274 J. D. Dana—Taconie Rocks and Stratigraphy. 
line of the quartzyte range of Bald Mountain on the boundary 
between Clarksburg and Williamstown; and its continuation 
northward. The shift is also exhibited in the Archean rocks. 
For directly north of the Stockbridge limestone of Clarksburg 
there is an undoubted Archean area—that of the ‘ Stamford 
granite’”—of the Vermont: survey,* and this Archzean area 
stands against the eastern side of the quartzyte range of Bald 
Mountain. So again to the south, in Berkshire, the quartzyte 
has in several places similar hornblendic Archzean rocks not far 
east of the outcrop of quartzyte. Thus the shift is marked in 
the three great formations of the country. 
b. Another westward shift, or apparent shift, occurs in South- 
ern Vermont, in the latitude of Bennington, and is about a mile 
in extent. The limestone limit on the east of the village of 
Bennington with the quartzyte range west of it shows, on the 
map, the abrupt shift very strikingly ; ; and it is seen also in the 
limestone limit west of the village. 
Such apparent shifts may correspond to actual westward or 
eastward displacements produced since the time when the 
deposits were formed; or they may indicate the course of the 
shore-lines of the ancient sea in which the deposits accumu- 
lated. Which is the right explanation is an important ques- 
tion. 
c. In central Berkshire, within the limestone limits, south of 
the line of Lee and Stockbridge, a region of high hills and 
ridges comprising Bear Mountain, covers the northern part of 
the town of Monterey and small parts of adjoining towns. It has — 
an east-and-west course, cuts short the limestone area, gives an 
east-and-west course to the Housatonic River (and to roads 
and railways), and to the limestone area of southern Monterey, 
(see map), and thus disturbs or goes athwart the feature-lines 
and Taconic trends of the valley. But the eastern limit of 
the limestone has no abrupt shift in its course. The summit 
of this Bear Mountain region is probably Archean. The dis- 
turbance in the direction of the feature. lines, which is appar- 
ently due to this area, extends also to ridges west and south- 
west, as that of Monument Mountain, and those between 
Monterey and Great Barrington, which have a.northwest trend 
instead of the usual north- -by- east. 
The question as to the origin of these changes in the courses 
of the rocks, or those of their outcrops, requires, for a safe 
reply, a consideration of the facts over a wider range of the 
formation ; and I recall here some of the features in Salisbury, 
Ct., and farther south. 
d. In Canaan and Salisbury the eastern or Stockbridge 
* See description of Section I, vol. ii, p. 601, by C. H. Hitchcock. The granite 
is hornblendic, and I found it to contain zircons. 
D 
