Wiedemann's Annalen, vol. xxiv. January 1885—O. Lehmann, on the melting-points of bodies in contact, and on the electrolysis of solid iodide of silver. A remarkable paper, accompanied with an elaborate plate describing phenomena of crystallisation observed chiefly with microscope at limiting edge of two crystallisable liquids or solutions. Iodide of silver presents certain closely-related phenomena under electrolysis, both in molten and in solid condition. Regular crystalline iodide of silver conducts an electric current, the silver being carried in the direction of the negative current through the crystal without its structure being disturbed. In its electrolysis, however, there appears a streaking in the direction of the flow of the current.— W. von Bezolcl, on a new kind of cohesion-figures. These experimental researches relate to the quasi-dendritic forms observed when one liquid descends through another.—L. Boltz-mann, on the possibility of founding a kinetic theory of gases on attractive forces alone. This is an attempt to dispense with Maxwell's hypothesis that molecules repel one another in the inverse fifth power of the distance, which he framed to account for the apparent perfect elasticity exhibited by molecules of gases. Boltzmann proposes a new theory, based on attraction, very similar to that recently independently propounded by Sir W. Thomson (NATURE, August 28, 1884).—O. Chwolson, on the calibration of the plug-rheostats of Siemens and Halske. This discusses corrections for the resistance of connecting-pieces, &c.—F. Kohlrausch, the electric conductivity of water distilled in vacua. A column of pure water I metre long and of I square millimetre section has a resistance of about 4 X 1010 ohms.—G. Kirchhoff, on the change of form which an elastic body experiences when it is magnetically or dielectrically polarised. This paper, originally published in the Proceedings of the Berlin Academy, deals analytically with the phenomenon of electro-striction investigated by Lorberg and others.—A. Schuster, on the discharge of electricity through gases. Treats of certain points in dispute between the author and Profs. Goldstein and E. Wiedemann. The author pronounces in favour of the view that all the phenomena of effect of magnetism, &c., upon the-discharge of the negative electrode may be explained if it be admitted that the negatively-charged portions of the gaseous molecules are driven off from the kathode.—E. Goldstein, on electric conduction in the vacuum. Discusses some experiments in which a carbon filament lamp was employed; the filament forming one electrode, a platinum wire being inserted through the glass to serve as another electrode for the discharge, which was obtained, without an induction-coil, with electromotive forces of about 300-350 volts.—Werner Siemens, contributions to the theory of magnetism. Describes experiments on partially-closed magnetic circuits of iron, giving rise to the opinion, that the harder a specimen of iron is, the greater is the value of the magnetising force at which the maximum of permeability is observed. Also, the magnetic resistance of air is from 480 to 500 times as great as that of iron.—II. Hertz, on the dimensions of unit of magnetic pole strength in different systems of measurement.—E. Ketteler, the optical constants of magnetic media. Develops equations relatingto Kundt's recent magneto-optic observations.—E. von Fleischl, the double refraction of light in fluids. Proves that in optically-active liquids the rotation is due to the existence of double refraction. Double-refracting liquids have no optic axis, and the wave-surface consists of two concentric spherical sheets,—W. von Voigt, on the measurement of the refractive indices of absorbing media. Recommends the prism method as more accurate than the total-reflection method.—W. von Voigt, on the theory of reflection and refraction at the boundary of crystalline media. New equations based on the author's theory of the reactions between matter and ether in transparent media, and leading to same conclusions as Kirchhoff's older theory.