Abstract
LONDON.
RoyaI Society, March 29.¢Sir J. J. Thomson, president, in the chair ¢Sir William Abney: The fourth colourless sensation in the spectrum sensation curve when measured in the centre of the retina. At the end of the last century the author carried out a large series of observations on the luminosity of spectra of very low density, but only tecently has he had an opportunity of working someof them out. Some time ago he published in the Phil. Trans. the three-colour sensations which apparertly suffice to account for all the spectrum colours. There was a doubt if in the mixture of the sensations to form these colours some account ought not to be taken of the colour sensation which appears when a coloured ray is diminished in intensity for all colour to be absent and only a colourless residue is left. The author confines himself to the colours received on the centre of the retina, for on the periphery other conditions exist. The paper shows the method of Qbservation which was employed, and, discussing the results, the author comes to the conclusion that the admixture of the colourless sensation with the three-colour sensations is so small as to be inappreciable, and that the sensation curves given in his paper, to which reference has been made, need no correction on this account.¢G. W. Walker: Magnetic inertia. It is showil that a magnetised body may be expected to possess magnetic inertia just as an electrified body posseses electric inertia. Tn the case of a sphere of radius a and magnetic moment m the inertia for acceleration parallel to the magnetic axis is 2/5rn2a¢3C¢2, and for acceleration perpendicular to the magnetic axis 4/5m2a¢3C2. (C is the velocity of radiation.) The order of magnitude of thIs inertia is considered in an astronomical as well as in ¢an atomic connection.¢F. Tinker: The selective proper- ties of the copper-ferrocyanide membrane. In the. present paper the selective properties of copper-ferrbcyanide have been studied by measuring the change in solution concentration which takes place when the dry colloid is immersed in cane-sugar solutions of various strengths. It is found that the sugar solutions become stronger, owing to the fact that the water and not the sugar is taken up selectively by the ferrocyanide. The experimental results lead to the hypothesis that a colloidal hydrate, Cu2FeCy6.3H20, is first formed, and that this colloidal hydrate then takes up still more moisture by adsorption. The amount of adsorbed moisture taken up by the colloid decreases as the strength of the solution in- creases. It is also shown in the paper that the side of a membrane in contact with pure water has a greater moisture content than the side in contact with sugar ¢ solution. This fact supports the hypothesis¢ first¢ advanced by Graham on experimental grounds¢ that osmosis across a membrane takes place because pure water induces a greater moisture pressure and concentration inside the membrane than the solution does.¢¢C M. Williams: X-ray analysis of the crystal. structure of rutile and cassiterite.¢Dr. J. G. Leathem Discontinuous fluid motion. The subject of the paper is the flow, with free stream-lines, of infinitely extended fluid past a finite obstacle with a sharp prow and curved sides. The methods of Levi-Civita, Cisotti, Villat, and Levy are compared with the writer¢s own method, and translated into formulations by curve- factors.
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Societies and Academies . Nature 99, 178–180 (1917). https://doi.org/10.1038/099178a0
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DOI: https://doi.org/10.1038/099178a0