Societies and Academies

Abstract

LONDON.Royal Society, June 13.—Sir Archibald Geikie, K.C.B., president, in the chair.-C. T. R. Wilson: An expansion apparatus for making visible the tracks of ionising particles in gases, and some results obtained by its use. The method of making visible and photographing the tracks is essentially that described in a previous communication. The apparatus has been enlarged and otherwise improved. The paths of alpha-particles are generally straight or nearly so until within about a mm. of the end (in air at atmospheric pressure) where they become bent. Portions of the tracks of beta-particles from radium have been photographed, the individual ions set free being made visible by the cloud particles condensed upon them, so that they may readily be counted. The photographs of the clouds formed when a narrow beam of X-rays is sent through the cloud chamber show the tracks of kathode or beta-particles starting within the primary beam and extending for some distance beyond it. There is no indication of any action of the X-rays other than the production of the corpuscular rays. The corpuscular rays appear to start in all directions, showing no preference for that of the primary beam.—Hon. R. J. Strutt: Chemically active modification of nitrogen, produced by the electric discharge. IV. (i) Active nitrogen is a highly endo-thermic body, but its energy is of the same order of magnitude as that of other chemical substances. (2) In the reversion of active to ordinary nitrogen, the number of atoms ionised is a very small fraction of the whole number concerned in the change. The ionisa-tion is a subordinate effect, and may be due to light of very short wave-length emitted in the reaction. (3) Additional experiments are described to prove that the change of active nitrogen is more rapid at low temperatures. This is thought to be connected with the monatomic character of the molecule, and to throw light on the connection between temperature and velocity of reaction in other cases.—Prof. J. C. McLennan: The series lines in the arc spectrum of mercury.-Prof J. C. McLennan: The constitution of the mercury green line = 5461 AU; and on the magnetic resolution of its satellites by an echelon grating. —Prof. W. H. Young: The convergence of certain series involving the Fourier constants of a function.—Prof. W. H. Young: Classes of summable functions and their Fourier series.—H. G. Moseley: The number of particles emitted in the transformation of radium. The number of particles emitted at the disintegration of each atom has been determined by measuring the current carried in vacuo by the radiation from a known quantity of active material. It is found that one atom of radium B and an atom of radium C together emit 2.20 particles on an average; that an atom of radium B emits the same number of particles as an atom of radium C, and that an atom of radium E appears to emit less than one particle. From measurements of the ionisation produced by active deposit of radium emitting a measured number of 0-particles, the number of ions produced by a i3-particle per cm. of path in air has been calculated. This number varies approximately as, where A is the absorption coefficient of the radiation for aluminium.—S. D. Carothers: Portland experiments on the flow of oil. The paper was j primarily the outcome of an attempt to obtain from the results of a series of experiments, which came into the writer's hands, a relation between velocity and resistance for oil. It was seen that a considerable number of the results of the experiments followed the capillary law, and attention was directed to determining where this broke down.—G. B. Jeffery: A form of the solution of Laplace's equation suitable for problems relating to two spheres.—A. LI. Hughes: The emission velocities of photo-electrons. This investigation was undertaken to determine the relations between the maximum velocity with which electrons are emitted from metallic surfaces illuminated by ultra-violet light and (a) the wave-length of the light and (&) the nature of the metal.