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to be answered. Do these Aurorse occur most frequently 

 during the greater frequency of maximum sun-spots, and 

 secondly, which portions of the Earth are most affected by 

 the greater activity of the Sun's energy which they represent? 

 When speaking of the return of the Sun's spots I need only 

 add that the shortest estimate of these cosmical gales or sun- 

 spot periods is 11 years, or according to some, 33 or even 69 

 years, in order to show that meteorological records, to be 

 trustworthy guides in the science of weather prediction, must 

 be extended over long periods of time, and that, therefore, we 

 cannot begin too early to record our observations. In a word, 

 for the sake of science and for the sake of its practical results, 

 it is very important to register phenomena within our reach 

 for comparison all over the world. The atmosphere round 

 the Earth, like the ocean, is one fluid, and effects observed in 

 one place of the globe are to be traced, if we could only trace 

 them, to causes in another. Excessive evaporation in Europe 

 may be, and probably is, accompanied by corresponding pre- 

 cipitation in other countries and in another hemisphere. In 

 this new sense " a touch of nature makes the whole world 

 kin." Evaporation may not be the cause of storms, but storms 

 and evaporation spring from the same cause. That cause is 

 proximately heat,producinglessatraosphericpressureand conse- 

 quently greater evaporation. But why is one year's heat greater 

 than the heat of many preceding years,and why is there,as there 

 can be no doubt there is, a periodicity in the weather and in 

 weather storms ? It has been satisfactorily shown among 

 others, by that excellent observer at the Mauritius, Mr. 

 Meldrum, that cyclones and consequent rainfall show a 

 periodicity, corresponding to the return of the maximum 

 frequency of sun-spots. The value of Mr. Meldrum's 

 observation and hypothesis communicated to the British 

 Association, which I have read with interest and commend to 

 your reading, will depend upon confirmatory investigation in 

 Australia, while the establishment of the law in the Southern 

 Hemisphere will not only carry with it a direct scientific 

 advantage of its own, but must prove to be a most profitable 

 contribution to the pursuit of science in the Old World and in 

 America. 



