On October 22,1707 almost two, thousand men lost their lives as the Isles of Scilly as fourBritish warships crashed on shallow water under the command of Sir Clowdisley Shovel(1). On the shallow water, the ships were caught on the rocks, sankalmost instantly with only few men surviving this catastrophe, and washed up onthe shore alive one of which was Sir Clowdisley himself.
When asked about the catastrophe he claimedthat kept record of the fleet’s location, however on later inspection hiscalculations were inaccurate (2). Duringthe exploration era, beginning of 15th century to the end of 18thcenty,accidents like that were very common as sailors were prone to getting lost atthe sea it is almost impossible to pinpoint where you are just by lookingaround you, as there is nothing but water. In order to navigate the seaaccurately with ought using modern satellites and Global Positioning Systems(GPS) the sailors needed a lot of variables to determine where they are one ofthe most important variables was keeping exact time on the ship. For the 21stcentury, the idea of keeping time is trivial however during the time of GalileoGalilei or Isaac newton the task of keeping precise time on a moving ship wasthought to be an impossible task until John Harrison came along. Due to theinability of determining the location of the fleet or the ship at the seacountless of lives and cargo were lost.
The earth isplatted with imaginary lines of latitude and longitude that data as far as to 150A.D. The latitude are vertical lines, each line being the same distance.
Thelatitude lines go through the North Pole and the South Pole the distancebetween each line is about sixty Nautical miles which is equivalent to hundredand ten kilometers. There is 15º difference between each latitude line. Thelongitude are horizontal lines with different lengths that travel from East toWest, the equator is the longest line of longitude (3). Sailors usethese imaginary lines to determine where they are in the world. The position of the ship relevant to the linelatitude at the time was relatively east to determine just by looking to thesky, the position of the stars, or the trajectory of the sun would show thesailors where they are. However, neither the sky or the sea could give any clueto the sailors about where they are on the longitude lines.
This iswhere the idea of time came into place. In order to figure out where the shipis relevant to the longitude line the sailor needs the exact time from theorigin of the journey, the exact time at the destination and lastly accuratetime onboard of the ship. Once the time is acquired the time difference betweenthe origin of the journey and the time on the ship can be used to determine theposition of longitude, each hour of time difference represents 15º or 60Nautical miles. During the exploration era the clock was already invented however,a pendulum-powered clock could not work at the sea due to a large number ofvariables. Firstly, the rolling of the ship would cause the pendulum to speedup or to slow down not giving an accurate time.
Additionally, the constantchange of temperature would cause the metal gears in a clock to shrink orexpand disturbing the fragile movement of the clock, furthermore thetemperature would affect the lubricant in the clock, which would additionallymess with the precision of the clock. Lastly, as you sail through largedistances the barometric pressure changes and Earth’s gravity changes atdifferent points of latitude which further interferes with keeping of time(4). This issue of keeping time at the sea was a major issue as manyEuropean countries that started to conquer the oceans lost many resources(England, Spain, Netherlands and Italy). In 1714, the British Parliament issueda Longitude Act, which stated that whoever comes up with the idea of accuratelymeasuring the ships Longitude within 30 geographical miles (5).
Theprice for the discovery was £20000. The countries earlier stated had similaracts put in place to figure out how to cross the sea without losing theresources which begun a long race to figure out how to cross the sea among themost intelligent people of the time. In 1736 JohnHarrison, an unnamed clockmaker without any formal education has proposed apromising idea on a trial voyage Lisbon. John Harrison has invented a firstever device that could keep time of the towns maiden time onboard of the ship;the marine chronometer.
On the way back to London aboard H.M.S. Centurion, JohnHarrison has demonstrated how his contraption could help navigate the seas ashe has proved that the ship on which he was about 60 miles off course (6) andthe chronometer only gained few seconds in its trial run.
However even as John Harrison has proved thathis device works he didn’t receive the price until many years later as themembers of the scientific comity did not want to accept Harrisons idea and theyhave changed the rules of the Longitude act in favor of astronomy over amechanical solution to the problem that Harrison has proposed (7). Additionally,the Board of Longitude did not have official headquarters to a great surpriseas they have existed for over fifty years when John arrived to London. Thegroup had never met witch in fact made it even more difficult to claim thereward. Hover John Harrison was a smart man and instead of proposing letters tothe board of longitude, he went to one of the most important people of theboard, Dr.
Edmond Halley who worked the Royal Observatory at Greenwich (8).Dr. Edmond Halley was impressed with Harrison’s idea and drawings however, heknew the comity would not accept the proposal, so he sent John to a famouswatchmaker George Graham knowing he would understand John idea. When he proposedhis idea and proved it works to the Board of Longitude, he only received £5000in 1763(9).
In 1773, John Harrison has finally received his prize; however,he could not use the money he received as he has died on 24 March 1776(10). John Harrisonhas spent five years assembling the first chronometer with the help of hisbrother, James Harrison; they have started assembling the device in 1730 andfinished in 1735. The first sea clock was named Harrison’s No. 1 what later wasshortened to H-1. The clock run on wooden gears (11). The structureof the clock is build-using brass.
This intricate design is unlike anythinganyone has ever seen before. The sea clock was contained within a wooden boxthat would only show the four shields. First for hours, second for minutes,third for seconds and the last one for the day of the month. However, the boxwas lost and what is left is a beautiful masterpiece, which shows all the gearsworking together in a harmony, with brass rod that stick out in a chaoticfashion that simulates the chaos of the sea. The H-1 is designed in suchfashion that it is unaffected by the swinging of the ship and makes up for thechange in temperature. The clock is frictionless which eliminates the need forlubrication. The clock was not only a working mechanism but also a form ofartwork with beautiful design engraved onto the front of the chronometer.
H-1is working to this day and is now located in the Royal Maritime Museum ofGreenwich (12). Once presented to the Royal Society, all thescientists were impressed with the design, only John, the only person in the roomto criticize his creation. John was to simply put a perfectionist. Dissatisfiedwith his first invention John proposed to the board that he would make a secondchronometer that will have improvements over H-1 and stated that unlike H-1 thenew model will be sent on an official trial voyage to the West Indies toofficially determine that the chronometer works. With little funds that Johnreceived from the Longitude board, he created a second chronometer, Harrison’sNo. 2 or H-2 within only two years.
Unlike the first sea clock, John Harrisonhas engraved “Made for His Royal Majesty George the 2nd, By order ofa Committee Held on 30th of June 1737. John engraved the quote on asilver plate on the front of the clock. Unlike its predecessor, H-2 is more ofa timepiece rather than a work of art as it does not have intricate pattern. Aspromised H-2 is smaller than H-1, as its footprint is significantly smallerhowever it stands taller than H-1. The H-2 had an improved source of power aswell as the gear were fully made of bronze.
This chronometer was presented tothe Board in January 1741, however by this time John was displeased with hiswork and therefore nobody took H-2 on a voyage, it never managed to serve its purpose(13). Bellow thereare two drawing by John Harrison and one of the pictures that were createdduring the reconstruction of the chronometers that outline the differencebetween the H-2 model of the chronometer and the H-3 model of the Chronometer.The two drawings show the movement of the gears and how the chronometers are animprovement over their respective predecessor. On the picture, bellow on the left(H-2) the movement is a lot simpler than the movement on the right (H-3). AsJohn tested the H-2, he has discovered that when strong centrifugal forces areapplied the movement, the forces would distort the movement.
Centrifugal forceis defined as “The apparent force, equal and opposite to the centripetalforce, drawing a rotating body away from the center of rotation, caused by theinertia of the body” (14). On the right, thedrawing shows how John has designed the H-3 to overcome the problem. In thedrawing on the right, John added another gear on a ball bearing (15). Nineteen yearshas passed until John Harrison has unveiled his next creation: Harrisons No. 3.The new sea clock was small enough to be deemed suitable for a captain’s cabin,however this was still a clock as Harrison never intended to make a pocket sizewatch. H-3 was made out of seven hundred and fifty-three hand made parts thatworked together flawlessly.
In order to save space, the chronometer two largecircular balances, mounted one above the other which are linked together bymetal ribbon that is controlled with a spring (16). In order tosolve the problem of temperature change Harrison came up with a solution thatis still used to this date in thermostats. A bi-metallic strip made out ofbrass and steel compensates for temperature change. This method relies on theelasticity of the metal, as the temperature changes different metals respond indifferent ways end expand at different rates (17). The Bi-metallicstrip is constructed by welding together brass and steel. As the temperatureincreases the brass extends more than steel dose and the strip curves towardssteel. As the temperature falls the strip comes back to its original size. In Harrison’schronometer the bi- metallic strip is attached to a spring.
The chronometer wasfinally finished in1757 In 1759Harrison has created its most famous chronometer: Harrison’s No.4 and was latera template for making watches. This chronometer was unlike any of his previous constructionas it resembled a watch rather than a bizarre clock, however it still wasn’t a watchas it was five inches in diameter (18). The chronometer is housed ina silver shell and on the inside, it is a state of arts as all the individualparts have stunning designs not for functionality but rather to impress the owner.Each part of the chronometer is finely engraved with a multiple fine chiselsand files. Using precision screwdrivers, the clock smith assembled all the piecestogether.
The pieces are so small that an eye piece is needed to precisely assemblethe chronometer. Other than precious metals, the moving parts are also composedout of jewels such as diamonds and rubies to provide a so little friction thatit could be neglected. Nobody knows how John Harrison managed to shape the jewelsinto the desired shapes, this was one of Harrison’s greatest secrets. To thisday H-4 is still in a functioning state however the current owners of the chronometerchose not to have it run as it is thought to be “most important time keeperever built”. In 1760 John has presented his new invention to the Board of Longitude,the board has decided to test the H-4 alongside H-3 chronometer as they were infavor of a clock rather than a watch as they believe a large clock could telltime more precisely rather than a small watch in 1761 the chronometer went onits first trial voyage to Jamaica.
The Board of longitude was satisfied withthe new model of the chronometer however they were still reluctant to payHarrison the prize money, before that they had to make sure that thechronometer can be recreated and therefore Harrison had to explain under oathhow the chronometer was made step by step he disassembled his greatestinvention.