Page:1888 Cicero's Tusculan Disputations.djvu/306

 being diffused through the universe, and performing all things with judgment and reason, attracts the extremities to the centre.

If, then, the world is round, and if on that account all its parts, being of equal dimensions and relative proportions, mutually support and are supported by one another, it must follow that as all the parts incline to the centre (for that is the lowest place of a globe) there is nothing whatever which can put a stop to that propensity in the case of such great weights. For the same reason, though the sea is higher than the earth, yet because it has the like tendency, it is collected everywhere, equally concentres, and never overflows, and is never wasted.

The air, which is contiguous, ascends by its lightness, but diffuses itself through the whole; therefore it is by nature joined and united to the sea, and at the same time borne by the same power towards the heaven, by the thinness and heat of which it is so tempered as to be made proper to supply life and wholesome air for the support of animated beings. This is encompassed by the highest region of the heavens, which is called the sky, which is joined to the extremity of the air, but retains its own heat pure and unmixed.

XLVI. The stars have their revolutions in the sky, and are continued by the tendency of all parts towards the centre. Their duration is perpetuated by their form and figure, for they are round; which form, as I think has been before observed, is the least liable to injury; and as they are composed of fire, they are fed by the vapors which are exhaled by the sun from the earth, the sea, and other waters; but when these vapors have nourished and refreshed the stars, and the whole sky, they are sent back to be exhaled again; so that very little is lost or consumed by the fire of the stars and the flame of the sky. Hence we Stoics conclude—which Panætius is said to have doubted of—that the whole world at last would be consumed by a general conflagration, when, all moisture being exhausted, neither the earth could have any nourishment, nor the air return again, since water, of which it is formed, would then be all consumed; so that only fire would subsist; and