Annalen der Physik und Chemie, No. 7.—In the opening paper, on electric limiting layers, Prof. Helmholtz studies the case where there is a difference of potential at the limiting surface of two different bodies, giving, along this surface, what he calls an “electric double layer,” as, e.g., when a zinc and a copper plate, in metallic connection, are approximated to each other, He groups together, in this relation, the phenomena of metallic electrodes in an undecomposed electrolyte, frictional electricity, flow of liquids on solids, and applies an explanation of the last-named case to various recorded phenomena of electrical action in. liquids.—Herr Beetz describes a new investigation of the heat-conducting power of various liquids. The differences in this property, according as the temperatures were above or below 20°, are made manifest, and the discrepancies of previous data in part explained. The phenomena of heat conduction in liquids are considered to depend on mechanical molecular processes, or friction phenomena, as Kohlrausch has shown to be the case with electrolytic conduction.—A paper by Herr Barus treats of the thermo-electric position and electric conductivity of steel inks relation to hardening. He shows that the steel bars examined fell into two classes, those of the one class (the harder) being electro-negative to copper, those of the other (the softer) electropositive. A simple method of classing steel is deduced from this.—In a second communication on experimental determination of. the velocity of light in crystals, Herr Kohlrausch finds that also for oblique sections of optically biaxial crystal Fresnel's theory of light-motion in crystals is fully in harmony with observation.—Remaining papers:—On elastic reaction in longitudinal extension, by Herr Neesen.—Researches on the elementary law of hydro-diffusion, by Herr H. F. Weber.—On the magnetic behaviour of pulverised iron, by Herr V. Waltenhofen.—On extra currents in conductors of various thickness, by Herr Herwig.