262 SNAKE MOUNTAIN. 



beneath the calciferous. This unnatural position is evidently produced by a dislocation. 

 The calciferous sandrock has been elevated by some cause to the height of the Trenton 

 limestone, and as a consequence has lifted up with itself all the rocks that were upon its 

 back. Hence the origin of the present altitude of Snake Mountain. The calciferous 

 sandrock here is a bluish gray limerock, with rather more lime than sand in its composi- 

 tion. Next occurs the chazy limestone, b (Fig. 167), exhibiting its characteristic fossil, 

 the Maclurea magna, near Mr. S. W. Smith's house, upon the road nearest the mountain. 

 This rock differs very little from the calciferous sandrock in its appearance. The 

 Trenton limestone, c, is found just east of the chazy in the hill, where we obtained the 

 Trinucleus concentricus, a characteristic fossil. This group can be traced both north and 

 south a great distance. Its character upon the section is quite slaty rather more so than 

 usual. Between the Utica slate, d, and Hudson River slate, e, we have not attempted to 

 draw the line upon the section. Both rocks are a calcareous slate, with small beds of 

 a black limestone interstratified with them, and occasionally branching veins of white cal- 

 cite ramify among the black slates. The lower portion of the slates is seen at Truman 

 Smith's house, and nearly the whole of the slate may be seen by climbing the northwest 

 corner of the mountain in the bed of a small brook. Most of these slates along the west 

 side of the mountain are covered by soil and debris from the rocks above. Further south 

 they appear near the house of Jesse Crane, 2d, in the northeast corner of Bridport, and 

 west of Cobble Hill, near the south line of Addison. The upper member of the Hudson 

 River group, is not seen at the northwest corner of the mountain. It is a curious silicious 

 limestone, y, almost destitute of stratification, occurring in beds that taper to nothing 

 almost abruptly. For instance, there is none of it on the line of the section, but less than 

 a mile south of it, at Cobble Hill, is nearly one hundred feet thick. This hill is capped 

 by it ; and it may be seen upon the carriage road to the top of Snake Mountain from the 

 west side. It is continuous from this point into Bridport and is quite thick. At Otter 

 Creek, between Addison and New Haven, it occurs in limited quantity also. 



The occurrence of this limestone has been perplexing to many who have tried to follow 

 the published sections describing this mountain, because it was not mentioned in any of 

 them, though it must have been seen by the authors of the sections. We think it satis- 

 factorily shown elsewhere in this Report, that it constitutes the upper portion of the Hud- 

 son River group as it is everywhere either above the slate or near the top. At Snake 

 Mountain it is entirely above the slates, adjoining the red sandrocks, g. 



Prof. Adams found graptolites in these slate rocks, which are now destroyed by fire. 

 We were unable to discover their locality, but cannot doubt that they exist here. 



The upper part of the slates, where the limestone does not appear, contain fragments 

 of grit and small layers of sandstone. A sketch of the appearance of the mixed rock is 

 given in Fig. 22. These irregular alternations continue for ten or fifteen feet when the 

 sandstone or grit appears without any mixture of slate. This mass of grit is what was 

 termed graywacke by old geologists. Of this, some portions are brecciated, belonging to 

 the variety called rubble by Prof. Eaton, one of the earliest of American geologists. 



The usual color of this red sandrock is reddish brown, and gray. The proportion of 

 lime in it varies exceedingly, and the character of the rock often changes abruptly in the 

 same stratum. As a general fact, the lower portion of it is calcareous, the middle silicious,- 



