"I was to learn that in the city of Washington there were no walls as we know them. They had the thickness and the height of walls, but the Father, constantly watching in the screen above his bed, could with the touch of his little finger disarrange and reassemble those immense sections of stone and metal in a thousand patterns, all preconceived it is true, to cope with all conceivable situations. I was to see the giant gears that could elevate within an instant the lowest depths of the city to the topmost level and transfer the Dome itself, that amazing architectural illusion, into the very bowels of the earth, miles below the muddy bottom of the Potomac. In all of the city only the Tube was fixed, and that solely because the shifting of its continental span was too monstrous an engineering feat even for those masters of the early days immediately after the establishment of the Atomic Curtain. It would have involved the balancing of the crust of the earth itself, and as in the case of Archimedes with his global lever, where was there such a fulcrum? "But the city, Washington, was a myriad of interchangeable parts, and at no moment since its construction could there possibly have been a master plan for it--nothing that any enemy could definitely say was thus and so, the plexus here, the exact place to strike at. Within the broad limit of its thousand patterns and countless thousands of lesser integral dispersions it existed only as the Father wanted it, and through his keyboard could instantly set it up. "I say that the lone exception was the Tube. That is true, the Tube was fixed, but its terminus could be sent whirling away from it, sealing it off. Conceive of the city, if you wish, as a series of spheres, one within the other, like a child's gyroscope, revolving when the impulse came from the integrocalculators, or expanding through the integration of chords from a larger outer sphere which then contracted into the lesser orbit. Too tough? It was for me. "It was much too tough a problem for me, and when I found myself enclosed within the comparatively narrow confines of that corridor, beyond the Father's--and Nedra's hall--I felt for the first time since Nedra's return with her newborn child that complete and imbecilic frustration that must come over those poor deviled rodents that psychologists force to pop through little doors to establish their reflex patterns. I stood stock still, my brain suddenly as empty as the corridor about me, numbed beyond comprehension for how long I do not know, until at last I became conscious of the spasms of my fingers."