en
dormant for, oh, maybe as long as a thousand years; there ought to be
a pretty good head of gas down there. And the magma'll be thick,
viscous stuff, like basalt on Terra. Of course, this won't be anything
like basalt in composition--it'll be intensely compressed metallic
fluorides, with a very high metal-content. The volcanoes we shot three
months ago yielded a fine flow of lava with all sorts of
metals--nickel, beryllium, vanadium, chromium, indium, as well as
copper and iron."

"What sort of gas were you speaking about?" she asked.

"Hydrogen. That's what's going to make the fireworks; it combines
explosively with fluorine. The hydrogen-fluorine combination is what
passes for combustion here; the result is hydrofluoric acid, the
local equivalent of water. See, the metallic core of this planet is
covered, much less thickly than that of Terra, with fluoride
rock--fluorspar, and that sort of thing. There's nothing like granite
here, for instance. That's why those big dunes, out there, are the
best Niflheim has in the way of mountains. The subsurface hydrogen is
produced when the acid filters down through the rock, combines with
pure metals underneath."

"Dr. Murillo's inside, now," the radioman said. "Just came out of the
inner airlock. He'll be up as soon as he gets out of his
pressure-suit."

"As soon as he gets here, I'll touch it off," the bearded man said.
"Everything set, de Jong?"

"Everything ready, Dr. Gomes," one of his assistants assured him.

The door at the rear of the control-cabin opened, and Juan Murillo,
the seismologist, entered, followed by an assistant. Murillo was a big
man, copper-skinned, barrel-chested; he looked like a third-or
fourth-generation Martian, of Andes Indian ancestry. He came forward
and stood behind Gomes' chair, looking down at the instruments. His
assistant stopped at the door. This assistant was not human. He was a
biped, vaguely humanoid, but he had four arms and a face like a
lizard's, and, except for some equipment on a belt, he was entirely
naked.

He spoke rapidly to Murillo, in a squeaking jabber. Murillo turned.

"Yes, if you wish, Gorkrink," he said, in the
English-Spanish-Afrikaans-Portuguese mixture that was Sixth Century,
A.E., Lingua Terra. Then he turned back to Gomes as the Ulleran sat
down in a chair by the door.

"Well, she's all yours, Lourenco, shoot the works."

Gomes stabbed the radio-detonator button in front of him. A voice came
out of the