Vol. 6$.^\ ORIGIN OF CERTAIN CANON-LIKE VALLEYS. 493 



Leicestershire and Rutland south of Melton Mowbray, to a height 

 exceeding in places 600 feet, indicates, I think, that the Trent basin 

 ■was then occupied by ice of considerable thickness, otherwise the 

 stream coming from the north-east should have continued to travel 

 westwards towards Burton-on-Trent. I suggest that it was the 

 Pennine ice, and especially that descending the valley of the 

 Derwent, which diverted the eastern glacier from its natural course. 

 At first, and before the arrival of the latter, the Pennine ice appears 

 to have extended for some distance to the south-east. 1 Mr. Lomas 

 and I noticed in 1904, for example, a section near Corby Station, 

 south of the River Welland, and 30 miles to the south-east of 

 Loughborough (shown on the map, PI. XXXIY), from which had 

 been taken a great number of big erratics, 80 or 90 per cent, of 

 which seemed to us to be Carboniferous. Many Carboniferous and 

 Mount-Sorrel boulders occur, moreover, to the east of the Soar 

 Valley. On the other hand, there is evidence of the extension, at 

 -a subsequent period, of the eastern ice-stream with its Chalky Drift 

 to the west of that river, Triassic Boulder-Clay containing Pennine 

 and Mount-Sorrel erratics being found there to be overlain by the 

 former. In 1904 there was a good section of this, now unfortu- 

 nately filled with water, in a brickyard at Leicester Forest. The 

 region between Derby and Loughborough seems to have been the 

 meeting-ground of the north-eastern and north-western ice. 



The intensely Chalky Drift of South Lincolnshire is shown on 

 the map (PI. XXXIII) by rings, the Chalky-Jurassic Boulder-Clay 

 of the lower ground by rings and dots, and the Drift of the Pennines 

 and the Vale of York by darker rings. 



The Glacial deposits which occur to the east of the Wolds 

 (represented on the map by black dots) seem to me to be the morainic 

 accumulations of the great glacier of the North Sea, The upper 

 portion, the ' Hessle Clay ' of Wood and Rome, was believed by them, 

 as by Mr. Jakes-Browne, to be considerably newer than the under- 

 lying Purple Clay, which, in its turn, is underlain in Holderness by 

 a basement Boulder-Clay containing chalk. 2 The maps of the 

 Geological Survey do not distinguish between these various beds, 

 nor have I attempted to do so. Eor my present purpose I group 

 them all, though perhaps belonging to different stages of the Glacial 

 Period, as North-Sea Drift. 



1 It should be stated that Mr. R. M. Deeley believes that the Chalky Boulder- 

 Clay glacier travelled westward as far at least as Hanbury, north-west of 

 Burton-on-Trent (Quart. Journ. Geol. Soc. vol. xlii, 1886, p. 457). It seems 

 to me, however, that the Pennine ice must have continued to occupy that region 

 at the period of maximum glaciation, although the Derwent glacier may 

 have been diverted from its earlier and south-easterly course by the pressure 

 of the north-eastern ice. I suggest that the Cretaceous detritus found in the 

 Hanbury district, although originally due to the latter, may have been trans- 

 ferred to the Derwent ice-stream where the two came into contact, and have 

 been carried thence westwards with the Carboniferous debris which is also 

 found in the Drift of that region. 



2 Mr. J. W. Stather informs me that the Chalky basement-clay of Holderness 

 contains many Scandinavian erratics. 



