310 
>S1K F. W. DYSOX, PROF. A. S. EDDINGTON AND MR. C. DAVIDSON ON A 
the stars shomi were measured. They were reduced by the same method as that 
employed for the “4-inch” photographs. With the exception of plates Nos. 15 and 
16, taken through clouds, the stars numbered 3, 4, 5, 6, 10, 11 and 12 are shown on all 
the plates ; the fainter stars 2, 7, 8 and 9 are sometimes shown, but No. 1, which is 
very near the sun, is always drowned in the corona. These plates were only measured 
in declination, as the right ascensions were of little weight. 
24. In the follomng table is given the value of a, the constant of the gravitational 
displacement, as calculated from the measures ; the apparent difference of scale e 
between the eclipse and comparison plates ; d the difference of orientation of the plates 
given by the measures of y, and depending on the adjustment of the plates in the 
measuring machine. 
Table IX. 
(r - 12"-3). 
No. of 
Eclipse 
Ref. No. of 
Comparison 
No. of 
Stars. 
Values of d, e, a. in Revolutions at 
50' Distance. 
a. at 
Sun’s Limb 
Plate. 
Plate. 
d. 
e. 
a. 
in Arc. 
1 
I84 
7 
r 
-fO-051 
r 
+0-089 
r 
+0-033 
n 
+ 1-28 
2 
I 84 
11 
-0-009 
+0-059 
+0-025 
+0-97 
3 
I 84 
8 
-0-074 
+ 0-101 
+0-028 
+ 1-09 
4 
I 84 
11 
-0-168 
+0-091 
+0-033 
+ 1-28 
5 
II3 
10 
+0-094 
+0-076 
+0-025 
+0-97 
6 
II3 
11 
-1 0-186 
+0 082 
+ 0-021 
+0-82 
J 
r 7 
iR 
12 
4-0-006 
+0-119 
0-000 
0-00 
i 
L 7 
18. 
7 
-0-054 
+0-166 
0-000 
0-00 
8 
IR 
10 
+0-093 
+0-064 
+ 0-021 
+0-82 
9 
iR 
7 
-0-096 
+0-129 
+0-008 
+0-31 
10 
iR 
10 
4-0 090 
+ 0-045 
+0-026 
+ 1-01 
11 
'^h 
10 
+0-073 
+0-061 
+0-032 
+ 1-21 
j 
ri 2 
ih 
11 
-0-009 
+ 0-102 
+0-049 
+ 1-91 
i 
L12 
17.. 
7 
- 0-102 
+0-114 
+0-019 
+0-74 
15 
6 
+ 0-111 
+0-036 
+0-018 
+0-70 
16 
153 
7 
- 0-002 
+0-037 
+0-018 
+0-70 
17 
8 
- 0-022 
+ 0-109 
+ 0-012 
+0-47 
18 
1^2 
7 
+0-045 
0-000 
+0-030 
+1-17 
Mean. 
+0-082 
+ 0-022 
+ 0-86 
Thus the mean value of a obtained from all the astrographic plates is 0"-86, a figure 
considerably less than that obtained from the 4-inch photographs. 
25. Reference to the diagram shows that the measurement of displacement depends 
essentially on the position of the stars Nos. 3 and 4 relative to 5 on one side and 6 
and 10 on the other. These are all bright stars, and in this respect their images are 
