That this argument applies principally to solid forged guns I am ready to admit; and that guns forged of hoops, rings, and bars, in smaller sections, are free from this objection, I am also ready to admit. These guns are, however, liable to objections equally fatal, both as regards their enduring and projective powers, as I shall presently show. Experience proves that brass guns are inferior, both in sharpness of shooting and in range, to cast-iron guns: this is undoubtedly attributable to the greater softness of brass than of cast iron; and for the same reason a wrought-iron gun, though made as sound as one of cast iron, would be inferior in these two important points. But when a wrought-iron gun is composed of many particles imperfectly secured (and no mechanical force is sufficient to secure perfect cohesion in large masses), the wrought becomes doubly inferior to the cast gun: a shot projected from such a gun starts from an unsound base; a large portion of the explosive force is absorbed by the variety of sections composing the gun, to the injury both of the accuracy and length of range of the projectile. The softer metals cannot be beneficially used in the construction of large guns, because they destroy the force of the expellant without making any equivalent return; and the softer the metal and the greater its substance, the more clearly is this important fact demonstrated. Thus, in experiments made with large cannon for increasing the weight of the gun beyond a certain proportion to that of the projectile, a gun of ten tons weight and ten inch bore would not exceed in range a gun of five tons, if the charge of powder were the same; on account of the indisputable fact that much more force of the expellant is destroyed, whilst more than double the force is absorbed for the recoil of the ten ton than of the five ton gun; and the loss from these two causes must materially affect the flight of the projectile, though fired at exactly the same elevation.
The great defect which experiment shows to exist in the hoop-and-stave wrought iron gun, and which renders the gun self-destroying, is separation at points between the trunnions and cascable of the gun. The force acting first upon the breech, it yields, and the force is then brought to bear upon the longitudinal portion of the gun behind the trunnions; the staves have thus to bear the first strain, and, after a few shots, become elongated. An opening of the hoops at their junction with each other (most frequently between the breech and trunnions) begins, after a very few shots, to be distinctly visible, and increases at every discharge, until further proceeding amounts to madness, or recklessness of human life.
That enormous engine, Mallet’s monster mortar, of which I give an [engraving] on [page 100], clearly proves this to be the case. It will be observed to be constructed with a solid cast iron breech end, the dimensions of which will be seen by referring to the engraving. Abutting upon this are a succession of wrought iron hoops, ingeniously inserted into each other, and more firmly secured by six outside staves of great dimensions, which, at the muzzle ring, pass through openings in the muzzle ring, with heads like enormous rivets. The binding power is given by “quoin-like” wedges, driven through the opposite end of the stave, beneath the projection of the cast breech, giving power to tighten the longitudinal binders by a blow when required.
Mallet’s Mortar.
Dimensions.
| Tons. | cwt. | qrs. | lbs. | |
|---|---|---|---|---|
| Cast iron base with wrought iron breech shrunk into bore | 21 | 19 | 0 | 2 |
| Wood carriage complete, with wrought iron screw and spanner for elevating mortar | 8 | 8 | 0 | 14 |
| Bottom part of mortar to fit on top of the breech | 7 | 5 | 3 | 23 |
| Part of mortar (a ring) to fit on the top of the above | 5 | 8 | 3 | 23 |
| Do.t of mdo.tar (do. | 3 | 0 | 2 | 13 |
| Muzzle ring | 1 | 2 | 3 | 12 |
| Wood ring | 0 | 0 | 1 | 0 |
| Wrought iron ring | 0 | 4 | 3 | 4 |
| Wrought iron conical ring to fix on top of muzzle ring | 0 | 3 | 3 | 25 |
| T-headed bolts, with gibs and keys for fixing mortar to base: may be called outer staves | 1 | 16 | 2 | 0 |
| Wood-wedges, &c., for elevating | 0 | 13 | 3 | 22 |
| Outer pin, with cross for turning mortar round | 0 | 8 | 3 | 14 |
| Total weight | 50 | 13 | 2 | 21 |
| Weight of shell unfilled, 26 cwt. 2 qrs.; diameter, 36 inches. | ||||