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216 The moon hath an Atmosphere. In the History of the Royal Academy of Sciences at Paris, for the year 1764. M. du Sejour says, It appears evident to him, from the most accurate observations made on the eclipse of the sun, on the 1st of April 1764, that the solar rays, in passing by the edge or limb of the moon, suffer an inflexion, which he supposes to be equal to four seconds and two thirds. He undertakes to enquire whether this inflexion is to be attributed to the Newtonian attraction, or to a refracting [[underlined]]medium[[/underlined]] surrounding the moon? and to shew, by clculations of the velocity of light, and of the quantity of matter in the moon, that, on the first of these suppositions, the curve, described by a ray passing by the limb of the moon, can differ only insensibly from a [[strikethrough]]straight[[/strikethrough]] strait line; consequently, that this [[underlined]]phenomenon[[/underlined]] cannot possibly be owing to the first of these two causes, and that therefore we ought to conclude that the moon is surrounded by an atmosphere.
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