CLINTON COUNTY. 
317 
add, however, that some of the beds which I now place in this rock, namely, the oolite and 
the encrinal mass, amounting in all to some twenty feet, Avere 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 Maclurea, 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 polished and unpolished, are 
placed in the State Collection. The flinty or cherty particles in this rock at Chazy are always 
found mineralizing 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. 
