354 



Mr. H. E. Ives on the 



Fiff. 1. 



joqIU. 



o Critical. PRsaueNcy 



• FLICKER 



X EQUALITY Of Br\CHTNZ 1 



.SI S4- St S3 



iZ &■/* 



.51 .S<r .Si .53 .60 .6i .6%: 



c^iric^u FKE^urwcr curves 



- c 



5 IV- 



' I ' ■ I 



Inverse Luminosity Curves by Critical Frequency, Equality of Brightness, 

 and Flicker Methods. 



fig. 2 *. In his work Haycraft adopts a different procedure 

 from that o£ the writer. The illumination is not kept 

 constant throughout the spectrum, but is taken as it naturally 

 occurs, consequently the ends are always much darker than 



* Haycraft, Joe. cit. 



