1878.] Superficial Gravels and Clays . 347 
its later sediments to its earlier ones. Nor does river adtion 
explain the angular and subangular character of the gravel, 
nor the presence of the largest stones at the base of the 
deposit. 
If, then, the physical evidence is so opposed to the theory, 
why should it be upheld ? Only, so far as I can understand, 
because the conclusion is started with that palaeolithic man 
is post-glacial, and only by the theory of the post-glacial 
excavation of the southern valleys can the post-glacial age 
of palaeolithic man be defended. But why should we 
commence with an assumption like this ? At Bedford the 
evidence is a repetition of that which we have in the 
Thames Valley, and I have shown in a former paper that 
at Hoxne* there is no proof of the post-glacial age of 
palaeolithic man. The palaeontological evidence is also 
hostile to Prof. Prestwich’s theory. At low levels in the 
Lower Thames Brick-earths the remains of Rhinoceros mega- 
rhinus , R. hemitcmhus, and Elephas aniiquus occur, all of 
which belong to the oldest pleistocene fauna of Europe. At 
much higher levels the stone-implements of palaeolithic man 
are found, along with the remains of the mammoth and the 
woolly rhinoceros. On the supposition that the remains 
have been entombed during the gradual excavation of the 
valley, the latter would be the oldest of the two faunas. 
The great mammals, the bones of which are found so plen- 
tifully at Brentford, would have lived long after the men 
who left their chipped flints at the much higher levels at 
Ealing. The affinities of the fauna found in the Lower 
Thames Brick-earths with that of the Cromer forest-bed 
are much closer than that found in the gravels. And in the 
valley of the Rhine the deposits, with the woolly rhinoceros 
and the mammoth, overlie those containing Elephas antiquus, 
whilst they ought, if Prof. Prestwich’s theory was correct, 
to underlie them. 
Mr. Alfred Tylor has propounded the theory that the 
gravels were spread out after the excavation of the valleys 
to their present depth. He supposes that the Glacial period 
was succeeded by a Pluvial period marked by an enormous 
rainfall, so that the river-floods reached far above their pre- 
sent limits, and deposited gravels and clays high up the 
slopes of the valleys. The highest beds may, he thinks, 
have been formed by rain-wash. He has also suggested 
that the gorging by ice of the mouths of the Somme, the 
* Quart. Journ. of Science, July, 1876. 
