SciEXTiFTc Lectures. 281 



Eclipses. 

 The first sight wliicli attracts attention when the last direct ray of 

 the sun has been cut off by the advancing moon is this ronnd orb in 

 almost inky blackness against a luminous background, and the whole 

 surrounded by a bright glory, which has received the name of the 

 corona, or crown. This appears to have been seen in all total eclipses, 

 for even ancient Greek authors mention it ; yet the descriptions and 

 representations of it vary in a remarkable degree. In some of the 

 drawings it is depicted as a bright halo, concentric with the black 

 disc of the moon, and of nearly uniform width ; in some it is a glory 

 of radiant beams ; in others some of the beams or twice or three 

 times the length of the rest ; sometimes there are four, sometimes two, 

 sometimes six such projecting beams of light. In judging of the 

 degree of accuracy in these, there are many considerations to be kept 

 in mind, such as — that the corona has only lately been made the sub- 

 ject of special observation ; that the observations have generally been 

 made through telescopes which magnified too much to allow the 

 whole disc of the sun and moon to be seen at once ; and that the 

 sketclies have almost always been made from memory at some subse- 

 quent time. I will show some of the representations which have 

 been published, that you may more fully appreciate the diversity of 

 forms assigned to the corona by different observers. 



The " Chromosphere. " 



In the views of total eclipses which I have exhibited, you have 

 probably observed another strange appearance, which is never al)sent 

 though often vailed from the naked eye by the brilliancy of its back- 

 ground of luminous radiance. I allude to the excrescences from 

 various portions of the sun's disc, which are most frequently seen as 

 rose-colored, sometimes, hov/ever, deep red, clear white or even yellow. 

 These are actually portions of the sun, and the moon in her motion 

 gradually hides those in front of her, and discloses those which are 

 on the other side. They are called the protuberances and it is only 

 within the last two 3'-ears that we have attained any definite knowl- 

 edge of their character. They are not always even in apparent contact 

 with the sun, but often seem to float like clouds above his surface, 

 and assume many fantastic shapes, curved, forked, twisted and 

 jagged. 



But it was the spectroscope, which at this total eclipse of 1868 

 was for the first time directed to the protuberance, that the largest 



