NO. 3 SOLAR RADIATION AND THE WEATHER — CLAYTON I9 



It is seen from the plots that the curves a and b for 1914, follow 

 the same general course. However, the solar curve is more irregular, 

 owing to the scanty broken observations ; but smoothing the com- 



puted values by the formula , the values of Avhich are 



shown by the broken curve, brings the two curves a and b into very 

 close agreement. The highest values are found in each on the 

 second and seventh to eighth days, and the lowest on the seventeenth 

 to eighteenth days. There are, however, some differences in the minor 

 fluctuations. In 191 5 the solar values were more numerous, and for 

 this year the solar and terrestrial values are in almost complete 

 accord, as will be seen by comparing plots a' and b'. Even the minor 

 fluctuations in one curve are visible in the other, the only notable 

 differences being the maximum on the twenty-seventh day, not shown 

 in the Buenos Aires temperature data. 



This comparison can leave little doubt but that in studying fluctua- 

 tion in temperature in Buenos Aires, we are also studying fluctuations 

 in solar radiation. 



For this reason the studies of possible periodic changes take on a 

 new interest. The results already obtained show periodic terms 

 approximating the period of a synodical solar rotation ; but, since the 

 sun has no fixed period of rotation, the interval varying from about 

 26.37 days for a synodical rotation at the equator to 39 days in 

 latitude 80°, it might well happen that eruptions or outbreaks in 

 different latitudes in the sun would cause a mixed or more or less 

 indefinite set of periods such as are indicated by the results, in which 

 the excess of radiation is predominant now in one latitude now in 

 another, thus giving rise to such variation in the predominant periods 

 as are observed. 



In order to study the question more in detail, the solar radiation 

 values and the temperatures at Buenos Aires were subjected to a 

 process of successive smoothing in order to separate the different 

 classes of oscillations. 



This process is illustrated in figure 5 by a series of curves. In this 

 figure, plot I is made from the provisional radiation values deter- 

 mined by the Astrophysical Observatory of the Smithsonian Institu- 

 tion in Chile. Plot 3 is the mean of three days. Plot 5 is the mean 

 of five days, etc., for each odd number of days to 11. In obtaining 

 these curves a few missing values were interpolated. In i there are 

 numerous rapid oscillations numbered i, 2, 3, 4, etc., with intervals 

 of two to four days between the maxima ; these are nearly smoothed 



