^20 EULOGY ON ALEXANDER VOLTA. 



some doubts, since, at the ordinary temperature, vapor mingles with 

 the atmospheric air in very small proportions. Volta regarded the work 

 I have just analyzed as a mere rough draught. 



Numerous other researches of the same kind to which he had applied 

 himself were to form part of a treatise which has never seen the light. 

 Besides, on this point science now seems complete, thanks to Gay-Lus- 

 sac and Dalton. The experiments of these ingenious physicists, made 

 at a time when Volta's treatise, though published, was known neither 

 in France nor in England, included all the gases, whether permanent or 

 ephemeral, in the law of the Italian scientist. They lead, moreover, in 

 every case, to the same co-efficient of expansion. 



ATMOSPHERIC ELECTRICITY. 



I will not resume the subject of Volta's researches on atmospheric 

 electricity until after having given a hasty sketch of the analogous ex- 

 periments preceding them. In order to judge judiciously of a traveler's 

 course, it is often necessary to view it at the same time from the start- 

 ing and finishing points. 



Dr. ^Yall, who wrote in 1708,' should be here named as the first, for in 

 one of his treatises is found this ingenious remark : " The light and 

 crackling noise of electrified bodies seems, tip to a certain point, to repre- 

 sent thunder and lightning." Stephen Grey published in 1735 a similar 

 remark. " It is probable," said this distinguished physicist, " that in time 

 some means of concentrating this electrical fire in larger quantities, will 

 be discovered, and also of increasing the power of an agent, which, if it 

 be allowable to compare small things with great, according to several 

 of my experiments, seems to have the nature of thunder and lightning." 



The majority of physicists saw merely comparisons in these passages. 

 They did not suppose that in finding a resemblance between the effects 

 of electricity and those of thunder, Wall and Grey claimed to infer 

 from it an identity of causes. This doubt, however, would not be appli- 

 cable to the sketch introduced by Nollet, in 174G, in his lectures on ex- 

 perimental physics. In that, for example, according to the author, a 

 storm-cloud, far above the earth, is nothing more than an electrified 

 body placed above a body which is not. Thunder in the hands of nature 

 is electricity in the hands of physicists. Several striking resemblances are 

 pointed out, and, in a word, nothing is wanting to complete this inge- 

 nious theory, except the only thing necessary to give it a definite place 

 in science, the sanction of direct experiment. 



Franklin's first views of the analogy between electricity and thunder 

 were, like those entertained by Nollet, mere conjectures; the whole dif- 

 ference between the two physicists being then reduced to a plan for an 

 experiment not mentioned by Nollet, and which seemed to promise de- 

 finitive proofs for or against the hypothesis. The object of this exper- 

 iment was to prove whether, during a storm, a metallic rod, insulated 



