The distribution of electricity in thunderclouds, II

The investigation of the distribution of electricity in thunderclouds described by Simpson and Scrase in 1937 has been continued at Kew Observatory. Alti-electrographs, which record the sign of the potential gradient, are sent upon small free balloons. Additional observations made during eight thunderstorms in the years 1937, 1938 and 1939 are discussed and the conclusions reached by Simpson and Scrase are confirmed. Each thundercloud has positive electricity in the upper half of the cloud, negative electricity in the lower half and in most storms if not in all there is a concentrated positive charge below the main negative charge. The generation of the positive and negative charge sin the main body of the cloud is ascribed to the impact of ice crystals and that of the positive electricity in the base of the cloud to the breaking of raindrops in an ascending current of air.