John Harrison (watchmaker)

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John Harrison

John Harrison (born March 24 . Jul / 3. April  1693 greg. In Foulby in Wakefield , Yorkshire , † 24 March 1776 in London ) was an English carpenter , inventor and self-taught watchmaker .

He solved the so-called length problem , for which England had offered a high price in 1714 , by developing a watch suitable for ships with high accuracy . For the first time, his clocks enabled precise mechanical time measurements and thus the precise determination of longitude at sea.

Life

Little is known about John Harrison's early life. He was the oldest of five children. In his youth he learned the carpentry trade from his father.

In 1713, when Harrison was just under 20, he constructed his first pendulum clock , which can still be seen in the exhibition rooms of the Worshipful Company of Clockmakers in Guildhall . The reason for building the clock and the question of where he obtained the necessary knowledge from are unclear. In 1715 and 1717 he built two very similar pendulum clocks.

In 1718 he married Elizabeth Barrel (1693-1726), with whom he had a son. After the death of his wife, Harrison married Elizabeth Scott (approx. 1702–1777) in 1726, with whom he had two other children.

Animation of the Grasshopper escapement

Between 1725 and 1727 Harrison constructed two large grandfather clocks together with his brother . He introduced important innovations such as the Grasshopper escapement and the rust pendulum . As a result, they achieved an enormous accuracy for the time (about one second deviation per month).

From 1727 John Harrison began to deal with the construction of ship clocks and the associated length problem.

The length problem

While the geographical latitude can be determined relatively easily with sufficient accuracy for seafaring, it is far more difficult to determine the longitude with a similar accuracy.

The English Parliament had in 1714 up to 20,000 pounds prize money for a workable solution to the length problem awarded. The prize money was graded according to the accuracy of the submitted method. It was not until a decade after the prize money was published that John Harrison dealt with this topic, which would stay with him until the end of his life. So far, no practical solutions have been found using astronomical navigation . To evaluate submitted proposals and the administration of funds that had long Commission ( Board of Longitude ) been established.

Harrison's vision

Well-known astronomers all over Europe tried to find astronomical solutions, in particular the lunar distance method, in which the angular distance of the moon to bright fixed stars in the vicinity of its orbit is determined. The astronomical approach was based on tables of star coverages , which at that time were sufficiently precisely calculable, but required the visibility of the moon and were difficult to use.

John Harrison, however, relied on clocks that were sufficiently accurate.

Harrison built his first pendulum clock with a wooden wheel train in 1713 and later, as the first important invention, compensated for the temperature dependence of the pendulum: a grid made of two types of metal rods with different thermal expansion ( steel and brass ) prevented the total length of the pendulum from changing in the event of temperature fluctuations.

He had achieved low-friction running of his grandfather clocks with his Grasshopper escapement , and lubrication-free wooden gears avoided deviations caused by resinifying oil. Checks by measuring star passages have shown the reduction of previous inaccuracies to less than a tenth.

After that, he wanted to design similarly accurate clocks for ships : he presented his concept in 1728, and his first model in 1735. He compensated for temperature fluctuations with bimetal and ship movements by connecting two identical pendulums with a spring (in the first draft) .

The chronometer was at the beginning of the journey to the solar time of known longitude, namely the Greenwich meridian , adjusted. The geographical longitude could be calculated with sufficient accuracy from the time difference between the displayed time and the local time determined (by bearing the sun or stars) - provided that the time was approximately to the second.

Successful tests

H1

A test drive with the first model developed by Harrison, today called the H1 , to Lisbon and back showed far greater accuracy than required for obtaining the price, but the duration of the journey did not meet the conditions of the tender.

Above all, Harrison, as a scientific layman , faced a learned body. That delayed the adoption of his idea for decades. Especially Sir Nevil Maskelyne (1732-1811), from 1765 court astronomer of the English royal family , relied on longitude determination with the lunar distance method until the end and changed the interpretation of the tender to Harrison's disadvantage.

H2

Harrison received just enough money from the stock of the length commission for an improved model H2 (1737), later for the ball-bearing H3 . Neither of these two watches was tested because England was at war with Spain and no one wanted to let such a device fall into enemy hands.

The groundbreaking model 4

H3
H4

A pocket watch , which he had made for himself by John Jefferys in London in 1753 and which was surprisingly accurate, moved Harrison to a completely new concept: He broke off the further development of the H3 and in 1759 presented a fourth model, with a diameter of 13 cm and 1.45 kg in weight far smaller and lighter than any of his previous pieces. A newly developed drive mechanism (remontoir d'égalité) was essential for the accuracy of the H4 . The principle is still used today in mechanical chronometers.

Fight for the prize money

On the 81-day trip to Jamaica, the H4 only showed a gear deviation of 5 seconds. Overall, it showed a deviation of 1 minute and 54.5 seconds when returning to England. However, its accuracy was suspected by critics as "accidental". Harrison was forced to dismantle and explain the watch and hand over construction drawings in front of the commission. Another watchmaker was supposed to use it to produce another copy of the same model (originally two were required). Harrison had received £ 10,000 in 1765 after addressing Parliament. He was allowed to suggest a specialist for the replica and decided on the London watchmaker Larcum Kendall , who had already helped him with the manufacture of his instruments.

H5

Harrison himself, already at an advanced age, had to build his next model without his original plans, but in collaboration with his son William he created another improved example, the H5 . After an audience with George III. the king personally tested the device. He expressed great satisfaction and stood up for Harrison on the commission; Nevertheless, the model was not recognized by the Board of Longitude . It was only after the King threatened to appear before Parliament in person that Harrison was granted an additional £ 8,750 in 1773, three years before his death.

John Harrison's tombstone

Length problem solved

It was not until James Cook returned from his second world tour on July 30, 1775 and confirmed the quality of the K1 , Kendall's exact copy of the H4, that most astronomers considered the problem of length to be solved.

The original of the H4 was out of the question for this trip due to the tests and the multiple dismantling. Three other watches hadn't been able to cope with the stresses of the trip. In the logbook , the initially skeptical Cook names Kendall's work (i.e. Harrison's invention) his never-failing guide . Harrison saw his vision come true eight months before his death. In 1959, the UK Antarctic Place-Names Committee named the Harrison Passage in Antarctica after him in memory of Harrison's accomplishments .

Development of the ship chronometer

A little later, skilled watchmakers developed cheaper watches that did the same thing. While the K1 (the copy of the H4) cost £ 500, then around 30% of the value of a smaller ship, watchmakers John Arnold and Thomas Earnshaw managed to simplify production to such an extent that chronometers came to around £ 70 by 1790. It wasn't until 1840 that every Royal Navy ship was equipped with a chronometer.

Harrison's great merit was to have proven that clocks with a rate uncertainty of a few seconds per day are technically feasible, which had been disputed until then (for example by Isaac Newton ).

The designations H1 to H5 date from around 1923. They were coined by Lieutenant-Commander Rupert Gould , who, in the course of researching his book The Marine Chronometer, its History and Development, rediscovered and repairs the disregarded instruments H1 to H4 in a storage room sat. They have since been in working order and as part of the collections of the Royal Observatory in the National Maritime Museum , Greenwich . They are exhibited in the Royal Observatory , which has marked the prime meridian since 1738 (worldwide: 1884) . H5 is owned by the London watchmakers' guild and as part of the Georg III collections. housed in the Science Museum .

motion pictures

Film documentaries

See also

literature

  • Joan Dash: The Hunt for Longitude. From the American by Tamara Willmann. Bertelsmann, Munich 2004, ISBN 3-570-12717-6 .
  • Philippe Despoix: Measure the world. Dispositive of the journey of discovery in the Age of Enlightenment. Translated from the French by Guido Goerlitz. Wallstein-Verlag, Göttingen 2009, ISBN 978-3-8353-0485-7 .
  • Rupert T. Gould: John Harrison and his Timekeepers. In: Mariner's Mirror. Vol. 21, No. 2, 1935, ISSN  0025-3359 , pp. 115-139, doi : 10.1080 / 00253359.1935.10658708 .
  • Rupert T. Gould: The Marine Chronometer. Its history and development. Potter, London 1923.
  • Dava Sobel , William JH Andrewes: Longitude - the illustrated edition. The true story of a lonely genius who solved the greatest scientific problem of his time . From the American by Matthias Fienbork and Dirk Muelder. Berlin-Verlag, Berlin 2010, ISBN 978-3-8270-0970-8 (English, original title: The illustrated Longitude. ).

Web links

Commons : John Harrison  - Collection of Images, Videos and Audio Files

Individual evidence

  1. ↑ The importance and economic scope of the problem can be estimated from the fact that a simple worker at that time earned around 10 pounds a year and a medium-sized seagoing ship cost around 2000 pounds. The prize money would now correspond to a larger double-digit million amount.
  2. ↑ Dava Sobel , William JH Andrewes: Longitude - the illustrated edition. The true story of a lonely genius who solved the greatest scientific problem of his time . From the American by Matthias Fienbork and Dirk Muelder. Berlin-Verlag, Berlin 2010, ISBN 978-3-8270-0970-8 , pp. 149 (English, original title: The illustrated Longitude. ).
personal data
SURNAME Harrison, John
BRIEF DESCRIPTION English watchmaker, inventor of the Grasshopper escapement and temperature compensation
DATE OF BIRTH April 3, 1693
PLACE OF BIRTH Foulby near Wakefield , Yorkshire
DATE OF DEATH March 24, 1776
Place of death London