22 Reviews— Prestwich on Valiey-Deposits. 
conceived, proves that the valleys must, in great part at all events, 
have been excavated since the high-level gravels were deposited. 
The evidence of the Loess, or brick-earth, is also of importance in 
the case; for this deposit occurs associated with the high-level 
gravels, and has all the character of the fine silt or sediment de- 
posited in places where the flood-waters, out of the direct channel 
of a turbid stream, remain for a time in a state of comparative re- 
pose. It contains, too, numerous land shells, occasionally intermixed 
with a few fresh-water species. Nor is this purely fluviatile 
character confined to the gravels and loess of the higher level, but 
extends to those of the lower level also. The whole phenomena, 
indeed, are in general such as might have been theoretically assigned 
to valleys formed by the erosion of rivers subject to periodical floods, 
though there are particular circumstances which tend to, show that 
the erosive power may have been greater during one part of the 
process of excavation than during another. 
One feature in the case is that in the high-level valley-gravels 
large boulders are of not unfrequent occurrence ; and there is an 
irregularity, confusion, and general want of stratification in the beds, 
which are also often contorted. Some of these boulders or blocks 
are as much as 8 feet by 3 feet in dimensions ; and in some instances, 
as in the Valley of the Waveney, where there are no hard rocks to 
furnish boulders, but the valleys traverse a Chalk district, large 
masses of flint, with sharp and intact angles, are common. The con- 
tortions, which are perhaps nowhere better seen than at St. Acheul, 
near Amiens, are such as sedimentary beds could never have 
assumed in a process of deposition by the mere action of water. In 
the low-level gravels, these contorted strata are generally absent; 
and, though large blocks are often common in them, yet they are 
generally more worn than in the upper gravels. The low-level 
gravels also usually present a more uniform bedding, and a greater 
abundance of beds of sand and fine gravel, with oblique lamination. 
Looking now at the Fauna and Flora of the high-level beds, Mr. 
Prestwich finds that, out of 109 land and fresh-water shells now in- 
habiting the South of England and the North of France, 36 species 
have been found in the flint-implement-bearing high-level gravels. 
Taking the group as a whole, it appears to have a wide range, but 
one more in a northern than in a southern direction; for whereas 
only 29 out of the 36 species are found in the plains or on the hills 
of Lombardy, no less than 34 range to Sweden, and 31 to Finland, 
a country in which only 77 species have been recorded. A great 
number of these molluses occur also in Siberia, for which country, 
however, there is no complete list of the land and fresh-water shells. 
The mammalian remains are at present confined to Elephas primi- 
genius, E. antiquus, Equus, Bos, and Cervus, among the latter pos- 
sibly C. Tarandus. Of these the Mammoth and woolly haired 
Rhinoceros appear to have inhabited countries possessing cold 
climates, while the Horse and Ox brave the winters of Siberia and 
North America, and the Reindeer appears to be essentially a north- 
ern animal. Of the flora of the high-level period, but little is known ; 
