482 NEW YORK STATE MUSEUM 



sketch of a portion of one of these surface exposures, which shows 

 the observed relations clearly. Just adjoining it on the east is 

 an exposure which shows chiefly syenite, but with inclosed blocks 

 of anorthosite. In these exposures neither of the two rocks has 

 the extreme basic character of the usual border phase of each,, 

 though the syenite is more basic than the normal rock. 



Granite. Both the anorthosite and the syenite, especially the 

 latter, are found cut by dikes and larger masses of granite. So 

 far' as the writer's experience goes this granite is always of a single, 

 easily recognized type which he has called the " Morris granite," 

 from its frequent occurrence on Mount Morris, south of Tuppei 

 lake. This is a quite uniform, red, very acid granite, constituted 

 almost wholly of red feldspar and quartz, other minerals being 

 usually not visible to the eye. It presents both a fine grained 

 and a coarse phase, the former being more common. The coarse 

 type is especially distinctive because of the segregation of most of 

 the quartz into coarse leaves or spindles, which are very prominent 

 in both the weathered and unweathered rock, and stripe the red 

 feldspar with streaks of dark, glassy quartz. In the other and 

 more common type the quartz shows as small, dark colored, 

 glassy spots in the prevailing red of the yet finer grained feldspar. 

 In some exposures the fine type appears as a border phase of the 

 coarse and the coarse type has not been seen without the pres- 

 ence of the other also. The fine type however frequently occurs 

 without the other being present, the narrower dikes of the rock 

 are always composed of it, and some of the larger ones also. The 

 coarse is not only found grading into the fine, but also appears 

 cut by it. 



The granite produced as an extreme phase of the syenite differ- 

 entiation differs much from the Morris granite in appearance. 

 It is usually coarse grained, though running locally into fine 

 types, is quite hornblendic, and is not especially quartzose. The 

 black blebs and streaks of hornblende distinguish it sharply from 

 the Morris type. In the coarse varieties the quartz tends to assume 

 the leaf form, but the quartz is usually subordinate to the horn- 

 blende in prominence. Varieties however do occur which are 

 distinctly intermediate between the normal types. 

 ■ These two granites belong unmistakably to the general group 

 of the later intrusives. Similar rocks are found here and there 

 within the general body of granitic gneisses of the region. But 



