LONDON. Royal Society, April 30.1—J. A. Todd: On twisted cubic curves which satisfy twelve conditions. The paper deals with the problem of determining the number of twisted cubic curves in space which satisfy the joint condition of meeting r lines in one point, s lines in two points, and of passing through t fixed points where r + s + 2t=12, so that the condition determines a finite number of curves. The simpler cases are treated by a variety of elementary methods; for the more complicated cases the principle of special position is employed, in which the given lines and points are made to assume particular positions in such a manner that the curves which are required fall into various classes, of which the number of curves in each is determined by simpler considerations.—H. T. Flint: A metrical theory and its relation to the charges and masses of the electron and proton. This paper points out the analogy ex-isting between the equations of the quantum theory and the electromagnetic equations of Maxwell, pointing to the existence of a definite natural metric in a five-dimensional continuum. Parallel displacements along the world lines in this continuum are associated with no change in length, but in the four-dimensional world the change of length is a periodic function, with a frequency proportional to the mass associated with the world line. This view leads at once to the inter-pretation of the ratio of the masses of the electron proton as a metrical ratio, and makes a unitary physical theory possible.—A. M. Mosharrafa: Material and radiational waves. The Maxwellian equations of electromagnetic and electron theory are derived from one set of basic relations in a manner which throws some light on the relationship between material and radiational waves, and accounts for the existence of exactly three types of physical entities, namely: posi-tive electricity, negative electricity, and radiation. It is shown that a physical entity may be associated with the propagation of a vector A in a direction n. If A and n are in the same direction, the entity is recognised as positive electricity, if in opposite directions as negative electricity, and if mutually perpendicular, then as radiation. In the general case, A will have both a longitudinal and a transverse component, corresponding to the co-existence of matter and radiation.—J. Guild: The colorimetric properties of the spectrum. The paper describes an investigation carried out at the National Physical Laboratory to determine the colorimetric properties of a group of seven subjects as obtained from direct measurements of the trichromatic coefficients of the spectrum on a trichromatic colorimeter. A proposal is made for the adoption of a set of standard data, to represent a normal eye for technical colorimetric purposes, based on the results of this investigation and those recently published by W. D. Wright.—C. Robinson and H. A. T. Mills: The colloid chemistry of dyes. The aqueous solutions of benzopurpurine 4B and its isomer prepared from m-tolidine (1, 2). Although benzopur-purine 4B is a well-known cotton substantive dye, its isomer prepared from m-tolidine has not sufficient affinity for cotton for it to be of practical use as a dye-stuff. An investigation of the solutions of these dye-stuffs has been carried out in order to see if corre-spondingly great differences could be found in their colloidal properties. The viscosity of their solutions (if not super-saturated) are the same and are of the order to be expected in an unhydrated colloid. The viscosity does not vary with rate of shear, and the con-ductivities are of the same order. On the other hand, ultra-filtration, flqcculation by electrolytes, and ultra-microscopic examination show marked differences between the two dyes, which may be explained if it is assumed that benzopurpurine 4B forms larger aggregates than the meta isomer. The osmotic pressures of the two dyes are almost the same; this can be accounted for in spite of the difference in particle size shown by experiments described. It is concluded that these dyes exist in solution as totally dissociated colloidal electrolytes, hydrolysis being negligible. G. B Deodhar: X-ray nondiagram lines. In the K and L series, nondiagram lines pairs are found which show approximately constant√ν⌈R differences. These seem to resemble the usual screening doublets.—T. E. Stern: The chemical constant of chlorine vapour and the entropy of crystalline chlorine. By statistical mechanics the molecular composition of chlorine gas is calculated, assuming that the ratio between the numbers of atoms of the two isotopes 35 and 37 is known. It is found in this calculation that the angu-lar momenta of nuclei are without effect upon the constitution of chlorine gas. The vapour pressure of chlorine crystals is also calculated and, finally, the entropy of chlorine per mole in the crystalline form at the absolute zero.—I. E. Knaggs: The molecular sym-metry of hexa-aminobenzene in the crystalline state and certain other properties of the substance. An examination of crystals of hexa-aminobenzene by the powder X-ray photographic method has shown the crystal symmetry to be that of the holohedral cubic class, the space-group being Oh2. There are 16 molecules in the unit cell of side 15.14 A., and the molecules possess a threefold axis of symmetry.—H. W. Melville and E. B. Ludlam: The effect of foreign gases on the lower critical oxidation limit of phos-phorus vapour. The experiments were carried out to test the equation originally proposed by Semenoff. In the present approximate state of the theory, the differences obtained are explained on the variation of the diffusion coefficient of the chain propagators into the foreign gas. The results show no correlation with those obtained for foreign gases at the upper critical oxidation limit.—L. Rosenhead: The lift on a flat plate between parallel walls. The effect of the walls is to increase the lift-coefficient, and curves and tables are given showing this increase for various values of the angle of attack and the ratio of chord of aerofoil to width of channel.—J. A. V. Butler and A. D. Lees: The behaviour of electrolytes in mixed solvents (3). The molecular refractivities and partial molar volumes of lithium chloride have been determined in a series of mixed water-alcohol solvents. It is found that the molecular refractivity is constant in each solvent over the range of concentrations investigated. Its value is scarcely affected by the presence of alcohol until the molar fraction of the latter is more than 20 per cent, and then falls off steadily to the value for pure alcohol. The effect of lithium chloride on the density of the solutions varies greatly with the composition of the solvent.—T. C. Marwick: An X-ray study of mannitol, dulcitol, and mannose. The relationship is traced be-tween the structures of mannitol and dulcitol, and between the structures of mannose and other sac-charides. (See also NATURE, Jan. 3, 1931, p. 11.)—G. I. Finch and J. C. Stimpson: The electrical con-dition of hot surfaces during the adsorption of gases. The electrical conditions of a carbon rod and a copper sheet have been studied at temperatures up to 850° C. in vacuo, and in contact with various gases. The re-sults of these experiments suggest that ‘normalisation’ of the carbon involves the evolution of occluded gases accompanied by structural changes in the surface, but that in the case of copper it involves a process of sintering.—A. B. D. Cassie and C. R. Bailey: Investi-gations in the infra-red region of the spectrum (3, 4). The absorption spectrum of carbon disulphide is described between the limits of 1μ and 22μ, and the results compared with those of Coblentz for the liquid. The molecule possesses a rectilinear structure, with probably a single linkage between the carbon and sulphur atoms. The Raman spectrum has been co-ordinated with the infra-red spectrum, and an explana-tion is offered for the appearance in both of the charac-teristic doublet associated with the inactive frequency.—D. R. M'Rae: Asymmetry observed in the stark component of Ha. A special grating having a very intense first-order spectrum on one side has been used to resolve the Stark components of Ha. Asymmetry is observed in the displacements of the components, and also in the relative intensities of the components. Altering the number of atoms in the initial states does not explain completely the asymmetry of intensities.—F. D. Miles: The apparent hemihedrism of crystals of lead chloride and some other salts. Lead chloride, which normally shows holohedral orthorhombic sym-metry, can, under certain specified conditions, be ob-tained from hot solutions containing dextrine in microscopic crystals consisting of a single form (a bi-sphenoid), which can have only axial symmetry. By reducing the concentration of dextrine this form can be gradually repressed. Normal crystals of lead chloride were grown and investigated by X-ray methods. The difficulty of X-ray work with crystals impervious to the radiation is emphasised, and a simple method is given for finding whether any given reflection will emerge from any crystal face. The structure con-tains two glide planes of symmetry. The symmetry is, therefore, in all probability holohedral. The idea that crystal faces lying opposite to each other across a plane of symmetry may behave differently to an optically-active reagent is supported. The cases described appear to be the first to demonstrate that the presence of optically-active material may induce the growth of a hemihedral crystal of a substance, the normal symmetry of which is certainly higher.—C. E. Wynn-Williams: The use of thyratrons for high speed automatic counting of physical phenomena. The thyratron may be regarded as a triode valve which contains a trace of mercury vapour or inert gas at low pressure. Under appropriate conditions, a positive voltage impulse of only a few micro-seconds' duration applied to the grid will cause an arc to strike between the anode and cathode (or filament). The arc then continues independently of further grid potential changes until the anode circuit is momentarily inter-rupted. In this respect the thyratron behaves as a very delicate, inertialess relay, capable of controlling considerable currents. Some circuits are described for utilising to the greatest advantage the ‘inertia-less relay’ characteristic of the thyratron, for high-speed automatic counting of voltage impulses set up by physical phenomena. Two impulses separated by as little as l/500th second can be separately recorded.