projectile rotation or spin on its longer axis. The rotatory motion keeps the shot steady during flight, and prevents its being subject to the special influence which caused the inaccuracy of smooth bore guns. A cylindrical projectile is heavier than the round shot of similar diameter. Thus the old 32-pounder was of 6-in. diameter, but the modern 6-in. rifled gun throws a projectile of 100 lbs. weight.
There are other advantages, on which it is unnecessary to dwell, but for many years artillerists had been seeking a satisfactory method of giving rotation to the projectile. One of the earliest inventors in this country was Mr Lancaster, who conceived the idea of making the bore of a gun slightly elliptical or oval, with a twist, so that a projectile of the same shape received a spin during its passage through the bore. Fairly successful experiments resulted in the construction of some of these guns and their employment in the siege of Sebastopol. But they were not reliable, and more than one burst. In the meantime a rifle had been adopted for the army in place of the old smooth bore musket, and it was only a question of working out the principle for larger guns.
In 1846 Major Cavalli, of the Sardinian army, and Baron Wahrendorff, a Swedish noble, had each brought forward a breech-loading rifled gun throwing cylindrical projectiles with pointed heads. Cavalli's gun was of 64-in. calibre, and had two grooves cut spirally along the bore. The projectiles had two winged projections which travelled in the grooves and caused rotation. The
