so happens
that calcareous skeletons, exactly similar to the Globigerinae of the
chalk, are being formed, at the present moment, by minute living
creatures, which flourish in multitudes, literally more numerous than
the sands of the sea-shore, over a large extent of that part of the
earth's surface which is covered by the ocean.

The history of the discovery of these living Globigerinae, and of the
part which they play in rock-building, is singular enough. It is a
discovery which, like others of no less scientific importance, has
arisen, incidentally, out of work devoted to very different and
exceedingly practical interests.

When men first took to the sea, they speedily learned to look out for
shoals and rocks; and the more the burthen of their ships increased,
the more imperatively necessary it became for sailors to ascertain
with precision the depth of the waters they traversed. Out of this
necessity grew the use of the lead and sounding-line; and, ultimately,
marine-surveying, which is the recording of the form of coasts and of
the depth of the sea, as ascertained by the sounding-lead, upon
charts.

At the same time, it became desirable to ascertain and to indicate the
nature of the sea-bottom, since this circumstance greatly affects its
goodness as holding ground for anchors. Some ingenious tar, whose name
deserves a better fate than the oblivion into which it has fallen,
attained this object by "arming" the bottom of the lead with a lump of
grease, to which more or less of the sand or mud, or broken shells, as
the case might be, adhered, and was brought to the surface. But,
however well adapted such an apparatus might be for rough nautical
purposes, scientific accuracy could not be expected from the armed
lead, and to remedy its defects (especially when applied to sounding
in great depths) Lieutenant Brooke, of the American Navy, some years
ago invented a most ingenious machine, by which a considerable portion
of the superficial layer of the sea-bottom can be scooped out and
brought up, from any depth to which the lead descends.

In 1853, Lieutenant Brooke obtained mud from the bottom of the North
Atlantic, between Newfoundland and the Azores, at a depth of more than
ten thousand feet, or two miles, by the help of this sounding
apparatus. The specimens were sent for examination to Ehrenberg of
Berlin, and to Bailey of West Point, and those able microscopists
found that this deep-sea mud was almost entirely c