II

Sect. i. Of the SOLAR SYSTEM.

the Sun; he always preserves a round, full,

. and bright Face, except when he is near hisQuadrate Alppct, when he appears some-what Gibbous, like the Moon three or fourDays before or after the Full: Therefore theOrbit of cf must include the Earth withinit, and also the Sun; for if he was betwixt| the Sun and us, at the Time of his inferior| Conjunction, he would either quite disap-' pear, or appear horned, as Venus and the| Moon do in that Position. Let S be the^tz. j*| Sun, T the Earth, and A, P Mars, both ins his Conjunction and Opposition to the Sun,f and in both Positions full; and B, C Mars ,

I at his Quadratures, when he appears some-| what Gibbous from the Earth at T : ’Tis| plain hence, that the Orbit of Mars does!f include the Earth, otherwise he could not{ come in Opposition to the Sun j and that it’ likewise includes the Sun, else he could notJ appear full at his Conjunction.

I Mars , when he is in Opposition to the

j Sun, looks almost seven Times larger ins Diameter, than when he is in Conjunction! with him j and therefore must needs be al-| most seven Times nearer to us in one Position$ than in the other: For the apparent Magni-\ tudes of far distant Objects increase or de-j crease in Proportion to their Distances fromI us. But Mars always keeps nearly at thez same Distance from the Sun; therefore it isplain, that it is not the Earth, but the Sunthat is the Center of his Motion. It