Sect. I. Of the SOLAR SYSTEM.

The Arches DG, EG, FG, the Differencesbetween the true and apparent Places of thesuperior Planets, are called the Parallaxesof the Earth’s annual Orb, as seen from thesePlanets. If thro’ the Sun we draw S H pa-rallel to AG, the Angles A S S, A y S,A F S, will be respectively equal to theAngles DSH, ESH, and FSH; and theAngle AGS is equal to the Angle GSH,whose Measure is the Arch GH; whichtherefore will be the Measure of the AngleAGS, the Angle under which the Semi-diameter AS of the Earth’s Orbit, is seenfrom the starry Heavens. Bat this Semi-diameter is nothing in respect to the im-mense Distance of the Heavens or FixedStars; for from thence it would appear un-der no sensible Angle, but look like a Point.And therefore in the Heavens the AngleGSH, or the Arch GH, vanishes; and thePoints G and H coincide; and the ArchesDH, EH, FH, may be considered as being ofthe fame Bigness with the Arches DG, EG,and FG, which are the Measures of theAngles A cf S, A % S, A F S; which An-Igles are nearly the greatest Elongation of the[Earth from the Sun, if the Earth be ob-served from the respective Planets, when[the Line G T? % S A, touches the Earth’s[Orbit in A. The nearer any of the superiorI Planets is to the Sun, the greater is theI Parallax of the Annual Orb, or the AngleI C under