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TaBLe II.—Atoms of Granitic Minerals. 
Atoms of | Atoms of | Atoms of | Atoms Atoms Atoms 
LocALITIEs. Silex Peroxides Protoxides of of of 
=k E=ips = Quartz. | Feldspar. Mica. 
Dalkey,. .... .| 1580 | 0-286 | 0-353 | — = ey, 
Fox-Rock, |. . .| 1:587 | 0-296 | 0-274 | 0-513 | 0-252 | 0-022 
Three-Rock,. . . .| 1°528 | 0-352 | 0-287 | 0-445 | 0-292 | 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, . . .| 1592 | 0-321 | 0-232 | 0-753 | 0-143 | 0-089 
Blackstairs, . | . .| 1-587 | 0°322 | 0- . 
Ballyleigh, . | . .| 1-593 | 0-271 | 0-257 | 0-397 | 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 :— 
Taste III.—Per- Centages. 
Locatiry. Quartz. Feldspar. Mica. 
Dalkey, .... _— — — 
Fox-Rock, ... 23°60 69-66 671 
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 :— 
