-),0~ that moment must be insulated from each other) and the holding together of the combined mass until a reasonable proportion of the uranium or plutonium atoms have undergone fission. A little reflection will indicate that the mechanism which can accomplish this must be ingenious and elaborate in the extreme, and é bom’ as a sabotage instrument could work out a much simpler device, the essential mechanism Perhaps could be broken down into small component parts such as are easily smuggled across national frontiers, the essential mass being provided by orude materials available locally in the target area, Those familiar with the present mechanismdo not consider such an eventuation likely. And if it required the smuggling of whole bombs, that too is perhaps possible. But the chances are that if two or three were successfully introduced into a country by stealth, the fourth or fifth would be discovered, Our federal police agencies have made an impressive demonstration in the past, with far less motivation, of their ability to deal with smugglers and saboteurs, ~n | Those, at any rate, are some of the facts to consider when reading a statement such as Professor Harold Urey was reported to have made: "An enemy who put twenty bombs, each with a time fuse, into twenty trunks, and checked one in the baggage room of the main railroad station in each of twenty leading American cities, could wipe this cowmtry off the map so far as military defense is concerned," 30 Quite apart from the question of whether twenty bombs, even if they were considerably more powerful than those used at Hiroshima and Nagasaki, could produce the results which Professor Urey assumes they would, the mode of 3 0. ¥ ; , The New Republic, December 31, 1945, p. 885, used by the New Republic, Ureyts remark, . The statement quoted is that and is probably not identical in wording with Prof,