Abstract
LONDON. Royal Society, February 8.—L. Bairstow, Miss B. M. Cave, and Miss E. D. Lang: The resistance of a cylinder moving in a viscous fluid. The equations of motion of a viscous fluid in the approximate form proposed by Oseen are taken as a basis for calculations of the resistance of a circular cylinder and the surface friction along a plane. In the case of the circular cylinder experimental information obtained at the N.P.L. is wholly suitable for the purposes of comparison with the present calculations. A resistance coefficient is found which is about 30 per cent. greater than that observed at the limit of the range of observation. Calculations for the plane show singularities at the edges, but lead to a resistance which is in rough agreement with experiment.— G. I. Taylor: The motion of ellipsoidal particles in. a viscous fluid. According to Dr. G. B. Jeffery ellipsoidal particles immersed in a moving viscous fluid assume certain definite orientations in relation to the motion of the fluid. Ellipsoidal particles of aluminium and immersed in water glass take up such positions, but they take a long time to get to those positions. In the meanwhile they oscillate in the way indicated in Dr. Jeffery's analysis.—W. E. Dalby: Further researches on the strength of materials. In a new apparatus, an alternating load, push and pull, can be applied to a test piece in such a way that the curves of load and elastic extension are recorded photographically. The yield in tension and compression is found to be substantially the same, and the modulus of elasticity is the same, but alternating load is met by alternating response. When a load of either sign is removed the response is elastic, but imperfectly so. When a load is re-applied, but of opposite sign to the load removed, the response is mainly plastic. By means of a new instrument an alternating torque can be applied to a test piece in such a way that the curves of torque and elastic twist are recorded photographically. This shows that alternating torque is met by an alternating response in shear. It is possible to predict a practical fatigue limit from these diagrams.—Lewis F. Richardson: Theory of the measurement of wind by shooting spheres upward. A steel sphere, about the size of a pea or a cherry, is shot upwards from a gun, which is not rifled. The gun is inclined from the vertical towards the advancing air, and the tilt adjusted by trial until the returning sphere falls very close to the gun. The tilt is then some measure of a weighted average of the wind, in the region extending from the ground up to the maximum height attained. This height is found from the time of absence of the sphere. The observation of the tilt and time is repeated for greater and greater heights in succession. Mathematically speaking, the problem involves a “linear integral equation of the first kind,” which is solved approximately by transforming it into a moderate number of algebraic simultaneous equations. In the general part of the theory an approximation which fails at the vertex of the trajectory is made. A special and sufficiently correct theory or a correction to the general theory meets this difficulty.— Ernest Wilson: On the susceptibility of feebly magnetic bodies as affected by tension. When magnetite is subjected to tensile stress of 50–130 kgrm. per sq. cm. as a maximum, the susceptibility for a given value of the magnetic force at first increases and then decreases as the specific load continuously increases, and exhibits a reversal point as in iron. The magnetic force at which the percentage increase in permeability has a maximum value is less than the magnetic force at which maximum susceptibility occurs.—L. C. Jackson and H. Kamerlingh Onnes: (1) Investigations on the paramagnetic sulphates at low temperatures; (2) Investigations on the paramagnetism of crystals at low temperatures.— W. D. Womersley: The specific heats of air, steam, and carbon dioxide.—D. W. Dye: The valve-maintained tuning fork as a precision time standard. The valve-maintained fork is steady in frequency to a degree beyond that required for most purposes. The most serious cause of variation of frequency is that due to temperature. The temperature must be kept constant to 0.1° C. if accuracy to one part in a hundred thousand is required. By the use of a special steel (“elinvar”) having a very small temperature coefficient of elasticity, it is probable that the variation of frequency with temperature could be reduced to one-tenth that of ordinary steel forks. The other factors causing variation of frequency are not themselves variable without attention to an extent which would cause a variation of more than a very few parts in a hundred thousand. By suitably choosing the capacities and the anode voltage, a variation of voltage of ±10 per cent. will cause a change of only about one part in a million in frequency.
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Societies and Academies. Nature 111, 241–244 (1923). https://doi.org/10.1038/111241a0
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DOI: https://doi.org/10.1038/111241a0