- Part V. Sect. i. § 1.] PLEISTOCENE. | 887 
‘tion of the striation is from S.S.E., which, in Caithness, is neatly at 
right angles to what might have been anticipated. This deflection 
has been attributed to the coalescence of the ice from Norway and 
from the northern Highlands in the basin of the North Sea, and its 
subsequent progress along the resultant north-westerly line into the 
Atlantic. But it may have been due to the fan-shaped spreading 
out of the vast mass of ice descending into the Moray Firth; for the 
strize on the south side of that inlet run E. by 8., and at last S.E., on 
the north-east of Aberdeenshire, showing that the ice on the one 
hand turned southwards into the North Sea, until it met the N.E. 
stream from Kincardineshire and the valleys of the Dee and Don, 
while on the other it moved northward so as no doubt to join the 
Scandinavian sheet, and march with it into the Atlantic. ‘The basin 
of the North Sea must have been choked up with ice in its northern 
parts, if not entirely. At that time England and the north-west of 
France were probably united, so that any portion of the North Sea 
basin not invaded by land-ice must have formed a lake, with its outlet 
by the hollow through which the Strait of Dover has since been 
opened. Ii has been suggested that during such a condition of things 
the widespread deposit termed Loess was formed, which covers so 
large a space in the lower plains of the Rhine and the north of 
Belgium (Hesbayan mud), and appears in the valleys of the south- 
east of England. 
The ice is computed to have been at least between 6000 and 
7000 feet thick in Norway, measured from the present sea-level. 
From the height at which its transported debris has been observed 
on the Harz, it is believed to have been at least 1470 feet thick 
there, and to have gradually risen in elevation as one vast plateau, 
like that which at the present time covers the interior of Greenland. 
Among the Alps it attained almost incredible dimensions. The 
present snowfields and glaciers of these mountains, large though 
they are, form no more than the mere shrunken remnants of the 
great mantle of snow and ice which then overspread Switzerland. 
In the Bernese Oberland, for example, the valleys were filled to the 
- brim with ice, which, moving northwards, crossed the great plain, 
and actually overrode a part of the Jura Mountains; for huge frag- 
ments of granite and other rocks from the central chain of the Alps 
are found high on the slopes of that range of heights. 
That the ice in its march across the land striated even the 
hardest rocks by means of the sand and stones which it pressed 
against them, is a proof that, to some extent at least, the terrestrial 
surface must have been at this time abraded and lowered in level. 
How far this erosion proceeded, or in other words, how much of the 
undoubtedly enormous denudation everywhere visible over the 
elaciated parts of Europe, is attributable to the actual work of Jand- 
ice, is a problem which may never be even approximately solved (see 
p. 838). The land had the same general features of mountain, valley, 
and plain as it has now, even before the ice settled down upon it. But 
