128 



Dr. W. Hnggins. 



A relatively very small amount of matter, under this diffusing 

 force, would suffice to give rise to the corona, and we can see how 

 the extremely attenuated state of the corona, consisting as it must 

 do, of minute particles widely separated, it may be by miles each 

 from the other, may have been rapidly brought about. 



It is now time to consider the gaseous matter which we know to be 

 associated with the coronal particles, but not to form a continuous 

 gaseous atmosphere. The gas which exists with the incandescent 

 particles, and which the spectroscope shows to have come from the 

 photosphere, may have been carried up as gas, or have been in part 

 distilled from the condensed matter which forms the coronal par- 

 ticles, under the enormous radiation to which they are exposed. 

 Such a view of the gas which is present in the corona, would not 

 be out of harmony with the circumstance that the amount of gas 

 relatively to the incandescent particles appears to vary (at the last 

 eclipse in Caroline Island it seems to have been but very sparingly 

 present), nor with the very different heights to which different 

 bright lines may be traced at different parts of the corona and at 

 different eclipses. Gases of different vapour-density would be 

 acted upon differently by an electric force of repulsion which varies 

 as the surface, and would to some extent be winnowed from each 

 other ; the lighter the gas, the more completely would it come under 

 the sway of repulsion, and so would be carried more rapidly to a 

 greater height than a gas more strongly held down by gravity. 

 The relative proportions, as well as the actual amounts, at different 

 heights in the corona, of the gases which the spectroscope shows to 

 exist there, would vary from time to time ; they would depend in fact 

 also on the largeness of supply from below, in other words, upon the 

 state of activity of the photosphere, and in this way there would 

 come about a relation probably between the corona and the promi- 

 nences. 



The varying amount of gas in different parts of the corona is illus- 

 trated by the following statement in the Report on the Eclipse of 

 1882, by Captain Abney and Professor Schuster : — 



"The ring in the green (1474) is particularly strong in the south- 

 western quadrant, and hardly visible at some other points of the sun's 

 limb. The yellow ring (D 3 ) is much fainter on the whole, but more 

 uniform all round the sun." 



Further on (p. 270) they say — " As regards the corona, we may 

 perhaps point out that hitherto the position of only one true coronal 

 line had been fixed, though two other lines had been suspected. The 

 corona during the late eclipse seems to have been especially rich in 

 lines. Thollon observed some in the violet without being able to fix 

 their position, and Tacchini could determine the position of four true 

 corona lines in the red ; from the photograph we have been able to 



