Omons, the author of a geographical poem entitled _The Image of the World_, composed in 1265, who was called the Lucretius of the thirteenth century, was not more advanced than the cosmographers of the former centuries of which we have hitherto spoken. The cosmographical part of his poem is borrowed from the system of Pythagoras and the Venerable Bede. He maintains that the earth is enveloped in the heavens, as the yoke in the white of an egg, and that it is in the middle as the centre is within the circle, and he speaks like Pythagoras of the harmony of the celestial spheres. Omons supposed also that in his time the terrestrial paradise was still existing in the east, with its tree of life, its four rivers, and its angel with a flaming sword. He appears to have confounded Hecla with the purgatory of St. Patrick, and he places the latter in Iceland, saying that it never ceases to burn. The volcanoes were only, according to him, the breathing places or mouths of the infernal regions. The latter he placed with other cosmographers in the centre of the earth. Another author, Nicephorus Blemmyde, a monk who lived during the same century, composed three cosmographical works, among them the following: _On the Heavens and the Earth, On the Sun and Moon, the Stars, and Times and Days_. According to his system the earth is flat, and he adopts the Homeric theory of the ocean surrounding the world, and that of the seven climates. Nicolas of Oresmus, a celebrated cosmographer of the fourteenth century, although his celebrity as a mathematician attracted the attention of King John of France, who made him tutor to his son Charles V., was not wiser than those we have enumerated above. He composed among other works a _Treatise on the Sphere_. He rejected the theory of an antichthonal continent as contrary to the faith. A map of the world, prepared by him about the year 1377, represents the earth as round, with one hemisphere only inhabited, the other, or lower one, being plunged in the water. He seems to have been led by various borrowed ideas, as, for instance, theological ones, such as the statement in the Psalms that God had founded the earth upon the waters, and Grecian ones borrowed from the school of Thales, and the theories of the Arabian geographers. In fact we have seen that Edrisi thought that half of the earth was in the water, and Aboulfeda thought the same. The earth was placed by Nicolas in the centre of the universe, which he represented by painting the sky blue, and dotting it over with stars in gold.