Edisonhasalwaysbeendeeplyinterestedin“conservation，“andmuchofhisworkhasbeendirectedtowardtheeconomyoffuelinobtainingelectricalenergydirectlyfromtheconsumptionofcoal。Indeed，itwillbenotedthattheexampleofhishandwritingshowninthesevolumesdealswiththeimportanceofobtainingavailableenergydirectfromthecombustiblewithouttheenormouslossintheinterveningstagesthatmakesourbestmodernmethodsofsteamgenerationandutilizationsobarbarouslyextravagantandwasteful。Severalyearsago，experimentinginthisfield，Edisondevisedandoperatedsomeingeniouspyromagneticmotorsandgenerators，based，asthenameimplies，onthedirectapplicationofheattothemachines。ThemotorisfoundedupontheprinciplediscoveredbythefamousDr。WilliamGilbert——courtphysiciantoQueenElizabeth，andtheFatherofmodernelectricity——thatthemagneticpropertiesofirondiminishwithheat。Atalight-redheat，ironbecomesnon-magnetic，sothatastrongmagnetexertsnoinfluenceoverit。Edisonemployedthispeculiarpropertybyconstructingasmallmachineinwhichapivotedbarisalternatelyheatedandcooled。Itisthusattractedtowardanadjacentelectromagnetwhencoldandisuninfluencedwhenhot，andastheresultmotionisproduced。
Thepyromagneticgeneratorisbasedonthesamephenomenon；itsaimbeingofcoursetogenerateelectricalenergydirectlyfromtheheatofthecombustible。
Thearmature，ormovingpartofthemachine，consistsinrealityofeightseparatearmaturesallconstructedofcorrugatedsheetironcoveredwithasbestosandwoundwithwire。Thesearmaturesareheldinplacebytwocircularironplates，throughthecentreofwhichrunsashaft，carryingatitslowerextremityasemicircularshieldoffire-clay，whichcoverstheendsoffourofthearmatures。Theheat，ofwhateverorigin，isappliedfrombelow，andtheshaftbeingrevolved，fourofthearmatureslosetheirmagnetismconstantly，whiletheotherfourgainit，sotospeak。
Asthemovingpartrevolves，therefore，currentsofelectricityaresetupinthewiresofthearmaturesandarecollectedbyacommutator，asinanordinarydynamo，placedontheupperendofthecentralshaft。
AgreatvarietyofelectricalinstrumentsareincludedinEdison'sinventions，manyoftheseinfundamentalorearlierformsbeingdevisedforhissystemsoflightandpower，asnotedalready。Therearenumerousothers，anditmightbesaidwithtruththatEdisonishardlyeverwithoutsomenewdeviceofthiskindinhand，asheisbynomeanssatisfiedwiththepresentstatusofelectricalmeasurements。Heholdsingeneralthatthemetersofto-day，whetherforheavyorforfeeblecurrents，aretooexpensive，andthatcheaperinstrumentsareanecessityofthetimes。
Theseremarksapplymoreparticularlytowhatmaybetermed，ingeneral，circuitmeters。InotherclassesEdisonhasdevisedanexcellentformofmagneticbridge，beinganingeniousapplicationoftheprinciplesofthefamiliarWheatstonebridge，usedsoextensivelyformeasuringtheelectricalresistanceofwires；thetestingofironformagneticqualitiesbeingdeterminedbyitinthesameway。Anotherspecialinstrumentisa“deadbeat“galvanometerwhichdiffersfromtheordinaryformofgalvanometerinhavingnocoilsormagneticneedle。Itdependsforitsactionupontheheatingeffectofthecurrent，whichcausesafineplatinum-iridiumwireenclosedinaglasstubetoexpand；thusallowingacoiledspringtoactonapivotedshaftcarryingatinymirror。Themirrorasitmovesthrowsabeamoflightuponascaleandtheindicationsarereadbythespotoflight。Mostnovelofalltheapparatusofthismeasuringkindistheodoroscope，whichislikethetasimeterdescribedinanearlierchapter，exceptthatastripofgelatinetakestheplaceofhardrubber，asthesensitivemember。
Besidesbeingaffectedbyheat，thisdeviceisexceedinglysensitivetomoisture。Afewdropsofwaterorperfumethrownonthefloorofaroomaresufficienttogiveaverydecidedindicationonthegalvanometerincircuitwiththeinstrument。Barometers，hygrometers，andsimilarinstrumentsofgreatdelicacycanbeconstructedontheprincipleoftheodoroscope；
anditmayalsobeusedindeterminingthecharacterorpressureofgasesandvaporsinwhichithasbeenplaced。
InthelistofEdison'spatentsattheendofthisworkmaybenotedmanyotherofhismiscellaneousinventions，coveringitemssuchaspreservingfruitinvacuo，makingplate-glass，drawingwire，andmetallurgicalprocessesfortreatmentofnickel，gold，andcopperores；buttomentiontheseinventionsseparatelywouldtrespasstoomuchonourlimitedspacehere。Hence，weshallleavetheinterestedreadertoexaminethatlistforhimself。
FromfirsttolastEdisonhasfiledintheUnitedStatesPatentOffice——inadditiontomorethan1400applicationsforpatents——some120caveatsembracingnotlessthan1500inventions。A“caveat“isessentiallyanoticefiledbyaninventor，entitlinghimtoreceivewarningfromtheOfficeofanyapplicationforapatentforaninventionthatwould“interfere“withhisown，duringtheyear，whileheissupposedtobeperfectinghisdevice。Theoldcaveatsystemhasnowbeenabolished，butitservedtoelicitfromEdisonamostastoundingrecordofideasandpossibleinventionsuponwhichhewasworking，andmanyofwhichheofcoursereducedtopractice。AsanexampleofEdison'sfertilityandtheendlessvarietyofsubjectsengaginghisthoughts，thefollowinglistofmatterscoveredbyONEcaveatisgiven。Itisneedlesstosaythatallthecaveatsarenotquitesofullof“plums，“butthisiscertainlyawonder。
Forty-onedistinctinventionsrelatingtothephonograph，coveringvariousformsofrecorders，arrangementofparts，makingofrecords，shavingtool，adjustments，etc。
Eightformsofelectriclampsusinginfusibleearthyoxidesandbroughttohighincandescenceinvacuobyhighpotentialcurrentofseveralthousandvolts；samecharacterasimpingementofX-raysonobjectinbulb。
Aloud-speakingtelephonewithquartzcylinderandbeamofultra-violetlight。
Fourformsofarclightwithspecialcarbons。
Athermostaticmotor。
Adeviceforsealingtogethertheinsidepartandbulbofanincandescentlampmechanically。
Regulatorsfordynamosandmotors。
Threedevicesforutilizingvibrationsbeyondtheultraviolet。
Agreatvarietyofmethodsforcoatingincandescentlampfilamentswithsilicon，titanium，chromium，osmium，boron，etc。
Severalmethodsofmakingporousfilaments。
Severalmethodsofmakingsquirtedfilamentsofavarietyofmaterials，ofwhichaboutthirtyarespecified。
Seventeendifferentmethodsanddevicesforseparatingmagneticores。
Acontinuouslyoperativeprimarybattery。
AmusicalinstrumentoperatingoneofHelmholtz'sartificiallarynxes。
Asirenworkedbyexplosionofsmallquantitiesofoxygenandhydrogenmixed。
Threeothersirensmadetogivevocalsoundsorarticulatespeech。
Adeviceforprojectingsound-wavestoadistancewithoutspreadingandinastraightline，ontheprincipleofsmokerings。
Adeviceforcontinuouslyindicatingonagalvanometerthedepthsoftheocean。
Amethodofpreventinginagreatmeasurefrictionofwateragainstthehullofashipandincidentallypreventingfoulingbybarnacles。
Atelephonereceiverwherebythevibrationsofthediaphragmareconsiderablyamplified。
Twomethodsof“space“telegraphyatsea。
Animprovedandextendedstringtelephone。
Devicesandmethodoftalkingthroughwaterforconsiderabledistances。
Anaudiphonefordeafpeople。
Sound-bridgeformeasuringresistanceoftubesandothermaterialsforconveyingsound。
Amethodoftestingamagnettoascertaintheexistenceofflawsintheironorsteelcomposingthesame。
Methodofdistillingliquidsbyincandescentconductorimmersedintheliquid。
Methodofobtainingelectricitydirectfromcoal。
Anengineoperatedbysteamproducedbythehydrationanddehydrationofmetallicsalts。
Deviceandmethodfortelegraphingphotographically。
Carboncruciblekeptbrilliantlyincandescentbycurrentinvacuo，forobtainingreactionwithrefractorymetals。
Deviceforexaminingcombinationsofodorsandtheirchangesbyrotationatdifferentspeeds。
FromoneoftheprecedingitemsitwillbenotedthatevenintheeightiesEdisonperceivedmuchadvantagetobegainedinthelineofeconomybytheuseoflampfilamentsemployingrefractorymetalsintheirconstruction。Fromanothercaveat，filedin1889，weextractthefollowing，whichshowsthatherealizedthevalueoftungstenalsoforthispurpose。“Filamentsofcarbonplacedinacombustiontubewithalittlechlorideammonium。Chloridetungstenortitaniumpassedthroughhottube，depositingafilmofmetalonthecarbon；orfilamentsofzirconiaoxide，oraluminaormagnesia，thoriaorotherinfusibleoxidesmixedorseparate，andobtainedbymoisteningandsquirtingthroughadie，arethuscoatedwithabovemetalsandusedforincandescentlamps。Osmiumfromavolatilecompoundofsamethusdepositedmakesafilamentasgoodascarbonwheninvacuo。“
In1888，longbeforetherearosetheactualnecessityofduplicatingphonographrecordssoastoproducereplicasingreatnumbers，Edisondescribedinoneofhiscaveatsamethodandprocessmuchsimilartotheonewhichwasputintopracticebyhiminlateryears。
Inthesamecaveathedescribesaninventionwherebythepowertoindentonaphonographcylinder，insteadofcomingdirectlyfromthevoice，iscausedbypowerderivedfromtherotationormovementofthephonogramsurfaceitself。Hedidnot，however，followupthisinventionandputitintopractice。Sometwentyyearslateritwasindependentlyinventedandpatentedbyanotherinventor。Afurtherinstanceofthiskindisamethodoftelegraphyatseabymeansofadiaphragminaclosedport-holeflushwiththesideofthevessel，andactuatedbyasteam-whistlewhichiscontrolledbyalever，similarlytoaMorsekey。Areceivingdiaphragmisplacedinanotherandnear-bychamber，whichisprovidedwithverysensitivestethoscopicear-pieces，bywhichtheMorsecharacterssentfromanothervesselmaybereceived。Thiswasalsoinventedlaterbyanotherinventor，andisinuseto-day，butwillnaturallyberivalledbywirelesstelegraphy。
StillanotherinstanceisseeninoneofEdison'scaveats，wherehedescribesamethodofdistillingliquidsbymeansofinternallyappliedheatthroughelectricconductors。AlthoughEdisondidnotfollowuptheideaandtakeoutapatent，thissystemofdistillationwaslaterhituponbyothersandisinuseatthepresenttime。
IntheforegoingpagesofthischaptertheauthorshaveendeavoredtopresentverybrieflyasketchynotionoftheastoundingrangeofEdison'spracticalideas，buttheyfeelasenseofimpotenceinbeingunabletodealadequatelywiththesubjectinthespacethatcanbedevotedtoit。Tothosewho，liketheauthors，havehadtheprivilegeofexaminingthevoluminousrecordswhichshowtheflightsofhisimagination，therecomesafeelingofutterinadequacytoconveytoothersthefullextentofthestorytheyreveal。
Thefewspecificinstancesaboverelated，althoughnotrepresentingatitheofEdison'swork，willprobablybesufficienttoenablethereadertoappreciatetosomeextenthisgreatwealthofideasandfertilityofimagination，andalsotorealizethatthisimaginationisnotonlyintenselypractical，butthatitworkspropheticallyalonglinesofnaturalprogress。
CHAPTERXXIV
EDISON'SMETHODININVENTING
WHILEtheworld'sprogressdependslargelyupontheiringenuity，inventorsarenotusuallypersonswhohaveadoptedinventionasadistinctprofession，but，generallyspeaking，areotherwiseengagedinvariouswalksoflife。Byreasonofmoreorlessinherentnativegeniustheyeithermakeimprovementsalonglinesofpresentoccupation，orelseevolvenewmethodsandmeansofaccomplishingresultsinfieldsforwhichtheymayhavepersonalpredilections。
Nowandthen，however，therearisesamansogreatlyendowedwithnaturalpowersandoriginalitythatthecreativefacultywithinhimistoostrongtoendurethehumdrumroutineofaffairs，andmanifestsitselfinalifedevotedentirelytotheevolutionofmethodsanddevicescalculatedtofurthertheworld'swelfare。Inotherwords，hebecomesaninventorbyprofession。SuchamanisEdison。Notwithstandingthefactthatnearlyfortyyearsagonotagreatwhileafterhehademergedfromtheranksofperipatetictelegraphoperatorshewastheownerofalargeandprofitablebusinessasamanufacturerofthetelegraphicapparatusinventedbyhim，thecallofhisnaturewastoostrongtoallowofprofitsbeinglaidawayinthebanktoaccumulate。Ashehimselfhassaid，hehas“toosanguineatemperamenttoallowmoneytostayinsolitaryconfinement。“Hence，allsuperfluouscashwasdevotedtoexperimentation。Inthecourseofyearshegrewmoreandmoreimpatientoftheshacklesthatboundhimtobusinessroutine，and，realizingthepowerswithinhim，hedrewawaygraduallyfrompurelymanufacturingoccupations，determiningdeliberatelytodevotehislifetoinventivework，andtodependuponitsresultsasameansofsubsistence。
Allpersonswhomakeinventionswillnecessarilybemoreorlessoriginalincharacter，buttothemanwhochoosestobecomeaninventorbyprofessionmustbeconcededamindmorethanordinarilyrepletewithvirilityandoriginality。ThatthesequalitiesinEdisonaresuperabundantiswellknowntoallwhohaveworkedwithhim，and，indeed，areapparenttoeveryonefromhismultipliedachievementswithintheperiodofonegeneration。
IfonewereallowedonlytwowordswithwhichtodescribeEdison，itisdoubtfulwhetheracloseexaminationoftheentiredictionarywoulddiscloseanyothersmoresuitablethan“experimenter——inventor。“
Thesewouldexpresstheoverrulingcharacteristicsofhiseventfulcareer。Itisasan“inventor“thathesetshimselfdowninthemembershiplistoftheAmericanInstituteofElectricalEngineers。Toattemptthestrictplacingofthesewordsinrelationtoeachotherexceptalphabeticallywouldbeequaltoanendeavortosolvetheoldproblemastowhichcamefirst，theeggorthechicken；foralthoughallhisinventionshavebeenevolvedthroughexperiment，manyofhisnotableexperimentshavecalledforththeexerciseofhighlyinventivefacultiesintheirveryinception。Investigationandexperimenthavebeenaconsumingpassion，animpellingforcefromwithin，asitwere，fromhispetticoatdayswhenhecollectedgoose-eggsandtriedtohatchthemoutbysittingoverthemhimself。Onemightbeinclinedtodismissthistrivialincidentsmilingly，asamerechildish，thoughtlessprank，hadnotsubsequentdevelopmentasachild，boy，andmanrevealedaborninvestigatorwithoriginalreasoningpowersthat，disdainingcrooksandbends，alwaysaimedatthecentre，and，liketheflightofthebee，wereaccurateanddirect。
Itisnotsurprising，therefore，thatamanofthiskindshouldexhibitaceaseless，absorbingdesireforknowledge，andanapparentlyuncontrollabletendencytoexperimentoneverypossibleoccasion，eventhoughhislastcentwerespentinthussatisfyingtheinsatiatecravingsofaninquiringmind。
DuringEdison'simmatureyears，whenhewasflittingaboutfromplacetoplaceasatelegraphoperator，hisexperimentationwasofadesultory，hand-to-mouthcharacter，althoughitwasalwaysnotablefororiginality，asexpressedinanumberofminorusefuldevicesproducedduringthisperiod。
Smallwonder，then，thatattheendofthesewanderings，whenhehadfoundaplaceto“restthesoleofhisfoot，“heestablishedalaboratoryinwhichtocarryonhisresearchesinamoremethodicalandpracticalmanner。Inthiswasthebeginningoftheworkwhichhassincemadesuchaprofoundimpressiononcontemporarylife。
Thereisnothingofthehelter-skelter，slap-dashstyleinEdison'sexperiments。Althoughallthelaboratoryexperimentersagreeintheopinionthathe“trieseverything，“itisnotmerelythemixingofalittleofthis，someofthat，andafewdropsoftheother，intheHOPEthatSOMETHINGwillcomeofit。
Noristhespiritofthelaboratoryworkrepresentedinthefollowingdialogueoverheardbetweentwoallegedcarpenterspickedupatrandomtohelponahurryjob。
“Howneardoesshefit，Mike？”
“Aboutaninch。“
“Nailher！”
Amostcasualexaminationofanyofthelaboratoryrecordswillrevealevidenceoftheminutestexactitudeinsistedonintheconductofexperiments，irrespectiveofthelengthoftimetheyoccupied。Edison'sinstructions，alwaysclearcutanddirect，followedbyhiskeenoversight，admitofnothinglessthanimplicitobservanceinalldetails，nomatterwheretheymaylead，andimpeltotheutmostminutenessandaccuracy。
TosomeextenttherehasbeenapopularnotionthatmanyofEdison'ssuccesseshavebeenduetomeredumbfoolluck——toblind，fortuitous“happenings。“
Nothingcouldbefurtherfromthetruth，for，onthecontrary，itisowingalmostentirelytothecomprehensivescopeofhisknowledge，thebreadthofhisconception，thedaringoriginalityofhismethods，andminutenessandextentofexperiment，com-
binedwithunwaveringpertinacity，thatnewartshavebeencreatedandadditionsmadetoothersalreadyinexistence。Indeed，withoutthistirelessminutiae，andmethodical，searchingspirit，itwouldhavebeenpracticallyimpossibletohaveproducedmanyofthemostimportantoftheseinventions。
Needlesstosay，masteryofitsliteratureisregardedbyhimasamostimportantpreliminaryintakingupanylineofinvestigation。Whatothersmayhavedone，bearingdirectlyorcollaterallyonthesubject，inprint，iscarefullyconsideredandsiftedtothepointofexhaustion。Notthathetakesitforgrantedthattheconclusionsarecorrect，forhefrequentlyobtainsvastlydifferentresultsbyrepeatinginhisownwayexperimentsmadebyothersasdetailedinbooks。
“Edisoncantravelalongawell-usedroadandstillfindvirginsoil，“remarkedrecentlyoneofhismostpracticalexperimenters，whohadbeenworkingalongacertainlinewithoutattainingthedesiredresult。
“Hewantedtogetaparticularcompoundhavingdefinitequalities，andIhadtriedinallsortsofwaystoproduceitbutwithonlypartialsuccess。Hewasconfidentthatitcouldbedone，andsaidhewouldtryithimself。IndoingsohefollowedthesamepathinwhichIhadtravelled，but，bymakinganundreamed-ofchangeinoneoftheoperations，succeededinproducingacompoundthatvirtuallycameuptohisspecifications。ItisnottheonlytimeIhaveknownthissortofthingtohappen。“
InspeakingofEdison'smethodofexperimenting，anotherofhislaboratorystaffsays：“Heisneverhinderedbytheory，butresortstoactualexperimentforproof。Forinstance，whenheconceivedtheideaofpouringacompleteconcretehouseitwasuniversallyheldthatitwouldbeimpossiblebecausethepiecesofstoneinthemixturewouldnotrisetothelevelofthepouring-point，butwouldgravitatetoalowerplaneinthesoftcement。This，however，didnothinderhimfrommakingaseriesofexperimentswhichresultedinaninventionthatprovedconclusivelythecontrary。“
Havingconceivedsomenewideaandreadeverythingobtainablerelatingtothesubjectingeneral，Edison'sfertilityofresourceandoriginalitycomeintoplay。Takingoneofthelaboratorynote-books，hewillwriteinitamemorandumoftheexperimentstobetried，illustrated，ifnecessary，bysketches。Thisbookisthenpassedontothatmemberoftheexperimentalstaffwhosespecialtrainingandexperiencearebestadaptedtothework。Herestrenuousnessisexpected；andanimmediatecommencementofinvestigationandpromptreportarerequired。Sometimesthesubjectmaybesuchastocallforalonglineoffrequenttestswhichnecessitatepatientandaccurateattentiontominutedetails。Resultsmustbereportedoften——daily，orpossiblywithstillgreaterfrequency。Edisondoesnotforgetwhatisgoingon；
butinhisdailytoursthroughthelaboratorykeepsintouchwithalltheworkthatisunderthehandsofhisvariousassistants，showingbyaninstantgraspofthepresentconditionsofanyexperimentthathehasafullconsciousnessofitsmeaninganditsreferencetohisoriginalconception。
Theyear1869sawthebeginningofEdison'scareerasanacknowledgedinventorofcommercialdevices。
Fromtheoutset，aninnaterecognitionofsystemdictatedthedesirabilityandwisdomofpreservingrecordsofhisexperimentsandinventions。Theprimitiverecords，coveringtheearliestyears，weremainlyjotteddownonloosesheetsofpapercoveredwithsketches，notes，anddata，pastedintolargescrap-
books，orpreservedinpackages；butwiththepassingofyearsandenlargementofhisinterests，itbecamethepracticetomakealloriginallaboratorynotesinlarge，uniformbooks。ThiscoursewaspursueduntiltheMenloParkperiod，whenheinstitutedanewregimethathasbeencontinueddowntothepresentday。Astandardformofnote-book，abouteightandahalfbysixinches，containingabouttwohundredpages，wasadopted。Anumberofthesebookswereandarenowalwaystobefoundscatteredaroundinthedifferentsectionsofthelaboratory，andinthemhavebeennotedbyEdisonallhisideas，sketches，andmemoranda。Detailsofthevariousexperimentsconcerningthemhavebeensetdownbyhisassistantsfromtimetotime。
Theselaterlaboratorynote-books，ofwhichtherearenowoveronethousandintheseries，areeloquentinthehistorytheyrevealofthestrenuouslaborsofEdisonandhisassistantsandthevastfieldsofresearchhehascoveredduringthelastthirtyyears。
Theyareoverwhelminglyrichinbiographicmaterial，butanalysiswouldbeaprohibitivetaskforoneperson，andperhapsinterestingonlytotechnicalreaders。
Theirpagescoverpracticallyeverydepartmentofscience。ThecountlessthousandsofseparateexperimentsrecordedexhibittheoperationsofamastermindseekingtosurpriseNatureintoabetrayalofhersecretsbyaskingherthesamequestioninahundreddifferentways。Forinstance，whenEdisonwasinvestigatingacertainproblemofimportancemanyyearsago，thenote-booksshowthatonthispointaloneaboutfifteenthousandexperimentsandtestsweremadebyoneofhisassistants。
Amostcasualglanceoverthesenote-bookswillillustratethefollowingremark，whichwasmadetooneofthewritersnotlongagobyamemberofthelaboratorystaffwhohasbeenexperimentingtherefortwentyyears：“EdisoncanthinkofmorewaysofdoingathingthananymanIeversaworheardof。Hetrieseverythingandneverletsup，eventhoughfailureisapparentlystaringhimintheface。
Heonlystopswhenhesimplycan'tgoanyfurtheronthatparticularline。Whenhedecidesonanymodeofprocedurehegiveshisnotestotheexperimenterandletshimalone，onlysteppinginfromtimetotimetolookattheoperationsandreceivereportsofprogress。“
Thehistoryofthedevelopmentofthetelephonetransmitter，phonograph，incandescentlamp，dynamo，electricaldistributingsystemsfromcentralstations，electricrailway，ore-milling，cement，motionpictures，andahostofminorinventionsmaybefoundembeddedinthelaboratorynote-books。Apassingglanceatafewpagesofthesewrittenrecordswillservetoillustrate，thoughonlytoalimitedextent，thethoroughnessofEdison'smethod。Itistobeobservedthatthesereferencescanbebutofthemostmeagrekind，andmustberegardedasmerelythrowingaside-lightonthesubjectitself。Forinstance，thecomplexproblemofapracticaltelephonetransmittergaverisetoaseriesofmostexhaustiveexperiments。
Combinationsinalmostinfinitevariety，includinggums，chemicalcompounds，oils，minerals，andmetalsweresuggestedbyEdison；andhisassistantsweregivenlonglistsofmaterialstotrywithreferencetopredeterminedstandardsofarticulation，degreesofloudness，andperfectionofhissingsounds。
Thenote-bookscontainhundredsofpagesshowingthatagreatmanythousandsofexperimentsweretriedandpassedupon。Suchremarksas“N。G。“；
“Prettygood“；“Whistlinggood，butnoarticulation“；
“Rattly“；“Articulation，whispering，andwhistlinggood“；“Bestto-nightsofar“；andothersarenotedoppositethevariouscombinationsastheyweretried。Thus，onemayfollowtheinvestigationthroughamazeofexperimentswhichleduptothesuccessfulinventionofthecarbonbuttontransmitter，thevitaldevicetogivethetelephoneitsneededarticulationandperfection。
Thetwohundredandoddnote-books，coveringthestrenuousperiodduringwhichEdisonwascarryingonhiselectric-lightexperiments，tellontheirfortythousandpagesormoreafascinatingstoryoftheevolutionofanewartinitsentirety。Fromthecrudebeginnings，throughallthevariedphasesofthisevolution，theoperationsofamastermindareapparentfromthecontentsofthesepages，inwhicharerecordedtheinnumerableexperiments，calculations，andteststhatultimatelybroughtlightoutofdarkness。
Theearlyworkonametallicconductorforlampsgaverisetosomeverythoroughresearchonmeltingandalloyingmetals，thepreparationofmetallicoxides，thecoatingoffinewiresbyimmersingtheminagreatvarietyofchemicalsolutions。Followinghisusualcustom，Edisonwouldindicatethelinesofexperimenttobefollowed，whichwerecarriedoutandrecordedinthenote-books。Hehimself，inJanuary，1879，madepersonallyamostminuteandsearchinginvestigationintothepropertiesandbehaviorofplating-iridium，boron，rutile，zircon，chromium，molybdenum，andnickel，undervaryingdegreesofcurrentstrength，onwhichtheremaybefoundinthenotesaboutfortypagesofdetailedexperimentsanddeductionsinhisownhandwriting，concludingwiththeremarkaboutnickel：“Thisisagreatdiscoveryforelectriclightinthewayofeconomy。“
Thisperiodofresearchonnickel，etc。，wasevidentlyatryingone，forafternearlyamonth'scloseapplicationhewrites，onJanuary27，1879：“Owingtotheenormouspowerofthelightmyeyescommencedtopainaftersevenhours'work，andIhadtoquit。“Onthenextdayappearsthefollowingentry：“Sufferedthepainsofhellwithmyeyeslastnightfrom10P。M。till4A。M。，whengottosleepwithabigdoseofmorphine。Eyesgettingbetter，anddonotpainmuchat4P。M。；butIloseto-day。“
The“tryeverything“spiritofEdison'smethodiswellillustratedinthisearlyperiodbyaseriesofaboutsixteenhundredresistancetestsofvariousores，minerals，earths，etc。，occupyingoverfiftypagesofoneofthenote-booksrelatingtothemetallicfilamentforhislamps。
But，asthereaderhasalreadylearned，themetallicfilamentwassoonlaidasideinfavorofcarbon，andwefindinthelaboratorynotesanamazingrecordofresearchandexperimentconductedintheminuteandsearchingmannerpeculiartoEdison'smethod。
Hisinquiriesweredirectedalongallthevariousroadsleadingtothedesiredgoal，forlongbeforehehadcompletedtheinventionofapracticallampherealizedbroadlythefundamentalrequirementsofasuccessfulsystemofelectricaldistribution，andhadgiveninstructionsforthemakingofagreatvarietyofcalculationswhich，althoughfarinadvanceofthetime，wereclearlyforeseenbyhimtobevitallyimportantintheultimatesolutionofthecomplicatedproblem。Thuswefindmanyhundredsofpagesofthenote-bookscoveredwithcomputationsandcalculationsbyMr。Upton，notonlyonthenumerousramificationsoftheprojectedsystemandcomparisonswithgas，butalsoonproposedformsofdynamosandtheproposedstationinNewYork。A
mererecitalbytitlesofthevastnumberofexperimentsandtestsoncarbons，lamps，dynamos，armatures，commutators，windings，systems，regulators，sockets，vacuum-pumps，andthethousandandonedetailsrelatingtothesubjectingeneral，originatedbyEdison，andmethodicallyandsystematicallycarriedonunderhisgeneraldirection，wouldfillagreatmanypageshere，andeventhenwouldserveonlytoconveyaconfusedimpressionofceaselessprobing。
Itispossibleonlytoabroad，comprehensivemindwellstoredwithknowledge，andbackedwithresistless，boundlessenergy，thatsuchadiversifiedseriesofexperimentsandinvestigationscouldbecarriedonsimultaneouslyandassimilated，eventhoughtheyshouldrelatetoaclassofphenomenaalreadyunderstoodandwelldefined。Butifwepausetoconsiderthatthecommercialsubdivisionoftheelectriccurrentwhichwasvirtuallyaninventionmadetoorder
involvedthesolutionofproblemssounprecedentedthateventheythemselveshadtobecreated，wecannotbutconcludethattheafflatusofinnategeniusplayedanimportantpartintheuniquemethodsofinvestigationinstitutedbyEdisonatthatandothertimes。
Theideaofattributinggreatsuccessesto“genius“
hasalwaysbeenrepudiatedbyEdison，asevidencedbyhishistoricremarkthat“Geniusis1percent。
inspirationand99percent。perspiration。“Again，inaconversationmanyyearsagoatthelaboratorybetweenEdison，Batchelor，andE。H。Johnson，thelattermadeallusiontoEdison'sgeniusasevidencedbysomeofhisachievements，whenEdisonreplied：
“Stuff！Itellyougeniusishardwork，stick-to-it-
iveness，andcommonsense。“
“Yes，“saidJohnson，“Iadmitthereisallthattoit，butthere'sstillmore。BatchandIhavethosequalifications，butalthoughweknewquitealotabouttelephones，andworkedhard，wecouldn'tinventabrand-newnon-infringingtelephonereceiverasyoudidwhenGouraudcabledforone。Then，howaboutthesubdivisionoftheelectriclight？”
“Electriccurrent，“correctedEdison。
“True，“continuedJohnson；“youweretheonetomakethatverydistinction。Thescientificworldhadbeenworkinghardonsubdivisionforyears，usingwhatappearedtobecommonsense。Resultsworsethannil。Thenyoucomealong，andaboutthefirstthingyoudo，afterlookingthegroundover，istostartoffintheoppositedirection，whichsubsequentlyprovestobetheonlypossiblewaytoreachthegoal。Itseemstomethatthisisprettyclosetothedictionarydefinitionofgenius。“
ItissaidthatEdisonrepliedratherincoherentlyandchangedthetopicofconversation。
Thisinnatemodesty，however，doesnotpreventEdisonfromrecognizingandclassifyinghisownmethodsofinvestigation。InaconversationwithtwooldassociatesrecentlyApril，1909，heremarked：
“Ithasbeensaidofmethatmymethodsareempirical。
Thatistrueonlysofaraschemistryisconcerned。
Didyoueverrealizethatpracticallyallindustrialchemistryiscolloidalinitsnature？Hardrubber，celluloid，glass，soap，paper，andlotsofothers，allhavetodealwithamorphoussubstances，astowhichcomparativelylittlehasbeenreallysettled。
MymethodsaresimilartothosefollowedbyLutherBurbank。Heplantsanacre，andwhenthisisinbloomheinspectsit。Hehasasharpeye，andcanpickoutofthousandsasingleplantthathaspromiseofwhathewants。Fromthishegetstheseed，anduseshisskillandknowledgeinproducingfromitanumberofnewplantswhich，ondevelopment，furnishthemeansofpropagatinganimprovedvarietyinlargequantity。So，whenIamafterachemicalresultthatIhaveinmind，Imaymakehundredsorthousandsofexperimentsoutofwhichtheremaybeonethatpromisesresultsintherightdirection。ThisIfollowuptoitslegitimateconclusion，discardingtheothers，andusuallygetwhatIamafter。Thereisnodoubtaboutthisbeingempirical；butwhenitcomestoproblemsofamechanicalnature，IwanttotellyouthatallI'veevertackledandsolvedhavebeendonebyhard，logicalthinking。“Theintenseearnestnessandemphasiswithwhichthiswassaidwereveryimpressivetotheauditors。Thisempiricalmethodmayperhapsbebetterillustratedbyaspecificexample。Duringthelatterpartofthestoragebatteryinvestigations，aftertheformofpositiveelementhadbeendeterminedupon，itbecamenecessarytoascertainwhatdefiniteproportionsandwhatqualityofnickelhydrateandnickelflakewouldgivethebestresults。Aseriesofpositivetubeswerefilledwiththetwomaterialsindifferentproportions——say，ninepartshydratetooneofflake；eightpartshydratetotwoofflake；sevenpartshydratetothreeofflake，andsoonthroughvaryingproportions。Threesetsofeachofthesepositivesweremade，andallputintoseparatetesttubeswithauniformtypeofnegativeelement。Thesewerecarriedthroughalongseriesofchargesanddischargesunderstricttestconditions。
Fromthetabulatedresultsofhundredsofteststherewereselectedthreethatshowedthebestresults。
These，however，showedonlythesuperiorityofcer-
tainPROPORTIONSofthematerials。ThenextstepwouldbetofindoutthebestQUALITY。Now，asthereareseveralhundredvariationsinthequalityofnickelflake，andperhapsathousandwaystomakethehydrate，itwillberealizedthatEdison'smethodsledtostupendousdetail，forthesetestsembracedatrialofallthequalitiesofbothmaterialsinthethreeproportionsfoundtobemostsuitable。Amongthesemanythousandsofexperimentsanythatshowedextraordinaryresultswereagainelaboratedbystillfurtherseriesoftests，untilEdisonwassatisfiedthathehadobtainedthebestresultinthatparticularline。
Thelaboratorynote-booksdonotalwaystellthewholestoryormeaningofanexperimentthatmaybebrieflyoutlinedononeoftheirpages。Forexample，theearlyfilamentmadeofamixtureoflampblackandtarismerelyasuggestioninthenotes，butitsmakingaffordedanexampleofEdison'spertinacity。Thesematerials，whenmixed，becameafriablemass，whichhehadfoundcouldbebroughtintosuchacohesive，putty-likestatebymanipulation，astobecapableofbeingrolledoutintofilamentsasfineasseven-thousandthsofaninchincross-section。
Oneofthelaboratoryassistantswastoldtomakesomeofthismixture，kneadit，androllsomefilaments。
AfteratimehebroughtthemasstoEdison，andsaid：
“There'ssomethingwrongaboutthis，foritcrumblesevenaftermanipulatingitwithmyfingers。“
“Howlongdidyoukneadit？”saidEdison。
“Oh！morethananhour，“repliedtheassistant。
“Well，justkeeponforafewhoursmoreanditwillcomeoutallright，“wastherejoinder。Andthisprovedtobecorrect，for，afteraprolongedkneadingandrolling，themasschangedintoacohesive，stringy，homogeneousputty。Itwasfromamixtureofthiskindthatspiralfilamentsweremadeandusedinsomeoftheearliestformsofsuccessfulincandescentlamps；indeed，theyaredescribedandillustratedinEdison'sfundamentallamppatentNo。223，898。
Thepresentnarrativewouldassumetheproportionsofahistoryoftheincandescentlamp，shouldtheauthorsattempttofollowEdison'sinvestigationsthroughthethousandsofpagesofnote-booksawaybackintheeightiesandearlynineties。Improvementofthelampwasconstantlyinhismindallthoseyears，andbesidesthevastamountofdetailexperimentalworkhelaidoutforhisassistants，hecarriedonagreatdealofresearchpersonally。Sometimeswholebooksarefilledinhisownhandwritingwithrecordsofexperimentsshowingeveryconceivablevariationofsomeparticularlineofinquiry；eachtrialbearingsometersecommentexpressiveofresults。InonebookappearthedetailsofoneoftheseexperimentsonSeptember3，1891，at4。30A。M。，withthecomment：
“Broughtuplamphigherthana16-c。p。240waseverbroughtbefore——Hurrah！”Notwithstandingthelatehour，heturnsovertothenextpageandgoesontowritehisdeductionsfromthisresultascomparedwiththosepreviouslyobtained。Proceedingdaybyday，asappearsbythissamebook，hefollowsupanotherlineofinvestigationonlamps，apparentlyfullofdifficulty，forafteronehundredandthirty-twootherrecordedexperimentswefindthisnote：“Saturday3。30wenthomedisgustedwithincandescentlamps。“Thisfeelingwasevidentlyevanescent，foronthesucceedingMondaytheworkwascontinuedandcarriedonbyhimaskeenlyasbefore，asshownbythenextbatchofnotes。
Thisistheonlyinstanceshowinganyindicationofimpatiencethattheauthorshavefoundinlookingthroughtheenormousmassoflaboratorynotes。AllhisassistantsagreethatEdisonisthemostpatient，tirelessexperimenterthatcouldbeconceivedof。
Failuresdonotdistresshim；indeed，heregardsthemasalwaysuseful，asmaybegatheredfromthefollowing，relatedbyDr。E。G。Acheson，formerlyoneofhisstaff：“IoncemadeanexperimentinEdison'slaboratoryatMenloParkduringthelatterpartof1880，andtheresultswerenotaslookedfor。I
consideredtheexperimentaperfectfailure，andwhilebemoaningtheresultsofthisapparentfailureMr。
Edisonentered，and，afterlearningthefactsofthecase，cheerfullyremarkedthatIshouldnotlookuponitasafailure，forheconsideredeveryexperimentasuccess，asinallcasesitcleareduptheatmosphere，andeventhoughitfailedtoaccomplishtheresultssoughtfor，itshouldproveavaluablelessonforguidanceinfuturework。IbelievethatMr。
Edison'ssuccessasanexperimenterwas，toalargeextent，duetothishappyviewofallexperiments。“
Edisonhasfrequentlyremarkedthatoutofahundredexperimentshedoesnotexpectmorethanonetobesuccessful，andastothatoneheisalwayssuspiciousuntilfrequentrepetitionhasverifiedtheoriginalresults。
Thispatient，optimisticviewoftheoutcomeofexperimentshasremainedpartofhischaracterdowntothisday，justashispainstaking，minute，incisivemethodsarestillunchanged。Buttothecareless，stupid，orlazypersonheisaterrorfortheshorttimetheyremainaroundhim。Honestmistakesmaybetolerated，butnotcarelessness，incompetence，orlackofattentiontobusiness。InsuchcasesEdisonisapttoexpresshimselffreelyandforcibly，aswhenhewasaskedwhyhehadpartedwithacertainman，hesaid：“Oh，hewassoslowthatitwouldtakehimhalfanhourtogetoutofthefieldofamicroscope。“
Anotherinstancewillbeillustrative。SoonaftertheBrocktonMassachusettscentralstationwasstartedinoperationmanyyearsago，hewroteanotetoMr。
W。S。Andrews，containingsuggestionsastofuturestations，partofwhichrelatedtothevariousemployeesandtheirduties。Afteroutliningthedutiesofthemeterman，Edisonsays：“Ishouldnottaketooyoungamanforthis，say，amanfromtwenty-
threetothirtyyearsold，brightandbusinesslike。
Don'twantanyonewhoyearnstoenteralaboratoryandexperiment。WehaveabadcaseofthatatBrockton；heneglectsbusinesstopotter。Whatwewantisagoodlampaverageandnounprofitablecustomer。Youshouldhavethesemenonprobationandsubjecttopassinganexaminationbyme。
Thiswillwakethemup。“
Edison'sexaminationsarenojoke，accordingtoMr。
J。H。Vail，formerlyoneoftheMenloParkstaff。“I
wantedajob，“hesaid，“andwasambitioustotakechargeofthedynamo-room。Mr。Edisonledmetoaheapofjunkinacornerandsaid：`Putthatto-
getherandletmeknowwhenit'srunning。'Ididn'tknowwhatitwas，butreceivedaliberaleducationinfindingout。Itprovedtobeadynamo，whichI
finallysucceededinassemblingandrunning。Igotthejob。“AnothermanwhosucceededinwinningaplaceasassistantwasMr。JohnF。Ott，whohasremainedinhisemployforoverfortyyears。In1869，whenEdisonwasoccupyinghisfirstmanufacturingshopthethirdfloorofasmallbuildinginNewark，hewantedafirst-classmechanician，andMr。Ottwassenttohim。“Hewasthenanordinary-lookingyoungfellow，“saysMr。Ott，“dirtyasanyoftheotherworkmen，unkempt，andnotmuchbetterdressedthanatramp，butIimmediatelyfeltthattherewasagreatdealinhim。“Thisistheconversationthatensued，ledbyMr。Edison'squestion：
“Whatdoyouwant？”
“Work。“
“Canyoumakethismachinework？”exhibitingitandexplainingitsdetails。
“Yes。“
“Areyousure？”
“Well，youneedn'tpaymeifIdon't。“
AndthusMr。Ottwenttoworkandsucceededinaccomplishingtheresultsdesired。TwoweeksafterwardMr。Edisonputhiminchargeoftheshop。
Edison'slifefairlyteemswithinstancesofunruffledpatienceinthepursuitofexperiments。Whenhefeelsthoroughlyimpressedwiththepossibilityofaccomplishingacertainthing，hewillsettledowncomposedlytoinvestigateittotheend。
Thisiswellillustratedinastoryrelatingtohisinventionofthetypeofstoragebatterybearinghisname。Mr。W。S。Mallory，oneofhisclosestassociatesformanyyears，istheauthorityforthefollowing：
“WhenMr。Edisondecidedtoshutdowntheore-
millingplantatEdison，NewJersey，inwhichIhadbeenassociatedwithhim，itbecameaproblemastowhathecouldprofitablytakeupnext，andwehadseveraldiscussionsaboutit。Hefinallythoughtthatagoodstoragebatterywasagreatrequisite，anddecidedtotryanddeviseanewtype，forhedeclaredemphaticallyhewouldmakenobatteryrequiringsulphuricacid。Afteralittlethoughtheconceivedthenickel-ironidea，andstartedtoworkatoncewithcharacteristicenergy。About7or7。30A。M。hewouldgodowntothelaboratoryandexperiment，onlystoppingforashorttimeatnoontoeatalunchsentdownfromthehouse。About6o'clockthecarriagewouldcalltotakehimtodinner，fromwhichhewouldreturnby7。30or8o'clocktoresumework。
Thecarriagecameagainatmidnighttotakehimhome，butfrequentlyhadtowaituntil2or3o'clock，andsometimesreturnwithouthim，ashehaddecidedtocontinueallnight。
“Thishadbeengoingonmorethanfivemonths，sevendaysaweek，whenIwascalleddowntothelaboratorytoseehim。Ifoundhimatabenchaboutthreefeetwideandtwelvetofifteenfeetlong，onwhichtherewerehundredsoflittletestcellsthathadbeenmadeupbyhiscorpsofchemistsandexperimenters。
Hewasseatedatthisbenchtesting，figuring，andplanning。Ithenlearnedthathehadthusmadeoverninethousandexperimentsintryingtodevisethisnewtypeofstoragebattery，buthadnotproducedasinglethingthatpromisedtosolvethequestion。
Inviewofthisimmenseamountofthoughtandlabor，mysympathygotthebetterofmyjudgment，andIsaid：`Isn'titashamethatwiththetremendousamountofworkyouhavedoneyouhaven'tbeenabletogetanyresults？'Edisonturnedonmelikeaflash，andwithasmilereplied：`Results！
Why，man，Ihavegottenalotofresults！Iknowseveralthousandthingsthatwon'twork。'
“AtthattimehesentmeoutWestonaspecialmission。Onmyreturn，afewweekslater，hisexperimentshadrunuptoovertenthousand，buthehaddiscoveredthemissinglinkinthecombinationsoughtfor。Ofcourse，weallrememberhowthebatterywascompletedandputonthemarket。
Then，becausehewasdissatisfiedwithit，hestoppedthesalesandcommencedanewlineofinvestigation，whichhasrecentlyculminatedsuccessfully。I
shouldn'twonderifhisexperimentsonthebatteryranupprettyneartofiftythousand，fortheyfillmorethanonehundredandfiftyofthenote-books，tosaynothingofsomethousandsoftestsincurvesheets。“
AlthoughEdisonhasanabsolutedisregardforthetotaloutlayofmoneyininvestigation，heisparticulartokeepdownthecostofindividualexperimentstoaminimum，for，asheobservedtooneofhisassistants：
“Agoodmanyinventorstrytodevelopthingslife-
size，andthusspendalltheirmoney，insteadoffirstexperimentingmorefreelyonasmallscale。“ToEdisonlifeisnotonlyagrandopportunitytofindoutthingsbyexperiment，but，whenfound，toimprovethembyfurtherexperiment。Onenight，afterreceivingasatisfactoryreportofprogressfromMr。
Mason，superintendentofthecementplant，hesaid：
“Theonlywaytokeepaheadoftheprocessionistoexperiment。Ifyoudon't，theotherfellowwill。
Whenthere'snoexperimentingthere'snoprogress。
Stopexperimentingandyougobackward。Ifanythinggoeswrong，experimentuntilyougettotheverybottomofthetrouble。“
Itiseasytorealize，therefore，thatacharactersothoroughlypermeatedwiththeseideasisnotapttostopandfigureoutexpensewheninhotpursuitofsomedesiredobject。Whenthatobjecthasbeenattained，however，anditpassesfromtheexperimentaltothecommercialstage，Edison'smonetaryviewsagaincomeintostrongplay，buttheytakeadiametricallyoppositeposition，forhethenbeginsimmediatelytoplantheextremeofeconomyintheproductionofthearticle。Athousandandoneinstancescouldbequotedinillustration；butastheywouldtendtochangetheformofthisnarrativeintoahistoryofeconomyinmanufacture，itwillsufficetomentionbutone，andthatarecentoccurrence，whichservestoillustratehowcloselyhekeepsintouchwitheverything，andalsohowtheinventivefacultyandinstinctofcommercialeconomyrunclosetogether。ItwasduringEdison'swinterstayinFlorida，inMarch，1909。Hehadreportssenttohimdailyfromvariousplaces，andstudiedthemcarefully，forhewouldwritefrequentlywithcomments，instructions，andsuggestions；andinonecase，commentingontheoilingsystematthecementplant，hewrote：“Youroillossesarenowgettinglower，Isee。“Then，aftersuggestingsomechangestoreducethemstillfurther，hewentontosay：
“Hereisachancetosaveamillperbarrelbasedonyourregulardailyoutput。“
ThisthoroughconsiderationofthesmallestdetailisessentiallycharacteristicofEdison，notonlyineconomyofmanufacture，butinallhiswork，nomatterofwhatkind，whetheritbeexperimenting，investigating，testing，orengineering。Tofollowhimthroughthelabyrinthinepathsofinvestigationcontainedinthegreatarrayoflaboratorynote-booksistobecomeinvolvedinamassofminutelydetailedsearcheswhichseektopenetratetheinmostrecessesofnaturebyanultimateanalysisofaninfinitevarietyofparts。Asthereaderwillobtainafullercomprehensionofthisidea，andofEdison'smethods，byconcreteillustrationratherthanbygeneralization，theauthorshavethoughtitwelltoselectatrandomtwotypicalinstancesofspecificinvestigationsoutofthethousandsthatarescatteredthroughthenotebooks。
Thesewillbefoundinthefollowingextractsfromoneofthenote-books，andconsistofEdison'sinstructionstobecarriedoutindetailbyhisexperimenters：
“Take，say，25lbs。hardCubanasphaltandseparateallthedifferenthydrocarbons，etc。，asfaraspossiblebymeansofsolvents。Itwillbenecessaryfirsttodissolveeverythingoutby，say，hotturpentine，thensuccessivelytreattheresiduewithbisulphidecarbon，benzol，ether，chloroform，naphtha，toluol，alcohol，andotherprobablesolvents。Afteryoucangonofurther，distiloffallthesolventssotheasphaltmaterialhasatar-likeconsistency。
Besurealltheashisoutoftheturpentineportion；now，afterdistillingtheturpentineoff，actontheresiduewithallthesolventsthatwereusedontheresidue，usingforthefirstthesolventwhichisleastlikelytodissolveagreatpartofit。Bythusmanipulatingthevarioussolventsyouwillbeenabledprobablytoseparatethecrudeasphaltintoseveraldistincthydrocarbons。Puteachinabottleafterithasbeendried，andlabelthebottlewiththeprocess，etc。，sowemaybeabletoduplicateit；alsogivebottleanumberanddescribeeverythingfullyinnote-book。“
“Destructivelydistilthefollowingsubstancesdowntoapointjustshortofcarbonization，sothattheresiduumcanbetakenoutoftheretort，powdered，andactedonbyallthesolventsjustastheasphaltinpreviouspage。
Thedistillationshouldbecarriedto，say，600degreesor700degreesFahr。，butnotcontinuedlongenoughtowhollyreducemasstocharcoal，butalwaysruntoblackness。Separatetheresiduuminasmanydefinitepartsaspossible，bottleandlabel，andkeepaccuraterecordsastoprocess，weights，etc。，soareproductionoftheexperimentcanatanytimebemade：Gelatine，4lbs。；asphalt，hardCuban，10lbs。；coal-tarorpitch，10lbs。；wood-pitch，10lbs。；Syrianasphalt，10lbs。；bituminouscoal，10lbs。；
cane-sugar，10lbs。；glucose，10lbs。；dextrine，10lbs。；
glycerine，10lbs。；tartaricacid，5lbs。；gumguiac，5lbs。；
gumamber，3lbs。；gumtragacanth，3Lbs。；anilinered，1lb。；anilineoil，1lb。；crudeanthracene，5lbs。；petroleumpitch，10lbs。；albumenfromeggs，2lbs。；tarfrompassingchlorinethroughanilineoil，2lbs。；citricacid，5lbs。；sawdustofboxwood，3lbs。；starch，5lbs。；shellac，3lbs。；gumArabic，5lbs。；castoroil，5lbs。“
Theempiricalnatureofhismethodwillbeapparentfromanexaminationoftheaboveitems；butinpur-
suingitheleavesalluncertaintybehindand，trustingnothingtotheory，heacquiresabsoluteknowledge。
Whatevermaybethementalprocessesbywhichhearrivesatthestarting-pointofanyspecificlineofresearch，thefinalresultsalmostinvariablyprovethathedoesnotplungeinatrandom；indeed，asanoldassociateremarked：“WhenEdisontakesupanypropositioninnaturalscience，hisperceptionsseemtobeelementallybroadandanalytical，thatistosay，inadditiontotheknowledgehehasacquiredfrombooksandobservation，heappearstohaveanintuitiveapprehensionofthegeneralorderofthings，astheymightbesupposedtoexistinnaturalrelationtoeachother。Ithasalwaysseemedtomethathegoestothecoreofthingsatonce。“
Althoughnothinglessthanresultsfromactualexperimentsareacceptabletohimasestablishedfacts，thisviewofEdisonmayalsoaccountforhispeculiarandsomewhatweirdabilityto“guess“correctly，afacultywhichhasfrequentlyenabledhimtotakeshortcutstolinesofinvestigationwhoseoutcomehasverifiedinamostremarkabledegreestatementsapparentlymadeoffhandandwithoutcalculation。
Mr。Uptonsays：“Oneofthemainimpressionsleftuponme，afterknowingMr。Edisonformanyyears，isthemarvellousaccuracyofhisguesses。Hewillseethegeneralnatureofaresultlongbeforeitcanbereachedbymathematicalcalculation。“Thiswassupplementedbyoneofhisengineeringstaff，whoremarked：“Mr。Edisoncanguessbetterthanagoodmanymencanfigure，andsofarasmyexperiencegoes，Ihavefoundthatheisalmostinvariablycorrect。Hisguessismorethanamerestarting-
point，andoftenturnsouttobethefinalsolutionofaproblem。Icanonlyaccountforitbyhisremarkableinsightandwonderfulnaturalsenseoftheproportionofthings，inadditiontowhichheseemstocarryinhisheaddeterminingfactorsofallkinds，andhastheabilitytoapplytheminstantlyinconsideringanymechanicalproblem。“
Whilethismysteriousintuitivepowerhasbeenofthegreatestadvantageinconnectionwiththevastnumberoftechnicalproblemsthathaveenteredintohislife-work，therehavebeenmanyremarkableinstancesinwhichithasseemedlittlelessthanprophecy，anditisdeemedworthwhiletodigresstotheextentofrelatingtwoofthem。Onedayinthesummerof1881，whentheincandescentlamp-industrywasstillinswaddlingclothes，EdisonwasseatedintheroomofMajorEaton，vice-presidentoftheEdisonElectricLightCompany，talkingoverbusinessmatters，whenMr。UptoncameinfromthelampfactoryatMenloPark，andsaid：“Well，Mr。Edison，wecompletedathousandlampsto-day。“Edisonlookedupandsaid“Good，“thenrelapsedintoathoughtfulmood。
Inabouttwominutesheraisedhishead，andsaid：
“Upton，infifteenyearsyouwillbemakingfortythousandlampsaday。“Noneofthosepresentventuredtomakeanyremarkonthisassertion，althoughallfeltthatitwasmerelyarandomguess，basedonthesanguinedreamofaninventor。Thebusinesshadnotthenreallymadeastart，andbeingentirelynewwaswithoutprecedentuponwhichtobaseanysuchstatement，but，asamatteroffact，therecordsofthelampfactoryshowthatin1896itsdailyoutputoflampswasactuallyaboutfortythousand。
TheotherinstancereferredtooccurredshortlyaftertheEdisonMachineWorkswasmoveduptoSchenectady，in1886。Oneday，whenhewasattheworks，Edisonsatdownandwroteonasheetofpaperfifteenseparatepredictionsofthegrowthandfutureoftheelectricalbusiness。Notwithstandingthefactthattheindustrywastheninanimmaturestate，andthatthegreatboomdidnotsetinuntilafewyearsafterward，twelveofthesepredictionshavebeenfullyverifiedbytheenormousgrowthanddevelopmentinallbranchesoftheart。
Whattheexplanationofthisgift，power，orintuitionmaybe，isperhapsbetterlefttothepsychologisttospeculateupon。IfoneweretoaskEdison，hewouldprobablysay，“Hardwork，nottoomuchsleep，andfreeuseoftheimagination。“Whetherornotitwouldbepossiblefortheaveragemortaltoarriveatsuchperfectionof“guessing“byfaithfullyfollowingthisformula，evenreinforcedbytheEdisonrecipeforstimulatingaslowimaginationwithpastry，isopenfordemonstration。
Somewhatalliedtothiscuriousfacultyisanothernolessremarkable，andthatis，theabilitytopointoutinstantlyanerrorinamassofreportedexperimentalresults。Whilemanyinstancescouldbedefinitelynamed，atypicalone，relatedbyMr。J。D。
Flack，formerlymastermechanicatthelampfactory，maybequoted：“Duringthemanyyearsoflampexperimentation，batchesoflampsweresenttothephotometerdepartmentfortest，andEdisonwouldexaminethetabulatedtestsheets。Heranovereveryitemofthetabulationsrapidly，and，apparentlywithoutanycalculationwhatever，wouldcheckofferrorsasfastashecametothem，saying：`Youhavemadeamistake；trythisoneover。'Ineverycasethesecondtestprovedthathewasright。Thiswonderfulaptitudeforinfalliblylocatinganerrorwithoutaninstant'shesitationformentalcalculation，hasalwaysappealedtomeveryforcibly。“
TheabilitytodetecterrorsquicklyinaseriesofexperimentsisoneofthethingsthathasenabledEdisontoaccomplishsuchavastamountofworkastherecordsshow。Examplesoftheminutenessofdetailintowhichhisresearchesextendhavealreadybeenmentioned，andastherearealwaysanumberofsuchinvestigationsinprogressatthelaboratory，thisabilitystandsEdisoningoodstead，forheisthusenabledtofollow，and，ifnecessary，correcteachonestepbystep。Inthisheisaidedbythegreatpowersofamindthatisabletofreeitselffromabsorbedconcentrationonthedetailsofoneproblem，andinstantlytoshiftoverandbecomedeeplyandintelligentlyconcentratedinanotherandentirelydifferentone。Forinstance，hemayhavebeenbusyforhoursonchemicalexperiments，andbecalleduponsuddenlytodeterminesomemechanicalquestions。
Thecompleteandeasytransitionistheconstantwonderofhisassociates，forthereisnoconfusionofideasresultingfromthesequickchanges，nohesitationorapparenteffort，butaplungeintothemidstofthenewsubject，andaninstantacquaint-
ancewithallitsdetails，asifhehadbeenstudyingitforhours。
Agoodstiffdifficulty——onewhichmay，perhaps，appeartobeanunsurmountableobstacle——onlyservestomakeEdisoncheerful，andbringsoutvariationsofhismethodsinexperimenting。Suchanoccurrencewillstarthimthinking，whichsoongivesrisetoalineofsuggestionsforapproachingthetroublefromvarioussides；orhewillsitdownandwriteoutaseriesofeliminations，additions，orchangestobeworkedoutandreportedupon，withsuchvariationsasmaysuggestthemselvesduringtheirprogress。Itisatsuchtimesasthesethathisunfailingpatienceandtremendousresourcefulnessareinevidence。Ideasandexpedientsarepouredforthinatorrent，andalthoughsomeofthemhavetemporarilyappearedtothestafftoberidiculousorirrelevant，theyhavefrequentlyturnedouttobetheonesleadingtoacorrectsolutionofthetrouble。
Edison'sinexhaustibleresourcefulnessandfertilityofideashavecontributedlargelytohisgreatsuccess，andhaveeverbeenacauseofamazementtothosearoundhim。Frequently，whenitwouldseemtoothersthattheextremeendofanapparentlyblindalleyhadbeenreached，andthatitwasimpossibletoproceedfurther，hehasshownthattherewereseveralwaysoutofit。Exampleswithoutnumbercouldbequoted，butonemustsufficebywayofillustration。Duringtheprogressoftheore-millingworkatEdison，itbecamedesirabletocarryonacertainoperationbysomespecialmachinery。Herequestedtheproperpersononhisengineeringstafftothinkthismatterupandsubmitafewsketchesofwhathewouldproposetodo。HebroughtthreedrawingstoEdison，whoexaminedthemandsaidnoneofthemwouldanswer。Theengineerremarkedthatitwastoobad，fortherewasnootherwaytodoit。Mr。Edisonturnedtohimquickly，andsaid：
“Doyoumeantosaythatthesedrawingsrepresenttheonlywaytodothiswork？”Towhichhereceivedthereply：“Icertainlydo。“Edisonsaidnothing。ThishappenedonaSaturday。HefollowedhisusualcustomofspendingSundayathomeinOrange。WhenhereturnedtotheworksonMondaymorning，hetookwithhimsketcheshehadmade，showingFORTY-EIGHTotherwaysofaccomplishingthedesiredoperation，andlaidthemontheengineer'sdeskwithoutaword。Subsequentlyoneoftheseideas，withmodificationssuggestedbysomeoftheothers，wasputintosuccessfulpractice。
DifficultiesseemtohaveapeculiarcharmforEdison，whethertheyrelatetolargeorsmallthings；
andalthoughthelargermattershavecontributedmosttothehistoryofthearts，thesamecarefulnessofthoughthasoftenbeenthemeansofleadingtoimprovementsofpermanentadvantageeveninminordetails。Forinstance，intheveryearliestdaysofelectriclighting，thesafeinsulationoftwobarewiresfastenedtogetherwasaseriousproblemthatwassolvedbyhim。Anironpotoverafire，someinsulatingmaterialmeltedtherein，andnarrowstripsoflinendrawnthroughitbymeansofawoodenclamp，furnishedareadilyappliedandadhesiveinsulation，whichwasjustasperfectforthepurposeastheregularandnowwell-knowninsulatingtape，ofwhichitwastheforerunner。
DubiousresultsarenottoleratedforamomentinEdison'sexperimentalwork。Ratherthanpassuponanuncertainty，theexperimentwillbedissectedandcheckedminutelyinordertoobtainabsoluteknowledge，proandcon。Thissearchingmethodisfollowednotonlyinchemicalorotherinvestigations，intowhichcomplexitiesmightnaturallyenter，butalsoinmoremechanicalquestions，wheresimplicityofconstructionmightnaturallyseemtoprecludepossibilitiesofuncertainty。Forinstance，atthetimewhenhewasmakingstrenuousendeavorstoobtaincopperwireofhighconductivity，strictlaboratorytestsweremadeofsamplessentbymanufacturers。Oneofthesesamplestestedoutpoorerthanapreviouslotfurnishedfromthesamefactory。
AreportofthistoEdisonbroughtthefollowingnote：“Perhapsthe——wirehadabadspotinit。
Pleasecutitupintolengthsandtesteachoneandsendresultstomeimmediately。“PossiblytheelectricalfraternitydoesnotrealizethatthisearnestworkofEdison，twenty-eightyearsago，resultedintheestablishmentofthehighqualityofcopperwirethathasbeentherecognizedstandardsincethattime。SaysEdisononthispoint：“IfurnishedtheexpertandapparatustotheAnsoniaBrassandCopperCompanyin1883，andheisthereyet。Itwasthisexpertandthiscompanywhopioneeredhigh-conductivitycopperfortheelectricaltrade。“
Norisitgenerallyappreciatedintheindustrythattheadoptionofwhatisnowregardedasamostob-
viousproposition——thehigh-economyincandescentlamp——wastheresultofthatcharacteristicforesightwhichtherehasbeenoccasiontomentionfrequentlyinthecourseofthisnarrative，togetherwiththecourageand“horse-sense“whichhavealwaysbeendisplayedbytheinventorinhispersistentpushingoutwithfar-reachingideas，inthefaceofpessimisticopinions。Asiswellknown，thelampsofthefirsttenortwelveyearsofincandescentlightingwereofloweconomy，buthadlonglife。Edison'sstudyofthesubjecthadledhimtotheconvictionthatthegreatestgrowthoftheelectric-lightingindustrywouldbefavoredbyalamptakinglesscurrent，buthavingshorter，thoughcommerciallyeconomicallife；
andaftergraduallymakingimprovementsalongthislinehedeveloped，finally，atypeofhigh-economylampwhichwouldintroduceamostradicalchangeinexistingconditions，andleadultimatelytohighlyadvantageousresults。Hisstartonthislamp，andanexpresseddesiretohaveitmanufacturedforregularuse，filledevensomeofhisbusinessassociateswithdismay，fortheycouldseenothingbutdisasteraheadinforcingsuchalamponthemarket。Hispersistenceandprofoundconvictionoftheultimateresultsweresostrongandhisargumentssosound，however，thatthecampaignwasenteredupon。
Althoughittooktwoorthreeyearstoconvincethepublicofthecorrectnessofhisviews，theideagraduallytookstrongroot，andhasnowbecomeanintegralprincipleofthebusiness。
InthisconnectionitmaybenotedthatwithremarkableprescienceEdisonsawthecomingofthemodernlampsofto-day，which，byreasonoftheirsmallconsumptionofenergytoproduceagivencandle-power，havedismayedcentral-stationmanagers。
Afewyearsagoaconsumptionof3。1wattspercandle-powermightsafelybeassumedasanexcellentaverage，andmanystationsfixedtheirratesandbusinessonsuchabasis。Theresultsonincomewhentheconsumption，asinthenewmetallic-
filamentlamps，dropsto1。25wattspercandlecanreadilybeimagined。Edisonhasinsistedthatcentralstationsaresellinglightandnotcurrent；andhepointstothepredicamentnowconfrontingthemastruthofhisassertionthatwhensellinglighttheyshareinallthebenefitsofimprovement，butthatwhentheysellcurrenttheconsumergetsallthosebenefitswithoutdivision。Thedilemmaisencounteredbycentralstationsinabewilderedway，asanovelandunexpectedexperience；butEdisonforesawthesituationandwarnedagainstitlongago。
Itisoneofthegreatestgiftsofstatesmanshiptoseenewsocialproblemsyearsbeforetheyariseandsolvetheminadvance。Itisoneofthegreatestattributesofinventiontoforeseeandmeetitsownproblemsinexactlythesameway。