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83-411: An atmospheric railway uses differential air pressure to provide power for propulsion of a railway vehicle. A static power source can transmit motive power to the vehicle in this way, avoiding the necessity of carrying mobile power generating equipment. The air pressure, or partial vacuum (i.e., negative relative pressure) can be conveyed to the vehicle in a continuous pipe, where the vehicle carries

166-509: A 1985 article in The New York Times , tallow was also used for frying at Burger King , Wendy's , Hardee's , Arby's , Dairy Queen , Popeyes , and Bob's Big Boy . Tallow is, however, making a comeback in certain nutrition circles. Greaves (also graves ) or cracklings is the fibrous matter remaining from rendering, typically pressed into cakes and used for animal feed , especially for dogs and hogs, or as fish bait . In

249-474: A U.S. Air Force C-17 Globemaster III flew using JP-8 conventional jet fuel in three of its engines and a 50/50 blend of JP-8 and HRJ biofuel made from beef tallow in one engine on August 23, followed by a flight with the same 50/50 blend in all four engines on August 24. On August 27, it flew using a blend of 50% JP-8, 25% HRJ, and 25% coal -based fuel made through the Fischer–Tropsch process , becoming

332-416: A composition of beeswax and tallow : this composition is solid at the temperature of the atmosphere, and becomes fluid when heated a few degrees above it. Over this valve is a protecting cover, which serves to preserve it from snow or rain, formed of thin plates of iron about five feet long hinged with leather, and the end of each plate underlaps the next in the direction of the piston's motion, thus ensuring

415-415: A diameter of 63 cm (25 in) with a slot at the top. The slot was closed by two leather flaps. The pumps were powered by two steam engines with a capacity of 200 hp, located between the two tunnels at Saint-Germain. Train speed on the ascent was 35 km/h (22 mph). On the descent the train ran by gravity as far as Pecq, where the steam locomotive took over for the run to Paris. The system

498-415: A diurnal or semidiurnal (twice-daily) cycle caused by global atmospheric tides . This effect is strongest in tropical zones, with an amplitude of a few hectopascals, and almost zero in polar areas. These variations have two superimposed cycles, a circadian (24 h) cycle, and a semi-circadian (12 h) cycle. The highest adjusted-to-sea level barometric pressure ever recorded on Earth (above 750 meters)

581-509: A few years. A modern proprietary system has been developed and is in use for short-distance applications. Porto Alegre Metro airport connection in Porto Alegre , Brazil, is one of them. In the early days of railways, single vehicles or groups were propelled by men or horses. As mechanical power came to be understood, locomotive engines were developed; the iron horse . These had serious limitations; in particular, being much heavier than

664-481: A full-scale model at Southwark. In 1840, Jacob Samuda and Clegg leased half a mile of railway line on the West London Railway at Wormholt Scrubs (later renamed Wormwood Scrubs ), where the railway had not yet been opened to the public. In that year Clegg left for Portugal, where he was pursuing his career in the gas industry. Samuda's system involved a continuous (jointed) cast iron pipe laid between

747-518: A junction with the London and Greenwich Railway (L&GR) to Croydon. At that time the L&;GR line was under construction, and Parliament resisted the building of two railway termini in the same quarter of London, so that the L&CR would have to share the L&GR's London Bridge station. The line was built for ordinary locomotive operation. A third company, the London and Brighton Railway (L&BR)

830-550: A line to a terminal at Bricklayers Arms. Arrangements were also made with the L&GR for them to add an extra track on the common section of their route. On 1 May 1844, the Bricklayers Arms terminus opened, and a frequent service was run from it, additional to the London Bridge trains. The L&CR line diverged to the south-west at Norwood Junction (then called Jolly Sailor , after an inn), and needed to cross

913-410: A location on Earth 's surface ( terrain and oceans ). It is directly proportional to the mass of air over that location. For numerical reasons, atmospheric models such as general circulation models (GCMs) usually predict the nondimensional logarithm of surface pressure . The average value of surface pressure on Earth is 985 hPa. This is in contrast to mean sea-level pressure, which involves

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996-487: A patent for their system. Soon after this, Joseph Samuda died and it was left to his brother Jacob to continue the work. The patent was in three parts: the first describing the atmospheric pipe and piston system, the second describing how in areas of plentiful water supply, the vacuum might be created by using tanks of water at differing levels; and the third section dealt with level crossings of an atmospheric railway. The Dublin and Kingstown Railway opened in 1834 connecting

1079-446: A piston running in the tube. Some form of re-sealable slot is required to enable the piston to be attached to the vehicle. Alternatively the entire vehicle may act as the piston in a large tube or be coupled electromagnetically to the piston. Several variants of the principle were proposed in the early 19th century, and a number of practical forms were implemented, but all were overcome by unforeseen disadvantages and discontinued within

1162-427: A pressure of about 2 atmospheres (1 atm of air plus 1 atm of water). Conversely, 10.3 m is the maximum height to which water can be raised using suction under standard atmospheric conditions. Low pressures, such as natural gas lines, are sometimes specified in inches of water , typically written as w.c. (water column) gauge or w.g. (inches water) gauge. A typical gas-using residential appliance in

1245-432: A separate piston. He never patented his ideas and they were not taken further by him. In 1824, a man called Vallance took out a patent and built a short demonstration line; his system consisted of a 6-foot (1.8 m) diameter cast iron tube with rails cast in to the lower part; the vehicle was the full size of the tube and bear skin was used to seal the annular space. Braking was accomplished by opening doors at each end of

1328-424: A standard lapse rate) associated with reduction of sea level from high elevations. The Dead Sea , the lowest place on Earth at 430 metres (1,410 ft) below sea level, has a correspondingly high typical atmospheric pressure of 1,065   hPa. A below-sea-level surface pressure record of 1,081.8 hPa (31.95 inHg) was set on 21 February 1961. The lowest non-tornadic atmospheric pressure ever measured

1411-504: A strip of burning cloth in a saucer of tallow grease—was an accessible substitute. Such a candle was often simply called a "dip" or, because of its low cost, a "farthing dip" or "penny dip". Early in the development of steam-driven piston engines, the hot vapors and liquids washed away most lubricants very quickly. It was soon found that tallow was quite resistant to this washing. Tallow and compounds including tallow were widely used to lubricate locomotive and steamship engines at least until

1494-414: A variable mixture of sodium salts of fatty acids , such as oleic and palmitic . Tallow is 100% fat , mainly of monounsaturated fats (52%) and saturated fats (42%), and contains no water, protein or carbohydrates (table). The fatty acid content of tallow is: Tallow is used mainly in producing soap and animal feed. A significant use of tallow is for the production of shortening . It

1577-443: Is a rendered form of beef or mutton suet , primarily made up of triglycerides . In industry, tallow is not strictly defined as beef or mutton suet. In this context, tallow is animal fat that conforms to certain technical criteria, including its melting point . Commercial tallow commonly contains fat derived from other animals, such as lard from pigs , or even from plant sources. The solid material remaining after rendering

1660-408: Is adapted two large cylinders, which exhaust fourteen cubic feet of air per second. The pressure in the air cauldron (claudieres) attached to the exhausting machines is equal to six absolute atmospheres. He described the valve: Throughout the entire length of the tube, a section is made in the top, leaving an open space of about five inches. In each cut edge of the section there is an offset, to catch

1743-483: Is also one of the main ingredients of the Native American food pemmican . With a smoke point of 480 °F (249 °C), tallow is traditionally used in deep frying and was preferred for this use until the rise in popularity of plant oils for frying. Before switching to pure vegetable oil in 1990, McDonald's cooked its French fries in a mixture of 93% beef tallow and 7% cottonseed oil . According to

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1826-484: Is as a lubricant for certain types of light engineering work, such as cutting threads on electrical conduit. Specialist cutting compounds are available, but tallow is a traditional lubricant that is easily available for cheap and infrequent use. The use of tallow or lard to lubricate rifles was the spark that started the Indian Mutiny of 1857 . To load the new Pattern 1853 Enfield Rifle , the sepoys had to bite

1909-414: Is called cracklings , greaves, or graves. It has been used mostly for animal food , such as dog food . In the soap industry and among soap-making hobbyists , the name tallowate is used informally to refer to soaps made from tallow. Sodium tallowate , for example, is obtained by reacting tallow with sodium hydroxide (lye, caustic soda) or sodium carbonate (washing soda). It consists chiefly of

1992-458: Is caused by the gravitational attraction of the planet on the atmospheric gases above the surface and is a function of the mass of the planet, the radius of the surface, and the amount and composition of the gases and their vertical distribution in the atmosphere. It is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition. The mean sea-level pressure (MSLP)

2075-511: Is instead reported in kilopascals. In the US weather code remarks, three digits are all that are transmitted; decimal points and the one or two most significant digits are omitted: 1,013.2 hPa (14.695 psi) is transmitted as 132; 1,000 hPa (100 kPa) is transmitted as 000; 998.7   hPa is transmitted as 987; etc. The highest sea-level pressure on Earth occurs in Siberia , where

2158-473: Is laid down in the centre of the track, which is sunk about one-third of its diameter in the bed of the road. For a distance of 5,500 yards the tube has a diameter of only 1¾ feet [i.e. 21 inches], the ascent here being so slight as not to require the same amount of force as is required on the steep grade to Saint Germain, where the pipe, for a distance of 3,800 yards, is 2 feet 1 inch [i.e. 25 inches] in diameter. The steam engines had accumulators: To each engine

2241-552: Is put together with deep socket joints, in each of which an annular space is left about the middle of the packing, and filled with a semi-fluid: thus any possible leakage of air into the pipe is prevented. At that time railways were developing rapidly, and solutions to the technical limitations of the day were eagerly sought, and not always rationally evaluated. Samuda's treatise put forward the advantages of his system: Samuda also rebutted criticisms of his system that had become widespread: In April 1844, Jacob and Joseph Samuda took out

2324-423: Is still used as a patch or projectile lubricant in present-day black powder arms. Tallow is used to make a biodegradable motor oil. Tallow is also used in traditional bell foundry , as a separation for the false bell when casting . Tallow can be used as flux for soldering . Mutton tallow is widely used as starch, lubricant and softener in textile manufacturing. Pretreatment processes in textiles include

2407-465: Is the atmospheric pressure at mean sea level . This is the atmospheric pressure normally given in weather reports on radio, television, and newspapers or on the Internet . The altimeter setting in aviation is an atmospheric pressure adjustment. Average sea-level pressure is 1,013.25 hPa (29.921 inHg; 760.00 mmHg). In aviation weather reports ( METAR ), QNH is transmitted around

2490-517: The Compagnie du Chemin de fer de Paris à Saint-Germain . They opened their 19 km line in 1837, but only as far as Le Pecq , a river quay on the left bank of the Seine, as a daunting incline would have been necessary to reach Saint-Germain-en-Laye , and locomotives of the day were considered incapable of climbing the necessary gradient, adhesion being considered the limiting factor. On hearing of

2573-494: The Dalkey Atmospheric Railway . A 15-inch traction pipe was used, with a single pumping station at Dalkey, at the upper end of the 2,400-yard run. The engine created 110 ihp and had a flywheel of 36 feet diameter. Five minutes before the scheduled departure of a train from Kingstown, the pumping engine started work, creating a 15-inch vacuum in two minutes. The train was pushed manually to the position where

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2656-472: The Siberian High often attains a sea-level pressure above 1,050 hPa (15.2 psi; 31 inHg), with record highs close to 1,085 hPa (15.74 psi; 32.0 inHg). The lowest measurable sea-level pressure is found at the centres of tropical cyclones and tornadoes , with a record low of 870 hPa (12.6 psi; 26 inHg). Surface pressure is the atmospheric pressure at

2739-1339: The troposphere , the following equation (the barometric formula ) relates atmospheric pressure p to altitude h : p = p 0 ⋅ ( 1 − L ⋅ h T 0 ) g ⋅ M R 0 ⋅ L = p 0 ⋅ ( 1 − g ⋅ h c p ⋅ T 0 ) c p ⋅ M R 0 ≈ p 0 ⋅ exp ⁡ ( − g ⋅ h ⋅ M T 0 ⋅ R 0 ) {\displaystyle {\begin{aligned}p&=p_{0}\cdot \left(1-{\frac {L\cdot h}{T_{0}}}\right)^{\frac {g\cdot M}{R_{0}\cdot L}}\\&=p_{0}\cdot \left(1-{\frac {g\cdot h}{c_{\text{p}}\cdot T_{0}}}\right)^{\frac {c_{\text{p}}\cdot M}{R_{0}}}\approx p_{0}\cdot \exp \left(-{\frac {g\cdot h\cdot M}{T_{0}\cdot R_{0}}}\right)\end{aligned}}} The values in these equations are: Atmospheric pressure varies widely on Earth, and these changes are important in studying weather and climate . Atmospheric pressure shows

2822-416: The vapour pressure is equal to the atmospheric pressure around the liquid. Because of this, the boiling point of liquids is lower at lower pressure and higher at higher pressure. Cooking at high elevations, therefore, requires adjustments to recipes or pressure cooking . A rough approximation of elevation can be obtained by measuring the temperature at which water boils; in the mid-19th century, this method

2905-514: The 1950s. (During World War II, the vast fleets of steam-powered ships exhausted the supply, leading to the large-scale planting of rapeseed because rapeseed oil also resisted the washing effect.) Tallow is still used in the steel rolling industry to provide the required lubrication as the sheet steel is compressed through the steel rollers . There is a trend toward replacing tallow-based lubrication with synthetic oils in rolling applications for surface cleanliness reasons. Another industrial use

2988-415: The L&BR line. The atmospheric pipe made this impossible on the flat, and a flyover was constructed to enable the crossing: this was the first example in the railway world. This was in the form of a wooden viaduct with approach gradients of 1 in 50. A similar flyover was to be built at Corbetts Lane Junction, where the L&CR additional line was to be on the north-east side of the existing line, but this

3071-455: The Pereire brothers to adopt the system for an extension to Saint Germain itself, and construction started in 1845, with a wooden bridge crossing the Seine followed by a twenty-arch masonry viaduct and two tunnels under the castle. The extension was opened on 15 April 1847; it was 1.5 km in length on a gradient of 1 in 28 (35 mm/m). The traction pipe was laid between the rails; it had

3154-558: The Southwark Ironworks; they were both members of the Institution of Civil Engineers. Samuel Clegg was a gas engineer and they worked in collaboration on their atmospheric system. About 1835, they read Medhurst's writings, and developed a small bore vacuum pipe system. Clegg worked on a longitudinal flap valve, for sealing the slot in the pipe. In 1838, they took out a patent "for a new improvement in valves" and built

3237-400: The US is rated for a maximum of 1 ⁄ 2  psi (3.4 kPa; 34 mbar), which is approximately 14 w.g. Similar metric units with a wide variety of names and notation based on millimetres , centimetres or metres are now less commonly used. Pure water boils at 100 °C (212 °F) at earth's standard atmospheric pressure. The boiling point is the temperature at which

3320-528: The United Kingdom were found to be affected, leading to objections from vegans and members of some religious communities. Tallow once was widely used to make molded candles before more convenient wax varieties became available—and for some time after since they continued to be a cheaper alternative. For those too poor even to avail themselves of homemade, molded tallow candles, the "tallow dip"—a reed that had been dipped in melted tallow or sometimes

3403-503: The atmospheric pressure at a given altitude. Temperature and humidity also affect the atmospheric pressure. Pressure is proportional to temperature and inversely related to humidity, and both of these are necessary to compute an accurate figure. The graph on the right above was developed for a temperature of 15 °C and a relative humidity of 0%. At low altitudes above sea level, the pressure decreases by about 1.2 kPa (12 hPa) for every 100 metres. For higher altitudes within

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3486-521: The atmospheric system on British lines, although the Paris – Saint Germain line continued until 1860. When the system was abolished in 1855, a 2-2-2 steam locomotive named Princess was employed, incidentally the first steam engine to be manufactured in Ireland. Although a small machine, it successfully worked the steeply graded line for some years. In 1835, the brothers Pereire obtained a concession from

3569-504: The cartridge open. It was believed that the paper cartridges that were standard issue with the rifle were greased with lard (pork fat), which was regarded as unclean by Muslims , or tallow (cow fat), which is incompatible with Hindu dietary laws . Tallow, along with beeswax , was also used in the lubricant for American Civil War ammunition used in the Springfield rifled musket . A combination of mutton tallow, paraffin wax and beeswax

3652-465: The dense atmospheric layer at low altitudes—the Earth's gravitational acceleration as a function of altitude can be approximated as constant and contributes little to this fall-off. Pressure measures force per unit area, with SI units of pascals (1 pascal = 1 newton per square metre , 1   N/m ). On average, a column of air with a cross-sectional area of 1 square centimetre (cm ), measured from

3735-560: The east side of the existing double track main line, and all the local trains in both directions would use it. The faster Brighton trains would be freed of the delay following a stopping train. Cubitt had been impressed during his visit to the Dalkey line, and the new L&CR third track would use atmospheric power. The local line would also be extended to Epsom, also as a single track atmospheric line. These arrangements were adopted and Parliamentary powers obtained on 4 July 1843, also authorising

3818-431: The edges of a valve which fits down upon it. The valve is made of a piece of sole leather half an inch thick, having plates of iron attached to it on both the upper and corresponding under side to give it strength ... which are perhaps one-fourth of an inch in thickness ... The plates are about nine inches long, and their ends, above and below, are placed three quarters of an inch apart, forming joints, so as to give

3901-404: The end of the section nearest to its steam engine, is opened by the compression of air in front of the piston, which necessarily takes place after it has passed the branch which communicates with the air-pump; the entrance separating valve, (that near the commencement of the next section of pipe,) is an equilibrium or balance valve, and opens immediately the piston has entered the pipe. The main pipe

3984-403: The exhaustion created in front of it. The continuous pipe is fixed between the rails and bolted to the sleepers which carry them; the inside of the tube is unbored, but lined or coated with tallow 1/10th of an inch thick, to equalize the surface and prevent any unnecessary friction from the passage of the travelling piston through it. The operation of the closure valve was to be critical: Along

4067-505: The extrapolation of pressure to sea level for locations above or below sea level. The average pressure at mean sea level ( MSL ) in the International Standard Atmosphere ( ISA ) is 1,013.25 hPa, or 1 atmosphere (atm), or 29.92 inches of mercury. Pressure (P), mass (m), and acceleration due to gravity (g) are related by P = F/A = (m*g)/A, where A is the surface area. Atmospheric pressure is thus proportional to

4150-547: The first United States Department of Defense aircraft to fly on such a blend and the first aircraft to operate from Edwards using a fuel derived from beef tallow. Tallow also has a use in printmaking, where it is combined with bitumen and applied to metal print plates to resist acid etching. The use of trace amounts of tallow as an additive to the substrate used in polymer banknotes came to light in November 2016. Notes issued in 24 countries including Canada, Australia, and

4233-404: The groove when the valve is shut, makes up the circle of the pipe, and prevents the air from passing the piston; one edge of this valve is securely held down by iron bars, fastened by screw bolts to a longitudinal rib cast on the pipe, and allows the leather between the plates and the bar to act as a hinge, similar to a common pump valve; the other edge of the valve falls into a groove which contains

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4316-546: The leather valve pliability, and at the same time firmness. Clayton records the name of the engineer, Mallet, who had been Inspector general of Public Works, and gives a slightly different account: Clayton says that Mallet used a plaited rope to seal the slot. He also says that vacuum was created by condensing steam in a vacuum chamber between runs, but that may have been a misunderstanding of the pressure accumulators. The London and Croydon Railway (L&CR) obtained its authorising Act of Parliament in 1835, to build its line from

4399-424: The lifting of each in succession. The piston carriage would open and then close the valve: To the underside of the first carriage in each train is attached the piston and its appurtenances; a rod passing horizontally from the piston is attached to a connecting arm, about six feet behind the piston. This connecting arm passes through the continuous groove in the pipe, and being fixed to the carriage, imparts motion to

4482-400: The line was opened to the public. In service, a typical speed of 30 mph was attained; return to Kingstown was by gravitation down the gradient, and slower. By March 1844, 35 train movements operated daily, and 4,500 passengers a week travelled on the line, mostly simply for the novelty. It is recorded that a young man called Frank Elrington was on one occasion on the piston carriage, which

4565-421: The mean (average) sea level to the top of Earth's atmosphere, has a mass of about 1.03 kilogram and exerts a force or "weight" of about 10.1 newtons , resulting in a pressure of 10.1 N/cm or 101   kN /m (101 kilopascals, kPa). A column of air with a cross-sectional area of 1   in would have a weight of about 14.7   lbf , resulting in a pressure of 14.7   lbf/in . Atmospheric pressure

4648-400: The past, it has been both favored and shunned in dog food . Tallow can be used for the production of biodiesel in much the same way as oils from plants are currently used. The United States Air Force has experimented successfully with the use of beef tallow in aviation biofuels . During five days of flight testing from August 23 to 27, 2010, at Edwards Air Force Base , California ,

4731-451: The pipe in a fit state to receive the next train. Entering and leaving the pipe was described: The continuous pipe is divided into suitable sections (according to the respective distance of the fixed steam engines) by separating valves, which are opened by the train as it goes along: these valves are so constructed that no stoppage or diminution of speed is necessary in passing from one section to another. The exit separating valve, or that at

4814-411: The pipe would be used in one direction only, and the fact that only one pumping station was erected suggests that trains were gravitated back to the lower end of the run after the atmospheric ascent, as was later done on the Dalkey line (below). Many of the runs were public. Samuda quotes the loads and degree of vacuum and speed of some of the runs; there seems to be little correlation; for example: There

4897-447: The piston bracket and closed again immediately behind it. A pumping station ahead of the train would pump air from the tube, and atmospheric pressure behind the piston would push it forward. The Wormwood Scrubs demonstration ran for two years. The traction pipe was of 9 inches diameter, and a 16 hp stationary engine was used for power. The gradient on the line was a steady 1 in 115. In his treatise, described below, Samuda implies that

4980-400: The piston entered the pipe, and the train was held on the brakes until it was ready to start. When that time came, the brakes were released and the train moved off. (The electric telegraph was later installed, obviating reliance on the timetable for engine operation.) On 17 August 1843, the tube was exhausted for the first time, and the following day a trial run was made. On Saturday 19 August,

5063-421: The port of Dún Laoghaire (then called Kingstown) to Dublin , Ireland ; it was a standard gauge line. In 1840, it was desired to extend the line to Dalkey, a distance of about two miles. A horse tramway on the route was acquired and converted: it had been used to bring stone from a quarry for the construction of the harbour. It was steeply graded (at 1 in 115 with a 440-yard stretch of 1 in 57) and heavily curved,

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5146-417: The power, before the days of practical electricity, was the use of either a cable system or air pressure. In 1799, George Medhurst of London discussed the idea of moving goods pneumatically through cast iron pipes, and in 1812, he proposed blowing passenger carriages through a tunnel. Medhurst proposed two alternative systems: either the vehicle itself was the piston, or the tube was relatively small with

5229-426: The rails of a railway track; the pipe had a slot in the top. The leading vehicle in a train was a piston carriage , which carried a piston inserted in the tube. It was held by a bracket system that passed through the slot, and the actual piston was on a pole ahead of the point at which the bracket left the slot. The slot was sealed from the atmosphere by a continuous leather flap that was opened immediately in advance of

5312-540: The rope in front of the piston connection and returned it afterwards. He built a demonstration line alongside the Kensington Canal , and issued a prospectus for his National Pneumatic Railway Association . He was unable to interest investors, and his system failed when the rope stretched. However, his concept, a small bore pipe with a resealable slot was the prototype for many successor systems. Jacob and Joseph Samuda were shipbuilders and engineers, and owned

5395-401: The sharpest being 570 yards radius. This presented significant difficulties to the locomotives then in use. The treasurer of the company, James Pim , was visiting London and hearing of Samuda's project he viewed it. He considered it to be perfect for the requirements of his company, and after petitioning government for a loan of £26,000, it was agreed to install it on the Dalkey line. Thus became

5478-461: The success of the Dalkey railway, the French minister of public works (M. Teste) and under-secretary of state (M. Le Grande) dispatched M. Mallet, inspecteur général honoraire des Ponts et Chaussées, to Dalkey. He wrote an exhaustive technical evaluation of the system installed there, and its potential, which included the results of measurements made with Joseph Samuda. It was through his interest that

5561-413: The train as the tube becomes exhausted; to the piston rod are also attached four steel wheels, (two in advance and two behind the connecting arm,) which serve to lift the valve, and form a space for the passage of the connecting arm, and also for the admission of air to the back of the piston; another steel wheel is attached to the carriage, regulated by a spring, which serves to ensure the perfect closing of

5644-434: The train through a continuous pipe or main, laid between the rails, which is exhausted by air pumps worked by stationary steam engines, fixed on the road side, the distance between them varying from one to three miles, according to the nature and traffic of the road. A piston, which is introduced into this pipe, is attached to the leading carriage in each train, through a lateral opening, and is made to travel forward by means of

5727-407: The upper surface of the pipe is a continuous slit or groove about two inches wide. This groove is covered by a valve, extending the whole length of the railway, formed of a strip of leather riveted between iron plates, the top plates being wider than the groove and serving to prevent the external air forcing the leather into the pipe when the vacuum is formed within it; and the lower plates fitting into

5810-409: The valve, by running over the top plates immediately after the arm has passed. A copper tube or heater, about ten feet long, constantly kept hot by a small stove, also fixed to the underside of the carriage, passes over and melts the surface of the composition (which has been broken by lifting the valve,) which upon cooling becomes solid, and hermetically seals the valve. Thus each train in passing leaves

5893-402: The vehicle. Vallance's system worked, but was not adopted commercially. In 1835, Henry Pinkus patented a system with a 9-square-foot (0.84 m) square section tube with a low degree of vacuum, limiting leakage loss. He later changed to a small-bore vacuum tube. He proposed to seal the slot that enabled the piston to connect with the vehicle with a continuous rope; rollers on the vehicle lifted

5976-519: The wagons in use, they frequently broke the rails. Also, lack of adhesion (i.e. slip) at the iron-to-iron wheel-rail interface was a limitation, for example in trials on the Kilmarnock and Troon Railway . Many engineers turned their attention to transmitting power from a static power source, a stationary engine , to a moving train. Such an engine could be more robust and with more available space, potentially more powerful. The solution to transmitting

6059-483: The weight per unit area of the atmospheric mass above that location. Pressure on Earth varies with the altitude of the surface, so air pressure on mountains is usually lower than air pressure at sea level. Pressure varies smoothly from the Earth's surface to the top of the mesosphere . Although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases. One can calculate

6142-602: The world in hectopascals or millibars (1 hectopascal = 1 millibar), except in the United States , Canada , and Japan where it is reported in inches of mercury (to two decimal places). The United States and Canada also report sea-level pressure SLP, which is adjusted to sea level by a different method, in the remarks section, not in the internationally transmitted part of the code, in hectopascals or millibars. However, in Canada's public weather reports, sea level pressure

6225-473: Was confirming Newton's theory of gravitation at and on Schiehallion mountain in Scotland, and he needed to measure elevations on the mountain's sides accurately. William Roy , using barometric pressure, was able to confirm Maskelyne's height determinations; the agreement was within one meter (3.28 feet). This method became and continues to be useful for survey work and map making. Tallow Tallow

6308-567: Was 1,084.8 hPa (32.03 inHg) measured in Tosontsengel, Mongolia on 19 December 2001. The highest adjusted-to-sea level barometric pressure ever recorded (below 750 meters) was at Agata in Evenk Autonomous Okrug , Russia (66°53'   N, 93°28'   E, elevation: 261 m, 856 ft) on 31 December 1968 of 1,083.8 hPa (32.005 inHg). The discrimination is due to the problematic assumptions (assuming

6391-439: Was 870 hPa (0.858 atm; 25.69 inHg), set on 12 October 1979, during Typhoon Tip in the western Pacific Ocean. The measurement was based on an instrumental observation made from a reconnaissance aircraft. One atmosphere (101.325 kPa or 14.7 psi) is also the pressure caused by the weight of a column of freshwater of approximately 10.3 m (33.8 ft). Thus, a diver 10.3 m under water experiences

6474-531: Was enormous public interest in the ideas surrounding atmospheric railways, and at the same time as Samuda was developing his scheme, others put other ideas forward. In 1841, Joseph Samuda published A Treatise on the Adaptation of Atmospheric Pressure to the Purposes of Locomotion on Railways . It ran to 50 pages, and Samuda described his system; first the traction pipe: The moving power is communicated to

6557-401: Was never made. Air pressure In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially

6640-459: Was not attached to the train. On releasing the brake, the light vehicle shot off at high speed, covering the distance in 75 seconds, averaging 65 mph (105 km/h). As this was the first commercially operating atmospheric railway, it attracted the attention of many eminent engineers of the day, including Isambard Kingdom Brunel , Robert Stephenson , and Sir William Cubitt . The line continued to operate successfully for ten years, outliving

6723-415: Was promoted and it too had to share the route into London by running over the L&CR. When the lines opened in 1839, it was found that congestion arose due to the frequent stopping services on the local Croydon line; this was particularly a problem on the 1 in 100 ascent from New Cross to Dartmouth Arms. The L&CR engineer, William Cubitt proposed a solution to the problem: a third track would be laid on

6806-532: Was technically successful, but the development of more powerful steam locomotives led to its abandonment from 3 July 1860, when steam locomotive ran throughout from Paris to Saint Germain, being assisted by a pusher locomotive up the gradient. This arrangement continued for more than sixty years until the electrification of the line. A correspondent of the Ohio State Journal described some details; there seem to have been two tube sections: An iron tube

6889-444: Was used by explorers. Conversely, if one wishes to evaporate a liquid at a lower temperature, for example in distillation , the atmospheric pressure may be lowered by using a vacuum pump , as in a rotary evaporator . An important application of the knowledge that atmospheric pressure varies directly with altitude was in determining the height of hills and mountains, thanks to reliable pressure measurement devices. In 1774, Maskelyne

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