VEINS IN SLATE. 



311 



FIG. 



Grit in slate, Suake Mountain. 



FIG. 2-26. 



Similar deposits, but more irregular, are found near the upper limits of these shales, 

 beneath the sandstone, capping Snake Mountain. The slates there are bright and shin- 

 ing, traversed by irregular seams of calcitc, as well as grit. Some of the layers near the 

 sandstone are composed of a soft, green, slaty matter. At 

 the junction there is an alternation, for a few feet, of the two 

 rocks, as the commencement of the one which is to succeed, 

 and thus the re-appearance of the mass beneath ; and fre- 

 quently large, irregular beds or portions of strata may be 

 observed, as in Fig. 225. The black spots are masses .of 

 grit lying in the midst of the slate, insulated from the sand- 

 stone above. These irregular alternations continue for ten 

 or fifteen feet, when the thick-bedded sandstone appears 

 without any interruption. This figure was drawn by Prof. Emmons, for the Geological 

 Report of the Second District, N. Y., page 280; where he says that these same irregular 

 alternations may be traced for several miles along the junction of these two rocks. 



Sometimes brecciated limestones are found imbedded in the slates of this group, in which 

 the fragments are derived of course from limestones of a previous age. In other slates, 



these fragments often contain the fossils of the group 

 from which they were derived. We have found 

 bowlders of this kind in Vermont, originally from 

 Canada. 



We have already referred to the veins of calcitc 

 which traverse the slates. So abundant are they in 

 some places that they deserve to be noticed as a distinct 

 variety. Along the shore of Lake Champlain, wher- 

 ever these calcareous shales are found, they are often 

 filled with these veins passing in every direction, 

 crossing each other or passing along parallel to each 



other. Fig. 226 represents No. j^ of the State Cabinet, which with Nos. ^ to 5^ are 

 from the north-east side of Pottier's Point, in Shelburne. The figure was taken from a 

 pebble. The shore is lined with similar pebbles. But they are less interesting than the 

 ledges, which for several rods are most beautifully covered with a network of dazzling 

 white veins upon a black ground. Large specimens of them ought to be in every cabinet 

 of geology in the country. For those who are studying the phenomena of veins this lo- 

 cality furnishes fine examples. Rarely in the most thoroughly metamorphic rocks have 

 we ever seen veins equal to them in number, fineness, and complexity. It is mysterious 

 how they could be formed, some of the veins being scarcely perceptible without a lens. 



Fig. 227 represents veins of quartz in clay slate, in a small bowlder from Butler's 

 Island. The bowlder is about four times larger than the figure, and is No. &*& in the 

 Cabinet. It is rather uncommon to find veins of quartz in this slate. 



Besides these veins that intertwine with one another, there are veins in the rock that 

 do not meet, being parallel, on the St. Albans coast. These veins appear in great abund- 

 ance, and by their beauty rival the netted veins of Shelburne and elsewhere. 



