﻿400 HIGH-LEVEL PLATEOEMS OF BODMIX MOOE. [Aug. I908, 



but in !N'orth Wales it was a fact that all the Glacial deposits were 

 superimposed upon the ' gravel-ore.' These deposits were in some 

 cases upwards of 200 feet thick, and the ore had been got by- 

 tunnelling along the surface of the underlying rock. The amount 

 of material derived from the lodes by subaerial waste in post-Glacial 

 times was quite insignificant in comparison with the ' gravel-ore,' 

 a fact which confirmed the Author's view that the Cornish material 

 was of considerable antiquity. 



The Peesident commented on the great interest of the paper, 

 which showed signs of an interaction between scientific research and 

 the renewed prosperity of the mining industry. The notion that 

 plains of erosion were commonly formed by rain and rivers seemed 

 to rest on an assumption that conditions remained unchanged for 

 an indefinitely-long interval ; but, apart from this, the Author 

 seemed to have given direct evidence of the marine origin of the 

 plains which he had described. The supposed frozen state of the 

 ground during the Glacial episode might be more readily admitted 

 if illustrated by existing instances. 



The AuTHOE, in reply, stated that he was not yet satisfied as to the 

 marine origin of the 1000-foot platform, but the 750-foot platform 

 seemed clearly to be part of a plain of marine denudation. It occurred 

 at apparently the same level on_ both sides of the granite-mass, with 

 a watershed of killas between the two occurrences. Purther, the 

 great rising feature formed by the junction of the granite and 

 killas, so conspicuous in many parts of Cornwall, was completely 

 lost where it crossed the 750-foot platform. In place of being in a 

 steep hill-face, it actually occurred well out on the flat ground (the 

 platform) at the foot of the latter. 



