Societies and Academies

Abstract

LONDON.Royal Society, March 1.Sir j. j. Thomson, president, in the chairProf. W. E. Dalby: A graphical method of drawing trajectories for high-angle fire. A previous paper by the author, printed in Series A, vol. xcii., p. 239, explained a graphical method of finding the range, time of flight, angle of elevation, and other elements of a trajectory, from the data given by a curve showing the resistance of a standard shell in terms of the velocity. The graphical method followed the analytical method laid down in the military text-books. The paper dealt with direct fire. which is officially defined as “fire under angle of elevation 150.” The present paper is a continuation of the paper referred to above, adapting the graphical method to high-angle fire. For this the density of the atmosphere has to be brought into the calculation as one of the variables of the problem. Briefly, the method consists in applying the graphical method explained in the first paper in a series of steps, dealing in each step first with the vertical element of the trajectory and then with the corresponding horizontal element of the trajectory. The magnitude of a step is so selected that the influence of the change of tenuity on the resistance is negligibly small during the part of the trajectory corresponding to the step. The value of a quantity corresponding to, but not the same as, the ballistic coefficient in direct fire is changed from step to step to allow for the changing value of the tenuity as the shot moves in its trajectory. The method is applied to determine the trajectory of a shell weighing 380 lb., fired from a 92-in. gun elevated to 40, taking the conditions of the shots fired during the Jubilee Trials in 1898.Earl of Berkeley, E. G. j. Hartley, and C. V. Burton: Osmotic pressures derived from vapour pressure measure- ments.Aqueous solutions of cane sugar and methyl glucoside. The paper forms a continuation of researches on the same subject already communicated to the society. If the ratio of the vapour pressure of a pure solvent to the vapour pressure of a solution is known, the osmotic pressure between the solution and the solvent can be theoretically calculated. Since the osmotic pressure is proportional to the logarithm of the ratio of the vapour pressures, a specially accurate determination of the value of the ratio is required in order to obtain good values for the osmotic pressure. The naper deals with the experimental arrangements for determining the vapour densities and the special precautions that have been taken to secure a high degree of accuracy. A number of corrections applicable to the simple theoretical formula have been examined, both experimentally and theoretically. The experimental results given refer to soludons of different deorees of concentration. The dissolved substances dealt with are cane-sugar and methyl glucoside and sulphuric acid, while the solvent in each case is water. The experiments were made at standard temperatures of o C. and o C.W. Wilson: The complete photo-electric mission from the alloy of sodium and potassium. The subject of this investieation is the law governing the variation of the complete photo-electric emission with the tern- perature of the source of full radiation causing it. Theoretcal considerations indicate that this law should be the same as that governing the temperature variation of the thermionic emission from hot bodies, namely, that expressed by the formula C=AT"e 2T