eminent astronomer, Mr. De la Rue, I have here (Figs. 58 and 59), photographs of the most interesting phenomena

FIG. 58.

observed at the last total eclipse. This diagram is a copy of a photograph taken by him during the eclipse of 1860 in Spain.

FIG. 59.

The first one of these was taken immediately after total obscuration, and the second just previous to the

reappearance of the sun. Now the extraordinary phenomena which are here noticed are to be the subject of very important investigations in August. When an eclipse is total, some wonderful protuberances or red flames are found to dart out from the surface of the sun to the enormous height of some 80,000 or 90,000 miles.1 The examination by the spectroscope of the light which these very singular flames give off is a matter which we all must look forward to with the greatest interest. Spectroscopes have been sent out to various parts of India under the care of very able observers, with particular instructions as to the examination of the lines which these flames give off. Whether these flames are gaseous, whether they give the spectra of bright lines, and, if so, with the lines of what substances these are coincident, are questions to which we may hope soon to have satisfactory answers.

These flames prove that the sun's atmosphere extends to a very great height above the ordinary and visible portion, and it is very remarkable that certain protuberances which were not visible to the naked eye even during a total eclipse, especially one which is like a cloud in the drawing, and was not seen by the observers, left its mark on the sensitive film; it emitted rays of a high degree of refrangibility, too weak to act upon the retina, but strong enough to produce the image on the sensitive plate.

In the next lecture I shall hope to bring before you the most interesting and important researches made by Professor Miller and Mr. Huggins on the subject of Stellar Chemistry.

1 According to Mr. Pogson's measurements the elevation of the 'great horn" was 3′ 23′′ above the sun's disc: this corresponds to a height of 90,995 miles (Baxendell).

Р

LECTURE V.-APPENDIX A.

SPECTROSCOPIC OBSERVATIONS OF THE SUN.

SINCE this lecture was delivered an observation has been made with respect to the sun only second in interest and importance to the results of Kirchhoff's celebrated discovery of the coincidence of the bright iron and dark solar lines and the reversal of the sodium spectrum. The striking nature of this discovery is rendered more evident by its having been made independently by two observers situated thousands of miles apart-by M. Janssen in India and Mr. Norman Lockyer in London. No less than two years ago1 Mr. Lockyer suggested that it might be possible by the use of the spectroscope to obtain evidence of the presence of the red prominences which total eclipses have revealed to us in the solar atmosphere, although they escape all other means of observation at other times. After many fruitless attempts to realize his hopes, Mr. Lockyer at last succeeded, on October 20, 1868, in obtaining the spectrum of a solar prominence; and he thus announces his important observation to the Royal Society through Dr. Sharpey :

"SIR,-I beg to anticipate a more detailed communication by informing you that, after a number of failures, which made the attempt seem hopeless, I have this morning perfectly succeeded in obtaining and observing part of the spectrum of a solar prominence.

"As a result I have established the existence of three bright lines in the following positions:

"I. Absolutely coincident with c.

"II. Nearly coincident with F.

III. Near D.

1 Proc. Roy. Soc. Oct. 11, 1866.

The third line (the one near D) is more refrangible than the two darkest lines by eight or nine degrees of Kirchhoff's scale. I cannot speak with exactness, as this part of the spectrum requires remapping.

"I have evidence that the prominence was a very fine one.

"The instrument employed is the solar spectroscope, the funds for the construction of which were supplied by the Government Grant Committee. It is to be regretted that its construction has been so long delayed.

"I have, &c.

"The Secretary of the Royal Society."

"J. NORMAN LOCKYER.

M. Janssen was sent by the French Government to observe the total eclipse at Guntoor in India, and on August 18th, when examining the bright lines exhibited by the spectra of the prominences visible during the totality, the thought struck him that it might be possible to see these lines when the sun was unobscured, and on trying the experiment on the next day he succeeded in his endeavour, "so that," he writes, "for the last seventeen days I have been working as in a perpetual eclipse." The results of his observations were communicated (Oct. 26, 1868) to the French Academy in the following words:

“La station de Guntoor a été sans doute la plus favorisée : le ciel a été beau, surtout pendant la totalité, et mes puissantes lunettes de près de trois mètres de foyer m'ont permis de suivre l'étude analytique de tous les phénomènes de l'éclipse.

"Immédiatement après la totalité, deux magnifiques protubérances ont apparu: l'une d'elles, de plus de trois minutes de hauteur, brillait d'une splendeur qu'il est difficile d'imaginer. L'analyse de sa lumière m'a immédiatement montré qu'elle était formée par une immense colonne gazeuse incandescente, principalement composée de gaz hydrogène.

"L'analyse des régions circumsolaires, où M. Kirchhoff place l'atmosphère solaire, n'a pas donné des résultats conformes à la théorie formulée par ce physicien illustre; ces résultats me paraissent devoir conduire à la connaissance de la véritable constitution du spectre solaire.

Mais le résultat le plus important de ces observations est la découverte d'une méthode, dont le principe fut conçu pendant l'éclipse même, et qui permet l'étude des protubérances et des régions circumsolaires en tout temps, sans qu'il soit nécessaire de recourir à l'interposition d'un corps opaque devant le disque du soleil. Cette méthode est fondée sur les propriétés spectrales de la lumière des protubérances, lumière qui se résout en un petit nombre de faisceaux très-lumineux, correspondant à des raies obscures du spectre solaire.

'Dès le lendemain de l'éclipse la méthode fut appliquée avec succès, et j'ai pu assister aux phénomènes présentés par une nouvelle éclipse qui a duré toute la journée. Les protubérances de la veille étaient profondément modifiées. Il restait à peine quelques traces de la grande protubérance et la distribution de la matière gazeuse était tout autre.

"Depuis ce jour, jusqu'au 4 septembre, j'ai constamment étudié le soleil à ce point de vue. J'ai dressé des cartes des protubérances, qui montrent avec quelle rapidité (souvent en quelques minutes) ces immenses masses gazeuses se déforment et se déplacent. Enfin, pendant cette période, qui a été comme une éclipse de dix-sept jours, j'ai recueilli un grand nombre de faits, qui s'offraient comme d'eux-mêmes, sur la constitution physique du soleil.

"Je suis heureux d'offrir ces résultats à l'Académie et au Bureau des Longitudes, pour répondre à la confiance qui m'a été témoignée et à l'honneur qu'on m'a fait en me confiant cette importante mission.”

The following abstract of Mr. Lockyer's full paper to the Royal Society1 gives the latest results of his observations, and clearly indicates the important additions to our knowledge of solar physics to which these researches will lead.

"The author, after referring to his ineffectual attempts since 1866 to observe the spectrum of the prominences with an instrument of small dispersive powers, gave an account of the delays which had impeded the construction of a larger one (the funds for which were supplied by the Government Grant 1 Proc. Roy. Soc. No. cvi. 1868.