CARTER : GLACIATION OF DON AND DEARNE VALLEYS. 431 
contour, forming a little flat valley about a quarter of a mile 
wide between Higher Stubbin and Wentworth, at the level of 
335 feet above O.D. This seemed to be an important demonstra- 
tion of the stability of the methods of investigation, and is 
confirmed in an interesting way by the level of Kiveton gorge, 
wliich appears to be the final outlet of the great Don lake, being 
at 330 feet above O.D. 
The Wentworth overflow (Fig. 8) is a little strike valley 
cutting through a narrow watershed, witli a marked escarpment 
on the eastern side, where there is the outcrop of a grit bed, 
and a smooth slope on the western side. But the present drain- 
age has no relation to this gap, and could not have formed it. 
The stream at the northern end, which runs by Elsecar, rises 
some distance to the west of the gap, and flows directly across 
its end. The same is true of the drainage of the Wentworth 
Woodhouse valley. 
When the glacier front thus extended from the spur at 
Stubbin to Barbot Hill, the drainage of the lake impounded 
in the Wentworth Woodhouse valley w^ould flow along the 
ice-front, and there is a notch at 203 feet west of Masbrough 
which would represent tins stage. When the ice lobe reached 
Masbrough and Sitwell Vale the Bother would be dammed, 
and we find a notch about a mile south-west of Greasbrough 
at 275 feet which would drain the western lakes into the Bother, 
and another dry valley east of Sitwell Vale, also at the 275-foot 
contour, which would take the overflow of the lake formed by 
the impounded drainage of the Bother, a lake which would 
stretch as far as Heath and Chesterfield. The ice-front w^ould 
by this time abut against the rising ground from Thrybergh to 
Conisbrough, and a narrow lake would be formed overflowing 
at Conisbrough Park into a channel at 260 feet above O.D., 
which leads into the gorge behind Conisbrough Castle. A slight 
further advance of the lobe of the first glacier through the gorge 
would close the Conisbrough Castle channel, and cause the lake 
to overflow at 260 feet into a channel leading straight to Balby 
(Fig. 9), which was then a little vaUey carrying off the drainage 
from the high ground about Edlington. For a time there would 
probably be a considerable stream of clear water flowing from this 
F 
