282 



METEOKOLOGY AND ALLIED SUBJECTS. 



vious work. The following table gives bis figures for the rainfall at 

 Madras. The first column gives the year of the solar-spot cycle. The 

 second column gives Wolfs relative numbers for the spots averaged 

 for the same yeiirs as the rainfall. The third column gives the mean 

 observed rainfall for several corresponding years of sun-spot cycles. 

 The fourth column gives the same means, after combining three of 

 these values in one, in order to diminish the irregularities : 



There seem to be two maxima and minima in the rainfall at Madras, 

 the minima coincidiug with the minima and maxima of the sun spots. 

 The result to which Meldrum has arrived at Madras shows how much 

 depends upon the method according to wliich the years are grouped. 

 Like Dr. Hunter, he himself had previously found a decided maximum 

 of rainfall at the time of the maximum of spots. Meldrum shows fur- 

 ther thait in the case of Edinburgh we obtain very different results when 

 we group the years as Dr. Hunter has done — that in fact we obtain a 

 minimum' of rainfall in the fifth or maximum year of sun spots. 



If in general the rainfall is above the mean in the years of sun-spot 

 maxima, and below the mean in the years of minima, then we must 



have the following equation: 



S-s R- 



where large S is the mean 



«/_S r'-iV 



value of sun-spot frequency for the whole period under investigation, 

 small s is the mean for the period during which the sun-spot frequency 

 is below the mean; small s' is the value for the period where the sun- 

 spot frequency is above the mean ; E, r, r' the corresponding annual 

 rainfalls for those years for which S, s, s' hold good. That the frequency 

 of sun spots has a simjile ratio to the rainfall is now evident from the 

 fact that the above equation apparently holds good approximately for 

 fifty-four stations in Great Britain, and thirty-four in America for the 

 interval 1824 to 1867. During this interval the rainfall was in excess 

 when the spots were in excess, and deficient when the spots were de- 

 ficient. The excess was .90 of an inch in England and 1.13 inches in 

 America ; and the deficiencies were .75 inches in England and .94 in 

 America. (Z. 0. G. M., 1879, Vol. XIV. p. 22.) 



S. A. Hill has ijublished the result of a short discussion as to the 



