﻿398 HIGH-LEVEL PLATFORMS OF BODMIX MOOR. fAug. I908, 



Mr. E. E. L. Dixon, after remarkiug on the interest which the 

 platform rising to the 430-foot level possessed from its extensive 

 development, not only in Cornwall and Devon, l?ut also in South 

 Wales, Ireland, and Britanny, proceeded to ask whether the evidence 

 at present available justified the conclusion that it was a plain of 

 marine denudation of the Pliocene Sea. In extent it was very 

 different from the notches upon which rested the raised beaches 

 around our coasts — in fact, it was approached only by the coast- 

 platform of Xorway recently described by Dr. i^ansen, who regarded 

 it as formed by a combination of marine and atmospheric erosion 

 during a period of oscillating sea-level. The platform, which he 

 described as being ' as much as 40 miles or even more ' broad, was 

 so much dissected by channels that waves could attack upstanding 

 rocks at a distance from its edge ; but no such channels existed over 

 wide areas of the Cornish plain. Moreover, the Norwegian coast was 

 fully exposed to the Atlantic, whereas parts of the Cornish plains, 

 such as Goss Moor, formed bottle-necked gulfs almost enclosed by 

 rising ground, where consequently wave-action would be reduced to 

 a minimum. 



The speaker quoted Mr. Eeid's conclusion that the sea which 

 deposited the Pliocene beds of Cornwall probably cut a notch at 

 about the 430-foot level, but considered that the plain upon which 

 some of the beds rested need not also have been eroded by the 

 Pliocene sea. He had noticed in the Pyrenees how the super- 

 position of marine beds on a platform of older rocks might lead to 

 wrong conclusions as to the formation of the latter, for he had 

 found that whereas, near Gavarnie, such a platform eroded in 

 crystalline rocks had been overlain bj- Hippurite-Limestone, and 

 had been consequently referred to as a plain of marine denudation 

 worn down by the Cretaceous sea, at a short distance on the other 

 side of the frontier it had been immediately overlain by a thin 

 group of red Permo-Triassic beds, succeeded in turn and with 

 apparent conformity by the Hippurite-Limestone. It was obvious 

 that the platform had been eroded long prior to the Cretaceous 

 submergence ; and also presumably — since the Permo-Trias had 

 rested in part on a denuded Hercynian granite-boss, and the great 

 interval between the intrusion of the one and the deposition of 

 the other had been a period of continental conditions — that the 

 ]3latform was an old desert-plain. 



However, the speaker felt, not only that the Author had done 

 great service in drawing attention to the remarkable Cornish plains, 

 but also that in any case his observations would provide a valuable 

 step towards the solution of a difficult problem. 



Prof. W. AV. Watts remarked that a very valuable part of the 

 paper was that which referred to the history of the Glacial Epoch 

 in a practically unglaciated area. But the point of greatest interest 

 to him was that it was clear from the paper that the successful 

 mining of tin and wolfram, and even china-clay, in this area was 

 the outcome of conditions not explicable by simple geological 

 principles, but requiring advanced geological research to explain 



