328 sm F. W. DYSOX, PROF. A. S. EDDINGTON AND MR. C. DAVIDSON ON A 
The residuals* in the separate comparisons reduced to arc are as follows. They do 
not appear to show any special peculiarities. 
Star. 
X residuals. 
y residuals. 
G. 
H. 
D. 
I. 
Mean. 
G. 
H. 
D. 
I. 
Mean. 
n 
n 
ft 
n 
n 
n 
n 
u 
// 
tt 
11 
+0-04 
-fO-70 
- - 
— 
— 
-fO-01 
+0-52 
— 
-■* 
— 
5 
-0-05 
-0-50 
+0-12 
+0-14 
-0-07 
-0-16 
-0-11 
+0-21 
-0-04 
-0-02 
4 
-0-30 
-0-40 
-0-18 
-i-0-02 
-0-21 
4-0-41 
+0-07 
-0-22 
-0-32 
-0-02 
3 
+0-16 
+0-30 
-0-13 
-0-32 
0-00 
-0-34 
-0-20 
+0-33 
+0-10 
-0-03 
6 
4-0-14 
-0-09 
-0-54 
-0-13 
-0-16 
+0-07 
-0-27 
-0-39 
-0-08 
-0-17 
10 
■' 
— 
-hO-73 
+0-27 
— 
— 
— 
+0-07 
+0-35 
— 
The average ^-residual is ±0"'22, which gives a probable error for y of ±0"-21. 
It is satisfactory that this agrees so nearly with the probable error (±0"-22) of the. 
check plates, shoAving that the images are of about the same degree of difficulty and 
therefore presumably comparable. The probable error of x is ±0"'25, but we are 
not so much concerned with this. 
The weight of the determination of 8 k is about 3 (strictly 3 • 23 for Plate X and 2 • 87 
for Plate W). The probable error of k is therefore ±0"-12, which corresponds to a 
probable error of ±0"-38 in the final values of the defiection. 
As the four determinations involve only two eclipse plates and are not wholly 
independent, and further small accidental errois may arise through inaccurate 
determination of the orientation, the probable error of our mean result will be 
a.bout ±0"-25. There is further the error of ±0"*14 affecting all fom’ results 
equally, arising from the determination of scale. Taking this into accomit, and 
including the small correction —0"-04 previously mentioned, our result may be 
written 
l"*61±0"-30. 
It will be seen that the error deduced in this way from the residuals is considerably 
larger than at first seemed likely from the accordance of the four results. Nevertheless 
the accuracy seems sufficient to give a fairly trustworthy confirmation of Einstein’s 
theory, and to render the half-deflection at least very improbable. 
38. It remains to consider the question of systematic error. The results obtained 
with a similar instrument at Sobral are considered to be largely vitiated by systematic 
* The residuals refer to the theoretical deflection l"-76, not the deduced deflections. 
