LONDON. Royal Society, Mar. 7.—T. M. Lowry and A. G Nasini: The molecular dimensions of organic compounds. Part 1: General considerations. A comparative study of the physical properties of benzen& with thiophen, toluene with a-methylthiophen, benzene with cyclohexane, all pairs with similar boiling and freezing points, shows that the vapours exhibit. regular increments rather than identity of properties; and the physical properties of the liquids and solids, depending on force-fields of molecules as well as on dimensions, show still wider differences.—A. G. Nasini: The molecular dimensions of organic compounds. Part 2. An apparatus, based on Rankine's method, has beeii constructed for measuring the viscosity of vapours, and Sutherland's constant and the mean collision area deduced for benzene and cyclohexane.—Part 3. A further modification of the apparatus is described, in which a zero pressure is used on the condensation side of the capillary. The viscosities of thiophen, methylthiophen and pyridine have been determined.—W. A. Bone and R. P. Frazer: A photo- graphic investigation of flame movements in carbonic oxide-oxygen explosions. A theoretical 2CO + O mixture is exploded at atmospheric pressure under varying conditions, such as ‘dryness,’ ‘source and intensity of ignition,’ as well as under the influence of superimposed ‘shock waves’ up to and including detonation. The new Fraser high-speed photographic machine was used. Progressive drying reduces flame velocity and hinders combustion, but the hindering effect can be overcome by a strong electric field. With superimposed ‘shock waves’ the speed at which a flame starts may be raised in successive abrupt steps. until it attains a speed approaching that of the ‘shock waves themselves.’—H. S. Patterson, R. Whytlaw Gray, and W. Cawoocl:—(1) Some observations on the condensation of water on smoke particles. Particles of non-hygroscopic smokes readily absorb water, thus increasing in size, if a small quantity of hydrogen chloride is present.—(2) The process of coagulation in smokes. Experimental graphs, especially for systems of low concentration, show distinct curvature in the direction indicated by theory. Smokes which are most. nearly homogeneous give coagulation graphs closely in agreement with Smoluchowski's theory as modified for aerial systems. The smokes studied are formed by molecular collision rather than by condensation aiound pre-existing nuclei.—(3) The electrified particles in smokes. A method has been worked out for counting directly charged and uncharged particles. The particles of low temperature volatilisation smokes are initially almost entirely uncharged particles, but the proportion of charged particles rises rapidly. Are smokes and magnesium oxide smokes are highly charged from the start.—(4) The structure of complex smoke particles. Arc smokes often consist of aggregates of great complexity, composed of minute particles, while smokes produced by volatilisation at lower temperature have much simpler structure.—J. G. Semple: Cremona transformations of space of four dimensions by means of quadrics and the reverse transformations.—S. Goldstein: On the vortex theory of screw propellers. When the distribution of circulation along the blades of a screw propeller is such that, for a given thrust, the energy lost in the slipstream is a minimum, then the flow far behind the propeller is the same as if the screw-surface formed by the trailing vortices was rigid and moved backwards along its axis with a constant velocity.—O. W. Richardson and P. M. Davidson: The spectrum of 112: the bands analogous to the parhelium line spectrum. Part 2. The data give a spectroscopic ionisation potential of H2 is 15 380 volts. This compares with Pauli's value 23.7 volts on the old quantum mechanics and with 15 26 ± 0.13 estimated from Burrau's computations on the wave mechanics using Witmen's value of the heat of dissociation of H2.—R. C. Johnson and R. K. Asundi: A new band system of carbon monoxide. Details are given of a new system corresponding to the transition 3′S—2′P.—I. Wailer and D. R. Hartree: On the intensity of total scattering of X-rays. General results due to Waller for radiation scattered by a many-electron atom (neglecting ‘relativity effects’)are used to give an approximate formula