1872.] DAKTNS — YORKSHIRE GIACIAL PHENOMEN-A. 387 



boulders and pebbles in tbeir lower jiart, where they seem to 

 be passing downwards into true boulder-gravels. 



The stones in the clay (A) were too dirty for me to see whether 

 they were scratched or not ; but it has the look of a true Boulder- 

 clay. As far as the York sections go, then, the kames lie between 

 two Boulder- clays ; they would thus seem to be the equivalents of 

 the middle drift, sands, and gravels of Lancashire. 



They contain mammalian remains. 



I think, then, that there is evidence for the following series of 

 events : — At one time the Yorkshire hills were covered with conti- 

 nental ice, as Greenland is now ; the vale of York was under water, 

 and formed an arm of the sea into which the great glacier descending 

 from the hills discharged its moraines, which were rolled about by 

 the tides and deposited as kames ; and subsequently, when the ice 

 no longer reached the coast, the previously deposited drift would 

 be rearranged by the tidal currents into kames ; perhaps the land 

 may have sunk gradually, so as even to bring new drift material 

 within the action of the sea. At all events the land at one time 

 stood low enough (say 400 feet below its present level) to allow of 

 the valley of the Aire becoming a strait through which the tide 

 played. 



The climate ameliorated, perhaps as the land went down, till the 

 universal ice-sheet vanished ; but the great dales, such as Wharfe- 

 dale, Wensleydale, Ribblesdale, &c., and their affluents had each a 

 glacier descending it ; these debouched at first in the sea, which 

 filled the dales as the sea does the Norwegian fjords, to the height 

 of 600 or 700 feet ; subsequently the glaciers retired from the sea- 

 level and finally vanished. 



Why during all this time there should have been no glacial 

 deposits formed on the eastern slope of the Pennine hills south of the 

 Aire basin, is a very puzzling matter, I can only pretend partially 

 to account for it by the following considerations. In the first place, 

 the farther south we go, of course, cceteris paribus, the milder the 

 climate becomes ; and every mile makes some difference. In the 

 second place, though one wonders why, if there were glaciers 

 descending from Whernside 2300 feet high, there should not also 

 have been glaciers on Kinder Scoot, 2000 feet high ; yet, though the 

 extreme points in the southern country are nearly as high as some 

 of the highest hills in the north, the general level of the country is 

 lower, and there is also not so much high ground superficially. And 

 lastly, when the land stood about 1200 feet lower than it now does, 

 (and the Lancashire drift in places reaches nearly as high as this), 

 what remained above water would be such a narrow belt of land that 

 there may well have been no land-ice. At the same time the sub- 

 mergence was not great enough to allow ice to float from the northern 

 area laden with drift, as the watershed between the Aire and Calder 

 is 1350 feet above the present sea-level. Perhaps the submergence 

 was not even as great as 1200 feet in the Aire basin : we have evi- 

 dence, in deposits of sand on the hill-side, of a submergence of 1000 

 feet ; but that is the most I know of. 



