The Long Earth

close!’
    And Joshua looked up, and up, at the building’s sheer face. It wasn’t exactly a miracle of architecture – it was unimpressive, in fact, save for its sheer scale. The blocks of black basalt-like rock from which it had been constructed had been roughly worked to fit, but were not of a uniform size. Even from here you could see gaps and imperfections, some of which had here and there been naturally mortared with what looked like bird guano and nests, but even that had evidently been a long time ago.
    Sally said, ‘Nice architecture. Somebody ordered “big and heavy and last for ever”, and got it. OK, let’s walk around to the entrance and dodge the rolling rock ball—’
    ‘No,’ said Lobsang sharply, standing stock still. ‘Change of plan. I have detected a rather more insidious danger.
The whole structure is radioactive
. Short range only, not remotely detectable – I do apologize. I suggest that we ambulate with alacrity back the way we came. No arguments. Please don’t waste breath until we are safe …’
    They didn’t exactly run; call it a very determined walk.
    Joshua asked, ‘So what is this place? Some kind of waste dump?’
    ‘Did you notice a multiplicity of signs that would indicate that entering this building unprepared is going to kill you? No, I didn’t either. The technological level appears much too low for this to be some kind of nuclear reactor, or other similar facility. I suspect they didn’t know what they were dealing with. I am speculating that this culture stumbled across a rather useful ore with interesting properties, perhaps a natural nuclear pile …’
    ‘Like Oklo,’ Joshua said.
    ‘In Gabon, yes. A natural concentration of uranium. They found something that made holy glass glow, perhaps … That would show the spirits at work, wouldn’t it?’
    Sally said, ‘Spirits that ultimately killed their acolytes.’
    Lobsang said, ‘We can at least look at some of the more distant caves before we depart. They should be far enough from the temple, or whatever this is, to be safe.’
    The first cave they chose to explore was big, wide, cool – and crowded with the dead.
    For a moment the three of them stood at the entrance of this house of bones. Joshua felt utterly dismayed at the sight, yet somehow it seemed an appropriate culmination of this lethally disappointing place.
    They walked in cautiously, stepping on clear earth where they could find it. The skeletons were fragile, often to the point of crumbling. The bodies must have been dumped in here, Joshua thought, perhaps in a rush, in the final days of the community when there was nobody left to dispose of them properly, however they had managed that disposal. But what were these creatures – or rather, what had they been? At first glance they might have been vaguely human. To Joshua’s inexpert eye they looked bipedal, as he could tell from the leg bones, the slim hips. But there was nothing humanoid about their sculpted, helmet-like skulls.
    In the heart of the cave the crew of the
Mark Twain
stood there rather helplessly. With a whir, Lobsang’s head turned steadily, and for once mechanically, with no human-like artifice, scanning and recording the symbols etched into the walls.
    Sally said, ‘Have you noticed? These corpses were not scavenged, not by animals. Nothing has disturbed them since they were dumped here.’
    Lobsang murmured as he worked, ‘I launched the usual drone craft, incidentally. There is no evidence of technology, of high intelligence, anywhere else on this version of Earth. Only here. The mystery deepens.’
    Sally grunted. ‘Perhaps the poisonous stuff that drew them here inspired them to their greatest cultural peak – before killing them. What an irony. Of course there is another possibility.’
    ‘What’s that?’ Joshua asked.
    ‘That the nuclear pile under that temple wasn’t natural at all. Merely very, very old …’
    Joshua and Lobsang had no response to that.
    ‘But still,’ Sally said, ‘a dinosaur civilization? It’s a unique find.’
    Joshua asked, ‘Dinosaurs?’
    ‘Look at those crested skulls.’
    ‘A civilization built by post-dinosaur evolutionary descendants, perhaps,’ Lobsang said fussily. ‘We must be precise about terms.’
    Joshua stared at a bit of bone, what was probably a finger, adorned with a gold ring, massive, set with sapphires. He bent and picked it up. ‘Look at this. It can’t be anything but decoration. They were