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Proposals for the future operation of the World Data Centre at Boulder, Colorado, include the provision of quality ratings by organizations submitting data, a method of holding on request or disposing of obsolete data, the employment of consultants, and the cataloguing of data not held by the centre.

As a way of explaining the evidence linking recorded radar meteor rates with solar activity, it has been suggested that variations of the atmospheric scale height at meteor ablation altitudes, themselves controlled by the Sun, may be responsible. A quantitative examination of a theoretical treatment by Kaiser (personal communication) now shows that the above suggestion is certainly plausible, and details the necessary scale height changes as a function of the meteor mass exponent.

IT is now well established that when a meteor enters the earth's atmosphere it creates a trail of electrons at a height of approximately 100 km.1–4. During the 1946 Giacobinid shower, Hey, Parsons and Stewart5measured the velocity of densely ionizing meteors by observing the radio wave scattered from the ionization at the head of the approaching meteor. We have recently succeeded in detecting the diffraction pattern of radio waves scattered from the electron trail as a meteor passes at right angles through the aerial beam. These observations lead directly to a measurement of the velocity of the meteor.

DURING the night of August 15-16, 1947, radio echoes were obtained apparently arising from a luminescent cloud which appeared near the end of an aurora streamer. The apparatus, which has been described elsewhere1,2, was in use for the study of meteoric ionization simultaneously on frequencies of 72 Mc./s. and 46 Mc./s. At Aug. 16d. 00h. 10m. U.T., an echo was observed intermittently on the 46 Mc./s. equipment at a range of 480 km. By 00h. 20m. the amplitude had increased to three times the normal noise-level. It then decreased with slow fluctuations in intensity, and after twenty minutes was lost in the noise-level at 00h. 30m. U.T. A second echo appeared at 460 km. range at 00h. 25m. U.T. and lasted for four minutes. Also at 00h. 10m. U.T., an increase in noise-level was apparent on both 72 and 46 Mc./s,. equipments over the range 450-600 km. The noise increase persisted and increased in range to 700 km. by 00h. 35m. U.T, when it disappeared. Simultaneously with the appearance of the echoes, a faint blue-grey auroral cloud appeared near the zenith at the upper tip of one of the streamers, which were at that time covering the whole of the northern sky. The streamers receded from the zenith but the cloud grew in intensity, and at 00h. 35m. U.T. broke into nine striations and rapidly faded. The radio echoes thus vanished when the cloud became striated. The entire aurora was visible from darkness on August 15d. to August 16d. 02h. 30m. U.T, but apart from the effects recorded above no other unusual echoes were observed.