Strata

perched incongruously in the whirring underworld. They had a new look unlike their surroundings, which were worn. Well-looked after, carefully maintained, but worn.
    Marco raised the subject while they were sitting with their backs against a dumbwaiter.
    ‘I know,’ he said. ‘If the disc people had an industrial revolution and then took a look at the underside of their world, it’d scare the life out of them.’
    Silver chewed on another mouthful of what, Marco presumed, was lightly-cooked shand.
    ‘It seems remarkably remiss of the disc builders to allow this dereliction,’ she said. ‘I have noticed quite a number of obviously broken-down devices. Surely they could be repaired?’
    ‘Who repairs the machines that do the repairing?’ said Marco. ‘A machine like the disc must blow a whole lot of fuses in a hundred years or so. What do you do when the robot that repairs the machines that make the parts for the factory that builds the robots that service the waldoes that make the fuses crashes its cog? Unless you get periodic servicing from outside, the disc gradually breaks down.’
    ‘We could ask the robot,’ said Silver.
    It was a sick joke. The robot would answer any direct question about the mechanical scenery – they had been treated to a ten-minute lecture onthe tide regulation machinery, for example – but ignored all the others. Marco had toyed with the idea of prising its lid off with something, but allowed caution to get the better of him.
    ‘The place with the red lights must have been out near the disc rim,’ said Silver. ‘I have a feeling we’re approaching the hub again. Perhaps we can ask Kin.’
    The robot, which had been sitting silently a few metres away, rolled forward.
    ‘We are refreshed?’ it asked cheerfully. ‘We will proceed?’
    They stood up stiffly. The cuboid robot led them along a catwalk that opened on to a wide circular gallery, brilliantly lit. Most of the light came from the luminous mist overhead, but an appreciable amount came from the tiny actinic sun.
    It floated perhaps a hundred metres over a perfect relief model of the disc surface, several hundred metres across. Except that relief maps didn’t have tiny clouds, trailing minute shadows across the land. Marco had never seen them with active volcanoes, either.
    There was no railing to the gallery. The disc-map glittered a metre below it, sunlight glinting off seas that looked disconcertingly real.
    Marco stared down for a long time. Then he said, ‘I give up. It’s beautiful. What’s it for?’
    ‘One thinks of architect’s models,’ rumbled Silver. ‘However, let me draw your attention toa flaw. See over there, just beyond the inland sea?’
    Marco squinted, and gave up. ‘No,’ he said. ‘The disc builders either had damn good eyesight or all this was just for show.’
    He looked around for the robot. It wasn’t there.
    ‘We wish to view the disc map more closely,’ Silver was saying to the empty air. Something like a flying slab of glass glided around the map from the far side and hovered in front of her. She stepped aboard gingerly. Under her weight it didn’t even wobble.
    ‘I see it,’ said Marco, ‘but I don’t believe it. How did you do it?’
    ‘Just a knack,’ said Silver. ‘I think I’m getting to understand the way things work around here. Coming?’
    The glass carpet responded neatly to Silver’s spoken directions. It skimmed across the map mere centimetres from the clouds. Marco had a strange urge to reach down and stir some into a cyclone. The map was frighteningly real. If he leaned over and touched it, would a giant hand appear in the disc sky?
    When the shand spoke again he looked down obediently through the glass.
    There was scarred land down there, burned and broken. And in the centre of it was a neat round hole.
    Later Silver found that raising the platformslightly magnified the scene immediately beneath. There appeared to be no limit to the resolving power. There were people down there, microscopic figures that were almost immobile.
    Only
almost
. Every second the scene flickered, and the figures took up slightly different positions. Marco spent an age entranced at the sight of a homunculus cutting wood.
Flick
– the axe in the air –
flick
– biting into the tree –
flick
– back in the air; and a wedge of raw wood bitten by magic out of the trunk.
    ‘It could be done,’ he said, half to himself. ‘All you’d have to do is correlate sensory inputs