( 371 ) 



bcinj? seven to one. Tlie mild 22-yeai' j^eriods Iiaxe, up lo llie present 

 time, contained altogether 12 severe wintei'S, only one of which was 

 exceptionally severe. 



It is now important to ascertain the character of this oscillation. 

 On the one hand there seemed to be some indication of a period 

 consisting of two consecntive 178-year periods (i.e. of 356 years), 

 but even our material does not cover a sufficiently long interval of 

 time to allow any reliable result in this direction to l)e derived. On 

 the other hand the rise and fall of the curve in the middle of the 

 178 year period is the most characteristic feature, and points to the 

 possibility of dividing the period into two. In fact the period can 

 be divided into two halves of 89 years, which show a remarkable 

 curve, somewhat different on the two sides (see diagram fig. II). 

 Perhaps this period of 89 years may be further divided into two 

 periods of 44.5 years. The depression in the middle of the 89-years 

 period is but indifferently indicated for all the sexere winters together, 

 but becomes more marked, if we take into account only the excep- 

 tionally severe winters. In the following list (Table I) the twelve 

 89-year periods xvhich are available since 848, have been entered, 

 each divided into intervals of 11 years, corresponding to the computed 

 normal maxima of solar activity (according to Nkwcomb). The last 

 inter\'al of each period contains 12 j'ears, which however has only 



T A B L E I. 



Distriljulioi of sovoro winters in perioffs of SO yoars (S'lS — lOlü) 

 (dividi'd into intervals of 11. 1 years). 



