160 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1&19. 
List of plates — Continued. 
Reference. 
Place. 
Date. 
Greenwich 
mean time. 
Expo- 
sure. 
Approx. 
Z. D. 
Barom- 
eter. 
Ther- 
mometer. 
Plate. 
K' 
Principe. . 
...do 
1919. 
May 29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
29 
h. m. s. 
2 13 9 
2 13 28 
2 13 46 
2 14 1 
2 14 20 
2 14 44 
2 15 6 
2 15 30 
2 15 53 
2 16 13 
2 16 37 
2 16 50 
2 17 15 
2 17 33 
2 17 47 
2 18 1 
s. 
5 
10 
3 
5 
10 
15 
5 
20 
3 
15 
10 
6 
10 
3 
2 
2 
46 
40 
46 
46 
46 
46 
46 
46 
46 
46 
46 
46 
46 
46 
46 
46 
in. 
29.45 
29.45 
29.45 
29.45 
29.45 
29.45 
29. 45 
29. 4,) 
29.45 
29.45 
29.45 
29.45 
29.45 
29.45 
29.45 
29.45 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
77.0 
S.R. 
L 
S.R. 
M 
...do 
S.R. 
N 
...do 
E. 

...do 
s.s. 
P 
...do 
s.s. 
Q 
...do 
S.R. 
R 
...do 
S.R. 
S 
...do 
S.S. 
T 
...do 
E. 
U 
...do 
S.R. 
...do 
S.S. 
W 
...do 
s. 
...do 
S.R. 
Y 
...do 
S.R. 
Z 
...do 
S.R. 
NOTES. 
Column 1. The letter is marked on the original plates (preserved at Cambridge Observa- 
tory). The number refers to the exposure, disregarding exposures taken without the 
8-inch stop. 
Column 2. The coordinates of Oxford Observatory are 5m. 3s. W., 51° 46' N., and of 
the site at Principe, 29m. 32s. E., 1° 40' N. 
Column 4. The mid instant of the exposure is given. Times for check plates at 
Principe v^ere only noted roughly. Times for the eclipse plates are deduced from the 
calculated time of totality, the interval from the end of one exposure to the beginning of 
the next being assumed uniform. 
Column 7. Readings at Principe were taken with an aneroid recording instrument, and 
therefore automatically reduced to the latitude of England. The barometer during our 
visit was practically constant, except for a regular semidiurnal wave of amplitude about 
0.05 inch. 
Column 9. Brand of plate : S„ Imperial Sovereign ; S. S., Imperial Special Sensitive ; 
S. R., Ilford Special Rapid ; E., Ilford Empress. Backed plates were used at Principe. 
The large proportion of Ilford Special Eapid plates used at the 
eclipse was due to the fact that experience in developing the check 
plates showed that these suffered less than the others from the high 
temperature of the water (78° F.). Ice was generally available for 
the check plates through the kindness of Sr. Grageira ; but the supply 
failed after the eclipse, and formalin was used to harden the films. 
This was unsatisfactory except for the Ilford Special Rapid plates, 
and so plates P, S, T, W were brought home undeveloped. The de- 
veloping at Principe was done at night, and the drying was acceler- 
ated by use of alcohol. 
The use of an 8-inch stop in front of the object glass was suggested 
to us by Mr. Davidson, who showed that a great improvement of the 
images resulted; it was originally intended, however, to use the full 
aperture for part of totality. Early measures of check plates made at 
Principe soon convinced us that the results from the full aperture 
