MOUNT GKEYLOCK. 159 



these are on the same vertical and horizontal scale. 1 The first section, A, 

 crosses the north end of the mass at North Adams; the last, O, toward its 

 south end, between Cheshire and Berkshire villages; and the others at more 

 or less regular intervals between. See map (PI. i) for section lines, and 

 Pis. xviii-xxn, for sections. 



The sections show that the range consists of a series of more or less 

 open or compressed synclines and anticlines, which, beginning near North 

 Adams, increase southerly in number and altitude with the increasing width 

 and altitude of the schist area, and then, from a point about a, mile and a 

 half south of the summit, begin to widen out and diminish in number and 

 height until they finally pass into a few broad and low undulations west of 

 Cheshire. 2 Between that point and the villages of Lanesboro and Berkshire 

 the folds become somewhat sharper and more compressed, and the schist 

 mass rapidly narrows. The most comprehensive and best substantiated of 

 these sections are those two which, beginning near South Adams, cross the 

 central ridge north and south of the summit and then follow the two great 

 western spurs and end near South Williamstown. These sections will now 

 be described in detail. 



1 Prof. E. Emmons (American Geology, vol. 1, p. 19) gave a section of Greylock running from 

 Cheshire harbor, across the summit, and Mount Prospect, to Sweet's Corners and Stone hill. 



Prof, .lames Halls section, from Petersburg to Adams, made between 1839 and 1844, but unpub- 

 lished, showed the synclinal structure of Greylock. 



Prof. E. Hitchcock (Vermont Report, vol. 2, pi. 15, tig. 5) gave a section similar to, hut less 

 detailed than that of Emmons. Both of these arc drawn on a greatly exaggerated vertical scale, and 

 represent the mountain as a simple syncline. 



Prof. J. D. Dana, in his paper on "Taconic Rocks and Stratigraphy" (p. 405), reproduces Emmons's 

 and Hitchcock's sections, and adds several fragmentary ones of his own. On the east side, one west of 

 North Adams (Fig. 17). another west of South Adams i Fig. 14); on the west side, one on the west 

 Hank of Mount Prospect and north of the Hopper (Fig. 15), and another on the south side of the Hop 

 per (Pig. 16); all of which simph, represent the relations of the schist to the limwtone on either 

 side of the syncline, along the base of the mountain. In his paper on the " Quartzite, Limestone, and 

 Associated Rocks of Great Barrington," etc. | L873, p. 273); and again in his paper "On the Relation 

 of the Geology of Vermont to that of Berkshire" ( 1N77, p. 263), he conjectures from the north aud 

 south trend of part of the "Hopper" depression thai the Greylock syncline comprises one or more 

 subordinate folds. 



-' The sections have all been carried dowu to the top of the quartzite which underlies the Stock- 

 bridge limestone. The observed dips have also been indicated on them to enable the reader to dis- 

 tinguish between matter of actual observation and of ordinary induction. The cleavage dips have 

 been similarly indicated, but on a separate line, and the cleavage foliation has also been shown on the 

 drawings crossing the stratification wherever both were observed, but it doubtless traverses the 

 greater part of the mass. 



