Note 701 — Chapter XI · —The Anthropo-Geography Of Rivers

For political boundaries, which are often adopted with little reference to race distribution, rivers serve fairly well. They are convenient lines of demarcation and strategic lines of defense, as is proved by the military history of the Rhine, Danube, Ebro, Po, and countless other streams. On the lower Zambesi Livingstone found the territories of the lesser chiefs defined by the rivulets draining into the main river. The leader of the Makololo formally adopted the Zambesi as his political and military frontier, though his people spread and settled beyond the river.701 Long established political frontiers may become ethnic boundaries, more or less distinct, because of protracted political exclusion. To the Romans, the Danube and Rhine as a northeastern frontier had the value chiefly of established lines in an imperfectly explored wilderness, and of strategic positions for the defense of an oft assailed border; but the long maintenance of this political frontier resulted in the partial segregation and hence differentiation of the people dwelling on the opposite banks.