52 George Clinch—Seulpturings of the Chalk Downs. 
Derosirs 1n THE Dry Vatteys. 
Generally speaking the Dry Chalk Valleys do not contain any 
considerable amount of deposits of hard and insoluble matter. Many 
are indeed quite free from such accumulations ; but some are partially 
occupied by beds of re-arranged Chalk; chalky matter interspersed 
with sand from the Wealden beds; flints, worn and unworn; 
ferruginous sandstone from the Lower Greensand; and masses of 
Sarsen Stone. 
An important and significant deposit occupies the bottom of the 
valley at Purley, near Croydon, a valley which, although now dry, 
once formed the upper part of the Wandle Valley (Fig. 1) when that 
river drained part of the Weald. It contains blocks of Sarsen Stone 
of large size, weighing about a ton, large blocks of equal weight of 
pebbly conglomerate, and numerous subangular flints as well as 
Tertiary pebbles. A good section of this was exposed when the 
waterworks at Purley were constructed. Sarsen blocks of smaller 
size, and chalky material and flints occur in the Coombe Rock at » 
Black Rock near Brighton. 
Denvuparion or THE WHALD. 
The relation of Chalk sculpturings to the denudation of the Weald 
was probably intimate. Strictly considered, it is clear that the very 
sculpturings with which this paper deals are but part of the process 
of the uncovering of the Wealden strata, by the erosion of the Chalk 
and other superincumbent deposits. Nevertheless the paucity of 
remains of the harder and more insoluble parts of the Chalk in the 
Wealden area is well known, and this circumstance has given rise to 
an extraordinary variation of opinions amongst geologists as to the 
force or forces which have removed the Chalk. ‘The elevation of the 
centre of the Weald is another important point, and unquestionably 
it has had much to do with this denudation. How far the actual 
upheaval may have broken up the Chalk cannot now be estimated 
with precision. ‘There can be no doubt that there was much disloca- 
tion and disruption, although the views expressed by some writers? 
on the subject seem to be extravagant. 
The Wet Valleys which cut through the Downs are probably the 
channels by which the eroding and transporting forces conveyed the 
material to other areas outside the Weald. What those forces in all 
probability were is a question upon which I shall have occasion to 
touch when dealing with the origin of the dry valleys; but, I may 
add, I do not for a moment suggest that anything of the nature of 
glaciers was the transporting force. 
Retation or Dry Caark Vatieys ro Cray-wira-Fiits. 
The origin of Clay-with-flints on the higher Chalk has long been 
a disputed point. Geologists are by no means agreed as to whether 
1 In Scepticism in Geology (pp. 44-5), William Longman suggested that ‘‘ the 
Chalk escarpments may have been parted asunder like the sinews of a shoulder of 
mutton on the application of a knife’? ; and Sir Henry Howorth in Ice or Water, 
vol. i, p. 525, holds that the Chalk beds were dragged apart over the softer under- 
lying strata for a distance of 25 miles. To my mind such an extended movement of 
the Chalk seems unlikely. 
