In Our Time - Longitude

Episode Date: May 13, 2021

Melvyn Bragg and guests discuss the search for Longitude while at sea. Following efforts by other maritime nations, the British Government passed the Longitude Act in 1714 to reward anyone who devised reliable means for ships to determine their longitude at sea. Mariners could already calculate how far they were north or south, the Latitude, using the Pole Star, but voyaging across the Atlantic to the Caribbean was much less predictable as navigators could not be sure how far east or west they were, a particular problem when heading for islands. It took fifty years of individual genius and collaboration in Britain and across Europe, among astronomers, clock makers, mathematicians and sailors, for the problem to be resolved.WithRebekah Higgitt Principal Curator of Science at National Museums ScotlandJim Bennett Keeper Emeritus at the Science MuseumAnd Simon Schaffer Professor of History and Philosophy of Science at the University of CambridgeProducer: Simon Tillotson

BBC Sounds, music, radio, podcasts. Thanks for downloading this episode of In Our Time. There's a reading list to go with it on our website, and you can get news about our programs if you follow us on Twitter at BBC In Our Time. I hope you enjoyed the programs. Hello, in 1714, the British government passed the Longitude Act to reward anyone who devised reliable means for ships to determine their longitude at sea. Ships could already calculate how far they were north or south, the latitude,

but voyaging across the Atlantic, for example, or to the Spice Islands, east to west, was much riskier. And he took 50 years of individual genius and deep collaborations among astronomers, clockmakers, mathematicians and mariners in Britain and across Europe for the problem to be resolved. With me to discuss the longitude question are Jim Bennett, Keeper Emeritus at the Science Museum,

Rebecca Higgott, principal curator of science and national museum Scotland, and Simon Schaffer, Professor of History and Philosophy of Science at the University of Cambridge. Simon Schaffer, when did marines begin to think they had a problem with longitude? The problem is very old. It's important, I think, to start with the idea of what longitude is. Lines of longitude, which are often called meridians, define one's east or west position on the earth.

Those lines run from pole to pole, and east or west are then defined as a distance from some chosen line. That model of longitude was ancient. It's discussed and measured out in the work of Ptolemy in the second century. It was discussed in classical India and China. I'm trying to get a time chart here. When did mariners begin to think they had a problem with longitude? It was very obvious from,

the medieval period that this was a crucial problem, because as voyages became longer and more demanding, and one was away from home port or from the coast for longer and longer periods, then the determination of position east or west became absolutely critical. And by the time of the European Renaissance voyages, as you mentioned, to the New World, as the Europeans called it, and then to the East Indies as well, to the Spice Islands. Those were journeys where determining how far east or west you were was absolutely crucial. What I read, I love to talk about workarounds, Simon. What were workarounds?

Yes, I mean, mariners were supremely skilled. they were able to determine their position with amazing accuracy. If you had a knowledge of the skies and stars, how stars changed their position during the night and during the year, you knew about the directions of winds and the movement of the sea, even the flights of birds. There are many examples. The population of Oceania provides a supreme one. where mariners were able to navigate over immense distances.

So where did this word workarounds come from then? In Europe, for example, Europeans were not the only people confronted by this problem, but it was a major problem for them. There were practical ways of finding your longitude without having a profound method for so doing. This was what mariners called longitude by account. which what you would do would be to determine the direction in which the ship was travelling. That was typically done with a mariner's compass. That would give you your bearing. You would estimate the speed

at which the vessel was travelling by throwing out a lead and then counting the number of knots in the line as it paid out, hence the word knots. And you'd measure the time with a sandglass. Those were the workarounds that allowed you to compute longitude by account without having any direct method of determining your longitude at sea. Thank you very much. Rebecca, Rebecca here, what could you do on land about longitude that you couldn't do at sea? Well, one thing you can do is sea landmarks. So that's one of the big differences between trying to work out where you are on land or chart where you are on land compared to being in the midst of an ocean, as opposed to sort of working along the coast. But also as mathematics, astronomy, technologies improved, there were methods of

measuring longitude that you could undertake on land that weren't available to mariners at sea. So it was long known, for example, that if you knew the time, the local time in two different places at the same sort of universal time, you could subtract one from the other as there's a direct relationship between time passing and difference in longitude. So if you could do that, if you could carry a reference time with you and compare that to another time, then that was obviously going to be a solution, but something that was very hard to do at sea. But on land, it was possible to do once pendulum clocks, sufficiently accurate clocks arrived in the middle of the 17th century. These were things that would keep time sufficiently well that you might be able to use them

in terms of comparison. You could also make observations of the skies much more easily if we're thinking pre-teloscopic days initially or later on once telescopes became available. They were something that was much easier to handle on land and you didn't have the problems of the motion of a ship. Can you tell the listeners where the demand was coming from as time went on the 17th century to resolve this question of longitude?

It's coming from different places. I think if we look at the sort of longer story, even before the 17th century, of where we see active interest arising in seeing this as a problem, defining it as a problem, and looking for technological, scientific kinds of solutions to it. And often that's coming from ambitious rulers. Longitude will enable them to get more accurately to the place they want to go to. Is that the top and bottom of it? Yes, more predictability.

better knowing the world around you. The promise, perhaps, that this is something that will make things more profitable for the nation and so on. That promise, though, is often being held out by the kinds of people who hope that they might be able to offer the solutions. So you might think it's the mariners saying, you know, we have these trixie methods. We have, you know, problems where we get less than can't sort of find ourselves again. But that doesn't necessarily seem to do the case. the people really pushing for this to be on the agenda and for rewards to be given were the people who might do well from them. So people like mathematicians, potentially instrument makers who could offer those solutions were obviously the ones most interested in this being something that would be well rewarded.

And it was the case that while the longitude bill was being discussed in the British Parliament, that a captain was said to have said that mariners did not want the longitude, as in they didn't miss it. they had sufficient techniques that they didn't feel that there was something missing from their arsenal of how to get around. Jim Bennett, how easy was it to calculate latitude by comparison? Oh, by comparison, it was much more simple. The night sky has plenty of clues for a mariner to find his latitude. The most obvious one is the star Polaris, a very bright star in the little bear, in Ursa Minor. So as that's increasingly used for direction. Mariner's notice that it was higher in the sky when they were

further north on the earth, lower in the sky when they were further south. So they started to use it for a position finding as well or a sort of position keeping. For example, if you want to seal a course east-west, you want to keep the polaris at roughly the same height in the sky, in your visible sky. And you might associate a particular height of Polaris with a particular landfall. So gradually, you're not thinking, we would think of this as latitude finding

or latitude keeping, but it isn't really. They're not really thinking about latitude at this stage. During the day, it's a little more complicated because you have to use the sun. It's still not too difficult. But if you think about it, the sun, the sun's altitude, Its angle above the horizon depends on the time of day, the time of year, and your latitude.

When they were looking for solutions, were there any help that magnetism could help? Magnetism introduces a different technique from the one we've been talking about so far, and which Simon introduced and indeed Rebecca referred to differences in local time. So time is involved in the methods we've thought about so far. It was thought that there would be a global pattern of this business, of this phenomenon of magnetic variation, which is the way the magnetic needle does not point directly north, but points a few degrees off to the east or the west. And that deviation or declination, as it's called, or variation is different around the globe. So it was thought that since it varies with latitude and longitude, we can measure our latitude, we can measure our variation and specialist. instruments were devised variation compasers for making that measurement, and we can deduce our

longitude. And that effort came to nothing because it's such an unpredictable variation, and in any case it varies over time. So it's changing with the passing years, as well as with place. Simon, Simon Schaffer, did things change in this 1714 act when the government said, in this country, as I had said before in France and the Netherlands in Spain, as I understand it, that there will be massive reward for someone solving the problem as they saw it at that time of longitude. Can you tell us something about that? Yes, in principle, that was a very dramatic change. The British state had already taken some initiatives in this area, notably the foundation of an astronomical observatory at Greenwich in 1675, the Royal Observatory, whose principal function it was declared was to establish

tables of the position of the moon so that longitude could be established at sea. But it's the 1714 Act that really starts to change the whole seascape of the longitude problem. The Act is the result, it's appropriate to emphasize this, of extremely energetic palimentary lobbying. Two London-based mathematicians, William Whiston and Humphrey Ditton, launched a lobby campaign in 1713, and within a year, thanks partly to their connections with the parliamentary committee, which summoned witnesses such as the then-president of the Royal Society, Isaac Newton, an act was passed to, as it was said, establish the safety and question. witness of voyages, the preservation of ships, the lives of men, the trade of Great Britain,

and the honour of the kingdom. And that's a magnificent summary of what it was hoped longitude could offer. The reward, equivalent to three million pounds these days, was an encouragement to a great number of people to bend their minds of this and suggestions kept flooding in. That's exactly right. The science, and scope of the reward encouraged very large numbers of schemes authored by, to use the 18th century term, projectors of variable credibility and variable trustworthiness. Crucial within the Act was the provision that there would be a number of commissioners of longitude, including representatives of the Admiralty of Parliament, of the Royal Society and the universities,

their job was under the Act to judge these schemes and to organise their trial. Significantly, the trial was supposed to be take the scheme on a voyage to the West Indies. The West Indies mattered because of the slave trade and of sugar. and that was the scheme that the act established. Rebecca, Rebecca Higgard, how likely did it seem that this would provoke a quick solution? It depended on your perspective, I think. Certainly those involved did think it would provoke responses and that there were things that would likely prove to be helpful in the near future.

There are others who saw this as being a fool's errand. There's lots of satire. but those more closely involved certainly could point to a number of likely contenders. Newton was working on the moon's theory, so the moon's motions trying to map those over time, drawing on observations made at the observatory in Greenwich, Paris and elsewhere. And although he found that very difficult, and he said his head never ate but with the moon, because he found it's such a difficult problem to solve the moon's motion, which is complex because of the different gravitational pulls of the Earth and the Moon and the Sun on each other.

But he said that it was already something that perhaps would lead to finding longitude by method known as the lunar distance method within two or three degrees. That's a fair amount if you're at sea. If a degree is about 60 nautical miles when you're at the equator, less when you go further north or south. But, you know, his sense was, and his clear steer to the Parliamentary Committee was that that, would be improved and they would get towards the degree or the half a degree, which were the levels of precision that were aimed at within the terms of the act. So you've got a top reward, the £20,000 reward should anyone be successful in finding longitude or keeping longitude within half a degree and half that amount, £10,000 within one degree. There was also

clockmakers working on clocks around this period. So although Newton felt that clockwork was unlikely to be sufficiently effective. Others were trying to push that. And then another astronomical method was using Jupiter's satellites and their motion, their eclipses as they went around Jupiter as a celestial timekeeper. And that was something that proved particularly effective on land mapping. But it was a small observation to make in the sky that required at the time very long telescopes, which of course are difficult to handle and use when on board a moving ship. Jim Bennett, this is where John Harrison, they became an extremely famous clockmaker and still is. That was when he entered the scene. What was he doing

that others weren't doing? Because he stuck on it for at least 40 years and he got the perfect chronometer. What made him so distinctive and so successful? What distinctive really is the word. Harrison came into the horological world as an outsider. He didn't follow the usual apprenticeship route. He had no experience of the London tree. He'd been a joiner in Lincolnshire. He'd read about the longitude prize. He was making clocks. He was interested in lots of things, but among them, clockwork.

And he was making wooden clocks, of course, because he was a joiner. But he had these ambitions which, in a way, were unusual. I mean, Rebecca mentioned the possibility of clockwork. Not many people in the London trade actually were interested in that. I mean, professional clockmakers really didn't think that clocks were going to become accurate enough. to keep the longitude within the limits prescribed. But an outsider might, almost in his ignorance, think that this was possible. And Harrison came as a new phenomenon then, somebody with enthusiasm, with commitment,

you know, with little experience. But somehow he convinced influential people. He comes to London for the first time in 1730 with his ideas. He convinces the leading clockmaker and watchmaker there, George Graham, who is a fellow of the Royal Society. He gets support at the Royal Society. He gets, when he comes back with a clock to show in 1737, he gets the Board of Longitude, or his influential new friends, get the Board of Longitude to meet for the first time

since the commissioners were appointed in 1714, and this is in 1737. So he was clearly a man of great, well, something that was something that was. It was hard to say it was charisma, but there was something there that made you pay attention. He was ingenious, certainly. He had lots of good ideas mechanically, which were original. But he also had the personal qualities, you know, of determination and tenacity and doggedness.

He just kept at it in a way that nobody else was doing. And his machines were impressive. I mean, they made an impact. And because he was an outsider, he was treated as a bit of a, a phenomenon, it was a sort of spectacle aspect to it. You could pay Harrison to let him show you his clocks. He was a kind of a showman in that respect. And the other interesting thing about Harrison was that he had it difficult to express himself. You know, perhaps he had an accent people weren't familiar with, but also he was, people find him incoherent. They didn't find

his explanations. It was possible to follow them. And yet, set a sense. that. He produced these wonderful, beautiful, elegant machines. So the idea got around that it was because he lacked training that he was such an innovative artist. Simon, Jim's mentioned how seriously people were taking Harrison's innovations eventually. What were the principal innovations that he was showing them, that impressed them? Because he began to get some money, he didn't get the reward, but he got a bit more to carry on with after seven years and a bit more to carry on with after another five years and a bit more, that sort of thing. That's right. Harrison eventually received a very substantial quantity of money under various

provisions, lobbies, frustrations and acts. What is striking exactly, as Jim has pointed out already, is the range of technical innovations that Harrison brought to the problem. Could you give us some examples? Absolutely. Think again what the problem is. It was well known that the most accurate kinds of clocks on land were pendulum clocks, but pendulums do not work at sea because ships move. So, Harrison's first problem was, how do you set up a clock? with a kind of driving mechanism that isn't going to be any kind of pendulum clock. And he designed a whole range of balance springs, of various forms, and made of various substances,

various metal, in order to drive the clock. His second problem, given that voyages along, was friction. Friction was his great enemy, because friction could disson. and perhaps even halt his timekeepers. Initially, Jim's pointed out that Harrison was a joiner, a carpenter. Harrison brilliantly used a special kind of wood lignum v. Thai, the wood of life, which lubricates itself because of its oil. So there was a lot of anti-friction lubrication built in to the four or five successive designs that Harrison built. Ultimately, he gave up on that and replace these bearings with jewels, rubies, diamonds, which display almost no friction. The price you have to pay, however, is that the clocks need oiling.

He designed new kinds of escapement, the device that pushes the wheel round. He invented what we now call a grasshopper escapement, which manages to move the wheels of the clock in a way that keeps it regular and which, which, minimises the force expended. And perhaps above all and most famously, he developed the very first versions of bimetallic strips, brass and steel strips that were riveted together and would compensate for temperature change because the two different metals expand at different rates as they're heated. We're talking about devices of an immense number of parts, so Harrison's first device had more than 1,400 parts. His third timekeeper had almost 700 parts. His ultimate device, his Sea Watch,

made in the 1750s and 60s, had these revolutionary designs, which were, again, to reinforce what Jim has told us, signs of his independence and originality. Unlike orthodox clockmakers, what Harrison had done was to invent a very high speed, rather weighty balance that went faster and with larger oscillations than a normal watch, yet it had been miniaturized enough to look like a plausible marine chronometer. And this device, what's now called H4, is one of, if not the great masterpiece of historical clockmaking. Thank you very much. Rebecca, enter Neville Maskely, 40 years younger than Harrison, astronomer became Astronomer Royal.

What difference did he make? If we just go back a little bit, so Maskelin, a younger man, a Cambridge-trained mathematician, who was born in London, came back to live in London, looking for a way to make a living from his skills, his interest in astronomy, so before he became Astronomer Royal. He got connected well with people in London, became a fellow of the Royal Society and found ways to make some living from those skills.

So he got some paid roles as an observer, for example, on the Transit of Venus expedition being organised and supported by the Royal Society and George III 1761. He conducted an observing programme there and also took that opportunity to trial the lunar tables produced by Tobias Mayer, which were significantly more accurate accounting. of the Moon's theory than had been available so far, and had some success with using those as a method of keeping track of longitude while making his voyage to and from St. Helena, which is where he observed the transit of Venus.

After he got back, he published on this method, also borrowing from the approach of Nicholas Louis de Lacay in France, who had published kind of pre-computed tables that would allow people to use the data of lunar theory in a way that would actually allow them to find their longitude through making observations when at sea. So he was somewhat invested in that as someone looking for a way, as I was saying, to make a living from these sorts of skills. He then also became a paid observer for the Board of Longitude, going on that voyage to the West Indies that was required by the act, as Simon explained earlier. And there he was helping to trial three different methods.

So this was when Harrison's watch was being trialled, so were Mayer's tables, and also a marine chair made by one, Christopher Owen, as a way of stabilising an observer enough, it was hoped to make observations of Dutus satellites. And he was again finding the lunar distance method, drawing and Mayer's tables, to be quite productive and quite fruitful. He came back from that voyage, unexpectedly, to find that he was in position to become the Astronomer Royal. So suddenly from being an observer for the board, he finds himself being a leading

figure on the board and in a position to influence how those three methods were judged, how they would be rewarded with a new act in 1765, and also to push forward something that became really significant, which was the publication of the Nautical Almanac, which was, again, producing these pre-computed tables that would support navigation at sea. These, Jim Bennett, thank you very much. Jim Bennett, Harrison's innovations might have seen promising, and masculine innovations were promising. And how was this working out when they went to sea?

The Harrison watch, of course, the age four watch, performed extraordinarily well at sea. There were two voyages to the West Indies, first to Jamaica, then to Barbados. And it raised all sorts of questions for the board. And the board realized that they had a problem now that they might actually have to part with the reward, they realized when they had to examine the 1714 Act that it was inconsistent in that they had to reward the going of a watch or whatever method was to the West Indies and back successfully, which had happened. But they also had to reward, and this was in the scene. same process, a method that was practicable at sea. And was this practical at sea? There was only one of these watches. It needed to be, it needed to be shown, they thought, that this watch could be

produced in great numbers. And by ordinary watchmakers, so some of the qualities that we've been talking about in Harrison suddenly became problematic. Was he, nature's mechanic? Was he a very special person, or could an ordinary watchmaker do this? Were his mechanisms so extraordinary and wonderful and ingenious that they couldn't be produced by ordinary watchmakers? So we couldn't have ships all carrying these chronometers. So suddenly there were all sorts of technical problems that they had to solve. So that was the problem that faced them, not that the watch hadn't performed very well, but how could this performance become generalized and become routine? That was their problem. Lunar distances worked very well as well, but there what had to be shown was that

ordinary seamen could actually perform the calculations involved. So what Masculin learned is that he had to set up this industry of pre-calculating all the difficult lunar distance calculations, which would be available in this Almanac years before the event, years before the year for which they were to be used, which could be taken at sea and consulted at sea. That meant. method required a lot more calculation, but seemed to be more rooted in a knowledge of the natural world, let's say, rather than in the uncertain world of mechanical performance. So it was tricky. There was a real clash of cultures, a real difference between these two cultures. In this clash, Simon Schaubb, who emerged as a leading figure by the middle of

the 18th century after the 1740 offer? Who benefited most, which way forward? was adopted? That's a really complicated question. For the reason that Jim has already outlined, there was within the provision of the legislation governing the longitude search, a tension between rewarding someone who invented a device or method, almanac, instrument, and making sure that that was feasible. Good way of thinking about it, is that this is after all, I think, an absolutely fascinating moment in the history of the British Industrial Revolution, because it brings together absolutely astonishing artisan skill, such as that exhibited by Harrison, and the demands of mass production, so that it was necessary to produce

sufficiently large numbers of timepieces, sufficiently large number of observational instruments, and sufficiently large number of copies of the Nordical Almanac so that the system would work across the globe. What we see, rather, is a combination. So mariners who really benefited from these innovations stuck, rather, to their conventional dead reckoning methods that they'd use each day and each night. And then perhaps once or twice a week,

they would consult their marine timepiece and then put off by some of the complexities of mathematical computation required. It was only once a fortnight or once a month that they'd indulge in fixing their position completely reliably using the lunar distance method. So it was a combination. What benefited above all was speed and reliability. One way of reading this whole history is that it's an event in the history of British insurance, because the British exerted more or less a monopoly over marine insurance, and the determination of longitude at sea was an absolutely decisive event in driving down transport and risk costs for voyages.

Rebecca, Simon mentioned the imminent arrival of the Industrial Revolution. How far did new technology, in your view, helped resolve the problem? It was very important. And the availability of the right kinds of craft skills in London was incredibly important. And the fact that there were others who could add to those innovations, changed them, draw on others that had been made in France, particularly, was hugely important turning this into something that was not quite industrial-level production when we're thinking of chronometers,

but turning a unique machine into something that by the end of the 18th century was more standard and something that then started to be termed a chronometer. So Harrison is not the one who produces the chronometer as it came to be used from that period onwards. It took lots of other individuals as well. And alongside that, we have the observing kinds of instruments as well.

So we haven't talked at all about the arrival of the quadrant or the octant or the sextant. So these handheld observing instruments that allowed through the principle of double reflection mariners to make much more accurate observations of the kinds of angles between heavenly bodies between the horizon and a star and so on. So those had to be produced and they had to be produced in a way that became more mechanised. There were engines produced. Jesse Ramston came up with the dividing engine as a way of automating the division of the scale on those instruments, so the degree scale that each of them held.

Jim Bennett, when he came to resolving the question, was there any instrument, any way of doing it that was primary, was it always a combination of instruments and ways of doing? Well, I think complementarity is very important here. That's to say there ended up being two viable methods with different, qualities and different properties and different applications, as Simon has told us. It was expected, I think, that the latitude, since the latitude was readily available, and when the longitude would be found, everything would be complete.

It didn't work out like that really at all. And it's interesting that solutions to technological problems often raise new ways of doing things that aren't positive in the problem. What happened here, I think, is that the chronometer and the sextant got combined in different routines of calculation that were unexpected in ways that allowed both the latitude and the longitude to be found in a single operation. It's important to realize that the chronometer could keep the time, could keep the longitude, if you like, but it couldn't find it. So if it stopped, you were finished. It was nothing you could do to recover your situation, except you then had to turn to the lunar method

to re-establish your longitude and start your chronometer again, so to speak, and indeed start your dead reckoning account again from a new longitude and latitude fix. So there was a lot of complementarity and a lot of originality in the way that was taken forward into what's called position line navigation, which really is a bringing together of all these different skills in a new forms of mathematical complexity. And this great kind of development of mathematical navigation was kind of brought to an end, if you like, by the electronic age.

Simon, what changed, what was it major change once there was greater certainty about a ship's position at sea, once they'd crack longitude? I think the most dramatic change of, above all is reliability. There's a huge amount of evidence that by certainly the mid-19th century, which is the period when marine chronometers really hold the stage on shipboard for position finding, the idea of sailing as fast as possible, as directly as possible, and with massively increased surity about the result, that had been secure. in a culture of imperial expansion and global exploitation, accumulation and loot,

the effects of those technical and practical changes were indeed going to be dramatic, as Jim has pointed out. And I think the entire story of the establishment of a range of methods for finding longitude at sea is an object lesson in the feedback between technical change and quite unpredictable consequences. Rebecca, that wasn't the end of it, was there? This advanced into the 19th century. War-shipping, more empire, more trade, these things continue. And we can see them being supported by more embedded systems. So the Royal Observatory at Greenwich continued to support the making of observations of the moon and stars to produce the North Kalamannock. We're increasing getting mariners being trained in these methods. The tools, the texts and so on are more widely available.

And one of the things we haven't talked about in terms of how they were used and perhaps just as important was using of those technologies and systems to carry out charting around the world of coastlines and rocks and so on. So it's all very well to know where you are, but if you don't know where the coast is or you don't know where rocks are that you might hit, then you're not much better off. So the production of charts, particularly by the British Admiralty, was a really important outcome of all these new tools.

And the sort of long-term impact for that in one way, I suppose, was the decision that Scranich would be, and it became, because it was being widely used through the Norse Klamanak and through the use of these charts, the prime meridian that would be. be the reference point for the whole world. So the zero degree longitude point passing through the main transit instrument that was used at Greenwich to make those observations. Can I ask you very briefly, that three of you, Simon, what does this episode tell us about the way that technology

can advance change? Yes, well, I think it kind of created that possibility, that belief that that there was a connection in that way. Remember, if you think in what we said about the 16th century, there were mathematicians who wanted to mathematicize the practice, the non-mathematical practice at that stage of navigation. And the story of latitude, but then more particularly longitude, really changes what we expect from that equation. I mean, it's successful.

The mathematical instruments are designed and used. The textbooks and manuals are written, a cadre of technically competent naval officers is formed, institutions of the state are created like the Royal Observatory in the Nautical Almanac office and the Board of Longitude and so on and so on. And this idea that the state has a role

in the technological development of systems of national importance grows out, I think, very largely from the success of this story. You can even see it, I think, in masculine. Maskeland says of the nautical almanac that when he defends its probity and its reliability and so on, he says that the legitimate expectations of the public are that the standards of the nautical almanac

will be as good as they possibly can be. And a failure of the nautical almanac then is a failure of a type of state craft which is only taking shape in the late 18th century. Can we move on, I'm afraid, to Rebecca. Do you have any longer-lasting conclusions from this particular episode in the history of inventions?

Yes, I'm sort of building what Jim was saying. The idea that the state might support innovation is an interesting one, and one that has varied, over time continues to vary today. The idea of a challenge prize, which is one of the takeaways people have from the story of the Longitude Act has resonated and continued to do. So this idea of, you know, an eye-catchingly large amount of money being mentioned

and that's bringing perhaps left field outside kinds of ideas in. But also I think we can learn that if we look at how the usable tools actually arrived, we're talking about something that is not just a one-off prize or reward, but actually more sustained kinds of investment. So Harrison himself was supported over a long period. Is it a huge interest from the board early on? They start giving him sums of money straight away in order to continue carrying out his work. And that's hugely unusual at the period.

And, you know, in a sense, we could see it as a kind of grant, which is the way we often fund science now. And something that needs sustained investment like the North Kalamannac, like an institution like the Royal Observatory. And Simon Schaffer, finally? Yeah, I completely back that up. I think the longitude story, as we've thought about it, combines lessons about the extraordinary capacity of singular individuals, especially singular artisans, with the indispensable role of what we might call public maintenance. Ultimately, the solution to the problem of longitude at sea was eternal vigilance and the maintenance of very large-scale institutions.

astronomical, computational, technical and indeed political. And without that maintenance system, the problem of longitude would never have been solved. Well, thank you very much. Thanks to Rebecca Higgott, Jim Bennett and Simon Schaffer, and to our studio engineer, Jackie Marjoram. Next week, it's Monkey Magic with Sandy and Pigsie in the Chinese novel Journey to the West from the Ming era. Thanks for listening. And the In Our Time podcast gets some extra time now with a few minutes of bonus material from Melvin and his guests. Would you like to say what should have been in the programme that wasn't there?

We should certainly have said something more if we'd only had time about sextant. Yes, I was supposed to say that. Because one of the decisive problems that all longitude methods at sea depend. on was the ability of someone on a moving deck in a storm to make an exquisitely precise angular measurement. But what worked was from the 1730s and 40s onwards the development of this amazing instrument, the quadrant, the Mariner's quadrant, the Sexton, which was portable enough to move with you and yet accurate enough to allow you to make these really precise observations. Rebecca? I think we've taken a very British view of this story and softened the

case. And I think we've mentioned, you know, other contributors, La Chai from France and Tobis Mayor in Hanover and others. But I think it's possible to tell a rather different story if you take a different perspective. It's not as if, although there's a sense of handing on, there was, you know, earlier a prize offered by the Spanish crown and then there's a reward offered from the Dutch States so we can sort of see that progression of maritime ambition which passes to France and Britain by the 18th century. But it's not as if they stop. It's not as if innovation there ceases and observations and mathematics in France. I mean, if we look at what gets rewarded in 1765 when the North Kalamannac is set up and Harrison

receives 10,000 pounds. They also decide to give a prize to Leonard Euler's widow to recognise the fact that the mathematics that helps the production of these lunar tables was the product of many individuals. So I think there are many other stories that we could tell that step away from the Board of Longitude and Harrison are masculine. Jim. Well, I was really struck by how big a story.

this is when we try to squeeze it into one program. So that's been a revelation to me that how much there is to say. One thing that is really important is hydrography. I mean, it's all very well finding your coordinate, your latitude and your longitude, but if you're plotting them on a poor chart, it's not much, it's pretty useless. So absolutely in parallel with this, some kind of hydrographic service was needed, which differed in different parts of the world, yes,

and was more centralized and governmentalized and some and more privatized in others and so on. But there is the underlying combination here as well of mathematical practice in improving projections and devising new ones and so on and measuring indeed. And here the sextant again comes into its own. Absolutely wonderful, extraordinary instrument.

I'm glad Simon made so much of that. But the production of charts, not just the drawing of them, but the organizational production. And the other thing, it's extraordinary about chart making and chart distribution, is the international dimension to it. charts are, I mean there were attempts, of course, in the early period of the so-called period of great discoveries of keeping charts secret. But I mean, that was doomed. That never, didn't work for long once there were more nations involved in making oceanic voyages.

It was impossible to keep them a secret. And then in the 18th and the 19th century, they just become international. And that's one of the reasons. of course why we have a Grinch Meridian and we have an international time system which everyone pretty well everyone agrees on and so on and it's an extraordinary example of international cooperation which remains. I really want to back up what Jim has just said

about charts and hydrography. That would require a completely different program. No pressure. With the foundation of the Hydographic Office and the extremely charismatic leadership for our 1829 of Francis Beaufort, that was a key moment in the application of the sea clock to navigation and charting and mapping.

So, for example, it's of great interest that on the Beagle voyage, the one that Darwin sailed on between 1831 and 1836, that was a survey voyage in South America and ultimately around the world. And Beagle on that voyage was carrying, I think, 22 chronometers. Now, not all of them were being used to determine the position of the ship. One of the key things they were also used for was they were taken on survey vessels and dinghies, for example, to assist the mapping of the coastline and of its principal features. That gives you, I think, on the one hand, an inkling of just how important these technical systems were.

And on the other hand, the immense labour, we talked about maintenance, the immense labour that hydrographers and navigators had to put in. The reason why you needed a hydrographic office, this was very much Beaufort's argument, was that maps could never be the finished article. They constantly had to be revised, positions refined, redetermined, remapped, the position of nautical hazards, obviously, could change. And I think Jim has made the point elsewhere.

It's a really profound one about this question of longitude, in particular mathematical navigation in general, that it's a superb example to think, about if you're trying to make sense of where the will to revise and correct and refine comes from. This is a story of constant attempts to make the world more accurately known. And it teaches us something about that. Thank you all very much indeed. Thank you, Jim and Simon and Rebecca.

And hope to see you again soon. In our time with Melvin Bragg is produced by Simon Tillotson. and Schaffer mentioned Darwin's voyage on the Beagle just there. And if you'd like to hear the In Our Time on that, you can go to BBC Sounds and search for Beagle. Before you go, can I quickly tell you about Tricky, BBC Radio 4's discussion podcast that's back for another series. I'm Miles, one of the producers. We put four people on our room face-to-face. There's no social media to hide behind or presenter to get in the way.

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