Wedge

wej, a well known device consisting of a piece of wood, metal, or other hard substance, thick at one end and sloping to a thin edge at the other. The wedge is used for splitting timber, quarrying rock, and for raising great weights or exerting intense pressure. A quick tap on the head of a wedge produces more effect than a heavier, sluggish blow. It is supposed that the tap sets up a tremor or vibration in the inclosing edges of the resisting substance, and that the wedge advances before the vibrating material can return. Something of the sort may be noticed in driving a nail. Lively taps force a nail into hard timber when heavy blows fail. Other conditions being equal, the thinner the wedge the greater its power. The sharp edge of cutting tools is an application of the principle of the wedge. The uselessness of a wedge until it has effected an entrance, and its power afterward, have given rise to several popular expressions, as "the entering wedge," "wedging his way in," etc.