IN the number of NATURE for June 6, Prof. Asaph Hall, of Washington Observatory, called attention to what he regards as a singular oversight in the history of this subject, viz., that in 1770–1773 Lagrange published an elaborate memoir at Turin under the title “Memoire sur l'utilite de la Methode de prendre le Milieu entre les resultats de plusieurs Observations, &c.” Prof. Hall remarks that the only notice of this memoir he has seen is contained in the Berliner Jahrbuch for 1853, and that in the abstract of a memoir of mine on the subject in the notices of the Royal Astronomical Society for April 1872, the name of Lagrange does not appear.