newton-system

система, совокупность; схема (оптическая); механизм, установка

- Henry Draper system

SUBJECT AREA: Mining and extraction technology

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A direct descendant of Sir Isaac Newton, Treadgold worked as a schoolmaster, mostly at Bath College, for eleven years after completing his studies at Oxford University. He gained a reputation as an energetic teacher who devoted much of his work to sport, but he resigned his post and returned to Oxford; here, in 1897, he learned of the gold rush in the Klondike in the Canadian northwest. With a view to making his own fortune, he took a course in geology at the London Geological College and in 1898 set off for Dawson City, in the Yukon Territory. Working as a correspondent for two English newspapers, he studied thoroughly the situation there; he decided to join the stampede, but as a rather sophisticated gold hustler.

As there were limited water resources for sluicing or dredging, and underground mining methods were too expensive, Treadgold conceived the idea of hydraulic mining. He designed a ditch-and-siphon system for bringing large amounts of water down from the mountains; in 1901, after three years of negotiation with the Canadian government in Ottawa, he obtained permission to set up the Treadgold Concession to cover the water supply to the Klondike mining claims. This enabled him to supply giant water cannons which battered the hillsides, breaking up the gravel which was then sluiced. Massive protests by the individual miners in the Dawson City region, which he had overrun with his system, led to the concession being rescinded in 1904. Two years later, however, Treadgold began again, forming the Yukon Gold Company, initially in partnership with Solomon Guggenheim; he started work on a channel, completed in 1910, to carry water over a distance of 115 km (70 miles) down to Bonanza Creek. In 1919 he founded the Granville Mining Company, which was to give him control of all the gold-mining operations in the southern Klondike region. When he returned to London in the following year, the company began to fail, and in 1920 he went bankrupt with liabilities totalling more than $2 million. After the Yukon Consolidated Gold Corporation had been formed in 1923, Treadgold returned to the Klondike in 1925 in order to acquire the assets of the operating companies; he gained control and personally supervised the operations. But the company drifted towards disaster, and in 1930 he was dismissed from active management and his shares were cancelled by the courts; he fought for their reinstatement right up until his death.

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SUBJECT AREA: Weapons and armour

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Lewis graduated from the US Military Academy, West Point, in 1884 and was commissioned into the Artillery. He soon displayed his technical aptitude and in 1891 patented an artillery ranging device. This was followed by further gunnery devices to improve artillery accuracy and a quick-firing field gun. He also displayed an interest in electricity and designed a car lighting system and wind-powered electric lighting.

In 1911 he patented the gun that bears his name. The significance of this compared with existing machine guns was its comparatively light weight, which enabled it to be carried and operated by one person. Even so, the US Army showed no interest and so Lewis, by now retired from the Army, moved to Europe and set up a factory to produce it at Liège in Belgium. At the outbreak of war he moved his operation to England and merged it with the Birmingham Small Arms Company. The Lewis gun became the British Army's standard light machine gun during the First World War and was also used on aircraft. The USA eventually had a change of heart and also used the Lewis gun.

Глоссарий компании Сахалин Энерджи: па, паскаль (Pa; Па)

• па

• паскаль

SUBJECT AREA: Land transport, Railways and locomotives

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Abt trained under N. Riggenbach and worked for his short-lived International Company for Mountain Railways during the 1870s, and subsequently invented the Abt rack system as an improvement on Riggenbach's ladder rack, in which the rungs gave trouble by working loose. Abt's rack system, in what became its usual form, comprises two machined racks side by side with their teeth staggered so that a tooth in one rack is opposite a recess in the other, and at least one tooth is always engaged with a locomotive's driving pinions. This system was first used in 1884 on the mixed rack-and-adhesion Harz Railway in Germany, and then largely superseded Riggenbach's system for new rack railways built worldwide to an eventual total of seventy-two, including the Snowdon Mountain Railway in the UK that was built in the 1890s. In many cases Abt himself designed locomotives and rolling stock, and supervised their construction.

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SUBJECT AREA: Architecture and building, Electricity, Land transport, Railways and locomotives

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Graduating from the United States Naval Academy, Annapolis, in 1878, Sprague served at sea and with various shore establishments. In 1883 he resigned from the Navy and obtained employment with the Edison Company; but being convinced that the use of electricity for motive power was as important as that for illumination, in 1884 he founded the Sprague Electric Railway and Motor Company. Sprague began to develop reliable and efficient motors in large sizes, marketing 15 hp (11 kW) examples by 1885. He devised the method of collecting current by using a wooden, spring-loaded rod to press a roller against the underside of an overhead wire. The installation by Sprague in 1888 of a street tramway on a large scale in Richmond, Virginia, was to become the prototype of the universally adopted trolley system with overhead conductor and the beginning of commercial electric traction. Following the success of the Richmond tramway the company equipped sixty-seven other railways before its merger with Edison General Electric in 1890. The Sprague traction motor supported on the axle of electric streetcars and flexibly mounted to the bogie set a pattern that was widely adopted for many years.

Encouraged by successful experiments with multiple-sheave electric elevators, the Sprague Elevator Company was formed and installed the first set of high-speed passenger cars in 1893–4. These effectively displaced hydraulic elevators in larger buildings. From experience with control systems for these, he developed his system of multiple-unit control for electric trains, which other engineers had considered impracticable. In Sprague's system, a master controller situated in the driver's cab operated electrically at a distance the contactors and reversers which controlled the motors distributed down the train. After years of experiment, Sprague's multiple-unit control was put into use for the first time in 1898 by the Chicago South Side Elevated Railway: within fifteen years multiple-unit operation was used worldwide.

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GW / PJGR

SUBJECT AREA: Land transport, Railways and locomotives

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John Urpeth Rastrick, son of an engineer, was initially articled to his father and then moved to Ketley Ironworks, Shropshire, c. 1801. In 1808 he entered into a partnership with John Hazledine at Bridgnorth, Shropshire: Hazledine and Rastrick built many steam engines to the designs of Richard Trevithick, including the demonstration locomotive Catch-Me-Who-Can. The firm also built iron bridges, notably the bridge over the River Wye at Chepstow in 1815–16.

Between 1822 and 1826 the Stratford \& Moreton Railway was built under Rastrick's direction. Malleable iron rails were laid, in one of the first instances of their use. They were supplied by James Foster of Stourbridge, with whom Rastrick went into partnership after the death of Hazledine. In 1825 Rastrick was one of a team of engineers sent by the committee of the proposed Liverpool \& Manchester Railway (L \& MR) to carry out trials of locomotives built by George Stephenson on the Killingworth Waggonway. Early in 1829 the directors of the L \& MR, which was by then under construction, sent Rastrick and James Walker to inspect railways in North East England and report on the relative merits of steam locomotives and fixed engines with cable haulage. They reported, rather hesitantly, in favour of the latter, particularly the reciprocal system of Benjamin Thompson. In consequence the Rainhill Trials, at which Rastrick was one of the judges, were held that October. In 1829 Rastrick constructed the Shutt End colliery railway in Worcestershire, for which Foster and Rastrick built the locomotive Agenoria; this survives in the National Railway Museum. Three similar locomotives were built to the order of Horatio Allen for export to the USA.

From then until he retired in 1847 Rastrick found ample employment surveying railways, appearing as a witness before Parliamentary committees, and supervising construction. Principally, he surveyed the southern part of the Grand Junction Railway, which was built for the most part by Joseph Locke, and the line from Manchester to Crewe which was eventually built as the Manchester \& Birmingham Railway. The London \& Brighton Railway (Croydon to Brighton) was his great achievement: built under Rastrick's supervision between 1836 and 1840, it included three long tunnels and the magnificent Ouse Viaduct. In 1845 he was Engineer to the Gravesend \& Rochester Railway, the track of which was laid through the Thames \& Medway Canal's Strood Tunnel, partly on the towpath and partly on a continuous staging over the water.

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See also: Stephenson, Robert

SUBJECT AREA: Textiles

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George Robinson is said to have been a Scots migrant who settled at Burwell, near Nottingham, in 1737, but there is no record of his occupation until 1771, when he was noticed as a bleacher. By 1783 he and his son were describing themselves as "merchants and thread manufacturers" as well as bleachers. For their thread, they were using the system of spinning on the waterframe, but it is not known whether they held a licence from Arkwright. Between 1776 and 1791, the firm G.J. \& J.Robinson built a series of six cotton mills with a complex of dams and aqueducts to supply them in the relatively flat land of the Leen valley, near Papplewick, to the north of Nottingham. By careful conservation they were able to obtain considerable power from a very small stream. Castle mill was not only the highest one owned by the Robinsons, but it was also the highest mill on the stream and was fed from a reservoir. The Robinsons might therefore have expected to have enjoyed uninterrupted use of the water, but above them lived Lord Byron in his estate of Newstead Priory. The fifth Lord Byron loved making ornamental ponds on his property so that he could have mock naval battles with his servants, and this tampered with the water supplies so much that the Robinsons found they were unable to work their mills.

In 1785 they decided to order a rotative steam engine from the firm of Boulton \& Watt. It was erected by John Rennie; however, misfortune seemed to dog this engine, for parts went astray to Manchester and when the engine was finally running at the end of February 1786 it was found to be out of alignment so may not have been very successful. At about the same time, the lawsuit against Lord Byron was found in favour of the Robinsons, but the engine continued in use for at least twelve years and was the first of the type which was to power virtually all steamdriven mills until the 1850s to be installed in a textile mill. It was a low-pressure double-acting condensing beam engine, with a vertical cylinder, parallel motion connecting the piston toone end of a rocking beam, and a connecting rod at the other end of the beam turning the flywheel. In this case Watt's sun and planet motion was used in place of a crank.

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производная единица системы единиц физических величин
производная единица
Единица производной физической величины системы единиц, образованная в соответствии с уравнением, связывающим ее с основными единицами или с основными и уже определенными производными.
Примеры
1. 1 м/с - единица скорости, образованная из основных единиц СИ - метра и секунды.
2. 1 Н - единица силы, образованная из основных единиц СИ - килограмма, метра, и секунды.
[РМГ 29-99]

EN

derived unit
unit of measurement for a derived quantity
NOTE 1 – Some derived units in the International System of Units (SI) have special names, e.g. hertz for frequency and joule for energy, but others have compound names, e.g. metre per second for speed. Compounds including units with special names are also used, e.g. volt per metre for the electric field strength, and newton metre for torque. See in particular ISO 31 and ISO/IEC 80000.
NOTE 2 – Derived units can also be expressed by using multiples and submultiples. For example, the metre per second, symbol m/s, and the centimetre per second, symbol cm/s, are derived units of speed in the SI. The kilometre per hour, symbol km/h, is a unit of speed outside the SI but accepted for use with the SI, because the unit hour is accepted for use with the SI. The knot, equal to one nautical mile per hour, is a unit of speed outside the SI, that is used by special interest groups.
Source: ISO/IEC GUIDE 99:2007 1.11
[IEV number 112-01-19]

FR

unité dérivée, f
unité de mesure d'une grandeur dérivée
NOTE 1 – Certaines unités dérivées dans le SI ont des noms spéciaux, par exemple le hertz pour la fréquence et le joule pour l'énergie, tandis que d'autres ont des noms composés, par exemple le mètre par seconde pour la vitesse. Les unités ayant des noms spéciaux sont aussi utilisées dans des noms composés, par exemple le volt par mètre pour le champ électrique et le newton mètre pour le moment de torsion. Voir en particulier l'ISO 31 et l'ISO/CEI 80000.
NOTE 2 – On peut aussi exprimer les unités dérivées en utilisant des multiples et des sous-multiples. Par exemple, le mètre par seconde, symbole m/s, et le centimètre par seconde, symbole cm/s, sont des unités dérivées de vitesse dans le SI. Le kilomètre par heure, symbole km/h, est une unité de vitesse en dehors du SI mais en usage avec le SI, parce que l'heure est une unité en usage avec le SI. Le nœud, égal à un mille marin par heure, est une unité de vitesse en dehors du SI, qui répond aux besoins spécifiques de certains groupes d’utilisateurs.
Source: ISO/IEC GUIDE 99:2007 1.11
[IEV number 112-01-19]

Тематики

• метрология, основные понятия

Синонимы

• производная единица

EN

• derived unit (of measurement)

DE

• abgeleitete Einheit

FR

• unité (de mesure) derivée

SUBJECT AREA: Ports and shipping, Railways and locomotives

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Joseph Samuda studied as a engineer under his elder brother Jacob and formed a partnership with him in 1832 as builders of marine steam engines. In 1838, with Samuel Clegg, they took out a patent for an atmospheric railway system. In this system a cast-iron tube, with a continuous sealed slot along the top, was laid between the rails; trains were attached to a piston within the tube by an arm, the slot being opened and resealed before and behind it. The tube ahead of the piston was exhausted by a stationary steam engine and the train propelled by atmospheric pressure. The system appeared to offer clean, fast travel and was taken up by noted contemporary railway engineers such as I.K. Brunel and C.B. Vignoles, but it eventually proved a failure as no satisfactory means of sealing the slot could at that time be found. It did, however, lead to experiments in the 1860s with underground, pneumatic-tube railways, in which the vehicle would be its own piston, and Samuda Bros, supplied cast-iron tubes for such a line. Meanwhile, Samuda Bros, had commenced building iron steamships in 1843, and although Jacob Samuda lost his life in 1844 as the result of an accident aboard one of the earliest built, the firm survived to become noted London builders of steamships of many types over the ensuing four decades. Joseph Samuda became a founder member of the Institution of Naval Architects in 1860, and was MP for Tavistock from 1865 to 1868 and for Tower Hamlets from 1868 to 1880.

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SUBJECT AREA: Domestic appliances and interiors

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Born in upstate New York, where his father was a small manufacturer, Edward Clark attended college at Williams and graduated in 1831. He became a lawyer in New York City and from then on lived either in the city or on his rural estate near Cooperstown in upstate New York. After a series of share manipulations, Clark acquired a one-third interest in Isaac M. Singer's company. They soon bought out one of Singer's earlier partners, G.B.Zeiber, and in 1851, under the name of I.M.Singer \& Co., they set up a permanent sewing machine business with headquarters in New York.

The success of their firm initially rested on marketing. Clark introduced door-to-door sales-people and hire-purchase for their sewing machines in 1856 ($50 cash down, or $100 with a cash payment of $5 and $3 a month thereafter). He also trained women to demonstrate to potential customers the capabilities of the Singer sewing machine. At first their sewing machines continued to be made in the traditional way, with the parts fitted together by skilled workers through hand filing and shaping so that the parts would fit only onto one machine. This resembled European practice rather than the American system of manufacture that had been pioneered in the armouries in that country. In 1856 Singer brought out their first machine intended exclusively for home use, and at the same time manufacturing capacity was improved. Through increased sales, a new factory was built in 1858–9 on Mott Street, New York, but it soon became inadequate to meet demand.

In 1863 the Singer company was incorporated as the Singer Manufacturing Co. and began to modernize its production methods with special jigs and fixtures to help ensure uniformity. More and more specialized machinery was built for making the parts. By 1880 the factory, then at Elizabethport, New Jersey, was jammed with automatic and semi-automatic machine tools. In 1882 the factory was producing sewing machines with fully interchangeable parts that did not require hand fitting in assembly. Production rose from 810 machines in 1853 to half a million in 1880. A new family model was introduced in 1881. Clark had succeeded Singer, who died in 1875, as President of the company, but he retired in 1882 after he had seen through the change to mass production.

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    Modern Science Focuses Not on Nature Itself, But on Abstract Representations of Nature

   To Newtonians, each question had its singular answer, one that would remain the same no matter who asked it, or why. But now, the uncertainty that undercuts every measurement of some fact in the real world compels the observer to choose which question to ask, which aspect of a phenomenon to study.

   The necessity of choice became overwhelmingly apparent when Heisenberg elevated uncertainty to a principle in quantum mechanics in 1927, having recognized that on the subatomic level the observer had to emphasize only one of a pair of properties to study at any one time. In one of the prominent interpretations of quantum mechanics, the idea took on a larger meaning: that in choosing what to study, the scientist in effect creates the object of his inquiry.... The impossibility of constructing a complete, accurate quantitative description of a complex system forces observers to pick which aspects of the system they most wish to understand....

   What one studies from among this wealth of choice depends on what one wants to know; the questions create-or at least determine-the range of possible answers. No such answer can be completely "true": instead of saying "This is what nature is like," they can claim only, "This is what nature seems like from here"-a vastly diminished claim from that of Newton. The critical issue raised by such subjectivity is how to decide what value each partial answer has, what connection it actually makes between the real world and our understanding of it. The object of study, the focus of much of modern science, has therefore shifted inward, to examine not nature itself but rather to study the abstract representations of nature, the choices made of what to leave in and what to drop out of any given study. (Levenson, 1995, pp. 228-229)

1) система первого

SUBJECT AREA: Canals

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Born in a remote area and with no material advantages, Brindley followed casual rural labouring occupations until 1733, when he became apprenticed to Abraham Bennett of Macclesfield, a wheelwright and millwright. Though lacking basic education in reading and writing, he demonstrated his ability, partly through his photographic memory, to solve practical problems. This established his reputation, and after Bennett's death in 1742 he set up his own business at Leek as a millwright. His skill led to an invitation to solve the problem of mine drainage at Wet Earth Colliery, Clifton, near Manchester. He tunnelled 600 ft (183 m) through rock to provide a leat for driving a water-powered pump.

Following work done on a pump on Earl Gower's estate at Trentham, Brindley's name was suggested as the engineer for the proposed canal for which the Duke of Bridge water (Francis Egerton) had obtained an Act in 1759. The Earl and the Duke were brothers-in-law, and the agents for the two estates were, in turn, the Gilbert brothers. The canal, later known as the Bridgewater Canal, was to be constructed to carry coal from the Duke's mines at Worsley into Manchester. Brindley advised on the details of its construction and recommended that it be carried across the river Irwell at Barton by means of an aqueduct. His proposals were accepted, and under his supervision the canal was constructed on a single level and opened in 1761. Brindley had also surveyed for Earl Gower a canal from the Potteries to Liverpool to carry pottery for export, and the signal success of the Bridgewater Canal ensured that the Trent and Mersey Canal would also be built. These undertakings were the start of Brindley's career as a canal engineer, and it was largely from his concepts that the canal system of the Midlands developed, following the natural contours rather than making cuttings and constructing large embankments. His canals are thus winding navigations unlike the later straight waterways, which were much easier to traverse. He also adopted the 7 ft (2.13 m) wide lock as a ruling dimension for all engineering features. For cheapness, he formed his canal tunnels without a towpath, which led to the notorious practice of legging the boats through the tunnels.

Brindley surveyed a large number of projects and such was his reputation that virtually every proposal was submitted to him for his opinion. Included among these projects were the Staffordshire and Worcestershire, the Rochdale, the Birmingham network, the Droitwich, the Coventry and the Oxford canals. Although he was nominally in charge of each contract, much of the work was carried out by his assistants while he rushed from one undertaking to another to ensure that his orders were being carried out. He was nearly 50 when he married Anne Henshall, whose brother was also a canal engineer. His fees and salaries had made him very wealthy. He died in 1772 from a chill sustained when carrying out a survey of the Caldon Canal.

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SUBJECT AREA: Mechanical, pneumatic and hydraulic engineering

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Although known as Clement in his professional life, his baptism at Asby and his death were registered under the name of Joseph Clemmet. He worked as a slater until the age of 23, but his interest in mechanics led him to spend much of his spare time in the local blacksmith's shop. By studying books on mechanics borrowed from his cousin, a watchmaker, he taught himself and with the aid of the village blacksmith made his own lathe. By 1805 he was able to give up the slating trade and find employment as a mechanic in a small factory at Kirkby Stephen. From there he moved to Carlisle for two years, and then to Glasgow where, while working as a turner, he took lessons in drawing; he had a natural talent and soon became an expert draughtsman. From about 1809 he was employed by Leys, Mason \& Co. of Aberdeen designing and making power looms. For this work he built a screw-cutting lathe and continued his self-education. At the end of 1813, having saved about £100, he made his way to London, where he soon found employment as a mechanic and draughtsman. Within a few months he was engaged by Joseph Bramah, and after a trial period a formal agreement dated 1 April 1814 was made by which Clement was to be Chief Draughtsman and Superintendent of Bramah's Pimlico works for five years. However, Bramah died in December 1814 and after his sons took over the business it was agreed that Clement should leave before the expiry of the five-year period. He soon found employment as Chief Draughtsman with Henry Maudslay \& Co. By 1817 Clement had saved about £500, which enabled him to establish his own business at Prospect Place, Newington Butts, as a mechanical draughtsman and manufacturer of high-class machinery. For this purpose he built lathes for his own use and invented various improvements in their detailed design. In 1827 he designed and built a facing lathe which incorporated an ingenious system of infinitely variable belt gearing. He had also built his own planing machine by 1820 and another, much larger one in 1825. In 1828 Clement began making fluted taps and dies and standardized the screw threads, thus anticipating on a small scale the national standards later established by Sir Joseph Whitworth. Because of his reputation for first-class workmanship, Clement was in the 1820s engaged by Charles Babbage to carry out the construction of his first Difference Engine.

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SUBJECT AREA: Domestic appliances and interiors, Textiles

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Son of Elias Howe, a farmer, he acquired his mechanical knowledge in his father's mill. He left school at 12 years of age and was apprenticed for two years in a machine shop in Lowell, Massachusetts, and later to an instrument maker, Ari Davis in Boston, Massachusetts, where his master's services were much in demand by Harvard University. Fired by a desire to invent a sewing machine, he utilized the experience gained in Lowell to devise a shuttle carrying a lower thread and a needle carrying an upper thread to make lock-stitch in straight lines. His attempts were so rewarding that he left his job and was sustained first by his father and then by a partner. By 1845 he had built a machine that worked at 250 stitches per minute, and the following year he patented an improved machine. The invention of the sewing machine had an enormous impact on the textile industry, stimulating demand for cloth because making up garments became so much quicker. The sewing machine was one of the first mass-produced consumer durables and was essentially an American invention. William Thomas, a London manufacturer of shoes, umbrellas and corsets, secured the British rights and persuaded Howe to come to England to apply it to the making of shoes. This Howe did, but he quarrelled with Thomas after less than one year. He returned to America to face with his partner, G.W.Bliss, a bigger fight over his patent (see I.M. Singer), which was being widely infringed. Not until 1854 was the case settled in his favour. This litigation threatened the very existence of the new industry, but the Great Sewing Machine Combination, the first important patent-pooling arrangement in American history, changed all this. For a fee of $5 on every domestically-sold machine and $1 on every exported one, Howe contributed to the pool his patent of 1846 for a grooved eye-pointed needle used in conjunction with a lock-stitch-forming shuttle. Howe's patent was renewed in 1861; he organized and equipped a regiment during the Civil War with the royalties. When the war ended he founded the Howe Machine Company of Bridgeport, Connecticut.

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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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