in the Granites of the Dublin and Wicklow Mountains. 421 



which the granite coutained, and that the felspar was an albitic 

 or soda felspar. Considerable doubts having been expressed as 

 to the accuracy of this statement, I undertook to search this 

 moimtain chain for felspar crystals, and having selected seven 

 specimens from widely distant localities, I submitted them to 

 analysis, and sent the results to your Journal, in the January 

 Number of which for the present year they were published ; the 

 average ratio of the potash to the soda in these felspars was 4'5 : 1, 

 a result which diifered so widely from Sir Robert Kane's state- 

 ment, that I expressed my inability to conceive how the felspar 

 which entered into the constitution of the rock could be desti- 

 tute of potash. 1 have preserved the specimens, and shall have 

 great pleasure in allowing Mr. Jennings to examine them at any 

 time he chooses. 



With a view to the direct determination of this question. 

 Professor Haughton undertook the analysis of a series of rock 

 specimens selected from different localities in the range, and 

 arrived at a result totally at variance with Sir Robert Kane's 

 assertion ; the average result of his analyses, as published in the 

 July Number of your Journal, gives for the ratio of the potash 

 to the soda in the rock specimens taken from the main chain, 

 4-822 : 2'967, or in round numbers 5 : 3. Professor Haughton's 

 analyses prove that the felspar, as found in large crystals, dif- 

 fers from that which enters into the constitution of the rock in 

 this respect, namely, that while potash predominates in both cases 

 over the soda, the ratio in the latter case is less than in the 

 former. 



The single analysis furnished by Mr. Jennings, although it 

 does not fall in perfectly with Professor Haughton's results, 

 must be pronounced to be equally inconsistent with Sir Robert 

 Kane's statement, which requires us to believe that the felspar 

 of the rock is destitute of potash. This is a complete statement 

 of the question so far as facts have come to light ; and I am in- 

 clined to thuik that if Sir Robert Kane still remains silent, the 

 scientific public, unable any longer to withhold their judgement, 

 will pronounce this question to be settled against him. Why he 

 should maintain this reserve on a purely scientific question I am 

 at a loss to understand, as he has had ample time to make good 

 the promise which he volunteered to the Royal Irish Academy 

 in February 1853. I find, moreover, on referring to public 

 documents, that he has made considerable progress in this in- 

 vestigation. In the Report of the Museum of Irish Industry, 

 made 2Gth January, 1854, he says, "The chemical officers of the 

 Museum have been occupied with a very extensive series of ana- 

 lyses (still in progress) of the fels})athic and other alkalifcrous 

 rocks of the mountain ranges south of Dublin; of this investi- 



