H. Arctowski — About Climatical Variations. 313 



sidered as being perfectly homogeneous, and then, because a 

 variation of about 18 or 19 years seems to exist. 



Utilizing Bigelow's tables of temperature data for the 

 United States, for 1873-1905, I made consecutive means of 

 decades of years and inscribed the departures on maps. 



To sum up the results obtained by the inspection of these 

 maps, I will say that the long-range variations of temperature, 

 of particular stations in the United States, are due to irregular 

 pendulations of macropleions and macromeions, that these pen- 

 dulations are complicated by the existence of slight see-saw 

 movements (or vibrations) which increase or decrease the 

 departures, making the macropleions more or less accentuated, 

 and that, iinally, the entire system of macropleions and macro- 

 meions moves up and down. This last movement is shown on 

 the maps by an increase in size of the macropleions and a 

 decrease of the macromeions or vice versa. This is the real 

 long range variation. The decade of 1873-1S82 is a typical 

 example of a widely spread out macropleion, the decade 1883- 

 1892 shows a predominant macromeion. 



For Europe, I also made maps giving the distribution of the 

 percentage of rainfall during the consecutive decades of 1851- 

 1905, and found that the macroombrons display phenomena 

 very similar to those of the thermopleionian variations. 



A priori, one may presume that the variations interesting 

 longer periods of years will also pendulate. I do not think that 

 this hypothesis is in contradiction with the results Ellsworth 

 Huntington has obtained from the discussion of historical data. 

 Concerning geological records it would be absolutely prema- 

 ture to express any opinion. 



But, for practical purposes, the brachypleionian variations 

 present a greater interest. As yet I have only studied the 

 brachypleions of Arequipa. 



3. Brachypleions of Arequipa. 



For this study I had to take the daily values of temperature 

 most kindly sent to me by Prof. Edw. C. Pickering. 1 made 

 5 day or pentade means, and then, consecutive monthly 

 means, — the pentade and not the day being the unit. In this 

 way I noticed that during certain years (1902, 1903, 1906 and 

 1907 in particular), a brachyehronic variation of about 55 days 

 duration, from one maximum to the following maximum, is 

 the most striking feature of the curves (fig. 3). 



The amplitudes of these variations may be as important as 

 the amplitudes of the pleionian variations, that is to say, equal 

 the value of the annual variation of temperature. 



