506 Prof. Marianini on the Currents 'produced by the 



small Leyden jars not having more than a square decimeter 

 of exterior coating, and with each of these I observed that the 

 re-electrometric deviations indicated that the induced currents 

 were directly contrary to the actuating. If, for example, the 

 discharge of the jar in the direction of the band, or of the ac- 

 tuating wire parallel to the actuated, proceeded from right to 

 left ; in the band, or in the neighbouring actuated wire, the 

 induced current passed from left to right: and, seeing in this 

 an analogy to the volta-electric induction of Faraday*, I felt 

 more and more persuaded that the phenomena observed pro- 

 ceeded really from Leyden-electrical induction. But I quickly 

 began to doubt it when I applied myself to confirm, with the 

 large jars, the results obtained with the small; for, on using 

 these, the deviations of theinstrument indicated that the induced 

 current, and that which caused it, proceeded in the same di- 

 rection in the two parallel and neighbouring conductors. 



I doubted whether, from the quantity of electricity being 

 different in proportion to the tension, a different distance 

 might not be required between the actuating and actuated 

 conductors, in order to produce the direct current in a given 

 manner in the latter ; and whether in such phaenomena there 

 might not be something analogous to the inversions of mag- 

 netization observed by Savary in steel needles, placed at dif- 

 ferent distances from the conductors through which he made 

 the discharges of great electrical batteries to pass. But what- 

 ever was the distance between the actuating and actuated 

 conductors, which I have varied from one millimeter to a 

 hundred, the inductions of the smaller jars were always di- 

 rectly opposite to those of the larger. 



I turned my attention to the construction of the little jars, 

 and I observed that they had the internal coatings formed of 

 cuttings of tin-foil and silvered paper ; I conjectured that the 

 difference of effects in the large and small jars might depend 

 on that discontinuity of the coating; and I long held this 

 opinion, from having observed that two large jars, having the 

 external coatings formed of so many small squares of tin-foil, 

 of about one centimeter square, attached to the glass, so that 

 between them might be a band of bare glass, of two or three 

 millimeters broad, acted in precisely the same manner as the 

 said small jars. But finally, having had some small jars pre- 

 pared with internal and external coatings adhering to the 

 glass, as in the large ones, I saw that they produced the cur- 

 rents by induction in the same direction as the large and small 

 jars with discontinuous coatings ; whence I was convinced that 



[* See Faraday'sJExperimental Researches in Electricity (26.), or Phil. 

 Mag., Second Series, vol. xi. p. 300. — Edit.] 



