DOUBLE-CURRENT MAGNETO-FARADIC APPARATUS. 285 



A. — In its pvactical application. 

 It has been shown that it possesses — 1. Two currents, the one an 

 extra current, the other an induced current, furnished by two 

 superposed coils, each having special properties. 2. Intermissions 

 tliat are slow or rapid, at the pleasure of the operator. 3. Currents 

 that are either alternate or in the same direction. 4. An exact 

 and truly medical graduation, which measures the largest and the 

 smallest doses with equal exactness, thanks to a combination of 

 graduator tubes with the mechanism which I have called the 

 moderator of the currents. 



B. — Under a plujsical aspect. 



(a). My apparatus shows that the metallic cylinders are in- 

 duced by the coils as much in a magneto-faradic as in a volta- 

 fai'adic insti'ument, which has been disputed by the celebrated 

 physicist of Vienna, Herr Dove ; and, further, that the reciprocal 

 influence of the coils and the cylinders is only exerted in the parts 

 of the coils that are covered by the cylinders, whence it follows 

 that the action of the latter occurs in a progressive manner, and in 

 arithmetical proportion. 



When, from lapse of time and by employment, the magnet 

 becomes weakened, its power may be restored without dismounting 

 the apparatus. The turns around the arms of the magnet of the 

 thick wire, which supplies the current of the primary coil, enable 

 us to restore to the magnet its original power, by passing the 

 current of a voltaic battery through the spirals formed by the 

 wire. The proceeding is thus accomplished : — the armature is 

 placed in contact with the magnet, and then the current from 

 a battery of eight or ten of Bunsen's elements is made to pass 

 through the primary coil, by placing the positive pole upon that 

 one of the springs of the intermissions which corresponds to the 

 north pole of the magnet, while the negative pole is brought into 

 contact with the spring to the opposite side. While the voltaic 

 current passes through the primary coil, the magnet gains con- 

 siderably in power (it will support a weight of forty kilogrammes), 

 and, when the current is interrupted, although the magnet loses a 

 great part of the force which it received from the voltaic current, 

 it yet preserves the maximum of magnetic intensity which it 

 received at the hands of the manufacturer. If the experiment be 

 repeated, with the poles of the battery current counterchanged, 

 the magnet is almost entirely demagnetised, but can be imme- 

 diately restored to its original power by acting as on the first 

 occasion. I have often repeated these experiments, and can at 

 any time magnetize or demagnetize my apparatus. 



