."

"Good God, you didn't know--"

"The rotaries backfired and used up all the oxygen in the engine room.
Worse, there's been a carbonic oxide seepage. The air is contaminated
throughout the ship. We'll have to open the ventilation valves
immediately. I've been waiting to see if--if you could breathe down
there. You're all right, aren't you? The air _is_ breathable?"

Lawton's face was dark with fury. "I was an experimental rat in the sky,
eh?"

"Look, Dave, we're all in danger. Don't stand there glaring at me.
Naturally I waited. I have my crew to think of."

"Well, think of them. Get those valves open before we all have
convulsions."

A half hour later charcoal gas was mingling with oxygen outside the
ship, and the crew was breathing it in again gratefully. Thinly
dispersed, and mixed with oxygen it seemed all right. But Lawton had
misgivings. No matter how attenuated a lethal gas is it is never
entirely harmless. To make matters worse, they were over the Atlantic
Ocean.

Far beneath them was an emerald turbulence, half obscured by eastward
moving cloud masses. The bubble was holding, but the morale of the crew
was beginning to sag.

Lawton paced the control room. Deep within him unsuspected energies
surged. "We'll last until the oxygen is breathed up," he exclaimed.
"We'll have four or five days, at most. But we seem to be traveling
faster than an ocean liner. With luck, we'll be in Europe before we
become carbon dioxide breathers."

"Will that help matters, Dave?" said the captain wearily.

"If we can blast our way out, it will."

The Captain's sagging body jackknifed erect. "Blast our way out? What do
you mean, Dave?"

"I've clamped expulsor disks on the cosmic ray absorbers and trained
them downward. A thin stream of accidental neutrons directed against the
bottom of the bubble may disrupt its energies--wear it thin. It's a
long gamble, but worth taking. We're staking nothing, remember?"

Forrester sputtered: "Nothing but our lives! If you blast a hole in the
bubble you'll destroy its energy balance. Did that occur to you? Inside
a lopsided bubble we may careen dangerously or fall into the sea before
we can get the rotaries started."

"I thought of that. The pilots are standing by to start the rotaries the
instant we lurch. If we succeed in making a rent in the bubble we'll
break out the helicoptic vanes and descend vertically. The rotaries
won't backfire again. I've had their burnt-out cylinder