All I know is a door into the dark. Outside, old axles and iron hoops rusting; Inside, the hammered anvil's short-pitched ring, The unpredictable fantail of sparks Or hiss when a new shoe toughens in water. The anvil must be somewhere in the centre, Horned as a unicorn, at one end and square, Set there immoveable: an altar Where he expends himself in shape and music. Sometimes, leather-aproned, hairs in his nose, He leans out on the jamb, recalls a clatter Of hoofs where traffic is flashing in rows; Then grunts and goes in, with a slam and flick To beat real iron out, to work the bellows.