ON COLOUR PHOTOMETRY. 





The above table gives a summation of the ordinates at each point of the scale of the 

 three coloured curves; in addition, the sixth and eleventh columns give the sum of the 

 ordinates multiplied by '37, which is the ratio between 133'7 and 360; and the 

 resulting curves, which show graphically the combination producing the grey light, 

 are No. IV. of figs. 16 and 17 (Plate 20). 



For convenience of comparison, we have reduced the luminosity curves to the 

 normal scale of wave-lengths, as shown in fig. 18, which has been made from the 

 following table : 



