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(170 [[left margin]] Gents Mag p. 130 [[/left margin]] [[underlined]]Of the Quantity of the Refraction of Light in the Moon's Atmosphere: And that the Neglect of this Refraction might cause an Error of some Degrees, in determining the Longitude by Eclipses of fixed stars.[[/underlined]] The last Eclipse of [[underlined]]Jupiter[[/underlined]] by the Moon as it appeared at [[underlined]]Worcester[[/underlined]], and as it must have appeared in other Places of a different Latitude, is abundantly sufficient to demonstrate, That the Rays of Light suffer indeed a very considerable Refraction, in their Passage close to the Moon: and this conformably to my Discourse sent to [[underlined]]London November[[/underlined]] 12, and printed in [[underlined]]January [[/underlined]] 1738, p.8 (or p. 163 of this book.) 2. As to the Quantity of y [superscript t] Refraction,(beside what I have mentioned concerning the Moon's Dichotomy &c.) I find it also as follows, by Observations of Eclipses of fixed Stars by the Moon; And likewise by the Observation and Projection of a total Solar Eclipse. In order to which I make the following Preparation. [[ left margin]] [[strikethrough]]Plate[[/margin strikethrough]] Fig. 45.[[/left margin]] In the Figure I, let T, L and S, placed in a plane perpendicular to the Ecliptic, and nearly in a right Line TLS, be supposed to be the Centers of the Earth, of the Moon and of the Sun. Set Ll and Tf be the semidiameters of the Moon & of the Earth; their Globes being increased by the Effect of the horizontal Refraction in their Atmospheres. And let Tf and L1 be the true Semidiameters of Earth and of the Moon. Let the Ray of Light TbR suffer a double Refraction in the Atmosphere of the Moon, and touch her Surface in 1. And so the Semidiameter of the Moon, as apparent at