Units of volume
Units of volume are essential measurements used to quantify the space occupied by a substance, whether solid, liquid, or gas. Throughout history, various cultures developed unique systems for measuring volume, often based on practical needs, such as agriculture and trade. Early methodologies primarily focused on weight, particularly for items with irregular shapes, until innovative approaches emerged, notably fluid displacement techniques popularized by the ancient Greek mathematician Archimedes. His insights led to the use of water for measuring the volume of objects, representing a significant advancement in volumetric measurement.
Different regions and eras contributed to the complexity of volume measurement systems. For example, the Romans had distinct measures for liquids and dry goods, while the English system evolved into a complicated set of units, leading to the British Imperial System. In contrast, the French Revolution sparked a movement towards standardization, resulting in the metric system, which introduced liters and eventually the International System of Units (SI), where the cubic meter became the base unit for volume. Despite this standardization, liters remain widely utilized globally. Additionally, measuring gas volumes has historically posed challenges, which were addressed by innovations in metering technology. Overall, the concept of volume measurement reflects a rich interplay of historical, scientific, and practical factors across cultures.
Units of volume
SUMMARY: A variety of units are used to measure volume throughout the world.
Measuring volume intrigued many scientists in the ancient world. For the most part, crops, stones, and other items were measured by weight rather than volume because of the relative ease of doing so—especially given the irregular shapes of many items. For solid items with irregular shapes, it seemed far too complicated to work out their volume, even if this could be done with any degree of accuracy. This notion changed dramatically with the ideas attributed to the famous Greek mathematician and inventor Archimedes of Syracuse (c. 287–212 BCE).
The tale of Archimedes is that he was given the task of determining the purity of the gold used to create the crown of King Hiero II—the king was worried that silver or base metals might have been used in its manufacture and were cleverly disguised. Pondering the problem while getting into a bathtub, Archimedes noticed that the water rose and the amount it rose was equal to the size of the parts of his body that were submerged. This led Archimedes to deduce that water could be used to measure the volume of items, such as the king’s crown. It could then be weighed against a block of pure gold of the same volume. It is said that when he realized that this could be done, Archimedes shouted “Eureka!” (“I have found it!”) and ran through the streets to tell everybody of his discovery, forgetting that he had not put his clothes on.
Whether the story of Archimedes is true—some historians doubt its veracity, although Galileo stated that he believed that it might well be true—the story does illustrate the use of fluid displacement, which can be used to easily measure the volume of irregularly shaped objects. This method does not seem to have been known before the Greeks. Certainly, the ancient Egyptians had major problems working out volume, and there are complicated equations and formulae on the Rhind Mathematical Papyrus, which dates to about 1700 BCE, illustrating that the Egyptians were already grappling with the subject.
The Romans had two systems for recording the measurement of volume. The first and most often used was for liquid measures and was based on a sextarius (from sester), which is roughly 0.54 liters. Six sesters made up one congius; four of these made up one urn; and two urns make one amphora. For dry measures, although a sester was still used and was of equivalent size, eight sesters equaled a gallon; two gallons made up one modius (also called “peck”); and three of these one quadrantal (also called “bushel”).
English
In use from the Middle Ages, the English ended up with an extremely complicated system of measuring volume, which was formalized as Imperial Measurements (later the British Imperial System). The smallest measure was a “mouthful,” with two of those making a “pony,” two ponies making a “jack,” two jacks making one “gill,” two gills making one “cup,” and two of those making a “pint.” The system continued with two pints making a “quart” (from “quarter gallon”), with two quarts equaling one “pottle,” and two pottles making a “gallon.” The next levels of measurements were “pecks,” “kennings,” “bushels,” “strikes,” “coombs,” “hogsheads,” and “butts” (also called “pipes”). A slightly different scale was used to measure wine and beer. Even when the British adopted the metric system in 1965, some of the old terminology (and measures) were still used, especially pints (for milk) and gallons (for gasoline). A bushel remains the standard measurement for wheat and other agricultural items. The Hoppus cubic foot continues to be used to measure volumes of timber.
Metric System
Although the English had numerous terms, medieval and early modern France had a vast range of measures of volume, which varied from one part of France to another, most arising for customary reasons. After the French Revolution, the new government sought to standardize all systems of measurement, including volume. This process saw the introduction, under Napoleon Bonaparte (1769-1821), of metrication, and, in turn, it led to the International System of Units (SI units). The SI is continually reevaluated and updated as necessary to ensure the most accurate measurements possible.
The original metric system had liters (or litres) as the measure of volume, and from 1901 until 1964, it was defined as being the volume of one kilogram of pure water heated to 4 degrees Centigrade and measured under a pressure of 760 millimeters of mercury.
When it came to devising the SI units, the liter was dropped as a measure, and the official base measurement for measuring volume became cubic meters (m3). The difference is not significant in all but scientific terms, although liters continue to be used by people worldwide. A cubic meter is equal to about 264 US gallons or 1,000 liters, and the US system's cubic foot (ft3) is about 1/35 of a cubic meter.
Gas Volume
While it was possible to measure the volumes of liquids easily (and also of solid objects by measuring the displacement of water of a similar quantity), measuring the volume of gas has long posed a problem. The problem was solved by the British civil engineer Samuel Clegg (1781–1861), who had worked on natural gas flues and designed a dry meter and then a water meter, which measured the amount of gas consumers used. This invention helped the gas industry in Britain—and later in other countries—measure gas and thereby charge customers based on usage.
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