192 



exploded by an electric discharge *, which he also employed to effect 

 chemical decomposition, Mr. Faraday succeeded in causing the needle 

 to deviate, both by the discharge of a battery, and by electricity pass- 

 ing directly from the conductor of the machine. In justice toM. Col- 

 ladon, we must remark, that the account which he gives of his expe- 

 riments affords no reasonable ground for doubting the accuracy of his 

 conclusions : the details are clear, and the numerous results unequi- 

 vocal f. We may also notice, that, in the same memoir, M. Colla- 

 don gives an account of some very interesting experiments, made with 

 a similar arrangement, on the magnetical effects of atmospherical 

 electricity, by which its power of causing deviations of the needle is 

 satisfactorily established. 



Mr. Faraday, in the comparison which he makes between the effects 

 produced by ordinary and by voltaic electricity, shows that the follow- 

 ing, though differing in degree, are common to both, viz. attraction 

 and repulsion, evolution of heat, magnetism, chemical decomposition, 

 physiological phenomena, the spark. To these proofs of the identity 

 of the electricities from these sources may be added, that batteries 

 have been charged from the voltaic pile, and that the shock from a 

 battery so charged could not be distinguished from that of the same 

 battery charged to the same extent from the conductor of a machine j. 

 We consider that this alone is strong evidence in favour of the iden- 

 tity of the electricities, although we do not quite agree with Van 

 Marum that it is conclusive. 



The effects hitherto obtained from magneto-electricity, the author 

 considers to be, evolution of heat, magnetism, physiological pheno- 

 mena, the spark. He has not himself effected chemical decomposition 

 by means of it ; and he considers that the effects which have been ob- 

 tained by others do not show true polar decomposition, but are similar 

 to those obtained by Wollaston in the decomposition of water. 



That magnetism and physiological phenomena are the only effects 

 which have yet been obtained by means of thermo-electricity, the 

 author attributes to its low degree of intensity. 



Mr. Faraday considers that the identity of the electricity of the 

 torpedo with common and voltaic electricity is satisfactorily esta- 

 blished, although some effects, attraction and repulsion, due to a state 

 of tension, evolution of heat, and the spark, have not yet been ob- 

 tained : and in this we fully concur. 



The general conclusion which the author draws from the collection 

 of facts which he brings forward, is, that " electricity, whatever may 

 be its source, is identical in its nature ;" and he attributes the dif- 

 ference in the degree to which the phenomena, when originating in 

 different sources, are observed, to the variable circumstances of quan- 

 tity and intensity. This manner of accounting for the difference in 

 the phenomena due to voltaic and to common electricity was adopted 

 very early in the inquiry, common electricity being considered as ex- 



* For this method of ignition we are indebted to Mr. W. Sturgeon. 

 Phil. Mag. 1828. 



f Annales de Chimie, 1826, torn, xxxiii. p. 62. 

 X Annales de Chimie, 1802, torn. xl. p. 289. 



