autobiography and selected essays-第16节

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cable　＇64＇　between　this　country　and　the　United　States　was　undertaken。

For　it　became　a　matter　of　immense　importance　to　know；　not　only　the

depth　of　the　sea　over　the　whole　line　along　which　the　cable　was　to

be　laid；　but　the　exact　nature　of　the　bottom；　so　as　to　guard　against

chances　of　cutting　or　fraying　the　strands　of　that　costly　rope。　　The

Admiralty　consequently　ordered　Captain　Dayman；　an　old　friend　and

shipmate　of　mine；　to　ascertain　the　depth　over　the　whole　line　of　the

cable；　and　to　bring　back　specimens　of　the　bottom。　　In　former　days；

such　a　command　as　this　might　have　sounded　very　much　like　one　of　the

impossible　things　which　the　young　prince　in　the　Fairy　Tales　is

ordered　to　do　before　he　can　obtain　the　hand　of　the　Princess。

However；　in　the　months　of　June　and　July；　1857；　my　friend　performed

the　task　assigned　to　him　with　great　expedition　and　precision

without；　so　far　as　I　know；　having　met　with　any　reward　of　that　kind。

The　specimens　of　Atlantic　mud　which　he　procured　were　sent　to　me　to

be　examined　and　reported　upon。*





*　See　Appendix　to　Captain　Dayman's　〃Deep…sea　Soundings　in　the　North

Atlantic　Ocean；　between　Ireland　and　Newfoundland；　made　in　H。M。S。

Cyclops。　　Published　by　order　of　the　Lords　Commissioners　of　the

Admiralty；　1858。〃　　They　have　since　formed　the　subject　of　an

elaborate　Memoir　by　Messrs。　Parker　and　Jones；　published　in　the

Philosophical　Transactions　for　1865。





The　result　of　all　these　operations　is；　that　we　know　the　contours

and　the　nature　of　the　surface…soil　covered　by　the　North　Atlantic；

for　a　distance　of　seventeen　hundred　miles　from　east　to　west；　as

well　as　we　know　that　of　any　part　of　the　dry　land。



It　is　a　prodigious　plainone　of　the　widest　and　most　even　plains　in

the　world。　　If　the　sea　were　drained　off；　you　might　drive　a　wagon

all　the　way　from　Valentia；　on　the　west　coast　of　Ireland；　to　Trinity

Bay；　in　Newfoundland。　　And；　except　upon　one　sharp　incline　about　two

hundred　miles　from　Valentia；　I　am　not　quite　sure　that　it　would　even

be　necessary　to　put　the　skid　on；　so　gentle　are　the　ascents　and

descents　upon　that　long　route。　　From　Valentia　the　road　would　lie

down…hill　for　about　200　miles　to　the　point　at　which　the　bottom　is

now　covered　by　1700　fathoms　of　sea…water。　　Then　would　come　the

central　plain；　more　than　a　thousand　miles　wide；　the　inequalities　of

the　surface　of　which　would　be　hardly　perceptible；　though　the　depth

of　water　upon　it　now　varies　from　10；000　to　15；000　feet；　and　there

are　places　in　which　Mont　Blanc　might　be　sunk　without　showing　its

peak　above　water。　　Beyond　this；　the　ascent　on　the　American　side

commences；　and　gradually　leads；　for　about　300　miles；　to　the

Newfoundland　shore。



Almost　the　whole　of　the　bottom　of　this　central　plain　（which　extends

for　many　hundred　miles　in　a　north　and　south　direction）　is　covered

by　a　fine　mud；　which；　when　brought　to　the　surface；　dries　into　a

greyish…white　friable　substance。　　You　can　write　with　this　on　a

blackboard；　if　you　are　so　inclined；　and；　to　the　eye；　it　is　quite

like　very　soft；　greyish　chalk。　　Examined　chemically；　it　proves　to

be　composed　almost　wholly　of　carbonate　of　lime；　and　if　you　make　a

section　of　it；　in　the　same　way　as　that　of　the　piece　of　chalk　was

made；　and　view　it　with　the　microscope；　it　presents　innumerable

Globigerinae　embedded　in　a　granular　matrix。



Thus　this　deep…sea　mud　is　substantially　chalk。　　I　say

substantially；　because　there　are　a　good　many　minor　differences；　but

as　these　have　no　bearing　on　the　question　immediately　before　us；

which　is　the　nature　of　the　Globigerinae　of　the　chalk；it　is

unnecessary　to　speak　of　them。



Globigerinae　of　every　size；　from　the　smallest　to　the　largest；　are

associated　together　in　the　Atlantic　mud；　and　the　chambers　of　many

are　filled　by　a　soft　animal　matter。　　This　soft　substance　is；　in

fact；　the　remains　of　the　creature　to　which　the　Globigerina　shell；

or　rather　skeleton；　owes　its　existenceand　which　is　an　animal　of

the　simplest　imaginable　description。　　It　is；　in　fact；　a　mere

particle　of　living　jelly；　without　defined　parts　of　any　kind

without　a　mouth；　nerves；　muscles；　or　distinct　organs；　and　only

manifesting　its　vitality　to　ordinary　observation　by　thrusting　out

and　retracting　from　all　parts　of　its　surface；　long　filamentous

processes；　which　serve　for　arms　and　legs。　　Yet　this　amorphous

particle；　devoid　of　everything　which；　in　the　higher　animals；　we

call　organs；　is　capable　of　feeding；　growing　and　multiplying；　of

separating　from　the　ocean　the　small　proportion　of　carbonate　of　lime

which　is　dissolved　in　sea…water；　and　of　building　up　that　substance

into　a　skeleton　for　itself；　according　to　a　pattern　which　can　be

imitated　by　no　other　known　agency。



The　notion　that　animals　can　live　and　flourish　in　the　sea；　at　the

vast　depths　from　which　apparently　living　Globigerinae　have　been

brought　up；　does　not　agree　very　well　with　our　usual　conceptions

respecting　the　conditions　of　animal　life；　and　it　is　not　so

absolutely　impossible　as　it　might　at　first　appear　to　be；　that　the

Globigerinae　of　the　Atlantic　sea…bottom　do　not　live　and　die　where

they　are　found。



As　I　have　mentioned；　the　soundings　from　the　great　Atlantic　plain

are　almost　entirely　made　up　of　Globigerinae；　with　the　granules

which　have　been　mentioned　and　some　few　other　calcareous　shells；　but

a　small　percentage　of　the　chalky　mudperhaps　at　most　some　five　per

cent　of　itis　of　a　different　nature；　and　consists　of　shells　and

skeletons　composed　of　silex；　or　pure　flint。　　These　silicious　bodies

belong　partly　to　the　lowly　vegetable　organisms　which　are　called

Diatomaceae；　and　partly　to　the　minute；　and　extremely　simple；

animals；　termed　Radiolaria。　　It　is　quite　certain　that　these

creatures　do　not　live　at　the　bottom　of　the　ocean；　but　at　its

surfacewhere　they　may　be　obtained　in　prodigious　numbers　by　the

use　of　a　properly　constructed　net。　　Hence　it　follows　that　these

silicious　organisms；　though　they　are　not　heavier　than　the　lightest

dust；　must　have　fallen；　in　some　cases；　through　fifteen　thousand

feet　of　water；　before　they　reached　their　final　resting…place　on　the

ocean　floor。　　And；　considering　how　large　a　surface　these　bodies

expose　in　proportion　to　their　weight；　it　is　probable　that　they

occupy　a　great　length　of　time　in　making　their　burial　journey　from

the　surface　of　the　Atlantic　to　the　bottom。



But　if　the　Radiolaria　and　Diatoms　are　thus　rained　upon　the　bottom

of　the　sea；　from　the　superficial　layer　of　its　waters　in　which　they

pass　their　lives；　it　is　obviously　possible　that　the　Globigerinae

may　be　similarly　derived；　and　if　they　were　so；　it　would　be　much

more　easy　to　understand　how　they　obtain　their　supply　of　food　than

it　is　at　present。　　Nevertheless；　the　positive　and　negative　evidence

all　points　the　other　way。　　The　skeletons　of　the　full…grown；　deep…

sea　Globigerinae　are　so　remarkably　solid　and　heavy　in　proportion　to

their　surface　as　to　seem　little　fitted　for　floating；　and；　as　a

matter　of　fact；　they　are　not　to　be　found　along　with　the　Diatoms　and

Radiolaria；　in　the　uppermost　stratum　of　the　open　ocean。



It　has　been　observed；　again；　that　the　abundance　of　Globigerinae；　in

proportion　to　other　organisms；　of　like　kind；　increases　with　the

depth　of　the　sea；　and　that　deep…water　Globigerinae　are　larger　than

those　which　live　in　shallower　parts　of　the　sea；　and　such　facts

negative　the　supposition　that　these　organisms　have　been　swept　by

currents　from　the　shallows　into　the　deeps　of　the　Atlantic。



It　therefore　seems　to　be　hardly　doubtful　that　these　wonderful

creatures　live　and　die　at　the　depths　in　which　they　are　found。



However；　the　important　points　for　us　are；　that　the　living

Globigerinae　are　exclusively　marine　animals；　the　skeletons　of　which

abound　at　the　bottom　of　deep　seas；　and　that　there　is　not　a　shadow

of　reason　for　believing　that　the　habits　of　the　Globigerinae　of　the

chalk　differed　from　those　of　the　existing　species。　　But　if　this　be

true；　there　is　no　escaping　the　conclusion　that　the　chalk　itself　is

the　dried　mud　of　an　ancient　deep　sea。



In　working　over　the　soundings　collected　by　Captain　Dayman；　I　was

surprised　to　find　that　many　of　what　I　have　called　the　〃granules〃　of

that　mud；　were　not；　as　one　might　have　been　tempted　to　think　at

first；　the　mere　powder　and　waste　of　Globigerinae；　but　that　they　had

a　definite　form　and　size。　　I　termed　these　bodies　〃coccoliths；〃　and

doubted　their　organic　nature。　　Dr。　Wallich　＇65＇　verified　my

observation；　and　added　the　interesting　discovery；　that；　not

unfrequently；　bodies　similar　to　these　〃coccoliths〃　were　aggregated

together　into　spheroids；　which　he　termed　〃coccospheres。〃　　So　far

as　we　knew；　these　bodies；　the　nature　of　which　is　extremely　puzzling

and　problematical；　were　peculiar　to　the　Atlantic　soundings。



But；　a　few　years　ago；　Mr。　Sorby；＇66＇　in　making　a　careful　examination

of　the　chalk　by　means　of　thin　sections　and　otherwise；　observed；　as

Ehrenberg　had　done　before　him；　that　much　of　its　granular　basis

possesses　a　definite　form。　　Comparing　these　formed　particles　wit