The Greeks and Romans were fertile as speculators, but as navigators they really did very little. Not until the last days of the Republic did the existence of lands beyond the sea become generally known. It was in the time of Sulla that Sertorius brought back the curious story that, when on an expedition to Bætica, he fell in with certain sailors, who declared that they had just returned from the Atlantic islands, which they described as distant ten thousand stadia, or about twelve hundred and fifty miles, from Africa, and as having a wonderful flora and a still more wonderful climate. It was not until a few years later that the Canaries became known as the Fortunate Islands. Notwithstanding all that had been done by the Tyrians and Carthaginians, Pliny refers to the Pillars of Hercules as the limit of navigation. No systematic effort to extend the boundaries of geographical knowledge can be attributed to the Romans. There was no international competition in trade, for the reason that Rome had come to be self-reliant, and, in theory at least, to possess everything that was of value. Interest therefore was purely speculative. There was no compass; there were none but small ships. Added to this, it must be said that there was a general and vivid horror of the western ocean. Pindar declared that no one, however brave, could pass beyond Gades; “for only a god,” he said, “might voyage in those waters.” The views of the Romans were set forth in somewhat systematic form by Strabo and Pomponius Mela. The work of Mela, written during the first half of the first century, had considerable influence throughout the Middle Ages. The first edition was printed in 1471 at Milan, and this was followed by editions at Venice in 1478 and 1482. Of far greater importance were the writings of Ptolemy. Near the end of the second century he not only brought together in systematic form the ideas of those who had gone before him, but he elaborated and set forth a system of his own. His work thus became a great source of geographical information throughout the twelve centuries that were to follow. The book, however, scarcely had any popular significance before the fifteenth century; for until that time it was locked up within the mysteries of the Greek language. But in 1409, a version in Latin disseminated his views throughout Europe. In one respect the theories of Ptolemy were exceptionally important in their bearing upon the western discoveries. It was his belief that the further extension of geographical knowledge was to be obtained by pushing the lines of investigation toward the west rather than toward the north or toward the south. It is of significance in the life of Columbus that the first edition of Ptolemy was printed in 1475, and that several other editions were issued from the press before 1492. It is also of interest to note that the views promulgated by the Alexandrian geographer were essentially the views held and advocated by Columbus.