What metaphors are used in The Blue Rim of Memory by Denise Levertov?

The poem is wholly metaphorical and divided into four primary images, each describing "the way sorrow enters the bone." Levertov turns to a historical reference, appropriate in discussing the concepts of memory, and to the natural world, specifically, fire, fish, and snow, to express the presence of sadness as it persists in the human mind, soul, and body.