Societies and Academies


    LONDON Royal Society, Feb. 5—C. F. Jenkin: The pressure exerted by granular material. A model consisting of a rectangular frame holding a single layer of steel discs was made which reproduces the leading phenoT maia observed in sand, particularly the effects of ‘arching’. The solutions are found for the forces exerted by the discs under a number of different conditions, including three typical examples of arching. In the light of these results, an apparatus was designed for measuring the pressure of sand on a retaining wall in which end arching was eliminated. The most important new result obtained is that the centre of pressure may be very much higher than was supposed, and that the pressure distribution on the wall is quite different from the triangular distribution commonly assumed.—F. L. Arnot: The diffraction of electrons in mercury vapour. An investigation of the angular scattering of electrons in mercury vapour over an angular range of from 18° to 126° is described. Results are shown for fifteen different velocities of the primary beam between 8 and 800 volts. All the scattering curves show distinct maxima and minima, maxima of four different orders being obtained. The absolute scattering of 82-volt electrons between 15° and 60° has been redetermined.—S. Rama Swamy: On the transmission of light by thin films of metal. Quantitative observations on the transmission coefficient of metal films for different wave-lengths of light in the visible range and its changes on heating the films are described and discussed. Thm films of gold and silver, obtained by cathodic sputtering, were heated in a furnace and their absorption spectra photographed at different temperatures, a pointolite lamp being the source of light. The transmission coefficient was deduced from the photometric measurements of the spectrograms.—D. C. Colbourne: The diurnal tide in an ocean bounded by two meridians. The diurnal tide is considered in an ocean on a rotating globe bounded by two meridians 60° apart and of uniform depth 12,700 ft. The solution of the general dynamical equations of the tides satisfying the required conditions is obtained by the introduction of a null function according to the method developed by Goldsbrough. By means of this solution the tidal amplitudes and phase angles at numerous points have been calculated. Amplitudes of the diurnal tide are considerably smaller than those of the semi-diurnal tide, and the range of values obtained for the phase is unusually limited.

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    Societies and Academies. Nature 127, 257–259 (1931).

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