Vastra's Third had melted into the background; I took over, to show this Dorotha Keefer what the Hall of Discoveries was all about.
The Hall is there for the purposes of getting Terry tourists and prospectors hotted up, so they'll spend their money poking around Heechee digs. There's a little of everything in it, from charts of the worked diggings and a large-scale Mercator map of Venus to samples of all the principal finds. I showed her the copy of the anisokinetic punch, and the original solid-state piezophone that had made its discoverer almost as permanently rich as the guys who marketed the punch. There were about a dozen fire-pearls, quarter-inch jobbies; they sat behind armor glass, on cushions, blazing away with their cold milky light. "They were what made the piezophone possible," I told her. "The machine itself, that's a human invention; but the fire-pearls are what makes it work-they convert pressure into electricity and vice versa."
"They're pretty," she said. "But why do they have to be protected like that? I saw bigger ones lying on a counter in the Spindle without anybody even watching them."
"That's a little different, Dorotha," I told her. "These are real." She laughed out loud. I liked her laugh. No woman looks beautiful when she's laughing hard, and girls who worry about looking beautiful don't do it. Dorotha Keefer looked like a healthy, pretty
woman having a good time, which, when you come down to it, is about the best way for a woman to look.
She did not, however, look quite good enough to take my mind off my need for the money to buy a new liver, so I got down to business. "The little red marbles over there are blood-diamonds," I told her. "They're radioactive. Not so much that they'll hurt you, but they stay warm. Which is one way you can tell the real one from a fake: Anything over about three centimeters is a fake. A real one that big generates too much heat-the square-cube law, you know. So it melts."
"So the ones your friend was trying to sell me-"
"Were fakes. Right."
She nodded, still smiling. "What about what you were trying to sell us, Audee? Real or fake?"
The Third of Vastra's House had discreetly vanished by then, so I took a deep breath and told Dorotha the truth. Not the whole truth, maybe, but nothing but the truth.
"All this stuff here," I said, "is what thousands of people have found after a hell of a lot of digging. It's not much. The punch, the piezophone, and two or three other gadgets that we can make work; a few busted pieces of things that they're still studying; and some trinkets. That's it."
"That's the way I heard it," she said. "And one more thing. None of the discovery dates on these things is less than twenty years old." She was smarter and better informed than I had expected.
"And the conclusion you can draw from that," I agreed, "is that as nothing new has been found lately, the planet has probably been mined dry. You're right. That's what the evidence seems to show. The first diggers found everything useful that there was to be found .. . so far."
"But you think there's more."
"I hope there's more. Look. Item. The tunnel walls. You see
they're all alike-the blue walls, perfectly smooth; the light coming from them that never varies; the hardness. How do you suppose the Heechee made them?"
"Why, I don't know."
"Neither do I. Or anybody else. But every Heechee tunnel is the same, and if you dig into them from the outside you find the same basic substrate rock, then a boundary layer that's sort of half wall-metal and half substrate, then the wall itself. Conclusion: The Heechee didn't dig the tunnels and then line them, they had something that crawled around underground like an earthworm, leaving these tunnels behind. And one other thing: they overdug. That's to say they dug lots of tunnels they didn't need, going nowhere, never used for anything. Does that suggest anything to you?"
"It must have been cheap and easy?" she guessed.
I nodded. "So it was probably an automatic machine, and there really ought to be at least one of them, somewhere on this planet, to find. Next item. The air. They breathed oxygen like we do, and they must have got it from somewhere. Where?"
"Why, there's oxygen in the atmosphere, isn't there?"
"Hardly any. Less than a half of a percent. And most of what there is isn't free oxygen; it's compounded into carbon dioxide and other garbage. There's no water vapor to speak of, either. Oh, a little-not as much as, for instance, sulfur dioxide. When water seeps out of the rock it doesn't come out as a fresh, clear spring. It goes into the air as vapor pretty fast. It rises-the water molecule being lighter than the carbon dioxide molecule. When it reaches a point where the sun can get at it it splits into hydrogen and oxygen. The oxygen and half the hydrogen mostly go into turning the sulfur dioxide into sulfuric acid. The rest of the hydrogen just escapes into space."
