Passing through various stages of development, the cannon came down to the Nineteenth Century, and was known generally as ordnance or artillery, and specifically as cannon or heavy guns, mortars for throwing shell at a great elevation, and howitzers for field, mountain, or siege, and which latter are lighter and shorter than cannon, and designed to throw hollow projectiles with comparatively small charges. The feature of importance in the cannon which contributed most to its efficiency was the rifling of the bore with spiral grooves. This, by giving a rotating effect to the projectile, caused it to maintain a truer flight by taking advantage of the law of physics that a rotating body tends to preserve its plane of rotation. The rifling of the barrels of firearms is, however, of very ancient origin. The British patent to Rotsipen, No. 71, of 1635, is an early disclosure of this art. The patent was granted him for “Fourteen yeares if he live soe long.” *  *  * “To draw or to shave barrells for pieces of all sortes straight even and smooth, and to make anie crooked barrell perfectly straight with greate ease, and to _rifle cutt out_ or screwe barrells as wyde or as close or as deepe or as shallowe as shalbe required, with greate ease.” The rifle grooves, however, were first made spiral or “screwed” by Koster, of Birmingham, about 1620, while straight grooves are said to have been in use as far back as 1498. In Berlin there is a rifled cannon of 1664 with thirteen grooves. Rifled cannon were first employed in actual service in Louis Napoleon’s Italian campaign of 1859, and were first introduced in the United States service by General James in 1861. About the middle of the Nineteenth Century a great impetus was given to the development of artillery by the Crimean War, followed by the Civil War of the United States.