'It appears so, Archchancellor.'

Ridcully lit his pipe. 'Well, mildly entertaining though it is to watch philosophers having a bath, can we simply ask Hex to find us a scientist who is definitely a scientist and who is regarded by other scientists as a scientist? Then all we have to do is find out if what he's doing is any use to us. We don't want to be all day at this, Stibbons.'

'Yes, sir. Hex, we—'

They were in a cellar. It was quite large, which was just as well because several of the wizards fell over upon landing. When they had picked themselves up and all found the right hat, they saw

...

... something familiar.

'Mr Stibbons?' said Ridcully.

'I don't understand ...' muttered Ponder. But it really was an alchemical laboratory. It smelled like one. Moreover, it looked like one. There were the big heavy retorts, the crucibles, the fire ...

'We know what alchemists are, Mr Stibbons.'

'Yes, er, I'm sorry, sir, something seems to have gone wrong ...' Ponder held out his hand. 'Book, please, Hex.'

A small volume appeared.

'"Great Men Of Science No.2",' Ponder read. 'Er ... if I can just take a quick look inside, Archchancellor ...'

'I don't think that will be necessary,' said the Dean, who had picked up a manuscript that was on the table. 'Listen to this, gentlemen: "... The spirit of this earth is ye fire in wch Pontanus digests his feculent matter, the blood of infants in wch ye 0 & 2) bath themselves, the unclean green Lion wch, saith Ripley, is y* means of joyning ye tinctures of 0 and 3), the broth wch Medea poured on ye two serpents, the Venus by meditation of wch 0 vulgar and the $ of 7 eagles saith Philalethes must be decocted ..." yada yada yada.'

He thumped the manuscript on to the table.

'Genuine alchemical gibberish,' he said, 'and I don't like the sound of it. What's "feculent" mean?

Do we dare find out? I think not.'

'Er ... the man who apparently lived here is described as a giant amongst scientists ...' muttered Ponder, leafing though the booklet.

'Really?' said Ridcully, with a dismissive sniff. 'Hex, please take us to a scientist. We don't mind where he is. Not some dabbler. We want someone who embodies the very essence of science.'

Ponder sighed, and dropped the booklet on to the ground.

The wizards vanished.

For a moment the book lay on the floorboards, front cover upwards showing its title: Great Men of Science No. 2: Sir Isaac Newton. Then it, too, vanished.

There was a thunderstorm grumbling in the distance, and black clouds hung over the sea. The wizards were back on a beach again. Why is it always beaches?' said Rincewind.

'Edges,' said Ridcully. 'Things happen on the edges.'

They had been happening here. At first glance the place looked like a shipyard that had launched its last ship. Large wooden constructions, most of them in disrepair, littered the sand. There were a few shacks, too, also with that hopeless look of things abandoned. There was nothing but desolation.

And an oppressive, silence. A few sea birds cried and flew away, but that only left the world to the sound of waves and the footfalls of the wizards as they approached the shacks.

At which point, another sound became apparent. It was a rhythmical cracking, a khss ... khss ...

khss behind which it was just possible to hear voices raised in song; the singers sounded as if they were far away and at the bottom of a tin bath.

Ridcully stopped outside the largest shack, from which the sound appeared to be issuing.

'Rincewind?' he said, beckoning. 'One for you, I think.'

'Yes, yes, all right,' said Rincewind, and entered with extreme caution.

It was dark inside, but he could see workbenches and a few tools, with a forgotten look about them. The shack must have been thrown up quickly. There wasn't even a floor; it had been built directly on the sand.

The singing was coming from a large horn attached to a device on a bench. Rincewind wasn't very good at technical things, but there was a large wheel projecting over the edge of the bench and it was turning slowly, probably because of the small weight, attached to it by string, which was gently descending towards the sand.

'Is everything okay?' said Ridcully, from outside.

'I've found a kind of voice mill,' said Rincewind.

'That's amazing,' said a voice from the shadows. 'That's exactly what my master called it.'

His name, he said, was Niklias the Cretan, and he was very old. And very pleased to see the wizards.

'I come up here sometimes,' he said. 'I listen to the voice mill and remember the old days. No one else comes here. They say it's the abode of madness. And they are right.'

The wizards were sitting around a fire of driftwood, that burned blue with the salt. They were tending to huddle, although they'd never admit it. They wouldn't have been wizards if they couldn't sense the strangeness in the place. It had the same depressing effect on the senses as an old battlefield. It had ghosts.

'Tell us,' said Ridcully.

'My master was Phocian the Touched,' said Niklias, and he said it the way of a man telling a story he'd told many times before. 'He was a pupil of the great philosopher Antigonus, who one day declared that a trotting horse must at all times have at least one foot on the ground, lest it fall over.

'There was much debate about this and my master, being very rich and also being a keen pupil, decided to prove that the philosopher was correct. Oh, dreadful day! For it was then the troubles began!

The old slave pointed to some derelict woodwork at the far end of the beach.

'That was our test track,' he said. 'The first of four. I helped him build it with my own hands.

There was a lot of interest at that time, and many people came to watch the tests. We had hundreds, hundreds of slaves lying in rows, peering through little slits at just one tiny area of the track each. It didn't work. They argued about what they had seen.'

Niklias sighed. 'Time, said my master, was important. So I told him about work gangs, and how songs helped us keep time. He was very excited about that, and after some thought we built the voice mill which you have heard. Do not be afraid. There is no magic in it. Sound makes things shake, does it not? Sound in the big parchment horn, which I stiffened with shellac, writes the pattern of the sounds it hears on a warm wax cylinder. We used the weighted wheel to spin the cylinder, and it worked quite well after we devised the rocking-trap mechanism. After that, we used it to inscribe the perfect song, and every dawn before we began work we would sing it with the machine. Hundreds of slaves, all singing in perfect time on this beach. The effect was amazing.'

'I bet it was,' said Ridcully.

'But still it did not work, no matter what we devised. A trotting horse travels too fast. My master told me that we must be able to count in tiny parts of time, and after much thinking we built the toc-toc machine. Would you care to see it?'

It was like the voice mill, but had a much bigger wheel. And a pendulum. And a big pointer. As the big wheel turned very slowly, smaller wheels inside the mechanism spun in a blur, and caused a long pointer to revolve against a white-painted wooden wall, along an arc covered in tiny markers. The whole device was mounted on wheels, and had probably taken four men to move.

'I come and grease it occasionally,' said Niklias, patting the wheel. 'For old time's sake.'

The wizards looked at one another with a tame surmise, which is a wild surmise that had been thought about for a while.

'It's a clock,' said the Dean.

'Pardon?' said Niklias.

'We have something like them,' said Ponder. 'We use them for telling the time.'

The slave looked puzzled. 'For telling the time what?' he said.