The mouth of the Senegal, then called Senaga, was entered in 1445 by the Portuguese navigator Dinas Diaz (who thought it a western arm of the Nile), and in 1455 Cadamosto ascended the river for some distance.
Associated with it are Francesco Pizigano (1367-1373), Francesco de Cesanis (1421), Giacomo Giroldi (1422-1446), Andrea Bianco (43-44) Giovanni Leardo (1442-1452), Alvise Cadamosto, who was associated with the Portuguese explorers on the west coast of Africa (1454-1456) and whose Portolano was printed at Venice in 1490, and Fra Mauro (1457).
It was possibly visited by Genoese navigators in 1291, and was certainly discovered by the Portuguese c. 1446, but was first explored for any distance from its mouth (1455) by the Venetian Alvise Cadamosto (q.v.), who published an account of his travels at Vicenza in 1507 (La Prima Navigazione per l'Oceano alle terre de' Negri della Bassa Ethiopia) .
At length the consecutive efforts of the navigators employed by Prince Henry of Portugal - Gil Eannes, Diniz Diaz, Nuno Tristam, Alvaro Fernandez, Cadamosto, Usodimare and Diego Gomez - made known the coast as far as the Gambia, and by the end of the 15th century the whole region was familiar to Europeans.
Slaveraiding continued ceaselessly; by 1446 the Portuguese had carried off nearly a thousand captives from the newly surveyed coasts; but between this time and the voyages of Cadamosto in 1455-1456, the prince altered his policy, forbade the kidnapping of the natives (which had brought about fierce reprisals, causing the death of Nuno Tristam in 1446, and of other pioneers in 1445, 1448, &c.), and endeavoured to promote their peaceful intercourse with his men.
After this the chief matters worth notice in Dom Henry's life are, first, the progress of discovery and colonization in the Azores - where Terceira was discovered before 1450, perhaps in 1445, and apparently by a Fleming, called "Jacques de Bruges" in the prince's charter of the 2nd of March 1450 (by this charter Jacques receives the captaincy of this isle as its intending colonizer); secondly, the rapid progress of civilization in Madeira, evidenced by its timber trade to Portugal, by its sugar, corn and honey, and above all by its wine, produced from the Malvoisie or Malmsey grape, introduced from Crete; and thirdly, the explorations o Cadamosto and Diogo Gomez.
We hear also of one Master Peter, who inscribed and illuminated maps for the infante; the mathematician Pedro Nunes declares that the prince's mariners were well taught and provided with instruments and rules of astronomy and geometry "which all map-makers should know"; Cadamosto tells us that the Portuguese caravels in his day were the best sailing ships afloat; while, from several matters recorded by Henry's biographers, it is clear that he devoted great attention to the study of earlier charts and of any available information he could gain upon the trade-routes of north-west Africa.