642 Prof. J. H. Jeans on the Analysis of 



of mercury with its extensive number of series lines forms 

 strong evidence in favour of the absolute accuracy of 

 Ryd berg's law. 



Note added Jidy 1910 : — Since the above was in press I 

 have remeasured the first few lines of the Principal Series, 

 using a small plane grating on the spectrograph in place of 

 the calcite prisms, with the following results : — 



X (air). 



on. 



X (air). 



f 5366-03 



{ 535396 



1 5316-95 



7 ... 



.. 4980-78 



8 ... 



.. 4889-79 



f 5120-84 







15102-49 



9 ... 



.. 4826-82 



15 hours exposure was required ; the lines given were 

 quite sharp, and their values are I think now correct to 

 about '1 unit ; the remaining lines were not sufficiently 

 developed to distinguish. 



The new lines in the footnote on p. 639 were also (except 

 the first two) remeasured with the grating, and the values 

 there given are the corrected ones. Most of these lines have 

 been observed by Stiles, Astrophys. Journal, vol. xxx. p. 48 

 (1909). 



LXVIII. On the Analysis of the Radiation from Electron 

 Orbits. By J. H. Jeans, M.A., F.R.S.* 



1. TN the present paper an attempt is made to examine the 

 JL nature of the radiation which would be emitted by 

 electrons describing orbits about various centres of force and 

 in fields of force of various kinds, with a view to collecting 

 evidence as to whether black-body radiation can be inter- 

 preted as radiation emitted in this way. 



In a previous paper f a proof has been given that if 

 radiation can be explained in this way, the orbits must be 

 described about centres of force varying as the inverse cube 

 of the distance. The present investigation confirms this 

 result in an independent manner, and tests how far such 

 radiation would be in agreement with that observed experi- 

 mentally. 



If [E\dX is the partition of radiant energy in matter, the 



* Communicated by the Author. 



t " On the Motion of Electrons in Solids," Phil. Mag. [6] xvii. p. 773 

 and xviii. p. 209 (1909). 



