326 PAST CLIMATES AND CLIMAXES. 



influence upon them" is regarded as purely inferential. Arctowski's dis- 

 covery of pleions and antipleions, or areas of temperature excess or deficit, 

 indicates that some extra-terrestrial cause is constantly producing short-lived 

 changes of temperature. Once formed, a pleion or antipleion swings back 

 and forth across a continent, or even into the ocean, carrying high or low 

 temperatures with it. It may last for years, and may diminish and then 

 increase in force again. 



Cyclonic storms have long been known to vary in munber and intensity 

 with the munber of sim-spots. This relation is clearly shown by Wolf, who 

 found that the munber of hurricanes per year varied from 1 or 2 at 17 sun- 

 spots to 8 at 88 sun-spots. In temperate regions, cyclonic storms are far 

 more numerous and important than in the tropics, and they are the controlling 

 factor in temperate climates. This is shown in the ciu:ve of tree growth 

 determined by Douglass for pine trees in northern Germany. The corre- 

 spondence of the growth curve with that of sun-spot cycles, and that of the 

 number of cyclonic storms from 1876 to 1891, is so close as to leave no doubt 

 of their correlation: 



" The curve of tree growth represents not only the number of summer storms, 

 but also the conditions of the winter. Where the curve is high the months of 

 February and March appear to have been fairly warm and dry. It will be 

 noticed that these conditions — ^that is, abundant storms and rain in summer 

 and an early heating up of the ground in spring — are typical of continental 

 climates. In oceanic climates, although the winters are on the whole warm 

 and wet, the springs are relatively cool and the summers are not apt to show 

 markedly more precipitation than the winters. In view of this we may 

 interpret the curves of figure 30 as meaning that when sun-spots are numerous, 

 relatively continental conditions of climate prevail in northern Germany. 

 This carries with it the implication that at such times the continental areas of 

 high pressure tend to become intensified in winter, so that the air blows out- 

 ward from them, and cylconic storms are compelled to move along the margins 

 of the continent rather than toward its interior. In the summer, on the 

 contrary, the low-pressure areas of the center of Europe appear to become 

 intensified, and this causes the winds to blow toward the interior and to bring 

 abtmdant moisture." 



Kullmer's law of the shift of the storm-traek. — This theory promises to be of 

 such unique importance in the correlation of present and past climates that 

 the student who is specially interested must be referred to the detailed dis- 

 cussions (Hvmtington, 1914: 189, 1914^: 497). Here the briefest summary 

 must sufiice. Himtington (1914' : 502) regards the correlation of the number 

 of storms and of sim-spots as probably of high importance, but states that 

 neither its importance nor verity can rival that of Kullmer's discovery. This 

 is the law that the shifting of storm-tracks corresponds to changes in the 

 number of sun-spots. The munber of storms seems not only to vary with the 

 number of svm-spots, but a pronounced shifting of the area of storminess also 

 appears to repeat itself regularly with each sun-spot cycle, and thus to be one 

 of the important laws of nature. The great area of excessive storminess in 

 southern Canada means that when sun-spots are munerous the main storm- 

 belt shifts northward, or rather, tends to spHt, the main part moving north, 

 while the smaller portion shifts southward and oceanward. As a result, the 



