H. Arctowski — About Climatical Variations. 307 



deficiency of temperature, I found that the difference in tem- 

 perature between these two vears must have been at least 

 0°-5 C. 



Coming back to the question of sunspots, I will simply 

 remark that 1893 was a year of maximum and 1900 a year 

 preceding closely a most accentuated minimum. But this ques- 

 tion is of less interest than the simple verification of the fact 

 that the temperature of the terrestrial atmosphere is not con- 

 stant. The simplest explanation of this fact is that the amount 

 of heat radiated by the sun and received by the earth varies 

 slightly. I will insist upon this question later. 



1. The pleionian variations. 



To simplify the reasoning I will define more plainly the ple- 

 ionian variations. 



To avoid the more or less regular annual variation, we have 

 to take yearly means. But it is indifferent how we count the 

 year, as long as we compare between them means of twelve 

 consecutive months. By making consecutive yearly means for 

 the one-year periods beginning with January, with February, 

 March, and so on, and by comparing the curves expressing the 

 succession of the figures, we can see how a negative departure 

 of a given year passes progressively to a positive departure of 

 another year. 



I made such consecutive temperature curves for the entire 

 series of observations recorded in Batavia, New York, and some 

 other places. For the years 1900 to 1909 I compared a great 

 number of such curves. Two facts of some importance are 

 clearly demonstrated. 



1°. That, although there are some most interesting agreements 

 with the curve expressing the sunspot cycle, this cycle cannot 

 be considered as being the main factor producing the pleionian 

 variations, simply because the pleionian crests and depressions 

 of the temperature curves repeat themselves 3 to 4 times more 

 often than the maxima and minima of the solar curve. 



And, 2°. The temperature curves of far distant stations, be- 

 longing to absolutely different climates, present in certain 

 cases such striking coincidences, that it is impossible to ascribe 

 them to simple chance circumstances. 



I may add that the consecutive curves of rainfall, of sun- 

 shine records and of atmospheric pressure, also display pleion- 

 ian variations and demonstrate the fact that we have to deal 

 with more or less periodical alterations of the atmospheric cir- 

 culation. 



In order to make comparisons, a standard curve was necessary. 

 The records of the exceptionally undisturbed climate of Are- 

 quipa, in Peru, gave this necessary standard. 



