Mr. A. Tylor on I he Quatenary Gravels of England. 2'6o 



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 by 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 

 escarpment 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, to 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 12°. 

 The escarpment is usually concealed under a coating of gravel or loess. 



Mr. Pjrestwich 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 separation which 

 in some cases may be shown to exist between 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. 



Mr. W. Boyd Dawkins objected to calling in hypothetical 

 causes to account for effects when existing causes are sufficient, and 

 cited the sudden melting of snow as a sufficient cause, as had 

 already been suggested by Mr. Prestwich. 



Sir Charles Lyell supported the same view, and mentioned a 

 case which had occurred at Salisbury some few years ago as an 

 instance of the effects of such floods. He also cited the existence 

 of flint implements in the gravels on either side of Southampton 

 "Water as evidence of the existence of man during a long period of 

 excavation of valleys. He also mentioned the discovery by Dr. 

 Harris of flint gravel identical with that of the present valleys be- 

 neath the basalt of Miocene date in Antrim. 



Mr. Searles V. Wood, Jun., insisted on the impossibility of even 

 an enormously increased rainfall filling the valleys as suggested by 

 Mr. Tylor, and pointed out the influence which such an accession 

 of fresh water must have had on the animal life in the estuaries. He 

 also mentioned tidal action ay an excavating agent in valleys. 



