A. Tylor on the Amiens Gravel. 325 
sections NQ and NOP cross the railway (see figs. § and 9, 
Plate IV). In fig. 8, M. Guillom found the chalk 8 feet below 
therails; in fig. 9, 14 feet below the rails, Mr. Prestwich has 
represented this railway-cutting as on one of his bands of chalk, 
dividing the valley-gravels into two horizons; and in conse- 
quence, I had the section N O P taken, as nearly as I could, on 
the same line as Mr. Prestwich, because I had always remarked 
gravel in the Montiers railway-cutting, and not chalk. I also 
give a section along this railway (see fig. 12, page 324). By 
the French survey, the chalk is 14 feet below the rails. In Mr. 
Prestwich’s section of the same place, it is 20 feet above the 
_ This difference of 34 feet added to the error in the height 
tails, before mentioned, of 31 feet, makes a total difference 
of 
of 65 fect in the height of the chalk between Mr, Prestwich 
: 
ay om, supposing I am correct in placing Mr. Prest- 
wich’s section on the line : 
Mr. Prestwich has recently informed me that he considers 
section was intermediate between the lines N O P and N Q. 
cy the railway-cutting ceases at the ballast-pit (fig. 12,) and 
there is an embankment to the west of that point for some dis- 
tance, it is difficult to place Mr. Prestwich’s section at any 
other point than where I supposed it was taken, on account of 
the configuration of the ground. Whether there was chalk, or 
tot, at any one point, is quite immaterial to my argument. I 
do not find the Montiers section at all as represented by Mr. 
Prestwich and Sir C. Lyell. (See fig. 12, p. 324) 
The Montiers section appears to be the one adopted as a type 
< the Somme district, first by Mr. Prestwich and afterward 
by Sir C. Lyell. Both authors represent, in several sections of 
bede mme, a great extent of chalk, separating highly inclined 
eds of gravel, which they have distinguished in age by its po- 
seg on above or below this outcrop of chalk, as upper- and lower- 
f -and low-level gravels. The sections which I place be- 
ore the Society appear to me, on the contrary, to show that 
istinction is not a real one, but that the deposit of gravel is 
val and continuous, deposited in concavities of an ancient chalk 
Re 6y, and is not highly inclined as represented in the ‘ Antiq- 
- Se Man’ and the ‘Philosophical Transactions,’ 
orets pS? 264, Phil. Trans. 1864, Mr. Prestwich gives a the- 
"tical account of the view he takes of the deposition of the 
Wiens Part of the upper-level gravels are represented as ré- 
fica untouched, while the valley is cut down 50 feet, and a 
gt set of gravels deposited at lower levels; my sections show 
nat there is no evidence of any such action, — ; 
dens. ue Views are extended by Mr. Prestwich to the oe 
Sage! the loess of St.-Acheul is considered a much older de- 
Sit than the loess at Montiers, 
