382 Mr. C. Meldrum on [Mar. 0, 



the mean duration of the period is 11 years ; but the intervals are less 

 favourable, being 5*3 years from the driest to the wettest, and 5*2 from 

 the wettest to the driest. The results for America are nearly the same. 

 In India the mean duration of the period is 10*8 years, the mean interval 

 from the driest to the wettest years 4*5, and from the wettest to the driest 

 5*8 years. For Australia we get a mean period of 10*7 years, with an 

 interval of 4-7 from the driest to the wettest years, and of 5-5 from the 

 wettest to the driest years. The means of the five results are as 

 follows : — Duration of period = 11 years ; interval from driest to wet- 

 test years = 4*8 years ; interval from wettest to driest years = 5*8 

 years. 



The mean rainfall of the globe (all the stations) gives the following 

 results : — Mean duration of period = 10*6 years ; mean interval from 

 driest to wettest years = 4*9 years; mean interval from wettest to 

 driest years = 6 years. 



For the river-depths the mean duration of the period is 11 years ; the 

 mean interval from minimum to maximum 3*8, and from maximum to 

 minimum 6*8 years. 



(12.) The results just given are of course only approximations. They 

 were, however, considered so favourable as to encourage a closer 

 examination ; so that whenever I procured a portion (at least) of the 

 Kew values of the sun-spot area, and of Wolf's relative numbers, I com- 

 pared the former with the rainfall from 1832 to 1867, and the latter 

 with the rainfall and river-depths for the longest possible periods, and 

 on the whole obtained very favourable results. 



(13.) Supposing (as Mr. J. Allan Broun does) that any connexion 

 that may subsist between sun-spots and rainfall may be approximately 

 represented by the equation A B = /A A, it is found that the values of/ 

 for Great Britain, the continent of Europe, America, India, and Aus- 

 tralia from 1832 to 1867 are all favourable, except for America, where 

 it is slightly unfavourable. 



(14.) There are, apparently, some discrepancies between the Kew 

 values and those of "Wolf for the period 1832-67. For when, in place 

 of A A (difference of sun-spot area from the mean) we take A r (difference 

 of Wolf's relative numbers from the mean), we obtain favourable values 

 of / for all the five districts. 



(15.) A comparison of Wolf's relative numbers with the rainfall of 

 each country for the longest possible periods also gives very favourable 

 results. The agreement of A E and S with A r, in regard to the signs 

 ( + ) and ( — ), is remarkable, especially for the period 1842 to 1872, during 

 which the rainfall of a portion of the southern hemisphere is represented. 

 The values of / in the equation A B = / A r are favourable for each 

 country, and (taking all the stations) they are also favourable for each 

 of the seven sub-periods, except the one 1832-41. The whole period 

 of 77 years gives for the rainfall of the globe A E = + • 05745 A r ; and 



