LONDON. Physical Society, March 13.—Jas. P. Andrews: The variation of Young's modulus at high temperatures. The variation is found for zinc, silver, phosphor-bronze, lead, and soda glass by a static method, to within about 150° of the melting-point. It varies exponentially with temperature, so that q (Young's Modulus) = q1e-b1t (where q1 and b1 are constants) up to a temperature roughly half-way from absolute zero to the melting-point, and q = q2e-b2t for the remainder.—E. G. Richardson: The critical velocity of flow past objects of aerofoil section. By observations of the “Æolian tones” of vibrators of aerofoil section, critical values for flow past an object of aerofoil section have been obtained of a fluid incident at various angles. The minimum value of VL/v for unsteady flow falls from 60 at o incidence to 45 at 20, and then more rapidly.—J. Brentano: A focussing method of crystal powder analysis by X-rays. For any given angle of reflection, a surface of double curvature can be found, such that it will reflect X-rays coming from one point, to any other definite point. For an element of this surface, situated so as to be distant from the two points by lengths a and b respectively, the relation sin α/sin β = a/b must be satisfied, where α and β are the glancing angles of incidence and of emergence of the X-rays with respect to the surface. An arrangement for crystal analysis based on this relation is discussed.