Astronomy explained upon Sir Isaac Newton's principles. And made easy to those who have not studied mathematics / To which are added, a plain method of finding the distances of all the planets from the sun, by the transit of Venus over the sun's disc, in the year 1761. An account of Mr. Horrox's observation of the transit of Venus in the year 1639; and, of the distances of all the planets from the sun, as deduced from observations of the transit in the year 1761. By James Ferguson.

  • Ferguson, James, 1710-1776.
Date:
1770
Catalogue details

Licence: Public Domain Mark

Credit: Astronomy explained upon Sir Isaac Newton's principles. And made easy to those who have not studied mathematics / To which are added, a plain method of finding the distances of all the planets from the sun, by the transit of Venus over the sun's disc, in the year 1761. An account of Mr. Horrox's observation of the transit of Venus in the year 1639; and, of the distances of all the planets from the sun, as deduced from observations of the transit in the year 1761. By James Ferguson. Source: Wellcome Collection.

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    13 She may havea Moon, al. though we cannot fee it, Of the Solar System, every eight years; her Conjunctions, Elongations, and ‘Times of rifing and fetting, being very nearly’ the fame, on the fame days, as before. a 46. Venus may have a Satellite or Moon, al- though it be undifcovered by us: which will not appear very furprifing, if we confider how incon-~ venieotly we are placed for feeing it. For it’s en- lightened fide can never be fully turned towards us, but when Venus is beyond the Sun; and then, as Venus appears little bigger than an ordinary Star, her Moon may be too {mall to be perceived the Sun, her full Moon has it’s dark fide towards us; and then we cannot fee it any more than we can our own Moon at the time of Change. When Venus is at her greateft Elongation, we have but one half of the enlightened fide of her Full Moon towards us; and even then it may be too far dif tant to be feen by us. But if fhe has a Moon, it The Earth. Fig. I. Jt’s diurnal and annual maption, the year 1761, unlefs it’s Orbit be confiderably inclined to the Ecliptic; for if it fhould be in con- junction or oppofition at that time, we can hardly imagine that 1t moves fo flow as to be hid by Venus all the fix hours that fhe will appear on the Sun’s:Ditc *. Pie % ke 47. The Earru is the next Planet above Venus in the Syftem. It is 82. millions of miles from the Sun, and goes round him (as in the circle ®) in 365 days 5 hours 49 minutes, from any Equi- nox or Solftice to the fame again: but from any fixed Star to the fame again, as feen from the Sun, in 365 days 6 hours and: 9 minutes; the former being the length of the Tropical year, and the the rate of 58 thoufand miles every hour; which motion, though 120 times fwifter than that of a * The tranfit is over fince this was wrote, and no Satellit > was feen with Venus on the Sun’s Difc. ya