112 Nichols and Franklin. — A Spectro-pliotonietvic 



in each of those stages of incandescence was measured by the 

 method already described. 



Table VI. 

 Comparison of a Bernstein incandescent lamp at the same candle-power. 



Wave-lengths. 



Bernstein lamp. 





Standard lamp. 



7530 



1-19 



6680 



1-08 



6080 



1-03 



5570 



0-97 



5185 



0-93 



4920 



0-91 



4685 



0-89 



4500 



0-87 



4340 



0-85 



The results of these determinations are given in Table VII 

 (see also figure 5). The brightness of the spectrum of the lamp 

 at 16 candles is taken as unity throughout, and the intensity of 

 the spectrum at other candle-powers is expressed in terms of 

 the brightness of the corresponding region of the former. 



Table VII. 



An Edison lamp at various degrees of incandescence, compared with the same 

 lamp at 16 candle-power. 





Intensity at 



Intensity at 



Intensity at 



Intensity at 



Intensity at 



Wave- 



4 candles. 



10 candles. 



16 candles. 



22 candles. 



28 candles. 



lengths. 



Intensity at 



Intensity a * 



Intensity at 



Intensity at 



Intensity at 





16 candles. 



16 candles. 



16 candles. 



] 6 candles. 



16 candles. 



7530 



0-34 



0-71 



1-00 



1-18 



1-56 



6680 



0-2S 



0-63 



1-00 



1-29 



1-71 



6080 



0-23 



0-58 



1-00 



1-34 



1-80 



5890 







1-00 







5570 



0-22 



0-55 



1-00 



1-37 



1-89 



5185 



019 



0-53 



1 00 



1-38 



1-97 



4920 



0-17 



0-52 



1-00 



1-38 



2-04 



4685 



0-16 



0-51 



1-00 



1-39 



2-12 



4500 



0-15 



0-51 



1-00 



1-39 



2-18 



4340 



0-14 



0-51 



1 00 



1-39 



2-24 



This method of presentation enables us, by inspection of the 

 table and curves, to see at a glance the changes which take 

 place in the spectrum of the lamp as the candle-power is in- 

 creased. With rising temperature the change is least in the 

 extreme red, the rate of change increasing rapidly as we ap- 

 proach the violet end of the spectrum. 



Thus the brightness of the spectrum in the neighborhood of 

 the A line, when the lamp is raised from 4 candles to 28 can- 



