GALVANISM. 



wur.l current, and so on : the downward current being negative, and the up- 

 ward positive from the upper surface of each copper disk, and the upp<>r 

 current being negative and the downward positive from the lower surface of 

 such disk. It is evident, therefore, that the downward currents would he al- 

 ternately positive and negative; and the same would be the case with, the 

 upward currents. Now, since the surfaces of contact of the metals would be 

 equal, these currents would have equal intensities, and accordingly each posi- 

 . live current would neutralize each negative current having the same direction. 

 ( The result would be, that if the lowest and highest disk of the pile were of the 

 I same metal, all the currents neutralizing each other, the pile would evolve no 

 electricity whatever; and if they were of different metals, all the downward 

 currents, except one, would neutralize each other, and that one would be posi- 

 live. The effect of the pile would therefore be the same as if it consisted of ; 

 only two disks, one of copper, and the other of zinc. 



Volta therefore saw the necessity of adopting some expedient by which all ' 

 the currents in the same direction should be of the same kind ; so that, for ex- 2 

 ample, all the descending currents should be negative, and all the ascending , 

 currents positive. If this could be accomplished, the current issuing from the ; 

 bottom of the pile would be a negative current as many times more intense 

 than one proceeding from a single pair of disks as there were surfaces of con- { 

 tact supplying currents, and the same would be true of the positive current '; 

 issuing from the top of the pile. ( 



To effect this, it was necessary to destroy the Galvanic action at all those sur- | 

 faces from which descending positive and ascending negative currents would pro- < 

 ceed ; that is, the lower surfaces of the copper disks and the upper surfaces of the J 

 zinc disks. But while this was effected, it was also essential thai the progress t 

 of the descending negative an.d ascending positive currents should still be un- 

 interrupted. The interposition of any substance which would have no sensible 

 Galvanic action on either of the metals between each disk of copper and the 

 disk of zinc immediately below it would attain one of these ends, since the 

 action of all the surfaces in which ascending negative or descending positive 

 currents could originate would thus be prevented. But in order to allow the 

 free progress of the remaining currents in each direction, such substance must 

 be a suiliciently free conductor of electricity. Volta selected, as the fittest 

 means of fulfilling these conditions, disks of wet cloth. They would be free 

 from any sensible Galvanic action on the metal, and their moisture would give j 

 them sufficient conducting power. 



Having discovered the principles by which this species of electricity can be \ 

 accumulated in quantity and strong currents obtained, he varied its form, and J 

 contrived the apparatus which is known by the name of La Couronne de Tosses. 

 This arrangement, which Volta himself most commonly used in his experi- 

 ments, consisted of a circle of cups filled with warm water, or a solution of 

 sea-salt. He immersed in each cup a plate of zinc and one of silver, not in 

 contact, and then established a metallic communication by means of wire be- 

 tween the zinc of one cup and the silver of the adjacent one. The positive 

 fluid was found to proceed from the extreme zinc plate, and the negative from 

 the extreme silver one, and a continuous current was obtained by connecting 

 these by any conductors of electricity. 



Profoundly impressed with the importance of the results likely to arise from 

 . the application of the powers of the pile in physical inquiries, and doubtless 

 \ animated by the desire for which he was honorably distinguished to extend all 

 ( possible encouragement and advantage to those engaged in the natural sciences, 

 ( Napoleon, then first consul, and surrounded by the splendor of his southern 

 > triumphs, invited Volta to visit Paris ; and there, at the Institute, before the 



