Intelligence and Miscellaneous Articles. 441 



after a certain time, becoming less inconstant, and may be compen- 

 sated by means of a shunt containing a standard element, and the 

 galvanometer brought back to zero. If, then, the electromagnet is 

 excited vnih a Aery powerful current, a permanent deflexion, is 

 observed in the galvanometer ; if the magnetizing current is opened, 

 especially if this be done with a certain rapidity, the galvanometer 

 returns to zero*. 



I shall publish as soon as possible the results of a special inves- 

 tigation of this phenomenon ; for the present I restrict myself to 

 indicating in this note the most interesting results hitherto ob- 

 served. 



The current produced by magnetism, and which I shall call gal- 

 vayiomar/netic, is independent of the direction and of the intensity 

 of the primary current. Whatever be the direction of this, the 

 galvanomagnetic current, through the bismuth fields hitherto ex- 

 amined, is in the galvanometer from the magnetized bismuth to the 

 nonmagnetized one, and in the liquid from the nonmagnetic metal 

 to the magnetic one. 



While the primary current varies greatly in intensity and also 

 in direction, the galvanomagnetic current maintains in general an 

 almost constant intensity, and also remains unchanged when the 

 primitive current passes through zero in changing its sign. 



The intensity of the galvanomagnetic current depends greatly 

 on the state of the surface of the bismuth, and to have regular 

 results it is necessary to carefully polish the bismuth wires. To 

 give an idea of the magnitude of the electromotive force of the gal- 

 vanomagnetic current, I may mention that in the various experiments 

 hitherto made under good conditions with various wires, and in 

 various modifications, it has varied from y^r^o ^° 2^0 o" ^^ ^ Daniell, 

 the magnetic field being produced by a Faraday's apparatus of 

 mean size excited by a current of 8 to 12 amperes, and with conical 

 poles 7 millim apart. 



With a less powerful magnetizing current the results are smaller ; 

 \\-ith a circuit of two amperes the galvanomagnetic current is scarcely 

 appreciable. 



The direction of the galvanomagnetic current is independent of 

 the direction of the field ; its intensity has sometimes varied a 

 little when the field was reversed and sometimes remained con- 

 stant. 



This research was carried out in the Physical Institution of the 

 Koman University with the means placed at my disposal. — Rendi- 

 conti della R. Accademia del Lincei, January 6, 1889. 



* It is unnecessary to say that the galvanometer was so distant from 

 the electromagnet that it was out of the sphere of its influence. It was 

 also ascertained that if the circuit was closed when the tube and the 

 bismuth wires were excluded, the magnetic field did not produce any 

 cmrent. 



Phil. Mag. S. 5. Yol. 27. No. 168. May 1889. 2 G 



