"Before advancing his proposition, he'd had his engineers draw up complete plans and specifications of the proposed cage and the necessary auxiliary equipment.
"The cage itself was to be a zeppelin-shaped projectile--But come, the Diamvator itself is due in five minutes."
Andrews arose and led the way to the terminal gate, and for the next few minutes Randall unobtrusively strolled around the circumference of the Earth-Tube, examining its massive steel barrier. He completed his circuit and was peering timidly through the steel lattice, when a long-drawn "whoooosh" and a metallic click sounded from the black depths.
He turned inquiringly to Andrews, who hastened to explain. "Closing of the air-locks," he said. "You see, the air is only partially exhausted from the Earth-Tube, so that the Diamvator will be held from the Tube sidewall during its free fall. Thus it does not attain the full acceleration of a freely falling body in a vacuum by a great deal. Consequently it does not approach its full pendular ascent from the Earth's center against gravitation.
"It lacks 'falling' to the surface of the Earth by over ten thousand feet, so some means had to be provided for propelling the Vator on up to the surface. To accomplish this, automatic air-locks were installed in the tube almost three hundred miles from either end, with other locks every few miles from there to the surface.
"When the Vator has passed a lower lock, both that one and the lock above it close, and air is admitted under high pressure below the Vator and exhausted above it, thus pushing the car up to the surface, where it is grasped and held by interlocking steel arms--"
Andrews was interrupted by a second "whoooosh" as the upper lock opened, followed immediately by the appearance of the bullet-shaped nose of the Diamvator.
Slowly the tube car ascended until its nose towered far above the heads of the milling crowd which by this time surrounded the terminal. Suddenly a harsh click told that the steel arms had gripped the Vator. Friction rollers whined as they rotated the car until its massive door coincided with the barrier gate.
As Andrews and Randall watched, the guard unlocked the gate and slid it into its slot, then unbarred the Vator door and pushed it open.