MONCKMAN : THE GLACIAL GEOLOGY OF BRADFORD. 153 
valley extending from the Hall to the Mill, of a large quantity 
of pebbles and sand evidently deposited in water. Mr. J. E. 
Wilson explains these and other similar beds by supposing that 
the ice, by blocking up the outlet in the lower part of the valley, 
forced back the water until it rose high enough to pass over the 
lowest part of the ridge at Wibsey Bank, which is about 600 feet 
above sea level. In this w^ay a lake was formed at Leventhorpe, 
and sand and pebbles were deposited by the streams flowing down 
Thornton and Bell Dean valleys. 
There is abundant evidence that ice came through Chellow 
Dean, but so far I have not been able to find limestones in the 
drift. Mr. 01 liver, however, found them at Lady Boyd, which 
is in the line joining Chellow with Lidget Green. All these things 
appear to show that the ice came through Chellow Dean and crossed 
over by Lidget Green to Grange Road, and so on to Bowling. 
There are, however, points that should be taken into con- 
sideration : — - 
1. Limestone boulders are reported by the Geological 
Survey at a point about level with Leventhorpe Hall 
(29), or south of the lake deposits mentioned above. 
2. Clay containing sandstone boulders, and pronounced to 
be true boulder clay by Mr. R. F. Dawson (8), is 
found on Wibsey Slack at 800 feet above sea level. 
3. The hills above Leventhorpe, in the Thornton Valley, 
have the form of glaciated hills, although their 
structure would lead one to expect a steep escarpment 
of sandstone at the top, and a gentle slope for the 
softer rocks underneath ; the outline (as seen from 
Daisy Hill when looking up the valley) is rounded like 
a roche moutonnee. 
4. At Clayton, when the workmen were digging a mill 
dam behind Benn's Mill, they cut into a clay deposit 
of great thickness, which I regard as of glacial origin. 
These facts appear to show that the ice was at one time 
higher than it was at the time that the Leventhorpe Lake was 
formed, and that there were changes of level in the ice (34 and 24), 
