Astronomy Explained upon Sir Isaac Newton's Principles

Ferguson reproduces the looped geocentric paths of Mercury and Venus, traced by machine from Cassini's figures, with the rule that 'the planets appear stationary at the sides of each loop, retrograde along the part of each loop nearest the Earth, and direct along the rest of their paths' (Article 138). He gives each planet's distance from the Sun when stationary, Mercury 28 degrees and Venus 47, to show that Mercury's orbit lies inside Venus's (Article 144), and explains why the stationary places shift from cycle to cycle (Article 146).