Societies and Academies

Abstract

LONDON. Royal Society, March 18.—S. Chapman, J. Topping, and J. Morrall: On the electrostatic potential energy, and the rhombohedral angle, of carbonate and nitrate crystals of the calcite type. Calculations have been made of the electrostatic potential energy of ionic lattices of the calcite type and for the sodium nitrate crystal, in which the lattice is of the same geometrical type, though the ionic charges are different. It seems probable that, owing to the fourfold positive charge in the C ions, the O ions of the CO3 group will be distorted from their natural symmetrical form, and consequently the electrostatic centre of the O ion will be nearer to the C nucleus than the O nucleus is. The calculations indicate that the electrostatic centre of the O ion is 0-9 A.U. distant from the centre of the C ion, compared with the value 1-25 A.U. given by X-ray measurements for the distance between the O and C nuclei. A similar result is obtained for NaNO3.-G. I. Finch and L. G. Co wen: Gaseous combustion in electric discharges. Pt. I. Steady direct current electric discharges are passed through electrolytic gas at 20-100 mm. pressures, and the rate of steam formation measured for varying conditions. It is found that the rate of combustion is determined only by the current, and up to a certain limiting current, combustion is confined to the cathode zone, depends upon the cathode material, and is directly proportional to the current. On exceeding this limiting current, combustion commences abruptly in the inter-electrode zone and is superposed upon cathodic combustion. This inter-electrodic combustion is also proportional to current, but, unlike the cathodic, is independent of the electrode material, and dependent upon gas pressure and separation of the electrodes. Little or no combustion takes place in the anode zone. Combustion seems to be primarily determined by ionisation of the gaseous medium for the current. The abrupt superposition of inter-electrodic combustion suggests a quantum effect, combustion in the inter-eiectrode zone depending upon a certain limiting potential fall being attained.-o C. N. Hinshelwood and W. K. Hutchison: A homogeneous unimolecular reaction: the thermal decomposition of acetone in the gaseous state. The temperature range used was 506° to.632° C. The heat of activation is 68,500 calories, and the results can be summarised by the equation lnk =34-95 - 68,500!RT. Calculation shows that the number of molecules reacting per second is about io5 times greater than the maximum number that could be activated by collision. The absolute rate at 835° Abs. is the same as that of the nitrogen pentoxide decomposition at 328° Abs.-H. Lamb: On wave resistance. The case considered is that of a solid of dimensions small compared with the depth below the free surface, travelling horizontally under water. Various particular cases of this have been worked out. There appears to be room for a more general investigation in which no assumption is made as to the form of the solid. The device employed for calculation of the resistance is to introduce small frictional forces, and to equate the work done against resistance to the dissipation of energy.-C. E. Eddy and A. H. Turner: The L emission series of mercury.-G. R. Goldsbrough: The properties of torsional vibrations. In order to bring out clearly the nature of the torsional vibrations in reciprocating engine shafts, a simplified model is chosen which emphasises the main characteristics. Even when friction is great, there are two critical speeds of shaft rotation corresponding to each term in the externally applied force.-E. T. Hanson: The theory of ship waves. The oscillations of a fluid under gravity, when the depth is variable or very great, have been worked out in two special cases. The theory is now extended very generally to cover a series of cases in which the fluid may be treated as a sea, bounded by a sloping shore on one side and extending indefinitely on the other. It is shown that, whenever the inclination of the shore to the horizontal is a submultiple of a right angle, the problem can be completely solved, and in each case there is a doubly infinite number of possible modes of motion under gravity. This extension makes it possible to calculate the precise effect of a sloping shore upon the formation of the beautiful wave pattern which often follows in the wake of a ship.-A. O. Rankine: The effect of temperature on the viscosity of air. The values of the viscosity of air obtained by Williams (Roy. Soc. Proc., A, vol. 110, p. 141) in the lower part of the temperature range are seriously in error. The conclusion that Sutherland's law of the variation of viscosity with temperature becomes invalid for air at the relatively high temperature of 250° C is not justified.