CARTER : THE EVOLUTION OF THE DOX RIVER-SYSTEM. 409 
On the western bank, almost opposite to these cols, the 
Rother receives two dip streams, Shire Brook and the Moss. 
My suggestion is that prior to the erosion of the subsequent 
valley of the Rother. the Moss and Shire Brook flowed east- 
wards on each side of Wales (Fig. 9) and united to form the 
Ryton, but that they were afterwards captured by the subse- 
quent Rother. At Woodhouse the Rother suddenh^ ceases 
to be a strike river, and cuts its way across the Treeton Rock 
to Ulley Beck, which flows in a wide old valley northwards 
along the strike of the Red Rock of Rotherham to join the Don. 
At the extreme southerly end of the Rother also, near 
Clay Cross, there are some curious features. The lop-sided 
course of the Amber and Press Brook, and the anomalous direc- 
tion of one or two of the feeders of the Rother, suggest that the 
Chesterfield branch of the river lias cut back sufficiently far 
to capture some of the head waters of the Amber, i.e., of the 
Derwent (Fig. 9. II.. III.). 
In attempting to frame a consistent explanation of these 
several difficulties, I venture to suggest that before the Permian 
escarpment reached its present level there were two rivers draining 
the slope from the central watershed eastwards, (1) the Ryton, 
with its twin heads. Shire Brook and the Moss ; (2) Barlow 
Brook, flowing into the Poulter by Clowne. From Shire Brook 
and the Moss subsequent streams began to eat north and south 
along the escarpment, and from Barlow Brook there were also 
working north and south subsequent streams, the Doe Lea and 
the infant Rother also along the line of the Permian escarpment. 
While higher up in the course of the Barlow the Chesterfield 
stream was another subsequent working along the belt of 
Middle Coal Measures west of the Lower Coal Measure anti- 
clinal of Brimington (Fig. 8). On the north Ulley Brook 
flowed northwards to the Don in a strike valley, and one of 
its branches worked its way gradually back into the water- 
shed at Treeton. 
The second stage in this evolution would be arrived at by 
the cutting back of the subsequent streams. South of Barlow 
Brook the Doe Lea and the Chesterfield stream lengthened 
their courses. Northwards the Drone bit deeper into the central 
