Whether sparsely or compactly distributed, such groups suffer the limitations inherent in their small size.

They are forever excluded from the historical significance attaching to the large, continuously distributed populations of fertile continental lands.
[Sidenote: Effect upon movements of peoples.] IV.

The next class belongs exclusively to the domain of geography, because it embraces the influence of the features of the earth's surface in directing the movements and ultimate distribution of mankind.

It includes the effect of natural barriers, like mountains, deserts, swamps, and seas, in obstructing or deflecting the course of migrating people and in giving direction to national expansion; it considers the tendency of river valleys and treeless plains to facilitate such movements, the power of rivers, lakes, bays and oceans either to block the path or open a highway, according as navigation is in a primitive or advanced stage; and finally the influence of all these natural features in determining the territory which a people is likely to occupy, and the boundaries which shall separate from their neighbors.
[Sidenote: River routes.] The lines of expansion followed by the French and English in the settlement of America and also the extent of territory covered by each were powerfully influenced by geographic conditions.

The early French explorers entered the great east-west waterway of the St.Lawrence River and the Great Lakes, which carried them around the northern end of the Appalachian barrier into the heart of the continent, planted them on the low, swampy, often navigable watershed of the Mississippi, and started them on another river voyage of nearly two thousand miles to the Gulf of Mexico.