Moreover, the parasitic y was treated as a consonant, hence our 'văcuum'.
In the penultima qu was treated as a single consonant, so that the vowel was pronounced long in āquam, ēquam, inīquam, lōquor. So it was after o, hence our 'collōquial'; but in earlier syllables than the penultima qu was treated as a double consonant, hence our 'subăqueous', 'equity', 'iniquity'.
Exceptions.
1. When the former of the two consonants was r and the latter another consonant than r, as in the series represented by larva, verbum, circus, corpus, laburnum, the vowels are a separate class of long vowels, though not really recognized as such. Of course our ancestors and the Gradus marked them long because in verse the vowel with the two consonants makes a long unit.
2. A fully stressed vowel before a mute and r, or before d or pl, was pronounced long in the penultima. Latin examples are labrum, Hebrum, librum, probrum, rubrum, acrem, cedrum, vafrum, agrum, pigrum, aprum, veprem, patrem, citrum, utrum, triplus, duplex, Cyclops. Moreover, in other syllables than the penultima the vowel in the same combinations was pronounced long if the two following vowels had no consonant between them, as patria, Hadria, acrius. (Our 'triple' comes from triplum and is a duplicate of 'treble'. Perhaps the short vowel is due to its passage through French. Our 'citron' comes from citronem, in which i was short.)
3. The preposition and adverb post was pronounced with a long vowel both by itself and in composition with verbs, but its adjectives did not follow suit. Hence we say in English 'pōstpone', but 'pŏsterior' and 'pŏsthumous'.
Monosyllables ending in a vowel were pronounced long, those ending in a consonant short. Enclitics like que were no real exception as they formed part of the preceding word. There were, however, some real exceptions.
1. Pronouns ending in -os, as hos, quos. These followed eos and illos.
2. Words ending in -es, as pes, res.