The Barddas of Iolo Morganwg, Vol. I., ed. by J. Williams Ab Ithel, , at sacred-texts.com
There are eight vowels or sounds,
A. E. I. O. U. W. Y. Y, (wy,) so called because it is the mutate of W.
p. 78 p. 79
; and after that, thus,
, which continued mostly
in use by the Bards and Teachers, until the time of Addav, son of Davydd, of Gilvai, called in some books Adam Davi, 1 who introduced five long vowels into the Abcedilros, namely, ; and, asserting that there was no occasion for , he abolished it, and appointed twelve vowels. Nevertheless, it was not that Addav who devised these five, for they had been long retained in memory, even for upwards of three hundred years; but they had no authority of Chair and Gorsedd. It was this authoritative privilege that was bestowed upon them in the time of the said Addav, who also restored to memory much of the primitive learning. His books were warranted by the authority of ancient memorial and art.
Thus, according to others,
, which is called the New Coelbren.