BEENARDSTON SERIES OP UPPER DEVONIAN. 291 



from twiuning or cleavage, and theu showing the strongest concentric extinc- 

 tion. Extinction in twinned pbtes, 14°-34°. Quartz is scarcely present. 



13. Am})liibolite from South Vernon, 10 rods north of limestone at E. G. 

 Scott's. A thin-fissile, greenish-gray rock, showing with lens many scales 

 of black biotite and rarely a sharply defined, light-brown prism of epidote. 



In section nearly the whole field is covered by a tangled network of 

 hornblende blades which show quite marked pleochroism. The colorless 

 background is for the most part feldspar, rarely showing twin striation, and, 

 as so often happens in these hornblende schists, wholly fresh and without 

 cleavage. Many scalariform or coraloidal groups of leueoxene occur, 

 rarely with a trace of black ore at center, bnt each separate crystalline 

 grain itself red-brown at center and colorless supci-ficially. No other ore 

 occurs. 



THE MICA AND AMPHIBOLITE SERIES. 



14. Mica-schist from Bemardston, Williams farm, from the bed of schist 

 west of the limestone. A dark-gray to black, very fine-grained, even- 

 bedded slate, with its glistening surface pitted here and there by hemi- 

 spherical hollows, from which small red dodecahedral garnets have fallen 

 and marked l)y minute white spots of shining muscovite scales just visible 

 to the eye, which often appear in fine double lines sharply parallel to each 

 other and inclosing a narrow dark center. They appear thus like minute 

 chiastolites. 



Under the microscope the rock shows a fine, scaly, colorless ground, 

 dusted abundantly with coaly matter, and with polarized light showing 

 in abundance minute muscovite scales and needles. These are emljedded 

 in a ground which shows aggregate polarization and is partly apolar and 

 apparently opal. Kaolin could not be detected, nor "clay-slate needles." 

 The much fissured garnets have often a black boundary, froin the accumu- 

 lation of the coaly matter expelled from the space they occupy, and within 

 this a broad decomposition band of chlorite in twisted scales, which often 

 extends nearly to the center of the crystal. They contain lai'ge grains of 

 quartz irregularly arranged. 



The centers of the minute chiastolite-like forms mentioned above prove 

 to be small, very impure, transversely placed biotites with flat sides and 

 raveled ends, having on each of their long sides bands, broader than them- 

 selves, of clear muscovite scales placed at right angles to the broad faces of 



