The British Imperial System of Weights and Measures was replaced by the European metric system in 1968, long enough ago, you might think, that the (not so) new system would by now have been seamlessly and universally adopted.
But the transition has never been universally accepted and some nostalgic souls still cling to the pounds, ounces, yards and inches of old. In fact, our ongoing attachment to Imperial units can be seen throughout contemporary British life – plenty of Brits born long after 1968 still instinctively think in feet and inches when describing someone’s height or refer to miles more readily than kilometres when judging the distance of a journey.
And it’s hard to imagine anyone ordering 473 ml of lager (otherwise known as a pint) in a pub. On the other hand, many Imperial units, such as the Gill (quarter of a pint), Barleycorn (1⁄3 of an inch) and League (3 miles) now seem distantly archaic.
Perhaps some of this lingering nostalgia is linked to the Imperial System’s association with the British Empire. Britain’s ability to introduce a standardised global system was undoubtedly a product of its all-conquering power. For those reluctant to measure the decline of the Empire in any measure, doing so in metric hectares instead of Imperial acres might be an indignity too far.
Origins of the Imperial System
The British Imperial System emerged from a long and complex history of local units that can be traced back to thousands of Roman, Celtic, Anglo Saxon and customary local units. While numerous familiar units of measurement, including the pound, foot and gallon, were in use before any attempt was made to standardise them, their values tended to be relatively inconsistent.
A locally understood 1 foot unit would only have approximated a foot used elsewhere. This inconsistency would have been less of an issue when travel and trading remained localised, but the first thin increments of globalisation demanded improved uniformity. Which is what standardisation was designed to deliver.
The traditional units that preceded the codification of the British Imperial system were often derived from amusingly subjective forms of measurement: a furlong was based on the length of a long furrow in a ploughed field; the yard was originally set as the distance between Henry I’s nose and the tip of his outstretched arm.
The Weights and Measures Act that came into effect during the reign of George IV in 1824 set out to overhaul such generalisations and establish a precisely defined uniformity of measurements. That Act and the later Act of 1878 both sought to apply some degree of scientific rigour and legislative standardisation to a set of customary definitions that had previously varied according to trade and locality.
A good example of the standardisation set out in the initial Weights and Measures Act can be found in the adoption of a new uniform gallon. This was defined as equal in volume to 10 pounds avoirdupois of distilled water, weighed at 62 °F with the barometer at 30 inches, or 77.421 cubic inches. This precise new unit replaced the varying definitions of wine, ale, and corn (wheat) gallons.
The metric revolution
The metric system that eventually came to replace British Imperial units emerged from the revolutionary ferment of late 18th Century France. The French revolutionaries aims went beyond overthrowing the monarchy – they wanted to transform society to reflect a more enlightened way of thinking.
The metric system was devised by the country’s preeminent scientific minds as a solution to the vagaries of measurement under the Ancien Régime, when it was estimated that at least 250,000 different units of weights and measures were in use.
The philosophy behind the metric system – that scientific reason rather than tradition should be used to formulate a standardised system of measurement – is illustrated in the conception of the metre as a unit that relates to nature. To this end it was decided that a metre should be one 10-millionth of the distance from the North Pole to the equator.
To determine this precise measurement a line of longitude running from the pole to the equator was established – an exceptionally challenging task in 1792. This line, which bisects the Paris Observatory, was called the Paris Meridian.
Interestingly, despite the extraordinary scientific rigor involved in the development of the new metric system, it didn’t take on – people were reluctant to give up traditional units of measurement, many of which were inextricably tied to customs and industries. Indeed, so widespread was the refusal to use the metric system that the French government effectively gave up trying to enforce it for the first half of the 19th Century.
But eventually the demands of the industrial revolution and the growing necessity of standardised units of measurement for trade, design, mapping and scientific research meant that the metric system had to prevail, in France and beyond. Today, the metric system is the official system of measurement for every country in the world except three: the United States, Liberia and Myanmar.