NO. lO SOLAR RADIATION AND WEATHER STUDIES ABBOT 



II 



5. Analysis of the Solar Variation 



The curve of solar variation contains, however, not only a number 

 of regular periodic constituents, but also accidental errors of nearly 

 as great amplitudes as the periodic terms themselves. These various 

 constituents, accidental and periodic, are confused together, and mutu- 



1.930 



Fig. 6. — The ii-month periodicity in solar variation. 



ally influence the graphic expressions of each other in the observed 

 curve. For the purpose of simplification it has seemed best to remove 

 the several periodic terms one by one, beginning with those of shortest 

 period. In the presence of confusing variations from other causes, 

 these short-period curves may be the most accurately investigated of 

 any because they present the largest numbers of cases which may 



