Under the vigorous direction of a small body of men of learning, of whom Sir Joseph Banks was the most illustrious, the African Association succeeded after years of disappointment in penetrating the veil of mystery in which the interior of northern Africa had so long been wrapped. Since the early African voyages of the Portuguese the conquest of India and of the New World had almost wholly absorbed the oversea activities of the maritime nations of Europe. Nevertheless, although the world had lost much of its interest in Africa, European trade with the Barbary and Guinea coasts had continued to increase. The slave trade largely accounted for the failure of Europeans to penetrate the interior from the coast of Guinea. In the middle of the eighteenth century it was estimated that there were a million negroes in America and that during the whole of the century six million slaves were shipped from different parts of Africa.