378

HISTORY OF PHYSICAL ASTRONOMY.

illustrious astronomer has given of the physical cause of the phenomenonwill be noticed presently.

The luminous ring was visible around the moon during the total eclipseof 1598. Jessenius, who observed the eclipse at Torgau in Germany ,remarked that during the greatest obscuration there appeared a brightlight shining around the moon* * * § . On this occasion, also, the phenomenonwas generally supposed to arise from a defect in the totality of the eclipse,although Kepler strenuously contended that such an explanation was atvariance with the relation between the values of the apparent diametersof the sun and moon, as computed for the time of the eclipse by the aidof the solar and lunar tables. He considered the phenomenon to beidentical in its nature with that observed during the eclipse of 1507, andto be a usual accompaniment of total eclipses of the sun.

The views of Kepler respecting the eclipses of 1507 and 1598 firstappeared in his “ Supplement to Vitellion,” which was published in theyear 1004. They received a striking confirmation from the observationsof the total eclipse of the sun which happened in the following year.On this occasion the eclipse was observed at Naples, under circumstanceswhich did not admit of any doubt respecting the existence of the ring.“ The whole body of the sun was effectually covered for a short time.The surface of the moon appeared quite black ; but around it there shonea brilliant light of a reddish hue, and uniform breadth, which occupied aconsiderable part of the heavens. ” j

During the total eclipse of the sun which happened on the 29th ofMarch, 1652, and which was visible in the British Isles , the moon wasseen surrounded by a ring of light. Dr. Wyberd, who observed this eclipseat Carrickfergus in the north of Ireland , has stated that when the sun wasreduced to a very' slender crescent of light, the moon all at once threw her-self within the margin of the solar disk with such agility, that she seemedto revolve like an upper millstone, affording a pleasant spectacle of rotatorymotion! He remarks, however, that in reality the sun -was totally eclipsed,and that the appearance was due to a corona of light around the moon,arising from some unknown cause. He adds, that it had a uniformbreadth of half a digit, or a third of a digit at least, that it emitted a brightand radiating light, and that it appeared concentric with the sun and moonwhen the two bodies were in conjunction J.

The luminous ring formed a conspicuous accompaniment of the totaleclipse of the sun which happened on the 12th of May, 1706. The de-scription of it given by MM. Plantade and Capies, who observed theeclipse at Montpellier , is clearer and more precise than any other thathad been hitherto recorded. As soon as the sun was totally eclipsed, thereappeared around the moon a very white light forming a kind of corona, thebreadth of which was equal to about 3'. Within these limits the light waseverywhere equally vivid, but beyond the exterior contour, it was less in-tense, and was seen to fade off gradually into the surrounding darkness,forming an annulus around the moon of about 8° in diameter §.

* Ad Vitellionem Paralipomena, p. 299.

f Kepler , De Stella Nova, p. 116, 4to., Prag., 1606.

t Wing, Astronomia JBritannica, p. 356.

§ Mem. Acad, des Sciences, 1706, p. 251.