60 



Prof. F. Allen on Four Transition Points in the 



the ^elevations can occur. There can be no doubt that the 

 rest*o£ the curve would coincide with the normal. 



Fiar. 4. 



Pi 



045 



040 



X 





Eye ) 

 X-66 

 Norr 



'atigu 

 Ofx. 

 -nal. — 



°d wh 



:h 





1 

 I 

 I 















1 















•035 





I 



\ 



1 











% 





\ 











i 







\ 



X 



\ 

 \ 











i 



•030 





\ 











f 















/ 



025 





\\ 

 \\ 

 \\ 











/ 





\\ 



V 









i 





•020 



v. 



015 1 







\ 







y 









V 







f 





•40^ '45 



50 -55 -60 

 Wa\/e Length. 



■65 



•70 -75 



stu< 



The transition point was thus narrowed down to the wave- 

 length X -66^0 /a- The eye, therefore, was fatigued with this 

 colour, and fijom the data obtained, Table IV., the curve in 

 fig. 4 was plojtted. 



