492 E. HUXTIXGTOX ^SOLAR HYPOTHESIS OF CXIMATIC CHA>'GES 



tradicti<Mis which beset the path of the investigator. The general opinion 

 may be expressed in the words of Hann :^' 



•The resolrs of rery nanierous and complex inTestigatioiis of the connection 

 of the sun-spot period with variHtions of the meteorological elements bare not 

 wholly corresponded to expectations. The influence of the scm-spots on the 

 meteorological elonents has been proved as comparatiTely imimportant. Only 

 in the most favorable cases is one in the position to considef that the traces of 

 a parallel coarse in the prepress of certain meteorological dements and in that 

 of the sim-spot freqtiency is proved. There can be no thought of the prediction 

 of the c-ourse of the weather on the grotmd of the sim-^ot cyde."* 



From this broad statement Hann goes on to show that the amount oi 

 agreement between sun-spots and climatic phenomena varies greatly, ac- 

 cording to the part of the earth and the precise climatic elements which 

 are investigated. The reader who would carr^' the matter farther is re- 

 ferred to the last chapter of volume 1 of Hann's Klimat<dogie and to thv 

 large number of references there cited. In general. Hann unqualifiedly 

 accepts the conclusions of Xewcomb and Koppen as given above. H»r 

 shows that aside from temperature the strongest evidence of a sun-spc«r 

 cycle is found when a single element, such as summer rains or tropical 

 cyclones, to take the best two examples, is considered alone, and when it 

 is investigated by the use of means for a large number of stations and 

 for long periods. When single stations or single sun-spot cycles are con- 

 sidered, there is likely to be no visible relation whatever. Such things a- 

 frosts do not seem to fit into the sun-spot cycle with any definite rela- 

 tionship, and there are often contradictory results when the same climati.: 

 element is investigated in different regions or different periods. In rain- 

 fall, as in temperature, there is decidedly more evidence of a sun-spo: 

 cycle within the tropics than in other parts of the world. 



Effect of ArcfoK-sl-i's pieions on the distribution of temperature. — 

 From what has just been said, it is evident that the temperate zone is the 

 critical region. It is there that we find the contradictions which are the 

 main objection to the solar hvpothesis. Students of the question have 

 apparently supposed that if the sun really does play an important part in 

 determining terrestrial variations of temperature, this ought to be as evi- 

 dent in the temperate zone as in the torrid. The work of Aretowski. 

 however, as I have shown in "The Climatic Factor* (pages 244-250 k 

 suggests that the apparent conflict between the evidence in equatorial 

 and temperate regions is the expectable condition. For example, in the 

 part of the torrid zone south of the equator his curves of fluctuations of 

 temperature agree cloeely in all longitudes. Coming north to Bombay. 



» J. Hann : Handboch dn- Klimatolosie. Stvttsmrt. 1906. roL 1. pfk. 355-356l 



