PARIS. Academy of Sciences, October 4.—M. Henri Deslandres in the chair.—E. Picard: The International Congress of Mathematics at Strasbourg.—The President announced the death of Sir Norman Lockyer, and described the main lines of the scientific work carried out by this distinguished astronomer and correspondant of the Academy.—A. Lacroix: A series of alkaline syenitic potassic rocks in sodium minerals from Madagascar.—G. Bigourdan: Corrections of the normal time-signals sent out by the Bureau international de l'Heure from January 1 to March 19, 1920. Two types of signal are sent out: ordinary signals for the purpose of navigation, railways, etc., and scientific or rhythmic signals for use in observatories. The corrections for the directing clock are tabulated; those for the time-signals will be given later.—C. Sauvageau: The membranes of some algae (Florideæ) and the setting of the gelosic hydrosol.—M. Gevrey: The determination of Green's functions.—T. Varopoulos: Some theorems of M. Rémoundos.—J. Soula: Generalisation of a theorem of M. Leau relating to the determination of the singular points of a function defined by a Taylor's series.—A. Bilimovitch: The intrinsic equations of motion of a solid body.—V. Vâlcovici: The hydrodynamical forces in movements differing between themselves by a uniform rotation of space.—J. Andrade: The problem of the spiral cylinder. —A. Vela: Observations of Nova Cygni. An account of work done on the new star at the Madrid Observatory. Maximum brightness, about 1.4 magnitude, was attained on August 24. A number of spectroscopic observations were made.—J. Bergengren: The absorption spectrum of phosphorus for the X-rays, The substances employed included ammonium phosphate, Bridgemann's black phosphorus, phosphoric acid, and commercial red phosphorus. It was found that the wave-lengths of the limits of absorption were different for the various kinds of phosphorus. This is the first time that the chemical state of an element has been found to have an influence on its X-ray spectrum.—M. de Broglie and A. Dauvillier: The fine structure of the absorption discontinuities in X-ray spectra. A discussion of some phenomena having a bearing on the results described in the preceding paper by M. Bergengren.—A. Dauvillier: The mechanism of the chemical reactions caused by the X-rays. The only mineral substances sensible to the action of the X-rays are crystals for which I. Langmuir, Born arid Landé, and Debye and Sherrer have supposed and proved the existence of an ionic structure. All other sensitive substances, colloids, electrolytes, glass, etc., also contain ions. The cause of the chemical actions would thus be due to the destruction of the negative ions, which would lose their electrons under the impact of the rapid electrons constituting the corpuscular radiation. The violet coloration of alkaline glasses, the photo-electric properties of crystals, and the colour-changes in platinocyanide screens are considered from this point of view.—H. Copaux and C. Philips: The heat of oxidation of beryllium. Direct combustion of the metal in compressed oxygen in the calorimetric bomb gave unsatisfactory results; the combustion of the metal was never complete. The figure required was hence derived indirectly by measuring the heats of solution of the metal and its oxide in dilute hydrofluoric acid. The heat of oxidation, 151.5 calories, was high, and ranges beryllium with calcium (160 calories), lanthanum, (148 calories), and magnesium (144 calories).—G. Denigès: The microchemical reactions of radium: its differentiation from barium by iodic acid. The usual reagents employed in the microchemical reactions of barium, hydrofluosilicic, oxalic, and tartane acids, tartar emetic, potassium ferrocyanide, and tartrate give identical results with barium and radium salts. Ammonium cyanurate, ammonium phosphomolybdate in ammonia solution, and potassium bromate, which are also good reagents for barium, give similar crystals, with radium compounds. Iodic acid, on the other hand, shows clear differences between the two metals, and reproductions of two microscope-slides are given to prove this. As showing the delicacy of the microchemical method, it is mentioned that afl experiments on the reactions of radium were carried out with 0.2 milligram of metallic radium added as the bromide.—R. Fosse: The qualitative analysis of cyanic acid.—A. Lumière and F. Perrin: A new class of hypnotics: the dialkylhomophthalimides. Starting with naphthalene, this is oxidised to phthalonic acid, which reduced bv hvdriodic acid leads to homophthalic acid, (CO.OH).C6H1. CH2CO.OH, the ammonium salt of which, evaporated to dryness and gently fused,gives the homophthalimide. From this dialkvl derivatives are readily obtained. Used as hypnotics, they possess the advantages of verv slight toxic power, and are practirallv free from unfavourable serondarv reation.—F. Kerforne: The tectonic of the Armorican massif.