Abstract
LONDON.
Royal Society, March 21.—Sir Archibald Geikie, K.C.B., president, in the chair.—Lord Rayleigh: The self-induction of electric currents in a thin anchor-ring.—Hon. R. J. Strutt: The after-luminosity of electric discharge in hydrogen observed by Hertz. Hertz observed that if Leyden-jar discharges were passed through hydrogen at a pressure of, say, 4 100 mm., the gas remains luminous for a small fraction of a second afterwards. It is concluded that Hertz's effect is due to the presence of sulphuretted hydrogen in the hydrogen employed. It is conjectured that sulphuretted hydrogen is decomposed by the discharge, that sulphur vapour emerges in a specially active state, and that it then unites with hydrogen, the blue glow accompanying this process. Prof. J. H. Poynting: The changes "in the dimensions of a steel wire when twisted, and on the pressure of distortional waves in steel. In a former paper (Proc.; Roy. Soc, A, vol. lxxxii., 1909) the author described experiments showing that when a loaded wire is twisted it lengthens by an amount proportional to the ! square of the angle of twist. In this paper it is shown that if the wire is previously straightened by heating it under tension, the lengthening is, within errors of measurement, the same for all loads which could be applied, so that, as was supposed, the only function of the load in the earlier experiments is to straighten the wire. In all wires examined so far, ! the lowering is symmetrical about a point a fraction of a turn always in the counter-clockwise direction from the condition of no twist.—H. S. Patterson, I R. S. Cripps, and R. Whytlaw-Gray: The orthobaric j densities and critical constants of xenon. Using a i carefully purified sample of xenon prepared from 150 c.c. of the gas lent by Sir William Ramsay, measurements were made of the orthobaric densities between the temperature limits of 16 and -66·8° C. The variation of the mean density of liquid and saturated vapour with temperature was found to follow closely Cailletet and Mathias's law, and the results are expressed by the equation Dt (= 1-205 -000305, where Dt = mean density at t° C. The slope of the diameter is abnormally large, and is practically identical with the value for the argon diameter recently found by Onnes. The constants Tc = 16·6°C. and Pc = 58·2 atms. were found, and the following were calculated from the results:-critical density, 1-115 grms. per c.c; density of liquid close to'boiling point, 3.063 grms. per c.c.; atomic volume close to boiling point, 42-7 grms. per c.c.-W. A. Harwood and Dr. J. E. Petavel: Experimental work on a new standard of light. The source of light consists of a strip of platinum heated by an electric current. The thermopiles measure the radiation passing through (a) a plate of black fluorspar, (6) a water-trough. The thermopiles are connected in opposition. As the current through the strip is increased, the intensity of the luminous radiation increases more rapidly than the intensity of the radiation of longer wave-leneth. ' Therefore, for a given thickness of the absorbing ! media and distance of the thermopiles, there will be one definite temperature at which the reading of a galvanometer in the thermopile circuit will be zero. A long series of experiments showed that the light could be kept constant within ±0-5 per cent, when a constant temperature was maintained by the above criterion.-J. A. Crowther: The distribution of the scattered Rdntgen radiation. Experiments have been made to determine accurately the distribution of the scattered Rontgen radiation round a radiator. It has been found that the radiation can be divided into two parts: a true scattered radiation, distributed in accordance with the usually accepted theory of the scattering, and an additional or excess radiation. The curves representing the distribution of the latter have been found to resemble those previously obtained for a parallel pencil of /3 rays after passing through thin sheets of matter.—E. A. Owen: The passage of homogeneous Rontgen rays through gases. (1) The absorption coefficient of the different homogeneous radiation in a light gas such as CO2 or SO= is proportional to the absorption of radiations in air. (2) The absorption of homogeneous radiation in a gas is proportional to the pressure of that gas. (3) For the homogeneous rays emitted by metals of atomic weight ranging from that of iron to that of molybdenum, the coefficient of absorption in the gases investigated is approximately inversely proportional to the fifth power of the atomic weight of the radiator which emits that characteristic radiation, i.e. λαω -5. (4) The amount of ionisation produced in a thin layer of a gas is directly proportional to the pressure of the gas. (5) The ionisation relative to air is approximately constant in the same gas for the different homogeneous rays. (6) The total number of ions produced by homogeneous beams of equal intensity is approximately the same in each gas for any particular typo of rays.—J. C. Chapman: Fluorescent Rontgen radiation from elements of high atomic weight.—J. A. Gray: The nature of y rays excited by $ rays. A determination has been made of the relative amount of emergent and incident y radiation excited in "radiators" of different thicknesses and differpnt materials. Results of the experiments are:-(1) The emergent y radiation is generally greater in amount than the incident radiation, and is more penetrating. (2) The ratio of emergent to incident y radiation is greater,. for radiators of the same material, the thinner the radiator; for radiators of different materials thick enough to stop the /3 rays, the lower the atomic weight of the radiator. (3) The results obtained point to the conclusion that the excited y ray is an entity, the direction of which is nearly that of the 0 ray exciting it. (4) The chance of' a |3 ray making a y ray is roughly proportional to the atomic weight of the radiator, provided the 16 ray spends its range in the radiator.
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Societies and Academies . Nature 89, 103–105 (1912). https://doi.org/10.1038/089103a0
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DOI: https://doi.org/10.1038/089103a0