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    PARIS Academy of Sciences, September 8.—M. Rolland, President, in the chair.—The sitting was opened by the President with a few remarks on the ninety-ninth anniversary of M. Chevreul, doyen of the Academy.—Researches on the general development of vegetation in an annual plant (continued): nitrous elements and mineral constituents, by MM. Berthelot and André.—Note on the general resolution of the linear equation in matrices of any order, by Prof. Sylvester.—Remarks on balloon steering, by M. Duroy de Bruignac. The author considers that the experiment of August 9 at Chalais introduces a new phase of aërial navigation; and that the problem hitherto regarded as hopeless may soon be completely solved. It must, however, always remain of difficult application, the results depending on two essential conditions: that is, the necessity of increasing the propelling power and of diminishing the resistance of the air. A simple calculation shows that this resistance is in proportion to the cube of the sine in the angle of incidence of the prevailing atmospheric current. Hence for the small angles, which are rightly preferred, we get a variation of from 2° to 4° double or treble, or thereabouts, a tremendous obstacle, which has to be overcome.—Observations of the new Borelly planet 240, made at the Observatory of Algiers, by M. Ch. Trépied,—Observations of the solar spots and faculæ made at the Observatory of the Collegio Romano during the second quarter of the present year, by M. Tacchini.—A new contribution to the question of the origin of the phosphates of lime in the South-West of France, by M. Dieulafait. The author refers these formations to the action of saline waters during the Tertiary epoch, analogous to if not identical with those of the lagoons at the present time. The saline and concentrated waters of these lagoons, which certainly existed in Tertiary times, played a double part in the production of the natural phosphates of lime. In the first place they attacked the limestone rocks far more actively than ordinary water could have done; and then they contribute directly phosphoric acid, which is still being deposited in the shallow lagoons of the Rhone delta.—Experiments made for the purpose of testing the influence of pulps and other artificially prepared foods on cow's milk, by MM. A. Andouard and V. Dézaunay. These experiments, carried on during the years 1883 and 1884, tended to show that the prepared foods acted injuriously on the milk, but increased the quantity of butter without affecting its quality.—On the solar coronas recently observed in Switzerland, at Nice, and elsewhere, by M. L. Thollon. From a comparative study of the different accounts received of these phenomena, the author concludes that they are not merely halos, but true coronas, that is, an effect of diffraction produced either by fine dust or by light particles of moisture present in the elevated regions of the atmosphere.—Description of a meteor observed at the Trocadéro Observatory on the night of September 5, by M. L. Jaubert.

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