338 
We have here in miniature the outlines of à process 
whi a grander scale, Smyth (©) has suggested for the 
differentiation of alkaline from subalkaline magmas. ; 
Review of differentiation.—The predominant potassic- 
aplites with the minor sodic-pegmatites, plus the volatile 
mineralizers, represent, approximately, m 
derived from the fractional crystallization of the granitic 
magma. 
n the 
have been one of straining off: of a residual liquid from a 
crystalline mass. 
turbed by external agencies for sufficiently long periods s 
allow of delicate adjustment of equilibrium in the presence o 
volatile mineralizers. : 
With the crystallization of the albite-pegmatites eni 
entiation appears to have closed. At a late stage in the 
consolidation of the microcline-aplite, the pneumatolytic action 
of mineralizers is represented by the parta toun 
pneumatoliths, and at a still later stage greisenization an 
kaolinization were developed 
. 
surrounding schists and quartzites. The seaward extension 
the granite is not known. Some evidence of the undergr cere 
extension of the granite, in an horizontal direction, is afforde 
. @)C. H. Smyth, jr.: Amer. Jour. Sci., 1913, 36, p. 42. 
