INTRODUCTION TO SOCIOLOGY 221
According to d'Arbois de Jubanville, the oldest Celtic settle- ments were to the East of the middle Rhine in the basin of the Main and upon both banks of the upper Danube. Toward the end of the seventh century before our era, too cramped for room, or driven back by other tribes, they divided into two groups. The one, turning toward the North Sea, occupied the northern plains of Germany and the British Isles; the other crossed the Rhine and established itself between the Atlantic Ocean and the Alps, spreading later into Spain, where it dominated from the sixth century until the Carthaginian conquest effected between the years 236 and 218. All of these Celtic populations thus spread by following river basins and natural highways, and, when neces- sary, by crossing mountains. It was impossible to confine them between rivers or mountains ; they even crossed the sea.
The Alps even were surmounted ; the Celtic invasion of Italy was quickly followed by the taking of Rome by the Gauls in 390. Some established themselves in the valley of the Po; the others, toward the southeast in the region between the Appennines and the Adriatic. At the same time, other tribes occupied Pannonia and northern Thrace. The Celtic race touched the Black Sea, and thence spread into Galatia in Asia Minor. In Europe, just as in Asia, this civilization was essentially fluvial and continental, and in reality interfluvial. Other movements, of settlements, of repulse, and of replacement, were produced in succession at the same time with regional differentiations. Thus the Belgae, driven out of Germany, settled from the Rhine to the Seine ; others estab- lished themselves in the center of Gaul. The Belgae also crossed the Channel and colonized Britain. As to the Ligurians, who occupied the whole basin of the Rhone and the upper portions of the Garonne and of the Seine, they were forced back toward the Mediterranean. All the divisions and subdivisions which were pro- duced in the mass of the Celtic populations were social combina- tions, of which the mountains and the rivers were only accessory elements and by no means decisive.
At the coming of Caesar, Gaul extended on the south to the middle and lower basin of the Garonne (it should be observed that it occupied both banks). On the east it touched and pene-
