220 THE AMERICAN JOURNAL OF SOCIOLOGY
frontiers, and to seek the facts which may serve as the basis of a positive theory in regard to this main problem.
If we consult the works especially of G. de Mortillat upon pre- historic France and the formation of the French nation, and other works not less remarkable, and put them in relation with geographical facts, we observe, in the age of reindeer and of caves, the well-established existence of more than five hundred caverns scattered through half a hundred of the present depart- ments of France. These caverns are in general distributed along, and on either side of, water-courses, streams, or rivers. There- fore, even at this remote period, water-courses, which were doubtless followed imperceptibly from source to mouth, no longer constituted, if they had ever done so, natural barriers or frontiers.
The same observation is applicable to the age of polished stone, characterized by megalithic monuments, dolmens, etc. The area of the megalithic monuments extends almost without inter- ruption from the beaches of Norway and Sweden along the coast of western Europe to the shores of Morocco, Algeria, and Tunis ; it follows the Rhone and the Saone upon either side, thence turns toward the east, through Chalons to Berlin. Outside of this extensive zone, embracing a uniform civilization, one does not find a trace of it ; but, whatever its inner subdivision into distinct groups, one perceives that this civilization was already both fluvial and littoral. According to Alexander Bertrand, it reappeared on the one side as far away as the foot of the Caucasus, and on the other, in Lencoran in Transcaucasia.
All these cave and megalithic populations were subdued by the Celts, and they were, moreover, distinct from the Ligurians, whose area of expansion was almost entirely outside of the limit of the regions occupied by the megalithic populations.
Another Indo-European current was oriental. Starting from the Black Sea and the valleys of the Caucasus, or the great plains of the Don and the Volga, it followed the banks of the Danube and the Dneiper. It established the lacustrine cities in the Swiss lakes, and as far as Lake Bourget in Savoy, as well as in those of the valleys of the Danube, always indifferently upon both banks ; and also in northern Italy.
