and we may search the _detritus_ that beaches and rivers push along
their beds, but _we shall not find any stones at all resembling those
of the till_."[1]

But we need not discuss any further this theory. It is now almost
universally abandoned.

We know of no way in which such waves could be formed; if they were
formed, they could not find the material to carry over the land; if
they did find it, it would not have the markings which are found in
the Drift, and it would possess marine fossils not found in the
Drift; and the waves would not and could not scratch and groove the
rock-surfaces underneath the Drift, as we know they are scratched and
grooved.

Let us then dismiss this hypothesis, and proceed to the consideration
of the next.

[1. "The Great Ice Age," p. 69.]

{p. 13}

CHAPTER IV.

WAS IT CAUSED BY ICEBERGS?

WE come now to a much more reasonable hypothesis, and one not without
numerous advocates even to this day, to wit: that the drift-deposits
were caused by icebergs floating down in deep water over the sunken