

Maxwell. 297 



unfavourably received by the most distinguished of Maxwell's 

 contemporaries. Helmholtz indeed ultimately accepted it, but 

 only after many years ; and W. Thomson (Kelvin) seems never 

 to have thoroughly believed it to the end of his long life. In 

 1888 he referred to it as a "curious and ingenious, but not 

 wholly tenable hypothesis,"* and proposedf to replace it by an 

 extension of the older potential theories. In 1896 he had some 

 inclination? to speculate that alterations of electrostatic force 

 due to rapidly-changing electrification are propagated by con- 

 densational waves in the luminiferous aether. In 1904 he 

 admittedg that a bar-magnet rotating about an axis at right 

 angles to its length is equivalent to a lamp emitting light of 

 period equal to the period of the rotation, but gave his final 

 judgment in the sentence|| : " The so-called electromagnetic 

 theory of light has not helped us hitherto." 



Thomson appears to have based his ideas of the propagation 

 of electric disturbance on the case which had first become 

 familiar to him that of the transmission of signals along a 

 wire. He clung to the older view that in such a disturbance 

 the wire is the actual medium of transmission ; whereas in 

 \ Maxwell's theory the function of the wire is merely to guide 

 the disturbance, which is resident in the surrounding dielectric. 



This opinion that conductors are the media of propagation 

 of electric disturbance was entertained also by Ludwig Lorenz 

 (&. 1829, d. 1891), of Copenhagen, who independently developed 

 an electromagnetic theory of lightH a few years after the 

 publication of Maxwell's memoirs. The procedure which 

 Lorenz followed was that which Kiemann had suggested** in 

 1858 namely, to modify the accepted formulae of electro- 

 dynamics by introducing terms which, though too small to be 



* Nature, xxxviii (1888) p. 571. t Brit. Assoc. Report, 1888, p. 567. 



J Cf. Bottouiley, in Nature, liii (1896), p. 268 ; Kelvin, ib., p. 316 ; J. Willard 

 Gibbs, ib., p. 509. 



Baltimore Lectures (ed. 1904), p. 376. || Ibid., preface, p. 7. 



H Oversiyt over det K. danske Vid. Selskaps Forhandliiiger, 1867, p. 26; Annul, 

 der Phys. cxxxi (1867), p. 243 ; Phil. Mag., xxxiv (1867), p. 287. 



** Cf. p. 268. Riemann's memoir was, however, published only in the same 

 year (1867) as Lorenz's. 



