158 PKOCEEDINGS OP THE GEOLOGICAL SOCIETT. [Feb. 7, 



same lines as that of the modern easterly streams. He pointed out 

 that the great W.N.W. disturbances, many, if not all, of which were 

 in part post-Tertiary, must be taken into account in this inquiry : 

 e. g. the synclinal of central Devon running into the English Channel 

 near the Isle of Wight — the anticlinal of the British Channel and 

 the Weald, which we know was a barrier in pre-Carboniferous times, 

 from the different character of the Coal-measures of Wales and the 

 Culm-measures of Devon — Mr. Godwin- Austen's ridge bringing up the 

 old rocks under London — the barriers which caused the Lower and 

 Upper Silurian of S. Wales to differ so much from those of K. 

 Wales and the Lake-district, and were the indirect cause of the 

 bosses of Silurian rocks which project through the newer rocks in 

 Central England — the barriers that divided the northern coal-fields — 

 the Craven Faults and the great valley which runs along them, — 

 these and many others have obviously affected recent denudation. 

 A slight tnt to the west would send the drainage again to the west 

 along some of them ; and the question involved the consideration of 

 all traces of changes of level. 



Prof. Duncan observed that one important point in the paper 

 was the hypothetical dip of the Chalk, on which the existence of 

 the Severn was made todepend; and commented on the denudations 

 which must have taken place during the Glacial and Pliocene periods. 

 He differed from the author in his view of the character of the 

 Oolitic period, which he regarded as one of great oscillation. As to 

 the amount of Palaeozoic land-surface in Cretaceous times, he main- 

 tained that the purity of the Chalk deposits and their freedom from 

 any terrestrial waste bore evidence of the distance of the land at that 

 time. The depth of the sea in which they were formed was immense ; 

 and in the Upper Cretaceous period the oscillations were also great. 

 He disputed the fact of the Miocene period of Europe having been 

 continental in character, especially as regards the upper and middle 

 parts of the deposits, in which Corals abundantly occurred. The 

 elevation of the Alps was, he maintained, of a slow progressive 

 character, which could hardly have affected so great an area as 

 supposed by Prof. Kamsay. 



Mr. Evans called attention to the relation of the present flow of 

 many rivers to the last elevation of the land at the close of the 

 Glacial period. The deposits of the Severn valley, he thought, 

 proved its preglacial origin, and consequently supported Prof. Eam- 

 say's argument ; but the condition of the land at the close of the 

 Glacial period was also to be fully taken into consideration, as the 

 previously existing channels had in many instances been obliterated 

 during that period. To a great extent Mr. Evans agreed with Prof. 

 Ramsay, but he would wish to see the explanation carried down to 

 a later date. 



Mr. Green remarked, in illustration of the retrogression of 

 escarpments, that he had had some opportunity of observing the 

 process while still in progress. In the Carboniferous rocks of the 

 north of England, where the dip of some hard rock was in a certain 

 direction and it was overlain by softer strata, it was constantly the 



