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| Long title | An Act to authorize the Use of the Metric System of Weights and Measures |
|---|---|
| Enacted by | the 39th United States Congress |
| Citations | |
| Statutes at Large | 14 Stat. 339 (1866) |
| Legislative history | |
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The Metric Act of 1866, also known as the Kasson Act, is a piece of United States legislation that legally protected use of the metric system in commerce from lawsuit, and provided an official conversion table from U.S. customary units. [1]
Congressman John A. Kasson from Iowa, then Chairman of the House Committee on Coinage, Weights, and Measures, proposed the act in his report of the Committee on Coinage, Weights, and Measures:
The metric system is already used in some arts and trades in this country, and is especially adapted to the wants of others. Some of its measures are already manufactured at Bangor, in Maine, to meet an existing demand at home and abroad. The manufacturers of the well-known Fairbanks scales state: “For many years we have had a large export demand for our scales with French weights, and the demand and sale is constantly increasing.” Its minute and exact divisions specially adapt it to the use of chemists, aphothecaries, the finer operations of the artisan, and to all scientific objects. It has always been and is now used in the United States coast survey. Yet in some of the States, owing to the phraseology of their laws, it would be a direct violation of them to use it in the business transactions of the community. It is therefore very important to legalize its use, and give to the people, or that portion of them desiring it, the opportunity for its legal employment, while the knowledge of its characteristics will be thus diffused among men. Chambers of commerce, boards of trade, manufacturing associations, and other voluntary societies, and individuals, will be induced to consider and in their discretion to adopt its use. The interests of trade among a people so quick as ours to receive and adopt a useful novelty, will soon acquaint practical men with its convenience. When this is attained—a period, it is hoped, not distant—a further act of Congress can fix a date for its exclusive adoption as a legal system. At an earlier period it may be safely introduced into all public offices, and for government service.
In the schedule of equivalents provided in the bill, extreme scientific accuracy is not expressed. The reasons follow. The exact length of the meter in inches and the weight of the kilogram in grains can of necessity be determined only approximately. The most careful determinations of these quantities now possible are liable to minute corrections hereafter, as more numerous observations are made and better instruments are used. Instead, therefore, of aiming at an accuracy greater, perhaps, than is attainable, it is more expedient to consult the convenience of the people by using the simplest numbers possible in the schedule, and yet such as shall be in fact more nearly exact than can ever be demanded in the ordinary business of life. These numbers are to be used in schools, and in practical life millions of times as multipliers and divisors, and every unnecessary additional figure is justly objectionable.
In a popular sense of the word, however, the numbers in the schedule may be said to be exact. The length of the meter, for example, is given as 39.37 inches. The mean of the best English and the best American determinations differs from this only by about the amount by which the standard bar changes its length by a change of one degree of temperature. Such accuracy is certainly sufficient for legal purposes and for popular use.
The Act was originally introduced as H.R. 596 in the 39th Congress. The House passed it on 17 May 1866; the Senate passed it on July 27, 1866; and it was presented to President Andrew Johnson and signed the next day.
The Act included a now-obsolete definition of the metric system and tables of units. (The notes at the end of some tables are not from the original document itself but are included for clarity.)
| Metric Denominations and Value | Equivalents in Denominations in Use | |
|---|---|---|
| Myriameter | 10,000 meters | 6.2137 Miles |
| Kilometer | 1,000 meters | 0.62137 Miles or 3,280 Feet & 10 Inches |
| Hectometer | 100 meters | 328 Feet & 1 Inch |
| Dekameter | 10 meters | 393.7 Inches |
| Meter | 1 meter | 39.37 Inches |
| Decimeter | 1⁄10 meter | 3.937 Inches |
| Centimeter | 1⁄100 meter | 0.3937 Inches |
| Millimeter | 1⁄1000 meter | 0.0394 Inches |
| Metric Denominations and Value | Equivalents in Denominations in Use | |
|---|---|---|
| Hectare | 10,000 square meters | 2.471 acres |
| Are | 100 square meters | 119.6 square yards |
| Centare | 1 square meter | 1550 square inches |
| Metric Denominations and Value | Equivalents in Denominations in Use | |||
|---|---|---|---|---|
| Name | Number of Liters | Cubic Measures | Dry Measures | Liquid Measures |
| Kiloliter | 1,000 liters | 1 cubic meter | 1.308 cubic yards | 264.17 gallons |
| Stère | - | 1 cubic meter | - | - |
| Hectoliter | 100 liters | 1⁄10 cubic meter | 2 bushels & 3.35 pecks | 26.417 gallons |
| Dekaliter | 10 liters | 10 cubic decimeters | 9.08 dry quarts | 2.6417 gallons |
| Liter | 1 liter | 1 cubic decimeter | 0.908 dry quarts | 1.0567 quarts |
| Deciliter | 1⁄10 liter | 1⁄10 cubic decimeter | 6.1022 cubic inches | 0.843 gills |
| Centiliter | 1⁄100 liter | 10 cubic centimeters | 0.6102 cubic inches | 0.338 fluid ounces |
| Milliliter | 1⁄1000 liter | 1 cubic centimeter | 0.061 cubic inches | 0.27 fluid drams |
Stère: [Greek > Stereo = "Solid"] A metric measurement of firewood or lumber equivalent to the cord.
| Metric Denominations and Value | Equivalents in Denominations in Use | ||
|---|---|---|---|
| Name | Number of grams | Weight of what quantity of water at maximum density | Avoirdupois Weight |
| Millier or Tonneau | 1,000,000 grams; [1,000 kilograms] | 1 cubic meter | 2204.6 pounds |
| Quintal | 100,000 grams; [100 kilograms] | 1 hectoliter | 220.46 pounds |
| Myriagram | 10,000 grams; [10 kilograms] | 10 liters | 22.046 pounds |
| Kilogram | 1,000 grams | 1 liter | 2.2046 pounds |
| Hectogram | 100 grams | 1 deciliter | 3.5274 ounces |
| Dekagram | 10 grams | 10 cubic centiliters | 0.3527 ounces |
| Gram | 1 gram | 1 cubic centiliter | 15.432 grains |
| Decigram | 1⁄10 gram | 1⁄10 cubic centiliter | 1.5432 grains |
| Centigram | 1⁄100 gram | 10 cubic milliliters | 0.1543 grains |
| Milligram | 1⁄1000 gram | 1 cubic milliliter | 0.0154 grains |
On August 9, 2007, the 1866 Act was amended by Pub. L. 110–69 (text) (PDF), the America COMPETES Act. It replaced the old definition of the metric system with the modern-day definition of SI.
The kilogram is the base unit of mass in the International System of Units (SI), having the unit symbol kg. 'Kilogram' means 'one thousand grams' and is colloquially abbreviated to kilo.
The litre or liter is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metres (m3). A cubic decimetre occupies a volume of 10 cm × 10 cm × 10 cm and is thus equal to one-thousandth of a cubic metre.
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement. Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.45359237 kilograms, and which is divided into 16 avoirdupois ounces. The international standard symbol for the avoirdupois pound is lb; an alternative symbol is lbm, #, and ℔ or ″̶.
Ton is any of several units of measure of mass, volume or force. It has a long history and has acquired several meanings and uses.
The tonne is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the short ton and the long ton. It is equivalent to approximately 2,204.6 pounds, 1.102 short tons, and 0.984 long tons. The official SI unit is the megagram (Mg), a less common way to express the same amount.
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories, since being standardized and adopted in 1832. The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures evolved by 1824 to create the imperial system, which was officially adopted in 1826, changing the definitions of some of its units. Consequently, while many U.S. units are essentially similar to their imperial counterparts, there are noticeable differences between the systems.
The mole (symbol mol) is a unit of measurement, the base unit in the International System of Units (SI) for amount of substance, a quantity proportional to the number of elementary entities of a substance. One mole contains exactly 6.02214076×1023 elementary entities (approximately 602 sextillion or 602 billion times a trillion), which can be atoms, molecules, ions, ion pairs, or other particles. The number of particles in a mole is the Avogadro number (symbol N0) and the numerical value of the Avogadro constant (symbol NA) expressed in mol-1. The value was chosen on the basis of the historical definition of the mole as the amount of substance that corresponds to the number of atoms in 12 grams of 12C, which made the mass of a mole of a compound expressed in grams, numerically equal to the average molecular mass or formula mass of the compound expressed in daltons. With the 2019 revision of the SI, the numerical equivalence is now only approximate but may be assumed for all practical purposes.
The metric system is a decimal-based system of measurement. The current international standard for the metric system is the International System of Units, in which all units can be expressed in terms of seven base units: the metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). These can be made into larger or smaller units with the use of metric prefixes.
The gram is a unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram.
Troy weight is a system of units of mass that originated in the Kingdom of England in the 15th century and is primarily used in the precious metals industry. The troy weight units are the grain, the pennyweight, the troy ounce, and the troy pound. The troy grain is equal to the grain unit of the avoirdupois system, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. One troy ounce equals exactly 31.1034768 grams.
The ounce is any of several different units of mass, weight, or volume and is derived almost unchanged from the uncia, an Ancient Roman unit of measurement.
The quintal or centner is a historical unit of mass in many countries which is usually defined as 100 base units, such as pounds or kilograms. It is a traditional unit of weight in France, Portugal, and Spain and their former colonies. It is commonly used for grain prices in wholesale markets in Ethiopia, Eritrea and India, where 1 quintal = 100 kg (220 lb).
Myria- (symbol my) is a now obsolete decimal metric prefix denoting a factor of 104 (ten thousand). It originates from the Greek μύριοι (mýrioi) (myriad). The prefix was part of the original metric system adopted by France in 1795, but was not adopted when the SI prefixes were internationally adopted by the 11th CGPM conference in 1960.
The gravitational metric system is a non-standard system of units, which does not comply with the International System of Units (SI). It is built on the three base quantities length, time and force with base units metre, second and kilopond respectively. Internationally used abbreviations of the system are MKpS, MKfS or MKS . However, the abbreviation MKS is also used for the MKS system of units, which, like the SI, uses mass in kilogram as a base unit.
The cubic metre or cubic meter is the unit of volume in the International System of Units (SI). Its symbol is m3. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère, still sometimes used for dry measure. Another alternative name, no longer widely used, was the kilolitre.
The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: Australia, Canada, New Zealand, South Africa, the United Kingdom and the United States. The agreement defined the yard as exactly 0.9144 meters and the avoirdupois pound as exactly 0.45359237 kilograms.
The imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
The myriagram is a former French and metric unit of mass equal to 10,000 grams. Although never as widely used as the kilogram, the myriagram was employed during the 19th century as a replacement for the earlier American customary system quarter, which was equal to 25 pounds (11,340 g).
Before it adopted the metric system in 1816, the area that now constitutes Belgium used a number of units of measurement to measure different types of quantities including length, mass, and area. Since 1820, the International Metric System has been compulsory in Belgium. Initially, different names were used for units like metre, litre, kilogram, etc.