In bodies of unequal sides there are as many measures as there are angles.

The earth is in contact with water and with air, and it gains as much weight from the water as from the air; which is nothing, if they have no motion. And this is taught us by the leaves of the grasses born at the bottom of the water, which rest upon the meadows, and by the leaves and branches of the trees, and likewise by the grasses born on the beds of the waters, which, not bending downward, make it plain that neither air nor water gives of its weight to the earth.

On the weight of water. Either the water has weight or it has not. And if it has weight, why does it not bend the leaves born on the bed where it rests? And if it does not bend them, it does not give of its heaviness to the bed of the water. And if it gives no heaviness, who sustains it? Its bed sustains it, but receives no weight, for it is proved that water has no weight except upon a liquid lighter than itself, such as air and fire and other liquids, like oil and the like. And if this is so, why does a vessel full of water weigh more in air than one full of air? It is not the water that weighs on their sides, but the full vessel weighs in air, which it will not do under water except by the weight of the material of which the vessel is made. The sea does the like upon the earth, its vessel, and the shores exposed to the air are the lips of the vessel that receives it. Which vessel, being joined to the rest of the earth, gives of its weight upon the air of its antipodes in the rising of the sea, because such antipodal seas correspond in weight one to another, being opposite; and by the inequality of their weights, and for this the sea stays in continual change of site, the centre of gravity that the earth has together with the water also changes its site.

Example of the centre of the world.

Imagine the earth to be drawn to the place of the moon together with the water, and that the element of air fills with itself the void of air that the departed earth leaves behind, and that a vessel full of air falls through the air: certainly that vessel, after many ventilated motions - that is, incident and reflected - will settle around the centre of the elements. And the centre of the elements will rest in the air that is inside the vessel, and will not touch the vessel. Or else imagine the earth hollowed out like a ball full of wind: then you will be certain that such a centre will not be in the earth, but in the air clothed by the earth.