For in that land was a strange custom. The office of king was the prize
of a race every seven years. Oisin's predecessor had consulted a Druid
as to the length of his own tenure, and had been told that he might keep
the crown for ever unless his son-in-law took it from him. Now the
king's only daughter was the finest woman in Tir na n'Og, or indeed in
the world; and the king naturally thought that if he could so deform his
daughter that no one would wed her he would be safe. So he struck her
with a rod of Druidic spells, which turned her head into a pig's head.
This she was condemned to wear until she could marry one of Fin Mac
Cumhail's sons in Erin. The young lady, therefore, went in search of Fin
Mac Cumhail's sons; and having chosen Oisin she found an opportunity to
tell him her tale, with the result that he wedded her without delay. The
same moment her deformity was gone, and her beauty as perfect as before
she was enchanted. Oisin returned to Tir na n'Og with her; and on the
first race for the crown he won so easily that no man ever cared to
dispute it with him afterwards. So he reigned for many a year, until one
day the longing seized him to go to Erin and see his father and his men.
His wife told him that if he set foot in Erin he would never come back
to her, and he would become a blind old man; and she asked him how long
he thought it was since he came to Tir na n'Og. "About three years," he
replied. "It is three hundred years," she said. However, if he must go
she would give him a white steed to bear him; but if he dismounted, or
touched the soil of Erin with his foot, the steed would return that
instant, and he would be left a poor old man. This inevitable
catastrophe occurred in his eagerness to blow the great horn of the
Fenians, in order to summon his friends around him. His subsequent
adventures with Saint Patrick, interesting though they are, are
unimportant for our present purpose.[149]

Perhaps the nearest analogue to this is the Italian Swan-maiden
_maerchen_, of the Island of Happiness. There a youth sets out to seek
Fortune, and finds her in the shape of a maiden bathing, whose clothes
he steals, obtaining possession thereby of her book of command, and so
compelling her to wed him. But in his absence his mother gives her the
book again, which enables her to return to her home in the Island of
Happiness. Thither her husband goes to seek her, and after a variety of
adventures he is reunited to her. A