118 Mineralogy and Geology of the White Mountains. 



through the vein, but is confined to a portion of one side, three 

 or four inches in thickness, and easily separable from the mass 

 of the vein. 



Trap Dikes cutting the White Mountains. 



At the foot of the gorge south of the Willey house, we find in 

 abundance fragments of altered slate, slaty trap and basalt, and I 

 am informed by a gentleman who passed over the mountain 

 through this gorge, that in the upper part near the top, it is crossed 

 by several trap dikes. Immense ruins lie at the foot of this and 

 the gorge back of the Willey house, which appear as firm as the 

 mountains, and are covered with grass, shrubs and trees, conceal- 

 ing their deformity ; but those who have read the description in 

 Vol. XV, of the wild devastation that reigned here, will at once 

 penetrate the deceptive veil which vegetation throws over the 

 whole scene. 



Dike in the Willey Gorge. 



From the melancholy associations of the last named gorge, my 

 attention was more particularly attracted to it. The lower portion 

 for a considerable distance is obstructed by the rocks and gravel 

 that have rolled down from above. There is a handsome vein 

 on the north side, of crystallized feldspar, of a pale yellowish hue, 

 with crystallized mica in granite. In the bed of the gorge, 

 where it is but thinly covered by debris, beautiful flesh-red feld- 

 spar occurs, with many small cavities containing crystals of the 

 same. Ruins of trap found here led me to ascend farther, and on 

 passing the debris, a trap dike appears, forming part of the bed of 

 the channel. Its width is from two to six feet, usually averaging 

 not more than four ; course N. E. and S. W., closely embraced 

 by the red feldspathic granite, which is worn down to the same 

 level with the trap. The dike is crossed about five hundred feet 

 from the bottom, by a quartz vein or dike four feet wide, with 

 parallel and vertical sides, at an angle of about 60°, the parts of 

 which, on the opposite sides of the gorge, would be joined by 

 right lines in the direction of its course, which indicates no dis- 

 turbance or shifting. 



In the bed of the channel may be seen the trap, the quartz 

 and the granite, all so interlaced, that it would seem impossible 

 to decide whether the trap or quartz were the intersected vein ; 

 or if they were not both contemporaneously injected, and that too 



