360 GALVANISM. 



chemical combination. In the theory proposed by Davy it is, moreover, viewed 

 as being otherwise instrumental in giving play to the affinities. That heat is 

 one of the means of exalting the electrical energy of bodies, is apparent from 

 its known effects on glass and tourmaline. But in the experiments now noticed, 

 more distinct and specific evidence is adduced of its direct electric agency. 

 A plate of sulphur was placed on an insulated plate of copper, and the temper- 

 ature of the bodies being gradually elevated, their electrical state was examined 

 at different stages of the experiment. At 56 the electricity was scarcely 

 sensible to a condensing electrometer; at 100 it affected the gold leaves 

 without the condenser, and increased in a still higher degree as the sulphur 

 approached its point of fusion. 



Since heat, therefore, increases the natural electrical energy of the com- 

 ponent particles of bodies, it gives them, according to the theory of Davy, 

 an increased tendency to combine chemically, if those energies be con- 

 trary. 



Hence, when a spark, or other sufficient source of heat, is introduced into a 

 mixture of oxygen and hydrogen, it renders the contiguous molecules of oxy- 

 gen more strongly negative, and those of hydrogen more strongly positive. In 

 virtue of their increased mutual attraction they combine, and in combining heat 

 is evolved, which affecting other contiguous molecules causes further combina- 

 tion, and so on until the combination is complete. 



According to this hypothesis, combination should be rapid, heat and light 

 intense, and the compound neutral in its properties, whenever the electrical 

 energies of the two constituents are strong and perfectly equal. But when 

 they are very unequal, the effects would be less vivid, and the compound would 

 have the acid or alkaline character, according as the energy of the negative or 

 positive constituent is in excess. 



The production of water from the combination of oxygen and hydrogen, and 

 the formation of the metallic salts, are adduced as examples of strong and 

 equal energies. Like examples are afforded by the nitrate, sulphate, and chlo- 

 rate of potash and muriate of lime, which severally, when touched upon a 

 large surface by plates of copper and zinc, gave no electrical signs. Subcar- 

 bonate of soda and borax, on the contrary, gave a slight negative charge, and 

 alum and superphosphate of lime a feeble positive charge. 



The next section of this remarkable paper professes to explain the author's 

 views of the " mode of action" of the Voltaic pile. The absence of that per- 

 spicuous style of expression which so generally characterizes his writings, in 

 this case justifies the supposition that his own perceptions on the subject of the 

 theory he proposes were not at the time very clear or well defined. It must 

 be recollected that Volta maintained that the source of electricity in the pile 

 was the contact of the dissimilar metals, and that the intervening fluid merely 

 acted the part of a conductor to carry away, in a continued stream, the positive 

 electricity from each zinc surface, and the negative electricity from each cop- 

 per surface. Fabroni and Creve, and afterward Wollaston and others, main- 

 tained that the source of tht electricity was the chemical action between the 

 zinc and the fluid, and that the intervening copper acted as a conductor to carry 

 away, in a continued stream, the positive electricity from one side of the fluid, 

 and the negative electricity from the other. Davy professed to reconcile these 

 conflicting hypotheses by admitting, with Volta, that the opposite currents were 

 propagated from the surface of contact of the zinc and copper ; but that the 

 liquid separating the pairs of plates did not, and could not, carry forward the 

 currents, as Volta maintained, by their conducting power, but that they effected 

 that object by the chemical action which took place between them and the j 

 zinc. This is our view of the theory proposed by Davy in the paper now re- / 



-X-v^-V/W 



