The rhetorical structure of Sonnet 130 is important to its effect. In the first quatrain, the speaker spends one line on each comparison between his mistress and something else (the sun, coral, snow, and wires—the one positive thing in the whole poem some part of his mistress is like. In the second and third quatrains, he expands the descriptions to occupy two lines each, so that roses/cheeks, perfume/breath, music/voice, and goddess/mistress each receive a pair of unrhymed lines. This creates the effect of an expanding and developing argument, and neatly prevents the poem—which does, after all, rely on a single kind of joke for its first twelve lines—from becoming stagnant.