Correspondence — Prof. A. H. Green, 141 



on such a conclusion ; nor will any one who has had a wide experience 

 of the ways and means by which terrestrial features have been 

 modelled. Dame Nature is not so short-handed, that where one agency 

 fails, she cannot find another. If Yulcan is at work in one place, so 

 also is the Ice King of the North in another. For my part, I believe 

 that in the formation of lakes numerous physical causes have at 

 various times, and in divers places, come into play. In the Jordan 

 Valley it may be concluded, from the scanty observations of travellers 

 regarding its geology, that there has been a great fracture ranging 

 along the base of the Moabite table land. In the case of Balaton 

 Lake there may have been a subsidence in a volcanic district ; in that 

 of Lough Neagh, fractures of the strata before the Glacial Period ; in 

 many large lakes in the centre of Ireland, there has been the dissolu- 

 tion of the limestone by water charged with carbonic acid gas; and 

 in the Cheshire plains there has been subsidence due to the melting 

 of subterranean beds of salt, as Mr. Ormerod long since suggested. 

 These are all diverse processes by which lakes are formed by other 

 than glacial erosion. But none of them apply in the cases of the 

 rock-basins of British mountains and other districts where the evi- 

 dences of glacial erosion are so striking, and where there are no 

 evidences of recent fractures of the strata, nor of volcanic terrestrial 

 movements, nor of solution of calcareous beds, nor of solution of beds 

 of salt. On the other hand, in default of other agencies, we are 

 forced to recognize the influence of those which have evidently been 

 at work in these districts ; and I cannot think that, in throwing over 

 so completely the theory of glacial erosion for all lakes, Mr. Judd 

 has sufficiently weighed the grounds for its acceptance, which have 

 from time to time been advanced by its author. Professor Ramsay, or 

 by those who support his views, such as Gastaldi of Turin, or James 

 Geikie amongst the " Scotch Geologists." 



I may observe, in conclusion, that both in the original memoir in 

 the Journal of the Geological Society, and in the Physical Geology 

 of Great Britain, Professor Ramsay especially eliminates "crater- 

 lakes, lagoons, and the lakes of Central Africa," from the class of 

 lakes to which his theory applies ; so that Mr. Judd's objection has 

 been anticipated by the author of the theory himself. (Phys. Geol. 

 and Geog., 3rd ed. p. 173.) 



Geological Survey Office, Dublin, Edward Hull. 



January, 1876. 



ME. JUDD OX GLACIAL EROSION AND SUBAEEIAL DENUDATION. 



Sir, — To fight other people's battles, especially when the other 

 people are perfectly well able to take care of themselves, is palpably 

 unnecessary, and might smack of meddlesome interference ; besides 

 well-intentioned advocacy is liable to damage even a good case, 

 unless the advocate is specially fitted for his task ; and then — but 

 no, I won't go on. I have given reason enough why I should not 

 try to discuss the arguments advanced by Mr. Judd in your January 

 Number against the theory of the Glacial Erosion of Rock Basins. 



But there are one or two points in that paper which I do feel less 



