Classic Poem

Likeness of sound,
With just enough of difference
To make a change of sense;
So we have contrast,
A piquancy,
And a certain victory of contrivance.
But Heaven keep us from an inevitable rhyme,
Or from a rhyme prepared!

Rhymed verse is a wide net
Through which many subtleties escape.
Nor would I take it to capture a strong thing,
Such as a whale.