546 
CAPTAIN W. DE W. ABNEY AND MAJOR-GENERAL E. R. FESTING 
proportion to which each beam was reduced at extinction, those in the fourth column 
the absolute luminosity of the beam. The last column gives the products of these 
two quantities, which are the luminosities at the extinction point. 
Table III.—Extinction by Central Portion of Normal Eye. 
I. 
11. 
III. 
IY. 
Y. 
j VI. 
Scale 
Wave- 
E. 
Reduction of 
original 
luminosity 
in millionths 
to cause 
extinction. 
L. 
Luminosity 
E x L 
Persistency curve 
650 
E 
(Maximum = 100). 
. 
number. 
length. 
of 
original beam. 
100 ' 
64 
63 
7,217 
7,082 
55,000 
30,000 
1 
300-0 
62 
7,957 
15,000 
2 
300-0 
61 
6,839 
7,500 
4 
300-0 
60 
6.728 
3,750 
7 
262-5 
59 
6,621 
1,900 
125 
237-5 
•34 
58 
6,520 
1,050 
21 
220-5 
•62 
57 
6,423 
650 
33 
214-5 
1-0 
56 
6,330 
380 
50 
190-0 
1-71 
55 
6,242 
272 
65 
176-8 
2-38 
54 
6,152 
196 
80 
156-0 
3-32 
53 
6,074 
140 
90 
1260 
4-64 
52 
5,996 
97 
96 
93-12 
6-70 
51 
5,919 
57 
99 
56-43 
11-40 
50 
5,850 
35 
100 
35-0 
18-6 
49 
5,783 
24 
99 
23-76 
27-1 
48 
5,720 
17 
97 
16-49 
38-2 
47 
5,658 
12-6 
92-5 
11-65 
51-6 
46 
5,596 
10-2 
87 
8-87 
63-7 
45 
5,538 
8-6 
81 
6-97 
75-6 
44 
5,481 
7-4 
75 
5-55 
87-8 
43 
5,427 
6-7 
69 
4-62 
97-0 
42 
5,373 
6-55 
62-5 
4-09 
99-5 
41 
5,321 
6-5 
57 
3-705 
100 
40 
5,270 
6-55 
50 
3-27 
98-5 
39 
5,221 
6-65 
42-5 
2-83 
97-5 
38 
5,172 
6'85 
36 
2-46 
95-0 
37 
5,128 
7-2 
29-5 
2T2 
90-0 
36 
5,085 
7-6 
24 
1-82 
81-3 
35 
5,043 
805 
18-2 
1-48 
80-0 
34 
5,002 
8-8 
14-2 
1-25 
74-0 
33 
4,963 
10-2 
10-5 
1-07 
63-0 
32 
4,924 
11-6 
8-5 
•988 
56-0 
31 
4.885 
13-6 
7-0 
•952 
47-7 
30 
4,848 
163 
5-5 
•896 
40-0 
29 
4,812 
20-5 
47 
•963 
31-7 
28 
4,776 
26-0 
4-0 
1-040 
25-0 
27 
4,742 
31-0 
3-5 
1-085 
20-9 
26 
4.707 
38-5 
2-3 
1-078 
16-9 
25 
4,674 
46-0 
2-3 
1-058 
14-1 
24 
4,639 
56-0 
1-82 
1-019 
11-6 
23 
4,608 
67-0 
1-6 
1-072 
9-7 
