Analysis of Chromic Iron Gre. 243 



Note. — On the evening of the meeting at which my investiga- 

 tions were presented to the Society, my friend, Dr. Bache of the 

 Girard College, gave an account of the investigations of Professor 

 Ettingshausen of Vienna, in reference to the improvement of the 

 magneto-electric machine, some of the results of which he had 

 witnessed at the University of Vienna about a year since. No 

 published account of these experiments has yet reached this 

 country, but it appears that Professor Ettingshausen had been 

 led to suspect the development of a current in the metal of 

 the keeper of the magneto-electric machine, which diminished 

 the effect of the current in the coil about the keeper, and hence 

 to separate the coil from the keeper by a ring of wood of some 

 thickness, and afterwards, to prevent entirely the circulation of 

 currents in the keeper, by dividing it into segments, and sepa- 

 rating them by a non-conducting material. I am not aware of 

 the result of this last device, nor whether the mechanical difficul- 

 ties in its execution were fully overcome. It gives me pleasure 

 to learn that the improvements, which I have merely suggested 

 as deductions from the principles of the interference of induced 

 currents (76,) should be in accordance with the experimental con- 

 clusions of the above named philosopher.* 



Art. II. — Analysis of a Chromic Iron Ore., first observed by 

 R. C. Taylor, Esq., at Mahobal, near Gibara, Island of Cuba; 

 by James C. Booth and M. Carey Lea. 



1. Description. — This mineral has a black color, and shining 

 metallic lustre, closely resembling Franklinite from New Jersey. 

 It is moderately brittle, exhibiting a chocolate brown streak, when 

 reduced to the finest powder. The mass consists of coarsely crys- 

 talline particles, aggregated together, with intervening talcose 

 matter, of a lighter color and softer texture than the chromic iron. 

 This crystalline structure is so evident, that triangular faces of 

 the octahedron are observable in a majority of the specimens. 



* The reader is referred to a subsequent paper by Prof. Henry, (containing im- 

 portant additions to the facts stated in this article,) of which an account is given 

 in the present Number, among the Proceedings of Am. Phil. Soc, under date ot 

 October 18, 1839.— £d5. 



