CHAZY LIMESTONE. 107 



3. Chazy Limestone. 



To the calciferous sandrock, succeeds the Chazy limestone. As a whole, it is a dark, 

 irregular, thick-bcddcd limestone. At Chazy, it contains many rough, irregular, flinty or 

 cherty masses, wliich have been found in places once occupied by a species of stone coral. 

 It appears to have been a Columnaria ; but generally the columns are so obscure and broken, 

 that it is difficult to determine the nature of the fossil. The mass is not uniformly of the 

 character described. At Esse.x the beds are more regular, and it presents externally a better 

 aspect, and forms in cons'equence a better building stone. As a limestone, it is purer than 

 the calciferous. Tlie principal foreign matter is silex in the form of chert, which is mostly 

 collected in those points where the stone corallines are imbedded. It is free from those brown 

 earthy spots so common in the limestone below, and also from the masses of calcareous spar 

 which appear almost characteristic of the calciferous sandrock. 



The position of the Cliazy limestone is clearly determined at Chazy, lyingbetween the cal- 

 ciferous and the birdseye limestone. This rock is wanting in the valleys of the Mohawk and 

 •Black river. 



There are three well marked fossils, which first make their appearance in this rock : the 

 Maclurea,* a Trochus, and the Columnaria. Besides these, there are numerous small fossils, 

 which the irregular bedding of the rock partially conceals. 



The entire thickness of this rock is not far from one hundred and thirty feet. It is deve- 

 loped at numerous localities along Lake Champlain, particularly at Essex, Essex county, and 

 at Chazy in Clinton county. It appears to be less constant, in the series composinir the 

 Champlain group, than several others ; still, as it occurs in a mass of so much thickness, 

 and at so many places, it appeared to be necessary to notice it as a distinct rock, inasmuch 

 too as it differed materially from the masses below and above it, in its fossils and in its struc- 

 ture. 



4. Birdseye Limestone. 



Generally a pure lijnestone : cnibiaccs drab colored layers, and similar to those in the 

 Calciferous Sandrock. — Structure. — Organic Remains. — Thichiess. 



The name for this rock is retained, in consequence of its having been employed very 

 generally by the geologists of this country ; and I have been more disposed to do it, as 

 its application is generally well understood. The name, it is true, is not very appropriate, 

 and besides there are other limestones to which the term birdseye has been given ; still, 

 they are not likely to be confounded with the birdseye limestone of the Champlain group. 



* This fossil was first described by C. A. LeSucr, under the generic name of Mciclurile, in honor of William McClure. As 

 the termination of the name is evidently erroneous, I propose to change it as above, in order to still preserve the commemoration 

 intended of a most munificent patron of science. It is evident from Mr. LeSuer's citation of the localities of this fossil, that he 

 labored under some mistake, as he gives Eighteen-raile creek as one where this fossil has been found. It probably never has 

 been found above the Trenton limestone. 



