152 



GREEN MOUNTAINS IN MASSACHUSETTS. 



south side of the Bald mountain spur, there is a small ledge in which the 

 stratification foliation dips 35° west, the cleavage foliation 25° to 30° east, 

 and a secondary cleavage horizontally or very low west. Some vertical 

 joints strike north to south through all these planes. 



V&s 



Fig. 52 — Thin section of sericite-chlorite-schist from locality 175, Goodcll hollow, the larger figure enlarged nearly 2 

 diameters and the smaller about 10 diameters, showing two cleavage foliations crossing the stratification. In preparing the 

 slide a fracture lias occurred along Cleavage I. From photographs. 



Secondary cleavage foliation occurs here and there in the Greylock 



CASE IX. 



Fig. 53 represents an enlarged section of plicated schist from locality 

 550, about 1,500 feet south of the top of Greylock. The area in the larger 

 and upper fragment measures 1£ by £ inches. The specimen from which 

 the section was made showed, in its original position in the ledge, a stratifi- 

 cation foliation about horizontal or dipping west at very low angle, crossed 

 by a cleavage foliation dipping 60° east. From the direction taken by the 

 breaks, which occurred in the preparation of the slide, it seems probable 

 that in some portions of the rock here the cleavage foliation dominates. 

 Fig. 46 represents a hand specimen from the same ledge in its natural posi- 



1 Two sets of cleavage planes arc noticed in the slate on Welden's island. Lake Champlain. Geol. 

 Report Vermont, vol. 1, p. 314. A. Baltzer, in the Beitrage zur geologischerj Karte der Schweiz (20te 

 Lieferung, Bern, 1880. Atlas, pi. m, (is;, s. and \m, figs. 14, 16) figures two cleavage foliations 

 traversing the same rock. Archibald Geikie, in his report on the recent work of the Geological Survey 

 in tin- northwest highlands of Scotland, describes a double foliation in eruptive gneiss. Quart. Jour. 

 Geol. Soc, London, vol. 44, Aug. 1888, p. 398-400. 



