Wadsworth.] 238 , [May 16, 



The micas were examined under the polariscope, showing that the 

 black one was uniaxial, while the silvery white one was biaxial, giv- 

 ing the following apparent inclination for the axes in the air. 



First specimen, mean of fifteen measurements, 69° 59' . 



Second specimen, mean of six measurements, 72° 21/. 



Third specimen, mean of three measurements, 67° 9'. 



The axes lie in the plane of the longer diagonal. 



Fusibility of the Amorphous Varieties of Quartz. 

 By M. Edward Wadsworth. 



Having occasion to examine and separate a number of specimens 

 of jasper from felsite, I was led to doubt the usual statements that 

 quartz in all its varieties is unaltered and infusible before the blow- 

 pipe, and that jasper can be distinguished from felsite by the former 

 being infusible, while the latter is fusible on the thin edges. 



I found on examining many specimens of chalcedony, agate, jas- 

 per, flint, opal, etc., that all fused from 5 to 6-J-, except some of the 

 jasper; many of the specimens of chalcedony swelling to twice their 

 normal size, curling in the flame, turning white, and forming a 

 white enamel or blebby glass. 



The fusibility of these varieties is doubtless owing to various bases 

 existing as impurities in the quartz. That in hand specimens jasper 

 maybe separated from compact feldspathic rocks by means of its 

 fusibility may be true, but until it is settled by chemical or micro- 

 scopical analysis, what shall be called jasper, and what felsite, the 

 distinguishing line seems, at least, to be obscure. 



The blowpipe used (Bunsen's gas blowpipe) gives a somewhat 

 higher temperature than the common blowpipe, but in the only case 

 tried, chalcedony was fused by means of a common blowpipe and a 

 small alcohol lamp. 



Mr. S. H. Scudder exhibited drawings of the wing of a 

 cockroach from the carboniferous formation of Pittston, 

 Penn., in the possession of Mr. R. D. Lacoe of that place. 



It lies on a piece of black carbonaceous shale, and was found in 

 the interconglomerate beds, or at not far from the same level as the 

 fossil cockroach described by Lesquereux from Frog Bayou, Arkan- 

 sas. It is a nearly perfect upper wing, an insignificant portion of 



