Now the final, most delicate and most dangerous part of the mission was about to begin. The current here flowed steadily and smoothly at a speed of almost one and a half knots, hardly anything to speak of; if it had been on the surface a good swimmer could have breasted it, a rowing boat made progress in it, a fast launch ignored it. Even below the sea the submarines paid the current scarcely any heed—when they were on their own. But now, with their massive tow, it became their primary consideration, for the thirty-foot thick and mile-long bridge had an immense surface area that the current pushed against, so strongly that it was doubtful if the united force of all the submarines could have held it steady much less gained against its pull. Therefore the attempt to put the bridge sections into place must be right the very first time.

In order to accomplish this the cables had to be secured on each side of the valley at the same time and locked into place. The towing lines from the submarines were fastened to the much more massive cables of the bridge, each over a yard in diameter, for these served a dual function, now being used for towing, but upon arrival they would become the permanent mooring cables that held the bridge in the correct position. The ones from the center section were the longest—well over a half mile in length because they had to connect to the buttresses at each end—while the others grew shorter and shorter the closer they came to the end. When in position this skein of steel cable would hold the bridge inflexibly in place as its buoyancy pulled them taut. Now it was a matter of securing them.

Below the lip of each edge of the canyon there was a great area of smoothed rock that was illuminated brilliantly by numerous lights, for what had to be done next had to be done by eye, the human eye, and no automatic machines could be of aid here. Massive, monstrous anchors had been drilled and cemented into the solid stone to hold the bridge in place, while secured to them were hulking fittings to which would eventually be attached the giant turnbuckles that would be used to tension the cables correctly. But that would come later, now the cables had to be secured quickly and easily. In order to do this, massive, spring-loaded, forged steel jaws projected from each anchor. When a cable was pressed across one of these sets of jaws they would be sprung .like a titanic rattrap and would snap shut instantly, their corrugated jaws latching fast while automatic electric motors tightened them even more. This was the plan and it had been tested many times in training and it should work. It must work!

Down, down, down, the massive construction fell, with its attentive tugs laboring hard, now pulling this way, now that, under the continuous instruction of the Brabbage engine. There was almost complete silence inside the submarines, aside from the whisper from the ventilation louvers and the distant hum of the engines, an occasional word spoken between the operators of the great computer. Despite the silence and the lack of activity the air of tension was so thick inside every one of the subs that there were those who had some difficulty in breathing, for this was it, the irreversible decision, the unchangeable moment.

Down steadily while the brightly lit anchors below grew larger on the screens, the bold red numbers above each of them standing out stark and clear, and down still more with the cliff coming closer and closer. Fists tightened and knuckles whitened as the pilots simply watched their charges control themselves under the tutelage of the computer brain, this waiting and watching infinitely more trying than any complex control effort would have been. Down. Every detail of the ancient stone and the clean sharpness of the new construction clear before them. Down.

“One and Nine attach, One and Nine attach. You are on your own!” The voice spoke quickly and clearly over the command circuits, booming from every speaker in every sub. This was the long awaited signal, manual command, the first subs on their way with their cables. Ten cables at each end of the bridge, numbers One and Two being the shortest on top of the pier, Nine and Ten the longest because, from the center of the span, their cables had to reach far down to the bottom of the pier. Now the two subs each with one of the pair of the longest and shortest cables had been released from computer command and were moving ahead on their own to attach their cables, racing at full speed to make their hookups. As soon as they had done this the next two subs would be sent in with their cables during the vital two minutes during which the tunnel would be in the right place at the right distance for hookup. Four cables were needed, on each end to anchor the bridge-tunnel against the pressure of the current. If these eight cables were secured the bridge would be held in place; the computations had been exact. Once these eight were in place the remaining mooring cables would be attached one at a time with greater precision. But those four cables had to be fastened first, if they were not there was no telling what disaster might occur as the bridge was swept out of position.

Nautilus II, motors whining at full speed, led the way towards the anchorage, O’Toole busy at last with the controls, yet even as he dived, remembering to ease off on the keel line and tighten up on the bow line that was fastened to the mooring cable like a spring, riding loosely until now. The drum and motor for this line were on a spar that jutted twenty feet from the sub’s nose and were easily visible in the forward camera. Sell before the sub had reached its goal the heavy mooring cable had been reeled in until it was snug against the end of the spar, the orange painted twenty-foot long section of cable just above it. This was the target area. As long as any portion of this colored area was snagged by the waiting jaws the hookup would be successful, for this area was well within the bending tolerances of the bridge and the natural arc of the cable. For precise measurements a two-foot wide black band was painted about the middle of the orange section, the area of optimum choice.

O’Toole handled the bulky submarine with an artist’s touch, spinning it on its beam ends so the spar pointed up and out at the waiting jaws, taking up the weight of the cable, being forced astern for a moment, then thrusting out—but not so fast that he rammed the pier. Up slowly, drifting, correcting, forward, the spar like an immense guiding finger reaching out for the target. Gus, standing behind the pilot, unconsciously held his breath as the pier moved closer and closer until it seemed they would ram into it.

“Got it!” O’Toole shouted with joy as the iron jaws, like a great metal alligator, slammed crunching shut on the cable just on the black band, so strongly they could feel the impact within the submarine. “And now clear and we’re away.”

He pressed the two buttons that sent an electric current through the wires inside the towing lines, a current which exploded the shackles that secured them to the anchoring cables. The smaller lines dropped free and the electric motors whined to run them in as the submarine backed away.

“Number Nine hooked as well.”

Gus said, looking at the scene from the keel pickup on his monitor screen. “Numbers Two and Ten begin approach,” he ordered into the command circuit.

At that precise moment it happened, just then at the worst possible time for the anchoring of the bridge, a moment when success and failure were suspended on a razor edge of seconds. But world time is a measurement on a different scale; rather say that geologic time is indifferent to mankind’s brief existence on the outer skin of the globe, experiencing thousands of years, or even hundreds of thousands of years, as the smallest unit. Pressures had been building in the Earth’s core as the tidal flow of molten rock pressed up against the solid crust that floated upon it, building pressure slowly but insistently, pressure that had to be relieved for it could not be endured too long. A seam deep in the rocks opened, a great mass shifted, stone grated on stone and the pressures were equalized, the Earth was at rest again. A small thing in geological time, too small to be even measured, or noticed, in comparison to the mighty forces always at work. Yet large enough to wreak havoc to man’s work.