Let us now go back to those southern countries and see what they had been doing toward maritime exploration during these thousand years and more when the Scandinavians were so busy in the north. It was principally perfecting the knowledge of the world their fathers knew. From the very first men had tried to make maps, and succeeded fairly well for small spaces; but to make a map of the whole world was a task that defied human knowledge for many centuries. After Aristotle’s time all men of education understood that the world was a sphere; and about 150 B. C. Hipparchus, borrowing an idea from the Babylonians, taught the Greeks that the way to place their towns and mountains and rivers and the outlines of the coast correctly upon a model of the world, was to determine their position by observations of the heavenly bodies. Thus the ideas of latitude and longitude originated. He could not apply his method practically very far, because there were few or no accurate astronomical observations away from a few cities in Egypt and Greece; but two hundred and fifty years later Ptolemy, a learned mathematician of Alexandria, gathered all the facts obtainable, and made an attempt which bore a rude resemblance to the truth and served as the best and almost the only account of the world for several hundred years. Ptolemy flourished about 150 A. D. His book describes Asia as far east as the Malayan peninsula, Africa south to Zanzibar and the Gulf of Guinea, and shows a knowledge of Europe as far north as the Shetland Islands (Ultima Thule) and Denmark; the original work seems to have contained no maps, but these were added to it about 500 A. D. by another mathematician named Agathodæmon. It is called the Almagest. Nothing of value was added to this during the long stagnant period of the world called the middle ages, when the love of learning declined and men fell back into the old traditions, even to the extent of being taught by their priests that it was a sin to believe that the world was round. In those times the Arabs of Bagdad nourished knowledge more than any one else, but even they did little for geography. Finally the people of Europe began to wake up and look at things for themselves, instead of tamely accepting whatever the Pope of Rome or somebody else told them, and going and coming as he directed, regardless of whether it was for their interest to do so or not. One of the first and one of the most important influences of this revival in a desire for learning and the means for larger activity among men was the sudden extension of navigation; and this could not have come about, nor amounted to much, had the mariner’s compass not been invented. [Illustration: “Off, thou Norseland Terror, clouding Hellas with the jealous wraith Which, the gods of old enshrouding, Froze their hearts, the poet saith!” ]