498 Prof. Marianini on the Currents produced by the 



I suspected that the deviations obtained in this and other 

 similar experiments might proceed, not from induction occa- 

 sioned immediately by the instantaneous current of the jar, 

 but from magneto-electric induction, produced by the tem- 

 porary magnetization of the iron cylinder surrounded by the 

 two coils. However, the cylinder being taken away, and a small 

 glass rod substituted, the same phoenomenon took place. 



II. As I made use of a jar highly charged and the wires 

 presented some metallic points uncovered, it was probable that 

 part of the current might make itself a passage from one wire 

 to the other, and that the effects observed might proceed from 

 a real current transferred into the wire of the re-electrometer, 

 and not from a movement of the electricity of the wire itself 

 excited by the current which was mafle to pass near it. 



A coil of large uncovered copper wire was enveloped in 

 four layers of silk; I then inclosed it in sixty coils of fine cop- 

 per wire covered with silk; with this apparatus I made many 

 trials, and I observed, — 1st, that with the small jar (having 

 little more than half a square decimeter of coating) the needle 

 always deviated from the part, whence it also deviated when 

 I discharged the jar itself, and in the same manner upon the 

 wire of the re-electrometer, as much as when I discharged it 

 upon the coil of uncovered copper wire (keeping the fine wire 

 in communication with that of the re- electrometer), as when 

 I put the coil of uncovered copper wire in communication with 

 this, and discharged the jar upon the fine wire ; 2nd, that with 

 the large jars (nineteen square decimeters of coating), if they 

 were highly charged, the needle deviated in the same manner 

 as when they were discharged upon the re-electrometric wire ; 

 but if they were slightly charged the deviation was different. 



III. I suspected that the copper coil might exhibit induc- 

 tion in proportion as it was itself magnetized, and that thence 

 the electricity might act instantaneously, as a magnet does 

 when introduced into a coil [or helix]. I wished then to 

 prove whether the copper might be magnetized by the dis- 

 charged electricities. 



Having covered a copper cylinder with silk I inclosed it in a 

 coil, as I was accustomed to do with the iron cylinders. Having 

 then placed it upon a magnetized needle, I caused some slight 

 discharges of Leyden jars to pass through the coil itself, both 

 "weak and strong ; but I never had the smallest indication of 

 magnetism in the copper. 



IV. Having taken the said copper cylinder from the needle, 

 I attached to its extremities two metallic wires, and these I 

 connected with the ends of the wire of a re-electrometer ; then 

 discharging the Leyden jar by means of the coil which sur-. 



