Thishowever，thoughaverballyintelligiblesupposition，isonethatcannot
berepresentedinthought;sinceunlimitedspaceisinconceivable。Butall
finiteformsofthehomogeneous——allformsofitwhichwecanknoworconceive，
mustinevitablylapseintoheterogeneity;andthelessheterogeneousmust
lapseintothemoreheterogeneous。Inthreeseveralwaysdoesthepersistence
offorcenecessitatethis。Settingexternalagenciesaside，eachunitof
ahomogeneouswholemustbedifferentlyaffectedfromanyoftherestby
theaggregateactionoftherestuponit。Theresultantforceexercisedby
theaggregateoneachunit，beinginnotwocasesalikeinbothamountand
direction，andusuallynotineither，anyincidentforce，evenifuniform
inamountanddirection，cannotproducelikeeffectsontheunits。Andas
thevariouspositionsofthepartsinrelationtoanyincidentforce，prevents
themfromreceivingitinuniformamountsanddirections，afurtherdifferenceintheeffectswroughtontheminevitablyarises。Onefurtherremarkisneeded。Theconclusionthatthechangeswithwhich
Evolutioncommences，arethusnecessitated，hastobesupplementedbythe
conclusionthatthesechangesmustcontinue。Theabsolutelyhomogeneous（supposing
ittoexist）mustloseitsequilibrium;andtherelativelyhomogeneousmust
lapseintotherelativelylesshomogeneous。Thatwhichistrueofanytotal
mass，istrueofthepartsintowhichitsegregates。Theuniformityofeach
suchpartmustasinevitablybelostinmultiformity，aswasthatofthe
originalwhole;andforlikereasons。Andthusthecontinuedchangescharacterizing
Evolution，insofarastheyareconstitutedbythelapseofthehomogeneous
intotheheterogeneous，andofthelessheterogeneousintothemoreheterogeneous，arenecessaryconsequencesofthepersistenceofforce。[AsmallchangeinthedefinitionofEvolutionindicatedinanoteat
theendofChapterXVIIofthispart，mustberecalledasinvolvingacorrelative
changeinthischapter。Here，asbefore，therequiredchange，thoughalready
implied（page367），hasnotbeensufficientlyemphasized，andlackofthe
emphasisinvitesmisinterpretation。Forreasonslikethosebeforegiven，
therequisiteexplanationscannotbemadeinthisplace。ThereaderwillfindtheminAppendixA。Repliestocertaincriticismsonthegeneraldoctrinesetforthinthis
chapterwillbefoundinAppendixC。]
Chapter20TheMultiplicationofEffects§156。Tothecauseofincreasingcomplexitysetforthinthelast
chapter，wehaveinthischaptertoaddanother。Thoughsecondaryinorder
oftime，itisscarcelysecondaryinorderofimportance。Evenintheabsence
ofthecausealreadyassigned，itwouldnecessitateachangefromthehomogeneous
totheheterogeneous;andjoinedwithit，itmakesthischangebothmore
rapidandmoreinvolved。Tocomeinsightofitwehavebuttopursueastep
furtherthatconflictbetweenforceandmatteralreadydelineated。Letusdothis。Asalreadyshown，whenthecomponentsofauniformaggregatearesubject
toauniformforce，theybeingdifferentlyconditioned，aredifferentlymodified。
Butwhilewehavecontemplatedthevariouspartsoftheaggregateasundergoing
unlikechanges，wehavenotyetcontemplatedtheunlikechangessimultaneously
producedonthevariouspartsoftheincidentforce。Thesemustbeasnumerous
astheothers。Indifferentiatingthepartsonwhichitfallsinunlikeways，
theincidentforcemustitselfbecorrespondinglydifferentiated。Instead
ofbeingasbefore，auniformforce，itmustthereafterbeamultiformforce
——agroupofdissimilarforces。Afewillustrationswillmakethistruthmanifest。Inthecase，latelycited，ofabodyshatteredbyviolentcollision，besides
thechangeofthehomogeneousmassintoaheterogeneousgroupofscattered
fragments，thereisachangeofthehomogeneousmomentumintoagroupof
momenta，heterogeneousinbothamountsanddirections。Similarlywiththe
forcesweknowaslightandheat。Afterthedispersionofthesebyaradiating
bodytowardsallpoints，theyarere—dispersedtowardsallpointsbythe
bodiesonwhichtheyfall。OftheSun\'srays，issuingfromhimoneveryside，
somefewstriketheMoon。ReflectedatallanglesfromtheMoon\'ssurface，
somefewofthesestriketheEarth。Byalikeprocessthefewwhichreach
theEarthareagaindiffused:someintospace，somefromobjecttoobject。
Andoneachoccasion，suchportionsoftheraysasaretransmittedinstead
ofreflected，undergorefractionsorotherchangeswhichequallydestroy
theiruniformity。Morethanthisistrue。Byconflictwithmatterauniform
forceisinpartchangedintoforcesdifferingintheirkinds。Whenonebody
isstruckagainstanother，thatwhichweusuallyregardastheeffect，is
achangeofpositionormotioninoneorbothbodies。Butthisisavery
incompleteviewofthematter。Besidesthevisiblemechanicalresult，sound
isproduced——avibrationinoneorbothbodiesandinthesurroundingair;
andundersomecircumstanceswecallthistheeffect。Moreover，theairhas
notsimplybeenmadetovibrate;ithashadcurrentsraisedinitbythe
transitofthebodies。Further，ifthereisnotthatgreatstructuralchange
whichwecallfracture，thereisadisarrangementoftheparticlesofthe
twobodiesaroundtheirpointofcollision;amountinginsomecasestoa
visiblecondensation。Yetmore，thiscondensationisaccompaniedbygenesis
ofheat。Insomecasesaspark——thatis，light——resultsfromtheincandescence
ofaportionstruckoff。Thusbytheoriginalmechanicalforceexpendedin
thecollision，atleastfivekindsofforceshavebeenproduced。Take，again，
thelightingofacandle。Primarily，thisisachemicalchangeconsequent
onariseoftemperature。Theprocessofcombinationhavingoncebeenset
goingbyextraneousheat，thereisacontinuedformationofcarbondioxide，
water，etc。Alongwiththisprocessofcombinationthereisaproduction
ofheat;thereisaproductionoflight;thereisanattendingcolumnof
hotgasesgenerated;therearecurrentscausedinthesurroundingair。Nor
doesthedecompositionofoneforceintomanyforcesendhere。Eachofthe
severalchangesworkedbecomestheparentoffurtherchanges。Thecarbon
dioxideformedwilleventuallycombinewithsomebase;orundertheinfluence
ofsunshinegiveupitscarbontotheleafofaplant。Thewaterwillmodify
thehygrometricstateoftheairaround;or，ifthecurrentofhotgases
containingitcomesagainstacoldbody，willbecondensed:alteringthe
temperature，andperhapsthechemicalstate，ofthesurfaceitcovers。The
heatgivenoutmeltsthesubjacenttallowandexpandswhateverelseitwarms。
Thelight，fallingonvarioussubstances，callsforthfromthemreactions
bywhichitisdecomposed，anddiverscoloursarethusproduced。Similarly
withthesesecondaryactions，whichmaybetracedoutintoever—multiplying
ramifications，untiltheybecometoominutetobeappreciated。Universally，
then，theeffectismorecomplexthanthecause。Whethertheaggregateon
whichitfallsbehomogeneousorotherwise，anincidentforceistransformed
bytheconflictintoanumberofforcesthatdifferintheiramounts，or
directions，orkinds;orinalltheserespects。Andofthisgroupofvariously—modifiedforces，eachultimatelyundergoesaliketransformation。Letusnowmarkhowtheprocessofevolutionisfurtheredbythismultiplication
ofeffects。Anincidentforcedecomposedbythereactionsofabodyinto
agroupofunlikeforces，becomesthecauseofasecondaryincreaseofmultiformity
inthebodywhichdecomposesit。Bythereactionsofthevariousparts，differently
modifiedaswehaveseentheymustbe，theincidentforceitselfmustbe
dividedintodifferentlymodifiedparts。Eachdifferentiateddivisionof
theaggregatethusbecomesacentrefromwhichadifferentiateddivision
oftheoriginalforceisagaindiffused。Andsinceunlikeforcesmustproduce
unlikeresults，eachofthesedifferentiatedforcesmustproduce，throughout
theaggregate，afurtherseriesofdifferentiations。Thissecondarycause
ofthechangefromhomogeneitytoheterogeneity，obviouslybecomesmorepotent
inproportionastheheterogeneityincreases。Whenthepartsintowhichany
evolvingwholehassegregateditself，havedivergedwidelyinnature，they
willnecessarilyreactverydiverselyonanyincidentforce——theywill
divideanincidentforceintosomanystronglycontrastedgroupsofforces。
Andeachofthembecomingthecentreofaquitedistinctsetofinfluences，
mustaddtothenumberofdistinctsecondarychangeswroughtthroughoutthe
aggregate。Yetanothercorollarymustbeadded。Thenumberofunlikeparts
ofwhichanaggregateconsists，isanimportantfactorintheprocess。Every
additionalspecializeddivisionisanadditionalcentreofspecializedforces，
andmustbeafurthersourceofcomplicationamongtheforcesatworkthroughout
themass——afurthersourceofheterogeneity。Themultiplicationofeffectsmustproceedingeometricalprogression。§157。Thescatteredpartsofanirregularnebulaincourseofbeing
drawntogetherorintegrated，cannotdisplayinadefinitemannerthesecondary
traitsofevolution:thesepresupposeanaggregatealreadyformed。Wecan
sayonlythatthehalf—independentcomponents，eachattractedbyalland
allbyeach，exhibitintheirvariousmomenta，differentintheiramounts
anddirections，amultiplicationofeffectsproducedbyasinglegravitativeforce。Butassumingthattheintegrativeprocesshasatlengthgeneratedasingle
massofnebulousmatter，thenthesimultaneouscondensationandrotation
showushowtwoeffectsoftheaggregativeforce，atfirstbutslightlydivergent，
becomeatlastwidelydifferentiated。Anincreaseofoblatenessinthisspheroid
musttakeplacethroughthejointactionofthesetwoforces，asthebulk
diminishesandtherotationgrowsmorerapid;andthiswemaysetdownas
athirdeffect。Thegenesisofheat，accompanyingaugmentationofdensity，
isaconsequenceofyetanotherorder——aconsequencebynomeanssimple;
sincethevariouspartsofthemass，beingvariouslycondensed，mustbevariously
heated。Actingthroughoutagaseousspheroid，ofwhichthepartsareunlike
intheirtemperatures，theforcesofaggregationandrotationmustworka
furtherseriesofchanges:theymustsetupcirculatingcurrents，bothgeneral
andlocal。Atalaterstagelightaswellasheatwillbegenerated。Thus
withoutdwellingonthelikelihoodofchemicalcombinationsandelectric
disturbances，itismanifestthat，supposingmattertohaveoriginallyexisted
inadiffusedstate，theonceuniformforcewhichcauseditsaggregation，
musthavebecomegraduallydividedintodifferentforces;andthateachfurther
stageofcomplicationintheresultingaggregate，musthaveinitiatedfurther
subdivisionsofthisforce——afurthermultiplicationofeffects，increasingthepreviousheterogeneity。Thissectionoftheargumentmayhoweverbeadequatelysustainedwithout
havingrecoursetoanysuchhypotheticalillustrationsastheforegoing。
TheastronomicalattributesoftheEarthwill，evenbythemselves，suffice
forourpurpose。Considerfirsttheeffectsofitsrotation。Thereisthe
oblatenessofitsform;thereisthealternationofdayandnight;there
arecertainconstantmarinecurrents;andtherearecertainconstantaerial
currents。Considernextthesecondaryseriesofconsequencesduetothedivergence
oftheEarth\'splaneofrotationfromtheplaneofitsorbit。Themanyvariations
oftheseasons，bothsimultaneousandsuccessive，whichpervadeitssurface，
arethuscaused。ExternalattractionoftheMoonandSunactingontheequatorial
protuberanceofthisrotatingspheroidwithinclinedaxis，producesthemotion
callednutation，andthatslowerandlargeronefromwhichfollowstheprecession
oftheequinoxes，withitsseveralsequences。Andthen，bythissameforce，aregeneratedthetides，aqueousandatmospheric。Perhaps，however，thesimplestwayofshowingthemultiplicationofeffects
amongphenomenaofthisorder，willbetosetdowntheinfluencesofany
memberoftheSolarSystemontherest。Aplanetdirectlyproducesinneighbouring
planetscertainappreciableperturbations，complicatingthoseotherwiseproduced
inthem;andintheremoterplanetsitdirectlyproducescertainlessvisible
perturbations。Hereisafirstseriesofeffects。Buteachoftheperturbed
planetsisitselfasourceofperturbations——eachdirectlyaffectsall
theothers。Hence，planetAhavingdrawnplanetBoutofthepositionit
wouldhaveoccupiedinA\'sabsence，theperturbationswhichBcausesare
differentfromwhattheywouldelsehavebeen;andsimilarlywithC，D，E，
etc。Herethenisasecondaryseriesofeffects;farmorenumerousthough
farsmallerintheiramounts。Astheseindirectperturbationsmusttosome
extentmodifythemovementsofeachplanet，thereresultsfromthematertiary
series;andsooninevermultiplyinganddiminishingwavesthroughouttheentiresystem。§158。IftheEarthwasformedbytheconcentrationofdiffusedmatter，
itmustatfirsthavebeenincandescent;andwhetherthenebularhypothesis
beacceptedornot，thisoriginalincandescenceoftheEarthmaynowberegarded
asinductivelyestablished——or，ifnotestablished，atleastrenderedso
probablethatitisagenerallyadmittedgeologicaldoctrine。Severalresults
ofthegradualcoolingoftheEarth——astheformationofacrust，thesolidification
ofsublimedelements，theprecipitationofwater，etc。——havebeenalready
noticed，andIagainrefertothemmerelytopointoutthattheyaresimultaneous
effectsoftheonecause，diminishingheat。Letusnow，however，observe
themultipliedchangesafterwardsarisingfromthecontinuanceofthisone
cause。TheEarth，fallingintemperature，mustcontract。Hencethesolid
crustatanytimeexistingispresentlytoolargefortheshrinkingnucleus，
and，beingunabletosupportitself，inevitablyfollowsthenucleus。But
aspheroidalenvelopecannotsinkdownintocontactwithasmallerinternal
spheroid，withoutdisruption:itwillrunintowrinklesastherindofan
appledoeswhenthebulkofitsinteriordecreasesfromevaporation。Asthe
coolingprogressesandtheenvelopethickens，theridgesconsequentonthese
contractionsmustbecomegreater，risingultimatelyintohillsandmountains;
andthelatersystemsofmountainsthusproducedmustnotonlybehigher，
aswefindthemtobe，butmustbelonger，aswealsofindthemtobe。Thus，
leavingoutofviewothermodifyingforces，weseewhatimmenseheterogeneity
ofsurfacearisesfromtheonecause，lossofheat——aheterogeneitywhich
thetelescopeshowsustobeparalleledontheMoon，whereaqueousandatmospheric
agencieshavebeenabsent。Butwehaveyettonoticeanotherkindofheterogeneity
ofsurface，simultaneouslycaused。WhiletheEarth\'scrustwasthin，the
ridgesproducedbyitscontractionsmustnotonlyhavebeensmallinheight
andlength，butthetractsbetweenthemmusthaverestedwithcomparative
smoothnessonthesubjacentliquidspheroid;andthewaterinthosearctic
andantarcticregionswhereitfirstcondensed，musthavebeenevenlydistributed。
Butasfastasthecrustgrewthickerandgainedcorrespondingstrength，
thelinesoffracturefromtimetotimecausedinit，occurredatgreater
distancesapart;theintermediatesurfacesfollowedthecontractingnucleus
withlessuniformity;andthereconsequentlyresultedlargerareasofland
andwater。Ifanyone，afterwrappinganorangeintissuepaperandobserving
bothhowsmallarethewrinklesand，howevenlytheinterveningspaceslie
onthesurfaceoftheorange，willthenwrapitinthickcartridge—paper，
andnoteboththegreaterheightoftheridgesandthelargerspacesthroughout
whichthepaperdoesnottouchtheorange，hewillseethatastheEarth\'s
solidenvelopethickened，theareasofelevationanddepressionbecamegreater。
Inplaceofislandsmoreorlesshomogeneouslyscatteredthroughoutanall—embracing
sea，theremusthavegraduallyarisenheterogeneousarrangementsofcontinent
andocean，suchaswenowknow。Thesesimultaneouschangesintheextent
andintheelevationofthelands，involvedyetanotherspeciesofheterogeneity
——thatofcoast—line。Atolerablyevensurfaceraisedoutoftheoceanwill
haveasimple，regularsea—margin;butasurfacevariedbytable—landsand
intersectedbymountain—chains，will，whenraisedoutoftheocean，have
anoutlineextremelyirregular，alikeinitsleadingfeaturesandinits
details。Thusendlessistheaccumulationofgeologicalandgeographical
resultsbroughtaboutbythisonecause——escapeoftheEarth\'sprimitiveheat。Whenwepassfromtheagencywhichgeologiststermigneous，toaqueous
andatmosphericagencies，weseealikeever—growingcomplicationofeffects。
Thedenudingactionsofairandwaterhave，fromthebeginning，beenmodifying
everyexposedsurface:everywhereworkingmanydifferentchanges。Asalready
said（§69）theoriginalsourceofthosegaseousandfluidmotionswhich
effectdenudation，isthesolarheat。Thetransformationofthisintovarious
modesofenergy，accordingtothenatureandconditionsofthematteron
whichitfalls，isthefirststageofcomplication。TheSun\'srays，striking
atallanglesaspherethatfrommomenttomomentpresentedandwithdrew
differentpartsofitssurface，andeachofthemforadifferenttimedaily
throughouttheyear，wouldproduceaconsiderablevarietyofchangeseven
werethesphereuniform。Butfallingastheydoonaspheresurroundedby
anatmospherecontainingwideareasofcloud，butwhichhereunveilsvast
tractsofsea，thereoflevelland，thereofmountains，thereofsnowand
ice，theycauseinitcountlessdifferentmovements。Currentsofairofall
sizes，directions，velocities，andtemperatures，aresetup;asarealso
marinecurrentssimilarlycontrastedintheircharacters。Inthisregion
thesurfaceisgivingoffvapour;inthat，dewisbeingprecipitated;and
inanother，rainisdescending——unlikenesseswhicharisefromthechanging
ratiobetweentheabsorptionandradiationofheatineachplace。Atone
hourarapidfallintemperatureleadstotheformationofice，withanaccompanying
expansionthroughoutthemoistbodiesfrozen;whileatanotherathawunlocks
thedislocatedfragmentsofthesebodies。Andthen，passingtoasecondstage
ofcomplication，weseethatthemanykindsofmotiondirectlyorindirectly
causedbytheSun\'srays，severallyproduceresultswhichvarywiththeconditions。
Oxidation，drought，wind，frost，rain，glaciers，rivers，waves，andother
denudingagentseffectdisintegrationsthataredeterminedintheiramounts
andqualitiesbylocalcircumstances。Actingonatractofgranite，such
agentshereworkscarcelyanappreciableeffect;therecauseexfoliations
ofthesurfaceandaresultingheapofdebrisandboulders;andelsewhere，
afterdecomposingthefeldsparintoawhiteclay，carryawaythiswiththe
accompanyingquartzandmica，anddeposittheminseparatebeds，fluviatile
ormarine。Whentheexposedlandconsistsofseveralunlikeformations，sedimentary
andigneous，changesproportionatelymoreheterogeneousarewrought。The
formationsbeingdisintegrableindifferentdegrees，therefollowsanincreased
irregularityofsurface。Theareasdrainedbyadjacentriversbeingdifferently
constituted，theseriverscarrydowntotheseaunlikecombinationsofingredients;
andsosundrynewstrataofdistinctcompositionsarise。Andhere，indeed，
wemayseeveryclearlyhowtheheterogeneityoftheeffectsincreasesin
ageometricalprogressionwiththeheterogeneityoftheobjectactedupon。
Letus，forthefullerelucidationofthistruthinrelationtotheinorganic
world，considerwhatwouldfollowfromanextensivecosmicalcatastrophe
——sayagreatsubsidencethroughoutCentralAmerica。Theimmediateresults
wouldthemselvesbesufficientlycomplex。Besidesthenumberlessdislocations
ofstrata，theejectionsofigneousmatter，thepropagationofearthquake
vibrationsmanythousandsofmilesaround，theloudexplosions，andtheescape
ofgases，therewouldbeaninrushoftheAtlanticandPacificOceans，a
subsequentrecoilofenormouswaves，whichwouldtraverseboththeseoceans
andproducemyriadsofchangesalongtheirshores，andcorrespondingatmospheric
wavescomplicatedbythecurrentssurroundingeachvolcanicvent，aswell
aselectricaldischargeswithwhicheruptionsareaccompanied。Butthese
temporaryeffectswouldbeinsignificantcomparedwiththepermanentones。
ThecomplexcurrentsoftheAtlanticandPacificwouldbealteredintheir
directionsandamounts。Thedistributionofheatachievedbythesecurrents
wouldbedifferentfromwhatitis。Thearrangementoftheisothermallines，
notonlyontheneighbouringcontinentsbuteventhroughoutEurope，would
bechanged。Thetideswouldflowdifferentlyfromwhattheydonow。There
wouldbemoreorlessmodificationofthewindsintheirperiods，strengths，
directions，qualities;andrainwouldfallscarcelyanywhereatthesame
timesandinthesamequantitiesasatpresent。Inthesemanychanges，each
includingcountlessminorones，maybeseentheimmenseheterogeneityof
theresultswroughtoutbyoneforce，whenthatforceexpendsitselfona
previouslycomplicatedarea:theimplicationbeingthatfromthebeginningthecomplicationhasadvancedatanincreasingrate。§159。Wehavenexttotracethroughoutorganicevolution，thissame
all—pervadingprinciple。Andhere，wherethetransformationofthehomogeneous
intotheheterogeneouswasfirstobserved，theproductionofmanychanges
byonecauseisleasteasytodemonstrateinadirectway。Hereditycomplicateseverything。Nevertheless，byindirectevidencewemayestablishourproposition。Bywayofpreparationobservehownumerousarethechangeswhichanymarked
stimulusworksonanadultorganism——ahumanbeingforinstance。Analarming
soundorsight，besidesimpressionsontheorgansofsenseandthenerves，
mayproduceastart，ascream，adistortionoftheface，atremblingconsequent
ongeneralmuscularrelaxation，aburstofperspiration，andperhapsanarrest
oftheheartfollowedbysyncope;andifthesystembefeeble，anillness
withitslongtrainofcomplicatedsymptommaysetin。Similarlyincases
ofdisease。Aminuteportionofthesmall—poxvirustakenintothesystem
will，inaseverecase，cause，duringthefirststage，rigors，heatofskin，
acceleratedpulse，furredtongue，lossofappetite，thirst，epigastricuneasiness，
vomiting，headache，patsinthebackandlimbs，muscularweakness，convulsions，
delirium，etc。;inthesecondstage，cutaneouseruption，itching，tingling，
sorethroat，swelledfauces，salivation，cough，hoarseness，dyspnoea，etc。;
andinthethirdstage，oedematousinflammations，pneumonia，pleurisy，diarrhoea，
inflammationofthebrain，ophthalmia，erysipelas，etc。:eachofwhichenumerated
symptomsisitselfmoreorlesscomplex。Nowitneedsonlytoconsiderthat
thisworkingofmanychangesbyoneforceonanadultorganism，mustbepartially
paralleledinanembryo—organism，tounderstandthatinittootheremust
beamultiplicationofeffects，evertendingtoproduceincreasingheterogeneity。