setting Sun. One minute and ten seconds from the time of total obscuration a third mountain became visible to the left of the other two. In colour it resembled the others. Beside it were some smaller peaks, all of them well defined.'

Mauvais noticed that the other two protuberances grew higher while the third was making its appearance. Near the end of the eclipse they were no less than two minutes of arc in height.

Biela, Schumacher, and others recognised a border of rose-coloured light surrounding a part of the Moon's limb at a lower level than that attained by the prominences. It is worthy of note that this phenomenon had been noticed earlier than the prominences themselves; for during the total eclipse of 1706, Captain Stannyan remarked that a blood-coloured streak of light appeared, before the Sun's limb emerged from behind the Moon. In 1715, also, Halley noticed that two or three seconds before the emersion, the Moon's limb appeared to be tinged with a dusky but strong red light, forming a long and narrow streak; and during the same eclipse, Louville saw what he describes as an arc of deep red colour along the edge of the Moon's disc. The latter astronomer was careful to assure himself that the appearance was no illusion, and to this end he brought the red arc into the middle of the telescopic field of view, when he found that the red colour remained unchanged. Don Ulloa, in 1778, and Ferrer, in 1806, had noticed a similar pheno

menon.

When the various accounts of the eclipse of 1842 came before the astronomical world, several theories were propounded in explanation of the red prominences. The theory that they are mountains in the Sun was for a while in favour; but Arago pointed out that some of them were too considerably inclined to the perpendicular to be so regarded. Others supposed them to be clouds in the solar atmosphere; while others again suspected them to be enormous flames. As ordinarily happens in such cases, there were not wanting those who denied that the coloured prominences had any real existence whatever. M. Faye, for example, asserted his belief that they are purely optical illusions mirages, perhaps, produced near the Moon's surface.'

The eclipse of 1851 removed these doubts for the most part, though it is to be noted in passing that despite the evidence obtained then, and yet again in 1860, there were some who continued, even until the great Indian eclipse of 1868, to deny that the coloured prominences and the rose-tinted arcs seen at a lower level could really be regarded as solar appendages.

During the total eclipse of 1851 many observers of great skill made drawings of the very remarkable prominences which were visible on that occasion. These pictures exhibited a sufficiently satisfactory agreement to convince the observers that they had all witnessed the same phenomena; though the discrepancies between the pictures afford instructive evidence of the difficulty of delineating with exactness the details presented

during eclipses. The following six pictures represent in order the work of the Astronomer-Royal, Mr. Dawes, Mr. Hind, Mr. Lassell, Mr. Gray, and Mr. Stephenson. Mr. Airy thus writes respecting the prominences:

The form of the prominences was most remarkable. That which I have marked a (fig. 58) reminded me of

The coloured prominences seen during the eclipse of 1851.

a boomerang. Its colour for at least two-thirds of its breadth from the convexity towards the concavitywas full lake-red; the remainder was nearly white. The most brilliant part of it was the swell farthest from the Moon's limb; this was distinctly seen by myself and my friends with the naked eye. I did not measure its height; but judging generally by its proportion to the Moon's diameter, it must have been three minutes of arc. This estimation perhaps belongs to a later

period of the eclipse. The prominence b was a pale white semicircle based on the Moon's limb. That marked c was a red detached cloud or balloon of nearly circular form, separated from the Moon's limb by a space differing in no way from the rest of the corona of nearly its own breadth. That marked d was a small triangular, or conical, red mountain, perhaps a little white in the interior. These were the appearances seen instantly after the formation of the totality. I employed myself in an attempt to delineate roughly the appearances on the western limb, and I took a hasty view of the country; I then remarked the Moon a second time. I believe (but I did not carefully remark) that the prominences a b c had increased in height; but d had now disappeared, and a new one, e, had risen up. It was impossible to see this change without feeling the conviction that the prominences belonged to the Sun, and not to the Moon. I again looked round, when I saw a scene of unexpected beauty. I went to my telescope with a hope that I might be able to make the polarization observations, when I saw that the sierra, or rugged line of projections shown at f, had arisen. The sierra was more brilliant than the other prominences, and its colour was nearly scarlet. The other prominences had perhaps increased in height, but no additional new ones had arisen. The appearance of the sierra nearly in the place where I had expected the appearance of the Sun warned me not now to attempt any other

physical observations. In a short time the white Sun burst forth, and the corona and every prominence vanished.'

Mr. Hind's narrative is as follows:- On first viewing the Sun without the dark glass after the commencement of totality, three rose-coloured prominences immediately caught my eye, and others were seen a few seconds later. The largest and most remarkable of them (a in Mr. Airy's drawing) was straight through two-thirds of its length, but curved like a sabre near the extremity, the concave edge being towards the horizon. The edges were of a full rosecolour, the central parts paler, though still pink. Twenty seconds, or thereabouts, after the disappearance of the Sun, I estimated its length at forty-five seconds of arc, and on attentively watching it towards the end of totality I saw it materially lengthened-probably to two minutes-the Moon having apparently left more and more of it visible as she travelled across the Sun. It was always curved, and I did not remark any change of form, nor the slightest motion during the time the Sun was hidden. I saw this extraordinary prominence four seconds after the end of totality, but at this time it appeared detached from the Sun's limb, the strong white light of the corona intervening between the limb and the base of the prominence. About ten degrees south of the above object I saw during the totality a detached triangular spot of the same rose-colour, suspended, as it were, in the light of the corona, which