Sw ae 
oe ee, we 
137 
former in the ratio of 6: 1; in the latter in theratio of 10:1. 
From these facts he drawn an inference which, from its im- 
portance, I shall quote from the Proceedings in his own 
words :— 
«<« The analysis of these waters have placed in view an- 
other fact of much interest in regard to the geognostic cha- 
racter of the granite of the Dublin mountains. In the water 
there were found both potash and soda, but the latter in 
very great excess. This indicates that the felspar of our 
Dublin granite is upon the whole a soda or albitic felspar, 
although in particular spots orthose, or potash felspar, may be 
found. ‘The fact has been also verified by a great’ number of 
analyses of specimens of granites from various parts of the 
great mass which extends from Dublin into the county of 
Wicklow. In all the analyses made, which included both 
ordinary granites and elvan or granite porphyries, both potash 
and soda were present, and the latter almost always so pre- 
ponderant as to lead to the conclusion that the potash should 
in most cases be considered to belong to the mica which the 
granite contained, and that the felspar was almost exclusively 
an albitic or soda felspar, containing only in some cases a small 
quantity of replacing potash.’—Proceedings, vol. v. p. 351, 
January 10, 1853. 
«¢ A statement so precise as this, and at the same time so 
novel, naturally called forth discussion; and accordingly I 
find that Dr. Apjohn, who was present when the communi- 
cation was made, expressed surprise at the fact, which he then 
learned for the first time, namely, that potash was either absent 
from the Dublin felspar, or, at most, only casually present, 
and then only in insignificant quantities; that Sir Robert 
Kane’s communication stated as a principal fact that which 
was wholly contrary to hisexperience. Dr. Apjohn considered 
this question one of such importance that he made it the sub- 
ject of a communication, which he shortly after laid before the 
Academy, in which he brought forward a number of facts 
