The recent discovery that the principles of the metric system were proposed in England over a century before they were adopted in France seems to deserve comment on Metric Views.
An Australian, Pat Naughtin, has recently drawn attention to a book by John Wilkins published in 1668. Wilkins was Oliver Cromwell’s brother-in-law, and his distinguished career included being Warden of Wadham College Oxford, Master of Trinity College Cambridge just before the arrival of the youthful Newton, Secretary of the Royal Society, Dean of Ripon and finally Bishop of Chester.
In his book, “An essay towards a real character, and a philosophical language”, Wilkins discusses the nature and variety of language and languages, and includes a short chapter on measurement, entitled, “Of measure”.
The first section of this chapter concerns number. Having considered division by eight, he concludes, “But because general custom hath already agreed upon the decimal way, therefore I shall not insist upon the change of it.” Not exactly a ringing endorsement of decimal systems, but the arguments for non-decimal systems, which continue to this day, seem already to have been lost three centuries ago.
The second section of the chapter looks at measurement of length, and volume, which Wilkins calls collectively, “magnitude”. The first issue he raises is the absence of a universal system of measurement. He says, “The several Nations of the World do not more differ in their Languages, than in the various kinds and proportions of these Measures. And it is not without great difficulty, that the measures observed by all those nations who traffick together, are reduced to that which is commonly known and received by anyone of them; which labour would be much abbreviated, if they were all of them fixed to an one certain Standard.” He then proposes that this should be “some natural standard or universal measure”, and that this should be of length as “the other measures might easily be fixed from thence.”
So, as well as proposing the principles of the metric system, he seems also to have foreseen the need for agreed international standards for units of measurement.
For the natural standard of length, he looks first at the height of the column of mercury in a barometer, which he calls the quicksilver experiment, and he rejects this because of its uncertainty. Quite right! He then says, “Some have conceived that this might be better done by subdividing a Degree upon the Earth: But there would be so much difficulty and uncertainty in this way as would render it impracticable”. This was the method originally used to define the metre, but French surveyors engaged on the meridian surveys of the 1730’s and 1790’s would at times probably have agreed wholeheartedly with Dr Wilkins. Finally, he recommends the pendulum, “which was first suggested by Doctor Christopher Wren”. The pendulum was seriously considered by the founders of the metric system for their standard of length, but finally rejected when it was realized the variation in the earth’s gravity with latitude meant that this could not be the universal measure they sought. Quite by chance, the pendulum recommended by Wilkins, based on experiments carried out by the Dutch physicist, Christiaan Huygens, is 997 mm long.
Wilkins then goes on to recommend additional units for length by dividing and multiplying his standard by ten, a hundred and a thousand. Units for “capacity” follow naturally by cubing his standard length, with decimal multiples and sub divisions.
For the standard of weight, known nowadays as mass, he proposes the standard of capacity filled with “distilled rainwater”. So the relationship between mass and volume that was sought by the founders of the metric system is also in the ‘Wilkins system’.
Finally, he proposes decimal currency, which any readers of Metric Views who have reached this point in the article will be happy for me to pass without comment.
Hitherto, most historians have agreed that a French priest, Gabriel Mouton, was the ‘founding father’ of the metric system. He proposed a decimal system of measurement in 1670, two years after Wilkins. Mouton based his standard on the length of one minute of arc of a great circle of the Earth (now called a nautical mile, 1852 metres). He also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). At that time, England and France enjoyed friendly relations, and it is possible Mouton could have learned of Wilkins’ work before making his proposals. Or this may be another example, like the miners’ safety lamp or the incandescent light bulb, of two people putting forward similar proposals at almost the same time but quite independently.
Clearly, Wilkins’ proposals, like those of Mouton, include the essential principles of the original metric system:
A universal standard of length
A simple relationship between length and volume
A simple relationship between volume and mass
Decimal multiplication and division of the standard units to give further units
Wilkins did not, of course, see the adoption of his proposals – he died in 1672 – and he might have been disappointed to learn they would be taken up and developed by the French, not the British. However, the development of the metric system beyond his proposals has depended a great deal on international cooperation. He would be pleased to learn of significant British contributions in areas he never foresaw, such as the addition of electrical units to the metric system as proposed by the British Association for the Advancement of Science in 1874. And he would probably be delighted that the simple and logical system he proposed has now become almost universal.
Further details of John Wilkins can be found at http://www.cl.cam.ac.uk/~rja14/wilkins/wilkins.html
The relevant pages of Wilkins’ book can be found at Pat Naughtin’s web site at: http://www.metricationmatters.com/docs/Wilkins_translation_2007-07-14.pdf