1107 



1000 two (unimportant) ones), after the IS^'^ century no excep- 

 tions. There are indications of a stronger anomaly at the middle 

 of the period, which, however, cannot be proved. 



VI. — The chance that the last quarter of a 89-year period 

 (826,25-848,5... 1894,25—1916,5) contains a smaller number of 

 hard winters than the preceding and following 22-year intervals is 

 0,88. Within the last quarter of a 89-year period the chance that 

 any winter will be severe (resp. very severe) is less than 0,4 (resp. 

 0,007), i.e. less than 7^ (Vs) of the general chance. In the neigboui-ing 

 22-year intervals (e.g. 1872—1894 and 1916—1938) this chance is 

 about 3 (5) times as great. 



VII. — Increased and accelerated activity of the solar surface 

 corresponds in general to the winter cold in Western Europe setting 

 in more forcibly and rapidly than usnal ; inversely a weakejied and 

 retarded activity of the sun corresponds to winters setting in later 

 and more mildly in a later part of the period. 



VIII. — It follows from our material that all the temperature 

 averages used since 1852, until now (e.g. 1852 to J 91 6) are too 

 high with respect to the trne mean. As far as can be judged at 

 present only a 89-year series might give a true average. Per meteo- 

 rological winter this will lie about 0°,18 below the average which 

 is now available from observations extending over some 65 years. 



77 

 Proceedings Royal Acad. Amsterdam Vol. XX. 



