[For those of you who don't know how English verse works: "wandered" is pronounced wandered not wandered and "lonely" is pronounced lonely not lonely. So you naturally say "I wandered lonely as a cloud" in a te-Tum te-Tum te-Tum te-Tum rhythm, which is called an iambic tetrameter because there are four (tetra) iambs (te-Tum).Now here's a funny thing: blank (unrhymed) verse is never, ever written in iambic tetrameters.
Got that? The same goes for a lot of normal sentences "A cup of tea" will always be "A cup of tea" because "a cup of tea" would just sound weird.
If there are five iambs it's called an iambic pentameter and goes te-Tum te-Tum te-Tum te-Tum te-Tum as in
My mistress eyes are nothing like the sun.
Shakespeare almost always wrote his plays in unrhymed iambic pentameters.]
There's a good, if strange, reason for this. When you're reading out verse with an odd number of feet you pause naturally at the end of each line for one extra beat. You pause for the time it would take to say te-Tum. So a guy playing Henry V will naturally say:
Once more unto the breach, dear friends, once more [pause]
Or fill the gap up with our English dead [te-Tum]
In peace there's nothing so becomes a man [te-Tum]
As modest stillness...
For some reason, the human brain adores even numbers. Nobody knows why. But we love even numbers so much that we will unconsciously insert a pause to make an iambic pentameter last as long as a hexameter would. Always the pause.
This does not, of course, apply to tetrameters, because you have an even number of feet. When you're reading a tetrameter you go straight from one line to the next.
I wandered lonely as a cloud
That floats on high oer vales and hills
When all at once I saw a crowd
A host of golden daffodils.
The only thing that marks the line endings is the rhyme. Now imagine if there weren't any rhymes in that Wordsworth poem. A listener would not know where the lines ended. This is a tetrameter so you have no pauses. The rhymes were the only markers of the line-endings. If a tetrameter doesn't have rhymes then it's just te-Tum te-Tum te-Tum te-Tum te-Tum te-Tum te-Tum te-Tum te-Tum te-Tum te-Tum for ever.
That's why unrhymed verse has to be written in a meter with an odd number of feet.
But what if you have four and a half feet? There, my dear, is the beauty. The mind of an Englishman requires four full feet, so if he is denied them he will insert a pause. If he is denied them by only half a foot, he will insert a half-foot pause. This creates a verse form of heart-breaking delicacy. Its most exquisite incarnation is Auden's Lullaby.
Lay you sleeping head, my love, [half beat]
Human on my faithless arm. [half beat]
Time and fevers burn away [half beat]
Individual beauty from
And thus can you write blank verse in tetrameters. The tiny pause has none of grandisonance of the kingly pentameter. It is so small as to be almost a stumble. A hesitation. And in that the meter finds its beauty. A snowflake would be rather dull if it were as big as a dog, but because it is so small the detail is beautiful. Anything miniature is beautiful.
Tum te-Tum te-Tum te-Tum
It's an iambic tetrameter, yet it's missing its head which means it's acephalous. "But wait a minute," I hear you cry from your lonely pantry, dear reader, "couldn't you just as easily call it a footless trochaic tetrameter?"
No, dear reader, you couldn't. And if I may say so I fear you're now being rather perverse. The Auden poem is naturally read as a headless iambic. If it were a footless trochaic, you would be reading it like this:
Tyger, tyger, burning bright
In the forests of the night
What immortal hand or eye etc etc
The trochee uses the on-beat which is a lot louder and coarser than the gentle iamb, which uses the off-beat. Anybody who has ever had the misfortune to read Hiawatha will know that it's the sort of verse that only a dope-addled thug could enjoy. The thing is, that in order to make you read it like that - Tum-te Tum-te Tum-te Tum - Blake had to begin the poem with three trochaic words. Auden didn't, so you don't. By the time Auden gets to such a line:
Beauty, midnight, vision die
The iambic rhythm is so firmly established that you read it gently.
Auden also uses this meter elsewhere.
Earth receive an honoured guest
William Yeats is laid to rest
And Pope employed it for his Dying Christian to His Soul:
Vital spark of heav'nly flame
Quit, o quit this mortal frame
But in both cases the rhyme detracts from the meter's natural delicacy. As a means of writing blank verse the acephalous iambic tetrameter is scandalously underused. Now go and read Lullaby, it's better than whatever you had planned. Here is a link.
Lines on the Face of W.H. Auden