The signing of the Metre Convention on 20 May 1875 by 17 nations, including Austria-Hungary, France, Germany, the Ottoman Empire, Russia and the USA, sounded the death knell of the imperial measurement system. In this article, Ronnie Cohen looks at an earlier proposal that was intended to make this system better fit for purpose.
In support of the retention of imperial units, it is claimed that binary subdivision, divisibility by three and the use of base 12 are more convenient. Though there are arguments in favour of bases other than 10, the imperial system uses many that have little to recommend them.
The report of the Parliamentary Select Committee on Weights and Measures of 1862 argued that it would be an obvious improvement to reduce all these bases to some harmonious form. The first question that arose was whether that form should be binary, decimal or duodecimal. One option that was seriously considered by the 1862 Committee was the decimalisation of imperial units, along with the decimalisation of the UK currency.
The 1862 Committee examined three options for the future use of measurements within the UK. These were:
- Retain the present system.
- Create a distinct UK decimal measurement system.
- Adopt the metric decimal system, in common with other countries.
Among the witnesses who appeared before the Select Committee, hardly any defended the present system established by the Act of 1824. The report of the Committee pointed out “that the best proof of the insufficiency of the present system for all the practical purposes of life is found in the adoption of so many systems better suited to their wants, by different classes of the people”.
It went on to say, “The superiority of a decimal system has long been acknowledged. Our engineers have, for a considerable time, made use of one. The decimal measuring-chain and decimal levelling staff are instruments familiar to them. Insurance companies have long employed decimals. The Equitable Insurance Company have kept their ledger on the pound and mil system for a hundred years.”
The Committee noted that, as the imperial measurement system was found to be inadequate, other systems were adopted that were more suitable to the task in hand, such as decimally computed grains for scientific purposes, bullion weights that used decimal multiples and divisions of the troy ounce, decimal coal weights, and the occasional use of the metric system for scientific use. There were other practical uses of decimal systems used with imperial units. In the manufacture of guns, the measurements used were in thousandths of inches. The Master of the Mint told the 1862 Committee that they used the decimal system at the Mint by dividing the troy ounce into tenths, hundredths and thousandths.
The report of the Select Committee continues, “The decimal scale, however, appears to us to be by far the most convenient for all transactions which become the subject of written accounts, and for all transactions, of whatever kind, in which great numbers of weights and measures are combined by addition or multiplication.”
Here are some quotes from the Select Committee report, recommending the decimalisation of some imperial units:
- “We beg particularly to indicate the decimal subdivision of the foot (which is even now usually engraved on foot rules and levelling staves), as one extensively used in the practice of engineers, and one which we would recommend for the recognition of Government in every case.”
- “That the name milyard, or some other to be fixed by Act of Parliament, be recognised as describing the measure of 1000 yards, without the necessity of further definition.”
- “That the only legal weights above one pound be, weights of multiples of 1 lb, not exceeding 10 lb; and weights of 10 lb and its multiples, not exceeding 100 lb. That the name ‘centner’, or some other be to fixed by Act of Parliament, be recognised as describing the weight of 100 lb, without the necessity of further definition.”
- “It has been proposed to make a stone 10 lb, a hundredweight 100 lb, to make 10 ounces in a pound, and to create a lower denomination, of which there should be 10 in an ounce.”
One member of the Select Committee, even suggested that the yard should be redefined as the length of a metre and the mile should be redefined as the length of a kilometre, and that they should be called the new yard and the new mile!
In an 1857 paper on standard decimal measures of length, Joseph Whitworth said, “I have long been convinced that great and rapid progress would be made in many branches of the mechanical arts if the decimal system of measures could be generally introduced. To state the case broadly, instead of our engineers and machinists thinking in eighths, sixteenths and thirty-seconds of an inch, it is desirable that they should think and speak in tenths, hundredths, and thousandths. I can assure those who have been accustomed to the fractional system that the change to the more perfect decimal one is easy of attainment, and, when once made, it will from its usefulness and convenience amply repay any trouble which may have attended its acquirement.” (Source:https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mechanical_Subjects/A_Paper_on_Standard_Decimal_Measures_of_Length)The
The Select Committee concluded that it would be more beneficial for the UK to adopt the same measurement system that was being adopted by many other countries, and it rejected the creation of a uniquely UK decimal system, saying that “… 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.”
Examples of decimal imperial units survived long after the report of the Select Committee had been forgotten. Civil engineers were still using levelling staffs graduated in feet and hundredths until the UK construction industry went metric in the early 1970s, and the thousandths of an inch advocated by Mr Whitworth have lingered in some of the by-ways of UK manufacturing industry right up to the present time. Curiously, the Americans sometimes decimalise the foot as suggested by the Committee – this is a US tape measure:
(A problem with using such a tape is that the tenths of a foot might be mistaken for inches.)
Thanks to US dominance of the aerospace industry after the Second World War, we measure altitude in feet not metres (and certainly not miles and yards) and engine thrust in thousands of pounds as an alternative to kN (but seldom in tons).
Would the extensive adoption of decimal imperial measures, as considered by the Committee, have helped to prolong the system’s life? This seems unlikely – The Metre Convention would soon ensure that imperial’s days were numbered. But the failure to adopt the Committee’s ideas for decimalisation of measures suggests that the imperial system’s survival for a further century was due to familiarity and inertia rather than utility.
A summary of the Select Committee report can be read at:
The full report can be downloaded as a free e-book from: http://books.google.co.uk/books/about/Report_from_the_Select_committee_on_weig.html?id=wI7nAAAAMAAJ