He looked over at Ismail as a thought occurred to him. 'What is it like now where she came from?' he asked.

The doctor cleared his throat. 'I don't know, Excellency.'

'Tell me what you have heard.'

'I have heard that Firanja west of Vienna is mainly divided between Andalusis and the Golden Horde. The Andalusis occupy the old Frankish lands and the islands north of it. They are Sunni, with the usual sufi and Wahhabi elements fighting for the patronage of the emirs. The east is a mix of Golden Horde and Safavid client princes, many of them Shiites Many sufi orders. They also have occupied the offshore islands, and the Roman peninsula, though it is mostly Berber and Maltese.'

The Sultan nodded. 'So they prosper.'

'I don't know. It rains there more than on the steppes, but there are mountains everywhere, or hills. There is a plain on the north coast where they grow grapes and the like. Al Andalus and the Roman peninsula do well, I gather. North of the mountains it is harder. It's said the lowlands are still pestilential.'

'Why is that? What happened there?'

'It's damp and cold all the time. So it is said.' The doctor shrugged. 'No one knows. It could be that the pale skin of the people there made them more susceptible to plague. That's what Al Ferghana said.'

'But now good Muslims live there, with no ill effects.'

'Yes. Balkan Ottomans, Andalusis, Safavids, the Golden Horde. All Muslim, except perhaps for some Jews and Zotts.'

'But Islam is fractured.' The Sultan thought it over, brushing the odalisque's red pubic hair with his palm. 'Tell me again, where did this girl's ancestors come from?'

'The islands off the north coast of Frankland,' the doctor ventured. 'England. They were very pale there, and some of the outermost islands escaped the plague, and their people were discovered and enslaved a century or two later. It is said they didn't even know anything had changed.'

'Good land?'

'Not at all. Forest or rock. They lived on sheep or fish. Very primitive, almost like the New World.'

'Where they have found much gold.'

'England was known more for tin than gold, as I understand it.'

'How many of these survivors were taken?'

'I have read a few thousand. Most died, or were bred into the general populace. You may have the only purebreds left.'

'Yes. And this one is pregnant by one of their men, I'll have you know. We care for the men as carefully as we do the women, to keep the line going.'

'Very wise.'

The Sultan looked at his Black Eunuch. 'I'm ready for Jasmina now.'

In came another girl, very black, her body almost twin to that of the white girl, though this one was not pregnant. Together they looked like chess pieces. The black girl replaced the white one on the bed. The Sultan stood and went to her.

'Well, the Balkans are a sorry place,' he mused, 'but farther west may be better. We could move the capital of the empire to Rome, just as they moved theirs here.'

'Yes. But the Roman peninsula is fully repopulated.'

'Venice too?'

'No. Still abandoned, Excellency. It is often flooded, and the plague was particularly bad there.'

Sultan Selim pursed his lips. 'I don't – ah – I don't like the damp.'

'No, Excellency.'

'well, we will have to fight them here. I will tell the troops that their souls, the most precious quarter grain of them, will rise up to the Paradise of Ten Thousand Years if they die in defence of the Sublime Porte. There they will live like I do here. We will meet these invaders down at the straits.'

'Yes, Excellency.'

'Leave me now.'

But when the Indian navy appeared it was not in the Aegean, but in the Black Sea, the Ottoman Sea. Little black ships crowding the Black Sea, ships with waterwheels on their sides, and no sails, only white plumes of smoke pouring out of chimneys topping black deckhouses. They looked like the furnaces of an ironworks, and it seemed they should sink like stones. But they didn't. They puffed down the relatively unguarded Bosporus, blasting shore batteries to pieces, and anchored offshore the Sublime Porte. From there they fired explosive shells into Topkapi Palace, also into the mostly ceremonial batteries defending that side of the city, long neglected as there had been no one to attack Konstantiniyye for centuries. To have appeared in the Black Sea – no one could explain it.

In any case there they were, shelling the defences until they were pounded into silence, then firing shot after shot into the walls of the palace, and the remaining batteries across the Golden Horn, in Pera. The populace of the city huddled indoors, or took refuge in the mosques, or left the city for the countryside outside the Theodosian walls; soon the city seemed deserted, except for some young men out to watch the assault. More of these appeared in the streets as it began to seem that the iron ships were not going to bombard the city, but only Topkapi, which was taking a terrific beating despite its enormous impregnable walls.

Ismail was called into this great artillery target by the Sultan. He boxed up the mass of papers that had accumulated in the last few years, all the notes and records, sketches and samples and specimens. He wished he could make arrangements to send it all out to the medical madressa in Nsara, where many of his most faithful correspondents lived and worked; or even to the hospital in Travancore, home of their assailants, but also of his other most faithful group of medical correspondents.

There was no way now to arrange such a transfer, so he left them in his rooms with a note on top describing the contents, and walked through the deserted streets to the Sublime Porte. It was a sunny day; voices came from the big blue mosque, but other than that only dogs were to be seen, as if Judgment Day had come and Ismail been left behind.

Judgment Day had certainly come for the palace; shells struck it every few minutes. Ismail ducked inside the outer gate and was taken to the Sultan, whom he found seemingly exhilarated by events, as if at a fair: Selim the Third stood on Topkapi's highest bartizan, in full view of the fleet bombarding them, watching the action through a long silver telescope.

'Why doesn't the iron sink the ships?' he asked Ismail. 'They must be as heavy as treasure chests.'

'There must be enough air in the hulls to make them float,' the doctor said, apologetic at the inadequacy of this explanation. 'If their hulls were punctured, they would surely sink faster than wooden ships.'

One of the ships fired, erupting smoke and seemingly sliding backwards in the water. Their guns shot forwards, one per ship. Fairly little things, like big bay dhows, or giant water bugs.

The shot exploded down the palace wall to their left. Ismail felt the jolt in his feet. He sighed.

The Sultan glanced at him. 'Frightened?'

'Somewhat, Excellency.'

The Sultan grinned. 'Come, I want you to help me decide what to take. I need the most valuable of the jewels.' But then he spotted something in the sky. 'What's that?' He clapped the telescope to his eye. Ismail looked up; there was a dot of red in the sky. It drifted on the breeze over the city, looking like a red egg. 'There's a basket hanging under it!' the Sultan exclaimed, 'and people in the basket!' He laughed. 'They know how to make things fly in the sky!'

Ismail shaded his eyes. 'May I use the spyglass, Excellency?'

Under white, puffy clouds, the red dot floated towards them. 'Hot air rises,' Ismail said, shocked as it became clear to him. 'They must have a brazier in the basket with them, and the hot air from its fire rises up into the bag and is caught there, and so the whole thing rises up and flies.'

The Sultan laughed again. 'Wonderful!' He took the glass back from Ismail. 'I don't see any flames, though.'