THE SOLAR HYPOTHESIS. 



249 



19(XI IWll 19fl2 I9nr, 1904 1905 190fl 1907 1908 1909 l!liil 



we will temporarily assume to be the variation of solar radiation) a slight rise of tempera- 

 ture took place at this time; north of the equator this rise causes a hump in the curves 

 for Key West, Tampa, and Savannah; at Raleigh it produces a distinct though unim- 

 portant maximum; at New York this maximum has become important, although not of 

 the first rank, while still farther to the north and east it becomes a primary phenomenon. 



In similar fashion other peculiarities can be traced throughout all the curves. Take 

 the month of March 1906, for example. The Arequipa curve shows merely an insig- 

 nificant little hump; in the Key West and Tampa cm-ves this begins to become impor- 

 tant: in those of Savannah, Raleigh, and 

 Washington it becomes of primary impor- 

 tance, while farther to the northeast it 

 once more drops into insignificance. Almost 

 any of the other peculiar features of the 

 curves can similarly be seen to show a 

 maximum development in certain latitudes, 

 and from there to decrease in intensity but 

 by no means to disappear. If Arctowski's 

 pleions are due to variations in the sun's 

 radiation, we should expect exactly this — 

 that is, we should expect to find that they 

 would vary in intensity and in their place 

 of origin, according to the season and other 

 circumstances which determine where the 

 sun's heat is most concentrated. Thus it 

 may happen that at one time a wave of 

 excessive temperature originates in the hot 

 center of the United States during summer, 

 let us say, and produces its maximum effect 

 there only a short time after its origin, 

 while under other circumstances the origin 

 of the wave may be in the North Atlantic 

 Ocean, or south of the equator, and its effect 

 may reach the central United States only in 

 an attenuated form after much delay. 



Taken as a whole the work of Arctowski 

 seems to indicate three things: 



(1) In regions having a pure equatorial 

 climate little influenced by outside causes, 

 variations of terrestrial temperature show 

 a general agreement with variations in the 

 solar constant. 



(2) Regions having a more complex climate, with temperatures dependent upon the 

 movement of large bodies of air and water, show the same type of variations, but with 

 pronounced irregularities and with a certain degree of delay; that these variations of 

 temperature are the same as Arctowski's pleions and anti-pleions can scarcely be questioned; 

 the pleions and anti-pleions of temperature appear to influence winds and storms, and thus 

 to determine the amount of rainfall, but this result is not necessarily direct nor immediate, 

 so that there is opportunity for the merging of one pleion with another or for the develop- 

 ment of other irregularities. 



(3) The response of vegetation (and especially of great trees like those of California) 

 to the variations in rainfall involves still other delays and opportunities for the obliteration 



Fio. 84. — Monthly Departures of Tomijcrature in North 

 .Vnicrica ConiparcJ with Arequipa in Peru, after Arc- 

 towski. 



The .\requipa curve is plotted on a vertical scale double that of the 

 others. 



