The Lost Science of John 'Longitude' Harrison

159 pp. Harrison, John (bap. 1693, d. 1776), horologist, was born at Foulby in the parish of Wragby, Yorkshire, where he was baptized on 31 March 1693, the eldest of five children of Henry Harrison (1665–1728) and his wife, Elizabeth, née Barber. His father was a joiner and was said to have worked for Sir Rowland Winn (d. 1721) at Nostel Priory, Wragby. In 1696 or 1697 the family moved to Barrow upon Humber, Lincolnshire, where Winn owned other estates. Henry Harrison was appointed parish clerk soon after his arrival. The younger Harrison was mainly self-taught, but a visiting clergyman lent him a copy of Nicholas Saunderson's lectures on natural philosophy, from which he made his own copy. These lectures introduced Harrison to the science of Sir Isaac Newton which his analytical mind enabled him to grasp. He was also interested in the theory of music and wrote extensively on the subject later in life. On 30 August 1718 he married Elizabeth Barrel at Barrow upon Humber; she died on 18 May 1726, and on 23 November that year he married Elizabeth Scott at Hampstead, Middlesex. She died in 1777. Two sons, John (1719–1738) and William (1728–1815), survived infancy. Harrison had been brought up to be a carpenter and joiner, and made very few clocks before he started his lifetime work on the development of the marine timekeeper. His earliest extant clock, signed and dated 1713, is in the collection of the Clockmakers' Company, London; one dated 1715 is in the Science Museum, London; and a third, dated 1717, is at Nostel Priory. All his early clocks are very similar and of an all-wood construction, a practice he followed until 1730. A fine extant turret clock was made by him about 1722 for Brocklesby, Lincolnshire. His experience with this clock led Harrison to his innovative ideas of escapement design, and ways to reduce friction, which were further developed in the precision longcase clocks of 1725–8 from which he claimed an accuracy of rate to within one second a month. These clocks included two of his greatest inventions: the 'gridiron' temperature compensated pendulum which consisted of a grid of five steel rods and four brass rods, and the 'grasshopper' escapement which provided an impulse to the pendulum with very low friction. The wooden wheels had brass pivots running in bushes of lignum vitae, a tropical hardwood containing naturally lubricating resin, and the clocks consequently required no extra lubrication, which eliminated problems caused by the poor oils of the period. In 1726 Harrison first heard of the 1714 Longitude Act (12 Anne c. 15), offering to reward anyone who could provide a method for determining longitude at sea within certain prescribed limits on a trial to the West Indies. The prizes were £10,000 for a determination to within 60 geographical miles, £15,000 to within 40 geographical miles and £20,000 to within 30 geographical miles. In 1730 Harrison described his recently made precision clocks, with a proposal to adapt this technology for a portable 'sea clock'. He travelled to London and presented his proposal to the astronomer royal, Edmond Halley, who persuaded him to visit the eminent clockmaker George Graham. The latter was amazed at Harrison's claims but appreciated the potential and gave encouragement and support, persuading Harrison to construct his design. Harrison returned to Barrow and completed the sea clock, a large machine of more than 72 lb, now referred to as 'H1', by 1735. When he took it back to London H1 became the fascination of scientists and the talking point of society. A certificate was signed by Halley, Graham, and three other fellows of the Royal Society suggesting that Harrison deserved public encouragement and that H1 should be given a sea trial. In 1736 he was sent on a voyage with H1 to determine the longitude of Lisbon. He was able to correct the ship's reckoning by nearly one and a half degrees, a success which resulted in the very first meeting of the commissioners of the board of longitude, on 30 June 1737. At this meeting Harrison was awarded £500 in two payments to enable him to make a further improved sea clock. By 1739 this clock, H2, a little larger and considerably heavier, was ready, but it was never tested at sea. A third sea clock, the lightest of these early timekeepers, was finished in 1759, having been beset by many technical problems. During this period, in 1749, the Royal Society awarded Harrison the Copley gold medal for his experimental work. During these same years Harrison set a size standard for all future marine timekeepers when finally in 1760 he produced his fourth timekeeper, his masterpiece, H4, the size of a large pocket watch with a diameter of 5.2 ins and weighing only 3 lb. This was sent on a trial to Jamaica in 1761 where, during the 81 day voyage, the watch lost 5.1 sec. after applying a 'rate' (an allowance made for the known daily performance of a timekeeper before a voyage, taken into account when making the final calculations). Unfortunately Harrison failed to mention this hitherto unknown practice of applying a rate before the voyage, which nullified the results of the trial, but the board of longitude was sufficiently impressed to award him £2500 to be paid in full subsequent to a second trial. In addition the board wanted him to divulge the technicalities of H4 and also required him to make two more watches. Harrison objected to these additional demands but a second trial was arranged in 1764, this time with an agreed rate for the watch of a gain of 1 sec. a day. The trial to Barbados was a resounding success, the error of the watch during the outward voyage of 47 days computed to 39.2 sec., equal to 9.8 geographical miles. This was three times better than required to win the full £20,000. The board could not believe the accuracy of the watch and insisted that it should be dismantled before a committee and that Harrison should explain the technology, which would then be published. It further stipulated that all the marine timekeepers made by Harrison were to be handed over to the board and that H4 was to be duplicated by an independent craftsman. Harrison would then be granted the balance of the first £10,000. They also reiterated that he would have to make two more watches before he could be awarded the second half of the prize. Despite considerable acrimony, in August 1765 the committee met at Harrison's house; he explained the intricacies with working drawings, satisfied the board, and eventually received the agreed sum of £7,500. Harrison was determined to get the further £10,000 to which he was already entitled. He was refused access to H4, which was being duplicated by the watchmaker, Larcum Kendall (1721–1795), but despite this Harrison completed another large watch, H5, in 1770. Harrison was now seventy-seven and considered that to make yet another watch as demanded by the board of longitude was asking too much and also beyond the terms of the Longitude Act of 1714. The board refused to yield. Kendall's copy, K1, completed in 1769, was recognized as of exceptional craftsmanship. It was taken by Captain James Cook on his second and third voyages of discovery and underpinned Cook's cartographic surveys in the southern hemisphere. Harrison, determined to settle his claim, appealed to George III in 1772. With the king's support H5 was put on test at the Royal Observatory at Kew for ten weeks resulting in a rate of less than 0.33 sec. a day. With these results Harrison approached the board of longitude again, but the commissioners refused to acknowledge the Kew trial. An appeal by Harrison to the prime minister, Lord North, eventually resulted in a further act of parliament (George III c. 77), whereby Harrison was awarded a final settlement of £8750 which, including all the payments over the years, came to a total of more than £20,000. Harrison was able to enjoy the recognition of his life's work for less than three years before his death, reputedly on his birthday, on 24 March 1776, in London. He was buried at St John's Church, Hampstead. - Oxford Dictionary of National Biography