177. A syllable is long if its vowel is long, or if its vowel is
followed by two consonants or by #x# or #z#: as,
#dūcēbās#; #volvunt#. In #dūcēbās# both the vowels and the syllables are
long; in #volvunt# the vowels are short, but the syllables are long; in
cases like the last the syllables (not the vowels) are said to be _long
by position_. #h# does not count as a consonant (58) and #qu#
(or #qv#, 27) has the value of a single consonant only: thus, in #adhūc#
and #aqua# the first syllable is short.
178. In prose or old dramatic verse a syllable with a short vowel before
a mute or #f# followed by #l# or #r# is not long: as #tenebrae#. In
other verse, however, such syllables are sometimes regarded as long. In
compounds such syllables are long in any verse: as #obruit#.