Bistre, or bister is a warm brown pigment, a burned oil extracted from the soot of wood, especially beech. It furnishes a fine transparentwash, but was chiefly employed in the same fashion as sepia and Indian ink for monochrome sketches. Research Bistre
Chinaware is a name given to porcelain (pottery made from kaolin), so called from China being the first country to supply it to Europeans. It is thought that the Chinese produced porcelain from ancient times, but it wasn't until around 500 AD that they perfected the art. Chinaware first came to Europe in the beginning of the 16th century and won immediate popularity for its beauty and novelty.
The European consumers thought it impossible to match the whiteness of Chinaware, until John Frederick of Saxony, an alchemist, discovered a means of producing a porcelain equal in whiteness to the Chinaware. This led to the establishment by the Government of a factory at Meissen which started to produce porcelain rivalling the Chinaware in beauty and quality.
In France also about the middle of the 18th century the celebrated factory at Sevres was set up and soon acquired a great renown. In England a porcfaiain work was established at Chelsea some years prior to 1745; it was made at Stratford-le-Bow about the same time, at Derby as early as 1750, at Worcester in 1751. About 1755 kaolin or porcelain clay was discovered in Cornwall, and this contributed greatly to improve the quality of English porcelain, which began to be largely manufactured in Staffordshire under the auspices of Josiah Spode and Thomas Minton.
Chinaware, when broken, presents a granular surface with a compact, dense, firm, hard, vitreous and durable texture. It is semi-transparent, with a covering of white glaze, clear, smooth, unaffected by all acids except hydroflouric acid, and able to withstand sudden changes of temperature. Research Chinaware
Chitin is a sort of transparent horny substance, the chief tissue-forming ingredient of the wing-cases of insects, and the shells of crabs and other crustaceans. Research Chitin
Diorama is a mode of painting and of scenic exhibition invented by Messrs. Daguerre and Bouton, and first exhibited in 1823. It secures a higher degree of illusion than the ordinary panorama, by a mode of uniting transparent painting to the usual opaque method, and causing the light to fall upon the picture both from before and behind. At the same time, by means of coloured transparent blinds, suspended both above and behind the picture, the rays of light can be intercepted and made to fall at pleasure in graduated tints upon every part of the picture in succession. The term is now populary applied to small-scal tableau or models in which three dimensional figures are shown against a painted background, and stuffed animals etc are displayed against a natural scene. Research Diorama
Dresden China is a popular term for a delicate, semi-transparent, highly-finished porcelain made around the Dresden area of Germany. The term is variously used, being applied to porcelain made at Meissen, Sitzendorf and Volkstedt. The chief characteristics of 'Dresden China' is the elaborate designs and delicate colouring. Thus frequently Dresden china is found in the form of exquisite porcelain figurines.
The manufacture resulted from an accidentaldiscovery made by Bottger, a young chemist, in 1710, and the vases, statuettes, groups of figures, candelabra, clocks, etc, manufactured during the 18th century are highly prized. They are more remarkable for excellence of execution than for purity of design. Research Dresden China
Enamel is a vitreous glaze of various colours fused to the surface of gold, silver, copper, and other substances. The art of enamelling, which is of great antiquity, was practised by the Assyrians and by the Egyptians, from whom it may have passed into Greece, and thence into Rome and its provinces, including Great Britain, where various Roman antiquities with enamelled ornamentation have been discovered. The enamelled gold cup given by King John to the corporation of Lynn, in Norfolk, proves that the art was known among the Normans. The Byzantines of the 10th century produced excellent cloisonne enamels on a gold base, the cloisonne process consisting in tracing the design in fillets of gold upon the gold plate and filling up the small moulds thus formed with enamels the design appearing in coloured enamels separated by thin gold partitions or cloisons. In some cases, however, the enamels were filled into hollows beaten out in the gold plate, which formed part of the field.
In the 12th century the town of Limoges acquired the high reputation for inlaid enamels which it held until the 14th century, aud re-acquired in the 16th for its painted enamels. The costliness of the sculptured ground had led the Italians early in the 14th century to substitute the practice of incising the design on the face of the plate, and then covering it with a transparent enamel. The further step, which made the Limousin workshops famous, consisted in the method of superficial enamelling, in which opaque colours or colours laid on a white opaque ground were used. The Limoges school degenerated greatly in the 17th century, but its method with certain modifications in detail is still employed.
The basis of all kinds of enamel is a perfectly transparent and fusibleglass, which is rendered either semitransparent or opaque by the admixture of metallic oxides. White enamels are composed by melting the oxide of tin with glass, and adding a small quantity of manganese or phosphate of calcium to increase the brilliancy of the colour. The addition of the oxide of lead, or antimony, or oxide of silver, produces a yellow enamel. Reds are formed by copper, and by an intermixture of the oxides of gold and iron. Greens, violets, and blues are formed from the oxides of copper, cobalt, and iron.
In the middle of the 18th century enamelling was largely applied to the decoration of snuff-boxes, tea-canisters, candlesticks, and other small articles. Of later years it was extensively applied to the coating of iron vessels for domestic purposes, the protection of the insides of baths, cisterns, and boilers, and the like. Enamelling in colours upon iron was common, iron plates being thus treated by means of various mixtures, and words and designs of various kinds being permanently fixed upon them by stencilling, for advertising, signboards, etc.
Frankincense is a name given to the oleo-resinous exudations from different species of conifers. American frankincense is obtained as a soft, yellow, resinous solid, with a characteristic turpentine odour, from Pinus Taeda. Another kind is exuded by the spruce fir, and forms a soft solid, the colour of which varies from white to violet red. From this Burgundy pitch is prepared by melting in water and straining through a cloth. The frankincense employed in religious ceremonies (also called also incense and olibanum) is a gum-resin obtained from Boswellia thurifera (or serrata), a tree somewhat resembling the sumach, belonging to the Amyridaceae, and inhabiting the mountains of India. It comes in semi-transparent yellowish tears, or sometimes in masses and possesses a bitter and nauseous taste, and is capable of being pulverized. When burned it exhales a strong aromatic odour, on which account it was much employed in the ancient temples, and still continues to be used in Catholic churches. Research Frankincense
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
Gum is a substance of various properties which exudes spontaneously from the bark of certain trees, such as the plum, the peach, etc; or from incisions made in the bark to facilitate the flow. Gums form non-crystalline rounded drops or tears, the purest varieties being transparent or translucent, of a pale yellow but sometimes of a dark colour.
When dissolved in water gum forms a thick, smooth fluid, with considerable viscosity. Some gums, such as gum-arabic, dissolve in water; others, like tragacanth, are only partially soluble; they are insoluble in alcohol. By being insoluble in alcoholgums are distinguished from resins. They have no odour, and only a very faint taste. The different kinds of gum receive their names from the countries from which they are imported - such as gum-arabic, gum-senegal, Barbary gum, East India gum, etc, and from individual features, as cherry-tree gum, tragacanth, etc. Gum-resins require water and alcohol to dissolve them. Research Gum
Horn is a general term applied to all hard and pointed appendages of the head, as in deer, cattle, etc, but as a term denoting a particular kind of substance nothing should be called horn which is not derived from the epidermis or outer, layer of the integument, whether on the trunk, hoofs, or head.
Horn is a tough, flexible, semi-transparent substance, most liberally developed in the horns of bovine animals, but also found in connection with the 'shell' of the tortoise, the nails, claws, and hoofs of animals, the beak of bird and turtle, etc
Horn is softened very completely by heat, so as to become readily flexible, and to adhere to other pieces similarly softened. True horn consists principally of an albuminoid principle, keratin, with a small portion of gelatine and a little phosphate of lime. In some species of animals the males only have horns, as for instance the stag. In cattle both male and female have horns, though there are also hornless cattle.
Horns differ widely in the case of different animals. Thus the horns of deer consist of bone, and are deciduous; those of the giraffe are independent bones, with a covering of hairy skin; those of oxen, sheep, and antelopes consist of a bony core covered by a horny sheath. The horns of the rhinoceros alone consist exclusively of horny matter. The horns of oxen, sheep, goats, and antelopes are never shed, except in the case of the prong-horned antelope. The number never normally exceeds four, and in the case of deer the horns are branched.
The various kinds of horns were formerly employed for many purposes. The principal formerly used in the arts are those of the ox, buffalo, sheep, and goat. Deer horns were almost exclusively employed for the handles of knives and of sticks and umbrellas. Those which furnish true horn can be softened by heat (usually in boiling water), cut into sheets of various thickness, which sheets may be soldered or welded together at the edges so as to form plates of large dimensions, and were formerly polished and dyed so as to imitate the much more expensive tortoise-shell. The clippings of horn may be welded together in the same manner, and were formerly made into snuff-boxes, powder horns, handles for umbrellas, knives, forks, etc. As horn has the valuable property of taking on and retaining a sharp impression from a die, many highly ornamental articles were also turned out. Combs for the hair were made from the flattened sheets, and out of the solid parts of buffalo horns beautiful carvings were made. Research Horn
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Bistre
