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; this represented a bold policy of inland expansion for that day.