lid of machinery, the unit itself being housed inside a transparent case. The components were working visibly in the midst of a mass of thin gluey substance.
As the thin air streamed up the giant shaft it passed into one giant valve in the machinery, went through an amplifying process by which heavier air pressure was added, and was then expelled by a piston system at the other side of the machine, a massive pipe being driven through the tough outer casing. The thing was virtually the mechanical heart of Mars pumping out good air from thin, spent currents.
"The Martians were damn good engineers, anyway," Val commented. "But just why did they need to give air to this cavern in particular when there is only a lot of balls in it that don't need air to work in . . . ?"
"Unless," Cliff mused, "they wanted intelligent life to come into this cavern and have a look round in order to start the machinery going. The air would invite anybody inside—as it did us. I'll bet, when we broke through the wall, we completed a circuit that started the air pump working."
Val's pipe crackled. "Say, maybe you've got something. Anyway, we can check up on that by examining the wall later. What we've got to do right now is find out what makes these balls tick."
He tugged out his gun and fired it experimentally at a corner of the heart's transparent casing. The beam simply glanced off. Val stared blankly.
"By all the saints, it's anilum!" he gasped. "Moulded anilum, at that, Ray guns will never penetrate this! It takes a temperature of something like 15,000° C. to melt it.
"Everything in this cave's made of anilum," said Cliff.
THE engineers glanced at each other, then with one accord they looked at the monster ball. Within it something was still ticking solemnly at regular three-second intervals.
"Say, something's just occurred to me," Val said presently. "Is it possible that we're right at the core of Mars and that this giant metal bail is natural? Or at least it was natural until it changed into unthinkably hard anilum.[1]
"So what?" Cliff's brows were knitted.
"If the Martian engineers found a way to hollow out its center, which is quite conceivable, they might have put something inside it. From the stuff out of the center they manufactured all these other little balls. We'd probably find by mathematics that the material used in these little balls equals the extracted mass from inside the larger one. In plain words, pressure changed nickle iron into anilum, but Martian science was clever enough to enable the Martians to find out how to bore through it and hollow it out. The seam of anilum which Fredison found seems to show that that seam was ejected volcanically, proving conclusively that it was from the bowels of Mars."
"Which might explain why we can't find anilum on Earth," Cliff mused. "So far our Earth has not ejected any of its deep baser material; only the upper molten metals. Deep down there will be anilum, but we shall never find it until Earth is as riddled with passages to its core as Mars now is. Yes, Val, I think you've got something . . . But I'll be damned if I understand the Mar-
- ↑ Every planet has a ball of metal in its center under terrific pressure—nickle iron center. In a normal planet like Earth it is a liquid solid—a paradoxical way of showing what pressure can do with a solid. But in a world like Mars, or the Moon, where the rest of the planet is practically dead and shrunken, the pressure round the center has relaxed, it might leave a solid ball of metal, which because of that pressure might become anilum.—Ed.
