One of the major difficulties in our approach to the subject stems from the general tendency to talk about the H-bomb as though it were just one weapon, which obviously it is not. As we know, it is several weapons in one package, which can be designed for various uses, depending on the intent of its designer. It is, on the one hand, a weapon that can cause total destruction by blast over a radius of ten miles, or an area of more than 300 square miles, with graduated lesser damage over a much larger area. Secondly, it is a weapon that can produce fires and severe flash burns over a radius of twenty miles—that is, over an area of more than 1,200 square miles. These two functions, destruction by blast and by fire, go together. They are inseparable as far as the bomb itself is concerned, though their relative effects can be regulated by the height from which the bomb is dropped, by the terrain over which it is used, and by its mode of delivery other than by air. Then, of course, there is the third weapon of terror, the tremendous quantities of deadly radioactive particles that the H-bomb may release in the atmosphere, which, as Dr. Einstein said, would bring within the range of technical possibilities “the annihilation of life on earth.” This, however, would depend on the choice and purpose of the designer. If he so chooses, he can design an H-bomb that would produce only slightly greater radioactivity than its A-bomb trigger. Or he can rig it in such a manner that one bomb would release into the atmosphere the equivalent of nearly five million pounds of radium that would poison the atmosphere for thousands of miles, killing all life wherever it goes. The catchword here is “rig,” and the rigging depends entirely, not on the contents of the bomb itself, but on the material of which its outer shell is composed. If, for example, the casing chosen is a material such as steel, the radioactivity produced would be practically harmless. If the shell is made of cobalt, the radiations released would cause untold havoc. The reason for the vast difference is not difficult to understand. The H-bomb, when it explodes, releases tremendous quantities of neutrons, the most penetrating particles in nature. As soon as it is liberated, a neutron enters the nucleus of the nearest element at hand. This may produce a wide variety of changes in the nature of the element penetrated by the neutron, the changes depending on the element. Some elements, such as cobalt, become intensely radioactive, others only mildly so, and still others not at all. Furthermore, each element thus made radioactive has its own characteristic decay period, lasting from seconds to many years, so that the designer of the bomb has a great variety to choose from.