and inclined to coalesce again when crushed, and the retracted pseudopodia are
occasionally seen forming minute bosses on the external surface of the shell; in
the other, the colour is a dusky brown inclining to grey, the fleshy matter is not
viscid, and there are no traces of the pseudopodia. Lastly, the definite boundaries
of the Globigerina-deposits, to which allusion has already been made, afford
presumptive evidence that the increase of the organisms is dependent on conditions
prevalent on the spot, and consequently evidence of vitality.
The association of the more extensive Globigerina-deposits with the Gulf
Stream and its several offshoots in the North Atlantic is dependent, I conceive,
on the vast supplies of car-bonate of lime brought down to it by the great rivers
that discharge themselves into the Gulf of Mexico and the Caribbean Sea.
Captain Maury combats the idea that the “ Mississippi is the Father of the Gulf
Stream,” and quotes Captain Livingstone as haring “ overturned this hypothesis
by showing that the volume of water which the Mississippi empties into the Gulf
of Mexico is not equal to the three-thousandth part of that which escapes from it
through the Gulf Stream.” He also points out that the water of the Mississippi is
fresh, whilst that of the Gulf Stream is sa lt; and that the waters of the Mexican
Gulf and Caribbean Sea are salter than the waters of like temperature in those
parts of the ocean through which the Gulf Stream flows, the phenomena being
accounted for by the excessive evaporation which takes place in the waters poured
into the Gulf Stream and Caribbean Sea by the great equatorial current*.
However true Captain Maury’s view may be with regard to the other saline
constituents of sea-water, I venture to think it cannot be so iu the case of the
carbonate of lime, or, indeed, the calcareous salts generally. These we know are
essentially derived from fresh-water discharges. The surface waters of the ocean
are those which contain the smallest quantity of calcareous matter. The great
equatorial current is quite superficial, and on the African side it only receives
the outpourings of two rivers, namely, the Niger and Senegal, which, though
large, are much inferior in size and extent to the Amazon, Orinoco, Magdalena,
Eio Grande, and Mississippi—one and all of which debouch into the equatorial
current either before or after it sweeps into the Caribbean Sea and Gulf of
Mexico, and pour forth into the waters destined to emerge again as the Gulf
Stream the vast stores cf calcareous matter they bring down from the interior of
* ‘ The Physical Geography of the Sea,’ p. 26 et seq.
the American continents. The massiveness of the shells, in the greater portion
of the Foraminiferous deposits obtained on the bed of the North Atlantic, clearly
shows that the material of which they are composed is present in its waters in
abundance. I f the views suggested by me regarding the increase of carbonate of
lime with the depth be correct, or even supposing the superabundant supply
indicated by the presence of the calcareous deposits to be due to the uninterrupted
supply of carbonate, irrespectively of its increase with the depth, the phenomena
here indicated serve to corroborate them, and we have presented to us an
example of disintegration of strata on the one hand, and reconstruction on the
other, on the grandest scale that the earth affords.
The facts connected with the discovery of highly organized radiate animals at
extreme depths may justly be regarded as establishing a new era in marine
zoology; for, if we attentively examine their bearings, we shall find that, whilst
they throw a flood of light on the conditions essential to the maintenance of life
in existing seas, they serve at the same time to explain anomalies in the history
of some of the older fossiliferous strata, and thus add another link to the chain
that binds the Present with the Past.
In order to render apparent the full significance of the Star-fish sounding, 1
shall endeavour briefly to detail the geogi’aphical relations of the locality in
which it was taken; the mode in which it was effected; the proofs that the
creatm-es were captured at the bottom; and, lastly, the reasons for believing that,
although originally a shallow-water species, these Star-fishes had gradually, and
through a long series of generations, accommodated themselves to the abnormal
conditions incident on the subsidence of the sea-bed.
The sounding was taken in lat. 59° 27' N., long. 26° 41' W., about halfway
between Cape Farewell and the north-west coast of Ireland,—the distances being,
from the nearest part of Greenland 500 miles, of Iceland (namely, the “ Blinde
Skier” rock) 250 miles, and the Eockall Shoal about 400 miles.
I t is a very notable fact that the position thus indicated is within 100 miles
to the north-eastward of that assigned to the “ Sunken land of Buss ” in old
charts *; and that, at a spot about 100 miles to the westward, where the previous
sounding was taken, a decrease of depth was indicated amountmg to 612
fathoms. For, since it is in the last degree improbable that the shallowest
* See Diary, pp. 63, 64, and 65.