On the Microcline Feldspar in the Dalkey Granites. 249 
GALBRAITH. 
Journal Geological Society, Dublin, 1856, p. 226. 
Dalke Three Lough Lough Glenma- | Glenda- Glen- 
ut Rock. Bray. Dan. calass. lough, malure. 
| 
Silica, . . : 64'00 65°40 65°44 65°05 64:19 63°60 64 48 
Alumina, = - 18 11 nly Gif bs 18°36 17-72 18°39 18°84 19°04 
Ferric Oxyde, : - = = = - - - 
Potash, . ° . 12 73 10°68 12°34 13°42 11°39 14°33 10°74 
. Soda, . e . 3 00 3°26 2°73 | - 2°75 2°95 1°92 2°64 
Lime, a - -| trace. trace. 0°80 0°23 070 trace. trace. 
Magnesia, J - 0 57 me de - trace. 0:34 0-40 1:02 
Loss by ignition, . 0°55 0°69 0°52 0°36 0°58 0°60 0°78 
98°96 | 99°51 100719 99°53 98°54 99°69 98°70 
Sp. Gravities, . . | 2°54 | 2°562 2°554 2°559 2°553 2°453 2°560 
Taking into consideration the difference of time and general 
conditions represented by these two series of analyses, it must be 
admitted that they singularly approach one another, so much so, 
that it may be assumed, chemically, that the Feldspars analyzed 
by Galbraith, were Microclines, and characteristic of the granites 
containing them. 
