its nock and the inertia of its weighted point, storing energy. Late in this throw, as the point moves faster and so offers less resistance, the dart releases most of this energy by springing away from the thrower. Some energy may also be recovered by the fletching as the projectile "fishtails" through the air. However, this energy is far less than is commonly stated and only effectively increases accuracy by counteracting the downward force on the tail. To maximize elastic energy storage and recovery, such darts should be held only by the nock and allowed to pivot as they are thrown. This requires a special tool called a spear-thrower. In Western culture these might be called atlatl borrowed from the Aztec, or in Australia the Aboriginal word woomera is used. Plumbatae or martiobarbuli Plumbatae or martiobarbuli were lead-weighted darts carried by infantrymen in Antiquity and the Middle Ages. The first examples seem to have been carried by the Ancient Greeks from about 500 B.C. onwards, but the best-known users were from the Roman and Byzantine armies. The best written source for these tactical weapons is Vegetius's treatise known as De Re Militari (1.17): Replacement by the arrow In Europe, the spear-thrower was supplemented by the bow and arrow in the Epipaleolithic period. By the Iron Age, the amentum, a strap attached to the shaft, was the standard European mechanism for throwing lighter javelins. The amentum gives not only range, but also spin to the projectile. Archery may be easier to learn and have a faster rate of fire, yet perhaps this system's greatest advantage over the spear-thrower is that ammunition is easier to make and transport. Since the dart must store almost all of the system's elastic energy, more care, planning, and weight of elastic material must be invested in its construction. In archery, the bulk of elastic energy is stored in the throwing device, rather than the projectile; arrow shafts can therefore be much smaller, and have looser tolerances for spring constant and weight distribution than spear-thrower darts. For example, stone dart points from the same set tend to vary in mass by no more than a few percent, and computer simulations show that this is necessary for efficient operation. Similar constraints exist for the length, diameter, and materials quality of the shaft. If the same amount of attention and material are instead invested into a bow, projectiles can