Societies and Academies

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    LONDON. Royal Society, May 20.—Sir William Crookes, president, in the chair.—H. Moore: The corpuscular radiation liberated in vapours by homogeneous X-radiation.—H. Richardson: The absorption in lead of χ rays emitted by radium B and radium C. (1) The absorption curves in lead of the radiations emitted by radium B and radium C have been determined and analysed. (2) In addition to the penetrating type of radiation for which μ = 0·5 (cm.-1) in lead, radium C has been found to emit soft types for which μ = 46, μ = 6·0, and μ = 1·5, and which are practically absorbed by 1·5 cm. of lead. (3) The analysis of the radium B absorption curve shows that in addition to the radiation μ = 40 in aluminium, the rays emitted consist of three types for which μ=46, μ = 6·0, and μ = 1·5 for lead. The close similarity of this latter radiation with that of the soft portion emitted by radium C, already observed by Rutherford and Andrade, has been established. (4) The absorption of the radiations in different elements has been examined and the bearing of the results discussed. No evidence of anomalous absorption has been found in the case of the penetrating radiations.—T. R. Merton: The application of interference methods to the study of the origin of certain spectrum lines. By measuring the limiting orders at which interference can be detected) for different radiations, certain deductions may be made as to the mass of the luminous particles and the temperature of the source. If the only circumstance which could possibly influence the width of spectrum lines set low pressures were the Doppler effect due to the motion of the luminous particles in the line of sight, the relative masses of particles emitting radiations from the same source of light might be calculated. As, however, there is reason to doubt the validity of this assumption under certain conditions, the conclusions which may be drawn with certainty from measurements of this kind-are an inferior limit for the mass of the luminous particles if the temperature of the source is known” or a superior limit to the temperature if the mass of the luminous particles is assumed. It is shown in the paper that the flame lines of calcium, strontium, and barium are probably due to molecules, whilst the H and K lines of calcium are to be attributed to calcium atoms. As the flame lines are members of series, it must be recognised that radiations from molecules may give rise to line series as well as band spectra. Lines of. the two spectra of argon have been investigated. The width of the lines of the red spectrum would appear to be accounted for by the Doppler effect. The lines of the blue spectrum are very broad in comparison with those of the red spectrum, and a satisfactory explanation of this has not been found. Spectrum lines of the “arc” type are broadened when condensed discharges are used as the method of excitation, but the difference in width of the lines in the blue and red spectra of argon is of another order of magnitude. The band spectrum associated with helium has been found to be enhanced when the gas is cooled to the temperature of liquid air, which might justify the suspicion that more than one atom was concerned in its production, but a comparison of the widths of the lines in the band spectrum with the ordinary helium lines makes it extremely probable that the band spectrum is due to atomic helium.

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    Societies and Academies . Nature 95, 388–389 (1915) doi:10.1038/095388a0

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