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
Ivory is an opaque, creamy white, hard, fine-grained, modified dentin that composes the upper incisor teeth of an elephant. Ivory is composed of curved layers of dentine alternating in shade, that intersect one another; the resulting lozenge-shaped structure is elastic and finely grained. The layers of a tusk are deposited from the central pulp, so that the innermost layer is the newest. Most commercial elephant ivory is obtained from the tusks of the African elephant, mainly from eastern and central Africa. (Most of the ivory of the western half of Africa is hard, whereas that from the eastern half is soft. Hard ivory is glassier in texture, harder to cut and more likely to crack than soft ivory.)
Fossil ivory, called odontolite, is a blue variety that is found in small quantities in the frozen soil of northern Siberia. Odontolite was produced by the mammoths of the Pleistocene geological epoch; its blue colour results from saturation by metallic salts. Carved ivory has been used for decorative purposes since the time of the ancient Egyptians. Small pieces of ivory are used for high-quality furniture inlays, chess pieces, and small jewellery. Larger pieces of ivory sometimes have been used in the manufacture of billiard balls, piano keys, and toilet articles.
During the late 1980s, as Africa's elephant herds declined, environmentalists led a world-wide effort to shut down the ivory trade; in 1989 the USA and the European Union banned all ivory imports. Tusks of several other animals such as hippopotamuses, narwhals, sperm whales, and walruses are commonly called ivory and have similar physical properties, and many plastic substitutes for ivory have been developed. Several ivory-like vegetable parts are also used in imitation of ivory; the ivory palm, for example, produces large, white, hard seeds, called ivory nuts, the endosperm of which is commonly known as vegetable ivory. In painting, ivory is a delicate colour deeper in tone than off-white, but not so deep as cream. Research Ivory
The knout was a Russian instrument of punishment. It consisted of a handle about 60 cm long, to which was fastened a flat leatherthong about twice the length of the handle, terminating with a large copper or brass ring; to this ring was affixed a strip of hide about five centimetres broad at the ring, and terminating at the end of 60 cm in a point. This was soaked in milk and dried in the sun to make it harder, and should it fall, in striking, the culprit on the edge, it would cut like a penknife. The culprit was bound erect to two stakes to receive the specified number of lashes on the back, and the tail of the knout was changed at every sixth stroke. Punishment by the knout often resulted in the death of the victim. It was abolished by Tsar Nicholas I. Research Knout
Spider Beetles is the common name for insects of the family Ptinidae, order Coleoptera, so named from their appearance which resembles a spider with three pairs of long legs. The adults frequently live on dry substances, while the larvae develop chiefly in grain, cereal products and dried plant material before tunnelling into harder material to pupate. Research Spider Beetles
A bullet is the projectile expelled from a gun. It is not synonymous with cartridge. Bullets can be of many materials, shapes, weights and constructions such as solid lead, lead with a jacket of harder metal, round- nosed, flat-nosed, hollow-pointed, etc. Research Bullet
Bronze is an alloy of copper, to which other metallic substances are sometimes added, especially zinc. It is a finegrained metal, taking a smooth and polished surface, harder and more fusible than copper, but not so malleable. In various parts of the world weapons and implements were made of this alloy before iron came into use, and hence the bronze age is regarded as one coming between the stone age and the iron age of prehistoric archeology.
Both in ancient and modern times bronze has been much used in making casts of all kinds, medals, bas-reliefs, statues, and other works of art; and varieties of it are also used for bells, gongs, reflectors of telescopes, and formerly for cannons, etc.
Bronze is of a reddish, brownish, or olive-green colour, and is darkened by exposure to the atmosphere. Ancient bronze generally contains from 4 to 15 percent of tin. The alloy of British bronze coinage at the start of the 20th century consisted of 94 parts of copper, 4 of tin, and 1 of zinc. An alloy of about 85 parts copper, 11 zinc, and 4 tin is used for statues. Bell-metal consists of 78 of copper and 22 of tin. An alloy called phosphor bronze, consisting of about 90 percent of copper, 9 of tin, and from .5 to .75 of phosphorus has been found to have peculiar advantages for certain purposes. The addition of phosphorus increases the homogeneousness of the compound, and by varying the proportion of the constituents the hardness, tenacity, and elasticity of the alloy may be modified at pleasure. Research Bronze
Chilled Iron is iron cast in metal moulds called chills, where, on account of the rapid conducting of the heat, the iron cools more quickly on the surface than it would do if cast in sand. Chilled iron is whiter and has a harder surface than iron cast in any other way. Research Chilled Iron
A file is a bar of cast-steel with small sharp-edged elevations on its surface called teeth, the use of which is to cut into or abrade metals, wood, ivory, horn, plastic etc.
Files are of various shapes, as flat, half-round, three-sided, square, or round, and are generally thickest in the middle, while their teeth are of various degrees of fineness and of different forms. A file whose teeth are in parallel ridges only is called single-cut or float-cut. Such are mostly used for brass and copper.
When there are two series of ridges crossing each other the file is double-cut, which is the file best suited for iron and steel.
Rasps are files which have isolated sharp teeth separated by comparatively wide spaces, and are used chiefly for soft materials such as wood, plastic and horn.
Each of these three classes of files is traditionally made in six different degrees of fineness, the coarsest being called rough, the next middle, followed by bastard, second-cut, smooth, and superfine or deadsmooth, each a degree finer than that which precedes it. Files were formerly made by the hand, The bionics, as the steel before it has teeth is called, were laid on the anvil and struck with the chisel, which rested obliquely on the blank, each blow raising a ridge or tooth. The strength of the blow depended on the hardness of the metal, and when one part is harder than another the workman altered his blows accordingly. When one side is covered with single cuts, if the file was to be double cut he added in the same manner a second series, crossing the others at a certain angle. In making fine files a good file-cutter would cut upwards of two hundred teeth within the space of an inch. The files, except those that are used for soft substances, were then hardened by heating them to a cherry-red colour and then dipping them in water. They were then finished by scouring and rubbing over with olive-oil and turpentine.
German silver also known as nickel silver or pack-fong is an alloy of copper, zinc and nickel. It was first made in Europe at Hildberghausen in Germany, but was invented by the Chinese long before. German silver is made in different proportions, amongst which the following may be mentioned. Spoons and forks were made from two parts copper, one nickel, and one zinc; knife and fork handles were typically made from 5 copper, 2 nickel, 2 zinc, a mixture closely resembling alloyed silver. The addition of lead produces an alloy which appears well fitted for casts, and for making candlesticks, etc. Iron or steel, on the other hand, makes the alloy whiter, harder, and more brittle. German silver is harder than silver, and takes a high polish. It melts at a red heat, the zinc being volatilized in the open air. It is attacked by the strong acids, but it is also affected by common organic acids, such as vinegar, and by some saline solutions. Research German Silver
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Glacier
