3rd. Next to absence of friction is the construction of the gun barrel. Already have we shown that the inner surface of a gun barrel requires to be like glass; next to this it is necessary that the metal should be composed of the most unyielding structure. Metals absorb force in proportion to their softness: a barrel constructed of lead gives the worst result of any metal; in truth, as is the increase of tenacity and density in the tube, so is the increase of range in projectiles. The wonderful results displayed by the use of steel guns of all descriptions bear out this assertion to the fullest extent. A yielding gun barrel may be compared to the dragging of a heavily loaded waggon over boggy ground, which rises in a wave before the wheels during its progress. 4th. Next in importance to the inflexibility of the gun barrel is the form of projectile best calculated to displace the atmosphere during its extended flight. Under the head of Rifles this subject will be more fully discussed; but, as thousands of years have stamped the arrow as being in accordance with nature’s laws, it should no doubt be the object of science to approximate the leaden projectile to that form as much as possible, and hence the cylindro-conoidal may be assumed to be the best form of projectile. That both Jacob’s and Whitworth’s bullets partake of a certain amount of “_wabbling_” motion after leading the muzzle of the gun is certain, from their length, as well as from the fact that in both the centre of gravity is in the hinder part of the bullet; thus they are both in reality bad in a scientific point of view. If any merit can be claimed for either, it is on account of the mechanical ingenuity displayed in neutralizing the effects of want of scientific principle. The want of principle, however, is not the only evil, were such guns to come into general use; their manufacture, in the hands of that portion of the gun trade which never estimates consequences, and never studies the theory of the science at all, but manufactures all fire-arms by “rule of thumb,” would prove dangerous in the extreme. The bursting of barrels in any attempt to project lengthened projectiles is of a very different description to that which ordinarily occurs, on account of the different direction in which the force is applied. In consequence of their greater length, and their increased friction against the sides of the barrel, they are more reluctantly set in motion--_i. e._, their inertia is with greater difficulty overcome. The result of this is, that in overcoming their inertia the greatest strain is exerted backward, on the breech of the gun; which, if not more firm than usual, is blown out, entering the forehead of the shooter: an accident which would prove fatal not only to the gun, but to the person who used it.