66 



person sitting for a photograph shows unconscious knowl- 

 edge of this fact, since he always expects the portrait to 

 omit defects which belong of course to the red end of the 

 spectrum and to bring out actinic beauties which n > mor- 

 tal eye can see.) It requires also much skill to photo- 

 graph the corona. This was successfully accomplished 

 for the first time in 1869, the photograph then obtained 

 comparing well with the more recent ones. It is custom- 

 ary to obtain a series of photographs with different times 

 of exposure, each of which will bear witness to a portion 

 of the corona. [Illustrated by a photograph taken in 

 Prof. Young's party, and by Mr. Whipple's photograph 

 of the corona in the 1869 eclipse.] 



It is interesting to compare the varied appearances of 

 the corona in different eclipses. In the recent eclipse it 

 was more elongated than usual, or at least the coronal 

 streamers were on this occasion noticed to extend further 

 from the sun than previously. The general outline was 

 also quite irregular, though in this respect it was not 

 unlike many others. 



[A series of views was here shown representing the 

 corona as seen in nine of the total eclipses that have been 

 observed during this century.] 



While the corona is still a very mysterious appearance, 

 yet the result of observations made in past years has 

 tended to establish the truth of certain theories with 

 regard to it. It belongs to the sun, and not to the moon. 

 It is not caused by our own atmosphere, as some have 

 thought, considering it to be a mere optical illusion. It is 

 undoubtedly true that its appearance is much modified by 

 local influences, but from the summit of Pike's Peak, 

 where the disturbing effects qf the atmosphere were less 

 than at other stations, it was seen in greater extent than 

 elsewhere. Its presence surrounding the sun, when the 



