tive, whose result will rarely be satisfactory.

The bombs that were dropped on Japan exploded 450 meters up in the air, and it has been estab-lished that this height is highly effective. If the defender is cer-tain of the moment of the bomb's launching, of its speed, and of its target, he can hinder and delay its arrival by sending out radio signals; this would make the bomb explode at a height greater than the target, and the effect would thus be lessened. But if the defender errs in his calculation, he is given no chance for a second try — the sword will have outrun the reproach! Some visionaries hold that it may prove possible to use electro-magnetic rays (electromagnetic waves) capable of locating bombs in the air, whatever they may be. But these rays have not yet been discovered, and there is no evidence that they might be discovered in the next fifty years.

Apart from the difficulties already mentioned, the experi-ences of the last war have proved to us that we cannot be one hundred percent certain of the result of air defense. In the air attack on London, 9 percent of the (V-1) bombs still hit the target; and this small proportion, in atomic bombs launched, is enough to annihilate any great city in the world. The first shots are usually on target, for they fall suddenly, without prior warning; even with a tight defense the danger is ever present, for a single mistake means the end.

The men of science know today of no protective weapon to ward off this danger, which threatens civilization with extinction and annihilation; their only hope lies in worldwide cooperation, and in mutual understanding to lay down a world law forbidding the use of atomic bombs — for there is no defense!