CHARACTER OF THE MIDDLE AGES.--The middle ages include the long interval between the first general irruption of the Teutonic nations towards the close of the fourth century, to the middle of the fifteenth century, when the modern era, with a distinctive character of its own, began. Two striking features are observed in the mediæval era. First, there was a mingling of the conquering Germanic nations with the peoples previously making up the Roman Empire, and a consequent effect produced upon both. The Teutonic tribes modified essentially the old society. On the other hand, there was a reaction of Roman civilization upon them. The conquered became the teachers and civilizers of the conquerors. Secondly, the Christian Church, which outlived the wreck of the empire, and was almost the sole remaining bond of social unity, not only educated the new nations, but regulated and guided them, to a large extent, in secular as well as religious affairs. Thus out of chaos, Christendom arose, a single homogeneous society of peoples. It was in the middle ages that the pontifical authority reached its full stature. The Holy See exercised the lofty function of arbiter among contending nations, and of leadership in great public movements, like the Crusades. Civil authority and ecclesiastical authority, emperors and popes, were engaged in a long conflict for predominance. Thus there are three elements which form the essential factors in Mediæval History,-the _Barbarian_ element, the _Roman_ element, with its law and civil polity, and with what was left of ancient arts and culture, and the _Christian_, or _Ecclesiastical_, element. As we approach the close of the mediæval era, a signal change occurs. The nations begin to acquire a more defined individuality; the superintendence of the church in civil affairs is more and more renounced or relinquished; there dawns a new era of invention and discovery, of culture and reform. PERIOD I. FROM THE MIGRATIONS OF THE TEUTONIC TRIBES TO THE CARLOVINGIAN LINE OF FRANK RULERS. (A.D. 375-751.) CHAPTER I. CAUSES OF THE FALL OF THE WESTERN EMPIRE: THE TEUTONIC CONFEDERACIES.