TACONIC SYSTEM. 
425 
in the Hudson-river and Utica slate groups and the argillite, and these are often traversed by- 
veins of quartz in every direction; red slate, red and green mottled slate, and red jaspery 
slate also occur. Talcose slate or talco-argillaceous slate is most common, and chloride or 
argillo-chloritic slate is not rare. 
A little farther to the west, the limestones, calciferous sandstones, and slaty limestones 
interstratified with the slates, appear and range parallel to the slates in parallel broken ridges 
that have no apparent connection, until their localities are marked on the map. Nearly all 
the township of Whitecreek is occupied by the Taconic rocks. They range along the west 
side of the Owlkill valley, north and south of Cambridge. The limestone, slate, talcy slate, 
and calciferous rocks form several parallel belts in this township, but none of the limestone 
assumes the character of a white crystalline limestone until beyond the line of New-York in 
the State of Vermont. A mile or two east of the State line, it is quarried for marble. It 
rarely acquires this character west of the talcose and chloride limestone, except where the 
rocks are penetrated by trappean and granitic veins; but almost all of the limestones east of 
the belt of talcose slate, except that near Whitehall, is converted into a white or grey crys¬ 
talline and dolomitic limestone, from Vermont to the Hudson river or Long-island sound. 
These and other highly altered rocks will be described as metamorphic rocks. 
In Rensselaer county, the talcose and chloritic rocks, and the limestones variously modi¬ 
fied by metamorphic agency, may be seen along the banks of the Hoosick river, between the 
mouth of the Tuttle Hoosick and the Vermont line, and thence on towards Williamstown. 
The river here crosses the Taconic mountain through a gorge, and the transverse section ex¬ 
hibits the nature and position of the strata. In some localities the limestone is a white, crys¬ 
talline, granular, dolomitic rock ; in others it is scarcely altered from the calciferous rocks, 
and the compact and sparry blue limestones. The slate is in some places like argillaceous 
slate and roof slate; in others it is highly talcose or chloritic, and the red slate is also quite 
common. 
Rocks of the same character, but less altered, the limestones being sparry, and the slates 
less talcose and chloritic, range along the western side and through the valley of the Little 
Hoosick in Petersburgh and Berlin. 
The Taconic mountain extends south through the east parts of Petersburgh, Berlin and 
Stephentown, into Columbia county, and it occupies a variable breadth also in the towns of 
Williamstown and Hancock in Massachusetts. It contains the same kinds of rocks as those 
described in the gorge through which the Hoosick crosses the Taconic mountain. The sur¬ 
face in very many places is strewed with boulders and loose fragments of milky quartz, much 
of which contains abundance of chlorite, in nests and in cavities in the rock. The chlorite 
is in small aggregated green scales. These loose masses of quartz are derived from the de¬ 
composition, disintegration and washing away of the slate rocks, in which they constituted 
parts of veins and nests ; and as the quartz withstands atmospheric agents and abrasion better 
than the slate, great quantities of it are found on and in the soil near to where it abounds in 
the slate rocks. 
Geol. 1st Hist. 
54 
