CARTER : GLACIATION OF DON AXD DEARNE VALLEYS. 429 
recent and rapid erosion. The ice-front remained sufficiently 
long at this point to allow of the gorge being cut more deeply 
than any of the adjoining valleys, and thus at the close of the 
Glacial Period it became the permanent course of the Dearne. 
The part of the old Dearne valley from Great Houghton to 
Frickley being thus left high and dry by the deflection of the 
Dearne at Darfield, became part of the low watershed of a little 
beck, Thurnscoe Dike, which found an easy escape by the notch 
(75 feet) at Carr Head, which had been cut lower than the Bolton 
valley (93 feet), and so became the permanent channel of this 
little stream, giving it the sharp bend that looks so curious on 
the map. 
A further advance of the glacier to the line joining Ardsley, 
Darfield, and Adwick would close tlie Dearne at Ardslej^ and 
form a lake wliich we may call the Barnsley lake (PI. LX., 
and Fig. 8), which would overflow^ by the col at Stairfoot, at the 
175-foot contour. A further advance to Wombwell and 
Swinton would dam the Dove and cause the Barnsley lake 
to enlarge into Worsborough Dale, and rise to the 270-foot 
contour, when it would overflow by the Wombwell valley. 
This is a strike valley excavated in the shales between 
the Oaks and the Woolley Edge Rocks. The little stream 
which flows out of the valley northwards into the Dove rises 
to the west in Wombwell Wood, flows over the Woolley Edge 
Rock across the dip, and only follows the strike when it reaches 
the valley. It can have had no part in excavating the central 
part of the valley, which is flat and streamless. Continuing 
the direction of the Wombwell valley south-eastwards, there is 
another strike valley west of Swinton also excavated in the shales 
underlying the Oaks Rock, the central part of w hich is stream - 
less, and forms a col at the 225-foot contour which held up the 
overflow from the Barnsley and Worsborough Lake, forming a 
Swinton Lake at that level. The overflow from this lower lake 
would reach the Don by way of Kilnhurst. 
In considering the further advance of the glacier to the 
Barbot Hill, Masbrough, and Sitwell Vale drifts, the author could 
not avoid the conclusion that it would press over the advanced 
spur at Stubbin (Plate LX.) up to, say, the 350-foot contour. 
