These different motions observed in the Planets, are easily illustrated, as followeth: The lesser circle round the Sun is the orbit of _Mercury_, in which he performs his revolution round the Sun, in about three months, or while the Earth is going thro’ ¼ part of her orbit, or from A to N. The numbers 1, 2, 3, _&c._ in the orbit of _Mercury_, show the spaces he describes in a week nearly, and the distance AB, BC, DC, _&c._ in the Earth’s orbit, do likewise show her motion in the same time. The letters A, B, C, _&c._ in the great orb, are the motions of _Mercury_ in the Heavens, as they appear from the Earth. Now if the Earth be supposed in A, and _Mercury_ in 12, near his superior conjunction with the Sun; a spectator on the Earth will see ☿, as if he were in the point of the Heavens A, and while ☿ is moving from 12 to 1, and from 1 to 2, _&c._ the Earth in the same time also moves from A to B, and from B to C, _&c._ All which time ☿ appears in the Heavens to move in a direct motion from A to B, and from B to C, _&c._ but gradually slower, until he arrives near the point G; near this place he appears stationary, or to stand still; and afterwards (tho’ he still continues to move uniformly in his own orbit, with a progressive motion) yet in the sphere of the fixed Stars he will appear to be retrograde, or to go backwards, as from G to H, from H to I, _&c._ until he has arrived near the point L, where again he will appear to be stationary; and afterwards to move in a direct motion from L to M, and from M to N, _&c._ What has been here shewed concerning the motions of _Mercury_, is also to be understood of the motions of _Venus_; but the conjunctions of _Venus_ with the Sun do not happen so often as in _Mercury_; for _Venus_ moving in a larger orbit, and much slower than _Mercury_, does not so often overtake the Earth. But the retrogradations are much greater in _Venus_ than they are in _Mercury_, for the same reasons. [Sidenote: _Fig. 2._]