New Magnetic Electrical Machine. 163 
platina crucible and ignited, whereby it was converted into ear- 
bonate of strontita. The results obtained were these : 
Sulphate of baryta, . : : : 65.55 
Carbonate of strontita, : ‘ ‘ 22.30 
Carbonate of lime, : k : 12.15 
_ So close is the approximation of thei numbers to what would 
be afforded by a definite compound of two atoms of sulphate of 
baryta, one atom of carbonate of strontita, and one atom of car- 
bonate of lime, that we are fully entitled to consider this as the 
constitution of the mineral. The analysis, corrected by the atomic 
theory on such a supposition, will give the following view, as the 
more exact composition of the substance under consideration : 
Sulphate of baryta, . : 65.22 
Carbonate of strontita, : : . 20.61 
Carbonate of lime, —.. 14.27 
The chemical sign of the isdeios will therefore be 2BaS+ 
Sr 6+Ga 6. 
The trivial name alludes to the three bases entering into its 
composition. In the natural system, it falls to the genus Hal- 
baryte, and I denominate it, specifically, Polyhalous, from the 
number of salts it contains. 
It is undoubtedly a very common mineral in the region from 
whence my specimens were sent; and occurs in a secondary 
limestone, associated with exabalizeed strontianite. 
Charleston, (S. C.) Feb. 21, 1838. 
Art. XIV.—New Magnetic Electrical Machine of great power, 
with two parallel horse-shoe magnets, and two straight rotating 
armatures, affording each, in an entire revolution, a constant 
_ current in the same direction ; by Cuas. G. Pace, M. D. 
a, Fig. 1. represent the two straight armatures, covered each 
mae eight hundred feet of No. 20 insulated copper wire ; 5 4, the 
two poles of one of the magnetic batteries. The other horse- 
shoe magnet, exactly parallel and opposite to this, is screened 
fron :S 
by the frame work of the machine. Its poles are the 
reverse of the former. ¢, is a strong brass strap, for securing the 
armatures to the shaft. At the other extremity of the armatures, 
is a similar one, fastened tight to the axis. The strap cis held 
