‘What are they doing?’ Polly wanted to know. ‘We call that probing,’ Medok told her. ‘They are testing for further supplies of gas.’ ‘More gas!’ ‘Oh yes. The process never stops.’ Medok was bitter. ‘We find one source, create a pressure point, fix cables to syphon it off, and then go on and do the same thing again. It’s never ending.’ The passageway where they were had several short corridors leading off it. Some ended by being blocked off by a wall; others ended in the rock itself. ‘Take a look at this one,’ said Jamie. Polly joined him. The short passage ended in a metal door. ‘Where does that go, I wonder?’ Medok peered over his shoulder. ‘There are a lot of doors like that.’ ‘It could lead to some old shaft,’ suggested Jamie. ‘A bit of the mine that has been worked out.’ He thumped the metal. It sounded thick and heavy. ‘Why would they want such a strong door?’ wondered Polly. ‘And it’s quite new,’ she said. They heard Officia returning and moved on to pretend they were probing the sides of the wall.
