Measuring the Universe

During the eighteenth and early nineteenth centuries there were hundreds of different systems of weights and measures in operation in the world. Many major European towns had their own versions of a foot and an inch. This made trade very cumbersome. In 1745 Bishop Fleetwood complained:

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In Britain and France weights and measures varied slightly from place to place during the eighteenth century. There were different systems of weights for metals, medicines and food and different capacities for different liquids. A wine gallon was about six-sevenths of an ale gallon. The standards used were still those of Elizabeth 1st’s reign. There was a recognition that this situation was unacceptable and, particularly during the second half of the century, attempts were made to improve it. In 1742 the Royal Society procured from Jonathan Sisson, a leading London instrument maker, a set of linear measures to send to Paris to compare with the French measures.

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In 1758 a committee set up by the government complained that the old standards were ‘all very coarsely made, the Divisions upon them not exact, the rods appear to be bent, and therefore very bad standards’. New standards were made but recommendations for establishing one gallon and one pound were not accepted.

In revolutionary France, Enlightenment thinkers were able to exert pressure for change, the chaotic situation being intolerable to those who wanted an ordered world based on reason.

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So protested a citizen of Angouleme. The time was ripe for an overhaul.

The metric system was introduced in 1790 with high ideals: The Act proposed that ‘it should establish the uniformity which Reason has vainly called for during so many centuries, and which must form a new bond between men’. Alongside the metric measures went the revolutionary calendar, the ten hour day and the 400-degree circle. The metric system alone survives. A metre was defined as one ten millionth of a quarter of the Earth's meridian on a line from Dunkirk to Barcelona. This line began to be measured in 1792. The metric system became legal in 1795 and Etienne Lenoir, the leading French revolutionary instrument maker, made the first standard metre.

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The introduction of the metric system into France was slow. Seventeen years after its legal introduction Napoleon was forced to sanction the ‘system usuel’ which substituted the old names and used the old fractions. In Britain the complexity was eventually reduced by the introduction of the Imperial System in 1826. This allowed only one system of weights (avoirdupois), one set of linear measures, and one set of capacity measures. New standards had to be made and were held by all the counties to ensure national consistency.