LONDON. Royal Society, June 26.—Sir J. J. Thomson, president, in the chair.—Dr. A. E. H. Tutton: Monoclinic double selenates of the cobalt group. This memoir deals with the four double selenates of the series R2M(SeO4)2.6H2O, in which M is cobalt and R is potassium, rubidium, cæsium, and ammonium. A complete crystallographic and physical investigation has been carried out on parallel lines to the work previously published concerning the magnesium, zinc, iron, and nickel groups, and to that concerning the complete analogous series of double sulphates. The results are in full accord with those derived from the previous investigations. Two dominant facts emerge, namely, (1) the progressive order of all the crystallographic and physical properties, following the progression of the atomic numbers (and therefore atomic weights) of the interchangeable alkali metals concerned, potassium, rubidium, and cæsium; and (2) the almost perfect isostructure—that is, congruency, coincidence, and equality of dimensions of the elementary cells of the monoclinic space-lattices—of the crystals of the ammonium and rubidium salts of the group. The progression with atomic number referred to under (1) is completely explained by the operation of Moseley's law, governing the progressive structural complexity of the atoms in accordance with the sequence of the atomic number.—Hertha Ayrton: A new method of driving off poisonous gases.—Dr. F. W. Aston: Experiments with perforated electrodes on the nature of the discharge in gases at low pressure. Experiments are described on the discharge between etectrodes of a large flat form perforated with a long narrow slit, the charge passing through the slit being collected and measured in a Faraday cylinder. Direct measurements made with the Faraday cylinder behind the cathode and at the same potential seem to indicate that about half the total current in the discharge is brought up to the cathode by positive ions. Attempts to discover the distribution of velocities in this stream show that this is, not directly determinable, owing to the very high ionisation in the region of the slit and other reasons, which are discussed. Using a perforated anode, it is found that as the distance from the cathode is increased arithmetically the current carried by the cathode rays into the Faraday cylinder decreases geometrically when the current is constant.—Mary Seegar and Prof. Karl Pearson: De Saint-Venant solution for the flexure of cantilevers of cross-section in the form of complete and curtate circular sectors; and the influence of the manner of fixing the built-in end of the cantilever on its deflection.—Dr. H. Jeffreys: The relation between wind and the distribution of pressure. A classification of some six hundred wind observations over the North Sea, according to their velocities and directions, showed that the most striking feature of the resulting values was their asymmetrical frequency distribution. From the fact that this was noticeable in nearly every class, it was inferred that it could be produced only by variation in turbulence or systematic contortion of the isobars, on a scale too small to be recorded on the weather map. The latter cause, however, and also such variations in turbulence as keep the coefficient of eddy viscosity the same at all heights, would lead to strong correlations between S/G and a, which are not observed. Hence it is concluded that the principal cause of variation in the relation of the surface wind to thei gradient is variation in the vertical distribution of turbulence; and it is shown that such variation could give the effects actually observed.—Prof. C. H. O'Donoghue: The blood vascular system of the Tuatara, Sphenodon punctatus.—G. H. Livens: The fundamental formulations of electro-dynamics. The object aimed at in this paper is the removal of certain difficulties, and discrepancies which exist in the usual formulations of electro-dynamic theory. After a brief statement of the differential theory in which a new equation,