﻿The Titer mod ynamical Tlxeory of Radiation. 57 



corresponding formulae in Prof. J. J. Thomson's ' Recent 

 Researches,' Articles 367 and 364 respectively. It will be 

 noticed that the great difference between his results and 

 those obtained here is that the complex constant B is evaluated 

 in ' Recent Researches,' but is left unevaluated in the present 

 discussion. As a matter of fact, the evaluation of B is 

 not required for the important inferences usually drawn 

 from these results, such as the mode of dependence of the 

 intensity of the scattered wave on the wave-length and on the 

 diameter of the wire, the determination of the direction in 

 which the scattered wave nearly vanishes, and the greater pro- 

 portional scattering when the electric intensity in the incident 

 wave is parallel to the wire than when it is perpendicular. 

 For a full discussion of the interpretation of formulae (2t>) 

 and (32) the student naturally turns to ' Recent Researches.' 

 8. It need hardly be pointed out that the discussions of 

 Articles 3 to 7 of the present paper are fundamentally the 

 same as those given by Prof. Thomson. The functions used 

 are, at most, different only by constant factors. The sole 

 advantage, but that an important one, claimed for the present 

 formulation is that it assumes no knowledge of Bessel's 

 functions on the part of the reader and makes no appeal to 

 formulae, but obtains from first principles all the approxi- 

 mations required. The work is thus greatly shortened and 

 simplified, and ought to be easily understood by many students 

 to whom the standard formulation presents difficult}'. 

 30th March, 1906. 



VI. On tlw Thermodynamical Theory of Radiation. By 

 J. H. Jeans, M.A., F.R.S., Professor of Applied Mathe- 

 matics in the University of Princeton *. 



1. f INHERE are two entirely distinct ways of attacking the 

 JL problem of determining the intensity and partition 

 of radiation from a body at a given temperature. 



One method is based on what is commonly termed the 

 " Thermodynamics of Radiation." Its fundamental conception 

 is that of a hot body surrounded by aether, in which the 

 partition of energy is such that the energy absorbed by the 

 matter from the sether in any time is exactly equal to that 

 yielded up by matter to sether. From the condition that 

 equilibrium of this kind shall exist, it has been shown by 

 Bartoli, Boltzmann, and \Yien, that the law of partition of 



* Communicated bv the Author. 



