The costliness of the wheel-lock, which was made in as many as ten separate pieces, greatly restricted its use as regards hand-guns, but it was applied generally to pistols, and pieces for the hunting field. Cavalry used weapons with this lock, as it was very inconvenient to manage the match-cord on horseback, especially as it required regulating with every shot fired. Ignition was accomplished by sparks which were caused by the friction of a steel wheel, notched long and crosswise, rubbing against a flint, or by the striking of the wheel against a cube of solid pyrites. The lock was wound up by a spanner, which hung at the soldier’s belt. The main details of this lock are as follow, viz.:--A serrated wheel, connected to the backplate by a chain and spring, forming with the backplate the bottom of the flashpan, and wound up by a spanner. With the wheel-barrel is connected one end of a strong spring, by a chain, which winds round the barrel when the wheel is turned, tightening the spring until the catch of a bar drops into a corresponding notch of the wheel, thus holding spring and wheel cocked. After winding up, the trigger is pressed, releasing the wheel, which revolves round with great energy, by means of the accumulated force lent it by the winding, and coming into contact with the pyrites in the cock produces the sparks that ignite the priming in the flashpan trough, and fires the piece. Various improvements in the mechanism of this lock took place from time to time. There are examples of wheel-lock weapons in the Tower of London dating from about the middle of the sixteenth century; a breech-loading harquebus, with a lock of something like the same date, is in the Musée d’Artillerie at Paris. A harquebus revolver, with seven barrels, may be seen in the Hohenzollern collection at Sigmaringen, and there are countless examples existing among the museums of Europe, and notably at Dresden. During the sixteenth century, and especially in the later half, the footman wore half-armour, and usually discharged his weapon from a prop. In a matchlock the match is lit at both ends. The air-gun was invented in Germany in 1560. In this weapon the bellows are wound up against a spring, which is released by pulling the trigger; the receiver is in the stock, and filled by a pump. The principle of rifling barrels was certainly applied as early as 1510, and there are very early examples of revolvers. There is one in the Tower of London with a matchlock, dating from about the middle of the sixteenth century. A patent for rifling barrels was taken out in London in 1635. It is said that the invention of grooved arms is due to Gaspard Kollner of Vienna, in 1498; other writers attribute it to August Kollner of Nuremberg, early in the sixteenth century; but whether the grooves were straight or spiral, or when they became the latter, is not so obvious; at all events, the principle was not much adopted for military arms before the seventeenth century.