Arc lamp
An arc lamp or arc light is a lamp that produces light by an electric arc. The carbon arc light, which consists of an arc between carbon electrodes in air, invented by Humphry Davy in the first decade of the 1800s, was the first practical electric light, it was used starting in the 1870s for street and large building lighting until it was superseded by the incandescent light in the early 20th century. It continued in use in more specialized applications where a high intensity point light source was needed, such as searchlights and movie projectors until after World War II; the carbon arc lamp is now obsolete for most of these purposes, but it is still used as a source of high intensity ultraviolet light. The term is now used for gas discharge lamps, which produce light by an arc between metal electrodes through an inert gas in a glass bulb; the common fluorescent lamp is a low-pressure mercury arc lamp. The xenon arc lamp, which produces a high intensity white light, is now used in many of the applications which used the carbon arc, such as movie projectors and searchlights.
An arc is the discharge. A high voltage is pulsed across the lamp to "ignite" or "strike" the arc, after which the discharge can be maintained at a lower voltage; the "strike" requires an electrical circuit with a ballast. The ballast performs two functions. First, when the power is first switched on, the igniter/starter sets up a small current through the ballast and starter; this creates a small magnetic field within the ballast windings. A moment the starter interrupts the current flow from the ballast, which has a high inductance and therefore tries to maintain the current flow; as a result, a high voltage appears across the ballast momentarily. The circuit will repeat this action; when the lamp sustains the arc, the ballast performs its second function, to limit the current to that needed to operate the lamp. The lamp and igniter are rating-matched to each other; the colour of the light emitted by the lamp changes as its electrical characteristics change with temperature and time. Lightning is a similar principle where the atmosphere is ionized by the high potential difference between earth and storm clouds.
The temperature of the arc in an arc lamp can reach several thousand degrees Celsius. The outer glass envelope can reach 500 degrees Celsius, therefore before servicing one must ensure the bulb has cooled sufficiently to handle. If these types of lamps are turned off or lose their power supply, one cannot restrike the lamp again for several minutes. However, some lamps can be restruck as soon; the Vortek water-wall plasma arc lamp, invented in 1975 by David Camm and Roy Nodwell at the University of British Columbia, Canada, made the Guinness Book of World Records in 1986 and 1993 as the most powerful continuously burning light source at over 300 kW or 1.2 million candle power. In popular use, the term arc lamp means carbon arc lamp only. In a carbon arc lamp, the electrodes are carbon rods in free air. To ignite the lamp, the rods are touched together, thus allowing a low voltage to strike the arc; the rods are slowly drawn apart, electric current heats and maintains an arc across the gap. The tips of the carbon rods are heated and the carbon vaporizes.
The carbon vapor in the arc is luminous, what produces the bright light. The rods are burnt away in use, the distance between them needs to be adjusted in order to maintain the arc. Many ingenious mechanisms were invented to effect the distance automatically based on solenoids. In one of the simplest mechanically-regulated forms the electrodes are mounted vertically; the current supplying the arc is passed in series through a solenoid attached to the top electrode. If the points of the electrodes are touching the resistance falls, the current increases and the increased pull from the solenoid draws the points apart. If the arc starts to fail the current drops and the points close up again; the Yablochkov candle is a simple arc lamp without a regulator, but it has the drawbacks that the arc cannot be restarted and a limited lifetime of only a few hours. The concept of carbon-arc lighting was first demonstrated by Sir Humphry Davy in the early 19th century, using charcoal sticks and a two thousand cell battery to create an arc across a 4-inch gap.
He mounted his electrodes horizontally and noted that, because of the strong convection flow of air, the arc formed the shape of an arch. He coined the term "arch lamp", contracted to "arc lamp" when the devices came into common usage. In the late nineteenth century, electric arc lighting was in wide use for public lighting; the tendency of electric arcs to flicker and hiss was a major problem. In 1895, Hertha Ayrton wrote a series of articles for the Electrician, explaining that these phenomena were the result of oxygen coming into contact with the carbon rods used to create the arc. In 1899, she was the firs
Manchester
Manchester is a city and metropolitan borough in Greater Manchester, with a population of 545,500 as of 2017. It lies within the United Kingdom's second-most populous built-up area, with a population of 3.2 million. It is fringed by the Cheshire Plain to the south, the Pennines to the north and east, an arc of towns with which it forms a continuous conurbation; the local authority is Manchester City Council. The recorded history of Manchester began with the civilian settlement associated with the Roman fort of Mamucium or Mancunium, established in about AD 79 on a sandstone bluff near the confluence of the rivers Medlock and Irwell, it was a part of Lancashire, although areas of Cheshire south of the River Mersey were incorporated in the 20th century. The first to be included, was added to the city in 1931. Throughout the Middle Ages Manchester remained a manorial township, but began to expand "at an astonishing rate" around the turn of the 19th century. Manchester's unplanned urbanisation was brought on by a boom in textile manufacture during the Industrial Revolution, resulted in it becoming the world's first industrialised city.
Manchester achieved city status in 1853. The Manchester Ship Canal opened in 1894, creating the Port of Manchester and directly linking the city to the Irish Sea, 36 miles to the west, its fortune declined after the Second World War, owing to deindustrialisation, but the IRA bombing in 1996 led to extensive investment and regeneration. In 2014, the Globalisation and World Cities Research Network ranked Manchester as a beta world city, the highest-ranked British city apart from London. Manchester is the third-most visited city after London and Edinburgh, it is notable for its architecture, musical exports, media links and engineering output, social impact, sports clubs and transport connections. Manchester Liverpool Road railway station was the world's first inter-city passenger railway station. Manchester hosted the 2002 Commonwealth Games; the name Manchester originates from the Latin name Mamucium or its variant Mancunium and the citizens are still referred to as Mancunians. These are thought to represent a Latinisation of an original Brittonic name, either from mamm- or from mamma.
Both meanings are preserved in Insular Celtic languages, such as mam meaning "breast" in Irish and "mother" in Welsh. The suffix -chester is a survival of Old English ceaster and from that castra in latin for camp or settlement; the Brigantes were the major Celtic tribe in. Their territory extended across the fertile lowland of what is now Stretford. Following the Roman conquest of Britain in the 1st century, General Agricola ordered the construction of a fort named Mamucium in the year 79 to ensure that Roman interests in Deva Victrix and Eboracum were protected from the Brigantes. Central Manchester has been permanently settled since this time. A stabilised fragment of foundations of the final version of the Roman fort is visible in Castlefield; the Roman habitation of Manchester ended around the 3rd century. After the Roman withdrawal and Saxon conquest, the focus of settlement shifted to the confluence of the Irwell and Irk sometime before the arrival of the Normans after 1066. Much of the wider area was laid waste in the subsequent Harrying of the North.
Thomas de la Warre, lord of the manor and constructed a collegiate church for the parish in 1421. The church is now Manchester Cathedral; the library, which opened in 1653 and is still open to the public today, is the oldest free public reference library in the United Kingdom. Manchester is mentioned as having a market in 1282. Around the 14th century, Manchester received an influx of Flemish weavers, sometimes credited as the foundation of the region's textile industry. Manchester became an important centre for the manufacture and trade of woollens and linen, by about 1540, had expanded to become, in John Leland's words, "The fairest, best builded and most populous town of all Lancashire." The cathedral and Chetham's buildings are the only significant survivors of Leland's Manchester. During the English Civil War Manchester favoured the Parliamentary interest. Although not long-lasting, Cromwell granted it the right to elect its own MP. Charles Worsley, who sat for the city for only a year, was appointed Major General for Lancashire and Staffordshire during the Rule of the Major Generals.
He was a diligent puritan, banning the celebration of Christmas. Significant quantities of cotton began to be used after about 1600, firstly in linen/cotton fustians, but by around 1750 pure cotton fabrics were being produced and cotton had overtaken wool in importance; the Irwell and Mersey were made navigable by 1736, opening a route from Manchester to the sea docks on the Mersey. The Bridgewater Canal, Britain's first wholly artificial waterway, was opened in 1761, bringing coal from mines at Worsley to central Manchester; the canal was extended to the Mersey at Runcorn by 1776. The combination of competition and improved efficiency halved th
Geissler tube
A Geissler tube is an early gas discharge tube used to demonstrate the principles of electrical glow discharge, similar to modern neon lighting. The tube was invented by the German physicist and glassblower Heinrich Geissler in 1857, it consists of a sealed evacuated glass cylinder of various shapes with a metal electrode at each end, containing rarefied gasses such as neon, argon, or air. When a high voltage is applied between the electrodes, an electrical current flows through the tube; the current dissociates electrons from the gas molecules, creating ions, when the electrons recombine with the ions, the gas emits light by fluorescence. The color of light emitted is characteristic of the material within the tube, many different colors and lighting effects can be achieved; the first gas-discharge lamps, Geissler tubes were novelty items, made in many artistic shapes and colors to demonstrate the new science of electricity. In the early 20th century, the technology was evolved into neon lighting.
Geissler tubes were mass-produced from the 1880s as novelty and entertainment devices, with various spherical chambers and decorative serpentine paths formed into the glass tube. Some tubes were elaborate and complex in shape and would contain chambers within an outer casing. A novel effect could be obtained by spinning a glowing tube at high speed with a motor; when an operating tube was touched by the hand the shape of the glowing discharge inside changed, due to the capacitance of the body. Simple straight Geissler tubes were used in early-20th-century scientific research as high voltage indicators; when a Geissler tube was brought near a source of high voltage alternating current such as a Tesla coil or Ruhmkorff coil, it would light up without contact with the circuit. They were used to tune the tank circuits of radio transmitters to resonance. Another example of their use was to find nodes of standing waves on transmission lines, such as Lecher lines used to measure the frequency of early radio transmitters.
Another use around 1900 was as the light source in Pulfrich refractometers. Geissler tubes are sometimes still used in physics education to demonstrate the principles of gas discharge tubes. Geissler tubes were the first gas discharge tubes, have had a large impact on the development of many instruments and devices which depend on electric discharge through gases. One of the most significant consequences of Geissler tube technology was the discovery of the electron and the invention of electronic vacuum tubes. By the 1870s better vacuum pumps enabled scientists to evacuate Geissler tubes to a higher vacuum; when current was applied, it was found that the glass envelope of these tubes would glow at the end opposite to the cathode. Observing that sharp-edged shadows were cast on the glowing tube wall by obstructions in the tube in front of the cathode, Johann Hittorf realized that the glow was caused by some type of ray travelling in straight lines through the tube from the cathode; these were named cathode rays.
In 1897 J. J. Thomson showed that cathode rays consisted of a unknown particle, named the electron; the technology of controlling electron beams resulted in the invention of the amplifying vacuum tube in 1907, which created the field of electronics and dominated it for 50 years, the cathode ray tube, used in radar and television displays. Some of the devices which evolved from Geissler tube technology: Vacuum tubes Xenon flash lamps Xenon arc lamps X-ray tubes Sodium vapor lamps used in streetlights "Neon" signs, which use both visible light discharge from neon and other gases and phosphor excitation from ultraviolet light Mercury vapor lamps Mass spectrometers Cathode ray tubes, employed in the oscilloscope and in television sets and computer display devices Electrotachyscope Fluorescent lamps Plasma globes William Crookes Cathode ray tube Crookes tube Induction coil Neon sign Plasma globe X-ray tube German inventors and discoverers Sparkmuseum: Crookes and Geissler Tubes Instruments for Natural Philosophy: Geissler Tubes Mike's Electric Stuff: Geissler Tubes The Cathode Ray Tube site Geissler and Crookes tubes shown working How to Make an Experimental Geissler Tube, Popular Science monthly, February 1919, Unnumbered page, Scanned by Google Books
Fluorescent lamp
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps; the typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Fluorescent lamp fixtures are more costly than incandescent lamps because they require a ballast to regulate the current through the lamp, but the lower energy cost offsets the higher initial cost. Compact fluorescent lamps are now available in the same popular sizes as incandescents and are used as an energy-saving alternative in homes; because they contain mercury, many fluorescent lamps are classified as hazardous waste.
The United States Environmental Protection Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal, some jurisdictions require recycling of them. Fluorescence of certain rocks and other substances had been observed for hundreds of years before its nature was understood. By the middle of the 19th century, experimenters had observed a radiant glow emanating from evacuated glass vessels through which an electric current passed. One of the first to explain it was the Irish scientist Sir George Stokes from the University of Cambridge in 1852, who named the phenomenon "fluorescence" after fluorite, a mineral many of whose samples glow because of impurities; the explanation relied on the nature of electricity and light phenomena as developed by the British scientists Michael Faraday in the 1840s and James Clerk Maxwell in the 1860s. Little more was done with this phenomenon until 1856 when German glassblower Heinrich Geissler created a mercury vacuum pump that evacuated a glass tube to an extent not possible.
Geissler invented the first gas-discharge lamp, the Geissler tube, consisting of a evacuated glass tube with a metal electrode at either end. When a high voltage was applied between the electrodes, the inside of the tube lit up with a glow discharge. By putting different chemicals inside, the tubes could be made to produce a variety of colors, elaborate Geissler tubes were sold for entertainment. More important, was its contribution to scientific research. One of the first scientists to experiment with a Geissler tube was Julius Plücker who systematically described in 1858 the luminescent effects that occurred in a Geissler tube, he made the important observation that the glow in the tube shifted position when in proximity to an electromagnetic field. Alexandre Edmond Becquerel observed in 1859 that certain substances gave off light when they were placed in a Geissler tube, he went on to apply thin coatings of luminescent materials to the surfaces of these tubes. Fluorescence occurred, but the tubes were inefficient and had a short operating life.
Inquiries that began with the Geissler tube continued as better vacuums were produced. The most famous was the evacuated tube used for scientific research by William Crookes; that tube was evacuated by the effective mercury vacuum pump created by Hermann Sprengel. Research conducted by Crookes and others led to the discovery of the electron in 1897 by J. J. Thomson and X-rays in 1895 by Wilhelm Roentgen, but the Crookes tube, as it came to be known, produced little light because the vacuum in it was too good and thus lacked the trace amounts of gas that are needed for electrically stimulated luminescence. While Becquerel was interested in conducting scientific research into fluorescence, Thomas Edison pursued fluorescent lighting for its commercial potential, he invented a fluorescent lamp in 1896 that used a coating of calcium tungstate as the fluorescing substance, excited by X-rays, but although it received a patent in 1907, it was not put into production. As with a few other attempts to use Geissler tubes for illumination, it had a short operating life, given the success of the incandescent light, Edison had little reason to pursue an alternative means of electrical illumination.
Nikola Tesla made similar experiments in the 1890s, devising high-frequency powered fluorescent bulbs that gave a bright greenish light, but as with Edison's devices, no commercial success was achieved. Although Edison had lost interest in fluorescent lighting, one of his former employees was able to create a gas-based lamp that achieved a measure of commercial success. In 1895 Daniel McFarlan Moore demonstrated lamps 2 to 3 meters in length that used carbon dioxide or nitrogen to emit white or pink light, respectively; as with future fluorescent lamps, they were more complicated than an incandescent bulb. After years of work, Moore was able to extend the operating life of the lamps by inventing an electromagnetically controlled valve that maintained a constant gas pressure within the tube. Although Moore’s lamp was complicated, was expensive to install, required high voltages, it was more efficient than incandescent lamps, it produced a closer approximation to natural daylight than contemporary incandescent lamps.
From 1904 onwards Moore's lighting system was installed in a number of offices. Its success contributed to General Electric’s motivation to improve the incandescent lamp its filament. GE’s efforts came to fruition with the invention of a tungsten-based filament; the extended lifespan and improved efficacy of incandescent bulbs negated one of the key advantages of Moore’s lamp, but GE purchased the relevant patents
Great Barrington, Massachusetts
Great Barrington is a town in Berkshire County, United States. It is part of Massachusetts Metropolitan Statistical Area; the population was 7,104 at the 2010 census. Both a summer resort and home to Ski Butternut, Great Barrington includes the villages of Van Deusenville and Housatonic, it is the birthplace of W. E. B. Du Bois. In 2012, Smithsonian magazine ranked Great Barrington #1 in its list of "The 20 Best Small Towns in America"; the Mahican Indians called the area Mahaiwe, meaning "the place downstream". It lay on the New England Path, which connected Fort Orange near Albany, New York, with Springfield and Massachusetts Bay; the first recorded account of Europeans in the area happened in August 1676, during King Philip's War. Major John Talcott and his troops chased a group of 200 Mahican Natives west from Westfield overtaking them at the Housatonic River in what now Great Barrington. According to reports at the time, Talcott's troops killed twenty-five Indians and imprisoned another twenty.
Today, a plaque for John Talcott marks the spot. On April 25, 1724 Captain John Ashley of Westfield, Massachusetts bought on behalf of himself and a committee of the Massachusetts General Court the land that became the towns of Great Barrington, Egremont, Mount Washington, Boston Corner for £460, three barrels of "sider," and thirty quarts of rum from 21 Native American sachems headed by Conkepot Poneyote; the Konkapot River in southwestern Massachusetts is named after him. The village was first settled by colonists in 1726 and from 1742–1761 was the north parish of Sheffield. In 1761, it was incorporated as Great Barrington, named after the village of Barrington, England. In the summer of 1774, 1,500 men shut down the Berkshire County Court in response to British oppression. In the winter of 1776, Henry Knox passed through Great Barrington while transporting the cannon from Fort Ticonderoga to the Siege of Boston. Due to his time in the area, he established an agricultural interest in the area of Great Barrington.
With the arrival of the railroad in the late 19th century, Great Barrington developed as a Gilded Age resort community for those seeking relief from the heat and pollution of cities. Wealthy families built grand homes called Berkshire Cottages here, as others would in Lenox and Stockbridge. Among the earliest estates was that built by New York City banker and art patron David Leavitt, who built an elaborate 300-acre estate, was soon followed by those of his sons nearby. Leavitt was instrumental in the development of the local Housatonic Railroad, serving as its president. Estates included Searles Castle, commissioned in 1888 by the widow of Mark Hopkins together with her second husband, Edward Francis Searles, "Brookside", built for William Hall Walker. In 1895, Colonel William L. Brown, part owner of the New York Daily News, presented Great Barrington with a statue of a newsboy, now a landmark on the western edge of town. Great Barrington is the birthplace of W. E. B. Du Bois, an African-American academic and civil rights activist, most known for being one of the co-founders of the National Association for the Advancement of Colored People in 1909.
Du Bois was born on February 23, 1868, at a house replaced by where present-day Route 23 would run. As a child, Du Bois attended the Congregational Church. Many of these church members donated. Du Bois lived in the town; the W. E. B. Du Bois Boyhood Homesite has a walking tour. In November 1885 electrical engineer William Stanley, Jr. a sometime Great Barrington resident working for George Westinghouse, began installing a demonstration transformer based alternating current lighting system. Stanley felt AC was an improvement over the direct current system being used by Thomas Edison, Stanley was trying to get Westinghouse to adopt it. Stanley had developed a series transformer, he built his components at the "Old Rubber Factory" south of Cottage Street and installed a Westinghouse steam engine powering a 500 volt Siemens generator. Stringing the power lines from tree to tree down the street, in March 1886 Stanley powered the system up and was able to expand it to the point where it could light 23 businesses along Main Street with little power loss over 4,000 ft.
The system's 500 AC volt current was stepped down to 100 volts using the new Stanley transformer to power incandescent lamps at each location. This was the world's first practical demonstration of a transformer/alternating current system and the basis of the AC systems that Westinghouse would begin installing that year. Arlo Guthrie's song "Alice's Restaurant," which runs for 18 1⁄2 minutes, is based on true-life events of the late 20th century in Great Barrington and the adjoining towns of Stockbridge and Lee; the Old Trinity Church, the home of Ray and Alice Brock at the time of these incidents, is now owned by Guthrie, is at 4 Van Deusenville Road in Great Barrington. On October 18, 1990, Richard Stanley purchased the old Miller Hotel known as the Barrington House. Stanley started to upgrade the building, evicting tenants, involved in drugs, he removed the 1960s aluminum facade and returned the historic building through renovation to its 1929 appearance. The town was the site of an F4 tornado around 7:00 PM on Memorial Day, May 29, 1995.
The tornado caused damage in the area. On November 15, 1995, Richard Stanley and Joseph Wasserman opened The Triplex Cinema in the heart of Great Barrington; this contributed to further developments in the town, changing the economy and enhanc
Mercury-vapor lamp
A mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb; the outer bulb may be clear or coated with a phosphor. Mercury vapor lamps are more energy efficient than incandescent and most fluorescent lights, with luminous efficacies of 35 to 65 lumens/watt, their other advantages are a long bulb lifetime in the range of 24,000 hours and a high intensity, clear white light output. For these reasons, they are used for large area overhead lighting, such as in factories and sports arenas as well as for streetlights. Clear mercury lamps produce white light with a bluish-green tint due to mercury's combination of spectral lines; this is not flattering to human skin color, so such lamps are not used in retail stores. "Color corrected" mercury bulbs overcome this problem with a phosphor on the inside of the outer bulb that emits white light, offering better color rendition.
They operate at an internal pressure of around one atmosphere and require special fixtures, as well as an electrical ballast. They require a warm-up period of 4 – 7 minutes to reach full light output. Mercury vapor lamps are becoming obsolete due to the higher efficiency and better color balance of metal halide lamps. Charles Wheatstone observed the spectrum of an electric discharge in mercury vapor in 1835, noted the ultraviolet lines in that spectrum. In 1860, John Thomas Way used arc lamps operated in a mixture of air and mercury vapor at atmospheric pressure for lighting; the German physicist Leo Arons studied mercury discharges in 1892 and developed a lamp based on a mercury arc. In February 1896 Herbert John Dowsing and H. S. Keating of England patented a mercury vapour lamp, considered by some to be the first true mercury vapour lamp; the first mercury vapor lamp to achieve widespread success was invented in 1901 by American engineer Peter Cooper Hewitt. Hewitt was issued U. S. Patent 682,692 on September 17, 1901.
In 1903, Hewitt created an improved version that possessed higher color qualities which found widespread industrial use. The ultraviolet light from mercury vapor lamps was applied to water treatment by 1910; the Hewitt lamps used a large amount of mercury. In the 1930s, improved lamps of the modern form, developed by the Osram-GEC company, General Electric company and others led to widespread use of mercury vapor lamps for general lighting; the mercury in the tube is a liquid at normal temperatures. It needs to be ionized before the lamp can produce its full light output. To facilitate starting of the lamp, a third electrode is mounted near one of the main electrodes and connected through a resistor to the other main electrode. In addition to the mercury, the tube is filled with argon gas at low pressure; when power is applied, there is sufficient voltage to ionize the argon and strike a small arc between the starting electrode and the adjacent main electrode. When ions and free electrons have been introduced into the arc tube, an arc initiates between the two main electrodes.
The heat from this arc vaporizes the liquid mercury inside the lamp which radiates green, yellow and ultraviolet emission lines when ionized. Continued vaporization of the liquid mercury increases the arc tube pressure to between 2 and 18 bar, depending on lamp size; the increase in pressure results in further brightening of the lamp. The entire warm-up process takes 4 to 7 minutes; some bulbs include a thermal switch which shorts the starting electrode to the adjacent main electrode, extinguishing the starting arc once the main arc strikes. The mercury vapor lamp is a negative resistance device; this means its resistance decreases as the current through the tube increases. So if the lamp is connected directly to a constant-voltage source like the power lines, the current through it will increase until it destroys itself. Therefore, it requires a ballast to limit the current through it. Mercury vapor lamp ballasts are similar to the ballasts used with fluorescent lamps. In fact, the first British fluorescent lamps were designed to operate from 80-watt mercury vapor ballasts.
There are self-ballasted mercury vapor lamps available. These lamps use a tungsten filament in series with the arc tube both to act as a resistive ballast and add full spectrum light to that of the arc tube. Self-ballasted mercury vapor lamps can be screwed into a standard incandescent light socket supplied with the proper voltage. A closely related lamp design called the metal halide lamp uses various compounds in an amalgam with the mercury. Sodium iodide and scandium iodide are in use; these lamps can produce much better quality light without resorting to phosphors. If they use a starting electrode, there is always a thermal shorting switch to eliminate any electrical potential between the main electrode and the starting electrode once the lamp is lit.. More modern metal halide systems do not use a separate starting electrode. Self-ballasted lamps are mercury vapor lamps with a filament inside connected in series with the arc tube that functions as an electrical ballast; this is the only kind of mercury vapor lamp that can be connected directly to the mains without an external ballast.
These lamps have only the same or higher efficiency than incandescent lamps of similar size
William Murdoch
William Murdoch was a Scottish engineer and inventor. Murdoch was employed by the firm of Boulton & Watt and worked for them in Cornwall, as a steam engine erector for ten years, spending most of the rest of his life in Birmingham, England. Murdoch was the inventor of the oscillating cylinder steam engine, gas lighting is attributed to him in the early 1790s the term "gasometer". However, Archibald Cochrane, ninth Earl of Dundonald, had in 1789 used gas for lighting his family estate. Murdoch made innovations to the steam engine, including the sun and planet gear and D slide valve, he invented the steam gun and the pneumatic tube message system, worked on one of the first British paddle steamers to cross the English Channel. Murdoch made a number of discoveries in chemistry. Murdoch remained an employee and a partner of Boulton & Watt until the 1830s, his reputation as an inventor has been obscured by the reputations of Matthew Boulton and James Watt and the firm they founded. William Murdoch was born in Lugar near Cumnock, Scotland, the third of seven children and the first son to survive beyond infancy.
A son of John Murdoch, a former Hanoverian artillery gunner and a Millwright and tenant of Bello Mill on the estate of James Boswell in Auchinleck, he was educated until the age of ten at the Old Cumnock Kirk School before attending Auchinleck school under William Halbert, author of a regarded arithmetic textbook. Murdoch excelled in mathematics. Murdoch learned the principles of mechanics, practical experimentation and working in metal and wood by assisting in his father's work. Together with his father, he built a "wooden horse" about 1763, his "Wooden Horse on Wheels" was a tricycle propelled by hand cranks. There are reports that in his youth Murdoch was responsible for the construction of one of the bridges over the River Nith, he is said to have carried out experiments in coal gas, using coal heated in a copper kettle in a small cave near his father's mill. However, there is no contemporary documentation. In 1777, at age 23, Murdoch walked to Birmingham, a distance of over 300 miles, to ask for a job with James Watt, the steam engine manufacturer.
Both Watt and Murdoch were aware of each other because of their connections with James Boswell, who had made several visits to Watt's workshop at Soho. Watt's partner Matthew Boulton was so impressed by Murdoch's wooden hat, made on a lathe of his own design, that he hired him. Murdoch began his career with Boulton and Watt in the pattern workshop of their Soho Foundry, making patterns for the casting of machine parts. By 1778 Watt wrote: if William Murdoch is not at home he should be sent for as he understands the patterns and care must be taken to avoid mistakes of which our engine shop has been too guilty, he Anglicised his name to "Murdock". Murdoch progressed to work in fitting and erecting steam engines and was sent from Soho for this purpose. By 1779 Boulton was writing to Watt: I think Wm. Murdock a valuable man and deserves every civility and encouragement. On his first solo job erecting an engine at Wanlockhead Mine, Murdoch made the first of many improvements to the standard Boulton and Watt engine by rearranging the gears to enable the steam valve to be worked automatically by the action of the exhaust shaft.
In September 1779 Murdoch was sent to Redruth in Cornwall as a senior engine erector, responsible for the erection, maintenance & repair of Boulton & Watt engines. These were used for pumping water out of the Cornish Tin mines, therefore the efficiency and efficacy of the engines was an important factor in the amount of tin, money, which could be extracted from a mine. At that time steam engines were not sold to customers but operated, maintained by the builders for groups or individuals known as'adventurers'; the engine manufacturers were paid not for a completed engine but through a complex formula calculated on the basis of that engine's performance, as Watt described: Our profits arise not from making the engine, but from a certain proportion of the savings in fuel which we make over any common engine, that raises the same quantity of water to the same height. Therefore, Murdoch's skill in getting the most out of his engines directly impacted upon Boulton and Watts profits; this he did so that by 1782 Boulton was writing: We want more Murdocks, for of all others he is the most active man and best engine erector I saw...
When I look at the work done it astonishes me & is owing to the spirit and activity of Murdoch who hath not gone to bed 3 of the nights. Due to the frequent problems which could occur with steam engines Murdoch was kept busy travelling around the area repairing and attempting to improve the performance of the engines under his care. In Cornwall at that time there were a number of engine erectors competing with each other, each with different technical methods of achieving the same ends; as a result, a great deal of copying of mechanical innovations and violation of patents went on through the reporting of casual conversations between engineers and practical observations of engine modifications. The risk of his patents being infringed was something which exercised Watt, so Murdoch was, in addition to his other activities, called upon to make reports and swear out affidavits for legal actions against Boulton & Watt's competitors. In the close knit and clannish Cornwall of the time this was sometimes at his own risk.
As one of his colleagues s
