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How John Harrison invented the first portable precision timekeeper

It’s been over 50 years now since Colonel Humphrey Quill wrote his biography (1966) of the great pioneer of the marine chronometer, John Harrison (1693–1776). Since then, there has been a increasing interest in Harrison and the events surrounding his inventions and discoveries. Indeed, over the years, this interest has caused something of a stir in academic history-of-science circles. This seems to have been because the discussion of Harrison’s achievements has mostly been published and brought to the attention of the public by non-academics.

Harrison was famously the inventor and creator of the first portable precision timekeeper, the marine chronometer.1993 saw the 300th anniversary of Harrison’s birth and many excellent celebrations, including a conference on longitude at Harvard University. This event inspired Dava Sobel’s accessible best-seller Longitude and it was this book which saw the beginning of real criticism from the academic world. Two of the main objections to Sobel’s book were her portrayal of Harrison as a lone genius, without support when he needed it most, and her portrayal of his nemesis, the astronomer royal, Nevil Maskelyne, as a villainous manipulator. Neither of these characterisations, critics said, was remotely true, and called for a better-balanced narrative of the facts.

H4 – Harrison’s prize-winning longitude watch and progenitor of the modern chronometer, completed in 1759. Used with permission by the National Maritime Museum.

Well, a balanced view is certainly a desirable thing, but for a proper balance, especially in a technological subject such as this, demands not only a full understanding of the facts surrounding the narrative but also a thorough knowledge of the technology itself. Regrettably, both of these have been lacking in some of the discussions to date. Harrison’s design for his fourth timekeeper was absolutely not “quite different” from the later chronometer, as has been claimed. H4, as it became known, contained several essential parts and technical details from which other people developed later designs for the successful chronometer.

At the beginning of the 18th century the quest for a way to find longitude at sea was becoming urgent. None of the several theoretical solutions, so clearly described but then doubted by Isaac Newton, seemed remotely viable. Following half a century’s work at Greenwich, the Astronomer Royal himself was despairing of perfecting what had seemed like the most promising solution, using astronomy.

What was needed was not a theoretical solution – there were plenty of those – but a method that was “practicable and useful at sea.” In other words, a method which a sailor, not an academic, could use to find his longitude on a ship when out of sight of land. The urgency to discover whether such a solution was possible at all was such that in 1714 the British government offered a reward of up to £20,000 for the successful demonstration of such a method.

H4 – Harrison’s prize-winning longitude watch and progenitor of the modern chronometer, completed in 1759. Used with permission by the National Maritime Museum.

This outcome was what the act of 1714 required, and the means of judging its success were clearly defined. And it was those terms which, throughout his creative life, Harrison was encouraged by the government’s commissioners to observe – the encouragement and observance clearly recorded in the minutes of the Board of Longitude, up until the 1750s. Harrison was thus justifiably annoyed when, during the 1750s and 60s, authorities began to “re-interpret”  the terms of the original act. The assurances and agreements shown to Harrison by earlier commissioners were ignored. New rules required evidence that the timekeepers could be reproduced in large numbers and by other craftsmen, things which were never contemplated in the original act.

Had those stipulations been proposed for inclusion in the act of 1714, which they could easily have been had it been deemed appropriate, one can readily imagine those drafting the requirements rejecting the suggestion, on the basis that the act was designed primarily to determine if such a thing were possible at all – “let us not run before we can walk.” If a viable method were brought forward and shown to work under the terms of the act, then the £20,000 would have been well spent. Although this was a large sum to a person, in terms of the Navy budget it was not. It was less than half the cost of a second-rate ship of the line. Saving just one vessel from shipwreck would doubly repay the cost. In the very likely event that such a method would need further development, then further acts might regulate further rewards for the fine-tuning of such methods. And this is precisely what happened, despite the commissioners’ reluctance to co-operate. The board subsequently funded a select few in the next generation of watchmakers to further develop Harrison’s design into something less complex and expensive – much in the way one sees the development of most technological products in our own times.

Clock B by Martin Burgess. Used with permission by the National Maritime Museum.

There is another part of precision horology – that of high accuracy land-based timekeeping, and John Harrison had revolutionary views in this area too. In 1976, mechanical engineer Bill Laycock wrote The Lost Science of John Longitude Harrison. The book outlined Harrison’s very different philosophy in pendulum clock design. Laycock’s work inspired horological sculptor Martin Burgess to create a pair of Harrison-type precision pendulum clocks. Burgess hoped these might prove the efficacy of Harrison’s design, and reach Harrison’s predicted performance of keeping time to within one second in 100 days. This kind of performance was not only unheard of in the 18th century but also in the present day, where even the best pendulum clocks have not attained such performance. Harrison’s claim has thus always been doubted by most in the traditional horological world, but independent trials are now proving that Harrison’s principles were correct, and the performance of one second in 100 days has been readily achieved.

Featured Image Credit: Pixabay

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