LONDON Royal Society, March 23.—G. I. FINCH and A. G. QUARRELL: The structure of magnesium, zinc and aluminium films. An electron diffraction camera is described in which the specimen is swept by a diffuse beam of electrons, thereby reducing the risk of injury to the specimen. The beam is then focused electro-magnetically. Oxide-free surfaces of magnesium, zinc, and aluminium on a platinum substrate, also vapours of these metals in transit between source and receiver, were obtained and examined by electron diffraction. The oxides of magnesium and zinc formed on the corresponding metal surfaces have also been examined. It is concluded from the results that (1) the abnormal crystal structures are caused by pseudomorphic strain effects whereby the substrate influences the positions taken up by the atoms of the metal or metal oxide layers formed thereon; (2) such pseudomorphic effects are no longer evident at the surface of sufficiently thick films; (3) for aluminium the pseudomorphic strain effects are confined to the two dimensions of the basal planes, because no such effect was to be observed in the third dimension; (4) magnesium, zinc and aluminium vapours are monatomic. E. C. POLLARD: Experiments on* the protons produced in the artificial disintegration of the nitrogen nucleus. Experiments to determine the manner of entry of the a-particle into the nitrogen nucleus have been made; these indicate that entry is in general over the top of the barrier, and the height of this barrier is fixed as between 4.1 × 106 and 4.4 × 106 electron volts. Further investigation of the absorption curve of the protons confirms the work of Steudel on this element and gives an indication of a second group, which can be ascribed to resonance entry of an α-particle of 3.5 × 106 electron volts energy.