On this communication Flamsteed remarks ; "The Captain is the first man I ever heard of that took notice of a red streak preceding the emersion of the Sun's body from a total eclipse. And I take notice of it to you [the Royal Society], because it infers that the Moon has an atmosphere; and its short continuance, if only 6 or 7 seconds' time, tells us that its height was not more than 5 or 6 hundredths part of her diameter"." The Red Flames were seen by Halley, Louville, and C. Hayes in 1715, and afterwards by Vassenius, at Göttenberg, who says:— "But what seemed in the highest degree worthy, not merely of observation, but also of the attention of the illustrious Royal Society, were some reddish spots which appeared in the lunar atmosphere without the periphery of the Moon's disc, amounting to 3 or 4 in number, one of which was larger than the other, and occupied a situation about midway between the south and west. These spots seemed in each instance to be composed of 3 smaller parts or cloudy patches of unequal length, having a certain degree of obliquity to the periphery of the Moon. Having directed the attention of my companion to the phenomenon, who had the eyes of a lynx, I drew a sketch of its aspect; but while he, not being accustomed to the use of the telescope, was unable to find the Moon, I, again with great delight, perceived the same spot, or, if you choose, rather the invariable cloud occupying its former situation in the atmosphere near the Moon's periphery "." A "Red-Flame" of a greenish-blue tinge has been noticed. This Arago considered to be an effect of contrast. The Red Flames have also been noticed in annular eclipses, as in that of 1737, observed by Maclaurin, which appears to be the earliest in which the phenomenon was seen; and in partial eclipses, of which that of 1605, observed by Kepler, is probably the first i. The aspect presented by the Moon during eclipses of the Sun is frequently very singular. Kepler stated that the Moon's surface is occasionally distinguishable by a ruddy hue. Baily, in his account of the annular eclipse of 1836, states, that "previous to the formation of the ring, the face of the Moon was perfectly black; but on looking at it through the telescope, during the annulus, the circumference was tinged with a reddish purple colour, which extended over the whole disc, but increased in density of • Phil. Trans., vol. xx. p. 2241. 1706. ↑ Mem. R.A.S., vol. xxi. p. 90. 1853. Phil. Trans., vol. xxviii. p. 135. 1733. h Phil. Trans., vol. xl. p. 181. 1737iDe Stella Nová, p. 116. * Epit. Astron., p. 895. colour, according to the proximity to the centre, so as to be in that part nearly black1." Vassenius in 1733 and Ferrer in 1806 are the only observers who state that they have seen the irregularities in the Moon's surface during a central eclipse, whether total or annular". Arago and others tried to do so in 1842, but failed. The fact that the lunar inequalities sometimes are seen and at other times are not seen is doubtless owing to meteorological causes. upon In 1842 Arago saw the dark contour of the Moon projected the bright sky 40m after the commencement of the eclipse. He ascribes the phenomenon to the projection of the Moon upon the solar atmosphere, the brightness of which, by an effect of contrast, rendered the outline of the Moon's dark limb discernible". The phenomenon appears to be a rare one: at least it is recorded by only 3 recent observers o. On several occasions attempts have been made to detect the Moon's shadow in the course of its passage over the surface of the Earth. Airy in 1851 succeeded in observing it, but he failed in 1842, in which year, however, Plana and Forbes were more fortunate. The difficulty arises from the immense velocity of the shadow-about 30 miles per minute. The earliest historical record of the eclipse-shadow being seen occurs in Duillier's account of the eclipse of May 12, 1705 P. According to M. Laussedat, one of the horns of the solar crescent in 1860 appeared for a short time rounded and truncated. The other horn was contracted nearly to a point, and a small patch of light wholly detached was visible beyond the extremity of this cusp. 1 Mem. R.A.S., vol. x. p. 17. 1838. m Phil. Trans., vol. xxxviii. p. 135, 1733; Trans. Amer. Phil. Soc., vol. vi. p. 267, 1809. n Annuaire, 1846, p. 372. 0 Noble, Pratt, and Neison, Month. Not., vols. xxvii. p. 185, March 1867, and xxxiii. pp. 468 and 577, June, &c. 1873; Ast. Reg., vol. xiii. p. 9, Jan. 1875. P Mém. Acad. des Sciences, 1706, p. 113 (Hist.); Phil. Trans., vol. xxv. p. 2243, 1706. CHAPTER III. THE TOTAL ECLIPSE OF THE SUN OF JULY 28, 1851. Observations by Airy.-By Hind.-By Lassell. OT the least interesting of the total eclipses of the Sun that have occurred within the last half-century was that of July 28, 1851. Though not visible in England, it was seen to great advantage in Sweden, to which country many astronomers went at the time for the purpose of observing the eclipse. The following remarks are from the pen of Sir G. B. Airy, the then Astronomer Royal, who observed the eclipse at Göttenberg: "The approach of the totality was accompanied with that indescribably mysterious and gloomy appearance of the whole surrounding prospect, which I have seen on a former occasion. A patch of clear blue sky in the zenith became purple-black while I was gazing on it. I took off the higher power with which I had scrutinized the Sun, and put on the lowest power (magnifying about 34 times). With this I saw the mountains on the Moon perfectly well. I watched carefully the approach of the Moon's limb to that of the Sun, which my graduated dark glass enabled me to see in great perfection: I saw both limbs perfectly well defined to the last, and saw the line becoming narrower, and the curves becoming sharper, without any distortion or prolongation of the limbs. I saw the Moon's serrated limb advance up to the Sun's, and the light of the Sun glimmering through the hollows between the mountain peaks, and saw these glimmering spots extinguished one after another in extremely rapid succession, but without any of the appearances which Mr. Baily has described. I have no means of ascertaining whether the darkness really was greater in the eclipse of 1842. I am inclined to think, that in the wonderful, and, I may say, appalling obscurity, I saw the grey granite hills, within sight of Hvaläs, more distinctly than the darker country surrounding the Superga. But whether, because in 1851 the sky was much less clouded than in 1842 (so that the transition was from a more luminous state of sky, to a darkness nearly equal in both cases), or from whatever cause, the suddenness of the darkness in 1851 appeared to be much more striking than in 1842. My friends, who were on the upper rock, to which the path |