CHAP. VIII. OF FLINT IMPLEMENTS IN ANCIENT GRAVEL. 141 



cause there are, here and there, patches of drift at heights 

 intermediate between the higher and lower gravel, and also 

 some deposits, showing that the river once flowed at eleva- 

 tions above as well as below the level of the platforiii of St. 

 Acheul. As yet, however, no patch of gravel skirting the 

 valley at heights exceeding one hundred feet above the 

 Somme has yielded flint tools or other signs of the former 

 sojourn of man in this region. 



Possibly, in the earlier geographical condition of this 

 country, the confluence of tributaries with the Somme afforded 

 inducements to a hunting and fishing tribe to settle there, 

 and some of the same natural advantages may have caused 

 the first inhabitants of Amiens and Abbeville to fix on the 

 same sites for their dwellings. If the early hunting and 

 fishing tribes frequented the same spots for hundreds or 

 thousands of years in succession, the number of the stone 

 implements lost in the bed of the river need not surprise us. 

 Ice-chisels, flint-hatchets, and S2)ear-heads may have slipped 

 accidentally through holes kept constantly open, and the 

 recovery of a lost treasure once sunk in the bed of the ice- 

 bound stream, inevitably swept away with gravel on the 

 breaking up of the ice in the spring, would be hopeless. 

 During a long winter, in a country affording abundance of 

 flint, the manufacture of tools would be continually in pro- 

 gress; and, if so, thousands of chips and flakes would be pur- 

 posely thrown into the ice-hole, besides a great number of 

 implements having flaws, or rejected as too unskilfully made 

 to be worth j)reserving. 



As to the fossil fauna of the drift, considered in relation to 

 the climate, when I took a collection which I had made of all the 

 more common species of land and fresh-water shells from the 

 Amiens and Abbeville drift, to my friend M. Deshayes at Paris, 

 he declared them to be, without exception, the same as those 

 now living in the basin of the Seine. This fact may seem at first 



