The Metric System

As early as 1584 Simon Stevenius had already proposed a decimal system of units and money in his book De Thiende. However, it was not until the French Revolution that the climate was conducive to creating a completely new system of units. In 1790 the French Academy of Science was commissioned by the National Assembly to design a new system of units for use throughout the world. They decided that this system should have the following attributes:

1. The system should consist of measuring units based on unvariable quantities in nature.

2. All units other than the base units should be derived from these base units.

3. Multiples and submultiples of the units should be decimal.

These principles still underpin the modern metric system. France created worldwide interest with this development and it resulted in 15 countries subscribing to the Metre convention in 1875. Through this the Bureau International des Poids et Mesures (BIPM) came into being. The BIPM now functions under the guidance of the Conférence Générale des Poids et Mesures (CGPM) which has delegates from all the countries that have subscribed to the convention. Over the years the metric system evolved, and in 1960 at the 11th CGPM the system was officially named the Système International d'Unités, or SI for short. The SI is the logical evolution of the metric system through the years and replaces all previous metric systems. It is a living dynamic system which is continually being improved to keep pace with devlopments in science and technology.

Some Metric System Conventions

• The unit of measure is the metre, not meter. The latter is a device used for measuring things. (Unless you live in the USA - in which case you will just have to live with the ambiguity.)

• The temperature interval of one degree Celsius equals exactly one Kelvin. Cesius temperature is related by the equation: t=T-T0, where T0=273.15 K, and T is the kelvin temperature.

• Using a comma to separate groups of three digits is not recommended - a space is preferable, since many countries use the comma as the decimal point marker. Both the USA and UK use the "dot on the line". So the following would be correct: 1 234 555.678 990.

• The term billion should be avoided since in most countries outside the USA (including the UK) it means a million-million (prefix tera), whereas in the USA it means a thousand million (prefix giga). Likewise the term trillion means million-million-million (prefix exa) in most countries outside the USA.

• The litre (liter in the US) is one of those units which is approved by the CGPM for use with the metric system.

• The official unit of volume in the SI is the cubic metre. However, since this is not convenient for much day-to-day use the CGPM has approved the use of the "other unit", the litre. The litre represents a cubic decimetre and you may use either the symbol "L" or "l" (capital or small "ell") to represent it. CPGM has not approved using any prefixes other than milli or micro with litre. It was originally defined as the volume occupied by 1kg of water. Subsequently it was found that this was not precisely 1 cubic decimetre, so the term litre was withdrawn. Later it was re-introduced officially as 1 cubic decimetre exactly. Because of this possible confusion its use in precision scientific measurements is discouraged.

Timeline for the Development of the Metric System

ca 1670 A French clergyman, Gabriel Mouton, proposes a standard linear measurement based upon the length of the arc of one minute of longitude on the Earth's surface and divided decimally.

ca 1760 The English developed a unit of length based upon that of a pendulum with a one-second period.

1795 The French government adopts a new system of length: the one ten-millionth part of the distance from the North Pole to the Equator when measured on a straight line running along the surface of the Earth through Paris. The metre, from the Greek word metron, is chosen as the unit name for this length.

1798 Survey completed, setting the length of the meter.

1799 Meter and kilogram reference standards created and deposited in the National Archives.

1812 The French resisted converting to the metric system. Napoleon was forced to restore the old units of measure (yards, inches, pounds, quarts).

1840 France mandates the use of the Metric System, hoping to make it universal.

1866 US legalizes use of the Metric System.v

1875 17 Countries sign the Treaty of the Metre including the US.

1889 CGPM (General Conference of Weights and Measures) creates new reference standards and distributes copies to member nations.

1900 Metric System already adopted by 35 countries including all industrialized nations except the British Commonwealth and the US.

1960 The SI (International System) units are adopted. These are built from seven independent base units: meter, kilogram, second, ampere, kelvin, mole, and candela.

1965 Great Britain adopts the Metric System

1968 South Africa adopts the Metric System

1969 New Zealand adopts the Metric System.

1970 Canada and Australia adopt the Metric System.

1975 US passes the Metric Conversion Act and establishes the US Metric Board to coordinate the voluntary conversion.

1982 The Office of Metric Programs replaces the Metric Board.

1988 The Omnibus Trade Bill becomes law and requires all federal agencies to use metric units in their procurements, grants, and business activities by 1992.

The History of Map Making

So many ancient peoples used maps that both the ability and the need to make maps appear to be universal. The earliest existing maps were made by the Babylonians about 2300 BC. Cut on clay tiles, they consisted largely of land surveys made for the purposes of taxation.

More extensive regional maps, drawn on silk and dating from the second century BC, have been found in China. One of the most interesting types of primitive map is the cane chart constructed by the Marshall Islanders in the South Pacific Ocean. This chart is made of a gridwork of cane fibers arranged to show the location of islands. The art of map making was advanced in both the Mayan and Inca civilizations, and the Inca, as early as the 12th century AD, made maps of the lands they conquered.

The first map to represent the known world is believed to have been made in the sixth century BC by the Greek philosopher Anaximander. It was circular in form and showed the known lands of the world grouped around the Aegean Sea at the center and surrounded by the ocean.

One of the most famous maps of classical times was drawn by the Greek geographer Eratosthenes about 200 BC. It represented the known world from England on the northwest to the mouth of the Ganges River on the east and to Libya on the south. The map was the first to show transverse parallel lines for equal latitudes. The map also had some meridians of longitude but they were irregularly spaced.

About AD 150 the Egyptian scholar Ptolemy published his geography containing maps of the world. These were the earliest maps to use a mathematically accurate form of conic projection. Because of the curvature of the earth, it is impossible to represent any portion of it on a flat surface without the adoption of a projection.

Following the fall of the Roman Empire, European map making all but ceased. Arabian seamen, however, made and used highly accurate charts during this same time period. Beginning in the 13th century, Mediterranean navigators prepared accurate charts of that sea, usually without meridians or parallels but provided with lines to show the bearings between important ports. In the 15th century, editions of Ptolemy's maps were printed in Europe.

A map produced in 1507 by Martin Waldseemuller, a German cartographer, probably was the first to apply the name America to the newly discovered transatlantic lands. The map, printed in 12 separate sheets, was also the first to clearly separate North and South America from Asia. Waldseemuller used the name America to honor the Italian navigator, Amerigo Vespucci (1454-1512), who first accepted South America as a new continent.

In 1570 the first modern atlas was published by the Flemish map maker, Abraham Ortelius. Gerardus Mercator (1512-94) of Belgium was considered one of the greatest cartographers of all times; the projections he devised for his world map proved invaluable to all future navigators.

The first maps to show compass variation were produced early in the 17th century; the first charts to show ocean currents were made about 1665. A complete topographic survey of France was issued in 1793, soon followed by Great Britain, Spain, Austria, and Switzerland. In the United States the Geological Survey was organized in 1879 for the purpose of making large-scale topographic maps of the entire country.

During the 20th century, map making underwent a series of major technical innovations, such as aerial photography and the use of satellites, which have permitted more accurate mapping of the outline of the United States.