245 Dewey’s Geological Section. 
with quartz. By the action of the weather, large rocks are. 
divided into innumerable prismatic bodies. A small stream, 
which rises in the mountains in the East part of Grafton, 
and runs westward into the Hudson, below Troy, affords 
an excellent opportunity for examining the position of this 
rock in numerous places. Occasionally there appear in 
this rock, beds, or veins, of a reddish argillaceous slate, in 
Grafton and Brunswick. 
Near Troy, the graywacke has a much finer texture, and 
darker colour, and some of it takes a fine polish.* Where 
-the graywacke stops near Troy, there begins a bed or stra- - 
tum of 
Argilaceous Slate-—It extends to the bank of the Hud- 
son, and has a similar inclination to the East. It must 
doubtless be considered as the next rock in order, or as 
forming an extensive bed in the graywacke. Itis full of 
natural seams, which divide it into small plates, and easily 
disintegrates. A large quantity, thrown into a street im 
Troy, has by the action of the weather, and constant travel- 
ling upon it, become in one year, complete clay. Both the 
graywacke and argillite are evidently transition rocks.* ‘The 
slate 1s very different from that which occurs in Williams- 
town, and along this part of the T'aconick range, and which 
seems to me clearly primitive. It will doubtless be found 
by future observation, that the roof-slate of Hoosack, N. ¥. 
which appears to be a continuation of the Taconick range, is — 
separated from the argillaceous transition slate, which ex- 
tends for many miles along the Hudson, below and above 
Troy, by the same stratum of graywacke. I noticed no 
graywacke-slate on this section, but it is found very perfect 
in Chatham, a few miles southeast of Albany. Specimens 
of the above rocks will soon be forwarded to the Geological 
society. 
Should you think the above worthy of publication, I 
should be glad to see it because this section will be pretty 
complete from twenty miles Kast of Connecticut river to 
the Hudson. 
* See Haton’s Geology. 
