Seciv frowned, his crumpled hair waving. "You could mimic the internal operation of the pig's anatomy. The car could carry tanks of Air, heated by a stock of wood in a nuclear-burning boiler and expelled through a valve orifice." With a delicate finger he reached out and poked at one flabby fin, tentatively. "You could even make an attempt at steering, by mounting these fins on gimbals worked from inside the craft. And the fart nozzles could be made directional, with a little ingenuity." The old man nodded approvingly to Adda. "A practical suggestion in many respects."

Adda — despite himself, Dura realized — swelled at the praise; Hosch looked disgruntled.

Farr said seriously, "But how could it survive the underMantle? Adda, I learned in the Bells that it's not pressure alone that would destroy such a craft, by crushing it..." He snapped his fist closed suddenly, making Dura flinch; she wondered where he'd learned such crude dramatic tricks. Farr went on, "Nuclear matter — ordinary matter — would dissolve."

Hosch said rapidly, "Well, of course it would. Anyone with a fingernail of experience knows that. Our Bells are protected from the pressure by magnetic fields sent down from the turbines in the City."

Seciv Trop shook his head. "That's a misapprehension, Supervisor. To be precise, the Bells are fed by electrical currents which are generated in the Harbor... but the protective magnetic shell is generated at the Bell itself, by superconducting hoops which girdle the Bell."

Hosch looked the old man up and down. "You're a Fisherman, I suppose. We must have been on different shifts..."

Muub touched Hosch's shoulder. "Seciv designed the current generation of Bells — the Bells you ride every day. Hosch, your life depends upon his expertise; it suits you ill to mock him."

Hosch subsided. "Well, what of it? The boy's point stands."

Seciv seemed impervious to offense. "One would simply need to gird this artificial pig around with superconducting hoops, and carry equipment to generate the magnetic field from within." He frowned. "Of course, the bulk of the craft would be increased."

Dura asked, "Wouldn't it get hot inside the wooden pig, with nuclear burning going on all the time?"

Seciv nodded. "Yes, that would be a difficulty... though not in itself insurmountable. A more serious problem would be the supply of propellant Air. Compression ratios in even our best-made tanks are not very high. Sufficient for a jaunt to the ceiling-farms in an Air-car, but hardly enough for an expedition of this magnitude." He eyed Adda sadly. "Again, perhaps this could be overcome. But there are two far more devastating flaws. First, a lack of stability. There is more to an Air-pig than an anus and a few fins, after all. The pig has six eyes to guide it..."

"Well," Adda said defensively, "you could have six windows of clearglass. Or more."