269 
gravel below, finer materials above. So similar, indeed, are 
these beds to those already described, both in constitution and 
in the animal remains they contain, that it will be unnecessary 
for me to give any further description of them. 
Finally, the lowest portion of the valley is at present 
occupied by a bed of gravel, covered by silt and peat, which 
latter is in some places more than twenty feet thick, and is 
extensively worked for fuel. These strata have afforded to 
the antiquaries of the neighbourhood, and especially to 
M. Boucher de Perthes, a rich harvest of interesting relics 
belonging to various periods. The depth at which these 
objects are found has been carefully noted by M. Boucher 
de Perthes. 
" Prenant," he says, " pour terme nioyen du sol de la 
vallee, une hauteur de 2 metres audessus du niveau de la 
Somme, c'est a 30 a 40 centimetres de la surface qu'on 
rencontre le plus abondamment les traces du moy en-age. 
Cinquante centimetres plus bas, on commence a trouver des 
debris romains, puis gallo-romains. On continue a, suivre 
ces derniers pendant un metre, c'est a dire jusqu'au niveau 
de la Somme. Apres eux, viennent les vestiges gaulois purs 
qui descendent sans interruption jusqu'a pres de 2 metres 
audessous de ce niveau, preuve de la longue habitation de ces 
peuples dans la vallee. C'est a un metre plus bas, ou a 4 
metres environ audessous de ce meme niveau, qu'on arrive au 
centre du sol que nous avons nomme Celtique, celui qui 
fouler ent les Gaulois primitives ou les peuples qui les pre- 
cederent ;" and which belonged therefore to the ordinary 
stone period. It is, however, hardly necessary to add that 
these thicknesses are only given by M. Boucher de Perthes 
" comme terme approximatif." 
The "Antiquites Celtiques" was published several years 
before the Swiss Archaeologists had made us acquainted with 
the nature of the Pfahlbauten ; but from some indications given 
