Vol.. 6, 1920 
ASTRONOMY: C. G. ABBOT 
677 
prominences, faculae. We have now, however, long passed the period of 
maximum sunspots, so that we should naturally expect the sun's radiation 
to be falling below the mean value of 1902-12. The results obtained by 
the Smithsonian observers at Calama, Chile, indicate quite otherwise. 
I have computed solar radiation values for each five days interval 
from July 1, 1919 to March 25, 1920. The mean value is never based on 
less than two observations, and this minimum occurs only in two instances. 
All other values depend on three days of observation, more often four, 
and very often five. 
One is immediately struck by the wide fluctuation of the mean values 
shown. The fluctuation of individual days naturally had a still wider 
range, reaching in fact to 8%. The mean values cover a range of 5%. 
With gradually diminishing swings, up and down, the radiation fell from 
June 1919 to early in October, then suddenly leaped up to a high mean 
value which it maintained until early in December, and then again 
suddenly leaped much further and remained from the end of December to 
the middle of March 1920 at a mean value far in excess of anything which 
we have any record of, continued for so long a time as three months 
during the whole fifteen years in which solar constant observations have 
been carried on with anything like regularity. Towards the end of 
March an extremely rapid fall of radiation occurred, so that individual 
values have run as low as 1.86 calories. 
1919 
A 
B 
c 
D 
E 
F 
June 
46 
84 
37 
39 
71 
53 
July 
36 
54 
47 
63 
57 
31 
Aug. 
53 
54 
38 
36 
51 
45 
Sept. 
28 
33 
30 
42 
31 
30 
Oct. 
18 
57 
49 
46 
59 
62 
Nov. 
60 
51 
60 
43 
47 
54 
Dec. 
55 
48 
54 
60 
67 
81 
1920 
Jan. 
69 
102(?) 
74 
78 
81 
70 
Feb. 
87 
60 
78 
77 
68 
Mar. 
77 
65 
70 
50 
10 
In view of this extraordinary march of solar radiation values, it may 
be recalled that we have been passing through an exceptionally cold and 
cloudy winter from about the first of December. The cloudiness has pre- 
vailed in South America as well as here, so that if it had not been for the 
introduction of the new method of observing, of which notice was given 
to the Academy at its last meeting, the observers would not have been able 
to give us this very continuous record. 
At first sight it looks paradoxical that a cold winter could accompany 
