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1720 In Science
The year 1720 in science and technology involved some significant events. Astronomy * February 10 – Edmond Halley is appointed as Astronomer Royal of England. Medicine * May – First patient admitted to the Westminster Public Infirmary, predecessor of St George's Hospital, London. * Dr Steevens' Hospital is established at Kilmainham, Dublin. * Great Plague of Marseille, the last major outbreak of bubonic plague in Europe. * English physician Richard Mead publishes ''A Short Discourse concerning Pestilential Contagion, and the Method to be used to prevent it''. Physics * Willem 's Gravesande publishes ''Physices elementa mathematica, experimentis confirmata, sive introductio ad philosophiam Newtonianam'', an introduction to Newtonian physics, in Leiden. Technology * A theodolite is developed by Jonathan Sisson of England. * Pinchbeck is invented by English watchmaker Christopher Pinchbeck; it is an alloy of 83% copper and 17% zinc, creating a strong, hard-wearing metal w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinchbeck (alloy)
Pinchbeck is a form of brass, an alloy of copper and zinc mixed in proportions so that it closely resembles gold in appearance. It was invented in the early 18th century by Christopher Pinchbeck (died 1732), a London clock-and watch-maker. Since gold was only sold in 18-carat quality at that time, the development of pinchbeck allowed ordinary people to buy gold 'effect' jewellery on a budget. The inventor allegedly made pinchbeck jewellery clearly labelled as such. Pinchbeck jewellery was used in places like stagecoaches where there was a risk of theft. The original Pinchbeck was made by Christopher Pinchbeck and his descendants until the 1830s. Later dishonest jewellers passed pinchbeck off as gold; over the years the name came to mean a cheap and tawdry imitation of gold. Today, depending on the dealer, "Pinchbeck" can mean original Pinchbeck or any gilt metal. Pinchbeck fell out of use in the second half of the 19th century, being replaced by low-carat gold which had been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differential Gear
A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analogue computers. Differentials can also provide a gear ratio between the input and output shafts (called the "axle ratio" or "diff ratio"). For example, many differentials in motor vehicles provide a gearing reduction by having fewer teeth on the pinion than the ring gear. History Milestones in the design or use of differentials include: * 100 BCE–70 BCE: The Antikythera mechanism has been dated to this period. It was discovered in 1902 on a shipwreck by sponge divers, and modern research suggests that it used a differential gear to determine the angle between the ecliptic positions of the Sun and Moon, and thus the phase of the Moon. * : ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bavaria
Bavaria, officially the Free State of Bavaria, is a States of Germany, state in the southeast of Germany. With an area of , it is the list of German states by area, largest German state by land area, comprising approximately 1/5 of the total land area of Germany, and with over 13.08 million inhabitants, it is the list of German states by population, second most populous German state, behind only North Rhine-Westphalia; however, due to its large land area, its population density is list of German states by population density, below the German average. Major cities include Munich (its capital and List of cities in Bavaria by population, largest city, which is also the list of cities in Germany by population, third largest city in Germany), Nuremberg, and Augsburg. The history of Bavaria includes its earliest settlement by Iron Age Celts, Celtic tribes, followed by the conquests of the Roman Empire in the 1st century BC, when the territory was incorporated into the provinces of Ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jacob Hochbrucker
Jacob Hochbrucker (also spelled ''Jakob Hochprugger''; 1673 – 28 May 1763) was an eighteenth-century harp maker and musician credited with the invention of the single-action pedal harp popularized in Europe between 1729 and 1750 by his descendants, and particularly by the Dauphine, Marie Antoinette, who performed on it after her arrival in Paris in 1770. Life and work Hochbrucker was probably born in Mindelheim. From 1699 he lived and worked in Donauwörth, where he also built lutes and violas. Around 1720 Hochbrucker invented the pedal mechanism to play the harp, adding to the instrument five (later increased to seven) pedals and connecting them to the hooks for the C, D, F, G, and B strings, thus allowing the player to alter the strings sound of a semitone and greatly extend the range of the instrument for the extraction of sounds. This ingenious chromatic system later became the subject matter of studies and extended considerations. In the second half of the 18th century, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pedal Harp
The pedal harp (also known as the concert harp) is a large and technologically modern harp, designed primarily for use in art music. It may be played solo, as part of a chamber ensemble, or in an orchestra. It typically has 47 strings with seven strings per octave, giving a range of six and a half octaves. In this type of harp the pedals alter the pitch of the strings, so that the pedal harp can easily play works written in any key (music), key. This is particularly important in the harmonically complex music of the Romantic (music), Romantic period and later 20th-century classical music. Parts Body and strings A pedal harp typically stands about high, is deep, and wide at the bass end of the soundboard. It weighs about . The body of the harp consists of a straight upright pillar, sometimes adorned with a crown at the top; a soundboard, which in most harps is pear-shaped with additional width at the bottom, although some older instruments have soundboards that are straig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Velocity
Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical quantity, quantity, meaning that both magnitude and direction are needed to define it. The Scalar (physics), scalar absolute value (Magnitude (mathematics), magnitude) of velocity is called , being a coherent derived unit whose quantity is measured in the International System of Units, SI (metric system) as metres per second (m/s or m⋅s−1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector. If there is a change in speed, direction or both, then the object is said to be undergoing an ''acceleration''. Definition Average velocity The average velocity of an object over a period of time is its Displacement (geometry), change in position, \Delta s, divided by the duration of the period, \Delt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Islands
The Channel Islands are an archipelago in the English Channel, off the French coast of Normandy. They are divided into two Crown Dependencies: the Jersey, Bailiwick of Jersey, which is the largest of the islands; and the Bailiwick of Guernsey, consisting of Guernsey, Alderney, Sark, Herm and some smaller islands. Historically, they are the remnants of the Duchy of Normandy. Although they are not part of the United Kingdom, the UK is responsible for the defence and international relations of the islands as it is for the other Crown Dependency, the Isle of Man, and the British Overseas Territories. The Crown Dependencies are neither members of the Commonwealth of Nations, nor part of the European Union. They have a total population of about , and the bailiwicks' Capital city, capitals, Saint Helier and Saint Peter Port, have populations of 33,500 and 18,207 respectively. "Channel Islands" is a geographical term, not a political unit. The two bailiwicks have been administered sepa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chronograph
A chronograph is a specific type of watch that is used as a stopwatch combined with a display watch. A basic chronograph has hour and minute hands on the main dial to tell the time, a small seconds hand to tell that the watch is running, and a seconds hand on the main dial usually equipped with a sweeping movement for precision accompanied by a minutes sub dial for the stopwatch. Another sub dial to measure the hours of the stopwatch may also be included on a chronograph. The stopwatch can be started, stopped, and reset to zero at any time by the user by operating pushers usually placed adjacent to the crown. More complex chronographs often use additional complications and can have multiple sub-dials to measure more aspects of the stopwatch such as fractions of a second as well as other helpful things such as the moon phase and the local 24-hour time. In addition, many modern chronographs include tachymeters on the bezels for rapid calculations of speed or distance. Louis M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal, a group 11 element, and one of the noble metals. It is one of the least reactivity (chemistry), reactive chemical elements, being the second-lowest in the reactivity series. It is solid under standard temperature and pressure, standard conditions. Gold often occurs in free elemental (native state (metallurgy), native state), as gold nugget, nuggets or grains, in rock (geology), rocks, vein (geology), veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as in electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold is resistant to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carat (purity)
The fineness of a precious metal object (coin, bar, jewelry, etc.) represents the weight of ''fine metal'' therein, in proportion to the total weight which includes alloying base metals and any impurities. Alloy metals are added to increase hardness and durability of coins and jewelry, alter colors, decrease the cost per weight, or avoid the cost of high-purity refinement. For example, copper is added to the precious metal silver to make a more durable alloy for use in coins, housewares and jewelry. Coin silver, which was used for making silver coins in the past, contains 90% silver and 10% copper, by mass. Sterling silver contains 92.5% silver and 7.5% of other metals, usually copper, by mass. Various ways of expressing fineness have been used and two remain in common use: ''millesimal fineness'' expressed in units of parts per 1,000 and '' karats'' or ''carats'' used only for gold. Karats measure the parts per 24, so that 18 karat = = 75% gold and 24 karat gold is considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zinc
Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity ( electrowinning). Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for prenatal and postnatal development. It is the second most abundant trace metal in humans after iron, an import ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
