Thecurseofthisworkandofallthatsucceededitforascoreofyearswasthenecessityofdependinguponchemicalbatteriesforcurrent，themachineusuallybeingself-containedandhaulingthebatteriesalongwithitself，asinthecaseofthefamousPageexperimentsinApril，1851，whenaspeedofnineteenmilesanhourwasattainedonthelineoftheWashington&Baltimoreroad。Tothisunfruitfulperiodbelonged，however，thecrudeideaoftakingthecurrentfromastationarysourceofpowerbymeansofanoverheadcontact，whichhasfounditspracticalevolutioninthemodernubiquitoustrolley；
althoughthepatentforthis，basedonhiscaveatof1879，wasgrantedseveralyearslaterthanthattoStephenD。Field，forthecombinationofanelectricmotoroperatedbymeansofacurrentfromastationarydynamoorsourceofelectricityconductedthroughtherails。Asamatteroffact，in1856andagainin1875，GeorgeF。Green，ajobbingmachinist，ofKalamazoo，Michigan，builtsmallcarsandtrackstowhichcurrentwasfedfromadistantbattery，enoughenergybeingutilizedtohaulonehundredpoundsoffreightoronepassengerupanddowna“road“twohundredfeetlong。Alltheworkpriortothedevelopmentofthedynamoasasourceofcurrentwassporadicandspasmodic，andcannotbesaidtohaveleftanytraceontheart，thoughitofferedmanysuggestionsastooperativemethods。
Thecloseofthesamedecadeofthenineteenthcenturythatsawtheelectriclightbroughttoperfection，sawalsotherealizationinpracticeofallthehopesoffiftyyearsastoelectrictraction。Bothutilizationsdependeduponthesupplyofcurrentnowcheaplyobtainablefromthedynamo。Theseartswereindeedtwins，feedingatinexhaustiblebreasts。
In1879，attheBerlinExhibition，thedistinguishedfirmofSiemens，towhoseingenuityandenterpriseelectricaldevelopmentowessomuch，installedaroadaboutone-thirdofamileinlength，overwhichthelocomotivehauledatrainofthreesmallcarsataspeedofabouteightmilesanhour，carryingsometwentypersonseverytrip。Currentwasfedfromadynamotothemotorthroughacentralthirdrail，thetwoouterrailsbeingjoinedtogetherasthenegativeorreturncircuit。Primitivebutessentiallysuccessful，thislittleroadmadeaprofoundimpressiononthemindsofmanyinventorsandengineers，andmarkedtherealbeginningofthegreatnewera，whichhasalreadyseenelectricityappliedtotheoperationofmainlinesoftrunkrailways。Butitisnottobesupposedthatonthepartofthepublictherewasanygreatamountoffaiththendiscernible；andforsomeyearsthepioneershadgreatdifficulty，especiallyinthiscountry，inraisingmoneyfortheirearlymodestexperiments。OfthegeneralconditionsatthismomentFrankJ。SpraguesaysinanarticleintheCenturyMagazineofJuly，1905，onthecreationofthenewart：“Edisonwasperhapsnearerthevergeofgreatelectric-railwaypossibilitiesthananyotherAmerican。Inthefaceofmuchadversecriticismhehaddevelopedtheessentialsofthelow-internal-
resistancedynamowithhigh-resistancefield，andmanyoftheessentialfeaturesofmultiple-arcdistribution，andin1880hebuiltasmallroadathislaboratoryatMenloPark。“