THE COMETS OF HARTWIG AND SWIFT.—MM. Schulhof and Bossert have investigated the elements of comets 1880 d and e, discovered respectively by Dr. Hartwig at Strasburg on September 29, and Mr. Lewis Swift at Rochester, New York, on October 11. Prof. Winnecke had conjectured that Hartwig's comet might have been identical with the comets of the years 1382, 1444, 1506, and 1560, with a period of revolution of 621/3 years. MM. Schulhof and Bossert formed six normal positions between September 30 and November 29 from observations at Paris, Strasburg, Berlin, Leipsic, Kiel, Kremsmunster, Lund, Florence, Marseilles, O'Gyalla, Clinton, and Washington, and on varying the distances from the earth at the first and fifth place until the other normals were represented as closely as possible, arrived at an elliptical orbit, but with a period of 1280 years: this result is necessarily uncertain under the circumstances, but it nevertheless appears to render so short a revolution as 62⅓ years in the highest degree improbable.