Research Results For 'Stream'

ARTESIAN WELLS

Artesian Wells, so called from the French province of Artois, where they appear to have been first used on an extensive scale, are perpendicular borings into the ground through which water rises to the surface of the soil, producing a constant flow or stream, the ultimate sources of supply being higher than the mouth of the boring, and the water thus rising by the well-known law. They are generally sunk in valley plains and districts where the lower pervious strata are bent into basin-shaped curves.

The rain falling on the outcrops of these saturates the whole porous bed, so that when the bore reaches it the water by hydraulic pressure rushes up towards the level of the highest portion of the strata. The supply is sometimes so abundant as to be used extensively as a moving power, and in arid regions for fertilizing the ground, to which purpose artesian springs have been applied from a very remote period. Thus many artesian wells have been sunk in the Algerian Sahara which have proved an immense boon to the district.

The water of most of these is potable, but a few are a little saline, though not to such an extent as to influence vegetation. The hollows in which London and Paris lie are both perforated in many places by borings of this nature. At London they were first sunk only to the sand B B, but latterly into the chalk c o. One of the most celebrated artesian wells is that of Crenelle near Paris, 1798 feet deep, completed in 1841, after eight years' work. Artesian wells are now common in many countries, and have been sunk to the depth of a mile or more. As the temperature of water from great depths is invariably higher than that at the surface, artesian wells have been made to supply warm water for heating manufactories, greenhouses, hospitals, fish-ponds, etc. Petroleum wells are generally of the same technical description. Artesian wells were later made with larger diameters than formerly, and altogether their construction was rendered much more easy after the industrial revolution.
Research Artesian Wells

BADLANDS

In geomorphology, badlands are areas of bare ground which have been intensely eroded by running water into a maze of miniature canyons and steep slopes. There may be hundreds of tiny stream channels within a single square kilometre or mile, with the channels containing water only after rainstorms. Common on clays and shales in areas where the climate is semi-arid, they occur also on the tip-heaps of mines, especially of china-clay workings, in areas where the climate is wetter. Resistant layers of rock are often left as cappings on pillars of softer rock; these structures are known as hoodoos, or pedestal rocks.
Research Badlands

DAM

A dam is a bank or construction of stone, earth, or wood etc across a stream or river for the purpose of keeping back the current to give it increased head, for holding back supplies of water, for flooding lands, for rendering the stream above the dam navigable by increased depth, and for generating electricity. Its material and construction will depend on its situation and the amount of pressure it has to bear. For streams which are broad and deep strong materials are required, usually stone masonry bound in hydraulic cement and a strong framework of metal or timber. The common forms of a dam are either a straight line crossing the stream transversely, or one or two straight lines traversing it diagonally, or an arc with its convex side towards the current.
Research Dam

DREDGING

Dredging is a term applied to the operation of removing mud, silt, and other deposits from the bottom of harbours, canals, rivers, docks, etc. The most simple dredging apparatus is the spoon apparatus, which consists of a strong iron ring or hoop, properly formed for making an impression upon the soft matter at the bottom, so as to scoop it into a large bag attached to the ring and perforated with a number of small holes. The means for working it is a long handle, a suspending rope, and a crane or sweep-pole planted in a boat.

Much more effective was the steam dredging-machine that became common during the 19th century. It had a succession of strong iron buckets on an endless chain, which traversed on a frame whose lower end was vertically adjustable so as to regulate the depth at which it worked. It was worked by steam, and the buckets tore up the matter at the bottom, raised it, and discharge it into punts or hoppers close to the dredging vessel. Various forms of steam - pump dredgers, in which suction-pipes were the chief features, were also used.

The river Clyde, from being a shallow stream, was converted, mainly by dredging, into a waterway carrying large vessels up to Glasgow.

Dredging rivers for gold has been largely carried on since the 19th century; and the gold-dredge may even be floated in water artificially supplied.

Dredging is also the operation of dragging the bottom of the sea for molluscs, plants, and other objects, it may be for scientific observation. The oyster-dredge is a light iron frame with a scraper like a narrow hoe on one side, and a bag attached to receive the oysters. The dredges used by naturalists are mostly modifications of or somewhat similar to the oyster-dredge. Scientific dredging assumed a high importance at the end of the 19th century for research into the life of deep-sea areas, before the invention of deep-sea diving equipment and cameras.
Research Dredging

GLACIER

Glaciers are icy masses of great bulk, harder than snow, yet not exactly like common ice, which cover the summits and sides of mountains above the snow-line. They are found in Switzerland, Scandinavia, the Andes, etc.

They extend down into the valleys often far below the snow-line, and bear a considerable resemblance to a frozen torrent. They take their origin in the higher valleys, where they are formed by the congelation and compression of masses of snow in that condition called by French writers neve, by German authors, firn.

The ice of glaciers differs from that produced by the freezing of still water, and is composed of thin layers filled with air-bubbles. It is likewise more brittle and less transparent. The glaciers are continually moving downwards, and not unfrequently reach the borders of cultivation. The rate at which a glacier moves generally varies from 45 to 60 cm in twenty-four hours.

At its lower end it is generally very steep and inaccessible. In its middle course it resembles a frozen stream
with an undulating surface, broken up by fissures or crevasses. As it descends it experiences a gradual diminution from the action of the sun and rain, and from the heat of the earth. Hence a phenomenon universally attendant on glaciers - the issue of a stream of ice-cold turbid water from their lower extremity. The descent of glaciers is shown by changes in the position of masses of rock at their sides and on their surface. A remarkable glacier phenomenon is that of moraines, as they are called, consisting of accumulations of stones and detritus piled up on the sides of the glacier, or scattered along the surface. They are composed of fragments of rock detached by the action of frost and other causes.

The fissures or crevasses by which glaciers are traversed are sometimes more than 30 meters in depth, and from being often covered with snow are exceedingly dangerous to travellers. One of the most famous glaciers of the Alps is the Mer de Glace, belonging to Mont Blanc, in the valley of Chamouni, about 1740 meters above sea level. It is more especially, however, in the chain of Monte Rosa that the phenomena of glaciers are exhibited in their greatest sublimity, as also in their most interesting phases from a scientific point of view.

Glaciers exist in all zones in which mountains rise above the snow-line. Those of Norway are well known, and they abound in Iceland and Spitzbergen. Hooker and other travellers gave accounts of those of the Himalaya. They are conspicuous on the Andes, while the Southern Alps of New Zealand rival in this respect the Alpine regions of Switzerland.

The problem of the descent of the glaciers is of extraordinary interest, and various theories have been put forward to account for it. It was shown by Professor Forbes, of Edinburgh, that a glacier moves very much like a river; the middle and upper parts faster than the sides and the bottom; and he showed that glacier motion was analogous to the way in which a mass of thick mortar or a quantity of pitch flows down in an inclined trough. His theory is known as the viscous theory of glaciers, which presupposes that ice is a plastic body, and this plasticity has been satisfactorily explained by Professor James Thomson of Glasgow by the phenomenon of the melting and refreezing of ice.

Water, he discovered, when subjected to pressure, freezes at a lower temperature than when the pressure is removed. Consequently when ice is subjected to pressure it melts; if it is relieved of pressure the water again solidifies. Therefore if two pieces of ice are pressed together, they tend to relieve themselves by melting at their points of contact, and the water thus produced immediately solidifies on its escape. If ice is strained in any way it similarly relieves itself at the strained parts, and a similar regelation follows. This, when applied to the glaciers, gives a complete explanation of their plasticity. Pressed downwards by the vast superincumbent mass, the ice gradually yields. Melting and re-freezing takes place at some parts, at others the gradual yielding at strained points goes on. In the latter process there is no visible melting, but there is the gradual yielding from point to point to the pressure above, and there is the transference relatively to each other of the molecules that constitute the, at first sight, solid mass. If, however, at certain points the strain is intense, the ice becomes extremely brittle. The latter fact disposes of Tyndall's objection to Forbes' theory, which was based on the fact that crevasses proved the brittleness, and not the viscosity of ice.
Research Glacier

GULF STREAM

The Gulf Stream is a well-known oceanic current, so called because it issues from the Gulf of Mexico. It owes its origin to the fact that the westward moving waters of the tropical portion of the Atlantic Ocean, encountering the eastward projection of South America, become divided into two currents, one setting southwards along the Brazilian coast, and the other northward past the mouths of the Amazon and Orinoco, into the Caribbean Sea. It then enters the Gulf of Mexico, and thence emerges through the Channel of Florida as the Gulf Stream. Its course is next to the north and eastwards, in a direction parallel to the coast of the United States, past Cape Hatteras, along the southern edge of the 'great banks' of Nantucket and Newfoundland (between the meridians of 48 and 60 degrees west), after which its course as a distinct current is less obvious.

In the earlier part of its course, especially when rounding the extremity of Florida, the Gulf Stream forms a well-defined current, distinguished by its high temperature and its deep blue or indigo colour. On account of the descent of the Polar or Baffin Bay current along the coast in a direction opposite to that of the Gulf Stream, the water on its inland side is colder than that to the eastward of it. The difference of temperature between the Gulf Stream and this cold current sometimes amounts to 20 or even 30 degrees Fahrenheit

The velocity of the Gulf Stream varies with its course. Within the Florida Channel it attains a mean of 65 miles per day, this sinks to 56 miles off Charleston, becomes 36 miles to 46 off Nautucket, and 28 miles to the south of the Newfoundland Banks; 300 miles to the eastward of Newfoundland its movement is hardly perceptible. At the bottom of the Florida Channel the observed temperature is 34 degrees that of the surface from 80 to 84 degrees Fahrenheit.
Research Gulf Stream

LABRADOR CURRENT

The Labrador Current is a cold ocean current flowing southwards off the coast of Labrador and meeting the warm Gulf Stream, causing dense fogs off Newfoundland.
Research Labrador Current

LAKES

Lakes are accumulations of water in hollows on the earth's surface. When they are drained by rivers their waters are fresh, but when they have no outlet they are salty, e.g. the Dead Sea, Sea of Aral, etc.
Lakes may owe their origin to:

1. The formation of a barrier across a river.


2. Earth movements.


3. Ice erosion.


4. Volcanic action.

The nehrungs of East Prussia are sand-spits which enclose the shallow salt-water lagoons or halls, such as Kurische Haff. Earth movements cause lake formation when subsidence occurs. This is most easily seen in rift valleys. Examples of rift valley lakes are the Dead Sea, Lakes Nyasa and Tanganyika in Africa, and Lake Torrens in Australia. These are all long, narrow, and very deep lakes.
In Cheshire, the removal of underground beds of salt has caused subsidence resulting in the 'meres' of the Weaver Valley. The 'folding' of the earth across the line of a river valley may partially block a river and help to form a lake. The study of a good physical map will reveal the connection between mountain building and the formation of Lake Geneva and Lake Constance in Switzerland. Where there are large areas of depressed lowland wide and shallow lakes are formed in the lowest part of the depression, for example the Sea of Aral in Asiatic Russia, Lake Balaton in Hungary, and Lake Eyre in Australia. Ice sheets and valley glaciers may scoop out hollows to form 'rock basins'. Mountain tarns and corrie lakes in North Wales and Scotland have been formed in this way. Water also accumulates in the hollows of unevenly- distributed glacial drift. Such are the lakes of East Prussia, and also those of the Cheshire-Shropshire borders near Ellesmere. Subsidence of the land surface and consequent lake formation may be directly related to volcanic action. Lough Neagh in Northern Ireland is a shallow lake formed by subsidence of this type. Lakes are often formed by the accumulation of water in the craters of extinct volcanoes, for example the Laachersee in the Eifel region of Germany.
Research Lakes

MILKY WAY

The Milky Way is the large, disk-shaped aggregation of stars, or galaxy , that includes the sun and its solar system. Its name is derived from its appearance as a faintly luminous band that stretches across earth's sky at night. This band is the disk in which the solar system lies. Its hazy appearance results from the combined light of stars too far away to be distinguished individually by the unaided eye. The individual stars that are distinct in the sky are those in the Milky Way galaxy that lie sufficiently close to the solar system to be discerned separately. From the middle northern latitudes, the Milky Way is best seen on clear, moonless, summer nights, when it appears as a luminous, irregular band circling the sky from the north-eastern to the south-eastern horizon. It extends through the constellations Perseus, Cassiopeia, and Cepheus. In the region of the Northern Cross it divides into two streams: the western stream, which is bright as it passes through the Northern Cross, fades near Ophiuchus, or the
Serpent Bearer, because of dense dust clouds, and appears again in Scorpio; and the eastern stream, which grows brighter as it passes southward through Scutum and Sagittarius. The brightest part of the Milky Way extends from Scutum to Scorpio, through Sagittarius. The centre is in the direction of Sagittarius and is about 26,000 light-years from the sun.
Research Milky Way

OBSEQUENT

In geography, the term obsequent is used to describe a river flowing into a subsequent stream in the opposite direction to the original slope of the land.
Research Obsequent

	The Probert Encyclopaedia was designed, edited and programed by Matt and Leela Probert ©1993 - 2009 The Probert Encyclopaedia Southampton, United Kingdom