corded history. Tropical Africa lacks a history; but all that has
been pieced together by ethnologists and anthropologists, in an effort
to reconstruct its past, shows incessant movement,--growth, expansion
and short-lived conquest, followed by shrinkage, expulsion or absorption
by another invader.[127] To this constant shifting of races and peoples
the name of historical movement has been given, because it underlies
most of written history, and constitutes the major part of unwritten
history, especially that of savage and nomadic tribes. Two things are
vital in the history of every people, its ethnic composition and the
wars it wages in defense or extension of its boundaries. Both rest upon
historical movements,--intrusions, whether peaceful or hostile, into its
own land, and encroachments upon neighboring territory necessitated by
growth. Back of all such movements is natural increase of population
beyond local means of subsistence, and the development of the war spirit
in the effort to secure more abundant subsistence either by raid or
conquest of territory.

[Sidenote: Evolution of the Historical Movement.]

Among primitive peoples this movement is simple and monotonous. It
involves all members of the tribe, either in pursuit of game, or
following the herd over the tribal territory, or in migrations seeking
more and better land. Among civilized peoples it assumes various forms,
and especially is differentiated for different members of the social
group. The civilized state develops specialized frontiersmen, armies,
explorers, maritime traders, colonists, and missionaries, who keep a
part of the people constantly moving and directing external expansion,
while the mass of the population converts the force once expended in the
migrant food-quest into internal activity. Here we come upon a paradox.
The nation as a whole, with the development of sedentary life, increases
its population and therewith its need for external movements; it widens
its national area and its circle of contact with other lands, enlarges
its geographical horizon, and improves its internal communication over a
growing territory; it evolves a greater mobility within and without,
which attaches, however, to certain classes of society, not to the
entire social group. This mobility becomes the outward expression of a
whole complex of economic wants, intellectual needs, and political
ambitions. It is embodied in the conquests which build up empires, in