,transcrib]'s ,note ,! punctuation & spell+ f ! orig9al text h be5 fai?fully pres]v$4 ,only obvi\s typographical errors h be5 correct$4 ,subscripts are repres5t$ z ,x#a4 ,sup]scripts are repres5t$ by ,x#a4 ,,h[ ,,x ,,works ,,au?or',s ,,note4 ,i beg to ?ank ! foll[+ g5tlem5 & firms = ! help !y h giv5 me 9 connection ) ! lett]press & illu/rations ( ,h[ ,x ,works-- ,messrs4 ,f4,j4,c4 ,pole & ,m4,g4 ,twe$ie 7= revision ( ,,ms472 ,w4 ,l9eham2 ,j4,f4 ,k5dall2 ,e4 ,eds]2 ,a4,d4 ,helps2 ,j4 ,limb2 ,! ,edison ,bell ,phonograph ,co42 ,messrs4 ,holmes & ,co42 ,! ,pelton ,:eel ,co42 ,messrs4 ,babcock & ,wilcox2 ,messrs4 ,siebe1 ,gorman1 & ,co42 ,messrs4 ,negretti & ,zambra2 ,messrs4 ,*ubb2 ,! ,yale ,lock ,co42 ,! ,micromet] ,eng9e]+ ,co42 ,messrs4 ,m>%all & ,sons2 ,! ,maign5 ,filt] ,co42 ,messrs4 ,broadwood & ,co4 ,illu/ration3 ,,on ,,! ,,footplate ,,( ,a ,,locomotive4 ,h[ ,x ,works ,deal+ 9 ,simple ,language ) ,/eam1 ,electricity1 ,light1 ,heat1 ,s\nd1 ,hydraulics1 ,optics1 etc4 & ) _! applications to ,app>atus 9 ,common ,use ,by ,,ar*ibald ,,williams ,au?or ( ,! ,romance ( ,mod]n ,inv5tion1 ,! ,romance ( ,m9+1 etc41 etc4 ,,?omas ,,nelson ,,& ,,sons ,london1 ,ed9burgh1 ,dubl91 & ,new ,york ,,preface4 ,h[ does x "w8 ,?is "q has be5 put to me s (t5 by p]sons "y & old t ,i h at la/ decid$ to answ] x 9 su* a mann] t a mu* l>g] public ?an t ) :i* ,i h p]sonal acqua9tance may be able to satisfy !mselves z to ! pr9ciples und]ly+ _m ( ! me*anisms met ) 9 ev]yday life4 ,9 ord] to include /eam1 electricity1 optics1 hydraulics1 !rmics1 light1 & a v>iety ( deta*$ me*anisms :i* _c be classifi$ "u any "o ( ^! heads1 )9 ! compass ( ab\t #dej pages1 ,i h to be cont5t ) a comp>atively brief treatm5t ( ea* subject4 ,?is brevity has 9 turn compell$ me to deal ) pr9ciples r ?an ) detail$ descriptions ( individual devices--?\gh 9 sev]al cases recogniz$ types are exam9$4 ,! read] w look 9 va9 = acc\nts ( ! ,y]kes telescope1 ( ! late/ ?+ 9 motor c>s1 & ( ! l>ge/ locomotive4 ,b he w be put 9 ! way ( und]/&+ ! ess5tial nature ( all telescopes1 motors1 & /eam-eng9es s f> z !y are at pres5t develop$1 :i* ,i ?9k may be ( great] ultimate pr(it to ! un9itiat$4 ,:ile c>eful to avoid puzzl+ ! read] by ! use ( my/]i\s phraseology ,i consid] t ! p>ts ( a ma*9e %\ld be giv5 _! te*nical names :]ev] possible4 ,to prev5t misconception1 _m ( ! diagrams accompany+ ! lett]press h words z well z lett]s writt5 on !m4 ,?is c\rse also obviates ! we>isome ref]5ce f text to diagram necessitat$ by ! use ( solit>y lett]s or figures4 ,i may add1 ) reg>d to ! diagrams ( ?is book1 t !y are purposely some:at unconv5tional1 n be+ drawn to scale nor con=m+ to ! canons ( pr(essional draughtsman%ip4 ,:]e advisable1 a "p ( a ma*9e has be5 exagg]at$ to %[ its details4 ,z a rule solid black has be5 pref]r$ to f9e %ad+ 9 sectional draw+s1 & all unnecess>y l9es are omitt$4 ,i w\ld "h ackn[l$ge my indebt$ness to my draughtsman1 ,mr4 ,frank ,hodgson1 = 8 c>e & indu/ry 9 prep>+ ! two hundr$ or m diagrams = :i* he 0 responsible4 ,f\r organs ( ! body--! eye1 ! e>1 ! l>ynx1 & ! he>t--are notic$ 9 appropriate places4 ,! eye is comp>$ ) ! cam]a1 ! l>ynx ) a re$ pipe1 ! he>t ) a pump1 :ile ! e> fitly op5s ! *apt] on ac\/ics4 ,! read] :o is unacqua9t$ ) physiology w ?us be enabl$ to appreciate ! bett] ^! m>vell\s devices1 f> m m>vell\s1 by reason ( _! absolutely automatic action1 ?an any creation ( human h&s4 ,a4,w4 ,,upl&s1 ,,/oke ,,poges1 ,,bucks4 ,,cont5ts4 ,*apt] ,i4--,,! ,,/eam-,,eng9e4 ,:at is /eam8--,! me*anical en]gy ( /eam--,! boil]--,! circulation ( wat] 9 a boil]--,! enclos$ furnace--,! multitubul> boil]--,fire-tube boil]s--,o!r types ( boil]s--,aids to combu/ion--,boil] fitt+s--,! safety-valve--,! wat]-gauge--,! /eam-gauge--,! wat] supply to a boil] #ac ,*apt] ,,ii4--,,! ,,conv]sion ,,( ,,heat ,,en]gy ,,into ,,me*anical ,,motion4 ,reciprocat+ eng9es--,d\ble-cyl9d] eng9es--,! function ( ! fly-:eel--,! cyl9d]--,! slide-valve--,! ecc5tric--,lap ( ! valve3 expansion ( /eam--,h[ ! cut-(f is manag$--,limit ( expansive work+--,comp\nd eng9es--,arrangem5t ( expansion eng9es--,comp\nd locomotives--,rev]s+ ge>s--,l9k+-up--,pi/on-valves--,spe$ gov]nors--,m>9e-spe$ gov]nors--,! cond5s] #dd ,*apt] ,,iii4--,,! ,,/eam ,,turb9e4 ,h[ a turb9e works--,! ,de ,laval turb9e--,! ,p>sons turb9e--,description ( ! ,p>sons turb9e--,! expansive action ( /eam 9 a ,p>sons turb9e--,balanc+ ! ?ru/--,advantages ( ! m>9e turb9e #gd ,*apt] ,,iv4--,,! ,,int]nal-,,combu/ion ,,eng9e4 ,! mean+ ( ! t]m--,action ( ! int]nal-combu/ion eng9e--,! motor c>--,! />t+-h&le--,! eng9e--,! c>burett]--,ignition ( ! *>ge--,advanc+ ! sp>k--,gov]n+ ! eng9e--,! clut*--,! ge>-box--,! comp5sat+ ge>--,! sil5c]--,! brakes--,spe$ ( c>s #hg ,*apt] ,v4--,,electrical ,,app>atus4 ,:at is electricity8--,=ms ( electricity--,magnetism--,! p]man5t magnet--,l9es ( =ce--,electro-magnets--,! electric bell--,! induction coil--,! cond5s]--,trans=mation ( curr5t--,uses ( ! induction coil #aab ,*apt] ,,vi4--,,! ,,electric ,,telegraph4 ,ne$le in/rum5ts--,influ5ce ( curr5t on ! magnetic ne$le--,me?od ( rev]s+ ! curr5t--,s\nd+ in/rum5ts--,telegraphic relays--,record+ telegraphs--,high-spe$ telegraphy #abg ,*apt] ,,vii4--,,wireless ,,telegraphy4 ,! transmitt+ app>atus--,! receiv+ app>atus--,syntonic transmission--,! advance ( wireless telegraphy #acg ,*apt] ,,viii4--,,! ,,telephone4 ,! ,bell telephone--,! ,edison transmitt]--,! granul> c>bon transmitt]--,g5]al arrangem5t ( a telephone circuit--,d\ble-l9e circuits--,telephone ex*anges--,subm>9e telephony #adg ,*apt] ,,ix4--,,dynamos ,,& ,,electric ,,motors4 ,a simple dynamo--,cont9u\s-curr5t dynamos--,multipol> dynamos--,excit+ ! field magnets--,alt]nat+ curr5t dynamos--,! transmission ( p[]--,! electric motor--,electric light+--,! inc&esc5t lamp--,arc lamps--,s]ies & p>allel arrangem5t ( lamps--,curr5t = electric lamps--,electroplat+ #aei ,*apt] ,x4--,,railway ,,brakes4 ,! ,vacuum ,automatic brake--,! ,we/+h\se air-brake #ahg ,*apt] ,,xi4--,,railway ,,signall+4 ,! block sy/em--,position ( signals--,int]lock+ ! signals--,lock+ ge>--,po9ts--,po9ts & signals 9 comb9ation--,work+ ! block sy/em--,s]ies ( signall+ op]ations--,s+le l9e signals--,! tra9 /aff--,tra9 /aff & ticket--,electric tra9 /aff sy/em--,int]lock+--,signall+ op]ations--,p[] signall+--,pneumatic signall+--,automatic signall+ #bjj ,*apt] ,,xii4--,,optics4 ,l5ses--,! image ca/ by a convex l5s--,focus--,relative position ( object & l5s--,correction ( l5ses = col\r--,sph]ical ab]ration--,di/ortion ( image--,! human eye--,! use ( spectacles--,! bl9d spot #bcj ,*apt] ,,xiii4--,,! ,,microscope1 ,,! ,,telescope1 ,,& ,,! ,,magic-,,lant]n4 ,! simple microscope--,use ( ! simple microscope 9 ! telescope--,! t]re/rial telescope--,! ,galilean telescope--,! prismatic telescope--,! reflect+ telescope--,! p>abolic mirror--,! comp\nd microscope--,! magic-lant]n--,! bioscope--,! plane mirror #bec ,*apt] ,,xiv4--,,s\nd ,,& ,,musical ,,in/rum5ts4 ,nature ( s\nd--,! e>--,musical in/rum5ts--,! vibration ( /r+s--,! s\nd+-bo>d & ! frame ( a piano--,! /r+s--,! /rik+ me*anism--,! quality ( a note #bgj ,*apt] ,,xv4--,,w9d ,,in/rum5ts4 ,longitud9al vibration--,columns ( air--,resonance ( columns ( air--,l5g? & tone--,! op5 pipe--,! ov]tones ( an op5 pipe--,:]e ov]tones are us$--,! arrangem5t ( ! pipes & p$als--,sep>ate s\nd-bo>ds--,v>ieties ( /ops--,tun+ pipes & re$s--,! bell[s--,electric & pneumatic actions--,! l>ge/ organ 9 ! _w--,human re$s #bhg ,*apt] ,,xvi4--,,talk+-,,ma*9es4 ,! phonograph--,! record]--,! reproduc]--,! gramophone--,! mak+ ( records--,cyl9d] records--,gramophone records #caj ,*apt] ,,xvii4--,,:y ,,! ,,w9d ,,bl[s4 ,:y ! w9d bl[s--,l& & sea breezes--,light air & moi/ure--,! b>omet]--,! column b>omet]--,! :eel b>omet]--,a v simple b>omet]--,! an]oid b>omet]--,b>omet]s & wea!r--,! div+-bell--,! div+-dress--,air-pumps--,pneumatic tyres--,! air-gun--,! self-clos+ door-/op--,! action ( w9d on oblique surfaces--,! balloon--,! fly+-ma*9e #cbb ,*apt] ,,xviii4--,,hydraulic ,,ma*9]y4 ,! siphon--,! bucket pump--,! =ce-pump--,! mo/ m>vell\s pump--,! blood *annels--,! c\rse ( ! blood--,! hydraulic press--,h\sehold wat]-supply fitt+s--,! ball-cock--,! wat]-met]--,wat]-supply sy/ems--,! h\sehold filt]--,gas traps--,wat] eng9es--,! cream sep>ator--,! hydro #cej ,*apt] ,,xix4--,,heat+ ,,& ,,light+4 ,! hot-wat] supply--,! tank sy/em--,! cyl9d] sy/em--,h[ a lamp works--,gas & gasworks--,automatic /ok+--,a gas gov]nor--,! gas met]--,inc&esc5t gas light+ #chf ,*apt] ,,xx4--,,v>i\s ,,me*anisms4 ,,clocks ,,& ,,wat*es3--,a %ort hi/ory ( timepieces--,! con/ruction ( timepieces--,! driv+ p[]--,! escapem5t--,comp5sat+ p5dulums--,! spr+ balance--,! cyl9d] escapem5t--,! lev] escapem5t--,comp5sat$ balance-:eels--,keyless w9d+ me*anism = wat*es--,! h\r h& tra94 ,,locks3--,! ,*ubb lock--,! ,yale lock4 ,,! ,,cycle3--,! ge>+ ( a cycle--,! free :eel--,! *ange-spe$ ge>4 ,,agricultural ,,ma*9es3--,! ?re%+-ma*9e--,m[+-ma*9es4 ,,"s ,,natural ,,ph5om5a3--,:y sun-heat v>ies 9 int5sity--,! tides--,:y high tide v>ies daily #daj ,,h[ ,,x ,,works4 ,*apt] ,i4 ,,! ,,/eam-,,eng9e4 ,:at is /eam8--,! me*anical en]gy ( /eam--,! boil]--,! circulation ( wat] 9 a boil]--,! enclos$ furnace--,! multitubul> boil]--,fire-tube boil]s--,o!r types ( boil]s--,aids to combu/ion--,boil] fitt+s--,! safety-valve--,! wat]-gauge--,! /eam-gauge--,! wat] supply to a boil]4 ,,:at ,,is ,,/eam8 ,if ice be heat$ above #cb ,fahr5heit1 its molecules lose _! cohesion1 & move freely r\nd "o ano!r--! ice is turn$ into wat]4 ,heat wat] above #bab ,fahr5heit1 & ! molecules exhibit a viol5t mutual repulsion1 &1 l dormant bees reviv$ by spr+ sun%9e1 sep>ate & d>t to & fro4 ,if conf9$ 9 an air-tight vessel1 ! molecules h _! flights curtail$1 & beat m & m viol5tly aga9/ _! prison walls1 s t e squ>e in* ( ! vessel is subject$ to a ris+ pressure4 ,we may comp>e ! action ( ! /eam molecules to t ( bullets fir$ f a ma*9e-gun at a plate m\nt$ on a spr+4 ,! fa/] ! bullets came1 ! great] w\ld be ! cont9u\s compression ( ! spr+4 ,,! ,,me*anical ,,en]gy ,,( ,,/eam4 ,if /eam is let into "o end ( a cyl9d] beh9d an air-tight b freely-mov+ pi/on1 x w bomb>d ! walls ( ! cyl9d] & ! pi/on2 & if ! unit$ pu% ( ! molecules on ! "o side ( ! latt] is great] ?an ! resi/ance on ! o!r side oppos+ its motion1 ! pi/on mu/ move4 ,hav+ ?us p>tly got _! lib]ty1 ! molecules become less active1 & d n ru% ab\t s vigor\sly4 ,! pressure on ! pi/on decreases z x moves4 ,b if ! pi/on 7 driv5 back to its orig9al position aga9/ ! =ce ( ! /eam1 ! molecul> activity--t is1 pressure--w\ld be re/or$4 ,we are "h assum+ t no heat has pass$ ?r\gh ! cyl9d] or pi/on & be5 radiat$ into ! air2 = any loss ( heat means loss ( en]gy1 s9ce heat is en]gy4 ,,! ,,boil]4 ,! combu/ion ( fuel 9 a furnace causes ! walls ( ! furnace to become hot1 :i* means t ! molecules ( ! sub/ance =m+ ! walls are ?r[n into viol5t agitation4 ,if ! walls are :at are call$ good conductors ( heat1 !y w transmit ! agitation ?r\gh !m to any surr\nd+ sub/ance4 ,9 ! case ( ! ord9>y h\se /ove ?is is ! air1 :i* itself is agitat$1 or gr[s w>m4 ,a /eam-boil] has ! furnace walls surr\nd$ by wat]1 & its function is to transmit molecul> movem5t 7heat1 or en]gy7 ?r\gh ! furnace plates to ! wat] until ! po9t is rea*$ :5 /eam g5]ates4 ,at atmosph]ic pressure--t is1 if n conf9$ 9 any way--/eam w\ld fill #a1faj times ! space :i* its molecules occupi$ 9 _! wat]y =mation4 ,if we seal up ! boil] s t no escape is possible = ! /eam molecules1 _! motion becomes m & m rapid1 & pressure is develop$ by _! beat+ on ! walls ( ! boil]4 ,!re is !oretically no limit to :i* ! pressure may be rais$1 provid$ t suffici5t fuel-combu/ion en]gy is transmitt$ to ! vaporiz+ wat]4 ,to raise /eam 9 l>ge quantities we mu/ employ a fuel :i* develops great heat 9 proportion to its weight1 is readily procur$1 & *eap4 ,coal fulfils all ^! conditions4 ,( ! #hjj million tons m9$ annually ?r\gh\t ! _w1 #djj million tons are burnt 9 ! furnaces ( /eam-boil]s4 ,a good boil] mu/ be--7#a7 ,/rong en\gh to )/& mu* high] pressures ?an t at :i* x is work$2 7#b7 s design$ z to burn its fuel to ! greate/ advantage4 ,ev5 9 ! be/-design$ boil]s a l>ge "p ( ! combu/ion heat passes ?r\gh ! *imney1 :ile a fur!r proportion is radiat$ f ! boil]4 ,pr(essor ,john ,p]ry#a consid]s t ?is wa/e am\nts1 "u ! be/ conditions at pres5t obta9able1 to elev5-twelf?s ( ! :ole4 ,we h to burn a %ill+swor? ( coal to capture ! en]gy /or$ 9 a p5nywor?4 ,yet ! /eam-eng9e ( to-day is ?ree or f\r times z effici5t z ! eng9e ( fifty ye>s ago4 ,?is is due to radical improvem5ts 9 ! design ( boil]s & ( ! ma*9]y :i* conv]ts ! heat en]gy ( /eam into me*anical motion4 ,,circulation ,,( ,,wat] ,,9 ,a ,,boil]4 ,if y place a pot fill$ ) wat] on an op5 fire1 & wat* x :5 x boils1 y w notice t ! wat] heaves up at ! sides & plunges d[n at ! c5tre4 ,?is is due to ! wat] be+ heat$ mo/ at ! sides1 & !re=e be+ lighte/ !re4 ,! ris+ /eam-bubbles also c>ry x up4 ,on rea*+ ! surface1 ! bubbles bur/1 ! /eam escapes1 & ! wat] loses "s ( its heat1 & ru%es d[n aga9 to take ! place ( /eam-lad5 wat] ris+4 ,illu/ration3 ,,fig4 #a4 ,illu/ration3 ,,fig4 #b4 ,if ! fire is v fi]ce1 /eam-bubbles may rise f all po9ts at ! bottom1 & imp$e d[nw>d curr5ts 7,fig4 #a74 ,! pot !n boils ov]4 ,fig4 #b %[s a me?od ( prev5t+ ?is tr\ble4 ,we l[] into our pot a vessel ( some:at small] diamet]1 ) a hole 9 ! bottom1 arrang$ 9 su* a mann] z to leave a space betwe5 x & ! pot all r\nd4 ,! upw>d curr5ts are !n sep>at$ entirely f ! d[nw>d1 & ! fire c be =c$ to a v mu* great] ext5t ?an be=e )\t ! wat] boil+ ov]4 ,?is v simple arrangem5t is ! basis ( _m devices = produc+ free circulation ( ! wat] 9 /eam-boil]s4 ,we c easily foll[ out ! process ( developm5t4 ,9 ,fig4 #c we see a simple ,u-tube dep5d+ f a vessel ( wat]4 ,heat is appli$ to ! left leg1 & a /eady circulation at once comm5ces4 ,9 ord] to increase ! heat+ surface we c ext5d ! heat$ leg into a long incl9e 7,fig4 #d71 b5ea? :i* ?ree lamps in/ead ( only "o are plac$4 ,! direction ( ! circulation is ! same1 b its rate is increas$4 ,illu/ration3 ,,fig4 #c4 ,a fur!r improvem5t results f increas+ ! numb] ( tubes 7,fig4 #e71 keep+ !m all on ! slant1 s t ! heat$ wat] & /eam may rise freely4 ,,! ,,enclos$ ,,furnace4 ,illu/ration3 ,,fig4 #d4 ,illu/ration3 ,,fig4 #e4 ,/ill1 a lot ( ! heat gets away4 ,9 a /eam-boil] ! burn+ fuel is enclos$ ei!r by fire-brick or a wat]-jacket1 =m+ "p ( ! boil]4 ,a wat]-jacket signifies a d\ble coat+ ( metal plates ) a space betwe51 :i* is fill$ ) wat] 7see ,fig4 #f74 ,! fire is n[ enclos$ mu* z x is 9 a kit*5 range4 ,b our boil] mu/ n be s wa/eful ( ! heat z is t useful h\sehold fixture4 ,on _! way to ! funnel ! flames & hot gases %\ld act on a v l>ge metal or o!r surface 9 contact ) ! wat] ( ! boil]1 9 ord] to give up a due proportion ( _! heat4 ,illu/ration3 ,,fig4 #f4--;,diagrammatic sket* ( a locomotive type ( boil]4 ,wat] indicat$ by dott$ l9es4 ,! arr[s %[ ! direction tak5 by ! air & hot gases f ! air-door to ! funnel4 ,,! ,,multitubul> ,,boil]4 ,illu/ration3 ,,fig4 #g4--,! ,babcock & ,wilcox wat]-tube boil]4 ,"o side ( ! brick seat+ has be5 remov$ to %[ ! arrangem5t ( ! wat]-tubes & furnace4 ,to save room1 boil]s :i* h to make /eam v quickly & at high pressures are l>gely compos$ ( pipes4 ,su* boil]s we call multitubul>4 ,!y are ( two k9ds--7#a7 ,wat]-tube boil]s2 9 :i* ! wat] circulates ?r\gh tubes expos$ to ! furnace heat4 ,! ,babcock & ,wilcox boil] 7,fig4 #g7 is typical ( ?is v>iety4 7#b7 ,fire-tube boil]s2 9 :i* ! hot gases pass ?r\gh tubes surr\nd$ by wat]4 ,! ord9>y locomotive boil] 7,fig4 #f7 illu/rates ?is =m4 ,! ,babcock & ,wilcox boil] is widely us$ 9 m9es1 p[] /ations1 &1 9 a modifi$ =m1 on %ipbo>d4 ,x consi/s ( two ma9 p>ts--7#a7 ,a drum1 ,h1 9 ! upp] "p ( :i* ! /eam collects2 7#b7 a gr\p ( pipes arrang$ on ! pr9ciple illu/rat$ by ,fig4 #e4 ,! boil] is seat$ on a rectangul> frame ( fire-bricks4 ,at "o end is ! furnace door2 at ! o!r ! exit to ! *imney4 ,f ! furnace ,f ! flames & hot gases rise r\nd ! upp] end ( ! slop+ tubes ,,tt into ! space ,a1 :]e !y play ^u ! "u surface ( ,h be=e plung+ d[nw>d aga9 among ! tubes into ! space ,b4 ,"h ! temp]ature is l[]4 ,! arr[s indicate fur!r j\rneys upw>ds into ! space ,c on ! "r ( a fire-brick division1 & pa/ ! d[n tubes ,,ss into ,d1 :5ce ! hot gases f9d an escape into ! *imney ?r\gh ! op5+ ,e4 ,x w be notic$ t ! greate/ heat is br\ght to be> on ,,tt ne> _! junction ) ,,uu1 ! uptake tubes2 & t e succe$+ passage ( ! pipes br+s ! gradually cool+ gases ne>] to ! d[ntake tubes ,,ss4 ,! pipes ,,tt are easily bru%$ & scrap$ aft] ! removal ( plugs f ! head]s into :i* ! tube ends are exp&$4 ,o!r well-kn[n wat]-tube boil]s are ! ,y>r[1 ,belleville1 ,/irl+1 & ,?orneycr(t1 all us$ = driv+ m>9e eng9es4 ,,fire-,,tube ,,boil]s4 ,fig4 #f %[s a locomotive boil] 9 section4 ,to ! "r is ! fire-box1 surr\nd$ on all sides by a wat]-jacket 9 direct communication ) ! b>rel ( ! boil]4 ,! inn] %ell ( ! fire-box is (t5 made ( copp]1 :i* )/&s ! fi]ce heat bett] ?an /eel2 ! out]1 l ! re/ ( ! boil]1 is ( /eel plates f #a_/b to #c_/d in* ?ick4 ,! %ells ( ! jacket are brac$ toge!r by a l>ge numb] ( rivets1 ,,rr2 & ! top1 or cr[n1 is /r5g!n$ by heavy longitud9al gird]s rivet$ to x1 or is brac$ to ! top ( ! boil] by long bolts4 ,a l>ge numb] ( fire-tubes 7only ?ree are %[n 9 ! diagram = ! sake ( simplicity7 ext5d f ! fire-box to ! smoke-box4 ,! mo/ p[]ful mammo? ,am]ican locomotives h #cej or m tubes1 :i*1 ) ! fire-box1 give #d1jjj squ>e feet ( surface = ! furnace heat to act ^u4 ,^! tubes are exp&$ at _! ends by a special tool into ! tube-plates ( ! fire-box & boil] front4 ,george ,/eph5son & 8 pr$ecessors exp]i5c$ great difficulty 9 r5d]+ ! tube-end jo9ts q wat]-tight1 b ! inv5tion ( ! exp&] has remov$ ?is tr\ble4 ,! fire-brick ar* %[n 7,fig4 #f7 9 ! fire-box is us$ to deflect ! flames t[>ds ! back ( ! fire-box1 s t ! hot gases may be ret>d$ some:at1 & _! combu/ion r5d]$ m p]fect4 ,x also helps to di/ribute ! heat m ev5ly ov] ! :ole ( ! inside ( ! box1 & prev5ts cold air f fly+ directly f ! fir+ door to ! tubes4 ,9 "s ,am]ican & ,cont95tal locomotives ! fire-brick ar* is replac$ by a wat] bridge1 :i* s]ves ! same purpose1 :ile giv+ additional heat+ surface4 ,! wat] circulation 9 a locomotive boil] is--upw>ds at ! fire-box end1 :]e ! heat is mo/ int5se2 =w>d along ! surface2 d[nw>ds at ! smoke-box end2 backw>ds along ! bottom ( ! b>rel4 ,,o!r ,,types ,,( ,,boil]s4 ,= small /ation>y l& eng9es ! v]tical boil] is mu* us$4 ,9 ,fig4 #h we h ?ree =ms ( ?is type--,a & ,b ) cross wat]-tubes2 ,c ) v]tical fire-tubes4 ,! furnace 9 e case is surr\nd$ by wat]1 & f$ ?r\gh a door at "o side4 ,illu/ration3 ,,fig4 #h4--;,diagrammatic repres5tation ( ?ree types ( v]tical boil]s4 ,! ,lanca%ire boil] is ( l>ge size4 ,x has a cyl9drical %ell1 measur+ up to #cj feet 9 l5g? & #g feet 9 diamet]1 trav]s$ f end to end by two l>ge flues1 9 ! re> "p ( :i* are situat$ ! furnaces4 ,! boil] is fix$ on a seat+ ( fire-bricks1 s built up z to =m ?ree flues1 ,a & ,,bb1 %[n 9 cross section 9 ,fig4 #i4 ,! furnace gases1 aft] leav+ ! two furnace flues1 are deflect$ d[nw>ds into ! *annel ,a1 by :i* !y pass und]nea? ! boil] to a po9t almo/ "u ! furnace1 :]e !y divide "r & left & travel ?r\gh cross passages into ! side *annels ,,bb1 to be l$ along ! boil]'s flanks to ! *imney exit ,c4 ,by ?is arrangem5t ! effective heat+ surface is greatly increas$2 & ! passages be+ l>ge1 natural draught g5]ally suffices to ma9ta9 prop] combu/ion4 ,! ,lanca%ire boil] is mu* us$ 9 factories & 79 a modifi$ =m7 on %ips1 s9ce x is a /eady /eam] & is easily kept 9 ord]4 ,illu/ration3 ,,fig4 #i4--;,cross & longitud9al sections ( a ,lanca%ire boil]4 ,9 m>9e boil]s ( cyl9drical %ape cross wat]-tubes & fire-tubes are (t5 employ$ to increase ! heat+ surface4 ,return tubes are also l$ ?r\gh ! wat] to ! funnels1 situat$ at ! same end z ! furnace4 ,,aids ,,to ,,combu/ion4 ,we may n[ turn our att5tion m p>ticul>ly to ! *emical process call$ combu/ion1 ^u :i* a boil] dep5ds = its heat4 ,ord9>y /eam coal conta9s ab\t #he p] c5t4 ( c>bon1 #g p] c5t4 ( oxyg51 & #d p] c5t4 ( hydrog51 besides traces ( nitrog5 & sulphur & a small incombu/ible residue4 ,:5 ! coal burns1 ! nitrog5 is releas$ & passes away )\t comb9+ ) any ( ! o!r elem5ts4 ,! sulphur unites ) hydrog5 & =ms sulphurett$ hydrog5 7also nam$ sulphur\s acid71 :i* is injuri\s to /eel plates1 & is l>gely responsible = ! decay ( tubes & funnels4 ,m ( ! hydrog5 unites ) ! oxyg5 z /eam4 ,! mo/ important elem5t 9 coal is ! c>bon 7kn[n *emically by ! symbol ,c74 ,its comb9ation ) oxyg51 call$ combu/ion1 is ! act :i* heats ! boil]4 ,only :5 ! c>bon pres5t has comb9$ ) ! greate/ possible am\nt ( oxyg5 t x w take into p>tn]%ip is ! combu/ion complete & ! full heat-value 7fix$ by sci5tific exp]im5t at #ad1ejj !rmal units p] p\nd ( c>bon7 develop$4 ,n[1 c>bon may unite ) oxyg51 atom = atom1 & =m c>bon monoxide 7,,co72 or 9 ! proportion ( "o atom ( c>bon to two ( oxyg51 & =m c>bon dioxide 7,,co#b74 ,! =m] gas is combu/ible--t is1 w admit ano!r atom ( c>bon to ! molecule--b ! latt] is saturat$ ) oxyg51 & w n burn1 or1 to put x o!rwise1 is ! product ( p]fect combu/ion4 ,a prop]ly design$ furnace1 suppli$ ) a due am\nt ( air1 w cause ne>ly all ! c>bon 9 ! coal burnt to comb9e ) ! full am\nt ( oxyg54 ,on ! o!r h&1 if ! oxyg5 supply is ineffici5t1 ,,co z well z ,,co#b w =m1 & !re w be a heat loss1 equal 9 extreme cases to two-?irds ( ! :ole4 ,x is !re=e necess>y t a furnace :i* has to eat up fuel at a great pace %\ld be artificially f$ ) air 9 ! proportion ( f #ab to #bj p\nds ( air = e p\nd ( fuel4 ,!re are two me?ods ( creat+ a viol5t draught ?r\gh ! furnace4 ,! fir/ is-- ,! =c$ draught2 v simply exemplifi$ by ! ord9>y bell[s us$ 9 e h\se4 ,on a %ip 7,fig4 #aj7 ! pr9ciple is develop$ z foll[s3--,! boil]s are situat$ 9 a comp>tm5t or comp>tm5ts hav+ no communication ) ! out] air1 except = ! passages d[n :i* air is =c$ by p[]ful fans at a pressure consid]ably great] ?an t ( ! atmosph]e4 ,!re is only "o way out--namely1 ?r\gh ! furnace & tubes 7or gas-ways7 ( ! boil]1 & ! funnel4 ,s ?r\gh ^! x ru%es1 rais+ ! fuel to :ite heat4 ,z may easily be imag9$1 ! temp]ature ( a /okehold1 especially 9 ! tropics1 is f> f pleasant4 ,9 ! ,r$ ,sea ! !rmomet] sometimes rises to #agj ,fahr5heit or m1 & ! poor /ok]s h a v bad "t ( x4 ,illu/ration3 ,,fig4 #aj4--,sket* %[+ h[ ! =c$ draught is produc$ 9 a /okehold & h[ x affects ! furnaces4 ,illu/ration3 ,,sc5e ,,9 ,,! ,,/okehold ,,( ,a ,,battle-,,%ip4 ,! second sy/em is t ( ! induc$ draught4 ,"h air is suck$ ?r\gh ! furnace by creat+ a vacuum 9 ! funnel & 9 a *amb] op5+ into x4 ,turn+ to ,fig4 #f1 we see a pipe ?r\gh :i* ! exhau/ /eam f ! locomotive's cyl9d]s is %ot upw>ds into ! funnel1 9 :i*1 & 9 ! smoke-box b5ea? x1 a /rong vacuum is =m$ :ile ! eng9e is runn+4 ,n[1 nature abhors a vacuum1 s air w get into ! smoke-box if !re be a way op54 ,!re is--?r\gh ! air-doors at ! bottom ( ! furnace1 ! furnace itself1 & ! fire-tubes2 & on ! way oxyg5 comb9es ) ! c>bon ( ! fuel1 to =m c>bon dioxide4 ,! p[] ( ! draught is s great t1 z "o (t5 notices :5 a tra9 passes dur+ ! night1 r$-hot c9d]s1 pluck$ f ! fire-box1 & dragg$ ?r\gh ! tubes1 are hurl$ f> into ! air4 ,x might be m5tion$ 9 p>5!sis t ! s-call$ smoke :i* p\rs f ! funnel ( a mov+ eng9e is ma9ly cond5s+ /eam4 ,a /eam%ip1 on ! o!r h&1 bel*es smoke only f its funnels1 z fre% wat] is f> too preci\s to wa/e z /eam4 ,we %all ref] to ?is lat] on 7p4 #gb74 ,,boil] ,,fitt+s4 ,! mo/ important fitt+s on a boil] are3--7#a7 ! safety-valve2 7#b7 ! wat]-gauge2 7#c7 ! /eam-gauge2 7#d7 ! me*anisms = fe$+ x ) wat]4 ,,! ,,safety-,,valve4 ,pr(essor ,?ur/on1 an em95t au?ority on ! /eam-eng9e1 has e/imat$ t a pla9 cyl9drical boil] c>ry+ #ajj lbs4 pressure to ! squ>e in* conta9s suffici5t /or$ en]gy to project x into ! air a v]tical di/ance ( #c-a_/b miles4 ,9 ! case ( a ,lanca%ire boil] at equal pressure ! di/ance w\ld be #b-a_/b miles2 ( a locomotive boil]1 at #abe lbs41 #a-a_/b miles2 ( a /eam tubul> boil]1 at #ge lbs41 #a mile4 ,accord+ to ! same writ]1 a cubic foot ( heat$ wat] "u a pressure ( f #fj to #gj lbs4 p] squ>e in* has ab\t ! same en]gy z "o p\nd ( gunp[d]4 ,/eam is a good s]vant1 b a t]rible ma/]4 ,x mu/ be kept "u /rict control4 ,h[ev] /rong a boil] may be1 x w bur/ if ! /eam pressure 9 x be rais$ to a c]ta9 po9t2 & "s device mu/ !re=e be fitt$ on x :i* w give ! /eam free egress be=e t po9t is rea*$4 ,a device ( ?is k9d is call$ a safety-valve4 ,x usually bl[s (f at less ?an half ! greate/ pressure t ! boil] has be5 prov$ by exp]im5t to be capable ( )/&+4 ,9 pr9ciple ! safety-valve d5otes an orifice clos$ by an accurately-fitt+ plug1 :i* is press$ aga9/ its seat on ! boil] top by a weight$ lev]1 or by a spr+4 ,z soon z ! /eam pressure on ! face ( ! plug exce$s ! c\nt]act+ =ce ( ! weight or spr+1 ! plug rises1 & /eam escapes until equilibrium ( ! oppos+ =ces is re/or$4 ,on /ation>y eng9es a lev] safety-valve is commonly employ$ 7,fig4 #aa74 ,! bl[+-(f po9t c be v>i$ by %ift+ ! weight along ! arm s z to give x a great] or less lev]age4 ,on locomotive & m>9e boil]s1 :]e %ocks & movem5ts h to be reckon$ )1 weights are replac$ by spr+s1 set to a c]ta9 t5sion1 & lock$ up s t !y _c be tamp]$ )4 ,illu/ration3 ,,fig4 #aa4--;,a ,,lev] ,,safety-,,valve4 ,v1 valve2 ,s1 seat+2 ,p1 p92 ,l1 lev]2 ,f1 fulcrum2 ,w1 weight4 ,! figures indicate ! positions at :i* ! weight %\ld be plac$ = ! valve to act :5 ! pressure rises to t numb] ( p\nds p] squ>e in*4 ,boil]s are te/$ by fill+ ! boil]s q full & 7#a7 by heat+ ! wat]1 :i* exp&s slightly1 b ) great pressure2 7#b7 by =c+ 9 additional wat] ) a p[]ful pump4 ,9 ei!r case a rupture w\ld n be att5d$ by an explosion1 z wat] is v inela/ic4 ,! days :5 an eng9e] c\ld sit on ! valves--t is1 screw !m d[n--to obta9 great] pressure1 are n[ pa/1 & ) !m a consid]able proportion ( ! dang]s ( high-pressure /eam4 ,! ,factory ,act ( #ahie1 9 =ce ?r\gh\t ! ,briti% ,isles1 provides t e boil] = g5]at+ /eam 9 a factory or work%op :]e ! ,act applies mu/ h a prop] safety-valve1 /eam-gauge1 & wat]-gauge2 & t boil]s & fitt+s mu/ be exam9$ by a compet5t p]son at lea/ once 9 e f\rte5 mon?s4 ,neglect ( ^! provisions r5d]s ! own] ( a boil] liable to heavy p5alties if an explosion occurs4 ,"o ( ! mo/ disa/r\s explosions on record took place at ! ,r$c> ,iron ,works1 ,york%ire1 9 ,june #ahie4 ,9 ?is case1 twelve out ( fifte5 boil]s rang$ side by side bur/1 ?r\gh "o prov+ too weak = its "w4 ,! fly+ fragm5ts ( ?is boil]1 /rik+ ! sides ( o!r boil]s1 explod$ !m1 & s ! damage 0 transmitt$ d[n ! l9e4 ,tw5ty m5 7 kill$ & injur$2 :ile masses ( metal1 weigh+ sev]al tons ea*1 7 hurl$ #bej y>ds1 & caus$ widespread damage4 ,! foll[+ is tak5 f a j\rnal1 dat$ ,decemb] #bb1 #ahie3 ,provid5ce 7,rhode ,isl&74--,a rec5t prophecy t a boil] w\ld explode betwe5 ,decemb] #af & #bd 9 a /ore has s]i\sly affect$ ! ,*ri/mas trade4 ,%opp]s are incr$ibly n]v\s4 ,"o /ore adv]tises1 ',no boil]s are be+ us$2 lifts runn+ electrically4' ,all /ores h _h _! boil]s inspect$4 ,,! ,,wat]-,,gauge4 ,no fitt+ ( a boil] is m important ?an ! wat]-gauge1 :i* %[s ! level at :i* ! wat] /&s4 ,! eng9e] mu/ cont9ually consult 8 gauge1 = if ! wat] gets too l[1 pipes & o!r surfaces expos$ to ! furnace flames may burn ?r\gh1 ) disa/r\s results2 :ile1 on ! o!r h&1 too mu* wat] w cause bad /eam+4 ,a section ( an ord9>y gauge is se5 9 ,fig4 #ab4 ,x consi/s ( two p>ts1 ea* furni%$ ) a gl&1 ,g1 to make a /eam-tight jo9t r\nd ! glass tube1 :i* is ins]t$ ?r\gh ! hole cov]$ by ! plug ,p#a4 ,! cocks ,t#a ,t#b are normally op51 all[+ ! +ress ( /eam & wat] respectively to ! tube4 ,cock ,t#c is kept clos$ unless = any reason x is necess>y to bl[ /eam or wat] ?r\gh ! gauge4 ,! holes ,c ,c c be clean$ out if ! plugs ,p#b ,p#c are remov$4 ,mo/ gauges on high-pressure boil]s h a ?ick glass scre5 9 front1 s t 9 ! ev5t ( ! tube break+1 ! /eam & wat] may n bl[ directly on to ! att5dants4 ,a fur!r precaution is to include two ball-valves ne> ! ends ( ! gauge-glass4 ,"u ord9>y conditions ! balls lie 9 depressions cle> ( ! ways2 b :5 a ru% ( /eam or wat] occurs !y are suck$ into _! seat+s & block all egress4 ,illu/ration3 ,,fig4 #ab4--,section ( a wat]-gauge4 ,on _m boil]s two wat]-gauges are fitt$1 s9ce any gauge may "w badly at times4 ,! glasses are te/$ to a pressure ( #c1jjj lbs4 or m to ! squ>e in* be=e use4 ,,! ,,/eam-,,gauge4 ,x is ( ! utmo/ importance t a p]son 9 *>ge ( a boil] %\ld "k :at pressure ! /eam has rea*$4 ,e boil] is !re=e fitt$ ) "o /eam-gauge2 _m ) two1 le/ "o might be unreliable4 ,!re are two pr9cipal types ( /eam-gauge3--7#a7 ,! ,b\rdon2 7#b7 ! ,s*ff]-,bud5b]g4 ,! pr9ciple ( ! ,b\rdon is illu/rat$ by ,fig4 #ac1 9 :i* ,a is a piece ( rubb] tub+ clos$ at "o end1 & at ! o!r drawn ov] ! nozzle ( a cycle tyre inflator4 ,if b5t 9 a curve1 z %[n1 ! section ( ! tube is an oval4 ,:5 air is pump$ 91 ! rubb] walls endeav\r to assume a circul> section1 because ?is %ape encloses a l>g] area ?an an oval ( equal circumf]5ce1 & !re=e makes room = a l>g] volume ( air4 ,9 do+ s ! tube /raight5s itself1 & assumes ! position indicat$ by ! dott$ l9es4 ,hang an empty inn] tube ( a pneumatic tyre ov] a nail & inflate x1 & y w get a good illu/ration ( ! pr9ciple4 ,illu/ration3 ,,fig4 #ac4--,%[+ ! pr9ciple ( ! /eam-gauge4 ,illu/ration3 ,,fig4 #ad4--;,b\rdon /eam-gauge4 ,"p ( dial remov$ to %[ me*anism4 ,9 ,fig4 #ad we h a ,b\rdon gauge1 ) "p ( ! dial face brok5 away to %[ ! int]nal me*anism4 ,t is a flatt5$ metal tube sold]$ at "o end into a holl[ ca/+1 into :i* screws a tap connect$ ) ! boil]4 ,! o!r end 7clos$7 is atta*$ to a l9k1 ,l1 :i* works an arm ( a quadrant rack1 ,r1 engag+ ) a small p9ion1 ,p1 actuat+ ! po9t]4 ,z ! /eam pressure rises1 ! tube ,t moves its free end outw>ds t[>ds ! position %[n by ! dott$ l9es1 & trav]ses ! arm ( ! rack1 s %ift+ ! po9t] r\nd ! scale4 ,z ! pressure falls1 ! tube gradually returns to its z]o position4 ,! ,s*ff]-,bud5b]g gauge dep5ds = its action on ! ela/icity ( a ?9 corrugat$ metal plate1 on "o side ( :i* /eam presses4 ,z ! plate bulges upw>ds x pu%es up a small rod re/+ on x1 :i* op]ates a quadrant & rack simil> to t ( ! ,b\rdon gauge4 ,! pr9ciple is employ$ 9 ano!r =m = ! an]oid b>omet] 7p4 #cbi74 ,,! ,,wat] ,,supply ,,to ,a ,,boil]4 ,! wat] inside a boil] is kept at a prop] level by 7#a7 pumps or 7#b7 injectors4 ,! =m] are mo/ commonly us$ on /ation>y & m>9e boil]s4 ,z _! me*anism is mu* ! same z t ( ord9>y =ce pumps1 :i* w be describ$ 9 a lat] *apt]1 we may pass at once to ! injector1 n[ almo/ univ]sally us$ on locomotive1 & sometimes on /ation>y boil]s4 ,at fir/ sight ! injector is a me*anical p>adox1 s9ce x employs ! /eam f a boil] to bl[ wat] into ! boil]4 ,9 ,fig4 #ae we h an illu/ration ( ! pr9ciple ( an injector4 ,/eam is l$ f ! boil] ?r\gh pipe ,a1 :i* t]m9ates 9 a nozzle surr\nd$ by a cone1 ,e1 connect$ by ! pipe ,b ) ! wat] tank4 ,:5 /eam is turn$ on x ru%es ) imm5se velocity f ! nozzle1 & creates a p>tial vacuum 9 cone ,e1 :i* soon fills ) wat]4 ,on meet+ ! wat] ! /eam cond5ses1 b n be=e x has imp>t$ "s ( its velocity to ! wat]1 :i* ?us ga9s suffici5t mom5tum to =ce d[n ! valve & f9d its way to ! boil]4 ,! ov]fl[ space ,o ,o betwe5 ,e & ,c all[s /eam & wat] to escape until ! wat] has ga!r$ ! requisite mom5tum4 ,illu/ration3 ,,fig4 #ae4--;,diagram illu/rat+ ! pr9ciple ( a /eam-injector4 ,illu/ration3 ,,fig4 #af4--,! ,giff>d injector4 ,a =m ( injector v commonly us$ is ,giff>d's 7,fig4 #af74 ,/eam is all[$ to ent] by screw+ up ! valve ,v4 ,z x ru%es ?r\gh ! nozzle ( ! cone ,a x takes up wat] & projects x into ! mix+ cone ,b1 :i* c be rais$ or l[]$ by ! p9ion ,d 7work$ by ! h&-:eel :eel %[n7 s z to regulate ! am\nt ( wat] admitt$ to ,b4 ,at ! c5tre ( ,b is an ap]ture1 ,o1 communicat+ ) ! ov]fl[4 ,! wat] passes to ! boil] ?r\gh ! valve on ! left4 ,x w be notic$ t ! cone ,a & ! "p ( ,b above ! orifice ,o contract d[nw>d4 ,?is is to conv]t ! pressure ( ! /eam into velocity4 ,bel[ ,o is a cone1 ! diamet] ( :i* increases d[nw>ds4 ,"h ! velocity ( ! wat] is conv]t$ back into pressure 9 ob$i5ce to a well-kn[n hydrome*anic law4 ,an injector does n "w well if ! fe$-wat] be too hot to cond5se ! /eam quickly2 & x may be tak5 z a rule t ! w>m] ! wat]1 ! small] is ! am\nt ( x inject$ by a giv5 weight ( /eam4#b ,"s injectors h flap-valves cov]+ ! ov]fl[ orifice1 to prev5t air be+ suck$ 9 & c>ri$ to ! boil]4 ,:5 an injector receives a sudd5 %ock1 su* z t produc$ by ! pass+ ( a locomotive ov] po9ts1 x is liable to fly (f--t is1 /op mom5t>ily--& !n s5d ! /eam & wat] ?r\gh ! ov]fl[4 ,if ?is happ5s1 bo? /eam & wat] mu/ be turn$ (f1 & ! injector be re/>t$2 unless x be ( ! self-/>t+ v>iety1 :i* automatically controls ! admission ( wat] to ! mix+-cone1 & all[s ! injector to pick up ( itself4 ,= economy's sake "p ( ! /eam expell$ f ! cyl9d]s ( a locomotive is sometimes us$ to "w an injector1 :i* passes ! wat] on1 at a pressure ( #gj lbs4 to ! squ>e in*1 to a second injector op]at$ by high-pressure /eam com+ direct f ! boil]1 :i* increases its velocity suffici5tly to ov]come ! boil] pressure4 ,9 ?is case only a fraction ( ! weight ( high-pressure /eam is requir$ to inject a giv5 weight ( wat]1 z comp>$ ) t us$ 9 a s+le-/age injector4 #a ,! ,/eam-,eng9e1 p4 #c4 #b ,by weight ( /eam is meant ! /eam produc$ by boil+ a c]ta9 weight ( wat]4 ,a p\nd ( /eam1 if cond5s$1 w\ld =m a p\nd ( wat]4 ,*apt] ,,ii4 ,,! ,,conv]sion ,,( ,,heat ,,en]gy ,,into ,,me*anical ,,motion4 ,reciprocat+ eng9es--,d\ble-cyl9d] eng9es--,! function ( ! fly-:eel--,! cyl9d]--,! slide-valve--,! ecc5tric--,lap ( ! valve3 expansion ( /eam--,h[ ! cut-(f is manag$--,limit ( expansive work+--,comp\nd eng9es--,arrangem5t ( expansion eng9es--,comp\nd locomotives--,rev]s+ ge>s--,l9k+-up--,pi/on-valves--,spe$ gov]nors--,m>9e-spe$ gov]nors--,! cond5s]4 ,hav+ treat$ at "s l5g? ! app>atus us$ = conv]t+ wat] into high-pressure /eam1 we may pass at once to a consid]ation ( ! me*anisms :i* conv]t ! en]gy ( /eam into me*anical motion1 or "w4 ,/eam-eng9es are ( two k9ds3--7#a7 reciprocat+1 employ+ cyl9d]s & cranks2 7#b7 rot>y1 call$ turb9es4 ,,reciprocat+ ,,eng9es4 ,illu/ration3 ,,fig4 #ag4--,sket* %[+ p>ts ( a horizontal /eam-eng9e4 ,fig4 #ag is a skeleton diagram ( ! simple/ =m ( reciprocat+ eng9e4 ,c is a cyl9d] to :i* /eam is admitt$ ?r\gh ! /eam-ways#c ,w ,w1 fir/ on "o side ( ! pi/on ,p1 !n on ! o!r4 ,! pressure on ! pi/on pu%es x along ! cyl9d]1 & ! =ce is transmitt$ ?r\gh ! pi/on rod ,p ,r to ! connect+ rod ,c ,r1 :i* causes ! crank ,k to revolve4 ,at ! po9t :]e ! two rods meet !re is a cros%ead1 ,h1 runn+ to & fro 9 a guide to prev5t ! pi/on rod be+ brok5 or b5t by ! oblique ?ru/s & pulls :i* x imp>ts ?r\gh ,c ,r to ! crank ,k4 ,! latt] is key$ to a %aft ,s c>ry+ ! fly-:eel1 or1 9 ! case ( a locomotive1 ! driv+-:eels4 ,! crank %aft revolves 9 be>+s4 ,! int]nal diamet] ( a cyl9d] is call$ its bore4 ,! travel ( ! pi/on is call$ its /roke4 ,! di/ance f ! c5tre ( ! %aft to ! c5tre ( ! crank p9 is call$ ! crank's ?r[1 :i* is half ( ! pi/on's /roke4 ,an eng9e ( ?is type is call$ d\ble-act+1 z ! pi/on is pu%$ alt]nately backw>ds & =w>ds by ! /eam4 ,:5 pi/on rod1 connect+ rod1 & crank lie 9 a /raight l9e--t is1 :5 ! pi/on is fully out1 or fully 9--! crank is said to be at a dead po9t2 =1 7 ! crank turn$ to su* a position1 ! admission ( /eam w\ld n produce motion1 s9ce ! ?ru/ or pull w\ld be entirely absorb$ by ! be>+s4 ,illu/ration3 ,,fig4 #ah4--,sectional plan ( a horizontal eng9e4 ,,d\ble-,,cyl9d] ,,eng9es4 ,illu/ration3 ,,fig4 #ai4 ,illu/ration3 ,,fig4 #bj4 ,locomotive1 m>9e1 & all o!r eng9es :i* mu/ be />t$ 9 any position h at lea/ two cyl9d]s1 & z _m cranks set at an angle to "o ano!r4 ,fig4 #ai demon/rates t :5 "o crank1 ,c#a1 ( a d\ble-cyl9d] eng9e is at a dead po9t1 ! o!r1 ,c#b1 has rea*$ a position at :i* ! pi/on ex]ts ! maximum ( turn+ p[]4 ,9 ,fig4 #bj ea* crank is at #de ) ! horizontal1 & bo? pi/ons are able to d "w4 ,! p[] ( "o pi/on is con/antly increas+ :ile t ( ! o!r is decreas+4 ,if s+le-action cyl9d]s are us$1 at lea/ ?ree ( ^! are ne$$ to produce a p]petual turn+ movem5t1 indep5d5tly ( a fly-:eel4 ,,! ,,function ,,( ,,! ,,fly-,,:eel4 ,a fly-:eel acts z a res]voir ( en]gy1 to c>ry ! crank ( a s+le-cyl9d] eng9e pa/ ! dead po9ts4 ,x is useful 9 all reciprocat+ eng9es to produce /eady runn+1 z a heavy :eel acts z a drag on ! effects ( a sudd5 increase or decrease ( /eam pressure4 ,9 a pump1 mangold-slic]1 cake-cru%]1 or *aff-cutt]1 ! fly-:eel helps ! op]ator to pass 8 dead po9ts--t is1 ^? p>ts ( ! circle describ$ by ! h&le 9 :i* he c d little "w4 ,,! ,,cyl9d]4 ,illu/ration3 ,,fig4 #ba4--;,diagrammatic section ( a cyl9d] & its slide-valve4 ,! cyl9d]s ( an eng9e take ! place ( ! muscul> sy/em ( ! human body4 ,9 ,fig4 #ba we h a cyl9d] & its slide-valve %[n 9 section4 ,fir/ ( all1 look at ,p1 ! pi/on4 ,r\nd x are :ite grooves1 ,r ,r1 9 :i* r+s are fitt$ to prev5t ! passage ( /eam pa/ ! pi/on4 ,! r+s are cut ?r\gh at "o po9t 9 _! circumf]5ce1 & slightly op5$1 s t :5 9 position !y press all r\nd aga9/ ! walls ( ! cyl9d]4 ,aft] a little use !y settle d[n to _! "w--t is1 we> to a true fit 9 ! cyl9d]4 ,ea* end ( ! cyl9d] is clos$ by a cov]1 "o ( :i* has a boss ca/ on x1 pi]c$ by a hole = ! pi/on rod to "w ?r\gh4 ,to prev5t ! escape ( /eam ! boss is holl[$ out true to accommodate a gl&1 ,g#a1 :i* is ?read$ on ! rod & screw$ up aga9/ ! boss2 ! int]nal space betwe5 !m be+ fill$ ) pack+4 ,/eam f ! boil] ent]s ! /eam-*e/1 & w\ld h access to bo? sides ( ! pi/on simultane\sly ?r\gh ! /eam-ways1 ,w ,w1 7 x n = ! ,,slide-,,valve1 a holl[ box op5 at ! bottom1 & long en\gh = its edges to cov] bo? /eam-ways at once4 ,betwe5 ,w ,w is ,e1 ! passage = ! exhau/ /eam to escape by4 ,! edges ( ! slide-valve are p]fectly flat1 z is ! face ov] :i* ! valve moves1 s t no /eam may pass "u ! edges4 ,9 our illu/ration ! pi/on has j begun to move t[>ds ! "r4 ,/eam ent]s by ! left /eam-way1 :i* ! valve is j comm5c+ to uncov]4 ,z ! pi/on moves1 ! valve moves 9 ! same direction until ! port is fully uncov]$1 :5 x beg9s to move back aga92 & j be=e ! pi/on has f9i%$ its /roke ! /eam-way on ! "r beg9s to op54 ,! /eam-way on ! left is n[ 9 communication ) ! exhau/ port ,e1 s t ! /eam t has done its duty is releas$ & press$ f ! cyl9d] by ! pi/on4 ,reciprocation is ?is backw>d & =w>d motion ( ! pi/on3 h5ce ! t]m reciprocat+ eng9es4 ,! l9e> motion ( ! pi/on rod is conv]t$ into rotatory motion by ! connect+ rod & crank4 ,illu/ration3 ,,fig4 #bb4--,p]spective section ( cyl9d]4 ,! use ( a crank appe>s to be s obvi\s a me?od ( produc+ ?is conv]sion t x is int]e/+ to le>n t1 :5 ,james ,watt produc$ 8 rotative eng9e 9 #aghj he 0 unable to use ! crank because x _h already be5 pat5t$ by "o ,mat!w ,wasbor\gh4 ,watt 0 n easily daunt$1 h[ev]1 & )9 a twelvemon? _h himself pat5t$ five o!r devices = obta9+ rotatory motion f a pi/on rod4 ,be=e pass+ on1 x may be m5tion$ t ,watt 0 ! fa!r ( ! mod]n--t is1 ! high-pressure--/eam-eng9e2 & t1 ow+ to ! imp]fection ( ! exi/+ ma*9]y1 ! difficulties he _h to ov]come 7 enorm\s4 ,on "o occasion he congratulat$ himself because "o ( 8 /eam-cyl9d]s 0 only ?ree-eigh?s ( an in* out ( tru? 9 ! bore4 ,n[adays a good firm w\ld reject a cyl9d] #a_/ejj ( an in* out ( tru?2 & 9 small petrol-eng9es #a_/ejjj ( an in* is sometimes ! greate/ limit ( error all[$4 ,illu/ration3 ,,fig4 #bc4--,! ecc5tric & its rod4 ,,! ,,ecc5tric is us$ to move ! slide-valve to & fro ov] ! /eam ports 7,fig4 #bc74 ,x consi/s ( ?ree ma9 p>ts--! %eave1 or circul> plate ,s1 m\nt$ on ! crank %aft2 & ! two /raps :i* encircle x1 & 9 :i* x revolves4 ,to "o /rap is bolt$ ! big end ( ! ecc5tric rod1 :i* engages at its o!r end ) ! valve rod4 ,! /raps are semicircul> & held toge!r by /rong bolts1 ,b ,b1 pass+ ?r\gh lugs1 or ?ick5+s at ! ends ( ! semicircles4 ,! %eave has a deep groove all r\nd ! edges1 9 :i* ! /raps ride4 ,! ecc5tricity or ?r[ ( an ecc5tric is ! di/ance betwe5 ,c#b1 ! c5tre ( ! %aft1 & ,c#a1 ! c5tre ( ! %eave4 ,! ?r[ mu/ equal half ( ! di/ance :i* ! slide-valve has to travel ov] ! /eam ports4 ,a tap]+ /eel w$ge or key1 ,k1 sunk half 9 ! ecc5tric & half 9 a slot 9 ! %aft1 holds ! ecc5tric /eady & prev5ts x slipp+4 ,"s ecc5tric %eaves are made 9 two p>ts1 bolt$ toge!r1 s t !y may be remov$ easily )\t dism\nt+ ! %aft4 ,! ecc5tric is 9 pr9ciple no?+ m ?an a crank p9 s exagg]at$ z to be l>g] ?an ! %aft ( ! crank4 ,its conv5i5ce lies 9 ! fact t x may be m\nt$ at any po9t on a %aft1 :]eas a crank c be situat$ at an end only1 if x is n actually a ,v-%ap$ b5d 9 ! %aft itself--9 :i* case its position is ( c\rse p]man5t4 ,,sett+ ,,( ,,! ,,slide-,,valve ,,& ,,ecc5tric4 ,! subject ( valve-sett+ is s ext5sive t a full exposition might we>y ! read]1 ev5 if space p]mitt$ its inclusion4 ,b inasmu* z ! effectiv5ess ( a reciprocat+ eng9e dep5ds l>gely on ! nature & arrangem5t ( ! valves1 we w glance at "s ( ! m elem5t>y pr9ciples4 ,illu/ration3 ,,fig4 #bd4 ,illu/ration3 ,,fig4 #be4 ,9 ,fig4 #bd we see 9 section ! slide-valve1 ! ports ( ! cyl9d]1 & "p ( ! pi/on4 ,to ! "r are two l9es at "r angles--! ?ick]1 ,c1 repres5t+ ! position ( ! crank2 ! ?9n]1 ,e1 t ( ! ecc5tric4 7,! position ( an ecc5tric is d5ot$ diagrammatically by a l9e drawn f ! c5tre ( ! crank %aft ?r\gh ! c5tre ( ! %eave47 ,! edges ( ! valve are 9 ?is case only broad en\gh to j cov] ! ports--t is1 !y h no lap4 ,! pi/on is ab\t to comm5ce its /roke t[>ds ! left2 & ! ecc5tric1 :i* is set at an angle ( #ij 9 advance ( ! crank1 is ab\t to beg9 op5+ ! left-h& port4 ,by ! "t t ,c has got to ! position orig9ally occupi$ by ,e1 ,e w be horizontal 7,fig4 #be7--t is1 ! ecc5tric w h f9i%$ its /roke t[>ds ! left2 & :ile ,c passes ?r\gh ! next "r angle ! valve w be clos+ ! left port1 :i* w cease to admit /eam :5 ! pi/on has come to ! end ( its travel4 ,! op]ation is repeat$ on ! "r-h& side :ile ! pi/on returns4 ,illu/ration3 ,,fig4 #bf4 ,x mu/ be notic$ "h--7#a7 t /eam is admitt$ at full pressure all ?r\gh ! /roke2 7#b7 t admission beg9s & ends simultane\sly ) ! /roke4 ,n[1 9 actual practice x is necess>y to admit /eam be=e ! pi/on has end$ its travel1 s z to cu%ion ! viol5ce ( ! sudd5 *ange ( direction ( ! pi/on1 its rod1 & o!r mov+ p>ts4 ,to effect ?is1 ! ecc5tric is set m ?an #ij 9 advance--t is1 m ?an :at ! eng9e]s call squ>e4 ,fig4 #bf %[s su* an arrangem5t4 ,! angle betwe5 ,e & ,e#a is call$ ! angle ( advance4 ,ref]r+ to ! valve1 y w see t x has op5$ an appreciable am\nt1 ?\gh ! pi/on has n yet />t$ on its rightw>ds j\rney4 ,,lap ,,( ,,! ,,valve--,,expansion ,,( ,,/eam4 ,9 ! simple =m ( valve t appe>s 9 ,fig4 #bd1 ! valve faces are j wide en\gh to cov] ! /eam ports4 ,if ! ecc5tric is n squ>e ) ! crank1 ! admission ( /eam la/s until ! v end ( ! /roke2 if set a little 9 advance--t is1 giv5 lead--! /eam is cut (f be=e ! pi/on has travell$ q along ! cyl9d]1 & readmitt$ be=e ! back /roke is accompli%$4 ,ev5 ) ?is lead ! work+ is v uneconomical1 z ! /eam goes to ! exhau/ at practically ! same pressure z t at :i* x ent]$ ! cyl9d]4 ,its prop]ty ( expansion has be5 neglect$4 ,b suppos+ t /eam at #ajj lbs4 pressure 7 admitt$ till half-/roke1 & !n sudd5ly cut (f1 ! expansive nature ( ! /eam w\ld !n cont9ue to pu% ! pi/on out until ! pressure _h decreas$ to #ej lbs4 p] squ>e in*1 at :i* pressure x w\ld g to ! exhau/4 ,n[1 obs]ve t all ! "w done by ! /eam aft] ! cut-(f is s mu* p[] sav$4 ,! av]age pressure on ! pi/on is n s high z 9 ! fir/ case2 /ill1 f a giv5 volume ( #ajj lbs4 pressure /eam we get mu* m "w4 ,,h[ ,,! ,,cut-,,(f ,,is ,,manag$4 ,illu/ration3 ,,fig4 #bg4--;,a slide-valve ) lap4 ,illu/ration3 ,,fig4 #bh4 ,look at ,fig4 #bg4 ,"h we h a slide-valve1 ) faces mu* wid] ?an ! /eam ports4 ,! p>ts m>k$ black1 ,p ,p1 are ^? correspond+ to ! faces ( ! valves %[n 9 previ\s diagrams 7p4 #ed74 ,! %ad$ p>ts1 ,l ,l1 are call$ ! lap4 ,by increas+ ! l5g? ( ! lap we increase ! range ( expansive work+4 ,fig4 #bh %[s ! pi/on full to ! left2 ! valve is j on ! po9t ( op5+ to admit /eam beh9d ! pi/on4 ,! ecc5tric has a ?r[ equal to ! bread? ( a port ! lap ( ! valve4 ,t ?is mu/ be s is obvi\s f a consid]ation ( ,fig4 #bg1 :]e ! valve is at its c5tral position4 ,h5ce ! v simple =mula3--,travel ( valve #b 7lap bread? ( port74 ,! pa? ( ! ecc5tric's c5tre r\nd ! c5tre ( ! %aft is indicat$ by ! usual dott$ l9e 7,fig4 #bh74 ,y w notice t ! angle ( advance1 d5ot$ by ! arr[ ,a1 is n[ v consid]able4 ,by ! "t t ! crank ,c has assum$ ! position ( ! l9e ,s1 ! ecc5tric has pass$ its dead po9t1 & ! valve beg9s to travel backw>ds1 ev5tually return+ to ! position %[n 9 ,fig4 #bh1 & cutt+ (f ! /eam supply :ile ! pi/on has /ill a consid]able "p ( its /roke to make4 ,! /eam !n beg9s to "w expansively1 & cont9ues to d s until ! valve assumes ! position %[n 9 ,fig4 #bg4 ,if ! valve has to h lead to admit /eam be=e ! end ( ! /roke to ! o!r side ( ! pi/on1 ! angle ( advance mu/ be increas$1 & ! ecc5tric c5tre l9e w\ld lie on ! l9e ,e#b4 ,!re=e--total angle ( advance angle = lap & angle = lead4 ,,limit ,,( ,,expansive ,,work+4 ,!oretically1 by increas+ ! lap & cutt+ (f ! /eam e>li] & e>li] 9 ! /roke1 we %\ld economize our p[] m & m4 ,b 9 practice a great difficulty is met )--namely1 t z ! /eam exp&s its temp]ature falls4 ,if ! cut-(f occurs e>ly1 say at "o-?ird /roke1 ! great expansion w r$uce ! temp]ature ( ! metal walls ( ! cyl9d] to su* an ext5t1 t :5 ! next spirt ( /eam ent]s f ! o!r end a consid]able proportion ( ! /eam's en]gy w be lo/ by cool+4 ,9 su* a case1 ! diff]5ce 9 temp]ature betwe5 admitt$ /eam & exhau/$ /eam is too great = economy4 ,yet we want to utilize z mu* en]gy z possible4 ,h[ are we to d x8 ,,comp\nd ,,eng9es4 ,9 ! ye> #ahec1 ,john ,eld]1 f\nd] ( ! %ipp+ firm ( ,eld] & ,co41 ,glasg[1 introduc$ ! comp\nd eng9e = use on %ips4 ,! /eam1 :5 exhau/$ f ! high-pressure cyl9d]1 pass$ into ano!r cyl9d] ( equal /roke b l>g] diamet]1 :]e ! expansion cont9u$4 ,9 mod]n eng9es ! expansion is ext5d$ to ?ree & ev5 f\r /ages1 accord+ to ! boil] pressure2 = x is a rule t ! high] ! initial pressure is1 ! l>g] is ! numb] ( /ages ( expansion consi/5t ) economical work+4 ,illu/ration3 ,,fig4 #bi4--,sket* ( ! arrangem5t ( a triple-expansion m>9e eng9e4 ,no valve ge> or supports1 etc41 %[n4 ,9 ,fig4 #bi we h a triple-expansion m>9e eng9e4 ,/eam ent]s ! high-pressure cyl9d]#d at1 say1 #bjj lbs4 p] squ>e in*4 ,x exhau/s at #ge lbs4 into ! l>ge pipe #b1 & passes to ! int]m$iate cyl9d]1 :5ce x is exhau/$ at #be lbs4 or s ?r\gh pipe #c to ! l[-pressure cyl9d]4 ,f9ally1 x is eject$ at ab\t #h lbs4 p] squ>e in* to ! cond5s]1 & is sudd5ly conv]t$ into wat]2 an act :i* produces a vacuum1 & dim9i%es ! back-pressure ( ! exhau/ f cyl9d] ,c4 ,9 fact1 ! cond5s] ex]ts a suck+ p[] on ! exhau/ side ( ,c's pi/on4 ,,arrangem5t ,,( ,,expansion ,,eng9es4 ,9 ! illu/ration ! cranks are set at angles ( #abj1 or a ?ird ( a circle1 s t "o or o!r is always at or ne> ! position ( maximum turn+ p[]4 ,:]e only two /ages are us$ ! cyl9d]s are (t5 arrang$ t&em1 bo? pi/ons hav+ a common pi/on rod & crank4 ,9 ord] to get a con/ant turn+ movem5t !y mu/ be m\nt$ sep>ately1 & "w cranks set at "r angles to "o ano!r4 ,,comp\nd ,,locomotives4 ,9 #ahgf ,mr4 ,a4 ,mallet introduc$ comp\nd+ 9 locomotives2 & ! practice has be5 l>gely adopt$4 ,! v>i\s types ( comp\nds may be classifi$ z foll[s3--7#a7 ,"o l[-pressure & "o high-pressure cyl9d]2 7#b7 "o high-pressure & two l[-pressure2 7#c7 "o l[-pressure & two high-pressure2 7#d7 two high-pressure & two l[-pressure4 ,! la/ class is v widely us$ 9 ,france1 ,am]ica1 & ,russia1 & seems to give ! be/ results4 ,:]e only two cyl9d]s are us$ 7& sometimes 9 ! case ( ?ree & f\r71 a valve arrangem5t p]mits ! admission ( high-pressure /eam to bo? high & l[-pressure cyl9d]s = />t+ a tra91 or mov+ x up heavy grades4 ,,rev]s+ ,,ge>s4 ,illu/ration3 ,,figs4 #cj1 #ca1 #cb4--,%[+ h[ a rev]s+ ge> alt]s ! position ( ! slide-valve4 ,! eng9es ( a locomotive or /eam%ip mu/ be rev]sible--t is1 :5 /eam is admitt$ to ! cyl9d]s1 ! eng9e] mu/ be able to s direct x ?r\gh ! /eam-ways t ! cranks may turn 9 ! desir$ direction4 ,! commone/ =m ( rev]s+ device 7inv5t$ by ,george ,/eph5son7 is kn[n z ,/eph5son's ,l9k ,ge>4 ,9 ,fig4 #cj we h a diagrammatic pres5tm5t ( ?is ge>4 ,e#a & ,e#b are two ecc5trics set squ>e ) ! crank at opposite ends ( a diamet]4 ,_! rods are connect$ to ! ends ( a l9k1 ,l1 :i* c be rais$ & l[]$ by means ( lev]s 7n %[n74 ,b is a block :i* c p>tly revolve on a p9 project+ f ! valve rod1 work+ ?r\gh a guide1 ,g4 ,9 ,fig4 #ca ! l9k is half rais$1 or 9 mid-ge>1 z driv]s say4 ,ecc5tric ,e#a has pu%$ ! l[] end ( ! l9k fully back2 ,e#b has pull$ x fully =w>d2 & s9ce any movem5t ( ! "o ecc5tric is c\nt]balanc$ by ! opposite movem5t ( ! o!r1 rotation ( ! ecc5trics w\ld n cause ! valve to move at all1 & no /eam c\ld be admitt$ to ! cyl9d]4 ,let u suppose t ,fig4 #cj d5otes "o cyl9d]1 crank1 rods1 etc41 ( a locomotive4 ,! crank has come to re/ at its half-/roke2 ! rev]s+ lev] is at ! mid-ge> not*4 ,if ! eng9e] desires to turn 8 cranks 9 an anti-clockwise direction1 he raises ! l9k1 :i* br+s ! rod ( ,e#a into l9e ) ! valve rod & presses ! block backw>ds till ! "r-h& port is uncov]$ 7,fig4 #ca74 ,if /eam be n[ admitt$1 ! pi/on w be pu%$ t[>ds ! left1 & ! eng9e w cont9ue to run 9 an anti-clockwise direction4 ,if1 on ! o!r h&1 he wants to run ! eng9e ! o!r way1 he w\ld drop ! l9k1 br++ ! rod ( ,e#b into l9e ) ! valve rod1 & draw+ ,v =w>d to uncov] ! re> port 7,fig4 #cb74 ,9 ei!r case ! ecc5tric work+ ! end ( ! l9k remote f ,b has no effect1 s9ce x m]ely causes t end to describe arcs ( circles ( :i* ,b is ! c5tre4 ,,l9k+ ,,up4 ,if ! l9k is only p>tly l[]$ or rais$ f ! c5tral position x /ill causes ! eng9e to run accord+ly1 b ! movem5t ( ! valve is decreas$4 ,:5 runn+ at high spe$ ! eng9e] l9ks up 8 rev]s+ ge>1 caus+ 8 valves to cut (f e>ly 9 ! /roke1 & ! /eam to "w m expansively ?an x c\ld ) ! lev] at full1 or end1 ge>2 s t ?is device n only r5d]s an eng9e rev]sible1 b also gives ! eng9e] an absolute comm& ov] ! expansion ratio ( ! /eam admitt$ to ! cyl9d]1 & furni%es a me?od ( cutt+ (f ! /eam altoge!r4 ,9 ,figs4 #cj1 #ca1 #cb1 ! valve has no lap & ! ecc5trics are set squ>e4 ,9 actual practice ! valve faces w\ld h lap & ! ecc5tric lead to correspond2 b = ! sake ( simplicity nei!r is %[n4 ,,o!r ,,ge>s4 ,9 ! ,goo* ge> = rev]s+ locomotives ! l9k does n %ift1 b ! valve rod & its block is rais$ or l[]$4 ,! ,allan ge> is s arrang$ t :5 ! l9k is rais$ ! block is l[]$1 & vice v]s4 ,^! are really only modifications ( ,/eph5son's pr9ciple--namely1 ! employm5t ( two ecc5trics set at equal angles to & on opposite sides ( ! crank4 ,!re are ?ree o!r =ms ( l9k-rev]s+ ge>1 & ne>ly a doz5 types ( radial rev]s+ devices2 b z we h already describ$ ! ?ree mo/ commonly us$ on locomotives & %ips1 !re is no ne$ to give p>ticul>s ( ^!4 ,be=e ! introduction ( ,/eph5son's ge> a s+le ecc5tric 0 us$ = ea* cyl9d]1 & to rev]se ! eng9e ?is ecc5tric _h to be loose on ! axle4 ,a lev] & ge> work$ by a treadle on ! footplate controll$ ! position ( ! ecc5trics4 ,:5 />t+ ! eng9e1 ! driv] put ! ecc5trics out ( ge> by ! treadle2 !n1 by means ( a lev] he rais$ ! small-ends#e ( ! ecc5tric rods1 &1 not+ ! position ( ! cranks1 or1 if m conv5i5t1 ! balance weight 9 ! :eels1 he1 by means ( ano!r h&le1 mov$ ! valves to op5 ! necess>y ports to /eam & work$ !m by h& until ! eng9e 0 mov+2 !n1 ) ! treadle1 he ?rew ! ecc5trics ov] to engage ! /uds1 at ! same "t dropp+ ! small-ends ( ! rods to engage p9s ^u ! valve sp9dles1 s t !y cont9u$ to keep up ! movem5t ( ! valve4#f ,"o w\ld imag9e t 9 mod]n %unt+ y>ds su* a device w\ld some:at delay op]ations6 ,,pi/on ,,valves4 ,9 m>9e eng9es1 & on _m locomotives & "s /ation>y eng9es1 ! ,d-valve 7%[n 9 ,figs4 #cj-cb7 is replac$ by a pi/on valve1 or circul> valve1 work+ up & d[n 9 a tubul> seat+4 ,x may be/ be describ$ z a rod c>ry+ two pi/ons :i* correspond to ! faces ( a ,d-valve4 ,in/ead ( rectangul> ports !re are op5+s 9 ! tube 9 :i* ! pi/on valve moves1 communicat+ ) ! /eam-ways into ! cyl9d] & ) ! exhau/ pipe4 ,9 ! case ( ! ,d-valve ! pressure above x is mu* great] ?an t bel[1 & consid]able friction arises if ! rubb+ faces are n kept well lubricat$4 ,! pi/on valve gets ov] ?is difficulty1 s9ce su* /eam z may leak pa/ x presses on its circumf]5ce at all po9ts equally4 ,,spe$ ,,gov]nors4 ,illu/ration3 ,,fig4 #cc4--;,a spe$ gov]nor4 ,practically all eng9es except locomotives & ^? kn[n z donkey-eng9es--us$ on cranes--are fitt$ ) "s device = keep+ ! rotatory spe$ ( ! crank con/ant )9 v n>r[ limits4 ,p]haps y h se5 a pair ( balls mov+ r\nd on a seat+ ov] ! boil] ( a ?re%+-eng9e4 ,!y =m "p ( ! gov]nor1 or spe$-controll]1 %[n 9 pr9ciple 9 ,fig4 #cc4 ,a belt driv5 by a pulley on ! crank %aft turns a small pulley1 ,p1 at ! foot ( ! gov]nor4 ,?is transmits motion ?r\gh two bevel-:eels1 ,g1 to a v]tical %aft1 f ! top ( :i* hang two heavy balls on l9ks1 ,k ,k4 ,two m l9ks1 ,l ,l1 connect ! balls ) a weight1 ,w1 :i* has a deep groove cut r\nd x at ! bottom4 ,:5 ! %aft revolves1 ! balls fly outw>ds by c5trifugal =ce1 & z _! velocity increases ! quadrilat]al figure conta9$ by ! f\r l9ks exp&s lat]ally & %ort5s v]tically4 ,! angles betwe5 ,k ,k & ,l ,l become less & less obtuse1 & ! weight ,w is drawn upw>ds1 br++ ) x ! =k ,c ( ! rod ,a1 :i* has ends engag+ ) ! groove4 ,z ,c rises1 ! o!r end ( ! rod is depress$1 & ! rod ,b depresses rod ,o1 :i* is atta*$ to ! sp9dle op]at+ a sort ( %utt] 9 ! /eam-pipe4 ,consequ5tly ! supply ( /eam is ?rottl$ m & m z ! spe$ increases1 until x has be5 s r$uc$ t ! eng9e sl[s1 & ! balls fall1 op5+ ! valve aga94 ,fig4 #cd %[s ! valve fully clos$4 ,?is =m ( gov]nor 0 inv5t$ by ,james ,watt4 ,a spr+ is (t5 us$ in/ead ( a weight1 & ! gov]nor is arrang$ horizontally s t x may be driv5 direct f ! crank %aft )\t ! int]v5tion ( bevel ge>+4 ,illu/ration3 ,,fig4 #cd4 ,! ,h>twell gov]nor employs a l9k motion4 ,y mu/ "h picture ! balls rais+ & l[]+ ! free end ( ! valve rod1 :i* c>ries a block mov+ 9 a l9k connect$ ) ! ecc5tric rod4 ,! l9k is pivot$ at ! upp] end1 & ! ecc5tric rod is atta*$ to ! l[]4 ,:5 ! eng9e is at re/ ! end ( ! valve rod & its block are dropp$ till 9 a l9e ) ! ecc5tric rod2 b :5 ! ma*9]y beg9s to "w ! block is gradually drawn up by ! gov]nor1 dim9i%+ ! movem5t ( ! valve1 & s %ort5+ ! p]iod ( /eam admission to ! cyl9d]4 ,gov]nors are ( special importance :]e ! load ( an eng9e is con/antly v>y+1 z 9 ! case ( a sawmill4 ,a good gov]nor w limit v>iation ( spe$ )9 two p] c5t4--t is1 if ! eng9e is set to run at #ajj revolutions a m9ute1 x w n all[ x to exce$ #aja or fall bel[ #ii4 ,9 v high-spe$ eng9es ! gov]n+ w prev5t v>iation ( less ?an "o p] c5t41 ev5 :5 ! load is at "o in/ant full on1 & ! next tak5 completely (f4 ,,m>9e ,,gov]nors4 ,^! mu/ be m quick-act+ ?an ^? us$ on eng9es provid$ ) fly-:eels1 :i* prev5t v sudd5 v>iations ( spe$4 ,! screw is light 9 proportion to ! eng9e p[]1 & :5 x is sudd5ly rais$ f ! wat] by ! pit*+ ( ! vessel1 ! eng9e w\ld race till ! screw took ! wat] aga91 unless "s regulat+ me*anism 7 provid$4 ,_m types ( m>9e gov]nors h be5 tri$4 ,! mo/ successful seems to be "o 9 :i* wat] is be+ con/antly =c$ by a pump driv5 (f ! eng9e %aft into a cyl9d] controll+ a ?rottle-valve 9 ! ma9 /eam-pipe4 ,! wat] escapes ?r\gh a leak1 :i* is adju/able4 ,z long z ! spe$ ( ! eng9e is normal1 ! wat] escapes f ! cyl9d] z fa/ z x is pump$ 91 & no movem5t ( ! pi/on results2 b :5 ! screw beg9s to race1 ! pump ov]comes ! leak1 & ! pi/on is driv5 out1 caus+ a ?rottl+ ( ! /eam supply4 ,,cond5s]s4 ,! cond5s] s]ves two purposes3--7#a7 ,x makes x possible to use ! same wat] ov] & ov] aga9 9 ! boil]s4 ,on ! sea1 :]e fre% wat] is n obta9able 9 l>ge quantities1 ?is is a matt] ( ! greate/ importance4 7#b7 ,x adds to ! p[] ( a comp\nd eng9e by ex]t+ a back pull on ! pi/on ( ! l[-pressure cyl9d] :ile ! /eam is be+ exhau/$4 ,illu/ration3 ,,fig4 #ce4--,! m>9e cond5s]4 ,fig4 #ce is a sectional illu/ration ( a m>9e cond5s]4 ,/eam ent]s ! cond5s] ?r\gh ! l>ge pipe ,e1 & passes among a numb] ( v ?9 copp] tubes1 ?r\gh :i* sea-wat] is kept circulat+ by a pump4 ,! pa? ( ! wat] is %[n by ! fea!rless arr[s4 ,x comes f ! pump ?r\gh pipe ,a into ! l[] "p ( a l>ge cap cov]+ "o end ( ! cond5s] & divid$ transv]sely by a diaphragm1 ,d4 ,pass+ ?r\gh ! pipes1 x rea*es ! cap atta*$ to ! o!r end1 & fl[s back ?r\gh ! upp] tubes to ! outlet ,c4 ,?is arrangem5t ensures t1 z ! /eam cond5ses1 x %all meet cold] & cold] tubes1 & f9ally be turn$ to wat]1 :i* passes to ! well ?r\gh ! outlet ,f4 ,9 "s cond5s]s ! positions ( /eam & wat] are rev]s$1 /eam go+ ?r\gh ! tubes outside :i* cold wat] circulates4 #c ,also call$ ports4 #d ,! bores ( ! cyl9d]s are 9 ! proportion ( #d3 #f3 #i4 ,! /roke ( all ?ree is ! same4 #e ,! ends fur!/ f ! ecc5tric4 #f ,! ,locomotive ( ,to-day1 p4 #hg4 ,*apt] ,,iii4 ,,! ,,/eam ,,turb9e4 ,h[ a turb9e works--,! ,de ,laval turb9e--,! ,p>sons turb9e--,description ( ! ,p>sons turb9e--,! expansive action ( /eam 9 a ,p>sons turb9e--,balanc+ ! ?ru/--,advantages ( ! m>9e turb9e4 ,m ?an two ?\s& ye>s ago ,h]o ( ,alex&ria produc$ ! fir/ app>atus to :i* ! "n ( /eam-eng9e c\ld rightly be giv54 ,its pr9ciple 0 practically ! same z t ( ! revolv+ jet us$ to spr9kle lawns dur+ dry wea!r1 /eam be+ us$ 9 ! place ( wat]4 ,f ! top ( a clos$ cauldron rose two v]tical pipes1 :i* at _! upp] ends _h %ort1 "r-angle b5ds4 ,betwe5 !m 0 hung a holl[ globe1 pivot$ on two %ort tubes project+ f its sides into ! upright tubes4 ,two little ,l-%ap$ pipes project$ f opposite sides ( ! globe1 at ! ends ( a diamet]1 9 a plane p]p5dicul> to ! axis4 ,on fire be+ appli$ to ! cauldron1 /eam 0 g5]at$4 ,x pass$ up ?r\gh ! upright1 ?r\gh ! pivots1 & into ! globe1 f :i* x escap$ by ! two ,l-%ap$ nozzles1 caus+ rapid revolution ( ! ball4 ,9 %ort1 ! fir/ /eam-eng9e 0 a turb9e4 ,curi\sly en\gh1 we h rev]t$ to ?is primitive type 7sci5tifically develop$1 ( c\rse7 9 ! mo/ mod]n eng9e]+ practice4 ,,h[ ,a ,,turb9e ,,works4 ,9 reciprocat+--t is1 cyl9d]--eng9es /eam is admitt$ into a *amb] & ! door %ut beh9d x1 z x 74 ,z x /ruggles to exp&1 x =ces out "o ( ! conf9+ walls--t is1 ! pi/on--& pres5tly ! door op5s aga91 & all[s x to escape :5 x has done its "w4 ,9 ,h]o's toy ! impact ( ! issu+ molecules aga9/ o!r molecules t h already em]g$ f ! pipes 0 us$4 ,"o may comp>e ! reaction to t ex]t$ by a ?r[n /one on ! ?r[]4 ,if ! ?r[] is /&+ on skates1 ! reaction ( ! /one w cause him to glide backw>ds1 j z if he _h pu%$ (f f "s fix$ object4 ,9 ! case ( ! reaction--namely1 ! ,h]o-type--turb9e ! nozzle f :i* ! /eam or wat] issues moves1 along ) bodies to :i* x may be atta*$4 ,9 action turb9es /eam is l$ ?r\gh fix$ nozzles or /eam-ways1 & ! mom5tum ( ! /eam is br\ght to be> on ! surfaces ( movable bodies connect$ ) ! %aft4 ,,! ,,de ,,laval ,,turb9e4 ,9 its e>lie/ =m ?is turb9e 0 a modification ( ,h]o's4 ,! :eel 0 m]ely a pipe b5t 9 ,s =m1 atta*$ at its c5tre to a holl[ v]tical %aft suppli$ ) /eam ?r\gh a /uff+-box at "o extremity4 ,! /eam blew out tang5tially f ! ends ( ! ,s1 caus+ ! %aft to revolve rapidly & "w ! ma*9]y 7usually a cream sep>ator7 m\nt$ on x4 ,?is motor prov$ v suitable = dairy "w1 b 0 too wa/eful ( /eam to be useful :]e high p[] 0 ne$$4 ,illu/ration3 ,,fig4 #cf4--,! :eel & nozzles ( a ,de ,laval turb9e4 ,9 ! ,de ,laval turb9e z n[ con/ruct$ ! /eam is bl[n f /ation>y nozzles aga9/ vanes m\nt$ on a revolv+ :eel4 ,fig4 #cf %[s ! nozzles & a turb9e :eel4 ,! :eel is made z a solid disc1 to ! circumf]5ce ( :i* ! vanes are dovetail$ sep>ately 9 a s+le r[4 ,ea* vane is ( curv$ section1 ! concave side direct$ t[>ds ! nozzles1 :i*1 z w be ga!r$ f ! transp>5t specim5 on ! "r ( our illu/ration1 gradually exp& t[>ds ! m\?4 ,?is is to all[ ! expansion ( ! /eam1 & a consequ5t ga9 ( velocity4 ,z x issues1 ea* molecule /rikes aga9/ ! concave face ( a vane1 &1 :ile *ang+ its direction1 is robb$ ( its k9etic en]gy1 :i* passes to ! :eel4 ,to turn once m to a /one-?r[+ comp>ison1 x is z if a boy 7 pelt+ ! :eel ) an enorm\s numb] ( t9y /ones4 ,n[1 escap+ high-pressure /eam moves v fa/ inde$4 ,to give figures1 if x ent]s ! small end ( a ,de ,laval nozzle at #bjj lbs4 p] squ>e in*1 x w leave ! big end at a velocity ( #dh miles p] m9ute--t is1 at a spe$ :i* w\ld take x "r r\nd ! _w 9 #h-a_/b h\rs6 ,! :eel itself w\ld n move at m ?an ab\t "o-?ird ( ?is spe$ z a maximum4#g ,b ev5 s1 x may make z _m z #cj1jjj revolutions p] m9ute4 ,a me*anical difficulty is n[ enc\nt]$--namely1 t aris+ f vibration4 ,no matt] h[ c>efully ! turb9e :eel may be balanc$1 x is practically impossible to make its c5tre ( gravity co9cide exactly ) ! c5tral po9t ( ! %aft2 9 o!r words1 ! :eel w be a bit--p]haps only a t9y fraction ( an ounce--heavi] on "o side ?an ! o!r4 ,?is want ( tru? causes vibration1 :i*1 at ! high spe$ m5tion$1 w\ld cause ! %aft to knock ! be>+s 9 :i* x revolves to pieces1 if--& ?is is ! po9t--^? be>+s 7 close to ! :eel ,m4 de ,laval m\nt$ ! :eel on a %aft long en\gh betwe5 ! be>+s to :ip1 or b5d a little1 & ! difficulty 0 surm\nt$4 ,! normal spe$ ( ! turb9e :eel is too high = direct driv+ ( "s ma*9]y1 s x is r$uc$ by means ( ge>+4 ,to dynamos1 pumps1 & air-fans x is (t5 c\pl$ direct4 ,,! ,,p>sons ,,turb9e4 ,at ! gr& naval review held 9 #ahig 9 hon\r ( ,que5 ,victoria's diamond jubilee1 "o ( ! mo/ notewor?y sights 0 ! little ,turb9ia ( #dd-a_/b tons bur!n1 :i* d>t$ ab\t among ! float+ =ts at a spe$ mu* surpass+ t ( ! fa/e/ de/roy]4 ,inside ! nimble little craft 7 eng9es develop+ #b1jjj horse p[]1 )\t any ( ! clank & vibration :i* usually reigns 9 ! eng9e-room ( a high-spe$ vessel4 ,! ,turb9ia 0 ! fir/ turb9e-driv5 boat1 & z su*1 ev5 ap>t f h] extraord9>y pace1 %e attract$ great att5tion4 ,s9ce #ahig ! ,p>sons turb9e has be5 in/all$ on _m %ips1 includ+ sev]al m5-(-w>1 & x seems probable t ! "t is n f> di/ant :5 reciprocat+ eng9es w be ab&on$ on all high-spe$ craft4 ,,description ,,( ,,! ,,p>sons ,,turb9e4 ,illu/ration3 ,,fig4 #cg4--,section ( a ,p>sons turb9e4 ,! ess5tial p>ts ( a ,p>sons turb9e are3--7#a7 ,! %aft1 on :i* is m\nt$ 7#b7 ! drum2 7#c7 ! cyl9drical cas+ inside :i* ! drum revolves2 7#d7 ! vanes on ! drum & cas+2 7#e7 ! balance pi/ons4 ,fig4 #cg %[s a diagrammatic turb9e 9 section4 ,! drum1 x w be notic$1 increases its diamet] 9 ?ree /ages1 ,d#a1 ,d#b1 ,d#c1 t[>ds ! "r4 ,f end to end x is /udd$ ) little vanes1 ,m ,m1 set 9 p>allel r+s small di/ances ap>t4 ,ea* vane has a curv$ section 7see ,fig4 #ch71 ! holl[ side fac+ t[>ds ! left4 ,! vanes /ick out f ! drum l %ort spokes1 & _! out] ends almo/ t\* ! cas+4 ,to ! latt] are atta*$ equally-spac$ r+s ( fix$ vanes1 ,f ,f1 po9t+ inw>ds t[>ds ! drum1 & occupy+ ! int]vals betwe5 ! r+s ( mov+ vanes4 ,_! concave sides also face t[>ds ! left1 b1 z se5 9 ,fig4 #ch1 _! l9e ( curve lies ! rev]se way to t ( ,m ,m4 ,/eam ent]s ! cas+ at ,a1 & at once ru%es ?r\gh ! vanes t[>ds ! outlet at ,b4 ,x meets ! fir/ r[ ( fix$ vanes1 & has its pa? s deflect$ t x /rikes ! r+ ( mov+ 7or drum7 vanes at ! mo/ effective angle1 & pu%es !m r\nd4 ,x !n has its direction *ang$ by ! r+ ( ,f ,f1 s t x may treat ! next r[ ( ,m ,m 9 a simil> fa%ion4 ,illu/ration3 ,,fig4 #ch4--;,blades or vanes ( a ,p>sons turb9e4 ,illu/ration3 ,"o ( ! l[-pressure turb9es ( ! ,c>mania1 9 cas+4 ,its size w be inf]r$ f comp>ison ) ! man /&+ ne> ! end ( ! cas+4 ,,! ,,expansive ,,action ,,( ,,/eam ,,9 ,a ,,turb9e4 ,on rea*+ ! end ( ,d#a x ent]s ! second1 or int]m$iate1 set ( vanes4 ,! drum "h is ( a great] diamet]1 & ! blades are long] & set some:at f>!r ap>t1 to give a fre] passage to ! n[ p>tly exp&$ /eam1 :i* has lo/ pressure b ga9$ velocity4 ,! process ( movem5t is repeat$ ?r\gh ?is /age2 & aga9 9 ,d#c1 ! l[-pressure drum4 ,! /eam !n escapes to ! cond5s] ?r\gh ,b1 hav+ by ?is "t exp&$ v _m times2 & x is f\nd advisable1 = reasons expla9$ 9 connection ) comp\nd /eam-eng9es1 to h a sep>ate turb9e 9 an indep5d5t cas+ = ! extreme /ages ( expansion4 ,! vanes are made ( brass4 ,9 ! turb9es ( ! ,c>mania1 ! huge ,cun>d l9]1 #a1aae1jjj vanes are us$4 ,! l>ge/ diamet] ( ! drums is #aa feet1 & ea* l[-pressure turb9e weighs #cej tons4 ,,balanc+ ,,( ,,?ru/4 ,! pu% ex]t$ by ! /eam on ! blades n only turns ! drum1 b presses x 9 ! direction 9 :i* ! /eam fl[s4 ,?is end ?ru/ is c\nt]balanc$ by means ( ! dummy pi/ons1 ,p#a1 ,p#b1 ,p#c4 ,ea* dummy consi/s ( a numb] ( discs revolv+ betwe5 r+s project+ f ! cas+1 ! di/ance betwe5 discs & r+s be+ s small t b little /eam c pass4 ,9 ! high-pressure comp>tm5t ! /eam pu%es ,p#a to ! left ) ! same pressure z x pu%es ! blades ( ,d#a to ! "r4 ,aft] complet+ ! fir/ /age x fills ! passage ,c1 :i* communicates ) ! second pi/on1 ,p#b1 & ! pressure on t pi/on negatives ! ?ru/ on ,d#b4 ,simil>ly1 ! passage ,e causes ! /eam to press equally on ,p#c & ! vanes ( ,d#c4 ,s t ! be>+s 9 :i* ! %aft revolves h b little ?ru/ to take4 ,?is =m ( comp5sation is necess>y 9 m>9e z well z 9 /ation>y turb9es4 ,9 ! =m] ! dummy pi/ons are s proportion$ t ! =w>d ?ru/ giv5 by !m & ! screw comb9$ is almo/ equal to ! ?ru/ aft ( ! mov+ vanes4 ,illu/ration3 ,"o ( ! turb9e drums ( ! ,c>mania4 ,note ! r[s ( vanes4 ,! drum is "h be+ te/$ = p]fect balance on two absolutely level supports4 ,,advantages ,,( ,,! ,,m>9e ,,turb9e4 7#a47 ,abs5ce ( vibration4 ,reciprocat+ eng9es1 h[ev] well balanc$1 cause a %ak+ ( ! :ole %ip :i* is v unpleasant to pass5g]s4 ,! turb9e1 on ! o!r h&1 be+ almo/ p]fectly balanc$1 runs s smoo?ly at ! highe/ spe$s t1 if ! h& be laid on ! cov]+1 x is sometimes almo/ impossible to tell :e!r ! ma*9]y is 9 motion4 ,z a consequ5ce ( ?is smoo? runn+ !re is little noise 9 ! eng9e-room--a pleasant contra/ to ! deaf5+ ro> ( reciprocat+ eng9es4 7#b47 ,turb9es occupy less room4 7#c47 ,!y are m easily t5d$4 7#d47 ,!y require few] repairs1 s9ce ! rubb+ surfaces are v small z comp>$ to ^? ( reciprocat+ eng9es4 7#e47 ,!y are m economical at high spe$s4 ,x mu/ be rememb]$ t a turb9e is ess5tially meant = high spe$s4 ,if run sl[ly1 ! /eam w escape ?r\gh ! _m passages )\t do+ mu* "w4 ,ow+ to its con/ruction1 a turb9e _c be rev]s$ l a cyl9d] eng9e4 ,x !re=e becomes necess>y to fit special a/]n turb9es to "o or m ( ! screw %afts1 = use :5 ! %ip has to be /opp$ or mov$ a/]n4 ,"u ord9>y conditions ^! turb9es revolve idly 9 _! cases4 ,! highe/ spe$ ev] atta9$ on ! sea 0 ! =ty-two miles p] h\r ( ! un=tunate ,vip]1 a turb9e de/roy] :i* develop$ #aa1ejj horse p[]1 ?\gh displac+ only #cgj tons4 ,?is velocity w\ld comp>e fav\rably ) t ( a good _m expresses on c]ta9 railways t we c\ld "n4 ,9 ! future ?irty miles an h\r w c]ta9ly be atta9$ by turb9e-driv5 l9]s4 #g ,ev5 at ?is spe$ ! :eel has a circumf]5tial velocity ( two-?irds t ( a bullet %ot f a ,lee-,met=d rifle4 ,a vane weigh+ only #bej gra9s 7ab\t #a_/b oz47 ex]ts "u ^! conditions a c5trifugal pull ( #ae cwt4 on ! :eel6 ,*apt] ,,iv4 ,,! ,,int]nal-,,combu/ion ,,eng9e4 ,! mean+ ( ! t]m--,action ( ! int]nal-combu/ion eng9e--,! motor c>--,! />t+-h&le--,! eng9e--,! c>burett]--,ignition ( ! *>ge--,advanc+ ! sp>k--,gov]n+ ! eng9e--,! clut*--,! ge>-box--,! comp5sat+ ge>--,! sil5c]--,! brakes--,spe$ ( c>s4 ,,! ,,mean+ ,,( ,,! ,,t]m ,,int]nal-,,combu/ion ,,eng9e4 ,9 ! case ( a /eam-boil] ! en]gy ( combu/ion is transmitt$ to wat] inside an air-tight vessel4 ,! fuel does n actually t\* ! work+ fluid4 ,9 ! gas or oil eng9e ! fuel is br\ght into contact & mix$ ) ! work+ fluid1 :i* is air4 ,x comb9es sudd5ly ) x 9 ! cyl9d]1 & heat en]gy is develop$ s rapidly t ! act is call$ an explosion4 ,coal gas1 m9]al oils1 alcohol1 petrol1 etc41 all conta9 hydrog5 & c>bon4 ,if air1 :i* contributes oxyg51 be add$ to any ( ^! 9 due proportion1 ! mixture becomes highly explosive4 ,on a light be+ appli$1 oxyg5 & c>bon unite1 also hydrog5 & oxyg51 & viol5t heat is g5]at$1 caus+ a viol5t molecul> bomb>dm5t ( ! sides ( ! vessel conta9+ ! mixture4 ,n[1 if ! mixture be compress$ x becomes hott] & hott]1 until a po9t is rea*$ at :i* x ignites spontane\sly4 ,e>ly gas-eng9es did n compress ! *>ge be=e ignition4 ,alphonse ,beau de ,ro*as1 a ,fr5*man1 fir/ ?\ght ( mak+ ! pi/on ( ! eng9e squeeze ! mixture be=e ignition2 & f ! ye> #ahfb1 :5 he propos$ ?is innovation1 ! success ( ! int]nal-combu/ion eng9e may be said to date4 ,illu/ration ,illu/ration3 ,,fig4 #ci4--,%[+ ! f\r /rokes t ! pi/on ( a gas-eng9e makes dur+ "o cycle4 ,,action ,,( ,,! ,,eng9e4 ,! gas-eng9e1 ! oil-eng9e1 & ! motor-c> eng9e are simil> 9 g5]al pr9ciples4 ,! cyl9d] has1 in/ead ( a slide-valve1 two1 or sometimes ?ree1 mu%room valves1 :i* may be describ$ z small & ?ick r\nd plates1 ) bevell$ edges1 m\nt$ on ! ends ( %ort rods1 call$ /ems4 ,^! valves op5 into ! cyl9d]1 upw>ds1 d[nw>ds1 or horizontally1 z ! case may be2 be+ pu%$ 9 by cams project+ f a %aft rotat$ by ! eng9e4 ,= ! pres5t we w conf9e our att5tion to ! s]ies ( op]ations :i* causes ! eng9e to "w4 ,?is s]ies is call$ ! ,beau de ,ro*as1 or ,otto1 cycle1 & includes f\r movem5ts ( ! pi/on4 ,ref]5ce to ,fig4 #ci w %[ exactly :at happ5s 9 a gas-eng9e--7#a7 ,! pi/on moves f left to "r1 & j z ! movem5t comm5ces valves ,g 7gas7 & ,a 7air7 op5 to admit ! explosive mixture4 ,by ! "t t ,p has rea*$ ! end ( its travel ^! valves h clos$ aga94 7#b7 ,! pi/on returns to ! left1 compress+ ! mixture1 :i* has no way ( escape op5 to x4 ,at ! end ( ! /roke ! *>ge is ignit$ by an inc&esc5t tube ,i 79 motor c> & "s /ation>y eng9es by an electric sp>k71 & 7#c7 ! pi/on flies out aga9 on ! explosion /roke4 ,be=e x rea*es ! limit position1 valve ,e 7exhau/7 op5s1 & 7#d7 ! pi/on flies back "u ! mom5tum ( ! fly-:eel1 driv+ out ! burnt gases ?r\gh ! /ill op5 ,e4 ,! cycle is n[ complete4 ,!re has be5 suction1 compression 7includ+ ignition71 combu/ion1 & exhau/ion4 ,x is evid5t t a heavy fly-:eel mu/ be atta*$ to ! crank %aft1 because ! en]gy ( "o /roke 7! explosion7 has to s]ve = ! :ole cycle2 9 o!r words1 = two complete revolutions ( ! crank4 ,a s+le-cyl9d] /eam-eng9e develops an impulse e half-turn--t is1 f\r times z (t54 ,9 ord] to get a m con/ant turn+ effect1 motor c>s h two1 ?ree1 f\r1 six1 & ev5 eight cyl9d]s4 ,f\r-cyl9d] eng9es are at pres5t ! mo/ popul> type = p[]ful c>s4 ,,! ,,motor ,,c>4 ,illu/ration3 ,,fig4 #dj4--,plan ( ! *assis ( a motor c>4 ,we w n[ proce$ to an exam9ation ( ! motor c>1 :i*1 9 addition to me*anical app>atus = ! transmission ( motion to ! driv+-:eels1 includes all ! fundam5tal adjuncts ( ! int]nal-combu/ion eng9e4#h ,fig4 #dj is a bird's-eye view ( ! *assis 7or works & :eels7 ( a c>1 f :i* ! body has be5 remov$4 ,/>t+ at ! left1 we h ! h&le = sett+ ! eng9e 9 motion2 ! eng9e 7a two-cyl9d] 9 ?is case72 ! fly-:eel1 inside :i* is ! clut*2 ! ge>-box1 conta9+ ! cogs = alt]+ ! spe$ ( revolution ( ! driv+-:eels relatively to t ( ! eng9e2 ! propell] %aft2 ! sil5c]1 = dead5+ ! noise ( ! exhau/2 & ! bevel-ge>1 = turn+ ! driv+-:eels4 ,9 ! p>ticul> type ( c> "h consid]$ y w notice t a direct1 or %aft1 drive is us$4 ,! %aft has at ea* end a flexible1 or univ]sal1 jo9t1 :i* all[s ! %aft to turn freely1 ev5 ?\gh x may n be 9 a l9e ) ! %aft project+ f ! ge>-box4 ,x mu/ be rememb]$ t ! eng9e & ge>-box are m\nt$ on ! frame1 betwe5 :i* & ! axles are spr+s1 s t :5 ! c> bumps up & d[n1 ! %aft describes "p ( a circle1 ( :i* ! ge>-box end is ! c5tre4 ,an alt]native me?od ( driv+ is by means ( *a9s1 :i* run r\nd sprocket 7cog7 :eels on ! ends ( a %aft cross+ ! frame j beh9d ! ge>-box1 & r\nd l>g] sprockets atta*$ to ! hubs ( ! driv+-:eels4 ,9 su* a case ! axles ( ! driv+-:eel are fix$ to ! spr+s1 & ! :eels revolve r\nd !m4 ,:]e a ,c>dan 7%aft7 drive is us$ ! axles are atta*$ rigidly to ! :eels at "o end1 & ext5d1 ?r\gh tubes fix$ to ! spr+s1 to bevel-:eels 9 a c5tral comp5sat+-ge> box 7( :i* m pres5tly74 ,sev]al p>ts--! c>burett]1 tanks1 gov]nor1 & pump--are n %[n 9 ! g5]al plan4 ,^! w be ref]r$ to 9 ! m detail$ acc\nt t foll[s4 ,,! ,,/>t+-,,h&le4 ,illu/ration3 ,,fig4 #da4--,! />t+-h&le4 ,fig4 #da gives ! />t+-h&le 9 "p section4 ,! h&le ,h is atta*$ to a tube :i* t]m9ates 9 a clut*1 ,c4 ,a p[]ful spr+ keeps ,c normally ap>t f a second clut*1 ,c#a1 key$ to ! eng9e %aft4 ,:5 ! driv] wi%es to />t ! eng9e he presses ! h&le t[>ds ! "r1 br+s ! clut*es toge!r1 & turns ! h&le 9 a clockwise direction4 ,z soon z ! eng9e beg9s to fire1 ! faces ( ! clut*es slip ov] "o ano!r4 ,,! ,,eng9e4 ,illu/ration3 ,,fig4 #db4--;,end & cross sections ( a two-cyl9d] motor4 ,we next exam9e ! two-cyl9d] eng9e 7,fig4 #db74 ,ea* cyl9d] is surr\nd$ by a wat]-jacket1 ?r\gh :i* wat] is circulat$ by a pump#i 7,fig4 #dc74 ,! heat g5]at$ by combu/ion is s great t ! walls ( ! cyl9d] w\ld soon become r$-hot unless "s ( ! heat 7 quickly c>ri$ away4 ,! pi/ons are ( trunk =m--t is1 long en\gh to act z guides & absorb ! oblique ?ru/ ( ! pi/on rods4 ,?ree or m pi/on r+s ly+ 9 slots 7n %[n7 prev5t ! escape ( gas pa/ ! pi/on4 ,x is int]e/+ to notice t ! effici5cy ( an int]nal-combu/ion eng9e dep5ds s l>gely on ! good fit ( ^! mov+ p>ts1 t cyl9d]s1 pi/ons1 & r+s mu/ be exce$+ly true4 ,a good firm w turn out /&>d p>ts :i* are well )9 #a_/ejjj ( an in* ( p]fect tru?4 ,x is also a wond]ful te/imony to ! quality ( ! mat]ials us$ t1 if prop]ly look$ aft]1 an eng9e :i* has made _m millions ( revolutions1 at ! rate ( #a1jjj to #b1jjj p] m9ute1 (t5 %[s no appreciable signs ( we>4 ,9 "o p>ticul> te/ an eng9e 0 run cont9u\sly = sev]al mon?s1 & at ! end ( ! trial 0 9 absolutely p]fect condition4 ,! cranks revolve 9 an oil-tight case 7g5]ally made ( alum9ium71 & dip 9 oil1 :i* !y spla% up into ! cyl9d] to keep ! pi/on well lubricat$4 ,! plate1 ,p ,p1 ?r\gh a slot 9 :i* ! pi/on rod works1 prev5ts an excess ( oil be+ flung up4 ,*annels are provid$ = lead+ oil into ! be>+s4 ,! cranks are #ahj ap>t4 ,:ile "o pi/on is be+ driv5 out by an explosion1 ! o!r is compress+ its *>ge prior to ignition1 s t ! "o action dead5s ! o!r4 ,!re=e two explosions occur 9 "o revolution ( ! cranks1 & none dur+ ! next revolution4 ,if bo? cranks 7 9 l9e1 ! pi/ons w\ld move toge!r1 giv+ "o explosion ea* revolution4 ,illu/ration3 ,,fig4 #dc4--,%[+ h[ ! wat] :i* cools ! cyl9d]s is circulat$4 ,! valve seats1 & ! inlet & exhau/ pipes1 are se5 9 section4 ,! inlet valve "h works automatically1 be+ pull$ 9 by suction2 b on _m eng9es--on all p[]ful eng9es--! inlet1 l ! exhau/ valve1 is lift$ by a cam1 le/ x %\ld /ick or "w irregul>ly4 ,?ree dott$ circles %[ ,a1 a cog on ! crank %aft2 ,b1 a lay cog1 :i* transmits motion to ,c1 on a %ort %aft rotat+ ! cam t lifts ! exhau/ valve4 ,c1 hav+ twice z _m tee? z ,a1 revolves at half its rate4 ,?is ensures t ! valve %all be lift$ only once 9 two revolutions ( ! crank %aft to :i* x is ge>$4 ,! cogs are tim$1 or arrang$1 s t ! cam beg9s to lift ! valve :5 ! pi/on has made ab\t sev5-eigh?s ( its explosion /roke1 & closes ! valve at ! end ( ! exhau/ /roke4 ,,! ,,c>burett]4 ,a motor c> g5]ally uses petrol z its fuel4 ,petrol is "o ( ! m volatile products ( petroleum1 & has a specific gravity ( ab\t #fhj--t is1 volume = volume1 its weight is to t ( wat] 9 ! proportion ( #fhj to #a1jjj4 ,x is extremely dang]\s1 z x gives (f an inflammable gas at ord9>y temp]atures4 ,b5z9e1 :i* we use to clean clo!s1 is practically ! same z petrol1 & %\ld be treat$ ) equal c>e4 ,! function ( a c>burett] is to r$uce petrol to a v f9e spray & mix x ) a due quantity ( air4 ,! device consi/s ( two ma9 p>ts 7,fig4 #dd7--! float *amb] & ! jet *amb]4 ,9 ! =m] is a contrivance = regulat+ ! petrol supply4 ,a float--a cork1 or air-tight metal box--is arrang$ to move freely up & d[n ! /em ( a ne$le-valve1 :i* closes ! inlet f ! tank4 ,at ! bottom ( ! *amb] are two pivot$ lev]s1 ,w ,w1 :i*1 :5 ! float re/s on !m1 tip up & lift ! valve4 ,petrol fl[s 9 & raises ! float4 ,?is all[s ! valve to s9k & cut (f ! supply4 ,if ! valve is a good fit & ! float is ( ! correct weight1 ! petrol w nev] rise high] ?an ! tip ( ! jet ,g4 ,illu/ration3 ,,fig4 #dd4--,section ( a c>burett]4 ,! suction ( ! eng9e makes petrol spirt ?r\gh ! jet 7:i* has a v small hole 9 its end7 & atomize itself aga9/ a spray+-cone1 ,a4 ,x !n passes to ! eng9e inlet pipe ?r\gh a numb] ( op5+s1 aft] mix+ ) air ent]+ f bel[4 ,an extra air inlet1 controllable by ! driv]1 is g5]ally add$1 unless ! c>burett] be ( a type :i* automatically ma9ta9s con/ant proportions ( air & vap\r4 ,! jet *amb] is (t5 surr\nd$ by a jacket1 ?r\gh :i* "p ( ! hot exhau/ gases circulate4 ,9 cold wea!r especially ?is is a valuable aid to vaporization4 ,illu/ration3 ,,fig4 #de4--,sket* ( ! electrical ignition arrangem5ts on a motor c>4 ,,ignition ,,( ,,! ,,*>ge4 ,all petrol-c>s n[ use electrical ignition4 ,!re are two ma9 sy/ems--7#a7 by an accumulator & induction coil2 7#b7 magneto ignition1 by means ( a small dynamo driv5 by ! eng9e4 ,a g5]al arrangem5t ( ! fir/ is %[n 9 ,fig4 #de4 ,a disc1 ,d1 ( "s insulat+ mat]ial--fibre or vulcanite--is m\nt$ on ! cam1 or half-spe$1 %aft4 ,into ! circumf]5ce is let a piece ( brass1 call$ ! contact-piece1 ?r\gh :i* a screw passes to ! cam %aft4 ,a movable plate1 ,m ,p1 :i* c be rotat$ conc5trically ) ,d ?r\gh "p ( a circle1 c>ries a wipe block at ! end ( a spr+1 :i* presses x aga9/ ,d4 ,! spr+ itself is atta*$ to an insulat$ plate4 ,:5 ! revolution ( ,d br+s ! wipe & contact toge!r1 curr5t fl[s f ! accumulator ?r\gh swit* ,s to ! wipe2 ?r\gh ! contact-piece to ,c2 f ,c to ,m ,p & ! induction coil2 & back to ! accumulator4 ,?is is ! prim>y1 or l[-t5sion1 circuit4 ,a high-t5sion curr5t is induc$ by ! coil 9 ! second>y circuit1 indicat$ by dott$ l9es4#aj ,9 ?is circuit is ! sp>k+-plug 7see ,fig4 #df71 hav+ a c5tral insulat$ rod 9 connection ) "o t]m9al ( ! second>y coil4 ,betwe5 x & a b5t wire project+ f ! iron cas+ ( ! plug 79 contact ) ! o!r t]m9al ( ! second>y coil ?r\gh ! metal ( ! eng9e1 to :i* "o wire ( ! circuit is atta*$7 is a small gap1 across :i* ! second>y curr5t leaps :5 ! prim>y curr5t is brok5 by ! wipe & contact p>t+ company4 ,! sp>k is int5sely hot1 & suffices to ignite ! compress$ *>ge 9 ! cyl9d]4 ,illu/ration3 ,,fig4 #df4--,section ( a sp>k+-plug4 ,,advanc+ ,,! ,,sp>k4 ,we w assume t ! position ( ,w 79 ,fig4 #de7 is su* t ! contact t\*es ,w at ! mom5t :5 ! pi/on has j complet$ ! compression /roke4 ,n[1 ! actual combu/ion ( ! *>ge occupies an appreciable "t1 & ) ! eng9e runn+ at high spe$ ! pi/on w\ld h travell$ "s way d[n ! cyl9d] be=e ! full =ce ( ! explosion 0 develop$4 ,b by rais+ lev] ,l1 ! position ( ,w may be s alt]$ t contact is made slightly be=e ! compression /roke is complete1 s t ! *>ge is fairly alight by ! "t ! pi/on has alt]$ its direction4 ,?is is call$ advanc+ ! sp>k4 ,,gov]n+ ,,! ,,eng9e4 ,!re are sev]al me?ods ( controll+ ! spe$ ( int]nal-combu/ion eng9es4 ,! op]at+ me*anism 9 mo/ cases is a c5trifugal ball-gov]nor4 ,:5 ! spe$ has rea*$ ! fix$ limit x ei!r 7#a7 raises ! exhau/ valve1 s t no fre% *>ges are drawn 92 7#b7 prev5ts ! op5+ ( ! inlet valve2 or 7#c7 ?rottles ! gas supply4 ,! la/ is n[ mo/ commonly us$ on motor c>s1 9 conjunction ) "s device = putt+ x out ( action :5 ! driv] wi%es to exce$ ! highe/ spe$ t x normally p]mits4 ,illu/ration3 ,,fig4 #dg4--,"o =m ( gov]nor us$ on motor c>s4 ,a sket* ( a neat gov]nor1 ) regulat+ atta*m5t1 is giv5 9 ,fig4 #dg4 ,! gov]nor %aft is driv5 f ! eng9e4 ,z ! balls1 ,b ,b1 increase _! velocity1 !y fly away f ! %aft & move ! arms1 ,a ,a1 & a slid+ tube1 ,c1 t[>ds ! "r4 ,?is rocks ! lev] ,r1 & all[s ! valves 9 ! inlet pipe to close & r$uce ! supply ( air & gas4 ,a w$ge1 ,w1 :i* c be rais$ or l[]$ by lev] ,l1 int]v5es betwe5 ! end ( ,r & ! valve /em4 ,if ?is lev] be lift$ to its highe/ position1 ! gov]n+ comm5ces at a l[] spe$1 z ! valve !n has b a %ort di/ance to travel be=e clos+ completely4 ,= high spe$s ! driv] depresses ,l1 =ces ! w$ge d[n1 & s m9imizes ! effect ( ! gov]nor4 ,,! ,,clut*4 ,! eng9e %aft has on its re> end ! fly-:eel1 :i* has a broad & heavy rim1 turn$ to a conical %ape inside4 ,close to ?is1 revolv+ loosely on ! %aft1 is ! clut* plate1 a heavy disc ) a broad edge s %ap$ z to fit ! inside ( a fly-:eel4 ,x is g5]ally fac$ ) lea!r4 ,a v /rong spr+ presses ! plate into ! fly-:eel1 & ! result+ friction is suffici5t to prev5t any slip4 ,projections on ! re> ( ! clut* engage ) ! ge>-box %aft4 ,! driv] ?r[s out ! clut* by depress+ a lev] ) 8 foot4 ,"s clut*es disp5se ) ! lea!r l9+4 ,^! are t]m$ metal to metal clut*es4 ,,! ,,ge>-,,box4 ,we n[ come to a v int]e/+ detail ( ! motor c>1 ! ge>-box4 ,! /eam-eng9e has its spe$ increas$ by admitt+ m /eam to ! cyl9d]s4 ,b an explosion eng9e mu/ be run at a high spe$ to develop its full p[]1 & :5 heavi] "w has to be done on a hill x becomes necess>y to alt] ! spe$ ratio ( eng9e to driv+-:eels4 ,our illu/ration 7,fig4 #dh7 gives a section ( a ge>-box1 :i* w s]ve z a typical example4 ,x provides ?ree =w>d spe$s & "o rev]se4 ,to und]/& h[ x works1 we mu/ /udy ! illu/ration c>efully4 ,p9ion #a is m\nt$ on a holl[ %aft turn$ by ! clut*4 ,into ! holl[ %aft projects ! end ( ano!r %aft c>ry+ p9ions #f & #d4 ,p9ion #f slides up & d[n ?is %aft1 :i* is squ>e at ?is po9t1 b r\nd inside ! loose p9ion #d4 ,p9ions #b & #c are key$ to a squ>e second>y %aft1 & are respectively always 9 ge> ) #a & #d2 b #e c be slid backw>ds & =w>ds s z to engage or dis5gage ) #f4 ,9 ! illu/ration no ge> is 94 ,if ! eng9e is work+1 #a revolves #b1 #b turns #c1 & #c revolves #d idly on its %aft4 ,illu/ration3 ,,fig4 #dh4--,! ge>-box ( a motor c>4 ,to get ! l[e/1 or fir/1 spe$ ! driv] moves 8 lev] & slides #e into ge> ) #f4 ,! transmission !n is3 #a turns #b1 #b turns #e1 #e turns #f1 #f turns ! propell] %aft ?r\gh ! univ]sal jo9t4 ,= ! second spe$1 #e & #f are dis5gag$1 & #f is mov$ up ! page1 z x 71 till projections on x int]lock ) slots 9 #d2 ?us driv+ #a1 #b1 #c1 #d1 %aft4 ,= ! ?ird1 or solid1 spe$1 #f is pull$ d[n into connection ) #a1 & c\ples ! eng9e %aft direct to ! propell] %aft4 ,! rev]se is accompli%$ by rais+ a long p9ion1 #g1 :i* lies 9 ! ge>-box "u #e & #f4 ,! drive !n is #a1 #b1 #e1 #g1 #f4 ,!re be+ an odd numb] ( p9ions n[ engag$1 ! propell] %aft turns 9 ! rev]se direction to t ( ! eng9e %aft4 ,illu/ration3 ,,fig4 #di4 ,,! ,,comp5sat+ ,,ge>4 ,e axle ( a railway tra9 c>ries a :eel at ea* end1 rigidly atta*$ to x4 ,:5 r\nd+ a corn] ! outside :eel has fur!r to travel ?an ! o!r1 & consequ5tly "o or bo? :eels mu/ slip4 ,! curves are made s g5tle1 h[ev]1 t ! am\nt ( slip is v small4 ,b ) a traction-eng9e1 motor c>1 or tricycle ! case is diff]5t1 = all h to describe circles ( v small diamet] 9 proportion to ! l5g? ( ! vehicle4 ,!re=e 9 e case a comp5sat+ ge> is fitt$1 to all[ ! :eels to turn at diff]5t spe$s1 :ile p]mitt+ !m bo? to drive4 ,fig4 #di is an exagg]at$ sket* ( ! ge>4 ,! axles ( ! mov+ :eels turn inside tubes atta*$ to ! spr+s & a c5tral cas+ 7n %[n71 & t]m9ate 9 l>ge bevel-:eels1 ,c & ,d4 ,betwe5 ^! are small bevels m\nt$ on a %aft support$ by ! driv+ drum4 ,if ! latt] be rotat$1 ! bevels w\ld turn ,c & ,d at equal spe$s1 assum+ t bo? axles revolve )\t friction 9 _! be>+s4 ,we w suppose t ! drum is turn$ #ej times a m9ute4 ,n[1 if "o :eel be held1 ! o!r w revolve #ajj times a m9ute2 or1 if "o be sl[$1 ! o!r w increase its spe$ by a correspond+ am\nt4 ,! av]age spe$ rema9s #ej4 ,x %\ld be m5tion$ t drum ,a has incorporat$ ) x on ! outside a bevel-:eel 7n %[n7 rotat$ by a small] bevel on ! end ( ! propell] %aft4 ,,! ,,sil5c]4 ,! petrol-eng9e1 z n[ us$1 emits ! products ( combu/ion at a high pressure4 ,if un*eck$1 !y exp& viol5tly1 & cause a p>tial vacuum 9 ! exhau/ pipe1 into :i* ! air ru%es back ) su* viol5ce z to cause a l\d noise4 ,devices call$ sil5c]s are !re=e fitt$1 to r5d] ! escape m gradual1 & split x up among a numb] ( small ap]tures4 ,! simple/ =m ( sil5c] is a cyl9drical box1 ) a numb] ( f9ely p]=at$ tubes pass+ f end to end ( x4 ,! exhau/ gases p\r+ into ! box ma9ta9 a con/ant pressure some:at high] ?an t ( ! atmosph]e1 b z ! gases are escap+ f x 9 a fairly /eady /ream ! noise becomes a g5tle hiss r ?an a pop4 ,!re are num]\s types ( sil5c]s1 b all employ ?is pr9ciple 9 "o =m or ano!r4 ,,! ,,brakes4 ,e c> c>ries at lea/ two brakes ( b& patt]n--"o1 usually work$ by a side h&-lev]1 act+ on ! axle or hubs ( ! driv+-:eel2 ! o!r1 op]at$ by ! foot1 act+ on ! transmission ge> 7see ,fig4 #dh74 ,! latt] brake is g5]ally arrang$ to )draw ! clut* simultane\sly4 ,te/s h prov$ t ev5 heavy c>s c be pull$ up 9 a/oni%+ly %ort di/ances1 consid]+ _! rate ( travel4 ,trials made 9 ! ,unit$ ,/ates ) a t\r+ c> & a f\r-9-h& coa* gave #be-a_/c & #gj feet respectively = ! di/ance 9 :i* ! spe$ c\ld be r$uc$ f sixte5 miles p] h\r to z]o4 ,,spe$ ,,( ,,c>s4 ,z reg>ds spe$1 motor c>s c rival ! fa/e/ express tra9s1 ev5 on long j\rneys4 ,9 fact1 feats p]=m$ dur+ ! ,gordon-,b5nett & o!r races h equall$ railway p]=mances ov] equal di/ances4 ,:5 we come to record spe$s1 we f9d a c>1 specially built = ! purpose1 cov]+ a mile 9 less ?an half a m9ute4 ,a spe$ ( ov] #abj miles an h\r has actually be5 rea*$4 ,eng9es ( #aej h4p4 c n[ be pack$ into a vehicle scal+ less ?an #a-a_/b tons4 ,ev5 on t\r+ c>s are (t5 f\nd eng9es develop+ #dj to #fj h4p41 :i* =ce ! c> up /eep hills at a pace no?+ less ?an a/oni%+4 ,9 ! future ! motor c> w revolutionize our modes ( life to an ext5t comp>able to ! *anges effect$ by ! adv5t ( ! /eam-eng9e4 ,ev5 s9ce #ahif1 :5 ! man-)-!-flag law 0 aboli%$ 9 ! ,briti% ,isles1 ! motor has r$uc$ di/ances1 op5$ up c\ntry di/ricts1 & g5]ally quick5$ ! pulses ( ! community 9 a mann] :i* makes x haz>d\s to prophesy h[ ! next g5]ation w live4 ,note4--,! au?or is mu* indebt$ to ,mr4 ,wilfrid ,j4 ,l9eham1 ,m4 ,in/4 ,c4,e41 = sev]al ( ! illu/rations :i* appe> 9 ! above *apt]4 #h ,/eam-driv5 c>s are n consid]$ 9 ?is *apt]1 z _! pr9ciple is mu* ! same z t ( ! ord9>y locomotive4 #i ,on "s c>s natural circulation is us$1 ! hot wat] fl[+ f ! top ( ! cyl9d] to ! tank1 f :i* x returns1 aft] be+ cool$1 to ! bottom ( ! cyl9d]4 #aj ,= explanation ( ! induction coil1 see p4 #abb ,*apt] ,v4 ,,electrical ,,app>atus4 ,:at is electricity8--,=ms ( electricity--,magnetism--,! p]man5t magnet--,l9es ( =ce--,electro-magnets--,! electric bell--,! induction coil--,! cond5s]--,trans=mation ( curr5t--,uses ( ! induction coil4 ,,:at ,,is ,,electricity8 ,( ! ultimate nature ( electricity1 z ( t ( heat & light1 we are at pres5t ignorant4 ,b x has be5 cle>ly e/abli%$ t all ?ree ph5om5a are b manife/ations ( ! en]gy p]vad+ ! univ]se4 ,by means ( suitable app>atus "o =m c be conv]t$ into ano!r =m4 ,! heat ( fuel burnt 9 a boil] furnace develops me*anical en]gy 9 ! eng9e :i* ! boil] fe$s ) /eam4 ,! eng9e revolves a dynamo1 & ! electric curr5t !reby g5]at$ c be pass$ ?r\gh wires to produce me*anical motion1 heat1 or light4 ,we mu/ rema9 cont5t1 !re=e1 ) assum+ t electricity is en]gy or motion transmitt$ ?r\gh ! e!r f molecule to molecule1 or f atom to atom1 ( matt]4 ,sci5tific inve/igation has taught u h[ to produce x at w1 h[ to h>ness x to our uses1 & h[ to measure x2 b n :at x is4 ,t "q may1 p]haps1 rema9 unansw]$ till ! end ( human hi/ory4 ,a great difficulty att5d+ ! explanation ( electrical action is ?is--t1 except 9 "o or two cases1 no comp>ison c be e/abli%$ betwe5 x & ! op]ation ( gases & fluids4 ,:5 deal+ ) ! /eam-eng9e1 any ord9>y intellig5ce soon grasps ! pr9ciples :i* gov]n ! use ( /eam 9 cyl9d]s or turb9es4 ,! diagrams %[1 x is hop$1 q pla9ly h[ x works4 ,b electricity is elusive1 invisible2 & ! greate/ au?orities _c say :at goes on at ! poles ( a magnet or on ! surface ( an electrifi$ body4 ,ev5 ! exi/5ce ( negative & positive electricity is problematical4 ,h[ev]1 we see ! effects1 & we "k t if "o ?+ is done ano!r ?+ happ5s2 s t we are at lea/ able to use t]ms :i*1 :ile conv5i5t1 are n at pres5t controv]t$ by sci5tific progress4 ,,=ms ,,( ,,electricity4 ,rub a vulcanite rod & hold "o end ne> "s t9y pieces ( pap]4 ,!y fly to x1 /ick to x = a "t1 & !n fall (f4 ,! rod 0 electrifi$--t is1 its surface 0 affect$ 9 su* a way z to be 9 a /ate ( molecul> /ra9 :i* ! contact ( ! pap] fragm5ts alleviat$4 ,by rubb+ l>ge surfaces & collect+ ! electricity 9 suitable receiv]s ! /ra9 c be made to relieve itself 9 ! =m ( a viol5t dis*>ge accompani$ by a bright fla%4 ,?is =m ( electricity is kn[n z /atic4 ,next1 place a copp] plate & a z9c plate into a j> full ( dilut$ sulphuric acid4 ,if a wire be atta*$ to !m a curr5t ( electricity is said to fl[ along ! wire4 ,we mu/ n1 h[ev]1 imag9e t any?+ actually moves along inside ! wire1 z wat]1 /eam1 or air1 passes ?r\gh a pipe4 ,pr(essor ,tr[bridge says1#aa ,no o!r ag5cy = transmitt+ p[] c be /opp$ by su* slight ob/acles z electricity4 ,a ?9 %eet ( pap] plac$ across a tube convey+ compress$ air w\ld be in/antly ruptur$4 ,x w\ld take a wall ( /eel at lea/ an in* ?ick to /& ! pressure ( /eam :i* is driv+ a #aj1jjj horse-p[] eng9e4 ,a ?9 lay] ( dirt b5ea? ! :eels ( an electric c> c prev5t ! curr5t :i* propels ! c> f pass+ to ! rail1 & !n back to ! p[]-h\se4 ,!re w\ld1 inde$1 be a puncture ( ! pap] if ! curr5t _h a suffici5t voltage1 or pressure2 yet ! fact rema9s t curr5t electricity c be v easily conf9$ to its conductor by means ( "s insulat+ or nonconduct+ envelope4 ,,magnetism4 ,! mo/ famili> =m ( electricity is t kn[n z magnetism4 ,:5 a b> ( /eel or iron is magnetiz$1 x is suppos$ t ! molecules 9 x turn & arrange !mselves ) all _! nor?-seek+ poles t[>ds ! "o end ( ! b>1 & _! s\?-seek+ poles t[>ds ! o!r4 ,if ! b> is balanc$ freely on a pivot1 x comes to re/ po9t+ nor? & s\?2 =1 ! e>? be+ a huge magnet1 its nor? pole attracts all ! nor?-seek+ poles ( ! molecules1 & its s\? poles ! s\?-seek+ poles4 7,! nor?-seek+ pole ( a magnet is m>k$ ,n41 ?\gh x is 9 reality ! s\? pole2 = unlike poles are mutually attractive1 & l poles repell5t47 ,!re are two =ms ( magnet--p]man5t & tempor>y4 ,if /eel is magnetiz$1 x rema9s s2 b s(t iron loses practically all its magnetism z soon z ! cause ( magnetization is )drawn4 ,?is is :at we %\ld expect2 = /eel is m closely compact$ ?an iron1 & ! molecules !re=e w\ld be able to turn ab\t m easily4#ab ,x is =tunate = u t ?is is s1 s9ce on ! rapid magnetization & demagnetization ( s(t iron dep5ds ! action ( _m ( our electrical me*anisms4 ,,! ,,p]man5t ,,magnet4 ,magnets are ei!r 7#a7 /raight1 9 :i* case !y are call$ b> magnets2 or 7#b7 ( horse%oe =m1 z 9 ,figs4 #ej & #ea4 ,by b5d+ ! magnet ! two poles are br\ght close toge!r1 & ! attraction ( bo? may be ex]cis$ simultane\sly on a b> ( /eel or iron4 ,,l9es ,,( ,,=ce4 ,9 ,fig4 #ej are se5 a numb] ( dott$ l9es4 ,^! are call$ l9es ( magnetic =ce4 ,if y lay a %eet ( pap] on a horse%oe magnet & spr9kle x ) iron du/1 y w at once notice h[ ! p>ticles arrange !mselves 9 curves simil> 9 %ape to ^? %[n 9 ! illu/ration4 ,x is suppos$ 7x _c be prov$7 t magnetic =ce /reams away f ! ,n4 pole & describes a circul> c\rse ?r\gh ! air back to ! ,s4 pole4 ,! same rem>k applies to ! b> magnet4 ,,electrical ,,magnets4 ,illu/ration3 ,,fig4 #ej4--,p]man5t magnet1 & ! l9es ( =ce emanat+ f x4 ,if an insulat$ wire is w\nd r\nd & r\nd a /eel or iron b> f end to end1 & has its ends connect$ to ! t]m9als ( an electric batt]y1 curr5t rotates r\nd ! b>1 & ! b> is magnetiz$4 ,by increas+ ! /r5g? & volume ( ! curr5t1 & multiply+ ! numb] ( turns ( wire1 ! attractive =ce ( ! magnet is increas$4 ,n[ disconnect ! wires f ! batt]y4 ,if ( iron1 ! magnet at once loses its attractive =ce2 b if ( /eel1 x reta9s x 9 "p4 ,in/ead ( a simple horse%oe-%ap$ b>1 two %ort] b>s rivet$ into a plate are g5]ally us$ = electromagnets ( ?is type4 ,coils ( wire are w\nd r\nd ea* b>1 & connect$ s z to =m "o cont9u\s :ole2 b ! wire ( "o coil is w\nd 9 ! direction opposite to t ( ! o!r4 ,! free end ( ea* goes to a batt]y t]m9al4 ,9 ,fig4 #ea y w notice t "s ( ! l9es ( =ce are deflect$ ?r\gh ! iron b> ,a4 ,!y pass m easily ?r\gh iron ?an ?r\gh air2 & w *oose iron by pref]5ce4 ,! attraction ex]cis$ by a magnet on iron may be due to ! ef=t ( ! l9es ( =ce to %ort5 _! pa?s4 ,x is evid5t t ! clos] ,a comes to ! poles ( ! magnet ! less w be ! di/ance to be travell$ f "o pole to ! b>1 along x1 & back to ! o!r pole4 ,illu/ration3 ,,fig4 #ea4--;,electro-magnet3 ,a1 armature2 ,b1 batt]y4 ,hav+ n[ consid]$ electricity 9 ?ree ( its =ms--/atic1 curr5t1 & rotatory--we w pass to "s ( its applications4 ,,! ,,electric ,,bell4 ,a fit device to beg9 ) is ! ,electric ,bell1 :i* has s l>gely replac$ wire-pull$ bells4 ,^! la/ cause a great deal ( tr\ble sometimes1 s9ce if a wire snaps x may be necess>y to take up c>pets & floor-bo>ds to put ?+s "r4 ,_! in/allation is n simple1 = at e corn] mu/ be put a crank to alt] ! direction ( ! pull1 & ! cranks mean increas$ friction4 ,b :5 electric wires h once be5 prop]ly in/all$1 !re %\ld be no ne$ = t\*+ !m = an indef9ite p]iod4 ,!y c be tak5 r\nd z _m corn]s z y wi% )\t los+ any ( _! conductivity1 & be plac$ :]ev] is mo/ conv5i5t = exam9ation4 ,"o bell may s]ve a l>ge numb] ( rooms if an indicator be us$ to %[ :]e ! call 0 made f1 by a c>d appe>+ 9 "o ( a numb] ( small w9d[s4 ,be=e answ]+ a call1 ! att5dant presses 9 a button to return ! c>d to its normal position4 ,9 ,fig4 #eb we h a diagrammatic view ( an electric bell & curr5t4 ,:5 ! bell-pu% is press$ 91 curr5t fl[s f ! batt]y to t]m9al ,t#a1 r\nd ! electro-magnet ,m1 ?r\gh ! pill> ,p & flat /eel spr+s ,s & ,b1 ?r\gh ! plat9um-po9t$ screw1 & back to ! batt]y ?r\gh ! pu%4 ,! circulation ( curr5t magnetizes ,m1 :i* attracts ! iron armature ,a atta*$ to ! spr+ ,s1 & draws ! hamm] ,h t[>ds ! gong4 ,j be=e ! /roke occurs1 ! spr+ ,b leaves ! tip ( ! screw1 & ! circuit is brok51 s t ! magnet no long] attracts4 ,h is c>ri$ by its mom5tum aga9/ ! gong1 & is )drawn by ! spr+1 until ,b once m makes contact1 & ! magnet is re-excit$4 ,! hamm] vibrations recur _m times a second z long z ! pu% is press$ 94 ,illu/ration3 ,,fig4 #eb4--,sket* ( an electric-bell circuit4 ,! electric bell is us$ = s _m purposes t !y _c all be not$4 ,x plays an especially important "p 9 telephonic in/allations to draw ! att5tion ( ! subscrib]s1 =ms an item 9 automatic fire & burgl> al>ms1 & is a necess>y adjunct ( railway signall+ cab9s4 ,,! ,,induction ,,or ,,ruhmkorff ,,coil4 ,ref]5ce 0 made 9 connection ) ! electrical ignition ( int]nal-combu/ion eng9es 7p4 #aja7 to ! induction coil4 ,?is is a device = increas+ ! voltage1 or pressure1 ( a curr5t4 ,! two-cell accumulator c>ri$ 9 a motor c> gives a voltage 7o!rwise call$ electro-motive =ce ,e4,m4,f47 ( #dd volts4 ,if y atta* a wire to "o t]m9al ( ! accumulator & bru% ! loose end rapidly across ! o!r t]m9al1 y w notice t a bright sp>k passes betwe5 ! wire & ! t]m9al4 ,9 reality !re are two sp>ks1 "o :5 !y t\*1 & ano!r :5 !y sep>ate1 b !y occur s closely toge!r t ! eye _c sep>ate ! two impressions4 ,a sp>k ( ?is k9d w\ld n be suffici5tly hot to ignite a *>ge 9 a motor cyl9d]1 & a sp>k f ! induction coil is !re=e us$4 ,illu/ration3 ,,fig4 #ec4--,sket* ( an induction coil4 ,we give a sket* ( ! induction coil 9 ,fig4 #ec4 ,x consi/s ( a core ( s(t iron wires r\nd :i* is w\nd a lay] ( co>se insulat$ wire1 d5ot$ by ! ?ick l9e4 ,"o end ( ! w9d+ ( ?is prim>y coil is atta*$ to ! batt]y1 ! o!r to ! base ( a hamm]1 ,h1 vibrat+ betwe5 ! end ( ! core & a screw1 ,s1 pass+ ?r\gh an upright1 ,t1 connect$ ) ! o!r t]m9al ( ! batt]y4 ,! action ( ! hamm] is precisely ! same z t ( ! armature ( an electric bell4 ,outside ! prim>y coil are w\nd _m turns ( a mu* f9] wire completely insulat$ f ! prim>y coil4 ,! ends ( ?is second>y coil are atta*$ to ! objects 79 ! case ( a motor c>1 ! insulat$ wire ( ! sp>k+-plug & a wire project+ f its out] iron cas+7 betwe5 :i* a sp>k has to pass4 ,z soon z ,h t\*es ,s ! circuit is complet$4 ,! core becomes a p[]ful magnet ) ext]nal l9es ( =ce pass+ f "o pole to ! o!r ov] & among ! turns ( ! second>y coil4 ,h is almo/ in/antane\sly attract$ by ! core1 & ! break occurs4 ,! l9es ( =ce n[ 7at lea/ s x is suppos$7 s9k into ! core1 cutt+ ?r\gh ! turns ( ! second>y1 & caus+ a p[]ful curr5t to fl[ ?r\gh !m4 ,! great] ! numb] ( turns1 ! great] ! numb] ( times ! l9es ( =ce are cut1 & ! /rong] is ! curr5t4 ,if suffici5tly int5se1 x jumps any gap 9 ! second>y circuit1 heat+ ! int]m$iate air to a /ate ( inc&esc5ce4 ,,! ,,cond5s]4 ,! sudd5 p>t+ ( ,h & ,s w\ld produce /rong sp>k+ across ! gap betwe5 !m if x 7 n = ! cond5s]1 :i* consi/s ( a numb] ( t9foil %eets sep>at$ by lay]s ( p>aff9$ pap]4 ,all ! odd %eets are connect$ ) ,t1 all ! ev5 ) ,t#a4 ,n[1 ! m rapid ! ext9ction ( magnetism 9 ! core aft] break ( ! prim>y circuit1 ! m rapidly w ! l9es ( =ce collapse1 & ! m int5se w be ! induc$ curr5t 9 ! second>y coil4 ,! cond5s] dim9i%es ! p]iod ( ext9ction v greatly1 :ile l5g!n+ ! p]iod ( magnetization aft] ! make ( ! prim>y curr5t1 & s decreas+ ! /r5g? ( ! rev]se curr5t4 ,,trans=mation ,,( ,,curr5t4 ,! diff]5ce 9 ! voltage ( ! prim>y & second>y curr5ts dep5ds on ! l5g? ( ! w9d+s4 ,if !re are #ajj turns ( wire 9 ! prim>y1 & #ajj1jjj turns 9 ! second>y1 ! voltage w be increas$ #a1jjj times2 s t a #d-volt curr5t is /epp$ up to #d1jjj volts4 ,9 ! l>ge/ induction coils ! second>y w9d+ absorbs #bjj-cjj miles ( wire1 & ! sp>k giv5 may be any?+ up to f\r feet 9 l5g?4 ,su* a sp>k w\ld pi]ce a glass plate two in*es ?ick4 ,x mu/ n be suppos$ t an induction coil increases ! am\nt ( curr5t giv5 (f by a batt]y4 ,x m]ely increases its pressure at ! exp5se ( its volume--/ores up its en]gy1 z x 71 until !re is en\gh to d :at a l[-t5sion fl[ c\ld n effect4 ,a fair comp>ison w\ld be to picture ! en]gy ( ! l[-t5sion curr5t z ! mom5tum ( a numb] ( small pebbles ?r[n 9 succession at a door1 say #ajj a m9ute4 ,if y w5t on pelt+ ! door = h\rs y might make no impression on x1 b if y c\ld knead e #ajj pebbles into a s+le /one1 & ?r[ ^! /ones "o p] m9ute1 y w\ld soon break ! door 94 ,any int]mitt5t curr5t c be trans=m$ z reg>ds its int5sity4 ,y may ei!r increase its pressure :ile decreas+ its rate ( fl[1 or amp]age2 or decrease its pressure & increase its fl[4 ,9 ! case t we h consid]$1 a cont9u\s batt]y curr5t is r5d]$ int]mitt5t by a me*anical contrivance4 ,b if ! curr5t comes f an alt]nat+ dynamo--t is1 is already int]mitt5t--! contact-break] is n ne$$4 ,!re w be m to say ab\t trans=mation ( curr5t 9 lat] p>agraphs4 ,,uses ,,( ,,! ,,induction ,,coil4 ,! induction coil is us$--7#a47 ,= pass+ curr5ts ?r\gh glass tubes almo/ exhau/$ ( air or conta9+ highly r>efi$ gases4 ,! lum9\s effects ( ^! ,geissl] tubes are v beautiful4 7#b47 ,= produc+ ! n[ fam\s ,x or ,rntg5 rays4 ,^! rays accompany ! light rays giv5 (f at ! negative t]m9al 7ca?ode7 ( a vacuum tube1 & are invisible to ! eye unless caught on a fluoresc5t scre51 :i* r$uces _! rate ( vibration suffici5tly = ! eye to be s5sitive to !m4 ,! ,rntg5 rays h ! peculi> prop]ty ( p5etrat+ _m sub/ances q opaque to light1 su* z metals1 /one1 wood1 etc41 & z a consequ5ce h prov$ ( great use to ! surgeon 9 localiz+ or det]m9+ ! nature ( an int]nal injury4 ,!y also h a det]r5t effect ^u canc]\s gr[?s4 7#c47 ,9 wireless telegraphy1 to cause p[]ful electric oscillations 9 ! e!r4 7#d47 ,on motor c>s1 = ignit+ ! cyl9d] *>ges4 7#e47 ,= electrical massage ( ! body4 #aa ,:at is ,electricity8 p4 #df4 #ab ,if a magnetiz$ b> be heat$ to :ite heat & tapp$ ) a hamm] x loses its magnetism1 because ! di/ance betwe5 ! molecules has increas$1 & ! molecules c easily return to _! orig9al positions4 ,*apt] ,,vi4 ,,! ,,electric ,,telegraph4 ,ne$le in/rum5ts--,influ5ce ( curr5t on ! magnetic ne$le--,me?od ( rev]s+ ! curr5t--,s\nd+ in/rum5ts--,telegraphic relays--,record+ telegraphs--,high-spe$ telegraphy4 ,take a small pocket compass & w9d sev]al turns ( f9e insulat$ wire r\nd ! case1 ov] ! top & "u ! bottom4 ,n[ lay ! compass on a table1 & turn x ab\t until ! coil is on a l9e ) ! ne$le--9 fact1 cov]s x4 ,next t\* ! t]m9als ( a batt]y ) ! ends ( ! wire4 ,! ne$le at once %ifts ei!r to "r or left1 & rema9s 9 t position z long z ! curr5t fl[s4 ,if y *ange ! wires ov]1 s rev]s+ ! direction ( ! curr5t1 ! ne$le at once po9ts 9 ! o!r direction4 ,x is to ?is conduct on ! "p ( a magnetic ne$le :5 9 a magnetic field t we owe ! exi/5ce ( ! ne$le telegraph in/rum5t4 ,,ne$le ,,in/rum5ts4 ,illu/ration3 ,,fig4 #ed4--,sket* ( ! side elevation ( a ,:eat/one ne$le in/rum5t4 ,probably ! be/-kn[n ne$le in/rum5t is ! ,cooke-,:eat/one1 l>gely us$ 9 signal-boxes & 9 "s po/-(fices4 ,a v]tical section ( x is %[n 9 ,fig4 #ed4 ,x consi/s ( a base1 ,b1 & an upright front1 ,a1 to ! back ( :i* are atta*$ two holl[ coils on ei!r side ( a magnetic ne$le m\nt$ on ! same %aft z a second dial ne$le1 ,n1 outside ! front4 ,! wires ,w ,w are connect$ to ! telegraph l9e & to ! commutator1 a device :i*1 :5 ! op]ator moves ! h&le ,h to "r & left1 keeps rev]s+ ! direction ( ! curr5t4 ,! ne$les on bo? receiv+ & transmitt+ in/rum5ts wag 9 accordance ) ! movem5ts ( ! h&le4 ,"o or m movem5ts =m an alphabetical lett] ( ! ,morse code4 ,?us1 if ! ne$le po9ts fir/ to left1 & !n to "r1 & comes to re/ 9 a normal position = a mom5t1 ! lett] ,a is signifi$2 "r-left-left-left 9 quick succession ,b2 "r-left-"r-left ,c1 & s on4 ,:]e a m>k+ in/rum5t is us$1 a dot signifies a left1 & a da% a "r2 & if a s\nd] is employ$1 ! op]ator judges by ! l5g? ( ! int]vals betwe5 ! clicks4 ,,influ5ce ,,( ,,curr5t ,,on ,a ,,magnetic ,,ne$le4 ,illu/ration3 ,,figs4 #ee1 #ef4--,! coils ( a ne$le in/rum5t4 ,! arr[s %[ ! direction tak5 by ! curr5t4 ,figs4 #ee & #ef are two views ( ! coils & magnetic ne$le ( ! ,:eat/one in/rum5t z !y appe> f beh9d4 ,9 ,fig4 #ee ! curr5t ent]s ! left-h& coil f ! left1 & travels r\nd & r\nd x 9 a clockwise direction to ! o!r end1 :5ce x passes to ! o!r coil & away to ! batt]y4 ,n[1 a coil ?r\gh :i* a curr5t passes becomes a magnet4 ,its pol>ity dep5ds on ! direction 9 :i* ! curr5t fl[s4 ,suppose t y are look+ ?r\gh ! coil1 & t ! curr5t ent]s x f y\r end4 ,if ! wire is w\nd 9 a clockwise direction1 ! ,s4 pole w be ne>e/ y2 if 9 an anti-clockwise direction1 ! ,n4 pole4 ,9 ,fig4 #ee ! ,n4 poles are at ! "r end ( ! coils1 ! ,s4 poles at ! left end2 s ! ,n4 pole ( ! ne$le is attract$ to ! "r1 & ! ,s4 pole to ! left4 ,:5 ! curr5t is rev]s$1 z 9 ,fig4 #ef1 ! ne$le moves ov]4 ,if no curr5t passes1 x rema9s v]tical4 ,,me?od ,,( ,,rev]s+ ,,! ,,curr5t4 ,illu/ration3 ,,fig4 #eg4--;,g5]al arrangem5t ( ne$le-in/rum5t circuit4 ,! %ad$ plates on ! left 7,b & ,r7 are 9 contact4 ,a simple me?od ( *ang+ ! direction ( ! curr5t 9 a two-in/rum5t circuit is %[n diagrammatically 9 ,fig4 #eg4 ,! pr9ciple is us$ 9 ! ,:eat/one ne$le in/rum5t4 ,! batt]y t]m9als at ea* /ation are atta*$ to two brass plates1 ,a ,b1 ,a#a ,b#a4 ,cross+ ^! at "r angles 7"u ,a ,a#a & ov] ,b ,b#a7 are ! flat brass spr+s1 ,l ,r1 ,l#a ,r#a1 hav+ buttons at _! l[] ends1 & fix$ at _! upp] ends to basebo>ds4 ,:5 at re/ !y all press upw>ds aga9/ ! plates ,a & ,a#a respectively4 ,r & ,l#a are connect$ ) ! l9e circuit1 9 :i* are ! coils ( dials #a & #b1 "o at ea* /ation4 ,l & ,r#a are connect$ ) ! e>?-plates ,e ,e#a4 ,an op]ator at /ation #a depresses ,r s z to t\* ,b4 ,curr5t n[ fl[s f ! batt]y to ,b1 !nce ?r\gh ,r to ! l9e circuit1 r\nd ! coils ( bo? dials ?r\gh ,l#a ,a#a & ,r to e>?-plate ,e#a1 ?r\gh ! e>? to ,e1 & !n back to ! batt]y ?r\gh ,l & ,a4 ,! ne$les assume ! position %[n4 ,to rev]se ! curr5t ! op]ator all[s ,r to rise into contact ) ,a1 & depresses ,l to t\* ,b4 ,! c\rse c be trac$ out easily4 ,9 ! ,:eat/one drop-h&le in/rum5t 7,fig4 #ed7 ! commutator may be describ$ z an insulat$ core on :i* are two %ort l5g?s ( brass tub+4 ,"o ( ^! has rubb+ aga9/ x a spr+ connect$ ) ! t]m9al ( ! batt]y2 ! o!r has simil> communication ) ! - t]m9al4 ,project+ f ea* tube is a spike1 & ris+ f ! basebo>d are f\r upright brass /rips n q t\*+ ! commutator4 ,^? on "o side lead to ! l9e circuit1 ^? on ! o!r to ! e>?-plate4 ,:5 ! h&le is turn$ "o way1 ! spikes t\* ! =w>d l9e /rip & ! re> e>? /rip1 & vice v]s :5 mov$ 9 ! opposite direction4 ,,s\nd+ ,,in/rum5ts4 ,sometimes little brass /rips are atta*$ to ! dial plate ( a ne$le in/rum5t = ! ne$le to /rike aga9/4 ,z ^! give diff]5t notes1 ! op]ator c compreh5d ! message by e> alone4 ,b ! mo/ widely us$ s\nd+ in/rum5t is ! ,morse s\nd]1 nam$ aft] its inv5tor4 ,= ?is a rev]sible curr5t is n ne$$4 ,! receiv] is m]ely an electro-magnet 7connect$ ) ! l9e circuit & an e>?-plate7 :i*1 :5 a curr5t passes1 attracts a little iron b> atta*$ to ! middle ( a pivot$ lev]4 ,! free end ( ! lev] works betwe5 two /ops4 ,e "t ! circuit is clos$ by ! transmitt+ key at ! s5d+ /ation ! lev] flies d[n aga9/ ! l[] /op1 to rise aga9 :5 ! circuit is brok54 ,! duration ( its /ay decides :e!r a long or %ort is meant4 ,,telegraphic ,,relays4 ,illu/ration3 ,,fig4 #eh4--,section ( a telegraph wire insulator on its arm4 ,! %ad$ circle is ! l9e wire1 ! two blank circles indicate ! wire :i* ties ! l9e wire to ! insulator4 ,:5 an electric curr5t has travell$ = a long di/ance ?r\gh a wire its /r5g? is mu* r$uc$ on acc\nt ( ! resi/ance ( ! wire1 & may be insuffici5t to cause ! electro-magnet ( ! s\nd] to move ! heavy lev]4 ,in/ead1 !re=e1 ( ! curr5t act+ directly on ! s\nd] magnet1 x is us$ to en]gize a small magnet1 or relay1 :i* pulls d[n a light b> & closes a second local circuit--t is1 "o at ! receiv] end--work$ by a sep>ate batt]y1 :i* has suffici5t p[] to op]ate ! s\nd]4 ,,record+ ,,telegraphs4 ,by atta*+ a small :eel to ! end ( a ,morse-s\nd] lev]1 by arrang+ an ink-well = ! :eel to dip into :5 ! end falls1 & by mov+ a pap] ribbon sl[ly along = ! :eel to press aga9/ :5 x rises1 a self-record+ ,morse ink] is produc$4 ,! ribbon-fe$+ app>atus is set 9 motion automatically by ! curr5t1 & cont9ues to pull ! ribbon along until ! message is complet$4 ,! ,hughes type-pr9t] cov]s a %eet ( pap] ) pr9t$ *>act]s 9 bold ,roman type4 ,! transmitt] has a keybo>d1 on :i* are m>k$ lett]s1 signs1 & numb]s2 also a type-:eel1 ) ! *>act]s on its circumf]5ce1 rotat$ by electricity4 ,! receiv] conta9s me*anisms = rotat+ ano!r type-:eel syn*ron\sly--t is1 9 "t--) ! fir/2 = %ift+ ! :eel across ! pap]2 = press+ ! pap] aga9/ ! :eel2 & = mov+ ! pap] :5 a fre% l9e is ne$$4 ,^! are too complicat$ to be describ$ "h 9 detail4 ,by means ( relays "o transmitt] may be made to "w five hundr$ receiv]s4 ,9 ,london a s+le op]ator1 controll+ a keybo>d 9 ! c5tral dispat*+ (fice1 causes typewritt5 messages to spell !mselves out simultane\sly 9 ma*9es di/ribut$ all ov] ! metropolis4 ,! tape ma*9e resembles t j describ$ 9 _m details4 ,! ma9 diff]5ce is t x pr9ts on a cont9u\s ribbon in/ead ( on %eets4 ,automatic electric pr9t]s ( "s k9d or o!r are to be f\nd 9 ! ve/ibules ( all ! pr9cipal hotels & clubs ( our l>ge cities1 & 9 ! (fices ( bank]s1 /ockbrok]s1 & newspap] editors4 ,9 ,london alone ov] #ejj million words are pr9t$ by ! receiv]s 9 a ye>4 ,,high-,,spe$ ,,telegraphy4 ,at c]ta9 seasons1 or :5 important political ev5ts are tak+ place1 ! telegraph s]vice w\ld become conge/$ ) news 7 !re n "s means ( transmitt+ messages at a mu* great] spe$ ?an is possible by h& signall+4 ,fifty words a m9ute is ab\t ! limit spe$ t a good op]ator c ma9ta94 ,by means ( ,:eat/one's automatic transmitt] ! rate c be increas$ to #djj words p] m9ute4 ,pap] ribbons are pun*$ 9 special ma*9es by a numb] ( cl]ks ) a s]ies ( holes :i* by _! position indicate a dot or a da%4 ,! ribbons are pass$ ?r\gh a special transmitt]1 ov] little electric bru%es1 :i* make contact ?r\gh ! holes ) surfaces connect$ to ! l9e circuit4 ,at ! receiv] end ! message is pr9t$ by a ,morse ink]4 ,x has be5 f\nd possible to s5d sev]al messages simultane\sly ov] a s+le l9e4 ,to effect ?is a di/ribut] is us$ to put a numb] ( transmitt]s at "o end ( ! l9e 9 communication ) an equal numb] ( receiv]s at ! o!r end1 f$ by a second di/ribut] keep+ p]fect "t ) ! fir/4 ,in/ead ( a signal com+ z a :ole to any "o in/rum5t x arrives 9 little bits1 b ^! foll[ "o ano!r s closely z to be practically cont9u\s4 ,by work+ a numb] ( automatic transmitt]s ?r\gh a di/ribut]1 a ?\s& words or m p] m9ute are easily dispat*$ ov] a s+le wire4 ,! ,pollak ,virag sy/em employs a pun*$ ribbon1 & ! receiv] traces out ! message 9 alphabetical *>act]s on a mov+ /rip ( s5sitiz$ photographic pap]4 ,a mirror atta*$ to a vibrat+ diaphragm reflects light f a lamp on to ! /rip1 :i* is automatically develop$ & fix$ 9 *emical ba?s4 ,! me?od ( mov+ ! mirror s z to make ! rays trace out words is extremely +5i\s4 ,messages h be5 transmitt$ by ?is sy/em at ! rate ( #ahj1jjj words p] h\r4 ,*apt] ,,vii4 ,,wireless ,,telegraphy4 ,! transmitt+ app>atus--,! receiv+ app>atus--,syntonic transmission--,! advance ( wireless telegraphy4 ,9 our la/ *apt] we review$ briefly "s sy/ems ( s5d+ telegraphic messages f "o po9t ( ! e>?'s surface to ano!r ?r\gh a circuit consi/+ p>tly ( an insulat$ wire & p>tly ( ! e>? itself4 ,! metallic portion ( a long circuit1 especially if x be a subm>9e cable1 is co/ly to in/all1 s t 9 q ! e>ly days ( telegraphy ef=ts 7 made to use ! e!r 9 ! place ( wire z "o conductor4 ,:5 a hamm] /rikes an anvil ! air ar\nd is viol5tly di/urb$4 ,?is di/urbance spreads ?r\gh ! molecules ( ! air 9 mu* ! same way z ripples spread f ! spla% ( a /one ?r[n into a pond4 ,:5 ! s\nd waves rea* ! e> !y agitate ! tympanum1 or drum membrane1 & we he> a noise4 ,! hamm] is "h ! transmitt]1 ! air ! conductor1 ! e> ! receiv]4 ,9 wireless telegraphy we use ! e!r z ! conductor ( electrical di/urbances4#ac ,m>coni1 ,slaby1 ,branly1 ,lodge1 ,de ,=e/1 ,pop(f1 & o!rs h inv5t$ app>atus = caus+ di/urbances ( ! requisite k9d1 & = detect+ _! pres5ce4 ,! ma9 features ( a wireless telegraphy outfit are %[n 9 ,figs4 #ei & #fa4 ,,! ,,transmitt] ,,app>atus4 ,we w fir/ consid] ! transmitt+ outfit 7,fig4 #ei74 ,x includes a batt]y1 dispat*+ key1 & an induction coil hav+ its second>y circuit t]m9als connect$ ) two wires1 ! "o lead+ to an e>?-plate1 ! o!r c>ri$ al(t on poles or susp5d$ f a kite4 ,9 ! l>ge /ation at ,poldhu1 ,cornwall1 = transatlantic signall+1 !re are special wood5 t[]s #bae feet high1 betwe5 :i* ! arial wires hang4 ,at _! upp] & l[] ends respectively ! e>? & arial wires t]m9ate 9 brass balls sep>at$ by a gap4 ,:5 ! op]ator depresses ! key ! induction coil *>ges ^! balls & ! wires atta*$ !reto ) high-t5sion electricity4 ,z soon z ! quantity collect$ exce$s ! resi/ance ( ! air-gap1 a dis*>ge takes place betwe5 ! balls1 & ! e!r r\nd ! arial wire is viol5tly di/urb$1 & waves ( electrical en]gy are propagat$ ?r\gh x4 ,! rapidity ) :i* ! dis*>ges foll[ "o ano!r1 & _! travell+ p[]1 dep5ds on ! /r5g? ( ! induction coil1 ! l5g? ( ! air-gap1 & ! capacity ( ! wires4#ad ,illu/ration3 ,,fig4 #ei4--,sket* ( ! transmitt] ( a wireless telegraphy outfit4 ,illu/ration3 ,,fig4 #fj4--;,a ,m>coni coh]]4 ,,receiv+ ,,app>atus4 ,! human body is q ins5sitive to ^! e!ric waves4 ,we _c feel1 he>1 or see !m4 ,b at ! receiv+ /ation !re is :at may be call$ an electric eye4 ,te*nically x is nam$ a coh]]4 ,a ,m>coni coh]] is se5 9 ,fig4 #fj4 ,inside a small glass tube exhau/$ ( air are two silv] plugs1 ,p ,p1 c>ry+ t]m9als1 ,t ,t1 project+ ?r\gh ! glass at bo? ends4 ,a small gap sep>ates ! plugs at ! c5tre1 & ?is gap is p>tly fill$ ) nickel-silv] p[d]4 ,if ! t]m9als ( ! coh]] are atta*$ to ^? ( a batt]y1 practically no curr5t w pass "u ord9>y conditions1 z ! p>ticles ( nickel-silv] t\* ea* o!r v lightly & make a bad contact4 ,b if ! coh]] is also atta*$ to wires lead+ into ! e>? & air1 & e!r waves /rike ^? wires1 at e impact ! p>ticles w coh]e--t is1 pack tightly toge!r--& all[ batt]y curr5t to pass4 ,! prop]ty ( cohesion ( small conductive bodies :5 influ5c$ by ,h]tzian waves 0 fir/ notic$ 9 #ahgd by ,pr(essor ,d4,e4 ,hughes :ile exp]im5t+ ) a telephone4 ,illu/ration3 ,,fig4 #fa4--,sket* ( ! receiv+ app>atus 9 a wireless telegraphy outfit4 ,we are n[ 9 a position to exam9e ! app>atus ( :i* a coh]] =ms "p 7,fig4 #fa74 ,fir/1 we notice ! arial & e>? wires1 to :i* are atta*$ o!r wires f batt]y ,a4 ,?is batt]y circuit passes r\nd ! relay magnet ,r & ?r\gh two *ok+ coils1 ^: function is to prev5t ! ,h]tzian waves ent]+ ! batt]y4 ,! relay1 :5 en]giz$1 br+s contact ,d aga9/ ,e & closes ! circuit ( batt]y ,b1 :i* is mu* m p[]ful ?an batt]y ,a1 & op]ates ! magnet ,m z well z ! tapp]1 :i* is practically an electric bell m9us ! gong4 7,! tapp] circuit is indicat$ by ! dott$ l9es47 ,we w suppose ! transmitt] ( a di/ant /ation to be at "w4 ,! electric waves /rike ! arial wire ( ! receiv+ /ation1 & cause ! coh]] to coh]e & pass curr5t4 ,! relay is clos$1 & bo? tapp] & ,morse ink] beg9 to "w4 ,! tapp] keeps /rik+ ! coh]] & %akes ! p>ticles loose aft] e cohesion4 ,if ?is 7 n done ! curr5t ( ,a w\ld pass cont9u\sly aft] cohesion _h once tak5 place4 ,:5 ! key ( ! transmitt] is press$ d[n1 ! waves foll[ "o ano!r v quickly1 & ! acquir$ conductivity ( ! coh]] is only mom5t>ily de/roy$ by ! tap ( ! hamm]4 ,dur+ ! impression ( a dot by ! ,morse ink]1 contact is made & brok5 repeat$ly2 b z ! armature ( ! ink] is heavy & sl[ to move x does n vibrate 9 "t ) ! relay & tapp]4 ,!re=e ! ,morse in/rum5t reproduces 9 dots & da%es ! %ort & long depressions ( ! key at ! transmitt+ /ation1 :ile ! tapp] works rapidly 9 "t ) ! relay4 ,! ,morse ink] is %[n diagrammatically4 ,:ile curr5t passes ?r\gh ,m ! armature is pull$ t[>ds x1 ! end ,p1 c>ry+ an ink$ :eel1 rises1 & a m>k is made on ! tape ,w1 :i* is mov$ cont9u\sly be+ drawn =w>d (f reel ,r by ! clockwork--or electrically-driv5 roll]s ,r#a ,r#b4 ,,syntonic ,,transmission4 ,if a numb] ( transmitt+ /ations are s5d+ out messages simultane\sly1 a jumble ( signals w\ld affect all ! receiv]s r\nd1 unless "s me?od 7 employ$ = r5d]+ a receiv] s5sitive only to ! waves int5d$ to influ5ce x4 ,also1 if di/9ction 7 impossible1 ev5 ) "o transmitt] 9 action its message might g to undesir$ /ations4 ,!re are v>i\s ways ( tun+ receiv]s & transmitt]s1 b ! pr9ciple und]ly+ !m all is analog\s to t ( me*anical vibration4 ,if a weight is susp5d$ f ! end ( a spiral spr+1 & giv5 an upw>d bl[1 x bobs up & d[n a c]ta9 numb] ( times p] m9ute1 e movem5t f />t to f9i% hav+ exactly ! same duration z ! re/4 ,! resi/ance ( ! air & ! int]nal friction ( ! spr+ gradually less5 ! amplitude ( ! movem5ts1 & ! weight f9ally comes to re/4 ,suppose t ! weight scales #cj lbs41 & t x naturally bobs tw5ty times a m9ute4 ,if y n[ take a fea!r & give x a pu% e ?ree seconds y c coax x into vigor\s motion1 assum+ t e pu% cat*es x exactly on ! reb\nd4 ,! same effect w\ld be produc$ m sl[ly if #f or #i second int]vals 7 sub/itut$4 ,b if y /rike x at #d1 #e1 or #g second int]vals x w gradually cease to oscillate1 z ! effect ( "o bl[ neutralizes t ( ano!r4 ,! same ph5om5on is witness$ :5 two tun+-=ks ( equal pit* are m\nt$ ne> "o ano!r1 & "o is /ruck4 ,! o!r soon picks up ! note4 ,b a =k ( unequal pit* w\ld rema9 dumb4 ,n[1 e electrical circuit has a natural p]iod ( oscillation 9 :i* its electric *>ge vibrates4 ,x is f\nd possible to tune1 or syntonize1 ! arial rod or wire ( a receiv+ /ation ) a transmitt]4 ,a v]tical wire ab\t #bjj feet 9 l5g?1 says ,pr(essor ,j4,a4 ,flem+1#ae has a natural "t p]iod ( electrical oscillation ( ab\t "o-million? ( a second4 ,!re=e if waves /rike ?is wire a million times a second !y w re9=ce "o ano!r & influ5ce ! coh]]2 :]eas a less or great] frequ5cy w leave x practically unaffect$4 ,by adju/+ ! receiv+ circuit to ! transmitt]1 or vice v]s1 selective wireless telegraphy becomes possible4 ,,advance ,,( ,,wireless ,,telegraphy4 ,! hi/ory ( wireless telegraphy may be summ$ up z foll[s3-- #ahdb4--,pr(essor ,morse s5t arial messages across ! ,susquehanna ,riv]4 ,a l9e conta9+ a batt]y & transmitt] 0 c>ri$ on po/s along "o bank & e>!d 9 ! riv] at ea* end4 ,on ! o!r bank 0 a second wire atta*$ to a receiv] & simil>ly e>!d4 ,:5ev] contact 0 made & brok5 on ! batt]y side1 ! receiv] on ! o!r 0 affect$4 ,di/ance ab\t #a mile4 #ahei4--;,james ,b[man ,l9dsay transmitt$ messages across ! ,tay at ,gl5c>se 9 a some:at simil> way4 ,di/ance ab\t #a_/b mile4 #ahhe4--,sir ,william ,preece signall$ f ,lav]nock ,po9t1 ne> ,c>diff1 to ,/eep ,holm1 an isl& 9 ! ,bri/ol ,*annel4 ,di/ance ab\t #e-a_/b miles4 ,9 all ^! electrical induction ( curr5t 0 employ$4 #ahhf4--;,h]tzian waves discov]$4 #ahie4--,pr(essor ,a4 ,pop(f s5t ,h]tzian wave messages ov] a di/ance ( #c miles4 #ahig4--,m>coni signall$ f ! ,ne$les ,hotel1 ,isle ( ,wight1 to ,swanage2 #ag-a_/b miles4 #aija4--,messages s5t at sea = #chj miles4 #aija1 ,dec4 #ag4--,messages transmitt$ f ,poldhu1 ,cornwall1 to ,hospital ,po9t1 ,newf\ndl&2 #b1jii miles4 ,mr4 ,m>coni has s p]fect$ tun+ devices t 8 transatlantic messages d n affect receiv]s plac$ on bo>d %ips cross+ ! ocean1 unless !y are purposely tun$4 ,atlantic l9]s n[ publi% daily small newspap]s conta9+ ! late/ news1 fla%$ ?r\gh space f l& /ations4 ,9 ! ,unit$ ,/ates ! ,de ,=e/ & ,fess5d5 sy/ems are be+ rapidly ext5d$ to embrace ! mo/ out-(-!-way di/ricts4 ,e navy ( importance has adopt$ wireless telegraphy1 :i*1 z 0 prov$ dur+ ! ,russo-,japanese ,w>1 c be ( ! greate/ help 9 direct+ op]ations4 #ac ,nam$ aft] _! fir/ discov]]1 ,dr4 ,h]tz ( ,c>lsruhe1 ,h]tzian waves4 #ad ,= long-di/ance transmission p[]ful dynamos take ! place ( ! induction coil & batt]y4 #ae ,te*nics1 vol4 ii4 p4 #eff4 ,*apt] ,,viii4 ,,! ,,telephone4 ,! ,bell telephone--,! ,edison transmitt]--,! granul> c>bon transmitt]--,g5]al arrangem5t ( a telephone circuit--,d\ble-l9e circuits--,telephone ex*anges--,subm>9e telephony4 ,= ! purposes ( ev]yday life ! telephone is ev5 m useful ?an ! telegraph4 ,telephones n[ connect "o room ( a build+ ) ano!r1 h\se ) h\se1 t[n ) t[n1 c\ntry ) c\ntry4 ,an inf9itely great] numb] ( words pass ov] ! telephonic circuits ( ! _w 9 a ye> ?an are transmitt$ by telegraph op]ators4 ,! telephone has become an important adjunct to ! transaction ( bus9ess ( all sorts4 ,its wires p5etrate ev]y:]e4 ,)\t mov+ f 8 desk1 ! ,london citiz5 may hold easy conv]se ) a ,p>isian1 a ,new ,york] ) a dwell] 9 ,*icago4 ,wond]ful z ! transmission ( signals ov] great di/ances is1 ! transmission ( human spee* s cle>ly t individual voices may be di/+ui%$ hundr$s ( miles away is ev5 m s4 ,yet ! in/rum5t :i* works ! miracle is ess5tially simple 9 its pr9ciples4 ,,! ,,bell ,,telephone4 ,illu/ration3 ,,fig4 #fb4--,section ( a ,bell telephone4 ,! fir/ telephone t came into g5]al use 0 t ( ,bell1 %[n 9 ,fig4 #fb4 ,9 a c5tral hole ( an ebonite cas+ is fix$ a p]man5t magnet1 ,m4 ,! cas+ exp&s at "o end to accommodate a coil ( insulat$ wire w\nd ab\t "o extremity ( a magnet4 ,! coil ends are atta*$ to wires pass+ ?r\gh small *annels to t]m9als at ! re>4 ,a circul> diaphragm1 ,d1 ( v ?9 iron plate1 clamp$ betwe5 ! concave m\?piece & ! cas+1 almo/ t\*es ! end ( ! magnet4 ,we w suppose t two ,bell telephones1 ,a & ,b1 are connect$ up by wires1 s t ! wires & ! coils =m a complete circuit4 ,words are spok5 into ,a4 ,! air vibrations1 pass+ ?r\gh ! c5tral hole 9 ! cov]1 make ! diaphragm vibrate t[>ds & away f ! magnet4 ,! di/ances ?r\gh :i* ! diaphragm moves h be5 measur$1 & f\nd n to exce$ 9 "s cases m ?an #a_/aj1jjj1jjj ( an in*6 ,its movem5ts di/ort ! %ape ( ! l9es ( =ce 7see p4 #aah7 emanat+ f ! magnet1 & ^!1 cutt+ ?r\gh ! turns ( ! coil1 induce a curr5t 9 ! l9e circuit4 ,z ! diaphragm approa*es ! magnet a circuit is s5t 9 "o direction2 z x leaves x1 9 ! o!r4 ,consequ5tly spee* produces rapidly alt]nat+ curr5ts 9 ! circuit1 _! duration & int5sity dep5d+ on ! nature ( ! s\nd4 ,n[ consid] telephone ,b4 ,! curr5ts pass+ ?r\gh its coil increase or dim9i% ! magnetism ( ! magnet1 & cause x to attract its diaphragm ) v>y+ =ce4 ,! vibration ( ! diaphragm di/urbs ! air 9 exact accordance ) ! vibrations ( ,a's diaphragm1 & spee* is reproduc$4 ,,! ,,edison ,,transmitt]4 ,! ,bell telephone may be us$ bo? z a transmitt] & a receiv]1 & ! p]man5t magnetism ( ! cores r5d]s x indep5d5t ( an electric batt]y4 ,b curr5ts g5]at$ by x are s m9ute t !y _c ov]come ! resi/ance ( a long circuit2 !re=e a batt]y is n[ always us$1 & ) x a special device z transmitt]4 ,if 9 a circuit conta9+ a telephone & a batt]y !re be a loose contact1 & ?is be %ak51 ! v>y+ resi/ance ( ! contact w cause electrical curr5ts ( v>y+ =ce to pass ?r\gh ! circuit4 ,edison introduc$ ! fir/ successful microphone transmitt]1 9 :i* a small plat9um disc connect$ to ! diaphragm press$ ) v>y+ =ce aga9/ a disc ( c>bon1 ea* disc =m+ "p ( ! circuit4 ,vibrations ( ! diaphragm caus$ curr5t to fl[ 9 a s]ies ( rapid pulsations4 ,illu/ration3 ,,fig4 #fc4--,section ( a granul> c>bon transmitt]4 ,,! ,,granul> ,,c>bon ,,transmitt]4 ,9 ,fig4 #fc we h a section ( a microphone transmitt] n[ v widely us$4 ,x 0 inv5t$1 9 its orig9al =m1 by an ,engli% cl]gyman nam$ ,hunn+s4 ,re/+ 9 a c5tral cavity ( an ebonite seat+ is a c>bon block1 ,c1 ) a face m\ld$ into a numb] ( pyramidal projections1 ,p ,p4 ,! space betwe5 ,c & a c>bon diaphragm1 ,d1 is pack$ ) c>bon granules1 ,g ,g4 ,c has direct contact ) l9e t]m9al ,t1 :i* screws into x2 ,d ) ,t#a ?r\gh ! brass cas+1 screw ,s1 & a small plate at ! back ( ! transmitt]4 ,voice vibrations compress ,g ,g1 & all[ curr5t to pass m freely f ,d to ,c4 ,?is =m ( microphone is v delicate1 & unequall$ = long-di/ance transmission4 ,illu/ration3 ,,fig4 #fd4--;,a diagrammatic repres5tation ( a telephonic circuit4 ,,g5]al ,,arrangem5t ,,( ,a ,,telephone ,,circuit4 ,9 _m =ms ( subscrib]'s in/rum5ts bo? receiv] & transmitt] are m\nt$ on a s+le h&le 9 su* a way z to be conv5i5tly plac$ = e> & m\?4 ,= ! sake ( cle>ness ! diagrammatic sket* ( a complete in/allation 7,fig4 #fd7 %[s !m sep>at$4 ,! transmitt]s1 x w be notic$1 are locat$ 9 batt]y circuits1 includ+ ! prim>y w9d+s ,p ,p#b ( induction coils4 ,! transmitt]s are 9 ! l9e circuit1 :i* includes ! second>y w9d+s ,s ,s#b ( ! coils4 ,we w assume t ! transmitt]s are1 9 ! fir/ in/ance1 bo? hung on ! hooks ( ! metallic swit*es1 :i* _! weight depresses to ! position indicat$ by ! dott$ l9es4 ,! h&le ( ! magneto-g5]ator at ! left-end /ation is turn$1 & curr5t passes ?r\gh ! clos$ circuit3--,l9e ,a1 ,e ,b#b1 contact #aj1 ! swit* #i2 l9e ,b1 #d1 ! o!r swit*1 contact #e1 & ,e ,b4 ,bo? bells r+4 ,bo? p>ties n[ lift _! receiv]s f ! swit* hooks4 ,! swit*es rise aga9/ contacts #a1 #b1 #c & #f1 #g1 #h respectively4 ,bo? prim>y & bo? second>y circuits are n[ complet$1 :ile ! bells are disconnect$ f ! l9e wires4 ,! pulsations set up by transmitt] ,t 9 prim>y coil ,p are magnifi$ by second>y coil ,s = transmission ?r\gh ! l9e circuit1 & affect bo? receiv]s4 ,! same ?+ happ5s :5 ,t#b is us$4 ,at ! end ( ! conv]sation ! receiv]s are hung on _! hooks aga91 & ! bell circuit is remade1 ready = ! next call4 ,illu/ration3 ,a ,,telephone ,,ex*ange4 ,,d\ble-,,l9e ,,circuits4 ,! curr5ts us$ 9 telephones pulsate v rapidly1 b are v feeble4 ,electric di/urbances caus$ by ! proximity ( telegraph or tram wires w\ld mu* int]f]e ) !m if ! e>? 7 us$ = ! return circuit4 ,x has be5 f\nd t a complete metallic circuit 7two wires7 is practically free f int]f]5ce1 ?\gh :]e a numb] ( wires are hung on ! same poles1 spee*-s\nds may be fa9tly induc$ 9 "o circuit f ano!r4 ,?is defect is1 h[ev]1 m9imiz$ by cross+ ! wires ab\t among !mselves1 s t any "o l9e does n pass r\nd ! correspond+ insulator on e pole4 ,,telephone ,,ex*anges4 ,9 a di/rict :]e a numb] ( telephones are us$ ! subscrib]s are put into connection ) "o ano!r ?r\gh an ex*ange1 to :i* all ! wires lead4 ,"o wire ( ea* subscrib] runs to a common e>?2 ! o!r t]m9ates at a swit*bo>d presid$ ov] by an op]ator4 ,9 an ex*ange us$ by _m subscrib]s ! t]m9als are di/ribut$ ov] a numb] ( swit*bo>ds1 ea* conta9+ #hj to #ajj t]m9als1 & att5d$ to by an op]ator1 usually a girl4 ,:5 a subscrib] wi%es to be connect$ to ano!r subscrib]1 he ei!r turns ! h&le ( a magneto g5]ator1 :i* causes a %utt] to fall & expose 8 numb] at ! ex*ange1 or simply depresses a key :i* works a relay at ! ex*ange & lights a t9y electric lamp4 ,! op]ator1 see+ ! signal1 connects h] telephone ) ! subscrib]'s circuit & asks ! numb] want$4 ,?is giv51 %e r+s up ! o!r subscrib]1 & connects ! two circuits by means ( an insulat$ wire cord hav+ a spike at ea* end to fit ! jack sockets ( ! swit*bo>d t]m9als4 ,! two subscrib]s are n[ 9 communication4 ,illu/ration3 ,,fig4 #fe4--,! headdress ( an op]ator at a telephone ex*ange4 ,! receiv] is fa/5$ ov] "o e>1 & ! transmitt] to ! *e/4 ,if a numb] on swit*bo>d ,a calls = a numb] on swit*bo>d ,c1 ! op]ator at ,a connects h] subscrib] by a jack cord to a trunk l9e runn+ to ,c1 :]e ! op]ator simil>ly connects ! trunk l9e ) ! numb] ask$ =1 aft] r++ up ! subscrib]4 ,! c5tral ex*ange ( "o t[n is connect$ ) t ( ano!r by "o or m trunk l9es1 s t a subscrib] may speak ?r\gh an indef9ite numb] ( ex*anges4 ,s p]fect is ! mod]n telephone t ! writ] rememb]s on "o occasion he>+ ! door-bell r+ 9 a h\se m ?an a hundr$ miles away1 ) :i* he 0 at ! mom5t 9 telephonic connection1 ?\gh ?ree ex*anges 7 9 ! circuit4 ,,subm>9e ,,telephony4 ,?\gh telegraphic messages are transmitt$ easily ?r\gh ?\s&s ( miles ( cable1#af subm>9e telephony is at pres5t re/rict$ to comp>atively %ort di/ances4 ,:5 a curr5t passes ?r\gh a cable1 electricity ( opposite pol>ity induc$ on ! outside ( ! cable damps ! vibration 9 ! conductor4 ,9 ! ,atlantic cable1 /rong curr5ts ( electricity are p\r$ p]iodically into "o end1 & ?\gh mu* enfeebl$ :5 !y rea* ! o!r !y are suffici5tly /rong to "w a v delicate mirror galvanomet] 7inv5t$ by ,"l ,kelv971 :i* moves a reflect$ ray up & d[n a scre51 ! direction ( ! movem5ts indicat+ a dot or a da%4 ,rev]sible curr5ts are us$ 9 transm>9e telegraphy4 ,! galvanomet] is affect$ l ! coils & small magnet 9 ,:eat/one's ne$le in/rum5t 7p4 #abh74 ,telephonic curr5ts are too feeble to p5etrate _m miles ( cable4 ,!re is telephonic communication betwe5 ,engl& & ,france1 & ,engl& & ,irel&4 ,b transatlantic telephony is /ill a ?+ ( ! future4 ,x is hop$1 h[ev]1 t by ins]t+ induction coils at int]vals along ! cables ! curr5ts may be /epp$ up f po9t to po9t1 & s get across4 ,turn+ to ,fig4 #fd1 we may suppose ,s to be on %ore at ! ,engli% end1 & ,s#b to be ! prim>y w9d+ ( an induction coil a hundr$ miles away 9 ! sea1 :i* magnifies ! enfeebl$ vibrations = a j\rney to ,s#c1 :]e !y are aga9 reviv$2 & s on1 till ! ,new ,_w is rea*$4 ,! difficulty is to devise induction coils ( great p[] ?\gh ( small size4 ,yet sci5ce advances n[adays s fa/ t we may live to he> words spok5 at ! ,antipodes4 #af ,9 #ahif ! late ,li ,hung ,*ang s5t a cablegram f ,*9a to ,engl& 7#ab1fjh miles71 & receiv$ a reply1 9 sev5 m9utes4 ,*apt] ,,ix4 ,,dynamos ,,& ,,electric ,,motors4 ,a simple dynamo--,cont9u\s-curr5t dynamos--,multipol> dynamos--,excit+ ! field magnets--,alt]nat+ curr5t dynamos--,! transmission ( p[]--,! electric motor--,electric light+--,! inc&esc5t lamp--,arc lamps--,s]ies & p>allel arrangem5t ( lamps--,curr5t = electric lamps--,electroplat+4 ,9 previ\s *apt]s we h incid5tally ref]r$ to ! conv]sion ( me*anical "w into electrical en]gy4 ,9 ?is we %all exam9e h[ x is done--h[ ! sil5tly sp9n+ dynamo develops p[]1 & :y ! motor sp9s :5 curr5t is pass$ ?r\gh x4 ,we mu/ beg9 by return+ to our fir/ electrical diagram 7,fig4 #ej71 & call+ to m9d ! invisible l9es ( =ce :i* p]meate ! e!r 9 ! imm$iate neighb\rhood ( a magnet's poles1 call$ ! magnetic field ( ! magnet4 ,_m ye>s ago 7#ahca7 ! great ,mi*ael ,f>aday discov]$ t if a loop ( wire 7 mov$ up & d[n betwe5 ! poles ( an electro-magnet 7,fig4 #ff7 a curr5t 0 induc$ 9 ! loop1 its direction dep5d+ ^u t 9 :i* ! loop 0 mov$4 ,! en]gy requir$ to cut ! l9es ( =ce pass$ 9 "s my/]i\s way into ! wire4 ,:y ?is is s we _c say1 b1 tak+ advantage ( ! fact1 electricians h gradually develop$ ! enorm\s ma*9es :i* n[ s5d vehicles sp9n+ ov] metal tracks1 light our /reets & h\ses1 & supply en]gy to innum]able factories4 ,illu/ration3 ,,fig4 #ff4 ,! /r5g? ( ! curr5t induc$ 9 a circuit cutt+ ! l9es ( =ce ( a magnet is call$ its pressure1 voltage1 or electro-motive =ce 7express$ %ortly ,e4,m4,f474 ,x may be comp>$ ) ! p\nds-to-!-squ>e-in* ( /eam4 ,9 ord] to produce an ,e4,m4,f4 ( "o volt x is calculat$ t #ajj1jjj1jjj l9es ( =ce mu/ be cut e second4 ,! voltage dep5ds on ?ree ?+s3--7#a47 ,! /r5g? ( ! magnet3 ! /rong] x is1 ! great] ! numb] ( l9es ( =ce com+ f x4 7#b47 ,! l5g? ( ! conductor cutt+ ! l9es ( =ce3 ! long] x is1 ! m l9es x w cut4 7#c47 ,! spe$ at :i* ! conductor moves3 ! fa/] x travels1 ! m l9es x w cut 9 a giv5 "t4 ,x foll[s t a p[]ful dynamo1 or me*anical produc] ( curr5t1 mu/ h /rong magnets & a long conductor2 & ! latt] mu/ be mov$ at a high spe$ across ! l9es ( =ce4 ,a ,,simple ,,dynamo4 ,9 ,fig4 #fg we h ! simple/ possible =m ( dynamo--a s+le turn ( wire1 w x y z1 m\nt$ on a sp9dle1 & hav+ "o end atta*$ to an insulat$ r+ ,c1 ! o!r to an insulat$ r+ ,c#a4 ,two small bru%es1 ,b ,b#a1 ( wire gauze or c>bon1 rubb+ cont9u\sly aga9/ ^! collect+ r+s1 connect !m ) a wire :i* completes ! circuit4 ,! armature1 z ! revolv+ coil is call$1 is m\nt$ betwe5 ! poles ( a magnet1 :]e ! l9es ( =ce are ?icke/4 ,^! l9es are suppos$ to /ream f ! ,n4 to ! ,s4 pole4 ,9 ,fig4 #fg ! armature has rea*$ a position 9 :i* y z & w x are cutt+ no1 or v few1 l9es ( =ce1 z !y move practically p>allel to ! l9es4 ,?is is call$ ! z]o position4 ,illu/ration3 ,,fig4 #fg4 ,illu/ration3 ,,fig4 #fh4 ,9 ,fig4 #fh ! armature1 mov+ at "r angles to ! l9es ( =ce1 cuts a maximum numb] 9 a giv5 "t1 & ! curr5t induc$ 9 ! coil is !re=e n[ mo/ int5se4 ,"h we mu/ /op a mom5t to consid] h[ to decide 9 :i* direction ! curr5t fl[s4 ,! armature is revolv+ 9 a clockwise direction1 & y z1 !re=e1 is mov+ d[nw>ds4 ,n[1 suppose t y re/ y\r left h& on ! ,n4 pole ( ! magnet s t ! arm lies 9 a l9e ) ! magnet4 ,po9t y\r =ef+] t[>ds ! ,s4 pole4 ,x w indicate ! direction ( ! l9es ( =ce4 ,b5d y\r o!r ?ree f+]s d[nw>ds ov] ! edge ( ! ,n4 pole4 ,!y w indicate ! direction 9 :i* ! conductor is mov+ across ! magnetic field4 ,/ick out ! ?umb at "r angles to ! =ef+]4 ,x po9ts 9 ! direction 9 :i* ! induc$ curr5t is mov+ ?r\gh ! ne>] half ( ! coil4 ,!re=e l9es ( =ce1 conductor1 & induc$ curr5t travel 9 planes :i*1 l ! top & two adjac5t sides ( a box1 are at "r angles to "o ano!r4 ,:ile curr5t travels f z to y--t is1 f ! r+ ,c#a to y--x also travels f x to w1 because w x rises :ile y z desc5ds4 ,s t a curr5t circulates ?r\gh ! coil & ! ext]ior "p ( ! circuit1 includ+ ! lamp4 ,aft] z y has pass$ ! l[e/ possible po9t ( ! circle x beg9s to asc5d1 w x to desc5d4 ,! direction ( ! curr5t is !re=e rev]s$2 & z ! *ange is repeat$ e half-revolution ?is =m ( dynamo is call$ an alt]nator or creator ( alt]nat+ curr5ts4 ,a well-kn[n type ( alt]nator is ! magneto ma*9e :i* s5ds %ocks ?r\gh any "o :o completes ! ext]nal circuit by hold+ ! brass h&les connect$ by wires to ! bru%es4 ,! fa/] ! h&le ( ! ma*9e is turn$ ! m frequ5t is ! alt]nation1 & ! /rong] ! curr5t4 ,illu/ration3 ,,fig4 #fi4 ,,cont9u\s-,,curr5t ,,dynamos4 ,an alt]nat+ curr5t is n s conv5i5t = "s purposes z a cont9u\s curr5t4 ,x is !re=e sometimes desirable 7ev5 necess>y7 to conv]t ! alt]nat+ into a uni-directional or cont9u\s curr5t4 ,h[ ?is is done is %[n 9 ,figs4 #fi & #gj4 ,9 place ( ! two collect+ r+s ,c ,c#a1 we n[ h a s+le r+ split longitud9ally into two portions1 "o ( :i* is connect$ to ea* end ( ! coil w x y z4 ,9 ,fig4 #fi bru% ,b has j pass$ ! gap on to segm5t ,c1 bru% ,b#a on to segm5t ,c#a4 ,= half a revolution ^! rema9 respectively 9 contact2 !n1 j z y z beg9s to rise & w x to desc5d1 ! bru%es cross ! gaps aga9 & ex*ange segm5ts1 s t ! curr5t is p]petually fl[+ "o way ?r\gh ! circuit4 ,! effect ( ! commutator#ag is1 9 fact1 equival5t to transpos+ ! bru%es ( ! collect+ r+s ( ! alt]nator e "t ! coil rea*es a z]o position4 ,figs4 #ga & #gb give end views 9 section ( ! coil & ! commutator1 ) ! coil 9 ! position ( m9imum & maximum effici5cy4 ,! arr[ d5otes ! direction ( movem5t2 ! d\ble dott$ l9es ! commutator end ( ! revolv+ coil4 ,illu/ration3 ,,fig4 #gj4 ,,practical ,,cont9u\s-,,curr5t ,,dynamos4 ,! electrical output ( our simple dynamo w\ld be increas$ if1 in/ead ( a s+le turn ( wire1 we us$ a coil ( _m turns4 ,a fur!r improvem5t w\ld result f m\nt+ on ! %aft1 inside ! coil1 a core or drum ( iron1 to entice ! l9es ( =ce )9 rea* ( ! revolv+ coil4 ,x is evid5t t any l9es :i* pass ?r\gh ! air outside ! circle describ$ by ! coil _c be cut1 & are wa/$4 ,illu/ration3 ,,fig4 #ga4 ,illu/ration3 ,,fig4 #gb4 ,! core is n a solid mass ( iron1 b built up ( a numb] ( v ?9 iron discs ?read$ on ! %aft & insulat$ f "o ano!r to prev5t electric eddies1 :i* w\ld int]f]e ) ! induc$ curr5t 9 ! conductor4#ah ,sometimes !re are op5+s ?r\gh ! core f end to end to v5tilate & cool x4 ,illu/ration3 ,,fig4 #gc4 ,we h already notic$ t 9 ! case ( a s+le coil ! curr5t rises & falls 9 a s]ies ( pulsations4 ,su* a =m ( armature w\ld be unsuitable = l>ge dynamos1 :i* accord+ly h a numb] ( coils w\nd ov] _! drums1 at equal di/ances r\nd ! circumf]5ce1 & a commutator divid$ into an equal numb] ( segm5ts4 ,! subject ( drum w9d+ is too complicat$ = brief treatm5t1 & we mu/ !re=e be cont5t ) notic+ t ! coils are s connect$ to _! respective commutator segm5ts & to "o ano!r t !y mutually assi/ "o ano!r4 ,a glance at ,fig4 #gc w help to expla9 ?is4 ,"h we h 9 section a numb] ( conductors on ! "r ( ! drum 7m>k$ ) a cross to %[ t curr5t is mov+1 z x 71 into ! page71 connect$ ) conductors on ! left 7m>k$ ) a dot to signify curr5t com+ out ( ! page74 ,if ! cross$ & dott$ conductors 7 respectively ! up & d[n turns ( a s+le coil t]m9at+ 9 a simple split commutator 7,fig4 #fi71 :5 ! coil _h be5 revolv$ ?r\gh an angle ( #ij "s ( ! up turns w\ld be asc5d+ & "s desc5d+1 s t conflict+ curr5ts w\ld arise4 ,yet we want to utilize ! :ole surface ( ! drum2 & by w9d+ a numb] ( coils 9 ! mann] h9t$ at1 ea* coil1 z x passes ! z]o po9t1 top or bottom1 at once g5]ates a curr5t 9 ! desir$ direction & re9=ces t 9 all ! o!r turns ( its own & ( o!r coils on ! same side ( a l9e drawn v]tically ?r\gh ! c5tre4 ,!re is ?us practically no fluctuation 9 ! pressure ( ! curr5t g5]at$4 ,! action ( s+le & multiple coil w9d+s may be comp>$ to t ( s+le & multiple pumps4 ,wat] is eject$ by a s+le pump 9 gulps2 :]eas ! fl[ f a pipe f$ by sev]al pumps arrang$ to deliv] consecutively is mu* m con/ant4 ,,multipol> ,,dynamos4 ,hi!rto we h consid]$ ! magnetic field produc$ by "o bi-pol> magnet only4 ,l>ge dynamos h f\r1 six1 eight1 or m field magnets set inside a cas+1 f :i* _! cores project t[>ds ! armature s z almo/ to t\* x 7,fig4 #gd74 ,! magnet coils are w\nd to give ,n4 & ,s4 poles alt]nately at _! armature ends r\nd ! field2 & ! l9es ( =ce f ea* ,n4 pole /ream ea* way to ! two adjac5t ,s4 poles across ! pa? ( ! armature coils4 ,9 dynamos ( ?is k9d sev]al pairs ( collect+ bru%es pick curr5t (f ! commutator at equidi/ant po9ts on its circumf]5ce4 ,illu/ration3 ,,fig4 #gd4--;,a ,holmes cont9u\s curr5t dynamo3 ,a1 armature2 ,c1 commutator2 ,m1 field magnets4 ,,excit+ ,,! ,,field ,,magnets4 ,until curr5t passes ?r\gh ! field magnet coils1 no magnetic field c be creat$4 ,h[ are ! coils suppli$ ) curr5t8 ,a dynamo1 />t+ = ! fir/ "t1 is excit$ by a curr5t f an outside s\rce2 b :5 x has once begun to g5]ate curr5t x fe$s its magnets itself1 & ev] aft]w>ds w be self-excit+1#ai ow+ to ! residual magnetism left 9 ! magnet cores4 ,illu/ration3 ,,fig4 #ge4--,p>tly f9i%$ commutator4 ,look c>efully at ,figs4 #gg & #gh4 ,9 ! fir/ ( ^! y w obs]ve t "p ( ! wire =m+ ! ext]nal circuit is w\nd r\nd ! arms ( ! field magnet4 ,?is is call$ a s]ies w9d+4 ,9 ?is case all ! curr5t g5]at$ helps to excite ! dynamo4 ,at ! />t ! residual magnetism ( ! magnet cores gives a weak field4 ,! armature coils cut ?is & pass a curr5t ?r\gh ! circuit4 ,! magnets are fur!r excit$1 & ! field becomes /rong]2 & s on till ! dynamo is develop+ full p[]4 ,s]ies w9d+ is us$ :]e ! curr5t 9 ! ext]nal circuit is requir$ to be v con/ant4 ,illu/ration3 ,,fig4 #gf4--,! bru%es ( a ,holmes dynamo4 ,fig4 #gh %[s ano!r me?od ( w9d+--! %unt4 ,mo/ ( ! curr5t g5]at$ passes ?r\gh ! ext]nal circuit #b1 #b2 b a "p is swit*$ ?r\gh a sep>ate w9d+ = ! magnets1 d5ot$ by ! f9e wire #a1 #a4 ,"h ! /r5g? ( ! magnetism does n v>y directly ) ! curr5t1 z only a small "p ( ! curr5t s]ves ! magnets4 ,! %unt w9d+ is !re=e us$ :]e ! voltage 7or pressure7 mu/ be con/ant4 ,illu/ration3 ,,fig4 #gg4--,sket* %[+ a s]ies w9d+4 ,illu/ration3 ,,fig4 #gh4--,%unt w9d+4 ,a ?ird me?od is a comb9ation ( ! two already nam$4 ,a w9d+ ( f9e wire passes f bru% to bru% r\nd ! magnets2 & !re is also a s]ies w9d+ z 9 ,fig4 #gg4 ,?is comp\nd me?od is adapt$ m especially = electric traction4 ,,alt]nat+ ,,dynamos4 ,^! h _! field magnets excit$ by a sep>ate cont9u\s curr5t dynamo ( small size4 ,! field magnets usually revolve inside a fix$ armature 7! rev]se ( ! arrangem5t 9 a direct-curr5t g5]ator72 or !re may be a fix$ c5tral armature & field magnets revolv+ outside x4 ,?is latt] arrangem5t is f\nd 9 ! great p[] /ations at ,niag>a ,falls1 :]e ! enorm\s field-r+s are m\nt$ on ! top ends ( v]tical %afts1 driv5 by wat]-turb9es at ! bottom ( pits #agh feet deep1 d[n :i* wat] is l$ to ! turb9es ?r\gh great pipes1 or p5/ocks4 ,! weight ( ea* %aft & ! field-r+ atta*$ totals ab\t ?irty-five tons4 ,?is mass revolves #bej times a m9ute1 & #e1jjj horse p[] is con/antly develop$ by ! dynamo4 ,simil> dynamos ( #aj1jjj horse p[] ea* h be5 in/all$ on ! ,canadian side ( ! ,falls4 ,illu/ration3 ,,fig4 #gi4 ,,transmission ,,( ,,p[]4 ,alt]nat+ curr5t is us$ :]e p[] has to be transmitt$ = long di/ances1 because su* a curr5t c be int5sifi$1 or /epp$ up1 by a trans=m] some:at simil> 9 pr9ciple to a ,ruhmkorff coil m9us a contact-break] 7see p4 #abb74 ,a typical example ( trans=mation is se5 9 ,fig4 #gi4 ,alt]nat+ curr5t ( #e1jjj volts pressure is produc$ 9 ! g5]at+ /ation & s5t ?r\gh conductors to a di/ant /ation1 :]e a trans=m]1 ,b1 r$uces ! pressure to #ejj volts to drive an alt]nat+ motor1 ,c1 :i* 9 turn op]ates a direct curr5t dynamo1 ,d4 ,?is dynamo has its t]m9al connect$ ) ! insulat$ or live rail ( an electric railway1 & its - t]m9al ) ! :eel rails1 :i* are metallically unit$ at ! jo9ts to act z a return4 ,on its way f ! live rail to ! return ! curr5t passes ?r\gh ! motors4 ,9 ! case ( trams ! conductor is ei!r a cable c>ri$ ov]head on /&>ds1 f :i* x passes to ! motor ?r\gh a trolley arm1 or a rail laid und]gr\nd 9 a conduit betwe5 ! rails4 ,9 ! top ( ! conduit is a slit ?r\gh :i* an arm c>ry+ a contact %oe on ! end projects f ! c>4 ,! %oe rubs cont9u\sly on ! live rail z ! c> moves4 ,to return = a mom5t to ! "q ( trans=mation ( curr5t4 ,:y1 x may be ask$1 %\ld we n s5d l[-pressure direct curr5t to a di/ant /ation /raight f ! dynamo1 in/ead ( alt]+ its nature & pressure8 ,or1 at any rate1 :y n use high-pressure direct curr5t1 & trans=m t8 ,! answ] is1 t to transmit a l>ge am\nt ( electrical en]gy at l[ pressure 7or voltage7 w\ld necessitate l>ge volume 7or amp]age7 & a big & exp5sive copp] conductor to c>ry x4 ,high-pressure direct curr5t is n easily g5]at$1 s9ce ! sp>k+ at ! collect+ bru%es z !y pass ov] ! commutator segm5ts gives tr\ble4 ,s eng9e]s pref] high-pressure alt]nat+ curr5t1 :i* is easily produc$1 & c be s5t ?r\gh a small & inexp5sive conductor ) little loss4 ,also its voltage c be trans=m$ by app>atus hav+ no revolv+ p>ts4 ,,! ,,electric ,,motor4 ,anybody :o und]/&s ! dynamo w also be able to und]/& ! electric motor1 :i* is m]ely a rev]s$ dynamo4 ,imag9e 9 ,fig4 #gj a dynamo tak+ ! place ( ! lamp & pass+ curr5t ?r\gh ! bru%es & commutator into ! coil w x y z4 ,n[1 any coil ?r\gh :i* curr5t passes becomes a magnet ) ,n4 & ,s4 poles at ei!r end4 7,9 ,fig4 #gj we w assume t ! ,n4 pole is bel[ & ! ,s4 pole above ! coil47 ,! coil poles !re=e try to seek ! contr>y poles ( ! p]man5t magnet1 & ! coil revolves until its ,s4 pole faces ! ,n4 ( ! magnet1 & vice v]s4 ,! l9es ( =ce ( ! coil & ! magnet are n[ p>allel4 ,b ! mom5tum ( revolution c>ries ! coil on1 & sudd5ly ! commutator rev]ses its pol>ity1 & a fur!r half-revolution takes place4 ,!n comes a fur!r rev]sal1 & s on ad inf9itum4 ,! rotation ( ! motor is !re=e m]ely a "q ( repulsion & attraction ( l & unlike poles4 ,an ord9>y compass ne$le may be conv]t$ into a t9y motor by pres5t+ ! ,n4 & ,s4 poles ( a magnet to its ,s4 & ,n4 poles alt]nately e half-revolution4 ,9 con/ruction & w9d+ a motor is practically ! same z a dynamo4 ,9 fact1 ei!r ma*9e c p]=m ei!r function1 ?\gh p]haps n equally well adapt$ = bo?4 ,motors may be run ) direct or alt]nat+ curr5t1 accord+ to _! con/ruction4 ,on electric c>s ! motor is g5]ally susp5d$ f ! :eel truck1 & a small p9ion on ! armature %aft ge>s ) a l>ge p9ion on a :eel axle4 ,"o great advantage ( electric traction is t e vehicle ( a tra9 c c>ry its own motor1 s t ! :ole weight ( ! tra9 may be us$ to get a grip on ! rails :5 />t+4 ,:]e a s+le /eam locomotive is us$1 ! adhesion ( its driv+-:eels only is available = ov]com+ ! in]tia ( ! load2 & ! :ole /ra9 ( />t+ is ?r[n on to ! =emo/ c\pl+s4 ,o!r advantages may be summ$ up z foll[s3--7#a7 ,ease ( />t+ & rapid accel]ation2 7#b7 abs5ce ( wa/e ( en]gy 79 ! %ape ( burn+ fuel7 :5 ! vehicles are at re/2 7#c7 abs5ce ( smoke & smell4 ,,electric ,,light+4 ,dynamos are us$ to g5]ate curr5t = two ma9 purposes--7#a7 ,to supply p[] to motors ( all k9ds2 7#b7 to light our h\ses1 factories1 & /reets4 ,9 private h\ses & !atres inc&esc5t lamps are g5]ally us$2 9 ! op5 air1 9 %ops1 & 9 l>g] build+s1 su* z railway /ations1 ! arc lamp is m (t5 f\nd4 ,,inc&esc5t ,,lamp4 ,if y take a piece ( v f9e iron wire & lay x across ! t]m9als ( an accumulator1 x becomes :ite hot & melts1 ow+ to ! heat g5]at$ by its resi/ance to ! curr5t4 ,a piece ( f9e plat9um wire w\ld become :ite hot )\t melt+1 & w\ld give out an int5se light4 ,"h we h ! pr9ciple ( ! gl[ or inc&esc5t lamp--namely1 ! int]position 9 an electric circuit ( a conductor :i* at once (f]s a high resi/ance to ! curr5t1 b is n de/roy$ by ! result+ heat4 ,9 ,fig4 #hj is %[n a fan propell+ liquid con/antly ?r\gh a pipe4 ,let u assume t ! liquid is "o :i* develops great friction on ! inside ( ! pipe4 ,at ! contraction1 :]e ! spe$ ( travel is mu* great] ?an else:]e 9 ! circuit1 mo/ heat w be produc$4 ,illu/ration3 ,,fig4 #hj4--;,diagram to %[ circulation ( wat] ?r\gh a pipe4 ,9 q ! e>ly days ( ! gl[-lamp plat9um wire 0 f\nd to be unreliable z reg>ds melt+1 & filam5ts ( c>bon are n[ us$4 ,to prev5t ! wa/+ away ( ! c>bon by comb9ation ) oxyg5 ! filam5t is enclos$ 9 a glass bulb f :i* practically all air has be5 suck$ by a m]cury pump be=e seal+4 ,illu/ration3 ,,fig4 #ha4--,! electrical c\nt]p>t ( ,fig4 #hj4 ,! filam5t takes ! place ( ! contraction 9 ! pipe4 ,! manufacture ( gl[-lamps is n[ an important indu/ry4 ,"o br& ( lamp#bj is made z foll[s3--,fir/1 cotton-wool is dissolv$ 9 *loride ( z9c1 & =ms a treacly solution1 :i* is squirt$ ?r\gh a f9e nozzle into a settl+ solution :i* h>d5s x & makes x coil up l a v f9e viol9 /r+4 ,aft] be+ wa%$ & dri$1 x is w\nd on a plumbago rod & bak$ 9 a furnace until only ! c>bon elem5t rema9s4 ,?is is ! filam5t 9 ! r\gh4 ,x is next remov$ f ! rod & tipp$ ) two %ort pieces ( f9e plat9um wire4 ,to make ! junction electrically p]fect ! filam5t is plung$ 9 b5z9e & heat$ to :it5ess by ! passage ( a /rong curr5t1 :i* deposits ! c>bon ( ! b5z9e on ! jo9ts4 ,! filam5t is n[ plac$ "u ! glass receiv] ( an air-pump1 ! air is exhau/$1 hydro-c>bon vap\r is introduc$1 & ! filam5t has a curr5t pass$ ?r\gh x to make x :ite hot4 ,c>bon f ! vap\r is deposit$ all ov] ! filam5t until ! requir$ electrical resi/ance is atta9$4 ,! filam5t is n[ ready = enclosure 9 ! bulb4 ,:5 ! bulb has be5 exhau/$ & seal$1 ! lamp is te/$1 &1 if pass$1 goes to ! f9i%+ dep>tm5t1 :]e ! two plat9um wires 7project+ ?r\gh ! glass7 are sold]$ to a c\ple ( brass plates1 :i* make contact ) two t]m9als 9 a lamp socket4 ,f9ally1 brass caps are affix$ ) a special wat]-tight & h>d cem5t4 ,,arc ,,lamps4 ,9 arc light+1 in/ead ( a contraction at a po9t 9 ! circuit1 !re is an actual break ( v small ext5t4 ,suppose t to ! ends ( ! wires lead+ f a dynamo's t]m9als we atta* two c>bon rods1 & t\* ! end ( ! rods toge!r4 ,! tips become :ite hot1 & if !y are sep>at$ slightly1 atoms ( inc&esc5t c>bon leap f ! positive to ! negative rod 9 a cont9u\s & int5sely lum9\s /ream1 :i* is call$ an arc because ! pa? ( ! p>ticles is curv$4 ,no arc w\ld be =m$ unless ! c>bons 7 fir/ t\*$ to />t inc&esc5ce4 ,if !y are sep>at$ too f> = ! /r5g? ( ! curr5t to bridge ! gap ! light w flick] or g out4 ,! arc lamp is !re=e provid$ ) a me*anism :i*1 :5 ! curr5t is cut (f1 causes ! c>bons to fall toge!r1 gradually sep>ates !m :5 x is turn$ on1 & keeps !m ap>t4 ,! pr9ciple employ$ is ! ef=t ( a coil ?r\gh :i* a curr5t passes to draw an iron rod into its c5tre4 ,"s ( ! curr5t fe$+ ! lamp is %unt$ ?r\gh a coil1 into :i* projects "o end ( an iron b> connect$ ) "o c>bon po9t4 ,a spr+ normally presses ! po9ts toge!r :5 no curr5t fl[s4 ,z soon z curr5t circulates ?r\gh ! coil ! b> is drawn upw>ds aga9/ ! spr+4 ,,s]ies ,,& ,,p>allel ,,arrangem5t ,,( ,,lamps4 ,:5 curr5t passes f "o lamp to ano!r1 z 9 ,fig4 #hb1 ! lamps are said to be 9 s]ies4 ,%\ld "o lamp fail1 all 9 ! circuit w\ld g out4 ,b :]e arc lamps are ?us arrang$ a special me*anism on ea* lamp %ort-circuits x 9 case ( failure1 s t curr5t may pass un9t]rupt$ly to ! next4 ,illu/ration3 ,,fig4 #hb4--;,inc&esc5t lamps connect$ 9 s]ies4 ,fig4 #hc %[s a numb] ( lamps set 9 p>allel4 ,"o t]m9al ( ea* is atta*$ to ! positive conductor1 ! o!r to ! negative conductor4 ,ea* lamp !re=e =ms an indep5d5t bridge1 & does n affect ! effici5cy ( ! re/4 ,p>allel s]ies signifies a comb9ation ( ! two sy/ems1 & w\ld be illu/rat$ if1 9 ,fig4 #hc1 two or m lamps 7 connect$ 9 s]ies gr\ps f "o conductor to ! o!r4 ,?is arrangem5t is (t5 us$ 9 arc light+4 ,illu/ration3 ,,fig4 #hc4--;,inc&esc5t lamps connect$ 9 p>allel4 ,,curr5t ,,= ,,electric ,,lamps4 ,?is may be ei!r direct or alt]nat+4 ,! =m] is commonly us$ = arc lamps1 ! latt] = inc&esc5t1 z x is easily /epp$-d[n f ! high-pressure ma9s = use 9 a h\se4 ,gl[-lamps usually take curr5t ( #aaj or #bej volts pressure4 ,9 arc lamps f$ ) direct curr5t ! tip ( ! positive c>bon has a b[l-%ap$ depression worn 9 x1 :ile ! negative tip is po9t$4 ,mo/ ( ! illum9ation comes f ! inn] surface ( ! b[l1 & ! positive c>bon is !re=e plac$ upp]mo/ to ?r[ ! light d[nw>ds4 ,an alt]nat+ curr5t1 ( c\rse1 affects bo? c>bons 9 ! same mann]1 & !re is no b[l4 ,! c>bons ne$ frequ5t r5ewal4 ,a p[]ful lamp uses ab\t #gj feet ( rod 9 #a1jjj h\rs if ! arc is expos$ to ! air4 ,"s lamps h p>tly enclos$ arcs--t is1 are surr\nd$ by globes p]=at$ by a s+le small hole1 :i* r5d]s combu/ion v sl[1 ?\gh prev5t+ a vacuum4 ,,electroplat+4 ,electroplat+ is ! art ( coat+ metals ) metals by means ( electricity4 ,silv]1 copp]1 & nickel are ! metals mo/ g5]ally deposit$4 ,! article to be coat$ is susp5d$ 9 a *emical solution ( ! metal to be deposit$4 ,fig4 #hd %[s a v simple plat+ outfit4 ,a is a batt]y2 ,b a vessel conta9+1 say1 an acidulat$ solution ( sulphate ( copp]4 ,a spoon1 ,s1 hang+ 9 ?is f a glass rod1 ,r1 is connect$ ) ! z9c or negative elem5t1 ,z1 ( ! batt]y1 & a plate ( copp]1 ,p1 ) ! positive elem5t1 ,c4 ,curr5t fl[s 9 ! direction %[n by ! arr[s1 f ,z to ,c1 ,c to ,p1 ,p to ,s1 ,s to ,z4 ,! copp] deposit$ f ! solution on ! spoon is replac$ by gradual dissolution ( ! plate1 s t ! latt] s]ves a d\ble purpose4 ,illu/ration3 ,,fig4 #hd4--;,an electroplat+ outfit4 ,9 silv] plat+1 ,p is ( silv]1 & ! solution "o ( cyanide ( potassium & silv] salts4 ,:]e nickel or silv] has to be deposit$ on iron1 ! article is (t5 giv5 a prelim9>y coat+ ( copp]1 z iron does n make a good junction ) ei!r ( ! fir/ two metals1 b has an aff9ity = copp]4 #ag ,f ! ,lat9 commuto1 ,i ex*ange4 #ah ,only ! drum type ( armature is treat$ "h4 #ai ,?is ref]s to cont9u\s-curr5t dynamos only4 #bj ,! ,rob]tson4 ,*apt] ,x4 ,,railway ,,brakes4 ,! ,vacuum ,automatic brake--,! ,we/+h\se air-brake4 ,9 ! e>ly days ( ! railway1 ! pull+ up ( a tra9 necessitat$ ! %utt+ (f ( /eam :ile ! /opp+-place 0 /ill a great di/ance away4 ,! tra9 gradually lo/ its velocity1 ! process be+ ha/5$ to a comp>atively small degree by ! screw-d[n brakes on ! eng9e & gu>d's van4 ,! goods tra9 ( to-day 9 _m cases /ill obs]ves ?is practice1 long obsolete 9 pass5g] traffic4 ,an advance 0 made :5 a *a91 runn+ along ! entire l5g? ( ! tra91 0 arrang$ s z to pull on subsidi>y *a9s bran*+ (f "u ea* c>riage & op]at+ lev]s connect$ ) brake blocks press+ on e pair ( :eels4 ,! gu>d /ra9$ ! ma9 *a9 by means ( a :eel ge> 9 8 van4 ,?is sy/em 01 h[ev]1 radically defective1 s9ce1 if any "o bran* *a9 0 %ort] ?an ! re/1 x alone w\ld get ! /ra94 ,fur!rmore1 x is obvi\s t ! snapp+ ( ! ma9 *a9 w\ld r5d] ! :ole arrangem5t p[]less4 ,accord+ly1 brakes op]at$ by /eam 7 tri$4 ,"u e c>riage 0 plac$ a cyl9d]1 9 connection ) a ma9 /eam-pipe runn+ "u ! tra94 ,:5 ! eng9e] wi%$ to apply ! brakes1 he turn$ high-pressure /eam into ! tra9 pipe1 & ! /eam1 pass+ into ! brake cyl9d]s1 drove out 9 ea* a pi/on op]at+ ! brake ge>4 ,un=tunately1 ! /eam1 dur+ its passage along ! pipe1 0 cond5s$1 & 9 cold wea!r fail$ to rea* ! re> c>riages4 ,wat] =m$ 9 ! pipes1 & ?is 0 liable to freeze4 ,if ! tra9 p>t$ accid5tally1 ! app>atus ( c\rse broke d[n4 ,hydraulic brakes h be5 tri$2 b ^! are op5 to sev]al objections2 & railway eng9e]s n[ make use ( air-pressure z ! mo/ suitable =m ( p[]4 ,:atev] air sy/em be adopt$1 exp]i5ce has %[n t ?ree features are ess5tial3--7#a47 ,! brakes mu/ be kept (f artificially4 7#b47 ,9 case ( ! tra9 p>t+ accid5tally1 ! brakes mu/ be appli$ automatically1 & quickly br+ all ! vehicles ( ! tra9 to a /&/ill4 7#c47 ,x mu/ be possible to apply ! brakes ) great] or less =ce1 accord+ to ! ne$s ( ! case4 ,at ! pres5t day "o or o!r ( two sy/ems is us$ on practically all automatically-brak$ c>s & coa*es4 ,^! are kn[n z--7#a7 ,! vacuum automatic1 us+ ! pressure ( ! atmosph]e on a pi/on f ! o!r side ( :i* air has be5 me*anically exhau/$2 & 7#b7 ! ,we/+h\se automatic1 us+ compress$ air4 ,! action ( ^! brakes w n[ be expla9$ z simply z possible4 ,,! ,,vacuum ,,automatic ,,brake4 ,"u ea* c>riage is a vacuum *amb] 7,fig4 #he7 rid+ on trunnions1 ,e ,e1 s t x may sw+ a little :5 ! brakes are appli$4 ,inside ! *amb] is a cyl9d]1 ! pi/on ( :i* is r5d]$ air-tight by a rubb] r+ roll+ betwe5 x & ! cyl9d] walls4 ,! pi/on rod works ?r\gh an air-tight /uff+-box 9 ! bottom ( ! cas+1 & :5 x rises op]ates ! brake rods4 ,x is obvi\s t if air is exhau/$ f bo? sides ( ! pi/on at once1 ! pi/on w s9k by reason ( its own weight & t ( its atta*m5ts4 ,if air is n[ admitt$ bel[ ! pi/on1 ! latt] w be pu%$ upw>ds ) a maximum pressure ( #ae lbs4 to ! squ>e in*4 ,! ball-valve ensures t :ile air c be suck$ f bo? sides ( ! pi/on1 x c be admitt$ to ! l[] side only4 ,illu/ration3 ,,fig4 #he4--,vacuum brake (f4 ,illu/ration3 ,,fig4 #hf4--,vacuum brake on4 ,let u imag9e t a tra9 has be5 /&+ 9 a sid+1 & t air has gradually fill$ ! vacuum *amb] by leakage4 ,! eng9e is c\pl$ on1 & ! driv] at once turns on ! /eam ejector1#ba :i* sucks all ! air out ( ! pipes & *amb]s ?r\gh\t ! tra94 ,! air is suck$ directly f ! "u side ( ! pi/on ?r\gh pipe ,d2 & f ! space ,a ,a & ! cyl9d] 7op5 at ! top7 ?r\gh ! *annel ,c1 lift+ ! ball1 :i*1 z soon z exhau/ion is complete1 or :5 ! pressure on bo? sides ( ! pi/on is equal1 falls back on its seat4 ,on air be+ admitt$ to ! tra9 pipe1 x ru%es ?r\gh ,d & into ! space ,b 7,fig4 #hf7 bel[ ! pi/on1 b is unable to pass ! ball1 s t a /rong upw>d pressure is ex]t$ on ! pi/on1 & ! brakes g on4 ,to ?r[ !m (f1 ! space bel[ ! pi/on mu/ be exhau/$4 ,?is is to be not$3 ,if !re is a leak1 z 9 ! case ( ! tra9 p>t+1 ! brakes g on at once1 s9ce ! vacuum bel[ ! pi/on is automatically brok54 ,illu/ration3 ,,fig4 #hg4--;,gu>d's valve = apply+ ! ,vacuum brake4 ,= ord9>y /ops ! vacuum is only p>tially brok5--t is1 an air-pressure ( b f #e to #aj lbs4 p] squ>e in* is admitt$4 ,= em]g5cy /ops full atmosph]ic pressure is us$4 ,9 ?is case x is advisable t air %\ld ent] at bo? ends ( ! tra92 s 9 ! gu>d's van !re is in/all$ an +5i\s automatic valve1 :i* c at any "t be op5$ by ! gu>d press+ d[n a lev]1 b :i* op5s ( itself :5 ! tra9-pipe vacuum is rapidly de/roy$4 ,fig4 #hg %[s ?is device 9 section4 ,seat$ on ! top ( an upright pipe is a valve1 ,a1 connect$ by a bolt1 ,b1 to an ela/ic diaphragm1 ,c1 seal+ ! bottom ( ! *amb] ,d4 ,! bolt ,b has a v small hole bor$ ?r\gh x f end to end4 ,:5 ! vacuum is brok5 sl[ly1 ! pressure falls 9 ,d z fa/ z 9 ! pipe2 b a sudd5 inru% ( air causes ! valve ,a to be pull$ (f its seat by ! diaphragm ,c1 z ! vacuum 9 ,d has n be5 brok5 to any appreciable ext5t4 ,air !n ru%es into ! tra9 pipe ?r\gh ! valve4 ,x is ?us evid5t t ! driv] controls ?is valve z effectively z if x 7 on ! eng9e4 ,^! em]g5cy valves are sometimes fitt$ to e vehicle ( a tra94 ,:5 a c>riage is slipp$1 taps on ea* side ( ! c\pl+ jo9t ( ! tra9 pipe are turn$ (f by ! gu>d 9 ! slip2 & :5 he wi%es to /op he m]ely depresses ! lev] ,e1 gradually op5+ ! valve4 ,"u ! van is an auxili>y vacuum *amb]1 f :i* ! air is exhau/$ by ! tra9 pipe4 ,if ! gu>d1 aft] ! slip has p>t$ f ! tra91 f9ds t he has appli$ 8 brakes too h>d1 he c put ?is *amb] into communication ) ! brake cyl9d]1 & re/ore ! vacuum suffici5tly to pull ! brakes (f aga94 ,:5 a tra9 has come to re/1 ! brakes mu/ be suck$ (f by ! ejector4 ,until ?is has be5 done ! tra9 _c be mov$1 s t x is impossible = x to leave ! /ation unprep>$ to make a sudd5 /op if necess>y4 ,,! ,,we/+h\se ,,air-,,brake4 ,?is sy/em is some:at m complicat$ ?an ! vacuum1 ?\gh equally reliable & p[]ful4 ,ow+ to ! complexity ( c]ta9 p>ts1 su* z ! /eam air-pump & ! triple-valve1 x is impossible to expla9 ! sy/em 9 detail2 we !re=e h rec\rse to simple diagrammatic sket*es1 :i* w help to make cle> ! g5]al pr9ciples employ$4 ,! air-brake1 z fir/ evolv$ by ,mr4 ,george ,we/+h\se1 0 a v simple affair--an air-pump & res]voir on ! eng9e2 a long pipe runn+ along ! tra92 & a cyl9d] "u e vehicle to "w ! brakes4 ,to /op ! tra91 ! high-pressure air collect$ 9 ! res]voir 0 turn$ into ! tra9 pipe to =ce out ! pi/ons 9 ! coa* cyl9d]s1 connect$ to x by %ort bran* pipes4 ,"o defect ( ?is /raight sy/em 0 t ! brakes at ! re> ( a long tra9 did n come into action until a consid]able "t aft] ! driv] turn$ on ! air2 & s9ce1 :5 dang] is imm95t1 a v few seconds are ( great importance1 ?is sl[ness ( op]ation 0 a s]i\s fault4 ,also1 x 0 f\nd t ! brakes on coa*es ne> ! eng9e w5t on long be=e ^? m di/ant1 s t dur+ a quick /op !re 0 a dang] ( ! =w>d coa*es be+ bump$ by ^? beh9d4 ,x goes )\t say+ t any coa*es :i* might break loose 7 uncontrollable4 ,mr4 ,we/+h\se !re=e pat5t$ 8 automatic brake1 n[ s l>gely us$ all ov] ! _w4 ,! brake ensures practically in/antane\s & simultane\s action on all ! vehicles ( a tra9 ( any l5g?4 ,illu/ration3 ,,fig4 #hh4--;,diagrammatic sket* ( ! details ( ! ,we/+h\se air-brake4 ,brake (f4 ,! pr9ciple ( ! brake w be ga!r$ f ,figs4 #hh & #hi4 ,p is a /eam-driv5 air-pump on ! eng9e1 :i* compresses air into a res]voir1 ,a1 situat$ bel[ ! eng9e or t5d]1 & ma9ta9s a pressure ( f #hj to #ij lbs4 p] squ>e in*4 ,a ?ree-way cock1 ,c1 puts ! tra9 pipe into communication ) ,a or ! op5 air at ! wi% ( ! driv]4 ,"u ea* coa* is a triple-valve1 ,t1 an auxili>y res]voir1 ,b1 & a brake cyl9d]1 ,d4 ,! triple-valve is ! mo/ notewor?y feature ( ! :ole sy/em4 ,! read] mu/ rememb] t ! valve %[n 9 ! section is only diagrammatic4 ,n[ = ! op]ation ( ! brake4 ,:5 ! eng9e is c\pl$ to ! tra91 ! compress$ air 9 ! ma9 res]voir is turn$ into ! tra9 pipe1 f :i* x passes ?r\gh ! triple-valve into ! auxili>y res]voir1 & fills x till x has a pressure (1 say1 #hj lbs4 p] squ>e in*4 ,until ! brakes are requir$1 ! pressure 9 ! tra9 pipe mu/ be ma9ta9$4 ,if accid5tally1 or purposely 7by turn+ ! cock ,c to ! position %[n 9 ,fig4 #hi71 ! tra9-pipe pressure is r$uc$1 ! triple-valve at once %ifts1 putt+ ,b 9 connection ) ! brake cyl9d] ,d1 & cutt+ (f ! connection betwe5 ,d & ! air1 & ! brakes g on4 ,to get !m (f1 ! pressure 9 ! tra9 pipe mu/ be made equal to t 9 ,b1 :5 ! valve w assume its orig9al position1 all[+ ! air 9 ,d to escape4 ,! =ce ) :i* ! brake is appli$ dep5ds ^u ! r$uction ( pressure 9 ! tra9 pipe4 ,a slight r$uction w\ld admit air v sl[ly f ,b to ,d1 :]eas a full escape f ! tra9 pipe w\ld op5 ! valve to its utmo/4 ,we h n repres5t$ ! means :]eby ! valve is r5d]$ s5sitive to ^! *anges1 = ! reason giv5 above4 ,illu/ration3 ,,fig4 #hi4--;,brake on4 ,! late/ =m ( triple-valve includes a device :i*1 :5 air is rapidly dis*>g$ f ! tra9 pipe1 z 9 an em]g5cy application ( ! brake1 op5s a port ?r\gh :i* compress$ air is also admitt$ f ! tra9 pipe directly into ,d4 ,x w easily be und]/ood t a d\ble advantage is h]eby ga9$--fir/1 9 utiliz+ a consid]able portion ( ! air 9 ! tra9 pipe to increase ! available brake =ce 9 cases ( em]g5cy2 &1 secondly1 9 produc+ a quick r$uction ( pressure 9 ! :ole l5g? ( ! pipe1 :i* accel]ates ! action ( ! brakes ) extraord9>y rapidity4 ,x may be add$ t ?is second>y communication is kept op5 only until ! pressure 9 ,d is equal to t 9 ! tra9 pipe4 ,!n x is cut (f1 to prev5t a return ( air f ,b to ! pipe4 ,an int]e/+ detail ( ! sy/em is ! automatic regulation ( air-pressure 9 ! ma9 res]voir by ! air-pump gov]nor 7,fig4 #ij74 ,! gov]nor is atta*$ to ! /eam-pipe lead+ f ! locomotive boil] to ! air-pump4 ,/eam f ! boil]1 ent]+ at ,f1 fl[s ?r\gh valve #ad & passes by ,d into ! pump1 :i* is ?us br\ght into op]ation1 & cont9ues to "w until ! pressure 9 ! ma9 res]voir1 act+ on ! "u side ( ! diaphragm #i1 exce$s ! t5sion to :i* ! regulat+ spr+ #g is set4 ,any excess ( pressure =ces ! diaphragm upw>ds1 lift+ valve #aa1 & all[+ compress$ air f ! ma9 res]voir to fl[ into ! *amb] ,c4 ,! air-pressure =ces pi/on #ab d[nw>ds & closes /eam-valve #ad1 ?us cutt+ (f ! supply ( /eam to ! pump4 ,z soon z ! pressure 9 ! res]voir is r$uc$ 7by leakage or use7 bel[ ! normal1 spr+ #g returns diaphragm #i to ! position %[n 9 ,fig4 #ij1 & p9-valve #aa closes4 ,! compress$ air previ\sly admitt$ to ! *amb] ,c escapes ?r\gh ! small port a to ! atmosph]e4 ,! /eam1 act+ on ! l[] surface ( valve #ad1 lifts x & its pi/on to ! position %[n1 & aga9 fl[s to ! pump1 :i* works until ! requir$ air-pressure is aga9 obta9$ 9 ! res]voir4 ,illu/ration3 ,,fig4 #ij4--;,air-pump ( ,we/+h\se brake4 #ba ,?is resembles ! upp] "p ( ! rudim5t>y wat] injector %[n 9 ,fig4 #ae4 ,! read] ne$ only imag9e pipe ,b to be connect$ ) ! tra9 pipe4 ,a ru% ( /eam ?r\gh pipe ,a creates a p>tial vacuum 9 ! cone ,e1 caus+ air f ! tra9 pipe to ru% into x & be expell$ by ! /eam bla/4 ,*apt] ,,xi4 ,,railway ,,signall+4 ,! block sy/em--,position ( signals--,int]lock+ ! signals--,lock+ ge>--,po9ts--,po9ts & signals 9 comb9ation--,work+ ! block sy/em--,s]ies ( signall+ op]ations--,s+le l9e signals--,! tra9 /aff--,tra9 /aff & ticket--,electric tra9 /aff sy/em--,int]lock+--,signall+ op]ations--,p[] signall+--,pneumatic signall+--,automatic signall+4 ,"u c]ta9 conditions--namely1 at %>p curves or 9 d>kness--! mo/ p[]ful brakes might n avail to prev5t a tra9 runn+ into ! re> ( ano!r1 if tra9s 7 all[$ to foll[ ea* o!r closely ov] ! l9e4 ,x is !re=e necess>y to introduce an effective sy/em ( keep+ tra9s runn+ 9 ! same direction a suffici5t di/ance ap>t1 & ?is is done by giv+ visible & easily und]/ood ord]s to ! driv] :ile a tra9 is 9 motion4 ,9 ! e>ly days ( ! railway x 0 cu/om>y to all[ a "t int]val betwe5 ! pass+s ( tra9s1 a tra9 n be+ p]mitt$ to leave a /ation until at lea/ five m9utes aft] ! />t ( a prec$+ tra94 ,?is me?od did n1 ( c\rse1 prev5t collisions1 z ! fir/ tra9 sometimes broke d[n soon aft] leav+ ! /ation2 & 9 ! abs5ce ( effective brakes1 its successor ran into x4 ,! adv5t ( ! electric telegraph1 :i* put /ations 9 rapid communication ) "o ano!r1 prov$ ( ! utmo/ value to ! safe work+ ( railways4 ,,! ,,block ,,sy/em4 ,"t limits 7 aboli%$ & di/ance limits sub/itut$4 ,a l9e 0 divid$ into blocks1 or l5g?s1 & two tra9s go+ 9 ! same direction 7 nev] all[$ on any "o block at ! same "t4 ,! signal-po/s c>ry+ ! movable arms1 or semaphores1 by means ( :i* ! signalman communicates ) ! eng9e-driv]1 are well kn[n to u4 ,!y are usually plac$ on ! left-h& side ( ! l9e ( rails to :i* !y apply1 ) _! arms po9t+ away f ! rails4 ,! side ( ! arms :i* faces ! direction f :i* a tra9 approa*es has a :ite /ripe pa9t$ on a r$ backgr\nd1 ! o!r side has a black /ripe on a :ite backgr\nd4 ,! di/ant & o!r signal arms v>y slightly 9 %ape 7,fig4 #ia74 ,a di/ant signal has a =k$ end & a ,v-%ap$ /ripe2 ! home & />t+ signals are squ>e-end$1 ) /raight /ripes4 ,:5 ! arm /&s horizontally1 ! signal is on1 or at dang]2 :5 dropp$1 x is (f1 & indicates ,all "r2 proce$4 ,at ! end ne>e/ ! po/ x c>ries a spectacle frame glaz$ ) panes ( r$ & gre5 glass4 ,:5 ! arm is at dang]1 ! r$ pane is opposite a lamp atta*$ to ! signal po/2 :5 ! arm drops1 ! gre5 pane rises to t position--s t a driv] is kept z fully in=m$ at night z dur+ ! day1 provid$ ! lamp rema9s alight4 ,illu/ration3 ,,fig4 #ia4--;,di/ant & home signals4 ,,position ,,( ,,signals4 ,on d\ble l9es ea* set ( rails has its own sep>ate signals1 & driv]s travell+ on ! up l9e take no notice ( signals meant = ! d[n l9e4 ,ea* signal-box usually controls ?ree signals on ea* set ( rails--! di/ant1 ! home1 & ! />t+4 ,_! respective positions w be ga!r$ f ,fig4 #ib1 :i* %[s a /ation on a d\ble l9e4 ,betwe5 ! di/ant & ! home an int]val is all[$ ( #hjj y>ds on ! level1 #a1jjj y>ds on a fall+ gradi5t1 & #fjj y>ds on a ris+ gradi5t4 ,! home /&s ne> ! approa* end ( ! /ation1 & ! />t+ at ! dep>ture end ( ! plat=m4 ,! la/ is sometimes re9=c$ by an advance />t+ signal "s di/ance f>!r on4 ,x %\ld be not$ t ! di/ant is only a caution signal1 :]eas bo? home & />t+ are /op signals4 ,?is means t :5 ! driv] sees ! di/ant on1 he does n /op 8 tra91 b slack5s spe$1 & prep>es to /op at ! home signal4 ,he mu/1 h[ev]1 on no acc\nt pass ei!r home or />t+ if !y are at dang]4 ,9 %ort1 ! di/ant m]ely w>ns ! driv] ( :at he may expect at ! home4 ,to prev5t damage if a driv] %\ld ov]run ! home1 x has be5 laid d[n t no tra9 %all be all[$ to pass ! />t+ signal ( "o box unless ! l9e is cle> to a po9t at lea/ a qu>t] ( a mile beyond ! home ( ! next box4 ,t po9t is call$ ! /&>d cle>+ po9t4 ,te*nically describ$1 a block is a l5g? ( l9e betwe5 ! la/ /op signal work$ f "o signal-box & ! fir/ /op signal work$ f ! next signal-box 9 advance4 ,illu/ration3 ,,fig4 #ib4--,%[+ position ( signals4 ,^? at ! top are (f4 ,,int]lock+ ,,signals4 ,a signalman _c l[] or re/ore 8 signals to _! normal positions 9 any ord] he likes4 ,he is compell$ to l[] !m z foll[s3--,/>t+ & home2 !n di/ant4 ,& re/ore !m--di/ant2 !n />t+ & home4 ,if a signalman 7 q indep5d5t1 he might1 aft] ! passage ( a tra91 re/ore ! home or />t+1 b =get all ab\t ! di/ant1 s t ! next tra91 :i* he wants to /op1 w\ld da% pa/ ! di/ant )\t w>n+ & h to pull up sudd5ly :5 ! home came 9 sight4 ,b by a me*anical arrangem5t he is prev5t$ f re/or+ ! home or />t+ until ! di/ant is at dang]2 &1 vice v]s1 he _c l[] ! la/ until ! o!r two are (f4 ,?is me*anism is call$ lock+ ge>4 ,,look+ ,,ge>4 ,!re are _m diff]5t types ( lock+ ge> 9 use4 ,x is impossible to describe !m all1 or ev5 to give p>ticul>s ( an elaborate lock+-frame ( any "o type4 ,b if we conf9e ourselves to ! simple/ comb9ation ( a /ud-lock+ app>atus1 su* z is us$ 9 small boxes on ! ,great ,we/]n ,railway1 ! read] w get an insight into ! g5]al pr9ciples ( ^! safety devices1 z ! same pr9ciples und]lie !m all4 ,illu/ration3 ,,fig4 #ic4--;,a signal lev] & its connections4 ,to move ! lev]1 ,c is press$ t[>ds ,b rais+ ! cat*-rod f its nick 9 ! rack1 ,g ,g ,g1 guides2 ,r ,r1 anti-friction roll]s2 ,s1 sockets = cat*-rod to "w 94 ,! lev]s 9 ! p>ticul> type ( lock+ ge> :i* we are consid]+ h ea* a tailpiece or tappet arm atta*$ to x1 :i* moves backw>ds & =w>ds ) ! lev] 7,fig4 #ic74 ,runn+ at "r angles to ?is tappet1 & close to x1 ei!r "u or above1 are ! lock b>s1 or /ud b>s4 ,ref] n[ to ,fig4 #id1 :i* %[s ! ends ( ! ?ree tappet arms1 ,d1 ,h1 & ,s1 cross$ by a b>1 ,b1 f :i* project ^! /uds4 ,! lev]s are all =w>d & ! signals all on4 ,if ! signalman tri$ to pull ! lev] atta*$ to ,d d[n ! page1 z x 71 he w\ld fail to move x on acc\nt ( ! /ud a1 :i* engages ) a not* 9 ,d4 ,be=e ?is /ud c be got free ( ! not* ! tappets ,h & ,s mu/ be pull$ ov]1 s z to br+ _! not*es 9 l9e ) /uds b & c 7,fig4 #ie74 ,! signalman c n[ move ,d1 s9ce ! not* easily pu%es ! /ud a to ! left 7,fig4 #if74 ,! signals mu/ be re/or$ to dang]4 ,z ,h & ,s are back-lock$ by ,d--t is1 prev5t$ by ,d f be+ put back into _! normal positions--,d mu/ be mov$ fir/4 ,! int]lock+ ( ! ?ree signals describ$ is m]ely repeat$ 9 ! int]lock+ ( a l>ge numb] ( signals4 ,illu/ration3 ,,fig4 #id4 ,illu/ration3 ,,fig4 #ie4 ,on ent]+ a signal-box a visitor w notice t ! lev]s h diff]5t col\rs3--,gre51 signify+ di/ant signals2 r$1 signify+ home & />t+ signals2 blue1 signify+ fac+ po9ts2 black1 signify+ trail+ po9ts2 :ite1 signify+ sp>e lev]s4 ,^! diff]5t col\rs help ! signalman to pick out ! "r lev]s easily4 ,to ! front ( ea* lev] is atta*$ a small brass tablet be>+ c]ta9 numb]s2 "o 9 l>ge figures on ! top1 !n a l9e1 & o!r numb]s 9 small figures b5ea?4 ,! l>ge numb] is t ( ! lev] itself2 ! o!rs1 call$ leads1 ref] to lev]s :i* mu/ be pull$ be=e t p>ticul> lev] c be releas$4 ,illu/ration3 ,,fig4 #if4 ,illu/ration3 ,,fig4 #ig4--,model signal equipm5t 9 a signall+ s*ool4 7,by p]mission ( ! ,g4,w4,r4 ,magaz9e74 ,,po9ts4 ,m5tion 0 made1 9 connection ) ! lev]1 ( po9ts4 ,be=e go+ fur!r we w glance at ! action ( ^! devices = enabl+ a tra9 to run f "o set ( rails to ano!r4 ,figs4 #ih & #ii %[ ! po9ts at a simple junction4 ,x w be notic$ t ! rails ( ! l9e to ! left ( ! po9ts are cont9u$ z ! out] rails ( ! ma9 & bran* l9es4 ,! inn] rails come to a %>p ,v-po9t1 & to ! left ( ?is are ! two %ort rails :i*1 by means ( %ift+ portions1 decide ! direction ( a tra9's travel4 ,9 ,fig4 #ih ! ma9 l9e is op52 9 ,fig4 #ii1 ! bran*4 ,! %ift+ p>ts are kept prop]ly spac$ by cross b>s 7or tie-rods71 ,a ,a4 ,illu/ration3 ,,fig4 #ih4--,po9ts op5 to ma9 l9e4 ,illu/ration3 ,,fig4 #ii4--,po9ts op5 to bran* l9e4 ,x might be ?\ght t ! :eels w\ld bump badly :5 !y rea* ! po9t ,b1 :]e !re is a gap4 ,?is is prev5t$1 h[ev]1 by ! b5t ends ,e ,e 7,fig4 #ih71 on :i* ! tread ( ! :eel re/s until x has rea*$ "s di/ance along ! po9t ( ,v4 ,! safety rails ,s ,r keep ! out] :eel up aga9/ its rail until ! ,v has be5 pass$4 ,,po9ts ,,& ,,signals ,,9 ,,comb9ation4 ,let u suppose t a tra9 is approa*+ ! junction %[n 9 ,figs4 #ih & #ii f ! left4 ,x is n en\gh t ! driv] %\ld "k t ! tracks are cle>4 ,he mu/ also be assur$ t ! track1 ma9 or bran*1 z ! case may be1 along :i* he has to g1 is op52 & on ! o!r h&1 if he 7 approa*+ f ! "r1 he w\ld want to be c]ta9 t no tra9 on ! o!r l9e 0 conv]g+ on 84 ,dang] is avoid$ & assurance giv5 by int]lock+ ! po9ts & signals4 ,to ! left ( ! junction ! home & di/ant signals are d\bl$1 !re be+ two semaphore arms on ea* po/4 ,^! are int]lock$ ) ! po9ts 9 su* a mann] t ! signals ref]r+ to ei!r l9e c be pull$ (f only :5 ! po9ts are set to op5 ! way to t l9e4 ,moreov]1 be=e any %ift+ ( po9ts c be made1 ! signals beh9d mu/ be put to dang]4 ,! conv]g5ce ( tra9s is prev5t$ by int]lock+1 :i* r5d]s x impossible to h bo? sets ( di/ant & home signals at ,all "r simultane\sly4 ,,work+ ,,( ,,block ,,sy/em4 ,we may n[ pass to ! work+ ( ! block sy/em ( signall+ tra9s f /ation to /ation on "o l9e ( a d\ble track4 ,ea* signal-box 7except1 ( c\rse1 ^? at t]m9i7 has electric communication ) ! next box 9 bo? directions4 ,! in/rum5ts us$ v>y on diff]5t sy/ems1 b ! pr9ciple is ! same2 s we w conc5trate our att5tion on ^? mo/ commonly employ$ on ! ,great ,we/]n ,railway4 ,!y are3--7#a47 ,two tapp]-bell in/rum5ts1 connect$ ) simil> in/rum5ts 9 ! adjac5t boxes on bo? sides4 ,ea* ( ^! r+s "o beat 9 ! correspond+ box e "t its key is depress$4 7#b47 ,two ,spagnoletti disc in/rum5ts--"o1 hav+ two keys1 communicat+ ) ! box 9 ! re>2 & ! o!r1 9 connection ) ! =w>d box1 hav+ no keys4 ,_! respective functions are to give signals & receive !m4 ,9 ! c5tre ( ! face ( ea* is a squ>e op5+1 beh9d :i* moves a disc c>ry+ two flags--,tra9 on l9e 9 :ite lett]s on r$ gr\nd1 & ,l9e cle> 9 black lett]s on a :ite gr\nd4 ,! key$ in/rum5t has a r$ & a :ite key4 ,:5 ! r$ key is depress$1 ,tra9 on l9e appe>s at ! op5+2 also 9 t ( a keyless disc at ! adjac5t signal-box4 ,a depression ( ! :ite key simil>ly gives ,l9e cle>4 ,a piece ( wire ) ! ends turn$ ov] & pass$ ?r\gh two eyes slides ov] ! keys1 & c be made to hold ei!r d[n4 ,9 addition to ^!1 telephonic & telegraphic in/rum5ts are provid$ to enable ! signalm5 to conv]se4 ,,s]ies ,,( ,,signall+ ,,op]ations4 ,illu/ration3 ,,fig4 #ajj4--,! signal+ in/rum5ts 9 ?ree adjac5t cab9s4 ,! fea!rless arr[s %[ ! connection ( ! in/rum5ts4 ,we may n[ wat* ! do+s ( signalm5 9 f\r successive boxes1 ,a1 ,b1 ,c1 & ,d1 dur+ ! passage ( an express tra94 ,signalman ,a calls signalman ,b's att5tion by "o beat on ! tapp]-bell4 ,b answ]s by repeat+ x to %[ t he is att5d+4 ,a asks1 ,is l9e cle> = pass5g] express8--f\r beats on ! bell4 ,b1 see+ t ! l9e is cle> to 8 cle>+ po9t1 s5ds back f\r beats1 & p9s d[n ! :ite key ( 8 in/rum5t4 ,l9e cle> appe>s on ! op5+1 & also at t ( ,a's keyless disc4 ,a l[]s />t+ signal4 ,tra9 moves (f4 ,a gives two beats on ! tapp] ,tra9 ent]+ section4 ,b p9s indicator at ,tra9 on l9e1 :i* also appe>s on ,a's in/rum5t4 ,a places signals at dang]4 ,b asks ,c1 ,is l9e cle>8 ,c repeats ! bell code1 & p9s indicator at ,l9e cle>1 %[n on ,b's keyless disc also4 ,b l[]s all signals4 ,tra9 passes4 ,b signals to ,c1 ,tra9 ent]+ section4 ,b signals to ,a1 ,tra9 out ( section1 & releases indicator1 :i* returns to normal position ) half ( ea* flag %[+ at ! w9d[4 ,b signals to ,c1 ,tra9 on l9e1 & sets all 8 signals to dang]4 ,c p9s indicator to ,tra9 on l9e4 ,c asks1 ,is l9e cle>8 ,b !re is a tra9 at /ation ,d1 & signalman ,d !re=e gives no reply1 :i* is equival5t to a negative4 ,! driv]1 on approa*+ ,c's di/ant1 sees x at dang]1 & sl[s d[n1 /opp+ at ! home4 ,c l[]s home1 & all[s tra9 to proce$ to 8 />t+ signal4 ,d1 :5 ! l9e is cle> to 8 cle>+ po9t1 signals ,l9e cle>1 & p9s indicator at ,l9e cle>4 ,c l[]s />t+ signals1 & tra9 proce$s4 ,c signals to ,d1 ,tra9 ent]+ section1 & ,d p9s indicator at ,tra9 on l9e4 ,c signals to ,b1 ,tra9 out ( section1 sets indicator at normal1 & puts signals at dang]4 ,& s ! process is repeat$ f /ation to /ation4 ,:]e1 h[ev]1 sections are %ort1 ! signalman is advis$ "o section ahead ( ! approa* ( a tra9 by an additional signal signify+1 ,fa/ tra9 approa*+4 ,! block indicator rem9ds ! signalman ( ! :]eab\ts ( ! tra94 ,unless 8 keyless indicator is at normal1 he may n ask1 ,is l9e cle>8 ,& until he signals back ,l9e cle> to ! box beh9d1 a tra9 is n all[$ to ent] 8 section4 ,9 ?is way a section ( l9e ) a full complem5t ( signals is always int]pos$ betwe5 any two tra9s4 ,,! ,,work+ ,,( ,,s+le ,,l9es4 ,we h dealt ) ! signall+ arrangem5ts p]ta9+ to d\ble l9es ( railway1 %[+ t a sy/em ( signals is necess>y to prev5t a tra9 runn+ into ! back ( its pr$ecessor4 ,:]e tra9s 9 bo? directions pass ov] a s+le l9e1 n only has ?is elem5t ( dang] to be dealt )1 b also ! possibility ( a tra9 be+ all[$ to ent] a section ( l9e f ea* end at ! same "t4 ,?is is effect$ 9 sev]al ways1 ! ess5ce ( ea* be+ t ! eng9e-driv] %all h 9 8 possession visible evid5ce ( ! p]mission accord$ him by ! signalman to ent] a section ( s+le l9e4 ,a ,,s+le ,,tra9 ,,/aff4 ,! simple/ =m ( work+ is to allocate to ! l5g? ( l9e a tra9 /aff--a piece ( wood ab\t #ad in*es long1 be>+ ! names ( ! /ations at ei!r end4 ,?is is adopt$ :]e only "o eng9e is us$ = work+ a section1 su* z a %ort bran* l9e4 ,9 a case l ?is !re is obvi\sly no dang] ( two tra9s meet+1 & ! tra9 /aff is m]ely ! au?ority to ! driv] to />t a j\rney4 ,no telegraphic communication is necess>y ) su* a sy/em1 & signals are plac$ only at ! ends ( ! l9e4 ,,tra9 ,,/aff ,,& ,,ticket4 ,on long l5g?s ( s+le l9e :]e m ?an "o tra9 has to be consid]$1 ! l9e is divid$ into blocks 9 ! way already describ$ = d\ble l9es1 & a /aff is assign$ to ea*1 ! /affs = ! v>i\s blocks diff]+ f ea* o!r 9 %ape & col\r4 ,! usual signals are provid$ at ea* /ation1 & block telegraph in/rum5ts are employ$1 ! only diff]5ce be+ t "o disc1 ( ! key patt]n1 is us$ = tra9s 9 bo? directions4 ,on su* a l9e x is1 ( c\rse1 possible t two or m tra9s may require to foll[ ea* o!r )\t any travell+ int]m$iately 9 ! opposite direction4 ,?is w\ld be impossible if ! /aff pass$ uni=mly to & fro 9 ! block section2 b x is arrang$ by ! introduction ( a tra9 /aff ticket us$ 9 conjunction ) ! /aff4 ,no tra9 is p]mitt$ to leave a /aff /ation unless ! /aff = ! section ( l9e to be trav]s$ is at ! /ation2 & ! driv] has ! /ricte/ possible in/ructions t he mu/ see ! /aff4 ,if a second tra9 is requir$ to foll[1 ! /aff is %[n to ! driv]1 & a tra9 /aff ticket h&$ him z 8 au?ority to proce$4 ,if1 h[ev]1 ! next tra9 ov] ! section w ent] f ! opposite end1 ! /aff is h&$ to ! driv]4 ,to r5d] ?is sy/em z safe z possible1 tra9 /aff tickets are ( ! same col\r & %ape z ! /aff = ! section to :i* !y apply1 & are kept 9 a special box at ! /ations1 ! key be+ atta*$ to ! /aff & ! lock s arrang$ t ! key _c be )drawn unless ! box has be5 lock$4 ,,electric ,,tra9 ,,/aff ,,& ,,tablet ,,sy/ems4 ,^! sy/ems ( work+ are developm5ts ( ! la/ m5tion$1 by :i* are secur$ great] safety & ease 9 work+ ! l9e4 ,on "s sections ( s+le l9e circum/ances (t5 necessitate ! runn+ ( sev]al tra9s 9 "o direction )\t a return tra94 ,= su* cases ! tra9 /aff ticket 0 introduc$2 b ev5 on ! be/ regulat$ l9es x is n always possible to secure t ! /aff %all be at ! /ation :]e x is requir$ at ! "r "t1 & cases h aris5 :]e1 no tra9 be+ available at ! /ation :]e ! /aff 01 x _h to be tak5 to ! o!r /ation by a man on foot1 caus+ mu* delay to traffic4 ,! electric tra9 /aff & tablet sy/ems ov]come ?is difficulty4 ,bo? "w on mu* ! same pr9ciple1 & we w !re=e describe ! =m]4 ,illu/ration3 ,,fig4 #aja4--;,an electric tra9 /aff hold]3 ,s ,s1 /affs 9 ! slot ( ! in/rum5t4 ,lean+ aga9/ ! side ( ! cab9 is a /aff %[+ ! key ,k at ! end = unlock+ a sid+ po9ts betwe5 two /ations4 ,! eng9e driv] _c remove ! /aff until ! po9ts h be5 lock$ aga94 ,at ea* end ( a block section a tra9 /aff in/rum5t 7,fig4 #aja7 is provid$4 ,9 ! base ( ^! in/rum5ts are a numb] ( tra9 /affs1 any "o ( :i* w\ld be accept$ by an eng9e-driv] z p]mission to travel ov] ! s+le l9e4 ,! in/rum5ts are electrically connect$1 ! me*anism secur+ t a /aff c be )drawn only by ! co-op]ation ( ! signalman at ea* end ( ! section2 t1 :5 all ! /affs are 9 ! in/rum5ts1 a /aff may be )drawn at ei!r end2 t1 :5 a /aff has be5 )drawn1 ano!r _c be obta9$ until ! "o out has be5 re/or$ to "o or o!r ( ! in/rum5ts4 ,! safety ( su* a sy/em is obvi\s1 z also ! assi/ance to ! work+ by hav+ a /aff available = a tra9 no matt] f :i* end x is to ent] ! section4 ,! me*anism ( ! in/rum5ts is q simple4 ,a d\ble-pol$ electro-magnet is en]giz$ by ! depression ( a key by ! signalman at ! fur!r end ( ! block into :i* ! tra9 is to run1 & by ! turn+ ( a h&le by ! signalman :o requires to )draw a /aff4 ,! magnet1 be+ en]giz$1 is able to lift a me*anical lock1 & p]mits ! )drawal ( a /aff4 ,9 its passage ?r\gh ! in/rum5t ! /aff revolves a numb] ( iron discs1 :i* 9 turn raise or l[] a swit* controll+ ! electrical connections4 ,?is causes ! electric curr5ts actuat+ ! electro-magnet to oppose ea* o!r1 ! magnetism to cease1 & ! lock to fall back1 prev5t+ ano!r /aff be+ )drawn4 ,x w naturally be ask$1 ,h[ is ! electrical sy/em re/or$8 ,we h said t !re 7 a numb] ( /affs 9 ea* in/rum5t--9 o!r words1 a giv5 numb] ( /affs1 usually tw5ty1 is assign$ to ! section4 ,assume t !re are t5 9 ea* in/rum5t1 & t ! swit* 9 ea* is 9 its l[] position4 ,n[ )draw a /aff1 & "o in/rum5t has an odd1 ! o!r an ev51 numb] ( /affs1 & simil>ly "o swit* is rais$ :ile ! o!r rema9s l[]$1 !re=e ! electrical circuit is out ( phase--t is1 ! curr5ts 9 ! magnets ( ea* /aff in/rum5t are oppos$ to "o ano!r1 & _c release ! lock4 ,! /aff travels ?r\gh ! section & is plac$ 9 ! in/rum5t at ! o!r end1 br++ ! numb] ( /affs to elev5--an odd numb]1 &1 :at is m important1 rais+ ! swit*4 ,bo? swit*es are n[ rais$1 consequ5tly ! electric curr5ts w support ea* o!r1 s t a /aff may be )drawn4 ,briefly1 !n1 :5 !re is an odd numb] ( /affs 9 "o in/rum5t & an ev5 numb] 9 ! o!r1 z :5 a /aff is 9 use1 ! signalm5 are unable to obta9 a /aff1 & consequ5tly _c give au?ority = a tra9 to ent] ! section2 b :5 !re is ei!r an odd or an ev5 numb] ( /affs 9 ea* in/rum5t a /aff may be )drawn at ei!r end on ! co-op]ation ( ! signalm54 ,we may add t1 :]e two in/rum5ts are 9 ! same signal-box1 "o = work+ to ! box 9 advance1 ! o!r to ! re>1 x is arrang$ t ! /affs p]ta9+ to "o section %all n fit ! in/rum5t = ! o!r1 & mu/ be ( diff]5t col\rs4 ,?is prev5ts ! driv] accid5tally accept+ a /aff belong+ to "o section z au?ority to travel ov] ! o!r4 ,,int]lock+4 ,! rem>ks made on ! int]lock+ ( po9ts & signals on d\ble l9es apply also to ! work+ ( s+le l9es1 ) ! addition t n only are ! di/ant1 home1 & />t+ signals int]lock$ ) ea* o!r1 b ) ! signals & po9ts gov]n+ ! approa* ( a tra9 f ! opposite direction--9 o!r words1 ! signals = ! approa* ( a tra9 to a /ation f "o direction _c be l[]$ unless ^? = ! approa* to ! /ation ( a tra9 f ! opposite direction are at dang]1 & ! po9ts correctly set4 ,,signall+ ,,op]ations4 ,9 ! work+ ( s+le l9es1 z ( d\ble1 ! signalman at ! /ation f :i* a tra9 is to proce$ has to obta9 ! cons5t ( ! signalman ahead1 ! s]ies ( que/ions to be signall$ be+ v simil> to ^? detail$ = d\ble l9es4 ,!re is1 h[ev]1 "o notable exception4 ,on long l5g?s ( s+le l9e x is necess>y to make arrangem5ts = tra9s to pass ea* o!r4 ,?is is done by provid+ loop l9es at int]vals1 a second pair ( rails be+ laid = ! accommodation ( "o tra9 :ile ano!r 9 ! opposite direction passes x4 ,to secure t m ?an "o tra9 %all n be on a section ( s+le l9e betwe5 two cross+-places x is laid d[n t1 :5 a signalman at a non-cross+ /ation is ask$ to all[ a tra9 to approa* 8 /ation1 he mu/ n give p]mission until he has notifi$ ! signalman ahead ( him1 ?us secur+ t he is n ask+ p]mission = tra9s to approa* f bo? directions at ! same "t4 ,bo? = s+le & d\ble l9e work+ a numb] ( rules design$ to deal ) cases ( em]g5cy are laid d[n1 ! guid+ pr9ciple be+ safety2 b we h n[ dealt ) all ! conditions ( ev]yday work+1 & mu/ pass to ! consid]ation ( ,illu/ration3 ,,fig4 #ajb4--;,an electric lev]-frame 9 a signall+ cab9 at ,didcot4 ,,p[] ,,signall+4 ,9 a p[] sy/em ( signall+ ! signalman is provid$ ) "s auxili>y means--electricity1 compress$ air1 etc4--( mov+ ! signals or po9ts "u 8 control4 ,x is /ill necess>y to h a lock+-frame 9 ! signal-box1 ) lev]s int]lock$ ) ea* o!r1 & connections betwe5 ! box & ! v>i\s po9ts & signals4 ,b ! frame is mu* small] ?an an ord9>y manual frame1 & b little =ce is ne$$ to move ! little lev]s :i* make or break an electric circuit1 or op5 an air-valve1 accord+ to ! p[]-ag5t us$4 ,,electric ,,signall+4 ,fig4 #ajb repres5ts ! lock+-frame ( a cab9 at ,didcot1 ,engl&1 :]e an all-electric sy/em has be5 in/all$4 ,wires lead f ! cab9 to motors situat$ at ! po9ts & signals1 :i* !y op]ate ?r\gh worm ge>+4 ,:5 a lev] is mov$ x closes a circuit & sets ! curr5t fl[+ ?r\gh a motor1 ! direction ( ! fl[ 7& consequ5tly ( ! motor's revolution7 dep5d+ on :e!r ! lev] has be5 mov$ =w>d or backw>d4 ,indicators arrang$ "u ! lev]s tell ! signalman :5 ! desir$ movem5ts at ! po9ts & signals h be5 complet$4 ,if any motion is n c>ri$ ?r\gh1 ow+ to failure ( ! curr5t or ob/ruction ( ! work+ p>ts1 an electric lock prev5ts him cont9u+ op]ations4 ,?us1 suppose he has to op5 ! ma9 l9e to an express1 he is oblig$ by ! me*anical lock+-frame to set all ! po9ts correctly be=e ! signals c be l[]$4 ,he might move all ! necess>y lev]s 9 due ord]1 yet "o set ( po9ts might rema9 op51 &1 7 ! signals l[]$1 an accid5t w\ld result4 ,b ?is _c happ51 z ! electric locks work$ by ! po9ts 9 "q block ! signal lev]s1 & until ! failure has be5 set "r1 ! signals mu/ rema9 at dang]4 ,! po9t motors are connect$ direct to ! po9ts2 b betwe5 a signal motor & its arm !re is an electric slot1 consi/+ ( a p[]ful electro-magnet :i* =ms a l9k 9 ! rod "w4 ,to l[] a signal x is necess>y t ! motor %all revolve & a control curr5t pass r\nd ! magnet to give x ! requisite attractive =ce4 ,if no control curr5t fl[s1 z w\ld happ5 7 any pair ( po9ts n 9 _! prop] position1 ! motor c h no effect on ! signal arm to l[] x1 ow+ to ! magnet lett+ g its grip4 ,fur!rmore1 if ! signal _h be5 already l[]$ :5 ! control curr5t fail$1 x w\ld rise to dang] automatically1 z all signals are weight$ to assume ! dang] position by gravity4 ,! signal control curr5ts c be brok5 by ! signalman mov+ a swit*1 s t 9 case ( em]g5cy all signals may be ?r[n simultane\sly to dang]4 ,,pneumatic ,,signall+4 ,9 ,engl& & ! ,unit$ ,/ates compress$ air is also us$ to d ! h>d lab\r ( ! signalman = him4 ,in/ead ( clos+ a circuit1 ! signalman1 by mov+ a lev] half-way ov]1 admits air to a pipe runn+ along ! track to an air res]voir plac$ beside ! po9ts or signal to :i* ! lev] relates4 ,! air op5s a valve & puts ! res]voir 9 connection ) a pi/on op]at+ ! po9ts or signal-arm1 z ! case may be4 ,?is movem5t hav+ be5 p]=m$1 ano!r valve 9 ! res]voir is op5$1 & air passes back ?r\gh a second pipe to ! signal-box1 :]e x op5s a ?ird valve controll+ a pi/on :i* completes ! movem5t ( ! lev]1 s %[+ ! signalman t ! op]ation is complete4 ,) compress$ air1 z ) electricity1 a me*anical lock+-frame is ( c\rse us$4 ,,automatic ,,signall+4 ,to r$uce exp5se1 & increase ! runn+ spe$ on l9es :]e ! sections are %ort1 ! tra9 is sometimes made to act z its own signalman4 ,! rails ( ea* section are all bond$ toge!r s z to be 9 metallic contact1 & ea* section is insulat$ f ! two neighb\r+ sections4 ,at ! fur!r end ( a section is in/all$ an electric batt]y1 connect$ to ! rails1 :i* lead ! curr5t back to a magnet op]at+ a signal /ation$ "s di/ance back on ! prec$+ section4 ,z long z curr5t fl[s ! signal is held at ,all "r4 ,:5 a tra9 ent]s ! section ! :eels & axles %ort-circuit ! curr5t1 s t x does n rea* ! signal magnet1 & ! signal rises to dang]1 & /ays !re until ! la/ pair ( :eels has pass$ out ( ! section4 ,%\ld ! curr5t fail or a vehicle break loose & rema9 on ! section1 ! same ?+ w\ld happ54 ,! human elem5t c ?us be practically elim9at$ f signall+4 ,to make ?+s absolutely safe1 a tra9 %\ld h positive control ov] a tra9 foll[+1 to prev5t ! driv] ov]runn+ ! signals4 ,on electric railways ?is has be5 effect$ by means ( contacts work+ 9 comb9ation ) ! signals1 :i* ei!r cut ! curr5t (f f ! section prec$+ t on :i* a tra9 may be1 or raise a trigg] to /rike an arm on ! tra9 foll[+ & apply its brakes4 ,*apt] ,,xii4 ,,optics4 ,l5ses--,! image ca/ by a convex l5s--,focus--,relative position ( object & l5s--,correction ( l5ses = col\r--,sph]ical ab]ration--,di/ortion ( image--,! human eye--,! use ( spectacles--,! bl9d spot4 ,light is a ?ird =m ( t en]gy ( :i* we h already treat$ two manife/ations--heat & electricity4 ,! di/+ui%+ *>act]i/ic ( e!r light-waves is _! extreme rapidity ( vibration1 :i* has be5 calculat$ to range f #gjj billion movem5ts p] second = violet rays to #djj billion = r$ rays4 ,if a beam ( :ite light be pass$ ?r\gh a prism x is resolv$ into ! sev5 visible col\rs ( ! spectrum--violet1 indigo1 blue1 gre51 yell[1 orange1 & r$--9 ?is ord]4 ,! human eye is mo/ s5sitive to ! yell[-r$ rays1 a photographic plate to ! gre5-violet rays4 ,all bodies fall into "o ( two classes--7#a7 ,lum9\s--t is1 ^? :i* are a s\rce ( light1 su* z ! sun1 a c&le flame1 or a r$-hot coal2 & 7#b7 non-lum9\s1 :i* become visible only by virtue ( light :i* !y receive f o!r bodies & reflect to our eyes4 ,,! ,,propagation ,,( ,,light4 ,light naturally travels 9 a /raight l9e4 ,x is deflect$ only :5 x passes f "o transp>5t m$ium into ano!r--= example1 f air to wat]--& ! m$iums are ( diff]5t d5sities4 ,we may reg>d ! surface ( a visible object z made up ( c\ntless po9ts1 f ea* ( :i* a div]g+ p5cil ( rays is s5t (f ?r\gh ! e!r4 ,,l5ses4 ,if a beam ( light enc\nt]s a transp>5t glass body ) non-p>allel sides1 ! rays are deflect$4 ,! direction !y take dep5ds on ! %ape ( ! body1 b x may be laid d[n z a rule t !y are b5t t[>d ! ?ick] "p ( ! glass4 ,! common burn+-glass is well kn[n to u4 ,we hold x up fac+ ! sun to conc5trate all ! heat rays t fall ^u x into "o int5sely brilliant spot1 :i* spe$ily ignites any inflammable sub/ance on :i* x may fall 7,fig4 #ajc74 ,we may imag9e t "o ray passes f ! c5tre ( ! sun ?r\gh ! c5tre ( ! glass4 ,?is is undeflect$2 b all ! o!rs are b5t t[>ds x1 z !y pass ?r\gh ! ?9n] p>ts ( ! l5s4 ,illu/ration3 ,,fig4 #ajc4--,%[+ h[ a burn+-glass conc5trates ! heat rays :i* fall ^u x4 ,x %\ld be not$ "h t sunlight1 z we call x1 is accompani$ by heat4 ,a burn+-glass is us$ to conc5trate ! heat rays1 n ! light rays1 :i*1 ?\gh !y are collect$ too1 h no ignit+ effect4 ,9 photography we use a l5s to conc5trate light rays only4 ,su* heat rays z may pass ?r\gh ! l5s ) !m are n want$1 & z !y h no practical effect are n tak5 any notice (4 ,to be ( real value1 a l5s mu/ be q symmetrical--t is1 ! curve f ! c5tre to ! circumf]5ce mu/ be ! same 9 all directions4 ,!re are six =ms ( simple l5ses1 z giv5 9 ,fig4 #ajd4 ,nos4 #a & #b h "o flat & "o sph]ical surface4 ,nos4 #c1 #d1 #e1 #f h two sph]ical surfaces4 ,:5 a l5s is ?ick] at ! middle ?an at ! sides x is call$ a convex l5s2 :5 ?9n]1 a concave l5s4 ,! names ( ! v>i\s %apes are z foll[s3--,no4 #a1 plano-convex2 ,no4 #b1 plano-concave2 ,no4 #c1 d\ble convex2 ,no4 #d1 d\ble concave2 ,no4 #e1 m5iscus2 ,no4 #f1 concavo-convex4 ,! ?ick-c5tre l5ses1 z we may t]m !m 7,nos4 #a1 #c1 #e71 conc5trate a p5cil ( rays pass+ ?r\gh !m2 :ile ! ?9-c5tre l5ses 7,nos4 #b1 #d1 #f7 scatt] ! rays 7see ,fig4 #aje74 ,illu/ration3 ,,fig4 #ajd4--,six =ms ( l5ses4 ,,! ,,cam]a4 ,illu/ration3 ,,fig4 #aje4 ,illu/ration3 ,,fig4 #ajf4 ,we said above t light is propagat$ 9 /raight l9es4 ,to prove ?is is easy4 ,get a piece ( c>dbo>d & prick a hole 9 x4 ,set ?is up "s di/ance away f a c&le flame1 & hold beh9d x a piece ( tissue pap]4 ,y w at once p]ceive a fa9t1 upside-d[n image ( ! flame on ! tissue4 ,:y is ?is8 ,turn = a mom5t to ,fig4 #ajf1 :i* %[s a p9hole cam]a 9 section4 ,at ! re> is a gr\nd-glass scre51 ,b1 to cat* ! image4 ,suppose t ,a is ! l[e/ po9t ( ! flame4 ,a p5cil ( rays div]g+ f x /rikes ! front ( ! cam]a1 :i* /ops !m all except ! "o :i* passes ?r\gh ! hole & makes a t9y lum9\s spot on ,b1 above ! c5tre ( ! scre51 ?\gh ,a is bel[ ! axis ( ! cam]a4 ,simil>ly ! tip ( ! flame 7above ! axis7 w\ld be repres5t$ by a dot on ! scre5 bel[ its c5tre4 ,& s on = all ! millions ( po9ts ( ! flame4 ,if we 7 to enl>ge ! hole we %\ld get a bright] image1 b x w\ld h less %>p outl9es1 because a numb] ( rays f e po9t ( ! c&le w\ld rea* ! scre5 & be jumbl$ up ) ! rays ( neighb\r+ p5cils4 ,n[1 ?\gh a good1 %>p photograph may be tak5 ?r\gh a p9hole1 ! "t requir$ is s long t photography ( ?is sort has little practical value4 ,:at we want is a l>ge hole = ! light to ent] ! cam]a by1 & yet to secure a di/9ct image4 ,if we place a l5s 9 ! hole we c fulfil our wi%4 ,fig4 #ajg %[s a l5s 9 position1 ga!r+ up a numb] ( rays f a po9t1 ,a1 & focuss+ !m on a po9t1 ,b4 ,if ! l5s has #a1jjj times ! area ( ! p9hole1 x w pass #a1jjj times z _m rays1 & ! image ( ,a w be impress$ on a s5sitiz$ photographic plate #a1jjj times m quickly4 ,illu/ration3 ,,fig4 #ajg4 ,,! ,,image ,,ca/ ,,by ,a ,,convex ,,l5s4 ,fig4 #ajh %[s diagrammatically h[ a convex l5s =ms an image4 ,f ,a & ,b1 ! extremities ( ! object1 a simple ray is consid]$ to pass ?r\gh ! c5tre ( ! l5s4 ,?is is n deflect$ at all4 ,two o!r rays f ! same po9ts /rike ! l5s above & bel[ ! c5tre respectively4 ,^! are b5t inw>ds & meet ! c5tral rays1 or come to a focus ) !m at ,a#a & ,b#a4 ,9 reality a c\ntless numb] ( rays w\ld be transmitt$ f e po9t ( ! object & collect$ to =m ! image4 ,illu/ration3 ,,fig4 #ajh4--,%[+ h[ an image is ca/ by a convex l5s4 ,,focus4 ,we mu/ n[ take special notice ( t ^w he>d s (t5 9 photographic talk--focus4 ,:at is meant by ! focus or focal l5g? ( a l5s8 ,well1 x m]ely signifies ! di/ance betwe5 ! optical c5tre ( ! l5s & ! plane 9 :i* ! image is =m$4 ,illu/ration3 ,,fig4 #aji4 ,we mu/ "h digress a mom5t to draw att5tion to ! ?ree simple diagrams ( ,fig4 #aji4 ,! object1 ,o1 9 ea* case is assum$ to be to ! "r ( ! l5s4 ,9 ! topmo/ diagram ! object is s f> away f ! l5s t all rays com+ f a s+le po9t 9 x are practically p>allel4 ,^! conv]ge to a focus at ,f4 ,if ! di/ance betwe5 ,f & ! c5tre ( ! l5s is six in*es1 we say t ! l5s has a six-in* focal l5g?4 ,! focal l5g? ( a l5s is judg$ by ! di/ance betwe5 l5s & image :5 ! object is f> away4 ,to avoid confusion1 ?is focal l5g? is kn[n z ! pr9cipal focus1 & is d5ot$ by ! symbol f4 ,9 ! middle diagram ! object is q ne> ! l5s1 :i* has to deal ) rays /rik+ its ne>] surface at an acut] angle ?an be=e 7reckon+ f ! c5tre74 ,z ! l5s c only deflect _! pa? to a fix$ degree1 !y w n1 aft] pass+ ! l5s1 come toge!r until !y h rea*$ a po9t1 ,f#a1 fur!r f ! l5s ?an ,f4 ,! ne>] we approa* ,o to ! l5s1 ! fur!r away on ! o!r side is ! focal po9t1 until a di/ance equal to t ( ,f f ! l5s is rea*$1 :5 ! rays em]ge f ! glass 9 a p>allel p5cil4 ,! rays n[ come to a focus no long]1 & !re c be no image4 ,if ,o be br\ght ne>] ?an ! focal di/ance1 ! rays w\ld div]ge aft] pass+ ?r\gh ! l5s4 ,,relative ,,positions ,,( ,,object ,,& ,,image4 ,illu/ration3 ,,fig4 #aaj4--,%[+ h[ ! position ( ! image alt]s relatively to ! position ( ! object4 ,f :at has be5 said above we d$uce two ma9 conclusions--7#a47 ,! ne>] an object is br\ght to ! l5s1 ! fur!r away f ! l5s w ! image be4 7#b47 ,if ! object approa*es )9 ! pr9cipal focal di/ance ( ! l5s1 no image w be ca/ by ! l5s4 ,to make ?is pla9] we app5d a diagram 7,fig4 #aaj71 :i* %[s five positions ( an object & ! relative positions ( ! image 79 dott$ l9es74 ,fir/1 we note t ! l9e ,a ,b1 or ,a ,b#a1 d5otes ! pr9cipal focal l5g? ( ! l5s1 & ,a ,c1 or ,a ,c#a1 d5otes twice ! focal l5g?4 ,we w take ! positions 9 ord]3-- ,position ,i4 ,object fur!r away ?an #b;f4 ,inv]t$ image small] ?an object1 at di/ance some:at exce$+ f4 ,position ,,ii4 ,object at di/ance #b;f4 ,inv]t$ image at di/ance #b;f1 & ( size equal to t ( object4 ,position ,,iii ,object ne>] ?an #b;f4 ,inv]t$ image fur!r away ?an #b;f2 l>g] ?an ! object4 ,position ,,iv4 ,object at di/ance f4 ,z rays are p>allel aft] pass+ ! l5s no image is ca/4 ,position ,v4 ,object at di/ance less ?an f4 ,no real image--t is1 "o t c be caught on a focuss+ scre5--is n[ giv5 by ! l5s1 b a magnifi$1 erect1 virtual image exi/s on ! same side ( ! l5s z ! object4 ,we %all ref] to virtual images at great] l5g? pres5tly4 ,x is hop$ t any read] :o practises photography w n[ und]/& :y x is necess>y to rack 8 cam]a out beyond ! ord9>y focal di/ance :5 tak+ objects at close qu>t]s4 ,f ,fig4 #aaj he may ga!r "o practically useful h9t--namely1 t to copy a diagram1 etc41 full size1 bo? x & ! plate mu/ be exactly #b;f f ! optical c5tre ( ! l5s4 ,& x foll[s f ?is t ! fur!r he c rack 8 cam]a out beyond #b;f ! great] w be ! possible enl>gem5t ( ! orig9al4 ,,correction ,,( ,,l5ses ,,= ,,col\r4 ,we h ref]r$ to ! sep>ation ( ! spectrum col\rs ( :ite light by a prism4 ,n[1 a l5s is "o =m ( prism1 & !re=e sorts out ! col\rs4 ,9 ,fig4 #aaa we assume t two p>allel r$ rays & two p>allel violet rays f a di/ant object pass ?r\gh a l5s4 ,a l5s has mo/ b5d+ effect on violet rays & lea/ on r$1 & ! o!r col\rs ( ! spectrum are int]m$iately influ5c$4 ,= ! sake ( simplicity we h tak5 ! two extremes only4 ,y obs]ve t ! po9t ,r1 9 :i* ! r$ rays meet1 is mu* fur!r f ! l5s ?an is ,v1 ! meet+-po9t ( ! violet rays4 ,a photograph] v seldom has to take a subject 9 :i* !re are n objects ( sev]al diff]5t col\rs1 & x is obvi\s t if he us$ a simple l5s l t 9 ,fig4 #aaa & got 8 r$ objects 9 good focus1 ! blue & gre5 portions ( 8 picture w\ld necess>ily be m or less out ( focus4 ,illu/ration3 ,,fig4 #aaa4 ,illu/ration3 ,,fig4 #aab4 ,?is defect c =tunately be correct$ by ! me?od %[n 9 ,fig4 #aab4 ,a comp\nd l5s is ne$$1 made up ( a cr[n glass convex elem5t1 ,b1 & a concave elem5t1 ,a1 ( fl9t glass4 ,= ! sake ( illu/ration ! two p>ts are %[n sep>at$2 9 practice !y w\ld be cem5t$ toge!r1 =m+ "o optical body1 ?ick] 9 ! c5tre ?an at ! edges--a m5iscus l5s 9 fact1 s9ce ,a is n s concave z ,b is convex4 ,n[1 x 0 discov]$ by a ,mr4 ,hall _m ye>s ago t if :ite light pass$ ?r\gh two simil> prisms1 "o ( fl9t glass ! o!r ( cr[n glass1 ! =m] _h ! great] effect 9 sep>at+ ! spectrum col\rs--t is1 violet rays 7 b5t aside m sudd5ly comp>$ ) ! r$ rays ?an happ5$ ) ! cr[n-glass prism4 ,look at ,fig4 #aab4 ,! r$ rays pass+ ?r\gh ! fl9t glass are b little deflect$1 :ile ! violet rays turn sudd5ly outw>ds4 ,?is is j :at is want$1 = x c\nt]acts ! unequal inw>d refraction by ,b1 & bo? sets ( rays come to a focus 9 ! same plane4 ,su* a l5s is call$ a*romatic1 or col\rless4 ,if y hold a common read+-glass "s di/ance away f l>ge pr9t y w see t ! lett]s are edg$ ) col\r$ b&s1 prov+ t ! l5s is n a*romatic4 ,a prop]ly correct$ photographic l5s w\ld n %[ ^! pretty edg+s4 ,col\r correction is necess>y also = l5ses us$ 9 telescopes & microscopes4 ,,sph]ical ,,ab]ration4 ,a l5s :i* has be5 correct$ = col\r is /ill imp]fect4 ,if rays pass ?r\gh all p>ts ( x1 ^? :i* /rike x ne> ! edge w be refract$ m ?an ^? ne> ! c5tre1 & a blurr$ focus results4 ,?is is t]m$ sph]ical ab]ration4 ,y w be able to und]/& ! reason f ,figs4 #aac & #aad4 ,two rays1 ,a1 are p>allel to ! axis & ent] ! l5s ne> ! c5tre 7,fig4 #aac74 ,^! meet 9 "o plane4 ,two o!r rays1 ,b1 /rike ! l5s v obliquely ne> ! edge1 & on t acc\nt are bo? turn$ %>ply upw>ds1 com+ to a focus 9 a plane ne>] ! l5s ?an ,a4 ,if ?is happ5$ 9 a cam]a ! results w\ld be v bad4 ,ei!r ,a or ,b w\ld be out ( focus4 ,! tr\ble is m9imiz$ by plac+ 9 front ( ! l5s a plate ) a c5tral circul> op5+ 9 x 7d5ot$ by ! ?ick1 d>k l9e 9 ,fig4 #aad74 ,! rays ,b ( ,fig4 #aac are /opp$ by ?is plate1 :i* is !re=e call$ a /op4 ,b o!r rays f ! same po9t pass ?r\gh ! hole4 ,^!1 h[ev]1 /rike ! l5s mu* m squ>ely above ! c5tre1 & are n unduly refract$1 s t !y are br\ght to a focus 9 ! same plane z rays ,a4 ,illu/ration3 ,,fig4 #aac4 ,illu/ration3 ,,fig4 #aad4 ,,di/ortion ,,( ,,image4 ,illu/ration3 ,,fig4 #aae4--,section ( a rectil9e> l5s4 ,! l5s we h be5 consid]+ is a s+le m5iscus1 su* z is us$ 9 l&scape photography1 m\nt$ ) ! convex side turn$ t[>ds ! inside ( ! cam]a1 & hav+ ! /op 9 front ( x4 ,if y possess a l5s ( ?is sort1 try ! foll[+ exp]im5t ) x4 ,draw a l>ge squ>e on a %eet ( :ite pap] & focus x on ! scre54 ,! sides in/ead ( be+ /raight b[ outw>ds3 ?is is call$ b>rel di/ortion4 ,n[ turn ! l5s m\nt r\nd s t ! l5s is outw>ds & ! /op inw>ds4 ,! sides ( ! squ>e w appe> to b[ t[>ds ! c5tre3 ?is is p9-cu%ion di/ortion4 ,= a long "t opticians 7 unable to f9d a rem$y4 ,!n ,mr4 ,george ,s4 ,cundell sugge/$ t two m5iscus l5ses %\ld be us$ 9 comb9ation1 "o on ei!r side ( ! /op1 z 9 ,fig #aae4 ,ea* produces di/ortion1 b x is c\nt]act$ by ! opposite di/ortion ( ! o!r1 & a squ>e is repres5t$ z a squ>e4 ,l5ses ( ?is k9d are call$ rectil9e>1 or /raight-l9e produc+4 ,we h n[ review$ ! ?ree *ief defects ( a l5s--*romatic ab]ration1 sph]ical ab]ration1 & di/ortion--& h se5 h[ !y may be rem$i$4 ,s we w n[ pass on to ! mo/ p]fect ( cam]as1 ,,! ,,human ,,eye4 ,! eye 7,fig4 #aaf7 is ne>ly sph]ical 9 =m1 & is surr\nd$ outside1 except 9 front1 by a h>d1 horny coat call$ ! scl]otica 7,s74 ,9 front is ! cornea 7,a71 :i* bulges outw>ds1 & acts z a transp>5t w9d[ to admit light to ! l5s ( ! eye 7,c74 ,inside ! scl]otica1 & next to x1 comes ! *oroid coat2 & inside t aga9 is ! ret9a1 or curv$ focuss+ scre5 ( ! eye1 :i* may be/ be describ$ z a network ( fibres ramify+ f ! optic n]ve1 :i* c>ries sight s5sations to ! bra94 ,! holl[ ( ! ball is full ( a jelly-l sub/ance call$ ! vitre\s hum\r2 & ! cavity betwe5 ! l5s & ! cornea is full ( wat]4 ,we h already se5 t1 9 focuss+1 ! di/ance betwe5 l5s & image dep5ds on ! di/ance betwe5 object & l5s4 ,n[1 ! ret9a _c be pu%$ ne>] to or pull$ fur!r away f its l5s1 l ! focuss+ scre5 ( a cam]a4 ,h[1 !n1 is ! eye able to focus %>ply objects at di/ances v>y+ f a foot to _m miles8 ,illu/ration3 ,,fig4 #aaf4--,section ( ! human eye4 ,z a prelim9>y to ! answ] we mu/ obs]ve t ! m convex a l5s is1 ! %ort] is its focus4 ,we w suppose t we h a box cam]a ) a l5s ( six-in* focus fix$ rigidly 9 ! position necess>y = obta9+ a %>p image ( di/ant objects4 ,x s happ5s t we want to take ) x a portrait ( a p]son only a few feet f ! l5s4 ,if x 7 a bell[s cam]a1 we %\ld rack out ! back or front4 ,b we _c d ?is "h4 ,s we place 9 front ( our l5s a second convex l5s :i* %ort5s its pr9cipal focus2 s t 9 effect ! box has be5 rack$ out suffici5tly4 ,nature1 h[ev]1 employs a mu* m p]fect me?od ?an ?is4 ,! eye l5s is pla/ic1 l a piece ( india-rubb]4 ,its edges are atta*$ to ligam5ts 7,l ,l71 :i* pull outw>ds & t5d to flatt5 ! curve ( its surfaces4 ,! normal focus is = di/ant objects4 ,:5 we read a book ! eye adapts itself to ! "w4 ,! ligam5ts relax & ! l5s decreases 9 diamet] :ile ?ick5+ at ! c5tre1 until its curvature is su* z to focus all rays f ! book %>ply on ! ret9a4 ,if we sudd5ly look ?r\gh ! w9d[ at some?+ outside1 ! ligam5ts pull on ! l5s envelope & flatt5 ! curves4 ,?is wond]ful l5s is a*romatic1 & free f sph]ical ab]ration & di/ortion ( image4 ,nor mu/ we =get t x is aid$ by an automatic /op1 ! iris1 ! c5tral hole ( :i* is nam$ ! pupil4 ,we say t a p]son has black1 blue1 or gray eyes accord+ to ! col\r ( ! iris4 ,l ! l5s1 ! iris adapts itself to all conditions1 contract+ :5 ! light is /rong1 & op5+ :5 ! light is weak1 s t z uni=m an am\nt ( light z conditions all[ may be admitt$ to ! eye4 ,mo/ mod]n cam]a l5ses are fitt$ ) adju/able /ops :i* c be made l>g] or small] by twi/+ a r+ on ! m\nt1 & are nam$ iris /ops4 ,! image ( any?+ se5 is ?r[n on ! ret9a upside d[n1 & ! bra9 rev]ses ! position aga91 s t we get a correct impression ( ?+s4 ,,! ,,use ,,( ,,spectacles4 ,illu/ration3 ,,fig4 #aag;a4 ,illu/ration3 ,,fig4 #aag;b4 ,illu/ration3 ,,fig4 #aah;a4 ,illu/ration3 ,,fig4 #aah;b4 ,! read] w n[ be able to und]/& )\t mu* tr\ble ! function ( a pair ( spectacles4 ,a great _m p ( all ages suff] f %ort-sight4 ,= "o reason or ano!r ! di/ance betwe5 l5s & ret9a becomes too great = a p]son to di/+ui% di/ant objects cle>ly4 ,! l5s1 z %[n 9 ,fig #aag;a1 is too convex--has its m9imum focus too %ort--& ! rays meet & cross be=e !y rea* ! ret9a1 caus+ g5]al confusion ( outl9e4 ,?is defect is simply rem$i$ by plac+ 9 front ( ! eye 7,fig4 #aag;b7 a concave l5s1 to disp]se ! rays some:at be=e !y ent] ! eye1 s t !y come to a focus on ! ret9a4 ,if a p]son's sight is ?us correct$ = di/ant objects1 he c /ill see ne> objects q pla9ly1 z ! l5s w accommodate its convexity = !m4 ,! sci5tific t]m = %ort-sight is myopia4 ,long-sight1 or hyp]metropia1 signifies t ! eyeball is too %ort or ! l5s too flat4 ,fig4 #aah;a repres5ts ! normal condition ( a long-sight$ eye4 ,:5 look+ at a di/ant object ! eye ?ick5s slightly & br+s ! focus =w>d into ! ret9a4 ,b its ?ick5+ p[] 9 su* an eye is v limit$1 & consequ5tly ! rays f a ne> object focus beh9d ! ret9a4 ,x is !re=e necess>y = a long-sight$ p]son to use convex spectacles = read+ ! newspap]4 ,z se5 9 ,fig4 #aah;b1 ! spectacle l5s conc5trates ! rays be=e !y ent] ! eye1 & s does "p ( ! eye's "w = x4 ,return+ = a mom5t to ! diagram ( ! eye 7,fig4 #aaf71 we notice a black pat* on ! ret9a ne> ! optic n]ve4 ,?is is ! yell[ spot4 ,vision is mo/ di/9ct :5 ! image ( ! object look$ at is =m$ on ?is "p ( ! ret9a4 ,! bl9d spot is t po9t at :i* ! optic n]ve ent]s ! ret9a1 be+ s call$ f ! fact t x is q ins5sitive to light4 ,! f9d+ ( ! bl9d spot is an int]e/+ little exp]im5t4 ,on a c>d make a l>ge & a small spot ?ree in*es ap>t1 ! "o an eigh?1 ! o!r half an in* 9 diamet]4 ,br+ ! c>d ne> ! face s t an eye is exactly opposite to ea* spot1 & close ! eye opposite to ! small]4 ,n[ direct ! o!r eye to ?is spot & y w f9d1 if ! c>d be mov$ backw>ds & =w>ds1 t at a c]ta9 di/ance ! l>ge spot1 ?\gh _m times l>g] ?an its fell[1 has completely vani%$1 because ! rays f x ent] ! op5 eye obliquely & fall on ! bl9d spot4 ,*apt] ,,xiii4 ,,! ,,microscope1 ,,! ,,telescope1 ,,& ,,! ,,magic-,,lant]n4 ,! simple microscope--,use ( ! simple microscope 9 ! telescope--,! t]re/rial telescope--,! ,galilean telescope--,! prismatic telescope--,! reflect+ telescope--,! p>abolic mirror--,! comp\nd microscope--,! magic-lant]n--,! bioscope--,! plane mirror4 ,9 ,fig4 #aai is repres5t$ an eye look+ at a vase1 ?ree in*es high1 situat$ at ,a1 a foot away4 ,if we 7 to place ano!r vase1 ,b1 six in*es high1 at a di/ance ( two feet2 or ,c1 n9e in*es high1 at ?ree feet2 or ,d1 a foot high1 at f\r feet1 ! image on ! ret9a w\ld 9 e case be ( ! same size z t ca/ by ,a4 ,we c !re=e lay d[n ! rule t ! app>5t size ( an object dep5ds on ! angle t x subt5ds at ! eye4 ,illu/ration3 ,,fig4 #aai4 ,to see a ?+ m pla9ly1 we g ne>] to x2 & if x be v small1 we hold x close to ! eye4 ,!re is1 h[ev]1 a limit to ! ne>ness to :i* x c be br\ght ) advantage4 ,! normal eye is unable to adapt its focus to an object less ?an ab\t t5 in*es away1 t]m$ ! lea/ di/ance ( di/9ct vision4 ,,! ,,simple ,,microscope4 ,illu/ration3 ,,fig4 #abj4 ,a magnify+ glass comes 9 useful :5 we want to exam9e an object v closely4 ,! glass is a l5s ( %ort focus1 held at a di/ance some:at less ?an its pr9cipal focal l5g?1 ,f 7see ,fig4 #abj71 f ! object4 ,! rays f ! head & tip ( ! p9 :i* ent] ! eye are d5ot$ by cont9u\s l9es4 ,z !y are deflect$ by ! glass ! eye gets ! impression t a mu* long] p9 is situat$ a consid]able di/ance beh9d ! real object 9 ! plane 9 :i* ! refract$ rays w\ld meet if produc$ backw>ds 7%[n by ! dott$ l9es74 ,! effect ( ! glass1 practically1 is to remove x 7! object7 to beyond ! lea/ di/ance ( di/9ct vision1 & at ! same "t to reta9 undim9i%$ ! angle x subt5ds at ! eye1 or1 :at am\nts to ! same ?+1 ! actual size ( ! image =m$ on ! ret9a4#bb ,x foll[s1 !re=e1 t if a l5s be ( su* %ort focus t x all[s u to see an object cle>ly at a di/ance ( two in*es--t is1 "o-fif? ( ! lea/ di/ance ( di/9ct vision--we %all get an image on ! ret9a five times l>g] 9 diamet] ?an w\ld be possible )\t ! l5s4 ,! two simple diagrams 7,figs4 #aba & #abb7 %[ :y ! image to be magnifi$ %\ld be ne>] to ! l5s ?an ! pr9cipal focus1 ,f4 ,we h already se5 7,fig4 #aji7 t rays com+ f a po9t 9 ! pr9cipal focal plane em]ge z a p>allel p5cil4 ,^! ! eye c br+ to a focus1 because x normally has a curvature = focuss+ p>allel rays4 ,b1 ow+ to ! p[] ( accommodation1 x c also focus div]g+ rays 7,fig4 #aba71 ! eye l5s ?ick5+ ! necess>y am\nt1 & we !re=e put our magnify+ glass a bit ne>] ?an ,f to get full advantage ( proximity4 ,if we _h ! object outside ! pr9cipal focus1 z 9 ,fig4 #abb1 ! rays f x w\ld conv]ge1 & ^! c\ld n be ga!r$ to a %>p po9t by ! eye l5s1 z x _c flatt5 m ?an is requir$ = focuss+ p>allel rays4 ,illu/ration3 ,,fig4 #aba4 ,illu/ration3 ,,fig4 #abb4 ,,use ,,( ,,! ,,simple ,,microscope ,,9 ,,! ,,telescope4 ,illu/ration3 ,,fig4 #abc4 ,let u n[ turn to ,fig4 #abc4 ,at ,a is a di/ant object1 say1 a hundr$ y>ds away4 ,b is a d\ble convex l5s1 :i* has a focal l5g? ( tw5ty in*es4 ,we may suppose t x is a l5s 9 a cam]a4 ,an inv]t$ image ( ! object is ca/ by ! l5s at ,c4 ,if ! eye 7 plac$ at ,c1 x w\ld di/+ui% no?+4 ,b if )drawn to ,d1 ! lea/ di/ance ( di/9ct vision1#bc beh9d ,c1 ! image is se5 cle>ly4 ,t ! image really is at ,c is prov$ by lett+ d[n ! focuss+ scre51 :i* at once cat*es x4 ,n[1 z ! focus ( ! l5s is twice d1 ! image w be twice z l>ge z ! object w\ld appe> if view$ directly )\t ! l5s4 ,we may put ?is into a v simple =mula3-- ,magnification focal l5g? ( l5s -------------------- d ,illu/ration3 ,,fig4 #abd4 ,9 ,fig4 #abd we h int]pos$ betwe5 ! eye & ! object a small magnify+ glass ( #b-a_/b-;in* focus1 s t ! eye c n[ cle>ly see ! image :5 "o-qu>t] d away f x4 ,b already magnifies ! image twice2 ! eye-piece aga9 magnifies x f\r times2 s t ! total magnification is #b #d #h times4 ,?is result is arriv$ at quickly by divid+ ! focus ( ,b 7:i* corresponds to ! object-glass ( a telescope7 by ! focus ( ! eye-piece1 ?us3-- #bj #h #b-a_/b ,! ord9>y a/ronomical telescope has a v long focus object-glass at "o end ( ! tube1 & a v %ort focus eye-piece at ! o!r4 ,to see an object cle>ly "o m]ely has to pu% 9 or pull out ! eye-piece until its focus exactly corresponds ) t ( ! object-glass4 ,,! ,,t]re/rial ,,telescope4 ,an a/ronomical telescope inv]ts images4 ,?is inv]sion is inconv5i5t = o!r purposes4 ,s ! t]re/rial telescope 7su* z is commonly us$ by sailors7 has an eye-piece comp\nd$ ( f\r convex l5ses :i* erect z well z magnify ! image4 ,fig4 #abe %[s ! simple/ =m ( comp\nd erect+ eye-piece4 ,illu/ration3 ,,fig4 #abe4 ,,! ,,galilean ,,telescope4 ,illu/ration3 ,,fig4 #abf4 ,a ?ird =m ( telescope is t inv5t$ by ! great ,italian a/ronom]1 ,galileo1#bd 9 #afji4 ,its pr9ciple is %[n 9 ,fig4 #abf4 ,! rays transmitt$ by ! object-glass are caught1 be=e com+ to a focus1 on a concave l5s :i* sep>ates !m s t !y appe> to meet 9 ! pa?s ( conv]g5ce d5ot$ by ! dott$ l9es4 ,! image is erect4 ,op]a-glasses are con/ruct$ on ! ,galilean pr9ciple4 ,,! ,,prismatic ,,telescope4 ,9 ord] to be able to use a long-focus object-glass )\t a long focuss+-tube1 a sy/em ( glass reflect+ prisms is sometimes employ$1 z 9 ,fig4 #abg4 ,a ray pass+ ?r\gh ! object-glass is reflect$ f "o po/]ior surface ( prism ,a on to ! o!r po/]ior surface1 & by x out ?r\gh ! front on to a second prism arrang$ at "r angles to x1 :i* passes ! ray on to ! comp\nd eye-piece4 ,! di/ance betwe5 object-glass & eye-piece is ?us practically trebl$4 ,! be/-kn[n prismatic telescopes are ! ,zeiss field-glasses4 ,illu/ration3 ,,fig4 #abg4 ,,! ,,reflect+ ,,telescope4 ,we mu/ n omit ref]5ce to ! reflect+ telescope1 s l>gely us$ by a/ronom]s4 ,! front end ( ! telescope is op51 !re be+ no object-glass4 ,rays f ! object fall on a p>abolic mirror situat$ 9 ! re> end ( ! tube4 ,?is reflects !m =w>ds to a focus4 ,9 ! ,newtonian reflector a plane mirror or prism is situat$ 9 ! axis ( ! tube1 at ! focus1 to reflect ! rays ?r\gh an eye-piece project+ ?r\gh ! side ( ! tube4 ,h]s*el's =m ( reflector has ! mirror set at an angle to ! axis1 s t ! rays are reflect$ direct into an eye-piece po9t+ ?r\gh ! side ( ! tube t[>ds ! mirror4 ,,! ,,p>abolic ,,mirror4 ,?is mirror 7,fig4 #abh7 is ( su* a %ape t all rays p>allel to ! axis are reflect$ to a common po9t4 ,9 ! m>9e se>*light a p[]ful arc lamp is arrang$ ) ! arc at ! focus ( a p>abolic reflector1 :i* s5ds all reflect$ light =w>d 9 a p5cil ( p>allel rays4 ,! mo/ p[]ful se>*light 9 exi/5ce gives a light equal to t ( #cej million c&les4 ,illu/ration3 ,,fig4 #abh4--;,a p>abolic reflector4 ,,! ,,comp\nd ,,microscope4 ,we h already obs]v$ 7,fig4 #aaj7 t ! ne>] an object approa*es a l5s ! fur!r (f beh9d x is ! real image =m$1 until ! object has rea*$ ! focal di/ance1 :5 no image at all is ca/1 z x is an inf9ite di/ance beh9d ! l5s4 ,we w assume t a c]ta9 l5s has a focus ( six in*es4 ,we place a light$ c&le f\r feet 9 front ( x1 & f9d t a %>p dim9i%$ image is ca/ on a gr\nd-glass scre5 held sev5 in*es beh9d x4 ,if we n[ ex*ange ! positions ( ! c&le & ! scre51 we %all get an enl>g$ image ( ! c&le4 ,?is is a simple demon/ration ( ! law ( conjugate foci--namely1 t ! di/ance betwe5 ! l5s & an object on "o side & t betwe5 ! l5s & ! correspond+ image on ! o!r be> a def9ite relation to ea* o!r2 & an object plac$ at ei!r focus w ca/ an image at ! o!r4 ,:e!r ! image is l>g] or small] ?an ! object dep5ds on :i* focus x occupies4 ,9 ! case ( ! object-glass ( a telescope ! image 0 at :at we may call ! %ort focus4 ,illu/ration3 ,,fig4 #abi4--;,diagram to expla9 ! comp\nd microscope4 ,n[1 a comp\nd microscope is practically a telescope ) ! object at ! long focus1 v close to a %ort-focus l5s4 ,a greatly enl>g$ image is ?r[n 7see ,fig4 #abi7 at ! conjugate focus1 & ?is is caught & /ill fur!r magnifi$ by ! eye-piece4 ,we may add t ! object-glass1 or objective1 ( a microscope is usually comp\nd$ ( sev]al l5ses1 z is also ! eye-piece4 ,,! ,,magic-,,lant]n4 ,! mo/ ess5tial features ( a magic-lant]n are3--7#a7 ,! s\rce ( light2 7#b7 ! cond5s] = conc5trat+ ! light rays on to ! slide2 7#c7 ! l5s = project+ a magnifi$ image on to a scre54 ,fig4 #acj %[s ^! diagrammatically4 ,! illum9ant is mo/ commonly an oil-lamp1 or an acetyl5e gas jet1 or a cyl9d] ( lime heat$ to int5se lum9osity by an oxy-hydrog5 flame4 ,! natural combu/ion ( hydrog5 is att5d$ by a great heat1 & :5 ! supply ( oxyg5 is artificially increas$ ! temp]ature ( ! flame rises enorm\sly4 ,! nozzle ( an oxy-hydrog5 jet has an int]ior pipe connect$ ) ! cyl9d] hold+ "o gas1 & an ext]ior1 & some:at l>g]1 pipe lead+ f t conta9+ ! o!r1 ! two be+ arrang$ conc5trically at ! nozzle4 ,by means ( valves ! proportions ( ! gases c be regulat$ to give ! be/ results4 ,illu/ration3 ,,fig4 #acj4--,sket* ( ! elem5ts ( a magic-lant]n4 ,! cond5s] is set some:at fur!r f ! illum9ant ?an ! pr9cipal focal l5g? ( ! l5ses1 s t ! rays fall+ on !m are b5t inw>ds1 or to ! slide4 ,! objective1 or object l5s1 /&s 9 front ( ! slide4 ,its position is adju/able by means ( a rack & a draw-tube4 ,! ne>] x is br\ght to ! slide ! fur!r away is ! conjugate focus 7see p4 #bci71 & consequ5tly ! image4 ,! exhibitor fir/ sets up 8 scre5 & lant]n1 & !n f9ds ! conjugate foci ( slide & image by rack+ ! l5s 9 or out4 ,if a v %ort focus objective be us$1 subjects ( microscopic proportions c be project$ on ! scre5 enorm\sly magnifi$4 ,dur+ ! siege ( ,p>is 9 #ahgj-ga ! ,p>isians e/abli%$ a balloon & pigeon po/ to c>ry lett]s :i* _h be5 copi$ 9 a m9ute size by photography4 ,^! copies c\ld be enclos$ 9 a quill & atta*$ to a pigeon's w+4 ,on receipt1 ! copies 7 plac$ 9 a special lant]n & ?r[n z l>ge writ+ on ! scre54 ,micro-photography has s9ce !n made great /rides1 & is n[ widely us$ = sci5tific purposes1 "o ( ! mo/ important be+ ! /udy ( ! cry/all9e =mations ( metals "u diff]5t conditions4 ,,! ,,bioscope4 ,liv+ pictures are ! mo/ rec5t improvem5t 9 magic-lant]n ent]ta9m5ts4 ,! negatives f :i* ! lant]n films are pr9t$ are made by pass+ a ribbon ( s5sitiz$ celluloid ?r\gh a special =m ( cam]a1 :i* fe$s ! ribbon pa/ ! l5s 9 a s]ies ( j]ks1 an exposure be+ made automatically by a revolv+ %utt] dur+ ea* re/4 ,! positive film is plac$ 9 a lant]n1 & ! int]mitt5t movem5t is repeat$2 b n[ ! s\rce ( illum9ation is beh9d ! film1 & light passes outw>ds ?r\gh ! %utt] to ! scre54 ,9 ! ,urban bioscope ! film travels at ! rate ( fifte5 miles an h\r1 upw>ds ( "o hundr$ exposures be+ made e second4 ,! impression ( cont9u\s movem5t arises f ! fact t ! eye _c get rid ( a visual impression 9 less ?an "o-t5? ( a second4 ,s t if a s]ies ( impressions foll[ "o ano!r m rapidly ?an ! eye c rid itself ( !m ! impressions w ov]lap1 & give "o ( motion1 if ! position ( "s ( ! objects1 or p>ts ( ! objects1 v>ies slightly 9 ea* succe$+ picture4#be ,,! ,,plane ,,mirror4 ,illu/ration3 ,,fig4 #aca4 ,?is *apt] may conclude ) a glance at ! common look+-glass4 ,:y d we see a reflection 9 x8 ,! answ] is giv5 graphically by ,fig4 #aca4 ,two rays1 ,a b1 ,a c1 f a po9t ,a /rike ! mirror ,m at ! po9ts b & c4 ,l9es b ,n1 c ,o1 drawn f ^! po9ts p]p5dicul> to ! mirror are call$ _! normals4 ,! angles ,a b ,n1 ,a c ,o are ! angles ( incid5ce ( rays ,a b1 ,a c4 ,! pa?s :i* ! rays take aft] reflection mu/ make angles ) b ,n & c ,o respectively equal to ,a b ,n1 ,a c ,o4 ,^! are ! angles ( reflection4 ,if ! eye is s situat$ t ! rays ent] x z 9 our illu/ration1 an image ( ! po9t ,a is se5 at ! po9t ,a#a1 9 :i* ! l9es ,d b1 ,e c meet :5 produc$ backw>ds4 ,illu/ration3 ,,fig4 #acb4 ,:5 ! v]tical mirror is replac$ by a horizontal reflect+ surface1 su* z a pond 7,fig4 #acb71 ! same ?+ happ5s4 ,! po9t at :i* ! ray f ! reflection ( ! spire's tip to ! eye appe>s to pass ?r\gh ! surface ( ! wat] mu/ be s situat$ t if a l9e 7 drawn p]p5dicul> to x f ! surface ! angles made by l9es drawn f ! real spire tip & f ! obs]v]'s eye to ! base ( ! p]p5dicul> w\ld be equal4 #bb ,glazebrook1 ,light1 p4 #aeg4 #bc ,glazebrook1 ,light1 p4 #aeg4 #bd ,galileo 0 sev]ely c5sur$ & imprison$ = d>+ to ma9ta9 t ! e>? mov$ r\nd ! sun1 & revolv$ on its axis4 #be ,= a full acc\nt ( ,animat$ ,pictures ! read] might advantage\sly consult ,! ,romance ( ,mod]n ,inv5tion1 pp4 #aff foll4 ,*apt] ,,xiv4 ,,s\nd ,,& ,,musical ,,in/rum5ts4 ,nature ( s\nd--,! e>--,musical in/rum5ts--,! vibration ( /r+s--,! s\nd+-bo>d & ! frame ( a piano--,! /r+s--,! /rik+ me*anism--,! quality ( a note4 ,s\nd diff]s f light1 heat1 & electricity 9 t x c be propagat$ ?r\gh matt] only4 ,s\nd-waves are matt]-waves1 n e!r-waves4 ,?is c be prov$ by plac+ an electric bell "u ! bell-glass ( an air-pump & exhau/+ all ! air4 ,e!r /ill rema9s inside ! glass1 b if ! bell be set 9 motion no s\nd is audible4 ,admit air1 & ! clang ( ! gong is he>d q pla9ly4 ,s\nd resembles light & heat1 h[ev]1 ?us f>1 t x c be conc5trat$ by means ( suitable l5ses & curv$ surfaces4 ,an e*o is a pro( ( its reflection f a surface4 ,be=e deal+ ) ! v>i\s appliances us$ = produc+ s\nd-waves ( a def9ite "*1 let u exam9e t wond]ful natural app>atus ,,! ,,e>1 ?r\gh :i* we receive ^? s5sations :i* we call s\nd4 ,illu/ration3 ,,fig4 #acc4--;,diagrammatic sket* ( ! p>ts ( ! e>4 ,fig4 #acc is a purely diagrammatic section ( ! e>1 %[+ ! v>i\s p>ts di/ort$ & out ( proportion4 ,beg9n+ at ! left1 we h ! out] e>1 ! lobe1 to ga!r 9 ! s\nd-waves on to ! membrane ( ! tympanum1 or drum1 to :i* is atta*$ ! fir/ ( a s]ies ( ossicles1 or small bones4 ,! la/ ( ^! presses aga9/ an op5+ 9 ! inn] e>1 a cavity surr\nd$ by ! bones ( ! head4 ,inside ! inn] e> is a wat]y fluid1 ,p1 call$ p]ilymph 7surr\nd+ wat]71 imm]s$ 9 :i* is a membranic envelope1 ,m1 conta9+ endolymph 7inside wat]71 also full ( fluid4 ,into ?is fluid project ,e ,e ,e1 ! t]m9ations ( ! auditory n]ve1 lead+ to ! bra94 ,:5 s\nd-waves /rike ! tympanum1 !y cause x to move inw>ds & outw>ds 9 a s]ies ( rapid movem5ts4 ,! ossicles op]at$ by ! tympanum press on ! little op5+ ,o1 cov]$ by a membrane1 & e "t !y pu% x 9 !y slightly squeeze ! p]ilymph1 :i* 9 turn compresses ! endolymph1 :i* affects ! n]ve-ends1 & telegraphs a s5sation ( s\nd to ! bra94 ,9 ,fig4 #acd we h a m develop$ sket*1 giv+ 9 full] detail1 ?\gh /ill n 9 _! actual proportions1 ! compon5ts ( ! e>4 ,! ossicles ,m1 ,i1 & ,s are respectively ! malleus 7hamm]71 incus 7anvil71 & /apes 7/irrup74 ,ea* is atta*$ by ligam5ts to ! walls ( ! middle e>4 ,! tympanum moves ! malleus1 ! malleus ! incus1 & ! incus ! /apes1 ! la/ press+ into ! op5+ ,o ( ,fig4 #acc1 :i* is sci5tifically kn[n z ! f5e/ra ovalis1 or oval w9d[4 ,z liquids are practically incompressible1 nature has made all[ance = ! squeez+ 9 ( ! oval w9d[ membrane1 by provid+ a second op5+1 ! r\nd w9d[1 also cov]$ ) a membrane4 ,:5 ! /apes pu%es ! oval membrane 91 ! r\nd membrane bulges out1 its ela/icity suffic+ to put a c]ta9 pressure on ! p]ilymph 7indicat$ by ! dott$ portion ( ! inn] e>74 ,illu/ration3 ,,fig4 #acd4--;,diagrammatic section ( ! e>1 %[+ ! v>i\s p>ts4 ,! inn] e> consi/s ( two ma9 p>ts1 ! co*lea--s call$ f its resemblance 9 %ape to a snail's %ell--& ! semicircul> canals4 ,ea* portion has its p]ilymph & endolymph1 & conta9s a numb] ( ! n]ve-ends1 :i* are1 h[ev]1 mo/ num]\s 9 ! co*lea4 ,we d n "k = c]ta9 :at ! functions ( ! canals & ! co*lea are2 b x is probable t ! =m] enables u to di/+ui% betwe5 ! int5sity or l\dness ( s\nds & ! direction f :i* !y come1 :ile ! latt] enables u to det]m9e ! pit* ( a note4 ,9 ! co*lea are ab\t #b1hjj t9y n]ve-ends1 call$ ! rods ( ,corti4 ,! normal e> has su* a range z to give ab\t #cc rods to ! semitone4 ,! great sci5ti/ ,helmholtz has advanc$ ! !ory t ^! little rods are l t9y tun+-=ks1 ea* respond+ to a note ( a c]ta9 pit*2 s t :5 a /r+ ( a piano is s\nd$ & ! air vibrations are transmitt$ to ! inn] e>1 !y affect only "o ( ^! rods & ! "p ( ! bra9 :i* x s]ves1 & we h ! impression ( "o p>ticul> note4 ,x has be5 prov$ by exp]im5t t a v s5sitive e> c di/+ui% betwe5 s\nds v>y+ 9 pit* by only #a_/fd? ( a semitone1 or b half ! range ( any "o ,corti fibre4 ,?is difficulty ,helmholtz gets ov] by sugge/+ t 9 su* an e> two adjac5t fibres are affect$1 b "o m ?an ! o!r4 ,a p]son :o has a good e> = music is presumably "o ^: ,corti rods are v p]fect4 ,unlucky p l ! g5tleman :o c\ld only recognize "o tune1 & t because p took (f _! hats :5 x comm5c$1 are physically defici5t4 ,_! ,corti rods _c be prop]ly develop$4 ,:at applies to "o s+le note applies also to ! elem5ts ( a musical *ord4 ,a doz5 notes may s\nd simultane\sly1 b ! e> is able to assimilate ea* & bl5d x ) its fell[s2 yet x requires a v s5sitive & well-tra9$ e> to pick out any "o "p ( a h>mony & conc5trate ! bra9's att5tion on t "p4 ,! e> has a mu* l>g] range ?an ! eye4 ,:ile ! =m] ranges ov] elev5 octaves1 b little m ?an a s+le octave is possible to ! latt]4 ,! quicke/ vibrations :i* /rike ! eye1 z light1 h only ab\t twice ! rapidity ( ! sl[e/2 :]eas ! quicke/ vibrations :i* /rike ! e>1 z a musical s\nd1 h m ?an two ?\s& times ! rapidity ( ! sl[e/4#bf ,to come to actual figures1 ! ord9>y e> is s5sitive to vibrations rang+ f #af to #ch1jjj p] second4 ,! bottom & top notes ( a piano make respectively ab\t #dj & #d1jjj vibrations a second4 ,( c\rse1 "s e>s1 l "s eyes1 _c compreh5d ! :ole scale4 ,! squeak ( bats & ! *irrup ( crickets are inaudible to "s p2 & dogs are able to he> s\nds f> too %rill to affect ! human auditory app>atus4 ,n ! lea/ int]e/+ "p ( ?is wond]ful organ is ! tympanic membrane1 :i* is provid$ ) muscles = alt]+ its t5sion automatically4 ,if we are /ra9+ our e>s to cat* a %rill s\nd1 we tight5 ! membrane2 :ile if we are gett+ ready = a deep1 l\d report l t ( a gun1 we all[ ! drum to slack54 ,! ,eu/a*ian tube 7,fig4 #acd7 communicates ) ! m\?4 ,its function is probably to keep ! air-pressure equal on bo? sides ( ! drum4 ,:5 "o cat*es cold ! tube is apt to become block$ by mucus1 caus+ unequal pressure & consequ5t p>tial deafness4 ,be=e leav+ ?is subject1 x w be well to rem9d our m y\?ful read]s t ! e> is delicately z well z wond]fully made1 & mu/ be treat$ ) respect4 ,sudd5 %\t+ into ! e>1 or a playful bl[1 may h mo/ s]i\s effects1 by bur/+ ! tympanum or injur+ ! arrangem5t ( ! t9y bones putt+ x 9 communication ) ! inn] e>4 ,,musical ,,in/rum5ts4 ,^! are contrivances = produc+ sonor\s %ocks foll[+ ea* o!r rapidly at regul> int]vals4 ,musical s\nds are di/+ui%$ f m]e noises by _! regul>ity4 ,if we %ake a numb] ( nails 9 a t9 box1 we get only a s]ies ( sup]impos$ & *aotic s5sations4 ,on ! o!r h&1 if we /rike a tun+-=k1 ! air is agitat$ a c]ta9 numb] ( times a second1 ) a pleasant result :i* we call a note4 ,we w beg9 our excursion into ! region ( musical in/rum5ts ) an exam9ation ( t v famili> piece ( furniture1 ,,! ,,pian(orte1 :i* means lit]ally ! s(t-/rong4 ,by _m *ildr5 ! piano is reg>d$ z a great nuisance1 ! swall[]-up ( "t :i* c\ld be mu* m agreeably occupi$1 & is accord+ly %[n mu* less respect ?an is giv5 to a phonograph or a musical-box4 ,yet ! mod]n piano is a v clev] piece ( "w1 admirably adapt$ = ! production ( sweet melody--if prop]ly h&l$4 ,! two =ms ( piano n[ g5]ally us$ are ! upright1 ) v]tical s\nd-bo>d & wires1 & ! gr&1 ) horizontal s\nd-bo>d4#bg ,,! ,,vibration ,,( ,,/r+s4 ,z ! pian(orte is a /r+$ in/rum5t1 "s att5tion %\ld be giv5 to ! subject ( ! vibration ( /r+s4 ,a /r+ 9 a /ate ( t5sion emits a note :5 pluck$ & all[$ to vibrate freely4 ,! pit* ( ! note dep5ds on sev]al conditions3--7#a7 ,! diamet] ( ! /r+2 7#b7 ! t5sion ( ! /r+2 7#c7 ! l5g? ( ! /r+2 7#d7 ! sub/ance ( ! /r+4 ,tak+ !m 9 ord]3--7#a47 ,! numb] ( vibrations p] second is inv]sely proportional to ! diamet] ( ! /r+3 ?us1 a /r+ "o-qu>t] ( an in* 9 diamet] w\ld vibrate only half z (t5 9 a giv5 "t z a /r+ "o-eigh? ( an in* 9 diamet]4 7#b47 ,! l5g? rema9+ ! same1 ! numb] ( vibrations is directly proportional to ! squ>e root ( ! t5sion3 ?us1 a /r+ /ra9$ by a #af-lb4 weight w\ld vibrate f\r times z fa/ z x w\ld if /ra9$ by a #a-lb4 weight4 7#c47 ,! numb] ( vibrations is inv]sely proportional to ! l5g? ( ! /r+3 ?us1 a "o-foot /r+ w\ld vibrate twice z fa/ z a two-foot /r+1 /ra9$ to ! same t5sion1 & ( equal diamet] & weight4 7#d47 ,o!r ?+s be+ equal1 ! rate ( vibration is inv]sely proportional to ! squ>e root ( ! d5sity ( ! sub/ance3 s t a /eel wire w\ld vibrate m rapidly ?an a plat9um wire ( equal diamet]1 l5g?1 & t5sion4 ,^! facts are important to rememb] z ! und]ly+ pr9ciples ( /r+$ in/rum5ts4 ,n[1 if y hang a wire f a cord1 & hang a heavy weight f ! wire1 ! wire w be 9 a /ate ( high t5sion1 & yield a di/9ct note if /ruck4 ,b ! volume ( s\nd w be v small1 mu* too small = a practical in/rum5t4 ,! surface ( ! /r+ itself is s limit$ t x sets up b feeble motions 9 ! surr\nd+ air4 ,n[ hang ! wire f a l>ge bo>d & /rike x aga94 ,! volume ( s\nd has greatly increas$1 because ! /r+ has transmitt$ its vibrations to ! l>ge surface ( ! bo>d4 ,to get ! full s\nd-value ( ! vibrations ( a /r+1 we evid5tly ought to s m\nt ! /r+ t x may influ5ce a l>ge s\nd+ surface4 ,9 a viol9 ?is is effect$ by /ra9+ ! /r+s ov] a bridge re/+ on a holl[ box made ( p]fectly ela/ic wood4 ,draw ! b[ across a /r+4 ,! l\d s\nd he>d proce$s n f ! /r+ only1 b also f ! :ole surface ( ! box4 ,,! ,,s\nd+-,,bo>d ,,& ,,frame ,,( ,a ,,piano4 ,a piano has its /r+s /ra9$ across a frame ( wood or /eel1 f a r[ ( hooks 9 ! top ( ! frame to a r[ ( tap]+ squ>e-end$ p9s 9 ! bottom1 ! wires pass+ ov] %>p edges ne> bo? ends4 ,! tun] is able1 on turn+ a p91 to t5sion its /r+s till x gives any desir$ note4 ,read]s may be int]e/$ to le>n t ! av]age t5sion ( a /r+ is #bge lbs41 s t ! total /ra9 on ! frame ( a gr& piano is any?+ betwe5 #bj & #cj tons4 ,to ! back ( ! frame is atta*$ ! s\nd+-bo>d1 made ( spruce fir 7! famili> ,*ri/mas tree74 ,?is is obta9$ f ,c5tral & ,ea/]n ,europe1 :]e x is c>efully select$ & prep>$1 z x is ess5tial t ! timb] %\ld be sawn 9 su* a way t ! gra9 ( ! wood runs 9 ! prop] direction4 ,,! ,,/r+s4 ,^! are made ( extremely /rong /eel wire ( ! be/ quality4 ,if y exam9e ! wires ( y\r piano1 y w see t !y v>y 9 ?ickness1 ! ?9ne/ be+ at ! treble end ( ! frame4 ,x is f\nd impracticable to use wires ( ! same gauge & ! same t5sion ?r\gh\t4 ,! mak]s !re=e use highly-t5sion$ ?ick wires = ! bass1 & f9]1 %ort] wires = ! treble1 tak+ advantage ( ! ?ree factors--weight1 t5sion1 & l5g?--:i* we h notic$ above4 ,! wires = ! deepe/ notes are wrapp$ r\nd ) f9e copp] wire to add to _! weight )\t increas+ _! diamet] at ! tun+-p9s4 ,!re are ab\t #fjj y>ds 7r\ghly "o-?ird ( a mile7 ( wire 9 a gr& piano4 ,,! ,,/rik+ ,,me*anism4 ,we n[ pass to ! app>atus = putt+ ! /r+s 9 a /ate ( vibration4 ,! gr& piano me*anism %[n 9 ,fig4 #ace may be tak5 z typical ( ! late/ improvem5ts4 ,! ess5tials ( an effective me*anism are3--7#a7 ,t ! bl[ deliv]$ %all be %>p & c]ta92 7#b7 t ! /r+ %all be imm$iately damp$1 or h its vibration *eck$ if requir$1 s z n to int]f]e ) ! succe$+ notes ( o!r /r+s2 7#c7 t ! hamm] %all be able to repeat ! bl[s 9 quick succession4 ,! hamm] has a head ( mahogany cov]$ ) felt1 ! ?ickness ( :i* tap]s gradually & regul>ly f an in* & a qu>t] at ! bass end to ?ree-sixte5?s ( an in* at ! extreme treble notes4 ,! entire eighty-five hamm]s = ! piano are cov]$ all toge!r 9 "o piece1 & !n !y are cut ap>t f ea* o!r4 ,! consi/5cy ( ! cov]+ is v important4 ,if too h>d1 x yields a h>% note1 & mu/ be r$uc$ to ! "r degree by prick+ ) a ne$le4 ,9 ! diagram ! felt is indicat$ by ! dott$ "p4 ,illu/ration3 ,,fig4 #ace4--,! /rik+ me*anism ( a gr& piano4 ,! action c>riage :i* op]ates ! hamm] is some:at complicat$4 ,:5 ! key is depress$1 ! left end rises1 & pu%es up ! :ole c>riage1 :i* is pivot$ at "o end4 ,! hamm] %ank is rais$ by ! jack ,b press+ ^u a knob1 ,n1 call$ ! not*1 atta*$ to ! "u side ( ! %ank4 ,:5 ! jack has ris5 to a c]ta9 po9t1 its arm1 ,b#a1 cat*es aga9/ ! button ,c & j]ks x f "u ! not* at ! v mom5t :5 ! hamm] /rikes1 s t x may n be block$ aga9/ ! /r+4 ,z x reb\nds1 ! hamm] is caught on ! repetition lev] ,r1 :i* lifts x to all[ ( p]fect repetition4 ,! *eck cat*es ! tail ( ! hamm] head dur+ its desc5t :5 ! key is rais$1 & prev5ts x com+ back viol5tly on ! c>riage & re/4 ,! tail is curv$ s z to w$ge aga9/ ! *eck )\t jamm+ 9 any way4 ,! mom5t ! c>riage beg9s to rise1 ! re> end ( ! key lifts a lev] connect$ ) ! damp] by a v]tical wire1 & raises ! damp] ( ! /r+4 ,if ! key is held d[n1 ! vibrations cont9ue = a long "t aft] ! bl[2 b if releas$ at once1 ! damp] /ifles !m z ! hamm] rega9s its seat4 ,a b>1 ,l1 pass+ along "u all ! damp] lift]s1 is rais$ by depress+ ! l\d p$al4 ,! s(t p$al slides ! :ole keybo>d along su* a di/ance t ! hamm]s /rike two only out ( ! ?ree /r+s allott$ to all except ! bass notes1 :i* h only "o /r+ apiece1 or two1 accord+ to _! dep? or l5g?4 ,9 "s pianos ! s(t p$al presses a special damp] aga9/ ! /r+s2 & a ?ird k9d ( device moves ! hamm]s ne>] ! /r+s s t !y deliv] a light] bl[4 ,^! two me?ods ( damp+ are conf9$ to upright pianos4 ,a high-class piano is ! result ( v c>eful workman%ip4 ,! me*anism ( ea* note mu/ be accurately regulat$ by its t9y screws to a m9ute fraction ( an in*4 ,x mu/ be ensur$ t e hamm] /rikes its bl[ at exactly ! "r place on ! /r+1 s9ce on ?is dep5ds ! musical value ( ! note4 ,! adju/m5t ( ! damp]s requires equal c>e1 & ! :ole "w calls = a s5sitive e> comb9$ ) skill$ me*anical k1 s t ! in/rum5t may h a light t\*1 /r5g?1 & c]ta9ty ( action ?r\gh\t ! :ole keybo>d4 ,,! ,,quality ,,( ,a ,,note4 ,if two /r+s1 alike 9 all respects & equally t5sion$1 are pluck$1 bo? w give ! same note1 b bo? w n necess>ily h ! same quality ( tone4 ,! quality1 or timbre1 z musicians call x1 is influ5c$ by ! pres5ce ( ov]tones1 or h>monics1 9 comb9ation ) ! fundam5tal1 or deepe/1 tone ( ! /r+4 ,! fact is1 t :ile a vibrat+ /r+ vibrates z a :ole1 x also vibrates 9 p>ts4 ,!re are1 z x 71 small waves sup]impos$ on ! big fundam5tal waves4 ,po9ts ( lea/ motion1 call$ nodes1 =m on ! /r+1 divid+ x into two1 ?ree1 f\r1 five1 etc41 p>ts1 :i* may be fur!r divid$ by subsidi>y nodes4 ,! /r+1 consid]$ z halv$ by "o node1 gives ! fir/ ov]tone1 or octave ( ! fundam5tal4 ,x may also vibrate z ?ree p>ts1 & give ! second ov]tone1 or twelf? ( ! fundam5tal2#bh & z f\r p>ts1 & give ! ?ird ov]tone1 ! d\ble octave4 ,n[1 if a /r+ be /ruck at a po9t correspond+ to a node1 ! ov]tones :i* require t po9t = a node w be kill$1 on acc\nt ( ! excessive motion imp>t$ to ! /r+ at t spot4 ,?us to hit x at ! middle kills ! octave1 ! d\ble octave1 etc42 :ile to hit x at a po9t "o-?ird ( ! l5g? f "o end /ifles ! twelf? & all its sub-multiples4 ,a fundam5tal note robb$ ( all its h>monics is h>d to obta91 :i* is n a matt] = regret1 z x is a mo/ un9t]e/+ s\nd4 ,to get a ri* tone we mu/ keep z _m useful h>monics z possible1 & !re=e a piano hamm] is s plac$ z to /rike ! /r+ at a po9t :i* does n int]f]e ) ! be/ h>monics1 b kills ^? :i* are objectionable4 ,pian(orte mak]s h discov]$ by exp]im5t t ! mo/ pleas+ tone is excit$ :5 ! po9t aga9/ :i* ! hamm] /rikes is "o-sev5? to "o-n9? ( ! l5g? ( ! wire f "o end4 ,! nature ( ! mat]ial :i* does ! actual /rik+ is also ( importance4 ,! h>d] ! sub/ance1 & ! %>p] ! bl[1 ! m prom95t d ! h>monics become2 s t ! work] has to regulate c>efully bo? ! duration ( ! bl[ & ! h>dness ( ! hamm] cov]+4 #bf ,tyndall1 ,on ,s\nd1 p4 #ge4 #bg ,a ,broadwood gr& is made up ( #aj1gjj sep>ate pieces1 & 9 its manufacture =ty sep>ate trades are conc]n$4 #bh ,twelve notes high] up ! scale4 ,*apt] ,,xv4 ,,w9d ,,in/rum5ts4 ,longitud9al vibration--,columns ( air--,resonance ( columns ( air--,l5g? & tone--,! op5 pipe--,! ov]tones ( an op5 pipe--,:]e ov]tones are us$--,! arrangem5t ( ! pipes & p$als--,sep>ate s\nd-bo>ds--,v>ieties ( /ops--,tun+ pipes & re$s--,! bell[s--,electric & pneumatic actions--,! l>ge/ organ 9 ! _w--,human re$s4 ,,longitud9al ,,vibration4 ,9 /r+$ in/rum5ts we are conc]n$ only ) ! transv]se vibrations ( a /r+--t is1 its movem5ts 9 a direction at "r angles to ! axis ( ! /r+4 ,a /r+ c also vibrate longitud9ally--t is1 9 ! direction ( its axis--z may be prov$ by draw+ a piece ( res9$ lea!r along a viol9 /r+4 ,9 ?is case ! h>monics /ep up at ! same rate z :5 ! movem5ts 7 transv]se4 ,let u sub/itute = a wire a /\t b> ( metal fix$ at "o end only4 ,! longitud9al vibrations ( ?is rod conta9 ov]tones ( a diff]5t ratio4 ,! fir/ h>monic is n an octave1 b a twelf?4 ,:ile a t5sion$ /r+ is divid$ by nodes into two1 ?ree1 f\r1 five1 six1 etc41 p>ts1 a rod fix$ at "o end only is capable ( produc+ only ^? h>monics :i* correspond to division into ?ree1 five1 sev51 n9e1 etc41 p>ts4 ,!re=e a free-end rod & a wire ( ! same fundam5tal note w\ld n h ! same timbre1 or quality1 ow+ to ! diff]5ce 9 ! h>monics4 ,,columns ,,( ,,air4 ,9 w9d in/rum5ts we employ1 in/ead ( rods or wires1 columns ( air z ! vibrat+ m$ium4 ,! note ( ! column dep5ds on its l5g?4 ,9 ! p5ny :i/le1 flute1 cl>ionet1 & piccolo ! l5g? ( ! column is alt]$ by clos+ or op5+ ap]tures 9 ! sub/ance encircl+ ! column4 ,,resonance ,,( ,,columns ,,( ,,air4 ,:y does a tube clos$ at "o end1 su* z ! %ank ( a key1 emit a note :5 we bl[ across ! op5 end8 ,! act ( bl[+ drives a ?9 %eet ( air aga9/ ! edge ( ! tube & causes x to vibrate4 ,! vibrations are confus$1 "s pulses occurr+ m frequ5tly ?an o!rs4 ,if we blew aga9/ ! edge ( a knife or a piece ( wood1 we %\ld he> no?+ b a hiss4 ,b :51 z 9 ! case :i* we are consid]+1 !re is a p>tly-enclos$ column ( air close to ! pulses1 ?is selects ^? pulses :i* correspond to its natural p]iod ( vibration1 & augm5ts !m to a su/a9$ & v audible musical s\nd4 ,illu/ration3 ,,fig #acf4--,%[+ h[ ! h>monics ( a /opp$ pipe are =m$4 ,9 ,fig4 #acf1 #a is a pipe1 clos$ at ! bottom & op5 at ! top4 ,a tun+-=k ( ! same note z ! pipe is /ruck & held ov] x s t ! prongs vibrate upw>ds & d[nw>ds4 ,at ! comm5cem5t ( an outw>d movem5t ( ! prongs ! air 9 front ( !m is compress$4 ,?is impulse1 imp>t$ to ! air 9 ! pipe1 runs d[n ! column1 /rikes ! bottom1 & returns4 ,j z x rea*es ! top ! prong is beg9n+ to move inw>ds1 caus+ a r>efaction ( ! air beh9d x4 ,?is effect also travels d[n & back up ! column ( air 9 ! pipe1 rea*+ ! prong j z x arrives at ! fur!/ po9t ( ! inw>d motion4 ,! process is repeat$1 & ! column ( air 9 ! pipe1 /rik+ on ! surr\nd+ atmosph]e at regul> int]vals1 greatly increases ! volume ( s\nd4 ,we mu/ obs]ve t if ! tun+-=k 7 ( too high or too l[ a note = ! column ( air to move 9 p]fect sympa?y ) x1 ?is increase ( s\nd w\ld n result4 ,n[1 :5 we bl[ across ! end1 we pres5t1 z x 71 a numb] ( vibrat+ tun+-=ks to ! pipe1 :i* picks out ^? air-pulses ) :i* x sympa?izes4 ,,l5g? ,,& ,,tone4 ,! rate ( vibration is f\nd to be inv]sely proportional to ! l5g? ( ! pipe4 ,?us1 ! vibrations ( a two-foot pipe are twice z rapid z ^? ( a f\r-foot pipe1 & ! note emitt$ by ! =m] is an octave high] ?an t ( ! latt]4 ,a "o-foot pipe gives a note an octave high] /ill4 ,we are "h speak+ ( ! fundam5tal tones ( ! pipes4 ,) !m1 z 9 ! case ( /r+s1 are associat$ ! ov]tones1 or h>monics1 :i* c be br\ght into prom95ce by increas+ ! pressure ( ! bla/ at ! top ( ! pipe4 ,bl[ v h>d on y\r key1 & ! note sudd5ly *anges to "o mu* %rill]4 ,x is ! twelf? ( ! fundam5tal1 ( :i* x has completely got ! upp] h&4 ,we mu/ n[ put on our ?9k+-caps & try to und]/& h[ ?is comes ab\t4 ,fir/1 let u note t ! vibration ( a body 79 ?is case a column ( air7 means a motion f a po9t ( re/ to a po9t ( re/1 or f node to node4 ,9 ! air-column 9 ,fig4 #acf1 #a1 !re is only "o po9t ( re/ = an impulse--namely1 at ! bottom ( ! pipe4 ,s t to pass f node to node ! impulse mu/ pass up ! pipe & d[n aga94 ,! di/ance f node to node 9 a vibrat+ body is call$ a v5tral segm5t4 ,rememb] ?is t]m4 ,!re=e ! pipe repres5ts a semi-v5tral segm5t :5 ! fundam5tal note is s\nd+4 ,:5 ! fir/ ov]tone is s\nd$ ! column divides itself into two vibrat+ p>ts4 ,:]e w ! node betwe5 !m be8 ,we might naturally say1 ,half-way up4 ,b ?is _c be s2 = if ! node 7 s situat$1 an impulse go+ d[n ! pipe w\ld only h to travel to ! bottom to f9d ano!r node1 :ile an impulse go+ up w\ld h to travel to ! top & back aga9--t is1 g twice z f>4 ,s ! node =ms itself "o-?ird ( ! di/ance d[n ! pipe4 ,f ,b to ,a 7,fig4 #acf1 #b7 & back is n[ equal to f ,b to ,c4 ,:5 ! second ov]tone is bl[n 7,fig4 #acf1 #c7 a ?ird node =ms4 ,! pipe is n[ divid$ into five semi-v5tral segm5ts4 ,& ) ea* succe$+ ov]tone ano!r node & v5tral segm5t are add$4 ,! law ( vibration ( a column ( air is t ! numb] ( vibrations is directly proportional to ! numb] ( semi-v5tral segm5ts into :i* ! column ( air inside ! pipe is divid$4#bi ,if ! fundam5tal tone gives #ajj vibrations p] second1 ! fir/ ov]tone 9 a clos$ pipe mu/ give #cjj1 & ! second #ejj vibrations4 ,,! ,,op5 ,,pipe4 ,a pipe op5 at bo? ends is capable ( emitt+ a note4 ,b we %all f9d1 if we exp]im5t1 t ! note ( a /opp$ pipe is an octave l[] ?an t ( an op5 pipe ( equal l5g?4 ,?is is expla9$ by ,fig4 #acg1 #a4 ,! air-column 9 ! pipe 7( ! same l5g? z t 9 ,fig4 #acf7 divides itself1 :5 an end is bl[n across1 into two equal portions at ! node ,b1 ! natural po9t to obta9 equilibrium4 ,a pulse w pass f ,a or ,a#a to ,b & back aga9 9 half ! "t requir$ to pass f ,a to ,b & back 9 ,fig4 #acf1 #a2 !re=e ! note is an octave high]4 ,illu/ration3 ,,fig4 #acg4--,%[+ h[ h>monics ( an op5 pipe are =m$1 ,b1 ,b#a1 & ,c are nodes4 ,! arr[s indicate ! di/ance travell$ by a s\nd impulse f a node to a node4 ,,! ,,ov]tones ,,( ,,an ,,op5 ,,pipe4 ,! fir/ ov]tone results :5 nodes =m z 9 ,fig4 #acg1 #b1 at po9ts "o-qu>t] ( ! l5g? ( ! pipe f ! ends1 giv+ "o complete v5tral segm5t & two semi-v5tral segm5ts4 ,! vibrations n[ are twice z rapid z be=e4 ,! second ov]tone requires ?ree nodes1 z 9 ,fig4 #acg1 #c4 ,! rate has n[ trebl$4 ,s t1 :ile ! ov]tones ( a clos$ pipe rise 9 ! ratio #a1 #c1 #e1 #g1 etc41 ^? ( an op5 pipe rise 9 ! proportion #a1 #b1 #c1 #d1 etc4 ,,:]e ,,ov]tones ,,are ,,us$4 ,9 ! flute1 piccolo1 & cl>ionet1 z well z 9 ! horn class ( in/rum5t1 ! ov]tones are z important z ! fundam5tal notes4 ,by artificially alt]+ ! l5g? ( ! column ( air1 ! fundam5tal notes are also alt]$1 :ile ! h>monics ( ea* fundam5tal are produc$ at w by v>y+ ! bl[+ pressure2 s t a cont9u\s *romatic1 or semitonal1 scale is possible ?r\gh\t ! compass ( ! in/rum5t4 ,,! ,,organ4 ,f ! !ory ( ac\/ics#cj we pass to ! practical application1 & conc5trate our att5tion ^u ! gr&e/ ( all w9d in/rum5ts1 ! pipe organ4 ,?is me*anism has a sep>ate pipe = e note1 prop]ly proportion$4 ,a section ( an ord9>y wood5 pipe is giv5 9 ,fig4 #ach4 ,w9d ru%es up ?r\gh ! foot ( ! pipe into a little *amb]1 clos$ by a block ( wood or a plate except = a n>r[ slit1 :i* directs x aga9/ ! %>p lip ,a1 & causes a flutt]+1 ! prop] pulse ( :i* is conv]t$ by ! air-column above into a musical s\nd4 ,illu/ration3 ,,fig4 #ach4--,section ( an ord9>y wood5 flue pipe4 ,9 ev5 ! smalle/ organs m ?an "o pipe is actuat$ by "o key on ! keybo>d1 = n only d pipes ( diff]5t %apes give diff]5t qualities ( tone1 b x is f\nd desirable to h ranks ( pipes ) _! bottom note ( diff]5t pit*es4 ,! l5g? ( an op5 pipe is measur$ f ! edge ( ! lip to ! top ( ! pipe2 ( a /opp$ pipe1 f ! lip to ! top & back aga94 ,:5 we speak ( a #af or #h foot rank1 or /op1 we mean "o ( :i* ! l[e/ note 9 ! rank is t produc$ by a #af or #h foot op5 pipe1 or _! /opp$ equival5ts 7#h or #d foot74 ,9 a big organ we f9d #cb1 #af1 #h1 #d1 & #b foot /ops1 & "s ( ^! repeat$ a numb] ( times 9 pipes ( diff]5t %ape & con/ruction4 ,,! ,,arrangem5t ,,( ,,! ,,pipes4 ,we w n[ /udy briefly ! me*anism ( a v simple s+le-keybo>d organ1 ) five ranks ( pipes1 or /ops4 ,illu/ration3 ,,fig4 #aci4--,! table ( a s\nd-bo>d4 ,x is necess>y to arrange matt]s s t ! press+ d[n ( "o key may make all five ( ! pipes belong+ to x speak1 or only f\r1 ?ree1 two1 or "o1 z we may desire4 ,! pipes are m\nt$ 9 r[s on a s\nd-bo>d1 :i* is built up 9 sev]al lay]s4 ,at ! top is ! upp] bo>d2 bel[ x come ! slid]s1 "o = ea* /op2 & und]nea? t ! table4 ,9 ,fig4 #aci we see "p ( ! table f bel[4 ,across ! "u side are fa/5$ p>allel b>s ) spaces 7%[n black7 left betwe5 !m4 ,two o!r b>s are fa/5$ across ! ends1 s t ea* groove is enclos$ by wood at ! top & on all sides4 ,! "u side ( ! table has %eets ( lea!r glu$ or o!rwise atta*$ to x 9 su* a mann] t no air c leak f "o groove to ! next4 ,upp] bo>d1 slid]s1 & table are pi]c$ ) r[s ( holes1 to p]mit ! passage ( w9d f ! grooves to ! pipes4 ,! grooves "u ! big pipes are wid] ?an ^? "u ! small pipes1 z !y h to pass m air4 ,! b>s betwe5 ! grooves also v>y 9 wid? accord+ to ! weight ( ! pipes :i* !y h to c>ry4 ,! slid]s c be mov$ 9 & out a %ort di/ance 9 ! direction ( ! axis ( ! r[s ( pipes4 ,!re is "o slid] "u ea* r[4 ,:5 a slid] is 91 ! holes 9 x d n correspond ) ^? 9 ! table & upp] bo>d1 s t no w9d c get f ! grooves to ! rank ov] t p>ticul> slid]4 ,fig4 #adj %[s ! mann] 9 :i* ! slid]s are op]at$ by ! little knobs 7also call$ /ops7 project+ f ! cas+ ( ! organ )9 conv5i5t rea* ( ! p]=m]'s h&s4 ,"o /op is 91 ! o!r drawn out4 ,illu/ration3 ,,fig4 #adj4 ,9 ,fig4 #ada we see ! table1 etc41 9 cross section1 ) a slid] out1 putt+ ! pipes ( its rank 9 communication ) ! grooves4 ,! same diagram %[s u 9 section ! little triangul> pallets :i* admit air f ! w9d-*e/ to ! grooves2 & ,fig4 #adb gives u an end section ( table1 slid]s1 & w9d-*e/1 toge!r ) ! rods1 etc41 connect+ ! key to its pallet4 ,:5 ! key is depress$1 ! /ick] 7a slight wood5 rod7 is pu%$ up4 ,?is rocks a backfall1 or pivot$ lev]1 to :i* is atta*$ ! pulld[n1 a wire p5etrat+ ! bottom ( ! w9d-*e/ to ! pallet4 ,z soon z ! pallet op5s1 w9d ru%es into ! groove above ?r\gh ! ap]ture 9 ! lea!r bottom1 & !nce to any "o ( ! pipes ( :i* ! slid] has be5 drawn out4 7,! slid]s 9 ,fig4 #adb are solid black47 ,x is evid5t t if ! s\nd-bo>d is suffici5tly deep f back to front1 any numb] ( r[s ( pipes may be plac$ on x4 ,illu/ration3 ,,fig4 #ada4 ,,p$als4 ,! organ p$als are connect$ to ! pallets by an action simil> to t ( ! keys4 ,! p$al /ops are g5]ally ( deep tone1 #cb-;foot & #af-;foot1 z !y h to su/a9 ! bass "p ( ! musical h>monies4 ,by means ( c\pl]s "o or m ( ! keybo>d /ops may be l9k$ to ! p$als4 ,,sep>ate ,,s\nd-,,bo>ds4 ,! keybo>d ( a v l>ge organ has z _m z five manuals1 or r[s ( keys4 ,ea* manual op]ates :at is practically a sep>ate organ m\nt$ on its own s\nd-bo>d4 ,illu/ration3 ,,fig4 #adb4 ,illu/ration3 ,,fig4 #adc4--;,g5]al section ( a two-manual organ4 ,! manuals are arrang$ 9 /eps1 ea* slightly ov]hang+ t bel[4 ,tak5 9 ord] f ! top1 !y are3--7#a47 ,e*o organ1 ( /ops ( small scale & v s(t tone1 enclos$ 9 a swell-box4 7#b47 ,solo organ1 ( /ops imitat+ or*e/ral in/rum5ts4 ,! wond]ful vox humana /op also belongs to ?is manual4 7#c47 ,swell organ1 conta9$ 9 a swell-box1 ! front & sides ( :i* h %utt]s :i* c be op5$ & clos$ by ! pressure ( ! foot on a lev]1 s z to regulate ! am\nt ( s\nd proce$+ f ! pipes inside4 7#d47 ,great organ1 includ+ pipes ( p[]ful tone4 7#e47 ,*oir organ1 ( s(t1 mell[ /ops1 (t5 enclos$ 9 a swell-box4 ,we may add to ^! ! p$al organ1 :i* c be c\pl$ to any b ! e*o manual4 ,,v>ieties ,,( ,,/ops4 ,we h already rem>k$ t ! quality ( a /op dep5ds on ! %ape & con/ruction ( ! pipe4 ,"s pipes are ( wood1 o!rs ( metal4 ,"s are rectangul>1 o!rs circul>4 ,"s h p>allel sides1 o!rs tap] or exp& t[>ds ! top4 ,"s are op51 o!rs /opp$4 ,! two ma9 classes into :i* organ pipes may be divid$ are3--7#a47 ,flue pipes1 9 :i* ! w9d is direct$ aga9/ a lip1 z 9 ,fig4 #ach4 7#b47 ,re$ pipes--t is1 pipes us$ 9 comb9ation ) a simple device = admitt+ air into ! bottom ( ! pipe 9 a s]ies ( gu/s4 ,fig4 #add %[s a /rik+ re$1 su* z is f\nd 9 ! ord9>y motor horn4 ,! ela/ic metal tongue :5 at re/ /&s a v %ort di/ance away f ! orifice 9 ! re$4 ,:5 w9d is bl[n ?r\gh ! re$ ! tongue is suck$ aga9/ ! re$1 blocks ! curr5t1 & spr+s away aga94 ,a free re$ has a tongue :i* vibrates 9 a slot )\t actually t\*+ ! sides4 ,h>monium & conc]t9a re$s are ( ?is type4 ,9 ! organ ! re$ admits air to a pipe ( ! correct l5g? to sympa?ize ) ! rate ( ! puffs ( air :i* ! re$ passes4 ,re$ pipes exp& t[>ds ! top4 ,,tun+ ,,pipes ,,& ,,re$s4 ,illu/ration3 ,,fig4 #add4--;,a re$ pipe4 ,pipes are tun$ by adju/+ _! l5g?4 ,! plug at ! top ( a /opp$ pipe is pull$ out or pu%$ 9 a trifle to flatt5 or %>p5 ! note respectively4 ,an op5 pipe1 if l>ge1 has a tongue cut 9 ! side at ! top1 :i* c be press$ inw>ds or outw>ds = ! purpose ( correct+ ! tone4 ,small metal pipes are flatt5$ by contract+ ! tops inw>ds ) a metal cone l a c&le-ext+ui%] plac$ ov] ! top & tapp$2 & %>p5$ by hav+ ! top splay$ by a cone pu%$ 9 po9t d[nw>ds4 ,re$s ( ! /rik+ v>iety 7see ,fig4 #add7 h a tun+-wire press+ on ! tongue ne> ! fix$ end4 ,! end ( ?is wire projects ?r\gh ! cas+4 ,by mov+ x1 ! l5g? ( ! vibrat+ "p ( ! tongue is adju/$ to correctness4 ,,bell[s4 ,diff]5t /ops require diff]5t w9d-pressures1 rang+ f #a_/aj lb4 to #a lb4 to ! squ>e in*1 ! re$s tak+ ! heavie/ pressures4 ,!re mu/ !re=e be z _m sets ( bell[s & w9d-*e/s z !re are diff]5t pressures want$4 ,a v l>ge organ consumes imm5se quantities ( air :5 all ! /ops are out1 & ! pump+ has to be done by a p[]ful gas1 wat]1 or electric eng9e4 ,e bell[s has a res]voir 7see ,fig4 #adc7 above x4 ,! top ( ?is is weight$ to give ! pressure requir$4 ,a valve 9 ! top op5s automatically z soon z ! res]voir has exp&$ to a c]ta9 fix$ limit1 s t !re is no possibility ( bur/+ ! lea!r sides4 ,illu/ration3 ,,fig4 #ade4--,! keybo>d & "p ( ! pneumatic me*anism ( ! ,h]e=d ,ca!dral organ4 ,c1 composition p$als = pu%+ out gr\ps ( /ops2 ,p 7at bottom71 p$als2 ,p ,p 7at top71 pipes c>ry+ compress$ air2 ,m1 manuals 7#d72 ,s ,s1 /ops4 ,,electric ,,& ,,pneumatic ,,actions4 ,we h m5tion$ 9 connection ) railway signall+ t ! signalman is sometimes reliev$ ( ! h>d manual lab\r ( mov+ signals & po9ts by ! employm5t ( electric & pneumatic auxili>ies4 ,! same is true ( organs & organi/s4 ,! t\* ( ! keys has be5 greatly light5$ by mak+ ! keys op5 air-valves or complete electric circuits :i* actuate ! me*anism = pull+ d[n ! pallets4 ,! /ops1 p$als1 & c\pl]s also employ p[]4 ,n only are ! p]=m]'s muscles sp>$ a lot ( heavy "w :5 compress$ air & electricity aid him1 b he is able to h ! console1 or keybo>d1 f> away f ! pipes4 ,f ! console1 ! play]1 sitt+ ) ! s+]s1 or 9 any desirable "p ( ! *oir or *ancel1 w\ld be able to comm& ! work+ ( ! :ole ( ! l>ge/ organ situat$ af> at ! we/]n end ( ! nave2 w\ld draw ea* /op 9 complete reliance on ! slid]s & ! s\nd-bo>d fulfill+ _! (fice2 444 &--m>vel ( x all--! play]1 us+ ! swell p$al 9 8 ord9>y mann]1 w\ld obta9 cresc5do & dim9u5do ) a m p]fect effect ?an by ! old way4#ca ,9 ca!drals x is no uncommon ?+ = ! diff]5t s\nd-bo>ds to be plac$ 9 positions f> ap>t1 s t to ! un9itiat$ !re may appe> to be sev]al indep5d5t organs scatt]$ ab\t4 ,yet all are absolutely "u ! control ( a man :o is sitt+ away f !m all1 b connect$ ) !m by a numb] ( tubes or wires4 ,! l>ge/ organ 9 ! _w is t 9 ! ,t[n ,hall1 ,sydney4 ,x has a hundr$ & tw5ty-six speak+ /ops1 five manuals1 f\rte5 c\pl]s1 & =ty-six comb9ation /uds4 ,! pipes1 ab\t #h1jjj 9 numb]1 range f ! enorm\s #fd-;foot contra-trombone to "s only a fraction ( an in* 9 l5g?4 ,! organ occupies a space #he feet long & #bf feet deep4 ,,human ,,re$s4 ,! mo/ wond]ful ( all musical re$s is f\nd 9 ! human ?roat1 9 ! anatomical "p call$ ! l>ynx1 situat$ at ! top ( ! tra*ea1 or w9dpipe4 ,slip a piece ( rubb] tub+ ov] ! end ( a pipe1 all[+ an in* or s to project4 ,take ! free "p ( ! tube by two opposite po9ts betwe5 ! fir/ f+]s & ?umbs & pull x until ! edges are /ret*$ tight4 ,n[ bl[ ?r\gh x4 ,! w9d1 =c+ its way betwe5 ! two rubb] edges1 causes !m & ! air inside ! tube to vibrate1 & a musical note results4 ,! m y /ra9 ! rubb] ! high] is ! note4 ,! l>ynx works on ?is pr9ciple4 ,! w9dpipe takes ! place ( ! glass pipe2 ! two vocal cords repres5t ! rubb] edges2 & ! aryt5oid muscles /& in/ead ( ! h&s4 ,:5 contract$1 ^! muscles br+ ! edges ( ! cords ne>] to "o ano!r1 /ret* ! cords1 & %ort5 ! cords4 ,a p]son gift$ ) a v good e> c1 x has be5 calculat$1 adju/ ! l5g? ( ! vocal cords to #a_/agjjj? ( an in*6 ,simultane\sly ) ! adju/m5t ( ! cords is effect$ ! adju/m5t ( ! l5g? ( ! w9dpipe1 s t ! column ( air 9 x may be ( ! "r l5g? to vibrate 9 unison4 ,"h aga9 is se5 a wond]ful provision ( nature4 ,! resonance ( ! m\? cavity is also ( great importance4 ,by alt]+ ! %ape ( ! m\? ! v>i\s h>monics ( any fundam5tal note produc$ by ! l>ynx are r5d]$ prom95t1 & s we get ! diff]5t vocal s\nds4 ,helmholtz has %[n t ! fundam5tal tone ( any note is repres5t$ by ! s\nd oo4 ,if ! m\? is adju/$ to br+ out ! octave ( ! fundam5tal1 o results4 a is produc$ by acc5tuat+ ! second h>monic1 ! twelf?2 ee by develop+ ! second & f\r? h>monics2 :ile = ah ! fif? & sev5? mu/ be prom95t4 ,:5 we :i/le we trans=m ! lips into a re$ & ! m\? into a pipe4 ,! t5sion ( ! lips & ! %ape ( ! m\? cavity decide ! note4 ,! lips are also us$ z a re$ = bl[+ ! flute1 piccolo1 & all ! brass b& in/rum5ts ( ! cornet ord]4 ,9 bl[+ a coa*-horn ! v>i\s h>monics ( ! fundam5tal note are br\ght out by alt]+ ! lip t5sion & ! w9d pressure4 ,a cornet is practically a coa*-horn roll$ up into a conv5i5t %ape & furni%$ ) ?ree keys1 ! depression ( :i* puts extra l5g?s ( tub+ 9 connection ) ! ma9 tube--9 fact1 makes x long]4 ,"o key l[]s ! fundam5tal note ( ! horn half a tone2 ! second1 a full tone2 ! ?ird1 a tone & a half4 ,if ! fir/ & ?ird are press$ d[n toge!r1 ! note s9ks two tones2 if ! second & ?ird1 two & a half tones2 & simultane\s depression ( all ?ree gives a drop ( ?ree tones4 ,! p]=m] ?us has sev5 possible fundam5tal notes1 & sev]al h>monics ( ea* ( ^! at 8 comm&2 s t by a prop] manipulation ( ! keys he c run up ! *romatic scale4 ,we %\ld add t ! cornet tube is an op5 pipe4 ,s is t ( ! flute4 ,! cl>ionet is a /opp$ pipe4 #bi ,x is obvi\s t 9 ,fig4 #acf1 #b1 a pulse w pass f ,a to ,b & back 9 "o-?ird ! "t requir$ = x to pass f ,a to ,b & back 9 ,fig4 #acf1 #a4 #cj ,! sci5ce ( he>+2 f ! ,greek v]b1 ,greek3 ak\e91 to he>4 #ca ,organs & ,tun+1 p4 #bde4 ,*apt] ,,xvi4 ,,talk+-,,ma*9es4 ,! phonograph--,! record]--,! reproduc]--,! gramophone--,! mak+ ( records--,cyl9d] records--,gramophone records4 ,9 ! ,pat5t ,(fice ,museum at ,s\? ,k5s+ton is a curi\s little piece ( ma*9]y--a metal cyl9d] m\nt$ on a long axle1 :i* has at "o end a screw ?read *as$ along x4 ,! screw end rotates 9 a socket ) a ?read ( equal pit* cut 9 x4 ,to ! o!r end is atta*$ a h&le4 ,on an upright ne> ! cyl9d] is m\nt$ a sort ( drum4 ,! membrane ( ! drum c>ries a ne$le1 :i*1 :5 ! membrane is agitat$ by ! air-waves set up by human spee*1 digs into a %eet ( t9foil wrapp$ r\nd ! cyl9d]1 press+ x into a helical groove turn$ on ! cyl9d] f end to end4 ,?is con/ruction is ! fir/ phonograph ev] made4 ,?omas ,edison1 ! wiz>d ( ! ,we/1 devis$ x 9 #ahgf2 & f ?is rude p>5t h desc5d$ ! beautiful ma*9es :i* record & reproduce human spee* & musical s\nds ) />tl+ accuracy4 ,illu/ration3 ,,fig4 #adf4--,! gov]nor ( a phonograph4 ,we d n propose to trace "h ! developm5t ( ! talk+-ma*9e2 nor w x be necess>y to describe 9 detail its me*anism1 :i* is probably well kn[n to mo/ read]s1 or c\ld be ma/]$ 9 a v %ort "t on p]sonal exam9ation4 ,we w cont5t ourselves ) say+ t ! wax cyl9d] ( ! phonograph1 or ! ebonite disc ( ! gramophone1 is g5]ally rotat$ by clockwork conceal$ 9 ! body ( ! ma*9e4 ,! spe$ ( rotation has to be v c>efully gov]n$1 9 ord] t ! record may revolve "u ! reproduc+ po9t at a uni=m spe$4 ,! pr9ciple ( ! gov]nor commonly us$ appe>s 9 ,fig4 #adf4 ,! la/ p9ion ( ! clockwork tra9 is m\nt$ on a %aft c>ry+ two triangul> plates1 ,a & ,c1 to :i* are atta*$ ?ree %ort l5g?s ( flat /eel spr+ ) a heavy ball atta*$ to ! c5tre ( ea*4 ,a is fix$2 ,c moves up ! %aft z ! balls fly out1 & pulls ) x ! disc ,d1 :i* rubs aga9/ ! pad ,p 7on ! end ( a spr+7 & sets up suffici5t friction to sl[ ! clockwork4 ,! limit rate is regulat$ by screw ,s4 ,,! ,,phonograph4 ,?\gh ! record+ & reproduc+ app>atus ( a phonograph gives v wond]ful results1 its con/ruction is q simple4 ,at ! same "t1 x mu/ be borne 9 m9d t an imm5se am\nt ( exp]im5t+ has be5 devot$ to f9d+ out ! mo/ suitable mat]ials & =ms = ! p>ts4 ,illu/ration3 ,,fig4 #adg4--,section ( an ,edison ,bell phonograph record]4 ,! record] 7,fig4 #adg7 is a little circul> box ab\t "o & a half in*es 9 diamet]4#cb ,f ! top a tube leads to ! horn4 ,! bottom is a circul> plate1 ,c ,c1 h+$ at "o side4 ,?is plate supports a glass disc1 ,d1 ab\t #a_/aej? ( an in* ?ick1 to :i* is atta*$ ! cutt+ /ylus--a t9y sapphire rod ) a cup-%ap$ end hav+ v %>p edges4 ,s\nd-waves ent] ! box ?r\gh ! horn tube2 b in/ead ( be+ all[$ to fill ! :ole box1 !y are conc5trat$ by ! %ift+ nozzle ,n on to ! c5tre ( ! glass disc ?r\gh ! hole 9 ,c ,c4 ,y w notice t ,n has a ball end1 & ,c ,c a socket to fit ,n exactly1 s t1 ?\gh ,c ,c & ,n move up & d[n v rapidly1 !y /ill make p]fect contact4 ,! disc is vibrat$ by ! s\nd-impulses1 & drives ! cutt+ po9t d[n into ! surface ( ! wax cyl9d]1 turn+ bel[ x 9 a clockwork direction4 ,! only dead weight press+ on ,s is t ( ,n1 ,c ,c1 & ! glass diaphragm4 ,illu/ration3 ,,fig4 #adh4--,p]spective view ( a phonograph record]4 ,z ! cyl9d] revolves1 ! record] is %ift$ cont9u\sly along by a lead+ screw hav+ "o hundr$ or m ?reads to ! in* cut on x1 s t x traces a cont9u\s helical groove f "o end ( ! wax cyl9d] to ! o!r4 ,?is groove is really a s]ies ( v m9ute ind5tations1 n exce$+ #a_/ajjj? ( an in* 9 dep?4#cc ,se5 "u a microscope1 ! surface ( ! record is a succession ( hills & valleys1 "s mu* l>g] ?an o!rs 7,fig4 #aea1 a74 ,a l\d s\nd causes ! /ylus to give a vigor\s dig1 :ile l[ s\nds sc>cely move x at all4 ,! wond]ful ?+ ab\t ?is s\nd-record+ is1 t n only are ! fundam5tal tones ( musical notes impress$1 b also ! h>monics1 :i* enable u to decide at once :e!r ! record is "o ( a cornet1 viol91 or banjo p]=mance4 ,fur!rmore1 if sev]al in/rum5ts are play+ simultane\sly ne> ! record]'s horn1 ! /ylus cat*es all ! diff]5t %ades ( tone ( e note ( a *ord4 ,!re are1 s to speak1 m9or hills & valleys cut 9 ! slopes ( ! ma9 hills & valleys4 ,illu/ration3 ,,fig4 #adi4--,section ( ! reproduc] ( an ,edison ,bell phonograph4 ,illu/ration3 ,,fig4 #aej4--,p]spective view ( a phonograph reproduc]4 ,! reproduc] 7,fig4 #adi7 is some:at m complicat$ ?an ! record]4 ,z be=e1 we h a circul> box communicat+ ) ! horn ( ! in/rum5t4 ,a ?9 glass disc =ms a bottom to ! box4 ,x is held 9 position betwe5 rubb] r+s1 ,r ,r1 by a screw coll>1 ,c4 ,to ! c5tre is atta*$ a little eye1 f :i* hangs a l9k1 ,l4 ,pivot$ at ,p f "o edge ( ! box is a float+ weight1 hav+ a circul> op5+ imm$iately "u ! eye4 ,! l9k passes ?r\gh ?is to ! left end ( a t9y lev]1 :i* rocks on a pivot project+ f ! weight4 ,to ! "r end ( ! lev] is affix$ a sapphire b>1 or /ylus1 ) a ball end ( a diamet] equal to t ( ! cutt+ po9t ( ! record]4 ,! float+ weight presses ! /ylus aga9/ ! record1 & also keeps ! l9k betwe5 ! rock+ lev] ( ! glass diaphragm 9 a /ate ( t5sion4 ,e bl[ giv5 to ! /ylus is !re=e transmitt$ by ! l9k to ! diaphragm1 :i* vibrates & s5ds an air-impulse into ! horn4 ,z ! impulses are giv5 at ! same rate z ^? :i* agitat$ ! diaphragm ( ! record]1 ! s\nds :i* !y repres5t are accurately reproduc$1 ev5 to ! h>monics ( a musical note4 ,,! ,,gramophone4 ,?is effects ! same purpose z ! phonograph1 b 9 a some:at diff]5t mann]4 ,! phonograph record] digs v]tically d[nw>ds into ! surface ( ! record1 :]eas ! /ylus ( ! gramophone wags f side to side & describes a snaky c\rse 7,fig4 #aea;b74 ,x makes no diff]5ce 9 talk+-ma*9es :e!r ! reproduc+ /ylus be mov$ sideways or v]tically by ! record1 provid$ t motion is imp>t$ by x to ! diaphragm4 ,illu/ration3 ,,fig4 #aea;a4 ,illu/ration3 ,,fig4 #aea;b4 ,illu/ration3 ,,fig4 #aea;c4--,section ( a gramophone reproduc]4 ,9 ,fig4 #aea;c ! con/ruction ( ! gramophone reproduc] is %[n 9 section4 ,a is ! cov] :i* screws on to ! bottom ,b1 & conf9es ! diaphragm ,d betwe5 itself & a rubb] r+4 ,! portion ,b is elongat$ into a tubul> %ape = connection ) ! horn1 an arm ( :i* slides ov] ! tube & presses aga9/ ! rubb] r+ ,c to make an air-tight jo9t4 ,! ne$le-c>ri] ,n is atta*$ at its upp] end to ! c5tre ( ! diaphragm4 ,at a po9t indicat$ by ! :ite dot a p9 passes ?r\gh x & ! cov]4 ,! l[] end is tubul> to accommodate ! /eel po9ts1 :i* h to be replac$ aft] pass+ once ov] a record4 ,a screw1 ,s1 work+ 9 a socket project+ f ! c>ri]1 holds ! po9t fa/4 ,! record moves horizontally "u ! po9t 9 a plane p]p5dicul> to ! page4 ,! groove be+ zigzag1 ! ne$le vibrates "r & left1 & rotat+ ! c>ri] a m9ute fraction ( an in* on ! pivot1 %akes ! glass diaphragm & s5ds waves ( air into ! horn4 ,! gramophone is a reproduc+ in/rum5t only4 ,! records are made on a special ma*9e1 fitt$ ) a device = caus+ ! record] po9t to describe a spiral c\rse f ! circumf]5ce to ! c5tre ( ! record disc4 ,"s gramophone records h z _m z #bej turns to ! in*4 ,! total l5g? ( ! trac+ on a t5-in* conc]t record is ab\t #a1jjj feet4 ,,! ,,mak+ ,,( ,,records4 ,= comm]cial purposes x w\ld n pay to make e record sep>ately 9 a record+ ma*9e4 ,! exp5se ( employ+ good s+]s & in/rum5tali/s r5d]s su* a me?od impracticable4 ,all ! records we buy are made f m\lds1 ! prep>ation ( :i* we w n[ briefly describe4 ,,cyl9d]1 ,,or ,,phonograph ,,records4 ,fir/ ( all1 a wax record is made 9 ! ord9>y way on a record+ ma*9e4 ,aft] be+ te/$ & approv$1 x is hung v]tically & c5trally f a rotat+ table pivot$ on a v]tical metal spike pass+ up ?r\gh ! record4 ,on "o side ( ! table is a piece ( iron4 ,on ea* side ( ! record1 & a small di/ance away1 rises a brass rod enclos$ 9 a glass tube4 ,! top ( ! rods are hook$1 s t pieces ( gold leaf may be susp5d$ f !m4 ,a bell-glass is n[ plac$ ov] ! record1 table1 & rods1 & ! air is suck$ out by a pump4 ,z soon z a good vacuum has be5 obta9$1 ! curr5t f ! second>y circuit ( an induction coil is s5t into ! rods support+ ! gold leaves1 :i* are volatiliz$ by ! curr5t jump+ f "o to ! o!r4 ,a magnet1 :irl$ outside ! bell-glass1 draws r\nd ! iron armature on ! pivot$ table1 & consequ5tly revolves ! record1 on ! surface ( :i* a v ?9 coat+ ( gold is deposit$4 ,! record is next plac$ 9 an electroplat+ ba? until a copp] %ell "o-sixte5? ( an in* ?ick has =m$ all ov] ! outside4 ,?is is tru$ up on a la! & encas$ 9 a brass tube4 ,! ma/]1 or orig9al wax record1 is remov$ by cool+ x till x contracts suffici5tly to fall out ( ! copp] m\ld1 on ! inside surface ( :i* are reproduc$1 9 relief1 ! ind5tations ( ! wax ma/]4 ,copies are made f ! m\ld by imm]s+ x 9 a tank ( melt$ wax4 ,! cold metal *ills ! wax t t\*es x1 s t ! m\ld soon has a ?ick wax5 l9+4 ,! m\ld & copy are remov$ f ! tank & m\nt$ on a la!1 :i* %apes & smoo?s ! inside ( ! record4 ,! record is loos5$ f ! m\ld by cool+4 ,aft] inspection = flaws1 x is1 if f\nd satisfactory1 pack$ 9 cotton-wool & add$ to ! saleable /ock4 ,gramophone ma/] records are made on a circul> disc ( z9c1 coat$ ov] ) a v ?9 film ( acid-pro( fat4 ,:5 ! disc is revolv$ 9 ! record+ ma*9e1 ! %>p /ylus cuts ?r\gh ! fat & exposes ! z9c b5ea?4 ,on imm]sion 9 a ba? ( *romic acid ! b>$ surfaces are bitt5 into1 :ile ! unexpos$ p>ts rema9 unaffect$4 ,:5 ! et*+ is consid]$ complete1 ! plate is c>efully clean$ & te/$4 ,a negative copp] copy is made f x by electrotyp+4 ,?is con/itutes ! m\ld4 ,f x z _m z #a1jjj copies may be made on ebonite plates by comb9$ pressure & heat+4 #cb ,! ,edison ,bell phonograph is "h ref]r$ to4 #cc ,"s ( ! sibilant or hiss+ s\nds ( ! voice are comput$ to be repres5t$ by depressions less ?an a million? ( an in* 9 dep?4 ,yet ^! are reproduc$ v cle>ly6 ,*apt] ,,xvii4 ,,:y ,,! ,,w9d ,,bl[s4 ,:y ! w9d bl[s--,l& & sea breezes--,light air & moi/ure--,! b>omet]--,! column b>omet]--,! :eel b>omet]--,a v simple b>omet]--,! an]oid b>omet]--,b>omet]s & wea!r--,! div+-bell--,! div+-dress--,air-pumps--,pneumatic tyres--,! air-gun--,! self-clos+ door-/op--,! action ( w9d on oblique surfaces--,! balloon--,! fly+-ma*9e4 ,:5 a *ild's rubb] ball gets slack ?r\gh a slight leakage ( air1 & loses "s ( its b\nce1 x is a common practice to hold x = a few m9utes 9 front ( ! fire till x becomes tempor>ily taut aga94 ,:y does ! heat h ?is effect on ! ball8 ,no m air has be5 =c$ into ! ball4 ,aft] p]us+ ! *apt] on ! /eam-eng9e ! read] w be able to supply ! answ]4 ,because ! molecules ( air da% ab\t m vigor\sly among "o ano!r :5 ! air is heat$1 & by /rik+ ! inside ( ! ball ) great] =ce put x 9 a /ate ( great] t5sion4 ,if we heat an op5 j> !re is no pressure develop$1 s9ce ! air simply exp&s & fl[s out ( ! neck4 ,b ! air t rema9s 9 ! j>1 be+ less 9 quantity ?an :5 x 0 n yet heat$1 weighs less1 ?\gh occupy+ ! same space z be=e4 ,if we took a v ?9 bladd] & fill$ x ) hot air x w\ld !re=e float 9 cold] air1 prov+ t heat$ air1 z we %\ld expect1 t5ds to rise4 ,! fire-balloon employs ?is pr9ciple1 ! air inside ! bag be+ kept artificially w>m by a fire burn+ 9 "s vessel atta*$ bel[ ! op5 neck ( ! bag4 ,n[1 ! sun %9es ) diff]5t degrees ( heat+ p[] at diff]5t p>ts ( ! _w4 ,:]e its effect is greate/ ! air !re is hotte/4 ,we w suppose1 = ! sake ( argum5t1 t1 at a c]ta9 mom5t1 ! air envelope all r\nd ! globe is ( equal temp]ature4 ,sudd5ly ! sun %9es out & heats ! air at a po9t1 ,a1 till x is _m degrees w>m] ?an ! surr\nd+ air4 ,! heat$ air exp&s1 rises1 & spreads out above ! cold air4 ,b1 z a giv5 dep? ( w>m air has less weight ?an an equal dep? ( cold air1 ! cold air at once beg9s to ru% t[>ds ,b & squeeze ! re/ ( ! w>m air out4 ,we may !re=e picture ! atmosph]e z made up ( a numb] ( cold] curr5ts pass+ along ! surface ( ! e>? to replace w>m curr5ts ris+ & spread+ ov] ! upp] surface ( ! cold air4 ,a simil> circulation takes place 9 a vessel ( heat$ wat] 7see p4 #ag74 ,,l& ,,& ,,sea ,,breezes4 ,a breeze :i* bl[s f ! sea on to ! l& dur+ ! day (t5 rev]ses its direction dur+ ! ev5+4 ,:y is ?is8 ,! e>? gr[s hot or cold m rapidly ?an ! sea4 ,:5 ! sun %9es hotly1 ! l& w>ms quickly & heats ! air ov] x1 :i* becomes light1 & is displac$ by ! cool] air ov] ! sea4 ,:5 ! sun sets1 ! e>? & ! air ov] x lose _! w>m? quickly1 :ile ! sea rema9s at practically ! same temp]ature z be=e4 ,s ! balance is *ang$1 ! heavi] air n[ ly+ ov] ! l&4 ,x !re=e fl[s seaw>ds1 & drives out ! w>m] air !re4 ,,light ,,air ,,& ,,moi/ure4 ,light1 w>m air absorbs moi/ure4 ,z x cools1 ! moi/ure 9 x cond5ses4 ,brea! on a plate1 & y notice t a wat]y film =ms on x at once4 ,! cold surface cond5ses ! wat] susp5d$ 9 ! w>m brea?4 ,if y wi% to dry a damp room y heat x4 ,moi/ure !n passes f ! walls & objects 9 ! room to ! atmosph]e4 ,,! ,,b>omet]4 ,?is prop]ty ( air is responsible = ! *anges 9 wea!r4 ,light1 moi/ure-lad5 air meets cold1 dry air1 & ! sudd5 cool+ =ces x to release its moi/ure1 :i* falls z ra91 or floats ab\t z cl\ds4 ,if only we are able to detect ! pres5ce ( w>m air-/rata above u1 we ought to be 9 a position to =etell ! wea!r4 ,we c judge ( ! specific gravity ( ! air 9 our neighb\rhood by means ( ! b>omet]1 :i* means weight-measur]4 ,! normal air-pressure at sea-level on our bodies or any o!r objects is ab\t #ae lbs4 to ! squ>e in*--t is to say1 if y c\ld imprison & weigh a column ( air "o in* squ>e 9 section & ( ! height ( ! _w's atmosph]ic envelope1 ! scale w\ld regi/] #ae lbs4 ,_m ye>s ago 7#afdc7 ,torricelli1 a pupil ( ,galileo1 fir/ calculat$ ! pressure by a v simple exp]im5t4 ,he took a long glass tube seal$ at "o end1 fill$ x ) m]cury1 &1 clos+ ! op5 end ) ! ?umb1 inv]t$ ! tube & plung$ ! op5 end bel[ ! surface ( a tank ( m]cury4 ,on remov+ 8 ?umb he f\nd t ! m]cury sank 9 ! tube till ! surface ( ! m]cury 9 ! tube 0 ab\t #cj in*es 9 a v]tical direction above ! surface ( ! m]cury 9 ! tank4 ,n[1 z ! upp] end 0 seal$1 !re mu/ be a vacuum above ! m]cury4 ,:at support$ ! column8 ,! atmosph]e4 ,s x 0 evid5t t ! d[nw>d pressure ( ! m]cury exactly c\nt]balanc$ ! upw>d pressure ( ! air4 ,z a m]cury column #cj in*es high & #a in* squ>e weighs #ae lbs41 ! air-pressure on a squ>e in* obvi\sly is ! same4 ,illu/ration3 ,,fig4 #aeb4--;,a ,=t9 b>omet]4 ,,=t9',s ,,column ,,b>omet] is a simple ,torricellian tube1 ,t1 ) ! l[] end subm]g$ 9 a little glass tank ( m]cury 7,fig4 #aeb74 ,! bottom ( ?is tank is made ( wa%lea!r4 ,to obta9 a read+ ! screw ,s1 press+ on ! wa%lea!r1 is adju/$ until ! m]cury 9 ! tank rises to ! tip ( ! little ivory po9t ,p4 ,! read+ is ! figure ( ! scale on ! face ( ! case opposite :i* ! surface ( ! column /&s4 ,illu/ration3 ,,fig4 #aec4 ,,! ,,:eel ,,b>omet] also employs ! m]cury column 7,fig4 #aec74 ,! l[] end ( ! tube is turn$ up & exp&$ to =m a tank1 ,c4 ,! po9t] ,p1 :i* travels r\nd a graduat$ dial1 is m\nt$ on a sp9dle c>ry+ a pulley1 ov] :i* passes a /r+ ) a weight at ea* end4 ,! heavi] ( ! weights re/s on ! top ( ! m]cury4 ,:5 ! atmosph]ic pressure falls1 ! m]cury 9 ,c rises1 lift+ ?is weight1 & ! po9t] moves4 ,?is =m ( b>omet] is n s delicate or reliable z ,=t9's1 or z ! siphon b>omet]1 :i* has a tube ( ! same %ape z ! :eel in/rum5t1 b ( ! same diamet] f end to end except = a contraction at ! b5d4 ,! read+ ( a siphon is ! di/ance betwe5 ! two surfaces ( ! m]cury4 ,a ,,v ,,simple ,,b>omet] is made by knock+ (f ! neck ( a small bottle1 fill+ ! body ) wat]1 & hang+ x up by a /r+ 9 ! position %[n 7,fig4 #aed74 ,:5 ! atmosph]ic pressure falls1 ! wat] at ! orifice bulges outw>ds2 :5 x rises1 ! wat] retreats till its surface is slightly concave4 ,illu/ration3 ,,fig4 #aed4 ,,! ,,an]oid ,,b>omet]4 ,on acc\nt ( _! size & weight1 & ! comp>ative difficulty ( transport+ !m )\t d]angem5t ( ! m]cury column1 column b>omet]s are n s g5]ally us$ z ! an]oid v>iety4 ,an]oid means )\t moi/ure1 & 9 ?is p>ticul> connection signifies t no liquid is us$ 9 ! con/ruction ( ! b>omet]4 ,fig4 #aee %[s an an]oid 9 detail4 ,! mo/ noticeable feature is ! vacuum *amb]1 ,v ,c1 a circul> box :i* has a top & bottom ( corrugat$ b ?9 & ela/ic metal4 ,sections ( ! box are %[n 9 ,figs4 #aef1 #aeg4 ,x is atta*$ at ! bottom to ! base bo>d ( ! in/rum5t by a screw 7,fig4 #aef74 ,f ! top rises a p91 ,p1 ) a transv]se hole ?r\gh x to accommodate ! p9 ,k ,e1 :i* has a triangul> section1 & /&s on "o edge4 ,illu/ration3 ,,fig4 #aee4--;,an an]oid b>omet]4 ,return+ to ,fig4 #aee1 we see t ,p projects ?r\gh ,s1 a p[]ful spr+ ( %eet-/eel4 ,to ?is is atta*$ a long arm1 ,c1 ! free end ( :i* moves a l9k rotat+1 ?r\gh ! p9 ,e1 a sp9dle m\nt$ 9 a frame1 ,d4 ,! sp9dle moves arm ,f4 ,?is pulls on a v m9ute *a9 w\nd r\nd ! po9t] sp9dle ,b1 9 opposition to a hairspr+1 ,h ,s4 ,b is m\nt$ on arm ,h1 :i* is q indep5d5t ( ! re/ ( ! an]oid4 ,illu/ration3 ,,fig4 #aef4 ,,fig4 #aeg4 ,! vacuum *amb] ( an an]oid b>omet] ext5d$ & compress$4 ,! vacuum *amb] is exhau/$ dur+ manufacture & seal$4 ,x w\ld naturally assume ! %ape ( ,fig4 #aeg1 b ! spr+ ,s1 act+ aga9/ ! atmosph]ic pressure1 pulls x out4 ,z ! pressure v>ies1 s does ! spr+ rise or s9k2 & ! slighte/ movem5t is transmitt$ ?r\gh ! multiply+ arms ,c1 ,e1 ,f1 to ! po9t]4 ,a good an]oid is s delicate t x w regi/] ! diff]5ce 9 pressure caus$ by rais+ x f ! floor to ! table1 :]e x has a c\ple ( feet less ( air-column re/+ ^u x4 ,an an]oid is !re=e a valuable help to m\nta9e]s = det]m9+ _! altitude above sea-level4 ,,b>omet]s ,,& ,,wea!r4 ,we may n[ return to ! consid]ation ( =eca/+ ! wea!r by movem5ts ( ! b>omet]4 ,! fir/ ?+ to keep 9 m9d is1 t ! in/rum5t is ess5tially a weight record]4 ,h[ is wea!r connect$ ) atmosph]ic weight8 ,9 ,engl& ! w>m s\?-we/ w9d g5]ally br+s wet wea!r1 ! nor? & ea/ w9ds f9e wea!r2 ! reason = ?is be+ t ! fir/ rea*es u aft] pass+ ov] ! ,atlantic & pick+ up a quantity ( moi/ure1 :ile ! second & ?ird h come ov]l& & deposit$ _! moi/ure be=e rea*+ u4 ,a s9k+ ( ! b>omet] h]alds ! approa* ( heat$ air--t is1 moi/ air--:i* on meet+ cold] air %$s its moi/ure4 ,s :5 ! m]cury falls we expect ra94 ,on ! o!r h&1 :5 ! glass rises1 we "k t cold] air is com+1 & z cold] air comes f a dry qu>t] we anticipate f9e wea!r4 ,x does n foll[ t ! same conditions are f\nd 9 all p>ts ( ! _w4 ,9 regions :i* h ! ocean to ! ea/ or ! nor?1 ! w9ds bl[+ !nce w\ld be ! ra9y w9ds1 :ile s\?-we/]ly w9ds might br+ hot & dry wea!r4 ,,! ,,div+-,,bell4 ,wat] is ne>ly #ggc times z heavy z air4 ,if we subm]ge a b>omet] a v little way bel[ ! surface ( a wat] tank1 we %all at once obs]ve a rise ( ! m]cury column4 ,at a dep? ( #cd feet ! pressure on any subm]g$ object is #ae lbs4 to ! squ>e in*1 9 addition to ! atmosph]ic pressure ( #ae lbs4 p] squ>e in*--t is1 !re w\ld be a #cj-lb4 absolute pressure4 ,z a rule1 :5 speak+ ( hydraulic pressures1 we />t ) ! normal atmosph]ic pressure z z]o1 & we w "h obs]ve ! practice4 ,illu/ration3 ,,fig4 #aeh4--;,a div+ bell4 ,! div+-bell is us$ to enable p to "w "u wat] )\t hav+ rec\rse to ! div+-dress4 ,a sket* ( an ord9>y div+-bell is giv5 9 ,fig4 #aeh4 ,x may be describ$ z a squ>e iron box )\t a bottom4 ,at ! top are l9ks by :i* x is atta*$ to a l[]+ *a91 & w9d[s1 protect$ by grids2 also a nozzle = ! air-tube4 ,illu/ration3 ,,fig4 #aei4 ,a simple model bell 7,fig4 #aei7 is easily made out ( a glass tumbl] :i* has _h a tap fitt$ 9 a hole drill$ ?r\gh ! bottom4 ,we turn (f ! tap & plunge ! glass into a vessel ( wat]4 ,! wat] rises a c]ta9 way up ! int]ior1 until ! air )9 has be5 compress$ to a pressure equal to t ( ! wat] at ! level ( ! surface inside4 ,! fur!r ! tumbl] is l[]$1 ! high] does ! wat] rise inside x4 ,evid5tly m5 c\ld n "w 9 a div+-bell :i* is invad$ ?us by wat]4 ,x is imp]ative to keep ! wat] at bay4 ,?is we c d by atta*+ a tube to ! tap 7,fig4 #afj7 & bl[+ into ! tumbl] till ! air-pressure exce$s t ( ! wat]1 :i* is %[n by bubbles ris+ to ! surface4 ,! div+-bell !re=e has atta*$ to x a hose ?r\gh :i* air is =c$ by pumps f ! atmosph]e above1 at a pressure suffici5t to keep ! wat] out ( ! bell4 ,?is pump+ ( air also ma9ta9s a fre% supply ( oxyg5 = ! work]s4 ,illu/ration3 ,,fig4 #afj4 ,inside ! bell is tackle = grappl+ any object t has to be mov$1 su* z a heavy /one block4 ,! div+-bell is us$ mo/ly = lay+ subm>9e masonry4 ,! bell1 slung ei!r f a crane on ! masonry already built above sea-level1 or f a specially fitt$ b>ge1 comes into action4 ,! block is l[]$ by its own crane on to ! bottom4 ,! bell desc5ds ^u x1 & ! crew seize x ) tackle susp5d$ inside ! bell4 ,in/ructions are s5t up z to ! direction 9 :i* ! bell %\ld be mov$ ) its burd51 & z soon z ! exact spot has be5 rea*$ ! signal = l[]+ is giv51 & ! /one settles on to ! cem5t laid ready = x4#cd ,= _m purposes x is necess>y t ! work] %\ld h m fre$om ( action ?an is possible :5 he is coop$ up inside an iron box4 ,h5ce ! inv5tion ( ! ,,div+-,,dress1 :i* consi/s ( two ma9 p>ts1 ! helmet & ! dress prop]4 ,! helmet 7,fig4 #afa7 is made ( copp]4 ,a brea/plate1 ,b1 %ap$ to fit ! %\ld]s1 has at ! neck a segm5tal screw bayonet-jo9t4 ,! headpiece is fitt$ ) a correspond+ screw1 :i* c be atta*$ or remov$ by "o-eigh? ( a turn4 ,! neck edge ( ! dress1 :i* is made 9 "o piece1 legs1 arms1 body & all1 is atta*$ to ! brea/plate by means ( ! plate ,p#a1 screw$ d[n tightly on x by ! w+-nuts ,n ,n1 ! bolts ( :i* pass ?r\gh ! brea/plate4 ,air ent]s ! helmet ?r\gh a valve situat$ at ! back1 & is l$ ?r\gh tubes along ! inside to ! front4 ,?is valve closes automatically if any accid5t cuts (f ! air supply1 & encloses suffici5t air 9 ! dress to all[ ! div] to rega9 ! surface4 ,! outlet valve ,o ,v c be adju/$ by ! div] to ma9ta9 any pressure4 ,at ! sides ( ! headpiece are two hooks1 ,h1 ov] :i* pass ! cords connect+ ! heavy lead weights ( #dj lbs4 ea* hang+ on ! div]'s brea/ & back4 ,^! weights are also atta*$ to ! knobs ,k ,k4 ,a pair ( boots1 hav+ #ag lbs4 ( lead ea* 9 ! soles1 complete ! dress4 ,?ree glaz$ w9d[s are plac$ 9 ! headpiece1 t 9 ! front1 ,r ,w1 be+ removable1 s t ! div] may ga9 free access to ! air :5 he is above wat] )\t be+ oblig$ to take (f ! helmet4 ,illu/ration3 ,,fig4 #afa4--;,a div]'s helmet4 ,by means ( telephone wires built into ! life-l9e 7:i* passes "u ! div]'s arms & is us$ = l[]+ & hoi/+7 easy communication is e/abli%$ betwe5 ! div] & 8 att5dants above4 ,! transmitt] ( ! telephone is plac$ inside ! helmet betwe5 ! front & a side w9d[1 ! receiv] & ! button ( an electric bell 9 ! cr[n4 ,?is la/ he c press by rais+ 8 head4 ,! life-l9e sometimes also includes ! wires = an electric lamp 7,fig4 #afb7 us$ by ! div] at dep?s to :i* daylight _c p5etrate4 ,! pressure on a div]'s body increases 9 ! ratio ( #d-a_/c lbs4 p] squ>e in* = e #aj feet t he desc5ds4 ,! ord9>y work+ limit is ab\t #aej feet1 ?\gh old h&s are able to /& great] pressures4 ,! record is held by "o ,james ,hoop]1 :o1 :5 remov+ ! c>go ( ! ,cape ,horn sunk (f ! ,s\? ,am]ican coa/1 made sev5 desc5ts ( #bja feet1 "o ( :i* la/$ = =ty-two m9utes4 ,illu/ration3 ,,fig4 #afb4--;,div]'s electric lamp4 ,a sket* is giv5 7,fig4 #afc7 ( div]s work+ bel[ wat] ) pneumatic tools1 f$ f above ) high-pressure air4 ,ow+ to 8 buoyancy a div] has little depress+ or pu%+ p[]1 & he _c bore a hole 9 a po/ ) an aug] unless he is able to re/ 8 back aga9/ "s firm object1 or is rop$ to ! po/4 ,pneumatic *ipp+ tools m]ely require hold+ to _! "w1 _! weight (f]+ suffici5t resi/ance to ! v rapid bl[s :i* !y make4 ,illu/ration3 ,,fig4 #afc4--;,div]s at "w bel[ wat] ) pneumatic tools4 ,,air-,,pumps4 ,illu/ration3 ,,fig4 #afd4 ,illu/ration3 ,,fig4 #afe4 ,m5tion hav+ be5 made ( ! air-pump1 we app5d diagrams 7,figs4 #afd1 #afe7 ( ! simple/ =m ( air-pump1 ! cycle tyre inflator4 ,! pi/on is compos$ ( two circul> plates ( small] diamet] ?an ! b>rel1 hold+ betwe5 !m a cup lea!r4 ,dur+ ! up/roke ! cup collapses inw>ds & all[s air to pass by x4 ,on ! d[n/roke 7,fig4 #afe7 ! edges ( ! cup exp& aga9/ ! b>rel1 prev5t+ ! passage ( air r\nd ! pi/on4 ,a d\ble-action air-pump requires a long1 well-fitt+ pi/on ) a cup on ea* side ( x1 & ! addition ( extra valves to ! b>rel1 z ! cups "u ^! circum/ances _c act z valves4 ,,pneumatic ,,tyres4 ,illu/ration3 ,,fig4 #aff4 ,illu/ration3 ,,fig4 #afg4 ,! action ( ! pneumatic tyre 9 r$uc+ vibration & increas+ ! spe$ ( a vehicle is expla9$ by ,figs4 #aff1 #afg4 ,:5 ! tyre enc\nt]s an ob/acle1 su* z a l>ge /one1 x laps ov] x 7,fig4 #aff71 & :ile support+ ! weight on ! :eel1 r$uces ! deflection ( ! direction ( movem5t4 ,:5 an iron-tyr$ :eel meets a simil> ob/acle x has to rise "r ov] x1 (t5 jump+ a consid]able di/ance into ! air4 ,! resultant motions ( ! :eel are indicat$ 9 ea* case by an arr[4 ,e *ange ( direction means a loss ( =w>d velocity1 ! loss increas+ ) ! viol5ce & ext5t ( ! *ange4 ,! pneumatic tyre also scores because1 on acc\nt ( its ela/icity1 x gives a kick (f aga9/ ! ob/acle1 :i* comp5sates = ! resi/ance dur+ compression4 ,illu/ration3 ,,fig4 #afh4--,section ( ! me*anism ( an air-gun4 ,,! ,,air-,,gun4 ,?is may be describ$ z a valveless air-pump4 ,fig4 #afh is a section ( a ,gem air-gun1 ) ! me*anism set ready = fir+4 ,9 ! /ock ( ! gun is ! cyl9d]1 9 :i* an accurately fitt+ & holl[ pi/on moves4 ,a p[]ful helical spr+1 turn$ out ( a solid b> ( /eel1 is compress$ betwe5 ! inside end ( ! pi/on & ! upp] end ( ! butt4 ,to set ! gun1 ! cat* is press$ d[n s t its hook$ end dis5gages f ! /ock1 & ! b>rel is b5t d[nw>ds on pivot ,p4 ,?is slides ! l[] end ( ! compress+ lev] t[>ds ! butt1 & a projection on ! guide ,b1 work+ 9 a groove1 takes ! pi/on ) x4 ,:5 ! spr+ has be5 fully compress$1 ! triangul> tip ( ! rock+ cam ,r engages ) a groove 9 ! pi/on's head1 & prev5ts recoil :5 ! b>rel is return$ to its orig9al position4 ,on pull+ ! trigg]1 ! pi/on is releas$ & flies up ! cyl9d] ) great =ce1 & ! air 9 ! cyl9d] is compress$ & driv5 ?r\gh ! bore ( ! b>rel1 block$ by ! lead5 slug1 to :i* ! :ole en]gy ( ! exp&+ spr+ is transmitt$ ?r\gh ! ela/ic m$ium ( ! air4 ,!re are sev]al o!r good types ( air-gun1 all ( :i* employ ! pr9ciples describ$ above4 ,,! ,,self-,,clos+ ,,door-,,/op is ano!r int]e/+ pneumatic device4 ,x consi/s ( a cyl9d] ) an air-tight pi/on1 & a pi/on rod work+ ?r\gh a cov] at "o end4 ,! o!r end ( ! cyl9d] is pivot$ to ! door frame4 ,:5 ! door is op5$ ! pi/on compresses a spr+ 9 ! cyl9d]1 & air is admitt$ pa/ a cup lea!r on ! pi/on to ! upp] "p ( ! cyl9d]4 ,?is air is conf9$ by ! cup lea!r :5 ! door is releas$1 & escapes sl[ly ?r\gh a leak1 all[+ ! spr+ to rega9 its %ape sl[ly1 & by ! ag5cy ( ! pi/on rod to close ! door4 ,,! ,,action ,,( ,,w9d ,,on ,,oblique ,,surfaces4 ,:y does a kite rise8 ,:y does a boat sail across ! w9d8 ,we c supply an answ] almo/ in/9ctively 9 bo? cases1 ,because ! w9d pu%es ! kite or sail aside4 ,x w1 h[ev]1 be wor? :ile to look = a m sci5tific answ]4 ,! kite _c travel 9 ! direction ( ! w9d because x is conf9$ by a /r+4 ,b ! face is s atta*$ to ! /r+ t x incl9es at an angle to ! direction ( ! w9d4 ,n[1 :5 a =ce meets an incl9$ surface :i* x _c c>ry along ) x1 b :i* is free to travel 9 ano!r direction1 ! =ce may be reg>d$ z resolv+ itself into two =ces1 com+ f ea* side ( ! orig9al l9e4 ,^! are call$ ! compon5t =ces4 ,illu/ration3 ,,fig4 #afi4 ,to expla9 ?is we give a simple sket* ( a kite 9 ! act ( fly+ 7,fig4 #afi74 ,! w9d is bl[+ 9 ! direction ( ! solid arr[ ,a4 ,! oblique surface ( ! kite resolves its =ce into ! two compon5ts indicat$ by ! dott$ arr[s ,b & ,c4 ,( ^! ,c only has lift+ p[] to ov]come ! =ce ( gravity4 ,! kite assumes a position 9 :i* =ce ,c & gravity c\nt]balance "o ano!r4 ,illu/ration3 ,,fig4 #agj4 ,a boat sail+ across ! w9d is act$ on 9 a simil> mann] 7,fig4 #agj74 ,! w9d /rikes ! sail obliquely1 & w\ld ?ru/ x to leew>d 7 x n = ! opposition ( ! wat]4 ,! =ce ,a is resolv$ into =ces ,b & ,c1 ( :i* ,c propels ! boat on ! l9e ( its axis4 ,! boat c be made to sail ev5 up ! w9d1 h] head be+ br\ght r\nd until a po9t is rea*$ at :i* ! =ce ,b on ! boat1 ma/s1 etc41 ov]comes ! =ce ,c4 ,! capability ( a boat = sail+ up w9d dep5ds on h] l9es & ! am\nt ( surface %e (f]s to ! w9d4 ,,! ,,balloon is a pe>-%ap$ bag--usually made ( silk--fill$ ) "s gas light] ?an air4 ,! t5d5cy ( a heavi] m$ium to displace a light] drives ! gas upw>ds1 & ) x ! bag & ! wick]-"w c> atta*$ to a network encas+ ! bag4 ,! tap]+ neck at ! l[] end is op51 to p]mit ! free escape ( gas z ! atmosph]ic pressure outside dim9i%es ) increas+ elevation4 ,at ! top ( ! bag is a wood5 valve op5+ inw>ds1 :i* c be drawn d[n by a rope pass+ up to x ?r\gh ! neck :5ev] ! a]onaut wi%es to let gas escape = a desc5t4 ,he is able to cause a v rapid escape by pull+ ano!r cord dep5d+ f a ripp+ piece ne> ! top ( ! bag4 ,9 case ( em]g5cy ?is is torn away bodily1 leav+ a l>ge hole4 ,! balla/ 7usually s&7 c>ri$ enables him to ma9ta9 a /ate ( equilibrium betwe5 ! upw>d pull ( ! gas & ! d[nw>d pull ( gravity4 ,to s9k he lets out gas1 to rise he ?r[s out balla/2 & ?is process c be repeat$ until ! balla/ is exhau/$4 ,! greate/ height ev] atta9$ by a]onauts is ! #g-a_/d miles1 or #cg1jjj feet1 ( ,messrs4 ,glai%] & ,coxwell on ,septemb] #e1 #ahfb4 ,! asc5t ne>ly co/ !m _! lives1 = at an elevation ( ab\t #cj1jjj feet !y 7 p>tly p>alyz$ by ! r>efaction ( ! air1 & _h n ,mr4 ,coxwell be5 able to pull ! valve rope ) 8 tee? & cause a desc5t1 bo? w\ld h di$ f want ( air4 ,illu/ration3 ,,fig4 #aga4 ,! fly+-ma*9e1 :i* sci5tific eng9e]s h s long be5 try+ to produce1 w probably be q indep5d5t ( balloons1 & w dep5d = its asc5sive p[]s on ! action ( air on oblique surfaces4 ,sir ,hiram ,maxim's exp]im5tal air-%ip embodi$ ! pr9ciples %[n by ,fig4 #aga4 ,on a deck 0 m\nt$ an eng9e1 ,e1 extremely p[]ful = its weight4 ,?is drove l>ge propell]s1 ,s ,s4 ,l>ge a]oplanes1 ( canvas /ret*$ ov] light frameworks1 7 set up ov]head1 ! =w>d end some:at high] ?an ! re>4 ,! ma*9e 0 run on rails s arrang$ z to prev5t x ris+4 ,un=tunately an accid5t happ5$ at ! fir/ trial & de/roy$ ! ma*9e4 ,9 actual flight x w\ld be necess>y to h a v]tical rudd] = alt]+ ! horizontal direction1 & a horizontal tail = /e]+ up or d[n4 ,! pr9ciple ( an a]oplane is t ( ! kite1 ) ?is diff]5ce1 t1 in/ead ( mov+ air /rik+ a captive body1 a mov+ body is propell$ aga9/ m or less /ation>y air4 ,! resolution ( =ces is %[n by ! arr[s z be=e4 ,up to ! pres5t "t no practical fly+-ma*9e has appe>$4 ,b exp]im5t]s are h>d at "w exam9+ ! conditions :i* mu/ be fulfill$ to enable man to claim ! dom9ion ( ! air4 #cd ,! ,romance ( ,mod]n ,me*anism1 p4 #bdc ,*apt] ,,xviii4 ,,hydraulic ,,ma*9]y4 ,! siphon--,! bucket pump--,! =ce-pump--,! mo/ m>vell\s pump--,! blood *annels--,! c\rse ( ! blood--,! hydraulic press--,h\sehold wat]-supply fitt+s--,! ball-cock--,! wat]-met]--,wat]-supply sy/ems--,! h\sehold filt]--,gas traps--,wat] eng9es--,! cream sep>ator--,! hydro4 ,9 ! la/ *apt] we saw t ! pressure ( ! atmosph]e is #ae lbs4 to ! squ>e in*4 ,suppose t to a v long tube hav+ a sectional area ( "o squ>e in* we fit an air-tight pi/on 7,fig4 #agb71 & place ! l[] end ( ! tube 9 a vessel ( wat]4 ,on rais+ ! pi/on a vacuum w\ld be creat$ 9 ! tube1 did n ! pressure ( ! atmosph]e =ce wat] up into ! tube beh9d ! pi/on4 ,! wat] w\ld cont9ue to rise until x rea*$ a po9t #cd feet p]p5dicul>ly above ! level ( ! wat] 9 ! vessel4 ,! column w\ld !n weigh #ae lbs41 & exactly c\nt]balance ! atmosph]ic pressure2 s t a fur!r rais+ ( ! pi/on w\ld n raise ! wat] any f>!r4 ,at sea-level1 !re=e1 ! lift+ p[] ( a pump by suction is limit$ to #cd feet4 ,on ! top ( a l(ty m\nta91 :]e ! air-pressure is less1 ! height ( ! column w\ld be dim9i%$--9 fact1 be proportional to ! pressure4 ,illu/ration3 ,,fig4 #agb4 ,illu/ration3 ,,fig4 #agc4 ,,! ,,siphon is an int]e/+ application ( ! pr9ciple ( suction4 ,by its own weight wat] may be made to lift wat] ?r\gh a height n exce$+ #cd feet4 ,?is is expla9$ by ,fig4 #agc4 ,! siphon pipe1 ,a ,b ,c ,d1 is 9 ! fir/ in/ance fill$ by suction4 ,! weight ( ! wat] betwe5 ,a & ,b c\nt]-balances t betwe5 ,b & ,c4 ,b ! column ,c ,d hangs1 z x 71 to ! heels ( ,b ,c1 & draws x d[n4 ,or1 to put x o!rwise1 ! column ,b ,d1 be+ heavi] ?an ! column ,b ,a1 draws x ov] ! topmo/ po9t ( ! siphon4 ,any p>t+ betwe5 ! columns1 provid$ t ,b ,a does n exce$ #cd feet1 is impossible1 z ! pressure ( ! atmosph]e on ! m\? ( ,b ,a is suffici5t to prev5t ! =mation ( a vacuum4 ,,! ,,bucket ,,pump4 ,we may n[ pass to ! commone/ =m ( pump us$ 9 h\ses1 /ables1 g>d5s1 etc4 7,fig4 #agd74 ,! pi/on has a l>ge hole ?r\gh x1 ov] ! top ( :i* a valve is h+$4 ,at ! bottom ( ! b>rel is a second valve1 also op5+ upw>ds1 seat$ on ! top ( ! supply pipe4 ,9 sket* 7a7 ! fir/ up/roke is 9 progress4 ,a vacuum =ms "u ! pi/on1 or plung]1 & wat] rises up ! b>rel to fill x4 ,! next diagram 7b7 %[s ! fir/ d[n/roke4 ,! plung] valve n[ op5s & all[s wat] to rise above ! pi/on1 :ile ! l[] closes "u ! pressure ( ! wat] above & ! pull ( t bel[4 ,dur+ ! second up/roke 7c7 ! wat] above ! pi/on is rais$ until x ov]fl[s ?r\gh ! sp\t1 :ile a fre% supply is be+ suck$ 9 bel[4 ,illu/ration3 ,,fig4 #agd4 ,,! ,,=ce-,,pump4 ,illu/ration3 ,,fig4 #age4 ,=ce-pump2 suction /roke4 ,illu/ration3 ,,fig4 #agf4 ,=ce-pump2 deliv]y /roke4 ,= driv+ wat] to levels above t ( ! pump a some:at diff]5t arrangem5t is requir$4 ,"o type ( =ce-pump is %[n 9 ,figs4 #age1 #agf4 ,! pi/on n[ is solid1 & ! upp] valve is situat$ 9 ! deliv]y pipe4 ,dur+ an up/roke ?is closes1 & ! o!r op5s2 ! rev]se happ5+ dur+ a d[n/roke4 ,an air-*amb] is g5]ally fitt$ to ! deliv]y pipe :5 wat] is to be lift$ to great heights or "u high pressure4 ,at ea* deliv]y /roke ! air 9 ! *amb] is compress$1 absorb+ "s ( ! %ock giv5 to ! wat] 9 ! pipe by ! wat] com+ f ! pump2 & its expansion dur+ ! next suction /roke =ces ! wat] gradually up ! pipe4 ,! air-*amb] is a v prom95t feature ( ! fire-eng9e4 ,a d\ble-action =ce-pump is se5 9 ,fig4 #agg1 mak+ an upw>d /roke4 ,bo? sides ( ! pi/on are "h utiliz$1 & ! pi/on rod works ?r\gh a wat]-tight /uff+-box4 ,! action ( ! pump w be easily und]/ood f ! diagram4 ,illu/ration3 ,,fig4 #agg4 ,,! ,,mo/ ,,m>vell\s ,,pump kn[n is ! he>t4 ,we give 9 ,fig4 #agh a diagrammatic sket* ( ! sy/em ( blood circulation 9 ! human body1 %[+ ! he>t1 ! art]ies1 & ! ve9s1 big & little4 ,! body is suppos$ to be fac+ ! read]1 s t ! left lung1 etc41 is to 8 "r4 ,illu/ration3 ,,fig4 #agh4--;,a diagrammatic repres5tation ( ! circulatory sy/em ( ! blood4 ,! he>t1 :i* =ces ! blood ?r\gh ! body1 is a l>ge muscle 7( ab\t ! size ( ! cl5*$ fi/7 ) f\r cavities4 ,^! are respectively kn[n z ! "r & left auricles1 & ! "r & left v5tricles4 ,!y are arrang$ 9 two pairs1 ! auricle upp]mo/1 sep>at$ by a fle%y p>tition4 ,betwe5 ea* auricle & its v5tricle is a valve1 :i* consi/s ( /rong membran\s flaps1 ) loose edges turn$ d[nw>ds4 ,! left-side valve is ! mitral valve1 t betwe5 ! "r auricle & v5tricle ! tricuspid valve4 ,! edges ( ! valves fall toge!r :5 ! he>t contracts1 & prev5t ! passage ( blood4 ,ea* v5tricle has a second valve ?r\gh :i* x ejects ! blood4 7,t ( ! "r v5tricle has be5 %[n d\ble = ! sake ( conv5i5ce47 ,! action ( ! he>t is ?is3--,! auricles & v5tricles exp&2 blood ru%es into ! auricles f ! *annels supply+ !m1 & di/5ds !m & ! v5tricles2 ! auricles contract & fill ! v5tricles bel[ q full 7!re are no valves above ! auricles1 b ! =ce ( contraction is n suffici5t to return ! blood to ! ve9s72 ! v5tricles contract2 ! mitral & tricuspid valves close2 ! valves lead+ to ! art]ies op52 blood is =c$ out ( ! v5tricles4 ,,! ,,blood ,,*annels are ( two k9ds--7#a7 ,! art]ies1 :i* lead ! blood into ! circulatory sy/em2 7#b7 ! ve9s1 :i* lead ! blood back to ! he>t4 ,! art]ies divide up into bran*es1 & ^! aga9 divide into small] & small] art]ies4 ,! smalle/1 t]m$ capill>ies 7,lat91 capillus1 a hair71 are m9ute tubes hav+ an av]age diamet] ( #a_/cjjj? ( an in*4 ,^! p]meate e "p ( ! body4 ,! capill>y art]ies lead into ! smalle/ ve9s1 :i* unite to =m l>g] & l>g] ve9s1 until :at we may call ! ma9 /reams are rea*$4 ,?r\gh ^! ! blood fl[s to ! he>t4 ,!re are ?ree ma9 po9ts ( diff]5ce betwe5 art]ies & ve9s4 ,9 ! fir/ place1 ! l>g] art]ies h ?ick ela/ic walls1 & ma9ta9 _! %ape ev5 :5 empty4 ,?is ela/icity p]=ms ! function ( ! air-*amb] ( ! =ce-pump4 ,:5 ! v5tricles contract1 driv+ blood into ! art]ies1 ! walls ( ! latt] exp&1 & _! contraction pu%es ! blood /eadily =w>d )\t %ock4 ,! capill>ies h v ?9 walls1 s t fluids pass ?r\gh !m to & f ! body1 fe$+ x & tak+ out wa/e matt]4 ,! ve9s are all ?9-wall$1 & collapse :5 empty4 ,secondly1 mo/ ve9s are furni%$ ) valves1 :i* prev5t blood fl[+ ! wrong way4 ,^! are simil> 9 pr9ciple to ^? ( ! he>t4 ,art]ies h no valves4 ,?irdly1 art]ies are g5]ally deeply set1 :ile _m ( ! ve9s run ne> ! surface ( ! body4 ,^? on ! front ( ! arm are specially visible4 ,place y\r ?umb on !m & run x along t[>ds ! wri/1 & y w notice t ! ve9s di/5d ow+ to ! clos+ ( ! valves j m5tion$4 ,art]ial blood is r$1 & comes out f a cut 9 gulps1 on acc\nt ( ! contraction ( ! ela/ic walls4 ,if y cut a ve91 blue blood issues 9 a /eady /ream4 ,! *ange ( col\r is caus$ by ! loss ( oxyg5 dur+ ! passage ( ! blood ?r\gh ! capill>ies1 & ! absorption ( c>bon dioxide f ! tissues4 ,! lungs are two ( ! great purifi]s ( ! blood4 ,z x circulates ?r\gh !m1 x gives up ! c>bon dioxide :i* x has absorb$1 & receives pure oxyg5 9 ex*ange4 ,if ! air ( a room is f\l1 ! blood does n get ! prop] am\nt ( oxyg54 ,= ?is reason x is advisable = u to keep ! w9d[s ( our rooms op5 z mu* z possible bo? day & night4 ,fatigue is caus$ by ! accumulation ( c>bon dioxide & o!r impurities 9 ! blood4 ,:5 we run1 ! he>t pumps blood ?r\gh ! lungs fa/] ?an !y c purify x1 & ev5tually our muscles become poison$ to su* an ext5t t we h to /op f %e] exhau/ion4 ,,! ,,c\rse ,,( ,,! ,,blood4 ,x takes r less ?an a m9ute = a drop ( blood to circulate f ! he>t ?r\gh ! :ole sy/em & back to ! he>t4 ,we may briefly summ>ize ! c\rse ( ! circulation ( ! blood ?us3--,x is expell$ f ! left v5tricle into ! aorta & ! ma9 art]ies1 :5ce x passes into ! small] art]ies1 & !nce into ! capill>ies ( ! bra91 /oma*1 kidneys1 etc4 ,x "h imp>ts oxyg5 to ! body1 & takes 9 impurities4 ,x !n ent]s ! ve9s1 & ?r\gh !m fl[s back to ! "r auricle2 is driv5 into ! "r v5tricle2 is expell$ into ! pulmon>y 7lung7 art]ies2 ent]s ! lungs1 & is purifi$4 ,x returns to ! left auricle ?r\gh ! pulmon>y ve9s2 ent]s ! left auricle1 passes to left v5tricle1 & s on4 ,a heal?y he>t beats f #abj times p] m9ute 9 a "o-ye>-old infant to #fj p] m9ute 9 a v ag$ p]son4 ,! normal rate = a middle-ag$ adult is f #hj to #gj beats4 ,he>t disease signifies ! failure ( ! he>t valves to close prop]ly4 ,blood passes back :5 ! he>t contracts1 & ! circulation is mu* enfeebl$4 ,by li/5+ ?r\gh a /e?oscope ! doctor is able to tell :e!r ! valves are 9 good ord]4 ,a hiss+ s\nd dur+ ! beat indicates a leakage pa/ ! valves2 a ?ump1 or clack1 t !y %ut completely4 ,,! ,,hydraulic ,,press4 ,x is a *>act]i/ic ( fluids & gases t if pressure be br\ght to be> on any "p ( a mass ( ei!r class ( bodies x is transmitt$ equally & undim9i%$ 9 all directions1 & acts ) ! same =ce on all equal surfaces1 at "r angles to ^? surfaces4 ,! great natural philosoph] ,pascal fir/ =mulat$ ?is rem>kable fact1 ( :i* a simple illu/ration is giv5 9 ,fig4 #agi4 ,two cyl9d]s1 ,a & ,b1 hav+ a bore ( "o & two in*es respectively1 are connect$ by a pipe4 ,wat] is p\r$ 91 & pi/ons fitt+ ! cyl9d]s accurately & ( equal weight are ins]t$4 ,on pi/on ,b is plac$ a load ( #aj lbs4 ,to prev5t ,a ris+ above ! level ( ,b1 x mu/ be load$ proportionately4 ,! area ( pi/on ,a is f\r times t ( ,b1 s t if we lay on x a #dj-lb4 weight1 nei!r pi/on w move4 ,! walls ( ! cyl9d]s & connect+ pipe are also press$ outw>ds 9 ! ratio ( #aj lbs4 = e "p ( _! int]ior surface :i* has an area equal to t ( pi/on ,b4 ,illu/ration3 ,,fig4 #agi4 ,illu/ration3 ,,fig4 #ahj4--,! cyl9d] & ram ( a hydraulic press4 ,! hydraulic press is an application ( ?is law4 ,cyl9d] ,b is repres5t$ by a =ce pump ( small bore1 capable ( deliv]+ wat] at v high pressures 7up to #aj tons p] squ>e in*74 ,9 ! place ( ,a we h a /\t cyl9d] ) a solid plung]1 ,p 7,fig4 #ahj71 c>ry+ ! table on :i* ! object to be press$ is plac$4 ,bramah1 ! inv5tor ( ! hydraulic press1 exp]i5c$ great difficulty 9 prev5t+ ! escape ( wat] betwe5 ! top ( ! cyl9d] & ! plung]4 ,if a gl& pack+ ( ! type f\nd 9 /eam-cyl9d]s 7 us$1 x fail$ to hold back ! wat] unless x 7 screw$ d[n s tightly z to jam ! plung]4 ,he tri$ all k9ds ( exp$i5ts )\t success2 & 8 inv5tion1 excell5t ?\gh x 0 9 pr9ciple1 seem$ doom$ to failure1 :5 8 =eman1 ,h5ry ,maudslay1#ce solv$ ! problem 9 a simple b mo/ ma/]ly mann]4 ,he _h a recess turn$ 9 ! neck ( ! cyl9d] at ! po9t =m]ly occupi$ by ! /uff+-box1 & into ?is a lea!r coll> ( ,u-section 7m>k$ solid black 9 ,fig4 #ahj7 0 plac$ ) its op5 side d[nw>ds4 ,:5 wat] rea*$ x1 x =c$ ! edges ap>t1 "o aga9/ ! plung]1 ! o!r aga9/ ! walls ( ! recess1 ) a degree ( tightness proportionate to ! pressure4 ,on wat] be+ releas$ f ! cyl9d] ! coll> collaps$1 all[+ ! plung] to s9k )\t friction4 ,! pr9ciple ( ! hydraulic press is employ$ 9 lifts2 9 ma*9es = b5d+1 drill+1 & rivet+ /eel plates1 or =c+ :eels on or (f _! axles2 = advanc+ ! bor+ %ield ( a tunnel2 & = o!r purposes too num]\s to m5tion4 ,,h\sehold ,,wat]-,,supply ,,fitt+s4 ,among ^!1 ! mo/ us$ is ! tap1 or cock4 ,:5 a h\se is s]v$ by ! t[n or di/rict wat] supply1 ! fitt+ ( prop] taps on all pipes connect$ ) ! supply is /ipulat$ = by ! wat]-works au?orities4 ,! old-fa%ion$ plug tap is unsuitable = controll+ high-pressure wat] on acc\nt ( ! sudd5ness ) :i* x *ecks ! fl[4 ,le/ ! read] %\ld h d\bts z to ! nature ( a plug tap1 we may add t x has a tap]+ cone ( metal work+ 9 a tap]+ socket4 ,on ! cone be+ turn$ till a hole ?r\gh x is br\ght into l9e ) ! *annel ( ! tap1 wat] passes4 ,a qu>t] turn closes ! tap4 ,illu/ration3 ,,fig4 #aha4--;,a screw-d[n wat] cock4 ,its place has be5 tak5 by ! screw-d[n cock4 ,a v common & effective patt]n is %[n 9 ,fig4 #aha4 ,! valve ,v1 ) a fac+ ( rubb]1 lea!r1 or "s o!r suffici5tly ela/ic sub/ance1 is atta*$ to a p91 ,c1 :i* projects upw>ds into ! sp9dle ,a ( ! tap4 ,?is sp9dle has a screw ?read on x engag+ ) a coll>1 ,b4 ,:5 ! sp9dle is turn$ x rises or falls1 all[+ ! valve to leave its seat+1 ,v ,s1 or =c+ x d[n on to x4 ,a pack+ ,p 9 ! neck ( ,b prev5ts ! passage ( wat] r\nd ! sp9dle4 ,to op5 or close ! tap completely is a matt] ( sev]al turns1 :i* _c be made fa/ en\gh to produce a wat]-hamm] 9 ! pipes by sudd5ly arre/+ ! fl[4 ,! read] w easily und]/& t if wat] fl[+ at ! rate ( sev]al miles an h\r is abruptly *eck$1 ! %ock to ! pipes c>ry+ x mu/ be v sev]e4 ,,! ,,ball-,,cock is us$ to fe$ a ci/]n automatically ) wat]1 & prev5t ! wat] ris+ too f> 9 ! ci/]n 7,fig4 #ahb74 ,wat] ent]s ! ci/]n ?r\gh a valve1 :i* is op5$ & clos$ by a plug fac$ ) rubb]4 ,! l[] extremity ( ! plug is flatt5$1 & has a rectangul> hole cut 9 x4 ,?r\gh ?is passes a lev]1 ,l1 atta*$ at "o end to a holl[ copp] sph]e1 & pivot$ at ! o!r on ! valve cas+4 ,?is cas+ is n q circul> 9 section1 = two slots are ca/ 9 ! circumf]5ce to all[ wat] to pass r\nd ! plug freely :5 ! valve is op54 ,! buoyancy ( ! copp] sph]e is suffici5t to =ce ! plug's face up t[>ds its seat+ z ! valve rises1 & to cut (f ! supply entirely :5 a c]ta9 level has be5 atta9$4 ,if wat] is drawn (f1 ! sph]e s9ks1 ! valve op5s1 & ! loss is made good4 ,illu/ration3 ,,fig4 #ahb4--;,an automatic ball-valve4 ,,! ,,wat]-,,met]4 ,illu/ration3 ,,fig4 #ahc4 ,"s consum]s pay a sum qu>t]ly = ! privilege ( a wat] supply1 & ! wat] company all[s !m to use z mu* z !y require4 ,o!rs1 h[ev]1 pref] to pay a fix$ am\nt = e ?\s& gallons us$4 ,9 su* cases1 a wat]-met] is requir$ to record ! consumption4 ,we app5d a sectional diagram ( ,k5n$y's pat5t wat]-met] 7,fig4 #ahc71 v widely us$4 ,at ! bottom is ! measur+ cyl9d]1 fitt$ ) a pi/on1 7#f71 :i* is made to move p]fectly wat]-tight & free f friction by means ( a cyl9drical r+ ( india-rubb]1 roll+ betwe5 ! body ( ! pi/on & ! int]nal surface ( ! cyl9d]4 ,! pi/on rod 7#be71 aft] pass+ ?r\gh a /uff+-box 9 ! cyl9d] cov]1 is atta*$ to a rack1 7#ae71 :i* ge>s ) a cog1 7#ac71 fix$ on a %aft4 ,z ! pi/on moves up & d[n1 ?is cog is turn$ fir/ 9 "o direction1 !n 9 ! o!r4 ,to ?is %aft is connect$ ! index me*anism 7to ! "r74 ,! cock-key 7#bd7 is s con/ruct$ t x c put ei!r end ( ! measur+ cyl9d] 9 communication ) ! supply or deliv]y pipes1 if giv5 a qu>t] turn 7see ,fig4 #ahd74 ,! weight$ lev] 7#ad7 moves loosely on ! p9ion %aft ?r\gh "p ( a circle4 ,f ! p9ion project two arms1 "o on ea* side ( ! lev]4 ,:5 ! lev] has be5 lift$ by "o ( ^! pa/ ! v]tical position1 x falls by its own weight on to a buff]-box re/1 7#ah74 ,9 do+ s1 x /rikes a projection on ! duplex lev] 7#ai71 :i* is jo9$ to ! cock-key1 & gives ! latt] a qu>t] turn4 ,9 ord] to foll[ ! work+ ( ! met]1 we mu/ keep an eye on ,figs4 #ahc & #ahd simultane\sly4 ,wat] is ent]+ f ,a1 ! supply pipe4 ,x fl[s ?r\gh ! cock d[nw>ds ?r\gh *annel ,d into ! l[] half ( ! cyl9d]4 ,! pi/on rises1 driv+ out ! wat] above x ?r\gh ,c to ! deliv]y pipe ,b4 ,j z ! pi/on completes its /roke ! weight1 rais$ by ! rack & p9ion1 topples ov]1 & /rikes ! key-arm1 :i* x s5ds d[n till /opp$ by ! buff]-box4 ,! tap is !n at "r angles to ! position %[n 9 ,fig4 #ahd1 & wat] is direct$ f ,a d[n ,c into ! top ( ! cyl9d]1 =c+ ! pi/on d[n1 :ile ! wat] admitt$ bel[ dur+ ! la/ /roke is =c$ up ! passage ,d1 & out by ! outlet ,b4 ,be=e ! pi/on has arriv$ at ! bottom ( ! cyl9d]1 ! lift] w h lift$ ! weight$ lev] f ! buff]-box1 & rais$ x to a v]tical position2 f !re x w h fall5 on ! "r-h& key-arm1 & h br\ght ! cock-key to its =m] position1 ready to beg9 ano!r upw>d /roke4 ,illu/ration3 ,,fig4 #ahd4 ,! index me*anism makes all[ance = ! fact t ! bevel-:eel on ! p9ion %aft has its direction rev]s$ at ! beg9n+ ( e /roke ( ! pi/on4 ,?is bevel engages ) two o!rs m\nt$ loosely on ! little %aft1 on :i* is turn$ a screw ?read to revolve ! index c\nt] :eels4 ,ea* ( ^! latt] bevels actuates ! %aft ?r\gh a rat*et2 b :ile "o turns ! %aft :5 rotat+ 9 a clockwise direction only1 ! o!r engages x :5 mak+ an anti-clockwise revolution4 ,! result is t ! %aft is always turn$ 9 ! same direction4 ,,wat]-,,supply ,,sy/ems4 ,! wat] = a t[n or a di/rict supply is got ei!r f wells or f a riv]4 ,9 ! =m] case x may be assum$ to be free f impurities4 ,9 ! latt]1 !re is ne$ = remov+ all ! objectionable & dang]\s matt] :i* riv] wat] always conta9s 9 a great] or less degree4 ,?is purification is accompli%$ by fir/ lead+ ! wat] into l>ge settl+ tanks1 :]e ! susp5d$ matt] s9ks to ! bottom4 ,! wat] is !n drawn (f into filtration b$s1 made 9 ! foll[+ mann]4 ,! bottom is cov]$ ) a ?ick lay] ( concrete4 ,on ?is are laid p>allel r[s ( bricks1 ! r[s a small di/ance ap>t4 ,!n come a lay] ( bricks or tiles plac$ close toge!r2 a lay] ( co>se gravel2 a lay] ( f9] gravel2 & a ?ick lay] ( s& at ! top4 ,! s& arre/s any solid matt] 9 ! wat] z x p]colates to ! gravel & dra9s bel[4 ,ev5 ! microbes1#cf ( microscopic size1 are arre/$ z soon z ! film ( mud has =m$ on ! top ( ! s&4 ,until ?is film is =m$ ! filt] is n 9 its mo/ effici5t condition4 ,e n[ & !n ! b$ is dra9$1 ! surface mud & s& c>efully dra9$ (f1 & fre% s& put 9 _! place4 ,a good filt] b$ %\ld n pass m ?an f two to ?ree gallons p] h\r = e squ>e foot ( surface1 & x mu/ !re=e h a l>ge area4 ,x is sometimes necess>y to s5d ! wat] ?r\gh a succession ( b$s1 arrang$ 9 t]races1 be=e x is suffici5tly pure = dr9k+ purposes4 ,,! ,,h\sehold ,,filt]4 ,:5 !re is any d\bt z to ! :olesom5ess ( ! wat] supply1 a small filt] is (t5 us$4 ,! microbe-/opp] is usually ei!r *>coal1 s&1 asbe/os1 or bak$ clay ( "s k9d4 ,9 ,fig4 #ahe we give a section ( a ,maign5 filt]4 ,r is ! res]voir = ! filt]$ wat]2 ,a ! filt] case prop]2 ,d a conical p]=at$ frame2 ,b a jacket ( asbe/os clo? secur$ top & bottom by asbe/os cords to ,d2 ,c p[d]$ c>bon1 betwe5 :i* & ! asbe/os is a lay] ( special *emical filt]+ m$ium4 ,a p]=at$ cap1 ,e1 cov]s 9 ! c>bon & prev5ts x be+ di/urb$ :5 wat] is p\r$ 94 ,! c>bon arre/s ! co>s] =ms ( matt]2 ! asbe/os ! f9]4 ,! asbe/os jacket is easily remov$ & cleans$ by heat+ ov] a fire4 ,illu/ration3 ,,fig4 #ahe4 ,! mo/ useful =m ( h\sehold filt] is "o :i* c be atta*$ to a tap connect$ ) ! ma94 ,su* a filt] is usually made ( porcela9 or biscuit *9a4 ,! ,b]kefeld filt] has an out] case ( iron1 & an int]ior holl[ c&le ( porcela9 f :i* a tube passes ?r\gh ! lid ( ! filt] to a /orage tank = ! filt]$ wat]4 ,! wat] f ! ma9 ent]s ! out] case1 & p]colates ?r\gh ! porcela9 walls to ! int]nal cavity & !nce fl[s away ?r\gh ! deliv]y pipe4 ,:atev] be ! type ( filt] us$ x mu/ be cleans$ at prop] int]vals4 ,a f\l filt] is v dang]\s to ^? :o dr9k ! wat] f x4 ,x has be5 prov$ by te/s t1 s f> f purify+ ! wat]1 an ineffici5t & contam9at$ filt] passes out wat] mu* m highly *>g$ ) microbes ?an x 0 be=e x ent]$4 ,we mu/ n !re=e ?9k t1 because wat] has be5 filt]$1 x is necess>ily safe4 ,! rev]se is only too (t5 ! case4 ,,gas ,,traps4 ,dang]\s microbes c be brea!d z well z drunk into ! human sy/em4 ,e communication betwe5 h\se & dra9s %\ld be mo/ c>efully trapp$4 ,! pr9ciple ( a gas trap betwe51 say1 a kit*5 s9k & ! dra9 to c>ry (f ! wat] is giv5 9 ,fig4 #ahf4 ,en\gh wat] always rema9s 9 ! b5d to rise above ! level ( ! elb[1 effectually keep+ back any gas t !re may be 9 ! pipe beyond ! b5d4 ,illu/ration3 ,,fig4 #ahf4--;,a trap = f\l air4 ,,wat]-,,eng9es4 ,be=e ! inv5tion ( ! /eam-eng9e human indu/ries 7 l>gely dep5d5t on ! motive p[] ( ! w9d & runn+ wat]4 ,b :5 ! infant nurs$ by ,watt & ,/eph5son _h gr[n into a giant1 bo? ( ^! natural ag5ts 7 depos$ f ! important position !y once held4 ,w9dmills 9 a /ate ( decay cr[n _m ( our hilltops1 & ! wat]-:eel :i* =m]ly br\ght weal? to ! mill] n[ rots 9 its m\nt+s at ! end ( ! dam4 ,except = pump+ & mov+ boats & %ips1 w9d-p[] f9ds its occupation gone4 ,x is too unc]ta9 9 quantity & quality to f9d a place 9 mod]n economics4 ,wat]-p[]1 on ! o!r h&1 has receiv$ a fre% lease ( life ?r\gh ! inv5tion ( ma*9]y s sci5tifically design$ z to use mu* m ( ! wat]'s en]gy ?an 0 possible ) ! old-fa%ion$ :eel4 ,illu/ration3 ,,fig4 #ahg4--;,a ,pelton :eel :i* develops #e1jjj horse-p[]4 ,obs]ve ! %ape ( ! d\ble buckets4 ,! turb9e1 ( :i* we h already spok5 9 our ?ird *apt]1 is n[ ! fav\rite hydraulic eng9e4 ,"s wat]-turb9es "w on mu* ! same pr9ciple z ! ,p>sons /eam-turb9e2 o!rs resemble ! ,de ,laval4 ,among ! latt] ! ,pelton :eel takes ! fir/ place4 ,by ! c\rtesy ( ! manufactur]s we are able to give "s int]e/+ details & illu/rations ( ?is device4 ,illu/ration3 ,,fig4 #ahh4--,pelton :eel m\nt$1 ) nozzle 9 position4 ,! :eel1 :i* may be ( any diamet] f six in*es to t5 feet1 has buckets set at regul> int]vals r\nd ! circumf]5ce1 /ick+ outw>ds4 ,ea* bucket1 z w be ga!r$ f our illu/ration ( an enorm\s #e1jjj h4p4 :eel 7,fig4 #ahg71 is compos$ ( two cups4 ,a nozzle is s arrang$ z to direct wat] on ! buckets j z !y rea* ! l[e/ po9t ( a revolution 7see ,fig4 #ahh74 ,! wat] /rikes ! bucket on ! p>tition betwe5 ! two cups1 :i* turns x "r & left r\nd ! inside ( ! cups4 ,! *ange ( direction transf]s ! en]gy ( ! wat] to ! :eel4 ,illu/ration3 ,,fig4 #ahi4--,spe$ regulator = ,pelton :eel4 ,! spe$ ( ! :eel may be automatically regulat$ by a deflect+ nozzle 7,fig4 #ahi71 :i* has a ball & socket jo9t to p]mit ( its be+ rais$ or l[]$ by a c5trifugal gov]nor1 ?us ?r[+ ! /ream on or (f ! buckets4 ,! p[] ( ! :eel is consequ5tly increas$ or dim9i%$ to meet ! *ange ( load1 & a con/ant spe$ is ma9ta9$4 ,:5 x is necess>y to wa/e z little wat] z possible1 a conc5tric tap]$ ne$le may be fitt$ inside ! nozzle4 ,:5 ! nozzle is 9 its highe/ position ! ne$le tip is )drawn2 z ! nozzle s9ks ! ne$le protrudes1 gradually decreas+ ! dis*>ge area ( ! nozzle4 ,pelton :eels are design$ to run at all spe$s & to use wat] ( any pressure4 ,at ,manit\1 ,colorado1 is an in/allation ( ?ree :eels op]at$ by wat] :i* leaves ! nozzle at ! enorm\s pressure ( #ice lbs4 p] squ>e in*4 ,x is int]e/+ to note t jets ( v high-pressure wat] (f] a/oni%+ resi/ance to any attempt to deflect _! c\rse4 ,a ?ree-in* jet ( #ejj-lb4 wat] _c be cut ?r\gh by a bl[ f a cr[b>4 ,9 ord] to get suffici5t pressure = work+ hydraulic ma*9]y 9 m9es1 factories1 etc41 wat] is (t5 l$ = _m miles 9 flumes1 or artificial *annels1 along ! sides ( valleys f ! s\rce ( supply to ! po9t at :i* x is to be us$4 ,by ! "t t po9t is rea*$ ! diff]5ce betwe5 ! gradi5ts ( ! flume & ( ! valley bottom has produc$ a diff]5ce 9 height ( "s hundr$s ( feet4 ,illu/ration3 ,,fig4 #aij4--,! ,laxey wat]-:eel1 ,isle ( ,man4 ,9 ! top "r-h& corn] is a ,pelton :eel ( proportionate size requir$ to d ! same am\nt ( "w ) ! same consumption ( wat] at ! same pressure4 ,! full-page illu/ration on p4 #chj af=ds a /rik+ te/imony to ! wond]ful progress made 9 eng9e]+ practice dur+ ! la/ fifty ye>s4 ,! huge wat]-:eel :i* =ms ! bulk ( ! picture is t at ,laxey1 9 ! ,isle ( ,man4 ,x is #gb-a_/b feet 9 diamet]1 & is suppos$ to develop #aej horse-p[]1 :i* is transmitt$ sev]al hundr$s ( feet by means ( wood5 rods support$ at regul> int]vals4 ,! p[] ?us transmitt$ op]ates a sy/em ( pumps 9 a lead m9e1 rais+ #bej gallons ( wat] p] m9ute1 to an elevation ( #a1bjj feet4 ,! driv+ wat] is br\ght "s di/ance to ! :eel 9 an und]gr\nd conduit1 & is c>ri$ up ! masonry t[] by pressure1 fl[+ ov] ! top into ! buckets on ! circumf]5ce ( ! :eel4 ,! little cut 9 ! upp] corn] repres5ts a ,pelton :eel drawn on ! same scale1 :i*1 giv5 an equal supply ( wat] at ! same pressure1 w\ld develop ! same p[] z ! ,laxey mon/]4 ,by ! side ( ! giant ! o!r appe>s a m]e toy4 ,,! ,,cream ,,sep>ator4 ,9 #ahfd ,d5m>k w5t to w> ) ,g]many1 & em]g$ f ! %ort /ruggle %orn ( ! prov9ces ( ,lau5burg1 ,hol/e91 & ,s*leswig4 ,! loss ( ! two la/1 ! faire/ & mo/ f]tile di/ricts ( ! k+dom1 0 inde$ griev\s4 ,! ,dani% k+ n[ rul$ only ov] a l& consi/+ l>gely ( moor1 m>%1 & dunes1 app>5tly wor?less = any purpose4 ,b ! ,danes1 ) admirable c\rage1 ent]$ ^u a second /ruggle1 ?is "t ) nature4 ,!y made roads & railways1 dug irrigation dit*es1 & plant$ =e/ trees2 & s gradually turn$ l>ge tracts ( :at _h be5 useless c\ntry into valuable possessions4 ,agriculture be+ mu* depress$1 ow+ to ! l[ price ( corn1 !y next gave _! att5tion to ! improvem5t ( dairy f>m+4 ,lab\r-sav+ ma*9]y ( all k9ds 0 introduc$1 none m important ?an ! device = sep>at+ ! fatty f ! wat]y con/itu5ts ( milk4 ,x w\ld n be too mu* to say t ! sep>ator is l>gely responsible = ! pres5t prosp]ity ( ,d5m>k4 ,illu/ration3 ,,fig4 #aia4--,section ( a ,cream ,sep>ator4 ,h[ does x "w8 asks ! read]4 ,c5trifugal =ce#cg is ! gov]n+ pr9ciple4 ,to expla9 its application we app5d a sectional illu/ration 7,fig4 #aia7 ( ,messrs4 ,burmei/] & ,wa9's h&-p[] sep>ator1 :i* may be tak5 z g5]ally repres5tative ( ?is class ( ma*9es4 ,inside a circul> cas+ is a cyl9drical b[l1 ,d1 m\nt$ on a %aft :i* c be revolv$ #e1jjj times a m9ute by means ( ! cog-:eels & ! screw ?read *as$ on x ne> ! bottom extremity4 ,milk fl[s f ! res]voir ,r 7support$ on a /\t arm7 ?r\gh tap ,a into a little di/ribut] on ! top ( ! sep>ator1 & f x drops into ! c5tral tube ,c ( ! b[l4 ,fall+ to ! bottom1 x is flung outw>ds by c5trifugal =ce1 f9ds an escape upw>ds ?r\gh ! holes a a1 & climbs up ! p]=at$ grid e1 ! surface ( :i* is a s]ies ( pyramidical excresc5ces1 & f9ally rea*es ! inn] surface ( ! drum prop]4 ,! velocity ( rotation is s trem5d\s t ! heavi] portions ( ! milk--t is1 ! wat]y--cr[d t[>ds ! po9t fur!/ f ! c5tre1 & keep ! light] fatty elem5ts away f contact ) ! sides ( ! drum4 ,9 ! diagram ! wat] is repres5t$ by small circles1 ! cream by small crosses4 ,z m milk ent]s ! drum x =ces upw>ds :at is already !re4 ,! cap ( ! drum has an inn] jacket1 ,f1 :i* at ! bottom all b t\*es ! side ( ! drum4 ,! di/ance betwe5 !m is ! m]e/ slit2 b ! cream is deflect$ up outside ,f into space ,e1 & escapes ?r\gh a hole "o-sixte5? ( an in* 9 diamet] p]=at+ ! plate ,g4 ,! cream is flung into space ,k & trickles out ( sp\t ,b1 :ile ! wat] flies into space ,h & trickles away ?r\gh sp\t ,a4 ,,! ,,hydro41 us$ 9 laundries = wr++ clo!s by c5trifugal =ce1 has a solid out] cas+ & an inn] p]=at$ cyl9drical cage1 revolv$ at high spe$ by a v]tical %aft4 ,! wet clo!s are plac$ 9 ! cage1 & ! ma*9e is />t$4 ,! wat] escapes ?r\gh ! p]=ations & runs d[n ! side ( ! cas+ to a dra94 ,aft] a few m9utes ! clo!s are dry en\gh = iron+4 ,s great is ! c5trifugal =ce t !y are consolidat$ aga9/ ! sides ( ! cage1 & c>e is ne$$ 9 _! removal4 #ce ,inv5tor ( ! la! slide-re/4 #cf ,liv+ g]ms2 "s v>ieties ! cause ( disease4 #cg ,t is1 c5tre-flee+ =ce4 ,wat] dropp$ on a sp9n+ top ru%es t[>ds ! circumf]5ce & is %ot (f at "r angles to a l9e drawn f ! po9t ( p>t+ to ! c5tre ( ! top4 ,*apt] ,,xix4 ,,heat+ ,,& ,,light+4 ,! hot-wat] supply--,! tank sy/em--,! cyl9d] sy/em--,h[ a lamp works--,gas & gasworks--,automatic /ok+--,a gas gov]nor--,! gas met]--,inc&esc5t gas light+4 ,,hot-,,wat] ,,supply4 ,a well-equipp$ h\se is n[adays expect$ to conta9 effici5t app>atus = supply+ pl5ty ( hot wat] at all h\rs ( ! day4 ,!re is little romance ab\t ! kit*5 boil] & ! pipes :i* ! plumb] & 8 satellites h sometimes to inspect & put "r1 b ! me?ods ( secur+ a prop] circulation ( hot wat] ?r\gh ! h\se are suffici5tly important & int]e/+ to be notic$ 9 ^! pages4 ,9 h\ses ( mod]ate size ! kit*5 range does ! heat+4 ,! two sy/ems ( /or+ & di/ribut+ ! heat$ wat] mo/ commonly us$ are--7#a7 ,! tank sy/em2 7#b7 ! cyl9d] sy/em4 ,,! ,,tank ,,sy/em is %[n diagrammatically 9 ,fig4 #aib4 ,! boil] is situat$ at ! back ( ! range1 & :5 a damp] is drawn ! fire & hot gases pass "u x to a flue lead+ to ! *imney4 ,! almo/ boil+ wat] rises to ! top ( ! boil] & !nce f9ds its way up ! fl[ pipe into ! hot-wat] tank ,a1 displac+ ! some:at cold] wat] !re1 :i* desc5ds ?r\gh ! return pipe to ! bottom ( ! boil]4 ,wat] is drawn (f f ! fl[ pipe4 ,?is pipe projects "s di/ance ?r\gh ! bottom ( ,a1 s t ! hotte/ portion ( ! cont5ts may be drawn (f fir/4 ,a tank situat$ 9 ! ro(1 & f$ f ! ma9 by a ball-cock valve1 communicates ) ,a ?r\gh ! siphon pipe ,s4 ,! b5d 9 ?is pipe prev5ts ! asc5t ( hot wat]1 :i* _c s9k ?r\gh wat] cold] ?an itself4 ,f ! top ( ,a an expansion pipe is l$ up & turn$ ov] ! cold-wat] tank to dis*>ge any /eam :i* may be g5]at$ 9 ! boil]4 ,a hot-wat] radiator = w>m+ ! h\se may be connect$ to ! fl[ & return pipes z %[n4 ,s9ce x op5s a %ort circuit = ! circulation1 ! wat] 9 ! tank above w n be s well heat$ :ile x is 9 action4 ,if cocks are fitt$ to ! radiator pipes1 ! am\nt ( heat ?us deflect$ c be gov]n$4 ,illu/ration3 ,,fig4 #aib4--,! tank sy/em ( hot-wat] supply4 ,a disadvantage ( ! tank sy/em is t ! tank1 if plac$ high en\gh to supply all fl[s1 is sometimes s f> f ! boil] t ! wat] loses mu* ( its heat 9 ! c\rse ( circulation4 ,also1 if = any reason ! cold wat] fails1 tank ,a may be entirely empti$1 circulation cease1 & ! wat] 9 ! boil] & pipes boil away rapidly4 ,,! ,,cyl9d] ,,sy/em 7,fig4 #aic7 is op5 to nei!r ( ^! objections4 ,in/ead ( a rectangul> tank up al(t1 we n[ h a l>ge copp] cyl9d] situat$ 9 ! kit*5 ne> ! range4 ,! fl[ & return pipes are cont9u\s1 & ! cold supply ent]s ! bottom ( ! cyl9d] ?r\gh a pipe ) a siphon b5d 9 x4 ,z be=e1 wat] is drawn (f f ! fl[ pipe1 & a radiator may be put 9 ! circuit4 ,s9ce !re is no draw-(f po9t bel[ ! top ( ! cyl9d]1 ev5 if ! cold supply fails ! cyl9d] w rema9 full1 & ! failure w be discov]$ long be=e !re is any dang] ( ! wat] 9 x boil+ away4 ,illu/ration3 ,,fig4 #aic4--,! cyl9d] sy/em ( hot-wat] supply4 ,boil] explosions are due to ob/ructions 9 ! pipes4 ,if ! expansion pipe & ! cold-wat] supply pipe freeze1 !re is dang] ( a slight accumulation ( /eam2 & if "o ( ! circulation pipes is also block$1 /eam mu/ g5]ate until some?+ has to g1#ch :i* is naturally ! boil]4 ,assum+ t ! pipes are q full to ! po9ts ( ob/ruction1 ! fracture w\ld result f ! expansion ( ! wat]4 ,/eam _c g5]ate unless !re be a space above ! wat]4 ,b ! exp&+ wat] has /or$ up ! heat :i* w\ld h rais$ /eam1 & ! mom5t expansion beg9s aft] fracture ?is en]gy is sudd5ly let loose4 ,/eam =ms in/antane\sly1 augm5t+ ! effects ( ! explosion4 ,f ?is x w be ga!r$ t all pipes %\ld be prop]ly protect$ aga9/ fro/2 especially ne> ! ro(4 ,ano!r cause ( disa/] is ! furr+ up ( ! pipes ) ! lime deposit$ by h>d wat] :5 heat$4 ,:5 h>d wat] is us$1 ! pipes w soon] or lat] be block$ ne> ! boil]2 & z ! deposit is too h>d to be scrap$ away1 p]iodical r5ewals are unavoidable4 ,,h[ ,a ,,lamp ,,works4 ,f heat+ we turn to light+1 & fir/ to ! ord9>y p>aff9 lamp4 ,! two *ief ?+s to notice ab\t ?is are ! wick & ! *imney4 ,! wick1 be+ made ( closely-wov5 cotton1 draws up ! oil by :at is kn[n z capill>y attraction4 ,if y dip ! ends ( two glass tubes1 "o half an in*1 ! o!r "o-eigh? ( an in* 9 diamet]1 into a vessel ( wat]1 y w notice t ! wat] rises high] 9 ! small] tube4 ,or get two clean glass plates & lay !m face to face1 t\*+ at "o end1 b kept slightly ap>t at ! o!r by "s small object4 ,if !y are p>tly subm]g$ p]p5dicul>ly1 ! wat] w rise betwe5 ! plates--fur!/ on ! side at :i* ! two plates t\*1 & less & less z ! o!r edge is approa*$4 ,! t5d5cy ( liquids to rise ?r\gh por\s bodies is a ph5om5on = :i* we _c acc\nt4 ,m9]al oil conta9s a l>ge proportion ( c>bon & hydrog52 x is !re=e t]m$ hydro-c>bon4 ,:5 oil rea*es ! top ( a light$ wick1 ! liquid is heat$ until x turns into gas4 ,! c>bon & hydrog5 unite ) ! oxyg5 ( ! air4 ,"s p>ticles ( ! c>bon app>5tly d n comb9e at once1 & z !y pass ?r\gh ! fi]y zone ( ! flame are heat$ to su* a temp]ature z to become highly lum9\s4 ,x is to produce ^! light-rays t we use a lamp1 & to burn our oil effici5tly we mu/ supply ! flame ) pl5ty ( oxyg51 ) m ?an x c\ld naturally obta94 ,s we surr\nd x ) a transp>5t *imney ( special glass4 ,! air inside ! *imney is heat$1 & rises2 fre% air ru%es 9 at ! bottom1 & is also heat$ & replac$4 ,z ! air passes ?r\gh1 ! flame seizes on ! oxyg54 ,if ! wick is turn$ up until ! flame becomes smoky & fl>es1 ! po9t has be5 pass$ at :i* ! induc$ *imney draught c supply suffici5t oxyg5 to comb9e ) ! c>bon ( ! vap\r1 & ! free c>bon escapes z smoke4 ,! bl[]-plate us$ to draw up a fire 7,fig4 #aid7 p]=ms exactly ! same function z ! lamp *imney1 b on a l>g] scale4 ,! plate prev5ts air pass+ /raight up ! *imney ov] ! coals1 & compels x to f9d a way ?r\gh ! fire itself to replace ! heat$ air ris+ up ! *imney4 ,illu/ration3 ,,fig4 #aid4--,%[+ h[ a bl[]-plate draws up ! fire4 ,,gas ,,& ,,gasworks4 ,a lamp is an app>atus = conv]t+ hydro-c>bon m9]al oil into gas & burn+ x effici5tly4 ,! gas-jet burns gases produc$ by driv+ (f hydro-c>bon vap\rs f coal 9 app>atus specially design$ = ! purpose4 ,gas-mak+ is n[1 9 spite ( ! competition ( electric light+1 s important an indu/ry t we %all d well to glance at ! processes :i* x includes4 ,coal gas may be produc$ on a v small scale z foll[s3--,fill a t9 cani/] 7! jo9ts ( :i* h be5 made by fold+ ! metal1 n by sold]+7 ) coal1 clap on ! lid1 & place x1 lid d[nw>ds1 9 a bright fire1 aft] pun*+ a hole 9 ! bottom4 ,vap\r soon beg9s to issue f ! hole4 ,?is is probably at fir/ only /eam1 due to ! coal be+ m or less damp4 ,b if a light$ mat* be pres5tly appli$ ! vap\r takes fire1 %[+ t coal gas prop] is com+ (f4 ,! flame la/s = a long "t4 ,:5 x dies ! cani/] may be remov$ & ! cont5ts exam9$4 ,mo/ ( ! c>bon rema9s 9 ! =m ( coke4 ,x is bulk = bulk mu* light] ?an coal1 = ! hydrog51 oxyg51 & o!r gases1 & "s ( ! c>bon h be5 driv5 (f by ! heat4 ,! coke itself burns if plac$ 9 a fire1 b )\t any smoke1 su* z issues f coal4 ,illu/ration3 ,,fig4 #aie4--,sket* ( ! app>atus us$ 9 ! manufacture ( coal gas4 ,our home-made gas yields a smoky & unsatisfactory flame1 ow+ to ! pres5ce ( c]ta9 impurities--ammonia1 t>1 sulphurett$ hydrog51 & c>bon bisulphide4 ,a gas factory mu/ be equipp$ ) means ( gett+ rid ( ^! objectionable con/itu5ts4 ,turn+ to ,fig4 #aie1 :i* displays v diagrammatically ! ma9 features ( a gas plant1 we obs]ve at ! extreme "r ! retorts1 :i* correspond to our cani/]4 ,^! are usually long fire-brick tubes ( ,d-section1 ! flat side at ! bottom4 ,"u ea* is a furnace1 ! flames ( :i* play on ! bottom1 sides1 & inn] end ( ! retort4 ,! out] end project+ beyond ! brickwork seat+ has an iron air-tight door = fill+ ! retort ?r\gh1 imm$iately beh9d :i* rises an iron exit pipe1 ,a1 = ! gases4 ,t>1 :i* vaporizes at high temp]atures1 b liquefies at ord9>y atmosph]ic heat1 mu/ fir/ be got rid (4 ,?is is effect$ by pass+ ! gas ?r\gh ! hydraulic ma91 a tubul> vessel half full ( wat] runn+ ! :ole l5g? ( ! retorts4 ,! end ( pipe ,a dips bel[ ! surface ( ! wat]1 :i* cond5ses mo/ ( ! t> & /eam4 ,! p>tly-purifi$ gas n[ passes ?r\gh pipe ,b to ! cond5s]s1 a s]ies ( inv]t$ ,u-pipes /&+ on an iron *e/ ) v]tical cross divisions betwe5 ! m\?s ( ea* ,u4 ,^! divisions dip into wat]1 s t ! gas has to pass up "o leg ( a ,u1 d[n ! o!r1 up ! fir/ leg ( ! second pipe1 & s on1 till all traces ( ! t> & o!r liquid con/itu5ts h cond5s$ on ! inside ( ! pipe1 f :i* !y drop into ! tank bel[4 ,! next /age is ! passage ( ! scrubb]1 fill$ ) coke ov] :i* wat] p]petually fl[s4 ,! ammonia gas is "h absorb$4 ,!re /ill rema9 ! sulphurett$ hydrog5 & ! c>bon bisulphide1 bo? ( :i* are extremely (f5sive to ! no/rils4 ,slak$ lime1 laid on trays 9 an air-tight comp>tm5t call$ ! lime purifi]1 absorbs mo/ ( ! sulphur\s elem5ts ( ^!2 & ! coal gas is !n fit = use4 ,on leav+ ! purifi]s x fl[s into ! gasomet]1 or ga%old]1 ! huge cake-l =m ( :i* is a v famili> object 9 ! environs ( t[ns4 ,! gasomet] is a cyl9drical box ) a dom$ top1 b no bottom1 built ( rivet$ /eel plates4 ,x /&s 9 a circul> tank ( wat]1 s t x may rise & fall )\t any escape ( gas4 ,! levity ( ! gas1 9 conjunction ) weights atta*$ to ! ends ( *a9s work+ ov] pulleys on ! framework surr\nd+ ! hold]1 suffices to raise ! hold]4 ,illu/ration3 ,,fig4 #aif4--,! l>ge/ ga%old] 9 ! _w3 ,s\? ,metropolitan ,gas ,co41 ,gre5wi* ,gas ,works4 ,capacity1 #ab1aeh1fjj cubic feet4 ,"s gasomet]s h an enorm\s capacity4 ,! record is at pres5t held by t built = ! ,s\? ,metropolitan ,gas ,co41 ,london1 by ,messrs4 ,clayton ,son ( ,le$s4 ,?is mon/] 7( :i* we app5d an illu/ration1 ,fig4 #aif7 is #cjj feet 9 diamet] & #ahj feet high4 ,:5 fully ext5d$ x holds #ab1aeh1fjj cubic feet ( gas4 ,ow+ to its imm5se size1 x is built on ! telescopic pr9ciple 9 six lifts1 ( #cj feet deep ea*4 ,! sides ( ea* lift1 or r+1 except ! topmo/1 h a section %ap$ some:at l ! lett] ,n4 ,two ( ! memb]s =m a deep1 n>r[ cup to hold wat]1 9 :i* ! dip memb] ( ! r+ above x rises & falls4 ,illu/ration3 ,,fig4 #aig4--;,draw+ retorts4 7,photo by ,f4 ,m>%47 ,,automatic ,,/ok+4 ,! lab\r ( fe$+ ! retorts ) coal & remov+ ! coke is exce$+ly sev]e4 ,9 ! illu/ration on p4 #djj 7made f a v f9e photograph tak5 by ,mr4 ,f4 ,m>% ( ,clifton7 we see a man engag$ 9 draw+ ! retorts ?r\gh ! iron doors at _! out] ends4 ,automatic ma*9]y is n[ us$ 9 l>ge gasworks = bo? op]ations4 ,"o ( ! mo/ +5i\s /ok]s is ! ,de ,br\w]1 %[n at "w 9 ,fig4 #aih4 ,! ma*9e is susp5d$ f an ov]head trolley runn+ on rails along ! face ( ! retorts4 ,coal falls into a funnel at ! top ( ! telescopic pipe ,p f hopp]s 9 ! /ory above1 :i* h op5+s1 ,h ,h1 controll$ by %utt]s4 ,! coal z x falls is caught by a rubb] belt work+ r\nd "p ( ! circumf]5ce ( ! l>ge :eel ,w & a numb] ( pulleys1 & is %ot into ! m\? ( ! retort4 ,! op]ator is se5 pull+ ! h&le :i* op5s ! %utt] ( ! hopp] above ! fe$-tube1 & swit*+ on ! #d h4p4 electric motor :i* drives ! belt & moves ! ma*9e ab\t4 ,"o ( ^! fe$]s w *>ge a retort #bj feet long 9 tw5ty-two seconds4 ,illu/ration3 ,,fig4 #aih4--;,de ,br\w] automatic retort *>g]4 ,a ,,gas ,,gov]nor4 ,"s read]s may h notic$ t late at night a gas-jet1 :i* a few h\rs be=e burn$ ) a some:at feeble flame :5 ! tap 0 turn$ fully on1 n[ becomes m & m vigor\s1 & f9ally may fl>e up ) a hiss+ s\nd4 ,?is is because _m ( ! burn]s f$ by ! ma9 supply+ ! h\se h be5 turn$ (f1 & consequ5tly !re is a great] am\nt ( gas available = ! jets /ill burn+1 :i* !re=e feel an increas$ pressure4 ,z a matt] ( fact1 ! pressure ( gas 9 ! ma9 is con/antly v>y+1 ow+ p>tly to ! irregul>ity ( ! deliv]y f ! gasomet]1 & p>tly to ! fact t ! numb] ( burn]s 9 action is n ! same = _m m9utes toge!r4 ,x mu/ also be rememb]$ t h\ses ne> ! gasomet] end ( ! ma9 w receive _! gas at a high] pressure ?an ^? at ! o!r end4 ,! gas /or$ 9 ! hold]s may be want$ = use 9 ! /reet lamps a few y>ds away1 or = o!r lamps sev]al miles di/ant4 ,x is !re=e evid5t t if !re be j en\gh pressure to give a good supply to ! ne>e/ lamp1 !re w be too little a %ort di/ance beyond x1 & none at all at ! extreme po9t2 s t x is necess>y to put on en\gh pressure to ov]come ! friction on all ^! miles ( pipe1 & give j en\gh gas at ! extreme end4 ,x foll[s t at all int]m$iate po9ts ! pressure is excessive4 ,gas ( ! av]age quality is burn$ to ! greate/ advantage1 z reg>ds its light-giv+ prop]ties1 :5 its pressure is equal to t ( a column ( wat] half an in* high1 or ab\t #a_/ej lb4 to ! squ>e in*4 ,) less x gives a smoky1 flick]+ light1 & ) m ! combu/ion is also imp]fect4 ,illu/ration3 ,,fig4 #aii4 ,e h\se supply %\ld !re=e be fitt$ ) a gas gov]nor1 to keep ! pressure con/ant4 ,a gov]nor frequ5tly us$1 ! ,/ott1 is %[n 9 section 9 ,fig4 #aii4 ,gas ent]s f ! ma9 on ! "r1 & passes into a circul> elb[1 ,d1 :i* has top & bottom ap]tures clos$ by ! valves ,v ,v4 ,atta*$ to ! valve %aft is a l>ge inv]t$ cup ( metal1 ! tip ( :i* is imm]s$ 9 m]cury4 ,! pressure at :i* ! gov]nor is to act is det]m9$ by ! weights ,w1 ) :i* ! valve sp9dle is load$ at ! top4 ,z soon z ?is pressure is exce$$1 ! gas 9 ,c ,c lifts ! metal cup1 & ,v ,v are press$ aga9/ _! seats1 s cutt+ (f ! supply4 ,gas _c escape f ,c ,c1 z x has n suffici5t pressure to =ce its way ?r\gh ! m]cury "u ! lip ( ! cup4 ,imm$iately ! pressure 9 ,c ,c falls1 ow+ to "s ( ! gas be+ us$ up1 ! valves op5 & admit m gas4 ,:5 ! fluctuations ( pressure are slight1 ! valves nev] close completely1 b m]ely ?rottle ! supply until ! pressure beyond !m falls to its prop] level--t is1 !y pass j z mu* gas z ! burn]s 9 use c consume at ! pressure arrang$ =4 ,gov]nors ( mu* l>g] size1 b work+ on mu* ! same pr9ciple1 are fitt$ to ! ma9s at ! po9t :]e !y leave ! gasomet]s4 ,!y are n1 h[ev]1 s5sitive to local fluctuations 9 ! pipes1 h5ce ! necessity = sep>ate gov]nors 9 ! h\se betwe5 ! met] & ! burn]s4 ,,! ,,gas-,,met] commonly us$ 9 h\ses acts on ! pr9ciple %[n 9 ,fig4 #bjj4 ,! air-tight cas+ is divid$ by horizontal & v]tical divisions into ?ree gas-*amb]s1 ,b1 ,c1 & ,d4 ,gas ent]s at ,a1 & passes to ! valve *amb] ,b4 ,! slide-valves ( ?is all[ x to pass into ,c & ,d1 & also into ! two circul> lea!r bell[s ,e1 ,f1 :i* are atta*$ to ! c5tral division ,g1 b are q indep5d5t ( "o ano!r4 ,illu/ration3 ,,fig4 #bjj4--,sket* ( ! bell[s & *amb]s ( a dry gas met]4 ,we w suppose t 9 ! illu/ration ! valves are admitt+ gas to *amb] ,c & bell[s ,f4 ,! pressure 9 ,c presses ! circul> head ( ,e t[>ds ! division ,g1 expell+ ! cont5ts ( ! bell[s ?r\gh an outlet pipe 7n %[n7 to ! burn]s 9 op]ation )9 ! h\se4 ,simultane\sly ! inflation ( ,f =ces ! gas 9 *amb] ,d also ?r\gh ! outlet4 ,! head-plates ( ! bell[s are atta*$ to rods & lev]s 7n %[n7 work+ ! slide-valves 9 ,b4 ,z soon z ,e is fully 91 & ,f fully exp&$1 ! valves beg9 to op5 & put ! inlet pipe 9 communication ) ,d & ,e1 & all[ ! cont5ts ( ,f & ,c to escape to ! outlet4 ,! movem5ts ( ! valve me*anism op]ate a tra9 ( c\nt+ :eels1 visible ?r\gh a glass w9d[ 9 ! side ( ! case4 ,z ! bell[s h a def9ite capacity1 e /roke t !y give means t a c]ta9 volume ( gas has be5 eject$ ei!r f !m or f ! *amb]s 9 :i* !y move3 ?is is regi/]$ by ! c\nt]4 ,! app>atus practically has two d\ble-action cyl9d]s 7( :i* ! bell[s ends are ! pi/ons7 work+ on ! same pr9ciple z ! /eam-cyl9d] 7,fig4 #ba74 ,! valves h ?ree ports--! c5tral1 or exhau/1 lead+ to ! outlet1 ! out] ones f ! inlet4 ,! bell[s are f$ ?r\gh *annels 9 ! division ,g4 ,,inc&esc5t ,,gas ,,light+4 ,! introduction ( ! electric arc lamp & ! inc&esc5t gl[-lamp seem$ at "o "t to spell ! doom ( gas z an illum9at+ ag5t4 ,b ! appe>ance 9 #ahhf ( ! ,welsba* inc&esc5t mantle = gas-burn]s op5$ a prosp]\s era 9 ! hi/ory ( gas light+4 ,! lum9osity ( a gas flame dep5ds on ! numb] ( c>bon p>ticles lib]at$ )9 x1 & ! temp]ature to :i* ^! p>ticles c be heat$ z !y pass ?r\gh ! int5sely hot outside zone ( ! flame4 ,by enri*+ ! gas 9 c>bon m light is yield$1 up to a c]ta9 po9t1 ) a flame ( a giv5 temp]ature4 ,to increase ! heat ( ! flame v>i\s devices 7 tri$ be=e ! introduction ( ! inc&esc5t mantle1 b !y 7 f\nd to be too %ort-liv$ to h any comm]cial value4 ,inv5tors !re=e s\ght = me?ods by :i* ! emission ( light c\ld be obta9$ f coal gas indep5d5tly ( ! inc&esc5ce ( ! c>bon p>ticles 9 ! flame itself2 & /ep by /ep x 0 discov]$ t gas c\ld be bett] employ$ m]ely z a heat+ ag5t1 to raise to inc&esc5ce sub/ances hav+ a high] emissivity ( light ?an c>bon4 ,dr4 ,au] von ,welsba* f\nd t ! sub/ances mo/ suitable = inc&esc5t mantles 7 ! oxides ( c]ta9 r>e metals1 ?orium1 & c]ium4 ,! mantle is made by dipp+ a cyl9d] ( cotton net into a solution ( nitrate ( ?orium & c]ium1 conta9+ #ii p] c5t4 ( ! =m] & #a p] c5t4 ( ! latt] metal4 ,:5 ! fibres are suffici5tly soak$1 ! mantle is )drawn1 squeez$1 & plac$ on a m\ld to dry4 ,x is next held ov] a ,buns5 gas flame & ! cotton is burn$ away1 :ile ! nitrates are conv]t$ into oxides4 ,! mantle is n[ ready = use1 b v brittle4 ,s x has to und]go a fur!r dipp+1 9 a solution ( gun-cotton & alcohol1 to r5d] x t\gh en\gh = pack+4 ,:5 x is requir$ = use1 x is susp5d$ ov] ! burn] by an asbe/os ?read wov5 across ! top1 a light is appli$ to ! bottom1 & ! collodion burn$ (f1 leav+ no?+ b ! heat-resi/+ oxides4 ,! burn] us$ ) a mantle is con/ruct$ on ! ,buns5 pr9ciple4 ,! gas is mix$1 z x em]ges f ! jet1 ) suffici5t air to r5d] its combu/ion p]fect4 ,all ! c>bon is burn$1 & ! flame1 ?\gh almo/ invisible1 is int5sely hot4 ,! mantle oxides conv]t ! heat en]gy ( ! flame into light en]gy4 ,?is is prov$ n only by ! int5se :it5ess ( ! mantle1 b by ! fact t ! heat issu+ f ! *imney ( ! burn] is n ne>ly s great :5 ! mantle is 9 position z :5 x is abs5t4 ,! inc&esc5t mantle is m ext5sively us$ e ye>4 ,9 ,g]many #ij p] c5t4 ( gas light+ is on ! inc&esc5t sy/em1 & 9 ,engl& ab\t #dj p] c5t4 ,we may notice1 z an int]e/+ example ( ! fluctuat+ =tunes ( inv5tion1 t ! once doom$ gas-burn] has1 ?anks to ,welsba*'s mantle1 9 _m in/ances replac$ ! inc&esc5t electric lamps t 7 to doom x4 #ch ,if1 ( c\rse1 !re is no safety-valve 9 prop] work+ ord] includ$ 9 ! in/allation4 ,*apt] ,,xx4 ,,v>i\s ,,me*anisms4 ,,clocks ,,& ,,wat*es3--,a %ort hi/ory ( timepieces--,! con/ruction ( timepieces--,! driv+ p[]--,! escapem5t--,comp5sat+ p5dulums--,! spr+ balance--,! cyl9d] escapem5t--,! lev] escapem5t--,comp5sat$ balance-:eels--,keyless w9d+ me*anism = wat*es--,! h\r h& tra94 ,,locks3--,! ,*ubb lock--,! ,yale lock4 ,,! ,,cycle3--,! ge>+ ( a cycle--,! free :eel--,! *ange-spe$ ge>4 ,,agricultural ,,ma*9es3--,! ?re%+-ma*9e--,m[+-ma*9es4 ,,"s ,,natural ,,ph5om5a3--,:y sun-heat v>ies 9 int5sity--,! tides--,:y high tide v>ies daily4 ,,clocks ,,& ,,wat*es4 ,a ,,%ort ,,hi/ory ,,( ,,timepieces4 ,! olde/ device = measur+ "t is ! sun-dial4 ,t ( ,ahaz m5tion$ 9 ! ,second ,book ( ,k+s is ! e>lie/ dial ( :i* we h record4 ,! obelisks ( ! ,egyptians & ! curi\s /one pill>s ( ! ,druidic age also probably s]v$ z %ad[-ca/]s4 ,! clepsydra1 or wat]-clock1 also ( great antiquity1 0 ! fir/ contrivance = gaug+ ! passage ( ! h\rs indep5d5tly ( ! motion ( ! e>?4 ,9 its simple/ =m x 0 a measure into :i* wat] fell drop by drop1 h\r levels be+ m>k$ on ! inside4 ,subsequ5tly a v simple me*anism 0 add$ to drive a po9t]--a float c>ry+ a v]tical rack1 engag+ ) a cog on ! po9t] sp9dle2 or a /r+ f ! float pass$ ov] a pulley atta*$ to ! po9t] & rotat$ x z ! float rose1 aft] ! mann] ( ! :eel b>omet] 7,fig4 #aec74 ,9 #hjg ,a4,d4 ,*>lemagne receiv$ f ! ,k+ ( ,p]sia a wat]-clock :i* /ruck ! h\rs4 ,x is ?us describ$ 9 ,gif=d's ,hi/ory ( ,france3--,! dial 0 compos$ ( twelve small doors1 :i* repres5t$ ! division ( ! h\rs4 ,ea* door op5$ at ! h\r x 0 int5d$ to repres5t1 & out ( x came a small numb] ( little balls1 :i* fell "o by "o1 at equal di/ances ( "t1 on a brass drum4 ,x might be told by ! eye :at h\r x 0 by ! numb] ( doors t 7 op51 & by ! e> by ! numb] ( balls t fell4 ,:5 x 0 twelve o'clock twelve horsem5 9 m9iature issu$ =? at ! same "t & %ut all ! doors4 ,s&-glasses 7 introduc$ ab\t #ccj ,a4,d4 ,except = special purposes1 su* z tim+ s]mons & boil+ eggs1 !y h n be5 ( any practical value4 ,! clepsydra naturally sugge/$ to ! me*anical m9d ! idea ( driv+ a me*anism = regi/]+ "t by ! =ce ( gravity act+ on "s body o!r ?an wat]4 ,! inv5tion ( ! weight-driv5 clock is attribut$1 l a good _m o!r ?+s1 to ,ar*im$es1 ! fam\s ,sicilian ma!matician ( ! ?ird c5tury ,b4,c42 b no record exi/s ( any actual clock compos$ ( :eels op]at$ by a weight prior to #aabj ,a4,d4 ,s we may take t ye> z op5+ ! era ( ! clock z we "k x4 ,ab\t #aejj ,pet] ,hele ( ,nuremb]g inv5t$ ! ma9spr+ z a sub/itute = ! weight1 & ! wat* appe>$ soon aft]w>ds 7#aebe ,a4,d474 ,! p5dulum 0 fir/ adopt$ = controll+ ! motion ( ! :eels by ,*ri/ian ,huyg5s1 a di/+ui%$ ,dut* me*anician1 9 #afei4 ,to ,?omas ,tompion1 ! fa!r ( ,engli% wat*mak+1 is ascrib$ ! hon\r ( fir/ fitt+ a hairspr+ to ! escapem5t ( a wat*1 9 or ab\t ! ye> #affj4 ,he also introduc$ ! cyl9d] escapem5t n[ s commonly us$ 9 *eap wat*es4 ,?\gh _m improvem5ts h be5 made s9ce 8 "t1 ,tompion manufactur$ clocks & wat*es :i* 7 excell5t timekeep]s1 & z a rew>d = ! b5efits conf]r$ on 8 fell[s dur+ 8 lifetime1 he 01 aft] dea?1 grant$ ! exceptional hon\r ( a re/+-place 9 ,we/m9/] ,abbey4 ,,! ,,con/ruction ,,( ,,timepieces4 ,a clock or wat* conta9s ?ree ma9 elem5ts3--7#a7 ,! s\rce ( p[]1 :i* may be a weight or a spr+2 7#b7 ! tra9 ( :eels op]at$ by ! driv+ =ce2 7#c7 ! ag5t = controll+ ! movem5ts ( ! tra9--?is 9 l>ge clocks is usually a p5dulum1 9 small clocks & wat*es a hairspr+ balance4 ,to ^! may be add$1 9 ! case ( clocks1 ! app>atus = /rik+ ! h\r4 ,,! ,,driv+ ,,p[]4 ,weights are us$ only 9 l>ge clocks1 su* z "o f9ds 9 halls1 t[]s1 & obs]vatories4 ,! great advantage ( employ+ weights is t a con/ant driv+ p[] is ex]t$4 ,spr+s occupy mu* less room ?an weights1 & are indisp5sable = portable timepieces4 ,! employm5t ( !m caus$ tr\ble to e>ly exp]im5t]s on acc\nt ( ! decrease 9 p[] :i* necess>ily accompanies ! uncoil+ ( a w\nd-up spr+4 ,jacob ,ze* ( ,prague ov]came ! difficulty 9 #aebe by ! inv5tion ( ! fusee1 a k9d ( conical pulley int]pos$ betwe5 ! b>rel1 or circul> drum conta9+ ! ma9spr+1 & ! tra9 ( :eels :i* ! spr+ has to drive4 ,! pr9ciple ( ! drum & fusee action w be und]/ood f ,fig4 #bja4 ,! ma9spr+ is a long /eel ribbon fix$ at "o end to an arbor 7! wat*mak]'s "n = a sp9dle or axle71 r\nd :i* x is tightly w\nd4 ,! arbor & spr+ are ins]t$ 9 ! b>rel4 ,! arbor is prev5t$ f turn+ by a rat*et1 ,b1 & click1 & !re=e ! spr+ 9 its ef=t to uncoil causes ! b>rel to rotate4 ,illu/ration3 ,,fig4 #bja4 ,a /r+ ( catgut 7or a v f9e *a97 is connect$ at "o end to ! circumf]5ce ( ! drum1 & w\nd r\nd x1 ! o!r end be+ fix$ to ! l>g] end ( ! fusee1 :i* is atta*$ to ! driv+-:eel ( ! wat* or clock by ! int]v5tion ( a rat*et & click 7n %[n74 ,to w9d ! spr+ ! fusee is turn$ backw>d by means ( a key appli$ to ! squ>e end ,a ( ! fusee arbor1 & ?is draws ! /r+ f (f ! drum on to ! fusee4 ,! =ce ( ! spr+ causes ! fusee to rotate by pull+ ! /r+ (f x1 coil by coil1 & s drives ! tra9 ( :eels4 ,b :ile ! ma9spr+1 :5 fully w\nd1 turns ! fusee by uncoil+ ! /r+ f ! smalle/ "p ( ! fusee1 x gets ! advantage ( ! l>g] radius z its en]gy becomes less5$4 ,! fusee is /ill us$ = m>9e *ronomet]s1 = "s clocks t h a ma9spr+ & p5dulum1 & occasionally = wat*es4 ,9 ! latt] x has be5 r5d]$ unnecess>y by ! introduction ( ! go+-b>rel by ,swiss wat*mak]s1 :o =m$ tee? on ! edge ( ! ma9spr+ b>rel to drive ! tra9 ( :eels4 ,?is k9d ( drum is call$ go+ because x drives ! wat* dur+ ! op]ation ( w9d+1 :i* is p]=m$ by rotat+ ! drum arbor to :i* ! inn] end ( ! spr+ is atta*$4 ,a rat*et prev5ts ! arbor f be+ turn$ backw>ds by ! spr+4 ,! adoption ( ! go+-b>rel has be5 made satisfactory by ! improvem5ts 9 ! v>i\s escapem5t actions4 ,,! ,,escapem5t4 ,illu/ration3 ,,fig4 #bjb4 ,! spr+ or weight transmits its p[] ?r\gh a tra9 ( cogs to ! escapem5t1 or device = regulat+ ! rate at :i* ! :eels are to revolve4 ,9 clocks a p5dulum is g5]ally us$ z ! controll+ ag5t4 ,galileo1 :5 a /ud5t at ,pisa1 notic$ t c]ta9 hang+ lamps 9 ! ca!dral !re swung on _! cords at an equal rate2 & on inve/igation he discov]$ ! pr9ciple t ! %ort] a p5dulum is ! m quickly w x sw+ to & fro4 ,z has already be5 obs]v$1 ,huyg5s fir/ appli$ ! pr9ciple to ! gov]n+ ( clocks4 ,9 ,fig4 #bjb we h a simple repres5tation ( ! dead-beat escapem5t commonly us$ 9 clocks4 ,! escape-:eel is m\nt$ on ! %aft ( ! la/ cog ( ! driv+ tra91 ! pallet on a sp9dle f :i* dep5ds a split arm embrac+ ! rod & ! p5dulum4 ,we mu/ be c>eful to note t ! p5dulum controls motion only2 x does n cause movem5t4 ,! escape-:eel revolves 9 a clockwise direction4 ,! two pallets a & b are s design$ t only "o c re/ on ! tee? at "o "t4 ,9 ! sket* ! slop+ end ( b has j be5 =c$ upw>ds by ! pressure ( a too?4 ,?is sw+s ! pallet & ! p5dulum4 ,! mom5tum ( ! latt] causes a to desc5d1 & at ! in/ant :5 b cle>s its too? a cat*es & holds ano!r4 ,! left-h& side ( a1 call$ ! lock+-face1 is "p ( a circle1 s t ! escape-:eel is held motionless z long z x t\*es a3 h5ce ! t]m1 dead beat--t is1 br\ght to a dead /op4 ,z ! p5dulum sw+s back1 to ! left1 "u ! influ5ce ( gravity1 a is rais$ & frees ! too?4 ,! :eel j]ks r\nd1 & ano!r too? is caught by ! lock+-face ( b4 ,aga9 ! p5dulum sw+s to ! "r1 & ! slop+ end ( b is pu%$ up once m1 giv+ ! p5dulum fre% impetus4 ,?is process repeats itself z long z ! driv+ p[] la/s--= weeks1 mon?s1 or ye>s1 z ! case may be1 & ! me*anism cont9ues to be 9 good work+ ord]4 ,,comp5sat+ ,,p5dulums4 ,metal exp&s :5 heat$2 !re=e a /eel p5dulum :i* is ( ! exact l5g? to gov]n a clock correctly at a temp]ature ( #fj w\ld become too long at #hj1 & sl[ ! clock1 & too %ort at #dj1 & cause x to ga94 ,9 common clocks ! p5dulum rod is (t5 made ( wood1 :i* ma9ta9s an almo/ con/ant l5g? at all ord9>y temp]atures4 ,b = v accurate clocks some?+ m effici5t is requir$4 ,graham1 ! p>tn] ( ,?omas ,tompion1 took advantage ( ! fact t diff]5t k9ds ( metal h diff]5t ratios ( expansion to produce a self-comp5sat+ p5dulum on ! pr9ciple illu/rat$ by ,fig4 #bjc4 ,he us$ /eel = ! rod1 & =m$ ! bob1 or weight$ end1 ( a glass j> conta9+ m]cury held 9 a /irrup2 ! m]cury be+ ( su* a height t1 z ! p5dulum rod l5g!n$ ) a rise ( temp]ature1 ! m]cury exp&$ upw>ds suffici5tly to keep ! di/ance betwe5 ! po9t ( susp5sion & ! c5tre ( gravity ( ! bob always ! same4 ,) a fall ( temp]ature ! rod %ort5$1 :ile ! m]cury sank 9 ! j>4 ,?is device has n be5 improv$ ^u1 & is /ill us$ 9 obs]vatories & o!r places :]e timekeep]s ( extreme precision are requir$4 ,! mill$ nut ,s 9 ,fig4 #bjc is fitt$ at ! end ( ! p5dulum rod to p]mit ! exact adju/m5t ( ! p5dulum's l5g?4 ,= wat*es1 *ronomet]s1 & small clocks ,,! ,,spr+ ,,balance takes ! place ( ! p5dulum4 ,we /ill h an escape-:eel ) tee? ( a suitable %ape to give impulses to ! controll+ ag5t4 ,!re are two =ms ( spr+ escapem5t1 b z bo? employ a hairspr+ & balance-:eel we w glance at ^! be=e go+ fur!r4 ,illu/ration3 ,,fig4 #bjc4 ,! hairspr+ is made ( v f9e /eel ribbon1 temp]$ to extreme ela/icity1 & %ap$ to a spiral4 ,! inn] end is atta*$ to ! arbor ( ! balance-:eel1 ! out] end to a /ud project+ f ! plate ( ! wat*4 ,:5 ! balance-:eel1 impell$ by ! escapem5t1 rotates1 x w9ds up ! spr+4 ,! en]gy ?us /or$ helps ! :eel to revolve ! o!r way dur+ ! lock+ ( a too? ( ! escape-:eel4 ,! "t occupi$ by ! w9d+ & ! unw9d+ dep5ds ^u ! l5g? ( ! spr+4 ,! /r5g? ( ! impulse makes no diff]5ce4 ,a /rong impulse causes ! spr+ to coil itself up m ?an a weak impulse w\ld2 b inasmu* z m en]gy is /or$ ! process ( unw9d+ is ha/5$4 ,to put ! matt] v simply--a /rong impulse moves ! balance-:eel fur!r1 b rotates x quickly2 a weak impulse moves x a %ort] di/ance1 b rotates x sl[ly4 ,9 fact1 ! pr9ciple ( ! p5dulum is also t ( ! hairspr+2 & ! duration ( a vibration dep5ds on ! l5g? ( ! rod 9 ! "o case1 & ( ! spr+ 9 ! o!r4 ,motion is transmitt$ to ! balance by "o ( two me?ods4 ,ei!r 7#a7 directly1 by a cyl9d] escapem5t2 or 7#b7 indirectly1 ?r\gh a lev]4 ,illu/ration3 ,,fig4 #bjd4--;,cyl9d] wat* escapem5t4 ,,! ,,cyl9d] ,,escapem5t is se5 9 ,fig4 #bjd4 ,! escape-:eel has %>p tee? set on /alks4 7,"o too? is remov$ to %[ ! /alk47 ,! balance-:eel is m\nt$ on a small /eel cyl9d]1 ) "p ( ! circumf]5ce cut away at ! level ( ! tee?1 s t if se5 f above x w\ld appe> l a 9 our illu/ration4 ,a too? is j beg9n+ to %ove its po9t "u ! ne>] edge ( ! op5+4 ,z x is =c$ =w>ds1 b is revolv$ 9 a clockwise direction1 w9d+ up ! hairspr+4 ,:5 ! too? has pass$ ! ne>] edge x flies =w>d1 /rik+ ! inside ( ! fur!r wall ( ! cyl9d]1 :i* holds x :ile ! spr+ uncoils4 ,! too? n[ pu%es its way pa/ ! o!r edge1 accel]at+ ! unw9d+1 &1 z x escapes1 ! next too? jumps =w>d & is arre/$ by ! outside ( ! cyl9d]4 ,! balance n[ rev]ses its motion1 is help$ by ! too?1 is w\nd up1 locks ! too?1 & s on4 ,,! ,,lev] ,,escapem5t is some:at m complicat$4 ,! escape-:eel tee? are lock$ & unlock$ by ! pallets ,p ,p#a project+ f a lev] :i* moves on a pivot 7,fig4 #bje74 ,! end ( ! lev] is =k$1 & has a squ>e not* 9 x4 ,on ! arbor ( ! balance-:eel is a roll]1 or plate1 ,r1 :i* c>ries a small p91 ,i4 ,two p9s1 ,b ,b1 project+ f ! plate ( ! wat* prev5t ! lev] mov+ too f>4 ,we mu/ fur!r notice ! little p9 ,c on ! lev]1 & a not* 9 ! edge ( ! roll]4 ,illu/ration3 ,,fig4 #bje4--,lev] wat* escapem5t4 ,9 ! illu/ration a too? has j pass$ "u ! impulse face b ( ,p#a4 ,! lev] has be5 mov$ upw>ds at ! "r end2 & its =k$ end has giv5 an impulse to ,r1 & ?r\gh x to ! balance-:eel4 ,! spr+ w9ds up4 ,! p9 ,c prev5ts ! lev] dropp+1 because x no long] has ! not* opposite to x1 b presses on ! circumf]5ce ( ,r4 ,z ! spr+ unw9ds x /rikes ! lev] at ! mom5t :5 ! not* & ,c are opposite4 ,! lev] is knock$ d[nw>ds1 & ! too?1 :i* _h be5 arre/$ by ! lock+-face a ( pallet ,p1 n[ presses on ! impulse face b1 =c+ ! left end ( ! lev] up4 ,! impulse p9 ,i receives a bl[1 assi/+ ! unw9d+ ( ! spr+1 & ,c aga9 locks ! lev]4 ,! same ?+ is repeat$ 9 alt]nate directions ov] & ov] aga94 ,,comp5sat+ ,,balance-,,:eels4 ,! wat*mak] has _h to ov]come ! same difficulty z ! clockmak] ) reg>d to ! expansion ( ! metal 9 ! controll+ ag5t4 ,:5 a metal :eel is heat$ its spokes l5g!n1 & ! rim rec$es f ! c5tre4 ,n[1 let u suppose t we h two rods ( equal weight1 "o ?ree feet long1 ! o!r six feet long4 ,to an end ( ea* we fa/5 a #b-lb4 weight4 ,we %all f9d x mu* easi] to wave ! %ort] rod backw>ds & =w>ds quickly ?an ! o!r4 ,:y8 ,because ! weight ( ! long] rod has m lev]age ov] ! h& ?an has t ( ! %ort] rod4 ,simil>ly1 if1 :ile ! mass ( ! rim ( a :eel rema9s con/ant1 ! l5g? ( ! spokes v>ies1 ! ef=t ne$$ to rotate ! :eel to & fro at a con/ant rate mu/ v>y also4 ,graham got ov] ! difficulty ) a rod by means ( ! comp5sat+ p5dulum4 ,?omas ,e>n%aw ma/]$ x 9 :eels by means ( ! comp5sat+ balance1 us+ ! same pr9ciple--namely1 ! unequal expansion ( diff]5t metals4 ,any "o :o owns a comp5sat$ wat* w see1 on /opp+ ! t9y fly-:eel1 t x has two spokes 7,fig4 #bjf71 ea* c>ry+ an almo/ complete semicircle ( rim atta*$ to x4 ,a close exam9ation %[s t ! rim is comp\nd$ ( an out] /rip ( brass weld$ to an inn] l9+ ( /eel4 ,! brass elem5t exp&s m ) heat & contracts m ) cold ?an /eel2 s t :5 ! spokes become elongat$ by a rise ( temp]ature1 ! pieces b5d inw>ds at _! free ends 7,fig4 #bjg72 if ! temp]ature falls1 ! spokes are %ort5$1 & ! rim pieces b5d outw>ds 7,fig4 #bjh74ci ,?is +5i\s contrivance keeps ! lev]age ( ! rim con/ant )9 v f9e limits4 ,! screws ,s ,s are ins]t$ 9 ! rim to balance x correctly1 & v f9e adju/m5t is made by means ( ! f\r t9y weights ,w ,w4 ,9 %ips' *ronomet]s1#dj ! rim pieces are sub-comp5sat$ t[>ds _! free ends to c\nt]act slight errors 9 ! prim>y comp5sation4 ,s delicate is ! comp5sation t a daily loss or ga9 ( only half a second is (t5 ! limit ( error4 ,illu/ration3 ,,fig4 #bjf4 ,,fig4 #bjg4 ,,fig4 #bjh4 ,a comp5sat+ wat* balance1 at normal1 sup]-normal1 & sub-normal temp]atures4 ,,keyless ,,w9d+ ,,me*anism ,,= ,,wat*es4 ,! inconv5i5ce atta*+ to a key-w\nd wat* caus$ ! ,swiss manufactur]s to put on ! m>ket1 9 #ahea1 wat*es :i* disp5s$ ) a sep>ate key4 ,^? ( our read]s :o c>ry keyless wat*es w be int]e/$ to le>n h[ ! w9d+ & sett+ ( ! h&s is effect$ by ! little s]rat$ knob enclos$ inside ! p5dant r+4 ,!re are two =ms ( go+-b>rel keyless me*anism--7#a7 ,! rock+ b>2 7#b7 ! %ift+ sleeve4 ,! rock+ b> device is %[n 9 ,figs4 #bji1 #baj4 ,! mill$ head ,m turns a cog1 ,g1 :i* is always 9 ge> ) a cog1 ,f4 ,?is cog ge>s ) two o!rs1 ,a & ,b1 m\nt$ at ea* end ( ! rock] ,r1 :i* moves on pivot ,s4 ,a spr+1 ,s ,p1 atta*$ to ! wat* plate presses aga9/ a small /ud on ! rock+ b>1 & keeps ,a normally 9 ge> ) ,c1 m\nt$ on ! arbor ( ! ma9spr+4 ,illu/ration3 ,,fig4 #bji4--,! w9d+ me*anism ( a keyless wat*4 ,to w9d ! wat*1 ,m is turn$ s z to give ,f an anti-clockwise motion4 ,! tee? ( ,f n[ press ,a d[nw>ds & keep x 9 ge> ) ,c :ile ! w9d+ is done4 ,a spr+ click 7m>k$ solid black7 prev5ts ! spr+ uncoil+ 7,fig4 #bji74 ,if ,f is turn$ 9 a clockwise direction x lifts ,a & prev5ts x bit+ ! tee? ( ,c1 & no /ra9 is ?r[n on ,c4 ,to set ! h&s1 ! little pu%-piece ,p is press$ inw>ds by ! ?umb 7,fig4 #baj7 s z to depress ! "r-h& end ( ,r & br+ ,b into ge> ) ,d1 :i* 9 turn moves ,e1 m\nt$ on ! end ( ! m9ute-h& %aft4 ,! h&s c n[ be mov$ 9 ei!r direction by turn+ ,m4 ,on releas+ ! pu%-piece ! w9d+-:eels engage aga94 ,! %ift+ sleeve me*anism has a bevel p9ion 9 ! place ( ,g 7,fig4 #bji7 ge>+ ) ! ma9spr+ cog4 ,! %aft ( ! knob ,m is r\nd :]e x passes ?r\gh ! bevel & c turn freely inside x1 b is squ>e bel[4 ,on ! squ>e "p is m\nt$ a little slid+ clut* ) tee? on ! top correspond+ ) ! o!r tee? on ! "u side ( ! bevel-:eel1 & tee? simil> to ^? ( ,g 7,fig4 #bji7 at ! end4 ,! clut* has a groove cut 9 ! circumf]5ce1 & 9 ?is lies ! end ( a spr+ lev] :i* c be depress$ by ! pu%-piece4 ,! me*anism mu* resembles on a small scale ! motor c> *ang+ ge> 7,fig4 #di74 ,normally1 ! clut* is pu%$ up ! squ>e "p ( ! knob %aft by ! spr+ s z to engage ) ! bevel & ! w9d+-:eels4 ,on depress+ ! clut* by means ( ! pu%-piece x ge>s ) ! m9ute-h& p9ion1 & lets g ( ! bevel4 ,illu/ration3 ,,fig4 #baj4--,! h&-sett+ me*anism 9 action4 ,9 "o =m ( ?is me*anism ! pu%-piece is disp5s$ )1 & ! m9ute-:eel p9ion is engag$ by pull+ ! knob upw>ds4 ,,! ,,h\r-,,h& ,,tra94 ,illu/ration3 ,,fig4 #baa4--,! h\r-h& tra9 ( a clock4 ,! tee? ( ! ma9spr+ drum ge> ) a cog on ! m9ute-h& %aft1 :i* also c>ries "o ( ! cogs ( ! escapem5t tra94 ,! %aft is p]mitt$ by ! escapem5t to revolve once an h\r4 ,fig4 #baa %[s diagrammatically h[ ?is is manag$4 ,! h\r-h& %aft ,a 7solid black7 c be mov$ r\nd inside ! cog ,b1 driv5 by ! ma9spr+ drum4 ,x c>ries a cog1 ,c4 ,?is ge>s ) a cog1 ,d1 hav+ ?ree times z _m tee?4 ,! cog ,e1 unit$ to ,d1 drives cog ,f1 hav+ f\r times z _m tee? z ,e4 ,to ,f is atta*$ ! coll> ,g ( ! h\r-h&4 ,f & ,g revolve outside ! m9ute-h& %aft4 ,on turn+ ,a1 ,c turns ,d & ,e1 ,e turns ,f & ! h\r-h&1 :i* revolves #a_/c ( #a_/d #a_/ab z fa/ z ,a4#da 99 99 99 99 99 ,,locks4 ,on ^! un=tunately necess>y me*anisms a great deal ( +5uity has be5 exp5d$4 ,) ! advance ( luxury & ! increas$ wor%ip ( weal?1 x becomes m & m necess>y to gu>d "o's belong+s aga9/ ! less scrupul\s memb]s ( society4 ,illu/ration3 ,,fig4 #bab4 ,! simple/ =m ( lock1 su* z is f\nd 9 desks & v *eap articles1 works on ! pr9ciple %[n 9 ,fig4 #bab4 ,! bolt is split at ! re>1 & ! upp] "p b5t upw>ds to =m a spr+4 ,! "u edge has two not*es cut 9 x1 sep>at$ by a curv$ excresc5ce4 ,! key m]ely presses ! bolt upw>ds aga9/ ! spr+1 until ! not*1 engag+ ) ! frame1 moves x backw>ds or =w>ds until ! spr+ drives ! tail d[n into ! o!r not*4 ,?is primitive device af=ds1 ( c\rse1 v little security4 ,an advance is se5 9 ! ,,tumbl] ,,lock4 ,illu/ration3 ,,fig4 #bac4 ,! bolt n[ c move only 9 a horizontal direction4 ,x has an op5+ cut 9 x ) two not*es 7,figs4 #bac1 #bad74 ,beh9d ! bolt lies ! tumbl] ,t 7indicat$ by ! dott$ l9e71 pivot$ at ! angle on a p94 ,f ! face ( ! tumbl] a /ud1 ,s1 projects ?r\gh ! hole 9 ! bolt4 ,?is /ud is =c$ into "o or o!r ( ! not*es by ! spr+1 ,s#a1 :i* presses on ! tail ( ! tumbl]4 ,illu/ration3 ,,fig4 #bad4 ,9 ,fig4 #bac ! key is ab\t to actuate ! lock+ me*anism4 ,! next diagram 7,fig4 #bad7 %[s h[ ! key1 z x ent]s ! not* on ! l[] side ( ! bolt to move x along1 also raises ! tumbl] /ud cle> ( ! projection betwe5 ! two not*es4 ,by ! "t t ! bolt has be5 fully %ot1 ! key leaves ! "u not* & all[s ! tumbl] /ud to fall into ! re> lock+-not*4 ,a lock ( ?is type also c be pick$ v easily1 z ! pick] has m]ely to lift ! tumbl] & move ! bolt along4 ,b>ron's lock1 pat5t$ 9 #aggh1 _h two tumbl]s & two /uds2 & ! op5+ 9 ! bolt _h not*es at ! top z well z at ! bottom 7,fig4 #bae74 ,?is made x necess>y = bo? tumbl]s to be rais$ simultane\sly to exactly ! "r height4 ,if ei!r 0 n lift$ suffici5tly1 a /ud c\ld n cle> its bottom not*2 if ei!r rose too f>1 x engag$ an upp] not*4 ,! *ances !re=e 7 greatly aga9/ a wrong key turn+ ! lock4 ,illu/ration3 ,,fig4 #bae4--,! bolt ( a ,b>ron lock4 ,,! ,,*ubb ,,lock is an amplification ( ?is pr9ciple4 ,x usually has sev]al tumbl]s ( ! %ape %[n 9 ,fig4 #baf4 ,! lock /ud 9 ^! locks projects f ! bolt itself1 & ! op5+s1 or gates1 ?r\gh :i* ! /ud mu/ pass z ! lock moves1 are cut 9 ! tumbl]s4 ,x w be notic$ t ! =w>d not* ( ! tumbl] has squ>e s]rations 9 ! edges4 ,^! engage ) simil> s]rations 9 ! bolt /ud & make x impossible to raise ! tumbl] if ! bolt beg9s to move too soon :5 a wrong key is ins]t$4 ,illu/ration3 ,,fig4 #baf4--,tumbl] ( ,*ubb lock4 ,fig4 #bag is a ,*ubb key ) eight /eps4 ,t ne>e/ ! head 7#h7 op]ates a circul> revolv+ curta91 :i* prev5ts ! introduction ( pick+ tools :5 a key is ins]t$ & p>tly turn$1 z ! key slot 9 ! curta9 is no long] opposite t 9 ! lock4 ,/ep #a moves ! bolt4 ,illu/ration3 ,,fig4 #bag4--;,a ,*ubb key4 ,9 ord] to %oot ! bolt ! height ( ! key /eps mu/ be s proportion$ to ! dep? ( _! tumbl]s t all ! gates 9 ! tumbl]s are simultane\sly rais$ to ! "r level = ! /ud to pass ?r\gh !m1 z 9 ,fig4 #bah4 ,"h y w obs]ve t ! tumbl] ,d on ! extreme "r 7lift$ by /ep #b ( ! key7 has a /ud1 ,d ,s1 project+ f x ov] ! o!r tumbl]s4 ,?is is call$ ! detector tumbl]4 ,if a false key or pick+ tool is ins]t$ x is c]ta9 to raise "o ( ! tumbl]s too f>4 ,! detector is !n ov]-lift$ by ! /ud ,d ,s1 & a spr+ cat* falls into a not* at ! re>4 ,x is n[ impossible to pick ! lock1 z ! detector c be releas$ only by ! "r key %oot+ ! bolt a little fur!r 9 ! lock+ direction1 :5 a projection on ! re> ( ! bolt lifts ! cat* & all[s ! tumbl] to fall4 ,! detector also %[s t ! lock has be5 tamp]$ )1 s9ce ev5 ! "r key _c move ! bolt until ! ov]lock+ has be5 p]=m$4 ,illu/ration3 ,,fig4 #bah4--;,a ,*ubb key rais+ all ! tumbl]s to ! correct height4 ,ea* tumbl] /ep ( a l>ge ,*ubb key c be giv5 "o ( ?irty diff]5t heights2 ! bolt /ep "o ( tw5ty4 ,by m]ely transpos+ ! ord] ( ! /eps 9 a six-/ep key x is possible to get #gbj diff]5t comb9ations4 ,by dim9i%+ or increas+ ! heights ! possible comb9ations may be rais$ to ! enorm\s total ( #g1ggf1jjj6 ,illu/ration3 ,,fig4 #bai4--,section ( a ,yale lock4 ,,! ,,yale ,,lock1 :i* comes f ,am]ica1 works on a q diff]5t sy/em4 ,its mo/ noticeable feature is t x p]mits ! use ( a v small key1 ?\gh ! numb] ( comb9ations possible is /ill enorm\s 7sev]al millions74 ,9 our illu/rations 7,figs4 #bai1 #bbj1 #bba7 we %[ ! me*anism controll+ ! turn+ ( ! key4 ,! keyhole is a n>r[ twi/$ slot 9 ! face ( a cyl9d]1 ,g 7,fig4 #bai71 :i* revolves inside a l>g] fix$ cyl9d]1 ,f4 ,z ! key is pu%$ 91 ! not*es 9 its upp] edge raise up ! p9s ,a#a1 ,b#a1 ,c#a1 ,d#a1 ,e#a1 until _! tops exactly rea* ! surface ( ,g1 :i* c n[ be revolv$ by ! key 9 ,fig4 #bbj1 & "w ! bolt ?r\gh ! m$ium ( ! arm ,h4 7,! bolt itself is n %[n47 ,if a wrong key is ins]t$1 ei!r "s ( ! l[] p9s w project upw>ds into ! fix$ cyl9d] ,f 7see ,fig4 #bba71 or "s ( ! p9s 9 ,f w s9k into ,g4 ,x is !n impossible to turn ! key4 ,illu/ration3 ,,fig4 #bbj4--,yale key turn+4 ,!re are o!r well-kn[n locks1 su* z ^? inv5t$ by ,bramah & ,hobbs4 ,b z ^! d n l5d !mselves readily to illu/ration no detail$ acc\nt c be giv54 ,we might1 h[ev]1 notice ! "t lock1 :i* is set to a c]ta9 h\r1 & c be op5$ by ! "r key or a numb] ( keys 9 comb9ation only :5 t h\r is rea*$4 ,ano!r v int]e/+ device is ! automatic comb9ation lock4 ,?is may h tw5ty or m keys1 any "o ( :i* c lock x2 b ! same "o mu/ be us$ to unlock x1 z ! key automatically sets ! me*anism 9 fav\r ( itself4 ,) su* a lock x w\ld be possible to h a diff]5t key = e day 9 ! mon?2 & if any "o key got into wrong h&s x w\ld be useless unless x happ5$ to be ! "o :i* la/ lock$ ! lock4 ,illu/ration3 ,,fig4 #bba4--,! wrong key ins]t$4 ,! p9s d n all[ ! lock to be turn$4 99 99 99 99 99 ,,! ,,cycle4 ,!re are a few features ( ?is useful & 9 "s ways wond]ful contrivance :i* %\ld be notic$4 ,fir/1 ,,! ,,ge>+ ,,( ,a ,,cycle4 ,to a good _m p ! expression ge>$ to #gj in*es1 or #fe1 or #hj1 z ! case may be1 conveys no?+ except ! fact t ! high] ! ge> ! fa/] "o ought to be able to travel4 ,let u !re=e exam9e ! mean+ ( su* a phrase be=e go+ f>!r4 ,! safety cycle is always ge>$ up--t is1 "o turn ( ! p$als w turn ! re> :eel m ?an once4 ,to get ! exact ratio ( turn+ spe$ we c\nt ! tee? on ! big *a9-:eel1 & ! tee? on ! small *a9-:eel atta*$ to ! hub ( ! re> :eel1 & divide ! =m] by ! latt]4 ,to take an example3--,! tee? are #ge & #cj 9 numb] respectively2 ! ratio ( spe$ !re=e #ge_/cj #e_/b #b-a_/b4 ,"o turn ( ! p$al turns ! re> :eel #b-a_/b times4 ,! ge> ( ! cycle is calculat$ by multiply+ ?is result by ! diamet] ( ! re> :eel 9 in*es4 ,?us a #bh-;in* :eel w\ld 9 ?is case give a ge> ( #b-a_/b #bh #gj in*es4 ,"o turn ( ! p$als on a ma*9e ( ?is ge> w\ld propel ! rid] z f> z if he 7 on a high ord9>y ) ! p$als atta*$ directly to a :eel #gj in*es 9 diamet]4 ,! ge>+ is rais$ or l[]$ by alt]+ ! numb] ratio ( ! tee? on ! two *a9-:eels4 ,if = ! #cj-too? :eel we sub/itut$ "o ( #be tee? ! ge>+ w\ld be-- #ge_/be #bh in*es #hd in*es4 ,a h&y =mula to rememb] is1 ge>+ ,t_/t ,d1 :]e ,t tee? on l>ge *a9-:eel2 t tee? on small *a9-:eel2 & ,d diamet] ( driv+-:eel 9 in*es4 ,two ( ! mo/ important improvem5ts rec5tly add$ to ! cycle are--7#a7 ,! free :eel2 7#b7 ! *ange-spe$ ge>4 ,,! ,,free ,,:eel is a device = enabl+ ! driv+-:eel to ov]run ! p$als :5 ! rid] ceases p$all+2 x r5d]s ! driv+-:eel free ( ! driv+ ge>4 ,x is a rat*et specially suit$ = ?is k9d ( "w4 ,f among ! _m patt]ns n[ m>ket$ we select ! ,micromet] free-:eel hub 7,fig4 #bbb71 :i* is extremely simple4 ,! rat*et-:eel ,r is atta*$ to ! hub ( ! driv+-:eel4 ,! small *a9-:eel 7or *a9-r+1 z x is (t5 call$7 turns outside ?is1 on a numb] ( balls runn+ 9 a groove *as$ 9 ! neck ( ! rat*et4 ,betwe5 ^! two p>ts are ! pawls1 ( half-moon %ape4 ,! driv+-:eel is assum$ to be on ! fur!r side ( ! rat*et4 ,to propel ! cycle ! *a9-r+ is turn$ 9 a clockwise direction4 ,?ree out ( ! six pawls at once engage ) not*es 9 ! rat*et1 & are held tightly 9 place by ! pressure ( ! *a9-r+ on _! re> ends4 ,! o!r ?ree are 9 a midway position4 ,illu/ration3 ,,fig4 #bbb4 ,:5 ! rid] ceases to p$al1 ! *a9-r+ becomes /ation>y1 b ! rat*et cont9ues to revolve4 ,! pawls (f] no resi/ance to ! rat*et tee?1 :i* pu% !m up into ! semicircul> recesses 9 ! *a9-r+4 ,ea* "o rises z x passes ov] a too?4 ,x is obvi\s t driv+ p[] _c be transmitt$ aga9 to ! road :eel until ! *a9-:eel is turn$ fa/ en\gh to ov]take ! rat*et4 ,,! ,,*ange-,,spe$ ,,ge>4 ,a ga9 9 spe$ means a loss 9 p[]1 & vice v]s4 ,by ge>+-up a cycle we are able to make ! driv+-:eel revolve fa/] ?an ! p$als1 b at ! exp5se ( control ov] ! driv+-:eel4 ,a high-ge>$ cycle is fa/ on ! level1 b a bad hill-climb]4 ,! l[-ge>$ ma*9e %[s to disadvantage on ! flat1 b is a good hill-climb]4 ,simil>ly1 ! express eng9e mu/ h l>ge driv+-:eels1 ! goods eng9e small driv+-:eels1 to p]=m _! special functions prop]ly4 ,9 ord] to travel fa/ ov] level c\ntry1 & yet be able to m\nt hills )\t undue ex]tion1 we mu/ be able to d :at ! motori/ does--*ange ge>4 ,two-spe$ & ?ree-spe$ ge>s are n[ v commonly fitt$ to cycles4 ,!y all "w on ! same pr9ciple1 t ( ! epicyclic tra9 ( cog-:eels1 ! me*anisms be+ s devis$ t ! hub turns m sl[ly ?an1 at ! same spe$ z1 or fa/] ?an ! small *a9-:eel1#db accord+ to ! wi% ( ! rid]4 ,we d n propose to d m "h ?an expla9 ! pr9ciple ( ! epicyclic tra91 :i* means a :eel on 7or runn+ r\nd7 a :eel4 ,lay a footrule on ! table & roll a cyl9d] along x by ! aid ( a second rule1 p>allel to ! fir/1 b re/+ on ! cyl9d]4 ,x w be f\nd t1 :ile ! cyl9d] advances six in*es1 ! upp] rule advances twice t di/ance4 ,9 ! abs5ce ( friction ! "w done by ! ag5t mov+ ! upp] rule is equal to t done 9 ov]com+ ! =ce :i* opposes ! =w>d motion ( ! cyl9d]2 & z ! di/ance ?r\gh :i* ! cyl9d] advances is only half t ?r\gh :i* ! upp] rule advances1 x foll[s t ! =ce :i* mu/ act on ! upp] rule is only half z great z t ov]come 9 mov+ ! cyl9d]4 ,! c>t] makes use ( ?is pr9ciple :5 he puts 8 h& to ! top ( a :eel to help 8 c>t ov] an ob/acle4 ,illu/ration3 ,,fig4 #bbc4 ,illu/ration3 ,,fig4 #bbd4 ,illu/ration3 ,,fig4 #bbe4 ,n[ see h[ ?is pr9ciple is appli$ to ! *ange-spe$ ge>4 ,! l[] rule is replac$ by a cog-:eel1 ,c 7,fig4 #bbc72 ! cyl9d] by a cog1 ,b1 runn+ r\nd x2 & ! upp] rule by a r+1 ,a1 ) int]nal tee?4 ,we may suppose t ,a is ! *a9-r+1 ,b a cog m\nt$ on a p9 project+ f ! hub1 & ,c a cog atta*$ to ! fix$ axle4 ,x is evid5t t ,b w n move s fa/ r\nd ,c z ,a does4 ,! am\nt by :i* ,a w get ahead ( ,b c be calculat$ easily4 ,we beg9 ) ! :eels 9 ! position %[n 9 ,fig4 #bbc4 ,a po9t1 ,i1 on ,a is exactly ov] ! topmo/ po9t ( ,c4 ,= ! sake ( conv5i5ce we w fir/ assume t in/ead ( ,b runn+ r\nd ,c1 ,b is revolv$ on its axis = "o complete revolution 9 a clockwise direction1 & t ,a & ,c move z 9 ,fig4 #bbd4 ,if ,b has #aj tee?1 ,c #cj1 & ,a #dj1 ,a w h be5 mov$ #aj_/dj #a_/d ( a revolution 9 a clockwise direction1 & ,c #aj_/cj #a_/c ( a revolution 9 an anti-clockwise direction4 ,n[1 com+ back to :at actually does happ51 we %all be able to und]/& h[ f> ,a rotates r\nd ,c relatively to ! motion ( ,b1 :5 ,c is fix$ & ,b rolls 7,fig4 #bbe74 ,b advances #a_/c ( di/ance r\nd ,c2 ,a advances #a_/c #a_/d #g_/ab ( di/ance r\nd ,b4 ,! fractions1 if r$uc$ to a common d5om9ator1 are z #d3g1 & ?is is equival5t to #dj 7numb] ( tee? on ,a73 #dj #cj 7tee? on ,a tee? on ,c47 ,to leave ! read] ) a v cle> idea we w summ>ize ! matt] ?us3--,if ,t numb] ( tee? on ,a1 t numb] ( tee? on ,c1 !n movem5t ( ,a3 movem5t ( ,b33 ,t t3 ,t4 ,"h is a two-spe$ hub4 ,let u c\nt ! tee?4 ,! *a9-r+ 7 ,a7 has #fd int]nal tee?1 & ! c5tral cog 7 ,c7 on ! axle has #af tee?4 ,!re are f\r cogs 7 ,b7 equally spac$1 runn+ on p9s project+ f ! hub-%ell betwe5 ,a & ,c4 ,h[ mu* fa/] ?an ,b does ,a run r\nd ,c8 ,apply ! =mula3--,motion ( ,a3 motion ( ,b33 #fd #af3 #fd4 ,t is1 :ile ,a revolves once1 ,b & ! hub & ! driv+-:eel w revolve only #fd_/hj #d_/e ( a turn4 ,to use sci5tific language1 ,b revolves #bj p] c5t4 sl[] ?an ,a4 ,?is is ! ge>+ we use = hill-climb+4 ,on ! level we want ! driv+-:eel to turn z fa/ z1 or fa/] ?an1 ! *a9-r+4 ,to make x turn at ! same rate1 bo? ,a & ,c mu/ revolve toge!r4 ,9 "o well-kn[n ge> ?is is effect$ by slid+ ,c along ! sp9dle ( ! :eel till x dis5gages itself f ! sp9dle1 & "o end locks ) ! plate :i* c>ries ,a4 ,s9ce ,b is n[ be+ pull$ r\nd at ! bottom z well z ! top1 x _c rotate on its own axis any long]1 & ! :ole tra9 revolves solidly--t is1 :ile ,a turns ?r\gh a circle ,b does ! same4 ,to get an increase ( ge>+1 matt]s mu/ be s arrang$ t ! drive is transmitt$ f ! *a9-:eel to ,b1 & f ,a to ! hub4 ,:ile ,b describes a circle1 ,a & ! driv+-:eel turn ?r\gh a circle & a "p ( a circle--t is1 ! driv+-:eel revolves fa/] ?an ! hub4 ,giv5 ! same numb] ( tee? z be=e1 ! proportional rates w be ,a #hj1 ,b #fd1 s t ! ge> rises #be p] c5t4 ,by means ( prop] me*anism ! p[] is transmitt$ 9 a ?ree-spe$ ge> ei!r 7#a7 f *a9-:eel to ,a1 ,a to ,b1 ,b to :eel l[ ge>2 or 7#b7 f *a9-:eel to ,a & ,c simultane\sly solid1 normal1 or middle ge>2 or 7#c7 f *a9-:eel to ,b1 ,b to ,a1 ,a to :eel high ge>4 ,9 two-spe$ ge>s ei!r #a or #c is omitt$4 99 99 99 99 99 ,,agricultural ,,ma*9es4 ,,! ,,?re%+-,,ma*9e4 ,bread w\ld n be s *eap z x is 7 ! flail /ill ! only means ( sep>at+ ! gra9 f ! /raw4 ,:at ! cream sep>ator has done = ! dairy indu/ry 7p4 #chd71 ! ?re%+-ma*9e has done = agriculture4 ,a page or two ought !re=e to be sp>$ = ?is useful inv5tion4 ,illu/ration3 ,,fig4 #bbf4--,section ( a ?re%+ ma*9e4 ,9 ,fig4 #bbf a v complete =e-&-aft section ( ! ma*9e is giv54 ,aft] ! b&s ( ! %eaves h be5 cut1 ! latt] are f$ into ! m\? ( ! drum ,a by ! fe$]1 :o /&s 9 ! fe$+-box on ! top ( ! ma*9e4 ,! drum revolves at a v high velocity1 & is fitt$ ) flut$ beat]s :i* act aga9/ a /eel concave1 or brea/work1 ,b1 ! gra9 be+ ?re%$ out ( ! /raw 9 pass+ betwe5 ! two4 ,! brea/work is provid$ ) op5 wires1 ?r\gh :i* mo/ ( ! ?re%$ gra91 cav+s 7%ort /raws71 & *aff passes on to a slop+ bo>d4 ,! /raw is flung =w>d on to ! %ak]s ,c1 :i* gradually move ! /raw t[>ds ! op5 end & ?r[ x (f4 ,any gra91 etc41 t has escap$ ! drum falls ?r\gh ! %ak]s on to ,d1 & works backw>ds to ! cav+ riddles1 or mov+ sieves1 ,e4 ,! ma9 bl[]1 by means ( a revolv+ fan1 ,n1 s5ds air along ! *annel ,x upw>ds ?r\gh ^! riddles1 bl[+ ! %ort /raws away to ! left4 ,! gra91 husks1 & du/ fall ?r\gh ,e on to ,g1 ov] ! end ( :i* !y fall on to ! *aff riddle1 ,h4 ,a second column ( air f ! bl[] drives ! *aff away4 ,! heavy gra91 se$s1 du/1 etc41 fall on to ,i1 ,j1 & ,k 9 turn1 & are %ak5 until only ! gra9 rema9s to pass along ,l to ! elevator bottom1 ,m4 ,an endless b& ) cups atta*$ to x scoops up ! gra91 c>ries x al(t1 & %oots x into hopp] ,p4 ,x !n goes ?r\gh ! %ak]s ,q1 ,r1 is du/$ by ! back end bl[]1 ,s1 & slides d[n ,t into ! op5 end ( ! rot>y scre5-drum ,u1 :i* is m\nt$ on ! slope1 s t z x turns ! gra9 travels gradually along x4 ,! fir/ half ( ! scre5 has wires set closely toge!r4 ,all ! small gra9 t falls ?r\gh ?is1 call$ ?irds1 passes into a hopp]1 & is collect$ 9 a sack atta*$ to ! hopp] m\?4 ,! seconds fall ?r\gh ! second half ( ! drum1 m widely spac$1 into _! sack2 & ! fir/s fall out ( ! end & ?r\gh a ?ird sp\t4 ,,m[+-,,ma*9es4 ,illu/ration3 ,,fig4 #bbg4 ,! ord9>y lawn--m[] employs a revolv+ reel1 built up ( spirally-arrang$ knives1 ! edges ( :i* pass v close to a %>p plate project+ f ! frame ( ! m[]4 ,ea* blade1 z x turns1 works along ! plate1 giv+ a %e>+ cut to any grass t may be caught betwe5 ! two cutt+ edges4 ,! action is t ( a pair ( scissors 7,fig4 #bbg71 "o blade repres5t+ ! fix$1 ! o!r ! mov+ knife4 ,if y place a cyl9d] ( wood 9 ! scissors x w be driv5 =w>d by ! clos+ ( ! blades1 & be m>k$ by !m z x passes along ! edges4 ,! same ?+ happ5s ) grass1 :i* is s s(t t x is cut "r ?r\gh4 ,,hay-,,cutt]4 ,! hay-cutt] is ano!r adaptation ( ! same pr9ciple4 ,a cutt]-b> is pull$ rapidly backw>ds & =w>ds 9 a frame :i* runs a few in*es above ! gr\nd by a crank driv5 by ! :eels ?r\gh ge>+4 ,to ! front edge ( ! b> are atta*$ by "o side a numb] ( triangul> knives4 ,! frame c>ries an equal numb] ( spikes po9t+ =w>d horizontally4 ,?r\gh slots 9 ^! ! cutt]-b> works1 & its knives give a draw+ cut to grass caught betwe5 !m & ! sides ( ! spikes4 99 99 99 99 99 ,,"s ,,natural ,,ph5om5a4 ,,:y ,,sun-,,heat ,,v>ies ,,9 ,,int5sity4 ,! m squ>ely p>allel heat-rays /rike a surface ! great] w be ! numb] t c affect t surface4 ,?is is evid5t f ,figs4 #bbh1 #bbi1 :]e ,a ,b is an equal di/ance 9 bo? cases4 ,! ne>] ! sun is to ! horizon1 ! m obliquely d its rays /rike ! e>?4 ,h5ce midday is necess>ily w>m] ?an ! ev5+1 & ! tropics1 :]e ! sun /&s ov]head1 are hott] ?an ! temp]ate zones1 :]e1 ev5 9 summ] at midday1 ! rays fall m or less on ! slant4 ,illu/ration3 ,,fig4 #bbh4 ,illu/ration3 ,,fig4 #bbi4 ,! atmosph]ic envelope :i* encompasses ! e>? t5ds to increase ! effect ( obliquity1 s9ce a slant+ ray has to travel fur!r ?r\gh x & is robb$ ( m heat ?an a v]tical ray4 ,,! ,,tides4 ,all bodies h an attraction = "o ano!r4 ,! e>? attracts ! moon1 & ! moon attracts ! e>?4 ,n[1 ?\gh ! effect ( ?is attraction is n visible z reg>ds ! solid "p ( ! globe1 x is /rongly manife/$ by ! wat] :i* cov]s a l>ge portion ( ! e>?'s surface4 ,! moon attracts ! wat] mo/ p[]fully at two po9ts1 t ne>e/ to x & t fur!/ away f x2 z %[n on an exagg]at$ scale 9 ,fig4 #bcj4 ,s9ce ! e>? & ! wat] revolve z "o mass daily on _! axis1 e po9t on ! circumf]5ce w\ld be daily ne>e/ to & fur!/ f ! moon at regul> int]vals1 & :]ev] !re is ocean !re w\ld be two tides 9 t p]iod1 7 ! moon /ation>y z reg>ds ! e>?4 7,x %\ld be cle>ly und]/ood t ! tides are n great curr5ts1 b m]e ?ick5+s ( ! wat]y envelope4 ,! inru% ( ! tide is due to ! tempor>y rise ( level47 ,illu/ration3 ,,fig4 #bcj4 ,illu/ration3 ,,fig4 #bca4 ,,:y ,,high ,,tide ,,v>ies ,,daily4 ,! moon travels r\nd ! e>? once 9 tw5ty-eight days4 ,9 ,fig4 #bca ! po9t a is ne>e/ ! moon at1 say1 twelve noon4 ,at ! end ( tw5ty-f\r h\rs x w h arriv$ at ! same position by ! compass1 b yet n be ne>e/ to ! moon1 :i* has 9 t p]iod mov$ on #a_/bh? ( a revolution r\nd ! e>?4#dc ,consequ5tly high tide w n occur till a has rea*$ position b & ov]tak5 ! moon1 z x 71 :i* takes ab\t an h\r on ! av]age4 ,?is expla9s :y high tide occurs at int]vals ( m ?an twelve h\rs4 ,illu/ration3 ,,fig4 #bcb4--,relative positions ( sun1 moon1 & e>? at spr+ tides4 ,illu/ration3 ,,fig4 #bcc4--,relative positions ( sun1 moon1 & e>? at neap tides4 ,,neap ,,tides ,,& ,,spr+ ,,tides4 ,! sun1 z well z ! moon1 attracts ! ocean1 b ) less p[]1 ow+ to its be+ s mu* fur!r away4 ,at c]ta9 p]iods ( ! mon?1 sun1 e>?1 & moon are all 9 l9e4 ,sun & moon !n pull toge!r1 & we get ! highe/1 or spr+ tides 7,fig4 #bcb74 ,:5 sun & moon pull at "r angles to "o ano!r--namely1 at ! fir/ & ?ird qu>t]s--! excresc5ce caus$ by ! moon is flatt5$ 7,fig4 #bcc71 & we get ! l[e/1 or neap tides4 #ci ,9 bo? ,figs4 #bjg & #bjh ! degree ( expansion is v greatly exagg]at$4 #dj ,z ! sun passes ! m]idian 7twelve o'clock1 noon7 ! *ronomet]'s read+ is tak51 & ! longitude1 or di/ance ea/ or we/ ( ,gre5wi*1 is reckon$ by ! diff]5ce 9 "t betwe5 local noon & t ( ! *ronomet]4 #da ,= mu* ( ! in=mation giv5 "h ab\t clocks & wat*es ! au?or is indebt$ to ,! ,hi/ory ( ,wat*es1 by ,mr4 ,j4,f4 ,k5dal4 #db ,we %all "h notice only ^? ge>s :i* are includ$ 9 ! hub ( ! driv+-:eel4 #dc ,! orig9al position ( ! moon is indicat$ by ! dott$ circle4 ,,index4 ,,note4--,figures 9 italics signify t an illu/ration ( ! ?+ ref]r$ to appe>s on ! page4 ,ab]ration1 sph]ical1 ( l5s1 #bdc4 ,ac\/ics1 #bid4 ,a*romatic l5s1 #bdc4 ,action c>riage ( piano1 #bhc4 ,advanc+ ! sp>k1 #ajb4 ,air-gun1 #cdb4 ,air-pump = cycle tyres1 #cdj2 = ,we/+h\se brake1 #aii4 ,alt]nat+ curr5ts1 #afd2 dynamo1 #afd4 ,amp]age1 #abe4 ,angle ( advance1 #eg1 #eh2 incid5ce1 #bfh2 reflection1 #bfh4 ,aorta1 #cfj4 ,arc lamp1 #ahb4 ,ar*im$es1 #dab4 ,armature1 #afb4 ,art]ies1 #ceh4 ,art]ial blood1 #cei4 ,atmosph]ic pressure1 #cej4 ,auditory n]ve1 #bgb4 ,automatic brakes1 #ahh2 signall+1 #bbh2 /ok]1 #cii4 ,backfall1 #bih4 ,balance-:eel1 #dai4 ,ball cock1 #cff1 #cfg4 ,balloon1 fire1 #cbc2 gas1 #cdg4 ,b>omet]1 an]oid1 #cbh1 #cbi2 & wea!r1 #cca2 ,=t9's1 #cbf2 mean+ (1 #cbe2 simple1 #cbh2 :eel1 #cbg4 ,beau de ,ro*as1 #hi4 ,bell1 div+1 #ccb2 electric1 #aai1 #abj4 ,bell[s ( organ1 #cjc4 ,bioscope1 #bff4 ,blades1 turb9e1 #ha1 #hc4 ,block sy/em1 #bja1 #bab4 ,blood1 art]ial1 #cei2 circulation (1 #cef1 #ceg1 #cfj2 v5\s1 #cei4 ,bl[]-plate1 #cic1 #cid4 ,boat1 sails (1 #cdf4 ,boil]1 ,babcock & ,wilcox1 #ba1 #bb2 explosions1 #cd1 #cia2 fire-tube1 #ba2 fitt+s1 #ca2 ,lanca%ire1 #be1 #bf2 locomotive1 #bj1 #bc2 multitubul>1 #ba2 pr9ciple (1 #ae2 /or$ en]gy 91 #cb2 v]tical1 #be2 wat] supply to1 #ci2 wat]-tube1 #ba4 ,brakes1 hydraulic1 #ahh2 motor c>1 #aaj2 railway1 #ahg2 vacuum1 #ahi1 #aij1 #aia2 ,we/+h\se1 #aid1 #aie1 #aig4 ,bramah1 #cfc1 #dcg4 ,breezes1 l& & sea1 #cbd4 ,bru%es ( dynamo1 #afa1 #agb4 ,buns5 burn]1 #dji4 ,burn+-glass1 #bcb4 ,cam]a1 !1 #bcc2 p9hole1 #bcd1 #bce4 ,canals1 semicircul>1 #bgc4 ,capill>y attraction1 #cib2 ve9s1 #ceh4 ,c>bon dioxide1 #bg1 #cei2 monoxide1 #bg4 ,c>burett]1 #ih1 #ii4 ,c>dan %aft1 #ic4 ,c>mania1 !1 #hc4 ,c5trifugal =ce1 #chb4 ,*ange-spe$ ge>1 #aje1 #ddb4 ,*assis ( motor c>1 #ib4 ,circulation ( wat] 9 a boil]1 #ag1 #ah1 #ai2 ( wat] 9 a motor c>1 #ie1 #ig4 ,cl>ionet1 #cjh4 ,clock1 fir/ weight-driv51 #dab2 wat]1 #daj4 ,clut* ( motor c>1 #aje4 ,coal1 z fuel1 #ae2 gas1 #cid2 gas mak+1 #cid2 gas plant1 #cif2 gas1 purification (1 #cig4 ,co*lea1 #bgc4 ,coh]]1 #adj4 ,coil1 ,ruhmkorff1 #aba4 ,coke1 #cie4 ,comb9ations 9 ,*ubb lock1 #dcf2 ,yale lock1 #dcf4 ,combu/ion1 #bf1 #cic2 p]fect1 #bh4 ,comp5sat+ ge>1 #ajg1 #ajh4 ,comp\nd eng9es1 #ei2 arrangem5t (1 #fa2 inv5tion (1 #ei4 ,comp\nd locomotives1 #fb4 ,comp\nd microscope1 #bfa4 ,cond5s]1 m>9e1 #ga1 #gb2 ( ,ruhmkorff coil1 #abc4 ,conduit1 #agf4 ,convex l5s1 image ca/ by1 #bcf4 ,conjugate foci1 #bfb4 ,cornet1 #cjh4 ,corti1 rods (1 #bgd4 ,coxwell1 #cdh4 ,cream sep>ator1 #cha1 #chc4 ,curr5t1 rev]sal ( electric1 #acj1 #aca2 trans=mation (1 #abd4 ,cu%ion+ ( /eam1 #ee4 ,cycle1 ge>+ (1 #dci4 ,cyl9d]1 hydraulic press1 #cfc2 /eam1 #di4 ,danes1 #chb4 ,dead po9t1 #dg4 ,de ,br\w] /ok]1 #dja4 ,detector 9 ,*ubb lock1 #dce4 ,div+-bell1 #ccb2 simple1 #ccc1 #ccd4 ,div+-dress1 #cce4 ,direction ( curr5t 9 dynamo circuit1 #afc4 ,div]'s feats1 #cch2 helmet1 #ccf2 lamp1 #cch4 ,donkey-eng9es1 #fh4 ,door/op1 self-clos+1 #cdd4 ,d\ble-cyl9d] eng9es1 #dg4 ,draught1 =c$1 #bh1 #bi2 induc$1 #bi4 ,drum & fusee1 #dad4 ,durability ( motor-c> eng9e1 #if4 ,d-valve1 #fg4 ,dynamo1 alt]nat+1 #afd1 #agd2 bru%es1 #agb2 comp\nd1 #agd2 cont9u\s-curr5t1 #afe2 multipol>1 #afi2 s]ies w\nd1 #agc2 %unt w\nd1 #agc2 simple1 #afa1 #afb4 ,e>1 !1 #bga1 #bgc2 a good1 #bgd1 #cjg2 s5sitiv5ess (1 #bge4 ,ecc5tric1 #eb1 #ec2 sett+ (1 #ec4 ,edison1 ,?omas1 #caj4 ,edison-,bell phonograph1 #caj4 ,electricity1 curr5t1 #aae2 =ms (1 #aac2 nature (1 #aab2 /atic1 #aad4 ,electric bell1 #aai1 #abj2 signall+1 #bbe2 slot1 #bbf4 ,electroplat+1 #ahe1 #ahf4 ,electro-magnets1 #aag4 ,endolymph1 #bgb4 ,eng9es1 comp\nd1 #ei2 donkey1 #fh2 d\ble-cyl9d]1 #dg2 int]nal-combu/ion1 #hg1 #ie2 reciprocat+1 #dd4 ,escapem5t ( timepieces1 #daf2 cyl9d]1 #dbj2 lev]1 #dba1 #dbb4 ,e!r1 #bgj4 ,eu/a*ian tube1 #bgf4 ,eye1 human1 #bdf1 #bdg2 self-accommodation (1 #bdh4 ,expansive work+ ( /eam1 #ef4 ,f>aday1 ,mi*ael1 #aei4 ,field1 magnetic1 #aei2 magnets1 #aga2 r+1 #agd4 ,filt]s1 #cgd2 ,maign51 #cgc2 ,b]kefeld1 #cgd4 ,filtration b$s1 #cgb4 ,flute1 #cjh4 ,fly+-ma*9es1 #cdh4 ,fly-:eel1 use (1 #dh4 ,focus1 mean+ (1 #bcg2 pr9cipal1 #bch4 ,foci1 conjugate1 #bfb4 ,=ce1 l9es (1 #aaf4 ,=ces1 compon5t1 #cde4 ,free :eel1 #ddj4 ,furr+-up ( pipes1 #cia4 ,fusee1 drum &1 #dad4 ,galileo1 #bei1 #cbe1 #daf4 ,galilean telescope1 #bei4 ,gas1 coal1 #cid2 gov]nor1 #djb2 met]1 #dje2 traps1 #cgd2 works1 #cid4 ,gasomet]1 #cig2 l>ge/1 #cih1 #cii4 ,gauge1 /eam1 #cf1 #ch2 wat]1 #ce1 #cf4 ,ge>1 comp5sat+1 #ajg1 #ajh4 ,ge>-box ( motor c>1 #aje4 ,ge>+ ( cycle1 #dci4 ,glai%]1 #cdh4 ,gl&1 #ej1 #cfc4 ,glass1 fl9t & cr[n1 #bdb4 ,go+-b>rel = wat*es1 #dae4 ,goo* rev]s+ ge>1 #fe4 ,gov]nors1 spe$1 #fg2 ( motor c>1 #ajc1 #ajd4 ,graham1 #dah4 ,gramophone1 #cag2 records1 #cai1 #cba2 reproduc]1 #cah4 ,hairspr+1 #dab4 ,hay-cutt]1 #dea4 ,he>t1 !1 #cee2 disease1 #cfa2 rate ( pulsation (1 #cfa2 size (1 #ceg4 ,heat ( sun1 #dea4 ,hele1 ,pet]1 #dab4 ,helmet1 div]'s1 #ccf4 ,helmholtz1 #bgd1 #cjh4 ,h]o ( ,alex&ria1 #gd4 ,h]s*el1 #bfa4 ,h]tz1 ,dr41 #ach4 ,h]tzian waves1 #ach4 ,hot-wat] supply1 #chf4 ,h\r-h& tra9 9 timepieces1 #dbi4 ,h\sehold wat] supply1 #cfd4 ,hughes type-pr9t]1 #acd4 ,hydraulic press1 #cfa1 #cfb4 ,hydro1 #che4 ,ignition ( *>ge 9 motor-c> cyl9d]1 #ajj1 #aja4 ,image & object1 relative positions (1 #bci2 di/ortion (1 #bde4 ,inc&esc5t gas mantle1 #djg2 electric lamp1 #agi4 ,incus1 #bgb4 ,index me*anism ( wat]-met]1 #cg4 ,indicator ( electric bell1 #aai4 ,induction coil1 #aba2 uses (1 #abe4 ,injector1 #ci2 ,giff>d's1 #da2 pr9ciple (1 #dj2 self-/>t+1 #db4 ,int]lock+ ( signals1 #bjd1 #bbb4 ,int]nal-combu/ion eng9e1 #hg4 ,iris ( eye1 #bdi2 /op1 #bdi4 ,kelv91 ,"l1 #aeh4 ,keyless w9d+ me*anism1 #dbe1 #dbf1 #dbh4 ,kite1 #cde4 ,lamp1 arc1 #ahb2 h[ x works1 #cib2 inc&esc5t1 #agi2 manufacture ( inc&esc5t lamps1 #ahj4 ,lap ( slide-valve1 #eg1 #ei4 ,l>ynx1 #cjf4 ,laxey :eel1 #chj1 #cha4 ,leads1 #bjh4 ,l5ses1 #bca2 correction ( = col\r1 #bdj1 #bda2 focus (1 #bcf2 rectil9e>1 #bde2 sph]ical ab]ration 91 #bdc4 ,lev]s1 signal1 col\rs (1 #bjh4 ,limit ( error 9 cyl9d]1 #eb4 ,light1 electric1 #agi2 nature (1 #bcj2 propagation (1 #bca4 ,li ,hung ,*ang1 #aeg4 ,l9dsay1 ,james ,b[man1 #ade4 ,l9es ( =ce1 #aaf1 #afb4 ,l9k+ up1 #fe4 ,locks1 #dcj2 ,b>ron1 #dcc2 ,bramah1 #dcg2 ,*ubb1 #dcc1 #dcd2 ,hobbs1 #dcg2 simple/1 #dca2 tumbl]1 #dcb2 ,yale1 #dcf4 ,lock+ ge> = signals1 #bje4 ,locomotive1 electric1 #agh2 advantages (1 #agi4 ,lungs1 #cei4 ,magic-lant]n1 #bfc1 #bfd4 ,magnet1 #aae2 p]man5t1 #aae1 #aaf2 tempor>y1 #aae4 ,magnetism1 #aae4 ,magnetic ne$le1 influ5ce ( curr5t on1 #abi4 ,ma9spr+1 inv5tion (1 #dab4 ,malleus1 #bgb4 ,m>coni1 #adj1 #adf4 ,m>9e *ronomet]s1 #dae2 delicacy (1 #dbe4 ,m>9e spe$ gov]nor1 #ga4 ,m>9e turb9e1 advantages (1 #hd4 ,maudslay1 ,h5ry1 #cfc4 ,maxim1 ,sir ,hiram1 #cdh4 ,micromet] free :eel1 #dda4 ,micro-photography1 #bfe4 ,microscope1 #bed2 comp\nd1 #bfa1 #bfc2 9 telescope1 #beg2 simple1 #bed4 ,m9]al oil1 #cib4 ,mirror1 p>abolic1 #bfa1 #bfb2 plane1 #bfg4 ,morse1 #acb1 #ade2 code1 #abh2 ink]1 #adb2 s\nd]1 #acb4 ,motor c>1 !1 #ib2 electric1 #agg4 ,m\?1 #cjg4 ,m[+-ma*9es1 #dej4 ,musical s\nds1 #bgg4 ,n]ve1 auditory1 #bgb2 optic1 #bdf4 ,nodes on a /r+1 #bhe2 column ( air1 #bia4 ,note1 fundam5tal1 #bhe2 quality (1 #bhe4 ,niag>a ,falls1 p[] /ation at1 #agd4 ,organ1 !1 #bid1 #cjj2 bell[s1 #cjc2 console1 #cje2 e*o1 solo1 swell1 great1 & *oir1 #cja2 electric & pneumatic1 #cje2 l>ge/ 9 ! _w1 #cjf2 p$als1 #bih2 pipes1 #bie2 pipes1 arrangem5t (1 #bie2 s\nd-bo>d1 #bif2 w9d-*e/1 #big4 ,otto cycle1 #ia4 ,ov]tones1 #bhe4 ,pallets ( organ1 #big4 ,p>allel arrangem5t ( electric lamps1 #ahd4 ,p>is1 siege (1 #bfe4 ,p$als ( organ1 #bih4 ,pelton :eel1 #cgg4 ,p5dulum1 #dab2 comp5sat+1 #dah1 #dai4 ,p]ilymph1 #bgb4 ,p]ry1 ,pr(essor1 #af4 ,petrol1 #ih4 ,phonograph1 #caj2 gov]nor1 #caa2 record]1 #cab1 #cac2 records1 mak+ (1 #cai2 reproduc]1 #cae2 trac+s on record (1 #cag4 ,pian(orte1 #bgg2 s\nd+-bo>d1 #bhj2 /rik+ me*anism1 #bha2 /r+s1 #bha4 ,piccolo1 #cjh4 ,pipes1 clos$1 #bhi2 flue1 #cja2 op51 #bib2 organ1 #bie2 re$1 #cja1 #cjb2 tun+1 #cjb4 ,pi/on valve1 #fg4 ,pneumatic tyres1 #cda4 ,poldhu1 signall+ /ation at1 #ach4 ,po9ts1 railway1 #bjh1 #baj2 & signals 9 comb9ation1 #baa4 ,poles ( a magnet1 #aae4 ,pop(f1 ,pr(essor ,a41 #ach1 #ade4 ,p[]1 transmission (1 #age4 ,preece1 ,sir ,william1 #ade4 ,prim>y w9d+ ( induction coil1 #abb4 ,pump1 air1 #cdj2 bucket1 #ceb1 #cec2 =ce1 #ced2 mo/ m>vell\s1 #cee2 ,we/+h\se air1 #aii4 ,railway brakes1 #ahg2 signall+1 #bjj4 ,rays1 conv]g+ & div]g+1 #bef2 heat1 conc5trat$ by l5s1 #bcb2 light1 #bcb1 #bce1 #bcf1 #bcg4 ,records1 ma/]1 #cai1 #cbj4 ,reciprocation1 #ea4 ,re$1 human1 #cjf2 pipes1 #cja1 #cjb4 ,reflect+ telescope1 #bfj4 ,relays1 telegraphic1 #acc1 #ada4 ,ret9a1 #bdg4 ,retorts1 #cie4 ,rev]s+ ge>1 #fb2 ,allan1 #fe2 ,goo*1 #fe2 radial1 #ff4 ,rock+ b> me*anism = wat*es1 #dbe4 ,rods ( ,corti1 #bgd4 ,ruhmkorff coil1 #aba1 #abb4 ,safety-valve1 #cb1 #cc1 #cia4 ,s&-glasses1 #daa4 ,scissors1 action (1 #dej4 ,second>y w9d+ ( induction coil1 #abb4 ,s]ies arrangem5t ( electric lamps1 #ahc4 ,s]ies w9d+ ( dynamo1 #agc4 ,%unt w\nd dynamo1 #agc4 ,sight1 long & %ort1 #bej4 ,signall+1 automatic1 #bbh2 electric1 #bbe2 pneumatic1 #bbe2 p[]1 #bbe4 ,signal lev]s1 #bjf4 ,signals1 int]lock+ (1 #bjd2 position (1 #bjb2 railway1 #bjj2 s+le l9e1 #bae4 ,sil5c] on motor c>s1 #aji4 ,siphon1 #cea4 ,slide-valve1 #di1 #ej1 #ea2 sett+ (1 #ec4 ,slid]s1 #big4 ,s\nd1 nature (1 #bgj2 bo>d ( organ1 #bif2 bo>d ( piano1 #bhj4 ,spagnoletti disc in/rum5t1 #bab4 ,sp>k+-plug1 #ajb4 ,spectacles1 use (1 #bdi4 ,spectrum1 col\rs (1 #bcj4 ,spe$ gov]nors1 #fg1 #fh1 #fi2 ,h>twell1 #gj2 m>9e1 #ga4 ,spe$ ( motor c>s1 #aaj4 ,spot1 bl9d1 9 eye1 #bea2 yell[1 9 eye1 #bea4 ,spr+ balance = wat*es1 #dai2 comp5sat+1 #dbc1 #dbd4 ,/apes1 #bgb4 ,/eam1 :at x is1 #ac2 en]gy (1 #ad2 eng9es1 #dd2 eng9es1 reciprocat+1 #de2 expansive work+ (1 #ei1 #ha2 gauge1 #cf2 gauge1 pr9ciple (1 #cg2 turb9e1 #gd2 turb9e1 ,de ,laval1 #gf1 #gg2 turb9e1 ,h]o's1 #gd2 turb9e1 ,p>sons1 #gi1 #hj2 volume (1 z comp>$ ) wat]1 #ae4 ,/eph5son1 ,george1 #fc1 #cge4 ,/op1 9 l5s1 #bdd2 iris1 #bdi2 use (1 #bdd4 ,sun-dial ( ,ahaz1 #daj4 ,syntonic transmission ( wireless messages1 #adc4 ,talk+-ma*9es1 #caj4 ,tapp] 9 wireless telegraphy receiv]1 #ada4 ,tappet arm1 #bje4 ,telegraph1 electric1 #abg2 insulator1 #acc2 ne$le1 #abh2 record+1 #acc2 s\nd]1 #acb4 ,telegraphy1 high-spe$1 #ace2 wireless1 #acg4 ,telephone1 #adg2 ,bell1 #adh2 circuit1 d\ble-l9e1 #aee2 circuit1 g5]al arrangem5t1 #aeb1 #aec2 ex*ange1 #aed1 #aee4 ,telephony1 subm>9e1 #aeg4 ,telescope1 #beg2 ,galilean1 #bei2 prismatic1 #bfj2 reflect+1 #bfj2 t]re/rial1 #bei4 ,?re%+-ma*9e1 #ddg1 #ddh4 ,?ur/on1 ,pr(essor1 #ca4 ,tides1 #deb2 high1 #dec2 neap & spr+1 #dee4 ,timbre1 #bhe4 ,tompion1 ,?omas1 #dab4 ,torricelli1 #cbe4 ,tra*ea1 #cjf4 ,tra9 /aff signall+1 #baf2 s+le1 #baf2 & ticket1 #bag2 electric1 #bah4 ,trans=mation ( curr5t1 #abd1 #agf4 ,transmission ( p[]1 #agd1 #age4 ,transmitt]1 ,edison telephone1 #aej2 granul> c>bon1 #aej1 #aea4 ,triple-valve1 #aif4 ,trolley arm1 #agf4 ,turb9es1 /eam1 #gd4 ,turb9ia1 !1 #gi4 ,tympanum1 #acg1 #bga1 #bgb4 ,univ]sal jo9t1 #ic4 ,vacuum brake1 #ahi1 #aij1 #aia4 ,vacuum *amb] ( an]oid b>omet]1 #ccj4 ,valve1 pi/on1 #fg2 safety1 #cb2 ( int]nal-combu/ion eng9e1 #hi4 ,valves ( ! he>t1 #ceg4 ,ve9s1 #ceh2 capill>y1 #ceh2 pulmon>y1 #cfa4 ,v5tral segm5ts1 #bia4 ,v5tricles1 #ceg4 ,vibration ( columns ( air1 #bhh1 #bhi2 ( rods1 #bhg2 ( /r+s1 #bgh2 ( /r+s1 conditions regulat+1 #bgh4 ,vip]1 !1 #hf4 ,virag1 ,pollak--high-spe$ telegraphy1 #acf4 ,vitre\s hum\r1 #bdf4 ,voltage1 #aba1 #afa4 ,v[el s\nds1 #cjh4 ,wasbor\gh1 ,mat!w1 #ea4 ,wat*es1 fir/1 #dab4 ,wat] cock1 #cfe2 eng9es1 #cge2 gauge1 #ce1 #cf2 jacket1 #ai1 #ie2 met]1 #cfh2 supply1 #cga2 turb9es1 #agd1 #cgf2 :eels1 #cge4 ,watt1 ,james1 #ea1 #fi1 #cge4 ,welsba* inc&esc5t mantle1 #djg4 ,we/+h\se air-brake1 #aid1 #aie1 #aig2 ,george1 #aid4 ,:eat/one ne$le in/rum5t1 #abh1 #aca2 automatic transmitt]1 #ace4 ,w9d1 :y x bl[s1 #cbc2 action ( on kites1 #cde2 on sails1 #cdf4 ,w9dmills1 #cge4 ,w9d[1 oval1 9 e>1 #bgb2 r\nd1 9 e>1 #bgb4 ,wireless telegraphy1 #acg2 advance (1 #ade2 receiv]1 #adj1 #ada2 syntonic1 #adc2 transmitt]1 #ach1 #aci4 ,yale lock1 #dcf1 #dcg4 ,yell[ spot1 9 eye1 #bea4 ,ze*1 ,jacob1 #dad4 ,zeiss field-glasses1 #bfj4 ,,! ,,end4