548 E. HUNTINGTON SOLAR HYPOTHESIS OF CLIMATIC CHANGES 



the southwest where the rainfall is decidedly more at times of many sun- 

 spots than of few. This is the area from which most of the American 

 evidence of desiccation during the past few thousand years is derived. 

 It includes the Big Trees of California and the ruins of New Mexico 

 and Arizona. Although many authors^ here as elsewhere, have doubted 

 whether the evidence of climatic changes is convincing, there seems to be 

 a growing tendency to think that such is the case. The matter has been 

 well set forth by Hewett, Henderson, and Eobbins,^^ who come to the 

 conclusion that the climate has suffered a distinct change toward aridity 

 since the days when the main Pueblo ruins were in their prime. On 

 Gregory's map, figure 15, this region is shown as one of the chief areas 

 where a change of this kind has occurred. 



The next feature of figures 16 and 17 is a discontinuous belt of scanty 

 rainfall at times of many sun-spots. It begins in Montana or Idaho, runs 

 southeastward, and then southward along the great plains to the Gulf of 

 Mexico. The center of this belt lies in the middle of the L'nited States, 

 not far from the center of Kansas. Here the deficiency during years of 

 many sun-spots amounts to 30 per cent of the average rainfall. It is 

 apparently a phenomenon which recurs whenever sun-spots are numerous, 

 for each of the three sun-spot cycles shows it. The figures for Hays, 

 Kansas, the station where the deficiency is most marked, are as follows : 



Date of 

 minimum 

 sun-spots. 



1877-1879. 

 1888-1890. 

 1900-1902. 



Ufiinfall dnrine 

 3 years of mini- 

 mum sun-spots. 



Inches. 



28.7 

 20.9 

 28.0 



Date of 

 maximum 

 sun-spots. 



1882-1884. 

 1893-1>95. 

 1905-1907. 



Rainfall during: 

 3 years of maxi- 

 mum sun-spots. 



Inches. 

 18.8 

 14.2 

 24.1 



\mount by whifh rainfall 



of m><ximum is levs than 



that of minimum. 



Inches. 



9.9 

 6.7 

 3.9 



The third prominent feature of the maps is an area of deficiency in the 

 northern part of the Atlantic Coast region. The rest of the country 

 shows no distinct- tendency toward either excess or deficiency. In gen- 

 eral one may say that, except for the Southwest, the United States is a 

 region where areas of diminished precipitation during times of many 

 sun-spots are scattered in such a way that they are the most prominent 

 feature. This, again, is in agreement with Gregory's map, where all of 

 the United States except the Southwest is spotted with plus signs, indi- 

 cating an increase of rainfall. It is also in agreement with Arctowski's^^" 



88 The Physiography of the Rio Grande Valley in New Mexico in Relation to Pueblo 

 Culture. Washington, 1913. 



38(1 H. Arctowski : Changes in the distribution of temperature in Europe and North 

 America. Annals N. Y. Academy of Sci., vol. 24. 1914, p. 103. 



