4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 7I 



days later, but following- values of 1.98 calories these maxima occur 

 earlier; namely, on the eighth and thirteenth day. Following low 

 values the differences are equally distinct; after 1.90 calories mini- 

 mum temperatures occur on the eighth and eighteenth days, while 

 after 1.92 minima occur on the sixth and seventeenth days. Near the 

 normal values of solar radiation the progressive change is less dis- 

 tinct ; but these also give some evidences of the shortening of the 

 interval. The mean radiation value is between 1.940 and 1.950 and 

 hence the numbers in column i are not symmetrical about the mean. 

 It is probably for this reason that the numbers after 1.90 are not 

 opposite in sign to those after 2.00. The opposition is nearer when 

 the values following 1.98 and those following 2.00 are averaged. In 

 that case the mean of the two will be about 0.45 calories above the 

 mean solar radiation and the- other, 1.900, about 0.45 below. 



Mean Temperatures at Buenos Aires Following Maxima and 

 Minima of Solar Radiation 



The above described researches led me to the conclusion that the 

 effect of short-period solar changes lasted for longer intervals than 

 at first supposed. 



A plot of the observed values of solar radiation shows a curve in 

 which large values of radiation are followed by other maxima at 

 variable intervals and with variable intensities. The preceding re- 

 search rendered it possible that maxima of great intensity wovild on 

 the average be followed by large changes of temperature at Buenos 

 Aires, while maxima of less intensity would be followed by tem- 

 perature maxima of less intensity separated by shorter intervals. 



Accordingly, beginning' with 1909 the various maxima and minima 

 of solar radiation were arranged in groups according to intensity, 

 the groups being separated as explained above by intervals of 0.020 

 calories. For each group, means of the departure from the normal 

 temperature at Buenos Aires were then computed for each of 39 

 days ; namely, five days preceding the observed solar maximum, and 

 for 33 days following. 



These means were divided into two groups :' the first for sun-spot 

 minimum including the years 1909 to 1914, and the second for sun- 

 spot maximum including the years 191 5, 1916, and 1918 (the values 

 for 1917 not being at hand). The results were as follows in tenths 

 of a decree Centigrade : 



