1864.| Watuion on the Atlantic Deep-sea Bed and its Inhabitants. 39 
It would occupy too much space were we to enter into the whole 
of the facts bearing on the muddy deposits, with whose presence, over 
a considerable area of the sea-bed, the sounding-machine has made 
us acquainted. But there is one point to which we must invite atten- 
tion, inasmuch as its importance can hardly be overestimated, and yet, 
strange to say, it has heretofore been almost entirely overlooked. 
In some of the deeper soundings, both on the North and Mid- 
Atlantic route, fragments of rocks have been brought up. How is 
the occurrence of these to be accounted for, and what does it betoken ? 
The question is an intricate one, and so far as our present information 
goes, does not seem to admit of a perfectly satisfactory solution. 
This much may be said, however; that their presence on the imme- 
diate surface layer of the sea-bed, is only reconcilable with one or 
other of the following suppositions:—They must either have been 
recently dropped by some means from the superincumbent waters ; 
have been deposited by floating ice during past periods of the earth’s 
history ; must occur in beds which were once exposed above the sur- 
face of the sea; or be drifting about the bottom through the action of 
currents. 
Now in no case hitherto recorded have these stones been of large 
size—probably not larger than a hazel nut—but they present un- 
doubted traces of attrition. Fish, as is well known, sometimes 
swallow small stones, and, as a matter of course, get rid of them 
in time ; but this would not meet the requirements of the first of the 
above suppositions, inasmuch as it is obviously improbable that so 
many fish with stones in their stomachs should be moving about the 
ocean, as would be necessary to account for the fact; and it is still 
more improbable, if not absolutely impossible, that fish could have 
conveyed such substances from the distant shores, where they are 
alone obtainable. So that viewing this circumstance in conjunction 
with the fact, that no floating ice nowadays traverses the areas referred 
to, it is quite certain that the matter is inexplicable on the first sup- 
position. 
If deposited from floating ice during past periods of the Earth’s 
history (according to the second supposition, which is by no means 
impossible), it follows as an inevitable consequence that the muddy 
deposits are local in character, and that certain areas of the sea-bed 
consist of bare rock ; or that they are swept away by currents as fast 
as they are produced. We regard the first of these two views as most 
conformable with the evidence ; for, although there is reason to be- 
lieve that deep-seated currents prevail with sufficient force, in some of 
the shallower tracts of the Atlantic, to move the fine particles of 
which these deposits are for the most part composed, there is no 
ground whatever for supposing that they are ever powerful enough to 
sweep along large objects, such as the stones of which we have been 
speaking. It will be seen, therefore, that we are fully justified in 
laying stress on the possibility that extensive areas of exposed rock 
may occur along the basin of the Atlantic, which have hitherto escaped 
detection. The third and fourth suppositions are thus disposed of 
likewise. 
