56 George Clinch—Sculpturings of the Chalk Downs. 
that if the valley were due to solution the gravel would have been let 
down with the lowering surface of the chalk, but the fact that it has 
been entirely swept out of the valley affords clear proof of erosion. 
There is abundant evidence of this, but for the present purpose it will 
suffice if reference is made to the excellent example in the Seaford 
district to which Mr. J. V. Elsden has recently drawn attention in 
his paper,' already mentioned, on the geology of that neighbourhood. 
That.a certain amount of sculpturing of the Chalk may be attributed 
to solution, either pluvial, or atmospheric, or both, particularly in 
association with joints or faults, is well known and indisputable. An 
excellent example may be seen at Box Hill, near Dorking, in Surrey, 
and there are many others. But in these the bottom of the depression 
is not regularly inclined downwards, like those of the typical Dry 
Valleys. 
Moreover, the solution theory leaves us much in want of some 
reasonable controlling force which, in the initial and early stages, 
would give form to the complete and elaborate valley system. If the 
solution theory were accepted we should expect deep ravines in the 
Chalk, following precisely or nearly the direction of the original stream 
or river which removed the clay capping. A certain broadening 
would doubtless follow in the course of time, but we should not expect 
such elaboration and development as we actually find. The erosion 
would be in the direction of depth rather than breadth, because the 
degraded clay on the sides of the valleys would still continue, to some 
extent, to protect the Chalk from rainfall and consequent solution. 
In a word, the solution theory involves vertical rather than lateral 
development, yet lateral development is one of the most noteworthy 
characteristics of the valleys. 
Another weak point, among many, about the solution theory is that 
it fails to account for Dry Valleys on the Chalk escarpment, where 
there is no controlling and protecting clay covering. 
Finally, { submit, the solution theory is effectually disproved by 
the rolled material in the valleys. 
Mr. Reid’s suggestion that upon the approach of mild temperature 
floods like mountain-torrents swept the loosened material out of the 
Chalk valleys, makes no sufficient allowance, I think, for the vast 
masses of ice which, wholly or in part, must have occupied the valleys. 
The presence of these ice-masses must haye tended to lateral erosion 
and consequent widening of the valleys. 
The porous nature of Chalk is a point with which Mr. Reid deals 
thoroughly, and I think his theory that the bed was rendered im- 
pervious by means of frost is one which has generally been accepted 
by geologists. But I do not think it at all likely that the frost 
extended downwards into the earth for some hundreds of feet, because 
there would doubtless be a protecting covering of snow. ‘Ten or 
twenty feet would be ample to render the Chalk impervious, and 
I cannot find evidence of frost at a greater depth. 
Those who have hitherto attempted to explain the denudation of the 
Weald and the formation of the Dry and Wet Valleys of the Chalk 
1 Q.J.G.5., vol. Ixv, pp. 442-61. 
