144 
ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1919. 
Green- 
wich 
mean 
time. 
Ther- 
mom- 
eter. 
Green- 
wich 
mean 
time. 
Ther- 
mom- 
eter. 
Green- 
wich 
mean 
time. 
Ther- 
mom- 
eter. 
Green- 
wich 
mean 
time. 
Ther- 
mom- 
eter. 
d. ft. m. 
28 22 45 
23 
15 
82.4 
84.2 
82.4 
d. h. m. 
28 23 30 
45 
29 
80.6 
82.4 
80.6 
d. h. m. 
29 15 
30 
45 
° 
82.0 
82.4 
83.1 
d. h. m. 
29 1 
15 
30 
83.8 
84.2 
SI. 2 
15. On June 7, having completed the development, we left Sobral 
for Fortaleza, returning on July 9 for the purpose of securing com- 
parison plates of the eclipse field. 
Before our departure we dismounted the mirrors and driving clocks 
which were brought into the house to avoid the exposure to dust. 
The telescopes and ccelostats were left in situ. Before removing 
the mirrors we marked their position in their cells so that they could 
be replaced in exactly the same position. 
After our return to Sobral the mirrors and clocks were remounted ; 
the photography of the eclipse field was commenced on the morning 
of July 11 (civil). The difficulty of finding the field with the ccelo- 
stats was overcome by making a rough hour circle on the heads of 
the ccelostats out of millimeter paper. 
The following is the list of exposures made on the field for com- 
parison with the eclipse photographs : 
[The reference numbers follow the civil dates.] 
Astrographic telescope. 
4-inch telescope. 
Refer- 
ence 
num- 
ber. 
Date. 
Green- 
wich 
mean 
time. 
Num- 
ber of 
expo- 
sures. 
Dura- 
tion. 
Alti- 
tude. 
Refer- 
ence 
num- 
ber. 
Date. 
Green- 
wich 
mean 
time. 
Num- 
ber of 
expo- 
sures. 
Durar 
tion. 
Alti- 
tude. 
h. m. 
s. 

h. m. 
s. 

Ill 
July 
10 
20 5 
3 
5 
28.9 
14i 
July 
13 
20 7 
2 
25 
32.4 
ll2 
20 16 
2 
5 
31.1 
142 
20 16 
2 
20 
34.3 
lis 
20 21 
1 
5 
32.2 
14i 
July 
13 
20 13 
3 
5 
33.7 
15i 
July 
14 
20 17 
2 
20 
35.4 
142 
20 17 
2 
5 
34.5 
152 
20 22 
2 
20 
36.4 
143 
20 19 
2 
5 
34.9 
loi 
July 
14 
20 15 
3 
5 
34. 9 
17i 
July 
16 
20 6 
3 
15 
34.7 
152 
20 20 
2 
5 
36.1 
172 
20 24 
2 
15 
3S. 6 
153 
20 23 
2 
5 
36.6 
17i 
July 
16 
20 2 
4 
3 
33.8 
1-2 
20 15 
3 
3 
36.6 
ISi 
July 
17 
19 57 
3 
20 
33.6 
IT3 
20 23 
2 
3 
38.3 
18s 
20 24 
2 
20 
39.2 
17< 
20 25 
2 
5 
38.8 
ISi 
July 
17 
19 50 
3 
4 
32.8 
IS2 
20 1 
2 
4 
34.4 
IS3 
20 20 
3 
4 
38.6 
IS4 
20 25 
2 
3 
39.5 
1 The 4-inch plate, No. 18i, was taken thi'ough the glass (see sec. 17, infra) to facilitate the measurement 
and is referred to as the scale plate. 
