214 H. Willy Wien on the Division of Energy in 



and explain the reason for the current belief that the higher 

 regions of the atmosphere and winds which come from them 

 are richer in ozone than the surface air : they also show that 

 there must be enough ozone in the whole atmosphere to have 

 an important bearing on the blue colour of the sky. Hartley 

 drew attention to this matter (Journ. Chem. Soc. xxxix. 

 1881), but as recent experiments have shown that oxygen in 

 sufficient quantity shows a blue colour by transmitted light, 

 the claims of ozone to a serious share in the blueness of the 

 sky have been rather neglected ; but if it is remembered that 

 the blueness of ozone is enormously stronger than that of 

 oxygen under the same conditions, it becomes apparent that 

 the quantity of ozone which has been theoretically shown to 

 have a probable existence in the atmosphere must exercise a 

 considerable influence on the colour of the sky and the colour 

 of distant objects. 



From what we have seen we have also to contemplate the 

 possibility of the existence of free ions of oxygen in the 

 outer regions of the atmosphere, but a discussion of the 

 effects of such must be reserved for a future paper. 



Melbourne, Aug. 1896. 



XXX. On the Division of Energy in the Emission-Spectrum 

 of a Black Body. By Willy Wien*. 



ALTHOUGH the influence of temperature on the radia- 

 tion of a black body and the division of this radiation 

 into its component wave-lengths can be deduced from the 

 electromagnetic theory of light by a purely thermodynamic 

 method, the application of the same process to the division of 

 the energy itself has not up to the present been successful. 



The cause of this lies in the fact that the dependence of 

 intensity on wave-length must be completely determinable 

 from the properties of the radiation, because the latter only 

 depends on the temperature, and not on the special properties 

 of single bodies. 



The radiation of a black body corresponds to the condition 

 of thermal equilibrium, and consequently to the maximum of 

 entropy. If, for example, a process were known by which 

 a change of wave-length could be brought about without any 

 expenditure of work, and without absorption in the sense of 

 an increase of entropy, then the division of energy in the 



* Translation furnished by Mr. J. Burke from Wiedemann's Annalen, 

 vol. lviii. p. 662 (1896). Communicated by Prof. G. F. FitzGerald, F.E.S. 



