THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



SUPPLEMENT to VOL. XXI. THIRD SERIES. 



LXXXV. On the Currents produced by the Actuation or In- 

 duction of instantaneous Electric Currents. By Professor 

 Stefano Marianini*. 



Currents produced by the Leyden-electrical Induction. 

 I. r T , HE facility with which, by means of the instruments 

 described in the preceding memoir f, the presence of 

 an instantaneous electric current in a metallic wire is detected, 

 encouraged me to seek indications also of the currents which 

 are derived from actuation or induction. 



I had surrounded a little cylinder of iron with two copper 

 wires covered with silk, which formed two parallel coils, and 

 having placed the cylinder upon the cap of a needle, I made 

 use of this apparatus as a re-electrometer, the delicacy of 

 which varied as I made the currents pass through one only 

 of the said coils, or through both at the same time, or joined 

 them so that the current had to pass through one first, and 

 then through the other; with these two parallel coils I made 

 my first attempt on the Leyden-electrical induction. Having 

 however taken that re-electrometric cylinder from the cap of 

 the needle, I connected one of the wires which surrounded it 

 with the ends of the coil of a re-electrometer, and the Leyden 

 jar being discharged upon the other wire, connecting its ex- 

 tremities with the two coatings, I have seen the needle of the 

 instrument deviate a similar number of degrees. 



* Translated from Memorie di Fisica Sperimentale scritte dal Professore 

 Stefano Marianini dopo it 1836. Anno Primo, 1837. Modena, 1838. 

 It was from the Anno Sccundo, 1838, of this work that the memoir by 

 the author inserted in Phil. Mag. S. 3. vol. xviii. p. 193 was translated. 

 Prof. Henry's researches on the induced currents of common electricity, 

 to which the memoir now given relates, will be found in Phil. Mag. S. 3. 

 vol. xvi. p. 551. The experiments of these philosophers were we believe 

 quite independent, and must have been nearly contemporaneous ; but the 

 priority is probably due to the Italian. — Edit. 



[f The preceding memoir here referred to relates to an instrument for 

 measuring the force both of instantaneous and non-instantaneous electric 

 currents. — Edit.] 



Phil. Mag. S. 3. No. 141 , §uppl. Vol. 21. 2 L 



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