Some of these characters occasionally perform the office of diphthongs. Thus, in the word fine, the vowel i has the diphthongal sound of the letters â è, as these are pronounced in French; and the vowel u frequently represents the diphthong eu (e-oo), as fume (fe-oom).
There are, besides, four different consonants for which we have no proper letters; namely, the initial consonant in the word thin, the initial consonant in then, the sibilating sound of sh, and the final consonant (marked ng), as in the word sing.
Consonants are generally divided into mutes and semi-vowels. The mutes are those which entirely, and at once, obstruct the sound of the vowel, and prevent its continuation. These are called perfect mutes. Those which do not suddenly obstruct it are called imperfect mutes.
Semi-vowels are those consonants which do not entirely obstruct the voice: but whose sounds may be continued at pleasure, thus partaking of the nature of vowels.
The nature of these consonants I proceed briefly to explain.
A vowel sound may be continued at pleasure, or it may be terminated, either by discontinuing the vocal effort, in which case it is not articulated by any consonant, as in pronouncing the vowel o; or by changing the conformation of the mouth, or relative position of the organs of speech, so that the vowel sound is lost by articulation, as in pronouncing the syllable or. It is to be observed, also, that a vowel may be articulated, not only by being terminated by a consonant, as in the example now given, but likewise by introducing the sound with that position of the organs, by which it had, in the former case, been terminated, as in pronouncing the syllable ro.
In pronouncing the consonants, there are five distinguishable positions of the organs[4]. The first is the application of the lips to each other, so as to close the mouth. Thus are formed the consonants p, b, and m.
In the second position, the under lip is applied to the fore teeth of the upper jaw; and in this manner we pronounce the consonants f and v.
The third position is, when the tongue is applied to the fore teeth; and thus we pronounce th.