Mound villages in river flood-plains.
The abundant fertility of river flood-plains inevitably attracts population and necessitates some kind of artificial protection against inundation. The most primitive form of this protection is obvious and widespread, restricted in neither locality nor race. When the flood season converts the flat plain of the White Nile below Gondokora (7° N. Lat.) into an extensive marsh, countless hills of the white ant emerge over the waters. During the dry season, the ants build up their hills to about ten feet, and then live in safety in the upper section during the flood. They greatly surpass in intelligence and constructive ability the human occupants of the valley, the low and wretched Kytch tribe of the Dinka Negroes, who like the ants are attracted by the natural vegetation of the flood-plain, and who use the ant-hills as refuge stations for themselves and their cattle during the flood.[602] Elsewhere in Africa the natives are more intelligent, for flood-plain villages built on artificial mounds have existed from the earliest times. Diodorus Siculus tells us that those of ancient Egypt, when the Nile was high, looked like the Cyclades Islands.[603] Similar ones are constructed by the Barotse tribe on the upper Zambesi.[604] The Niger River, rising in the Foota Jallon and Kong Mountains which form a region of heavy rainfall from February to July, inundates a plain of several thousand square miles for a distance of 250 miles above Timbuctoo. Here again the villages of the agricultural Song-hoi duplicate those of Egypt, built on the same clay mounds, wreathed in the same feathery palms, and communicating with one another only by small boats.[605] The same picture is presented by the Yangtze Kiang plain during the summer overflow—low artificial hills rising from the expanse of muddy water and topped with trees and villages, while sampans moored to their base show the means of communication.[606] In the broad flood-plain of the lower Mississippi River, the chronicles of the De Soto expedition state that the Indian villages visited stood "on mounds made by art." The Yazoo River Indians, at the commencement of the eighteenth century, had their cabins dispersed over the low deltaic land on earthen mounds made by their own hands. There is also strong evidence that some of the works of the Mound-builders in the "bottoms" of the middle and lower Mississippi served as protected sites for the dwellings of their chiefs.[607]
Diking of rivers.
Such meager provisions against inundation suffice for the sparse population characterizing the lower stages of civilization, but they must be supplemented for the increasing density of higher stages by the embankment of the stream, to protect also the adjacent fields. Hence the process of confining rivers within dikes goes back into gray antiquity. Those of the Po and its tributaries were begun before the political history of the Lombardy plains commenced. Strabo mentions the canals and dikes of Venetia, whereby a part of the country was drained and rendered tillable.[608] The main Po has been embanked for centuries as far up as Cremona, a distance of 600 miles, and the Adige to Verona.[609] But the most gigantic dike system in the world is that of the Hoangho, by which a territory the size of England is won from the water for cultivation.[610] The cost of protecting the far spread crops against the autumn floods has been a large annual expenditure and unceasing watchfulness; and this the Chinese have paid for two thousand years, but have not always purchased immunity. Year by year the Yellow River mounts higher and higher on its silted bed above the surrounding lowlands, increasing the strain on the banks and the area of destruction, when its fury is uncaged. The flood of 1887 covered an area estimated at 50,000 square miles, wiped out of existence a million people, and left a greater number a prey to famine.[611] So the fertile Chengtu plain of the Min River, supporting four millions of people on its 2,500 square miles of area, owes its prosperity to the embanking and irrigating works of the engineer heroes, Li Ping and his son, who lived before the Christian era. On the temple in their honor in the city of Kuan Hsien is Li Ping's motto, incised in gold: "Dig the bed deep, keep the banks low." For twenty-one centuries these instructions have been carried out. The stone dikes are kept low to permit a judicious amount of flooding for fertilization, and every year five to six feet of silt are removed from the artificial channel of the Min. To this work the whole population of the Chengtu plain contributes.[612] [See map page 8.]
Social gain by control of the water.
In such organized struggles to reduce the domain of the water and extend that of the dry land, the material gain is not all: more significant by far is the power to co-operate that is developed in a people by a prolonged war against overwhelming sea or river. A common natural danger, constantly and even regularly recurring, necessitates for its resistance a strong and sustained union, that draws men out of the barren individualism of a primitive people, and forces them without halt along the path of civilization. It brings a realizing sense of the superiority of common interests over individual preferences, strengthens the national bond, and encourages voluntary subservience to law.
This is the social or political gain; but this is not all. The danger emanating from natural phenomena has its discoverable laws, and therefore leads to a first empirical study of winds, currents, seasonal rainfall and the whole science of hydraulics. With deep national insight, the Greeks embodied in their mythology the story of Perseus and his destruction of the sea monster who ravaged the coast, and Hercules' killing of the many-headed serpent who issued from the Lernean Marshes to lay waste the country of Argos. Even so early a writer as Strabo states that yet earlier authorities interpreted Hercules' victory over the river god of the Achelous as the embankment of that stream and the draining of its inundated delta tract by the national benefactor.[613] So the Chinese, whose land abounds in swamps and devastating rivers, have a long list of engineer heroes who embanked and drained for the salvation and benefit of mankind. It is highly probable that the communal work involved in the construction of dikes and canals for the control of the Hoangho floods cemented the Chinese nationality of that vast lowland plain, and supplied the cohesive force that developed here at a very remote period a regularly organized state and an advancing civilization.