About the timeline
The voyage between France and Saint-Domingue was about 4 to 7 weeks at the time (it would be cut down to 15-18 days by the mid-1850s). The anonymous colonist who wrote the memoir Mon Odyssée left Bordeaux on 20 July 1791 on Le Bouillant with his family and arrived in Saint-Domingue two days before the insurrection of the 22-24 August 1791 (Popkin, 2011). Thesée, in her study of the Romberg trading house in Bordeaux, gives 5-6 weeks for a merchant ship to cross the Atlantic from Bordeaux to Saint-Domingue (Thesée, 1972). Ducoeurjoly, in 1802, dedicated several pages to the voyage from France in his Manuel des habitans de Saint-Domingue, where, among other useful tips (Is there a hairdresser (perruquier) on board? No, you will have to learn do that yourself, otherwise a sailor with dirty hands will take care of your hair), he told his readers that the trip lasted about 40-45 days (Ducoeurjoly, 1802).
The quote about the "white slaves" comes from a letter dated 20 October 1789 and written by the Intendant (chief administrator) of Saint-Domingue François Barbé-Marbois (it is cited for instance by historian David Geggus in The Haitian Revolution: A Documentary History, from which I borrow much of what follows unless indicated otherwise). That's three months after the Storming of the Bastille, and enough time for the news to arrive to the island, from Le Havre, Bordeaux, or Nantes.
About the quote
François Barbé-Marbois, a French diplomat who had been previously posted in the United States, had been appointed to Saint-Domingue in 1785, and, as it often happens in colonial situations, the "foreigner" butted heads with the colonists, who were already willing to get rid of French tutelage and of the système de l'exclusif (which prohibited them from trading with non-French merchants). Barbé-Marbois was notably involved in the trial of Nicolas Lejeune in 1788, a coffee planter who had been denounced by his own slaves for the tortures he inflicted to them (an official report concluded that "the details would make you shudder with horror"). Lejeune's fellow white planters had intimidated the courts into acquitting him, and Barbé-Marbois, though far from being an abolitionist, was extremely concerned about the effect of the colonists' cruelty on the enslaved. The official report cited above worried that, after witnessing the injustice committed by the judges in the Lejeune case, the slaves would no longer bother to turn to the courts: "reduced to despair, [they] will have no other recourse but revenge". And then, the following year, the Revolution happened, and Barbé-Marbois felt that he was sitting on a powder keg. He wrote on 25 September 1789:
The news of what has been happening in Paris and the kingdom up to July 20 is known here through a multitude of publications, which at first caused some agitation…. The public went very much further than the truth in its speculations…. Our chief concern is with the impression this news has on the slaves. We have omitted no necessary precaution for keeping them within the bounds of obedience. Perhaps the most effective precaution is preventing all the excesses and cruelty of which they were too often the victims.
His next letter, the one dated 10 October, is even more tense:
For ten or twelve days, we have avoided taking up the national cockade, wary of anything that might give the slaves the idea of rallying round a symbol…. It attracts the slaves’ attention far too much; they call it the sign of the emancipation of the whites. We are informed — and people even write us from far-flung corners of the colony — that in the accounts the slaves give one another of the revolution, they are all agreed on one point that seems to have struck them spontaneously. This is that the white slaves have killed their masters and that, now they are free, they govern themselves and have recovered possession of the land. It would be dangerous just trying to destroy these false rumors with a truthful explanation, and we encourage people everywhere to keep silent without adopting an air of mystery.
By then, the colonists were taking "justice" in their own hands and were punishing slaves in ways that "cried out for judicial pursuit". Barbé-Marbois felt impotent: he was watching with horror the white colonists lash out at their slaves to prevent sedition, and he thought that telling slaves what was happening in France would basically make the island erupt in flames. And no matter what he did, information was coming out:
The books from Europe concerning liberty also circulate in Saint Domingue in spite of the precautions we have taken to prevent it. There is so much contact between free people and slaves that it is impossible they don’t know about the efforts being made on their behalf.
His last letter dated 17 October concludes rather ominously:
No officials in the kingdom find themselves in such a critical position as we do. We are acting in the presence of 450,000 slaves who are perhaps only waiting for the first sign of division among the whites to throw themselves into the most terrible uprising.
After that, Barbé-Marbois was forced out of Saint-Domingue by the colonists.
As we can see from Barbé-Marbois' reports, information was very difficult to contain at this stage. The three main populations of the Saint-Domingue - the white colonists, the "free men of colour" (the mixed-race men and women who were as numerous as the whites and often as wealthy), and the enslaved, were all deeply involved in politics, for different reasons: the whites wanted some form of independance/autonomy from France, the free coloured (and the free blacks) wanted equal rights with the whites, and the enslaved wanted to be free. In any case, the debates about the status of each population had been going on for a while, both in France and in the colonies.
Of course, we cannot be sure that random enslaved people did talk about the "white slaves" just a mere months after July 1789: that's what Barbé-Marbois was told - presumably by friendly white or free coloured people -, and it certainly fit his "Saint-Domingue is a powder keg" narrative. But blacks of all conditions had access to information and more than a few were literate, Toussaint Louverture and Henri Christophe among them. This is certainly true for urban slaves who were in close contact with the rest of the population, notably the usually literate free coloured and the free blacks. There's a particularly amusing report by the Chamber of Agriculture in 1785 about the freedom of the enslaved blacks in Cap Français, where the slave population reached 30,000 at the Sunday market: the author complains that the "line of demarcation between whites and slaves has almost vanished" and demands that the authorities put a stop to the insolence of those uppity slaves who don't even step aside to let a white man pass. But even rural slaves had opportunities to meet, organize, and exchange information, for instance in Sunday markets and weekend festivities (Geggus, 1994). Domestic slaves who had learned to read and write were able to forge passes that indicated that they were on errand for a master, making them hard for authorities to distinguish them from free blacks (Flick, 1990). The legendary gathering of the Bois-Caïman of August 1791 that started the insurrection was possibly an amalgamation of two different meetings: a political one that took place on the 14 and a religious one held on the 24 (Geggus, 2002). The 14 August meeting brought together about 200 hundred people, most of them commandeurs, ie plantation foremen (that Geggus calls the "slave elites"), and a report to the Revolutionary Comité de Salut Public claims that a "mulatto or quarteroon man" read to them various papers announcing the decisions of the King and the National Assembly and the arrival of troops from France (Garran de Coulon, 1797).
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