31G 
THE GEOLOGIST. 
The great value of Mr. Prestwich's paper is in the minute details of the 
sections and geographical areas of distribution of the flint implement beds at 
Amiens, Abbeville, and Hoxne. The sections at Abbeville and Amiens are 
flTst accurately described. 
Map of the Amiens' District. 
" Abbeville and Amiens are both situated in the valley of tne Somme, the 
first at a distance of about fourteen miles, and the second of forty-one miles, 
from the sea. The surrounding district consists of gently undulating elevated 
plains of chalk, capped here and there by outliers of tertiary strata, and else- 
where partly bare and partly covered by a few feet of fine light red or yellow 
loam and clay, in places mixed with angular fragments of flints. The river 
vaUeys are narrow, often exhibit on their flanks thick deposits of loam and 
gravel, while the middle is usually a flat level of marsh and peat overlyiug 
gravel. The loam, brick-earth, or loess, forms a very marked feature in this 
usually bare chalk district, being principally accumulated in thick irregular 
and local masses on the sides and flanks of the valleys. This is especially the 
case for some distance both above and below Amiens, as well as up the greater 
number of the lateral vaUeys. It extends to various elevations. A bed of 
gravel also spreads over some of the lower hiUs flanking the valley of the 
Somme, For full particulars of the geology of the district, I beg, however, 
to refer to the works of M. Buteux and Dr. Ravin. 
" The fall of the Somme valley is very gradual, its elevation at Abbeville 
above the level of mean tide of the sea being eighteen feet, at Amiens sixty 
feet. Between these towns the mean width of the valley, which varies but 
little, is rather less than a mile. The hiUs rise gradually to heights generally 
of from two hundred to four hundred feet, and nowhere exceed six hundred to 
six hundred and fifty feet above the sea-level, and that more in the interior of 
the department. The pits in which the flint implements have hitherto been 
observed are all in or near the main valley of the Somme. 
" Abbeville. — According to M. Boucher de Perthes, the principal localities 
where flint implements have been found are, the village of Menchecourt, a 
suburb at the foot of the hiU on the north-west side of Abbeville, the town of 
