The Sphere of the World with Commentaries

would happen to someone proceeding from the south towards the north. The cause of this matter, however, is the swelling of the Earth. Likewise, if the Earth were flat from the east to the west, the stars would rise just as quickly for the westerners as for the easterners, which is clearly false. Likewise, if the Earth were flat from the north to the south and conversely, the stars that would be of perpetual appearance to someone would always appear to him wherever he might proceed, which is false. But that it is flat appears to the sight of men because of its excessive size.

THAT WATER IS ROUND.

That water also has a swelling and tends toward roundness is evident in this way: let a mark be placed on the seashore and let a ship depart from the harbor, and it may withdraw to such an extent that an eye located near the base of the mast cannot see the mark. When the ship is stationary, however, the eye of the same person located at the top of the mast will clearly see that mark. But the eye located near the base of the mast ought to see the mark better than the one that is at the top, as is evident by lines drawn from both to the mark; and there is no other cause for this matter than the swelling of the water. For let all other impediments be excluded, such as clouds and rising vapors. Likewise, since water is a homogeneous body, the whole will be of the same nature as its parts; but the parts of water, as happens in droplets and dews on grasses, naturally seek a round form, therefore so too does the whole whose parts they are.

THAT THE EARTH IS THE CENTER OF THE WORLD.

That the Earth is situated in the middle of the firmament is evident in this way. To those existing on the surface of the Earth, the stars appear of the same size whether they are in the middle of the sky, or near the rising, or near the setting; and this is because the Earth is equidistant from them. If, indeed, the Earth approached