240 J. P. Hall— Short Cycle in Weather. 



(4) Is this exciting influence thermal or magnetic ? Dr. 

 Kceppen, a division officer of the North German Weather 

 Service, believes that as between the maximum and minimum 

 stages of the 11-year sunspot cycle, there is enough difference 

 in the heat received from the sun to be sensible at the earth's 

 equator, and to have an effect on the general circulation of the 

 air.* This is in conflict with the view that the variations 

 in solar radiation are too slight to be appreciable ; but if it 

 were true of the 11-year cycle, it might also hold good for 

 shorter periods. Fritz's evidence of a 27-day temperature 

 oscillation at Yivi on the Congo for a single year, is inade- 

 quate to prove this. But were a similar phenomenon noticed 

 at a dozen or more widely separated equatorial stations, the 

 fact would possess great significance ; since along the Equator 

 there are no cyclonic systems passing, with winds coming first 

 from a warmer and then from a cooler quarter. Moreover, 

 Lockyer has presented some spectroscopic evidence of the 

 occurrence of great changes from year to year in the temper- 

 ature of spots,f which has not yet been followed up to a satis- 

 factory conclusion. The discovery of a "heat pole" on the 

 sun, such as Buys Ballot believed in, would harmonize well 

 with a periodical temperature oscillation outside the range of 

 moving high and low pressure systems, and also with the 

 thermo-dynamic theory of storm formation and intensification, 

 of which Espy, Abbe and Ferrel have been such able expound- 

 ers, but against which a fresh revolution has recently broken 

 out in meteorological circles. On the other hand, great mag- 

 netic storms have long been regarded, but without much proof, 

 as precursors of weather changes ; and in many isolated in- 

 stances, like the great typhoon which smote Mauritius on 

 April 29, 1892, notable atmospheric disturbances have been 

 immediately preceded by exceptional agitation of the needle. 

 Dr. Meldrum, for forty years Secretary of the Meteorological 

 Society of Mauritius, has long believed such coincidences to 

 be significant, and he is not alone in that belief. 



* Harm's " Kliinatologie," p. 707. 



f " Chemistry of the Sun," pp. 310-24. 



