What poetic form do both montagu's and swift's poems use?

Lady Mary Wortley Montagu used iambic tetrameter rhyming couplets is some poems such as "The Lover: A Ballad" and in others free mingling of iambs, also with rhyming couplets, on the other hand, Jonathan Swift uses rhyming pairs of lines, both used rhyming couplets.

onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.