Ch. V.] PRIMARY SCHISTOSE ROCKS. 63 



Mr. Weaver also gives an excellent account of the associa- 

 tion of granite with the slates ; from which we find that 

 entirely detached portions of the former occur in the latter 

 rocks, after the same manner as the granite in the slate of 

 Cornwall. Thus, "in following the northern ravine from 

 Glenismaule upwards, we meet with granite alone for about 

 three fourths of the ascent, when mica-slate appears in contact 

 with and resting upon the granite ; the strata standing nearly 

 on their edges, ranging N. E. and S. W., and dipping 75 to 

 the N. W. In this spot the granite exhibits some disposition 

 towards the structure of gneiss, but to a small extent only. 

 A little higher up the mica-slate is better exposed, and con- 

 tains thin layers of quartz, sometimes pure, sometimes mixed 

 in part with felspar. Considerably higher up a bed of small- 

 grained granite occurs in the mica-slate, about six inches 

 wide, the range and dip being the same as the slate; and 

 within a few inches of this bed of granite is another of the 

 same width, but of short continuance, terminating abruptly at 

 the S. W. and edging out on the N. E., being thus completely 

 enclosed in the mica-slate, the laminae of which follow the line 

 of the granitic bed, which is about fifteen feet in length. 

 We next come to a third bed of granite, but of less dimen- 

 sions, or rather to a vein, terminating also abruptly in the 

 mica-slate; and upon its sides we perceive portions of the 

 latter rock impressing and indenting the former in a very 

 singular manner. There are also layers and veins of quartz, 

 a few inches thick, either pure, or mixed with felspar, termi- 

 nating likewise abruptly in the mica-slate." 



" Higher up this ravine is a short compressed elliptical 

 mass of granite, enclosed between the laminae of the mica-slate; 

 and beyond this is the horizontal section of what appears to 

 be a granite vein nearly enveloping a portion of mica- slate. 

 The parallelism of the laminae of the mica-slate does not 

 appear to be affected by this disposition of the granite." * 



* Geol. Trans., vol. v. pp. 155, 156. 



