Final answer:
The figure of speech exemplified in the lines from 'Rime of the Ancient Mariner' is alliteration, characterized by the repetition of the 'f' sound in close succession.
Step-by-step explanation:
The figure of speech found in the excerpt from the Rime of the Ancient Mariner is alliteration. Alliteration is the repetition of consonant sounds at the beginning of words close together in a phrase or line of poetry. In the provided lines, 'The fair breeze blew, the white foam flew, The furrow followed free,' the repetition of the 'f' sound is a clear example of alliteration. This literary device is often used to create rhythm and can enhance the musicality of the verse, which is certainly the case in Samuel Taylor Coleridge's poem.