On longitude in BBC History Magazine

A piece that I wrote for BBC History Magazine, which appeared in 2014, has been made available by someone (Morgan High History Academy, anyone?) as a PDF online here. With some nice pictures, courtesy of the National Maritime Museum, and some good editing, courtesy of the magazine’s editors, it’s perhaps worth a look.

Longitude in Lisbon

Cross-posted from the Longitude Project Blog.

I have just returned from a visit to Lisbon, where I had been invited to speak about the Longitude Act and project at the Seminário Nacional de Historia da Matemática. An added bonus of the visit was that an exhibition marking the tercentenary of the first Longitude Act had just opened at the Museu da Marinha.

It was a small display on the first floor that succeeding in getting across many of the key points about the Act, the various contenders for rewards and the Portuguese context. There were three cases of books, tables and charts, two of navigational instruments and a series of wall text and graphic panels.

The first panel was welcome reading, pointing out a long history, several valid areas of research and the development of two of these – the chronometer and lunar distances – as workable solutions in the second half of the 18th century. Although John Harrison was mentioned in the panel dealing with the development of timekeepers, the exhibition did not present either him or chronometers as the most significant part of the story.

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Other panels were devoted to the navigational methods used before the Act, magnetic variation, Jupiter’s satellites, lunar distances, chronometers and the Portuguese context. The last of these included the role of Jupiter’s satellites in settling longitudes on land, especially those that had been contested by Spain and Portugal.

IMG_0147Objects included an altaziumth compass (to measure magnetic variation), a telescope (linking to Jupiter’s satellites, but not a type that could have been used for this tricky observation) a box chronometer and several instruments for astronomical observation.

Included among the printed material were books on navigation, ephemerides and almanacs. Among them were an 18th-century edition of the Nautical Almanac, a French account of testing timekeepers at sea, and several Portuguese ephemerides, including those based on the observations of the observatory at Coimbra University.

Two early charts on display also made use of a Portuguese prime meridian, and theIMG_0152 19th-century almanacs clearly played on a sense of history – a reminder of Portugal’s stellar role in maritime navigation in the past – and a claim to a central position in the globe, marking the division of the two hemispheres and the old and new worlds.

I got a good sense of the importance of Portugal’s maritime past to the nation during my visit to Lisbon. The conference was held at the Escola Naval where naval history and, by extension, the histories of navigation, mathematics and astronomy, were very evident. While Greenwich and other maritime location in Britain tend to celebrate the 18th-century Navy above all, many sites in Lisbon have (mostly 20th-century) paintings, mosaics and statues to the heroic navigators of the 15th and 16th centuries.

I was fascinated to learn about the myth-making surrounding the Sagres “School of Navigation“, supposedly founded by Henry the Navigator, and also the extent to which the regime of the 20th-century dictatorship had consciously developed and celebrated this heroic maritime and imperial history – to the benefit of institutions like the Naval School, observatory, museum and planetarium.

IMG_0149

Being a guest at the naval base, and visiting the naval museum (still directed by a uniformed naval officer, who was kind enough to guide me around), was a truly memorable experience. I particularly enjoyed being entertained over lunch in the officers’ dining room with stories of the school, and having to teach and learn lunar navigation techniques.

The saying in the Portuguese Navy is that “the moon lies”, emphasising all the many things that can go wrong with instruments, observations and calculations, especially when officers are less and less used to performing them. However, the tables and sextants are still there as back up, not least because of concern about the ease with which GPS signals can be blocked or (more dangerously) tampered with.

Best of all, I was told a story of a ship’s commander, making for a large island but hampered by very poor weather and the loss of one navigation system after another. Left with just radar and dead reckoning, for a moment the moon appeared and he took his chance to take observations. Making his calculations, he couldn’t believe the result: “the moon lies”, he said to himself. But, continuing on his course, the island still didn’t appear and, eventually, he decided to go back to the lunar observation and try his luck – radar soon picked up the target destination.

It sounded like the tale of an old salty sea dog but, later that day, I met the man himself. He was in youthful middle age. The moon sometimes lies but, it turns out, sometimes, even now, she can still be pretty helpful.

 

There was no such thing as the Longitude Prize #2

I am reposting part of this post from the Longitude Project blog, as a timely reminder, because there *is* now such a thing as the Longitude Prize. It is also on Twitter and much in the media as it heads toward official launch next week. The six potential challenges for the new £10 million prize will be explored on Horizon on 22 May, in a programme that will also look back at the original longitude story. I will appear briefly as a talking head in a film on challenge prizes on The One Show tonight, failing to make the points outlined below. [Update: just heard that my contribution has been cut from the brief film – boo!]

Despite having, back stage, had some impact on how Nesta have been thinking about their prize, the media focus remains on the story of a “prize” that was won by John Harrison. Having just done a talk last night pointing out that Newton was right to say longitude was “not to be found by Clock-work alone” – and that, in fact, the timekeeping method could never have taken off without the complementary lunar-distance method working in tandem with it – I turn back to this post. There was no prize. Harrison did not win it. He did not solve the longitude problem single handed. It made sense for the Board of Longitude to back both methods.

….

There was no such thing as the Longitude Prize. From the beginning, as well as using the term “reward” not “prize”, the Longitude Act offered a range of sums depending on the accuracy achieved. Later on, with subsequent acts, the possible rewards proliferated, initially with the realisation that Harrison needed to be supported with ‘grants’ of money while developing his clocks and, by the 1770s, with knowledge that a handful of sea watches was not a complete solution and that benefit would be gained by offering further rewards for improvements to techniques and hardware.

Derek Howse’s article on the Finances of the Board of Longitude reveals what was spent by the Commissioners. Between 1714 and 1828, rewards accounted for only 33% of spending, while overheads (23%), expeditions (15%) and publications (29%) made up the rest. The total spent on rewards was £52,534, of which £22,000 went to Harrison. This sum was made up of a number of payments between 1737 and 1764 to improve and test his timekeepers, £7500 paid in 1765 (a further sum being on offer to take this up to a £20,000 reward if two more sea watches could be made, one by Harrison and one by another maker) and £8750 was awarded by an act of parliament in 1773.

It’s a matter of interpretation as to whether this process constitutes receiving the maximum reward. A number of the payments to Harrison had required additional acts (in 1762, 1754 and 1765) and, ultimately, all the money came from government as a result of the original Act of Parliament. However, the final payment did not appear in the Board’s accounts, which confirms the fact that this final move took place outside the Commissioners’ decision-making process.

More interesting to me is who received the other £30,534. Happily, Howse’s article lists all the reward recipients in an appendix. The bulk of the rewards post-date 1765, when the Board played its hand and divided out rewards between the two successful methods, timekeeping and lunar distances. While Harrison received his £7500 in October 1765, in May:

  • Leonhard Euler was paid £300 “for Theorums furnished by him to assist Professor Mayer in the Construction of Lunar tables”
  • Maria Mayer was paid £3000 as a posthumous reward to her husband Tobias “for his having constructed a Set of Lunar Tables” and to her for making them property of the Commissioners
  • Catherine Price, Edmond Halley‘s daughter, was paid £100 for handing over several of Halley’s manuscripts, which the Commissioners believed “may lead to discoveries useful to navigation”.

While Harrison’s work was the cause of the Commissioners beginning to meet, keep minutes and spend money, there were other pre-1765 pay-outs. Christopher Irwin received £600 in 1762-3 for his marine chair (designed to allow observations of Jupiter’s satellites on board ship) and way back in 1741, William Whiston was paid £500 “For procuring a new Sett of Astronomical Instruments for finding out the Longitude on the Coasts of this Kingdom with the Variations of the Needle and for enabling him to make Observations with them”.

Harrison was certainly the biggest single beneficiary of the Longitude Acts, but balanced against that are the many involved in lunar distances. There are the rewards to Euler and Mayer, but 1765 also saw the beginning of investment in the computing work (£35,559 to 1828) and publication of the Nautical Almanac. There had already been expenditure on lunar-distance-related hardware, salaries for trials and expeditions and later sums were paid out for work on astronomical tables, for example £1537 between 1770-93 for Charles Mason‘s efforts and £1,200 to Josef de Mendoza y Rios for his longitude tables in 1814.

Post-1765 there were numerous rewards, mostly of tens or hundreds of pounds. The largest, after Harrison’s, was divvied up among the officers and crew of HMS Hecla and Griper in 1820, who received £5000 for reaching 110°W within the Article Circle, after discovery of the North West Passage became one of the Board’s interests in the 1818 Act. The Arctic voyages also led to Edward Sabine being given £1000 in 1826 for his pendulum experiments. Those who helped develop the chronometer as a commercial product, John ArnoldThomas Earnshaw and Thomas Mudge, were each rewarded with £3000.

Although there was in the 18th-century a sense of competitiveness and occasional reference to a longitude prize (of which more in a later post [since published here]), suggesting that there was a single pay-out that Harrison did or did not win misses both the richness of the history of the Board of Longitude and obscures the way that longitude solutions were developed and used.

 

Astronomers Royal, scientific advice and engineering

Cross-posted from The H Word blog, where this post first appeared on 12 September 2013.

The collapsed Tay Bridge

This evening, the Astronomer Royal, Lord Rees, will weigh into the debate about climate change and geoengineering in an address at the British Science Festival.

Finding such fixes, as well as more efficient forms of alternative energy, may well be problems focused on by the new challenge prize that Rees has helped set up. That he, as Astronomer Royal, will be judging what has been called a new ‘Longitude Prize’, seems appropriate, but the innovations under consideration may be a long way from his own field of astronomy and cosmology.

Today the post of Astronomer Royal is honorary. It means simply, as Alok Jha’s article on Rees’s speech suggests, that he is “one of Britain’s most senior scientists”. Like a Chief Scientific Advisor, or the head of a scientific society, the Astronomer Royal can be expected to give all sorts of opinions about science and science policy, straying at least occasionally, if they wish, well beyond their area of research.

Was it always like this? Yes and no. Until the 1970s the post of Astronomer Royal was synonymous with director of the Greenwich Observatory (at GreenwichHerstmonceux and then Cambridge). Before the 19th century, the AR was also an active observer, in fact only one of two observers in the institution.

Nevertheless, Astronomers Royal were often called upon to make judgements and offer advice in areas that did not relate to making observations or managing an observatory. Because the Royal Observatory was funded by government, being under the administration of first the Board of Ordnance and then the Admiralty, there was potential for them to be asked to consider a whole range of technical and scientific issues.

For much of the AR’s history, the most obvious place in which this happened was the Board of Longitude. While many of the ideas under consideration were astronomical (involving knowledge of astronomical theory, mathematics, optics and instrumentation), others were based on geomagnetism or, of course, horology. Understanding clocks and timekeeping was essential to astronomy, but the specifics of horological theory and manufacture would have been beyond the AR’s experience.

ARs also advised on areas like cartography, instrument design and weights and measures, that involved techniques closely allied to astronomy. But they were also asked to consider a wide range of fields of interest to the Admiralty and other branches of government, simply because they ended up being their available scientific expert.

One of the ARs who most obviously became the government’s go-to scientific and technical guy was George Airy, who was in position from 1835 to 1881. Airy covered a great deal of ground, intellectually and practically. Unlike all his predecessors he was not much involved with daily observations and he had a significantly larger workforce at the Observatory, onto which observation, calculation and even management could be delegated.

Airy, for example, did a considerable amount of work on the effect of iron ships’ hulls on compass use and design. He also advised, like many other ARs, on education and he was involved in the organisation of the Great Exhibition. He was, perhaps most intriguingly, called in to advise the Great Western Railway on track gauges and the engineer Thomas Bouch about the pressures that might be exerted by wind on the planned rail bridge crossing the Forth.

That latter advice got him into trouble. It was first applied by Bouch to the Tay Bridge and, when that collapsed in 1879 [see image above], Airy was called in by the enquiry. He claimed that his advice had been specific to the circumstances of the Forth and the design for that bridge (which was now speedily discarded). The enquiry agreed, suggesting that Bouch had “must have misunderstood the nature of [Airy’s] report”.

Airy did know quite a lot about engineering. He was, apart from anything else, closely involved with the design of large instruments and their mounts at Greenwich. Times and the nature and range of expertise have changed considerably since the 19th century, however. Lord Rees is not an Astronomer Royal who can offer specific or technical engineering expertise, rather he is calling for research and funding. Whether or not you agree with his statements is a different matter.

Barbados or bust: longitude on trial

Cross-posted from The H Word blog, where this post first appeared on 9 September 2013.

barbados

Barbados beach scene (perhaps not quite what Nevil Maskelyne experienced in 1763)

On 9 September 1763 a young curate and Fellow of Trinity College, Cambridge, set off for Portsmouth. He was to travel to Barbados on a voyage that would test the accuracy and practicality of three different methods of finding longitude at sea. At stake were potential rewards from the Board of Longitude.

The curate, Nevil Maskelyne, was also an astronomer and mathematician who became Astronomer Royal in 1765. I am currently editing a book of essays centred around Maskelyne, which, like the book I am co-authoring on the history of longitude, is due out next year for the tercentenary of the first Longitude Act. Working toward that anniversary, I spotted this one.

Back in 1763, Maskelyne was instructed to do two things. Firstly, he was to make longitude-determining astronomical observations during the voyage and, secondly, to make observations on land when the ship arrived in order to determine the island’s position, a prerequisite for an effective trial.

The three “methods” under trial in 1763 would be deemed successful if they succeeded in predicting Barbados’s longitude to within a degree or half a degree. They were:

1) A marine chair made by Christopher Irwin that was intended to steady an observer to allow him to measure the positions of Jupiter’s satellites at sea. (Eclipses of Jupiter’s moons were already used as a celestial timekeeper* to determine longitude on land: these were the observations Maskelyne made at Barbados.)

2) The latest version of the lunar tables of Tobias Mayer, which helped predict the position of the Moon and allow it to be used as a timekeeper using the lunar-distance method.

3) The latest mechanical marine timekeeper, and first sea watch, made by John Harrison.

Maskelyne and his assistant, Charles Green, were to make the ship-board observations and calculations necessary for the use of the first two methods. Harrison’s watch, now known as H4, would travel out separately with Harrison’s son William.

All of the methods worked in theory; the sea trial was to establish whether they worked reliably in practice. Only Irwin’s chair was a failure. Remarkably, two plausible methods of finding longitude had, finally, come to fruition at almost exactly the same time:

1757: Mayer sent his theory of the Moon’s motion to the Board of Longitude. It proved capable of making pretty good predictions – an object that had defeated Isaac Newton’s best efforts. Harrison, who had received rewards amounting to £2750 during 1737-1757, abandoned the development of his large marine clocks (H1H2H3) and thew his efforts into his watch.

1761: The potential of Mayer’s tables and the lunar-distance method was demonstrated by Maskelyne and his assistant, Robert Waddington, during a voyage to St Helena, where they had been sent by the Royal Society to observe the transit of Venus. Harrison sent his watch on trial to Jamaica and claimed an excellent result. Unfortunately, the trial was declared void because of uncertainties about the longitude of Jamaica and the watch’s rate, Harrison had to make do with another £1500.

1763: The Barbados trial was the really significant one – Mayer’s tables (via the lunar-distance method) and Harrison’s watch were both officially found to have met the necessary criteria. The Board of Longitude had two methods on their hands… potentially.

The lunar-distance method was complex and time-consuming and could only become useful if enough navigators were trained to undertake the required observations and calculations. Ideally, part of the work needed to be done for them, via the publication of regularly updated predictive and pre-calculated tables.

Harrison’s watch had worked well, but the question was whether another such machine could ever be made. Could one be made by another workshop? Could a marine timekeeper be made that was less costly than the exquisite H4?

In 1765, an Act was passed that divvied up the spoils and aimed to help make these potential methods “practicable and useful”. Harrison would receive £10,000 only if he revealed his method (i.e. the mechanism and the methods and materials involved in the construction of his watch) to other artisans. A further £10,000 would be paid out if more timekeepers could be made and successfully tried.

Tobias Mayer had died in 1762, but £3000 was paid to his widow in return for his papers. £300 went to the mathematician Leonhard Euler as a reward for his equations, which had greatly enhanced the accuracy of Mayer’s tables. A further £5000 was held out as a reward for the future improvement of the tables and, perhaps most significantly, the Board committed to the regular publishing of a Nautical Almanac, to be overseen by the brand new Astronomer Royal, Nevil Maskelyne.

The Barbados trial was not a competition or a race for a prize, although Christopher Irwin certainly found his marine chair out of the running. Rather, it confirmed two promising methods that required further investment. The Board of Longitude committed to this, seeing that they were not mutually exclusive. The lunar-distance method could be made available more quickly and was the only means of checking the performance of a ship-board timekeeper.

While Harrison’s paranoid belief that Maskelyne was prejudiced against him and his watch has become the dominant version of this story, it is not backed by the evidence. As Astronomer Royal and Commissioner of Longitude from 1765-1811, Maskelyne was to aid the development of both of the methods that his 1763 voyage had helped to prove.

* The difference in longitude of two places is equal to the difference in their local times.

Advising government: did Isaac Newton get it wrong?

Cross-posted from The H Word blog.

Just as today, governments past took advice about science. Isaac Newton gave evidence on solving the longitude problem. Was his advice as counter-productive as many have said?

Isaac Newton

There have been a lot of posts lately in the Guardian Science blogs about the role of the new chief scientific adviser, Mark Walport. While finding myself in the novel position of attempting to offer some thoughts to this incoming chief, I have also been co-writing a book about the search for longitude at sea, much of which revolves around issues of the relationships between skill, expertise, government and the public.

It turns out, of course, that advisers to government have often drawn flack, usually from those who stood to lose out financially as a result of their advice. Sometimes, though, that criticism comes as a result of hindsight. Given posterity’s tendency to condescend, that criticism is not always fair.

When the first Longitude Act was passed in 1714, the Walport equivalent was Isaac Newton. Although most often thought of as a solitary genius with apples falling on his head in Lincolnshire or writing an incomprehensible but revolutionary book in Cambridge, Newton was also to be an MP, Master of the Mint, President of the Royal Society and adviser to government.

When parliament considered a petition that asked for rewards to be offered to those who could help solve the problem of finding longitude at sea, Newton’s evidence was very clearly incorporated into the Act as written. As, thereafter, an ex officio Commissioner of Longitude, Newton also became one of those who judged submitted ideas and advised on whether they might be worth supporting.

It has become common to blame Newton for deflecting the commissioners and British government from what has been judged as the “correct” path to a successful outcome. It has been suggested that Newton was naturally biased to favour astronomical solutions and had little time for or interest in clocks as the way forward.

It seems clear that Newton did think that astronomical methods would – at some point – provide a successful solution. He believed that his evidence about their potential accuracy was reflected in the several levels of reward offered in the 1714 Act. In addition, the fact that the Act indicates that a reward might be payable after a single successful trial may show an assumption that the answer would lie in something universally applicable, like astronomy, rather than a machine.

Usually seen as most damning is the fact that Newton stated several times that longitude was not to be found by clockwork. He also suggested that clocks put forward for reward should be examined and trialled by others before the commissioners need meet to consider them.

Such facts have led some to declare that “even Newton could get it wrong”. Such a view has been put forward in histories of longitude and, unsurprisingly, by those writing the biography of John Harrison, whose disputes with the commissioners and well-rewarded sea clocks are well known. However, it has also been stated in Richard S Westfall’s biography of Newton that (p. 837)

His deprecation of clocks may have helped later to delay the acceptance of Harrison’s chronometers [sic], which did in fact offer a practical determination of longitude at sea.

Leaving aside the fact that Harrison’s unique watch left the British public a long way from possessing a practical solution, is it fair to say that Newton was prejudiced against clocks and retarded the putting of government funds into this method? Nope. Not really.

Firstly, Newton was dead right that longitude “is not to be found by Clockwork alone”, so long as astronomical methods were the only way of checking that an on-board clock was behaving itself.* As he said, a clock might be able to keep track of longitude but, should the clock stop or become erratic, only astronomy could help find longitude again. This essentially remained true until wireless radio signals could be used to compare a ship’s local time (determined astronomically) with a broadcast reference time.

Newton was also not so prejudiced against clocks that he did not wish to be bothered by applications from their makers, or at least no more than he was by any other such applications. In the case of astronomical methods, too, he advised that they be examined by other experts before being presented to the commissioners.

We also know that, several years earlier, Newton had been interested in Henry Sully‘s ideas for making a longitude timekeeper – something he went on to do in the 1720s – and had encouraged him, even passing on information about another horological novelty that he had come across.

Newton certainly could be wrong – I am sure that everyone can think of a few examples – but not really about this.

The difference in longitude between two places is equivalent to the difference in local time.