Tunnels 03, Freefall

there are four concentric spheres, one within the other, like those dolls from Russia that fit inside each other. Then in the eighteenth century, another chap called Symmes resurrected the idea. He-- WHUP! " Dr. Burrows cried as his feet slipped out from under him. He skied a distance in the loose shale covering the slope, then managed to right himself. "Nearly lost it there."
    "I think you did," Will muttered.
    "Where was I? Yes, Symmes' contribution to the theory was there were two whopping great holes in each of the Poles, and that the gas escaping from these was the cause of the Aurora Borealis -- the northern lights, as they're called... or maybe Halley proposed that."
    "Dad, I've heard all this before, so why are you banging on about it again now?" Will asked a little tetchily.
    "Because those ancient people I was researching in the Great Plain have to have gone somewhere . They can't simply have been jumping to their deaths down the Pore or the other voids. This wasn't some flash-in-the-pan aberration that took place one day when an entire race decided to commit mass suicide at all," Will pointed out. "It's a myth."
    Dr. Burrows went on regardless. "No with these people, it had to have been more than that... I mean they even built a temple in praise of the other world that they believed was deep inside the planet, calling it their Garden of the Second Sun . The triptych I saw in the temple clearly demonstrates that they thought it was some sort of idyllic place, some sort of Utopia."
    "Maybe the spiders gobbled them up?" Will suggested mischievously.
    "That doesn't make any sense -- they wouldn't have gone to all the trouble of making the map on the stone tablets or carving their three-pronged symbol near the submarine, or wherever it is. No, they were deadly serious about it all... they were on their way somewhere... but where?"
    As Will didn't offer any sort of opinion, they walked in silence until Dr. Burrows spoke again.
    "Back in the sixties some oddball professor claimed that a technologically-advanced race inhabited the inner world, and that they had flying saucers."
    Will had just about had enough. "Right, so Symmes and the other guys were all nutty professors with wacky theories. Your point is...?" he said brusquely.
    "They might not have been that crazy," Dr. Burrows replied.
    "Wait," will said, stopping in his tracks.
    Dr. Burrows looked at Will expectantly, thinking that he had just had a brain wave, that he was about to impart some revelation that would shed light on where the ancient race had gone.
    It was as though there was a battle of ideologies taking place in Dr. Burrows' head, like a tug of war between two opposing teams. The stronger team, with a grey-bearded Charles Darwin as its captain, was made up of all the scientists, historians and other great thinkers that Dr. Burrows had looked up to and tried to emulate all his academic and professional life. The opposing team consisted of rather more unconventional figures, including the likes of Halley and Symmes, and their captain was Lucretius, who in the first century BC had convinced everyone the world was flat as a pancake.
    As a matter of course, Dr. Burrows would normally have been cheering on Charles Darwin's team, but now as the rope creaked and the two teams strained, he found himself strangely drawn to the unconventional team. It was as if he was beginning to take the Hollow Earth theories seriously.
    "What is it, Will? Have you thought of something?" Dr. Burrows asked with bated breath.
    But instead of shedding light on the fate of the ancient people, the only light the boy shed was from his lantern, which he was directing towards a nearby passage. It led off to the right of the main trail, and Will was slowly moving towards it. "If we're close to where the submarine was, this might have been one of the tunnels we tried, but didn't take because of the teen spiders?" Switching his lantern off, he flipped the night vision device down over his eye so he could see further inside the passage. "Dad, does it look familiar to you?" he asked eventually.
    "I... think... it... does," Dr. Burrows said slowly, rubbing his chin.
    Will was impressed. "Really?"
    "There's something about that piece of rock up there at the top -- the way it hangs down."
    "That's amazing! You remember that?" Will asked.
    "Yes, because I noticed it was unusual at the time. It's obviously from the Ignoramic class... and I reckon it could be Stupidite."
    "You mean