Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

     Again, we view
From dark recesses things that stand in light,
Because, when first has entered and possessed
The open eyes this nearer darkling air,
Swiftly the shining air and luminous
Followeth in, which purges then the eyes
And scatters asunder of that other air
The sable shadows, for in large degrees
This air is nimbler, nicer, and more strong.
And soon as ever 'thas filled and oped with light
The pathways of the eyeballs, which before
Black air had blocked, there follow straightaway
Those films of things out-standing in the light,
Provoking vision- what we cannot do
From out the light with objects in the dark,
Because that denser darkling air behind
Followeth in, and fills each aperture
And thus blockades the pathways of the eyes
That there no images of any things
Can be thrown in and agitate the eyes.
     And when from far away we do behold
The squared towers of a city, oft
Rounded they seem,- on this account because
Each distant angle is perceived obtuse,
Or rather it is not perceived at all;
And perishes its blow nor to our gaze
Arrives its stroke, since through such length of air
Are borne along the idols that the air
Makes blunt the idol of the angle's point
By numerous collidings. When thuswise
The angles of the tower each and all
Have quite escaped the sense, the stones appear
As rubbed and rounded on a turner's wheel-
Yet not like objects near and truly round,
But with a semblance to them, shadowily.
Likewise, our shadow in the sun appears
To move along and follow our own steps
And imitate our carriage- if thou thinkest
Air that is thus bereft of light can walk,
Following the gait and motion of mankind.
For what we use to name a shadow, sure
Is naught but air deprived of light. No marvel:
Because the earth from spot to spot is reft
Progressively of light of sun, whenever
In moving round we get within its way,
While any spot of earth by us abandoned
Is filled with light again, on this account
It comes to pass that what was body's shadow
Seems still the same to follow after us
In one straight course. Since, evermore pour in
New lights of rays, and perish then the old,
Just like the wool that's drawn into the flame.
Therefore the earth is easily spoiled of light
And easily refilled and from herself
Washeth the black shadows quite away.