SENSATIONS IN TERMS OF LUMINOSITY. 



283 



respectively, to give equal areas with the RS area in Column VI. Column IX. is 

 Column VL repeated, and Columns X. and XI. show the curves for the GS and BS 

 when of equal areas, hence the ordinates, when equal, give white. These last curves 

 are shown in fig. 8. The above equation is not very different from that obtained 



Fig. 6. 



Percentage composition in sensations of the spectrum colours, normal spectrum. 



Fig. 7. 



; 











\ 



\ 



\ 



\, 



\ 



\ 



Normal luminosity curve in wave-lengths (electric light). Divided into sensation luminosities. 



from the prismatic spectrum of the same light. Any difference is caused in all 

 probability by the colour of the light reflected by the grating, together with that 

 caused by the necessary error of observation. 



A comparison of the curves in figs. 5 and 8 shows what an effect the compression 

 and extension of the red and blue of the spectrum has on the shape and appearance 



2 02 



