Final answer:
Alliteration refers to the repetition of consonant sounds which can be seen in the line 'They stretched in never-ending line' with the repetition of the 's' sound.
Step-by-step explanation:
The question pertains to identifying a line demonstrating alliteration in the poem "The Lake of the Dismal Swamp" by Thomas Moore. Alliteration is defined as the repetition of the same consonant sound at the beginning of words that are in close proximity to each other within a line or sentence.
While the poem "The Lake of the Dismal Swamp" has not been provided in the materials above, an example of a line featuring alliteration from "I Wandered Lonely as a Cloud" by William Wordsworth could be: "They stretched in never-ending line." In this line, we see the repetition of the 's' consonant sound which constitutes alliteration.
When analyzing poetry, it's beneficial to keep in mind various forms of literary devices such as rhyme, repetition, assonance, consonance, and more, as they all contribute to the texture and rhythm of the poem.