Tag: Royal Society

Book Review: Huygens–The Man Behind the Principle by C.D. Andriesse

huygens-man-behind-principle-c-d-andriesseThis post is a review of C.D. Andriesse’s biography “Huygens: The Man Behind the Principle”. Huygens Principle concerns the propagation of light but he carried out a wide range of research, including work on clocks, Saturn (discovering its moon “Titan” and hypothesizing the existence of its rings), buoyancy, circular motion, collisions, musical scales and pendulums. Huygens has made passing appearances in my blog posts on the French Académie des Sciences, on telescopes and also on clocks.

On the face of it is surprising that he is not better known, looking around for biographies of him one finds a rather short list. Andriesse puts this down to much of the personal documentation being in Dutch. The scientist in me feels there should be some quantitative way of measuring how “well known” a historical figure is now, and how “important” they were – I suspect this is an impossible programme. On completing the book I suspect a couple of factors play a part here: Huygens represents something of a transitional figure between the work of Galileo/Descartes, and Newton/Leibniz. Similarly his practical work on clocks and telescopes was impressive for its time but superseded not long thereafter. What we do now in physics owes much more to Newton than to Galileo, furthermore Newton although not prolific published more promptly than Huygens and was President of the Royal Society for 20 or so years before his death in post, whilst Huygens left L’Académie des Sciences sometime before his death in not particularly auspicious circumstances. It isn’t entirely clear whilst reading the book, but it becomes obvious that frequently Huygens’ work was done over long periods and only published quite a long time after it was started, often posthumously.

Huygens was born in the Hague in 1629 and died 1695. Christiaan Huygens’ father, Constantijn was a senior Dutch diplomat and a regular correspondent with René Descartes. Constantijn also met Francis Bacon (and was clearly impressed by him), Bacon and Descartes were important in shaping the development of science in the early 17th century. Bacon in particular set the scene for the way of doing science both in the Royal Society and  L’Académie des Sciences. Constantijn set his son off on a regime of study in the classics, with a view to him becoming a lawyer and following in his footsteps as a diplomat. Sometime around 1643, when Christiaan was 14 years old he started to show promise in mathematics.

Huygens senior provided introductions to Marin Mersenne who introduced him to those circles who became the Académie des Sciences in France. Christiaan Huygens was a paid director of science at L’Académie from its foundation in 1666 until he was excluded from it shortly after the death of Jean-Baptiste Colbert, founder of the organisation and his principle patron, in 1683. The exclusion arose from a combination of the loss of this patron, religious differences, absence due to illness, personal vendettas, opposition to membership of any foreigner and his demand for higher remuneration. Aside from this period at L’Académie, Huygens appears to have lived on the wealth and position of his father.

There’s no doubt that he made significant contributions in the area of mechanics, going beyond what Galileo and Descartes had done but his work was superseded almost immediately by that of Newton, and Leibniz, particularly in the methods of calculus which they developed. Calculus is a tool which makes much of the complex geometrical work that Huygens did obsolete. Leibniz was an informal pupil of Huygens, and they kept up a lengthy correspondence. He also had some exposure to Isaac Newton via the Royal Society.

Andriesse claims that Huygens wrote the first physics formula, relating to collisions. I think we should probably take this with a pinch of salt, but looking at the work he did do on circular motion, collisions, buoyancy, the motion of the pendulum and the shape of a catenary as well as his work on optics it is all very familiar to those that studied physics (at least to the age of 18).

Alongside his mathematical and theoretical physics work, Huygens also made contributions to the development of both clocks and telescopes. He introduced the pendulum clock, and a design of his was tested for determining the longitude by the Dutch East India Company. In practical terms this was not successful but it was a valiant first try. He also made lenses and constructed his own telescopes, here he appears to have been a competent technician and an able theoretician but not reaching the level of Newton, who constructed his own reflecting telescope – the first practical example of its type which was not exceeded for some 30 years or so.

This is a detailed biography of Huygens, drawing heavily on his personal correspondence and covering his scientific achievements in some depth, in the manner of Abraham Pais biography of Einstein. Although the book is pretty readable, the style is odd in places – Huygens is referred to frequently as “”Titan” without any real explanation as to why – it may be that in the original Dutch version, entitled “Titan kan niet slapen” (“Titan can not sleep”) this is a bit more obvious. The author also throws in the odd “Iris” when referring obliquely to sex (at least I think that’s what he’s doing!). Occasionally bits of information are scattered through the text, so we learn when Huygens is born and only 10 pages later do we learn where. There is no strong distinction of when Huygens started working on a publication and when it was actually published.

Perhaps more seriously Andriesse makes an attempt at Freudian analysis of some of Huygens illness, I’m no expert in this but I suspect this approach would be considered out-dated these days. It is also here that the translation perhaps wobbles a bit, with Huygens described as having “symptoms of the hypochondriac” which I think may be a mistranslation of melancholia hypochondriaca which I believe refers more generally to mental illness than the specific modern “hypochondria”.

This said, Andriesse’s biography of Huygens is well worth reading. Christiaan Huygens himself is an interesting subject who made important scientific discoveries across a range of areas.


My Evernotes for the book are here.

Book review: Ingenious Pursuits by Lisa Jardine

IngeniousPursuits““Ingenious Pursuits” by Lisa Jardine is the second book I have recently recovered from my shelves, first read long ago – the first being “The Lunar Men”. The book covers the late 17th and early 18th century, and is centred around members of the Royal Society in London but branching out from this group. It is divided thematically, with segues between each chapter.

My edition is illustrated with Joseph Wright of Derby’s “An experiment on a bird in the air pump”, painted in 1768. As a developing historical pedant this mismatch in dates has been irritating me!

The book opens with a chapter on Isaac Newton, the first Astronomer Royal John Flamsteed, Edmond Halley and the comet which would eventually take Halley’s name. It’s also an early example of an argument over “open data”, Flamsteed was exceedingly reluctant to give “his” data on the motions of planets to Newton to use in his calculations. Halley is pivotal in this, not so much through the scientific work he did, but through his work as a conduit between the prickly Newton and Flamsteed.

Robert Hooke features strongly in the second chapter alongside Robert Boyle; Hooke had originally been the wealthy Boyle’s pet experimenter – in particular he was operator for the “air pump”, a temperamental device for evacuating a glass vessel. The early Royal Society recognising his skills, persuaded Boyle to allow them to take him on as Curator of Experiments for the Society. Hooke was also involved with Christopher Wren in surveying London after The Great Fire, and designing many of the new buildings. In fact they also designed buildings with one eye to fitting experiments into them, particularly ones requiring a long uninterrupted drop. One sometimes gets the impression of a highly industrious Hooke implementing the vague imaginings of a series of aristocratic Society members. The constant battles with temperamental equipment will ring a bell with many a modern scientist. Robert Hooke is a central character throughout the book, Lisa Jardine has written a biography of him.

Hooke was also responsible for Micrographia a beautiful volume of images observed principally through a microscope, of insects and plants. Antonie Van Leeuwenhoek, a Dutch civil servant and microscopist also supplied his microscopic observations to the Royal Society. It’s interesting that both Leeuwenhoek and later Jan Swammerdam, both based in the Netherlands, were very keen to communicate their results to the Royal Society in London. Interactions with the academiciens in Paris were more formal with another Dutchman, Christian Huygens, a central figure in the French group. Scientific discovery was already a highly international operation.

This was a period in which serious large scale surveying was first undertaken, the French started their great national survey under Cassini. The British, under the direction of Sir Jonas Moore, set up the Royal Observatory at Greenwich, where Flamsteed was employed. Timekeeping was a part of this surveying operation. Finding the latitude, how far you are between equator and pole, is relatively straightforward; finding your longitude – where you are East-West direction is far more difficult. One strategy is to use time: the earth turns at a fixed rate and as it does the sun appears to move through the sky. You can use this behaviour to fix a local noon time: the time at which the sun reaches the highest point in the sky. If, when you measure your local noon, you can also determine what time it is at some reference point Greenwich, for example, then you can find your longitude from the difference between the two times.

To establish the time at your reference point you can either use the heavens as a clock, one method is the timing of the eclipses of the inner moon of Jupiter (Io with a period of 1.8 days), or you can use a mechanical clock. In fact it’s from observations of these eclipses that the first experimental indications of a finite speed of light were identified by Ole Rømer. In the late 17th century the mechanical clock route was starting to become plausible: the requirement is to construct a timepiece which keeps accurate time over long sea journeys, at the equator (the worst case) a degree of longitude is 60 nautical miles and is equivalent to 4 minutes in time. Christian Huygens and Robert Hooke were both producing advances in horology, and would be in (acrimonious) dispute over the invention of the spring driven clock for some time. Huygens’ introduction of the pendulum clock in 1656 produced a huge improvement in accuracy, from around 15 minutes in a day to 15 seconds following further refinement of the original mechanism.

Ultimately the mechanical clock method would win out but only in the second half of the 18th century.This astronomical navigation work was immensely important to nations such as Britain, French and the Netherlands who would even collaborate over measurements in periods when they were pretty much at war. Astronomy wasn’t funded for “wow” it was funded for “where”.

Also during this period there was a growing enthusiasm for collecting things. At the Cape of Good Hope in South Africa, Hendrik Adriaan Van Reede was to start adding more native plants to the local botanic garden on behalf of the Dutch East India Company. The Dutch built their commercial horticulture tradition in this period. In France, botany was only second to astronomy in the money it received from the Academie des Sciences. Again, plants were not collected for fun but for trade. In England Sir Hans Sloane was to start collecting; bringing chocolate back from the West Indies, which he marketed as milk chocolate, popular alongside another exotic botanical product: coffee. He was also to bring back the embalmed body of his employer for the trip, the Duke of Albemarle. Sloane was to continue collecting throughout his life, absorbing the collections of others by purchase or bequest – his collection was to go on to form the foundation of the British Museum collection. In Oxford Elias Ashmole, of Ashmolean Museum fame, was to acquire the collection of the planthunter John Tradescant under rather murky circumstances. The collectors of the time were somewhat indiscriminate and not particularly skilled at organising their rather personally driven collections. In their defence though there was no good taxonomy at the time so raw collecting was a start.

The final thematic chapter is largely about medicine, at the time medicine was in a pretty woeful state. Over the preceding years advances had been made in describing the structure of the human body and William Harvey had identified a function: the circulation of blood. However fixing it when it went wrong was not a strength at that time: surgeons “cutting for the stone” were becoming quite agile but there were few reliable drugs and a wide range of positively unhelpful practices.

The book finishes with an epilogue drawing parallels between the discovery of the structure of DNA, and the intense personal story around it, with the interactions between the people discussed previously at the heart of this book. There is also a “Cast of Characters” which provides a handy overview of the book (should I forget its contents again). Compared to The Lunar Men it is an easier read perhaps because it is more discursive around themes rather than providing great detail.


My Evernotes on this book are here

L’Académie des Sciences


I’ve written a number of times on the Royal Society, Britain’s leading and oldest learned society, often via the medium of book reviews but also through a bit of data wrangling. This post concerns the Académie des Sciences, the French equivalent of the Royal Society. It has gone through several evolutions, and is has been one of five academies inside the Institut de France since its founding in 1795. As a physical scientist the names of many members of the Académie are familiar to me; names such as Coulomb, Lagrange, Laplace, Lavoisier, Fourier, Fresnel, Poisson, Biot, Cassini, Carnot …

The reason I’m interested in scientific societies is that, as a practitioner, I know they are part of the way science works – they are the conduit by which scientists* interact within a country and how they interact between countries. They are a guide to who’s hot and who’s not in science at a particular moment in time, with provisos for the politics of the time. As I have remarked before much of the “history” taught to scientists comes in the form of Decorative Anecdotes of Famous Scientists, this is my attempt to go beyond that narrow view.

The Académie des Sciences was founded in France in 1666 only a few years after the Royal Society which formally started in 1660. It appears to have grown from the group of correspondents and visitors to Marin Mersenne. In contrast to the Royal Society it was set up as a branch of government, directed by Jean-Baptiste Colbert who had proposed the idea to Louis XIV. The early Academy ran without any statutes until 1699 when it gained the Royal label. The Academy was based on two broad divisions of what were then described as mathematical sciences (astronomy, mathematics and physics) and “physical” sciences (anatomy, botany, zoology and chemistry) within these divisions were elected a number of academicians, and others of different grades. Numbers were strictly limited: in 1699 there were 70 members and even now there are only 236. Unlike the Royal Society, funded by member subscriptions, the Academy was funded by government – giving a number of generous pensions to senior academicians to conduct their scientific work.

The Academy avoided discussion of politics and religion, echoing the founding principles of the Royal Society, and was explicit in making links to foreign academics giving them the formal status of correspondent. This political neutrality was sustained through the French Revolution: although the Academy was dissolved for a few years at the height of the Terror and was subsequently reformed with essentially the same membership as before the revolution. Furthermore work on revising the French system of weights and measures carried on through the Revolution.

The Scholarly Societies Project has an overview of publications by- and about the Academy. The earliest scientific papers of the Academy appear in “Journal des Sçavans”, which commenced publication in 1665, shortly before the “Philosophical Transactions of the Royal Society” and therefore the earliest scientific journal published in Europe. From 1699 a sequence of work is published in “Histoire de l’Académie royale des sciences” until 1797.  Finally “Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences” has been published since 1835. Most of which are freely available as full-text digitized editions at Gallica (the French National Library).

The British government established the Longitude Prize in 1714, by act of parliament, to award the inventor of a simple and practical method for determining the longitude at sea. Subsequently Rouillé de Meslay invested a similar prize for the Academy, which commenced in 1720. This sequence of Academy prizes was awarded yearly to answer particular questions and alternated between subjects in the physical sciences and subjects in navigation and commerce. Those in commerce and navigation revolved around shipping: with questions on anchors, masts, marine currents and so forth. These prizes were open to all, not just members of the Academy. Subsequently the Academy became a clearing house for a whole range of prizes, these are described in more detail in “Les fondations de prix à l’Académie des sciences : 1714-1880” by E. Maindron.

In summary, although similar in their principles of supporting science, scientific communication and providing scientific support to the state and commerce the Royal Society and the Académie des Sciences differ in their internal structure and relationship with the state. The Academy being more closely aligned and funded by the state, certainly in formal terms, and rather more limited in its membership.

In common with the Royal Society the membership records of the Académie are available to play with and in common with the Royal Society they are in the form of PDF files which are a real pain to convert back into nicely structured data. I could engage in a lengthy rant on the inequities of locking up nice data in a nasty read-only format but I won’t!


  • Image is “Colbert présente à Louis XIV les membres de l’Académie Royale des Sciences crée en 1667” by Testelin Henri (1616-1695)
  • *Yes, Becky, I know you don’t want me to use “scientist” in reference to people living before the term was first coined in the 19th century ;-)


MacTutor History of Mathematics Archive is the best English language resource I’ve found on the Académie des Sciences. Winners of the Grand Prix can also be found on this site.

Book review: Isambard Kingdom Brunel by L.T.C. Rolt

800px-Carvedras_ViaductThis week I’ve been reading L.T.C. Rolt’s “Isambard Kingdom Brunel: The definitive biography of the engineer visionary, and Great Briton”. The book was written in 1957, it comes with a substantial foreword highlighting the unrivalled access that Rolt had to the Brunel family papers referring back to Samuel Smiles, an early biographer of the Victorian engineers, as an inspiration. It also contains a couple of provisos as to how current thinking differs from Rolt’s book, slightly in Rolt’s dismissal of one of Brunel’s contemporary critics and more substantially in his accusation that his business partner, John Scott Russell, was largely responsible for the enormous difficulties faced in the construction of the ship SS Great Eastern.

The book is divided into three parts: the first covering Brunel’s early life, marriage and training. The second his role in the Great Western Railway and the third in his ship building activities.

Isambard Kingdom Brunel lived 1806-59; he had a French father, Marc Brunel who had fled France following the Revolution and an English mother, Sophia Kingdom. Marc Brunel was a significant engineer in his own right, responsible for one of the earliest production lines (for sailing “block” manufacture). Before the age of sixteen the young Isambard was apprenticed to Henry Maundslay (in London) an engineer and Abraham-Louis Breguet (in Paris) a maker of chronometers, watches and scientific instruments – both men exceedingly highly regarded in their field.

Isambard’s first engineering job was as the onsite engineer for the Thames Tunnel which his father had designed, at the time Isambard was 20. The tunnelling was enabled by his father’s invention of the tunnelling shield, tunnelling seems a generous description of the process – really it was “building a brick tube slightly beneath (and sometimes not) the floor of the Thames River”. The whole enterprise was highly dangerous, with the Thames breaking through into the tunnel several times – killing a number of the tunnellers. The tunnel was not finished during Isambard’s tenure.

Following this experience Brunel started to put forward plans for engineering jobs around the country; one of his first designs was for the Clifton Suspension Bridge in 1831, at the time this came to nothing in part because of the Bristol Riots which had come about when the House of Lords voted down the Great Reform Act. Meanwhile he was also commissioned to act as engineer for what he called the “Great Western Railway”, linking London to Bristol – having surveyed an initial route. His plan was accepted and much of his initial work was in pushing an act through parliament to enable the building. It’s striking just how mobile Brunel was in his days of supervising the building of the Great Western Railway, in a time before railways and other rapid means of transport he was criss-crossing the 120 miles of the route at a staggering rate. He seems to have this in common with William Smith – maker of the first geological map of Great Britain.

The Great Western Railway ultimately extended into Devon and Cornwall, where Brunel constructed a series of timber viaducts. None of these remain in their original form, they were built at a time when cheap, very durable timber was available from the Baltic, subsequently supplies of timber were not so cheap, or durable and such structures became uneconomic and were replaced with brick or masonry. Also in the West Country Brunel constructed an “atmospheric railway” between Exeter and Newton Abbott. The engineering high points of the Great Western Railway were the Royal Albert Bridge at Saltash, and the Box Tunnel – outside Bath.

The final third of the book covers Brunel’s shipbuilding activities, the SS Great Western – the first purpose built trans-Atlantic steam ship, the SS Great Britain an early iron-hulled and propeller-driven trans-Atlantic passenger ship and finally the SS Great Eastern. The Great Eastern was accurately described as a leviathan – eventually completed in 1858, it was not surpassed in size or weight for 40 years. Its construction: delayed, over-budget, subject to protracted legal and commercial wrangling, accident prone, appears to have contributed to Brunel’s early death. Originally the ship was intended for the England-Australia route, its enormous size meant it should have been able to make the journey without re-fuelling with coal. Ultimately it was most successfully used as a cable-laying ship – laying the first trans-Atlantic telegraph cable, its large size meant it could carry a lot of cable and the combination of paddle and propeller drive meant it was exceedingly manoeuvrable.

One activity I was unaware of was Brunel’s part in designing, building and shipping a temporary hospital to the Crimea, at Renkioi, this task was completed in just five months from start to end.

A couple of things strike me about Brunel: firstly, the work he was doing was at the cutting edge of technology – when he planned the Great Western Railway the first passenger railway in the world had only just been built, the SS Great Britain was amongst the first propeller and iron-hulled ships, similarly the atmospheric railway – yet these were enterprises on a large scale. Secondly, the engineer was much more in the board room and in parliament arguing for enabling acts than is the case now. As a result of a fractious episode of “In our time” I flippantly suggested that Brunel built steam engines for fun, but reading this book – I don’t think he did, there’s little sense of joy, only driving ambition. I am still enormously in awe of Brunel. I am a sort of scientist who sees no great division between science and engineering, men like Brunel had a scientific approach to their work but also left a lasting, tangible mark on Britain not only in the things they physically built but the ideas and methods they introduced. I’ve attended a conference dinner on the SS Great Britain, where we toasted IKB rather than the queen.

As a memorial to Isambard Kingdom Brunel the Institute of Civil Engineers determined to complete the Clifton Suspension Bridge, shortly after his death. I think he would have liked it, both as a memorial and a thing of engineering beauty.

Further Reading: Analysing the paint on the Saltash Bridge (here and here) by Patrick Baty.

Nevil Maskelyne and Maiden-pap


SchehallionOSThis post is about Nevil Maskelyne and his 1775 measurements of the Scottish mountain, Schiehallion (know locally at the time as Maiden-pap), made in order to determine the mass of the earth. My interest in this was stimulated by the Gotthard Base Tunnel breakthrough, since the precision of drilling seemed pretty impressive (8cm horizontal, 1cm vertical see here). There’s a technical explanation of the surveying here. You may wonder how these two things are related.

It’s all about gravity: gravity is the force exerted by one object on another by virtue of their masses. The force is proportional to the masses of the two objects multiplied together divided by the distance between the centres of the two objects squared. This is Isaac Newton’s great insight, although he only applied it to the orbits of celestial bodies. The mass of an object depends on both its density and its volume.

Maskelyne measured the mass of Schiehallion by looking at the deviation of a plumb line from vertical. The problem for the Gotthard Tunnel is that, if you’re surveying underground, measuring the vertical could be hard because if the density of the rocks around you is different in different directions then a plumb-line will deviate from vertical. Actually it’s probably not a huge problem for the Gotthard Base Tunnel, the deviations Maskelyne measured were equivalent to about 1cm over the 14km length of the Gotthard Base Tunnel sections. Furthermore Maskelyne was looking at an isolated mountain: density of about 2500kgm-3 surrounded by air: density about 1kgm-3, under the Alps the variations in density will be far smaller. So we can relax – density variations probably won’t be an important effect. Although it’s interesting to note that the refraction of light by air is significant in the Gotthard Tunnel survey.

Oddly, Newton didn’t consider Maskelyne’s measurements possible, thinking that the force of gravity was insignificant for objects more mundane than worlds. However he demonstrated that for a largish mountain (3 miles high and 6 miles wide) there would be a deviation of the plumb line from vertical of “2 arc minutes”. Angles are measured in degrees (symbol:o) – there are 360o in a circle. Conventionally, if we wish to refer to fractions of a degree we talk about “minutes of arc”, there are 60 minutes in a degree; or even “seconds of arc” – there are 60 seconds of arc in 1 minute of arc. 1 second of arc is therefore 1/1,129,600th of a circle. At the time of Newton’s writing (1687) this deviation of 2 minutes of arc would have been measurable.

Why is measuring the mass of a mountain a job for the Astronomer Royal, as Nevil Maskelyne was at the time? Measuring how much a plumb line is deflected from the vertical is not simple because normally when we want to find vertical we use a plumb line (crudely a string with a weight at the end). The route out of this problem is to use the stars as a background against which to measure vertical. Maskelyne’s scheme was as follows:

  1. Find a mountain which stands isolated from it’s neighbours, with a ridge line which runs East-West and is relatively narrow in the North-South direction. This layout makes experiments and their analysis as simple as possible.
  2. Measure the deviation of a plumb line against a starry background at two points: one to the north of the ridgeline and one to the south (the plumb line will deviate in opposite directions at these two locations).
  3. Carefully survey the whole area, including the location of the the two points where you measured the plumb line and the size and shape of the mountain.
  4. Calculate the mass of the mountain from the survey of its size and shape (which gives you it’s volume) and the density of the rocks you find on the surface.
  5. From the mass of the mountain and the deviation of the plumb line you can work out the density, and therefore mass, of the earth

Measuring the location of stars to the required accuracy is a tricky business since they appear to move as the earth turns and the precision of the required measurement is pretty high. I worked out that using the 3m zenith sector (aka “telescope designed to point straight up”) the difference in pointing direction is about 0.1mm for the two stations – this was measured using a micrometer – essentially a a fine-threaded screw where main turns of the thread only add up to a small amount of progress. The ground survey doesn’t have such stringent requirements, although rather more time was spent on this survey than the stellar measurements.

Reading the 1775 paper that Maskelyne wrote is illuminating: at one point he lists the various gentleman who have visited him at his work! The work was paid for by George III who had provided money to the Royal Society for Maskelyne to measure the “transit of Venus”, some cash was left over from this exercise and the king approved it’s use for weighing the earth.

The value for the density of the earth that Maskelyne measured 235 years ago is about 20% less than the currently accepted value – not bad at all!


  1. The wikipedia article is good, including history and physics of the measurements (equations for those that want): http://en.wikipedia.org/wiki/Schiehallion_experiment
  2. This presentation to the Royal Philosophical Society in Glasgow in 1990 has a lot of historical background: http://www.sillittopages.co.uk/schie/schie90.html
  3. Maskelyne’s initial paper “An account of observations made on the mountain Schehallien for finding its attraction” Phil. Trans., 1775, 65, 500-542 is surprisingly readable, and provides details of the experimental measurements. The final analysis of the data was published later.
  4. Map of Schiehallion on Bing (OS mode): http://bit.ly/g1tufF