Six-minute summary: John Harrison

Hello readers! It’s time for another six-minute summary. Today we’re exploring the life of John Harrison, an eighteenth-century English clockmaker. If you’ve heard of him already, it is likely in the context of the “longitude problem” which hindered ocean navigation for most of human history. John Harrison’s solution was a clock with unparallelled time-keeping capabilities – but it took him multiple decades and extensive trial and error to finalise the design. His tale is one of extreme perfectionism and tenacity.

Early life

Harrison was born in 1693 in Foulby, West Yorkshire (1.398469°W). Not a lot is known about his childhood, but it is often reported that at the age of six, when Harrison was in bed recovering from smallpox, he was given a pocket-watch with which to amuse himself – not just to envisage the passage of time and feel the thrill of his own finite existence, but to deduce the function of its moving parts. Soon after this, his family relocated to Barrow-upon-Humber, Lincolnshire, which he called home for the rest of his life.

Harrison’s stepfather was a carpenter, and Harrison followed in his footsteps. He repaired grandfather clocks, and at the age of twenty, he built one himself – entirely out of wood. Between 1715 and 1728, he made three more with the help of his younger brother, James, who was also a skilled carpenter.

In 1718, aged 25, Harrison married Elizabeth Barret in Barrow-upon-Humber church. Sadly, she died just eight years later – but in that very same year, Harrison married another woman named Elizabeth in the very same church (I suppose we could infer that he was a man averse to change?). He was also a keen musician and became choirmaster for the church – yet another indication that he was imbued with a divine sense of rhythm.

The wooden clock

Harrison’s first grandfather clock, from 1713, is now in the Science Museum in London (0.166667°W). The mechanical parts are made from lignum vitae, a wood which comes from trees in the Caribbean and South America. It is strong and tough, and so dense that it sinks in water. Most importantly, lignum vitae is self-lubricating. Most mechanical clocks at the time were made from metal and needed oil to lubricate their moving parts. This oil would spoil and become more viscous over time, causing the clock desynchronise, and often damaging the mechanism. Lignum vitae solved this problem; in fact, some of Harrison’s clocks still operate with precision today.

The longitude problem

In 1714, British Parliament (0.116667°W) passed the Longitude Act. The Board of Longitude was established with the sole aim of encouraging scientists and engineers to devise ways of calculating longitude on ocean voyages. They offered up to £20,000 (£4 million in modern money) to anyone who could present a viable solution. Specifically, the reward was £10,000 for anyone who could calculate latitude to within 1 degree, £15,000 for within 40 minutes, and £20,000 for less than half a degree.

(For any readers that muddle longitude and latitude, here’s a brief reminder: latitude is your proximity to the equator, and longitude is your proximity to the Greenwich meridian line, which passes between the poles through the Royal Observatory in Greenwich, London.)

Navigating across continents is relatively easy due to the presence of identifiable landmarks; navigating across vast, featureless oceans is impossible without a means to keep track of your position. Sailors could calculate their latitude based on the position of the sun and the stars, but the only way to calculate longitude was by dead reckoning – i.e., calculating your position based on your velocity and the time that has elapsed since you last knew your position.

In essence, the longitude problem boiled down to a matter of timekeeping. A clock halfway across the Atlantic had to display the same time as a clock back in London in order for calculations to be accurate – a small amount of drift could lead to huge uncertainties, and these would be compounded over long voyages, leading to ships arriving hundreds of miles from their intended destination.

Navigation before Harrison

The earliest way of determining longitude required a solar eclipse – an event which happens at a fixed time, no matter where on Earth an observer is located. The ancient Greeks knew this, as did ancient Hindu astronomers, and Islamic scholars in the middle ages. Indeed, Christopher Columbus tried calculating his longitude in this manner on two occasions, but was off by a catastrophic 13 and 38 degrees.

Another method was to identify when the sun reached its peak in the sky, or to use observations of the moon. After the invention of the telescope in the early 17th century, other astronomical observations could be used, such as the apparent rotation of the stars around the celestial pole. Unfortunately, the calculations usually took around four hours to complete – much too long to be useful, and with a high chance of making a mistake!

The pendulum clock was patented by Christian Huygens (of Saturn ring fame) in 1657, and manufactured in Paris (2.349410°E). It was accurate to about ten seconds per day, as Huygens had invented a balance spring to control the pendulum oscillations. However, the pendulums (much like myself) could not operate on ships that tilted and listed while at sea. Almanacs of astronomical data remained the best way of calculating longitude; indeed, the almanacs published by the Royal Observatory in 1767 became the global standard, which is why we still use the Greenwich meridian line today.

Before the almanacs entered circulation, a popular navigation method was to sail at a fixed latitude until seeing land. However, this massively increased journey times – effectively forcing ships to travel two sides of a triangle – which increased the risk of starvation and scurvy. This method also made it very difficult to find small targets such as islands. Without a reliable means to calculate longitude, navigational mistakes were causing countless deaths.

Introducing H-1

Harrison heard about the longitude problem and realised that he had a good chance of cracking it. He got to work designing a clock, then headed to London in 1730 to seek financial assistance for constructing it. Edmund Halley, the Astronomer Royal (of comet fame), was impressed by Harrison’s work and teamed him up with instrument maker George Graham, who helped make his designs a reality. The clock took five years to build.

Harrison presented his first attempt (H-1) to the Royal Society. Apparently he struggled to explain his ideas in a coherent manner, and so they stepped in on his behalf to approach the Board of Longitude. H-1 was deemed to be the first clock worthy of a sea trial, and in 1736, Harrison travelled with his invention on a preliminary test to Lisbon and back. It performed incredibly well on the return voyage, allowing Harrison to predict their landfall correctly, while the ship master was out by sixty miles. However, Harrison was disappointed by the performance of H-1 on the outward journey, so he held back from sending it on the official test voyage to the West Indies.

Introducing H-2

In 1737, Harrison moved to London to develop H-2, a more compact and resilient version of H-1. He worked on it for three years, then abandoned it when he discovered a serious flaw in the design. He realised why H-1 had performed poorly on the outward journey; the bar balances within the clock had been influenced by the ship turning on its vertical axis (yaw) as it tacked down the English Channel. H-2 had inherited the same problem, so he cancelled all of his work and moved on to H-3.

Introducing H-3

For his next clock, Harrison adopted circular balances to withstand the effects of yaw. He worked on H-3 for a staggering 17 years before he was happy with it, and even then it did not perform as well as he wished. The timing of its wheels was not isochronous, and Harrison could not fix this without understanding the physics and mechanical properties of the springs he used – theories which would not be established for another two centuries.

Introducing H-4

Harrison then decided to make a simpler, smaller watch for the longitude problem. He had already designed a precision watch for his own use in the 1750s, which had been made for him by John Jefferys, so he knew it was possible. He spent six years on H-4, which was finished in 1759. It looked like a giant pocket-watch, over five inches in diameter, and it could run for 30 hours.

By now, Harrison was 68 years old, and in no state to accompany his clock on long voyages. Instead, his son William accompanied H-4 to Jamaica and back. The clock lost only two seconds a day while at sea, and when it arrived in Kingston, it had an error of just 1.25 minutes – which was a massive success.

Unfortunately, the Board of Longitude was not impressed. They demanded another trial, suggesting that the Jamaica test had been a stroke of luck. H-4 (and William) were put on another voyage to Barbados, where H-4 once again proved itself to be incredibly accurate. And again, the Board of Longitude claimed that this was another stroke of luck.

Harrison asked for the longitude prize money, as H-4 had satisfied all the requirements. However, the Board of Longitude only offered him £10,000, and withheld the other £10,000 until he surrendered H-4 to them.

Introducing H-5

While the Board of Longitude held H-4 hostage, Harrison started work on H-5. He wrote that he felt “extremely ill used” by the men on the board, from whom he had “expected better treatment”. When looking for support for H-5, he managed to secure an audience with George III. The king was very impressed, and tested H-5 himself, before pressuring the Board of Longitude to give Harrison his prize money. In 1773, they finally relented and gave Harrison £8,750 – but he never received the full award. In fact, nobody ever did.

The Maskelyne problem

Harrison’s poor treatment by the Board of Longitude could have numerous explanations, including the fact that he had a relatively humble background, a limited education, and existed outside the scientific sphere. It has also been suggested that a particular individual – Neville Maskelyne – may have deliberately impeded his progress.

Maskelyne was also working on solving the longitude problem, but with astronomical observations rather than clocks. He was sent on the same test voyage to Barbados, and his astronomical method was only 30 miles out, whereas Harrison was 10 miles out. Maskelyne argued that his method was superior, as it only required astronomical charts rather than rare and expensive equipment. He also claimed that the accuracy H-4 was due to two sources of inaccuracy cancelling out (how he evidenced this, I have no idea).

Upon his return from Barbados, Maskelyne was made Astronomer Royal. This placed him on the Board of Longitude, allowing him to decide whether Harrison, his rival, could win the longitude prize. To my understanding, there is no solid proof of him deliberately blocking Harrison’s work – but with such a clear conflict of interest, you can’t help but wonder.

Later life

Over the course of his clock-making career, Harrison was awarded £23,065 from the Board of Longitude – more than anyone else ever received in the 114 years that the Board existed. This money made him a millionaire by today’s standards, so he lived comfortably and had ample funds for his research. He died in 1776 at the age of 82.

Not just clocks!

Harrison’s wondrous clocks were not his only inventions. Harrison is also credited with inventing the bimetallic strip, which he included in the design of H-3. By making rods with sections of brass and iron, thermal expansions and contractions cancelled out, meaning that the rods didn’t warp when heated. He included a similar design in a pocket watch he made for himself – which also included a mechanism that allowed the watch to continue running while being wound.

Another fascinating design from Harrison is the grasshopper escapement: a control device that allowed the rhythmic release of energy to keep a pendulum swinging. This design was included in his grandfather clocks, made with lignum vitae – and the lack of lubricating oil meant that these clocks suffered relatively little degradation, and were still running in 2005 (and maybe even later – this is the most recent report I could find).

Legacy

Sadly, Harrison’s clocks were never used as navigation tools. A guide to using chronometers was published in 1794, but they remained too expensive for most ships. Over time, their price came down, with later designers such as Thomas Earnshaw simplifying their design to enable mass production. Between 1800 and 1850, chronometers finally replaced Maskelyne’s astronomical methods. When Charles Darwin sailed on the HMS Beagle, the ship took 22 chronometers to ensure accurate timekeeping.

By the end of the nineteenth century, clocks could be synchronised across the world using telegraph, and then by radio. Today, we calculate positions using satellites, and most of us have never given much thought to pre-satellite ocean navigation methods.

Harrison was largely forgotten after he died, possibly because he didn’t have the connections or influence to promote his works. His clocks were rediscovered in the Royal Observatory in the 1920s by Rupert Gould, who documented and restored them, and gave them the names H-1 to H-5 (Harrison did not refer to them as such). Unfortunately, despite being a huge admirer of Harrison’s work, Gould’s attempts to salvage the original devices would induce panic attacks in modern conservationists. Thankfully the damage he caused was minor, and clocks H-1 to H-4 are on display at the Royal Observatory today. H-1 to H-3 are still working; unfortunately, H-4 cannot operate without oil, which cannot be used without causing degradation. H-5 is on display at the Science Museum.

Another work inspired by Harrison is the Corpus Clock at Corpus Christi College, Cambridge (0.117640°E), which has a grasshopper escapement displayed at the top inside a model grasshopper, which rhythmically opens and closes its jaws and is known as the “time eater”.

Having finally been recognised for his genius decades after his death, Harrison now has a memorial tablet in Westminster Abbey (0.116667°W), next to George Graham and Thomas Tompion, two other famous clock makers who are buried there.

In summary…

John Harrison was a genius engineer with admirable dedication towards solving one of the greatest problems of his time. Sadly, his engineering solutions were so far ahead of their time that they could not be easily manufactured, and it was only decades after his death that chronometers became the gold-standard of ocean navigation. Thankfully, his legacy has become more well-known in recent years, although we still know relatively little about him compared to many of his scientific and engineering contemporaries.

Happy reading, and have a lovely week!