ANTIQUITY OP MAN. 229 



We shall be better able to judge of these proba- 

 bilities when we shall have considered the next case 

 presented to us, that of the river gravels containing 

 implements believed to have been made by man. If 

 we stand on one of the beds of gravel quarried at St. 

 Acheul, near Amiens, we may see before us the broad 

 flat valley of the Somme, with the little stream flowing 

 between banks of alluvium 100 feet below us. But 

 the ground on which we stand is a loess or river mud 

 with fresh- water shells, and below this are many feet 

 of river-gravel made up mainly of the flints which fill 

 the underlying chalk, and in this gravel, at great 

 depths from the surface, have been found numerous 

 flint implements which it seems difficult to explain 

 unless they have been wrought by man. Ancient 

 miners, it is true, may have worked galleries, since 

 fallen in, through these gravels ; and in visiting this 

 place in 1865, I believe I could perceive some indi- 

 cations of this ; but the general impression conveyed 

 is, that they were mixed with the gravel by the floods 

 of a stream representing the River Somme, but strag- 

 gling over the country at a height of 100 feet above 

 its present bed. This implies that at the time in 

 question the valley was either not cut out, or filled 

 with some material since swept away, and that the 

 water-flow of the river was going on in a manner not 

 favourable to erosion of its bed. Such conditions 

 evidently bring before us considerable changes of level, 

 which we must, I think, be prepared to face more 

 boldly than has been customary with writers on this 



