390 MACHTA removal can be predicted better than, for example, the insult of the ionizing radiation to man can be interpreted. Predicting the fate of injections at higher altitudes in the stratosphere presents a less satisfying picture. Experience from such sources is limited to two man-made injections, Preliminary indications suggest that the arrival times and locations from both are surprisingly similar despite differences in explosion heights. Partitioning between the hemi- Spheres appears to be about equal for injections at 17°N.If the information on source strength is approximately correct, the fallout data suggest that peak ground-level concentrations fall very short of those one would find by diluting the source uniformly into the entire atmosphere. Thus, if a rough calculation, made withthe assumption of a uniform distribution throughout the whole atmosphere, suggests no health concern, the use of more sophisticated procedures becomes unnecessary. A major problem in many cases of pollutant transport of a high stratospheric debris is the particulate settling speeds. If there is significant settling out of particulates, extrapolation from past nuclear tests will be incorrect. REFERENCES 1. L. Machta, Mechanisms for Determining Global Fallout, in Fallout from Nuclear Weapons Tests, Hearings before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, Congress of the United States, Vol. 2, pp. 778-806, May 5-8, 1959. 2. L. B. Lockhart, Jr., R. A. Baus, R. J. Patterson, Jr., and A. W. Saunders. Jr., Radiochemical Analyses of Air-Filter Samples Collected During 1958, Report NRL-5390, U. S. Naval Research Laboratory. Aug. 14, 1959. 3. L. Machta, The Nuclear Radiation Program of the International Geophysical Year, Annals of the International Geophysical Year—1964., 4, E. R. Reiter, A Case Study of Radioactive Fallout, J. Appl. Meteor., 2(6): 691-705 (1963). 5. J. L. Heffter, The Variation of Horizontal Diffusion Parameters with Time for Travel Periods of One Hour or Longer, J. Appl. Meteor., in press. 6. L. Machta, H. L. Hamilton, Jr., L. F. Hubert, R. J. List, and K. M. Nagler, Airborne Measurement of Atomic Debris, J. Meteor., 14: 165-167 (1957). 7. R. J. List, K. Telegadas, and G. J. Ferber, Meteorological Evaluation of the Sources of Iodine-131 Contamination in Pasteurized Milk, Science, 146: 59- 64 (1964). 8, E. F. Danielsen, The Laminar Structure of the Atmosphere and Its Relation to the Concept of a Tropopause, Archiv. Meteor. Geophys. Bioklim., All(9: 293-332 (1959). ; 9. L. Machta, R. J. List, and K. Telegadas, Inventories of Selected Long- Lived Radioisotopes Produced During Nuclear Testing, in Fallout Program Quar- terly Summary Report, USAEC Report HASL~-142, pp, 243-271, Health and Safety Laboratory, Jan. 1, 1964. 10. W. F. Libby, Radioactive Strontium Fallout, Proc. Natl. Acad. Sci., 42(6): 364-390 (1946). 11. United Nations, Report of the United Nations Scientific Committee on the Effects of Atomic Radiation, General Assembly, 19th Session, Suppl. 14 (A/ 5814), New York, 1964.