368 



TRANSACTIONS OF THE 



again, are so easily separable from the slate, and have 

 walls so distinct, that, under any other circumstances, 

 they would be taken without hesitation for true veins. 



12. Fragments of slate are visible in several of the 

 veins, though they have not been observed in the main 

 body of the granite. 



13. The clay slate is occasionally intersected by nu- 

 merous small quartz veins, some of which are traversed 

 by the granite veins ; others, on the contrary, traverse 

 and heave both the granite veins and the other quartz 

 veins. An instance of such heaves has been noticed, 

 where one of the granite veins is heaved three feet to the 

 left by a quartz vein in which slate is mixed with the 

 quartz : by another, two granite veins are heaved to 

 the left, one nearly 3 feet, the other 6 inches. 



14. At some sites, where the junction of the granite 

 and slate takes place, they appear at some points so com- 

 pletely intermixed, as almost to exclude any other idea 

 than that of contemporaneous formation, although at 

 other points the junction is distinct and regular. 



15. In most other places, where the junction occurs, 

 the slate reposes on the granite, without any appearance 

 of a dislocation or disturbance of the strata. 



from the union of some of the veins with the granite 

 mass, it has been concluded that the veins and the mass 

 are contemporaneous ; if so, was the whole formed before 

 or after the slate ? Some have considered that they were 

 ridges protuberating from the mass of the granite, the 

 spaces between which were afterwards filled with slate. 

 The horizontal veins to be met with in their vicinity, 

 would, however, seem to oppose this last conclusion. 



Others again have considered, that both the veins and 

 the mass are posterior to the slate, although they differ 

 in their opinions as to the mode of their formation. 



From the^intimate union which subsists between some 

 of the granite veins and the slate which contains them, it 



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