so converted into a 9-in. muzzle-loading rifled gun and subjected to severe tests in 1863. With a charge of 16 lbs. of powder projectiles up to 680 lbs. weight were fired from it. The recoil was naturally violent under such conditions. It smashed carriages, and then the gun was suspended in iron slings. It broke these, however, and flung itself out of them on to the ground, but did not burst. This eventually occurred with 32 lbs. of powder and a 200-lb. shot. The evidence of increased strength given by a coiled iron barrel led to a number of smooth bores being converted in this way and employed until comparatively recently in the navy. A steel barrel was subsequently used.
When it was decided to revert to muzzle-loading for new guns the Woolwich system was adopted. This consisted of a steel barrel with a series of wrought-iron coils shrunk over it by being put on when heated. They thus tightly gripped the inner tube, and enabled it to sustain the explosion of a heavy charge without rupture. The strength of the gun was considered to lie in the outer coils; the steel tube gave a hard surface to the bore and a homogeneous material for the rifling process. This tube was made from a solid ingot of steel, turned and then bored out to the required diameter. It was thus the most costly part of the gun, while the boring and rifling processes required considerable time before the rest of the parts could be added.
In 1865 we began equipping our ships with guns of this construction. As an advance on the 68-pounder a gun of 7-in. calibre and 6½ tons weight was pro-
