165 years ago, in his opening address at the London meeting of the International Statistical Congress, held on 16 July 1860, Prince Albert drew attention to the measurement muddle prevalent at the time, and was in no doubt that the muddle would have to go.

Words from his speech were included in the 1862 Report From The Select Committee On Weights And Measures, dated 15 July 1862.

“The different weights, measures, and currencies in which different statistics are expressed, cause further difficulties and impediments: suggestions with regard to the removal of these have been made at former meetings, and will, no doubt, be renewed.”

Prince Albert, 16 July 1860

In his speech, Prince Albert also advocated for decimalisation of British currency:

“We fancy here that our Pound, as the largest available unit, with its Florin, offers great advantages, particularly if further subdivided decimally.”

Prince Albert’s remarks followed the recent Great Exhibition of 1851, which he co-organised. The 1862 Report says of the Great Exhibition, “The jurors of that Exhibition experienced the greatest embarrassment from the various, Weights and Measures used by the exhibitors of different countries.”

The need for a decimal system of measurement

The 1862 Select Committee Report noted that the need to simplify calculations involving measurement units had already led to the creation of improvised decimal units in various sectors – such as Gunter’s chain of 100 links, which itself was one tenth of a furlong. It was noted too that the Equitable Insurance Company had kept their ledger on the pound (£) and mil (£0.001) system for a hundred years already.

Not mentioned in the Report, was a more recent development in which Joseph Whitworth had introduced decimal measures for engineering. His newly improvised unit, the thou, which was equal to one thousandth of an inch, was proposed in his Standard Decimal Measures of Length, published in 1857.

The Report listed three alternative ways forward:

1. Retain the current system of weights and measures.
2. Create a new decimal system of weights and measures of our own.
3. Adopt, in common with other countries, the metric decimal system of weights and measures.

The second of these was dismissed, as “it would involve almost as much difficulty to create a special decimal system of our own as simply to adopt the Metric decimal system, in common with other nations; and if we did so create a special national system, we should, in all likelihood, have to change it again in a few years, as the commerce and intercourse between, nations increased, into an international one.”

Much evidence was included in the Report in favour of adopting the metric system:

“The Metric system is soon learnt; “any person” says Mr. Fellows, “in a quarter or in half an hour would be able to master the whole Metric system.””

“… there is nothing so difficult to a man of imperfect education as to take an invoice of 10 tons 3 qrs. or 7 cwts. and 18 lbs., at 25s. and 11d. the cwt.;” though he “can readily understand it when it is put into kilogrammes and francs.”

Perhaps the most convincing argument concerned the amount of time wasted by school pupils learning the current system:

“The time which the use of a decimal system would save in education has been generally stated (on the authority of schoolmasters) to be at least a year.”

References

On Opening The International Statistical Congress, London, 16 July 1860.
https://www.gutenberg.org/files/61205/61205-h/61205-h.htm#Page_250

Report From The Select Committee On Weights And Measures, 15 July 1862.
https://ukma.org.uk/wp-content/uploads/2017/07/met1862.pdf

Report From The Select Committee On Weights And Measures (with appendix), 15 July 1862.
https://babel.hathitrust.org/cgi/pt?id=mdp.39015086763235&seq=10

The English bishop John Wilkins was not the only one who developed a decimal-based measurement system that predates the metric system. Anders Bure, a Swedish mathematician and cartographer who lived from 1571 to 1646, developed a different decimal system that used the Swedish foot as the base unit. He tried to introduce this system of weights and measures in Sweden in the seventeenth century. Georg Stiernhielm, a Swedish civil servant, linguist and poet who lived from 1598 to 1672, later recommended this system should become the standard. This system was used between 1855 and 1889. Then Sweden changed over to the metric system on 1 January 1889.

The Swedish decimal measurement system was based on existing Swedish units of length that were redefined plus three newly created units of length for this new system. The new units were the scruple, the grain and the reef. While it was developed as a system of weights and measures, it was primarily intended for length measurements.

The units of length used in this system were:

• Scruple (Swedish name: skrupel, from Latin scrupulus, SI equivalent = 0.0296904 mm) – newly introduced in decimal system
• Grain (Swedish name: gran, from Latin granum, SI equivalent = 0.296904 mm) – newly introduced in decimal system
• New Line (Swedish name: nylinje, SI equivalent = 2.96904 mm)
• Decimal Inch (Swedish name: decimaltum, SI equivalent = 29.6904 mm)
• Foot (Swedish name: fot, SI equivalent = 296.904 mm)
• Pole (Swedish name: stång, SI equivalent = 2.96904 m)
• Reef (Swedish name: rev, SI equivalent = 29.6904 m) – newly introduced in decimal system

Like the metric system, the old Swedish decimal measurement system used a base of 10. Thus, there were 10 scruples to a grain, 10 grains to a new line, 10 new lines to a decimal inch, 10 decimal inches to a Swedish foot, 10 Swedish foot to a pole and 10 poles to a reef.

Note that the Swedish inch and foot differ from the English units that share the same names. For comparison, the English inch is exactly 25.4 mm, and the English foot is exactly 304.8 mm.

The Swedes also saw the benefits of a decimal (i.e. base 10) measurement system, so they developed a national version of such as system like the English, before the metric system was invented. The problem with using different national base 10 systems is mutual compatibility. The metric system was invented to overcome the problems with numerous mutually incompatible national and regional measurement systems. It was intended to be a single standardised measurement system for international use. Hence, the slogan used for the metric system was “for all people, for all time”.

Sources and further reading:

• https://sv.wikipedia.org/wiki/Decimalsystemet
• https://sv.wikipedia.org/wiki/Rev_(längdmått)
• https://en.wikipedia.org/wiki/Anders_Bure
• https://en.wikipedia.org/wiki/Georg_Stiernhielm

Martin Vlietstra attended the St Cross Centre for the History and Philosophy of Physics (HAPP) one-day conference in Oxford on Saturday 7 June 2025 and has written a report about the conference for Metric Views.

The one-day Conference “Measure for Measure: A History of Measurement,” sponsored by the St Cross Centre for the History and Philosophy of Measurement1 took place in the Andrew Wiles Building on 7th June 2025. Five lectures were delivered by eminent researchers, starting with a historian who had studied units of measure used by ancient civilisations and ending with a lecture on the philosophy of measurement. Each lecture was followed by an opportunity to put questions to the speakers. The third lecture, which was devoted to the development of SI, was probably the most applicable to UKMA members with the other lectures putting SI into perspective.

One theme that came across in many of the lectures was that any unit of measure should be accessible, useful and consistent.

• The term “accessible” means that the unit could easily be verified – for example, a “foot” is accessible as most people have two feet.
• The term “useful” means that the unit must also be practicable – for example stating that the direct distance between the London Eye and the Embankment is three minutes’ walk [the author’s example!] is not very practicable as the Thames is about 250 m wide at that point!
• The term “consistent” is self-explanatory – the original definition of a foot does not produce a consistent unit of measure as my foot is probably different in length to your foot. In contrast, the length of a metre is the same worldwide.

Each of the five lectures are now described.

James Vincent:2 Ancient Measures from the Body to the State

The first speaker introduced the concept of measurement as it applied to ancient civilisations where the various parts of the body were used – the foot, the finger, the palm, the hand, the cubit and the fathom to mention a few. He went on to explain that these units had been found by archaeologists on measuring sticks used by the ancient Egyptians.  He went on to explain how standardisation had crept into the Egyptian state, one of the important reasons being the remarking of boundaries after the Nile’s annual flood subsided. He also mentioned that the ancient Egyptians had two different cubits – the common cubit and the royal cubit, but the hieroglyphics did not explain how and when each was used. After standardisation had taken place, one of the “sins” for which ancient Egyptians were expected to “confess” before death was falsification of measures.

Dr Jane Wess:3 A History of Measuring Instruments

Dr Wess described many measuring instruments. The earliest devices were the measuring sticks and sundials used in Ancient Egypt. She went on to show photographs illustrating measuring devices including weighing devices, internal callipers and external callipers that had been recovered from the ruins of Pompeii. Other instruments included a variety of tools used for navigation and surveying dating from Roman times to the early 20th century. She then moved on to various clocks showing pictures of the earliest clocks (mounted in church towers) and then to the Harrison pocket watches used by navigators in the late eighteenth century followed by a decimal clock dating from the French Revolution. Nineteenth century measuring devices included a variety of galvanometers which reminded the audience (or at any rate me) that the standardisation of electrical units of measure, which was pioneered by Maxwell and Thompson (Lord Kelvin), used metric units as their basis.

Prof Richard Brown:4 The Measure of All Things: The Development of the Metric System and the International System of Units

From a UKMA perspective, Professor Brown’s lecture was the most informative. In the first part of his lecture, he outlined what he considered to be the most significant events that led up to the signing of the Metre Convention. The events that he chose were:

• 1668 – John Wilkin’s Paper on a Universal Measure
• 1791-1799 – The development of the metric system during the French Revolution
• 1812-1837 – The establishment of mesures usuelles in France
• 1851, 1855 – The Great Exhibitions of London and Paris respectively
• 1867 – Geodetic standards and the Expositions Universelles (Berlin)
• 1872 – Invitations to the Metre Convention issued by the French
• 1875 – Signing of the Metre Convention on 20 May 1875
• 1889 – Acceptance of the new international prototype metres and kilograms by the CGPM

During his talk, Prof Brown highlighted the refusal of the British Government to sign up to the Metre Convention in 1875 and only finally signed up in 1884 when they wished to calibrate the standard yard against the standard metre. Prof Brown also drew to attention that it was a British company, Johnson Mathey who provided the alloys needed to cast the prototype metres and kilograms.

He then skipped over the history of the development of the metric system, picking up the thread again in 1948 when it was proposed to standardise electrical measurements. The resulting standardisation resulted in the setting up in 1960 of SI with six base units. The mole was adopted as a base unit in 1971 when the physicists and the chemists agreed to use the Carbon 12 atom as the basis for a common definition of the mole.

After describing how the definition of the metre had changed – in 1889, it was defined as the length of the international prototype metre, in 1960, it was defined in terms of the wavelength of light emitted by a Krypton-86 lamp and in 1983, in terms of the speed of light. This led to a discussion of how, in 2017, the CGPM agreed to redefine all the base units, apart from time, on physical constants of nature. Time remains tied to a substance – namely the frequency of light emitted by a specified transition of the electrons in a caesium 133 atom.

On being asked on the future of the SI, he suggested that in the 2030’s one might see a redefinition of the second though he gave no hint as to how it might be redefined.

Prof Hasok Chang5: ‘To see the world in a grain of sand’: Measuring unobservables through the ages.

Professor Chang’s talk centred on measuring quantities that we cannot see. The first example that he gave how Eratosthenes measured the circumference of the earth. He knew that at the equinox, the sun was directly overhead at Syene (modern day Aswan) because it shone directly down a well. At the equinox, he measured the angle of the sun’s rays at midday at Alexandria and knowing the distance between Alexandria and Syene and assuming that the earth was spherical he calculated that the earth’s circumference was about 252,000 stadia. Depending on the value of the stadium, this gave a value of width between 2.4% below and 0.6% above the currently accepted value.

He then gave a discourse on the measurement of temperature and how, when we measure temperature, we make the assumption that the material we use in the thermometer expands linearly with temperature. Can we justify this assumption? He went on to cite other similar problems and pointing out the assumptions we make along the way – for example, was Eratosthenes justified in assuming that the earth was a sphere?

Dr Jo Wolff:6 Can we be Realists about Measurement

Dr Wolff examined the philosophy behind the definitions and use of units of measure. In particular she asked what is meant by assigning numbers to measurements. As an example, she stated the obvious: “1+2=3”. Shen went on to point out that if we took a balance and placed a 1 lb weight and 2 lb weight alongside each other on one scale-pan, it would be balanced by a 3 lb weight in the other scale-pan. If we renamed the weights to 454 g, 907 g they would still be balanced by a weight that was (454 + 907) g, making the concept of weighing invariant with respect to choice of units. She contrasted this with the measurement of temperature. If the thermometer read 20°C, it would also read 68°F. if now we double the 20°C to get 40°C, we cannot just double the Fahrenheit reading – 40°C = 104, not 136°F (68×2 = 136).

She went on to explain the philosophical implications of such “irregularities.” Although she did not mention the Beaufort Scale or the Rockwell hardness scales by name, she devoted part of her talk to the philosophy of measurements that are based on arbitrary observations.

Prof Robert Fox:7 Summary

The events of the day were summarised by Professor Fox. He summarised the various historical events that were mentioned and also mentioned the Michelson–Morley experiment of 1887 in which they attempted to measure the speed of the earth relative to the “aether”. Although the experiment failed in its original objective, it was the first experiment to suggest that the speed of light is constant – something which is now assumed in the definition of the metre.

Prof Fox went on to emphasise the need for there to be agreement between nations in respect of units of measure and how the SI met this need.

Conclusions

This was certainly an interesting day for the academically inclined as is shown by the number of highly qualified academics who took part in the proceedings.

Notes

1. University of Oxford
2. Author of “Beyond Measure: The Hidden History of Measurement”
3. Formerly University of Edinburgh
4. Director of the National Physical Laboratory, Visiting Professor at University of Surrey
5. University of Cambridge
6. University of Edinburgh
7. University of Oxford

When the latest Traffic Signs Regulations and General Directions (TSRGD) came into force in April 2016, imperial-only restriction signs for height, width and length were no longer authorised. However, the Traffic Signs Manual (TSM) that provides guidance to road contractors on signage has not been updated since 2009 and still includes imperial-only restriction signs to this day. Six months ago, I asked my local MP to contact the Secretary of State for Transport to ask why the Department for Transport has been promoting the use of unauthorised imperial-only road signs since 2016. I received a reply from the DfT a few days ago.

This is the email I sent to my local MP Sarah Sackman on 19 December 2024:

“Dear Sarah Sackman MP

On page 98 Chapter 8 Part 1 of the Traffic Signs Manual (TSM), there are diagrams for both imperial-only width and imperial-only height restriction signs for use in road works and temporary situations – signs which have not been authorised for new sign installations since the Traffic Signs Regulations General Directions (TSRGD) 2016 came into force in April 2016.

The TSM has been promoting the illegal use of imperial-only vehicle restriction signs since 2016.

The diagram for weight restriction signs is also obsolete as it includes the now unauthorised upper case “T” symbol to represent tonne. The diagram for this sign was corrected to show the lower case “t” in the 2011 amendment to the TSRGD.

Can you please ask the Secretary of State for Transport why the Department for Transport has been promoting the use of unauthorised imperial-only road signs and unauthorised weight restriction signs for the last eight years.

Here is the link to TSRGD 2016:
https://www.legislation.gov.uk/uksi/2016/362/pdfs/uksi_20160362_en.pdf

Here is the link to Chapter 8 Part 1 of the Department for Transport’s TSM:
https://assets.publishing.service.gov.uk/media/5a74adeaed915d7ab83b5ab2/traffic-signs-manual-chapter-08-part-01.pdf

Ronnie Cohen”

On 4 February 2025, I got an email telling me that Sarah Sackman has written to the Department for Transport on my behalf.

On 10 July 2025, Sarah Sackman received the following reply from the DfT, which she forwarded to me:

Why wasn’t the TSM updated at the same time as the TSRGD? Why is it taking the DfT so long to update the TSM to bring its guidance into line with the current road sign regulations? For the last 9 years, the TSM has endorsed and promoted the use of unauthorised (i.e. illegal) width and height restriction signs. I got no explanation for the long delay to update the TSM and why the discrepancy between the TSM and TSRGD has been allowed to persist for so long. It is a symptom of the continuing measurement mess as the UK struggles to move forward on metrication. It does the government no credit at all.

For more information about this issue, see https://metricviews.uk/2024/12/05/does-the-traffic-signs-manual-promote-the-illegal-use-of-imperial-only-vehicle-restriction-signs/.

On 19 May 2025, the UK concluded a new agreement with the European Union amid cries of betrayal from the pro-Brexit press. While UKMA has no position on UK-EU relations or on this new agreement, it is a case study to show how it is possible to implement policies such as the completion of the Metric Programme, which started in 1965, while resisting attacks from a hostile media.

This new agreement covered the key issues of fishing, farming exports, defence and security, further talks on a cross-border youth experience scheme, passport e-gates and carbon and energy. The government was delivering on its election promise to get a Brexit reset deal to forge closer relations between the UK and the EU. The government released an official statement to say that the agreement will support British businesses, back British jobs, and put more money in people’s pockets and that the package will help make food cheaper, slash red tape, open up access to the EU market and add nearly £9 billion to the UK economy by 2040.

Predictably, various pro-Brexit newspapers criticised the agreement. These were some of the headlines that appeared in these newspapers:

• “Six biggest bombshells in Keir Starmer’s EU-UK Brexit ‘reset’ deal”, Daily Express, 19 May 2025
• “UK-EU reset deal: Globalist Keir Starmer is pushing Britain back into the European Union by stealth, former Brexit party MEP Alex Phillips tells the Mail’s ‘Apocalypse Now?’ podcast”, Daily Mail, 22 May 2025
• “BREXIT BETRAYED Starmer ‘done up like a kipper’ as he agrees EU surrender deal allowing foreign trawlers to plunder UK waters for YEARS”, The Sun, 19 May 2025
• “Starmer trying to ‘kiss goodbye to Brexit’”, Daily Telegraph, 19 May 2025

There were a few days of negative headlines and critical articles in the pro-Brexit press after the agreement was reached with the EU, but the press soon moved on. In the official statement, Prime Minister Sir Keir Starmer made the case for the agreement. UKMA takes no position on this agreement.

Why can’t the government do the same to conclude the UK’s long drawn-out metrication progress by making the case for metrication and completing the UK’s transition to the metric system? This example shows how to fight against a hostile press successfully while making the case for metrication and getting on with the job.