All well and good, but no matter how much air they blasted into the charcoal fire, causing the iron to run white as the sun and liquid as water, or even thinner, the cannons that resulted were just as prone to cracks as before. And Nadir would appear, unannounced, aware of even the latest results. Clearly he had his spies in the compound, and did not care if Bahram knew it. Or wanted him to know it. And so he would show up, not pleased. His look would say, More, and quickly! even as his words reassured them that he was confident they were doing the best they could, that the Khan was pleased with the flight tables. He would say, 'The Khan is impressed by the power of mathematics to stave off Chinese invaders,' and Bahram would nod unhappily, to indicate he had got the message even if Khalid had studiously avoided seeing it, and he would hold back from asking after the assurance of an amun for Iwang the following spring, thinking it might be best to trust to Nadir's good will at a better time, and go back to the shop to try something else.

A New Metal, a New Dynasty, a New Religion

Just as a practical matter, then, Bahram was getting interested in a dull grey metal that looked like lead on the outside and tin on its interior.

There was obviously very much sulphur in the mercury – if that whole description of metals could be credited – and it was, at first, so nondescript as to pass notice. But it was proving in various little demonstrations and trials to be less brittle than iron, more ductile than gold, and, in short, a different metal than those mentioned by Al Razi and Ibn Sina, strange though that was to contemplate. A new metal! And it mixed with iron to form a kind of steel that seemed as if it would work well as cannon barrel material.

'How could there be a new metal?' Bahram asked Khalid and Iwang. 'And what should it be called? I can't just keep calling it the grey stuff.'

'It's not new,' Iwang said. 'It was always there among the rest, but we're achieving heats never before reached, and so it expresses out.'

Khalid called it leadgold as a joke, but the stuck name stuck for lack of another. And the metal, found now every time they smelted certain bluish copper ores, became part of their armoury.

Days passed in a fever of work. Rumours of war to the east increased. In China, it was said, barbarians were again crashing over the Great Wall, bringing down the rotten Ming dynasty and setting that whole giant off in a ferment of violence that was now rippling outwards from it. This time the barbarians came not from Mongolia but Manchuria, northeast of China, and they were the most accomplished warriors ever yet seen in the world, it was said, and very likely to conquer and destroy everything in their path, including Islamic civilization, unless something was done to make a defence against them possible.

So people said in the bazaar, and Nadir too, in his more circuitous way, confirmed that something was happening; and the feeling of danger grew as the winter passed, and the time for military campaigns came around again. Spring, the time for war and for plague, the two biggest arms of six armed death, as Iwang put it.

Bahram worked through these months as if a great thunderstorm were always visible, just topping the horizon to the east, moving backwards against the prevailing winds, portending catastrophe. Such a painful edge this added to the pleasure he took in his little family, and in the larger familial existence of the compound: his son and daughter racing about or fidgeting at prayers, dressed impeccably by Esmerine, and the very politest of children, except when enraged, which both of them had a tendency to become to a degree that astonished both their parents. It was one of their chief topics of conversation, in the depths of the night, when they would stir and Esmerine go out briefly to relieve herself, then return and pull off her shift again, her breasts silvery raindrops spilling down her ribs in the moonlight, over Bahram's hands as he warmed them, in that somnolent world of second watch sex that was one of the beautiful spaces of daily life, the salvation of sleep, the body's dream, so much warmer and more loving than any other part of the day that it was sometimes hard in the mornings to believe it had really happened, that he and Esmerine, so severe in dress and manner, Esmerine who ran the women at their work as hard as Khalid had at his most tyrannical, and who never spoke to Bahram or looked at him except in the most businesslike way, as was only fitting and proper, had in fact been transported together with him to whole other worlds of rapture, in the depths of the night in their bed. As he watched her work in the afternoons, Bahram thought: love changed everything. They were all just animals after all, creatures God had made not much different from monkeys, and there was no real reason why a woman's breasts should not be like the udders on a cow, swinging together inelegantly as she leaned forwards to work at one labour or another; but love made them orbs of the utmost beauty, and the same was true of the whole world. Love put all things under a description, and only love could save them.

In searching for a provenance for this new 'leadgold', Khalid read through some of the more informative of his old tomes, and he was interested when he came on a passage in jabir Ibn Hayyam's ancient classic 'The Book of Properties', penned in the first years of the jihad, in which jabir listed seven metals, namely gold, silver, lead, tin, copper, iron and kharsini, meaning 'Chinese iron' dull grey, silver when polished, known to the Chinese themselves as paitung, or 'white copper'. The Chinese, jabir wrote, had made mirrors of it capable of curing the eye diseases of those who looked into them. Khalid, whose eyes got weaker every year, immediately set to the manufacture of a little mirror of their own leadgold, just to see. Jabir also suggested kharsini made bells of a particularly melodious tone, and so Khalid had the rest of the quantity they had on hand cast into bells, to see if their tone was especially pretty, which might help secure the identification of the metal. All agreed that the bells tinkled very prettily; but Khalid's eyes did not improve after looking into a mirror of the metal.

'Call it kharsini,' Khalid said. He sighed. 'Who knows what it is? We don't know anything.'

But he continued to try various demonstrations, writing voluminous commentaries on each test, through the nights and on to many a sleepless dawn. He and Iwang pursued their studies. Khalid directed Bahram and Paxtakor and jalil and the rest of his old artisans in the shops to build new telescopes, and microscopes, and pressure gauges, and pumps. The compound had become a place where their skills in metallurgy and mechanical artisanry combined to give them great power to make new things; if they could imagine something, they could make some rude first approximation of it. Every time the old artisans were able to make their moulds and tools more exactly, it allowed them to set their tolerances finer still, and thus as they progressed, anything from the intricacies of clockwork to the massive strength of waterwheels or cannon barrels could be improved. Khalid took apart a Persian carpetmaking device to study all its little metal pieces, and remarked to Iwang that combined with a rack and pinion, the device might be fitted with stamps shaped like letters, instead of threaders, in arrays that could be inked and then pressed against paper, and a whole page thus written all at once, and repeated as many times as one liked, so that books became as common as cannonballs. And Iwang had laughed, and said that in Tibet the monks had carved just such inkblocks, but that Khalid's idea was better.

Meanwhile Iwang worked on his mathematical concerns. Once he said to Bahram, 'Only a god could have thought these things in the first place. And then to have used them to embody a world! if we trace even a millionth part of it, we may find out more than any sentient beings have ever known through all the ages, and see plainly the divine mind.'