autobiography and selected essays-第20章

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coralline　could　not　have　fixed　itself；　if　the　Crania　had　been

covered　up　with　chalk　mud；　and　could　not　have　lived　had　itself　been

so　covered　it　follows；　that　an　inch　of　chalk　mud　could　not　have

accumulated　within　the　time　between　the　death　and　decay　of　the　soft

parts　of　the　sea…urchin　and　the　growth　of　the　coralline　to　the　full

size　which　it　has　attained。　　If　the　decay　of　the　soft　parts　of　the

sea…urchin；　the　attachment；　growth　to　maturity；　and　decay　of　the

Crania；　and　the　subsequent　attachment　and　growth　of　the　coralline；

took　a　year　（which　is　a　low　estimate　enough）；　the　accumulation　of

the　inch　of　chalk　must　have　taken　more　than　a　year：　and　the　deposit

of　a　thousand　feet　of　chalk　must；　consequently；　have　taken　more

than　twelve　thousand　years。



The　foundation　of　all　this　calculation　is；　of　course；　a　knowledge

of　the　length　of　time　the　Crania　and　the　coralline　needed　to　attain

their　full　size；　and；　on　this　head；　precise　knowledge　is　at　present

wanting。　　But　there　are　circumstances　which　tend　to　show；　that

nothing　like　an　inch　of　chalk　has　accumulated　during　the　life　of　a

Crania；　and；　on　any　probable　estimate　of　the　length　of　that　life；

the　chalk　period　must　have　had　a　much　longer　duration　than　that

thus　roughly　assigned　to　it。





Thus；　not　only　is　it　certain　that　the　chalk　is　the　mud　of　an

ancient　sea…bottom；　but　it　is　no　less　certain；　that　the　chalk　sea

existed　during　an　extremely　long　period；　though　we　may　not　be

prepared　to　give　a　precise　estimate　of　the　length　of　that　period　in

years。　　The　relative　duration　is　clear；　though　the　absolute

duration　may　not　be　definable。　　The　attempt　to　affix　any　precise

date　to　the　period　at　which　the　chalk　sea　began；　or　ended；　its

existence；　is　baffled　by　difficulties　of　the　same　kind。　　But　the

relative　age　of　the　cretaceous　epoch　may　be　determined　with　as

great　ease　and　certainty　as　the　long　duration　of　that　epoch。



You　will　have　heard　of　the　interesting　discoveries　recently　made；

in　various　parts　of　Western　Europe；　of　flint　implements；　obviously

worked　into　shape　by　human　hands；　under　circumstances　which　show

conclusively　that　man　is　a　very　ancient　denizen　of　these　regions。



It　has　been　proved　that　the　old　populations　of　Europe；　whose

existence　has　been　revealed　to　us　in　this　way；　consisted　of

savages；　such　as　the　Esquimaux　are　now；　that；　in　the　country　which

is　now　France；　they　hunted　the　reindeer；　and　were　familiar　with　the

ways　of　the　mammoth　and　the　bison。　　The　physical　geography　of

France　was　in　those　days　different　from　what　it　is　nowthe　river

Somme；＇69＇　for　instance；　having　cut　its　bed　a　hundred　feet　deeper

between　that　time　and　this；　and；　it　is　probable；　that　the　climate

was　more　like　that　of　Canada　or　Siberia；　than　that　of　Western

Europe。



The　existence　of　these　people　is　forgotten　even　in　the　traditions

of　the　oldest　historical　nations。　　The　name　and　fame　of　them　had

utterly　vanished　until　a　few　years　back；　and　the　amount　of　physical

change　which　has　been　effected　since　their　day；　renders　it　more

than　probable　that；　venerable　as　are　some　of　the　historical

nations；　the　workers　of　the　chipped　flints　of　Hoxne　or　of　Amiens　＇70＇

are　to　them；　as　they　are　to　us；　in　point　of　antiquity。



But；　if　we　assign　to　these　hoar　relics　of　long…vanished　generations

of　men　the　greatest　age　that　can　possibly　be　claimed　for　them；　they

are　not　older　than　the　drift；　or　boulder　clay；　which；　in　comparison

with　the　chalk；　is　but　a　very　juvenile　deposit。　　You　need　go　no

further　than　your　own　sea…board　for　evidence　of　this　fact。　　At　one

of　the　most　charming　spots　on　the　coast　of　Norfolk；　Cromer；　you

will　see　the　boulder　clay　forming　a　vast　mass；　which　lies　upon　the

chalk；　and　must　consequently　have　come　into　existence　after　it。

Huge　boulders　of　chalk　are；　in　fact；　included　in　the　clay；　and　have

evidently　been　brought　to　the　position　they　now　occupy；　by　the　same

agency　as　that　which　has　planted　blocks　of　syenite　from　Norway　side

by　side　with　them。



The　chalk；　then；　is　certainly　older　than　the　boulder　clay。　　If　you

ask　how　much；　I　will　again　take　you　no　further　than　the　same　spot

upon　your　own　coasts　for　evidence。　　I　have　spoken　of　the　boulder

clay　and　drift　as　resting　upon　the　chalk。　　That　is　not　strictly

true。　　Interposed　between　the　chalk　and　the　drift　is　a

comparatively　insignificant　layer；　containing　vegetable　matter。

But　that　layer　tells　a　wonderful　history。　　It　is　full　of　stumps　of

trees　standing　as　they　grew。　　Fir…trees　are　there　with　their　cones；

and　hazel…bushes　with　their　nuts；　there　stand　the　stools　of　oak　and

yew　trees；　beeches　and　alders。　　Hence　this　stratum　is　appropriately

called　the　〃forest…bed。〃



It　is　obvious　that　the　chalk　must　have　been　up…heaved　and　converted

into　dry　land；　before　the　timber　trees　could　grow　upon　it。　　As　the

boles　of　some　of　these　trees　are　from　two　to　three　feet　in

diameter；　it　is　no　less　clear　that　the　dry　land　this　formed

remained　in　the　same　condition　for　long　ages。　　And　not　only　do　the

remains　of　stately　oaks　and　well…grown　firs　testify　to　the　duration

of　this　condition　of　things；　but　additional　evidence　to　the　same

effect　is　afforded　by　the　abundant　remains　of　elephants；

rhinoceroses；　hippopotomuses　and　other　great　wild　beasts；　which　it

has　yielded　to　the　zealous　search　of　such　men　as　the　Rev。　Mr。　Gunn。＇71＇



When　you　look　at　such　a　collection　as　he　has　formed；　and　bethink

you　that　these　elephantine　bones　did　veritably　carry　their　owners

about；　and　these　great　grinders　crunch；　in　the　dark　woods　of　which

the　forest…bed　is　now　the　only　trace；　it　is　impossible　not　to　feel

that　they　are　as　good　evidence　of　the　lapse　of　time　as　the　annual

rings　of　the　tree…stumps。



Thus　there　is　a　writing　upon　the　walls　of　cliffs　at　Cromer；　and

whoso　runs　may　read　it。　　It　tells　us；　with　an　authority　which

cannot　be　impeached；　that　the　ancient　sea…bed　of　the　chalk　sea　was

raised　up；　and　remained　dry　land；　until　it　was　covered　with　forest；

stocked　with　the　great　game　whose　spoils　have　rejoiced　your

geologists。　　How　long　it　remained　in　that　condition　cannot　be　said；

but　〃the　whirligig　of　time　＇72＇　brought　its　revenges〃　in　those　days

as　in　these。　　That　dry　land；　with　the　bones　and　teeth　of　generations

of　long…lived　elephants；　hidden　away　among　the　gnarled　roots　and

dry　leaves　of　its　ancient　trees；　sank　gradually　to　the　bottom　of

the　icy　sea；　which　covered　it　with　huge　masses　of　drift　and　boulder

clay。　　Sea…beasts；　such　as　the　walrus；　now　restricted　to　the

extreme　north；　paddled　about　where　birds　had　twittered　among　the

topmost　twigs　of　the　fir…trees。　　How　long　this　state　of　things

endured　we　know　not；　but　at　length　it　came　to　an　end。　　The　upheaved

glacial　mud　hardened　into　the　soil　of　modern　Norfolk。　　Forests　grew

once　more；　the　wolf　and　the　beaver　replaced　the　reindeer　and　the

elephant；　and　at　length　what　we　call　the　history　of　England　dawned。



Thus　you　have　within　the　limits　of　your　own　county；　proof　that　the

chalk　can　justly　claim　a　very　much　greater　antiquity　than　even　the

oldest　physical　traces　of　mankind。　　But　we　may　go　further　and

demonstrate；　by　evidence　of　the　same　authority　as　that　which

testifies　to　the　existence　of　the　father　of　men；　that　the　chalk　is

vastly　older　than　Adam　himself。



The　Book　of　Genesis　informs　us　that　Adam；　immediately　upon　his

creation；　and　before　the　appearance　of　Eve；　was　placed　in　the

Garden　of　Eden。　　The　problem　of　the　geographical　position　of　Eden

has　greatly　vexed　the　spirits　of　the　learned　in　such　matters；　but

there　is　one　point　respecting　which；　so　far　as　I　know；　no

commentator　has　ever　raised　a　doubt。　　This　is；　that　of　the　four

rivers　which　are　said　to　run　out　of　it；　Euphrates　and　Hiddekel　＇73＇

are　identical　with　the　rivers　now　known　by　the　names　of　Euphrates

and　Tigris。



But　the　whole　country　in　which　these　mighty　rivers　take　their

origin；　and　through　which　they　run；　is　composed　of　rocks　which　are

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