7 
ten feet in the course of a few days, and, therefore, there are 
no high-level gravels, which, so far as thickness is concerned, 
might not have been deposited in the course of a few weeks, 
or even a few days/’ * * * § 
Turning to other witnesses, we find Professor Morris, alluding 
to the Thames gravel, saying, — “ I am inclined to consider it as 
resulting from fluviatile action, and that at a period when a 
river far more deep and extensive than the present stream 
flowed along the valley ,”f 
And Mr. Evans , — “ Certainly, the whole character of the 
deposits is more in accordance with their resulting from the 
occasional flooding of the streams than from any other cause. 
If this be so, who shall tell at what intervals such floods 
occurred, and what was the average effect of each in deepening 
the valleys ? ”J 
Mr. Tylor calculates that in the pluvial period there must 
have been 120 times as much water per acre as at present. It 
is impossible to conceive causes now in operation, on the present 
scale, producing continuously any such phenomena. It is not , 
necessary for my argument to show more than the full admis- 
sion, by the most distinguished geological observers, that there 
must have been a sufficient departure from the present esta- 
blished course of things to form and place these gravels. So 
Dupont, — attributing the formation of the valleys to rains far 
more powerful and prolonged than the present, — “ Aussi 
devons-nous rechereher, dans une augmentation des pluies, la 
raison des masses d’eau qui donnerent naissance h nos vallees 
et admettre que la quantite d’eau qui tombait alors sous nos 
latitudes, etait plus grande qu’aujourdhui.”§ 
M. Dupont estimates that at the beginning of the mammoth 
age the valley of the Meuse was eight miles broad at Dinant, 
and at the close of the same period less than one mile. “ Les 
phenomenes physiques se produisaient sur une immense 
echelle.”|| Afterwards the water ceased to conquer the land, 
and has been barely able to continue its present channel. 
Mr. A. Tylor, in the year 1868, brought forward proofs of 
excessive rainfalls during the formation of the river-valleys, and 
characterized the period during which it occurred as the 
“ pluvial period.” He discussed these questions in his papers 
* Philosophical Transactions, part ii., 1864, p. 299. 
t Quarterly Journal of the Geological Society, vol. vi. p. 223. 
+ Evans, Stone Implements, p. 620. 
§ Dupont, 1' Homme pendant les Ages de la Pierre. Bruxelles, 1872. 
|| lb., p. 125. 
