CHAP. VIII. LOWER-LEVEL GRAVELS OF THE SOMME VALLEY. 121 



CHAPTER Vm. 



POST-PLIOCENE ALLUVIUM AVITH FLINT IMPLEMENTS OF THE 

 VALLEY OF THE SOMME, 



Concluded. 



FLUVIO-MARINE STRATA, WITH FLIST IMPLEMENTS, NEAR ABBEVILLE 



MARINE SHELLS IN SAME CYRENA FLUMINALIS MAMMALIA — ENTIRE 



SKELETON OF RHINOCEROS FLINT IMPLEMENTS, WHY FOUND LOW DOWN 



IN FLUVIATILE DEPOSITS RIVERS SHIFTING THEIR CHANNELS — RELA- 

 TIVE AGES OF HIGHER AND LOWER-LEVEL GRAVELS SECTION OF ALLU- 

 VIUM OF ST. ACHEUL TWO SPECIES OF ELEPHANT AND HIPPOPOTAMUS 



COEXISTING WITH MAN IN FRANCE VOLUME OF DRIFT, PROVING AN- 

 TIQUITY OP FLINT IMPLEMENTS ABSENCE OF HUMAN BONES IN TOOL- 

 BEARING ALLUVIUM, HOW EXPLAINED VALUE OF CERTAIN KINDS OF 



NEGATIVE EVIDENCE TESTED THEREBY HUMAN BONES NOT FOUND IN 



DRAINED LAKE OF HAARLEM. 



TN the section of the valley of the Somme, given at p. 106 

 -'- (fig. 7), the successive formations newei* than the chalk 

 are numbered in chronological order, beginning with the 

 most modern, or the peat, which is marked No. 1, and 

 which has been treated of in the last chapter. Next in the 

 order of antiquity are the lower-level gravels, No. 2, which we 

 have now to describe ; after which the alluvium, No. 3, found 

 at higher levels, or about eighty and one hundred feet above 

 the river-plain, will remain to be considered. 



I have selected, as illustrating the old alluvium of the 

 Somme occuri'ing at levels slightly elevated above the present 

 river, the sand and gravel pits of Menchecourt, in the north- 

 west suburbs of Abbeville, to which, as before stated, p. 94, 

 attention was first drawn by M. Boucher de Perthes, in his 

 work on Celtic antiquities. Here, although in every adjoin- 



