A short compendium of the duty of artillerists [electronic resource] : shewing the method of exercise with light fieldpieces; of ascertaining the true line of direction and elevation, corresponding with the bore of a gun; with a description of the instruments, for that process. Also, an easy method of finding the distance of an object, by a plain table; with its particular description. Also, observations on experimental gunnery. By Amasa Smith, major of artillery in the militia of Massachusetts.