450 
Proceedings of the Eoyal Irish Academy, 
Insoluble Matter. 
Silica and titanic acid (trace), . 
29-51 
79-7 
per cent. 
Ferric oxide and alumina, . 
4-74 
12-9 
n 
Lime, 
0-79 
2-2 
>) 
Manganous oxide and magnesia, 
0-87 
2-3 
)) 
1-09 
2-9 
37-00 
100-0 
It is interesting to compare this analysis of the insoluble matter 
with those of the orthoclase felsites, I^o. 2 and IS'o. 9, given by Dana 
System of Mineralogy," 5th edition, p. 358). 
No. 2. 
No. 9. 
Silica, .... 
. . 81-24 
79-55 
Alumina, 
. . 9-78 
11-31 
Ferric oxide, . 
. . . 0-64 
0-42 
Magnesia, . . * 
. . . 0-21 
0-10 
Lime, .... 
. . . 0-78 
2-52 
Soda, .... 
. . 3-34 
3-68 
Potash, . . . . 
. . 3-10 
2-38 
Water, .... 
0-69 
99-09 
100-65 
As the insoluble portion of the sample analysed by Mr. Adeney 
was probably the part of the rock relatively unaltered, it may be 
presumed that the containing rock is really an altered felsite, and in 
this respect is comparable with certain of the Cambrian rocks which 
occur in the vicinity of Dublin. Judging it might be of interest to 
have the quartz vein assayed for gold, I forwarded, in NTovember of 
1888, samples of the iron ore and quartz to Mr. F. Claudet of London, 
and he reported having found traces of gold in the samples assayed. 
The precise limits of the deposit have not been clearly determined ; 
but from trials made in the neighbourhood of the Quarry, there can be 
no doubt but that it extends over a sufficiently large surface to allow of 
its being worked industrially if the ore could be utilized for the pro- 
duction of iron. That it is intimately related to the quartz lodes 
described, can hardly admit of a doubt ; and that thermal action was 
the essential cause of the alteration of the rock is an inference which 
may be fairly drawn from the nature of the ore and its associations. 
