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LXIV. Intelligence and Miscellaneous Articles. 



ON VARIOUS CASES OF INTERMISSION OF THE VOLTAIC CURRENT. 

 BY A. CAZIN. 



TN pursuing the researches which I have undertaken on the heat 

 -■- of electromagnets, I have had occasion to observe several cases 

 °* intermission of the voltaic current, which, I believe, have not 

 Jet been brought into notice. 



Experiment 1. — A voltaic circuit is formed of 20 average Bun sen 

 elements and a coil of 960 turns containing an iron tube 8 centims. 

 in diameter and about 1 millim. thick. It can be closed or opened 

 at will by means of a platinum point and a layer of mercury, which 

 communicate respectively with each of the rheophores. 



When the platinum is not in contact with the mercury, and they 

 are put into communication with the armatures of a condenser with 

 a glass plate (armed surface 3 square metres), a continued rustling 

 is heard in the iron nucleus. The same effect is produced when, 

 the condenser being omitted, a layer of alcohol is interposed between 

 the mercury and the platinum point. The noise ceases when the 

 alcohol is removed so that the platinum and mercury are sepa- 

 rated by a layer of air, and also when the point is dipped into the 

 mercury. 



These facts indicate that the current passes through the glass in 

 the first case, and through the alcohol in the second, and that its 

 passage is intermittent. The nucleus of iron undergoes a rapid 

 succession of alternate magnetizations and demagnetizations ; and 

 each demagnetization occasions a faint sound in the nucleus. The 

 rapid succession of these noises constitutes the rustling which is 

 heard. 



When the iron nucleus resounds, a galvanometer indicates only 

 a continuous current. In fact it cannot indicate any thing else 

 when the intermissions are very close to one another. 



I think that the cause of the intermission is the condensing action 

 of the glass and the alcohol ; when the two faces of the insulating 

 body, which are in contact with the rheophores, have acquired a 

 certain electric potential, a discharge takes place through the insu- 

 lating layer; the magnetism of the nucleus increases during the 

 charging of the condenser, and diminishes during its discharge ; 

 the noise is produced during the diminution of the magnetism; 

 after each discharge a certain time elapses before the condenser is 

 recharged ; and the same phenomenon is reproduced indefinitely. 



It is readily ascertained that the nucleus resounds during the di- 

 minution of its magnetism : we have only to immerse the platinum 

 point in the mercury, and then withdraw it ; at the moment when 

 the spark issues at the point of interruption, a relatively intense 

 sound is heard in the nucleus. It is solely the rupture of the cir- 

 Phil. Mag. S, 4. Vol. 46. No. 308. Dec. 1873. 2 K 



