Unit of Candle-power in White Light, 73 



the final candle-power value obtained for the high-efficiency 

 lamps (set 6). 



(a) By the cascade method ; 



(b) By comparison in one step. 



2. The accuracy to which photometric readings of this 

 description are repeated by any observer and the probable 

 errors of the results. 



3. The order of agreement with other National Labora- 

 tories in the values assigned to high-efficiency glow-lamps 

 which differ in the hue of their radiation from the flame 

 standards from which the fundamental units are derived. 



4. The constants of the pentane lamp with changes of 

 humidity, barometer, and temperature. 



5. The constancy of the unit of candle-power maintained 

 through the medium of electric sub-standards. 



1. Values of Candle-power obtained for the Il'ujh Efficiency 

 Tungsten Lamps. 



The precise numerical values obtained for the individual 

 lamps are not of immediate interest. For the purpose of 

 this paper each set of lamps may be considered as one lamp. 

 If there was evidence in the course of the work that any one 

 lamp was undergoing a progressive change it was discarded, 

 so that the figures given may be assumed in each case to be 

 those for a set of lamps whose candle-powers have remained 

 unchanged during the comparison. 



Throughout the work the average of all six observers 

 has been taken as giving the true value for any set of 

 lamps. For the purpose, therefore, of showing the dif- 

 ferences of individual observers, this average value is taken 

 as 100 for each of the six sets of lamps measured by the 

 cascade method. The observers are designated by the 

 letters A, B, C, D, E, and F. 



Table II. gives a summary of the results. Observer A 



Table II. — Summary of Cascade Observations, each Set 

 being compared by each Observer against the one 

 immediately above it. 



Observer. 



A. 



B. 



c. 



D. 



E. 



F. 



Average. 



Set 1 



100-00 



100-00 



10000 



100-00 



100-00 



100-00 



100 



•> 

 >i w 



99-0. 



99-4, 



99-9 



99-8- 



100-8, 



1003, 



100 



i „ 3 



99-4, 



99-:{ s 



99-9 



99-9,. 



L00-8, 



100-4. 



100 



„ 4 



98-9-, 



990, 



99'8 4 



100-3, 



loi-a, 



100-5 



100 



., 5 



98-7, 



98-7,, 



997., 



100-4- 



101-4,. 



100-8, 



100 



„ (; 



98-5j 



98-6 x 



99'6 fl 



100-7, 



101-4, 100-9. 



100 



