Leonardo Dati, who composed a geographical poem entitled _Della Spera_, during this century, advanced no further. A coloured planisphere showed the earth in the centre of the universe surrounded by the ocean, then the air, then the circles of the planets after the Ptolemaic system, and in another representation of the same kind he figures the infernal regions in the centre of the earth, and gives its diameter as seven thousand miles. He proves himself not to have known one half of the globe by his statement of the shape of the earth--that it is like a T inside an O. This is a comparison given in many maps of the world in the middle ages, the mean parallel being about the 36th degree of north latitude, that is to say at the Straits of Gibraltar; the Mediterranean is thus placed so as to divide the earth into two equal parts. John Beauvau, Bishop of Angiers under Louis XL, expresses his ideas as follows:-- "The earth is situated and rests in the middle of the firmament, as the centre or point is in the middle of a circle. Of the whole earth mentioned above only one quarter is inhabited. The earth is divided into four parts, as an apple is divided through the centre by cutting it lengthways and across. If one part of such an apple is taken and peeled, and the peel is spread out over anything flat, such as the palm of the hand, then it resembles the habitable earth, one side of which is called the east, and the other the west." The Arabians adopted not only the ideas of the ancients, but also the fundamental notions of the cosmographical system of the Greeks. Some of them, as _Bakouy_, regarded the earth as a flat surface, like a table, others as a ball, of which one half is cut off, others as a complete revolving ball, and others that it was hollow within. Others again went as far as to say that there were several suns and moons for the several parts of the earth.