JOHN
HARRISON LONGITUDE
The
story of longitude is a fascinating one for all
sorts of reasons, class snobbery, bureaucracy, the
intervention of the King, the invaluable importance
to the British nation, a battle between a clockmaker
& an astronomer. For me, it’s the
life long quest of a humble carpenter from a small
village on the Nostell Priory near Wakefield, John
Harrison, 24 March 1693 - 1776. Like Will
Shakespeare, John died on his birthday, he was 83.
Without the facility of accurate longitude, ships
were forever getting lost at sea, constantly on
the lookout for any kind of land, or worse running
aground at night when they weren't expecting to
be anywhere near land. The search for a solution
to this problem of longitude was regarded so important
that, in 1714, Queen Anne proclaimed a reward of
£10,000 for any method capable of determining a
ship's longitude within one degree; and £20,000
within one half a degree (several million
packets of lovely Pork Scratchings by today’s standard)
to the first person who invented a practical means
of measuring longitude.
In the eighteenth century the determination of longitude
at
sea was not a problem of know how, it was a problem
of reliability. Clocks in the 1700’s could
be accurate but pendulums, climate changes, and
size, all made accurate time keeping impossible
at sea, you
need to consider that for every 15° of longitude
you travel east your local time moves ahead one
hour, travel west and time moves back an hour.
By knowing the local time at two different points
on the globe you can use the difference to plot
your longitude. Latitude is even easier to plot.
If you know the day of the year, you need only observe
the elevation of the sun above the horizon at noon
and correct it for the tilt of the earth, then mark
your longitude (North-South) & latitude (East-West)
on a chart and you have your position. Just
4 minutes out in time would plot your position 1°
off course.
Despite this obvious timepiece solution, astronomers
of the day were hell bent on an astrological solution.
Some other suggestions put before the board of Longitude
gave me some amusement and included a plan to somehow
anchor ships every 100 miles across the worlds oceans
and have them fire a cannon in succession at midday,
ridiculous but nothing compared to another suggestion;
to cut a wound to a dog's leg and bandage it, then
take the dog to sea leaving the blooded bandage
on shore. At midday a trusted individual back
on shore would sprinkle some "Powder of Sympathy"
(whatever that is) on to the blooded bandage.
This would then, apparently, by some kind of spooky
magic, cause the wounded dog now at sea to bleed
and cry in pain thus indicating to the ship's Captain
that it was midday back in London. Thankfully,
the carpenter John Harrison was on the job.
He had already built a clock entirely out of wood
that was as accurate as anything made by the finest
British clock makers. I recall reading somewhere
that John got his fascination for clocks when, at
age of six, he was given a watch to amuse him while
in bed with smallpox. He spent hours listening to
it and studying its movement.
Harrison’s quest for an accurate marine timepiece
would take him his whole life, spending over five
years building his first effort, H1, a large device
weighing over 70 pounds. As pendulums had
proved unreliable at sea, he engineered a system
of two large brass balances connected by springs.
Since the balances were opposed to each other the
effect of the ships roll would be minimal. The Board
of Longitude deemed H1 worthy for sea trial. This
was successful and Harrison was sent home with some
cash (£500) to build H2. This was completed while
England was at war with Spain and was never tested
at sea. Still not happy, John took over seventeen
years building H3, using different metals to counter
the effects of temperature, adding numerous cogs
and springs, each counteracting the effect of another,
only to realise the answer to longitude had been
in his pocket since he was a boy, his first pocket
watch. A pocket watch gets jiggled about
yet can keep good time. Johns first three clocks
were all brilliant but heavy cumbersome instruments.
Discarding H3, work on H4 began. It was a
thing of true beauty: a large pocket watch, twelve
centimetres in diameter, with a jewelled mechanism
that was the product of, in John’s words, "fifty
years of self denial, unremitting toil, and ceaseless
concentration. I think I may make bold to say, that
there is neither any other mechanism or mathematical
thing in the world that is more beautiful or curious
in texture than this my watch or timekeeper for
the longitude."
(John should have taken a holiday - he may have
saved a few years building H3...)
By now 68 years old, John’s next step was to prove
H4 would keep accurate time at sea. In November
1761, Harrison entrusted his precious watch to his
son and co-worker, William. The Board of Longitude
placed the clock aboard the ship Deptford, bound
for Jamaica. It was in a case with four locks; William
Harrison, Governor Lyttleton of Jamaica, Captain
Dudley Digges, and his lieutenant, all had keys
and had to be present when the case was unlocked
and the clock was wound. The first leg of
the voyage from Spithead to Madeira generated unusual
interest in the timepiece since the ship's beer
had spoiled and the crew didn't want to cross the
Atlantic with only water to drink. Nine days out
the Deptford's longitude by dead reckoning was 13
degrees 50 minutes west, but by Harrison's calculations
15 degrees 19 minutes west, a difference of 100+
miles. Sceptical, but committed to testing the timepiece,
the Captain kept to young Harrison's course and
sure enough they sighted land right where it should
be. If they had altered course and gone by dead-reckoning
they would have missed Madeira altogether.
Arriving at Jamaica was just as successful. Deptford's
Captain followed young Harrison's calculations and
arrived there three days before another ship that
had left port ten days before the Deptford. H4 was
taken ashore and checked against Jamaica's longitude
as determined by astronomical calculations. Making
a predetermined allowance for two and two-thirds
seconds a day for error it was found to be five
seconds slow - an error of 1.25 minutes in longitude,
more than close enough for the great prize.
However, the Board of Longitude decided the Jamaica
test was a fluke and refused to pay. Possibly the
fact that his rival for the Prize, the Astronomer
Royal Nevil Maskelyne was a member of the Board
of Longitude and had an influence on this decision.
Eventually, the Board gave Harrison £2,500 and said
that further sea trials would be necessary. So,
in March 1764 William set sail for Barbados aboard
the Tartar. Once again, the timepiece performed
magnificently; an error of only 34.4 seconds over
seven weeks, or on the round trip less than a tenth
of a second per day.
In 1765 the Board of Longitude agreed "the
said timekeeper had kept its time with sufficient
correctness". However, another spanner
in the works, the Board decided that Harrison would
have to turn all four clocks over to them for testing
and reproduction, and only then he would receive
£7,500, or half the reward. The other half would
be available only on completion and testing of two
more timepieces.
Harrison, I guess still pissed for not looking at
his pocket watch sooner, felt "extremely ill
used by the gentlemen who I might have expected
better treatment from". He decided to try and
enlist the aid of King George III. He asked for,
and was granted, an audience with the King who became
extremely annoyed with the Board. King George tested
the clock himself at the palace and when it had
lost only four and a half seconds in ten days he
is known to have said "... these people
have been cruelly wronged... ". The King told
Harrison, "By God, Harrison, I will see you
righted!" Armed with the King's backing, John
Harrison petitioned Parliament for his full reward.
Harrison finally received his reward in 1773.
In 1776, James Cook took a replica of H4 with him
on his third trip around the world. Cook didn’t
survive the voyage - he was murdered in 1779 on
the beach in Hawaii. However, the replica
clock proved itself many times over........
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