PRESENT STATUS OF SOLAR HYPOTHESIS 487 



maximum as compared with minimum sun-spots. His figures can scarcely 

 be questioned, although his theoretical conclusions are not equally con- 

 vincing. His main conclusion is expressed as follows (page 379) : 



"A study of the annual departures [from mean ternperature] over many re- 

 gions of the globe in equatorial and middle latitudes shows consistently a 

 fluctuation corresponding with that of the solar spots. The maximum fluctua- 

 tion in the general average is 0.13° C. on each side of the mean for tropical 

 regions. [The maximum temperature comes at times of minimum sun-spots,] 

 The entire amplitude of the change is therefore 0.26° C. [0.47° F.], or somewhat 

 less than half a degree of the Fahrenheit scale." 



Several points in this conclusion deserve emphasis. In the first place, 

 JSTewcomb does not stand alone. Koppen^^ has made a similar study, al- 

 though not quite so exhaustive. His conclusion agrees with that of New-. 

 comb. He finds that at the equatorial stations which he made use of the 

 difference between the temperature at periods of maximum and minimum 

 sun-spots amounts to 0.75° C, while in temperate latitudes it decreases 

 and becomes less and less noticeable, the average being 0.54° for regions 

 beyond the tropics. The variations of temperature within the tropics 

 may be seen in the following table, which shows the amount by which the 

 mean temperature for individual years of the sun-spot cycle is above or 

 below the mean for a long series of years. The table is that of Koppen, 

 but it has here been copied from Hann^s Klimatologie, volume 1, page 

 356: 



Table 1 



Variations of Mean Temperature within the Tropics in the Sun-spot Cycle 



Sun-spot minimum (ap- Sun-spot maximum (ap- 

 proximately) +0.33" C. proximately) — 0..32° C. 



1 year after minimum.... -f0.15 6 years after minimum... — 0.27 



2 years after minimum... — 0.04 7 years after minimum... — 0.14 



3 years after minimum... — 0.21 8 years after minimum... +0.08 



4 years after minimum... — 0.28 9 years after minimum... +0.30 



10 years after minimum.. +0.41 



The maximum temperature comes about 0.9 of a year before the sun- 

 spot minimum, while the minimum temperature practically coincides 

 with the maximum of sun-spots.^^^ 



11 W. Koppen : ijber mehrjahrige Perioden der Witternng ins besondere iiber die II-, 

 jiihrige Periode der Temperatur. 



After this paper was in type there came to hand an important article by Koppen 

 (W\ Koppen: Lufttemperaturen, Sonnenfilecke und Vulcanausbriiche ; Meteorologische 

 Zeitschrift, vol. 7, 1914, pp. 305-328). In this he reviews his former conclusions on 

 the basis of a greatly increased body of metcoi-ological data, most of which have been 

 arranged by ,T. Mielke (Archiv der Seewart, Jahrgang 1913; Hamburg, 1914). All 

 parts of the world whei-e records are available have been considered, and the data cover 



