a Shawnee village situated on both sides of the river below the
mouth of the Scioto, with about a hundred houses on the north bank and
forty on the south.[687] The small and unique nation of the Mandan
Indians were found by Lewis and Clark near the northern bend of the
Missouri in 1804, in two groups of villages on opposite sides of the
river. They had previously in 1772 occupied nine villages lower down the
stream, two on the east bank and seven on the west.[688] The Connecticut
River settlers of early colonial days laid out all their towns straight
across the valley, utilizing the alluvial meadows on both banks for
tillage, the terraces for residence sites, and the common river for
intercourse.[689]

[Sidenote: Tendency toward ethnic and cultural unity in a river valley.]

Every river tends to become a common artery feeding all the life of its
basin, and gradually obliterating ethnic and cultural differences among
the peoples of its valley. The Nile, with its narrow hem of flood-plain
on either bank and barrier sands beyond, has so linked race and history
in Egypt and Nubia, that the two countries cannot be separated. A common
highway from mountains to sea, a common frontier of trackless desert
have developed here a blended similarity of race, language and culture
from the delta to Kordofan. The Hamitic race seems to have originated in
the south and migrated northward down the Nile towards the delta. Later
the whole valley, north and south, received the same Semitic or Arab
immigration, which spread from Cairo to the old Sudanese capital of
Sennar, while a strain of negro blood has filtered in from the
equatorial black belt and followed the current down to the sea.[690] The
culture of the valley originated in Lower Egypt, and, with that easy
transmissibility which characterizes ideas, it moved upstream into
Ethiopia, which never evolved a culture of its own. Just as noticeable
is the political interplay. The rule of the Pharaohs extended far up the
Nile, at times to the Third Cataract at 20 deg. N.L.; and at one period
Ethiopian kings extended their sway over Egypt. At another, a large body
of mutinous Egyptian soldiers abandoned their country and their wives,
and emigrated along the one line of slight resistance open to them into
Ethiopia, to found there a new state and new families by marriage with
native women, thus contributing to the amalgamation of races in the
valley.

[Sidenote: Identity of country with riv