LONDON Physical Society, February 16. T. SMITH: (1) Integrals of products of experimentally determined magnitudes. The integral of a product of quantities known only for discrete values of a variable is given correctly by the simple sum of the products for uniformly distributed values of the variable. Nothing is gained by increasing the number of component products beyond the number of observed values of either factor. (2) Condensed tables for colour-computation. It is sometimes sufficient in the spectrophotometry of coloured materials for the determination of their colour co-ordinates on the C.I.E. system to take measurements at intervals of 10 mt. instead of the standard interval of 5 mt. Special tables have been computed for use in these cases. C. E. WYNN-WILLIAMS: A relay memory for a thyratron counter. An automatic mechanism consisting of sixteen interconnected relays and capable of carrying out a complicated cycle of operations in correct sequence in less than half a second. The apparatus is used in conjunction with a valve amplifier and an automatic thyratron counter for the analysis of a-particle groups by means of a magnetic focusing method. The relay mechanism arranges for alternate comparative counts of x-particles to be made under two different sets of experimental conditions. W. G. PENNEY: A note on the twisting-frequency in ethylene. From the experimental value for the fundamental twisting-frequency in ethylene, the magnitude of a certain carbon-carbon exchange integral J is determined as 0-72 b OlO electron-volts. According to this result, the energy needed to twist one of the CH2 groups through an angle r/2 with respect to the other about the C-C axis is 1-0 ± 0-2. This agrees well with the experimental value for the heat of activation of dimethyl maleate to dimethyl fumarate. F. C. CONNELLY: The instantaneous projection ofHherm-ionic valve characteristics. Two mirror oscillographs are employed with axes at right angles, one indicating the anode current and the other the grid potential. A suitable alternating voltage of small amplitude from a 50-cycle supply is applied to the grid, causing the characteristic to be traced out 50 times a second, and persistence of vision causes the whole curve to be visible. The instrument indicating current is a Sprenger oscillograph, while the voltage-controlled vibrator is a special instrument designed for the purpose.