TEST A: EXPLOSION IN AIR 



by the aerologists, and that only deserted ocean areas 

 received the continuous and invisible fall-out of radio- 

 active materials. 



Fortunately, the contaminated region healed itself 

 relatively promptly. The fission products themselves 

 lost a large fraction of their potency in a matter of 

 hours, and lateral and vertical mixing with unaffected 

 air proceeded rapidly. Within a short period the ma- 

 terials were dispersed throughout thousands of cubic 

 miles of air. The materials were now so extremely dilute 

 as to be harmless. Nevertheless, various scientific 

 groups in America and in Europe are reported in the 

 newspapers as having detected slight changes in the 

 radioactivity in the atmosphere some days after the 

 explosion. There is no doubt that, like the ashes thrown 

 into the air in the explosion of the Krakatao many years 

 ago, the fission products circled the globe for many 

 months. 



NUCLEAR RADIATION 



Gamma radiation dominated the repertory of nu- 

 clear radiations. Alpha particles, beta particles, and 

 neutrons were, of course, produced in abundance, but 

 being light particles they were rather effectively 

 blocked or slowed by collision with atoms in the air. 

 Many of them failed to penetrate more than ten or a 

 hundred feet of air; few of them reached beyond the 

 innermost target vessels. And even on these vessels 

 their effects were of questionable importance in view 



21 



