432 
GEOLOGY OF THE FIRST DISTRICT. 
stone continued ranging northward to within a short distance of the outlet of Whiting’s pond, 
where it was succeeded by the slate as described in a preceding page. 
The rock, from Canaan four corners to Canaan centre, is slate, which is highly talcose 
in some places. At Canaan centre, east from the tavern, is a bed of limestone, which is 
traversed by veins of carbonate of lime and quartz. The cut of the railroad a quarter to half 
a mile south of Canaan centre, exposes a beautiful section of the slate rocks, of purplish 
and grey colors. Quartz veins penetrate the rock in every direction, without any of that 
regularity that is usually expected to be seen in veins. The quartz contains brown spar; 
and where this has decomposed, an earthy oxide of manganese remains, and sometimes it 
shows traces of the original crystalline texture of the.mineral.* The occurrence of this mine¬ 
ral in some quantity in the rocks of this region, and its easy decomposition, will, perhaps, 
account for the abundance of wad, or earthy oxide of manganese, observed in this region, 
and described among the alluvial depositions on page 121 of this volume. 
About half a mile south of Canaan centre, a ridge of siliceous rock, perfectly injected 
with quartz, permeating every part of the mass, crosses the strata from northwest to south¬ 
east. It is four to six rods wide on the surface, and analogous to much of the rock in the 
hills south of it, and also to the boulders in the northeast part of Chatham and northwest 
part of New-Lebanon, and the ridge above Rider’s mills. 
The rocks down the valley of Green river, between Austerlitz and Green-river village, are 
talcy slate on the right bank. The mountains on the left bank abut in echelon upon the val¬ 
ley of Green river. 
The limestone in the Copake valley, north of Hillsdale, between-mills and the Bap¬ 
tist church, ranges northwest and southeast. 
South from Hillsdale, Messrs. Merrick and Cassels traced the grey and bluish limestone 
from near the gate on the Columbia turnpike, east of Hillsdale, to Copake meeting-house. 
In one place on that road, two miles south of the gate, it rises in a perpendicular ledge about 
thirty feet. Near this place the road is cut through the limestone, which is slaty, and 
somewhat similar in character to that at the outlet of Whiting’s pond. The strike is south- 
southeast. North of Copake, in the fork of the roads, is a small hill, called Mount Tom, 
the base of which is slate, but the top and southeast side are of slaty blue limestone dipping 
to the east like ^he slate. In many places in this vicinity, the rock is the sparry limerock, 
checkered with the veins of calc spar and quartz. 
At Griffin’s mills in Copake, on the west side of Copake flats, the limestone was observed 
by Prof. Cassels, who traced it along the eastern base of the mountain on the western side of 
the Ancram valley, about two and a half miles to the northward, where he left off tracing it, 
to examine the slate of the mountain, along the base of which the limestone ranges. These 
rocks were seen nearly in contact, both dipping highly to the east, and the slate apparently 
* This mineral has, I suppose, been analyzed by Prof. Beck, the Mineralogist of the. Survey. It evidently contains more 
manganese than any of the ordinary varieties of brown spar; but as this is isomorphous with iron, it may combine by replace¬ 
ment to any extent. 
