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One of the literary devices used in the poem is Metaphor.

Metaphor is one of the most widely used literary devices. It occurs when the write refers to a meaning or identity ascribed to one subject by way of another.

Explanation:

In the first 5 lines, you see Lawrence applying attributes of living things to non-living things.

For example:

a)  "When the sun from the west, beyond Pisa, beyond the mountains of Carrara  Departs,..."

b) "When the tired flower of Florence is in gloom..."

In A he says "the sun departs" instead of "the sun sets"

in B he posits that the flower of Florence is tired and gloomy.

Overall tonality is one of sadness and he uses metaphoric imagery to communicate this perfectly.

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