1095 



1. T 11 e integration method, recently recommended by 

 W. Schmidt (Vienna)^) and in its main lines already followed by 

 Buys Ballot for his determination of the so-called "snrpliis valne". 



This method, when applied to the different groups of our material 

 (cold and mild, cold winters only, severe winters only, etc.) ultima- 

 tely did not yield more than a rather vague indication of six fluc- 

 tuations between about 1340 and 1870, hence a period averaging 

 abont 90 years. 



2. A geometrical method has been applied to the data 

 by Mr. J. W. JSf. le Heux. This interesting investigation yielded as 

 probable result a periodicity of about 85 years, perhaps one of 

 4 X ^^ years, followed by 8o-year periods. 



3. A graphical method, which may be considered as a 

 simplification of Schuster's periodogram. In this way the intervals 

 45, 58, 72, 82, 90. 105, 225 were found as possibly periodical ; 90 

 and 225 seeming to have the greatest probability. 



4. The harmonic analysis. Notwithstanding the impurity 

 and incompleteness of the material this method too has been tried. 

 With the kind collaboration of Dr. J. P. van der Stok the elaborate 

 calculations were commenced at the Meteorological Observatory at 

 De Bilt. The prospect of success was so little promising, however, 

 that it was decided to stop the work. 



Putting everything together, these attempts have not led to a 

 decisive result. It is a remarkable fact that also for the periodicity 

 of sun-spots even Fourier's method, applied by Turner, Kimura and 

 others, has yielded contradictory and for the greater part doubtful 

 results. Have we to conclude that there exists no periodicity in the 

 abnormal winters, or is the terrestrial phenomenon the result of a 

 complex of periods which it is for the present impossible to dis- 

 entangle — as is the case with the activity of the sun, for which 

 nobody denies the existence of periodicities and the preponderance 

 of a nearly eleven year period? Tha;t the fluctuations in terrestrial 

 temperature really reflect, though in a small degree only, the 

 variations in the solar activity, cannot be doubted: this point was 

 settled by the investigations of Koppen, Nohdmann, Newcomb, Braak and 

 others*), and since for the winters of the Western part of Europe 



I) Dr. W. Schmidt. "Nachweis von Perioden langer Dauer"'. Meteor. Zeitschr. 

 1911, 9 and 1913, 8. (On the proof of the existence of long periods). 



») S. Newcomb. Astrophys. Journal 1901. A. Wolfer. Meteor. Zeits. 1902, 

 Astron. Mitteilungen XGlll and following years. Annals of the Observatory Batavia. 

 etc. See for a literature index Jul. v. Hann's Handbuch der Klimatologie, Bd. I, 

 3d Ed. (1908), p. 354 Ü. 



