CALCIFEROUS SANDSTONE. 



267 



Occasionally there are quite thick beds of a very pure drab-colored limestone (the third 

 variety) in the upper part of this formation, resembling the limestone of the birdseye 

 series. It is particularly abundant on the east shore of Lake Champlain in the southwest 

 part of Orwell, and the northwest part of Benson. They are Nos. if e to jf^. 



In the upper part of this rock there is a brecciatecl limestone. The fragments are never 

 more than an inch in length, and the variety resembles breccias in the Chazy and 

 Devonian limestones. It is not common in the calciferous sandstone. The specimens 

 of it in the State Cabinet, are Nos. ^ and jfj, from West Haven and Orwell. 



It is not unusual to find beds of pure silicious sandstone interstratified with the lime- 

 stones, and in lithological character it cannot be distinguished from the Potsdam sand- 

 stone. These beds are the most abundant in the lower members of the calciferous group, 

 and may be seen in Vermont, both in the east and west parts of West Haven (No. jf^), 

 and in the east part of Shoreham. They vary in thickness from a few inches to twenty feet. 



There is a peculiar variety of this rock quite well developed along the shore of Lake 

 Champlain for twenty miles below Whitehall. It is a clay slate, somewhat calcareous. 

 It reminds one rather of the slates and shales of the silurian rocks in Europe, than of the 

 sandstones and limestones of this age usual in North America. There are many fucoidal (?) 

 markings upon them, and the specimens ring like iron when struck with a hammer. 

 It was noticed first upon the south side of Larrabee's Point in Shoreham, and it was so 

 near the Maclurea magnet, that we then supposed it to belong to the Chazy limestone. We 

 have found no distinct fossils in it ; and have placed it in the calciferous group because it 

 is generally associated with its sandy and drab-colored limestones, and is always below 

 characteristic fossils of the Chazy. One mile south of Chipman's Landing, in Orwell, this 

 slate may be found with a glazed surface. The thickness of it at this point is about 

 seventy feet. For two miles this slate may be seen along the lake shore, in the south 

 part of Orwell. Its calcareous character is evidenced by numerous deposits of calcareous 

 tufa at its base. 



The sixth and last variety is represented by a large specimen in the Cabinet from Mount 

 Independence, a part of which is represented in Fig. 170. It was supposed to belong to 

 the Potsdam sandstone, until a drop of acid revealed a small percentage of carbonate of 

 lime in its composition. Its position agrees exactly with the fucoidal layer described by 

 Prof. Emmons in his Report on the Geology of the second district of New York, pages 

 270, 271. He rarely found it more than fifteen feet thick, and it was invariably found at 

 the base of the calciferous. The most southern extremity of it in New York is at Crown 

 Point, eleven miles north of its location in Vermont, at Mount Independence. Its thick- 

 ness at this place cannot be more than eight or ten feet. 



Locality. 



Whitehall, N. Y., 

 West Haven, south part, 

 West Haven, west part, 

 West Haven, southwest part, 

 Benson, west shore, 

 Benson, northwest corner, 



STRIKE AND DIP. 



Strike. Cleavage. 



N. and S., 

 N. 10 E., 

 N. 10 E., 



Dip. Observer. 



5E., E.H.,jr.andA.D.H. 



10 E., E. H., jr. and A. D. H. 



5 E., C. H. H. 



3 E., C. H. H. 



7 E., C. H. H. and A. D. H. 



8-15 E., A. D. H. 



