On the Nature of the Universe (Oxford World’s Classics) (30 page)

Flowing and falling from things and moving away.

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For there is always something streaming off

From the surface of things which they eject. And this,

When it meets some things, passes through them, like glass

Especially. But when it meets rough stone

Or solid wood at once it is broken up,

And then it cannot reproduce an image.

But when the object opposed is bright and compact

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As a mirror is, none of these things occurs;

For it cannot pass through it, as it does through glass,

And also it cannot be broken up, so much

Safety the smoothness never forgets to give.

That is why the images stream back to us.

However suddenly you place a thing

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In front of a mirror, at once its image appears;

So you may know that from the surface of things

There is a constant and perpetual flow

Of thin shapes and thin tissues everywhere.

Therefore in a short time many images

Come into being, so you may rightly call

The origin of them instantaneous.

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The sun must send out many beams of light

In a short time, to fill the world with it,

So in one moment many images

Are borne in many ways into all parts.

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Whichever way we turn a mirror, something

Makes answer to us of like form and colour.

Consider this now: when the weather has been

Most brilliant, suddenly the sky becomes

Gloomy and ugly so that you might think

That all the dark from Acheron had fled

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And filled the mighty caverns of the sky.

So foul a night of clouds has massed together

And the black face of fear lours from on high;

And the image of these clouds, how small it is,

No man can tell or reasonably describe.

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I now explain how fast these images move

And what velocity as they swim through the air

Is given them, a brief hour for a mighty space,

Where each with varied impulse makes its course.

And this I tell in words both sweet and few.

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Better the swan’s brief song than that cry of cranes

Spread by the south wind through the clouds on high.

First, you may very often see that things

Light and of minute elements move swiftly.

Of such kind are the sun’s light and its heat

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Because they are made of minute elements

Which are hit, at it were, and cross immediately

The intervening space hit by a blow that follows:

For instantly light follows light, and flash

Is triggered off by flash, like a team of oxen.

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In much the same way therefore the images

Must be able to run through space incalculable

In a moment of time; first, since a very small impulse

From far behind is enough to set them in motion,

Since with so swift a lightness they rush on.

Next, since their texture is so very fine

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That they can easily penetrate anything

And ooze as it were through the intervening air.

Consider this too: certain particles

Which rise from deep down, like the sun’s heat and light,

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Are seen at the very instant of daybreak

Through the whole space of heaven to pour themselves

And fly over land and sea and flood the sky;

What then of those already on the surface

When they are thrown off and nothing checks their flight?

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Faster and further clearly they must go

And cover a distance many times as great

In the same time that it takes the sun

To spread its light abroad across the sky.

This also especially seems to show most truly

The speed at which these images are borne:

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A smooth surface of water is exposed

To a clear sky at night, at once the stars

And constellations of the firmament

Shining serene make answer in the water.

Now do you see how in an instant the image

Falls from the edge of heaven to the edge of earth?

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Wherefore again and yet again I say

How marvellously swift the motion is

Of the bodies which strike our eyes and make us see.

And odours flow perpetually from things,

As cold from rivers, heat from the sun, and spray

From the sea which scours the walls along the shore.

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And always different sounds fly through the air.

Again, a damp taste of salt enters our mouths

When we walk by the sea; and when we watch wormwood

Being mixed with water we sense its bitterness.

So does from all things always something flow

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And everywhere into all parts spreads abroad.

And no delay or rest is given this flow

Since we constantly feel it, and all things always

We can see and smell, and hear the sound of them.

Again, a shape that is handled in the dark

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Is recognized to be the same we see

In the clear light of day. It follows then

That sight and touch derive from a like cause.

If we touch something square and it stimulates

Our senses in the dark, what can it be

That in the light comes to our sight as square,

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If not an image of it?

Images therefore clearly are the cause

Of vision, and without them nothing can be seen.

Now these images I speak of are flying around

Everywhere and sprayed about in all directions;

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But since it is only with our eyes we see them

It follows that only where we turn our sight

There all things strike it with their form and colour.

Also the image enables us to see

How far away things are, and to distinguish

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Distances, for when it is sent off

At once it drives and pushes all the air

That is between the object and our eyes,

And this air all passes through our eyeballs

And brushes the pupils as it were in going through.

This is the reason why we can see how far

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Away things are, and the greater the volume of air

That is driven before it and the longer the stream

That brushes our eyes, the more distant

And far removed the thing is seen to be.

And all this happens extremely rapidly,

You may be sure, so that at the same moment

We see both what a thing is and how far away.

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And here is a thing that need not cause surprise—

That objects can be perceived though the images

That strike our eyes cannot themselves be seen.

For when wind blows slowly on us and bitter cold

Flows round, we do not feel each particle

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Of wind or cold, but rather the whole at once,

And we feel blows falling upon our body, as if

Something were striking it, and giving us the feeling

Of its own body coming from outside.

And when we knock a stone with a toe, we touch

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Just the outer surface of it and the surface colour,

But we do not feel this by our touch, but rather

The hardness of the stone deep down inside.

Now I will tell you why the image is seen

Beyond the mirror; for certainly it seems

To be far withdrawn and lie deeply within.

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We see things in the same way through open doors

When the doorway gives an open view through it

And lets us see many things outside the house.

This vision is caused by a double stream of air.

For first the air this side of the doorposts is seen,

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Then follow the doorposts themselves both right and left,

And then the light outside and the second stream

Of light brushes the eyes, and finally

The objects which are really seen out of doors.

The same thing happens when a mirrored image

Projects itself on to our sight: on its way to our eyes

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It drives and pushes all the air between

Itself and our eyes, and makes us feel this first

Before we see the mirror. But when we have seen

The mirror itself also, at once the image

That travels from us to it and is reflected

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Comes back to our eyes, pushing a stream of air