ARCTOWi^KI, VOLCANIC DUST VEILS 169 



interval between the pleionian crests of 1891 and 1897 of the Batavia 

 curve is due to a missing crest which is well marked on the Stockholm 

 curve. 



Sux-SPOTS AXD Atmospheric Temperature 



The conclusion so far is that the thennopleionian variations cannot be 

 ascribed to more or less frequent reoccurrences of volcanic dust veils. In 

 exceptional cases, sucli as the Krakatoa eruption, atmospheric tempera- 

 ture has been affected practically all over the world; but even then the 

 pleionian crests of the consecutive 3'early temperature curves have simply 

 been partially erased, or modified in such a way that there can be no 

 doubt that the antipleionian depressions which followed w^ere not due to 

 the presence of volcanic haze. 



The hypothesis that the pleionian variations of temperature have an 

 extra-terrestrial cause is therefore a perfectly logical conclusion. 



In order to prove that this hypothesis is well founded, it will be neces- 

 sary to demonstrate the existence of a correlation between atmospheric 

 temperature and solar radiation, or perhaps some other phenomenon of 

 which the "solar constant" is a function. 



It has been presumed that differences in the extent or relative position 

 of the Zodiacal light might be such a phenomenon.®^ Variations of the 

 solar corona could possibly also have some effect on the radiant energ}' 

 transmitted towards the earth, f^ but it seems more probable that atmos- 

 pheric temperature is directly affected by changes occurring on the sun's 

 surface or solar atmosphere.®^ The well known sun-spot cycle of about 

 11 years' mean duration proves it very well. 



It was Alfred Gautier®* who, as far back as 1844, discovered the rela- 

 tion that exists between atmospheric temperature and the solar cycle. 



**! E. Belot : "La matiere zodiacale et la constante solaire," C. R. Ac. Sci. Paris, vol. 

 157, p. 757. 1913. 



^2 A. Crova : "Etude de I'intensite calorifique de la radiation solaire au moyen de 

 Tactinometre enregistreur," Annales de chimie. . .ser. 6, vol. 14, p. 543. Paris, 1888. 



Some arguments in favor of this hypothesis may also be found in the following 

 papers : 



S. P. Laxglev : "The Heat Radiation of the Corona," Astroph. Journal, vol. 12, p. 

 371. 1900. 



C. G. Abbot : "A Bolometric Study of the Solar Corona," Publ. Astron. Soc. Pacific, 

 vol. 20, p. 86. 1908. 



.TOHX A. MiLi-EU : "The Position of Certain Coronal Streams on the Assumption 

 that the Corona is a Mechanical Product," Astroph. Jour., vol. 33, p. 303. 1911. 



^ S. P. Laxgley : "The Solar Atmosphere, an Introduction to an Account of Researches 

 made at the Allegheny Observatory," Amer. Jour. Sci., ser. 3, vol. 10. p. 489. 1875. 



J. Hahx : "Contributions to the Theory of the Sun," Annals Roy. Obs. Edinburgh, 

 vol. 1, p. 74. 1902. 



^ Alfred Gadtier : "Recherches relatives a I'influence que le nombre et la permanence 

 des taches observees sur le disque du soleil peuvent exeroer sur les temperatures terres- 

 tres," Annales de chim. et de phys., ser. 3. vol. 12. j). 57. 1844. 



