CONTAINING FLINT IMPLEMENTS, AND ON THE LOESS. 
249 
But although it was evident that there were old land surfaces and possibly old rivers, 
there was no evidence that any supply of water could have existed to fill such large 
valleys ; and the present streams seemed totally inadequate to have spread out such vast 
beds of gravel and sand, by far the greater part of which are also without organic 
remains to indicate their origin. Sir Charles Lyell, who advocated the fluviatile origin 
of these lower valley-gravels, considered that it would be “ a rash inference” to conclude 
“ that rivers in general have grown smaller, or become less liable to be flooded than 
formerly” *. This view, more or less modified, was held also by many other distinguished 
geologists. I could not accept it, because it seemed to me that to form such beds of 
gravel some greater water force must have been in operation than that which now 
obtains ; at the same time, the hydrographical basins and the watersheds being the same 
as they were at that Quaternary period, I did not see whence the larger supply of water, 
which seemed to me indispensable, could have been obtained. 
That valleys have been excavated by rivers was the hypothesis brought forward by 
Hutton and Playfair f. It has been frequently advocated since; but the opinion has 
made little progress, owing to the absence of proof of how such an operation could have 
been effected, and to the insufficient physical and palaeontological evidence. The subject, 
as far as regards Auvergne, was ably touched upon by Mr. Poulett ScropeJ in 1827, 
and discussed and argued more fully by Croizet and Jobert§ in 1828. Some remark- 
able cases were described by these geologists, to show, from the position of old shingle- 
beds preserved under masses of basalt, high above the present rivers, that the rivers 
in that part of France had excavated the valleys in which they now flow ; but the 
cause of such phenomena remained unexplained, and the date undetermined. 
Mr. Godwin-Austen showed, so early as 1837 ||, that in Devonshire there were ter- 
races of gravel fringing the valleys; and in 1851 and 1855 ^j*, in correlating these and 
other quaternary deposits, he considered that the ancient low-level alluvia of the Thames 
and Seine valleys, and the old beach and the Elephant-beds of Brighton, were anterior 
to the Boulder Clay, and he was further of opinion that river- and ice-action had played 
an important part in producing these valley deposits. Sir Charles Lyell also discussed 
with his usual ability the question of the origin of valleys, and of ancient river-alluvia 
and river-terraces, both in his ‘Principles’ and in his ‘Elements’**, but without 
attaching to the phenomena the importance I would show them to possess in such 
valleys as those of the Thames and the Seine. He was rather disposed to attribute the 
erosion of some lower parts of the valley of the Seine to sea-actionff. Mr. Trimmer 
* Op. cit. pp. 70 & 84. f Theory of the Earth, vol. ii. p. 401. 
+ Memoir on the Geology of Central France, 1st edit. pp. 163-4. 
§ Ossemens Fossiles du dept, du Puy-de-Dome, pp. 66-88. 
|| Trans. Geol. Soc. 2nd series, vol. vi. p. 439. 
if Q- Journ. Geol. Soc. vol. vii. p. 136, and vol. xiii. p. 40. 
** Op. cit. p. 85, and Principles of Geology, 9th edit. pp. 219 & 484. 
tt Op. cit. p. 269 & 271. ++ Quart. Journ. Geol. Soc. vol. ix. p. 286. 
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