43 



breadth of the vein is various ; in some places no more than twelve 

 or fifteen yards, in others as much as twenty-five, and even thirty, 

 and perhaps considerably more, as it cannot in many places be 

 exactly measured. It rises above the surface of the hill side from 

 fifteen to forty feet, and with several undulations runs in a general 

 N.N.E. and S.S.W. direction. 



In the northern part of its course it is interposed as a bed between 

 the strata of slate. To the south of the high road, on the side of a 

 little stream, it is seen intersecting the beds at a small angle. A 

 little farther south the ground rises, and the vein does not appear 

 upon the surface ; but on the lowering of the ground still farther 

 south, it again emerges from beneath the slate and occupies the sur- 

 face for some distance. A similar overlapping occurs farther north, 

 near the high road. 



The appearance of this plutonic rock, now as a bed interposed 

 among the strata, and again as a vein intersecting them, and the un- 

 dulating course which it pursues, point out its posterior origin and the 

 nature of the resisting force. This is plainly to be found in the pecu- 

 liar undulations and twisted forms which everywhere characterize the 

 mica slate, indicating the power- 

 ful compressing forces which 

 acted upon it while yet plastic 

 under the influence of heat. 



Near the summit of the 

 ridge, and at a curvature in 

 the vein, the outer or salient 

 angle is intersected by a dike 

 of greenstone and basalt, in 

 such a manner that a portion 

 of the felspathic rock is isolated 

 between the whin dike and the 

 mica slate on the west side, and 

 the continuation of the vein lies 

 on the same side of the dike as 

 before the intersection. The an- 

 nexed sketch, which is a ground 

 plan, shows the mode of this 

 intersection, one of the most 

 singular we have ever met with. 



The dike is very distinctly 

 traceable for several hundred yards towards the north-east, the 

 surface occupied by it rising into conical hummocks. It is then 



(a a) Vein of felspathic rock, 

 (b &) Altered schist. 

 (c c) Dike of greenstone and oasalt. 

 (dd) Mica slate. 



