Abstract
LONDON. Royal Society, February 26.—Sir J. J. Thomson, president, in the chair.—L. F. Richardson: Some measurements of atmospheric turbulence. The eddyshearing stress on the ground is deduced from pilotballoon observations. Values on land in any consistent dynamical units are found to range from 0.0007 to 0.007 times the value of m2/p, where m is the mean momentum per volume up to a height of 2 km. and p is the density. Evidence is given to show that the eddy viscosity across the wind at Lindenberg increases with height, and, except near the ground, is much greater than the eddy viscosity along the wind.In parts iv. and v. the spreading of a lamina of smoke is considered. Osborne Reynolds's eddy stresses are studied. For one occasion an attempt was made to measure simultaneously all six components of stress by observing the motion of thistledown. The three direct stresses are easily measured. Not so the shearing stresses;however, one was found to be 2.4 times its probable error. The theory of the scattering of particles is summarised, and numerical values are derived from scattering. The “turbulivity” ξ is estimated from the rising cumuli in calm weather and found to be 106, applicable only in the sense of friction. Thus the whole range of ξ observed in the free atmosphere was from seven to a million, in contrast with 0.2 in perfectly still air. The eddy stresses observed have ranged in absolute value from 0.004 to no dynes cm-2.-J. H. Hyde: The viscosities and compressibilities of liquids at high pressure. In the first place, experiments were made todeterminethechangeinthevalueofthe kinematical viscositv (n/p) of the various oils, and after this investigation was completed apparatus was designed for the determination of the change in density with pressure. The apparatus used for the determination of the kinematical viscosity consisted essentially of a system of two horizontal (the upper one of capillary dimensions) and two vertical tubes forming a closed circuit of liquor under pressure, the lower half of the circuit containing mercury and the upper half the liquid under test. One end of the tubular frame rests on a horizontal knife-edge, and the frame is supported in a horizontal position by a spiral spring. On the mercury being displaced by a given amount, flow will take place round the circuit owing to the difference of head, and it is evident that if the spring be so designed that its rate of extension is equal to the rate of change of head of the mercury, flow of the liquid under test will take place through the capillarv tube under a constant pressure-difference and at a velocity which can be calculated from the rate of extension of the spring. In this way all the data required for the determination of the absolute kinematic viscosity of the fluid weredetermined. The determinations of the variation in density under pressure were made by measuring the decrease in volume of known quantity of the liquid enclosed in a steel cylinder sealed at one end and closed at the other bv a long steel plunger. The cylinder and plunger were enclosed in a pressure vessel and the motion of the plunder for any particular pressure was measured. The density was calculated from the decrease in the volume thus measured. From the values of the densitv (o) and those of the kinematicaT viscositv (n'p) obtained for the oils, the values of the absolute viscosity (n) were calculated. The results show that the absolute viscosity of all the oils tested increasesconsiderablywithpressure.—A.Russell: The capacity coefficients of spherical conductors. It is proved that the capacity coefficient of a spherical conductor equals its radius, together with the capacity of the condenser formed by the spherical surface on one side and the images in it of all external objects connected in parallel on the other. This theorem leads at once to relations between the capacity coefficients of a system of two spheres and the capacities of certain spherical condensers which lessens very appreciably the labour involved in computing the values of these coefficients which are required in practical work. The mutual coefficient also is given in terms of the capacity of a spherical condenser, and other relations between the various capacities used by engineers and physicists are proved. Finally, a method of finding the approximate value of the capacity between a sphere and distant large conductors is given.—C. Cuthbertson and Maude Cuthbertson: The refraction and dispersion of carbon dioxide, carbon monoxide, and methane. The refractivity of the above-named gases has been measured at eight points in the visible spectrum between λ 6708–4800. The work was undertaken with the object of ascertaining the refractive power of the carbon atom, on the assumption of the validity of Hie additive law. By deducting the refractivity of the oxygen or hydrogen atoms from that of the carbon compound values are obtained from which the refractivity of carbon can be expressed in the form
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Societies and Academies. Nature 105, 57–59 (1920). https://doi.org/10.1038/105057a0
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DOI: https://doi.org/10.1038/105057a0