In this improved Revolver, the force required to pull back the hammer, a, is regulated by a double spring, w, so as to diminish as the hammer is drawn back; and at the moment of firing a slight pull of the trigger is sufficient. Another improvement consists in the addition to the chambered breech, d, of a projecting tube, which prevents the spindle on which it turns from becoming foul; and there is also a safety bolt added, as a protection against accidental firing.
The plan of making the mere action of drawing the trigger turn the chambered breech and pull back the hammer, as originally contrived by Mr. Adams, required so much force to pull the trigger as to interfere materially with the accuracy of aim. There was danger, also, in that mode of turning the chambered breech, arising from premature firing. In Mr. Ells's Revolver these objections are in a great measure obviated; first, by the action of the double spring, by which the force required is diminished as the trigger is pulled farther back; and in the second place, by making the shoulder of the hammer catch into a small notch, which holds it at full cock, until, by a further pull of the trigger, the pistol is fired.
An improvement in the art of war, no less important than the Revolver, was introduced nearly at the same time. The Revolver affords a formidable means for attack or defence at short distances, whilst the Minié Rifle extends the destructive range of fire-arms far beyond the distance to which the ordinary musket ball could reach. The principle of rifling gun barrels was first made known in the specification of an invention patented in 1789, by Mr. Wilkinson, the improvement he effected being thus described:—"The gun, or piece of ordnance, after being bored in the usual method, hath cut therein two spiral grooves, which run the whole length of the bore. These curves, according to their curvature, will give a circular motion to the shot during its flight."
The spiral grooves, when the bullets are rammed down, cause the ball to offer greater resistance, therefore the explosive force of the gunpowder is brought to act upon them more completely before they leave the gun barrel; and the rotary motion imparts greater steadiness to the ball. Rifled barrels, therefore, carry the balls farther, and increase the accuracy of the aim. They, however, require increased power and longer time to ram down the ball in loading, and the risk of bursting the gun is increased if the ball be not rammed close upon the powder. For these reasons, they were considered unfit to be employed generally by soldiers, and they were entrusted only to select corps of rifle shooters. The object of Captain Minié's invention was to facilitate the loading of rifles, by contriving a bullet which might be easily rammed in, and would expand in the act of firing, so as to fill up the grooves. What is commonly called the Minié Rifle is, in fact, only a Minié Rifle Ball, for the barrels of the guns are nearly the same as the ordinary grooved rifles.
The ball is an elongated one, with a hollow cone at the bottom, into which is fixed an iron button. When the gun is fired, the button is forced into the cone, and expands the lead, which thus fills up the grooves and gives a spiral direction to the bullet. The Minié ball serves the purpose excellently for a short time, but after firing several rounds the iron button is forced through the lead, leaving a portion of it behind, which clogs up the barrel, and renders it unfit for use.
Several substitutes for iron were tried, to remove that inconvenience, and it was at length found that the button might be dispensed with altogether, for the hollow cone is of itself sufficient to expand the lead. The balls are, therefore, now made in that manner at the Government gun manufactory at Enfield, and the rifled guns now used in the army, which carry bullets to the distance of a mile and more, are called the Enfield Rifle. The cost of each of these rifles to the Government is stated to be £3 4s. 7½d. As the balls are made to slip into the barrels easily, they can be loaded as readily as the common musket: and they will carry three times the distance, with much more certainty.
[CENTRIFUGAL PUMPS.]
Many ingenious men have vainly attempted to apply what has been erroneously called "centrifugal force" as a motive power, conceiving that the effort made by bodies to fly off when whirled round in a circle was occasioned by a force generated by their rotation. The experiment of the "whirling table," which is commonly shown to illustrate centrifugal action, tends to confirm the notion that force is generated; for it is there seen that, when the velocity of rotation is doubled, the centrifugal force is quadrupled, and that it continues to increase in a geometrical ratio. It has, therefore, been conceived that a power might be generated of indefinite amount; for as a double velocity can be communicated by doubling the moving power, whilst the tendency to fly off at the circumference is quadrupled, there appeared to be a creation of power which, if properly applied, would realize perpetual motion.