terrible force, could have scratched and dented the rocks, could it
have made long, continuous lines and grooves upon them? But the fact
is, the _striæ_ on the face of the rocks covered by the Drift are
_not_ continuous;

[1. Dana's "Text-Book," p. 275.

2. "Popular Science Monthly," January, 1878, p. 320.]

{p. 100}

they do not indicate a steady and constant pressure, such as would
result where a mountainous mass of ice had caught a rock and held it,
as it were, in its mighty hand, and, thus holding it steadily, had
scored the rocks with it as it moved forward.

"The groove is of irregular depth, its floor rising and falling, as
though hitches had occurred when it was first planed, the great
chisel meeting resistance, or being thrown up at points along its
path."[1]

What other results would follow at once from contact with the comet?

We have seen that, to produce the phenomena of the Glacial age, it
was absolutely necessary that it must have been preceded by a period
of heat, great enough to vaporize all the streams and lakes and a
large part of the ocean. And we have seen that no mere ice-hypothesis
gives us any clew to the cause of this.

Would the comet furnish us with such heat? Let me call another