Kitap 2
5.3
It is clear that we are in one or other of these hemispheres, namely, the north; we cannot be in both: Broad rivers roll, and awful floods between, But chief the ocean.Odyssey xi. 156, 157.Odyssey xi. 156, 157. And next is the torrid zone. But neither is there any ocean in the midst of the earth wherein we dwell, dividing the whole thereof, nor yet have we any torrid region. Nor is there any portion of it to be found in which the climata are opposite to those which have been described as characterizing the northern temperate zone.
5.4
Assuming these data, and availing himself likewise of astronomical observations, by which the position of every place is properly determined, whether with respect to the circles parallel to the equator, or to those which cut these latter at right angles, in the direction of the poles, the geometer measures the region in which he dwells, and [judges of the extent of] others by comparing the distance [between the corresponding celestial signs]. By this means he discovers the distance from the equator to the pole, which is a quarter of the largest circle of the earth; having obtained this, he has only to multiply by four, the result is the [measure of the] perimeter of the globe.
