388 
THE EVOLUTION OF THE DON RIVER-SYSTEM. 
BY W. LOWER CARTER, M.A., F.G.S. 
Whilst making a study of river development in Yorkshire 
a few years ago my attention was attracted to the Don, whose 
pecuUarly erratic course evidently had an interesting history. 
My surprise was great when no reference to this problem could 
be found in the geological hterature to which I had access. The 
present paper is an attempt to explain this interesting physical 
history. 
I. — The Don River-System. 
The River Don. between its source in the moorlands of 
the Pennine Chain and its outflow into the Ouse at Goole, has 
a roughly semi-circular course (PI. LIIL). Rising in the Middle 
Grits of the Millstone Grit Series, at an elevation of 1,500 feet 
above O.D., it flows eastwards to Dunford Bridge (1,000 feet), 
where it is reinforced by powerful feeders north and south. 
It then flows eastwards over the Rough Rock, across the strike 
of the beds and the main faults, and enters the Lower Coal 
Measures at Hazlehead. At Thurlstone it cuts a gorge through 
the Grenoside Rock, and then traverses the overlying Penistone 
sandstones and shales. At Penistone the Don receives the 
waters of Scout Dike, which, from its source in the moorlands, 
runs direct east as a dip river (Broadstone Dike), to Ingbircli- 
worth, and then takes a sudden bend to the south-east along 
the strike of the Penistone sandstones. At Penistone the Don 
ceases to be a dip river and, changing its direction, runs to the 
south-east along the strike of the Penistone sandstones in a 
V-shaped vaUey,. the eastward bank of which rises at Hoyland 
Swaine to 910 feet, and at Thurgoland to 810 feet, but between 
these two is a col (730 feet) but little above the contour of the 
river bed at Penistone (700 feet). The Don quickly deepens its 
channel to COO feet at Thurgoland and to 500 feet at Wortley. 
Between Thurgoland and Wortley the character of the Don Valle}' 
suddenly changes from a comparative!}^ broad and smooth-sloped 
va-le to a precipitous gorge, through which the river flows in bold 
bends, crossing and re-crossing the bedding, and taking to the 
