第4章

Wearenowbroughttooneoftheprofoundestspeculationsofmoderntimes，thevortex-atomtheoryofHelmholtzandThomson，inwhichtheevolutionofordinarymatterfrometherisplainlyindicated。Thereaderfirstneedstoknowwhatvortex-motionis； andthishasbeensobeautifullyexplainedbyProfessorClifford，thatIquotehisdescriptionentire:“Imaginearingofindia-rubber，madebyjoiningtogethertheendsofacylindricalpiece(likealead-pencilbeforeitiscut)，tobeputuponaroundstickwhichitwilljustfitwithalittlestretching。Letthestickbenowpulledthroughtheringwhilethelatteriskeptinitsplacebybeingpulledtheotherwayontheoutside。Theindia-rubberhasthenwhatiscalledvortex-motion。Beforetheendswerejoinedtogether，whileitwasstraight，itmighthavebeenmadetoturnaroundwithoutchangingposition，byrollingitbetweenthehands。Justthesamemotionofrotationithasonthestick，onlythattheendsarenowjoinedtogether。Alltheinsidesurfaceoftheringisgoingoneway，namely，thewaythestickispulled；andalltheoutsideisgoingtheotherway。Suchavortex-ringismadebythesmokerwhopurseshislipsintoaroundholeandsendsoutapuffofsmoke。Theoutsideoftheringiskeptbackbythefrictionofhislipswhiletheinsideisgoingforwards；thusarotationissetupallroundthesmoke-ringasittravelsoutintotheair。“Inthesecases，andinothersaswecommonlyfindit，vortex-motionowesitsorigintofrictionandisafterawhilebroughttoanendbyfriction。 Butin1858theequationsofmotionofanincompressiblefrictionlessfluidwerefirstsuccessfullysolvedbyHelmholtz，andamongotherthingsheprovedthat，thoughvortex-motioncouldnotbeoriginatedinsuchafluid，yetsupposingitoncetoexist，itwouldexisttoalleternityandcouldnotbediminishedbyanymechanicalactionwhatever。Avortex-ring，forexample，insuchafluid，wouldforeverpreserveitsownrotation，andwouldthusforeverretainitspeculiarindividuality，being，asitwere，markedofffromitsneighbourvortex-rings。UponthismechanicaltruthSirWilliamThomsonbasedhiswonderfullysuggestivetheoryoftheconstitutionofmatter。Thatwhichispermanentorindestructibleinmatteristheultimatehomogeneousatom；andthisisprobablyallthatispermanent，sincechemistsnowalmostunanimouslyholdthatso-calledelementarymoleculesarenotreallysimple，butowetheirsensibledifferencestothevariousgroupingsofanultimateatomwhichisalikeforall。 Relativelytoourpowersofcomprehensiontheatomendureseternally；thatis，itretainsforeverunalterableitsdefinitemassanditsdefiniterateofvibration。Nowthisisjustwhatavortex-ringwoulddoinanincompressiblefrictionlessfluid。 Thusthestartlingquestionissuggested，Whymaynottheultimateatomsofmatterbevortex-ringsforeverexistinginsuchafrictionlessfluidfillingthewholeofspace？SuchahypothesisisnotlessbrilliantthanHuyghens’sconjecturalidentificationoflightwithundulatorymotion；anditismoreoveralegitimatehypothesis，sinceitcanbebroughttothetestofverification。SirWilliamThomsonhasshownthatitexplainsagreatmanyofthephysicalpropertiesofmatter:itremainstobeseenwhetheritcanexplainthemall。 OfcoursetheetherwhichconveysthermalandluminousundulationsisnotthefrictionlessfluidpostulatedbySirWilliamThomson。Themostconspicuouspropertyoftheetherisitsenormouselasticity，apropertywhichweshouldnotfindinafrictionlessfluid。“Toaccountforsuchelasticity，“saysProfessorClifford(whoseexpositionofthesubjectisstillmorelucidthanthatofourauthors)，“ithastobesupposedthatevenwheretherearenomaterialmoleculestheuniversalfluidisfullofvortex-motion，butthatthevorticesaresmallerandmorecloselypackedthanthoseof[ordinary]matter，formingaltogetheramorefinelygrainedstructure。Sothatthedifferencebetweenmatterandetherisreducedtoameredifferenceinthesizeandarrangementofthecomponentvortex-rings。Now，whatevermayturnouttobetheultimatenatureoftheetherandofmolecules，weknowthattosomeextentatleasttheyobeythesamedynamiclaws，andthattheyactupononeanotherinaccordancewiththeselaws。Until，therefore，itisabsolutelydisproved，itmustremainthesimplestandmostprobableassumptionthattheyarefinallymadeofthesamestuff，thatthematerialmoleculeissomekindofknotorcoagulationofether。“[5] [5]FortnightlyReview，June，1875，p。784。 AnotherinterestingconsequenceofSirWilliamThomson’spregnanthypothesisisthattheabsolutehardnesswhichhasbeenattributedtomaterialatomsfromthetimeofLucretiusdownwardmaybedispensedwith。Somewhatinthesamewaythatalooselysuspendedchainbecomesrigidwithrapidrotation，thehardnessandelasticityofthevortex-atomareexplainedasduetotheswiftrotarymotionofasoftandyieldingfluid。Sothatthevortex-atomisreallyindivisible，notbyreasonofitshardnessorsolidity，butbyreasonoftheindestructiblenessofitsmotion。 Supposing，now，thatweadoptprovisionallythevortextheory，——thegreatpowerofwhichiswellshownbytheconsiderationjustmentioned，——wemustnotforgetthatitisabsolutelyessentialtotheindestructiblenessofthematerialatomthattheuniversalfluidinwhichithasanexistenceasavortex-ringshouldbeentirelydestituteoffriction。Onceadmiteventhemostinfinitesimalamountoffriction，whileretainingtheconceptionofvortex-motioninauniversalfluid，andthewholecaseissofaralteredthatthematerialatomcannolongerberegardedasabsolutelyindestructible，butonlyasindefinitelyenduring。Itmayhavebeengenerated，inbygoneeternity，byanaturalprocessofevolution，andinfutureeternitymaycometoanend。Relativelytoourpowersofcomprehensionthepracticaldifferenceisperhapsnotgreat。 Scientificallyspeaking，HelmholtzandThomsonareaswellentitledtoreasonupontheassumptionofaperfectlyfrictionlessfluidasgeometersingeneralareentitledtoassumeperfectlineswithoutbreadthandperfectsurfaceswithoutthickness。Perfectlinesandsurfacesdonotexistwithintheregionofourexperience；yettheconclusionsofgeometryarenonethelesstrueideally，thoughinanyparticularconcreteinstancetheyareonlyapproximatelyrealized。Justsowiththeconceptionofafrictionlessfluid。Sofarasexperiencegoes，suchathinghasnomorerealexistencethanalinewithoutbreadth；andhenceanatomictheorybaseduponsuchanassumptionmaybeastrueideallyasanyofthetheoremsofEuclid，butitcangiveonlyanapproximativelytrueaccountoftheactualuniverse。Theseconsiderationsdonotatallaffectthescientificvalueofthetheory；buttheywillmodifythetenourofsuchtranscendentalinferencesasmaybedrawnfromitregarding，theprobableoriginanddestinyoftheuniverse。 Theconclusionsreachedinthefirstpartofthispaper，whileweweredealingonlywithgrossvisiblematter，mayhaveseemedboldenough；buttheyarefarsurpassedbytheinferencewhichourauthorsdrawfromthevortextheoryastheyinterpretit。Ourauthorsexhibitvariousreasons，moreorlesssound，forattributingtotheprimordialfluidsomeslightamountoffriction；andinsupportofthisviewtheyadduceLeSage’sexplanationofgravitationasadifferentialresultofpressure，andStruve’stheoryofthepartialabsorptionoflight-raysbytheether，——questionswithwhichourpresentpurposedoesnotrequireustomeddle。ApartfromsuchquestionsitiseverywayprobablethattheprimaryassumptionofHelmholtzandThomsonisonlyanapproximationtothetruth。Butifweaccredittheprimordialfluidwithevenaninfinitesimalamountoffriction，thenwearerequiredtoconceiveofthevisibleuniverseasdevelopedfromtheinvisibleandasdestinedtoreturnintotheinvisible。Thevortex-atom，producedbyinfinitesimalfrictionoperatingthroughwellnighinfinitetime，istobeultimatelyabolishedbytheagencywhichproducedit。Inthewordsofourauthors，“Ifthevisibleuniversebedevelopedfromaninvisiblewhichisnotaperfectfluid，thentheargumentdeducedbySirWilliamThomsoninfavouroftheeternityofordinarymatterdisappears，sincethiseternitydependsupontheperfectfluidityoftheinvisible。Infine，ifwesupposethematerialuniversetobecomposedofaseriesofvortex-ringsdevelopedfromaninvisibleuniversewhichisnotaperfectfluid，itwillbeephemeral，justasthesmoke-ringwhichwedevelopfromair，orthatwhichwedevelopfromwater，isephemeral，theonlydifferencebeinginduration，theselastingonlyforafewseconds，andtheothersitmaybeforbillionsofyears。“Thus，asourauthorssupposethat“theavailableenergyofthevisibleuniversewillultimatelybeappropriatedbytheinvisible，“theygoontoimagine，“atleastasapossibility，thattheseparateexistenceofthevisibleuniversewillsharethesamefate，sothatweshallhavenohuge，useless，inertmassexistinginafteragestoremindthepasser-byofaformofenergyandaspeciesofmatterthatislongsinceoutofdateandfunctionallyeffete。 Whyshouldnottheuniverseburyitsdeadoutofsight？“ Inonerespectperhapsnomorestupendoussubjectofcontemplationthanthishaseverbeenofferedtothemindofman。 Incomparisonwiththelengthoftimethusrequiredtoeffacethetinyindividualatom，theentirecosmicalcareerofoursolarsystem，oreventhatofthewholestarrygalaxy，shrinksintoutternothingness。Whetherweshalladopttheconclusionsuggestedmustdependontheextentofourspeculativeaudacity。 Wehaveseenwhereinitsprobabilityconsists，butinreasoninguponsuchascalewemayfitlybecautiousandmodestinacceptinginferences，andourauthors，wemaybesure，wouldbethefirsttorecommendsuchmodestyandcaution。Evenatthedimensionstowhichourtheorizinghasheregrown，wemayforinstancediscernthepossiblealternativeofasimultaneousorrhythmicallysuccessivegenerationanddestructionofvortex-atomswhichwouldgofartomodifytheconclusionjustsuggested。Butherewemustpauseforamoment，reservingforasecondpapertheweightierthoughtsastofuturitywhichourauthorshavesoughttoenwrapinthesesublimephysicalspeculations。 UPtothispoint，howeverremotefromordinaryevery-daythoughtsmaybetheregionofspeculationwhichwehavebeencalledupontotraverse，wehavestillkeptwithinthelimitsoflegitimatescientifichypothesis。Thoughwehaveventuredforagoodlydistanceintotheunknown，wehavenotyetbeenrequiredtoabandonourbaseofoperationsintheknown。Oftheviewspresentedintheprecedingpaper，somearewellnighcertainlyestablished，someareprobable，somehaveasortofplausibility，others——towhichwehaverefrainedfromgivingassent——maypossiblybetrue；butnoneareirretrievablybeyondthejurisdictionofscientifictests。Nosuggestionhassofarbeenbroachedwhichaverylittlefurtherincreaseofourscientificknowledgemaynotshowtobeeithereminentlyprobableoreminentlyimprobable。Wehavekeptprettyclearofmeresubjectiveguesses，suchasmenmaywrangleaboutforeverwithoutcomingtoanyconclusion。Thetheoryofthenebularoriginofourplanetarysystemhascometocommandtheassentofallpersonsqualifiedtoappreciatetheevidenceonwhichitisbased；andthemoreimmediateconclusionswhichwehavedrawnfromthattheoryareonlysuchasarecommonlydrawnbyastronomersandphysicists。Thedoctrineofanintermolecularandinterstellaretheriswrappedupinthewell-establishedundulatorytheoryoflight。SuchisbynomeansthecasewithSirWilliamThomson’svortex-atomtheory，whichto-dayisinsomewhatthesameconditionastheundulatorytheoryofHuyghenstwocenturiesago。