Irisis’s blue eyes flashed. ‘You couldn’t manage a dung fight in a pigsty! I’ll be crafter here one day, over you! Then you’ll know it.’ She stood by the door as Tiaan went out. There was no chance to put the book back.

Returning to her bench, Tiaan watched Irisis across the room as she donned goggles and mask and sat down at her grinding wheel. It began to whine and the artisan took up a crystal. Soon the air was full of drifting specks.

Tiaan worked fruitlessly for hours, until her head drooped. She laid it on the bench, then realised that the manufactory was silent. It must be midnight. Plodding to her room, she washed in a basin of cold water and fell onto her straw-stuffed pallet.

As soon as her head hit the pillow, Tiaan’s worries returned and, though exhausted, she found herself wide awake. She went over her problems again and again, quite uselessly. Finally, knowing she was never going to get to sleep, she lit a candle, locked her door and took out the forbidden book.

She did not open it immediately. Tiaan was not sure she should look at it at all, but if she took it back to the crafter’s workshop, Irisis’s spies would tell her at once. If she handed it in to the overseer after this delay there would be suspicion that she’d read it first. The scrutator had watchers in the manufactory and little escaped their attention. She would be marked for life.

She considered hurling it into one of the furnaces when no one was looking. However, if the book was protected by a spell, as such things often were, anything might happen. Besides, books were precious, sacred things and Tiaan could not imagine burning one. She could hide it, but what if someone unsuitable found it? What if it fell into the hands of the enemy?

Tiaan opened the book. The paper had a lovely silky feel. The text was written in a number of different hands, no doubt a copy. The language was the common speech spoken throughout the south-east, so she could read the words, though they made little sense. That was not surprising. Her day book, which contained details of her work on controllers, would be equally incomprehensible to most people. Then, as she was flipping through, a heading caught her eye.

Application of the Special Theory to the Powering of Mechanical Contrivances

My Special Theory of Power describes the diffuse force, or field, that surrounds and permeates the fabric of nodes. It is this force that mancers have drawn upon since the Secret Art was first used, at least seven millennia ago. However, mancing has always been restricted by our inability to understand the field: where it comes from, how it changes over time and how it can safely be used.

Furthermore, all drawn power must pass through the mancer first, which causes aftersickness, and the greater the power the worse the effects. Too great a drain of power will be, and has proven many times, horribly fatal.

The traditional solution has been to enchant an artefact, such as a mirror, ring or jewel, and simply trigger the device when needed. This also has problems: artefacts are notoriously difficult to control, may become corrupted over time (witness the Mirror of Aachan) and once discharged are useless until they can be recharged.

Yet we know the ancients used devices with the capacity to replenish themselves. We do not know how that was done, but how else can we explain such long-lived devices as the Mirror, Yalkara’s protected fortress of Havissard, or contrivances that used such prodigious quantities of power as Rulke’s legendary construct?

The field, the weakest of the five elemental forces, is the only one we mancers have ever been able to tap. Nonetheless, much can be done with it. My Special Theory enables us to understand the diffuse force, and perhaps create a controller apparatus to tap it safely. Instead of all power being drawn through the mancer, with its limitations of frail flesh, the mancer simply senses the field and draws just enough power to channel the flow, via the ultradimensional ethyr, directly into the controller. The controller can then transmit it to power the contrivance, whether this be a mechanical cart, a pump or any other mechanism required.

Being a humble theoretician, I will leave the design of such devices to those with the aptitude and interest in such things. Suffice it to say that any such device should comprise the following components …

Tiaan knew all about such devices; that was her work. She skipped forward a few paragraphs.

The process may generate a shifting aura about the crystal powering the controller, perhaps mimicking the aurora-like field about the node from which the power was drawn. A nearby sensitive might be able to detect this aura, though in normal use it is expected to be insignificant …

Tiaan put the book down. This was the very document wherein Nunar first set down the principles of controllers, nearly a hundred years ago. Her theory had enabled the construction of clankers and certain other secret devices, without which the war would have been lost long ago.

She ploughed on. Nunar went on to speculate about a General Theory of Power, which would deal with nodes themselves, the several different strong forces they were expected to be made of, how they related to each other and, finally, how such prodigious forces might be tapped. Nunar noted, however, that nodal forces might never be tapped safely. She also mentioned the holy grail of theoretical mancers, the Unified Power Theory, which would reconcile all the forces mancers knew of, weak and strong, in terms of a single field. Nunar closed the section by stating that such a theory seemed as far off as ever.

Tiaan hid the book behind a loose brick in the wall, under her bed. It seemed no use at all.

She dozed briefly, her head crackling with fractured crystal dreams, to wake with the answer in her mind. She must design a device to test the faulty hedrons and read what had happened to them. Only then could she find a way to solve the problem. Sitting up in bed, Tiaan reached for slate and chalk and began sketching.

She had just completed a rough sketch, and blown out her candle, when Tiaan heard the rattle and groan of a clanker coming up the road. It had to be Ky-Ara returning. Since it was practically dawn, she dressed and went out.

A sleepy attendant with a lantern was opening the side gate as she arrived. Gi-Had was there too. He must have returned in the night. Tiaan watched the monster emerge from the dark. The clanker had covered lanterns on the front, a broad, segmented body made of overlapping plates of armour, and four pairs of mechanical legs driven by ingenious gearing. It was large enough to carry ten people and all their gear, though in bone-shaking discomfort. The shooter’s platform on top, with its mechanical catapult and javelard, was empty.

The clanker clumped into the shed and stopped. The mechanism creaked and groaned, then there was silence save for the whine of the twin iron flywheels that stored power in case the field was interrupted momentarily. The flywheels would still be going at dinnertime, slowly running down.

The back hatch opened. A slim young man climbed out, pack in one hand, a satchel in the other. He stretched, gave the machine an anxious pat on the flank and turned around.

Ky-Ara was not overly tall. His lean, handsome face was marred by a weak jaw. A shock of wiry hair stood out in all directions. His dark eyes were red-rimmed. There was a smudge of black grease across one cheek. Despite all that, Tiaan rather liked the look of him.

‘It’s good to have her whole again,’ Ky-Ara said to Gi-Had, avoiding Tiaan’s eye. ‘After the controller died… I thought I’d never drive her again.’

His face crumbled. The bond between clanker and operator was intense, almost like that between lovers, and a threat to it had been known to cause mental breakdown. Ky-Ara looked close to one now. Tiaan felt for him.