Invented the tools and methodology to
determine a ship's longitude
while at sea
Born: March 24, 1693
Died: March 24, 1776
The Longitude problem
"Whereas, in order to the finding out of the
longitude of places for perfecting navigation and
astronomy, we have resolved to build a small
observatory within Our Park at Greenwich..."
King Charles II
For every 15° that one travels eastward, the local time
moves one hour ahead. Similarly, travelling West, the
local time moves back one hour for every 15° of
Therefore, if we know the local times at two points
on Earth, we can use the difference between them to
calculate how far apart those places are in longitude,
east or west.
Royal Observatory, Greenwich
This idea was very important to sailors and
navigators in the 17th century. They could measure the
local time, wherever they were, by observing the Sun,
but navigation required that they also know the time at
some reference point, e.g. Greenwich, in order to
calculate their longitude. Although accurate pendulum
clocks existed in the 17th century, the motions of a
ship and changes in humidity and temperature would
prevent such a clock from keeping accurate time at sea.
King Charles II founded the Royal Observatory in 1675
to solve the problem of finding longitude at sea. If an
accurate catalogue of the positions of the stars could
be made, and the position of the Moon then measured
accurately relative to the stars, the Moon's motion
could be used as a natural clock to calculate Greenwich
Time. Sailors at sea could measure the Moon's position
relative to bright stars and use tables of the Moon's
position, compiled at the Royal Observatory, to
calculate the time at Greenwich. This means of finding
Longitude was known as the 'Lunar Distance Method'.
In 1714, the British Government offered, by Act of
Parliament, £20,000 for a solution which could provide
longitude to within half-a-degree (2 minutes of time).
The methods would be tested on a ship, sailing...
"over the ocean, from Great Britain to any such
Port in the West Indies as those Commisioners
Choose... without losing their Longitude beyond the
limits before mentioned...and should prove to be...tried and found Practicable and Useful at Sea."
A body known as the Board of Longitude was set up to
administer and judge the longitude prize. They received
more than a few weird and wonderful suggestions. Like
squaring the circle or inventing a perpetual motion
machine, the phrase 'finding the longitude' became a
sort of catchphrase for the pursuits of fools and
lunatics. Many people believed that the problem simply
could not be solved.
John Harrison (1693-1776)
The longitude problem was eventually solved by a working
class joiner from Lincolnshire with little formal
education. John Harrison took on the scientific and
academic establishment of his time and won the longitude
prize through extraordinary mechanical insight, talent
Harrison was born in Foulby, near Wakefield, in
Yorkshire in 1693 but his family moved to Barrow, in
Lincolnshire, when he was quite young. His father was a
carpenter and John followed in the family trade. He
built his first longcase clock in 1713, at the age of
20. The mechanism was made entirely from wood, which was
not a curious choice of material for a joiner. Three of
Harrison's early wooden clocks have survived; the first
(1713) is in London, at the Worshipful Company of
Clockmakers' Collection in Guildhall;. the second
(1715), is in the Science Museum; the third (1717) is at
Nostell Priory in Yorkshire.
He married his first wife, Elizabeth, in 1718. She
died just eight years later and he remarried within six
months, to another Elizabeth.
During the latter part of his early career, he worked
with his younger brother James. Their first major
project was a revolutionary turret clock for the stables
at Brocklesby Park, seat of the Pelham family. The clock
was revolutionary because it required no lubrication.
18th century clock oils were uniformly poor and one of
the major causes of failure in clocks of the period.
Rather than concentrating on improvements to the oil,
Harrison designed a clock which didn't need it. It was
radical thinking of this sort that would be important
later on, when he tackled the problem of designing a
During the mid-1720s, John and James designed a
series of remarkable precision longcase clocks, to see
how far they could push the capabilities of the design.
By inventing a pendulum rod made of alternate wires of
brass and steel, Harrison eliminated the problem of the
pendulum's effective length increasing in warmer
weather, slowing the clock. As a result, Harrison's
regulators from this period achieved an accuracy of one
second in a month, a performance far exceeding the best
London clocks of the day.
To solve the longitude problem, Harrison would have
to devise a portable clock which kept time to the same
accuracy as these precision regulators...
number 1 (H1)
Constructed between 1730 and 1735, the H1 is essentially
a portable version of Harrison's precision wooden
It is spring-driven and only runs for one day
(the wooden clocks run for eight days). The moving parts
are controlled and counterbalanced by springs so that,
unlike a pendulum clock, H1 is independent of the
direction of gravity.
The animation illustrates how the linked
balance mechanism works. It ensures that any change in
motion which affects one of the balances is compensated
for by the same effect on the other balance.
H1 was brought to London in 1735 and displayed to the
scientific community. Harrison was besieged by requests
from both scientists and socialites to see the
In 1736, Harrison and his timekeeper traveled to
Lisbon aboard the ship Centurion to test the
clock, and returned on the Orford. H1 performed
well in the trial, keeping time accurately enough for
Harrison to correct a misreading of the Orford's
longitude on the return voyage. However, Harrison did
not ask for a second trial but, instead, requested
financial assistance from the Board of Longitude to make
a second marine timekeeper.
H2 & H3 (1737-1759)
number 2 (H2)
Larger and heavier than H1, H2 is of fundamentally
the same design as H1. Harrison began work on H2 in 1737
but in 1740 realised its design was wrong. The bar
balances did not always counter the motion of a ship, a
deficiency that could be corrected if the balances were
Harrison requested more money from the Board to work
on a third timekeeper.
Harrison worked on his third timekeeper from 1740 to
1759. After 19 years of labour, it failed to reach the
accuracy required by the Board of Longitude.
Marine Chronometer number 3 (H3)
H3 incorporated two inventions of Harrison's:
A bimetallic strip, to compensate the balance
spring for the effects of changes in temperature
A caged roller bearing, the ultimate version of
his anti-friction devices.
Both of these inventions are used in a variety of
Despite these innovations, work on H3 seemed to lead
nowhere and its ultimate role was to convince Harrison
that the solution to the longitude problem lay in an
entirely different design.
In 1753, Harrison commissioned London watchmaker John
Jefferys to make him a watch following Harrison's own
designs. The watch was intended for Harrison's own
personal use - to help with his astronomical observing
and clock testing. No one in the 1750s thought of the
pocket watch as a serious timekeeper. However, Harrison
discovered with his new watch that if certain
improvements were made, it had the potential to be an
In 1755, as well as asking for continued support for
the construction of H3, he asked the Board of Longitude
... to make two watches, one of such size as may
be worn in the pocket & the other bigger... having
good reason to think from the performance of one
already executed... that such small machines may be
render'd capable of being of great service with
respect to the Longitude at Sea...
H4 is completely different from the other three
timekeepers. Just 13 cm in diameter and weighing 1.45
kg, it looks like a very large pocket watch. Harrison's
son William set sail for the West Indies, with H4,
aboard the ship Deptford on 18 November 1761.
They arrived in Jamaica on 19 January 1762, where the
watch was found to be only 5.1 seconds slow! It was a
remarkable achievement but it would be some time before
the Board of Longitude was sufficiently satisfied to
award Harrison the prize.
A second trial of H4 was arranged and William
departed for Barbados aboard the Tartar on 28
March 1764. As with the first trial, William used H4 to
predict the ship's arrival at Madeira with extraordinary
accuracy. The watch's error was computed to be 39.2
seconds over a voyage of 47 days, three times better
than required to win the £20,000 longitude prize. The
Board of Longitude, however, implied that the watch was
a fluke and would not be satisfied unless others of the
same kind could be made and tested. Harrison would be
paid £10,000 as soon as he disclosed his secrets and
handed over his mechanisms to the Astronomer Royal, with
the remaining £10,000 being paid when other timekeepers
of the same type, accurate enough to find longitude to
within 30 miles, were made.
Winning the Longitude Prize
Although the performance of H4 during its second sea
trial was three times better than the two minutes
accuracy required to win the longitude prize, the Board
of Longitude remained unconvinced. They stated that half
of the prize money would be paid once Harrison had
disclosed the workings of H4 to a specially-appointed
committee. They also implied that H4's accuracy was a
fluke and that copies of the watch should be made and
tested. Finally, all four of Harrison's timekeepers
should be handed over to the Board once he had received
At first, Harrison refused to accept any of these
proposals, but the Board was equally adamant. After
several weeks, both John and William agreed to disclose
the inner workings of H4.
In August 1765, a panel of six experts gathered at
Harrison's house in London and examined the watch. One
week later, they were satisfied that the disclosure was
complete and had signed a certificate to this effect.
The Board then insisted that the four timekeepers should
be handed over to them, and asked Harrison to recommend
someone who could copy H4. Reluctantly, he recommended
Larcum Kendall, a leading watchmaker who had probably
contributed to the construction of H4, and finally
received the first half of the longitude prize.
In order to qualify for the second half of the prize,
Harrison had to make at least two more watches and have
them tested. The Board of Longitude insisted that he
make these copies of H4 himself, but took the original
away for testing at the Royal Observatory. Nevil
Maskelyne, who had been appointed Astronomer Royal in
1765, remained unconvinced that a watch could be more
reliable than the lunar distance method for finding
Kendall's copy of
John Harrison (now in his seventies) and William
worked on a fifth timekeeper (H5), while Kendall made
good progress on his copy of H4. Kendall's watch, now
known as K1, was completed in 1769 and inspected in
early 1770 by the same panel that had examined H4.
William Harrison was also present and admitted that the
copy was exceptional.
Board of Longitude was asked to consider H5 and
K1 as the two copies of H4, but told John and William,
in no uncertain terms, that both copies of H4 should be
made by the Harrisons.
John, now 79 years old, made an appeal to the highest
authority in Britain.
On 31 January 1772, an approach
was made to King George III, via a letter to his private
astronomer at Richmond, Dr Stephen Demainbray. William
was summoned for an interview with the King himself, at
which the King is said to have remarked
... these people have been cruelly wronged..., and
By God, Harrison, I will see you righted!
H5 was put on trial by the King himself in 1772, and
performed superbly. The Board of Longitude, however,
refused to recognise the results of this trial, so John
and William petitioned Parliament. They were finally
awarded £8750 by Act of Parliament in June 1773. Perhaps
more importantly, John Harrison was finally recognised
as having solved the longitude problem.
In the meantime, Captain Cook had set out on his
second voyage of discovery with K1, Kendall's copy of
H4. He returned in July 1775, after a voyage of three
years, which ranged from the Tropics to the Antarctic.
The daily rate of K1 never exceeded 8 seconds
(corresponding to a distance of 2 nautical miles at the
equator) during the entire voyage and Cook referred to
the watch as
...our faithful guide through all the
vicissitudes of climates.
It is not known for certain whether Harrison knew of
this success, but Cook's voyage proved beyond doubt that
longitude could be measured from a watch.
John Harrison died almost one year after Cook's
return, on 24 March 1776, in his house at Red Lion
Square, London. It was his 83rd birthday.
Rupert Thomas Gould's father (the composer,
William Monk Gould) had intended his son for a
life as a Navy Officer and a promising start
under Beatty and Jellicoe had augured well, but
a severe nervous breakdown at the outbreak of
the First World War ended Rupert's career in
In 1916 he was transferred to work in the Hydrographic
Office of the Navy, where his talents with pen and ink
were highly valued, and in 1919 he was promoted to the
rank of Lieutenant-Commander (retired).
However, fine as his illustration was, he was much more
than just an artist/draughtsman. Gifted with a
photographic memory, R.T. Gould has been described as a
veritable Renaissance Man. During the trauma of his
first breakdown, for the first six months of which he
was unable to speak, his interests turned to the occult.
He had always been interested in scientifically
unexplained occurrences ('The X Files' would have
fascinated him) and he was the first to write a series
of factual books on such matters, in the late 1920s. He
was, for example, the first to systematically
investigate the case of the Loch Ness monster, which he
concluded did exist, and he published his results (The
Loch Ness Monster and Others) in 1934.
One of his most notable passions was Antiquarian
Horology; at the top of the long list of the talents and
interests which Gould possessed was a profound learning
in the history of time measurement. In 1923 he wrote the
definitive work on the Marine Chronometer (The
Marine Chronometer, its History and Development), a
work so thoroughly researched and beautifully written
that it still has no equal today; the book is
particularly valued for its fine and careful pen-and-ink
illustrations of mechanisms, drawn by the author.
Gould's skills were also practical. In 1920, during his
research for his book, he discovered the great
timekeepers by Harrison - the most important timekeepers
ever constructed - neglected in the Royal Observatory's
stores. He gained permission to restore them to their
former glory, a project that was to occupy him for much
of the rest of his life and which was to alienate him
from his wife and family; he was separated from his wife
in a high profile case, heard at the Royal Courts of
Justice in 1927.
In spite of two further severe nervous breakdowns, one
in 1925 and another at the outbreak of the Second World
War, Gould managed to cram many other interests and
activities into his short life. He was a dedicated
tennis player and his knowledge of the history and rules
of the game led him to umpire on centre court at
Wimbledon on many occasions during the 1930s. His
interest in all things mechanical included a fascination
for studying and collecting typewriters and he wrote the
first history of the instrument. Throughout the 1930s
and 1940s he delighted children across the country with
his educational broadcasts on BBC Radio's 'Childrens'
Hour' as 'The Stargazer', and in the mid-1940s he joined
that select group of eccentrics who broadcast as 'The
Brains Trust'. The most famous of the Brains Trust
panellists, Professor Joad, was Gould's bete noir and
regular sparring partner on the air waves. Gould died in
1948 at just 57 years old. The previous year the British
Horological Institute had awarded him the BHI gold
medal, its highest honour for contributions to horology.
The above biography was written by
the extremely talented
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