John Harrison facts for kids

Quick facts for kids John Harrison
Thomas King's 1767 portrait of John Harrison, located at the Science and Society Picture Library, London
Born	3 April [O.S. 24 March] 1693 Foulby, near Wakefield, West Riding of Yorkshire, England
Died	24 March 1776(1776-03-24) (aged 82) London, England
Nationality	English
Known for	Bimetallic strip Gridiron pendulum Grasshopper escapement Longitude by chronometer Marine chronometer
Awards	Copley Medal (1749) Longitude rewards (1737 & 1773)
Scientific career
Fields	Horology & Carpentry

John Harrison (born April 3, 1693 – died March 24, 1776) was a super clever English carpenter and clockmaker. He taught himself everything he knew! He invented the marine chronometer, which is a special clock that could keep perfect time at sea. This invention solved a huge problem: how to figure out a ship's exact east-west position, called longitude, while sailing.

Harrison's amazing invention changed navigation forever. It made long sea journeys much safer. Before him, many ships got lost or crashed because they couldn't tell their exact location. This problem was so important that the British government offered a huge prize of up to £20,000 (a massive amount of money back then!) to anyone who could solve it. This prize was part of the 1714 Longitude Act. Even though Harrison solved the problem, he had a tough time getting the full prize because of some political issues.

Harrison showed his first design in 1730. He spent many years making better versions, creating new technologies for keeping time. He eventually focused on what he called "sea watches." The Board of Longitude helped him by supporting his work and testing his designs. Towards the end of his life, he finally got the recognition and money he deserved from Parliament. In 2002, a BBC poll even named him one of the 100 Greatest Britons.

Early Life and Clever Inventions

John Harrison was born in Foulby, a small village in Yorkshire, England. He was the first of five children. His stepfather was a carpenter at a nearby estate called Nostell Priory.

Around 1700, John's family moved to Barrow upon Humber. John followed in his father's footsteps as a carpenter. In his free time, he loved to build and fix clocks. There's a story that when he was six, he had smallpox and was given a watch to play with. He spent hours listening to it and studying its tiny moving parts. This showed his early fascination with how things worked!

He also loved music and became the choirmaster for the church in Barrow.

A drawing of the inside of an old English longcase (grandfather) clock.

John built his first tall clock in 1713 when he was 20. The whole inside of the clock was made of wood! Three of his early wooden clocks still exist today. One is in the Science Museum in London, another is also there, and a third is at Nostell Priory in Yorkshire. The Nostell clock even has clear sides so you can see the wooden gears working!

John Harrison got married twice. First to Elizabeth Barret in 1718, and after she passed away, he married Elizabeth Scott in 1726.

In the early 1720s, Harrison was asked to build a new turret clock for a place called Brocklesby Park. This clock still works today! Like his other clocks, it had wooden parts made from oak and lignum vitae. But this clock also had new features to keep time even better, like the grasshopper escapement. This was a special part that helped control the clock's movement.

Between 1725 and 1728, John and his brother James, who was also a skilled carpenter, made at least three very accurate tall clocks. These clocks also used wooden parts. During this time, John invented the gridiron pendulum. This pendulum was made of different metals (brass and iron) that expanded and shrunk in opposite ways when the temperature changed. This meant the pendulum stayed the same length, making the clock much more accurate! Many people think these clocks were the most accurate in the world at that time.

Harrison was a genius at improving clocks. He also invented the "grasshopper escapement." This part helped release the clock's power step-by-step. It had almost no friction and didn't need oil, which was a big deal because oils back then weren't very good and could mess up the clock.

A famous clockmaker named George Graham helped Harrison a lot with money and advice. The Astronomer Royal, Edmond Halley, introduced them. This support was very important for Harrison, as he sometimes found it hard to explain his ideas clearly.

The Big Problem: Finding Longitude

Longitude lines on the globe

Imagine a map of the Earth with lines going from the North Pole to the South Pole. These lines are called longitude lines. They tell you how far east or west a place is from a special starting line called the prime meridian. Knowing your longitude was super important for sailors, especially when they were close to land. If they didn't know their exact east-west position, they could easily crash their ship after a long journey. In Harrison's time, trade and sailing were growing fast, so avoiding shipwrecks was a huge deal!

Many ideas were suggested to find longitude at sea. One common idea was to compare the local time on the ship with the known time at a reference place, like Greenwich in England. This meant you needed a clock that could keep perfect time, no matter what.

Harrison decided to solve the problem directly by building a super reliable clock. But this was incredibly difficult! The clock had to work perfectly even with changes in temperature, pressure, or humidity. It also had to stay accurate for a long time, resist salty air, and keep ticking on a constantly moving ship. Many smart scientists, like Isaac Newton, thought it was impossible to build such a clock. They preferred other methods, like using the moon's position.

Harrison's First Sea Clocks

Henry Sully's clock (Fig.1) with its special parts and how it was hung on a ship (Fig.7).

Before Harrison, another clockmaker named Henry Sully tried to make a clock for finding longitude in the 1720s. His clock worked well only when the sea was calm. Harrison's clocks, though much bigger, were similar in some ways.

In 1730, Harrison designed his own sea clock to try for the Longitude prize. He went to London to get help with money. He showed his ideas to Edmond Halley, who then sent him to George Graham, a top clockmaker. Graham was so impressed that he lent Harrison money to build a model of his "Sea clock." Harrison used wooden wheels and his special "grasshopper" escapement. Instead of a pendulum, he used two linked weights that swung back and forth.

It took Harrison five years to build his first sea clock, known as H1. He showed it to members of the Royal Society, who told the Board of Longitude about it. The Board thought it was good enough for a real test at sea. In 1736, Harrison sailed to Lisbon on a ship called HMS Centurion.

The clock lost some time on the way there, but it worked very well on the way back! The captain and sailing master of the ship praised Harrison's design. The master said his own calculations had put the ship 60 miles off course, but Harrison's clock had correctly predicted their true location.

This wasn't the long trip across the Atlantic that the Board wanted, but they were impressed. They gave Harrison £500 to keep working. By 1737, Harrison had moved to London and started building H2, a smaller and stronger version. By 1741, H2 was ready. But Britain was at war, and the clock was too important to risk it falling into enemy hands. Harrison then stopped working on H2 because he found a big problem with its design. He realized that the ship's movements could affect the clock's accuracy. This made him decide to use round balance wheels in his next clock, H3.

The Board gave him another £500, and Harrison spent 17 years working on H3. Even with all his effort, H3 didn't work exactly as he wanted. The problem was that Harrison didn't fully understand how the springs in the clock worked, which affected its accuracy. However, building H3 taught him a lot. He invented two important things during this time: the bimetallic strip (used in thermometers) and the roller bearing (used to make things move smoothly).

The Amazing Sea Watches