1 64 PREHISTORIC EUROPE. 



north of France of an ice-sheet like that which covers Green- 

 land. In proof of this he points to the fact that the Union biA- 

 feux is abundantly charged with angular fragments of flint, 

 besides a number of whole flint-nodules. But these last are so 

 much cracked and fissured internally, that they generally fall 

 into pieces while they are being extracted from the loam. 

 Their cracked condition he attributes to the action of frost, and 

 as they now lie buried beyond the influence of atmospheric 

 changes, he infers that they must have been split by frost at the 

 time of their entombment in the limon. Again, the loam 

 which encloses them is composed of very unequally-sized grains, 

 which he thinks could not have been deposited at one and the 

 same time by water. Had the limon been an aqueous accumu- 

 lation, he believes that the coarser and finer granules would have 

 been laid down at different times and in different places. The 

 upper part of the deposit (terre a briques), on the other hand, is 

 composed of uniformly-sized grains, and is thus in his opinion 

 the result of aqueous levigation. It owes its origin to the 

 washing and re-arranging of the limon btifcux. The latter, he 

 thinks, was accumulated in the state of clay, and along with the 

 broken flints was formed by the action of frost and ice. It has 

 been derived from the destruction of the rocks upon or near to 

 which it occurs, and changes its character as these change theirs. 

 M. de Mercey then points out that the flint-bearing loam pre- 

 sents a very irregular surface of contact with the rocks upon 

 which it reposes — this surface being quite unlike one which 

 aqueous erosion would have produced. The Chalk and other 

 strata have been irregularly trenched and excavated, so that the 

 loam descends ever and anon into pockets and cavities. Again, 

 he shows that the stony loam spreads like a sheet over the sur- 

 face of the rocks, and is not disposed in terrace-shaped accumu- 

 lations. It follows all the undulations of the ground — covering 

 hollows, slopes, and elevations alike. He alludes further to the 

 form of the ground, which frequently presents the appearance of 

 parallel ridges and intervening hollows, of a character which 

 betokens some other mode of origin than that of erosion by the 



