Note 209 — BOOK II. AN ACCOUNT OF THE WORLD AND THE ELEMENTS.

A planet appears to be stationary, i. e. to be referred to the same point of the zodiac, when it is so situated with respect to the earth, that a straight line passing through the two bodies forms a tangent to the smaller orbit. The apparent motion of the planets, sometimes direct and at other times retrograde, with their stationary positions, is occasioned by the earth and the planets moving in concentric orbits, with different velocities. One hundred and twenty degrees is the mean distance at which the three superior planets become stationary. We have an elaborate dissertation by Marcus, on the unequal velocities of the planets, and on their stations and retrogradations, as well according to the system of Aristotle as to that of Copernicus; Ajasson, ii. 316 et seq. He remarks, and, I conceive, with justice, “... ce n’est pas dans les traités d’astronomie de nos savans que l’on doit puiser les détails destinés à éclaircir le texte des chapitres xii, xiii, xiv et xv du second livre de Pline.... Je ne dis rien des commentaires de Poinsinet, d’Hardouin et d’autres savans peu versés en matière d’astronomie, qui ont fait dire à Pline les plus grandes absurdités.”