SUMMARY / RELATED TOPICS

Limestone

Limestone is a carbonate sedimentary rock, composed of the skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate. A related rock is dolomite, which contains a high percentage of the mineral dolomite, CaMg2. In old USGS publications, dolomite was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolomites or magnesium-rich limestones. About 10% of sedimentary rocks are limestones; the solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses: as a building material, an essential component of concrete, as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, as a popular decorative addition to rock gardens.

Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as foraminifera; these organisms secrete shells made of aragonite or calcite, leave these shells behind when they die. Other carbonate grains composing limestones are ooids, peloids and extraclasts. Limestone contains variable amounts of silica in the form of chert or siliceous skeletal fragment, travertine. Secondary calcite may be deposited by supersaturated meteoric waters; this produces speleothems, such as stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance; the primary source of the calcite in limestone is most marine organisms. Some of these organisms can construct mounds of rock building upon past generations. Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone does not form in deeper waters. Limestones may form in lacustrine and evaporite depositional environments.

Calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors with weathered surfaces. Limestone may be crystalline, granular, or massive, depending on the method of formation. Crystals of calcite, dolomite or barite may line small cavities in the rock; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls.

Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the mountain building process, limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group. Two major classification schemes, the Folk and the 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 and cement; the Folk system uses two-part names. 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; the Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains. Robert J. Dunham published his system for limestone in 1962. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles.

Dunham names are for rock families. His work considers whether or not the grains were in mutual contact, 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 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, it adds some diagenetic patterns and can be summarized as follows: See: Carbonate platform About 10% of all sedimentary rocks are limestones. Limestone is soluble in acid, therefore forms many erosional landforms; these include limestone pavements, pot holes, cenotes and gorges. Such erosion landscapes are known as karsts. Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks, it is therefore associated with hills and downland, occurs

Representation of the People Act 1948

The Representation of the People Act 1948 was an Act of the Parliament of the United Kingdom that altered the law relating to parliamentary and local elections. It is noteworthy for abolishing plural voting, including by the abolition of the twelve separate university constituencies. Part I of the Act declared that in future the United Kingdom would be divided into single-member borough constituencies and county constituencies; these terms replaced the former designations of parliamentary borough/division of a parliamentary borough and parliamentary county/division of a parliamentary county. There were to be 613 such constituencies, in place of the 591 under previous legislation; these were to be the only constituencies, the Act thus abolished the university constituencies. Constituencies, represented by more than one MP were abolished. Persons eligible to vote were to be British subjects of "full age" and "not subject to any legal incapacity to vote", provided that they were registered to vote in the constituency.

Each voter was only permitted to cast a single vote in one constituency if for some reason they were registered in more than one. The arrangements which had given plural votes to electors who met a property qualification because of their business or shop premises were abolished; each constituency was to have an electoral registration officer, to compile the electoral register. In England and Wales, this officer was the clerk of the appropriate borough council. An electoral register was to be published in Autumn of each year. Qualifications for an elector to be registered were set out, with residence in the constituency on a specified date being the principal requirement. There was an additional "service qualification" for members of the armed forces and other persons outside the state on diplomatic or other Crown business, their spouses. Electors were to vote in person, except in exceptional circumstances in which a proxy vote might be permitted; each constituency was to be divided into polling districts by the registration officer, to designate polling places within each district.

Rules were laid down for the process: for instance each civil parish in an English or Welsh county constituency was to be a separate district. Where a group of thirty electors felt that they were not provided with a convenient polling place, they were entitled to petition the Secretary of State for a review; the procedures for recounts and for choosing the winning candidate by lot in the event of a tie were laid down. A candidate who received less than an eighth of the total number of votes cast would forfeit their monetary deposit. Part I dealt with the appointment and duties of the returning officer. In England and Wales these were to be either the high sheriff of a county, the sheriff of a county corporate, the mayor of a borough or the chairman of an urban district council, as appointed by the Home Secretary. In Scotland the returning officer was to be a sheriff of a local sheriffdom, in Northern Ireland the under-sheriff of a county or county borough; the electorate for local elections was larger than that for parliamentary elections.

Apart from those resident in the district, there was an additional "non-resident qualification" to vote where an owner or tenant occupied rateable land or premises therein of the yearly value of not less than ten pounds. The electoral registration officer appointed under Part I of the Act was to compile a local government register, although the two registers could be combined, with the names of those persons registered only as local government electors marked. Electors were not permitted to be registered more than once in a single local government district if they occupied multiple premises. There was no prohibition on voting in different local authority areas, however. Polling districts were to be delineated and polling places designated by the registration officer. In the absence of other arrangements these were to be identical to those used for parliamentary elections. Part III of the Act set new limits for the expenses that candidates were permitted to pay their election agent. In a county constituency this was to be plus 2d for each name in the electoral register.

Among other restrictions, no supporter of a candidate was permitted to use a motor vehicle to bring an elector to the polls, or to loan or rent such a vehicle to an elector, unless the vehicle was first registered with the returning officer. There was to be a limit of one vehicle per 1,500 electors in a county constituency and 2,500 in a borough constituency; the broadcast of any programme relating to an election on a radio station other than one operated by the British Broadcasting Corporation was prohibited. This prohibition extended to broadcasters outside the state; each candidate was allowed to send an election address to each elector post free, was entitled to the use of a room in a publicly funded school in which to hold meetings. Part IV altered the dates for the holding of local elections in Wales. County councillors were to be elected in the first week of April, all other councillors in the first week of May. All borough elections were to be held on the same day, set by the Home Secretary.

The date for other elections was to be set by the appropriate co

Misraq Este

Misraq Este is one of the woredas in the Amhara Region of Ethiopia. Part of the Debub Gondar Zone, Misraq Este is bordered on the south by the Abay River which separates it from the Misraq Gojjam Zone, on the west by Mirab Este and Dera, on the northwest by Fogera, on the north by Farta, on the northeast by Lay Gayint, on the east by Simada. Towns in Misraq Este include Mekane Yesus. Based on the 2007 national census conducted by the Central Statistical Agency of Ethiopia, this woreda has a total population of 210,825, of whom 107,555 are men and 103,270 women; the majority of the inhabitants practiced Ethiopian Orthodox Christianity, with 97.08% reporting that as their religion, while 2.91% of the population said they were Muslim