Horology

See also: INDEX BY SUBJECT AREA

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al-Jazari, Ibn al-Razzaz

Arnold, John

Bain, Alexander

Barlow, Edward

Breguet, Abraham-Louis

Burgi, Jost

Cady, Walter Guyton

Ctesibius of Alexandria

Dondi, Giovanni

Essen, Louis

Graham, George

Grimthorpe, Edmund Beckett, Baron

Guillaume, Charles-Edouard

Harrison, John

Harwood, John

Hetzel, Max

Hipp, Matthäus

Hooke, Robert

Huygens, Christiaan

Leonardo da Vinci

Le Roy, Pierre

Leschot, Georges Auguste

Lioret, Henri Jules

Marrison, Warren Alvin

Mudge, Thomas

Richard of Wallingford, Abbot

Riefler, Sigmund

Shortt, William Hamilton

Sinclair, Sir Clive Maries

Su Song

Tompion, Thomas

Warren, Henry Ellis

Yi-Xing

Zhang Sixun

horology

horology

horology

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horology

• horology

• watchmaking

horology, time, timing

SUBJECT AREA: Horology

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Huygens was born into a cultured and privileged class. His father, Constantijn, was a poet and statesman who had wide interests. Constantijn exerted a strong influence on his son, who was educated at home until he reached the age of 16. Christiaan studied law and mathematics at Ley den University from 1645 to 1647, and continued his studies at the Collegium Arausiacum in Breda until 1649. He then lived at The Hague, where he had the means to devote his time entirely to study. In 1666 he became a Member of the Académie des Sciences in Paris and settled there until his return to The Hague in 1681. He also had a close relationship with the Royal Society and visited London on three occasions, meeting Newton on his last visit in 1689. Huygens had a wide range of interests and made significant contributions in mathematics, astronomy, optics and mechanics. He also made technical advances in optical instruments and horology.

Despite the efforts of Burgi there had been no significant improvement in the performance of ordinary clocks and watches from their inception to Huygens's time, as they were controlled by foliots or balances which had no natural period of oscillation. The pendulum appeared to offer a means of improvement as it had a natural period of oscillation that was almost independent of amplitude. Galileo Galilei had already pioneered the use of a freely suspended pendulum for timing events, but it was by no means obvious how it could be kept swinging and used to control a clock. Towards the end of his life Galileo described such a. mechanism to his son Vincenzio, who constructed a model after his father's death, although it was not completed when he himself died in 1642. This model appears to have been copied in Italy, but it had little influence on horology, partly because of the circumstances in which it was produced and possibly also because it differed radically from clocks of that period. The crucial event occurred on Christmas Day 1656 when Huygens, quite independently, succeeded in adapting an existing spring-driven table clock so that it was not only controlled by a pendulum but also kept it swinging. In the following year he was granted a privilege or patent for this clock, and several were made by the clockmaker Salomon Coster of The Hague. The use of the pendulum produced a dramatic improvement in timekeeping, reducing the daily error from minutes to seconds, but Huygens was aware that the pendulum was not truly isochronous. This error was magnified by the use of the existing verge escapement, which made the pendulum swing through a large arc. He overcame this defect very elegantly by fitting cheeks at the pendulum suspension point, progressively reducing the effective length of the pendulum as the amplitude increased. Initially the cheeks were shaped empirically, but he was later able to show that they should have a cycloidal shape. The cheeks were not adopted universally because they introduced other defects, and the problem was eventually solved more prosaically by way of new escapements which reduced the swing of the pendulum. Huygens's clocks had another innovatory feature: maintaining power, which kept the clock going while it was being wound.

Pendulums could not be used for portable timepieces, which continued to use balances despite their deficiencies. Robert Hooke was probably the first to apply a spring to the balance, but his efforts were not successful. From his work on the pendulum Huygens was well aware of the conditions necessary for isochronism in a vibrating system, and in January 1675, with a flash of inspiration, he realized that this could be achieved by controlling the oscillations of the balance with a spiral spring, an arrangement that is still used in mechanical watches. The first model was made for Huygens in Paris by the clockmaker Isaac Thuret, who attempted to appropriate the invention and patent it himself. Huygens had for many years been trying unsuccessfully to adapt the pendulum clock for use at sea (in order to determine longitude), and he hoped that a balance-spring timekeeper might be better suited for this purpose. However, he was disillusioned as its timekeeping proved to be much more susceptible to changes in temperature than that of the pendulum clock.

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SUBJECT AREA: Horology, Telecommunications

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Alexander Bain was born into a crofting family in a remote part of Scotland. He was apprenticed to a watchmaker in Wick and during that time he was strongly influenced by a lecture on "Heat, sound and electricity" that he heard in nearby Thurso. This lecture induced him to take up a position in Clerkenwell in London, working as a journeyman clockmaker, where he was able to further his knowledge of electricity by attending lectures at the Adelaide Gallery and the Polytechnic Institution. His thoughts naturally turned to the application of electricity to clockmaking, and despite a bitter dispute with Charles Wheatstone over priority he was granted the first British patent for an electric clock. This patent, taken out on 11 January 1841, described a mechanism for an electric clock, in which an oscillating component of the clock operated a mechanical switch that initiated an electromagnetic pulse to maintain the regular, periodic motion. This principle was used in his master clock, produced in 1845. On 12 December of the same year, he patented a means of using electricity to control the operation of steam railway engines via a steam-valve. His earliest patent was particularly far-sighted and anticipated most of the developments in electrical horology that occurred during the nineteenth century. He proposed the use of electricity not only to drive clocks but also to distribute time over a distance by correcting the hands of mechanical clocks, synchronizing pendulums and using slave dials (here he was anticipated by Steinheil). However, he was less successful in putting these ideas into practice, and his electric clocks proved to be unreliable. Early electric clocks had two weaknesses: the battery; and the switching mechanism that fed the current to the electromagnets. Bain's earth battery, patented in 1843, overcame the first defect by providing a reasonably constant current to drive his clocks, but unlike Hipp he failed to produce a reliable switch.

The application of Bain's numerous patents for electric telegraphy was more successful, and he derived most of his income from these. They included a patent of 12 December 1843 for a form of fax machine, a chemical telegraph that could be used for the transmission of text and of images (facsimile). At the receiver, signals were passed through a moving band of paper impregnated with a solution of ammonium nitrate and potassium ferrocyanide. For text, Morse code signals were used, and because the system could respond to signals faster than those generated by hand, perforated paper tape was used to transmit the messages; in a trial between Paris and Lille, 282 words were transmitted in less than one minute. In 1865 the Abbé Caselli, a French engineer, introduced a commercial fax service between Paris and Lyons, based on Bain's device. Bain also used the idea of perforated tape to operate musical wind instruments automatically. Bain squandered a great deal of money on litigation, initially with Wheatstone and then with Morse in the USA. Although his inventions were acknowledged, Bain appears to have received no honours, but when towards the end of his life he fell upon hard times, influential persons in 1873 secured for him a Civil List Pension of £80 per annum and the Royal Society gave him £150.

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See also: Bakewell, Frederick C.

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SUBJECT AREA: Horology

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When Breguet was 11 years old his father died and his mother married a Swiss watchmaker who had Paris connections. His stepfather introduced him to horology and this led to an apprenticeship in Paris, during which he also attended evening classes in mathematics at the Collège Mazarin. In 1775 he married and set up a workshop in Paris, initially in collaboration with Xavier Gide. There he established a reputation among the aristocracy for elegant and innovative timepieces which included a perpétuelle, or self-winding watch, which he developed from the ideas of Perrelet. He also enjoyed the patronage of Marie Antoinette and Louis XVI. During the French Revolution his life was in danger and in 1793 he fled to Neuchâtel. The two years he spent there comprised what was intellectually one of his most productive periods and provided many of the ideas that he was able to exploit after he had returned to Paris in 1795. By the time of his death he had become the most prestigious watchmaker in Europe: he supplied timepieces to Napoleon and, after the fall of the Empire, to Louis XVIII, as well as to most of the crowned heads of Europe.

Breguet divided his contributions to horology into three categories: improvements in appearance and functionality; improvements in durability; and improvements in timekeeping. His pendule sympathique was in the first category and consisted of a clock which during the night set a watch to time, regulated it and wound it. His parachute, a spring-loaded bearing, made a significant contribution to the durability of a watch by preventing damage to its movement if it was dropped. Among the many improvements that Breguet made to timekeeping, two important ones were the introduction of the overcoil balance spring and the tourbillon. By bending the outside end of the balance spring over the top of the coils Breguet was able to make the oscillations of the balance isochronous, thus achieving for the flat spring what Arnold had already accomplished for the cylindrical balance spring. The timekeeping of a balance is also dependent on its position, and the tourbillon was an attempt to average-out positional errors by placing the balance wheel and the escapement in a cage that rotated once every minute. This principle was revived in a simplified form in the karussel at the end of the nineteenth century.

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SUBJECT AREA: Horology

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Born Edmund Beckett Denison, he was educated at Eton and Trinity College, Cambridge, where he studied mathematics, graduating in 1838. He was called to the Bar in 1841 and became a Queen's Counsel in 1854. He built up a large and lucrative practice which gave him the independence to pursue his many interests outside law. His interest in horology may have been stimulated by a friend and fellow lawyer, J.M. Bloxham, who interestingly had invented a gravity escapement with an affinity to the escapement eventually used by Denison. Denison studied horology with his usual thoroughness and by 1850 he had published his Rudimentary Treatise on Clock and Watchmaking. It was natural, therefore, that he should have been invited to be a referee when a disagreement arose over the design of the clock for the new Houses of Parliament. Typically, he interpreted his brief very liberally and designed the clock himself. The most distinctive feature of the clock, in its final form, was the incorporation of a gravity escapement. A gravity escapement was particularly desirable in a public clock as it enabled the pendulum to receive a constant impulse (and thus swing with a constant amplitude), despite the variable forces that might be exerted by the wind on the exposed hands. The excellent performance of the prestigious clock at Westminster made Denison's form of gravity escapement de rigueur for large mechanical public clocks produced in Britain and in many other countries. In 1874 he inherited his father's baronetcy, dropping the Denison name, but later adopted the name Grimthorpe when he was created a Baron in 1886.

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SUBJECT AREA: Horology

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Little is known about Tompion's early life except that he was born into a family of blacksmiths. When he was admitted into the Clockmakers' Company in 1671 he was described as a "Great Clockmaker", which meant a maker of turret clocks, and as these clocks were made of wrought iron they would have required blacksmithing skills. Despite this background, he also rapidly established his reputation as a watchmaker. In 1674 he moved to premises in Water Lane at the sign of "The Dial and Three Crowns", where his business prospered and he remained for the rest of his life. Assisted by journeymen and up to eleven apprentices at any one time, the output from his workshop was prodigious, amounting to over 5,000 watches and 600 clocks. In his lifetime he was famous for his watches, as these figures suggest, but although they are of high quality they do not differ markedly from those produced by other London watchmakers of that period. He is now known more for the limited number of elaborate clocks that he produced, such as the equation clock and the spring-driven clock of a year's duration, which he made for William III. Around 1711 he took into partnership his nephew by marriage, George Graham, who carried on the business after his death.

Although Tompion does not seem to have been particularly innovative, he lived at a time when great advances were being made in horology, which his consummate skill as a craftsman enabled him to exploit. In this he was greatly assisted by his association with Robert Hooke, for whom Tompion constructed a watch with a balance spring in 1675; at that time Hooke was trying to establish his priority over Huygens for this invention. Although this particular watch was not successful, it made Tompion aware of the potential of the balance spring and he became the first person in England to apply Huygens's spiral spring to the balance of a watch. Although Thuret had constructed such a watch somewhat earlier in France, the superior quality of Tompion's wheel work, assisted by Hooke's wheel-cutting engine, enabled him to dominate the market. The anchor escapement (which reduced the amplitude of the pendulum's swing) was first applied to clocks around this time and produced further improvements in accuracy which Tompion and other makers were able to utilize. However, the anchor escapement, like the verge escapement, produced recoil (the clock was momentarily driven in reverse). Tompion was involved in attempts to overcome this defect with the introduction of the dead-beat escapement for clocks and the horizontal escapement for watches. Neither was successful, but they were both perfected later by George Graham.

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SUBJECT AREA: Horology

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Most clepsydra clocks, such as that of al-Jarazi, measured time continuously by the constant flow of a liquid and most mechanical clocks measure time discontinuously by means of an escapement. The clepsydra clock devised by Zhang Sixun in 976 and completed in 979 was unusual as it incorporated an escapement. It consisted of a large wheel with buckets around its periphery. A constant stream of water was directed into one of the buckets until it reached a predetermined weight, this released the wheel, allowing it to rotate to a new position where the process was repeated (this mechanism may have been introduced by the Chinese astronomer and mathematician Zhang Heng in the second century). The water was later replaced by mercury to prevent freezing in winter. With suitable gearing the movement of the wheel was used to drive a celestial globe, a carousel for written time announcements and jacks for audible time signals. This clock has not survived and is known only from the work Hsin I Hsiang Fa Yao (New Armillary Sphere and Celestial Globe System Essentials), which was printed in 1172 and is ascribed to Su Song. This work also describes two similar but later astronomical clock towers with water-wheel escape-ments. Several models of the water-wheel escapement have been constructed from the description in this work.

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horology, clock-making, science of making timepieces or any other kind of devices for measuring time.

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horology

SUBJECT AREA: Horology

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Graham's father died soon after his birth, so he was raised by his brother. In 1688 he was apprenticed to the London clockmaker Henry Aske, and in 1695 he gained his freedom. He was employed as a journeyman by Tompion in 1696 and later married his niece. In 1711 he formed a partnership with Tompion and effectively ran the business in Tompion's declining years; he took over the business after Tompion died in 1713. In addition to his horological interests he also made scientific instruments, specializing in those for astronomical use. As a person, he was well respected and appears to have lived up to the epithet "Honest George Graham". He befriended John Harrison when he first went to London and lent him money to further his researches at a time when they might have conflicted with his own interests.

The two common forms of escapement in use in Graham's time, the anchor escapement for clocks and the verge escapement for watches, shared the same weakness: they interfered severely with the free oscillation of the pendulum and the balance, and thus adversely affected the timekeeping. Tompion's two frictional rest escapements, the dead-beat for clocks and the horizontal for watches, had provided a partial solution by eliminating recoil (the momentary reversal of the motion of the timepiece), but they had not been successful in practice. Around 1720 Graham produced his own much improved version of the dead-beat escapement which became a standard feature of regulator clocks, at least in Britain, until its supremacy was challenged at the end of the nineteenth century by the superior accuracy of the Riefler clock. Another feature of the regulator clock owed to Graham was the mercury compensation pendulum, which he invented in 1722 and published four years later. The bob of this pendulum contained mercury, the surface of which rose or fell with changes in temperature, compensating for the concomitant variation in the length of the pendulum rod. Graham devised his mercury pendulum after he had failed to achieve compensation by means of the difference in expansion between various metals. He then turned his attention to improving Tompion's horizontal escapement, and by 1725 the cylinder escapement existed in what was virtually its final form. From the following year he fitted this escapement to all his watches, and it was also used extensively by London makers for their precision watches. It proved to be somewhat lacking in durability, but this problem was overcome later in the century by using a ruby cylinder, notably by Abraham Louis Breguet. It was revived, in a cheaper form, by the Swiss and the French in the nineteenth century and was produced in vast quantities.

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See also: Barlow, Edward; Guillaume, Charles-Edouard

SUBJECT AREA: Horology, Metallurgy

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Guillaume came from a family of clock-and watchmakers. He was educated at the Gymnasium in Neuchâtel and at Zurich Polytechnic, from which he received his doctorate in 1883 for a thesis on electrolytic capacitors. In the same year he joined the International Bureau of Weights and Measures at Sèvres in France, where he was to spend the rest of his working life. He retired as Director in 1936. At the bureau he was involved in distributing the national standards of the metre to countries subscribing to the General Conference on Weights and Measures that had been held in 1889. This made him aware of the crucial effect of thermal expansion on the lengths of the standards and he was prompted to look for alternative materials that would be less costly than the platinum alloys which had been used. While studying nickel steels he made the surprising discovery that the thermal expansion of certain alloy compositions was less than that of the constituent metals. This led to the development of a steel containing about 36 per cent nickel that had a very low thermal coefficient of expansion. This alloy was subsequently named "invar", an abbreviation of invariable. It was well known that changes in temperature affected the timekeeping of clocks by altering the length of the pendulum, and various attempts had been made to overcome this defect, most notably the mercury-compensated pendulum of Graham and the gridiron pendulum of Harrison. However, an invar pendulum offered a simpler and more effective method of temperature compensation and was used almost exclusively for pendulum clocks of the highest precision.

Changes in temperature can also affect the timekeeping of watches and chronometers, but this is due mainly to changes in the elasticity or stiffness of the balance spring rather than to changes in the size of the balance itself. To compensate for this effect Guillaume developed another more complex nickel alloy, "elinvar" (elasticity invariable), whose elasticity remained almost constant with changes in temperature. This had two practical consequences: the construction of watches could be simplified (by using monometallic balances) and more accurate chronometers could be made.

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See also: Le Roy, Pierre

SUBJECT AREA: Horology, Ports and shipping

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John Harrison was the son of a carpenter and was brought up to that trade. He was largely self-taught and learned mechanics from a copy of Nicholas Saunderson's lectures that had been lent to him. With the assistance of his younger brother, James, he built a series of unconventional clocks, mainly of wood. He was always concerned to reduce friction, without using oil, and this influenced the design of his "grasshopper" escapement. He also invented the "gridiron" compensation pendulum, which depended on the differential expansion of brass and steel. The excellent performance of his regulator clocks, which incorporated these devices, convinced him that they could also be used in a sea dock to compete for the longitude prize. In 1714 the Government had offered a prize of £20,000 for a method of determining longitude at sea to within half a degree after a voyage to the West Indies. In theory the longitude could be found by carrying an accurate timepiece that would indicate the time at a known longitude, but the requirements of the Act were very exacting. The timepiece would have to have a cumulative error of no more than two minutes after a voyage lasting six weeks.

In 1730 Harrison went to London with his proposal for a sea clock, supported by examples of his grasshopper escapement and his gridiron pendulum. His proposal received sufficient encouragement and financial support, from George Graham and others, to enable him to return to Barrow and construct his first sea clock, which he completed five years later. This was a large and complicated machine that was made out of brass but retained the wooden wheelwork and the grasshopper escapement of the regulator clocks. The two balances were interlinked to counteract the rolling of the vessel and were controlled by helical springs operating in tension. It was the first timepiece with a balance to have temperature compensation. The effect of temperature change on the timekeeping of a balance is more pronounced than it is for a pendulum, as two effects are involved: the change in the size of the balance; and the change in the elasticity of the balance spring. Harrison compensated for both effects by using a gridiron arrangement to alter the tension in the springs. This timekeeper performed creditably when it was tested on a voyage to Lisbon, and the Board of Longitude agreed to finance improved models. Harrison's second timekeeper dispensed with the use of wood and had the added refinement of a remontoire, but even before it was tested he had embarked on a third machine. The balance of this machine was controlled by a spiral spring whose effective length was altered by a bimetallic strip to compensate for changes in temperature. In 1753 Harrison commissioned a London watchmaker, John Jefferys, to make a watch for his own personal use, with a similar form of temperature compensation and a modified verge escapement that was intended to compensate for the lack of isochronism of the balance spring. The time-keeping of this watch was surprisingly good and Harrison proceeded to build a larger and more sophisticated version, with a remontoire. This timekeeper was completed in 1759 and its performance was so remarkable that Harrison decided to enter it for the longitude prize in place of his third machine. It was tested on two voyages to the West Indies and on both occasions it met the requirements of the Act, but the Board of Longitude withheld half the prize money until they had proof that the timekeeper could be duplicated. Copies were made by Harrison and by Larcum Kendall, but the Board still continued to prevaricate and Harrison received the full amount of the prize in 1773 only after George III had intervened on his behalf.

Although Harrison had shown that it was possible to construct a timepiece of sufficient accuracy to determine longitude at sea, his solution was too complex and costly to be produced in quantity. It had, for example, taken Larcum Kendall two years to produce his copy of Harrison's fourth timekeeper, but Harrison had overcome the psychological barrier and opened the door for others to produce chronometers in quantity at an affordable price. This was achieved before the end of the century by Arnold and Earnshaw, but they used an entirely different design that owed more to Le Roy than it did to Harrison and which only retained Harrison's maintaining power.

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See also: Burgi, Jost; Huygens, Christiaan