CLINTON COUNTY. ;j[7 



add, however, that some of the beds whicli I now place in this rock, namely, the oohtc and 

 the encrinal mass, amounting in all to some twenty feet, were not included in this estimate. 

 It was not until after my return from the field, that I saw the necessity of placing these 

 strata in the chazy rock. 



The thickness of the chazy limestone can nowhere be so well determined as at the locality 

 I have described, though it appears at numerous points. In determining its limits, I have 

 been governed by the presence of the Maclurca, a fossil which certainly has never been found 

 in the trenton limestone above, nor in the calciferous sandrock below ; but whether it is ever 

 found in the birdseye, I am not so certain, and farther observations are required to set the 

 question at rest. 



I have described this rock as one which, for economical purposes, will not appear important. 

 This is true of a large portion of it, as it exists at Chazy. There are, however, some strata 

 even there, whose regularity and freedom from cherty matter will place it among the useful 

 rocks. When even-bedded, or when a tolerably pure limestone and without concretions, it is 

 very much employed for jambs, or the less important parts of a fireplace. When sawed, a 

 very large proportion of the slabs present a surface marked with arborescent forms, which 

 are probably fucoids. The surfaces, too, on weathering, exhibit in relief the same appear- 

 ances. All are, however, too much without character, to entitle them to a particular descrip- 

 tion ; and it is not certain that they are vegetables, as in pasty masses, when two or three 

 materials enter into a composition, there is a strong tendency for one or more to separate and 

 assume this arborescent form. 



In the use of this material for jambs, etc , it has an important property not possessed by 

 the fine black marbles, viz. strength ; and hence it is suitable for all those parts which are to 

 sustain much weight. 



This rock, I may remark also, might sometimes be employed as a cheap black marble, 

 when it is not so hard as to occupy too much time in giving it a finished polish. There is 

 usually, however, too much grey in the polished face to form an ornamental material, and the 

 general appearance is somewhat muddy. Specimens, both pohshed and unpolished, are 

 placed in the State Collection. The flinty or cherty particles in this rock at Chazy are always 

 found minerahzing a species of Columnaria : the columns are smaller than in the one which 

 is figured in page 276, but they are so much distorted that the species cannot be determined. 



Birdseye Limestone. 



Three varieties of this rock were noticed in Chazy : a dark and a light variety with drab- 

 colored layers intervening. The two first break with the usual brittleness and conchoidal 

 fracture; the latter is tough, and somewhat siliceous. The fossil common to this rock 

 {Fucoides demissus of Conrad), is replaced wholly by calcareous spar ; in consequence of 

 which, organic traces are entirely obliterated. All of the mass which breaks with a conchoi- 

 dal fracture, is a pure carbonate of lime : it is entirely free from visible particles of uncrys- 

 tallized earthy matter. 



