142 
‘¢On the occasion when Dr. Apjohn made his communi- 
cation, I find that Sir Robert Kane repeated his statement as 
to the nature of these granites, together with the grounds on 
which he rested it. ‘The idea,’ viz., that the predominant 
characters of the granite district of Dublin and Wicklow was 
the presence of soda felspars, ‘ was founded not merely on the 
results of the analysis of the waters read at the last meeting, 
and which in itself he did not consider very important, but 
was the result of a widely-spread series of observations, which, 
on another occasion, he hoped to be able to bring before the 
Academy.’— Vol. v. p. 382, February 28, 1853. 
‘“¢ Feeling, as I do, a great interest in this question, I con- 
fess I have for a long time looked forward with some anxiety 
for the production of these analyses; and I hope I may be 
allowed, on the part of the Academy, to express the hope, 
that at no distant day Sir Robert Kane will lay before the 
Academy what I am sure will be esteemed a most valuable 
communication. Independently of my wish to arrive at the 
settlement of a scientific question, I feel some anxiety on the 
subject for another reason, namely, my utter inability to re- 
concile Sir Robert Kane’s statement, with regard to the results 
of his rock analyses, with what (at least to my own satisfac- 
tion) I think I have succeeded in proving. The granite of 
Dublin and Wicklow, as I have said, consists of three ele- 
ments, quartz, mica, and felspar. Of these quartz, as is well 
known, contains no alkali, and may be therefore dismissed 
from our consideration. Mica contains both alkalies, but the 
potash always in great excess. Felspar, the third element, con- 
tains, as I have shown, both potash and soda, but the former 
always in great excess, in the ratio, namely, of 9:2. This being 
the case, I cannot in any way see how a rock, which is a mix- 
ture of these three constituents, should on analysis yield ‘both 
potash and soda; but the latter, viz., soda, almost always so 
preponderant, as to lead to the conclusion that the potash 
should, in most cases, be considered to belong to the mica 
