Phenomena of Wells and Springs in Drift Material
Drift material, loose material left on the surface by a retiring glacier, plays a part in wells and springs. (a) Beds of clay variously disiposed in a mass of sandy materials. (b) Wells sunk in different situations, and finding a supply of water only when a bed of clay is reached. A well on top of a hill may be shallower than one at the foot. (c) The surface of the earth. (d) Outcrop bed of clay, causing a spring. If the porous materials contain fragments of limestones, these spring waters are hard, and d. A well carried below its supplying-bed may lose its water again.