armed only with stone or bronze
axe, and they rebuffed even man of the iron age. War and hunting parties
had to move along the natural clearings of the rivers, the tracks of
animals, or the few trails beaten out in time by the natives themselves.
Primitive agriculture has never battled successfully against the phalanx
of the trees. Forests balked the expansion of the Inca civilization on
the rainy slope of the Andes, and in Central Africa the negro invaded
only their edges for his yam fields and plantain groves. The earliest
settlements in ancient Britain were confined to the natural clearings of
the chalk downs and oolitic uplands; and here population was chiefly
concentrated even at the close of the Roman occupation. Only gradually,
as the valley woodlands were cleared, did the richer soil of the
alluvial basins attract men from the high, poor ground where tillage
required no preliminary work. But after four centuries of Roman rule and
Roman roads, the clearings along the river valleys were still mere
strips of culture mid an encompassing wilderness of woods. When the
Germanic invaders came, they too appropriated the treeless downs and
were blocked by the forests.[140] On the other hand, grasslands and
savannahs have developed the most mobile people whom we know, steppe
hunters like the Sioux Indians and Patagonians. Thus while the forest
dweller, confined to the highway of the stream, devised only canoe and
dugout boat in various forms for purposes of transportation, steppe
peoples of the Old World introduced the use of draft and pack animals,
and invented the sledge and cart.

[Sidenote: Effect of geographical horizon.]

Primitive peoples carry a drag upon their migrations in their restricted
geographical outlook; ignorance robs them of definite goals. The
evolution of the historical movement is accelerated by every expansion
of the geographical horizon. It progresses most rapidly where the
knowledge of outlying or remote lands travels fastest, as along rivers
and thalassic coasts. Rome's location as toll-gate keeper of the Tiber
gave her knowledge of the upstream country and directed her conquest of
its valley; and the movement thus started gathered momentum as it
advanced. Caesar's occupation of Gaul meant to his generation simply the
command of the roads leading from the Mediterranean to the northern
sources of tin and amber, and the establishment of frontier outposts to
protect the land boundaries of Italy; thi