ON SUNSPOTS AND BAINFALL. 257 



means almost In the same years of the common period, and the epochs of 

 maximum and minimum sunspots coincide nearly with the epochs of 

 minimum and maximum rainfall. 



IX. — Summary of Results. 



65. If we knew exactly the annual rainfall for the whole globe during 

 the four sunspot periods 1824-67, and found that it varied as the sun's 

 spotted area varied, we should conclude that there was very strong 

 evidence of a causal connection between the two phenomena, especially 

 when it was considered that the comparative frequence or absence of solar 

 spots, faculas. and prominences indicated a variation in the sun's radiant 

 energy, upon which the variations in terrestrial meteorology mainly 

 depend. But as we do not know the total annual rainfall over the whole 

 sui'face of the earth, and have only approximate values of the annual 

 amounts of solar maculation, all that can be done is to compare the rain- 

 fall at the greatest possible number of stations in different parts of the 

 world with the available values of the sunspot areas, and see whether 

 there is anything approaching to a correspondence. This has been done 

 in the preceding pages, chiefly for the years 1824-67, and th« principal 

 results may be summarised as follows : — 



(1.) The mean rainfalls of Great Britain, the Continent of Europe, 

 America, and India, as represented by all the returns that have been re- 

 ceived, have, notwithstanding some anomalies, varied as Wolf's sunspot 

 numbers have varied, and the epochs of minimum and maximum rainfall 

 have nearly coincided with those of the sunspots. 



(2.) The rainfall at five stations in the southern hemisphere for 

 shorter periods give similar results. 



(3.) The levels of the principal rivers of Central Europe have also 

 varied with the sunspots, although, as in the case of the rainfall, there 

 are discrepancies. 



(4.) The rainfalls at individual stations, such as Edinburgh, Paris, 

 New Bedford, Bombay, &c, afford unmistakable evidence of a connection 

 between sunspots and rainfall. 



(5.) The variations in the levels of individual rivers of Central 

 Europe, such as the Rhine and Elbe, give similar evidence. 



(6.) The results obtained by taking each sunspot cycle separately are 

 all favourable, with the exception of those for the cycle 1 834-43, which 

 are unfavourable for ten stations in America and three stations in India, 

 but favourable for thirty-seven stations in Europe. 



(7.) When the final results for each country are combined, by taking 

 means of all of them (Table XXXIIL), it is found that the rainfall and 

 the sunspots are below or above their respective means in the same years, 

 and that the epochs of maximum and minimum rainfall apparently coin- 

 cide with the epochs of maximum and minimum sunspots. 



(8.) The mean range of rainfall variation for the four cycles from 

 1824 to 1867, taking all the stations, is about 4 inches, and the annual 

 mean rainfall 38- 5 inches. 



(9.) There is a tendency to a double oscillation in the rainfall, a small 

 second maximum and minimum occurring after the principal maximum. 

 This is especially the case in India. 



(10.) The principal maximum and minimum epochs of the rainfall do 

 not occur at the same time in different countries, but oscillate to the 



1878. s 



