] 62 Dr. Faraday's Experimental Researches in Electricity. 



mon electricity (309. 327.)? has been that selected by several 

 experimenters as the test of chemical action (336. 346.). It 

 is a fact, too, that many philosophers are still drawing distinc- 

 tions between the electricities from different sources; or at 

 least doubting whether their identity is proved. Sir Humphry 

 Davy, for instance, in his paper on the Torpedo*, thought it 

 probable that animal electricity would be found of a peculiar 

 kind; and referring to that, in association with common elec- 

 tricity, voltaic electricity and magnetism, has said, " Distinc- 

 tions might be established in pursuing the various modifica- 

 tions or properties of electricity in these different forms, &c." 

 Indeed I need only refer to the last volume of the Philosophi- 

 cal Transactions to show that the question is by no means 

 considered as settled f. 



266. Notwithstanding, therefore, the general impression of 

 the identity of electricities, it is evident that the proofs have 

 not been sufficiently clear and distinct to obtain approbation 

 from all those who were competent to consider the subject; 

 and the question seemed to me very much in the condition 

 of that which Sir H. Davy solved so beautifully, — namely, 



* Phil. Trans. 1829, p. 17- " Common electricity is excited upon non- 

 conductors, and is readily carried off by conductors and imperfect con- 

 ductors. Voltaic electricity is excited upon combinations of perfect and 

 imperfect conductors, and is only transmitted by perfect conductors or im- 

 perfect conductors of the best kind. Magnetism, if it be a form of elec- 

 tricity, beiongs only to perfect conductors; and, in its modifications, to a 

 peculiar class of them 3 . Animal electricity resides only in the imperfect 

 conductors forming the organs of living animals, &c." 



f Phil. Trans. 1832, p. 259. Dr. Davy, in making experiments on the 

 torpedo, obtains effects the same as those produced by common and voltaic 

 electricity, and says that in its magnetic and chemical power it does not 

 seem to be essentially peculiar, — p. 274; but he then says, p. 27o, there 

 are other points of difference; and after referring to them, adds," How 

 are these differences to be explained ? Do they admit of explanation simi- 

 lar to that advanced by Mr. Cavendish in his theory of the torpedo; or 

 may we suppose, according to the analogy of the solar ray, that the elec- 

 trical power, whether excited by the common machine, or by the voltaic 

 battery, or by the torpedo, is not a simple power, but a combination of 

 powers, which may occur variously associated, and produce all the varieties 

 of electricity with which we are acquainted ?" 



At p. 279 of the same volume of Transactions is Dr. Ritchie's paper, 

 from which the following are extracts: " Common electricity is diffused 

 over the surface of the metal; — voltaic electricity exists within the metal. 

 Free electricity is conducted over the surface of the thinnest gold leaf as 

 effectually as over a mass of metal having the same surface ; — voltaic elec- 

 tricity requires thickness of metal for its conduction," p. 280 : and again, 

 " The supposed analogy between common and voltaic electricity, which was 

 so eagerly traced after the invention of the pile, completely fails in this 

 case, which was thought to afford the most striking resemblance," p. 291. 



a Dr. Ritchie has shown this is not the case, Phil. Trans. 1832, p. 294. 



