THE RECENT ECLIPSE OF THE SUN. 



19 



flames. They are not, properly speaking, flames at all, but masses of 

 gas glowing with intensity of heat. 1 



Many of the most important discoveries recently made respecting 

 the sun relate to these wonderful objects ; but in this place I shall 

 refrain from speaking more about them than seems necessary to illus- 

 trate the subject of the corona ; for, as a matter of fact, the observers 

 during the late eclipse turned scarcely a thought to the colored promi- 

 nences, nor is it likely that any thing new respecting them will ever 

 be learned during total eclipses of the sun. 



Outside the sierra and the prominences, the true corona is seen. 

 To ordinary vision, and probably also even under the scrutiny of pow- 

 erful telescopes, it appears to be divided into two distinct portions. 

 There is in the first place an inner and brighter region, extending ap- 

 parently to a distance from the sun equal to about one-fifth of his 

 diameter. The outline of this inner corona is uneven but not radiated, 

 and, though not sharply defined, appears yet to be very definitely 

 indicated by the rapid falling off of lustre beyond its limits. The inner 

 corona has been described as of a white, pearly lustre by some observ- 

 ers ; but under the most favorable conditions it appears, when care- 

 fully observed, to have a somewhat ruddy hue. 



Extending much farther from the sun, how far is not as yet known, 

 is the radiated corona. It is much fainter than the inner corona, and 

 its light grows fainter and fainter with distance from the sun, until 

 lost to view on the dark but not black background of the sky. 

 Through this faint and softly-graduated corona extend radiations of 

 somewhat greater brightness. It is between these radiations that 

 those dark gaps or rifts appear, which have figured so much in the 

 narratives of recent eclipse observations. The dark gaps are, indeed, 

 more striking features than the radiations which form them ; but it 

 must be remembered, nevertheless, that the radiations are the only 

 positive features in this case, the gaps being merely regions where 

 there are no radiations. 



We may typically represent the corona, as it had been revealed to 

 us during former eclipses, by the accompanying sketch from a photo- 

 graph taken by Mr. Brothers at Syracuse during the eclipse of Decem- 

 ber, 1870. Only, it must be remembered that the photograph may not 

 represent the full extent of the corona, while many details of its struct- 

 ure are too delicate to be shown in a figure so small as is here given. 

 It will be understood further that the inner part, marked r, is much 

 brighter than the whole of the outer part, marked c, and that this out- 

 er part shades off gradually into the dark background of the sky. 



1 In a gas-flame there is (as our meters tell us) a continual supply of gas, which mixes 

 with the oxygen of the air, and undergoes what is called combustion. But in the sun's 

 colored prominences the hydrogen enters into no chemical combination, at least none 

 such as we are familiar with. Simply by the intense heat to which it is exposed it glows, 

 just as iron glows when it is heated sufficiently. 



