In one of the old books called Welsh Triads, in which all things are classed by threes, there is a description of three men called "The Three Generous Heroes of the Isle of Britain." One of these--named Nud or Nodens, and later called Merlin--was first brought from the sea, it is stated, with a herd of cattle consisting of 21,000 milch cows, which are supposed to mean those waves of the sea that the poets often describe as White Horses. He grew up to be a king and warrior, a magician and prophet, and on the whole the most important figure in the Celtic traditions. He came from the sea and at last returned to it, but meanwhile he did great works on land, one of which is said to have been the building of Stonehenge. This is the way, as the old legends tell, in which the vast stones of Stonehenge came to be placed on Salisbury Plain. It is a thing which has always been a puzzle to every one, inasmuch as their size and weight are enormous, and there is no stone of the same description to be found within hundreds of miles of Salisbury Plain, where they now stand. The legend is that Pendragon, king of England, was led to fight a great battle by seeing a dragon in the air. The battle was won, but Pendragon was killed and was buried on Salisbury Plain, where the fight had taken place. When his brother Uther took his place, Merlin the enchanter advised him to paint a dragon on a flag and bear it always before him to bring good fortune, and this he always did. Then Merlin said to him, "Wilt thou do nothing more on the Plain of Salisbury, to honor thy brother?" The King said, "What shall be done?" Then Merlin said, "I will cause a thing to be done that will endure to the world's end." Then he bade Utherpendragon, as he called the new king, to send many ships and men to Ireland, and he showed him stones such as seemed far too large and heavy to bring, but he placed them by his magic art upon the boats and bore them to England; and he devised means to transport them and to set them on end, "for they shall seem fairer so than if they were lying." And there they are to this day.