THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



SEPTEMBER 1889. 



XXIV. On the Mechanics of Luminosity. 



By E. Wiedemann*. 



[Plate in.] 



ALTHOUGH we possess numerous measurements of the 

 positions of lines in the spectrum, and although many 

 attempts have been made to measure the distribution of lumi- 

 nosity and energy in the spectrum, and to express the same 

 by means of formulas, yet the experiments are few which have 

 for their object to obtain an insight into the mechanics of 

 luminosity. In general, we have contented ourselves with in- 

 vestigating the intensity of radiation without investigating 

 the energy of the vibrating particles which emit the light, 

 upon which it depends. 



In what follows we shall attempt to fix the data for in- 

 vestigating the mechanics of luminosity, to verify particular 

 conclusions by means of experiment, and to determine the 

 numerical value of the quantities which occur. 



The present research is a continuation of earlier investi- 

 gations of minef. 



* Wied. Ann. xxxvii. p. 177. Translated from a separate impression 

 communicated by the Author. 



t E. Wiedemann, Wied. Ann. v. p. 506 (1878) ; vi. p. 298 (1879) ; 

 ix. p. 157 (1880) j x. p. 202 (1880) ; xviii. p. 508 (1883) ; xx. p. 756 (1883) ; 

 xxxiv. pp. 446 and 464 (1888). Sitzungsber. d. Societas physio-meclica Er- 

 langen vom 1 Aug. 1887. Bull. Soc. de phgs. genevoise 6 Oct. 1887. 

 I shall return more at length to numerous obligations to the above- 

 mentioned works — where no special acknowledgment is made — upon a 

 future opportunity. The results of this investigation themselves were 

 communicated to the Physico-Medical Society of Erlangen on Dec. 10, 

 1888. 



Phil. Mag. S. 5. Vol. 28. No. 172. Sept. 1889. N 



