338 Reports and Proceedings, 



Geological Society of London. — May Gth, 1868. — " On tlie Qua- 

 ternary Gravels of England." By Alfred Tylor, Esq., F.L.S., F.G.S. 



Mr Tylor first compared, by means of sections and models, the 

 gravels of the Aire Valley at Bingley, of the Taff Vale between 

 Quakers' Yard Junction and Aberdeen Junction, and of the Valley 

 of the Rhonda near its junction with the Taff. He then described 

 the cave-section of Bacon Hole, Gower, and the sections exposed at 

 Crayford, Eritli, and Salisbury, comparing the angles of deposition 

 of gravel-beds concealing the escarpment of the Chalk in these last 

 three localities with the same conditions at Brighton and Sangatte. 



By comparing the gravel-beds at different levels, and upon strata 

 of different age and configuration, he showed in what respect they 

 differ from each other. The bulk and height of the Quaternary de- 

 posits had strengthened the conviction which he expressed in his 

 previous paper (on the Amiens gravel), that there was a long period, 

 reaching nearly to the Historical epoch, in which the rainfall was 

 excessive, and which he termed the " Pluvial period." 



These sections also led the author to the following conclusions : — 

 (1) That the debris was deposited b}'' land-floods, and that the mode 

 of deposition was quite distinct from that of moraines produced by 

 the melting of ice. (2) That the character of the deposits in the 

 valleys of the Aire, Taff, and Rhonda proves that they were formed 

 under similar conditions. (3) That these gravel-beds point to a 

 Pluvial period of great intensity and duration. (4) That the ice- 

 action of which there is evidence was subordinate to the aqueous 

 action. (5) That the fossiliferous Quaternary deposits have been 

 best preserved where they have been formed in cavities lying be- 

 tween the edge of the bank of a river, estuary, or sea, and an es- 

 carpment running parallel with it at no great distance, (6) That 

 the immediate source of the gravels was the high land adjoining the 

 rivers, whence they had been washed down by rain, with the assist- 

 ance of lateral streams, into the lower ground, where they had come 

 into contact with larger quantities of running water, had been mixed 

 with rolled materials, and spread in thick beds over the bottoms and 

 slopes of valleys or the sides of escarpments. (7) That the surface of 

 such a deposit rarely slopes at more than 2° or 4*^, while the slope 

 of the beds lower in the series near the escarpment averages V2P. 

 The escarpment is usually concealed under a coating of graA^el or loess. 



Discussion. — Mr. Prestwich dissented from the view of the author, 

 that the valleys had been excavated to their present depth before 

 the gravels were deposited ; and, with reference to a former paper, 

 explained that Mr. Tylor and himself had taken different points of 

 observation near Montiers, and that his own views as to the separa- 

 tion, which in some cases may be shown to exist betwen the high 

 and low level gravels, were correct. 



Mr. Evans also combated Mr. Tylor's views, and pointed out 

 the difficulty of accounting for deposits of gravel such as are at 

 present found in valleys already excavated to their present depth. 



