Societies and Academies

Abstract

LONDON. Royal Society, February 14.—C. Chree and R. E. Watson: Atmospheric pollution and potential gradient at Kew Observatory, 1921 and 1922. The pollution results were obtained from one of Dr. Owens's pollu tion recorders, while the potential gradient results were obtained from the records of the Kelvin water-dropping electrograph. Absolute values of pollution and potential in general increase together, while the range of the regular diurnal variation of potential gradient is larger on days of high than on days of low pollution. The diurnal inequalities chiefly employed were based on the 10 selected days a month used in the ordinary course for the Kew annual tables.—E. Wilson and E. F. Herroun: On the electrical con ductivity of magnetite. The effects of impressed voltage, temperature, compressive stress, and magnet isation upon the electrical conductivity of certain varieties of magnetite are recorded. At constant temperature, electrical resistance fell as impressed voltage increased, the gradient increasing with voltage. Specimens heated to a moderate temperature (150° C.) showed no change in resistance on return to room temperature, but when heated to the region of 900° C. permanent reduction in resistance was produced in the highly permeable magnetites. In all cases resistance was reduced by increasing temperature, the coefficient reaching or even exceeding 0-012, diminishing rapidly as temperature was raised. The ratio of resistance found at liquid-air temperature to that at room temperature reached the value 972 in the highly permeable magnetite, and was as low as 165 in the other variety. No permanent change in resistance followed cooling in liquid air. The maximum value of the compressive stress used was about 1000 kg. per square centimetre. At atmospheric temperature the resistance in the direction of stress and at right angles thereto was diminished by loading. At about 900° C. the reduction in resistance was of the order of 10 per cent. The effect of magnetisation was in all cases to reduce resistance. In a field of 1520 C.G.S. units the reduction in one variety amounted to 3-3 per cent.—C. E. T. Mann: The determination of coefficients of diffusion in gels by means of chemical analysis, and a comparison of results obtained from those yielded by the indicator method. Chlorides were used, but the method is equally applicable to other substances. A relationship, apparently linear, between diffusion and the degree of dissociation of the solute is recorded.—C. E. P. Brooks: The difference-periodogram-a method for the rapid determination of short period icities. A period of approximate length 2U being suspected, the series of observations is divided into sections of length U, and the mean values for each of these sections evaluated. If these mean values are a, b, c, d, etc., a new series of figures (a-zb +c)-(-2C+d), etc., is formed, and a graph drawn with a horizontal time scale. In the resulting curve all periods except those between i -4!! and 4!! are eliminated. If this curve shows a cycle of length C, the corresponding cycle in the original observations is of length 2CU/(C + 2U). In order to discriminate between the two possible cycles, the process is repeated with another value of U.—J. Proudman and A. T. Doodson: The principal constituent of the tides of the North Sea. The principal lunar semi diurnal constituent of the tides is discussed. A chart has been constructed showing the co-tidal and co-range lines over the whole area of the North Sea. These lines are characterised by three amphidromic points-one in the Flemish Bight, one about 100 miles to the west of the coast of South Denmark, and one just off the south-west coast of Norway. A chart showing the mean flow of energy indicates a counter-clockwise circulation much stronger on the west than on the east.—D. H. Bangham and F. P. Burt: The behaviour of gases in contact with glass surfaces. The rates at which different gases are taken up by a large surface of glass have been measured at different pressures and at o° C. The data indicate that equilibrium was not achieved, even though in one case the experiment was extended for five weeks. Practically all the time-sorption data are fairly represented by the empirical equation Sm=K, where S is the sofption value at time t, and m and t are constants. The quantities of different gases taken up under similar conditions are closely parallel with their solubilities in water, but even when the surface is highly desiccated these quantities exceed those required to form molecular layers.