FOX-STllANGWAYS : GLACIAL PHENOMExNA NEAR YORK. 
17 
buttress between the two streams of ice which piled up their deposits 
of clay and gravel on either side. With the exception of the northern 
portion of these hills, and a narrow band along their eastern flank, 
no superficial beds have been found except the few patches of drift 
marked on the map, and which are all of a local character. On the 
eastern side, the existence of a large sheet of ice is shown by the 
morainic mounds which have been heaped up along its edges, and 
which attain a height of 400 feet at Reighton and 600 feet on 
Seamer Moor ; and also by the blocking up of the old valleys in this 
part of the county, which has in many cases completely changed the 
original courses of the streams and reversed their flow. This is, 
however, rather beyond the ground we are now considering, and, as 
I have gone into the subject in some detail elsewhere, it is needless to 
say more about it now.''' 
On the western side of the Jurassic hills the most striking 
evidence of the presence of an ice sheet flowing to the south is the 
gradual decline of the glacial deposits from 800 feet on the northern 
hills to 400 feet opposite Thirsk, and not more than 200 feet to the 
north-east of York, where they terminate in a series of mounds and 
ridges, which it is the purpose of the present meeting of the Society 
to investigate, t To the south of these mounds there is a complete 
alteration in the character of the superficial beds, and although there 
is a good deal of drift here and there, it is largely of a local character, 
consisting mainly of Chalk and Liassic gravel, which is found in great 
quantity capping the low hills from Stamford Bridge southwards to 
the Humber. 
The manner in which these extra-morainic beds were laid down 
is, however, a question that is as yet far from settled, and we require 
to know a good deal more of their nature before propounding a 
theory that will suit all the requirements of the case. I am at 
present engaged in examining a portion of these beds in the Mid- 
land Counties, and I hope at some future date to be able to offer an 
opinion on the subject. 
So much for the general conditions which may have given rise 
* Trans. Leicester Lit. and Phil. Soc, vol. iii., p. 333, (1894). 
t There is very little true boulder clay above 600 feet on these hills ; above 
this level the drift is more gravelly and of a local character. Barrow, loc. cit. 
B 
