A Body loses its Colour at a greater or less distance, as the Eye and the Object are at a greater or less height from the Earth: This Proposition I thus demonstrate; The Air being more or less dense as it is nearer or more remote from the Earth, it follows, that where the Eye and the Object are but a little elevated above the Surface of the Earth, the grossness and density of the Interposed Air must weaken and obscure the Colour of the Object: But when both the Eye and the Object are considerably rais'd above the lowest Region of the Air, the pureness and subtilty of the Medium, will yield an easy Passage to the Species of the Object, so that the Eye will receive them without any sensible Diminution of their Lustre. In fine, that variety and degradation, observable in the Colour of an Object, is not only owing to the Light, which at different Hours of the Day is unequally splendid, but to the different Rarity and Density of the Atmosphere, through which the Colour is transmitted to the Eye.