vessel is receding, if any bright object be fixed to the mast, it seems gradually to descend and finally to become invisible. And the ocean, which we admit to be without limits, if it had any other figure, could it cohere and exist without falling, there being no external margin to contain it? And the same wonder still recurs, how is it that the extreme parts of the sea, although it be in the form of a globe, do not fall down? In opposition to which doctrine, the Greeks, to their great joy and glory, were the first to teach us, by their subtile geometry, that this could not happen, even if the seas were flat, and of the figure which they appear to be. For since water always runs from a higher to a lower level, and this is admitted to be essential to it, no one ever doubted that the water would accumulate on any shore, as much as its slope would allow it. It is also certain, that the lower anything is, so much the nearer is it to the centre, and that all the lines which are drawn from this point to the water which is the nearest to it, are shorter than those which reach from the beginning of the sea to its extreme parts[457]. Hence it follows, that all the water, from every part, tends towards the centre, and, because it has this tendency, does not fall. CHAP. 66.—HOW THE WATER IS CONNECTED WITH THE EARTH. OF THE NAVIGATION OF THE SEA AND THE RIVERS. We must believe, that the great artist, Nature, has so arranged it, that as the arid and dry earth cannot subsist by itself and without moisture, nor, on the other hand, can the water subsist unless it be supported by the earth, they are connected by a mutual union. The earth opens her harbours, while the water pervades the whole earth, within, without, and above; its veins running in all directions, like connecting links, and bursting out on even the highest ridges; where, forced up by the air, and pressed out by the weight of the earth, it shoots forth as from a pipe, and is so far from being in danger of falling, that it bounds up to the highest and most lofty places. Hence the reason is obvious, why the seas are not increased by the daily accession of so many rivers[458]. (66.) The earth has, therefore, the whole of its globe girt, on every side, by the sea flowing round it. And this is not a point to be investigated by arguments, but what has been ascertained by experience. CHAP. 67. (67.)—WHETHER THE OCEAN SURROUNDS THE EARTH.