BERNAEDSTON SERIES OF UPPER DEVONIAN. 293 



iu abundance gi-aius of an opaque black ore, often partly changed to opaque 

 white. There are other gi-aius of an opaque yellowish-white material of the 

 same shape and size. These are apparently menaccanite and leucoxene. 



The only distinguishing- characteristics to separate the present and the 

 preceding rock are the somewhat coarser texture of the ground in the former, 

 the larger size of the transverse biotite, and the somewhat more perfect crys- 

 tallization of the staurolite and garnet. They may well have derived their 

 material from the same source and have been subjected to almost precisely 

 the same influences during metamorphism. 



The above descriptions were wiitten for the two rocks when it was 

 supposed that the western schist dipped below the limestone, while the east- 

 ern rested upon the quartzite above, and the rocks were studied in the hope 

 of huding some peculiarity by which they could be separately traced. They 

 are now believed to be part of the same stratum, and the detailed descrip- 

 tions above attest their lithological identity. 



1 6. Mica-schist from Purple's quany. A dark-gray, fissile, gametiferous 

 muscovite-schist, differing from the upper schi.st of the Williams farm only 

 in the gi-eater abundance of garnet. 



In a ground of musco\dte scales abundantly strewn with coaly matter 

 occur many garnets inclosing scales of muscovite and bounded by a decom- 

 position layer of chlorite in scales parallel to the side. The sti-ongly 

 dickroic biotite plates, much dusted with coaly matter, are bounded on P 

 b}' broad layers of vertical musco^'ite scales, which in one place inclose a 

 layer of fresh orthoclase. 



17. Massive ampliil)olite from Beniardston, east of village, and just east 

 of J. Nelson's, the first house on the road turning north after jiassiug the Fall 

 River bridge. Dark-grav, jointed, massive rock in heavy bed, associated 

 with thin bed of limestone. Effervesces abundantly with cold hydrochloric 

 acid, esjiecially around the wisps of hornblende, and shows then with the lens 

 hornblende, biotite, magnetite, and plagioclase. ^luch magnetite removed 

 from the powder 1)y the magnet. The microscope shows few scattered 

 wisps of hornblende needles, gi'oups of grains of black ore not associated 

 mth leucoxene. The hornblende shows weak absorption and pleochi-oism. 



18. Massive amphibolite from Bernardston, north of R. Park's, locality C 

 cited by Professor Dana (14. 342). (See PI. V, fig. 3, for section.) A mas- 

 sive, l^lack, fine-grained, diorite-like rock. The microscope shows the rock 



