Proposal of some new Methods of improving the Theory of Jupiter's Satellites

Read before the Royal Society on February 18 & 25, 1773, A Letter to the Rev. Nevil Maskelyne, F. R. S. Astronomer Royal, from Mr. Bailly, of the Royal Academy of Sciences at Paris: Containing a Proposal of some new Methods of improving the Theory of Jupiter's Satellites. Translated from the French, with the Original underneath presents some new approaches for measuring the characteristics of Jupiter's satellites. .The measurement of celestial structures often varied, dependent upon who was doing the measuring. Mr. Bailly came up with "...two methods...for perfecting the theory of the satellites of Jupiter. The former of these methods serves to measure their diameters, and the latter intended to make observations comparable with each other, although made in different places, and with different instruments..." The item also includes, at the end, a four-page addition titled "Notes on the Foregoing Paper, by the Rev. Samuel Horsely".

The item is a First Edition, extracted and disbound from The Philosophical Transactions of the Royal Society, Vol. 63, Part I For the Year 1773, pages 185-216. The pages, which measure approximately 6 1/4 x 8 1/2 inches, are tanned, but the text is clear and easily read. The overall condition of the item is good/very good.

The illustrations accompanying this description show the first page of Mr. Bailly's letter, while the second illustration shows the first page of the Rev. Horsely's Notes on the Foregoing Paper.

Jean-Sylvain Bailly (15 September 1736 – 12 November 1793) was a French astronomer, mathematician, and political leader of the early part of the French Revolution. He presided over the Tennis Court Oath, served as the mayor of Paris from 1789 to 1791 and was ultimately guillotined during the Reign of Terror. Bailly published his Essay on the theory of the satellites of Jupiter in 1766, an expansion of a presentation he had made to the Academy in 1763. It was followed up in 1771 by a noteworthy dissertation, On the inequalities of light of the satellites of Jupiter. and in 1778 he was elected a foreign member of the Royal Swedish Academy of Sciences. [Wikipedia]

The Reverend Dr Nevil Maskelyne FRS (6 October 1732 – 20 July 1811) was the fifth English Astronomer Royal. He held the office from 1765 to 1811. [Wikipedia]

Samuel Horsley (15 September 1733 – 4 October 1806) was a British churchman, bishop of Rochester from 1792. Horsley was elected a Fellow of the Royal Society in 1767; and secretary in 1773, but, in consequence of a difference with the president (Sir Joseph Banks) he withdrew in 1784. [Wikipedia]