A highway of migration cannot be the abode of a pure race. Its inhabitants necessarily represent the successive human groups by which it has been overrun.[29] The Alsatian of the present day is, accordingly, a product of racial mingling. But the blending has conferred distinctiveness, and Alsatians, claiming a nationality of their own, find valid arguments in racial antecedents no less than in geographical habitation. The uniform appearance of the Alsatian region strikes the traveler at every point of the fertile Ill valley, where the soil is colored by a reddish tinge which contrasts strongly with the greens and grays of surrounding regions. By race also the Alsatian represents a distinct group in which the basal Alpine strain has been permeated by strong admixtures of Nordic blood. The confusion of dark and fair types represent the two elements in the population. In a broader sense the Alsatians are identical with the Swiss population to the south and the Lorrains and Walloons to the north--in fact, they are related to the peoples of all the districts which once constituted the Middle Kingdom of Burgundy. Although sharply defined by nature, Alsace never acquired independence. Its situation between the areas peopled by two powerful continental races was fatal to such a development. But the influence of its physical setting always prevailed, for, despite its political union with Frenchmen or Germans, the region has always been recognized as an administrative unit defined by the surface features which mark it off from surrounding regions. The influence of topographic agencies has even been felt within the province. The separation of Lower from Higher Alsace originated in a natural boundary, formed by a marshy and forest-clad zone extending from the Tännchal and Hochkönigsberg mountains to the point of nearest convergence between the Rhine and the Vosges. This inhospitable tract first separated the two Celtic tribes known as the Sequani and the Mediomatrici. Later, it afforded a convenient demarcation for the Roman provinces of Maxima Sequanorum and Tractus Mediomatricorum. The two archbishoprics of Besançon and Mayence, both of Middle-Age fame, were similarly divided. The coins of Basel and of Strassburg point to the subsistence of this line during the Renaissance, when two distinct territories of economic importance extended over the region. In the administrative France of modern days, the departments of Bas-Rhin and Haut-Rhin again reveal adherence to the dividing line provided originally by nature. Finally after the German annexation of 1871 the “districts” constituted under German authority, with Colmar and Strassburg as their chief towns, conformed once more with the historical line of division.