Anglo–Dutch Exchange and the New Science: A Chapter of Accidents

When William III of Orange regained his place as Stadholder of the United Provinces in 1672, Sir Constantijn Huygens’s eldest son, Constantijn junior, was installed in his father’s place as the Prince’s trusted personal secretary.

In 1676, while campaigning with William of Orange in military operations against the French on the Dutch–French border, Constantijn Huygens junior wrote home to his wife to get her to order one of his brother Christiaan’s new balance-spring watches at The Hague, and to have it sent to him in the field:

Wednesday. 17 [June 1676]. I presented Monsieur the Prince with a letter to the Court in favour of my brother [Christiaan], but he set it aside together with other things that he was delaying signing. I wrote to my father telling him this, and to my wife concerning my watch.1

His new timepiece reached him a month later:

Saturday. 18 [July 1676]. This evening we began trench engagement. Major de Beaumont, called Merode, and the Surgeon of Rhinegrave were killed there. His Excellency’s attack was undertaken by the regiment of guards; the Duke of Osnaburg’s was undertaken by the regiments of Offelen, Beaumont and Hofwegen. It is openly said that His Excellency ought to rejoin the other army. My watch, that I had had made at The Hague, arrived.2

Already this adds a curious edge to a familiar period of early-modern scientific discovery: at the same time Constantijn was corresponding with Christiaan and other members of his family about the new ‘monstre’, he was procuring safe-conducts for Christiaan and Lodewijk to travel from France (where Christiaan’s presence was increasingly an embarrassment as tensions rose between France and the United Provinces), through Spanish- governed territory, to The Hague. While England, France and the United Provinces were on a war footing with one another on-and-off throughout the second half of the seventeenth century, national boundaries in no way inhibited, apparently, the free traffic and exchange of innovative science and technology.

The picture I am painting in this book as a whole, of an ongoing to- and-fro exchange of ideas, influence and taste between the United Provinces and England throughout the seventeenth century, provides a particularly clear context for the history of science. There is a large literature on Dutch and English scientific innovation in the seventeenth century, and some work on the affinities between the two sets of practitioners.3 The contributions of outstanding Dutch scientists like the microscopists Anton van Leeuwenhoek of Delft and Jan Swammerdam, and all-round ‘virtuosi’, or scientific amateurs, like Sir Constantijn Huygens’s son Christiaan, were reported regularly to the Royal Society in London. The entrepreneurial Henry Oldenburg’s journal, Philosophical Transactions of the Royal Society, was available on the Continent almost as soon as it left the London presses – individuals often requested sections of an issue they were particularly interested in, which could be sent even more easily by post.

Nor ought we to forget the tourists. In the summer of 1668, Thomas Browne’s son Edward went to the United Provinces on an extended sightseeing tour. He made a point of visiting distinguished Dutch medical men, as part of his preparation for his intended future career as a physician. In Amsterdam, he records in his diary, he saw at first hand the work of the anatomist and microscopist Frederik Ruysch, internationally famous for his invention of a method for injecting the fine vessels in cadavers with tinted wax for display purposes:

Dr Reus [Ruysch] showed us many curiosities in anatomy, as the skeleton of young children; foetuses of all ages so neatly set together and as white as your frogs’ bones which my brother Thomas prepared; the lymphatic vessels so preserved as to have the valves seen in them; the liver so excarnated as to show the minute vessels, all shining and clear; the muscles of the children dissected and kept from corruption.4

Browne also met the famous Dutch microscopist and anatomist Jan Swammerdam:

Dr Swammerdam showed us many of his experiments which he has in his book De Respiratione; he includes a bladder in a glass, the bladder represents the lungs, the glass the thorax; draw out the air out of the glass and afterward the bladder will receive no air by the greatest force whatsoever. It is hard to relate all his experiments with syringes and double vessels without figures and a long discourse. Besides these he showed us a very fair collection of insects, a stagfly of a very strange bigness, an Indian forty-foot [snake], the fly called ephemeron and many other curiosities.5

Yet Dutch and English scientists have largely been treated by historians as though they operated in separate spheres, their work intersecting or overlapping only when correspondence between parties on either side of the Narrow Sea brought information to each other’s attention. What I shall show in this chapter and the next, in two extended examples, both involving a particular scientific favourite of mine, Robert Hooke (for which I make only a mild apology), is how very much more interestingly and closely involved these activities were.

On 23 January 1675, Sir Constantijn Huygens’s second son, Christiaan, who had for almost ten years been the leading scientist at the Royal Society’s French counterpart, the Académie royale des sciences in Paris, drew in his notebook a sketch of a coiled hair-spring with one end attached to the centre of the balance of a pocket watch, and wrote underneath it, ‘eureka’. The exclamation signified his triumph at having devised a method of harnessing the isochronous properties of an oscillating balance attached to a coiled spring, to allow it to be used to regulate the mechanism of a compact timekeeper, just as a swinging pendulum could regulate a clock.6

A week later Huygens sent a letter to Henry Oldenburg, secretary of the Royal Society in London, officially lodging with the Society an anagram cryptically containing the secret of his spring-driven balance. On 20 February, having heard that his French clockmaker Isaac Thuret had gone to the authorities claiming the clock he had made to Huygens’s technical specifications was his own, Huygens went public with his timekeeping breakthrough. He rapidly secured a French privilège, or patent, and published an account of it, with diagrams, in the next issue of the journal of the Académie royale des sciences.

On 20 February Huygens also wrote to Oldenburg disclosing the solution to the cipher: ‘The arbor of the moving ring [the balance wheel] is fixed at the centre of an iron spiral.’ He proceeded to enlarge on this with a verbal description:

The fact is, this invention consists of a spring coiled into a spiral, attached at the end of its middle [i.e. the interior end of the coil] to the arbor of a poised, circular balance which turns on its pivots; and at its other end to a piece that is fast to the watch-plate. Which spring, when the Ballance- wheel is once set a going, alternately shuts and opens its spires, and with the small help it hath from the watch-wheels, keeps up the motion of the Ballance-wheel, so as that, though it turn more or less, the times of its reciprocations are always equal to one another.7

London’s leading expert in timekeeper development, the Curator of Experiments at the Royal Society, Robert Hooke, learned of Huygens’s claim to be the first to invent a spring-regulated clock while dining with Robert Boyle (son of the Earl of Cork, and a distinguished scientist who had once employed Hooke as his laboratory assistant) on 25 February 1675 (old style). The following day Hooke lodged a formal complaint at a meeting of the Royal Society. He reminded the members that he had himself produced spring-regulated clocks at their meetings on several occasions in the 1660s, and declared that Huygens’s version was ‘not worth a farthing’. The affair rumbled on for several years. In the end, Huygens’s priority claim was by and large accepted, even in England. Although, in spite of Oldenburg’s best efforts, he was never granted an English patent for his balance-spring watch, he was issued with patents or licences in France and the northern Netherlands, and is today generally credited with this significant innovation in horology.

But was this really how it was? Instead of rushing to look for a ‘winner’ in the ‘race’ to find a precise longitude timekeeper (a clock accurate enough over long periods to allow calculation of a vessel’s east–west position on the open sea), perhaps we should take our cue from the draft notes for a lecture by Hooke delivered around 1676, responding to Huygens’s ‘eureka moment’, and preserved in the treasure-trove of Sloane scientific papers in the British Library. In it he queries Huygens’s claim to single- handed solution of the problem:

He should also have Remembred that Golden Rule to doe to others as he would have others doe to him & not to have vaine gloriously & most Disingenuously Indeavourd to Deprive others of their Inventions that he might magnify himself and with the Jack Daw pride himself in the plumes of others.8

In the spirit of which, and in the light of the fact that my story so far has shown that there was a free flow of ideas and culture to and fro between London and The Hague throughout the period in question, I propose to take another look at the evidence, to try to decide whether Hooke might have been right. Did that Anglo–Dutch exchange of ideas effectively amount to an international collaboration, and ought the two men in fact have been given the credit for a groundbreaking horological invention, the balance-spring regulator for a pocket watch? The story begins in the Netherlands in the 1650s, almost twenty years before Huygens’s eureka moment.

Almost a decade after the execution of Charles I, and at the height of the English Commonwealth, the Scottish courtier Sir Robert Moray and his old friend Alexander Bruce (later 2nd Earl of Kincardine) were both living in exile in the Low Countries.9 Bruce was attached to the itinerant court of Charles II, while Moray had settled in Maastricht, where he was part of a substantial English garrison assisting the Dutch Orangists to protect the southern Protestant Dutch border.10 The two were staunch Royalists whose families had been closely involved in the fortunes of the Stuarts. Now, cut off from familiar social circles, and with no likelihood (or so it seemed) that they would ever be able to return to Britain, both were occupying their spare time in recreational scientific activities – Moray had a chemistry laboratory complete with a number of stills, and both men were interested in pharmaceuticals and medical remedies.11

They were also interested in precision timekeepers. In April 1658, Moray wrote to Bruce (who was at this point in Bremen, where his family had salt and coal business interests):

I haue a second=watch can measure pulses, but no art can make a watch measure 2 minutes equally, unless yong Zulicom [Christiaan Huygens] at The Hague have found it out, who they say makes clocks that fail not a minute in 6 moneths. But this you will beleave as litle as I do, for I can demonstrate that it must go wrong to keep foot with the sun.12

A week later, Moray was able to tell Bruce (who had moved on to Hamburg) that he had now seen and handled one of the new pendulum clocks:

I have yet to tell you that I have this day seen an exceeding pretty invention of a new way of watch, which indeed I take to be the very exactest that ever was thought upon. The Rhyngrave shew it me. It is long since I heard of it, but did not expect what now I see. The inventor undertakes it shall not vary one minute in 6 moneths, and verily I think he is not much too bold. He is a young gentleman of 22, second son to Zulicon [Sir Constantijn Huygens], the Prince of Orange’s secretary, a rare mathematician, excellent in all the parts of it. I need not describe it to you till we meet, and then I believe I may get you a sight of it.13

Moray’s brief examination of the clock had whetted his horological appetite. The local Commander had shown it to him because it had a defect, and Moray could see what that was:

I find the greatest matter I have at hand to do it with, is that clock I told you of in my last. It is one of the prettiest tricks you ever saw. It stayed no longer here than just to let me see it, as if God had sent it hither of purpose. It was a good part of the time in my hands. It hath a defect and the Rhyngrave sent it to me to considder of, for all that buy them oblige themselves not to put them into workemen’s hands. I needed not look upon it long to know all was in it. I needed no more for that than the very first glance I had of it. The rest is but matter of adjusting of numbers for the wheels and pinions.

However, he had thought it best to advise that the clock be returned to its maker, Solomon Coster. But if Bruce were prepared to put up the money, he went on, the two of them together could easily construct an improved version of Huygens’s clock:

If I thought you had a mind to bestow 40 dollars or some less on one of them I would think to have it ready for you against you come. Never any other design made wanrests14 go so equally … If I make any, I will make it beat another time than this doeth, for it beats at the rate of 80 strokes of the wanrest or thereby to a minute, and I will make it beat just 60 which will be the seconds, and will put an index to shew them. But there is no end of tricks of this kind. When you come to the shop you may perhaps find there will and weal.15

Moray had clearly not at this point met Christiaan Huygens in person, but he was aware of his reputation. Since Christiaan’s father, the diplomat and lifelong servant of the Princes of Orange Sir Constantijn Huygens, boasted about his son – his ‘Archimedes’, as he called him in letters to the eminent French thinkers Mersenne and Descartes – on every possible occasion, and Moray and he moved in the same circles, this is not surprising.16 It is likely that Bruce already knew the Huygens family too, as they were supporters of Charles II and his sister Mary Stuart, and frequenters of the social and cultural court circle of Elizabeth of Bohemia. By September that year he certainly had met Christiaan, and they had established a shared interest in maritime timekeepers. Bruce was one of the recipients of a presentation copy of Huygens’s Horologium (1658), the book in which he announced his invention of the pendulum clock.17

In any case, it is Moray who is urging Bruce to take an active interest in the new pendulum clocks, which he himself clearly understands a good deal about already. And Bruce soon had ample occasion to follow his friend’s advice.

The following year, in 1659, Alexander Bruce married Veronica van Aerssen van Sommelsdijck, daughter of Cornelis van Aerssen, Heer van Sommelsdijck, the wealthiest man, and one of the most politically prominent, in the United Provinces, and set up home in The Hague. The van Aerssens were a distinguished diplomatic family, who had served the house of Orange for three generations. They were neighbours of the Huygenses in het Plein, the smartest quarter of The Hague, close to the Mauritshuis.18 On the eve of the Restoration of Charles II, Bruce – now the Earl of Kincardine – became an extremely rich and influential man in Holland, and a family friend of one of the most celebrated horologists in Europe. He retained his Scottish rank and position also – Samuel Johnson’s friend and biographer James Boswell was a direct descendant.

From Moray’s correspondence we learn that Alexander Bruce and Christiaan Huygens began working on clocks together almost as soon as they met. In early 1660 Moray (now in Paris, probably helping negotiate the terms of the return to the English throne of Charles II), wrote responding to a description of this work by Bruce:

If all Mr Zulicom’s addition to his invention be no more but the making of a clock of the size that the pendule beats the seconds, that is every stroak takes up a second, I do not considder that of all. For I know the pendule must be about a yard long to do that, and it is believed here that all the church clock’s in The Hague are made after his way, so that they ever strike all at once, for so it hath been said here to our Queen [Henrietta Maria]. I have not seen his book, nor think it can be bought here. therefore think of sending me one. If you recommend it to Sir Alexander Hume19 and bid him send it by some of the Earl of St Albans’s servants it will come safe. If I see him here I will talk to him of his perspective glasses, and mean to make my court with him upon your account.20

So Moray and Huygens had still not met, though Moray was intent on their doing so, to discuss lenses and telescopes, and in order that he might ‘make [his] court’ on Bruce’s account.

In summer 1660, Sir Robert Moray returned to London, where he was given a senior Scottish appointment in the new government of Charles II, and became part of the close inner circle of courtiers, with lodgings within Whitehall Palace itself.21 By now Bruce has ordered a Huygens-designed clock for Moray, at his own expense, the delivery of which Moray was eagerly awaiting:

I am well pleased with Mr Zulicem’s ordering of my clock. Let it be so, and I will thank him when I see him. I have not time now to talk of that curiosity you mention,22 but where people think it needless and that those watches are best that have the pendule fast to the axeltree that hath the two pallets,23 but I am not yet of their mind, nor for that advantage he speaks of in the stoppers24 you mention. I shall onely say more of this that if the watch do not mark the inequality of the days, it goes not equally.25

Alexander Bruce and his Dutch wife, meanwhile, settled into a well-to- do international lifestyle which involved moving between the family home in The Hague, London, and Bruce’s family home (and coalmines) at Culross (Fife) in Scotland.26 In 1668, for example, Veronica’s mother, in a letter to Constantijn Huygens congratulating him on the marriage of his son Constantijn junior, tells him that she is currently staying with her daughter and son-in-law at Culross:

[Dutch] I shall be going home shortly, because the winter is coming on. I regret that I did not come here three months earlier, then I would have made a little progress with the language. [French] And I would have had the contentment of spending [more] time with the Count of Kincardine and my daughter, and this agreeable peace and civility. [Dutch] It is very beautiful and fruitful here. The Lord of Kincardine’s house lies on a high hill and the park is delightfully close by. My daughter is extremely sad that I am leaving.27

To make herself feel more at home, Veronica laid out the garden at Culross in the Dutch style, and planted it with imported Dutch tulips.

The Royal Society was established in London on 28 November 1660 by a group of scientific enthusiasts that also included John Wilkins, Robert Boyle and Christopher Wren.28 Sir Robert Moray and Alexander Bruce were founder members. The records show them to have been extremely active, usually together, in the Society’s early meetings.29 Precision timekeepers were on the agenda of these from the outset, particularly Huygens’s new pendulum clocks. The pendulum improved the accuracy of mechanical clocks dramatically: from a variance of fifteen to thirty minutes a day, to less than a minute.30 Its potential for naval and military use looked extremely promising.

Throughout the 1660s, the records of the Royal Society document a steady sequence of experiments involving pendulums and other isochronous oscillators in timekeeping.31 Moray was not the only enthusiast, but his prominent position (he chaired the meetings) meant that his encouragement of improvements to Huygens’s published designs was important.

Christiaan Huygens paid his first visit to London in April 1661, as part of the official United Provinces delegation attending Charles II’s coronation. His existing Anglo–Dutch social connections helped him to develop cordial social relations with those with similar scientific and technological interests to his own in London. Almost the first courtesy call he paid was on Bruce’s Dutch wife Veronica, to fulfil a commission from a Dutch mutual friend he had spent time with in Paris.32 The next day Bruce took Huygens to a meeting of the Royal Society at Gresham College, at which Moray was presiding, following which Dr Goddard (a prominent member) took Huygens to his Gresham rooms and showed him three handsome pendulum clocks.33

Thereafter Huygens spent much of his time in the company of Bruce and Moray, both of whom, we should remember, spoke fluent French and good Dutch and had many Dutch social connections, and other Fellows of the Royal Society.34 He did not even bother to attend the coronation of Charles II, preferring to observe a lunar eclipse with members of the Society. Bruce showed Huygens pendulum clocks of his own design, in which the Dutchman took a particular interest.35 John Evelyn tells us in his diary that he and Huygens visited the clockmaker Ahasuerus Fromanteel on 3 May, ‘to see some pendules’.36

By the time Huygens returned to The Hague in late May, a deep and lasting friendship had been established between himself and Moray, his relationship with Bruce had been consolidated, and he was also well integrated with other leading members of the Royal Society. Thereafter he took a close personal interest in advancing the cause of pendulum clocks in Britain, both scientifically and commercially. Shortly after his return to The Hague, Huygens asks Moray in a letter how the long-pendulum clock, ordered from Huygens’s clockmaker and paid for by Bruce, was performing (Moray confessed in a separate letter to Bruce a month later that he had still not had time to have it properly set up by a clockmaker);37 Huygens also helped procure clocks for Lord Brouncker, the President of the Royal Society.38 In June 1661 Henry Oldenburg paid a courtesy visit to Huygens at The Hague, on his way back to England from unspecified business in Bremen and elsewhere in the Netherlands (Oldenburg had received his university education at Utrecht). He too conducted a vigorous correspondence with Huygens following his return to London.39There was talk of Moray and Brouncker visiting The Hague later in the same year. These plans came to nothing, but the point is, there was a regular to-and-fro of like-minded individuals, with Anglo–Dutch interests going back ten or more years, and with an interest in science, between London and The Hague throughout the 1660s.

In October 1662, Bruce arrived in The Hague on one of his regular round trips to and from his home in Culross, having used the journey in both directions to test pendulum clocks modified to his own design for their suitability as longitude timekeepers.40According to Bruce, it was the success of these first trials which convinced Huygens that it was worth pursuing the possibility of adapting his new clocks to determine longitude at sea. He reminded Huygens later:

At my first arivall at the Hage, after the tryall I had made betwixt Scotland & [The Hague] of my watch, when you did me the favour to see me at my chamber, we fell upon the subject of the going of the pendule watches at sea; & you told me positively then that it was your opinione that it was impossible, that you hade been making experiments of it, and all the effects of them was, to be settled in that opinion by them: you did lykewise urge reasons of the impossibility of it.41

It is not clear whether Bruce’s marine clock had been built for him in Holland or England, by Dutch or English technicians, but it was certainly pendulum-regulated.42 He later told Huygens that this clock of his was the same one he had had in his possession in London eighteen months earlier when he and Huygens met there, and that it differed significantly from Huygens’s:

I came afterwards to see that watch by which you hade made your experiment; & I believe you will acknowledge that it was so farre different from mine in the whole way of it that it is not lyke they should ever have met. And the rather I thinke this, that I showed you at London 18 moneths before that tyme the same watch which receaved very small amendments thereafter; & if you hade thought that way able to bring it to passe, you might from that view have ordered one to be made for your tryell.43

Encouraged by their mutual interest and complementary expertise, Bruce and Huygens now began working collaboratively at The Hague, adapting pendulum clocks for sea travel. Bruce favoured clocks with short pendulums for portability; it was he who added a ‘double crutch’ to keep the pendulum swinging in a single plane, and designed the methods of support and suspension which it was hoped would protect the clocks from the most violent of motions arising from storms and high seas – Huygens had simply tried suspending them from ropes.44

It was the wealthy Bruce who paid for two state-of-the-art pendulum clocks, made by Huygens’s current preferred Dutch clockmaker, Severijn Oosterwyck, which they agreed Bruce would test on his next journey to Britain, this time to London. By December the clocks were almost ready, and the two men were spending a lot of time together. On 4/14 December 1662, Christiaan told his brother Lodewijk that he had been slow responding to a letter ‘because of several visits I have received, and principally by that of Mr Brus [Bruce], who did not leave me alone for a single moment all afternoon. And he has been doing that quite often, ever since we set about perfecting our invention for [measuring] Longitudes.’45

In other words, the earliest trials of pendulum-regulated longitude timekeepers – much discussed by historians of science – began as a robustly Anglo–Dutch venture. And once Bruce arrived in London, the correspondence with Huygens that followed demonstrates an extraordinary level of continuing Anglo–Dutch collaboration, with the English contributors now making the running.

For two weeks Huygens waited anxiously for news from London. He consulted the van Aerssens, but even they had not yet heard from their son-in-law. Eventually he received a letter from Bruce, written on 2 January 1663 (old style). He apologised for having ‘forgotten’ to write, blaming this on the fact that he had nothing very positive to tell Huygens about the performance of ‘his’ (that is, Bruce’s) clocks. The sea trials of the two pendulum timekeepers during his journey to London had not been a success. As they left the harbour, the ‘packet-boat’ which Bruce had secured for the crossing was hit by a contrary wind, ‘and the boat was so small that even though it really was not a storm, the ship was shaken more strongly than one can shake a cradle, so that the suspending shaft [vis] that went into the ball and socket [boule] broke under the vibrations of the ship, and the older [clock] fell, while the newer [clock] stopped’.46

A flurry of letters from Bruce and Sir Robert Moray to Huygens followed, detailing what had happened during the trials, and describing work the two Scots were now carrying out together in London to improve the clocks’ performance against the next trials. On 9/19 January Moray wrote to Huygens from London to tell him that he and Bruce were in discussions about ‘your clocks’, and ‘the design which would make them succeed at sea’. More modifications, then, were being undertaken, this time with the help of the English clockmaker Ahasuerus Fromanteel, whose son John had recently returned from several years’ training in The Hague, learning to manufacture the new pendulum clocks with Huygens’s original clockmaker Salomon Coster.47 The clock which had fallen during the journey was too badly damaged to be repaired, and was replaced by one entirely manufactured in London by Fromanteel.

‘I advised [Mr Bruce] to try the clocks two at a time,’ wrote Moray to Huygens, ‘and to adjust them well beforehand on land.’48 This must have irritated Huygens, who had made precisely these preparations before Bruce set sail.49 He replied immediately, assuring Moray that Bruce had already told him exactly what had happened to the clocks, and that he, Huygens, was undeterred and keen to conduct further, longer-distance trials. In a postscript he added that he was about to write to Bruce, as soon as he had finished some further modifications to ‘my clock’.50

On 16 January 1663 (old style) Bruce wrote to tell Huygens that the damaged clocks were about to arrive (they had been held up at customs): ‘I expect them to morrow and then I shall show them to Sir Robert Moray & lett yow know their [his] opinions of them.’51 Huygens remained optimistic. ‘The lack of success you have had does not bother me,’ he responded, ‘nor does it diminish my good opinion of our undertaking’.52 He told Bruce that he had begun modifying his clock design in consultation with his Dutch clockmaker Severijn Oosterwijk, and would let him know how the improved mechanisms behaved.53

At the beginning of March 1663, Moray wrote to Huygens letting him know that he and Bruce were going to conduct further trials ‘at sea, going as far as the Dunes, to try out Mr Bruce’s clocks, which he is trying to adjust to the best of his ability’.54 (Note that for Moray, ‘your clocks’ (Huygens’s) have now become ‘Mr Bruce’s clocks’, though essentially the same two timepieces are involved.) The usually conciliatory and tentative Moray continues, somewhat testily:

You are right in saying that the movement of large boats is gentler than that of small ones, but in heavy swells, particularly when the wind is head on, or when the ship is at anchor, the shocks are stronger and more violent. But what I fear most is not the agitation the ship gives to the whole body of the clock (though I am worried that that may have its effect also) but rather that the sudden movements of the ship downwards, and in the contrary direction, which in the one case will make the pendulum slow down, in the other will accelerate it, sometimes making it heavier, sometimes lighter, and either way unequally, which it seems to me is bound to cause deregulation in the mouvement of the clock’s mechanism. But it still seems worth testing this experimentally.55

This critical commentary on the whole Bruce–Huygens project suggests that Moray, usually genial and urbane, is drawing on broader Royal Society discussions which had taken place concerning the performance of the clocks. Indeed, I’m afraid this sounds awfully as if it was drafted by Hooke.56

Sure enough, we learn that Lord Brouncker (President of the Royal Society) and Robert Hooke (Curator of Experiments) had both taken part in those trials ‘at sea, going as far as the Dunes’ on ‘one of his Majesties Pleasure-Boats’.57 And according to Hooke, they ‘experimentally found [the method of suspension] useless to that effect’, though Hooke claimed he could see ways to correct the deficiencies of Bruce’s ball-and-socket suspension arrangement.58 Both Hooke and Brouncker had experience working with precision timekeepers, and both had an interest in perfecting their use to determine longitude at sea.59 Both were now collaborating with Bruce (who, we recall, had impeccable connections on both sides of the Narrow Sea, in London and The Hague) in the hope of achieving a clock-based solution to the longitude problem.60

So by early 1663, Robert Hooke has joined the team of Dutch, Scottish and English clock experts collaborating in the development of precision longitude timekeepers. As he later insisted, he had been conducting experiments with clock design for several years; now that experience is funnelled into the Bruce–Huygens project.

As far as Huygens was concerned, Hooke was a background figure in the activities of the Royal Society, an experimentalist and instrument- maker, who was inclined to make exaggerated claims about his technical competence. Both Moray and Brouncker were well-informed amateurs, with a private and a professional interest in precision timekeepers (both owned state-of-the-art clocks and watches themselves, and knew how to look after them).61 For the purposes of the longitude-timekeeper developments and trials, Hooke was their expert technician, acting as adviser and consultant at the English end of design and testing, who fed his results into Moray and Brouncker’s dealings on this topic with the Royal Society (including Bruce and Huygens). Everything Hooke told Moray was directly communicated to Huygens; all Huygens’s comments were relayed back to the Royal Society. The fact that England and Holland were at war for much of this period was apparently irrelevant.62

This two-way investigative traffic between London and The Hague provides a context for the collection of scattered papers belonging to Hooke which are now in the Wren Library at Trinity College, Cambridge. These are undated, but the first section seems to correspond to a period of ongoing discussions between Hooke, Brouncker and Moray (with some interventions by Wilkins and Boyle), preparatory to Hooke’s lodging a patent claim for a longitude clock of his own design on behalf of the Royal Society, during the period 1663–65.63 After Hooke’s death, his friend and executor Richard Waller claims to have seen the draft patent document in Moray’s hand among Hooke’s papers.64 We are now in a position to note that Moray was also the person who had drafted a competing patent on behalf of Bruce and Huygens for their longitude timekeepers, which was being negotiated at exactly the same time.

On 13 January 1664, ten months after Hooke had assisted at the trials of the Bruce–Huygens clocks and pronounced them unsatisfactory, Brouncker reported to the Royal Society that Hooke had ‘discovered’ to himself, Sir Robert Moray and Bishop John Wilkins (Hooke’s mentor, and a founder of the Society) in confidence ‘an invention which might prove very beneficial to England, and to the world’.65 The Society agreed to pay up to £10 for trials. Moray later described it as ‘an invention of his for measuring time at sea better than pendulum clocks can, and indeed as well as they do on land’, and told Huygens that Hooke had been working on it for some time. He had ‘given a proof [preuve] of it to the President, on a watch which I lent him’. However, Moray added that ‘having compared it to his own pendulum clock [the President] found that [Hooke’s] did not keep good time’.66 On 15 September Hooke wrote to his patron Robert Boyle that he hoped ‘shortly to make some observations … with an exact timekeeper, which, I have some reason to believe, shall not be much excelled by any whatever. But these are not yet completed.’

On 18 January 1665, it was announced at the Royal Society meeting that Hooke was ready to apply for a patent for his longitude timekeeper.67 At the meeting in question doubts had been expressed as to how satisfactorily the Bruce–Huygens clocks had performed during lengthy trials to Guinea and back (I will return to these trials shortly). The Society had backed the Guinea trials heavily, and staked a lot on their success; now Hooke offered them an alternative timekeeper.

Hooke’s first biographer, Richard Waller, has preserved a fragment of a memoir by Hooke himself, describing what happened next:

I shew’d a Pocket-watch, accommodated by a Spring, apply’d to the Arbor of the Ballance to regulate the motion thereof; concealing the way I had for finding the Longitude; this was so well approv’d of, that Sir Robert Moray drew me up the form of a Patent, the principal part whereof, viz. the description of the Watch, so regulated, is his own hand Writing, which I have yet by me.68

Waller goes on to confirm Hooke’s statement on the strength of original documents then in his possession, shortly after Hooke’s death:

In confirmation of what is abovesaid, I met with a Draught of an Agreement between the Lord Brouncker, Mr. Boyle, and Sir Robert Moray, with Robert Hooke Master of Arts to this purpose, that Robert Hooke should discover to them the whole of his Invention to measure the parts of Time at Sea as exactly and truly as they are at Land by the Pendulum Clocks invented by Monsieur Huygens […] as also of a Warrant to be granted by the King to Robert Hooke, M.A. &c. for a Patent for the sole use of the said Invention for fourteen Years, and sign’d by his Majesty’s Command, William Morrice.69

This last document surfaced briefly at auction some years ago, only to disappear again to a private buyer.70 It clearly confirms all the key points from Waller’s account: it describes (in Hooke’s hand, inserted into a document largely in Morrice’s) a spring-regulated longitude timekeeper, ‘different from all other watches or clockes by hauing instead of a Ballance a Spring of mettall/wood/quill/bone/glass or other fit matter so aplied to the Arbor of the Ballance that it makes it moue alwise equally’; it is signed by William Morrice in his capacity as Secretary of State, a position he held until September 1668; and it also invokes the names of Sir Geoffrey Palmer ‘Attorney Generall’ and Sir Heneage Finch ‘Solicitor Generall’ (both men left these posts before 1670). It allows us to say with reasonable confidence therefore, though sadly without the evidence before us, that Hooke had indeed come close to applying for such a patent, in direct response to the Bruce–Huygens pendulum-clock-based attempts at a longitude timekeeper, during the first half of 1665.

There is no doubt that Hooke’s idea of using springs as isochronous regulators in place of pendulums was transmitted to Huygens by both Moray and Oldenburg. On 30 September 1665, for example, the very day on which Moray told Huygens in a letter that Hooke had demonstrated a spring-regulated clock or watch to himself and Lord Brouncker two years earlier, Moray wrote to Oldenburg, in a letter, now lost, that Waller saw:

You will be the first that knows when his [Huygens’s] Watches will be ready, and I will therefore expect from you an account of them, and if he imparts to you what he does, let me know it; to that purpose you may ask him if he doth not apply a Spring to the Arbor of the Ballance, and that will give occasion to say somewhat to you; if it be that, you may tell him what Hooke has done in that matter, and what he intends more.71

Hooke’s not-so-confidential negotiations with Brouncker, Moray and Wilkins to obtain a patent on behalf of the Royal Society for Hooke’s longitude timekeeper broke down in mid-1665. The senior officers of the Society were of the opinion that because Hooke insisted on stating that a spring regulator could be applied to a timekeeper in many different ways, no patent would be granted, since to do so would be to inhibit developments other than Hooke’s based on the same principle.

At precisely the same time that they were dealing ‘in secret’ with Hooke’s proposed revolutionary designs for longitude timekeepers, Brouncker and Moray had taken it upon themselves to move the Bruce–Huygens clock trials onto a more systematic footing, with the Royal Society’s official backing. They arranged for Robert Holmes, captain of the Jersey, to carry the two pendulum clocks to and from Lisbon in 1663, and then on a longer voyage to Guinea and back in 1663–64.72

For the history of development of longitude timekeepers these trials were a turning point. By contrast with Bruce’s trials, those conducted during Holmes’s voyages, particularly on the voyage to Guinea, were spectacularly successful. The clocks ran well throughout the journey, Holmes set them regularly and kept them running, and crucially, the clocks allowed Holmes to make a calculation of his position at a key moment in the Guinea voyage which revealed the inadequacy of traditional longitude- finding methods.

On the return journey, Holmes had been obliged to sail several hundred nautical miles westwards in order to pick up a favourable wind. Having done so, the Jersey and the three ships accompanying her sailed several hundred more miles north-eastwards, at which point the four captains found that water was running worryingly low on board. Holmes’s three fellow captains produced three conflicting calculations of their current position based on traditional dead-reckoning, but all agreed that they were dangerously far from any potential source of water. Not so, declared Holmes. According to his calculations – based on the pendulum clocks – they were a mere ninety miles west of Fuego, one of the Cape Verde islands. He persuaded the party to set their course due east, and the very next day, around noon, they indeed made landfall on Fuego, exactly as predicted.73 Huygens’s clocks had saved the day.

This was exactly the kind of publicity the pendulum timekeepers needed in order to capture the public imagination. Moray’s report of this dramatic success, in a letter to Huygens dated 23 January 1665, is clear as to its impact: ‘At last Captain Holmes has returned, and the account he has given us of the experiment with the pendulum clocks leaves us in absolutely no doubt as to their success.’74

The following day Huygens replied. He was delighted to hear of Holmes’s triumph with the clocks; every line of the account gave him the greatest pleasure, and he thanked Moray for being the bearer of such good tidings.75 Holmes’s report was published verbatim in the Royal Society’s Philosophical Transactions and in French in the Journal des sçavans, and eventually featured as the unique account of a sea trial of pendulum clocks to be included in Huygens’s landmark book the Horologium Oscillatorium, published in 1673.76 Right down to the present day, the spectacular success of these trials is invoked as the crucial evidence on the basis of which Huygens’s pendulum-clock timekeepers take their place as a significant step in the progression from the theoretical aspiration to determine longitude at sea using a precision clock, to the realisation of that dream with John Harrison’s longitude timekeeper in the following century.

The success of the Holmes trials probably led directly to Moray and Brouncker abandoning attempts to agree a patent document with Hooke. By this time too, ironically, Moray had given up hope of getting Bruce and Huygens to agree a fair distribution of financial reward, and abandoned their patent bid also.77

So it might appear that there is some justice in the fact that Huygens has continued to receive most of the credit for early longitude clock trials, and developments culminating in the balance-spring-regulated pocket watch, ever since. But my own research has recently uncovered evidence to suggest that Hooke deserves more credit, and Huygens perhaps a little less.

The problem with the story I have just recounted is that Sir Robert Holmes (as he later became) was not known as a person who could be relied upon. He is, in fact, infamous as the hot-tempered, violent and uncontrollable commander of the English fleet whose impetuous exploits were responsible for starting both the second and the third Anglo–Dutch wars. He had served under Prince Rupert and James, Duke of York, and eventually rose to the rank of Admiral. In 1664, on the very voyage on which he was supposed to be testing the Bruce–Huygens clocks, he sacked the Dutch trading stations along the coast of Guinea one by one, seizing goods and property and laying waste the settlements.78 On his return he was twice imprisoned in the Tower of London (on 9 January and 14 February 1665), either for having gone beyond orders or for failing to bring back adequate amounts of booty, it is not quite clear which. His actions led directly to the Dutch declaring war on 22 February 1665, by announcing that they would retaliate against any British shipping in the Guinea region, at which point Holmes was released and pardoned, in order to command his Majesty’s forces. In August 1666 he attacked and destroyed by fire 150 East Indiamen in the Vlie estuary and sacked the town of Westerschelling on adjacent Terschelling island.

Samuel Pepys (at that time in overall charge of supplies at the Navy Board) was afraid of Holmes: ‘an idle, proud, conceited, though stout fellow’. On several occasions he expressed reluctance at having to deal with him on matters of naval discipline. After the second Dutch war Holmes was rewarded for his exploits with the Governorship of the Isle of Wight; he eventually became extremely rich and somewhat more respectable.79

It was Huygens himself who was the first to raise concern about Holmes’s report (as a Dutchman, he might be expected to have a particularly low opinion of Holmes’s integrity). On 6 February 1665, in his first response to Moray, after expressing his delight at the dramatic outcome of the trials he added a small caveat:

I have to confess that I had not expected such a spectacular result from these clocks. To give me ultimate satisfaction, I beg you to tell me what you and your colleagues at the Royal Society think of this Relation [of Holmes’s], and if the said Captain seems a sincere man whom one can absolutely trust. For it must be said that I am amazed that the clocks were sufficiently accurate to allow him by their means to find such a tiny island [as Fuego].80

On 6 March, Huygens was still pressing Moray for ‘something of the detail of what you have learned from Mr Holmes, principally in order to know how the clocks behaved in a storm, and if in that climate rust did not eventually cause them to stop’.81

The matter of Holmes’s trustworthiness was raised at the 8 March meeting of the Royal Society, at which Huygens’s concerns were raised, and his letter of 6 March read:

There being also mention made again of Major Holmes’s relation of the late performances of the pendulum watches in his voyage to Guinea, it was affirmed by several of the members, that there was an error in that relation, as to the island named therein; and that it was not the island of Fuego, which the Major’s ships had touched in order to water there, but another thirty leagues distant from it.82

Samuel Pepys (recently elected a Fellow) was ‘desired to visit the Major, and to inquire farther concerning this particular for the satisfaction of the society’. This meant visiting Holmes in the Tower, where he was imprisoned for his conduct towards the Dutch settlements at Guinea during his voyage.83 On 14 March Pepys attended ‘a farewell dinner which [Sir John Robinson, Lieutenant of the Tower] gives Major Holmes at his going out of the Tower’, ‘Here a great deal of good victuals and company.’84

On 15 March both Pepys and Moray reported on their dealings with Holmes. Pepys had spoken to the Master of ‘the Jersey ship’ – that is, Holmes’s own vessel:

The said master affirmed, that the vulgar reckoning proved as near as that of the watches, which [the clocks], added he, had varied from one another unequally, sometimes backward, sometimes forward, to 4, 6, 7, 3, 5 minutes; as also that they had been corrected by the usual account. And as to the island, at which they had watered, the said master declared, that it was not Fuego, but another thirty miles distant from the same west- ward.85

According to the Master of Holmes’s ship, then, there was not much to choose between the old way of calculating longitude, and that using the new clocks. Moray, who had spoken to Holmes himself, corrected ‘some mistakes in the number of the leagues formerly mentioned’. He confirmed that the ships had not watered on Fuego, ‘yet they had made that island at the time, which the Major had foretold, and were gone from thence to another, more convenient, for watering’.86

This was the meeting at which, immediately following Moray’s rather obviously fudged report, Hooke told the Royal Society ‘that he intended to put his [own] secret concerning the longitude into the hand of the president, to be disposed of as his lordship should think fit’. In his opinion, ‘no certainty could be had from [pendulum] watches for the longitude’.

At the very next meeting, on 22 March, ‘Mr Pepys was desired to procure the journals of those masters of ships, who had been with Major Holmes in Guinea, and differed from him in the relation concerning the pendulum watches.’87 Nothing further is heard, however, of discrepancies between the ships’ journals and his ‘relation concerning the pendulum clocks’. Had that convivial dinner a week earlier perhaps predisposed Pepys to draw a veil over the matter? Holmes’s account has been firmly lodged on the record ever since.

However, a presentation copy of Holmes’s Guinea voyage journals, which Pepys had indeed procured, as instructed by the Royal Society, survives in the Pepys Library at Magdalene College, Cambridge. This is a fair copy of the journal, prepared for James, Duke of York. I believe that I am one of the first scholars to have consulted it in the context of the Holmes trials, on that voyage, of Huygens’s longitude clocks.88

Holmes’s journal is extremely full and specific. It is also rather well written – Holmes has a nice line in racy narratives, particularly where bombarding and plundering Dutch merchant ships is concerned.89 Day by day he chronicles the progress of his band of ships, the Jersey, the Brill, the Golden Lyon and the Expedition. Only once in the course of the entire journal does he mention the pendulum clocks (in connection with the incident we have already heard about), and it is hard to see how they could have been kept going steadily throughout, given naval battles with Dutch East India- men in which (for instance) Holmes’s topmast and mainsail were shot away.

In July Holmes was on San Thome off the west coast of Africa, reprovi- sioning and rewatering. He set out for home on 11 August. For more than a month strong currents, contrary winds and becalmings bedevilled him. By the third week of September his small fleet was well and truly lost on the open seas. There is a full sequence of entries relating to Holmes and his fellow captains getting lost and running short of water, which does, uniquely in the entire journal, mention ‘pendula’. It was with great reluctance that Holmes’s companions agreed to turn westwards. It was three days before they sighted land, during which time variable winds took them in several different directions. As Pepys had learned, they did not land on Fuego, but some time later on another of the Cape Verde Islands, Brava. Holmes had, at the very least, made greatly exaggerated claims for the part the clocks had played in the incident.

But once Holmes had lodged his misleading report, with its bravura account of the spectacular accuracy of the pendulum clocks, Huygens’s claim to priority in relation to longitude timekeepers was assured. The account was prominently reprinted in 1673 in his Horologium Oscillatorium, and was followed within the year by the announcement from Paris of the balance-spring watch. Huygens’s impressive sequence of horological innovations – pendulum clock (1658), longitude pendulum timekeeper (1665) and balance-spring regulator (1674) – entitled him to precedence over others working close to him, and assured his lasting reputation as the pre-eminent figure in the field. By this time, however, both Moray and Oldenburg were of the opinion that Huygens was overstating his personal claims for priority. When the Horologium Oscillatorium appeared, strong protests were lodged by the most senior members of the Royal Society. The President, Lord Brouncker, John Wallis and Sir Christopher Wren all wrote to Huygens, reminding him – with chapter and verse – of the contributions made to his unfolding horological theory and practice by English virtuosi. They reminded him that Hooke’s circular pendulum had been demonstrated and discussed at several meetings, that Bruce’s modifications to the marine timekeepers had been crucial to their success, that Brouncker and Huygens had together debated the tautochronism of the cycloidal pendulum at length, that Wren had rectified the cycloid ahead of Huygens. All of these contributions were inadequately acknowledged in Huygens’s work, or (in the case of Hooke) not at all.90

On 27 June 1673, Oldenburg himself urged Huygens to be more generous in his acknowledgements, and urged a more collaborative approach in the interest of scientific progress: ‘If candour reigned everywhere, what friendships might we be able to establish amongst the learned, and what advantages might the public derive?’91

What is most extraordinary about the vexed (and still unresolved) issue of who was really entitled to claim priority, first for allegedly accurate pendulum clocks carried at sea, and subsequently for the spring-regulated pocket watch, is how little the Anglo–Dutch wars apparently impinged on intellectual exchange between the participant scientists and technicians. It is as if the ferocious naval battles, marauding gangs invading colonial settlements, and predatory incursions into each other’s national territories had little or no impact on the lives of those engaged in professional life in either country. How else could it have been proposed that Dutch clocks be given to an English naval commander to test while on a confrontational expedition to the west coast of Africa whose stated aim was to seize Dutch goods and assets?

Equally, the unanimous chorus of Fellows of the Royal Society chastising Christiaan Huygens in 1673 for having, in his claiming of priority for longitude clocks, been ungenerous in his ackowledgements of English (or at least Scottish) efforts in the same field surely needs to be taken with a pinch of salt: ‘what friendships might we be able to establish amongst the learned, and what advantages might the public derive?’

The Horologium Oscillatorium, in which Christiaan Huygens made his full and final claims to priority in pendulum clocks and timekeepers designed to determine longitude, was published in France and ostentatiously dedicated to the French King, Louis XIV. At the time of publication, France was at war with the United Provinces, and England was temporarily allied with the French. If Huygens’s position in Paris was tenuous, his relations with the English were doubly so. Unable to cope with the emotional pressures, in 1676 Christiaan Huygens succumbed to some sort of nervous illness, of a kind which had caused his collapse some years earlier (on that occasion he had been granted a year’s sick leave by the French authorities). This time his brother-in-law, sister Susanna’s husband Philips Doublet, was sent to Paris to cheer him up, to no avail. Instead he brought Christiaan back to The Hague in July. ‘The life that I lead there [in Paris] disagrees with me,’ Christiaan wrote to his brother Constantijn junior, who was in the field with Prince William on military manoeuvres against the French. ‘I left as if I would return. But I do not believe I shall ever go back to Paris’.

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