will fall first, near the explosion. Lighter ones will be carried or winds, hundreds or perhars thousands of miles, before settling to the ground naturally from the force of gravitv, or more rapidly should they become rixed in a weather front and be brought down ina rainfall, aenerally referred to as "local fallout." This is what is It is heavily radioactive in nature and lands within a few hours, or days. It contains "mixed fission products"-- that is, isotopes of many kinds, i.,e., strontium, cesium, lodine, zinc, cobalt, giving off beta and gamma radiations of different energies. Generally this local fallout can be seen in a cigar-shaped pattern, with the lightest activity at the outer edges and the heaviest toward the center. Not all of the fallout, however, comes down in the first few hours or days. This is the material which has heen injected into the stratosphere (a zone beainning at ahout 40,000 feet). The particles which have ascended to this height and above in the towering cloud are verv fine and light, like particles of smoke, These radioactive vearticles will he circulated about in the stratosphere--which rarely has clouds and in which the temperature is relatively constant--until it has spread out all over the earth, This Material will take months and years before it has returned to the earth's Surface, The radioactivity, which may be soread throughout the world more or less uniformlv, will return to the earth in the same manner, although it is possible that some areas of the world will receive heavier amounts of this fallout than others. Yow this radinactivity, once it has returned to the earth, comes to be consumed and retained bv man is due to one of the unique properties of radioactive materials,