Following the discovery of America, sea voyages and the search for new lands increased, as the prosperity or ruin of a nation could depend on trade and exploration. What a ship vitally needed, besides a good captain and a good crew, was a clock capable of measuring time with precision. The accurate measurement of time on the high seas was the only practical way of calculating the ship’s longitude, and thus its east-west position. Determining the latitude was relatively easy using instruments such as the sextant or the astrolabe. But establishing the longitude (the position of a ship to the east or west of the meridian used as a point of reference) was far more difficult.Voyages lasted for many months and an error of even a few degrees in the course of the ship could mean ending up in uncharted waters, far away from the intended destination.
The art of measuring time
The Marine Chronometer
This brought with it the added dangers of shipwreck on unexpected rocks, supplies running out, and the onset of diseases, especially scurvy. Philip III of Spain was the first to arrange a competition for a solution to this problem. In 1598 he offered a payment of 6,000 ducats, a life annuity of 2,000 ducats and a prize of 1,000 ducats in cash. His example was soon followed by the French, the Venetians and the Dutch, but the largest reward was offered by the English. An Act was passed by the Parliament in 1714 offering a prize of £10,000 for any method capable of determining longitude to within one degree; £15,000 for a method accurate to 40 minutes of arc; and £20,000 for a method accurate to 30 minutes of arc (half a degree). One degree of longitude at the equator was the equivalent of 60 nautical miles (about 110 kilometres or 68 miles), and shorter distances as the North or South Pole were approached. The author David Landes observed that no project had ever mobilised so much talent, and the list of famous names involved sounded like the cast of a Hollywood movie on the history of science:Galileo, Pascal, Hooke, Huygens, Leibniz and Newton.
The solution to this great problem laid in the development of an accurate timekeeper. At that time, the pendulum clock was sufficiently accurate, but it had one fatal drawback: the pendulum could not maintain a regular swing when subjected to the movements of the ship. The challenge and rewards offered for a solution to the longitude problem spurred on the best scientists of Europe throughout the 17th and 18th centuries. The winner of the £20,000 prize (the equivalent of some $5-6 millions today) was not a great astronomer or a well-known clockmaker but a self-taught carpenter: John Harrison. Harrison’s first clock was completed in 1735. Known as H1, it was very large, weighing over 33 kilograms (73 pounds), and at first glance it was an unlikely navigational instrument. However, having been tested at sea the results were sufficiently satisfactory for the organisers of the ompetition to give Harrison £500 to enable him to carry out further research and experiments.
In the 18 years which followed Harrison produced two more clocks, H2 and H3, which were never tested on board ship. In 1759 Harrison produced his masterpiece, H4, which remains a milestone in the history of timekeeping. It was quite different from the complex clocks Harrison had previously produced, resembling an ordinary pocket watchof unusually large size – over 13 centimetres (5 inches) in diameter. Placed in a wooden box and resting on a cushion, H4 was taken on board HMS Deptford, together with Harrison’s son William.
The ship sailed from Spithead in 1761 with Jamaica as its destination. On its arrival after 11 ½ weeks at sea, the clock had lost only five seconds (after adjusting for its rate), the equivalent of 1/50 of a degree. Harrison claimed the prize but the committee decided that another trial was needed.
In February 1764 William Harrison and H4 sailed on HMS Tartar for Barbados. After 156 days at sea, the clock had gained 15 seconds after rate correction. This was an average error of under 1/10 of a second per day and a longitudinal error of 9.75 minutes of arc. This trial confirmed the birth of “the most famous chronometer that ever has been or ever will be made”, an accolade bestowed by Rupert Gould in “The Marine Chronometer: Its History and Development” (Antique Collectors’ Club, Woodbridge, Suffolk).
In the event, Harrison had to wait another nine years for the reward he was owed, eventually receiving it only three years before his death on 24 March 1776. In addition to Harrison’s original chronometer, several replicas of H4 were made which were also very successful.
One of these was K1, made by Larcum Kendall. It was used on HMS Resolution which sailed the Pacific under the command of Captain James Cook. K2, a simplified version of H4, was used on HMS Bounty, the ship on which the mutiny against Captain Bligh took place. With John Harrison’s chronometer the art of measuring time made a massive leap forward, and his designs soon became the target of international espionage as other countries tried to appropriate his technical innovations. Marine chronometers were the most accurate portable clocks ever produced.
Many other brilliant craftsmen contributed to their success over the years, such as the Englishmen Thomas Mudge, George Graham, John Arnold, Thomas Earnshaw, Daniel Quare, the Frenchmen Pierre Le Roy and Jean-Antoine Lepine, and the Swiss Abraham-Louis Perrelet, Ferdinand Berthoud and Abraham- Louis Breguet. Over the centuries the centre of innovations in timekeeping left its birthplace in Italy, spreading through Germany, Holland, England and France before finally arriving in its chosen country, Switzerland.