Phenomena of Granite Veins. 



493 



width as a, a, : d, d, is a third vein ; as is proved by its intersecting; 

 the two first. It is six inches wide: c, c, is a fourth vein, two inches 

 wide, intersecting d, d, longitudinally, and distinguished from that by 

 being of a much coarser texture. This is a very unusual occurence; 

 one which I have myself never seen ; and we have here also granite of 

 four epochs ; so that this example, if there be no mistake in its repre- 

 sentation, is a very interesting one. 



(34) Granite Veins in Mica slate ; Williamsburg. 



In No. 35 a large protruding mass of granite rises from the soil at 

 the north end of a naked ledge of mica slate, which is two rods w 7 ide, 

 as represented on the sketch; From this mass of granite an irregular 

 vein proceeds nearly in the direction of the layers of slate, embrac- 

 ing two or three nearly insulated strips of mica slate. I am not 

 aware that any very instructive inference can be derived from this 

 case, except that it seems to me impossible to impute to deposition 

 from water, a mass of granite thus irregularly intruded among the 

 mica slate. It occurs in the west part of Whately. 



