_The Origin of the Round Towers_ (the first branch of the question proposed by the Royal Irish Academy) is really only part of a much wider problem which had long engaged the attention of earnest, capable, and industrious archæologists, with whose names the reader of this work is likely to become only too familiar. The Round Towers are merely one class of more or less elaborate architectural or monumental remains, scattered all over Ireland, and bearing unmistakable signs of a very remote antiquity.[16] That these remains are inseparably connected in time and origin, seems to be proved by the fact that no writer upon the subject of the Round Towers had hitherto been able to treat of the latter exclusively, without taking into consideration the “crosses” or “temples,” or other subdivisions of the whole, and that neither Dr. Petrie nor his rival claimed exemption from the same necessity. A great portion of their respective works on the Round Towers is devoted, for instance, to a consideration of other antiquities; and what is perhaps the most valuable part of O’Brien’s,--namely, that upon which his assumption of a _pagan_ origin chiefly rests,--is the result of investigation into the nature of that symbolism for which the sculptured crosses are so remarkable. It seemed, in fact, impossible for those who studied the subject carefully to resist the conclusion that all these remains belong to a period when Ireland was inhabited by a race which differed in many respects from the Irish of a later date. In Dr. Petrie’s opinion, that race consisted of the early Christian missionaries and their proselytes; in O’Brien’s, it belonged to an era far antecedent to Christianity itself; and so far, he is at one with the leading authorities who preceded him. Limiting his statement to the Round Towers, Dr. Petrie informs us[17] that, up to the time at which he undertook to decide the matter, two theories prevailed as to the “origin” of these structures: (1) That they were erected by the Danes; (2) that they were of Phœnician origin. But O’Brien discards the Danes altogether, and only allows a very subordinate part indeed to the Phœnicians, namely, that of having, as sea-carriers, assisted to convey the _Tuath-de-danaans_ to Ireland. For the grounds upon which Dr. Petrie attributes an exclusively Christian origin to the Round Towers inquirers must be referred to the body of his work, where they will find it most ingeniously, if not quite ingenuously, argued at much length that these structures were erected between the fifth and thirteenth centuries of our era by Christian founders. An outline of his rival’s argument to the contrary is given in the annexed “Synopsis.” The difference between the respective methods of the two theorists is very marked, and here the advantage does not rest with O’Brien. Petrie is calm, precise, authoritative; O’Brien fervid, rambling, and passionately expostulative.