THE 
AMERICAN GEOLOGIST 
Vol. VIII. JULY, 1891. No. 1. 
THE GREYLOCK SYNCLINORIUM.* 
T. Nelson Dale, Newport, R. I. 
The topography of the NW. part of Massachusetts is marked 
by three main parallel mountain masses having the N. NE. trend 
common to the Appalachian system. The most westerly of these 
is the Taconic range, the crest of which divides the states of New 
York and Massachusetts; the most easterly, situated about ten 
miles east of the N. Y. line is Hoosac Mt. traversed by the Hoosac 
tunnel, while the central one is Mt. Greylock, the prevailing rock 
of which, farther south, merges in that of the Taconic range. 
Mt. Grreylock forms a topographical unit, measuring about 14 
miles in length and averaging about 5 in width, and consists 
mainly of one central and two lateral subordinate ridges with the 
same N. NE. trend. The "saddle," from which it derives one of 
its ancient names, and which is a conspicuous object all through 
Berkshire county, is formed by a SW. bend in the central ridge 
between Greylock summit proper (3505 feet above sea Ica'cI) on 
the north and Saddle Ball (3300 ft.) on the south. These are 
about two miles apart, and the lowest part of the saddle is 2000 
ft. above sea level. 
*Abstract of a report by T. Nelson Dale, Assistant Geologist U. S. G. 
S. to Raphael Purapelly, Geologist in charge of the Archean Division, 
covering field work done by the writer in 188t)-1888 assisted during a 
portion of the time by Win. H. Hobbs. This abstract is published by 
permission of the Director of the U. S. Geol. Survey. The full report, 
amply illustrated, and entitled "Mt. Greylock, its areal and structural 
geology,'' goes to make up, together with a monograph by Raphael 
Pumpelly and one by J. E. Wolff, a memoir on the Green mountains, 
now in course of publication by the Survey. 
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