Contradictory as these statements appear, they may easily be ranged into two separate theories of pagan or Christian origin. Dr. Petrie has been the great supporter of the latter opinion, now almost generally received. He founds his opinion: (1) On the assumption that the Irish did not know the use of lime mortar before the time of St. Patrick. For this assumption, however, he gives no evidence. (2) On the presence of certain Christian emblems on some of these towers, notably at Donaghmore and Antrim. But the presence of Christian emblems, like the cross on the Ogham stones, may merely indicate that Christians wished to consecrate them to Christian use. (3) On the assumption that they were used as keeps or monastic castles, in which church plate was concealed, or wherein the clergy could shelter themselves from the fury of Danes, or other invaders. But it is obvious that towers would have been built in a different fashion had such been the object of those who erected them. The late Mr. D'Alton has been the most moderate and judicious advocate of their pagan origin. He rests his theory (1) on certain statements in our annals, which, if true, must at once decide the dispute. The Annals of Ulster mention the destruction of fifty-seven of them in consequence of a severe earthquake, A.D. 448. He adduces the testimony of Giraldus Cambrensis, who confirms the account of the origin of Lough Neagh by an inundation, A.D. 65, and adds: "It is no improbable testimony to this event, that the fishermen beheld the religious towers (_turres ecclesiasticas_), which, according to the custom of the country, are narrow, lofty, and round, immersed under the waters; and they frequently show them to strangers passing over them, and wondering at their purposes" (_reique causas admirantibus_). This is all the better evidence of their then acknowledged antiquity, because the subject of the writer was the formation of the lough, and not the origin of the towers. Mr. D'Alton's (2) second argument is, that it was improbable the Christians would have erected churches of wood and bell towers of stone, or have bestowed incomparably more care and skill on the erection of these towers, no matter for what use they may have been intended, than on the churches, which should surely be their first care.[163]