oi in oil; ou in sound.

When only one of the vowels is sounded, the diphthong is called IMPROPER,
because then, as one of the vowels is silent, it is not properly a
DIPHTHONG, though it takes that name; as, oa in boat, ui in suit, where a
and i are silent.

The following diphthongs are in common use, viz.: oi, oy, ou, ow, ae, ai,
au, aw, ay, ea, ei, eo, eu, ew, ey, ia, ie, oa, oe, ua, ue, ui; as in
toil, boy, round, plow, seal, coal, head, sail, say, aught, yeoman. Of
these, oi, oy, ou, and ow are generally proper diphthongs; though
sometimes ou and ow are improper, as in famous, where o is silent, and in
slow, where w is silent.

A Triphthong is the union of three vowels in one syllable; as, eau in
beau, iew in view. The triphthong is properly a union of letters, not
sounds.



OF THE VARIOUS SOUNDS.

All the vowels, and some of the consonants, have several sounds; in this
book these sounds are indicated by diacritical marks, as in the following
tables:



TABLE OF VOCALS.
Long Sounds.