Summary of Longitude and Latitude
Daniel Ho, Chief Editor
Chapter 1:
Imaginary Line
Jiang Xun
Lines of latitude and longitude began to appear at least three centuries before
the birth of Christ. By A.D. 150, the cartographer and astronomer Ptolemy had plotted
them on his first world atlas. The latitude lines stay parallel to each other from the
Equator to the poles. The longitude lines connect the North and South Pole in great
circles. Any sailor can measure his latitude accurately by the length of day, or by the
light of the sun. The measurement of longitude meridians, by comparison, is more
difficult to achieve. To learn the longitude at sea, one needs to know what the time is
aboard ship and also the time at the homeport at that very same moment. Precise
knowledge of the hour in two different places at once was unattainable during the era
of pendulum clocks. The problem of measurement of longitude persisted over four
centuries. John Harrison, a mechanical genius, devoted his life to solving this problem.
He invented a clock that would carry the true time from the homeport to any place in
the world. His followers modified Harrison’s invention, and enabled it to be widely
used. In 1773, John Harrison claimed his monetary reward for solving the problem of
longitude measurement.
Chapter 2:
The Sea Before Time
Mao-Chang Liang
Calculating longitude at sea was a nightmare for seamen in the fifteenth through
seventeenth centuries. At that period, sea captains relied on “dead reckoning” to
gauge the distance from the home port. Confusion of longitude would lead seamen
to misjudge their whereabouts when they were sailing at sea. Without replenishment
of fresh water, fruits, and vegetables, sailors were dying of thirst and of the dreaded
disease, scurvy. The situation was not improved until the eighteenth century, when
John Harrison invented his innovative time device. On its virgin journey to Lisbon,
the ship was only about sixty miles off course on its return voyage home to London.
After forty years of contention, Harrison finally won the great prize.
It was a
milestone invention for sailing the seas.
Chapter 3: Adrift in a Clockwork Universe
Weifu Guo
After realizing the importance of the longitude problem, people first turned to the
sky for the solution, in hopes of reading longitude from the relative positions of the
celestial bodies. The first option was suggested by Werner in 1514 ----the motion of
the moon, which was later proved impractical due to the complexity of the moon’s
motion. Then in 1610 Galileo proposed using the eclipse of Jupiter’s moons to
determine the longitude, after he discovered the regularity of these moons’ motions.
However, despite Galileo’s adherence, this method was also regarded as impractical
and rejected at that time. But after later improvements by Galileo and his followers,
the method was finally adopted as a standard method for determining longitude on
land(only) and won great success in mapmaking. This success stimulated further
demand for finer and better predictions of eclipses of the Jupiter’ moons and caused a
series of advancements in astronomy observations, including the establishments of the
Paris Observatory, the Greenwich Observatory, and the discovery of light velocity.
However a practical solution to the longitude problem at sea still remains unclear.
Chapter 4:
Time in a Bottle
Mao-Chang Liang
Finding longitude at sea was a difficult ordeal until John Harrison invented a
more accurate clock.
It had been suspected by some clock enthusiasts that a
timekeeper might be able to solve the longitude problem, by comparing the home-port
time with the local time. This required a mechanical clock that could measure the
time constantly and accurately. Galileo, who first worked on the pendulum problem,
found that the swinging frequency of a pendulum is determined by its length.
first pendulum clock was built by his son, Vincenzo Viviani.
The
Later on, Christiaan
Huygens, Galileo’s heir and a gifted astronomer, claimed he arrived at the idea for the
pendulum clock independently of Galileo. He also made marine timekeepers, based
on the pendulum principles, which led him to great success in keeping track of the
ship’s longitude.
In order to circumvent the problem of confounded motion of a
swinging pendulum when sailing on a stormy day, he invented a spiral balance spring
as an alternate solution.
This created a conflict between Hook, who was known in
describing the motion of a vibrating spring, named as Hook’s law in physics, and
himself, which was never resolved.
Chapter 5:
Powder of Sympathy
Mao-Chang Liang
At the end of the seventeenth century, even members of learned societies debated
the means to a longitude solution.
Various proposals were published.
Amongst the
offbeat approaches was a most colorful theory: the wounded dog theory, by Sir
Kenelm Digby. The method was to use certain powders to heal a wounded dog.
When sprinkling this special powder, the dog would cry the next day at the same time,
telling the timekeeper it had been one day. The wound could not be totally healed
until the voyage was ended. This is inhumane. A much more realistic solution was
to measure the angle between the actual and magnetic poles by magnetic compass,
because the two (or three) poles were not aligned; the angle depended on the
longitude. This was extremely difficult even by modern technologies, because of
crustal magnetism.
heavens.
Another solution was based on the distribution of stars in the
The required data went far beyond that which had existed.
This
technique was also the one that postponed Harrison’s milestone invention from
succeeding.
In 1997, Whiston and Ditton proposed the solution of exploding a bomb
at midnight in London.
This could tell seamen the time in London.
By comparing
it with the local time, they could judge their whereabouts. Although Whiston and
Ditton were not successful in solving the longitude problem, they united the shipping
interests in London, and demanded that Parliament provide a great prize for those who
surmounted barriers of the longitude problem.
Chapter 6:
The Prize
Jiang Xun
In 1714, a committee was assembled to evaluate the proposals for measuring
longitude. The committee members asked advice from Isaac Newton. Newton thought
that existing means for determining longitude were correct in theory but difficult to
execute. In addition, he thought that astronomical solutions were more promising than
the clock. The longitude committee incorporated Newton’s testimony in an official
report. The board welcomed all potential solutions from any field of science or art.
They gave awards to help poor inventors. To judge the accuracy of every proposal,
they tested it on board. One of the inventors, Thacker, developed a new clock
installed in a vacuum chamber and declared it the best method of all. However,
Thacker’s clock did not take into consideration the change of temperature. Even under
ideal circumstance, Thacker’s clock erred by as much as six seconds a day. As the
science of astronomy developed, the lunar distance method gained credence. Newton
continued to believe that the regular motions of the clockwork universe would prevail
in guiding ships at sea, and that the clock could only be a useful accessory to
astronomical computation. Newton died in 1727, and therefore did not live to see the
great longitude prize awarded to the self-educated clockmaker.
Chapter 7:
Cogmaker’s Journal
Jiang Xun
John Harrison was born in 1693. As a teenager, he learned woodworking from
his father. He completed his first pendulum clock before he was twenty years old. The
clock was constructed almost entirely of wood. A good mechanical clock had to be
evaluated by the clockwork universe, and this was done through the application of
some mathematical equations. Harrison not only understood these calculations but
also made his own astronomical observations and worked out the equation by himself.
No one knows when Harrison learned about the longitude prize. He attempted to think
of a way to estimate longitude. Most pendulums at that time expanded with heat and
contracted with cold. Harrison eliminated the problem by using the bound-together
metals. The metals would counteract each other’s changes in length as the temperature
varied, so the pendulum never went too fast or too slow. Harrison tested the accuracy
of the clock against the regular motions of stars. Harrison’s clocks never erred more
than a single second in a whole month. However, the pendulum could not operate
correctly in a rolling ocean. Harrison began picturing a movable set of seasaws that
would withstand the strongest waves. When he had thought out the novel idea to his
own satisfaction, he applied this idea to the longitude problem.
Chapter 8 The Grasshopper Goes to Sea
Weifu Guo
John Harrison’s sea clock solution to the longitude problem was welcomed by
Astronomer Royal, Edmond Halley, and also by then well-known watchmaker,
George Graham, after his arrival in London in 1730. With their help and
encouragement, the Harrison brothers finished the first sea clock---Harrison No. 1 in
1735. H-1’s successful performance during its trial run to Lisbon in the following year,
didn’t err more than a few seconds in twenty-four hours, greatly impressed the sea
captains and the Board of Longitude. But Harrison himself was not satisfied with it,
and proposed to make more improvements before the official trial to the West Indies.
Four years later, the second marine timekeeper H-2 was born, which also gained full
backing from the Royal Society after its passing various rigorous tests. This time it
was again Harrison himself who didn’t think H-2 was good enough. Nearly another
20 years passed before his completion of H-3. Meanwhile, the success of H-1
continued to impress more and more people and gained wide approval especially from
watchmakers.
Chapter 9:
Hands on Heaven’s Clock
Ross Cheung
This chapter is in stark contrast to the previous chapter. While Chapter 8
was a glowing optimistic account of John Harrison's successes with his clock, Chapter
9 is a chronicle of the developments in the attempts to use astronomical observations
to solve the longitude problem, developments that provided the primary competition
to Harrison's clock.
Until the mid-18th century, astronomers lacked the observations
and instruments required for determining longitude accurately.
However, in 1731, two inventors independently came up with the quadrant,
an instrument capable of using the moon and other celestial objects to determine
longitude. New additions were soon added, resulting in the sextant, a device capable
of measuring distances between the moon, the sun, and the stars. Navigators, armed
with the sextant and detailed star charts, could now quickly and easily determine their
position. The quadrant relied on decades of careful, detailed mapping of the sky by
Royal Astronomers such as John Flamsteed, Edmond Halley, and James Bradley.
Bradley's ascension to the title of Royal Astronomer, however, posed a problem to
John Harrison.
While Halley had always been sympathetic to Harrison's quest to
build his clock, Bradley tended to believe in the astronomical solution to the longitude
problem.
He had worked hard on charting the sky, and had been helped
tremendously by the observations of the German mapmaker Tobias Mayer, whose
accurate lunar tables helped to solve a critical problem with the astronomical method,
that of charting the moon's complex and seemingly irregular orbit. With so many
people working on the lunar distance method, it was no surprise that the astronomical
method received most of the attention of the members of the Board of Longitude, all
of whom endorsed it over John Harrison's seemingly overly-simple mechanical
solution.
This would be the source of the problems Harrison would soon face.
Chapter 10:
The Diamond Timekeeper
Mao-Chang Liang
“Rome was not built in one day;” all the milestone inventions take an enormous
amount of time and brain power from intellectuals to accomplish.
John Harrison
spent nineteen years in building H-3; while he made a turret clock in two years and
two revolutionary sea clocks within nine years; why he took so long to build H-3 is
still inexplicable. H-3’s two major innovations, still present now-a-days, are the
bi-metallic strip, which was used to minimize the stretches of pivot equipment due to
ambient temperature variation, and the antifriction device. H-3 was designed to be
in shipshape condition.
This was Harrison’s first applicable sea clock.
He did not
win the longitude prize until the next generation sea clock, H-4, came out.
John Jefferys’ great technology that enabled him to complete H-4.
It was
It was only three
pounds in weight and five inches in diameter. H-4 is exhibited at London’s National
Maritime Museum, drawing millions of visitors a year. It could run, if curators would
allow it to, but to run it would be to ruin it. Because of the friction-free design,
Harrison was forced to use oil to lubricate it. (The messy oil used for horological
lubrication mandated regular maintenance.)
Even if the watch could be kept
lubricated, the natural process of deterioration would limit the life of parts to three or
four centuries.
The watch would become a very different object from the one
Harrison bequeathed to us three centuries ago.
Chapter 11:
Trial by Fire and Water
Mao-Chang Liang
Even though Harrison was successful in measuring longitude, it was not his time.
He was unfairly treated first by John Flamsteed, then by James Bradley, and finally by
Nevil Maskelyne. Maskelyne was well educated, and believed that measuring the
lunar distance was the unique solution to the longitude problem.
In 1761, two trials
were assigned to both H-3 and H-4 together on the same voyage, from London to the
port of Portsmouth, by the Board of Longitude, and escorted by William Harrison,
John Harrison’s son. At the trial, William suspected that Bradley had deliberately
delayed the schedule for his personal gain.
By holding up the Harrison trial, Bradley
could buy time for Maskelyne to produce proof positive supporting the lunar distance
method. Even with this obstruction, the clocks still kept running and at the port of
Jamaica, H-4 had lost only five seconds, after its 81-days at sea.
witnessed the results.
Captain Digges
Upon its arrival home, the total adjusted error amounted to
just under two minutes, which had met the requirements that the Longitude Act
demanded.
The great prize should have gone to the Harrisons then and there.
Instead of 20,000 pounds, John Harrison received only 1,500, in recognition that his
watch had been an invention of considerable utility to the public, but was not yet in
great use for determining longitude.
In May 1762, Maskelyne published the
astronomical data plus the directions for using it when sailing at sea: “The British
Mariner’s Guide.” He performed two trial voyages and believed that he had secured
the prize, though he did not.
In 1773, three years before John Harrison’s passing
away, after a forty-year-long struggle and a painful tug-of-war with fate, John
Harrison received the full monetary reward.
Chapter 12:
A Tale of Two Portraits
Jiang Xun
There are two portraits of John Harrison made during his lifetime. The first is a
formal portrait by Thomas King. The other is an engraving by Peter Joseph Tassaert.
In the painting, Harrison sat surrounded by all his inventions except for H-4. The
reason H-4 is missing from the oil portrait is that Harrison didn’t have it on hand at
that time. After the second trial of the watch H-4 in the summer of 1764, the
commissioners conceded that the Watch proved to be three times more accurate than
the requirement. That autumn, the board gave half the reward money to Harrison, on
the condition that Harrison hand in all clocks with a disclosure of the clockwork
inside H-4. He needed to supervise production of two copies of H-4 in order to
receive the full prize. Eventually, Harrison dismantled the watch piece by piece. The
board asked Harrison to reassemble the watch. The watch was locked in its box and
was sequestered in a storeroom at the Admiralty. It was at this juncture that Mr. King
painted Mr. Harrison. In April of 1766, after Harrison’s portrait was completed, the
board decided to subject the timekeeper to a new trial. They gave all clocks to
Harrison’s rival, Larcum Kendall, for the trial. Although H-4 had traveled on a boat
down the Thames to Greenwich for its trial, the three large sea clocks were destroyed
on their way through the streets of London. The portrait of Harrison in profile by Mr.
Tassaert, which dates from about 1770, depicts the disgruntled mood of the aging
watchmaker.
Chapter 13:
The Second Voyage of Captain James Cook
Jiang Xun
Harrison had wanted Captain Cook to take the original H-4. However, the Board
of Longitude said that H-4 had to stay within the kingdom until the rest of the
longitude prize had been decided. H-4, which had won praise from three captains, had
failed its ten-month trail at the Royal Observatory. In its ten-month trial, Maskelyne
concluded that Harrison’s watch could not be depended upon to ascertain the
Longitude within a degree. Previous records proved, however, that Mr. Harrison’s
watch had already kept the longitude within half a degree or better. Maskelyne
thought that the timekeeper might enhance the lunar distance method but never
supplant it. Harrison complained that H-4 had been put in direct sunlight in the trial.
Meanwhile, the thermometer for measuring the timekeeper’s temperature lay in the
shade. Seeking the positive proof of H-4, the board hired a new watchmaker, Larcum
Kendall to attempt an exact copy. Kendall finished his reproduction, K-1, after two
and a half years’ work. Cook took the K-1 copy on his world tour. Harrison,
meanwhile, had finished a timekeeper, H-5. George III turned H-5 over to his private
science tutor and observatory director for a six-week indoor trial. The watch behaved
badly at first due to a few lodestones nearby. After they removed the lodestones, the
H-5 worked perfect. After ten weeks of daily observation, he was proud that H-5 had
proved accurate to within one-third of one second per day. Harrison felt happier when
Cook returned from his second voyage with praise for the K-1 copy.
Chapter 14:
The Mass Production of Genius
Weifu Guo
Though significant to the horology and to the longitude problem, Harrison’s
watch was too complex and expensive for mass production and wide usage. Neither
did Kendall’s nor Mudge’s efforts manage to facilitate the mass production of a
reliable timekeeper at sea.
It was John Arnold and Thomas Earnshaw who made
mass production possible. Both of them had a prodigious output during their lifetime.
Arnold was also well-known for making miniature watches while Earnshaw devised a
key timekeeping component called the spring detent escapement that needed no oil,
for which he and Arnold had a fight over their conflicting originality claims. Thanks
to the advancement by them, the price of chronometers finally dropped down to an
affordable level for most captains by the 1780s. It quickly began to replace lunar
methods on shipboard due to its simpler operation and higher accuracy. To cope with
the great demand for chronometers, the usage and assignment of chronometers was
coordinated first by the Board of Longitude, and then by the hydrographer of the
Royal Navy after the dissolution of the former in 1828.
Chapter 15:
In the Meridian Courtyard
Ross Cheung
The chapter begins with a description of the Royal Observatory at
Greenwich, England, focusing primarily on the choice of this location as the Prime
Meridian, which today is the standard by which Universal Greenwich mean time and
"zero" longitude is determined. Nevil Maskelyne, the fifth Royal Astronomer, was
responsible for moving the prime meridian here.
All of the lunar-solar and
lunar-stellar distances contained in his comprehensive "Nautical Almanac" were listed
from the Greenwich meridian, with the result being that sailors all over the world
calculated their longitude from Greenwich, making it the first universal reference
point.
The increasing use of chronometers did not spell the end of the Greenwich
prime meridian, however, as sailors continued to use the meridian so that they could
verify their chronometers.
In 1884, representatives from 26 countries voted to make
the Greenwich meridian the prime meridian of the world, with the chief competitors,
the French, stubbornly holding on to their Paris Observatory meridian for another 27
years. Ever since, the Greenwich observatory has been keeping the "zero" longitude
as well as the Greenwich mean time.
Meanwhile, all of John Harrison's clocks are displayed inside the
Observatory for all to see. Thanks to the restoration work of several important
individuals over the centuries, three of the four are still working today, while the
fourth (the smaller "pocket-watch") is preserved for posterity.