power and electricity being tried, hydraulic power was introduced, and has proved more suitable for the purpose than any other method. Now the heaviest projectiles, weighing half a ton or more, are lifted with the greatest ease and exactness to the required position by hydraulic power, are pushed into their places by the same power which does a like office for the charge of explosive, closes and fixes the breech, and does not desist until its task is finished. In the latest appliances, the machinery is made interlocking, so that, at least in the system introduced lately by Messrs. Vickers, no one operation connected with loading the gun can be performed until its immediate predecessor has been accomplished. With a view to securing more rapid and accurate fire this firm has introduced a modification of the breech mechanism by what is known as a “pure couple.” The hydraulic breech mechanisms just alluded to are used for the largest guns, such as the 12-inch weapons, and have also been installed on the Japanese ships for the 10-inch guns. The guns can be loaded at the required angle of elevation, the advantage claimed for this being that the sight can be kept on the target all the time. The pressure to which guns are subjected when the charge explodes is enormous. One reason why they do not burst is that they have not time to do so. How rapidly the pressure arises against the sides of the gun and then against the projectile to expel it from the bore, was shown by experiments which Sir Andrew Noble conducted some time ago with a 6-inch gun of 100 calibres length of bore. Practically instantaneously with the ignition of the charge, that is to say in about the four-hundredth part of a second, a maximum pressure against the interior of the gun of 22 tons per square inch was reached, but this declined to about 13 tons per square inch in about the twelve-hundredth part of a second more. But by that time the projectile had left the gun, and was rushing, faster than the eye could follow it, towards its mark.