Huygens, Christiaan

SUBJECT AREA: Horology

[br]

[br]

[br]

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.

[br]

Huygens, Christiaan Huygens.

n. Huygens (Christiaan, Nederlans astronoom, fysicus en wiskundige)

Cristian Huygens, Christian Huygens, Huygens.

Christian Huygens, Christiaan Huygens.

Christiaan Huygens.

SUBJECT AREA: Horology, Ports and shipping

[br]

[br]

[br]

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.

[br]

See also: Burgi, Jost; Huygens, Christiaan

See also: INDEX BY SUBJECT AREA

[br]

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

Christiaan Huygens

Christiaan Huygens

Christiaan Huygens

SUBJECT AREA: Photography, film and optics

[br]

[br]

[br]

Galileo began studying medicine at the University of Pisa but soon turned to his real interests, mathematics, mechanics and astronomy. He became Professor of Mathematics at Pisa at the age of 25 and three years later moved to Padua. In 1610 he transferred to Florence. While still a student he discovered the isochronous property of the pendulum, probably by timing with his pulse the swings of a hanging lamp during a religious ceremony in Pisa Cathedral. He later designed a pendulum-controlled clock, but it was not constructed until after his death, and then not successfully; the first successful pendulum clock was made by the Dutch scientist Christiaan Huygens in 1656. Around 1590 Galileo established the laws of motion of falling bodies, by timing rolling balls down inclined planes and not, as was once widely believed, by dropping different weights from the Leaning Tower of Pisa. These and other observations received definitive treatment in his Discorsi e dimostrazioni matematiche intorno a due nuove scienzi attenenti alla, meccanica (Dialogues Concerning Two New Sciences…) which was completed in 1634 and first printed in 1638. This work also included Galileo's proof that the path of a projectile was a parabola and, most importantly, the development of the concept of inertia.

In astronomy Galileo adopted the Copernican heliocentric theory of the universe while still in his twenties, but he lacked the evidence to promote it publicly. That evidence came with the invention of the telescope by the Dutch brothers Lippershey. Galileo heard of its invention in 1609 and had his own instrument constructed, with a convex object lens and concave eyepiece, a form which came to be known as the Galilean telescope. Galileo was the first to exploit the telescope successfully with a series of striking astronomical discoveries. He was also the first to publish the results of observations with the telescope, in his Sidereus nuncius (Starry Messenger) of 1610. All the discoveries told against the traditional view of the universe inherited from the ancient Greeks, and one in particular, that of the four satellites in orbit around Jupiter, supported the Copernican theory in that it showed that there could be another centre of motion in the universe besides the Earth: if Jupiter, why not the Sun? Galileo now felt confident enough to advocate the theory, but the advance of new ideas was opposed, not for the first or last time, by established opinion, personified in Galileo's time by the ecclesiastical authorities in Rome. Eventually he was forced to renounce the Copernican theory, at least in public, and turn to less contentious subjects such as the "two new sciences" of his last and most important work.

[br]