lO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



from August, 1 918, to December, 1930. I then added their amplitudes 

 algebraically. This produced a curve which obviously bore a con- 

 siderable resemblance to the curve A of figure 3 throughout its whole 

 extent. This indicated that both 8- and 11 -month periociicities have 

 prevailed in solar radiation since 1918. 



I now desired to search for longer periodicities. It seemed better 

 to use monthly mean values for this, as given in table 4 and figure 

 3, A. Having read from the curve of combined departures of 8-month 

 and ii-month periodicities the departures for the second decade of 

 each month from 1918 to 1930, I subtracted these from curve A, 

 figure 3, and replotted the again-revised data. This curve seemed to 

 indicate the existence of a periodicity of 45 months. Arranging the 

 corrected solar values in lines of consecutive 45's, and proceeding as 

 previously, the following result appeared : 



45-month period 



Direct Means 29 32 41 35 37 28 41 33 41 44 47 37 43 45 



Smoothed Means 33 33 34 35 36 37 38 39 40 41 42 43 43 44 



Smoothed Departures — 7 — 7 —6 — s — 4 ^3 ^2 — i o +i +2 +3 +3 ^-4 



Direct Means 44 45 41 38 46 46 44 46 41 SO 43 43 47 44 



Smoothed Means 44 45 45 45 46 46 46 46 46 46 45 45 45 45 



Smoothed Departures +4 +5 +5 +5 +6 +6 +6 +6 +6 +6 +5 +5 +5 +5 



Direct Means 44 39 40 40 38 48 40 47 47 41 41 39 40 39 



Smoothed Means 45 45 45 44 44 43 43 42 41 41 40 39 37 36 



Smoothed Departures +s +5 +5 +4 +4 +3 +3 +2 +1 +1 o — i —3 —4 



Direct Means 36 35 31 



Smoothed Means 35 34 33 



Smoothed Departures — 5 —6 — 7 



After removing the 45-month periodicity as in former cases, there 

 seemed to exist a periodicity of 25 months, which by similar treatment 

 resulted as follows : 



25-month period 



Direct Means 30 33 30 37 34 32 41 38 38 38 38 37 38 44 



Smoothed Means 32 32 33 34 34 35 35 36 37 38 39 39 40 40 



Smoothed Departures — 8 — 8 — 7 —6 —6 — 5 — 5 — 4 — 3 — 2 — i — i o o 



Direct Means 41 44 43 40 43 42 42 43 42 40 33 



Smoothed Means 40 41 41 42 42 42 42 42 41 40 35 



Smoothed Departures o +1 +1 +2 +2 +2 +2 +2 +1 —5 



Removing the 25-month periodicity, as before, a nearly smooth curve 

 resulted in which the 68-month period corresponding to a half sun-spot 

 period was clearly seen. The coordinates of the five periods discovered 

 are as follows : 



Coordinates of Periods 



_ Length Arnjilitude Date of Zero 



in Months in Calories Departure 



68 .014 Dec. IS, 1929 



45 -013 Sept. IS, 1930 



25 .010 Nov. IS, 1929 



■ I oof) Dec. I, 1929 



8 .005 May i, 1930 



