GEOLOGY. 



45 



A second, but less vigorous, return of similar conditions was 

 preceded by a period of upheaval, and warm temperate climate, 

 during which the seas were reforested and the rivers cut out 

 deep channels almost to their former beds. Thus the Ouse at 

 York flowed in a deep, precipitous ravine, with sides rising 

 50 to 100 feet. The return of cold in most places removed 

 almost every vestige of such hollows. This time there appears 

 to have been more oi floating ice, at any rate at the lower levels, 

 and gravels, false-bedded sands, etc., were produced, followed 

 by a general levelling up of the deeper hollows, especially near 

 the river, by brick-earths. Sometimes remote, elevated, or 

 unusually large depressions were only partially filled, leaving 

 tarns and ponds, which quickly changed to peat beda. Askham 

 Bog, for instance, appears to be of this nature. 



After the subsidence of this inundation we have nothing 

 further of importance to chronicle, and so with a table of the 

 thickness of the beds, as nearly as we are in a position to 

 register it, and of the area of the surface which they cover, this 

 chapter may be brought to a conclusion. 



Feb. 1S88. 



