Speaking of the diphthong _ai_, Walker, in the "Principles of English
Pronunciation" prefixed to his _Dictionary_, says (Art. 202.):
"The sound of this diphthong is exactly like the long slender sound of
_a_; thus, _pail_ a vessel, and _pale_ a colour, are perfectly the same
sound."
This sound is analysed (Art. 225.) as follows:
"This triphthong (_aye_) is a combination of the slender sound of _a_,
heard in _pa-per_; and the _e_ in metre."
The sound, therefore, is a combination of _two simple_ sounds. But in a
previous article (8.) _a_, _e_, _o_ are called _simple_ vowels; or
(according to his definition):
"Those which are formed by _one_ conformation of the organs only; that
is, the organs remain exactly in the _same_ position at the _end_ as at
the _beginning_ of the letter; whereas, in the _compound_ vowels _i_
and _u_, the organs _alter_ their position before the letter is
completely sounded."
Walker, therefore, makes the sound to be "_combination_ of _two simple_
sounds," although he had already declared it to be a _simple_ sound. Now,
strange to say, Dr. Richardson, in his very valuable contribution to our
literature, viz. his 8vo. _Dictionary_ (a veritable _Richardson_, very long
ago foretold by Joe Miller), is guilty of the same inconsistency. In the
"Grammatical and Etymological Examination adapted to the Dictionary," he
reckons _thirteen simple_ vowels in our language. The _tenth_ is the "long
slender sound of _a_," as Walker would call it; and the sound is given us
(according to Richardson) in these words: "_Lame_, _Tame_, _Crane_,
_Faint_, and _Layman_." My Query is, ought not this sound to be transferred
from the _simple vowels_ under the _true diphthongs_? And ought we not to
distinguish between the pronunciation of _pail_ and _pale_, just as we do
between _neigh_, and _né_ (French); _bait_ and _bête_ (French); or between
_pay_ and _pe_ (Welsh); _tay_ and _te_ (Welsh)? It is worthy of remark,
that the Welsh language has only the _simple_ sound, _not_ the
_diphthongal_?