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 gradualdiminution 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 Zealandrival 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
Francois Joseph Victor Broussais was a French physician. He was born in 1772 and died in 1838. He is regarded as the founder of what was called the physiological system of medicine. According to his theory irritability was the fundamental property of all living animal tissues, and every malady proceeded from an undue increase or diminution of that property. Research Francois Broussais
A bathometer is an apparatus invented by William Siemens in 1861 to measure the depth of water without submerging a sounding line. Its action depends on the diminution of the effect of gravitation on the surface of the water as compared with its effect on the earth, owing to the mass of water (of less density) which replaces earth (of greater density); which is duly registered. Research Bathometer
An eudiometer is a chemical apparatus introduced by Joseph Priestley in 1770, originally designed for ascertaining the purity of the air or the quantity of oxygen it contains, but later employed generally in the analysis of gaseous mixtures. The eudiometer consists of a graduated glass tube, either straight or bent in the shape of the letter U, hermetically sealed at one end and open at the other. Two platinumwires, intended for the conveyance of electric sparks through any mixture of gases, are inserted through the glass near the closed end of the tube, and approach but do not touch each other. The electric spark causes chemical combination to take place between the oxygen in the gas to be analysed, and hydrogen which has been introduced into the tube, and the nature and proportion of the constituents of the gaseous mixture are determined by the diminution in volume after the passing of the spark. Or certain substances, such as causticpotash, pyrogallic acid, etc, may be introduced into the closed tube in order to absorb the gases present one by one. Research Eudiometer
Evaporation is the conversion of a liquid by heat into vapour, which passes into the atmosphere. The process of evaporation is constantly going on at the surface of the earth, but principally at the surface of the sea, of lakes, rivers, and pools. The vapour thus formed, being specifically lighter than atmospheric air, rises to considerable heights above the earth's surface; and afterwards, by a process of cooling, is partially condensed, forms clouds, and finally descends in rain. The effect of evaporation is to reduce the temperature of the evaporating liquid; and the most intense degree of cold with which we are acquainted is caused by the evaporation of volatile liquids, such as ether, or, still better, liquid air. In the animal body evaporation from the skin and lungs is one of the most obvious causes of diminution of temperature. Research Evaporation
In physics, expansion is the enlargement or increase in the bulk of bodies, in consequence of a change in their temperature. This is one of the most general effects of heat, being common to all bodies whatever, whether solid or fluid. The expansion of fluids varies considerably, but, in general, the denser the fluid, the less the expansion; thus water expands more than mercury, and spirits of wine more than water; and, commonly, the greater the heat, the greater the expansion; but this is not universal, for there are cases in which expansion is produced, not by an increase, but by a diminution of temperature. Water, in cooling, ceases to contract at 42 degrees Fahrenheit.; and at about 39 degrees, just before it reaches the freezing point (32 degrees), it begins to expand again, and more and more rapidly as the freezing point is reached. This expansion is about one-eleventh of its bulk, and accounts for the bursting of pipes, etc, when water is freezing in them. Research Expansion
Gold is a bright yellow coloured, rare, precious metal element with the formulae Au and a relative hardness of 3 occurring in nature in widely distributed small amounts. The main source of gold is in gold-quartz veins where gold was deposited from mineral bearing solutions. When the veins weather, the gold is separated from the quartz and mechanically settles on the stream floor as a placer deposit. The fineness of gold is measured in carats. 24 carat gold is pure, 22 carat gold is 22 parts gold to two parts other metals and so on. Gold is seldom used for any purpose in a state of perfect purity on account of its softness, but is combined with some other metal to render it harder. Standard gold, or the alloy formerly used for the gold coinage of Britain, consists of twenty-two parts of gold and two of copper (being thus 22 carats fine). Articles of jewelry are made of every degree of fineness up to 22 carats, i.e. 22 parts of gold to 2 of alloy.
Gold is one of the most ductile and malleable of all the metals It is one of the heaviest of the metals, and not being liable to be injured by exposure to the air, is well suited for making coins and jewelry. Its ductility and malleability are very remarkable. It may be beaten into leaves so exceedingly thin that one grain in weight will cover 56 square inches. It is also extremely ductile; a single grain may be drawn into a wire 500 feet long, and an ounce of gold covering a silver wire is capable of being extended upwards of 1300 miles. It may also be melted and remelted with scarcely any diminution of its quantity. It is soluble in nitro-muriatic acid or aqua regia, and in a solution of chlorine. Its specific gravity is 19.3, or it is about nineteen times heavier than water.
The alloy of gold and silver is found already formed in nature. It is of a paler yellow than pure gold, while the copperalloy has a colour bordering upon reddish yellow. Palladium, rhodium, and tellurium are also met with as alloys of gold.
Gold has been found in larger or smaller quantities in nearly all parts of the world. It is commonly found in reefs or veins among quartz, and in alluvial deposits. Among the latter may be ranked the deposits in river beds, from which the gold is obtained by dredging. Dredging is even employed where the water has to be brought by artificial means. When gold is in rock, quarrying, crushing, washing, and treatment with mercury are employed. The rock is crushed by machinery, and the crushed material is treated with mercury, which dissolves the gold, forming a liquid amalgam, after which the mercury is volatilized, and the gold left behind. Two other processes are also in use, viz. the chlorination and the cyanide. In the former the gold is transformed into soluble gold chloride, and the metal is obtained from this solution by means of sulphuretted hydrogen. The cyanide process is especially useful for ores containing tellurium, or for ores in a fine state of division, and con^sists in dissolving the metal in potassiumcyanide solutions, from which it can be obtained by various means. The gold obtained by these methods always contains silver, from which it is separated by the process known as 'parting'.
In alluvial (or placer) deposits it is extracted by washing, in the form of dust, grains, laminae, or nuggets. After the gravel has been turned over and the nuggets have been taken out, the remainder is washed to recover the finer particles of gold. In washing in the pan - 'panning out' - a quantity of the 'dirt', free from stones, is put into a shallow dish with a slight depression in the middle. It is then mixed with water, and the dish held with one side lower than the other, while by a gentle motion the sand and other lighter bodies are washed over the edge of the pan, and the heavy matters containing the gold remain at the bottom. The 'dolly' or 'tossing tub' is a circular tub for washing rather fine stuff that has been sifted. The 'cradle' consists of a short box or trough two meters long, mounted on a kind of rockers, and slightly inclined to allow the mud to run off. A box, with a bottom of iron plate perforated with holes, is placed over the higher end of the trough. The 'pay dirt' (i.e. gravel or sand containing a sufficient amount of gold to be profitably worked) is thrown into this box, and water is run or poured upon it. The finer portion is thus carried through the holes, and directed by an inclined plate into the trough. The cradle is rocked from side to side, the light matters are carried away by the water, and the particles of gold and other heavy matters lodge behind the 'rimes', or transverse bars of wood, with which the bottom of the trough is fitted, and are afterwards collected.
Where practicable, the method known as 'sluicing' is often adopted for treating alluvial deposits. The 'sluices' consist of troughs called 'flumes', in sections about 3.5 meters long, inclined on trestles. The bottom of the sluice-box is crossed by 'riffle' bars of wood or iron. The smallest of the sluices consists of two such sections. Into the upper one the gravel is thrown, and the lower end is closed by an iron grid to keep back the pebbles and large stones, while the sand, etc, pass through to the lower trough. In this it deposits ite gold and heavy matters behind the riffle bars. In the longer sluices (say 75 meters long) the lower end of the upper section is not blocked, but near it the bottom consists of an iron grating - the 'grizzly'. The large stones are washed forward over the grating, but the sand and fine particles carried by the water fall through it on to the second section of the sluice. In some cases the fine sand, after passing through the first section of the sluice, falls on inclined tables covered witli blankets, rough cloth, or hides witli. the hairy side up, over which it flows in a thin stream. These 'blanket-strakes' serve to arrest and recover the fine gold. In other cases amalgamated copper plates are employed for the same purpose.
Where water is plentiful, 'hydraulic mining' is the cheapest mode of working. Under this system, 'deep leads' (which are alluvial deposits covered over with more recent matter in ancient river beds) and other alluvial deposits are worked by washing down the gravel by means of a powerful jet of water.
In quartz mining - and the case is similar with the hard, solid 'banket' formation of South Africa that contains tlie gold - the ore to be crushed is first passed through a 'stone-breaker' or 'ore crusher', and is further crushed by the 'stamps' or other grinding mill. The ordinary stamp-battery consists, in its lower part, of a cast-iron 'mortar-box', fitted on one or both sides with a fine screen. At the bottom of this box is a row of iron blocks called 'dies', upon which the stamps, or heavy cylindrical cast-iron blocks, are made to rise and fall by means of cams, being thus kept pounding away at the ore in the mortar-box. A stream of water is admitted, and carries the crushed material through the screens. Mercury is fed into the mortar-boxes in small quantities, and much of the gold is retained there on amalgamated copper plates. Slightly inclined amalgamated plates arranged in steps are placed in front of the battery, and over these the crushed orepulp passes slowly, the gold being retained by the amalgamated surfaces. The remaining product, or 'tailings', which may still contain some gold, is then treated either by 'concentration' and the concentrates chlorinated, or the whole is treated by the cyanide process.
For the concentrating process 'vanners' are generally employed. These consist of a slightly sloping table, formed of an endless travelling belt of rubber, which is stretched over rollers and so mounted as to be capable of violent agitation (the vibrations numbering 200 a minute) while moving slowly in an upward direction. The pulp is led on at the higher end, and the flow of water carries the light matters down the slope, the separation being greatly assisted by the shaking movement. The heavy matters only are carried forward by the belt over the higher end, and pass into a box below, being then known as 'concentrates'.
At one time large supplies of gold were obtained from Peru, Bolivia, and other parts of the New World. A rich source of the supply has long been the UralMountains, whence gold is still obtained. An immense increase in the world's production was caused by the discovery of gold in California in 1848, and Australia in 1851, while the South African gold-fields caused a similar increase. It is only since 1886 that the Transvaal became a great gold-producing area, the chief locality being the Witwatersrand.
In Western Australia many mines were opened at the end of the 19th century, and the Yukon district of Canada (Klondike) was also recognized as a gold-field in the 19th century. There are also gold-mines in India that have been worked with great success. Gold has been found in various parts of the United Kingdom, as in Sutherlandshire, Wicklow, and many places in Wales.
Early English architecture was the first of the pointed or Gothic styles of architecture that prevailed in England. It succeeded the Norman in the reign of Richard I (1189), and continued to the end of the reign of Henry II in 1272, a period of 123 years when it gradually merged into the Decorated style - some argue that the early English style continued until 1307.
One of the leading peculiarities in this style is the form of the windows, which are narrow in proportion to their height, and terminate in a pointed arch, resembling the blade of a lancet. Throughout the early period of the style they are very plain, particularly in small churches;
but in cathedrals and other large buildings the windows, frequently combined two or more together, are carried to a great height, are richly and deeply moulded, and the jambs ornamented with slender shafts. On the eastern and western fronts of small churches the windows are often combined in this manner, with a circular window above and a richly moulded door below; but in large buildings there is often more than one range of windows, and the combinations are very various. Though
separated on the outside, these lancets are in the interior combined into one design, thus giving the first idea of a compound window.
The doorways are in general pointed, and in rich buildings sometimes double; they are usually moulded, and enriched with the tooth-ornament. The buttresses are often very bold and prominent, and are frequently carried up to the top of the building with but little diminution, and terminate in acutely-pointed pediments, which, when raised above the parapet, produce in some degree the effect of pinnacles. In this style, likewise, flying-buttresses were first introduced, and the buttresses themselves much increased in projection owing to the comparative lightness of the walls, which required some counter-support to resist the outward pressure of the vaulting.
The roof in the Early English style appears always to have been high pitched, and the towers surmounted by lofty pointed spires, as at Salisbury Cathedral. In the interior the arches are usually lancet-shaped, and the pillars often reduced to very slender proportions. As if to give still greater lightness of appearance, they are frequently made up of a centre pillar, surrounded by slight detached shafts, only connected with the pillar by their capitals and bases, and bands of metal placed at intervals. These shafts are generally of Purbeckmarble, the pillar itself being of stone, and from their extreme slenderness they sometimes appear as if quite inadequate to support the weight above them. Some of the best examples are to be seen in SalisburyCathedral.
The architects of this style carried their ideas of lightness to the utmost limits of prudence, and their successors have been afraid to imitate their example. The abacus of the capitals is generally made up of two bold round mouldings, with a deep hollow between. The foliage is peculiar, generally very gracefully drawn, and thrown into elegant curves; it is usually termed stiff-leaved, from the circumstance of its rising with a stiff stem from the neck-mould of the capital. The trefoil is commonly imitated, and is very characteristic of the style. The mouldings of this style have great boldness, and produce a striking effect of light and shade. They consist chiefly of rounds separated by deep hollows, in which a peculiar ornament, called the dog's-tooth, is used, whenever ornament can be introduced. This ornament is as characteristic of the Early English as the zigzag is of the Norman. Research Early English
In music, a diminution is the imitation of, or reply to, a subject, in notes of half the length or value of those the subject itself within the counterpoint. Research Diminution
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Glacier
