Visibility of the Different Colours of the Spectrum. 721 



accuracy in this region as measurements would give, because 

 it was found impossible to get figures for the second and fourth 

 columns of the preceding table for this region. 



Fiff. 3. 

















/ 



Visibility Curves and 

 Energy Curve. 















* 



/ 



/ 



\ / 

 \ / 



/ \ 

 / \ 











\ 

 \ 



\ 

 \ 



\ 



V 

 \ 











\ 

 \ 

 \ 

 \ 

 \ 

 \ 

 \ 

 \ 











\ 



A 











\ 





1 



"* 



Tk 



1 A 



J I" 



ISOMyU. 



600 t>$0 



According to our results, then, at an illumination of 

 metre-candle, the maximum visibility is at 502 ma, and at 



