Accentual, Alliterative (Old English style)
Get this: Pound is translating an Ancient Greek poem for the sake of writing this canto, which is itself a nod to medieval Italian poetry. And the form and meter he decides to use are… from old English poetry (we're talking maybe around 1100 A.D.). So the guy definitely knows the tradition of world poetry and isn't afraid to show it.
It might be a tricky thing to get your head around, but Old English poetry uses a different kind of meter than the one you're probably used to. Old English poetry only cares about the number of stressed syllables per line, leaving the number of unstressed syllables totally random. Confused yet? Don't sweat it. Let's look at an example. Here's how you might want to read the first line of "Canto I":
And then went down to the ship, (1)
For Old English poetry, you just focus on what's stressed: "then went down" and "ship." Why is that? Well, the stressed syllables would need to linked, either through alliteration), internal rhyme or both. In the case of line 1, we get internal rhyme with "then" and "went." This type of meter is called "accentual" meter, and it came about because, back in the Old English day, only the very richest of the people had an Internet connection… We're kidding, gang. Actually, very few people could read, or had access to books. So the rules of "accentual" meter made sure that poems would follow predictable forms that made them easier to memorize and pass on.
Want another example? Well, there's both internal rhyme and alliteration in a phrase like "Bore sheep aboard her" (4). "Bore" and "aboard" rhyme, and they also have some near alliteration (more like consonance) with the B sounds in both words.
So, in an old-style poem about an old-style hero, it pretty much stands to reason that our man Pound would reach back through time for some of this old-style form and meter, eh? He's sort of like that friend you have with the fascination for vintage fashion. Here, though, Pound is rocking some seriously old style.