 In the seventeenth century, the Jesuits had two colleges, one at Loanda, another, of minor importance, at San Salvador.On the whole, Christianity never took firm root, and was early brought into discredit by the slave-trading Portuguese.While the Portuguese always confined themselves to the Lower Congo, as early as the seventeenth century the missionaries had traversed the course of the Zaire, and a seventeenth-century map has been discovered which traces the river according to data supplied by them.