CLIMATIC CYCLES. 



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The period of 11 years is an average, the sun-spot cycle actually varying 

 from 7 to 17 years. From 1750 to 1823, the 1 1-year cycle was little in evidence ; 

 from 1823 to 1900 it was well-marked, but the intensity was variable. The 

 average munber of sun-spots within ths period of accmrate record has varied 

 from to 154.4 per year. The number of spots at maxima varies from 50 to 

 150 approximately, the majority of maxima falling between 80 and 130. The 

 number of spots at minima varies from in 1810 and 1913 to 11. The fol- 

 lowing tables are extracted from those of Wolfer (1902 : 193) : 



