368 



GALVANISM. 



countenanced the idea that very feeble electric energies would produce like 

 effects more slowly, in proportion to their weakness. To illustrate this by im- 

 mediate experiment, he tied a piece of clean bladder over one end of a glass 

 tube three quarters of an inch in diameter, and two inches long, and filled it 

 with water holding -3^ of its weight of salt in solution. Placing it on a shil- 

 ling, he connected the silver with the surface of the water by a wire of zinc, 

 and found that alkali was transmitted through the bladder to the silver by the 

 attraction of the negative electricity. Decisive indications of this were ob- 

 tained in five minutes. The efficacy of a power so feeble confirms the con- 

 jecture that similar agents may be instrumental in various animal secretions. 

 The blood, which is alkaline, supplies the bladder with matter in which acid 

 is strongly manifested ; while an excess of alkali, above that contained in the 

 blood, is manifested in bile. These effects would be explained by admitting a 

 permanent state of positive electricity in the kidneys, and negative electricity 

 in the liver. The coincidence of this view with the guesses of Napoleon, al- 

 ready mentioned, is curious and interesting.* 



The last great discovery of Davy directed the attention of the philosophers 

 of the continent to the same field of inquiry : and, much as had been expected 

 from the powers of the pile when its illustrious inventor expounded its nature 

 and properties to the assembled members of the Institute in 1801, it was now, 

 from day to day, rendered more evident that these powers were inadequately 

 estimated, and imperfectly understood, and that it was still destined to enrich 

 every branch of physical science by the development of new and unlooked-for 

 phenomena. Napoleon, in the magnificent spirit with which his encouragement 

 of the sciences was always manifested, had presented to the laboratory of the 

 Polytechnic School a Voltaic apparatus of immense magnitude and power. 

 With this instrument MM. Gay-Lussac and Thenard undertook an experimental 

 investigation of the powers of the pile, with the view of determining more 

 especially the influence which the number of the metallic elements, and the 

 nature of the liquid used to charge the pile, have on its chemical action. As- 

 suming, as a modulus of the chemical energy of the pile, the quantity of gas 

 evolved in the process of decomposition in a given time, they arrived at the 

 following conclusions: 1. The decomposing energy depends conjointly on 

 the conducting power of the liquid under decomposition, and on the nature of 

 that which is used to charge the pile. 2. It is greater when the pile is charged 

 with a mixture of acid and salt, than with salt alone. 3. The chemical 

 effects are proportional to the force of the acids by which it is put in action : 

 and, 4. They do not augment in the same ratio as the number of pairs of plates, 

 but very nearly in the ratio of the cube root of that number. 



That part of the electro-chemical theory of Davy in which the negative 

 character natural to certain physical elements, and the positive to others, is as- 

 sumed, was implicitly, if not expressly, included in the hypothesis of Grotthus. 

 Without such a supposition, the series of decompositions and recompositions 

 imagined by that philosopher could scarcely be admitted. The probable con- 

 nexion of chemical attractions with electric forces had been also conjectured 

 by Hube it his Traite de Physique, and Ritter obscurely expressed some ideas 

 of the same kind. Immediately before the commencement of Davy's re- 

 searches, Oersted, since so celebrated for his discoveries in electro-magnetism, ( 

 promulgated a theory,! in which he maintained that all the phenomena of chem- j 

 istry might be regarded as the result of two general forces common to all mat- i 

 ter, and that the same forces produced those effects which were rendered sen- 



* See Philosophical Magaziue, vol. xxxiii., p. 1088. 

 t Recherchea sur 1'Identite des Forces Chimiqo 

 1813. 



miques et Electriqucs. Traduit de PAllemand. 



