EULOGY OX ALEXANDER VOLTA. 131 



trometer, when the straics instantly diverge. It was proved, too, by the 

 same means, that the two metals are in opposite states of electricity ; 

 that the zinc is positive and the copper negative. By i-epeating several 

 times the contact of the two disks, their separation from, and contact 

 with, the condenser in turns, Yolta succeeded, as with an ordinary 

 machine, in producing bright sparks. After these experiments, the the- 

 ory of galvanic phenomena was fully established. 



The production of electricity by the mere contact of dissimilar metals 

 was ranked among the most important and best-established facts of the 

 physical sciences. If, after this, there was anything left to be desired, 

 it was an easy means of increasing this kind of electricity. Such means ' 

 are now known to all experimentalists, and it is to Volta's genius that 

 they are indebted for them. 



At the beginning of the year 1800, (the date of so wonderful a dis- 

 covery could not be passed over in silence,) in consequence of some the- 

 oretical views, the illustrious professor contrived a high column, con- 

 sisting of pairs of copper and zinc, each pair being separated from the 

 adjoining ones by pieces of moist cloth, scrupulous care being taken not 

 to invert this order. But, a priori, what was to be exi)ected from such 

 a combination ? Well, I do not hesitate to say that this apparently inert 

 mass, this singular assemblage, this pile of so many pairs of dissimilar 

 metals separated by a small quantity of liquid, is, with respect to the 

 singularity of its effects, the most marvelous instrument ever invented 

 by man, without even excepting the telescope and steam-engine. 



1 am quite sure I shall escape all reproach of. exaggeration if, in the 

 enumeration I am about to make of the properties of Volta's apparatus, 

 I shall be allovred to cite both those properties discovered by this scien- 

 tist and those whose discoveries are due to his successors. 



Every one will remark in the short description I have given of the 

 composition of the pile, that its two extremities are necessarily dissim- 

 ilar ; that if zinc be at the base copper must be at the top, and conversely. 

 These two extremities are called the 2^0 J es. 



Let us now suppose two wires attached to the opposite poles, copper 

 and zinc, of a voltaic pile ; the apparatus, so arranged, being ready for 

 the ditferent experiments I wish to describe. 



If one of the wires alone be grasped no sensation is felt; but the 

 moment both are touched a violent shock is experienced. This, as is 

 evident, is nothing more than the phenomenon of the famous Leyden jar, 

 which, in 174G, excited in so high a degree the wonder of all Europe. But 

 the jar could only be used once; after each shock it being necessary to 

 recharge it to repeat the experiment; the pile, on the contrary, supplying 

 a thoasiind successive shocks. It may be compared consequently with 

 regard to the nature of its effects to the Leyden jar, with this additional 

 proviso, that after ea(;h discharge it immediately retuins itself to its 

 original condition. 



If the wire from the zinc pole is placed on the end of the tongue, and 



