John Harrison, the world's first marine chronometer, H1, H2, H3, H4

feature	Description
inhibition	Highly developed balance wheel with spring-loaded compensation balance
balance spring	Spiral shape with temperature compensation (bimetal)
Power reserve	approximately 30 hours
Stone storage	Rubies for friction reduction
Gear adjustment	Fine adjustment mechanism via micrometer screw
Percussion mechanism / drive	Spring balancer with chain & worm gear (Fusée) – uniform torque

feature	H4
Year	Completed in 1759
diameter	approx. 13 cm
Gait deviation	~ 1 second/day
Meaning	First portable, seaworthy chronometer
Place today	Royal Observatory Greenwich
inventor	John Harrison (1693–1776)

 

In 1714, the English Parliament offered a high reward of 20,000 pounds sterling to anyone who could invent a suitable measuring instrument to accurately determine geographical longitude, as the major problem was still timekeeping and determining position at sea.

With the help of optical instruments, local time could long be calculated from the measured altitude of the sun or stars. However, the ship's position could not be determined from local time alone. For example, the latitude could be determined from the sun's midday altitude, but not the longitude.

The " Board of Longitude " commission was established to manage the prize money and to evaluate submitted proposals.

Harrison's first marine chronometer, H1, was completed in 1735 and stood 54 cm tall, weighing 33 kilograms. In this early model, temperature fluctuations were compensated for by a bimetallic strip. Ship movements were balanced by connecting two identical pendulums with a spring, an imitation of the cross-beat principle.

A test voyage from May 19th to May 26th , 1736 , saw Harrison sail to Lisbon and back on the ship "Centurion." This voyage demonstrated a far higher level of accuracy than required to win the prize. However, the duration of the journey did not meet the competition's requirements. Furthermore, Harrison, a layman in science, was judging a panel of experts.

Harrison moved to London with his brother in 1737. Two further models, named H2 and H3, of similar design and size, followed, but these were never tested on a ship. John and James Harrison worked together to build the H2 (66 cm high) until 1739. The brothers then parted ways. Harrison alone developed the H3 (53 cm high). He hoped to complete it within two years, but did not apply for testing until 1760.

Harrison was now using jewel bearings with lubricants and bimetallic compensation. It was only with the H4 , which, at just under 13 cm in diameter, was also considerably smaller than its predecessors, that he finally achieved his breakthrough. On a voyage to Jamaica, it lost only 5.1 seconds in 81 days.

Rejection of his inventions and belated satisfaction

The commission remained critical and refused to pay Harrison the prize money. Instead, he had to disassemble the watch and explain it before the panel. He was also compelled to hand over his construction drawings, which another watchmaker could use to recreate the model. This commission went to watchmaker Larcum Kendall , who then copied the H4.

Harrison had to build his next model, the H5 , without his earlier original plans. With the help of his son William , he succeeded in producing an even further improved version. Only after King George III personally tested the instrument and championed it did Harrison receive the well-deserved prize money and recognition from the Board of Longitude , just a few years before his death.

John Harrison died on March 24 , 1776 in London .

Original text of the biography of John Harrison in the Encyclopedia of Watchmaking

John Harrison was a brilliant technician who became a self-taught watchmaker, born in Foulby near Pontefract, in the county of York, in 1693. He learned the trade of his father, who was a carpenter but also repaired clocks, surveyed land and engaged in various other mechanical tasks.

From childhood, young Harrison took great pleasure in machines driven by gears, and he eagerly seized every opportunity to learn more about them, often spending entire nights writing and drawing.

It proved very advantageous for him that his father moved to Barrow in Lincoln County in 1700, where a neighboring clergyman took the eager boy under his wing. From him, he received a notebook transcribed from Saunderson's lectures, which he meticulously copied along with the figures it contained and studied diligently. He thus perfected his skills in watchmaking to such an extent that he could present himself as an inventor in the field.

Harrison's clocks initially featured wooden wheels that operated without lubrication. He invented the rust pendulum (a temperature compensation mechanism), the Grasshopper escapement, bearings that functioned without lubrication, the auxiliary spring to keep the movement running while winding, and many other improvements to grandfather and pocket watches.

In 1726, he had crafted two pendulum clocks incorporating his invention of temperature compensation (rust pendulum) and the Grasshopper escapement. These clocks surpassed all previous achievements in accuracy for stationary clocks. Their rate deviation over the course of a month was barely more than one second.

Harrison now sought to achieve a similar level of perfection in marine chronometers by compensating for the ship's movements and fluctuating temperatures. He hoped this would lead to a solution to the longitude problem (i.e., determining longitude during a sea voyage), presumably also because a huge prize had been offered for solving this problem.

In 1714, Parliament offered a prize of 20,000 pounds sterling for the invention of a solution that would allow a ship's longitude to be determined to within half a degree, or 30 English nautical miles, on a sea voyage yet to be determined. 15,000 shillings (20,000 pounds) would be awarded to the person whose strategy could accurately determine the longitude to within 40 nautical miles, and 10,000 shillings to the person whose strategy could accurately determine the longitude to within 60 nautical miles.

Alongside many ideas that seem crazy from today's perspective, the scientific establishment at the time favored astronomical solutions, which, however, were highly dependent on weather and mathematically extremely complex, and could not yet be calculated (lunar distances). Driven by the idea that longitude could be determined at sea using a very precise clock, Harrison designed such a mechanism.

After drawing up a design for what he believed to be a marine chronometer for determining longitude, he traveled to London in 1728, hoping to obtain support from the Board of Longitude for the construction of such a machine. When he approached Edmund Halley, the Astronomer Royal at the time, with his ideas, Halley referred him to G. Graham (a clockmaker), who, fascinated by Harrison's ideas, advised him to build his chronometer before submitting anything about it.

He returned home and did not return to London until 1735 with his first completed marine chronometer. To have this chronometer tested, Harrison had to take it on a sea voyage to Lisbon the following year. Since the excellence of his invention was evident on this voyage, Halley, Graham, Bradley, and Smith could not withhold their highest praise. He received preliminary support in 1737.

Two years later, he presented a second, simplified and improved marine clock to the Board of Longitude, and in 1741 a third, smaller, even simpler and more perfect one, in which the greatest error in timekeeping was only 3 to 4 seconds per week. In 1749, the Royal Society awarded him the Copley Medal, which was given to the person who had made the most useful invention or discovery during the year.

At the same time, the Society earnestly recommended him to the commissioners of the Board of Longitude. Although Harrison did not believe he could improve his marine chronometer to any greater degree, he continued working on his invention. A pocket watch he had made for himself in 1753 by John Jefferys in London , which proved surprisingly accurate, prompted Harrison to pursue a completely new approach. He completed the improvements to his third chronometer and incorporated all his research findings into this new timepiece.

To maintain constant spring tension, a remotoir was installed, which winds the clock every 7 1/2 seconds. The escapement is a heavily modified verge escapement; the crown wheel has 15 teeth, and the pallets are made of diamond. The bearings are made of rubies, and the endstones of the cap jewels are made of diamond. Harrison completed this clock, now called the H4, in 1761; it has the form of a large pocket watch, approximately 6 inches in diameter.

This fourth clock combined all the advantages of the previous ones and surpassed them. It only needed cleaning every three years and kept time regardless of its position. Its inventor preferred to call it the 'timekeeper', and it was given to a ship sailing to Jamaica by the 'Board of Longitude' for testing.

Despite the fact that this examination was entirely in Harrison's favor, he still received only a portion of the prize stipulated by the Act of Parliament of 1714. To be absolutely certain, the Board of Longitude requested that the Duke of Nivernais, then the French ambassador to the court in London, bring in two commissioners from Paris to participate in the examination.

Camus and Ferdinand Berthoud were chosen for this task; they were joined by Lalande, who was in London at the time. All three could not help but admire Harrison's genius and wealth of resources. Nevertheless, the members of the Board of Longitude feared reproaches from Parliament if they now allowed the full prize money to be paid out;

Therefore, in 1764, they arranged for the inventor's son, William Harrison, who had also accompanied the clock on the voyage to Jamaica, to undertake a second journey with it to Barbary. On this voyage, the ingenious machine once again fully proved its excellence, demonstrating greater accuracy than required by the Act of Parliament. Harrison was then further required to provide the commissioners of the Board of Longitude with a detailed description of his clock and to enable another clockmaker to produce a similar machine. Both of these requirements were met, and Harrison finally received the remainder of the principal prize in full.

It was high time, for Harrison had already reached the age of 75 and, due to the many difficulties he had faced, was filled with bitterness towards humanity. Two years later, he contracted gout, and on March 24, 1776, he died of old age at the age of 83. His three earlier marine chronometers (also called marine or ship's chronometers), made before the invention of the true 'timekeeper', are preserved as historically significant artifacts in the Royal Observatory at Greenwich.

Source: Watchwiki, AI