1. Delannoy, J., and Weill, G., C.R. Acad. Sci., Paris, 247, 806 (1958).
2. Gadsden, M., and Salmon, K., Nature, 182, 1598 (1958).
3. Barbier, D., Delannoy, J., and Weill, G., C.R. Acad. Sci., Paris, 247, 886 (1958).
4. The consequences of this fact have been treated in a series of papers by Blamont and Donahue, Chamberlain and Hunten and by Galperin and their collaborators. References may be found in Blamont, J. E., Donahue, T. M., and Stull, V. R., Ann. Geophys., 14, 253 (1958); Chamberlain, J. W., Hunten, D. M., and Mack, J. E., J. Atm. and Terr. Phys., 12, 153 (1958) and Galperin, G. I., “The Airglow and the Aurorae”, 95, edit. by Armstrong and Dalgarno (Pergamon Press, London, 1956).
5. Barber, D. R., Nature, 183, 384 (1959).