J. D. Dana—Taconice Rocks and Stratigraphy. 409 
direction of dip, and all in harmony with the idea of an anti- 
clinal (northward in dip of axis) spanning the valley, with 
limestone as the inferior rock. Farther north a section cross- 
ing the same valley continued across Monument Mountain 
(p. 402) presents a closely parallel case, leading to the same 
view of the stratigraphic relations. The quartzyte of the east 
end of the anticlinal over the valley covers the western flank 
of Bear Mountain from Devany’s quarry nearly to Stockbridge. 
Studying the facts connected with some of the other quartz- 
ytic ridges within the limestone area with an equal readiness 
for either conclusion under consideration, it is difficult to avoid 
the conclusion that the limestone is the older formation. 
But doubts are introduced—not by the idea that Potsdam is 
sandstone or quartzyte and sandstone or quartzyte is Potsdam, 
but by the Berkshire fact that some of the quartzyte is unques- 
tionably Potsdam or Cambrian. This appears to be true of 
the quartzyte of Bald Mountain between northern Williams- 
town and Clarksburg, as inferred from its position with refer- 
ence,to the Archean mountain just eastward, and its connec- 
tion with the great eastern range of quartzyte in Vermont. It 
is true of that of southeastern Pittsfield, eastern Lenox, eastern 
Lee, eastern Tyringham, in which cases Archzean rocks are 
near by, a little to the eastward, and the quartzyte usually dips 
westward toward the limestone as if passing underneath it, and 
at one locality has been observed to pass beneath it. 
In the case of the quartzyte over the west slope and base of 
Bear Mountain, referred to above, the fact that Archzean prob- 
ably makes the higher part of this mountain* is good reason for 
reconsidering the conclusion which has been drawn, and ques- 
SS 
tioning whether the fold in Monument Mountain is not the 
reverse of that on page 403, as here figured. The question has 
*In my paper of 1873, in vol. v of this Journal, p. 367, and vi, p. 263, I 
describe a garnet rock consisting of garnet, quartz ‘and some hornblende, as occur- 
ring near the summit of Bear Mountain; and as I have not found any similar rock 
elsewhere in the limestone series, and its aspect is Archean, I have now little 
doubt of its Archzean relations. The loose mass of chondroditic limestone fouud 
on the south margin of the high region, as reported in the same paper, I believe 
to be further evidence for the same conclusion. 
