e found.

As I have mentioned, the soundings from the great Atlantic plain are
almost entirely made up of _Globigerinoe_, with the granules which have
been mentioned, and some few other calcareous shells; but a small
percentage of the chalky mud--perhaps at most some five per cent. of it--
is 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 _Diatomaceoe_, 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 surface--where 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 _Globigerinoe_ 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 _Globigerinoe_ 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
_Globigerinoe_, in proportion to other organisms, of like kind, increases
with the depth of the sea; and that deep-water _Globigerinoe_ 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.[2]