John Harrison


John Harrison (Foulby, March 24, 1693 – March 24, 1776) was an English watchmaker, famous for having designed and put into operation the first high-precision marine chronometer, with which it was possible to determine the longitude accurately when long distances had been traveled. His main merit is to have solved the problem of longitude by using chronometers built by himself.

Few details are known of Harrison”s early years. It is known that he was born in Foulby, (Yorkshire), on March 24, 1693, being the first of the five siblings that there would eventually be in the family. John was the son of a humble carpenter and it is not surprising that already from the beginnings of his youth he showed serious indications of his great ability in building and understanding the operation of different machinery. Some biographers say that during an attack of smallpox at the age of six he had to stay in bed, and during this time he devoted himself to investigate and design clockwork mechanisms, researching a real machinery. Many authors put the story in doubt due to the humble character of Harrison”s family (clocks were very expensive and very scarce pieces).

The first watch

It can be said that for the first thirty years of his life he was a humble carpenter who went completely unnoticed. He finished his first pendulum clock in 1713 (before his twentieth birthday), and it is not known how he was able to get into such a project, let alone what previous knowledge he applied. This first clock can be seen today in a display case in the museum of the “Most Excellent Guild of Clockmakers” in Guildhall (London). The uniqueness of this clock is not that it was John”s first but that it was built entirely of oak and boxwood. Harrison later built two other wooden clocks, in 1715 and 1717.

The family

In 1718 he married Elizabeth Barrel “La Tifon” (10 years younger than him) and the following summer their first son was born. After this period of happiness his wife fell ill and died shortly after his son”s seventh birthday. After six months he remarried Elizabeth Scott, with whom he had two children: William, born in 1728, who was to be one of his staunchest supporters, and Elizabeth, born in 1732, of whom little is known except the date of her birth. His eldest son, born of his marriage to Elizabeth Barrel, died shortly after his 18th birthday.

Period as associate watchmaker

During the period from 1725 to 1727 he partnered with his brother James and they built case and grandfather clocks, almost all signed James, although there is no watchmaker today who has the slightest doubt about the actual authorship of these clocks. In this period Harrison invented the grill pendulums and the grasshopper escapement. In the first invention, the name of the grill comes from the frame shape of the pendulum that is composed of several parallel strips of different metals that manage to compensate for the dilatations caused by temperature changes; the final arrangement of the pendulum reminds that of a grill for roasting meat. The grasshopper escapement is named after the movements of the insect”s hind legs. The Harrison brothers spent their evenings checking the accuracy of their machines against the passing of the stars over the profiles of Barrow”s buildings, and mention that these clocks never made an error of more than one second (by way of comparison, the best pocket watches of the time were several dozen minutes late per day).

The problem of length

How the existence of the longitude problem could have come to Harrison is not known. It is quite possible that he heard it from a sailor in the nearby port of Hull, and it is also quite possible that he believed in his ability to solve it. By 1720 Harrison was already a famous clockmaker and Charles Pelham hired him to build a clock on the tower of his house in Brocklesby Park (this clock works today). The unusual thing about this clock is that it contains all the beginnings and trials of what would eventually become his most famous chronometers, capable of solving the problem of longitude.

Harrison was soon able to observe that there was little to increase the accuracy of a pendulum when it was subjected to the swaying of a ship sailing in a storm; he had to forget the idea of using pendulums. Harrison devised a plan and laid it before the Board of Longitude in London in 1730. By this time this institution was 15 years old and was constantly receiving mediocre and uninteresting applications. In London he visited Halley and later the watchmaker George Graham, who became his patron.

The famous series of watches

A conversation with watchmaker and instrumentalist George Graham catapulted Harrison into a series of technical trials on variants of clockwork machinery. It took him five years to come up with a design he briefly called H-1 (Harrison First), which ran on wooden gearwheels and looked unlike any watch ever seen before. The Harrison brothers made a trip down the Humber River to check that it was working properly and in 1735 it was delivered to George Graham, a sea expedition was called to Lisbon to test the accuracy of the machine and finally on June 30, 1737 the Council met (for the first time in 23 years) to examine the machinery. Harrison, instead of terminating his work, asked for more funds.

In 1741 he presented another machine to the Council: the H-2, and it was Harrison himself who convinced the members that his work was not finished, so this machine did not go to sea. Harrison returned to his work, trying to improve with an improved version of the H-2.

Harrison, then 48 years old and living in London, locked himself in his workshop and was hardly heard from during the twenty years it took him to build the H-3. No one can explain that it took him two years to build a tower clock (when he had hardly any experience), that in nine years he built two innovative clocks and that he spent nearly 20 years on the H-3. It should not be forgotten that during this time of construction of the H-3, his son William, a teenager, may well have helped him.

There was one more clock in the series, the penultimate, the H-4 of 1760, the smallest of the series. The Council determined in that same year to make the maritime tests of both watches (the H-3 and the H-4) in a sea voyage in which his son William and the two watches would go to Jamaica. The H-4 was only five seconds late after eighty days at sea. On returning from the voyage, the watch met the expectations set by the Council, but there were last minute problems that called into question the checks made in Jamaica by William.

Another test was proposed: in 1764 they set sail for Barbados and again successfully passed the tests. The Council was slow to accept the data from this second voyage, but in the meantime, other expeditions (including that of Captain James Cook) followed one after the other, all of them with very successful results.

End of story

While awaiting the Board”s decision, Harrison began the design of his latest watch, the H-5. In those days he considered himself hostage to the Board for the numerous and unjustified refusals to grant him the agreed award, and felt that after three years of complaints he had had enough, since he felt “Extremely hurt at being used by gentlemen from whom better treatment might have been expected.”

Consequently, while the first example of the H-5 was being tested on the high seas, he decided to build a second example of the new chronometer, which he presented to King George III to request his help. After an audience with his son William, who explained the situation of his father and his watches, the King was extremely annoyed with the attitude of the Board of Longitude. He personally tested the second specimen of the H-5 at the palace, and after ten weeks of daily observations (between May and July 1772), the chronometer showed an accuracy of one-third of a second per day. George III then advised Parliament that the full award should be given to Harrison, after threatening to appear before the chamber to personally reprimand the parliamentarians. Finally, on April 24, 1773, when he was already 80 years old, Harrison received from Parliament an award rewarding his achievements in the amount of 8,750 pounds; added to the 10,000 pounds previously received for revealing the workings of his machine, almost equaling the initial reward but not getting the official prize (which was never awarded to anyone). He only survived for three more years.

Harrison”s work is scattered in the showcases of various museums in England. He also left some small written works, of lesser interest. But his main effort was concentrated on the construction of an accurate and robust clock.


This 34 kg watch was the first in the series of chronometers capable of competing and challenging the requirements of the longitude problem. The watch has four dials: one for the hours, one for the minutes, the third for the seconds and the fourth for the day of the week. The watch is not signed.

Protected by a 122 cm side glass case, today it is kept in the National Maritime Museum in London. It works properly, winding it up daily.


This bronze clock weighed 39 kilos and was of smaller proportions than its predecessor. It passed the rigorous tests conducted by the Royal Society in 1741-1742.


It is the lightest of Harrison”s first three marine chronometers: it weighs about 27 kg (seven less than the H-1) and has 753 internal parts. You can see from the design that he wanted to decrease the size of the instrument.


Tiny watch, compared to the previous ones, 127 mm in diameter and very light (1360 g), it represents one of the first portable watches with an acceptable accuracy (1 s per day) for the time. It is signed by John Harrison and his son, and he himself dates it to 1759. In this watch, he used a mysterious combination of rubies and diamonds as the axle-securing device. The H-4 currently resides immobile in the showcases of the Maritime Museum in London due to the improper treatment to which its machinery was subjected by researchers of the past, but when it is wound the energy lasts thirty hours.


Harrison developed the H-5 model with a design very similar to the H-4, simplifying some mechanical aspects to increase reliability. Today, the H-5 is owned by the Worshipful Company of Clockmakers of London and is on display at the en:Clockmakers” Museum in London as part of the institution”s collection. Since 2015 the collection has been on display at the Science Museum in London.


  1. John Harrison
  2. John Harrison
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