[ 247 ] 
VII. Theoretical Considerations on the Conditions under which the (Drift)* * * § Deposits 
containing the Bemains of Extinct Mammalia and Flint Implements were accumu- 
lated , , and on their Geological Age. By Joseph Prestwich, Esq., F.B.S., F.G.S. 
Received March 20, — Read March 27, 1862. 
On the Loess of the Valleys of the South of England, and of the Somme and the 
Seine. By Joseph Prestwich, Esq., F.B.S., F.G.S. 
Received May 15, — Read June 19, 1862. 
[Note. — By permission of the Council of the Royal Society these two papers have been incorporated. At the 
time of reading the first paper, the author felt difficulties respecting the origin of the Loess, which led him 
to defer the consideration of the subject. When he afterwards brought forward the second paper, 
it proved so clearly complemental to the first, that the rearrangement of the two became desirable and 
almost necessary. This has also enabled the author to shorten both papers. The main portion of the 
second now appears in § 4. The bracketed remarks in the Introduction are inserted in consequence of 
a suggestion made to the author that it would be desirable to state in what respect the views advocated 
by him differ from those previously brought forward. Returned May 21, 1863.] 
§ 1. INTRODUCTORY REMARKS. 
In the paper I had the honour to lay before the Royal Society in May 1859 f, on the 
occurrence of Flint Implements in France and in England associated with the remains 
of extinct mammalia, I postponed the consideration of the theoretical questions involved, 
to allow time for a more complete investigation of the physical phenomena. The facts 
I sought on that occasion to establish were, — 1, the artificial nature of the Flint- 
implements ; 2, their occurrence in undisturbed ground ; 3, their contemporaneity with 
the extinct animals ; and 4, their postglacial origin. Subsequent researches by myself J 
and other geologists have confirmed my views upon these several points §. 
When I first visited Amiens in 1859, the opinion I formed was that the St. Acheul 
gravel-beds were deposited before those of St. Roch, and that the excavation of the 
* The term “ Drift ” has been hitherto used as a convenient expression for the superficial beds generally ; 
but as the relative positions of these beds are becoming better determined, we shall now be able to drop this 
term and introduce others of greater precision. 
t Philosophical Transactions, vol. cl. p. 277. See also Mr. Evans’s paper, Archaeologia, vol. xxxviii. p. 280. 
+ Journ. Geol. Soc. vol. xvii. p. 362, where the various localities are mentioned. 
§ Flower, Quart. Joum. Geol. Soc. vol. xvi. p. 190, June 1859. Gaudry, Comptes Rendus, Oct. 1859, p. 465. 
G. Pottchet, Actes du Mus. d’Hist. Nat. de Rouen, 1860, p. -33. L’Abbe Cochet, Mem. de la Soc. d’Emulation 
d’ Abbeville, 1858—61, p. 607. Evans, Archaeologia, vol. xxxix. p. 5, 1861. See also Sir Charles Lyell’s 
Address at the Aberdeen Meeting of the British Association, Sept. 1859 ; Mr. Leonard Horner’s Anniversary 
Address to the Geol. Soc. Feb. 1861 ; Sir Roderick Murchison’s Address, Brit. Assoc. Sept. 1861. 
MDCCCLXIV. 2 M 
