ANCIENT GLACIERS IN EASTERN HEMISPHERE. 179 



has been produced on the flanks of the Cornish hills prob- 

 ably, as the late S. V. Wood, Jr, suggested, by the slip- 

 ping of material over a permanently frozen subsoil. 



" For the remainder of the southern area the evidence is 

 plain that there has been no considerable subsidence dur- 

 ing glacial times. The presence over large areas of chalk 

 country of the ' clay with flints ' — a deposit produced by 

 the gradual solution of the chalk and the accumulation 

 in situ of its insoluble residue — is absolute demonstration 

 that for immense periods of time the country has been ex- 

 empt from any considerable aqueous action. The enor- 

 mous accumulations of china clay upon the granite bosses 

 of Cornwall and Devon tell the same tale. A few erratics 

 have been found at low levels at various points on the 

 southern coasts, usually not above the reach of the waves. 

 These consist of rocks which may have been floated by 

 shore-ice from the Channel Islands or the French coast, 



" This imperfect survey of the evidence against the sup- 

 posed submergence has been rendered the more difficult by 

 the fact that it is not considered necessary to produce the 

 evidence of marine shells in all cases. Indeed, it has been 

 argued that post-Tertiary beds covering thousands of square 

 miles might be absolutely destitute of shells without preju- 

 dice to the theory of their formation in the sea. 



" But such a suggestion, one would think, could hardly 

 come from anyone familiar with marine Tertiary deposits, 

 or even with the appearance of modern sea-beaches. Ad- 

 mitting, however, for the purposes of argument, that the 

 beaches along a great extent of coast might be devoid of 

 shells, it cannot be argued that the deep waters were desti- 

 tute of life ; and hence the boulder-clays, if of marine origin, 

 should contain a great abundance of shells and other re- 

 mains, and, once entombed, it is beyond belief that they 

 could all be removed from such a deposit in the short lapse 

 of post-glacial time. 



" Now, some of the boulder-clays — as, for example, those 



