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A spear-thrower or atlatl (〔(【引用サイトリンク】 publisher = Dictionary.com )〕 ; ) is a tool that uses leverage to achieve greater velocity in dart-throwing, and includes a bearing surface which allows the user to store energy during the throw. It may consist of a shaft with a cup or a spur at the end that supports and propels the butt of the dart. The spear-thrower is held in one hand, gripped near the end farthest from the cup. The dart is thrown by the action of the upper arm and wrist. The throwing arm together with the atlatl acts as a lever. The spear-thrower is a low-mass, fast-moving extension of the throwing arm, increasing the length of the lever. This extra length allows the thrower to impart force to the dart over a longer distance, thus imparting more energy and ultimately higher speeds. Common modern ball throwers (molded plastic shafts used for throwing tennis balls for dogs to fetch) use the same principle. A spear-thrower is a long-range weapon and can readily impart to a projectile speeds of over . Spear-throwers appear very early in human history in several parts of the world, and have survived in use in traditional societies until the present day, as well as being revived in recent years for sporting purposes. In the United States the Nahuatl word ''atlatl'' is often used for revived uses of spear-throwers, and in Australia the Aboriginal word ''woomera''. The ancient Greeks and Romans used a leather thong or loop, known as an ''ankule'' or ''amentum'', as a spear-throwing device.〔Howard L. Blackmore. (2000) ''Hunting Weapons: From the Middle Ages to the Twentieth Century'', page 103 "... the air'.31 A device which enabled all but the heaviest of spears to be cast a respectable distance was the spear thrower. ... It was known to the Greeks as the ankuli and to Romans as the amentum.3 The spear was rested in the hand and ..."〕 ==Design== Spear-thrower designs may include improvements such as thong loops to fit the fingers, the use of flexible shafts, stone balance weights, and thinner, highly flexible darts for added power and range. Darts resemble large arrows or thin spears and are typically from in length and 9 to 16 mm (3/8" to 5/8") in diameter. Another important improvement to the spear-thrower's design was the introduction of a small weight (between 60 and 80 grams) strapped to its midsection. Some atlatlists maintain that stone weights add mass to the shaft of the device, causing resistance to acceleration when swung and resulting in a more forceful and accurate launch of the dart. Others claim that spear-thrower weights add only stability to a cast, resulting in greater accuracy. Based on previous work done by William S. Webb, William R. Perkins〔(【引用サイトリンク】title=Atlatls & Primitive Technology )〕 claims that spear-thrower weights, commonly called "bannerstones," and characterized by a centered hole in a symmetrically shaped carved or ground stone, shaped wide and flat with a drilled hole and thus a little like a large wingnut, are a rather ingenious improvement to the design that created a silencing effect when swung. The use of the device would reduce the telltale "zip" of a swung atlatl to a more subtle "woof" sound that did not travel as far and was less likely to alert prey or other humans. Robert Berg's theory is that the bannerstone was carried by hunters as a spindle weight to produce string from natural fibers gathered while hunting, for the purpose of tying on fletching and hafting stone or bone points. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spear-thrower」の詳細全文を読む スポンサード リンク
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