Piles

Piles are usually squared logs of wood used in engineering operations, such as dams, bridges, and roads (see COFFERDAM, &c.) They are sharpened at the point, and, if necessary, protected with iron points, to enable them to cut through the strata they encounter as they are driven into the ground. Piles are also used for permanent works, when they are driven through loose soil till they reach a firm bottom, and thus form a foundation on which buildings, roads, &c. may be placed. Cast-iron is also used for piles, which are cast hollow. Common piles are driven in by machines called pile-drivers. In these a heavy weight (or monkey) is raised to a considerable height between two gnides, and then let fall on the head of the pile. The application of steam to these drivers has made them very powerful engines—Nasmyth's steam-hammer being a well-known instance. See also LAKE-DWELLINGS.