In the slow progress of discovery, the perils endured by the officers and men employed by Don Henry, from the Moors and Negroes, frequently occasioned murmurs against his plans of discovery; but the several clusters of islands, the Madeiras, Cape Verd, and Açores, formed a succession of maritime and commercial colonies, and nurseries for seamen, which took off from the general obloquy attending the tedious and hitherto unsuccessful attempts to penetrate farther into the southern hemisphere, and afforded a perpetual supply of navigators, and a stimulus to enterprize. The original prejudices against the possibility of navigating or existing in the torrid zone still subsisted, and although the navigators of Don Henry had gradually penetrated to within ten degrees of the equator, yet the last successive discovery was always held forth by the supporters of ignorant prejudice, as that which had been placed by nature as an insurmountable barrier to farther progress in the Atlantic. In this situation, the settlement of the Açores was of considerable importance. In 1457, Don Henry procured the grant of many valuable privileges to this favourite colony, the principal of which was the exemption of the inhabitants from any duties on their commerce to the ports of Portugal and even of Spain. In 1461, a fort was erected in the isle of Arguin on the African coast of the Moors, to protect the trade carried on there for gold and negro slaves. Next year, 1462, Antonio de Noli, a Genoese, sent by the republic to Portugal, entered into the service of Don Henry, and in a voyage to the coast of Africa, discovered the islands which are known by the name of the Cape de Verd Islands, though they lie 100 leagues to the westward of that Cape. In the same year Pedro de Cintra, and Suera de Costa, penetrated a little farther along the coast of Africa, and discovered the river or Bay of Sierra Liona or Mitomba, in lat. 8° 30' N. This constituted the last of the Portuguese discoveries, carried on under the direct influence and authority of Don Henry, the founder and father of modern maritime discovery, as he died next year, 1463, at Sagres, in the sixty-seventh year of his age; and, for a time, the maritime enterprise of the Portuguese nation was palsied by his death.