GEOLOGY. 43 



seems nearly coeval with the Crag Pliocene of the Eastern 

 Counties. The animal remains which belong to the earlier 

 Tertiar}' systems indicate the prevalence of an almost tropical 

 climate. There is a gradual change towards the close, until 

 the upper Pliocene beds contain fossil shells of very similar 

 type to those now found on our coasts. At the beginning of 

 the Recent or Pleistocene Age our islands were then only a 

 portion of the main continent. The German Ocean, at any 

 rate in great part, was an extensive forest. Our main rivers 

 flowed in broad valleys far below their present level. The Ouse at 

 York, for example, was 70 feet lower, or nearly 50 feet below the 

 present sea level. The present main features of hill and valley, 

 however, were already in existence. Naturally these vast forest 

 regions were inhabited by the characteristic mammalian fauna 

 of the period. The most notable feature is the commingling of 

 types now confined to tropical regions, such as the elephant, 

 rhinoceros, and hippopotamus, with others belonging to more 

 temperate regions, as the Bos primigenius and Megaceros. 

 The Kirkdale hysena-den contains most of these and other 

 mammals characteristic of this time. 



A very considerable subsidence now occurred, when intense 

 cold was the prevailing feature — the Glacial Period. All our 

 mountains and loftier hills became glacial centres, the ice of 

 which appears to have coalesced during the times of intensest 

 cold into a vast ice-sheet, under which the whole of Yorkshire 

 (and England as far as the Thames) was overwhelmed. Nothing, 

 unless it were the highest points in West Yorkshire, remained 

 uncovered. The local ice was constrained to move under the 

 influence of the more extensive ice-fields produced by the Lake 

 Mountains and Scotland. The main current, even to the sea- 

 coast, has evidently been from the north-west, or perhaps more 

 westerly in the northern districts. Large blocks of granite from 

 Shap Fell, and other rocks peculiar to the Cumbrian Mountains 

 or Scotch hills, have been raised up over the Pennine ridge, 

 which at its lowest point is elevated 1450 feet above the sea 



Feb. 1888. 



