Astronomy explained upon Sir Isaac Newton's principles / [James Ferguson].

  • James Ferguson
Date:
[1794]
Catalogue details

Licence: Public Domain Mark

Credit: Astronomy explained upon Sir Isaac Newton's principles / [James Ferguson]. Source: Wellcome Collection.

    41/576 page 23
    or hazinefs around her, which would make the Stars look fainter, when they are feen through it. But obfervation proves, that the Stars which difap- pear behind the Moon, retain their full luftre until they fecm to touch her very edge, and then they vanifh in a moment. This has been often obferved by Aftronomers, - but particularly by Cassini of the Star r in the bread: of Virgo, which appears hngle and round to the bare eye; but through a refrafting Telefcope of i6 feet appears to be two Stars fo near together, that the diftance between them feems to be but equal to one of their appa- rent diameters. The Moon was obferved to pafs over them on the aift of April 1720, N. S. and as her dark edge drew near to them, it caufed no change in their colour or fituation. At 25 min. 14 fee. paft 12 at night, the moft wefterly of thefe Stars was hid by the dark edge of the Moon : and in feconds afterward, the moft eafterly Star was hid : each of them difappearing behind the Moon in an inftanr, without any preceding diminution of magnitude or brightnefs which by no means could have been the cafe if there were an Atmo- fphere round the Moon ; for then, one of the Stars falling obliquely into it before the other, ought by refraftion to have fuffered fome change in its co- lour, or in its diftance from the other Star which was not yet entered into the Atmofphere. But no fuch alteration could be perceived, though the ob- fervation was performed with the utmoft attention to that particular j and was very proper to have made fuch a difeovery. The faint light which has been feen all round the Moon, in total Eclipfesof the Sun, has been obferved, during the time of darknefs, to have its center coincident with the center of the Sun ; and was therefore much more likely to arife from the Atmofphere of the Sun than from that of the Moon ; for if it had been owing to the latter, its center would have gone along with the Moon’s. C 4 59.If A proof of the Moon’s ha*ing no Atmo- fpheie.
    digitised image 1
    digitised image 2
    digitised image 3