n the
hydrogen. We need twice as much hydrogen as oxygen, so the inner tube
has twice the volume delivery as the outer. See?"

"Yes. But what is the solid silver bar in the center of the inner
tube?"

"That's the electrical connection for the starter battery. There's a
small, short-lived chemical battery, like the ones in an ordinary
pocket radio, except that they're built to deliver a high-voltage,
high-amperage current for about a tenth of a second. That activates
the H-O cell, you see. Also, that silver stud depresses the
corresponding stud in the female plug, which turns on the gas flow
before it makes the connection with the starter battery. Follow?"

Hull didn't look as though he did, but he nodded gamely. "Then what
happens?"

"Then the hydrogen and the oxygen come together in the fuel cell and,
instead of generating heat, they generate electric current. That
current is fed into the radio unit, and the signal is sent to Pluto.
Real simple."

"I see," Hull said. "Well ... go ahead."

Smith telescoped the two leads together and began turning the collar
on the female plug.

He screwed it up as far as it would go.

And nothing happened.

"What the hell?" asked Smith of no one in particular. He tried to
twist it a little harder. Nothing happened. The threads had gone as
far as they would go.

"What's the matter?" Jayjay asked.

"Damfino. No connection. Nothing's happening. And it's as tight as it
will go."

"Are the gases flowing?" Jayjay asked.

"I don't know. These things aren't equipped with meters. They're
supposed to work automatically."

Jayjay pushed Smith aside. "Let me take a look."

Smith frowned as though he resented an ordinary passenger shoving him
around, but Jayjay ignored him. He cocked his head to one side and
looked at the connection. "Hm-m-m." He touched it with a finger. Then
he wet the finger with his tongue and touched the connection again.
"There's no gas flow, Smith."

"How do you know?" Smith was still frowning.

"There's a gap there. That tapered thread isn't in tight. If there
were any gas flowing, it would be leaking out." Before Smith could say
anything Jayjay began unscrewing the coupling. When it came apart, it
looked just the same as it had before Smith had put it together.

In the dim glow from the emergency lights, it was difficult to see
anything.

"Got an electric torch?" Jayjay asked.

Smith pushed himself away from the screamer panel and came back afte