I cannot count the pebbles in the brook.
Well hath He spoken: "Swear not by thy head.
Thou knowest not the hairs," though He, we read,
Writes that wild number in His own strange book.

I cannot count the sands or search the seas,
Death cometh, and I leave so much untrod.
Grant my immortal aureole, O my God,
And I will name the leaves upon the trees,

In heaven I shall stand on gold and glass,
Still brooding earth's arithmetic to spell;
Or see the fading of the fires of hell
Ere I have thanked my God for all the grass.

Gilbert Keith Chesterton

http://www.poemhunter.com/poem/eternities/