When they disembarked on to the platform above the Bottomless Pit, they straightened their safety helmets and looked up into the roof of the cavern hundreds of feet above their heads, where the remains of primitive wooden ladders still protruded from the rock.
Then they gazed down into the green water far below as the guide told them about the lead miners who’d hurled tons of rock into it. They listened politely to his stories about the Devil, who the miners believed had lived at the bottom of the lake, and about the giant white serpent that was supposed to emerge from the water and roam the passages, seeking human prey.
‘And, of course, it’s the high lead content of the rock that gives the water its green colour,’ he said.
The guide was about to turn off the lights and lead his party back to the boat. But one visitor had been leaning over the parapet and staring closely at the water. He was an old physics professor, and he had a question.
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‘Excuse me, sir,’ he said. ‘I understand it’s the lead that makes the water green. But what causes the bubbles?’
Puzzled, the guide looked over the parapet. ‘What do you mean?’
‘The bubbles, see? Oh, and another thing - the smell?’
The guide wasn’t a man to be frightened by his own stories of giant white serpents. But even he could see there was something in the lake seventy feet below. It was pale and bloated, and it almost shimmered in the lime- green water as bubbles of gas burst around it.
And one thing he was sure of. The thing was rising slowly to the surface, gradually re-emerging from the depths of the Bottomless Pit.
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