PARIS Academy of Sciences, September 1.—M. Rolland, President, in the chair.—Some remarks on the subject of the theory of the figure of the planets, by M. F. Tisserand. The author's calculations and estimates of their present form are based on the assumption that the celestial bodies were originally in the fluid state, subject only to the mutual attraction of their constituent elements, and endowed with a rotatory movement with very slight angular velocity. Their outer surface would thus be somewhat that of a revolving ellipsoid.—Researches on the general development of vegetation in an annual plant: functions of the hydrocarbon elements, by MM. Berthelot and André.—Note on the general resolution of the linear equation in matrices of any order, by Prof. Sylvester.—Remarks on the attempts made at. various times to solve the problem of aërial navigation, by M. Laussedat. The author supplies a rapid sketch of the progress of aërostatics in connection with the Commission lately appointed by the Academy to examine the claims of priority of various inventors. He considers that General Meusnier was the first to introduce the elongated shape of the balloon, the screw as the propelling agent, and the principle of the “ballonnet” or air-bag, rediscovered by M. Dupuy de Lôme. M. Conté is credited with great improvements in the construction of spherical balloons, and M. Alcan is stated to have anticipated M. H. Giffard by several years in the application of steam to aërial navigation,—Comparison between the coloured electro-chemical and thermal rings of Nobili and others, by M. C. Decharme.—Observations of the planet 240 discovered at the Observatory of Marseilles on August 27, 1884, by M. Borrelly.—Determination of the wavelengths of the chief rays and bands of the infra-red solar spectrum, by M. Henri Becquerel. Tabulated results are given for the chief bands in millionths of millimetres.—Remarks on the formation and development of the nervous cellules in the spinal marrow of mammals, by M. W. Vignal.—Note on the recent luminous phenomena observed around the sun in Switzerland (second communication), by M. F. A. Forel. A second trip to the Alps, undertaken towards the end of August, enables the author to confirm and complete the details already communicated to the Academy. Aëronauts are invited to study some of these light-effects, and especially the red corona round the sun, scarcely perceptible from the plains and low elevations, but perfectly visible at altitudes of from 3000 to 6000 feet above the sea-level.—Account of the optical telegraph recently established between the islands of Mauritius and Réunion, by M. Bridet. The telegraph set up on Lacroix Peak in Réunion and Vert Peak in Mauritius was completed on the night of July 12-13, when messages were freely exchanged between the two islands.