374 Mr. E. Edser. An Extension of 



V. " The Nature of the Antagonism between Toxins and Anti- 

 toxins." By Dr. C. J. MARTIN and Dr. T. CHERRY. Com- 

 municated by Dr. HALLIBURTON, F.R.S. 



VI. " Some Differences in the Behaviour of Real Fluids from 

 that of the Mathematical Perfect Fluid." By A. MALLOCK. 

 Communicated by Lord EAYLEIGH, F.R.S. 



VII. " On the Heat dissipated by a Platinum Surface afc High 

 Temperatures." By J. E. PETAVET. Communicated by 

 LORD RAYLEIGH, F.R.S. 



" An Extension of Maxwell's Electro-magnetic Theory of Light 

 to include Dispersion, Metallic Reflection, and allied Phe- 

 nomena." By EDWIN EDSER, A.R.C.S. Communicated 

 by Captain W. DE W. ABNEY, C.B., F.R.S. Received 

 February 18, Read March 10, 1898. 



The Electro-magnetic Theory of Light, as left by Maxwell, gave no 

 explanation of dispersion, and led to conclusions in some respects 

 inconsistent with the results of experiments on metallic reflection. 

 There seems to be little doubt as to the general direction in which it 

 would be necessary to modify that theory in order to give a satis- 

 factory account of these phenomena. Electrical conduction has been 

 considered by many to be inseparably connected with the motion of 

 charged atoms, whilst the properties of a dielectric have been found 

 to admit of an explanation on somewhat similar lines ; consequently 

 it would appear necessary, where fluctuations in the electric field of 

 frequencies as great as those of light are concerned, to expressly 

 formulate the reactions of the atoms or molecules composing the 

 medium through which the disturbances are propagated. The 

 mechanical theories of light, when modified in a similar manner, have 

 been found capable of giving a more or less comprehensive account of 

 dispersion and metallic reflection; and it would appear that the 

 assumptions necessitated in the present case are at least as admissible 

 as those which have been made elsewhere. No doubt a theory with 

 any pretension to finality must include a satisfactory account of the 

 nature of the luminiferous ether and of electricity, perhaps even of 

 the ultimate constitution of atoms ; and Mr. Larmor's investigations 

 show how far we can even now go in this direction. On the other 

 hand, a less comprehensive theory, depending only on the known laws 

 of electrical actions, may prove not without value, if, whilst explaining 

 the observed phenomena, it enables us to form a clear mental picture 

 of the processes involved. 



