1880.] NATURAL SCIENCES OF PHILADELPHIA. 249 



tiou of the instrument. Bissectrix apparently parallel to the 

 fibres, Probabljr orthorhombic. Common serpentine and Wil- 

 liamsite show no double refraction. 



Damourite. 



1. Culsagee, N. C. In scales : analyzed by Koenig. 



(F. A. Genth.) 66°lt'±. 



2. Unionville, Pa. " Emerylite : " irregular h3-per- 



bolas. (A. X.S.) 69°35'±:. 



3. Unionville, Pa. On corundum. 72°. 



4. Unionville, Pa. " Corundellite." (J. M. Car- 



deza.) 12°. 



5. Horsjoberg, Sweden. (T. D. Rand.) 72°25'. 



6. Chester Co., Pa. " Margarite : " irregular, show- 



ing sometimes four hyperbolas. (A. N. S.) T2°30'. 



1. Haywood, N. C. "Altered from corundum." (F. 



A. Genth ) 74°. 



8. Unionville, Pa. Analyzed by Sharpless. (F. A. 



Genth.) U°10'. 



9. Unionville, Pa. Analyzed by Koenig. (F. A. 



Genth.) 74°15'. 



10. Newtown, Conn. With Cyanite. 74°24^ 



11. Newlin, Chester Co. "Margarite." (A. X. S.) 75°50'. 



It is evident that the minerals labelled Emerylite, Corundellite, 

 Margarite, etc., are all Damourite. 



Euphyllite. 



.1. Chester Co., Pa. (A. N. S.) 37°-40°. 



2. Unionville, Pa. "Original." (F. A. Genth.) 36°30'. 



A thicker piece in which the h^-perbolas were very dim, had an 

 angle of 45°±. 



This result is interesting, as the optical angle given by Silliman 



is 71°. 



Cookeite. 



Paris, Me. In small scales. 42°40'. 



17 



