Unit of Candle-power in White Light. 69 



ranging from the lowest to the highest efficiencies, enables a 

 set of standards of suitable colour to be chosen for whatever 

 test has to be undertaken. As gas-filled lamps develop and 

 come more into use, there would seem to be no reason why 

 the system should not be extended to very high efficiencies 



SET0 



Fig. 2. 



Photometer. 



SET (2 



* "-($& Comparisc 



\$tp - Lamps. 



SET© 



SET© C_ _ 



5) n c_ 



SET (6? U 



Diagram showing scheme of " Cascade "' comparison used in tlie realiza- 

 tion of the unit of Candle-power in Lamps operating at l'~> watts 

 per mean Horizontal Caudle (Set G). 



