1. The axis is a straight line north, which passes through the center of the globe of the sphere, and is called axis because the sphere revolves on it like a wheel, or it may be because the Wain is there. Chapter 37. On the poles of the heavens. 1. The poles are little circles which run on the axis. Of these one is the northern which never sets and is called Boreas; the other is the southern which is never seen, and is called Austronotius. Chapter 38. On the _cardines_ of the heavens. 1. The _cardines_ of the heavens are the ends of the axis, and are called _cardines_ (hinges) because the heavens turn on them, or because they turn like the heart (_cor_). Chapter 40. On the gates of the heavens. 1. There are two gates of the heavens, the east and the west. For by one the sun appears, by the other he retires. Chapter 42. On the four parts of the heavens. 1. The _climata_ of the heavens, that is, the tracts or parts, are four, of which the first part is the eastern, where some stars rise; the second, the western, where some stars set; the third, the northern, where the sun comes in the longer days; the fourth, the southern, where the sun comes in the time of the longer nights. 4. There are also other _climata_ of the heavens, seven in number, as if seven lines from east to west, under which the manners of men are dissimilar, and animals of different species appear; they are named from certain famous places, of which the first is Meroe; the second, Siene; the third, Catachoras, that is Africa; the fourth, Rhodus; the fifth, Hellespontus; the sixth, Mesopontus; the seventh, Boristhenes.[270] [270] For map showing the _climata_ see Konrad Miller, _Die ältesten Weltkarten_ (Stuttgart, 1895), vol. iii, p. 127. Chapter 43. On the hemispheres. 1. A hemisphere is half a sphere. The hemisphere above the earth is that part of the heavens the whole of which is seen by us; the hemisphere under the earth is that which cannot be seen as long as it is under the earth. Chapter 44. On the five circles of the heavens. 1. There are five zones in the heavens, according to the differences of which certain parts of the earth are inhabitable, because of their moderate temperature, and certain parts are uninhabitable because of extremes of heat and cold. And these are called zones or circles for the reason that they exist on the circumference of the sphere. 2. The first of these circles is called the Arctic, because the constellations of the Arcti are visible enclosed within it; the second is called the summer tropic, because in this circle the sun makes summer in northern regions, and does not pass beyond it but immediately returns, and from this it is called tropic.