This letter written by Lavigerie to a Catholic mission in subsaharan Africa, calls for collaboration between evangelisation and abolitionism in Africa. The two are seen by Lavigerie as closely interlinked: "missionaries cannot usefully evangelise in those vast regions overrun by slave traders" (1), and abolitionism could not act without European funding, often through the churches. The letter gives an overview of contemporary slavery in Africa, as Lavigerie calls on eye-witness accounts of European travellers and missionaries, including Livingstone, Stanley and Cameron, to confirm his description of an extensive slave trade in Sudan and throughout much of east and central Africa. Lavigerie compares the Indian ocean trade to the transatlantic trade, in order to draw attention to conditions on board the dhows. He also summarises the late nineteenth century abolitionist movement.