OF THP] RETINA TO LIGHT AND COLOUR. 
179 
Fig. 9. 
In the following observ^ations the illumination by the D light was much reduced, 
being only ‘23 AL, and for certain reasons, which will be apparent, the ray at scale 
number 417 was substituted for that at scale number 36. The other three rays 
were the same as before (fig. 10), 
Table XIIL 
' Extent of fields in degrees. 
Angle of field_ ^ 
in degrees. 
Red Li. 
D. ' 
SN 41-7 
Blue Li. 
0 
23 
25 
15 
28 
30) 
28 
27 
16 
32 
60 
35 
37 
21 
40 
90 
^T 
38 
40 
23 
47 
120 
35 
37 
22 
42 
1.50 
27 
30 
18 
35 
180 
23 
25 
16 
28 
1.50^ 
25 
26 
16 
29 
120 
28 
30 
18 
32 
90 
u 
29 
30 
18 
34 
60 
26 
27 
17 
30 
30 
23 
25 
16 
28 
2 A 2 
