Mr. J. N. Lockyer on Recent Discoveries in Sola?- Physics. 143 



Now most of you will see in a moment that here was a clear 

 issue, which probably the spectroscope, and possibly nothing else, 

 could solve ; for the spectroscope is an instrument whose special 

 metier it is to deal with radiation and absorption. It tells us that 

 the light radiated from different bodies gives us spectra of different 

 kinds according to the nature of the radiating body — continuous 

 spectra without bright lines in the case of solids and liquids, and 

 bright lines, with or without continuous spectra, in the case of gases 

 and vapours. It tells us also that absorption dims the spectrum 

 throughout its length when the absorption is general, and dims it 

 here and there only when the absorption is selective, the well-known 

 Fraunhofer lines being, as you will readily see, an instance of the 

 latter kind. So that we have general and selective radiation, and 

 general and selective absorption. 



Now, then, with regard to the English theory, if there were more 

 absorption in a spot than elsewhere, we might expect evidences of 

 absorption ; that is, the whole solar spectrum would be visible in the 

 spectrum of a spot, but it would be dimmed, either throughout the 

 length of the spectrum or in places only. 



With regard to the French theory, only radiating gaseous matter 

 to deal with, we should, according to the then generally received 

 idea, get bright lines only in the spot-spectrum. 



Here then was a tempting opportunity, and one which I consi- 

 dered myself free to use ; for, although the spectroscope had then 

 been employed (and you all know how nobly employed) for four 

 years in culling secrets from stars and nebulae, there was not, so far 

 as I know, either published or unpublished observation on the sun, 

 the nearest star to us. The field was therefore open for me, and I was 

 not entering into another man's labour, when, on the 4th of March, 

 1866, I attached a small spectroscope to my telescope in order to 

 put the rival theories to a test, and thus bring another power to bear 

 on a question which had remained a puzzle since it was first started 

 by Galileo some two and a half centuries ago. 



What I saw I will describe more fully by and by. It is suffi- 

 cient here to mention that it was in favour of the English theory. 

 There was abundant evidence of absorption in the spots, and there 

 vms not any indication of gaseous radiation. 



Having then thus spectroscopically broken ground on the sun, a 

 very natural inquiry was how next to employ this extension of a 

 method of research, the discovery of which Newton had called, nearly 

 two hundred years before, " the oddest, if not the most considerable, 

 detection which hath hitherto been made in the operations of nature." 



There seemed one question which the spectroscope should now 

 put to the sun above all others, and it was this : — 



"Assuming this absorbing atmosphere to encircle the sun, in ac- 

 cordance with the general idea and Kirchhoff's hypothesis, what are 

 those strange red flames seen apparently in it at total eclipses, jut- 

 ting here and there from beyond the sun's hidden periphery, and 

 here again hanging cloudlike ? " 



