Analysis of Chromic Iron Ore. 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 w 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.* 
Arr. I].—Analysis of a Chromic Iron Ore, first observed by 
R.C. Taytor, Esq., at Mahobal, near Gibara, Island of Cuba; 
by James C. Boorn 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. 
reader is referred to a cubsequent paper by Prof. Henry, (containing im- 
portant additions to the pence in this article ,yof which an account is given 
in the present Number, among of Am. Phil. ry under date of 
October 18, 1839.—Eds. 
