Further attempts were made in succeeding years. The Portuguese continually advanced and once brought home fish nets which they had taken from the natives to prove that the lands beyond the Cape were inhabited. Soon they penetrated to regions where they found gold-dust and other valuable products, which were taken in honor of the Infante. In consideration of the tremendous expense and the incalculable exertion involved in these voyages the matter of profit was alone taken into account. Naturally no heed was paid to their scientific importance. Explorations beyond the Cape at last proved very profitable and many vessels returned with large cargoes of slaves, for Europeans at that time were not ashamed of man-stealing. They hunted their human victims openly and even used dogs to run down their prey. Slavery was not abhorrent to them. They thought it natural that God should reward their man-stealing with success. A chronicle of the year 1444 says: “At last it pleased God to compensate them for their great suffering in His service with a glorious day’s efforts, for altogether, in men, women, and children, they captured one hundred and sixty-five head.” An important discovery in the year 1445 removed many erroneous conceptions. Dinas Diaz in that year sailed farther south than any navigator had gone before. He passed Cape Blanco, reached the southern line of the Great Desert, and found a region green with palms, and people with black skins. The spot he discovered was called the “Green Cape.” He proved that the theory that the tropics were uninhabitable was false. Aristotle had maintained that the tropical regions must be unpeopled because the overpowering heat of the sun’s rays would destroy all vegetation. Other scholars, among them Ptolemy, were of the same opinion. The theory indeed was so universally accepted at the beginning of the fifteenth century that many a bold adventurer was deterred from making explorations in that direction. In the same year, however, the Senegal, which Diaz had passed unobserved, was discovered on a second voyage. The river was declared to be a branch of the Egyptian Nile. In the following year the Portuguese met with a serious disaster on the African coast. Two vessels, owing to the misplaced confidence of their commanders in the negroes, ventured too near and were greeted by a shower of poisoned arrows. The wounded explorers died after reaching Lisbon, two months later, without having seen anything but sky and water. This disaster, however, did not deter other brave navigators from undertaking further explorations beyond the Green Cape, though they dreaded the poisoned arrows of the natives more than any hardships or perils of the sea. About this time the Azores were colonized by the Portuguese, for these islands had been so little disturbed by man that even the birds could easily be taken by the hand. Henry, the Infante, bestowed the islands upon the explorers as an hereditary tenure.