168 ON THE LONG-PERIOD INEQUALITY IN RAINFALL. 



in the second place we wish to find the nature and laws of 

 this connexion should it be proved to exist, 



(2) If the various meteorological elements at the va- 

 rious stations of the earth are found to present the same 

 periodic inequalities as those which characterize sun-spots, 

 this must be taken as decisive in favour of a connexion of 

 some sort between the two, quite irrespective of the exact 

 form of the inequalities. Nor will this evidence be invali- 

 dated if an inequality at one station should be different in 

 form from that at another. 



(3) Assuming the probability (from the evidence already 

 brought forward) of such a connexion, the most natural 

 hypothesis is that which supposes that the sun has inequa- 

 lities which affect his radiating-power. Hence it is of 

 great importance (as proposed by Professor Stokes and 

 others) to ascertain by judicious actinometrical experi- 

 ments whether the heating effect of the sun^s rays be in 

 reality variable. 



(4) In absence of actinometrical results, we have 

 grounds for believing that the magnetic activity of the 

 sun is greatest at epochs of maximum sun-spots ; and it 

 seems most natural that the meteorological activity of our 

 luminary should be greatest when his magnetical activity 

 is greatest. 



From the reasoning of the paper to which this note is 

 added we may conclude that there is no evidence which 

 can be deduced from rainfall against this hypothesis. 



(5) But while there is considerable preliminary evidence 

 in favour of a variability in the heating-power of the sun, 

 and while this is constantly accumulating, we must not 

 deem it impossible that the sun affects the earth in some 

 other way. 



There is ground for supposing that the moon affects 

 both the magnetism and meteorology of the earth in a way 



