Voyage length and death rate do not track each other

Records of early slaving voyages between 1534 and 1700 allow two quantities to be measured for each arrival region in the Caribbean: how long the crossing took, and what share of the captives died on it. The two do not line up. Voyages to the Dutch islands were typically longer than those to British or French colonies and still returned lower mortality. Time at sea therefore explains less than one would expect. What appears to weigh more is the condition people were in when they boarded, which depended on how far they had been marched to the coast, how long they were held in barracoons there, and what diseases were circulating at that particular embarkation point. Alongside that sit the practices of the carrier: how tightly the hold was packed, what water and food were issued, whether the sick were treated at all. Death on the Middle Passage was a variable owners could influence, and the figures show which owners bothered.

Kongo kings had been trying for a century to open a direct line to Rome that Portugal could not cut. In 1604 Alvaro II sent Antonio Nsaku ne Vunda, the Mani Vunda, holder of the oldest religious office in the kingdom and the authority that sanctioned the king's own. He was held up for years in Spain. He landed at Civita Vecchia mortally ill, attended by a few servants and a Spanish Carmelite who had visited the Kongo as a young man, and reached Rome on 5 January 1608, the eve of Epiphany, the feast that celebrates the kings of the world coming to Christ with gifts. Pope Paul V came to his room. The ambassador commended the king and church of the Kongo to him and died. The scene was painted into the frescoes of the Vatican Library and his bust stands in Santa Maria Maggiore.

In March 1685 the French crown issued the edict known as the Code Noir. Its sixty articles set out how enslaved people in the French colonies were to be held, fed, clothed, punished, married, baptised and buried. It required conversion to Catholicism and expelled Jews from the colonies. It defined the enslaved as movable property while also treating them as persons capable of crime and of religious duty, a contradiction the colonial courts spent a century managing. It fixed that a child followed the condition of its mother, which made every child born to an enslaved woman the property of her owner and made rape profitable. It placed some limits on masters, requiring rations and clothing and forbidding certain killings, and enforcement of those limits was rare. The edict framed French colonial slavery until 1848. Saint-Domingue was the colony where it governed the most people, and the people it governed there ended it themselves in 1793.

Louis XIV of France and William III of England closed their war in 1697 by exchanging territory neither of them had ever seen. The Treaty of Ryswick was a general settlement covering Europe, North America and the Caribbean, and among its terms Spain gave up the western third of Hispaniola to France. Spain had held nominal title to the whole island for two centuries and had governed the western end of it hardly at all, its own settlers having withdrawn eastward long before. France received the piece that turned out to matter. Over the following century Saint-Domingue produced revenue on a scale that is hard to state without sounding careless. By the 1780s the colony was worth more to France, in trade and customs receipts, than the thirteen British colonies of North America were worth to Britain. One third of one Caribbean island out-earned the eastern seaboard of a continent. That is the wealth the enslaved population created, and it is the wealth they carried out of the empire with them.