CHANGES DURING A SOLAR-SPOT PERIOD. 



145 



falls, I confess I was scarcely prepared to expect that the 

 results of rainfall observations would agree so closely with 

 those of barometric pressure and temperature. 



Instead of comparing the differences between the amounts 

 of rainfall, it would perhaps be more correct to compare 

 their ratios; but the results would be substantially the 

 same. Thus, dividing the entire series of n years into 

 three groups — the first including the four years 1858-61 

 (one of which was a year of maximum frequency of solar 

 spots), the second the four years 1862-65, and the third 

 the three years 1866-68 (one of which was a year of mini- 

 mum frequency) — we have the following amounts and 

 their ratios : — 





Sum of rainfall 



under S.E. and 



S. winds. 



Sum of rainfall 



under S.W. and 



W. winds. 



Ratio. 





in. 



40*24 

 49*10 

 5606 



in. 

 62*13 



40*05 

 2609 



064 



1*22 

 2*14 



Here we have a small ratio in years of maximum solar 

 activity, and a large ratio in years of minimum, and a ratio 

 of intermediate value for the intervening years. 



It will, I think, be admitted that the results of tins 

 investigation support very strongly the hypothesis which 

 led me to undertake it. They show also strikingly that 

 the future progress of meteorology must depend to a much 

 greater extent than has been generally supposed upon the 

 knowledge we may obtain of the nature and extent of the 

 changes which are constantly taking place on the surface 

 of the sun ; and therefore, in the interests of meteoro- 

 logical science, it is evidently very desirable that observa- 

 tions of solar phenomena should be greatly multiplied, by 

 the establishment, in various parts of the world, of obser- 

 vatories specially devoted to this object, so that a con- 



SER. III. vol. v. L 



