INTRODUCTION TO SOCIOLOGY 773
to serve as a buffer. It was not able to defend the left bank of the Rhine, nor to prevent the invasion of the Romans. As early as the year 43 these had founded the colonies or military frontiers of Lugdunum and of Colonia Rauraca near Basel. Only the popu- lation of the Alps had remained free in their high valleys. The conquest of Gaul advanced the Roman sway at once to the Rhine ; it encompassed all the intermediate basins, with all their ethnical and political subdivisions.
Thus at the time of Caesar's death, after the kingdom of luba had been annexed to the province of Africa, the whole circum- ference of the Mediterranean Sea belongs to Rome, except the two extremities of the south coast. Still at different points the sphere of penetration is yet but little extended, as in Dalmatia, where the ties between the two parts of the empire have remained feeble. After the battle of Actium, Augustus will see to this.
At the middle of the third century after Christ the Roman Empire exceeds, not only in latitude, but also in longitude, all known civilizations. Rome has politically leveled all geographic boundaries, all ethnical divisions; it has absorbed^ the Etruscans, the Greeks, the Phoenicians, the Egyptians, the Aryans, the Semites, the Hamites. Of the ancient historical states there remain but Persia, restored in 226 by the Sassanides, India, which consisted politically of the greater part of the peninsula, and China. These begin to entertain indirect relations with the nations at the coast of the Mediterranean. Thus the civilization embraces most river and sea basins, and reaches to the Atlantic, the Indian, and even the Pacific Ocean. It has proceeded, toward the north, to Britanny and a part of Germany. Beyond the Rhine and the Danube the Germans, and farther east the Slavs, represent a niveau still inferior to that of the nations which are contained within the boundaries of the empire. Between Europe and Asia are the Mongolian nomads. Yet as no frontier was impervious, the infiltrations continue from without to the interior of the empire, and from within to the outlying regions.
Yet the development of a pre-eminently military empire has doubtless not proceeded without any drawback, in spite of the progressive and organic differentiation of its peaceful elements,
