Variously (and Very) Iambic
To truly get the meter that drives "The Broken Heart," you have to be down with the iamb. If you're not already, though, don't worry. We can totally hook you up.
You see, the iamb is just a two-syllable pair in which the first syllable is unstressed and the second syllable is stressed. It makes a daDUM sound, like the beat you would hear when you say "allow" out loud. (Try it, why don't you?) The iamb is the base unit of rhythm for all the lines in this poem, a.k.a. the poem's foot.
That seems simple enough, right? Well, it's about to get slightly trickier.
Donne, being the poetic technician that he is, varies the number of iambs in his lines. Luckily for us, though, he keeps that variation consistent from stanza to stanza. In all four of the poem's eight-line stanzas (which are also called octaves), the first three lines are written in iambic tetrameter, followed by a line of iambic pentameter, followed then by two more lines of iambic tetrameter, then wrapped up by two last lines of iambic tetrameter.
Now, don't get thrown by this he-meter, she-meter talk. A line of iambic tetrameter is just a line with four (tetra- means four) iambs, while iambic pentameter is just a line with five iambs (penta- means five). Let's check out what that looks like:
He is stark mad, whoever says,
That he hath been in love an hour,
Yet not that love so soon decays,
But that it can ten in less space devour;
Who will believe me, if I swear
That I have had the plague a year?
Who would not laugh at me,if Ishould say
I saw a flash of powder burn a day? (1-8)
You should hear those iambic daDUMs rolling through every line—four of them in lines 1-3, 5, and 6, and five in lines 4, 7, and 8. The pattern holds up in the second, third, and fourth stanza.
Along with this complex rhythmic symmetry, we also have a regular and complex rhyme scheme: ABABCCDD. That is, each letter represents that line's end rhyme.
Noticing a theme here? We have set patterns both in terms of form and meter here, but the patterns themselves are pretty complex. It's not the case that every line has the same meter, nor does every line rhyme with the one that came before it. Instead, Donne throws us regularly-timed curve balls, which we think is pretty appropriate for a poem about how love is the ultimate curve ball. At the same time, the facts of love are pretty predictable. It lures us in and, at least once in our lives, it consumes us totally. We all have to face the overwhelming, and potentially devastating, complexities of love at one point or another. The way this poem is put together is a nifty reminder of that fact.