GALVANISM. 



sible in electric attractions and repulsions. This work, however, was exclu- 

 sively of a speculative kind, unsupported by any experiments which could give 

 force or validity to the theory it proposed. 



The electro-chemical theory of Davy was the first which had ever professed 

 to be based on clear and wuii-ascertained facts. It was laid down as a funda- 

 mental principle in this theory, that when two bodies, the particles of which 

 are in opposite electrical states, and sufficiently exalted to enable their electric 

 attraction to overcome the force of aggregation of their particles, ar* brought 

 into contact, they will unite, and heat and light will be developed by n com- 

 bination of the two electric fluids. When the combination is effected, all signs 

 of electricity cease, as would necessarily ensue from the union of the two 

 fluids, but by what power the aggregation of the new compound was main- 

 tained was not explained. 



Berzelius and Ampere, who, of all the philosophers of the continent, evinced 

 most justice and candor in their appreciation of Davy's merit, took up the 

 electro-chemical theory, which was not pursued through its consequences by 

 its author, owing probably to the natural disposition of his mind to investigate 

 new facts rather than discuss the merits of hypotheses. Berzelius assumed 

 that the constituent atoms of bodies were not only naturally electrical, as Davy 

 had maintained, but that they possessed electric polarity, and that the intensi- 

 fies of their poles are unequal. He investigated, in the tirst place, the two > 

 ' uestions, How electricity exists in bodies? and, How it is that some bodies 

 are naturally negative, and others sometimes positive and sometimes negative ? 



A body never becomes electric, without manifesting the two opposite electric 

 principles, either in different parts of it, or in the sphere of its action ; when 

 the two electricities appear separately in a continuous body, they are always 

 found on opposite sides. The tourmaline and some other crystals offer an ex- 

 ample of this. But, since the parts of a body possess the same properties as 

 the body itself, it is necessary to admit that bodies are composed of atoms, 

 each of which has an electric polarity, and its poles have unequal intensities. 

 On this polarity depend the chemical phenomena, and its unequal intensity is 

 the cause of the different force exercised by their affinities. Bodies are ac- 

 cordingly electro-positive or electro-negative in combining, according as the 

 influence of the one or other of their atomic poles predominates. 



The degree of polarity in this theory is influenced by the temperature. 

 Thus many substances at common temperatures manifest but feeble electric 

 polarity, which, at a red-heat, show a very strong one. 



No combination can be effected unless thr polarized molecules of one or 

 both of the combining bodies have free mobility among each other, each being 

 at liberty to turn on its own centre in any direction, so that the particles may 

 present toward each other their contrary poles in obedience to their electric 

 attraction. This condition renders it necessary that one or both of the com- 

 bining bodies be in the fluid state. 



The vulnerable point of this theory was found in the phenomena of aggre- 

 gation. In what manner can the electric forces which it assumes produce the 

 hardness, brittleness, ductility, and tenacity, of different species of solids, the 

 viscidity of liquids, or the elasticity of gases ? 



Berzelius admits that these effects are not explicable by this hypothesis. 

 M. Ampere attempted to solve this question,* by assuming that the atoms of 

 bodies possessing each its proper electricity, in virtue of which they are ur.ited 

 in combinations in the same manner as two leaves of paper oppositely electri- 

 fied adhere to each other, also act by their electricity on the electricity of the 



'Journal de Physique, 1821. 



