EULOGY ON ALEXANDER VOLTA. 135 



of a paste of flour and milk. The disks, of course, being piled up in 

 the same order, their dissimilar surfaces, or, I should say, the tin and 

 manganese surfcices of two contiguous pairs, are in contact. Here, then, 

 we have the two metallic elements, of different kinds, which constitute 

 what were called j;af>s in the description of Volta's first pile. With 

 regard to the intermediary conducting liquid, those who object to apply 

 the name of dry piles to those of Zamboni will discover the cause of the 

 humidity in the hygrometrical property always preserved by the paper 

 placed between each plate of tin and layer of powdered manganese. 



The wonderful results obtained by physicists by means of voltaic 

 piles are owing undoubtedly, in a measure, to the remarkable improve- 

 ments introduced by them in the construction of these apparatus; but 

 the chief cause is the enormous dimensions they have succeeded in giv- 

 ing them. The metallic pairs in Volta's first i)iles were scarcely larger 

 than a five-franc piece. In M. Children's pile each element had a sur- 

 face of thirty-two English square feet. Volta, as well as can be dis- 

 covered from the analysis I have just given of his views, accounted for 

 the development of electricity by the mere contact of the two metals of 

 diiiereut natures constituting each pair. The liquid between them 

 simply performed the office of conductor. This theory, called the 

 theory of contact, was attacked at an early date by Fabroni, one of 

 Volta's countrymen. He supposed that the oxidation of the metallic 

 surfaces of the pairs, induced by the liquid touching them, was the 

 principal cause of the phenomena of the pile. Wollaston, some time 

 after, developed this same idea with his usual sagacity. Davy sup- 

 ported it, in his turn, by ingenious experiments; and finally, to-day, 

 this chemical theory of the pile prevails almost unanimously among 

 physicists. 



I hazarded the opinion, just now, with some timidity, that the pile 

 was the most marvellous instrument ever invented by the human mind. 

 If, in the enumeration you have just heard of its difi'erent properties, 

 my voice has not been altogether without power, I might now repeat 

 my first assertion and consider it thoroughly established. 



According to some biographers, Volta's brain, exhausted by long- 

 continued work, and especially by the production of the pile, refused to 

 furnish anything more. Others saw, in an obstinate silence of nearly 

 thirty years, only the effects of a puerile fear, which the illustrious 

 physicist had not the courage to overcome. He feared, it is said, that 

 on comparing his more recent researches with those on electricity by 

 contact, the public would immediately conclude that his mind was 

 weakened. These two explanations are doubtless very ingenious, but 

 they labor under the signal defe(;t of being entirely superfluous. For 

 the pile w^as invented in 1800, and two ingenious essays, one on the 

 "Phenomenon of Hail," (Le phenomene de la grele,) and the other on 

 the "Periodicity of storms and the cold accompanying them," (Ija 

 periodicite des orages et le froid qui les accompagne,) were not i)ul)- 

 lished until six and seventeen vears after. 



