Towards the close of the eighteenth century, short cast-iron guns called "carronades" were introduced by Gascoigne of the Cannon Iron Works, Scotland. They threw heavy shots at low velocity with great battery effect. They were for a long time in use in the British navy. The sailors called them "smashers." The entire battery of the Victory, Nelson's famous flag-ship at the battle of Trafalgar, amounting to a total of 102 guns, was composed of "carronades" varying in size from thirty-two to sixty-eight pounders. They were mounted on wooden truck carriages and were given elevation by handspikes applied under the breech, a quoin or a wedge shaped piece of wood being pushed in to hold the breech up in position. They were trained by handspikes with the aid of side-tackle and their recoil was limited by a stout rope, called the breeching, the ends of which were secured to the sides of the ship. The slow match was used for firing, the flint lock not being applied to naval guns until 1780. About the middle of the nineteenth century, the design of guns began to receive much scientific thought and consideration. The question of high velocities and flat trajectories without lightening the weight of the projectile was the desideratum; the minimum of weight in the cannon itself with the maximum in the projectile and the force with which it could be propelled were the ends to be attained. In 1856 Admiral Dahlgren of the United States Navy designed the _Dahlgren_ gun with shape proportioned to the "curve of pressure," which is to say that the gun was heavy at the breech and light at the muzzle. This gun was well adapted to naval use at the time. From this, onward, guns of high pressure were manufactured until the pressure grew to such proportions that it exceeded the resisting power, represented by the tensile strength of cast iron. When cast, the gun cooled from the outside inwardly, thus placing the inside metal in a state of tension and the outside in a state of compression. General Rodman, Chief of Ordnance of the United States Army, came forward with a remedy for this. He suggested the casting of guns hollow and the cooling of them from the inside outwardly by circulating a stream of cold water in the bore while the outside surface was kept at a high temperature. This method placed the metal inside in a state of compression and that on the outside in a state of tension, the right condition to withstand successfully the pressure of the powder gas, which tended to expand the inner portions beyond the normal diameter and throw the strain of the supporting outer layers. This system was universally employed and gave the best results obtainable from cast iron for many years and was only superseded by that of "built up" guns, when iron and steel were made available by improved processes of production.