GRADUAL OVERTHROW OF THE EMPIRE.--When we speak of the destruction of the Roman Empire by the barbarians, we must not imagine that it was sudden, as by an earthquake. It was gradual. Had the empire not been undermined from within, it would not have been overthrown from without. The Roman armies were recruited by bringing numerous barbarians into the ranks. At length whole tribes were suffered to form permanent settlements within the boundaries of the empire. A "king" with his entire tribe would engage to do military service in exchange for lands. More and more both the wealth and the weakness of Rome were exposed to the gaze of the Germanic nations. Their cupidity was aroused as their power increased. Meantime the barbarians were learning from their employers the art of war, and were gaining soldierly discipline. Their brave warriors rose to places of command. They made and unmade the rulers, and finally became rulers themselves. Another important circumstance is, that most of the Germanic tribes were converts to Christianity before they made their attacks and subverted the throne of the Cæsars. In fine, there was a long preparation for the great onset of the barbarian peoples in the fifth century. CAUSES OF THE FALL OF THE EMPIRE.--But the success of the barbarian invasions presupposes an internal decay in the empire. It was one symptom of a conscious decline, that the conquering spirit was chilled, and the policy was adopted of fixing the limits of the Roman dominion at the Rhine and the Danube. Rome now stood on the defensive. The great service of the imperial government, for which it was most valued, was to protect the frontiers. This partly accounts for the consternation of _Augustus_, when, in the forests of Germany, the legions of _Varus_ were destroyed (p. 172). The essential fact is, that Rome became unable to keep up the strength of its armies. _First_, there were lacking the men to fill up the legions. The civil wars had reduced the population in Italy and in other countries. The efforts of _Augustus_ to encourage marriage by bounties proved of little avail. _Secondly_, the class of independent Italian yeomen, which had made up the bone and sinew of the Roman armies, passed away. Slavery supplanted free labor. _Thirdly_, in the third century terrible plagues swept over the empire. In 166 a frightful pestilence broke out, from which, according to _Niebuhr_, the ancient world never recovered. It was only the first in a series of like appalling visitations. _Fourthly_, the death of liberty carried after it a loss of the virtue, the virile energy, by which Rome had won her supremacy. _Fifthly_, the new imperial system, after _Diocletian_, effective as it was for maintaining an orderly administration, drained the resources of the people. The municipal government in each town was put into the hands of _curiales_, or the owners of a certain number of acres. They were made responsible