type in so far as the explosive effect is the result of the very rapid liberation of a large quantity of energy in a relatively small space. It differs however from other bombs in three important respects. First, the amount of energy released by an atomic bomb is a thousand or more times as great as that produced by the most powerful T.N.T. bombs. Secondly, the explosion is accompanied by highly penetrating and deleterious invisible rays, in addition to intense heat and light. Finally, the substances remaining after the explosion are radioactive, emitting harmful radiations.