Note 2 — CHAP. II. A brief Description of the Solar System.

If a thread be tied loosely round two pins stuck in a table, and moderately stretched by the point of a black lead pencil carried round by an even motion and light pressure of the hand, an oval or ellipsis will be described; the two points where the pins are fixed being called the foci or focuses thereof. The Orbits of all the Planets are elliptical, and the Sun is placed in or near to one of the foci of each of them: and that in which he is placed, is called the lower focus.