Ecclesiastes 1:7

All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again.

All the rivers run into the sea; yet the sea is not full,.... Which flow from fountains or an formed by hasty rains; these make their way to the sea, yet the sea is not filled therewith, and made to abound and overflow the earth, as it might be expected it would. So Seneca says {z} we wonder that the accession of rivers is not perceived in the sea; and Lucretius {a} observes the same, that it is wondered at that the sea should not increase, when there is such a flow of waters to it from all quarters; besides the wandering showers and flying storms that fall into it, and yet scarce increased a drop; which he accounts for by the exhalations of the sun, by sweeping and drying winds, and by what the clouds take up. Homer {b} makes every sea, all the rivers, fountains, and wells, flow, from the main ocean. Hence Pindar {c} calls the lake or fountain Camarina the daughter of the ocean But Virgil {d} makes the rivers to flow into it, as the wise man here; with which Aristotle {e} agrees. So Lactantius {f} says, "mare quod ex fluminibus constat", the sea consists of rivers. Both may be true, for, through secret passages under ground, the waters of it are caused to pass back again to their respective places from whence they flowed, as follows;

unto the place from whence the rivers come, thither they return again; this also illustrates the succession of men, age after age, and the revolution of things in the world, their unquiet and unsettled state; and the unsatisfying nature of all things; as the sea is never full with what comes into it, so the mind of man is never satisfied with all the riches and honour he gains, or the knowledge of natural things he acquires; and it suggests that even water, as fluctuating a body as it is, yet has the advantage of men; that though it is always flowing and reflowing, yet it returns to its original place, which man does not. And from all these instances it appears that all things are vanity, and man has no profit of all his labour under the sun.

{z} Nat. Quaest. l. 3. c. 4.
{a} De Rerum Natura, l. 6.
{b} Iliad. 21. v. 193, &c.
{c} Olymp. Ode 5. v. 4.
{d} "Omnia sub magna", &c. Georgic. l. 4. v. 366, &c.
{e} Meterolog. l. 1. c. 13.
{f} De Orig. Error. l. 2. c. 6.