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.]

[Sidenote:  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