Ramusio imagined that the discoveries of Cada Mosto might tend to great importance, as he considered the rivers Senegal and Rio Grande to be branches of the Niger, by which means the Europeans might open a trade with the rich kingdoms of Tombuto and Melli on that river, and thus bring gold from the countries of the Negroes, by an easier, safer, and more expeditious manner, than as conveyed by the Moors of Barbary by land, over the vast and dangerous deserts that intervene between the country on the Niger and Senegal rivers, and Barbary.  As, by the account of Leo, salt is the most valuable commodity throughout the countries of the Negroes, Ramusio proposed that the ships should take in cargoes of salt at the island of Sal, one of the Cape de Verds, and thence supply the countries on the Niger, which was reported to be navigable for 500 miles into the interior; and that they should bring back gold and slaves in return; the latter to be brought to market at St Jago, another of the Cape de Verd islands, where they would be immediately bought up for the West Indies.  All this fine speculation, however, rested on mistaken foundations; as the Niger is altogether an inland river, running to the east, and has no communication with the Senegal and Gambia, which run west into the Atlantic.  Yet time, and the civilization of the natives on the Senegal and Gambia, may hereafter realize this scheme of a valuable traffic into the interior of Africa; but it is fervently to be hoped, that the trade in slaves may never be revived.

In his preface, after an apology for his performance, and making a declaration of his strict adherence to truth in all the particulars he relates, Cada Mosto gives some account of the infant Don Henriquez, or Henry, of Portugal, the great author and promoter of maritime discoveries.  He praises him, as a prince of a great soul and sublime genius, and of great skill in astronomy; and adds, that he applied himself entirely to the service of Christ, by making war against the Moors.  While on death-bed, in 1432, Don John, king of Portugal, exhorted his son Don Henry to pursue his laudable and holy purpose, of persecuting the enemies of the Christian faith, which he promised to perform; and, accordingly, with the assistance of his brother Don Duarte, or Edward, who succeeded to the throne of Portugal, he made war in Fez with success for many years.  Afterwards, the more effectually to harass the Moors, he used to send his caravels, or ships of war, annually, to scour the coasts of Azafi, or Al Saffi, and Messa, on the coast of Africa, without the Mediteranean, by which he did them much damage.  But, having in view to make discoveries along that western coast, he ordered them every year to advance farther towards the south.  They accordingly proceeded till they came to a great cape, which put a stop to their progress southwards for several years, being afraid to go beyond it; whence it took the name it still retains of Cape Non[2]; meaning, that such as went beyond should never return.  Don Henry, however, was of a different opinion, and adding three other caravels to those which had been at the cape, sent them again next year to make the attempt.  They accordingly penetrated about 100 miles beyond that cape, where they found only a sandy coast with no habitations, and returned back to Portugal.