John Harrison – the master craftsman who solved the Longitude Challenge

On October 22 1707 a fleet of the Royal Navy under the command of Admiral Sir Cloudesley Shovell encountered severe weather near the Scilly Isles off the south-west coast of England. Four ships ran aground and were wrecked with the loss of 1400 sailors including Shovell himself. The main cause of the disaster was the inability of the seamen to accurately calculate their positions. In those days navigators had great difficulty in ascertaining their longitude – how far east or west they were.

The Scilly naval disaster was one of the worst catastrophes at sea and caused much consternation in Britain. So much so that in 1714 the British Parliament passed the Longitude Act offering a series of rewards of up to £20,000 for anyone who could find a simple, precise and practical way of determining a ship’s longitude. It was the first example of a major public crowdsourced competition and the prize was huge by the standards of the day (equivalent to almost 3 million pounds today).

John Harrison was a self-educated carpenter and clock-maker from Yorkshire who dedicated his life to solving the longitude problem. He was born near Wakefield in 1693, the son of a carpenter. As a boy he was always fascinated by clocks and he built his first longcase clock at the age of 20. As befits a carpenter it was made almost entirely of wood. Over the next decades he introduced several significant innovations in clock design so that by the late 1720s Harrison and his brother James were making the most accurate clocks in the world.
His innovations included the gridiron pendulum, made of brass and iron rods in order to eliminate thermal expansion, and the grasshopper escapement – a brilliant invention to control the release of the clock’s power. Unlike other clocks of the day his were designed to be practically frictionless and required no lubricants.

The Longitude Challenge

global-146441_1280Longitude is the measure of the location of a place on Earth east or west of a north-south line such as the prime meridian which runs through Greenwich in London. It ranges up to 180° eastward and −180° westward. There were two main approaches to the problem of establishing exact longitude at sea. One was based on astronomical observations and lunar distances but these were difficult and did not give enough precision. The other approach was based on timekeeping. For each 15° west one sails the day starts and ends one hour later so if you can measure noon from the position of the sun where you are and you know the time at the place you left then you can calculate exactly how far east or west you have traveled. The problem was how to produce a clock which was not affected by the motion of the ship or the changes in temperature, pressure and humidity on the journey. These variables had defeated many fine clock makers. Sir Isaac Newton was among many who thought that a sufficiently accurate clock could not be built.

In 1730, Harrison moved to London and started the design of a marine clock to compete for the Longitude Prize. He spent time networking and raising finance. He recruited some powerful allies, including Edmond Halley, the Astronomer Royal and George Graham, the country’s leading clockmaker.

It took Harrison five years to build his first Sea Clock (H1 as it is known). He showed it to members of the influential Royal Society (of Sciences) who helped him present it to the Board of Longitude, the body authorised to award the prize. They were impressed and asked for a sea trial. This took place in 1736 on a voyage from London to Lisbon and back. The clock lost time on the outward voyage but proved very accurate on the return trip.

The Board of Longitude was impressed and granted Harrison £500 for further development. He started the design of a second sea clock. In 1741 after three years of development it was ready for a sea trial but by then Britain was at war with Spain and the invention was considered too important to risk capture by the Spanish. In any event Harrison was dissatisfied with the design of H2 and used the hiatus to start work on a new clock, H3. He spent a further 17 years trying to perfect this clock but despite incorporating many ingenious new features he was unable to get it to perform with complete accuracy in a maritime environment. Eventually he reached the conclusion that a watch design would be superior in performance and practicability.

In 1759 with the help of some of London’s finest craftsmen, Harrison built his masterpiece, the world’s first truly accurate marine watch (H4). It was a complex and highly novel design. He demonstrated how it could be used to calculate longitude. Harrison was 68 years old when the watch was sent on transatlantic trial in 1761. It lost just 5 seconds in 81 days on the outward journey to Jamaica. Everyone expected the prize to be awarded but the Board considered that the result might have been down to luck and demanded another trial. Harrison, his family and supporters were outraged but the second trial went ahead this time to Barbados and once again the watch proved accurate losing 37 seconds. Again his opponents on the Board attributed the results to luck and refused to pay out. The matter was raised in Parliament which offered Harrison £10000 in compensation.

Harrison requested an audience with King George III who took his side. The King’s own tests showed that Harrison’s watch was accurate to within one third of a second per day. Eventually when he was 80 years old and following pressure from the King, Parliament granted him a further £8750 but neither he (nor anyone else) ever received the full Longitude Prize. He died on his 83rd birthday, 24 March 1776.
Harrison’s marine chronometer was widely adopted in the years that followed. Captain Cook depended on it when mapping his discovery of Australia and Pacific islands.

Lessons for Innovators

Harrison showed enormous dedication and persistence in pursuit of his goal. Despite many setbacks he kept focused on refining and improving his designs and their manufacture.

He used networks, collaborators and important contacts to raise finance and gain influence. He could not have achieved what he did working as a lone inventor.

Based on a chapter in Think like an Innovator by Paul Sloane published by Pearson.


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