CHARACTERISTICS OF THE DRIFT BEDS. 



3G1 



FIG. 201. 



I 



Europe carries us back far indeed in years, 

 but a little way only, when measured by 

 geological standards, and we must there- 

 fore solve this question by examining the 

 drift gravels themselves, the materials of 

 which they are composed, and the positions 

 which they so occupy, as to determine, if 

 possible, the conditions under which they 

 were deposited, and the lapse of time which 

 they indicate. 



Fig. 201 gives a section across the valley 

 of the Somme at Abbeville, taken from the 

 memoir in the Philosophical Transactions,* 

 by Mr. Prestwich, who has long studied 

 the quaternary beds, and has done more 

 than any other man to render them intel- 

 ligible. We should find almost the same 

 arrangement and position of the different 

 beds not only at St. Acheul, but elsewhere 

 along the valley of the Somme, wherever 

 the higher beds of gravel have not been 

 removed by subsequent action of the river. 

 Even at St. Valery, at the present mouth 

 of the river, I found a bed of gravel at a 



r^ 



considerable height above the level of the 



* sea. 



This would seem to show that at 

 f the period of these high-level gravels, the 

 I English Channel was narrower than it is 

 ^ at present, as indeed we know to have 

 | been the case down to historical times. So 

 early as 1605, our countryman Verstegan 

 of pointed out that the waves and tides were 

 eating away our coasts. Sir C. Lyellf gives much information 

 * Phil. Trans. 1860. t See Principles of Geology, p. 315. 



