Plummet

In gunnery, is a simple line and bob for pointing mortars. A plummet is also used for regulating the march of infantry. It is made by means of a musket-ball, suspended by a silk string, upon which the required lengths are marked; the length is measured from the point of suspension to the centre of the ball. The different lengths of these plummets are as follows: for common time, 90 steps in a minute, 17.37 inches; quick time, 110 steps in a minute, 11.6 inches; double time, 165 steps in a minute, 5.17 inches.