from the mica and hornblende, and manufactured a white or yellow clay
out of the one, which it deposited in great sheets by itself, as west
of the Mississippi; while it ground up the mica and hornblende and
made blue or red clays, which it laid down elsewhere, as the red
clays are spread over that great stretch of fifteen hundred miles to
which I have referred.

{p. 35}

Can any one suppose that ice could so discriminate?

And if it by any means effected this separation of the particles of
granite, indissolubly knit together, how could it perpetuate that
separation while moving over the land, crushing all beneath and
before it, and leave it on the face of the earth free from commixture
with the surface rocks?

Again: the ice-sheets which now exist in the remote north do not move
with a constant and regular motion southward, grinding up the rocks
as they go. A recent writer, describing the appearance of things in
Greenland, says:

"The coasts are deeply indented with numerous bays and fiords or
firths, which, when traced inland, are almost invariably found to
terminate against glaciers. Thick ice frequently appears, too,
crowning the exposed sea-cliffs, from the edges of which _it droops
in thick, tongue-like, and stalactitic projections_, until its own
weight forces it to break away and topple down the precipices into
the sea."[1]