68 



Prof. F. Allen on Four Iranskion Points in tli 



this latter tvpe of curve to the single violet elevation tvpe 

 exhibited by that obtained for the wave-length X'400/^. 

 fig. 17, which was known from previous work*. 



Fiff. 13. 

















1 



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\ 

























































\\ 



















\v 

















o 



z 

 o 



°V 



I 



















V 



















•0* 



\ 



















\ 



















k 



••«— 



^ 



















EYE 

 GREE 



-AT1GUE0 WITH 



















NORf> 



1AI 







.4 



op 



.5 



WAV 







; LENG 



THS. 

 3 



.7 









In the process of 



the third transition 



* Note. — The readings obtained when the eye was fatigued with the 

 wave-lengths X '440 ju and X -400 fx are given in the paper already referred 

 to, viz. : "Effect on Persistence of Vision, etc., 1 ' Phys. Rev. vol. xi. By 

 some oversight the corresponding normal persistency readings were 

 omitted from that paper, and they are now given here : — 



X. 



"758 fi 

 •715 



•680 

 •647 



Normal 

 Persistence. 

 •0182 

 •0156 

 •0134 

 ■0121 



sec. 



X. 



•622 ix 

 •573 



•507 

 •465 



Normal 

 Persistence 

 •0113 sec. ! 

 •0105 J 

 •0120 

 •0154 



•428 [x 



•409 



•400 



Normal 

 Persistence. 

 •0203 sec. 

 •0249 

 •0277 



