237 
TaBLE II.—Atoms of Granitic Minerals. 
Atoms of | Atoms of | Atoms of | Atoms Atoms Atoms 
LocaLiTIEs. Silex Peroxides Protoxides of of of 
=a = (i), = Quartz. | Feldspar. Mica. 
| 
Dalkey,. . . . . «| 1°530 0-286 | 0°353 — — — 
Fox-Rock, ... .| 1°587 0°296 0274 0-513 0°252 0:022 
Three-Rock,. . . .' 1°528 0°352 0-287 0-445 0:222 0:065 
Enniskerry, . . . .| 1°613 0:282 0:225 0:770 0°168 0:057 
Ballyknocken, . . .| 1°540 0:317 0-283 0°442 0-249 0°034 
Kilballyhugh, . . .| 1°592 0°321 0:232 0°753 0°143 0:089 
Blackstairs, . . . .| 1°587 0°322 | 0:239 0°714 07156 0:083 
Ballyleigh, . . . .| 1:593 0271 0°257 0:597 0:243 0:014 
‘‘ Calculating, by the method already described, the per- 
centages of quartz, felspar, and mica, contained in the different 
granites, we find the following :— 
TasBie II].—Per- Centages. 
LocaLiry. Quartz. Feldspar. Mica. 
Dalkey, . ... _ _ _ 
Fox-Rock, . . .| 23°60 69-66 6-71 
Three-Rock, . .| 20°47 59°68 19-82 
Enniskerry,. . .| 35°42 45°83 17°38 
Ballyknocken,. .| 20°33 68°97 10°37 
Kilballyhugh,. .| 34°64 38°37 27:14 
Blackstairs, . .| 32°84 41-19 25°31 
Ballyleigh, . . .| 26°63 67°45 4:27 
‘¢ From the foregoing calculations it follows, that, with the 
exception of the Dalkey granite, the granites of the main chain 
examined might be represented by combinations of quartz, feld- 
spar, and mica, in which the quartz is the most regular mine- 
ral, considered with reference to its per-centage. 
** The following Table contains analyses of granite belong- 
ing to the second group, and supposed to be newer than the 
others :-— 
