318 GEOLOGY OF THE SECOND DISTRICT. 



This rock alternates liere with a series of strata, which I have not elsewhere observed. 

 They incline to the yellowish brown colors of the calciferous, and take in silex largely. The 

 whole thickness is at least fifty feet, and there is a great diversity among the layers them- 

 selves. A mass about fifteen feet thick contains innumerable individuals of a species of 

 Atrypa, which, so far as observation has proved, is the lowest position of this genus. Above 

 all these diverse layers, the birdseye again appears in its usual form, with a thickness of about 

 fifteen feet, when it is succeeded by the trenton limestone. This is tlie arrangement at Chazy 

 village, and the strata intervening between the two beds of birdseye are all laid bare by the 

 Little Chazy river, which flows over them. 



Some localities of this rock near Chazy, furnish layers which may answer for marble. It 

 is a sound rock, and perfectly free from fractures or shakes ; and where light colors are 

 preferred, this would probably be esteemed. 



This rock, in common with the black marble of Isle La Motte, polishes, and, when properly 

 managed, receives a high lustre ; and as it is a pure carbonate of lime, free from earthy 

 matter, or silex, it polishes and works with ease. 



This rock weathers only to a slight depth, the outside becoming lighter colored — an ash ; 

 but it appears like a mere film upon the surface. It does not possess the strength of the tren- 

 ton or calciferous, but breaks like flint with a slight smart blow. This is an objection to its 

 employment for some purposes. 



This rock is one of the most valuable in this county for furnishing a pure quicklime. The 

 Redford Glass Company use no other than is furnished from it at Chazy ; and though the rock 

 itself is dark colored, it burns white, and produces a pure lime. 



Black Marble. 



Between the birdseve and the trenton limestones, there is a mass of black marble, which I 

 have already described under the name of Black Marble of Isle La Motte. This rock is not 

 wholly confined, even in this section, to this small island. Bordering the shore at the steam- 

 boat landing at Chazy, this mass of black limestone is exposed ; but as it has not been laid 

 open cither by artificial means, or naturally, it was impossible to arrive at its value. The 

 fact of its existence is clear, and it seems to be exposed or laid bare by the removal of the 

 trenton limestone. 



The most important quarries of this mass are at the island opposite the landing, and pro- 

 bably half a mile distant. Upon the island are two quarries, one at the north, and the other at 

 the soutii ; and what is worthy of observation, is, that each extremity of the island is raised 

 up, while a depression runs through the middle, which in some parts is below high water. 

 This mass occupies the same geological position as the black marble at Glen's falls, already 

 described ; and though it is comparatively a thin mass, it still deserves a place in our system 

 of rocks. 



One of the most common fossils of this mass is a columnaria, which is very large and fine 

 at Chazy. It is the same as that which is found in the Chazy limestone, though the birdseye 



