288 M. L. Loreirz on the Identity of the 



to demonstrate a new member in the chain which connects the 

 various manifestations of the forces ; I shall prove that in ac- 

 cordance with the laws for the propagation of electricity under 

 the action of free electricity, and of the electrical currents of the 

 surrounding media, which we can deduce from experiment, pe- 

 riodical electrical currents are possible which in every respect 

 behave like the vibrations of light ; from which it indubitably fol- 

 lows that the vibrations of light are themselves electrical currents. 



We know that light is produced by a wave-motion with very 

 rapid periodical motions which we may call vibrations. It is 

 the peculiarity of these vibrations that they are at right angles 

 to the direction in which the wave of light travels ; and we may 

 say that this peculiarity has not found a correct explanation in 

 the theory of elasticity, or in the analogous one of Cauchy ; for, 

 apart from the fact that this theory necessitates the assumption 

 of a special medium (the luminous aether, which moreover stands 

 quite isolated and separate from any other observation or de- 

 monstrable connexion with other forces), even with this assump- 

 tion, and the various hypotheses of Cauchy, it is scarcely pos- 

 sible to imagine a medium in which a wave-motion could travel 

 without a trace of longitudinal vibrations. Convinced that this 

 theory cannot give a real, but only a factitious explanation even of 

 the peculiarity of light (the transverse vibrations), I had formerly 

 drawn attention to the fact that variable electrical currents, which 

 induce in closed conductors currents that are parallel with the 

 original ones, are similar to the vibrations of light, which in a 

 certain sense also induce parallel vibrations. But as the laws of 

 induced currents, generally admitted and based on experiment, 

 did not directly lead to the expected result, the question was 

 whether it was not possible so to modify the laws assumed that 

 they would embrace both the experiments on which they rest 

 and the phenomena which belong to the theory of light. 



Kirchhoff (Pogg. Ann. vol. cii.) has expressed the laws of the 

 motion of electricity in bodies with constant conducting-power 

 by the folio wiug equations, 



n1 /dQ, 4 dV\ 

 ni fdQ, 4 dV\ 



ni /dn 4rfw\. 



a) 



in which u, v, w are the components of the electrical density of 

 the current in the point x y z, k the constant conducting- 



