Page:Historic highways of America (Volume 15).djvu/102

 to get rid of the surplus water. Water is a heavy, limpid fluid, hard to confine and easy to let loose. It is always seeking for a chance to run down a hill; always trying to find its lowest level."

An essential feature of a good road is good drainage, and the principles of good drainage remain substantially the same whether the road be constructed of earth, gravel, shells, stones, or asphalt. The first demand of good drainage is to attend to the shape of road surface. This must be "crowned," or rounded up toward the center, so that there may be a fall from the center to the sides, thus compelling the water to flow rapidly from the surface into the gutters which should be constructed on one or both sides, and from there in turn be discharged into larger and more open channels. Furthermore, it is necessary that no water be allowed to flow across a roadway; culverts, tile, stone, or box drains should be provided for that purpose.

In addition to being well covered and drained, the surface should be kept as smooth as possible; that is, free from ruts, wheel tracks, holes, or hollows. If any of