It was commonly held in the middle ages that the earth is divided into five zones, only two of which may be inhabited. This was a theory advanced by a Greek scientist in the fifth century before our era,[21] and was given currency in medieval times chiefly, perhaps, through the works of Macrobius.[22] At first these zones were conceived as belts drawn across the heavens; later they came to be considered as divisions of the earth’s surface. It will be noted that our author uses the older terminology and speaks of the zones as belts on the heaven;[23] it may be inferred, therefore, that he derived his information from one of the earlier Latin treatises on the nature of the universe.[24] For two thousand years it was believed that human life could not exist in the polar and torrid zones. Even as late as the fifteenth century European navigators had great fear of travel into the torrid zone, where the heat was thought to grow more intense as one traveled south, until a point might be reached where water in the sea would boil. The author of the _King’s Mirror_ seems to doubt all this. He regards the polar zones as generally uninhabitable; still, he is sure that Greenland lies within the arctic zone; and yet, Greenland “has beautiful sunshine and is said to have a rather pleasant climate.”[25] He sees quite clearly that the physical nature of a country may have much to do with climatic conditions. The cold of Iceland he ascribes in great part to its position near Greenland: “for it is to be expected that severe cold would come thence, since Greenland is ice-clad beyond all other lands.”[26] He conceives the possibility that the south temperate zone is inhabited. “And if people live as near the cold belt on the southern side as the Greenlanders do on the northern, I firmly believe that the north wind blows as warm to them as the south wind to us. For they must look north to see the midday and the sun’s whole course, just as we, who dwell north of the sun, must look to the south.”[27] Footnote 21: Parmenides of Ela (ca. 480 B.C.). Nansen, _In Northern Mists_, I, 12. Footnote 22: See below, p. 147 (c. xix). Cf. _Ibid._, 123. Footnote 23: C. xix. Footnote 24: Probably from the writings of Isidore, who speaks of the zones as belts on the heavens. _Etymologiae_, iii, c. xliv; xiii, c. vi; _De Natura Rerum_, c. x. Footnote 25: C. xix. Footnote 26: C. xiii. Footnote 27: C. xxi.