The Sunday herald. [volume] (Washington [D.C.]) 1866-1887, 1880-05-09
SECRETS or THE SEA DEprHS.

Admiralty ,his scientific plan for a circumnavi-
CATION expedition which resulted in sending
the Challenger" he expressed the belief
that the key to the Interpretation of much
cot the past history of our globe is at present
"lying at the bottom of the sea waiting to
"be brought up" Although the materials
of that voyage have not yet been fully
worked up, and it will he some years yet
before a general resume of the geological re-
suits can be given, enough is already known
to fully Justify Professor Carpenters remark
able prediction. People with a cursory idea
of geological science know that the prevalent
theory until recently has been that of Sir
Charles Lyell, who held that the carth's sur
face had been subject to periods of elevation |
and subsidence, so that what had once been |
continents had become sea bottom. and vice |
versa. The investigation of the ocean bed by |
Captain (now Sir George Mares has utterly |
disproved this, and shown the correctness of
the doctrine propounded by Professor Dana, |
that the existing continental areas of dry |
land and ocean basins were formed as such |
in the first instance upon the original con-
soldation of the earth's crust and its shrink
age upon the liquid mass within. Or, as
Professor Geikie, in his recent lecture on
Geographical Evolution puts it
The present continental ridges have probably
always existed In some foim: and corollary We
may infer that The present deep ocsdn basins Hkc-
rise dots from The remotsst geological antiquity.
The common idea that the ocean bed is
filling up with the earthly deposits washed
off the land is also shown by the i" Challen-
ger " explorations to be entirely erronc-
Gus. Such deposits do not extend into the
deep sea, or the real ocean basins. but are
deposited wholly upon the marginal belt Of
sea floor skirting the land. This is shall
low rim, in reality submerged portion Of he
continental platforms, and 4" it is here" says
Professor Geikie, Z" that nature has always
" strewn the dust of continents to be-.
Professor Carpenter says:
| We know for certain that the sands and clays
washed OIL the land-whether hy the action the ice
| or river waters on Its surface, by the weming
away of its margin by the of the sca-slnk to
| the sea-bottom long before they reach the deeper
ahysses not the least trace of such sediments hor-
| ing been opy,ci.re found a. distance from the
| continental platforms. And thus the study Of the
deposits on the oceanic sei-bed has fully confirmed
the conclusion drawn from the present conguration
of the earth's surface to the general persistence of
those original inequalities which have respectively
served as the bases of the existing continents AMI the
floors OF the great basins.
The three great oceanic arcas-the Allan
tie, the Indian and Southern. and the Pa
ciic--all have the same characteristic: an
abrupt declivity dividing the true basin, at
n few hundred miles distance, sometimes
less, from land, from the depressed rim re-
ferred to above. The deepest trustworthy
sounding yet made was between New Guinea
and the average depth of the ocean floors is
at least two and half miles, or Is, oOO
feet. a striking popularity of the ocean
floor is its extraordinary natness, so that :" il
the bottom of the mid-ocean were laid dry
an observer standing on almost any spot o
it would find himself surrounded by
, "plain only comparable to that of the Nortl
, American prairies or the South American
"pampas."
Quite as interesting as the topography o
, the sea bed, or the character of its deposits
t which comprise animals living at a depth o
t over four miles, in water below the freezin!
: point, perfect darkness, and enduring pres
sure of four tons to the square inch-are th
thermal phenomena revealed by the - Chal
"lenger ;" soundings. The extreme coldnes
/ of the whole body of the ocean water (excep
n in the North Atlantic) saving thin stratum
of about four hundred fathoms at the top, i
one of the most marvellous of things to tn
/ unscicntiiic mind Thus, says Professor Car
u penter:
Tile thermal condition of the Southern Ocean Is Ell
tirely dominated by the great mass of glacii
T. water that has been cooled down In the Antaicti
area: and that 1t Is so to speak, rsS.rroir n
II coid, the outflow from which keeps down the ten
perature of every part OF the oceanic In free
munication with II. This see best In the Pacih,
& whose vast basin is almost entirely filed by
glacial sub glacial codness the surface Of whic
i In the intertropical region there floats layer who
A. temperature rises rapidly from the lower limit 4
To 500 at the surface and whose thickness nowhe
W more than oRs-ffth of the whole depth This excel
tiona stratum which clearly derives Its heat from Il
direct action of the solar rays upon Its surface pr,
Is gressively tlns away In either hemisphere as 1t
traced from the tropic to the parallel of 5jo where
" disappears altogether, except In the Kuro Swo g
OF stream p1 tllt racine, WHcn hlantS
Japan toward Behrings Strait.
u" All this is most important, and we con
oil mend to those interested in physics IL
1t whole of Professor Carpenters article in IL
an Nineteenth Century for April This cold III
i, derstratum which forms the bulk of Il
ocean water sometimes falls degree or tv
below the freezing point of fresh water:
ct In the south Atlantic at 80 s. lat, at a depth
2, 900 fahoms, the lowest stratum Of oJsolut.Ly gL
cai cdter at temperature beneath 800 had the emo
T. nous thickness of 900 fathoms this overlaid
another stratum OF J. 900 fathoms, In which the ten
~ perature slowly from $50 at Its to 36
nv Its upper suface and this again by another OF alo
500 fathoms which showed a further rise at Its upp
IL surface To 400, the remaining 400 fathoms being
limit at which the solar rays exert any direct heath
influence.
es The thermal condition OF the North Atianti
IS however, is very different. The "Porc
ire pine" temperature soundings showed Il
3, general thickness of the warm upper stratu
TO De from 500 to 800 fathoms. This is d,
:" to the ridge in the ocean bed between Gree
'i- land and Iceland, which impedes the on
lrt flow of the deepest stratum or coolest wat
ii. of the Arctic basin. singular fact ~
-, dicted by Dir. Carpenter was found to he tru
the Challenger" party finding the war
upper stratum hinHeSt under the Equato
aS This is due TO the meeting Of the Arctic al
III Antarctic underilows causing an uprising
'e- cold water toward the surface, and creatii
Ire the equatorial currents of warm surfa
en water setting toward the Poles. But Il
upper stratum in the North Atlantic is II
~ only exceptionally deep hut exceptional
warm In consequence of the evaporati
~ produced by its long exposure TO the sun
Nv excess of salt makes it
heavier than the colder water whl,s should ulheTw
H occupy ITS place In the BASIN and consequently ST
pt sues Itself for the latter by graytaon to the DEF
ms of several hundred athoms Thus II conveys the
heat dowmMaId. 3D. hmch . manmer 20 nAke