arated from one another,
and submitted to microscopic examination, either as opaque or as
transparent objects. By combining the views obtained in these various
methods, each of the rounded bodies may be proved to be a
beautifully-constructed calcareous fabric, made up of a number of
chambers, communicating freely with one another. The chambered bodies
are of various forms. One of the commonest is something like a
badly-grown raspberry, being formed of a number of nearly globular
chambers of different sizes congregated together. It is called
Globigerina, and some specimens of chalk consist of little else than
Globigerinae and granules.

[Illustration: GLOBIGERINA.]

Let us fix our attention upon the Globigerina. It is the spoor of the
game we are tracking. If we can learn what it is and what are the
conditions of its existence, we shall see our way to the origin and
past history of the chalk.

A suggestion which may naturally enough present itself is, that these
curious bodies are the result of some process of aggregation which has
taken place in the carbonate of lime; that, just as in winter, the
rime on our windows simulates the most delicate and elegantly
arborescent foliage--proving that the mere mineral matter may, under
certain conditions, assume the outward form of organic bodies--so this
mineral substance, carbonate of lime, hidden away in the bowels of
the earth, has taken the shape of these chambered bodies. I am not
raising a merely fanciful and unreal objection. Very learned men, in
former days, have even entertained the notion that all the formed
things found in rocks are of this nature; and if no such conception is
at present held to be admissible, it is because long and varied
experience has now shown that mineral matter never does assume the
form and structure we find in fossils. If anyone were to try to
persuade you that an oyster-shell (which is also chiefly composed of
carbonate of lime) had crystallized out of sea-water, I suppose you
would laugh at the absurdity. Your laughter would be justified by the
fact that all experience tends to show that oyster-shells are formed
by the agency of oysters, and in no other way. And if there were no
better reasons, we should be justified, on like grounds, in believing
that Globigerina is not the product of anything but vital activity.

Happily, however, better evidence in proof of the organic nature of
the Globigerinae than that of analogy is forthcoming. It