54 PKKSIDKNTIA]. AJJJ^EESS SKCTIOX C. 



maxima, the number of spots occasiouallj'- reaclnii<^" tew or 

 none, then gradnally increasing* j^ear by year to a maximum 

 varying" from 50 to 150 spots, then fliminishing- again 

 gradually to few or none. With such a wide variation of 

 cycle duration and of maxima, it is, of course, impossible to 

 predict years ahead, but it is found that the average cycle 

 since sunspots could first be counted has been slightly over 

 eleven years, and that the growth-ring records of trees corre- 

 spond with the known cycles during that period, and so can 

 be accepted as proof for earlier times. What the exact 

 climatic effect is, or how it is produced, maj^ be debated, but 

 it seems that the more spots the less luminous or the more 

 veiled is the sun ; that there may be one or more successive 

 years of high or of low sunspot activity ; that the whole baric 

 system of the earth is affected thereby in its migrations, and 

 that one result is that hot and comparatively rainless seasons 

 occur when sunspots are few, while duller, colder and more 

 rainy seasons occur when or soon after they are abundant. 

 I say " soon after " because the local action anywhere is not 

 altogether a direct one, and though the migrations of the 

 baric system and of anticyclones, etc., may he a direct action, 

 these sometimes affect local rainfalls one or even two years 

 later, and in methods of local ap])lication which, so far 

 as South Africa is concei'iied, are still far from clear, though 

 this delaj^ed action has been noted in connection Avitli the 

 eastern rainfall. 



Although sunspot appearances and reactions have been 

 carefully followed and detailed in connection with the Northern 

 Hemisphere, little has been published concerning these 

 phenomena as thej^ affect the Southern Hemisphere, but just 

 because of the Senate Select rommittee's finding, already 

 mentioned, that " there are not sufficient data available to 

 define any such cycles." there is the more reason why this 

 subject siiould receive the closest investigation, not only as 

 an abstract and interesting theory, but as a proved cause- 

 and^effect elsewhere, and also on account of its intensely -jirac- 

 tical bearing on the possibilities and probabilities of plant-life 

 and ag-ricultural operations in near future years from any 

 given date, some of the North American States having' their 

 cycles of " fat years " and of " lean years " in legard to 

 ordinary agricultural crops, directly related to tlio weather 

 cycles. In Africa it is clear that Joseph kncAv something 

 about the result, if not the cause, when he stored grain in 

 Eg-ypt durino' the several full years, which he predicted would 

 be followed by lean years 4,000 years ago. 



All writers on the subject agree lliat. in addition to the 

 definite sunspot cycles, there are other rainfall cycles, some 

 longer, some shorter, simultaneously at work, the cairses of 

 which are less clearly understood, but wliich croj) records 

 and tree-ring records show to be fairly constant, and it is 

 known that when several of these cycles fall due at one 

 time, and occur when due, ihe rainfall I'ecord becomes an 

 unusuallv heavv one. 



