426 
GEOLOGY 0?' THE FIRST DISTRICT, 
Prof. Dewey described these rocks between Williamstown and Troy in 1820. Speaking 
of the rocks of the Taconic range in Williamstown, he says : “ It will be recollected that 
the rocks of the Taconic range in this town were stated to be argillaceous slate, chlorite 
slate, and talcose slate. The last predominates, and abounds on the descent of the range into 
the valley of Petersburgh. This valley, of variable breadth, extends several miles north and 
south, and is traversed by a stream which runs northward into Hoosick river. In this valley 
is found abundantly the same mi.xture of chlorite and quartz which is so common in Williams¬ 
town, though the two valleys are separated by the Taconic range having an elevation of one 
thousand to one thousand four hundred feet.” “ On the west side of this valley, and about 
seventeen miles east of Troy, lies chlorite slate, very distinctly characterized. It is some¬ 
times narrow, and sometimes two or three miles m width, often rising into hills two hundred 
or three hundred feet high.”* 
Much of the slate called talcose slate, is not the talcose slate composed of quartz, and talc 
described by some authors, but its composition would be expressed generally by talco-argil- 
laceous slate, and in some places by talco-micaceous slate. 
The slate rocks are talcy, and associated with red, green and chloritic slates on the hills 
east of Tuckawassick kill in the northeast part of Nassau and southwest part of Berlin. The 
same may be seen south of Nassau. 
In Columbia county, the Taconic rocks occupy almost the whole of the eastern line of the 
county between Massachusetts and New-York. A mountain range of these, rocks occu¬ 
pies the eastern part of New-Lebanon, Canaan, Austerlitz, Hillsdale, Copake and Ancram. 
Several gorges cross these mountains, the principal of which are, 1st, that through which the 
railroad from Boston to Albany passes, south of Whiting’s pond in Canaan ; 2d, in the south 
part of Canaan, called Canaan gap ; 3d, that of Green river, which extends west through 
Austerlitz ; 4th, that in Ancram and Northeast, between Winchell’s mountain and Mount 
Washington. 
The Taconic rocks in Columbia county will be more particularly described near Lsbcuion 
springs ; near the route of the Albany and Stockbridge railroad; near the Boston and Albany 
turnpike, and the Hudson and Hartford or Columbia turnpike ; since they are near great 
thoroughfares, and consequently easy of access. 
The rock at Lebanon springs is a slaty limestone, with talc between its layers ; and a 
careless observer might, by very casual observation, call it talcose slate. This limestone is 
greyish, and is underlaid a little farther north by bluish compact and sparry limestone. The 
dip is about thirty degrees to the eastward, and the strike is N. 30° or 40° E. Talcy slate 
succeeds the limestone a few rods east of the springs, on the Pittsfield road. In the first and 
second ravine east of the springs, the rock is seen, in place, dipping eastwardly at an angle of 
forty to sixty degrees. A. fault of the strata is believed to have been observed near the springs, 
but it was not traced out. Talcy slate is visible in situ, at short intervals from the springs to 
* Prof, Dewey’s Geological section; American Journal of Science, Vol. 2, p. 240; and he gave a more detailed account of 
Western Massachusetts in Vol. 8. 
