Astronomy Explained Upon Sir Isaac Newton's Principles, and Made Easy to Those who Have Not Studied Mathematics To which are Added, a Plain Method of Finding the Distances of All the Planets from the Sun, by the Transit of Venus Over the Sun's Disc, in the Year 1761. An Account of Mr. Horrox's Observation of the Transit of Venus in the Year 1639: And, of the Distances of All the Planets from the Sun, as Deduced from Observations of the Transit in the Year 1761