From decimal fractions to sand yachts – the unbelievably fertile mind of Simon Stevin

Of all the people who contributed to the evolution of modern science at the beginning of the seventeenth century and who have disappeared from popular perception under the over dimensioned shadow cast by Galileo, one of the most fascinating is the Netherland’s engineer Simon Stevin. Stevin is usually referred to as an engineer but in reality he was a jack-of-all-trades, mathematician, physicist, astronomer, engineer, inventor, music theorist, political advisor and army quartermaster.

Simon Stevin Source: Wikimedia Commons

Simon Stevin was the illegitimate son of Antheunis Stevin and Cathelijne von van der Poort probably born in Bruges around 1548. This and the fact that he seems to have come from an affluent background and was apparently well educated are all we know about his origins. In 1571 he became a merchants clerk in Antwerp and between 1571 and 1577 he travelled to Prussia, Poland, Denmark, Norway and Sweden. In 1577 he returned to Bruges where he was appointed city clerk a position he held until 1581 when he moved north to Leiden. It is not known why Stevin left Bruges for Leiden; his motive might have been religious, political or something else altogether. In Leiden he enrolled in a Latin school in 1581 and then the university in 1583 where he stayed until 1590 but appears never to have graduated. At the university he became friends with Maurits of Nassau the son of Willem I, Prince of Orange, who led the Dutch revolt against the Spanish Habsburgs. Maurits, who later became Stadtholder of the Dutch Republic and commander of the Dutch army, and Stevin remained close friends until Stevin’s death in 1620 and Stevin became Maurits’ technical and scientific advisor and tutor. Initially he was simply engineer but in 1604 he was appointed quartermaster-general of Dutch army.

Portrait of Maurits, Prince of Orange-Nassau School of Michiel Jansz. van Mierevelt Source: Wikimedia Commons

For Maurits he wrote textbooks on a wide range of mathematical and technical subjects, as well as organising and setting up a school of engineering at the university in Leiden. He wrote original scientific works as well as general surveys of the science and technology of the age. His published works include books on mathematics, mechanics, astronomy, navigation, military science, engineering, music theory, civics, dialectics, bookkeeping, geography and house building. He wrote his books in the vernacular and in doing so coined much of the necessary Dutch vocabulary for science and technology, some of which has been replaced since his times but much of which is still in use. However, much of his work was translated into Latin and/or French and was so available and known to other researchers in Europe.

Probably his most well known work is De Thiende (Tenths), a twenty-nine-page booklet in which he explained how to use decimal fractions. He did not originate the concept, Chinese and Islamic mathematician had already been using decimal fractions for several centuries before Stevin but he did introduce and make popular the idea in Europe. In mathematics he also wrote interesting forward-looking textbooks oh arithmetic and algebra, as well as linear perspective.

In physics he worked on statics some fifty years before Galileo developing and continuing the work of Archimedes. His most famous discovery here was the law of the inclined plane, which he demonstrated using a chain of wreaths. His demonstration shows that the effective component of gravity is inversely proportional to the length of the inclined plane. What Stevin is in principle using here is the theory of the parallelogram of forces, something learnt in schools today using vector algebra but Stevin is using it a couple of centuries before vector algebra existed.

Stevin’s proof of the law of equilibrium on an inclined plane, known as the “Epitaph of Stevinus”. Source: Wikimedia Commons

Of historical interest is that Stevin, unlike Galileo, actually did drop balls from a church tower and also hypothesised that objects in a vacuum would fall at the same rate irrespective of weight.

Having dealt with statics, Stevin next turned to hydrostatics, another discipline that he inherited from Archimedes, and here he was the first to demonstrate the so-called hydrostatic paradox i.e. that the pressure in a liquid is independent of the shape of the vessel and the area of the base, but depends solely on its depth. This discovery is often falsely attributed to Blaise Pascal.

In his book on astronomy published in 1608, Stevin revealed himself to be an unconditional supporter of Copernican heliocentricity at a time when very few were prepared to make such a commitment. He also accepted that the tides were caused by the moon, also a forward-looking commitment for the times. Being a Dutchman he of course wrote on the principles of navigation giving a clear explanation of steering a ship along a loxodrome or rhumb line as originally propagated by the Portuguese mathematician Pedro Nunez and used by Mercator in his famous Mercator projection.

As an engineer Stevin wrote on military fortification. Of course, as a Netherlander he also wrote on hydraulic engineering designing new types of sluices and locks, as well as better windmills for drainage work. In many areas his work was of a very practical nature but always looking for ways to improve machines or find better solutions for mechanical tasks.

In music theory, a very hot topic at the time, Stevin rejected a couple of thousand years of highly emotional debate on the subject of the intervals of the scale and proposed what is now known as equal temperament. He was not the first to do so, he was anticipated by Galileo’s father Vincenzo amongst others, but was almost certainly not aware of the fact.

On a somewhat more frivolous level he designed and built sand or land yachts (Zeilwagen) for Maurits. Wind driven carriages had existed in China for a thousand years before Stevin built his and illustrated in the Theatrum Orbis Terrarum of Abraham Ortelius in 1584 and in Mercator’s Atlas slightly later and it can be assumed that this was the source of inspiration for Stevin’s own vehicles.

Wind chariot or land yacht (Zeilwagen) designed by Simon Stevin for Prince Maurice of Orange (Engraving by Jacques de Gheyn). Source: Wikimedia Commons

Stevin collected all of his mathematical writings into his two volume Wisconstighe Ghedachtenissen in 1608, which were published simultaneously in both French and Latin; the latter translation being carried out by Willebrord Snel. A modern edition of The Principle Works of Simon Stevin in 5 volumes was published in Amsterdam 1955–1968.

Stevin wrote extensively over a very wide ranch of scientific, mathematical and technological subjects. His writings were always lucid, up to date and very often-contributed new concepts, ideas, methods and discoveries, some of which were very significant. He was in his own lifetime highly influential, both of the Snels knew him personally and Willebrord did much to spread his work. Isaac Beeckman consulted his unpublished papers from which he much profited.

I have one personal puzzle concerning Stevin’s work. When Hans Lipperhey demonstrated his newly invented telescope to Maurits in The Hague in September 1608, Simon Stevin had already been Maurits’ scientific advisor for more than twenty years and was without doubt the leading scientific and technological authority in the young Dutch Republic, but I know of no reaction, comment, statement or whatever from Stevin on this sensational new discovery. For me as a historian of the telescope his silence is deafening.