108 James Geikie — On Changes of Climate^ 



To what extent England was submerged during the interglacial 

 periods does not at present appear. I cannot agree with those 

 geologists who hold that the Moel Tryfan beds were deposited 

 during the same period of submergence as the " Middle Sand " 

 series of the north-west of England ; and it may also be strongly 

 doubted whether the Macclesfield deposits should be referred to this 

 horizon. It may quite well be that the Middle Sand at Blackpool 

 contains the same fossils as the high-level drift at Macclesfield, but 

 it does not therefore follow that the beds at these places were thrown 

 down during the same period. If it can be shown that several 

 oscillations of climate characterized the Glacial epoch, then it must 

 be admitted that the same species might appear and disappear, and 

 appear again, according as the conditions were favourable or un- 

 favourable to their existence in our seas. Similarity of fossils, there- 

 fore, cannot be taken exclusively as proof of contemporaneity. The 

 " Middle Sands " of Lancashire and Cheshire tail out against the 

 gradually rising ground at a height considerably below that attained 

 by the Moel Tryfan and Macclesfield beds, and this of itself is good 

 evidence against the contemporaneity of these latter with the Middle 

 Sands. I agree, therefore, with Mr. Searles V. Wood, who appears 

 inclined to relegate the Moel Tryfan and Macclesfield deposits to 

 the period of great submergence (the kame series of Scotland). If 

 a submergence to the extent of 1400 feet or more ever took place in 

 Scotland during the deposition of the boulder-earth and clay (which 

 are probably the equivalents of the Lancashire and Cheshire boulder- 

 clays), it could hardly fail to have left some, traces behind it. But 

 there is no evidence of any such great interglacial depression having 

 occurred at any period previous to the accumulation of the kames 

 and high-level beaches. Professor Eamsay, it will be remembered, 

 many years ago expressed his opinion that the beds at Moel Tryfan, 

 from which Mr. Trimmer and he obtained shells, were laid down 

 during the excessive subsidence that followed on the close of the 

 period of vast glaciers, and preceded the era of small local glaciers. 

 In short, the beds referred to appear to come into the same place in 

 the series as the high-level beaches or shelves of Scotland, which are 

 clearly of later age than all the boulder-clays. 



The kames and erratics of Scotland are also represented in Eng- 

 land by esker-drift and large ice-floated blocks and boulders. Over 

 wide districts occur sporadic mounds and interrupted sheets, patches, 

 and cappings of sand and gravel, with boulders, which geologists 

 generally agree in considering to be of later date than the till, 

 boulder-clay, and associated beds of sand, gravel, etc., in the 

 northern and eastern districts of England. It is uncertain, how- 

 ever, whether the representatives of the Scottish clays with Arctic 

 shells have yet been detected. The occurrence of so many marine 

 clays belonging to different periods of the Glacial epoch, makes it 

 difficult to determine this point, for, like Mr. Wood, I am not dis- 

 posed to place much reliance on fossil evidence taken by itself. It 

 is highly probable, however, that the Nar Clay and the Hessle 

 Clay may occupy, as Mr. Wood has suggested, the same general 



