Taking advantage of Rome's preoccupation, Carausius, who had charge of a Roman fleet, under Diocletian, to repress the Saxon pirates, betrayed his trust, and assumed the sovereignty of Britain in 287 A.D. For six years he ruled an independent kingdom, to be betrayed, in his turn, and murdered by his minister Allectus, who succeeded him. Three years later Rome resumed her authority, and Allectus was slain. Constantine is accused by the historian Zosimus of having withdrawn the soldiers from the forts of Britain to the towns, where they became effeminate. Now Emperor succeeded Emperor in rapid succession. Soon Rome had all she could do to keep {17} the Goths at bay; and, in 410 A.D., Honorius wrote to the Britons to tell them they must look to themselves for safety. Experts differ as to when the Romans actually abandoned the island, but it is safe to say that it was early in the fifth century. Rome's hold on Britain had thus lasted nearly four centuries; and when we remember that it is not much more than four centuries since Columbus discovered America, we can better realize how thoroughly Roman in that period the island and the people must have become. "Under the _Pax Romana_, established by Agricola," writes Mr. H. Rushton Fairclough in _Art and Archæology_, Vol. I. No. 2, "Roman temples, forums, dwelling-houses, baths and porticoes had sprung up everywhere; and, above all, Roman schools, where the youth of the land learnt with pride to adopt the tongue and dress of the conquerors." And this was when more than three centuries of Roman rule were yet to come! {18} CHAPTER III DESCRIPTIVE What is this Wall like, of which we have heard so much? It consists of three parts: 1. A Stone Wall with a ditch on its northern side. 2. A series of forts, mile-castles and Wall turrets, connected by roads. 3. An earthwork known as "The Vallum," consisting of a deep central ditch and two (frequently three and sometimes four) earthern mounds, running always to the south of the Wall and its fortifications. Excavations and inscriptions have now pretty well established the order and the period in which the different parts were constructed, and it appears to have been as follows: 1. Agricola built a series of forts (including Corbridge and Carlisle) across the isthmus, about 79 A.D., with a road, afterwards known as the Stanegate, connecting them. 2. Hadrian first built a new line of forts a short distance to the north of the Stanegate line. {19} [Illustration: Fig. 1.--Section showing the relative positions of the Stone Wall, the Vallum and the Military Way.] {20} 3. Hadrian then constructed the Vallum, as a limes or boundary, slightly to the south of these forts, yet everywhere north of the older line of Agricola.