RIFLE, or RIFLED, a term applied to muskets or pieces of ord nance when their bores are furrowed with spiral grooves. It is probably derived from an Anglo-Saxon word signifying to rive or tear ; the grooves or channels being formed by a machine which scrapes away the substance of the barrel interiorly in parallel and spiral directions.
It is not precisely known at what time rifled barrels were first employed in warfare, but P. Daniel states (` Hist. de In Milice Frau caise,' liv. vi.) that the carabithere of the French cavalry were furnished with such arms; he also observes that they had been invented long before the time at which he wrote, and that he had seen them used before that class of troops war formed into a regiment. This circumstance took place in 1692, and we may therefore conclude that rifled arms were known on the continent about the middle of the 17th century. The historian describes the care/dues reyees, as he calla them, as being grooved in a circular manner along the whole of the barrel ; and ho asserts that the range of the balls fired from them was very considerable. Rifled arms do not appear to have been intro duced in the British service till the time of the American Revolu tionary war.
It is sometimes asserted that grooved barrels were introduced by Gaspard Zollner of Vienna, in 1493, but these grooves were parallel to the axis of the piece, and were only intended to take off the foulness of the discharge and assist in loading. It may accidentally have been discovered that by making the grooves spina, greater accuracy was obtained. It is also asserted that elongated projectilca were fired from rifles many years ago, as, for instance, it is stated that Hamilton of Bothwell-haugh shot the regent Murray with a cylindro-conical bullet. But it is difficult to determine this with any certainty. Under the head of GUNNERY the effect of the rotation of a projectile has been in vestigated, and it is there shown that except when the axis of rotation is coincident with the lino of flight, or epeakIng more correctly as the trajectory is a curve, except when the axis is tangential to the trajec tory, the effect of rotation on a projectile passing through the air is to deflect it more or lees from the direction in which it is projected. This effect is duo to the fact of the surface of the projectile being more or lee rough, and to the stmoaphere being more condensed in front than behind it from its high velocity. But it is not the direct result, if we may so term it, of the greater friction in front than behind the centre of gravity, as is often erroneously elated, and this the experi ments of Professor Magnus of Berlin have shown. Indeed, the direct effect of this friction would be to deflect the ball in exactly the opposite direction to what in practice is found to be the case. A ball, for instance, rotating on a vertical axis, when the anterior surface is moving from right to left, would, the air being more condensed before than behind, meet with a great resistance to rotation from the friction of the air in front, which would not be counter-balanced by an equal resistance in the opposite direction behind ; but as the rotation in front is from right to left, this resistance would in effect tend to deflect the centre of gravity from left to right. Now in practice it is
found that a rotation from right to left deflects the ball to the/left, so that it is evident that some other force must be called into action which overcomes this direct effect of friction. Now one half of the ball, supposing it to be cut into two hemispheres by the plane of the trajectory, is rotating with, and the other half in a contrary direction to, its motion of translation, and the surface of the ball not being perfectly smooth, the air ie assisted in rushing past the former hemisphere, while It is retarded in passing the latter, and becomes more condensed. The experiments of Professor Magnus, in which a current of air was thrown on a rotating cylinder, clearly showed by an arrangement of vanes, which It Is unnecessary to explain here, that the rotating cylinder caused a current in the air In contact with it, in the direction of the rotation which, where it met the current thrown on it by the blowing fan, produced a greater pressure of the air on that portion of the cylinder : that is, where the Letter current was moving in an oppose direction to the former. Returning again to the ball rotating from right to left, this will account for a greater pressure on the right side than on the left, tending to deflect the ball to the left, and this cause of deflection is found to overcome the tendency before spoken of to deflect it to the right. The figs. 1 and 2 on the accompanying diagram may make this clearer. The motion of rotation is in both eases Indicated by the arrow on the circumference, the motion of translation by the arrow in the circle. Fig. 1 gives the resultant direction from friction only ; fig. 2 allows the condensation of air from the two currents meeting. It is most probable that the velocity of rotation is not so rapidly destroyed as the velocity of translation, which will acuotuat for the Literal deviation of a rotating projectile being found in practice to increase in a much greater ratio than the distance :—the trajectory being in fact a curve of double curvature. This was very well shown by Robins, to whom the first investigation, and indeed the principal portion of our present knowledge of this subject is due, in his experi ment before the Royal Society in 1746, in the gardens of the Charter page 1G5, 'kneels • Treatise on Artillery '), where he fired a bullet from a bent gun-barrel through two paper screens, and on to a walL Tho bullet followed the direction of the bent portion of the barrel in passing through the first screen and partially through the second, but the place where it struck the wall was on the other aide of the line of direction of the straight portion of the barrel. The end of the barrel being bent to the left, the bullet in rolling against it in its passage out hail received a rotatory movement, its anterior hemi sphere moving from left to right, which for the reasons before stated caused it to deflect to the right, and the velocity of translation diminishing more rapidly than the velocity of rotation, this deflection was in a curve. This curve being combined with the curve caused by the action of gravity gives a curve of double curvature.