422 CARTER : GLACIATION OF DOX AX'D DEARXE VALLEYS. 
flanks of the Hambledon and Cleveland Hills, rising from 200 
feet at Sheriff Hutton to 400 feet near Thirsk and 600 feet at 
Northallerton. This moraine contains Shap granite, Lake 
Country rocks, and other erratics characteristic of the Stainmoor 
glacier. On the other hand, the right lateral moraine, which 
extends along the lower slopes of the Pennine Chain by Knares- 
borough and Fountains Abbey, to Masham, contains Carbon- 
iferous Limestone, Yoredale limestones, and cherts, and other 
erratics characteristic of the Pennine valleys, and especially 
of Wensleydale. There is a medial moraine passing from AUerton 
Park in a north-westerty direction to Bedale and Richmond, 
which shows the characteristic features of medial rock trains, 
being a union of the rock trains of the converging glaciers. 
Accordingly we find that the erratics on the western side of this 
medial moraine are of the Pennine type, whilst those on the 
eastern side belong to the Stainmoor series. This appears to 
me to be the key to the Don and Dearne problem. The ex- 
cellent definition of the glacial phenomena up to York, compared 
with the lack of definite features southwards, led the late Pro- 
fessor Carvell Lewis to terminate the glacial advance at that city, 
and to explain all the southerly drift deposits by a great lake 
and iceberg carriage. But I make bold to say that if there is a 
deposit of land-ice Till in Yorkshire it is at Balby, and that the 
Staincross section can only be explained by glacier action on 
the spot. The more the glaciation of England is studied the 
more thoroughly does the conviction come home that there 
have been many and varying conditions successively existing 
over the same area, and therefore lake conditions at one period 
do not exclude land glaciers at another over the same district. 
Professor Carvell Lewis subsequently notes* that he had found 
traces of a much older series of glaciers, more extensive than 
those so plainly indicated by their moraines, the relics of which 
had been largely removed, the striae obliterated, and the area 
reduced to the appearance of a non-glaciated district. This is 
the conclusion to which I had been forced in the Don area 
before I saw the above note, and it is to the extension of the 
Wensleydale glacier, reinforced it may be by the Nidderdale, 
* Glacial Geology of Great Britain, &c., p. 60. 
