HISTOftY OF PHYSICAL ASTRONOMY.

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spectrum, except the red, as in the case of the terrestrial clouds whenthey are seen illuminated by the sun after his disappearance under thehorizon.

2°. The radial appearance which the protuberances exhibited to M.Eugene Bouvard can only be explained by the supposition of the rays ofthe sun forcing tlieir way through the interstices of the clouds contiguousto his luminous surface, and illuminating the particles of the solar atmo-sphere situate beyond in the line of their emanation. So also with respectto the luminous points observed by M. Yalz, it is impossible otherwise toaccount for the constant emanation of the rays outwards in a directionnormal to the moon’s limb.

3°. The zone of a deep red colour observed at Toulon towards the partof the moon’s limb where the sun was about to emerge, clearly indicatesthe accumulation of nebulous matter in the lower regions of the solaratmosphere, as well as the condensation of the circumambient fluid ofwhich the latter is composed, towards the surface of the sun, arising fromthe pressure of the superincumbent strata.

The indications of a solar atmosphere afforded by phenomena bearinga strong resemblance to clouds and nebulous strata , as well as by the ap-pearance of rays in a direction normal to the suns limb * * * § , althoughchiefly conspicuous during the total eclipses of 1733 and 1842, have pre-sented themselves on numerous other occasions in a greater or less de-gree of developement. As this is a point of considerable importance inthe question relative to the physical constitution of the sun, it perhapsmay not be out of place to give a brief statement of all those observationswhich tend more especially to illustrate it.

Captain Stannyan, who observed the total eclipse of 1700 at Berne,states, that the emersion of the sun was jmeceded by a blood-red streak oflight from its left limb, which continued not longer than six or sevenseconds of time f.

A similar phenomenon was remarked by both Halley and Louville onthe occasion of the total eclipse of 1715. Halley, in his account of theeclipse, states, that about two or three seconds before the emersion, a longand very narrow streak of a dusky but strong red light, seemed to colourthe dark edge of the moon on the western side where the sun was justcoming out J. Louville states that, towards the end of the total ob-scuration, there was seen about the moon’s limb, at the place where thesun was about to emerge, an arc of a deep red colour. In order to obtainan assurance that the phenomenon was not due to the aberration of thetelescope, he took the precaution of viewing it through the very centreof the object-glass, when he found that it exhibited the same colour asbefore §.

Don Ulloa, in his account of the total eclipse of 1778, speaks of a pointof red light which appeared on the edge of the moon’s disk near the placewhere the sun was about to emerge. It first became visible about aminute and a quarter before the reappearance of the sun. It then

* It has been mentioned in the account of the appearance presented by the luminousring during the total eclipse of 1733, that there were seen emanating from it rays ofunequal length , which constantly maintained the same position. This description isclearly at variance with the supposition of the phenomenon being due to the irregular

scintillation of a luminous object.

t Phil. Trans., 1706, p. 2240. J Phil. Trans., 1715, p. 250.

§ Mem. Acad, des Sciences, 1715, p. 93.