A. Tylor on the Amiens Gravel. 321 
The existence of such a pluvial period is demonstrated by 
the size, constitution, and level of the fluviatile gravel and 
loess deposits at Amiens and other well-known localities, 
@ rivers certainly existed to a later date than the glacial 
period, as they formed such large terraces of loess over the gla- 
cial gravels. If we were to judge of the age of these later de- 
its, such as the loess escarpments at Amiens and Clapton, 
their modern appearance and by their being unaltered by 
weather and not cut into by streams, we should place them al- 
most in the historical period. The Amiens sections of loess 
accord with those of the Rhine and other rivers. The differ- 
ence between this loess deposit at Amiens and the present warp 
of the Somme ought to be an index of the rainfall in the plu- 
vial period, when the loess was deposited, as compared with 
that falling at the present time; and we may Kock at these 
gravels and loess beds as registering rain-gauges, 
@ same manner, the comparative rainfall at the epoch of 
the deposition of gravels might be estimated approximately by 
omparing the dimensions of the blocks of Grés and large flints 
moved by fresh water in the gravel-period with the size of the 
materials moved in the same valleys at the present time 
The existence of a glacial period almost necessitates that of a 
pluvial period, commencing prior to the glacial, and continu- 
Ing after it, occupying a region south of that occupied by the 
ice and snow, 
We should have had no cause for surprise if, when the theory 
of a period of ice and snow in these latitudes was first broached, 
the probability of arainy period south of the Thames had been 
also deduced from aconsideration of the effects of so large a 
Mass of ice and snow on the country and atmosphere bordering 
on the ice-land, but possessing a warmer climate. : 
© have the evidence in almost all wet valleys of the river 
..) Occupying a small groove cut in the ancient valleys, 
Which valleys I believe, were shaped to their present configura- 
ei im such a rainy period as I have inferred. Every wet valley 
* number of dry valleys opening into it, which bear the 
: — of having been shaped by water and continual showers 
Uring the pluvial period. 
wery,, Pots of difference between other authors who have 
- — Tespecting the Somme Valley and myself are as fol- 
te the appendix to Mr, Prestwich’s paper in the ‘ Philosoph- 
* 1, ensactions,’ M. Pinsard gives the height of the railway 
8 Neuville as 83 feet above the mean tide at Havre. 
_ Survey made for me by M. Guillom, Principal engineer of 
8400p, Ser—Sacoxn Surtes, Vou. XLVI, No. 138—Noy., 1868. 
