88-554: Railways with a track gauge of 3 ft 6 in ( 1,067 mm ) were first constructed as horse-drawn wagonways . The first intercity passenger railway to use 3 ft 6 in was constructed in Norway by Carl Abraham Pihl . From the mid-nineteenth century, the 3 ft 6 in gauge became widespread in the British Empire . In Africa it became known as the Cape gauge as it
176-455: A Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa . For comparison, concrete typically has a crushing strength of about 40 MPa. Although limestones show little variability in mineral composition, they show great diversity in texture. However, most limestone consists of sand-sized grains in a carbonate mud matrix. Because limestones are often of biological origin and are usually composed of sediment that
264-457: A bloom of cyanobacteria or microalgae . However, stable isotope ratios in modern carbonate mud appear to be inconsistent with either of these mechanisms, and abrasion of carbonate grains in high-energy environments has been put forward as a third possibility. Formation of limestone has likely been dominated by biological processes throughout the Phanerozoic , the last 540 million years of
352-434: A carbonate rock outcrop can be estimated in the field by etching the surface with dilute hydrochloric acid. This etches away the calcite and aragonite, leaving behind any silica or dolomite grains. The latter can be identified by their rhombohedral shape. Crystals of calcite, quartz , dolomite or barite may line small cavities ( vugs ) in the rock. Vugs are a form of secondary porosity, formed in existing limestone by
440-612: A central quartz grain or carbonate mineral fragment. These likely form by direct precipitation of calcium carbonate onto the ooid. Pisoliths are similar to ooids, but they are larger than 2 mm in diameter and tend to be more irregular in shape. Limestone composed mostly of ooids is called an oolite or sometimes an oolitic limestone . Ooids form in high-energy environments, such as the Bahama platform, and oolites typically show crossbedding and other features associated with deposition in strong currents. Oncoliths resemble ooids but show
528-449: A change in environment that increases the solubility of calcite. Dense, massive limestone is sometimes described as "marble". For example, the famous Portoro "marble" of Italy is actually a dense black limestone. True marble is produced by recrystallization of limestone during regional metamorphism that accompanies the mountain building process ( orogeny ). It is distinguished from dense limestone by its coarse crystalline texture and
616-949: A composition reflecting the organisms that produced them and the environment in which they were produced. Low-magnesium calcite skeletal grains are typical of articulate brachiopods , planktonic (free-floating) foraminifera, and coccoliths . High-magnesium calcite skeletal grains are typical of benthic (bottom-dwelling) foraminifera, echinoderms , and coralline algae . Aragonite skeletal grains are typical of molluscs , calcareous green algae , stromatoporoids , corals , and tube worms . The skeletal grains also reflect specific geological periods and environments. For example, coral grains are more common in high-energy environments (characterized by strong currents and turbulence) while bryozoan grains are more common in low-energy environments (characterized by quiet water). Ooids (sometimes called ooliths) are sand-sized grains (less than 2mm in diameter) consisting of one or more layers of calcite or aragonite around
704-412: A considerable fraction of the limestone bed. At depths greater than 1 km (0.62 miles), burial cementation completes the lithification process. Burial cementation does not produce stylolites. When overlying beds are eroded, bringing limestone closer to the surface, the final stage of diagenesis takes place. This produces secondary porosity as some of the cement is dissolved by rainwater infiltrating
792-483: A drop of dilute hydrochloric acid is dropped on it. Dolomite is also soft but reacts only feebly with dilute hydrochloric acid, and it usually weathers to a characteristic dull yellow-brown color due to the presence of ferrous iron. This is released and oxidized as the dolomite weathers. Impurities (such as clay , sand, organic remains, iron oxide , and other materials) will cause limestones to exhibit different colors, especially with weathered surfaces. The makeup of
880-621: A few million years, as this is the most stable form of calcium carbonate. Ancient carbonate formations of the Precambrian and Paleozoic contain abundant dolomite, but limestone dominates the carbonate beds of the Mesozoic and Cenozoic . Modern dolomite is quite rare. There is evidence that, while the modern ocean favors precipitation of aragonite, the oceans of the Paleozoic and middle to late Cenozoic favored precipitation of calcite. This may indicate
968-455: A few thousand years. As rainwater mixes with groundwater, aragonite and high-magnesium calcite are converted to low-calcium calcite. Cementing of thick carbonate deposits by rainwater may commence even before the retreat of the sea, as rainwater can infiltrate over 100 km (60 miles) into sediments beneath the continental shelf. As carbonate sediments are increasingly deeply buried under younger sediments, chemical and mechanical compaction of
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#17328957640431056-490: A high percentage of the mineral dolomite , CaMg(CO 3 ) 2 . Magnesian limestone is an obsolete and poorly-defined term used variously for dolomite, for limestone containing significant dolomite ( dolomitic limestone ), or for any other limestone containing a significant percentage of magnesium . Most limestone was formed in shallow marine environments, such as continental shelves or platforms , though smaller amounts were formed in many other environments. Much dolomite
1144-435: A limestone sample except in thin section and are less common in ancient limestones, possibly because compaction of carbonate sediments disrupts them. Limeclasts are fragments of existing limestone or partially lithified carbonate sediments. Intraclasts are limeclasts that originate close to where they are deposited in limestone, while extraclasts come from outside the depositional area. Intraclasts include grapestone , which
1232-466: A lower Mg/Ca ratio in the ocean water of those times. This magnesium depletion may be a consequence of more rapid sea floor spreading , which removes magnesium from ocean water. The modern ocean and the ocean of the Mesozoic have been described as "aragonite seas". Most limestone was formed in shallow marine environments, such as continental shelves or platforms . Such environments form only about 5% of
1320-525: A lower diversity of organisms and a greater fraction of silica and clay minerals characteristic of marls . The Green River Formation is an example of a prominent freshwater sedimentary formation containing numerous limestone beds. Freshwater limestone is typically micritic. Fossils of charophyte (stonewort), a form of freshwater green algae, are characteristic of these environments, where the charophytes produce and trap carbonates. Limestones may also form in evaporite depositional environments . Calcite
1408-523: A mechanism for dolomitization, with one 2004 review paper describing it bluntly as "a myth". Ordinary seawater is capable of converting calcite to dolomite, if the seawater is regularly flushed through the rock, as by the ebb and flow of tides (tidal pumping). Once dolomitization begins, it proceeds rapidly, so that there is very little carbonate rock containing mixed calcite and dolomite. Carbonate rock tends to be either almost all calcite/aragonite or almost all dolomite. About 20% to 25% of sedimentary rock
1496-448: A plausible source of mud. Another possibility is direct precipitation from the water. A phenomenon known as whitings occurs in shallow waters, in which white streaks containing dispersed micrite appear on the surface of the water. It is uncertain whether this is freshly precipitated aragonite or simply material stirred up from the bottom, but there is some evidence that whitings are caused by biological precipitation of aragonite as part of
1584-449: A radial rather than layered internal structure, indicating that they were formed by algae in a normal marine environment. Peloids are structureless grains of microcrystalline carbonate likely produced by a variety of processes. Many are thought to be fecal pellets produced by marine organisms. Others may be produced by endolithic (boring) algae or other microorganisms or through breakdown of mollusc shells. They are difficult to see in
1672-583: A railway, ran a high-pressure steam locomotive with smooth wheels on an 'L' section plateway near Merthyr Tydfil , but it was more expensive than horses. He made three trips from the iron mines at Penydarren to the Merthyr-Cardiff Canal and each time broke the rails that were designed for horse wagon loads. There was general doubt at the time that smooth wheels could obtain traction on smooth rails. This resulted in proposals using rack or other drive mechanisms. Mr Blenkinsop of Middleton Colliery patented
1760-619: A result, in 1767, they began to make cast iron rails. These were probably 6 ft (1.829 m) long, with four projecting ears or lugs 3 in (75 mm) by 3 + 3 ⁄ 4 in (95 mm) to enable them to be fixed to the sleepers . The rails were 3 + 3 ⁄ 4 in (95 mm) wide and 1 + 1 ⁄ 4 in (30 mm) thick. Later, descriptions also refer to rails 3 ft (914 mm) long and only 2 in (50 mm) wide. A later system involved L-shaped iron rails or plates , each 3 ft (914 mm) long and 4 in (102 mm) wide, having on
1848-616: A vertical pin on the truck fitting into the gap between the planks to keep it going the right way. The miners called the wagons Hunde ("dogs") from the noise they made on the tracks. Around 1568, German miners working in the Mines Royal near Keswick used such a system. Archaeological work at the Mines Royal site at Caldbeck in the English Lake District confirmed the use of " hunds ". In 1604, Huntingdon Beaumont completed
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#17328957640431936-452: A wagonway to a fully steam-powered railway was gradual. Railways up to the 1830s that were steam-powered often made runs with horses when the steam locomotives were unavailable. Even in the steam age, it was convenient to use horses in station yards to shunt wagons from one place to another. Horses do not need lengthy times to raise steam in the boiler, and can take shortcuts from one siding to another. At Hamley Bridge tenders were called for
2024-709: A wagonway was proposed to connect the mines at West Durham , Darlington and the River Tees at Stockton , George Stephenson successfully argued that horse-drawn wagonways were obsolete and a steam-powered railway could carry 50 times as much coal. In 1825 he built the locomotive Locomotion for the Stockton and Darlington Railway in England's northeast, which became the world's first public steam railway in 1825, via both horse power and steam power on different runs. Stationary steam engines for mining were generally available around
2112-416: Is a type of carbonate sedimentary rock which is the main source of the material lime . It is composed mostly of the minerals calcite and aragonite , which are different crystal forms of CaCO 3 . Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as
2200-560: Is also favored on the seaward margin of shelves and platforms, where there is upwelling deep ocean water rich in nutrients that increase organic productivity. Reefs are common here, but when lacking, ooid shoals are found instead. Finer sediments are deposited close to shore. The lack of deep sea limestones is due in part to rapid subduction of oceanic crust, but is more a result of dissolution of calcium carbonate at depth. The solubility of calcium carbonate increases with pressure and even more with higher concentrations of carbon dioxide, which
2288-482: Is an uncommon mineral in limestone, and siderite or other carbonate minerals are rare. However, the calcite in limestone often contains a few percent of magnesium . Calcite in limestone is divided into low-magnesium and high-magnesium calcite, with the dividing line placed at a composition of 4% magnesium. High-magnesium calcite retains the calcite mineral structure, which is distinct from dolomite. Aragonite does not usually contain significant magnesium. Most limestone
2376-402: Is carbonate rock, and most of this is limestone. Limestone is found in sedimentary sequences as old as 2.7 billion years. However, the compositions of carbonate rocks show an uneven distribution in time in the geologic record. About 95% of modern carbonates are composed of high-magnesium calcite and aragonite. The aragonite needles in carbonate mud are converted to low-magnesium calcite within
2464-474: Is clusters of peloids cemented together by organic material or mineral cement. Extraclasts are uncommon, are usually accompanied by other clastic sediments, and indicate deposition in a tectonically active area or as part of a turbidity current . The grains of most limestones are embedded in a matrix of carbonate mud. This is typically the largest fraction of an ancient carbonate rock. Mud consisting of individual crystals less than 5 μm (0.20 mils) in length
2552-416: Is commonly white to gray in color. Limestone that is unusually rich in organic matter can be almost black in color, while traces of iron or manganese can give limestone an off-white to yellow to red color. The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk. The density correspondingly ranges from 1.5 to 2.7 g/cm . Although relatively soft, with
2640-420: Is controlled largely by the amount of dissolved carbon dioxide ( CO 2 ) in the water. This is summarized in the reaction: Increases in temperature or decreases in pressure tend to reduce the amount of dissolved CO 2 and precipitate CaCO 3 . Reduction in salinity also reduces the solubility of CaCO 3 , by several orders of magnitude for fresh water versus seawater. Near-surface water of
2728-545: Is converted to low-magnesium calcite. Diagenesis is the likely origin of pisoliths , concentrically layered particles ranging from 1 to 10 mm (0.039 to 0.394 inches) in diameter found in some limestones. Pisoliths superficially resemble ooids but have no nucleus of foreign matter, fit together tightly, and show other signs that they formed after the original deposition of the sediments. Silicification occurs early in diagenesis, at low pH and temperature, and contributes to fossil preservation. Silicification takes place through
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2816-503: Is deposited close to where it formed, classification of limestone is usually based on its grain type and mud content. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera . These organisms secrete structures made of aragonite or calcite, and leave these structures behind when they die. Other carbonate grains composing limestones are ooids , peloids , and limeclasts ( intraclasts and extraclasts [ ca ] ). Skeletal grains have
2904-460: Is described as coquinite . Chalk is a soft, earthy, fine-textured limestone composed of the tests of planktonic microorganisms such as foraminifera, while marl is an earthy mixture of carbonates and silicate sediments. Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. The solubility of calcium carbonate ( CaCO 3 )
2992-617: Is described as micrite . In fresh carbonate mud, micrite is mostly small aragonite needles, which may precipitate directly from seawater, be secreted by algae, or be produced by abrasion of carbonate grains in a high-energy environment. This is converted to calcite within a few million years of deposition. Further recrystallization of micrite produces microspar , with grains from 5 to 15 μm (0.20 to 0.59 mils) in diameter. Limestone often contains larger crystals of calcite, ranging in size from 0.02 to 0.1 mm (0.79 to 3.94 mils), that are described as sparry calcite or sparite . Sparite
3080-462: Is distinguished from micrite by a grain size of over 20 μm (0.79 mils) and because sparite stands out under a hand lens or in thin section as white or transparent crystals. Sparite is distinguished from carbonate grains by its lack of internal structure and its characteristic crystal shapes. Geologists are careful to distinguish between sparite deposited as cement and sparite formed by recrystallization of micrite or carbonate grains. Sparite cement
3168-560: Is one of the first minerals to precipitate in marine evaporites. Most limestone is formed by the activities of living organisms near reefs, but the organisms responsible for reef formation have changed over geologic time. For example, stromatolites are mound-shaped structures in ancient limestones, interpreted as colonies of cyanobacteria that accumulated carbonate sediments, but stromatolites are rare in younger limestones. Organisms precipitate limestone both directly as part of their skeletons, and indirectly by removing carbon dioxide from
3256-473: Is otherwise chemically fairly pure, with clastic sediments (mainly fine-grained quartz and clay minerals ) making up less than 5% to 10% of the composition. Organic matter typically makes up around 0.2% of a limestone and rarely exceeds 1%. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragments (such as sponge spicules, diatoms , or radiolarians ). Fossils are also common in limestone. Limestone
3344-472: Is produced by decaying organic matter settling into the deep ocean that is not removed by photosynthesis in the dark depths. As a result, there is a fairly sharp transition from water saturated with calcium carbonate to water unsaturated with calcium carbonate, the lysocline , which occurs at the calcite compensation depth of 4,000 to 7,000 m (13,000 to 23,000 feet). Below this depth, foraminifera tests and other skeletal particles rapidly dissolve, and
3432-514: Is secondary dolomite, formed by chemical alteration of limestone. Limestone is exposed over large regions of the Earth's surface, and because limestone is slightly soluble in rainwater, these exposures often are eroded to become karst landscapes. Most cave systems are found in limestone bedrock. Limestone has numerous uses: as a chemical feedstock for the production of lime used for cement (an essential component of concrete ), as aggregate for
3520-621: Is used to distinguish it from other narrow gauges. In Japan the 1,067 mm ( 3 ft 6 in ) gauge, along with other narrow gauges, is referred to as kyōki ( 狭軌 ) , which directly translates as narrow gauge , to differentiate it from the Shinkansen lines. It is defined in metric units. It is commonly referred to as 三六軌間 ( 36 gauge ) , which derives from the 3 ft 6 in. Similar, but incompatible without wheelset adjustment, rail gauges in respect of aspects such as cost of construction, practical minimum radius curves and
3608-593: The Aire & Calder Navigation , running from Wakefield to Outwood , a distance of approximately 3 miles (4.8 km). Edge-rails (with a side rack) were used on the nearby Middleton-Leeds rack railway (a length of this rail is on display in Leeds City Museum ). The wheels of an edgeway have flanges, like modern railways and tramways. Causewaying is also done on modern level crossings and tramways. These two systems of constructing iron railways continued to exist until
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3696-708: The Wollaton Wagonway , built to transport coal from the mines at Strelley to Wollaton Lane End, just west of Nottingham , England . Wagonways have been discovered between Broseley and Jackfield in Shropshire from 1605, used by James Clifford to transport coal from his mines in Broseley to the Severn River. It has been suggested that these are somewhat older than that at Wollaton. The Middleton Railway in Leeds , which
3784-445: The lumberjacks moved on to other stands of timber as each area was cleared. At least one such pole road system reportedly extended some 20 miles (32 km). Typically the pole rails were logs of 8 to 12 inches (20 to 30 cm) diameter, laid parallel directly on the ground without cross-ties , and joined end-to-end with lap joints and wooden pegs . Rolling stock typically had wheels either with concave rims that hugged
3872-423: The maximum physical dimensions of rolling stock are: Dual gauge between 1,067 mm ( 3 ft 6 in ) gauge and another similar gauge can make these bonus gauges. Barbados Railway ( converted to 2 ft 6 in or 762 mm gauge) (defunct) Wagonways Wagonways (also spelt Waggonways ), also known as horse-drawn railways and horse-drawn railroad consisted of
3960-712: The 1960s, the gauge was referred to in official South African Railways publications as 1,065 mm ( 3 ft 5 + 15 ⁄ 16 in ) instead of 1067 mm. In Sweden, the gauge was nicknamed Blekinge gauge , as most of the railways in the province of Blekinge had this gauge. Colonial Gauge was used in New Zealand. In Australia, this gauge is typically referred to as narrow gauge in comparison to 4 ft 8 + 1 ⁄ 2 in ( 1,435 mm ) standard gauge or 5 ft 3 in ( 1,600 mm ) broad gauge. In some instances, simply 3 foot 6 inch — or in rarer cases medium gauge —
4048-496: The Earth's history. Limestone may have been deposited by microorganisms in the Precambrian , prior to 540 million years ago, but inorganic processes were probably more important and likely took place in an ocean more highly oversaturated in calcium carbonate than the modern ocean. Diagenesis is the process in which sediments are compacted and turned into solid rock . During diagenesis of carbonate sediments, significant chemical and textural changes take place. For example, aragonite
4136-430: The accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life. About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. The remaining carbonate rock is mostly dolomite , a closely related rock, which contains
4224-434: The base of roads, as white pigment or filler in products such as toothpaste or paint, as a soil conditioner , and as a popular decorative addition to rock gardens . Limestone formations contain about 30% of the world's petroleum reservoirs . Limestone is composed mostly of the minerals calcite and aragonite , which are different crystal forms of calcium carbonate ( CaCO 3 ). Dolomite , CaMg(CO 3 ) 2 ,
4312-657: The beds. This may include the formation of vugs , which are crystal-lined cavities within the limestone. Diagenesis may include conversion of limestone to dolomite by magnesium-rich fluids. There is considerable evidence of replacement of limestone by dolomite, including sharp replacement boundaries that cut across bedding. The process of dolomitization remains an area of active research, but possible mechanisms include exposure to concentrated brines in hot environments ( evaporative reflux ) or exposure to diluted seawater in delta or estuary environments ( Dorag dolomitization ). However, Dorag dolomitization has fallen into disfavor as
4400-462: The depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles, based on criteria such as whether the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of
4488-469: The deposits are highly porous, so that they have a spongelike texture, they are typically described as tufa . Secondary calcite deposited by supersaturated meteoric waters ( groundwater ) in caves is also sometimes described as travertine. This produces speleothems , such as stalagmites and stalactites . Coquina is a poorly consolidated limestone composed of abraded pieces of coral , shells , or other fossil debris. When better consolidated, it
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#17328957640434576-601: The early 19th century. In most parts of England the plate-rail was preferred. Plate-rails were used on the Surrey Iron Railway (SIR), from Wandsworth to West Croydon . The SIR was sanctioned by Parliament in 1801 and finished in 1803. Like the Lake Lock Rail Road , the SIR was available to the public on payment of tolls; previous lines had all been private and reserved exclusively for the use of their owners. Since it
4664-406: The earth's oceans are oversaturated with CaCO 3 by a factor of more than six. The failure of CaCO 3 to rapidly precipitate out of these waters is likely due to interference by dissolved magnesium ions with nucleation of calcite crystals, the necessary first step in precipitation. Precipitation of aragonite may be suppressed by the presence of naturally occurring organic phosphates in
4752-399: The first refers to the grains and the second to the cement. For example, a limestone consisting mainly of ooids, with a crystalline matrix, would be termed an oosparite. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample. Robert J. Dunham published his system for limestone in 1962. It focuses on
4840-572: The formation of distinctive minerals from the silica and clay present in the original limestone. Two major classification schemes, the Folk and Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks . Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). The Folk system uses two-part names;
4928-553: The fully loaded wagons downhill to a canal or boat dock and then return the empty wagons back to the mine. Until the beginning of the Industrial Revolution , rails were made of wood, were a few inches wide and were fastened end to end, on logs of wood or "sleepers", placed crosswise at intervals of two or three feet. In time, it became common to cover them with a thin flat sheathing or "plating" of iron, in order to add to their life and reduce friction. This caused more wear on
5016-429: The geologic record are called bioherms . Many are rich in fossils, but most lack any connected organic framework like that seen in modern reefs. The fossil remains are present as separate fragments embedded in ample mud matrix. Much of the sedimentation shows indications of occurring in the intertidal or supratidal zones, suggesting sediments rapidly fill available accommodation space in the shelf or platform. Deposition
5104-637: The horses, equipment and tracks used for hauling wagons, which preceded steam-powered railways . The terms plateway , tramway , dramway , were used. The advantage of wagonways was that far bigger loads could be transported with the same power. The earliest evidence is of the 6 to 8.5 km (3.7 to 5.3 mi) long Diolkos paved trackway, which transported boats across the Isthmus of Corinth in Greece from around 600 BC. Wheeled vehicles pulled by men and animals ran in grooves in limestone , which provided
5192-544: The inner side an upright ledge or flange, 3 in (76 mm) high at the centre and tapering to 2 in (51 mm) at the ends, for the purpose of keeping the flat wheels on the track. Subsequently, to increase strength, a similar flange might be added below the rail. Wooden sleepers continued to be used—the rails were secured by spikes passing through the extremities—but, circa 1793, stone blocks began to be used, an innovation associated with Benjamin Outram , although he
5280-481: The level of the top of the flanges. In 1790, Jessop and his partner Outram began to manufacture edge-rails. Another example of the edge rail application was the Lake Lock Rail Road in the West Riding of Yorkshire (now West Yorkshire ) used primarily for coal transport. The railway charged a toll and opened for traffic in 1798, making it the world's oldest public railway. The route started at Lake Lock, Stanley , on
5368-525: The middle of the 18th century. Wagonways and steam-powered railways had steep uphill sections and would employ a cable powered by a stationary steam engine to work the inclined sections. British troops in Lewiston, New York used a cable wagonway to move supplies to bases before the American Revolutionary War . The Stockton and Darlington had two inclined sections powered by cable. The transition from
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#17328957640435456-410: The ocean basins, but limestone is rarely preserved in continental slope and deep sea environments. The best environments for deposition are warm waters, which have both a high organic productivity and increased saturation of calcium carbonate due to lower concentrations of dissolved carbon dioxide. Modern limestone deposits are almost always in areas with very little silica-rich sedimentation, reflected in
5544-587: The patent for an improved method of rolling rails was granted in 1820 to John Birkinshaw , of the Bedlington Ironworks . His rails were wedge-shaped in section, much wider at the top than at the bottom, with the intermediate portion or web thinner still. He recommended that they be made 18 ft (5.49 m) long, suggesting that several might be welded together end to end to form considerable lengths. They were supported on sleepers by chairs at intervals of 3 ft (914 mm), and were fish-bellied between
5632-426: The reaction: Fossils are often preserved in exquisite detail as chert. Cementing takes place rapidly in carbonate sediments, typically within less than a million years of deposition. Some cementing occurs while the sediments are still under water, forming hardgrounds . Cementing accelerates after the retreat of the sea from the depositional environment, as rainwater infiltrates the sediment beds, often within just
5720-482: The relative purity of most limestones. Reef organisms are destroyed by muddy, brackish river water, and carbonate grains are ground down by much harder silicate grains. Unlike clastic sedimentary rock, limestone is produced almost entirely from sediments originating at or near the place of deposition. Limestone formations tend to show abrupt changes in thickness. Large moundlike features in a limestone formation are interpreted as ancient reefs , which when they appear in
5808-460: The rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright (1992). It adds some diagenetic patterns to the classification scheme. Travertine is a term applied to calcium carbonate deposits formed in freshwater environments, particularly waterfalls , cascades and hot springs . Such deposits are typically massive, dense, and banded. When
5896-479: The sediments increases. Chemical compaction takes place by pressure solution of the sediments. This process dissolves minerals from points of contact between grains and redeposits it in pore space, reducing the porosity of the limestone from an initial high value of 40% to 80% to less than 10%. Pressure solution produces distinctive stylolites , irregular surfaces within the limestone at which silica-rich sediments accumulate. These may reflect dissolution and loss of
5984-662: The sediments of the ocean floor abruptly transition from carbonate ooze rich in foraminifera and coccolith remains ( Globigerina ooze) to silicic mud lacking carbonates. In rare cases, turbidites or other silica-rich sediments bury and preserve benthic (deep ocean) carbonate deposits. Ancient benthic limestones are microcrystalline and are identified by their tectonic setting. Fossils typically are foraminifera and coccoliths. No pre-Jurassic benthic limestones are known, probably because carbonate-shelled plankton had not yet evolved. Limestones also form in freshwater environments. These limestones are not unlike marine limestone, but have
6072-435: The sleepers by two iron spikes, half-round wooden cross sleepers employed on embankments and stone blocks 20 in (508 mm) square by 10 in (254 mm) deep in cuttings. The fish-bellied rails were found to break near the chairs and starting in 1834, they were gradually replaced with parallel rails weighing 50 lb/yd (24.8 kg/m). In 1804, Richard Trevithick , in the first recorded use of steam power on
6160-412: The supply of horses, in part because normal railway staff lacked horse handling skills. Wooden rails continued to be used for temporary railroads into the twentieth century. Some timber harvesting companies in the southeastern United States created pole roads using unmarketable logs, which were effectively free, to create tracks at a cost of between $ 100 and $ 500 per mile. Permanence was not an issue, as
6248-500: The support points. As used by George Stephenson on the Stockton & Darlington , and Canterbury & Whitstable lines, they weighed 28 lb/yd (13.9 kg/m). On the Liverpool and Manchester Railway they were usually 12 or 15 ft (3.66 or 4.57 m) long and weighed 35 lb/yd (17.4 kg/m) and were fastened by iron wedges to chairs weighing 15 or 17 lb (6.8 or 7.7 kg) each. The chairs were in turn fixed to
6336-500: The term "railway". As of 2024 , very few horse or cable freight railways are operating, notable examples being the cable-hauled St Michael's Mount Tramway and the Reisszug , which has been in continuous operation since around 1900. A few passenger lines continue to operate, including the horse-hauled Douglas Bay Horse Tramway and the cable-hauled San Francisco cable cars . Limestone Limestone ( calcium carbonate CaCO 3 )
6424-532: The top of the pole rails, or un-flanged wheels with separate guide wheels running against the side of each rail. Steam traction engines and some purpose-built locomotives were successfully used for hauling trains of logs. For example, Perdido was built by Adams & Price Locomotive and Machinery Works of Nashville, Tennessee in 1885 for the Wallace, Sanford and Company sawmill at Williams Station, Alabama , where it hauled up to seven cars of 3 or 4 logs each. This
6512-509: The track element, preventing the wagons from leaving the intended route. The Diolkos was in use for over 650 years, until at least the 1st century AD. Paved trackways were later built in Roman Egypt . Such an operation was illustrated in Germany in 1556 by Georgius Agricola (image left) in his work De re metallica . This line used "Hund" carts with unflanged wheels running on wooden planks and
6600-552: The use of cogged wheels in 1811 and in 1812, the Middleton Railway (edgeway, rack rail) successfully used twin cylinder steam locomotives made by Matthew Murray of Holbeck , Leeds . George Stephenson made his first steam locomotive in 1813 (patented 1815) for the Killingworth colliery, and found smooth wheels on smooth rails provided adequate grip. Although he later recounted that they called this locomotive 'My Lord' as it
6688-533: The water by photosynthesis and thereby decreasing the solubility of calcium carbonate. Limestone shows the same range of sedimentary structures found in other sedimentary rocks. However, finer structures, such as lamination , are often destroyed by the burrowing activities of organisms ( bioturbation ). Fine lamination is characteristic of limestone formed in playa lakes , which lack the burrowing organisms. Limestones also show distinctive features such as geopetal structures , which form when curved shells settle to
6776-553: The water. Although ooids likely form through purely inorganic processes, the bulk of CaCO 3 precipitation in the oceans is the result of biological activity. Much of this takes place on carbonate platforms . The origin of carbonate mud, and the processes by which it is converted to micrite, continue to be a subject of research. Modern carbonate mud is composed mostly of aragonite needles around 5 μm (0.20 mils) in length. Needles of this shape and composition are produced by calcareous algae such as Penicillus , making this
6864-509: The wooden rollers of the wagons and towards the middle of the 18th century, led to the introduction of iron wheels. However, the iron sheathing was not strong enough to resist buckling under the passage of the loaded wagons, so rails made wholly of iron were invented. In 1760, the Coalbrookdale Iron Works began to reinforce their wooden-railed tramway with iron bars, which were found to facilitate passage and diminish expenses. As
6952-534: The world, which are classified as narrow-gauge railways . This gauge is sometimes called Cape gauge , named after the Cape Colony in what is now South Africa, which adopted it in 1873. "Cape gauge" was used in several English-speaking countries. The equivalent of Cape gauge is used in other languages, such as the Dutch kaapspoor , German Kapspur , Norwegian kappspor and French voie cape . After metrication in
7040-399: Was a geared engine (4.5 to 1 gear ratio ), driving four individually-rotating concave-rim wheels on stationary axles via chain drives; powerful but running less than 5 miles per hour (8.0 km/h). Still later, modified semitrailer tractors have been used. As steam power gradually replaced horse power throughout the 19th century, the term "wagonway" became obsolete and was superseded by
7128-690: Was adopted as the standard gauge for the Cape Government Railways in 1873, although it had already been established in Australia and New Zealand before that. It was adopted as a standard in New Zealand , South Africa , Indonesia , Japan , the Philippines , Taiwan , and Queensland (which has the second largest narrow gauge network in the world) in Australia. There are approximately 112,000 kilometres (70,000 mi) of 1,067 mm gauge track in
7216-570: Was built in 1758 as a wagonway, later became the world's first operational railway (other than funiculars), albeit in an upgraded form. In 1764, the first railway in America was built in Lewiston, New York as a wagonway. Wagonways improved coal transport by allowing one horse to deliver between 10 and 13 long tons (10.2 and 13.2 t ; 11.2 and 14.6 short tons ) of coal per run— an approximate fourfold increase. Wagonways were usually designed to carry
7304-467: Was financed by Lord Ravensworth , it seems that it was known at the time as Blücher . In 1814 William Stewart was engaged by Parkend Coal Co in the Forest of Dean for the construction of a steam locomotive, which when trialled was reported to be successful. Stewart did not receive his expected reward and the two parties parted on bad terms. Stewart was 'obliged to abandon the engine to that Company'. In 1821,
7392-526: Was first used by William Jessop on a line that was opened as part of the Charnwood Forest Canal between Loughborough and Nanpantan in Leicestershire in 1789. This line was originally designed as a plateway on the Outram system, but objections were raised to laying rails with upstanding ledges or flanges on the turnpike . This difficulty was overcome by paving or "causewaying" the road up to
7480-444: Was generally established. Wheels tended to bind against the flange of the plate rail and mud and stones would build up. The manufacture of the rails themselves was gradually improved. By making them in longer lengths, the number of joints per mile was reduced. Joints were always the weakest part of the line. Another advance was the substitution of wrought iron for cast iron, though that material did not gain wide adoption until after
7568-416: Was likely deposited in pore space between grains, suggesting a high-energy depositional environment that removed carbonate mud. Recrystallized sparite is not diagnostic of depositional environment. Limestone outcrops are recognized in the field by their softness (calcite and aragonite both have a Mohs hardness of less than 4, well below common silicate minerals) and because limestone bubbles vigorously when
7656-399: Was not the originator. This type of rail was known as the plate-rail, tramway-plate or way-plate, names that are preserved in the modern term " platelayer " applied to the workers who lay and maintain the permanent way . The wheels of flangeway wagons were plain, but they could not operate on ordinary roads as the narrow rims would dig into the surface. Another form of rail, the edge rail ,
7744-545: Was used by individual operators, vehicles would vary greatly in wheel spacing ( gauge ) and the plate rail coped better. In South Wales again, where in 1811 the railways were connected with canals, collieries, ironworks, and copper works, and had a total length of nearly 150 miles (241 km), the plateway was almost universal. But in the North of England and in Scotland the edge-rail was held in greater favor, and soon its superiority
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