After the decadence of the School of _Candida Casa_, Christianity in Scotland seems to have been in abeyance, till it was revived in the sixth century by the arrival of fresh light and energy from Ireland. From that period till the twelfth century the religion and culture of Scotland were entirely derived from that country. It is therefore necessary, in order to follow the origin and development of ecclesiology and art in Scotland, to trace generally their history in Ireland, and to mark the influence of the latter country on the former. Owing to the disturbed state of Britain after the withdrawal of the Romans in the beginning of the fifth century, and the eruptions of the Goths in Gaul, many Christian refugees found their way to Ireland. Christianity was thus introduced, and, during the fifth century, spread rapidly under the instructions of St. Palladius, a reputed emissary of Rome, and St. Patrick, the patron Saint of Ireland. At first the Church seems to have assumed a peculiar collegiate form, consisting of groups of seven bishops placed together in one church; but in the sixth century the monastic rules were introduced, and at once took root and spread with wonderful rapidity amongst the various tribes. Under St. Finnian, after a short time, there are said to have been three thousand monks in the monastic school of Clonard. Columba, one of his twelve disciples, born in 521, founded several monasteries in Ireland, amongst others those of Derry and Kells, Raphoe in Donegal, and Durrow in Meath. In 558 the great monastery of Bangor was founded by St. Comgall, one of Columba’s companions, and is said to have contained thousands of monks.[8] These monasteries were tribal institutions, and were well suited to the social relations of the country. The abbots were connected with the leading families of the tribes, and succeeded one another according to the rules of succession which prevailed amongst the chiefs. Many of the monasteries were established with the consent of the chiefs, and it frequently happened that on such occasions a “rath,” or native fortress, was presented to the founder by the head of the tribe, as a place of security in which his monastic dwellings might be erected.[9] These structures were generally of a slight and simple nature, consisting of huts made of branches or wattles, covered with turf or clay. The churches or oratories were also constructed with wood. The whole establishment seems to have resembled the primitive fortresses of the Celts, consisting of a great enclosing wall or rampart, with temporary erections within. At a later time wooden boards were substituted for wattles, and the roofs were covered with thatch. Dr. Reeves states that St. Palladius erected three churches of oak, while St. Patrick is said to have built one with stone, because no wood was to be found in the locality.[10]