420 
GEOLOGY OF THE FIRST DISTRICT. 
Columbia county, and farther south in Hillsdale, Copake, Ancram and Gallatin (Vide Plate 
10 , fig. 14; and PL 23, fig. 7). 
In most of the localities that will answer for roofing slate, the lamina of cleavage and of 
deposition are coincident. This is evident, 1st, by the distinct stratification of the rock; 
2d, by its frequent striped aspect parallel to these divisions; and 3d, by the vegetable im¬ 
pressions (graptolites) being situated on and parallel to these cleavage planes, and not trans¬ 
verse to them. 
Details. The roofing slate ranges through Rensselaer county, from two miles west of Leba- 
•non springs to the northeast corner of Hoosick; thence north in Washington county through 
the towns of Whitecreek, Jackson, Salem, Hebron, Granville and Hampton; and thence 
an unknown distance into Vermont. There are many places where it may be wrought for 
roofing slates, when there shall be facilities for transportation, such as to enable the proprie¬ 
tors or adventurers to send them to market without too great an expense. At present the 
Welch slates can be afforded in our coast markets at a less price than the Hoosick slates, 
although the facilities for raising these slates are very great. The expense of transport over 
land to Troy, and a prepossession in favor of the Welch slate, has prevented the Hoosick 
quarries from being wrought as extensively as they might have been. The prepossession in 
favor of the Welch slate is believed to be unfounded. As beautiful slates are obtained from 
the Hoosick quarries as I have ever seen, and they are as durable. There are two qualities 
of the slate obtained from these quarries, viz. the blue, and the grey or fucoidal slate. The 
former retain their bright bluish surfaces for many years, and probably will as long as the 
slate shall last; they do not show the slightest indications of change after many years expo¬ 
sure. 
There is another stratum of slate several feet thick, containing a multitude of the most 
beautiful impressions of plants, supposed to be fucoids. This stratum makes good slates for 
use, but they are not as beautiful, and they become greyish in a few years. These are sold 
at a much less price than the blue slates; and it is supposed, that in consequence of the 
change of color, the quarries do not sustain as high a reputation as they did in former years. 
The principal quarries are those of Closes Warren, one mile north of Hoosick corners ; and 
those of Obadiah Crane, two miles northeast of the above. 
The strata dip to the eastward about thirty degrees, but they are somewhat bent. The 
curves are so large, (having radii from one hundred to three hundred feet,) that the masses 
taken out do not show any distinct curvature. The strata are intersected by thin veins of 
quartz, which is frequently fibrous. 
A range of roof-slate extends from New-Lebanon through Canaan, Austerlitz, Hillsdale, 
Copake, Ancram, and Pulver’s corners in Northeast. It is believed to be the same as that 
in which the Hoosick quarries are located. Quarries of roof-slate have been opened in this 
range of rock in many places. The most important are those in New-Lebanon, about one 
and a half miles from the springs on the east face of the mountain. One belongs to Charles 
B. Gillet; the other, which is about a half or three-quarters of a mile north of the first. 
