Imagery: The imagery of the hymn is very rich and diverse. Longfellow uses a lot of personifications, similes, metaphors, and other literary figures to create the aesthetic atmosphere of the poem.
Personification: The most widely used device of the poem is personification. The central image of the poem is the Night that is a personification of the beloved woman. Personification is used through the whole poem: the Night has clothes ("the trailing garments" and "sable skirts"). Moreover, the Night is spelled with the capital letter like a person's name. In the fifth stanza the poet describes it as a human being: "Oh holy Night!... Thou layest thy fingers on the lips of Care...", and the Night is like a wise teacher who consoles the poet. Moreover, the Night is a kind of divine force. The adjective "holy" contributes to the image of the Night as a saintly and pure woman. In the last stanza the Night is the most beloved woman, divine, heavenly beautiful, pure and fair. It even has wings like an angel: "Descend with broad-winged flight". The comparison of the Night with the beloved woman is kept throughout the poem.
Longfellow does not ignore even "little" words, he enriches even the simplest and the humblest of them. The definite article before the Night contributes to the meaning of the poem in general and to the image of the Night in particular. It is always with the article and capitalized. With the help of this device the poet emphasizes personification. The Night is not an abstract phenomenon, it is a person, the beloved woman.
Metaphor: Another figure of speech that is widely used in the poem is metaphor. "The sable skirts" of the Night are "all fringed with light", so the image created by the poet is magic and light. The "perpetual peace" also flows from the fountain of cool air. This metaphor creates a feeling of calmness and