Current by the Rotation of a Magnet. 145 



magnet ; for instance in the decomposition of water, the oxygen was. 



disengaged at first in one tube and the hydrogen in the other; at the 



next semi-revolution the hydrogen was evolved in the first, and the 



oxygen in the second ; of course the two gases were mingled in each 

 tube. 



To obtain them separate, M. Pixii attached to this apparatus the 

 bascule, which M. Ampere invented to change the currents in his 

 electro-dynamic experiments. The bascule in this new apparatus 

 supports a rod, upon which rests a semi-circle attached to the mag- 

 net, and which holds the bascule depressed on one side during a semi- 

 revolution of the magnet, and during the next semi-revolution, the 

 bascule becomes free, and is depressed on the other side by a spring. 



On the first trial of this arrangement, the bascule plunged alter- 

 nately into the troughs filled with mercury, like the bascules of M. 

 Ampere ; but when the movement became rapid, the mercury was so 

 powerfully agitated as to leap out of the troughs. 



M. Pixii obviated this inconvenience by substituting, for the mer- 

 cury, small plates of copper, amalgamated upon the surface to render 

 more perfect their contact with the points of the bascules which strHce 

 them alternately. By this ingenious arrangement, the electric cur- 

 rent, in the part of the conducting wire beyond the bascule, takes 

 place always in the same direction ; whence it follows that oxygen 

 alone is disengaged in one of the tubes and hydrogen in the other, 

 and the two gases are obtained separate. 



It is worthy of remark, that all the other circumstances remaining 

 the same, the decomposition of the water becomes more rapid in 

 this case than when the electric current is alternating ; which is, prob- 

 ably, owing to die molecules of the water being previously and prop- 

 erly disposed for decomposition ; whereas, when the current is alter- 

 nating, it is necessary that they turn themselves at each semi-revolu- 

 tion of the magnet. 



As to the sparks and shocks, and the action upon the leaves of the 

 electroscope, they are alike produced by a current in the same di- 

 rection and the alternating current, since all these phenomena result 

 from an instantaneous action of electricity developed in the conduct- 

 ing wire, sufficient to charge the condenser as far as the tension of 

 the current permits. 



Prof. Emmet had not seen the articles, on electro magnetism, contained in the 

 nine last Nos. of the Ann. de Chim. et de Phys. to Sept. 1332, inclusive, when the 

 proof of his paper passed through his hands.— Ed. 



Vol. XXIV.— No. 1. 19 



