46 THE CLIMATE OF AUSTRALASIA 



intervals, though for long such cases were only 

 sufficient to tantalize men with single instances, 

 and inflict the keener disappointment when 

 they were referred to the weather of the world 

 at large. 



Four chief weather cycles have been 

 proposed. The first and most famous is a cycle 

 of n x / 9 years, in which the round of weather 

 changes is attributed to the influence of sun 

 spots. There is no doubt that our weather 

 ultimately depends upon the sun. Rain, for 

 instance, is the result of a process of distillation, 

 by which water is raised from the sea by the 

 sun's heat ; the moisture thus produced is 

 carried inland by air currents, which are driven 

 by the sun's power ; the moisture is then 

 chilled till it falls as rain. The process is 

 identically the same as in the distillation of 

 water ; the steam which is raised by the fire is 

 chilled in a condenser. If the power of the fire 

 lessen, the distillation must go slower. Lessen 

 the evaporation on the Indian Ocean, and the 

 rainfall in Central Australia is necessarily 

 reduced. That connection is inevitable and 

 obvious. 



The sun's power varies in different years. 

 Its surface is sometimes clear, bright, and un- 

 spotted ; and at other times, as conspicuously 

 last October, it is marked with black spots, due 

 to a great change in the outer envelope of the 

 sun. The number of these sun spots varies in 

 a cycle, the length of which, on an average, is a 



