Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

     Now is the place, meseems, in these affairs
To prove for thee this too: nothing corporeal
Of its own force can e'er be upward borne,
Or upward go- nor let the bodies of flames
Deceive thee here: for they engendered are
With urge to upwards, taking thus increase,
Whereby grow upwards shining grains and trees,
Though all the weight within them downward bears.
Nor, when the fires will leap from under round
The roofs of houses, and swift flame laps up
Timber and beam, 'tis then to be supposed
They act of own accord, no force beneath
To urge them up. 'Tis thus that blood, discharged
From out our bodies, spurts its jets aloft
And spatters gore. And hast thou never marked
With what a force the water will disgorge
Timber and beam? The deeper, straight and down,
We push them in, and, many though we be,
The more we press with main and toil, the more
The water vomits up and flings them back,
That, more than half their length, they there emerge,
Rebounding. Yet we never doubt, meseems,
That all the weight within them downward bears
Through empty void. Well, in like manner, flames
Ought also to be able, when pressed out,
Through winds of air to rise aloft, even though
The weight within them strive to draw them down.
Hast thou not seen, sweeping so far and high,
The meteors, midnight flambeaus of the sky,
How after them they draw long trails of flame
Wherever Nature gives a thoroughfare?
How stars and constellations drop to earth,
Seest not? Nay, too, the sun from peak of heaven
Sheds round to every quarter its large heat,
And sows the new-ploughed intervales with light:
Thus also sun's heat downward tends to earth.
Athwart the rain thou seest the lightning fly;
Now here, now there, bursting from out the clouds,
The fires dash zig-zag- and that flaming power
Falls likewise down to earth.