autobiography and selected essays-第21章

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either　of　the　same　age　as　the　chalk；　or　of　later　date。　　So　that　the

chalk　must　not　only　have　been　formed；　but；　after　its　formation；　the

time　required　for　the　deposit　of　these　later　rocks；　and　for　their

upheaval　into　dry　land；　must　have　elapsed；　before　the　smallest

brook　which　feeds　the　swift　stream　of　〃the　great　river；　the　river

of　Babylon；〃＇74＇　began　to　flow。





Thus；　evidence　which　cannot　be　rebutted；　and　which　need　not　be

strengthened；　though　if　time　permitted　I　might　indefinitely

increase　its　quantity；　compels　you　to　believe　that　the　earth；　from

the　time　of　the　chalk　to　the　present　day；　has　been　the　theatre　of　a

series　of　changes　as　vast　in　their　amount；　as　they　were　slow　in

their　progress。　　The　area　on　which　we　stand　has　been　first　sea　and

then　land；　for　at　least　four　alternations；　and　has　remained　in　each

of　these　conditions　for　a　period　of　great　length。



Nor　have　these　wonderful　metamorphoses　of　sea　into　land；　and　of

land　into　sea；　been　confined　to　one　corner　of　England。　　During　the

chalk　period；　or　〃cretaceous　epoch；〃　not　one　of　the　present　great

physical　features　of　the　globe　was　in　existence。　　Our　great

mountain　ranges；　Pyrenees；　Alps；　Himalayas；　Andes；　have　all　been

upheaved　since　the　chalk　was　deposited；　and　the　cretaceous　sea

flowed　over　the　sites　of　Sinai　and　Ararat。



All　this　is　certain；　because　rocks　of　cretaceous；　or　still　later；

date　have　shared　in　the　elevatory　movements　which　gave　rise　to

these　mountain　chains；　and　may　be　found　perched　up；　in　some　cases；

many　thousand　feet　high　upon　their　flanks。　　And　evidence　of　equal

cogency　demonstrates　that；　though；　in　Norfolk；　the　forest…bed　rests

directly　upon　the　chalk；　yet　it　does　so；　not　because　the　period　at

which　the　forest　grew　immediately　followed　that　at　which　the　chalk

was　formed；　but　because　an　immense　lapse　of　time；　represented

elsewhere　by　thousands　of　feet　of　rock；　is　not　indicated　at　Cromer。



I　must　ask　you　to　believe　that　there　is　no　less　conclusive　proof

that　a　still　more　prolonged　succession　of　similar　changes　occurred；

before　the　chalk　was　deposited。　　Nor　have　we　any　reason　to　think

that　the　first　term　in　the　series　of　these　changes　is　known。　　The

oldest　sea…beds　preserved　to　us　are　sands；　and　mud；　and　pebbles；

the　wear　and　tear　of　rocks　which　were　formed　in　still　older　oceans。



But；　great　as　is　the　magnitude　of　these　physical　changes　of　the

world；　they　have　been　accompanied　by　a　no　less　striking　series　of

modifications　in　its　living　inhabitants。



All　the　great　classes　of　animals；　beasts　of　the　field；　fowls　of　the

air；　creeping　things；　and　things　which　dwell　in　the　waters；

flourished　upon　the　globe　long　ages　before　the　chalk　was　deposited。

Very　few；　however；　if　any；　of　these　ancient　forms　of　animal　life

were　identical　with　those　which　now　live。　　Certainly　not　one　of　the

higher　animals　was　of　the　same　species　as　any　of　those　now　in

existence。　　The　beasts　of　the　field；　in　the　days　before　the　chalk；

were　not　our　beasts　of　the　field；　nor　the　fowls　of　the　air　such　as

those　which　the　eye　of　men　has　seen　flying；　unless　his　antiquity

dates　infinitely　further　back　than　we　at　present　surmise。　　If　we

could　be　carried　back　into　those　times；　we　should　be　as　one

suddenly　set　down　in　Australia　before　it　was　colonized。　　We　should

see　mammals；　birds；　reptiles；　fishes；　insects；　snails；　and　the

like；　clearly　recognisable　as　such；　and　yet　not　one　of　them　would

be　just　the　same　as　those　with　which　we　are　familiar；　and　many

would　be　extremely　different。



From　that　time　to　the　present；　the　population　of　the　world　has

undergone　slow　and　gradual；　but　incessant　changes。　　There　has　been

no　grand　catastropheno　destroyer　has　swept　away　the　forms　of　life

of　one　period；　and　replaced　them　by　a　totally　new　creation；　but　one

species　has　vanished　and　another　has　taken　its　place；　creatures　of

one　type　of　structure　have　diminished；　those　of　another　have

increased；　as　time　has　passed　on。　　And　thus；　while　the　differences

between　the　living　creatures　of　the　time　before　the　chalk　and　those

of　the　present　day　appear　startling；　if　placed　side　by　side；　we　are

led　from　one　to　the　other　by　the　most　gradual　progress；　if　we

follow　the　course　of　Nature　through　the　whole　series　of　those

relics　of　her　operations　which　she　has　left　behind。



And　it　is　by　the　population　of　the　chalk　sea　that　the　ancient　and

the　modern　inhabitants　of　the　world　are　most　completely　connected。

The　groups　which　are　dying　out　flourish；　side　by　side；　with　the

groups　which　are　now　the　dominant　forms　of　life。



Thus　the　chalk　contains　remains　of　those　strange　flying　and

swimming　reptiles；　the　pterodactyl；　the　ichthyosaurus；　and　the

plesiosaurus；　which　are　found　in　no　later　deposits；　but　abounded　in

preceding　ages。　　The　chambered　shells　called　ammonites　and

belemnites；　which　are　so　characteristic　of　the　period　preceding　the

cretaceous；　in　like　manner　die　with　it。



But；　amongst　these　fading　remainders　of　a　previous　state　of　things；

are　some　very　modern　forms　of　life；　looking　like　Yankee　pedlars

among　a　tribe　of　Red　Indians。　　Crocodiles　of　modern　type　appear；

bony　fishes；　many　of　them　very　similar　to　existing　species　almost

supplant　the　forms　of　fish　which　predominate　in　more　ancient　seas；

and　many　kinds　of　living　shellfish　first　become　known　to　us　in　the

chalk。　　The　vegetation　acquires　a　modern　aspect。　　A　few　living

animals　are　not　even　distinguishable　as　species；　from　those　which

existed　at　that　remote　epoch。　　The　Globigerina　of　the　present　day；

for　example；　is　not　different　specifically　from　that　of　the　chalk；

and　the　same　may　be　said　of　many　other　Foraminifera。　　I　think　it

probable　that　critical　and　unprejudiced　examination　will　show　that

more　than　one　species　of　much　higher　animals　have　had　a　similar

longevity；　but　the　only　example；　which　I　can　at　present　give

confidently　is　the　snake's…head　lamp…shell　（Terebratulina　caput

serpentis）；　which　lives　in　our　English　seas　and　abounded　（as

Terebratulina　striata　of　authors）　in　the　chalk。



The　longest　line　of　human　ancestry　must　hide　its　diminished　head

before　the　pedigree　of　this　insignificant　shell…fish。　　We

Englishmen　are　proud　to　have　an　ancestor　who　was　present　at　the

Battle　of　Hastings。　　The　ancestors　of　Terebratulina　caput　serpentis

may　have　been　present　at　a　battle　of　Ichthyosauria　in　that　part　of

the　sea　which；　when　the　chalk　was　forming；　flowed　over　the　site　of

Hastings。　　While　all　around　has　changed；　this　Terebratulina　has

peacefully　propagated　its　species　from　generation　to　generation；

and　stands　to　this　day；　as　a　living　testimony　to　the　continuity　of

the　present　with　the　past　history　of　the　globe。





Up　to　this　moment　I　have　stated；　so　far　as　I　know；　nothing　but

well…authenticated　facts；　and　the　immediate　conclusions　which　they

force　upon　the　mind。



But　the　mind　is　so　constituted　that　it　does　not　willingly　rest　in

facts　and　immediate　causes；　but　seeks　always　after　a　knowledge　of

the　remoter　links　in　the　chain　of　causation。



Taking　the　many　changes　of　any　given　spot　of　the　earth's　surface；

from　sea　to　land　and　from　land　to　sea；　as　an　established　fact；　we

cannot　refrain　from　asking　ourselves　how　these　changes　have

occurred。　　And　when　we　have　explained　themas　they　must　be

explainedby　the　alternate　slow　movements　of　elevation　and

depression　which　have　affected　the　crust　of　the　earth；　we　go　still

further　back；　and　ask；　Why　these　movements？



I　am　not　certain　that　any　one　can　give　you　a　satisfactory　answer　to

that　question。　　Assuredly　I　cannot。　　All　that　can　be　said；　for

certain；　is；　that　such　movements　are　part　of　the　ordinary　course　of

nature；　inasmuch　as　they　are　going　on　at　the　present　time。　　Direct

proof　may　be　given；　that　some　parts　of　the　land　of　the　northern

hemisphere　are　at　this　moment　insensibly　rising　and　others

insensibly　sinking；　and　there　is　indirect；　but　perfectly

satisfactory；　proof；　that　an　enormous　area　now　covered　by　the

Pacific　has　been　deepened　thou