120 LIGHT SCIENCE FOR LEISURE HOURS. 



have thought it right, however, to refer to the 

 peculiarity because the appearance of interstices or 

 double spaces, between prominences of considerable 

 brightness, is often observed by means of the spectro- 

 scope independently of total eclipses. The green and 

 red zones of the corona were well developed on the 

 western as well as on the eastern edge of the sun, 

 while the blue remained faint and ill defined.' 



It seems tolerably clear that Kespighi saw, in the 

 green image, the full extension of the inner corona ; 

 for the edge of that image was well defined, as it would 

 certainly not have been if the observed extension had 

 depended only on the observer's power of recognising 

 faint luminosity. In the latter case there would have 

 been a gradual fading off, precisely as in the case of 

 the blue image. It is important to notice this point ; 

 because Mr. Lockyer (probably observing under less 

 favourable conditions) could only trace the green image 

 of the inner corona to a height of about two minutes, 

 or less than one-third of the height observed by 

 Respighi ; and we might be led to infer that as Respighi 

 saw the green coronal image extending so much farther 

 from the sun than as observed by Lockyer, so under 

 yet more favourable circumstances the image might 

 have appeared higher still. The well-defined outline 

 recognised by Respighi renders this inference inad- 

 missible ; and we may in fact regard the extension of 

 the inner corona as definitely determined by his ob- 

 servations. On the other hand, the relatively small 

 extension of the blue image does not necessarily prove 



