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Physics. — '^The period Icili/ of solar phenomena and the corre- 

 sponding periodicity In the variations of meteorological and 

 earth-magnetic elements, explained hij the dispersion of light." 

 \W Prof. W. H. Julius. 



(Communicated in llie meeting of Scploail)er 2G, 1903). 



Table of contents. 

 Introduction. 



I. The path of the projection of the Eartli on the Sun. The probable origin of the 

 1 1-year period. 



II. The variability of the solar radiation. 



III. The periodical variations in the appearance of the Sun. 



1. Sun-spots and taeniae. 



2. Prominences. 



IV. The periodicity in the variations of meteorological and earth-magnetic elements. 



1. Do these phenomena require the hypothesis that the Sun exhibits a varying 

 activity V 



2. Effects of the movement of tlie Earth through the irregular field of llie 

 Sun's radiation. 



A. The semi-annual and annual periods in the position of tlie Eartli in 

 the irregular held of radiation. 



B. The periodicity of the fluctuations of ilhuninatiun which coincides with 

 the periodicity of solar phenomena. 



3. Polar lights. 



4. The annual variation in the diurnal ine(|ualily of terrestrial magnetism. 

 Ü. Magnetic disturbances. 



G. The annual variation in the daily oscillations of atmospheric pressure. 



7. 'Ihe annual and secular variations of atmospheric pressure. 



8. Cosmic influence on other terrestrial phenomena. 

 Summary of results. 



IXTIiODUCTION. 



The whole science of asti'oph3'sics rests on the hypothesis that 

 the same laws, which we have recognized by obseryatioii and 

 experimental research, hold good for other celestial bodies as well 

 as for the Earth, and that ^ve are justified in applying to the Sun 

 and the comets, to nebulae and double stars, the results of thermo- 

 dynamics, of spectrum-analysis, of the theory of electrons. It would 

 therefore be illogical to make an exceptioii with regard to our 

 knowledge of the refraction and dispersion of light in masses of 

 variable optical density ; and by adhering to the supposition, that in the 

 Sun and its nearest vicinity the light travels in straight lines, we 

 should take an untenable standpoint. 



