148 NEW YORK STATE MUSEUM 



Lake Champlain: it is a fine grained, gray, brittle, limestone, 30 

 feet in its greatest thickness: and the most conspicuous of its 

 fossils is one of which the nature is somewhat obscure, but which 

 was regarded as the stem of some marine plant. 



Standing in an upright position, perpendicular to the strata the 

 ends of the stems are seen on the surface of the layers, to which 

 they give a peculiar dotted appearance, from which the rock has 

 derived its name, and by which, as well as by its characteristic 

 color and fracture, it is easily recognized. It is a valuable rock 

 for economical uses, as it is a good building stone, and dresses well 

 under the chisel ; it is quarried to a considerable extent at various 

 points in the Mohawk valley. 



Black River Limestone 



To the Birdseye limestone succeeds a thin mass, amounting in 

 all to only 10 or 12 feet, but classed as a distinct rock from having 

 a somewhat peculiar mineral character and containing a peculiar 

 set of fossils. It is a dark, thick-bedded, compact, hard limestone, 

 fine grained and taking a high polish, and is worked as a black 

 marble at Glens Falls on the Hudson river, and at Isle La Motte 

 on Lake Champlain. It is also well seen at Watertown, Jefferson 

 county, in the banks of the Black river from which locality it has 

 been named. 



In the last place it is lumpy and irregular in texture, and not fit 

 for good masonry or marble; and is known among quarrymen as 

 ' the seven foot tier.' In the Mohawk valley it seems to have been 

 deposited in only a few places, the Birdseye being generally 

 covered directly by the Trenton. 



Trenton Limestone 



Above the Black river limestone (or where this is absent, lying 

 upon the Birdseye), is one of the most interesting repositories of 

 organic remains in the state; a thick group of limestone strata, 

 usually black and fine grained with seams of slate toward the 

 lower part, but gray and crystalline near the top. 



