ ( ! oscillat+ curr5ts is exactly copi$ by ! curr5t f ! batt]y1 :i* curr5t is l$ ?r\gh a telephone or a s5sitive galvanomet]4 ,x may occur to read]s to inquire :y ! oscillat+ curr5ts are n pass$ direct to a galvanomet]4 ,! answ] is t because !y are oscillat+ a v s5sitive galvanomet] is n possible4 ,true1 ! ,duddell !rmo-galvanomet] has be5 m5tion$ 9 ?is connection1 b al?\gh x is a beautiful in/rum5t x _c comp>e = delicacy ) ! direct-curr5t galvanomet]s4 ,! latt] are easily a hundr$ ?\s& times m s5sitive4 ,b ! tr\ble c be ov]come by rectify+ ! oscillat+ curr5ts1 by pass+ !m ?r\gh a unidirectional conductor--"o1 t is1 :i* passes curr5t "o way only4 ,^! rem9d "o ( a turn/ile z in/all$ at c]ta9 public places1 :i* let y out b w n let y 9 unless y pay4 ,9 fact !y w n let y 9 at all4 ,9 l mann] rectifi]s w only all[ ^? curr5ts to pass :i* are fl[+ 9 "o direction1 & s !y cut out e alt]nate oscillation1 ?us produc+ some?+ v l cont9u\s curr5t1 :i* c be detect$ by ! v delicate galvanomet]s :i* are usable :]e cont9u\s curr5ts are conc]n$1 or m (t5 by a telephone receiv]4 ,! rectify+ conductors are 9 _m cases cry/als1 h5ce ^! detectors are call$ ,cry/al ,detectors4 ,c>borundum is a fav\rite = ?is purpose4 ,& t br+s u to ! important "q ( ! secrecy ( wireless communication1 & ! measures tak5 to prev5t confusion f ! numb] ( indep5d5t messages fly+ ?r\gh ! air at ! same "t4 ,?is c be l>gely a*iev$ by ! aid ( resonance4 ,tra9s ( waves flung out by "o ant5na may /rike sev]al o!r ant5nae1 b unless ! latt] are 9 tune ) ! s5d+ app>atus !y w probably n be affect$ appreciably4 ,let "o ( !m1 h[ev]1 be 9 tune1 & x w pick up easily ! message :i* is n notic$ by ! o!rs4 ,x is z if ?ree p wat*+ a di/ant lamp 7 affect$ by a =m ( col\r-bl9dness :i* r5d]$ !m practically bl9d to all col\rs except "o4 ,suppose "o c\ld see r$ only1 ! o!r blue & ! ?ird yell[4 ,a light s5t ?r\gh a blue glass be+ robb$ ( all rays except ! blue ones w\ld be visible only to ! man :o c\ld see blue4 ,! man :o c\ld see blue w\ld1 9 l mann]1 be q bl9d to light s5t ?r\gh r$ or yell[ glass4 ,ea* ( !m1 9 fact1 c\ld be signall$ to q indep5d5tly ( ! o!rs by simply s5d+ him rays ( ! col\r to :i* 8 eyes 7 s5sitive4 ,9 precisely ! same way ea* wireless receiv] is or c be made mo/ s5sitive to waves ( a p>ticul> l5g? & practically bl9d to all o!rs4 ,! op]ator c adju/ 8 app>atus = c]ta9 pre>rang$ wave-l5g?s1 & s he c communicate ) secrecy to /ations ^: wave-l5g? he kn[s4 ,! *ange1 ( c\rse1 is made by alt]+ ! capacity1 or inductance1 or bo?4 ,! in/rum5ts c be s calibrat$ t x is q easy to make ! alt]ation4 ,!n1 ant5nae c be s con/ruct$ t messages c be receiv$ ) mo/ read9ess f "o p>ticul> direction4 ,9 o!rs1 !y c be receiv$ f any direction1 b ! direction c be discov]$4 ,?is1 x w be easy to see1 is ( great value to %ips 9 a fog4 ,ant5nae made ) a %ort v]tical "p & a long horizontal "p radiate be/ 9 ! direction away f :i* _! horizontal "p po9ts4 ,?is is ( great advantage 9 /ations :i* are built specially to communicate ) o!r p>ticul> /ations4 ,9 su* cases ! ant5na is c>efully built1 s z to po9t 9 ! requir$ direction4 ,su* ant5nae also receive m readily ^? signals :i* come f ! direction away f :i* !y are po9t+4 ,ref]5ce has be5 made already to ! int]e/+ fact t wireless communication is easi] at night ?an 9 ! daytime4 ,t is probably because ( ! ionisation ( ! atmosph]e by ! action ( sunlight4 ,along ) ! visible sunlight !re comes to u f ! sun a quantity ( light kn[n z ultra-violet1 s9ce x makes its effect kn[n 9 ! spectrum ( sunlight beyond ! violet1 :i* is ! limit ( visibility at "o end ( ! spectrum4 ,we _c see x b x affects photographic plates p[]fully4 ,x has en]getic *emical p[]s1 & x has ! ability to make ! air m conductive ?an x is ord9>ily4 ,comp>atively little ( x p5etrates our atmosph]e1 b x mu/ ex]cise a good deal ( influ5ce a little high] up4 ,n[ read]s w rememb] t ! process by :i* electro-magnetic waves are propagat$ is *eck$ :5 ! waves /rike a conductor4 ,! en]gy 9 ! waves is !n employ$ 9 caus+ curr5ts 9 ! conductor in/ead ( =m+ m waves4 ,& s p>tially conductive air =ms a p>tial b>ri] to ! waves4 ,! effect is n appreciable 9 ! case ( ! t9y waves ( light & heat1 b x is 9 ! case ( ! long wireless waves4 ,ev]yone has se5 ! waves ( an advanc+ tide com+ up a s&y bea*1 & has notic$ h[ ! dry s& 7a good conductor ( wat]7 sucks up & de/roys ! =emo/ ripples4 ,9 l mann] are ! wireless waves suck$ up by ! p>tially conductive atmosph]e4 ,b ! effect ( ! ultra-violet light does n la/ long1 & s1 at night-"t1 x disappe>s4 ,!re=e messages c be s5t bett] at night ?an by day4 ,= wireless telephony :at is want$ is a cont9u\s un9t]rupt$ tra9 ( waves1 su* z ^? f ! ,p\ls5 arc1 & a receiv] ( ! magnetic type4 ,! coh]] is no good = ?is purpose1 s9ce x ei!r /ops ! curr5t entirely or lets x fl[ copi\sly4 ,! magnetic detectors1 h[ev]1 respond to ! v>iations 9 ! /r5g? ( ! incom+ waves4 ,z ! latt] increase or decrease 9 /r5g? s does ! magnetic detector give out /rong] or weak] signals4 ,s a telephone transmitt] ( ! ord9>y type is made to v>y ! /r5g? ( ! oscillations at ! s5d+ end1 :ile an ord9>y telephone receiv] is plac$ 9 s]ies ) ! detector at ! receiv+ end4 ,?us e slight v>iation correspond+ to s\nd waves spok5 into ! transmitt] is reproduc$ 9 ! receiv]4 ,x is /range t wireless telephony has n made great] progress1 = x may be said1 on ! ^w ( "o ( ! greate/ au?orities1 t wireless telephony is simpl] & easi] ?an telephony ?r\gh a subm>9e cable4 ,9 ! latt] !re are almo/ insup]able ob/acles caus$ by ! capacity & inductance ( ! circuit1 :ile 9 ! wireless me?od !re is v little difficulty4 ,!re are1 ( c\rse1 sev]al s-call$ sy/ems ( wireless telegraphy 9 use4 ,!re is ! ,m>coni 9 ,great ,brita92 ! secret ,admiralty sy/em 9 ! ,briti% ,navy2 ! ,de ,=e/ 9 ! ,unit$ ,/ates2 ! ,telefunk5 9 ,g]many1 n to m5tion ! promis+ ,p\ls5 sy/em4 ,& !re are /ill o!rs4 ,b x w\ld be futile to attempt to expla9 h[ !y diff] f "o ano!r 9 a "w l ?is4 ,9 pr9ciple !y are alike4 ,! precise =ms ( in/rum5t us$ may v>y1 b ev5 !re !re is mu* 9 common betwe5 !m4 ,z "t goes on !re w inevitably be a t5d5cy to m & m uni=mity4 ,t is always ! case1 = "s ?+s are inh]5tly bett] ?an o!rs1 & rival sy/ems1 al?\gh ea* is work+ along its own l9es1 always come to v mu* ! same result 9 ! end4 ,)\t mak+ any comp>isons1 x is safe to say t if ! ,telefunk5 sy/em1 = example1 has any po9ts ( sup]iority ov] ! ,m>coni1 ! latt] w soon] or lat] f9d out ! fact1 & w modify _! app>atus accord+ly4 ,9 all probability ?is w op]ate bo? ways1 & "s ?+s :i* ! ,g]man sy/em is n[ us+ w give place to ^? :i* ! ,briti% h 9 op]ation4 ,9 ano!r v mod]n indu/ry ?is is v app>5t4 ,hav+ att5d$ & c>efully /udi$ sev]al annual exhibitions ( fly+ ma*9es1 ,i h notic$ ) great int]e/ h[ ! v>y+ types ( a few ye>s ago are m]g+ into ! m or less uni=m types ( to-day4 ,& x has be5 ! same ) wireless telegraphy1 & w be /ill m s 9 ! future4 ,! be/ means ( g5]at+ ! waves & ! be/ means ( detect+ !m at a di/ance--t is ! :ole problem1 & all ! work]s 9 x w soon] or lat] come to mu* ! same conclusions z to :i* are ! be/ ways4 ,pat5ts may d a little to delay ?is1 b n mu*4 ,= "o ?+1 pat5ts only la/ a few ye>s4 ,= ano!r1 a pat5t only cov]s a p>ticul> way ( do+ a p>ticul> ?+4 ,a ma*9e t is t]m$ pat5t is (t5 ! subject ( a hundr$ pat5ts1 ea* cov]+ a p>ticul> little po9t4 ,x is well-nigh impossible to pat5t a :ole ma*9e4 ,a g5]al pr9ciple _c be pat5t$1 only a p>ticul> application ( t pr9ciple1 & s !re are 9 a great _m cases little v>iations ( a pat5t$ me?od :i* are q z good z ! pat5t$ "o1 & :i* c be us$ freely4 ,s ev5 pat5ts w n h mu* effect1 9 all probability1 ^u ?is unification process4 ,b1 h[ev] t may be1 !re is no d\bt t ! :ole _w owes a deep debt ( gratitude to ! m5 :o h work$ out ?is mo/ b5efic5t ( inv5tions4 ,x is difficult to ?9k ( a s+le "o :i* has ev] br\ght su* a load ( b5efits to poor1 /ruggl+ humanity z ?is has4 ,! %ip 9 di/ress1 ! ligh?\se man on 8 lonely islet1 ! explor] 9 ! ,pol> regions1 ! pione] settl] 9 ! new l&s--9 fact1 j ^? :o mo/ ne$ "s connect+ l9k ) _! fell[s--are ! p to :om ! wireless telegraph br+s aid & com=t4 ,all hon\r to ! m5 :o h done x4 ,,*apt] ,,xiii ,,h[ ,,pictures ,,c ,,be ,,s5t ,,by ,,wire ,! s5d+ ( a message by telegraph is easily und]/&able4 ,v>i\s comb9ations ( two simple signs1 su* z %ort s\nds & long s\nds1 c readily be made to indicate lett]s by :i* ! words c be spelt out4 ,nor does ! s5d+ ( s\nd ov] a wire make a v great dem& ^u ! cr$ulity4 ,we all "k t s\nd consi/s ( innum]able little waves 9 ! air1 & by ! simple/ ( devices ^! c be conv]t$ into v>iations 9 an electric curr5t1 :i* v>iations1 by means equally simple1 c be made to re-conv]t !mselves back into s\nd waves at ! o!r end4 ,b to transmit a picture is ano!r matt] altoge!r4 ,x seems b>ely possible 9 ! case ( a draw+ su* z a p5-&-ink sket*1 :i* consi/s ( a comp>atively small numb] ( def9ite l9es2 b ) a %ad$ sket* or a photograph1 ) its gradations ( light & %ad[--to transmit su* w\ld seem to be beyond ! b\nds ( possibility1 did we n "k t x has be5 done4 ,! description ( ! me?ods w !re=e con/itute a n un9t]e/+ subject = a *apt]4 ,x is wor?y ( rem>k t an attempt along ^! l9es 0 made _m ye>s ago by a man nam$ ,caselli1 & a description ( ?is pione] app>atus w =m a good introduction to ! lat] developm5ts4 ,9 ,fig4 #ac we see a squ>e :i* repres5ts a %eet ( t9foil1 ^u :i* is drawn1 9 non-conductive ink1 a simple geometrical figure4 ,! ink may be grease1 or %ellac v>ni%1 inde$ !re are _m sub/ances :i* are available = use z an insulat+ ink4 ,across ! squ>e !re are a numb] ( p>allel dott$ l9es1 b ^!1 x mu/ be und]/ood1 are n actually drawn ^u ! foil--_! purpose w be app>5t 9 a mom5t4 ,suppose t we connect ! foil to "o pole ( a batt]y1 & ! o!r pole by a flexible wire to a metal p5 or /ylus4 ,if we place ! po9t ( ! p5 9 contact ) ! foil1 we make a complete circuit1 ?r\gh :i*1 ( c\rse1 curr5t w fl[4 ,b if1 ) x1 we t\* "o ( ! non-conductive l9es1 !re w be no curr5t4 ,illu/ration3 ,,fig4 #ac ,illu/ration3 ,,fig4 #ad ,tak+ a rul]1 !n1 let u draw ! po9t ( ! /ylus across ! foil 9 a s]ies ( p>allel /raight l9es4 ,x is ^! excursions ( ! /ylus :i* ! dott$ l9es are int5d$ to repres5t4 ,= ne>ly ! :ole ( ! "t curr5t w be fl[+2 b :5ev] ! /ylus is cross+ "o ( ! l9es ( non-conductive ink !re w be a mom5t>y cessation4 ,?us1 ! read] w beg9 to p]ceive1 we obta9 :at we may call an electrical repres5tation ( ! figure drawn ^u ! foil4 ,& n[ let u turn to ,fig4 #ad4 ,!re1 too1 is a squ>e1 b 9 ?is case x is n foil1 b pap] :i* has be5 soak$ 9 prussiate ( pota%4 ,! reason = introduc+ ?is *emical is t x is susceptible to electrical action4 ,:]ev] curr5t passes ?r\gh x1 x becomes *ang$ into ,prussian blue1 s t if we place ! po9t ( a p5 ^u ! pap]1 & cause curr5t to fl[ out ( t po9t ?r\gh ! pap]1 !re we get a blue dot4 ,if1 :ile ! curr5t is fl[+1 we draw ! p5 along1 we get a blue l9e4 ,fig4 #ac !re=e repres5ts 9 pr9ciple ! s5d+ app>atus ( ,caselli's writ+ telegraph1 :ile ,fig4 #ad repres5ts ! receiv+ in/rum5t4 ,! two p5s are connect$ toge!r by ! ma9 wire1 9 su* a mann] t1 :5 ! po9t ( ! "o is 9 contact ) ! b>e foil curr5t fl[s out ( ! o!r & into ! pap]2 b z ! =m] crosses an ink l9e all curr5t ceases4 ,if1 !n1 :ile ! s5d+ p5 is drawn l9e by l9e across ! foil1 ! o!r is drawn at ! same spe$1 l9e by l9e1 across ! *emically prep>$ pap]1 we %all get on ! latt] a s]ies ( l9es z %[n 9 ,fig4 #ad almo/ cont9u\s1 b brok5 "h & !re4 ,ea* breakage repres5ts a passage ( ! s5d+ p5 across a l9e1 & tak5 toge!r1 z w be se51 !y con/itute a reproduction ( ! geometrical figure drawn ^u ! foil4 ,z %[n1 ! l9es are r f> ap>t1 & s ! reproduction is n a v good "o4 ,!y are only drawn s1 h[ev]1 9 ord] t ! pr9ciple may be %[n ! m cle>ly4 ,!y may be drawn s t !y ov]lap1 & !n ! effect is v mu* bett]1 ! receiv$ picture be+ almo/ an exact reproduction ( ! o!r4 ,x w be notic$ t an ess5tial to ! success ( ?is me?od is t ! two p5s %\ld move 9 p]fect unison1 & t 0 ! great difficulty4 ,caselli us$ an arrangem5t ( p5dulums1 ! be/ ?+ available at ! "t4 ,! reproduction is1 9 photographic language1 a negative1 a some:at unsatisfactory feature ( ! me?od4 ,a simple modification1 h[ev]1 ( ! electrical connections w rev]se t1 s t ! reproduction %all be a positive4 ,!re are two ways ( cutt+ (f a curr5t f any p>ticul> circuit4 ,"o is to int]pose a resi/ance1 ?r\gh :i* curr5t _c pass 9 an appreciable quantity1 & ! o!r is to provide a second pa? = ! curr5t s mu* easi] ?an ! fir/ t practically all ! curr5t w pass t way1 leav+ ! fir/ circuit1 to all int5ts & purposes1 free4 ,x is z if a f>m] wi%$ to /op p pass+ across a c]ta9 field4 ,two me?ods w\ld be op5 to him3 "o to put up a high gate ov] :i* no "o w\ld d>e to climb1 & ! o!r to provide a %ort cut s mu* m pleasant & conv5i5t ?an ! old pa? t no "o hav+ ! *oice ( ! two ways w\ld ?9k ( go+ ! old way4 ,:at ! f>m] w\ld call a %ort cut ! electrician calls a %ort circuit1 & a %ort circuit is (t5 a m conv5i5t way ( cutt+ (f a curr5t ?an a swit* :i* int]poses resi/ance4 ,at all ev5ts1 9 a case l ?is1 a %ort circuit enables t to be accompli%$ :i* w\ld be v difficult by any o!r means4 ,9 ! app>atus z already describ$ ! batt]y _h to drive ! curr5t along a long wire1 t]m9at+ at ! di/ant receiv+ in/rum5t1 :5ce ! curr5t return$ via ! e>?4 ,! foil & p51 act+ z a k9d ( electrical tap1 controll$ ?is4 ,:5 foil & p5 t\*$1 ! tap 0 op5 & curr5t fl[$4 ,:5 ! l9e ( non-conductive ink int]pos$ itself1 ! tap 0 (f & ! fl[ ceas$4 ,b connect ! batt]y directly to ! wire1 & place ! foil & p5 9 a %ort bran* circuit1 & ! :ole ?+ is rev]s$4 ,!n ! op5+ ( ! tap s5t curr5t to ! o!r end2 n[ ! op5+ ( ! tap causes x to fl[ r\nd ! %ort bran* & leave ! ma9 wire4 ,!n ! clos+ ( ! tap /opp$ ! curr5t rea*+ ! f>!r end2 n[ x causes x to d s4 ,9 fact1 ! entire action ( ! app>atus is completely rev]s$1 & ! b>e p>ts ( ! foil become repres5t$ by blank pap]1 :ile ! insulat+ l9es produce ! m>ks4 ,9 %ort1 a positive results in/ead ( a negative4 ,su* 0 ! s*eme ( ,caselli ye>s ago4 ,x is m5tion$ "h at "s l5g?1 s9ce ! pr9ciple ( x is l>gely re-us$ 9 an improv$ =m 9 ! mo/ successful ( mod]n app>atus = a l purpose4 ,x und\bt$ly 0 a v excell5t s*eme1 simple & effective1 :i* ought to h succe$$2 b x did n d s1 = ! suffici5t reason t at t "t k ( electricity & skill 9 con/ruct+ delicate me*anism 7 n s highly develop$ z !y are to-day4 ,= success1 z has already be5 said1 "o ?+ 0 ess5tial1 & t ?+ v difficult to obta9--a p]fect syn*ronism betwe5 "o /ylus & ! o!r4 ,if ! "o 7 b ! slighte/ degree out ( /ep ) ! o!r1 failure foll[$ inevitably4 ,s ! electrical transmission ( sket*es dropp$ = ! "t be+4 ,m rec5tly a p]fectly successful solution ( ! problem has come 9 ano!r way altoge!r4 ,?is app>atus1 at fir/ call$ ! telautograph1 b n[ kn[n z ! telewrit]1 x w be m conv5i5t to ref] to lat]4 ,( mod]n sy/ems = ! transmission ( pictures ! mo/ successful1 probably1 are ! ,korn telautograph & ! ,?orn-,bak] telectrograph4 ,bo? ( ^! are able to transmit v fair reproductions ( photographs besides l9e draw+s4 ,! difficulty ) photographs is1 ( c\rse1 t _m p>ts ( !m are n ( equal blackness or :it5ess1 b %ade (f gradually f "o into ! o!r4 ,take ! case ( a simple portrait4 ,"p ( ! subject's face w be pure :ite1 :ile ! side 9 %ad[ w be comp>atively d>k4 ,!re is no h>d & fa/ l9e betwe5 ! two1 b by a gradation ?r\gh an inf9ite numb] ( %ades ! "o tones into ! o!r4 ,h[ c x be possible to convey t1 m or less me*anically1 ov] a wire8 ,! solution is due to ! fact t ! eye w bl5d toge!r a numb] ( di/9ctly diff]5t %ades1 if prop]ly arrang$1 into a gradual *ange4 ,really ! *ange is /ep by /ep1 b ! effect is app>5tly q cont9u\s4 ,?is c be se5 9 ! half-tone illu/rations 9 ?is book4 ,close exam9ation w %[ t su* a picture is cut up into small squ>es4 ,9 ! pure :ite "p ! squ>es are invisible1 :ile 9 ! p]fectly black p>ts1 if !re be any1 !y are s m]g$ into "o ano!r z to be insep>able4 ,b ev]y:]e else 9 ! picture x w be se5 t !re are squ>es ea* ) a dot 9 ! middle4 ,9 ! d>k] p>ts ! dots are l>ge2 9 ! light] ones !y are small4 ,we get ! effect almo/ ( col\r1 al?\gh ! picture is done entirely 9 black ink4 ,! eye does n see ! individual dots :5 we are j look+ at ! picture2 we h to exam9e x v closely to f9d !m4 ,yet !y are !re all ! "t1 & x is simply ! peculi> action ( ! eye :i* sees beautiful half-tones1 %ad+ imp]ceptibly "o into ano!r1 :]eas 9 real fact !re are only a va/ numb] ( equidi/ant dots1 all equally black4 ,we see1 !re=e1 t x is possible to split up a picture ( any k9d into a numb] ( small squ>es & to treat ea* squ>e z be+ ( equal d>kness ?r\gh\t4 ,!n1 if we c communicate by wire t p>ticul> degree ( d>kness to a di/ant /ation1 :]e ! small p>ts c be put toge!r 9 _! prop] ord] & giv5 _! correct %ade1 ! picture z con/ruct$ at ! receiv+ end w be some?+ l t at ! s5d+ end4 ,& we h only to make ! size ( ea* sep>ate squ>e small en\gh to obta9 a copy :i* w resemble ! orig9al v closely inde$4 ,9 ! e>ly days x 0 actually propos$ to telegraph pictures by ord9>y telegraphy1 us+ ?is pr9ciple4 ,! sugge/ion 0 to agree ^u a code ( tw5ty-six %ades1 ea* call$ by a lett] ( ! alphabet4 ,"o %ade 0 to be a1 ! next b1 & s on4 ,!n ! picture 0 to be divid$ up into squ>es1 & ! p>ticul> %ade ( ea* squ>e telegraph$ by means ( ! correspond+ lett]4 ,! %ades ?us communicat$ 7 to be put toge!r at ! receiv+ end1 on a pre>rang$ sy/em1 & s ! picture 0 to be built up4 ,giv5 pl5ty ( "t1 t s*eme might be mod]ately successful1 b to get a really good reproduction ! subdivision ne$s to be s m9ute1 & ! numb] ( squ>es1 !re=e1 s imm5se1 t x w\ld be quick] to s5d ! picture by tra9 ?an to telegraph x by su* labori\s means4 ,9 a fairly co>se half-tone block ! squ>es are1 say1 #bejj to ! squ>e in*4 ,t numb] ( lett]s w\ld !re=e h to be telegraph$ = e squ>e in* ( picture transmitt$1 to say no?+ ( ! difficulty ( build+ up a picture ( su* a great numb] ( p>ts & giv+ to ea* ! desir$ %ade4 ,t idea1 abortive ?\gh x is 9 its crude =m1 illu/rates v cle>ly ! fundam5tal pr9ciple on :i* ?is "w is done4 ,! problem is really to devise a ma*9e :i* w d t same ?+ rapidly & automatically divide up ! orig9al into a l>ge numb] ( squ>es1 & !n s5d an electric curr5t to repres5t ea* squ>e1 su* curr5t by its /r5g? to indicate ! %ade ( ! squ>e3 & f9ally a simil> in/rum5t is ne$$ to act z receiv]1 & to reproduce ^? squ>es 9 ! prop] ord]1 giv+ to ea* its correct %ade4 ,9 practically all ( !m ! me*anism is rotatory1 ! orig9al be+ plac$ ^u a drum :i* turns r\nd "u a /ylus1 or its equival5t1 :ile ! /ylus gradually travels along f end to end aft] ! mann] ( ! ne$le ( a phonograph1 or else ! same result be+ a*iev$ by ! drum itself hav+ an endwise movem5t z well z a rotative "o4 ,! receiv+ in/rum5t is ( simil> =m1 & bo? mu/ />t toge!r1 move at ! same spe$ & inde$ pres]ve a p]fect correspond5ce ) ea* o!r4 ,if ! di/ance be great betwe5 ! two !re may be difficulties due to ! ret>dation ( ! curr5ts pass+ betwe5 !m4 ,electricity does n pass ?r\gh long wires1 p>ticul>ly if !y be "u ! sea1 ) any?+ l ! quickness :i* we are apt to ?9k4 ,ov] a %ort l9e & "u fav\rable circum/ances ! receipt ( a telegraph signal at ! f>!r end is practically in/antane\s1 b on long l9es1 & "u c]ta9 conditions1 t is f> f be+ ! case4 ,!n some?+ has to be done to quick5 ! action ( ! curr5t1 or else ! receiv+ drum mu/ be made to lag beh9d ! s5d+ drum by ! requisite am\nt4 ,9 "s cases1 too1 ! transmitt+ app>atus loses a little "t 9 s5d+ (f ! curr5ts1 & t1 too1 has to be all[$ =1 s t1 all ?+s consid]$1 ! read] w see t ! successful solution ( ?is problem is h$g$ ab\t ) _m subtle difficulties :i* are probably only appreciat$ by ^? :o are well acqua9t$ by sad exp]i5ce ) ! little vag>ies ( bo? electricity & me*anical devices4 ,nei!r ( !m does q :at we want x to d2 ea* suff]s f little faults1 :i* 9 ! case ( a delicate problem l ?is1 :]e a diff]5ce ( a hundr$? ( a second w\ld be fatal to success1 introduce difficulties almo/ insup]able4 ,to transmit l9e draw+s1 ,pr(essor ,korn uses a s5d+ in/rum5t v l t ( ,caselli4 ,! picture is plac$1 ei!r by h& or photographically1 ^u a %eet ( copp] foil1 :i* is fix$ r\nd ! rotat+ cyl9d]1 ! l9es be+ =m$ ( non-conduct+ mat]ial4 ,! foil be+ electrifi$ & ! /ylus connect$ to ! l9e or ma9 wire1 curr5ts pass to ! f>!r end j z 9 ! old app>atus4 ,at ! receiv+ end ! drum is cov]$ ) photographic pap] & enclos$ 9 a light-tight box4 ,?r\gh a hole 9 ?is box a f9e p5cil ( light passes f a lamp1 suitable l5ses be+ us$ to ensure t ! p5cil %all h1 z x 71 a v f9e po9t1 produc+ a v small spot ( light ^u ! pap]4 ,if ! light rema9s q /eady1 ! drum mean:ile rotat+1 a l9e w be drawn by x ^u ! pap] :i* w be visible :5 ! latt] is develop$4 ,s9ce ! drum n only turns ^u its axis1 b also moves endwise "o hundr$? ( an in* at e revolution1 ?is l9e w be a spiral1 ! turns ( :i* w be "o hundr$? ( an in* ap>t4 ,?us ! pap] w be black$1 practically uni=mly1 all ov]4 ,%\ld ! int5sity ( ! light v>y1 h[ev]1 ! l9e w at times be light] ?an at o!rs1 :ile1 %\ld x be cut (f altoge!r = a mom5t1 !n !re w be a correspond+ gap 9 ! l9e1 & x is easy to see t if ^! light] p>ts or gaps occur 9 ! correct places !y w =m a picture4 ,9 o!r words1 by controll+ t light we c build up a picture ^u ! pap]4 ,! "q is h[ to control x4 ,pr(essor ,korn uses a =m ( ! ,e9?ov5 galvanomet] already describ$4 ,in/ead ( ! silv]$ fibre g5]ally employ$ 9 ?is in/rum5t1 a silv] wire is fitt$1 ! movem5t ( :i* p>tly or entirely cuts (f ! p5cil ( light4 ,! ,korn transmitt] = photographs is q diff]5t1 al?\gh ! receiv] is practically ! same z :at has j be5 describ$4 ,! basis ( x is a peculi> p[] possess$ by ! metal sel5ium :5 9 a c]ta9 /ate4 ,?is1 l all metals1 is a conductor ( electricity1 b ( c\rse (f]s resi/ance 9 "s degree4 ,n[ ! special feature ( sel5ium is t its resi/ance is r$uc$ if light %9e ^u x4 ,suppose1 !n1 t curr5t be fl[+ ?r\gh a mass ( sel5ium & t ! latt] be sudd5ly illum9at$ brightly1 ! resi/ance w at once fall & ! curr5t increase4 ,on ! o!r h&1 %\ld ! light fall+ ^u ! sel5ium dim9i%1 its resi/ance w increase & ! curr5t fl[+ ?r\gh x w decrease4 ,9 %ort1 giv5 a suitable arrangem5t1 ! curr5t fl[+ 9 a circuit ( :i* a sel5ium cell =ms a "p w increase or decrease ) ! increase or decrease 9 ! light fall+ ^u ! cell4 ,a :ile ago ! pap]s 7 tell+ /rik+ /ories ( a way by :i* bl9d p1 s x 0 said1 7 to be recomp5s$ = ! loss ( _! sight--a new s5se1 z x 71 0 to be giv5 !m by :i* !y c\ld he> light1 ev5 if !y c\ld n see x4 ,all ?is _h ref]5ce to ?is curi\s prop]ty ( sel5ium1 x be+1 ( c\rse1 an und\bt$ fact t x w v>y an electric curr5t 9 accordance ) ! v>iations 9 ! light1 & if t curr5t be l$ ?r\gh a telephone receiv] a man1 by hold+ t to 8 e>1 c\ld1 9 a s5se1 he> ! v>iations 9 ! light4 ,illu/ration3 ,,! ,,telewrit] ,?is rem>kable in/rum5t transmits actual writ+ & draw+s1 ! receiv+ p5 copy+ precisely ! movem5ts ( ! s5d+ p5 ,9 ! ,korn transmitt] = photographs sel5ium is employ$ z foll[s3--,a transp>5t photograph is made1 on a celluloid or gelat9e film1 & ?is is fix$ ^u a glass cyl9d] m\nt$ z already describ$4 ,a p5cil ( light falls ^u ?is 9 mu* ! same way z 9 ! case ( ! receiv] j describ$1 &1 z ! cyl9d] revolves1 describes a f9e spiral l9e all r\nd & r\nd x4 ,moreov]1 ! light passes "r ?r\gh ! photograph & falls ^u a mirror inside1 (f :i* x is reflect$ on to a sel5ium cell4 ,at e mom5t1 !n1 ! light is fall+ ^u "s small "p ( ! photograph1 & ! am\nt ( x :i* gets ?r\gh & ultimately rea*es ! sel5ium dep5ds ^u ! d5sity ( t "p4 ,curr5t1 mean:ile1 is fl[+ f a batt]y ?r\gh ! sel5ium1 & !nce ov] ! ma9 wire to ! di/ant /ation4 ,z ! light p5cil traces its spiral pa? ov] ! roll$ up photograph e v>iation 9 ! d5sity ( ! picture is reproduc$ z a v>iation 9 ! curr5t ?r\gh ! sel5ium4 ,?is1 at ! remote end1 op]ates ! ,e9?ov5 galvanomet]1 ! movem5ts ( :i* v>y ! %ade ( ! spiral l9e be+ drawn ^u ! photographic pap]4 ,?is process takes place ) rem>kable cel]ity1 s t 9 a few m9utes ! innum]able v>iations con/itut+ a complete photograph c be transmitt$ & fai?fully record$ at ! di/ant end ( ! wire4 ,b p]haps ! mo/ successful ( ^! me?ods is t kn[n z ! telectrograph4 ,x is surpris+ly l ! s*eme ( ,caselli 9 pr9ciple1 & =ms ano!r example ( ! fact t good ideas (t5 fail ?r\gh lack ( ! prop] means to c>ry !m out4 ,mr ,?orne-,bak]1 ! inv5tor ( ! telectrograph1 has _h at 8 disposal accumulat$ /ores ( k & skill :i* did n exi/ 9 ,caselli's "t4 ,consequ5tly ! =m] has made a brilliant success :]e 8 pr$ecessor produc$ only an int]e/+ b some:at ineffective attempt4 ,ref]5ce has be5 made already to ! half-tone blocks :]e9 a ho/ ( small dots ( v>y+ sizes make up a picture4 ,n[ in/ead ( p>allel r[s ( dots p>allel l9es ( v>y+ ?ickness w give v mu* ! same result4 ,! =m] are made by photograph+ ! picture ?r\gh a %eet ( glass rul$ ) two sets ( l9es at "r angles to ea* o!r4 ,! latt] c be made by us+ a scre5 ) l9es "o way only in/ead ( two ways4 ,x is !re=e q easy = a blockmak] to produce a process block :]e9 l9es are us$ in/ead ( dots4 ,= ?is p>ticul> purpose1 h[ev]1 x is n an ord9>y block t is ne$$1 al?\gh x is 9 ess5tials v simil>4 ,! picture to be transmitt$ is photograph$ ?r\gh a scre5 z if a half-tone block 7 to be made4 ,! negative s obta9$ is !n pr9t$ by ! gum process on to a %eet ( s(t lead &1 aft] wa%+1 ! picture rema9s ^u ! lead 9 ! =m ( l9es ( insoluble gum on a backgr\nd ( b>e lead4 ,a squeeze 9 a press drives ! gum into ! lead1 & s gives ! :ole %eet a smoo? surface ov] :i* a /ylus w ride easily1 b :i* is1 nev]!less1 made up ( conductive p>ts & non-conductive p>ts1 ! latt] =m+ ! picture4 ,! lead %eet is !n put ^u a revolv+ cyl9d] & turn$ "u a mov+ /ylus 9 ! mann] ) :i* we are n[ famili>4 ,! %eet is plac$ ) ! l9es l5g?wise ( ! cyl9d] s t curr5t passes to ! /ylus except z x passes ov] ! bread? ( ! l9es1 & s simil> l9es are built up at ! di/ant end4 ,! receiv+ me*anism is ( ! electro-*emical type :i* ,caselli us$4 ,! curr5t passes f ! receiv+ /ylus to ! pap]1 & !re makes its m>k 9 a way t w be und]/ood f ! description ( ! e>li] app>atus4 ,! supreme advantage ( ?is me?od ( work+1 ov] t ( ,pr(essor ,korn1 is t ! op]ator c see :at he is do+4 ,to obta9 good results1 a numb] ( electrical adju/m5ts h to be made1 & :e!r he has got !m "r or wrong c be se5 z soon z ! picture beg9s to gr[ ^u ! receiv+ pap]4 ,if a little readju/m5t be ne$$ ! op]ator sees x & c set ?+s "r be=e ! really important "p ( ! picture beg9s to appe>1 :]eas ) ! ,korn app>atus he does n "k :at is happ5+ at all1 s9ce he c see no?+ until ! picture is f9i%$ & ! photographic pap] has be5 develop$4 ,x w be app>5t1 too1 to anyone :o has c>efully consid]$ ! wireless telegraphy *apt]s1 t x ought to be possible to make ! s5d+ /ylus or its equival5t control a wireless transmitt] & a wireless receiv] to op]ate ! receiv+ /ylus1 s z to be able to s5d pictures by wireless4 ,exp]im5ts to ?is end h be5 made ) "s measure ( success1 & soon] or lat] we are almo/ sure to he> t ! difficulties1 :i* are by no means small1 h be5 ov]come4 ,b we _c conclude ?is *apt] )\t a full] ref]5ce to t m>vell\s inv5tion1 ! telewrit]4 ,9 ?is a man makes a sket* ) a p5 on a piece ( pap]1 or maybe he writes a message1 & simultane\sly a p51 hundr$s ( miles away if ne$ be1 does precisely ! same ?+4 ,! receiv+ in/rum5t draws ! sket* l9e by l9e1 or x transcribes ! message 9 ! actual h&writ+ ( ! s5d]4 ,a little t\*1 almo/ weird 9 its naturalness1 is t e n[ & !n ! receiv+ p5 leaves ! pap] & dips itself into a bottle ( ink1 aft] :i* x resumes its "w at ! v spot :]e x left (f4 ,n[ h[ ! complicat$ l9es & curves1 ! /rokes & dots :i* make up a writt5 language1 ev5 ! little %akes & defects :i* give ea* man's writ+ a p]sonality ( its own1 h[ all ^! c be s5t ov] a wire is at fir/ sight v difficult to und]/&4 ,! inv5tor ( ?is app>atus has discov]$ an extremely simple way ( do+ x4 ,b ev5 he does n attempt to d x ) "o wire1 x %\ld be said1 = he uses two4 ,?is is no drawback :51 z is (t5 ! case1 x is us$ 9 conjunction ) a telephone1 = ! latt]1 to be effective1 also requires two wires4 ,ye>s ago s+le wires 7 employ$ = telephones z = telegraphs1 ! circuit be+ complet$ ?r\gh ! e>?4 ,b ! difficulty arose t e wire ?r\gh :i* curr5ts fl[ is apt to induce curr5ts 9 neighb\r+ wires--! induction coil is bas$ ^u t fact--& s messages 9 "o wire 7 ov]he>d on o!rs1 or1 :at 0 p]haps m annoy+ /ill1 ! dots & da%es pass+ 9 a telegraph wire w\ld produce l\d noises 9 a telephone wire t happ5$ to be ne>4 ,! use ( two wires1 h[ev]1 entirely removes t tr\ble1 = ! neighb\r+ curr5t !n induces two curr5ts in/ead ( "o1 "o 9 ea*1 & x s happ5s t ^! are oppos$ to ea* o!r1 s t !y neutralise ea* o!r4 ,s e telephone wire n[ is d\ble & !re=e is ready1 z x 71 to h ! telewrit] fitt$ to x4 ,b ev5 ) two wires ! difficulty seems insup]able until we rememb] t ! mo/ complex ( curves c be resolv$ into two simple movem5ts4 ,! s5d+ p51 ) :i* ! orig9al writ+ or draw+ is done1 is atta*$ to ! junction ( two light rods4 ,! f>!r end ( ea* rod is atta*$ to ! end ( a light crank fix$ s t x c rotate or oscillate1 aft] ! mann] ( cranks1 9 ! plane ( ! desk ^u :i* ! pap] lies4 ,all ! jo9ts m5tion$ are ( ! h+e nature1 s t z ! p5 is mov$ ab\t ! rods turn1 m or less1 "o way or ! o!r1 ! two cranks4 ,?is simple me*anism1 x w be obs]v$1 c>ries out v effectively ! pr9ciple j m5tion$1 = x resolves ! motion ( ! p51 no matt] h[ complicat$ x may be1 into a simple rotat+ motion ( ! two cranks4 ,s ! cranks turn ?is way or t z ! draughtsman makes 8 picture1 & x is v easy to arrange t _! movem5t %all v>y ! /r5g? ( two electric curr5ts1 :]eby we obta9 electric curr5ts v>y+ 9 accordance ) ! movem5t ( ! cranks4 ,?is is done by mak+ ea* crank op]ate a v>iable resi/ance or rheo/at4 ,:5 9 its extreme position on "o side ! crank p]mits curr5t to fl[ freely1 b z x moves ov] to ! o!r extreme position ! resi/ance 9 ! pa? ( ! curr5t is increas$4 ,su* an arrangem5t is a common feature 9 electrical app>atus4 ,s curr5t f a batt]y fl[s to ! two wires lead+ to ! di/ant /ation1 ea* pass+ ?r\gh ! rheo/at connect$ to "o ( ! cranks4 ,we may ?9k ( ! rheo/ats z taps :i* c be turn$ on or (f by ! action ( ! cranks4 ,let u imag9e t crank a is 9 ! position :5 ! curr5t fl[s freely--:5 ! electrical tap is fully op52 !n a /rong curr5t w fl[ along wire a1 return+ to ! s5d+ batt]y via ! e>?4 ,z t crank is mov$ ! curr5t w gradually be r$uc$1 until1 if x be mov$ "r ov] to ! o!r extreme1 ! curr5t w be at its feeble/4 ,illu/ration3 ,,fig4 #ae4--;,a ,message receiv$ by ,telewrit]4 ,arriv$ at ! o!r end1 ?is curr5t passes to a device :i* we may describe simply z a magnet s arrang$ t its action pulls r\nd a crank aga9/ ! re/ra9+ action ( a spr+4 ,n[ ! /rong] ! curr5t ! m does t magnet pull & ! f>!r does ! receiv+ crank turn4 ,! s5d+ crank v>ies ! resi/ance1 ! resi/ance v>ies ! curr5t1 ! curr5t v>ies ! /r5g? ( ! receiv+ magnet1 & ! magnet v>ies ! position ( ! receiv+ crank4 ,prop]ly adju/$1 !n1 ! motion ( ! crank at ! "o end is communicat$ ?r\gh t long *a9 ( causes & effects1 until at la/ x is repeat$ exactly by ! movem5t ( ! crank at ! o!r end4 ,! same ?+ occurs simultane\sly ov] ea* ( ! two wires1 crank a at ! s5d+ end communicat+ ov] wire a to crank a at ! o!r end1 :ile crank b communicates its motion ov] wire b to ! o!r crank b4 ,ea* s5d+ crank is closely imitat$ 9 its e action by ! correspond+ "o at ! di/ant /ation4 ,! two receiv+ cranks are connect$ by light rods to ! receiv+ p5 9 precisely ! same way t ! s5d+ p5 is connect$4 ,consequ5tly1 n only are ! sep>ate movem5ts ( ! two cranks repeat$ at ! remote /ation b ! complex movem5ts ( ! s5d+ p51 :i* gave rise to ! actions ( ! cranks1 are also convey$ to1 & repeat$ by1 ! record+ p54 ,! movem5ts ( ! fir/ p5 are resolv$ into rotat+ motions by ! two cranks1 ^! are transf]r$ to ! o!r cranks1 & _! movem5ts are 9 turn conv]t$ back into ! writt5 curves4 ,?us z ! p5 9 ! arti/'s h& draws 8 sket*1 s does ! automatic h& at ! o!r place1 x may be at a great di/ance1 repeat fai?fully 8 "w1 & ! sket* gr[s l9e by l9e simultane\sly at bo? ends4 ,!re is n space "h to detail h[1 by ano!r curr5t sup]pos$ ^u ^? ref]r$ to already1 ! receiv+-p5 is made to dip itself p]iodically into ! inkwell at ! w ( ! s5d]4 ,by a cunn+ use ( alt]nat+ curr5t ?is is done )\t 9 any way int]f]+ ) ! action ( ! cranks z describ$ above4 ,b ( c\rse !re is a sev]e limitation to ! usefulness ( ?is ma*9e1 inasmu* z ! draw+ has to be made at ! "t ( transmission1 & x c only be put on ! wire by ! h& ( ! arti/ himself4 ,,*apt] ,,xiv ,a ,,wond]ful ,,example ,,( ,,sci5ce ,,& ,,skill ,9 ! prec$+ *apt] ref]5ce 0 made to ! fact t = ! successful s5d+ ( pictures by wire "o ?+ 0 necess>y above all o!rs4 ,t "o ?+ consi/s 9 mak+ two ma*9es1 p]haps hundr$s ( miles ap>t1 />t work+ toge!r1 /op toge!r &1 :5 work+1 turn at exactly ! same spe$4 ,let ! read] j picture ! problem to himself1 & ask himself h[ su* an arrangem5t c be possible4 ,let him ?9k ( a t[n two hundr$ miles away & !n m$itate on ! possibility ( mak+ a ma*9e work+ 9 8 own room & ano!r 9 t di/ant t[n ma9ta9 p]fect unanimity 9 _! movem5ts4 ,! result ( su* reflection w probably be ! ass]tion t su* a ?+ is beyond ! b\nds ( possibility4 ,!n he w f9d ! foll[+ description ( h[ x is done extremely int]e/+4 ,9 ! fir/ place x mu/ be und]/ood t ea* ma*9e is driv5 by an electric motor4 ,! motors are design$ to run at #cjjj revolutions p] m9ute1 & !y drive ! cyl9d]s ( ! ma*9es ?r\gh ge>+ s arrang$ t ! latt] turn at #ej revolutions p] m9ute4 ,n[ ( all ma*9es p]haps ! mo/ docile & easily manag$ is ! direct-curr5t electric motor4 ,ea* su* ma*9e is made ) a view to its work+ at a c]ta9 spe$1 b t c be v>i$ )9 c]ta9 limits1 by simply v>y+ ! =ce ( ! curr5t :i* drives x4 ,& t =ce c be v easily v>i$ by ! use ( an in/rum5t call$ a rheo/at or v>iable resi/ance4 ,we are all famili> ) ! way 9 :i* ! eng9e-driv] regulates ! spe$ ( a locomotive1 by means ( a valve 9 ! /eam-pipe4 ,! op5+ & clos+1 m or less1 ( ! valve enables ! spe$ to be *ang$ at w & adju/$ to a nicety4 ,! rheo/at is to ! electric curr5t :at ! valve is to ! /eam2 x c be op5$ & clos$1 m or less1 z necess>y4 ,by x ! curr5t driv+ ! motor c be made /rong] or weak]1 & z t *ange is made s does ! spe$ ( ! motor *ange accord+ly4 ,?us we see t !re is at h& ! means ( sett+ a motor to "w at any desir$ spe$4 ,! difficulty1 h[ev]1 is to tell :5 ! desir$ spe$ has be5 atta9$4 ,"o c c\nt ! revolutions ( a ma*9e at two or ?ree revolutions p] m9ute ) a c]ta9 am\nt ( accuracy1 b fifty revolutions p] m9ute are m ?an "o c\ld c\nt correctly4 ,/ill less c\ld we c\nt ! #cjjj revolutions e m9ute ( ! motors4 ,?us1 ev5 if we _h ! two motors side by side1 we %\ld h extreme difficulty 9 mak+ !m "w at ! same spe$ exactly4 ,"o might be do+ #cjjj :ile ! o!r did #biij or #cjaj & we %\ld be none ! wis]4 ,& :5 we sep>ate ! two by a di/ance ( _m miles1 ! task ( syn*ronis+ !m is ev5 worse4 ,b =tunately !re is a simple contrivance by :i* we c tell v accurately ! spe$ ( a motor4 ,! read] has already be5 famili>is$1 9 previ\s *apt]s1 ) ! diff]5ce betwe5 direct or cont9u\s electric curr5ts & alt]nat+ ones4 ,x is ! cont9u\s sort :i* is us$ to drive ^! motors1 b a slight addition to ! ma*9e w make x s t :ile direct curr5t is put 91 to drive x1 alt]nat+ curr5t c be drawn out ( x4 ,two little insulat$ metal r+s are fitt$ on to ! sp9dle ( ! ma*9e1 & ^! are connect$ 9 c]ta9 ways to ! wires ( ! motor2 !n aga9/ ^! r+s1 z !y turn1 !re rub two little metal arms1 call$1 because ( _! sweep+ action1 bru%es2 & f ^! bru%es we c draw ! alt]nat+ curr5t4 ,= our pres5t purpose ! importance ( ?is lies 9 ! fact t ! rate at :i* t curr5t w alt]nate dep5ds ^u ! spe$ ( ! motor4 ,z ! motor increases or decreases 9 spe$1 s w ! rate ( alt]nation increase or decrease4 ,s t if we c measure ! rate at :i* ! curr5t drawn f ! motor is alt]nat+1 we %all "k f t ! rate at :i* ! ma*9e is work+4 ,?is we c d by ! aid ( a frequ5cy met]4 ,! work+ ( ?is is bas$ ^u ! act+ ( a tun+-=k4 ,ev]yone kn[s t a giv5 tun+-=k always gives out ! same note4 ,! note dep5ds ^u ! rate at :i* ! =k vibrates1 & ! reason t "o =k always gives ! same note is because x always vibrates at ! same rate4 ,t rate1 9 turn1 dep5ds ^u its l5g?4 ,if "o 7 to file a little (f ! end ( a tun+-=k1 its note w\ld be rais$1 because its rate ( vibration w\ld become fa/]4 ,simil>ly1 l5g!n+ ! =k w\ld result 9 a l[] note be+ giv54 ,?us1 a tun+-=k1 or any b> ( /eel held by "o end1 & free to vibrate at ! o!r1 gives u a /&>d ( spe$ :i* is v reliable4 ,& x s happ5s t we c easily use a set ( su* =ks to te/ ! rate ( alt]nation ( an alt]nat+ curr5t4 ,g5]ally speak+1 alt]nat+ curr5t is no use = en]gis+ a magnet4 ,! *ief reason = t is t ! curr5t t5ds to get *ok$ up1 z x 71 9 ! coil4 ,alt]nat+ curr5t trav]ses a coil v reluctantly inde$4 ,x is1 h[ev]1 possible to make an electric magnet ( special design :i* w "w suffici5tly well ) alt]nat+ curr5t to answ] our pres5t purpose4 ,& x w be cle> t j z ! alt]nat+ curr5t itself consi/s ( a s]ies ( %ort curr5ts1 s ! =ce ( ! magnet w be int]mitt5t2 x w give n a /eady pull1 z is usually ! case ) magnets1 b a succession ( little tugs4 ,!re w1 9 fact1 be "o tug = e alt]nation ( ! curr5t4 ,a simple =m ( motor fitt$ up z j describ$1 & rotat+ at #cjjj revolutions p] m9ute1 w\ld give out #ajj alt]nations p] second4 ,if1 !n1 su* curr5t 7 employ$ to en]gise a magnet1 t magnet w\ld give #ajj tugs p] second4 ,s a small /eel b> ( ! "r l5g? to give #ajj vibrations p] second c be fix$ ) its free end ne>ly t\*+ su* a magnet1 & :5 ! curr5t is turn$ on x w v soon be vibrat+ vigor\sly4 ,= ! tugs ( ! magnet w agree ) ! natural rate ( vibration ( ! b>4 ,& j z ! two p5dulums describ$ 9 ,*apt] ,,xii4 respond$ readily to ea* o!r1 s ! b> responds readily to ! pulls ( ! magnet4 ,b increase or decrease ! rate ( alt]nation ev] s slightly1 & t sympa?y betwe5 magnet & b> is de/roy$4 ,! b> w n !n respond4 ,x w only answ] :5 ! pulls ( ! magnet & ! natural rate ( vibration ( ! b> exactly correspond4 ,s x is usual to place five or six su* b>s ) _! ends ne> ! "o magnet4 ,! l5g?s ( ! b>s v>y slightly1 s t ! rates ( vibration are1 say1 #ih1 #ii1 #ajj1 #aja1 #ajb respectively4 ,let u1 9 imag9ation1 adju/ ! spe$ ( a supposititi\s motor until we get t :i* corresponds to #ajj alt]nations4 ,we swit* on ! curr5t & at fir/1 possibly1 we get no response f any ( ! vibrat+ b>s4 ,j a t\* to ! h&le ( ! rheo/at & we notice t b> #ajb %[s signs ( life4 ,we see !n t our fir/ spe$ 0 mu* too fa/1 & t r$uc+ x has br\ght x d[n to #ajb1 :i* is /ill a little too fa/4 ,j a little m movem5t ( ! h&le1 & #ajb beg9s to relapse into quiet1 :ile #aja %[s animation4 ,a little m movem5t & #aja gives place to #ajj1 & !n we "k t our motor is work+ at ! desir$ spe$4 ,if our motor _h be5 too sl[ to comm5ce )1 x w\ld h be5 #ih :i* fir/ got into action1 b ! me?od ( adju/m5t w\ld h be5 precisely ! same4 ,& ?us we see ! :ole s*eme4 ,we regulate ! spe$ by ! rheo/at1 & mean:ile t tell-tale /ream ( alt]nat+ curr5t comes fl[+ out ( ! motor to indicate to u :at ! spe$ is1 :ile ! frequ5cy met]1 ) its v>i\s vibrat+ b>s1 int]prets to u ! message :i* ! alt]nat+ curr5t br+s to u4 ,s by wat*+ ! met] we "k :5 we h got ! spe$ t we desire4 ,b ev5 t is only half ! battle4 ,we h se5 h[ to make a ma*9e turn at any desir$ spe$1 & s we c adju/ any two1 s t !y revolve at ! same spe$1 b we h n se5 h[ to />t & /op ! two ma*9es at ! same "t4 ,fir/ ( all1 x mu/ be und]/ood t 9 ! case ( ! receiv+ ma*9e !re is a friction clut*1 z x is t]m$1 betwe5 ! motor & ! cyl9d] :i* x is driv+4 ,t means t :ile1 "u ord9>y circum/ances1 ! motor drives ! cyl9d] r\nd1 we c1 if we l1 hold ! latt] /ill )\t /opp+ ! motor4 ,:5 we d s1 ! connection betwe5 ! two simply slips4 ,s if we fit a cat* on ! cyl9d] :i* is capable ( hold+ x f rotat+1 we c /ill />t ! motor1 & ! latt] w "w4 ,!n1 ! mom5t ! cat* is releas$ ! cyl9d] w beg9 to turn too4 ,! commone/ =m ( friction drive is ! flat lea!r belt ^u two pulleys1 :i* ev]yone has se5 at "s "t or o!r 9 a factory4 ,& x w be q easy to conceive h[1 if "o ( ! driv5 ma*9es 7 to /ick1 ! belt might simply slip ^u "o ( ! pulleys1 yet1 z soon z ! ma*9e became free aga91 x w\ld rotate j z x did be=e4 ,x is j ! same ) :at we are consid]+4 ,! motor works cont9u\sly at its prop] spe$1 b ! cyl9d] c be /opp$ :5 desir$ by ! cat*4 ,comb9$ ) ! cat* is an electro-magnet1 & ?r\gh its coils !re fl[s ! curr5t ( electricity :i* is engag$ 9 pr9t+ ! picture on ! cyl9d]4 ,if a magnet be arrang$ to attract ano!r magnet1 x w d s only :5 ! en]gis+ curr5t fl[s "o way4 ,:5 x fl[s ! o!r way1 x does n attract4 ,!re=e x is easy to arrange matt]s s t ! pr9t+ curr5t1 ?\gh pass+ ?r\gh ! coil ( ! magnet1 %all n pull op5 ! cat*4 ,b if t curr5t be rev]s$ 9 direction = a mom5t ! magnet gives a pull1 op5 flies ! cat*1 & away goes ! cyl9d] ^u its revolution4 ,?us1 we see1 all t is necess>y to />t ! receiv+ cyl9d] is to rev]se ! curr5t = a mom5t4 ,& n[ let u turn our att5tion to ! s5d+ ma*9e4 ,^u its cyl9d] !re is an arrangem5t :i* automatically rev]ses ! curr5t fl[+ to ! ma9 wire once 9 e revolution4 ,normally ! curr5t fl[s to ! wire z describ$ 9 ! la/ *apt]1 c>ry+ by means ( its v>iations ! details ( ! picture = reproduction by ! receiv+ ma*9e at ! o!r end4 ,b = an in/ant once 9 e revolution t curr5t is int]rupt$ & a curr5t s5t 9 ! opposite direction in/ead4 ,?is ! s5d+ ma*9e does ( itself1 q automatically4 ,& n[ ! read] kn[s ( all ! app>atus2 x rema9s only to see h[ ! diff]5t p>ts "w 9 comb9ation4 ,/&+ by ! s5d+ ma*9e we fir/ ( all turn on ! curr5t1 :i* goes c\rs+ along ! wire to ! di/ant /ation4 ,!n we set ! motor to "w & ! cyl9d] beg9s to rotate4 ,be=e x has complet$ a s+le revolution ! rev]s] is op]at$1 & j = a mom5t ! rev]se curr5t goes to ! wire4 ,on arrival at ! o!r end t lifts ! cat* & ! receiv+ cyl9d] />ts4 ,t fir/ p>tial revolution ( ! s5d+ cyl9d] c\nts = no?+4 ,real bus9ess beg9s :5 ! rev]s] fir/ acts1 & t is ! mom5t :5 ! receiv+ cyl9d] also beg9s to move4 ,simil>ly1 :5 ! s5d+ cyl9d] /ops x s5ds no m rev]s$ curr5ts1 & s ! receiv+ cyl9d] is caught by ! cat* & n releas$4 ,s />t+ & /opp+ are q automatic4 ,! same arrangem5t enables a cont9ual readju/m5t ( ! relative spe$ ( ! two cyl9d]s to take place4 ,) all ! be/ devices1 ! tun+-=ks & ! re/1 x is /ill impossible to atta9 p]fect unanimity1 b ! v>iation 9 a s+le revolution _c be en\gh to matt]2 x is only :5 ! error 9 "o revolution goes on multiply+ itself t s]i\s diff]5ce might arise1 & t is prev5t$ 9 ! foll[+ beautifully simple way4 ,! motor :i* drives ! receiv+ drum is s regulat$ t x travels slightly fa/] ?an does ! o!r4 ,?us ! receiv+ cyl9d] completes e revolution slightly 9 advance ( ! o!r1 & consequ5tly x is /opp$ & held by ! cat* e "t4 ,! cat* reta9s x1 ( c\rse1 until ! rev]se curr5t arrives & releases x4 ,?us n only does ! s5d+ cyl9d] />t ! o!r :5 ! op]ations fir/ comm5ce1 b x does s e revolution4 ,e revolution1 !re=e1 ! two cyl9d]s />t toge!r4 ,s ! two cyl9d]s are set1 accord+ to ! frequ5cy met]1 at z ne>ly z possible exactly ! correct spe$s1 & ! action ( ! rev]s]1 ! rev]se curr5t & ! cat*1 ensures q automatically t at ! comm5cem5t ( e revolution !re %all be p]fect agreem5t betwe5 ! two4 ,no accumulation ( errors c possibly occur1 & ! problem1 ?\gh app>5tly s difficult1 if n insup]able1 at fir/ sight1 is surm\nt$4 ,,*apt] ,,xv ,,sci5tific ,,te/+ ,,& ,,measur+ ,sci5ce1 :e!r x be ( ! pure v>iety1 t :i* is pursu$ = its own sake--= ! m]e gre$ = k--or appli$ sci5ce1 ! purpose ( :i* is to assi/ manufacture1 is bas$ entirely ^u accurate te/+ & measur+4 ,x is only by discov]+ & inve/igat+ small diff]5ces 9 size1 weight or /r5g? t "s ( ! mo/ important facts c be br\ght to light4 ,!re are "s problems1 too1 t defy !ory1 s9ce !y are too complicat$2 !y involve too _m !ories all at once1 & su* c only be solv$ by accurate te/s4 ,& all ^! necessitate ! use ( v +5i\s & (t5 co/ly devices4 ,electrical measur+ in/rum5ts 7 ( suffici5t importance & int]e/ to w>rant a *apt] ( _! own1 b !re are _m o!rs ( great value1 & n )\t int]e/ to ! g5]al read]4 ,= example1 "s ye>s ago !re 0 a collision 9 ! ,sol5t1 j (f ,c[es1 betwe5 ! cruis] ,hawke & ! giant l9] ,olympic4 ,! cause ( ?is 0 a subject ( dispute & ( litigation2 ! !ori/s !oris$2 "s rea*$ ! conclusion t ! ,hawke 0 to blame1 & o!rs ! ,olympic2 & :]e doctors disagree :o %all decide8 ,x 0 wisely decre$ t te/s %\ld be made to settle ! "q4 ,! ma9 po9t 0 ?is4 ,! (fic]s ( ! ,hawke1 by f> ! small] vessel1 av]r$ t !y 7 drawn out ( _! c\rse by suction caus$ by ! movem5t ( s l>ge a %ip z ! ,olympic 9 ! comp>atively n>r[ & %all[ wat]s ( ! ,sol5t2 9 o!r words1 t ! ,olympic 9 mov+ ?r\gh ! wat] caus$ a swirl+1 eddy+ motion 9 ! wat]1 t5d+ to draw a light] vessel t[>ds itself4 ,& t is j "o ( ^? problems ) :i* !ory is unable to deal4 ,s x 0 transf]r$ to ! ,national ,physical ,laboratory at ,t$d+ton1 ne> ,london1 = inve/igation by exp]im5t4 ,at ?is in/itution1 :i* is a semi-national "o1 !re is a tank con/ruct$ = purposes su* z ?is4 ,! ^w tank leads u to und]e/imate its size some:at1 = x is #did feet long & #cj feet wide4 ,x is solidly con/ruct$ ( concrete1 ) a m9iature set ( docks at "o end1 & a slop+ bea* at ! o!r4 ,on ei!r side are rails ^u :i* run trollys :i* support ! ends ( a bridge :i* spans ! :ole4 ,?is bridge c be propell$ along1 by means ( electric motors op]at+ ! :eels ( ! trollys1 f "o end ( ! tank to ! o!r1 at any desir$ spe$1 )91 ( c\rse1 reasonable limits1 & f x may be t[$ any model :i* x is desir$ to te/4 ,! models us$ are usually made ( wax1 by means ( a ma*9e specially design$ = ! purpose4 ,x %\ld be expla9$ t ! plans ( a %ip consi/ ( a s]ies ( curves1 ea* ( :i* repres5ts ! cont\r ( ! vessel at "o p>ticul> height4 ,= example1 if y c imag9e a %ip cut horizontally into slices ( uni=m ?ickness1 !n ea* slice c\ld be %[n on ! draw+ 7! %e> plan1 z x is t]m$7 by a curv$ l9e4 ,ne> ! keel ! l9es w\ld1 ( c\rse1 be almo/ /raight1 b !y w\ld bulge m & m z !y occur high] up4 ,& :at ?is ma*9e is requir$ to d is to make1 quickly & economically1 a wax model :i* %all be an exact reproduction1 on a small scale1 ( ! vessel "u discussion4 ,x may be--x mo/ (t5 is--a %ip z yet unbuilt1 ! behavi\r ( :i* x is desir$ to te/4 ,or x may be an exi/+ vessel1 z x 0 9 ! case m5tion$ j n[4 ,h[ev] t may be1 ! model is made f ! draw+s4 ,a block ( wax re/s ^u a table1 :ile ! draw+ is spread ^u a bo>d ne> by4 ,a po9t] is mov$ by h& along "o ( ! l9es1 & its movem5t is repeat$ by a rapidly revolv+ cutt] :i* cuts away ! wax to a simil> curve4 ,by suitable adju/m5ts ! cutt] c be made to magnify or r$uce ! size1 s z to produce any desir$ scale4 ,?us e l9e is gone ov] & a simil> curve cut 9 ! wax at ! correct height4 ,( c\rse ?is only produces a lump ( wax %ap$ 9 /eps1 z x 71 b x is !n q easy to trim x d[n by h&1 s z to produce a smoo? model ( ! %ip1 p]fectly accurate 9 its %ape1 & a copy on a small scale ( ! vessel portray$ on ! draw+4 ,x c also be holl[$ out1 balla/$ ) weights inside1 & s made to s9k to any desir$ level1 !reby repres5t+ ! vessel :5 fully load$1 half load$ & s on4 ,all sorts ( unequal load+ c be produc$ if ne$$1 inde$ e condition ( ! real %ip c be imitat$ 9 ! model4 ,x c !n be t[$ to & fro 9 ! tank by ! travell+ c>riage describ$ above4 ,! spe$ ( t[+ c be v>i$ by *ang+ ! spe$ ( ! motors :i* drive x4 ,! =ce ne$$ to pull ! model ?r\gh ! wat] is measur$ by means ( a dynamomet] :i* regi/]s ! pull on ! t[+ app>atus4 ,a matt] v (t5 ne$+ inve/igation is ! %ape & size ( ! wave ?r[n up by ! b[ ( ! vessel1 & ( t left beh9d h]1 kn[n z ! b[ wave & ! /]n wave respectively4 ,^! waves repres5t wa/$ en]gy1 = !y are no use & are produc$ actually by ! p[] ( ! eng9es ( ! %ip z !y drive h] along4 ,! ideal %ip w\ld cause no waves1 b s9ce t is a degree ( p]fection impossible ev5 to hope =1 ! %ipbuild] has to cont5t himself by s design+ 8 %ips t ^! waves %all be z small z possible4 ,! waves are record$ photographically1 9 "s cases by ! k9ematograph4 ,"s ( ! l>ge %ipbuild]s h _! own tanks1 & s h ! naval au?orities ( ! great naval ,p[]s4 ,! "o at ,t$d+ton 0 e/abli%$ ?r\gh ! munific5ce ( a fam\s ,briti% %ipbuild]1 ,mr ,y>r[1 :o n only defray$ ! co/ ( con/ruction1 b gave an end[m5t to assi/ 9 its upkeep4 ,x is int5d$ to s]ve ! ne$s ( ! small] build]s :o h n tanks ( _! own1 & also = ! inve/igation ( matt]s ( g5]al int]e/ to %ipbuild]s1 & = su* te/s z t relat+ to ! ,hawke & ,olympic4 ,9 ?is la/-nam$ case1 ( c\rse1 two models 7 made1 "o to repres5t ea* %ip1 & !y 7 t[$ along 9 su* a way z to imitate v closely ! movem5ts ( ! %ips at ! "t :5 !y collid$4 ,x 0 z ! result ( ^! te/s t ! ,olympic 0 ord]$ to pay damages to ! ,admiralty1 x be+ held t %e 0 ! cause ( ! accid5t4 ,a v int]e/+ inve/igation ( ?is k9d 0 rec5tly c>ri$ out 9 ! tank at ! ,unit$ ,/ates ,navy ,y>d4 ,! port ( ,new ,york consi/s v l>gely ( jetties project+ out f ! banks ( ! riv]4 ,) ! gr[? ( ! ,atlantic l9] ! old jetties _h become too %ort1 & que/ions arose z to ! elongation ( !m4 ,if x 7 done1 h[ w\ld x effect ! curr5t 9 ! riv]1 & ! h&l+ ( %ipp+ g5]ally8 ,if1 on ! o!r h&1 x 7 n done1 :at w\ld be ! effect ( ! %ips ly+ ) _! ends project+ out into ! /ream unprotect$ by a jetty4 ,to det]m9e ^! po9ts ! exp]im5tal tank 0 conv]t$ into a model ( ! ,new ,york ,h>b\r1 or at all ev5ts ( t "p 9 connection ) :i* ^! que/ions arose4 ,a false floor 0 put 91 s z to make ! dep? exactly "r 9 proportion to ! wid?4 ,little model jetties 7 arrang$ to repres5t exactly ! real ones1 :ile aga9/ !m 7 moor$ model vessels1 s t ! effect ^u !m c\ld be obs]v$ z ! model ( ! l>ge vessel 0 t[$ pa/4 ,9 addition to ?is1 special appliances 7 arrang$ = f9d+ out :at ! di/urbance might be :i* ! movem5t ( a giant l9] produces "u ! surface z well z above x4 ,= ?is purpose buoyant balls 7 employ$1 moor$ at v>i\s di/ances bel[ ! surface1 f :i* ?9 rods project$ upw>ds1 ! movem5t ( :i* r5d]$ visible ! movem5ts ( ! subm]g$ balls & !re=e ! effects ( ! "u-wat] curr5ts4 ,all ^! ?+s _h to be obs]v$ at "o & ! same "t--! mov+ model itself1 ! models alongside ! jetties1 ! commotion on ! surface1 ! sway+s to & fro ( ! rods atta*$ to ! subm]g$ floats--all1 or mo/ ( :i*1 at all ev5ts1 x 0 impossible to make self-record+4 ,yet1 see+ t x 0 ( ! utmo/ importance t ! relations betwe5 all ^! ?+s %\ld be obs]v$1 & record$ f "t to "t z ! model 0 t[$ along1 x is evid5t t some?+ mu/ be done1 & a cunn+ use ( ! k9ematograph solv$ ! problem q easily4 ,at v>i\s po9ts comm&+ a good view ( ! model h>b\r & its %ipp+ ^! ma*9es 7 plac$1 & s sev]al s]ies ( photographs 7 obta9$1 by ! /udy ( :i* all ! diff]5t movem5ts c\ld be se5 & comp>$4 ,a l>ge dial too 0 rigg$ up ^u ! travell+ c>riage by :i* ! model 0 t[$1 a f+] on :i* d5ot$ ! di/ance :i* ! c>riage _h travell$ at any mom5t4 ,?is l>ge dial came into ea* photograph1 ( c\rse1 & s ea* picture bore ^u itself a cle> record ( t p>ticul> mom5t 9 ! voyage ( ! model to :i* x ref]r$4 ,?us we see an in/ance ( h[ ! v late/ & mo/ up-to-date me?ods ( amusem5t are sometimes appli$ to s]ve v practical purposes4 ,ak9 to ! exp]im5ts ^u %ips are a]ial exp]im5ts to det]m9e matt]s connect$ ) ! navigation ( ! air4 ,at ,b>r[-9-,furness ! great firm ( ,vick]s1 %ipbuild]s & armam5t manufactur]s1 & latt]ly build]s ( a]ial craft = ! ,briti% ,admiralty1 h erect$ a ma*9e = te/+ ! effici5cy ( a]ial propell]s & o!r ?+s ( a k9dr$ nature4 ,^u ! top ( a tall t[] !re is pivot$ a long arm ( light iron framework4 ,to ! end ( ?is a propell] c be fix$1 s t z ! arm revolves !re is produc$ almo/ exactly ! same conditions z ^? :i* prevail :5 a propell] drives an a]oplane or /e]able balloon4 ,by means ( suitable me*anism ! propell] c be turn$ at any desir$ spe$1 ) ! result t x drives ! arm r\nd & r\nd ^u its pivot on ! top ( ! t[]4 ,! =ce :i* ! propell] ?us ex]ts c easily be measur$1 & s c be det]m9$ su* que/ions z ! mo/ effici5t spe$ = ea* type ( propell]1 ! p[] :i* any p>ticul> "o c develop1 ! be/ =m = ea* p>ticul> ne$1 & s on4 ,mat]ials1 too1 require ! mo/ c>eful te/+1 9 ord] t !y may be put to ! be/ possible use 9 mod]n ma*9]y & /ructures4 ,= example1 anyone c measure ! /r5g? ( a spr+1 b :at d we "k z to its la/+ p[]8 ,spr+s (t5 h to =m "p ( a ma*9e 9 :i* !y are /ret*$ & compress$ millions ( times1 & ! "q arises z to :at is ! be/ %ape & mat]ial = ! purpose4 ,x may be t ! spr+ :i* works be/ a few times w be ! fir/ to become we>y1 = ) repeat$ /ra9 su* ?+s z /eel get tir$1 j z ! human frame does4 ,n[ t is a matt] :i* w yield to no calculation1 ! only way to det]m9e x is actual te/4 ,s a me*anism has to be employ$ :i* w ext5d & compress ! spr+ ov] & ov] aga91 j z x w be 9 actual use1 ) a c\nt] ( ! nature ( a cyclomet] to c\nt h[ _m times x has be5 subject$ to ?is di/ortion4 ,!n ! app>atus is set go+ & left to itself = h\rs1 or ev5 = days1 dur+ :i* "t x may "w ! spr+ millions ( times4 ,?is may g on until x breaks1 or else x may be done a pre>rang$ numb] ( times1 & !n ! spr+ tak5 out & te/$ by o!r means to see h[ its /r5g? has be5 affect$4 ,metal b>s are (t5 subject$ to sudd5 bl[s1 light 9 !mselves b (t repeat$4 ,! po9t to be det]m9$ !n is h[ _m times ! bl[ may fall be=e p]man5t injury is done to ! b>4 ,to inve/igate su* matt]s we h ! repeat$-impact ma*9e4 ,! b> is held 9 a suitable hold]1 "u a hamm] :i* gives x a bl[1 ! =ce ( :i* c be easily regulat$1 at regul> int]vals1 ! numb] ( bl[s be+ c\nt$ by a suitable record+ me*anism4 ,ultimately ! b> breaks1 "u a bl[ ! l ( :i* x c endure s+ly )\t any app>5t /ra9 at all4 ,! ma*9e1 by ! way1 c be caus$ to turn ! b> r\nd to "s degree aft] ea* bl[1 s t x is /ruck f all directions 9 succession4 ,! microscope1 too1 has e/abli%$ its place 9 ! te/+ laboratory4 ,x is a v valuable adjunct to *emical & me*anical te/s4 ,suppose1 = example1 t a b> ( /eel is be+ inve/igat$2 x c be put into a ma*9e & pull$ until x breaks 9 two4 ,! ma*9e regi/]s ! am\nt ( ! pull :i* 0 appli$4 ,or a small piece c be put "u a press & compress$ to any desir$ degree4 ,x c also be te/$ by impact or ev5 pull$ ap>t by a sudd5 bl[1 z describ$ 9 ,me*anical ,inv5tions ( ,to-day4 ,! b> c be support$ by its ends & load$ or pull$ d[n 9 ! c5tre1 s t its p[] ( resi/+ b5d+ c be det]m9$4 ,x c be judg$1 too1 f its *emical composition4 ,/eel1 9 p>ticul>1 dep5ds = its prop]ties v l>gely ^u its *emical composition4 ,! diff]5ce betwe5 ca/-iron1 wr\ght-iron & /eel1 also ! diff]5ces betwe5 ! innum]able v>ieties ( /eel1 are due almo/ entirely to ! admixture ( a c]ta9 p]c5tage ( c>bon ) ! metal4 ,?is c be asc]ta9$ by *emical analysis4 ,?is =m ( inquiry has ! advantage ov] ! m purely me*anical me?ods 9 t ! latt]1 = ! mo/ "p1 h to be appli$ to ! b> z a :ole1 :]eas ! quality may v>y 9 diff]5t p>ts1 ! surface 9 p>ticul> be+ liable to diff] f ! int]ior4 ,9 su* cases1 "o analysis c be made ( a piece cut f ! surface & ano!r ( a piece f ! c5tre4 ,& x is "h1 too1 t microscopical analysis comes 94 ,= ?is purpose a piece is sawn (f ! b>1 & ! end gr\nd p]fectly smoo?4 ,?is is !n wa%$ 9 a suitable *emical1 su* z a mild acid1 :i* acts diff]5tly ^u ! diff]5t mat]ials ( :i* ! metal is built up1 !reby r5d]+ !m visible "o f ano!r4 ,a photograph tak5 ?r\gh a microscope !n %[s ! /ructure ( ! metal2 h[ ! diff]5t con/itu5ts are built toge!r4 ,?is is kn[n z metallographic te/+1 & its advantage z comp>$ ) *emical analysis is t ! latt] %[s1 z we might say1 :at are ! bricks ( :i* ! ?+ is built1 :ile ! =m] %[s h[ ! bricks are arrang$4 ,inde$ x is h>dly correct to speak ( ! advantage or sup]iority ( "o ov] ! o!r1 s9ce ea* is ! complem5t ( ! o!r1 supply+ ! in=mation :i* ! o!r fails to give4 ,& !re are o!r me*anical te/s :i* h n yet be5 m5tion$4 ,!re are ma*9es :i* twi/ a b> s z to discov] its p[] to resi/ torsion1 !re are o!rs :i* apply a d[nw>d pressure on "o "p ( ! b> & an upw>d "o on an adjac5t "p1 s z to %[ its capabilities 9 )/&+ %e>+ /ra94 ,moreov]1 _m ( ^! te/s are n[adays1 9 a well-equipp$ te/+-h\se1 c>ri$ out 9 conjunction ) ! use ( heat4 ,x /&s to reason t a "p ( a ma*9e :i* w h to "w "u consid]able heat may h to be ( diff]5t mat]ial f a "p :i* works "u a normal temp]ature4 ,9 "s cases ! b> is surr\nd$ by a spiral wire ?r\gh :i* electric curr5t is pass+1 & by ! regulation ( ?is curr5t any desir$ temp]ature c be set up 9 ! b>4 ,or x may be plac$ 9 a ba? ( hot oil 9 su* a way t ! b> %all be rais$ to any temp]ature requir$1 )\t int]f]+ ) ! ma*9]y :i* ex]ts ! t5sion or pressure1 or :atev] x be4 ,ye>s ago su* elaborate te/s z ^! 7 nev] ?\ght (4 ,!re are c]ta9 well-kn[n figures1 to be f\nd 9 all eng9e]+ text-books1 :i* give :at /resses diff]5t mat]ials ought to be able to /&1 & ^! 71 & are /ill1 to a l>ge ext5t1 reli$ ^u1 x be+ tak5 = grant$ t ! mat]ial us$ w be up to ! av]age /&>d4 ,9 l>ge & important works1 h[ev]1 ! te/+ has be5 develop$ ^u sci5tific l9es1 s t x is kn[n f actual exp]im5t :at ea* p>ticul> ?+ is capable (4 ,?is n only means security b economy1 = x is sometimes f\nd t a sub/ance is /rong] ?an x is ?\ght to be1 & s ?+s made ( x c be design$ to give ! requisite /r5g? light] & *eap] ?an !y w\ld h be5 o!rwise4 ,"s ( ! ma*9es employ$ are ( enorm\s /r5g?1 capable ( ex]t+ a pull or a compression (1 x may be1 #ajj tons or m4 ,!y are (t5 made1 too1 ) self-record+ appliances1 :]eby ! c\rse ( ! te/ is set d[n automatically ^u a *>t4 ,= example1 :5 a b> is be+ te/$ = t5sion1 x is desirable to "k n only ! actual pull "u :i* x came 9 two1 b ! behavi\r ( ! te/ piece dur+ ! p]iod be=e t4 ,x beg9s to /ret* z soon z ! t5sion is appli$1 !oretically at all ev5ts1 & if ! metal 7 p]fectly ductile x w\ld /ret* cont9u\sly z ! load increases1 until at la/ ! break+ /ress is rea*$4 ,b 9 actual practice x probably /ret*es some:at by fits & />ts1 & a record ( t fact w be ( great value 9 e/imat+ ! /r5g? ( ! mat]ial 9 actual "w4 ,= su*1 an automatically made record1 :i* c be /udi$ at leisure1 is ( ! utmo/ importance4 ,b p]haps ! f9e/ in/ance ( sci5tific me?ods 9 manufacture is to be f\nd 9 ! me?ods by :i* /&>d p>ts ( ma*9es are measur$1 s z to ensure t !y %all be int]*angeable4 ,x may surprise ! casual read] to be told t an absolutely exact measurem5t is an impossibility4 ,x is safe to say t out ( a million simil> articles--articles made ) ! int5tion t !y %all be exactly alike--!re are no two :i* are1 9 fact1 absolutely simil>4 ,!y may be made ) ! same ma*9es & ! same tools1 h&l$ by ! same man1 b ma*9es & tools we> or get out ( adju/m5t1 :ile man's liability to err is prov]bial4 ,a/ronom]s are ! greate/ exp]ts 9 ! art ( measurem5t1 & !y recognise ! possibility1 nay1 ! probability1 ( error s frankly z to make e measurem5t sev]al times ov]2 if x be an important "o !y make x1 if possible1 a great _m times ov]1 & !n take ! av]age ( ! results4 ,by ?is means !y elim9ate1 to a c]ta9 ext5t at any rate1 ! error :i* _c be avoid$4 ,t process is to all[ = errors on ! "p ( _! in/rum5ts1 = ! mo/ "p4 ,to deal ) p]sonal errors ano!r me?od is us$ z well1 = x is kn[n t "s obs]v]s h a natural t5d5cy to err on "o side m or less1 :ile o!rs t5d to make mi/akes 9 "s degree on ! o!r side4 ,?is t5d5cy to err is kn[n z ! p]sonal equation ( ! obs]v]1 & !re are ma*9es & te/s by :i* ! p]sonal equation ( ea* man c be det]m9$1 or p]haps x w\ld be m correct to say e/imat$1 s t 9 all obs]vations made by him ! prop] all[ance c be add$ or d$uct$4 ,b ( c\rse x w\ld be extremely difficult to apply su* me?ods 9 a work%op4 ,x w\ld nev] d to h to measure ev]y?+ sev]al times ov]1 hop+ t ! av]age w\ld come out 9 su* mann] z to indicate t ! ?+ be+ measur$ 0 ! size requir$4 ,in/ead1 !re=e1 ( wa/+ "t seek+ an accuracy :i* is kn[n to be unatta9able1 ! manufactur+ eng9e] adopts a sci5tific sy/em ( measurem5t :]e9 a c]ta9 am\nt ( inaccuracy is det]m9$ ^u z p]missible1 & !n simple appliances are us$ to see t x does1 9 fact1 fall )9 ^? limits4 ,= in/ance1 a r\nd b> is to be made1 say1 an in* 9 diamet]4 ,n[ we "k f :at has j be5 said t1 :5 made1 we h no means ( tell+ :e!r ! b> is really & truly an in* 9 diamet] or n4 ,we consid]1 !n1 :at x is =1 & decide1 say1 t x w be ne> en\gh s long z we are sure t x is n l>g] ?an "o in* plus "o ?\s&?1 nor less ?an "o in* m9us "o ?\s&?4 ,s long z x does n exce$ or fall %ort ( its reput$ size by m ?an "o ?\s&? ( an in*1 !n we "k t x w answ] its purpose4 ,n[1 hav+ come to t decision1 we c build up a sy/em ^u :i* any intellig5t workman c proce$1 ) ! result t all ! in* b>s :i* he makes w be ! same size )9 ! limits ( #a_/ajjj ov] or "u1 s t ! greate/ possible diff]5ce betwe5 any two w be #a_/ejj4 ,?is sy/em involves ! use ( two gauges = e size4 ,! man employ$ ^u mak+ "o-in* b>s has a plate ) a hole 9 x #a-a_/ajjj in*es 9 diamet] & ano!r hole #iii_/ajjj ( an in* 9 diamet]4 ,"o ( ^! is ! g 9 gauge2 ! o!r is ! n g 94 ,s t all he has to d1 9 ord] to be q sure t 8 "w is "r1 is to see t x c be pok$ ?r\gh "o ( ^! holes1 b n ?r\gh ! o!r4 ,no tr\ble at all1 x w be obs]v$1 adju/+ f9e measur+ appliances1 simply a plate ) two holes 9 x1 & ! workman c be sure t he is turn+ out articles e "o ( :i* is practically correct1 ) no v>iation beyond a slight inequality too small to matt]4 ,& probably at "s o!r "p ( ! factory !re is a man mak+ articles ea* ( :i* has a hole 9 x1 into :i* ?is b> mu/ fit4 ,h[ does he manage8 ,he is provid$ ) a gauge some:at ! %ape ( a dumb-bell1 "o end ( :i* is slightly l>g] ?an ! o!r4 ,"o is ! g 9 end1 ! o!r ! n g 9 end4 ,if ! hole :i* he makes w p]mit ! =m] to ent]1 b w refuse admittance to ! latt]1 !n he kn[s t t hole is suffici5tly ne> its reput$ size to answ] its purpose4 ,illu/ration3 ,by p]mission ( ,! ,m9+ ,eng9e]+ ,co41 ,%effield ,a ,,m9]s' ,,rescue ,,team ,^! m5 are equipp$ ) brea?+ app>atus :i* enables !m to pass safely ?r\gh ! deadly fumes aft] an explosion1 to rescue _! un=tunate comrades ,9 ! in/ances m5tion$1 a ?\s&? ( an in* ei!r way has be5 m5tion$ z ! limit ( inaccuracy1 or ! tol]ance1 z x is sometimes t]m$1 b (t5 ! limits are mu* n>r[] ?an t4 ,! gauges !mselves are a case 9 po9t1 = !y mu/ be true )91 say1 a t5-?\s&?1 or ev5 less4 ,& !y too are *eck$ by ma/] gauges ( a f9] degree ( accuracy /ill1 be+ made by ! mo/ labori\s me?ods1 & *eck$ ov] & ov] aga91 s z to rea* ! utmo/ limits 9 ! way ( correctness4 ,s ?is me?odical sci5tific sy/em ( limit gauges is bas$ ^u ! pr9ciple ( hav+ "o gauge limit+ ! error "o way & ano!r def9+ x 9 ! o!r4 ,any?+ simpl] or m effective x w\ld be impossible to conceive4 ,x is due v l>gely to ?is sy/em t _m manufactur$ articles are n[ s mu* *eap] ?an !y us$ to be4 ,= x enables ea* individual "p to be made :olesale on a l>ge scale1 by ma*9es specially adapt$ to ! "w1 op]at$ by m5 specially tra9$ to "w !m1 ) ! practical c]ta9ty t ^! p>ts :5 assembl$ toge!r w fit ea* o!r4 ,9 conclusion1 !re is ano!r v int]e/+ in/rum5t :i* 0 fir/ made = a purely utilit>ian use--namely1 ! inve/igation ( ! me?ods ( mak+ col\r$ glass--b :i* has s9ce be5 appli$ to "s int]e/+ problems 9 pure sci5ce4 ,x is call$ ! ultra-microscope4 ,x mu/ fir/ be po9t$ out t !re is a limit to ! p[] ( ! ord9>y microscope1 beyond :i* ! skill ( ! optician _c g4 ,he is baffl$ at t po9t n because ( any lack ( ability on 8 own "p1 b because ( ! nature ( light itself4 ,an opaque object1 unless x be self-lum9\s1 :i* few ?+s are1 c only be se5 by reflect$ light4 ,g5]ally speak+1 we see ?+s because !y reflect 9 "s degree ! light :i* falls ^u !m4 ,b light consi/s ( waves1 & :5 we rea* an object s m9ute t its diamet] is ab\t half ! wave-l5g? ( light1 !n we _c see x because x is unable to reflect ! light on acc\nt ( its smallness4 ,we c see ?is any day by ! seaside1 or by a riv] or l>ge pond4 ,!re x is evid5t t ! waves & ripples are reflect$ by su* ?+s z l>ge /ones1 wood po/s or any?+ ( any size :i* come 9 _! way2 b :5 a wave enc\nt]s an object mu* small] ?an itself x simply swall[s x up1 z x 71 fl[s all ov] x or ar\nd x1 )\t be+ 9 any way reflect$ by x4 ,& x is j ! same ) ! waves ( light2 !y are unaffect$ by ob/acles bel[ a c]ta9 size1 & s are n reflect$ by !m4 ,= ?is reason ?+s small] ?an ab\t a sev5-?\s&? ( a millimetre _c possibly be se5 by a microscope 9 ! ord9>y way4 ,b if an object c be made self-lum9\s1 !n x c be se51 :atev] its size1 if ! magnify+ p[] ( ! microscope be great en\gh4 ,s ?is ultra-microscope1 z x is call$1 is really an ord9>y microscope ( ! highe/ p[] possible1 ) an add$ app>atus = mak+ ! t9y p>ticles :i* are be+ s\ght = self-lum9\s4 ,?is is done by direct+ ^u !m a p5cil ( light ( exce$+ int5sity4 ,g5]at$ by p[]ful arc lamps1 ! light is conc5trat$ by a sy/em ( l5ses until x is ( an almo/ incr$ible brightness1 aft] :i* x falls ^u ! object4 ,n[ at fir/ sight ?is seems to be no diff]5t f ! usual proc$ure ) a microscope1 & !re appe>s to be no reason :y x %\ld be m successful1 b ! explanation is ?is3 light is a =m ( en]gy1 & ! waves ( ?is v int5se beam1 fall+ ^u ! object1 ?r[ x into a /ate ( viol5t agitation1 by virtue ( :i* x %9es1 n ) reflect$ light1 b ) light ( its own4 ,x is n t ! waves are reflect$1 b t !y s %ake up ! p>ticle t x gives (f light waves itself4 ,& ?us x comes )9 ! range ( human vision4 ,9 ?is way1 n only h ! v small p>ticles ( col\r+ matt] 9 glass be5 se5 individually1 b x is ?\ght t ! actual molecules ( matt] h be5 se51 or if n ! molecules individually1 little gr\ps ( molecules1 danc+ & cap]+ ab\t1 j z sci5tific p = ye>s h believ$ !m to be do+1 al?\gh !y c\ld n see !m4 ,s "h we h an in/ance 9 :i* manufacture has aid$ sci5ce--an inv]sion ( ! usual ord] ( ?+s4 ,,*apt] ,,xvi ,,col\r ,,photography ,photography has introduc$ _m ( ! g5]al public to a bran* ( practical sci5ce :i* o!rwise !y w\ld nev] h c>$ mu* ab\t4 ,! action ( light ^u c]ta9 *emicals1 ! subsequ5t action ^u ! same ( o!r *emicals1 su* z develop]s1 ton+ solutions & s on1 =m a v well-kn[n region ( ! doma9 ( sci5ce4 ,& ?is is1 too1 a bran* ( *emi/ry 9 :i* ! practical inv5tor has be5 v busy4 ,! ef=ts1 !re=e1 :i* h be5 made to inv5t ways ( produc+ photographic pictures :i* %all give to ! objects _! natural col\rs1 w probably be ( special int]e/ 9 a book l ?is4 ,( ^! !re are two v well-kn[n sy/ems1 & to !m we w ma9ly conf9e our att5tion4 ,x %\ld fir/ be po9t$ out1 h[ev]1 t :at we are discuss+ is q diff]5t f ! simple or?o*romatic plates :i* are us$ by _m photograph]s4 ,^! latt] are coat$ some:at diff]5tly f o!r plates1 ) a view to _! giv+ a m reali/ic picture1 b ! result is /ill 9 "o col\r4 ,!y are1 9 fact1 a little m s5sitive to diff]5ces 9 col\r ?an ord9>y plates1 s t col\rs :i* appe>1 :5 ! latt] are us$1 v mu* ! same1 appe>1 :5 or?o*romatic plates are employ$1 a little diff]5t4 ,b ! diff]5ce 9 col\r 9 ! object photograph$ is only1 ev5 !n1 repres5t$ by a diff]5ce 9 %ade 9 ! picture4 ,! object is1 x may be1 9 _m col\rs1 9 all ! col\rs1 v likely1 b ! picture is only 9 "o4 ,& ! /ep f t to a col\r$ picture is a v long "o4 ,true1 ! solution ( ! problem is v simple 9 pr9ciple1 yet ! practical difficulties are s great t ev5 n[ !y h n be5 entirely ov]come4 ,let u fir/ ( all exam9e ! pr9ciple4 ,sunlight1 by :i* photographs are usually tak51 appe>s to ! eye :ite & col\rless4 ,x is n really s1 h[ev]1 z c be prov$ by analys+ x ) ! spectroscope4 ,9 ?is in/rum5t a flat beam ( light1 hav+ pass$ ?r\gh a n>r[ slit1 falls ^u a prism ( glass1 f :i* x em]ges z a broad b&1 kn[n z ! spectrum4 ,?is b& c be se5 ^u a scre51 or c be exam9$ ?r\gh a telescope4 ,s f> f be+ :ite & col\rless1 x consi/s ( ! mo/ lovely col\rs4 ,at "o end ( ! spectrum is a beautiful r$1 :i*1 z ! eye travels along1 imp]ceptibly m]ges into orange1 :i* 9 turn m]ges into yell[1 aft] :i* we f9d gre51 blue1 indigo & violet1 9 ! ord] nam$4 ,^! sev5 are kn[n z ! prim>y col\rs1 b x is q a mi/ake to suppose t !re are sev5 cle>ly def9$ & di/9ct col\rs4 ,! col\rs s *ange1 "o into ano!r1 t _! numb] is really inf9ite4 ,! sev5 names indicate sev5 po9ts 9 ! spectrum1 :]eat ! col\rs are suffici5tly di/9ct f o!rs to w>rant a sep>ate "n be+ giv5 to !m4 ,we call ! />t+ col\r r$1 = example1 & z we pass our eyes along we p]ceive a con/ant *ange1 & :5 t *ange has become suffici5tly pron\nc$ to ju/ify our do+ s1 we call ! new col\r orange4 ,cont9u+1 we f9d ! orange *ang+ into some?+ else1 & :5 x has gone f> en\gh1 we br+ 9 a ?ird "n1 yell[1 & s on to ! violet4 ,?us we see ! division into sev5 col\rs is arbitr>y1 & only = our own conv5i5ce1 s9ce ! :ole numb] ( col\rs is innum]able4 ,pass+ ?r\gh a prism is n1 h[ev]1 ! only means by :i* :ite light c be split up4 ,:5 ! sun %9es ^u a blue fl[]1 = in/ance1 ! blue petals p]=m a p>tial sep>ation2 !y reflect ! blue "p ( ! sunlight1 & absorb all ! re/4 ,a r$ fl[] likewise reflects ! r$ "p ( ! sunlight & absorbs ! re/4 ,x is because ?+s c ?us discrim9ate1 reflect+ "s k9ds ( light & absorb+ ! rema9d]1 t we p]ceive ?+s 9 diff]5t col\rs4 ,x foll[s1 !re=e1 t :5 we look ^u a l&scape1 or a field ( fl[]s1 we receive into our eyes an enorm\s v>iety ( col\r$ lights4 ,! :ite sunlight furni%es ea* ?+ we see ) a flood ( :ite light1 & ea* ?+ accord+ to its nature1 reflects m or less4 ,a :ite fl[] reflects ! :ole1 a pure black object reflects none1 b ! great majority ( ?+s reflect "s "p or o!r ( t inf9ite v>iety ( :i* :ite light really consi/s4 ,s a view at all v>i$ s5ds to our eyes a v>iety ( col\rs1 almo/ z manifold z ! col\rs ( ! spectrum1 :i*1 z has be5 said1 are inf9ite4 ,& ! task ( reproduc+ !m1 or ev5 ( produc+ a simil> g5]al effect1 ^u a piece ( pap] seems at fir/ sight beyond ! b\nds ( possibility4 ,b =tunately !re is a way by :i* we c produce1 approximately at all ev5ts1 ! int]m$iate col\rs by mixtures ( ! o!rs4 ,! second col\r ( ! spectrum1 = example1 orange1 c be obta9$ by mix+ its neighb\rs on ei!r h&--namely1 r$ & yell[4 ,we c1 inde$1 imitate v closely ! imp]ceptible *ange f r$ to yell[ ?r\gh orange1 by skilful mixture ( r$ & yell[ pigm5ts4 ,fir/ !re is ! pure r$1 !n j a sugge/ion ( yell[ is add$2 m & m yell[ br+s u to orange2 aft] :i* by gradually dim9i%+ ! am\nt ( r$ we rea* ! pure yell[4 ,next1 by introduc+ blue pigm5t1 we c gradually *ange ! yell[ into gre51 & fur!r manipulation ( ! same two col\rs w lead u on to pure blue4 ,inde$ by mixtures ( r$1 yell[ & blue we c obta9 almo/ all ! p]ceptible v>ieties ( col\r4 ,& x mu/ be rememb]$ t :51 by mix+ blue & yell[ pigm5ts1 we get ! effect ( gre51 t is only ! result ( an optical illusion4 ,! p>ticles ( :i* ! yell[ pigm5t is made rema9 yell[1 & ! p>ticles ( blue rema9 blue4 ,! "o sort reflect yell[ light to our eyes1 ! o!r sort reflect blue light1 & ow+ to :at 9 "o s5se may be call$ a defect 9 our vision1 ^! two m+l+ toge!r look z if ! :ole 7 gre54 ,9 ! spectrum we see real gre5 light2 f gre5 pa9t made by mix+ yell[ & blue1 we only see an imitation or artificial gre54 ,if ! p>ticles 7 l>ge en\gh1 we %\ld see ! yell[ & ! blue ones q sep>ate1 b s9ce !y are too small = u to see at all1 except 9 ! mass1 our eyes bl5d ! :ole toge!r into ! int]m$iate col\r4 ,?us we see t1 al?\gh ! v>iety ( col\rs is inf9ite1 we c = practical purposes reproduce z mu* diff]5ce z our eyes c p]ceive by ! judici\s bl5d+ ( ?ree--namely1 r$1 yell[ & blue4 ,& !re is a fur!r =tunate fact--we c filt] light4 ,! r$ glass ) :i* ! photograph] cov]s 8 d>k-room lamp looks r$1 & ?r[s a r$ light into ! room1 because x is act+ z a filt] to ! light proce$+ f ! lamp beh9d x4 ,! lamp is s5d+ out light ( _m col\rs1 b ! glass is only transp>5t to ! r$4 ,x holds up all ! o!rs b lets ! r$ pass freely4 ,s if we 7 to take a photograph ?r\gh a r$ scre51 we %\ld get on ! plate only ^? p>ts :i* 7 m or less r$ 9 col\r4 ,= example1 if we ?us photograph$ a gr\p ( ?ree fl[]s1 "o r$1 "o orange & "o yell[1 ! r$ "o w\ld come out prom95tly1 ! orange "o w\ld come out fa9tly1 & ! yell[ "o n at all4 ,!n suppose we took ! same picture aga9 ?r\gh a yell[ scre54 ,9 t case ! yell[ fl[] w\ld be prom95t1 ! orange w\ld aga9 be fa9t1 b ! r$ w\ld be abs5t4 ,hav+ got1 9 imag9ation1 two su* negatives1 let u make two c>bon pr9ts1 "o (f ea*4 ,& let ! pr9t (f ! fir/ negative be r$1 :ile t (f ! second is yell[4 ,let ea* be1 9 fact1 ( ! same col\r z ! scre5 ?r\gh :i* ! picture 0 tak54 ,f9ally1 let ! two films be plac$ 9 contact "o ^u ! o!r4 ,on hold+ ! two up to ! light1 :at %\ld we see8 ,we %\ld see a r$ fl[]1 = !re w\ld be a r$ fl[] cle>ly def9$ ^u "o film co9cid+ ) a blank transp>5t space ^u ! o!r film4 ,we %\ld see1 too1 a yell[ fl[]1 = a cle>ly def9$ yell[ fl[] on ! second film w\ld co9cide ) a cle> space ^u ! fir/4 ,we %\ld see also an orange-col\r$ fl[]1 = !re w\ld be a fa9t r$ image ( x1 & a fa9t yell[ image ( x1 "o on ea* film1 ly+ "o ov] ! o!r1 produc+ ! same effect z a mixture ( yell[ & r$ pigm5ts4 ,?us by tak+ two negatives ?r\gh two col\r$ scre5s1 & !n col\r+ ! pr9ts to correspond1 we c obta9 ?ree col\rs 9 ! f9i%$ picture4 ,by tak+ a ?ird negative1 ?r\gh a blue scre51 we c\ld add imm5sely to ! range ( col\rs obta9able4 ,inde$1 ) ?ree films1 r$1 yell[ & blue respectively1 made ?r\gh ?ree scre5s ( ! same col\r1 a v>iety ( col\rs practically inf9ite c be obta9$4 ,s ! pr9ciple is q simple2 ! difficulty is 9 c>ry+ x out4 ,= ! ?ree k9ds ( light h n ! same photographic p[]1 & s to avoid upsett+ ! balance ( ! col\rs diff]5t exposures w\ld be requir$ = ea*4 ,!n !re is ! difficulty ( s manipulat+ ! films z to get !m "o ov] ano!r exactly4 ,anyone :o has tri$ ! h&l+ ( c>bon pr9ts w readily realise h[ difficult ?is w\ld be4 ,x is possible & has be5 done1 b ! process is too unc]ta9 & too labori\s to be ( g5]al use4 ,b ! same result c be atta9$ m or less automatically1 z ! foll[+ descriptions w %[4 ,let u turn to ! ,lumi]e auto*rome process1 by :i* ! results desir$ c be 9 a l>ge measure atta9$ by me?ods ( manipulation comp>atively simple4 ,illu/ration3 ,by p]mission ( ,! ,m9+ ,eng9e]+ ,co41 ,ltd41 ,%effield ,,pneumatic ,,hamm] ,,drill ,?is tool is us$ by m9]s = mak+ holes 9 h>d rock1 prelim9>y to bla/+4 ,note ! spray ( wat]1 :i* prev5ts ! /one du/ ris+ & gett+ into ! m9]'s lungs4--,see p4 #bbj ,! plates us$ = ?is are ( a v special nature4 ,9 ! fir/ place1 !re is ! basis ( glass1 b ^u t !re is laid :at we might t]m ! selective scre54 ,?is is a lay] ( />* gra9s1 ( exce$+ smallness4 ,! size ( !m is z little z a half a ?\s&? ( an in* & !re are ab\t f\r millions ( !m on e squ>e in* ( plate4 ,next1 ^u ! scre5 ( />* gra9s is a lay] ( wat]pro( v>ni%1 :ile ov] t is ! ord9>y s5sitive emulsion su* z =ms ! ess5tial "p ( ! usual non-col\r plate4 ,n[ ! />* gra9s :i* =m ! scre5 are1 be=e !y are laid on1 /a9$ 9 ?ree col\rs4 ,"s are blue1 "s r$1 & "s a yell[i%-gre51 :i* exp]i5ce %[s is pref]able to pure yell[4 ,! diff]5tly col\r$ gra9s are well mix$1 & :5 ! scre5 is held to ! light & look$ ?r\gh ! effect is almo/ t ( cle> glass4 ,t is because r$ rays f ! r$ gra9s1 & gre5 & blue rays f ! gra9s ( ^? col\rs1 all proce$ to ! eye m+l$ toge!r4 ,?is plate is plac$ 9 ! cam]a diff]5tly f ! usual way1 s9ce ! glass side is turn$ t[>ds ! l5s4 ,! light1 !re=e1 aft] ent]+ ! cam]a1 passes ?r\gh ! glass1 !n ?r\gh ! scre51 & f9ally falls ^u ! s5sitive film4 ,suppose1 !n1 t ! cam]a 7 po9t$ to a r$ wall2 r$ light w\ld fall ^u ! plate &1 pass+ ?r\gh ! r$ gra9s1 w\ld act ^u ! s5sitive film beh9d !m4 ,! blue & gre5 gra9s1 on ! o!r h&1 w\ld /op ^? rays :i* fell ^u !m1 & s ^? p>ts ( ! s5sitive film :i* !y cov] w\ld rema9 unaffect$ by light4 ,!n1 if t plate 7 to be develop$1 a d>k1 opaque spot w\ld be produc$ ^u ! film "u ea* r$ gra91 ! film "u ! o!r gra9s rema9+ transp>5t4 ,h5ce1 :5 held up to ! light & look$ ?r\gh1 ! plate w\ld appe> a gre5i%-blue1 = all ! r$ gra9s w\ld be cov]$ up4 ,9 l mann]1 if ! wall 7 blue in/ead ( r$1 a gre5i%-r$ plate w\ld result1 :ile if x 7 gre51 ! plate w\ld be a purple1 ! result ( ! comb9ation ( r$ & blue4 ,b ?is1 x w be se51 is a topsy-turvy effect1 ! exact opposite ( :at we want1 s t x is =tunate t by a simple *emical me?od we c set x "r4 ,aft] a fir/ developm5t 9 ! ord9>y way ! plate is plac$ 9 ano!r ba? & expos$ to /rong daylight1 ) ! result t ^? p>ts :i* 7 d>k5$ by ! fir/ developm5t become cle> & ! p>ts :i* 7 cle> become opaque4 ,?us1 aft] ?is tw(old developm5t ( ! photograph ( ! r$ wall1 we f9d ourselves 9 possession ( a r$ plate1 9 :i* only ! r$ gra9s are visible1 s9ce all ! o!rs are cov]$ up by opaque p>ts ( ! s5sitive film4 ,! photograph ( ! blue wall w also1 aft] x has be5 subject$ to ! d\ble developm5t1 %[ blue only1 & ! same ) ! gre54 ,b suppose t in/ead ( a r$ wall or a blue wall we focus our cam]a ^u "o :i* is half r$ & half blue4 ,!n x is easy to p]ceive t we %all get a plate :i* is half "o col\r & half ! o!r4 ,moreov]1 x foll[s t a wall cov]$ ) a mosaic ( r$1 blue & gre5 w\ld give u a plate duly col\r$ 9 ! same way4 ,b :5 we g a /ep fur!r & photograph1 say1 a l&scape1 :i* may conta9 a va/ range ( col\rs1 we f9d a difficulty 9 believ+ t !y c all be r5d]$ by ! simple process ( cov]+ or leav+ uncov]$ gra9s ei!r blue1 r$ or gre54 ,x c be done1 h[ev]1 s9ce ! o!r col\rs may be made up ( two or m ( ^! ?ree 9 v>y+ proportions4 ,= example1 %\ld !re be some?+ 9 ! l&scape ( a d>k]1 m blue1 %ade ( gre5 ?an ! gre5 gra9s1 !n ! light proce$+ f t object1 :ile pass+ freely ?r\gh ! gre5 gra9s ^u :i* x falls1 w slightly p5etrate ! neighb\r+ blue ones z well1 & s at t po9t on ! plate !re w be n only gre5 gra9s visible1 b "s ( ! blue gra9s p>tly visible also4 ,! light f ! blue gra9s w ent] ! eye along ) t f ! gre5 gra9s1 & by s do+ w add j t am\nt ( blue to ! gre5 z to give x ! "r %ade4 ,aft] ?is mann] is ! :ole picture built up4 ,x is1 ( c\rse1 really a mosaic1 consi/+ entirely ( little col\r$ pat*es1 b s9ce !y are s small none c be se5 individually1 all m]g+ toge!r 9 ! eye s z to =m a picture 9 :i* col\rs *ange imp]ceptibly f "o into ano!r4 ,to sum up1 !n1 :at happ5s is ?is4 ,we />t ) a lay] ( col\r$ gra9s2 ! action ( tak+ & develop+ ! photograph cov]s up "s ( ^! gra9s & leaves o!rs expos$1 & ! action ( ! light is su* t ^? :i* are left visible produce a picture closely resembl+ ! orig9al1 n only 9 =m b 9 col\r4 ,b !re is "o o!r int]e/+ po9t ab\t ?is process :i* des]ves m5tion4 ,! diff]5tly col\r$ lights are n ( ! same p[] photographically4 ,r$ light1 z we "k well1 is v weak 9 ?is respect1 :]e=e1 we use x 9 ! d>k-room4 ,a fa9t r$ light w h no p]ceptible effect ^u a plate unless x be expos$ to x = "s "t4 ,blue light1 on ! o!r h&1 is v active1 & 7 ! blue & r$ lights to be all[$ to act equally on ! auto*rome plate1 ! result w\ld be mu* too blue4 ,x is !re=e necess>y to h&icap ! blue light1 z x 71 by plac+ a r$di%-yell[i% scre5 ei!r j 9 front (1 or j beh9d1 ! l5s to cut (f a proportion ( ! blue rays4 ,! o!r v successful process is kn[n z ! ,dufay diopti*rome process4 ,x diff]s v little f ! ,lumi]e except 9 detail1 ! selective scre5 be+ =m$ ( small col\r$ squ>es in/ead ( by a mass ( little gra9s4 ,9 bo?1 x w be notic$1 ! result is a s+le positive4 ,x is n1 z 9 ord9>y photography1 a negative (f :i* any desir$ numb] ( positive pr9ts c be made4 ,&1 moreov]1 x is a transp>5cy3 x _c be view$ except by light %9+ ?r\gh x4 ,! results are1 h[ev]1 extremely beautiful1 :5 well done1 & anyone :o c>es to try ei!r ( ^! me?ods ( work+ w be well repaid = ! tr\ble involv$4 ,,*apt] ,,xvii ,,h[ ,,sci5ce ,,aids ,,! ,,/rick5 ,,colli] ,no?+ is m *>act]i/ic ( ! pres5t age ?an ! c>e :i* is1 q rightly1 exp5d$ ^u ! com=t & safety ( ^? :o d ! manual lab\r ( ! community4 ,! /ores ( sci5tific k & skill are drawn ^u freely = ?is end1 & "s v int]e/+ examples c be giv5 ( ! truly sci5tific me?ods :i* h be5 evolv$1 n only = prev5t+ injuries ( any k9d1 b = succ\r+ ^? :o may1 despite ^? precautions1 fall victims to disease or accid5t4 ,an example has already be5 giv5 ( ! sci5tific inve/igation into ! nature ( colli]y explosions & ! be/ means ( prev5t+ !m4 ,we h se5 !re h[ exp5se has be5 p\r$ out lavi%ly 9 fitt+ up ! exp]im5tal gall]y or artificial pit1 & h[ ! mo/ cunn+ me*anical & electrical devices h be5 press$ into ! s]vice 9 ord] to f9d out j :at happ5s :5 an explosion occurs4 ,x has be5 relat$ h[ ^! inve/igations h reveal$ ) c]ta9ty ! true cause ( ! explosions & !reby l$ ! way to _! prev5tion4 ,b ) x all !re is /ill an occasional disa/]1 occurr+1 sometimes1 at ! be/ & mo/ c>efully manag$ colli]ies4 ,& !re=e x is /ill necess>y to provide = rescu+ ! un=tunate m5 :o are affect$4 ,x is wor? rem>k1 "h1 t colli]y explosions are1 all ?+s consid]$1 a v r>e occurr5ce4 ,because ( _! dramatic sudd5ness1 & ! numb] ( lives :i* are commonly lo/ 9 a s+le disa/]1 we are apt to magnify _! sev]ity 9 our m9ds & to picture ! life ( ! m9] z a v haz>d\s "o4 ,9 po9t ( fact1 ! expectation ( life1 z ! insurance p call x1 is q z great among ! coal-m9]s z among any class ( manual lab\r4 ,& ( ^? :o d meet an untimely end !re are m lo/ ?r\gh isolat$ accid5ts1 involv+ "o or two m51 ?an 9 ! great disa/]s4 ,to meet ^! isolat$ cases sci5ce is almo/ p[]less4 ,= ! mo/ "p1 !y are due to falls ( mat]ial f ! ro( ( ! m9e1 or "s simple accid5t ( t k9d1 caus$ by an error ( judgm5t or lack ( c>e on ! "p ( fell[-workm51 & ! only safegu>d aga9/ su* is ! mo/ c>eful & sy/ematic sup]vision1 :i*1 9 ,great ,brita9 at all ev5ts1 is rigidly appli$4 ,! und]gr\nd /aff are v c>efully organis$ ) ?is end 9 view1 & ! :ole is sup]vis$ by ,gov]nm5t inspectors4 ,no am\nt ( sci5tific inve/igation or inv5tion w help mu* 9 ^! matt]s4 ,) ! explosion or fire1 h[ev]1 x is diff]5t1 = !re subtle =ces & /range *emical influ5ces come into play ) :i* sci5ce is specially well fitt$ to deal4 ,to a great _m p ! fir/ news ( organis$1 tra9$ & sci5tifically equipp$ rescue p>ties came at ! "t ( ! t]rible ,c\rri]es disa/] 9 ,france1 :5 ov] #ajjj m5 lo/ _! lives4 ,= !n a p>ty ) app>atus hurri$ f ,g]many & play$ a prom95t "p 9 ! rescue op]ations4 ,b un=tunately ! glam\r ( _! p]=mance 0 some:at dimm$ by ! fact t aft] !y _h done all !y c\ld1 & _h gone home aga91 m m5 7 rescu$4 ,_m1 read+ ( t fact1 7 incl9$ to sc(f at ! new-fangl$ ideas1 ?9k+ t aft] all ! old way ( work+ ) a p>ty ( brave b untra9$ & (t5 ignorant volunte]s 0 bett] ?an ! new way ( work+ ) equipp$ & tra9$ m54 ,x c]ta9ly did seem z if ! =m] _h succe$$ :]e ! latt] _h fail$4 ,b t 0 q a mi/ake1 z subsequ5t ev5ts h %[n1 & 9 all probability x 0 due to ! fact t ! un9/ruct$ p>ty 7 local m51 ?or\ghly famili> ) ! m9e 9 :i* !y 7 work+1 its geography & its special local conditions1 :]eas ! tra9$ m5 came f f> away4 ,at all ev5ts ! pione] "w ( ! ,g]mans 9 ! matt] ( rescue teams has be5 amply ju/ifi$ by ! fact t o!r p h copi$ !m1 & none m ?or\ghly ?an ! m9+ au?orities ( ,great ,brita94 ,inde$ we see "h ano!r in/ance ( ! rem>kable way 9 :i* ! ,briti% p1 ?\gh a little sl[ to take up a new idea1 d take x up :5 x has once be5 e/abli%$1 & 9 su* a way t !y are soon among ! =emo/ 9 its use4 ,! ,g]mans1 all hon\r to !m1 />t$ ! rescue teams1 b at ?is mom5t !re are rescue teams & /ations = _! tra9+ 9 ,brita9 second to none 9 ! _w4 ,( ^! !re is a spl5did example 9 ! ,rhondda ,valley1 9 ,s\? ,wales1 support$ & work$ by ! own]s ( ! pits 9 t di/rict1 besides o!rs at ,ab]d>e1 9 ! same neighb\rhood1 at ,mansfield1 to s]ve ! colli]ies 9 ,d]by%ire & ,nott+ham%ire2 inde$ rescue /ations are n[ dott$ ?r\gh\t ! m9+ di/ricts4 ,! g5]al idea ( ^! /ations is z foll[s4 ,! build+ is c5trally situat$ 9 ! di/rict :i* x is int5d$ to s]ve1 & 9 x are kept an ample supply ( ! necess>y appliances1 9 ! %ape ( brea?+ app>atus1 :i* enables m5 to walk unhurt ?r\gh poison\s gas1 reviv+ app>atus1 by :i* p>tially suffocat$ m5 c be br\ght r\nd aga9 by ! adm9i/ration ( oxyg51 toge!r ) quantities ( t valuable gas 9 suitable portable cyl9d]s4 ,ev]y?+ :i* =e?\ght c sugge/ z ev5 possibly useful 9 an em]g5cy is kept 9 a con/ant /ate ( read9ess4 ,& all ! :ile a swift motor c> /&s ready to c>ry !m to ! sc5e ( op]ations4 ,b ! appliances are ( little use )\t m5 to "w !m1 :o "k !m & c tru/ !m4 ,! case ( ,david1 :o felt able to d bett] "w ) 8 sl+ & /one ?an 9 all ! panoply ( ,saul's arm\r1 because he _h n prov$ x1 is typical ( a univ]sal human in/9ct4 ,a man feels saf] un>m$1 or simply arm$1 ?an he does ) ! mo/ elaborate weapons 9 :i* he has n le>n$ to h confid5ce4 ,& !re=e ! m5 :o may be call$ ^u to "w ?is app>atus are fir/ taught to h confid5ce 9 x4 ,ea* /ation has its in/ructor1 :o is usually also ! g5]al sup]9t5d5t ( ! /ation1 & gall]ies 9 :i* ! in/ruction c be c>ri$ out4 ,volunte]s are call$ = 9 ea* colli]y & a numb] ( ! mo/ suitable m5 are *os5 to und]go tra9+1 pref]5ce be+ giv51 v naturally1 to ^? :o are already tra9$1 z =tunately s _m workm5 are n[adays1 9 ambulance "w4 ,^! *os5 m5 !n repair at int]vals to ! /ation to und]go a prop] c\rse ( in/ruction4 ,! in/ructor1 (t5 an ex-non-commission$ (fic] 9 ! ,royal ,eng9e]s1 accu/om$1 !re=e1 to eng9e]+ matt]s1 & also to sy/ematic discipl9e1 !re puts !m ?r\gh a c\rse ( drill ! object ( :i* is to tea* !m to "w toge!r z a squad "u ! ord]s ( a prop]ly con/itut$ *ief4 ,?us :5 call$ ^u 9 "s em]g5cy !re w be no confusion1 b ea* man w "k :at to d1 & a few %ort words ( comm& f ! *ief w s]ve bett] ?an ! long explanations :i* w\ld be necess>y ) an undiscipl9$ body4 ,x welds ! individual m51 z x 71 into a smoo?ly work+ ma*9e1 !reby increas+ ! effici5cy ( ! :ole4 ,& arrangem5ts are made :]eby1 %\ld ! lead] fail1 ano!r man /eps into 8 place ( au?ority at once & )\t "q4 ,!n1 hav+ ?us br\ght !m "u a suitable discipl9e1 ! in/ructor takes 8 m5 into ! exp]im5tal gall]y4 ,?is may be describ$ z a long1 l[1 n>r[ %$1 9 :i* are timb] props & beams1 rails on ! floor1 heaps ( coal1 all ?+s1 9 fact1 :i* may t5d to make x closely resemble ! actual work+s ( a coal-m9e aft] !y h be5 %ak5 & %att]$ by ! =ce ( an explosion4 ,! great difficulty1 9 a real disa/]1 arises f :at are kn[n z falls4 ,! ro( ( ! m9e is normally support$ by timb]s1 & ^! ! explosion moves1 s t 9 places _m tons ( ! e>? ( :i* ! ro( ( ! m9e consi/s w fall & block completely ! roads or tunnels :i* communicate f ! %aft to ! places :]e ! m5 are at "w4 ,^!1 ( c\rse1 h to be remov$ or burr[$ ?r\gh be=e ! m5 imprison$ 9 ! di/ant work+s c be rea*$4 ,! rescue p>ty d n1 ( c\rse1 wait to cle> away ! :ole ( ?is debris1 only j en\gh to enable !m to crawl ?r\gh or ov] x1 b ev5 !n x (t5 repres5ts ! wa/e ( preci\s h\rs1 & ! exp5diture ( great ex]tions1 to get pa/ a fall4 ,s at int]vals falls are made 9 ! gall]y1 9 ord] t m5 may be practis$ 9 deal+ ) !m4 ,illu/ration3 ,by p]mission ( ,w4 ,e4 ,g>=?1 ,esq41 ,pontefract ,,an ,,artificial ,,coal ,,m9e ,^! two photographs %[ ! cl\ds ( flame & smoke issu+ f ! m\? ( ! ,artificial ,coal ,m9e dur+ ! exp]im5ts describ$ 9 ! text ,x may be int]e/+ to give a brief /atem5t ( ! tra9+ und]gone by ! m5 at ! ,mansfield ,rescue ,/ation4 ,9 t case1 x %\ld be /at$1 ! gall]y is made d\ble1 s t m5 c g "o way & return ! o!r back to _! />t+-po9t4 ,hav+ donn$ _! brea?+ app>atus1 !y ent] ! gall]y1 :i*1 by ! way1 is fill$ ) smoke & f\l gas4 ,pass+ along x1 !y enc\nt] two falls1 :i* !y mu/ get ov] or ?r\gh2 !n !y h to set twelve timb] props z might be necess>y to ma9ta9 ! safety ( a damag$ road 9 ! m9e2 all t !y d ?ree times ov]4 ,!n !y are requir$ to br+ up & lay #bej bricks1 a ?+ :i* might also be necess>y 9 an actual em]g5cy1 aft] :i* !y h to fix up brattice clo? 9 a "p ( ! gall]y4 ,"o ( ! fir/ duties1 ( c\rse1 = a rescue p>ty is to re/ore ! circulation ( air 9 ! m9e1 & brattice clo? is a r\gh k9d ( clo? :i* is put to guide ! air curr5ts4 ,t done1 !y h to take a dummy repres5t+ a man ( #ad /one1 put x on a /ret*]1 & c>ry x r\nd ! gall]y & ov] ! falls4 ,f9ally1 !y re/ore ! timb]1 bricks & clo?1 & _! turn ( "w is done4 ,! total "t requir$ = ?is is two h\rs1 & dur+ ! :ole ( t p]iod !y are1 ( c\rse1 brea?+ n ! natural air1 b ! artificial atmosph]e provid$ = !m by ! app>atus ) :i* ea* man is provid$4 ,! *ief po9t ( ?is "p ( ! tra9+1 z has be5 rem>k$ already1 is to accu/om ! m5 to ! we>+ ( ! app>atus & to do+ "w 9 x4 ,by ?is means !y ga9 confid5ce 9 x1 & get to "k t x w n fail !m 9 ! "t ( trial4 ,! c\rse ( in/ruction consi/s ( t5 drills su* z has be5 describ$1 aft] :i* ! m5 are call$ up twice a ye>1 j to refre% _! memories4 ,"o side ( ! gall]y is glaz$1 s t ! in/ructor c wat* 8 m5 at "w )\t ( necessity be+ inside himself1 & !re are em]g5cy doors z well1 :i* c be op5$ to let a man out %\ld ! ordeal be too mu* = him4 ,! necess>y fumes are g5]at$ 9 a /ove & driv5 into ! gall]y by a fan4 ,! /ations are beautifully fitt$ up1 ) ba?s = ! m5 to wa% aft] _! some:at dirty exp]i5ce 9 ! gall]y1 & ev]y?+ is done = _! conv5i5ce & welf>e4 ,! advantage ( ?is sy/ematic tra9+ ( a great numb] ( m5 is t !re are m5 at ea* colli]y :o c be call$ ^u :5 ne$$4 ,! team ( /rang]s1 z has be5 rem>k$1 p>tially fail$ at ,c\rri]es1 l>gely because !y 7 /rang]s1 b :5 e colli]y has a team ready1 compos$ ( its own m51 !n cle>ly !re is ! greate/ *ance ( success4 ,! c5tral /ation ( ! di/rict is ! tra9+-gr\nd :]e ! m5 g f all ! colli]ies to get ! exp]i5ce & in/ruction1 & :]e a res]ve /ore ( appliances is kept4 ,9 _m cases1 ( c\rse1 ! colli]ies h _! own appliances1 s t "w c be begun at once1 )\t hav+ to wait = t f ! rescue /ation1 b ! latt] =ms a res]ve 9 case ( ne$1 &1 be+ kept "u ! c>e ( an exp]t1 x is naturally always 9 ! be/ possible work+ ord]4 ,to give an idea ( ! co/ ( ^! /ations1 x may be /at$ t ! "o at ,por?1 9 ! ,rhondda ,valley1 co/1 includ+ equipm5t1 ,l#gjjj1 :ile ! "o at ,mansfield co/ ,l#cjjj4 ,?is fir/ co/ & ! exp5se ( ma9t5ance is borne by ! colli]ies ( ! di/rict 9 proportion to ! quantity ( coal :i* !y raise4 ,& n[ we c turn to ! app>atus itself1 )\t :i* ! organisation already describ$ w\ld be ( little value4 ,!re are sev]al makes ( ^!1 b a description ( ! p>ticul> app>atus us$ at ! two /ations m5tion$ w s]ve z an illu/ration4 ,! purpose1 ( c\rse1 is to give ! we>] an atmosph]e ( 8 own1 :i* he c c>ry ab\t ) him1 & :i* w r5d] him q indep5d5t ( ! ord9>y atmosph]e & q indiff]5t to ! poison\s nature ( ! gases ar\nd him4 ,to ?is end 8 m\? & no/rils mu/ be cut (f f ! out] _w altoge!r4 ,!re are two ways ( do+ ?is4 ,9 ! "o !re is us$ a helmet1 or p]haps mask w\ld be ! bett] t]m4 ,?is fits "r ov] ! man's face1 an air-tight jo9t be+ made betwe5 ! helmet & 8 head by means ( a rubb] wa%] :i* c be inflat$ ) air4 ,! inflation is accompli%$ by squeez+ a rubb] ball on ! "r-h& side ( ! helmet4 ,9 ! c5tre is a glass w9d[ ?r\gh :i* he c see easily1 & s9ce ?is is apt to become cl\d$ by ! dampness ( 8 brea? !re is a wip] inside1 :i* c be turn$ by a knob on ! outside1 s t by simply turn+ 8 knob ) 8 h& he c clean ! w9d[ at any "t t may be necess>y4 ,two s(t pads inside ! helmet be> "o on ! man's =ehead & ! o!r on 8 *91 & ^!1 work+ 9 conjunction ) a /rap :i* passes "r r\nd ! back ( 8 head1 keep ! ?+ firmly 9 position4 ,9 addition !re is comb9$ ) ! helmet a lea!r skull-cap :i*1 be+ cont9u$ d[n beh9d1 gives good protection to ! head & neck4 ,! o!r =m ( app>atus consi/s ( a m\?-piece & nose-clip4 ,! m\?-piece1 z its "n implies1 fits 9 ! man's m\?1 be+ support$ & kept 9 position by a /rap pass+ beh9d ! back ( 8 head4 ,comb9$ ) x is a little screw clip :i* closes 8 no/rils4 ,! man also we>s a lea!r skull-cap1 f :i* /raps dep5d to be> ! weight ( ! m\?-piece & its atta*$ tubes1 s t ! weight does n fall ^u 8 m\?4 ,ei!r ( ^! arrangem5ts1 x is cle>1 cuts him (f f communication ) ! out] air1 b t is only half ! problem1 = he mu/ be giv5 a sub/itute or he w be suffocat$4 ,?is "p ( ! appliance he c>ries1 knapsack fa%ion1 ^u 8 back4 ,fir/ !re is a rectangul> case1 call$ ! reg5]ator1 )1 bel[ x1 two small cyl9d]s ( compress$ oxyg54 ,a suitable arrangem5t ( pipes connects ^! toge!r1 & to ! helmet or m\?-piece z ! case may be4 ,:5 ! man exhales1 z we all "k1 ! air :i* he !n dis*>ges f 8 lungs is defici5t 9 oxyg5 & in/ead conta9s c>bonic acid gas4 ,! latt] mu/ be got rid ( & replac$ by pure oxyg54 ,! exhal$ air is !re=e l$ d[n a pipe to ! reg5]ator1 :]e x comes into contact ) sev]al trays ( cau/ic soda1 a *emical :i* has a great aff9ity = c>bonic acid4 ,! result is t ! latt] gas is extract$ f ! impure air1 f9d+ a m cong5ial home 9 ! cau/ic soda4 ,x is !n necess>y to re/ore ! normal quantity ( oxyg51 & s1 z ! air passes on1 x meets1 9 a little app>atus kn[n z an injector1 a spray ( pure oxyg5 f ! cyl9d]s4 ,?us1 aft] be+ purifi$ & re-oxyg5at$1 ! air passes on ?r\gh m pipes to ! helmet or m\?-piece1 to be brea!d once m4 ,! app>atus conta9s suffici5t oxyg5 & cau/ic soda = ?is to g on = a space ( two h\rs4 ,b dur+ times ( extra ex]tion a man ne$s m air ?an at o!rs1 = :i* provision has to be made1 & s on 8 *e/ ! rescu] c>ries a flexible bag divid$ into two comp>tm5ts4 ,?r\gh "o ( ^! ! exhal$ air passes on its way to ! reg5]ator1 :ile ?r\gh ! o!r ! oxyg5at$ air fl[s on its way to ! man's m\?4 ,:5 he is brea?+ h>d1 !n1 dur+ a mom5t ( extra ex]tion1 & :51 !re=e1 he is turn+ out bad air fa/] ?an x c be purifi$1 & draw+ 9 pure air fa/] ?an x c be produc$1 ?is bag comes to 8 aid4 ,f ! /ore ( oxyg5at$ air 9 "o side ( x he draws ! extra :i* he requires1 :ile ! o!r side /ores up tempor>ily ! excess ( vitiat$ air1 until ! reg5]ator is able to ov]take its "w4 ,?us at all times1 :e!r brea?+ ord9>ily or heavily1 ! app>atus c respond to 8 dem&s4 ,! spray ( oxyg5 z x escapes f ! cyl9d]s into ! injector has ! effect ( driv+ ! air along1 s t ! circulation ?r\gh ! tubes & ! reg5]ator is automatic1 & ! f\l air fl[s away f ! man's m\? & ! new air comes back to him q )\t ef=t on 8 "p4 ,z "t goes on1 ( c\rse1 & ! /or$ oxyg5 becomes us$ up1 ! pressure 9 ! cyl9d]s falls1 :i* fall1 %[n ^u a little pressure-gauge1 tells ! man h[ mu* long] "t he has be=e he mu/ return = fre% supplies ( oxyg5 & soda4 ,fre% cyl9d]s ( oxyg5 c be connect$ up v quickly 9 place ( ! empty ones1 :ile a fre% reg5]ator c be put 91 or new cau/ic soda suppli$1 9 a v %ort "t4 ,! sup]9t5d5t ( ! ,mansfield /ation has inv5t$ :at is t]m$ a self-rescue app>atus1 to be us$ 9 conjunction ) t :i* has be5 describ$ above4 ,x is simpl] & light] ?an ! rescue app>atus1 & w n keep a man suppli$ ) air = m ?an an h\r or an h\r & a qu>t]4 ,moreov]1 x is n automatic1 s9ce ! fl[ ( oxyg5 has to be controll$ by ! man himself4 ,s9ce1 h[ev]1 x consi/s only ( a m\?-piece1 a brea?+-bag & a cyl9d] ( oxyg51 x is v portable1 & may well be c>ri$ by a rescue p>ty = ! use ( any m5 :o may be discov]$ alive beyond ! dang] zone4 ,x may well happ51 inde$ x (t5 has happ5$1 t a remote "p ( a m9e1 al?\gh cut (f f ! %aft by passages full ( aft]-damp1 z ! f\l gases caus$ by ! explosion are t]m$1 may itself conta9 fairly pure air 9 :i* m5 c live = a long "t4 ,if su* m5 be rea*$1 ! difficulty is to get !m ?r\gh ! passages conta9+ ! bad air4 ,consequ5tly a rescue p>ty :i* c>ri$ "o or two ( ^! light =ms ( app>atus c\ld equip su* m5 ) !m & !n !y c\ld pass out ) safety4 ,ano!r use1 ! "o1 9 fact1 f :i* ! appliance draws its "n1 is ! facility ) :i*1 by its aid1 a man c\ld set "r a *ance defect 9 8 ord9>y rescue app>atus4 ,suppose1 = example1 t a fully equipp$ man f\nd some?+ wrong1 :]eby he 0 prev5t$ f gett+ 8 prop] supply ( purifi$ air4 ,!n1 if ! p>ty _h "o ( ! self-rescue sets ) !m1 he c\ld slip (f 8 helmet or m\?-piece1 quickly replac+ x1 = a "t1 ) ! self-rescue m\?-piece4 ,?is might enable him to rea* safety1 or ev5 to put ! o!r app>atus "r & !n don x once m4 ,! :ole ?+ c be pack$ up into a small t9 case :i* c be slung ov] "o %\ld]1 & ) ! oxyg5 cyl9d] slung ov] ! o!r "o ! complete outfit c be c>ri$ q easily by a man 9 addition to :at he is we>+ himself4 ,/ill ano!r =m ( brea?+ appliance may well be tak5 on ^! rescue exp$itions1 & t is ! reviv+ app>atus1 = use ^u ^? :o h app>5tly ceas$ to brea!4 ,9 ?is case a mask is put ov] ! suff]]'s m\? & nose1 & !n ! turn+ ( a lev] into a c]ta9 position causes oxyg5 to escape f a cyl9d] 9 su* a way z to cause a suction :i* empties ! man's lungs ( ! bad gases :i* h laid him l[4 ,t done1 ano!r movem5t ( ! lev] & a deep brea? ( oxyg5 fl[s into 8 lungs 9 _! place4 ,?us by alt]nat+ ! positions ( ! lev] an artificial respiration is set up f> m effective ?an c possibly be atta9$ by ! ord9>y me?od ( mov+ ! man's arms & press+ 8 *e/4 ,inde$ !re are cases1 su* z :5 8 arms or ribs are injur$1 :5 ! ord9>y me?od is impossible1 b x is h>d to imag9e an in/ance :5 ?is b5efic5t app>atus c\ld n be us$1 & s long z !re be any sp>k ( life left 9 ! poor fell[ !re seems to be e reason to expect a complete revival z ! result ( its use4 ,( c\rse !re are _m o!r places :]e poison\s gases are likely to be met )1 su* z gas-works1 *emical-works1 limeworks1 & s on1 :]e ?is app>atus may be kept ) advantage1 9 case ( accid5t4 ,inde$ all t has be5 describ$ above has its use ap>t f colli]y explosions1 al?\gh !y are ! out/&+ opportunities = its employm5t4 ,old work+s1 tunnels :i* h be5 empty = a "t1 sew]s--all ^! h1 on occasion1 to be ent]$1 n to m5tion h\ses full ( smoke1 or factories full ( *emical fumes1 all ( :i* =m cases 9 :i* ! rescue app>atus w\ld f9d useful employm5t4 ,,*apt] ,,xix ,,h[ ,,sci5ce ,,helps ,,to ,,keep ,,u ,,well ,"o bran* ( sci5ce--m$ical sci5ce--conc]ns itself almo/ entirely ) heal?1 b x w\ld be out ( place to ref] to su* matt]s "h1 ev5 if ! pres5t writ] 7 capable ( do+ ju/ice to ! subject4 ,a new m$ic9e or a new me?od ( op]at+ ^u a suff]+ pati5t w\ld be q correctly describ$ z a sci5tific m>vel1 b x is n ( su* t ?is *apt] deals1 b r ) ^? great works by :i* ! eng9e]1 (t5 taught by ! m$ical man1 promotes ! heal? ( a :ole community4 ,mo/ important ( ^!1 p]haps1 is ! provision ( pure wat]4 ,"s places are m =tunately situat$ ?an o!rs 9 ?is respect1 be+ ne> /reams fl[+ d[n f m\nta9s cle> & unpollut$1 :i* c be drunk aft] ! m9imum ( purification4 ,o!rs h to make use ( ! wat]s ( a mod]ately clean riv]1 z ,london does ^? ( ! ,?ames & ,lea1 9 :i* cases ! greate/ c>e has to be ex]cis$ 9 ! filtration ( ! liquid be=e x c be s5t out ?r\gh ! ma9s = dome/ic consumption4 ,9 ?is p>ticul> doma9 inv5tion has be5 comp>atively sl[4 ,!re are novel pumps1 x is true1 = h&l+ ! wat]1 su* z ! ,humphrey ,gas ,pump1 :i* ! ,metropolitan ,wat] ,bo>d 7,london7 h in/all$ = fill+ _! great res]voirs at ,*+=d4 ,9 ^! an explosion ( gas is ! motive =ce4 ,wat] fl[s by gravitation into a huge iron pipe clos$ at ! top b op5 at ! bottom4 ,x is s arrang$ t a quantity ( gas %all be entrapp$ 9 ! upp] end1 :i*1 be+ explod$ by an electric sp>k1 drives ! mass ( wat] out4 ,"s ( x1 toge!r ) a quantity ( fre% wat]1 pres5tly comes surg+ back1 entrapp+ a fre% supply ( gas & caus+ a new explosion2 & s x goes on ov] & ov] aga94 ,! p>ticul> pumps at ! wat]works ref]r$ to dis*>ge ab\t f\rte5 tons ( wat] at ea* explosion1 ( :i* !re are n9e e m9ute4 ,! special effect ( ^! ma*9es1 h[ev]1 is n to improve ! public heal? s mu* z to relieve ! public pocket1 = _! *ief feature is t !y "w m economically ?an any o!r k9d ( pump4 ,! filt]s1 by :i* ! wat] is purifi$1 are simply lay]s ( s&1 mu* ! same z h be5 9 use = _m ye>s1 al?\gh 9 "s cases *emi/ry is br\ght 9 & ! "w ( ! filt]s aid$ by ! action ( precipitants4 ,^! are sub/ances :i* comb9e 9 "s way ) ! impurities 9 ! wat]1 & c>ry !m to ! bottom ( ! tank or res]voir1 :ile ! pure wat] rema9s to be drawn (f f ! top4 ,?is is also ! mo/ usual me?od by :i* wat] is s(t5$4 ,h>dness 9 wat] is due to ! pres5ce ( c]ta9 salts :i* are dissolv$ out ( ! gr\nd z ! wat] p]colates ?r\gh x1 & :i* are abs5t f ra9-wat]4 ,to get rid ( ^! ! h>d wat] has *emicals mix$ ) x 9 a tank1 f :i* x fl[s sl[ly ?r\gh ano!r tank4 ,! effect ( ! add$ *emicals is to conv]t ! soluble salts 9 ! wat] into insoluble p>ticles1 :i* !n t5d to fall d[n to ! bottom ( ! conta9+ vessel4 ,! sl[ passage ?r\gh ! second tank is int5d$ to give ! p>ticles "t to settle4 ,illu/ration3 ,,sectional ,,view ,,( ,,hydraulic ,,buff] ,,& ,,runn+-,,out ,,presses ,,( ,a #fj-,,p\nd] ,,gun ,f9ally1 to make sure t ^! h be5 all got rid (1 ! wat] trav]ses a filt]1 & !n x is = all practical purposes z s(t z ra9-wat]4 ,"s p are fright5$ ( ?is artificially s(t5$ wat]1 on ! gr\nd t *emicals h be5 add$ to x1 suppos+1 app>5tly1 t :5 !y use su* wat] !y are really employ+ a *emical solution4 ,t is q wrong1 h[ev]1 = ! add$ *emicals1 comb9+ ) ! h>dness1 =m sub/ances :i* are q easily extract$ f ! wat] altoge!r4 ,if we lik5 ! h>dness to a numb] ( pickpockets 9 a cr[d1 & ! add$ *emicals to a numb] ( policem5 :o come 9 to arre/ ! said pickpockets1 f9ally leav+ ! cr[d free f bo? pickpockets & policem51 we get a simple illu/ration ( :at takes place4 ,b almo/ equally important z ! provision ( pure wat] is ! effective deal+ ) ! dra9age ( a l>ge t[n4 ,mu* (f5sive matt] fl[s "u ! /reets ( our t[ns & cities1 & if x is n to become a nuisance x mu/ be sci5tifically dealt )4 ,ye>s ago ! dra9s ( ,london simply empti$ !mselves into ! ,?ames1 until1 9 #ahfd1 two l>ge dra9s 7 con/ruct$1 "o on ea* side (1 & approximately p>allel )1 ! riv]1 to int]cept ! old dra9s & to c>ry _! cont5ts to po9ts _m miles d[n t[>ds ! sea4 ,ev5 t1 h[ev]1 by no means abat$ ! evil1 = x simply transf]r$ x to a new place4 ,! riv] 0 z f\l z ev]4 ,william ,morris1 9 ,news f ,n[h]e1 pictures ! cat*+ ( salmon 9 ! ,?ames (f ,*elsea1 :ile "o ( ,london's prom95t citiz5s1 ref]r+ to :at 0 be+ done 9 ! direction ( purify+ ! riv]1 jocosely promis$ ! memb]s ( ,p>liam5t a little fly-fi%+ at ,we/m9/]4 ,equally remote1 x is to be fe>$1 f actual accompli%m5t1 ^! two prophecies d c]ta9ly indicate ! t5d5cy ( ev5ts1 = sci5ce has enabl$ ! au?orities to relieve ! long-suff]+ riv] ( mu* ( ! pollution :i* !y us$ to ?ru/ into x4 ,! fir/ great /ep 0 ! introduction1 9 #ahhg1 ( a treatm5t 9 pr9ciple v l t j describ$ = s(t5+ wat]4 ,! liquid f ! dra9s is ga!r$ into l>ge res]voirs1 :]e *emicals are add$ to x1 caus+ ! heavi] matt] to be precipitat$ 9 ! =m kn[n z sludge4 ,! liquid portion1 or efflu5t1 z x is call$1 :i* is left is dis*>g$ into ! riv] j z ! tide is ebb+1 s t x is c>ri$ "r away1 &1 be+ comp>atively in(f5sive1 x pollutes ! riv] v little inde$4 ,! sludge1 on ! o!r h&1 is pump$ into special /eam]s1 :i* c>ry x d[n to a c]ta9 spot (f ! ,?ames ,e/u>y1 :]e !y drop x into ! sea4 ,! curr5ts at ! p>ticul> spot *os5 are su* t none ( x returns to ! riv]4 ,= a simil> purpose electrolysis has be5 employ$4 ,9 ?is process ! sewage is made to fl[ betwe5 two iron plates :i* are connect$ up to a s\rce ( electric curr5t s t !y =m electrodes1 :ile ! sewage is ! electrolyte4 ,! curr5t decomposes ! liquid sewage1 caus+ *lor9e & oxyg5 to be deposit$ ^u t plate :i* =ms ! anode4 ,?is deodorises & purifies ! sewage1 9 addition to :i* iron salts are =m$ on ! iron plates1 ! effect ( :i* is to precipitate ! solid p>ticles4 ,?us ! same result is a*iev$ z :5 *emicals are us$1 ! ma9 diff]5ce be+ t in/ead ( *emicals be+ add$1 !y are produc$ by ! passage ( ! curr5t4 ,b1 f ! sci5tific po9t ( view1 ! mo/ int]e/+ process ( all is t 9 :i* bact]ia or microbes are br\ght into ! s]vice4 ,! fact is famili> to mo/ p t !re are c]ta9 m9ute organisms :i* cause t]rible diseases4 ,x is n s well kn[n t !re are /ill m ( !m ^: action is extremely b5efic5t4 ,! writ] has se5 ^! m9ute liv+ ?+s describ$ 9 a popul> book z insects1 b !y really belong to a l[ ord] ( plant life1 &1 z has be5 said 9 an e>li] *apt]1 9 spite ( ! l[l9ess ( _! /atus 9 ! ord] ( creation1 !y are able to accompli% c]ta9 *emical processes :i* baffle ! clev]e/ m54 ,!y are p>ticul>ly good1 or "s ( !m are at any rate1 at =m+ comp\nds 9 :i* nitrog5 =ms a "p4 ,fur!r1 !y c be divid$ into two classes1 ! a]obic & ! ana]obic4 ,! =m] "w be/ 9 air1 :ile ! latt] ne$ an abs5ce ( air :ile !y p]=m _! functions4 ,aft] :i* prelim9>y explanation we c proce$ to describe h[ !y are induc$ to c>ry on ?is valuable "w = mank9d4 ,! sewage fl[s fir/ ( all into a tank f :i* light & air are exclud$ z f> z possible4 ,!re ! ana]obic microbes fl\ri% & multiply1 & 9 ! c\rse ( _! life "w !y conv]t ! sewage into an in(f5sive liquid4 ,aft] an appropriate int]val ! liquid passes to filt]-b$s1 :]e x trickles ov] & ?r\gh b$s ( coke1 ! effect ( :i* is to a]ate x v ?or\ghly1 :]eby ! a]obic microbes come into action1 complet+ ! good "w1 s t no?+ is left except a clean1 col\rless & od\rless liquid4 ,inde$ x is m ?an t1 = ! microbes h turn$ ! (f5sive matt] into nitrog5\s comp\nds :i*1 z we h se5 9 a previ\s *apt]1 are ! be/ f]tilis]s4 ,h5ce ?is efflu5t1 if plac$ ^u ! soil1 is ( great value4 ,! advantage ( ?is to t[ns :i* are n bless$1 l ,london1 ) a broad riv] & ! sea ne> at h& ne$s no explanation4 ,! bact]ia necess>y to c>ry on ! process are always pres5t 9 sewage1 & aft] any p>ticul> plant has be5 9 op]ation = a little :ile !re results an accumulation ( !m1 s t ! process becomes m & m active z "t goes on4 ,me*anical +5uity has s arrang$ matt]s t a sewage disposal plant on ?is sy/em c be made q automatic1 requir+ little or no att5tion = mon?s toge!r1 ! raw sewage fl[+ 9 at "o end1 :ile ! od\rless1 h>mless efflu5t p\rs out at ! o!r4 ,&1 moreov]1 s p[]ful is ! action ( ^! b5efic5t bact]ia t %\ld disease g]ms come d[n 9 ! sewage !y soon de/roy !m4 ,no *emicals are ne$$1 = ! bact]ia repl5i% !mselves4 ,no sludge is left1 ev]y?+ be+ turn$ into ! h>mless efflu5t4 ,&1 x may be said once m1 disease g]ms are de/roy$4 ,( all ! valuable inv5tions ( mod]n times ?is is surely n "o ( ! lea/4 ,,*apt] ,,xix ,,mod]n ,,artill]y ,ev5 z late z ! "t ( ! ,crimean ,w> guns1 ev5 ! l>ge/1 7 made ( t extremely common mat]ial1 ca/-iron4 ,9 fact1 s f> z mat]ial w5t1 !re 0 no diff]5ce betwe5 a gun & a wat]-pipe4 ,x 0 ! ne$ = "s mat]ial possess+ /r5g? comp>able ) t ( /eel comb9$ ) ! ease ( production ( ca/-iron :i* l$ ,sir ,h5ry ,bessem] to exp]im5t 9 ! manufacture ( /eel4 ,out ( ^? exp]im5ts came ,bessem] /eel & its ne> relative1 ,siem5s /eel1 two mat]ials ( univ]sal application at ! pres5t "t1 s t to ! ne$s ( ! artill]yman we owe two inv5tions :i* h prov$ ( inf9ite value 9 peace z well z 9 w>4 ,if any p>ticul> piece ( ordnance c be said to be ! prime fav\rite ) ! ,engli%-speak+ peoples1 x is ! big naval gun4 ,) bo? ,briti% & ,am]icans ! navy takes pride ( place2 bo? nations are giv5 to contemplat+ ) pleasure ! numb] ( dreadn\ghts :i* !y possess1 & ! di/+ui%+ feature ( a dreadn\ght is ! l>ge numb] ( big guns :i* x c>ries4 ,( ! late/ ( ^! gigantic weapons "o may n speak1 b mu* is already public prop]ty conc]n+ ! #ab-;in* gun :i* ! orig9al ,dreadn\ght c>ri$1 & :i* is probably foll[$ 9 its g5]al features by ! /ill great] guns ( ! mo/ rec5t %ips4 ,a gun is spok5 ( by its calibre1 :i* means ! inside diamet]1 or1 to use ano!r expression1 ! size ( ! bore4 ,s ! #ab-;in* naval gun is #ab in*es 9 ! bore4 ,its l5g? is 9 "s cases #de calibres & 9 o!rs #ej calibres4 ,9 o!r words1 "s are #de feet long & o!rs #ej feet4 ,:y ! diff]5ce8 someone may ask4 ,! answ] is t ! long] ones are an improv$ type4 ,! extra l5g? gives long] range & h>d] hits1 z is q app>5t aft] a little ?\ght4 ,! explosive goes (f & =?) comm5ces to drive ! %ell t[>ds ! muzzle4 ,s long z x is 9 ! gun ! %ell is be+ pu%$ fa/] & fa/]1 b s soon z x leaves ! muzzle ! pu%+ ceases & ! %ell is left to pursue its c\rse ) its own mom5tum4 ,!re=e1 g5]ally speak+1 "o may say t ! long] ! gun ! fa/] w be ! spe$ ( ! %ell z x leaves ! muzzle1 ! f>!r w x g & ! h>d] w be ! bl[ at a giv5 range4 ,incid5tally ?is explanation reveals ! ne$ = diff]5t k9ds ( explosive4 ,! propellant ^: function x is to drive ! %ell out ( ! gun is diff]5t f t ) :i* ! %ell is itself fill$4 ,! =m] ne$s to act comp>atively sl[ly1 s t x may cont9ue its pu%+ action dur+ ! :ole "t t ! %ell is travell+ along ! gun4 ,x might be ev] s p[]ful1 b 7 its action too sudd5 x w\ld simply t5d to bur/ ! gun1 )\t imp>t+ v mu* spe$ to ! %ell4 ,on arrival at its de/9ation1 h[ev]1 ! %ell ne$s to bur/ sudd5ly & viol5tly4 ,ano!r int]e/+ "q arises at ?is po9t4 ,see+ h[ fa/ is ev5 ! sl[e/ spe$ at :i* a projectile travels1 h[ c x be possible to measure ! rate at :i* a %ell issues f "o ( ^! mon/] guns4 ,ne$less to say1 x is electricity :i* makes a ?+ app>5tly s difficult really q easy4 ,ne> ! gun is set up a frame ) a wire zigzagg+ to & fro across x1 9 su* a mann] t :5 ! gun is fir$ ! %ell is b\nd to cut ! wire4 ,electric curr5t is made to pass ?r\gh ?is wire on its way to a suitable h\se 9 :i* are record+ in/rum5ts1 :]e x en]gises a magnet & s holds some?+ up4 ,n[ x is easy to see t z soon z ! %ell cuts ! wire ! curr5t w /op1 ! magnet w let g & ! some?+ w drop4 ,at a c]ta9 di/ance f>!r on !re is a second frame ) wires ^u x1 ?r\gh :i* passes a second curr5t1 :i* is also l$ to ! in/rum5t h\se1 :]e x aga9 op]ates a second magnet4 ,:5 ! fir/ magnet releases its hold x drops some?+1 to wit1 a long lead weight4 ,:5 ! second magnet lets g x p]mits a second weight to fall aga9/ ! fir/ & make a d5t or scrat* ^u x4 ,! long] ! int]val betwe5 ! action ( ! two magnets ! high] up ^u ! lead weight w ! scrat* be4 ,! app>atus1 9 %ort1 w regi/] ! di/ance fall5 ?r\gh by ! lead weight betwe5 ! break+ ( ! wire 9 ! fir/ frame & ! break+ ( ! wire 9 ! second frame4 ,n[ a fall+ object1 if only x has su* weight t ! resi/ance ( ! air is negligible1 falls accord+ to a well-und]/ood law1 :i* law x obeys ) ! utmo/ accuracy4 ,!re=e ! di/ance fall5 by ! weight betwe5 ! passage ( ! %ell ?r\gh two po9ts gives a v accurate record ( ! "t tak5 to travel f "o to ! o!r4 ,( c\rse sev]al su* frames c be us$ if desir$ 9 ! same way4 ,b to return to ! gun itself4 ,x is n m]ely "o piece ( metal b sev]al tubes beautifully fitt$ "o inside ano!r4 ,moreov]1 9 ! ,briti% gun at all ev5ts1 betwe5 two ( ! tubes !re is a space fill$ ) wire4 ,?is wire is p]haps bett] describ$ z /eel tape1 & is ( ! f9e/ mat]ial = ! purpose1 flexible & trem5d\sly /rong4 ,x is w\nd r\nd & r\nd "o ( ! tubes until !re are _m miles ( x on a s+le gun4 ,x is w\nd tightly1 too1 by means ( special ma*9]y4 ,! purpose ( ! wire is to resi/ crack+4 ,! solid /eel tubes may crack1 &1 z is ! way ) all cracks1 ^! w t5d to gr[ long] & long]4 ,! _m turns ( wire1 h[ev]1 w n crack4 ,ev5 if a few turns %\ld break1 ! damage w n spread1 & ! gun c probably g on z if no?+ _h happ5$4 ,! mat]ial ( :i* ^! guns are made is nickel *rome gun /eel4 ,/eel is ord9>ily an alloy ( iron & c>bon1 b ?is metal also conta9s traces ( nickel & *romium1 :i* make x specially suitable = its special purpose4 ,ea* ( ! tubes ( :i* ! gun is =m$ />t z an +ot1 a m]e lump ( metal1 b r\ghly %ap$4 ,! requisite mixture is obta9$ 9 a furnace & ! molt5 metal is run out into a m\ld4 ,! +ot is heat$ aga9 & press$ "u enorm\s hydraulic presses until x is approximately ! %ape requir$4 ,?is press+ n only produces ! desir$ %ape1 x also improves ! quality ( ! metal4 ,! r\gh =g+ is !n bor$ out1 to make x into a tube4 ,"o is incl9$ to wond] :y ! +ot is n ca/ holl[ to comm5ce )1 & s save ! lab\r ( bor+ x all out lat]4 ,! explanation ( ?is is t c]ta9 impurities are always pres5t 9 ! metal & ^! always ga!r toge!r 9 ! "p :i* sets la/4 ,n[ 9 a solid block or +ot x is cle> t ! c5tre is ! "p :i* w set la/1 & h5ce t is ! "p :]e ! impurities w congregate4 ,!n1 :5 ! c5tre "p is all bor$ out ! impurities are entirely remov$4 ,! tube is %ap$ ext]nally by be+ turn$ 9 a la!4 ,! inn]mo/ tube is n simply smoo?4 ,!re is a spiral groove1 call$ ! rifl+1 runn+ r\nd & r\nd1 screw fa%ion1 inside x4 ,! purpose ( ?is is to give ! %ell a sp9n+ action :i* causes x to keep po9t =emo/ ?r\gh\t its flight4 ,b = ?is ! %ell w\ld t5d to turn ov] & ov]1 result+ 9 unc]ta9 & inaccurate flight4 ,! %ell is a little small] ?an ! bore ( ! gun1 b ne> its base x has an encircl+ b& ( s(t copp]1 :i* b& is a tight fit 9 ! gun4 ,! s(t copp] cru%es into ! rifl+1 :]eby ! %ell obta9s its sp9n+ action4 ,! l>ge guns are m\nt$ 9 pairs1 ea* pair on a turntable1 by ! movem5t ( :i* to "r or left !y are tra9$ ^u ! di/ant t>get4 ,! turntable is surr\nd$ by a wall ( ?ick arm\r & is cov]$ by an iron hood or ro(4 ,9 addition to be+ turnable to "r or left1 !re is1 ( c\rse1 provision = rais+ or depress+ ! direction 9 :i* ea* gun is po9t+4 ,!y ne$ always to po9t m or less upw>ds1 & ! p>ticul> angle dep5ds ^u ! range or di/ance ( ! object aim$ at4 ,?is is asc]ta9$ by range-f9d+ in/rum5ts & communicat$ to ! (fic]s 9 ! turrets1 z ! cov]$ turntables are call$4 ,! guns are !n elevat$ or depress$ to suit ! range4 ,ea* gun re/s ^u a cradle :i* is itself fitt$ ^u a slide4 ,:5 x is fir$ x kicks backw>ds1 aga9/ ! =ce ( a buff] ( spr+s1 or a hydraulic or pneumatic cyl9d]4 ,?us aft] ea* %ot ! gun moves backw>ds ^u ! slide1 b ! hydraulic app>atus br+s x back aga9 into position = fir+ almo/ in/antane\sly4 ,9 naval guns all ! movem5ts1 includ+ t ( ! turntable1 are by p[]1 ei!r hydraulic or electric1 or a comb9ation ( ! two4 ,! load+ is also by p[]4 ,! %ells & ammunition are kept well d[n t[>ds ! bottom ( ! %ip1 "u ea* turret4 ,lifts br+ !m up f !re to a *amb] j b5ea? ! turntable1 kn[n z ! work+ *amb]4 ,"h a small quantity only is kept1 & t = z %ort a "t z possible be=e x is s5t up by o!r hoi/s /raight to ! guns !mselves4 ,! hoi/s are s arrang$ t1 no matt] h[ !y may be elevat$ or depress$1 ! ammunition is deliv]$ exactly opposite ! bree*1 z ! re> end ( a gun is t]m$4 ,!n a me*anical ramm] pu%es x /raight 94 ,illu/ration3 ,,rifles ,,( ,,diff]5t ,,nations 7,see ,app5dix7 ,! bree* ( ! gun is clos$ by a beautiful piece ( me*anism call$ ! bree*-block4 ,x is really a huge plug :i* securely closes ! end ( ! gun1 a p>tial turn aft] x is 9 place fix+ x firmly en\gh to resi/ all ! =ce ( ! explosion4 ,yet x c be fre$ & swung back ^u h+es 9 a few seconds4 ,at ! same mom5t t x is op5$ a jet ( air bl[s into ! gun1 cle>+ out all effects ( ! rec5t explosion4 ,! process ( fir+ "o ( ^! guns may ?us be summ>is$4 ,! turntable is swivell$ to "r or left until ! gunn]s1 look+ ?r\gh ! sights1 :i* are really telescopes1 see ! object /raight 9 front ( !m4 ,mean:ile ! sights h be5 set accord+ to ! range--t is to say1 !y h be5 s set 9 relation to ! gun itself t :5 !y po9t directly at ! t>get ! gun w be po9t$ upw>ds at exactly ! "r angle = t range4 ,! :ole ?+1 !re=e1 gun & sights comb9$1 is tilt$ upw>ds or d[nw>ds z may be necess>y until ! sights po9t directly at ! object aim$ at4 ,!n at a signal ! gun is fir$ by electricity4 ,! %ock causes ! gun to slide backw>ds ^u its support+ slide1 b ! buff]s1 hav+ tak5 ! %ock automatically1 return x to its position aga92 ! aim is ?us undi/urb$ & x is ready = ! next %ot4 ,^! enorm\s guns c be fir$ at ! rate ( "o %ot e fifte5 seconds4 ,field guns are 9 pr9ciple v simil> to ^!1 only1 ( c\rse1 !y are mu* small] & are m\nt$ ^u c>riages1 s t !y c be quickly mov$ f place to place4 ,x mu/ be borne 9 m9d1 h[ev]1 t !re are 9 ! case ( l& guns two di/9ct types4 ,field guns1 l naval guns1 fire /raight at _! t>get2 h[itz]s or mort>s fire upw>ds ) a view to lett+ ! %ell fall on ! t>get f above4 ,! latt] are1 g5]ally speak+1 %ort1 fat1 /umpy guns1 z comp>$ ) ! long1 sl5d] field guns4 ,9 ! field all guns h to be load$ by h&4 ,! elaborate sy/em ( hoi/s :i* enables ! great naval guns to be load$ ) su* rapidity is obvi\sly impossible4 ,t has to be comp5sat$ = by ! skill & quickness ( ! gunn]s !mselves1 & x is inde$ a/oni%+ to see ) :at deftness !y c h&le ! heavy & dang]\s projectiles4 ,) all guns1 ( :atev] k9d1 range-f9d+ is ( ! utmo/ importance4 ,no projectile1 h[ev] fa/ x may travel1 really moves 9 a /raight l9e4 ,x mu/ be fir$ m or less upw>ds 9 ord] to comp5sate = ! d[nw>d pull ( gravity4 ,if ! elevation be insuffici5t ! %ell w fall %ort2 if x be too mu* x may g beyond ! m>k1 or x may fall %ort1 accord+ to circum/ances4 ,j ! "r elevation is absolutely ess5tial = good %oot+4 ,& = t to be a*iev$ ! range mu/ be kn[n ) ! utmo/ possible accuracy4 ,!re are v>i\s sy/ems & in/rum5ts us$ = ?is purpose1 b all dep5d ^u ! same pr9ciple4 ,x is ! pr9ciple und]ly+ all survey+ & all a/ronomy2 inde$ x is ! only possible pr9ciple = measur+ a di/ance :5 y _c actually g & lay a measure ^u x or by x4 ,x is bas$ ^u a peculi> prop]ty ( a triangle4 ,9 ! case ( e triangle :i* has /raight sides1 if we "k ! size ( two ( ! angles & ! l5g? ( "o ( ! sides we c easily calculate all t !re is to be kn[n ab\t t triangle4 ,we unconsci\sly use ! pr9ciple :5 we judge a di/ance ) our eyes4 ,we focus ea* eye sep>ately ^u ! object :i* we are look+ at4 ,9 o!r words1 ea* ( our eyes looks along a /raight l9e t]m9at+ 9 ! object4 ,^? two l9es1 toge!r ) a l9e jo9+ our two eyes1 =m a triangle4 ,! l9e betwe5 our eyes is ! base1 ! l9e ( :i* we "k ! l5g?1 :ile ! directions 9 :i* we po9t our eyes give u ! angles at ea* end ( ! base4 ,f ?is we are able to judge ! di/ance ( ! object4 ,( c\rse !re is probably n "o ( u :o kn[s ! l5g? ( t natural base 9 in*es1 b t does n matt] 9 ?is case1 s9ce x is always ! same :atev] we may look at1 & s ! m]e incl9ation ( ! eyes gives u a means ( comp>+ di/ances4 ,:5 we judge by ! eye alone1 :at we really d is to draw ^u our exp]i5ce & consci\sly or unconsci\sly comp>e ! di/ance :i* we are e/imat+ ) "s o!rs :i* we already "k4 ,9 survey+1 a telescope is set up at "o end ( a base-l9e & po9t$ fir/ at ! o!r end ( ! base-l9e & !n at ! di/ant object4 ,a scale ) :i* ! in/rum5t is provid$ gives u ! size ( ! angle betwe5 ! two4 ,!n ! same ?+ is done at ! o!r end ( ! base & ! simil> angle !re is obta9$4 ,! l5g? ( ! base be+ kn[n1 ! di/ance ( ! remote object c !n be calculat$4 ,9 ! same way two obs]vations c be made1 "o at ea* end ( a %ip1 ! l5g? ( ! %ip =m+ ! base-l9e4 ,or an in/rum5t c be made by :i* two obs]vations c be made simultane\sly by ! same man4 ,?is is done by means ( mirrors :i* are turn$ s t ! same object is se5 9 bo? ( !m1 app>5tly 9 a /raight l9e4 ,! ext5t to :i* "o ( !m has to be turn$ gives ! angle1 & ! in/rum5t =ms ! base4 ,anyone ) ! slighte/ geometrical exp]i5ce w p]ceive at once t ! be/ results are obta9$ :5 ! base-l9e is ( consid]able l5g?1 & h5ce small portable range-f9d+ in/rum5ts su* z c be easily c>ri$ & us$ by "o man are necess>ily less accurate ?an an arrangem5t su* z has be5 sugge/$ above1 :]e two obs]v]s "w simultane\sly f ! two ends ( a %ip4 ,9 _m cases1 h[ev]1 ! self-conta9$ in/rum5t is ! only "o :i* x is possible to use1 & :5 ! in/rum5t is well made & 9 exp]i5c$ h&s ! results are surpris+ly good4 ,z us$ 9 survey+1 = example1 :]e ! base-l9e may be any?+1 accord+ to circum/ances1 & ! angles may likewise v>y at bo? ends1 elaborate trigonometrical calculations h to be p]=m$ to arrive at ! desir$ result4 ,if1 h[ev]1 ! base-l9e be always ! same1 & "o ( ! angles be always a "r angle1 ! di/ance ( ! di/ant object w v>y ) ! rema9+ angle4 ,inde$ ! scale by :i* t angle is measur$ c be made to give n degrees1 b ! di/ance ( ! object4 ,portable range-f9d]s1 !re=e1 9 _m cases h "o reflector set = a "r angle & only "o ( ! reflectors movable4 ,! in/rum5t !n %[s ! di/ance ( ! object at a glance4 ,?is is impossible 9 ! case ( two sep>ate obs]vations on a %ip4 ,9 t case ! base is always ! same1 b s9ce ! %ip _c be set at "r angles to ! object :5ev] a range has to be f\nd1 bo? angles h to be measur$4 ,!re is1 h[ev]1 a beautifully simple little me*anism 9 :i* two po9t]s are set "o to ea* ( ! two angles1 & ! di/ance is !n %[n in/antly4 ,,app5dix ,a ,,description ,,( ,,! ,,rifles ,,%[n ,,at ,,page #bdj ,,! ,,g]man ,,maus] c fire =ty r\nds a m9ute--m ?an any o!r rifle us$ 9 ! w>4 ,! rifle is ( ! #ahih patt]n1 weighs #i lb4 #ad oz4 ) bayonet fix$1 & is sight$ f #bai to #bahg y>ds4 ,! magaz9e holds five c>tridges1 pack$ 9 *>g]s4 ,z ! rifle is n provid$ ) a cut-(f1 x _c be us$ z a s+le-load]4 ,) its long b>rel & long bayonet x gives a /abb+ l5g? ( #e ft4 #i 94--#h 94 long] ?an ! ,briti%4 ,,! ,,au/rian ,,rifle is ! ,mannli*]4 ,?is rifle is v fa/ 9 action z a snap back & =? ( ! wri/ is suffici5t to op]ate x4 ,x is1 h[ev]1 m try+ = prolong$ "w1 ow+ to ! ?r[+ ( ! /ra9 only on ! wri/4 ,)\t ! bayonet ! rifle weighs only #h lb4 #e oz41 ! lighte/ ( all1 yet ! bullet--#bdd gra9s--is ! heavie/ us$ by any ( ! bellig]5ts4 ,! rifle is sight$ f #daj to #bacb y>ds1 & ! b>rel has a f\r-groove rifl+4 ,,! ,,briti% ,,lee-,,enfield--,,m>k ,,iii--is ! outcome ( ! ,s\? ,african ,w>4 ,x is n too long = horseback & is yet q effici5t = infantry4 ,! b>rel is #be 94 long & has five grooves 9 ! rifl+4 ,x is sight$ f #bjj to #bhjj y>ds4 ,! rifle is fitt$ ) a magaz9e :i* holds t5 c>tridges pack$ 9 *>g]s1 ea* ( :i* conta9s five r\nds1 s t ! magaz9e is fill$ ) t5 r\nds 9 two motions4 ,! rifle is also fitt$ ) a cut-(f1 :i* enables x to be us$ z a s+le-load]4 ,x is altoge!r a mo/ effici5t weapon4 ,,! ,,fr5* ,,lebel is ( ! #ahhf-ahic patt]n1 & ) bayonet fix$ is long] ?an any o!r rifle4 ,x weighs1 )\t bayonet1 #i lb4 #c-a_/b oz4 ,! tube magaz9e "u ! b>rel conta9s eight c>tridges2 x takes1 ( c\rse1 long] to *>ge ?an a magaz9e load$ ) a *>g]4 ,x does n fire z _m %ots a m9ute z "s ( ! o!r rifles 9 ! field4 ,! position ( ! magaz9e is indicat$ by ! crosses4 ,! rifle is sight$ f #bgc to #bahg y>ds1 & ! bullet weighs #aih gra9s4 ,,! ,,belgian ,,army uses ! #ahhi patt]n ,maus]1 :i* weighs j ov] #h lb4 & is sight$ f #edg to #bahg y>ds4 ,! magaz9e holds five c>tridges c>ri$ 9 clips2 n hav+ a cut-(f1 ! rifle _c be us$ z a s+le-load]4 ,x has f\r grooves 9 its rifl+ & measures #d ft4 #b-a_/d 941 or1 ) ! bayonet1 #d ft4 #aa-c_/d 94 ,! bayonet is %ort & flat4 ,,! #c ,,l9e ,,nagant ( ,russia is #a_/d lb4 heavi] ?an ! ,briti% rifle & is ov] #g 94 long]4 ,! triangul> bayonet is always fix$ & nev] remov$ f ! rifle4 ,! magaz9e ( ! rifle is ( ! box type & holds five c>tridges4 ,! rifle is capable ( dis*>g+ tw5ty-f\r bullets to ! m9ute4 ,a useful feature is ! int]rupt]1 :i* prev5ts jamm+ ( two c>tridges4 ,,! ,,italian ,,mannli*]-,,c>cano is ( ! #ahia patt]n4 ,x weighs1 )\t bayonet1 j ov] #h lb4 #f oz4 & measures #ej-c_/d 94 ,! b>rel1 #cj-c_/d 94 long1 has a f\r-groove rifl+4 ,! box magaz9e1 fix$ "u receiv] )\t cut-(f1 holds six c>tridges4 ,! magaz9e holds six r\nds1 & ! rifle is capable ( dis*>g+ fifte5 r\nds a m9ute4 ,,index ,a ,accumulators or second>y batt]ies1 #fe ,a]ial craft exp]im5ts1 #bjb ,a]obic & ,ana]obic bact]ia1 #bcd ,aft]damp1 #bbh ,alcohol z a fuel1 #di ,alt]nat+ curr5t1 #ce1 #aic ,alt(ts1 artificial coal m9e at1 #aci ,alum9ium1 #acc ,amalgam1 #aag ,ammet]s1 #be ,ammonia 9 mak+ ice1 #gb ,ammunition = big guns1 #bdj ,amp]es1 #bb1 #bd ,analysis & syn!sis1 #dc ,anode1 #ee ,ans*utz1 ,dr1 #if ,ant5nae1 #afb1 #aga ,an?rac5e oil1 #dh ,arc1 !1 9 wireless1 #afe ,argon1 ! gas1 #ge ,artesian wells1 #de ,atmosph]e1 a unit ( measure1 #gb ,atoms1 #ef ,avogadro's ,con/ant1 #cc ,b ,bact]ia1 b5efic5t1 #bcd ,ball mill1 !1 #aae ,batt]y1 electrical1 #bc ,b5z9e1 #de1 #dh ,bessem]1 ,sir ,h41 #bcf ,bl[pipe1 oxyhydrog51 #abj ,bo>d ( ,trade ,unit1 !1 #bb ,boil+ wat]1 #aj1 #gf ,bore ( a gun1 #bcf ,b\ld]s1 bla/+1 #bj ,branly1 #aff ,brattice clo?1 #bbd ,bree* ( a big gun1 #bdj ,br5nan torp$o1 !1 #ajb ,brew+1 #ej ,br9e 9 ma*9e-made cold1 #gj ,budd+ ( yea/1 !1 #ea ,c ,calibre ( a gun1 #bcf ,capacity1 #aec ,capacity & inductance1 electrical prop]ties1 #afa ,c>bolic oil1 #dh ,c>bon1 #aa ,c>bonic acid gas1 #aj ,c>burett]1 !1 #df ,c>diograms1 #cb ,caselli1 #agf ,ca?ode1 #ee ,cav5di%1 inve/igations (1 #gc ,cellulose1 #ab1 #dd ,c5trifugal t5d5cy1 #aae ,"* ( a ligh?\se1 #hf ,*>ge & curr5t1 #cb ,*$dite1 #ac ,*emicals 9 wat]works1 #bcb ,*emi/ry1 organic & inorganic1 #db ,*lorate ( pota%1 #ab ,*loride ( soda1 #eh ,*ronograph1 !1 #ada ,cl>k's ,cell1 #bc ,coal & oil1 #dg ,coal1 burnt1 #aj ,coal-du/ an explosive1 #aj ,coal-du/1 explosions f1 #aci ,coal-pit*1 #dh ,coal-t>1 #dh ,coa/+ lights1 #hj ,coh]]1 !1 #ajc1 #afb1 #afg ,coke 9 smelt+1 #abe ,colli]y explosions1 #acg ,colli]y explosions1 rescue app>atus1 #bbf ,col\rs ( ! spectrum1 #bac ,col\rs ( fl[]s1 #bac ,compass1 a %ip's1 #ia ,compress$ air 9 torp$oes1 #ajj ,conc5trates1 #aae ,cond5s]s 9 wireless1 #afc ,cons]vation ( en]gy1 #acb ,contact mak]s1 #ade ,coronium1 ! gas1 #gd ,corundum1 #acd ,c\lombs1 #bc ,c\rri]es colli]y disa/]1 #bba ,creosote1 #dh ,creosote oil1 #dh ,crooks1 ,sir ,w41 #cc ,cru%+ mills1 #aae ,cry/al detectors1 #aga ,curie1 ,m4 & ,mme41 #cc ,curtis & ,h>vey1 #i ,cyanide process1 !1 #aah ,cyanog51 #aah ,cymog5e1 #de ,d ,detectors1 #afg ,detonator1 !1 #ad ,dextro-glucose1 #ea ,diamonds1 #ace ,diesel eng9es1 #df ,direct-curr5t electric motor1 #aia ,dirt-aug]1 !1 #ae ,dit*es1 bla/+1 #ah ,dra9age1 #bcc ,du ,pont ,p[d] ,company1 #i ,duddell1 ,w4 ,h41 #cg ,dufay diopti*rome process1 #bai ,dynamite1 :at x is1 #i1 #ab2 9 agriculture1 #ac2 fir+ a *>ge1 #af2 fruit trees1 #af2 m>%y ponds1 #ag2 dit*es1 #ah2 tree /umps1 #ai2 b\ld]s1 #ai2 wells1 #bj ,dynamo1 !1 #fe ,e ,eddy/one ,ligh?\se1 #hj ,edison's accumulator1 #ff ,e9?ov51 ,pr(41 #cj ,electric arc1 !1 #abc ,electric furnace1 #abe ,electric fuse1 !1 #af ,electrical ,in]tia1 #aec ,electrical batt]y1 #bc2 pressure1 #bc2 cells1 #bc2 measure1 #bd2 magnetism1 #be ,electricity1 #bb2 ! curr5t1 #ef2 electro-plat+1 #eh2 purification ( metals1 #fa2 second>y batt]ies1 #fb ,electrode1 #ee ,electrolysis1 #ee1 #agj2 9 dra9age1 #bcd ,electrolyte1 #ee ,electromet]1 !1 #cb1 #cd ,electro-plat+1 #eh ,electros1 #fj ,electroscope1 !1 #cd ,endosp]m1 !1 #ej ,eng9es driv5 by oil fuel1 #df ,enzymes1 #ej ,e!r1 #de1 #adi ,e?yl alcohol1 #di ,explosions1 #i2 9 m9es1 #acg ,explosive l9k1 !1 #ajd ,explosives = guns1 #bcg ,f ,falls 9 a coal m9e1 #bbc ,f]m5tation1 #ej ,fess5d51 ,r4 ,a41 #afi ,field guns1 #bda ,filt]s 9 wat]works1 #bcb ,fire-damp1 #acg ,fir+-p9 ( torp$o1 #ajb ,fla%+ lights1 #ha ,fog1 effects (1 #hb ,fog signals1 #hh ,fractional di/illation1 #gf ,frequ5cy1 #cf ,frequ5cy met]1 #aic ,friction clut*1 #aie ,frue vann]1 !1 #aaf ,fruit trees & dynamite1 #af ,fuses1 fir+1 #bj ,g ,galvanomet]1 !1 #bg1 #agj ,gangue1 !1 #aab ,gauges1 #bjh ,gelignite1 #ab ,glyc]9e 9 explosives1 #aa ,gold1 #aaj ,guid+ lights1 #ha ,gyroscope1 !1 #ic1 #ajj ,h ,half-tone illu/rations1 #aha ,h>d-pan1 #ad ,h>ris1 ,sir ,w4 ,s41 #cf ,hawke & ,olympic1 collision betwe51 #aih ,head ( ! torp$o1 #ii ,heat & electricity1 #cg ,heat ( ! electric arc1 #abc ,heat1 te/+ by1 #bje ,helium1 #cc1 #ge ,h]tz1 #aed ,h[itz]s1 #bda ,hughes1 ,pr(41 #aei ,humphrey ,gas ,pump1 #bca ,hydraulic+1 #aab ,hydro-c>bons1 #de ,hydrog51 liquid1 #gc ,hydromet]1 !1 #fe ,hydro/atic valve ( torp$o1 #aja ,hyp]-radial app>atus1 #hh ,i ,ice1 ma*9e-made1 #ga ,indigo1 syn!tic1 #dd ,inductance1 #aed ,induction coil = wireless1 #afb ,induction furnaces1 #abi ,insulat+ ink1 #agg ,int]f]5ce ( light waves1 #aei ,ionisation ( ! atmosph]e1 #agb ,iron1 #aji ,j ,jupit]'s moons1 #aej ,k ,kelv91 ,"l1 #bh ,k]os5e1 #df ,kieselguhr1 #ab ,kil[att1 !1 #be ,k9ematograph 9 coal m9e exp]im5ts1 #adf ,korn1 ,pr(41 #ahc ,krypton1 ! gas1 #ge ,l ,leclan*e cell1 !1 #bc ,leyd5 j>1 !1 #aec ,light1 spe$ (1 #aea ,light waves1 #aea ,ligh?\se1 !1 #gh ,ligh?\se lamp1 !1 #hc ,limit gauges1 #bji ,liquid air1 #gc ,lodge1 ,sir ,o41 #aei1 #afa ,lumi]e auto*rome process1 #baf ,m ,magnetic detector1 ! fir/1 #afh ,magnetic pole1 !1 #ij ,magnetism1 #be ,magnets1 #be ,mak+ light1 !1 #gi ,malt/]1 !1 #ej ,mansfield ,rescue ,/ation1 !1 #bbd ,m>coni1 #afa ,m>%y ponds1 to remove by dynamite1 #ag ,ma% tun1 !1 #ej ,ma/] compass1 !1 #ig ,ma/] records1 #fj ,maxwell1 ,j4 ,c41 #aeb ,measur+ by electrolysis1 #fb ,m5deluff's table1 #gd ,m]cury1 #aad ,metallographic te/+1 #bje ,metals1 te/+1 #bjd ,me?ane gas1 #aj1 #abd ,me?yl alcohol1 #di1 #ec ,microbes1 _! use1 #dc ,m9e-lay+1 #aje ,m9e-sweep+1 #ajg ,molecules1 #ef ,morris1 ,william1 #bcc ,mud1 gold f1 #abb ,muirhead1 ,dr1 #afg ,murette or p$e/al ( ligh?\se lamp1 #he ,n ,naph?a1 #de ,national ,physical ,laboratory1 #aii ,natural frequ5cy1 #afa ,neon1 ! gas1 #ge ,nickel *rome gun /eel1 #bci ,nitric acid1 #aa ,nitro-cotton1 #ab ,nitro-glyc]9e1 #aa ,nitrog5 gas1 #i ,nobel1 inv5tor ( dynamite1 #ab1 #ace ,nodes1 #aeg ,o ,ohm1 !1 #bb1 #bd ,ohmmet]1 !1 #bg ,ohm's law1 #bg ,oil1 m9]al1 #dd ,oil-produc+ c\ntries1 #dg ,optical app>atus ( ligh?\se1 #hf ,ord]s ( ligh?\se app>atus1 #hh ,ores1 #aaj ,or?o*romatic plates1 #bab ,oscillations1 electrical1 #cf ,oscillatory circuit1 #aed ,oscillograph1 ,duddell's1 #ci ,oxide ( iron1 #acc ,oxyacetyl5e flame1 !1 #aca ,oxyg5 gas1 #aj ,oxyhydrog5 jet1 #acj ,p ,p>aff9 wax1 #de ,pat5ts1 #agd ,p]iodicity1 #cf ,p]sonal equation1 !1 #bjg ,petrol1 #de1 #eb ,petroleum1 #dd ,phonograph1 !1 #fj ,plans ( a %ip1 #aii ,plates ( ! second>y batt]y1 #fd ,plat9um1 #ahd ,plumbago 9 plat+1 #ei ,p\ls5 arc1 !1 #agc ,p\ls51 ,valdem>1 #afe ,pressure gauges1 #adc ,prie/ly1 inve/igations (1 #gc ,prim>y col\rs1 #bac ,prisms1 reflection (1 #he ,process blocks1 #ahf ,projectiles1 velocity (1 #bcg ,propell]s ( ! torp$o1 #ii ,propell]s1 te/+ a]ial1 #bjc ,pr\t's anonym\s essay1 #gd ,prussiate ( pota%1 #agg ,purification ( metals1 #fb ,q ,quadrant electromet]1 !1 #ce ,qu>tz1 #aac2 fibre1 #ca1 #aca ,r ,radium1 #cc ,ramsey1 ,sir ,w41 #ge ,range-f9d+1 #bdj1 #bdb ,rayleigh1 ,"l1 #gd ,receiv+ in/rum5ts = wireless1 #afb ,record vann]1 !1 #aaf ,rectifi]1 !1 #cg1 #aga ,r$ rays ( light1 #hb ,reflection by prisms1 #hd ,reflectors1 ligh?\se1 #hd ,reiss electrical !rmomet]1 #cf ,repeat$-impact te/+ ma*9e1 #bjd ,rescue teams = colli]y accid5ts1 #bba1 #bbb ,resi/ance weld+1 #abf ,resonance1 an exp]im5t1 #afj ,reviv+ app>atus = coal m9es1 #bbi ,rheo/at1 !1 #ahh1 #aia ,rhigol5e1 #de ,rifl+ ( a gun1 #bci ,rubb]1 syn!tic1 #dd ,rubies1 artificial1 #aca ,rudd]s ( a torp$o1 #ajj ,ru!r=d1 ,pr(41 #cc1 #afh ,s ,sac*>9e1 #dh ,saltpetre1 #ab ,s*w>tzkopff torp$o1 !1 #ii ,scilly ,isl& ligh?\se1 #hj ,sea1 gold 9 !1 #abj ,second>y batt]y1 !1 #fb ,sectors1 #ha ,sel5ium1 #ahd ,self-rescue app>atus1 a1 #bbh ,%ale1 oil f1 #de ,%ells = guns1 #bci ,%ips1 te/+ by models1 #bjj ,%ort circuit1 #agi ,%unt1 !1 #afe ,sight+ a big gun1 #bda ,silica1 #acc ,skat+ r9ks1 ice 91 #ga ,sludge & efflu5t ( dra9age1 #bcc ,sp>k detectors1 #aff ,sp>k-gap1 #afb ,spectrum1 !1 #bac ,sp9?>iscopes1 #cc ,spirits1 #eb ,spr+s1 te/+1 #bjc ,/amps = cru%+ qu>tz1 #aac ,/>* gra9s 9 col\r photography1 #bag ,/ep-d[n & /ep-up trans=m]s1 #abg ,/r+ galvanomet]1 !1 #cj ,subm>9e m9es1 #ajd ,subm>9e telephone1 #hh ,sulphuric acid1 #aa1 #dc ,sunlight1 composition (1 #bac ,syn*ronism1 difficulties (1 #ahb1 #aia ,syn!tic sub/ances1 #dd ,t ,tamp+1 #ae ,tank = te/+ at ,t$d+ton1 #bja2 ,new ,york h>b\r1 #bja ,telautograph1 !1 #ahj ,telectograph1 !1 #ahj1 #ahe ,telegraph key = wireless1 #afb ,telewrit]1 !1 #ahg ,temp]ature1 measur+1 #ch ,tesla1 ,nicola1 #afd ,te/+ by heat1 #bje ,te/+ ma*9es1 #bjf ,!rmit1 #ace ,!rmo-c\ple1 !1 #ch ,!rmo-galvanomet]1 !1 #cg ,?omson ,mirror ,galvanomet]1 !1 #bh ,?omson1 ,pr(41 ,s41 #aei ,torp$o1 !1 #ih ,tra9+ /ation at ,por?1 #bbe ,trans=m]1 !1 #abg ,transmitt+ in/rum5ts1 #afc ,trav]s1 ,pr(41 #ge ,tree /umps1 bla/+1 #ai ,tun+-=k a /&>d ( spe$1 #aic ,turret ( a battle%ip1 #bdj ,u ,ultra-microscope1 !1 #bji ,ultra-violet rays1 #agb ,v ,v>ley & ! ,atlantic cable1 #bh ,vasel9e1 #df ,ve9s or lodes1 #aac ,vick]s1 #bjb ,voltmet]1 !1 #bf ,volts1 #bb1 #bd ,w ,wat] a s\rce ( heat1 #abd ,wat]1 s(t & h>d1 #bcb ,watt1 !1 #bd ,waves caus$ by %ips1 record+1 #bjj ,wax models ( %ips1 #aii ,weld+ by electricity1 #abe ,wells1 bla/+1 #bj ,welsba* mantle1 !1 #abd ,:itehead1 #ii ,wire guns1 #bch ,wireless telegraphy1 #afa1 #agc ,wireless torp$o1 !1 #ajb ,wood-meal 9 explosives1 #ab ,wood _s1 #di ,work+ fluid1 !1 #fh ,y ,yea/1 #ea ,z ,z]o1 #fh ,z9c 9 gold recov]y1 #aai 99 99 99 99 99 ,,! ,,riv]side ,,press ,,limit$1 ,,ed9burgh #aiag