New Magnetic Electrical Machine. 163 



platina crucible and ignited, whereby it was converted into car- 

 bonate of strontita. Tiie results obtained were these : 



Sulphate of baryta, . . . . 65.55 

 Carbonate of strontita, . . . 22-30 



Carbonate of lime, . . . . 12.15 

 So close is the approximation of these 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 species will therefore be 2 Ba S -|- 

 SrC+CaC. 



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 crystallized strontianite. 



Charleston, (S. C.) Feb. 21, 1838. 



Art. XIV. — New Magnetic Electrical Machine of great power, 

 with two parallel horse-shoe magnets, and tvjo straight rotating 

 armatures, affording each, in an entire revolution, a constant 

 current in the same direction ; by Chas. G. Page, M. D. 



a a. Fig. 1. represent the two straight armatures, covered each 

 with eight hundred feet of No. 20 insulated copper wire ; h h, the 

 two poles of one of the magnetic batteries. The other horse- 

 shoe magnet, exactly parallel and opposite to this, is screened 

 from view by the frame work of the machine. Its poles are the 

 reverse of the former, c, 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 c is held 



