,,optical ,,projection ,a ,,treatise ,,on ,,! ,,use ,,( ,,! ,,lant]n ,,9 ,,exhibition ,,& ,,sci5tific ,,demon/ration ,,by ,,lewis ,,wright ,,au?or ,,( ',,light3 ,a ,,c\rse ,,( ,,exp]im5tal ,,optics' #e,,? ,,edition ,,re-,,writt5 ,,& ,,br\ght ,,up-,,to-,,date ,,by ,,russell ,s4 ,,wright1 ,m4,i4,e4,e4 ,,9 ,,two ,,p>ts ,,"p ,i ,,! ,,projection ,,( ,,lant]n ,,slides ,,) ,,illu/rations ,,longmans1 ,,gre51 ,,& ,,co4 #ci ,,pat]no/] ,,r[1 ,,london1 ,e4,c4 ,,f\r? ,,av5ue #cj,,? ,,/reet1 ,,new ,,york ,,bombay1 ,,calcutta1 ,,& ,,madras #aibj 7,all rights res]v$7 99 99 99 99 99 v ,,preface ,,to ,,! ,,fif? ,,edition ,! fir/ edition ( ?is "w 0 writt5 by my fa!r1 ! late ,mr4 ,lewis ,wright1 & 0 publi%$ 9 #ahij4 ,! reception t x receiv$ te/ifi$ to ! fact t x met a long-felt want1 & successive editions 7 publi%$ 9 #ahie1 #aija1 & #aijf4 ,my fa!r1 un=tunately1 met 8 dea? 9 a railway accid5t 9 #aije1 & ! corrections & additions to ! la/ edition1 :i* _h be5 to a c]ta9 ext5t prep>$ by him1 7 complet$ & writt5 by myself1 & ! "w z publi%$ !n 0 aga9 repr9t$ 9 #aiaa4 ,z ! orig9al text is n[ ?irty ye>s old1 x has seem$ bett] entirely to re-write ! :ole book r ?an make fre% revisions1 ! m s z ! la/ t5 ye>s h se5 great advances 9 ! sci5ce ( ,lant]n ,projection1 & especially 9 ! developm5ts ( ,acetyl5e & ,electric ,light+4 ,x has also seem$ be/ at ! pres5t juncture to issue ! book 9 two p>ts1 ! fir/ deal+ ) ! ,projection ( ,lant]n ,slides only1 & ! second ) ! ,demon/ration ( ,opaque & ,microscopic ,objects1 ,sci5tific ,ph5om5a & accessory app>atus1 includ+ ,c9ematograph ,projection4 ,x mu/ ( necessity be _m mon?s be=e ?is second volume c be produc$1 = ! simple reason t ,optical vi ,in/rum5t ,mak]s h z yet h>dly _h "t to turn r\nd aft] ! w> & produce _! new models1 & !re=e any su* book writt5 n[ c\ld d little m ?an describe app>atus t 0 on ! m>ket prior to #aiad4 ,! pres5t "w1 !re=e1 deals solely ) ! exhibition ( ,lant]n ,slides 9 ! ,optical ,lant]n1 & z su* ,i tru/ w be f\nd ( value to ,s*oolma/]s1 ,social ,work]s1 ,lectur]s1 &1 9 fact1 to all :o use ! lant]n z a means ( illu/ration4 ,,russell ,s4 ,,wright4 ,janu>y #aibj4 99 99 99 99 99 vii ,,cont5ts ,,*apt] ,,page ,i4 ,,introductory #a ,,ii4 ,,! ,,illum9ant #c ,,iii4 ,,p>aff9-,,oil ,,lamps1 ,,inc&esc5t ,,gas ,,& ,,_s ,,burn]s #f ,,iv4 ,,! ,,acetyl5e ,,light #aa ,v4 ,,limelight ,,& ,,! ,,acetyl5e ,,bla/ #af ,,vi4 ,,! ,,electric ,,light #ci ,,vii4 ,,! ,,optical ,,sy/em ,,( ,a ,,lant]n #eg ,,viii4 ,,! ,,body ,,( ,,! ,,lant]n #gj ,,ix4 ,,lant]n ,,boxes1 ,,/&s1 ,,read+ ,,lamps1 ,,etc4 #gf ,x4 ,,scre5s ,,& ,,scre5 ,,/&s #gi ,,xi4 ,,! ,,practical ,,manipulation ,,( ,a ,,lant]n #hb viii ,,illu/rations ,,fig4 ,,page #a4 ,oil ,lamp #f #b4 ,inv]t$ ,inc&esc5t ,lamp #h #c4 ,me?ylat$ ,_s ,burn] #i #d4 ,luna ,lamp #aj #e4 ,! ,moss ,g5]ator #ab #f4 ,! ,a4,l4 or ',popul>' ,model #ad #g4 ,acetyl5e ,jet #ae #h4 ,oxyg5 ,cyl9d] 9 hemp cov] #ag #i4 ,d\ble ,lev] ,key #ah #aj4 ,f9e ,adju/m5t ,valve #ai #aa4 ,con/ruction ( ,be>d's ,regulator #bj #ab4 ,be>d's ,regulator #ba #ac4 ,regulator & ,gauge #bb #ad4 ,gas-bags #bd #ae4 ',bl[-?r\gh' ,nozzles #be #af4 ',bl[-?r\gh' ,jet #be #ag4 ,mix$ ,jet #bg #ah4 ,mix$ ,jet1 ,gwy] patt]n #bg #ai4 ,mix+ ,*amb] ( ,jet #bh #bj4 ',injector' ,jet #cj #ba4 ',gridiron' ,saturator #cb #bb4 ',p5dant' ,saturator #cc #bc4 ,fallot ,air ,bla/ #cg #bd4 ,fallot ,air ,bla/1 & ,cyl9d] #cg #be4 ,lime-tongs #ci #bf4 ,univ]sal ,h&-f$ ,arc ,lamp #de #bg4 #df #bh4 ,resi/ance #di #bi4 ',scissors' ,arc ,lamp #ea #cj4 ',"r-angl$' ,arc ,lamp #eb #ca4 ',we/m9/]' ,arc ,lamp #ec #cb4 ,arc ,lamp ) ,induction ,r+ #ef #cc4 ,! ,optical ,sy/em ( a ,lant]n fac+ p4 #eg #cc;,a4 ,optical ,sy/em ( ,lant]n #eg #cd4 ,optical ,sy/em )\t ,cond5s] #ei #ce4 ,action ( ,cond5s] #ei #cf4 ,=ms ( ,cond5s]s #fj #cg4 ,d\ble ,slid+ ,c>ri] #fb #ch4 ,be>d's ,dissolv+ ,c>ri] #fc #ci4 ,focuss+ ,action ( ,l5s #fd #dj4 ,a*romatic ,l5s #fe #da4 ,petzval ,comb9ation #ff #db4 ,hughes' ,%ort-,range ,lant]n #ga #dc4 ,long-,range ,lant]n #gb #dd4 ,connections = a ,bi-unial ,lant]n #gc #de4 ,be>d's ,circulat+ ,wat] ,tank #ge #df4 ,quadruple ,lant]n ,/& #gh #dg4 ,read+ ,lamp #gi #dh4 ,roll] ,scre5 #hj #di4 ,portable ,scre5 ,/& #ha #ej4 ,adju/m5t ( ! ,light #hd 99 99 99 99 99 #a ,,optical ,,projection ,a ,,treatise ,,on ,,! ,,use ,,( ,,! ,,optical ,,lant]n ,,*apt] ,i ,,introductory ,lant]n ,projection1 z commonly und]/ood1 may be broadly subdivid$ into two bran*es3 7,a7 ,! ,projection ( ,lant]n ,slides1 & 7,b7 ,! ,projection ( ,sci5tific ,ph5om5a1 ,opaque ,objects1 ,microscopic ,specim5s1 c41 usually ref]r$ to broadly "u ! head+ ( ',sci5tific ,demon/ration4' ,to ^! two classes may p]haps n[ be add$ a ?ird1 viz4 ,! ,projection ( ,s-call$ ,liv+ ,pictures1 or1 9 o!r words1 ! ,c9ematograph4 ,9 ! e>li] editions ( ?is "w bo? ,a & ,b 7 dealt ) 9 ! same volume1 b1 z !re are ?\s&s :o require to use a lant]n = ! demon/ration ( lant]n slides only1 & :o h no int]e/ or conc]n ) ,sci5ce ,projection1 x has seem$ to ! writ] t ! "w might1 ) advantage1 be divid$ into two portions1 ,vol4 ,i4 deal+ ) slides only1 & ,vol4 ,,ii4 ) ! v>i\s adaptations ( ! sci5ce lant]n4 ,?is pres5t book !re=e only deals ) ! exhibition ( lant]n slides1 & z su* x w1 ,i tru/1 be f\nd to be ( real assi/ance to ! ord9>y us] ( ! optical lant]n1 includ+ cl]gym51 s*oolma/]s1 army & cadet (fic]s1 & o!rs #b :o require advice & in/ruction 9 ! pur*ase or use ( a lant]n4 ,! ess5tial p>ts ( a lant]n are3 7a7 ,a slide-hold] or c>ri] to hold ! slide2 7b7 a l5s to 'focus' x on ! scre52 7c7 a cond5s] to conv]ge ! light ^u slide & l5s2 7d7 a s\rce ( light or radiant to provide ! necess>y illum9ation2 & 7e7 a body or framework to hold ! :ole toge!r4 ,all possible v>iations 9 *oice ( a suitable lant]n relate to "o or ano!r ( ! above p>ts1 & w be treat$ ( 9 turn2 b1 =tunately1 we h ?is all-important simplification t e ord9>y ,engli% lant]n slide is ! same /&>d size1 viz4 #c in*es squ>e4 ,"s ,cont95tal & ,am]ican slides diff] 9 "o dim5sion f ! above1 b n en\gh to cause any s]i\s difficulty1 & ! conv5i5t ,engli% /&>d is be+ gradually adopt$ ?r\gh\t ! _w4 ,! v>ieties ( slide-hold]s or c>ri]s are !re=e comp>atively few & are *iefly conc]n$ ) ! "q ( rapidly & easily *ang+ ! slides4 ,! *oice ( a focuss+ l5s or objective is ma9ly a matt] ( ! size ( picture requir$1 & ! mo/ conv5i5t di/ance f ! scre5 = ! lant]n to be plac$4 ,v>iations 9 cond5s]s1 :i* are comp>atively small1 are usually only a matt] ( con=m+ ^! ) ! size or type ( objective to be us$1 & %\ld be left to ! manufactur]'s judgm5t4 ,! "q ( a suitable radiant is p>tly a matt] ( ! am\nt ( illum9ation requir$1 & p>tly t ( ! practical possibilities2 = example1 if electric curr5t is available "s =m ( electric light is usually ! mo/ conv5i5t1 z well z ! lea/ exp5sive1 b :]e ?is is n ! case1 p>aff9-oil1 me?ylat$ _s1 inc&esc5t gas1 acetyl5e1 limelight1 c41 are alt]natives :i* all h _! uses & mu/ be consid]$ on _! own m]its4 ,sometimes1 z = example 9 ! case ( a travell+ lectur]1 a lant]n is requir$ fitt$ ) a range ( l5ses = #c halls ( diff]5t size1 & also ) a v>iety ( illum9ants1 & ?is 9 mo/ lant]ns c be easily provid$ =4 ,! body is usually a matt] ( ta/e & price only1 & may range f a simple b effici5t %ell ( ,russian iron to an elaborate mahogany in/rum5t ) a brass front1 screw tilt+ arrangem5ts & o!r adornm5ts2 b ( late ye>s !re has be5 a :olesome reaction aga9/ unnecess>y f9i%1 & a simple metal body ( "s description is n[ *iefly ! ord] ( ! day4 ,9 ! =ego+ rem>ks ! v>i\s p>ts ( a lant]n h be5 m5tion$ 9 :at ,i %\ld consid] ! correct ord]1 />t+ f ! slide & slide-hold]1 & s to speak build+ up ! re/ ( ! in/rum5t r\nd ^! items2 b ,i n[ propose some:at to v>y ! proc$ure & = conv5i5ce deal 9 detail fir/ ) ! ,radiant1 or ,illum9ant4 99 99 99 99 99 ,,*apt] ,,ii ,,! ,,illum9ant ,! fir/ necessity = lant]n projection is a /rong light1 & ?is c be obta9$ f a v>iety ( s\rces1 ! pr9cipal means 9 common use be+ approximately 9 ord] ( excell5ce z foll[s3 p>aff9-oil1 inc&esc5t _s1 inc&esc5t gas1 acetyl5e1 acetyl5e air bla/1 oxyhydrog5 7limelight71 oxye!r1 & electric light 9 its v>i\s =ms4 ,! ideal *>act]i/ics to be s\ght = are 7#a7 great intr9sic brilliancy2 7#b7 m9imum size ( lum9\s spot2 7#c7 fre$om f flick]2 7#d7 fre$om f smell2 7#e7 abs5ce ( any prepond]at+ col\r2 7#f7 *eapness2 & 7#g7 conv5i5ce4 ,!re is no "q :atev] z to :i* ( ! available s\rces ( light mo/ p]fectly comb9es all ! above if x is available1 viz4 ! electric arc4 ,if a curr5t supply is 9 #d ! build+1 ?is =m ( light+ easily excels all o!rs1 except possibly 9 ! matt] ( flick]1 & ev5 9 ?is respect !re is v little fault to be f\nd ) x4 ,f all o!r po9ts ( view x is wellnigh p]fect1 inasmu* z x provides an extremely conc5trat$ & int5sely lum9\s spot1 ( almo/ p]fect :it5ess 7if any?+ slightly blui%71 no smell1 comp>atively little heat1 conv5i5t & inexp5sive4 ,s great is ! advantage ( ! electric arc t attempts h be5 made to use x f accumulators 9 places :]e a curr5t supply is n available1 b ?is _c be s]i\sly recomm5d$1 except 9 special cases4 ,:]e an electric supply is1 h[ev]1 available !re c be no real *oice1 :e!r ! lant]n is requir$ = use 9 a l>ge hall or a small class-room4 ,! advantages ( us+ ! arc are s great t no o!r me?od ne$ be s]i\sly consid]$4 ,! "o real objection t ,i h he>d urg$ aga9/ x is due1 curi\sly en\gh1 to its v p]fection1 & t is1 t x l5ds itself to su* exce$+ly %>p def9ition t any slight imp]fection 9 ! slide is too fai?fully reproduc$ on ! scre51 = :i* reason x is sometimes recomm5d$ t ! op]ator %all "w ) ! objective ! lea/ fraction out ( focus2 b ?is is a matt] = individual ta/e & judgm5t4 ,if1 h[ev]1 !re is no possibility ( us+ ! electric curr5t1 "o ( ! o!r s\rces ( illum9ation mu/ p]=ce be adopt$1 & = a l>ge hall ?is c only be limelight 9 "o ( its _m =ms1 viz4 oxyhydrog51 oxye!r1 oxyacetyl5e1 c4 ,z reg>ds results on ! scre51 ?is light comp>es well ev5 aga9/ ! electric arc1 b x involves ! exp5se & tr\ble ( compress$ gas cyl9d]s1 or ! inf9itely worse rec\rse to ! n[ obsolete me?od ( fill+ gas-bags4 ,limelight is !re=e n[ b little us$ 9 ?is c\ntry1 z ! majority ( l>ge halls are equipp$ ) ! electric #e curr5t1 & = small] build+s x is deem$ unnecess>y & too exp5sive4 ,,acetyl5e is und\bt$ly ! illum9ant mo/ 9 fav\r next to electric light1 z ! light is brilliant en\gh to illum9ate a picture #ab feet 9 diamet] at a di/ance up to1 say1 #cj feet f ! scre51 & ?is suffices 9 a l>ge majority ( cases1 & acetyl5e is comp>atively *eap1 & reasonably simple to "w4 ,,inc&esc5t-,,gas is (t5 employ$ = small class-rooms & is fairly effective = a picture n exce$+ #i or #aj feet 9 diamet]1 & ! same c be said ( ! same type ( burn] heat$ by me?ylat$ _s4 ,,p>aff9-,,oil is ! poore/ ( all pres5t-day =ms ( lant]n illum9ants4 ,! flame is l>ge1 impair+ ! def9ition1 yell[ 9 col\r1 unev5 9 illum9ation1 liable to smoke & smell1 & b>ely equal to inc&esc5t gas 9 illum9at+ p[]4 ,x is !re=e go+ gradually out ( use 9 ?is c\ntry1 b 9 out-(-!-way places1 especially abroad1 x is sometimes ! only practicable light1 & is !re=e /ill employ$ f ! be/ ( all reasons1 necessity4 ,x is n ! int5tion ( ! au?or to give precise work+ in/ruction = all & e v>iety ( ! above illum9ants z manufactur$ by diff]5t firms4 ,= su* ! read] mu/ be ref]r$ to ! directions usually issu$ by ! mak]s !mselves1 b a g5]al description ( ! v>i\s types (f]$ = *oice w n be out ( place1 & x w be m conv5i5t to beg9 ) ! poore/1 viz4 p>aff9-oil1 & f9i% ) ! mo/ p]fect1 ! electric arc4 99 99 99 99 99 #f ,,*apt] ,,iii ,,p>aff9-,,oil ,,lamps1 ,,inc&esc5t ,,gas ,,& ,,_s ,,burn]s ,illu/ration3 ,,fig4 #a4--,oil ,lamp4 ,!re are sev]al v>ieties ( oil lamps on ! m>ket1 b 9 practically e case !y take ! same g5]al =m1 a metal res]voir slid+ 9 grooves 9 ! lant]n body & hold+ approximately a p9t ( oil ) 7usually7 f\r wicks ne>ly p>allel1 b slightly conv]g+ f re> to front1 ^! enclos$ 9 a flame *amb] ( ,russian iron1 ) loose well-anneal$ ends ( %eet glass & an adju/able reflector at ! back1 or sometimes ! reflector itself =ms ! re> end ( ! flame *amb]4 ,! *imney mu/ be tall & is n[ usually made adju/able1 ?\gh ,i h nev] be5 able to trace any real advantage f ?is complication #g 7,fig4 #a74 ,! :ole secret ( obta9+ ! be/ results f ^! lamps may be summ$ up--good oil & p]fect cleanl9ess2 & x is wond]ful :at c be done :5 ^! po9ts are prop]ly att5d$ to4 ,c>e %\ld be tak5 9 trimm+ ! wicks to see t no *>r$ p>ts fall d[n betwe5 ! wick hold]s1 b x makes little diff]5ce :e!r ! trimm+ is done ) scissors or by rubb+ ) ! f+]4 ,special lamp scissors are sold by all mak]s ) a l>ge flat on "o side to cat* ! portions cut (f4 ,^! lamps %\ld be well rubb$ ov] ! la/ ?+ be=e use1 z p>aff9-oil is apt to 'creep1' & ! op]ator does n want to be told t 8 app>atus is sugge/ive ( a fri$ fi% %op4 ,9 work+ ) ^! lamps x is difficult to avoid a d>k /reak d[n ! c5tre ( ! %eet1 repres5t+ ! space betwe5 ! two c5tre wicks2 to a c]ta9 ext5t ?is c be obviat$ by adju/+ ! reflector1 & 9 any case is n v obvi\s :5 ! slide is 9 place4 ,lamps con/ruct$ ) ei!r ?ree or five wicks are bett] 9 ?is respect1 b ! =m] are usually consid]$ to be too poor 9 illum9at+ p[]1 & ! latt] are apt to crack ! %eet-glass ends by excessive heat4 ,,inc&esc5t ,,gas4--,inc&esc5t gas burn]s d n ne$ mu* description1 z !y are practically simil> to ^? 9 g5]al use = h\se light+4 ,!y may be ei!r ( ! erect or inv]t$ =ms1 ! latt] be+ pref]able ow+ to ! light be+ m conc5trat$1 & a reflector is provid$ to increase ! illum9ation 7,fig4 #b74 ,^! reflectors %\ld be sph]ical & s adju/$ t ! radiant is 9 ! c5tre ( curvature1 ?us ensur+ t ! light f ! reflector passes aga9 ?r\gh ! orig9al s\rce4 ,if ?is po9t is n att5d$ to1 we %all be deal+ ) ess5tially two s\rces ( light in/ead ( "o1 to ! detrim5t ( ! def9ition4 ,! same rem>k applies to e lant]n illum9ant #h :i* is supplem5t$ by a reflector1 & x is extraord9>y h[ (t5 x is neglect$ by ! manufactur]4 ,( c\rse ! opacity ( ! illum9ant de/roys mu* ( ! effici5cy ( ! reflector1 & h5ce 9 ! case ( inc&esc5t gas mantles !re is n mu* real ga9 9 mak+ use ( !m1 b ) ^! comp>atively weak illum9ants e fraction tells1 & ! reflector does n add mu* to ! co/4 ,illu/ration3 ,,fig4 #b4--;,inv]t$ ,inc&esc5t ,lamp4 ,9 light ! inv]t$ gas burn] is v little sup]ior to oil1 b x is :it]1 slightly m conc5trat$1 & fre] f smell1 & !re=e to be reg>d$ z pref]able if a supply ( gas is available4 ,,me?ylat$ ,,_s ,,burn]s4--,inc&esc5t mantles heat$ by me?ylat$ _s are also l>gely us$1 & provide a light decid$ly sup]ior to gas & ne>ly equal to acetyl5e4 ,"s arrangem5t mu/ be made = volatilis+ ! _s & driv+ ! vap\r out "u pressure1 & ! mo/ usual contrivance is some:at z illu/rat$ 9 ,fig4 #c4 ,9 ?is app>atus ! _s is conta9$ 9 a metal res]voir at ! re> & air pressure is provid$ by a pair ( rubb] balls & valves aft] ! mann] ( a m$ical spray4 ,suffici5t #i pressure hav+ be5 obta9$1 ! liquid _s is =c$ into a vaporis+ *amb] imm$iately beh9d ! mantle1 & a k9d ( m9iature pit*=k1 ) its prongs wrapp$ 9 asbe/os wool1 is soak$ 9 _s1 & pu%$ ov] ! brass fitt+ ( ! burn] 9 su* a way t :5 light$ ! flame heats ! *amb] & volatilises ! _s4 ,! burn] c n[ be lit1 & al?\gh ! =k burns out 9 ! c\rse ( a m9ute or s1 ! heat f ! mantle itself is !reaft] suffici5t to vaporise ! _s z rapidly z requir$4 ,?is lamp works exce$+ly well 9 practice1 b has "o drawback1 viz4 t x is possible to obta9 too mu* pressure & squirt liquid _s ?r\gh ! burn]1 :5 x naturally cat*es fire & may ev5 run on to ! floor4 ,illu/ration3 ,,fig4 #c4--,me?ylat$ ,_s ,burn]4 ,an accid5t ( ?is sort is r>e & usually h>mless ev5 if x does occur1 b an audi5ce is easily fright5$1 & h5ce ?is burn] %\ld only be us$ by an op]ator ) exp]i5ce4 ,an altoge!r bett] arrangem5t is t made by ,messrs4 ,hughes ( ,k+sl& & kn[n z ! ',luna' ,lamp 7,fig4 #d74 ,9 ?is burn] !re is no pump & no volatilis+ *amb]2 #aj ! _s is conta9$ z be=e 9 a metal res]voir & a sep>ate burn] und]nea? is us$ to keep ?is suffici5tly hot to bo? vaporise ! _s & provide ! necess>y pressure4 ,! heat c be regulat$ by means ( an adju/able %ea? to ! burn]1 & a simple safety valve provides aga9/ an excess ( vap\r4 ,i d n say t an accid5t ( ! sort previ\sly ref]r$ to is impossible ev5 ) ?is burn]1 b ,i h nev] he>d ( x happ5+1 & ! lamp is c]ta9ly ! be/ app>atus ( its k9d t ,i am acqua9t$ )4 ,illu/ration3 ,,fig4 #d4--,luna ,lamp4 ,,inc&esc5t ,,electric ,,lamps4--,inc&esc5t electric lamps ( ! ord9>y metal or c>bon filam5t type are also frequ5tly us$ 9 small class-rooms1 & %\ld be m5tion$ "h1 z !y provide approximately ! same illum9ation z a gas mantle1 or 9 "s cases r bett]4 ,x w1 h[ev]1 be m conv5i5t to deal ) ! "q ( electric light+ z a :ole 9 ! *apt] devot$ to x4 ,x w suffice "h to say t lamps are made = ! purpose ) a special filam5t arrang$ to provide a conc5trat$ light1 ! ord9>y type be+ almo/ useless 9 ?is respect1 & t small batt]y lamps1 work$ by a suitable accumulator1 c also be us$1 b except "u v special circum/ances are h>dly wor? ! tr\ble ( keep+ ! batt]ies *>g$4 99 99 99 99 99 #aa ,,*apt] ,,iv ,,acetyl5e ,!re is no d\bt t at pres5t acetyl5e holds second place to electric light 9 popul>ity = optical lant]n "w4 ,! light is good2 n1 x is true1 s good z limelight or ! electric arc1 b /ill suffici5t = a picture up to #ab feet 9 diamet] at a work+ di/ance f ! scre5 ( n m ?an #cj feet1 & ?is suffices = ! l>ge majority ( halls4 ,x has great advantages ov] limelight 9 conv5i5ce & *eapness1 al?\gh on bo? ^! po9ts x mu/ yield place to ! electric arc1 always provid+ t curr5t is available1 & !re=e x is *iefly us$ 9 c\ntry di/ricts & 9 gas-lit halls 9 l>ge t[ns4 ,acetyl5e gas is =m$1 z is well kn[n1 by ! action ( wat] ^u c>bide ( calcium1 & ! g5]ators con/ruct$ = lant]n "w are ess5tially ! same 9 con/ruction z = o!r purposes4 ,! alt]ations introduc$ are *iefly direct$ t[>ds obta9+ a light z /eady z possible f a comp>atively small g5]ator1 &1 secondly1 t[>ds ! entire elim9ation ( smell1 :i* obvi\sly is f> m s]i\s 9 a lecture hall ?an1 = in/ance1 on a motor c>4 ,! g5]ators 9 mo/ common use may be divid$ into two classes1 i4e4 ^? on ! gasomet] pr9ciple 9 :i* ! c>bide is gradually l[]$ into ! wat]1 & ^? 9 :i* ! wat] is all[$ sl[ly to ga9 access to ! c>bide4 ,a good example ( ! =m] is p]haps t made by ,messrs4 ,moss ( ,birm+ham1 ?\gh !re are sev]al o!rs equally good1 & cle> & explicit directions = work+ %\ld be suppli$ by ! mak]s4 ,! ,moss ,g5]ator 7,fig4 #e7 consi/s ( a tall iron vessel ,a fitt$ ) a gas tap at bottom1 ?is communicat+ #ab ) a v]tical iron tube )9 ! vessel4 ,into ?is conta9] fits ! inn] bell or conta9] ,b1 divid$ int]nally into two conc5tric portions entirely sep>at$ f ea* o!r1 b connect$ by ! pipe ,p ,p & ! tap ,t4 ,a guide inside ! bell encircles ! iron tube 9 ! out] tank & prev5ts rotation4 ,into ! inn] portion fits aga9 ! c>bide-conta9] 7%[n sep>ately on ! left71 :i* is lock$ :5 9 place by giv+ x a half turn1 :5 a hook inside ! bell engages ) ! l[] edge ( ! c>bide conta9] & prev5ts x f fall+4 ,! c>bide conta9] is fitt$ ) a s]ies ( %elves1 & ! cont5ts ( a #b lb4 t9 ( c>bide %\ld be r\ghly divid$ among !m2 !re is no ne$ to make any accurate division4 ,! c>bide us$ %\ld be t kn[n z in* me%1 & %\ld be pure4 ,t describ$ z '*emically' treat$ is apt to give tr\ble by ov]-g5]ation 9 ^! gasomet]s & %\ld be scrupul\sly avoid$4 ,illu/ration3 ,,fig4 #e4--,! ,moss ,g5]ator4 ,! c>bide hav+ be5 plac$ 9 ! receptacles1 ^! %\ld be clos$ by means ( ! loose flap & ! :ole pu%$ into ! bell & secur$4 ,wat] %\ld be p\r$ into ! out] vessel up to a m>k on ! iron tube1 & ! bell plac$ 9 position4 ,! l[] tap be+ !n turn$ on & ! upp] "o clos$1 air f ! out] portion ( ! bell c gradually escape by means ( ! iron tube & l[] tap1 & ! bell gradually s9ks by its own weight until x is on ! bottom1 b /ill #ac no wat] c rea* ! c>bide1 ! air imprison$ 9 ! inn] portion ( ! bell effectually exclud+ x4 ,! l[] tap %\ld n[ be connect$ by means ( india-rubb] or flexible metallic tub+ to ! burn] 9 ! lant]n 7( :i* m anon71 & ! upp] tap on ! g5]ator turn$ on1 ! tap or taps on ! burn] be+ likewise op5$4 ,! air f ! inn] portion ( ! bell c n[ escape by ! pipe ,p ,p into ! out] "p1 & !nce ?r\gh ! iron tube1 & out ?r\gh tub+ & jet1 & z x does s wat] w rise 9 ! int]ior & attack ! c>bide4 ,9 a few mom5ts ! burn] c be lit2 b ! gas1 be+ g5]at$ f> 9 excess ( requirem5ts1 & fill+ bo? ! inn] & out] portions ( ! bell fa/] ?an x c escape1 lifts ! latt] until ! c>bide is entirely out ( ! wat]1 :5 9 a few m9utes g5]ation ceases4 ,if ! jet is left burn+ ! bell w gradually s9k aga9 z ! gas is us$ up1 & %\ld !reaft] ma9ta9 an automatic balance )\t att5tion4 ,x c be turn$ (f at any mom5t by simply clos+ ! taps at ! jet or1 bett]1 ! l[] tap at ! g5]ator1 :5 ! bell rises suffici5tly to take ! c>bide out ( ! wat]2 b if x is requir$ to leave ! g5]ator unlit = a consid]able "t1 x is bett] to turn (f ! tap on ! top fir/4 ,?is causes ! inn] portion ( ! bell to fill ) gas :i* _c escape1 & z t 9 ! out] "p burns out1 ! bell s9ks to ! bottom & rema9s !re1 ! gas itself imprison$ 9 ! inn] *amb] exclud+ ! wat] f ! c>bide4 ,! exact arrangem5t v>ies 9 diff]5t patt]ns ( g5]ator1 b ! above may be tak5 z r\ghly indicat+ ! action1 & fur!r in=mation may always be obta9$ f ! mak] or deal]4 ,empty+ %\ld always be done out ( doors1 z ! od\r ( acetyl5e gas is mo/ objectionable1 & = ! same reason rubb] tubes1 c41 %\ld be securely ti$ on1 s t ! slighte/ escape may be avoid$4 #ad ,if ! exhibition has be5 a %ort "o x w (t5 be f\nd t ! upp] cells h n be5 affect$ by ! wat]1 9 :i* case !y may be put back 9 ! t9 & us$ aga91 b x is n g5]ally advisable to put 9 less ?an ! full *>ge to beg9 ) z ! weight ( ! c>bide plays a def9ite "p 9 secur+ ! smoo? action ( ! app>atus4 ,! sludge %\ld be ?r[n away 7x =ms a good manure = ! g>d57 & ! entire g5]ator ?or\ghly dri$1 o!rwise ru/ w quickly appe>4 ,illu/ration3 ,,fig4 #f4--,! ,a4,l4 or ',popul>' ,model4 ,!oretically "o ( ^! g5]ators may be fill$ & left /&+ indef9itely1 b 9 practice x is n advisable1 z ! damp 9 ! atmosph]e is apt to produce a v sl[ g5]ation ( gas1 suffici5t (t5 to cause a decid$ smell4 ,( g5]ators :i* act by admitt+ wat] to ! c>bide p]haps ! be/ kn[n is ! ,a4,l4 or ',popul>' ,model 7,fig4 #f71 ?is be+1 9 fact1 a patt]n design$ = motor-c> head-lights1 b :i* answ]s well = lant]n "w4 ,its exact op]ation ne$ h>dly be describ$ "h 9 full detail4 ,x w suffice to say t ! wat] ga9s access to ! c>bide by 'creep+' up betwe5 two conc5tric copp] cones1 & 9 ! ev5t ( ov]-g5]ation ! pressure ( ! gas automatically *ecks ! fl[4 ,?is g5]ator is small] ?an ! gasomet] patt]n1 & h5ce c be recomm5d$ = portability2 b 9 my exp]i5ce ! light is n q s /eady1 & ! control r less delicate1 !reby caus+ on occasions a p]ceptible smell1 especially if left /&+ = a consid]able "t4 ,!re are o!r types ( g5]ators1 su* z ! ',wat] #ae dropp+' v>iety1 9 :i* ! wat] drips on to ! c>bide1 & ! rev]se1 9 :i* f9e granulat$ c>bide drops a little at a "t into wat]2 b ^! types are n v frequ5tly met ) & ne$ h>dly be describ$4 ,x %\ld nev] be =gott5 t acetyl5e is an explosive gas & %\ld be treat$ z su*4 ,se>*+ = a leak ) a light$ mat*1 ?\gh p]haps p]missible :5 ! op]ator kn[s 8 bus9ess1 may be a dang]\s proce$+ :5 ! contr>y is ! case4 ,illu/ration3 ,,fig4 #g4--;,acetyl5e ,jet4 ,acetyl5e burn]s are g5]ally ( ! ',batsw+' type1 & are z a rule f\r 9 numb]1 m\nt$ 9 a r[ ) a reflector beh9d1 ea* burn] be+ sep>ately controll$ by its own tap 7,fig4 #g74 ,an acetyl5e flame is v smoky1 & c>e mu/ be tak5 t ! burn]s are n turn$ too high4 ,a nipple clean]1 consi/+ ( a f9e wire 9 a %ort h&le1 c usually be obta9$ f any deal]1 & is v h&y4 ,acetyl5e gas c also be us$ = lant]n illum9ation 9 q ano!r way1 viz4 by a bla/ f a bl[pipe1 9 comb9ation ) ei!r air or oxyg51 on to a special ',pa/ille' provid$ = ! purpose1 or an ord9>y limelight jet c be us$4 ,^! me?ods entail ! use ( acetyl5e "u pressure1 & are s analog\s to limelight t ,i %all = conv5i5ce deal ) !m 9 ! *apt] devot$ to t illum9ant4 99 99 99 99 99 #af ,,*apt] ,v ,,limelight ,,& ,,! ,,acetyl5e ,,bla/ ,! illum9ation possible ) ?is light is almo/ unlimit$1 & = really l>ge halls x is1 z rem>k$ be=e1 ! only sub/itute = ! electric arc4 ,x consi/s ess5tially ( a bl[pipe flame1 compos$ ( oxyhydrog51 oxye!r1 oxyspirit1 oxy-acetyl5e1 c41 or acetyl5e air bla/1 heat+ to inc&esc5ce a block ( lime1 or o!r refractory mat]ial1 & ! ess5tial feature is t "o at lea/ ( ^! gases mu/ be "u pressure4 ,?irty ye>s ago ?is 0 usually a*iev$ by /or+ ! gas 9 rubb] bags1 & obta9+ ! requisite pressure by means ( heavy weights2 b except 9 a v few outly+ di/ricts ?is me?od has n[ be5 completely sup]s$$ by ! use ( compress$ gas cyl9d]s4 ,! e>li] editions ( ?is "w conta9$ v full directions = manufactur+ gas = /orage 9 bags1 b x is s exceptional n[ to f9d an op]ator :o uses ?is me?od t x seems h>dly necess>y to devote mu* space to x1 & ! same may be said ( automatic oxyg5 'g5]ators4' ,! pres5t "w w !re=e deal *iefly ) compress$ gas cyl9d]s4 ,mo/ elaborate precautions are n[ en=c$ by ! ,bo>d ( ,trade to ensure ! absolute safety ( ^!1 & any d\bt exi/+ f occasional accid5ts ( ye>s ago may be promptly dismiss$4 ,humanly speak+1 an accid5t n[adays _c happ51 except by su* wilful neglig5ce on ! "p ( ! mak] or fill] z w\ld almo/ r5d] ! culprit subject to crim9al proce$+s4 ,compress$ gas cyl9d]s are pa9t$ a di/9ctive col\r1 oxyg5 = example be+ black & coal gas or hydrog5 r$2 ! screw connections to ! pumps1 & all nozzle #ag & regulator fitt+s1 are made ) a totally diff]5t screw & !re=e _c be int]*ang$2 ! cyl9d]s !mselves are b\nd by law to be reanneal$ & rete/$ "u hydraulic pressure at regul> int]vals2 ! /eel itself has to be ( a gu>ante$ quality2 &1 9 fact1 e possible risk is gu>d$ aga9/4 ,! mo/ usual sizes ( cyl9d]s suppli$ = lant]n exhibitions are ^? conta9+ #f1 #ab1 #bj1 or #dj cubic feet1 & are usually s5t out 9 wood5 or hemp cases4 ,illu/ration3 ,,fig4 #h4--,oxyg5 ,cyl9d] 9 hemp cov]4 ,fig4 #h %[s a #ab-;foot cyl9d] 9 its hemp case1 ! approximate size )\t case be+ #bb 94 by #d 94 ,?is size cyl9d] w supply an av]age limelight jet = j ov] two h\rs4 ,! extra p[]ful jets z us$ = c9ematograph "w or = illum9at+ a v l>ge scre5 take a good deal m1 b = ! usual app>atus z suppli$ = ord9>y lant]n purposes ?is is a pretty safe figure4 ,a #ab-;foot cyl9d] is !re=e ! fav\rite size = a lant]n exhibition la/+ f an h\r to "o & a half h\rs1 z x leaves a fair m>g9 = gas us$ 9 adju/+ ! in/rum5t1 c41 & a #bj-;foot cyl9d] w usually suffice = two su* exhibitions4 ,! price ( gas p] cubic foot v>ies ) ! size ( ! cyl9d]1 be+ less = l>ge cyl9d]s ?an = small ones1 & ! co/ ( transit is also less 9 proportion--h5ce x is frequ5tly an economy to hire a l>ge cyl9d] & reta9 x = sev]al exhibitions4 ,on ! o!r h& mo/ suppli]s *>ge a small r5t if a cyl9d] is reta9$ beyond a def9ite #ah "t1 s ?is is a "q to be decid$ by ea* us] on its own m]its4 ,alt]natively1 ( c\rse1 cyl9d]s c be pur*as$1 & ! "q ( r5t does n !n come 92 also gas is suppli$ a little *eap] 9 a cu/om]'s own cyl9d] ?an if s5t on hire4 ,if pur*ase is decid$ on x is frequ5tly an economy to buy two1 or two ( ea* gas1 if coal gas cyl9d]s are requir$ z well4 ,illu/ration3 ,,fig4 #i4--;,d\ble ,lev] ,key4 ,! :ole cont5ts ( ! cyl9d]s c !n be us$ up )\t wa/e1 z if a cyl9d] %\ld become exhau/$ dur+ ! c\rse ( a lecture1 x is only a matt] ( a m9ute or two to *ange ov] to ! sp>e "o1 :]eas ! compressors are requir$ by law to empty out e cyl9d] return$ to !m = refill+1 & any rema9+ gas is !reby wa/$4 ,x is extremely tantalis+1 to say ! lea/ ( x1 to f9d ! pressure gauge indicat+ t !re is1 say1 #h feet ( gas rema9+ 9 a cyl9d]1 & to be compell$ to wa/e ?is or else risk runn+ %ort = ! next exhibition1 & duplicate cyl9d]s are ! only way ( avoid+ ! loss4 ,! cyl9d]s are fill$ to a pressure ( #abj atmosph]es1 or #ahjj lb4 p] squ>e in*1 & are clos$ by /rong screw nozzles4 ,! keys = op5+ or clos+ ^! are ( ?ree types1 viz4 ! ',t' patt]n1 ',spann]' patt]n1 & t kn[n z ! ',d\ble ,lev]' type4 ,?is latt] is s made t 9 clos+ ! valve x %uts up to half its l5g? & #ai op5s out to d\ble ! lev]age :5 be+ us$ to op5 ! cyl9d] 7,fig4 #i74 ,! idea is to avoid ! possibility1 :i* has be5 kn[n to occur1 ( ! cyl9d] valve be+ screw$ d[n by a p[]ful wri/ & defy+ ! ef=ts ( ! despair+ lant]ni/ to op5 x4 ,illu/ration3 ,,fig4 #aj4--;,f9e ,adju/m5t ,valve4 ,cyl9d] nozzles are un=tunately n yet /&>dis$1 b ^? mo/ frequ5tly met ) 9 ?is c\ntry are ^? adopt$ by ! ,briti% ,oxyg5 ,company1 bo? oxyg5 & coal gas cyl9d]s be+ fitt$ ) correspond+ int]nal screws #g_/h in* diamet]1 ^? = oxyg5 be+ "r-h&$1 & ^? = coal gas left-h&$1 & 9 ea* case t]m9at$ at ! bottom by a holl[ metal cone4 ,z su* an int]nal screw _c obvi\sly be connect$ to a piece ( rubb] tub+1 "s type ( screw connector mu/ be employ$1 & ?is may take "o ( ?ree =ms3 7#a7 ,a simple connect+ nozzle1 7#b7 a f9e adju/m5t valve1 or 7#c7 a regulator4 ,! fir/ is seldom us$ 9 practice = lant]n "w1 = ! reason t ! direct pressure ( a full cyl9d] 7#abj atmosph]es7 _c be *eck$ or controll$ by a tap on ! jet1 z ! int]v5+ rubb] tub+ w\ld ei!r bur/ or bl[ (f1 & mu/ !re=e be regulat$ at ! cyl9d] nozzle itself1 & gradually readju/$ z ! pressure dim9i%es4 ,to a*ieve ?is regulation ) ! ord9>y cyl9d] key is difficult1 ?\gh possible to a c>eful op]ator1 b = a slight extra exp5se a comb9$ nozzle & f9e adju/m5t valve 7,fig4 #aj7 c be obta9$1 & regulation ) ?is is #bj inf9itely easi]4 ,! be/ plan ( all1 h[ev]1 is to use an automatic regulator1 :i* n only r$uces ! pressure s z to p]mit ( ! requir$ adju/m5ts be+ made at ! jet-taps1 b also ma9ta9s a practically /eady supply z ! cyl9d] empties1 !reby obviat+ cont9ual readju/m5ts4 ,regulators are n[ s inexp5sive t !y h come into almo/ univ]sal use1 & are g5]ally reckon$ an indisp5sable "p ( a limelight lant]n equipm5t4 ,! =m ( regulator 9 mo/ common use is t usually kn[n z ',be>d's1' hav+ be5 orig9ally design$ & pat5t$ by ,messrs4 ,r4 ,be>d ,sons1 ?\gh z ! pat5t has n[ expir$ x is op5 to any firm to make ! same article if !y desire4 ,illu/ration3 ,,fig4 #aa4--;,con/ruction ( ,be>d's ,regulator4 ,! con/ruction ( ,be>d's ,regulator is %[n 9 ,fig4 #aa4 ,! gas ent]s f bel[ into a rubb] bag1 ,c1 f :i* x c em]ge ?r\gh ! nozzle4 ,any accumulation ( gas raises ! bell[s aga9/ ! pressure ( a spiral spr+ press+ x d[n1 & ?is br+s into action an arrangem5t ( s-call$ ',lazy ,lev]s1' :i* 9 turn presses d[n a small conical valve & closes ! supply f ! cyl9d]1 ?is valve re-op5+ imm$iately ! pressure dim9i%es4 ,! outw>d =m ( ?is regulator is %[n 9 ,fig4 #ab1 #ba :i* incid5tally also illu/rates ! usual =m ( connection to ! cyl9d]1 ref]r$ to lat] on4 ,9 ,be>d's ,regulator ! pressure at :i* ! gas c be deliv]$ is det]m9$ by ! /r5g? ( ! spiral spr+1 & c only be alt]$ by *ang+ ?is spr+4 ,illu/ration3 ,,fig4 #ab4--;,be>d's ,regulator4 ,9 practice ,be>d's ,regulators are suppli$ set to a l[ pressure = ord9>y mix$ or 'bl[-?r\gh' jets & = a high] pressure 7#ad-af in*es7 = 'injector' jets4 ,at ?is latt] pressure ! rubb] tub+ us$ mu/ be fairly ?ick & /rong & well ti$ on1 & ev5 s ! taps ( ! jet %\ld n be turn$ entirely (f unless ! gas at ! cyl9d] is likewise turn$ (f imm$iately aft]w>ds4 ,! ,briti% ,oxyg5 ,company make a regulator :i* c be set to any desir$ pressure1 b x is n q s delicate 9 its action z ,be>d's1 & ,messrs4 ,cl>kson also make a patt]n regulator :i* is widely us$ & well spok5 (4 ,! atta*m5t ( any ( ^! fitt+s to ! cyl9d] is a some:at peculi> "o1 z w be se5 on ref]5ce to ,fig4 #aj or ,fig4 #ab4 ,! regulator or nozzle ends at its l[] extremity 9 a screw & cone1 ! latt] be+ int5d$ to make a gas-tight connection ) ! int]nal cone on ! cyl9d]1 & ov] ?is screws a loose w+ piece ) ano!r out] screw1 ?is latt] fitt+ ! ?read 9 ! cyl9d]4 ,9 mak+ ! connection c>e mu/ be tak5 t ! w+ piece is n screw$ too f> d[n ! inn] screw1 or ! cone w n rea* d[n & make a tight fit on its #bb seat+2 9 its correct position ! w+ piece :5 clamp$ d[n %\ld leave a turn or two ( its ?read expos$1 9 ord] to ensure t ! cone does b$ prop]ly4 ,illu/ration3 ,,fig4 #ac4--,regulator & ,gauge4 ,c>e %\ld be tak5 t ! nozzle ( ! cyl9d] is free f du/ be=e atta*+ any ( ^! fitt+s3 ! be/ plan is fir/ to bl[ into x1 & f9ally wipe x r\nd ) ! f+]4 ,mo/ pr(essional op]ators hamm] ! w+ piece home ) a spann] or o!r conv5i5t implem5t a b>b>\s me?od & really unnecess>y if ! cones are 9 good condition1 b1 nev]!less1 almo/ always adopt$ 9 practice4 ,,pressure ,,gauges4--,^! are useful 9 det]m9+ ! am\nt ( gas rema9+ 9 a cyl9d] & are ( a v usual type2 !y may ei!r be screw$ on to ! cyl9d] be=e comm5c+ to "w & tak5 (f aga9 to screw on ! regulator1 or !y c be suppli$ fitt$ to ! regulator itself1 9 :i* case !y c be obs]v$ dur+ ! c\rse ( ! exhibition 7,fig4 #ac74 ,z ! same gauge may be us$ = cyl9d]s ( diff]5t sizes 7?\gh nev] = ^? conta9+ #bc diff]5t gases71 !y simply regi/] 9 atmosph]es1 & kn[+ t a full cyl9d] %[s a pressure ( #abj atmosph]es1 ! requisite calculation mu/ be made to det]m9e h[ _m cubic feet are unus$4 ,9 ! case ( oxyg5 cyl9d]s an approximate idea ( ! am\nt ( gas rema9+ c be got by weigh+ x c>efully :5 kn[n to be ei!r absolutely full or absolutely empty1 & re-weigh+ x :5 in=mation is requir$4 ,oxyg5 weighs approximately #a4d oz4 p] cubic foot1 & ?is is easily detect$ by an av]age scale4 ,coal gas is too light to be gaug$ 9 ?is way4 ,,gas-,,bags ,,& ,,g5]ators4--,x has already be5 rem>k$ t !re are two alt]native me?ods ( obta9+ gas "u pressure = limelight purposes1 viz4 gas-bags & g5]ators 7! latt] = oxyg5 alone3 !re is no good hydrog5 g5]ator t ,i "k (74 ,9 bo? ^! cases ! oxyg5 is g5]at$ by heat+ a mixture ( *lorate ( pota% & manganese black oxide4 ,9 ! case ( gas-bags ! gas is prep>$ be=eh& & pass$ ?r\gh suitable purifi]s into a rubb] gas-bag4 ,) a g5]ator ! oxyg5 is evolv$ dur+ ! exhibition itself2 b ?is me?od has nev] come into v g5]al use4 ,coal gas or hydrog5 is v seldom home g5]at$2 a gas-bag c1 if necess>y1 be fill$ a few miles away & br\ght full to ! place ( exhibition1 or fill$ on ! spot if gas is laid on2 or1 fail+ ?is1 acetyl5e or e!r1 or ev5 me?ylat$ _s may be utilis$ in/ead4 ,! bags 9 use are plac$ betwe5 d\ble pressure bo>ds 7if bo? gases are requir$ "u pressure7 & weights suffici5tly heavy plac$ on ! top 7,fig4 #ad71 or ) a 'bl[-?r\gh' jet only ! oxyg5 ne$ be /or$ 9 a bag & ! coal gas us$ f ! supply ma94 ,cyl9d]s h1 h[ev]1 s univ]sally sup]s$$ ^! appliances1 t space is h>dly w>rant$ 9 fully describ+ !m1 especially z any op]ator wi%+ to adopt #bd ! process c obta9 full directions f any responsible deal]4 ,,limelight ,,jets4--,^! are ( ?ree g5]al types1 viz4 ! ',bl[-?r\gh1' ! ',mix$1' & ! ',injector4' ,( ^! ! ',bl[-?r\gh' is n[ v little made1 hav+ be5 l>gely sup]s$$ by ! ',injector' patt]n1 b1 z !re are hundr$s 9 common use 9 ?is c\ntry1 !y _c yet be reg>d$ z a ?+ ( ! pa/4 ,illu/ration3 ,,fig4 #ad4--;,gas-bags4 ,! exact design ( ?is jet v>ies consid]ably1 b all are alike 9 ?is1 t a jet ( coal gas is burn$ at ! orifice ( a m or less op5 nozzle1 & a /ream ( oxyg5 bl[n ?r\gh x on to a cyl9d] ( lime :i* x !reby r5d]s inc&esc5t4 ,fig4 #ae repres5ts ! v>i\s designs *iefly adopt$ = ?is jet1 t m>k$ ,a be+ p]haps ! mo/ usual1 ?\gh ,c is also frequ5tly met )4 ,9 light-giv+ p[] !re is n mu* to *oose betwe5 ! v>i\s types2 probably ,d on ! :ole is ! be/ 9 ?is respect1 b s mu* dep5ds ^u ! exact position ( ! two nozzles1 & ! smoo?ness or o!rwise ( t #be provid$ = ! oxyg5 bla/1 t exact comp>isons are difficult4 ,illu/ration3 ,,fig4 #ae4--';,bl[-?r\gh' ,nozzles4 ',bl[-?r\gh' jets are ! weake/ =m ( limelight z us$ at ! pres5t day1 & may be tak5 r\ghly z "s #ej p] c5t4 bett] ?an acetyl5e1 or 9 o!r words1 suffici5t to illum9ate a #ab-;foot picture at a di/ance ( "s #dj to #ej feet2 b _! advantage is1 or 01 t !y only requir$ "o gas 7oxyg57 "u pressure1 ! coal gas supply be+ obta9$ f ! ord9>y h\se ma94 ,illu/ration3 ,,fig4 #af4--';,bl[-?r\gh' ,jet4 ,?is advantage is n[ %>$ by ! m rec5tly introduc$ ',injector' jets1 :i* give a f> bett] light1 & h !re=e r5d]$ ! ',bl[-?r\gh' type ne>ly ext9ct4 ,! g5]al con/ruction ( a ',bl[-?r\gh' jet is %[n 9 ,fig4 #af1 & x w be se5 t a %ort v]tical sp9dle is #bf provid$ to c>ry ! lime cyl9d]1 & t ?is c be rotat$ f ! back by means ( bevell$ ge> :eels1 :i* at ! same "t screw ! sp9dle up & d[n4 ,a lime cyl9d] ( ! usual patt]n be+ plac$ on ?is sp9dle c be rotat$ f "t to "t to expose a fre% surface1 z t 9 use gradually becomes 'pitt$' by ! bla/1 :ile ! screw provides suffici5t v]tical movem5t to ensure t a complete rotation does n br+ r\nd ! same position aga94 ,"s arrangem5t is also g5]ally provid$ by :i* ! di/ance betwe5 ! lime sp9dle & ! jet c be adju/$4 ,! exact position ( ?is does n matt] )9 a reasonable m>g91 b limes v>y 9 size1 & ',pa/illes1' & o!r sub/itutes = limes1 :i* w be ref]r$ to lat]1 v>y /ill m1 at any rate z reg>ds ?is adju/m5t4 ,! av]age di/ance :i* gives ! be/ result is usually ab\t half an in*1 & once set ne$ n be alt]$ ) t p>ticul> jet unless a lime ( diff]5t size is employ$2 m9or v>iations due to limes be+ drill$ slightly out ( c5tre1 c41 d n s]i\sly matt]4 ,!re is no accept$ rule = col\r+ jet-taps 9 accordance ) ! cyl9d]s1 & al?\gh jets are sometimes met ) pa9t$ 9 ?is way1 i4e4 r$ = coal gas & black = oxyg51 x is m usual to f9d coal gas taps black & oxyg5 bright1 or sometimes bo? black or bo? bright4 ,c>e mu/ !re=e be tak5 t ! "r cyl9d] is connect$ to ! "r tap on ! jet1 b !re %\ld be no difficulty 9 tell+ :i* is :i*1 & =tunately any mi/ake1 ev5 if x be made1 is q h>mless4 ,,! ,,mix$-,,gas ,,or ,,d\ble-,,pressure ,,jet4--,?is jet is fundam5tally diff]5t f ! 'bl[-?r\gh' =m1 inasmu* z ! two gases are comb9$ 9 "o mix+ *amb] be=e combu/ion1 & burn 9 _! correct proportions at "o nipple4 ,x is usually /at$ t ?is jet necessitates bo? gases be+ "u equal or approximately equal pressure1 b ?is #bg is n lit]ally accurate1 & ,i h giv5 _m a lant]n exhibition ) "o ( ^! jets1 us+ coal gas f ! ord9>y supply1 & oxyg5 f a cyl9d]4 ,to use a mix$ jet 9 ?is way ne$s c>e1 z a v slight excess ( oxyg5 puts ! light out ) a 'pop' :i*1 al?\gh n dang]\s1 is disconc]t+1 :ile ! light obta9$ "u ^! conditions is v little bett] ?an ) a 'bl[-?r\gh' jet1 & f> inf]ior to ! ',injector' jets to be describ$ next4 ,illu/ration3 ,,fig4 #ag4--,mix$ ,jet4 ,illu/ration3 ,,fig4 #ah4--,mix$ ,jet1 ,gwy] patt]n4 ,! mix$-gas jet is int5d$ !n to be us$ ) bo? gases "u pressure1 & is ! only jet to be s]i\sly #bh consid]$ 9 cases :]e a really p[]ful light is requir$4 ,! p[] ( ?is jet is inde$ almo/ unlimit$1 & ^? made ) l>ge bores1 su* = example z us$ = c9ematograph "w1 provide a light am\nt+ (t5 to "s two or ?ree ?\s& c&les1 & consume an enorm\s am\nt ( gas2 b ! ord9>y patt]n1 ) a nipple ( "o-tw5tie? to "o-sixte5? ( an in* bore1 & us+ "s #e feet ( ea* gas p] h\r1 or p]haps slightly m = ! coal gas1 w suffice = all ord9>y "w4 ,illu/ration3 ,,fig4 #ai4--,mix+ ,*amb] ( ,jet4 ,! mix$-gas jet1 l ! 'bl[-?r\gh1' is made 9 _m =ms1 b ^! may be r\ghly divid$ into two ma9 types1 viz4 ^? ) small mix+ *amb]s imm$iately bel[ ! nipple 7,fig4 #ag71 & ^? ) l>g] *amb]s 9 ! horizontal "p ( ! jet z 9 ! ',gwy]' patt]n 7,fig4 #ah74 ,! con/ruction ( ! mix+ *amb] itself v>ies also1 b t advocat$ by my fa!r1 ! orig9al au?or ( ?is "w1 is g5]ally foll[$1 ! *amb] be+ pack$ ) alt]nate discs pi]c$ z 9 ,fig4 #ai1 :i* ensures a ?or\gh mixture ( ! gases4 ,a lay] or two ( gauze is (t5 introduc$ z well by way ( fur!r improvem5t4 ,! di/ance betwe5 ! lime & nipple is mu* less ?an ) ! 'bl[-?r\gh' jet1 & ! adju/m5t has to be m exactly made4 ,ab\t #a_/h in* is approximately correct = a jet ( mod]ate p[]1 & r m = a bigg] bore2 also c>e mu/ be tak5 to turn ! lime frequ5tly1 z ! latt] 'pits' pretty quickly ) ^! jets1 & if x is neglect$ ! jet may spurt back out ( ! hole1 :i* is gradually =m$1 & crack ! cond5s]4 #bi ,!re is /ill an errone\s op9ion extant t ^! jets are dang]\s1 & if ! op]ator is work+ ) ! n[ obsolete gas-bags x is c]ta9ly a fact t an accid5t 9 c>eless h&s is possible2 b ) cyl9d]s !re is1 s f> z ,i "k1 no possibility ev5 ( an accid5t "u ord9>y conditions4 ,x is true t if too mu* oxyg5 is turn$ on ! jet may sudd5ly g out ) a l\d snap or pop1 & ?is is 9 reality a m9iature explosion 9 ! mix+ *amb]2 b x c 9 any case h>dly be s]i\s en\gh to matt]1 ?\gh ,i h f\nd aft] su* a snap t ! gauze pack+1 inside ! *amb] above ref]r$ to1 has be5 pi]c$ "r ?r\gh1 &1 :5 fir/ lit aft]w>ds1 ! jet has = a few m9utes burnt ) a *>act]i/ic gre5 flame1 d5ot+ ! pres5ce 9 ! gas ( f9e copp] or brass p>ticles4 ,to obta9 a good light ) ^! jets1 & 9 fact ) all jets1 great c>e mu/ be tak5 t ! nipple is absolutely smoo?1 o!rwise ! flame is b\nd to hiss4 ,! simple/ plan is to slightly r\gh5 a suitable siz$ ne$le ) em]y pap] & to burni% ! inside ( ! nipple f "t to "t ) ?is4 ,especially if !re has be5 "o ( ! 'snaps' ref]r$ to is x desirable to see t ! inside ( ! nipple is ?or\ghly smoo? & poli%$4 ,,manipulation ,,( ,,! ,,mix$-,,gas ,,jet4--,on ?is po9t !re is n mu* to be said4 ,a good h>d /one lime mu/ be us$--'s(t' limes are useless = ?is jet--& ! coal gas flame %\ld be lit fir/1 & ! lime ?or\ghly heat$ ) ?is be=e ! oxyg5 is sl[ly turn$ on4 ,z ! oxyg5 increases ! flame w gradually disappe> & ! light increase1 until x is at a maximum = t p>ticul> am\nt ( coal gas4 ,?is latt] c !n be turn$ on a little m1 & m oxyg5 pass$ to balance x until ! jet beg9s to 'ro>1' :5 we are gett+ ! maximum light = t p>ticul> siz$ nipple4 ,:5 ! two gases are1 h[ev]1 9 ! prop] proportion to give ! be/ light1 !re w always be a slight excess ( coal gas flame visible play+ ab\t ! lime4 #cj ,,! ,,injector ,,jet4--,?is is ess5tially a mix$ jet1 & 9 outw>d appe>ance diff]s b little f "o ( ! ord9>y type 7,fig4 #bj71 b is s con/ruct$ t ! pressure ( oxyg5 'sucks' coal gas into ! mix+ *amb]1 & s obviates all necessity = ! latt] be+ "u pressure4 ,) ?is jet !re is little or no dang] ( ! jet 'snapp+' out ?r\gh a surplus ( oxyg51 z ! great] ! fl[ ( ?is gas1 ! great] ! suction on ! coal gas side4 ,! light is n q equal to a good mix$ jet1 b v ne>ly s1 & !re=e ?is jet is des]v$ly ga9+ 9 fav\r e day4 ,illu/ration3 ,,fig4 #bj4--';,injector' ,jet4 ,"o po9t mu/ be not$3 ! oxyg5 itself mu/ be "u great] pressure ?an ) ! ord9>y mix$ jet if ! be/ light is to be obta9$1 & !re=e a special regulator mu/ be us$1 or "o ( ord9>y type modifi$ 7:i* c easily be done by ! mak]71 & rubb] connections mu/ be securely ti$ bo? on to jet & regulator1 z ! pressure requir$ to "w ?is jet to advantage1 :ile n en\gh to bur/ a rubb] tube1 is en\gh to bl[ x (f an easy fitt+ connection4 ,,! ,,oxye!r ,,light4--,?is is practically simil> to ! oxyhydrog51 except t e!r vap\r is us$ 9 place ( ! hydrog5 or coal gas4 ,! me?od adopt$ consi/s ess5tially ( pass+ a /ream ( oxyg5 ?r\gh a vessel pack$ ) "s por\s mat]ial 7su* z cotton wool or cotton gauze7 :i* is saturat$ ) e!r4 ,! oxyg5 #ca becomes saturat$ ) e!r vap\r1 & ! mixture is !n us$ 9 place ( ! coal gas supply 9 a d\ble-pressure jet1 an additional supply ( free oxyg5 be+ /ill requir$ ?r\gh ! ord9>y oxyg5 tap4 ,! arrangem5t is *eap1 z x disp5ses ) ! necessity = a coal gas cyl9d]1 & effective1 z ! light is little1 if at all inf]ior to ! oxyhydrog51 b diff]s f ! latt] 9 ?is1 t ) c>eless h&l+ an accid5t is possible4 ,9 compet5t h&s !re is no dang]1 & ,i h us$ e!r saturators myself scores ( times )\t "o s+le contretemps2 b x %\ld n be entru/$ to any *ance amateur4 ,! use ( ! e!r light has a curi\s hi/ory4 ,9 ! e>li] days be=e ! prop] con/ruction ( e!r saturators 0 und]/ood1 & gas-bags 7 /ill 9 vogue1 x 0 l>gely condemn$ on ! score ( dang]4 ,mod]n improvem5ts 9 app>atus r5d]$ x p]fectly safe aga9/ any?+ b gross c>elessness or bungl+1 & ! ,london ,c\nty ,c\ncil & o!r simil> bodies imm$iately suppli$ x broadca/ to elem5t>y s*ools 79 disreg>d ( w>n+s (f]$ by myself & o!rs71 :]e x 0 (t5 entru/$ to incompet5t op]ators or ev5 s5ior boys4 ,s f> z ,i "k no s]i\s accid5t ev] result$1 a pretty conclusive pro( t ! light is really safe1 b 9 "t ! ,london ,c\nty ,c\ncil realis$ t ! univ]sal adoption ( ?is illum9ant 0 n advisable1 & ,i believe n[ prohibit x altoge!r 9 halls lic5s$ by !m = ent]ta9m5ts4 ,9 "t1 no d\bt1 !y w le>n to adopt a sane policy betwe5 ! two extremes1 b at pres5t ! (ficial attitude 9 _m localities has plac$ e!r saturators out ( ! runn+1 & be=e pur*as+ "o ! w\ld-be op]ator %\ld asc]ta9 t he w be all[$ to use x4 ,e!r saturators z made at ! pres5t day may be divid$ into two pr9cipal patt]ns1 viz4 ^? 9 :i* saturator & jet are comb9$ 9 "o piece ( app>atus #cb :i* fits bodily into ! lant]n1 & saturators :i* are us$ outside & connect$ by means ( tub+ to any ord9>y oxyhydrog5 d\ble-pressure jet4 ,bo? =ms h _! advantages & disadvantages2 ! fir/ patt]n t5ds to become too w>m f its position 9 ! lant]n & g5]ates e!r vap\r too quickly1 :ile ! second has ! fault ( becom+ too cold 7ow+ to evaporation ( ! e!r7 & !re=e n vaporis+ quickly en\gh4 ,illu/ration3 ,,fig4 #ba4--';,gridiron' ,saturator4 ,writ+ at ! pres5t date1 :5 manufactur]s are sl[ly beg9n+ to resume _! normal occupations aft] ! /ress ( w> "w1 x is impossible to say exactly :at models w or w n be made1 b ,i w m5tion "o typical example ( ea* patt]n z made 9 pre-w> days4 ,! fir/ ( ^! is ! ',gridiron' 7,fig4 #ba71 adopt$ l>gely by ! ,london ,c\nty ,c\ncil 9 ! days ,i h ref]r$ to1 & c]ta9ly "o ( ! be/ design$ saturators ev] put on ! m>ket4 ,9 ! ',gridiron' saturator !re are ?ree taps3 two at ! #cc re> & "o 9 front1 betwe5 ! saturator & ! mix+ *amb]4 ,betwe5 ! re> taps is ! inlet = ! oxyg51 :i* divides into two *annels1 t on ! left pass+ upw>ds ?r\gh ! ,u tube %[n 9 ! illu/ration 7! correspond+ tube on ! "r is m]ely a dummy71 & !nce ?r\gh ! saturator & out ?r\gh ! horizontal tube & tap into ! mix+ *amb]1 :5ce ! saturat$ /ream ( oxyg5 f9ally passes to ! nipple1 & ! comb9ation burns ) a :iti% flame closely resembl+ t produc$ by coal gas4 ,illu/ration3 ,,fig4 #bb4--',p5dant' ,saturator4 ,! o!r *annel = ! oxyg5 is to ! "r1 d[n ! v]tical tube %[n !re 7! l[] v]tical tube on ! left is also a dummy71 und]nea? ! saturator1 & f9ally com+ up into ! mix+ *amb] f bel[1 trans=m+ ! :ite flame into an int5sely hot bl[pipe exactly z x does ) a coal gas jet4 ,! front tap controls ! supply ( saturat$ e!r to ! mix+ *amb]1 & :]eas at fir/ a good /ream ( oxyg5 is ne$$ to pick up en\gh e!r1 by degrees z ! in/rum5t w>ms 9 ! lant]n1 ! oxyg5 pass+ ?r\gh ! saturator c be cut (f entirely1 & ev5 !n ! front tap mu/ be gradually clos$ d[n to prev5t ! hot e!r com+ (f too fa/4 ,!re is a disagreeable feel+ ( 'sitt+ on ! safety-valve' 9 do+ ?is1 b 9 reality ! pressure is nev] likely to become great en\gh to cause dang]4 ,( saturators = use outside ! lant]n ! be/-kn[n is probably ! ',p5dant' 7,fig4 #bb74 ,) ?is in/rum5t ! oxyg5 supply is connect$ to ! inlet m>k$ ,a2 ,b goes #cd direct to ! oxyg5 tap ( any ord9>y mix$-gas jet2 :ile ,c1 f :5ce issues ! saturat$ /ream1 is connect$ to ! coal gas tap ( ! jet4 ,:i*ev] patt]n is us$1 ! ess5tial ?+ is to keep a good supply ( oxyg5 well saturat$4 ,if ! lime becomes inc&esc5t )\t any free oxyg51 or x is f\nd t ?is requires gradually turn+ (f1 x indicates t ! saturation is becom+ defective1 & to cont9ue is to risk ! jet snapp+ out4 ,9 ! case ( an outside saturator su* z ! ',p5dant1' ?is may ev5 bl[ (f ! connect+ tubes ) a l\d report1 ?\gh no worse accid5t is likely to happ51 & = ?is reason an outside saturator %\ld be plac$ z close to ! jet z possible1 s t ! rubb] tube may be kept %ort1 & incid5tally ?is keeps ! saturator w>m & accel]ates vaporisation4 ,z e!r vap\r usually conta9s a c]ta9 am\nt ( moi/ure :i* does n vaporise to any great ext5t1 ?is gradually accumulates & ! capacity ( ! in/rum5t becomes r$uc$4 ,x is !re=e usually necess>y to return a saturator to ! mak]s e n[ & aga9 = repack+4 ,! only real dang] ) a mod]n saturator is n 9 us+ b 9 fill+4 ,?is %\ld be done if possible 9 ! op5 air1 & at any rate nev] ne> a light4 ,ord9>y sulphuric e!r ( specific gravity #gbj-gcj is usually consid]$ ! be/1 & a qu>t] ( a p9t w keep an ord9>y small-bore jet go+ = ne>ly two h\rs4 ,m precise directions are usually s5t out by ! mak]s1 & z ! v>i\s patt]ns ( saturator 9 use are pretty num]\s1 x w\ld be useless "h to attempt m detail$ in/ructions = work+4 ,,oxy-,,acetyl5e ,,jets4--,any good mix$ gas jet may be us$ ) acetyl5e in/ead ( coal gas1 provid$ t x is "u pressure m or less correspond+ to t f an oxyg5 cyl9d]1 & at ! pres5t day !re is no difficulty 9 obta9+ ?is1 9 civilis$ c\ntries at all ev5ts1 by #ce means ( compress$ or1 to speak m correctly1 'dissolv$' acetyl5e cyl9d]s1 ref]r$ to lat] on4 ,) an ',injector' jet !re is no ne$ = ! acetyl5e gas to be "u pressure at all1 & a simple g5]ator su* z describ$ on page #ab w answ] p]fectly1 ?\gh 9 practice v seldom us$4 ,) su* a g5]ator ! pressure is s l[ t 9 _m cases ! jet w n ev5 burn until "s oxyg5 is turn$ on2 b ?is introduces no real difficulty1 z ) a good ',injector' a snap is practically impossible1 provid$ ! g5]ator is l>ge en\gh to evolve suffici5t acetyl5e4 ,x is f> bett] 9 e way1 h[ev]1 to use ! acetyl5e f a cyl9d]1 j z ) coal gas4 ,only 9 ?is case ! cyl9d] is completely fill$ ) a por\s mat]ial1 & ?is aga9 fill$ ) liquid acetone or o!r suitable fluid1 9 :i* ! acetyl5e is dissolv$ z rapidly z x is pump$ into ! cyl9d]4 ,to compress acetyl5e 9 ! ord9>y way is nei!r safe nor practicable2 b ^! 'dissolv$' cyl9d]s are n[ us$ ext5sively = bo? oxy-acetyl5e weld+ & motor c> light+1 & may be entirely reli$ ^u4 ,! ,d4,a4 7,dissolv$ ,acetyl5e7 ,company 7 ! pione]s 9 ?is c\ntry ( ! indu/ry1 & _! me?ods ( bus9ess are peculi> & +5i\s4 ,! us] is reque/$ 9 ! fir/ place to pur*ase a cyl9d]1 & he !n becomes ! own] ( a cyl9d]1 b n ( "o p>ticul> cyl9d]4 ,a li/ is suppli$ to him ( v>i\s depots 9 ! c\ntry :]e ! ,company's cyl9d]s are /or$1 & :5 empty he c1 on paym5t ( a fix$ sum1 ex*ange 8 empty cyl9d] = a full "o1 :i* !n becomes 8 cyl9d] pro tem4 ,?is saves ! delay & exp5se ( return+ a cyl9d] to ,london1 & incid5tally cle>s ! cu/om] ( any "q ( det]ioration1 ?is be+ obvi\sly cov]$ by degrees ) ea* individual ex*ange4 ,! sy/em 0 fir/ introduc$ 9 connection ) ! light+ ( c>s & only applies to ! /&>d size = ?is purpose1 viz4 #bj cubic feet capacity1 #cf b z ?is is1 on ! :ole1 ! mo/ conv5i5t size = lant]n "w also1 ! limitation is n a disadvantage4 ,! arrangem5t is also 9 vogue to a less ext5t ) cyl9d]s ( #f feet capacity 7a size sometimes us$ = motor cycles71 b ! depots ( ex*ange are at pres5t f> few] = ?is size4 ,! oxy-acetyl5e bla/ is mu* hott] ?an ! ord9>y oxyhydrog51 & !re=e produces a m int5se light4 ,i h !re=e us$ x ) success on occasions :5 ev5 ! ord9>y limelight w\ld fail1 & ! *oice has la9 betwe5 an oxyhydrog5 jet ( enorm\s bore 7&1 ( c\rse1 correspond+ consumption ( gas71 & ! oxy-acetyl5e4 ,= ?is v reason great c>e mu/ be tak5 only to use ! h>de/ limes1 & ev5 !n to use ! lime-turn+ movem5t frequ5tly1 or ! lime w pit or crack & a brok5 cond5s] foll[4 ,,! ,,fallot ,,acetyl5e ,,light4--,?is light consi/s ( a jet ( acetyl5e "u pressure1 )\t oxyg51 b produc+ its own air bla/ f ! atmosph]e by suction1 mu* z ! ',injector' jet does1 b ! rev]se way r\nd4 ,! light is bett] ?an ) an ord9>y acetyl5e jet1 ?\gh n q s good z ) a 'bl[-?r\gh' jet2 b z x only requires a cyl9d] ( dissolv$ acetyl5e1 or ev5 a ',pressure' g5]ator1 x is fa/ com+ into fav\r4 ,! peculi>ity ( ! ,fallot app>atus is t1 in/ead ( provid+ a direct beam ( light 9 ! direction ( ! scre51 x projects ! beam backw>ds on to a concave mirror1 & x is ! reflect$ light f ?is t is us$ 7,fig4 #bc74 ,in/ead ( a lime is us$ a sph]ical ',pa/ille' ( peculi> composition1 & be=e use ea* pa/ille mu/ be burnt (f exactly l an inc&esc5t gas mantle1 aft] :i* x is extremely fragile & difficult to h&le4 ,to use ?is illum9ant "o l5s ( ! cond5s] mu/ be remov$1 ! curvature ( ! mirror tak+ its place1 & x w be se5 at once t ! pa/ille itself w get 9 its own #cg light & ?r[ a %ad[1 :i* actually happ5s1 b x is h>dly p]ceptible unless specially look$ =4 ,illu/ration3 ,,fig4 #bc4--;,fallot ,air ,bla/4 ,a complete ,fallot ,air ,bla/ ,outfit1 ) cyl9d]1 f9e adju/m5t valve1 pressure gauge & burn]1 ) two sp>e pa/illes1 is %[n 9 ,fig4 #bd1 b if pref]r$ a regulator1 su* z previ\sly describ$ = oxyg51 c be us$ in/ead ( ! f9e adju/m5t valve4 ,illu/ration3 ,,fig4 #bd4--;,fallot ,air ,bla/1 & ,cyl9d]4 #ch ,,fallot ,,oxy-,,acetyl5e ,,bla/4--,?is is simil> to ! =ego+1 utilis+ oxyg5 f a cyl9d] in/ead ( air1 & ! light is equal to a p[]ful limelight1 & may be consid]$ z an effici5t sub/itute1 ?\gh = long range "w ! %ad[ be=e allud$ to becomes m noticeable 7= optical reasons :i* ne$ n be "h discuss$74 ,! ,fallot ,company also make a special ',pressure ,g5]ator' :i* c be us$ in/ead ( a ,d4,a4 ,cyl9d]2 b my exp]i5ce ( ?is s f> is t1 al?\gh p]fectly safe1 ! bla/ f x is a little un/eady z comp>$ ) a cyl9d]4 ,,limes ,,& ,,accessories4--,limes = ,optical ,lant]n "w are usually suppli$ 9 ! =m ( cyl9d]s1 ! 'ord9>y' size be+ #g_/h in* 9 diamet] & ab\t #a in*es long1 ) a hole drill$ longitud9ally to take ! lime p94 ,extra l>ge limes up to #b in*es 9 diamet] are suppli$ = m p[]ful jets4 ,s-call$ 's(t' limes us$ to be recomm5d$ = 'bl[-?r\gh' jets z giv+ a bett] light ?an 'h>d' limes1 b ! advantage1 if any1 is v little1 & ^! limes are n[ v seldom he>d (1 possibly because 'bl[-?r\gh' jets !mselves are becom+ less & less us$1 & 's(t' limes w n /& ! heat ( a mix$ or ',injector' jet = long4 ',h>d' limes are turn$ out ( ! h>de/ /one lime1 & mu/ be kept 9 seal$ t9s until us$1 z !y rapidly dis9tegrate :5 expos$ to ! air4 ,!re are "o or two qu>ries kn[n to provide ! be/ lime = lant]n purposes1 & ! v>i\s good br&s on ! m>ket practically h ! same orig9 z reg>ds raw mat]ial1 ?\gh call$ by diff]5t trade names2 & ! ',h>dazion' 7h>d z iron7 limes1 plac$ on ! m>ket "s ye>s ago by a well-kn[n :olesale firm1 to be c\nt]$ %ortly aft] by ! ',h>da/il' 7h>d] /ill7 br&1 are1 ,i take x1 legitimate ?\gh amus+ in/ances ( phonetic adv]tisem5t4 ,ev5 ! be/ ( limes is liable to crack "u ! heat #ci ( a p[]ful jet1 & s a pair ( lime-tongs %\ld always be provid$1 & !re is no?+ bett] ?an ! simple =m %[n 9 ,fig4 #be1 & :i* is1 or %\ld be1 sold by all deal]s4 ,illu/ration3 ,,fig4 #be4--,lime-tongs4 ,,sub/itutes ,,= ,,limes4--,a good sub/itute = lime1 t w give ! same light1 /& heat equally z well1 & n det]iorate if expos$ to ! atmosph]e1 has long be5 s\ght =1 & "s ( ! m rec5tly discov]$ refractory mat]ials are m or less satisfactory4 ',mabor' limes1 = example1 belong to ?is class1 & s d "s ( ! 'pa/illes1' :i* be=e ! w> came *iefly f ,france & to a less ext5t f ,g]many4 99 99 99 99 99 ,,*apt] ,,vi ,,! ,,electric ,,light ,! electric curr5t provides ! light = an optical lant]n1 ?\gh x may take v>i\s =ms1 su* z ! inc&esc5t gl[-lamp 9 "s %ape or o!r1 ! comp>atively new ,ediswan ',po9tolite' lamp1 ! enclos$ arc1 & ! op5 arc4 ,?is little book is n a treatise on electricity1 b a few elem5t>y notes may n be out ( place1 & may be ( assi/ance to ! non-te*nical lant]ni/4 ,! fir/ po9t !n to be consid]$ 9 adopt+ ! electric light = ! purpose ( lant]n projection is ! "* ( ! supply1 & ! in=mation requir$ may be summ$ up ?us3 7#a7 ,e4,m4,f41 voltage1 or t5sion 7^! ?ree expressions hav+ exactly ! same mean+72 7#b7 amprage or am\nt ( curr5t available2 7#c7 :e!r curr5t is 7a7 cont9u\s1 con/ant1 or direct 7aga9 ?ree words mean+ #dj ! same ?+71 or 7b7 alt]nat+4 ,! ,e4,m4,f4 or t5sion corresponds to pressure1 to use ! me*anical analogy ( a wat] pipe1 & ! amprage to volume1 & ! voltage ( ! supply curr5ts 9 ?is c\ntry are usually betwe5 #ajj & #bej volts4 ,private light+ sets are frequ5tly z l[ z #ej1 & curr5t d]iv$ f accumulators may be any?+ f a few volts & upw>ds4 ,p[] curr5ts1 su* z commonly employ$ = tramways1 c41 are usually ab\t #ejj volts1 b ! use ( ^! curr5ts = light+ purposes1 ?\gh practicable1 is n to be advocat$4 ,ampres & volts are conv]tible t]ms 9 a s5se2 t is to say1 a curr5t ( #aj ampres at #ajj volts requires ! same horse-p[] to g5]ate x z "o ( #e ampres at #bjj volts1 or #bj ampres at #ej volts1 b !y are by no means conv]tible z reg>ds _! effici5t use = our purpose4 ,! ampres us$ multipli$ by ! numb] ( volts give ! total p[] consum$ 9 watts1 & #ajjj watts us$ = "o h\r repres5t #a unit z *>g$ = on our dread$ light+ bills4 ,! curr5t available f a public supply may be said to be unlimit$ s f> z our purpose is conc]n$1 & ! am\nt actually us$ dep5ds only on ! total electrical resi/ance ( our circuit1 & ?is is measur$ 9 ohms1 ! ?ree factors1 viz4 volts1 ampres1 & resi/ance1 be+ connect$ by ! well-kn[n & simple equation ,c ,e _/ ,r1 ,c repres5t+ ! curr5t 9 ampres1 ,e ! t5sion or ,e4,m4,f4 7electro-motive =ce7 9 volts1 & ,r ! resi/ance 9 ohms4 ,! total curr5t we c use1 h[ev]1 is limit$ by ! size ( ! cable laid on 9 ! build+1 & ?is is automatically safegu>d$ 7or %\ld be7 by ! fuses1 :i* consi/1 z is g5]ally kn[n1 ( ?9 wires or /rips ( t9 or lead fix$ on a fuse bo>d 9 an easily accessible place1 & :i* melt directly ! curr5t exce$s a safe am\nt 9 ampres4 ,:atev] me?od ( light+ we use !re=e1 en\gh resi/ance mu/ always be kept 9 ! circuit to ensure #da t no m curr5t c pass ?an has be5 provid$ =1 & 9 ! case ( an arc lamp ?is usually means a resi/ance or rheo/at be+ reta9$ 9 ! circuit 9 addition to ! arc itself1 ?r\gh :i* ! curr5t is pass$ & absolutely wa/$1 ?\gh =tunately ! wa/e 9 money is negligible1 & = reasons to be discuss$ lat] su* a resi/ance is necess>y ) an optical lant]n arc lamp 9 any case4 ,9 ! case ( a gl[-lamp1 ! entire resi/ance is provid$ by ! filam5t ( ! lamp itself1 & t is :y an ord9>y metal or c>bon filam5t lamp1 = say #bjj volts1 has to be manufactur$ ) an extremely long & sl5d]1 & !re=e fragile1 filam5t1 :ile ) an ord9>y pocket-tor*1 :i* is usually suppli$ ) curr5t f a dry batt]y ( "s #c or #d volts only1 ! filam5t c be %ort & ?ick4 ,speak+ g5]ally1 gl[-lamps on a l[ voltage curr5t c be made m effici5t ?an on a high "o1 & are also long] liv$ = v obvi\s reasons2 b1 on ! o!r h&1 ! transmission ( curr5t ov] long di/ances is *eap] ! high] ! t5sion1 z = a giv5 numb] ( watts ! amprage is less1 & !re=e small] cables c be employ$4 ,on ! :ole1 !n1 curr5ts ( #bjj to #bej volts h dur+ rec5t ye>s become m common ?an #ajj1 9 spite ( great] difficulties 9 mak+ ! lamps2 b occasionally "o f9ds a hall :]e two or m lamps are wir$ 9 s]ies1 two #ajj-volt lamps = example be+ wir$ toge!r 9 s]ies on a #bjj-volt circuit4 ,if we are us+ curr5t = our lant]n f an ord9>y lamp socket1 ?is is a possibility t mu/ be borne 9 m9d4 ,! same consid]ations1 viz4 ! economy ( transmitt+ p[] at high t5sion & ( us+ x at a l[] "o1 h be5 ma9ly responsible = ! rapidly increas+ numb] ( alt]nat+ curr5t circuits n[ met )1 especially 9 sp>sely populat$ di/ricts4 ,an alt]nat+ curr5t ma9 is "o 9 :i* ! curr5t rev]ses its direction1 usually 9 ?is c\ntry #ej1 b sometimes #fj1 #hj1 #ij1 or ev5 #ajj times #db p] second 7!re be+ un=tunately 9 ,great ,brita9 no /&>d ',p]iodicity' or numb] ( cycles p] second71 & = te*nical reasons :i* ne$ n be ent]$ ^u "h1 ) ^! alt]nat+ curr5ts ! t5sion & amprage c be mutually conv]t$ by means ( trans=m]s1 s t curr5t c be transmitt$ at s high a t5sion1 = in/ance1 z #aj1jjj volts1 & us$ at a voltage ( #ej or #ajj or :atev] is requir$1 ! amprage available be+ increas$ 9 inv]se ratio z ! t5sion is decreas$4 ,! same ready p[] ( trans=mation un=tunately does n apply to ! cont9u\s curr5t1 or alt]nat+ curr5ts w\ld probably nev] h be5 he>d (1 b z x is !y are v common4 ,= gl[-lamps x is immat]ial :i* curr5t is available1 b = arc lamps ! cont9u\s is mu* to be pref]r$1 ?\gh bo? c be utilis$4 ,) ^! initial rem>ks1 ,i w n[ take 9 ord] ( illum9ation ! v>i\s me?ods ( utilis+ ! electric curr5t = optical lant]n "w4 ,,! ,,electric ,,gl[-,,lamp4--,! ord9>y metal filam5t lamp is n v suitable = lant]n "w1 ! light n be+ suffici5tly conc5trat$1 b f :at has already be5 said1 x w be evid5t t ?is me?od ( light+ is m suitable :]e curr5ts ( l[ voltage are available4 ,an extremely good & int5se light c be obta9$ f a comp>atively small batt]y ( accumulators1 :i* c easily be c>ri$ 9 ! h&1 & a %ort & ?ick metal filam5t lamp1 simil> to ^? suppli$ ) a p[]ful electric tor*2 & ?is arrangem5t is actually us$ to "s ext5t by travell+ lectur]s1 b ! mess & tr\ble ( keep+ ! accumulators 9 ord] h prev5t$ ! me?od be+ g5]ally adopt$4 ,:5 alt]nat+ curr5t is available su* a lamp w "w well ) a trans=m] to /ep d[n ! voltage to ! requir$ degree1 & ! arrangem5t is simple1 *eap1 & effici5t1 & produces a light at lea/ equal to t f #dc acetyl5e4 ,9 comp>atively small halls1 :]e ! curr5t is alt]nat+1 ?is is und\bt$ly ! be/ me?od ( work+1 z x is simpl] ?an ! arc & amply brilliant en\gh = all practical purposes4 ,) ! cont9u\s curr5t ! problem is n s simple1 z trans=mation ( voltage is n an easy matt]1 & a gl[-lamp on2 say1 a #bjj-volt circuit involves a long & fragile filam5t1 :i* x is difficult to arrange 9 a small space4 ,_m ye>s ago ! ,ediswan ,company produc$ a ',focus' lamp = ! purpose1 ) ! filam5t arrang$ 9 ! =m ( a squ>e grid1 & ?is lamp gave a light ( ab\t #ajj c&les1 & 0 fairly successful = a small room4 ,m rec5tly ! ,osram ,company introduc$ a simil> lamp ) a metal filam5t arrang$ some:at 9 ! =m ( a cone1 & ?is lamp also suffic$ = a small class-room4 ,x 01 ,i believe1 made 9 ,g]many & 0 practically unobta9able dur+ ! w>4 ,i und]/& ! ,osram ,company are at pres5t arrang+ to manufacture x 9 ?is c\ntry1 b up to ! "t ( writ+ x has n made its appe>ance4 ,none ( ^! lamps work$ direct on a public light+ circuit c be reg>d$ z really satisfactory1 z x has be5 f\nd impossible s f> to get a conc5trat$ light2 ! #ajj-volt lamps h1 ( c\rse1 be5 sup]ior to ^? made = #bjj or #bej1 b !y are all = lant]n purposes f> beh9d l[ voltage lamps1 :i* are really good :5 a suitable curr5t c be obta9$4 ,,! ,,po9tolite ,,lamp4--,?is lamp produc$ by ! ,ediswan ,company is 9 reality a m9iature arc ) tung/5 electrodes 9 a highly exhau/$ vacuum bulb4 ,to attempt a te*nical description w\ld be beyond ! scope ( ?is book2 x w suffice to say t ! action dep5ds ^u ! same pr9ciple z ! v>i\s wireless vacuum valves or ! ,coolidge ,x-ray tube4 ,?is lamp requires a peculi> />t+ device :i* is suppli$ ) x1 & gives a good1 int5se1 & conc5trat$ #dd light1 n equal to ! ord9>y arc or to limelight1 b comp>+ well ) any o!r =m ( illum9ant4 ,x c only be us$ ) ! cont9u\s curr5t4 ,,! ,,n]n/ ,,lamp4--,?is lamp at ! pres5t mom5t is practically non-exi/5t 9 ?is c\ntry1 hav+ be5 made exclusively 9 ,g]many4 ,also z rec5t improvem5ts 9 metal filam5t lamps h r5d]$ x almo/ obsolete = ord9>y light+ purposes1 x is1 ,i ?9k1 v d\btful :e!r x is /ill manufactur$ ev5 9 t c\ntry1 & h5ce ,i d n propose to wa/e space 9 an ext5sive description4 ,x w suffice to say t ! lamp consi/s ( "o or m /raight rods or filam5ts ( a refractory mat]ial1 :i* are semi-conduct+ to ! electric curr5t :5 hot1 b non-conduct+ :5 cold4 ,to comm5ce ) ! filam5t mu/ be heat$1 & 9 ! lamps z suppli$ = lant]n "w ?is is usually done by means ( a _s lamp1 :i* c be remov$ imm$iately ! curr5t beg9s to pass1 z ! filam5t is !reaft] ma9ta9$ at a :ite heat automatically4 ,a ?ree-filam5t ,n]n/ lamp gives z mu* z #ajjj c&les1 b x is extremely hot1 & ! light r diffuse4 ,! filam5ts are also v fragile1 s on ! :ole ! lamp 0 nev] v mu* 9 fav\r2 b on ! o!r h& x consum$ v little curr5t1 & c\ld be work$ f any ord9>y h\se light+ ma91 po9ts :i* l$ to its adoption 9 c]ta9 cases4 ,,! ,,electric ,,arc4--,we n[ come to ! light = optical lant]n "w1 ! brighte/1 ! mo/ conc5trat$1 ! *eape/1 ! easie/ to "w1 9 fact1 ! illum9ant :i* comb9es all ! virtues & b few drawbacks1 b ( c\rse requires "o indisp5sable condition1 viz4 electric curr5t laid on4 ,?is curr5t may be ( any voltage f #gj-bej1 or ev5 high]2 x may be cont9u\s or alt]nat+1 ?\gh ! =m] is to be pref]r$2 & x requires a cable = at lea/ #e ampres1 & = a l>ge hall #aj or #ab ampres4 ,! simple/ =m ( arc lamp = lant]n purposes is ! #de h&-f$ type z illu/rat$ 9 ,fig4 #bf4 ,! ess5tial feature is ! pair ( c>bon rods1 ! rema9d] ( ! app>atus consi/+ ( me*anical adju/m5ts to 'fe$' ^! z !y burn away1 & to accurately ma9ta9 !m 9 _! prop] positions & 9 ! optical c5tre ( ! lant]n4 ,j because ! electric arc provides s small & conc5trat$ a light1 x is ( extreme importance t ! c5tr+ %\ld be exact2 & h5ce me*anical movem5ts are usually provid$ = ?is :i* are unnecess>y ) o!r illum9ants4 ,illu/ration3 ,,fig4 #bf4--;,h&-f$ ,arc ,lamp4 ,! :ole "q ( optical adju/m5ts has1 h[ev]1 be5 left ov] = a future *apt]1 z x m or less applies to :atev] illum9ant is us$4 ,! illu/ration %[s a lamp arrang$ = cont9u\s curr5t1 ! upp] c>bon1 :i* mu/ be connect$ to ! positive wire1 be+ l>g] ?an ! l[] 7! negative71 & v slightly beh9d x4 ,! light f a cont9u\s curr5t arc lamp comes *iefly f ?is upp] or positive c>bon1 #df :i* 'crat]s' z x is us$1 & ?is arrangem5t has ! effect ( radiat+ ! light 9 ! direction requir$ 7,fig4 #bg74 ,! positive c>bon is usually ( ! 'cor$' type1 t is provid$ ) a core ( s(t] c>bon1 z ?is assi/s ! 'crat]+' action1 :ile ! negative is g5]ally us$ 'solid1' t is homog5e\s "r ?r\gh4 ,! arc has to be '/ruck' 9 ! fir/ place by t\*+ ! c>bons toge!r = a mom5t by ! me*anical means provid$1 & !n sep>at+ !m to ! work+ di/ance1 :i* is approximately #a_/h in*4 ,!y mu/ !n be ma9ta9$ at t di/ance by 'fe$+' z !y sl[ly burn away1 & ?is 'fe$+' 9 arc lamps = lant]n "w is usually done by h&1 z 9 ! lamp illu/rat$ 9 ,fig4 #bf1 b may be done by an automatic arrangem5t1 z w be describ$ lat]4 ,illu/ration3 ,,fig4 #bg4 ,! curr5t is really c>ri$ across ! arc by convection1 or 9 o!r words conduct$ by a bridge ( :ite hot c>bon p>ticles1 :i* cont9ually /ream across f ! positive c>bon to ! negative1 & ?is bridge1 :ile conduct+ ! curr5t1 int]poses a v consid]able resi/ance 7o!rwise x w\ld n ( c\rse become hot74 ,a c]ta9 pot5tial or t5sion is !re=e necess>y if a giv5 curr5t is to be ma9ta9$1 & ?is pot5tial has to be great] ! long] ! arc & also 7?\gh n 9 direct proportion7 ! small] ! c>bons4 ,:51 h[ev]1 ev]y?+ is 9 ! be/ proportion1 i4e4 l5g? ( arc1 size ( c>bons1 & curr5t pass+1 ! pot5tial at ! arc lamp t]m9als requir$ is approximately #de volts1 & ?is may be tak5 z a fix$ figure = any curr5t4 ,! l5g? ( arc to give ! be/ results may also be tak5 #dg z approximately fix$ at #a_/h in*1 & ! v>iable factor = diff]5t curr5ts z requir$ is provid$ by alt]+ ! sizes ( c>bons employ$4 ,! error mu/ n be made1 h[ev]1 ( assum+ t an ,e4,m4,f4 ( #de volts is suffici5t to "w an arc lamp1 z ! m9imum 9 practice is at lea/ #fe volts1 & #ajj or ev5 #bjj volts are advantage\s4 ,i h come across m ?an "o private g5]at+ in/allation :]e ! innoc5t own] has put 9 a dynamo = #de or #ej volts1 dep5d+ ^u "s c>elessly writt5 /atem5t t ?is is suffici5t4 ,:y a high] ,e4,m4,f4 is requir$ c be simply expla9$4 ,take = in/ance an av]age h&-f$ arc lamp z us$ = lant]n "w & consum+1 say1 #aj ampres4 ,take also1 z a fact1 ! /atem5t giv5 above t ! necess>y ,e4,m4,f4 at ! actual t]m9als ( ! arc lamp may be accept$ z a con/ant at #de volts1 & rev]t+ to ! equation giv5 on page #dj1 ,c ,e _/ ,r1 & sub/itut+ ^! figures we get-- ,curr5t 7#aj ampres7 ,e 7#de volts7 _/ ,r 7,resi/ance ( ,arc74 ,x is !re=e obvi\s t "u ^! exact conditions ! resi/ance or back ,e4,m4,f4 ( ! arc1 z x is t]m$1 mu/ equal #d4e ohms4 ,n[ suppose ! lamp left = a few seconds unatt5d$1 :ile ! c>bons are burn+ away & ! arc is l5g!n+2 9 a v few mom5ts ! resi/ance w h increas$1 ow+ to ! great] di/ance betwe5 ! c>bons1 & we w suppose x to h become #e ohms in/ead ( #d4e4 ,! curr5t pass+ w n[ be #de _/ #e #i ampres only4 ,9 o!r words1 a v slight l5g!n+ ( ! arc has r$uc$ ! curr5t1 & !re=e ! light1 by #aj p] c5t4 ,n only s1 b #de volts be+ ne$$ to ma9ta9 an arc ( #dh normal l5g?1 x is insuffici5t to ma9ta9 a long] "o1 & 9 practice ! effect ( leav+ an arc "u ^! conditions to itself = ev5 a few seconds is t x goes out1 to ! annoyance ( ! lectur] & ! confusion ( ! op]ator4 ,x is j possible to "w an arc lamp ) a total ,e4,m4,f4 ( #de volts by giv+ "o's :ole att5tion to x & nev] tak+ ! h& (f ! fe$+ h&le2 b 9 practice no "o ) any exp]i5ce w\ld attempt x4 ,! arc w\ld almo/ c]ta9ly g out sev]al times dur+ ! exhibition4 ,n[1 take an example ( a simil> arc lamp consum+ #aj ampres b work$ f a supply ( #bjj volts4 ,our equation ,c ,e _/ ,r mu/ !n obvi\sly become ,c 7#aj ampres7 ,e 7#bjj volts7 _/ ,total ,resi/ance 7#bj ohms74 ,! resi/ance ( ! arc itself be+ ! same z be=e1 viz4 #d4e ohms1 x is obvi\sly necess>y to put an extra fix$ resi/ance equal to #ae4e ohms 9 s]ies ) x 9 ord] to make up ! total ( #bj ohms4 ,n[ leave ! arc unatt5d$ until ! resi/ance ( #d4e ohms has aga9 become #e ohms2 ! only effect is t our curr5t1 in/ead ( rema9+ at #aj ampres1 has become #bjj _/ #bj4e or #i4h ne>ly1 a diff]5ce :i* is imp]ceptible4 ,?is is n all1 = x is an elem5t>y rule 9 electrical sci5ce t ! total ,e4,m4,f4 ( any circuit di/ributes itself along t circuit 9 proportion to ! di/ribution ( resi/ance4 ,9 o!r words1 our orig9al ,e4,m4,f4 ( #bjj volts w s di/ribute itself z to res]ve1 s to speak1 an ,e4,m4,f4 ( #de volts = ! arc1 :ile ! resi/ance ( ?is rema9s at #d4e ohms1 b directly ?is resi/ance increases1 ! ,e4,m4,f4 at ! arc lamp t]m9als automatically rises1 & !re=e ! actual dim9ution 9 curr5t is ev5 less ?an ! figures above quot$4 #di ,%\ld ! arc t5d to 'break' or g out1 ! resi/ance across x automatically becomes inf9ite & ! :ole #bjj volts is at t mom5t available to prev5t ! occurr5ce4 ,"u ^! conditions1 !re=e1 ! op]ator c safely leave ! arc = _m m9utes at a "t4 ,9 c>ry+ out exp]im5tal "w ,i h (t5 left ! lant]n1 walk$ up to ! scre51 discuss$ results ) a fri5d1 & walk$ back1 & ! arc has %[n no signs ( misbehavi\r :atev]4 ,illu/ration3 ,fig4 #bh4--,resi/ance4 ,9 practice any curr5t f #ajj volts to #bej volts may be consid]$ z satisfactory = lant]n "w ) a suitable resi/ance4 ,less ?an ?is involves fe$+ ! arc r frequ5tly1 & m may give a na/y %ock1 %\ld ! op]ator inadv]t5tly t\* a live wire1 ?\gh ,i h work$ an arc lamp on a curr5t ( z mu* z #ejj volts4 ,! resi/ance usually consi/s ( a suitable l5g? ( wire ( high resi/ance 7,iron1 ,g]man ,silv]1 or ^? alloys kn[n z ,plat9oid1 ,eureka1 ,mangan91 ,beacon1 c41 are mo/ commonly us$7 w\nd 9 spirals on a frame1 & is g5]ally suppli$ adju/able 7,fig4 #bh71 s t m or less curr5t may be us$ z desir$4 ,^! resi/ances get pretty hot 9 use1 & c>e mu/ be tak5 t !y are plac$ :]e !y _c scor* woodwork1 c41 & 9 cases :]e ! lant]n is a fixture x is a good plan to h ! resi/ance bolt$ up aga9/ a wall once & = all4 ,! resi/ance may be plac$ any:]e 9 ! circuit1 s long z ! curr5t passes ?r\gh x1 !n ?r\gh ! arc lamp 7or vice v]s71 & back to ! o!r #ej pole ( ! supply ma92 x does n matt] 9 ! lea/ :]eab\ts x comes4 ,9 cases1 h[ev]1 :]e "o pole ( ! supply ma9 is e>!d1 x is a good ?+ to place ! resi/ance 9 ! 'live' side1 z ?is keeps ! arc lamp )9 #de volts ( e>? pot5tial :ile x is work+1 to ! com=t ( ! op]ator %\ld he t\* a t]m9al or wire1 ?\gh ) an ord9>y light+ ma9 !re is no real fe> ( a dang]\s %ock 9 any case4 ,! am\nt ( curr5t requir$ dep5ds ( c\rse on ! size ( ! %eet1 l5g? ( ! hall1 & d5sity or o!rwise ( ! slides2 b x is usually accept$ 9 practice t ! effici5t light f a cont9u\s curr5t arc lamp equals #ajj c&les p] ampre1 & !re=e a #aj-;ampre arc w give #ajjj c&les4 ,?is is suffici5t = all ord9>y halls & slides1 b :]e ^! latt] are v d5se1 z = example ) ! ,lumire ?ree-col\r process1 z mu* z #bj or #be ampres may be requir$4 ,9 ^! cases "s special precautions mu/ be tak5 = keep+ ! slides cool1 or ! result may be disa/r\s1 b ?is is a "q t w be ref]r$ to 9 a lat] *apt]4 ,a curr5t ( #aj ampres is pretty safe = all ord9>y slides1 & may be tak5 z ! normal curr5t us$ 9 l>ge halls1 ?\gh 9 arrang+ = ! wir+ x is z well to /ipulate = at lea/ #ab or ev5 #ae ampres1 especially z !re mu/ necess>ily be a mom5t>y increase ( curr5t at ! in/ant ! arc is '/ruck4' ,,v>ieties ,,( ,,h&-,,f$ ,,arc ,,lamps4--,! patt]n ( h&-f$ arc lamp illu/rat$ 9 ,fig4 #bf is only typical ( _m ( ! same g5]al design1 & !re are o!rs 9 :i* ! design itself is fundam5tally diff]5t4 ,( ^! ! ',scissors' arc lamp made by sev]al firms des]ves m5tion on acc\nt ( its simplicity & *eapness4 ,z its "n implies1 ! me*anism resembles a pair ( scissors1 ! c>bons be+ atta*$ to ! ends ( a pair ( lev]s h+$ toge!r #ea 7,fig4 #bi74 ,9 ?is lamp c5tr+ movem5ts are usually disp5s$ )1 ! arc be+ clamp$ on to a tray p9 z 9 ! case ( a limelight jet4 ,?is is n1 ( c\rse1 s conv5i5t1 & a fur!r disadvantage ( ?is patt]n arc lamp is t ! fe$+ process gradually alt]s ! position & angle ( ! c>bons4 ,9 fact1 ! "o great m]it ( ! lamp is *eapness1 & :]e exp5se is an object1 x %\ld c]ta9ly be consid]$4 ,illu/ration3 ,,fig4 #bi4--',scissors' ,arc ,lamp4 ,yet ano!r arc lamp des]v+ ( m5tion is ! ',p>allel1' a "n aga9 v aptly *os51 z ! two c>bons are ei!r exactly p>allel to ea* o!r or v slightly incl9$4 ,9 ! =m] case ! arc has to be '/ruck' by t\*+ ! ends ( ! c>bon rods ) a piece ( metal or c>bon4 ,( ! actual manipulation ( ?is lamp ,i h _h v little practical exp]i5ce1 b ,i h he>d x well spok5 (1 ?\gh ,i believe x has s f> only be5 made = curr5ts ( #e ampres or s4 ,yet ano!r type :i* mu/ n be ignor$ is ! ',"r-angl$' patt]n 7,fig4 #cj71 a "n aga9 self-descriptive4 ,! horizontal c>bon is ! positive1 & ! v]tical ! #eb negative1 & ?is lamp aga9 is made by sev]al manufactur]s 9 slightly diff]5t =ms4 ,?is patt]n lamp is 9 my exp]i5ce ! be/ ( all = small curr5ts1 say1 ( #e ampres or s1 b inf]ior to ,fig4 #bf = curr5ts ( #aj ampres or m4 ,?is la/ rem>k p]haps h>dly applies to alt]nat+ curr5ts1 :i*1 h[ev]1 ,i h n yet discuss$4 ,i _c conclude ?is brief category ( arc lamps )\t ref]r+ to ! enclos$ patt]n1 ( :i* ! ',we/m9/]' is p]haps ! be/-kn[n & mo/ popul> 7,fig4 #ca74 ,illu/ration3 ,,fig4 #cj4--',"r-angl$' ,arc ,lamp4 ,?is is a lamp ( ! "r-angl$ type1 b ! arc burns 9 a cyl9drical glass *amb]1 n air-tight1 b p>tially s4 ,aft] burn+ a few m9utes ! oxyg5 9 ?is *amb] becomes us$ up & its place is tak5 by c>bonic-acid gas & o!r products ( combu/ion1 aft] :i* ! c>bons burn away v mu* m sl[ly1 & !re=e require fe$+ at mu* great] int]vals4 ,?is lamp aga9 is *iefly made = small curr5ts n exce$+ #e ampres 7& c !re=e be us$ f any ord9>y lamp socket71 & = a mod]ate-siz$ hall is on ! #ec :ole z *eap1 effici5t & simple a lamp z any ,i am acqua9t$ )4 ,x c be suppli$ ) or )\t me*anical c5tr+ movem5ts z requir$1 & is usually s5t out ) its own resi/ance = ! p>ticul> curr5t on :i* x is to be us$1 s t x only requires connect+ up to ! ne>e/ lamp socket1 & is ready = use4 ,illu/ration3 ,,fig4 #ca4--',we/m9/]' ,arc ,lamp4 ,x is n suffici5t = any?+ l>g] ?an a #ab-;foot %eet or = work+ at a great] di/ance ?an1 say1 #dj feet1 b )9 ^! limits ! lamp1 & 9 fact any good #e-;ampre arc lamp1 w be f\nd q satisfactory & saves ! exp5se ( putt+ 9 a special cable4 ,,automatic ,,arc ,,lamps4--,arc lamps = lant]n "w 9 :i* ! fe$+ is done automatically are also made4 ,l h&-f$ lamps1 !y v>y 9 exact design1 b all1 or practically all1 are s design$ t ! c>bons are br\ght toge!r by means ( spr+s or weights1 & "s =m ( 'brake' controll$ by a sy/em ( electro-magnets *ecks ! #ed movem5t4 ,z ! c>bons burn away ! arc l5g!ns1 ! curr5t weak5s1 ! electro-magnets lose _! grip1 & ! c>bons move toge!r until ! increas+ curr5t puts on ! brake aga94 ,"s ( ^! lamps are 'semi-automatic' only1 t is to say1 ! arc has to be /ruck by h&1 :ile o!rs p]=m ?is op]ation automatically z well1 usually by an additional magnet :i* draws back ! c>bons by ! correct am\nt aft] ! arc is /ruck4 ,my frank advice to int5d+ lant]ni/s is to leave ^! lamps alone4 ,"s ( !m are satisfactory up to a po9t1 b !y are all apt to be 'jumpy1' & on ! :ole ! h&-f$ type is 9 my op9ion to be pref]r$4 ,,arc ,,lamps ,,on ,,alt]nat+ ,,curr5ts4--,! alt]nat+ curr5t is n s good z ! cont9u\s = lant]n "w ) arc lamps3 ! light p] ampre is n s great1 ! light has an irritat+ habit ( travell+ r\nd ! c>bons & !re is always a slight 'hum4' ,! sum total ( ^! drawbacks is no?+ v s]i\s1 provid$ t prop] arrangem5ts are adopt$1 & ,i h frequ5tly manipulat$ arc lamps on alt]nat+ circuits ) su* good results t pr(essional lectur]s h at fir/ refus$ to believe t ! circuit really 0 alt]nat+4 ,z x is frequ5tly /at$ t to obta9 a /eady light ) an alt]nat+ curr5t is impossible1 ,i c und]/& _! surprise1 & ,i c also und]/& ! /atem5t 9 "q1 z ! problem is usually tackl$ on entirely wrong l9es4 ,x is almo/ always /at$ t arc lamps = alt]nat+ curr5ts %\ld be arrang$ ) ! c>bons v]tical1 & _m mak]s actually s con/ruct _! lamps z to all[ ( ?is4 ,to obta9 a /eady light "u ^! conditions is impossible & ,i pity anyone :o attempts x2 b ! /atem5t t ?is is ! be/ me?od ( work+ has be5 repeat$ s (t5 t x seems to h be5 tak5 = grant$4 ,! be/ arrangem5t 79 my h&s at any rate7 is to #ee slant ! c>bons z = ! cont9u\s curr5t1 & also to h ! upp] c>bon cor$ & ! l[] "o solid1 b to use a r l>g] l[] c>bon ?an w\ld be correct if ! ma9 7 cont9u\s4 ,also ! upp] c>bon %\ld n be q s f> back z ) ,d4,c42 to h ! front edges ( ! two c>bons practically 9 l9e is ab\t correct1 b ! exact position %\ld be c>efully adju/$ to obta9 ! /eadie/ light1 & x w be f\nd t a slight alt]ation makes a consid]able diff]5ce4 ,x is also a great help to h a weak electro-magnet1 or its equival5t1 s arrang$ t x t5ds by its influ5ce to keep ! arc to ! front4 ,on "s lamps ?is is provid$ =1 z ev5 ) a cont9u\s curr5t x is q h>mless &1 if any?+1 b5eficial2 b1 if n1 any compet5t me*anic c easily fit an ',induction ,r+1' consi/+ ( a s+le turn ( /\t copp] wire1 :i* has suffici5t magnetic influ5ce to d all t is requir$ 7,fig4 #cb74 ,?is r+ mu/ be wir$ 9 s]ies ) ! arc itself1 & z ! curr5t pass+ 9 x automatically rev]ses 9 syn*ronism ) ! arc1 its effect is always to deflect ! arc 9 ! same direction1 & c>e mu/ ( c\rse be tak5 t x is s wir$ t ! deflection is =w>d & n backw>d4 ,?is is ! exact arrangem5t ,i h myself adopt$1 & ,i nev] exp]i5ce any difficulty on ! score ( ! arc w&]+4 ,"r-angl$ arc lamps1 z describ$ on pages #eb & #ec1 are also v effici5t on ,a4,c4 ma9s1 & frequ5tly ^! lamps are already equipp$ ) electro-magnets = ! purpose requir$4 ,! 'hum' ( an alt]nat+ curr5t _c be altoge!r elim9at$1 b c be r$uc$ to a m9imum by r$uc+ ! voltage z f> z possible4 ,z has be5 already said1 ! ,a4,c4 l5ds itself readily to trans=mation ( voltage1 & ,i f9d 9 practice #ij-ajj to #ef be ideal4 ,m ?an ?is is incl9$ to be noisy1 & less is apt to result 9 an un/eady arc4 ,! arrangem5t1 !re=e1 :i* ,i recomm5d f long exp]i5ce is to employ a trans=m] to r$uce ! ,e4,m4,f4 to #ajj volts or !reab\ts1 & !n "w ) a resi/ance 9 ! usual way 7if ! orig9al curr5t is #ajj volts1 ( c\rse no trans=m] is requir$7 ) a prop]ly con/ruct$ arc lamp fitt$ ) an induction r+ or electro-magnet4 ,no difficulty %\ld !n be exp]i5c$ 9 obta9+ a good1 /eady1 & fairly quiet light4 ,illu/ration3 ,,fig4 #cb4--;,arc ,lamp ) ,induction ,r+4 ,any little 'hum' rema9+ c be sil5c$ to a v consid]able ext5t by plac+ ! entire lant]n on a ?ick block ( saddl]s' felt1 b 9 practice ,i h nev] f\nd ?is necess>y ) ord9>y curr5ts1 ?\gh a few abnormal circuits :]e ! 'p]iodicity' is v high are noisi] ?an o!rs4 ,illu/ration3 ,,fig4 #cc4--,,! ,,optical ,,sy/em ,,( ,a ,,lant]n4 #eg ,! foll[+ table gives ! sizes & p>ticul>s ( c>bons = v>i\s curr5ts t ,i h f\nd be/ 9 actual practice3 ,,cont9u\s ,,curr5t ,ampres4 ,c>bon ,cor$4 - ,c>bon ,solid4 #g-aj #ab mm4 #g mm4 #aj-ae #ac 11 #h 11 #ae-bj #af 11 #aj 11 ,,alt]nat+ ,,curr5t ,ampres4 ,upp] ,c>bon ,cor$4 ,l[] ,c>bon ,solid4 #g-aj #ab mm4 #aj mm4 #aj-ae #ac 11 #aa 11 #ae-bj #af 11 #ac 11 99 99 99 99 99 ,,*apt] ,,vii ,,! ,,optical ,,sy/em ,,( ,a ,,lant]n ,illu/ration3 ,,fig4 #cc;,a4--,optical ,sy/em ( ,lant]n4 ,z previ\sly not$1 ! ess5tial p>ts ( an ,optical ,lant]n are1 9 ord] f re> to front3 7#a7 ,! illum9ant2 7#b7 ! cond5s]2 7#c7 ! slide & slide /age2 7#d7 ! objective1 to :i* mu/ be add$1 7#e7 ! body or framework :i* holds ! :ole toge!r4 ,fig4 #cc is a diagrammatic repres5tation ( ! entire optical sy/em & ,fig4 #cc;,a %[s all ! v>i\s p>ts 9 situ3 ,a be+ ! illum9ant1 %[n 9 ,fig4 #cc #eh z an arc lamp1 ,b ! cond5s]1 ,c ! slide /age1 & ,d ! objective4 ,! f\ndation1 s to speak1 ( ! :ole in/rum5t is ( c\rse ! slide1 :i*1 z made 9 ?is c\ntry1 consi/s ( a squ>e ( glass #c in*es diamet]1 ! slide itself be+ some:at less ?an ?is on acc\nt ( ! b9d+1 c42 9 mak+ calculations x is usually tak5 z a #c-;in* circle4 ,slides are usually made by b9d+ toge!r ) /rips ( pap] or clo? two su* squ>es1 on "o ( :i* is ! photographic film or pa9t+ =m+ ! picture1 ! o!r be+ simply a pla9 cov] glass plac$ ov] ! slide surface to protect x1 & betwe5 ! two be+ plac$ a pap] mask ) an ap]ture ( :atev] size or %ape is requir$1 t ( ! a=esaid #c-;in* circle be+ usually tak5 z ! /&>d or normal dim5sion = ?is ap]ture4 ,! slide be+ illum9at$ by "o ( ! v>i\s me?ods discuss$ 9 ! previ\s *apt]s1 is focuss$ on ! scre5 by ! objective1 :i* mu/ be select$ accord+ to ! size ( picture requir$ & ! di/ance betwe5 lant]n & scre54 ,^! po9ts w be gone into lat]1 & also details z to v>i\s types ( objectives & _! respective advantages2 b x may be said "h t a lant]n objective consi/s usually ( a comb9ation ( l5ses ( #b in*es or #b in*es diamet] m\nt$ 9 a rackwork focuss+ sy/em at a di/ance f ! slide ( #f in*es to #ah in*es1 accord+ to ! l5g? ( its 'focus4' ,z our slide is f #c to #c in*es diamet]1 x is evid5t t all ! light radiat+ f ?is _c possibly get ?r\gh ! objective unless x is conv]g$ ^u x1 & to d ?is is ! function ( ! cond5s]4 ,! foll[+ two diagrams1 ,figs4 #cd & #ce1 w make ! matt] cle>4 ,s repres5ts our glass slide ( #c in*es cle> diamet]1 ,r ! radiant or illum9ant1 & ,l our objective1 %[n "h = ! sake ( simplicity z a s+le l5s4 ,! slide is well illum9at$ by ! light emanat+ f #ei ,r1 b x is obvi\s t ! bulk ( ?is light w nev] pass ?r\gh ! l5s1 &1 9 fact1 only ! v c5tre ( ! slide w "u ^! circum/ances appe> ^u ! scre5 at all4 ,illu/ration3 ,,fig4 #cd4--,optical ,sy/em )\t ,cond5s]4 ,illu/ration3 ,,fig4 #ce4--;,action ( ,cond5s]4 ,:at is evid5tly want$ is to conv]ge ^! out] rays1 or 9 o!r words to b5d !m 9 s t !y also pass ?r\gh ! objective1 & ?is is ! function ( ! cond5s] z illu/rat$ 9 ,fig4 #ce4 ,! cond5s] is "h repres5t$ also by a s+le l5s1 b 9 practice x also is inv>iably con/ruct$ ( two or ev5 ?ree l5ses1 = bo? optical & me*anical reasons4 ,x is evid5t f ! above diagrams t ! cond5s] mu/ be some:at l>g] 9 diamet] ?an ! slide itself1 & cond5s]s = ord9>y lant]n "w are usually #d in*es to #d in*es diamet]4 ,! =m] size #fj w suffice if ! cond5s] is plac$ v close to ! slide1 b x is (t5 advisable to leave a little int]v5+ space1 especially if ! illum9ant is a p[]ful "o1 9 ord] to all[ any cond5sation ( moi/ure readily to evaporate & escape4 ,h5ce lant]ns = long range "w 7:i* involve1 ( c\rse1 good illum9ation7 are usually made ) cond5s]s ( #d in*es diamet]4 ,lant]n cond5s]s ( to-day usually take "o ( ! two =ms %[n 9 ,fig4 #cf1 b ! exact curve mu/ be left to ! manufactur]1 z ! focus ( ! cond5s] mu/ h a def9ite relation to t ( ! objective4 ,tak+1 h[ev]1 ! design ( ,e1 ! mo/ common ( all1 ! two l5ses %\ld n be exactly simil> unless ! objective is pretty %ort 9 focus1 or1 9 o!r words1 unless ! di/ance ( ! illum9ant on ! "o h& & t ( ! objective on ! o!r are approximately equal4 ,if ! lant]n is int5d$ = long range "w1 t is equipp$ ) a long focus objective1 ! front compon5t ( ! cond5s] %\ld also be con/ruct$ long] 9 focus 7t is to say1 ) a %all[] curve7 ?an ! re> "o1 & x is amaz+ h[ c>eless manufactur]s are 9 ?is respect4 ,if1 z is (t5 ! case1 ! lant]n is fitt$ ) sev]al objectives ( diff]5t foci1 x is usually necess>y to supply alt]native cond5s]s also1 or at lea/ to supply an int]*angeable front compon5t4 ,illu/ration3 ,,fig4 #cf4--;,=ms ( ,cond5s]s4 ,if ! entire cond5s] is too long 9 focus1 light is lo/2 if too %ort1 x is impossible to obta9 an ev5 disc1 z !re is inv>iably a d>k pat* ei!r 9 ! c5tre or r\nd ! edges4 ,! m\nt+ ( ! cond5s] also v>ies ) diff]5t mak]s2 b x mu/ be rememb]$ 9 any case t x gets #fa extremely hot1 especially ! back compon5t1 & h5ce ! glass mu/ be m\nt$ loose 9 its cell1 o!rwise !re is great dang] ( x crack+4 ,also ! space betwe5 ! compon5ts %\ld be well v5tilat$1 9 ord] to provide = ! escape ( moi/ure :i* usually at ! />t ( a lant]n exhibition is deposit$ ^u ! glass1 & %\ld be got rid ( be=e ! actual lecture comm5ces4 ,ev5 ) all c>e1 ! back compon5t ( a cond5s] w sometimes crack1 ?\gh su* an accid5t %\ld be a r>e occurr5ce2 & h5ce a pr(essional op]ator w usually provide himself ) a sp>e l5s1 & ! cond5s] %\ld be s con/ruct$ t x c readily be *ang$1 & ) z little delay z possible4 ,cond5s] l5ses z made 9 ?is c\ntry are usually gr\nd f ! glass kn[n z ',engli% ,cr[n1' & comp>atively r>ely crack2 b !y are v slightly gre5 9 col\r4 ,fr5* cond5s]s1 on ! o!r h&1 are :it]1 b ! glass is m brittle1 & a fracture a m common occurr5ce4 ,! ,fr5* v>iety are 7or 7 be=e ! w>7 *eap] & g5]ally met ) 9 *eap] in/rum5ts4 ,m exp5sive lant]ns are usually fitt$ ) ,engli% cond5s]s1 z ! t+e ( gre5 is almo/ imp]ceptible1 & ! advantage z reg>ds great] security pretty consid]able4 ,,! ,,slide ,,c>ri] ,,& ,,slide ,,/age4--,tak+ /ill ! optical sy/em ( ! lant]n 9 ord] f back to front1 we n[ come to ! slide1 slide c>ri]1 & slide /age4 ,! slide itself has already be5 describ$1 & ! c>ri] is simply a me*anical contrivance1 usually ( wood1 design$ = ! purpose ( readily *ang+ ! pictures & :i* 9 its turn fits into ! /age ( ! lant]n4 ,x may be ask$ :y1 if slides are n[ always made to a /&>d size1 ! slide c>ri] %\ld n itself be built into ! lant]n & =m ! /age2 b ! answ] is1 9 ! fir/ place1 t slides ( a diff]5t size1 i4e4 ,am]ican or ,cont95tal1 may be met )1 #fb & also t !re are v>i\s me*anical slides on ! m>ket--= example1 *romotropes or sci5tific models1 su* = in/ance z are made to illu/rate ! movem5ts ( ! planet>y bodies--& ^! slides are p]man5tly m\nt$ 9 wood5 frames :i* c\ld n be put into a c>ri]4 ,! commone/ =m ( c>ri] is t kn[n z ! ',d\ble ,slid+' patt]n 7,fig4 #cg71 :i* consi/s ( a frame ) two ap]tures = ! slide1 & an out] frame ?r\gh :i* ?is itself slides & :i* fits ! /age ( ! lant]n4 ,illu/ration3 ,,fig4 #cg4--;,d\ble ,slid+ ,c>ri]4 ,?is c>ri]1 z w be se51 all[s ! next picture to be plac$ 9 position 9 ! second ap]ture :ile ! =m] "o is be+ project$1 & at a signal f ! lectur]1 ! inn] frame slides smoo?ly ?r\gh ! out]1 & ! slides are !reby *ang$4 ,?is c>ri] is simple1 *eap1 & quiet 9 its action2 its "o disadvantage is t ea* alt]nate slide has to be ins]t$ f opposite sides ( ! lant]n1 & unless ! op]ator is fairly tall ?is almo/ necessitates an assi/ant4 ,nev]!less1 ! c>ri] is ! mo/ popul> ( any1 its o!r advantages1 especially z reg>ds price1 be+ s great4 ,x is usually con/ruct$ 9 su* a way t ! slide1 z x moves out f ! c5tral position1 automatically rises 9 its groove 9 ord] to facilitate quick removal4 ,ano!r patt]n des]v$ly popul> is t kn[n z #fc ',be>d's ,dissolv+ ,c>ri]' & is %[n 9 ,fig4 #ch4 ,9 ?is +5i\s c>ri] all ! slides are ins]t$ f ! same side1 ! oncom+ slide be+ pu%$ 9 front ( its pr$ecessor1 & be+ !re=e some:at out ( focus x produces a blur on ! scre54 ,! movem5t is p]=m$ by pu%+ 9 a project+ h&le1 & on )draw+ ?is ! slide :i* is f9i%$ ) comes ) x1 & ! f9i% ( ! movem5t presses ! new slide back until x is 9 its prop] position & 9 focus4 ,illu/ration3 ,,fig4 #ch4--;,be>d's ,dissolv+ ,c>ri]4 ,! entire action is simpl] ?an x s\nds1 & ! tempor>y blurr+ ( ! image on ! scre5 dur+ ! process ( *ang+ is suppos$ to give some:at ! effect ( ',dissolv+ ,views1' & h5ce ! "n ',dissolv+ ,c>ri]4' ,?is appliance is ?ree times ! price ( ! ',d\ble ,slid+' patt]n1 b ! fact t x is work$ f "o side only is a decid$ advantage1 ?\gh on ! o!r h& x is n 7unless great c>e is us$7 q s sil5t 9 its action z ! ',d\ble ,slid+' type4 ,a fur!r modification ( ?is c>ri] adapts x to take any ( ! recognis$ '=eign' sizes ( slides1 s t if a few ,am]ican ones1 = in/ance1 are met ) among a collection ( ,engli% manufacture1 !re is no ne$ to *ange ! c>ri]4 #fd ,!re are o!r v>ieties ( c>ri]s on ! m>ket :i* !re is no ne$ p>ticul>ly to describe1 su* z1 = example1 c>ri]s fitt$ ) roll] curta9s to give ! effect ( a curta9 roll+ up1 magaz9e c>ri]s to hold tw5ty-f\r or m slides & exhibit !m 9 rotation1 & o!r patt]ns too num]\s to m5tion4 ,( ^! ! read] mu/ be left to judge = himself1 b1 g5]ally speak+1 simplicity 9 a c>ri] is ! mo/ important po9t to be look$ =1 & complications1 h[ev] +5i\s1 %\ld be avoid$4 ,illu/ration3 ,,fig4 #ci4--;,focuss+ ,action ( ,l5s4 ,! lant]n /age mu/ also receive consid]ation1 b x w be bett] to discuss x z "p ( ! me*anical con/ruction ( ! lant]n4 ,,! ,,objective is really ! mo/ vital "p ( a lant]n1 z ! def9ition ( ! picture almo/ entirely dep5ds ^u ! excell5ce or o!rwise ( ?is l5s4 ,?is w be obvi\s at once :5 x is realis$ t ! objective has to project on to ! di/ant scre5 a greatly magnifi$ image ( ! comp>atively small lant]n slide1 & ! int5d+ pur*as] is /rongly advis$ to economise almo/ any:]e r ?an on ?is item4 ,! action ( a l5s 9 focuss+ ! image is p]haps be/ expla9$ by a simple diagram 7,fig4 #ci71 f :i* x w be se5 t all ! rays proce$+ f any "o po9t on ! object are re-conv]g$ 7:5 ! l5s is 9 focus7 to a def9ite po9t on ! image1 & ! p]fection ( ! picture dep5ds ^u ! l5s p]=m+ ?is function accurately4 #fe ,! imp]fections are *iefly two1 viz4 ^? kn[n z *romatic & sph]ical ab]ration respectively4 ,*romatic ab]ration simply means t all ! col\rs compos+ ! orig9al beam (1 say1 :ite light are n equally refract$ or conv]g$1 & !re=e d n meet aga9 at ! same spot 7! well-kn[n prism or lu/re effect71 & reveals itself by col\r$ fr+es r\nd ! edges ( ! v>i\s details 9 ! picture4 ,illu/ration3 ,,fig4 #dj4--;,a*romatic ,l5s4 ,by sph]ical ab]ration we mean t ! light fall+ ^u ! c5tre ( a l5s is n br\ght to a focus at exactly ! same spot z ! m>g9al rays1 & a g5]al want ( def9ition is ! result1 usually accompani$ also by a want ( 'flatness' 9 ! image1 t is to say ! edges ( ! picture d n focus at ! same "t z ! c5tre4 ,*romatic ab]ration is easily cur$ by us+ an a*romatic or comp\nd l5s made by cem5t+ toge!r two l5ses ( cr[n & fl9t glass respectively1 z 9 ,fig4 #dj4 ,x w be se5 t ! fl9t glass compon5t by itself is a concave l5s & !re=e neutralises 9 "p1 or 9 :ole1 ! convex cr[n l5s4 ,fl9t glass has bo? great] disp]sive p[] & also great] refractive p[] ?an cr[n glass1 b =tunately n to ! same degree2 h5ce a comp\nd l5s made 9 ?is way & ) curves c>efully work$ out may h its *romatic effect entirely neutralis$ :ile reta9+ v consid]able refractive or 'focuss+' p[]1 & simple a*romatic objectives ( ?is type are q inexp5sive4 ,9 lant]ns int5d$ = ,sci5ce demon/ration1 z di/9ct f ! m]e projection ( slides1 l5ses ( ?is patt]n are v frequ5tly us$1 z !y w project ! latt] :5 requir$ reasonably well1 & = ! demon/ration ( #ff exp]im5ts or ( app>atus on ! scre5 h advantages t ne$ n be discuss$ "h4 ,= v long focus l5ses also !y are sometimes employ$1 z ! tr\ble f sph]ical ab]ration is mu* less app>5t ) l5ses ( long focus ?an ) %ort1 & ! diff]5ce 9 exp5se is mu* m 9 ! =m] case ?an 9 ! latt]4 ,= %ort focus l5ses1 h[ev]1 z us$ 9 mod]ate-siz$ halls1 !y are n good en\gh1 & ! type ( l5s almo/ univ]sally employ$ is t kn[n z ! ',petzval' comb9ation 7,fig4 #da74 ,illu/ration3 ,,fig4 #da4--,petzval ,comb9ation4 ,?is l5s really consi/s ( two a*romatic comb9ations1 ! pair at ! front be+ cem5t$ toge!r1 & t at ! re> hav+ an air space betwe54 ,! comb9ation is s design$ t ! sph]ical ab]ration ( ! "o pair neutralises t ( ! o!r1 & ! result is or %\ld be a l5s correct$ bo? = *romatic & sph]ical ab]ration4 ,^! l5ses1 h[ev]1 v>y v mu* 9 ! p]fection ( _! results1 & z !y are at pres5t usually import$ 9 bulk f ,france1 ! cu/om] does well to insi/ ^u a demon/ration ( 8 own p>ticul> lant]n be=e acceptance4 ,! magnify+ p[] ( a l5s dep5ds ^u its 'focus' multipli$ by its di/ance f ! scre51 & ! focus 9 ! case ( a simple l5s is easily det]m9$ by ! famili> 'burn+-glass' exp]im5t1 t is by focuss+ an image ( ! sun ^u a piece ( pap] & measur+ accurately #fg ! di/ance ! l5s mu/ be away to produce ! mo/ conc5trat$ spot4 ,9 practice x is suffici5tly accurate to focus a di/ant w9d[1 or o!r lum9\s object1 ^u ! pap]1 any error obta9$ by ?is me?od be+ = ord9>y purposes a negligible "o4 ,) a comp\nd l5s1 su* z a ',petzval' comb9ation1 ?is me?od does n hold good1 z ! optical c5tre ( su* a l5s is n necess>ily midway betwe5 its two compon5ts4 ,! actual focus c be got pretty approximately by focuss+ a w9d[ or o!r object z be=e & measur+ ! di/ance f "o def9ite po9t 7say ! front edge ( "o ( ! l5s cells7 to ! pap]1 !n turn+ x r\nd & tak+ a second measurem5t f ! same po9t1 ! mean betwe5 ! two measurem5ts giv+ ! actual focus4 ,9 practice ! 'simple equival5t focus1' z x is t]m$1 ( a lant]n l5s is usually det]m9$ by measur+ ! magnification ( ! image ?r[n ^u ! scre51 :51 by kn[+ ! orig9al size ( ! slide 7a '/&>d' slide ( #c in*es diamet] is usually tak57 & ! di/ance betwe5 lant]n & scre51 we get ! focus f ! foll[+ v simple equation3 ,diamet] ( picture on scre5 ,di/ance betwe5 l5s & scre5 79 feet7 79 feet7 ----------------------------- --------------------------------- ,diamet] ( slide 79 in*es7 ,focus ( l5s 79 in*es7 or p]haps m simply /ill3 ,di/ance betwe5 l5s ,diamet] ( slide & scre5 79 feet7 79 in*es7 ---------------------------------------- -- ,focus ( l5s 9 in*es2 ,diamet] ( picture 79 feet7 or1 if we "k ! focus ( ! l5s b want to "k h[ f> f ! scre5 we mu/ g to produce a giv5-siz$ picture1 ! =mula w be3 #fh ,diamet] ( picture ,focus ( l5s 79 feet7 79 in*es7 ------------------------------------ ,di/ance requir$ 79 feet74 ,diamet] ( slide 79 in*es7 ,x is h&y = ! lant]ni/ to rememb] t1 deal+ ) a /&>d #c-;in* slide1 a #f-;in* l5s w always give a picture ^: diamet] is "o-half ! di/ance f l5s to scre51 a #ab-;in* l5s half ?is aga9 or "o-qu>t]1 & a #i-;in* l5s half-way betwe5 ! two4 ,be>+ ^! simple figures 9 m9d1 ! approximate di/ance c usually be guess$ suffici5tly ne> = ! fir/ trial1 & !n ! lant]n %ift$ a little ne>] or ! rev]se z requir$4 ,! foll[+ table may1 h[ev]1 be useful1 z %[+ readily ! magnification produc$ at diff]5t di/ances by l5ses ( giv5 foci3 ---------------------------------------- ----------------------- ,disc ,focus ,focus ,focus ,focus ,focus ,focus ,focus want$ #d 94 #f 94 #h 94 #aj 94 #ab 94 #ae 94 #ah 94 ---------------------------------------- ----------------------- feet4 ft4 94 ft4 94 ft4 94 ft4 94 ft4 94 ft4 94 ft4 94 #i #ac #f #ah #j #bd #j #cj #j #cf #j #de #j #ed #j #ab #ah #j #bd #j #cb #j #dj #j #dh #j #fj #j #gb #j #ae #bb #f #cj #j #dj #j #ej #j #fj #j #ge #j #ij #j #ah #bg #j #cf #j #dh #j #fj #j #gb #j #ij #j #ajh #j #bj #cj #j #dj #j #ec #d #ff #h #hj #j #ajj #j #abj #j #be #cg #f #ej #j #ff #h #hc #d #ajj #j #abe #j #aej #j #cj #de #j #fj #j #hj #j #ajj #j #abj #j #aej #j #ahj #j ---------------------------------------- ----------------------- ,,! ,,diamet] ,,( ,,! ,,objective4--,! diamet] ( ! objective mu/ dep5d to a c]ta9 ext5t ^u its focus 9 ! case ( a d\ble comb9ation su* z a ,petzval4 ,^! l5ses consi/1 z has already be5 said1 ( two a*romatic compon5ts "s di/ance ap>t1 & = te*nical consid]ations1 :i* ne$ n be discuss$ "h1 ! di/ance betwe5 ^! compon5ts is usually ab\t two-?irds ( ! focal l5g?4 ,?is is n a univ]sal rule1 z ! l5ses ( diff]5t mak]s v>y a good deal2 b x is g5]ally a fact #fi t ! long] ! focus ( ! l5s ! great] is usually ! sep>ation betwe5 ! two l5s sy/ems4 ,! entire l5s !re=e m\nt$ 9 its tube resembles a tunnel ( v>y+ l5g? accord+ to its focus1 & ?r\gh ?is tunnel a cone ( light rays h to be pass$4 ,x is pla91 !re=e1 t a l5s ( long focus1 :i* 9 practice means a long tube l5g?1 mu/ be made also ( l>ge diamet]1 or a portion ( ! cone w be cut (f1 ) a consequ5t loss ( light4 ,9 practice l5ses up to #f in*es focus are usually made ( #b in*es diamet]1 & !re is no advantage 9 a l>g] size4 ,) a l5s ( #h in*es focus !re is a slight ga9 9 increas+ ! diamet] to #b-c_/h 7! next '/&>d' size71 & l5ses ( long] focus ?an ?is %\ld c]ta9ly be #b-c_/h in*es up to1 say1 #ab in*es focus1 :5 a l5s ( #c in*es diamet] is pref]able4 ,^! l>ge l5ses are1 h[ev]1 v exp5sive1 bo? 9 !mselves & also on acc\nt ( ! fact t _! weight entails heavy & exp5sive brass m\nt+1 & h5ce l5ses up to #ad or #ae in*es focus are (t5 suppli$ 9 ! #b-c_/h size = reasons ( economy4 ,to sum up1 %ort-range lant]ns1 z !y are call$1 are usually fitt$ ) l5ses ( #b in*es diamet]1 & long-range in/rum5ts ei!r ) #c-;in* l5ses or ! int]m$iate size ( #b-c_/h in*es4 ,if a lant]n is pur*as$ = ei!r long or %ort-range "w1 x is usually fitt$ ) a brass front = a l>ge l5s1 & s arrang$ t a %ort] focus l5s ( #b in*es diamet] c easily be int]*ang$1 utilis+ ! same brass m\nt+4 ,l5ses ( v>iable focus h also be5 design$1 9 :i* an additional l5s c be add$ or subtract$ to increase or decrease ! focal l5g?2 b no?+ v practical has yet be5 a*iev$ 9 ?is direction1 & !re=e ^! ',omnifocal' l5ses h nev] come into g5]al fav\r4 ,objectives l cond5s]s want clean+ at times1 & c>e mu/ be tak5 n to scrat* ! glass1 z ! concave l5s ( ea* compon5t is ( fl9t glass1 & v s(t4 ,a #gj clean *amois lea!r is ! be/ ?+ to use1 b a s(t clo?1 or ev5 a h&k]*ief1 may be employ$ ) c>e4 ,x is v important t a l5s be reassembl$1 aft] clean+1 ! correct way1 z a s+le l5s rev]s$ w\ld utt]ly spoil ! def9ition4 ,! front compon5t is usually balsam$ toge!r1 & !re=e all t is ne$$ is to see t ! :ole comb9ation is n rev]s$4 ,9 ! ,petzval sy/em ?is l5s %\ld h its convex con/itu5t t[>ds ! scre5 7,fig4 #da74 ,! back comb9ation is usually loose1 & ! two l5ses are sometimes sep>at$ by a ?9 brass r+4 ,9 ! ,petzval l5s ! concave elem5t %\ld be inside1 ) its concave surface outw>ds1 ! deep curve ( ! o!r l5s %\ld fit into ?is concavity1 & ! flatt] curve face t[>ds ! cond5s]4 ,"o or two mak]s1 h[ev]1 h introduc$ a modification ( ! ,petzval sy/em 9 :i* ! :ole ( ?is back comb9ation is rev]s$1 & ! exact arrangem5t %\ld !re=e be not$ v c>efully :5 tak+ ! l5s to pieces4 99 99 99 99 99 ,,*apt] ,,viii ,,! ,,body ,,( ,,! ,,lant]n ,we n[ come to ! me*anical con/ruction ( ! optical lant]n1 & a great v>iety ( design pres5ts itself1 accord+ to price1 type 7i4e4 %ort range or long range71 & ! individual ideas ( ! v>i\s mak]s4 ,lant]n bodies z a rule are n[ made ( metal1 al?\gh up till q rec5tly ! bett] class in/rum5ts 7 m usually made ( poli%$ mahogany l9$ int]nally ) iron2 b !re has ( late be5 a cons5sus ( op9ion 9 fav\r ( metal only4 ,9 ! *eap] lant]ns ?is metal body is usually made ei!r ( ,russian iron or ( %eet-iron t9n$ & japann$1 #ga !re be+ little to *oose ei!r 9 price or quality betwe5 ! two v>ieties1 & 9 all b ! v *eape/ in/rum5ts ! front is usually ( brass4 ,9 bett] lant]ns ! body is m (t5 made ( enamell$ /eel1 ! front z be=e be+ ( brass2 b brass1 copp]1 or alum9ium are also us$ occasionally = ! body ( ! lant]n4 ,illu/ration3 ,,fig4 #db4--;,hughes' ,%ort-,range ,lant]n4 ,9 decid+ ^u ! type ( body to be pur*as$ ! ma9 consid]ations to be borne 9 m9d are3 7#a7 ,! type or types ( illum9ant to be us$1 a p[]ful arc lamp = example requir+ a l>g] body ?an is necess>y = a weak] radiant2 7#b7 ! size & position ( ! l5s to be c>ri$1 a ,petzval objective ( say #c in*es diamet] :i* has to be support$ at ! end ( a long brass m\nt = long-range "w obvi\sly dem&+ a body ( great] /r5g? & rigidity ?an is requir$ ) a #f-;in* focus l5s ( #b in*es diamet]2 7#c7 price4 ,fig4 #db %[s an extremely good lant]n body = %ort-range "w made by ,messrs4 ,hughes1 ! illu/ration depict+ ! in/rum5t complete ) a ',luna' me?ylat$ _s lamp1 ?\gh1 ( c\rse1 any o!r illum9ant suitable = a small lant]n c\ld be us$ in/ead4 #gb ,?is lant]n illu/rates well "o po9t t has already be5 emphasis$ z important1 viz4 ! v5tilation ( ! cond5s]4 ,x w be notic$ t ?is is plac$ outside ! body ( ! in/rum5t in/ead ( inside z is usual ) l>g] bodies1 & t wide slots are cut 9 ! cond5s] m\nt to all[ free escape ( /eam4 ,o!r po9ts ( ?is excell5t design are ! screw adju/m5t to ! slide /age 7facilitat+ ! use ( special slides1 su*1 = example1 z ^? illu/rat+ ! movem5ts ( ! planet>y bodies :i* sometimes involve ! use ( extra ?ick frames7 & a simple b effici5t tilt+ arrangem5t to ! base4 ,illu/ration3 ,,fig4 #dc4--,long-,range ,lant]n4 ,su* a lant]n is h>dly suitable = a p[]ful arc lamp or limelight jet1 or = heavy long-range l5ses1 b is a v good typical in/rum5t = use 9 mod]ate-siz$ halls1 & a lant]n ( ?is g5]al type is usually f\nd 9 lant]n catalogues1 ?\gh1 ( c\rse1 ! exact designs v>y accord+ to ! ideas ( ! manufactur]4 ,( lant]ns = long-range "w a good example is p]haps ,messrs4 ,newton ,co4's ',int]m$iate' patt]n 7,fig4 #dc74 ,?is aga9 is only typical ( _m o!rs by ! v>i\s mak]s1 b ! pr9cipal po9ts are common to all4 ,^! are3 7#a7 ,! l>ge & well-v5tilat$ body2 7#b7 ! long #gc basebo>d2 7#c7 ! /rong & massive brass front necess>y to c>ry ! l>ge long-range l5ses2 7#d7 ! velvet curta9 at ! back to close 9 any /ray light f a p[]ful arc lamp4 ,illu/ration3 ,,fig4 #dd4--;,connections = a ,bi-unial ,lant]n4 ,! two =ego+ designs are p]haps suffici5tly typical ( lant]n bodies 9 g5]al to make fur!r detail$ description ( individual designs unnecess>y2 b ref]5ce %\ld be made to features :i* special requirem5ts may r5d] advisable4 ,"u ?is head+ m5tion mu/ be made ( ,bi-unials or ,d\ble ,lant]ns1 z us$ = ! once fam\s ',dissolv+ ,views4' ,a bi-unial lant]n consi/s ess5tially ( two diff]5t in/rum5ts1 ea* complete ) its limelight jet or o!r illum9ant--front1 cond5s]s1 objective1 c41 usually m\nt$ on "o body--& ) "s arrangem5t = 'dissolv+' or turn+ ! light 9 ea* lant]n gradually on & (f4 ,fig4 #dd %[s ! back view ( su* a lant]n ) two limelight jets & dissolv+ tap1 ?is piece ( me*anism 7%[n bel[ 9 ! illu/ration7 be+ s arrang$ t :5 ! lev] is horizontal bo? lant]ns are on full1 b mov+ ! lev] ei!r way cuts (f ! gas supply to "o lant]n4 ,9 ! case ( limelight ! tap %\ld always op]ate by cutt+ (f ! oxyg5 supply 9 advance ( ! coal gas 79 ord] to avoid a 'snap'71 & ! latt] %\ld nev] be cut (f entirely1 b a small bead ( flame left to keep ! jet alight1 until ! lant]n is requir$ = ! next slide4 #gd ,?is is usually arrang$ = by means ( a bye-pass1 & a bye-pass is sometimes provid$ on ! oxyg5 side z well1 b is usually disc>d$ 9 practice4 ,a bi-unial lant]n c be work$ 9 ! same way ) acetyl5e gas1 b ) ! electric arc x is impossible to turn ! light on & (f gradually1 & 9 practice dissolv+ mu/ be done by keep+ bo? lant]ns fully alight1 & us+ a dissolv+ %utt]1 t is a movable %utt] t cov]s ea* objective alt]nately4 ,! same arrangem5t mu/ be us$ ) o!r illum9ants1 su* z oil1 only 9 ?is case ! lant]ns mu/ be m\nt$ side by side1 on acc\nt ( ! tall *imneys4 ,) oil lamps ! arrangem5t answ]s fairly well1 ! dissolv+ fan1 z x is t]m$1 be+ made ) s]rat$ edges :i* give ! gradual oblit]ation requir$2 b ) ! electric arc ! extremely %>p def9ition becomes a s]i\s difficulty1 & a good dissolv] = ?is illum9ant has nev] yet be5 f\nd1 ?\gh1 9 view ( ! fact t dissolv+ views are m or less a ?+ ( ! pa/1 ! matt] _c be reg>d$ z important4 ,! advantages claim$ = a d\ble lant]n are two3 fir/1 a ',dissolv+' effect by :i* "o picture fades gradually into ! next1 & :i* is suppos$ to be m pleas+ ?an ! movem5t ( a c>ri]2 & second1 ',dissolv+ ,effects' c be %[n1 su* z exhibit+ a l&scape by day & *ang+ x into a moonlight sc5e1 or br++ on ! appe>ance ( a sn[/orm1 :i* c easily be done by means ( a roll] slide1 ) m9ute p]=ations %[n 9 motion by ! second lant]n :ile ! l&scape rema9s on ! scre5 f ! fir/4 ,9 ! days :5 dissolv+ views 7 all ! vogue1 a ?ird or ev5 a f\r? lant]n has be5 add$ = m complicat$ effects1 & at ! fam\s ,polyte*nic demon/rations ( ye>s ago1 ,i believe t z _m z six 7 sometimes employ$4 ,9 ^! days ( ! c9ematograph x is d\btful h[ f> int]e/ 9 su* effects c\ld be reviv$1 & a lant]n has #ge gradually come to be look$ on m z an in/rum5t = %[+ illu/rations z requir$ by ! lectur] r ?an z a pleas+ exhibition 9 itself1 & z dissolv+ views h lo/ _! attraction1 ! d\ble or triple lant]n has be5 relegat$ to ! limbo ( antiquity4 ,illu/ration3 ,,fig4 #de4--;,be>d's ,circulat+ ,wat] ,tank4 ,among o!r 'special' lant]ns %\ld be m5tion$ models made ) wat]-cool$ /ages1 = use ) v delicate slides4 ,?is elaboration is n necess>y ) ord9>y slides & illum9ants ( mod]ate p[]1 b :]e v delicate slides1 su* z specim5s ( natural col\r photography1 h to be %[n1 x is an advisable precaution to pass ! beam ( light fir/ ?r\gh a tank ( wat] 9 ord] to absorb ! heat4 ,lant]ns int5d$ = ?is "w are usually con/ruct$ ) a k9d ( d\ble /age1 a glass tr\gh ( wat] fitt+ into ! re> ap]ture & ! slide-c>ri] into ! front "o4 ,su* an arrangem5t answ]s q well = mo/ purposes1 b = extreme cases lant]ns are equipp$ ) a tr\gh connect$ to a l>ge outside tank & complete circulatory sy/em1 aft] ! mann] ( ! cool+ tank ( a gas eng9e4 ,su* a lant]n1 con/ruct$ by ,messrs4 ,be>d1 is illu/rat$ 9 ,fig4 #de1 & x w be se5 t 9 ?is in/rum5t ! wat] tr\gh is plac$ betwe5 ! l5ses ( ! cond5s]4 #gf ,?is is a v good position1 z ! beam ( light at ?is po9t is1 or %\ld be1 p>allel1 :]eas betwe5 ! cond5s] & ! slide x is conv]g5t1 & !re=e a cond5s] ( a l>g] diamet] ?an ! slide mu/ be employ$ 9 ! latt] case if ! tr\gh is ( consid]able wid?4 ,:ile deal+ ) ',special' lant]n bodies1 we %\ld p]haps j m5tion "h ! num]\s patt]n lant]ns made = ! demon/ration bo? ( lant]n slides & ( ,sci5tific ,ph5om5a1 su* z ! projection ( insect life or o!r microscopic objects1 pol>is$ light exp]im5ts1 electrical app>atus1 opaque objects1 c4 ,a detail$ description ( ^! lant]ns & h[ to use !m belongs to ! second "p ( ?is "w1 z also does ! popul> c9ematograph2 b educational in/itutes1 & ev5 boys' clubs1 :5 consid]+ ! pur*ase ( a lant]n1 might well reflect :e!r x w\ld be advisable to sp5d a little m money 9 ! acquisition ( an in/rum5t :i* c be utilis$ = a v>iety ( purposes4 99 99 99 99 99 ,,*apt] ,,ix ,,lant]n ,,boxes1 ,,/&s1 ,,read+ ,,lamps1 ,,etc4 ,hav+ n[ discuss$ all ! ess5tial p>ts ( a lant]n1 ! next po9ts to be consid]$ are ^? ( lant]n boxes & /&s4 ,x is be/ to take ^! toge!r1 z m (t5 ?an n a lant]n is arrang$ to /& ^u its box dur+ use1 & ! plan is bo? conv5i5t & simple4 ,! :ole "q is "o to be settl$ ^u its own m]its 9 ea* individual case4 ,sometimes nei!r box nor /& is want$ at all4 ,! lant]n is put away into a lock$-up cupbo>d or o!r safe place1 & us$ ^u a p]man5t support or 7z is (t5 ! case 9 a *ur*7 f a gall]y at ! back4 #gg ,9 mo/ cases1 h[ev]1 a box ( "s sort is desirable1 & ! two ma9 consid]ations are /r5g? & simplicity4 ,all pat5t arrangem5ts1 su*1 = example1 z ^? 9 :i* ! sides ( ! box fall d[n & provide trays = ! slides1 are beautiful 9 !ory1 b _c be recomm5d$ 9 practice4 ,a good1 simple & sub/antial box is :at is requir$1 pref]ably pa9t$ black1 & provid$ ) /rong h&les4 ,"o addition may be p]mitt$1 viz4 a tilt+ top4 ,"s means = tilt+ ! lant]n is always advisable1 z x is seldom conv5i5t to raise ! in/rum5t to ! level ( ! c5tre ( ! scre51 & a slight upw>d elevation does n appreciably di/ort ! image4 ,?is arrangem5t = tilt+ may be ei!r embodi$ 9 ! lant]n itself1 z = in/ance 9 ! in/rum5t %[n 9 ,fig4 #db1 or may be provid$ = on ! box or on ! /&1 if a /& is us$4 ,x is1 p]haps1 an elaboration t may be reg>d$ z n /rictly necess>y1 z a book or two or o!r article may be plac$ "u ! lant]n base z requir$2 b a tilt+ arrangem5t is s conv5i5t t x c be /rongly recomm5d$1 & ! addition is n exp5sive4 ,= l>ge1 long-range lant]ns a /rong deal box1 on :i* ! lant]n c /&1 is usually all t x is desirable to pur*ase 9 ! way ( a support4 ,a good solid table c usually be f\nd1 :i* w d all ! re/1 z x mu/ be rememb]$ t a slight tilt at a long range means a good deal ( total elevation4 ,:]e ?is is n procurable a /& mu/ be provid$1 & ?is = a l>ge lant]n %\ld be /rong & rigid4 ,any?+ 9 ! way ( a collapsible tripod %\ld be avoid$1 b su* an arrangem5t z ,fig4 #df is q good & rigid en\gh = all practical purposes4 ,= a small lant]n a tripod /& is q suitable1 ?\gh c>e mu/ be tak5 t "o ( ! legs does n get kick$1 ei!r by accid5t or design1 or ! result may be a cata/rophe4 #gh ,slide ,boxes4--,on ?is subject n mu* ne$ be said4 ,! v>iety ( patt]ns on ! m>ket is endless1 "s be+ design$ f ! po9t ( view ( safe transit by po/1 o!rs = conv5i5ce ( /orage & classification4 ,x is ess5tially a case :]e ea* individual us] mu/ use 8 or h] ta/e1 & 9 any case ! "q ( ! box is "o = ! own] ( ! slides r ?an = ! lant]ni/4 ,illu/ration3 ,,fig4 #df4--,quadruple ,lant]n ,/&4 ,,read+-,,desks1 ,,lamps1 ,,& ,,signals4--,"s =m ( read+ lamp = ! lectur] is g5]ally consid]$ to be "p ( a lant]ni/'s equipm5t1 & ! mo/ usual patt]n is fitt$ ) a c&le1 aft] ! mann] ( a c>riage lamp1 or else con/ruct$ to burn colza or o!r vegetable oil1 su* z suppli$ = cycle lamps4 ,oil gives ! bright] light1 b is apt to get spill$ 9 transit1 h5ce a c&le lamp is ! m #gi conv5i5t = a travell+ lectur]1 :ile oil is to be pref]r$ if transport is n a factor to be consid]$4 ,^! lamps are usually con/ruct$ ) a r$ fla%+ signal at ! re>1 actuat$ by a simple lev]1 by :i* ! lectur] c communicate 8 wi% = a *ange ( slide1 c41 to ! lant]ni/ 7,fig4 #dg74 ,illu/ration3 ,,fig4 #dg4--,read+ ,lamp4 ,!re are v>i\s o!r devices us$ = ! same purpose1 su* z a ca/anet1 to be held 9 ! lectur]'s h& & click$ :5 necess>y1 an electric bell to r+ 9 ! lant]n box1 c4 ,if ?is latt] is us$ x is usual to remove ! gong1 ! buzz ( ! hamm] be+ suffici5tly l\d )\t x4 ,"s lectur]s aga9 pref] to use no su* app>atus at all1 b simply to say ',next slide' z requir$1 or to tap on ! floor ) a po9t]1 & ! *oice ( a suitable means ( communication betwe5 lectur] & lant]ni/ mu/ be l>gely a matt] ( individual selection4 ,m elaborate read+-desks are also suppli$ by mo/ mak]s1 b "h aga9 judgm5t mu/ l>gely come into play 9 :at is h>dly a te*nical matt]4 99 99 99 99 99 ,,*apt] ,x ,,scre5s ,,& ,,scre5 ,,/&s ,! be/ ( all scre5s = lant]n purposes is und\bt$ly a smoo? :itewa%$ wall1 & ?is is n[ provid$ 9 _m halls :]e lant]n exhibitions are usual4 ,9 places :]e ?is is n practicable ! next be/ sub/itute is a canvas #hj scre51 :i* rolls up & d[n 7,fig4 #dh74 ,?is c be obta9$ f any good mak]1 b aga9 c only really be us$ z a fixture 9 ! hall :]e ! lant]n is to be us$4 ,x c1 h[ev]1 be fitt$ into a wood5 box :i* c be pa9t$ or v>ni%$ to suit ! o!r ar*itecture1 & ! provision ( su* a scre5 is to be /rongly recomm5d$ :5ev] possible4 ,if portability is requir$1 a l95 or calico %eet t c be fold$ up is necess>y1 b ?is c nev] be hung absolutely flat1 & also loses a consid]able am\nt ( light by transmission4 ,illu/ration3 ,,fig4 #dh4--,roll] ,scre54 ,a s-call$ 'transp>5t' %eet is made ( v ?9 l951 & int5d$ to "w ) ! lant]n beh9d x1 %[+ ! picture ?r\gh ! l95 to ! audi5ce on ! o!r side1 b ?is is seldom us$ except 9 ! op5 air = religi\s or political meet+s1 c4 ,an opaque %eet c be _h 9 "o piece up to #i feet squ>e2 l>g] sizes ?an ?is mu/ h at lea/ "o seam1 & mo/ skilful sew+ is necess>y1 especially ) l>ge %eets consi/+ ( sev]al /rips sewn toge!r4 ,%eets su* z ^! are usually suppli$ ) ei!r eyelet holes r\nd ! edges or else l95 tapes sewn on1 & ! exact me?od ( hang+ mu/ be left to circum/ances4 #ha ,9 ! case ( a small %eet x w be suffici5t to /ret* x at ! f\r corn]s1 & ?is c (t5 be done by screw+ into ! walls or "s conv5i5t gird] two screw eyes & simil> eyes into ! floor1 all f\r be+ consid]ably f>!r ap>t ?an ! size ( ! %eet4 ,illu/ration3 ,,fig4 #di4--,portable ,scre5 ,/&4 ,a /\t cord be+ !n pass$ ?r\gh ! two upp] eyes1 long en\gh = bo? ends to rea* ne> ! floor1 "o end ( ea* c be fa/5$ to ! two top corn]s ( ! %eet & ! latt] drawn up1 ! two bottom corn]s be+ aft]w>ds /ret*$ & ti$ d[n tightly to ! l[] eyes4 ,9 ! case ( l>ge %eets ?is h>dly suffices1 & x w be f\nd necess>y to fa/5 ! %eet at int]vals all r\nd or x w exhibit awkw>d creases1 & ?is aga9 is a matt] :]e ! lant]ni/ mu/ use 8 own initiative accord+ to ! possibilities4 ,9 "s halls ! erection ( a %eet 9 ! way above describ$ is a %e] impossibility1 & 9 su* cases a frame mu/ be made by nail+ /rips ( wood toge!r1 or bett] by utilis+ a portable scre5 /& 7,fig4 #di74 ,^! /&s are usually made ( bamboo1 ) %ort brass connect+ tubes1 & ! me?od ( us+ !m is s obvi\s t a description ne$ h>dly be giv54 ,! scre5 frames are suppli$ by all ! lead+ opticians1 b an int5d+ pur*as] w\ld be well advis$ to see "o erect$ be=e ord]+4 ,i h actually se5 a #ab-;foot scre5 frame (f]$ = sale t 0 too weak to c>ry its own weight1 let alone ! weight ( ! %eet6 99 99 99 99 99 #hb ,,*apt] ,,xi ,,! ,,practical ,,manipulation ,,( ,a ,,lant]n ,hav+ n[ describ$ ! optical lant]n 9 its v>i\s =ms & ! m important accessories1 we come to ! "q ( practical manipulation4 ,9 mak+ arrangem5ts = an exhibition ! fir/ ?+ to be se5 to is to ensure t e accessory t w be requir$ w be !re1 & ! be/ plan is to make a complete li/ ( all sundries to be provid$4 ,su* items z /r+ 7= ! %eet71 lime tongs if limelight is us$1 pli]s = *ang+ c>bons if ! arc is to be ! illum9ant1 screw-driv]1 mat*es1 ! key ( ! lant]n box1 & o!r simil> items1 are likely to be left beh9d unless su* a li/ is made & c>efully *eck$4 ,on arriv+ at ! hall1 ! fir/ ?+ to be done z a rule is to get up ! %eet1 aft] :i* ! pr(essional op]ator g5]ally beg9s to feel happy aga94 ,! next ?+1 if x has n be5 done fir/1 is to det]m9e ! position ( ! lant]n1 & ?is1 z has be5 expla9$ 9 ,*apt] ,,vii1 is a matt] ( ! size ( picture to be %[n & ! focus ( ! objective4 ,x is a mi/ake to %[ too l>ge a picture2 a little ':ite' r\nd ! edges is a good ?+1 & x is bett] to h a small disc well illum9at$ ?an a l>ge "o less bright4 ,conv5i5ce1 h[ev]1 mu/ also be consid]$1 & x is (t5 ju/ifiable to g back a few feet f>!r ?an o!r consid]ations w\ld dictate 9 ord] to place ! lant]n 9 a gall]y or o!r spot :]e x is out ( ! way4 ,hav+ fix$ ! position ( ! lant]n1 x %\ld be got into place1 ! cable or tub+ connect$ or :atev] else is necess>y1 accord+ to ! illum9ant to be us$4 ,x %\ld !n be lit up1 ! fla%] ( ! l5s op5$1 & ! light #hc c5tr$ suffici5tly to produce "s sort ( disc ^u ! scre54 7,x is1 ( c\rse1 presum$ t ! l5ses1 c41 h previ\sly be5 clean$47 ,a c>ri] %\ld n[ be plac$ 9 ! /age & a slide ins]t$ into x1 & ! me?od ( do+ s requires a little explanation4 ,! slide mu/ be plac$ 9 ! c>ri] upside d[n1 z w be obvi\s to anyone :o has /udi$ ,*apt] ,,vii1 b 9 addition to ?is x mu/ be turn$ ! correct way1 o!rwise ! picture w be rev]s$ f left to "r4 ,?is 9 ! case ( c]ta9 subjects1 su* z a copy ( a picture1 may n greatly matt]2 b 9 slides depict+ build+s or l&scapes ) :i* ! audi5ce may be famili>1 or worse /ill1 pr9t+ or writ+1 is a s]i\s blund]4 ,slides made by a comm]cial firm w usually be 'spott$1' t is to say1 w h two :ite spots on ! face ( ! slide :5 ! latt] is view$ 9 its correct position1 & at ! top4 ,! slides %\ld be turn$ upside d[n & plac$ 9 ! c>ri] ) ! spots1 ( c\rse1 n[ at ! bottom & t[>ds ! cond5s]4 ,if a slide is n spott$ x %\ld be view$ z x is to appe> on ! scre51 & !n plac$ 9 ! c>ri] ) ! face t 0 t[>ds ! op]ator z he view$ x turn$ to ! cond5s]1 & ( c\rse inv]t$4 ,! above rem>ks apply only 9 cases :]e ! image is ?r[n on ! scre52 9 ! comp>atively r>e in/ances :]e x is %[n ?r\gh ! latt] ! slides mu/ be turn$ r\nd lat]ally1 b ( c\rse /ill inv]t$4 ,! slide hav+ be5 plac$ 9 ! /age x %\ld be 'focuss$' by rack+ ! objective 9 or out1 & if necess>y pull+ out ! draw tube z well until ! image on ! scre5 is %>ply def9$4 ,s f> ! light has only be5 r\ghly c5tr$1 suffici5tly s to enable ! slide to be focuss$1 & to complete ! op]ation bo? slide & c>ri] %\ld next be tak5 out ( ! lant]n1 leav+ a cle> disc on ! scre51 & ?is disc may resemble any ( ! appe>ances %[n 9 ,fig4 #ej4 #hd ,if x resembles ,a ! light mu/ be mov$ to ! left1 if l ,b to ! "r1 l ,c x mu/ be l[]$1 l ,d x mu/ be rais$1 always mov+ x to ! side opposite to ! d>k %ade until ?is is c5tral on ! disc4 ,if x n[ resembles ,e1 ! light mu/ be mov$ ne>] ! cond5s]2 if1 on ! contr>y1 ! c5tre is d>k1 x mu/ be drawn back until f9ally ! circle %\ld be z ne>ly z possible cle> & bright all ov]1 z at ,f4 ,illu/ration3 ,,fig4 #ej4--;,adju/m5t ( ! ,light4 ,x is important to note t ?is adju/m5t _c be prop]ly made :ile a slide is 9 position1 & nei!r c x be made until ! lant]n has be5 focuss$1 s ! above proc$ure is ! only way to get a satisfactory result4 ,) "s ( ! l>g] illum9ants1 su* z a p>aff9-oil lamp1 !re are no c5t]+ adju/m5ts1 ! size ( ! radiant r5d]+ exact c5t]+ unnecess>y1 & g5]ally speak+ ! small] ! lum9\s po9t1 ! m exact mu/ ! op]ation be4 ,9 ! case ( su* illum9ants z acetyl5e or limelight #he c>e mu/ be tak5 t !y are turn$ fully on be=e c5t]+1 o!rwise turn+ on ! full] am\nt aft]w>ds w raise ! position ( ! lum9\s spot4 ,! c5t]+ a*iev$1 ! slide c>ri] may be replac$1 ! fir/ slides plac$ 9 position1 ! rema9d] arrang$ 9 _! prop] ord]1 ! sy/em ( signall+ ) ! lectur] det]m9$1 & all is ready4 ,if !re is /ill an int]val be=e comm5c+1 ! light may be swit*$ (f or turn$ out1 or 9 ! case say ( limelight1 turn$ d[n v l[ until want$4 ,x is ( extreme importance to see t all ! slides are 9 _! "r ord]1 ?\gh ! duty ( see+ to ?is usually re/s ) ! lectur] r ?an ) ! op]ator4 ,i rememb] he>+ ( "o lecture on ! life ( ,que5 ,victoria1 :5 ! lectur] ann\nc$1 ',! next picture w be a photograph ( ! ,royal ,pr9ce :o = _m ye>s %>$ ! ,?rone ) our graci\s ,sov]eign4' ,at ! words ! op]ator br\ght on ! next slide1 :i* prov$ to be a re/or$ specim5 ( a prehi/oric mon/] 7tableaux674 ,su* mi/akes 'br+ d[n ! h\se1' b 9 s]i\s lectures1 & especially at religi\s s]vices1 _c be too c>efully gu>d$ aga9/4 ,m5tion has already be5 made ( ! liability ( moi/ure to cond5se on ! surfaces ( ! cond5s]s or slides1 & to avoid ?is1 s f> z ! cond5s]s are conc]n$1 x is well to light up say t5 m9utes be=e ! lant]n is actually want$1 or alt]natively to take out ! cond5s]s & ?or\ghly w>m !m 9 front ( a /ove1 or to place !m wrapp$ 9 a clo? on hot-wat] pipes4 ,! slides %\ld 9 ! same mann] be w>m$ be=e us+ & %\ld be f9ally held above ! lant]n or plac$ on ! top1 if ?is is flat1 ! la/ ?+ be=e be+ plac$ 9 ! c>ri]4 ,if ^! precautions are omitt$1 on a cold night ! fir/ surface ( ! cond5s] w become s cov]$ ) moi/ure z to almo/ obscure ! slide1 & ?is w quickly disappe> #hf ) ! heat ( ! lant]n4 ,next1 ! two inn] surfaces ( ! cond5s]s w behave 9 turn 9 ! same way1 & w take consid]ably long] to cle>1 especially if ! v5tilation ( ! cond5s] is poor2 !n ! f\r? surface w take up ! runn+1 & f9ally1 :5 ! lant]ni/ is congratulat+ himself t ! tr\ble is ov]1 ea* successive slide w become affect$ 9 ! same way4 ,) an op]ator :o kn[s 8 bus9ess1 none ( ^! tr\bles %\ld occur4 ,,accid5ts4--,^! w occur sometimes1 ev5 9 ! be/ manag$ exhibition2 ! rubb] tub+ fe$+ a limelight jet gets k9k$ or trodd5 on1 or a fuse melts if electric light is be+ us$1 c41 & out goes ! light4 ,9 su* cases a l\d reque/ su* z1 ',w\ld y m9d turn+ up ! light = a m9ute1 please1' accompani$ by a good-hum\r$ laugh1 usually allays ! fe>s ( 'n]vy' p4 ,an op]ator mu/ nev] get 'n]vy' himself4 ,i h kn[n ( m ?an "o fiasco because "s little hit* occurr$1 & two or ?ree timid ladies cr[d$ r\nd & ask$ anxi\s que/ions1 till ! lant]ni/ lo/ 8 head4 ,9 "o su* case ! cauti\s sup]9t5d5t at a *ildr5's ent]ta9m5t decid$ t x w\ld be saf] n to h ! exhibition at all1 simply because a regulator 0 n screw$ tightly en\gh into a cyl9d] to prev5t an escape ( gas1 only ! op]ator 7a some:at y\?ful "o7 _h be5 driv5 to ! v]ge ( lunacy by cont9ual que/ions ( ! /&>d type1 ',are y sure x is safe8' ',w x bl[ up8' ',are y c]ta9 y und]/& x8' c41 c4 ,m s]i\s accid5ts1 su* z ! entire lant]n gett+ upset1 ought nev] to occur1 & x is up to ! lant]ni/ to take :atev] precautions he deems necess>y to safegu>d 8 in/rum5t4 ,) a juv5ile audi5ce1 = example1 x is (t5 a good ?+ to arrange a b>ricade ( =ms r\nd ! lant]n & to see t no "o comes )9 x4 ,f9ally1 ':atev] is wor? do+ at all is wor? do+ well1' & ?is is z true ( lant]n exhibit+ z ( any?+ #hg else4 ,!re are a deplorable numb] ( lant]n exhibitions giv5 ) ! %eet hang+ 9 creases1 dirty l5ses1 light poorly adju/$ & c5tr$1 & occasionally slides %[n upside d[n4 ,a consci5ti\s lant]ni/ %\ld see to e detail2 slip%od me?ods1 z 9 ev]y?+ else1 mean poor results4 ,pr9t$ by ,,spottiswoode1 ,,ballantyne ,,co4 ,,ltd4 ,col*e/]1 ,london ,eton1 ,engl&