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The page reads: THE ASTROPHYSICAL JOURNAL AN INTERNATIONAL REVIEW OF SPECTROSCOPY AND ASTRONOMICAL PHYSICS VOLUME LXXIII JANUARY 1931 NUMBER 1 POSITIONS, ORBIT, AND MASS OF PLUTO BY SETH B. NICHOLSON AND NICHOLAS U. MAYALL ABSTRACT Positions and orbit of Pluto. Positions of Pluto were obtained from photographs taken by M. L. Humason in I919 with the 1o-inch Cooke triplet and from photographs taken with the 6o- and 10o-inch reflectors in 1930. Orbital elements were computed which include the perturbations of the four major planets. The resulting period is 247.6268 years, which corresponds to a mean distance of 39.45743 astronomical units. The time of perihelion passage is 1989 Nov. 6.98 U.T., and the eccentricity 0.24852. I. POSITIONS AND ORBIT OF PLUTO As soon as it was announced that a trans-Neptunian object had been discovered by Tombaugh at the Lowell Observatory, the records of photographs taken at the Mount Wilson Observatory were examined to see whether any prediscovery positions could be ob-tained. The only photographs which could show images of the newly discovered object were four of a series begun in December, 1919, by M. L. Humason in a search for trans-Neptunian planets.