"What the hell's a booster collar?" Stelmer pleaded.

"And a transfer tube?" Patterson added, forgetting his question of a few seconds before.

"There were tubes running all over the ship that were used for moving objects, and people, from place to place," Jassilane answered. "You must know them because I've seen them on the plans of the ship that your engineers have drawn."

"We kind of half-guessed what they were," Hunt supplied. "But we were never really sure about how they worked. Is this another G-trick?"

"Right," Jassilane said. "Local fields inside the tubes provided the motive force. That collar next door is simply a type of amplifier that was fitted around the tube to boost and smooth the field strength. There'd be one--oh--every thirty feet or so, depending on how wide the tube was."

"You mean people went hurtling through these things?" Patterson sounded distinctly dubious.

"Sure. We've got them in the Shapieron too," Jassilane replied nonchalantly. "The main elevator that some of your people have already been in runs in one. That one uses an enclosed capsule running inside, but the smaller ones don't. In those you just freefall."

"How do you avoid colliding with somebody?" Steliner asked. "Or are they strictly one-way?"

"Two-way," Jassilane told him. "A tube would usually carry a split field, half up and half down. The traffic can be segregated without problems. The collar contributes to that too--part of it is what we call a'beam edge delimiter.'"

"So how d'you get out?" Stelmer persisted, still clearly fascinated by the idea.

"You decelerate through a localized pattern of standing waves that's triggered as you approach the drop-out point you've selected," Jassilane said. "You enter in much the same way . . ."

The conversation degenerated into a long discussion on the principles of operation and traffic control employed in the networks of transfer tubes built into Ganymean spacecraft and, as it turned out, most Ganymean buildings and cities. Throughout it all, Patterson's question as to how it worked never did get answered.

After spending some time examining a few more items from the ship, the party left that section of the base to continue their tour. They followed another corridor to the subsurface levels of the Site Operations Control Building and ascended several flights of stairs to the first floor. From there an elevated walkway carried them into an adjacent dome, constructed over the head of number-three shaft. Eventually, after negotiating a labyrinth of walkways and passages, they were standing in the number-three high-level airlock anteroom. A capsule was waiting beyond the airlock to take the first half-dozen of them down to the workings below the surface. By the time the capsule had returned and made its third descent, the whole party was together again deep inside the ice crust of Ganymede.

Accompanied by Jassilane, two other Ganymeans, and Commander Hew Mills, the senior officer of the uniformed UNSA contingent at Pithead, Hunt emerged from the capsule into number-three low-level anteroom. From there a short corridor brought them at last to the low-level control room, where the rest of the party was already gathered. Nobody took any notice of the new arrivals; all eyes were fixed on the view that confronted them from beyond the expanse of glass that constituted the far wall of the control room.

They were looking out over a vast cavern hewn and melted from the solid ice, shining a hundred different hues from gray to brilliant white in the light from a thousand arc lamps. The far side of the cavern was lost to view behind a forest of huge steel jacks and columns of ice left intact to support the roof. There, immediately before them, stretching away into the distance and cutting a clean swath through the forest, was the Ganymean ship.

Its clean, graceful lines of black metal were broken at scores of points where sections of the hull had been removed to gain access or to remove selected parts of the internal machinery. In some places the ship resembled the skeleton of a whale stranded on a beach, just a series of curving ribs soaring toward the cavern roof, to mark where whole sections of the ship had been stripped down. Latticeworks of girders and metal tubing adorned its sides in irregular and untidy clusters, in some places extending fully from floor to roof, supporting a confusion of catwalks, ladders, platforms, ramps, rigs, and winches wreathed intermittently in bewildering tangles of hydraulic and pneumatic feed tubes, ventilator pipes and electrical supply lines.

Scores of figures labored all across the panorama: up on the scaffolding by the hull, down among the maze of stacked parts and fittings that littered the floor, high on the walkways clinging to the rough-hewn walls of ice and standing on the top of the hull itself. In one place a gantry was swinging clear a portion of the outer skin; in another, the sporadic flashing of an oxyacetylene torch lit up the interior of an exposed compartment; further along, a small group of engineers was evidently in conference, making frequent gestures at information being presented on a large, portable view-screen. The site was a bustle of steady, deliberate, earnest activity.

The Earthmen waited in silence while the Ganymeans took in the scene.

Eventually Jassilane said, "It's quite a size . . . certainly as large as we expected. The general design is definitely a few steps ahead of anything that was flying when we left Minerva. ZORAC, what do you make of it?"

"Toroidal sections protruding from the large cutaway portion three hundred feet along from where you're standing are almost certainly differential resonance stress inductors to confine focus of the beam point for the main drive," ZORAC answered. "The large assembly on the floor immediately below you, with the two Earthmen standing in front of and underneath it is unfamiliar, but suggests an advanced design of an aft compensating reactor. If so, propulsion was probably by means of standard stress-wave propagation. If I am correct, there should be a forward compensating reactor in the ship too. The Earthmen at Main have shown me diagrams of a device that looks like one, but to be sure we should make a point of looking inside the nose end to check it firsthand. I would also like an opportunity to view the primary energy-convertor section and its layout."

"Mmm . . . it could be worse," Jassilane murmured absently.

"What was that all about, Rog?" Hunt asked him. The Giant half turned and raised an arm toward the ship.

"ZORAC has confirmed my own first impressions," he said. "Although that ship was built some time after the Shapieron , the basic design doesn't seem to have altered too much."

"There's a good chance it might help you get yours fixed then, huh?" Mills chimed in.

"Hopefully," Jassilane agreed.

"We'd need to see it close-up to be sure," Shilohin cautioned. Hunt turned to face the rest of the party and spread his arms with palms upturned. "Well, let's go on down and do just that," he said.

They moved away from the viewing window and threaded their way through and between the equipment racks and consoles of the control room to a door on the opposite side to descend to the lower floor. After the door had closed behind the last of the party, one of the duty operators at the consoles half turned to one of his colleagues.

"See Ed, I told ya," he remarked cheerfully. "They didn't eat anybody."

Ed frowned dubiously from his seat a few feet away.

"Maybe they're just not hungry today," he muttered.

On the floor of the cavern, immediately below the window, the mixed group of Ganymeans and Earthmen emerged through an airlock and began making their way across the steel-mesh flooring and through the maze of assorted engineering toward the ship.