Geography

​Let it be assumed, then, that the earth together with the sea is spherical, having one and the same surface with the high seas. For the projecting part of the earth, being small and capable of escaping notice in such a great magnitude, would be concealed, so that we do not speak of the spherical shape in these matters as if it were turned on a lathe, nor as the geometer does in strict theory, but with reference to perception, and that rather rough. Let it then be conceived as having five zones, and the equator as a circle positioned in it, and another circle parallel to this, defining the frigid zone in the northern hemisphere, and some circle passing through the poles cutting these at right angles. Since the northern hemisphere contains two quadrants of the earth, which the equator makes with the circle through the poles, in each of these a quadrilateral region is cut off, of which the northern side is half of the parallel circle near the pole, and the southern side is half of the equator, while the remaining sides are segments of the circle through the poles, opposite to each other and equal in length. In one of these two quadrilaterals (and it would seem to make no difference in which of the two) we say that our inhabited world is situated, washed all around by the sea and resembling an island; for it has been said that this is demonstrated both by perception and by reason. But if anyone disbelieves this argument, it would make no difference for geography to make it an island, or to concede to this which we have received from experience, namely, that from the east on both sides there is a circumnavigation, and also from the west, except for a few of the middle regions. And it makes no difference whether these are bounded by sea or by uninhabitable land; for the geographer seeks to describe the known parts of the inhabited world, and leaves the unknown parts alone, just like those outside of it. And it will be sufficient to complete the whole shape of the so-called island by connecting a straight line between the furthest points of the coastal voyage on either side.

​Let the island, then, be assumed to lie in the said quadrilateral. And we must grasp its apparent size, by taking away from the whole size of the earth our hemisphere, and from this its half, and from this again the quadrilateral in which we say the inhabited world lies. And similarly concerning its shape, we must conceive its appearance, adapting it to our hypotheses. But since the segment of the northern hemisphere between the equator and the parallel circle near the pole taken parallel to it is a spondylos in shape, and the circle cutting the hemisphere in half through the pole also cuts the spondylos in half and makes the quadrilateral, it will be clear that the quadrilateral is half of the surface of the spondylos, upon which lies the Atlantic Ocean, and the inhabited world is a chlamys-shaped island in this, being a part less than half of the quadrilateral. And this is evident both from geometry and from the abundance of the surrounding sea, which covers the extremities of the continents on both sides and draws them together into a tapered shape, and thirdly, from its maximum length and width; of which, the length is seventy thousand stadia, for the most part bounded by a sea no longer navigable because of its magnitude and emptiness, while the other, being less than thirty thousand stadia, is defined by the region uninhabitable on account of heat or cold. For that part of the quadrilateral which is uninhabitable on account of heat itself, having a width of eight thousand eight hundred stadia, and a maximum length of one hundred and twenty-six thousand stadia, which is half of the equator, the remaining part would be greater.