Tag Archives: Greenwich

The problem of longitude & the lone genius who solved it

Let’s face it. We are spoiled nowadays when it comes to navigation. All we need to do is to enter our destination into our phone and we get step by step directions there. We don’t even need a physical map anymore. 

But let’s face it. It hasn’t always been that simple and that easy. For a lot of human history, getting to where we want to go was not that quick and easy and that brings us to today’s topic–the problem of longitude. And one man sought to solve that. He was an English clockmaker named John Harrison. 

You might be asking yourself what is the big deal about longitude or what is longitude, for that matter?

Well, time to think back to middle school geography class. 

Take out a globe. Notice the grid pattern. Those lines are meant for navigation and helping you pinpoint your place on the earth. The horizontal lines are known as latitude and run east-west. The vertical lines are called longitude and run north-south. Finding latitude is relatively easy to do but longitude isn’t. So why? 

The short answer is that latitude had reference points that were easily available and they were also easy enough to measure and use for guidance, even without the use of sophisticated instruments. Longitude, on the other hand, was much less obvious and needed very accurate tools and tables of information for their measurement to be useful. 

In other terms, latitude is your position north or south of the equator and longitude is your location east or west of the prime meridian or zero degrees which happens to go through Greenwich, England. Both are imaginary lines circling the earth and on a modern map they form a grid of lines at right angles to each other that enable you to locate your position. These terms and the method of mapping with a geometric grid are relatively recent in history. 

Latitude has been widely used by humans since they took to exploring the seas and perhaps even earlier than that, as they moved to new places on land, leaving a locality with landmarks. This is because latitude has an obvious reference in the sky–a map or chart featuring the sun during the daytime and the moon, stars, and planets at night. As you move north and south, the map in the sky changes. By simply looking up, you could measure where you were in relation to the changes in location of these celestial bodies. Their position as they rose and set was easy enough to observe, but their height above the horizon also changed as you moved north and south and this too could be estimated with quite reasonable accuracy by different methods. 

This whole celestial reference formed a chart of its own, and although it changed through the night and through the seasons, and even presented a different view of the bodies depending upon your location, these changes were all gradual and formed a pattern which many communities and civilizations were able to observe and record and often in stunning detail and insight. This accumulated body of knowledge was passed on from generation to generation and people were able to use it to determine their position north or south relative to the equator.

The quest to determine longitude involved a number of possible answers, three of which had the potential of being accurate. Observing Jupiter’s moons held possibility and could be used on land; remember that there was no such thing as light pollution and so the night sky was a lot more detailed and brilliant than we see it now. Observing the moon through the lunar distance method also presented a very precise answer. There was also the concept of using the difference in time between a known location and your location as a means of calculating longitude was also well known. However, all of these needed very precise observations of the different celestial bodies and in the case of the first two, very detailed recordings of their patterns of movement, and tedious calculations to arrive at an answer. The time of day was also needed. The instruments required–telescopes, sextants, timepieces, and so forth–were gradually improving in accuracy, but did not begin to meet the requirements needed until the 1700s and into the 1800s.

The difference in time that eventually gave practical access to longitude at sea used a specific reference that was within the east-west moving chart in the sky. Lying within this was also a north-south oscillation. All of the bodies rising in the sky to a high point above the horizon and then setting again the west. This change in height above the horizon could be seen on earth as a north-south vector within the east-west motion. The highest point was due north or south in the sky and always occurred at the midpoint between when a body rose and set, and this midpoint was a constant reference as it occurred at the same time each day. 

It was one of these midpoints, along with Harrison’s invention, which helped provide a practical solution to the longitude problem. The point is called local noon, the point at which the sun was highest in the sky. Whereas sunrise or sunset changes time each day, local noon was always the same time  and thus a precise reference point for checking the time each day no matter where you were. If you could then just check your time against a known location, then presto! You could calculate your longitude relative to the known location….And this is where our clockmaker steps into the story. 

John Harrison was a self-educated English carpenter and clockmaker who invented the marine chronometer, the long-sought after device for solving the problem of calculating longitude while at sea. 

He was born in Foulby in Yorkshire, England, on April 3, 1693, the first of five children. Around 1700, the family moved to Barrow upon Humber in Lincolnshire. He followed his father’s trade as a carpenter but also built and repaired clocks in his spare time. Legend has it that when he was six, lying in bed with smallpox, he was given a watch to amuse himself and he spent hours listening to it and studying its moving parts. It would be the beginning of a lifelong fascination. 

He also had a lifelong fascination with music and eventually became choirmaster for the Barrow parish church. 

In 1713, at the age of 20, he built his first longcase clock whose mechanism was entirely made of wood. Three of his early clocks have survived and are now on display at the Science Museum in London. On August 30, 1718, John Harrison married Elizabeth Barret at the Barrow church. After her death in 1726, he married Elizabeth Scott on November 23, 1726, at the same church. 

Between 1725 and 1728, John and his brother James made at least three precision longcase clocks and these have been thought by some to have been the most accurate clocks in the world at the time. Harrison was a man of many skills and he used these to systematically improve the performance of the pendulum clock. He invented the gridiron pendulum which consisted of alternating brass and iron rods assembled so that the thermal expansions and contractions essentially cancel each other out. Another example of his inventive genius was the grasshopper escapement–a control device for the step-by-step release of a clock’s driving power. It was virtually frictionless, requiring no lubrication because the pallets were made of wood. This was key at a time when lubricants and degradation were little understood. 

In his work on sea clocks he was continually assisted, including financially, by the watchmaker and instrument maker George Graham. It was Graham who introduced Harrison to the Royal Astronomer Edmund Halley (yes, the Edmund Halley, as in Halley’s comet), who championed Harrison and his work. This support was essential for Harrison, as he was supposed to have found it difficult to communicate his ideas. 

As mentioned, longitude is one’s east or west of a north-south line called the prime meridian. Knowledge of a ship’s east-west position was crucial when approaching land. After a long voyage, cumulative errors in dead reckoning frequently led to shipwrecks and a great loss of life. Avoiding such disasters became critical in Harrison’s lifetime, as global trade was dramatically on the rise. After the Scilly naval disaster in 1707, the British Parliament offered a prize of £20,000 which is equivalent to $4.5 million today. This prize was under the 1714 Longitude Act.

In 1730, Harrison designed a marine clock to compete for the Longitude prize. After receiving financial assistance from Graham, he got to work. It took him five years to build his first sea clock called H1. He demonstrated it to the Royal Society who then spoke on his behalf to the Board of Longitude. It was the first proposal that the board considered worthy of a sea trial. In 1736, he sailed to Lisbon on the HMS Centurion. He sailed back on the Orford after the Centurion’s captain died in Lisbon. The clock lost time on the outward voyage but performed well on the return trip with both the captain and the sailing master of the Orford praising the design. The master noted that his own calculations had placed the ship sixty miles east of its true landfall which had been correctly predicted by Harrison using H1. It was not the transatlantic voyage demanded by the Board of Longitude, but they were impressed enough to grant Harrison another £500 for further development. Harrison had already moved to London by that point and got back to work on what would be H2 which had a more compact and rugged design. In 1741, H2 was ready but by that time Britain was at war with Spain in the War of Austrian Succession and the mechanism was deemed too important to risk falling into Spanish hands.   In any event, Harrison had discovered a serious design flaw in the concept of the bar balances; he had not recognized that the period of oscillation of the bar balances could be affected by the yawning of the ship. This led him to adopt circular balances in the Third Sea Clock or H3. The Board granted him another £500 and while waiting for the war to end, he proceeded to work on H3. 

He spent the next seventeen years working on H3 but despite his best efforts he could not get it to work as he wished. After thirty years of experimentation, Harrison found much to his surprise that some of the watches made by Graham’s successor, Thomas Mudge, kept time just as accurately as his huge sea clocks. He then realized that a mere watch could actually do the job and was a much more practical option for use as a marine timekeeper. In the early 1750s, he had already designed a precision watch for his own use. It was the first watch that contained a compensation for temperature variations and also the first watch that continued running while being wound.  Aided by some of London’s finest craftsmen, he proceeded to design and make the world’s first successful marine timekeeper that allowed a navigator to accurately assess his ship’s position in longitude and prove that it could be done by using a watch. This was to be his masterpiece and is engraved with his signature, marked Number 1 and dated A.D. 1759. 

After two sea trials, the watch was found to be accurate to an error of one nautical mile. Despite this, the Board attributed the accuracy to mere luck and refused to hand over the prize. Harrison and his son, William, who had taken over on the sea trials due to his father’s age, were understandably outraged. To add insult to injury, the Reverend Nevil Maskelyne who championed the lunar distances method, had been named Astronomer Royal and was therefore on the Board and he gave a negative report of the watch. 

Harrison began working on H5 while extensive land testing was conducted on the first, which he felt was being held hostage by the Board. After three years he had enough and enlisted the aid of none other than King George III. In the spring of 1772, he obtained an audience with the king who was extremely annoyed with the Board. King George tested the H5 at the palace and after ten weeks found it to be accurate within a third of a second. He advised Harrison to petition Parliament for the full prize after threatening to appear in person to dress them down. Finally in 1773, when he was eighty years old, he was awarded £8, 750 or around two million dollars today. He never received the official reward and, in fact, no one ever did. In total, he received £23, 065 for his work on chronometers. This made him the equivalent of a multi-millionaire today and gave him a reasonable income in the final decade of his life.

Captain James Cook used K1, a copy of H4, on his second and third voyage, having used the lunar distance method on the first. His log is full of praise for the watch and the charts of the South Pacific he made using the watch were remarkably accurate. K2 was loaned to Lt. William Bligh, commander of the HMS Bounty, but was retained by Fletcher Christian following the infamous mutiny. It was recovered from Pitcairn Island until 1808 and then made its way through several hands until reaching the National Maritime Museum in London. 

While the Lunar Distances method would complement and even rival the marine chronometer initially, Harrison’s chronometer would overtake it in the nineteenth century. The more accurate Harrison timepiece led to the much-needed calculation of longitude, making it fundamental to the modern age. By the early nineteenth century, navigation at sea without one was considered unwise or even unthinkable. Using a chronometer to aid navigation simply saved lives and ships–the insurance industry, self-interest, and common sense did the rest in making the device a universal tool of maritime trade. 

Harrison died on March 24, 1776, at the age of 82, just shy of his eighty-third birthday. He was buried in the graveyard of St. John’s Church in Hampstead, in north London, along with his second wife Elizabeth and later his son William. His tomb was restored in 1879 by the Worshipful Company of Clockmakers, even though Harrison had never been a member. On March 24, 2006, a memorial tablet to Harrison was unveiled in Westminster Abbey, finally giving him the recognition he deserves. The memorial shows a meridian line in two metals to highlight his most widespread invention, the bimetallic strip thermometer. The strip is engraved with its own longitude of 0 degrees, 7 minutes, and 35 seconds West. On April 3, 2018, Google celebrated his 325th birthday by making a Google Doodle for its homepage. Harrison came in 39th in the BBC’s 2002 public poll of the 100 Greatest Britons. 

After World War I, Harrison’s chronometers were rediscovered at the Royal Greenwich Observatory by retired naval officer Lieutenant Commander Rupert T. Gould. They were in a highly decrepit state and Gould spent many years documenting, repairing and restoring them. He was the first to designate them from H1 to H5. Even though Gould made modifications and repairs that would not meet today’s standards of museum conservation, he is credited with having ensured that they survived as working mechanisms to this day. He also wrote a book, The Marine Chronometer, which remains the authoritative work on the subject. In 1995, Dava Sobel wrote a book on Harrison’s work entitled Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time became the first popular bestseller on the topic of horology. 

Today, H1, H2, H3, and H4 can be seen on display in the Royal Observatory at Greenwich. H1, H2 and  H3 still actually work. H4 is kept in a stopped state due to the fact that, unlike the first three, it requires lubrication and so would degrade as it runs. H5 is owned by the Worshipful Company of Clockmakers and since 2015 has been on display at the Science Museum in London.

One of the controversial claims that he made was that of being able to build a clock more accurate than any competing design. He also claimed to have designed a clock capable of keeping accurate time to within one second over a span of 100 days. He was ridiculed at the time for having made an outlandish claim. He had drawn a design but had never built the clock himself. But in 1970, Martin Burgess, a Harrison expert and a clockmaker himself, endeavoured to build the clock as designed. He studied the plans and built two versions that were dubbed Clock A and Clock B. Clock A became the Gurney Clock which was given to the city of Norwich in 1975, while Clock B lay unfinished in his workshop until it was acquired in 2009 by Donald Saff. The completed Clock B was submitted to the National Maritime Museum in Greenwich for further study. It was found that the clock could potentially meet Harrison’s claim. So the clock’s design was carefully checked and adjusted. Finally, over a 100 day period from January 6 to April 17, 2015, the clock was secured in a transparent case in the Royal Observatory and left to run untouched, apart from regular winding. Upon the completion of its run, it was found to have lost only ⅝ of a second, meaning that Harrison’s design was fundamentally sound. If we ignore the fact that it used materials unavailable had it been built in 1762, and run continuously since then without correction, it would, as of today, be slow by just nine minutes and 51 seconds. The Guinness Book of World Records has declared this clock to be the “most accurate mechanical clock with a pendulum swinging in free air.”

It’s a testament to a true mechanical genius and one that deserves to be more well-known.