In the course plotting room, the final calculations were being made. Wind direction and velocity aloft had been noted across half the planet. This had some importance on the launching and landing end but had no significance when the bomb itself was out of the atmosphere. The target had been figured and refigured. Actually, the target was anywhere on the continent of North America. If this bomb struck anywhere in the Mississippi valley, the whole watershed below the striking point would be scoured clean of all life. Water carrying radiation downstream would account for that. "Zero minus fifteen minutes!" On the outside of the mountain, in a special observatory constructed for this precise purpose, radar scopes for tracking the rocket were ready. Instruments in the laboratory there were for the purpose of changing the course of the super bomb, if it veered too far from its destination. The technicians there were on their toes. They had no guards to encourage them but they needed none. They knew what would happen if this bomb failed to land and the fault was traced to their door. What would happen when the bomb landed? Hell would happen! Probably the crust of the Earth would open up in a hole miles in depth. Meteor Crater, in Arizona, would be the work of a child compared to the result of this explosion. What had happened at Hiroshima and Nagasaki would be nothing in comparison. The possibility existed that the molten magma of the core of the planet would gush forth. No one knew for sure whether or not this would happen. If it did take place, the result might be the sudden appearance of a lake of over-flowing lava. The shock waves from the bomb would probably be strong enough to pull down every skyscraper that still remained standing in America. The effect on the watershed where the bomb landed would be almost complete catastrophe. If it struck on any of the rivers or streams flowing into the Mississippi, the water supply of all cities downstream to New Orleans would be contaminated. Nobody knew what the effect of the fall-out from this bomb would be. High air currents might carry radioactive particles for thousands of miles from the explosion point, where they would fall as a gentle but very deadly rain upon the Earth below. "_Zero minus ten minutes!_" The high, thin note of a violin appeared in the vast underground cavern. Amid the scurrying of feet, the shouts of the foremen bossing the work gangs, and the occasional cracking of the rifles of the guard, the sound was unheard by the ears. But deeper centers heard it. The first man to go was a fat engineer. Sighing, he stumbled and fell. When he did not rise a guard approached him. As the guard determined that the man was snoring, he lifted his rifle. The engineer died without awakening. Another shot rang out as another man went to sleep, then continued on to join his fathers.