{p. 73}

"It is a finely levigated silico-aluminous earth--formed by the
disintegration of feldspathic or granite rocks."[1]

The particles ground out of feldspar are finer than those derived
from mica and hornblende, and we can readily understand how the great
forces of gravity, acting upon the dust of the comet's tail, might
separate one from the other; or how magnetic waves passing through
the comet might arrange all the particles containing iron by
themselves, and thus produce that marvelous separation of the
constituents of the granite which we have found to exist in the Drift
clays. If the destroyed world possessed no sedimentary rocks, then
the entire material of the comet would consist of granitic stones and
dust such as constitutes clays.

The stones are reduced to a small size by the constant attrition:

"The stones of the 'till' are not of the largest; indeed, bowlders
above four feet in diameter are comparatively seldom met with in the
till."[2]

And this theory is corroborated by the fact that the eminent German
geologist, Dr. Hahn, has recently discovered an entire series of
organic remains in meteoric stones, of the class called _chrondites_,
and which he identifies as belonging to classes of sponges, corals,
and crinoids. Dr. Weinland, another distinguished German,
corroborates these discoveries; and he has also found fragments in
these stones very much like the youngest marine chalk in the Gulf of
Mexico; and he thinks he sees, under the microscope, traces of