On his return to Portugal he established himself on the rocky promontory of Sagres, and devoted himself to the encouragement of the exploration of the coasts of Africa. Under his direction expedition after expedition set out. First Cape Bojador to the south of the Moroccan coast was doubled by Gil Eannes in 1434[51]. In 1441-2 Antonio Gonsalvez and Nuno Tristam passed Cape Blanco on the Sahara coast, and on the return journey called at the Rio d’Ouro or River of Gold[52], whence they brought back some gold dust and ten slaves. These slaves having been sent by Prince Henry to Pope Martin V, the latter conferred upon Portugal the right of possession and sovereignty over all countries that might be discovered between Cape Blanco and India. In 1445 a Portuguese named João Fernandez made the first over-land exploration, starting alone from the mouth of the Rio d’Ouro, and travelling over seven months in the interior. In the following year the river Senegal was reached, and Cape Verde was doubled by Diniz Diaz; and in 1448 the coast was explored as far as the Gambia river. In 1455-6 Ca’ da Mosto (a Venetian in Portuguese service) and Uso di Mare (a Genoese) discovered the Cape Verde Islands, and visited the rivers Senegal and Gambia, bringing back much information in regard to Timbuktu, the trade in gold and ivory with the coast, and the over-land trade routes from the Niger to the Mediterranean. It is asserted by the Portuguese that some years later two Portuguese envoys actually reached Timbuktu; but the truth of this assertion is somewhat problematical, since, had they done so, they would probably have dissipated to some extent the excessive exaggerations regarding the wealth and importance of the Songhai capital. In 1460 Diego Gomes reached the river and mountain peninsula of Sierra Leone; the last named from the incessant rumble of thunderstorms making the mountain range roar like a lion. In 1462, two years after the death of Prince Henry, Pedro de Sintra explored the coast as far as Cape Palmas in modern Liberia. By 1471 the whole Guinea coast had been followed to the Gold Coast and on past the Niger delta, to the Cameroons and as far south as the Ogowe.