146. If the Earth kept always at _E_, it is evident that the Stationary
places of Mercury and Venus would always be in the same points of the
Heavens where they were before. For example; whilst Mercury _m_ goes
from _h_ to _n_, according to the order of the letters, he appears to
describe the arc _ABCDE_ in the Heavens, direct: and whilst he goes from
_n_ to _h_, he seems to describe the same arc back again, from _E_ to
_A_, retrograde: always at _n_ and _h_ he appears stationary at the same
points _E_ and _A_ as before. But Mercury goes round his Orbit, from _f_
to _f_ again, in 88 days; and yet there are 116 days from any one of his
Conjunctions, or apparent Stations, to the same again: and the places of
these Conjunctions and Stations are found to be about 114 degrees
eastward from the points of the Heavens where they were last before;
which proves, that the Earth has not kept all that time at _E_, but has
had a progressive motion in it’s Orbit from _E_ to _t_. Venus also
differs every time in the places of her Conjunctions and Stations; but
much more than Mercury; because, as Venus describes a much larger Orbit
than Mercury does, the Earth advances so much the farther in it’s annual
path before Venus comes round again.
[Sidenote: The Elongations of all Saturn’s inferiour Planets as seen
from him.]
147. As Mercury and Venus, seen from the Earth, have their respective
Elongations from the Sun, and Stationary places; so has the Earth, seen
from Mars; and Mars, seen from Jupiter; and Jupiter, seen from Saturn.
That is, to every superiour Planet, all the inferiour ones have their
Stations and Elongations; as Venus and Mercury have to the Earth. As
seen from Saturn, Mercury never goes above 2-1/2 degrees from the Sun;
Venus 4-1/3; the Earth 6; Mars 9-1/2; and Jupiter 33-1/4: so that
Mercury, as seen from the Earth, has almost as great a Digression or
Elongation from the Sun, as Jupiter seen from Saturn.
[Sidenote: A proof of the Earth’s annual motion.]
148. Because the Earth’s Orbit is included within the Orbits of Mars,
Jupiter, and Saturn, they are seen on all sides of the Heavens; and are
as often in Opposition to the Sun as in Conjunction with him. If the
Earth stood still, they would always appear direct in their motions,
never retrograde nor stationary. But they seem to go just as often
backward as forward; which, if gravity be allowed to exist, affords a
sufficient proof of the Earth’s annual motion.
[Sidenote: Fig. III.