Effect on Masonry

—The effect of a projectile against masonry is to form a truncated conical hole, terminated by another of a cylindrical form. The material in front of and around the projectile is broken and shattered, and the end of the cylindrical hole even reduced to powder. The exterior opening varies from four to five times the diameter of the projectile, and the depth varies with the size and density of the projectile, and its velocity. When a projectile strikes against a surface of oak, as the side of a ship, it will not stick if the angle of incidence be le than 15°, and if it do not penetrate to a depth nearly equal to its diameter. Solid cast-iron shot break against granite, but not against freestone or brick. Shells are broken into small fragments against each of these materials.