500 MR, P. F. KENDALL ON A SYSTEM OF [ Aug. 1902, 
great Memoir on the Jurassic Rocks of Yorkshire. Mr. Fox-Strang- 
ways suggests that there was an original depression on the site 
of the present overflow, occupied by a small stream flowing towards 
Malton (Mem. Geol, Surv. ‘Jurassic Rocks of Britain’ vol. i, 
1892, pp. 423-24) :— 
‘ Now, if we suppose the eastern end of the Vale ef Pickering to be blocked by 
Boulder-Clay, the drainage must naturally find its way out at the lowest point; 
this appears to have been at the head of the little valley which we suppose to 
have occupied the position of the present course of the Derwent below Malton. 
By gradually lowering the higher part of this valley, it would in course of 
time change its slope to the opposite direction, and eventually drain the Vale 
of Pickering, which during this period must have been a lake............. 
‘The edge of the escarpment, where it is cut by the present valley at Kirkham, 
is between 200 and 250 feet above sea-level; the level of the Boulder-Clay 
which now blocks the Vale of Pickering near Filey is 130 feet; so that it only 
requires the Glacial deposits along the seacoast to have been about 100 feet 
thicker, to have sent the water over the depression to the south of Malton.’ 
Mr. Fox-Strangways recognized that such a lake should have 
left. traces of its strand-lines, and made the following observations 
on that point :— 
‘The most marked terrace at the present time is that on the north side of 
the valley at Hutton Bushel, the level of which is a little more than 200 feet 
above the sea, that is, exactly at the level that a beach would be formed when the 
exit from this lake was across the hills south of Malton. Below this there are 
two minor terraces, not so well marked, at about the 100- and 140-foot contour, 
which probably denote periods during which the denudation of the Malton 
gorge was for a time checked. Besides this there are no distinctly marked 
terraces, but there is a considerable amount of gravel here and there, all of 
which is below the 250-foot contour.’ 
While in thorough agreement with Mr. Fox-Strangways as to 
the main lines of his explanation, and very grateful for the valuable 
data which he has furnished, I am compelled to differ from him 
regarding three points—small points indeed, but, in view of my work 
in other areas, important. 
The first relates to the nature of the barrier which held up the 
waters of Lake Pickering. Mr. Fox-Strangways considers that it was 
a barrier of Boulder-Clay, which has since been lowered by denu- 
dation to the extent of 100 feet. Such an amount of post-Glacial 
denudation, except in the erosion of a valley or gorge, is quite 
unparalleled. Everywhere we find moraines, drumlins, eskers, 
and kettle-holes preserving their sharpness of form in great per- 
fection; and I find it much easier to believe that the ice which laid 
deposits upon the tops of the hills, at altitudes of 450 to 600 feet, 
both north and south of the Filey barrier, was the obstruction. I 
think that Mr. Fox-Strangways will himself accept this explanation, 
which indeed he offers for a similar case at Scalby, only a few miles 
to the northward. 
Another point of difference is very similar. I have mentioned 
that there are two breaches in the hills which shut the Vale of 
Pickering to the westward—the one by which the Derwent makes 
its escape, and the Coxwold-Gilling depression. The difference 
between their respective summit-levels is very small, but in the 
