u 



THE 

 I.ON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



AUGUST 1907; 



\ 



XYlI. On the Electrical Origin of the Radiation from Hot 

 Bodies. By J. J. Thomson, M.A., F.R.S* 



SO many investigations, theoretical as well as experimental, 

 have been made on the radiation emitted by bodies at 

 various temperatures, that a paper on this subject seems 

 to call for some apology. Some o£ the theoretical investi- 

 gations, however, are of such an extremely general character, 

 that perhaps others besides myself may have found some 

 difficulty in following them and in appreciating their rigour: 

 and it is possible that there may be room for an investigation 

 in which the radiation is supposed to be produced in a way 

 which admits of comparatively simple treatment. 



The idea on which this investigation is based is, that the 

 radiation from hot bodies is analogous to Rontgen radiation : 

 i. e., consists of a series of electromagnetic pulses produced 

 by the stopping or starting of charged corpuscles in the hot 

 body. I suggested the possibility of this origin of radiation 

 in a paper presented to the International Congress of Physics 

 at Paris, 1900 (Rapport, t. iii. p. 148) ; but the subject 

 acquired importance by a remarkable investigation by 

 Lorentz (Amsterdam Proceedings, 1902-3, p. 666), who 

 showed that, on this view, the energy in the radiation with 

 exceedingly long wave-length is given by the expression 



* Communicated by the Author. 

 Phil Mag. S. 6. Vol. 14. No. 80.' Aug. 1907. Q 



