Mr William Stevenson on the Origin of Granite. 171 



chiefly of quartz, with a little mica. A little to eastward, a 

 beautiful, pure, flesh-red felspar has been erupted in three 

 or four places. This, by combining with the micaceous 

 schists, has become a splendid large-grained granite, con- 

 taining many crystals of black tourmaline. 



7. Aberdeenshire. — At Cove (about five miles S.E. from 

 Aberdeen) the junction of the granite with the primary 

 schists is beautifully shewn. The appearances here presented 

 are highly interesting and instructive, and seem quite to 

 confirm the proposition stated in the beginning of this 

 paper. The schists here are generally very distinctly strati- 

 fied and laminated, and dip to S.S.W. and S.W. at angles 

 of 40° and upwards to near 90°. They are much intersected 

 by quartz veins crossing the strike from N.E. to S.W. They 

 also contain numerous intercalated beds or stratiform masses 

 of red felspar, some of which pass into a regular granite by 

 acquiring quartz and mica from the adjoining schists, and 

 all of them show more or less a tendency to become granitic. 

 In some places the felspar is pure, in others associated with 

 quartz alone, and again, in other places, with mica to the 

 exclusion of quartz. The schists are metamorphosed from a 

 finely laminated magnesian clay-slate to talc and mica slates, 

 which again become gneiss in the vicinity of the granite, 

 b} r the interlamination of felspar. Where the felspathic 

 mass is considerable, a regular granite is formed by a mix- 

 ture of the felspar with the quartz and mica of the schists. 

 At the junction the granite is generally very large-grained. 

 From this mass the veins and apparent beds exposed in the 

 sea-cliff proceed. One of the veins is five or six feet thick 

 at the bottom, thinning to about two or three at the top of 

 the cliff. It is generally a medium-grained granite, but in 

 many places almost wholly flesh-coloured felspar. A thin 

 seam of large-grained granite (three-fourths of an inch 

 thick, and almost entirely felspar and mica) occurs at the 

 junction with the schist. Fragments of the latter are also 

 enclosed in the granite in many places. The schists appear 

 to have been simply argillo-arenaceous strata, metamor- 

 phosed first into a sort of clay slate, then into mica slate, 

 "with the characteristic quartz layers ; next, b} T a higher 



vol. in. z 



