PART EIGHT

ON THE HORIZON

[936] a. What the true site of the horizon is.

Horizons lie at various distances from the eye, seeing that we call horizon the place where the brightness of the air ends at the boundary of the earth; and it is seen in as many positions along one and the same perpendicular above the centre of the world as there are heights of the eye that beholds it. For the eye, placed at the skin of a calm sea, sees that horizon near, about half a mile off; and if a man raises his eye by the measure of his whole height, the horizon is seen distant from him by seven miles, and thus at every degree of height he discovers the horizon more remote from himself. Whence it happens that those who are on the summits of the high mountains near the sea see the circle of the horizon very far from them; but those who are inland do not have the horizon at an equal distance, because the surface of the earth is not equally distant from the centre of the world, and so is not of perfect sphericity, as is the skin of water; and this is the cause of such variety of distances between the eye and the horizon.

Never will the horizon of the sphere of water be higher than the soles of the feet of him who beholds it while standing in contact with those soles, by the same contact that the boundary of the sea has with the boundary of the land uncovered by the waters.

b. The horizon of the sky is sometimes very near, and above all for one who finds himself beside the summits of the mountains, and he sees it generated at the edge of that summit; and turning back toward the horizon of the sea he will see it most remote.