220 ANNUAL OP SCIENTIFIC DISCOVERY. 



that by contact they became excited. Thus, a particle of sulphur became 

 negative when placed in contact with a particle of copper, which last was 

 simultaneously rendered positive : the appli cation of heat intensified the 

 charge, until at a certain point the tension of the two electricities became 

 so high that they suddenly re- combined, carrying with them the molecules 

 of copper and sulphur, which were thus intimately mingled, whilst evolu- 

 tion of heat and light resulted from the combination of the two electrici- 

 ties. Ampere and Berzelius subsequently attempted to remove some of 

 the difficulties which were encountered in endeavoring to make Davy's 

 theory embrace all chemical phenomena. Ampere considered each element 

 to be permanently endowed with a definite amount of one or the other 

 electricity, being thus invariably either electro- positive or electro-negative 

 to an extent dependent upon the intensity of the charge. Such a naturally 

 charged molecule Ampere imagined to attract around it an atmosphere of 

 the opposite electricity of corresponding intensity, and that, when two 

 molecules oppositely charged were brought in contact, their atmospheres of 

 electricity united, giving rise to the heat and light of chemical combination, 

 whilst the original charge retained the attracting molecules in permanent 

 union. Although this theory elucidated some points which Davy's view 

 left unexplained, yet it would not be difficult to start several very serious 

 objections to it : the attempted removal of these gave rise to the electro- 

 chemical theory of Berzelius, who supposed that each element contained 

 the two electricities, but that the one was more powerfully developed than 

 the other, as in the case of a magnet, in which one pole, by being divided 

 was apparently weaker than the other. In chemical combination, Ber- 

 zelius imagined that one of the electricities of each element was dis- 

 charged, producing the heat and light of chemical action, whilst the other 

 was retained and served to hold the elements in combination. But 

 these attempts of Ampere and Berzelius to improve the theory of 

 Davy succeeded perhaps less in perfecting our views of electro- chemical 

 phenomena than in demonstrating the necessity for much further research 

 before these phenomena could be satisfactorily interpreted ; for these theo- 

 ries, in which different degrees of affinity were explained by differences in. 

 the degree of electrical excitement, have been proved radically defective by 

 the remarkable discovery of Prof. Faraday, that compounds, whose ele- 

 ments were united by the most dissimilar degrees of affinity, required 

 equal quantities of electric force for their decomposition. Such defects in 

 the attempts to account for chemical phenomena by electrical agency led 

 Dumas and other chemists to reject altogether the idea of electro-chemical 

 combination. Dumas regarded a chemical compound as a group of mole- 

 cules connected by a single force in a manner analogous to a planetary 

 system, and the chemical character of a compound as dependent upon the 

 position of the separate molecules, and not upon their individual character. 

 This view w'ould not have received such extensive adoption, nor been the 

 parent of such numerous and brilliant discoveries in the organic portion of 

 the science, if it had not contained a profound truth : nevertheless, the 



