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(164 how to determine it, by [[strikethrough]] the four [[/strikethrough]] ^[[insertion]] the four [[/insertion]] apparent Contacts of the Sun and of the Moon, or at least by some of them. [[left margin]] Moon's Atmosphere Refracts the light. [[/left margin]] 5. And, that there is a sensible Refraction of Light in the Moon's Atmosphere, is evident to one, from an Observation which I made in the Royal Observatory at [[underline]] Paris [[/underline]], above fifty years ago. For I observed there, with a Telescope of about twenty Feet, an Occul^[[insert]] t [[/insert]]ation of a considerable Star by the Moon; when, to my great Surprise, the Star seemed to touch the Moon, for a very considerable Time, before it disappeared. And I suppose that many other persons have had, or will have, frequent Occasions of making the like Observations. 6. And indeed, altho' that Atmosphere, in which we can observe no Clouds, were ever so thin and pure; yet its Refraction must needs be supposed very sensible; since, in our terrest[[insert]] r [[/insert]]ial Atmosphere, the Horizontal Refraction of Light amounts to about 34' Minutes. [[left margin]] Light from the Sun strongest on the Moon [[strikethrough]] at [[/strikethrough]] in Solar Eclipses [[/left margin]] 7. Add to this, that altho' the mean Degree of Light and Heat, which the Sun spreads upon the Surfaces of the Moon and of the Earth, be almost the same thro' the whole Year: Yet the Light of the Sun which shines upon the Surface of the Moon, at the Time of a Solar Eclipse, is considerably stronger. [[left margin]] Case of a Ray Refracted at a planet. [[/left margin]] 8. If an horizontal Ray of Light were so refracted near any Planet, as to have the Center of its Curvature in the Center of the Globe itself; it would move round the Globe, in a concentric Circle, as long as the Globe's Atmosphere might not alter the Swiftness of that Ray of Light. [[left margin]] Another case of D. [[superscript]] o [[/superscript]] [[/left margin]] 9. But an horizontal Ray of Light that has its Passage free, sinks all along under its own Horizon; and describes, within the Atmosphere, a Line of an hyperbolical Kind. Whereas, in that Part of its Way, in which the Refraction can have no sensible Effect, it describes two Lines that are sensibly Straight. And their Inclination to one another is mea: