21. In the middle of the fourth century you have, politically, what Gibbon calls "the final division of the _Eastern_ and _Western Empires_." This really means only that the Emperor Valentinian, yielding, though not without hesitation, to the feeling now confirmed in the legions that the Empire was too vast to be held by a single person, takes his brother for his colleague, and divides, not, truly speaking, their authority, but their attention, between the east and the west. To his brother Valens he assigns the extremely vague "Præfecture of the East, from the lower Danube to the confines of Persia," while for his own immediate government he reserves the "warlike præfectures of Illyricum, Italy, and Gaul, from the extremity of Greece to the Caledonian rampart, and from the rampart of Caledonia to the foot of Mount Atlas." That is to say, in less poetical cadence, (Gibbon had better have put his history into hexameters at once,) Valentinian kept under his own watch the whole of Roman Europe and Africa, and left Lydia and Caucasus to his brother. Lydia and Caucasus never did, and never could, form an Eastern Empire,--they were merely outside dependencies, useful for taxation in peace, dangerous by their multitudes in war. There never was, from the seventh century before Christ to the seventh after Christ, but _one_ Roman Empire, which meant, the power over humanity of such men as Cincinnatus and Agricola; it expires as the race and temper of these expire; the nominal extent of it, or brilliancy at any moment, is no more than the reflection, farther or nearer upon the clouds, of the flames of an altar whose fuel was of noble souls. There is no true date for its division; there is none for its destruction. Whether Dacian Probus or Noric Odoacer be on the throne of it, the force of its living principle alone is to be watched--remaining, in arts, in laws, and in habits of thought, dominant still in Europe down to the twelfth century;--in language and example, dominant over all educated men to this hour.
22. But in the nominal division of it by Valentinian, let us note Gibbon's definition (I assume it to be his, not the Emperor's) of European Roman Empire into Illyricum, Italy, and Gaul. I have already said you must hold everything south of the Danube for Greek. The two chief districts immediately south of the stream are upper and lower Moesia, consisting of the slope of the Thracian mountains northward to the river, with the plains between it and them. This district you must notice for its importance in forming the Moeso-Gothic alphabet, in which "the Greek is by far the principal element",[28] giving sixteen letters out of the twenty-four. The Gothic invasion under the reign of Valens is the first that establishes a Teutonic nation within the frontier of the empire; but they only thereby bring themselves more directly under its spiritual power. Their bishop, Ulphilas, adopts this Moesian alphabet, two-thirds Greek, for his translation of the Bible, and it is universally disseminated and perpetuated by that translation, until the extinction or absorption of the Gothic race.