Again, as respects the corona, all the evidence we have is opposed to the conception that the phenomenon is atmospheric. It shows two regions, which, though not separated by well-defined limits from each other, may yet be regarded as, in a sense, distinct. There is an inner and brighter portion, which the sesquipedalians have proposed to call the leucosphere,-apparently on the lucus a non lucendo principle, for it is neither white nor spherical. And there is the outer portion, much less brilliant, and much more strikingly radiated. Neither one part nor the other presents a single feature suggestive of an atmospheric nature;l and the certainty that the two portions belong to a single object affords yet more conclusive evidence against this interpretation of the corona. But the rays of the corona are of a somewhat remarkable nature. When well seen, as during the eclipse of 1868, they are pointed; and even during so unfavourable an eclipse as that of December last, the dark spaces between the rays are seen to widen rapidly with increased distance from the sun. These pointed radiations serve to show that coronal rays must be, in reality, shaped somewhat as cones, having their bases towards the sun. The idea is startling enough, but, admitting the accuracy of the pictures made during well-seen eclipses, and of the Astronomer-Royal's account of the corona during the eclipses of 1851 and 1860, there is no escape from the conclusion here stated. It is not more certain that the sun is a globe, and not a flat disc as he seems to be, than that the coronal radiations are not flat pointed rays, but cone-shaped. Yet no one will suppose that there are a number of monstrous coneshaped masses-atmospheric or otherwise - standing, as it were, upon the sun's surface. I can see no other way of accounting for these conical extensions than by regarding them as phenomena indicating some form of repulsive action exerted by the sun.
1 I am here referring to the possibility that the corona may be due to some species of solar atmosphere. The theory that the corona is due to light in our own atmosphere has now at length been definitely abandoned by all astronomers.
But whatever opinion we may form on this and kindred problems, it seems clear that we must regard the envelope discovered by Professor Young as the only true solar atmosphere: and a very strange and complex atmosphere it is. Nothing yet learned respecting the sun's surroundings surpasses in interest this fiery envelope, in which some of the most familiar of our metals appear as glowing vapours. If anything could add to the interest attaching to the coloured prominences and sierra, it is the fact now revealed that they are propelled through this wonderful envelope, over which they float for a while with strangely changing figure. Truly the study of solar physics, which twenty years ago seemed at a stand-still, is advancing with rapid strides; and it seems scarcely possible to exaggerate the interest either of what has been already revealed, or of the discoveries which are likely to be effected during the approaching eclipse.
From the St. Paul's Magazine for May 1871.
Addendum. - Doubts were urged, for some time after this paper appeared, as to the reality of Young's discovery. But during the total eclipse of December 1871, and yet again during the annular eclipse of 1872, decisive evidence was obtained in its favour, and it is now received by all.