Jerry White (activist)

Jerry White (born June 7, 1963) is Professor of Practice at the University of Virginia and President of JW Impact Strategies, LLC. He is known for co-leading high-impact campaigns, including the historic International Campaign to Ban Landmines, co-recipient of the 1997 Nobel Peace Prize, working closely with the late Diana, Princess of Wales and Her Majesty Queen Noor of Jordan. White is a Senior Ashoka Fellow, recognized for a lifetime of social entrepreneurship in service to humanity. He is a Gabelli Fellow at the Gabelli School of Business in New York City, working to scale social innovation through Jesuit institutions worldwide. He co-founded Survivor Corps, formerly Landmine Survivors Network, created by and for survivors to help victims of war rebuild their lives.
Background.
In 1984, White lost his leg in a landmine accident. According to an interview he gave to the Israeli Channel 10, he came to Israel to learn Hebrew as part of his studies of Judaism (though his roots are Irish Catholic). On one occasion he visited northern Israel with a few other American backpackers to follow the Biblical prophets' footsteps. When they reached the Banias River in the Golan Heights, they decided to go off the beaten track and set up their camp on a nearby hill, where White stepped on a landmine. He said they later learned that the hill was Tel Azaziat, a former battlefield in which many mines had been laid during the 1960s. White said he was hospitalized in the Sheba Medical Center at Tel HaShomer, and despite having the possibility to receive good medical treatment in the United States, he decided to stay at Tel HaShomer until he was fully recovered and rehabilitated, because he was impressed with the center's methods of rehabilitating people with serious limb injuries.
Following this incident, White became a co-founder of Survivor Corps (together with Ken Rutherford). He led efforts to draft and enact human rights and humanitarian laws that promote and protect the rights of 650 million people with disabilities.
White arranged for, and escorted, Diana, Princess of Wales, on her last humanitarian mission, to Bosnia and Herzegovina, and then spearheaded efforts to promote a mine-free Middle East with King Hussein and Queen Noor of Jordan. In 2010, White secured an unprecedented Knesset vote in Israel to clear old minefields, including the Baptism Site of Jesus on the Jordan River.
White has appeared and published extensively in the media; testified before the United States Congress and the United Nations; and received several awards in recognition of his humanitarian and human rights leadership, including: the Rumi Award for Interreligious Diplomacy in 2015; the Superior Honor Award from the U.S. State Department in 2014; the Roots of Peace Global Humanitarian Award in 2010; the first International UNA Humanitarian Prize from Sir Paul McCartney and Heather Mills in 2003; the 2001 Paul G. Hearne/American Association of People with Disabilities Leadership Award; the 2000 Mohammed Amin Humanitarian Award; Brown University's 2000 William Rogers Alumni Award; the Center for International Rehabilitation's Leadership Award in 1999. The 1997 Nobel Prize for Peace was awarded to the International Campaign to Ban Landmines and its first coordinator Jody Williams.
Professional.
White began his career at the Brookings Institution and Council on Foreign Relations where he served as a research assistant. He later became Assistant Director of the Wisconsin Project on Nuclear Arms Control, an editor for the award-winning publication "Risk Report", and in the late 1990s served on the Board of Directors of the Amputee Coalition of America. In these positions White campaigned against weapons of mass destruction via interviews and publications in newspapers and journals such as "The New York Times", "The Washington Post", "The Wall Street Journal" and "The New Republic".
In 1995, White co-founded Landmine Survivors Network with Ken Rutherford, later Survivor Corps, which pioneered techniques in war victim assistance, providing tens of thousands of amputees with peer mentors, artificial limbs and job training. Survivor Corps brings conflict survivors together to promote reconciliation and rebuilding through community service projects. White and Rutherford's leadership in the International Campaign to Ban Landmines helped secure the 1997 Mine Ban Treaty and the Cluster Munitions Ban Treaty.
Between 2010 and 2012 Jerry served as Executive Co-Chair of the Abraham Path Initiative with Founder William Ury. As a Senior Ashoka Fellow appointed in 2009, White has worked with hundreds of young leaders from over 60 countries.
In April 2012 White was appointed Deputy Assistant Secretary for Partnerships and Learning at the US State Department's Bureau of Conflict and Stabilization Operations (CSO). While at CSO, he was responsible for strategic planning for the Bureau, and he introduced advanced conflict analytics and agent-based modeling to develop data-driven strategies to counter the spread of violence across the Middle East and North Africa.
After leaving the State Department in January 2015, Jerry founded Global Impact Strategies Inc. (giStrat) and Global Covenant Partners (GCP). Global Impact Strategies is a startup that offers advanced decision analytics at the nexus of business, politics and security. giStrat combines a scientific, data-driven approach with predictive algorithms to analyze complex domestic and international events and the influential stakeholders driving likely outcomes. giStrat offers "Clarity in a Complex World" to corporations, governments and philanthropies. Global Covenant Partners is a small non-profit created to coordinate and facilitate a growing movement of religious actors, scholars, policymakers, and civil society organizations dedicated to preventing religion-related violence, protecting its targets, and rehabilitating its victims.
White is a Professor of Practice at the University of Virginia, a "University appointment reserved for distinguished professionals who have been recognized nationally or internationally for contributions to their field." At UVA White teaches a popular course titled "Religion, Violence and Strategy: How to Stop Killing in the Name of God?" His work with Professor Peter Ochs to inhibit religion-related violence across the Mideast and North Africa was profiled in Virginia Magazine:
"I Will Not Be Broken".
In May 2008, he published his book, "I Will Not Be Broken: 5 Steps to Overcoming a Life Crisis", containing a detailed account of his injury, his recovery and his work on the international campaign to ban landmines culminating in the founding of Landmine Survivors Network, later renamed Survivor Corps. The book has since been re-issued in paperback as "Getting Up When Life Knocks You Down: 5 Steps to Overcoming a Life Crisis".
Personal.
Jerry White used to live in the Mediterranean island of Malta with his wife Kelly and four children.
He holds a bachelor's degree from Brown University, a master’s of business administration from the University of Michigan, and an honorary doctorate from Mount Sinai School of Medicine. In 2005 White delivered the commencement speech at the Ross School of Business, University of Michigan, where he had recently been awarded an MBA from the Ross School of Business. In May 2010 White delivered the commencement address at the Mendoza Graduate School of Business, University of Notre Dame. He was profiled in University of Michigan's Dividend Magazine in May 2017
White is a Senior Ashoka Fellow, recognized internationally as a social entrepreneur working on complex issues of peace and justice. He is the recipient of several humanitarian and human rights awards.
References.
http://biggsandbussen.com/2020/12/im-no-mother-teresa-and-neither-are-you/


Ferdinand de Lesseps

Ferdinand Marie, vicomte de Lesseps (; 19 November 1805 – 7 December 1894) was a French diplomat and later developer of the Suez Canal, which in 1869 joined the Mediterranean and Red Seas, substantially reducing sailing distances and times between Europe and East Asia.
He attempted to repeat this success with an effort to build a Panama Canal at sea level during the 1880s, but the project was devastated by epidemics of malaria and yellow fever in the area, as well as beset by financial problems, and the planned Lesseps Panama Canal was never completed. Eventually, the project was bought out by the United States, which solved the medical problems and changed the design to a non-sea level canal with locks. It was completed in 1914.
Ancestry.
The origins of Lesseps' family are traceable back as far as the end of the 14th century. His ancestors, it is believed, came from Spain, and settled at Bayonne during the region's occupation by the English. One of his great-grandfathers, Pierre de Lesseps (Bayonne, 2 January 1690 – Bayonne, 20 August 1759), son of Bertrand Lesseps (1649–1708) and wife (m. 18 April 1675) Louise Fisson (1654–1690), was town clerk and at the same time secretary to Queen Maria Anna of Neuburg, widow of Charles II of Spain.
From the middle of the 18th century the ancestors of Lesseps followed diplomatic careers, and he himself occupied several diplomatic posts from 1825 to 1849. His uncle was ennobled by King Louis XVI, and his father was made a count by Emperor Napoleon I. His father, Mathieu de Lesseps (Hamburg, 4 May 1774 – Tunis, 28 December 1832), was in the consular service; his mother, Catherine de Grévigné (Málaga, 11 June 1774 – Paris, 27 January 1853), was Spanish on her mother's side, and aunt of the countess of Montijo, mother of the Empress Eugénie. She was a daughter of Henri de Grevigné (baptised Notre-Dame-aux-Fonts, Liège, 2 June 1744) and wife (m. Málaga, 1766) Francisca Antonia Gallegos (1751–1853).
Early years.
Ferdinand de Lesseps was born November 19, 1805 in Versailles, Yvelines. He had a sister, Adélaïde de Lesseps (1803–1879), married to Jules Tallien de Cabarrus (19 April 1801 – 1870), and two brothers, Théodore de Lesseps (Cádiz, 25 September 1802 – Saint-Germain-en-Laye, 20 May 1874), married in 1828 to Antonia Denois (Paris, 27 September 1802 – Paris, 29 December 1878), and Jules de Lesseps (Pisa, 16 February 1809 – Paris, 10 October 1887), married on 11 March 1874 to Hyacinthe Delarue.
His first years were spent in Italy, where his father was occupied with his consular duties. He was educated at the College of Henry IV in Paris. From the age of 18 years to 20 he was employed in the commissary department of the army. From 1825 to 1827 he acted as assistant vice-consul at Lisbon, where his uncle, Barthélemy de Lesseps, was the French "chargé d'affaires". This uncle was an old companion of Jean-François de La Pérouse and the only survivor of the expedition in which La Pérouse perished. Barthélemy de Lesseps had left the expedition in Kamchatka to travel to St Petersburg overland.
Career.
Diplomatic.
In 1828 Lesseps was sent as an assistant vice-consul to Tunis, where his father was consul-general. He aided the escape of Youssouff, pursued by the soldiers of the Bey, of whom he was one of the officers, for violation of the seraglio law. Youssouff acknowledged this protection given by a Frenchman by distinguishing himself in the ranks of the French army at the time of the French conquest of Algeria. Lesseps was also entrusted by his father with missions to Marshal Count Bertrand Clausel, general-in-chief of the army of occupation in Algeria. The marshal wrote to Mathieu de Lesseps on 18 December 1830: "I have had the pleasure of meeting your son, who gives promise of sustaining with great credit the name he bears."
In 1832 Lesseps was appointed vice-consul at Alexandria. While the vessel, in which Lesseps sailed to Egypt, was in quarantine at the Alexandrian lazaretto, M. Mimaut, consul-general of France at Alexandria, sent him several books, among which was the memoir written upon the previously filled and abandoned Ancient Suez Canal, according to Napoleon Bonaparte's instructions, by the civil engineer Jacques-Marie Le Père, one of the scientific members of the French expedition.
This work struck Lesseps's imagination, and was one of the influences that gave him the idea of constructing a canal across the African isthmus. Fortunately for Lesseps, Muhammad Ali, the viceroy of Egypt, owed his position in part to the recommendations made on his behalf to the French government by Mathieu de Lesseps, who was consul-general in Egypt when Ali was a colonel. Because of this, Lesseps received a warm welcome from the viceroy and became good friends with his son, Said Pasha. Politically, the British were allied with the Ottoman capital in Istanbul—to prevent the Russians from Black Sea access to the Mediterranean Sea—and had also repelled Ali's attempt to invade the Ottoman capital in 1833. The French were able to manoeuvre in Egypt under Ali's graces by playing off the British aggression against Ali in Istanbul.
In 1833 Lesseps was sent as consul to Cairo, and soon afterwards given the management of the consulate general at Alexandria, a post that he held until 1837. While in Egypt he encountered and was influenced by Barthélemy Prosper Enfantin, who was working on a dam north of Cairo for Ali while preaching for a union of the Mediterranean and Red Seas. While he was there an epidemic of plague broke out and lasted for two years, resulting in the deaths of more than a third of the inhabitants of Cairo and Alexandria. During this time Lesseps went from one city to the other with zeal and energy. Towards the close of the year 1837 he returned to France, and on 21 December married Agathe Delamalle (1819–1853), daughter of the government prosecuting attorney at the court of Angers. By this marriage de Lesseps became the father of five sons: Charles Théodore de Lesseps (1838–1838), Charles Aimé de Lesseps (1840–1923), Ferdinand Marie de Lesseps (1842–1846), Ferdinand Victor de Lesseps (1847–1853) and Aimé Victor de Lesseps (1848–1896).
In 1839 Lesseps was appointed consul at Rotterdam, and in the following year transferred to Málaga, the ancestral home of his mother's family. In 1842 he was sent to Barcelona, and soon afterwards promoted to the grade of consul general. In the course of a bloody insurrection in Catalonia, which ended in the bombardment of Barcelona, de Lesseps offered protection to a number of men threatened by the fighting regardless of their factional sympathies or nationalities. From 1848 to 1849 he was minister of France at Madrid.
In 1849 the government of the French Republic sent Lesseps to Rome to negotiate the return of Pope Pius IX to the Vatican. He tried to negotiate an agreement whereby Pope Pius could return peacefully to the Vatican but also ensuring the continued independence of Rome. But, during negotiations, the elections in France caused a change in the foreign policy of the government – Alexis de Tocqueville replaced the previous foreign minister. Lesseps course was disapproved; he was recalled and brought before the Council of State. Louis-Napoleon needed a scapegoat and Lesseps was an easy target. Lesseps was accused of causing dishonor to the French army and was censured although he was not told to leave the Foreign Ministry.
Lesseps was created on 30 August 1851 the 334th Commander and then the 200th Grand Cross of the Order of the Tower and Sword.
Lesseps then retired from the diplomatic service, and never again occupied any public office. In 1853 he lost his wife and his son Ferdinand Victor at a few days' interval. In 1854, the accession to the viceroyalty of Egypt of Said Pasha gave Lesseps a new impulse to act upon the creation of a Suez Canal.
Suez Canal.
Lesseps had corresponded at least once with the Société d'Études du Canal de Suez during the reign of Abbas I in Egypt, but Abbas had closed off most of Egypt to foreign influence. Upon Abbas' assassination in 1854, Lesseps, made inquiries with a former, if short-term, acquaintance and successor in Egypt, Said Pasha. On 7 November 1854 he landed at Alexandria; on the 30th of the same month Said Pasha signed the concession authorizing him to build the Suez Canal.
A first scheme, initiated by Lesseps, was immediately drawn out by two French engineers who were in the Egyptian service, Louis Maurice Adolphe Linant de Bellefonds called "Linant Bey" and Mougel Bey. This project, differing from others that were previously presented or that were in opposition to it, provided for a direct link between the Mediterranean and the Red Sea. After being slightly modified, the plan was adopted in 1856 by the civil engineers constituting the International Commission for the piercing of the isthmus of Suez. Encouraged by the engineers' approval, Lesseps no longer allowed anything to stop him. He listened to no adverse criticism and receded before no obstacle. Neither the opposition of Lord Palmerston, who considered the projected disturbance as too radical and a danger to the commercial position of Great Britain. Lesseps was similarly not deterred by the opinions entertained, in France as well as in England, that the sea in front of Port Said was full of mud which would obstruct the entrance to the canal, and that the sands from the desert would fill the trenches.
Lesseps succeeded in rousing the patriotism of the French and obtaining by their subscriptions more than half of the capital of two hundred million francs which he needed in order to form a company, but could not attract any substantial capital contribution from the public in England or other foreign countries. The Egyptian government thus subscribed for eighty million francs worth of shares.
The Compagnie universelle du canal maritime de Suez was organized at the end of 1858. On 25 April 1859 the first blow of the pickaxe was given by Lesseps at Port Said. During the following ten years, Lesseps had to overcome the continuing opposition of the British government preventing the Sultan from approving the construction of the canal, and at one stage he even had to seek the support of his cousin, Empress Eugenie, to persuade the Emperor Napoleon III to act as arbitrator in the disputes. Finally, on 17 November 1869, the canal was officially opened by the Khedive, Ismail Pasha.
While in the interests of his canal Lesseps resisted the opposition of British diplomacy to an enterprise which threatened to give France control of the shortest route to India, he acted loyally towards Great Britain after Disraeli acquired the Suez shares belonging to the Khedive, by admitting to the board of directors of the company three representatives of the British government. The consolidation of interests which resulted, and which was strengthened by the addition in 1884 of seven more British directors, chosen from among shipping merchants and business men, increased, for the benefit of all concerned, the commercial character of the enterprise.
Lesseps steadily endeavored to keep out of politics. If in 1869 he appeared to deviate from this principle by being a candidate at Marseille for the Corps Législatif, it was because he yielded to the entreaties of the Imperial government in order to strengthen its goodwill for the Suez Canal. Once this goodwill had been shown, he bore no malice towards those who rendered him his liberty by preferring Léon Gambetta. Afterward, Lesseps declined the other candidatures that were offered to him: for the Senate in 1876, and for the Chamber in 1877. In 1873 he became interested in a project for uniting Europe and Asia by a railway to Mumbai, with a branch to Beijing. The same year, he became a member of the French Academy of Sciences. He subsequently encouraged Major Roudaire, who wished to transform a stretch of the Sahara into an inland sea to increase rainfall in Algeria.
Lesseps accepted the presidency of the French committee of Leopold II of Belgium's International African Society. From this position he facilitated Pierre Savorgnan de Brazza's explorations, and acquired stations that Brazza subsequently abandoned to the French government. These stations were the starting-point of French Congo. Lesseps was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1879.
From 17 November 1899 to 23 December 1956, a monumental statue of Ferdinand de Lesseps by Emmanuel Frémiet stood at the entrance of the Suez Canal.
Panama Canal attempt.
In May 1879 a congress of 136 delegates (including Lesseps) assembled in the rooms of the Société de géographie in Paris, under the presidency of Admiral de la Roncire le Noury, and voted in favor of the creation of a Panama Canal, which was to be without locks, like the Suez Canal. Lesseps was appointed President of the Panama Canal Company, despite the fact that he had reached the age of 74. It was on this occasion that Gambetta bestowed upon him the title of "Le Grand Français". However, the decision to dig a Panama Canal at sea level to avoid the use of locks, and the inability of contemporary medical science to deal with epidemics of malaria and yellow fever, doomed the project.
In February 1880, Lesseps arrived in New York City to raise money for the project. When he stayed at the Windsor Hotel, its staff flew the French flag in his honor. He met the American Society of Civil Engineers and the Geographic Society while touring the area. Lesseps then went to Washington D.C., met with President Rutherford B. Hayes, and testified to the House Interoceanic Canal Committee. He later went to Boston, Chicago, and several other American cities to raise interest and capital for the project.
In June 1880, Lesseps gave a speech in Liverpool where he was able to find support from a Captain Peacock, who felt the canal project was worth supporting as it would provide routes to save time.
Lesseps went with his youngest child to Panama to see the planned pathway. He estimated in 1880 that the project would take 658 million francs and eight years to complete. After two years of surveys, work on the canal began in 1882. However, the technical difficulties of operating in the wet tropics dogged the project. Particularly disastrous were recurrent landslides into the excavations from the bordering water-saturated hills, and the death toll from malaria and yellow fever. In the end, insufficient financial capital and financial corruption ended the project. The Panama Canal Company declared itself bankrupt in December 1888 and entered liquidation in February 1889.
The failure of the project is sometimes referred to as the Panama Canal Scandal, after rumors circulated that French politicians and journalists had received bribes. By 1892 it emerged that 150 French deputies had been bribed into voting for the allocation of financial aid to the Panama Canal Company, and in February 1893 Lesseps, his son Charles (born 1849), and a number of others faced trial and were found guilty. Lesseps was ordered to pay a fine and serve a prison sentence, but the latter was overturned by the Court of Cassation on the grounds that it had been more than three years since the crime was committed. Ultimately, in 1904 the United States bought out the assets of the Company and resumed work under a revised plan.
Second marriage and issue.
In Paris on November 25, 1869—a week after the opening of the Suez Canal—Lesseps married his second wife, who was a third his age. Louise-Hélène Autard de Bragard was born on the island of Mauritius in 1848 at Plaines Wilhems and died on 29 January 1909 at Château de La Chesnay in Guilly, Vatan, Indre.
She was the daughter of Gustave Adolphe Autard de Bragard, a former Magistrate of Mauritius, and wife Marie-Louise Carcenac (1817–1857), daughter of Pierre Carcenac (1771–1819) and wife Marie Françoise Dessachis. Eleven of her twelve children (six boys and six girls) with Lesseps survived their father:
Statue of Liberty.
On 11 June 1884, Levi P. Morton, the Minister of the United States to France, gave a banquet in honor of the Franco-American Union and in celebration of the completion of the Statue of Liberty. Ferdinand de Lesseps, as head of the Franco-American Union, formally presented the statue to the United States, saying:
This is the result of the devoted enthusiasm, the intelligence and the noblest sentiments which can inspire man. It is great in its conception, great in its execution, great in its proportions; let us hope that it will add, by its moral value, to the memories and sympathies that it is intended to perpetuate. We now transfer to you, Mr. Minister, this great statue and trust that it may forever stand the pledge of friendship between France and the Great Republic of the United States.
In October 1886, Lesseps traveled to the United States to speak at the dedication ceremony of the Statue of Liberty on the date of the 28th, and attended by President Grover Cleveland.
Death.
Lesseps died at Château de La Chesnaye in Guilly, Vatan, Indre, on 7 December 1894. He was buried in Père Lachaise Cemetery in Paris. The grave stands at one of the junctions amongst other large family tombs.
Legacy.
In 1956 Egyptian President Gamal Nasser used his name in a radio speech, as the codeword to his army to raid the Suez Canal Company's offices on 26 July 1956. This was the first step to the Suez Canal's nationalization. In the course of the raid and seizure of the canal by Egypt, the statue of Lesseps at the entrance of the Suez Canal was removed from its pedestal, to symbolize the end of European ownership of the waterway. The statue now stands in a small garden of the Port Fuad shipyard.
In popular culture.
Lesseps was portrayed by Tyrone Power in the 1938 film "Suez", with Loretta Young, a film which provoked complaints and legal action from Lesseps' family and the Egyptian government.
In addition, Manuel Soto played the part in a 1944 Spanish feature film, "Eugenia de Montijo". On television, Guy Marchand played Lesseps in the 1983 French/German mini-series "L'homme de Suez", and John Walters portrayed him in "The Panama Canal", an episode of the 2003 BBC docu-drama series "Seven Wonders of the Industrial World".
Lesseps appears as a great engineer in the game "Civilization V".
Lesseps is also discussed extensively in the David McCullough book, "The Path Between the Seas".


Pendulum

A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing.
From the first scientific investigations of the pendulum around 1602 by Galileo Galilei, the regular motion of pendulums was used for timekeeping, and was the world's most accurate timekeeping technology until the 1930s. The pendulum clock invented by Christiaan Huygens in 1658 became the world's standard timekeeper, used in homes and offices for 270 years, and achieved accuracy of about one second per year before it was superseded as a time standard by the quartz clock in the 1930s. Pendulums are also used in scientific instruments such as accelerometers and seismometers. Historically they were used as gravimeters to measure the acceleration of gravity in geo-physical surveys, and even as a standard of length. The word "pendulum" is new Latin, from the Latin "pendulus", meaning 'hanging'.
Simple gravity pendulum.
The "simple gravity pendulum" is an idealized mathematical model of a pendulum. This is a weight (or bob) on the end of a massless cord suspended from a pivot, without friction. When given an initial push, it will swing back and forth at a constant amplitude. Real pendulums are subject to friction and air drag, so the amplitude of their swings declines.
Period of oscillation.
The period of swing of a simple gravity pendulum depends on its length, the local strength of gravity, and to a small extent on the maximum angle that the pendulum swings away from vertical, "θ"0, called the amplitude. It is independent of the mass of the bob. If the amplitude is limited to small swings, the period "T" of a simple pendulum, the time taken for a complete cycle, is:
where formula_2 is the length of the pendulum and formula_3 is the local acceleration of gravity.
For small swings the period of swing is approximately the same for different size swings: that is, "the period is independent of amplitude". This property, called isochronism, is the reason pendulums are so useful for timekeeping. Successive swings of the pendulum, even if changing in amplitude, take the same amount of time.
For larger amplitudes, the period increases gradually with amplitude so it is longer than given by equation (1). For example, at an amplitude of "θ"0 = 0.4 radians (23°) it is 1% larger than given by (1). The period increases asymptotically (to infinity) as "θ"0 approaches formula_4 radians (180°), because the value "θ"0 = formula_4 is an unstable equilibrium point for the pendulum. The true period of an ideal simple gravity pendulum can be written in several different forms (see Pendulum (mathematics) ), one example being the infinite series:
where formula_7 is in radians.
The difference between this true period and the period for small swings (1) above is called the "circular error". In the case of a typical grandfather clock whose pendulum has a swing of 6° and thus an amplitude of 3° (0.05 radians), the difference between the true period and the small angle approximation (1) amounts to about 15 seconds per day.
For small swings the pendulum approximates a harmonic oscillator, and its motion as a function of time, "t", is approximately simple harmonic motion:
where formula_9 is a constant value, dependent on initial conditions.
For real pendulums, the period varies slightly with factors such as the buoyancy and viscous resistance of the air, the mass of the string or rod, the size and shape of the bob and how it is attached to the string, and flexibility and stretching of the string. In precision applications, corrections for these factors may need to be applied to eq. (1) to give the period accurately.
Compound pendulum.
Any swinging rigid body free to rotate about a fixed horizontal axis is called a compound pendulum or physical pendulum. The appropriate equivalent length formula_10 for calculating the period of any such pendulum is the distance
from the pivot to the "center of oscillation". This point is located under the center of mass at a distance from the
pivot traditionally called the radius of oscillation, which depends on the mass distribution of the pendulum. If most of the mass is concentrated in a relatively small bob compared to the pendulum length, the center of oscillation is close to the center of mass.
The radius of oscillation or equivalent length formula_10 of any physical pendulum can be shown to be
where formula_13 is the moment of inertia of the pendulum about the pivot point,
formula_14 is the mass of the pendulum, and formula_15 is the distance between the pivot point and the center of mass.
Substituting this expression in (1) above, the period formula_16 of a compound pendulum is given by
for sufficiently small oscillations.
For example, a rigid uniform rod of length formula_18 pivoted about one end has moment of inertia formula_19.
The center of mass is located at the center of the rod, so formula_20 Substituting these values into the above equation gives formula_21. This shows that a rigid rod pendulum has the same period as a simple pendulum of 2/3 its length.
Christiaan Huygens proved in 1673 that the pivot point and the center of oscillation are interchangeable. This means if any pendulum is turned upside down and swung from a pivot located at its previous center of oscillation, it will have the same period as before and the new center of oscillation will be at the old pivot point. In 1817 Henry Kater used this idea to produce a type of reversible pendulum, now known as a Kater pendulum, for improved measurements of the acceleration due to gravity.
History.
One of the earliest known uses of a pendulum was a 1st-century seismometer device of Han Dynasty Chinese scientist Zhang Heng. Its function was to sway and activate one of a series of levers after being disturbed by the tremor of an earthquake far away. Released by a lever, a small ball would fall out of the urn-shaped device into one of eight metal toad's mouths below, at the eight points of the compass, signifying the direction the earthquake was located.
Many sources claim that the 10th-century Egyptian astronomer Ibn Yunus used a pendulum for time measurement, but this was an error that originated in 1684 with the British historian Edward Bernard.
During the Renaissance, large hand-pumped pendulums were used as sources of power for manual reciprocating machines such as saws, bellows, and pumps. Leonardo da Vinci made many drawings of the motion of pendulums, though without realizing its value for timekeeping.
1602: Galileo's research.
Italian scientist Galileo Galilei was the first to study the properties of pendulums, beginning around 1602. The earliest extant report of his research is contained in a letter to Guido Ubaldo dal Monte, from Padua, dated November 29, 1602. His biographer and student, Vincenzo Viviani, claimed his interest had been sparked around 1582 by the swinging motion of a chandelier in Pisa Cathedral. Galileo discovered the crucial property that makes pendulums useful as timekeepers, called isochronism; the period of the pendulum is approximately independent of the amplitude or width of the swing. He also found that the period is independent of the mass of the bob, and proportional to the square root of the length of the pendulum. He first employed freeswinging pendulums in simple timing applications. His physician friend, Santorio Santorii, invented a device which measured a patient's pulse by the length of a pendulum; the "pulsilogium". In 1641 Galileo dictated to his son Vincenzo a design for a pendulum clock; Vincenzo began construction, but had not completed it when he died in 1649. The pendulum was the first harmonic oscillator used by man.
1656: The pendulum clock.
In 1656 the Dutch scientist Christiaan Huygens built the first pendulum clock. This was a great improvement over existing mechanical clocks; their best accuracy was improved from around 15 minutes deviation a day to around 15 seconds a day. Pendulums spread over Europe as existing clocks were retrofitted with them.
The English scientist Robert Hooke studied the conical pendulum around 1666, consisting of a pendulum that is free to swing in two dimensions, with the bob rotating in a circle or ellipse. He used the motions of this device as a model to analyze the orbital motions of the planets. Hooke suggested to Isaac Newton in 1679 that the components of orbital motion consisted of inertial motion along a tangent direction plus an attractive motion in the radial direction. This played a part in Newton's formulation of the law of universal gravitation. Robert Hooke was also responsible for suggesting as early as 1666 that the pendulum could be used to measure the force of gravity.
During his expedition to Cayenne, French Guiana in 1671, Jean Richer found that a pendulum clock was minutes per day slower at Cayenne than at Paris. From this he deduced that the force of gravity was lower at Cayenne. In 1687, Isaac Newton in "Principia Mathematica" showed that this was because the Earth was not a true sphere but slightly oblate (flattened at the poles) from the effect of centrifugal force due to its rotation, causing gravity to increase with latitude. Portable pendulums began to be taken on voyages to distant lands, as precision gravimeters to measure the acceleration of gravity at different points on Earth, eventually resulting in accurate models of the shape of the Earth.
1673: Huygens' "Horologium Oscillatorium".
In 1673, 17 years after he invented the pendulum clock, Christiaan Huygens published his theory of the pendulum, "Horologium Oscillatorium sive de motu pendulorum". Marin Mersenne and René Descartes had discovered around 1636 that the pendulum was not quite isochronous; its period increased somewhat with its amplitude. Huygens analyzed this problem by determining what curve an object must follow to descend by gravity to the same point in the same time interval, regardless of starting point; the so-called "tautochrone curve". By a complicated method that was an early use of calculus, he showed this curve was a cycloid, rather than the circular arc of a pendulum, confirming that the pendulum was not isochronous and Galileo's observation of isochronism was accurate only for small swings. Huygens also solved the problem of how to calculate the period of an arbitrarily shaped pendulum (called a "compound pendulum"), discovering the "center of oscillation", and its interchangeability with the pivot point.
The existing clock movement, the verge escapement, made pendulums swing in very wide arcs of about 100°. Huygens showed this was a source of inaccuracy, causing the period to vary with amplitude changes caused by small unavoidable variations in the clock's drive force. To make its period isochronous, Huygens mounted cycloidal-shaped metal 'chops' next to the pivots in his clocks, that constrained the suspension cord and forced the pendulum to follow a cycloid arc (see cycloidal pendulum). This solution didn't prove as practical as simply limiting the pendulum's swing to small angles of a few degrees. The realization that only small swings were isochronous motivated the development of the anchor escapement around 1670, which reduced the pendulum swing in clocks to 4°–6°.
1721: Temperature compensated pendulums.
During the 18th and 19th century, the pendulum clock's role as the most accurate timekeeper motivated much practical research into improving pendulums. It was found that a major source of error was that the pendulum rod expanded and contracted with changes in ambient temperature, changing the period of swing. This was solved with the invention of temperature compensated pendulums, the mercury pendulum in 1721 and the gridiron pendulum in 1726, reducing errors in precision pendulum clocks to a few seconds per week.
The accuracy of gravity measurements made with pendulums was limited by the difficulty of finding the location of their center of oscillation. Huygens had discovered in 1673 that a pendulum has the same period when hung from its center of oscillation as when hung from its pivot, and the distance between the two points was equal to the length of a simple gravity pendulum of the same period. In 1818 British Captain Henry Kater invented the reversible Kater's pendulum which used this principle, making possible very accurate measurements of gravity. For the next century the reversible pendulum was the standard method of measuring absolute gravitational acceleration.
1851: Foucault pendulum.
In 1851, Jean Bernard Léon Foucault showed that the plane of oscillation of a pendulum, like a gyroscope, tends to stay constant regardless of the motion of the pivot, and that this could be used to demonstrate the rotation of the Earth. He suspended a pendulum free to swing in two dimensions (later named the Foucault pendulum) from the dome of the Panthéon in Paris. The length of the cord was . Once the pendulum was set in motion, the plane of swing was observed to precess or rotate 360° clockwise in about 32 hours.
This was the first demonstration of the Earth's rotation that didn't depend on celestial observations, and a "pendulum mania" broke out, as Foucault pendulums were displayed in many cities and attracted large crowds.
1930: Decline in use.
Around 1900 low-thermal-expansion materials began to be used for pendulum rods in the highest precision clocks and other instruments, first invar, a nickel steel alloy, and later fused quartz, which made temperature compensation trivial. Precision pendulums were housed in low pressure tanks, which kept the air pressure constant to prevent changes in the period due to changes in buoyancy of the pendulum due to changing atmospheric pressure. The best pendulum clocks achieved accuracy of around a second per year.
The timekeeping accuracy of the pendulum was exceeded by the quartz crystal oscillator, invented in 1921, and quartz clocks, invented in 1927, replaced pendulum clocks as the world's best timekeepers. Pendulum clocks were used as time standards until World War 2, although the French Time Service continued using them in their official time standard ensemble until 1954. Pendulum gravimeters were superseded by "free fall" gravimeters in the 1950s, but pendulum instruments continued to be used into the 1970s.
Use for time measurement.
For 300 years, from its discovery around 1582 until development of the quartz clock in the 1930s, the pendulum was the world's standard for accurate timekeeping. In addition to clock pendulums, freeswinging seconds pendulums were widely used as precision timers in scientific experiments in the 17th and 18th centuries. Pendulums require great mechanical stability: a length change of only 0.02%, 0.2 mm in a grandfather clock pendulum, will cause an error of a minute per week.
Clock pendulums.
Pendulums in clocks (see example at right) are usually made of a weight or bob "(b)" suspended by a rod of wood or metal "(a)". To reduce air resistance (which accounts for most of the energy loss in precision clocks) the bob is traditionally a smooth disk with a lens-shaped cross section, although in antique clocks it often had carvings or decorations specific to the type of clock. In quality clocks the bob is made as heavy as the suspension can support and the movement can drive, since this improves the regulation of the clock (see Accuracy below). A common weight for seconds pendulum bobs is . Instead of hanging from a pivot, clock pendulums are usually supported by a short straight spring "(d)" of flexible metal ribbon. This avoids the friction and 'play' caused by a pivot, and the slight bending force of the spring merely adds to the pendulum's restoring force. The highest precision clocks have pivots of 'knife' blades resting on agate plates. The impulses to keep the pendulum swinging are provided by an arm hanging behind the pendulum called the "crutch", "(e)", which ends in a "fork", "(f)" whose prongs embrace the pendulum rod. The crutch is pushed back and forth by the clock's escapement, "(g,h)".
Each time the pendulum swings through its centre position, it releases one tooth of the "escape wheel" "(g)". The force of the clock's mainspring or a driving weight hanging from a pulley, transmitted through the clock's gear train, causes the wheel to turn, and a tooth presses against one of the pallets "(h)", giving the pendulum a short push. The clock's wheels, geared to the escape wheel, move forward a fixed amount with each pendulum swing, advancing the clock's hands at a steady rate.
The pendulum always has a means of adjusting the period, usually by an adjustment nut "(c)" under the bob which moves it up or down on the rod. Moving the bob up decreases the pendulum's length, causing the pendulum to swing faster and the clock to gain time. Some precision clocks have a small auxiliary adjustment weight on a threaded shaft on the bob, to allow finer adjustment. Some tower clocks and precision clocks use a tray attached near to the midpoint of the pendulum rod, to which small weights can be added or removed. This effectively shifts the centre of oscillation and allows the rate to be adjusted without stopping the clock.
The pendulum must be suspended from a rigid support. During operation, any elasticity will allow tiny imperceptible swaying motions of the support, which disturbs the clock's period, resulting in error. Pendulum clocks should be attached firmly to a sturdy wall.
The most common pendulum length in quality clocks, which is always used in grandfather clocks, is the seconds pendulum, about long. In mantel clocks, half-second pendulums, long, or shorter, are used. Only a few large tower clocks use longer pendulums, the 1.5 second pendulum, long, or occasionally the two-second pendulum, which is used in Big Ben.
Temperature compensation.
The largest source of error in early pendulums was slight changes in length due to thermal expansion and contraction of the pendulum rod with changes in ambient temperature. This was discovered when people noticed that pendulum clocks ran slower in summer, by as much as a minute per week (one of the first was Godefroy Wendelin, as reported by Huygens in 1658). Thermal expansion of pendulum rods was first studied by Jean Picard in 1669. A pendulum with a steel rod will expand by about 11.3 parts per million (ppm) with each degree Celsius increase, causing it to lose about 0.27 seconds per day for every degree Celsius increase in temperature, or 9 seconds per day for a change. Wood rods expand less, losing only about 6 seconds per day for a change, which is why quality clocks often had wooden pendulum rods. The wood had to be varnished to prevent water vapor from getting in, because changes in humidity also affected the length.
Mercury pendulum.
The first device to compensate for this error was the mercury pendulum, invented by George Graham in 1721. The liquid metal mercury expands in volume with temperature. In a mercury pendulum, the pendulum's weight (bob) is a container of mercury. With a temperature rise, the pendulum rod gets longer, but the mercury also expands and its surface level rises slightly in the container, moving its centre of mass closer to the pendulum pivot. By using the correct height of mercury in the container these two effects will cancel, leaving the pendulum's centre of mass, and its period, unchanged with temperature. Its main disadvantage was that when the temperature changed, the rod would come to the new temperature quickly but the mass of mercury might take a day or two to reach the new temperature, causing the rate to deviate during that time. To improve thermal accommodation several thin containers were often used, made of metal. Mercury pendulums were the standard used in precision regulator clocks into the 20th century.
Gridiron pendulum.
The most widely used compensated pendulum was the gridiron pendulum, invented in 1726 by John Harrison. This consists of alternating rods of two different metals, one with lower thermal expansion (CTE), steel, and one with higher thermal expansion, zinc or brass. The rods are connected by a frame, as shown in the drawing at the right, so that an increase in length of the zinc rods pushes the bob up, shortening the pendulum. With a temperature increase, the low expansion steel rods make the pendulum longer, while the high expansion zinc rods make it shorter. By making the rods of the correct lengths, the greater expansion of the zinc cancels out the expansion of the steel rods which have a greater combined length, and the pendulum stays the same length with temperature.
Zinc-steel gridiron pendulums are made with 5 rods, but the thermal expansion of brass is closer to steel, so brass-steel gridirons usually require 9 rods. Gridiron pendulums adjust to temperature changes faster than mercury pendulums, but scientists found that friction of the rods sliding in their holes in the frame caused gridiron pendulums to adjust in a series of tiny jumps. In high precision clocks this caused the clock's rate to change suddenly with each jump. Later it was found that zinc is subject to creep. For these reasons mercury pendulums were used in the highest precision clocks, but gridirons were used in quality regulator clocks.
Gridiron pendulums became so associated with good quality that, to this day, many ordinary clock pendulums have decorative 'fake' gridirons that don't actually have any temperature compensation function.
Invar and fused quartz.
Around 1900, low thermal expansion materials were developed which could be used as pendulum rods in order to make elaborate temperature compensation unnecessary. These were only used in a few of the highest precision clocks before the pendulum became obsolete as a time standard. In 1896 Charles Édouard Guillaume invented the nickel steel alloy Invar. This has a CTE of around 0.5 µin/(in·°F), resulting in pendulum temperature errors over 71 °F of only 1.3 seconds per day, and this residual error could be compensated to zero with a few centimeters of aluminium under the pendulum bob (this can be seen in the Riefler clock image above). Invar pendulums were first used in 1898 in the Riefler regulator clock which achieved accuracy of 15 milliseconds per day. Suspension springs of Elinvar were used to eliminate temperature variation of the spring's restoring force on the pendulum. Later fused quartz was used which had even lower CTE. These materials are the choice for modern high accuracy pendulums.
Atmospheric pressure.
The effect of the surrounding air on a moving pendulum is complex and requires fluid mechanics to calculate precisely, but for most purposes its influence on the period can be accounted for by three effects:
Increases in barometric pressure increase a pendulum's period slightly due to the first two effects, by about 0.11 seconds per day per kilopascal (0.37 seconds per day per inch of mercury or 0.015 seconds per day per torr). Researchers using pendulums to measure the acceleration of gravity had to correct the period for the air pressure at the altitude of measurement, computing the equivalent period of a pendulum swinging in vacuum. A pendulum clock was first operated in a constant-pressure tank by Friedrich Tiede in 1865 at the Berlin Observatory, and by 1900 the highest precision clocks were mounted in tanks that were kept at a constant pressure to eliminate changes in atmospheric pressure. Alternatively, in some a small aneroid barometer mechanism attached to the pendulum compensated for this effect.
Gravity.
Pendulums are affected by changes in gravitational acceleration, which varies by as much as 0.5% at different locations on Earth, so precision pendulum clocks have to be recalibrated after a move. Even moving a pendulum clock to the top of a tall building can cause it to lose measurable time from the reduction in gravity.
Accuracy of pendulums as timekeepers.
The timekeeping elements in all clocks, which include pendulums, balance wheels, the quartz crystals used in quartz watches, and even the vibrating atoms in atomic clocks, are in physics called harmonic oscillators. The reason harmonic oscillators are used in clocks is that they vibrate or oscillate at a specific resonant frequency or period and resist oscillating at other rates. However, the resonant frequency is not infinitely 'sharp'. Around the resonant frequency there is a narrow natural band of frequencies (or periods), called the resonance width or bandwidth, where the harmonic oscillator will oscillate. In a clock, the actual frequency of the pendulum may vary randomly within this resonance width in response to disturbances, but at frequencies outside this band, the clock will not function at all.
"Q" factor.
The measure of a harmonic oscillator's resistance to disturbances to its oscillation period is a dimensionless parameter called the "Q" factor equal to the resonant frequency divided by the resonance width. The higher the "Q", the smaller the resonance width, and the more constant the frequency or period of the oscillator for a given disturbance. The reciprocal of the Q is roughly proportional to the limiting accuracy achievable by a harmonic oscillator as a time standard.
The "Q" is related to how long it takes for the oscillations of an oscillator to die out. The "Q" of a pendulum can be measured by counting the number of oscillations it takes for the amplitude of the pendulum's swing to decay to 1/"e" = 36.8% of its initial swing, and multiplying by 2"π".
In a clock, the pendulum must receive pushes from the clock's movement to keep it swinging, to replace the energy the pendulum loses to friction. These pushes, applied by a mechanism called the escapement, are the main source of disturbance to the pendulum's motion. The "Q" is equal to 2"π" times the energy stored in the pendulum, divided by the energy lost to friction during each oscillation period, which is the same as the energy added by the escapement each period. It can be seen that the smaller the fraction of the pendulum's energy that is lost to friction, the less energy needs to be added, the less the disturbance from the escapement, the more 'independent' the pendulum is of the clock's mechanism, and the more constant its period is. The "Q" of a pendulum is given by:
where "M" is the mass of the bob, "ω" = 2"π"/"T" is the pendulum's radian frequency of oscillation, and "Γ" is the frictional damping force on the pendulum per unit velocity.
"ω" is fixed by the pendulum's period, and "M" is limited by the load capacity and rigidity of the suspension. So the "Q" of clock pendulums is increased by minimizing frictional losses ("Γ"). Precision pendulums are suspended on low friction pivots consisting of triangular shaped 'knife' edges resting on agate plates. Around 99% of the energy loss in a freeswinging pendulum is due to air friction, so mounting a pendulum in a vacuum tank can increase the "Q", and thus the accuracy, by a factor of 100.
The "Q" of pendulums ranges from several thousand in an ordinary clock to several hundred thousand for precision regulator pendulums swinging in vacuum. A quality home pendulum clock might have a "Q" of 10,000 and an accuracy of 10 seconds per month. The most accurate commercially produced pendulum clock was the Shortt-Synchronome free pendulum clock, invented in 1921. Its Invar master pendulum swinging in a vacuum tank had a "Q" of 110,000 and an error rate of around a second per year.
Their Q of 103–105 is one reason why pendulums are more accurate timekeepers than the balance wheels in watches, with "Q" around 100–300, but less accurate than the quartz crystals in quartz clocks, with "Q" of 105–106.
Escapement.
Pendulums (unlike, for example, quartz crystals) have a low enough "Q" that the disturbance caused by the impulses to keep them moving is generally the limiting factor on their timekeeping accuracy. Therefore, the design of the escapement, the mechanism that provides these impulses, has a large effect on the accuracy of a clock pendulum. If the impulses given to the pendulum by the escapement each swing could be exactly identical, the response of the pendulum would be identical, and its period would be constant. However, this is not achievable; unavoidable random fluctuations in the force due to friction of the clock's pallets, lubrication variations, and changes in the torque provided by the clock's power source as it runs down, mean that the force of the impulse applied by the escapement varies.
If these variations in the escapement's force cause changes in the pendulum's width of swing (amplitude), this will cause corresponding slight changes in the period, since (as discussed at top) a pendulum with a finite swing is not quite isochronous. Therefore, the goal of traditional escapement design is to apply the force with the proper profile, and at the correct point in the pendulum's cycle, so force variations have no effect on the pendulum's amplitude. This is called an "isochronous escapement".
The Airy condition.
Clockmakers had known for centuries that the disturbing effect of the escapement's drive force on the period of a pendulum is smallest if given as a short impulse as the pendulum passes through its bottom equilibrium position. If the impulse occurs before the pendulum reaches bottom, during the downward swing, it will have the effect of shortening the pendulum's natural period, so an increase in drive force will decrease the period. If the impulse occurs after the pendulum reaches bottom, during the upswing, it will lengthen the period, so an increase in drive force will increase the pendulum's period. In 1826 British astronomer George Airy proved this; specifically, he proved that if a pendulum is driven by an impulse that is symmetrical about its bottom equilibrium position, the pendulum's period will be unaffected by changes in the drive force. The most accurate escapements, such as the deadbeat, approximately satisfy this condition.
Gravity measurement.
The presence of the acceleration of gravity "g" in the periodicity equation (1) for a pendulum means that the local gravitational acceleration of the Earth can be calculated from the period of a pendulum. A pendulum can therefore be used as a gravimeter to measure the local gravity, which varies by over 0.5% across the surface of the Earth. The pendulum in a clock is disturbed by the pushes it receives from the clock movement, so freeswinging pendulums were used, and were the standard instruments of gravimetry up to the 1930s.
The difference between clock pendulums and gravimeter pendulums is that to measure gravity, the pendulum's length as well as its period has to be measured. The period of freeswinging pendulums could be found to great precision by comparing their swing with a precision clock that had been adjusted to keep correct time by the passage of stars overhead. In the early measurements, a weight on a cord was suspended in front of the clock pendulum, and its length adjusted until the two pendulums swung in exact synchronism. Then the length of the cord was measured. From the length and the period, "g" could be calculated from equation (1).
The seconds pendulum.
The seconds pendulum, a pendulum with a period of two seconds so each swing takes one second, was widely used to measure gravity, because its period could be easily measured by comparing it to precision regulator clocks, which all had seconds pendulums. By the late 17th century, the length of the seconds pendulum became the standard measure of the strength of gravitational acceleration at a location. By 1700 its length had been measured with submillimeter accuracy at several cities in Europe. For a seconds pendulum, "g" is proportional to its length:
Kater's pendulum.
The precision of the early gravity measurements above was limited by the difficulty of measuring the length of the pendulum, "L" . "L" was the length of an idealized simple gravity pendulum (described at top), which has all its mass concentrated in a point at the end of the cord. In 1673 Huygens had shown that the period of a rigid bar pendulum (called a "compound pendulum") was equal to the period of a simple pendulum with a length equal to the distance between the pivot point and a point called the center of oscillation, located under the center of gravity, that depends on the mass distribution along the pendulum. But there was no accurate way of determining the center of oscillation in a real pendulum.
To get around this problem, the early researchers above approximated an ideal simple pendulum as closely as possible by using a metal sphere suspended by a light wire or cord. If the wire was light enough, the center of oscillation was close to the center of gravity of the ball, at its geometric center. This "ball and wire" type of pendulum wasn't very accurate, because it didn't swing as a rigid body, and the elasticity of the wire caused its length to change slightly as the pendulum swung.
However Huygens had also proved that in any pendulum, the pivot point and the center of oscillation were interchangeable. That is, if a pendulum were turned upside down and hung from its center of oscillation, it would have the same period as it did in the previous position, and the old pivot point would be the new center of oscillation.
British physicist and army captain Henry Kater in 1817 realized that Huygens' principle could be used to find the length of a simple pendulum with the same period as a real pendulum. If a pendulum was built with a second adjustable pivot point near the bottom so it could be hung upside down, and the second pivot was adjusted until the periods when hung from both pivots were the same, the second pivot would be at the center of oscillation, and the distance between the two pivots would be the length "L" of a simple pendulum with the same period.
Kater built a reversible pendulum (shown at right) consisting of a brass bar with two opposing pivots made of short triangular "knife" blades "(a)" near either end. It could be swung from either pivot, with the knife blades supported on agate plates. Rather than make one pivot adjustable, he attached the pivots a meter apart and instead adjusted the periods with a moveable weight on the pendulum rod "(b,c)". In operation, the pendulum is hung in front of a precision clock, and the period timed, then turned upside down and the period timed again. The weight is adjusted with the adjustment screw until the periods are equal. Then putting this period and the distance between the pivots into equation (1) gives the gravitational acceleration "g" very accurately.
Kater timed the swing of his pendulum using the "method of coincidences" and measured the distance between the two pivots with a micrometer. After applying corrections for the finite amplitude of swing, the buoyancy of the bob, the barometric pressure and altitude, and temperature, he obtained a value of 39.13929 inches for the seconds pendulum at London, in vacuum, at sea level, at 62 °F. The largest variation from the mean of his 12 observations was 0.00028 in. representing a precision of gravity measurement of 7×10−6 (7 mGal or 70 µm/s2). Kater's measurement was used as Britain's official standard of length (see below) from 1824 to 1855.
Reversible pendulums (known technically as "convertible" pendulums) employing Kater's principle were used for absolute gravity measurements into the 1930s.
Later pendulum gravimeters.
The increased accuracy made possible by Kater's pendulum helped make gravimetry a standard part of geodesy. Since the exact location (latitude and longitude) of the 'station' where the gravity measurement was made was necessary, gravity measurements became part of surveying, and pendulums were taken on the great geodetic surveys of the 18th century, particularly the Great Trigonometric Survey of India.
Relative pendulum gravimeters were superseded by the simpler LaCoste zero-length spring gravimeter, invented in 1934 by Lucien LaCoste. Absolute (reversible) pendulum gravimeters were replaced in the 1950s by free fall gravimeters, in which a weight is allowed to fall in a vacuum tank and its acceleration is measured by an optical interferometer.
Standard of length.
Because the acceleration of gravity is constant at a given point on Earth, the period of a simple pendulum at a given location depends only on its length. Additionally, gravity varies only slightly at different locations. Almost from the pendulum's discovery until the early 19th century, this property led scientists to suggest using a pendulum of a given period as a standard of length.
Until the 19th century, countries based their systems of length measurement on prototypes, metal bar primary standards, such as the standard yard in Britain kept at the Houses of Parliament, and the standard "toise" in France, kept at Paris. These were vulnerable to damage or destruction over the years, and because of the difficulty of comparing prototypes, the same unit often had different lengths in distant towns, creating opportunities for fraud. During the Enlightenment scientists argued for a length standard that was based on some property of nature that could be determined by measurement, creating an indestructible, universal standard. The period of pendulums could be measured very precisely by timing them with clocks that were set by the stars. A pendulum standard amounted to defining the unit of length by the gravitational force of the Earth, for all intents constant, and the second, which was defined by the rotation rate of the Earth, also constant. The idea was that anyone, anywhere on Earth, could recreate the standard by constructing a pendulum that swung with the defined period and measuring its length.
Virtually all proposals were based on the seconds pendulum, in which each swing (a half period) takes one second, which is about a meter (39 inches) long, because by the late 17th century it had become a standard for measuring gravity (see previous section). By the 18th century its length had been measured with sub-millimeter accuracy at a number of cities in Europe and around the world.
The initial attraction of the pendulum length standard was that it was believed (by early scientists such as Huygens and Wren) that gravity was constant over the Earth's surface, so a given pendulum had the same period at any point on Earth. So the length of the standard pendulum could be measured at any location, and would not be tied to any given nation or region; it would be a truly democratic, worldwide standard. Although Richer found in 1672 that gravity varies at different points on the globe, the idea of a pendulum length standard remained popular, because it was found that gravity only varies with latitude. Gravitational acceleration increases smoothly from the equator to the poles, due to the oblate shape of the Earth, so at any given latitude (east–west line), gravity was constant enough that the length of a seconds pendulum was the same within the measurement capability of the 18th century. Thus the unit of length could be defined at a given latitude and measured at any point along that latitude. For example, a pendulum standard defined at 45° north latitude, a popular choice, could be measured in parts of France, Italy, Croatia, Serbia, Romania, Russia, Kazakhstan, China, Mongolia, the United States and Canada. In addition, it could be recreated at any location at which the gravitational acceleration had been accurately measured.
By the mid 19th century, increasingly accurate pendulum measurements by Edward Sabine and Thomas Young revealed that gravity, and thus the length of any pendulum standard, varied measurably with local geologic features such as mountains and dense subsurface rocks. So a pendulum length standard had to be defined at a single point on Earth and could only be measured there. This took much of the appeal from the concept, and efforts to adopt pendulum standards were abandoned.
Early proposals.
One of the first to suggest defining length with a pendulum was Flemish scientist Isaac Beeckman who in 1631 recommended making the seconds pendulum "the invariable measure for all people at all times in all places". Marin Mersenne, who first measured the seconds pendulum in 1644, also suggested it. The first official proposal for a pendulum standard was made by the British Royal Society in 1660, advocated by Christiaan Huygens and Ole Rømer, basing it on Mersenne's work, and Huygens in "Horologium Oscillatorium" proposed a "horary foot" defined as 1/3 of the seconds pendulum. Christopher Wren was another early supporter. The idea of a pendulum standard of length must have been familiar to people as early as 1663, because Samuel Butler satirizes it in "Hudibras":
In 1671 Jean Picard proposed a pendulum-defined 'universal foot' in his influential "Mesure de la Terre". Gabriel Mouton around 1670 suggested defining the "toise" either by a seconds pendulum or a minute of terrestrial degree. A plan for a complete system of units based on the pendulum was advanced in 1675 by Italian polymath Tito Livio Burratini. In France in 1747, geographer Charles Marie de la Condamine proposed defining length by a seconds pendulum at the equator; since at this location a pendulum's swing wouldn't be distorted by the Earth's rotation. James Steuart (1780) and George Skene Keith were also supporters.
By the end of the 18th century, when many nations were reforming their weight and measure systems, the seconds pendulum was the leading choice for a new definition of length, advocated by prominent scientists in several major nations. In 1790, then US Secretary of State Thomas Jefferson proposed to Congress a comprehensive decimalized US 'metric system' based on the seconds pendulum at 38° North latitude, the mean latitude of the United States. No action was taken on this proposal. In Britain the leading advocate of the pendulum was politician John Riggs Miller. When his efforts to promote a joint British–French–American metric system fell through in 1790, he proposed a British system based on the length of the seconds pendulum at London. This standard was adopted in 1824 (below).
The metre.
In the discussions leading up to the French adoption of the metric system in 1791, the leading candidate for the definition of the new unit of length, the metre, was the seconds pendulum at 45° North latitude. It was advocated by a group led by French politician Talleyrand and mathematician Antoine Nicolas Caritat de Condorcet. This was one of the three final options considered by the French Academy of Sciences committee. However, on March 19, 1791 the committee instead chose to base the metre on the length of the meridian through Paris. A pendulum definition was rejected because of its variability at different locations, and because it defined length by a unit of time. (However, since 1983 the metre has been officially defined in terms of the length of the second and the speed of light.) A possible additional reason is that the radical French Academy didn't want to base their new system on the second, a traditional and nondecimal unit from the "ancien regime".
Although not defined by the pendulum, the final length chosen for the metre, 10−7 of the pole-to-equator meridian arc, was very close to the length of the seconds pendulum (0.9937 m), within 0.63%. Although no reason for this particular choice was given at the time, it was probably to facilitate the use of the seconds pendulum as a secondary standard, as was proposed in the official document. So the modern world's standard unit of length is certainly closely linked historically with the seconds pendulum.
Britain and Denmark.
Britain and Denmark appear to be the only nations that (for a short time) based their units of length on the pendulum. In 1821 the Danish inch was defined as 1/38 of the length of the mean solar seconds pendulum at 45° latitude at the meridian of Skagen, at sea level, in vacuum. The British parliament passed the "Imperial Weights and Measures Act" in 1824, a reform of the British standard system which declared that if the prototype standard yard was destroyed, it would be recovered by defining the inch so that the length of the solar seconds pendulum at London, at sea level, in a vacuum, at 62 °F was 39.1393 inches. This also became the US standard, since at the time the US used British measures. However, when the prototype yard was lost in the 1834 Houses of Parliament fire, it proved impossible to recreate it accurately from the pendulum definition, and in 1855 Britain repealed the pendulum standard and returned to prototype standards.
Other uses.
Seismometers.
A pendulum in which the rod is not vertical but almost horizontal was used in early seismometers for measuring Earth tremors. The bob of the pendulum does not move when its mounting does, and the difference in the movements is recorded on a drum chart.
Schuler tuning.
As first explained by Maximilian Schuler in a 1923 paper, a pendulum whose period exactly equals the orbital period of a hypothetical satellite orbiting just above the surface of the Earth (about 84 minutes) will tend to remain pointing at the center of the Earth when its support is suddenly displaced. This principle, called Schuler tuning, is used in inertial guidance systems in ships and aircraft that operate on the surface of the Earth. No physical pendulum is used, but the control system that keeps the inertial platform containing the gyroscopes stable is modified so the device acts as though it is attached to such a pendulum, keeping the platform always facing down as the vehicle moves on the curved surface of the Earth.
Coupled pendulums.
In 1665 Huygens made a curious observation about pendulum clocks. Two clocks had been placed on his mantlepiece, and he noted that they had acquired an opposing motion. That is, their pendulums were beating in unison but in the opposite direction; 180° out of phase. Regardless of how the two clocks were started, he found that they would eventually return to this state, thus making the first recorded observation of a coupled oscillator.
The cause of this behavior was that the two pendulums were affecting each other through slight motions of the supporting mantlepiece. This process is called entrainment or mode locking in physics and is observed in other coupled oscillators. Synchronized pendulums have been used in clocks and were widely used in gravimeters in the early 20th century. Although Huygens only observed out-of-phase synchronization, recent investigations have shown the existence of in-phase synchronization, as well as "death" states wherein one or both clocks stops.
Religious practice.
Pendulum motion appears in religious ceremonies as well. The swinging incense burner called a censer, also known as a thurible, is an example of a pendulum. Pendulums are also seen at many gatherings in eastern Mexico where they mark the turning of the tides on the day which the tides are at their highest point. See also pendulums for divination and dowsing.
Education.
Pendulums are widely used in science education as an example of a harmonic oscillator, to teach dynamics and oscillatory motion. One use is to demonstrate the law of conservation of energy. A heavy object such as a bowling ball or wrecking ball is attached to a string. The weight is then moved to within a few inches of a volunteer's face, then released and allowed to swing and come back. In most instances, the weight reverses direction and then returns to (almost) the same position as the original release location — "i.e." a small distance from the volunteer's face — thus leaving the volunteer unharmed. On occasion the volunteer is injured if either the volunteer does not stand still or the pendulum is initially released with a push (so that when it returns it surpasses the release position).
Torture device.
It is claimed that the pendulum was used as an instrument of torture and execution by the Spanish Inquisition in the 18th century. The allegation is contained in the 1826 book "The history of the Inquisition of Spain " by the Spanish priest, historian and liberal activist Juan Antonio Llorente. A swinging pendulum whose edge is a knife blade slowly descends toward a bound prisoner until it cuts into his body. This method of torture came to popular consciousness through the 1842 short story "The Pit and the Pendulum" by American author Edgar Allan Poe but there is considerable skepticism that it actually was used.
Most knowledgeable sources are skeptical that this torture was ever actually used. The only evidence of its use is one paragraph in the preface to Llorente's 1826 "History", relating a second-hand account by a single prisoner released from the Inquisition's Madrid dungeon in 1820, who purportedly described the pendulum torture method. Modern sources point out that due to Jesus' admonition against bloodshed, Inquisitors were only allowed to use torture methods which did not spill blood, and the pendulum method would have violated this stricture. One theory is that Llorente misunderstood the account he heard; the prisoner was actually referring to another common Inquisition torture, the "strappado" (garrucha), in which the prisoner has his hands tied behind his back and is hoisted off the floor by a rope tied to his hands. This method was also known as the "pendulum". Poe's popular horror tale, and public awareness of the Inquisition's other brutal methods, has kept the myth of this elaborate torture method alive.
Notes.
The value of g reflected by the period of a pendulum varies from place to place. The gravitational force varies with distance from the center of the Earth, i.e. with altitude - or because the Earth's shape is oblate, g varies with latitude.
A more important cause of this reduction in g at the equator is because the equator is spinning at one revolution per day, so the acceleration by the gravitational force is partially canceled there by the centrifugal force.


Uplands station

Uplands is an under construction station on the Airport Link of the Trillium Line in Ottawa, Ontario. It is being constructed as part of the Stage 2 O-Train expansion and is scheduled for completion in 2022. The station will consist of two side platforms and is part of the only double tracked segment of the Airport Link.


Coca Codo Sinclair Dam

The Coca Codo Sinclair Dam is a hydroelectric dam in Ecuador. It is located on the Coca River in Napo Province, east of Quito. It is the largest energy project in Ecuador. The dam was constructed by Sinohydro Corporation for $2.25 billion.
The plant became fully operational in November 2016. It has a capacity of 1,500 megawatts.
Funding of dam.
Over the years, China provided $19 billion in the form of loans to Ecuador for the construction of "bridges, highways, irrigation, schools, health clinics and a half dozen dams" as well as the Coca Codo Sinclair dam. According to an article in "The New York Times", Ecuador repays its debt to China by providing China with oil "at a discount". By 2018, this meant that China kept 80 percent of oil produced in Ecuador. The loan from China’s Export-Import Bank for the Coca Codo Sinclair Dam amounts to $1.7 billion with an interest rate of 7% interest over 15 years which is $125 million a year in interest alone.
Post construction.
As of December 2018, 7,648 large and small cracks were identified in the generator hall, surrounding equipment. The cracks were first discovered in 2014 but the full extent of them is unknown as a thorough assessment would include deconstructing portions of the power plant which is cost prohibitive.
After the dam became operational, its reservoir caused regressive erosion upstream and water absent of sediment released from the dam has caused high rates of erosion downstream which likely led to two oil spills after pipelines along the river lost their footings. Downstream erosion, if left unchecked can undermine the dam and other oil infrastructure by 2022.


Jacob Hostetter

Jacob Hostetter (May 9, 1754June 29, 1831) was a member of the U.S. House of Representatives from Pennsylvania.
Biography.
Jacob Hostetter was born near York in the Province of Pennsylvania. He attended the common schools and worked as a clockmaker. He was a member of the general assembly of Pennsylvania from 1797 to 1802. He was elected as a Republican to the Fifteenth Congress to fill the vacancy caused by the resignation of Jacob Spangler. He was reelected as a Republican to the Sixteenth Congress. He moved to Ohio and settled in Columbiana, Ohio, where he died on June 29, 1831.


Atmos clock

Atmos is the brand name of a mechanical torsion pendulum clock manufactured by Jaeger-LeCoultre in Switzerland which does not need to be wound manually. It gets the energy it needs to run from temperature and atmospheric pressure changes in the environment, and can run for years without human intervention.
The clock is driven by a mainspring, which is wound by the expansion and contraction of liquid and gaseous ethyl chloride in an internal hermetically sealed metal bellows. The ethyl chloride vaporises into an expansion chamber as the temperature rises, compressing a spiral spring; with a fall in temperature the gas condenses and the spiral spring expands, winding the mainspring.
This motion constantly winds the mainspring. A temperature variation of only one degree in the range between and , or a pressure variation of 3 mmHg, was calculated to provide energy for two days' operation for an early prototype, while for a more recent Atmos 540 model the corresponding value has been computed as 4.3 days per °C.
To run the clock on this small amount of energy, everything in the Atmos must be as friction-free as possible. For timekeeping it uses a torsion pendulum, which consumes less energy than an ordinary pendulum. The torsion pendulum has a period of precisely one minute; thirty seconds to rotate in one direction and thirty seconds to return to the starting position. This is thirty times slower than the 0.994 m (39.1 in) seconds pendulum typically found in a longcase clock, where each swing (or half-period) takes one second.
History.
The first clock powered by changes in atmospheric pressure and temperature was invented by Cornelis Drebbel in the early 17th century. Drebbel built as many as 18 of these, the two most notable being for King James VI & I of Britain, and Rudolf II of Bohemia. The King James clock was known as the Eltham Perpetuum, and was famous throughout Europe. It is mentioned in two works of Ben Jonson.
Clocks powered by atmospheric pressure and temperature changes were subsequently developed by Pierre de Rivaz in 1740, and by James Cox and John Joseph Merlin (Cox's timepiece) in the 1760s. The Beverly Clock in Dunedin, New Zealand, is still running despite never having been manually wound since its construction in 1864.
The first Atmos clock was designed by Jean-Léon Reutter, an engineer in Neuchâtel, Switzerland, in 1928.
This noncommercial prototype, which predated the Atmos name but is now known unofficially as Atmos 0, was driven by a mercury-in-glass expansion device. The mechanism operated on temperature changes alone.
On 1 June 1929, Compagnie Générale de Radio (CGR) in France began manufacturing the first commercial model, Atmos 1, which used a mercury and ammonia bellows power source. On 27 July 1935, Jaeger-LeCoultre took over production of Atmos 1 while it developed a second design which used the present ethyl chloride power source. This model later named the Atmos 2, was announced on 15 January 1936, but problems delayed full production until mid-1939. Subsequent models were based on this design. To date, over 500,000 Atmos clocks have been produced.


Giovanni Martini da Udine

Giovanni Martini or Giovanni Martini da Udine (1470/75 – September 30, 1535) was an Italian painter and sculptor of the Renaissance, born in Udine between 1470 and 1475. With Pellegrino da San Daniele he is one of the main representatives of Renaissance art in the Friuli region of north-east Italy.
Biography.
A member of a family of artists, Giovanni was the son of Martin and the grandson of Domenico da Tolmezzo.
For many years, he was identified as the painter, also from Udine, who signed "John the Baptist" and worked in Udine and in the Friuli, between the end of the 15th and early 16th century. Currently these works are attributed to Giovanni Battista da Udine, a follower of Alvise Vivarini.
Giovanni Martini's first signed work, in 1501, is the altarpiece "St. Mark and St. John the Baptist, with Saints Stephen, Jerome, Ermacore, Abbot Anthony, and the Blessed Bertrand", located in the Chapel of St. Mark in Udine Cathedral. This work was highly criticized by Giacomo Gordino, the dean of the chapter of the cathedral, in a letter to Domenico Grimani, Patriarch of Aquileia, complaining of the martial aspect given to St. Mark by the painter, which may be a portrait of Antonio Loredan, lieutenant of Friuli. Another altarpiece, the "St. Ursula Altarpiece", dated 1507 on its back, was created for the Saint Peter Martyr church in Udine. These two altarpieces demonstrate Martini's knowledge of the works of Alvise Vivarini and Cima da Conegliano, and are connected with the traditions of Friuli.
In 1507 he inherited his father and uncle's workshop and took on the tradition of carved wooden altars, adapting the traditional Gothic style of Friuli to the fashion of the Venetian Renaissance. He completed a wooden altar in 1515 for the church of Santa Maria delle Grazie in Prodolone (in San Vito al Tagliamento). The rhythm of the composition of the statues of this set shows a still strong link with the tradition of the school of Tolmezzo in the Quattrocento.
The most representative of Martini's wooden altars is that in Mortegliano, which he completed in 1526. For this impressive work he was paid the enormous sum for the time of 1180 ducats. The altar, which stands more than five meters high and is the largest in Friuli, consists of 60 statues. It is divided into registers and subdivided into individual cells, as previously, but it has a spatial continuity through the columns of the architectural framework, as can be seen for example linking the "Pietà" group and the "Dormitio Virginis". It is regarded not only as the artist's masterpiece, but also as one of the highest expressions of wooden sculpture of the Renaissance.
Other examples can be found in the parish churches of Faedis and Remanzacco.
Works.
Martini's principal mature painted works are


Joshua Field (engineer)

Joshua Field FRS (1786 – 11 August 1863) was a British civil engineer and mechanical engineer.
Field was born in Hackney in 1786, his father was John Field a corn and seed merchant who was later to become Master of the Worshipful Company of Merchant Taylors. Field was a pupil of dockyard engineer Simon Goodrich from 1803 to 1805.
Commissioned by Samuel Bentham, the Inspector-general of naval works, he worked with Samuel Goodrich to develop tools for mass-producing ships' blocks at Portsmouth Dockyard. The block mills they designed required ten unskilled men to take the place of 110 skilled craftsmen, and have been recognised as the first use of machine tools for mass production.
They were built by Henry Maudslay between 1802 and 1806, and represented the first steam-powered manufactory in any dockyard.
He then joined Maudslay to form the firm of Messrs. Maudslay, Sons and Field of Lambeth. One of their projects was to build engines for the SS Great Western's Atlantic crossing of 1838.
He was a prolific engineer working with the Atlantic Telegraph Company on machinery for cable laying, the Metropolitan Board of Works on sewage systems and Isambard Kingdom Brunel on his steamships.
Field joined seven other young engineers who, in 1817, decided to found the Institution of Civil Engineers as a more accessible institution than the established but élitist Society of Civil Engineers founded by John Smeaton in 1771.
He served as their vice-president in 1837, and he continued to hold that office until elected president on 18 January 1848, being the first mechanical engineer to hold the presidency and the only one of the original proposers to hold the post. In his inaugural address, delivered on 1 February, he alluded particularly to the changes which had then been introduced into steam navigation which allowed for a greater capacity and speeds. On 3 March 1836 he became a fellow of the Royal Society, and was also a member of the Society of Arts.
Field died at his residence, Balham Hill House, Surrey, on 11 August 1863, aged 76 and was interred at West Norwood Cemetery in a Portland stone sarcophagus.
Family.
His daughter, Matilda Field, married Dr Thomas H. Gladstone. Their children included the embryologist, Reginald John Gladstone FRSE (1865-1947).
Reginald married his first cousin (i.e. also a grandchild of Field) Ida Millicant Field in 1912.
Notes.


Robert Reid (pipemaker)

Robert Reid (1784 – 1837) is widely acknowledged as the creator of the modern form of the Northumbrian Smallpipes. He lived and worked at first in Newcastle upon Tyne, but moved later to the nearby town of North Shields at the mouth of the Tyne, probably in 1802. North Shields was a busy port at this time. The Reids were a family with a long-standing connection to piping; Robert's father Robert Reed (sic), a cabinet maker, had been a player of
"the Northumbrian big-pipes", and an associate of James Allan, his son Robert was described later by James Fenwick as "a beautiful player as well as maker" of smallpipes, while Robert's son James (1814–1874) joined his father in the business. Robert died in North Shields on the 13th or 14th of January 1837, and his death notice in the Newcastle Journal referred to him as a "piper, and as a maker of such instruments is known from the peer to the peasant, for the quality of their tone, and elegance of finish". He is buried in the graveyard of Christ Church, North Shields. His wife Isabella died in 1849, of cholera. There were repeated outbreaks of the disease at this time especially in the poor 'low town', near the river, where the Reids lived.
After Robert's death, James continued the business alone, in particular maintaining pipes, although there are a few sets made solely by James, who was also a piper. Robert's daughter Elizabeth, Elizabeth Oliver after her marriage, was a piper too, the first known female Northumbrian piper, and was, together with James, an informant of the Ancient Melodies Committee when they were collecting material for the Northumbrian Minstrelsy. She later wrote to J. W. Fenwick, and he stated that the set of "Dorrington Lads" was "as played by Robert Reid, and his son James, also his daughter Elizabeth Oliver"; in a letter to Fenwick in 1883, she said it was "most likely the same copy that poor Will Allen was trying to play when his Spirit was called Home to a more blissful rest." Given the similarity between this version and that in the William Dixon manuscript, she may well have been right. An identical version had appeared in the Rook manuscript, of 1840, suggesting that Rook learned it from the Reids, perhaps from Robert himself. As the two texts are note for note identical, despite a gap in time of more than 40 years, it can be seen that Elizabeth was a very careful informant. A complex variation set on "Maggie Lauder" in Fenwick's manuscript collection, not in his hand, is stated by him to be Mrs. Oliver's copy, 'as she had learned it from her father'. She seems to have had a significant collection of manuscript music from her father, but it is not known to have survived. A number of tunes from James Reid also appear in Fenwick's manuscript; in all there are 12 tunes there with a provenance from one or other of the Reids.
Pipemaking.
Simple closed chanter smallpipes had existed since the late 17th century (possibly being described in the Talbot manuscript from about 1695) but became standard in Northumberland during the 18th. Keys were not added until around 1800 -John Peacock's tune book (c1800) includes "A compleat drawing of J. Peacock's New Invented Pipe Chanter with the addition of four keys". As John Dunn was closely associated with Peacock at this time, Dunn may well have been the first to construct such an instrument, but sets of Reid pipes from this time onwards started including keys, and more keys were added to the design over the following years.
The Clough family had a 7 key set with a Reid chanter that Tom Clough stated had been made for his great grandfather Henry (1789–1842); this oral tradition, if correct, would date the set to around 1810 or 1820.
Another such chanter, dated c. 1820, is shown below - the four views show respectively:
The stamp used by Reid to mark instruments he made is shown here.
Francis Wood, himself a pipemaker, has written "From an instrument maker’s perspective, the Reid chanters appear extraordinary objects, a fine example of ideal design, which mysteriously seems to have emerged fully formed without any apparent evolution with the exception of the rare examples of 6 key chanters lacking the D sharp key. Some changes of detail occur throughout Reid’s career but what remains evident and constant is the extreme economy and functionality of the design, in which little is purely decorative. Every detail is generally present for a practical reason, to a degree that is remarkable. The very compact keywork also conforms to that principle. The outline of the keys remains close to the chanter stem with no part unduly projecting, a particularly neat construction that reduces the vulnerability of the keywork to accidental damage. Players will notice an immediately comfortable hold on the chanter, with keywork that is lightly and evenly sprung and with pleasantly rounded key-touches which accommodate differing angles of finger action. These are all characteristics which are evident on some finely made modern pipes but they are by no means universal."
By the 1830s 14 key chanters were available, of which a fine example, with 5 drones, is found in the Morpeth Chantry Bagpipe Museum. Reputedly, Tom Clough described this as “the finest set I ever played on”. Some detail of this set's keywork is shown here.
The key arrangements found in this period have remained largely unchanged since.
A complex set assembled by James Reid, from parts made by his father, with six drones, was used as the frontispiece of James Fenwick's "Instruction Book for the Northumbrian Smallpipes", published in 1896. This set was probably one made for Cornelius Stanton shortly before Stanton's death. Only one such set is known.
Some 77 sets of pipes wholly or partially by Reid survive; some 45 in private hands and perhaps 10 are actively played; a number of sets by the Reids are also in public collections, most numerously in the Morpeth Chantry Bagpipe Museum.
Robert Reid was also active in making Union Pipes; the precursor to modern Uilleann pipes. Henry Clough (I) was known to play a Reid set of Union pipes including regulators; surviving parts of this set are now in private hands.


Ball bearing motor

A ball bearing motor is an unusual electric motor that consists of two ball-bearing-type bearings, with the inner races mounted on a common conductive shaft, and the outer races connected to a high current, low voltage power supply. An alternative construction fits the outer races inside a metal tube, while the inner races are mounted on a shaft with a non-conductive section (e.g. two sleeves on an insulating rod). This method has the advantage that the tube will act as a flywheel. The motor rarely starts without assistance, having effectively zero static torque, but once rotation begins the motor will accelerate until it reaches a steady speed, the direction of rotation is determined by the initial spin. Although ball bearing motors can reach reasonably high speeds they are very inefficient, producing significant torque typically requires so much power that the bearings are heated to several hundred degrees.
S. Marinov suggests that the device produces motion from electricity without magnetism being involved, operating purely by the resistance heating causing an asymmetric thermal expansion of the balls in the bearings as they rotate. The same explanation is given by Watson, Patel and Sedcole for rotating cylinders (instead of balls). However, H. Gruenberg has given a thorough theoretical explanation based on pure electromagnetism (and neglecting the thermal effects completely).
Also, P. Hatzikonstantinou and P. G. Moyssides claim to have found an excellent agreement between the results from the electromagnetic theory and the experiments measuring the total power and efficiency of the motor.


Michelangelo Sapiano

Michelangelo Sapiano (March 19, 1826 – December 2, 1912) was a Maltese clock maker and inventor born in Mqabba, Malta.
Early life.
Michelangelo Sapiano was born in Mqabba in 1826. When he was 14 years of age he opened a watch repair shop and at such a young age he managed to repair the clock found in the Parish Church of Mqabba when other clock makers couldn’t do so. This paved the way for him to become famous and gave him the courage to start making clocks. He went to live in Luqa when he was 21 years of age after he married a girl from the town.
Achievements.
Sapiano is most famous for large clocks which were made for churches, convents and sacristies in various towns and villages in Malta and Gozo and also for a large clock he made for the Church of Saint Catherine of Alexandria in Egypt.
His masterpiece is a grandfather clock which till a few years ago could be found in No.11, Pawlu Magri Street, Luqa, the house (which still exists) where Michelangelo Sapiano used to live after he married. The clock can now be found in the Mdina Cathedral Museum. For this clock he was awarded a silver medal in an Industrial Exhibition which was held in 1864. Apart from showing the time, days and date this clock also shows the phases of the moon and the time at which the sun rises and goes down. This clock also has a mechanism which marks when a year is a leap year.
Sapiano made other interesting inventions. He invented an alarm clock, which at the time of ringing, produced a spark and lighted a candle to show the time. Another clock he invented had a moving globe with the world map, and every half an hour it showed the position of the world in relation to the sun. He made other precision instruments, including a balance for the Malta Customs, to take weights from 700 lbs down to a fraction of an ounce. For his wife he made a mechanical egg timer with a bell, and to know the time at night he devised a mantel clock to which a long string was attached which would chime the most recent time when pulled in the darkness.
Sapiano was awarded a certificate and a gold medal by the Society of Arts, Manufacture and Commerce on the 26 February 1908. He died on the 2 December 1912.


Christian Ludewig Theodor Winkelmann

Christian Ludewig Theodor Winkelmann, also spelled Winckelmann (3 November 1812 – 7 February 1875) was a German piano maker.
Life.
Born in Braunschweig, Winkelmann was the son of a master carpenter. He first worked with luthier Carl Rautmann in Wolfenbüttel and in 1837 he founded a piano factory in Brunswick. The first 3 uprights were made at home. Then grand pianos were made. In 1851, through the pianist Henry Litolff, an association was formed with the piano manufacturer Friedrich Zeitter from Vienna who introduced some innovations such as iron frames. This increased production from 60 to 80 instruments per year. The company named Zeitter & Winkelmann was one of the largest piano manufacturers in northern Germany.
In 1860, Winkelmann was appointed a supplier of pianos for the ducal court.
Winkelmann's grandson was the tenor Hermann Winkelmann and his great grandson the tenor Hans Winckelmann.


Francesco Maria De Regi

Francesco Maria De Regi (Milan, 1720 – 1794) was an Italian mathematician.
He was a Barnabite priest. He worked particularly on hydraulic engineering. At twenty-four he took the chair of mathematics, specially created for him, in the school of the Collegio of Sant'Alessandro in Milan.