PLATE VII. 
SHEAR-ZONES (" HOGBACKS "). 
(.4) Diagram of thin section of ''sea-green" Cambrian slate from Williams and 
Edwards 1 quarry in Wells, Vermont. Enlarged 2 diameters. Section across the 
cleavage and an incipient "hogback," showing the two bends in opposite direc- 
tions and developed in but two places into fractures. Secondary fractures at 
15° to cleavage cross the zone. A calcareous strip, possibly a trace of bedding, 
crosses the cleavage at 45°. All the fractures filled with calcite. 
(B), (C), (D) Microscopic drawings from above thin section, enlarged 40 diame- 
ters, showing in reversed position the outlines of several of the vertical and diag- 
onal fractures within and at edge of zone. 
(E) Diagram from specimen of "hogback," from E. E. Lloyd's sea-green slate 
quarry, Poultney, Vermont. 
(F) Slate from within a fully developed "hogback," showing outline of fracture. 
Same location as E. 
(G) Same location as above slate, showing two "hogbacks." 
(H) Diagram from specimen of Cambrian slate from Eddy Hill, Fair Haven, Ver- 
mont, showing development of "hogbacks." Secondary quartz occurs along the 
~ fractures. Reduced one-half. 
(I) Shear-zone in Silurian schist 1| miles east of Rupert, Vermont. 
(A') Diagram from specimen from top of the Pattern, in Pawlet, Vermont. 
(L) Diagram from thin section of Cambrian slate from Eddy Hill, Fair Haven, Ver- 
mont, enlarged two diameters, showing one of the main fractures of a "hogback " 
with diagonal fractures which are filled with quartz, and beside it slip-cleavage. 
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