1882.] 



President's Address. 



321 



A complete photograph of the spectrum of the prominences and 

 the corona was for the first time obtained. The prominences give a 

 spectrum in which the lines of calcium bear a conspicuous part by 

 their intensity. The ultra-violet hydrogen lines, photographed in 

 star spectra by Dr. Huggins, were seen, as well as a number of un- 

 known lines. 



The corona gives a very complicated spectrum. Close to the limb 

 of the sun the spectrum was so nearly continuous and so strong as to 

 hide any lines which might have been present. Further away the 

 continuous spectrum fades off, the region of the solar group G appears 

 occupied by an absorption band, and a large number of coronal lines 

 hitherto unobserved appear in the ultra-violet. 



In addition to these photographs one was obtained in a camera, in 

 front of whose lens a prism was placed without a collimator. This 

 photograph allows us to study the spectra of different prominences. 

 As the picture was produced on one of Captain Abney's infra-red 

 plates, all the tints of the prominences ranging from the ultra-red to 

 the ultra-violet made their impressions, and some interesting differences 

 in the spectra of different prominences can be noticed. 



But, beside taking part in this expedition, Mr. Lockyer has continued 

 with unwearied perseverance his observations on the spectra of solar 

 prominences and spots, and has recently combined with these the 

 results obtained by him during the late eclipse. During this eclipse 

 he made naked eye observations, which he considers to be of a crucial 

 character between the two rival hypotheses regarding the nature of 

 the sun's atmosphere. The results of this investigation have in his 

 opinion considerably strengthened the views which he first put for- 

 ward in 1873 on the constitution of the solar atmosphere. A state- 

 ment of these views will be found in a paper by him recently read 

 before the Society. 



In the present state of the questions there raised, it must I think 

 be admitted that, after giving all due weight to the facts and reason- 

 ings adduced by Mr. Lockyer, additional and varied observations are 

 greatly to be desired ; and that no opportunity reasonably available, 

 for adding to our knowledge of the subject, should be neglected. 

 And, therefore, without committing myself or the Society to the 

 support of any particular proposal or expedition, I think that it may 

 be fairly claimed as a prima facie duty on the part of the present 

 generation to obtain as many faithful records of the various pheno- 

 mena occurring during solar eclipses as possible. 



From a discussion of the meridian observations of Mars made during 

 the favourable opposition of 1877, at Washington, Leiden, Melbourne, 

 Sydney, and the Cape, Professor Eastman has deduced the value 

 8" "953 for the solar parallax — a value which, though considerably 

 larger than any of those found by other methods, agrees closely with 



