,,! ,,libr>y ,,( ,,"w ,,& ,,play ,,c>p5try ,,& ,,woodwork ,by ,edw9 ,w4 ,fo/] ,,electricity ,,& ,,its ,,ev]yday ,,uses ,by ,john ,f4 ,woodhull1 ,ph4,d4 ,,g>d5+ ,,& ,,f>m+ ,by ,ell5 ,eddy ,%aw ,,home ,,decoration ,by ,*>les ,frankl9 ,w>n]1 ,sc4,d4 ,,h\sekeep+ ,by ,elizabe? ,hale ,gilman ,,me*anics1 ,,indoors ,,& ,,out ,by ,fr$ ,t4 ,hodgson ,,ne$lecraft ,by ,effie ,ar*] ,ar*] ,,outdoor ,,sports1 ,,& ,,games ,by ,claude ,h4 ,mill]1 ,ph4,b4 ,,outdoor ,,"w ,by ,m>y ,rog]s ,mill] ,,work+ ,,9 ,,metals ,by ,*>les ,conrad ,sleffel4 ,illu/ration3 ,draw+ by ,j4 ,hodson ,r$man4 ,h>old ,s5d+ ! ,c4 ,q4 ,d4 ,message 7,see page #cee74 ,! ,libr>y ( ,"w & ,play ,,electricity ,,& ,,its ,,ev]yday ,,uses ,,by ,,john ,f4 ,,woodhull1 ,,ph4,d4 ,illu/ration ,mc,g,o,w,e,n-,,mai] ,,co4 ,,*icago1 ,,ill4 ,,all ,,rights ,,res]v$1 ,,includ+ ,,t ,,( ,,translation ,,into ,,=eign ,,languages1 ,,includ+ ,,! ,,sc&9avian ,,copyright1 #aiaa1 ,,by ,,d\bl$ay1 ,,page ,,company ,,preface ,:y d we pursue "o me?od :5 in/ruct+ an individual boy out ( s*ool1 & a v diff]5t me?od :5 tea*+ a class ( boys 9 s*ool8 ,! s*ool me?od ( tea*+ ! dynamo is to beg9 ) ! b> magnet &1 ?r\gh a s]ies ( ?irty or =ty lessons on fundam5tal pr9ciples1 lead up to ! dynamo1 :i* is !n pres5t$1 ) consid]able att5tion to detail1 z a composite application ( pr9ciples4 ,?is might be /yl$ ! syn!tic me?od4 ,he :o tea*es a boy out ( s*ool is pretty likely to rev]se ?is ord] & pursue ! analytic me?od4 ,! class 9 s*ool has v little influ5ce 9 det]m9+ ! ord] ( proc$ure4 ,! lone pupil ) 8 que/ions almo/ :olly det]m9es ! ord] ( proc$ure4 ,out ( s*ool no "o has ! c\rage to d5y in=mation to a hungry boy2 9 s*ool we pr(ess to put a ban ^u in=mation giv+1 & we d q effectually dead5 8 s5se ( hung]4 ,! s*ool me?od r>ely yields fruit :i* la/s beyond ! exam9ation p]iod2 on ! o!r h&1 a consid]able numb] ( boys h become electrical exp]ts )\t ! aid ( a s*ool4 ,?is book is ! /ory ( h[ my boy & ,i /udi$ electricity toge!r4 ,we h _h no o!r me?od ?an to attack our problems directly1 & pr9ciples h come 9 only :5 !y 7 ne$$4 ,my boy _h le>n$ to read :5 v "y by hav+ /ories read to him :ile he wat*$ ! pr9t$ pages4 ,! con/ruction ( s5t5ces out ( words & words out ( lett]s _h come to him v incid5tally b all 9 due "t1 & :5 he fir/ w5t to s*ool r late 9 life = a beg9n] he f\nd himself m pr(ici5t ?an ! o!r boys ( 8 own age bo? 9 read+ & 9 und]/&+ ! pr9t$ pages4 ,i c\ld see no good reason :y he %\ld n pursue ! same me?od 9 /udy+ electricity4 ,we live 9 a mod]n ap>tm5t h\se 9 a great city4 ,my boy likes to visit eng9e rooms & talk ) ! eng9e]s ab\t _! ma*9]y4 ,8 "m & ,i always enc\rage him to talk ) u ab\t ! ?+s 9 :i* he is mo/ int]e/$4 ,if ! family is alone at d9n]1 he is q likely to lead ! conv]sation into ! field ( electricity4 ,:5 p>ticul>ly burd5$ ) my "w ,i h le>n$ to f9d relief by giv+ an aft]noon to ,h>old1 :o g5]ally takes me to "s electrical /ore or p[] /ation or to ride by electric tra9 out into ! c\ntry4 ,,cont5ts ,,*apt] ,,page ,i4 ,! ,dynamo & ,! ,p[] ,/ation #c ,,ii4 ,dynamo cont9u$--,! ,magnet #aa ,,iii4 ,! ,ammet] #be ,,iv4 ,! ,wattmet] #ce ,v4 ,! ,electric ,motor #dc ,,vi4 ,applications ( ! ,electro-magnet #eg ,,vii4 ,electric ,heat+ #ig ,,viii4 ,applications ( ,electric ,heat+ #ajg ,,ix4 ,light+ a ,summ] ,camp by ,electricity #afj ,x4 ,h[ ,electricity ,feels #afh ,,xi4 ,! ,electric ,sp>k+ ,equipm5t = a ,gasol5e ,eng9e #agh ,,xii4 ,electricity ,f ,c5tral ,/ations #bjd ,,xiii4 ,electricity ,f an ,old ,mill #bah ,,xiv4 ,do+ ,*ores by ,electricity #bdj ,,xv4 ,electric curr5ts f ,*emical ,action & ,*emical ,action f ,electric ,curr5ts #bdh ,,xvi4 ,electrocution at ,millville #bga ,,xvii4 ,! ,telephone #bgd ,,xviii4 ,electric ,bell ,outfit = ! ,cottage #bif ,,xix4 ,us+ ,electricity to ,aid ! ,memory #cjj ,,xx4 ,! ,electric ,brick ,ov5 #cje ,,xxi4 ,electric ,waves #cji ,,xxii4 ,r++ ,bells & ,light+ ,lamps by ,electric ,waves #cbd ,,xxiii4 ,telegraph+ by ,electric ,waves #cbi ,,xxiv4 ,halley's ,comet & ,electric ,waves #ccc ,,xxv4 ,h[ ! ,idea ( a ,univ]sal ,e!r ,develop$ #cci ,,xxvi4 ,electric ,curr5ts ,_c ,be ,conf9$ to ,wires #cdi ,,xxvii4 ,wireless ,telegraphy ,9 ,e>ne/ #cee ,,illu/rations ,h>old ,s5d+ ! ,c4 ,q4 ,d4 ,message ,frontispiece ,,fac+ ,,page ,te/+ a ,g5]ator #h ,wir+ #af ,wattmet] #dj ,te/+ ! ,telegraphy ,outfit #fb ,electric ,bell #gb ,feel+ ,electricity #agd ,op]at+ ! ,swit*bo>d #bjd ,induction ,coil ( a ,wireless #ccj ,,electricity ,,& ,,its ,,ev]yday ,,uses ,i ,,! ,,dynamo ,,& ,,! ,,p[] ,,/ation ,"o day ,h>old express$ a desire to see ! dynamos1 five miles away1 :i* furni% ! electric light 9 our ap>tm5t4 ,s ,i told him to invite 8 be/ fri5d to accompany u & we w\ld g4 ,:5 we 7 "s di/ance f ! /ation ! boys notic$ ! v tall *imneys & inquir$ :y tall *imneys 7 ne$$ = dynamos4 ,i expla9$ t ! dynamos 7 run by /eam-eng9es1 & /eam-eng9es requir$ ! burn+ ( coal4 ,oh6 said ,erne/1 ,h>old's fri5d1 ,i read 9 ! pap] t electricity is ! rival ( /eam & is go+ to drive out ! /eam-eng9e4 ,i sugge/$ t we 7 ab\t to see "s /eam-eng9es driv+ electricity out ( t p[] /ation4 ,b m s]i\sly1 ,i expla9$ t /eam-eng9es 7 us$ = _m ye>s z locomotives to draw ! tra9s on ! elevat$ railroads ( ,new ,york ,city1 & :5 at la/ !y 7 displac$ by electric tra9s "s p ?\ght t x 0 a case ( electricity driv+ out /eam1 :]eas :at _h really happ5$ 0 t ! /eam p[] = runn+ ^? tra9s _h be5 conc5trat$ at a c5tral /ation1 & its p[] 0 m]ely transmitt$ to ! tra9s by means ( electricity4 ,! tra9s 71 !re=e1 run by /eam p[] q z mu* z ev]4 ,9 l mann]1 ! surface c>s ( ,new ,york a few ye>s ago 7 run by a cable1 :i* 0 m]ely a v long belt us$ to transmit to ! c>s ! p[] ( /eam-eng9es locat$ at a c5tral /ation4 ,:5 !y 7 *ang$ to electric c>s1 electricity became ! successful rival ( no?+ else ?an a twi/$ wire cable4 ,! c>s /ill run by /eam p[] z be=e1 b t p[] is transmitt$ by electricity in/ead ( ! disc>d$ cable4 ,/eam has driv5 out ! horse z a p[] = draw+ /reet c>s1 & electricity has enabl$ u to ga!r all ! /eam eng9es into c5tral /ations1 :]e n[ !y are furni%+ ! p[] = mov+ surface1 elevat$1 & subway c>s = /reet traffic1 z also tra9s = suburban travel4 ,c5tral /ation /eam-eng9es are produc+ a va/ am\nt ( p[]1 di/ribut$ all ov] ! city by means ( electricity1 = do+ a great v>iety ( "w & = furni%+ electric light & heat1 all ( :i* we %all pres5tly /udy4 ,j be=e we g into ?is c5tral /ation1 c y tell me h[ ! elevator is run 9 our ap>tm5t h\se8 ,x is an electric elevator1 said ,h>old4 ,& :]e does ! electricity come f8 ,i inquir$4 ,well1 ,i "k t x comes f ! /reet ma9s1 b d !y come f ?is p[] /ation8 ,yes1 said ,i1 & we w n[ g 9 & see ! /eam-eng9es :i* lift y up /airs _m times ea* day by s5d+ electricity to run t elevator4 ,if y *oose to d s1 y may claim = purposes ( discussion t y\r elevator is run by /eam4 ,z we ent]$ ! build+ we came fir/ to ! dynamo room & bo? boys notic$ t ! tone :i* met _! e>s 0 t :i* ,i _h produc$ = !m 9 ! telephone ! night be=e4 ,i %all try to %[ y be=e we get ?r\gh1 ,i said1 t ^! dynamos are do+ some?+ :i* makes iron pulsate sixty times a second & t t is ! cause ( ! pit* ( ?is tone4 ,b let u beg9 ) ! coal :i* is ! s\rce ( all ?is p[]4 ,?is p>ticul> /ation at ! pres5t "t is burn+ =ty tons ( coal an h\r4 ,t is z mu* z ,mr4 ---- uses to heat 8 twelve-room h\se = a :ole ye>4 ,"o p\nd ( coal is capable ( lib]at+ en\gh en]gy to supply #e-c_/d horse-p[] = an h\r4 7,writt5 = %ort #e-c_/d ,h4,p4,h47 ,"o ton ( coal is capable ( furni%+ 7#b1jjj #e-c_/d7 #aa1ejj ,h4,p4,h4 ,=ty tons w\ld yield #dfj1jjj ,h4,p4,h4 ,b ! be/ furnaces1 boil]s1 & /eam-eng9es are t]ribly wa/eful ( en]gy4 ,ab\t n9e t5?s ( all ?is en]gy is wa/$ & only "o t5?1 or ab\t #df1jjj horse-p[] p] h\r1 is deliv]$ by ! /eam-eng9es to ! dynamos4 ,coal is already sc>ce 9 ! _w & ! supply is rapidly be+ exhau/$4 ,mean:ile we are gr[+ m dep5d5t ^u coal4 ,a c5tury ago we us$ sc>cely any p[] except t ( m51 horses1 & ox51 & :at little heat m5 !n us$ came *iefly f wood4 ,!y liv$ 9 cold h\ses1 att5d$ cold *ur*es & s*ools1 did n ride 9 /eam or electric c>s1 & did n h p[] plants4 ,our wood is ne>ly all gone1 our coal is go+1 & we are v rapidly gr[+ m dep5d5t ^u heat & p[]1 our *ief s\rce ( :i* is coal4 ,w9d p[] is too unc]ta9 to dep5d ^u1 & we turn$ our backs ^u wat]-p[] :5 we began to cr[d into cities4 ,:at little wat]-p[] !re is1 h[ev]1 is ne>ly all 9 use4 ,!re is great ne$ bo? t we le>n h[ to save ! major "p ( ! en]gy ( ! coal :i* we n[ wa/e1 & t we f9d a sub/itute = ! coal to use :5 t is gone4 ,a "p ( ! heat f ! =ty tons ( coal :i* is be+ burn$ 9 ?is p>ticul> p[] plant goes into ! wat] 9 ! boil]s4 ,x conv]ts ?is wat] into /eam4 ,! /eam1 if free to exp& into ! air1 w\ld occupy ab\t "o ?\s& sev5 hundr$ times ! volume ( ! wat]4 ,we compel x to exp& ?r\gh ! cyl9d]s ( ! /eam-eng9e1 us+ its =ce ( expansion to make :eels g ar\nd--to make ! dynamo revolve4 ,^! dynamos are n devices = produc+ p[] b m]ely = transmitt+ ! p[] ( ^! /eam-eng9es to f> away places :]e x may be us$1 z1 = in/ance1 9 our ap>tm5t h\se1 :]e we are unwill+ to walk up/airs & want "s p[] to c>ry u4 ,our own ap>tm5t is fifty feet above ! /reet4 ,i weigh "o hundr$ & sixty-five p\nds4 ,if ,i walk up /airs f ! /reet to our ap>tm5t 9 "o m9ute1 :i* is ! rate ( a r sl[ elevator1 ,i "w at ! rate ( "o qu>t] ( a horse-p[]4 ,"o hundr$ & sixty-five p\nds rais$ two hundr$ feet 9 "o m9ute requires "o horse-p[]4 ,y boys ea* weigh ab\t half z mu* z ,i d1 & if "o ( y walks up ! same /airs 9 "o m9ute y ex]t half ! p[] t ,i d1 or if y run up ! /airs 9 half a m9ute y ex]t ! same p[]1 t is1 "o qu>t] ( a horse-p[]4 ,:5 we ?ree walk up toge!r 9 "o m9ute we ex]t "o half horse-p[]4 ,if we all ?ree run up ! /airs 9 half a m9ute we exp5d "o horse-p[]4 ,n[1 ! spe$ ( elevators = ap>tm5t h\ses is ab\t "o hundr$ feet a m9ute4 ,we are unwill+ to walk up /airs1 n because we are lazy b because we h ! ,new ,york ha/e1 & s we employ elevators :i* run at ! rate ( ab\t "o hundr$ feet a m9ute4 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,te/+ a ,g5]ator ,^! dynamos enable u to employ ! p[] ( ?is c5tral /ation to run ! elevator 9 our ap>tm5t h\se4 ,"h is a dynamo roll+ ov] n[ 9 ! act ( s5d+ out p[]1 "s ( :i* goes to t elevator2 & /&+ beside x is ano!r wait+ to be us$ :5 necess>y4 ,exam9+ ^! dynamos1 we f9d t !y are compos$ ( no?+ else ?an iron & copp]4 ,ab\t all t we c say ( ^! my/]i\s ma*9es is t ! mov+ iron g5]ates ! electricity & ! copp] leads x away4 ,illu/ration3 ,fig4 #a ,ea* "o ( ^! dynamos has _m hundr$ tons ( iron 9 x4 ,a huge :eel ( iron1 ?irty-two feet 9 diamet]1 "o hundr$ feet 9 circumf]5ce1 portions ( :i* are surr\nd$ by insulat$ copp] conductors1 =ms ! c5tre-piece ( ! ma*9e4 ,?is movable "p weighs f\r hundr$ tons4 ,ar\nd ab\t ?is is a fix$ r+ ( iron1 portions ( :i* are surr\nd$ by insulat$ copp] conductors4 ,ord9>ily ! r+ :i* is /ation>y is call$ '! field1' & ! :eel1 :i* rotates1 is call$ '! armature1' al?\gh ^! t]ms are sometimes rev]s$ = c]ta9 reasons4 ,! movable "p 9 ^! ma*9es rotates ab\t once a second1 t is1 its circumf]5ce moves a little fa/] ?an a mile a m9ute4 ,! iron mov+ at ?is high rate ( spe$ creates e!r /reams or electric curr5ts1 :i* are l$ (f by ! copp] conductors4 ,! g5]ation ( electricity on a l>ge scale requires l>ge masses ( iron & high velocity4 ,i notic$ t ! boys /ood be=e ?is ma*9e 9 a /ate ( utt] bewild]m5t1 bewild]$ z a man :o is told t :at he _h consid]$ nor? is really s\?1 bewild]$ z a man :o1 hav+ w&]$ ?r\gh a maze ( city /reets1 looks up at l5g? & unexpect$ly f9ds ! build+ he has be5 seek+ t[]+ be=e him4 ,! que/ions !y ask$ 7 entirely )\t ?\ght4 ,:at is inside ( x8 ,simply m iron & copp]1 su* z y see on ! surface1 ,i repli$4 ,b :at makes x g8 ,! /eam eng9es1 ( c\rse1 f\r ( :i* y see1 are c\pl$ directly to ea* dynamo4 ,b :]e does x get its electricity8 ,don't =get t y are look+ at a g5]ator ( electricity4 ,big mass ( iron--rapid motion6 ,t is ! :ole tru?4 ,b x _c satisfy y z an answ] until y h become us$ to x4 ,we h se5 all t we ought to see "h to-day4 ,let u drop ! :ole matt] n[1 b return to my laboratory to-morr[1 & ,i w give y ! next /ep :i* w help y4 ,! boys did no talk+ ^u _! return j\rney4 ,:e!r "o may say !y 7 ?9k+ or n ,i _c tell1 b c]ta9ly _! ideas 7 incubat+4 ,,ii ,,! ,,dynamo1 ,,cont9u$--,,! ,,magnet ,:5 we _h ga!r$ at my laboratory ! next day ,i took d[n a spool ( "o p\nd ,no4 #bd cotton-cov]$ copp] wire 7,fig4 #b ,a71 :i* _h its c5tre fill$ ) wire nails4 ,! boys _h se5 x be=e & rememb]$ x4 ,) flexible wires ,i connect$ ! two ends ( ! wire on ?is spool to a s5sitive ammet]1 ,b1 :i* _h its z]o 9 ! middle ( ! scale1 & ,i laid d[n ^u ! table a b> magnet1 ,c4 ,illu/ration3 ,fig4 #b ,"h1 ,i said1 is a dynamo complete4 ,! b> magnet furni%es ! 'field' & ?is spool ( copp] wire1 ,a1 :i* ,i w move back & =? imm$iately ov] ! magnet f end to end1 is '! armature4' ,d & e are ! l9e wires & ! circuit is complet$ ?r\gh ! ammet] to %[ :e!r we are g5]at+ electricity4 ,& n[ z ,i move ?is armature along ! field y see ! ne$le ( ! ammet] move to ! "r f z]o to t54 ,:5 ! armature is mov$ 9 ! opposite direction along ! field ! ne$le moves 9 ! opposite direction pa/ z]o & on to t5 at ! left4 ,! mov+ ( ! ne$le 9 ! ammet] %[s t we are g5]at+ electricity4 ,! sw++ to & fro ( ! ne$le %[s t we are g5]at+ an alt]nat+ curr5t ( electricity4 ,x is a m]e matt] ( detail :e!r we move ! armature or ! field1 z ,i w %[ y by lett+ ! spool ,a re/ quietly ^u ! table & mov+ ! magnet to & fro l5g?wise across ! end ( ! spool4 ,or ,i may accompli% ! same results by mov+ !m bo? 9 opposite directions4 ,x is simply necess>y t !y move ) ref]5ce to ea* o!r4 ,"s dynamos are made ) /ation>y fields & rotat+ armatures1 "s ) /ation>y armature & rotat+ fields1 & "s ) bo? p>ts design$ to rotate 9 opposite directions4 ,magnetism is n conf9$ to ! magnet4 ,x ext5ds m or less widely into ! region ab\t x4 ,x is ?is region affect$ by ! magnet t we designate its magnetic field4 ,by br++ ?is s5sitive compass ne$le into ! region ( ?is b> magnet f all directions1 ,i %[ y t x has a slight p[] to *ange ! direction ( ! ne$le :5 ab\t a foot away4 ,?is p[] gr[s rapidly great] z ! di/ance gr[s less4 ,( c\rse its field ext5ds r indef9itely1 b we may say t ?is p>ticul> magnet has an appreciable field ext5d+ ab\t "o foot 9 all directions f x4 ,we f9d ^u exam9ation t "s magnets h bigg] & /rong] fields ?an o!rs1 t all h _! /ronge/ fields :5 fir/ magnetiz$ & lose _! /r5g? gradually1 b nev] entirely4 ,we f9d t h>d5$ iron & /eel hold magnetism long] ?an s(t iron1 b all iron is magnetiz$ some:at at all times4 ,iron t is feebly magnetiz$ c be made into a /rong magnet by br++ x into a /rong magnetic field4 ,! e>? is a feeble magnet1 & t is :y x gives direction to ! compass ne$le4 ,t is also probably ! reason :y e piece ( iron ^u ! e>? is a magnet1 or1 to put ! cause back ano!r /ep1 we may say t :atev] causes ! e>? to be a magnet also causes e piece ( iron ^u ! e>? to be likewise a magnet4 ,b ?anks to ,o]/$ 9 ,d5m>k 9 #ahai & ,f>aday 9 ,engl& 9 #ahba & ,joseph ,h5ry 9 ,albany1 ,n4 ,y41 9 #ahbg1 we h le>n$ to make exce$+ly p[]ful magnets by s5d+ a curr5t ( electricity 9 a :irl ar\nd ! iron4 ,?is is ! mean+ ( ! coils ( copp] wire ar\nd iron cores 9 ! dynamo1 9 electric bells1 9 telegraph s\nd]s1 9 motors1 etc41 etc4 ,to prev5t ! electric curr5t f tak+ ! %orte/ r\te1 ?r\gh ! iron core or ?r\gh ! successive lay]s ( copp] wire1 ! iron core & ! wire mu/ be cov]$ ) some?+ l wood or pap] or cotton or silk or rubb]--su* ?+s z electricity does n readily pass ?r\gh--t is1 insulat+ mat]ial4 ,joseph ,h5ry1 :ile tea*+ 9 ! ,albany ,academy1 0 ! fir/ to make electro-magnets4 ,!re 0 no su* ?+ z wire cov]$ ) an insulat+ mat]ial !n 9 ! m>ket1 & he w\nd all 8 wire ) silk ribbon4 ,b 9 ! ye> #ahcd he made magnets :i* lift$ ?irty-five hundr$ p\nds1 to ! a/oni%m5t ( e "o4 ,a pair ( su* electro-magnets z ,i h "h 7,fig4 #c71 ea* consi/+ ( "o p\nd ( ,no4 #bd cotton cov]$ copp] wire1 eight hundr$ feet long1 w\nd 9 "o ?\s& turns ab\t an iron core two in*es 9 diamet]1 w lift sev]al hundr$ p\nds3 mu* m ?an we ?ree c lift1 z ,i %all n[ %[ y4 ,illu/ration3 ,fig4 #c ,! cores ( ! two magnets 7 bolt$ fa/ to an iron beam1 & a l>ge b> ( iron ) a r+ 9 x 0 laid across ! o!r free ends ( ! magnet cores4 ,i made connections ) ! electric light+ circuit 7t 9 my laboratory is :at is call$ a direct curr5t71 & s5t a curr5t ( electricity ar\nd ! coils4 ,! two boys & ,i tugg$ at ! r+ 9 ! iron b> to no avail4 ,we 7 unable to pull ! iron b> away f ! magnet4 ,b :5 ,i op5$ ! swit* & cut (f ! electric curr5t1 "o boy ) "o f+] 9 ! r+ lift$ ! b> ) p]fect ease4 ,electro-magnets are n[ made ) a magnetic int5sity #ij1gjj times t ( ! e>?'s magnetism4 ,electro-magnets are us$ = hoi/+ iron ca/+s weigh+ _m tons4 ,"h is a picture ( an electro-magnet lift+ a :ole wagon load ( kegs ( nails f ! wagon to ! hold ( a %ip4 ,electro-magnets are our only means ( utiliz+ electricity = p[]4 ,x is ! pull ( electro-magnets t moves ! electric c>4 ,electro-magnets are n[ us$ = pull+ all ! tra9s out ( ! ,gr& ,c5tral ,depot 9 ,new ,york ,city4 ,let u n[ comp>e ! /r5g? ( our electro-magnet ) t ( ! b> magnet us$ 9 our =m] exp]im5t4 ,i op5$ & clos$ ! swit*1 :i* s5t ! electric curr5t ?r\gh my magnet coils at frequ5t int]vals1 & ! two boys1 ea* ) a compass ne$le1 se>*$ ! field = magnetic effects4 ,!y f\nd t ! magnetic field ext5d$ six or eight feet1 b ?is piece ( rese>* 0 brok5 up by a new idea :i* appe>$ to /rike !m bo? at ! same in/ant1 = !y %\t$ bo? toge!r1 ,let's use ?is electro-magnet 9 place ( ! b> magnet = our dynamo exp]im5t6 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,wir+ ,t is surely ! next /ep 9 our programme1 said ,i1 b y w ne$ a /eam-eng9e to move an armature 9 ?is magnetic field1 w y n1 judg+ f ! /ruggle we _h ) t iron b> a few m9utes ago8 ,! boys look$ q hopeless until ,i said1 ,! be/ ?+ ab\t ! electro-magnet rema9s yet to be told4 ,y h p]fect control ( its /r5g? by *ang+ ! am\nt ( electricity :i* y s5d ar\nd ! coil4 ,by means ( an in/rum5t :i* works l ! motorman's controll] on ! electric c>1 ,i may control ! am\nt ( electricity :i* fl[s1 j z well z y may control ! fl[ ( wat] by a faucet or /op-cock4 ,by ?is means ,i w control ! /r5g? ( ! magnet s t y may move ! armature 9 y\r dynamo exp]im5t4 ,9 #ahba1 ,f>aday1 at ! ,royal ,in/itution1 ,london1 le>n$ t he c\ld produce magnetism by means ( ! electric curr5t1 &1 9 #ahca1 he le>n$ t ! rev]se 0 also true1 namely1 t he c\ld produce electricity f magnetism4 ,?is idea com+ z ! result ( t5 ye>s ( incessant se>* made him %\t & dance l a *ild4 ,y are feel+ a little ( ! pleasure ( 8 discov]y4 ,illu/ration3 ,fig4 #d ,i !n fa/5$ "o ( ! coils ^u ! table und]nea? a small b5* 7,fig4 #d7 & s5t an electric curr5t ar\nd x4 ,! o!r coil1 ,b1 connect$ ) ! ammet] 0 pu%$ back & =? along ! surface ( ! b5* ov] ?is coil4 ,! boys f\nd t ! m electric curr5t ,i s5t ar\nd ! coil ,a1 t is1 ! /rong] ,i made ! magnetic field1 ! h>d] x 0 to move ! coil ,b4 ,!y f\nd t ! ne>] ,b 0 to ,a ! h>d] x 0 to move x4 ,!y f\nd t ! fa/] !y mov$ ,b ! m electricity 0 produc$4 ,!y tri$ lay+ ,b ^u its side ^u ! b5* & ?us mov+ x4 ,!y tri$ tak+ ,b (f ! b5* & mov+ x on all sides ( ,a4 ,!y f\nd x mu* h>d] to move 9 "s ways ?an 9 o!rs1 b 9 all cases !y f\nd t ! h>d] !y _h to "w ! m electricity 0 develop$1 z 0 %[n by ! ammet]4 ,! dynamo is any ma*9e :i* w conv]t me*anical "w into electricity4 ,! magneto is "o =m ( a dynamo :i* y h us$ mu* at ! summ] cottage1 b h nev] se5 ! inside (4 ,"h are sev]al 7see ,figs4 #e1 #f1 & #h7 :i* ,i w let y exam9e inside & out1 & ) ^! ,i mu/ leave y to y\rselves = a "t4 ,:5 ,i return$ ,i ask$ ! boys :y ^! dynamos 7 call$ magnetos4 ,because !y h /eel magnets = _! fields1 !y repli$4 ,!re are sev]al magnets b5t 9 ! %ape ( a horse%oe4 ,yes1 ,i said1 9 ?is case ! field is made /rong] by tak+ sev]al magnets4 ,h y notic$ any armature8 ,yes1 x is made ( iron ) insulat$ copp] wire w\nd ar\nd x4 ,please recall t ! am\nt ( en]gy y exp5d 9 go+ up/airs dep5ds on two ?+s3 7#a7 y\r weight & 7#b7 ! spe$ ) :i* y move4 ,also recall t ! am\nt ( electricity y c\ld g5]ate ) a dynamo dep5d$ ^u ! am\nt ( en]gy y exp5d$4 ,!re=e1 ! /r5g? ( ! electric curr5t :i* ?is ma*9e may produce dep5ds ^u two ?+s3 7#a7 ! /r5g? ( ! magnetic field aga9/ :i* y mu/ pull & 7#b7 ! spe$ ( ! motion ( ! armature4 ,evid5tly ?is field is made z /rong z x is possible to make x ) /eel magnets4 ,n[ is !re any device = giv+ high spe$ to ! armature8 ,yes1 inde$1 said ! boys1 "o has a pulley s t x may be connect$ by a belt ) a gas eng9e1 & ! o!rs h ea* a l>ge cog-:eel work+ into a small] "o4 ,we f\nd 9 "o ( !m t a s+le revolution ( ! crank gave six revolutions to ! armature4 ,i f\nd t ! boys _h made l>ge-siz$ draw+s ( ! p>ts1 & 7 prep>+ to report on ! magneto z a =m ( dynamo at ! next meet+ ( ! ,sci5ce ,club1 :i* we _h />t$ among ! boys 9 s*ool4 ,illu/ration3 ,fig4 #e ,i w loan y "s app>atus s t y may give a v int]e/+ demon/ration on t subject1 said ,i1 only let me %[ y h[ to use x fir/4 ,connect ! b9d+ po/s ,d & ,e ( ?is magneto 7,fig4 #e7 ) my ammet]4 ,turn ! crank v sl[ly & notice t ! ne$le ( ! ammet] sw+s to & fro ) ea* revolution ( ! armature4 ,t %[s t y h n only a dynamo1 b an alt]nat+ curr5t dynamo4 ,illu/ration3 ,fig4 #f ,n[ connect ! b9d+ po/s d & e ( ?is magneto 7,fig4 #f7 ) a %ort piece ( copp] wire4 ,turn ! crank & y notice t ?is dynamo r+s two electric bells4 ,turn sl[ly & y notice t ! alt]nations ( ! curr5t are numb]$ by ! /rokes on ! bells4 ,! hamm] sw+s to & fro j z ! ne$le ( ! ammet] did4 ,ea* bell !re=e receives "o /roke ( ! hamm] = ea* revolution ( ! armature4 ,n[ try to turn ! crank /eadily at ! rate ( "o revolution p] second4 ,! armature is mak+ six revolutions1 or cycles1 p] second & y n[ h n only an alt]nat+ curr5t dynamo b a six-cycle alt]nat+ curr5t dynamo4 ,! light+ circuit us$ 9 our ap>tm5t is a sixty-cycle alt]nat+ curr5t4 ,to be sure ! armature ( ! dynamo :i* g5]ates t curr5t revolves only once a second1 b x c>ries coils en\gh ^u its rim to make t numb] ( alt]nations4 ,n[ connect ?is telephone receiv] ) ! b9d+ po/s ,d & ,e ( ?is magneto 7,fig4 #g74 ,unscrew ! cap ( ! receiv]4 ,move to "o side ! iron diaphragm & turn sl[ly ! crank ( ! magneto4 ,notice t ! diaphragm vibrates 9 "t ) ! alt]nations ( ! dynamo4 ,replace ! diaphragm1 screw on ! cap1 hold ! receiv] to y\r e> & turn ! crank z fa/ z y c4 ,y w probably be able to make ab\t sixte5 cycles p] second4 ,! receiv] 9 t case is giv+ =? a s\nd ( ! same pit* z a sixte5-foot clos$ organ-pipe4 ,illu/ration3 ,fig4 #g ,connect ! telephone receiv] to ! b9d+ po/s ,d & ,e ( ?is magneto 7,fig4 #h71 & by means ( a belt connect ! pulley to ?is s]ies ( cog-:eels4 ,n[ y may turn ! crank & readily make ! armature revolve at ! rate ( sixty cycles p] second1 & y notice t y get ! same tone t we he>d 9 ! dynamo room ( ! p[] /ation & ! same tone ! telephone receiv] gave :5 ,i connect$ x to a coil 9 our ap>tm5t4 ,! tone :i* is produc$ by sixty vibrations p] second is v ne>ly t ( ! ,c two octaves bel[ middle ,c on ! piano4 ,try x along ) ! piano & y w f9d x a little flat4 ,?is /r+ on ! piano is mak+ sixty-f\r vibrations p] second4 ,illu/ration3 ,fig4 #h ,illu/ration3 ,fig4 #i ,n[ connect ?is m9iature telephone swit*bo>d lamp ) ! magneto 7,fig4 #i7 & turn ! crank fa/4 ,! lamp lights up to full brilliancy & y notice t ! light is /eady1 al?\gh x is made by an alt]nat+ curr5t pass+ ?r\gh ! filam5t 9 "o direction1 /opp+ entirely1 & !n pass+ 9 ! opposite direction4 ,! filam5t has no "t to cool (f1 provid$ y turn fa/ en\gh1 b try turn+ a little sl[] & y w notice ! flick]+ ( ! lamp4 ,,iii ,,! ,,ammet] ,illu/ration3 ,fig4 #aj ,at ! la/ meet+ ( ! ,sci5ce ,club s _m que/ions 7 ask$1 :i* ! demon/rators c\ld n answ]1 t a programme committee1 to :om su* que/ions might be ref]r$ !reaft]1 0 appo9t$4 ,x 0 made ! duty ( ?is committee to assign to v>i\s memb]s ! task ( se>*+ = satisfactory answ]s1 & :5 ! mat]ial 0 ready to be report$ to ! club1 ! programme committee det]m9$ ! "t & ord] ( pres5tation4 ,i f\nd t ,i _h be5 made an honor>y memb] ( ?is committee & t x 0 expect$ t ,i %\ld /e] ! committee4 ,i told !m t ,i accept$ ?is appo9tm5t ) ! und]/&+ t ! fell[ :o /e]s is always ! smalle/ man 9 ! crew1 & if !y w\ld d all ! "w ,i w\ld enjoy ! honor>y title ( cockswa94 ,secretly1 h[ev]1 ,i appreciat$ t ?is 0 9 effect add+ sev]al c\rses to my already r heavy programme4 ,i mu/1 "u ! rgime1 direct a l>ge numb] ( inexp]i5c$ /ud5ts 9 libr>y rese>*1 9 laboratory rese>*1 & 9 ! art ( giv+ demon/rations ) app>atus & exp]im5ts to audi5ces4 ,! mo/ urg5t que/ions1 z also ^? :i* 7 next 9 ! natural ord]1 conc]n$ ! ammet]4 ,i told ! committee to make t ! subject ( ! next meet+ & to s5d to my laboratory on a c]ta9 day ! p]son or p]sons :om !y might appo9t to report ^u x4 ,illu/ration3 ,fig4 #aa ,i f9d t ! boys nev] come s+ly1 b g5]ally 9 pairs4 ,:5 ! boys came !y f\nd ly+ ^u ! table an ammet] 7,fig4 #aa74 ,i told "o ( !m to take out ! ?ree screws 9 ! front & remove ! face ( ! in/rum5t4 ,i _h told ! boys t ! in/rum5t co/ sixty doll>s & t lett+ !m op5 x 0 l lett+ !m op5 my wat*4 ,z soon z ! face came (f "o ( ! boys exclaim$ t f my ref]5ce to ! wat* he _h expect$ to see v complicat$ ma*9]y ) _m :eels1 b f ! exce$+ simplicity ( ! me*anism he c\ld n see :y x %\ld co/ sixty doll>s4 ,i told him t al?\gh x 0 a f9e piece ( workman%ip x 0 =tunately v easy to und]/&1 & ,i ask$ !m if x rem9d$ !m ( any?+ else t !y _h ev] se54 ,aft] a few mom5ts ( reflection !y agre$ t x 0 v mu* l "o ( ! magnetos4 ,well1 said ,i1 :]e is ! field8 ,illu/ration3 ,fig4 #ab ,is ?is horse%oe arrangem5t a magnet8 !y inquir$4 ,!re is a compass ne$le "r at y\r h& wait+ to answ] t "q1 ,i repli$4 ,!y imm$iately f\nd t x 0 a magnet4 ,well1 ,i said1 to be really sure t x is a magnet y mu/ f9d a portion ( x t w repel a portion ( y\r compass ne$le z well z o!r portions 9 bo? horse%oe & ne$les :i* attract ea* o!r4 ,:]eupon1 !y f\nd t ! portion m>k$ ,n 7,fig4 #ac7 repell$ ! blue end ( ! compass ne$le & attract$ /rongly ! bright end ( ! ne$le1 :ile ! portion m>k$ ,s did ! rev]se4 ,we w call ,n & ,s ! poles ( ! magnet4 ,?is is simply a /eel b> magnet b5t into ! %ape ( a horse%oe4 ,illu/ration3 ,fig4 #ac ,y told u1 rem>k$ "o ( ! boys1 t /eel magnets gradually lose _! /r5g?4 ,h[ !n c ?is be correct z a measur+ in/rum5t8 ,x is ! purpose ( ! iron case to enable ?is magnet to reta9 its magnetism1 & if y w exam9e its field1 z we did t ( ano!r magnet ^u a =m] occasion1 y w f9d t al?\gh ?is is a /rong /eel magnet its field does n ext5d outside ( ! iron case4 ,x is z ?\gh we c\ld box up magnetism & keep x f escap+4 ,n[ if ?is is l ! magneto1 :]e is ! armature8 ,! spool-l ?+ betwe5 ! poles ( ! magnet looks j l ! armature 9 "o ( ! magnetos4 ,yes1 x has an iron core ) a coil ( insulat$ wire ar\nd x1 & y rememb] t :5 an electric curr5t is s5t ar\nd a piece ( iron1 t iron is made into a magnet1 & if x is a magnet x mu/ h poles4 ,x is v delicately pois$ ^u a pivot & w act exactly l y\r compass ne$le1 :i* is also a little magnet ) poles4 ,i w s5d an electric curr5t ?r\gh ! wire :i* surr\nds ?is armature1 & y notice t ! ne$le :i* x c>ries moves to ! "r4 ,notice t ! l[] end ( ?is armature acts l ! blue end ( y\r compass ne$le 9 t x is repell$ f ! pole ,n ( ! field & is attract$ t[>d ,s ( ! field4 ,9 l mann]1 ! upp] end or pole ( ! armature is repell$ f ,s & attract$ to ,n ( ! field4 ,! blue end ( ! compass ne$le is call$ its nor? pole because x po9ts nor? "u ! magnetic influ5ce ( ! e>?1 & s we may call ! l[] end ( ! armature its nor? pole4 ,! electric curr5t :i* ,i am s5d+ ?r\gh ! armature comes fir/ ?r\gh "o ord9>y #af-;c&le-p[] electric lamp :i* y see light$ on ?is 'resi/ance bo>d1' z x is call$1 & y notice t ! ne$le po9ts to 4#e4 ,?is means t half an amp]e ( electricity is pass+ ?r\gh ?is lamp4 ,i w n[ s5d ! curr5t ?r\gh a #cb-;c&le-p[] lamp1 & y notice t ! ne$le po9ts to "o1 indicat+ t "o amp]e is requir$ to light t lamp4 ,b :at prev5ts ! ne$le f go+ f>!r1 & :at br+s x back to z]o ea* "t8 ,! boys discov]$ a v small spr+1 l ! hair spr+ ( a wat*1 coil$ ar\nd ! pivot ( ! armature4 ,s1 !n1 "o amp]e ( electricity gives magnetism to ?is armature s t x may pull aga9/ its coil$ spr+ h>d en\gh to c>ry ! ne$le to ! po9t "o4 ,twice z mu* electricity w give x magnetism en\gh to c>ry x to two1 & s on across ! scale4 ,! full "n ( ?is in/rum5t is ,amp]e met]1 :i* by usage has be5 %ort5$ to ammet]4 ,x 0 nam$ 9 hon\r ( ,&r ,m>ie ,ampre1 :o 0 born at ,lyons1 9 ,france1 9 #agge1 ! ye> our ,revolution>y ,w> broke out4 ,he di$ 9 #ahcf4 ,:5 ,o]/$ made 8 fam\s discov]y ( ! action ( an electric curr5t ^u a magnetic ne$le1 9 #ahai1 ,ampre 0 9 middle life 7=ty-f\r71 & took up ! same l9e ( rese>* ) great vig\r4 ,! next ye>1 #ahbj1 he discov]$ :at y w d\btless enjoy r$iscov]+ n[4 ,y w notice t ! b9d+ po/s on ! bottom ( ?is ammet] are m>k$1 "o positive1 1 & ! o!r1 negative -4 ,! electric curr5t n[ ent]s ! in/rum5t by ! po/ m>k$ & aft] pass+ ar\nd ! armature leaves by ! po/ m>k$ -4 ,i w rev]se ! connections & ?us s5d ! curr5t ar\nd ! armature 9 ! o!r direction1 & y notice t its poles are n[ rev]s$4 ,! l[] end :i* 0 =m]ly ! nor? pole ( ! armature has n[ become ! s\? pole1 z prov5 by ! fact t x is repell$ f ! s\? pole ( ! field & attract$ to its nor? pole4 ,?is c>ri$ ! ne$le to ! left1 & inasmu* z ! z]o is 9 ! middle ( ! scale we may ) ?is in/rum5t bo? measure ! am\nt ( curr5t & tell its direction4 ,y w recall t :5 we connect$ ! magneto ) ?is in/rum5t1 x indicat$ t ! magneto s5t ! curr5t fir/ 9 "o direction & !n 9 ! o!r1 :i* we call an 'alt]nat+ curr5t4' ,b y notice t ! curr5t :i* ,i am us+ 9 ?is laboratory fl[s cont9u\sly 9 "o direction4 ,?is is call$ ! 'direct curr5t4' ,we %all f9d out h[ a dynamo may produce a direct curr5t at ano!r "t4 ,let u n =get1 h[ev]1 t we h repeat$ ,ampre's discov]y1 & f\nd out t ! direction 9 :i* we s5d ! curr5t ar\nd an electro-magnet det]m9es :i* end %all be its nor? & :i* its s\? pole4 ,if y w note c>efully :i* way ! wire is w\nd ar\nd ! armature y w see t :5 ,i s5d ! curr5t 9 at ! positive po/ x is pass+ ar\nd ! nor? pole ( ! armature opposite to ! direction 9 :i* ! h&s ( a clock move4 ,if ,i rev]se ! curr5t x passes ar\nd ! l[] end ( ! armature 9 ! same direction z ! h&s ( a clock move & !n ?is end becomes a s\? pole4 ,?is is ',ampre's rule1' & x is :at c&idates = admission to college are v c>eful to le>n4 ,be=e we replace ! face ( ?is ammet] ,i mu/ call y\r att5tion to a wire runn+ by a %ort cut f "o b9d+ po/ to ! o!r1 s 7,fig4 #ad74 ,suppose a repres5ts ! wire ar\nd ! armature4 ,electricity1 l wat]1 goes m readily ?r\gh a big conductor ?an a small "o & m readily ?r\gh a %ort ?an a long conductor4 ,if s & a 7 wat] pipes1 ea* hav+ a /op-cock1 we might easily adju/ ! cocks s t "o t5? ( ! wat] w\ld g ?r\gh a & n9e t5?s ?r\gh s4 ,or1 inde$1 )\t /op-cocks1 ! size & l5g? ( s & a might be s apportion$ t "o t5? ( ! wat] w\ld fl[ ?r\gh a & n9e t5?s ?r\gh s4 ,?is is precisely ! adju/m5t :i* has be5 made ) ref]5ce to ! fl[ ( electricity ?r\gh ?is in/rum5t4 s is call$ a '%unt4' ,:5 ! %unt is out all ! curr5t goes ?r\gh a & :5 ! %unt is 9 only "o t5? ( ! curr5t goes ?r\gh a4 ,i h two o!r %unts1 ea* ( :i* may be put 9 ! place ( s4 ,) ! second only "o hundr$? ( ! curr5t goes ?r\gh a & ) ! ?ird only "o ?\s&? ( ! curr5t goes ?r\gh a4 ,?us ,i h an in/rum5t :i* w measure any?+ f "o ?\s&? ( an amp]e up to t5 amp]es4 ,illu/ration3 ,fig4 #ad ,9 ?is laboratory we pay ab\t "o c5t = an amp]e ( electricity = "o h\r4 ,twice z mu* coal mu/ be consum$ to furni% two amp]es z "o1 & twice z mu* coal mu/ be consum$ to furni% an amp]e = two h\rs z = "o h\r4 ,h5ce we ne$ an in/rum5t :i* w keep acc\nt ( "t z well z am\nt ( curr5t4 ,su* an in/rum5t we mu/ look into next4 ,j be=e we pass to t1 h[ev]1 let me ask if y h ev] he>d ( a '%unt-w\nd' dynamo4 ,c y guess f ! way we h j us$ ! ^w '%unt' :at ! expression c\ld mean ) ref]5ce to a dynamo8 ,)\t hesitation ! boys told me t x meant t ! field & armature 7 w\nd p>allel to "o ano!r1 z %[n by diagram 9 ,fig4 #ae4 ,9 :i* case ! electric curr5t :i* ! ma*9e g5]ates divides1 "p ( x go+ ar\nd ! field & "p ar\nd ! armature4 ,ano!r type1 call$ s]ies-w\nd dynamos1 is indicat$ by diagram 9 ,fig4 #af1 9 :i* case ! electric curr5t goes ?r\gh field & armature 9 succession4 ,"u ei!r ( ^! circum/ances1 h[ c ! armature move ) ref]5ce to ! field8 ,! answ] w appe> 9 ! next *apt]4 ,illu/ration3 ,fig4 #ae ,illu/ration3 ,fig4 #af ,,iv ,,! ,,wattmet] ,we 7 able to ma9ta9 connections betwe5 ! b9d+ po/s ( ! ammet] & ! movable armature ( flexible wires because ! armature nev] moves m ?an "o ?ird ( a revolution1 b we n[ wi% to exam9e an in/rum5t 9 :i* ! armature mu/ n only make a complete revolution b mu/ cont9ue to revolve 9 ! same direction indef9itely4 ,h[ are connections made s t an electric curr5t may pass f ! fix$ b9d+ po/s to ! wire ( ! mov+ coil8 ,i w lift ! cov] (f ?is in/rum5t1 :i* is call$ a wattmet]1 & let y f9d ! answ] to t "q4 ,i s5t ?r\gh ! in/rum5t ! curr5t f a #cb-;c&le-p[] lamp4 ,accord+ to ! ammet]1 :i* 0 also 9 circuit1 ! am\nt 0 "o amp]e4 ,! armature ( ! wattmet] revolv$ sl[ly & x 0 n long be=e ! boys report$ t connections = ! curr5t 7 made by /rips ( metal slid+ on metal plates4 ,! ends ( ! armature wire 7 fa/5$ "o to "o plate & ! o!r to ! o!r plate1 & ! metal /rips bru% along ov] ! surfaces ( ! plates4 7,t is :y !y are call$ bru%es1 ,i said47 ,& ! bru%es slide f "o plate to ! o!r ea* "t ! armature makes half a revolution4 7,t is1 ! bru%es *ange ! connection & ?us *ange ! poles ( ! armature at ! prop] in/ant s t !y are always attract$ to ! poles ( ! field t[>d :i* !y are mov+47 ,?is is call$ a commutator4 ,notice t :ile ! ammet] 0 l ! magneto 9 hav+ a /eel magnet = its field1 ! wattmet] is l ! dynamo 9 hav+ electro-magnets = bo? armature & field4 ,notice 9 ! second place t ?is in/rum5t is an electric motor s9ce x is made to revolve by an electric curr5t4 ,if x 7 made to revolve by "s o!r p[] x w\ld g5]ate electricity & w\ld !n be call$ a dynamo4 ,inde$1 let me tell y some?+ :i* mu/ at pres5t be no?+ m ?an a puzzle to y4 ,e ma*9e1 :ile x is be+ driv5 by an electric curr5t z an electric motor1 is1 at ! same "t1 act+ z a dynamo to g5]ate a curr5t 9 ! opposite direction4 ,notice 9 ! ?ird place t ?is is a %unt-w\nd in/rum5t4 ,! curr5t :i* is s5t into ! in/rum5t divides1 & "p ( x goes ?r\gh ! field1 :ile "p goes ?r\gh ! armature4 ,motors1 z well z dynamos1 are ei!r %unt-w\nd or s]ies-w\nd4 ,b notice f9ally t ! axle on :i* ! armature is c>ri$ has a cyclomet] arrangem5t :i* keeps acc\nt ( ! numb] ( revolutions4 ,! armature is go+ sl[ly en\gh = u to c\nt ! revolutions4 ,) wat* 9 h& we f\nd t x made "o hundr$ & tw5ty revolutions p] m9ute4 ,i next br\ght ! curr5t to ! wattmet] ?r\gh a #af-;c&le-p[] lamp & ! ammet]1 connect$ 9 s]ies1 %[$ t half an amp]e 0 pass+4 ,we c\nt$ ! revolutions ( ! wattmet] & f\nd !m to be sixty p] m9ute4 ,"h1 !n1 is a simple electric motor :i* w regi/] ! am\nt ( electricity we use4 ,x w regi/] ! same am\nt :e!r we use "o amp]e = "o h\r or half an amp]e = two h\rs or two amp]es = half an h\r4 ,9 any case ?is product is call$ "o amp]e h\r4 ,b ! words pr9t$ ^u ! dials ( ?is in/rum5t are n amp]e h\rs1 b watt h\rs & ! "n ( ! in/rum5t is wattmet]4 ,?is next requires explanation4 ,foll[ me 9 a little r\ndab\t j\rney & ! matt] w be readily und]/ood :5 view$ f ano!r approa*4 ,illu/ration3 ,fig4 #ag ,:5 we 7 e/imat+ ! en]gy requir$ to climb ! /airs ( an ap>tm5t h\se1 we ne$$ to take into acc\nt two factors1 7#a7 our weight & 7#b7 ! "t :i* we took 9 climb+ !m4 ,! am\nt ( coal burn$1 /eam g5]at$1 electricity produc$1 to run our elevator dep5ds ^u two factors1 7#a7 its weight & 7#b7 its spe$4 ,t idea is fundam5tal4 ,let u get at x 9 /ill ano!r way4 ,suppose we h a mill pond1 7,fig4 #ag1 ,a74 ,we con/ruct a p5/ock p & in/all a wat]-:eel1 ,s1 to op]ate a mill4 ,our bus9ess increases & we in/all m ma*9]y 9 our mill & mu/ h m p[] to run x4 ,we h two ways ( gett+ x1 7#a7 we may l5g!n our :eel & enl>ge our p5/ock s t a great] weight ( wat] w fall ^u ! :eel1 or 7#b7 we may l5g!n our p5/ock & move ! :eel f>!r d[n s t ! wat] w fall ^u ! :eel ) great] velocity4 ,x is j s ) ! electric curr5t4 ,l wat] x is driv5 on 9 its c\rse by pressure4 ,! unit = electric pressure is call$ a volt4 ,if we wi% to drive ! wattmet] or any o!r electric motor twice z fa/ z n[1 we may *oose :e!r we %all d s by d\bl+ ! volts ( pressure or by d\bl+ ! amp]es ( quantity4 ,! electric pressure on our ma9s is ab\t "o-hundr$ & t5 volts4 ,we ?ree toge!r weigh #ccj p\nds4 ,our elevator br\ght u up /airs at ! spe$ ( #ajj feet p] m9ute4 ,x requires "o horse-p[] to raise #ccj p\nds #ajj feet 9 a m9ute4 ,! ammet] 9 ! eng9e room %[$ t #g amp]es ( electricity 7 s5t ?r\gh ! motor ( ! elevator to br+ u up4 ,t is1 sev5 amp]es at #aaj-volt pressure give "o horse-p[]4 ,9 ! (fice build+ across ! /reet :]e !y use a #bbj-volt curr5t #c-a_/b amp]es are requir$ to take u up /airs at ! same spe$4 ,x is necess>y t ! same am\nt ( coal be consum$ to furni% ! horse-p[] ( en]gy :e!r we supply x by means ( sev5 amp]es at #aaj volts or #c-a_/b amp]es at #bbj volts4 ,y notice t ! product is #ggj 9 ea* case4 ,! "n giv5 to ?is product is watts4 ,m accurately #gdf watts ( electrical p[] are equival5t to "o horse-p[]4 ,! "n ( ?is unit commemorates ! fam\s inv5tor ( ! /eam eng9e1 ,james ,watt 7#agcf-ahai74 ,8 monum5t n[ ov]looks ! ,clyde at 8 native t[n1 ,gre5ock1 ,scotl&4 ,to light a c]ta9 lamp1 to heat a c]ta9 laundry iron1 to furni% a c]ta9 am\nt ( p[] = an electric motor1 we mu/ h a def9ite numb] ( watts4 ,we may *oose :e!r we w h x at high or l[ voltage ) correspond+ly l[ or high numb] ( amp]es4 ,illu/ration3 ,fig4 #ah ,we w n[ connect ) our laboratory curr5t a #cb-;c&le-p[] lamp1 an ammet]1 & a wattmet]1 all 9 s]ies1 ,fig4 #ah1 & 9 p>allel ) ^! a volt met]4 ,?is la/ in/rum5t indicates ! electric pressure4 ,its me*anism w be exam9$ lat]4 ,! volt met] indicates #aaj volts & ! ammet] %[s t "o amp]e is pass+4 ,! filam5t 9 ! lamp resi/s ! passage ( ! curr5t4 ,x gets q hot & gives =? z mu* light z ?irty-two c&les4 ,its resi/ance is j su* t #aaj volts ( pressure s5d "o amp]e ?r\gh x4 ,we w n[ take ! read+ ( ! wattmet]1 note ! "t & read x aga9 lat]4 ,"o h\r lat] its index %[$ t #aaj watt h\rs ( electrical en]gy _h be5 conv]t$ into light & heat4 ,?is at ! usual rate1 co/s #a4a c5ts1 "o c5t p] hundr$ watt h\rs or t5 c5ts p] ?\s& watt h\rs1 call$ a kil[att h\r4 ,! m common #af-;c&le-p[] lamp co/s ab\t half a c5t an h\r to op]ate4 ,x requires "o horse-p[] to keep f\rte5 ( !m burn+4 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,wattmet] ,i w n[ take y to see ! wattmet] :i* measures all ! electric en]gy us$ 9 ?is build+4 ,y note d[n its read+ & ! date & ! next "t y come we w read x aga9 & ?us f9d out h[ mu* electricity has be5 us$ = electric lights1 = electric v5tilat+ fans1 = electric elevators1 = electric ov5s1 & electric irons 9 ! s*ool ( h\sehold arts1 = electric motors to run la!s & o!r ma*9es 9 ! s*ool ( te*nical arts1 = electric exp]im5ts 9 my laboratories & lecture room1 = electric vacuum clean]s &1 la/ly1 = pump+ ! pipe organ 9 *apel4 ,i saw by ! boys' faces z !y dep>t$ :at w\ld be ! next "q t !y w\ld br+ to me4 ,kn[+1 h[ev]1 t ! h\r 0 up1 !y 7 too polite to press x !n4 ,v ,,! ,,electric ,,motor ,9 a few days ,i receiv$ a telephone message1 ask+ if ,i c\ld appo9t an h\r to meet ! programme committee 9 my laboratory4 ,i mu/ confess t my pleasure 9 ^! meet+s _h increas$ s mu* t ,i 0 q ready to slight o!r duties1 if ne$ be1 to engage 9 !m4 ,moreov]1 s9ce my bus9ess 0 education x 0 n difficult = me to reg>d ^! meet+s 9 ! light ( a duty q z important z my regul> class in/ruction--p]haps m effective4 ,at any rate ! boys & ,i manag$ to get toge!r4 ,may ,god =give ! man :o essays to tea* boys1 b does n love to be ) !m4 ,( c\rse at ! la/ meet+ ( ! ,sci5ce ,club e "o want$ to "k h[ we ran a pipe organ by electricity4 ,moreov] ! ,electrical ,%[ 0 com+ on 9 ! city1 & c[s 7 to be milk$ by electricity1 di%es 7 to be wa%$ by electricity1 rugs & furniture 7 to be clean$ by electricity1 & innum]able di/ract+ & di/ress+ ?+s 7 to take place4 ,i told ! boys t really only two k9ds ( ?+s 7 to be done by electricity at ! %[1 & if !y w\ld give me two "o-h\r appo9tm5ts ,i w\ld furni% !m ) ! key to ! :ole %[4 ,we might z well beg9 to-day ) ! pipe organ "q4 ,a pipe organ is op]at$ by air4 ,x has bell[s :i* are simply "o =m ( an air pump4 ,a boy is (t5 employ$ to turn a crank :i* works ! bell[s4 ,d[n 9 ! basem5t und]nea? our pipe organ ,i w %[ y h[ a half-horse-p[] electric motor takes ! place ( a boy4 ,we f\nd a d>k & dirty corn] :]e a boy us$ to /& & turn a crank e "t /hetically incl9$ p enjoy$ an organ recital 9 ! room above4 ,sci5ce1 :i* has n be5 giv5 cr$it = be+ humanit>ian1 put an electric motor into t d>k corn] & s5t ! boy up /airs to he> ! music4 ,! motor grumbl$ at ! dirt 9 ! corn] & compell$ ! janitor to keep x clean4 ,! electric motor1 bett] ?an any device ,i "k1 en=ces ju/ice1 b nev] requires m]cy1 or at lea/ r>ely receives x4 ,x comes ne>] ?an any o!r ma*9e to pay+ back all t y put into x4 ,x is mo/ economical :5 work+ up to its full capacity4 ,i recomm5d t y look x ov] c>efully & aft] a few m9utes tell me :at y h se5 9 x4 ,illu/ration3 ,fig4 #ai ,! boys said t x look$ j l a dynamo4 ,we mu/ n =get t x is a dynamo1 b is "h us$ z a motor by s5d+ an electric curr5t ?r\gh x4 ,?is fact1 t a dynamo might be driv5 by an electric curr5t & s]ve z a mov] ( o!r ma*9]y1 0 fir/ publicly exhibit$ 9 #ahgc at ! ,vi5na ,exhibition1 & by _m believ$ to h be5 discov]$ by accid5t at t exhibit4 ,b :y does x look l a dynamo8 ,x has a field ^: magnetism is produc$ by an electric curr5t s5t ?r\gh coils ( wire1 & x has an armature ^: magnetism is likewise produc$ by ! electric curr5t4 ,if x 7 us$ z a dynamo1 :]e w\ld x get ! electric curr5t to magnetize its field8 ,f its own mov+ armature4 ,is x adapt$ = direct curr5t8 ,yes4 ,x has a commutator & bru%es4 ,is x %unt- or s]ies-w\nd8 ,%unt-w\nd1 z %[n by diagram 9 ,fig4 #bj4 ,illu/ration3 ,fig4 #bj ,suppose we treat ! ma*9e z a dynamo4 ,br+ ! ends ( ! l9e wire toge!r1 ?us1 z we say1 clos+ ! circuit4 ,by "s ext]nal =ce let u cause ! armature to rotate & "u ! influ5ce ( ! magnetic field x w g5]ate an electric curr5t1 "p ( :i* w pass ?r\gh ! field & "p ?r\gh ! l9e circuit4 ,we may adju/ ! relative am\nt ( wire 9 field & l9e s t any portion ( ! curr5t we *oose w pass ?r\gh ! field4 ,! am\nt ( curr5t x w g5]ate dep5ds1 7#a7 ^u ! /r5g? ( ! field & 7#b7 ^u ! spe$ ( ! armature4 ,its field1 al?\gh nev] entirely )\t magnetism1 is v feeble at fir/1 & h5ce 9 ! fir/ in/ance a v small curr5t w be g5]at$ 9 ! mov+ armature4 ,?is1 h[ev]1 w /r5g!n ! field slightly1 & z ! field is /r5g!n$ ! armature w g5]ate m curr5t1 & ?us by a mutual reaction ! ma*9e gradually builds up to full /r5g?4 ,illu/ration3 ,fig4 #ba ,:5 n[ we use ! ma*9e z a motor1 an electric curr5t mu/ be s5t along ! l9e wires 9 ! opposite direction 7,fig4 #ba7 f :i* x w\ld come out ( ! ma*9e :5 act+ z a dynamo4 ,x w !n be notic$ t1 al?\gh ! direction ( ! curr5t ?r\gh ! field is ! same1 :e!r ! ma*9e is us$ z a dynamo or a motor1 ! direction ?r\gh ! armature1 :5 us$ z a motor1 is ! rev]se ( t :5 us$ z a dynamo4 ,y may p]haps be able to notice t ! am\nt ( wire on ! field is consid]ably m ?an t on ! armature4 ,n[ if y w trace ! wires c>efully y w f9d t !re is provid$ a way ( supplem5t+ ! wire ( ! armature ) "s m wire 9 :at is call$ ! rheo/at1 ,fig4 #bb4 ,?is wire1 or portions ( x1 is introduc$ into ! armature circuit :5 ! ma*9e fir/ />ts4 ,:51 h[ev]1 ! ma*9e has />t$ & ! armature is mov+ )9 ! influ5ce ( a magnetic field1 x plays ! "p ( a dynamo at ! same "t t x is act+ z a motor4 ,two conflict+ & opposite electro-motive =ces !re=e exi/ 9 ! armature at ! same "t4 ,9 ,fig4 #bb ! arr[ a repres5ts ! direction ( ! electro-motive =ce :i* is impress$ ^u ! armature1 & ! arr[ b repres5ts ! c\nt]-electro-motive =ce :i* ! mov+ armature develops4 ,illu/ration3 ,fig4 #bb ,?is c\nt]-electro-motive =ce1 :i* develops :ile ! ma*9e is 9 motion1 makes x unnecess>y to hold back ! curr5t long] by ! extra resi/ance ( ! rheo/at & h5ce t is usually cut out4 ,be+ us$ only = />t+ purposes & look+ l a box1 x is g5]ally call$ ! />t+ box4 ,if n[ x 0 int5d$ t ?is motor %\ld run at a con/ant spe$1 z is (t5 ! case1 no o!r gov]nor w\ld be ne$$ ?an ?is c\nt]-electro-motive =ce1 = :5ev] ! ma*9e beg9s to g fa/]1 on acc\nt ( r$uc$ load1 its c\nt]-electro-motive =ce increases z ! spe$ & holds 9 *eck ! impress$ electro-motive =ce4 ,?is acts v p]fectly z a gov]nor1 & motors op]ate ) notori\sly con/ant spe$ "u v>iable loads4 ,b1 ( c\rse1 9 ?is pres5t in/ance ! motor is requir$ to "w at a v>iable spe$4 ,x mu/ pump air sl[ly = ! s(t passages ( music1 & x mu/ "w ! pump to its utmo/ = ! v /rong passages4 ,illu/ration3 ,fig4 #bc ,to und]/& h[ an electric motor may pump an organ & h its spe$ automatically controll$1 let u exam9e ! diagram 9 ,fig4 #bc4 ,! motor m causes ! %aft ,s to revolve1 c>ry+ ! crank ,c ar\nd ) x4 ,! rod r causes a b1 ! l[] side ( ! bell[s1 to rise & fall1 ?is side be+ h+$ at b4 ,! side b c1 is fix$4 ,:5 ! side a b is pu%$ upw>d by ! crank rod ! valve f closes & ! air 9 ! comp>tm5t h pu%es op5 ! valve g & ent]s ! comp>tm5t j4 ,! upp] side d e1 ( ?is comp>tm5t rises z x is fill$ ) air4 ,weights ,k1 ,k1 ,k1 re/ on ! top ( ?is & air ducts lead f ?is comp>tm5t to ! pipes ( ! organ4 ,! keys ( ! organ op]ate air cocks :i* op5 & close ! air ducts connect$ ) ! organ-pipes4 ,a *a9 connect$ ) e passes ar\nd ! axle ( ! :eel l & has a weight ,w ^u its l[] end4 ,! :eel l c>ries a /rip ( brass n1 :i* slides ov] metal po9ts p1 p1 p1 etc4 ,! successive po9ts are connect$ by coils ( wire to furni% resi/ance4 ,?is s]ies ( coils is call$ a rheo/at4 ,! wires t & u =m a loop f ! armature ( ! motor & connect ?is rheo/at 9 s]ies ) ! armature4 u is connect$ ) ! brass /rip n4 ,notice t :5 ! comp>tm5t j is full ( air & ! side d e1 is lift$ to its greate/ height ! /rip n is mov$ to ! l[e/ po9t p1 & ! electric curr5t mu/ pass f u ?r\gh all ! resi/ance ( ! rheo/at 9 ord] to get back to ! armature by ! wire t4 ,?is makes ! motor g v sl[ly4 ,:5 d e s9ks d[n1 ! /rip n moves to ! upp] po9ts p1 & ! resi/ance is r$uc$ /ep by /ep1 enabl+ ! motor to quick5 its spe$ & pump fa/] z m air is requir$4 ,small motors 9 ord] to be effective mu/ travel at high spe$4 ,?is motor :5 mov+ at its highe/ spe$ makes #a1hjj revolutions p] m9ute4 ,! bell[s on ! o!r h& ne$s to be l>ge & move sl[ly 9 ord] to be effici5t4 ,h5ce ! motor is n 9 reality connect$ directly to ! %aft ,s1 b causes ! %aft to revolve by means ( a s]ies ( pulleys & belts4 ,! pulley on ! motor is ?ree in*es 9 diamet]4 ,x is connect$ by a flat lea!r belt ) a :eel ?irty in*es 9 diamet]4 ,:5 ! motor !re=e1 makes #a1hjj revolutions p] m9ute ?is :eel makes #ahj revolutions p] m9ute4 ,! axle ( ?is :eel c>ries a small cog-:eel ?ree in*es 9 diamet] & x is connect$ by a *a9 belt ) a cog :eel on ! %aft ,s 7,fig4 #bc74 ,?us ?is %aft revolves ?irty times p] m9ute1 t is1 ! rod r rises & falls ea* second4 ,a pull ( "o p\nd on ! rim ( ! motor pulley w cause a pull ( sixty p\nds on ! cogs ( ! :eel ^u ! %aft ,s4 ,if ! second belt 7 lea!r1 a sixty-p\nd pull w\ld cause x to slip on ! small] pulley4 ,h5ce ! second belt is a /eel *a9 & ! :eels h cogs1 or sprockets1 l a bicycle4 ,illu/ration3 ,fig4 #bd ,! organi/ be=e beg9n+ to play closes a d\ble-pole1 s+le-?r[ swit* 7,fig4 #bd71 :i* s5ds ! electric curr5t to ! motor4 ,! motor pumps air until ! bell[s is full1 & if ! organi/ delays play+1 ! /rip ( brass n 7,fig4 #bc7 is c>ri$ bel[ ! l[e/ po9t p1 ?us cutt+ (f ! curr5t & /opp+ ! motor4 ,z soon z he uses "s ( ! air 9 ! bell[s1 h[ev]1 n rises & makes contact ) ! po9ts p & ! motor />ts4 ,?is sugge/s t a some:at simil> ?+ is accompli%$ "u electric c>s :i* h air brakes4 ,an electric motor pumps ! air & compresses x 9 a tank4 ,:5 ! pressure rea*es a c]ta9 po9t1 say sixty p\nds p] squ>e in*1 x automatically %uts (f ! electric curr5t f ! motor :i* works ! pump4 ,b :5 ! motorman uses "s ( ! air to apply ! brakes to ! :eels1 & ! pressure 9 ! tank falls bel[ sixty p\nds1 ! electric curr5t is aga9 automatically turn$ on to ! motor4 ,( c\rse if an electric motor c op]ate a pump to compress air x may also "w a pump to exhau/ air4 ,?is is :at is done 9 a vacuum clean]4 ,! electric pump z x is call$ 7:i* means a pump work$ by an electric motor71 exhau/s "s ( ! air f a comp>tm5t 9 ! ma*9e1 & ! atmosph]e press+ 9 ?r\gh nozzle & hose c>ries du/ f rugs & furniture ) x into ! comp>tm5t4 ,! be/ vacuum clean]s w produce a pressure ( sev5 or eight p\nds p] squ>e in*1 ab\t half an atmosph]e4 ,?is w remove du/ f ! w>p & wo( ( a rug bett] ?an our greate/ hurricanes c :5 ! rugs are hung ^u a l9e4 ,!re are ?ree k9ds ( air pumps 9 use ) vacuum clean]s3 7#a7 bell[s1 7#b7 rotat+ disk or fan1 7#c7 pi/on4 ,to milk c[s by electricity is simply to apply ! vacuum-clean] idea to ! process1 &1 9 g5]al1 do+ ?+s by electricity usually means do+ !m by "s ma*9e t is made to g by an electric motor4 ,?is !n is ! fir/ key to ! ,electrical ,%[1 & if y w rememb] to look fir/ = ! motor x may remove mu* ( ! my/]y f "s ( ! exhibits4 ,9 _m cases x is n necess>y to h a complete electric motor1 b simply an electro-magnet to d ! "w4 ,9 boo? ,no4 #ef y w f9d a piano play$ by electricity4 ,its keys are mov+1 b no h&s /rike !m4 ,!re is no gho/ at "w "h4 ,a little /rip ( iron has be5 plac$ ^u ! "u side ( ea* key & a small electro-magnet is plac$ "u t4 ,x is only necess>y t wires %\ld run f ^! electro-magnets to two dry-batt]y cells & to pu% buttons1 & a p]son f> away may play ! piano4 ,9 reality1 h[ev]1 x is n a p]son b a roll ( punctur$ pap] t op5s & closes ! electric circuits to ^! v>i\s magnets und]nea? ! keys4 ,x (t5 happ5s t y see a p]son play+ a pipe organ ) 8 keybo>d f> remov$ f ! organ itself4 ,9 ?is case ! keys simply act z pu% buttons to close ! electric circuit ?r\gh electro-magnets plac$ 9 ! organ itself4 ,^! electro-magnets op]ate ! air valves ( ! v>i\s pipes4 ,illu/ration3 ,fig4 #be ,y call at "s ap>tm5t h\se :]e !re is no hall boy1 b a r[ ( pu% buttons labell$ ) ! names ( ! t5ants4 ,y pu% a button & ! door :i* 0 lock$ op5s app>5tly ( its own accord4 ,to say t ! door op5s by electricity is only to add my/]y4 ,:at does happ5 is t an electric bell up 9 ! ap>tm5t r+s 9 response to y\r pu% ( ! button1 & 9 reply ! t5ant pu%es a button & ! door is unlat*$ by an electro-magnet conceal$ 9 ! door cas+ 7,fig4 #be74 ,s ,i w\ld say t ! fir/ key to ! ,electric ,%[ or to ! multitude ( electrical appliances :i* y meet 9 life is ! electro-magnet4 ,consid] ! motor z "o illu/ration ( its use4 ,if y are really to und]/& ! ,electric ,%[ y %\ld g twice4 ,i advise go+ ) ?is key alone fir/ & note d[n all ! applications ( electro-magnets :i* y c f9d !re4 ,:5 y h done s ,i %all be glad to h y\r report4 ,,vi ,,applications ,,( ,,! ,,electro-,,magnet ,x became q ! rage n[ among ! boys to f9d z _m uses ( electro-magnets z possible4 ,^! 7 report$ & expla9$ to ! club & a li/ kept4 ,?is li/ includ$3 #a4 ,dynamo4 #b4 ,magneto4 #c4 ,ammet]4 #d4 ,wattmet]4 #e4 ,motor4 #f4 ,electric piano & organ play]s4 #g4 ,electric door op5]s4 ,already notic$ 9 ! prec$+ pages1 & ! foll[+3 #h4 ,! ,electric ,sp9n] 7,fig4 #bf74--;,a toy full ( in/ruction4 ,! /&>d is a /eel magnet :i* produces a magnetic field4 ,inside ( ?is is an electro-magnet :i* s]ves z an armature4 ,pla9ly visible on its %aft is a commutator to :i* ! electric curr5t f a dry cell is s5t4 ,?is causes ! armature to revolve & c>ry ) x a s]ies ( col\r disks :i* may be adju/$ s z to %[ :at t9t or %ade results f mix+ col\rs 9 v>i\s proportions4 ,illu/ration3 ,fig4 #bf ,illu/ration3 ,fig4 #bg ,illu/ration3 ,fig4 #bh #i4 ,! ,electric ,eng9e 7,fig4 #bg74--,?is toy1 ) "o dry batt]y cell1 develops p[] en\gh to run sev]al o!r toy ma*9es4 ,! diagram 9 ,fig4 #bh w make its plan ( op]ation pla94 ,b is ! batt]y cell1 c ! electro-magnets1 a an armature ( iron4 ,by a rod ?is armature is connect$ ) a crank on ! axle :i* c>ries ! fly :eel f4 ,ano!r crank1 d1 ^u ! same axle s]ves l a pu% button to close ! electric circuit at ! "r in/ant4 ,! wire g f ! batt]y cell encircles ! electro-magnet c & !n is connect$ to ! iron base ( ! toy4 ,:5 ! crank d t\*es ! conductor e1 :i* is a spr+1 ! electric curr5t passes ar\nd ! magnet1 ! magnet pulls ! iron armature a1 & ?is gives an impulse to ! :eel f ^: mom5tum c>ries x ar\nd dur+ t portion ( ! revolution :5 d is sep>at$ f e & a is rec$+ f ! magnet4 ,x is cu/om>y to say t ! circuit is clos$ ?r\gh ! base ( ! ma*9e1 b ?is language requires int]pretation4 ,x means t a way is provid$ = ! electric curr5t to pass ?r\gh ! base4 ,a p]son :o is exp]t 9 language b n 9 electricity might expect u to say ! circuit is op5 ?r\gh ! base4 ,illu/ration3 ,fig4 #bi #aj4 ,! ,telegraph ,s\nd] 7,fig4 #bi74--,?is 0 a toy half a c5tury ago1 b s9ce ! days ( ,samuel ,f9ley ,breese ,morse x has become ( va/ comm]cial importance4 ,! ,we/]n ,union ,telegraph ,company 9 #aiji _h #baa1eac miles ( poles & cables1 #a1chb1ejj miles ( wire1 #bd1cba (fices1 s5t #fh1jec1dci messages1 receiv$ #cj1eda1jgb4ee1 exp5d$ #bc1aic1ife4ff1 & _h #g1cdg1ajf4hi 9 pr(its4 ,9 ! ,unit$ ,/ates m ?an #ic1jjj1jjj & 9 ! _w at l>ge m ?an #fjj1jjj1jjj messages are s5t annually1 & !re are m5 /ill liv+ :o sc(f$ at ,morse's ideas z impracticable4 ,x is int]e/+ to contemplate :at w\ld happ5 to ! ,/ock ,ex*ange1 to ! newspap]s1 to ! railroads1 to ! congressman address+ 8 con/itu5ts f ! floor ( a legislative *amb]1 to bus9ess 9 g5]al1 if ! _w 7 depriv$ ( ! telegraph4 ,a few ye>s ago a telegraph despat* 0 s5t f ,new ,york to ,san ,francisco1 ,tokio1 ,london1 & back to ,new ,york1 #db1hgb miles1 9 ?ree m9utes less ?an an h\r4 ,electricity c travel ar\nd ! _w 9 a fraction ( a second1 ! "t 0 consum$ 9 repeat+ ! message4 ,i once s5t a message f ,new ,york to ,new ,hav5 to ann\nce t ,i 0 com+1 & aft]w>d took my tra9 & rea*$ ,new ,hav5 9 "t to receive my own message & pay ! mess5g] boy4 ,b ,i h nev] lo/ fai? 9 ! b5efic5t results ( ,morse's lab\rs4 ,morse 7#agia-ahgb7 0 an arti/ & ! fir/ ,presid5t ( ! ,national ,academy ( ,design4 ,he 0 likewise a pr(essor 9 ,new ,york ,univ]sity & con/ruct$ 8 fir/ exp]im5tal telegraph l9e ^u ! ,univ]sity campus 9 #ahce4 ,8 fir/ public l9e 0 built f ,wa%+ton to ,baltimore 9 #ahdd4 ,! ,we/]n ,union ,telegraph ,company 0 incorporat$ 9 #ahef4 ,( c\rse ! "w ( ,morse re/$ ^u t ( ,o]/$1 9 ,cop5hag51 :o1 9 #ahai1 discov]$ electro-magnetism1 & ^u t ( ,joseph ,h5ry ( ,albany1 :o 9 #ahbg fir/ insulat$ ! wires4 ,illu/ration3 ,fig4 #cj ,! application ( ! electro-magnet to produc+ telegraphic signals w be und]/ood by ref]r+ to ,fig4 #cj4 ,b is ! g5]ator ( an electric curr5t--sometimes a batt]y & sometimes a dynamo4 ,"o wire f ?is goes to ! e>?1 ,e4 ,! o!r wire goes ?r\gh a key1 :i*1 l a pu% button or a swit*1 s]ves to op5 or close ! circuit4 ,?is is normally clos$ :5 n 9 use4 ,?r\gh ?is ! curr5t passes ar\nd ! electro-magnet ,s1 :i* attracts ! armature a1 caus+ x to click aga9/ a metal /op1 h5ce x is call$ ! s\nd]4 ,f ?is ! curr5t passes along ! l9e wire to a di/ant /ation & !re ?r\gh ! s\nd] & clos$ key to ! e>?4 ,!re is likely to be a g5]ator at ea* /ation4 ,! curr5t mu/ run cont9ually ?r\gh ! sy/em4 ,if a batt]y is employ$1 ! copp] sulphate1 or gravity cell1 to be describ$ lat]1 is *os51 because x w endure cont9u$ usage bett] ?an any o!r4 ,! op]ator1 9 s5d+ signals1 op5s ! circuit1 ! magnets cease to hold d[n ! armatures1 & !y are rais$ by spr+s & /rike aga9/ metallic /ops above4 ,x is cu/om>y to say t ! circuit is complet$ ?r\gh ! e>?4 ,?is /atem5t misleads "s p]sons into imag9+ an electric curr5t capable ( corrod+ wat] pipes & decompos+ *emical comp\nds1 pass+ ?r\gh ! e>? betwe5 /ations4 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,te/+ ! ,telegraphy ,outfit ,p]haps x w help to a bett] und]/&+ ( ! tru? if we ?9k ( a city pump+ wat] out ( ! ocean1 say to fight fire1 & dispos+ ( x aga9 into ! ocean4 ,! ocean curr5ts ?us produc$ are n likely to be de/ructive4 ,inde$1 j z we measure height f ! ocean level z z]o1 s we measure electric pressures z f ! z]o level ( ! e>?'s electrical /ate4 ,illu/ration3 ,fig4 #ca ,! key us$ by telegraph]s is repres5t$ 9 ,fig4 #ca4 ,x has connect$ ) x a swit* to keep ! circuit clos$ :5 ! key is n 9 op]ation4 ,! ,morse code ( signals consi/s ( dots & da%es1 :5 pr9t$1 z foll[s3 a 4 - b - 4 4 4 c 4 4 4 etc4 ,op]ators le>n to read ! message by ! int]vals betwe5 s\nds4 ,a dot consi/s ( two taps ( ! s\nd] ) a %ort int]val betwe51 & a da% consi/s ( two taps ) a long] int]val betwe54 ,"o tap ( ! s\nd] is caus$ by its desc5d+ ^u ! metal /op bel[ & ano!r by its ris+ aga9/ ! upp] /op4 ,telegraph s\nd]s are op]at$ on ab\t a qu>t] ( an amp]e ( curr5t if f a batt]y circuit1 or on ab\t "o t5? ( an amp]e f a dynamo circuit4 ,! dynamo circuit is suppli$ ) m volts ( electric pressure1 & h5ce its p[] is ample to cause ! armature to /rike ! metal /ops h>d en\gh to be he>d by ! op]ator4 ,= example a batt]y circuit may supply to ! s\nd] a curr5t ) ^! *>act]i/ics3 #b volts 4#be amp]es 4#e watts1 :ile a dynamo circuit may give3 #f volts 4#a amp]e 4#f watts4 ,telegraph l9e wires are usually b>e1 ! insulation be+ m]ely ! glass knobs at ! poles4 ,clean wat] is a v good insulator b dirty wat] is a fairly good conductor4 ,a wet telegraph pole may br+ s mu* curr5t to e>? z to prev5t all s\nd]s on ! l9e f op]at+4 ,h5ce ! l9e is sep>at$ f ! poles by glass4 ,! poles are ab\t "o hundr$ & ?irty-two feet ap>t1 mak+ =ty to ! mile4 ,! wires are usually galvaniz$ iron "o six? ( an in* 9 diamet]4 ,copp] conducts six times z well z iron1 & is n[ replac+ iron 9 ! l9es4 ,morse laid a subm>9e telegraph l9e 9 ,new ,york ,h>b\r & sugge/$ a cable across ! ocean4 ,b t gigantic und]tak+ _h to await ! ma/]ful intellig5ce ( ,"l ,kelv9 & ! indomitable w ( ,cyrus ,w4 ,field4 ,a subm>9e cable 0 laid across ! ,/rait ( ,dov] 9 #ahej4 ,x 0 cut by ! an*or ( a fi%]man a few h\rs aft] x 0 laid4 ,! fir/ attempt to lay a subm>9e cable across ! ,atlantic ,ocean 0 made 9 #aheg4 ,two %ips ( w>1 ! ,agamemnon ( ,great ,brita9 & ! ,niag>a ( ! ,unit$ ,/ates1 engag$ 9 ?is und]tak+4 ,?ree hundr$ miles _h be5 laid :5 ! cable p>t$ :]e ! ocean 0 m ?an two miles deep4 ,william ,?omson 0 on bo>d ! ,agamemnon z electrical exp]t4 ,he w5t home to /udy & improve ! me?ods4 ,! next ye>1 #aheh1 ! ,agamemnon & ! ,niag>a met 9 midocean ea* ) a portion ( ! cable on bo>d4 ,! splice 0 made1 & ! ,agamemnon />t$ t[>d ,irel& & ! ,niag>a t[>d ,newf\ndl&4 ,:5 six miles ap>t ! cable broke4 ,! %ips met aga91 made a new splice & aga9 />t$ 9 opposite directions4 ,!y laid eighty miles & ! cable p>t$ a second "t4 ,!y met aga91 splic$ & laid two hundr$ miles :5 x p>t$ = ! ?ird "t4 ,!y met a f\r? "t1 made ! splice & succe$$ 9 lay+ ! fir/ cable f ,irel& to ,newf\ndl& on ,augu/ #e1 #aheh4 ,9 a few weeks ! insulation fail$ & no m messages c\ld be s5t4 ,sev5 ye>s 7 sp5t 9 /udy+ ! problem1 & aga9 9 #ahfe ! ,great ,ea/]n1 a mammo? %ip1 />t$ to lay ! cable4 ,william ,?omson 0 aga9 on bo>d z ! exp]t4 ,:5 twelve hundr$ miles _h be5 laid ! cable p>t$ 9 deep wat]4 ,?ree times ! cable 0 grappl$ & br\ght "p way to ! surface & lo/ aga94 ,! ,great ,ea/]n return$ to l&4 ,! next ye>1 #ahff1 ! ,great ,ea/]n1 hav+ on bo>d ,william ,?omson 7,"l ,kelv971 ,mr4 ,cann+1 ! eng9e] ( ! exp$ition1 & ,capta9 ,&]son1 9 comm&1 laid ! cable :i* has work$ successfully ev] s9ce4 ,?omson1 ,cann+1 & ,&]son 7 knight$ z a result ( _! lab\rs4 ,sir ,william ,?omson 7#ahbd-aijg71 aft]w>d ,"l ,kelv91 is cr$it$ ) hav+ solv$ ! difficult electrical problems connect$ ) ?is ent]prise4 ,cyrus ,w4 ,field 7#ahai-ahib71 born 9 ,/ockbridge1 ,mass41 help$ to secure ! _m millions ( doll>s necess>y to c>ry ! "w to completion4 ,!re are n[ sev5ty-?ree cables connect+ ,europe & ,am]ica1 & two across ! ,pacific ,ocean4 ,cable rates are3 ,new ,york to ,engl&1 ,france1 ,g]many1 or ,holl& tw5ty-five c5ts a ^w1 to ,switz]l& ?irty c5ts a ^w1 & to ,japan "o doll> & ?irty-?ree c5ts a ^w4 ,illu/ration3 ,fig4 #cb ,! boys 7 kept v busy n[ look+ up hi/orical & biographical sket*es1 z well z work+ up ! _m applications ( ! electro-magnet4 ,! next to be report$ 03 #aa4 ,! ,relay 7,fig4 #cb74--,telegraph+ f #c1jjj to #aj1jjj miles "u ! ocean is full ( difficulties n n[ to be expla9$4 ,( c\rse :5 we attempt to telegraph _m miles ^u l& we f9d t ! resi/ance ( ! wire cuts d[n ! /r5g? ( ! curr5t s t x w n move ! s\nd]4 ,?is1 h[ev]1 is readily obviat$ by ! relay devis$ by ,morse4 ,x simply s]ves z an automatic key to close a circuit4 ,a diagram w make ?is cle> 7,fig4 #cc74 ,suppose ! l9e wire to be v long & on acc\nt ( its resi/ance ! curr5t is too feeble to op]ate a s\nd]4 ,x is likely to be ab\t 4#jbe amp]e :]e ! local s\nd] may require 4#be amp]e or t5 times z mu*4 ,x is easily possible to w9d a magnet 7,fig4 #cc71 ,r1 su* t 4#jbe amp]e w close ! armature a1 s t x may complete a local circuit :5 x w\ld n make noise en\gh = a s\nd]4 ,b may repres5t a local batt]y ( any desir$ /r5g? :i* may op]ate ! s\nd] ,s ( t /ation z l\dly z may be desir$4 ,illu/ration3 ,fig4 #cc ,illu/ration3 ,fig4 #cd #ab4 ,annunciator 7,fig4 #cd74--,we live 9 a fif?-floor ap>tm5t4 ,:5 we pu% ! button to call ! elevator a ,no4 #e appe>s 9 ! annunciator 9 ! elevator c>4 ,?is tells ! elevator boy :]e ! call comes f4 ,take out two or ?ree screws & ! annunciator op5s1 reveal+ a s]ies ( electro-magnets l ! "o %[n 9 ,fig4 #ce4 ,:5 an electric curr5t passes ar\nd ! coil x pulls back an iron cat* & all[s a numb] to drop s z to %[ ?r\gh a small w9d[4 ,! elevator boy1 hav+ not$ t ! call is f ! fif? floor1 pu%es up ! numb] & ! iron cat* holds x until ! coil is magnetiz$ aga9 by an electric curr5t4 ,illu/ration3 ,fig4 #ce ,illu/ration3 ,fig4 #cf ,illu/ration3 ,fig4 #cg ,! annunciator has a bell to call att5tion4 ,a cable ( six wires ent]s ?is annunciator 7,fig4 #cf74 ,"o wire goes direct to ! bell & ! o!r five rea* ! bell ?r\gh ! sep>ate coils ( ! electro-magnets :i* control ! drops4 ,b h[ are electrical connections made betwe5 a mov+ elevator c> & ! pu% buttons on v>i\s floors8 ,! diagram 9 ,fig4 #cg %[s ?is 9 elevation4 ,b repres5ts a batt]y ( sev]al dry cells locat$ 9 ! basem5t4 ,"o wire f x runs direct to ! pu% buttons #a1 #b1 #c1 #d1 #e1 locat$ ^u ! five floors ( ! h\se4 ,! o!r wire f ! batt]y1 toge!r ) wires f ea* ( ! five pu% buttons1 all run to a po9t1 ,a1 half-way up ! elevator %aft4 ,"h ! six wires are ga!r$ into a cable long en\gh to rea* ei!r to ! top or ! bottom ( ! elevator %aft4 ,! o!r end ( ?is cable ent]s ! elevator c> & runs to ! annunciator4 ,! wire f ! batt]y goes direct to ! bell4 ,! wires f ! v>i\s pu% buttons g ?r\gh correspond+ly numb]$ electro-magnets to ! bell4 ,:51 !re=e1 we pu%$ ! button on ! fif? floor1 we clos$ ! gap 9 ! electric circuit at t po9t4 ,! curr5t came up f ! batt]y1 pass$ ?r\gh ! button1 w5t d[n ! cable to ! c>1 w5t ?r\gh electro-magnet ,no4 #e1 w5t ?r\gh ! bell1 & return$ direct to ! batt]y1 ?us complet+ ! circuit4 ,annunciators are us$ ab\t build+s to call o!r att5dants1 besides ! elevator boy4 ,!y are likewise us$ 9 burgl> al>ms to in=m ! h\sehold] :i* door or w9d[ is be+ =c$4 ,!y are us$ 9 ! fire dep>tm5t to tell :at "p ( ! city ! call came f4 ,illu/ration3 ,fig4 #ch #ac4 ,! ,electric ,bell & ,buzz] 7,fig4 #ch74--,s common a ?+ z an electric bell really belongs to ! pres5t g5]ation4 ,bells 7 ei!r novelties or toys :5 ,i 0 y\r age4 ,!y co/ !n _m times :at !y d n[ & !n 7 poorly made4 ,nobody d>$ to tru/ !m = front-door bells4 ,x 0 necess>y to h a c>d p]man5tly po/$ ov] ! pu% button say+1 ,if ! bell does n r+1 knock4 ,9 ^? days batt]ies 7 tr\blesome to c>e =1 h\ses 7 n wir$ :5 built1 & no "o _h le>n$ ! art ( conceal+ ! wires neatly4 ,! buzz] is simply a bell m9us gong & hamm]4 ,^? %[n 9 ,fig4 #ch r+ well on a s+le dry cell4 ,a cell co/+ twelve c5ts op]at$ "o = two ye>s :ile x 0 us$ z a call bell f d9+ room to kit*51 ! curr5t requir$ be+ 4#ae amp]e4 ,illu/ration3 ,fig4 #ci ,illu/ration3 ,electric ,bell ,! connections are %[n 9 ! diagram 7,fig4 #ci74 ,suppose ! curr5t to ent] at ! b9d+ po/ a1 pass ar\nd ! magnets b & !n to ! po/ c4 ,! armature d normally re/s aga9/ ! po/ c & ! curr5t f9ds its way along ?is to ! po/ e & !nce back to ! batt]y4 ,b z soon z ! curr5t passes1 b becomes a magnet & pulls ! armature d away f ! po/ c1 ?us break+ ! circuit1 :5 b ceases to be a magnet & a spr+ pu%es ! armature d back aga9/ ! po/ c to repeat ! op]ation4 ,! armature d c>ries a hamm] :i* /rikes ! gong f4 ,if ! wire1 :i* is usually connect$ ) ! b9d+ po/ e1 is connect$ ) ! po/ c1 ! clatt] bell is *ang$ to a s+le-/roke bell1 & if ! gong & hamm] are remov$ ! bell is *ang$ to a buzz]4 ,illu/ration3 ,fig4 #dj ,9 ! case ( ! buzz]1 by *ang+ ! l5g? ( ! armature or by weight+ x1 we may *ange ! "t ( its vibrations & its tone4 ,! connections betwe5 batt]y pu% button & bell =m a complete circuit4 ,9 ,fig4 #dj ,b repres5ts a batt]y1 usually ( dry cells1 ,b' repres5ts ! bell1 & ,p repres5ts ! pu% button4 ,! electric circuit is op51 7t is1 !re is a break 9 ! conductor7 at ,p until "s "o pu%es ! button1 t is1 simply pu%es aga9/ a spr+ s z to cause a piece ( metal to bridge ! gap 9 ! conductor4 ,!n we say ! circuit is clos$4 ,illu/ration3 ,fig4 #da ,illu/ration3 ,fig4 #db ,pu% button devices & swit*es are innum]able4 ,9 e case !y are simply devices = pu%+ "o piece ( metal aga9/ ano!r & complet+ ! circuit = an electric curr5t4 ,e "o %\ld unscrew & exam9e a few ( !m1 bo? = ! pleasure ( see+ h[ !y "w & to le>n h[ to make !m "w :5 !y sometimes fail4 ,n only 9 bells b 9 all o!r in/rum5ts :]e electro-magnets are us$1 ! magnets are plac$ 9 pairs1 fa/5$ toge!r ^u an iron base4 ,!y are w\nd s t ! free ends are made opposite poles by ! electric curr5t4 ,l a horse%oe magnet1 !y =m "o magnet4 ,! two poles ?us plac$ are mutually helpful & ea* is /rong] ?an x w\ld be if sep>at$ f ! o!r4 ,illu/ration3 ,fig4 #dc #ad4 ,electric ,clocks1 ,self-w9d+ ,clocks1 ,programme ,clocks4--,a pret5ti\s-look+ ?+ :i* appe>$ l a di% pan ) a glass bottom 0 op5$ by ! boys & f\nd to be ! simple/ ( all clocks4 ,x _h an electro-magnet l t 9 ,fig4 #dd4 ,a /rip ( iron act+ z an armature across ! free ends ( ?is magnet1 pu%$ l a f+] aga9/ ! cogs ( a :eel4 ,?is :eel 0 on ! axle ( ! m9ute h& & x _h sixty cogs4 ,! electric circuit 0 clos$ ?r\gh ! magnet = an in/ant ea* m9ute & ! armature pu%$ ! :eel ahead "o cog4 ,?us x made "o complete revolution 9 an h\r4 ,a tra9 ( f\r o!r cog-:eels caus$ ! h\r h& to trail aft] at "o twelf? ! spe$ ( ! m9ute h&4 ,?is ma*9]y made simply a small h&ful 9 an eighte5-in* /amp$-metal di%-pan co/+ fifte5 doll>s4 ,illu/ration3 ,fig4 #dd ,a self-w9d+ clock 0 op5$ & f\nd to conta9 two dry batt]y cells1 an electro-magnet :i* op]at$ v mu* l t ( a clatt] bell1 ! hamm] l a f+] pok+ aga9/ ! cogs ( a :eel4 ,once an h\r ! long h& clos$ ! circuit ?r\gh ! batt]y & ! magnet & its armature swung back & =? long en\gh to give ! cog :eel "o complete revolution & w9d a spr+1 :i* x c>ri$ ^u its axle4 ,?is spr+ kept ! clock runn+ "o h\r1 until ! next w9d+4 ,illu/ration3 ,fig4 #de ,! programme clocks :i* 7 exam9$ 7 self-w9d+ clocks1 b 7 connect$ by wires to ! ma/] clock :i* correct$ !m ea* h\r4 ,ea* "t ! long h& ( ! ma/] clock came to twelve x clos$ an electric circuit ?r\gh all ! clocks 9 ! sy/em4 ,9 ea* clock ! curr5t pass$ ar\nd an electro-magnet & caus$ x to pull an armature aga9/ a metal /op & set ea* long h& exactly at twelve4 ,?is ma/] clock is sometimes situat$ _m miles away & may correct ! "t = a :ole city4 ,?us a ma/] clock at ,wa%+ton1 ,d4 ,c41 furni%es /&>d "t to all p>ts ( ! ,unit$ ,/ates4 ,! ma/] clock :i* we exam9$ also clos$ ! circuit at prop] int]vals ?r\gh a s]ies ( programme bells plac$ 9 ! v>i\s class rooms1 & ^! call$ & dismiss$ classes automatically4 #ae4 ,wat*man's ,"t ,detector 7,fig4 #de74--,?is is a device to compel a wat*man to make 8 appo9t$ trips4 ,pu% buttons or swit*es are di/ribut$ ab\t ! build+ at v>i\s po9ts1 & x is made 8 duty to close ! circuits at ^! po9ts at /at$ times4 ,:5 he does s1 ! fact is record$ by electro-magnets punctur+1 or1 9 "s way1 m>k+ a revolv+ "t c>d 9 ! clock4 ,illu/ration3 ,fig4 #df #af4 ,circuit ,break]s 7,fig4 #df74--;,electro-magnets are us$ to op5 swit*es & ?us protect dynamos & o!r ma*9es aga9/ a l>g] electric curr5t ?an !y are able to c>ry4 ,! swit* is held clos$ by a spr+ :i*1 by an adju/+ device1 may be tight5$ or loos5$4 ,a dynamo :i* we exam9$ _h its circuit break] adju/$ s t x w\ld rema9 clos$ if any curr5t "u #aejj amp]es pass$1 b if a great] curr5t ?an t pass$ x w\ld /r5g!n ! magnet suffici5tly to op5 ! swit* & ?us break ! circuit4 #ag4 ,sep>at+ ,iron f ,ore4--,9 #ahig ,edison fir/ propos$ to use an electro-magnet to sep>ate iron f cru%$ e>?4 ,fig4 #dg repres5ts ! process4 ,e is an electro-magnet4 ,s is ! /ream ( cru%$ ore conta9+ iron4 ,gravity w\ld cause all ! mat]ial to fall into b9 ,a1 b ! electro-magnet ,e pulls t portion ( ! mat]ial :i* is magnetic to "o side s t x falls into ! b9 ,b4 ,illu/ration3 ,fig4 #dg ,illu/ration3 ,fig4 #dh #ah4 ,lift+ ,magnets4--,electro-magnets are made = use ) hoi/+ app>atus to save ! tr\ble ( manipulat+ grappl+ hooks1 etc4 ,!y may lift b>rels & boxes ( iron1 ! wood ( ! b>rel or box be+ transp>5t1 we say1 to ! magnetic influ5ce4 ,t is1 ! magnet w attract iron ?r\gh ! wood j z light w %9e ?r\gh glass4 ,su* magnets are us$ to pick up f ! bottom ( ! sea cases ( h>dw>e f wreck$ %ips4 7,see ! accompany+ illu/ration1 ,fig4 #dh47 ,9 su* cases ! electric conductors :i* lead to & encircle ! magnets mu/ be well insulat$ f ! wat] ( ! sea1 o!rwise ! electric curr5t w\ld take ! %ort] pa? f "o l9e wire ?r\gh ! sea wat]1 :i* is a fairly good conductor1 & back by ! o!r l9e wire1 r ?an g ! pa? ( great] resi/ance ar\nd ! magnet4 ,electro-magnets are com+ into use 9 f\ndries1 etc41 = lift+ heavy iron ca/+s4 ,illu/ration3 ,fig4 #di #ai4 ,electro-,magnet on ,/>t+ ,box4--,z 0 expla9$ "u electric motors1 a />t+ box is simply a s]ies ( resi/ance coils r1 r1 r1 r1 r1 9 ,fig4 #di4 ,:5 ! motor is n 9 use ! swit* l re/s ^u ! po9t #a & no electric curr5t passes4 ,:5 ! swit* is mov$ to po9t #b1 ! curr5t ent]+ at a passes to ! pivot ( ! swit* & up ! metal /rip l to ! po9t #b1 !n ar\nd ! s]ies ( coils1 r1 r1 r1 r1 r1 to ! po/ b & !nce back to ! g5]ator4 ,z ! swit* is mov$ to ! "r1 ! curr5t passes ?r\gh less & less ( ?is resi/ance until1 :5 x rea*es po9t #g1 all ! coils ( resi/ance are cut out1 t is1 !y are n 9 ! pa? ( ! curr5t4 ,n[ ! motor has rea*$ its full spe$ & is develop+ en\gh c\nt]-electro-motive =ce to protect itself aga9/ too mu* curr5t4 ,?r\gh a %unt1 h[ev]1 a portion ( ! curr5t passes f a to b ar\nd ! electro-magnet e1 ! two poles ( :i* are pres5t$ to ! metal /rip l1 :i* mu/ be ( iron4 ,?is magnet holds ! swit* ov] s long z ! curr5t is on1 b :5 ! curr5t is cut (f1 by op5+ a swit* 9 ! l9e wire1 e ceases to be a magnet & l is c>ri$ back to po9t #a by a spr+4 ,?us an extra resi/ance mu/ always be 9 circuit :5 ! motor is fir/ />t$4 ,^? :o />t motors are expect$ to move ! lev] l ( ! />t+ box sl[ly f po9t to po9t1 paus+ a second or two on ea* to give ! motor "t to acquire prop] spe$ = its protection4 ,h[ too great a curr5t w\ld burn out a motor w be expla9$ lat]4 ,! motor man h&les a lev] = />t+ 8 c>1 :i* works l t ( ! />t+ box4 ,8 />t+ box1 h[ev]1 is call$ a controll]4 ,al?\gh x accompli%es ! same result z ! />t+ box x has a :olly diff]5t & va/ly m complex me*anism ?an t already describ$4 ,! elevator boy1 :o runs our electric elevator1 h&les a lev] :i* also does ! same ?+ ?r\gh f> diff]5t me*anism4 ,inde$1 9 8 case electro-magnets are us$ to prev5t him f cutt+ out resi/ance too fa/ if he %\ld move 8 lev] too quickly4 #bj4 ,/>t+ ,swit*es = ,electric ,elevators4--,! motor man has to be in/ruct$ p>ticul>ly h[ he %\ld h&le ! lev] ( 8 controll]1 & he is tru/$ to foll[ 8 directions to "s ext5t1 h[ev] lack+ 9 intellig5ce & integrity he may be4 ,b ! elevator boy receives sc>cely any in/ructions ab\t 8 ma*9e1 &1 inde$1 8 ma*9e has be5 con/ruct$ pretty ne>ly foolpro(4 ,x w automatically correct 8 errors ( managem5t4 ,if he ?r[s ! h&le f "o extreme to ! o!r1 all resi/ance _c be ?r[n out in/antly1 b ?is is accompli%$ by a s]ies ( electro-magnets clos+ "o swit* aft] ano!r & ?us cutt+ out resi/ance gradually4 #ba4 ,arc ,lamp ,fe$4--,z w be expla9$ lat]1 an arc lamp mu/ h its c>bons t\*+ "o ano!r :5 ! curr5t is fir/ ?r[n on1 & !n ! c>bons mu/ be drawn ap>t f a qu>t] to half an in*4 ,! upp] c>bon is lift$ away f ! l[] "o by a portion ( ! curr5t pass+ by means ( a %unt ar\nd an electro-magnet4 ,illu/ration3 ,fig4 #ej ,illu/ration3 ,fig4 #ea ,illu/ration3 ,fig4 #eb #bb4 ,volt met]4--,! volt met] measures ! pressure ( an electric curr5t4 ,! volt met] :i* we exam9$ look$ outside l our ammet]1 & :5 we remov$ ! face x appe>$ inside l an ammet]4 ,!re 0 ! /eel magnet ( horse%oe %ape to furni% a field 7,fig4 #ea71 & !re 0 an electro-magnet pois$ betwe5 its poles = an armature4 ,! armature 9 ! volt met]1 h[ev]1 _h w\nd ^u x f9] wire & m ( x ?an 0 ! case 9 ! ammet]4 ,!re 0 no %unt wire 9 ! volt met] z !re 0 9 ! ammet]4 ,we connect$ 9 s]ies a fluid cell 7to be describ$ lat]71 ! ammet]1 & ! volt met] 7,fig4 #eb74 ,! ammet] %unt 0 remov$ s t all ! curr5t w5t ?r\gh its armature4 ,! volt met] ne$le w5t to "o :i* 0 two ?irds ( ! scale 7,fig4 #ec71 & ! ammet] ne$le indicat$ 4#jaf4 ,t is1 ?is p>ticul> cell c pu% sixte5 ?\s&?s ( an amp]e ?r\gh ! resi/ance ( ?is volt met]1 & 4#jaf amp]e pass+ ?r\gh ! armature ( ?is volt met] w magnetize x suffici5tly to move x aga9/ its spr+1 say sixty degrees4 ,illu/ration3 ,fig4 #ec ,illu/ration3 ,fig4 #ed ,illu/ration3 ,fig4 #ee ,we put into ! circuit a lot m f9e wire = resi/ance1 ,r 7,fig4 #ed71 s t ! volt met] ne$le w5t only half z f> z be=e1 t is to 4#e4 ,! ammet] indicat$ only half z mu* z be=e1 t is 4#jjh amp]e4 ,we put 9 resi/ance en\gh to br+ ! volt met] ne$le d[n to 4#be & ! ammet] indicat$ "o qu>t] ( ! orig9al curr5t4 ,we put 9 less resi/ance1 br++ ! volt met] ne$le to 4#ge1 & ! ammet] indicat$ ?ree f\r?s ( ! orig9al curr5t4 ,evid5tly ! volt met] is m]ely an ammet] ) a diff]5t scale m>k$ ^u its c>d4 ,) a p5 we m>k$ ^u ! c>d ( ! volt met] a true ammet] scale 7,fig4 #ee74 ,illu/ration3 ,fig4 #ef ,9 ord] to und]/& ! volt met]1 let u turn our att5tion = a mom5t to ,fig4 #ef4 ,i h arrang$ ! wat] tank ,t at su* a height above ! faucet ,f t :5 ! faucet is op5$ "o qu>t ( wat] w fl[ 9 a m9ute4 ,if ,i p>tially close ! faucet1 mak+ ! op5+ "o half z l>ge 7t is1 (f]+ twice ! resi/ance to ! fl[71 half a qu>t w fl[ 9 a m9ute4 ,if ,i make ! resi/ance f\r times z great only "o qu>t] ( a qu>t w fl[ 9 a m9ute4 ,x is evid5t t ,i c\ld arrange a scale und]nea? ! h&le ( ! faucet to indicate ! quantity ( wat] fl[+1 j z ! ammet] & volt met] indicate ! quantity ( electricity :i* fl[s4 ,if n[ t mu* is und]/ood1 x w be easy to le>n h[ ! wat] faucet may be us$ to measure wat] pressure & ! volt met] 9 l mann] us$ to measure electric pressure4 ,hav+ set ! faucet s t a qu>t w fl[ p] m9ute1 let u put on a long] tube p1 & move ! tank up to ano!r %elf s t ! di/ance f ! wat] level 9 ! tank to ! faucet is twice z great z be=e4 ,"u ! increas$ pressure wat] runs ?r\gh ! faucet twice z fa/ & we n[ get two qu>ts p] m9ute4 ,i purposely plac$ ! tank out ( sight beh9d a p>tition s t y might practise judg+ ! wat] pressure by ! fl[ at ! faucet4 ,we _c v well talk ab\t pressure 9 qu>ts4 ,we might talk ab\t x 9 p\nds1 b if we us$ ?is app>atus mu* we %\ld probably get into ! habit ( talk+ ab\t ! pressure f "o %elf1 two %elves1 ?ree %elves1 etc4 ,9 ord] t ! pressure might rema9 ne>ly con/ant dur+ ! exp]im5t we w\ld probably introduce resi/ance 7t is1 p>tially close ! faucet7 s t ! wat] level %\ld n fall mu*4 ,we might1 = example1 set ! faucet s t half a p9t w\ld fl[ 9 a m9ute :5 ! tank 0 on ! fir/ %elf4 ,!n a p9t p] m9ute w\ld fl[ :5 ! tank 0 on ! second %elf & "o & a half p9ts p] m9ute :5 ! tank 0 on ! ?ird %elf1 etc4 ,?us we %\ld inf] ! pressure by measur+ ! quantity4 ,"o m illu/ration & ! case w be cle>4 ,to save ! tr\ble ( measur+ ! quantity ( wat] :i* fl[s ?r\gh ! faucet1 suppose ,i introduce ! device repres5t$ 9 ,fig4 #eg4 ,w is a small wat] :eel comp>able to ! armature ( ! volt met]4 ,x c>ries a po9t] :i* moves ov] a scale j z 9 ! case ( ! volt met]4 ,illu/ration3 ,fig4 #eg ,x has a spr+ coil$ ar\nd its axle :i* t5ds to keep ! po9t] at #j1 z 9 ! case ( ! volt met]4 ,! tank is plac$ ^u ! fir/ %elf1 ! faucet is fix$ s t a small am\nt ( wat] fl[s & ! ne$le moves to a c]ta9 figure ^u ! scale4 ,we w m>k ?is po9t "o & call x fir/-%elf pressure4 ,! tank is lift$ to ! second %elf & ! index moves to ano!r po9t1 :i* we w m>k two & call x second-%elf pressure4 ,! tank is lift$ to ! ?ird %elf & ! index moves to a ?ird po9t1 :i* we w m>k ?ree & call x ?ird-%elf pressure1 etc4 ,ord9>ily we measure wat] pressure ) an in/rum5t :i* all[s no wat] to run to wa/e1 b 9 measur+ electric pressure by ! volt met] "s curr5t mu/ pass ?r\gh ! in/rum5t1 j z 9 ! case ( our wat]-:eel illu/ration 9 ,fig4 #eg4 ,we put 9 l>ge resi/ance s z to make ?is curr5t z small z possible1 :ile we let en\gh pass to move ! armature4 ,illu/ration3 ,fig4 #eh ,n[ let u return to ! volt met] itself4 ,by ref]r+ to ,fig4 #ee1 we see t x requires 4#jbd amp]e to move ! ne$le ( ! volt met] cle> across ! scale1 & we h f\nd t "o fluid cell 0 able to s5d en\gh curr5t ?r\gh ! resi/ance ( ! armature to move ! ne$le two ?irds ( ! way across ! scale4 ,at ?is po9t we f9d ,fig4 #a1 :i* might be read "o-cell pressure4 ,we pref] to commemorate ! "n ( "o ( ! work]s 9 ! field ( electricity & call ?is pressure a volt aft] ,aless&ro ,volta 7#agde-ahbg71 born at ,como1 ,italy4 ,x is ! electric pressure :i* is produc$ by "o fluid cell ( a c]ta9 k9d4 ,we say1 !n1 t "o volt pu%es ?r\gh ! resi/ance ( ?is armature 4#jaf amp]e4 ,half a volt w\ld pu% ?r\gh ! resi/ance ( ! armature half z mu* curr5t or 4#jjh amp]e4 ,at ?is po9t we put 4#e4 ,?us ea* ( ! figures 9 ! l[] r[ 7,fig4 #ee7 %[s :at "p ( a volt is requir$ to s5d en\gh curr5t ?r\gh ?is p>ticul> armature to move ! ne$le to t po9t4 ,illu/ration3 ,fig4 #ei ,we f\nd out h[ mu* wire 0 w\nd ^u ! armature & put exactly ! same am\nt 9 ! outside resi/ance1 ,r 7,fig4 #ei74 ,! ne$le n[ %[$ t "o volt is able to pu% ?r\gh twice ! resi/ance ( ! armature only half z mu* curr5t1 & ! ne$le /opp$ at 4#jjh amp]e4 ,if ?is 7 to be ! resi/ance 9 ! volt met] circuit "o volt %\ld /& "u 4#jjh amp]e & two "u 4#jaf & ?ree "u 4#jbd4 ,x is evid5t !n1 t1 if we "k ! int]nal resi/ance ( a volt met]1 we may make x capable ( measur+ great] electrical pressures by add+ ! prop] am\nt ( resi/ance4 ,by putt+ at ,r1 7,fig4 #ei7 n9e times ! int]nal resi/ance ( ! in/rum5t1 ?us multiply+ ! total resi/ance t5fold1 ! figures ^u ! scale ( volts may be read z :ole numb]s f "o to fifte54 ,9 ?is case x w require fifte5 cells to pu% ! ne$le cle> across ! scale & t5 cells to pu% x two ?irds ( ! way across4 ,if n[ we add en\gh ext]nal resi/ance to multiply ! resi/ance ( ! armature a hundr$ fold x w require #aej volts to pu% 4#jbd ( an amp]e ?r\gh ! armature & pull its ne$le cle> across ! scale4 ,9 ?is case ! figures ^u ! scale ( volts are multipli$ by "o hundr$ & read f t5 to "o hundr$ & fifty4 ,su* a scale w\ld adapt ?is volt met] = use ) our #aaj-volt light+ circuit4 ,volt met]s are made ) a s]ies ( su* ext]nal resi/ances1 call$ multipli]s1 atta*$ s t !y may be easily ?r[n into ! circuit4 ,x is evid5t t we ne$ "s t]m s t we may speak ( quantities ( resi/ance4 ,?is ne$ has giv5 rise to a unit ( resi/ance call$ an ohm1 aft] ,george ,simon ,ohm 7#aghi-ahed7 born at ,erlang] 9 ,bav>ia4 ,two in*es ( ,no4 #cf ,g]man silv] wire1 su* z is w\nd ^u ! armature ( ?is volt met]1 gives "o ohm ( resi/ance4 ,!re are #abe in*es ( ?is wire ^u ! armature4 ,its resi/ance is1 !re=e1 #fb4e ohms1 & we may1 !re=e1 say t "o volt ( electric pressure c pu% ?r\gh #fb4e ohms ( resi/ance 4#jaf ( an amp]e ( curr5t4 ,ohm discov]$ ?is relation%ip 9 #ahbg1 & =mulat$ x z foll[s3 volts_/ohms amp]es 7n1 h[ev]1 us+ ^! words74 7#a volt7_/7#fb4e ohms7 4#jaf amp]e4 #fb4e7 #a4jjjj 74#jaf #fbe ---- #cgej #cgej ---- ,?is is call$ ,ohm's law1 z e c&idate = college admission w he> & he> aga94 ,illu/ration3 ,fig4 #fj ,volt met]s & armatures = ! alt]nat+ curr5t h electro-magnets = _! fields z well z = _! armatures4 ,su* in/rum5ts are equally well adapt$ = ei!r direct or alt]nat+ curr5ts4 ,= :5 ! curr5t rev]ses its direction x rev]ses 9 field & armature alike1 & ?us a repulsion betwe5 l poles is ma9ta9$4 ,su* an in/rum5t1 h[ev]1 _c respond to z slight a curr5t z ^? previ\sly describ$1 s9ce !y mu/ consume "s en]gy 9 bo? field & armature4 #bc4 ,telephone ,receiv] 7,fig4 #fa74--;,x requires a /ret* nei!r ( ! imag9ation nor ( ! tru? to call a telephone receiv] an electro-magnet1 al?\gh p]haps x has nev] be5 call$ t be=e4 ,we took x ap>t & f\nd t x consi/$ ( a /eel-b> magnet m 7,fig4 #fb71 ) a small spool ( wire w ar\nd "o end ( x4 ,! ends ( ! wire on ! spool run along inside ! h>d rubb] %ell to ! two b9d+ po/s a & b at ! o!r end4 ,a disk ( %eet iron ,s is held 9 ! l>ge end ( ! case v ne> to1 b n q t\*+1 ! end ( ! magnet4 ,:5 an alt]nat+ curr5t is s5t ?r\gh ! wire ^u ! spool x causes rapid *anges 9 ! /r5g? ( ! magnetic field1 if n rev]sals ( ! poles ( ! field1 & ! iron disk is made to vibrate1 keep+ "t ) ! alt]nations ( ! curr5t4 ,illu/ration3 ,fig4 #fa ,illu/ration3 ,fig4 #fb ,9 ?is laboratory we h se5 t our curr5t has sixty alt]nations p] second4 ,:5 x is connect$ ) ! receiv] ! disk1 !re=e1 makes sixty vibrations p] second1 & produces a tone :i* has v ne>ly ! pit* ( ,c two octaves bel[ ! middle ,c ^u ! piano4 #bd4 ,sp>k ,coil 7,fig4 #fc74--,! automobile sp>k coil :i* we h already us$ is an electro-magnet4 ,! batt]y s5ds a curr5t ?r\gh wire coil$ ar\nd an iron core4 ,at "o end ( ?is iron core is an iron armature :i* is made to vibrate 9 precisely ! same mann] z ! armature ( an electric bell4 ,?is makes & breaks ! curr5t & causes rapid *anges 9 ! /r5g? ( ! field4 ,a rapidly *ang+ magnetic field may be us$ to develop electricity 9 a conductor1 z we h already se5 9 ! case ( ! dynamo4 ,illu/ration3 ,fig4 #fc ,h[ x is us$ 9 ! automobile sp>k coil w be %[n lat]4 ,x is suffici5t n[ to m5tion x z a case ( a magnetic field produc$ by an electric curr5t pass+ ?r\gh a wire coil$ ar\nd an iron core1 or1 9 %ort1 an electro-magnet4 ,induction coils1 ,ruhmkorff coils1 & trans=m]s1 to be describ$ lat]1 are closely relat$ to ?is4 ,!y all create magnetic fields 9 ! same way & are all electro-magnets4 ,illu/ration3 ,fig4 #fd4 ,trans=m]s ,,vii ,,electric ,,heat+ ,x 0 ,wa%+ton's bir?day4 ,! s*ools 7 to h a holiday & ! ,sci5ce ,club 0 to hold a special1 op5 meet+ at :i* ,i _h be5 ask$ to pres5t ! subject ( electricity 9 ! h\sehold4 ,i repli$ to ! programme committee t t 0 too l>ge a subject1 b t ,i w\ld talk ^u electric heat+4 ,i w>n$ !m1 h[ev]1 t x w\ld be a dry /udy1 & n an ent]ta9m5t4 ,!y repli$ t ! fa!r ( 8 c\ntry _h be5 born at a "t ( ! ye> :5 ! wea!r 0 unfav\rable to outdoor sports1 & t ,febru>y usually f\nd !m acclimat$ to vigor\s /udy4 ,nei!r !y nor _! fri5ds object$ to /udy if x seem$ to h a motive4 ,i f\nd an audi5ce compos$ ( old & "y1 m5 & wom51 girls & boys4 ,mo/ ( !m _h left s*ool--_m ( !m because _! tea*]s ?\ght !y 7 incompet5t to cont9ue4 ,illu/ration3 ,fig4 #fe ,n f> f "h is a :eel 9 ! middle ( a :eel 444 z = _! r+s !y are s high t !y are dreadful 444 & ! _s ( ! liv+ creature is 9 ! :eels4 ,^? :eels are n[ s5d+ ! electric curr5t to ?is room = our exp]im5ts4 ,i propose to %[ t we conv]t electricity into heat by (f]+ resi/ance to its fl[4 ,exp]i5ce tea*es u t resi/ance to motion always produces heat4 ,at ,niag>a ,falls ?\s&s ( tons ( wat] desc5d at ! rate ( "o hundr$ & sixty feet 9 ?ree seconds4 ,:5 ! wat] rea*es ! bottom ( ! falls1 x is mov+ a little fa/] ?an a mile a m9ute4 ,! resi/ance :i* ?is mass meets aft] its fall ret>ds its motion & g5]ates heat4 ,hundr$s ( meteors fall into our atmosph]e daily1 travell+ a ?\s& times z fa/ z ! wat]s ( ,niag>a ,falls4 ,! resi/ance to _! motion1 :i* our atmosph]e (f]s1 heats !m :ite hot1 melts !m1 vaporizes !m1 burns !m up1 s t v few ( !m rea* ! solid e>? 9 a solid condition4 ,an iron spile driv]1 measur+ two cubic feet1 weighs ab\t half a ton4 ,:5 x falls sixte5 feet ^u ! end ( a spile x is mov+ at ! rate ( tw5ty miles an h\r4 ,! en]gy ( ?is mov+ mass dep5ds ^u bo? its weight & its velocity1 & :5 its motion is arre/$ by ! spile t en]gy ( motion is l>gely conv]t$ into heat en]gy1 f :i* bo? ! spile & ! spile driv] get hot4 ,a piece ( iron may be made r$ hot by p\nd+ x ) a trip hamm]4 ,c\nt ,rum=d f\nd1 9 #agih1 :ile bor+ cannon 9 ! ars5al at ,muni*1 t ! resi/ance :i* ! iron (f]$ to ! motion ( ! bor+ tool furni%$ heat en\gh to boil wat]4 ,sev5 hundr$ & sev5ty-eight foot p\nds ( me*anical en]gy :5 conv]t$ into heat w\ld raise "o p\nd ( wat] 7"o p9t7 "o degree4 ,?is is call$ ! ,briti% !rmal unit4 ,! spile driv]1 weigh+ #ajjj p\nds1 fall+ #af feet ^u a spile1 produces heat en\gh to raise #a p9t ( wat] #bj degrees4 ,illu/ration3 ,fig4 #ff ,"h are two b9d+ po/s1 a & b1 #h feet ap>t 7,fig4 #ff71 connect$ by copp] wires ) ! dynamo circuit4 ,! volt met] indicates #aab volts ( pressure4 ,i w close ! circuit by /ret*+ betwe5 a & b #h feet ( ,no4 #bd iron wire4 7,?is wire is ab\t ! ?ickness ( a common p947 ,! iron wire (f]s resi/ance to ! fl[ ( ! electric curr5t1 !reby produc+ heat--heat en\gh z y see to make ! wire :ite hot1 inde$ heat en\gh to raise x to some?+ ov] two ?\s& degrees ,fahr41 = n[ y see x has melt$4 ,we w put 9 a fre% piece ( wire & connect also ! ammet] 9 ! circuit 7,fig4 #fg74 ,z ,i close ! circuit ! ne$le ( ! ammet] at fir/ indicates #bj or #cj amp]es1 b 9 a second drops to #h amp]es1 & rema9s !re a second until ! wire melts & falls ap>t4 ,"o hundr$ & twelve volts ( electric pressure are able to pu% #h amp]es ( electricity ?r\gh ?is wire :5 hot4 ,illu/ration3 ,fig4 #fg 7#aab volts7_/7#ad ohms7 #h amp]es #aab volts #h amp]es #hif watts #gdf watts "o horse-p[] ,h5ce x requir$ ab\t "o & "o fif? horse-p[] to melt ! wire 9 a second1 & ! heat produc$ 0 a little less ?an "o ,briti% !rmal unit1 a unit mu* us$ by eng9e]s4 #a p\nd rais$ #a foot #a foot p\nd #eej foot p\nds p] second #a horse-p[] #ggh foot p\nds 7#a4d ,h4-,p47 #a ,b4 ,t4 ,u4 7,briti% !rmal unit7 heat requir$ to raise #a p\nd ( wat] #a ,fahr5heit #a volt #a amp]e #a watt #gdf watts #a horse-p[] ,9 ord] to hold back #aab volts ( electric pressure s t n m ?an eight amp]es ( electricity %\ld pass1 ! iron wire mu/ h (f]$ ab\t #ad ohms ( resi/ance4 ,! behavi\r ( ! ammet] ne$le %[$ t ! wire (f]$ v mu* less resi/ance :5 cold ?an :5 hot4 ,inde$ eight feet ( ,no4 #bd iron wire (f]s ab\t "o & "o ?ird ohms resi/ance :5 cold1 h5ce heat _h increas$ its resi/ance to ! passage ( ! electric curr5t t5fold4 ,?is piece ( iron wire (f]$ resi/ance to ! fl[ ( ! electric curr5t4 ,x (f]$ resi/ance to ! motion ( ! dynamo4 ,?is (f]$ resi/ance to ! /eam-eng9e :i* drives ! dynamo4 ,?is caus$ ! gov]nor ( ! eng9e to op5 & pass m /eam f ! boil]4 ,?is r$uc$ ! pressure at ! /eam gauge4 ,?is caus$ ! fireman to %ovel m coal into ! furnace4 ,! heat ( ! burn+ coal melts ! wire1 b x does x only aft] sev]al *anges4 ,fir/1 x is conv]t$ into me*anical en]gy 9 ! /eam-eng9e ) great loss--ab\t n9e t5?s be+ lo/4 ,second1 x is conv]t$ into electrical en]gy by ! dynamo1 ) "s loss1 &1 ?ird1 x is conduct$ to ! iron wire & conv]t$ back to heat ) /ill fur!r loss4 ,x is evid5t t ! mo/ economical way to heat ! wire w\ld be to take x to ! furnace4 ,yet all electric cook+ is done by s5d+ electric curr5t ?r\gh wires emb$d$ 9 ! walls ( ! cook+ ut5sils1 & x is ! mo/ wa/eful me?od ( us+ ! en]gy /or$ 9 coal t has yet be5 devis$4 ,illu/ration3 ,fig4 #fh ,t m]ely connect+ ! b9d+ po/s a & b 7,fig4 #fg7 by a small piece ( wire %\ld ?r[ a load ^u ! dynamo miles away2 %\ld (f] resi/ance to its motion1 & make x require #a4ah horse-p[] m ( en]gy to keep up its spe$ ( revolution1 is1 inde$1 uncanny4 ,i w attempt to make x seem m real4 ,at "o end ( ! lecture table ,i h a rot>y pump ,p 7,fig4 #fh74 ,! end ( ! rubb] tube a1 :i* leads to ! pump is ly+ ^u ! table outside ( ! tank ( wat]1 ,t4 ,:ile ?+s are 9 ?is condition ,i move ! crank :i* op]ates ! pump ) p]fect ease4 ,n[ :ile /ill turn+ ! crank ,i pick up ! tube a & drop its free end into ! wat] tank4 ,i _c n[ conceal ! fact1 ev5 if ,i 7 dispos$ to d s1 t ,i mu/ "w h>d to keep ! pump go+4 ,! pump itself tells y by its lab\r$ s\nd t x is work+ h>d1 & ! /ream ( wat] :i* issues f ! pipe b tells h[ mu* "w ,i am p]=m+4 ,! pump is dis*>g+ five & a half p9ts ( wat] p] second1 t is #e4e p\nds1 & x raises ?is wat] #aj feet4 ,h5ce ,i am do+ #ee foot p\nds ( "w p] second1 :i* requires "o t5? ( a horse-p[]4 ,"h is a lad :o cons5ts to try ! exp]im5t = u4 ,he turns ! crank easily :ile ,i am hold+ ! tube a out ( ! wat]1 b :5 ,i l[] x into ! wat] he f9ds ! resi/ance s great t1 tug h[ev] mu* he may1 he is unable to keep ! pump go+4 ,at ! o!r end ( ! table ,i h a small h& dynamo1 ,d 7,fig4 #fh71 ,m is an ammet]1 ,v is a volt met]1 ,s is a swit*4 ,all ! wires are good-siz$ copp]1 & (f] little resi/ance1 except t /ret*$ betwe5 ! b9d+ po/s a & b4 ,?is is a piece ( f9e ,g]man silv] wire4 ,:ile ! swit* is op5 ,i turn ! crank ( ! dynamo ) p]fect ease4 ,a small am\nt ( curr5t is go+ ?r\gh ! volt met]1 b ?is is too slight to (f] any p]ceptible resi/ance to ! motion ( ! ma*9e4 ,notice t ! volt met] ne$le moves accord+ to ! spe$ ( revolution4 ,if ,i turn ! crank once a second ! ne$le /&s at #be volts4 ,! electric pressure increases or decreases accord+ to :e!r ,i rotate ! armature fa/] or sl[]4 ,n[ ,i w attempt to keep ! ma*9e revolv+ at a con/ant rate :ile ,i close ! swit* ,s1 & surely y mu/ see t ,i h h>d "w to d s4 ,! wire a b has n[ become r$ hot4 ,! volt met] %[s #be volts ( pressure1 & ! ammet] %[s #c amp]es ( curr5t4 ,tw5ty-five volts #c amp]es #ge watts1 :i* require "o t5? ( a horse-p[] 7#gdf watts #a horse-p[]74 ,! lad n[ takes my place at turn+ ! ma*9e & f9ds x easy :5 ! swit* is op51 b ,i actually ov]load him by m]ely clos+ ! swit*4 ,heat+ ! wire r$ hot requires m en]gy ?an he is able to put =?4 ,i propos$ to ! presid5t t my lecture close at ?is po9t1 & t ea* "o 9 ! room h a *ance to feel ! load :i* 0 ?r[n ^u ! dynamo ea* "t x 0 requir$ to heat ! wire4 ,i sugge/$ t ea* p]son %\ld get a realiz+ s5se ( ?is fact1 fir/ by do+ ! "w himself1 & second by go+ home & reflect+ ^u ?is h9t4 ,:5 ! swit* is clos$ ?ree amp]es ( electricity pass ar\nd ! circuit4 ,?is increases ! magnetism 9 bo? ! field & ! armature ( ! dynamo1 & x requires "o t5? ( a horse-p[] m to keep ! armature mov+ )9 ! field aga9/ ?is magnetic pull4 ,i fur!r desir$ to ann\nce t dur+ ?is h\r ,i _h deliv]$ to !m ! second key to ! ,electrical ,%[ :i* ,i _h promis$ a few days ago4 ,! second key is3 ,heat 7& light7 is produc$ by (f]+ resi/ance to ! fl[ ( ! electric curr5t4 ,! fir/ key is ! electro-magnet4 ,^! two unlock all ! my/]ies ( ! %[4 ,! presid5t clos$ ! =mal ex]cises ) ! faceti\s rem>k t ,i _h w>n$ !m be=e ! lecture t !y mu/ "w1 s n[ ea* w\ld be expect$ to take a turn at ! cranks ( ! pump & dynamo4 ,,viii ,,applications ,,( ,,electric ,,heat+ ,! programme committee decid$ t ea* memb] ( ! ,sci5ce ,club %\ld busy himself look+ = applications ( electric heat+ & %\ld consult me freely ab\t ! matt]4 ,my telephone 0 kept busy1 my laboratory 0 9 great dem&1 & we 7 all gett+ a good deal m education ?an ! s*ool 0 giv+ u cr$it =4 ,! boys g5]ally came to me 9 pairs1 & ea* pair hav+ work$ up "s illu/ration ( heat produc$ by electricity report$ x to ! club4 ,^! 7 spread by ! secret>y 9 due =m ^u ! m9utes ( ! club & con/itut$ ,! ,proce$+s ( ! ,sci5ce ,club4 ,illu/ration3 ,fig4 #fi #a4 ,! ,electric ,sad ,iron 7,fig4 #fi74--,remov+ ?ree screws ! iron comes ap>t1 reveal+ a lot ( ,no4 #bd ,g]man silv] wire w\nd ^u a %eet ( mica4 ,?is is put betwe5 o!r %eets ( mica 7,fig4 #gj7 & tuck$ away )9 ! body ( ! iron4 ,g]man silv] (f]s ab\t twice ! resi/ance ( iron :5 x is cold1 b1 at ! temp]ature ( ! sad iron :5 9 use1 !re is n mu* diff]5ce betwe5 ! resi/ance ( ! two metals4 ,g]man silv] wire1 h[ev]1 does n ru/ z iron wire w\ld1 & h5ce x is *os54 ,g]man silv] is an alloy ( copp]1 z9c1 & nickel4 ,illu/ration3 ,fig4 #gj ,we put ! #aab-volt curr5t ^u ?is wire ( ! iron1 & accord+ to ! ammet] x pass$ #d amp]es4 ,its resi/ance mu/ !re=e h be5 #bh ohms4 7#aab volts7_/7#bh ohms7 #d amp]es ,electricity co/s u ab\t #aj c5ts p] kil[att h\r4 ,t is #aj c5ts = #ajjj watts = an h\r1 or #a c5t = a hundr$ watts = an h\r1 or1 on a #ajj-volt curr5t1 #a c5t = an amp]e = an h\r4 ,x1 !re=e1 co/s ab\t #d c5ts or1 m accurately1 #d-a_/b c5ts an h\r to heat ?is iron4 ,p]sons sometimes c>ry electric irons ) !m1 :5 !y travel1 to iron pocket h&k]*iefs & o!r small articles :ile /opp+ at a hotel4 ,be=e connect+ an iron 9 a *&eli] "o mu/ "k ! voltage us$ 9 ! build+4 ,if ! voltage 9 use 9 ! build+ is n ! same z t /amp$ ^u ! iron1 x is n safe to connect x4 ,n kn[+ ?is1 _m p]sons h _h ! emb>rassm5t ( bl[+ a fuse & ext+ui%+ _! own lights1 & p]haps ^? ( o!rs 9 ! same build+1 & v likely also ru9+ ! iron4 ,suppose we take = example ?is iron /amp$ #aaj ,v2 #djj ,watts4 7,a slight v>iation ( #e or #aj volts w n injure an iron47 ,! wire 9 ?is iron we f\nd to (f] ab\t #bh ohms resi/ance :5 hot1 & x lets pass #d amp]es4 ,?is is ab\t all ! curr5t :i* x is able to c>ry )\t melt+4 ,n[ suppose a #bbj-volt curr5t is us$ 9 ! build+ :]e x is propos$ to connect ! iron4 ,?is w\ld =ce ?r\gh ! wire en\gh curr5t to melt x4 ,! wire 0 se5 to be at a v dull-r$ heat :5 exam9$ 9 a d>k room4 ,its temp]ature 0 ab\t n9e hundr$ degrees4 ,at ?is temp]ature its resi/ance is ab\t ?ree times :at x is :5 cold4 ,we e/imat$ by measurem5ts t ! iron conta9$ ab\t tw5ty-five feet ( ! wire4 ,! boys !n took tw5ty-five feet ( ,no4 #bd ,g]man silv] wire & /ret*$ x betwe5 two nails driv5 up 9 ! laboratory 7,fig4 #ga1 a b74 ,! dynamo curr5t 0 !n s5t ?r\gh ?is4 ,! end1 c1 ( ! wire f ! dynamo 0 provid$ ) a metal clip :i* c\ld be slid along on ! ,g]man silv] wire4 ,slid+ ?is to ! left1 & ?us %ort5+ ! di/ance on ! ,g]man silv] wire ?r\gh :i* ! curr5t mu/ pass1 increas$ ! am\nt ( curr5t & heat$ ! wire hott]4 ,! resi/ance decreases z ! wire is %ort5$4 ,illu/ration3 ,fig4 #ga ,! boys w\nd ?is wire ^u a piece ( asbe/os bo>d 7,fig4 #gb71 ab\t n9e in*es squ>e & "o eigh? ( an in* ?ick1 tak+ c>e to keep ! successive turns half an in* ap>t4 ,asbe/os pap] 0 wrapp$ ar\nd ?is4 ,! two ends ( ! wire 7 left free = connections4 ,?is !y call$ a hot plate4 ,illu/ration3 ,fig4 #gb #b4 ,electric ,hot ,plate 7,fig4 #gc74--,?is :5 op5$ 0 f\nd to h wire coil$ up inside 9 ! same mann] z ! sad iron4 ,inde$ ! sad iron support$ bottom side up makes a p]fectly good hot plate4 ,! p>ticul> hot plate :i* we exam9$ _h a ?ree-po9t swit* :i* gave ?ree diff]5t heats = ! plate4 7,see ,fig4 #gd47 ,:5 ! swit* ,s is ^u ! fir/ po9t ! curr5t goes ?r\gh #aab ohms ( resi/ance & #a amp]e passes3 7#aab volts7_/7#aab ohms7 #a amp]e ,illu/ration3 ,fig4 #gc ,illu/ration3 ,fig4 #gd ,?is w>ms ! plate slightly--en\gh to keep food w>m :i* has be5 already cook$4 ,?is co/s ab\t "o c5t an h\r4 ,:5 ! swit* is plac$ ^u ! second po9t ! curr5t goes ?r\gh #ef ohms ( resi/ance & #b amp]es pass4 7#aab volts7_/7#ef ohms7 #b amp]es4 ,?is makes ! plate w>m] & is adapt$ to c]ta9 cook+ processes4 ,x co/s ab\t two c5ts an h\r4 ,:5 ! swit* is plac$ ^u ! ?ird po9t ! curr5t goes ?r\gh #bh ohms ( resi/ance & #d amp]es pass4 7#aab volts7_/7#bh ohms7 #d amp]es4 ,illu/ration3 ,fig4 #ge ,we plac$ ^u ?is hot plate a bas9 conta9+ #a p9t ( wat] 7equals #a p\nd7 & heat$ x f ! temp]ature ( ! room 7#fh degrees7 to boil+ 7#bab degrees7 9 #g m9utes & !n put an egg 9 & boil$ x #c m9utes4 ,us+ #d amp]es = #aj m9utes co/ two ?irds ( a c5t4 ,if x takes #g m9utes to boil a p9t ( wat] x w\ld require #a h\r to boil a gallon ^u ?is hot plate us+ #d amp]es1 or #ddh watts4 ,t is1 x co/s u ab\t #d4e c5ts a gallon to boil wat] by electricity4 ,! co/ is usually put at ?ree & a half c5ts p] gallon1 b mu* dep5ds ^u conditions4 #c4 ,travell]'s ,cook] 7,fig4 #ge74--,?is consi/s ( a hot plate ) a cov]$ bas9 p]man5tly atta*$ to x4 #d4 ,electric ,c(fee ,p]colator 7,fig4 #gf7 consi/s ( a hot plate ) a c(fee p]colator to sit ^u x4 ,! c(fee p]colator might sit ^u any o!r hot plate or ?is hot plate might s]ve any o!r purpose1 b p d n seem to ?9k ( t4 ,illu/ration3 ,fig4 #gf #e4 ,electric ,*af+-,di% 7,fig4 #gg7 consi/s m]ely ( an electric hot plate ) a *af+-di% atta*$4 ,! electric c(fee p]colators & *af+ di%es require f #cjj to #fjj watts accord+ to size4 ,if us$ on ! #aaj-volt curr5t !y take ab\t #c to #f amp]es1 & if adapt$ to ! #bbj-volt curr5t !y take f #a-a_/b to #c amp]es1 b co/ ! same to op]ate 9 ei!r case4 ,!y h connect$ ) !m flexible cords & plugs to screw into ! lamp sockets4 ,illu/ration3 ,fig4 #gg #f4 ,electric ,broil]s are m]ely hot plates1 g5]ally corrugat$ to conduct (f ! melt$ fat4 ,"o t we exam9$ _h a swit* = ?ree heats3 l[1 requir+ #cfj watts--co/s #c4f c5ts p] h\r2 m$ium1 requir+ #fjj watts--co/ #f c5ts p] h\r2 high1 requir+ #abhj watts--co/ #ab4h c5ts p] h\r4 #g4 ,electric ,ov54--,?is "o has d\ble walls to reta9 ! heat & has two l>ge hot plates1 "o on ! bottom & "o on ! top4 ,x is l>ge en\gh to hold f\r loaves ( bread4 ,x requir$ #aebj watts = #dj m9utes to heat x to ! bak+ temp]ature & "o h\r to bake ! bread4 ,h5ce ! co/ ( ! electricity is ab\t #be c5ts1 ab\t :at ! bread w\ld co/ 9 ! m>ket4 #h4 ,electric ,incubator4--,?is is simply a well-v5tilat$ ov5 w>m$ by an electric hot plate & automatically controll$ s t x keeps a con/ant temp]ature ( #ajc degrees4 ,"u ^! conditions *ick5s hat* f h5s' eggs 9 ?ree weeks4 ,an incubator = #e doz5 eggs 0 f\nd to take #be c5ts' wor? ( electricity = ! :ole process ( incubation4 #i4 ,electric ,toa/]4--,! wire coil$ up 9 sad irons & hot plates becomes hot en\gh to scor* clo? & pap]1 & ev5 set fire to !m if !y come 9 direct contact4 ,we prov$ ?is by op5+ ! iron & t\*+ pap] to ! wire :ile x 0 c>ry+ ! curr5t4 ,we also light$ a cig> by t\*+ x to ! wire4 ,electric toa/]s h ! hot ,g]man silv] wire simply cov]$ by a scre54 #aj4 ,electric ,cig> ,light]s 7,fig4 #gh74--,! "o we exam9$ hung by a flexible cord f ! *&eli]4 ,x _h a small disk on ! side :i* conta9$ a lot ( f9e wire cov]$ by p]=at$ mica4 ,! wire became r$ hot :5 ! pu% button 9 ! h&le 0 press$4 ,x took half an amp]e ( #aaj-volt curr5t1 & op]at$ only :ile ! button 0 pu%$4 ,z ne> z we c\ld calculate x co/ 4#jjjc ( a c5t to light a cig>4 ,illu/ration3 ,fig4 #gh ,illu/ration3 ,fig4 #gi #aa4 ,electric ,curl+ ,iron 7,fig4 #gi74--,"o :o has flat hair ne$s no curl+ iron1 b ^? :o h r\nd hair may curl x tempor>ily1 if !y w unscrew an electric light bulb & screw into its socket ! plug ( an electric curl+ iron4 ,! flexible cord conta9s two wires insulat$ f ea* o!r4 ,"o ( ^! wires is atta*$ to ! out] %ell ( ! plug1 ! o!r wire is atta*$ to ! c5tral button ( ! plug4 ,^! make connections ) ! two sep>ate dynamo wires 9 ! socket4 ,! curr5t comes d[n "o ( ! wires 9 ! flexible cord1 passes ?r\gh a coil ( f9e ,g]man silv] wire inside ( ! curl+ iron1 & returns by ! o!r wire 9 ! flexible cord4 ,! small wire 9 ! curl+ iron (f]s #bbj ohms ( resi/ance :5 hot & passes half an amp]e ( ! #aaj-volt curr5t4 7#aaj volts7_/7#bbj ohms7 4#e amp]e4 #ab4 ,electric ,sold]+ ,irons 7,fig4 #hj74--,or copp]s1 z !y %\ld be call$1 are ideal implem5ts = sold]+4 ,!y rema9 cont9ually at ! prop] temp]ature & are free f corrosion4 ,!y require f #ee to #bbj watts4 ,on ! #aaj-volt curr5t !y take f "o half to two amp]es4 ,illu/ration3 ,fig4 #hj #ac4 ,electric ,heat+ ,pad 7,fig4 #ha74--,?is consi/s ( resi/ance wire inside ( a pad ( s(t mat]ial4 ,x ma9ta9s a temp]ature ( #ahj degrees1 & is an excell5t sub/itute = a hot wat] bag4 ,x conta9s ab\t two hundr$ & tw5ty ohms ( resi/ance & requires ! same curr5t z a #af-;c&le-p[] lamp4 ,illu/ration3 ,fig4 #ha #ad4 ,electric ,fuses 7,fig4 #hb74--;,fuses are made ( %ort pieces ( wire or ?9 %eet metal4 ,! metal is an alloy ( lead & t9 :i* melts at a l[ temp]ature4 ,!y d]ive _! "n f ! fact t !y readily fuse or melt4 ,a build+ is wir$ 9 v>i\s sep>ate circuits4 ,! size ( ! copp] wires us$ 9 ea* circuit is det]m9$ by ! am\nt ( curr5t :i* ! circuit is expect$ to c>ry4 ,ea* circuit is protect$ by "o or m fuses4 ,^! melt & cut (f ! curr5t :5ev] too mu* passes = ! copp] conductor to c>ry )\t gett+ hot4 ,! fuse wire melts at ab\t six hundr$ degrees1 :ile ! copp] w n melt until x rea*es ne>ly two ?\s& degrees4 ,?is temp]ature is suffici5t to set fire to wood1 pap]1 & clo?4 ,:5 any fuse melts1 ! curr5t is cut (f f all *&eli]s1 etc41 9 ! p>ticul> circuit controll$ by ! fuse4 ,?is produces con/]nation among p :o d n und]/& ! function ( a fuse4 ,!y become panic-/rick5 & beg9 to trample _! neighb\rs to dea? 9 ! !atre or on ! electric tra9 :5 !y he> t a fuse is bl[n 7:i* is ! electrician's way ( say+ t x has melt$74 ,ev]yone %\ld "k t a fuse is a safety device4 ,x is always enclos$ 9 a box l9$ ) %eet iron or asbe/os1 s t x is impossible = ! fla%1 :i* occurs :5 ! circuit is brok51 to set fire to any?+4 ,illu/ration3 ,fig4 #hb ,illu/ration3 ,fig4 #hc #ae4 ,electric ,gas ,light] 7,fig4 #hc74--,^! usually h two or ?ree small1 dry batt]y cells 9 ! h&le4 ,by pu%+ a button 9 ! h&le connection is made betwe5 ?is batt]y & a %ort piece ( resi/ance wire 9 ! tip4 ,?is wire gets r$ hot & lights ! gas4 ,x is a surprise to _m t we c light illum9at+ gas )\t br++ a flame to x1 & x is equally surpris+ t "s flames1 or at lea/ sp>ks1 may n be able to light ! gas4 ,! fact is t x is :olly a matt] ( temp]ature & k9d ( gas4 ,iron heat$ to dull r$ w n light ! illum9at+ gas n[ be+ furni%$ 9 ,new ,york ,city1 :ile iron at a bright r$ heat w d s4 ,iron may be hot en\gh to light illum9at+ gas b too cool to light gasol5e vap\r1 :i* requires a dazzl+ :ite heat4 ,iron :i* is j "u ! temp]ature at :i* x gives any light may set fire to wood & pap]4 ,aft] x has cool$ a good deal bel[ t1 x w set fire to sulphur1 & :5 x has cool$ s t "o may hold x 9 ! h&1 x is /ill hot en\gh to set fire to phosphorus4 ,! gl[+ end ( a light$ cig>1 ! sp>k made by /rik+ fl9t1 or ! sp>k f a sp>k coil ) a feeble batt]y1 all fail to set fire to gasol5e vap\r1 simply because !y are n hot en\gh4 ,fre% batt]y cells mu/ occasionally be put 9 ! h&le ( ! electric gas light]4 ,f\r facts reg>d+ ! resi/ance ( wires x is well to rememb]3 #a4 ,! long] ! wire ! m resi/ance x (f]s to ! electric curr5t4 #b4 ,! small] ! diamet] ( ! wire ! m resi/ance x (f]s4 #c4 ,"s mat]ials (f] m resi/ance ?an o!rs1 = example1 iron ab\t six times z mu* z copp] & ,g]man silv] ab\t twelve times z mu* z copp]4 #d4 ,! common metals (f] m resi/ance :5 hot ?an :5 cold1 ab\t d\ble ! resi/ance :5 heat$ to five hundr$ degrees4 ,x is ! rev]se ) c>bon1 :i* (f]s m resi/ance :5 cold ?an :5 hot4 ,! c>bon filam5t lamp (f]s ab\t d\ble ! resi/ance :5 cold z :5 light$ to full brilliancy4 #af4 ,electric ,fla%] 7,fig4 #hd74--;,= automatically fla%+ electric lights4 ,! "o :i* we exam9$ 0 con/ruct$ accord+ to ! plan %[n 9 ,fig4 #he4 ,! light+ circuit is br\ght to ! b9d+ po/s b & c4 ,a small insulat$ wire ( high resi/ance connects b & c1 be+ w\nd ar\nd ! metal b> a b4 ,! resi/ance ( ?is wire1 :5 add$ to t ( lamps1 p]mits n m ?an "o fif? ( an amp]e to pass1 & ?is w>ms ! wire slightly4 ,! b> a b is compos$ ( two /rips ( metal1 brass above & iron bel[4 ,heat exp&s brass m ?an iron4 ,! result is t :5 ! curr5t is turn$ on1 ! b> beg9s to curve d[nw>d until pres5tly x t\*es ! metal base ( c4 ,!n ! full curr5t requir$ to light ! lamps :i* are 9 circuit passes4 ,:ile ! circuit is clos$ ?r\gh ! l>ge metal /rips n en\gh passes ?r\gh ! f9e wire to w>m x4 ,on cool+1 a b curves upw>d & breaks ! connection ) c1 & n[ ! curr5t beg9s aga9 to w>m up ! small wire4 ,illu/ration3 ,fig4 #hd ,illu/ration3 ,fig4 #he ,! fla%] t we exam9$ 0 adapt$ to op]ate3 "o #cb-;c&le-p[] lamp2 or two #af-;c&le-p[] lamps2 or f\r #h-;c&le-p[] lamps1 on a "o amp]e circuit ( #aaj-volt pressure4 ,let u see :at w\ld happ5 if x 7 connect$ ei!r ) a curr5t ( high] voltage or a circuit ( m lamps4 ,suppose we h a #cb-;c&le-p[] c>bon filam5t lamp 9 circuit4 ,?is requires "o amp]e to light x4 ,its resi/ance :5 hot is #aaj ohms4 7#aaj volts7_/7#aaj ohms7 #a amp]e4 ,:5 cold its resi/ance is ab\t d\ble or #bbj ohms4 ,! ,g]man silv] wire ( ! electric fla%] (f]s #ccj ohms ( resi/ance1 & toge!r !y make #eej ohms4 ,?us ! curr5t is cut d[n to 4#b amp]e4 7#aaj volts7_/7#ccj #bbj ohms7 4#b amp]e ,suppose n[ we %\ld und]take to use ! same fla%] & ! same lamp on a #bbj-volt curr5t4 ,?is might pu% m curr5t ?r\gh ?an ! small wire c\ld c>ry4 ,x might melt1 or its insulation might burn (f be=e a made contact ) b2 if n ! lamp w\ld c]ta9ly burn out aft] ! contact4 ,if we und]took to op]ate ) ?is fla%] sev]al #cb-;c&le-p[] lamps in/ead ( "o ^u ! #aaj-volt circuit1 ! result w\ld be ! same1 = 9 t case ! resi/ance w\ld be r$uc$ &1 !re=e1 a great] curr5t w\ld pass ?an ! wire c\ld c>ry )\t undue heat+4 ,illu/ration3 ,fig4 #hf ,! boys 7 at fir/ tr\bl$ to see h[ increas+ ! numb] ( lamps 9 a circuit w\ld decrease ! resi/ance 9 t circuit4 ,fig4 #hf 0 drawn to expla9 ! matt]4 ,! lamps l1 l1 l1 etc41 are connect$ 9 p>allel4 ,ea* lamp makes an indep5d5t connection f "o fe$ wire to ! o!r4 ,! fla%] a acts z a swit* to close ! circuit = ! :ole4 ,n[ if we ?9k ( ^! wires z pipes to conduct wat] we w\ld say t wat] fl[s f ,d to ,e ?r\gh t5 pipes m readily ?an ?r\gh "o4 ,x w\ld meet ) only "o t5? z mu* resi/ance4 ,! result w\ld be ! same1 if we %\ld sub/itute = ! t5 pipes "o pipe t5 times z l>ge 9 cross section4 ,s x is ) wires :i* are conduct+ electricity4 ,introduce two 9 p>allel1 & y all[ twice z mu* curr5t to pass by r$uc+ ! resi/ance to "o half4 ,t5 p>allel conductors r$uce ! resi/ance to "o t5? & all[ t5 times z mu* curr5t to pass4 ,illu/ration3 ,fig4 #hg ,x is to be notic$ t ?is fla%] is an automatic swit* :i* is op5$ or clos$ accord+ to temp]ature4 ,remove ! f9e wire f a & we h precisely ! device :i* regulat$ ! temp]ature 9 our electric incubator4 ,suppose ! !rmo/at 7z x is call$ 9 t case7 is plac$ )9 ! egg *amb] :i* is to be kept at #ajc degrees4 ,a screw 9 ! metal /rip c und]nea? ! end ( a may be set s t x w normally t\* a4 ,suppose n[ ! brass /rip is und]nea? ! /rip ( iron 9 a4 ,z ! hot plate w>ms up ! egg *amb]1 ! brass w exp& m ?an ! iron1 & ! b> w curve upw>d & break ! connection ) c4 ,z soon z ! curr5t /ops ! temp]ature ( ! *amb] beg9s to fall1 & ! b> curves d[nw>d aga9 until connection is made4 ,?is device is capable ( adju/m5t s z to keep ! temp]ature con/antly at #ajc degrees or any o!r desir$ degree4 ,! device is 9 use = scores ( diff]5t purposes1 includ+ ! regulation ( temp]ature 9 s*ool rooms4 #ag4 ,electric ,c> ,heat]s4--,t5 or fifte5 ye>s ago !re 7 no heat$ /reet c>s 9 ,new ,york ,city4 ,n[ !y are all heat$ by electricity & _! maximum & m9imum temp]atures are regulat$ by law4 ,! resi/ance wire may be se5 9 coils und]nea? ! c> seats4 ,electric /reet c>s usually op]ate on a #ejj or #fjj-volt curr5t4 ,! am\nt ( curr5t us$ = heat+ v>ies f #b to #ab amp]es4 ,p]haps #c amp]es may be tak5 z an av]age4 #ejj ,v #c a #aejj w #a-a_/b kil[atts4 ,x co/s ! l>ge electric railway companies ab\t #a4e c5ts p] kil[att h\r to g5]ate _! supply ( curr5t4 ,eighte5 h\rs is consid]$ a c> day4 #a-a_/b kil[atts #ah h\rs #bg kil[att h\rs4 #bg kil[att h\rs at #a4e c5ts #dj c5ts p] c> day4 #ah4 ,heat+ ,ap>tm5ts by ,electricity4--,= heat+ ap>tm5ts by electricity ! same sort ( app>atus is us$ z t already describ$ = heat+ c>s4 ,a family ( f\r adults1 liv+ 9 an eight-room ap>tm5t ) at lea/ #abj cubic feet ( fre% air admitt$ p] m9ute1 w use on an av]age t5 amp]es ( ! #aaj-volt curr5t4 ,! co/ w be ab\t two doll>s & fifty c5ts p] day or sev5ty-five doll>s p] mon?4 ,al?\gh ?is is z mu* z ! entire r5tal ( a p]fectly com=table ap>tm5t1 ! novelty & ! conv5i5ce attract t5ants & ! extra co/ ( r5t does n det] !m4 ,illu/ration3 ,fig4 #hh #ai4 ,electric ,b$room ,heat]4--,"o ( ! boys con/ruct$ a heat] = 8 own room z foll[s3 ,he procur$ a box eight in*es deep by eighte5 in*es squ>e on ! bottom4 ,?is he l9$ ) asbe/os pap]4 ,he !n /ood x ^u its side & arrang$ f\r inc&esc5t light sockets z %[n 9 ,fig4 #hh4 ,^! 7 connect$ by a flexible cord to a plug :i* he c\ld ins]t 9 place ( a lamp 9 ! *&eli]4 ,he plac$ ?is heat] on ! floor und]nea? ! w9d[ & usually _h #af-;c&le-p[] lamps 9 ! sockets4 ,he claim$ t x 0 a jolly foot w>m] & kept ! room com=table )\t o!r heat4 ,he turn$ on f "o to f\r lamps accord+ to 8 ne$ & replac$ ! #af-;c&le-p[] lamps by #cb-;c&le-p[] lamps :5 ! wea!r 0 extremely cold4 ,i rem>k$ t he mu/ h light along ) heat by ?is arrangem5t1 & ,i %\ld ?9k t might be objectionable :5 he desir$ to sleep at night4 ,he said t he always turn$ x (f1 & op5$ ! w9d[ at night1 always pref]r+ a cold room to sleep 94 ,illu/ration3 ,fig4 #hi #bj4 ,cook+ ) ,inc&esc5t ,lamps4--,?is piece ( app>atus 0 devis$ by ! boys & us$ 9 my laboratory4 ,a %eet iron bas9 a1 0 inv]t$ ov] f\r #af-;c&le-p[] inc&esc5t lamps1 %[n 9 elevation by ,fig4 #hi1 & %[n 9 plan by ,fig4 #ij4 ,! sides ( ! bas9 7 cut s z to admit ! glass globes ( ! lamps1 b ! sockets & keys 7 outside1 s t x 0 conv5i5t to turn on & (f ! lamps sep>ately1 ?us us+ "o half to two amp]es ( curr5t1 z desir$4 ,?is re/$ ^u ano!r bas91 b4 ,bas9 b 0 cov]$ ) asbe/os = ! lamps to lie on & ! :ole 0 atta*$ to a bo>d base1 c4 ,a flexible cord & plug all[$ u to atta* ?is to ! *&eli]4 ,a p9t ( wat] 0 boil$ ^u ?is /ove 9 fifte5 m9utes1 & refre%m5ts h be5 s]v$ hot f x repeat$ly4 ,illu/ration3 ,fig4 #ij #ba4 ,electric ,fireless ,cook]4--,!re are five indictm5ts aga9/ ord9>y cook+ processes4 #a4 ,!y heat ! h\se 9 summ]4 #b4 ,!y conv]t :at w\ld be pleasant flav\rs 9 ! food into noxi\s od\rs ab\t ! h\se4 #c4 ,!y _c be controll$ ) reg>d to "t & temp]ature z sci5tific exp]im5ts %\ld be4 #d4 ,!y conf9e ! cook too closely & are n suffici5tly automatic4 #e4 ,!y are wa/eful ( fuel4 ,x w\ld seem t electricity might enable u to cure mo/ ( ^! evils4 ,to be sure ! production ( heat by electricity is wa/eful ( fuel1 & x seems d\btful h[ ! acc\nt w balance reg>d+ ! fif? item4 ,b ! rema9+ f\r items furni% a v hopeful field = rese>*4 ,i use ! la/ ^w advis$ly1 & ?9k x is j z applicable to high s*ool boys z to univ]sity /ud5ts4 ,aft] exp]im5t+ a:ile ! boys & ,i conclud$ to give a d9n] p>ty 9 ! laboratory & invite a few fri5ds to te/ ! results ( our cook+4 ,we procur$ a cyl9d] ( magnesia su* z is us$ = cov]+ l>ge /eam-pipes4 ,?is 0 inv]t$ ov] our electric /ove :i* 0 illu/rat$ 9 ,fig4 #hi4 ,! magnesia 0 cut at ! bottom1 s z to give access to ! key sockets ( ! lamps1 7,fig4 #ia74 ,fir/ ^u ! electric /ove 0 plac$ a cov]$ di% conta9+ a roa/ ( lamb4 ,above ?is 0 ano!r di% conta9+ a vegetable1 & ^u ! top ( t 0 a pudd+4 ,a flat piece ( magnesia 0 us$ z a cov] to ! :ole4 ,?r\gh a hole 9 ?is 0 susp5d$ a !rmomet]4 ,illu/ration3 ,fig4 #ia ,?is fireless cook] 0 sitt+ 9 ! c5tre ( ! d9n] table :5 ! gue/s ga!r$ ar\nd x4 ,we _h ^! problems = inve/igation3 #a4 ,w ?is cook] heat ! h\se 9 summ]8 ,all te/ifi$ t !y did n "k t !re 0 any heat ab\t x until !y laid _! h&s ^u x1 & !n !y f\nd x only v slightly w>m4 #b4 ,is !re any smell ( cook+ "h8 ,! process has be5 c>ri$ on f />t to f9i% "r on ?is table4 ,all agre$ t no smell c\ld be detect$4 ,i !n turn$ (f ! electric curr5t :i* _h be5 runn+ until n[ & s]v$ ! meat & vegetable1 leav+ ! pudd+ inside to be kept w>m by ! hot walls ( ! cook]4 #c4 ,reg>d+ ! control ( ! process3 we 7 us+ #cb-;c&le-p[] lamps1 :i* gave u a v>iable curr5t1 f #j to #d amp]es1 & a wat* & a !rmomet]4 ,we _h control1 b z yet lack$ k ( h[ x %\ld be us$4 ,9 ! pres5t case we _h arbitr>ily decid$ to beg9 ) temp]ature ( #djj degrees1 cont9ue x = #bj m9utes1 !n turn (f all ! electric curr5t1 & let ! temp]ature fall gradually4 ,?is _h be5 done at our conv5i5ce 9 ! morn+ be=e s*ool4 ,at a qu>t] be=e twelve we _h f\nd ! temp]ature at #bjj degrees1 & turn$ on all ! curr5t1 & n[1 at five m9utes pa/ twelve o'clock1 all te/ifi$ t ! lamb 0 p>ticul>ly good--nei!r too well done nor und]cook$1 & t its flav\r 0 bett] ?an usual4 ,z = economy ( fuel1 we f9d at lea/ t we get bett] results f inc&esc5t lamps ?an f hot plates us$ 9 ! same app>atus1 & ! electric equipm5t enables u to put ! heat exactly :]e x is ne$$ & n[h]e else4 #bb4 ,inc&esc5t ,lamp4--,we feel q ju/ifi$ 9 putt+ ! inc&esc5t lamp "u ! head+1 ,applications ( ,electric ,heat+1 s9ce ! electric lamps 9 g5]al use conv]t #if p] c5t4 ( ! electric en]gy into heat & only #d p] c5t4 into light4 ,!y 7 orig9ally made by introduc+ a %ort piece ( f9e wire into ! circuit1 *oos+ ! k9d ( wire1 its diamet]1 & its l5g? s z to make ! prop] relation betwe5 resi/ance & voltage1 9 ord] t en\gh curr5t might pass to make x :ite hot1 b n q melt x4 ,plat9um wire 0 fir/ *os5 because x w\ld /& ! highe/ heat )\t melt+ & )\t ru/+4 ,we w pass our #aab-volt curr5t ?r\gh #i feet ( ! ,no4 #bd iron wire4 ,! wire is heat$ to bright r$1 b does n melt z x did :5 we us$ #h feet 9 a =m] exp]im5t4 ,! increas$ l5g? has add$ resi/ance1 &1 z y see by ! ammet]1 cut ! curr5t d[n f #h to #g4e amp]es4 ,i w n[ d>k5 ! room & y f9d t x is giv+ light en\gh to read by4 ,b y notice t ! light is gr[+ dimm]1 its col\r is gr[+ r$d]1 & ! ammet] indicates t less curr5t is pass+4 ,i w cut (f ! curr5t & let y exam9e ! wire & y notice t a cru/ has =m$ ^u x4 ,?is is due to ! oxyg5 ( ! air :i* unites ) ! iron1 =m+ iron ru/4 ,iron ru/ does n conduct electricity4 ,we h conv]t$ ,no4 #bd iron wire into a wire ( small] diamet] ) a %ea? ( iron ru/ ar\nd x4 ,we might prev5t ! ru/+ by putt+ ! wire 9 a glass globe & exhau/+ ! air f x4 ,i h "h a piece ( ,no4 #bd plat9um wire :i* has ab\t ! same resi/ance z iron wire :5 cold1 b y notice t ,i may use a v mu* %ort] l5g? ?an ,i did ( ! iron wire because x w endure a v mu* high] heat )\t melt+4 ,r$uc+ ! l5g? w\ld r$uce ! resi/ance1 b r$uc+ ! resi/ance w\ld all[ m curr5t to pass4 ,if m curr5t %\ld pass x w\ld make ! wire hott]1 & rais+ ! temp]ature w\ld increase ! resi/ance1 :i* w\ld cut d[n ! curr5t1 etc4 ,by slid+ ! clip c 7,fig4 #ib71 along1 ,i f9ally rea* a po9t :]e conditions balance s t ,i get a v brilliant light1 dang]\sly ne> ! fus+ po9t ( ! plat9um :i* is ?ree ?\s& degrees above ! boil+ po9t ( wat]4 ,9 #ahgi ,mr4 ,?omas ,a4 ,edison lit]ally se>*$ ! :ole _w = some?+ bett] ?an plat9um = ! filam5t ( an inc&esc5t lamp4 ,he f9ally decid$ ^u *>r$ ?reads ( a bamboo :i* he f\nd 9 ,japan4 ,no rese>* 0 ev] m timely ?an ?is4 ,:]eas !re 0 practically no electric light+ be=e #ahhj1 soon aft] t !re began a ph5om5al dem& = c>bon filam5t lamps4 ,9 #ahij1 #hjj1jjj ( ^! lamps 7 manufactur$ 9 ! ,unit$ ,/ates4 ,9 #aijj ! numb] _h ris5 to #be1jjj1jjj4 ,9 #aiji c5tral /ations 7 supply+ electric curr5t to #da1hjg1idd inc&esc5t electric lights4 ,by f> ! greate/ numb] are /ill made ) c>bon filam5ts4 ,illu/ration3 ,fig4 #ib ,illu/ration3 ,fig4 #ic ,we exam9$ an ord9>y #aaj-volt #af-;c&le-p[] c>bon filam5t lamp1 7,fig4 #ic74 ,z ne> z we c\ld e/imate1 its filam5t measur$ ab\t eight in*es 9 l5g?4 ,we broke op5 ! bulb ( ?is lamp by lay+ x ^u ! table & tapp+ x ) a bo>d4 ,! bulb broke ) r a l\d noise & ! brittle c>bon filam5t broke into _m pieces4 ,we f\nd "o ( ^! pieces & measur$ its diamet] ) a wire gauge1 7,fig4 #id74 ,x 0 ! same size z ,no4 #cc wire1 :i* we also f\nd by ! wire gauge 0 ! size ( ,no4 #ij sew+ cotton4 ,! diamet] ( ,no4 #cc wire 0 giv5 ^u ! wire gauge z 4#jjg in*4 ,:5 light$1 ! filam5t ( ?is lamp _h look$ to be ab\t ! size ( ,no4 #ah wire1 :i* has a diamet] ( 4#jd4 ,t is1 ! filam5t :5 light$ look$ six times z ?ick z x really 04 ,^? :o use sew+ cotton le>n quickly to "k ! size ( ! ?read by its numb]4 ,s ^? :o h mu* to d ) wire easily le>n ! sy/em ( designat+ sizes by numb]s4 ,"h are "s select$ figures easy to rememb]4 ,a trolley wire is ab\t "o ?ird ( an in* 9 diamet]4 ,x is designat$ z ,no4 #j4 ,notice 9 ! foll[+ table t z ! numb]s rise by six ! diamet]s are divid$ by two4 ,notice also t z ! diamet]s dim9i% by two ! resi/ance increases by f\r4 ,illu/ration3 ,fig4 #id ,,table ,,( ,,resi/ance ,,( ,,copp] ,,wires ,nos4 ,diamet] ,resi/ance #j 4#cb in* #ajefj feet to ! ohm #f 4#af #bfdj #ab 4#jh #ffj #ah 4#jd #afe #bd 4#jb #dj #cj 4#ja #aj #cf 4#jje #b4e #db 4#jjc #a #aj1efj feet equal two miles4 ,numb] #cf is ! wire us$ ^u ! spools ( telegraph receiv]s4 ,!y (f] #ge ohms ( resi/ance & !re=e conta9 #cj feet ( wire 7#cj #b4e #ge74 ,^! resi/ances are = ord9>y s*ool room temp]atures4 ,s9ce iron has six times1 & ,g]man silv] twelve times ! resi/ance ( copp]1 divide ! figures ( ! ?ird column by six1 & ! table w answ] = iron wire1 or divide ^? figures by twelve & ! table may be us$ = ,g]man silv] wire1 ?us3 ,numb] ,feet to ! ,ohm ,nos4 ,diamet] ,copp] ,iron ,g]man ,silv] #j 4#cb in* #ajefj #agfj #hhj #f 4#af #bfdj #ddj #bbj #ab 4#jh #ffj #aaj #ee #ah 4#jd #afe #bg #ad #bd 4#jb #dj #f #cb in* #cj 4#ja #aj #a4e #h #cf 4#jje #b4e 4#de #b #db 4#jjc #a #b in* #a ,^! figures are n exact1 b useful4 ,we procur$ a /r+ ( eight small lamps 7,fig4 #ie71 su* z are us$ 9 light+ ,*ri/mas trees4 ,ea* 0 m>k$ #ad volt1 #b-;c&le-p[]4 ,! c>bon filam5t ( ea* 0 ab\t "o in* long & app>5tly ! same diamet] z t ( ! #af-;c&le-p[] lamp4 ,:5 ! #aaj-volt curr5t 0 s5t ?r\gh ! gr\p ( eight connect$ 9 s]ies !y seem$ to give ab\t ! same light z ! s+le #af-;c&le-p[] lamp4 ,x is z ?\gh ! filam5t ( ! #af-;c&le-p[] lamp _h be5 cut into eight pieces1 & di/ribut$ ?r\gh eight small lamps4 ,we introduc$ an ammet] into ! circuit & f\nd t half an amp]e ( electricity pass$ ?r\gh ! s+le #af-;c&le-p[] lamp--& half an amp]e likewise pass$ ?r\gh ! gr\p ( eight #b-;c&le-p[] lamps4 ,illu/ration3 ,fig4 #ie ,! #aaj-volt curr5t c pu% an amp]e ( electricity ?r\gh eight in*es ( c>bon ?read sev5 ?\s&?s ( an in* 9 diamet]1 & :5 ?is happ5s ! filam5t gets hot en\gh to give out z mu* light z sixte5 /&>d c&les4 ,9 ! place ( ! #af-;c&le-p[] lamp1 we put a #cb-;c&le-p[] #aaj-volt lamp4 ,! ammet] indicat$ "o amp]e4 ,! c>bon filam5t 0 l>g] 7,no4 #cj1 diamet] 4#ja in*71 s z to all[ m curr5t to pass4 ,an #h-;c&le-p[] #aaj-volt lamp 0 sub/itut$2 "o qu>t] ( an amp]e pass$4 ,a #d-;c&le-p[] #aaj-volt lamp 0 us$2 "o eigh? ( an amp]e pass$4 ,a #ajj-;c&le-p[] #aaj-volt lamp 0 sub/itut$2 ?ree amp]es ( curr5t pass$ ?r\gh x4 ,9 all ^! cases ! lamps :i* pass$ ! l>g] curr5t _h ! l>g] filam5ts4 ,a little practice w\ld enable "o to di/+ui% betwe5 ^! lamps )\t labels by exam9+ _! filam5ts4 ,among ^! #aaj-volt lamps1 x is to be not$ t ! am\nt ( light :i* !y give is proportional to ! am\nt ( curr5t :i* !y pass4 ,& x is conv5i5t to rememb] t "o amp]e ( electricity = "o h\r co/s ab\t "o c5t4 ,we introduc$ into ! socket a ,hylo lamp 7,fig4 #if74 ,! filam5t1 ,a1 took half an amp]e ( electricity1 gave #af-;c&le-p[] ( light1 & co/ half a c5t an h\r4 ,:5 ! lamp 0 turn$ 9 its socket ! curr5t 0 swit*$ (f ( ! filam5t ,a1 & on to ! filam5t a4 ,?is took 4#jc ( an amp]e1 gave "o c&le-p[] ( light1 & co/ 4#jc ( a c5t an h\r1 or at ! rate ( ab\t #c4jj a ye>1 burn+ cont9u\sly day & night4 ,illu/ration3 ,fig4 #if ,! uses ( su* a lamp are app>5t 9 rooms :i* h no daylight4 ,h[ev]1 a wall swit* at ! entrance ( su* a room1 mak+ x easy to ?r[ on & (f ! light entirely1 seems to be a m satisfactory arrangem5t4 ,"o ( ! boys connect$ a wattmet] 9 ! circuit ) a hylo lamp & f\nd t ! small filam5t did n pass curr5t en\gh to move ! armature ( ! wattmet]4 ,h5ce t may be burn$ alone )\t affect+ ! consum]'s bills4 ,we took a #af-;c&le-p[] #bbj-volt lamp1 & light$ x by a #bbj-volt curr5t4 ,! met] %[$ t x all[$ only "o qu>t] ( an amp]e to pass4 ,! filam5t 0 v mu* small] ?an t 9 ! #aaj-volt1 #af-;c&le-p[] lamp4 ,! pressure 0 twice z great z be=e1 b ! resi/ance 0 f\r times z great1 & h5ce only half z mu* curr5t pass$4 ,we f9d t x co/s j z mu* to g5]ate "o qu>t] ( an amp]e at #bbj-volt pressure z x does to g5]ate half an amp]e at #aaj-volt pressure4 ,we mu/1 ( c\rse1 pay = electricity accord+ to ! co/ ( produc+ x4 ,to produce 4#e amp]e at #aaj-volt pressure co/s ! same z "o amp]e at #ee-volt pressure1 or 4#be amp]es at #bbj volts4 ,x w be notic$ t ! products ( ! two factors 9 ea* case are ! same4 ,! product ( an amp]e multipli$ by a volt is a watt4 ,9 ea* ( ! above ?ree cases ! am\nt ( electrical en]gy is #ee watts4 ,?is w produce a def9ite quantity ( light--ab\t #af c&le-p[] :5 ! c>bon filam5t is us$1 & ?is quantity does n v>y z ei!r volts or amp]es1 b z ! product ( ^!1 namely1 watts4 ,ea* ( ^! lamps is call$ a #ee-watt lamp1 &1 s9ce !y ea* give #af c&le-p[] ( light1 a c>bon filam5t lamp gives "o c&le-p[] ( light = ?ree & a half watts ( electricity4 ,electricity = light+ purposes usually co/s #aj c5ts p] kil[att h\r1 t is1 #aj c5ts = #ajjj watts = "o h\r1 or "o c5t = #ajj watts = "o h\r4 ,h5ce a #ee-watt lamp co/s a trifle m ?an half a c5t = "o h\r1 or exactly 4#ee c5ts1 & a #cb-;c&le-p[] lamp co/s #a4a c5ts p] h\r4 ,we introduc$ into ! socket a #dh-;c&le-p[] #aaj-volt tung/5 lamp 7,fig4 #ig71 & turn$ on ! #aaj-volt curr5t4 ,! ammet] %[$ #ee amp]e4 ,h5ce ! lamp is a #fj-watt lamp1 & requires "o & a qu>t] watts p] c&le-p[]4 ,t is1 ! metal tung/5 is ne>ly ?ree times z effici5t z c>bon = produc+ light f electricity4 ,illu/ration3 ,fig4 #ig ,) p9c]s we broke (f ! tip ( a #cb-;c&le-p[] c>bon filam5t lamp1 mak+ a small hole 9 ! l>ge end ( ! bulb4 ,! air ru%$ 94 ,we !n put ! lamp 9 ! socket & turn$ on ! curr5t4 ,! c>bon filam5t gl[$ z usual1 & sl[ly burn$ up1 gr[+ small] z x did s4 ,! ammet] :i* 0 9 circuit %[$ t ! curr5t1 :i* 0 "o amp]e at ! beg9n+1 grew /eadily less z ! filam5t grew small]1 until f9ally :5 x 0 ab\t "o qu>t] ( an amp]e1 ! circuit 0 brok5 by ! filam5t burn+ 9 two4 ,we remov$ ! lamp f ! socket & ) a dropp] tube introduc$ a little lime wat]1 & %ook x to absorb any gas :i* might h be5 =m$ 9 !re4 ,x became milky :ite1 z x always does :5 introduc$ :]e c>bon has be5 burn$4 ,?is w\ld be a suffici5t pro( t ! filam5t 0 made ( c>bon1 if we did n already "k x4 ,! air is exhau/$ f ^! bulbs to prev5t ! c>bon filam5t f burn+ up4 ,illu/ration3 ,fig4 #ih ,! c>bon filam5t lamps 71 z has be5 said1 ! inv5tion ( ,mr4 ,?omas ,a4 ,edison 9 #ahgi4 ,su* a /atem5t mu/1 h[ev]1 be qualifi$ by ! ass]tion t ?is1 l ne>ly all inv5tion1 0 b ! consummation ( a long l9e ( rese>*es made by _m m5 = _m ye>s4 ,! e>ly filam5ts 7 made ( bamboo ?read1 *>r$1 b n[ !y are drawn l spid]'s web out ( a /icky liquid & c>boniz$ at a high temp]ature4 ,!y are atta*$ 9 ! lamp to %ort pieces ( plat9um wire :i* are seal$ ?r\gh ! glass walls ( ! bulb4 ,"o wire connects ) ! brass coll> ( ! bulb1 & ! o!r ) ! c5tral piece ( brass at ! base ( ! bulb4 ,we dissect$ a socket & f\nd t :5 ! lamp is plac$ 9 ! socket1 ! coll> ( ! lamp is screw$ into ! coll> ( ! socket1 & ! base ( ! lamp comes 9 contact ) a brass spr+ 9 ! bottom ( ! socket 7,fig4 #ih74 ,! spr+ is connect$ ) "o copp] wire br++ electricity f ! dynamo4 ,! coll> is connect$ ) ! o!r wire f ! dynamo4 ,?is connection is made & brok5 by turn+ ! key ( ! socket4 ,! wires are made ( copp] s9ce copp] is a p>ticul>ly good conductor ( electricity4 ,no electricity c fl[ unless ?is circuit is complete4 ,socket keys & wall swit*es make or close gaps 9 ?is circuit4 ,no copp] wires = c>ry+ electric-light+ curr5t are small] ?an ,no4 #ab1 :i* has a diamet] ( 4#jh or ab\t "o twelf? ( an in*4 ,! int5tion is to h z little resi/ance to ! curr5t z possible1 except 9 ! filam5t ( ! lamp itself4 ,!re resi/ance is purposely introduc$ 9 ord] to conv]t electricity into light1 light )\t heat if t 7 possible1 b s9ce t has n yet be5 f\nd possible1 heat = ! sake ( ! accompany+ light4 ,unhappily only #d p] c5t4 ( ! electrical en]gy goes into light & #if p] c5t4 goes into useless1 or ev5 h>mful1 heat4 ,! tung/5 lamps1 :i* are n[ com+ into use1 are ne>ly ?ree times z effici5t 9 ! production ( light z are ! c>bon filam5t lamps4 ,! dynamo ex]ts its entire pressure ^u ! lamp & furni%es curr5t z foll[s3 ,a dynamo ( #aaj-volt pressure gives3 #a amp]e #aaj watts1 ?r\gh a #cb-;c&le-p[] lamp1 co/ "o c5t an h\r1 or 4#e amp]e #ee watts1 ?r\gh a #af-;c&le-p[] lamp1 co/ half a c5t an h\r1 or 4#be amp]e #bg-a_/b watts1 ?r\gh an #h-;c&le-p[] lamp1 co/ a qu>t] ( a c5t an h\r4 ,a dynamo ( #bbj-volt pressure gives3 4#e amp]e #aaj watts1 ?r\gh a #cb-;c&le-p[] lamp1 co/ "o c5t an h\r1 or 4#be amp]e #ee watts1 ?r\gh a #af-;c&le-p[] lamp1 co/ half a c5t an h\r1 or 4#abe amp]e #bg-a_/b watts1 ?r\gh an #h-;c&le-p[] lamp1 co/ a qu>t] ( a c5t an h\r4 ,! c>bon filam5t lamps1 b>r+ accid5ts1 h a natural life v>y+ f #fjj to #ajjj h\rs ( actual inc&esc5ce4 ,at ! end ( t p]iod ! filam5t has become s ?9 t x w fall ap>t by ord9>y usage4 ,x is nev] pr(itable1 h[ev]1 to use !m = _! :ole lifetime4 ,! lamp gradually volatilizes c>bon & deposits x ^u ! inn] walls ( ! bulb1 produc+ a smoky appe>ance & %utt+ (f light4 ,z ! filam5t gr[s ?9n] by ?is process1 x (f]s great] resi/ance to ! curr5t1 & z ! am\nt ( curr5t gr[s less ! proportion ( light to curr5t gr[s rapidly less1 s t at la/ in/ead ( pay+ = #c4e watts ( electricity p] c&le-p[] ( light "o mu/ pay = p]haps sev5 or eight watts p] c&le-p[]4 ,we pay fifte5 c5ts apiece = #af-;c&le-p[] lamps1 & x is economy to r5ew !m ab\t twice a ye>1 if !y are burn$1 say ?ree h\rs a day1 or a little ov] five hundr$ h\rs4 ,x is int]e/+ to note t :5 a direct curr5t is us$ ! evaporation f ! c>bon filam5t always takes place at ! negative end alone1 t is1 ! end f :i* ! curr5t is leav+ ! lamp4 ,if an alt]nat+ curr5t is us$ ! evaporation goes on f all p>ts ( ! filam5t alike4 ,?is is a case ( evaporation f ! solid /ate4 ,c>bon does n boil bel[ #f1jjj degrees1 & ! filam5t rea*es ab\t #b1dej degrees4 ,tantalum1 tung/51 & osmium lamps h metal filam5ts4 ,^! metals are bett] conductors ?an c>bon b unlike c>bon _! resi/ance increases z _! temp]ature rises1 & _! special virtue is t !y are capable ( endur+ an extremely high temp]ature )\t melt+4 ,! wire us$ 9 "s ( ^! filam5ts is z small z 4#jjb ( an in*1 or ,no4 #dd4 ,9 ord] to furni% suffici5t resi/ance to prev5t ! #aaj-volt curr5t f melt+1 !y (t5 h a l5g? exce$+ two feet4 ,?is is lac$ back & =? )9 ! small bulb4 ,at ! temp]ature ( bright inc&esc5ce _! resi/ance may be increas$ z mu* z fivefold & sometimes becomes ab\t t5 ohms to ! in*4 ,l all metals !y are m brittle :5 cold ?an hot4 ,h5ce :5 clean+ su* lamps x is advisable to turn on ! curr5t to avoid break+ ! filam5t by j>r+4 ,filam5ts :i* are too fragile to endure ! j> ( ord9>y railway travel1 :5 cold1 h gone ?r\gh railway wrecks safely :5 light$4 ,x is a g5]al rule t good conductors ( electricity gr[ m resi/ant z ! temp]ature rises :ile non-conductors resi/ less z ! temp]ature rises4 ,h5ce ! insulat+ mat]ial :i* is us$ to cov] copp] wires fails to protect if highly heat$4 ,if a #aaj-volt lamp is put into a #bbj-volt circuit1 "o might expect t ! lamp w\ld burn out )\t do+ fur!r damage to ! circuit1 b ?is is n ! case4 ,z ! filam5t approa*es its melt+ po9t1 #fjjj degrees1 x becomes s good a conductor t x c>ries curr5t en\gh to melt a fifte5 amp]e fuse4 ,x is1 !re=e1 ! fuse t protects ! circuit & n ! burn+ out ( ! lamp4 ,! bulb conta9+ ! highly heat$ c>bon vap\r w\ld conduct ! curr5t z an arc lamp does4 ,illu/ration3 ,fig4 #ii #bc4 ,arc ,lamp4--,we fa/5$ two electric light c>bons to ! ends ( copp] wires connect$ = ! #aaj-volt curr5t4 ,a rheo/at1 ,r 7,fig4 #ii71 9 circuit1 0 set at #f4e ohms4 ,"o l[] c>bon 0 fa/5$ into a clamp1 & ! o!r 0 t\*$ to x1 & !n drawn away ab\t ?ree-eigh?s ( an in*4 ,a v brilliant light 0 produc$4 ,probably ab\t #ahjj c&le-p[]4 ,! ammet] ,a %[$ #aj amp]es1 & ! volt met] ,v %[$ #de volts4 #de volts #aj amp]es #dej watts1 #ahjj c&le-p[]1 #be watts p] c&le-p[]4 ,! arc light is ! *eape/ ( all lights b is too dazzl+ly bright = h\sehold purposes4 ,x is us$ = outdoor light+ *iefly1 & p>ticul>ly = l>ge se>*-lights4 ,! temp]ature is ov] #fjjj degrees1 :i* boils ! c>bon & fills ! gap betwe5 ! two p5cils ) a /ream ( c>bon vap\r4 ,?is conducts ! curr5t l ! filam5t 9 an inc&esc5t lamp4 ,! air gap betwe5 ! c>bon p5cils w\ld h a resi/ance ( _m ?\s& ohms if x 7 n = ! pres5ce ( ! c>bon vap\r4 ,! hot c>bon vap\r r$uces ! resi/ance ( ?is space to #d4e ohms4 7#de volts7_/7#d4e ohms7 #aj amp]es4 or 7#aaj volts7_/7#f4e #d4e ohms7 #aj amp]es4 ,! c>bon p5cils acc\nt = "p ( ?is resi/ance--n m ?an a ?ird ( an ohm h[ev]4 ,x is evid5t t arc lamps 9 use mu/ h an automatic me*anism :i* %all p]mit ! c>bons to t\* :5ev] ! curr5t is n pass+1 b :i* %all draw !m ap>t to ! prop] di/ance aft] ! c>bon vap\r has be5 =m$1 or1 z we say1 aft] ! arc has be5 e/abli%$4 ,?is me*anism is no?+ else ?an electro-magnets :i* are op]at$ by ! light+ circuit itself4 ,x may require ?\ghtful exam9ation to recognize ^! z electro-magnets1 9 e case1 b t is :at !y are4 ,sometimes !y are coils ( wire1 :i* d n h iron cores & armatures sep>ate to be sure--b nev]!less !y h bo? ( ^! unit$ 9 "o movable rod1 & !y produce magnetic fields4 ,suppose ,i pass an electric curr5t ar\nd ?is coil ,a 7,fig4 #ajj74 ,! region ab\t ! coil becomes a magnetic field ) its nor? pole situat$ at a po9t 9 space1 say ,n4 ,! influ5ce ( ?is field causes ! iron rod to become a magnet ) its s\? pole upp]mo/1 & if ! curr5t is /rong en\gh1 & ! field :i* x produces is /rong en\gh1 x w lift ! iron rod up into ! coil4 ,by v>y+ ! /r5g? ( ! curr5t y see ,i may make ?is rod dance up & d[n 9 space t\*+ no?+--a v]itable gho/ dance4 ,illu/ration3 ,fig4 #ajj ,x may be pettifogg+ to say t ! upp] portion ( ?is iron rod is ! core ( ! magnetic field1 & its l[] portion is ! armature4 ,yet ?is is "r1 & pettifogg+ may be "r :5 x is ! only way to br+ out ! fact4 ,our great /udy n[ is to produce light )\t heat1 or at lea/ to come z ne> to x z ! firefly does4 ,! firefly gives #ih p] c5t4 light & two p] c5t4 heat4 ,! arc lamp gives #ab p] c5t4 light & #hh p] c5t4 heat4 ,! c>bon filam5t gives #d p] c5t4 light & #if p] c5t4 heat4 ,:5 we h made consid]able progress 9 t direction we %all take electric lamps out ( ! *apt] on electric heat+ & =m a new *apt] on electric light+4 ,"o might expect t a rod made ( c>bon w\ld quickly burn up1 p>ticul>ly :5 rais$ to ! exce$+ high temp]ature ( ! electric arc4 ,:ile x is true t c>bon 9 ! =m ( *>coal burns s readily t x is us$ in/ead ( k9dl+s = light+ a fire1 c>bon 9 ! =m ( graphite 9 our s-call$ lead p5cils & c>bon z x is prep>$ = electric light p5cils burns only v sl[ly ev5 at exce$+ly high temp]atures4 ,! c>bon rods us$ 9 arc lamps endure a temp]ature ( ov] #fjjj degrees1 )\t los+ m ?an "o in* an h\r1 & half ( t is simply volatiliz$--n burn$4 ,"o ( ! mo/ int]e/+ improvem5ts ev] made 9 ! arc light is t ( enclos+ ! arc 9 an inn] glass globe4 ,?is globe is clos$ airtight bel[ ) a small op5+ above4 ,:5 ! arc is =m$ ! oxyg5 ( ! air 9 ! inn] globe is soon consum$ & !n combu/ion is no long] possible4 ,we illu/rat$ ?is by an exp]im5t4 ,an ord9>y cork 0 *os5 to fit ! l>ge end ( an arg& lamp *imney & ?r\gh a hole 9 ?is 0 pass$ "o ( ! c>bon rods 7,fig4 #aja74 ,a metal clamp made connections betwe5 ?is c>bon & ! negative wire f ! dynamo4 ,! o!r c>bon1 atta*$ by a clamp to ! positive wire1 0 ?ru/ d[n into ! upp] end ( ! *imney until x t\*$ ! negative c>bon1 & !n drawn upw>d a %ort di/ance1 draw+ an arc1 z we say4 ,?is soon makes an atmosph]e )9 ! *imney :]e combu/ion _c g on = want ( oxyg54 ,! arc1 h[ev]1 cont9ues to gl[ z 9 ! op5 air1 & ! c>bons may be drawn fur!r ap>t ?an 9 ! op5 air )\t break+ ! arc1 h5ce m ( ! ext]nal resi/ance may be cut out & a high] voltage put ^u ! lamp4 ,illu/ration3 ,fig4 #aja ,c>bons :i* burn out 9 a s+le night if us$ 9 op5 arc lamps la/ two weeks 9 enclos$ arc lamps4 ,! l[] c>bon1 :5 remov$ f ! lamp *imney ( ! la/ exp]im5t1 s]v$ z a lead p5cil to write on pap]4 ,! positive c>bon w\ld n make a m>k on pap]4 ,9 all arc lamps c>bon is di/ill$ f ! positive p5cil1 cond5s+ ^u ! negative p5cil z graphite1 :i* is ! mat]ial us$ 9 mak+ lead p5cils4 ,!y are call$ lead p5cils because !y 7 orig9ally made ( lead1 b n[ !y are made ( graphite :i* is m9$ f ! e>?4 ,z soon z ! arc is brok5 x becomes evid5t t ! positive c>bon has be5 heat$ mu* ! hott] ( ! two1 a fact t c\ld n be detect$ :ile x 0 light$ because ( ! dazzl+ brightness ( ! arc4 ,! negative c>bon turns black almo/ imm$iately1 :ile ! positive c>bon rema9s at a bright r$ heat = "s "t4 ,?is fact ne$s to be borne 9 m9d :5 adju/+ arc light c>bons 9 se>*-lights1 /]eopticons1 & all l app>atus 9 :i* ! light mu/ be plac$ at ! focus ( a l5s4 ,t is1 x is necess>y to "k f :at po9t ! light really comes & x is necess>y to h "s adju/+ device to keep ?is po9t cont9ually at ! focus ( ! l5s4 #bd4 ,se>*-,light4--7,fig4 #ajb74 ,?is is simply an arc lamp ) reflectors beh9d x & l5ses 9 front ( x4 ,! :ole app>atus is pivot$ s z to be easily made to %9e 9 any direction4 ,! function ( ! l5ses & ! reflectors is to collect /ray rays ( light & s5d !m all out 9 ! same direction4 ,?is is %[n 9 ,fig4 #ajc :]e = simplicity ! l5s is repres5t$ z a s+le piece4 ,l repres5ts a po9t ( light :i* w naturally s5d its rays out 9 all directions z ! radii ( a sph]e2 m1 m1 m repres5ts a bright reflect+ surface :i* is giv5 t peculi> curve call$ a p>abola4 ,x has ! unique faculty ( reflect+ 9 a p>allel direction all ! rays :i* may fall ^u x f ,l1 s long z ,l is kept at t p>ticul> po9t call$ ! focus1 a b is a l5s ( glass :i* has t peculi> curve t enables x to b5d all rays :i* fall ^u x f ,l1 s t !y may pass out p>allel4 ,illu/ration3 ,fig4 #ajb #be4 ,/]eopticon4--,?is also has ! necess>y devices to ga!r ! rays ( ! arc lamp & s5d !m =? p>allel1 & 9 addition x has a s]ies ( l5ses :i* produce ^u a di/ant scre5 an enl>g$ picture ( any transp>5t object held 9 ^! p>allel rays4 ,illu/ration3 ,fig4 #ajc ,illu/ration3 ,fig4 #ajd #bf4 ,burgl>'s ,fla%-,light4--,!re are _m =ms ( ?is4 ,! "o we exam9$ is repres5t$ 9 ,fig4 #ajd4 ,we unscrew$ a metal r+ at ! left-h& end & f\nd1 fir/ a glass l5s & beh9d t a m9iature electric light1 requir+ ?ree volts & half an amp]e4 ,we knew1 !re=e1 t x mu/ be suppli$ ) two cells1 s9ce "o cell may give n m ?an #a4e volts4 ,we also knew t x w\ld only be us$ to fla% a light1 s9ce if dry cells are requir$ to furni% half an amp]e cont9u\sly !y soon run d[n4 ,beh9d ! lamp !re 0 a bright metal reflector--! l5s & reflector are fairly well repres5t$ 9 ,fig4 #ajc4 ,! filam5t ( ! lamp is connect$ ) two small batt]y cells 9 ! h&le4 ,^! may be remov$ & replac$ by new ones by unscrew+ a cap at ! "r-h& end4 ,! circuit is clos$ by a metal spr+ on ! side ( ! tube1 :i* acts z a pu% button4 ,x is situat$ :]e x may be conv5i5tly press$ by ! ?umb4 ,! small batt]ies necess>ily h a %ort life & mu/ be replac$ q frequ5tly4 ,be+ a special ?+ !y co/ ne>ly twice :at ! regul> dry cell does4 ,illu/ration3 ,fig4 #aje #bg4 ,m]cury ,vap\r ,lamp4--,?is is an int]e/+ v>iety ( arc light 9 :i* ! vap\r ( m]cury takes ! place ( ! vap\r ( c>bon4 ,g1 9 ,fig4 #aje1 repres5ts a glass tube f :i* ! air has be5 exhau/$4 ,! wires ( ! light+ circuit are fus$ into ! ends ( ! tube4 ,at "o end1 & 9 contact ) "o ( ^! wires1 is a small pool ( m]cury4 ,by pull+ ! cord c ! tube is tilt$ on ! pivot p1 s t a /ream ( m]cury fl[s along ! :ole l5g? ( ! tube & closes ! electric circuit4 ,:5 ! tube falls back into its normal position1 z repres5t$ 9 ! figure1 ! electric arc p]si/s ^u ! m]cury vap\r4 ,inc&esc5t m]cury vap\r gives light /rong 9 gre51 blue1 & violet1 b defici5t 9 r$ & yell[4 ,x1 !re=e1 gives no?+ its natural appe>ance b ca/s a gha/ly hue ov] ev]y?+4 ,?is lamp 0 inv5t$ 9 #aijb1 by ,pet] ,coop]-,hewitt1 gr&son ( ! f\nd] ( ,coop] ,union 9 ,new ,york ,city4 ,x gives a v suitable light = mak+ photographic pr9ts1 & is mu* us$ = t4 ,?is lamp op]ates ^u ! #aaj-volt circuit4 ,x is ! longe/ /ep yet tak5 t[>d gett+ light )\t heat1 b p]haps %[s :at we mu/ expect :5 we rea* t goal1 namely1 unsatisfactory col\r values 9 ! light4 ,probably su* is ! case ) ! firefly4 #bh4 ,! ,moore ,light4--,9 #ahif ,pr(4 ,d4 ,mc,farland ,moore br\ght out 8 vacuum tube light 7,fig4 #ajf74 ,we visit$ an ord9>y dry goods /ore :i* _h be5 equipp$ ) ?is4 ,glass tub+ is put toge!r v mu* z "o w\ld put up a /ove pipe or a job ( plumb+4 ,! jo9ts are fus$ & made air-tight by play+ a flame ^u !m aft] ! pipe is up 9 place4 ,?is pipe is l$ ar\nd into all nooks & corn]s :]e !re w\ld be d>k places4 ,! air is pump$ out ( ?is tube & a trifl+ am\nt ( "s vap\r is introduc$1 ! k9d v>y+ accord+ to ! t9t ( col\r :i* is desir$4 ,illu/ration3 ,fig4 #ajf ,metal t]m9als are fus$ into ! ends ( ?is tube4 ,! tube we saw 0 sev5ty-five feet long4 ,a #ajjj-volt alt]nat+ curr5t is appli$ to ! t]m9als & ! vap\r becomes inc&esc5t1 fill+ ! :ole tube full ( light4 ,! fir/ ?+ t ! boys rem>k$ 0 t al?\gh ! room 0 brilliantly light$ no object ca/ a %ad[4 ,x seem$ z ?\gh light 0 ev]y:]e & !re 0 no *ance to scre5 x (f4 #bi4 ,! ,n]n/ ,lamp4--,9 #ahig ! ,n]n/ lamp appe>$ 9 ,g]many4 ,x is a good illu/ration ( an insulat+ sub/ance becom+ a conductor :5 heat$ to a high temp]ature4 ,! gl[]1 z x is call$1 is compos$ ( "o or sev]al %ort rods ( clay-l mat]ial4 ,?is is fir/ heat$ by s5d+ ! electric curr5t ?r\gh resi/ance wire plac$ directly und]nea? x & connect$ 9 %unt ) x4 ,:5 x gets hot1 curr5t beg9s to pass ?r\gh x1 & is automatically cut (f f ! resi/ance coil4 ,! gl[] produces an int5sely bright & :ite light al?\gh x does n itself exce$ ! temp]ature ( #agdb degrees4 ,electric in/allations are n[ s c>efully con/ruct$ t fires f poor insulation are v r>e4 ,less ?an "o fire 9 ?ree hundr$ appe>s to be traceable to t cause4 #cj4 ,electric ,weld+4--,no?+ is m common 9 electrical matt]s ?an heat produc$ by poor contacts4 ,9 ?is laboratory are two *&eli]s1 ea* controll$ by a wall swit*4 ,aft] ! curr5t has be5 on ! *&eli]s = half an h\r y w always f9d "o ( ^? wall swit*es w>m1 :ile ! o!r is n p]ceptibly w>m] ?an o!r objects 9 ! room4 ,! explanation is t !re is poor contact 9 "o ( !m4 ,:5 two metal conductors t\* "o ano!r at a m]e po9t ! electric curr5t1 9 pass+ f "o ( ^! conductors to ! o!r across su* a n>r[ bridge1 meets resi/ance & develops heat--sometimes heat en\gh to fuse ! po9t1 & ei!r break ! contact1 or1 :at is m likely1 />t a m9ute arc at t po9t4 ,9 "s cases ?is makes ! app>atus dang]\sly hot1 & 9 o!r cases x bridges ! gap ) a broad] & bett] contact--a true electric weld4 ,electric weld+ is appli$ to ev]y?+1 f *ick5 f5ce to railway rails4 ,enorm\sly l>ge curr5ts are us$ = ! purpose1 9 "s cases z high z #ej1jjj amp]es be+ employ$4 ,! rails ( railroads are weld$ end to end by a curr5t ( sev]al ?\s& amp]es s5t ?r\gh ! jo9t by p]haps two or ?ree volts4 ,! jo9t heats & fuses toge!r m]ely because ! poor contact (f]s resi/ance to ?is enorm\s curr5t4 ,,ix ,,light+ ,a ,,summ] ,,camp ,,by ,,electricity ,summ] _h arriv$4 ,! ,sci5ce ,club _h held its la/ meet+ = ! season4 ,h>old _h engag$ ?ree o!r boys to sp5d ! summ] at ! f>m4 ,i _h ! ro( ( an old mill re%+l$ & gave x to !m = a camp4 ,!y 7 to make x ov] inside4 ,i s5t ! boys to ! c\ntry z e>ly z x 0 possible = !m to get away4 ,x w\ld be six weeks lat] be=e ,i c\ld foll[ !m4 ,illu/ration3 ,fig4 #ajg ,:5 ,i did arrive ,i f\nd !y _h elaborate s*emes inde$4 ,! fir/ floor ( ! mill _h be5 p>tition$ (f into rooms1 z %[n 9 diagram 7,fig4 #ajg71 a1 b1 c & d be+ b$rooms2 e 0 a wa% room1 ! l ( :i* has nev] be5 se5 be=e4 ,x _h n occurr$ to me t ! mill pond m1 :i* came to ! v corn] ( ! build+1 w\ld furni% ! boys a complete sy/em ( city wat]-works4 ,at g1 9 ! corn] ( ?is room1 !y _h cut a hole 9 ! floor & nail$ slats across ^u ! "u side ( ! timb]s1 mak+ a depress$ floor = a %[] ba?4 ,?is 0 directly ov] a /ream ( wat] :i* issu$ f ! mill pond4 ,hang+ f ! ceil+ ov] ?is spot 0 ! nozzle ( a g>d5 hose4 ,! o!r end ( ?is hose ran into ! mill pond4 ,! nozzle 0 capable ( deliv]+ ei!r a /ream or a %[]1 accord+ to :i* way x 0 twi/$ 9 its socket4 ,x 0 also capable ( %utt+ (f entirely ! fl[ ( wat]4 ,! boys ask$ me to hold my h& 9 ! %[]1 & to my a/oni%m5t x 0 w>m4 ,:at1 pray1 is y\r heat+ sy/em8 ,i inquir$4 ,!y invit$ me to g & see4 ,moor$ outside 9 ! mill pond at ! corn] ( ! build+ 0 our motor boat1 :i* ! boys 7 all[$ to use freely & :i* !y und]/ood z well z any "o4 ,illu/ration3 ,fig4 #ajh ,!y said t ord9>ily !y us$ = ! %[] ! cool wat] ( ! lake1 :i* !y mu* pref]r$1 & :i* ran ( its own accord1 ! lake be+ a trifle high] ?an ! nozzle ( ! %[]1 b kn[+ my antipa?y = ! cold ba? !y _h slipp$ ! end ( ! rubb] hose ov] ! outlet pipe ( ! pump :i* s]v$ to cool ! gasol5e eng9e 9 ! boat4 ,! eng9e unc\pl$ f ! propell] 0 heat+ & pump+ wat] = my %[] ba?1 & ,i imm$iately accept$ ! invitation to enjoy x4 ,c]ta9ly no ba? 0 ev] m delightful ?an t "o1 com+1 z x did1 at ! close ( a hot1 dirty ride f ! city4 ,i _h ha/5$ ! ba?1 because x 0 already dusk & ,i _h no c&le at ! mill1 b sudd5ly ! room light$ up z if by magic4 ,i saw !n :at _h be=e escap$ my notice1 a m9iature electric lamp1 six-volt1 two-c&le-p[]1 tung/51 su* z are us$ = tail lights on automobiles4 ,s9ce tung/5 requires ab\t #a4be watts p] c&le-p[] x 0 a #b4e-watts lamp1 & s9ce x 0 adapt$ to six volts x w\ld take ab\t f\r t5?s ( an amp]e4 #f volts 4#d amp]e #b4d watts4 ,! little wire filam5t look$ to be ab\t #a4e in*es long4 ,its resi/ance mu/ h be5 #ae ohms4 #f volts_/#ae ohms 4#d amp]e4 ,a batt]y ( five cells 0 us$ to furni% electric curr5t = ! lamp4 ,lamps 7 in/all$ 9 ! b$rooms also & 7 n int5d$ to be us$ m ?an half an h\r at a "t4 ,dry batt]y cells are excell5t = ?is purpose1 & = s small a curr5t ! *eape/ dry cells are z good z ! m exp5sive ones4 ,^! co/ fifte5 c5ts a cell4 ,!y 7 connect$ by %ort pieces ( b>e copp] wire2 ,no4 #ah 9 s]ies1 z %[n 9 ,fig4 #aji4 ,a wire ran f ! c5tral 7c>bon7 b9d+ po/ ( "o cell to ! m>g9al 7z9c7 b9d+ po/ ( ! next cell4 ,?is batt]y 0 plac$ on a %elf 9 a conv5i5t place4 ,a b>e copp] wire1 ,no4 #ah1 0 atta*$ to ! c>bon po/ at "o end ( ! batt]y & ano!r to ! z9c po/ at ! o!r end ( ! batt]y1 & ^! two wires ran to all ! rooms :]e lamps 7 plac$4 ,! wires 7 fa/5$ up on ! walls by /aples1 tak+ c>e t !y %\ld n[h]e come 9 contact ) ea* o!r & %ort circuit ! batt]y4 ,:5ev] x 0 necess>y = "o wire to cross ano!r1 small pieces ( pa/ebo>d 7 tack$ up to prev5t _! t\*+ ea* o!r4 ,! lamps ,l 7,fig4 #aji7 7 connect$ to ^! wires 9 p>allel4 ,!y co/ =ty c5ts apiece1 & ! m9iature sockets1 into :i* !y 7 screw$1 co/ five c5ts ea*4 ,"o ( ^! sockets 0 screw$ to ! side ( ! door cas+ 9 ea* b$room4 ,wires 7 atta*$ to ! l9e wires1 simply by twi/+ !m toge!r4 ,"o ( ^! came d[n to "o side ( ! socket & ! o!r came to ! o!r side ( ! socket ?r\gh a swit*1 s1 made ( a /rip ( %eet z9c4 ,! co/ ( ! entire in/allation 0 z foll[s3 #e dry cells at #ae;c 4#ge #e4b cp41 #f-volt tung/5 lamps at #dj;c #b4jj #e m9iature wall sockets at #e;c 4#be ,wire1 etc4 4#bj ---- #c4bj ,illu/ration3 ,fig4 #aji ,suppose ea* lamp is us$ ?irty m9utes a day = #ajj days1 mak+ a total ( fifty h\rs4 ,!re are five lamps1 mak+ a total ( #bej lamp h\rs4 ,ea* lamp takes 4#d ( an amp]e1 mak+ a total ( #ajj amp]e h\rs4 ,! lamps are op]at$ at six volts1 mak+ a total ( #fjj watt h\rs4 #ajj days 4#e an h\r ea* day --- #ej h\rs #e lamps --- #bej lamp h\rs 4#d amp]e = ea* lamp --- #ajj amp]e h\rs #f volts --- #fjj watt h\rs ,?is am\nt ( electrical en]gy w\ld co/ six c5ts if g5]at$ by a dynamo4 ,x is g5]ally /at$ t electricity co/s fifty times z mu* if g5]at$ by batt]y z by dynamo4 ,9 ?is case ! batt]y actually did s]ve = ! :ole season ( #ajj days & 0 n exhau/$ at ! end ( ! season4 ,inde$1 s9ce t season1 ! boys h f\nd t batt]y cells :i* _h be5 too mu* exhau/$ = use on ! eng9e s]v$ v well on ! lamps4 ,by use ! cells lose1 n mu* 9 voltage1 b 9 ! ability to furni% suffici5t quantity 9 amp]es to make ! hot sp>k requir$ = ignit+ ! mixture ( gasol5e & air 9 an eng9e cyl9d]4 ,:5 !y h be5 disc>d$ = use ) ! eng9e !y may /ill furni% ! small am\nt ( curr5t requir$ = ! lamps--provid$ n too _m lamps are us$ at "o "t4 ,! dynamo curr5t is always surpris+ly *eap :5 comp>$ ) t produc$ by a batt]y1 b1 on ! o!r h&1 we are nev] z economical 9 ! use ( ! dynamo curr5t z we are ) t ( ! batt]y4 ,if all five ( ! lamps 9 ! above equipm5t 7 light$ at ! same "t & kept burn+ = half an h\r1 ! batt]y w\ld run d[n r badly & w\ld n fully recov]4 ,b if "o only is us$ at a "t & = n m ?an ?irty m9utes1 or if m ?an "o is us$ at a "t & = a proportionately %ort] p]iod1 ! batt]y w receive no damage4 ,dry batt]y cells may be pur*as$ = ei!r tw5ty-five c5ts or fifte5 c5ts ea*4 ,! *ief diff]5ce is t ! =m] are capable ( giv+ l>g] curr5t ?an ! latt]1 :5 work+ aga9/ v small resi/ance4 ,= example1 ! =m] may give tw5ty to tw5ty-five amp]es on a %ort circuit1 t is1 connect$ directly ) ! ammet] )\t o!r resi/ance1 :ile ! latt] may give n m ?an six to t5 amp]es "u simil> conditions4 ,= mo/ purposes1 o!r ?an ignit+ gasol5e eng9es1 9 :i* dry cells are us$1 an exce$+ly small curr5t is requir$4 ,! electric bell1 = example1 may n require m ?an 4#b ( an amp]e & t int]mitt5tly4 ,n[ x is f\nd by exp]i5ce t ! dry cells :i* are only capable ( furni%+ on %ort circuit six to t5 amp]es w la/ q z long 9 bell "w z "o :i* may give on %ort circuit tw5ty to tw5ty-five amp]es4 ,h5ce x is good economy to buy !m4 ,:at a f9e sitt+ room y h "h6 7,fig4 #ajg1 f47 ,:5 d y expect to fit x up8 said ,i4 ,in/antly rem9d+ myself1 h[ev]1 t boys d n want a sitt+ room1 ,i inquir$ :at !y int5d$ to use ?is f9e1 l>ge room =4 ,!y told me t !y _h plans = mak+ a ma*9e %op out ( t4 ,! idea _h be5 sugge/$ by a c\nt] %aft :i* /ill hung f ! ceil+1 & !y _h discov]$ t ! old mill :eel w\ld /ill roll ov] if ! p5/ock 7 repair$4 ,i repli$ t ,i w\ld see :at c\ld be done ab\t t sometime4 ,on ! next day matt]s conc]n+ ! motor boat engag$ our att5tion4 ,x ,,h[ ,,electricity ,,feels ,:at is m fickle & yet m fasc9at+ ?an a motor boat8 ,on ! morn+ aft] my arrival at ,millville ! boys want$ me to g out ) !m 9 ! motor boat on ! mill pond1 z our beautiful little lake is call$4 ,ea* "o took a h& at try+ to />t ! boat1 b al?\gh %e _h act$ p]fectly well ! day be=e1 on ?is morn+ no "o c\ld get a s+le explosion4 ,! swit* 0 clos$4 ,! gasol5e 0 turn$ on4 ,! c>buretor valves 7 set at ! m>k4 ,! sp>k coils respond$ ) _! famili> buzz4 ,%e _h be5 prim$ &1 :5 %e _h refus$ to respond to ?is treatm5t1 ! pet valves 7 op5$ & ! :eel roll$ ov] sev]al times to sweep out ! cyl9d]s4 ,b absolutely no?+ mov$ h]--nei!r coax+ nor gibes4 ,sudd5ly "s "o roll$ ! :eel ov] = ! five-hundr$? "t & %e />t$ & behav$ well all day4 ,all ?is w\ld n h giv5 u ! slighte/ aggravation if we c\ld only h f\nd out :at 0 ! matt] & :at x 0 we f9ally did to correct x4 ,b ?is we %all probably nev] "k1 & h5ce we are wor%ipp]s ( ! motor boat :ile we cont9ue to di/ru/ x & compla9 ( x4 ,:ile ! boat 0 runn+ "o ( ! boys notic$ t a b9d+ po/ at ! end ( "o ( ! sp>k plugs seem$ to be loose4 ,he inadv]t5tly put out 8 h& to tight5 x & receiv$ a t]rific %ock4 ,?is rais$ ! "q among ! boys1 :y "o gets a %ock f "s ( ! b9d+ po/s 9 ! electrical equipm5t b n f o!rs4 ,i sugge/$ t we run 9 & call at ! h\se to get my portable measur+ in/rum5t 7,fig4 #aaj7 & a little lun*1 & !n g up to ! upp] end ( ! lake & take our "t 9 exam9+ ! electrical equipm5t ( ! boat4 ,illu/ration3 ,fig4 #aaj ,! eng9e _h two cyl9d]s4 ,!re 7 two batt]ies--"o = ea* cyl9d]4 ,ea* batt]y consi/$ ( five dry cells l ! "o repres5t$ 9 ,fig4 #aaa4 ,n[1 :y don't ,i feel ! electricity :5 ,i t\* ! b9d+ po/s ( ?is dry cell8 inquir$ "o ( ! boys z he h&l$ "o ( ! cells :i* we _h tak5 out4 ,well1 ,i'll give y two reasons :y d y n feel x1 said ,i4 ,fir/1 because y 7 t\*+ only "o b9d+ po/ at a "t4 ,y mu/ t\* bo? ( ! b9d+ po/s ( ! batt]y cell at ! same "t1 s t ! electric curr5t may pass f "o po/ to ! o!r ?r\gh y\r body4 ,second1 ev5 :5 y d t\* bo? b9d+ po/s at ! same "t y feel no curr5t1 simply because y (f]$ probably ab\t #ajj1jjj ohms ( resi/ance to ! passage ( ! curr5t & inasmu* z ! "o cell ex]ts only #a4e volts ( pressure1 x c\ld s5d only ab\t 4#jjjjjae ( an amp]e ?r\gh y4 ,?is y _c feel4 ,illu/ration3 ,fig4 #aaa 7#a4e volts7_/7#ajj1jjj ohms7 4#jjjjjae amp]es4 ,i n[ connect my in/rum5t z a volt met] betwe5 ! b9d+ po/s ( ! cell & y see x indicates #a4e volts1 & :5 ,i connect x = an in/ant z an ammet] y see x indicates tw5ty amp]es4 ,t is twice z mu* z !y use = execut+ crim9als by electricity4 ,s y see if y c\ld r$uce y\r resi/ance suffici5tly ?is "o batt]y cell might kill y4 ,"s p h less resi/ance ?an o!rs4 ,! resi/ance ( ! body is *iefly 9 ! out] sk94 ,if "o's h&s are dry & 8 sk9 has be5 made t\gh & horny by h>d "w1 he has _m times ! resi/ance ( "o ^: h&s are moi/ & ^: sk9 is ?9 & t5d]4 ,suppose we select ! tip ( ! tongue z ! portion ( ! body :i* w (f] ! lea/ resi/ance & w be mo/ s5sitive to slight electric curr5ts4 ,let u !n connect "o dry cell ) ! ammet] & place ! tip ( ! tongue betwe5 ! b>e ends ( ! wire at ,t 7,fig4 #aab74 ,illu/ration3 ,fig4 #aab ,i h connect$ ! ammet] s t x w indicate ?\s&?s ( an amp]e1 & y see t ! ne$le moves only slightly4 ,we _c call x m ?an 4#jja amp]e4 ,ea* boy 9 turn tri$ s5d+ ! curr5t ?r\gh 8 tongue & ea* tri$ to tell h[ x felt4 ,"o said x t+l$1 ano!r said x felt w>m1 ano!r said x ta/$ s\r & ! o!r said he did n feel or ta/e any?+4 ,well1 ,i said1 :e!r y feel any?+ or n "o-?\s&? ( an amp]e is pass+ ?r\gh y\r tongue & y are (f]+ fifte5 hundr$ ohms ( resi/ance4 7#a4e volts7_/7#aejj ohms7 4#jja amp]e ,y\r h& (f]s ne>ly sev5ty times z mu* resi/ance z y\r tongue4 ,suppose we try increas+ ! voltage1 or pressure1 ( our electric curr5t4 ,we w connect 9 s]ies ! t5 cells1 mak+ a batt]y :i* y see by ! volt met] gives fifte5 volts ( pressure4 ,we n[ f9d t hav+ t5 times ! pressure x s5ds t5 times z mu* curr5t z =m]ly ?r\gh ! tongue4 7#ae volts7_/7#aejj ohms7 4#ja amp]e ,ea* "o n[ te/ifi$ t ! batt]y s5t all ! curr5t he c>$ to take ?r\gh 8 tongue4 ,if !y s5d "o ?\s& times z mu* z t ?r\gh a crim9al no wond] x kills him4 ,x produces a twit* :5 ! contact is fir/ made1 aft]w>d a decid$ s5sation ( w>m? & acid ta/e4 ,if we %\ld increase ! voltage t5fold m1 say ! #aaj-volt dynamo curr5t 7direct curr5t71 & t\* ! b>e conductors ) our h&s1 ! ammet] w\ld indicate ab\t 4#jja amp]e4 ,t is1 al?\gh ?is curr5t has ab\t sev5ty times z mu* pu%1 or voltage1 z a dry cell1 no m electricity passes ?r\gh ! f+]s ?an did ?r\gh ! tongue 9 ! prec$+ exp]im5t ) "o cell4 ,! f+]s (f] s mu* great] resi/ance4 ,by wett+ ! f+]s & press+ !m firmly ^u ! b>e wires1 we may make ! ammet] read 4#ja1 t is1 we may increase ! curr5t t5fold by r$uc+ ! resi/ance to "o t5?4 ,b !re is no?+ disagreeable ab\t ! feel+4 ,if ! same exp]im5t is tri$ ) ! #aaj-volt alt]nat+ curr5t1 al?\gh ! quantity ( curr5t :i* passes ?r\gh ! f+]s is ! same z be=e1 ! t+l+ is m p]ceptible ?an 9 ! case ( ! direct curr5t4 ,if we jo9 toge!r sev5ty-five dry cells1 giv+ a voltage ( #aab1 & press ! b>e wires ) our wet f+]s1 ! ammet] w indicate 4#ja1 b !re is no t+l+ s5sation1 m]ely a slight w>m?4 ,! batt]y curr5t1 be+ cont9u\s1 causes no twit*+ ( ! muscles :ile ! contact is clos$4 ,! direct curr5t dynamo furni%es a slightly pulsat+ curr5t4 ,h5ce1 "o may tell by ! feel+ :e!r an electric curr5t comes f a batt]y or a direct curr5t dynamo4 ,! alt]nat+-curr5t dynamo gives a surg+ ( electricity back & =? 9 ! wires1 & ?is may be di/+ui%$ f ! direct curr5t by its feel+2 :51 h[ev]1 ! numb] ( alt]nations p] second is increas$ v greatly1 "o may receive ?r\gh ! body consid]able quantities ( electricity )\t feel+ x4 ,) a v high frequ5cy curr5t "o may put himself 9 circuit & light a #af-;c&le-p[] lamp )\t any disagreeable s5sation4 ,! out] sk9 is our *ief insulation4 ,if x is dry & well t\gh5$ by "w x (f]s a resi/ance ( ov] #ajj1jjj ohms ^u g5tle contact4 ,a w\nd$ spot1 or places l ! tongue ) moi/1 ?9 sk91 may (f] a resi/ance z l[ z #ejj ohms4 ,if "o has a p9 prick or a spl9t] 9 8 h& :i* he _c locate1 he may hold "o b>e wire ( a #aaj-volt alt]nat+ circuit 9 "o h& & move ! o!r b>e wire ab\t on ! suspect$ region1 & "k :5 x rea*es ! spot by a t+l+ s5sation4 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,feel+ ,electricity ,"o may t\* lightly ! #bbj-volt direct curr5t & sc>cely note any diff]5ce betwe5 ?is & ! #aaj-volt direct curr5t1 because "o is n v s5sitive to ! diff]5ce betwe5 4#jja amp]e & 4#jjb amp]e pass+ ?r\gh 8 body4 7#ajj volts7_/7#ajj1jjj ohms7 4#jja amp]e1 & 7#bjj volts7_/7#ajj1jjj ohms7 4#jjb amp]es ,physicians treat c]ta9 ailm5ts by ! use ( ! electric curr5t4 ,= ?is purpose !y inv>iably use a pulsat+ or alt]nat+ curr5t & r$uce ! resi/ance by us+ metal h&les & wet sponges = contact ) ! sk91 b ev5 s a v small am\nt ( curr5t passes4 ,! mod]ate twit*+ ( ! muscles seems to be ! end s\ght4 ,m5 :o are suppos$ to be kill$ by electric %ocks (t5 die f o!r causes4 ,a man p]*+ ^u an electric light pole1 repair+ wires1 may come 9 contact ) a wire *>g$1 say1 to #bjjj volts4 ,he may receive a %ock :i* ?r[s him 9 an unconsci\s condition across ano!r live wire :i* burns its way into 8 fle%1 or he may fall to ! gr\nd & be kill$ by ! fall4 ,a workman may hold a tool s z to %ort circuit a curr5t ?r\gh x1 mak+ x r$ hot 9 8 h&s4 ,s _m m5 :o h be5 %ock$ into unconsci\sness by high voltage curr5ts h recov]$ consci\sness lat] t we _c say h[ mu* curr5t is requir$ to kill a man4 ,= ! execution ( crim9als #ahjj to #bjjj volts are us$1 & by special metal contacts t5 to f\rte5 amp]es are =c$ ?r\gh ! body4 ,! fir/ execution ( a crim9al by electricity 0 p]=m$ 9 ,s+ ,s+ ,prison1 ,new ,york ,/ate1 9 #ahij4 ,!re 0 at t "t a hot controv]sy among exp]ts ov] ! "q :e!r dea?1 or m]ely unconsci\sness1 c\ld be produc$ by electricity4 ,to be on ! safe side ! legislature pass$ a law requir+ t ! electrocution ( a crim9al %\ld be foll[$ imm$iately by ! dissection ( 8 body4 ,only six /ates out ( =ty-n9e h ?us f> adopt$ t me?od ( capital puni%m5t1 five h aboli%$ capital puni%m5t1 & ?irty-eight /ill pref] hang+ to electrocution4 ,b x %\ld be rememb]$ t x is amp]es1 n volts1 t kill4 ,"o (t5 he>s ! mean+less expression1 he receiv$ #bjjj volts into 8 body4 ,! volts indicate ! pressure1 analog\s to p\nds p] squ>e in* ( wat] pressure4 ,amp]es ( electricity are analog\s to gallons ( wat]4 ,x is possible to h exce$+ly high voltage ( electricity )\t amp]es en\gh to d damage4 ,:5 "o holds 8 f+] ne> to a rapidly mov+ lea!r belt & a /ream ( sp>ks passes betwe5 ! f+] & ! belt1 ! voltage may be #ej1jjj or ev5 #ajj1jjj1 b ! quantity 9 amp]es is too small to d any damage or ev5 produce mu* s5sation4 ,a simil> ?+ is true :5 "o produces sp>ks by rubb+ a cat's back1 or lights ! gas by a sp>k produc$ by rubb+ ! feet ^u a c>pet4 ,su* sp>ks are m9iature lightn+ dis*>ges4 ,! real lightn+ does damage because x furni%es quantity1 measurable 9 amp]es1 z well z extremely high volts ( pressure4 ,at ?is po9t ,i 0 rem9d$ by ! boy :o _h receiv$ a %ock f ! eng9e t morn+ t he _h t\*$ only "o b9d+ po/4 ,h[ !n _h he clos$ a circuit ?r\gh 8 body1 & h[ c\ld he receive su* a t]rible %ock :5 !re 7 only a few batt]y cells to produce ! electric curr5t4 ,i repli$ t he _h ! di/9ction ( hav+ enc\nt]$ ab\t a #ejjj-volt curr5t4 ,9 ! language ( ! newspap]s he might say1 ,took #ejjj volts & /ill live4 ,we mu/ next proce$ to %[ h[ he really did close ! circuit & h[ ! sp>k coil enables a batt]y ( a few dry cells to produce exce$+ly high voltages4 ,,xi ,,! ,,electrical ,,sp>k+ ,,equipm5t ,,= ,a ,,gasol5e ,,eng9e ,"u ! %ade ( a great sug> maple1 ) ,millville ,lake spread be=e u1 we took ap>t & exam9$ ! entire equipm5t = produc+ ! electric sp>ks to explode ! mixture ( gasol5e & air 9 ! cyl9d]s ( our motor boat4 ,! eng9e has two cyl9d]s4 ,= ea* cyl9d] !re is a sep>ate batt]y & sp>k coil4 ,inasmu* z ! electrical outfit is duplicat$ = ea* cyl9d] x w be necess>y = u to consid] ! case ( "o cyl9d] only4 ,:5 ?is eng9e is runn+1 #gjj explosions p] m9ute are produc$ 9 ea* cyl9d]4 ,9 "o-twelf? ( a second ! foll[+ f\r ev5ts take place3 #a4 ,! cyl9d] is swept cle> ( ! products ( combu/ion =m$ by ! la/ explosion4 #b4 ,f\r drops ( gasol5e are vaporiz$ & mix$ ) "o qu>t ( air & pu%$ into ! cyl9d] by ! pressure ( ! atmosph]e4 #c4 ,?is mixture is compress$ by ! pi/on 9 ! cyl9d] to ab\t "o-fif? its orig9al volume4 #d4 ,! mixture is heat$ to its k9dl+ temp]ature1 :i* is above #bjjj degrees4 ,x !n burns ) a sudd5 expansion1 :i* drives ! pi/on be=e x & pu%es ! crank :i* is conceal$ 9 ! l[] end ( ! cyl9d] half-way ar\nd4 ,! crank is atta*$ to ! %aft1 :i* c>ries ! fly-:eel ^u "o end & ! propell] :eel ^u ! o!r end4 ,! mom5tum ( ! mov+ p>ts--*iefly t ( ! fly-:eel--suffices to accompli% ! rema9+ half ( ! revolution4 ,t any ma*9e c\ld be devis$ :i* c\ld repeat ^! f\r ev5ts #gjj times a m9ute 0 un?9kable a few ye>s ago4 ,! fir/ m5 :o ?\ght t a gasol5e eng9e c\ld be a practical ?+ 7 consid]$ vision>ies1 b n[ !y are f\nd to be m practicable ?an /eam eng9es4 ,!y are s effici5t t !y compete ) ! /eam eng9e ^u its own gr\nd1 &1 9 addition1 !y h op5$ up regions ( usefulness :i* ! /eam eng9e c nev] exploit4 ,s f> z we c see1 !y h a p]man5t monopoly ( ! navigation ( ! air4 ,x is ) ! f\r? ev5t m5tion$ above1 viz41 k9dl+ ! explosive mixture1 t we are n[ conc]n$4 ,! high temp]ature requir$ = ?is is obta9$ by =c+ an electrical curr5t aga9/ resi/ance4 ,five dry batt]y cells w\ld v readily heat a %ort piece ( f9e wire to a suffici5tly high temp]ature to explode ! mixture1 b x is impossible to alt]nately heat & cool a wire twelve times a second4 ,x is too sl[ an op]ation4 ,! only o!r me?od kn[n at pres5t is to imitate ! lightn+ & =ce an electric curr5t aga9/ ! resi/ance ( ! air ) suffici5t p[] to produce ! requir$ heat4 ,?is1 h[ev]1 requires an extremely high voltage--at lea/ #ejjj volts1 & our batt]y ( five cells has n m ?an sev5 & a half volts ( pressure4 ,! int]e/+ "q !n is1 h[ does ! sp>k coil enable u to raise ! voltage f #g to #ejjj4 ,to help t[>d an und]/&+ ( ! matt] ,i took sev5 small wire nails :i* ,i f\nd 9 ! boat--!y 7 sixp5ny f9i%+ nails4 ,i !n took two or ?ree y>ds ( ,no4 #bd insulat$ magnet wire1 su* z is us$ ^u electric bells1 etc4 ,i use x m (t5 ?an any o!r wire1 & always h "s ab\t ! boat4 ,i fa/5$ "o end ( ?is wire to "o ( ! b9d+ po/s ( a dry cell 7,fig4 #aac71 a1 & atta*$ bran*es c & d to x4 ,! o!r end1 b1 0 left free to act z a swit* = clos+ ! circuit by t\*+ x to ! rema9+ b9d+ po/4 ,illu/ration3 ,fig4 #aac ,illu/ration3 ,fig4 #aad ,illu/ration3 ,fig4 #aae ,"o boy !n t\*$ ! b>e ends c & d to ! tip ( 8 tongue1 :ile ,i t\*$ repeat$ly ! b9d+ po/ ) b4 ,!re 01 ( c\rse1 no s5sation4 ,we n[ w\nd a portion ( ! wire ^u ! bundle ( nails1 lay+ on ab\t fifty turns4 7,see ,fig4 #aad47 ,! tongue 0 n[ plac$ at ,t & b 0 t\*$ a few times to ! free b9d+ po/4 ,a v decid$ %ock 0 felt1 n :ile ! end ( ! wire 0 re/+ ^u b1 b at ! in/ant ( t\*+ & aga9 at break+ ! connection4 ,! %ock 0 noticeably /rong] at ! in/ant ( break+ ?an ( mak+ ! connection4 ,!re 0 also a sp>k =m$ :5 ! connection 0 brok51 :i* did n appe> be=e ! coil 0 made4 ,we next w\nd on m ( ! wire--ab\t fifty m turns 7,fig4 #aae74 ,:5 n[ connections 7 made & brok5 at b ! tongue at ,t felt a mu* m decid$ %ock1 & a l>g] sp>k occurr$ at b :5 ! circuit 0 brok54 ,bo? ! tongue & ! sp>k indicate t ! voltage is creep+ up v rapidly 9 ?is s]ies ( exp]im5ts4 ,we next connect$ two cells 9 s]ies1 !n ?ree1 f\r1 & f9ally five cells 9 place ( ! "o4 ,! sp>k grew l>g] & fatt]1 z ! boatm5 say1 ) ea* addition ( a cell4 ,x 0 n pleasant to use ! tongue 9 ! exp]im5t aft] ! numb] ( cells exce$$ two4 ,i remov$ ! bran* d f ! wire b & connect$ x to ! b9d+ po/1 z %[n 9 ,fig4 #aaf4 ,i !n remov$ ! cry/al f my wat* & p\r$ into x a little gasol5e4 ,i rubb$ ! ends ( b & d toge!r ov] ?is1 & :5 !y sep>at$ ! sp>k :i* 0 produc$ w\ld n light ! gasol5e4 ,we _h made a coil :i* produc$ a sp>k t look$ l a m9iature flame1 b /ill 0 n hot en\gh to set fire to gasol5e vap\r4 ,x simply ne$s m iron 9 ! core & m turns ( wire ab\t x4 ,br++ ! ends ( ! wires toge!r & sep>at+ !m is some:at l draw+ an arc ) ! arc light c>bons4 ,x requires a va/ly high] voltage to make a sp>k jump across an air gap ?an x does to lead x across ?us4 ,illu/ration3 ,fig4 #aaf ,! k9d ( coil we h made 7only l>g]7 is v mu* us$ 9 h\ses z a gas-light+ coil 7to be describ$ lat]74 ,x is v mu* us$ also = explod+ gasol5e eng9es4 ,x g5]ally passes "u ! "n ( ! make & break coil4 ,! revolv+ %aft ( ! eng9e is made to pu% toge!r ! ends ( ! wire & sep>ate !m at ! "r in/ant to make ! sp>k = explosion4 ,( c\rse ?is is done inside ( ! eng9e cyl9d]4 ,t type ( coil does n (f] resi/ance en\gh to protect ! batt]y1 & dry cells soon run d[n if us$ ) x4 ,! coils t we h 9 ?is boat are some:at diff]5t f t1 ! details ( :i* we _c n[ entirely expla94 ,!y (f] en\gh resi/ance to cut ! curr5t requir$ ( ! batt]y d[n to "o ?ird :at ! make & break coil w\ld take & at ! same "t !y raise ! voltage s mu* high] t ! sp>k w jump across an air gap )\t be+ l$ across z an arc4 ,h5ce !y are call$ jump sp>k coils4 ,illu/ration3 ,fig4 #aag ,x w be rememb]$ t :5 we 7 /udy+ ! dynamo we produc$ an electric curr5t by mov+ a magnet4 ,we may n[ add t an electric curr5t may be produc$ by simply *ang+ ! /r5g? ( a magnetic field4 ,! coil t we h j made creates a magnetic field 9 ! region ab\t itself :5ev] a curr5t is pass+ ?r\gh x4 ,! tongue at ,t 7,fig4 #aag7 detects an extra curr5t :ile ! magnetic field is be+ produc$1 or :ile x is dy+ away1 or x w detect any slight v>iations 9 ! /r5g? ( ! curr5t :i* produces ! magnetic field4 ,x is cu/om>y to di/+ui% betwe5 ^! two curr5ts4 ,! batt]y curr5t :i* produc$ ! magnetic field is call$ ! prim>y curr5t & ! curr5t :i* is detect$ by ! tongue is call$ ! second>y curr5t4 ,! prim>y curr5t 9 our exp]im5ts _h only a few volts ( pressure1 f "o to sev54 ,! second>y curr5t _h _m volts1 z indicat$ by ! sp>k4 ,if we rub ! end ( ! wire c across ! b9d+ po/ "u b 7,fig4 #aag7 no sp>k occurs4 ,! curr5t does n 9 ?is case g ?r\gh ! coil1 & no second>y curr5t is produc$4 ,:5ev] we t\* ! wire b to t po/ we h1 9 addition to ! prim>y curr5t :i* has n voltage en\gh to produce a sp>k1 a second>y curr5t fl[+ 9 ! same wire at ! same "t & hav+ voltage en\gh to produce a sp>k4 ,! prim>y curr5t is cont9u\s :ile ! contact is clos$2 ! second>y curr5t is mom5t>y1 z ! tongue detects1 & is produc$ only :ile *anges are be+ made 9 ! /r5g? ( ! magnetic field4 ,we w n[ take ano!r piece ( wire & w9d ^u ! coil ab\t two hundr$ m turns1 leav+ ?is out] coil :olly disconnect$ f ! inn] "o1 7,fig4 #aah74 ,i connect c & d1 ! t]m9als ( :at we may call ! second>y coil1 ) my measur+ in/rum5t & ,i connect a1 "o ( ! t]m9als ( ! prim>y coil1 ) ! batt]y4 ,i !n rub b1 ! o!r prim>y t]m9al across ! free b9d+ po/ ( ! batt]y4 ,at ! in/ant ( clos+ ! prim>y circuit--t is1 ( build+ up ! magnetic field--a second>y curr5t is induc$ 9 ! second>y coil1 :i* la/s = only an in/ant1 too brief a "t = ! ne$le to measure x1 al?\gh its motion indicates bo? ! pres5ce & ! direction ( ! induc$ curr5t4 ,:ile ! prim>y circuit rema9s clos$--t is1 :ile no *ange is occurr+ 9 ! /r5g? ( ! magnetic field--! ne$le returns to z]o1 indicat+ no second>y curr5t4 ,b :5 n[ ! prim>y circuit is brok5 & ! magnetic field loses its /r5g?1 ! ne$le indicates a mom5t>y curr5t 9 ! second>y coil & 9 ! opposite direction f :at x _h be5 at fir/4 ,illu/ration3 ,fig4 #aah ,if1 !re=e1 ,i rapidly make & break ! curr5t at b ,i produce an alt]nat+ curr5t 9 ! second>y coil4 ,i w connect c & d ) a m9iature lamp &1 re/+ a co>se file ^u ! free b9d+ po/1 ,i w rake ! end ( ! wire b up & d[n ^u ?is file s t1 z x dances along ^u ! file1 x w rapidly make & break ! prim>y circuit1 & !re=e rapidly *ange ! /r5g? ( ! magnetic field4 ,y notice t ! lamp lights up mod]ately well4 ,x is be+ light$ by an alt]nat+ curr5t4 ,i move ! wire a little m sl[ly & y see ! flick] ( ! alt]nations4 ,accord+ to ! label ^u ! lamp x requires t5 volts1 & our batt]y c\ld n give t4 ,we h !re=e /epp$ up ! voltage z we say & we h a v]itable /ep-up trans=m]4 ,9 ?is case ! prim>y & second>y circuits are entirely sep>ate4 ,x is a famili> fact t diff]5t electric curr5ts may pass ?r\gh ! same wire at ! same "t )\t app>5t conflict4 ,we s5d num]\s telegraph despat*es ?r\gh ! same wire at ! same "t4 ,x is q z easy = sev]al pairs ( p]sons to telephone ov] ! same wire at ! same "t z x is = ^? same sev]al pairs to c>ry on sep>ate conv]sations 9 ! same room at ! same "t1 at1 say1 an aft]noon tea4 ,we may use ! same wire at ! same "t to c>ry direct & alt]nat+ curr5ts4 ,?is fact 0 fir/ discov]$ 9 #aijb by ,b$ell ( ,cornell ,univ]sity4 ,prim>y & second>y curr5ts d n require sep>ate prim>y & second>y coils to convey !m4 ,!y may or may n be connect$ into "o cont9u\s coil4 ,x is q immat]ial :e!r !y are connect$ or n s long z !y are 9 ! same magnetic field4 ,inde$1 x seems t ! field outside ( ! wire may be q z important z ! wire itself4 ,illu/ration3 ,fig4 #aai ,we h n[ #ajj turns 9 ! prim>y & #bjj turns 9 ! second>y coils4 ,let u connect b ) c s z to make "o cont9u\s circuit ( #cjj turns4 ,let u !n put a bran* ^u b to connect ) ! batt]y1 ?us hav+ #ajj turns = ! prim>y circuit1 & put a bran* ^u a to connect ) ! lamp1 ?us hav+ #cjj turns ^u ! lamp1 7,fig4 #aai74 ,:5 n[ we rub b ^u ! file1 z be=e1 ! lamp lights up m brightly ?an be=e1 indicat+ t we h /epp$ up ! voltage /ill high]4 ,v>y+ ! /r5g? ( ! magnetic field induces a second>y curr5t & ! voltage ( ! induc$ curr5t is det]m9$1 9 "p1 by ! numb] ( turns 9 ! second>y circuit4 ,if :at we h be5 say+ is true we ought to be able to get ^! same results f an electric bell4 ,to te/ ?is we connect$ wires ) a & c1 7,fig4 #abj71 & s9ce ,i knew t ! second>y curr5t at ,s w\ld be too sev]e = ! tongue we decid$ to feel x ) ! h&s4 ,= ?is purpose we want a l>g] surface ?an ! wires !mselves (f] = contact ) ! h&s1 & s ,i twi/$ ! b>e end ( ea* wire ar\nd an iron spike4 ,! f\r boys !n arrang$ !mselves 9 l9e1 jo9+ h&s1 & ! boy at ea* end ( ! l9e held a spike 9 8 free h&4 ,?us we _h put ! enorm\s resi/ance ( f\r human bodies jo9$ 9 s]ies 9 ! second>y circuit4 ,:5 n[ ,i connect$ two dry cells ) a & b 7,p1 ,fig4 #abj7 ! hamm] ( ! bell act$1 l ! file 9 ! =m] case1 z int]rupt] ( ! prim>y circuit4 ,z x rapidly made & broke ! prim>y circuit1 x produc$ rapid *anges 9 ! /r5g? ( ! magnetic field & ?us induc$ a second>y curr5t :i* ! boys all felt4 ,! fact t x =c$ its way ?r\gh f\r bodies %[s t its voltage 0 high4 ,! high voltage 0 also indicat$ by ! sp>k :i* always occurr$ 9 ! bell4 ,! prim>y circuit 9 ?is case has n m ?an ?ree volts :ile ! second>y has m ?an a hundr$4 ,we h x 9 our p[] to give ! second>y curr5t almo/ any voltage we *oose1 ) ?is limitation ea* increase 9 voltage necessitates a proportional sacrifice ( quantity4 ,! watt p[] induc$ 9 ! second>y circuit _c exce$ t contribut$ to ! prim>y circuit--inde$ _c q equal x s9ce !re is "s loss 9 heat4 ,illu/ration3 ,fig4 #abj ,suppose we op]ate a bell on a prim>y curr5t hav+ ?ree volts & 4#be amp]e1 t is1 4#ge watt4 ,suppose !n ! voltage ( ! second>y curr5t is /epp$ up to fifty times ?ree1 or #aej volts4 ,! quantity ( second>y curr5t w be f\nd to be some:at less ?an "o fiftie? ( 4#be or 4#jje amp]e4 ,! #aej-volt alt]nat+ curr5t f ! bell is m tol]able ?an t f a #aej-volt dynamo1 because ! quantity is limit$ 9 ! =m] case4 ,our sp>k coil has a vibrator :i* acts precisely l ! hamm] ( ! bell to make & break ! prim>y circuit & ?us make rapid *anges 9 ! magnetic field produc$ by ! prim>y coil4 ,! prim>y coil ( ! sp>k coil is _m times l>g] ?an ! coil ( ! bell1 t is1 x conta9s _m m turns ( wire4 ,x has mu* m iron 9 ! core4 ,we use ^u x five cells in/ead ( ! two cells ^u ! bell4 ,! result ( all ?is is t we h a mu* m p[]ful magnetic field ?an t 9 ! bell & _m m watts ( en]gy f :i* to induce a second>y curr5t4 ,n[ ! numb] ( turns employ$ 9 ! second>y circuit ( our sp>k coil is v great1 /epp+ its voltage up to ?\s&s :]e ! bell induc$ hundr$s4 ,illu/ration3 ,fig4 #aba ,suppose we n[ repeat our exp]im5t 9 :i* we tri$ to light ! gasol5e 9 ! wat* cry/al1 us+ n[ ! sp>k coil ( ! boat in/ead ( our small home-made coil4 ,9 ,fig4 #aba1 ,b is ! batt]y ( five dry cells4 ,s is a swit*4 ,v is ! vibrator1 :i*1 l ! hamm] ( an electric bell1 makes & breaks ! prim>y circuit4 ,( c\rse ! coil has a core ( iron1 al?\gh t is n "h repres5t$1 &1 ( c\rse1 ! coil has _m hundr$ turns in/ead ( ! few "h repres5t$1 & ( c\rse also x is built up ( _m lay]s in/ead ( "o z "h repres5t$4 ,! second>y has v _m m turns ?an ! prim>y1 b ^? 9 :i* ! prim>y curr5t passes are common to bo? circuits4 ,!re is also a cond5s]--n "h repres5t$1 & n to be describ$ 9 ?is book4 ,! result ( all ?is is t ! second>y circuit has a voltage ( betwe5 #ejjj & #aj1jjj1 & a sp>k jumps across ! gap at c betwe5 "o sixte5? & "o eigh? ( an in* long4 ,?is sp>k is hot en\gh to light ! gasol5e :i* ,i h put 9 ! wat* cry/al at c4 ,illu/ration3 ,fig4 #abb ,let u return to ! bell = a few m9utes4 ,i h "h a m9iature lamp :i* requires #aj volts & 4#a amp]e1 t is1 #a watt1 :i* ,i w connect at ,s 7,fig4 #abb74 ,:5 n[ ,i close ! prim>y circuit ) two cells at ,p y notice t ! lamp lights up1 b fa9tly4 ,x is n receiv+ 4#a amp]e4 ,rememb] we h only 4#ge watt at our disposal & ?is lamp requires #a watt4 ,h5ce x is gett+ only ?ree qu>t]s en\gh en]gy4 ,we connect 9 a ?ird cell & n[ x lights up to full brilliancy4 ,! resi/ance ( ?is lamp mu/ be ab\t #ajj ohms4 7#aj volts7_/7#ajj ohms7 4#a amp]e ,! resi/ance ( ! f\r boys might h be5 #fj1jjj ohms1 & ! voltage ( ! second>y circuit might 9 t case h be51 say1 #aej4 7#aej volts7_/7#fj1jjj ohms7 4#jjeb amp]e ,h[ does x happ5 t ! second>y curr5t _h a pressure ( #aej volts on ! boys b _c supply ev5 ! #aj volts requir$ by ! lamp8 ,p]haps we c be br\ght to appreciate ! answ] to t "q be/ by ask+ ourselves "s o!rs q l x4 ,:y did n ! man :o built our mill two g5]ations ago locate x ^u ! small /ream t fl[$ ne> 8 h\se8 ,! small /ream 0 m conv5i5tly locat$ = him & x has q z mu* fall z he got at ! foot ( ?is lake4 ,we sometimes express ! fact by say+ t ! head ( wat] or ! wat] pressure 0 q z mu* 9 "o ( ^! cases z ! o!r4 ,"o boy said t ! /ream sometimes gives out4 ,ano!r "o said t x nev] did h wat] en\gh to run t :eel4 ,und\bt$ly ! tr\ble is ) ! quantity1 said ,i1 b ,i want to %[ y t we _c ma9ta9 ! pressure unless !re is suffici5t quantity back ( x4 ,illu/ration3 ,fig4 #abc ,9 ,fig4 #abc1 suppose ,a repres5ts a small1 slim tank ( wat] ?ree feet high4 ,! wat]-:eel ,w1 requires "o gallon ( wat] a m9ute pu%$ along by a ?ree-foot head ( wat] pressure to run x4 ,! supply pipe ,s is br++ into ! tank n m ?an "o qu>t ( wat] p] m9ute4 ,a gate at ,r enables u to regulate ! fl[ ( wat]1 z we regulate ! fl[ ( electricity1 by us+ m or less resi/ance4 ,n[ x is evid5t t if we close ! gate1 or p>tially close x1 & all[ ! tank to fill ) wat]1 we may !n op5 ! gate & run ! :eel = a %ort "t1 b ! level ( ! wat] 9 ! tank soon beg9s to fall & ! pressure gr[s less & ! :eel /ops mov+4 ,x is j s ) all g5]ators ( electric curr5t4 ,if we take f !m m ?an !y c supply cont9u\sly ! voltage falls4 ,?is is notori\sly true ( dry cells4 ,l ! wat] tank repres5t$ 9 ,fig4 #abc1 !y run d[n if us$ cont9u\sly to furni%1 say1 "o amp]e ( curr5t1 b !y may furni% x = a %ort "t1 ! voltage rapidly fall+ mean:ile4 ,!n if giv5 a %ort re/ !y pick up & w aga9 furni% full pressure4 ,! voltage ( a dry cell falls some:at :5 x is requir$ to give ! v small am\nt ( curr5t requir$ to actuate a volt met]1 say 4#jae amp]e4 ,h5ce1 our volt met] w n q correctly %[ :at ! voltage ( a s+le cell w\ld be on op5 circuit4 ,notice t1 :5 ,i put "o cell ^u ?is volt met] ! ne$le %[s #a4db volts2 b :5 ,i put f\r cells 9 s]ies ^u x ! ne$le indicates six volts1 z ne>ly z we c read x4 ,t is1 ! voltage ( ea* cell 9 ?is case appe>s to be #a4e4 ,:at has increas$ ! voltage ( a cell f #a4db to #a4ej8 ,simply ?is3 :5 4#jae amp]e1 ! am\nt requir$ by ! volt met]1 0 tak5 f "o cell x r$uc$ its pressure1 b :5 a multipli] ) t5 times ! resi/ance 0 add$ we secur$ our read+ by us+ only 4#jjf amp]e ( curr5t1 & ?is did n appreciably r$uce ! true pressure ( ! cells4 ,! induc$ curr5t f our bell :5 held back by #fj1jjj ohms ( resi/ance 9 ! f\r boys 0 able to pu% ) #aej volts ( pressure1 & 4#jjbe amp]e pass$ )\t noticeably r$uc+ ?is pressure1 b :5 ! same curr5t 0 held back by only #ajj ohms 9 ! filam5t ( ! lamp ne>ly =ty times z mu* curr5t pass$1 & ! pressure dropp$ to some?+ less ?an t5 volts4 ,we w try an exp]im5t to %[ h[ ! voltage w sudd5ly fall :5 we r$uce ! resi/ance ( y\r f\r bodies4 ,illu/ration3 ,fig4 #abd ,fill ^! two empty t9 pails 9 :i* our lun* 0 br\ght ) wat] f ! lake & spr9kle 9 ! salt left ov] f ! lun*4 ,n[ twi/ a b>e copp] wire ar\nd ! bail ( ea* pail & connect ^! ) ! bell s z to get ! induc$ curr5t f its magnet4 7,see ,fig4 #abd47 ,let ! two pails ( wat] be ! t]m9als ( ! two wires at ,s4 ,n[ y f\r boys wet y\r h&s 9 ! wat] & !n jo9 h&s1 & ^? at ! two ends ( ! l9e put y\r free h&s ^u ! outside ( ! pails ( wat] :ile ,i close ! prim>y circuit4 ,y ( c\rse feel ! curr5t j z y did :5 y held ! spikes 9 y\r h&s 9 a =m] exp]im5t4 ,b n[ y two end boys put y\r free h&s into ! salt wat]1 & y in/antly get a v sm>t %ock4 ,! resi/ance is no long] #fj1jjj4 ,x has dropp$ way d[n to #bjjj1 & if ! voltage _h rema9$ at #aej y w\ld h receiv$ a t]rible %ock1 b ! voltage has dropp$ d[n to five4 ,x is z ?\gh y _h be5 pu%+ v h>d aga9/ a po/ & x sudd5ly gave way4 ,y _c pu% aga9/ a ?+ :i* (f]s no resi/ance4 ,s ! voltage falls :5 resi/ance is r$uc$1 & p>ticul>ly if ! s\rce ( supply has v little capacity4 ,"h is ano!r exp]im5t y mu/ try :5 y g back to ! city4 ,at a c]ta9 wat] faucet 9 my laboratory ! pressure is disagreeably high4 ,! wat] fl[s ) great =ce & spatt]s badly4 ,we c easily r$uce ! pressure s t ! wat] w fl[ 9 a limpid /ream4 ,fig4 #abe %[s ! situation2 f is ! faucet1 & 9 ! pipe und]nea? ! s9k !re is a /op-cock c4 ,?is may be adju/$ p]man5tly s t ! faucet f w act pleasantly4 ,! same ?+ is repres5t$ aga9 at ! gas /ove4 ,let f 9 ! ,fig4 #abe repres5t a gas cock at ! /ove4 ,suppose ! pressure is s high t ! gas flames pass m gas ?an is readily consum$4 ,x is possible to adju/ a /op-cock l c fur!r back 9 ! pipe s z to produce hott] flames1 get rid ( ! poison\s fumes ( half burn$ gas1 & cut d[n ! mon?ly gas bills "o half4 ,illu/ration3 ,fig4 #abe ,my g>d5 hose w usually ?r[ a /ream across ! /reet1 :i* is v desirable :5 "o wi%es to spr9kle ! /reet1 b ?is pressure is disa/r\s :5 ,i wi% to spr9kle ! fl[]s4 ,turn+ d[n ! /op-cock at ! nozzle makes x %oot a small] /ream b m spiteful 9 pressure1 knock+ ! fl[]s to pieces & wa%+ ! soil away f _! roots4 ,b if ,i p>tially close ! /op-cock at ! side ( ! h\se :]e ! hose is atta*$ ,i may h ! /ream ( wat] fl[ z g5tly z ,i *oose4 ,i %\ld meet precisely ! same situation if ,i tri$ to r+ an ord9>y electric bell by a #aaj-volt curr5t1 & ,i %\ld use ! same me?od ( ov]com+ ! difficulty4 ,! great virtue ( ! dynamo is t x c furni% a l>ge supply s t ! voltage is kept con/ant on a great fl[ ( curr5t4 ,illu/ration3 ,fig4 #abf ,i h n =gott5 ! "q1 b h tri$ to "w t[>d its answ] all ?is "t4 ,! "q is1 :y did ,erne/ get a %ock ?is morn+ :5 he t\*$ only "o b9d+ po/1 & :5 ! batt]y ( five cells is n capable ( giv+ %ocks to any "o :o t\*es its b9d+ po/s directly8 ,we ne$ "o m diagram to give ! f9al answ]4 ,9 ,fig4 #abf e repres5ts ! b9d+ po/ f :i* ! %ock 0 receiv$4 ,b is ! batt]y ( five cells1 ,c is ! sp>k coil1 ,g is ! eng9e cyl9d]1 f is ! sp>k plug4 ,:5 "o wi%es to />t ! eng9e he closes ! swit* ,s4 ,?is makes a cont9u\s conductor f ! batt]y to ! metal cyl9d] itself4 ,z ! eng9e rolls ov] x closes ! gap 9 ! conductor at d = an in/ant4 ,! prim>y circuit is !n complet$ & ! curr5t passes f ,b to ! cyl9d]1 ?r\gh ! metal ( ! cyl9d] to d1 !n to ! coil ,c1 :]e x passes ?r\gh a portion ( ! coil & !n back to ! batt]y4 ,! vibrator on ! coil causes ! magnetic field to rapidly v>y 9 /r5g?4 ,?is induces a second>y curr5t 9 ! :ole coil :i*1 because x passes ?r\gh a v great numb] ( turns1 has a high voltage4 ,?is passes f ,c ?r\gh ,b to ! base ( ! eng9e1 !n up ! walls ( ! cyl9d] to ! plug f1 !n jumps across ! gap at a1 caus+ ! sp>k :i* explodes ! mixture ( gasol5e & air 9 ! cyl9d]4 ,! sp>k plug f is porcela9--an exce$+ly good insulator4 ,?r\gh ! c5tre ( ?is passes a wire f a to e4 ,! curr5t passes up ?is & back to ,c4 ,n[ ! eng9e re/s ^u ! floor ( ! boat1 & ,erne/ /ood ^u ! same floor4 ,! wood ( ?is floor :5 dry & clean is a v good insulator1 b :5 wet1 & p>ticul>ly :5 wet ) wat] t has ev] s slight an am\nt ( any salt 9 solution1 x becomes a conductor = su* high t5sion curr5ts4 ,:5 !re=e ,erne/1 /&+ ^u ! floor ( ! boat1 t\*$ ! b9d+ po/1 e1 ?is induc$ curr5t ( high voltage f\nd x ab\t z easy to pass f ! metal ( ! eng9e cyl9d] ?r\gh ! wood to 8 body & ?r\gh 8 body to e z to jump across ! %ort air gap at a4 ,!re are two ?+s ^u :i* he may congratulate himself4 #a4 ,:ile ! coil /epp$ up ! voltage s high x r$uc$ ! available quantity ( ! curr5t1 s t ! %ock 0 a safe "o4 #b4 ,he receiv$ only a portion ( ! curr5t :i* pass$4 ,! major "p ( x pass$ across ! gap at a1 o!rwise we %\ld h notic$ t ! eng9e miss$ an explosion :5 he t\*$ ! b9d+ po/4 ,! only "p ( ?is electrical outfit f :i* "o may receive a %ock is t l9e f e to ,c4 ,! greate/ diff]5ce 9 electric pressure is always to be f\nd betwe5 ! two extremities ( ! electric g5]ator2 z1 = example1 betwe5 ! c>bon end & ! z9c end ( ! batt]y1 ! positive & negative poles ( ! dynamos2 ! "r-h& & left-h& end ( ?is coil4 ,s9ce ! "r-h& end is connect$ by good conductors ) ! metal ( ! eng9e & ) ! floor ( ! boat & ?r\gh x ) our bodies1 we are 9 ! same electrical condition z ! "r end ( ! coil2 b ! left-h& end & ! wire connect+ x ) e are =c$ by ! v>y+ magnetic field into a v diff]5t /ate ( electric t5sion1 & x is insulat$ f ! eng9e & f u by ! porcela9 sp>k plug4 ,we say t ! diff]5ce 9 pot5tial betwe5 ! two sides ( ?is sy/em is #ejjj to #aj1jjj volts4 ,! wat] 9 ?is lake fl[s ?r\gh ! /ream at ! o!r end ( ! lake to ! ocean4 ,! wat] ( ! ocean evaporates to =m cl\ds4 ,cl\ds drift ov] ! l& & drop _! ra9 to repl5i% ! lake4 ,! diff]5ce 9 wat] level betwe5 ?is lake & ! ocean is tw5ty feet4 ,a diff]5ce 9 wat] level is :at makes x a wat] p[] & x is :at occasion$ ! build+ ( our mill4 ,?is diff]5ce ( wat] level corresponds 9 our electric g5]ators to ! diff]5ce 9 pot5tial4 ,! diff]5ce 9 pot5tial ma9ta9$ by our batt]y ( five cells :5 n produc+ curr5t is #g4e volts4 ,! diff]5ce 9 pot5tial betwe5 ! two ends ( our coil1 :5 ! batt]y is agitat+ its magnetic field1 is p]haps a ?\s& times z mu*1 or #gejj volts4 ,! boys took _! swim 9 ! lake & aft]w>d1 :ile we 7 all on %ore ly+ on ! grass1 !y br\ght up aga9 ! "q ( ! ma*9e-%op4 ,!y 7 anxi\s to "k if ,i _h any plans 9 reg>d to x4 ,i said ,i _h be5 ?9k+ ab\t x a good deal ov] night b _h be5 wait+ to he> _! plans4 ,well1 !y ?\ght x w\ld be good to h a turn+ la!1 b c\ld n ?9k ( any?+ else unless x might be a gr9d/one run by p[]4 ,i said ,i _h ?\ght ( a ,c5tral ,/ation ,electric ,plant4 ,at ?is !y all sat up4 ,hydro-electric /ations are ! prop] ?+ n[1 ,i rem>k$4 ,on ! ,rio ,gr&e ,riv] 9 ,colorado !y are con/ruct+ sev]al plants :]e wat] p[] w be utiliz$ to g5]ate electricity = use m ?an "o hundr$ & fifty miles away4 ,= transmitt+ electricity to su* a di/ance !y /ep up ! voltage1 or electro-motive =ce z x is call$1 to #ajj1jjj volts4 ,!y are h>ness+ ! ,au ,sable ,riv] 9 ,mi*igan to g5]ate electricity & transmit x at #ace1jjj volts e4 m4 f4 to t[ns ne>ly two hundr$ miles away4 ,electricians use e4 m4 f4 = electro-motive =ce1 j z y boys use exams4 z slang = ! motive =ce 9 s*ool4 ,( c\rse we are aw>e t s9ce #ahif "s ( ! wat] p[] ( ,niag>a _h be5 conv]t$ into electric p[] to run /reet c>s & factories & furni% electric light & electric heat z f> away z ,buffalo1 tw5ty-six miles di/ant4 ,ab\t #ah1jjj1jjj are n[ be+ inve/$ 9 hydro-electric ent]prises ev5 9 ,mexico4 ,by ?is "t ! boys 7 all /&+ up & />+ at me1 :ile ,h>old inquir$ if ,i 7 talk+ 9 my sleep4 ,i h at any rate succe$$ 9 wak+ y all up1 said ,i1 & :at ,i h said is n altoge!r a joke4 ,let me expla9 some:at at l5g?4 ,,xii ,,electricity ,,f ,,c5tral ,,/ations ,l>ge dynamos g5]ate electricity v mu* m *eaply ?an small ma*9es c1 & ma*9es :i* h a full load cont9ually produce ! curr5t v mu* m *eaply ?an ^? :i* run ^u v light load "p ( ! "t4 ,! l>ge/ c5tral /ations ) load ev5ly di/ribut$ = ! :ole day c\ld furni% electricity pr(itably at f\r c5ts p] kil[att h\r4 ,!re are _m small electric light+ plants :i* furni% curr5t f sund[n to midnight only at fifte5 c5ts p] kil[att h\r1 ) little pr(it4 ,! trans=m] 7,fig4 #abg7 makes x possible to ga!r all ?is g5]ation ( electricity = sp>sely settl$ di/ricts into l>ge c5tral /ations1 locat$ sometimes f> away f ! consum] p]haps1 :]e !re is abundant p[] 9 "s wat]-fall1 ?us sav+ ! exp5se ( coal = runn+ ! dynamos4 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,op]at+ ! ,swit*bo>d ,a few ye>s ago !re 7 no c5tral /ations = ?is purpose4 ,n[ accord+ to ! late/ c5sus reports !re are 9 ! ,unit$ ,/ates ab\t #cj1jjj plants1 includ+ ^? :i* belong to c]ta9 cities1 t g5]ate electricity = sale1 & !re are twice z _m m isolat$ plants to furni% light & p[] 9 factories1 hotels1 etc4 ,illu/ration3 ,fig4 #abg ,! money inve/$ 9 c5tral /ation bus9ess n[ exce$s six billion doll>s1 & ! annual output ( electric curr5t is suffici5t to keep eight billion #af-;c&le-p[] c>bon filam5t electric lights burn+ cont9u\sly night & day4 ,all ?is has m ?an d\bl$ 9 ! la/ five ye>s4 ,c5tral /ations are n[ furni%+ ab\t five times z mu* curr5t = heat+1 cook+1 & *>g+ automobiles z !y did five ye>s ago4 ,ab\t "o ?ird ( all ! c5tral /ations dep5d on wat] p[]4 ,illu/ration3 ,fig4 #abh ,illu/ration3 ,fig4 #abi ,we might take z ! type ( hydro-electric c5tral /ation1 t is1 "o :i* g5]ates electricity by wat]-p[]1 ! ,gl5wood ,/ation ( ! ,c5tral ,colorado ,p[] ,company4 ,?is /ation has two #ijjj horse-p[] wat] turb9es4 ,ea* wat]-:eel drives an alt]nat+-curr5t g5]ator :i* develops #djjj volts ( e4 m4 f4 ,^! wat] :eels & g5]ators are %[n 9 ,fig4 #abi4 ,! p5/ocks are to be se5 com+ ?r\gh ! back wall ( ! build+4 ,!y br+ wat] at #agj foot head1 or ab\t sev5ty-five p\nds p] squ>e in* /atic 7/&+7 pressure4 ,?ree huge trans=m]s1 ea* weigh+ tw5ty-six tons1 /ep up ! e4 m4 f4 f #djjj to #ajj1jjj volts4 ,^! are ! cyl9d]s %[n 9 ,fig4 #acj4 ,!y simply conta9 a great _m coils ( copp] wire ) a va/ am\nt ( iron at ! c5tre4 ,!y accompli% 9 a l>ge way :at our sp>k coil does 9 a less] degree4 ,b :y g to all ?is exp5se to produce su* a dang]\s & tr\blesome voltage8 ,! answ] briefly is1 t :ile x is dang]\s & tr\blesome ! exp5se is n s great z x w\ld be to supply by any o!r me?od ! electric curr5t requir$4 ,d5v] & num]\s o!r places1 l>ge & small1 require electric curr5t4 ,f "o to two hundr$ miles away on ! ,gr&e ,riv]1 !re is va/ p[] runn+ to wa/e4 ,we h to *oose on ! "o h& betwe5 buy+ p[] 9 ! %ape ( coal & di/ribut+ p[] plants to ^? v>i\s localities :]e electricity is ne$$1 & on ! o!r us+ ?is wat]-p[]1 :i* is n[ runn+ to wa/e1 to g5]ate electricity :i* we may transmit & di/ribute ?r\gh\t ! "o hundr$ & eighty-five miles to ,d5v]1 ,leadville1 ,b\ld]1 ,dillon1 ,idaho ,spr+s1 etc4 ,b electric en]gy transmitt$ a long di/ance suff]s great loss4 ,illu/ration3 ,fig4 #acj ,suppose1 = in/ance1 ,i ne$$ to supply fifty amp]es at "o hundr$-volt pressure t5 miles di/ant f ! g5]ator1 & _h a conductor ! size ( a trolley wire to br+ ! curr5t4 ,! resi/ance ( ! trolley wire is "o ohm = e two miles1 or five ohms4 ,! drop 9 voltage is f\nd by multiply+ ! amp]es ( curr5t by ! ohms ( resi/ance4 ,t5 miles f ! c5tral /ation1 !re=e1 ! drop on fifty amp]es w\ld be #ej #e #bej volts4 ,x w\ld1 !re=e1 be necess>y to ma9ta9 a pressure ( #cej volts at ! g5]ator to deliv] ! fifty amp]es at #ajj volts4 ,! en]gy suppli$ by ! g5]ator is #cej volts #ej amp]es #ag1ejj watts #ag4e ,k4 ,w4 ,! en]gy deliv]$ to ! consum] is #ajj volts #ej amp]es #ejjj watts #e ,k4 ,w4 ,9 ord] to deliv] fifty c5ts' wor? ( electricity p] h\r to ! consum] x w\ld1 9 ?is case1 be necess>y to g5]ate #a4ge wor? ( electricity at ! c5tral /ation4 ,t is1 ab\t sev5ty p] c5t4 ( ! en]gy g5]at$ w\ld be wa/$ 9 transmission4 ,if n[ we decide to g5]ate ?is electrical en]gy at t5 times z high voltage x w be necess>y to transmit only "o t5? z _m amp]es1 or five4 ,9 ?is case ! drop 9 voltage w\ld be #e amp]es #e ohms #be volts4 ,x w\ld be necess>y to ma9ta9 #ajbe volts ( pressure at ! g5]ator to deliv] to ! consum] ! five amp]es at #ajjj volts #ejjj watts4 ,t is1 to deliv] #ejjj watts 9 ?is case we mu/ g5]ate #ajbe volts #e amp]es #eabe watts1 & less ?an #b-a_/b p] c5t4 ( ! en]gy g5]at$ w\ld be lo/ 9 transmission4 ,if n[ ! consum] mu/ h 8 en]gy deliv]$ at #ajj volts1 we mu/ introduce a /ep-d[n trans=m] at 8 end ( ! l9e :i* may give him #ej amp]es at #ajj volts #ejjj watts4 ,?is trans=m]1 be+ small1 w cause a loss ( #ae or #bj p] c5t41 b if !re 7 a v l>ge am\nt to trans=m x might be done ) a loss ( only #d p] c5t4 ,illu/ration3 ,fig4 #aca ,illu/ration3 ,fig4 #acb ,x is n ?\ght to be advisable to raise ! voltage at ! g5]ator high] ?an #djjj4 ,?is w n suffice to supply l>ge work+ curr5ts to a great] di/ance ?an ab\t six or eight miles4 ,= a di/ance ( #aj miles #fjjj volts are desirable2 = #ej miles #cj1jjj volts2 = #ajj miles #fj1jjj volts2 = #afe miles #ajj1jjj volts2 & = #bjj miles #abj1jjj volts4 ,notice t 9 ?is table ! voltage rises at ! rate ( #fjj p] mile4 ,s9ce x is n desirable = ! g5]ator itself to produce a high] voltage ?an #djjj1 we mu/ dep5d ^u trans=m]s to produce ^! high voltages4 ,let u !n consid]1 a little m 9 detail1 ! con/ruction ( a trans=m]4 ,i h "h "s draw+s ( "o :i* ,i propose t we make 9 ! ma*9e %op1 & use 9 our c5tral /ation equipm5t 9 ! future4 ,we w procure ! ?9ne/ & s(te/ %eet iron possible & cut out ( x a lot ( pieces %ap$ l ! lett] ,h ) ! dim5sions %[n 9 ,fig4 #aca4 ,^! are to be pil$ "o ^u ano!r1 ) /rips ( pap] betwe51 until ! pile is #a-a_/b in*es ?ick4 ,!n f\r pieces ( bo>d are to be bolt$ to ! sides ( ^! 7,fig4 #acb74 ,! dim5sions ( ea* ( ! f\r blocks1 is to be #g-a_/b in*es long by #c in*es wide by #a-a_/b in*es ?ick4 ,^u ! cross b> ( ! ,h we w w9d #djj turns ( ,no4 #ab d\ble cotton-cov]$ copp] wire1 br++ out ! ends = future atta*m5ts1 & !n w9d on #abjj turns ( ,no4 #aj d\ble cotton-cov]$ copp] wire4 ,! wire w fill ! space betwe5 ! blocks z indicat$ by ! diagram 9 ,fig4 #acc4 ,we w !n cut /rips ( ! %eet iron #f in*es long by #a-a_/d in*es wide1 & bridge across ! ends ( ! ,h1 pry+ op5 ! leaves ( %eet iron & tuck+ !m 9 betwe5 z %[n 9 ,fig4 #acd4 ,we %all !n drill a hole at ea* corn] & bolt !m 9 place4 ,b9d+ po/s w be plac$ at a1 b1 c1 & d 7,fig4 #acd71 & ! two ends ( ! ,no4 #ab wire w be br\ght to a & b & ^? ( ! ,no4 #ah wire w be br\ght to c & d4 ,go+ ?r\gh all ?is detail ( con/ruction has probably made y lose sight ( ! ess5tial features ( ?is trans=m]4 ,let u = a mom5t turn back & see :at !y are4 ,we h a l>ge coil ( wire #c in*es long & #g-a_/b in*es 9 diamet]4 ,x is compos$ ( a co>se w9d+ & a f9e w9d+1 :i* we may designate z ! prim>y & second>y coils1 if we *oose4 ,( c\rse ! only reason = hav+ diff]5t sizes ( wire is s t we may s5d l>g] curr5ts ?r\gh "o ?an ! o!r4 ,! coil has a lam9at$ iron core1 t is1 x is compos$ ( lay]s ( %eet iron4 ,^! lay]s are insulat$ f "o ano!r4 ,?is is ess5tial1 al?\gh we _c expla9 :y n[4 ,b p]haps ! mo/ ess5tial feature ( ! trans=m] is t iron ext5ds cle> ar\nd f "o pole ( ?is electro-magnet to ! o!r4 ,fig4 #ace repres5ts a section ?r\gh ! coil made 9 ! plane ( e f g 7,fig4 #acd74 ,! core ( ! magnet is repres5t$ z heavily %ad$4 ,! magnetic circuit is said to be clos$ f "o pole ( ?is magnet to ! o!r ?r\gh ! /rips ( iron :i* pass across ! ends & d[n ! sides ( ! coil4 ,! arr[s %[ ! pa? ( ! magnetic circuit4 ,! dott$ portion %[s :]e ! copp] wire may be suppos$ to h be5 cut across4 ,inasmu* z ! electric curr5t is induc$ 9 ! second>y circuit by cont9ually v>y+ ! /r5g? ( ! magnetic field z mu* z possible1 ! alt]nat+ curr5t is ! mo/ desirable to use 9 ! prim>y4 ,if ! direct curr5t 7 us$ an int]rupt] w\ld be necess>y1 :i* w\ld ( c\rse produce too mu* sp>k+ :5 any b l[ t5sion curr5ts are us$ 9 ! prim>y circuit4 ,! mo/ int]e/+ & curi\s fact ab\t ! trans=m] is t ! voltages ( ! prim>y & second>y curr5ts are 9 exact proportion to ! numb] ( turns 9 ! wire ( ! two circuits4 ,illu/ration3 ,fig4 #acc ,illu/ration3 ,fig4 #acd ,illu/ration3 ,fig4 #ace ,9 our trans=m] ! numb] ( turns 9 ! coil betwe5 ! b9d+ po/s a & b is #djj & ! numb] ( turns betwe5 c & d is #abjj4 ,if n[ we connect a #aab-volt alt]nat+ curr5t ) ! b9d+ po/s a & b1 a volt met] connect$ across betwe5 c & d w %[ #ccf volts1 & if b & c be connect$ by a %ort wire1 br++ 9 #afjj turns into ! second>y circuit1 a volt met] connect$ across betwe5 a & d w %[ a voltage ( #ddh4 ,or if1 leav+ b & c /ill connect$ by a %ort wire1 we connect ! #aab-volt alt]nat+ curr5t to a & d a volt met] connect$ across betwe5 a & b w %[ #bh volts1 or if connect$ betwe5 c & d x w %[ #hd volts1 & if f9ally ! #aab-volt curr5t is connect$ to c & d ! pressure betwe5 a & b w be #cg-a_/c4 ,illu/ration3 ,fig4 #acf ,! /ory1 !n1 ( ! c5tral /ation :i* we h *os5 z a type is briefly ?is3 ,fall+ wat] makes dynamos revolve1 g5]at+ a #djjj-volt alt]nat+ curr5t4 ,?is curr5t is s5t ?r\gh ! prim>y w9d+s ( trans=m]s4 ,! second>y w9d+s ( ^! trans=m]s h tw5ty-five times z _m turns z ! prim>y coils4 ,?is /eps up ! voltage f #djjj to #ajj1jjj1 mak+ x necess>y to s5d only "o tw5ty-fif? z _m amp]es ov] ! l9es z w\ld be requir$ at #djjj volts1 & r$uces ! loss 9 transmission to ne>ly "o tw5ty-fif?4 ,at ! o!r end ( ! l9e ! curr5t trav]ses ! second>y w9d+s ( trans=m]s1 & ! consum] receives 8 curr5t f prim>y coils :i* may /ep ! e4 m4 f4 d[n to any requir$ volts ( pressure1 g5]ally #aaj4 ,n[ ,i %all be glad to h y consid] :e!r ?is sugge/s any practicable problems = u "h 9 ,millville4 ,! sun is ne>ly sett+ & ,i suppose ! family is expect+ me home4 ,illu/ration3 ,fig4 #acg ,,xiii ,,electricity ,,f ,,an ,,old ,,mill ,millville is only a "n or r a rem9isc5ce4 ,!re 0 once a village "h1 b n[ its population has all gone ) ! tide d[n ! riv]1 ev5 its gho/ appe>s to h dep>t$4 ,! ru9s h all fall51 except ! mill1 :i* we propose to revivify4 ,i _h built a summ] cottage on ! %ore ( ! lake1 ab\t "o mile f ! mill4 ,! absolute /illness ( ! place *>m$ me :5 worn out by ! noise & heat & dirt & smell ( ! city4 ,"h ev5 ! owl twitt]$ s(tly z if afraid to di/urb ! sil5ce4 ,! sil5ce :i* 0 su* a boon to me seem$ to be oppressive to ! y\ng] memb]s ( ! family4 ,to prev5t !re=e _! becom+ dissatisfi$ ) ! place & wi%+ to g to o!r resorts1 ,i plann$ to h "s ( _! be/ fri5ds sp5d mu* ( ! summ] ) u1 & ,i enc\rag$ _! plans = mak+ use ( ! mill4 ,i w n (f] ?is z an excuse = introduc+ electricity into a sleep+ valley4 ,inde$1 electricity has always disport$ itself !re 9 ! lightn+1 jump+ f cl\d to m\nta9 peak z ,i h se5 x n[h]e else on e>?4 ,! next "t ,i saw ! boys !y _h ambiti\s plans inde$4 ,! p5/ock at ! mill 0 to be repair$4 ,! wat]-:eel 0 to drive an alt]nat+ curr5t dynamo4 ,! voltage ( ?is curr5t 0 to be /epp$ up by a trans=m]4 ,x 0 to be transmitt$ to ! cottage & !re ! e4 m4 f4 0 to be /epp$ d[n aga9 by ano!r trans=m]4 ,my wife sugge/$ t if x int]f]$ ) ! simple life x w\ld h to /ep d[n & out4 ,h>old1 h[ev]1 assur$ 8 "m t !y 7 go+ to simplify ev]y?+--ev5 ! subject ( electricity4 ,_! plans 73 ,to light ! cottage by electricity2 introduce a numb] ( electric back logs1 ) col\r$ glass bottles2 heat ! fireless cook] by electricity2 pump ! wat] = ! h\se by electricity2 run "m's sew+ ma*9e by electricity2 run ! wa%+ ma*9e & wr+] by electricity2 heat sad irons by electricity2 p]colate c(fee1 wa% di%es & run ! vacuum clean] by electricity2 op]ate ! door bell & ! telephone & w9d ! clock by electricity4 ,i 0 sure t if !y c>ri$ out ^! plans !y w\ld /ay 9 ,millville at lea/ t summ]1 s ,i said g ahead4 ,we fix$ ! p5/ock4 ,! boys e/imat$ t #aj cubic feet ( wat] p] second w\ld pass ?r\gh x4 ,!y said t a cubic foot ( wat] weigh$ #fb4e p\nds & #aj cubic feet weigh$ #fbe p\nds4 ,!y said x fell at ! rate ( #g v]tical feet a second1 mak+ #dcge foot-p\nds p] second4 ,b #eej foot-p\nds p] second is "o horse-p[]1 h5ce ?is is ab\t #h horse-p[]4 ,s9ce "o horse-p[] is equival5t to #gdf watts ( electricity1 we h1 if we c\ld g5]ate x )\t loss1 said ! boys1 ne>ly ! equival5t ( #f kil[atts ( electricity1 or ab\t #ed amp]es at #aaj volts4 ,!re 7 sev]al ?+s !y want$ to "k be=e !y c\ld g fur!r ) _! plans4 #a4 ,h[ _m ( ^! electrical appliances we w\ld be likely to use at "o "t4 #b4 ,h[ mu* curr5t ea* device w\ld require4 #c4 ,h[ mu* !y mu/ all[ = losses 9 g5]at+ ! curr5t1 9 transmitt+ x1 & 9 trans=m+ x4 ,we assur$ !m t we w\ld nev] use m ?an tw5ty amp]es1 say1 two ?\s& watts at "o "t4 ,!y might in/all a fuse1 or circuit break] 9 our l9e to protect _! plant aga9/ a great] load f u4 ,i told !m t !y might all[ #bj p] c5t4 loss ( en]gy at ! dynamo 9 conv]t+ wat]-p[] into electric-p[]4 ,i w\ld sugge/ g5]at+ _! curr5t at #aae e4 m4 f4 & /epp+ x up to #dfj = transmission to u1 & !n /epp+ x d[n to ab\t "o hundr$ & t5 volts = our use4 ,!y might c\nt on ab\t "o-?ird loss on our supply1 t is1 !y w\ld ne$ to g5]ate ab\t ?ree ?\s& watts 9 ord] to deliv] u #bjjj watts4 ,i sugge/$ mak+ our l9e ( ,no4 #f copp] wire1 :i* has a resi/ance ( two ohms to ! mile4 ,! di/ance f ! mill to ! cottage is "o mile1 & ! complete circuit !re=e w\ld require two miles ( wire1 or f\r ohms ( resi/ance4 ,if we />t ) #cjjj watts & lose #ad p] c5t4 9 trans=m+ we %all h #behj watts to transmit4 ,if ! voltage has be5 /epp$ up f\rfold !re w be ab\t #e4f amp]es to transmit :i* w suff] a loss ( #bb4d volts 9 pass+ ?r\gh f\r ohms ( resi/ance on ! l9e4 ,! loss 9 transmission w be ab\t #e p] c5t41 & we %all h on arrival at ! cottage ab\t two ?\s& f\r hundr$ & fifty watts ) a voltage ( #dcg4f4 ,if n[ 9 /epp+ ?is d[n to "o f\r? ! voltage1 viz41 #aji4d1 we lose #ad p] c5t41 we %all h left some?+ ov] two ?\s& "o hundr$ watts1 or ne>ly tw5ty amp]es4 ,assum+ t y are able to g5]ate #dhjj watts ( electricity & t #cjjj watts mu/ be furni%$ = transmission to ! cottage1 y h left #ahjj watts1 :i* w give y some?+ ov] fifte5 amp]es at #aae volts = use 9 y\r ma*9e %op4 ,i sugge/ t we get a dynamo :i* w g5]ate bo? alt]nat+ & direct curr5t--! alt]nat+ curr5t y w s5d to ! cottage1 & ! direct curr5t y w h = use at ! ma*9e %op4 ,b h[ is x possible = a dynamo to g5]ate bo? alt]nat+ & direct curr5t at ! same "t8 ,illu/ration3 ,fig4 #ach ,illu/ration3 ,fig4 #aci ,recall t all dynamos are g5]ators ( alt]nat+ curr5t4 ,if ! bru%es re/ ^u r+s ^u ! axle !y s5d =? alt]nat+ curr5t--b if ! bru%es re/ ^u commutator b>s !y s5d =? direct curr5t4 ,n[ we w h two sets ( bru%es1 "o pair ( :i* %all re/ ^u ! r+s on ! axle1 & !y w collect alt]nat+ curr5t = ! cottage1 :ile ! o!r pair w slide ov] ! commutator b>s & collect direct curr5t = ! ma*9e %op4 ,i h con/ruct$ a model :i* w make x pla94 ,"h is a piece ( a broom h&le 7,fig4 #ach71 "o foot long1 :i* %all repres5t ! axle ( an armature4 a b c d is a /\t wire :i* repres5ts ! coil ( ! armature4 ,9 ?is case x has no iron at its c5tre4 ,nev]!less x w s]ve z an armature hav+ "o loop ( its coil left4 e & f are r+s1 saw$ f a piece ( brass pipe1 :i* fit snugly ^u ! axle4 ,ano!r r+ ( ! brass pipe 0 saw$ l5g?wise1 z %[n 9 ,fig4 #aci4 ,^! two halves are also fa/5$ ^u ! axle & "o end ( ! wire loop1 c1 is fa/5$ to "o ( ^!1 & ! o!r end ( ! loop1 b1 is fa/5$ to ! o!r half ( ! r+4 ,^! two halves ( ! piece ( brass pipe are plac$ s t _! edges are ne> to ea* o!r b d n t\* on ei!r side ( ! axle4 ,! two ends ( ?is wire loop are also connect$ ) ! r+s e & f4 ,a %ort wire connects b & e & ano!r connects c & f pass+ ?r\gh ! wood ( ! axle1 z %[n by ! dott$ l9e4 ,we w n[ revolve ?is loop sl[ly ab\t its axle 9 a /rong magnetic field4 ,to produce ?is field ,i w s5d two amp]es ( electricity ?r\gh ! coils ( wire 7,fig4 #adj71 :i* surr\nd two iron pole pieces t are screw$ into an iron base4 ,betwe5 ! poles ,n & ,s ( ?is electro-magnet we w ?ru/ ?is wire loop & revolve x z an armature v sl[ly4 ,mean:ile ,i connect two wires to my s5sitive ammet] & let _! free ends bru% along on ! r+s e & f4 ,! ne$le ( ! ammet] sw+s to & fro = ea* half revolution ( ! armature1 %[+ an alt]nat+ curr5t ( 4#ja amp]es4 ,if ?is armature _h _m turns ( wire in/ead ( ?is "o loop1 if x _h an iron core1 & if x %\ld revolve at high spe$1 ! results w\ld diff] 9 degree b n 9 k9d4 ,illu/ration3 ,fig4 #adj ,we w n[ move ! wires :i* are act+ z bru%es ov] to ! metal pieces b & c4 ,:5 n[ we revolve ! armature ! ne$le sw+s to ! "r1 & j z ! ne$le is ab\t to sw+ back ea* bru% slides f ! plate on :i* x is rubb+ to ! opposite "o & ! ne$le gets ano!r impulse =w>d4 ,if ! armature is turn$ rapidly ! pulses disappe> & ! ne$le /&s con/antly at ab\t 4#jae amp]es4 ,?is !n is bo? an alt]nat+ & a direct curr5t dynamo4 ,x simply ne$s m iron1 m copp] wire1 & m rapid motion1 to give u ! #dhjj watts ( electrical en]gy we are seek+4 ,b h[ %all we produce ! curr5t :i* we wi% to s5d ar\nd ! spools ( ! field8 inquir$ ! boys4 ,connect ! field ) ! bru%es :i* rub ^u ! commutator1 ,i repli$4 ,x w magnetize its own field4 99 99 99 99 99 ,z good luck w\ld h x1 we f\nd t ! l$ge ( rock :i* furni%$ ! basis = ! mill dam 0 imm$iately und]nea? ! floor at ! nor? end ( ! ma*9e %op4 ,^u ?is we built up a solid f\ndation = ! dynamo4 ,our wat]-:eel gave a spe$ ( #bdj revolutions p] m9ute to ! c\nt] %aft4 ,a pulley ( two feet 9 diamet] ^u ?is c\nt] %aft 0 belt$ to ! pulley ( "o foot 9 diamet] ^u ! dynamo--?us giv+ its armature a spe$ ( #dhj revolutions p] m9ute4 ,we _h to fix a gov]nor ^u ! wat]-:eel to keep ?is spe$ con/ant at v>y+ loads4 ,! voltage is v s5sitive to slight *anges 9 ! spe$ ( ! g5]ator4 ,we _h next to plan :at equipm5t we %\ld ne$ = ! ma*9e %op & to decide :]e to locate ea* ma*9e4 ,! fir/ ma*9e we in/all$ 0 a la! adapt$ = use bo? ) metals & wood4 ,among ! adjuncts ( ?is 7 all sorts ( drills1 *isels1 circul> saws1 gr9d+ & burni%+ tools1 etc4 ,! second ma*9e locat$ 0 a small =ge ) an electric fan to furni% ! bla/4 ,^! 7 foll[$ by a small b& saw & a small plan]4 ,! fif? ma*9e 0 a big gr9d/one & ! six? 0 an em]y :eel4 ,! boys _h a long discussion1 runn+ ?r\gh sev]al days1 on ! "q :e!r ^! ma*9es %\ld be belt$ to ! c\nt] %aft1 & ?us get p[] directly f ! wat]-:eel1 or :e!r ea* ma*9e %\ld be op]at$ by an electric motor atta*$ to x4 ,h>old said3 ,suppose ,i want to saw a piece ( wood requir+ a horse-p[]1 ,i mu/ />t an eight horse-p[] wat]-:eel :i* w run a six-horse-p[] dynamo :i* w op]ate a two-horse-p[] motor t w revolve ! saw4 ,!re is a loss 9 ea* ma*9e1 & ! light] ! load ! great] ! loss4 ,9 ord] t ! motor may deliv] "o horse-p[] to ! saw1 x mu/ receive f ! dynamo1 say1 "o & "o-half horse-p[]1 & 9 ord] t ! dynamo may deliv] to ! motor "o & "o-half horse-p[]1 x mu/ receive f ! wat]-:eel1 say1 two horse-p[]4 ,:at is ! matt] ) my sav+ "t & en]gy by saw+ (f ! block ) my own "r arm8 ,b1 said ,erne/1 y =get t ?is wat]-:eel & ! dynamo mu/ run all ! "t by ! t]ms ( our agreem5t ) ! cottage1 & !y w run fairly well load$1 s t ! />t+ ( ! saw w n entail any su* losses z y reckon4 ,fur!rmore ! wat]-p[] is runn+ to wa/e1 anyway4 ,y simply div]t its *annel :5 y />t all ?is ma*9]y4 ,t's all4 ,& la/ly1 if ! saw requires a horse-p[]1 z y say1 y\r "r arm c\ld n furni% x4 ,oh1 int]pos$ ,dyne1 x w\ld take a horse-p[] to d x z quickly z ! ma*9e does1 b ,h>old simply proposes to take m "t 9 saw+ ! block & less 9 runn+ ! ma*9]y4 ,an infant c d ! "w ( a horse if y give him proportionally m "t4 ,i don't l ! idea1 drawl$ ,erg1 t ?is ma*9]y has got to be kept runn+ all ! "t4 ,:5 w a fell[ get a *ance to sleep or g a-fi%+ or h any vacation1 ) ?is c5tral-/ation ma*9e %op on 8 h&s all ! "t8 ,i _h inquir$ h[ ! la/ two boys won _! nicknames ( ,dyne & ,erg & _h be5 in=m$ t "o 0 v ke5 ab\t d9+ & ! o!r _h a great av]sion = "w4 ,!y _h d\btless se5 ^! t]ms some:]e 9 _! read+ ( physics1 b !y appe>$ to h =gott5 _! significance by a too famili> use ( !m4 ,i told !m t ^! 7 sacr$ t]ms1 ! fir/ be+ a "n = ! unit ( =ce1 :ile ! second designat$ ! unit ( "w4 ,bo? boys said t "u ^? circum/ances !y w\ld l to %$ ! names4 ,! names1 h[ev]1 /uck & ! boys !mselves might1 ,i ?9k1 be said to ex]cise a maximum ( p[] ) ! lea/ wa/e ( en]gy4 ,?is idea ( runn+ ! plant cont9u\sly _h evid5tly receiv$ no att5tion hi!rto & x bid fair to qu5* all ! en?usiasm until ,i came to ! rescue by propos+ a /orage batt]y4 ,if we c procure a batt]y 9 :i* we may /ore en]gy1 :i* %all always be on draught by m]ely pu%+ a button1 "o :i* is n injur$ by ov]*>g+ nor too rapid dis*>g+1 nor ev5 by complete dis*>ge2 "o :i* is n injur$ by /&+ idle = any l5g? ( "t1 ei!r *>g$ or dis*>g$2 & f9ally "o :i* is practically foolpro(--we want to try x4 ,i propose t y appo9t a committee to look into x4 ,b at any rate ?is ent]prise mu/ g on ev5 if ,i h to hire a man to live 9 ! l(t ( ! mill & keep ! ma*9]y go+4 ,illu/ration3 ,fig4 #ada ,no man 9 ! l(t1 said ,dyne1 :ile ,i h my rations4 ,!re w be no ne$ = him s long z ,i c /ore en]gy "h1 said ,erg1 s let ! job ( equipp+ ! e/abli%m5t g on 9 ! regul> fa%ion4 ,aft] a long confab "o ev5+ at ! mill we settl$ ^u ! arrangem5t %[n 9 ,fig4 #ada4 ,d repres5ts ! location ( ! doors & ,w t ( ! w9d[s4 ,! equipm5t is designat$ z foll[s3 ,a1 saw2 ,b1 plan]2 ,c1 la!2 ,e1 em]y :eel2 ,f1 gr9d/one2 ,g1 dynamo2 ,h1 =ge2 ,i1 /orage batt]y2 ,j1 swit*bo>d2 ,k & ,l1 c\nt] %afts susp5d$ f ! ceil+4 ,! wat]-:eel is belt$ directly to ! c\nt] %aft ,l4 ,?is revolves at ! rate ( #bdj r4 p4 m4 ,a two-foot pulley on ?is %aft is belt$ to a "o-foot pulley on ! dynamo ,g1 giv+ ! dynamo a spe$ ( #dhj4 ,a #d-;in* pulley on ?is c\nt] %aft is belt$ to a #af-;in* pulley on ! gr9d/one ,f1 giv+ ! /one a spe$ ( #fj r4 p4 m41 or "o revolution p] second4 ,a #cb-;in* pulley on %aft ,l is belt$ to an #h-;in* pulley on ! c\nt] %aft ,k1 giv+ a spe$ ( #d times #bdj1 or #ifj r4 p4 m4 #ab-;in* pulleys on ?is %aft are belt$ to #f-;in* pulleys on ea* ( ! ma*9es ,a1 ,b1 & ,c1 giv+ !m a spe$ ( #aibj r4 p4 m41 & a #af-;in* pulley on ?is %aft is belt$ to a #d-;in* pulley on ! em]y :eel1 giv+ x a spe$ ( #chdj r4 p4 m4 ,z soon z ev]y?+ 0 9 runn+ ord]1 ,h>old took 8 "m d[n to ! ma*9e %op & />t$ all ! ma*9]y go+ at once1 & :ile !y /ood 9 ! middle ( ! room ,i he>d him expla9+ to h] h[ %e might f9d out ! spe$ ( ea* ma*9e4 ,he said t %e mu/ />t ) ! gr9d/one1 because t goes sl[ly en\gh to c\nt4 ,%e held h] wat* 9 h& & c\nt$ ! numb] ( revolutions 9 a m9ute1 z he direct$1 & f\nd !m to be sixty4 ,!n he ask$ h] to judge h[ mu* l>g] ! pulley on ! gr9d/one 0 ?an ! correspond+ "o on ! c\nt] %aft4 ,%e said t %e ?\ght x look$ f\r times z l>ge4 ,he told h] t %e _h x j "r1 & expla9$ t ! %aft mu/ move f\r times z fa/ z ! /one1 or #bdj4 ,n[ h[ fa/ d y ?9k ! em]y :eel is go+8 ,%e ackn[l$g$ t %e _h no idea4 ,well1 said he1 :5 y get real us$ to x y c tell by ! tone a :eel makes j ab\t h[ fa/ x is go+4 ,!n he expla9$ h[ %e might calculate its spe$ by look+ at ! pulleys1 & %e f\nd t ! c\nt] %aft 0 go+ f\r times z fa/ z ! %aft ,l & t ! em]y :eel 0 go+ f\r times z fa/ z ,k4 ,h5ce x 0 go+ sixte5 times z fa/ z ,l1 or #chdj r4 p4 m4 ,8 "m said %e ?\ght t x 0 fasc9at+ to /& 9 ! middle ( ! room ) ! sl[ly mov+ gr9d/one on "o h& & em]y :eel mov+ sixty-f\r times z fa/ on ! o!r h& & ?9k t !y 7 propell$ by ! same wat]-:eel4 ,i h&$ ,h>old a spe$ indicator :i* ,i _h j receiv$1 7,fig4 #adb71 ! me*anism ( :i* 0 all visible4 ,h>old look$ at x = a m9ute & f\nd /at$ ^u x t ! :eel ,b _h #ajj cogs1 & he v quickly inf]r$ t ! axle ,a1 ^: screw ?reads fitt$ into ^! cogs1 mu/ revolve "o hundr$ times ea* "t ! :eel ,b revolves once4 ,! tip end ( ?is axle _h a s(t rubb] cap ,c4 ,)\t sugge/ion f me he soon held ?is rubb] %oe aga9/ ! end ( ! axle ( ! em]y :eel & c\nt$1 n ?irty-eight1 b ?irty-six revolutions ( ! :eel ( ! spe$ indicator 9 "o m9ute4 ,?is puzzl$ him & he inquir$ h[ x happ5$ t ! em]y :eel made only #cfjj r ?an #chdj revolutions p] m9ute4 ,illu/ration3 ,fig4 #adb ,well1 said ,i1 we always h to c\nt on belts slipp+ "s1 p>ticul>ly ^u v fa/ mov+ pulleys & ^u v small pulleys4 ,"h are two belts to slip1 & /ill y are los+ only ! effect ( "o revolution ( ! c\nt] %aft ,l 9 a m9ute4 ,gr9d some?+ on ! em]y :eel & y w f9d t ! belts w slip m4 ,9 fact1 gr9d+ ^u ! em]y :eel w compel ! wat]-:eel to g m sl[ly until its gov]nor op5s & gives x m wat]4 ,! wat]-:eel makes fifte5 revolutions p] m9ute & ! em]y :eel goes #bef times z fa/ z t4 ,"o p\nd ( resi/ance at ! em]y :eel is l #bef p\nds ( resi/ance at ! wat]-:eel4 ,y notice ! same ?+ :5 y use ! saw or plan]1 or ev5 pres5t a *isel to a piece ( s(t wood 9 ! turn+ la!4 ,! only ma*9e "h t x is important to keep runn+ at con/ant spe$ is ! dynamo4 ,we %all probably notice ! dimm+ ( our lights at ! cottage e "t y saw a block or gr9d ) ! em]y :eel or ev5 poli% ) ! felt buff]1 because ! spe$ ( ! dynamo w slack5 = a mom5t & ! voltage w drop a little4 ,9 addition to s5d+ electric curr5t to ! cottage ! dynamo 0 to keep ! batt]y /or$ all ! "t4 ,ea* ma*9e _h an appropriate motor atta*$ to x :i* c\ld run x by draw+ curr5t directly f ! batt]y :5 ! wat]-:eel 0 n runn+4 ,?us if "o want$ to %>p5 8 pocket knife he m]ely clos$ a swit* at ! la! & us$ ! small /one1 or if he wi%$ to %>p5 8 lead p5cil he put x 9 ! la! & appli$ a *isel to x4 ,^! motors 7 all adapt$ to ! #aaj-volt direct curr5t & ! batt]y conta9$ fifty-sev5 cells1 ea* cell be+ rat$ a little "u two volts4 ,! boys frequ5tly discuss$ possible comb9ations 9 ?is sy/em4 ,i sp5t a great deal ( "t loaf+ ar\nd among !m 9 a comatose condition1 & !y talk$ q z freely :5 ,i 0 ar\nd z :5 !y 7 alone among !mselves4 ,"o day ,i he>d ,dyne say1 ,suppose we %\ld /ore 9 a res]voir ! wat] :i* comes d[n ! p5/ock dur+ a day & /ore all ! electricity x w g5]ate 9 a day 9 a /orage batt]y1 !n at night let ! batt]y run ! dynamo backw>d z a motor1 & t turn ! wat]-:eel backw>d z a rot>y pump1 we %\ld h ! wat] 9 ! upp] res]voir to beg9 "w ) ! next morn+ & ! problem ( p]petual motion w\ld be solv$4 ,aw1 :y d y want to d all t1 said ,erg1 :5 nature is do+ x = u8 ,erne/ said he _h a bett] s*eme ?an t4 ,he w\ld turn ! batt]y curr5t on to all ! motors 9 ! room & !y w\ld run ! c\nt] %afts =w>d & ! c\nt] %afts w\ld run ! dynamo =w>d & ! dynamo w\ld *>ge ! batt]y1 & s y c\ld keep up ! motion p]petually if y want$ to4 ,get out y\r p5cils1 said ,h>old1 z he took d[n a copy ( ,h\/on & ,k5nelly4 ,let u see h[ we w\ld come out if we tri$ ,dyne's proposition =1 say1 tw5ty h\rs1 /or+ ! en]gy f ! fall+ wat] = t5 h\rs 9 ! batt]y & !n us+ ?is en]gy dur+ ! next t5 h\rs = re-/or+ ! wat] 9 ! upp] pond4 ,we w say t ! wat]-:eel furni%es eight horse-p[] = t5 h\rs--eighty horse-p[] h\rs4 ,i notice x is /at$ 9 ?is book t small dynamos are usually unable to deliv] m ?an #ge p] c5t4 ( ! en]gy impress$ ^u !m1 & /orage batt]ies & motors deliv] ab\t #hj p] c5t4 ( ! en]gy impress$ ^u !m4 ,! acc\nts w\ld1 !re=e1 /& z foll[s3 ,dynamo ,horse-p[] ,h\rs ,dr4 ,cr4 ,to en]gy impress$ by wat]-:eel #hj ,by en]gy deliv]$ to /orage batt]y #fj ,by loss 9 heat #bj --------- #hj #hj 7,assum+ t ! batt]y 0 able to receive all ! dynamo c\ld give47 ,,/orage ,,batt]y ,,acc\nt ,to en]gy impress$ by dynamo #fj ,by en]gy deliv]$ back to dynamo runn+ z motor #dh ,by loss 9 heat #ab --------- #fj #fj ,dynamo ,runn+ z ,motor ,horse-p[] ,h\rs ,dr4 ,cr4 ,to en]gy impress$ by batt]y #dh ,by en]gy deliv]$ back to wat]-:eel #cf ,by loss 9 heat #ab --------- #dh #dh 7,?is dynamo be+ a p>ticul>ly ineffici5t motor47 ,we _c give ! acc\nt ( a wat]-:eel act+ z a pump1 because su* a ma*9e has n yet be5 p]fect$4 ,x is evid5t h[ev] t if a wat]-:eel c\ld be devis$ t %\ld be a p]fect pump1 ! losses 9 ?is *a9 ( ma*9]y are m ?an half2 inde$1 ! acc\nts %[ !m to be #fj p] c5t4 ,we %\ld1 !re=e1 be able to return less ?an half ! wat] drawn f ! lake ea* day1 & we %\ld rapidly move t[>d bankruptcy4 ,well1 said ,erne/1 my proposition is m successful ?an t1 because x sets out to be a fool proposition4 ,x 0 fir/ sugge/$ by ! snake :o und]took to swall[ himself4 ,suppose ! acc\nt does tap] d[n f eighty to "o1 s does ! snake1 b he /ill rema9s wise z a s]p5t4 ,our acc\nt w\ld /& z foll[s3 ,dynamo ,batt]y ,motors #cf #bg #bg #bj #bj #ae #ae #ab #ab #i #i #g #g #e #e #d #d #c #c #b #b #a #a 4#h 4#h 4#f 4#f 4#dh 4#dh 4#cf 4#cf 4#bg 4#bg 4#bj 4#bj 4#ae 4#ae 4#ab 4#ab 4#ji 4#ji 4#jg 4#jg 4#je 4#je 4#jd 4#jd 4#jc 4#jc 4#jb 4#jb 4#ja 4#ja 4#jjc ,x is evid5t t :ile our en]gy w\ld dw9dle cont9ually we %\ld nev] q come out ( ! little end ( ! horn1 s9ce any numb] may dim9i% by #bj p] c5t4 ( itself indef9itely4 ,let u get at some?+ practical1 said ,erg4 ,h[ are we go+ to furni% electricity to ! cottage :5 ! dynamo is n runn+8 ,if we put a /orage batt]y at ! cottage1 h[ are we go+ to /ore x hav+ no?+ b alt]nat+ curr5t up !re2 & if we attempt to transmit curr5t f our c5tral /ation batt]y1 h[ are we go+ to get along ) ! drop 9 ! voltage8 ,i'll tell y h[ to d t1 said ,dyne4 ,!y want #bj amp]es & ! l9e (f]s #d ohms ( resi/ance4 ,t means a drop ( #hj volts4 ,we h simply to provide a subsidi>y batt]y ( #dh cells1 :i* we may ?r[ 9 s]ies ) our #eg cells :5 we supply electricity to ! cottage1 & !n !y w h ! "r voltage = use out !re4 ,yes1 said ,erg1 z he roll$ ov]1 !y w h ! "r voltage :5 !y use #bj amp]es1 b :at w happ5 if !y simply turn on "o lamp4 ,! drop 9 voltage !n w be 74#e amp]es #d ohms 7 #b volts2 #aje cells at #a4h volts a cell w s5d out !re #ahi volts m9us ! drop ( #b volts1 leav+ #ahg volts ^u a lamp adapt$ to #aaj volts1 & x w imm$iately burn out4 ,! same ?+ w\ld happ5 to any s+le piece ( app>atus if ! curr5t 0 turn$ ^u x alone4 ,! only ?+ !y c\ld d if !y want$ to light a lamp1 say 9 ! middle ( ! night to take a dose ( m$ic9e1 w\ld be to />t up all toge!r1 all _! lamps1 sew+ ma*9e1 wr+]1 di%wa%]1 fireless cook]1 vacuum clean]1 etc41 etc41 to keep d[n ! voltage s t "o lamp w\ld n burn out4 ,i h read1 said ,erne/1 t !y use rectifi]s1 :i* conv]t ! alt]nat+ into direct curr5t1 = /or+ batt]ies4 ,^! are mu* us$ ov] ! c\ntry4 ,electric automobiles run by /orage batt]ies1 & 9 ! great majority ( communities !re is no o!r electric curr5t ?an ! alt]nat+4 ,s !y w\ld be helpless )\t ! rectifi]4 ,we %\ld !n get ano!r batt]y ( fifty-five cells = ! cottage & keep x /or$ by us+ a rectifi] ) our alt]nat+ curr5t4 ,b all _! equipm5t up !re1 said ,erne/1 is adapt$ to ! alt]nat+ curr5t4 ,( :at use w\ld a direct curr5t be to !m8 ,well1 said ,h>old1 x is all ! same :e!r y h alt]nat+ or direct curr5t on lamps1 cook+ app>atus1 etc41 & ,i h und]/ood t !y h motors :i* run on bo? alt]nat+ & direct curr5ts4 ,if s1 t w\ld fix !m up all "r4 ,! boys n[ turn$ to me = ! fir/ "t to inquire :e!r motors c\ld be obta9$ :i* w\ld run on bo? alt]nat+ & direct curr5t1 & ,i repli$ t small motors = runn+ sew+ ma*9es1 vacuum clean]s1 etc41 7 made :i* w\ld s]ve u1 p]haps n economically1 b z !y 7 ! only solution to our problem we c\ld get along ) !m4 ,:y don't !y h alt]nat+ curr5t batt]ies8 inquir$ ,erg4 ,well1 x is "t t we le>n$ ab\t ! nature ( batt]ies1 said ,i1 if y boys are go+ to h two /orage batt]ies to c>e =4 ,,xiv ,,do+ ,,*ores ,,by ,,electricity ,*ores 7 my salvation 9 y\?1 & ^? *ores 7 n trifles4 ,i 0 made to feel t ! :ole family dep5d$ on my milk+ ! c[s1 br++ 9 ! eggs1 keep+ ! wood box full ( wood1 ! wat] pail full ( wat] br\ght f ! old well1 *urn+ ! butt]1 fe$+ & wat]+ ! animals1 & p]=m+ a multitude ( regul> daily & weekly tasks4 ,z ,i grew old] my responsibilities 7 all[$ to increase proportionally s t ,i might feel "s measure ( ! dignity ( be+ a ma9/ay & a support ( ! family4 ,long be=e ,i rea*$ manhood occasional opportunities 7 pres5t$ = me to play ! full "p ( a man4 ,^! sometimes came dur+ a tempor>y abs5ce or sickness ( my fa!r1 b m (t51 z ,i le>n$ aft]w>d1 by 8 skilfully elim9at+ himself f ! situation s t ,i might try my p[]s4 ,we attempt 9 ! pres5t g5]ation to furni% a sub/itute = ! old "t *ores by our daily programme 9 s*ool or 9 summ] camp1 b ,i (t5 wond] :e!r ?is r\nd ( trifles c make m54 ,c "o gr[ great )\t hav+ a *ance to feel occasionally t ! _w dep5ds ^u :at he does8 ,illu/ration3 ,fig4 #adc ,! great advantage ( ,millville to u all lies 9 ! fact t my wife is a good organiz]4 ,%e imm$iately saw t ! introduction ( electricity into ! cottage enabl$ h] to assign *ores to u all4 ,^! *ores 7 assign$ s t ! e/abli%m5t ran l clock-"w4 ,on ,monday morn+ 9 a l>ge room1 call$ ! wa% room1 %e arrang$ ! soil$ clo!s 9 five piles4 ,pile ,no4 #a conta9$ %eets & pill[ cases2 ,no4 #b1 :ite %irts1 %irtwai/s1 & o!r />*$ clo!s2 ,no4 #c1 und]clo!s2 ,no4 #d1 t[els1 etc41 & ,no4 #e1 col\r$ clo!s4 ,"h /ood a wa%+ ma*9e run by electric motor & a wr+] run by ! same motor 7,fig4 #adc74 ,by ! side ( x sat a tub = r9s+ wat] & next to t a tub = blu+ wat]4 ,two boys plac$ a wa% boil] ov] a two-burn] oil /ove1 put five pails ( wat] into x1 & cut up "o cake ( laundry soap :i* !y also put 94 ,:5 ?is 0 boil+ hot1 ab\t half ( x 0 p\r$ into ! wa%+ ma*9e4 ,! o!r half 0 to take its place lat] 9 ! wa%+ ma*9e4 ,! fir/ pile ( clo!s 0 put 9 & ! motor run = five m9utes4 ,?is bat* 0 !n run ?r\gh ! wr+] into ! r9s+ wat]1 & !n aga9 ?r\gh ! wr+] into ! blu+ wat]1 & !n ?r\gh ! wr+] a ?ird "t into ! clo!s basket1 & hung ^u ! l9e out doors 9 ! cle> sun%9e1 :i* did m ?an all else to make !m sweet & clean4 ,a basket ( su* clo!s f ! l9e makes y want to plunge y\r face "r into x & take a good :iff4 ,!re is no?+ l x except a m[ full ( new hay4 ,! piles ( soil$ clo!s foll[ "o ano!r ?r\gh ?is s]ies ( tubs on ab\t a fifte5 to tw5ty m9utes headway1 s t ! :ole family wa%+ is done :olly by two boys inside ( two h\rs4 ,ea* pile aft] ! fir/ is giv5 t5 m9utes 9 ! wa%+ ma*9e4 ,on ,tuesday ! iron+ is done ) electric irons 7,fig4 #add74 ,on ,friday ! h\se is clean$ by ! vacuum clean]1 run by electricity 7,fig4 #ade74 ,illu/ration3 ,fig4 #add ,illu/ration3 ,fig4 #ade ,on ,saturday a lot ( bak+ is done 9 a s]ies ( fireless cook]s 7,fig4 #adf74 ,! sew+ ma*9e runs m ?an ev] be=e4 ,i he> ,x is su* fun to sew ) an electric motor4 ,& ! electric fan :i* ,h>old in/all$ = 8 "m ov] ! sew+ ma*9e makes t ! coole/ spot 9 ! h\se4 ,illu/ration3 ,fig4 #adf ,illu/ration3 ,fig4 #adg ,*ores d n take all ( ! "t1 nor mo/ ( ! "t4 ,!y are simply ! important ?+s :i* mu/ be done "r on "t4 ,mean:ile !re is pl5ty ( "t = o!r ?+s & a va/ lot ( exp]im5t+ goes on d[n at ! mill4 ,x is my *ief ent]ta9m5t to /roll d[n !re e day & look on4 ,"o day ,i f\nd ?is project on trial3 ,on ! floor 7,fig4 #adh1 f7 ( ! room ov] ! wa% room at ! mill a l>ge dripp+ pan ,a1 0 set on blocks ( wood s t "o corn] 0 l[] ?an ! re/4 ,a rubb] pipe1 ,b1 br\ght wat] to ?is pan f ! mill pond1 an inv]t$ faucet1 c1 regulat+ ! fl[4 ,! ov]fl[ f ! pan fell into a funnel1 d1 ! /em ( :i* w5t ?r\gh a hole 9 ! floor4 ,a %ort piece ( rubb] pipe connect$ ?is ) ! nozzle1 e1 ( a g>d5]'s spr9kl+ c1 :i* hung f ! ceil+ 9 ! comp>tm5t = ! %[] ba?4 ,electric lamps atta*$ to a bo>d1 g1 7 inv]t$ ov] ! pan ( wat]1 s t ! bulbs ( ! lamps 7 imm]s$ 9 ! wat]4 ,! electric curr5t = ^! lamps 0 controll$ by a swit*1 h1 plac$ by ! side ( ! wat] faucet4 ,:5 "o want$ a %[] he c\ld h x z cold or z hot z he *ose by adju/+ prop]ly ! swit* & ! faucet4 ,moreov]1 x 0 n necess>y = him to wait1 = w>m wat] fl[$ imm$iately4 ,illu/ration3 ,fig4 #adh ,9 discuss+ ?is ! boys said t a #cb-;c&le-p[] lamp us$ #aaj watts1 & t s9ce #if p] c5t4 ( ! en]gy suppli$ to ! lamps w5t into heat ea* lamp trans=m$ #aje watts ( electrical en]gy into heat4 ,b #ajj watts suffic$ to raise "o p9t 7"o p\nd7 ( wat] five degrees 9 "o m9ute4 ,!y us$ sev5 lamps or ab\t "o horse-p[]1 & adju/$ ! fl[ s t ! %[] deliv]$ "o qu>t ( lake wat] p] m9ute w>m$ = a tepid ba?4 ,illu/ration3 ,fig4 #adi ,! next "t ,i saunt]$ d[n to ! mill ! boys 7 work+ on :at !y call$ an electric %[] ba?4 ,!y _h fa/5$ ^u ! wall ( ! ba? room an electric bell 7,fig4 #adi71 & plac$ on a %elf ne> by a batt]y ( two dry cells1 ,p4 ,! swit* :i* clos$ ?is prim>y circuit 0 on ! wall by ! side ( ! faucet & electric heat+ swit* 7,fig4 #adh74 ,"o ( ! wires1 ,s1 = ! second>y circuit 0 c>ri$ up & connect$ to ! pan ,a 7,fig4 #adh74 ,! o!r wire 0 fa/5$ to a %eet ( z9c ab\t a foot squ>e1 :i* lay ^u ! floor ( ! %[] ba?4 ,! idea 0 t :5 "o 0 tak+ a %[] ba?1 if he *ose to v>y 8 s5sations he might /ep ^u ! %eet ( z9c1 close ! swit* 9 ! prim>y circuit & let ! second>y curr5t pass ?r\gh 8 body by way ( ! %[]4 ,!y said t x 0 p>ticul>ly prescrib$ = sl[ p4 ,speak+ ( *ores1 ( c\rse ! mo/ insi/5t *ore 0 to keep ! /orage batt]ies /or$4 ,?is process gave rise to _m que/ions1 ?r\gh :i* ! in=mation conta9$ 9 ! next *apt] 0 br\ght out4 ,,xv ,,electric ,,curr5ts ,,f ,,*emical ,,action ,,& ,,*emical ,,action ,,f ,,electric ,,curr5ts ,luigi ,galvani 7#agcg-agih7 ( ,bologna1 ,italy1 9 #aghf unwitt+ly produc$ an electric curr5t f *emical action4 ,because he 0 eag]ly seek+ o!r results he mis9t]pret$ ?is4 ,sev]al words 9 ! diction>y are becom+ ei!r obsolete or misnom]s4 ,= example1 galvanism is an old-fa%ion$ ^w = an electric curr5t4 ,! expression galvanic electricity is a relic ( ! ab&on$ idea t !re are sev]al k9ds ( electricity1 ( :i* ,galvani discov]$ "o4 ,galvaniz$ iron is :olly a misnom]4 ,x is a "n us$ = iron :i* has be5 coat$ ) z9c1 & x sugge/s ! idea t someh[ ! z9c is coat$ ^u ! iron by means ( an electric curr5t1 :]eas 9 fact x is done by dipp+ ! iron into melt$ z9c4 ,aless&ro ,volta 7#agde-ahbg7 ( ,como1 ,italy1 took up ! discov]y ( ,galvani1 int]pret$ x correctly1 & p]fect$ ! me?od ( produc+ electricity by *emical action4 ,:at ^! two m5 really discov]$ 0 t x is possible to produce cont9u\s curr5ts ( electricity4 ,be=e t electricity 0 kn[n only by ! in/antane\s dis*>ge or sp>k4 ,f ! "n ( ,volta is d]iv$ ! ^w volt1 :i* designates ! unit ( electro-motive =ce4 ,! adjective voltaic is synonym\s ) galvanic1 z voltaic or galvanic cell1 voltaic or galvanic curr5t4 ,= a long "t x 0 ?\ght t su* an adjective 0 ne$$ to designate electric curr5ts g5]at$ by *emical action z a peculi> k9d ( electricity4 ,we no long] ?9k ( electricity :i* is g5]at$ by *emical action z diff]5t f t g5]at$ by a dynamo or f any o!r s\rce4 ,= ab\t sev5ty-five ye>s aft] ! discov]y ( ,galvani *emical action 0 our only me?od ( g5]at+ curr5ts ( electricity1 & x is l>gely ow+ to ! inadequacy ( ?is me?od ( production t s few uses = electricity 7 discov]$ previ\s to ! p]fection ( ! dynamo ab\t a ?ird ( a c5tury ago4 ,two ?+s h conspir$ to br+ ab\t ?is age ( electricity4 7#a7 ,! dynamo r$uc$ ! co/ ( production f five doll>s to t5 c5ts p] kil[att h\r4 7#b7 ,mank9d grew extravagant1 greatly increas$ ! numb] ( ?+s :i* x consid]$ necess>y1 & at l5g? became bo? able & will+ to sp5d m = ! ?+s :i* x dem&$4 ,! s-call$ voltaic cell is ( sc>cely m ?an academic int]e/ n[4 ,! s*ool :i*1 z a rule1 foll[s half a c5tury beh9d practical life1 has taught & /ill tea*es ! philosophy ( ! galvanic cell ) great p>ticul>ity4 ,x is n[ be+ urg$ to und]take ! tea*+ ( ! dynamo4 ,mean:ile ! dynamo has almo/ driv5 out ( exi/5ce all electric batt]y cells except ! /orage cell & ! s-call$ dry cell1 & ea* ye> ! dynamo is encroa*+ m & m ^u ! t]ritory ( ! dry cell4 ,9 ! pres5t day1 :5 a pass5g] ^u a /reet c> pu%es a button to /op ! c>1 he uses1 n a voltaic cell1 b a #ejj-volt dynamo curr5t to r+ a small buzz]1 & x co/s ! company n "o-hundr$? "p z mu* z x w\ld to furni% him a batt]y equipm5t to d ! same ?+4 ,small dynamos & magnetos are displac+ dry batt]y cells 9 ! sp>k+ equipm5t ( motor boats & automobiles4 ,we lift$ a dry batt]y cell out ( its pa/ebo>d case & f\nd t x 0 conta9$ 9 a metal cup ( %eet z9c4 ,! top ( ?is 0 seal$ ov] airtight ) pit*1 ! purpose ( :i* is to prev5t ?is dry cell f dry+ up4 ,we dug away ! h>d5$ pit* & f\nd a black p[d] :i* 0 di/9ctly moi/4 ,9 case ! pit* becomes crack$ or a hole appe>s 9 ! z9c cup1 ! moi/ure passes out & ! cell ceases to act z a g5]ator ( electric curr5t4 ,! z9c cup _h a l9+ ( pa/ebo>d on ! sides & ! bottom1 simil> to ! pa/ebo>d :i* envelop$ ! outside1 only ! l9+ 0 q moi/4 ,a corrugat$ rod ( c>bon ab\t an in* 9 diamet] occupi$ ! middle ( ! cup1 & ! space ar\nd x 0 pack$ full ( a mixture ( ammonium *loride1 manganese dioxide1 & o!r sub/ances l pla/]1 etc41 :i* diff] ) diff]5t cells4 ,a dry cell :i* has be5 long 9 use is q apt to %[ /a9s ^u its pa/ebo>d case4 ,^! are caus$ by holes :i* appe> 9 ! z9c4 ,! production ( electric curr5t by ! cell is dep5d5t :olly ^u a *emical action betwe5 ! z9c & ! ammonium *loride :i* results 9 ! de/ruction ( bo?4 ,?is *emical action _c g on )\t moi/ure4 ,! z9c cup ( ! p>ticul> cell :i* we 7 exam9+ appe>$ to be intact1 & we proce$$ to dig out ! black p[d]4 ,its black col\r is due to ! manganese dioxide4 ,ammonium *loride is :ite4 ,we lift$ out ! c>bon rod & scrap$ ! z9c cup clean4 ,! b9d+ po/s atta*$ to bo? ! z9c cup & ! c>bon rod 7 left intact4 ,into ! z9c cup we n[ p\r$ a tumbl]ful ( wat] & add$ ab\t a qu>t] ( its volume ( hydro*loric acid1 sett+ ! :ole into a l>ge b[l to gu>d aga9/ disa/]4 ,bubbles ( gas 7 =m$ rapidly1 caus+ ! liquid to eff]vesce z a tumbl] ( soda wat] w\ld d4 ,we inv]t$ an empty tumbl] ov] ! cup s z to collect ?is gas4 ,9 ab\t two m9utes we lift$ ! tumbl]1 /ill hold+ its m\? d[nw>d1 & br\ght a light$ mat* to x4 ,!re 0 a fla% & ! cont5ts burn$ ) a pale-blue flame4 ,"s ( ! z9c _h unit$ ) "s ( ! hydro*loric acid & set free hydrog5 gas1 :i* is "o ( ! con/itu5ts ( ! acid4 ,?is is typical ( *emical actions4 ,some?+ simil> takes place betwe5 ! ammonium *loride & ! z9c4 ,?ree int]e/+ ?+s occur 9 ?is exp]im5t3 #a4 ,*emical action1 j describ$1 is produc$4 #b4 ,heat is produc$4 ,?is 0 v evid5t :5 we took ! z9c cup up 9 our h&s4 ,x 0 z hot z ?\gh boil+ wat] _h be5 put into x4 #c4 ,an electro-motive =ce is produc$4 ,?is we %[$ by connect+ "o end ( a piece ( copp] wire to ! b9d+ po/ ( ! z9c cup & ! o!r end ( ! wire to an electric bell4 ,ano!r wire ran f ! bell to ! c>bon rod4 ,:5 ! c>bon rod 0 l[]$ into ! acid ! bell rang4 ,)9 t5 m9utes holes began to appe> 9 ! side ( ! z9c cup4 ,! acid cont5ts began to fl[ out into ! b[l1 & n long aft] ! z9c fell to pieces4 ,aft] fifte5 or tw5ty m9utes ! action began to gr[ less4 ,! acid 0 be+ us$ up z well z ! z9c4 ,if en\gh acid is add$ ! z9c w :olly disappe>4 ,we h *os5 sub/ances :i* w\ld produce /rik+ results 9 ?is exp]im5t1 b ! same sort ( ?+ is go+ on ab\t u cont9ually4 ,"o summ] by ! sea%ore ,i fa/5$ a brass plate ^u my boat ) two screws--"o ( brass & "o ( galvaniz$ iron4 ,! plate 0 atta*$ bel[ ! wat] l9e s t x might be act$ ^u by ! salt wat]4 ,)9 ?ree weeks ! head ( ! galvaniz$ iron screw _h entirely dissolv$1 :ile ! brass screw 0 z good z ev]4 ,a galvaniz$ iron screw ne> by b n 9 contact ) ! brass 0 /ill 9 z good ord] z ev]4 ,i _h simply made an electric batt]y cell out ( ! ocean by dipp+ into x z9c & brass 9 contact4 ,a mo/ int]e/+ relation%ip exi/s betwe5 ! ?ree k9ds ( activity 9 ! cell1 :i* h be5 m5tion$1 viz43 7#a7 *emical action2 7#b7 production ( heat2 7#c7 production ( electric curr5t4 ,z has be5 already not$1 *emical action produces heat4 ,conv]sely1 if we apply heat to ! cell we greatly increase its *emical action4 ,we h also not$ t *emical action produces an electric curr5t1 b unless ! curr5t is all[$ to fl[ ?r\gh "s ext]nal *annel l a clos$ circuit ( wire ! *emical action is greatly re/ra9$ or entirely *eck$4 ,illu/ration3 ,fig4 #aej ,9 a glass tumbl] ,i put a rod ( pure z9c 7,fig4 #aej1 ,zn71 & an electric light c>bon1 ,c4 ,a %ort wire1 a1 0 arrang$ = connect+ ! two ext]nally4 ,9 ! tumbl] 0 put "s wat] ) ab\t "o t5? its volume ( sulphuric acid4 ,no *emical action 0 evid5t until ! wire 0 t\*$ to ! z9c1 clos+ ! circuit4 ,!n bubbles ( hydrog5 gas ga!r$ ^u ! surface ( ! c>bon rod1 & clung to x v t5aci\sly4 ,we lift$ out ! c>bon rod & r9s$ (f ! bubbles 9 ano!r tumbl] ( wat]1 & !n return$ ! c>bon to its place 9 ! cell4 ,! exp]im5t 0 repeat$ _m times1 & ea* "t no bubbles ( hydrog51 :i* is 9 ?is case ! sign ( ! *emical action1 appe>$ until ! circuit 0 clos$ = ! fl[ ( ! electric curr5t4 ,incid5tally x %\ld be said t ! am\nt ( hydrog5 produc$ by ! *emical action is a measure ( ! am\nt ( electric curr5t produc$4 ,incid5tally also x %\ld be said t ! bubbles ( hydrog5 cl++ to ! c>bon rod *eck & almo/ /op bo? ! *emical action & ! production ( electric curr5t :5 ! circuit is clos$4 ,if n[ we put 9 sodium bi*romate to use up ! hydrog5 z fa/ z x is produc$ we may h a cont9u\s curr5t :5ev] ! circuit is clos$4 ,*emical action does n entirely cease 9 ?is cell :5 ! circuit is op5$4 ,b if two cells are prep>$1 & "o is left ) its circuit clos$ :ile ! o!r rema9s ) its circuit op51 x w be f\nd t ! z9c disappe>s & ! acid is us$ up 9 ! clos$ cell 9 a %ort "t1 :ile ^! rema9 n greatly *ang$ = a long "t 9 ! cell on :i* ! circuit is op54 ,no cell w rema9 =ev] )\t *emical action1 yet a dry cell :i* might use up its z9c & ammonium *loride 9 a few h\rs if ! circuit is clos$ may be kept idle ?ree or f\r ye>s1 & /ill be able to furni% electricity en\gh to r+ a bell4 ,"s p]sons feel defraud$ if ! au?or ( a book fails to give !m all ! new words & conv5tional t]ms :i* belong to any subject4 ,= su* "h is a page or s4 ,x is conv5tional to speak ( ! electric curr5t z fl[+ f ! c>bon ?r\gh ! wire to ! z9c1 al?\gh e "o has suspicions t x may fl[ 9 ! o!r direction or ev5 t x may n fl[ at all4 ,x is conv5tional to designate any "p ( ! circuit f :i* ! curr5t comes z positive 77 to any o!r "p t[>d :i* x fl[s1 ?is latt] be+ consid]$ negative to ! =m] & designat$ 7-74 ,! curr5t is conceiv$ ( z mak+ a complete circuit1 f c>bon to z9c ?r\gh ! wire & f z9c to c>bon ?r\gh ! liquid4 ,h5ce1 ! b9d+ po/ ( ! c>bon rod is call$ ! pole & t ( ! z9c is call$ !-pole1 :ile ! z9c rod or plate b5ea? ! surface ( ! fluid is call$ ! plate & ! c>bon is call$ !-plate4 ,! liquid is t]m$ ! electrolyte4 ,! sodium bi*romate1 introduc$ to cause ! hydrog5 to unite ) oxyg51 is call$ an oxidiz+ ag5t or ev5 a depol>iz+ ag5t1 & hydrog5 collect+ ^u ! negative plate is said to pol>ize ! cell4 ,hydrog5 may be made to collect ^u ! c>bon or negative plate until ! electric curr5t rev]ses its direction4 ,! hydrog5 is said to be m - ?an ! z9c4 ,if we connect ! z9c & c>bon rods ) ! wires br++ an electric curr5t f ! dynamo we may make ei!r "o positive z we *oose1 accord+ to :i* is connect$ ) ! positive wire4 ,hydrog5 bubbles w collect ^u :i*ev] plate we make ! negative "o4 ,:5 we s5d an electric curr5t f ! dynamo into ?is cell x is call$ an electrolytic cell1 & :5 x is us$ to g5]ate an electric curr5t x is call$ a batt]y cell4 ,9 ei!r case ! electrolyte is decompos$ & put ?r\gh a *emical *ange1 ?\gh ! *emical action 9 "o case is ! rev]se ( t 9 ! o!r1 & ! direction ( ! electric curr5t 9 "o case is ! rev]se ( t 9 ! o!r4 ,= example let u consid] ! case ( a z9c rod & a c>bon rod imm]s$ 9 sulphuric acid & ! ext]nal circuit clos$4 ,! curr5t passes z indicat$ by ! arr[s 9 ,fig4 #aea1 & ! *emical actions result 9 hydrog5 leav+ ! sulphuric acid & z9c tak+ its place1 =m+ z9c sulphate4 ,?is is a :ite salt & = purposes ( ?is exp]im5t mu/ rema9 dissolv$ 9 wat]4 ,s f> we h be5 consid]+ a g5]ator ( electricity--a batt]y cell4 ,we may introduce some?+ at m1 say a motor1 :i* w indicate t an electric curr5t is fl[+4 ,at l5g? ! cell ceases to g5]ate curr5t & is1 z we say1 run d[n4 ,suppose n[ we sub/itute a dynamo 9 place ( ! motor 9 ?is circuit1 connect+ x s t ! c>bon rod %all be its positive pole & ! z9c its negative pole4 ,we n[ call ?is an electrolytic cell1 7,fig4 #aeb74 ,! curr5t w decompose ! z9c sulphate4 ,! z9c w be coat$ ^u ! z9c rod & hydrog5 w be procur$ f ! wat] pres5t1 ( :i* x is a con/itu5t1 to =m aga9 sulphuric acid z orig9ally4 ,illu/ration3 ,fig4 #aea ,illu/ration3 ,fig4 #aeb ,we %all ?us re/ore ! conditions :i* prevail$ 9 ! fir/ case z repres5t$ 9 ,fig4 #aea4 ,h#b,,s#d is ! *emi/'s designation ( sulphuric acid & ,zn,s,o#d is 8 expression = z9c sulphate4 ,! exp]im5t illu/rates a /orage batt]y s call$4 ,x might bett] be call$ a *emical trans=m]4 ,x is :olly unnecess>y t "o rod be compos$ ( z9c4 ,if we beg9 ) bo? rods ( c>bon imm]s$ 9 a solution ( ,zn,s,o#d1 & s5d into ?is cell ! dynamo curr5t1 ! c>bon :i* acts z ! negative pole w be coat$ ) z9c 9 a %ort "t1 & we %all h 9 effect a rod ( z9c & "o ( c>bon z be=e4 ,aft] a m9ute or two we may disconnect ! g5]ator & sub/itute 9 its place a bell z indicator1 & x w r+1 %[+ t we h trans=m$ electrical en]gy into *emical en]gy :i* is n[ be+ retrans=m$ into electrical en]gy4 ,we say t we /ore electricity by ?is means1 :i* is1 h[ev]1 no m true ?an t a f>m] /ores 8 f>m 9 ! bank :5 he sells x & deposits ! money until he %all ne$ x to buy ano!r f>m4 ,"h is a v beautiful blue salt4 ,i w drop a few cry/als ( x into a tumbl] ( wat] & dip 9 two c>bon p5cils connect$ to ! dynamo curr5t1 us+ betwe5 fifty & sixty ohms ( resi/ance 9 ! circuit s z to h two amp]es fl[+4 ,aft] a m9ute or two ,i lift out ! negative c>bon & y see t x is well plat$ ) copp]4 ,! blue salt is copp] sulphate4 ,if we weigh ! negative c>bon1 bo? be=e & aft] ! exp]im5t1 we %all f9d t copp] has be5 deposit+ at ! rate ( "o ounce 9 twelve h\rs4 ,if we r$uce ! curr5t "o half1 mak+ x "o amp]e1 x w deposit copp] at ! rate ( "o ounce 9 tw5ty-f\r h\rs4 ,"o amp]e w sep>ate ?ree ounces ( lead 9 a day f a solution ( any lead salt2 x w sep>ate 4#i ounce ( iron 9 a day f a solution ( any iron salt1 & x w lib]ate f wat]1 :i* is a comp\nd ( hydrog51 "o gallon ( ! gas 9 t5 h\rs4 ,! am\nt ( *emical action is a measure ( ! am\nt ( electrical en]gy exp5d$4 ,be=e ! pres5t =m ( comm]cial wattmet] 0 devis$ electrolytic cells 7 us$ to det]m9e :at ! consum]'s bill = electricity %\ld be ea* mon?4 ,^! *emical met]s conta9$ a solution ( z9c sulphate = ! electrolyte & bo? ! positive & ! negative plates 7 ( z9c4 ,:ile ! curr5t is pass+1 z9c f ! solution is coat$ ^u ! negative plate & z9c f ! positive plate takes its place 9 ! solution1 ?us ma9ta9+ a con/ant /r5g? ( solution4 ,"h are ?ree iron nails4 ,i propose t y plate "o ) z9c & ano!r ) copp] & !n expose all ?ree to ! wea!r & see :i* w ru/4 ,i propose t y replate all ! spoons at ! cottage & ! metal tops ( ! salt cell>s ) silv]4 ,electro-plat+ results bett] if done sl[ly4 ,t5 volts & 4#a amp]e w be suffici5t curr5t4 ,9 ! /orage batt]y we g5]ally use lead = bo? positive & negative plates & dilute sulphuric acid = ! electrolyte4 ,hydrog5 is lib]at$ at ! positive plate & oxyg5 unites ) ! negative plate4 ,:5 ! *>g+ curr5t is cut (f ! *emical action rev]ses1 & an electric curr5t is produc$ by ! cell4 ,9 all o!r batt]ies !re is a de/ruction ( "o plate & ( ! electrolyte1 :i* _c be fully re/or$ by a *>g+ curr5t1 al?\gh 9 ! case ( ! lead & sulphuric acid comb9ation ! *>g+ & dis*>g+ ( ! cell may g on alt]nately = a v long p]iod )\t p]man5t *ange or loss ( any sub/ance except wat]4 ,!re is1 h[ev]1 pl5ty ( loss ( en]gy 9 ?is z 9 o!r trans=m]s4 ,"o hundr$ amp]e h\rs ( curr5t exp5d$ to *>ge a /orage batt]y w yield f sev5ty-five to eighty-five amp]e h\rs :ile ! batt]y is dis*>g+4 ,! lead /orage batt]y is1 h[ev]1 full ( disappo9tm5ts = ^? :o d n prop]ly c>e = x4 ,x is irretrievably ru9$ if neglect$ & all[$ to *>ge too f>1 or dis*>ge too f>1 or evaporate too mu* wat]1 etc4 ,! voltage ( a lead cell mu/ n rise above #b4b nor fall bel[ #a4h4 ,x mu/ n be all[$ to furni% at any "o "t a great] numb] ( amp]es ?an x is rat$ =4 ,x mu/ n /& idle too mu*4 ,x mu/ n be clean$ up & put away = a p]iod4 ,9 fact1 ! lead-sulphuric acid batt]y is s poorly adapt$ to our ne$ t ,i feel dispos$ to try ,mr4 ,edison's new /orage batt]y4 ,?is has nickel hydrate pack$ 9 tubes ( metallic nickel = ! positive plates & iron oxide press$ into pockets 9 a %eet ( metallic iron = ! negative plate4 ,a solution ( potassium hydrate 9 wat] is us$ = ! electrolyte4 ,?is is said to be un9jur$ by be+ empti$ out & left idle1 z our batt]ies mu/ be = a l>ge "p ( ! ye>4 ,! e4 m4 f4 ( ?is batt]y is less ?an t ( ! lead batt]y1 be+ only #a4b volts4 ,we %all !re=e ne$ n9ety-six cells 7type ,b-#d7 = ! ma*9e %op & n9ety-"o cells ( ! same k9d = ! cottage4 ,our dynamo w be unable to *>ge at "o "t m ?an sixty ( ^! cells connect$ 9 s]ies4 ,! p>ticul> *ore :i* y boys mu/ p]=m is to see t ! voltage ( ^! batt]ies is ma9ta9$ at ab\t #a4b4 ,x %\ld be *>g$ up to #a4h volt at lea/ once a week & nev] all[$ to dis*>ge to a l[] pressure ?an "o volt4 ,! level ( ! electrolyte mu/ be ma9ta9$ "o half in* above ! plate by add+ di/ill$ wat] occasionally4 ,a few ye>s ago e /ud5t ( *emi/ry 0 m or less agitat$ by ! ?\ght t m ?an half ( e clay bank 0 compos$ ( metal ne>ly z valuable1 or at lea/ z co/ly1 z gold4 ,?is is alum9um4 ,by all ! me?ods !n kn[n x 0 a v difficult & exp5sive process to extract ! metal f ! clay4 ,at l5g?1 by ! p]fect+ ( ! dynamo1 ! *emi/ _h "u 8 control great & p[]ful electric curr5ts :i* enabl$ him to unlock any *emical comp\nd h[ev] refractory & isolate its elem5ts4 ,z a result alum9um became common en\gh & *eap en\gh = ev5 kit*5 ut5sils4 ,! metal calcium :i* a %ort "t ago 0 an exce$+ly r>e sub/ance wor? #dj an ounce is n[ fairly abundant & *eap = *emical exp]im5ts1 al?\gh x has no qualities :i* w give x an ext5d$ use4 ,p[]ful electric curr5ts1 su* z are obta9$ at ,niag>a1 enable u to comb9e elem5ts into hi!rto unkn[n *emical comp\nds4 ,c>bon & silicon are made to unite to =m c>borundum1 :i* vies ) ! diamond = h>dness4 ,c>bon & calcium unite to =m calcium c>bide1 us$ ) wat] to =m acetyl5e gas4 ,9 su* processes ! int5se heat ( ! electric arc--p]haps #fjjj degrees--is employ$1 toge!r ) ! electrolytic action ( ! curr5t1 to sep>ate & comb9e sub/ances4 ,enorm\s curr5ts are us$ 9 ! electric furnaces = produc+ *emical reactions--f #ajjj to #cj1jjj amp]es at a "t4 ,electric curr5ts pass+ ?r\gh ! human body exp5d _! en]gy p>tly 9 heat & p>tly 9 electrolysis4 ,s simple & h>mless a ?+ z common salt w\ld become a virul5t poison if x c\ld be electroliz$ 9 ! body into its elem5ts sodium & *lor9e4 ,let u make use ( an electric curr5t to decompose wat] into its elem5ts1 hydrog5 & oxyg54 ,i h a ?ree-ounce wide-m\!d bottle 7,fig4 #aec7 & ?r\gh its cork ,i pass two %ort pieces ( ,no4 #bd plat9um wire by pu%+ a /\t ne$le ?r\gh fir/4 ,i fill ?is bottle ) pure wat] & cut a slight furr[ 9 ! side ( ! cork1 :]e wat] may drip out :5 ! gas is produc$ 9 ! bottle4 ,we cr[d ! cork firmly into ! m\? ( ! bottle & inv]t x4 ,no wat] drops out4 ,we b5d ! ends ( ! plat9um wires into hooks & hang ^u !m ! wires br++ ! dynamo direct curr5t4 ,!re is no evid5ce ( *emical action4 ,pure wat] is an exce$+ly poor conductor ( electricity4 ,let u n[ put ab\t fifty-five ohms ( resi/ance into ! dynamo circuit1 s t x w pass ab\t two amp]es1 & put a v small p9* ( salt into ! wat]1 :i* makes x s good a conductor t its resi/ance may be ignor$4 ,:5 n[ we close ! circuit1 z be=e1 a brisk eff]vesc5ce takes place4 ,bubbles ( gas rapidly =m on ! plat9um wires & break away1 ris+ ?r\gh ! liquid4 ,twice z _m =m on ! negative wire z on ! positive "o4 ,z ^! gases rise to ! top ( ! bottle an equal volume ( ! wat] drips out ?r\gh ! small hole 9 ! cork4 ,illu/ration3 ,fig4 #aec ,two amp]es ( electricity w lib]ate two fluid ounces ( hydrog5 at ! negative pole & "o fluid ounce ( oxyg5 at ! positive pole1 9 five m9utes4 ,h5ce 9 five m9utes ! bottle %\ld be full ( a mixture ( two gases1 two ?irds ( :i*1 by volume1 is hydrog5 & "o ?ird oxyg54 ,we w cat* ! wat] :i* drips out s t we may measure x4 ,! bottle be+ n[ full ( gas ,i %ut (f ! curr5t1 & remov+ ! cork ,i br+ a flame to its m\?4 ,a v l\d & />tl+ explosion takes place4 ,we p\r ! wat] back into ! bottle1 & x seems to fill x z well z be=e4 ,we h decompos$ a few drops ( wat]--n en\gh to measure--into two gases1 "o ( :i*1 ! hydrog51 occupi$ two ?irds ( ! bottle1 & ! o!r1 oxyg51 occupi$ ! rema9+ ?ird4 ,at ord9>y temp]atures !y w\ld n reunite1 b :5 rais$ to _! k9dl+ temp]ature !y unit$1 produc+ light1 heat1 a l\d noise1 & ! few drops ( wat] :i* _h be5 orig9ally decompos$ by ! curr5t4 ,?is is ! electrolysis ( wat]4 ,i wond] if any su* *emical action took place 9 ,erne/'s body :5 he receiv$ t sev]e %ock on ! motor boat ! o!r day4 ,x is significant t ! dry batt]y cell mu/ be moi/ 9 ord] t *emical action may g on 9 x4 ,comp>e ) t fact sev]al o!rs t we may le>n f obs]vation1 = example3 ,bak+ p[d]s mu/ be kept dry to reta9 _! /r5g?4 ,t is1 if !y get moi/ *emical action w beg9 9 !m1 & ! gas :i* is "o ( ! products ( ?is *emical action w pass (f4 ,n[ x is ! sole function ( bak+ p[d]s to produce gas )9 ! d\gh1 & if ! gas has :olly or p>tially escap$ !y w fail to make ! bread /uff light4 ,! same reasons obta9 = keep+ seidlitz p[d]s & o!r eff]vesc+ salts1 su* z vi*y & kiss+51 dry4 ,x is to prev5t ! *emical action :i* is provok$ by ! pres5ce ( wat]4 ,! same ?+ is true ( ! ru/+ ( iron1 & ! v>i\s k9ds ( corrosion ( metals4 ,we may prev5t su* action indef9itely by keep+ !m dry4 ,b]ries1 fruits1 meats1 milk1 eggs1 gra9--all k9ds ( foods--are pres]v$ f spoil+--f *emical *anges--by dry+ !m & keep+ !m dry4 ,! same ?+ is true ( wood1 pap]1 clo?1 etc4 ,a wood5 f5ce po/ may la/ f five to t5 ye>s4 ,a f5ce rail1 be+ less expos$ to moi/ure1 may la/ two or ?ree times z long4 ,! int]ior wood ( a h\se may la/ a c5tury or two1 :ile ! ext]ior wood1 be+ expos$ to ! wea!r1 may require repairs v frequ5tly4 ,%+les on ! ro( d n la/ z long z %+les on ! side ( ! h\se4 ,^? on a /eep ro( la/ long] ?an ^? on a flatt] "o4 ,a pit* ( at lea/ =ty-five degrees 9 a ro( is desirable to keep x dry4 ,! nor? & we/ sides ( a h\se be+ lea/ expos$ to /orm 9 ?is climate la/ ! long]4 ,preci\s books1 records1 de$s1 wills1 etc41 on pap] mu/ be pres]v$ 9 dry air4 ,a sail w keep /rong & :ite if kept dry4 ,b x is impress$ ^u u by our exp]i5ces t sunlight is ev5 m pot5t ?an moi/ure to produce *emical *ange4 ,photographic processes are dep5d5t ^u ! p[] ( light to produce *emical *anges4 ,! fad+ ( our tape/ries & our g>m5ts1 ! tann+ ( our sk9s1 ! developm5t ( gre5 mat]ial 9 ! leaves ( plants1 all are evid5tly ! direct result ( sunlight4 ,a picture hung on ! wall prev5ts ! wall pap] beh9d x f be+ fad$ by ! light1 or x prev5ts ! wood beh9d x f be+ turn$ yell[ by ! light4 ,folds 9 our g>m5ts prev5t !m f be+ fad$ all alike4 ,v _m sub/ances to be f\nd 9 a *emical laboratory1 9 a drug /ore1 or 9 a kit*5 mu/ be kept 9 ! d>k if !y are to be gu>d$ aga9/ *emical *ange4 ,no exp]i5c$ h\sewife w\ld let a b>rel ( fl\r or potatoes sit 9 ! sun1 & e h\sewife kn[s t ! sun is ! be/ ag5t = br++ ab\t ^? *emical *anges :i* %e desires4 ,h5ce %e puts h] b$d+1 h] milk pans1 h] bread box1 h] butt] j>1 etc41 out to sun4 ,%e has op5 plumb+1 t ! sun may ent] ^? d>k & dirty corn]s4 ,if y w\ld gu>d a sub/ance aga9/ *emical *ange1 keep x 9 a dry1 d>k place4 ,we h come to associate ! sun & ! wea!r z dis9tegrat+ =ces4 ,h5ce ! s\? & ea/ sides ( ! build+ ne$ mo/ frequ5t repairs4 ,e "o :o has made "t exposures 9 photography kn[s t ! sunlight f ! ea/ is1 z a rule1 two or ?ree times z p[]ful z t f ! we/4 ,!re is less moi/ure & du/ 9 ! air to scre5 u f ! e>ly morn+ sun ?an f ! late aft]noon sun4 ,:5 !re is en\gh moi/ure 9 ! air to make ! sun look r$1 ^? rays f x :i* w\ld produce *emical action1 call$ act9ic rays1 are cut (f4 ,photographic processes are !n exce$+ly sl[4 ,x is l expos+ a plate 9 a d>k room beh9d ! ruby glass4 ,b our daily exp]i5ces tea* u t n only moi/ure & light b also heat /imulates *emical action4 ,we re/ra9 *emical action by cold :5 we put ?+s 9 ! ice box4 ,we ha/5 *emical action by heat :5 we put ?+s on ! /ove4 ,w9t] re/ra9s all ! *emical activities ( nature1 & summ] quick5s all ! vegetable & m9]al k+doms into *emical activity4 ,if we w\ld pres]ve a sub/ance f *emical *ange we mu/ keep x 9 a cool1 d>k1 dry place4 ,n[ ^? conditions :i* w fav\r ! *emical activity ( a batt]y cell w enable x to produce electricity1 & ^? conditions :i* w re/ra9 *emical action w enable u to pres]ve ! cell f runn+ d[n4 ,b we h lately le>n$ t o!r =ms ( radiation besides light & heat exi/ & aid 9 *emical action4 ,we may produce radiographs--pictures on photographic plates--)\t light b ) invisible rays1 :i* are ak9 to light & to electricity4 ,,xvi ,,electrocution ,,at ,,millville ,! old mill 0 infe/$ ) rats4 ,my wife laid d[n to ! boys ! pr9ciple t good h\sekeep]s 7 nev] tr\bl$ ) v]m9 ( any k9d4 ,! rats' sole occupation is to se>* = food4 ,if y don't fe$ !m !y w n /ay ) y4 ,b ! boys said t !y 7 glad ( a *ance to try an exp]im5t on ! rats4 ,s "o day :5 ,i w5t d[n to ! mill ,i f\nd !m discuss+ ! possibility ( kill+ ! rats by electricity4 ,h>old said t he _h read t x took mu* less electricity to kill any animal ?an to kill a man1 & he w\ld l to try1 = in/ance1 :e!r ! %ock :i* !y _h receiv$ f a bell w\ld kill a rat4 ,well1 :o's go+ to sit by1 said ,erg1 to close ! prim>y circuit :5 ! rat happ5s to get himself into ! second>y circuit8 ,make him close x himself by "s device1 said ,erne/4 ,!y h a regul> ?or\ghf>e1 a beat5 highway1 along by ! wall1 "u ! mill & up ?r\gh a hole 9 ! floor ( my b$room1 said ,dyne4 ,illu/ration3 ,fig4 #aed ,illu/ration3 ,fig4 #aee ,well1 said ,h>old1 ,i propose an electric trap :i* %all h two comp>tm5ts4 ,we w keep *eese 9 ! inn] comp>tm5t1 ! walls ( :i* %all be ( wires s t ! rats may see ! *eese4 ,! floor ( ! out] ap>tm5t %all be cov]$ ) wire1 z %[n 9 ,fig4 #aed4 ,! wires ( ! second>y circuit f ! bell 7,fig4 #aef7 %all be fa/5$ to ! b9d+ po/s b & c 7,fig4 #aed74 ,! p>tition d %all be a sw+ door into ! ap>tm5t ,a :]e ! *eese is4 ,?is is %[n 9 pr(ile 9 ,fig4 #aee4 d mu/ act z a swit* to close ! prim>y circuit ?r\gh ! bell ,p 7,fig4 #aef74 ,we w h ?ree dry cells 9 ! prim>y circuit4 ,n[ ?is is ! way x w "w3 ,a rat comes up f "u ! mill ) wet & slimy feet--j suit$ = mak+ contact = ! electric curr5t to ent] 8 body4 ,! smell ( ! *eese attracts him4 ,he circles ar\nd ! trap sev]al times1 wat*+ ! *eese 9 ap>tm5t ,a ?r\gh ! wire scre54 ,he sees a n>r[ op5+ into ?is ap>tm5t "u ! door d4 ,he puts himself 9 position ^u ! floor ( ! out] ap>tm5t ,b1 8 feet bridg+ ! gaps betwe5 ! two sy/ems ( wires belong+ to ! second>y circuit4 ,:5 he ?ru/s 8 head "u ! door & pu%es x1 x sw+s 9 a little1 br++ "o metal /rip aga9/ ano!r1 :i* belongs to ! prim>y circuit4 ,?is closes t circuit4 ,he w nev] he> ! bell r+1 = ! electric curr5t :i* w %ock him to dea? travels #ahf1jjj miles p] second1 :ile 8 s5sations travel only sixty miles an h\r4 ,if ! involunt>y recoil ( 8 muscles does n make him jump back1 s t ! door w %ut & /op ! bell f r++1 ,dyne w be awak5$ & he w close ! door1 s9ce we w put ! trap at t hole :]e ! rats ent] 8 b$room4 ,illu/ration3 ,fig4 #aef ,! next night ?ree rats 7 electrocut$ by ?is device4 ,i told ! boys !y _h s _m int]e/+ ?+s go+ on at ! mill t we %\ld h to h a telephone betwe5 x & ! cottage s t we c\ld talk !m ov]4 ,,xvii ,,! ,,telephone ,! telephone 0 ! great inv5tion ( our c5t5nial ye>1 #ahgf4 ,eli%a ,gray & ,alex&] ,graham ,bell ea* claim$ to h be5 ! inv5tor4 ,x is q probable t ea* did discov] x indep5d5tly1 b ! result ( ! long pat5t suit 0 t ! c\rt aw>d$ ! claim to ,bell4 ,x is1 !re=e1 kn[n z ! ,bell telephone4 ,_m :o in/all$ telephones dur+ ! fir/ few ye>s ( _! exi/5ce _h !m tak5 out aga9 z nuisances4 ,!y are f> great] nuisances n[ ?an at t "t1 b ! necessity ( !m has come ^u u & entirely enslav$ u4 ,!re 7 m ?an elev5 billion messages s5t by telephone 9 ! ,unit$ ,/ates 9 #aijg4 ,! capital inve/$ 9 telephone bus9ess 0 #had1faf1jjd4 ,! income = t ye> 0 #ahd1dfa1gdg4 ,all ( ^! items _h m ?an d\bl$ dur+ ! previ\s five ye>s4 ,9 #ahhj !re 7 ab\t eight times z _m miles ( telegraph wires z ( telephone wires4 ,9 #aijg1 !re 7 ab\t eight times z _m miles ( telephone wires z ( telegraph wires4 ,! ,bell sy/em _h #c1acb1jfc /ations1 & indep5d5t companies _h #b1ihf1eae /ations 9 #aijg4 ,! fir/ telephone l9e ran f ,salem to ,bo/on1 ,mass4 ,?is 0 9 #ahgg4 ,! next ye> ! fir/ telephone ex*ange 0 e/abli%$4 ,x 0 eight ye>s be=e a telephone l9e 0 ext5d$ f ,bo/on to ,new ,york4 ,on ,octob] #ah1 #ahib1 ! fir/ telephone message 0 s5t f ,new ,york to ,*icago4 ,previ\s to #ahie telephon+1 l telegraph+1 0 done by "o wire1 us+ ! e>?1 z we say1 to complete ! circuit4 ,b at ab\t t "t electric c> & electric light+ l9es became s common t !y int]f]$ ) telephon+4 ,^! curr5ts runn+ 9 l9es p>allel to ! telephone wires induc$ curr5ts 9 !m1 & :5 a p]son put a receiv] to 8 e> = conv]sation he he>d ! hum ( electric light dynamos & ! buzz ( electric c>s s l\d t conv]sation 0 q impossible4 ,! next /ep 0 to introduce a return wire--! d\ble metallic circuit z we call x4 ,?us outside curr5ts induce equal & opposite curr5ts 9 ! two wires ( ! circuit1 :i* neutralize ea* o!r4 ,x 0 ?is same ye>1 #ahie1 t ! c5tral batt]y sy/em 0 introduc$ into telephone equipm5t4 ,?is is n usually a batt]y at all1 b a dynamo4 ,! price ( all electrical supplies 9 #ahie 0 ab\t "o t5? :at x _h be5 9 #ahhe1 & at ! same "t ! goods 7 ( f> bett] quality4 ,important telephone pat5ts expir$ 9 ?is ye>1 & imm$iately private & indep5d5t l9es began to be e/abli%$4 ,x 0 also 9 #ahie t ! telephone company began to use an automatic regi/]+ device :i* enabl$ x to *>ge telephone rates accord+ to ! numb] ( calls4 ,! boys unscrew$ ! end ( a telephone receiv] 7,fig4 #aeg7 & f\nd inside a p]man5t magnet made ( sev]al /eel b>s bolt$ toge!r 7,fig4 #aeh74 ,?is 0 %[n to be a magnet by pres5t+ a small pocket compass to ei!r end4 ,! left-h& end ( ?is magnet prov$ to be its nor? pole by repell+ ! blue end ( ! compass ne$le4 ,illu/ration3 ,fig4 #aeg ,illu/ration3 ,fig4 #aeh ,illu/ration3 ,fig4 #aei ,on ! left-h& end ( ! magnet 0 a small spool ( ,no4 #cf copp] wire1 silk cov]$4 ,x (f]$ #ge ohms ( resi/ance1 & s9ce x takes #b-a_/b feet ( ?is wire to furni% #a ohm ( resi/ance ! spool conta9s #ahg-a_/b feet4 ,a ?9 disc ( s(t iron 4#ja in* 9 ?ickness is held by ! h>d rubb] case v ne> to b n q t\*+ ?is end ( ! magnet4 ,we drew ?is disc to "o side1 z %[n 9 ,fig4 #aei1 & connect$ ! receiv] by wires to a magneto4 ,we turn$ ! crank ( ! magneto sl[ly & ! iron disk danc$ up & d[n1 keep+ "t ) ! revolutions ( ! armature4 ,! magneto furni%$ an alt]nat+ curr5t1 :i*1 :5 x fl[$ ar\nd ! coil 9 "o direction1 /r5g!n$ ! pole ( ! magnet1 & 9 ! rev]se direction weak5$ ! pole4 ,:5 ! crank 0 turn$ s z to produce tw5ty to ?irty revolutions ( ! armature p] second ! danc+ ( ! disc s\nd$ l ! l[ hum produc$ by ! w+ ( a humm+ bird4 ,:5 a l>ge1 wide-m\!d bottle 0 br\ght ne> to ?is ! s\nd 0 greatly re9=c$1 z ! s\nd ( a bee becomes l\d] :5 he appe>s at y\r op5 w9d[4 ,we next replac$ ! iron disc & put on ! cap aga94 ,we !n connect$ ! receiv] at ,s 7,fig4 #afj7 & connect$ two dry cells at p4 ,:5 ! prim>y circuit 0 clos$ ! disc vibrat$ 9 "t ) ! hamm] ( ! bell mak+ ! same tone4 ,we sub/itut$ = ! bell a s]ies ( buzz]s4 ,! smalle/ _h an armature ab\t "o in* long1 :ile t ( ! l>ge/ 0 ab\t two in*es long4 ,! %ort] ! armature ! fa/] x vibrat$1 & ! high] 0 ! pit* ( its tone4 ,we arrang$ ^! z %[n 9 ,fig4 #afa4 ,a1 ,c1 ,d1 ,e & ,f are ! buzz]s4 ,b is a batt]y ( two cells & ,g1 ,h1 ,i1 ,j & ,k are spr+s ( %eet brass :i* act z pu% buttons4 ,by op]at+ ^u ^! spr+s ) "o's f+]s1 z ^u ! keys ( an organ1 x 0 possible to repres5t ! tones ( a re$ organ aft] a fa%ion4 ,! armatures are re$s & !y are made to vibrate by electro-magnets4 ,we call$ x an electric organ4 ,! telephone receiv] 0 connect$ at ,t1 & ! wires :i* l$ to x 7 l5g!n$ s t ! receiv] might be a long di/ance away4 ,! disc 9 ! receiv] kept "t ) ! armature ( ea* buzz] :5 x s\nd$ & fai?fully reproduc$ its s\nd4 ,b ! /range/ ?+ 0 t :5 any two buzz]s s\nd$ toge!r1 or1 inde$1 if all five buzz]s s\nd$ toge!r1 ! receiv] respond$ to !m all at ! same "t1 s t a p]son 9 ano!r room or 9 ano!r h\se1 ) ! receiv] at 8 e>1 might he> exactly :at ^? did :o 7 9 ! same room ) ! buzz]s4 ,! wires f ! receiv] 7 connect$ ) ! coil 9 ea* buzz] s z to get ! induc$ curr5t1 z %[n 9 detail 9 ,fig4 #afj4 ,illu/ration3 ,fig4 #afj ,illu/ration3 ,fig4 #afa ,illu/ration3 ,fig4 #afb ,we took a telephone induction coil 7,fig4 #afb7 & fa/5$ x to a bo>d z repres5t$ 9 ,fig4 #afc1 ,i4 ,"o wire ( ! prim>y circuit 0 fa/5$ to ! b9d+ po/ a4 ,! o!r wire f ! prim>y coil pass$ to ! swit* ,s & !n to ! batt]y4 ,f ! batt]y ! wire ran to ! b9d+ po/ b4 ,c is a /eel tun+ =k4 ,! second>y circuit is clos$ ?r\gh a telephone receiv]4 ,^! wires are ext5d$ s t ! receiv] is too f> di/ant = ! tun+ =k to be he>d ?r\gh ! air4 ,:5 ! swit* ,s is clos$ ! tun+ =k acts z ! int]rupt] = ! prim>y circuit1 & x int]rupts accord+ to its "t ( vibration4 ,if1 = in/ance1 ! =k gives ! tone ( middle ,c on ! piano x vibrates #bef times a second4 ,x int]rupts ! prim>y circuit #bef times a second4 ,x induces an alt]nat+ curr5t ( ! same frequ5cy 9 ! second>y circuit4 ,! diaphragm ( ! telephone receiv] vibrates 9 p]fect "t ) ! tun+ =k & produces ! same tone z ! tun+ =k4 ,we _h a s]ies ( tun+ =ks giv+ a v>iety ( tones1 :i* we c\ld sub/itute "o aft] ano!r 9 place ( ?is "o4 ,! receiv] reproduc$ accurately ! tone ( ea* "o ( !m4 ,illu/ration3 ,fig4 #afc ,illu/ration3 ,fig4 #afd ,we took a small induction coil 7,fig4 #afd7 c & fa/5$ "o end ( ! prim>y circuit to a batt]y1 ,b4 ,! wire at ! o!r end ( ! prim>y circuit 0 b5t into a hook h4 ,?is hook 0 adju/$ ab\t a qu>t] ( an in* f ! end ( ! iron core ( ! coil4 ,! o!r wire f ! batt]y 0 atta*$ to ! /eel /r+s ( a piano1 ,p4 ,:5 ! coil c 0 br\ght ov] a /r+ & ! hook h 0 all[$ to pass b5ea? ! /r+ & t\* x v g5tly1 ! prim>y circuit 0 clos$ ?r\gh ! /r+1 :i* s]v$ z an int]rupt] ( ! curr5t & vibrat$ accord+ to its tone4 ,! second>y coil1 n repres5t$ 9 ! figure1 0 connect$ to a di/ant telephone receiv]1 :i* reproduc$ ! tones ( ! piano /r+s4 ,produc+ a tone is m]ely a matt] ( mak+ some?+ vibrate ) ! requir$ frequ5cy4 ,x may be a piano /r+1 or a tun+ =k1 or a re$ ( an electric buzz]1 or ! diaphragm ( a telephone receiv]4 ,if x vibrates #bef times a second1 x w produce ! same tone z middle ,c on a piano2 if x vibrates #eab times a second x w produce ! ,c :i* is an octave above1 & if #abh times a second an octave bel[ middle ,c4 ,! human voice is produc$ by vocal cords 9 ! ?roat1 :i* vibrate ) ! prop] frequ5cy to give any requir$ tone4 ,b h[ c we make ! human voice act z an int]rupt] ( ! prim>y circuit8 ,an exam9ation ( ! telephone transmitt] w supply ! answ] to ?is "q4 ,illu/ration3 ,fig4 #afe ,illu/ration3 ,fig4 #aff ,! boys aft] tak+ ! transmitt] 7,fig4 #afe7 ap>t proce$$ to make "o :i* %\ld answ] ! purpose z foll[s3 ,a block ( wood ab\t "o in* ?ick & ?ree in*es squ>e 7,fig4 #aff71 ,a1 0 holl[$ out1 mak+ a cone-%ap$ cavity ab\t "o half in* deep & "o in* broad4 ,?is cavity 0 fill$ ) small pieces ( graphite1 ,g1 made by cutt+ up a lead p5cil4 ,an old t9-type1 ,d1 0 laid ov] ?is z a diaphragm & tack$ ar\nd ! edges4 ,a b9d+ po/1 ,e1 pass$ ?r\gh ! block1 its head be+ buri$ 9 ! graphite at ! bottom ( ! cavity4 ,! b9d+ po/ ,f furni%$ contact ) ! t9-type4 ,"o dry cell 0 plac$ at ,b & ! s5sitive ammet] 0 connect$ at ,c4 ,! ne$le %[$ t al?\gh a small curr5t 0 pass+ x 0 con/antly v>y+ 9 /r5g?4 ,tapp+ ^u ! table1 walk+ across ! floor ( ! room1 %\t+1 & p>ticul>ly :i/l+1 caus$ v>iations 9 ! conduct+ p[] ( ! graphite & consequ5tly v>iations 9 ! curr5t /r5g?4 ,?is is precisely ! condition we wi%$ to produce 9 ! prim>y circuit4 ,illu/ration3 ,fig4 #afg ,we next sub/itute = ! ammet] at ,c ! prim>y & second>y coil ( ! telephone4 ,9 ,fig4 #afg ,t is ! transmitt]1 ,b is a batt]y ( two dry cells1 ,p is ! prim>y w9d+ ( ! coils1 & ,s is ! second>y w9d+4 ,to ?is a telephone receiv]1 ,r is connect$ by wires long en\gh to rea* into ano!r room4 ,a p]son hold+ ! receiv] at 8 e> c\ld he> ev]y?+ said or done 9 ! room :]e ! transmitt] 0 almo/ z pla9ly z ?\gh he 7 pres5t 9 ! room4 ,illu/ration3 ,fig4 #afh ,two su* transmitt]s 7 made & ! second "o 0 plac$ 9 ! room :]e ! receiv] _h be51 :ile a second receiv] 0 in/all$ ne> ! fir/ transmitt]4 ,! arrangem5t is %[n 9 ,fig4 #afh4 ,t is ! transmitt] at "o end ( ! l9e & ,t' ! transmitt] at ! o!r end4 ,b & ,b' are ! batt]ies at ea* end1 ,p & ,p' ! prim>y coils1 ,s & ,s' ! second>y coils & ,r & ,r' ! receiv]s4 ,) ?is arrangem5t two p]sons c>ri$ on a conv]sation ) p]fect ease1 hold+ ! receiv]s to _! e>s1 pres5t+ _! m\?s to ! transmitt]s & speak+ 9 mod]ate tones4 ,h & ,h' are hooks ^u :i* ! receiv]s are to be hung :5 n 9 use4 ,^! hooks act z swit*es to op5 & close ! prim>y circuit4 ,a spr+ normally pu%es ! hook upw>d & closes ! circuit1 b :ile ! receiv] is hang+ ^u x ! circuit is op5 at ?is po9t4 ,?us ! batt]y is sav$ f runn+ d[n :5 ! telephone is n 9 use4 ,! wires 7 f9ally ext5d$ f ! mill to ! cottage & ?is equipm5t 0 in/all$ at ea* end4 ,x w be notic$ t ! second>y circuit includes two receiv]s & two second>y coils besides ! wire ( ! l9es to (f] resi/ance4 ,! receiv]s (f] #ge ohms ( resi/ance ea*4 ,! second>y coils (f] #bej ohms ea* & ! l9e wires betwe5 ! mill & ! cottage (f] #ajj ohms4 ,?is makes a total ( #gej ohms = ! second>y circuit4 ,b ! rapid alt]nations :i* are induc$ 9 ! second>y circuit imp$e ! electric curr5t t5 times z mu* z ! resi/ance already m5tion$4 ,:5 consid]+ alt]nat+ curr5ts pass+ ?r\gh coils ( wire we are oblig$ to take into acc\nt two k9ds ( resi/ance3 #a4 ,ohmic resi/ance4 #b4 ,imp$ance4 ,y boys und]/& ! resi/ance to ! fl[ ( ! electric curr5t1 :i* we h s (t5 measur$ 9 ohms4 ,b ,i want to %[ y t !re is ano!r k9d ( resi/ance :i* alt]nat+ curr5t meets4 ,"h is a coil conta9+ #ajjj feet ( ,no4 #bj copp] wire4 ,i ?r[ on to x1 = only an in/ant1 ! #aaj-volt direct curr5t1 & ! ammet] reads #aa amp]es1 %[+ t x (f]s a resi/ance ( #aj ohms to ! direct curr5t4 ,i n[ ?r[ on ! alt]nat+ curr5t1 & ! ammet] %[s only a small fraction ( an amp]e4 ,! surg+ ( ! curr5t back & =? induces a c\nt] electro-motive =ce1 9 ! successive lay]s ( ! coil1 :i* we call imp$ance4 ,9 ! exp]im5t :i* we h j p]=m$ imp$ance is fifty times z important a factor z ohmic resi/ance4 ,imp$ance dep5ds *iefly ^u ! frequ5cy ( alt]nation4 ,! imp$ance 9 telephone circuits is p>ticul>ly l>ge because ( ! extremely high frequ5cy ( ! alt]nations produc$ by ! tones ( ! human voice1 ^! be+ usually n f> f t5 times z rapid z ^? ( alt]nat+ curr5ts 9 common use4 ,we may e/imate ! total resi/ance ( our telephone circuit z equival5t to #gejj ohms4 ,our second>y coils h =ty times z _m turns z ! prim>y coils1 & by means ( !m ! voltage is /epp$ up to some:]e ne> "o hundr$ on op5 circuit4 ,:5 clos$ ?r\gh ! l9e1 h[ev]1 ! voltage drops d[n to ab\t t54 ,! result is t ! actual curr5t :i* passes betwe5 ! cottage & ! mill :5 we telephone is n f> f 4#jja amp]e4 ,we may1 h[ev]1 he> a :isp] transmitt$ by 4#jjjjja amp]e or less4 ,! tone ,e :i* is produc$ by ! t5? key above middle ,c on ! piano1 is ! "o mo/ readily he>d ov] ! telephone4 ,x is produc$ by any?+ :i* vibrates #fdj times p] second4 ,illu/ration3 ,fig4 #afi ,we us$ ,no4 #ab galvaniz$ iron wire = our telephone l9es4 ,two miles ( ,no4 #ab copp] wire w\ld (f] #af ohms ( resi/ance4 ,! iron wire (f]s ab\t #ajj ohms4 ,b ?is is a trifle :5 comp>$ ) ! total resi/ance4 ,we us$ a d\ble metallic circuit s z to avoid ! effects ( inductance f our electric light+ circuit4 ,illu/ration3 ,fig4 #agj ,! next ?+ t we 7 oblig$ to consid] 0 "s arrangem5t = call+ p]sons to ! telephone = conv]sation4 ,we decid$ to use magnetos & alt]nat+ curr5t bells4 ,fig4 #afi %[s ! ess5tial me*anism ( ! bells4 ,! bell at ea* end ( ! l9e consi/s ( two gongs a1 b & a b1 ) a hamm] c1 c betwe5 !m4 ,?is hamm] is atta*$ to an iron armature h1 h1 pivot$ ov] ! electro-magnets1 m1 m1 9 su* a way t x rocks back & =? :5 an alt]nat+ curr5t passes ?r\gh ! l9es d e1 f g4 ,! bells at bo? ends ( ! l9e always r+ toge!r1 s9ce !y are connect$ 9 s]ies4 ,a magneto 7,fig4 #agj7 is situat$ at ea* end ( ! l9e4 ,?is1 z has be5 previ\sly expla9$1 is a g5]ator ( electricity1 9 :i* ! field is furni%$ by /eel magnet1 ,m4 ,! armature ,a is a coil ( wire ^: ends are 9 contact ) ! lead+ out wires d & c by means ( bru%es :i* slide ^u r+s4 ,! armature is revolv$ by h&4 ,! crank & cog :eels employ$ to produce high spe$ are n %[n 9 ! figure4 ,by turn+ ! armature rapidly ?is magneto w develop #fj volts e4 m4 f4 on op5 circuit4 ,! magnets ( ! bells are w\nd ) a v l>ge numb] ( turns ( v f9e wire1 s t 4#jbe amp]e is suffici5t to r+ !m4 ,illu/ration3 ,fig4 #aga ,figure #aga %[s h[ ! magneto at ei!r end ( ! l9e is introduc$ into ! circuit = ! purpose ( r++ ! bells4 ,b & ,b' repres5t ! bells1 m & m' ! magnetos1 & ,p & ,p' repres5t swit*es4 ,spr+s pu% !m upw>d s t !y normally close ! circuit ?r\gh ! bells4 ,:5 a p]son at ,p wi%es to call ano!r at ,p' he pu%es ! swit* ,p d[n s z to br+ 8 magneto m into s]ies ) ! bells4 ,:5 n[ he turns ! crank & g5]ates ! electric curr5t1 bo? bells r+4 ,8 own bell s]ves ! purpose ( tell+ him t ! l9e is op]at+ all "r4 ,! o!r bell calls ! p>ty desir$ = conv]sation4 ,z soon z ! op]ator removes 8 f+] f ! swit* ,p ! spr+ ?r[s x upw>d aga91 leav+ 8 bell 9 circuit1 s t he may be call$ at any "t1 b cutt+ out ( ! circuit 8 magneto1 :i* w\ld introduce unnecess>y resi/ance4 ,! same wires :i* c>ri$ ! curr5t = r++ ! telephone bells c>ri$ also ! curr5t = op]at+ ! telephone receiv]4 ,:5 ! receiv] is remov$ f ! hook x releases a tw(old swit*4 ,?is s]ves ! d\ble purpose ( clos+ ! prim>y circuit ?r\gh ! local batt]y & sub/itut+ ! telephone receiv] circuit = ! bell-r++ circuit ^u ! l9e4 ,we us$ fifty *e/nut poles to c>ry our l9e betwe5 ! mill & ! cottage4 ,ea* pole _h a cross b>1 on "o end ( :i* ! electric light & p[] wires 7 c>ri$ & on ! o!r end ! telephone wires4 ,glass insulators prev5t$ ! wires f com+ 9 contact ) ! wood ( ! cross b>s4 ,! necessity = ?is 0 impress$ ^u ! boys by some?+ :i* happ5$ :ile !y 7 /r++ ! wires4 ,! telephone app>atus at ! mill _h be5 in/all$ & ! two lead+ out wires _h be5 connect$ to x4 ,"o ( ^! 0 coil$ up on ! floor1 :ile ! o!r _h be5 /rung along ^u ! poles = half a mile1 b _h n yet be5 atta*$ to ! insulators on ! poles4 ,:ile ! boys 7 lun*+ at ! mill1 "o ( !m gave ! crank ( ! magneto a turn1 :51 to ! a/oni%m5t ( all1 ! bell rang4 ,! circuit _h be5 complet$ ?r\gh ! damp wood ( ! mill1 ?r\gh ! damp wood ( "s ( ! poles1 & ?r\gh ! e>?4 ,aft] lun* ! wire1 s f> z x _h be5 /rung1 0 fa/5$ to ! insulators ^u ! poles4 ,b :5 "s "o turn$ ! crank ( ! magneto ! bell /ill rang4 ,we walk$ along ! l9e to see :]e ! difficulty 04 ,we f\nd ! end ( ! l9e ab\t half a mile f ! mill dangl+ free f ! gr\nd1 b t\*+ a tall spe> ( grass4 ,:5 ?is 0 mov$ away f ! spe> ( grass ! magneto c\ld no long] r+ ! bell4 ,! slight curr5t requir$ to r+ ?is bell--4#jbe amp]e--_h f\nd its way ?r\gh ! spe> ( grass1 ?r\gh ! woodwork ( ! mill & ?r\gh ! e>?4 ,we _h no soon] got ! two telephone wires prop]ly /rung & atta*$ to ! hundr$ glass insulators :5 a ?und] /orm came up1 & drove u back to ! mill = %elt]4 ,pretty soon ! bell rang & we1 suppos+ t "s "o at ! cottage 0 try+ to call1 w5t to ! in/rum5t1 b c\ld get no response1 nor c\ld we make ! bell r+4 ,lightn+ _h s5t an alt]nat+ curr5t ov] ! l9e :i* rang ! bell1 b ! /r5g? ( ! curr5t 0 too great = our coils ( f9e wire & "o ( !m 0 burn$ out1 z we say4 ,9 o!r words1 ! wire _h melt$ at ! po9t :]e x (f]$ ! greate/ resi/ance4 ,! burn$-out coil 0 replac$1 & !n we in/all$ lightn+ arre/]s :i* 7 ( two k9ds4 ,! fir/ 7 simply fuses :i* 7 introduc$ into ! l9e to protect x aga9/ any curr5t too l>ge = ! app>atus to c>ry1 & ! second 0 a plate1 c 7,fig4 #agb74 ,^! are to be f\nd ^u ! top ( ! magneto cases4 ,a wire is connect$ ) c1 & its o!r end is gr\nd$ by be+ connect$ ) a piece ( iron pipe :i* is driv5 deep into moi/ e>?4 ,illu/ration3 ,fig4 #agb ,! plate a b is ins]t$ 9 ! l9e1 & ! gap betwe5 ?is & ! plate c (f]s suffici5t resi/ance s t ! telephone circuit suff]s no leakage at ?is po9t1 b lightn+ has su* extremely high t5sion t x readily passes across ?is gap & f9ds its way to ! e>? )\t damag+ ! in/rum5ts4 ,we h already notic$ t our alt]nat+ curr5t dynamo1 :i* produces #fj vibrations p] second 9 ! telephone receiv]1 causes x to give a tone v ne>ly l ! ,c1 :i* is two octaves bel[ middle ,c ^u ! piano4 ,c requires #fd vibrations p] second4 ,we may spe$ up our dynamo s z to make x yield a tone exactly l ,c or ev5 above x4 ,dr4 ,cahill ( ,holyoke1 ,mass41 has devis$ an organ 9 :i* alt]nat+ curr5t dynamos produce ! necess>y numb] ( vibrations = ea* tone4 ,! "n telh>monium has be5 propos$ = ?is organ4 ,x has a sep>ate dynamo = ea* tone1 ea* dynamo hav+ a frequ5cy correspond+ to ! tone requir$ ( x4 ,! dynamo1 = in/ance1 :i* produces middle ,c makes ! electric curr5ts surge back & =? #bef times a second1 & ?is causes ! diaphragm ( a telephone receiv] to vibrate #bef times a second1 & ?is s5ds =? #bef air waves p] second1 & :5 ^! rea* our e>s we recognize ! tone we call middle ,c4 ,! frequ5cy ( alt]nation 9 a dynamo may be increas$ by ei!r increas+ its spe$ ( revolution or by increas+ ! numb] ( coils ^u its armature4 ,mr4 ,cahill's great organ looks l a l>ge ma*9e %op ) _m c\nt] %afts ge>$ s z to run at diff]5t spe$s4 ,on ea* %aft are a l>ge numb] ( little dynamos ^: armatures h v>i\s numb]s ( coils4 ,! organi/1 :o may be f> remov$ f ?is ma*9e %op1 f+]s an ord9>y keybo>d4 ,ea* key op5s & closes a swit*1 ?us br++ into action its own dynamo4 ,if ! key :i* is kn[n z ,c1 "o octave bel[ middle ,c1 is press$ d[n1 a swit* closes ! circuit betwe5 ! telephone & a dynamo :i* gives #abh d\ble alt]nations ( curr5t4 ,! tone :i* is produc$ by #abh vibrations p] second is ! "o mo/ (t5 he>d f a man's voice 9 ord9>y conv]sation4 ,ano!r key br+s into action ^u ! same telephone receiv]--& at ! same "t if desir$--a dynamo :i* gives twice z _m alt]nations p] second & produces ! tone mo/ (t5 he>d 9 female conv]sation4 ,x is middle ,c4 ,ano!r key might br+ into action a dynamo :i* gives #fd vibrations p] second to ! diaphragm ( ! telephone receiv]4 ,?is w\ld s5d =? a tone v ne>ly l ! base note ( our #fj-;cycle alt]nat+ curr5t dynamo4 ,! foll[+ table %[s a s]ies ( t5 tones :i* might be produc$ by ! same little piece ( %eet iron 9 a telephone receiv] play$ ^u by t5 dynamos at ! same "t4 ,! :ole li/ ( t5 tones w\ld s\nd well :5 produc$ simultane\sly4 ,! great my/]y is t ! iron disc c vibrate 9 su* a complex mann]4 ,x is important to note1 h[ev]1 t ! numb] ( vibrations 9 ea* ( ! upp] tones is a multiple ( t ( ! l[e/ tone3 #bnd octave above ,c--#ajbd 7 #af #fd7 ,middle ,c ,g -- #gfh 7 #ab #fd7 ,e -- #fdj 7 #aj #fd7;,a #a/ octave above ,c -- #eab 7 #h #fd7 ,middle ,c ,g -- #chd 7 #f #fd7 ,e -- #cbj 7 #e #fd7 ,middle ,c ,c -- #bef 7 #d #fd7;,b #a/ octave bel[ ,g -- #aif 7 #c #fd7 ,middle ,c ,c1 -- #abh 7 #b #fd7;,c #bnd octave bel[ ,c11-- #fd 7 #a #fd7 ,middle ,c ,c ,! tone mo/ easily reproduc$ by ! vocal cords ( a man4 ,b ,! tone mo/ easily reproduc$ by ! vocal cords ( a woman4 ,a ,! tone :i* ! telephone receiv] responds to mo/ readily4 ,! table cov]s ! range ( ! human voice1 male & female4 ,all ! int]m$iate tones1 ) _! %>ps & _! flats1 are produc$ ea* by its own sep>ate dynamo4 ,! insignificant am\nt ( curr5t requir$ to op]ate a telephone receiv] makes x possible to furni% ! music ( ^! dynamos to _m & f> di/ant telephones4 ,?is naturally sugge/s ! idea ( hav+ a great musician p]=m ^u ! keybo>d & h _m auditors scatt]$ ab\t ! city 9 _! private homes or ev5 9 _m public halls1 = ! telephone receiv] c readily be made audible to a good-siz$ audi5ce4 ,,xviii ,,electric ,,bell ,,outfit ,,= ,,! ,,cottage ,! boys ask$ me :at arrangem5t ( electric bells we ne$$ at ! cottage & s ,i gave !m ?is problem to "w out by !mselves3 #a4 ,we want a bell 9 ! kit*5 to be rung by a pu% button at ! front door4 ,b !re are times :5 no "o is 9 ! kit*5 & h5ce1 #b4 ,we want a bell up/airs to make a s+le /roke :5ev] ! kit*5 bell is rung f ! front door4 #c4 ,we want a floor pu% "u ! d9+-room table :i* w cause ! kit*5 bell to r+ a s+le /roke4 #d4 ,we want a pu% button 9 ! d9+-room :i* w cause bo? bells to clatt] & call p f _! b$s1 f ! piazza1 ! lawn1 etc41 to _! meals4 ,?is equipm5t ne$s only "o batt]y ( two dry cells1 two bells1 ?ree pu% buttons & ab\t two hundr$ feet ( wire4 ,x %\ld co/ less ?an five doll>s4 ,! boys drew _m plans & tri$ _m s*emes & at la/ det]m9$ ^u ! plan %[n 9 ,fig4 #agc4 ,p is ! floor pu% "u ! d9+-room table4 ,:5 ! circuit is clos$ at ?is po9t ! curr5t leaves ! batt]y f ! c>bon pole c1 passes up & ar\nd ! magnets ( ! kit*5 bell & back to ! z9c pole ( ! batt]y z by way ( ! pu% button ,p4 ,all o!r circuits are op54 ,illu/ration3 ,fig4 #agc ,p is ! pu% button at ! front door4 ,:5 ! circuit is clos$ at ?is po9t ! curr5t leaves ! batt]y at c1 passes up to ! "r-h& b9d+ po/ ( ! kit*5 bell & divides1 "p go+ ?r\gh ea* bell4 ,! portion ( ! curr5t :i* goes ?r\gh ! kit*5 bell passes ar\nd ! magnets & ?r\gh ! armature to ! left-h& b9d+ po/ be=e x c f9d a pa? back to ! batt]y4 ,h5ce1 ! kit*5 bell clatt]s4 ,! portion ( ! curr5t :i* passes to ! upp] bell goes ar\nd its magnets & f9ds a pa? back f ! middle b9d+ po/ to ! batt]y by way ( ,p4 ,h5ce ! bell up/airs r+s ) a s+le /roke4 ,p is a pu% button situat$ ^u ! wall by ! side ( ! door :i* leads f ! d9+-room to ! kit*54 ,:5 ! circuit is clos$ at ?is po9t1 ! curr5t leaves ! batt]y at c1 passes up to ! "r-h& b9d+ po/ ( ! kit*5 bell & divides1 "p ( x go+ ?r\gh ea* bell4 ,! portion :i* goes ?r\gh ! kit*5 bell passes ar\nd its magnets & ?r\gh its armature to ! left-h& b9d+ po/1 !n up to ! middle b9d+ po/ ( ! upp] bell1 ?r\gh its armature to its left-h& b9d+ po/ & back to ! batt]y by way ( ! pu% button ,p4 ,! o!r portion ( ! curr5t passes directly up to ! "r-h& b9d+ po/ ( ! upp] bell1 ar\nd its magnets1 & ?r\gh its armature to its left-h& b9d+ po/1 !nce back to ! batt]y by way ( ! pu% button ,p4 ,h5ce1 bo? bells clatt] & keep "t ) ea* o!r4 ,! upp] bell w r+ indep5d5tly ( ! l[] bell1 b ! l[] bell is dep5d5t ^u ! upp] "o to op5 & close its circuit1 some:at z a relay4 ,soon aft] ! cottage _h be5 equipp$ ) electric bells ,i w5t to ! mill "o day & f\nd a pu% button at ! door4 ,^u go+ 9 ,i 0 curi\s to exam9e ! electric bell outfit ( t place & f\nd :at is illu/rat$ 9 ,fig4 #agd4 ,illu/ration3 ,fig4 #agd ,a swit*1 ,s1 _h be5 atta*$ to ! bell4 ,! boys said t :5 !y felt well !y kept ! swit* ^u ! left-h& po9t & ! bell rang z a clatt] bell4 ,:5 !y felt a little sick !y put ! swit* ^u ! middle po9t & ! bell rang ) a s+le /roke1 b :5 !y felt v sick !y put ! swit* ^u ! dead po9t & ! bell did n r+ at all4 ,,xix ,,us+ ,,electricity ,,to ,,aid ,,! ,,memory ,= ! sp>k+ equipm5t ( ! motor boat we use dry cells :i* h an int]nal resi/ance ( n m ?an 4#jf ohm4 ,!y w1 :5 %ort circuit$ ?r\gh ! ammet] = only an in/ant1 give #be amp]es4 7#a4e volt7_/74#jf ohm7 #be amp]es ,:5 we all[ = a slight resi/ance 9 ! ammet] itself1 & = ! drop 9 voltage1 we see t ! int]nal resi/ance ( a cell mu/ be ev5 less ?an 4#jf ohm4 ,aft] be+ us$ ab\t two mon?s ^u ! motor boat ^! cells develop m int]nal resi/ance1 & !y w !n %[ n m ?an six to t5 amp]es :5 %ort circuit$ ?r\gh an ammet]4 ,!y are !n n reliable = ignition ( ! eng9e1 b are q z good z ev] = bell-r++1 & (t5 cont9ue s = m ?an a ye>4 ,! result is t we always h m p>tly run-d[n dry cells ?an we c use4 ,see+ !m ab\t has /imulat$ ! boys to devise ways = us+ !m4 ,! h\sekeep] is di/ract$ by c>ry+ on s _m cook+ processes at "o "t4 ,%e =gets ! eggs1 & lets !m boil five m9utes in/ead ( ?ree because ! c(fee mu/ p]colate twelve m9utes1 & %e lets ! c(fee p]colate tw5ty in/ead ( twelve m9utes because ! biscuit mu/ bake tw5ty m9utes1 & ! biscuit are =gott5 because ! pies mu/ come out 9 ?irty m9utes1 & ! cake 9 =ty m9utes4 ,all ?is worries ! cook4 ,h>old is a sympa!tic boy & ent]s into ! tr\bles ( o!rs4 ,i _h at "o "t %[n him h[ to bore a hole 9 a glass plate 9 five or t5 m9utes by us+ a r\nd file wet ) wat]4 ,"o day he pres5t$ ! kit*5 ) a clock1 int5d$ to relieve ! burd5$ memory ( ! cook4 ,?is is repres5t$ 9 ,fig4 #age4 ,illu/ration3 ,fig4 #age ,an ord9>y kit*5 clock _h a hole bor$ ?r\gh ! glass :i* cov]s its face4 ,?is glass is easily mov$ ar\nd 9 its metal rim1 br++ ! hole ov] any desir$ m9ute ^u ! face4 ,"o wire ( ! batt]y is atta*$ to a leg ( ! clock1 ! o!r goes to a bell1 & !n ! wire f ! bell is pok$ ?r\gh ?is hole4 ,:5 ! m9ute h& rea*es t po9t ! electric curr5t is clos$ ?r\gh ! metal ( ! clock1 & ! bell r+s w>n+ t ! eggs1 c(fee or :at n are done4 ,we ea* urg$ t our memories %\ld %>e 9 ! vacation1 & appli$ = "o ( ^! outfits4 ,i took "o ( ! clocks & cut back ! m9ute h& s z to make x %ort] ?an ! h\r h&1 & !n _h ! hole 9 ! glass made s t ! h\r h& %\ld close ! electric circuit4 ,?is 0 kept at my /udy table & rem9d$ me ( my appo9tm5ts4 ,"s us$ ^! clocks to al>m !mselves 9 ! morn+ :5 !y slept ov]time4 ,ano!r rem9d] is %[n 9 ,fig4 #agf4 ,c is a float :i* rises & falls ) ! wat] 9 our h\se tank4 ,a cord runn+ ov] two pulleys connects ?is ) a weight1 d1 hang+ 9 front ( a scale ^u ! wall ( ! kit*54 ,?is indicates h[ mu* wat] !re is at any "t 9 ! tank1 :i* is situat$ 9 ! g>ret4 ,! boys arrang$ a bell & batt]y s t :5 ! tank is ne>ly empty ! weight d w pull upw>d a spr+1 a1 & make x close ! circuit ?r\gh ! bell to w>n t wat] mu/ be pump$4 ,:5 ! tank is ne>ly full ! weight d pu%es d[n ! spr+ b & r+s ! bell aga94 ,illu/ration3 ,fig4 #agf ,h>old said t yea/ cakes 7 ! heavie/ tax ^u our memories4 ,if "s "o />t$ = ! village /ore1 be=e he got out ( he>+1 a call w\ld come aft] him1 ,i =got ! yea/ cake4 ,please put t on ! li/4 ,:5 "o return$ f ! village /ore ) num]\s packages1 he w\ld g5]ally he>1 ,my yea/ cake 0 =gott54 ,we tri$ all sorts ( s*emes to get rid ( ?is yea/-cake nuisance1 & f9ally adopt$ ,h>old's curl$ bread project4 ,we _h built a brick ov5 out back ( ! h\se = exp]im5tal purposes4 ,h>old propos$ t ! boys bake a mon?'s supply ( bread at a "t1 &1 :5 x 0 a day or two old1 cut x all into ?9 slices & let x dry4 ,^! slices curl$ up z !y dri$ & 7 kn[n z curl$ bread4 ,a fl\r b>rel 0 fill$ ) x ea* mon?4 ,x kept p]fectly any l5g? ( "t4 ,! family vot$ x to be bett] ?an crack]s & bett] ?an fre% bread/uff ( any k9d4 ,h>old's sugge/ion reg>d+ yea/ cakes work$ s well & 0 su* a relief to our memories t ,i propos$ he next attack ! problem ( ! (t5 =gott5 salt 9 cook+4 ,,xx ,,! ,,electric ,,brick ,,ov5 ,we _h no end ( exp]im5ts ) brick ov5s4 ,"o ( ! mo/ int]e/+ 0 t :]e9 we us$ ! brick fireplace z an ov5 & did ! family bak+ 9 x4 ,on a cold morn+ we w\ld build up a sm>t wood fire 9 ! fireplace & enjoy x dur+ breakfa/ "t4 ,!n we %ovell$ out ! coals & ! a%es1 & %ut x up tight ) a %eet iron arrangem5t & utiliz$ ! heat /or$ 9 ! bricks = do+ all sorts ( cook+4 ,our outdoor brick ov5 & our mon?ly bak+ day 7 su* a success t !y l$ to ! con/ruction ( ano!r ov5 ( small] dim5sions = ! kit*54 ,?is "o 0 heat$ by electric lamps--"o 9 ea* ( ! eight corn]s4 ,x _h d\ble glass doors 9 front s t ! cook+ process might be wat*$4 ,! glass ( ! inn] door w\ld be cl\d$ ) moi/ure = a :ile1 :5 ! cook+ fir/ began1 b ?is w\ld soon cle> up1 & !n ! lamps enabl$ u to wat* ! col\r *anges 9 bak+1 etc4 ,! lamps 9 ! upp] "p ( ! ov5 7 connect$ ) a diff]5t swit* f ^? 9 ! l[] "p ( ! ov51 s t we 7 able to control ! br[n+ on top or bottom at pleasure4 ,h>old introduc$ a device = automatically controll+ ! temp]ature ( ?is ov54 ,illu/ration3 ,fig4 #agg ,/rips ( brass & iron1 ,b & ,i 7,fig4 #agg71 7 rivet$ toge!r4 ,^! 7 fa/5$ 9 ! socket ,a4 ,!y are %[n edgewise 9 ! diagram4 ,! upp] end ( ?is comp\nd /rip is free to b5d back & =? 9 ! plane ( ! pap]1 z "h repres5t$4 ,!y normally t\* ! screw ,c4 ,"o ( ! electric light wires runs f ! lamps 9 ! ov5 to ?is screw ,c4 ,"o wire ( ! dynamo circuit ,g goes to ! lamps1 & ! o!r connects ) ,a4 ,?us ! comp\nd /rip acts z a swit* to op5 & close ! circuit ^u ! lamps4 ,?is !rmo/at1 z x is call$1 0 plac$ inside ( ! ov54 ,heat causes brass to exp& m ?an iron & !re=e :5 ! temp]ature rea*es a c]ta9 height ! !rmo/at curves1 s z to break ! contact ) ,c1 & ! lamps g out4 ,:5 ! temp]ature falls a little ! !rmo/at /raight5s until contact is aga9 made ) ,c4 ,c is a screw & c be made to advance or rec$e 9 its socket ,e1 s t ! temp]ature ( ! ov5 may be ma9ta9$ at any po9t desir$4 ,! wire ( ! screw ,c ext5ds to ! outside ( ! ov51 :]e x c>ries an index1 ,d1 ov] ! face ( a dial1 z %[n 9 ,fig4 #agh4 ,illu/ration3 ,fig4 #agh ,! cook may set ?is index at any desir$ degree1 & ! lamps w indicate :5 t degree has be5 rea*$4 ,! ?+ to be bak$ is !n put inside & ! clock1 illu/rat$ 9 ,fig4 #age1 is set s z to w>n :5 ! "t is up4 ,! electric sp>k :i* occurs :5 ! !rmo/at breaks contact ) ,c causes ! metals to corrode at t po9t1 & corrod$ metals are poor conductors4 ,?is corrosion is due to ! oxyg5 ( ! air4 ,!re is "o metal--! exp5sive plat9um--:i* is n corrod$ by ! electric sp>k4 ,we drill$ small holes 9 ! end ( ! screw ,c & 9 ! brass /rip & p\nd$ into ^! holes little pieces ( plat9um wire4 ,h>old said he felt l a d5ti/ fill+ a too?4 ,?is furni%$ good1 clean contact at all times4 ,x takes a long "t to heat up ! brick ov51 b x holds its heat a long "t & makes an excell5t fireless cook] aft] ! lamps are turn$ out4 ,x does n all[ heat to escape into ! kit*51 :i* makes x a com=t 9 our summ] cottage4 ,we are all becom+ daft on sl[ly cook$ food--a sort ( rip5+ process :i* gives "t = ! *emical *anges to take place & develops ! f9e/ flav\rs ( ! food4 ,,xxi ,,electric ,,waves ,mu* has be5 said ab\t br++ "y p up to d :at !y don't l to d s z to make !m /rong & virtu\s4 ,my own life has always be5 guid$ by a diff]5t pr9ciple4 ,x is3 ,f9d some?+ wor? :ile :i* y w enjoy do+1 & d x ) y\r might4 ,i am br++ up my boy on ! same pr9ciple4 ,9 ,septemb] we h a real desire to get back to our "w 9 ! city1 & 9 ,june we h an eag] long+ = ! occupations ( ,millville4 ,i am n aw>e t !re is any "p ( my "w :i* ,i w\ld l to be reliev$ f1 & ,h>old & 8 "m said t !y 7 n[ ready to return to ! city ap>tm5t ) real pleasure = a w9t]4 ,"o ev5+ we 7 seat$ ab\t ! d9n] table :5 ,h>old ask$ me h[ electricity c\ld travel )\t wires4 ,i repli$1 ,x travels z light does4 ,b ,i am v mu* puzzl$ to "k :y x ev] foll[s a wire :5 light does n4 ,?is did n settle ! "q & left u bo? unsatisfi$1 s ,i told him to invite two or ?ree ( 8 be/ fri5ds 9 to-morr[ ev5+1 & ,i w\ld p]=m "s exp]im5ts = !m t w\ld at lea/ help !m to ?9k fur!r ^u ?is subject4 ,:5 ! ev5+ came ,i %[$ ! boys an automobile sp>k coil to :i* ,i _h atta*$ two knobs1 a & b 7,fig4 #agi71 & ) :i* ,i _h connect$ two dry batt]y cells4 ,:5 ,i t\* ! wire c to ! b9d+ po/ d a sp>k passes betwe5 ! knobs a & b4 ,:5 ?is sp>k occurs at lea/ f\r k9ds ( waves pass out 9 all directions f ! sp>k gap betwe5 ! knobs4 ,illu/ration3 ,fig4 #agi ,fir/1 s\nd waves g ?r\gh ! air4 ,our e>s detect ^!4 ,if ! air is remov$ f ar\nd ! app>atus no s\nd wave c g =?4 ,a c>eful exam9ation ( ! int]nal e> %[s u t x is con/ruct$ s z to respond to su* air waves4 ,second1 light waves g =?4 ,^! affect our eyes4 ,we are bl9d to ! fir/ k9d ( waves & deaf to ! second4 ,! light waves travel )\t air--some:at bett] )\t air ?an ) air4 ,a microscopic exam9ation ( ! eye indicates t x is con/ruct$ s z to respond to waves4 ,we believe !re are waves 9 ! e!r :i* fills all space4 ,s\nd waves travel 9 air at ! rate ( "o mile 9 five seconds4 ,we _h ?is nicely illu/rat$ at ! sea %ore "o summ]4 ,! /eam] t\*$ ea* morn+ at a :>f :i* we c\ld pla9ly see two miles di/ant4 ,we c\ld see ! /eam arise :5 %e blew ! w>n+ :i/le1 & ) our wat*es we f\nd t x always requir$ t5 seconds = ! s\nd to rea* u aft] we saw ! /eam ( ! :i/le4 ,?is at lea/ %[$ u t x takes five seconds long] = s\nd waves to travel a mile ?an x does = light waves to travel ! same di/ance4 ,= light _h to travel ! same di/ance be=e we c\ld see ! /eam arise f ! :i/le4 ,al?\gh ! "t x takes = light to travel a mile is inconceivably small1 we h a simple me?od ( f9d+ out t x requires eight m9utes = light waves to come to u f ! sun4 ,! satellites ( ! planet ,jupit]1 9 revolv+ ab\t t body1 disappe> & reappe> at regul> int]vals1 act+ z fla% lights to m>k "t4 ,illu/ration3 ,fig4 #ahj ,! e>?1 be+ #ib1jjj1jjj miles di/ant f ! sun1 is #ahd1jjj1jjj miles f>!r f ,jupit] :5 at ,b ?an x is :5 at ,a4 7,see ,fig4 #ahj47 ,x is f\nd by obs]vation t sixte5 m9utes m are requir$ = ! light waves f a reappe>+ satellite to rea* u at ,b ?an :5 we are at ,a4 ,h5ce eight m9utes w\ld be requir$ = light waves to travel ! di/ance f ! sun to ! e>?4 ,al?\gh light travels at ! inconceivable velocity ( #ahf1jjj miles p] second1 ! ne>e/ /> is s f> di/ant t x takes light ?ree & a half ye>s to come f x to u4 ,! ,nor? /> requires =ty-two ye>s to s5d its light to u1 & ,arcturus is s f> away t waves ( light s5t out f x "o hundr$ & sixty ye>s ago are only j rea*+ u n[1 & if x %\ld cease to s5d =? light n[ m5 w\ld cont9ue to see x = five g5]ations yet to come4 ,a ?ird k9d ( wave :i* goes =? 9 ! e!r f ! sp>k gap ( our coil is a heat wave4 ,?is affects nei!r our eyes nor our e>s1 b ,i w und]take to make y consci\s ( x by ano!r me?od4 ,illu/ration3 ,fig4 #aha ,be=e a mixture ( gasol5e vap\r & air c be ignit$ its temp]ature mu/ be rais$ to ab\t #bjjj degrees ,fahr5heit4 ,i w %[ t heat waves pass out f ?is sp>k gap by plac+ my wat* cry/al fill$ ) gasol5e und]nea? ! knobs ( ! sp>k coil1 7,fig4 #aha74 ,:5 n[ ,i close ! electric circuit at ! batt]y ! mixture ( gasol5e vap\r & air j above ! wat* cry/al is ignit$4 ,if ,i increase ! di/ance betwe5 ! knobs y /ill he> ! crackle ( ! s\nd waves & see ! light waves1 b ! mixture ( gasol5e vap\r & air does n ignite1 because !re are n heat waves en\gh4 ,! automobili/ expresses ?is fact by say+ a fat sp>k or a w>m sp>k is ne$$4 ,a batt]y :i* has ceas$ to give a suffici5tly hot sp>k to explode ! mixture ( gasol5e & air 9 ! cyl9d] ( a gasol5e eng9e may s]ve all o!r purposes q z well z ev]4 ,x may r+ bells almo/ z long z x ev] w\ld4 ,i prov$ t ! temp]ature = ignit+ a mixture ( gasol5e vap\r & air 0 ne>ly z high z melt+ iron1 by heat+ an iron rod to a dull r$ heat & br++ x to ! wat* cry/al conta9+ gasol5e4 ,x did n take fire4 ,i %[$ t x c\ld n be ignit$ by a light$ cig>1 nor ev5 by a gl[+ coal tak5 f ! fire4 ,x 0 necess>y to heat ! iron rod to a v bright r$ heat--ne>ly :ite heat1 or ne>ly to its melt+ po9t1 be=e x w\ld ignite ! mixture4 ,^! heat waves are e!r waves1 diff]+ f light only 9 hav+ great] wave l5g?4 ,!y travel at ! spe$ ( light1 !y travel bett] )\t air ?an ) air4 ,!y come f ! sun & all o!r light-giv+ bodies4 ,inde$1 an ord9>y inc&esc5t electric lamp gives out ab\t tw5ty-f\r times z mu* en]gy 9 heat z 9 light4 ,heat waves are be+ ?r[n (f f all bodies :i* are ar\nd u4 ,! /eam radiators are plac$ 9 ?is room = ! express purpose ( s5d+ out heat waves ?r\gh ! e!r 9 ?is room4 ,?is is ! *ief me?od ( di/ribut+ heat1 & x is h9d]$ r ?an help$ by ! pres5ce ( ! air4 ,! walls1 ceil+1 floor1 furniture1 p--ev]y?+ "h is s5d+ out heat waves4 ,! f\r? k9ds ( waves1 :i* g out f ! sp>k gap ( our coil1 are also waves 9 ! e!r4 ,!y are /ill long] ?an heat or light4 ,we h e>s = s\nd1 eyes = light1 & temp]ature s5sation = heat1 b z yet we h n evolv$ a delicate s5se organ = detect+ electric waves4 ,at lea/ few ( u claim to h su* a s5se4 ,i w1 h[ev]1 und]take to make y feel electricity4 ,i !n adju/$ ! coil s t ea* boy might take a mild electric %ock f x by t\*+ ! two knobs4 ,t is by plac+ himself 9 ! sp>k gap4 ,!y agre$ t al?\gh !y c\ld n he>1 see1 ta/e1 or smell electricity !y 7 a little m famili> ) x n[1 hav+ felt x4 ,s\nd waves 9 air1 z giv5 out by ! piano1 v>y 9 l5g? f1 say1 f\r in*es to =ty feet1 ^? hav+ ! %ort] wave l5g? be+ ! high] pit*$ tones4 ,light waves 9 ! e!r1 z giv5 out by ! sun1 v>y 9 l5g? f1 say1 #a_/fjjjj to #a_/hjjjj ( an in*1 ^? hav+ ! %ort] wave l5g? be+ ! violet-col\r$ light1 :i* may be se5 9 ! ra9b[1 & ^? hav+ ! long] wave l5g? be+ ! r$-col\r$ light ( ! ra9b[ or ! sunset4 ,heat waves1 :i* are also waves 9 ! e!r1 v>y 9 l5g? f above #a_/hjjjj to1 say1 #a_/ejjj ( an in*4 ,ro5tg5 or ,x waves are e!r waves1 %ort] ?an light2 :ile ,h]tzian1 or wireless telegraph waves are v long e!r waves1 v>y+ f a few feet to _m rods 9 l5g?4 ,^? us$ by ,m>coni 9 s5d+ despat*es across ! ,atlantic ,ocean are z long z #ajjj feet1 f\r or five ( !m cov] a mile1 & #ab1jjj ( !m cov] ! :ole di/ance f ,cape ,cod to ,poldhu4 ,electric waves are easily brok5 up into ! %ort] heat waves1 or ! /ill %ort] light waves4 ,on ! o!r h& ,ro5tg5 waves are readily trans=m$ into ! long] light waves1 & are ?us br\ght )9 our p[]s ( vision4 ,s\nd waves ( v>i\s l5g?s 7( high & l[ pit*7 all travel at ! same spe$ 7"o mile 9 five seconds71 else h[ w\ld ! piccolo & ! bass horn ( ! di/ant b& s\nd toge!r4 ,s e!r waves ( v>i\s l5g?s 7light1 heat1 electricity1 etc47 all travel at ! same spe$1 i4 e41 #ahf1jjj miles p] second4 ,= detect+ ! electric waves :i* may be s5t out f ! sp>k gap ( our automobile sp>k coil ,i %all ask y to help me prep>e a special piece ( app>atus4 ,"o boy may file ?is silv] t5-c5t piece & ano!r may file ?is nickel five-c5t piece1 ea* ga!r+ ! fil+s ^u a piece ( pap]4 ,a ?ird boy may select a piece ( glass tub+ ab\t "o eigh? ( an in* 9 ! inside diamet]1 & ) a ?ree-corn]$ file cut (f a %ort piece1 ab\t "o & a half in*es long1 & smoo? ! ends ) a wet file4 ,a f\r? boy may select a piece ( /\t copp] wire ne>ly z l>ge z ! bore ( ! glass tub+1 & cut f x two pieces1 ea* ab\t two in*es long4 ,w9d "o end ( ea* ( ^! ) ?read to make !m fit snugly 9 ! glass tub+4 ,illu/ration3 ,fig4 #ahb ,coh]] ,we ?ru/ "o ( ! wires into ! tube1 !n mix$ equal p>ts ( ! silv] & nickel fil+s & put z mu* ( ! mixture into ! tube z we c\ld hold ^u ! tip ( a p5knife blade1 & !n ?ru/ 9 ! o!r copp] wire4 7,see ,fig4 #ahb47 ,! ends ( ! wire 7 ab\t "o eigh? ( an in* ap>t & ! gap 0 loosely fill$ ) ! metal fil+s4 ,?is 0 connect$ by %ort pieces ( copp] wire1 z %[n 9 ,fig4 #ahc1 to a dry batt]y cell1 ,b1 & a s5sitive ammet]4 ,:5 all connections 7 made ! ne$le ( ! ammet] rema9$ at z]o1 %[+ t no electric curr5t 0 pass+1 t is1 ! batt]y cell 0 unable to s5d any electricity ?r\gh ! metal fil+s4 ,?is is ! app>atus :i* is to help u detect electric waves :5 !y pass ab\t u4 ,electricity has be5 call$ invisible light1 t is1 invisible to our eyes1 & ?is app>atus has be5 call$ an electric eye because x w detect electric waves 9 ! e!r1 j z our eyes may detect light waves pass+ ?r\gh ! e!r4 ,illu/ration3 ,fig4 #ahc ,we plac$ ! automobile sp>k coil ^u ! table ne> to ! tube conta9+ ! fil+s ( silv] & nickel1 & z soon z we made a sp>k pass betwe5 ! knobs ! ammet] ne$le mov$ half way across ! scale1 indicat+ t ! sp>k _h someh[ influ5c$ ! metal fil+s 9 ! tube s t n[ !y p]mitt$ ! batt]y cell to s5d "s electric curr5t ?r\gh !m & ?r\gh ! ammet]4 ,i ask$ "o ( ! boys to tap ! tube slightly ) a lead p5cil s z to j> ! metal fil+s1 & z soon z he did s ! ne$le ( ! ammet] w5t back to z]o4 ,illu/ration3 ,fig4 #ahd ,! sp>k coil s5t electric waves out 9 e direction1 & ^? :i* hit ! metal fil+s made !m coh]e toge!r4 ,9 t condition !y all[$ ! dry cell to s5d ?r\gh !m en\gh curr5t to move ! ne$le ( ! ammet]4 ,tapp+ ! tube made ! metal fil+s break ap>t aga91 9 :i* condition !y d n all[ ! curr5t ( ! cell to pass 9 suffici5t quantity to move ! ne$le4 ,?is tube is call$ a coh]]1 because ! fil+s 9 x coh]e toge!r4 ,! app>atus !n s]ves to indicate :5 electric waves are pass+4 ,z yet1 h[ev]1 x w\ld n respond :5 ! sp>k coil 0 m ?an "o foot away4 ,our next /ep 0 to atta* extra pieces ( wire1 ea* t5 or twelve feet long1 at ei!r end ( ! coh]]1 z indicat$ 9 ,fig4 #ahd4 ,"o ( ^! wires 0 /ret*$ out ^u ! floor :ile ! o!r "o 0 connect$ ) ! wire ( a picture hang+ ^u ! wall4 ,we n[ f\nd t ! coh]] w\ld respond :5 ! sp>k coil 0 op]at$ sev]al feet away4 ,! extra wires :i* we _h atta*$ to ! coh]] are call$ ant5n1 because !y sugge/ ! long feel]s or ant5n ( "s insects4 ,illu/ration3 ,fig4 #ahe ,our next /ep 0 to put ant5n ^u ! sp>k coil also1 z %[n 9 ,fig4 #ahe4 ,"o ( ^! wires 0 /ret*$ out ^u ! floor1 :ile ! o!r "o 0 connect$ ) ! wire ( a picture hang+ ^u ! wall on ! opposite side ( ! room f :]e ! coh]] 04 ,we n[ f\nd t ! coh]] w\ld respond :5 ! sp>k coil 0 op]at$ 9 ! f>!/ "p ( ! room4 ,) ! wires :i* 7 ly+ ^u ! floor ext5d+ t[>d ea* o!r1 b lack+ sev]al feet ( t\*+1 ! coh]] respond$ :5 ! sp>k coil 0 op]at$ 9 v>i\s o!r rooms ( ! h\se1 al?\gh ! doors betwe5 7 %ut4 ,:5 ! floor wires 7 connect$ to ! wat] pipes ! coh]] w\ld respond :5 ! sp>k coil 0 op]at$ 9 a neighb\r+ h\se4 ,we tri$ a simil> exp]im5t1 sub/itut+ an ord9>y electric bell = ! sp>k coil4 ,! coh]] or electric eye detect$ t e!r waves 7 s5t =? f an electric bell e "t a sp>k 0 produc$ 9 ! bell4 ,= ?is purpose connections 7 made1 z %[n 9 ,fig4 #ahf4 ,"o dry batt]y cell 0 us$ to r+ ! bell4 ,! floor wire a1 or1 z x is usually call$1 ! gr\nd wire1 0 connect$ to ! b9d+ po/ #a1 & ! o!r ant5na 0 connect$ to ! screw #c1 & !n support$ al(t on a picture hung ^u ! wall4 ,) ?is transmitt] we s5t waves across ! room :i* 7 detect$ by ! coh]]4 ,illu/ration3 ,fig4 #ahf ,we con/ruct$ a simple sp>k coil z foll[s3 ,we b\ght a p\nd ( ,no4 #bd s+le cotton cov]$ copp] wire1 su* z is us$ 9 ! electro-magnets ( bells4 ,x 01 :5 we b\ght x1 w\nd ^u a wood5 spool4 ,we fill$ ! hole 9 ! c5tre ( ?is spool ) wire nails4 ,"o dry cell 0 connect$ ) ?is 7,fig4 #ahg74 ,:5 ! wires at d 7 t\*$ toge!r1 & !n sep>at$1 a sp>k 0 produc$ at t po9t4 ,a gr\nd wire 0 connect$ at b1 & an ant5na at c1 z be=e4 ,us+ ?is app>atus n[ z a transmitt] ( e!r waves1 we f\nd t ! coh]] detect$ !m4 ,illu/ration3 ,fig4 #ahg ,we next gave our att5tion to mak+ *anges 9 ! receiv+ app>atus1 n to *ange ! coh]]1 b to provide sub/itutes = ! ammet]4 ,a s5sitive relay 0 procur$1 :i* is ess5tially l a bell or buzz] except t x does n clatt]4 ,x w be readily und]/ood1 by ref]r+ to ! accompany+ ,fig4 #ahh1 t ,r is a coil ( insulat$ wire ar\nd an iron core exactly l :at we see 9 ! electric bell4 7,9 practice !re w be a pair in/ead ( "o ( !m47 ,su* coils are call$ electro-magnets1 because :5 electricity fl[s 9 ! wires !y become magnets1 & w attract iron4 ,a is an iron spr+1 ,b is a dry batt]y cell & ,c is ! coh]]4 ,:5ev] an e!r wave passes ! coh]] p]mits ! batt]y cell to s5d a curr5t ar\nd ! magnet ( ! relay1 & x attracts ! iron spr+ a1 s t x hits aga9/ ! metal po/ d ) a click4 ,:5ev] we us$ ?is to respond to e!r waves ! click ( ! relay sugge/$ ! telegraph s\nd]4 ,h[ x s]v$ 9 wireless telegraphy w appe> 9 ! foll[+ pages4 ,illu/ration3 ,fig4 #ahh ,,xxii ,,r++ ,,bells ,,& ,,light+ ,,lamps ,,by ,,electric ,,waves ,illu/ration3 ,fig4 #ahi ,h>old 0 to h a bir?day p>ty1 to :i* _m ( 8 s*ool fri5ds 7 invit$4 ,= ?is occasion he prep>$1 ) my help1 to p]=m = ! girls & boys "s electrical exp]im5ts1 & p>ticul>ly to give all :o *ose to try x an electric %ock4 ,= ?is purpose he _h !m all jo9 h&s1 & ! electric *>ge 0 s5t ?r\gh ! :ole l9e at once4 ,"o ?+ he did %ock$ 8 "m m ?an any?+ else4 ,he in/itut$ a mock c\rt1 at :i* "o ( ! boys 0 tri$1 convict$ & condemn$ to be execut$ by electricity4 ,! :ole affair 0 enact$ ) no great solemnity1 b ! electrical exp]im5t 0 vot$ a great success by ! execut$ crim9al4 ,! foll[+ gr\p ( exp]im5ts1 h[ev]1 seem$ to give ! mo/ satisfaction3 ,on a table 0 plac$ ! coh]] connect$ to ! relay1 & 9 ano!r room 0 plac$ ! sp>k coil = s5d+ e!r waves4 ,he _h ?is op]at$ by a conf$]ate :om he *ose = ! purpose4 ,he !n connect$ two wires to ! relay1 "o at d & ! o!r at e 7,fig4 #ahi74 ,^! ran to a batt]y cell & a bell 9 a f> corn] ( ! room4 ,at a giv5 signal 7a c\gh7 ! conf$]ate made a sp>k at ! sp>k coil 9 ! o!r room2 ?is s5t e!r waves ?r\gh ! p>tition betwe5 ! rooms2 ! e!r waves caus$ ! coh]] to pass electricity f ! dry cell ,no4 #a1 to close ! relay spr+ ,r4 ,?is act$ l a swit* to close ! second circuit ?r\gh ! dry cell ,no4 #b & ! bell1 :i* rang out to ! surprise ( all4 ,x cont9u$ to r+ until he tapp$ ! coh]] tube & broke ap>t ! fil+s4 ,:5 ?is _h be5 tri$ to ! satisfaction ( all1 ! company 0 invit$ to ano!r room4 ,"h !y f\nd an electric tra9 ) tracks1 tra9 %$s1 /ations1 tunnels1 bridges1 swit*es1 signals1 etc41 arrang$ ^u a c5tre table4 ,! electric tra9 0 to be />t$ by e!r waves4 ,a wire f ! railroad track 0 connect$ ) e ( ! relay 7,see ,fig4 #aij74 ,a wire f d ( ! relay 0 connect$ to ! ?ird rail ?r\gh a batt]y ( suffici5t /r5g? 7,batt]y #b74 ,! electric tra9 complet$ ! circuit by connect+ ! tracks ) ! ?ird rail4 ,all he>d ! crack ( ! sp>k coil 9 ! adjo9+ room1 & saw ! tra9 />t imm$iately4 ,e!r waves _h caus$ batt]y #a to close ! relay ,r4 ,?is _h clos$ ! circuit s t batt]y #b might run ! tra91 ( c\rse by means ( a motor 9 ! tra94 ,he tapp$ ! coh]]4 ,! relay spr+ ,r flew op5 & ! tra9 /opp$4 ,pres5tly ano!r crack f ! adjo9+ room1 & ! tra9 in/antly />t$ aga94 ,:5 all ! details ( ! electric tra9 _h be5 exam9$ ! company 0 invit$ to g to ! d9+ room1 :i* 0 dimly light$ by c&les4 ,all 7 seat$ & busily conv]s+ :5 ! crackl+ noise ( ! sp>k coil 0 aga9 he>d1 & a gr\p ( little electric lights fla%$ =? ^u a bir?day cake4 ,! wires f ! lamps & a batt]y to run !m _h be5 connect$ ) ! b9d+ po/s d & e ( ! relay4 ,illu/ration3 ,fig4 #aij ,! *&eli] ov] ! d9+-room table _h a p5dant pu% button ,a 7,fig4 #aia71 ) :i* ! regul> electric lights c\ld be turn$ on & (f4 ,?is ,i _h remov$ & ext5d$ ! wires d[n ^u ! table4 ,x 0 only necess>y to connect ^! to ! b9d+ po/s d & e ( ! relay1 & ! next wave f ! sp>k coil light$ ! *&eli]4 ,illu/ration3 ,fig4 #aia ,! flexible wires und]nea? ! d9+-room table ) :i* ! maid is usually summon$ f ! kit*5 7 next ext5d$ up & connect$ ) d & e ( ! relay1 & ! maid 0 call$ 9 by an e!r wave4 ,%e br\ght ) h] a tray 9 ! c5tre ( :i* /ood an e>!nw>e cup1 su* z is us$ = bak+ cu/>d4 ,?is _h be5 fill$ ) a mixture ( granulat$ sug> & p[d]$ potassium *lorate4 ,f\r dry batt]y cells /ood ar\nd ?is ^u ! tray connect$ 9 s]ies 7,fig4 #aib74 ,a v small iron wire connect+ two ( ^! cells dipp$ into ! sug> mixture4 ,two wires f ! batt]y 7 connect$ to d & e ( ! relay4 ,at ! prop] signal an e!r wave 0 s5t out by ! sp>k coil4 ,! coh]] clos$ ! relay & ! relay act$ z a pu% button to close ! circuit ( ! f\r cells ^u ! tray4 ,! f9e wire dipp+ into ! sug> & potassium *lorate got r$ hot4 ,?is caus$ ! mixture to fla% up & burn 9 mo/ beautiful col\r$ flames4 7,fig4 #aic74 ,illu/ration3 ,fig4 #aib ,illu/ration3 ,fig4 #aic ,on ?is occasion ,h>old's fri5ds gave him1 ) due =malities1 ! degree ( ,e4 ,e41 :i* !y said meant electrical exp]t1 & ev] s9ce t night he has be5 call$ ! exp]t4 ,i inquir$ ( ! "y folks1 z _! p>ty 0 break+ up1 if !y und]/ood ,h>old's explanations ( all ^! ?+s1 & he repli$ t he at any rate und]/ood !m bett] hav+ attempt$ to expla9 !m4 ,,xxiii ,,telegraph+ ,,by ,,electric ,,waves ,! next "t ,h>old & ,i exp]im5t$ we arrang$ some?+ to save u ! tr\ble ( tapp+ ! coh]] ea* "t we us$ x4 ,we employ$ simply an electric bell1 ,b 7,fig4 #aid71 f :i* we remov$ ! gong4 ,by ref]5ce to ! figure ! arrangem5t w be und]/ood4 ,ea* "t e!r waves cause ! metal fil+s to coh]e & ! batt]y ,b#a closes ! relay ,r1 batt]y ,b#b causes ! hamm] ( ,b#c to tap aga9/ ! coh]]4 ,?is causes ! curr5t to cease to fl[ f ,b#a & ! relay op5s aga9 by its own spr+4 ,illu/ration3 ,fig4 #aid ,illu/ration3 ,fig4 #aie ,our next addition 0 a telegraph s\nd] z %[n 9 ,fig4 #aie4 ,b#a is a s+le dry cell1 ,c is ! coh]]1 ,r is ! relay1 ,b#b is n[ a batt]y ( ?ree cells4 ,"p ( its curr5t goes to ,b#c1 ! tapp] = ! coh]]1 & "p ( its curr5t goes to ! electro-magnet ( ! telegraph s\nd] ,s4 ,ord9>ily a spr+ holds ! iron /rip d up aga9/ ! metal /op a1 b :5 ! curr5t passes ?r\gh ! electro-magnet x pulls d[n ?is iron /rip ) a click aga9/ ! metal /op e4 ,b :ile ?is is happ5+ ,c is be+ tapp$ by ,b1 & is ready to respond to ea* wave4 ,x 0 only necess>y n[ to h "s code ( signals 9 ord] to communicate by telegrams4 ,we le>n$ ! sy/em ( dots & da%es1 or %ort & long p]iods m>k$ (f by ! s\nd]1 :i* all telegraph]s use & :i* is kn[n z ! ,morse alphabet1 & v soon ,h>old & ,i 7 telegraph+ f "o room to ano!r messages ( sev]al s5t5ces at a "t1 ! ,morse alphabet be+ told (f on ! sp>k coil & be+ receiv$ ?r\gh ! coh]] & telegraph s\nd]4 ,x 0 n long be=e ,h>old & "o ( ! neighb\rs' boys 7 ex*ang+ messages betwe5 _! homes1 ea* hav+ a sp>k coil & ! necess>y receiv+ app>atus1 & hav+ ext5d$ _! ant5n to ! top ( ! build+s into :at are call$ 9 ! wireless language a]ials4 ,illu/ration3 ,photograph by ,hel5 ,w4 ,cooke4 ,induction ,coil ( a ,wireless ,! fev] = wireless telegraphy spread l wild-fire among ! boys4 ,9 a few mon?s !y _h =m$ a wireless club4 ,!y _h ea* read any:]e f t5 to ?irty books & articles ^u ! subject1 & _h secur$ ! late/ improv$ app>atus4 ,!y made x a practice to sp5d h\rs daily at _! in/rum5ts pick+ up & keep+ on file messages :i* 7 s5t to & f /eam]s leav+ ! h>b\r = ,european ports4 ,on "o occasion !y %[$ me f ^! files scores ( messages--fond1 p]sonal1 & suppos$ly private f>ewells to fri5ds & communications betwe5 bus9ess p>tn]s :i* !y w\ld nev] h made on l& )\t fir/ clos+ ! (fice door4 ,! boys _h acquir$ a mass ( te*nical k ^u ! subject :i* f> exce$$ my compreh5sion4 ,b _! tea*]s 9 s*ool compla9$ t !y w\ld le>n no?+ else1 & "s ( ! boys _h already receiv$ w>n+ t !y might fail ( promotion4 ,h[ to h compell+ int]e/s )\t rid+ hobbies is ! great problem = bo? boys & m54 ,i h kn[n _m boys :o c\ld1 or at lea/ w\ld1 d no?+ well 9 s*ool or out1 except "s specialty l manual tra9+ or sci5ce4 ,9 lat] ye>s !y 7 s defici5t 9 education t !y c\ld hold no wor?y position 9 any?+4 ,my anxiety 0 to save my boy f su* a fate4 ,i 0 det]m9$ t he %\ld h a fair %>e ( all k9ds ( culture4 ,to ?is end we read toge!r mu* ( biography1 hi/ory & classical lit]ature1 anci5t & mod]n1 ?r\gh ! m$ium ( ! ,engli% language4 ,z bo? prev5tion & cure ( ! wireless telegraph mania ,i deem$ x n necess>y to suppress en?usiasm1 nor to introduce obvi\sly useless tasks = ! sake ( ! tra9+ :i* might be 9 !m4 ,my me?od 01 on ! contr>y1 to enc\rage my boy to h sev]al hobbies :i* he might ride ) en?usiasm1 b to make x a rigor\s rule to ex*ange 8 m\nt occasionally4 ,,xxiv ,,halley',s ,,comet ,,& ,,electrical ,,waves ,illu/ration3 ,fig4 #aif ,x 0 ! ye> #aiaj & ,halley's comet 0 approa*+ ! sun4 ,on ,may #ah its tail might be expect$ to rea* ! e>?4 ,a/ronom]s _h reque/$ all :o might be possess$ ( wireless telegraph app>atus to wat* on t day = any peculi> behavi\r ( _! app>atus s t evid5ce might be obta9$ :e!r or n ! comet s5ds =? su* e!r waves z we call electricity4 ,h>old desir$ me to expla9 ! :ole matt] to 8 gr\p ( fri5ds1 :i* ,i did on a subsequ5t ev5+1 z foll[s3 ,al?\gh ,halley's comet has come )9 ! e>?'s orbit ab\t ?ree ?\s& times s9ce its fir/ record$ appe>ance1 ,i "k ( no man liv+ :o c give a satisfactory acc\nt ( hav+ se5 x4 ,any "o :o has se5 x be=e mu/ be at lea/ sev5ty-five ye>s old1 = x requires sev5ty-five ye>s to make "o complete circuit ( its own orbit4 ,b no "o :o is n[ sev5ty-five c\ld h obs]v$ x intellig5tly1 & ev5 "o :o is n[ eighty-five ye>s old w\ld h to tell :at he saw :5 he 0 t5 ye>s old & has rememb]$ = sev5ty-five ye>s4 ,fur!rmore1 any acc\nt ( h[ x look$ on a =m] return is no guide to h[ x may appe> on ?is trip4 ,y may prop]ly ?9k ( ! comet z a gr\p ( solid pieces no bigg] ?an ! /ones y may ?r[1 scatt]$1 two or ?ree to ! mile1 ?r\gh a space #ab1ejj miles broad4 ,?is extremely ?9 cl\d ( p>ticles does n reflect en\gh sunlight to be visible1 ev5 9 a telescope1 9 any "p ( its j\rney1 & h5ce we %\ld be :olly unaw>e ( its exi/5ce if x did n sometimes h ! /range faculty ( giv+ out light ( its own :ile 9 t "p ( its own orbit ne>e/ to ! sun4 ,at su* a "t !re is a hazy light envelop+ ! mass ( small bodies1 & /ream+ away sometimes _m million miles f !m4 ,! mass ( small bodies is g5]ally ref]r$ to z ! nucleus1 & ! /ream ( lum9\s gas :i* ! nucleus gives =? is call$ ! tail1 ?\gh x rem9ds me m ( a se>*-light4 ,x does n trail along beh9d ! comet b always po9ts away f ! sun 7,fig4 #aig74 ,! normal ?+ = a comet to d is to beg9 to develop a fa9t light & a %ort /ream] z x gets ne> to ! sun1 to h its light gr[ bright] & its /ream] to gr[ long] until x rea*es ! po9t ne>e/ ! sun1 & !n to h its light gr[ dimm] & ! /ream] gr[ %ort] z x rec$es f ! sun4 ,illu/ration3 ,fig4 #aig ,x has _m times be5 sugge/$ t ?is /range se>*-light appe>ance may be an electrical ph5om5on1 "s =m ( e!r waves :i* ! comet s5ds =? :5 "u ! imm$iate influ5ce ( ! sun4 ,b n all comets are alike 9 ?is matt]1 nor does ! same comet always act alike on succe$+ trips1 s t we may n pr$ict :at ,halley's comet w d on ?is visit4 ,x w\ld be natural to suppose t ,halley's comet1 l radium1 might 9 "t lose ! p[] to radiate (f mat]ial1 9 :i* case x might at l5g? become :olly invisible to u1 ev5 ?\gh x cont9u$ to travel 9 its wont$ pa?4 ,our only way ( kn[+ ( its exi/5ce !n w\ld be t on its returns "s ( its small pieces might be attract$ to ! e>? & ent] our atmosph]e z meteors4 ,?is sort ( ?+ is cont9ually happ5+1 & may be ! la/ rem9d]s ( once brilliant comets4 ,= almo/ a c5tury x has be5 ! common belief t light is m]ely a wave motion 9 ! e!r4 ,our eyes respond to e!r waves ( c]ta9 l5g? only4 ,waves a little long] ?an ^? :i* affect our eyes are felt by u z heat waves4 ,waves /ill long] ?an ^? ( heat are ! s-call$ electric waves4 ,^! we use 9 wireless telegraphy4 ,!re are /ill %ort] waves ?an ^? ( light4 ,^! affect ! s5sitive plate 9 photography4 ,!y help to =m ! gre5 mat]ial 9 ! leaves ( plants & ! brilliant col\rs 9 fl[]s4 ,!y assi/ 9 ! fad+ ( our clo!s & ! tann+ ( our sk94 ,^! are call$ *emical waves4 ,/ill %ort] waves 9 ! e!r ?an ^? ( :i* we h j spok5 are ! ,x rays1 & all ! /range ?+s :i* !y may d h n yet be5 det]m9$4 ,c]ta9 x is t !y c make dreadful sores 9 our fle%4 ,!y c p5etrate ?r\gh wood & pap]1 b n metals4 ,!y pass readily ?r\gh fle%1 b n bones4 ,all su* e!r waves are treat$ 9 a book by ,sylvanus ,p4 ,?ompson1 entitl$ ',light ,visible & ,invisible1' 9 :i* he po9ts out t electricity1 heat1 light1 *emical rays1 etc41 are all alike 9 be+ e!r waves1 & ?is 0 suspect$ by ,james ,cl]k ,maxwell & o!rs half a c5tury ago1 & has come n[ to be q g5]ally believ$4 ,halley's comet1 already hav+ be5 se5 ^u ?is return1 mu/ be s5d+ out ^? e!r waves :i* we call light2 :e!r x is also s5d+ =? "s ( ! o!r k9ds ( e!r waves may yet be det]m9$4 ,my audi5ce be+ *iefly compos$ ( ^? p]sons :o 7 pres5t at ,h>old's bir?day p>ty1 !y press$ me to tell !m m ab\t wireless telegraphy & simil> matt]s1 & s ,i agre$ to give !m at "s future date "s acc\nt ( ! hi/ory ( ^! ideas4 ,b my pres5t purpose 0 to />t an int]e/ 9 a/ronomy z an antidote = ! wireless epidemic1 & s ,i invit$ all :o desir$ to d s to come aga9 "o week f t ev5+1 br++ ) !m su* op]a & field glasses z !y might be able to secure4 ,i promis$ to %[ !m h[ to make a telescope su* z ,galileo _h m ?an ?ree hundr$ ye>s ago4 ,i agre$ to g out ) !m sev]al ev5+s & scan ! sky ) our telescopes1 & to tell !m ( "s readable books & articles ^u a/ronomical matt]s4 ,,xxv ,,h[ ,,! ,,idea ,,( ,a ,,univ]sal ,,e!r ,,develop$ ,! ev5+ = ! meet+ ( ! ,sci5ce ,club _h arriv$4 ,its memb]%ip _h increas$ t5fold )9 a ye>4 ,at its mon?ly meet+s1 :i* 7 op5 to ! public1 an audi5ce ( two hundr$1 old & "y1 0 usually pres5t--a numb] ab\t ?ree times t ( ! regul> memb]%ip4 ,g5]al sci5ce 0 n[ ! /udy ( ?is club4 ,at its weekly meet+s1 :i* only memb]s att5d$1 ! /udies ( specific topics by individuals1 (t5times illu/rat$ by exp]im5ts1 7 report$4 ,^! meet+s 7 held 9 "o ( my laboratories1 :ile ! op5 mon?ly meet+ 0 always held 9 my lecture room1 ) "s r fam\s speak]s to in/ruct ! audi5ce4 ,an en?usia/ic fri5d ( sci5ce _h giv5 a fund ) ! /ipulation t we %\ld engage ! s]vices ( ^? :o bo? knew _! subjects & _h acquir$ ! art ( pres5tation4 ,! fund 0 #aj1jjj & x yield$ #ejj a ye>4 ,i ?9k beyond "q x 0 do+ m = sci5ce ?an any o!r fund ( t5 times t am\nt :i* c be m5tion$4 ,on ! p>ticul> ev5+ ( :i* ,i am ab\t to speak1 ! lectur] told ! memb]s ( ! ,sci5ce ,club frankly h[1 beg9n+ at ! age ( ?irte51 he _h sp5t =ty ye>s ( enjoym5t 9 /udy1 t he _h always f\nd great satisfaction 9 ! /udy ( anci5t civilizations & lit]atures4 ,he _h be5 =tunate1 he said1 9 hav+ tea*]s e>ly 9 life :o c\ld make ^! subjects full ( mean+ to him4 ,8 greate/ satisfaction1 h[ev]1 dur+ ! la/ tw5ty-five ye>s _h be5 f\nd 9 trac+ ! developm5t ( mod]n sci5ce1 bo? 9 ! evolution ( its !ories & 9 its applications to mod]n indu/ries4 ,he said he 0 sure t "y p ( high-s*ool age w\ld f9d x pr(itable to le>n1 = in/ance1 h[ ! mod]n !ory ( combu/ion _h develop$ sl[ly ?r\gh ! c5turies1 ev5 if to d s !y mu/ curtail some:at _! /udy ( h[ ,greece & ,rome develop$ & decl9$4 ,he said t sci5ce furni%$ a trem5d\sly ri* field ( /udy = "y p1 :i* z yet _h be5 unt\*$ by our s*ools1 fir/1 because educational cons]vatism _h made x impossible to det]m9e ! relative importance ( subjects ( /udy1 &1 second1 because education 9 sci5ce _h1 = a brief p]iod1 f\nd its wor/ enemies )9 its own camp4 ,he w\ld l especially to comm5d on ?is ev5+ "s hi/orical /udies 9 sci5ce1 & _h *os5 = 8 subject1 ,h[ ! ,idea ( a ,univ]sal ,e!r ,develop$4 ,m5 seem to talk freely n[ ab\t ! transmission ( light1 heat1 & electricity by means ( ! e!r4 ,h[ did ?is idea arise8 ,is x a product ( wild imag9ation8 or did ! idea develop out ( exp]i5ces :i*1 if giv5 to any p]son ( fair intellig5ce1 w\ld yield ! same result8 ,a little ov] ?irty ye>s ago1 at ! ,royal ,in/itution ( ,great ,brita91 ,james ,cl]k ,maxwell 7#ahca-ahgi7 deliv]$ a lecture on ,action at a ,di/ance4 ,x 0 no new subject1 b r "o ( ! olde/ & mo/ (t5 discuss$ subjects f ! days ( ! anci5t ,greeks d[n to ! pres5t4 ,we talk ( gravitation z an attraction or pull betwe5 ! v>i\s bodies ( ! univ]se1 b h[ c !y pull "o ano!r )\t "s mat]ial bond betwe58 ,?is 0 ,sir ,isaac ,newton's great puzzle :i* he nev] solv$1 ?\gh he exp5d$ ^u x ! greate/ ef=ts ( 8 great intellect4 ,! sun appe>s to repel ! tail ( ! comet1 yet h[ c !re be a pu% )\t int]v5+ mat]ial ) :i* to pu%8 ,:5 we speak ( light p\r+ or /ream+ 91 d we ?9k ( x z a sub/ance8 ,:5 we speak ( w>m bodies los+ heat1 or :5 we cov] !m to keep ! heat 91 are we ?9k+ ( heat z a sub/ance8 ,:at are heat1 light1 electricity1 magnetism1 & gravitation8 ,^! are no new que/ions4 ,!y are c]ta9ly old] ?an hi/ory4 ,v>i\s ideas h prevail$ at diff]5t times4 ,x is mu* easi] to *ange our ideas ?an to *ange our language4 ,y occasionally see & he> ! words calorie & caloric us$ 9 connection ) heat4 ,!y /& = an idea1 ab&on$ = ?ree g5]ations1 t heat is a sub/ance call$ caloric1 :i* saturates w>m bodies & dra9s out ( !m :5 !y cool (f4 ,i h>dly ?9k ^! ideas ei!r arise or fall )\t good & suffici5t reason4 ,ea* !ory has be5 ! natural conclusion f our obs]vations ( nature z f> z we h gone ) !m4 ,to be sure1 x is difficult = u to see h[ m5 acquir$1 f any obs]vations ( nature1 ! idea ( light :i* seems to h prevail$ previ\s to ! "t ( ,ari/otle1 ?ree & a half c5turies ,b4,c4 ,?is idea 0 t objects 7 made visible by some?+ project$ f ! eye itself4 ,/ill1 ! que/ions :i* ,i h indicat$ reg>d+ heat1 light1 & electricity h impell$ m5 = _m c5turies to obs]ve nature = h9ts z to ! answ]s4 ,! doctr9e ( ! univ]sal e!r z a m$ium = transmitt+ wave motions1 & ( light1 heat1 & electricity z be+ motions ( diff]5t wave l5g?1 is ! natural conclusion ( ! pres5t "t4 ,x may give place to ano!r !ory :5 we h fur!r facts to reason ^u4 ,imag9e y\r nev] hav+ se5 a h>p or o!r musical in/rum5t4 ,w\ld x require a long "t1 d y ?9k1 = y to f9d out its use1 at lea/ to ?is ext5t1 t x w produce tones :5ev] ! /r+s are made to vibrate8 ,t ! %ort /r+s vibrate m rapidly ?an ! long ones1 & at ! same "t produce tones ( a high] pit*8 ,imag9e t hav+ become famili> ) ! h>p y %\ld successively come ^u scores ( o!r musical in/rum5ts ( v diff]+ types4 ,y w\ld soon become adept at div9+ _! uses4 ,n[1 a /udy ( ! microscopic /ructure ( ! eye1 = "o ?+1 w\ld sugge/ t light may be 9 ! nature ( a vibration4 ,scores ( o!r l9es ( /udy 9 a simil> mann] h at l5g? br\ght all :o pursue !m to ! conclusion t light is a =m ( vibration4 ,rob]t ,hooke 9 ,engl& 7#afca-agjc7 & ,*ri/ian ,huyg5s 9 ,holl& 7#afbi-afie71 back 9 ! sev5te5? c5tury seem to h be5 ! fir/ to give expression to ?is idea1 :i* 0 no?+ m ?an an inkl+ 9 ,hooke's m9d1 b :i* 0 ! necess>y result ( obs]vations on ! "p ( ,huyg5s4 ,= ne>ly a c5tury ! idea lay dormant1 l>gely because ,sir ,isaac ,newton 7#afdb-agbg71 ! clev]e/ ?9k] ( 8 "t1 oppos$ x4 ,x 0 p]haps un=tunate = ! success ( ! !ory t ,huyg5s1 its f\nd]1 adopt$ ! ^w e!r1 = t 0 an old t]m1 & _h be5 v badly ov]work$4 ,! ^w e!r1 or !r z x 0 (t5 writt51 _h be5 inv5t$ 9 ! days ( ignorance1 = su* fooli% reasons z3 7a7 because nature abhors a vacuum1 or 7b7 = planets to swim 91 or 7c7 to con/itute electric atmosph]es & magnetic effluvia1 or 7d7 to convey s5sations f "o "p ( our bodies to ano!r4 ,:5 we rememb]1 says ,maxwell1 ! mis*iev\s influ5ce on sci5ce :i* hypo!ses ab\t !rs us$ =m]ly to ex]cise1 we c appreciate ! horror ( !rs :i* sob]-m9d$ m5 _h dur+ ! eighte5? c5tury4 ,newton 9 ,engl& 7#afdb-agbg7 & ,laplace 9 ,france 7#agdi-ahbg7 /\tly oppos$ ! undulatory !ory ( ,huyg5s & *ampion$ a corpuscul> or emission !ory1 t light-giv+ & heat-giv+ bodies emit a subtile fluid4 ,!re is no o!r in/ance 9 ! :ole hi/ory ( mod]n physics 9 :i* tru? 0 s long kept d[n by au?ority4 ,fresnel 7#aghh-ahbg7 & ,arago 7#aghf-ahec7 9 ,france appe> to be ! only p]sons dur+ ! eighte5? c5tury :o caught a cle> vision ( ! tru? ( ! undulatory !ory4 ,b x rema9$ = ,mr4 ,?omas ,"y 7#aggc-ahbi71 a colleague ( ,sir ,humphrey ,davy at ! ,royal ,in/itution1 9 8 ,bak]ian lecture 7#ahja7 on ,!ory ( ,light & ,col\r to br+ toge!r su* good evid5ce = ! e!r wave !ory t x has h>dly be5 que/ion$ s9ce4 ,"y1 l ,davy1 0 a mo/ rem>kable man 9 lit]ature & 9 sci5ce4 ,x 0 he :o fir/ deciph]$ ! ,rosetta ,/one1 n[ 9 ! ,briti% ,museum1 & gave u a key to ! ,egyptian hi]oglyphics4 ,probably he 0 ! only man :o 0 able to ov]?r[ ! influ5ce ( ,newton's au?ority ev5 a c5tury aft] ,newton did 8 "w4 ,f>aday's 7#agia-ahfg7 *ief "w z director ( ! laboratory ( ! ,royal ,in/itution1 ,london1 0 a /udy ( e!r ph5om5a1 p>ticul>ly electric & magnetic4 ,ab\t sev5ty-five ye>s ago he became impress$ ) ! fact t al?\gh wires may give direction to an electric curr5t ! electric influ5ce is n conf9$ to ! wires1 b may p]meate m or less widely ! region ab\t !m4 ,ne>ly fifty ye>s ago ,maxwell 7#ahca-ahgh7 pr(essor ( physics at ,cambridge ,univ]sity1 ,engl&1 conceiv$ ! idea t light is electricity ( a v %ort wave l5g?4 ,ne>ly tw5ty-five ye>s ago ,he9ri* ,h]tz 7#aheg-ahid71 9 ,g]many1 prov$ by exp]im5ts ! exi/5ce ( electric waves1 & measur$ _! l5g? & velocity1 det]m9+ _! v>i\s *>act]i/ics z comp>$ ) light4 ,ab\t fifte5 ye>s ago ,m>coni develop$ a wireless telegraph app>atus1 :i* made x possible to use electric waves = purposes ( communication4 ,?irte5 ye>s ago 7#ahig7 ! fir/ wireless telegraph company 0 =m$4 ,elev5 ye>s ago 7#ahii7 ! int]national ya*t races 9 ,new ,york ,h>b\r 7 report$ by wireless telegraph1 & bullet9 bo>ds 9 ,new ,york ,city ann\nc$ to wait+ cr[ds ! details ( ! race :ile x 0 9 progress4 ,ne>ly t5 ye>s ago 7#aija7 wireless despat*es 7 fir/ s5t across ! ,atlantic ,ocean4 ,wireless telegraphy 0 op5$ = public use 9 #aije1 & v soon ! company began to cop]ate ) ! regul> telegraph companies4 ,ne>ly all coa/wise & trans-,atlantic /eam]s are n[ equipp$ ) wireless telegraph outfits1 & a law has pass$ bo? h\ses ( ,congress mak+ x obligatory on ! "p ( /eam]s :i* c>ry fifty or m pass5g]s to h su* equipm5t4 ,on sev]al disabl$ /eam]s1 notably ! ,republic1 loss ( life has be5 av]t$ by ! wireless em]g5cy call = help1 to :i* ! capta9s ( all /eam]s feel oblig$ to respond4 ,if y desire to communicate ) a fri5d :o left = ,europe sev]al days ago1 y simply write him a telegram1 address+ x to 8 %ip1 & deliv] x at y\r ne>e/ telegraph (fice4 ,ea* telegraph (fice has a record ( ! location ( e %ip hav+ a wireless telegraph outfit4 ,x despat*es y\r message to ! wireless /ation along ! coa/ :i* is ne>e/ to y\r fri5d's /eam]1 & f ?is /ation x is s5t on ! e!r to ! %ip4 ,or 9 "s cases x may be repeat$ f "o %ip to ano!r along ! ,atlantic highway until x rea*es ! desir$ "o4 ,?us also news ( important ev5ts on ei!r cont95t is di/ribut$ daily on bo>d %ips :i* are cross+ ! ocean4 ,!re are said to be m ?an #ej1jjj amateur wireless /ations 9 ! ,unit$ ,/ates1 & already ,congress is tak+ /eps to regulate ! use ( ! wireless telegraph 9 ord] to prev5t int]f]5ce ) ,gov]nm5t & o!r important messages4 ,m ?an ?ree doz5 books & c\ntless magaz9e articles h already be5 writt5 ^u wireless or e!r wave telegraphy4 ,hundr$s h & ?\s&s are contribut+ to our k ( e!r wave ph5om5a4 ,if ! names ( all :o h said or done some?+ to r5d] /able ! f\ndations ( ?is idea ( a univ]sal e!r1 ^: undulations acc\nt = ! ph5om5a ( heat1 light1 & electricity1 7 to be m5tion$1 ! li/ w\ld conta9 ne>ly all ! important work]s 9 ! field ( physics = ! la/ c5tury4 ,,xxvi ,,electric ,,curr5ts ,,_c ,,be ,,conf9$ ,,to ,,wires ,h>old said t if electricity 0 s mu* l light t x c\ld g )\t wires he ?\ght light ought to be en\gh l electricity to be conduct$ by wires on occasions4 ,i told him t ,i _h no hope ( be+ able to conf9e light to a wire2 inde$1 if ! ,sci5ce ,club w\ld give me an opportunity ,i w\ld %[ !m t ev5 :5 electricity foll[s ! g5]al direction ( a wire its influ5ce is n conf9$ to ! wire4 ,z a result ( ?is bid ,i receiv$ an invitation to address an op5 meet+ ( ! ,sci5ce ,club4 ,illu/ration3 ,fig4 #aih ,9 my fir/ exp]im5t on t occasion ,i took a "o-p\nd spool ( ,no4 #bd cotton-cov]$ copp] wire & cr[d$ ! hole 9 ! spool full ( wire nails ,a 7,fig4 #aih74 ,i disconnect$ ! wires f an electric drop lamp & connect$ !m to b & c1 ! ends ( ! wire f ! spool4 ,our electric light+ circuit 0 :at is call$ ! alt]nat+ curr5t4 ,i also _h a second spool1 ,b1 precisely l ! fir/4 ,! wires f ?is 7 connect$ to a m9iature lamp1 ,l1 su* z is us$ at ! swit*bo>d ( a telephone ex*ange4 ,we !n screw$ ! drop-light plug into ! *&eli] & turn$ on ! electric curr5t4 ,i br\ght spool ,b ) ! m9iature lamp ne> to spool ,a1 z %[n 9 ,fig4 #aii1 & :5 x 0 )9 a di/ance ( ab\t two in*es ! little lamp light$ up to full brilliancy1 ?us %[+ t :ile ! electric curr5t is pass+ 9 ! wire ( spool ,a its influ5ce is n conf9$ to ! wire1 b exhibits itself 9 ! region outside ( ! wire4 ,to illu/rate /ill fur!r ?is fact we sub/itut$ an electric bell 9 ! place ( ! lamp ,l1 & :5 ! spool ,b 0 br\ght ne> to ,a ! bell rang4 ,b ! mo/ /rik+ illu/ration 0 obta9$ :5 a telephone receiv] 0 put 9 ! place ( ,l4 ,) ?is held to ! e> :ile ! spool ,b 0 br\ght t[>d ,a a humm+ s\nd c\ld be he>d :5 ,b 0 ab\t a foot di/ant f ,a4 ,?is s\nd grew rapidly l\d] z ,b approa*$ ,a1 until1 :5 ! spool ,b re/$ ^u ! spool ,a1 a s\nd l ! peal ( a pipe organ 0 he>d all ov] ! ap>tm5t4 ,! tone 0 v ne>ly t ( ! key on ! piano :i* is two octaves bel[ middle ,c4 ,i unscrew$ ! cap on ! l>ge end ( ! telephone receiv]1 took x (f1 & mov$ ! ?9 iron diaphragm to "o side1 :5 x began to dance ab\t at great spe$4 ,x 0 keep+ "t ) ! dynamo1 five miles away1 :i* g5]at$ ! electric curr5t4 ,! dynamo *ang$ ! direction ( ! electric curr5t sixty times p] second1 & ?is made sixty vibrations p] second4 ,! dynamo s5t out e!r waves :i* affect$ ! telephone receiv]1 al?\gh ! receiv] 0 n connect$ to ! dynamo by wires4 ,to emphasize ! fact t ! dynamo _h light$ ! lamp1 rung ! bell & made ! telephone receiv] hum )\t be+ connect$ ) !m1 ,i repeat$ all ^! exp]im5ts 9 a diff]5t way4 ,spool ,a1 connect$ z be=e ) ! electric light+ circuit1 0 conceal$ b5ea? ! table4 ,= spool ,b ,i sub/itut$ spool ,c 7,fig4 #aii71 on :i* ! wire 0 w\nd s z to appe> l a c&le/ick4 ,on ! top ( ?is 0 plac$ ! m9iature electric lamp screw$ into a m9iature socket & connect$ to ! wires ( ! spool4 ,?is ,wit*es' ,c&le1 z we call$ x1 0 sitt+ unlight$ ^u ! table :5 ,i call$ att5tion to ! fact t if ,i mov$ x to a c]ta9 spot ^u ! table x fla%$ into full light4 7,( c\rse ?is spot 0 directly ov] spool ,a47 ,i mov$ x sl[ly away f t spot & its light sl[ly grew dim & disappe>$4 ,illu/ration3 ,fig4 #aii ,on ! table 0 also sitt+ a cream pit*] 9 :i* ,i _h plac$ spool ,b ) a buzz] atta*$ to x4 ,rem>k+ t ?is pit*] groan$ = m cream :5ev] x 0 empty1 & ?us ( its own accord call$ ! wait]1 ,i mov$ x to ! spot on ! table directly ov] spool ,a1 :5 ! buzz] gave =? a s\nd l a husky bumble-bee %ut up 9 a res\nd+ bottle4 ,at ?is signal my assi/ant came 9 & took up ! pit*] & plac$ my silk hat ^u ! table1 :5 x in/antly boom$ =? a base note two octaves bel[ middle ,c ( ! piano4 ,out ( ! hat ,i took a coil & ! telephone receiv] & ! my/]y 0 solv$4 ,illu/ration3 ,fig4 #bjj ,9 #ahai ,hans ,*ri/ian ,o]/$ 9 ,d5m>k 7#aggg-ahea7 fir/ not$ t ! region ab\t a wire c>ry+ an electric curr5t has an influ5ce ^u a magnet4 ,i w %[ ?is fact by a simple exp]im5t4 ,i magnetize a /\t sew+ ne$le by draw+ x f end to end across ! pole ( a /eel magnet1 & by means ( a triangul> piece ( pap] & a f9e ?read ,i susp5d x a few in*es above ! table 7,fig4 #bjj74 ,i !n lay ^u ! table a piece ( wire p>allel ) ! ne$le & fa/5 "o end ( x to "o b9d+ po/ ( a dry cell4 ,:5ev] ,i t\* ! o!r end ( ! wire to ! o!r b9d+ po/ ( ! cell1 ?us s5d+ an electric curr5t ?r\gh ! wire1 ! magnetiz$ ne$le is deflect$ at "r angles4 ,?is exp]im5t1 p]=m$ by ,o]/$1 seems to h />t$ ,f>aday ^u t wond]ful s]ies ( rese>*es :i* has result$ 9 giv+ u ! dynamo4 ,,xxvii ,,wireless ,,telegraphy ,,9 ,,e>ne/ ,we _h decid$ to let ,h>old make a trip to ,europe alone4 ,! fir/ message f him aft] 8 dep>ture 0 a brief note to 8 "m say+ t !y _h _h a turbul5t voyage1 b all _h l&$ safely ^u ! o!r side1 none ! worse = _! exp]i5ces4 ,! next day a numb] ( lett]s came to me f total /rang]s4 ,"o ( ^! ran z foll[s3 ,my ,de> ,sir3 ,prompt$ by my own impulses1 & urg$ to d s by ! pass5g]s "u my *>ge1 ,i improve ?is fir/ opportunity to express to y our high appreciation = y\r noble b v mode/ son1 to :om m ?an to any "o else we owe ! lives ( all on bo>d our fat$ %ip4 ,i am s5d+ ?is direct to y bo?1 because ,i und]/& a fa!r's he>t & because ! "y man escap$ z soon z we came to l&1 )\t any ( u le>n+ 8 address4 ,i beg y w communicate to him ! desire ( ! presid5t ( our company to meet him & p]sonally to ?ank him = 8 gallant conduct4 ,i am also in/ruct$ to say t :5ev] ,h>old desires to cross ! ocean ! be/ :i* any %ip ,i may comm& c af=d w be 8 )\t *>ge4 ,v respectfully y\rs1 -------- ,capta94 ,s4 ,s4 ,ano!r lett] 0 ! foll[+3 ,my ,de> ,sir3 ,p]mit me to congratulate y on hav+ su* a h]oic & self-possess$ son4 ,we1 8 fell[ pass5g]s1 are1 if possible1 z pr\d ( him z y mu/ be4 ,i fe> t 8 acc\nt ( ! affair w n d himself full ju/ice1 & s1 ) y\r p]mission1 ,i w give y ! full details z ,i h ga!r$ !m f ! pass5g]s1 f ! crew1 & f my own obs]vation4 ,dur+ ! la/ night ( our voyage a ?ick fog clos$ ab\t u4 ,! con/ant bl[+ ( ! fog :i/le made ! night dismal4 ,few p]sons slept at all4 ,ab\t two o'clock 9 ! morn+ ! %ip /ruck a reef1 & in/antly x seem$ z ?\gh e p]son on t %ip rea*$ ! decks at ! same "t4 ,! wat] p\r$ 9 & put out ! fires4 ,! %ip heel$ badly1 & x seem$ t any m9ute %e might slip (f ! reef on :i* %e 0 re/+ into deep wat] & g d[n4 ,to add to our horror fire broke out4 ,x seems to h />t$ 9 ! wireless op]ator's room4 ,v mu* damage 0 done to ! wireless outfit itself1 & ! op]ator 0 badly burn$1 s mu* s t he 0 tak5 to ! %ip's hospital suff]+ ) _m pa9ful & dang]\s w\nds4 ,mean:ile ! flames spread rapidly & we 7 unable to summon help4 ,! crew & _m ( ! pass5g]s f\ght ! flames1 b ) little success4 ,9 ! mid/ ( our despair ^w pass$ ar\nd ! %ip t an unkn[n boy f among ! pass5g]s 0 s5d+ ! ,c4 ,q4 ,d4 message to all ! _w by wireless4 ,x 0 aft]w>d le>n$ t y\r ,h>old 0 ! y\?4 ,he _h repair$ ! damag$ app>atus suffici5tly to e/abli% connection ) a /orage batt]y :i* he f\nd1 &1 "u ! capta9's direction1 0 s5d+ =? t hurry call = help kn[n to all ! wireless frat]nity & he$$ by all sea-f>+ m54 ,i le>n$ t y\r boy 0 n a regul> op]ator1 b t someh[ he _h le>n$ to s5d ?is message & also to s5d out ! capta9's calculations ( our position at sea4 ,he 0 also able to detect t 8 call _h be5 he>d & t help 0 com+1 al?\gh he c\ld n und]/& mu* t came to 8 in/rum5t 9 reply to 8 calls4 ,i le>n$1 also1 t he 0 "o ( ! fir/ to rea* ! op]ator's room & to give assi/ance4 ,he 0 himself badly burn$1 s mu* s t "o h& 0 be+ dress$ by a nurse :ile he 0 cont9ually us+ ! o!r to op]ate 8 in/rum5t4 ,i c te/ify1 my de> sir1 t he appe>$ to be ! calme/ & mo/ self-possess$ p]son on bo>d t %ip1 z ,i saw him 9 ! gl>e ( ! dreadful flames :i* lit up ! blacke/ night4 ,i am an arti/ & w\ld l to attempt to pa9t t sc5e1 :i* has left its la/+ impression ^u my s\l4 ,i beg t y w all[ me to exhibit x = a "t 9 sev]al ( our gall]ies & f9ally pres5t x to y\r family4 ,help came none too soon4 ,we 7 all transf]r$ to o!r boats1 b ! sea 0 ris+1 & sc>cely _h we rea*$ a safe di/ance :5 ! burn+ %ip slipp$ into ! sea & disappe>$4 ,i d n "k by :i* boat y\r son rea*$ ! l&4 ,9 ! great confusion ,i lo/ sight ( him at la/4 ,he has d\btless communicat$ ) y by ?is "t1 & ,i %all e/eem x a great fav\r if y w put me 9 communication ) him aga94 ,9 ord] t ,i may d ju/ice to him 9 ! pa9t+ ,i w\ld l to arrange ) him a few sitt+s :ile he is 9 ,europe4 ,c\ld y k9dly s5d me a photograph ( him :i* w assi/ me some:at8 ,mo/ s9c]ely & gratefully y\rs1 --------4 ,! lett] conta9$ sev]al ref]5ces to mutual acqua9tances4 99 99 99 99 99 ,h>old's lett]s h be5 frequ5t & full ( ! pleasure he is hav+ 9 ,european travel1 b ! only ?+ he has said ab\t ! voyage is t x 0 n wor? s mu* fuss4 ,illu/ration ,,! ,,c\ntry ,,life ,,press ,,g>d5 ,,city1 ,n4 ,y4 99 99 99 99 99 ,transcrib]'s ,notes3 ,obvi\s typos & inconsi/5cies 9 spell+ h be5 correct$3 p#ca4 intrum5t - in/rum5t p#ce4 manta9 - ma9ta9 p#dh4 repres5ts ! ! c\nt]-electro-motive =ce p#fd4 #b volts 4#a amp]e 4#f watts4 - #f volts 4#a amp]e 4#f watts4 ,! correct voltage is d$uc$ f ! prec$+ p>agraph4 p#ada4 #ee amp]e - 4#ee amp]e p#afh4 famil> - famili> p#agc4 preceptible - p]ceptible p#bbi4 - p#bcj4 c\nt]%aft - c\nt] %aft p#bei4 ,h#b,,s#d - ,h#b,,s#d p#bie4 ,note ,c ref]s to ,c n ,c & ^! %\ld be labell$ ,c1 & ,c11 to d5ote octaves bel[ middle ,c4 p#caf4 electri-tricity - electricity p#cef4 oufit - outfit ,?r\gh\t ! text3 ,! few cases ( volt-met] h be5 *ang$ to volt met] :i* has be5 us$ = ! majority ( ! text4 ,! s+le in/ances ( watt met] & watt-met] h be5 *ang$ to wattmet] :i* has be5 us$ = ! majority ( ! text4 ,! few cases ( electro magnet h be5 *ang$ to electro-magnet :i* has be5 us$ = ! majority ( ! text4 ,9 ! ,table ( ,cont5ts3 ,*apt] ,,xii page numb] *ang$ f #aah to #bah ,*apt] ,,xv "n *ang$ f ,electricity f ,*emical ,action & ,*emical ,action f ,electricity to mat* text :i* reads ,,electric ,,curr5ts ,,f ,,*emical ,,action ,,& ,,*emical ,,action ,,f ,,electric ,,curr5ts ,9 ! ,table ( ,illu/rations3 ,op]at+ a ,swit*bo>d *ang$ to mat* caption :i* reads ,op]at+ ! ,swit*bo>d p#fc4 ,! example ( ,morse code giv5 is correct = ,orig9al or ,am]ican ,morse4 ,x has "s diff]5ces f ,cont95tal or ,int]national ,code :i* is ! curr5t /&>d4 ,! spac+ ( ! dots is significant4