The words quoted indicate the nature of the diphthongal system.
1. Diphthongs with the semivowel w, a) preceding, as in the French word roi, b) following, as in the English word new.
2. Diphthongs with the semivowel y, a) preceding, as is common in the languages of the Lithuanic and Slavonic stocks, b) following, as in the word oil.
3. Triphthongs with a semivowel both preceding and following.
The diphthongs in English are four; ow as in house, ew as in new, oi as in oil, i as in bite, fight.
[§ 206]. Chest, jest.—Here we have compound consonantal sounds. The ch in chest is t + sh (σ), the j in jest is d + zh (ζ). I believe that in these combinations one or both the elements, viz., t and sh, d and zh, are modified; but I am unable to state the exact nature of this modification.
[§ 207]. Ng.—The sound of the ng in sing, king, throng, when at the end of a word, or of singer, ringing, &c. in the middle of a word, is not the natural sound of the combination n and g, each letter retaining its natural power and sound; but a simple single sound, of which the combination ng is a conventional mode of expressing.
[§ 208]. Other terms, chiefly relating to the vowels, have still to be explained. The é of the French has been called fermé, or close (Italian, chiuso). Its opposite, the a in fate, is open.
Compared with a in fate, and the o in note, a in father,
and the aw in bawl, are broad, the vowels of note and fate being slender.