The Sphere of the World with Commentaries

parallels, as if equidistant, not because as much as the first is distant from the second, so the second is distant from the third—for this is false, as has now appeared—but because any two circles joined together are equidistant from each other throughout every part of them, and they are called the equinoctial parallel, the summer solstice parallel, the winter solstice parallel, the arctic parallel, and the antarctic parallel. It is also to be noted that the four smaller parallels, namely the two tropics, the arctic parallel, and the antarctic parallel, distinguish five zones or regions in the heaven. Whence Virgil in the Georgics: "Five zones hold the heaven: of which one is always red with the flashing sun, and always scorched by fire." There are also distinguished the same number of regions on the earth directly underlying the aforementioned zones. Whence Ovid in the first book of the Metamorphoses: "The same number of regions press the earth. Of which, the one that is in the middle is not habitable because of heat. Deep snow covers two; the same number he placed between both, and gave them a temperate climate, flame mixed with cold." That zone, therefore, which is between the two tropics is called uninhabitable because of the heat of the sun running always between the tropics. Similarly, the region of the earth directly underlying that is called uninhabitable because of the heat of the sun running over it. Those two zones, however, which are circumscribed by the arctic circle and the antarctic circle around the poles of the world, are uninhabitable because of excessive cold, because the sun is removed far from them. Similarly, it is to be understood regarding the regions of the earth directly underlying them. Those two zones, however, of which one is between the summer tropic and the arctic circle, and the remaining one which is between the winter tropic and the antarctic circle, are habitable and temperate, being between the heat of the torrid zone which exists between the tropics and the coldness of the extreme zones which are around the poles of the world. Understand the same regarding the regions of the earth directly underlying them.