Societies and Academies

Abstract

LONDON. Royal Society, March 2.—Sir Charles Sherrington, president, in the chair.—L. N. G. Filon and H. T. Jessop: On the stress-optical effect in transparent solids strained beyond the elastic limit. The stress-optical effect in glass under simple pressure exhibits no time-effect at ordinary temperatures, but in celluloid under simple tension there is a marked creep in both stress-optical effect and strain even under very moderate loads. The observations can be explained on the assumption that celluloid consists of a mixture of two constituents having different elastic and plastic properties and different stressoptical coefficients, the optical-effect in each being strictly proportional to the stress.—W. E. Curtis: The structure of the band spectrum of helium. Measurements of grating photographs of three of the principal helium bands show that the chief features of their structure are accounted for by the quantum theory of band spectra. In each of the three bands a new type of series is found. The spectrum is considered to be due to an unstable helium molecule, having a moment of inertia of about 1.8 × 10-40 gm.cm.2.—S. Datta: The spectrum of beryllium fluoride. The spectrum of beryllium fluoride consists of six groups of bands, all in the ultra-violet between λ 2800 and λ 3400, and all fading off towards the red. The strongest band at λ 3009 includes three series of lines, which depart considerably from the usual type of formula. The groups of bands are similar to one of the groups given by magnesium fluoride.—W. G. Palmer: The catalytic activity of copper. Pt. III. The effect upon the catalytic (dehydrogenating) activity of copper of adding to the metal varying proportions of weak dehydrogenating catalysts, ferric, manganous, zinc, and magnesium oxides, is described. Magnesium and manganous oxides enhance the activity of the copper, if present in quantity greater than 1 to 2 per cent., while zinc and ferric oxides reduce the activity. It is considered that small proportions of oxide (less than 1 to 2 per cent.) destroy the activity of the copper, owing to solution in the metal leading to diminished adsorption of the alcohol attacked.—G. B. Jeffery: (1) The motion of ellipsoidal particles immersed in a viscous fluid. (2) The rotation of two circular cylinders in a viscous fluid, (i) Einstein has shown that the viscosity of a fluid containing solid spherical particles in suspension is given by μ (1 + 2.5 V), where μ, is the viscosity of the pure fluid and V is the total volume of the particles per unit volume of the suspension. This result is ex tended to ellipsoidal particles and it is shown that the factor 2.5 is reduced but always lies between 2 and 2.5 and depends upon the shape of the paitides. (2) The problem of the rotation of a circular cylinder in a fluid contained in a non-concentric cylindrical vessel which may itself rotate about its axis can be solved in finite terms; that of the rotation of two parallel cylinders in an infinite fluid is in general insoluble; i.e. there is no steady motion for which the fluid is at rest at infinity.