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6 volumetric measures from the mens ponderia in Pompeii, a municipal institution for the control of weights and measures (79 A. D.). A unit of volume is a unit of measurement for measuring volume or capacity, the extent of an object or space in three dimensions.
The other units of length and mass, and all units of area, volume, and derived units such as density were derived from these two base units. Mesures usuelles (French for customary measures) were a system of measurement introduced as a compromise between the metric system and traditional measurements. It was used in France from 1812 to 1839.
On 7 April 1795, the metric system was formally defined in French law using six units. Three of these are related to volume: the stère (1 m 3) for volume of firewood; the litre (1 dm 3) for volumes of liquid; and the gramme, for mass—defined as the mass of one cubic centimetre of water at the temperature of melting ice. [10]
The systems formalised the concept of a collection of related units called a coherent system of units. In a coherent system, base units combine to define derived units without extra factors. [4]: 2 For example, using meters per second is coherent in a system that uses meter for length and seconds for time, but kilometre per hour is not coherent.
A derived unit is used for expressing any other quantity, and is a product of powers of base units. For example, in the modern metric system, length has the unit metre and time has the unit second, and speed has the derived unit metre per second. [5]: 15 Density, or mass per unit volume, has the unit kilogram per cubic metre. [5]: 434
The Winchester bushel is the volume of a cylinder 18.5 in (470 mm) in diameter and 8 in (200 mm) high, which gives an irrational number of approximately 2150.4202 cubic inches. [4] The modern American or US bushel is a variant of this, rounded to exactly 2150.42 cubic inches, less than one part per ten million less. [ 5 ]
[4] [5] The mouthful was still a unit of liquid measure during Elizabethan times. [6] The principal Egyptian standards from small to large were the ro, hin, hekat , and khar.) [ 7 ] Because of the lack of official definitions, many of these units will not have a consistent value.
The system can be traced back to the measuring systems of the Hindus [18]: B-9 and the ancient Egyptians, who subdivided the hekat (about 4.8 litres) into parts of 1 ⁄ 2, 1 ⁄ 4, 1 ⁄ 8, 1 ⁄ 16, 1 ⁄ 32, and 1 ⁄ 64 (1 ro, or mouthful, or about 14.5 ml), [19] and the hin similarly down to 1 ⁄ 32 (1 ro) using hieratic notation, [20] as ...