Wedge (0. Eng. wecg, a mass of metal, cognate with Dutch wig, wigge, Dan. vaegge, &c.; in Lith. the cognate form outside Teut. is found in wagis, a peg, spigot; there is no connexion with "weigh," "weight," which must be referred to the root wegh, to lift, carry, draw, cf. Lat. vehere, whence "vehicle," &c.), a piece of wood or metal, broad and thick at one end, and inclined to a thin edge or point at the other, used as a means for splitting wood, rocks, &c., of keeping two closely pressing surfaces apart, or generally for exerting pressure in a confined space. The "wedge" has sometimes been classed as one of the simple mechanical powers, but it is properly only an application of the inclined plane.
In meteorology, the term "wedge" is used of a narrow area of high pressure between two adjacent cyclonic systems, which takes the form of a wedge or tongue, as do the isobars representing it on a weather-chart. A wedge moves along between the rear of a retreating cyclone and the front of one advancing, and may be regarded as a projection from an anticyclonic system lying to one side of the course of the cyclones. As the crest of the wedge (i.e. the line of highest pressure) passes over any point the wind there changes suddenly from one direction almost to the opposite, while the clearing weather of the retreating cyclone and the temporary fine weather after its passing are quickly succeeded by a break indicating the approach of the following cyclone. Conditions exactly opposite to those accompanying a wedge are provided by a "V-shaped depression."
