A brief lapse into technical terms may be permitted in summarizing the gun’s growth in power. The term “muzzle energy” is used to describe the work which the projectile is capable of performing when it leaves the bore. It is expressed in foot-tons, i. e., the number of tons which the energy stored in the shot would lift to a height of one foot. The figures as to this for the 32-pounder of the century’s beginning, for the United States 13-inch rifle and for the 111-ton English gun, are, respectively, 642, 33,627, and 54,690 foot-tons. Again, the round shot from the 32-pounder lost from the resistance of the air, in a range of 1200 yards, 76 per cent of its energy; while this loss, with the United States 13-inch, in a range of 1000 yards, is but 11 per cent. Finally, if the cast-iron shot of the 32-pounder were fired against armor-plate, it would lose, in breaking itself up, two thirds of its remaining energy, leaving at 1200 yards but 51 foot-tons for effective work; while with the modern armor-piercing shell the entire energy left at the end of the range is expended upon the armor-plate. It will be seen then that the immeasurable superiority of modern guns is owing both to their great increase in energy and to their wiser disposition of that which has been attained. The gun has maintained fully during the century its primacy among naval weapons. It is true that, in theory and on paper, its supremacy has at times been questioned; but as to its two rivals, the ram would seem to be rather the weapon of accident than action, and the torpedo has yet to score in battle against ships in motion, while the precision, rapidity, and power of the gun grow more deadly with every passing year. VI. THE DEVELOPMENT OF ARMOR. Armor and the gun are natural and now hereditary foes. The function of the one is to resist, that of the other ever to attack. Since the beginning of the modern era in navies, there has been ceaseless strife for mastery between these two elements of warship design, the gun ever becoming more powerful, and the armor—at first through growing thickness and later through improved material—opposing a steadily more stubborn front. The official report of an English committee made in the year 1860 states that,— “Vessels clothed in rolled-iron plates of four and a half inches’ thickness are to all practicable purposes invulnerable against any projectile that can be brought to bear against them at any range.”