A little of this, a little of that, this poem boogies however it wants to. "That the Science of Cartography is Limited" is written in free verse. Move along, iambic pentameter fans; Boland's poem can't be chained down to a set verse form.
If you read this poem aloud to yourself, you'll notice that it sounds different than a poem written in a traditional form. It's very conversational; it feels like the speaker is telling you a story about this time she went for a drive and discovered an overshadowed part of Ireland's history. You feel like she's confiding in you, in a super secret reader-writer huddle. Regular rhyme and meter would probably heighten the feeling of artificiality in the poem, and dampen its intimacy, so Boland prefers writin' more like she's talkin'. That is, if every sentence out of her mouth were totally brilliant poetry (and frankly, we wouldn't be surprised if that were true).
But Boland does do some work with form. Just think about how the title acts as the first line of the poem. Or how Boland isolates important lines such as:
Look down you said: this was once a famine road (8)
Where they died, there the road ended (16)
Isolating these lines emphasizes their importance to the speaker's story. These one-line stanzas also add some dramatic pauses to the piece, which is appropriate to the gravity of the topic.
Boland also makes use of her poetic freedom in other ways: she's got all kinds of strange line breaks (also known as enjambments) in lines such as:
… and when I take down
the map of this island, it is never so
I can say here is
the masterful, the apt rendering of
the spherical as flat, nor
an ingenious design which persuades a curveinto a plane,
Though she's talking here about "ingenious" maps, Boland's language is fragmented and uneven. Through her form, she sneakily undermines the map's "masterful"-ness. These maps are not as complete, as whole, as we might like to think.
Free verse thus gives Boland the liberty to emphasize, undermine, and just plain play with lines at will. And considering that this poem is about the horrific mistreatment of the starving Irish poor by the English, this Irish poet's freedom (expressed by her free verse) is no small matter. How do you like them apples, Brits?