clocks

clocks

clociau

clocks

clociau

clocks

clociau

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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Al-Jazari entered the service of the Artuqid Kings of Diyar Bakir c.1180. In 1206 the then King, Nasir al-Din, instructed him to write a book describing the things he had constructed, among which were six water clocks. The timekeeping mechanism of these clocks was not innovative and was derived from earlier Hellenistic examples. Unlike Chinese and Hellenistic water clocks, al-Jazari's clocks had no astronomical indications and were intended to display the time, in temporal or unequal hours, both audibly and visually in an arresting and entertaining manner. The timekeeping was controlled by the flow of water from a vessel which contained a float to operate the clock mechanism. An ingenious device was used to ensure that the flow of water was constant during the day and could be set to a different constant flow during the night, to allow for the variation in the length of the temporal hours. Al-Jazari's clocks have not survived, but models have been constructed from the description and illustrations in the manuscripts.

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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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Burgi entered the service of Duke William IV of Hesse in 1579 as Court Clockmaker, although he also assisted William with his astronomical observations. In 1584 he invented the cross-beat escapement which increased the accuracy of spring-driven clocks by two orders of magnitude. During the last years of the century he also worked on the development of geometrical and astronomical instruments for the Royal Observatory at Kassel.

On the death of Duke Wilhelm in 1603, and with news of his skills having reached the Holy Roman Emperor Rudolph II, in 1604 he went to Prague to become Imperial Watchmaker and to assist in the creation of a centre of scientific activity, subsequently becoming Assistant to the German astronomer, Johannes Kepler. No doubt this association led to an interest in mathematics and he made significant contributions to the concept of decimal fractions and the use of exponential notation, i.e. the use of a raised number to indicate powers of another number. It is likely that he was developing the idea of logarithms at the same time (or possibly even before) Napier, for in 1620 he made his greatest contribution to mathematics, science and, eventually, engineering, namely the publication of tables of anti-logarithms.

At Prague he continued the series of accurate clocks and instruments for astronomical measurements that he had begun to produce at Kassel. At that period clocks were very poor timekeepers since the controller, the foliot or balance, had no natural period of oscillation and was consequently dependent on the driving force. Although the force of the driving weight was constant, irregularities occurred during the transmission of the power through the train as a result of the poor shape and quality of the gearing. Burgi attempted to overcome this directly by superb craftsmanship and indirectly by using a remontoire. This device was wound at regular intervals by the main driving force and fed the power directly to the escape wheel, which impulsed the foliot. He also introduced the crossbeat escapement (a variation on the verge), which consisted of two coupled foliots that swung in opposition to each other. According to contemporary evidence his clocks produced a remarkable improvement in timekeeping, being accurate to within a minute a day. This improvement was probably a result of the use of a remontoire and the high quality of the workmanship rather than a result of the cross-beat escapement, which did not have a natural period of oscillation.

Burgi or Prague clocks, as they were known, were produced by very few other makers and were supplanted shortly afterwards by the intro-duction of the pendulum clock. Burgi also produced superb clockwork-driven celestial globes.

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See also: Briggs, Henry

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f

1. der Uhren: changeover to summer (bzw. winter, Am. daylight-saving [bzw. standard]) time, putting the clocks forward bzw. back

2. bei Reisen: die Zeitumstellung macht mir zu schaffen it takes me a while to get used to being in a different time zone, the time difference takes some getting used to; weitS. I suffer from jet lag; momentan: auch I’m feeling jet-lagged

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1) (= Zeitänderung) changing the clocks, putting the clocks back/forward

2) (= Zeitunterschied) time difference

* * *

f changing the clocks

* * *

Zeitumstellung f

1. der Uhren: changeover to summer (bzw winter, US daylight-saving [bzw standard]) time, putting the clocks forward bzw back

2. bei Reisen:

die Zeitumstellung macht mir zu schaffen it takes me a while to get used to being in a different time zone, the time difference takes some getting used to; weitS. I suffer from jet lag; momentan: auch I’m feeling jet-lagged

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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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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1 to put back (retrasar) (cita, reloj).

2 to be slow (reloj).

3 to delay, to detain, to hold up, to put back.

María atrasó el bus a propósito Mary delayed the bus on purpose.

María atrasó la reunión dos días Mary delayed the meeting two days.

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► verbo transitivo

1 (gen) to delay, postpone, put back; (reloj) to put back

► verbo intransitivo

1 (reloj) to be slow

► verbo pronominal atrasarse

1 (tren etc) to be late

2 (quedarse atrás) to fall behind

■ el corredor se atrasó en el último kilómetro de la carrera the runner fell behind in the last kilometre of the race

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atrasarse en los pagos to fall behind, be in arrears

* * *

VT [+ progreso] to slow down; [+ salida etc] to delay; [+ reloj] to put back

VI [reloj] to lose time, be slow

atrasarse

* * *

verbo transitivo

a) < reloj> to put back

b) <reunión/viaje> to postpone, put back

atrasarse v pron

1) reloj to lose time

2) (en estudios, trabajo, pagos) to fall behind, get behind

3) país/industria to fall behind

4) (esp AmL) ( llegar tarde) avión/tren to be late, be delayed; persona to be late

5) menstruación to be late

* * *

= delay, hold up, hold + Nombre + back, retard.

Ex. It would be wise to delay reading these until you have had some experience in using the scheme.

Ex. Unfortunately, goods of Community origin can also be held up by the surveillance system, often for several weeks.

Ex. Despite the improvements in the 17th edition, the scheme has been held back for years by the old policy of 'integrity of numbers' referred to above, the effects of which are not likely to be quickly mitigated.

Ex. Without the floppy disk, data processing on microcomputers would have been severely retarded.

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* atrasarse = run + late, be late (for).

* * *

verbo transitivo

a) < reloj> to put back

b) <reunión/viaje> to postpone, put back

atrasarse v pron

1) reloj to lose time

2) (en estudios, trabajo, pagos) to fall behind, get behind

3) país/industria to fall behind

4) (esp AmL) ( llegar tarde) avión/tren to be late, be delayed; persona to be late

5) menstruación to be late

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* * *

atrasar [A1 ]

1 ‹reloj› to put back

hay que atrasar los relojes una hora we have to put the clocks back one hour

2 ‹reunión/fecha/viaje› to postpone, put back

han atrasado la salida the departure has been delayed

problemas financieros han atrasado la conclusión de las obras the completion of the work has been held up by financial problems

«reloj» to lose time

A «reloj» to lose time

este reloj se atrasa this watch loses time

el reloj se me atrasa un minuto cada hora my watch loses one minute every hour

B (en los estudios, el trabajo) to fall behind, get behind

se atrasaron en el pago del alquiler they fell behind o got into arrears with the rent

C «país/industria» to fall behind

durante este período el país se atrasó en ciencia y tecnología during this period the country fell behind o lost ground in the area of science and technology

nos estamos atrasando respecto a nuestros vecinos we are falling behind our neighbors

D ( esp AmL) (llegar tarde) «avión/tren» to be late, be delayed; «persona» to be late

me atrasé porque había mucho tráfico I was delayed or held up by the traffic

E «menstruación» to be late

F (Ur) «enfermo» to get worse

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a) ‹ reloj› to put back

b) ‹reunión/viaje› to postpone, put back

a) [ reloj] to lose time;

◊ se me ha atrasado 15 minutos it's 15 minutes slow

b) (esp AmL) ( llegar tarde) [avión/tren] to be late, be delayed;

a) (en estudios, trabajo, pagos) to fall behind, get behind

b) [país/industria] to fall behind

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♦ vt

1. [poner más atrás] to move (further) back

2. [en el tiempo] [reunión, viaje, reloj] to put back;

atrasaron la fecha de la reunión they put back the date of the meeting

3. Dep [balón] to pass back

♦ vi

♦ See also the pronominal verb atrasarse

* * *

I v/t reloj put back; fecha postpone, put back

II v/i de reloj lose time

* * *

atrasar vt

: to delay, to put off

atrasar vi

: to lose time

♦ See also the reflexive verb atrasarse

* * *

atrasar vb

1. (retrasar el reloj) to put back [pt. & pp. put]

2. (aplazar) to postpone / to put off [pt. & pp. put]

3. (ir lento) to be slow

1 to postpone.

retrasaron la fecha de la reunión the meeting was postponed, they put back the date of the meeting

2 to delay, to hold up.

María retrasó la fiesta Mary delayed the party.

El chico retrasó al grupo The boy delayed the group.

3 to slow down, to hold up.

La lluvia retrasa el despegue The rain slows up the take-off.

4 to set back.

5 to put back (reloj).

habrá que retrasar los relojes una hora the clocks will have to be put back an hour

6 to pass back (sport) (balón).

7 to be slow (reloj).

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► verbo transitivo

1 (atrasar) to delay, put off, postpone

■ un accidente retrasó el tren the train was delayed by an accident

2 (reloj) to put back

3 DEPORTE to pass back

■ el público protestaba porque los jugadores retrasaban el balón the crowd protested because the players were passing the ball back

► verbo intransitivo

1 (ir atrás) to fall behind

■ retrasa en física he's behind in physics

2 (llegar tarde) to be late

3 (reloj) to be slow

► verbo pronominal retrasarse

1 (atrasarse) to be late, arrive late, be delayed

2 (reloj) to be slow

3 (trabajo, conocimientos, pagos) to fall behind

* * *

1) to delay

2) postpone

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- retrasarse

* * *

1. VT

1) (=aplazar) [+ suceso, acción] to postpone, put off; [+ fecha] to put back

2) (=retardar) to delay, hold up

3) [+ reloj] to put back

VI [reloj] to be slow

retrasarse

* * *

verbo transitivo

1)

a) < persona> to make... late

b) <producción/proceso> to delay, hold up

2) <partida/fecha> to postpone

3) < reloj> to put back

retrasarse v pron

a) ( llegar tarde) to be late

b) producción/trámite to be delayed, be held up

c) (en trabajo, estudios, pagos) to fall behind

* * *

= delay, put back, set back, hold + Nombre + back, retard, hold up.

Ex. It would be wise to delay reading these until you have had some experience in using the scheme.

Ex. The spiral begins its downward swirl very early in life when a child has difficulty learning to read since this puts him back in his other school work.

Ex. But if set-off did occur and threatened to set back and spoil subsequent impressions of the first forme, the tympan cloth could be rubbed over with lye to clean it.

Ex. Despite the improvements in the 17th edition, the scheme has been held back for years by the old policy of 'integrity of numbers' referred to above, the effects of which are not likely to be quickly mitigated.

Ex. Without the floppy disk, data processing on microcomputers would have been severely retarded.

Ex. Unfortunately, goods of Community origin can also be held up by the surveillance system, often for several weeks.

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* retrasar el avance = retard + progress.

* retrasar el desarrollo de Algo = push back + development.

* retrasar el envejecimiento = retard + aging.

* retrasarse = run + late, be late (for).

* * *

verbo transitivo

1)

a) < persona> to make... late

b) <producción/proceso> to delay, hold up

2) <partida/fecha> to postpone

3) < reloj> to put back

retrasarse v pron

a) ( llegar tarde) to be late

b) producción/trámite to be delayed, be held up

c) (en trabajo, estudios, pagos) to fall behind

* * *

* * *

retrasar [A1 ]

1 ‹persona› to make … late

el tráfico nos retrasó the traffic made us late, we were delayed by the traffic, we got held up in the traffic

2 ‹producción/proceso› to delay, hold up

B «persona» ‹partida/fecha› to delay, put off, postpone

C ‹reloj› to put back

«reloj» to run slow

1 (llegar tarde) to be late

date prisa, que estoy or voy retrasado hurry up, I'm late

el tren se retrasó the train was o arrived late

2 «producción/trabajo/trámite» to be delayed, be held up

3 (en el trabajo, los estudios) to fall behind; (en los pagos) to fall behind, get into arrears

se retrasó en presentar el informe she was late submitting the report

me he retrasado con esta traducción I'm behind with this translation

* * *

a) ‹ persona› to make … late;

◊ el tráfico nos retrasó we got held up in the traffic

b) ‹producción/proceso› to delay, hold up;

◊ la niebla retrasó la salida del avión the departure (of the plane) was delayed by fog

c) ‹partida/fecha› to postpone

d) ‹ reloj› to put back

a) ( llegar tarde) to be late

b) [producción/trámite] to be delayed, be held up

c) (en trabajo, estudios, pagos) to fall behind;

◊ se retrasó en presentarlo she was late (in) submitting it

d) [ reloj] to run slow

* * *

♦ vt

1. [aplazar] to postpone;

retrasaron la fecha de la reunión the meeting was postponed, they put back the date of the meeting

2. [demorar] to delay, to hold up

3. [hacer más lento] to slow down, to hold up;

4. [reloj] to put back;

habrá que retrasar los relojes una hora the clocks will have to be put back an hour

5. Dep [balón] to pass back

♦ vi

♦ See also the pronominal verb retrasarse

* * *

I v/t

1 proceso, movimiento hold up, delay

2 reloj put back

3 reunión postpone, put back

4 pelota pass back

II v/i

1 de reloj lose time

2 en los estudios be behind

* * *

retrasar vt

1) demorar, retardar: to delay, to hold up

2) : to put off, to postpone

♦ See also the reflexive verb retrasarse

* * *

retrasar vb

1. (en general) to delay / to hold up [pt. & pp. held]

2. (reloj) to put back [pt. & pp. put]

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: Electronics and information technology, Horology

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After serving an apprenticeship with a clock-maker in Blaubeuren, Hipp worked for various clockmakers before setting up his own workshop in Reutlingen in 1840. In 1842 he made his first electric clock with an ingenious toggle mechanism for switching the current, although he claimed that the idea had occurred to him eight years earlier. The switching mechanism was the Achilles' heel of early electric clocks. It was usually operated by the pendulum and it presented the designer with a dilemma: if the switch made a firm contact it adversely affected the timekeeping, but if the contact was lightened it sometimes failed to operate due to dirt or corrosion on the contacts. The Hipp toggle switch overcame this problem by operating only when the amplitude of the pendulum dropped below a certain value. As this occurred infrequently, the contact pressure could be increased to provide reliable switching without adversely affecting the timekeeping. It is an indication of the effectiveness of the Hipp toggle that it was used in clocks for over one hundred years and was adopted by many other makers in addition to Hipp and his successor Favag. It was generally preferred for its reliability rather than its precision, although a regulator made in 1881 for the observatory at Neuchâtel performed creditably. This regulator was enclosed in an airtight case at low pressure, eliminating errors due to changes in barometric pressure. This practice later became standard for observatory regulators such as those of Riefler and Shortt. The ability of the Hipp toggle to provide more power when the clock was subjected to an increased load made it particularly suitable for use in turret clocks, whose hands were exposed to the vagaries of the weather. Hipp also improved the operation of slave dials, which were advanced periodically by an electrical impulse from a master clock. If the electrical contacts "chattered" and produced several impulses instead of a single sharp impulse, the slave dials would not indicate the correct time. Hipp solved this problem by producing master clocks which delivered impulses that alternated in polarity, and slave dials which only advanced when the polarity was changed in this way. Polarized impulses delivered every minute became the standard practice for slave dials used on the European continent. Hipp also improved Wheatstone's chronoscope, an instrument that was used for measuring very short intervals of time (such as those involved in ballistics).

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SUBJECT AREA: Horology

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Riefler's father was a scientific-instrument maker and clockmaker who in 1841 had founded the firm of Clemens Riefler to make mathematical instruments. After graduating in engineering from the University of Munich Sigmund worked as a surveyor, but when his father died in 1876 he and his brothers ran the family firm. Sigmund was responsible for technical development and in this capacity he designed a new system of drawing-instruments which established the reputation of the firm. He also worked to improve the performance of the precision clock, and in 1889 he was granted a patent for a new form of escapement. This escapement succeeded in reducing the interference of the clock mechanism with the free swinging of the pendulum by impulsing the pendulum through its suspension strip. It proved to be the greatest advance in precision timekeeping since the introduction of the dead-beat escapement about two hundred years earlier. When the firm of Clemens Riefler began to produce clocks with this escapement in 1890, they replaced clocks with Graham's dead-beat escapement as the standard regulator for use in observatories and other applications where the highest precision was required. In 1901 a movement was fitted with electrical rewind and was encapsulated in an airtight case, at low pressure, so that the timekeeping was not affected by changes in barometric pressure. This became the standard practice for precision clocks. Although the accuracy of the Riefler clock was later surpassed by the Shortt free-pendulum clock and the quartz clock, it remained in production until 1965, by which time over six hundred instruments had been made.

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See also: Marrison, Warren Alvin

SUBJECT AREA: Horology

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Warren studied electrical engineering at the Boston Institute of Technology (later to become the Massachusetts Institute of Technology) and graduated in 1894. In 1912 he formed the Warren Electric Clock Company to make a battery-powered clock that he had patented a few years earlier. The name was changed to the Warren Telechron (time at a distance) Company after he had started to produce synchronous clocks.

In 1840 Charles Wheatstone had produced an electric master clock that produced an alternating current with a frequency of one cycle per second and which was used to drive slave dials. This system was not successful, but when Ferranti introduced the first alternating current power generator at Deptford in 1895 Hope-Jones saw in it a means of distributing time. This did not materialize immediately because the power generators did not control the frequency of the current with sufficient accuracy, and a reliable motor whose speed was related to this frequency was not available. In 1916 Warren solved both problems: he produced a reliable self-starting synchronous electric motor and he also made a master clock which could be used at the power station to control accurately the frequency of the supply. Initially the power-generating companies were reluctant to support the synchronous clock because it imposed a liability to control the frequency of the supply and the gain was likely to be small because it was very frugal in its use of power. However, with the advent of the grid system, when several generators were connected together, it became imperative to control the frequency; it was realized that although the power consumption of individual clocks was small, collectively it could be significant as they ran continuously. By the end of the 1930s more than half the clocks sold in the USA were of the synchronous type. The Warren synchronous clock was introduced into Great Britain in 1927, following the setting up of a grid system by the Electricity Commission.

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