Reviews — Prestwich on Valley-Deposits. a1 
of river-valleys, and especially of the numerous localities where flint 
implements have now been found in beds of undisturbed fluviatile 
gravel. The Valley of the Waveney at Hoxne, the Valley of the 
Lark at Icklingham, that of the Ouse at Bedford, the deposits near 
Reculver and Whitstable, the Valley of the Somme near Abbeville 
and Amiens, that of the Seine near Paris, and that of the Oise near 
Creil are all passed under examination ; and, had the deposits near 
Salisbury and on the shores of Southampton Water been known as 
productive ‘of flint implements at the time when this paper was 
written, the evidence afforded by them would no doubt have been 
adduced as corroborative of that of the other cases. The testimony 
afforded by the lithological examination of the valley-gravels 
amounts to this, that all the materials of which they are formed 
can be referred to rocks or to older drift-deposits traversed by the 
valleys or their tributaries ; and that in no instance can the direct 
introduction of any foreign element be proved. The necessary de- 
duction is that the transporting agent by which the mass of materials 
composing the gravel has been brought to its present position, must 
have been in each case limited in its operation to the same hydro- 
graphical basins as those drained by the present rivers. 
This point is well illustrated by a sketch-map, showing the source 
and distribution of some of the Quaternary Valley-deposits of 
parts of England and France, which exhibits at a glance how and 
why in the Valley of the Seine, for instance, pebbles of the granitic 
and porphyritic rocks do not occur in its gravels until after its 
junction with the Yonne, which brings them down from the Morvan ; 
and how and why in the Valley of the Oise pebbles of the paleozoic 
strata of the Ardennes occur ; while in the Valley of the Somme, 
the watershed of which is in part conterminous with that of the 
Oise, such pebbles are entirely absent. 
The valley-gravels are divided by Mr. Prestwich into two classes, 
the ‘high-level’ and the ‘low-level ;’ not that it is possible to draw 
any exact line of demarcation between them, as the one sometimes 
shades insensibly into the other. Still they are the two ‘ extremes 
of a series marking a long period of time, and probably formed 
under analogous but not identical conditions.’ ‘The broad dis- 
tinction consists in one being on hills of various heights flanking 
the valley, while the other occupies the immediate river-valley, 
always following its main channel, and constantly rising on its sides 
to the height of several feet, or where the valley is broad, forming 
low terrace-platforms on its sides.’ They represent, in fact, portions 
of the drifted matter accumulated in the beds of the rivers at atime 
when they ran at a higher level than at present, and which happen 
to have been left undisturbed by the stream during their farther 
and subsequent excavations of their valleys. ‘That the high-level 
eravels, sometimes 100 feet and upwards above the levels of the 
present rivers, and on the flanks of valleys a mile in width, were 
deposited by river-action, is abundantly proved by the presence in 
them of fluviatile shells ; while their elevation, so far above the 
reach of any floods of the present rivers that can possibly be 
