On the nature of things (books 1 - 3)   

No less, and theirs a body of mortal birth
No less, than every kind which hereon earth
Is so abundant in its members found.
Which well perceived if thou hold in mind,
Then Nature, delivered from every haughty lord,
And forthwith free, is seen to do all things
Herself and through herself of own accord,
Rid of all gods. For- by their holy hearts
Which pass in long tranquillity of peace
Untroubled ages and a serene life!-
Who hath the power (I ask), who hath the power
To rule the sum of the immeasurable,
To hold with steady hand the giant reins
Of the unfathomed deep? Who hath the power
At once to rule a multitude of skies,
At once to heat with fires ethereal all
The fruitful lands of multitudes of worlds,
To be at all times in all places near,
To stablish darkness by his clouds, to shake
The serene spaces of the sky with sound,
And hurl his lightnings,- ha, and whelm how oft
In ruins his own temples, and to rave,
Retiring to the wildernesses, there
At practice with that thunderbolt of his,
Which yet how often shoots the guilty by,
And slays the honourable blameless ones!

Ere since the birth-time of the world, ere since
The risen first-born day of sea, earth, sun,
Have many germs been added from outside,
Have many seeds been added round about,
Which the great All, the while it flung them on,
Brought hither, that from them the sea and lands
Could grow more big, and that the house of heaven
Might get more room and raise its lofty roofs
Far over earth, and air arise around.
For bodies all, from out all regions, are
Divided by blows, each to its proper thing,
And all retire to their own proper kinds:
The moist to moist retires; earth gets increase
From earthy body; and fires, as on a forge,
Beat out new fire; and ether forges ether;
Till Nature, author and ender of the world,
Hath led all things to extreme bound of growth:
As haps when that which hath been poured inside
The vital veins of life is now no more
Than that which ebbs within them and runs off.
This is the point where life for each thing ends;
This is the point where Nature with her powers
Curbs all increase. For whatsoe'er thou seest
Grow big with glad increase, and step by step
Climb upward to ripe age, these to themselves
Take in more bodies than they send from selves,
Whilst still the food is easily infused
Through all the veins, and whilst the things are not
So far expanded that they cast away
Such numerous atoms as to cause a waste
Greater than nutriment whereby they wax.
For 'tmust be granted, truly, that from things
Many a body ebbeth and runs off;
But yet still more must come, until the things
Have touched development's top pinnacle;
Then old age breaks their powers and ripe strength
And falls away into a worser part.