oze, after the
calcareous matter has been by some means removed. An ordinary mixture of
calcareous _Foraminifera_ with the shells of pteropods, forming a fair
sample of _Globigerina_ ooze from near St. Thomas, was carefully washed,
and subjected by Mr. Buchanan to the action of weak acid; and he found
that there remained after the carbonate of lime had been removed, about 1
per cent. of a reddish mud, consisting of silica, alumina, and the red
oxide of iron. This experiment has been frequently repeated with
different samples of _Globigerina_ ooze, and always with the result that
a small proportion of a red sediment remains, which possesses all the
characters of the red clay."

* * * * *

"It seems evident from the observations here recorded, that _clay_, which
we have hitherto looked upon as essentially the product of the
disintegration of older rocks, may be, under certain circumstances, an
organic formation like chalk; that, as a matter of fact, an area on the
surface of the globe, which we have shown to be of vast extent, although
we are still far from having ascertained its limits, is being covered by
such a deposit at the present day.

"It is impossible to avoid associating such a formation with the fine,
smooth, homogeneous clays and schists, poor in fossils, but showing worm-
tubes and tracks, and bunches of doubtful branching things, such as
Oldhamia, silicious sponges, and thin-shelled peculiar shrimps. Such
formations, more or less metamorphosed, are very familiar, especially to
the student of palaeozoic geology, and they often attain a vast thickness.
One is inclined, from the great resemblance between them in composition
and in the general character of the included fauna, to suspect that these
may be organic formations, like the modern red clay of the Atlantic and
Southern Sea, accumulations of the insoluble ashes of shelled creatures.

"The dredging in the red clay on the 13th of March was usually rich. The
bag contained examples, those with calcareous shells rather stunted, of
most of the characteristic deep-water groups of the Southern Sea,
including _Umbellularia, Euplectella, Pterocrinus, Brisinga, Ophioglypha,
Pourtalesia_, and one or two _Mollusca_. This is, however, very rarely
the case. Generally the red clay is barren, or contains only a very small
number of forms."

It must be admitted that it is very difficult, at present, to frame any
satisfactory explanation