Review of ‘Longitude – The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time’
by Dava Sobel

Cover for The Illustrated Longitude - Galleon foundering in heavy seas

Cover for The Illustrated Longitude

Dava Sobel’s popular little book (208 pages) is pretty much essential reading for any Scientific Tourist planning to visit Greenwich.  Even if you are not, or if you have already been, I think it is still worth picking up this intriguing, easy to read tale as background reading.*  At its heart, as the subtitle tells, is the story of a ‘little man’ struggling against the odds, and the opposition of some of the greatest scientific minds of his time, to solve a vital practical problem by sheer (and self-taught) engineering ingenuity. Greenwich and the Royal Observatory are central to this story, and you can still see the practical results, including the machines by which the problem was solved.  For more on Greenwich, see Royal Greenwich.

*But please do read my comments towards the end of this review regarding the strict veracity of Sobel’s storytelling.  Caveat lector!

Royal Observatory Greenwich - Established in 1675 by Charles II to Solve the Longitude Problem

Royal Observatory Greenwich – Established in 1675 by Charles II to Solve the Longitude Problem

The problem mentioned was, of course, the finding of longitude at sea. The desperate need for an accurate, reliable, relatively simple to use, and above all, portable, way to solve this problem had been acknowledged by all the major maritime nations for at least a couple of hundred years.  The Age of Exploration had revealed the vastness of the world, and the potential for wealth through trade, not to mention conquest, but without a reliable way to determine longitude, all too often both mercantile and naval voyages were a leap into the dark, with the chances of returning alive discouragingly low.

The technology of sailing vessels had advanced to the stage where ships could carry goods (or war) across the globe, but navigation once out of sight of land remained literally hit or miss; with a high chance of getting disastrously lost or bumping into some island or continent. Furthermore, open ocean voyages were often far longer than they had to be, because instead of taking the shortest great circle route, sailors would follow a parallel of latitude (which was comparatively easy to determine) until they reached some recognisable landmass where they could get their bearings and turn north or south as required. But this was now the age of the Scientific Revolution, when new ideas, new mathematics, new physics, and above all, new astronomy, tantalisingly promised a solution.

Although people had navigated by the stars for millennia, new charts and new instruments meant that much more precise calculations could be made, and many solutions to the longitude problem based on celestial navigation were proposed. Kepler, Copernicus and Galileo had shown the heavens to be like some vast clockwork; ordered, precise and predictable, and Newton was well on the way to explaining why. So it was understandable that some of the best minds thought that the way forward lay in the eternal celestial cycles of the sun, moon, planets and stars.

However, the practical difficulties of observing from a moving ship in uncertain weather, not to mention the difficulties of predicting the relative motions, rendered all of the proposals useless. Even the best of them, the Lunar Distance method, was not only impractical and extremely complex, but could not work when weather obscured the moon, and the technique becomes significantly more difficult for the 13 or so days every month, when the moon can only be seen at night.

John Harrison – Shown with his H4 Marine Chronometer

John Harrison – Shown with his H4 Marine Chronometer

And it is here that Sobel’s story really begins; for there is another way to determine longitude with comparatively simple observations, as long as you know the time. More specifically, you need to know the difference between local time (which depends on your longitude) and the time at some reference point on a known longitude (or meridian.) The problem here is that there was no technology at the time that was capable of the required accuracy and reliability. If fact, no instrument could get within several orders of magnitude of what was needed, even in the most stable of environments, much less under the rigours of a sea voyage. And it looked quite unlikely that any such technology could be developed. Into this situation steps a complete unknown, a carpenter with little formal education and no training in clock making; John Harrison.

Harrison was clearly a most remarkable man, and his story is intertwined with the great and the good (and the not-quite-as-good as they perhaps might have been) scientific minds of his day. At least two of his first clocks, built entirely of wood, are still running today, almost 300 years later! Alas, the one at Brocklesby Hall is regrettably in private hands and not open to the public – for shame! He was to build the most accurate and reliable timepieces of his time, thereby solving the longitude problem. I will leave Sobel to tell his story.

Harrison's Chronometer H1

Harrison’s Chronometer H1

Harrison's second attempt, the H2

Harrison’s Second Attempt, the H2

What I would like to muse upon are a number of more general themes in the history of science that emerge, and relate the book’s subject matter to Greenwich.

Firstly, the Board established to encourage people trying to find a way to ‘discover the longitude’ behaved as such committees all too often do. That is, it became dominated by certain individuals with their own axe to grind, it became fixated on a particular solution to the exclusion of other approaches, and it greatly underestimated the scope for innovation.

Harrison's Chronometer H4 - Which Proved the Practicality of Chronometers to Determine Longitude at Sea

Harrison’s Chronometer H4 – Which Proved the Practicality of Chronometers to Determine Longitude at Sea

Even Newton discounted the possibility of improving a chronometer to the required accuracy, writing

‘One [method] is by a Watch to keep time exactly. But, by reason of the motion of the Ship, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity in different Latitudes, such a watch hath not yet been made.” adding that, “But when the Longitude at sea is once lost, it cannot be found again by any watch.’ – presumably thinking that carrying a reserve was not possible.

There is an amusing echo of this attitude when, 250 years later, the Astronomer Royal discounted the idea of space travel with the words,

It’s utter bilge. I don’t think anybody will ever put up enough money to do such a thing . . . What good would it do us? If we spent the same amount of money on preparing first-class astronomical equipment we would learn much more about the universe . . . It is all rather rot“,  just a year before the first Sputnik was sent into orbit, and only 13 years before the first manned landing on the moon.

The mechanism of H4

The Mechanism of H4

I’m reminded of Clarke’s 3 Laws of Prediction (by Arthur C Clarke who, amongst other achievements, predicted the geosynchronous satellite). Clarke’s first law states;
‘When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.’
Perhaps there was some excuse for the Board in the zeitgeist, where the efforts and achievements of man were compared so unfavourably with the eternal perfection of the world as created by god. The church still held great sway over society and the body politic. Halley, who was to become Astronomer Royal and play a major part in this story, was accused of atheism and denied a professorship at Oxford. Halley was also later censured by the Royal Society for proposing an mechanical explanation for Noah’s Flood, in the form of a comet. So perhaps attempting to use human ingenuity rather than celestial means was seen as hubris, bordering on heresy.  By the way, Halley was a renowned Scientific Tourist in his own right, having commanded two naval expeditions to make astronomical observation.  See Edmond Halley – An Illustrious Scientific Tourist

Secondly, Sobel makes much of the fact that Harrison was an untrained outsider. Others were working towards similar solutions to the problems but, without Harrison’s originality and single minded obsession, it might have been many years before his work would be matched. Few clockmakers at the time would have considered taking on such a project, knowing the years of effort and expense it would require.

Thirdly, there is the matter of the prize. It opened the competition to outsiders. The government was already funding research projects, among them the Royal Observatory, but offering such a substantial reward must have sustained Harrison. Mind you, it also encouraged so many frankly barmy or utterly impracticable entries that the Board was inundated and didn’t bother even convening for several years. Yet this principle of offering a prize was already well-established and obtains to this very day, as we see with the X Prize for spaceship technology.

One of 24 Marine Chronometers carried aboard HMS Beagle.

One of 24 Marine Chronometers Carried Aboard HMS Beagle.

Lastly, and perhaps most importantly, there is that wonderful synergy of science and technology; each driving and being driven by the other. The need for raw data drove the development of instruments and mathematical techniques, and the improved instruments enabled the theorists to extend and improve their understanding and explanations. Observations of celestial objects and events demanded a theory of gravity to explain them, and the science of mechanics predicted the observations which would map the solar system. Harrison developed springs to drive his timepieces, and Hooke explained their behaviour with mathematical precision. All this can be observed at Greenwich, in either the Observatory or the Maritime museum. Four of Harrison’s chronometers can be seen at the Observatory, as well as many of the instruments that were used to chart the heavens, which can be seen in situ. Three of Harrison’s chronometers are still running, while the fourth (the great ‘pocket watch style H4) is stopped for preservation but, like the others, it has now been restored to running order. Greenwich became the centre of world time, and science still uses Greenwich Mean Time (or it’s more modern equivalent, Universal Time), navigation became safer and more reliable, and the resulting wealth can be seen all around you in Greenwich.

Caveat Lector!

If, perhaps, Sobel’s narrative concentrates too much on the drama and ‘human interest’ of Harrison’s fight for recognition of his achievements, acceptance of his ideas, and for the very considerable reward offered, then we can forgive her because of the life she breathes into the history of science and ideas. The dramatis personae of this tale include Newton and Hooke, Wren, Halley and Flamsteed, just to mention a few. Sobel’s style is light, and provides a narrative backstory to a visit to Greenwich, which seriously enhances the readers’ appreciation of an important site.

However, what might be more difficult to overlook is Sobel’s somewhat cavalier attitude to factual accuracy, in as far as it can be determined in  matters of history; specifically, her repetition of some rather apocryphal stories which enhance the drama and appeal to our narrative prejudices, but which don’t stand up to scrutiny. For instance, the story of Sir Cloudesley Shovell hanging the junior officer (or rating, as some versions have it) who dared to (correctly) question his superior’s estimation of the fleet’s position, turns out to be highly questionable [The Shipwreck of Sir Cloudesley Shovell, on the Scilly Islands in 1707].  As does her very next anecdote about Shovell’s survival until he is murdered and despoiled of his jewellery on the beach.  Although, to be fair, she does insert the disclaimer ‘purportedly’ to the latter tale.  These rather lurid stories are really more suited to the tabloid-reader than to a Scientific Tourist, but I’m willing to take them in the same spirit in which I take the ‘colour’ so often added by over-enthusiastic local guides at sites all over the world, i.e. with more amusement (recognising their eye to a tip for pleasing the crowd) than credence.

Furthermore, Sobel’s rather Disneyfied  version of events appears both over-simplified and rather more partial (in the cause of a satisfying narrative?) than the complexities and subtleties of historical and scientific veracity would support.  As always, the truth is both less simplistic and infinitely more fascinating than it may appear on the superficial level required by a fast-paced story.  By concentrating on the somewhat romantic tale of Harrison, Sobel obscures the context in which her story is set.

Hopefully, Sobel’s Longitude and Greenwich itself will inspire and intrigue you enough to pick up the rather more scholarly, Finding Longitude – How Ships, Clocks and Stars Helped Solve The Longitude Problem.   I believe this book was commissioned to accompany a major exhibition at Greenwich in 2014, and it makes the maximum use of the resources (including the  scholars) there to present the wider (and deeper) tale behind the science of navigation and the longitude problem.  So it makes an ideal companion for really seeing the artefacts therein (and indeed the place itself) in their  scientific and technological context.


Try to get the later edition, The Illustrated Longitude (published 1998), which adds many much needed illustrations to the earlier text.


Longitude – The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. Dava Sobel. Walker, 1995 ISBN 978-0-8027-1529-6 OCLC 183660066

Illustrated Longitude, Dava Sobell and WJH Andrews, Viking, 1998, ISBN-13: 978-0670884728

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