Near the end of the sonnet, Wordsworth uses an allusion to the Greek gods Proteus and Triton to describe the sea. In the ancient Greek religion, both gods were associated with the sea. Triton was the son of the chief sea god Poseidon and his wife Amphitrite, a sea goddess herself, and he was believed to have lived in a golden palace at the bottom of the sea. Greek art and writings often depicted Triton as a merman wielding a large seashell that doubled as a trumpet. Triton came to be known as the messenger and herald of his father Poseidon, for which purpose he used his horn. Thus, for Wordsworth, the sound of Triton’s horn implies that there is some meaning or message being communicated. To describe the sound of the sea as Triton’s horn reflects Wordsworth’s own desire to be instructed and guided by nature.

Proteus has a more complicated and obscure history in Greek myth, with many accounts portraying him quite differently. However, in most depictions, Proteus is a primordial sea god with the gift of prophecy and ability to see all events past, present, and future.