514 
NATURE 
¢ 
[ Oc¢. 27, 1870 
that which the Norse-speaking Icelanders hold to the modern 
Scandinavians. 
If the facts be as I have now stated them, the ovws probandt 
seems to me to lie upon those who affirm that a complete stop 
was put to the formation of Chalk before the commencement of 
the Tertiary period. If, on the other hand, the continuity of the 
existing Chalk-deposit with that which formed the Chalk of 
Dover Cliffs be admitted, the question, whether we can be 
rightly said to be ‘‘still living in the Cretaceous Epoch” seems 
to me one of terms rather than of essentials. 
That we could not expect to find the Cretaceous Fauna as a 
whole in our modern Chalk, is evident from the considerations 
admirably set forth in a parallel case by the President of the 
Linnean Society, in his last Annual Address. 
The difference is undoubtedly most marked in the Mollusca ; 
only one shell, the Zérebratula caput-serpentis, having at present 
been shown to be common to the Cretaceous and the Modern 
period. But the positive evidence of continuity afforded by the 
persistency of all the types which maze the chalk, as well as of 
numerous forms of Echinoderms, Sponges, and Foraminifera 
which are among its characteristic inhabitants, appears to us to 
outweigh the negative evidence afforded by the larger amount 
of change that has taken place in the Molluscan Fauna, for 
which it would not be difficult to assign probable reasons. 
Further, it is to be borne in mind that the successive beds of 
the Cretaceous formation differ from each otherin a very marked 
manner ; so that we could not expect to find, in any one deposit, 
more than a small part of that evsemble which is commonly 
spoken of as ‘‘the Cretaceous Fauna.” What we mean by the 
expression to which Sir Roderick Murchison has taken exception, 
is simply that the facts and deductions we have brought together 
justify the assumption of the continuous prevalence of the same 
general Physical and Biological conditions, in the deep sea that 
separates the northern parts of the European and American con- 
tinents, from the time when the Chalk of those continents was 
raised into dry land to the present date. ‘This is perfectly com- 
patible with those changes in the conditions of the shallower 
portions, which have given origin to the long succession of 
Tertiary deposits. 
Passing from this topic, I now proceed to other points on 
which the researches of Prof. Wyville Thomson and myself 
appear to us to invalidate Geological doctrines that have gained 
general currency. 
Up to the commencement of the recent exploration of the 
Deep Sea bottom by means of the Dredge, the doctrine pro- 
pounded by Prof. Edward Forbes as to the limitation of Animal 
Life toa depth of 300 or 400 fathoms, and the consequently 
zoic character of all deposits formed at depths exceeding that 
amount, was generally accepted by Geologists; partly on 
account of the deservedly high authority of its originator, and 
partly because it appeared to afford a simple explanation of 
phenomena which had long perplexed Geologists and Palaon- 
tolovists, viz., the occurrence at various epochs of vast accumu- 
lations of sedimentary strata apparently altogether devoid of 
organic remains. The indications obtained by the Sounding 
apparatus, of the existence, not merely of humble Foraminifera, 
but of Annelids, Echinoderms and Crustacea, at depths far 
exceeding Edward Forbes’s limits, were not generally accepted, 
either by Zoologists or Paldeontologists, as indicating the pre- 
sence of a varied and abundant Fauna on the ocean bottom ; 
for although Dr. Wallich, with a sagacity to which I have uni- 
formly endeavoured to do full justice, had argued that they 
should be, it was specially noticed that these researches gave no 
evidence of the existence, at great depths, either of Mollusks or 
of Zoophytes—the two groups whose fossil remains are usually 
of the highest Palzeontological significance. 
Now the Dredgings which were carried down in the Lightning 
Expedition of 1869 to 650 fathoms, and in the Porcupine Ex- 
pedition of 1869 to 2,435 fathoms, have established beyond 
all reasonable question that a varied and abundant Fauna 
may exist on the sea-bottom without any limit as to depth and 
pressure; and they have further rendered it probable that, putting 
aside those Animals which are necessarily restricted by the nature 
of their food to the depth to which living Vegetation extends, a 
large proportion may accommodate themselves by gradual modi- 
fication to any amount of chazge in depth and pressure ; so that 
the assumption that the occurrence of particular types is signi- 
ficant of the depth at which a formation was deposited, can no 
longer be upheld, except in the case of animals essentially littoral. 
For example, no doctrine has been more generally accepted than 
tively shallow water ; the large West Indian representatives of 
that group being found growing on coral reefs, and a like habitat 
having obviously been peopled by them in the Carboniferous 
epoch. Yet, in the Porcupine dredgings of the present year, a 
large Pentacrinus, closely allied to the West Indian species, has 
been obtained near the coast of Portugal from a depth of about 
800 fathoms ; and the little Rhizocrinus, with another small 
Apiocrinoid, which I hope soon to describe under the name of 
Wyvillocrinus, were found last year, the former at 862 fathoms, 
the latter at 2,435. 
Further, the Lightning and the Porcupine dredgings have fully 
established the position that the distribution of marine life is much 
more closely related to the /emperature of the ocean-bottom, than 
to its depth. This is most clearly evidenced by the results of the 
careful exploration of the Channel of from 500 to 650 fathoms 
depth, which separates the plateau that supports the northern 
extremity of Scotland from the Faroe Banks. For we have 
shown that, whilst the szface-teniperature of this Channel is 
everywhere nearly the same, and indicates a derivation of its 
upper stratum from a warmer source, a considerable part of the 
deeper portion of this Channel is covered by a frigid stream, 
bringing a temperature as low as 29°5° from the Arctic Ocean ; 
this stream having in some places a depth of 2,000 feet. Thus 
the bottom of this Channel is divided into a warm area, on which 
the bottom-temperature at depths of from 500 to 600 fathoms 
is about 45°, and a co/d avea on which the bottom-temperature 
at like depths is 30°, or even lower. We have traced these. 
two areas at corresponding depths within about twenty miles of 
each other ; and where the bottom was unequal,—the slope of 
the plateau at the edge of the cold area, or of a bank in its 
midst, raising its bottom out of the co/d stream into the warm 
which overlies it—a difference of 18°5° was found within efeh¢t 
miles. No contrast could well be more striking than that which 
presented itself between the Faunce of these two areas. The 
Globigerina-mud was rigorously limited to the warm ; and of the 
animals living on its surface a large proporiion were character- 
istic of the warmer-temperate seas. The bottom of the cold 
area consisted of sand and stones; and of the animals which 
were abundantly distributed over it, a large proportion were 
essentially Boreal. In the shallower portions of the cold area, 
where an intermediate bottom temperature prevailed, an inter- 
mixture of the two Faunz, corresponding with the border posi- 
tion of this area between the Temperate and the Boreal pro- 
vinces, was readily traceable. 
Here, then, we have the remarkable fact that two deposits 
may be taking place within a few miles of each other, at the 
same depth and on the same Geological horizon (the area of one 
penetrating, so to speak, the area of the other), of which not only 
the Mineral character but the Fauna are alike different ;—that 
difference being due on the one hand to the direction of the 
current which has furnished their materials, and on the other to 
the temperature of the water brought by that current. If the 
cold area were to be raised above the surface, so that the de- 
posit at present in progress upon its bottom should become the 
subject of examination, by some Geologist of the future, 
he would find this to consist of a Sandstone formed by the 
disintegration of older rocks, the Fauna of which would 
in great degree bear a Boreal character: whilst if a por- 
tion of the warm area were elevated at the same time, 
the Geologist would be perplexed by the stratigraphical con- 
tinuity with the preceding of a Cretaceous formation, the pro- 
duction of which entirely depends upon the extensive development 
of the humblest forms of animal life under the influence of a 
higher temperature, and which includes not only an extraordinary 
abundance of Sponges, but a great variety of other animal re- 
mains, several of them belonging to the warmer-temperate 
regions. He would naturally suppose these widely different 
climatic conditions to have prevailed at different periods, and 
would probably have had recourse to the hypothesis of a “ fault ” 
to account for the phenomenon. And yet these Formations have 
been shown to be going on together, at corresponding depths, 
over wide contiguous areas of the sea-bottom ; in virtue solely of 
the fact that one area is traversed by an Equatorial, and the 
other by a Polar current. Further, in the midst of the land 
formed by the elevation of the Cold area, our Geologist would 
find hills some 1,800 feet high, covered with a Sandstone con- 
tinuous with that of the land from which they rise, but rich in 
remains of animals belonging to a more temperate province ; and 
might easily fall into the mistake of supposing that two such 
different Faunze occurring at different levels must indicate two 
that of the limiiation of the Pedunculate Crinoids to compara- | distinct climates separated in time ; instead of indicating, as they 
