274 
CAPTAIN W. DE W. ABNEY ON THE TRANSMISSION 
§ XXII. Relative Colour Brightness of different Parts of the Solar Spectrum. 
Rood, in his ‘ Modem Chromatics,’ gives the value of the brightness of different parts 
of the spectrum under the head of different colours. His Table he constructed from 
Vierordt's curve, which General Festing and myself criticised in our paper on 
“Colour Photometry.” Taking a June day near mid-day, the following values were 
derived, and they are compared with Rood’s :— 
Rood’s scale. 
Rood’s nomenclature of colour. 
Rood’s value 
of brightness. 
Absey’s value 
of brightness. 
0 to 149 
Red. 
54 
65 
149 „ 194 
Orange-red. 
140 
138 
194 „ 210 
Orange . 
80 
61 
210 „ 230 
Orange-yellow. 
114 
77 
230 „ 240 
Yellow. 
54 
39 
240 „ 344 
Yellow-green and green-yellow . 
327 
365 
344 „ 447 
Green and bine-green .... 
134 
183 
447 ,, 495 
Cyan blue. 
32 
33 
495 „ 806 
Bine and bine- violet. 
60 
36 
806 „ 1000 
Violet. 
5 
3 
In this scale A = 0, a = 40‘05, B = 74-02, C = 11271, D = 220-31, E = 363-11, 
F = 493-22, G = 753-58, H = 1000. 
Table of Wave-lengths. 
Scale number. 
\ 
1 
A 4 
44 
662 
52 
45 
629 
64 
46 
601 
76"5 
47 
577 
90 
48 
557 
104 
49 
538 
120 
50 
519 
138 
51 
502 
158 
52 
487 
178 
53 
474 
198 
54 
464 
216 
55 
454 
235 
56 
445 
255 
57 
436 
276 
58 
428 
298 
