Bolghai said, ‘Of course the emissions and absorptions vary depending on the plant or beast enclosed, and indeed on its conditions – if the horse is agitated or not, resting or exercising, for instance. All these things we can study.’

Uzzia asked, ‘Who is the man in the box?’

Bolghai seemed puzzled by the question. 'Who? Why – he is the subject. I sent specifications to the slavers regarding size and weight and general health. I hope to extend the studies to compare different ethnicities, ages, health conditions – sex, of course. I am not concerned with who.

‘What is most important is the conclusion. Which is this.’ With the air of a showman he walked them past the compartments containing the grass, the grain. ‘Vegetables, plants, trees – as they grow these things absorb the fixed gas from the air. But if they are burned they release that gas again. Whereas animals, from sheep to pigs to men, they release the fixed gas as they breathe. All of this in the processes of their lives, you see – it seems accurate, as you say, Pyxeas, to think of life as a kind of slow burning, animal life at least. Plants and animals, absorption and release—’

‘Yes, yes. And together they shape the atmosphere – and it shapes them. But to what end, what end? And how does this relate to the longwinter? For somehow it must . . .’

‘Quite so,’ Bolghai said. ‘To explore that I am also running studies of the physical properties of fixed air. Perhaps that will offer some clues. But the properties are subtle, the apparatus unwieldy and preliminary. Nevertheless I have some first results. We can proceed to that when we’re done here.’

‘Good, good,’ Pyxeas murmured. The two scholars wandered off, talking, debating.

Servants stood by Uzzia and Avatak, heads bent, waiting for instructions.

‘I want to get out of here,’ whispered Avatak.

‘Yes. And I’ve got deals to do. We’ve delivered Pyxeas to his scholar; we’ve done our jobs for now. Let’s go.’

42

Uzzia wandered through Daidu, reacquainting herself with a city she’d visited once before. Avatak followed her, gradually finding his bearings.

Within its double walls the city was laid out like a board game played by giants, the rectangle of walls enclosing a grid-pattern of streets, with tidy blocks of houses and inns and manufactories, temples and schools, all on a tremendous scale. Avatak, a boy from a chaotic land of ice and water, even having visited Northland’s mighty Wall, felt utterly out of place in this vision of stone and geometry.