Mr. J. Prestwich on the Drift Deposits. 59 



On the contrary, he refers the phenomena to long-continued river- 

 action. 



An account is then given of the valley of the Somme, and it is stated 

 that the relation between the high- and low-level gravels, which 

 could not be proved with respect to St. Acheul and St. Roch, has 

 been made clearly apparent at Montiers near Amiens, by the opening 

 of a new ballast-pit on the side of the railway, some 50 feet above 

 the level of the old gravel-pits in the valley just below, and in which 

 latter flint-implements were first found by the author in the spring 

 of last year. In the upper ballast-pit a considerable number of land 

 and freshwater shells and some mammalian bones have been found, 

 but as yet no flint-implements. This deposit, as also the now well- 

 known flint-implement-bearing beds of St. Acheul, are considered to 

 belong to the high-level gravels, whilst the gravel of St. Roch and 

 that of the old Montiers pits are placed with the low-level gravels. 

 Both sets of gravels are also developed in the neighbourhood of 

 Abbeville, and both there contain flint-implements ; Moulin Quignon 

 belonging to the higher level, and Menchecourt aud Mautort (village) 

 to the lower level. 



In the course of last year M. Gosse discovered flint-implements in 

 association with the I'emains of the Mammoth in some gravel-pits 

 near the well of Grenelle at Paris. This bed belongs to the low-level 

 gravel. The same gravel is also worked to the S.E. of Paris at the 

 Gare d'lvry, where, as at Montiers, it abuts against the hill-side. 

 On the hill above, and 115 feet higher, there occurs at Gentilly a 

 deposit of sand and gravel, with land and freshwater shells and mam- 

 malian remains, precisely like that at St. Acheul. At Charonne, on 

 the opposite side of the valley and distant 4 miles, a similar deposit, 

 corresponding in its height above the river, in its collection of fresh- 

 water shells, and in its mineral contents, is met with. No flint- 

 implements have yet been found in these beds, but in every other 

 respect they agree with the gravel of St. Acheul. These deposits, 

 which have been described by M. Duval and M. Charles d'Orhigny, 

 contain the same debris as the present Seine valley, and amongst it 

 fragments of granite derived from the hills of the Morvau, at a 

 distance of 120 miles from Paris. 



It is then shown, by reference to the works of M. Leymerie, M. 

 Cornuel and other geologists, that the valleys of the Seine and of its 

 tributaries above Paris are occasionally flanked by heights capped 

 with gravel containing at places remains of the Elephant, Deer, 

 Horse, &c. In some instances these gravels rise to a height of 190 

 feet above the river, but the general height is from 60 to 150 feet. 

 Sometimes they expand to a breadth of 4 to 5 miles, but they more 

 usually form narrow belts. Various other French authors are then 

 quoted, to show that the same structure prevails in the valleys of 

 the Oise (where one instance of a flint-implement is recorded by M. 

 de Verneuil), of the Marne, the Aire, the Aube, and their numerous 

 tributaries ; and in each instance it is shown that the materials, 

 both of the high- and low-level gravels, are derived strictly from the 

 district through which the valley passes ; that only the Seine valley 



