Whitewater kayaking is the sport of paddling a kayak on a moving body of water a whitewater river. Whitewater kayaking can range to demanding, extreme whitewater. Paddling on rivers and oceans is as old as the Stone Age; the raft, the catamaran, the canoe and the kayak evolved depending on the needs and environment of the indigenous peoples in different parts of the world. The modern day kayak most originated about 8,000 years ago along the Siberian coast line by the Yupik and transformed from the open canoe, via the Aleut and Inuit, into an enclosed kayak; the first boats made were hard to sink because they contained inflated seal bladders, which made them ideal for navigating whitewater. The Greek, Herodotus, 484-425 BC, wrote in his travel diaries about boats with which merchandise was brought from Armenia to Babylon; the boats were made of a wooden framework, covered with animal skins. Mules hauled the precious skins back to Armenia; the Russian, Grigori Ivanovitch Langsdorff, reported from his trip around the world on the ease and elegance of paddling Eskimo kayaks/canoes.
The Scot, John MacGregor, came back from his North American trip full of excitement about the kayak/canoe and in 1860 started building six boats that resembled Eskimo canoes/kayaks, weighing app. 80 lb. In 1866 he published the book A Thousand Miles in the Rob Roy Canoe; the timing was right and the book became a resounding success. With the Industrial Revolution leading to more leisure time in the middle of the 19th century, people in Europe started to enjoy floating down rivers in all kinds of contraptions taking in nature only available to a selected few. 1905, Alfred Heurich, an architectural student from Leipzig, invented the "Faltboot", a folding kayak called Folboat in the US. Heurich went on to paddle over 100,000 km on lakes. 1907, Alfred Klepper, a master seamster from Rosenheim, bought the patent, improved the rigidity with a lever system and started production. Born was the Western culture's invention of a paddle craft that for the first time in human history that allowed hardy enthusiasts to see wild river sections and canyons never before seen by the human eye.
The design made it not only suitable for whitewater but easy to travel with and affordable. World War I stopped any progress. 1920s, boating on WW with Folboats developed. Boaters flocked to lakes by train or bus. During that time, the Austrian, Edi Hans Pawlata reinvented the Eskimo roll. 1927, Franz von Alber, Klaus and Arndt von Rautenfeld, claimed to have independently developed a roll with their sea kayaks. Early 1930s, Walter Frentz, Herbert Rittlinger and a handful of others became pioneers and advocates of WW kayaking with documentaries and books. 1933, Adolf Hitler started to dissolve kayak clubs. They did not serve his plan and the impact on the sport was devastating. World War II brought the paddle sport to a total halt.1946/48, Depending on the region, the Allies lifted the ban on river travel in Germany. Paddle clubs were again allowed to form. 1952, Walter Frentz, published an inspiring book In den Schluchten Europas. The book was based on his river trips prior to World War II. Publications in those days told great stories with awesome pictures of first descents but with little information regarding river conditions.
The tough times of the post war era had come to an end and people traveled abroad again looking for adventures with Folboats and canoes. 1955, Herbert Baschin in Stuttgart built the first polyester/fiber kayak. Despite the much improved maneuverability and material, Baschin’s hard shell was received with skepticism by paddle sport enthusiasts who were in love with their folboats and depended on public transportation; the ice broke. The hard shell kayak was hauled to rivers and remote put-ins that were not accessible before. In the late 60s the WW sport started from Europe to spread around the world and transformed from adventure trips into a hardcore sport. With it came safety consciousness and protective gear. 1973, Tom Johnson, a racer and trainer from Kernville, California designs and markets the Hollowform: the first roto-molded polyethylene boat. It was mass-produced by a garbage can manufacturing company; these indestructible boats revolutionized the sport, took off in California. Paddlers no longer had to repair their boats during and after trips.
They began to be able to use rocks as part of the strategy of negotiating difficult rapids. Hard runs became more accessible to less-skilled paddlers. In 1978, Bill Masters, a kayaker and inventor in Liberty SC further perfected rotational molding for kayaks with his company Perception Kayaks. Bill advanced the sport of whitewater kayaking beyond any of his predecessors through consistent innovations in manufacturing and design, his patented processes are still used to this day. 1980 the manufacturer Prijon in Rosenheim introduced polyethylene to Europe which made WW boating maintenance and repair free in giant contrast to the Faltboot which had started it all. 1980 Holger Machatschek, together with ESKIMO kayak company in Landsberg, developed the first 2.2 m playboat called Topolino which galvanized kayaking into many new and exciting forms of extreme sports. There are five "sub-categories" in whitewater kayaking: Riverrunning is the essential - and some would say most artful - form of kayaking.
Whereas its derivative forms have evolved in response to the challenges posed by riverrunning, such as pushing the levels of
Nashville is the capital and most populous city of the U. S. state of Tennessee. The city is located on the Cumberland River; the city's population ranks 24th in the U. S. According to 2017 estimates from the U. S. Census Bureau, the total consolidated city-county population stood at 691,243; the "balance" population, which excludes semi-independent municipalities within Davidson County, was 667,560 in 2017. Located in northern Middle Tennessee, Nashville is the main core of the largest metropolitan area in Tennessee; the 2017 population of the entire 14-county Nashville metropolitan area was 1,903,045. The 2017 population of the Nashville—Davidson–Murfreesboro–Columbia combined statistical area, a larger trade area, was 2,027,489. Named for Francis Nash, a general of the Continental Army during the American Revolutionary War, the city was founded in 1779; the city grew due to its strategic location as a port and railroad center. Nashville seceded with Tennessee during the American Civil War and in 1862 became the first state capital to fall to Union troops.
After the war the city developed a manufacturing base. Since 1963, Nashville has had a consolidated city-county government, which includes six smaller municipalities in a two-tier system; the city is governed by a mayor, a vice-mayor, a 40-member metropolitan council. Reflecting the city's position in state government, Nashville is home to the Tennessee Supreme Court's courthouse for Middle Tennessee. Nashville is a center for the music, publishing, private prison and transportation industries, is home to numerous colleges and universities such as Tennessee State University, Vanderbilt University, Belmont University, Fisk University, Lipscomb University. Entities with headquarters in the city include Asurion, Bridgestone Americas, Captain D's, CoreCivic, Dollar General, Hospital Corporation of America, LifeWay Christian Resources, Logan's Roadhouse, Ryman Hospitality Properties; the town of Nashville was founded by James Robertson, John Donelson, a party of Overmountain Men in 1779, near the original Cumberland settlement of Fort Nashborough.
It was named for the American Revolutionary War hero. Nashville grew because of its strategic location, accessibility as a port on the Cumberland River, a tributary of the Ohio River. By 1800, the city had 345 residents, including 136 enslaved African Americans and 14 free African-American residents. In 1806, Nashville was incorporated as a city and became the county seat of Davidson County, Tennessee. In 1843, the city was named as the permanent capital of the state of Tennessee; the city government of Nashville owned 24 slaves by 1831, 60 prior to the war. They were "put to work to build the first successful water system and maintain the streets." The cholera outbreak that struck Nashville in 1849–1850 took the life of former U. S. President James K. Polk. There were 311 deaths from cholera in 1849 and an estimated 316 to about 500 in 1850. By 1860, when the first rumblings of secession began to be heard across the South, antebellum Nashville was a prosperous city; the city's significance as a shipping port made it a desirable prize as a means of controlling important river and railroad transportation routes.
In February 1862, Nashville became the first state capital to fall to Union troops. The state was occupied by Union troops for the duration of the war; the Battle of Nashville was a significant Union victory and the most decisive tactical victory gained by either side in the war. Afterward, the Confederates conducted a war of attrition, making guerrilla raids and engaging in small skirmishes, with the Confederate forces in the Deep South constantly in retreat. In 1868, a few years after the Civil War, the Nashville chapter of the Ku Klux Klan was founded by Confederate veteran John W. Morton. Chapters of this secret insurgent group formed throughout the South. In 1873 Nashville suffered another cholera epidemic, as did towns throughout Sumner County along railroad routes and the Cumberland River. Meanwhile, the city had reclaimed its important shipping and trading position and developed a solid manufacturing base; the post–Civil War years of the late 19th century brought new prosperity to Nashville and Davidson County.
These healthy economic times left the city with a legacy of grand classical-style buildings, including the Parthenon in Centennial Park, near downtown. On April 30, 1892, Ephraim Grizzard, an African-American man, was lynched in a spectacle murder in front of a white mob of 10,000 in Nashville, his lynching was described by journalist Ida B. Wells as: "A naked, bloody example of the blood-thirstiness of the nineteenth century civilization of the Athens of the South." From 1877 to 1950, a total of six lynchings of blacks were conducted in Davidson County, most in the county seat of Nashville near the turn of the century. By the turn of the century, Nashville had become the cradle of the Lost Cause of the Confederacy, as the first chapter of the United Daughters of the Confederacy was founded here and the Confederate Veteran magazine was published here. Most "guardians of the Lost Cause" lived near Centennial Park. At the same time, Jefferson Street became the historic center of the African-American community.
It remained so until the federal government s
Carding is a mechanical process that disentangles and intermixes fibres to produce a continuous web or sliver suitable for subsequent processing. This is achieved by passing the fibers between differentially moving surfaces covered with card clothing, it breaks up locks and unorganised clumps of fibre and aligns the individual fibers to be parallel with each other. In preparing wool fibre for spinning, carding is the step; the word is derived from the Latin carduus meaning thistle or teasel, as dried vegetable teasels were first used to comb the raw wool. These ordered fibres can be passed on to other processes that are specific to the desired end use of the fibre: Cotton, felt, woollen or worsted yarn, etc. Carding can be used to create blends of different fibres or different colours; when blending, the carding process combines the different fibres into a homogeneous mix. Commercial cards have rollers and systems designed to remove some vegetable matter contaminants from the wool. Common to all carders is card clothing.
Card clothing is made from a sturdy flexible backing in which spaced wire pins are embedded. The shape, length and spacing of these wire pins are dictated by the card designer and the particular requirements of the application where the card cloth will be used. A version of the card clothing product developed during the latter half of the 19th century and found only on commercial carding machines, whereby a single piece of serrated wire was wrapped around a roller, became known as metallic card clothing. Carding machines are known as cards. Fibre may be carded by hand for hand spinning. Science historian Joseph Needham ascribes the invention of bow-instruments used in textile technology to India; the earliest evidence for using bow-instruments for carding comes from India. These carding devices, called kaman and dhunaki, would loosen the texture of the fibre by the means of a vibrating string. At the turn of the eighteenth century, wool in England was being carded using pairs of hand cards, it was a two-stage process:'working' with the cards opposed and'stripping' where they are in parallel.
In 1748 Lewis Paul of Birmingham, invented two hand driven carding machines. The first used a coat of wires on a flat table moved by foot pedals; this failed. On the second, a coat of wire slips was placed around a card, wrapped around a cylinder. Daniel Bourn obtained a similar patent in the same year, used it in his spinning mill at Leominster, but this burnt down in 1754; the invention was developed and improved by Richard Arkwright and Samuel Crompton. Arkwright's second patent for his carding machine was subsequently declared invalid because it lacked originality. From the 1780s, the carding machines were set up in mills in the north of mid-Wales. Priority was given to cotton but woollen fibres were being carded in Yorkshire in 1780. With woollen, two carding machines were used: the first or the scribbler opened and mixed the fibres, the second or the condenser mixed and formed the web; the first in Wales was in a factory at Dolobran near Meifod in 1789. These carding mills produced yarn for the Welsh flannel industry.
In 1834 James Walton invented the first practical machines to use a wire card. He patented this machine and a new form of card with layers of cloth and rubber; the combination of these two inventions became the standard for the carding industry, using machines first built by Parr and Walton in Ancoats, from 1857 by Jams Walton & Sons at Haughton Dale. By 1838, the Spen Valley, centred on Cleckheaton had at least 11 card clothing factories and by 1893, it was accepted as the card cloth capital of the world, though by 2008 only two manufacturers of metallic and flexible card clothing remained in England, Garnett Wire Ltd. dating back to 1851 and Joseph Sellers & Son Ltd established in 1840. Baird from Scotland took carding to Massachusetts in the 1780s. In the 1890s, the town produced one-third of all machine cards in North America. John and Arthur Slater, from Saddleworth went over to work with Slater in 1793. A 1780s scribbling mill would be driven by a water wheel. There were 170 scribbling mills around Leeds at that time.
Each scribbler would require 15–45 horsepower to operate. Modern machines are driven by belting from an overhead shaft via two pulleys. Carding: the fibres are separated and assembled into a loose strand at the conclusion of this stage; the cotton comes off of the picking machine in laps, is taken to carding machines. The carders line up the fibres nicely to make them easier to spin; the carding machine consists of one big roller with smaller ones surrounding it. All of the rollers are covered with small teeth, as the cotton progresses further on the teeth get finer; the cotton leaves the carding machine in the form of a sliver. In a wider sense carding can refer to the four processes of willowing, lapping and drawing. In willowing the fibers are loosened. In lapping the dust is removed to create a flat lap of fibres. In drawing a drawing frame combines 4 slivers into one. Repeated drawing increases the quality of the sliver allowing for finer counts to be spun; each sliver will have thin and thick spots, by combining several slivers together a more consistent size can be reached.
Since combining several slivers produces a thick rope of cotton fibres, directly after being
A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but provide water for activities such as irrigation, human consumption, industrial use and navigability. Hydropower is used in conjunction with dams to generate electricity. A dam can be used to collect water or for storage of water which can be evenly distributed between locations. Dams serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions; the earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC. The word dam can be traced back to Middle English, before that, from Middle Dutch, as seen in the names of many old cities; the first known appearance of dam occurs in 1165. However, there is one village, mentioned in 1120; the word seems to be related to the Greek word taphos, meaning "grave" or "grave hill". So the word should be understood as "dike from dug out earth".
The names of more than 40 places from the Middle Dutch era such as Amsterdam and Rotterdam bear testimony to the use of the word in Middle Dutch at that time. Early dam building took place in the Middle East. Dams were used to control the water level, for Mesopotamia's weather affected the Tigris and Euphrates rivers; the earliest known dam is the Jawa Dam in Jordan, 100 kilometres northeast of the capital Amman. This gravity dam featured an 9-metre-high and 1 m-wide stone wall, supported by a 50 m-wide earth rampart; the structure is dated to 3000 BC. The Ancient Egyptian Sadd-el-Kafara Dam at Wadi Al-Garawi, located about 25 km south of Cairo, was 102 m long at its base and 87 m wide; the structure was built around 2800 or 2600 BC as a diversion dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards. During the Twelfth Dynasty in the 19th century BC, the Pharaohs Senosert III, Amenemhat III and Amenemhat IV dug a canal 16 km long linking the Fayum Depression to the Nile in Middle Egypt.
Two dams called Ha-Uar running east-west were built to retain water during the annual flood and release it to surrounding lands. The lake called "Mer-wer" or Lake Moeris is known today as Birket Qarun. By the mid-late third millennium BC, an intricate water-management system within Dholavira in modern-day India was built; the system included 16 reservoirs and various channels for collecting water and storing it. One of the engineering wonders of the ancient world was the Great Dam of Marib in Yemen. Initiated somewhere between 1750 and 1700 BC, it was made of packed earth – triangular in cross section, 580 m in length and 4 m high – running between two groups of rocks on either side, to which it was linked by substantial stonework. Repairs were carried out during various periods, most important around 750 BC, 250 years the dam height was increased to 7 m. After the end of the Kingdom of Saba, the dam fell under the control of the Ḥimyarites who undertook further improvements, creating a structure 14 m high, with five spillway channels, two masonry-reinforced sluices, a settling pond, a 1,000 m canal to a distribution tank.
These extensive works were not finalized until 325 AD and allowed the irrigation of 25,000 acres. Eflatun Pınar is a Hittite spring temple near Konya, Turkey, it is thought to be from the time of the Hittite empire between the 15th and 13th century BC. The Kallanai is constructed of unhewn stone, over 300 m long, 4.5 m high and 20 m wide, across the main stream of the Kaveri river in Tamil Nadu, South India. The basic structure dates to the 2nd century AD and is considered one of the oldest water-diversion or water-regulator structures in the world, still in use; the purpose of the dam was to divert the waters of the Kaveri across the fertile delta region for irrigation via canals. Du Jiang Yan is the oldest surviving irrigation system in China that included a dam that directed waterflow, it was finished in 251 BC. A large earthen dam, made by Sunshu Ao, the prime minister of Chu, flooded a valley in modern-day northern Anhui province that created an enormous irrigation reservoir, a reservoir, still present today.
Roman dam construction was characterized by "the Romans' ability to plan and organize engineering construction on a grand scale." Roman planners introduced the then-novel concept of large reservoir dams which could secure a permanent water supply for urban settlements over the dry season. Their pioneering use of water-proof hydraulic mortar and Roman concrete allowed for much larger dam structures than built, such as the Lake Homs Dam the largest water barrier to that date, the Harbaqa Dam, both in Roman Syria; the highest Roman dam was the Subiaco Dam near Rome. Roman engineers made routine use of ancient standard designs like embankment dams and masonry gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the other basic dam designs, unknown until then; these include arch-gravity dams, arch dams, buttress dams and multiple arch buttress dams, all of which were known and employed by the 2nd century AD. Roman workforces were the first to build dam bridges, such as the Bridge of Valerian in Iran
Historic districts in the United States
Historic districts in the United States are designated historic districts recognizing a group of buildings, properties, or sites by one of several entities on different levels as or architecturally significant. Buildings, structures and sites within a historic district are divided into two categories and non-contributing. Districts vary in size: some have hundreds of structures, while others have just a few; the U. S. federal government designates historic districts through the United States Department of Interior under the auspices of the National Park Service. Federally designated historic districts are listed on the National Register of Historic Places, but listing imposes no restrictions on what property owners may do with a designated property. State-level historic districts may follow similar criteria or may require adherence to certain historic rehabilitation standards. Local historic district designation offers, by far, the most legal protection for historic properties because most land use decisions are made at the local level.
Local districts are administered by the county or municipal government. The first U. S. historic district was established in Charleston, South Carolina in 1931, predating the U. S. federal government designation by more than three decades. Charleston city government designated an "Old and Historic District" by local ordinance and created a board of architectural review to oversee it. New Orleans followed in 1937, establishing the Vieux Carré Commission and authorizing it to act to maintain the historic character of the city's French Quarter. Other localities picked up on the concept, with the city of Philadelphia enacting its historic preservation ordinance in 1955; the regulatory authority of local commissions and historic districts has been upheld as a legitimate use of government police power, most notably in Penn Central Transportation Co. v. City of New York; the Supreme Court case validated the protection of historic resources as "an permissible governmental goal." In 1966 the federal government created the National Register of Historic Places, soon after a report from the U.
S. Conference of Mayors had stated Americans suffered from "rootlessness." By the 1980s there were thousands of federally designated historic districts. Some states, such as Arizona, have passed referendums defending property rights that have stopped private property being designated historic without the property owner's consent or compensation for the historic overlay. Historic districts are two types of properties and non-contributing. Broadly defined, a contributing property is any property, structure or object which adds to the historical integrity or architectural qualities that make a historic district, listed locally or federally, significant. Different entities governmental, at both the state and national level in the United States, have differing definitions of contributing property but they all retain the same basic characteristics. In general, contributing properties are integral parts of the historic context and character of a historic district. In addition to the two types of classification within historic districts, properties listed on the National Register of Historic Places are classified into five broad categories.
They are, structure, site and object. All but the eponymous district category are applied to historic districts listed on the National Register. A listing on the National Register of Historic Places is governmental acknowledgment of a historic district. However, the Register is "an honorary status with some federal financial incentives." The National Register of Historic Places defines a historic district per U. S. federal law, last revised in 2004. According to the Register definition a historic district is: a geographically definable area, urban or rural, possessing a significant concentration, linkage, or continuity of sites, structures, or objects united by past events or aesthetically by plan or physical development. A district may comprise individual elements separated geographically but linked by association or history. Districts established under U. S. federal guidelines begin the process of designation through a nomination to the National Register of Historic Places. The National Register is the official recognition by the U.
S. government of cultural resources worthy of preservation. While designation through the National Register does offer a district or property some protections, it is only in cases where the threatening action involves the federal government. If the federal government is not involved the listing on the National Register provides the site, property or district no protections. For example, if company A wants to tear down the hypothetical Smith House and company A is under contract with the state government of Illinois the federal designation would offer no protections. If, company A was under federal contract the Smith House would be protected. A federal designation is little more than recognition by the government that the resource is worthy of preservation. In general, the criteria for acceptance to the National Register are applied but there are considerations for exceptions to the criteria and historic districts have influence on some of those exceptions; the National Register does not list religious structures, moved structures, reconstructed structures, or properties that have achieved significance within the last 50 years.
However, if a property falls into one of those categories and are "integral parts of districts that do meet the criteria" an exception allowing their listing will be made. Historic dis
Rock Island, Tennessee
Rock Island is an unincorporated community in the northeastern-most portion of Warren County, United States. The town is named after an island on the Caney Fork River just below the confluence of the Rocky River. Rock Island is home to Rock Island State Park. Many different houses and marinas can be found here. Rock Island is a popular destination during the summer season, it is known for scenic bluffs. Boats can be seen on the river riding by; the state park offers many different hiking trails as well as a sand bar. The Chickamauga Path, which spanned Middle Tennessee north-to-south, connecting the area with Kentucky and Alabama, forded the Caney Fork at a large rock island; this path became the Old Kentucky Road, which parallels the modern State Route 136. Another trail, known as the Black Fox Trail, passed east-to-west just south of Rock Island. In 1793, in the latter part of the Cherokee–American wars, a skirmish was fought at Rock Island between a small contingent of soldiers pursuing several Chickamaugas, who had stolen horses.
The Tennessee historian J. G. M. Ramsey reported: pursued them to a large camp near the Rock Island ford of the Cany Fork, where he took much spoils. Evening coming on, he withdrew from the camp, about a mile, to an eminence, where he halted his men, they lay on their arms all night." The Chickamauga were beaten back. Among the earliest settlers in Middle Tennessee settled at Rock Island in the late 1790s, they included Joseph Terry. In 1806, Rock Island became the county seat for the newly created White County and court was held in Terry's cabin; the new county encompassed all of what is now White and Warren Counties, parts of the counties of Cannon, Coffee, DeKalb, Grundy and Van Buren Counties. Rock Island was the county seat for three years. General John D. Rodgers, veteran of the War of 1812 and Seminole Wars owned a tavern and operated a ferry just above the island. Gen. Andrew Jackson presided over several sessions of the Tennessee Supreme Court here; the town by the river remained an important point along the Old Kentucky Road until the coming of the railroad in 1881.
Rock Island is home to Rock Island State Park & Great Falls Dam
A cofferdam is an enclosure built within, or in pairs across, a body of water to allow the enclosed area to be pumped out. This pumping creates a dry work environment for the work to be carried out. Enclosed coffers are used for construction or repair of permanent dams, oil platforms, bridge piers, et cetera, built within or over water; these cofferdams are welded steel structures, with components consisting of sheet piles and cross braces. Such structures are dismantled after the construction work is completed. For dam construction, two cofferdams are built, one upstream and one downstream of the proposed dam, after an alternative diversion tunnel or channel has been provided for the river flow to bypass the foundation area of the dam; these cofferdams are a conventional embankment dam of both earth- and rock-fill, but concrete or some sheet piling may be used. Upon completion of the dam and associated structures, the downstream coffer is removed and the upstream coffer is flooded as the diversion is closed and the reservoir begins to fill.
Depending on the geography of a dam site, in some applications, a "U"-shaped cofferdam is used in the construction of one half of a dam. When complete, the cofferdam is removed and a similar one is created on the opposite side of the river for the construction of the dam's other half; the cofferdam is used on occasion in the shipbuilding and ship repair industry, when it is not practical to put a ship in drydock for repair work or modernization. An example of such an application is the lengthening of ships. In some cases a ship is cut in two while still in the water, a new section of ship is floated in to lengthen the ship; the cutting of the hull is done inside a cofferdam attached directly to the hull of the ship. The cofferdam is replaced while the hull sections are welded together again; as expensive as this may be to accomplish, the use of a drydock might be more expensive. See caisson. A 100-ton open caisson, lowered more than a mile to the sea floor in attempts to stop the flow of oil in the Deepwater Horizon oil spill has been called a cofferdam.
It did not work. A cofferdam may refer to an insulating space between two watertight bulkheads or decks within a ship. A cofferdam can be a ballast space. Cofferdams are employed to ensure that oil or other chemicals do not leak into machinery spaces. If two different cargoes that react dangerously with each other are carried on the same vessel, one or more cofferdams are required between the cargo spaces. Portable cofferdams can be frame and fabric cofferdams that can be reused. Inflatable cofferdams are stretched across the site inflated with water from the prospected dry area. Frame and fabric cofferdams are covered with watertight fabric. Once the area is dry, water still remaining from the dry area can be siphoned over to the wet area. A device, used in dental medicine to isolate site of the treatment from the rest of oral cavity. See Dental dam Caisson, a similar watertight structure The dictionary definition of cofferdam at Wiktionary Nautical Terms at phrontistery.info Portable Cofferdam at phrontistery.info Temporary Cofferdam