After some time usefully employed in acquiring and diffusing a competent knowledge of cosmopographical, nautical, and astronomical science, Don Henry resolved to devote a considerable portion of the revenue which he enjoyed as Grand Master of the Order of Christ, in continuing and extending those projects of nautical discovery which had long occupied his attention. Accordingly, about the year 1418, a new expedition of discovery was fitted out for the express purpose of attempting to surmount the perils of Cape Bojador. In this expedition Juan Gonzales Zarco and Tristan Vaz Texeira, two naval officers of the household of Don Henry, volunteered their services; and, embarking in a vessel called a _barcha_[3], steered for the tremendous cape. The Portuguese were hitherto ignorant of the prevailing winds upon the coast of Africa, and the causes by which their influence is varied or increased. Near the land, and between the latitudes of 28° and 10° north, a fresh gale almost always blows from the N.E. Long sand-banks, which extend a great way out to sea, and which are extremely difficult to be distinguished in the mornings and evenings, and the prevailing currents, were powerful obstacles to the enterprise of these navigators. About six leagues off Cape Bojador, a most violent current continually dashes upon the breakers, which presented a most formidable obstacle to the brave but inexperienced mariners. Though their voyage was short, they encountered many dangers; and, before they could reach the cape, they were encountered by a heavy gale from the east, by which the billows of the Atlantic became too heavy to be resisted by their small vessel, and they were driven out to sea. On losing sight of their accustomed head lands, and being forced into the boundless ocean for the first time, the ships company gave themselves up to despair; but, on the abatement of the tempest, they found themselves unexpectedly within view of an island, situated about 100 leagues west from the coast of Africa. With extreme joy they beheld the coast of this island extending about twenty miles in length, to which they gave the name of Puerto Santo, because first discovered upon the feast of All Saints. This is the smaller of the Madeiras, being only about two miles broad; and, as the only roadstead is upon the south-west side, the Portuguese probably anchored upon that side to be under the lee shelter of the island from the remnants of the tempest from which they had happily escaped.