RAINFALL DURING A SOLAR-SPOT PERIOD. 149 



The mean ratio is 3*01 ; and the ratios for the years of 

 maximum solar-spot frequency are all above this mean, 

 while those for minimum years are all below it, with only 

 one unimportant exception. 



In order now to eliminate as far as possible the effects 

 of accidental disturbing causes, we may take the means of 

 the ratios of every three successive years ; and in this way 

 we obtain the corrected ratios in the fifth column of the 

 above table. For convenience of comparison I have added 

 in the sixth column the number of groups of solar spots 

 observed in each year by Schwabe ; and a glance at the two 

 sets of numbers will show the remarkably close agreement 

 which exists between them in the times of their maxima 

 and minima, which seems to me fully to justify the con- 

 clusion that both classes of phenomena are intimately 

 connected, either as cause and effect, or as effects of the 

 same cause. 



Excluding the amounts of rain which fell during calms, 

 the corrected ratios become : — 



18 55 277 



1856 2-15 



1857 3'3 2 



1858 5'4<> 



1859 G'3 1 



i860 6*42 



1861 4-37 



1862 404 



1863 2-80 



It will be observed that the course of these numbers is 

 almost identical with that of the numbers obtained when 

 the amounts of rain which fell during calms are combined 

 with those which fell under north-east, east, and north- 

 west winds. 



The close agreement which has thus been shown to exist 

 at St. Petersburg between the times of maximum and 

 minimum frequency of solar spots, and those of the varia- 

 tions in the distribution of rainfall under different winds, 

 gives increased value to the results derived from the Oxford 

 observations, and affords additional support to the hypo- 



