Time in History: Views of Time From Prehistory to the Present Day

by G. J. Whitrow

  Two different ways of solving the problem of a ship's longitude were suggested. One was astronomical, being based on observing the position of the moon relative to the stars. This method was proposed in 1514 by Johann Werner of Nuremberg ( 1468-1522) and became known as the lunar-distance method. The other, first suggested in 1553 by Gemma Frisius of Louvain ( 1508-55), depended on the development of an accurate chronometer that would be designed so as to withstand the disturbances associated with transport by sea. It would be set to give the

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  time on the prime meridian, and this would be compared with the local time (e.g. noon) of the place where the ship was situated.

  In 1567 Philip II of Spain offered a substantial reward for a successful way of determining longitude at sea, and this reward was greatly increased thirty years later. Among those applying for the prize was Galileo, who realized that the discovery he had made with the aid of his telescope in 1610, of the four principal satellites of Jupiter and their occultations by that planet might be the basis of an accurate celestial timekeeper. He submitted his method in 1616, but the Spaniards did not regard it as a practical proposition. Galileo also contributed to the chronometric method of solving the problem by drawing attention to the possibility of using the pendulum as a controller of mechanical clocks. Later that century, as we have seen, the pendulum clock was successfully developed by Huygens, but although he was convinced that his clocks could be used to determine accurate longitudes they tended to be erratic except on land or on a calm sea.

  Meanwhile the lunar-distance method had been revived in Paris by J.-B. Morin ( 1583- 1656), who suggested that an observatory was needed to provide the required data. Following the creation in 1666 of the Académie Royale des Sciences by Louis XIV at the instigation of the great statesman Colbert, the Paris Observatory was founded a year later. 'Finding the longitude' was also one of the subjects that engaged the Royal Society of London, established by Charles II in 1660, and led to the founding of the Royal Observatory at Greenwich in 1675.

  Any astronomical method for finding differences of longitude must assume that for practical purposes the earth rotates uniformly. Since solar days vary throughout the year, the first Astronomer Royal, John Flamsteed ( 1646-1719). decided to check this assumption by concentrating on sidereal time. With the aid of two clocks installed in 1676 in the Octagon Room in the Royal Observatory at Greenwich he concluded that the earth does rotate uniformly, a result which was not challenged for 250 years. These clocks had been made by Thomas Tompion ( 1639- 1713), who has been called 'The father of English clockmaking'.1 Like some of the earlier English clockmakers he began as a blacksmith. In due course he became a friend of Robert Hooke ( 1635-1704), Curator of Experiments at the Royal Society, and through him met Flamsteed. The two clocks he made for Flamsteed could each run automatically for a year.

  Although the expression 'finding the longitude' was often used as a catch-phrase like 'squaring the circle' to denote something thought to be

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  impossible, the need to solve the problem became acute after a spectacular maritime disaster on 29 September 1707 when Admiral Sir Clowdisley Shovel and some 2,000 other sailors were drowned because bad navigation had caused four ships of the Royal Navy, on the way home from Gibraltar, to capsize on the Gilstone Ledges in the Scilly Isles. This disaster led to a public outcry for navigation to be made more accurate. 'Finding the longitude' seemed to be the key to this, as was made clear by Sir Isaac Newton when he appeared before a Parliamentary Committee that had been set up to examine the problem:

  That, for determining the Longitude at Sea, there have been several Projects, true in theory, but difficult to execute. One is a Watch to keep Time exactly, but, by reason of the motion of the Ship at Sea, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity in different latitudes, such a Watch has not yet been made.2

  As a result, on 8 July 1714 Queen Anne gave the Royal Assent to A Bill for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea. A prize of 20,000 was offered, equivalent to over £1 million today, for a method of determining the longitude at sea to within thirty geographical miles at the end of a voyage to the West Indies. One 'geographical mile' is equivalent to one arc-minute of longitude at the Equator (6,087 ft). Since one degree of longitude corresponds to 4 minutes of time, award of the full prize meant that the chronometer had to be accurate to within 2 minutes after about 6 weeks of sailing. Smaller prizes were offered for accuracy to within 40 miles (15,000) and sixty miles (10,000). The power to make the award was vested in a special Board of Longitude, the Commissioners of which were twenty- two sailors, politicians, and scholarly experts who were answerable direct to Parliament.

  For years this government Act did little to diminish general scepticism about the possibility of solving the problem. Jonathan Swift in the 'Voyage to Laputa', the third of Gulliver's Travels, published in 1726, remarked that only if Gulliver became immortal like the Struldbrugs would he 'then see the discovery of the longitude, the perpetual motion, the universal medium, and many other great inventions brought to the utmost perfixtion'.3 Nine years later the painter Hogarth went even further by including in the final madhouse scene of 'The Rake's Progress' a man who is trying to calculate the longitude! Despite the large prize offered, over twenty years elapsed before the Commissioners had anything to record in their minutes, so great appeared to be the difficulties in arriving

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  at a satisfactory solution. Nevertheless, the practical need to solve the problem became ever more pressing. In April 1741 after Commodore (later Admiral) Anson in the Centurion, accompanied by other vessels, had rounded Cape Horn, an unsuspected easterly current prevented him from travelling as far westward as he thought. Since many of his men were dying from scurvy, he was anxious to land on the island of Juan Fernandez for fresh vegetables, but the double uncertainty concerning the longitude of his ships and that of the island (a consequence of the inability of explorers to determine the longitude of their discoveries) meant that it was nearly the middle of June before he had arrived there. This delay cost the lives of nearly seventy of his men.

  By an ironical coincidence, some five years previously the Centurion had been the first ship in the history of navigation to carry, on a trial voyage to Lisbon, a clock which it was thought might provide a practical means of determining longitude at sea. The dock used in this test had a special kind of balance-spring, since it had been realized for more than half a century that pendulum clocks were not suitable for use at sea, because of the effects of pitching and rolling. Balance-springs, however, were found to be particularly sensitive to changes of temperature, losing time in hot weather and gaining it in cold. In the case of the pendulum clock the first horologist to overcome a similar difficulty was Tompion's former assistant George Graham ( 1673-1751). In 1726 he used mercury to counteract the expansion and contraction of the pendulum. It was arranged that, for example for a rise in temperature, the upward expansion of mercury in the bob would counteract the downward expansion of the steel pendulum rod, so that the period of swing of the pendulum was unaltered. Already, in 1715, he had invented an improved form of escapement, known as the dead-beat escapement. Although Graham's regulator clock of 1730 which involved both these devices proved to be an excellent timekeeper on land, it did not solve the problem of determining longitude at sea.

  The honour of solving that problem fell to John Harrison ( 1693-1776), who was originally a carpenter in Yorkshire. With his brother James he first of all produced, in 1728, a clock with a pendulum made of brass and steel rods so arranged that it was practically temperature-independent. This clock also had a complicated escapement involving a minimum of friction, which had been another source of inaccuracy in clocks. The Harrisons then went on to invent an accurate chronometer for use at sea. By 1735 it was completed and the following year, on the recommendation of the Royal Society, it was tried out

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  successfully on a voyage of the Centurion to Lisbon. This chronometer involved two straight-bar balances, with a ball at each end, which were pivoted at their centres and were connected by helical springs and cross-wires so as to swing as if geared together, but with far less friction. It was found that the motion of a ship had very little effect on their period of oscillation. As in the Harrisons' earlier clock, an ingenious combination of brass and steel rods varied the tension in the springs so as to compensate for the effect of changes of temperature. This device was the first system of compensation for temperature applied to a balance-clock, and the machine itself was the first accurate marine chronometer.

  Following the successful trial of this chronometer on the voyage to Lisbon, the Board of Longitude met on 24 June 1737. John Harrison was present, but instead of asking that his chronometer should be tested on a voyage to the West Indies he offered to make an improved version for that purpose. The Board of Longitude resolved to advance him 500. Harrison's second chronometer, however, was never given a trial at sea, presumably because war with Spain had broken out and so it would have been exposed to the danger of capture. It is also possible that Harrison may have had some doubts about its performance.4 Be that as it may, another seventeen years were to elapse while he concentrated on producing a third clock, which he intended to be his masterpiece. Throughout these years the Royal Society, influenced by Graham, helped to support him and in 1749 bestowed on him its highest award, the Copley Medal.

  Harrison's third chronometer was the most complicated of all his machines, containing no fewer than 753 separate parts. At last, in 1757, he notified the Board of Longitude that he proposed to compete with it for the 20,000 prize. At the same time he offered to make a much smaller timekeeper to serve as an auxiliary. This proposal was accepted, and aided by his son William John Harrison constructed his famous 'watch', which on test he found to be as accurate a timekeeper as his third chronometer, while possessing the advantage of being much more portable. It was a large silver watch just over 5 in. in diameter. In outward appearance it resembled the ordinary 'carriage-watch of the period, but in essentials it was similar to his third chronometer except for the escapement, which was a greatly improved version of the usual verge watch-escapement of the period. (A detailed description of this famous chronometer has been given by Gould.5) Because of its accuracy and portability Harrison decided to compete with this fourth chronometer alone. Consequently, it was officially submitted for trial on the journey

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  to Jamaica in 1762. It easily passed the test, being only 5 seconds slow on arrival there, corresponding to one and a quarter arc-minutes of longitude, which in the latitude of Jamaica was less than one geographical mile. Harrison, therefore, expected to receive the 20,000 prize. Instead, the Board of Longitude allowed him only 2,500 on account, because in their opinion the longitude of Jamaica was not known accurately enough to provide a sufficiently precise standard of time!

  Meanwhile others were competing for awards from the Board of Longitude. Because of the complicated nature of the moon's motion (it was the only problem that Newton said ever made his head ache!), the lunar-distance method of determining longitude was not of practical use until the German astronomer Tobias Mayer ( 1723-62) produced his tables of the moon's motion with the aid of calculations that had been made by the great mathematician Leonhard Euler ( 1707-83). Mayer submitted his application for the Board of Longitude's prize in 1755. Ten years later his widow was awarded 3,000 in recognition of his achievement and 500 pounds was awarded to Euler.

  After much argument and delay over Harrison's prize a second official trial of his fourth chronometer was undertaken some two years after the first, on a voyage to Barbados. Because of his age, John Harrison did not travel on either voyage but his son William went instead. On the second voyage he was accompanied by two astronomers, one of whom was Nevil Maskelyne, who shortly afterwards became Astronomer Royal. They were instructed to determine the longitude of their observationpoint on Barbados astronomically. By this time the new lunar tables, due to Euler and Tobias Mayer, were available, and the sextant had replaced the clumsier quadrant. Consequently, celestial observations were not only easier to make but could be more accurately determined and readily checked.

  Early in 1765 it was reported to the Board of Longitude that the chronometer's error was only 38.4 seconds (in seven weeks) corresponding to 9.8 geographical miles at the latitude of Barbados.6 Although this result was three times better than required, the Board remained sceptical and refused to pay Harrison until he had made a full disclosure on oath of the details of the mechanism of his chronometer. The Board would then pay him 10,000, less the £2,500 already paid to him in 1762 after the Jamaica trial. The remaining 10,000 they refused to pay until he had made two more successful timekeepers. Eventually, Harrison accepted the first half of the reward. By 1770 he had made, with his son's help, a fifth timekeeper which was a slightly improved version of the fourth.

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  Meanwhile King George III's interest had been aroused, and at an audience at Windsor granted to Harrison and his son he exclaimed, 'By God, Harrison, I will see you righted!'7 The fifth chronometer was then tested at the King's private observatory at Kew. In ten weeks its total error was only four and a half seconds. Nevertheless, the Board of Longitude objected that this trial had not been authorized by them and they refused to accept its results. Harrison then petitioned the House of Commons, where his case was supported by Fox and Burke, among others. As a result, the Board finally decided to pay Harrison another 8,750, arguing that the remaining £1,250 pounds had already been paid to him many years earlier on the understanding that his second and third chronometers should become the property of the Board! He died three years later.

  Harrison's achievement proved to be a landmark in the history of time measurement. Only after the success of the Jamaica trial in 1762 did most makers of clocks and watches begin to realize that high-precision timekeeping at sea was a practical possibility. Harrison's success also had a tremendous influence on the construction of maritime charts. In the second of Captain Cook's voyages of exploration in the South Pacific between 1772 and 1775 an exact replica of Harrison's fourth chronometer enabled him to construct maps of the coastlines of Australia and New Zealand of great accuracy.

  Outstanding among those in other countries in the eighteenth century who contributed to the development of the marine chronometer was Pierre Le Roy ( 1717-85). In 1754 he succeeded his father in the post of 'Horloger du Roi' to Louis XV of France. By then he had invented an improved form of escapement known as the 'detached escapement, in which the motion of the balance was effectively a free vibration, subject only to minimal disturbance at the instants of receiving impulse and actuating the escapement. Later Le Roy invented the 'compensation balance', which corrected the effect of change of temperature in altering the elasticity of the spring and the moment of inertia of the balance. Although Harrison was indisputably the first man to make a satisfactory marine timekeeper, the modern chronometer owes more to the inventions of Le Roy.8 Contemporary with Le Roy was his rival Ferdinand Berthoud ( 1729-1807), who was born in Switzerland but spent nearly all his working life in France. Although Berthoud did not have Le Roy's profound understanding of the basic principles of chronometry, he was like Harrison a superb craftsman who continually made improvements to his machines. Nevertheless, they remained complicated and expensive.

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  Meanwhile in England there was a concerted move to simplify marine chronometers and make them cheap enough for the ordinary navigator. The two principal pioneers in this important development were John Arnold ( 1736-99) and Thomas Earnshaw ( 1749-1829). In particular, Earnshaw improved the compensation balance that had been invented by Le Roy. As a result, from about 1825 marine chronometers became standard equipment in all ships of the Royal Navy, the East India Company having already insisted on this in their ships some years previously.

  The discovery
of historical perspective

  The eighteenth century was important in the history of time not only because of the invention of the marine chronometer, but also because the spirit of intellectual optimism that characterized the age of enlightenment, as that century came to be called, was based on a forward-looking attitude to time. The thinker who has been particularly associated with the emergence of this point of view is Leibniz, who maintained that this is 'the best of all possible worlds'. Although he has often been derided for this claim, which indeed took a severe knock from the great Lisbon earthquake of 1755, in fairness to him the emphasis should be placed on the word 'Possible', for he did not believe that this world is actually 'Perfect'. R. Nisbet's recent book on the history of the idea of progress has drawn attention to the following passage in Leibniz essay 'On the Ultimate Origination of Things' which makes this quite clear.

  To realize in its completeness the universal beauty and perfection of the works of God, we must recognize a certain perpetual and very free progress of the whole universe such that it is always going forward to greater improvement. . . .

  And to the possible objection that, if this were so, the world ought long ago to have become a paradise, there is a ready answer. Although many substances have already attained a great perfection, yet on account of the infinite divisibility of the continuous, there always remain in the abyss of things slumbering parts which have yet to be awakened, to grow in size and worth, and in a word, to advance to a more perfect state. And hence no end of progress is ever reached.9