302 
ME. PEESTWICH OX FLENT-DIPLEIMEETS. 
the meantime that, although these flints are so numerous in one pit at St. Acheul. they 
are scarcer in the other pits in the same fleld ; that at Menchecourt they are mre, still 
rarer at St. Gilles, more common again at the Champ de Mars; whilst at the lai-ge 
gravel pits^ of St. Eoch, Boves, and Montiers near Amiens, where the St. Acheul disco- 
veries were perfectly well known, and search has been frequently made, I could neither 
And, nor procure from the men, any flint-implements. See Appendix (D.) 
§ 4. GEOLOG-ICAE COxWDEEATIOAS. 
I should not wish, until after fuller study of the district, to enter on the question 
regarding the mode of formation of the above-described deposits of Abbeville and Amiens, 
beyond pointing out, that, at the former place, the ewdence of the lower beds of Menche- 
court having been deposited partly in fresh water, and partly in salt or brackish water, 
seems sufficiently clear and distinct. Apart from the latter condition, the St. Acheul 
sands (c), as well as the lower gravel [d) contaming the flint-implements, may also be 
attributed to a like accumulation under fresh water. The upper beds {h) in both cases 
are, I believe, of entirely different origin, and belong to a class of phenomena of fai’ 
wider extent and generality. At the same time, while postponing the more theoretical 
questions, the one concerning the relative age of the deposits can, to a certain extent, 
be considered independently upon the evidence of the organic remains and of correla- 
tion ; and certain general conclusions may be ventured upon. 
It is probable that subsequently to that phase of the Glacial period marked by the 
Boulder Clay, the area of dry land became more extended, and on it there lived the 
Elejphas primigenius and E. antiquus. Rhinoceros tichorliinus, Hgcena sjjelcea, 'svith species 
of Deer, Horse, and other animals, mostly of extinct, but some of species not to be distin- 
guished from the recent ; whilst the waters of both sea and land were tenanted almost 
exclusively by shells of recent species still common in this and adjacent coim fries. The 
remains of this old surface we find in deposits, which everywhere contain a similar group 
of organic remains, and occur mostly in old valleys or at moderate elevations. They arc 
never overlaid by other fossiliferous deposits, and I believe them all to belong to a state 
of things which immediately preceded the present order. One feature of these deposits 
is, that although closely related to the present configuration of the smiace, yet they are 
always more or less independent of it. They are often near present lines of drainage, 
yet could not, as a whole, possibly have been formed under their operation. The 
deposits described in the preceding pages are, there is little doubt, of this age, and they 
have many analogues in France and England. The Menchecourt beds bear a '^ ery close 
resemblance (the marine characters apart) to those of Fishertonf near Sahsbury J. The 
deposit of St. Acheul is like, in many respects, the Ilford and the Brentford beds, whilst 
that of Moulin Quignon and St. Gilles closely resembles the gravel beds at Croydon, 
Wandsworth Common, and some other places near London. 
* All on a lower level than St. Acheul, but with like mauunalian remains, —showing like wear. 
t Quart. Journ. Geol. Soc. vol. xi. p. 102. 
J Also of Orton, near Peterborough, where marine remains do occur. 
