Facultative (supernumerary) accents.

A necessary termination in a combination of an unaccented plus an
accented plus an unaccented syllable (-- / --). The dissyllable is the
only exception.

The facultative accent is opposed to the regular recurrence in each
line of dissyllabic and trisyllabic elements, which elements caused
the rhythm of Latin verse.

Spanish rhythm is a rhythm of series, of strophes, not a rhythm of
regularly recurring accents within a verse.

Verses of ten or twelve syllables, however, lend themselves more
readily to rhythm from regularly recurring stress.

_Decasyllabic Verse_: A verse of ten syllables may be formed by the
triple repetition of the trisyllable -- -- /. One extra unaccented
syllable is admissible when the verse is _llano_; and two when the
verse is _esdrújulo_.

Scheme:

-- -- / -- -- / -- -- , _agudo_.
-- -- / -- -- , -- -- , -- _llano_.
-- -- / -- -- / -- -- / -- -- _esdrújulo_.

_Dodecasyllable Verse_: A verse of twelve syllables, with
the stress on the second, fifth, eighth, and eleventh syllables,