Decimal system
The House of Lords, England
During a discussion in the British House of Lords, about the Weights And Measures Bill (Metric System) of 1904, Lord Belhaven and Stenton made a curious observation about slide rules and the metric system.
It is quoted here in full:
“There is another advantage which is gained by the use of a decimal system. The slide rule is hardly known, at all events it is very little in use with us, but on the Continent it is in constant use for every sort of calculation. A sum in multiplication or division can be worked at a glance by means of this instrument, but it is quite useless where mixed quantities of feet and inches, or tons, cwts and lbs are used. A curious illustration of this occurred to me yesterday. I was in a mathematical instrument maker's shop in the Strand, and I noticed a slide rule. I asked if many were sold, and was told that hitherto very few, but that now there was a demand for them by electrical engineers. As electrical calculations are all on a decimal system, this is a strong confirmation of the above statement. In the same way accurate calculations can be made by logarithms with wonderful celerity where a decimal system prevails”. [1]
A few things stand out:
“the slide rule is hardly known ... very little in use with us, but on the Continent ... constant use for every sort ...”:
In the 19th century, on the Continent, England was seen as a forerunner in the use of slide rules as noted by J.A. Sedlacek,[2] who wrote, “It is said that the use of the slide rule in England is so widespread that no tailor makes a pair of trousers without including a pocket just for carrying a 'sliding rule'. During such a time, it is difficult to understand why the slide rule does not enjoy such well-deserved recognition in our own country.”
Furthermore, the English government used excise slide rules as early as the 18th century. In determining the tax on alcohol, many strange non-metric measures occurred.[3]“quite useless where mixed quantities of feet and inches, or tons, cwts, and lbs. are used”:
Slide rules are ideally suited for converting non-metric units. For conversion of metric units you do not need a slide rule.... In addition, the scales on a slide rule may have a non-metric format. For example, the Farmar's Spirit Rule (1902, see Figure 1) had a scale I with a subdivision into shillings and pence (2/6 is 2 shillings and 6 pence, or 2.5 shillings).Alexander Charles Hamilton, the 10th Lord Belhaven and Stenton (1840-1920), was a colonel in the Royal Engineers and Fellow of the Royal Geographical Society.[4] He brought the Bill into the House of Lords, but the actual originator was Lord Kelvin.[5] For both men you might expect that their knowledge of the slide rule went beyond hearsay.
The metric system had been allowed to be used for contracts and dealings in the UK since 1864. Since 1897 it was allowed to be used for all purposes, and even taught at schools. But the metric system was not yet mandatory and was not widely used. The House of Lords passed the Weights And Measures (Metric System) Bill in 1904 which, with a two-year transition period, would make the metric system compulsory. The House of Commons, however, put a stop to this. The metric system is still not fully implemented a century later.[6]
Figure 1: Part of a Farmar's Spirit Rule (Herman's Archive nr. 2690).
References
Lords Chamber: Weights And Measures (Metric System) Bill Hl Volume 130: debated on Tuesday 23 February 1904, available via Hansard .
Dieter Von Jezierski (Rodger Shepherd transl.), “Slide Rules: A Journey Through Three Centuries”, Astragal Press, 2000, page16.
Thomas Wyman, “Brewing Beer and the Collection of Excise Taxes”, Proceedings of the 17th International Meeting of Slide Rule Collectors, September, 2011, page 64.
Cokayne, et al, The Complete Peerage, Volume II, 1912, page 97-98.
William H. Seaman, “The Discussion in the British Parliament on the Metric Bill”, Science New Series, 21(524) Jan 13, 1905, page 72-75.
UK Metric Association, UK Metric Timeline.
A Dutch version of this paper is published in MIR 85, May 2021