184 
CAPTAIN ABNEY ON THE SENSITIVENESS 
the whole spectrum. The different rays were first allowed to 23ass through the 
annulus at 0°; and, subsequently, measures were made after ]3assing through it, when 
its readings were 35, 70 . . . 280°, as every added 35° halved the previous intensity. 
The D light coming through the slit with the annulus at 0°, measured 4’5 AL. The 
following were the luminosities of the other rays coming through the same slit ; 
red lithium, '5 AL; SN 41'7, 3‘2 AL; and blue lithium, '3 AL (fig. 13). 
Table XVI. 
Degrees 
auiiulus. 
Intensity 
of ray. 
Reading of horizontal field in degrees. 
O O 
Red Lithium. 
D. 
Scale No. 417. 
Blue Lithium. 
Temporal. 
Nasal. 
Temporal. 
Nasal. 
Temporal. 
Nasal. 
Temporal. 
Nasal. 
0 
] 
54 
42 
57 
45 
43 
33 
61 
48 
35 
2 
50 
38 
53 
41 
39 
29 
57 
44 
70 
1 
4 
47 
36 
49 
37 
35 
27 
53 
42 
105 
1 
B 
43 
32 
45 
34 
32 
24 
50 
38 
140 
1 
1 G 
39 
29 
41 
31 
28 
22 
46 
34 
175 
3 2 
35 
26 
37 
28 
25 
19 
42 
31 
210 
1 
Oi 
32 
24 
33 
26 
21 
16 
39 
29 
245 
1 
12 8 
28 
20 
30 
23 
17 
14 
o5 
26 
280 
2 5 6 
24 
18 
26 
20 
14 
13 
31 
25 
We find from the above that the average diminution in field for each reduction of 
half intensity on the tenq)oral side is 3‘75°, and on the nasal side close upon 3°. 
Using these figures, the above table would be as follows :— 
Table XVII. 
Degrees 
annulus. 
Intensity 
of ray. 
Reading of horizontal field in degrees. 
Red Lithium. 
D. 
Scale No. 417. 
Blue Lithium. 
Temporal. 
Nasal. 
Temporal. 
Nasal. 
Temporal. 
Nasal. 
Temporal. 
Nasal. 
0 
1 
54 
42 
57 
45 
43 
33 
61 
48 
35 
1 
2 
51 
39 
53 
42 
39 
30 
57 
45 
70 
1 
4 
46-5 
36 
49-5 
39 
35-5 
27 
53o 
42 
105 
1 
8 
4375 
33 
46 
36 
32 
24 
50 
39 
140 
1 
1 6 
39 
30 
42 
33 
28 
21 
46 
36 
175 
1 
3 2 
35 
27 
38 
30 
24 
18 
42 
33 
210 
(3 ' l 
31-5 
24 
34-5 
27 
20-5 
15 
38" 5 
30 
245 
1 
1 2 8 
28 
21 
31 
24 
17 
12 
35 
27 
280 
1 
2 5 6 
21 
18 
27-UU 
21 
13 
9 
31 
21 
