400 CARTER : THE EVOLUTION OF THE DON RIVER-SYSTEM. 
times, it would be found that the plateau with its three great 
grits, the Grenoside, Greenmoor, and Wharncliffe Rocks, would 
stretch unbroken from Wharncliffe Chase to Langsett, the 
northern area being drained by the Don, which I suppose then 
to be reinforced by the head waters of the Little Don (Fig. 5) 
and a feeder, which we may call " the Wortley " for convenience, 
draining the northern slope of the Chase. Southwards the whole 
of the drainage was collected by powerful, wide-stretching 
streams, the Ewden, the Loxley, and the Rivelin, and collected 
in the strike river flowing south to Sheffield, which we may 
term " the Worrall " (Fig. 4). Thus the struggle for the Wharn- 
cliffe watershed between the Wortley and the Worrall would 
be most unequal from its commencement. The Wortley, having 
only a small fall towards its parent river, and a limited watershed, 
would be very unfavourably situated for successful attack ; 
whilst the Worrall, reinforced by its powerful feeders, with their 
great combined area of watershed, and a steep fall towards the 
Sheaf, would be able to cut its way back into the watershed 
powerfully and rapidly. It is evident that oiong each of the 
lines of advantage for River Capture the Worrall was far superior 
to the Wortley. At an early stage the Worrall was able to 
capture the Loxley and the Ewden, if they were original conse- 
quents, but they may be simply feeders which worked their way 
back into the moorlands with power to deepen their valleys 
rapidly as the principal stream cut down its channel. 
As the Worrall cut its way down and back into the Wharn- 
cliffe plateau, it would be able to annex successively the feeders 
of the Wortley, the beginnings of the Little Don at Deepcar 
(Fig. 4, II.), the stream B to the north on the opposite bank, 
and then the eastward feeder A from the Chase at Wortley, 
leaving the col at Thurgoland (675 feet) dry (Fig. 4, III.). The 
great denuding power of the southern river would enable each 
of these streams to deepen its bed with increasing rapidity, 
and would give power to such lateral feeders as E (Fig. 4, III.) 
to cut through the secondary watershed and tap A at an inter- 
mediate point between Wortley and Deepcar, thus leaving the 
dry col (560 feet) at Wortley (Fig. 4, IV.). The Little Don 
meanwhile cutting back along the junction of the Millstone Grit 
