208 MR. G. CLINCH ON THE SCULPTURES OF THE [May 1909, 



13. On the Sculptures of the Chalk Downs in Kent, Surrey, and 

 Sussex. By George Clinch, F.G.S., F.S.A. Scot. (Read 

 April 7th, 1909.; 



[Abstract.] 



The Author classifies the various forms of sculpture of the Chalk 

 Downs under three heads, namely, (1) dry valleys of simple form, 

 (2) dry valleys of complex form, and (3) wet valleys. He draws 

 attention to the relatively small catchment-areas of the dry valleys, 

 and to the large number of tributary valleys found in some dis- 

 tricts, two points which he considers have not hitherto received 

 entirely satisfactory explanation. 



While accepting the view that frozen conditions in former times 

 altered the drainage-system of the Chalk, he argues that the most 

 potent excavating force was the frost itself, acting on Chalk satu- 

 rated or highly charged with water. He points out the following- 

 peculiarities of dry Chalk valleys : — (1) the great size and breadth 

 of the valleys in relation to their catchment-basins ; (2) the rami- 

 fications of some of the valley-systems ; and (3) the termination 

 of many dry valleys just short of the crest of the Chalk Downs. 



In order to account for these phenomena, the Author propounds 

 the following theories : — 



(1) The chief part of the valley, during and after periods of 

 low temperature, being occupied by a mass of ice, erosion of the 

 Chalk would naturally be more active at the sides than in the 

 bottom of the valley : lateral development and sometimes elaborate 

 ramification being the result. 



(2) The diminution of the catchment-area, due to the cutting- 

 back of the valley towards the highest level, would have the effect 

 of removing one of the chief agents in the breaking-up of the 

 Chalk, with the result that the valley would die out just short of 

 the crest of the Chalk Downs. 



Discussion. 



Mr. E. A. Martin wished to point out that the dry valleys of the 

 Southern Downs, ending quite close to the edge of the escarpment, 

 are merely instances of arrested development. When the lowering 

 of the Wealden watershed took place, some of the southward-flowing 

 streams ceased to flow. Of those that remained, what are now the 

 Adur, Arun, etc. have persisted until modern times ; others were cut 

 off when their work was but half done, hence the gaps at Findon, 

 north of Worthing, and Clayton, north of Brighton, or, in the North 

 Downs, at Merstham. There is thus a regular sequence from the 

 high and dry valleys, and the deeply-cut river-bearing valleys of the 

 present day. The streams which prevailed over those that ceased, 



