Prof. ]\Iiller o>i some Crystallized Ftirnace Products. 293 



Oxide of Chrome. 



Oxide of chrome obtained in tbe laboratory by Wohlcr and 

 Ebclmcn, and found by Blake as a furnace product, occurs in 

 crystals belonging to tbe rbonibobedral system, isomorphous with 

 h?ematite,and exhibiting tbe forms 1 1 1, 1 1 0, 1 00, 1 1, 3 1 1 

 (Gurit, Uebersiclit der pijrogenneten klbistUchen Minerulien, p. 48). 

 Some small crystals formed during a metallurgical process carried 

 OQ in tbe United States, were lately given to me for examination 

 by Dr. Percy. One of these, about 1 millim. loug,0-5 millim. wide, 

 audO'l millim. thick, is a combination of the forms 111, 110, 



1 0, 3 1 1, A crystal of about half the size of the preceding 

 is a combination of the forms 111, 1 T 0, 10 0, I 2 2, 3 1 1, 



2 01. A third crystal, about 0'33 millim. long, 0'2 millim. 

 wide, and 0'06 millim. thick, is a combination of the forms 

 111, lIO, 10 0, 113 4, 10 4 3. In the first crystal the 

 observed value of 1 0, 1 was 94° 10'-3. In the second the 

 observed value of 1 0, 1 was 94° 4'-9, and that of 1 2 2, 

 100 was 115°28'-4. The celebrated Brooke collection, for 

 which the ]\lineralogical Aluseum of this University is indebted 

 to the liberality of Charles Brooke, Esq., contains a crystal ob- 

 tained by Wohler's method, which, as usual in crystals thus 

 obtained, is a twin having a face of the form 10 for the twin 

 face. The individuals of which it is composed arc combinations 



