ON COLOUR PHOTOMETRY. 
441 
Dr. Pole’s observations. 
Original 
readings. 
Reduced 
readings. 
Scale reading. 
Intensify. 
Scale reading. 
Intensity. 
55'3 
7-0 
55-3 
2-5 
535 
9-5 
53 5 
3-4 
5P85 
17-0 
51-85 
6-2 
51-2 
26-0 
51-2 
9-5 
50-7 
37-0 
50-7 
13-5 
50-35 
55-0 
50-35 
20-2 
50-1 
71-0 
50-1 
26-0 
49-8 
95-0 
49-8 
35-0 
49-35 
122-0 
49-35 
45-0 
49-1 
142-0 
49-1 
52-0 
48-8 
167-0 
48-8 
61-0 
48-35 
199-0 
48-35 
73-0 
47-95 
238-0 
47-95 
87-0 
47-5 
260-0 
47-5 
93-0 
46-8 
277-0 
46-8 
98-0 
46-2 
260-0 
46-2 
93-0 
45"85 
238-0 
45-85 
87-0 
45-3 
199-0 
45-3 
73-0 
45-1 
167-0 
45-1 
61-0 
45-0 
142-0 
45-0 
52-0 
44-8 
122 0 
44-8 
450 
44-6 
95-0 
44-6 
35-0 
44-45 
71-0 
44-45 
26-0 
44-35 
55-0 
44 35 
20-2 
44-05 
370 
44-05 
13-5 
43-9 
26-0 
43-9 
95 
43-6 
17-0 
43-6 
6-2 
43-5 
9-5 
4.35 
3-4 
43-35 
7-0 
43-35 
2-5 
42-8 
0 
42-8 
0 
Observer R. —The next colour-blind person whom we examined we will call E. 
We were very anxious to obtain observations from him, as one of us had seen him 
some years ago tested by the wool test—an operation, we may remark, which appears 
to be so unpleasant to the victim, that some persons who had undergone it were 
deterred by the recollection of it from submitting themselves to our test. We had 
some slight difficulty in persuading E to do so. Subsequently, however, he remarked 
that our method was not unpleasant,” 
E’s curve and that of H (which we shall presently discuss) seem to us to be 
typical. It will be seen that with E there is scarcely any perception in the red. 
At C the luminosity of the spectrum to him is only -g-th and at D only about |rds 
of the normal perception. Again he is slightly deficient in perception of the Vue 
rays; but, as will be seen, not so much as is H. Fig. 6, Plate 24, shows his curve 
compared with the normal. Like G’s it had to be reduced in height by using a factor 
which represents the ratio of the illuminating value of the candle as seen by him to 
MDCCCLXXXVI. 3 L 
