The use of explosive shell in high-angle discharge dates back to the fifteenth century. From Paixhans’ works, “La Nouvelle Arme,” published in 1821, came the stimulus to its development and to its deadly service, in our time, in horizontal fire. The “common shell” for the United States 13-inch rifle is made of forged steel, weighs 1100 pounds, and carries within it a bursting charge of 50 pounds of powder, ignited by a percussion fuse set in its base. It will penetrate 6 or 7 inches of armor and then explode within the ship. The United States “armor-piercing shell” is manufactured from crucible steel, alloyed with chromium; it is tempered to extreme hardness at the point, which carries a cap of soft metal. The function of the latter would appear to be that of a support to the shoulder of the projectile, or as a lubricant thereto, since, without the cap, the shell is broken or deformed in the attack on armor of surface hardened steel. To resist the crushing strain in its passage through massive plate, the walls of this shell must be so thick that no charge of gunpowder will burst it. Hence, as a rule, the shell is fired unloaded, although recently there have been adopted to some extent bursting charges of some high explosive, such as gun-cotton, joveite, or picric acid. In closing this brief review of the progress of ordnance, but passing mention can be made of matters minor, but in themselves of much importance. Gun carriages, or mounts, are now intricate mechanisms, practically the whole service of large ordnance being performed by electric and hydraulic machinery. The rapid fire principle has been extended to pieces of 6-inch calibre, and bids fair to pass beyond that limit. Its success in increasing largely the number of shots within a given time lies in special breech-blocks, aiming devices, and prepared cartridges. Machine guns of rifle-calibre, partly or wholly automatic, have been so developed as to be capable of firing 1200 rounds per minute. The discharge of high explosives in large quantity was effected with success by the United States steamer Vesuvius off Santiago. The torpedo-gun afloat, however, would appear to be still in a tentative condition.