Abstract
PARIS.Academy of Sciences, August 17.—M. Bouquet de la. Grye.in the chair.—A.problem relating to the theory of orthogonal systems and the method of the mobile trihedron: Gaston Darboux.—The detection of a particular class of rays which may be emitted by the sun: H. Dsslandres. An attempt at an explanation of the phenomenon of the second twilight. M., Durand-Gréville has recently shown that this phenomenon is a general one, and is not confined to mountainous districts. If there are solar radiations of wave-length smaller than o-i μ, possessing' an index of refraction greater than the known rays, and for which the ratio n-i/d(n being the refractive index and d the density of the gas) is five or six times greater than with the luminous rays, the sunset for these rays would be about fifteen minutes after the sunset visible to the eye. It is further supposed that these ultra-violet rays excite phosphorescence in the atmospheric particles. These hypotheses would account for the second twilight, but further proof of the existence of such ultra-violet rays is necessary. —A hailstorm which followed the path of a high-tension circuit: J. Violle. This destructive hailstorm moved about 14 kilometres, and had a width of about 2 kilometres. It was remarked that its direction coincided very exactly with that of a high-tension line (45,000 volts). Owing to the fact that the permission of the owners had to be obtained in fixing this line, its course was sinuous. The most serious damage was done in the immediate neighbourhood of the wire, decreasing to the right and left, and ceasing altogether at about 800 metres to 1000 metres on each side. One of the owners of the district where the storm commenced was about 400 metres from the line, and observed three large spheres, twice as large as a man's head, which remained for a moment suspended, and the explosion of which was immediately followed by the fall of hail. These observations raise an interesting question as to the relation between these destructive hailstorms and lines transmitting electric energy under high voltage.—Periodic functions: P. Cousin.—The formation of fogs in presence of the radium emanation: Mme. Curie. The production of a mist in moist gases by the action of the radium emanation has been pointed out in an earlier communication. In the present paper an attempt is made to trace the cause of,this phenomenon. It appears to be due to a chemical o reaction under the influence of the emanation. In some cases the nature of the products has been determined with certainty; with carbon dioxide a little carbon monoxide is produced; air gives some oxides of nitrogen; sulphur and air produce traces of sulphurous and sulphuric acids. The mists produced are composed of very minute drops, not. electrically charged.—Anatomical researches on the vegetative apparatus of the Geraniacese: Abel Legault.—The origin of the colour of black grapes: Philippe Malvezin. An account of the production of the red colour in grapes picked before the colour had developed. The results are in accord with the view of Duclaux, that there is only one chromogenic material in the grape, the transformation of which takes place under the simultaneous influence of air, heat, and possibly light.—The radioactivity of certain springs producing goitre: M. Répin. Various theories have been proposed to account for the production of goitre by certain waters. Two of these, the presence of a distinctive micro-organism or the presence of a rare mineral element, are regarded by the author as untenable from his researches. One singular property of such waters has been known for some time—the power of producing ^ goitre disappears spontaneously after a certain lapse of time. This appeared to resemble the disappearance of radio-activity in certain mineral waters, and the author has examined several springs, well, known to have the property of causing goitre, from this point of view. Three such springs were examined, and all were found to be radio-active, the one possessing the greatest radioactivity also being the one best known for its goitre-pro-ducing properties. There would, thus appear to be a distinct parallelism between the two phenomena, and further work is being carried on from this point of view. —The optical properties of some contractile elements: Mile. Doris L. Mackinnon and Fred. Vies. The contractile elements appear to form two groups from the. point of view of their reaction between crossed Nicols; in the one the lighting is. due to double refraction (muscular elements in general), in the other the lighting is due to depolarisa-tion (cilia).—The changes in the nuclei of the lecithogenic cells of Rhabdocœles Paul Hallez.—The persistence, of the pronephros in Teleostea: Frédéric Guitel.—The fossil flora of Lugarde, Cantal: P. Marty.
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Societies and Academies . Nature 78, 408 (1908). https://doi.org/10.1038/078408a0
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DOI: https://doi.org/10.1038/078408a0