The distress of his subjects under these circumstances seems to have drawn the thoughts of "the good Amenemhat" to the devising of some system which should effectually remedy these evils, by preventing their occurrence. In all countries where the supply of water is liable to be deficient, it is of the utmost importance to utilize to the full that amount of the life-giving fluid, be it more or be it less, which the bounty of nature furnishes. Rarely, indeed, is nature absolutely a niggard. Mostly she gives far more than is needed, but the improvidence or the apathy of man allows her gifts to run to waste. Careful and provident husbanding of her store will generally make it suffice for all man's needs and requirements. Sometimes this has been effected in a thirsty land by conducting all the rills and brooks that flow from the highlands or hills into subterranean conduits, where they are shielded from the sun's rays, and prolonging these ducts for miles upon miles, till every drop of the precious fluid has been utilized for irrigation. Such is the _kareez_ or _kanat_ system of Persia. In other places vast efforts have been made to detain the abundant supply of rain which nature commonly provides in the spring of the year, to store it, and prevent it from flowing off down the river-courses to the sea, where it is absolutely lost. For this purpose, either huge reservoirs must be constructed by the hand of man, or else advantage must be taken of some facility which nature offers for storing the water in convenient situations. Valleys may be blocked by massive dams, and millions of gallons thus imprisoned for future use, as is done in many parts of the North of England, but for manufacturing and not for irrigation purposes. Or naturally land-locked basins may be found, and the overflow of streams at their flood-time turned into them and arrested, to be made use of later in the year.