104 Nichols and Franklin — A Spectro-photometric 





Table I 



(Lime-light.) 







Lime freshly ignited. 



Lime in final state of incandescence. 



Region of the 







Lime-light 



Spectrum. 



Lime-light 



Lime-light 

 Standard lamp. 



Gas-light. 





Standard lamp. 



(Reduced from observa- 

 tions of W. H. Picker- 









ing.) 



A=7530 



0-65 



0-49 





6685 



0-76 



072 







6562 









0-76 



6080 



0-89 



0-89 





5890 



1-00 



1-00 



1-00 



5570 



1-24 



1-18 







5185 



2-10 



1-32 





5180 









1-10 



4920 



3-84 



1-62 





4685 



5-38 



1-81 







4500 



10-80 



2-08 



2-28 



It will be seen that the lime-light, in its final condition is 

 relatively twice as bright in the violet (7=4500), and relatively 

 L one-half as bright in the ex- 



treme red (A=7530) as an 

 argand gas flame or the stand- 

 ard incandescent lamp. The 

 comparison of our results with 

 those of Pickering is of in- 

 terest because of the evidence 

 it affords that the quality of 

 the lime-light remains nearly 

 constant under presumably 

 very different conditions. The 

 two sets of results were ob- 

 tained by entirely different 

 methods. Pickering used a 

 diffraction grating and 

 brought the spectra under ob- 

 servation to equal brightness 

 by varying the distance of the 

 standard lamp from the slit. 

 His standard consisted of a 

 portion of a gas flame which 

 was decidedly redder than the 



. ^ ure \ Curves of relative intensities game flame taken ag a whole# 



m the spectrum of the lime -light. Curve TTT , , . , •. , 



I, gives results of measurements upon the We USeda glass prism, brought 



freshly ignited lime. Curve II, upon lime the two spectra to equal bright- 



in permanent state of incandescence. nesg ty m eans of a pair of 



Nicol's prisms and adopted a standard which was relatively 

 about three-fourths as bright in the red and five-fourths as 

 bright in the violet as Pickering's standard. 



