240 Transactions of the South African Philosophical Society. 



not recur till somewhere about 1914, yet it is part of the Lockyer 

 cyclical work to connect Bruckner's cycle with a major cycle of 

 sunspots. Now, 1870 was the big sunspot maximum of the century, 

 and 1870 plus 35 will bring us to 1905, our present year. To repeat, 

 then, although 1905 is not Bruckner's year of maximum rainfall, the 

 Lockyer discovery makes it a particularly important year of maximum 

 sunspots. 



South African rainfall records are too short to afford much scope 

 for studying the influence of Bruckner's cycle on South African 

 rainfall. The Eoyal Observatory has rainfall records for 64 years, 

 and Maritzburg-Gardenscliff, in Natal, for 51 years. These show 

 no tendency for rainfall to recur in 35 years ; but two very dry years 

 at the Eoyal Observatory are separated by 35 years, and two droughts 

 in Natal recur at 35 years. It is too soon yet to say whether this 

 correspondence is accidental. 



The " Storm " Cycle of 9 and 10 Years alternating. 



Two years ahead lies the most powerful of the three Cape weather 

 cycles — the so-called " Storm cycle." This I propose to discuss next 

 year. It is for practical purposes the same as Eussel's 19-year 

 Australian weather cycle. This cycle has also cropped up in other 

 countries. It is noteworthy that 19 years is the period of revolution 

 of the moon's nodes. 



Cyclical Diagrams. 



With this explanation of the three Cape weather cycles I will now 

 proceed to call your attention to the cyclical diagrams on the wall. 

 I have selected these out of a much larger number in my possession 

 to which, it will be understood, I refer in the course of the following 

 remarks. The diagrams selected, namely, Eoyal Observatory, Cape 

 Town : Grahamstown : and Durban : have been chosen on account of 

 the length and reliability of their records. The first point that will 

 strike you on looking at these cyclical diagrams is the wonderful 

 regularity with which South African rains fit into these three weather 

 cycles. I know of no other country in the world where the rainfall 

 shows the same regularity. 



For the light, though precious, rains of the interior districts less 

 dependence can be placed on cyclical regularity. To a large extent 

 the cyclical rains are masked by irregular and by local rains. But 

 I have seen no South African rainfall where the indications of cyclical 

 influence could not be traced. 



Bruckner's world-wide researches show a reversal phase for inland 



