effect will be, as the retarding influences of the air will reduce the momentum of the shot every instant afterwards. But then comes the question, which appears to have been very much overlooked; will the effects produced be beneficial or not? If we wish to obtain the deepest penetration, the bullets fired at the shortest distance answer, No.

"In forming our opinions of the effects produced, we must, however, guard ourselves against taking a one-sided view of the case, which the examination of the sand alone, or the firing of small shot against pasteboard, would certainly cause. It is important to remember that time is necessary for the destruction of momentum, or rather of velocity; and the less the time which is employed, the greater must be the effort exerted; or, in other words, the force requisite for the destruction of any velocity is greater as the time occupied in its destruction is less.' It is evident, then, that the bullets which penetrate the shortest distance require less time to do so than the others, and that, therefore, more force is exerted. This, however, must be considered with reference only to very short ranges; for at ranges greater than 200 yards the penetration will be less, in consequence of the reduced velocity of the shot, which is caused by the longer resistance of the air. It will, therefore, be found that every kind of gun, rifle, &c., has one particular distance at which it can do most execution, and this distance can only be ascertained by making experiments on various substances, at different ranges, with various weights of shot and different quantities and qualities of powder. And though it may appear somewhat paradoxical, it is nevertheless true, that one gun will not cause its shot to penetrate so deep as another at a particular range, simply because it shoots too strong, or with more velocity than the other, the action of the shot and the reaction of the substance fired at being equal."

VARIETIES IN THE FORM OF THE GROOVES ALMOST

INFINITE.

The use of a spiral groove in some form is extremely old, and since its first introduction the varieties of shape which have been tried are beyond calculation. The number of

grooves, their form, and the quickness of the twist, have all varied as far as it was possible; and by the Americans a twist increasing in quickness has been very generally adopted, their chief writer on the subject (Chapman) strongly insisting upon it. But whatever may be the plan adopted, unless the workmanship is good and true, it will not succeed; while, on the other hand, if the grooves are well cut, the rifle will shoot well with almost any of the methods of rifling which are now adopted by the chief authorities on this subject. The arguments for and against each of the rival plans at present in vogue would occupy many pages, and after all they would, perhaps, lead to no satisfactory solution of the problem. Much practice is required in adapting together all the elements upon which success depends, for barrels and grooves which will suit one ball will be useless with another, and vice versa. Now, as every rifle-maker has his fancy, and as he will have brought all his experience to bear upon it, the best plan is to accept him and his work with all faults, instead of interfering with him. If you go to Purdey for a rifle, you will get one with two grooves, the shooting of which will be equal, if not superior, to any which can be brought against it; while if he took your order for a three-grooved rifle, it would probably be inferior to those made by many gunmakers of a celebrity far inferior to his.

RIFLE BARRELS.

The barrels of rifles are either made of twisted iron, as described for shot-guns, or they are forged of solid steel, and afterwards bored; or they are made with a longitudinal line of welding, if they are intended for common purposes. The first is the plan always adopted for double barrels, which would be too heavy if made out of the solid. Solid steel barrels are used where weight is necessary to resist recoil or vibration, and if very accurate shooting is required, they are superior to all others. In either mode, a perfect cylinder is first obtained, which is afterwards rifled on the plan to be presently described. The weight of the Enfield barrel (4 lb. 2 oz.) is the lowest for the length (3 feet 3 inches) compatible with safety and efficiency.

THE METHOD OF RIFLING.

There are several machines by which the spiral grooves may be cut in the interior of a barrel, but all proceed upon the principle that a cutter of the shape of the groove is passed backwards and forwards in a spiral manner through it, the barrel itself being fixed. The annexed engravings show one of the best and most simple plans adopted by Messrs. Prince and Green in London, and by Mr. Rigby in Dublin. Fig. 66

represents a strong iron table upon which are fixed two slotted frames. One of these a has two sliding vices travelling on it, and capable of firmly securing the barrel b ready for the cutter c. This is attached to a rod which passes through a square hole in the plate d, and is driven backwards and forwards in a perfectly straight line by the rollers working in the two slots e e. The strong rod f, figs. 66 and 67, is made to work backwards and forwards by the wheel shown in fig. 67, the horizontal line being preserved by the slots e e, fig. 66, and the hole in the centre of the plate d. Here, then, we have a very simple plan for producing a steady yet powerful horizontal motion for the rod which carries the cutter, and which in the ordinary way

would cut a straight groove through the barrel on one of its sides, if passed backwards and forwards through it. Next come the two problems, first, how to cut a spiral instead of a straight groove? and, secondly, how is this spiral to be made quick or slow? That is, how shall we form a turn in one foot, two feet, three feet, &c., at discretion? It must be noticed that the section of the rod is square, and that it passes through a square hole in the plate d. Now, by

Fig.67.

DRIVING-WHEEL OF RIFLING MACHINE.

twisting this square rod on itself, the cutter attached to its extremity, as it glides through the hole, takes a corresponding twist, and if this is made one in three feet, the groove will be cut exactly of the same twist. Thus we have both problems solved. The twisting of the rod causes the groove to be spiral, while the amount of its twist settles that of the barrel. We have thus shown how one groove is made, and all that is necessary in order to cut two, three, or any other number of grooves, is either to keep the barrel fixed and alter the position of the plate d for each groove, or to let the plate remain, and move the barrel in a corre

sponding manner. Both modes are adopted by different makers, but in the machine shown in figs. 66 and 67, the plate is made to revolve, and each of the circles shown upon it is divided accurately into either two, three, four, five, six, seven, eight, or nine equal sections, so that if a barrel is to be cut with three grooves, the circle with three equal divisions is used, and the plate being moved in exact correspondence with them, the work is beautifully correct. So also the shape of the cutter determines the form of the groove, being nearly semicircular for the oval bore of Mr. Lancaster, as shown in the engraving illustrating Captain Beaufoy's celebrated work, "Scloppetaria." Again, for a groove with sharp angles, the cutter is made correspondingly sharp, for as it traverses backwards and forwards, it leaves its mark exactly of its own shape, allowing for the slight vibration inseparable from the working of a rod confined at one end only.

The principle, therefore, upon which all rifle grooves are made is the same, though in the next chapter the variation will be shown to be immense in the modes by which that principle is applied.

TECHNICAL TERMS.

One of the most important defects in a rifle is, the existence of such a space between the ball and the sides of the barrel, or of its grooves, as to allow of an escape of gas generated by the explosion of the powder. This, of course, is attended with a corresponding loss of power, and is known among rifle makers and shooters by the term " Windage." I have already, at p. 306, given a definition of "upsetting;" but there are three terms constantly used in rifle shooting which require some notice here. These are 1st, "The line of fire;" 2nd, "The aim ;" and 3rd, "The trajectory." The line of fire is the indefinite projection of the axis of the barrel. The aim is a straight line drawn from the centre of the back sight to the top of the front one, and prolonged to the object at which the rifle is directed. Lastly, the trajectory is the curve actually described by the ball in its passage through the air, and greater or less in proportion to its velocity.