ON COI.ol I: IMIOTOMETRT. 



Gas Light. 



\ 



The second column of the above table gives the comparative intensity of the gas 

 light we used, taking the intensity of all the rays in the electric light as 100 (see 

 Plate 22, fig. 25). The rapid loss of intensity towards the blue evidently would 

 much modify the quantities of red, blue, and green necessary to match the black and 

 white sectors when compared in light of this description. The other columns of the 

 table give the ordinates of the calculated luminosity curves of fig. 26. 



The three sectors were matched as before by us in this light, and it was found that 

 148 green, 119 red, and 93 blue were required to balance 116 of white. 



The area of the curve for the white representing a sector of 133'7, as before, is 534 

 that for 116 would therefore be 116/1337 of 534, or 464. 



The areas of the curves of the three coloured sectors on the above proportion are 

 as follows: Emerald green 199, vermilion 238, French ultramarine 27 '6, making a 

 total of 464-6. 



We also tested R. by gas light with the same three coloured discs. The red being 

 the same as the green to him, we varied the red at pleasure, and got the following 

 results : 



4 c 2 



