LONDON Physical Society, Feb. 3. F. J. W. WHIPPLE: Relations between the combination coefficients of atmospheric ions. The principal object of the paper is to put forward for consideration a formula, η12 - ηew10 = 4π1 which indicates that the combination coefficient η12 for small ions and large ions of the opposite sign exceeds the coefficient η10 for small ions and uncharged nuclei, and further that the difference between the two coefficients depends on the mobility wl of the small ions. The experimental evidence for the formula is discussed as well as possible applications. G. P. THOMSON, NORMAN STUART and C. A. MURISON: The crystalline state of thin spluttered films of platinum. Films of platinum spluttered in various gases have been examined by the method of electron diffraction. They often show patterns which indicate that the small crystals are oriented with one face parallel to the surface of the specimen, the crystals being otherwise at random and in many cases the crystals are very small, of the order 5 × 10-7 cm. Some films of platinum dioxide showed crystals of the order 2 × 10-7 cm. E. V. APPLETON and R. NAISMITH: Weekly measurements of upper atmospheric ionisation. The ionisation is 2.2 times as intense on a summer noon as on a winter noon, and, in general, was slightly less in 1932 than in 1931. This reduction is due to the approach of sunspot minimum, and, with other evidence, suggests that the ionising agency from the sun varies by as much as 60 per cent during the 11-year solar period. Although ultra-violet light is accepted as the major ionising agency, thunderstorms most probably constitute one of the subsidiary causes, as previously suggested by C. T. R. Wilson. J. A. RATCLIFFE and E. L. C. WHITE: An automatic recording method for wireless investigations of the ionosphere. The Breit and Tuve method is employed, and both the transmitter and the time base at the receiver are synchronised with the A.C. mains. Some specimen records are reproduced and are used to illustrate the normal diurnal variation of equivalent height. Attention is directed to a common ‘abnormal’ occurrence of increase of ionisation in the lower (E) region, during the hours of darkness, without a corresponding increase in the upper (F) region, due possibly to storm clouds, as suggested by C. T. R. Wilson.