M0RTIMFR : SECTIONS OF DRIFT. 
379 
with ice, (except where there was a free and lengthy flow into 
the sea) would be such as to convert hill and dale into one firmly 
knit mass of immoveable ice to a level with the summits of the 
hills. Over this compact mass, the upper portion of the land-ice 
would slide eastwards ; at first comparatively slovjly over the outer 
ridge of the chalk hills, but with increased velocity and effect on 
their inner slope, and would grind down, or push before it, all out- 
standing peaks of chalk ; hence arise the displaced masses of rock 
and the great accumulation of small chalk gravel at the inner edge 
of the wolds. This shearing tendency of the upper portion of the 
ice-caps, would be not to excavate, or even to deepen the then exist- 
ing dales, but to plane down the tops of the hills, and press small 
gravel into the cracks and rents in the ice filling the dales, which 
gravel would slowly sink, and in great part finally reach the bottom 
of the valleys where we often find it. 
Some of the main dales, such as the one terminating in 
" Garton Slack," and the great Mid-wold valley, which runs from 
Wharram-le-street. with little interruption, to Bridlington, having 
free and somewhat straight courses in an easterly and south-easterly 
direction into the glacial sea, have had their sides rounded and 
worn back, and their bottoms raised by part of the material removed 
from their sides by the moving ice. (I know of no proof that ice ever 
deepened the chalk dales of Yorkshire.) At the same time, the 
steep narrow-bottomed valleys which occur almost everywhere 
along the outer side of the wolds, were securely sealed with 
motionless ice, as before pointed out, so that their sharp outlines 
were protected and preserved for a long time from every kind of 
of denudation. 
Besides the preservation of the dales, this capping of ice may 
probably assist us in explaining another interesting and very 
puzzling feature, with regard to the irregular distribution of 
glacial drift on the high parts of the wolds. It is only at the east" 
em extremity of the chalk along the cliffs from Sewerby to Speeton, 
and to the extent of about one mile inland, that the boulder clays 
