302 A, Tylor on the Amiens Gravel. 
Art, XXX.—On the Amiens Gravel; by Atrrep Tron, 
Esq., F.G.S.* Plates III and IV. 
7 I. Lyrropwucrion. 
THE exact position, character, and equivalents of the Qua- 
ternary deposits of the valley of the Somme have been fre 
quently discussed. On the authority of certain sections and 
plans of Amiens and Abbeville, the correctness of which will be 
examined hereafter, theoretical views pe ie the relative 
ages of different parts of the gravel and of different partsof 
the valley of the Somme have been promulgated by Mr. Prest- 
wich, and repeated by Sir C. Lyell and others. 
These geologists have asserted :-— ar 
First, that there were two valley-gravels of distinct age at 
Amiens and Abbeville, one named. by them the upper and the 
other the lower valley-gravel ; i a 
Secondly, that the upper gravel was the older of the two; — 
an ] 
Thirdly, that the valley of the Somme was excavated to & 4 
the upper valley- 
the lower valley- 
us, hones 4 
uman implements, and oa 
yond the limit of floods, and therefore, that these grav ‘oe 
only have been deposited at St.-Acheul before the river-¢ 
‘was cut down to its present level. he remains — 
The general effect of these assertions was to refer the a 
of man found in $t-Acheul back to an indefinite date, | 
rated from the Historical period by an interval during e 
valleys were excavated or deepened 40 or 50 feet. 966,¢ 1 su 
: = 7 ? 
: : a to 
remains, and that the age of these deposits was © a tate | 
= Historical period,—also that the upper and lo 
 & the Somme were continuous and of one period. 
i. 
* From the Quarterly Journal of the Geological Society for May, 18° 
t Quart. Journ. Geol. Soc., vol. xxii, p. 463. 
