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173 in reference to the apparent Disc of the Earth. [[left margin]] Diameters of [[image-symbol for sun]],[[image--symbol for moon]], and Hor. Refr. of [[image-symbol for moon]]'s Atmosphere assigned; Different from Sir I.N. [[/left margin]] 28. I concluded once upon some Suppositions, That the real Semidiameter of the Moon being made of 100 Parts, the real Semidiameter of the Earth must be made of 336,10554 Parts; which Sir [[underlined]] Isaac Newton [[/underlined]] makes of 365 Parts. The Difference is of 28,89446 Parts. From whence I concluded also, That the horizontal Refraction in the Atmosphere of the Moon is of 1'14'',2746; whose Double is 2'20'',5492. This I thought fit to mention, it being of the utmost Consequence in determining the Longitude both at Land and at Sea, by Eclipses of fixed Stars. But I intend to revise and publish those or the like Calculations, if God grants me Time and Health, and likewise to facilitate the Use of them, for Mathematicians or Navigators of a moderate Capacity. [[left margin]] Eclipses of [[image--symbol for Jupiter]]'s Satellites deficient without the above corrections.[[/left margin]] 29. But as to the rectifying / the Theory of the Satellites of [[underlined]Jupiter[[/underlined]] or [[underlined]S^a turn[[/underlined], by Eclipses of those Planets by the Moon; one of which Eclipses is expected on the 18th of this Month of [[underlined]] November[[/underlined]]; I [[strikethrough]]find[[/strikethrough]] fear that Astronomers will find themselves greatly mistaken, if they neglect, in their Rectifications, what I have now said, or have further to say. For otherwise they may as well perplex and corrupt the Theory of those Satellites, as render it more perfect. Gent. Mag. 1738. p. 8&c N. Facio, [[underlined]] Duillier.[[/underlined]] [[underlined]]Worcester[[/underlined]] Nov? 12. 1737.