[51]. Smith’s Optics, § 1197.
[52]. All Circles appear ellipses in an oblique view, as is evident by looking obliquely at the rim of a bason. For the true figure of a Circle can only be seen when the eye is directly over it’s center. The more obliquely it is viewed, the more elliptical it appears, until the eye be in the same plane with it, and then it appears like a straight line.
[53]. Here we must suppose the Sun to be no bigger than an ordinary point (as ·) because he only covers a Circle half a degree in diameter in the Heavens; whereas in the figure he hides a whole sign at once from the Earth.
[54]. Here we must suppose the Earth to be a much smaller point than that in the preceding note marked for the Sun.
[55]. If the Earth were cut along the Equator, quite through the center, the flat surface of this section would be the plane of the Equator; as the paper contained within any Circle may be justly termed the plane of that Circle.
[56]. The two opposite points in which the Ecliptic crosses the Equinoctial, are called the Equinoctial Points: and the two points where the Ecliptic touches the Tropics (which are likewise opposite, and 90 degrees from the former) are called the Solstitial Points.
[57]. The Equinoctial Circle intersects the Ecliptic in two opposite points, called Aries and Libra, from the Signs which always keep in these points: They are called the Equinoctial Points, because when the Sun is in either of them, he is directly over the terrestrial Equator; and then the days and nights are equal.
[58]. In this discourse, we may consider the Orbits of all the Satellites as circular, with respect to their primary Planets; because the excentricities of their Orbits are too small to affect the Phenomena here described.
[59]. If a Globe be cut quite through upon any Circle, the flat surface where it is so divided, is the plane of that circle.
[60]. The Figure shews the Globe as if only elevated about 40 degrees, which was occasioned by an oversight in the drawing: but it is still sufficient to explain the Phenomena.