Abstract
PARIS.
Academy of Sciences, October 19.—M. Duchartre in the chair.—Memoir on the underground temperatures observed at the Muséum d'Histoire Naturelle, during the winter 1890–91, by M. Henri Becquerel. A thermo-electric arrangement was used for the determination of the temperatures beneath two surfaces, one of which was covered with sand and devoid of vegetation, whilst the other had grass and some plants growing upon it. The two soils were similar, and in each case the temperatures were taken at five points, having depths ranging between 5 cm. and about 60 cm. The observations extend from November 1, 1890, to March 31, 1891, the temperatures being taken at 6 am. and 3 p.m. daily. These have been plotted, and the resulting curves strikingly show the variations which occurred in the interval, and the extinction of detail with increased depth. The diurnal variation at the greatest depth was a few tenths of a degree, whilst that of the air was about 14°. At a depth of 18 cm. beneath the sandy covering the variation was the same as in air, but at all the other points the effect was reversed—that is, the temperature fell from 6 a.m. to 3 p.m., and rose during the night. It also appears from the observations that Fourier's theory of the differential relation existing between temperature, time, and depth of thermometer represents very well the propagation of heat in a superficial layer of soil, and that the coefficient of conductivity of this layer for determined conditions of humidity may be deduced from observations of underground temperatures. A certain thickness of earth protects the roots of plants from the effects of a sharp frost, but it may not be equally efficacious against a long one of less intensity, for the velocity of propagation of a variation of temperature, and the depth at which this variation is felt, depends upon the duration of its period. A layer of grass, covering soil, has the same protecting effect during the winter as that of about 50 cm. of mould.—Researches on the cause of rheumatic diathesis, by M. F. P. le Roux.—Observations of Wolf's periodic comet, made at Algiers Observatory with the telescope of 0˙50 m. aperture, by MM. Rambaud and Sy. Observations for position were made on August 4, 5, 8, and 31, and on September 7.—On the reduction, to a canonical form, of equations from derived partials of the first order and the seeond degree, by Mr. Elliot.—On cyclic systems, and on the deformation of surfaces, by M. E. Cosserat.—Calculation of the magnetic rotation of the plane of polarization of light, by M. G. Hinrichs. The simple law connecting the rotation of the plane of polarization with the thickness of the medium traversed is shown to be applicable to the molecular rotation of a normal paraffin.—On a new method for estimating nitric acid and the total nitrogen, by M. E. Boyer. The method is founded upon the reduction of nitric acid to ammonia, by oxalates and sulphur, in the presence of soda-lime.—On the action of nitric acid on dimethyl ortho-anisidine, by M. P. van Romburgh.—On the globulicide power of blood serum, by M. G. Daremberg. The author terms “pouvoir globulicide” the power possessed by the serum of the blood of one animal to destroy the red corpuscles of the blood of another of a different species. And the destructive power of serum for microbes is called “pouvoir microbicide.” The effects produced in each case have been studied.—On the nature of the movement of the chromatophores of Cephalopods, by M. C. Phisalix.
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Societies and Academies. Nature 44, 632 (1891). https://doi.org/10.1038/044632b0
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DOI: https://doi.org/10.1038/044632b0