Drainage

Proce of removing water from the soil by means of open or underground artificial conduits. It is of benefit both in removing surplus water and admitting air to the pores of the soil, whereby chemical action resulting in the setting free of plant-food is induced. It has been extensively carried on in all parts of the world. In Holland large tracts have been reclaimed from the inundations of the ocean by the construction of dikes and by pumping. The sanitary condition of a country is found to be greatly improved by the drainage of marshes and low lands. The drainage of cities is effected by sewers, which were first built by the Romans. The drainage canals and tunnel, completed 1894, for the protection of the City of Mexico, are among the greatest engineering works of modern times.