9 o SCIENCE PROGRESS 



escence of St. Acheul II. after a considerable interval of time, 

 with but little alteration of form, but a marked change in 

 the material used. 



Leaving this case undecided, how are we to account for 

 the association of the ioo ft. level with such much later types 

 in England than in France ? Are we to suppose that the 

 industries actually arrived earlier in the former country, or 

 that the emergence of the land was later ? Or, again, can we 

 find a geographical explanation ? The change in river-level 

 may have been due not to an earth-movement, but to a greater 

 proximity of the sea ; and since the North Sea and the English 

 Channel were then distinct, and the one received the Thames 

 and the other the Somme, we might suppose that this encroach- 

 ment of the sea took place earlier in the Channel than in the 

 North Sea. But against this supposition must be set the 

 fact that all the Lower Palaeolithic industries are associated 

 in Belgium with a low river-level ; so that it seems wiser to 

 wait for further evidence before arriving at any conclusion. 



As to the age of the raised beaches, which, as we have seen, 

 M. Commont places at the end of the Chellean period, geologists 

 are by no means agreed ; but Mr. Dewey, 1 in one of the latest 

 attempts to date them, regards them as pre-Chellean, the 

 cemented sands which often overlie them being ascribed to the 

 Chellean period ; and since the shelf on which the beach rests 

 is only 10-15 ft- above O.D., it follows that the main valleys 

 must have been excavated almost to their present depth in 

 pre-Palaeolithic times. This agrees closely with the conclusion 

 arrived at independently by M. Rutot, 2 who finds several 

 " eolithic " industries underlying the Chellean in the Belgian 

 valleys, only a few feet above the present river-bed ; and if 

 we accept it, then the land must have sunk considerably before 

 the Chellean gravel of the 100 ft. terrace was deposited ; it 

 rose again, however, during or after the Acheulean period, and 

 it is to disturbance of the old beach material at this second 

 rise that we may attribute the Acheulean implement found in 

 the Brighton raised beach. 3 



But before accepting Mr. Dewey's conclusion we must 

 scrutinise carefully its foundations. Briefly stated, his argu- 



1 Geol. Mag. New Series, Dec. V. vol. x. p. 154. 

 3 Bull. Soc. Belg. Geol. vol. xx. (1906), p. 27. 

 3 Proc. Geol. Assoc, vol. xxvi. (191 5), p. 3. 



