J. D. Dana—Taconic Rocks and Stratigraphy. 395 
In the main Taconic range, along the Massachusetts bound: 
ary, the schists are chloritic hydromica schists, and on the east- 
ern sides often garnetiferous, especially to the southward. In 
an east and west line through South Williamstown and Grey- 
lock they continue to be chloritic hydromica schists from the 
New York boundary to the eastern slope of Greylock, or seven 
miles, where are some portions that might be designated true 
mica schist; a mile and a haii east of Greylock summit, near 
the east foot of the Greylock mass, the rock would be ordinarily 
called mica schist; and this is true, also, farther north, abreast 
(west) of the village of North Adams, as seen at the little rail- 
road tunnel, although the mica is slightly greasy to the toucb. 
The mica schist is sometimes muscovite schist, often biotite 
schist, but generally both micas are present. 
Looking at Berkshire as a whole, in the part of it east of a 
straight line drawn through the county, southward, from Grey- 
lock to the northeastern corner of Mt. Washington in South 
Keremont, about S. 15° W. in course, the schists are nearly all 
‘ miea schist, while to the west of the same line, they are nearly 
all chloritic hydromica schist. A ridge in Lanesboro (which 
is nearly on this line), has the schist intermediate between 
hydromica and mica schist, inclining most to the latter. This 
line throws to the west the high ridges, Tom Ball and Maple 
Hill, of West Stockbridge, which are of chloritic. hydromica 
schist, and to the east, ridges near by on the east of these. 
But to one going over the region the transition would be found 
to be a very gradual shading from one to the other, some 
portions at the northeastern foot of Tom Ball almost meriting 
a place with the mica schist. 
Fifteen miles south, in Canaan, N. Y. (nearly west of Pitts- 
field), the schist west of the limestone is a very thin, slaty, 
glossy roofing slate; that of the ridge east of it, north of 
Queechy Lake, a coarse chloritic hydromica schist, except near 
the boundary of Lebanon (at B, on the map, a high point called 
Douglass Knob) where it becomes quartzose, a very hard 
chloritic quartz rock, not schistose; the high knob is the 
source of the famous bowlder trains that cross Richmond into 
Lenox, first studied out by Dr. Stephen Reid, of Pittsfield. 
Hast of the N. by H. and S. by W. line drawn from Grey- 
lock to the northeast base of Mt. Washington, the larger part 
of the mica schist is extremely arenaceous; and it often gradu- 
ates imperceptibly into a bedded quartzyte, or alternates with 
strata of quartzyte, both that of the thin-bedded kind, and of 
the hard and massive, precisely as described in Part I of this 
paper for Southern Berkshire and the adjoining part of Connec- 
ticut; and, as there, the rock usually contains minute tourma- 
lines. The narrow ridge entering the town of Great Barrington 
from Sheffield west of tne railroad, consists of bedded quartzyte 
