116 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



tioned by those writers on page 222 of their paper before the German 

 Plijsical Society.* 



For very high temperatures no experimental data for the radiation 

 from carbon exist excepting the measurements described by Lucas, f It 

 has been rutlier the fashion to leave Lucas's work altogether out of 

 account as being hopelessly at variance with more recent results. Kay- 

 ser, t for example, after giviiig Lucas's data, says, — 



/Croo° -iOOO" ■2000" 



Figure 24. 



^ooo" 



Zu fahchen Schlussen gelangt audi Lucas, durch Versuche welche das 

 Verdampfen der Kohle in Frage zu stellen scheinen. 



His results, nevertheless, which I have given graphically in Figure 24, 

 appear to me to be of significance. His formula for the relation of tem- 

 perature to current, t = 25 i, must of course be regarded as only ap- 

 proximately correct even at moderate temperatures. The curve for the 

 relation between the current i;i a carbon and the temperature, up to about 



* Lummer and Pringsheim, Verhandl. d. Deutschen Physikal. Gesellscli (1899) 

 p. 222. 



t Lucas, Comptes Rendus, C. 1454 (1884). 

 J Kayser, Ilandbuch der Spectroscopie, I. 157. 



