Societies and Academies


    LONDON. Physical Society, November 27.—Dr. A. Russell, vice- president, in the chair.—A. F. Ilallimond: Note on the conduction of electricity at point contacts. The “characteristic” or volt-ampere curves given by various “point” contacts when the voltage is slowly varied are dealt with. The curves were plotted by means of a form of rocking mirror galvanometer, which projected the characteristic as the path of a spot of light on the screen, the co-ordinates being respectively proportional to the current and voltage. The first part describes the behaviour of a typical contact, zincite-tellurium. The second part describes the results obtained on examining the characteristics for the forty-five contacts possible between ten chosen substances. The results in all cases are similar to those given by zincite-tellurium. No line could be drawn separating “metallic” contacts from those in which one or both conductors were “crystals.” In the third part the conclusion is drawn that in a contact yielding the unilateral (high resistance) curve, the resistance lies within the surface of the member standing higher in the series.—T. Barratt: Thermal conductivity of badly conducting solids. The thermal conductivities of typical solids of low thermal conductivity have been determined by the method employed by the author for pure metals and alloys. The substances tested include electrical insulators, such as glass, fused silica, and ebonite, various kinds of wood, and some partial conductors of electricity—viz., carbon and graphite. It has been shown that the thermal conductivity k is given by

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    Societies and Academies . Nature 94, 440–442 (1914).

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