ny reward of that kind. The
specimens of Atlantic mud which he procured were sent to me to be
examined and reported upon.[29]

The result of all these operations is, that we know the contours and the
nature of the surface-soil covered by the North Atlantic, for a distance
of 1,700 miles from east to west, as well as we know that of any part of
the dry land.

It is a prodigious plain--one of the widest and most even plains in the
world. If the sea were drained off, you might drive a wagon all the way
from Valentia, on the west coast of Ireland, to Trinity Bay, in
Newfoundland. And, except upon one sharp incline about 200 miles from
Valentia, I am not quite sure that it would even be necessary to put the
skid on, so gentle are the ascents and descents upon that long route.
From Valentia the road would lie down hill for about 200 miles to the
point at which the bottom is now covered by 1,700 fathoms of sea-water.
Then would come the central plain, more than a thousand miles wide, the
inequalities of the surface of which would be hardly perceptible, though
the depth of water upon it now varies from 10,000 to 15,000 feet; and
there are places in which Mont Blanc might be sunk without showing its
peak above water. Beyond this, the ascent on the American side
commences, and gradually leads, for about 300 miles, to the Newfoundland
shore.

Almost the whole of the bottom of this central plain (which extends for
many hundred miles in a north and south direction) is covered by a fine
mud, which, when brought to the surface, dries into a greyish-white
friable substance. You can write with this on a blackboard, if you are
so inclined; and, to the eye, it is quite like very soft, greyish chalk.
Examined chemically, it proves to be composed almost wholly of carbonate
of lime; and if you make a section of it, in the same way as that of the
piece of chalk was made, and view it with the microscope, it presents
innumerable _Globigerinae_, embedded in a granular matrix.

Thus this deep-sea mud is substantially chalk. I say substantially,
because there are a good many minor differences: but as these have no
bearing on the question immediately before us,--which is the nature of
the _Globigerinae_ of the chalk,--it is unnecessary to speak of them.

_Globigerinae_ of every size, from the smallest to the largest, are
associated together in the Atlantic mud, and the chambers of many are
filled by a soft animal matter. This soft substance is