186 D. MACKINTOSH ON THE DEIFT-DEPOSITS 



than about 600 ft. above the sea-level, which contains many- 

 glaciated stones, and which, I noiu believe, may have been accumu- 

 lated under land-ice. The yellow or yellowish-brown clay above it 

 rises to much higher levels, contains fewer glaciated stones, and 

 differs from the blue in the kind of boulders or relative percentage 

 of different kinds of boulders it contains. Above the brown clay, at 

 intervals, there is a great thickness of sand or gravel, which often 

 forms esker-like mounds, as in« the neighbourhood of Esholt and 

 Bingley, in the valley of the Aire. In the plain of Craven the 

 numerous large and curvilinear mounds, which have been regarded 

 as glacial moraines, may be seen in sections to consist of sand 

 or clay with numerous well-rounded and evidently waterworn 

 stones. Between York and Lancaster, by way of the Aire or 

 Wharfe valleys and the plain of Craven, the sand and fine gravel 

 (which are scarcely ever found at high levels) were probably not 

 distributed until after the emergence of the higher parts of the 

 Pennine Hills-^in other words, until the valleys had become 

 converted into straits and sea-lochs. As may often be seen in 

 Cheshire and Lancashire, there is sometimes in the West Riding the 

 appearance of a cleanly-eroded surface of sand or fine gravel uncon- 

 formably overlain by clay, loam, or coarse gravel, with good-sized 

 boulders. At Marley sand-pit, near Keighley, sand at least 20 ft. 

 thick is unconformably surmounted by 10 ft. of loamy clay, with 

 striated boulders (see fig. 3) up to 2 ft. in diameter (1870). North 



Fig. 3. — Section in Marley Sand-pit, near Keighley. 



A 



A. Upper Boulder-clay. B. Sand and fine gravel. 



of the White Hart Inn (between Aberford and Bramham) a bed of 

 dark clay and sand is covered with sand and gravel which had evi- 

 dently been eroded before the deposition of a capping of reddish clay 

 with boulders. Other instances might be stated. I have not had 

 an opportunity of ascertaining how far these Upper Boulder-clays 

 may represent the Hessle clay of East Yorkshire ; but I believe they 

 are on the same horizon as the much more continuous Upper 

 Boulder- clay of the plain of Lancashire and Cheshire and of the 

 valleys on the western side of the Pennine Hills. 



Concluding RemarJcs and Suggestions. 



After much consideration and correspondence with geologists, I 

 have been induced to leave open the question of the correlation of 

 the Norfolk " till," Middle Glacial sand, great Chalky Clay, purple 



