In Donne's poem, "A Valediction: Forbidding Mourning", he uses the two stiff parts of a mathematical compass as a metaphor for marriage. His wife is the center compass part that stays in one place, but it is connected to the other part of the compass which moves around, which represents Donne having to leave for a time, but like the moving compass part, they both make a circle and come back to where it started held fast to the stationary part of the compass, his wife .