Yol. 65.] CHALK-DOWNS IN KENT, STJEEBY, AND SUSSEX. 209 



certainly succeeded in overcoming the natural porosity of the Chalk. 

 This, the speaker contended, was in consequence of another 

 •characteristic of the Chalk when ground down to powder hy running 

 water, namely its ability to make itself a puddled, water-bearing 

 bed. Many of the Downland dew-ponds are held up by a chalk- 

 puddled bottom, seemingly contradictory though it may be to the 

 well-known porosity of chalk in the field. 



Mr. G. "W. Young thought that the Author had given scant 

 attention to the more recent literature on the subject. The matter 

 had been fully discussed by Mr. Jukes-Browne in the Geological 

 Survey Memoir (' Cretaceous Rocks of Britain,' vol. iii). Had the 

 Author consulted that, he would scarcely have ignored what the 

 speaker regarded as an important factor in the production of these 

 dry chalk-valleys, namely, the solution of the chalk by rain along 

 lines of weakness (joints) especially where unprotected by a clay- 

 covering. 



The Atxthoe, in thanking the Fellows of the Society for their 

 kind reception of his paper, regretted that he was unable, owing to 

 the lateness of the hour, to reply fully to all the points which had 

 been raised in the discussion. 



Replying to the remarks of Mr. E. A. Martin and Mr. G. W. 

 Young, the Author said that he was unable to find sufficient 

 evidence for the origin and development of the dry valleys in the 

 simple forces of atmospheric solution, even when the clay-capping 

 of the Chalk had been removed locally by former streams or rivers. 

 These explanations, although applicable in a restricted degree and 

 in reference to some of the simple valleys, did not, he submitted, 

 adequately account for the development of the sinuous ramifica- 

 tions of complex valley-systems, and were equally insufficient to 

 explain the absence of chalk-debris in many of the coombes. 



Q. J. G. S. No. 258. 



