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to spread witli unequal intensilv tliron,2;li space. Consequently the 

 Earth moves through an irregulai' tield of radiation. And althonuh 

 we know the refractive power of the coronal uases to be but small, 

 still we mav assume that those kinds of ravs, which uiideru-o anomal- 

 ous dispersion, will be liable to a rather strong incurxation and 

 their beams to variation in diveriiencv, especially in those places 

 where they travel closely along the surfaces of discontinuity. 



On this principle vv^e base our explanation of the periodically 

 varying iidluence, which an almost uiichanging Sun exercises on 

 terrestrial |)henomena. 



^l. Thi' S('nii-((i/i)//(i/ (I ml itinniiil jktuxIs in lln- jmsltlvii of the 

 Earth ill the irrct/ii/tfr jichi <>/' nn /id f ion. 



At great distances from the centre of the Sini the surfaces ot 

 discontinuity become nearly tlat. Those which are Jiear the plane of 

 the equator will be almost parallel to it. This assumption is in liai'- 

 mony with the appearance of the structural lines of the outer corona 

 as well as with theoretical considerations. 



If now we suppose the surfaces of discontinuity to be (geometric- 

 ally) i)rolonged to the orbit of the Earth, it is evident that they will 

 intersect its surface in a series of parallel circles, but the position of 

 these circles with regard to the parallels of the Earth, will change 

 with the position of the Earth in its orbit. Let us consider some 

 particular positions. 



Ki' 



Fig. 2, a represents the |)ositioii of the Earth on the 21"' of 

 March, as seen from the Sun. In the spring the Sun's south pole is 



