A river system is a system of communication. It therefore makes a bond of union between the people living among its remoter sources and those settled at its mouth. Every such river system forms geographically an unbroken whole. Only where a wild, torrent-filled gorge, like the Brahmaputra's path through the Himalayas, interrupts communication between the upper and lower course, is human life in the two sections divorced. But such cases are rare. Even the River Jhelam, which springs with mad bounds from the lofty Vale of Kashmir through the outer range of the Himalayas down to its junction with the Indus, carries quantities of small logs to be used as railway sleepers; and though it shatters a large per cent. of them, it makes a link between the lumber men of the Kashmir forests and British railroad engineers in the treeless plains of the Indus.[681]
The effect of common water supply in arid lands.
In arid lands, where the scant and variable streams are useless for navigation, but invaluable for irrigation, a rival interest in the limited water supply leads almost inevitably to conflict, and often to the political union of the peoples holding the upper and lower courses, in order to secure adjustment of their respective claims. The ancient Salassi of the upper Doria Baltea Valley in the Alps drew off all the water of the stream for washing gold, and thus deprived the agricultural people lower down the valley of the water necessary for irrigation. The result was frequent wars between the two tribes.[682] The offensive is taken by the downstream people, whose fields and gardens suffer from every extension of tillage or increase of population in the settlements above them. Occasionally a formal agreement is a temporary expedient. The River Firenze and other streams watering southern Trans-Caspia have their sources in the mountains of northern Persia; hence the Russians, in the boundary convention with Persia of 1881, stipulated that no new settlement be established along these streams within Persian territory, no extension of land under cultivation beyond the present amount, and no eduction of the water beyond that necessary to irrigate the existing fields.[683] Russia's designs upon Afghanistan aim not only at access to India, but also at the control of the upper Murghab River, on whose water depends the prosperity of the Pendjeh and Merv oases.[684] In such regions the only logical course is the extension of the political frontier to the watershed, a principle which Russia is applying in western Asia, and which California applied in drawing her eastern boundary to include even Goose Lake.
Union of opposite river banks.
Rivers unite. Ancient Rome grew up on both banks of the Tiber, and extended her commercial and political supremacy up and down stream. Both sides of the Rhine were originally occupied by the Gallic tribes, whose villages were in some instances bisected by the river. Cæsar found the Menapii, a Belgian people on the lower Rhine, with their fields, farmhouses and villages on both banks.[685] Then the westward advance of the Teutonic tribes gradually transformed the Rhine into a German river, from the island of Batavia at its mouth up to the great elbow at the foot of the Jura Mountains.[686] To the American Indians even the widest rivers were no barriers. Christopher Gist, exploring the Ohio in 1751, found 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]
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° 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.