[en] The full effects of a nuclear explosion are (perhaps fortunately) as yet hardly apprehended by the mass of mankind: such an explosion, either at ground level or at above atmospheric height, could have effects extending over millions of square kilometres. The authors attempt, in simple terms, to assess these effects, starting with the actual ignition process, the subsequent forms of energy distribution (assuming a symmetrical and homogeneous atmosphere) and concluding with the final results, with some possible precautionary measures. (F.N.S.)