- 
Dr. Hitchcock on some Phenomena of Drift. 261 
The rock forming these blocks, I incline © 
to refer to the talcose slate of the Taconic 
Mountain ; and yet it is quite distinct from 
the usual talcose slate of that range, which 
forms the west part of Richmond. It isa 
very hard and tough rock, of a greenish 
color, and often considerably granular, re- 
sembling the older varieties of graywacke. 
It frequently contains veins of what ap- 
pears to be picrosmine, which is quite 
characteristic, and readily identifies it with 
the rock in Canaan. In some spots on 
the parent range, we can see the places 
where the ragged fragments were torn off 
by some giant force, and the.fracture has 
yet a considerable degree of freshness,—for 
this is one of the most enduring of all 
tocks, being highly magnesian. This ridge, 
it ought to be remarked, is a part of the 
Taconic range, which here is separated 
into several rather low ridges. On the 
west of the ridge in Canaan, succeed lime- 
Stone, clay-slate, and the oldest of the Si- 
lurian or graywacke rocks. 
As we go east from the parent range, 
the west ridge, as we enter Massachusetts, 
is the common talcose slate of the Taconic. 
Then succeeds, in the valley of Richmond, 
a crystalline limestone; then mica slate in | 
State line. 
Richm’d. 
*sya07q fo uw. ay7 fo anos ay, Fu0pp uorzoagy 
Lenox Mountain; then limestone to the 
Housatonic; and finally, in Beartown Moun- 
tain, quartz rock and gneiss. .These rocks 
are not marked on the map, because they 
are of no great importance to the point 
in hand. 
Vol. xxix, No. 2.—July-Sept. 1845. 34 
