The last line is in fact an alexandrine — an iambic hexameter, which occurs occasionally in some iambic pentameter texts as a variant line, most commonly the final line of a passage or stanza, and has a tendency, as in this example, to break in the middle, producing a symmetry, with its even number of syllables split into two halves, that contrasts with the "asymmetry" of the 5-beat pentameter line. Pope exemplifies "swiftness" partly through his use of contraction: two extra implied syllables squeezed into the metrical template between the first 2 ictuses:-