290 PREHISTORIC EUROPE. 



utter destruction. In the opener low grounds they are found 

 in greater force, although in such places they almost invariably 

 afford more or less strong evidence of having been subjected to 

 much erosion and crumpling. But the farther we recede from 

 the principal centres of glaciation, and the nearer we approach 

 the extreme limits reached by the ice-sheets, the more extensive 

 and the less disturbed do interglacial deposits become. In 

 a word, they occur in best preservation where the erosive power 

 of the ice was weakest ; they are entirely wanting where we 

 have every reason to believe that the grinding force was 

 strongest. 



If we look at the interglacial beds themselves with any 

 attention, it is very rarely indeed that we shall not find proof of 

 their having been subjected to more or less crushing and erosion. 

 The overlying till or boulder -clay cuts into them again and 

 again — they are often caught lip and involved with the till — 

 and crumpling and contortion are frequently conspicuous. No 

 one who has paid much attention to glacial matters will doubt 

 that all this powerful erosion and confusion is due to the 

 passage of ice over the beds. It may be taken as proved, there- 

 fore, that an ice -sheet does under certain conditions ride over 

 incoherent deposits of gravel, sand, silt, clay, and peat, without 

 entirely obliterating them. But all interglacial beds, even in 

 highly- glaciated Scotland, are not equally crumpled and con- 

 torted. Occasionally the layers of sand and laminated clay hie 

 quite horizontal, even when the till cuts down, as it were, to the 

 depth of 20 feet and more into the stratified deposits. We have, 

 therefore, further proof that ice may roll its bottom-moraine 

 over incoherent deposits without disturbing the horizontahty of 

 their bedding, although at the same time these same deposits 

 may here and there be abruptly cut out and truncated. 



If such has taken place in the valleys of a well -glaciated 

 country like Scotland, it surely cannot be unreasonable to infer 

 that in a less ice-worn country, in a region where the ice was 

 not so thick, and where its motion was slower, interglacial beds 

 should be much better preserved. If the ice has spared, in hilly 



