( (^fi;^ ) 



iji tlio sliadiiiji' of soiiic of llir sjroiijicsl lines of ii-oii and a i'ew 

 otlioi' ('k'iiieiils a siniilai- siriiciiii-c was ohsoi-Nod. Ilio compoiienl lijies 

 IxMiii»' taiiil, iiohiiloiis, and close loncllior. 



Tho plale which showed the slnicliii-e of // and A' mosl |tlainl\-, 

 displavod an additional pecniiai-ily, as on il I he u'eneral shading of 

 I hose lines was nnnsnally weak. 



in IIai.k's ahnoi'nial speclrnni ^), which was charactei'ized l)^ Ihe 

 extreme weakness of the shaded backgronnd of many al>soi'pti<tn lines, 

 maxima and minima of intensity were also distin.i>nishal)le nnder a 

 microscope, though they did jiot a|)|)ear so clear nor so regnlarh- 

 arranged as in the case described l)y Jkwktj.. 



If we snppose the principal cause of the shading of the Franidiofer 

 lines not to l)e the ahsorption. hnt i-ather the anomalons disjjersion 

 of the \va\es, which in the s|>ecti'nm are situated on eitlier side the 

 cejili-al al>soi-|)tion line '), we can easily account for the ])henomenon, 

 l»efoi-e mentioned, as well as for the iact, that in veiy i-are cases 

 only it shows distinctly. 



Let us consider a nari-ow l)eam of light of an exactly defined 

 wave-length, belonging to the shaded background of a Fi-auidiofer 

 line. This beam has emerged from the deeper layei-s of the Sun 

 with a certain divergence; we sup|)ose it to ])i'Oceed i]i the ai)i)i'oxi- 

 mate direction of the structure lines of the coi'ona (I.e.]) .51)7). Let 

 its wave-length be somewhat greatei- than that of the absorption 

 line; for this kind of light, the medium will then possess a jiositive 

 r.'fraclion constajit, and the sepai-ate rays of the l)eam will cur\e 

 about the denser parts of the "tubulai-'" structui'e. If w e had su|>posed 

 the wave-length to be a little less than that of the absoi-ptiou line, 

 the refraction constant woidd have been negitive and the ra\s 

 would have cui-\-ed about the rarei- parts of the coronal structui'e. 

 In either case the <livei-gence of oin- monochromatic beam will alter- 

 nately diminish ami increase, ajid this |)articidar kind of light will 

 rea<'li the Earth with an intensity, determijied by the degree ot 

 divergence (convergence perhaps) with which the beam left the 

 ultimate traces of the corona. 



^Vitll res|»ect to a beam of otliei- light, the wax'e-lenglh of which 

 dilfers imly slightly less from that of the absorption line, the medium 

 w ill have a consid(M'ably greater refraction constant, so that tli(^ rays 

 of this |>articnlai- beam may lia\'e made a ben<l, or part of a bend, 

 more than those, belonging to the former beam, on their way thi-ongh 



1) C. K. Ham;. .\sli()|jliysicnl .loiuniil, XVi. p. 2:}-2, 1902. 

 ■i) \V. H. JuLiLs. l»ioc Küv. Acad. Amst. IV, p. 589—002. 



