304 LOESS. 



thickness of three hundred feet. The greatest development 

 of it which I have seen in the north of France was in a pit 

 in the Rue de la Chevalerie, near Ivry, where it was twenty- 

 two feet thick ; some of this, however, may have been recon- 

 structed loess brought down by rain from the higher ground 

 in the immediate neighbourhood. Assuming that this loess 

 is composed of fine particles deposited from standing or 

 slowly-moving waters, we might be disposed to wonder at 

 not finding in it any traces of vegetable remains. We know, 

 ^however, from the arrangement of the nails and hasps that 

 in some of the St. Acheul tombs wooden coffins were used, 

 while the size of the nails shows that the planks must have 

 been tolerably thick ; yet every trace of wood has been re- 

 moved, and not even a stain is left to indicate its presence. 

 We need not, therefore, wonder at the absence of vegetable 

 remains in the drift. 



Such is a general account of those gravel pits which lie at 

 a height of from eighty to one hundred and fifty feet above 

 the present water level of the valleys, and which along the 

 Somme are found in some places even at a height of two 

 hundred feet. 



Let us now visit some of the pits at the lower levels. At 

 about thirty feet lower, as for instance at Menchecourt, near 

 Abbeville, and at St. Roch, near Amiens, where the gravels 

 slope from a height of sixty feet down to the bottom of the 

 valley, we find almost a repetition of the same succession ; 

 coarse sub-angular gravel below, finer materials above. So 

 similar, indeed, are these beds to those already described, 

 that it will be unnecessary for me to give any special de- 

 scription of them. 



It seems highly probable that when the fauna and flora 

 of the upper and lower level gravels shall have been more 

 thoroughly investigated, they will be found to be almost 

 identical. At present, however, the species obtained from 



