554 



CAPTAIN ABNEY AND MAJOR-GENERAL FESTLNC 

 French Ultramarine. Sector = '97 of Emerald Green. 



The above tables give the figures on which the curves were based. Column I. 

 gives the spectrum scale, and Column II. the original readings. Columns III. and 

 IV. give the adopted readings at the different scale numbers. Column V. gives, in 

 the cases of red and blue, the ordinates reduced in proportion to the angles of the 

 sectors, as explained above. The last column but one gives the ordinates of the curve 

 of luminosity of the light reflected from white card, which is the outer curve in fig. 5 

 (Part I.). The last column gives the ordinates of the luminosity curves of the colours. 



Reverting to fig. 17, if the area of the outer curve, which is 534, represents the total 

 amount of light reflected from a white card sector of 133'7, the areas of the curves for 

 the green, red, and blue, which are respectively 221, 156'3, and 47'9, represent the 

 amount of light from the coloured sectors; and the total of these, or 425 '2, represents 

 the amount of light reflected from the disc made up of the coloured sectors. 



Now the black and white disc which, when rotated, matched the coloured disc, con- 

 sisted of black and white in the proportions of 278 : 82, and we find that the black 

 paper reflects 8 '3 3 per cent, of white light ; the proportion of white to the whole disc 

 was therefore (82 + '0833 X 278, or) 105 to 360, the amount of light reflected from 

 the disc should therefore be represented by 105/1337 of 534, or 419'4, a result coin- 

 ciding within the limits of error of observation with that just obtained for the 

 coloured disc. 



