lectures on evolution-第3章

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testimonial　evidence；　and　it　may　be　that；　where　the

circumstances　are　not　perfectly　clear　and　intelligible；　it　is　a

dangerous　and　unsafe　kind　of　evidence；　but　it　must　not　be

forgotten　that；　in　many　cases；　circumstantial　is　quite　as

conclusive　as　testimonial　evidence；　and　that；　not　unfrequently；

it　is　a　great　deal　weightier　than　testimonial　evidence。

For　example；　take　the　case　to　which　I　referred　just　now。

The　circumstantial　evidence　may　be　better　and　more　convincing

than　the　testimonial　evidence；　for　it　may　be　impossible；　under

the　conditions　that　I　have　defined；　to　suppose　that　the　man　met

his　death　from　any　cause　but　the　violent　blow　of　an　axe　wielded

by　another　man。　The　circumstantial　evidence　in　favour　of　a

murder　having　been　committed；　in　that　case；　is　as　complete　and

as　convincing　as　evidence　can　be。　It　is　evidence　which　is　open

to　no　doubt　and　to　no　falsification。　But　the　testimony　of　a

witness　is　open　to　multitudinous　doubts。　He　may　have　been

mistaken。　He　may　have　been　actuated　by　malice。　It　has　constantly

happened　that　even　an　accurate　man　has　declared　that　a　thing　has

happened　in　this；　that；　or　the　other　way；　when　a　careful

analysis　of　the　circumstantial　evidence　has　shown　that　it　did

not　happen　in　that　way；　but　in　some　other　way。



We　may　now　consider　the　evidence　in　favour　of　or　against　the

three　hypotheses。　Let　me　first　direct　your　attention　to　what　is

to　be　said　about　the　hypothesis　of　the　eternity　of　the　state　of

things　in　which　we　now　live。　What　will　first　strike　you　is；　that

it　is　a　hypothesis　which；　whether　true　or　false；　is　not　capable

of　verification　by　any　evidence。　For；　in　order　to　obtain　either

circumstantial　or　testimonial　evidence　sufficient　to　prove　the

eternity　of　duration　of　the　present　state　of　nature；　you　must

have　an　eternity　of　witnesses　or　an　infinity　of　circumstances；

and　neither　of　these　is　attainable。　It　is　utterly　impossible

that　such　evidence　should　be　carried　beyond　a　certain　point　of

time；　and　all　that　could　be　said；　at　most；　would　be；　that　so　far

as　the　evidence　could　be　traced；　there　was　nothing　to　contradict

the　hypothesis。　But　when　you　look；　not　to　the　testimonial

evidencewhich；　considering　the　relative　insignificance　of　the

antiquity　of　human　records；　might　not　be　good　for　much　in　this

casebut　to　the　circumstantial　evidence；　then　you　find　that

this　hypothesis　is　absolutely　incompatible　with　such　evidence　as

we　have；　which　is　of　so　plain　and　so　simple　a　character　that　it

is　impossible　in　any　way　to　escape　from　the　conclusions　which　it

forces　upon　us。



You　are；　doubtless；　all　aware　that　the　outer　substance　of　the

earth；　which　alone　is　accessible　to　direct　observation；　is　not

of　a　homogeneous　character；　but　that　it　is　made　up　of　a　number

of　layers　or　strata；　the　titles　of　the　principal　groups　of　which

are　placed　upon　the　accompanying　diagram。　Each　of　these　groups

represents　a　number　of　beds　of　sand；　of　stone；　of　clay；　of

slate；　and　of　various　other　materials。



On　careful　examination；　it　is　found　that　the　materials　of　which

each　of　these　layers　of　more　or　less　hard　rock　are　composed　are；

for　the　most　part；　of　the　same　nature　as　those　which　are　at

present　being　formed　under　known　conditions　on　the　surface　of

the　earth。　For　example；　the　chalk；　which　constitutes　a　great

part　of　the　Cretaceous　formation　in　some　parts　of　the　world；　is

practically　identical　in　its　physical　and　chemical　characters

with　a　substance　which　is　now　being　formed　at　the　bottom　of　the

Atlantic　Ocean；　and　covers　an　enormous　area；　other　beds　of　rock

are　comparable　with　the　sands　which　are　being　formed　upon　sea…

shores；　packed　together；　and　so　on。　Thus；　omitting　rocks　of

igneous　origin；　it　is　demonstrable　that　all　these　beds　of　stone；

of　which　a　total　of　not　less　than　seventy　thousand　feet　is

known；　have　been　formed　by　natural　agencies；　either　out　of　the

waste　and　washing　of　the　dry　land；　or　else　by　the　accumulation

of　the　exuviae　of　plants　and　animals。　Many　of　these　strata　are

full　of　such　exuviaethe　so…called　〃fossils。〃　Remains　of

thousands　of　species　of　animals　and　plants；　as　perfectly

recognisable　as　those　of　existing　forms　of　life　which　you　meet

with　in　museums；　or　as　the　shells　which　you　pick　up　upon　the

sea…beach；　have　been　imbedded　in　the　ancient　sands；　or　muds；　or

limestones；　just　as　they　are　being　imbedded　now；　in　sandy；　or

clayey；　or　calcareous　subaqueous　deposits。　They　furnish　us　with

a　record；　the　general　nature　of　which　cannot　be　misinterpreted；

of　the　kinds　of　things　that　have　lived　upon　the　surface　of　the

earth　during　the　time　that　is　registered　by　this　great　thickness

of　stratified　rocks。　But　even　a　superficial　study　of　these

fossils　shows　us　that　the　animals　and　plants　which　live　at　the

present　time　have　had　only　a　temporary　duration；　for　the　remains

of　such　modern　forms　of　life　are　met　with；　for　the　most　part；

only　in　the　uppermost　or　latest　tertiaries；　and　their　number

rapidly　diminishes　in　the　lower　deposits　of　that　epoch。　In　the

older　tertiaries；　the　places　of　existing　animals　and　plants　are

taken　by　other　forms；　as　numerous　and　diversified　as　those　which

live　now　in　the　same　localities；　but　more　or　less　different　from

them；　in　the　mesozoic　rocks；　these　are　replaced　by　others　yet

more　divergent　from　modern　types；　and；　in　the　paleozoic

formations；　the　contrast　is　still　more　marked。　Thus　the

circumstantial　evidence　absolutely　negatives　the　conception　of

the　eternity　of　the　present　condition　of　things。　We　can　say；

with　certainty；　that　the　present　condition　of　things　has　existed

for　a　comparatively　short　period；　and　that；　so　far　as　animal　and

vegetable　nature　are　concerned；　it　has　been　preceded　by　a

different　condition。　We　can　pursue　this　evidence　until　we　reach

the　lowest　of　the　stratified　rocks；　in　which　we　lose　the

indications　of　life　altogether。　The　hypothesis　of　the　eternity

of　the　present　state　of　nature　may　therefore　be　put　out

of　court。





Fig。　1。Ideal　Section　of　the　Crust　of　the　Earth。



　

We　now　come　to　what　I　will　term　Milton's　hypothesisthe

hypothesis　that　the　present　condition　of　things　has　endured　for

a　comparatively　short　time；　and；　at　the　commencement　of　that

time；　came　into　existence　within　the　course　of　six　days。　I　doubt

not　that　it　may　have　excited　some　surprise　in　your　minds　that　I

should　have　spoken　of　this　as　Milton's　hypothesis；　rather　than

that　I　should　have　chosen　the　terms　which　are　more　customary；

such　as　〃the　doctrine　of　creation；〃　or　〃the　Biblical　doctrine；〃

or　〃the　doctrine　of　Moses；〃　all　of　which　denominations；　as

applied　to　the　hypothesis　to　which　I　have　just　referred；　are

certainly　much　more　familiar　to　you　than　the　title　of　the

Miltonic　hypothesis。　But　I　have　had　what　I　cannot　but　think　are

very　weighty　reasons　for　taking　the　course　which　I　have　pursued。

In　the　first　place；　I　have　discarded　the　title　of　the　〃doctrine

of　creation；〃　because　my　present　business　is　not　with　the

question　why　the　objects　which　constitute　Nature　came　into

existence；　but　when　they　came　into　existence；　and　in　what　order。

This　is　as　strictly　a　historical　question　as　the　question　when

the　Angles　and　the　Jutes　invaded　England；　and　whether　they

preceded　or　followed　the　Romans。　But　the　question　about　creation

is　a　philosophical　problem；　and　one　which　cannot　be　solved；　or

even　approached；　by　the　historical　method。　What　we　want　to　learn

is；　whether　the　facts；　so　far　as　they　are　known；　afford　evidence

that　things　arose　in　the　way　described　by　Milton；　or　whether

they　do　not；　and；　when　that　question　is　settled　it　will　be　time

enough　to　inquire　into　the　causes　of　their　origination。



In　the　second　place；　I　have　not　spoken　of　this　doctrine　as　the

Biblical　doctrine。　It　is　quite　true　that　persons　as　diverse　in

their　general　views　as　Milton　the　Protestant　and　the　celebrated

Jesuit　Father　Suarez；　each　put　upon　the　first　chapter　of　Genesis

the　interpretation　embodied　in　Milton's　poem。　It　is　quite　true

that　this　interpr