381 



M0URNE KILLINET. 



Mountains. 

 (Mr. Cairnes.) (Mr. Keightley.) 



KrNGSTOWN. 



Thbke Rock. 



These Rock. 



(Mr. England.) 



(Mr. Foster.) 



(Mr. England.) 



Silex, . 65-17 . . 65-03 









Alumina, 19-37 . . i860 









Lime, . . 0-67 . . 0'02 

















Potash, . . 5-99 . . 12-73 . . 



. . 965 . 



. 4-15 . . 



. 5-72 



Soda, . . 8-80 . . 1-14 . . 



. . 1-64 . 



. 4-34 . . 



. 6-89 



Loss, 2-46 









100-00 100-00 



According, then, to these experiments, in the felspar of 

 Killiney and Kingstown the potash greatly predominates. 

 In that of the Three Rock Mountain the two alkalies are pre- 

 sent in nearly equal quantities ; while even in that of the 

 Mourne range, long considered as an albite, the ratio of the 

 quantity of the vegetable to that of the mineral alkalies is that 

 of 2 to 3. 



These results are so different from those announced by Sir 

 Robert Kane, that the discrepancy can scarcely be due to er- 

 rors of experiment, while it is, at the same time, difficult to 

 suggest any other probable explanation of it. It may, indeed, 

 be suggested, that the felspar of the Dublin granite is subject 

 to variation as respects the relative proportions of its alkaline 

 constituents ; and it is just possible that, by some singular 

 chance, while the specimens he operated upon contained no 

 alkali but soda, those which were employed in my experiments 

 contained potash also, and in large relative quantity. Upon 

 this explanation, however, I do not feel disposed to lay much 

 stress, when I recollect that Sir Robert Kane's researches on 

 this subject have been, as he informs us, very extensive, and 

 that he considers the conclusion at which he has arrived as 

 " verified by a great number of analyses of specimens of gra- 

 nites from various parts of the great mass which extends from 

 Dublin into the county of Wicklow." His analyses, however, 

 it should be recollected, were analyses, not of felspar, but of 



