These calculations are nearly synonymous with those furnished by Hipparchus, who tells us, that supposing the size of the globe as stated by Eratosthenes to be correct, we can then subtract from it the extent of the inhabited earth, since in noting the celestial appearances [as they are seen] in different countries, it is not of much importance whether we make use of this measure, or that furnished by later writers. Now as the whole circle of the equator according to Eratosthenes contains 252,000 stadia, the quarter of this would be 63,000, that is, the space from the equator to the pole contains fifteen of the sixty divisions711 into which the equator itself is divided. There are four [divisions] between the equator and the summer tropic or parallel passing through Syene. The distances for each locality are calculated by the astronomical observations.
It is evident that Syene is under the tropic, from the fact that during the summer solstice the gnomon at mid-day casts no shadow there. As for the meridian of Syene, it follows very nearly the course of the Nile from Meroe to Alexandria, a distance of about 10,000 stadia. Syene itself is situated about midway between these places, consequently from thence to Meroe is a distance of 5000 stadia. Advancing 3000 stadia southward in a right line, we come to lands unfitted for habitation on account of the heat. Consequently the parallel which bounds these places, and which is the same as that of the Cinnamon Country, is to be regarded as the boundary and commencement of the habitable earth on the south. If, then, 3000 stadia be added to the 5000 between Syene and Meroe, there will be altogether 8000 stadia [from Syene] to the [southern] extremity of the habitable earth. But from Syene to the equator there are 16,800 stadia, (for such is the amount of the four-sixtieths, each sixtieth being equivalent to 4200 stadia,) and consequently from the [southern] boundaries of the habitable earth to the equator there are 8800 stadia, and from Alexandria 21,800.712 Again, every one is agreed that the voyage from Alexandria to Rhodes, and thence by Caria and Ionia to the Troad, Byzantium, and the Dnieper, is in a straight line with the course of the Nile.713
Taking therefore these distances, which have been ascertained by voyages, we have only to find out how far beyond the Dnieper the land is habitable, (being careful always to continue in the same straight line,) and we shall arrive at a knowledge of the northern boundaries of our earth.
Beyond the Dnieper dwell the Roxolani,714 the last of the Scythians with which we are acquainted; they are nevertheless more south than the farthest nations715 we know of beyond Britain. Beyond these Roxolani the country is uninhabitable on account of the severity of the climate. The Sauromatæ716 who live around the Mæotis, and the other Scythians717 as far as the Scythians of the East, dwell farther south.