NO. 7 THE ATMOSPHERE AND THE SUN CLAYTON 49 



There are also east to west movements of the waves, and there 

 are probably returnin,c^ waves toward the poles of less intensity ; so 

 that the observed phenomena are extremely complex. The analyzed 

 wave movements are subject however to apparently simple laws, and 

 can, therefore, probably be computed and combined to produce ob- 

 served conditions. 



The observed data of sun-spot numbers and solar radiation values 

 when subjected to harmonic analysis for the ii-year period 1917 to 

 1928 show that the dominating- period of about 11 years in sun 

 spots is no more marked in solar radiation values than the subhar- 

 monics of |, ^. ^, etc., of the ii-year period which have ampli- 

 tudes nearly as large as the ii-year period itself. 



When the pressure observations in the Tropics are subjected to 

 harmonic analysis they show periods resembling in amplitude those 

 of solar radiation values and not those of sun spots. The analyses of 

 the data in higher latitudes show that the amplitudes of the subhar- 

 monics increase with latitude, so that in high latitudes in the neigh- 

 borhood of the pole the subharmonics become vastly more important 

 than the primary period. 



A study of the possibility of analyzing the data at each particular 

 part of the earth with the view to discovering fixed periodic cycles 

 indicates that if such cycles exist, the amplitudes are subject to 

 wide variations and even to inversion of phase from time to time. 

 However, when the complex cycles are analyzed individually and 

 averages taken for a small nmnber of successive cycles, it is possible 

 to project them into the future and combine and plot them in a curve 

 which at times has a striking resemblance to observed data. As knowl- 

 edge of methods and laws of change progress, this kind of fore- 

 casting will undoubtedly be done with increasing accuracy. 



