A woman is saying goodbye to her lover, and the first language she reaches for is bookkeeping. The title calls her "his mistress", though the words are of course written by a male poet. Her faithfulness is "the debt / Which to thy memory stands as due", and she wants it "sealed" like a contract. Even her grief is a payment: "Take then tribute of my tears." Love, in Robert Herrick's hands, becomes a kind of economy in which feelings are owed, paid and returned with interest.
The mood darkens in the middle. "So long as I have fears / To prompt me, I shall ever / Languish and look, but thy return see never." The fear is the engine of the poem, and the sentence behaves like the waiting it describes. It drags across three lines, and its long final line is the longest in the poem. The rhyme on "ever" and "never" pairs her endless pining with the return she may never see. She never says he won't come back. She says only that as long as she is afraid, she will keep looking, so the despair is conditional and human rather than absolute.
Then comes the turn, "Oh then", and with it a request that is both tender and inventive. He is asked to "Print thy lips into the air". Printing is something done to wax or paper, and it echoes the "seal" of the opening, so the kiss becomes a signature pressed into empty space. She will then "kiss thy kiss", a phrase that quietly admits she cannot kiss him. She can kiss only the impression he leaves behind. The air becomes a postal service, and its courier is chance: "Whenas some kind / Wind / Shall hither waft it". Her comfort depends on a wind that might not blow, and the word "some" makes any breeze as good as any other.
The lineation turns this into a small performance. The phrase "by this means" is cut in two, with "Means" stranded on the next line, and "Wind" stands alone as a single-word line. Lines that had been seven or eight syllables shrink to two or three, and the poem briefly thins out into something light enough to be carried. The reader's eye has to drop down the page, just as the kiss has to travel.
The rhyme is tidy, a run of couplets: forget/debt, due/you, tears/fears, despair/air. The tidiness makes the ending land. "Lieu" rhymes with "due" and "you", so the last couplet returns to the sound of the first stanza, and "in lieu" brings back the vocabulary of exchange. The debtor of the opening now overpays: "My lips shall send a thousand back to you." Her grammar shifts as well. What depends on the wind is hedged ("I may kiss thy kiss"), but what depends on her is flat certainty ("shall send"). The last line is also one of the poem's fullest, a plain ten syllables without a pause. Most of the diction is short and plain. "Languish" is the one soft, drawn-out word, and it falls where she is most helpless.
Herrick's poem matters because it takes an old situation, a parting with no promise of return, and answers it with wit instead of lament. The conceit of kisses carried on the wind is ingenious, but it never cancels the fear that sits in the middle of the poem. The wit is how she survives the fear. She cannot control whether he returns, so she invents a ritual she can control, and she makes the gesture generous by promising a thousand kisses for one. In a handful of short lines, the poem turns absence into a transaction in which, for once, the speaker has the upper hand.