I thought there might be a hidden source of buoyancy somewhere. It would take a lot of air bubbles to turn this ship into a balloon, but there are large vacuum chambers under the multiple series condensers in the engine room which conceivably could have sucked in a helium leakage from the carbon pile valves. And there are bulkhead porosities which could have clogged."

"Yeah," muttered Slashaway, scratching his head. "I see what you mean, sir."

"It was no soap. There's nothing inside the ship that could possibly keep us up. Therefore there must be something outside that isn't air. We know there is air outside. We've stuck our heads out and sniffed it. And we've found out a curious thing.

"Along with the oxygen there is water vapor, but it isn't H2O. It's HO. A molecular arrangement like that occurs in the upper Solar atmosphere, but nowhere on Earth. And there's a thin sprinkling of hydrocarbon molecules out there too. Hydrocarbon appears ordinarily as methane gas, but out there it rings up as CH. Methane is CH4. And there are also scandium oxide molecules making unfamiliar faces at us. And oxide of boron—with an equational limp."

"Gee," muttered Slashaway. "We're up against it, eh?"

Lawton was squatting on his hams beside an emergency 'chute opening on the deck of the Penguin's weather observatory. He was letting down a spliced beryllium plumb line, his gaze riveted on the slowly turning horizontal drum of a windlass which contained more than two hundred feet of gleaming metal cordage.

Suddenly as he stared the drum stopped revolving. Lawton stiffened, a startled expression coming into his face. He had been playing a hunch that had seemed as insane, rationally considered, as his wild idea about the bulkhead porosities. For a moment he was stunned, unable to believe that he had struck pay dirt. The winch indicator stood at one hundred and three feet, giving him a rich, fruity yield of startlement.

One hundred feet below him the plummet rested on something solid that sustained it in space. Scarcely breathing, Lawton leaned over the windlass and stared downward. There was nothing visible between the ship and the fleecy clouds far below except a tiny black dot resting on vacancy and a thin beryllium plumb line ascending like an interrogation point from the dot to the 'chute opening.

"You see something down there?" Slashaway asked.

Lawton moved back from the windlass, his brain whirling. "Slashaway there's a solid surface directly beneath us, but it's completely invisible."

"You mean it's like a frozen cloud, sir?"

"No, Slashaway. It doesn't shimmer, or deflect light. Congealed water vapor would sink instantly to earth."

"You think it's all around us, sir?"

Lawton stared at Slashaway aghast. In his crude fumblings the gym slugger had ripped a hidden fear right out of his subconsciousness into the light.

"I don't know, Slashaway," he muttered. "I'll get at that next."

A half hour later Lawton sat beside the captain's desk in the control room, his face drained of all color. He kept his gaze averted as he talked. A man who succeeds too well with an unpleasant task may develop a subconscious sense of guilt.

"Sir, we're suspended inside a hollow sphere which resembles a huge, floating soap bubble. Before we ripped through it it must have had a plastic surface. But now the tear has apparently healed over, and the shell all around us is as resistant as steel. We're completely bottled up, sir. I shot rocket leads in all directions to make certain."

The expression on Forrester's face sold mere amazement down the river. He could not have looked more startled if the nearer planets had yielded their secrets chillingly, and a super-race had appeared suddenly on Earth.

"Good God, Dave. Do you suppose something has happened to space?"

Lawton raised his eyes