Mention two metaphors or comparisons made by Robert Frost in the poem, Birches.

As the stir cracks and crazes their enamel.
Soon the sun's warmth makes them shed crystal shells 10
Shattering and avalanching on the snow-crust—

Enamel is a metaphor for ice, and in addition shed is a metaphor for melting.

When he says that he "dreams of going back" to being a "swinger of birches," he is using that image as a metaphor for a state of being, for a time of life (old age), and for the condition of youth.

And so I dream of going back to be.

One could do worse than be a swinger of birches.