J. S. Webb. — Notes on the Zodiacal Light. xlix 



has suggested that the bodies which yield us this mysterious light are wholly 

 gaseous, and form the source of our November meteors. 



M. Liais, to whose previous communication Signor Respighi refers in his 

 letter to the Comptes Rendus de L'Academie des /Sciences, Tome 74, p. 514, 

 19th Feb., 1872, has long held the opinion that the Solar Corona and the 

 Zodiacal Light are phenomena intimately connected with one another. He 

 endeavours to reconcile the different results they give when examined by 

 the polariscope by suggesting that the bodies which, when seen as the Zodiacal 

 Light, reflect the solar rays from their surfaces, when they approach the sun 

 so closely as to form part of the corona are rendered gaseous and incandescent 

 by the excessive temperature to which they are subjected. (Comptes Rendus, 

 Tome 74, p. 263, 22nd Jan., 1872.) His observations serve to connect the 

 Zodiacal Light with that of the Corona ; those of Signor Respighi and others 

 demonstrate an intimate likeness between the former and the light of the 

 Aurora, whilst others, still more numerous, have shown independently that at 

 least a part of the Coronal Light is identical in its character with that of the 

 Aurora. I shall not attempt a technical account of these. Plate IX., in 

 Schellen's " Spectrum Analysis," English Translation, 1872, exhibits very 

 clearly the coincidence between certain lines observed in the spectrum of 

 the Corona with those which are peculiar to the Aurora. One of these is the 

 "line in the green," observed by Signor Respighi in the spectrum of the 

 Zodiacal Light. Recent observations of the Aurora have shown that it also 

 yields a faint, almost continuous, spectrum situated similarly to that which 

 Respighi and Liais describe as belonging to the Zodiacal Light. Further, the 

 eclipse observations of December last have shown definitely that besides the 

 lines shown in the plate just referred to, the Corona also yields a continuous 

 spectrum, a part only of which is due to reflected solar light. We must 

 conclude from all this that, though these three phenomena are far from being 

 shown to be identical in character, and although it is not probable that they 

 are so, they have at least one character in common. Though suspected before 

 it is only now that this has been positively demonstrated. 



It appears then that the revelations of the spectroscope as to the nature of 

 the Zodiacal Light do not invalidate Mr. Skey's hypothesis that it is yielded 

 by gaseous bodies driven ofi" from the sun during solar cyclones. They 

 nevertheless show that this is not a complete explanation of the phenomenon. 

 The argument for the existence of solid or liquid reflecting bodies in the 

 envelope which the non-polarization of the light affords is in the meantime 

 unanswerable, and is supported by the results of spectroscopic observation. 

 But, so far as our knowledge will carry us, we must assume that attenuated 

 gaseous matter also exists in the region of the Zodiacal Light, and that at 

 least a part of the light we see is caused by electric action upon such matter. 



