ch give rise to moraines on its surface;[12] and, as
rocks from Cumberland and Ireland were carried by the ice-sheet to the Isle
of Man, there must have been a very long period during which the ice-sheets
of Britain and Ireland terminated in the ocean and sent off abundance of
rock-laden bergs into the surrounding seas; and the same thing must have
occurred along all the coasts of Northern Europe and Eastern America.

We cannot therefore doubt that throughout the greater part of the duration
of a glacial epoch the seas adjacent to the glaciated countries would
receive continual deposits of large rocks, rock-fragments, and gravel,
similar to the material of modern and ancient moraines, and analogous to
the drift and the numerous travelled blocks which the ice has undoubtedly
scattered broadcast over every glaciated country; and these rocks and
boulders would be imbedded in whatever deposits were then forming, either
from the matter carried down by rivers or from the mud ground off {66} the
rocks and carried out to sea by the glaciers themselves. Moreover, as
icebergs float far beyond the limits of the countries which gave them
birth, these ice-borne materials would be largely imbedded in deposits
forming from the denudation of countries which had never been glaciated, or
from which the ice had already disappeared.

But if every period of high excentricity produced a glacial epoch of
greater or less extent and severity, then, on account of the frequent
occurrence of a high phase of excentricity during the three million years
for which we have the tables, these boulder and rock-strewn deposits would
be both numerous and extensive. Four hundred thousand years ago the
excentricity was almost exactly the same as it is now, and it continually
increased from that time up to the glacial epoch. Now if we take double the
present excentricity as being sufficient to produce some glaciation in the
temperate zone, we find (by drawing out the diagram at p. 171 on a larger
scale) that during 1,150,000 years out of the 2,400,000 years immediately
preceding the last glacial epoch, the excentricity reached or exceeded this
amount, consisting of sixteen separate epochs, divided from each other by
periods varying from 30,000 to 200,000 years. But if the last glacial epoch
was at its maximum 200,000 years ago, a space of three million years will
certainly include much, if not all, of the Tertiary period; and even if it
does not, we have no rea