'Just trying to lighten the mood, Dean.'

'But we can release just enough for all kinds of useful work,' said Ponder, already struggling.

'Like heating my study,' said the Lecturer in Recent Runes. 'My water jug was iced up again this morning.'

'Exactly!' said Ponder, striking out madly for a useful Lie-to-Wizards. 'We can use it to boil a great big kettle! That's all it is! It's perfectly harmless! Not dangerous in any way! That's why the University Council let me build it! You wouldn't have let me build it if it was dangerous, would you?'

He gulped down the water.

As one man, the assembled wizards took several steps back­wards.

'Let us know what it's like up there,' said the Dean.

'Bring us back some rocks. Or something,' said the Lecturer in Recent Runes.

'Wave to us', said the Senior Wrangler. 'We've got quite a good telescope.'

Ponder stared at the empty glass, and readjusted his mental sights once more.

'Er, no,' he said. 'The fuel has to go inside the reacting engine, you see. And then ... and then ...'

He gave up.

'The magic goes round and round and it comes up under the boiler that we have plumbed in and the university will then be lovely and warm,' he said. 'Any questions?'

'Where does the coal go?' said the Dean, 'It's wicked what the dwarfs are charging these days.'

'No, sir. No coal. The heat is ... free,' said Ponder. A little bead of sweat ran down his face.

'Really?' said the Dean. 'That'll be a saving, then, eh, Bursar? Eh? Where's the Bursar?'

'Ah ... er ... the Bursar is assisting me today, sir,' said Ponder. He pointed to the high gallery over the court. The Bursar was standing there, smiling his distant smile, and holding an axe. A rope was tied around the handrail, looped over a beam, and held a long heavy rod suspended over the centre of the reaction engine.