Dr. Petrie, who is a high authority, believes that they were built between the years 890 and 1238, when the Danes were in the habit of invading Ireland and plundering the ecclesiastical establishments. One of the most perfect of these towers, at Antrim, is ninety-two feet in height and forty-nine feet in circumference at the bottom; the summit terminates in a cone twelve feet high, which, with the tower itself, is of undressed stone, the walls being two feet nine inches in thickness. The door is on the north side at a height of seven feet nine inches from the ground. The tower was apparently divided into four stories by timber floors, which, of course, vanished long ago. Each of the three lower stories is lighted by a square window, and the upper story by four square perforations opening to the cardinal points. It stands in the grounds of a mansion. The turf between the two shows the dim outline of buildings, supposed to be those of a monastery founded by Aodh, a disciple of St. Patrick, the earliest notice of which occurs in the year 495. It was destroyed during the Danish incursions. The walls of the chapel at Monasterboice are standing firm and strong, but without a roof, and the grounds surrounding them and the ruins of the monastery are still used for the burial of the families of the parish. It is a free cemetery and belongs to the government and not to the Catholic Church. Anybody--Protestant, Quaker, or Jew--can lay his tired bones down under the hospitable trees by application to the secretary of the board of public works. The oldest grave is that of Bishop O'Rourke, who was buried there in 982; the latest, marked by a clumsy wooden cross, was made in 1907. What people go there to see are three splendid Celtic crosses, the finest specimens of the kind in Ireland, and that means the universe. They are believed to have been erected in the fifth century in honor of St. Patrick, St. Columba, and St. Bridget. This, however, is questionable. One of them bears the inscription, "A prayer for Murriduch, by whom was made this cross." From the Irish Annals it may be learned that two men of that name have lived in this neighborhood, both of wealth and distinction, and they died, one in the year 844 and the other in 924. It is entirely probable that either of them may have erected the splendid monoliths. The largest is twenty-seven feet high, and all of them are covered with carvings of religious subjects. The crosses of Monasterboice have been photographed and reproduced many times, and models have been shipped to all parts of the world. Perfect replicas may be found in the museum at Dublin. Four miles further on are the ruins of Mellifont Abbey, which was founded in the twelfth century, and has had an important part in the political as well as the ecclesiastical history of Ireland.