CORNISH POST-TERTIARY GEOLOGY. 51 



of Devon had been read, I visited the spot, and am inclined to think 

 that the boulder vs^as brought by floating ice. These observations 

 lead me to conclude that Cornwall was at a much greater altitude, 

 but sinking during the Glacial epoch, and that although partaking 

 in the subsidence which caused the submergence of land to a depth 

 of 1,500 feet in the districts further north, its greater altitude when 

 the subsidence began allowed of the existence of a dry land area till 

 its close, which was marked by the formation of the raised beaches 

 when the land stood at an average of 15 feet below its present level. 

 It was during this last period, when glacial conditions were passing 

 away, that I conceive the granite boulder was floated from districts 

 far to the north, or from Ireland. In the accompanying table of 

 classification I have ventured to insert such hypotheses as the fore- 

 going to bridge over the breaks occasioned by the paucity of early 

 Pleistocene deposits in Cornwall. 



