In the excerpt from "Sea Fever" by John Masefield, the most notable sound device used is alliteration. Alliteration is the repetition of the same initial consonant sound in nearby words. In the line "And quiet sleep and a sweet dream when the long trick's over," the repeated "s" sound in "sleep," "sweet," and "trick's" creates a musical and rhythmic effect. This enhances the auditory experience of the poem and helps to convey the calm and peaceful imagery of the sea and dreaming.
Alliteration is commonly used in poetry to create a sense of unity, rhythm, and emphasis. It can also contribute to the overall mood and tone of the poem. In this case, the alliteration adds a soothing and contemplative quality to the verse, complementing the theme of longing for the sea and the desire for rest and tranquility.