The monastery including the whole group of monastic buildings was generally, but not always, surrounded by a strong rampart, commonly circular or elliptical, after the manner of the homesteads of the laity. The enclosure with its bounding rampart was designated in Irish by various names. When the wall was of earth it was called a _rath_, or _lios_. If surrounded by a stone wall it was known as a _caiseal_ or sometimes a _cathair_.[158] Sometimes the monks located themselves in a rath or lios surrendered by a friendly chief,[159] and sometimes the monks built the enclosure themselves.[160] So much was the rampart a feature of the Irish monastery that we find it in connection with the monasteries founded by Irish monks in foreign lands. A _vallum monasterii_ is mentioned by Adamnan,[161] and Columbanus utilised the walls of the old Roman _castrum_ to serve as the _vallum_ for his monastery at Luxeuil.[162] The monastery proper was the space enclosed by the vallum and included the church or churches, the oratories, the refectory, the kitchen, the school, the armarium—a chamber for the preservation of books and literary apparatus, sometimes a special scriptorium, the hospice or guest house, the cells for the monks, and the officinae or workshops for the smith and the carpenter.[163] Outside of the vallum were the various other indispensable buildings connected with the monastery of which the storehouse and the mill are the most important. There was usually a byre for the cows situated in convenient pasture land. If the monastery was located inland there was a fish pond; or a convenient harbour, if near the sea. The various buildings occupied different situations according to local convenience.[164] The structure of these early monasteries was of a simple and inexpensive character. Like the early Celtic churches, they were built at first of earth, wattles, or wood. It was not until the eighth century that stone buildings began to be substituted for wooden ones, as a protection against the ravages of the Danes.[165] The simplicity and temporary character of these early foundations would account for the quickness with which monastic cities sprang up as well as for the fact that comparatively few material remains of these monastic settlements are now to be seen. They are now remembered chiefly for the great spiritual and literary heritage which they were the means of transmitting. They were of various sizes. Those planted on barren islands off the coast of Ireland and Scotland must have been small. In each of the great monasteries of Clonard, Bangor and Clonfert there were 3000, including probably both monks and students. St. Molaise had 1,500 at Mungret, St. Gobban had 1000 and so on down to the school of St. Mobi at Glasnevin with 50. This last number, fifty, seems to have been the usual number in the smaller monastic schools.[166] DAILY LIFE IN AN IRISH MONASTERY: