NO. 3 SOLAR RADIATION AND THE WEATHER CLAYTON 9 



oscillations of about lo to ii days, up to 30 days following the solar 

 measurements. 



The differences between values near the mean ; namely, between 

 those following 1.960 and those following 1.920 show much shorter 

 waves, as is seen in the plot of A2. 



Now the question arises, are these waves set up by solar outbursts 

 of energy producing" successive waves of temperature like those 

 which might result in water from a pebble thrown into a bowl ? or do 

 they respond to solar periodicities which exist in the sun itself ? 



Means of Solar Radiation Values Preceding and Following 

 Maxima and Minima of Different Intensities 



To test this question, all the observed values of solar radiation 

 since the beginning of observations were taken from the reports of 

 the Smithsonian Institution and the maxima and minima of radiation 

 were read off from the plotted curves. These maxima and minima 

 were then divided into groups separated by intervals of 0.020 calories. 

 The first group embraced all maxima above 1.990 calories, the second, 

 all values between 1.970 and 1.989 calories, the third, between 1.950 

 and 1.969, etc. The means of these groups were about 2.000, 1.980, 

 1.960, 1.940, etc. Observations were missing for the year 1907 and 

 have not yet been received for the year 191 7. For each group of 

 maxima, averages of the radiation values were obtained for each of 

 79 days ; namely, for five days preceding the maximum of radiation 

 and for 74 days following the maximum. The observations were 

 very much interrupted, but for each day the sum of all the observed 

 values was divided by the number of observations. 



The values preceding and following minima of solar radiation, 

 were treated in the same way. The results are shown in table V for 

 five days preceding and 40 days following the observations of maxima 

 of radiation. These results are plotted in figure 2. In curve S, which 

 shows the mean values preceding and following the maxima of about 

 2.000 calories, it is seen that there are various irregularities in the 

 curve, but that two chief maxima are observed at 11 and 22 days. 

 In curves S^ and S6 where the results are shown separately for sun- 

 spot maximum and sun-spot minimum these maxima are equally 

 distinct in both curves. The curve S^ for the time of sun-spot maxi- 

 mum shows also very regular secondary maxima at intervals of 

 three and a half days. At sun-spot minimum this interval becomes 

 more nearly five and a half days. 



L 



