1877.] Discussion on Mr. BalVs paper. 145 



and having himself then recently left the School of Mines in London, he 

 had been much struck with what appeared to him to be the undue amount 

 of attention given to little details, which any one might observe for him- 

 self, and the slight amount of attention given to the geological structure 

 of the country, its orographical features and similar matters of high impor- 

 tance, but less obvious, especially to students. But he also thought it 

 probable that Dr. Feistmantel had somewhat confused his authorities. 

 The formation of pot-holes in streams was an obvious phenomenon, which is 

 almost too common to deserve notice, but he understood that the point of 

 many of the communications enumerated by Dr. Feistmantel was, that 

 the holes described occurred in places where it was impossible to account 

 for them by stream action, which is a very different matter ; and which 

 would furnish a reasonable ground for describing them. But in that case, 

 they were clearly irrelevant as affording a justification for the publication 

 of elaborate descriptions of pot-holes occurring in streams. 



Mr. W. T. Blanfoed said, — I agree fully with Mr. Ball, and I can 

 confirm his remarks on the common occurrence of pot-holes both in streams 

 and on the sea coast. I believe it would be difficult to find a rocky stream 

 in the country in which none occur. He is undoubtedly correct also in the 

 reasons he has assigned for the paucity of notices of those phenomena in 

 the published memoirs of the Survey. It would be absurd to devote space 

 to the record of useless details about a common form of erosion with which 

 geologists are familiar, and which has been well known and explained in 

 elementary works for at least a quarter of a century. 



The greater part of the papers by European geologists which are 

 quoted by Dr. Feistmantel appear to me to refer to a different subject. 

 He has described pot-holes in streams, with which all field geologists are 

 well acquainted, and the origin of which is obvious ; the European and Amer- 

 ican writers have described holes on hill sides, and even on the summit of 

 a watershed, a very different matter. The latter is the case with the papers 

 by Brogger and Reusch, Helmersen, and Jackson, or with three out of the 

 five papers mentioned by Dr. Feistmantel in the Proceedings, and the other 

 two are only short notes. 



Mr. Ball said : — After the remarks of Mr. H. Blanford and of the 

 Chairman I do not think there is anything left for me to reply to. Dr. 

 Feistmantel's paper may be a valuable one, that is not the question. My 

 object has simply been to point out certain errors of fact published in the 

 Proceedings. I have to regret that Dr. Feistmantel has not, apparently, 

 quite understood this to be the sole object of my paper, and has not availed 

 himself more completely of the opportunity which has now been afforded 

 him of withdrawing his former statements, which are justly objected to by, 

 I believe, most of the members of the Gfeological Survey. 



