On this globe, representing the world, Strabo and the cosmographers of his time placed the habitable world in a surface which he describes in the following way: "Suppose a great circle, perpendicular to the equator, and passing through the poles to be described about the sphere. It is plain that the surface will be divided by this circle, and by the equator into four equal parts. The northern and southern hemispheres contain, each of them, two of these parts. Now on any one of these quarters of the sphere let us trace a quadrilateral which shall have for its southern boundary the half of the equator, for northern boundary a circle marking the commencement of polar cold, and for the other sides two equal and opposite segments of the circle that passes through the poles. It is on one such quadrilateral that the habitable world is placed." He figures it as an island, because it is surrounded on all sides by the sea. It is plain that Strabo had a good idea of the nature of gravity, because he does not distinguish in any way an upper or a lower hemisphere, and declares that the quadrilateral on which the habitable world is situated may be any one of the four formed in this way. The form of the habitable world is that of a "chlamys," or cloak. This follows, he says, both from geometry and the great spread of the sea, which, enveloping the land, covers it both to the east and to the west and reduces it to a shortened and truncated form of such a figure that its greatest breadth preserved has only a third of its length. As to the actual length and breadth, he says, "it measures seventy thousand stadia in length, and is bounded by a sea whose immensity and solitude renders it impassable; while the breadth is less than thirty thousand stadia, and has for boundaries the double region where the excess of heat on one side and the excess of cold on the other render it uninhabitable." The habitable world was thus much longer from east to west than it was broad from north to south; from whence come our terms _longitude_, whose degrees are counted in the former direction, and _latitude_, reckoned in the latter direction. Eratosthenes, and after him Hipparchus, while he gives larger numbers than the preceding for the dimensions of the inhabited part of the earth, namely, thirty-eight thousand stadia of breadth and eighty thousand of length, declares that physical laws accord with calculations to prove that the length of the habitable earth must be taken from the rising to the setting of the sun. This length extends from the extremity of India to that of Iberia, and the breadth from the parallel of Ethiopia to that of Ierne.