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Return to Old News home pageby Paul Chrastina
John Harrison's interest in clocks and watches originated during his childhood.
According to tradition, Harrison survived a life-threatening bout of smallpox
comforted by the steady ticking of a pocket watch that had been placed by
his bedside. As a teenager growing up near the English port town of Hull,
Harrison began to design and build clocks for the wealthy merchants of the
town.
In 1714, when he was twenty-one years old, Harrison heard that a grand prize
of 20,000 pounds sterling was being offered by the British Parliament for
a solution to the problem of determining a ship's longitude at sea. A Board
of Longitude had been appointed to study the problem and to award the prize
to anybody who solved it.
Accurate measurment of a ship's longitude, or position to the east or west
of a given point on the globe, was considered by many sailors to be an unsolvable
problem in navigation. In the two centuries that European nations had been
regularly sending ships across the Atlantic Ocean to the New World, many
had been lost or stranded far from their original destinations because their
captains were unable to determine their exact location while crossing the
open ocean.
Although many methods had been proposed to solve this serious navigational
problem, only two seemed to hold out any promise of a solution.
The first method involved the use of an extremely accurate clock. The second
made use of equally precise astronomical observations.
The "clock method" was based on the fact that local time advances
from east to west with the turning of the earth on its axis. If a ship's
captain could keep one clock on board his ship that was set to the time
at his home port, and a second clock which was carefully reset each day
at 12:00 noon, when the sun shone directly overhead, he could then keep
track of the distance his ship had traveled based on the discrepancy between
the two clocks. A relatively simple set of calculations could be used to
convert the number of hours of time difference into the number of miles
traveled by the ship.
The main problem with this method was that the technology of the early 1700s
had yet to produce a clock that would run accurately over a period of days,
let alone the weeks and months involved in ocean voyages.
If clockmakers couldn't guarantee that their clocks kept accurate time on
land, the difficulties of building a clock that would remain trustworthy
on board a ship seemed insurmountable, considering the added stresses of
nautical temperature extremes, corrosive saltwater and the tossing of a
ship's deck in rough seas.
Spurred on by the rich prize offered by Parliament, John Harrison became
obssessed with building a clock that would be accurate, rugged, and reliable
enough to determine longitude at sea.
Meanwhile, many astronomers were working on the alternative possible method
of determining a ship's longitude, which did not require an accurate clock.
This alternative method was based on using observations of the movements
of the moon, the sun, and various stars and planets. Celestial observations
were already being used routinely by sailors to determine a ship's north-south
position, or latitude. What was needed was a chart of celestial movements,
predicted from careful observations taken at several different longitudes,
that a captain could refer to while making the same observations from his
ship's deck.
Many members of the Board of Longitude were astronomers by profession, and
were somwhat biased in favor of astronomical methods of solving navigational
problems. Nevertheless, the members of the Board were favorably impressed
in 1735, when John Harrison presented them with a clock which, he said,
was accurate enough to determine longitude at sea.
Harrison had been working on his longitude clock for twenty years. He claimed
that it was the world's most accurate timekeeper, yet the clock was large
and crude by modern standards. It weighed seventy-five pounds and rested
inside a four-foot-square box.
When the clock was tested, it appeared to be quite accurate, but Harrison
did not immediately ask for the prize money. Instead, he pointed out some
flaws that had come to his attention, and insisted that he could build an
even better clock, if the Board saw fit to advance him a research and design
budget of 500 pounds.
Impressed by Harrison's skill and honesty, the Board agreed to advance him
the money to continue his work, hoping for an improved version of his clock,
or "marine chronometer."
Over the course of the next twenty-five years, the Board of Longitude granted
John Harrison five separate installments of 500 pounds apiece. In return,
the clockmaker produced a series of increasingly sophisticated and accurate
clocks.
The fourth clock made by John Harrison was actually an oversized pocket
watch that weighed only three pounds and measured five inches in diameter.
It was completed in 1760, when Harrison was 67 years old. This watch finally
seemed trustworthy enough to meet the exacting criteria of the longitude
competition. In a trial run made from England to Jamaica in 1762, Harrison's
watch was found to have lost only five seconds in 81 days, a small enough
margin of error to determine the ship's longitude to within 18 miles.
Unfortunately for the enterprising clockmaker, he found that he suddenly
faced competition for the enormous cash prize. An English astronomer named
Nevil Maskelyne had perfected a very complex method of determining longitude
based on observations of the moon. No clock was necessary to use Maskelyne's
technique, but it demanded great skill and patience.
Maskelyne's technique required calm seas for viewing the sky, and also that
the moon and a number of important reference stars be clearly visible. Once
the relative position of the moon was accurately measured, calculations
that took up to four hours to complete were required to determine the correct
longitude of the observers. Any small errors made during these tortuous
calculations could throw the entire procedure off, resulting in potentially
huge errors in the final calculation of longitude.
Despite these disadvantages, Maskelyne's technique appealed to many members
of the Board of Longitude because of its intellectual purity. They liked
the notion that a skilled mathematician could find longitude by Maskelyne's
technique, without relying on special gadgets.
Influenced by these university-trained astronomers, who favored Maskelyne
and privately snubbed Harrison as "the mechanic," the Board demanded
a second trial run of Harrison's watch, this time on a sea journey from
England to Barbados. The trial was completed in 1764, and the watch was
again found to have performed almost perfectly in keeping the time and determining
the ship's longitude.
The Board took possession of Harrison's watch, but gave him only half of
the prize money. The second half of the prize, Harrison was informed, would
be awarded only if he built two additional replicas of the watch, to prove
that its carefully documented performance was not a fluke of luck.
As John Harrison grudgingly returned to his workshop, Nevil Maskelyne asked
the Board of Longitude to let him borrow Harrison's watch for "observation."
Maskelyne had recently been appointed to the influential position of "astronomer
royal" at the court of King George III, so the Board agreeably sent
the watch to Maskelyne's observatory at Greenwich, near London.
Oddly enough, Harrison's watch, which had proved extremely accurate on two
long sea voyages and had been praised by expert watchmakers as the finest
timepiece ever made, began to lose as much as twenty seconds a day while
under Maskelyne's observation. John Harrison heard rumors that Maskelyne
was treating the watch roughly during its daily winding, and that he deliberately
bolted the instrument near a south-facing window, where the sun's rays caused
it to heat up and lose time.
After "simulating" the effects of six Atlantic Ocean crossings,
Maskelyne concluded that "Mr. Harrison's watch cannot be depended upon
to keep the Longitude within one degree in a voyage of six weeks."
Damning with faint praise, Maskelyne added that Harrison's watch might be
useful at times--when his own technique of lunar observation was hindered
by overcast skies, for example.
After the simulated trials were finished, Harrison asked that his watch
be returned. His request was denied.
Finally, the 79-year old Harrison could take no more of the impasse created
by Nevil Maskelyne and his friends on the Board of Longitude, and asked
his son William to petition King George III for assistance.
The king interviewed William Harrison. After hearing of the troubles that
the elderly watchmaker had endured, the king seemed lost in thought, and
was heard to mutter under his breath, "These people have been cruelly
treated...." Then King George looked up and proclaimed "By God,
Harrison, I will see you righted!"
King George learned that the Board of Longitude had commissioned a copy
of Harrison's watch. The king borrowed this copy and observed it, meeting
daily with William to observe its accuracy. After ten weeks of careful observation,
the monarch was satisfied that Harrison's clockwork was accurate to within
one second every three days.
Harrison went again before the Board of Longitude, this time with the support
of the king. After final negotiations with Parliament, Harrison was awarded
the balance of the prize money and was belatedly recognized as the first
to have solved the longitude problem. He died three years later at the age
of 83, on his birthday, March 24, 1776.
SOURCES:
Longitude. by Dava Sobel. Walker and Co. 1995.
Revolution in Time: Clocks and the Making of the Modern World. by David
S. Landes. Belknap Press, 1983.
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