([3.]) Before final t and m, and, in words of more than one syllable, before final r and l ([132]): compare amat, amem, with amās and amēs.
[36]. All vowels are long which are:
([1]) Weakened from a diphthong ([96-101]; [108]), or which are the result of contraction ([118]): as, concīdō from caedō; cōgō from co-agō.
([2]) Lengthened by compensation ([121]): as, quīnī for *quincnī.
([3]) Before nf, ns, often before nc followed by a consonant, and, in some cases, before gn ([122]).
[PRONUNCIATION OF VOWELS.]
[37]. The following English sounds come nearest to the Latin pronunciation of the vowels:
[38]. Long vowels. ā had the sound of a in father; ē that of a in fate (but see [39]); ī that of i in machine; ō that of o in tone; ū that of u in rule.
[39]. It must be noted, however, that all English long vowels, save a as in father, are more or less diphthongal, that is, they become gradually closer ([46]); a in fate ends in a vanishing sound of ee (not heard in the ê of French fête), and o in no ends in the sound of oo. Similarly the long e sound in he becomes closer and ends in a sound similar to the y in year. In Latin all long vowels had one sustained sound.