The Armstrong big muzzle-loading guns were formed with the Woolwich system of rifling or grooving, the projectiles being fitted with studs to correspond to the grooves. The muzzle-loading guns varied from the 7-inch 7-ton gun to the 16-inch 80-ton gun. The 8-inch was 118 inches in length, the 9-inch 125 inches, and so on, up to the 16-inch gun, which was 288 inches in length; the last-named took a charge of 450 lb., and fired a projectile weighing 1,684 lb. with a muzzle velocity of 1,590 foot seconds and a muzzle energy of 29,530 foot tons, capable of penetrating at the muzzle between 24 and 25 inches of wrought iron. By 1877 the initial velocity of rifled projectiles had been increased from 1,600 to 2,100 foot seconds, and the energies by nearly 75 per cent., so that a further reconstruction of artillery became compulsory. It was not until after 1881 that the Admiralty definitely adopted heavy breech-loading guns for its armed cruisers. Even as late as 1885 the squadron sent to sea when it was feared that trouble with Russia was brewing, included thirteen battleships, not one of which had a breech-loading gun of more than 6 inches diameter. As a contrast to this, all the heavy guns of the Russian ships were breech-loaders. What would have happened to the English ships had hostilities occurred, and had the Russian gunners been able to use their weapons properly, is best left to conjecture, but it might have proved a sorry day in the naval history of England. Even by 1894 muzzle-loaders were still in use in the Navy. The Woolwich Armstrong breech-loading guns varied from 12-pounders of 3 inches to the 16.25-inch 111-ton gun, the length of which was equal to 30 calibres. The last-named gun took a charge of 960 lb. of powder, and fired a projectile weighing 1,800 lb. with a muzzle velocity of 2,087 foot seconds, and a muzzle energy of 54,390 foot tons, calculated to penetrate over 36 inches of wrought iron at the muzzle. Gunpowder not being powerful enough for these great weapons, other explosives were introduced, which had, among other advantages, that of being much more powerful. The principal of these explosives at present in use is cordite.