This poem is divided up into chunks of four lines. In poetry, a chunk of lines is called a stanza (it works like a paragraph does in prose). If you want to get extra-fancy, you can call a four-line stanza a quatrain. (For more on any tricky poetry terms, check out our super-helpful Literature Glossary.)
If you count them up, you'll see that there are twelve four-line stanzas in this poem. All that even spacing helps give the poem a calm, controlled feeling, even though the lines turn out to be about blood and guts and poison and grisly death.
The rhyme scheme in this poem is just as even and regular as the spacing. Each stanza has two pairs of rhyming lines (we call those couplets). We'll show you how that works by putting in letters to represent the rhyming sounds:
Now that I, tying thy glass mask tightly, A
May gaze thro' these faint smokes curling whitely, A
As thou pliest thy trade in this devil's-smithy— B
Which is the poison to poison her, prithee? B
See how that works? Two pairs: tightly/whitely and smithy/prithee. Easy as can be! You'll see that same pattern of rhyming couplets in every stanza of the poem.
Now for the meter, which is a little trickier. The basic unit of this poem's meter is called an anapest. That's a big word that just means two unstressed syllables followed by a stressed syllable. So the rhythm would go like this: da-da-DUM, da-da-DUM, da-da-DUM. That doesn't mean that Browning follows that rhythm perfectly in every line. Like most poets, he changes things up a little when he feels the need. We'll show you how it works, using the second stanza (stressed syllables in bold):
He is with her, and they know that I know
Where they are, what they do: they be lieve my tears flow
While they laugh, laugh at me, at me fled to the drear
Empty church, to pray God in, for them!—I am here.
See how that works? There's an odd man out every now and then (like that "He" in line 5), but for the most part it goes da-da-DUM da-da-DUM, da-da-DUM. Also, we should point out that there are four anapests in each line. In fancy poetry talk, we call a four beat line "tetrameter" ("tetra" just means four). So the full, all-dressed-up name for this poem's meter is (drum roll please…) anapestic tetrameter.
So what's the point of all of this? How does all this technical stuff help us understand what the poem means? Well, we think it's all part of the kind of tricky balance Browning is working out between beauty and horror. He's talking about really ugly things, but he does it in this beautiful, orderly, and controlled way. Even when he's describing someone's horrible death, the lines keep rolling rhythmically along. That's how this poem gets inside your head – it forces you to think about the beauty of ugliness and the ugliness of beauty. Deep, huh?