116 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



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

 Physical Society.* 



For very high temperatures no experimental data for the radiation 

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

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

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

 ser, $ for example, after giving Lucas's data, says, — 



Jcroo" 2ooo° 3ooo' 



Figure 24. 



y-ooo* 



Zu jahchen Schliissen gelangt audi Lucas, durch Versucke 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 in a carbon and the temperature, up to about 



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

 p. 222. 



t Lucas, Comptes Rendus, 0. 1454 (1884). 

 % Kayser, Handbuch der Spectroscopic, I. 157. 



