NO. 4 TEMPERATURE VARIATIOXS IX THE NORTH ATLANTIC 1 59 



tinique) in May, 1902, Santa i\Iaria (Guatemala) in October 1902, 

 Colima (Southern Mexico) February and March 1903, Katmai 

 (Alaska) in June, 1912. and many others. The small dust particles 

 reflect and scatter the solar radiation. A diminution of the heat 

 available to warm the earth makes itself distinctly felt in the pyrheli- 

 ometric curve, as measurements they cite tend to show. The 

 pyrheliometric curve has well-marked minima in the years 1884-5, 

 1890-91, and 1903, corresponding with great volcanic eruptions. By 

 combining in a certain way the mean of this curve and the inverted 

 sun spot curve together, they produce a curve from the year 1880 

 to 1909, which has very great similarity with the curve for the 

 anomalies of the maximum temperatures of the United States at 

 fifteen stations and also with the curve for the yearly temperature 

 of the earth at forty-seven stations. 



Arctowski has studied the climatic and temperature variations in 

 dififerent regions of the earth in numerous papers (1908- 191 5). He 

 comes to the conclusion that rythmical variations keep step with the 

 variations in the solar activity, which show a well-marked eleven- 

 year period, but the variations do not run parallel all over the earth. 

 At most places they go oppositely to the sun spots, so that the aver- 

 age temperature of the earth is considerably lower (at least 0.5° C.) 

 at sun spot maximum than at minimum. In some scattered regions 

 the temperature variations go in the same direction as the sun spots, 

 but not always regularly. He finds (1909, p. 124) that in a year of 

 maximum sun spots like 1893, the pleions as he calls them (that is to 

 say, the regions of positive temperature anomalies) are isolated on 

 a ground of negative anomalies, while during years of sun spot 

 minima like 1900 conversely the antipleions (that is, regions of nega- 

 tive temperature anomalies) are the isolated spots. 



The most sharply marked period in most of Arctowski's tempera- 

 ture curves, particularly of tropical stations, is not the eleven-year 

 period, but a shorter somewhat irregular one whose average length 

 is 2.75 years, and which is the same as that found by Bigelow and 

 the two Lockyers. Indeed this shorter period variation he finds 

 so predominently that he recently (1915, p. 171) has spoken of it 

 as certain that the variations in Arequipa (Peru) or in the equa- 

 torial type of temperature curves apparently have nothing in com- 

 mon with the eleven-year period, though a certain correlation can 

 exist. He is of the opinion that the shorter variations are brought 

 forth by corresponding shorter variations in the solar activity. V'ol- 

 canic dust, Arctowski believes himself to have shown (1915) has 



