Societies and Academies

Abstract

LONDON. Royal Society, March 4.—Sir William Crookes, president, in the chair.—Prof. W. A. Bone, Prof. H. L. Callendar, and H. J. Yates: A bolometric method of determining the efficiency of radiating bodies. In view of the increasing uses of incandescent surfaces in heating operations of all kinds, the authors have investigated, as a scientific problem, the measurement of radiant efficiencies of such surfaces, by a bolometric method, which can be standardised by direct comparison with a radio-balance, and which the authors propose to substitute for the existing water-radio-meter-cum-thermopile method (known as the “Leeds method”) used hitherto. The paper describes the construction and use of a new bolometer, specially designed for the purposes in view, in which the radiation from an incandescent surface, falling on a blackened coil of platinum wire, can be determined in absolute units for the increase in the electrical resistance of the receiving coil, the area of which is sufficiently small to allow of the instrument being standardised from a source of known intensity. And, by way of example, the application of the method to the measurement of both the absolute radiation of a gas fire and its “distribution factor,” is described and discussed.—E. Chappell: The simplification of the arithmetical processes of involution and evolution. An arithmetical process can be said to be completely simplified when it is reduced to either addition or subtraction. The invention of logarithms completely simplified multiplication and division, but involution and evolution were only replaced by multiplication and division, so that these processes may still be laborious even with the use of logarithms. The paper describes a table of the logarithms of numbers recently compiled, by the use of which involution and evolution are also completely simplified. The frequency with which fractional indices, positive and. negative, occur in most branches of modern experimental science gives rise to the hope that the tables in question will accomplish for the modern investigator what logarithms did for the man of science of the seventeenth century.—F. E. Rowett: The elastic properties of steel at moderately high temperatures. The difference in the behaviour of hard-drawn steel tubes, before and after annealing, under stress, led to the experiments described in the paper. At a suitable temperature a hard-drawn tube, which contains a good deal of amorphous material, behaves like a viscous fluid, that is, it flows more or less freely under stress, whereas, at the same temperature, an annealed tube being crystalline will flow in a much less degree, corresponding to the small amount of amorphous material in it. At a temperature of about 300° C. a hard-drawn tube shows properties similar to those of pitch at ordinary temperatures or of glass at a temperature rather below its softening point. It is still highly elastic under rapidly varying stress, but flows perceptibly when the stress is applied for a long time. On the other hand, in the annealed tube at 300° C. the energy dissipated in a cycle of stress is still almost independent of the time taken over cycle. At a higher temperature, for example, at 540° C, the hard-drawn tube flows rapidly and continues to flow for a long period, though at a diminishing rate, under a shear stress of less than one ton per square inch. Moreover, like pitch or glass, the steel at this temperature shows considerable elastic after-working. If the stress be suddenly removed the immediate elastic recovery is followed by a slow backward flow which persists for many minutes.—Prof. J. W. Nicholson: The laws of series spectra. The paper contains a critical analysis of the diffuse, sharp, and principal series of helium, especially in the light of recent interferometer measurements of the leading lines of these series. The investigation depends on a mode of accurate calculation of the limits of series, not dependent on the type of formula used. The limits of series with many lines, for which a Hicks formula is already known, can be calculated with extreme accuracy by a new method. Interferometer measures of leading lines of helium series enable the best form of the series to be obtained. This form is ah extension of that of Rydberg, dependent on m + μ and not m. The value of Rydberg's constant, 109679-2, given by Curtis for hydrogen, is the true value for the arc spectrum of helium, and is, in fact, a rigorous constant for arc spectra. Spark spectra are not treated. The Rydberg-Schuster law of limits is exact for helium. It seems probable that μ is a simple fraction the denominator of which is a multiple of 5, as Halm has suggested. It is exactly 0·7 for the short series of helium.