亥姆霍兹论力的守恒.docx
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亥姆霍兹论力的守恒.docx
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亥姆霍兹论力的守恒
IntroductoryNote
HermannvonHelmholtz;TranslatedbyEdmundAtkinson
HERMANNLUDWIGFERDINANDVONHELMHOLTZwasbornatPotsdam,nearBerlin,onAugust31,1821.Hisfatherwasamanofhighculture,ateacherinthegymnasium,whoseinfluenceensuredtohissonthefoundationsofabroadgeneraleducation.HismotherwasadescendantfromWilliamPenn,theEnglishQuaker.
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Helmholtzearlyshowedmathematicalability,andwishedtodevotehislifetothestudyofphysics;butpracticalconsiderationsledhimtotakeupmedicine,andhebecameasurgeoninthePrussianarmy.Hebeganthepublicationoforiginalcontributionstosciencein1842,andforfifty-twoyears,tillhisdeathin1894,hecontinuedtoproduceinanunbrokenstream.Heheldasuccessionofacademicpositions,teachingphysiologyatKönigsberg,Bonn,andHeidelberg,andforthelasttwenty-threeyearsofhislifefillingthechairofphysicsatBerlin.
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Thetitlesofhisprofessorships,however,giveaveryinadequateideaofhisrange.Hiscontributionstosciencecovermedicine,physiology,optics,acoustics,mathematics,mechanics,andelectricity.Hisinterestsinscienceandartcametogetherinhisworkonesthetics,andhehadalivelyappreciationofpainting,poetry,andmusic.
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ThepracticeofpopularlecturingonscientificsubjectswasalmostunknowninGermanywhenHelmholtzbegan,andhedidmuchtogiveitdignityandtosetastandard.Hisownlectures,asthereaderofthefollowingpaperswillperceive,aremasterpiecesoftheirkind.“Thematter,”saysabiographer,“isdiscussedbyamaster,whobringstobearuponitallhiswealthoflearningandresearch,whilethereistheever-enduringinterestthatattachestoanexpositionbyonewhoisgivingforthfromhisowntreasury.”Itisfortunateforthelaymanwhenascientistandthinkerofthefirstorderhastheskillandtheinclinationtosharewiththeoutsideworldtherichharvestofhisbrilliantandlaboriousresearch.
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OntheConservationofForce
IntroductiontoaSeriesofLecturesDeliveredatCarlsruheintheWinterof1862–1863
HermannvonHelmholtz;TranslatedbyEdmundAtkinson
ASIhaveundertakentodeliverhereaseriesoflectures,IthinkthebestwayinwhichIcandischargethatdutywillbetobringbeforeyou,bymeansofasuitableexample,someviewofthespecialcharacterofthosesciencestothestudyofwhichIhavedevotedmyself.Thenaturalsciences,partlyinconsequenceoftheirpracticalapplications,andpartlyfromtheirintellectualinfluenceonthelastfourcenturies,havesoprofoundly,andwithsuchincreasingrapidity,transformedalltherelationsofthelifeofcivilisednations;theyhavegiventhesenationssuchincreaseofriches,ofenjoymentoflife,ofthepreservationofhealth,ofmeansofindustrialandofsocialintercourse,andevensuchincreaseofpoliticalpower,thateveryeducatedmanwhotriestounderstandtheforcesatworkintheworldinwhichheisliving,evenifhedoesnotwishtoenteruponthestudyofaspecialscience,musthavesomeinterestinthatpeculiarkindofmentallabour,whichworksandactsinthesciencesinquestion.
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OnaformeroccasionIhavealreadydiscussedthecharacteristicdifferenceswhichexistbetweenthenaturalandthementalsciencesasregardsthekindofscientificwork.Ithenendeavouredtoshowthatitismoreespeciallyinthethoroughconformitywithlawwhichnaturalphenomenaandnaturalproductsexhibit,andinthecomparativeeasewithwhichlawscanbestated,thatthisdifferenceexists.NotthatIwishbyanymeanstodeny,thatthementallifeofindividualsandpeoplesisalsoinconformitywithlaw,asistheobjectofphilosophical,philological,historical,moral,andsocialsciencestoestablish.Butinmentallife,theinfluencesaresointerwoven,thatanydefinitesequencecanbutseldombedemonstrated.InNaturetheconverseisthecase.Ithasbeenpossibletodiscoverthelawoftheoriginandprogressofmanyenormouslyextendedseriesofnaturalphenomenawithsuchaccuracyandcompletenessthatwecanpredicttheirfutureoccurrencewiththegreatestcertainty;orincasesinwhichwehavepowerovertheconditionsunderwhichtheyoccur,wecandirectthemjustaccordingtoourwill.Thegreatestofallinstancesofwhatthehumanmindcaneffectbymeansofawell-recognisedlawofnaturalphenomenaisthataffordedbymodernastronomy.Theonesimplelawofgravitationregulatesthemotionsoftheheavenlybodiesnotonlyofourownplanetarysystem,butalsoofthefarmoredistantdoublestars;fromwhich,eventherayoflight,thequickestofallmessengers,needsyearstoreachoureye;and,justonaccountofthissimpleconformitywithlaw,themotionsofthebodiesinquestioncanbeaccuratelypredictedanddeterminedbothforthepastandforfutureyearsandcenturiestoafractionofaminute.
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Onthisexactconformitywithlawdependsalsothecertaintywithwhichweknowhowtotametheimpetuousforceofsteam,andtomakeittheobedientservantofourwants.Onthisconformitydepends,moreover,theintellectualfascinationwhichchainsthephysicisttohissubjects.Itisaninterestofquiteadifferentkindtothatwhichmentalandmoralsciencesafford.Inthelatteritismaninthevariousphasesofhisintellectualactivitywhochainsus.Everygreatdeedofwhichhistorytellsus,everymightypassionwhichartcanrepresent,everypictureofmanners,ofcivicarrangements,ofthecultureofpeoplesofdistantlandsorofremotetimes,seizesandinterestsus,evenifthereisnoexactscientificconnectionamongthem.Wecontinuallyfindpointsofcontactandcomparisoninourconceptionsandfeelings;wegettoknowthehiddencapacitiesanddesiresofthemind,whichintheordinarypeacefulcourseofcivilisedliferemainunawakened.
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Itisnottobedeniedthat,inthenaturalsciences,thiskindofinterestiswanting.Eachindividualfact,takenbyitself,canindeedarouseourcuriosityorourastonishment,orbeusefultousinitspracticalapplications.Butintellectualsatisfactionweobtainonlyfromaconnectionofthewhole,justfromitsconformitywithlaw.Reasonwecallthatfacultyinnateinusofdiscoveringlawsandapplyingthemwiththought.Fortheunfoldingofthepeculiarforcesofpurereasonintheirentirecertaintyandintheirentirebearing,thereisnomoresuitablearenathaninquiryintoNatureinthewidersense,themathematicsincluded.Anditisnotonlythepleasureatthesuccessfulactivityofoneofourmostessentialmentalpowers;andthevictorioussubjectionstothepowerofourthoughtandwillofanexternalworld,partlyunfamiliar,andpartlyhostile,whichistherewardofthislabour;butthereisakind,Imightalmostsay,ofartisticsatisfaction,whenweareabletosurveytheenormouswealthofNatureasaregularly-orderedwhole—akosmos,animageofthelogicalthoughtofourownmind.
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Thelastdecadesofscientificdevelopmenthaveledustotherecognitionofanewuniversallawofallnaturalphenomena,which,fromitsextraordinarilyextendedrange,andfromtheconnectionwhichitconstitutesbetweennaturalphenomenaofallkinds,evenoftheremotesttimesandthemostdistantplaces,isespeciallyfittedtogiveusanideaofwhatIhavedescribedasthecharacterofthenaturalsciences,whichIhavechosenasthesubjectofthislecture.
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ThislawistheLawoftheConservationofForce,atermthemeaningofwhichImustfirstexplain.Itisnotabsolutelynew;forindividualdomainsofnaturalphenomenaitwasenunciatedbyNewtonandDanielBernoulli;andRumfordandHumphryDavyhaverecogniseddistinctfeaturesofitspresenceinthelawsofheat.
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ThepossibilitythatitwasofuniversalapplicationwasfirststatedbyDr.JuliusRobertMayer,aSchwabianphysician(nowlivinginHeilbronn),intheyear1842,whilealmostsimultaneouslywith,andindependentlyofhim,JamesPrescotJoule,anEnglishmanufacturer,madeaseriesofimportantanddifficultexperimentsontherelationofheattomechanicalforce,whichsuppliedthechiefpointsinwhichthecomparisonofthenewtheorywithexperiencewasstillwanting.
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Thelawinquestionasserts,thatthequantityofforcewhichcanbebroughtintoactioninthewholeofNatureisunchangeable,andcanneitherbeincreasednordiminished.Myfirstobjectwillbetoexplaintoyouwhatisunderstoodbyquantityofforce;or,asthesameideaismorepopularlyexpressedwithreferencetoitstechnicalapplication,whatwecallamountofworkinthemechanicalsenseoftheword.
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Theideaofworkformachines,ornaturalprocesses,istakenfromcomparisonwiththeworkingpowerofman;andwecanthereforebestillustratefromhumanlabourthemostimportantfeaturesofthequestionwithwhichweareconcerned.Inspeakingoftheworkofmachinesandofnaturalforceswemust,ofcourse,inthiscomparisoneliminateanythinginwhichactivityofintelligencecomesintoplay.Thelatterisalsocapableofthehardandintenseworkofthinking,whichtriesamanjustasmuscularexertiondoes.Butwhateveroftheactionsofintelligenceismetwithintheworkofmachines,ofcourseisduetothemindoftheconstructorandcannotbeassignedtotheinstrumentatwork.
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Now,theexternalworkofmanisofthemostvariedkindasregardstheforceorease,theformandrapidity,ofthemotionsusedonit,andthekindofworkproduced.Butboththearmoftheblacksmithwhodelivershispowerfulblowswiththeheavyhammer,andthatoftheviolinistwhoproducesthemostdelicatevariationsinsound,andthehandofthelace-makerwhowor
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