29. =Constantius and Constantine.= =296--337.=--Allectus was overthrown and slain by Constantius, who, however, did not rule, as Carausius and Allectus had done, by mere right of military superiority. The Emperor Diocletian (=285--305=) discovered that the whole Empire, stretching from the Euphrates to the Atlantic, was too extensive for one man to govern, and he therefore decreed that there should in future be four governors, two principal ones named Emperors (_Augusti_), and two subordinate ones named Caesars. Constantius was first a Caesar and afterwards an Emperor. He was set to govern Spain, Gaul, and Britain, but he afterwards became Emperor himself, and for some time established himself at Eboracum (_York_). Upon his death (=306=), his son Constantine, after much fighting, made himself sole Emperor (=325=), overthrowing the system of Diocletian. Yet in one respect he kept up Diocletian's arrangements. He placed Spain, Gaul, and Britain together under a great officer called a Vicar, who received orders from himself and who gave orders to the officers who governed each of the three countries. Under the new system, as under the old, Britain was not treated as an independent country. It had still to look for protection to an officer who lived on the Continent, and was therefore apt to be more interested in Gaul and Spain than he was in Britain. 30. =Christianity in Britain.=--When the Romans put down the Druids and their bloody sacrifices, they called the old Celtic gods by Roman names, but made no further alteration in religious usages. Gradually, however, Christianity spread amongst the Romans on the Continent, and merchants or soldiers who came from the Continent introduced it into Britain. Scarcely anything is known of its progress in the island. Alban is said to have been martyred at Verulamium, and Julius and Aaron at Isca Silurum. In =314= three British bishops attended a council held at Arles in Gaul. Little more than these few facts have been handed down, but there is no doubt that there was a settled Church established in the island. The Emperor Constantine acknowledged Christianity as the religion of the whole Empire. The remains of a church of this period have recently been discovered at Silchester. 31. =Weakness of the Empire.=--The Roman Empire in the time of Constantine had the appearance rather than the reality of strength. Its taxation was very heavy, and there was no national enthusiasm to lead men to sacrifice themselves in its defence. Roman citizens became more and more unwilling to become soldiers at all, and the Roman armies were now mostly composed of barbarians. At the same time the barbarians outside the Empire were growing stronger, as the tribes often coalesced into wide confederacies for the purpose of attacking the Empire.