THE SUN'S CORONA AND HIS SPOTS. 21 



resemblance is, indeed, not indicated in the rough copy of 

 the photographs which illustrates Mr. Lockyer's paper ; 

 but it is clearly seen in the photographs themselves, and in 

 the fine engraving which has been formed from them for the 

 illustration of the volume which the Astronomical Society pro- 

 poses to issue (some time in the present century, perhaps). 



Now, in July, 1878, the corona presented an entirely dif- 

 ferent appearance. Mr. Lockyer, in a telegram sent to the 

 Daily JVews, describes it as small, of pearly lustre, and having 

 indications of definite structure in two places only. Several 

 long rays were seen ; but the inner corona was estimated as 

 extending to a height of about 70,000 miles from the sun's 

 surface. The most remarkable change, however, was that 

 which had taken place in the character of the corona's 

 spectrum or, in other words, in the physical structure of 

 the corona. The bright lines or bright images of the inner 

 corona (according as it was examined through a slit or with- 

 out one) were not seen in July, 1878, showing that no part, 

 or at least no appreciable part, of its light came from glowing 

 gaseous matter. But also the dark lines seen by Janssen in 

 1871 were wanting on this occasion, showing that the corona 

 did not shine appreciably by reflecting sunlight The spec- 

 trum was, in fine, a continuous rainbow-tinted streak, such as 

 that given by glowing solid or liquid matter. 



The inference clearly is: i. That in July, 1878, the gaseous 

 matter which had been present in the corona in 1871 was 

 either entirely absent or greatly reduced in quantity ; 2. 

 The particles of solid or liquid (but probably solid) matter 

 which, by reflecting sunlight, produced a considerable por- 

 tion of the corona's light in 1871, were glowing with heat in 

 July, 1878, and shone in the main with this inherent light; and 

 3. The entire corona was greatly reduced in size in July, 1878, 

 as compared with that which formed the ' starlike decoration ' 

 around the black body of the moon in December, 1871. 



We cannot, however, accept the theory that such a 

 corona as was seen in 1871 invariably surrounds the sun 

 in years of great disturbance, while the corona of last month 



