Round towers of about 18 feet in external diameter, and varying in height from 60 to about 110 feet, are frequently found in connection with the earlier monastic establishments of Ireland. The question of their origin and uses long occupied much antiquarian attention. In the seventeenth and eighteenth centuries they had been regarded by archæologists as the work of the Danes; but towards the close of the latter century General Vallancey propounded various theories, which assumed them to be of Phœnician or Indo-Scythian origin, and to have contained the sacred fire from whence all the fires in the kingdom were annually rekindled. By those who affirmed their Christian origin they were successively declared to be anchorite towers in imitation of that of St. Simon Stylites, and penitential prisons, and thus theories were multiplied until they became almost as numerous as the towers themselves. Each succeeding writer, instead of elucidating, appeared to involve the subject in deeper mystery than ever--a mystery that was proverbial until dispelled by George Petrie in his great work on _The Origin and Uses of the Round Towers of Ireland_, which was received, with good cause for the effusion, as ‘the most learned, the most exact, and the most important ever published upon the antiquities of the ancient Irish nation.’ That the general conclusions embodied in this work were arrived at after a long and patient investigation, not only of the architectural peculiarities of the numerous round towers, but also of the ecclesiastical structures usually found in connection with them, is sufficiently shown by the many references to, and illustrations of, examples scattered over the whole country. But Petrie also, with the assistance of the best Celtic scholars in Ireland, sought in the ‘Annals’ and other Irish MSS. for references to such buildings as it was the custom of the early inhabitants to erect; and from these hitherto-neglected sources of information, much light was thrown upon the subject of ancient Irish ecclesiastical architecture. The following is a summary of Petrie’s conclusions:-- 1. That the Irish ecclesiastics had, from a very early period, in connection with their cathedral and abbey churches, campaniles or detached belfries, called in the Irish ‘Annals’ and other ancient authorities by the term _Cloictheach_, ‘House of a bell.’ 2. That no other building, either round or square, suited to the purpose of a belfry, has ever been found in connection with any church of an age anterior to the twelfth century, with the single exception of the square belfry attached to a church on Inis Clothrann or Clorin, an island in Lough Ree, which seems to be of earlier date.