Societies and Academies

Abstract

PARIS.Academy of Sciences, August 7.—M. Lœwyin the chair.—On the periodic maxima of spectra, by M. Aymonet.—On the heat spectrum of fluorine, by M. E. Carvallo. A comparison between the results obtained by the author and simultaneously by Messrs. Rubens and Snow, of Berlin. In those portions which are common to all three observers, the agreement is perfect, although the results were arrived at by very different methods.—On the absorption of light by liquid bromine, by M. Charles Camichel. Liquid bromine absorbs luminous rays very energetically, especially the most refrangible ones. Thus, a thickness of bromine of a wave length and a half of D light exerts a considerable absorptive action upon the green ray of thallium, and a layer of six times that thickness absorbs the same radiation to such an extent that measurements become difficult. A drop of bromine was introduced between two pieces of glass constructed for observing Newton's rings. These glasses were mounted in a screw frame resting upon the carriage of a dividing engine, by means of which they could be moved in front of one of the collimators of a Gouy spectro-photometer. The thickness of the layer was measured by observing Newton's rings in monochromatic light. Two luminous pencils proceeded from the same source, one traversing the polarising collimator, the other the bromine glasses and then the ordinary collimator. Two patches were thus produced, which were equalised by the analyser when the bromine glasses were full and empty respectively. It was found that the absorption followed the exponential law between thicknesses of 0˙5 and sixty times the principal wave length of sodium.—On the origin of atmospheric oxygen, by Mr. T. L. Phipson. Various plants, such as Poa, Trifolium, Antirrhinum and Convolvulus were placed under glass shades with their roots immersed in water containing free carbonic acid and certain salts, shut off from the light, and their upper portions exposed to a north light in atmospheres of carbonic acid, hydrogen, and nitrogen respectively. It was found that in carbonic acid the plants were able to live for some time, but did not prosper. In hydrogen they fared better, but the gas gradually disappeared, probably combining with the oxygen evolved by the plants. Convolvulus throve very well in an atmosphere of nitrogen, especially if mixed with a third part of carbonic acid. After several weeks the composition of the gas began to approach that of our atmosphere, no change of volume having taken place, The bearing of these facts upon the history of the earth's atmosphere may prove important.—Of the isomorphism of anhydrous alums, by M. T. Klobb.—Influence of solar radiation upon plants, by M. G. Landel. Variations of intensity of solar radiation appear always to act in the same sense upon plants, as regards the quantity of flowers and the proportion of red pigment colouring the various parts. These variations differ much according to the species. In some the red pigment is well developed in the shade, whilst others remain perfectly green. The inflorescence in certain species does not seem to be sensibly modified by shade; in others the number of flowers is less.—The young bulbs of the Dioscoreæ, by M. C. Queva.