381 
MOURNE : 
MounrTAINS. KILINEY. KincstowN. THREE ROCE. THREE RoOcK. | 
(Mr. Cairnes.) (Mr. Keightley.) (Mr. England.) (Mr. Foster.) (Mr. England.) : 
Silex, . 65°17... 65:03 
Alumina, 19°37 .. 1860 
Lime, . . 0°67... 0:02 
Magnesia, ...... 0:02 
Posh, .. 009... 127d... 900... Sloe e OTe 
ee se OOO ss LE a eee POS. see ee ORO 
Meme ea es es 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 ofthe 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 
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