On the nature of things (books 1 - 3)   

And thereupon dividedly to see
How the sweet water, after filtering through
So often underground, flows freshened forth
Into some hollow; for it leaves above
The primal germs of nauseating brine,
Since cling the rough more readily in earth.
Lastly, whatso thou markest to disperse
Upon the instant- smoke, and cloud, and flame-
Must not (even though not all of smooth and round)
Be yet co-linked with atoms intertwined,
That thus they can, without together cleaving,
So pierce our body and so bore the rocks.
Whatever we see...
Given to senses, that thou must perceive
They're not from linked but pointed elements.

The which now having taught, I will go on
To bind thereto a fact to this allied
And drawing from this its proof: these primal germs
Vary, yet only with finite tale of shapes.
For were these shapes quite infinite, some seeds
Would have a body of infinite increase.
For in one seed, in one small frame of any,
The shapes can't vary from one another much.
Assume, we'll say, that of three minim parts
Consist the primal bodies, or add a few:
When, now, by placing all these parts of one
At top and bottom, changing lefts and rights,
Thou hast with every kind of shift found out
What the aspect of shape of its whole body
Each new arrangement gives, for what remains,
If thou percase wouldst vary its old shapes,
New parts must then be added; 'twill follow next,
If thou percase wouldst vary still its shapes,
That by like logic each arrangement still
Requires its increment of other parts.
Ergo, an augmentation of its frame
Follows upon each novelty of forms.
Wherefore, it cannot be thou'lt undertake
That seeds have infinite differences in form,
Lest thus thou forcest some indeed to be
Of an immeasurable immensity-
Which I have taught above cannot be proved.

And now for thee barbaric robes, and gleam
Of Meliboean purple, touched with dye
Of the Thessalian shell...
The peacock's golden generations, stained
With spotted gaieties, would lie o'erthrown
By some new colour of new things more bright;
The odour of myrrh and savours of honey despised;
The swan's old lyric, and Apollo's hymns,
Once modulated on the many chords,
Would likewise sink o'ermastered and be mute:
For, lo, a somewhat, finer than the rest,
Would be arising evermore. So, too,
Into some baser part might all retire,
Even as we said to better might they come:
For, lo, a somewhat, loathlier than the rest
To nostrils, ears, and eyes, and taste of tongue,
Would then, by reasoning reversed, be there.
Since 'tis not so, but unto things are given
Their fixed limitations which do bound
Their sum on either side, 'tmust be confessed