108 



Dr. W. Huggins. 



The Bakerian Lecture. — " On the Corona of the Sun." By 

 William Huggins, D.C.L., LL.D., F.R.S. Received June 

 11, 1885. Read June 11, 1885. 



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Philostratus, " Life of Apollonius," bk. viii, ch. xxiii 

 (ed. Leipzic, 1709). 



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" Plut. Opera Mor. et Phil.," vol. ix, p. 682 

 (ed. Leipzic, 1778). 



The sun is the only star the corona of which we have been able to 

 observe, for all other stars are too distant to give true images in the 

 telescope. If the snn were removed to a distance equal to that of the 

 nearest star, its disk would subtend less than the one-hundredth of a 

 second of arc. We have also to consider the small relative brightness 

 of the corona, the light from which has been estimated at different 

 times to be from T ^- oM to about the •joo^ooo P ai> t of the sun's light. 

 It is, indeed, possible that stars which have a higher temperature 

 than our sun, are surrounded by coronae of greater extent and bright- 

 ness. 



At the eclipse of 1882, some information was obtained of the sun's 

 condition in relation to that of the brighter stars. The photographs 

 of the more refrangible part of the spectra of stars, which I had the 

 honour to lay before this Society in 1879,* gave a clue by which the 

 stars could be arranged in a serial order, at the head of which stand 

 the bright stars Yega and Sirius. I ventured to suggest that the 

 differences in their spectra might be due primarily to temperature ; 

 and even to make the further suggestion, that the hotter stars were 

 probably the younger stars, and that we had obtained possibly some 

 indications of the relative ages of the stars. The position of the sun 

 came some distance down in the series, very near the position of 

 Capella, and just above the stars which begin to show a yellow tinge 

 in their light. In the ordinary solar spectrum it is difficult to 

 distinguish the ultra-violet group of hydrogen lines, upon the 

 character of which this serial arrangement was mainly based, but in 

 the photograph of the spectrum of the corona obtained during the 

 Egyptian eclipse, Captain Abney and Professor Schuster have been 

 able to recognise very thin bright lines corresponding to the lines of 

 this group. t These lines were not due to the corona, but to 



* " Proc. Roy. Soc.," mo\. 30, p. 20 ; also " Phil. Trans.," vol. 171, p. 669. 

 f "Phil. Trans.," 1883, p. 267. 



