The rapid unfolding of the geographical horizon in a young land communicates to an expanding people new springs of mobility, new motives for movement out and beyond the old confines, new goals holding out new and undreamt of benefits.  Life becomes fresh, young, hopeful.  Old checks to natural increase of population are removed.  Emigrant bands beat out new trails radiating from the old home.  They go on individual initiative or state-directed enterprises; but no matter which, the manifold life in the far-away periphery reacts upon the center to vivify and rejuvenate it.

[Sidenote:  Relation of ethnic to political expansion.]

The laws of the territorial growth of peoples and of states are in general the same.  The main differences between the two lies in the fact that ethnic expansion, since it depends upon natural increase, is slow, steady, and among civilized peoples is subject to slight fluctuations; while the frontiers of a state, after a long period of permanence, can suddenly be advanced by conquest far beyond the ethnic boundaries, often, however, only to be as quickly lost again.  Therefore the important law may be laid down, that the more closely the territorial growth of a state keeps pace with that of its people, and the more nearly the political area coincides with the ethnic, the greater is the strength and stability of the state.  This is the explanation of the vigor and permanence of the early English colonies in America.  The slow westward protrusion of their frontier of continuous settlement within the boundaries of the Allegheny Mountains formed a marked contrast to the wide sweep of French voyageur camp and lonely trading-station in the Canadian forests, and even more to the handful of priests and soldiers who for three centuries kept an unsteady hold upon the Spanish empire in the Western Hemisphere.  The political advance of the United States across the continent from the Alleghenies to the Mississippi, thence to the Rocky Mountains, and thence to the Pacific was always preceded by bands of enterprising settlers, who planted themselves beyond the frontier and beckoned to the flag to follow.  The great empires of antiquity were enlarged mechanically by conquest and annexation.  They were mosaics, not growths.  The cohesive power of a common ethnic bond was lacking; so was the modern substitute for this to be found in close economic interdependence maintained by improved methods of communication.  Hence these empires soon broke up again along lines of old geographic and ethnic cleavage.  For Rome, the cementing power of the Mediterranean and the fairly unified civilization which this enclosed sea had been evolving since the dawn of Cretan and Phoenician trade, compensated in part for the lack of common speech and national ideals throughout the political domain.  But the Empire proved in the end to be merely a mosaic, easily broken.

[Sidenote:  Relation of people and state to political boundary.]