dr 





180-9 





m 



— 



dr = 



39-3 



m 



— 



dr = 



'0263 



532 Hutchins — New Method of Measuring Light Efficiency. 



From these readings we have 



m — 202*2 



n = 2531 • 



d = 45-00 



r — 4-028 n 



This result is subject to a plus correction of 13 per cent 

 because of the loss of light to that amount in passing through 

 the water cell. Applying this correction, we get -0296 for 

 the light efficiency. 



A second determination made after resetting the screen and 

 changing the sensibility of the galvanomter gave *0323. The 

 mean of the two is -0309 and the departure from the mean 

 6 per cent. The result may be considered very satisfactory 

 considering the large change in apparent efficiency produced 

 by a small displacement of the screen. 



Nichols and Coblentz* found '033 from integration of the 

 energy curve of a cylindrical acetylene flame, and '030 from a 

 comparison of the transmission curve through water and 

 iodine in bisulphide of carbon. 



Bowdoin College, Oct. 30, 1909. 



* Physical Eeview, Oct. 1903. 



