Societies and Academies

Abstract

LONDON. Royal Society, Jan. 15.—Lord Rayle®gh: Iridescent colours of birds and insects. The reflection spectra of various brilliantly coloured insects have been examined in the ultra-violet. Morpho butterflies and Urania moths show ultra-violet maxima in general agreement with the theory of interference. Iridescent beetles showing a deep rod colour at normal incidence may be made to pass through all the colours of the spectrum to violet, provided that arrangements are made to annul refraction at the air-chitin surface. Some of the golden beetles show transmission spectra of bands which vary continuously in position with the part of the specimen examined. Moist chlorine gas does not destroy the colours of Morpho or of Urania, though the black background is bleached nor does chlorine decolorise the metallic beetles. The colours of all kinds of feathers, however, are rapidly discharged. Peacock feathers undergo a progressive change of colour in ultra-violet light or long-continued sunlight. Generally speaking, the colours become more refrangible. Other feathers, even when blue, are slowly decolorised without change of refrangibility. Morpho butterflies and Urania also lose colour without change of refrangibility. Fading under light or chlorine in these cases would seem to favour the idea of a pigment, but it is attributed to the breaking down of an interference structure.—O. W. Richardson and L. G. Grimmett: The emission of electrons under the influence of chemical action at lower gas pressures. A method is described by which partial pressures of phosgene can be controlled and their changes measured down to 10-5 mm. mercury. The electron omission from NaK in this gas has been measured down to directly measured pressures of 10-5 and to extrapolated pressures of 5 10-7 mm. under various conditions. In contrast to the results at pressures abovo 10-3 mm., the emission is now found to be a function of the gas pressure as Richardson originally supposed. The experimentally determined velocity distribution function among the electrons approaches a limit as the pressure is reduced.—A. J. Allmand and A. Puttick: The sorption of carbon tetrachloride at low pressures by activated charcoals (Part 4). Work has been done on the effect of high temperature evaluation on the nature of vapour isothenals on charcoal. It has been found that the carbon tetrachloride iso thermal on at least one charcoal has a discontinuous structure. If a sufficiently high charging pressure of sorbate is used, a reversible isothermal can be obtained.—D. Marshall and Sir Thomas Stanton: The eddy system in the wake of flat circular plates in three-dimensional flow. The paper describes experiments on the flow of water in steady motion past flat circular plates normal to the direction of motion. The nature of the flow is renderod visible by colouring the streams, and simultaneous photographs on two planes at right angles of the motion in the wake of the plates were obtained. At speeds lying between a well-defined upper limit and a lower limit well above that corresponding with a state of flow in which the inertia terms are negligible, a permanent vortex ring was observed at the back of the plate. When the speed exceeded the upper limit the substance of the ring was discharged downstream in a series of vortices of definite pitch and periodicity.—J. Chadwick, J. E. R. Constable, and E. C. Pollard: Artificial disintegration by α-particles. The protons omitted by certain elements when bombarded by α-particles have been examined by an electrical method. Except in the cases of fluorine and sodium, the disintegration protons consisted of different groups. The origin of these groups is explained on the assumption that the protons and α-particlos contained in a nucleus are in definite energy levels. The mass defects of certain nuclei formed in the disintegration processes are deduced.