74 



A, represents the present river Somme ; a, recent alluvium ; 

 h, h', h", Loess on different levels, and of different ages ; c, low 

 level Gravel ; d, high level Gravel. Now it is supposed that the 

 upper bed of Gravel marked d was, at one time, the level of 

 the water course ; that shortly prior to that time, in Pliocene 

 or early Post-Pliocene period, the cold was so severe as to be 

 called the Glacial epoch, and that the greater part of England 

 was submerged. The high-level Gravel marks a period of a 

 gradual increase in temperature, and consequently denudation 

 proceeded more rapidly. It is rarely more than 20 feet thick, 

 and has an average of about 12 feet. The low level c varies 

 from 10 to 30 feet above present water level, and it is mainly 

 in this deposit that the remains of flint implements, which are 

 admitted to be tlie work of human agency, have been found, 

 associated with the remains of extinct mammalia. 



I would particularly call your attention to the Loess, or brick 

 earth (fe, V, h".) This is thought to be the result of river floods, 

 commencing at the period of the highest valley Gravels, and 

 continued down to the end of that of the lowest valley Gravel ; 

 that the higher beds (fc) were formed at the time the higher level 

 gravels were being accumulated in the bed of the old river ; the 

 bed (6') after the valley [d] was left dry, whilst the lower beds [h") 

 result from inundation of the river after the excavation of the 

 valley (C), and when the higher levels were beyond the reach of 

 floods. 



Careful examinations have been made along the French coast, 

 and a remarkable resemblance is found in the Estuarine 

 deposits — more particularly the low level ones — to those on our 

 own coasts. Probably the English Channel was much narrower 

 than at present, and there is reason to think that at the period 

 of the higher Gravels, or slightly antecedent to that time, the 

 two coasts were joined ; in other words, that there was then no 

 English Channel.* 



* As I hope to be able to visit the Drift deposits of the east coast of England, 

 I purpose to give a supplemental paper to show how far the Severn, Avon, 

 and Evenlode dr-ifts can be correlated with them, and also with the ideal section 

 just given. 



