Letter, from [A. J. F.] Yvon Villarceau to Sir John Herschel, dated at Paris Autograph letter signed by sender. Thanks John Frederick William Herschel for his interest in Yvon Villarceau's work on double stars. Yvon Villarceau sends a copy of a note on double stars published in the Academie des Sciences for consideration by the Royal Astronomical Society Raises a problem of agreement between Newtonian theory and observational data. Yvon Villarceau feels astronomical studies in France are slowing down. 16 November 1849