A parallax (the apparent displacement or change caused by the position of observation; alteration-Oxford English Dictionary) is a perception. The perspective here radically shifts from a person perceiving to a person interpreting. Maureen Mulhern builds on images: a fish twisting at the tail, the merciless rain, a cold translucent hand; and these images gather into a cyclical, fluid perception: "such complete light passing/Through two bodies; a moment/of suspension, before a wave leans/Into the next wave, descending back, a slight/Vertigo of gravity between us."
