REPORT OF THE SECRETARY. 85 
perature in South America, with a few exceptions that may easily have resulted 
from errors in the measurements of solar radiation. At Buenos Aires the ratio 
of temperature change to solar change at the time of greatest solar activity 
was found from the averages of several years to be 1.4 C. for each change of 
1 per cent in solar radiation. Since the extreme solar values range about 6 per 
cent on either side of the mean, there might result departures from the normal 
at Buenos Aires from this cause of about 8.5 C. The extreme departure from 
the normal observed at Buenos Aires during the last 13 years has been 11.5 C. 
The results of these researches have led me to believe that the existing abnor- 
mal changes which we call weather have their origin chiefly, if not entirely, 
in the variation of solar radiation. 
Naturally, these results, which are supported by an enormous 
amount of careful and conscientious computation on the part of the 
forecasting division of the Argentine meteorological service, are of 
extreme interest. They point to the great desirability of equipping 
in different cloudless regions of the world several observatories de- 
signed for the measurement of the solar constant of radiation. The 
chief of the Argentine weather service, Mr. Wiggin, desires very 
much to take over the South American station of the Smithsonian 
Institution, to be maintained by the Argentine meteorological serv- 
ice. ‘Tentative arrangements were entered into between Dr. Abbot 
and Mr. Wiggin for this purpose, which, however, require the further 
appreval of the Argentine Government to become effective. If suit- 
able arrangements for the transfer can be made, it is hoped to employ 
the funds thereby set loose for the establishment by the Smithsonian 
Institution of a solar station in Egypt. 
From Argentina, Messrs. Moore and Abbot returned immediately 
to Calama. 
Measurements of the Solar Constant of Radiation at Calama, 
Chile—When Dr. Abbot reached Calama he found that Messrs. 
Moore and Abbot had prepared data giving the pyrheliometry, the 
transparency of the atmosphere for nearly 40 wave lengths, the func- 
tion p/psc, and pyranometer values representing the intensity of the 
radiation of the sky in a zone 15° wide surrounding the sun. All 
these values were tabulated with solar constant values for 60 days 
of observation and for each day at periods when the air masses were 
2 and 3, respectively. 
We have felt very keenly the desirability of devising some method 
of determining the solar constant of radiation which would be inde- 
pendent of changes in the transparency of the atmosphere during 
the period of observation. It had been hoped that this might be 
done in some simple way by the aid of the pyranometer, that instru- 
ment which we devised several years ago for the purpose of measur- 
ing the brightness of the sky. It is well known that when the sky 
becomes more hazy the direct beam of the sun is reduced in intensity, 
but the scattered light of the sky at the same time is increased. <Ac- 
12573°—21——7 
