the age of invention-第26部分

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lf　in　earnest　to　the　problem　of　the　lamp。　His　first　search　was　for　a　durable　filament　which　would　burn　in　a　vacuum。　A　series　of　experiments　with　platinum　wire　and　with　various　refractory　metals　led　to　no　satisfactory　results。　Many　other　substances　were　tried；　even　human　hair。　Edison　concluded　that　carbon　of　some　sort　was　the　solution　rather　than　a　metal。　Almost　coincidently；　Swan；　an　Englishman；　who　had　also　been　wrestling　with　this　problem；　came　to　the　same　conclusion。　Finally；　one　day　in　October；　1879；　after　fourteen　months　of　hard　work　and　the　expenditure　of　forty　thousand　dollars；　a　carbonized　cotton　thread　sealed　in　one　of　Edison's　globes　lasted　forty　hours。　〃If　it　will　burn　forty　hours　now；〃　said　Edison；　〃I　know　I　can　make　it　burn　a　hundred。〃　And　so　he　did。　A　better　filament　was　needed。　Edison　found　it　in　carbonized　strips　of　bamboo。

Edison　developed　his　own　type　of　dynamo；　the　largest　ever　made　up　to　that　time；　and；　along　with　the　Edison　incandescent　lamps；　it　was　one　of　the　wonders　of　the　Paris　Electrical　Exposition　of　1881。　The　installation　in　Europe　and　America　of　plants　for　service　followed。　Edison's　first　great　central　station；　supplying　power　for　three　thousand　lamps；　was　erected　at　Holborn　Viaduct；　London；　in　1882；　and　in　September　of　that　year　the　Pearl　Street　Station　in　New　York　City；　the　first　central　station　in　America；　was　put　into　operation。

The　incandescent　lamp　and　the　central　power　station；　considered　together；　may　be　regarded　as　one　of　the　most　fruitful　conceptions　in　the　history　of　applied　electricity。　It　comprised　a　complete　generating；　distributing；　and　utilizing　system；　from　the　dynamo　to　the　very　lamp　at　the　fixture；　ready　for　use。　It　even　included　a　meter　to　determine　the　current　actually　consumed。　The　success　of　the　system　was　complete；　and　as　fast　as　lamps　and　generators　could　be　produced　they　were　installed　to　give　a　service　at　once　recognized　as　superior　to　any　other　form　of　lighting。　By　1885　the　Edison　lighting　system　was　commercially　developed　in　all　its　essentials；　though　still　subject　to　many　improvements　and　capable　of　great　enlargement；　and　soon　Edison。　sold　out　his　interests　in　it　and　turned　his　great　mind　to　other　inventions。

The　inventive　ingenuity　of　others　brought　in　time　better　and　more　economical　incandescent　lamps。　From　the　filaments　of　bamboo　fiber　the　next　step　was　to　filaments　of　cellulose　in　the　form　of　cotton；　duly　prepared　and　carbonized。　Later　（1905）　came　the　metalized　carbon　filament　and　finally　the　employment　of　tantalum　or　tungsten。　The　tungsten　lamps　first　made　were　very　delicate；　and　it　was　not　until　W。　D。　Coolidge；　in　the　research　laboratories　of　the　General　Electric　Company　at　Schenectady；　invented　a　process　for　producing　ductile　tungsten　that　they　became　available　for　general　use。

The　dynamo　and　the　central　power　station　brought　the　electric　motor　into　action。　The　dynamo　and　the　motor　do　precisely　opposite　things。　The　dynamo　converts　mechanical　energy　into　electric　energy。　The　motor　transforms　electric　energy　into　mechanical　energy。　But　the　two　work　in　partnership　and　without　the　dynamo　to　manufacture　the　power　the　motor　could　not　thrive。　Moreover；　the　central　station　was　needed　to　distribute　the　power　for　transportation　as　well　as　for　lighting。

The　first　motors　to　use　Edison　station　current　were　designed　by　Frank　J。　Sprague；　a　graduate　of　the　Naval　Academy；　who　had　worked　with　Edison；　as　have　many　of　the　foremost　electrical　engineers　of　America　and　Europe。　These　small　motors　possessed　several　advantages　over　the　big　steam　engine。　They　ran　smoothly　and　noiselessly　on　account　of　the　absence　of　reciprocating　parts。　They　consumed　current　only　when　in　use。　They　could　be　installed　and　connected　with　a　minimum　of　trouble　and　expense。　They　emitted　neither　smell　nor　smoke。　Edison　built　an　experimental　electric　railway　line　at　Menlo　Park　in　1880　and　proved　its　practicability。　Meanwhile；　however；　as　he　worked　on　his　motors　and　dynamos；　he　was　anticipated　by　others　in　some　of　his　inventions。　It　would　not　be　fair　to　say　that　Edison　and　Sprague　alone　developed　the　electric　railway；　for　there　were　several　others　who　made　important　contributions。　Stephen　D。　Field　of　Stockbridge；　Massachusetts；　had　a　patent　which　the　Edison　interests　found　it　necessary　to　acquire；　C。　J。　Van　Depoele　and　Leo　Daft　made　important　contributions　to　the　trolley　system。　In　Cleveland　in　1884　an　electric　railway　on　a　small　scale　was　opened　to　the　public。　But　Sprague's　first　electric　railway；　built　at　Richmond；　Virginia；　in　1887；　as　a　complete　system；　is　generally　hailed　as　the　true　pioneer　of　electric　transportation　in　the　United　States。　Thereafter　the　electric　railway　spread　quickly　over　the　land；　obliterating　the　old　horsecars　and　greatly　enlarging　the　circumference　of　the　city。　Moreover；　on　the　steam　roads；　at　all　the　great　terminals；　and　wherever　there　were　tunnels　to　be　passed　through；　the　old　giant　steam　engine　in　time　yielded　place　to　the　electric　motor。

The　application　of　the　electric　motor　to　the　〃vertical　railway；〃　or　elevator；　made　possible　the　steel　skyscraper。　The　elevator；　of　course；　is　an　old　device。　It　was　improved　and　developed　in　America　by　Elisha　Graves　Otis；　an　inventor　who　lived　and　died　before　the　Civil　War　and　whose　sons　afterward　erected　a　great　business　on　foundations　laid　by　him。　The　first　Otis　elevators　were　moved　by　steam　or　hydraulic　power。　They　were　slow；　noisy；　and　difficult　of　control。　After　the　electric　motor　came　in；　the　elevator　soon　changed　its　character　and　adapted　itself　to　the　imperative　demands　of　the　towering；　skeleton…framed　buildings　which　were　rising　in　every　city。

Edison；　already　famous　as　〃the　Wizard　of　Menlo　Park；〃　established　his　factories　and　laboratories　at　West　Orange；　New　Jersey；　in　1887；　whence　he　has　since　sent　forth　a　constant　stream　of　inventions；　some　new　and　startling；　others　improvements　on　old　devices。　The　achievements　of　several　other　inventors　in　the　electrical　field　have　been　only　less　noteworthy　than　his。　The　new　profession　of　electrical　engineering　called　to　its　service　great　numbers　of　able　men。　Manufacturers　of　electrical　machinery　established　research　departments　and　employed　inventors。　The　times　had　indeed　changed　since　the　day　when　Morse；　as　a　student　at　Yale　College；　chose　art　instead　of　electricity　as　his　calling；　because　electricity　afforded　him　no　means　of　livelihood。

From　Edison's　plant　in　1903　came　a　new　type　of　the　storage　battery；　which　he　afterwards　improved。　The　storage　battery；　as　every　one　knows；　is　used　in　the　propulsion　of　electric　vehicles　and　boats；　in　the　operation　of　block…signals；　in　the　lighting　of　trains；　and　in　the　ignition　and　starting　of　gasoline　engines。　As　an　adjunct　of　the　gas…driven　automobile；　it　renders　the　starting　of　the　engine　independent　of　muscle　and　so　makes　possible　the　general　use　of　the　automobile　by　women　as　well　as　men。

The　dynamo　brought　into　service　not　only　light　and　power　but　heat；　and　the　electric　furnace　in　turn　gave　rise　to　several　great　metallurgical　and　chemical　industries。　Elihu　Thomson's　process　of　welding　by　means　of　the　arc　furnace　found　wide　and　varied　applications。　The　commercial　production　of　aluminum　is　due　to　the　electric　furnace　and　dates　from　1886。　It　was　in　that　year　that　H。　Y。　Castner　of　New　York　and　C。　M。　Hall　of　Pittsburgh　both　invented　the　methods　of　manufacture　which　gave　to　the　world　the　new　metal；　malleable　and　ductile；　exceedingly　light；　and　capable　of　a　thousand　uses。　Carborundum　is　another　product　of　the　electric　furnace。　It　was　the　invention　of　Edward　B。　Acheson；　a　graduate　of　the　Edison　laboratories。　Acheson；　in　1891；　was　trying　to　make　artificial　diamonds　and　produced　instead　the　more　useful　carborundum；　as　well　as　the　Acheson　graphite；　which　at　once　found　its　place　in　industry。　Another　valuable　product　of　the　electric　furnace　was　the　calcium　carbide　first　produced　in　1892　by　Thomas　L。　Wilson　of　Spray；　North　Carolina。　This　calcium　carbide　is　the　basis　of　acetylene　gas；　a　powerful　illuminant；　and　it　is　widely　used　in　metallurgy；　for　welding　and　other　purposes。

At　the　same　time　with　these　developments　the　value　of　the　alternating　current　came　to　be　recognized。　The　transformer；　an　instrument　developed　on　foundations　laid　by　Henry　and　Faraday；　made　it　possible　to　transmit　electrical　energy　over　great　distances　with　little　loss　of　power。　Alternating　currents　were　transformed　by　means　of　this　instrument　at　the　source；　and　were　again　converted　at　the　point　of　use　to　a　lower　and　convenient　potential　for　local　distribution　and　consumption。　The　first　extensive　use　of　the　alternating　current　was　in　arc　lighting；　where　the　higher　potentials　could　be　employed　on　series　lamps。　Perhaps　the　chief　American　inventor　in　the　domain　of　the　alternating　current　is　Elihu　Thomson；　who　began　his　useful　career　as　Professor　of　Chemistry　and　Mechanics　in　the　Central　High　School　of　Philadelphia。　Another　great　protagonist　of　the　alternating　current　was　George　Westinghouse；　who　was　quite　as　much　an　improver　and　inventor　as　a　manufacturer　of　machinery。　Two　other　inventors；　at　least；　should　not　be　forgotten　in　this　connection：　Nicola　Tesla　and　Charles　S。　Bradley。　Both　of　them　had　worked　for　Edison。

The　turbine　（from　the　Latin　turbo；　meaning　a　whirlwind）　is　the　name　of　the　motor　which　drives　the　great　dynamos　for　the　generation　of　electric　energy。　It　may　be　either　a　steam　turbine　or　a　water　turbine。　The　steam　turbine　of　Curtis　or　Parsons　is　today　the　prevailing　engine。　But　the　development　of　hydro…electric　power　has　already　gone　far。　It　is　estimated　that　the　electric　energy　produced　in　the　United　States　by　the　utilization　of　water　powers　every　year　equals　the　power　product　of　forty　million　tons　of　coal；　or　about　one…tenth　of　the　coal　which　is　consumed　in　the　production　of　steam。　Yet　hydro…electricity　is　said　to　be　only　in　its　beginnings；　for　not　more　than　a　tenth　of　the　readily　available　water　power　of　the　country　is　actually　in　use。

The　first　commercial　hydro…station　for　the　transmission　of　power　in　America　was　established　in　1891　at　Telluride；　Colorado。　It　was　practically　duplicated　in　the　following　year　at　Brodie；　Colorado。　The　motors　and　generators　for　these　stations　came　from　the　Westinghouse　plant　in　Pittsburgh；　and　Westinghouse　also　supplied　the　turbo…generators　which　inau