Tompion

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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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

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Barlow was the son of Edward Booth, but he adopted the surname of his godfather, the Benedictine monk Ambrose Barlow, as a condition of his will. In 1659 he entered the English College at Lisbon, and after being ordained a priest he was sent to the English mission. There he resided at Parkhall in Lancashire, the seat of Mr Houghton, with whom he later collaborated on the horizontal escapement.

At a time when it was difficult to produce a light to examine the dial of a clock or watch at night, a mechanism that would indicate the hours and subdivisions of the hour audibly and at will was highly desirable. The count wheel, which had been used from the earliest times to control the striking of a clock, was unsuitable for this purpose as it struck the hours in sequence. If the mechanism was set off manually to determine the time, the strike would no longer correspond with the indications on the dial. In 1675 Barlow invented rack striking, where the hour struck was determined solely by the position of the hour hand. With this mechanism it was therefore possible to repeat the hour at will, without upsetting the sequence of striking. In 1687 Barlow tried to patent a method of repeating for watches, but it was rejected by James II in favour of a system produced by the watchmaker Daniel Quare and which was simpler to operate. He was successful in obtaining a patent for a horizontal escapement for watches in 1695, in collaboration with William Hough ton and Thomas Tompion. Although this escapement was little used, it can be regarded as the forerunner of the cylinder escapement that George Graham introduced c. 1725.

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1) Naval: muzzle protector, nose plug, tampion

2) Military: muzzle tampion

3) Engineering: muzzle plug

4) Arms production: tompion

1) Naval: buckler plate, hawse flap, tompion

2) Engineering: hawse buckler

3) Sakhalin energy glossary: buckler

4) Yachting: hole hawse pipe cap

1) Naval: muzzle bag

2) Arms production: muzzle cover, tompion

muffler, scarf, tompion.

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► nombre masculino invariable

1 scarf, muffler

• scarf

• tompion

SUBJECT AREA: Horology

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Louis Essen joined the National Physical Laboratory (NPL) at Teddington in 1927 after graduating from London University. He spent his whole working life at the NPL and retired in 1972; his research there was recognized by the award of a DSc in 1948. At NPL he joined a team working on the development of frequency standards using quartz crystals and he designed a very successful quartz oscillator, which became known as the "Essen ring". He was also involved with radio frequency oscillators. His expertise in these fields was to play a crucial role in the development of the caesium clock. The idea of an atomic clock had been proposed by I.I.Rabbi in 1945, and an instrument was constructed shortly afterwards at the National Bureau of Standards in the USA. However, this device never realized the full potential of the concept, and after seeing it on a visit to the USA Essen was convinced that a more successful instrument could be built at Teddington. Assisted by J.V.L.Parry, he commenced work in the spring of 1953 and by June 1955 the clock was working reliably, with an accuracy that was equivalent to one second in three hundred years. This was significantly more accurate than the astronomical observations that were used at that time to determine the second: in 1967 the second was redefined in terms of the value for the frequency of vibration of caesium atoms that had been obtained with this clock.

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See also: Marrison, Warren Alvin

SUBJECT AREA: Horology, Mechanical, pneumatic and hydraulic engineering

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Son of Revd John Hooke, minister of the parish, he was a sickly child who was subject to headaches which prevented protracted study. He devoted his time while alone to making mechanical models including a wooden clock. On the death of his father in October 1648 he was left £100 and went to London, where he became a pupil of Sir Peter Lely and then went to Westminster School under Dr Busby. There he learned the classical languages, some Hebrew and oriental languages while mastering six books of Euclid in one week. In 1653 he entered Christ Church College, Oxford, where he graduated MA in 1663, after studying chemistry and astronomy. In 1662 he was appointed Curator of Experiments to the Royal Society and was elected a Fellow in 1663. In 1665 his appointment was made permanent and he was given apartments in Gresham College, where he lived until his death in 1703. He was an indefatigable experimenter, perhaps best known for the invention of the universal joint named after him. The properties of the atmosphere greatly engaged him and he devised many forms of the barometer. He was the first to apply the spiral spring to the regulation of the balance wheel of the watch in an attempt to measure longitude at sea, but he did not publish his results until after Huygens's reinvention of the device in 1675. Several of his "new watches" were made by Thomas Tompion, one of which was presented to King Charles II. He is said to have invented, among other devices, thirty different ways of flying, the first practical system of telegraphy, an odometer, a hearing aid, an arithmetical machine and a marine barometer. Hooke was a small man, somewhat deformed, with long, lank hair, who went about stooped and moved very quickly. He was of a melancholy and mistrustful disposition, ill-tempered and sharp-tongued. He slept little, often working all night and taking a nap during the day. John Aubrey, his near-contemporary, wrote of Hooke, "He is certainly the greatest Mechanick this day in the World." He is said to have been the first to establish the true principle of the arch. His eyesight failed and he was blind for the last year of his life. He is best known for his Micrographia, or some Physiological Descriptions of Minute Bodies, first published in 1665. After the Great Fire of London, he exhibited a model for the rebuilding of the City. This was not accepted, but it did result in Hooke's appointment as one of two City Surveyors. This proved a lucrative post and through it Hooke amassed a fortune of some thousands of pounds, which was found intact after his death some thirty years later. It had never been opened in the interim period. Among the buildings he designed were the new Bethlehem (Bedlam) Hospital, the College of Physicians and Montague House.

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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

SUBJECT AREA: Electronics and information technology, Horology

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Marrison received his high-school education at Kingston Collegiate Institute, Ontario, and in 1914 he entered Queen's University in Kingston. He graduated in Engineering Physics in 1920, his college career having been interrupted by war service in the Royal Flying Corps. During his service in the Flying Corps he worked on radio, and when he returned to Kingston he established his own transmitter. This interest in radio was later to influence his professional life.

In 1921 he entered Harvard University, where he obtained an MA, and shortly afterwards he joined the Western Electric Company in New York to work on the recording of sound on film. In 1925 he transferred to Western Electric's Bell Laboratory, where he began what was to become his life's work: the development of frequency standards for radio transmission. In 1922 Cady had used the elastic vibration of a quartz crystal to control the frequency of a valve oscillator, but at that time there was no way of counting and displaying the number of vibrations as the frequency was too high. In 1927 Marrison succeeded in dividing the frequency electronically until it was low enough to drive a synchronous motor. Although his purpose was to determine the frequency accurately by counting the number of vibrations that occurred in a given time, he had incidentally produced the first quartz-crystal -ontrolled clock. The results were sufficiently encouraging for him to build an improved version the following year, specifically as a time and frequency standard.

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SUBJECT AREA: Horology

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Shortt entered the Engineering Department of the London and South Western Railway as an engineering cadet in 1902, remaining with the company and its successors until he retired in 1946. He became interested in precision horology in 1908, when he designed an instrument for recording the speed of trains; this led to a long and fruitful collaboration with Frank HopeJones, the proprietor of the Synchronome Company. This association culminated in the installation of a free-pendulum clock, with an accuracy of the order of one second per year, at Edinburgh Observatory in 1921. The clock's performance was far better than that of existing clocks, such as the Riefler, and a slightly modified version was produced commercially by the Synchronome Company. These clocks provided the time standard at Greenwich and many other observatories and scientific institutions across the world until they were supplanted by the quartz clock.

The period of a pendulum is constant if it swings freely with a constant amplitude in a vacuum. However, this ideal state cannot be achieved in a clock because the pendulum must be impulsed to maintain its amplitude and the swings have to be counted to indicate time. The free-pendulum clock is an attempt to approach this ideal as closely as possible. In 1898 R.J. Rudd used a slave clock, synchronized with a free pendulum, to time the impulses delivered to the free pendulum. This clock was not successful, but it provided the inspiration for Shortt's clock, which operates on the same principle. The Shortt clock used a standard Synchronome electric clock as the slave, and its pendulum was kept in step with the free pendulum by means of the "hit and miss" synchronizer that Shortt had patented in 1921. This allowed the pendulum to swing freely (in a vacuum), apart from the fraction of a second in which it received an impulse each half-minute.

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See also: Marrison, Warren Alvin