2S% M. Marianini on an analogy 



In place of a pair of plates communicating with the wire 

 of the galvanometer, I substituted another much more weak, 

 formed like the preceding of two plates, equal in dimen- 

 sions to the first, one of tvn,, and the other of brass. I with- 

 drew the exciting wire which put the two other plates in com- 

 munication. As in the preceding experiment, I tried the elec- 

 tro-magnetic effect. I obtained a deviation of about three 

 degrees. 1 restored the exciting wire to the zinc and copper 

 plates, and renewed the experiment. The effect was the same. 



The rtsults obtained from other similar experiments, in which 

 oppposite electric currents act, produced by two elementary 

 Voltaic apparatuses, either of equal or different power, by 

 employing fluids endowed with a greater or less conduct- 

 ing faculty, present the same fact. With the intention of 

 crossing two currents, one produced by an elementary appara- 

 tus, and the other by a compound apparatus, I removed from 

 the cube the two plates of copper and zinc, put in communica- 

 tion by means of the exciting wire. I substituted two similar 

 plates of brass. I made one communicate with the positive 

 pole, and the other with the negative pole of an apparatus a 

 couronne de tasses, of twenty pairs, in each of which the active 

 surface was about six centimetres square. The elementary 

 battery in communication with the galvanometer, was formed 

 of two plates, the one of zinc, the other of lead, adapted to 

 two opposite faces of the cube, in the manner already indicated. 

 Having put the electric currents in motion, by plunging the pro- 

 jecting extremity of the four plates into salt water, the needle 

 of the galvanometer deviated ten degrees. I suppressed the 

 communication between the brass and the poles of the appa- 

 ratus a couronne de tasses. I restored, as usual, the commu- 

 nication with the pair of lead and zinc with the fluid ; the de- 

 viation was still the same. 



Instead of the compound battery of the experiment which I 

 have described, I substituted another, also twenty pairs, whose 

 plates had a surface nearly quadruple. I repeated the experi- 

 ment without changing the elementary battery, and I again 

 obtained the same result. 



I raised the compound battery to 100 pairs, and in ano- 

 ther experiment to 200 ; and nevertheless, in causing the weak 



