THE WHEEL ---
The English word "wheel" comes from the Proto-Indo-European *kwekwlo-, which meant "circle" and which was an extended form of the root *kwel- meaning "to revolve, move around, sojourn, dwell". This is also the root of the Greek "kuklos" and the Sanskrit "cakram", both meaning "circle" or "wheel". The Latin word "rota" comes from the Proto-Indo-European *rotā-, extended o-grade form of the root *ret- meaning "to roll, revolve".
Notably there are no macroscopic wheels in macroscopic animals or plants, though some animals can roll. Whether this is a case of human ingenuity topping nature's "blind ingenuity" is a continuing source of debate. It should, however, be noted that microscopic wheels do exist in nature such as in ATP synthaseand bacterial flagellum.
Most authorities regard the wheel as one of the oldest and most important inventions, which originated in ancient Mesopotamia (modern Iraq) in the 5th millennium BC, originally in the function of potter's wheels. The wheel reached India and Pakistan with the Indus Valley Civilization in the 3rd millennium BC. In China, the wheel is certainly present with the adoption of the chariot in ca. 1200 BC, and Barbieri-Low (2000) argues for earlier Chinese wheeled vehicles in, from maybe 2000 BC. The earliest depiction of what may be a wheeled vehicle (here a wagon -- four wheels, two axles), is on the Bronocice pot, a ca. 4000 BC clay pot excavated in southern Poland.
The wheel reached Europe and India (the Indus Valley civilization) in the 4th millennium BC. In China, the wheel is certainly present with the adoption of the chariot in ca. 1200 BC, and Barbieri-Low (2000) argues for earlier Chinese wheeled vehicles, circa 2000 BC. Whether there was an independent "invention of the wheel" in East Asia or whether the concept made its way there after jumping the Himalayan barrier remains an open question.
Although they did not develop the wheel proper, the Olmec and certain other western hemisphere cultures seem to have approached it, as wheel-like worked stones have been found on objects identified as children's toys dating to about 1500 BC.
The invention of the wheel thus falls in the late Neolithic and may be seen in conjunction with the other technological advances that gave rise to the early Bronze Age. Note that this implies the passage of several wheel-less millennia, even after the invention of agriculture. Looking back even further, it is of some interest that although paleoanthropologists now date the emergence of anatomically modern humans to ca. 150,000 years ago, 143,000 of those years were "wheel-less". That people with capacities fully equal to our own walked the earth for so long before conceiving of the wheel may be initially surprising, but populations were extremely small through most of this period and the wheel, which requires an axle and socket to be actually useful, is not so simple a device as it may seem.
Early wheels too were simple wooden disks with a hole for the axle. Note that because of the structure of wood a horizontal slice of a trunk is not suitable, as it does not have the structural strength to support weight without collapsing; rounded pieces of longitudinal boards are required. The oldest such wheel, believed to have been made by the Alekern tribe, was found by the Slovenian archeologist Dr. Anton Velušček and his team in 2002 at the Ljubljana Marshes (Ljubljansko barje), some 20 kilometres southeast of Ljubljana, Slovenia. According to the experts in Vienna, Austria, the specimen was manufactured somewhere between 3350 and 3100 BC and is even older than others of similar construction found in Switzerland and Germany.
The spoked wheel was invented more recently, and allowed the construction of lighter and swifter vehicles. The earliest known examples are in the context of the Andronovo culture, dating to ca 2000 BC. Shortly later, horse cultures of the Caucasus region used horse-drawn spoked-wheel war chariots for the greater part of three centuries. They moved deep into the Greek peninsula where they joined with the existing Mediterranean peoples to give rise, eventually, to classical Greece after the breaking of Minoan dominance and consolidations led by pre-classical Sparta and Athens. Celtic chariots introduced an iron rim around the wheel in the 1st millennium BC. The spoked wheel has been in continued use without major modification until the 1870s, when wire wheels and pneumatic tyres were invented .
The invention of the wheel has also been important for technology in general, important applications including the water wheel, the cogwheel (see also antikythera mechanism), the spinning wheel, the astrolabe or torquetum. More modern descendants of the wheel include the propeller, the jet engine, the flywheel (gyroscope) and the turbine.
The wheel has also become a strong cultural and spiritual metaphor for a cycle or regular repetition (see chakra, reincarnation, Yin and Yang among others). In the coat of arms of Panama a winged wheel is a symbol of progress.
In July 2001, the wheel was the object of an Australian "innovation patent" as a "circular transportation facilitation device". The innovation patent was obtained by John Keogh, a lawyer from Melbourne, Australia, with the declared intention of demonstrating flaws in the recently introduced innovation patent system. Innovation patents are intended for minor innovations that do not qualify as patentable inventions, and an innovation patent is not the same as a patent. Applications for innovation patents, like Mr. Keogh's wheel application, are not examined by IP Australia, the Australian Patent Office, before they are registered.
Mechanics and function --- : The wheel (with axle) is considered one of the simple machines and lies near the starting point of advanced human technology (advanced, that is, in comparison with even earlier mechanical innovations such as stone/bone knives and axes, tension-sprung projectiles, scoops and shovels).
When wheels are used in conjunction with axles, either the wheel turns on the axle or the axle turns in a vehicle (as in a cart) or a housing (as in a mill). The mechanics are the same in either case.
The low resistance to motion (compared to dragging) is explained as follows (refer to friction):
the normal force at the sliding interface is the same.
the sliding distance is reduced for a given distance of travel.
the coefficient of friction at the interface is usually lower.
Bearings are used to reduce friction at the interface.
Example:
If dragging a 100 kg object for 10 m along a surface with μ = 0.5, the normal force is 981 N and the work done (required energy) is (work=force x distance) 981 × 0.5 × 10 = 4905 joules.
Now give the object 4 wheels. The normal force between the 4 wheels and axles is the same (in total) 981 N, assume μ = 0.1, and say the wheel diameter is 1000 mm and axle diameter is 50 mm. So while the object still moves 10 m the sliding frictional surfaces only slide over each other a distance of 0.5 m. The work done is 981 x 0.1 x 0.5 = 49 joules.
Additional energy is lost at the wheel to road interface. This is termed rolling resistance which is predominantly a deformation loss.
OX-DRAWN PLOW ---
The plough (American spelling: plow) is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting. Ploughs are also used by industry underseas, for the laying of cables, as well as preparing the earth for side-scan sonar in a process used in oil exploration.
The plough can be regarded as a development of the pick, or of the spade. Ploughs were initially pulled by humans, later by oxen, and later still in some countries, by horses. Modern ploughs are, in industrialized countries, powered by tractors.
Ploughing has several beneficial effects. The major reason for ploughing is to turn over the upper layer of the soil. This may also incorporate the residue from the previous crop into the soil. Ploughing reduces the prevalence of weeds in the fields, and makes the soil more porous, easing later planting. Excessively deep ploughing or digging brings up subsoil and mixes subsoil with topsoil. This can damage the soil.
The early German word before sound-shift is plug and in Old Prussian plugis. After the German sound shift (p = pf) it became the modern German word Pflug.
History of the plough --- Pre-Industrial Revolution --- : When agriculture was first developed, simple hand held digging sticks or hoes would have been used in highly fertile areas, such as the banks of the Nile where the annual flood rejuvenates the soil, to create furrows wherein seeds could be sown. In order to regularly grow crops in less fertile areas, the soil must be turned to bring nutrients to the surface.
The domestication of oxen in Mesopotamia, perhaps as early as the 6th millennium BC, provided mankind with the pulling power necessary to develop the plough. The very earliest ploughs were simple scratch-ploughs and consisted of a frame holding a vertical wooden stick that was dragged through the topsoil.
These were much later developed into mouldboard ploughs (American spelling: moldboard) that turned the soil in one run across the field, depositing the weeds and undecomposed remains of the previous crop under the soil and raising the rain-percolated nutrients back to the surface. This plough also allowed for ploughing while the ground was wet. The water was drained due to channels formed under the overturned earth. Despite a number of innovations, the Romans never achieved the heavy wheeled mouldboard plow, the first linguistic evidence for the heavy wheeled moulded plow appears sometime before or in the 6th century with scattered Slavic groups.
The mouldboard, carried below the frame, is tipped with a share (also called a ploughshare), an asymmetric arrow-shaped device designed to slice through the ground horizontally as it moves forward. It also has a coulter, a sharpened blade or disc, attached to the frame of the plough to cut down through the ground, ahead of the share, and also to cut deepset and tough roots. A runner extending from behind the share to the rear of the plough controls the direction of the plough, because it is held against the bottom land-side corner of the new furrow being formed. The holding force is the weight of the sod, as it is raised and rotated, on the curved surface of the moldboard. Because of this runner, the mouldboard plough is harder to turn around than the scratch plough, and its introduction brought about a change in the shape of fields -- from mostly square fields into longer rectangular "strips" (hence the introduction of the furlong).
The Girard (or Gerard) plough was developed in the early 14th century in what is now Belgium by Girard de Liege. It was the first plough design to encompass the use of an iron blade.
The first commercially successful iron plough was the Rotherham plough, developed by Joseph Foljambe in Rotherham, England, in 1730. It was durable and light, and was engineered after the mathematical principles of James Small, who designed a mouldboard that would cut, lift and turn over the strip of earth. (All the major components of the Rotherham plough had been well known in China for millennia, and diffusion of technology from China, probably by the Dutch, is highly likely).
Post-Industrial Revolution --- : Steel ploughs were developed during the Industrial Revolution and were lighter and more durable than ploughs made of iron or wood. The cast-steel plough was developed by U.S. blacksmith John Deere in the 1830s. By this time the hitch, to the draught animals, was adjustable so that the wheel at the front was held onto the ground. The first steel ploughs were walking ploughs, having two handles held by the ploughman to provide a degree of control over the depth and location of the furrow behind the draughting force. The ploughman often was also controlling the draught animal(s). Riding ploughs with wheels and a seat for the operator came later, and often had more than one share.
A single draught horse can normally pull a single-furrow plough in clean, light, soil but in heavier soils two animals are needed, one walking on the land and one in the furrow. For ploughs with two or more furrows, one or more horses have to walk on the loose, ploughed, sod -- and that makes hard going for them. It is usual to rest such animals every half hour for about ten minutes.
Steam Ploughing
The advent of the steam tractor allowed steam engines to pull ploughs. In Europe, counterbalanced wheeled units were drawn by cables across the fields by pairs of Fowler engines. In America the firm soil of the Plains allowed direct pulling with big Case, Reeves or Sawyer Massey breaking engines. Gang plows of up to 14 bottoms were used. Often these big ploughs were used in regiments of engines, so that there would be ten steamers each drawing a plough. In this way hundreds of acres could get turned over in a day. Only steam engines had the power to draw the big units. When gas engines appeared, they had neither the strength nor the ruggedness compared to the big steamers. Only by reducing the number of shares did the work get done.
The Stump-jump plough is an Australian invention of the 1870s, designed to cope with the breaking up of new farming land, that contains many tree stumps and rocks that would be very expensive to remove from paddocks. The plough uses a moveable weight to hold the ploughshare in position. When a tree stump or other obstruction such as a rock is encountered, the ploughshare is thrown upwards, clear of the obstacle, to avoid breaking the harness or linkage of the whole plough; ploughing can be continued when the weight is returned to the earth after the obstacle is passed.
A simpler system, developed later, uses a concave disk (or a pair of them) set at a large angle to the direction of progress, that uses the concave shape to hold the disk into the soil -- unless something hard strikes the circumference of the disk, causing it to roll up and over the obstruction. As the arrangement is dragged forward, the sharp edge of the disk cuts the soil, and the concave surface of the rotating disk lifts and throws the soil to the side. It doesn't make as good a job as the mouldboard plough (but this is not considered a disadvantage, because it helps fight the wind erosion), but it does lift and break up the soil.
IRRIGATION SYSTEM ---
Irrigation is the replacement or supplementation of rainfall with water from another source in order to grow crops or plants. In contrast, agriculture that relies only on direct rainfall is sometimes referred to as dryland farming.
Overview --- : The water source for irrigation may be a nearby or distant body of lake or frozen water such as a river, spring, lake, aquifer, well, or snowpack. Depending on the distance of the source and the seasonality of rainfall, the water may be channelled directly to the agricultural fields or stored in reservoirs or cisterns for later use. In addition, the "harvesting" of local rain that falls on the roofs of buildings or on nearby unfarmed hills and its use to supplement the rain that falls directly on farmed fields also involves irrigation.
Various types of irrigation techniques differ in how the water obtained from the source is distributed within the field. In general, the goal is to supply the entire field uniformly with water, so that each plant has the amount of water it needs, neither too much nor too little.
Types of irrigation --- Flood irrigation --- : Ditches, furrows, and basins may be dug with hand tools, turned with a plow pulled by an animal or tractor, or precisely fashioned using laser-guided instruments depending on economic and physical factors such as the size of the field, the types of technology available, and the cost of manpower. Plants are grown in raised beds, listed rows, drilled or planted into flat basins. Water may be distributed throughout the field via canals, unlined ditches, or furrows, between the rows or beds by use of rigid gated plastic or aluminum water pipe, layflat plastic with holes punched at each furrow, concrete or plastic lined ditches, or unlined ditches.
Where ditches are used, siphon tubes move water from the main ditch to the furrow. When pipes are used, water flow can be controlled by turning it on or off at the local source or by using automatic or manually controlled gates to transfer it from one set of ditches to another. Unless the field is small or very level, parts of it may suffer from water-logging while other parts may be too dry. Depending on heat, wind, and soil permeability, much water may be lost before it can benefit the plants. Automatic valves, also known as surge valves, can increase the efficiency of furrow irrigation because they alternately wet the furrows and allow the soil infiltration rate to slow prior to using the furrow for actual irrigation.
Once common in the United States, many surface irrigation systems have been replaced because of high labor costs and increasing demands on water resources. Surface irrigation also has a tendency to raise the water table in some areas and cause soil salination, requiring drainage. These types of systems are still common in other parts of the world.
Overhead (sprinkler) irrigation --- : In overhead or sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns or by lower-pressure sprays. A system utilizing sprinklers, sprays, or guns mounted overhead on permanently installed risers is often referred to as a solid-set irrigation system. Some sprinklers can also be hidden below ground level, if aesthetics is a concern, and pop up in response to increased water pressure. This type of system is commonly used in lawns, golf courses, cemeteries, parks, and other turf areas.
Sprinklers that spray in a fixed pattern are generally called sprays or spray heads. Sprays are not usually designed to operate at pressures above 30 lbf/in² (200 kPa), due to misting problems that may develop. Higher pressure sprinklers that rotate are called rotors and are driven by a ball drive, gear drive, or impact mechanism. Rotors can be designed to rotate in a full or partial circle. Guns are similar to rotors, except that they generally operate at very high pressures of 40 to 130 lbf/in² (275 to 900 kPa) and flows of 50 to 1200 US gal/min (3 to 76 L/s), usually with nozzle diameters in the range of 0.5 to 1.9 inches (10 to 50 mm). Guns are used not only for irrigation, but also for industrial applications such as dust suppression and logging.
Sprinklers may also be mounted on movable platforms connected to the water source by a hose. Automatically moving wheeled systems known as travelers may irrigate large areas such as small farms, sports fields, and cemeteries unattended. Some of these utilize a length of polyethylene tubing wound on a steel drum. As the traveler is pulled across the field, the hose is wound onto the drum by water pressure or a powered engine. Other travelers use a flat rubber hose that is dragged along behind. At the low tech end, such as in a small greenhouse or landscape, a person may be watering each plant individually with a hose end sprinkler or even a watering can.
One drawback of overhead irrigation is that much water can be lost because of high winds or evaporation, and irrigating the entire field uniformly can be difficult or tedious if the system is not properly designed. Water remaining on plants' leaves may promote fungal and other diseases. If fertilizers are included in the irrigation water, plant leaves can be burned, especially on hot, sunny days.
Overhead irrigation is generally the best solution for watering lawns and golf courses, although drip irrigation is gaining in popularity in some lawn applications. (See also center pivot irrigation.)
Manually assembled systems of piping that are broken down to permit tillage and harvesting are sometimes called "hand set" or "hand move pipe". These are also commonly used on athletic fields where permanently installed sprinklers or outlets are not desired or where low initial costs are a factor.
Center pivot irrigation --- : Center pivot irrigation is a form of overhead irrigation consisting of several segments of pipe (usually galvanized steel or aluminum) joined together and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length. The system moves in a circular pattern and is fed with water from the pivot point at the center of the arc. These systems are common in parts of the United States where terrain is flat.
Most center pivot systems now have drops hanging from a u-shaped pipe called a gooseneck attached at the top of the pipe with sprinkler heads that are positioned a few feet (at most) above the crop, thus limiting evaporative losses. Drops can also be used with drag hoses or bubblers that deposit the water directly on the ground between crops. The crops are planted in a circle to conform to the center pivot. This type of system is known as LEPA (Low Energy Precision Application).
Originally, most center pivots were water powered. These were replaced by hydraulic systems (T-L) and electric motor driven systems (Lindsay, Reinke, Valley, Zimmatic). Most systems today are driven by an electric motor mounted low on each span. This drives a reduction gearbox and transverse driveshafts transmit power to another reduction gearbox mounted behind each wheel. Reinke sprinklers have strobe lights when running. Valleys have regular lights. Reinke sprinklers are kind of red covered. Most new sprinklers are Zimmatics with drops.
Center pivot equipment can also be configured to move in a straight line, where the water is pulled from a central ditch. In this scenario, the system is called a linear move irrigation system.
Lateral move (Side roll, Wheel line) irrigation --- : A series of pipes, each with a wheel of about 1.5 m diameter permanently affixed to its midpoint and sprinklers along its length, are coupled together at one edge of a field. Water is supplied at one end using a large hose. After sufficient water has been applied, the hose is removed and the remaining assembly rotated either by hand or with a purpose-built mechanism, so that the sprinklers move 10m across the field. The hose is reconnected. The process is repeated until the opposite edge of the field is reached.
This system is less expensive to install than a center pivot, but much more labor intensive to operate, and it is limited in the amount of water it can carry. Most systems utilize 4 or 5 inch diameter aluminum pipe. One feature of a lateral move system is that it consists of sections that can be easily disconnected. They are most often used for small or oddly-shaped fields, such as those found in hilly or mountainous regions, or in regions where labor is inexpensive.
Drip, or trickle irrigation --- :Water is delivered at or near the root zone of plants, drop by drop. This type of system can be the most water-efficient method of irrigation, if managed properly, since evaporation and runoff are minimized. In modern agriculture, drip irrigation is often combined with plastic mulch, further reducing evaporation, and is also the means of delivery of fertilizer. The process is known as fertigation.
Deep percolation, where water moves below the root zone, can occur if a drip system is operated for too long of a duration or if the delivery rate is too high. Drip irrigation methods range from very high-tech and computerized to low-tech and relatively labor-intensive. Lower water pressures are usually needed than for most other types of systems, with the exception of low energy center pivot systems and surface irrigation systems, and the system can be designed for uniformity throughout a field or for precise water delivery to individual plants in a landscape containing a mix of plant species. Although it is difficult to regulate pressure on steep slopes, pressure compensating emitters are available, so the field does not have to be level. High-tech solutions involve precisely calibrated emitters located along lines of tubing that extend from a computerized set of valves. Both pressure regulation and filtration to remove particles are important. The tubes are usually black (or buried under soil or mulch) to prevent the growth of algae and to protect the polyethylene from degradation due to ultraviolet light. But drip irrigation can also be as low-tech as a porous clay vessel sunk into the soil and occasionally filled from a hose or bucket. Subsurface drip irrigation has been used successfully on lawns, but it is more expensive than a more traditional sprinkler system. Surface drip systems are not cost-effective (or aesthetically pleasing) for lawns and golf courses.
Subirrigation --- : Subirrigation also sometimes called seepage irrigation has been used for many years in field crops in areas with high water tables. It is a method of artificially raising the water table to allow the soil to be moistened from below the plants' root zone.
Subirrigation is also used in commercial greenhouse production, usually for potted plants. Water is delivered from below, absorbed upwards, and the excess collected for recycling. Typically, a solution of water and nutrients floods a container or flows through a trough for a short period of time, 10-20 minutes, and is then pumped back into a holding tank for reuse. Subirrigation in greenhouses requires fairly sophisticated, expensive equipment and management. Advantages are water and nutrient conservation, and labor-saving through lowered system maintenance and automation. It is similar in principle and action to subsurface drip irrigation.
How an irrigation system works ---
Most commercial and residential irrigation systems are "in ground" systems, which means that everything is buried in the ground. With the pipes, sprinklers, and irrigation valves being hidden, it makes for a cleaner, more presentable landscape without garden hoses or other items having to be moved around manually.
The beginning of a sprinkler system is the water source. This is usually a tap into an existing (city) water line or a pump that pulls water out of a well or a pond.
History of irrigation
Evidence exists of irrigation in Mesopotamia and Egypt as far back as the 6th millennium BC.
There is also evidence of ancient Egyptian pharaohs in the twelfth dynasty using the natural lake of the Fayûm as a reservoir to store surpluses of water for use during the dry seasons, as the lake swelled annually as caused by the annual flooding of the Nile. Ancient visitors reported the appearance of "an artificial excavation, as reported by classic geographers and travellers" (CATHOLIC ENCYCLOPEDIA: Egypt: I. GENERAL DESCRIPTION: Flora and Agriculture).
Developed in ancient Persia the Qanat is among the oldest known irrigation methods developed and still used today. 'Qanats are constructed as a series of well-like vertical shafts, connected by gently sloping tunnels.' meaning that the receiving populus was always lower than the source, the source being higher and connected to these Qanats which had many exit points for the water (vertical shafts)at villages and pastures.
Irrigation Works of Ancient Sri Lanka were one of the most complex irrigation systems of the ancient world, the sinhalese managed to build major irrigation schemes to support the agriculture which thrived at the time. The sinhalese civilization is responsible for the invention of the valve pit which remains unchanged to-date. Highly complex use of trigonometry and other engineering aspects such as soil mechanics, built environment had been used for the construction of these schemes.King Parakrama Bahu (1153–1186 AD) had been responsible for the construction or the restoration of 165 dams, 3910 canals, 163 major tanks (reservoirs) and 2376 minor tanks, all in a reign of 33 years.
In the Zana Valley of the Andes Mountains in Peru, archaeologists found remains of 3 irrigation canals radiocarbon dated from the 4th millennium BC, the 3rd millennium BC and the 9th century. These canals are the earliest record of irrigation in the New World. Traces of a canal possibly dating from the 5th millennium BC were found under the 4th millennium canal.(Dillehay, et al., 2005)
The Indus Valley Civilization in Pakistan and North India (from circa 2600 BC) also had an early canal irrigation system.
In ancient China the Dujiangyan Irrigation Systemwas built in 250 BC which irrigated a large area and it still supplies with water nowadays.
By the middle of the 20th century, the advent of diesel and electric motors led for the first time to systems that could pump groundwater out of major aquifers faster than it was recharged. This can lead to permanent loss of aquifer capacity, decreased water quality, ground subsidence, and other problems. The future of food production in such areas as the North China Plain, the Punjab, and the Great Plains of the US is threatened.
Problems in irrigation
Competition for surface water rights.
Depletion of underground aquifers.
Ground subsidence (e.g. New Orleans, Louisiana)
Buildup of toxic salts on soil surface in areas of high evaporation. This requires either leaching to remove these salts and a method of drainage to carry the salts away or use of mulch to minimize evaporation.
Overirrigation because of poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution.
RUNNING WATER ---
In most developed nations drinking water is piped to homes and is available on tap. Usually it is safe water.
The provision of tap water requires a massive infrastructure of piping, pumps, and water purification works. The cost of tap water is a small fraction of that of bottled water, often as little as a ten-thousandth.
The same water supply that is used for drinking is also used for washing, flushing water closets (toilets), washing machines, and dishwashers. Experimental attempts have been made to introduce non-potable greywater or rainwater for these secondary uses.
In many areas, fluoride is added to the tap water as a means to improve public dental health. This remains a controversial issue in terms of the health, freedoms and rights of the individual.
The availability of clean tap water brings major public health benefits. Usually, the same administration that provides tap water is also responsible for the removal and treatment before discharge or reclamation of wastewater.
Tap water use ---
According to a 1999 American Water Works Association Research Foundation study on residential end uses of water in the United States, Americans drink more than 1 billion glasses of tap water per day. Daily indoor per capita water use in a typical single family home is 69.3 gallons (260 litres). Overall use falls into the following categories:
Toilets - 26.7%
Clothes Washers - 21.7%
Showers - 16.8%
Faucets - 15.7%
Leaks - 12.7%
Other Domestic Uses - 2.2%
Baths - 1.7%
Dishwashers - 1.4%
Trivia ---
Tap water may contain different types of metal ions; the area of the world one lives in is a determining factor of this.
WATER-POWERED MILLS ---
A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour or lumber production, or metal shaping (rolling, grinding or wire drawing). A watermill that only generates electricity is more usually called a hydroelectric plant.
The technology behind the watermill is somewhat older than that of the windmill. The ancient Greeks and Romans are known to have used the technology; the Romans used both fixed and floating water wheels and introduced water power to other countries of the Roman Empire. So-called 'Greek Mills' used water wheels with a vertically-mounted shaft. A "Roman Mill" features a horizontally-mounted shaft. Greek style mills are the older and simpler of the two designs, but only operate well with high water velocities and with small diameter millstones. Roman style mills are more complicated as they require gears to transmit the power from a shaft with a horizontal axis to one with a vertical axis. The Cistercian Order built huge mill complexes all over Western Europe during the medieval period.
Operation of a watermill ---
Typically, water is diverted from a river or impoundment or mill pond to a turbine or water wheel, along a channel or pipe (variously known as a flume, head race, mill race, leat, leet[1], or penstock). The force of the water's movement drives the blades of a wheel or turbine, which in turn rotates an axle that drives the mill's other machinery. Water leaving the wheel or turbine is drained through a tail race, but this channel may also be the head race of yet another wheel, turbine or mill. The passage of water is controlled by sluice gates that allow maintenance and some measure of flood control; large mill complexes may have dozens of sluices controlling complicated interconnected races that feed multiple buildings and industrial processes.
There are three kinds of water mill: undershot, overshot and horizontal. The oldest of these were horizontal mills in which the force of the water, striking a simple paddle wheel set horizontally in line with the flow turned a runner stone balanced on a shaft leading directly up from the wheel. The problem with this type of mill arose from the lack of gearing; the speed of the water directly set the maximum speed of the runner stone which, in turn, set the rate of milling.
At some point gearing was invented. This allowed the mill designers to employ a large mill wheel set perpendicular to the mill race (this is the type of water wheel we generally think of when we imagine a water mill). This large wheel drove a shaft which turned a smaller face wheel set with pegs that, in turn, turned a lantern gear attached to the shaft which drove the runner stone (additional gearing might allow a single water wheel to drive as many as four stones). Each step in the process increased the gear ratio which increased the maximum speed of the runner stone. Adjusting the sluice gate and thus the speed of the water past the main wheel allowed the miller to finely adjust the speed of his stone(s) depending on the type of grain being milled.
A later innovation was the overshot wheel. With an undershot wheel, in which the main water wheel is simply set into the flow of the mill race there exists an inherent inefficiency stemming from the fact that the wheel itself, entering the water behind the main thrust of the flow driving the wheel, followed by the lift of the wheel out of the water ahead of the main thrust, actually impedes its own operation. The overshot wheel solves this problem by bringing the water flow to the top of the wheel. The water fills buckets built into the wheel (rather than the simple paddle wheel design of undershot wheels). As the buckets fill, the weight of the water starts to turn the wheel. The water spills out of the bucket on the down side into a spillway leading back to river. Since the wheel itself is set above the spillway, the water never impedes the speed of the wheel. This type of mill requires the construction of a dam on the river above the mill and a more elaborate millpond, sluice gate, mill race and spillway.
Toward the end of the 1800s, the invention of the Pelton wheel encouraged some mill owners in at least North America to replace over- and undershot wheels with penstocks and Pelton wheel turbines. By the early 20th century, availability of cheap electrical energy made the water mill obsolete; although in North America, some smaller rural mills continued to operate commercially into the 1960s. A few historic mills (for example, at the Wayside Inn) still operate for demonstration purposes to this day.
A unique type of water mill is the tide mill. This mill might be of any kind, undershot, overshot or horizontal but it does not employ a river for its power source. Instead a mole or causeway is built across the mouth of a small bay. At low tide, gates in the mole are opened allowing the bay to fill with the incoming tide. At high tide the gates are closed, trapping the water inside. At a certain point a sluice gate in the mole can be opened allowing the draining water to drive a mill wheel or wheels. This is particularly effective in places where the tidal differential is very great (such as the Bay of Fundy in Canada where the tides can rise fifty feet!), or the now derelict village of Tide Mills in the UK.
Other water mills can be set beneath large bridges where the flow of water between the stanchions is faster. At one point London bridge had so many water wheels beneath it that bargemen complained that passage through the bridge was impaired.
A final, rather elegant, water wheel innovation places the wheel in a boat anchored in midstream. The flow of the river past the boat turns the wheel and drives the millstone.
"Run of the river" schemes do not divert water at all and usually involve undershot wheels, and some types of water wheel (usually overshot steel wheels) mount a toothed annular ring near the outer edge that drives machinery from a spur gear rather than taking power from the central axle. However, the basic mode of operation remains the same; gravity drives machinery through the motion of flowing water.
IRON MINING ---
Iron is the second-most abundant metal in the Earth's crust after aluminium. It is one of the most commonly used metals in the modern world. Iron as a metal in elemental form is rarely used on its own. Most of the iron extracted today is converted to steel, an alloy of iron and carbon, which proves to be more useful than iron. Steel has good domestic as well as industrial use, mainly because it does not corrode easily, and because of its high tensile strength. It is far less brittle than iron.
The common ores of iron are hematite [Fe2O3], limonite [Fe2O3].xH2O, magnetite [Fe3O4] and siderite [FeCO3]. Iron from hematite is usually extracted through the carbon reduction process.
The iron ore with carbon in the form of coke (once charcoal) and limestone are added to a blast furnace (temperatures of at least 1300°C, but now usually 2000°C). The product of the blast furnace process is not pure iron, but pig iron which contains 4-5% carbon and silicon, which must be removed in further processes. An earlier process (which did produce fairly pure wrought iron used a bloomery, where the iron was kept in the solid state throughout, but this was gradually abandoned because it could not easily be scaled up.
The steps in the extraction of iron by carbon reduction method are:
1. Hot air is pumped into the blast furnace through the bottom. The carbon reacts the oxygen to produce carbon dioxide:
C + O2 → CO2
2. After carbon dioxide is formed, excess carbon reacts with it to form carbon monoxide - the main reducing reagent in the furnace.
CO2 + C → 2CO + Δ
3. The carbon monoxide in the blast furnace reacts with the hematite (iron(III) oxide). This occurs because the carbon monoxide reacts with the oxygen in the compound and forms carbon dioxide. This effectively reduces the iron oxide as the iron gains three electrons in the process and becomes iron atoms:
Fe2O3 + 3CO → 2Fe + 3CO2
4. While the iron is being extracted, the limestone flux reacts with the impurities in the ore and melts them to form slag, which effectivly prevents the impurities from affecting the reduction of the iron ore:
CaCO3 → CaO + CO2
CaO + SiO2 → CaSiO3
PAPERMAKING ---
Papermaking refers to the process of making modern-day paper, a material which is ubiquitous today for writing and packaging. The invention of papermaking is usually ascribed to the Chinese court official Cai Lun. Papermaking is one of the Four Great Inventions of ancient China, alongside the compass, gunpowder, and printing.
History
The word paper comes from the ancient Egyptian writing material called papyrus, which was woven from papyrus plants. Papyrus was produced as early as 3000 BCE in Egypt, and in ancient Greece and Rome. Further north, parchment or vellum, made of processed sheepskin or calfskin, replaced papyrus, as the papyrus plant requires subtropical conditions to grow. In China, documents were ordinarily written on bamboo, making them very heavy and awkward to transport. Silk was sometimes used, but was normally too expensive to consider. Indeed, most of the above materials were rare and costly. The Chinese court official Cai Lun described the modern method of papermaking in AD 105; he was the first person to describe how to make paper from wood pulp. Archeologically, true paper had been excavated in China dated from the 2nd century BC. It spread slowly outside of China; other East Asian cultures, even after seeing paper, could not figure out how to make it themselves. Instruction in the manufacturing process was required, and the Chinese were reluctant to share their secrets. The technology was first transferred to Korea in 600 and then imported to Japan by a Buddhist priest, Dam Jing from Goguryeo, around 610, where fibres (called bast) from the mulberry tree were used. After further commercial trading and the defeat of the Chinese in the Battle of Talas, the invention spread to the Middle East, where it was adopted in India and subsequently in Italy in about the 13th century. They used hemp and linen rags as a source of fiber. Rags from old clothing, etc. were commonly bought by rag collectors and sold to paper makers. As printing on rag paper became more popular, the supply of rags became more and more inadequate and other sources of fiber were actively sought. A great deal of experimentation took place. The oldest known paper document in the West is the Missel of Silos from the 11th century.
Significance
Some historians speculate that paper was the key element in global cultural advancement. According to this theory, Chinese culture was less developed than the West in early ancient times because bamboo, while abundant, was a clumsier writing material than papyrus; Chinese culture advanced during the Han Dynasty and preceding centuries due to the Chinese invention of paper; and Europe advanced during the Renaissance due to the introduction of paper and the printing press.
Paper remained a luxury item through the centuries, until the advent of steam-driven paper making machines in the 19th century, which could make paper with fibres from wood pulp. Although older machines predated it, the Fourdrinier paper making machine became the basis for most modern papermaking. Together with the invention of the practical fountain pen and the mass produced pencil of the same period, and in conjunction with the advent of the steam driven rotary printing press, wood based paper caused a major transformation of the 19th century economy and society in industrialized countries. Before this era a book or a newspaper was a rare luxury object and illiteracy was the norm. With the gradual introduction of cheap paper, schoolbooks, fiction, non-fiction, and newspapers became slowly available to nearly all the members of an industrial society. Cheap wood based paper also meant that keeping personal diaries or writing letters ceased to be reserved to a privileged few. The office worker or the white-collar worker was slowly born of this transformation, which can be considered as a part of the industrial revolution.
Method
A rather loose description of how paper is made by hand: Fibers are floated in a slurry, a thick soup of water and fibers, in a large vat. A wire screen mould with a wooden frame (somewhat similar to an old window screen) is used to scoop some of the slurry out of the vat. The wooden frame is called a "deckle." The impressions in paper caused by the wires in the screen that run sideways are called "laid lines" and the impressions made, unusually from top to bottom, by the wires holding the other wires together are called "chain lines." Watermarks are created by weaving a name into the wires in the mould. This is also basically true of Oriental moulds made of other substances, such as bamboo. Hand-made paper generally folds and tears more evenly along the laid lines.
The wooden frame or deckle leaves the edges of the paper slightly irregular and wavery. This wavy edge is called the "deckle edge" and is one of the indications that the paper was made by hand. Deckle-edged paper is occasionally mechanically imitated today to create the impression of old-fashioned luxury.
Returning to the process: the slurry in the screen mould is artfully sloshed around the mould until it forms an over-all thin coating. The fibers are allowed to settle and the water to run out. When the fibers have stabilized in place but are still damp, they are turned out onto a felt sheet (which oddly enough was made by a similar "matting" process) which was generally made of an animal product such as wool or rabbit fur, and the screen mold immediately reused. Layers of paper and felt build up in a pile and a weight is placed on top to press out water and keep the paper fibers flat and tight. When the paper pages are dry, they are frequently run between rollers to produce a harder writing surface. Papers are made of different surfaces depending on their intended purpose. Paper intended for printing or writing with ink is fairly hard, while paper to be used for water color, for instance, is fairly soft.
Unfortunately, the wood-based paper was more acidic and more prone to discolor and disintegrate over time, through processes known as slow fires. Documents written on more expensive rag paper were more stable. Both rag and woodpulp paper will develop tan spots called "foxing" caused by impurities or fungi reacting with humidity. The majority of modern book publishers now use acid-free paper. Modern newspapers are commonly printed on cheaper high-acid paper which turns tan and disintegrates rather rapidly, especially in the presence of strong light and humidity.
Paper sizes
In the beginning of Western papermaking, the paper size was fairly standard. A page of paper is referred to as a "leaf." When a leaf was printed on without being folded, the size was referred to as "folio." It was roughly equal to the size of a newspaper sheet.
When it was folded once, it produced four sides or pages, and the size of the pages or a book made of such pages was referred to as "quarto" (4to).
If the original sheet was folded in half again, the result was eight sides, referred to as "octavo" (8vo), which is the size that most books, such as the average novel, use to this day.
An "octavo" folding produces four leaves, the first two and the second two will be joined at the top by the second fold. The top edge is usually "trimmed" to make it possible to look freely at each side of the leaf. However, many books are found that have not been trimmed on the top, and these pages are referred to as "unopened." Many people reading "unopened" books will use their finger, a pencil, or some other inadequate instrument to rip open the top of the pages, leaving an irregular tear. A letter opener or a knife carefully used is a more appropriate tool.
An octavo book produces a printing puzzle. Pieces of paper are printed when they are folio size. To provide for the proper alignment of numbered pages, pages 8 and 1 are printed right-side-up on the bottom of the sheet, and pages 4 and 5 are printed up-side-down on the top of the same sheet. On the opposite side, pages 2 and 7 are printed right-side-up on the bottom of the sheet, and pages 6 and 3 are printed up-side-down on the top of the sheet. When the paper is folded twice and the folds trimmed, the pages fall into proper order.
Try folding a paper in half by turning the top half down and creasing it, and then fold it in half again by turning the left side over the right. You have the format for an octavo page arrangement. If you number the pages in order and then open the paper to full size, you will see the numbers as described above.
Smaller books are produced by folding the leaves again to produce 16 pages, known as a "sixteen-mo" (16mo). Other folding arrangements produce yet smaller books such as the thirty-two-mo (32mo).
When a standard-sized octavo book is produced by a large leaf folded two times, two leaves joined at the top will be contained in the resulting fold (which ends up in the gulley between the pages). This group of 8 numberable pages is called a "signature" or a "gathering." Traditionally, printed signatures were stacked on top of each other in a "sewing frame" and each signature was sewn through the inner fold to the signature on top of it. The sewing ran around leather bands or fabric tapes along the backs of the signatures to stabilize the growing pile of signatures.
The leather bands originally used in the West to stabilize the backs of sewn books appear as a number of ridges under the leather on the spine of leather books.
The ends of the leather strips or fabric bands were sewn or glued onto the cover boards and reinforced the hinging of the book in its covers.
WRITING SYSTEM ---
A writing system is a type of symbolic system used to represent elements or statements expressible in language.
General properties
Writing systems are distinguished from other possible symbolic communication systems in that one must usually understand something of the associated language in order to successfully read and comprehend the text. Contrast this with other possible symbolic systems such as information signs, painting, maps, and mathematics, which do not necessarily depend upon prior knowledge of a given language in order to extract their meaning.
Every human community possesses language, a feature regarded by many as an innate and defining condition of humankind. However, the development and adoption of writing systems has occurred only sporadically. Once established, writing systems are on the whole modified more slowly than their spoken counterparts, and often preserve features and expressions which are no longer current in the discourse of the speech community. The great benefit conferred by writing systems is their ability to maintain a persistent record of information expressed in a language, which can be retrieved independently of the initial act of formulation.
All writing systems require:
a set of defined base elements or symbols, individually termed characters or graphemes, and collectively called a script;
a set of rules and conventions understood and shared by a community, which arbitrarily assign meaning to the base elements, their ordering, and relations to one another;
a language (generally a spoken language) whose constructions are represented and able to be recalled by the interpretation of these elements and rules;
some physical means of distinctly representing the symbols by application to a permanent or semi-permanent medium, so that they may be interpreted (usually visually, but tactile systems have also been devised).
Basic terminology
The study of writing systems has developed along partially independent lines in the examination of individual scripts, and as such the terminology employed differs somewhat from field to field.
The generic term text may be used to refer to an individual product of a writing system. The act of composing a text may be referred to as writing, and the act of interpreting the text as reading. In the study of writing systems, orthography refers to the method and rules of observed writing structure (literal meaning, "correct writing"), and in particular for alphabetic systems, includes the concept of spelling.
A grapheme is the technical term coined to refer to the specific base or atomic units of a given writing system. Graphemes are the minimally significant elements which taken together comprise the set of "building blocks" out of which texts of a given writing system may be constructed, along with rules of correspondence and use. The concept is similar to that of the phoneme used in the study of spoken languages. For example, in the Latin-based writing system of standard contemporary English, examples of graphemes include the majuscule and minuscule forms of the twenty-six letters of the alphabet (corresponding to various phonemes), marks of punctuation (mostly non-phonemic), and a few other symbols such as those for numerals (logograms for numbers).
Note that an individual grapheme may be represented in a wide variety of ways, where each variation is visually distinct in some regard, but all are interpreted as representing the "same" grapheme. These individual variations are known as allographs of a grapheme (compare with the term allophone used in linguistic study). For example, the minuscule letter a has different allographs when written as a cursive, block, or typed letter. The selection between different allographs may be influenced by the medium used, the writing instrument, the stylistic choice of the writer, and the largely unconscious features of an individual's handwriting.
The terms glyph, sign and character are sometimes used to refer to a grapheme. Common usage varies from discipline to discipline; compare cuneiform sign, Maya glyph, Chinese character. The glyphs of most writing systems are made up of lines (or strokes) and are therefore called linear, but there are glyphs in non-linear writing systems made up of other types of marks, such as Cuneiform and Braille.
Writing systems are conceptual systems, as are the languages to which they refer. Writing systems may be regarded as complete according to the extent to which they are able to represent all that may be expressed in the spoken language.
History of writing systems
Writing systems were preceded by proto-writing, systems of ideographic and/or early mnemonic symbols. The best known examples are:
Symbols on tortoise shells in Jiahu, ca. 6600 BC
Vinca script (Tărtăria tablets), ca. 4500 BC
Early Indus script, ca. 3500 BC
The invention of the first writing systems is roughly contemporary with the beginning of the Bronze Age in the late Neolithic of the late 4th millennium BC. The Sumerian archaic cuneiform script and the Egyptian hieroglyphs are generally considered the earliest writing systems, both emerging out of their ancestral proto-literate symbol systems from ca. 3200 BC with earliest coherent texts from about 2600 BC.
The Chinese script may have originated independently of the Middle Eastern scripts, around 1200 BC. The pre-Columbian Mesoamerican writing systems (including among others Olmec and Maya scripts) are also generally believed to have had independent origins.
It is thought that the first true alphabetic writing appeared around 2000 BC, as a representation of language developed by Semitic workers in Egypt (see History of the alphabet). Most other alphabets in the world today either descended from this one innovation, many via the Phoenician alphabet, or were directly inspired by its design.
Types of writing systems
The oldest-known forms of writing were primarily logographic in nature, based on pictographic and ideographic elements. Most writing systems can be broadly divided into three categories: logographic, syllabic and alphabetic (or segmental); however, all three may be found in any given writing system in varying proportions, often making it difficult to categorise a system uniquely. The term complex system is sometimes used to describe those where the admixture makes classification problematic.
Logographic writing systems
A logogram is a single written character which represents a complete grammatical word. Most Chinese characters are classified as logograms.
As each character represents a single word (or, more precisely, a morpheme), many logograms are required to write all the words of language. The vast array of logograms and the memorization of what they mean are the major disadvantage of the logographic systems over alphabetic systems. However, since the meaning is inherent to the symbol, the same logographic system can theoretically be used to represent different languages. In practice, this is only true for closely related languages, like the Chinese languages, as syntactical constraints reduce the portability of a given logographic system. Both Korean and Japanese use Chinese logograms in their writing systems, with most of the symbols carrying the same or similar meanings. However, the semantics, and especially the grammar, are different enough that a Chinese text is not readily understandable to a Japanese or Korean reader.
While most languages do not use wholly logographic writing systems many languages use some logograms. A good example of modern western logograms are the Hindu-Arabic numerals — everyone who uses those symbols understands what 1 means whether he or she calls it one, eins, uno, or ichi. Other western logograms include the ampersand &, used for and, and the at sign @ , used in many contexts for at.
Logograms are sometimes called ideograms, a word that refers to symbols which graphically represent abstract ideas, but linguists avoid this use, as Chinese characters are often semantic–phonetic compounds, symbols which include an element that represents the meaning and element that represents the pronunciation. Some nonlinguists distinguish between lexigraphy and ideography, where symbols in lexigraphies represent words, and symbols in ideographies represent words or morphemes.
The most important (and, to a degree, the only surviving) modern logographic writing system is the Chinese one, whose characters are used, with varying degrees of modification, in Chinese, Japanese, Korean, Vietnamese, and other east Asian languages. Ancient Egyptian hieroglyphics and the Mayan writing system are also systems with certain logographic features, although they have marked phonetic features as well, and are no longer in current use.
Syllabic writing systemsAs logographic writing systems use a single symbol for an entire word, a syllabary is a set of written symbols that represent (or approximate) syllables, which make up words. A symbol in a syllabary typically represents a consonant sound followed by a vowel sound, or just a vowel alone. In a true syllabary there is no systematic graphic similarity between phonetically related characters (though some do have graphic similarity for the vowels). That is, the characters for "ke", "ka", and "ko" have no similarity to indicate their common "k"-ness. Compare abugida, where each grapheme typically represents a syllable but where characters representing related sounds are similar graphically (typically, a common consonantal base is annotated in a more or less consistent manner to represent the vowel in the syllable).
Syllabaries are best suited to languages with relatively simple syllable structure, such as Japanese. The English language, on the other hand, allows complex syllable structures, with a relatively large inventory of vowels and complex consonant clusters, making it cumbersome to write English words with a syllabary. To write English using a syllabary, every possible syllable in English would have to have a separate symbol, and whereas the number of possible syllables in Japanese is no more than about fifty-sixty, in English there are many thousands.
Other languages that use syllabic writing include Mycenaean Greek (Linear B) and Native American languages such as Cherokee. Several languages of the Ancient Near East used forms of cuneiform, which is a syllabary with some non-syllabic elements.
Alphabetic writing systems
An alphabet is a small set of letters — basic written symbols — each of which roughly represents or represented historically a phoneme of a spoken language. The word alphabet is derived from alpha and beta, the first two symbols of the Greek alphabet.
In a perfectly phonological alphabet, the phonemes and letters would correspond perfectly in two directions: a writer could predict the spelling of a word given its pronunciation, and a speaker could predict the pronunciation of a word given its spelling. Each language has general rules that govern the association between letters and phonemes, but, depending on the language, these rules may or may not be consistently followed.
Perfectly phonological alphabets are very easy to use and learn, and languages that have them (for example, Finnish or Serbian) have much lower barriers to literacy than languages such as English, which has a very complex and irregular spelling system. As languages often evolve independently of their writing systems, and writing systems have been borrowed for languages they were not designed for, the degree to which letters of an alphabet correspond to phonemes of a language varies greatly from one language to another and even within a single language. In modern times, when linguists invent a writing system for a language that didn't previously have one, the goal is usually to make a perfectly phonological alphabet. An example of such writing systems is the "IPA" (International Phonetic Alphabet), another, older one, is the completion of Serbian language.
Abjads
The first type of alphabet that was developed was the abjad. An abjad is an alphabetic writing system where there is one symbol per consonant. Abjads differ from regular alphabets in that they only have characters for consonantal sounds. Vowels are not usually marked in abjad.
All known abjads (except maybe Tifinagh) belong to the Semitic family of scripts, and derive from the original Northern Linear Abjad. The reason for this is that Semitic languages and the related Berber languages have a morphemic structure which makes the denotation of vowels redundant in most cases.
Some abjads (like Arabic and Hebrew) have markings for vowels as well, but only use them in special contexts, such as for teaching. Many scripts derived from abjads have been extended with vowel symbols to become full alphabets, the most famous case being the derivation of the Greek alphabet from the Phoenician abjad. This has mostly happened when the script was adapted to a non-Semitic language.
The term abjad takes its name from the old order of the Arabic alphabet's consonants Alif, Bá, Jim, Dál, though the word may have earlier roots in Phoenician or Ugaritic.
Abjad is still the word for alphabet in Arabic, Malay, and Indonesian.
Abugidas
An abugida is an alphabetic writing system whose basic signs denote consonants with an inherent vowel and where consistent modifications of the basic sign indicate other following vowels than the inherent one.
Thus, in an abugida there is no sign for "k", but instead one for "ka" (if "a" is the inherent vowel), and "ke" is written by modifying the "ka" sign in a way that is consistent with how one would modify "la" to get "le". In many abugidas the modification is the addition of a vowel sign, but other possibilities are imaginable (and used), such as rotation of the basic sign, addition of diacritical marks, and so on.
The obvious contrast is with syllabaries, which have one distinct symbol per possible syllable, and the signs for each syllable have no systematic graphic similarity. The graphic similarity comes from the fact that most abugidas are derived from abjads, and the consonants make up the symbols with the inherent vowel, and the new vowel symbols are markings added on to the base symbol.
The Ethiopic script is an abugida, although the vowel modifications in Ethiopic are not entirely systematic. Canadian Aboriginal Syllabics can be considered abugidas, although they are rarely thought of in those terms. The largest single group of abugidas is the Brahmic family of scripts, however, which includes nearly all the scripts used in India and Southeast Asia.
The name abugida is derived from the first four characters of an order of the Ge'ez script used in some religious contexts. The term was coined by Peter T. Daniels.
Featural writing systems
A featural script represents finer detail than an alphabet. Here symbols do not represent whole phonemes, but rather the elements (features) that make up the phonemes, such as voicing or its place of articulation. Theoretically, each feature could be written with a separate letter; and abjads or abugidas, or indeed syllabaries, could be featural, but the only prominent system of this sort is Korean Hangul. In Hangul, the featural symbols are combined into alphabetic letters, and these letters are in turn joined into syllabic blocks, so that the system combines three levels of phonological representation.
Directionality
Different scripts are written in different directions. The early alphabet could be written in any direction: either horizontal (left-to-right or right-to-left) or vertical (up or down). It could also be written boustrophedon: starting horizontally in one direction, then turning at the end of the line and reversing direction. Egyptian hieroglyph is one such script, where the beginning of a line written horizontally was to be indicated by the direction in which animal and human ideograms are looking.
The Greek alphabet and its successors settled on a left-to-right pattern, from the top to the bottom of the page. Other scripts, such as Arabic and Hebrew, came to be written right-to-left. Scripts that incorporate Chinese characters have traditionally been written vertically (top-to-bottom), from the right to the left of the page, but nowadays are frequently written left-to-right, top-to-bottom, due to Western influences, a growing need to accommodate terms in the Roman alphabet, and technical limitations in popular electronic document formats. The Mongolian alphabet is unique in being the only script written top-to-bottom, left-to-right; this direction originated from an ancestral Semitic direction by rotating the page 90° counter-clockwise to conform to the appearance of Chinese writing. Scripts with lines written away from the writer, from bottom to top, also exist, such as several used in the Philippines and Indonesia.
Writing systems on the computer
Different ISO/IEC standards are defined to deal with each individual writing systems to implement them in computers (or in electronic form). Now most of those standards are re-defined in a better collective standard, the ISO 10646, also known as Unicode. In Unicode, each character, from all languages' writing systems, is given a unique identification number, known as its code point. The computer's Operating System interprets the code for different characters (and languages) from files, and it retrieves appropriate characters from the font file (for that code), so the characters can be displayed on the page or screen.
A keyboard is the device most commonly used for writing via computer. The keyboard generates very specific standardized codes when keys are pressed. By using a combination of keys with Ctrl, Alt, Shift, Function, Caps Lock, Num Lock, Numeric keypad, Option, Command, etc modifier keys, various character codes are generated and sent to the CPU. The operating system intercepts and converts those signals to the appropriate characters, (based on the keyboard layout for the language codepage, input method environment, fonts, etc which are used in that specific computer), and then delivers those converted codes and characters to the running processes application software, video adapter, etc, which displays the characters on the screen.
In computers and telecommunication systems, graphemes and other grapheme-like units that are required for text processing are represented by "characters" that typically manifest in encoded form. For technical aspects of computer support for various writing systems, see the articles UCS (Universal Character Set), CJK (Chinese, Japanese, Korean) and Bi-directional text, as well as Category:Character encoding.
Best of luck in writing this out.
J.F.