26 TRANSACTIONS OF THE [ocr. 1%, 
geology in the immediate vicinity of Great Barrington has been 
carefully studied by J. D. Dana.’ Its stratigraphical features 
have been represented by him in a cross-section from the hill 
west of the village, eastward through the village, which occupies 
the low portion of the valley, to Hast Mountain, which bounds 
the Housatonic valley on the east. 
On the summit of the hill, at the west end of the section, 
given in his paper, we find an outcrop (/) of the ‘‘ Stockbridge 
limestone,” as a coarse white crystalline variety, then a stratum, 
over three hundred feet in thickness, of mica-schist (and gneiss) 
(s), quartzyte (7), and micaceous gneiss (s), and then a layer of 
** limestone,” all these members dipping eastward at an angle 
‘of 45° to 55°. Then at P, near the centre of the valley, rises 
the isolated ridge of ‘‘ limestone” (/), called Mt. Peter, dipping 
70° to 80° to the eastward, and again another (at 7), east of the 
river (#7), on the lower slope of Kast Mountain, dipping 80° to 
-85° to the westward. In regard to these outcrops of so-called 
““ limestones,” Dana observes: ‘‘This section introduces a new 
element, an upper stratum of limestone, overlying the upper 
schist where the upper quartzyte would be looked for. The 
limestone is a bluish-gray and firm granular variety. Some por- 
tions are quite pyritiferous. I have been unable to find evidence 
that this limestone isa continuation, in full, of that of Egre- 
mont. ‘The section terminates eastward in a thick stratum of 
contorted gneiss (S*), with one hundred and twenty feet of 
quartzyte above. ‘The gneiss dips eastward 60° to 50° in the 
outcrop nearest the limestone, diminishing eastward to 50° and 
40°, with the strike about N 10° E. Some of the outcrops of 
limestone and gneiss are not over ten yards apart. The uncon- 
formability between the gneiss and limestone is evidence of a 
fault along a fracture.” 
A year afterward (October, 1873), Prof. Dana withdrew this ~ 
conclusion as to the existence of a second independent stratum 
of limestone at Great Barrington : 
‘<The importance of settling this point has led to the delay in 
the publication of this continuation of my memoir. Having 
been recently over the ground again, I have finally arrived at 
the conclusion that the ridge of schist west of Great Barrington 
is actually the course of a synclinal, and, that, therefore, the 
Great Barrington limestone stratum dips under it, and is noth- 
ing but the Stockbridge stratum. There is no outcropping 
schist found to the south of it. Again, the connection of the 
quartzyte of this ridge with that of the south end of Tom Ball 
(a high ridge three miles northwest of Great Barrington), and 
' Amer. Jour. Science, 3, iv. (1872), v. and vi. (1873). 
