Vera Caslavska is a Czech gymnast. She was born in 1942 at Prague. Originally a promising ice skater, when she was fifteen she was invited to take part in trials to find gymnastic talent and trained with Bosakova, going on to win 22 titles in Olympic, World and European championships including the gold medal at the 1964 and 1968 Olympic Games for the combined exercises, at the 1964 Olympic Games she also won the gold medal for the beam and the vault. She was famed also for her floor routine known as the 'Mexican Hat Dance', which was greeted with rapturous applause by audiences. Research Vera Caslavska
The sagittal suture runs longitudinally along the crest of the head from the frontal bone to the occipital. This suture joins the two parietal bones in the middle of the cranial vault. The sagittal suture intersects the coronal suture perpendicularly, and the lambdoid suture in a tripartite manner. Research Sagittal Suture
Glass is an artificial hard, brittle, transparent or translucent, noncrystalline solid, consisting of metal silicates or similar compounds fused with an alkali. In its finest qualities glass is quite transparent, and is used for making windows, mirrors, bottles, composite armour plate for armoured fighting vehicles etc.
The ancient Egyptians carried the art of making glass to great perfection, and are known to have practised it as early as 2000 BC, if not earlier. The Assyrians, the Phoenicians, the Greeks and Etruscans were all acquainted with the manufacture. The Romans attained peculiar excellence in glass-making, and among them it was applied to a great variety of purposes. Among the most beautiful specimens of their art are the vases adorned with engraved figures in relief; they were sometimes transparent, sometimes of different colours on a dark ground, and very delicately executed. The Portland or Barberini vase is almost the only surviving specimen of this kind. The mode of preparing glass was known long before it was thought of making windows of it. The first mention of this mode of using glass is to be found in
Lactantius, in the 3rd century AD. St Jerome also speaks of glass being so used in 422 AD.
Benedict Biscop introduced glass windows into Britain in 674 AD. In church windows it was used from the 3rd century. The Venetians were long celebrated for their glass manufacture, which was established before 700 AD. Britain did not become distinguished for glass until about the commencement of the 16th century.
The excise laws relative to the glass manufacture were at one time complicated in the extreme, and tended to check improvements in glass-making. These laws were repealed in 1845 by Sir Robert Peel, as part of his free-trade policy, and beneficial effects were immediately apparent in the improved quality, cheapness, and greater variety of descriptions of glass produced. Traditionally, glass is largely made in France, Germany, Belgium, and the United States. For coloured glass Bohemia has long had a high reputation.
The first mention of the manufacture of glass in the United States is in Captain John Smith's 'History of Virginia', in which he speaks of a glass factory having been founded at Jamestown in 1615, and a second in 1622. The work was coarse, being chiefly confined to bottles. In 1754, a successful factory was established in Brooklyn by Bamper, a Dutchman. In 1779, factories were founded at Temple, New Hampshire, and in 1795 the industry was begun at Pittsburgh. By 1813 there were five glass factories at Pittsburgh. In 1840 there were eighty-one factories in the United States, by 1870, 201 factories flourished in different places and since then the industry rapidly increased.
Glass is formed by the fusion of siliceous matter, such as powdered flint or fine sand, together with some alkali, alkaline earth, salt, or metallic oxide. The nature of the glass will depend upon the quality and proportion of the ingredients of which it is formed; and thus an infinite variety of kinds of glass may be made, but in commerce five kinds are usually recognized:
1. Bottle or coarse green glass. 2. Broad, spread, or sheet window-glass. 3. Crown-glass, or the best window-glass. 4. Plate-glass, or glass of pure soda. 5. Flint-glass, or glass of lead.
Coloured glass may be mentioned as a sixth kind. The physical properties of glass are of the highest importance. Perhaps the chief of these is its transparency, and next to that its resistance to acids (except hydrofluoric acid). It preserves its transparency in a considerable heat, and its expansibility is less than that of any other known solid. Its great ductility, when heated, is also a remarkable property. It can, in this state, be drawn into all shapes, and even be spun into the finest threads. It is a bad conductor of heat, and is very brittle. It is usually cut by the diamond.
The works in which glass is made are called glass-houses. They were traditionally constructed of brick, and made of conical form. A large vault was made in the interior of the cone, extending from side to side, and of sufficient height to allow workmen to wheel in and out rubbish from beneath the furnace, which was placed over the vault, and separated from it by an iron grating. The materials used for the formation of the glass are sometimes calcined in a calcar or fritting furnace, and a chemical union between the ingredients commenced, forming a frit. But this process is not essential, and the materials, after being ground and thoroughly mixed up together, are usually placed at once in melting pots or crucibles made of Stourbridgefire-clay, or other similar material, the melting-pots being then placed in the melting furnace or oven. This is a kind of reverberatory furnace, traditionally circular in form, arched or domed above, and capable of keeping up an intense heat. The crucibles are placed in the furnace at equal distances from each other round the circumference, each pot being opposite to an opening in the wall of the furnace in order that the crucible may be charged or discharged by the workman from without. In the 19th century a furnace called a tankfurnace came into use which enabled melting pots to be dispensed with, as the material could be melted in and worked from the furnace directly.
The use of the annealingfurnace, is also essential in glass-making, the process of allowing the glass to cool there being called annealing. Unless this process be carefully managed, the articles formed in the glass-house can be of no use, from their liability to break by the slightest scratch or change of temperature.
Sheet glass is the commonest description of glass. It is composed of various ingredients in varying proportions, usually of sand, chalk, or limestone, sulphate of soda, and cullet or broken glass. A coarse variety of it may be made of a mixture of two parts by measure of soap-boilers' waste, one of soda-ash and one of cleaned sand. In France the materials employed are commonly: sand 100 parts, sulphate of soda 30, carbonate of lime 30, coke to aid in the reduction of the sulphate of soda 5, with some bioxide of manganese to correct the greenish tinge that glass with a soda base possesses. Traditionally when the materials were properly melted a quantity was taken out of the pot on the end of an iron tube about 5 feet long, and the workman by blowing into and swinging the tube while heating and reheating the glass, imparted a cylindrical shape to the newly-formed product. The rounded extremity of the cylinder (which was about 4 feet long or more) was softened in the furnace in order to enable the workman to blow a hole in it. This opening was made by heating the cylinder and then stopping up the tube with the thumb, when the expansion of the air caused the cylinder to burst open at the end. The other rounded end was detached after cooling by winding round its circumference a thread of red hot glass, which caused a clear fracture. The cylinder was then split open parallel to its axis by a diamond, and then conveyed to the flattening furnace where it was heated and opened out into a flat sheet of glass. It was afterwards placed in the annealingfurnace.
Crown glass is differently formed by different makers, but its composition is essentially the same as the best sheet glass. It used to be the only window-glass made in Britain, but its manufacture had been almost or altogether superseded by that of sheet glass by the start of the 20th century. The ingredients being melted and at the proper temperature, a quantity of the glass was withdrawn by the tube (to the amount, by successive addition, usually of 10 lbs in all). By various manipulations this from having the form of a hollow oblate spheroid was made to assume the form of a thin circular plate, with a thick part called the bull's eye in the centre, being the point at which an iron rod was attached to it for the purpose of causing it to revolve rapidly and spread out into a sheet before the furnace. The bull's eye used to be commonly seen in the windows of humble dwellings, the pieces of glass containing them being cheap.
Flint-glass or Crystal is one of the kinds largely made, being employed especially for table utensils, globes, ornaments, etc. Powdered flint was formerly employed in its manufacture, but fine white sand has been substituted. The other materials are red-lead or litharge, and pearl-ash (carbonate of potash). The following is said to be a good mixture : Fine white sand, 300 parts; red-lead or litharge, 200; refined pearl-ash, 86; nitre, 20; with a small quantity of arsenic and manganese. The furnace is kept at a very high temperature until the whole of the materials are fused. When the glass becomes translucent the temperature is diminished until it becomes a tenacious mass. Suppose a glass vessel is to be made, the iron tube is put into the crucible, and the required quantity of glass lifted out, which after certain adjustments is rolled into a cylindrical form on an iron table called the merver or marver. The workman
then blows the glass into the form of a hollow globe, and re-heats and blows until the globe becomes of the required thinness. An iron rod called the punty is now attached to the end of the glass furthest from the tube, and the tube detached. The workman now heats the glass on the punty, and sitting down upon a chair with smooth arms, he lays the punty upon them, and rolling it with his left hand he gives the glass a rotatory motion, while with an instrument in his right, somewhat like a pair of sugar-tongs, he enlarges or contracts the different parts of the vessel until it assumes the requisite shape. A pair of shear's is al.so made use of in certain cases. The article is then detached from the punty, and carried to the annealingfurnace. Many of the articles, after coming from the annealingfurnace, are sent to the cutter or grinder. The operation of grinding is performed by wheels of various diameter and of various edges, some of iron, others of stone, and some of wood. Rich and delicate designs may be cut upon the articles by means of small wheels of copper and steel upon which emery is kept constantly falling.
Ornamental figures may also be engraved, or rather etched, upon articles of glass by means of hydrofluoric acid, care being taken to place a coating of some substance over the parts not to be acted upon. Various ornamental forms are given to the surface of glass vessels by metallic moulds. The mould is usually of copper, with the figure cut on its inside, and opens with hinges to permit the glass to be taken out. The angles of moulded objects are always less sharp than those of cut-glass.
Green or bottle-glass is formed of the coarsest materials, such as coarse sea or river sand, lime, and clay, and the most inferior alkalies, as soap-boilers' waste, and the slag of iron ore. A cheap mixture for this kind of glass may be made of common sand and lime, with a little clay and sea salt. The manipulations of the traditional glass-blower in fashioning bottle-glass into various forms were in general the same as those performed by the flint-glass blower. Wine and beer bottles, which are required to be all of a certain capacity, are blown in moulds, so that their containing portion may be as nearly as possible of the requisite size. When the articles are made they are carried to the annealingfurnace. Green bottle-glass is preferable to all other kinds for vessels required to contain corrosive substances; it is less fusible than flint glass, and
thus is better calculated for many chemical purposes.
Plate-glass is a fine and thick glass cast in sheets. One maker's ingredients are as follows: white sand, 300 lbs; soda, 200; lime, 30; oxide of manganese, 2; oxide of cobalt, 3 ounces; and fragments of glass (cullet) equal to the weight of sand. After being melted in large crucibles, and the liquid glass having been thoroughly skimmed, it is transferred by a copper ladle to smaller pots (cuvettes). When the glass in the smaller crucible is ready for casting it is poured upon an iron casting-table, and a large metal cylinder moved along spreads the glass into a broad uniformsheet. The subsequent stages of the process are concerned with the discovery of flaws, the squaring of the edges, the grinding of the surfaces plane, the grinding of the sides, and the polishing. Before grinding and polishing the glass is what is called common 'rough plate,' and in this state it is much used for roofing, cellar-lighting, etc, being non-transparent. 'Rolled plate,' which is cast on a table that imparts a surface of grooves, flutings, lines, etc, is extensively used for the same purposes.
There are several other kinds of glass that may be noticed. Pressed glass is flint-glass formed into articles by pressing into moulds of iron or bronze, a fine surface being afterwards attained by heating so that a thin film on the surface melts.
Slag glass is glass from the slag of blast-furnaces mixed with other ingredients; it is largely used for bottles.
Optical glass is made of special varieties of flint and crown glass.
Strass, which was used for imitating gems, was a very dense flint-glass, colours being imparted by metallic oxides.
Spun glass is glass in the form of very fine threads, in which state it may be woven into textile fabrics of great beauty.
Toughened or hardened glass, having certain properties owing to its being heated to the melting point and plunged into an oleaginous mixture, was invented prior to the start of the 20th century, but was not developed into a working product until the mid-20th century, and is now very commonly used for windows.
Coloured glass is of two kinds - entirely coloured, the colouring matter being melted along with the other ingredients; or partially coloured, a quantity of white glass being gathered from one pot, and dipped into the other containing the coloured glass, by which the whole receives a skin of coloured glass. The colouring matters are chiefly the metallic oxides. A beautiful yellow colour is imparted by silver in union with alumina (powdered clay and chloride of silver being used), also by uranium and by glass of antimony; red colours by oxide of iron, copper, and gold; green by protoxide of iron, oxide of copper, oxide of chromium, &c.; blue by cobalt; orange by peroxide of iron with chloride of silver. ohemia is particularly famous for its manufactures of articles in coloured glass. Research Glass
Time Lock is a drama starring Robert Beatty, Lee Patterson, Betty McDowall and Vincent Winter in a story about experts racing against time to try and rescue a young boy accidentally locked in a bank vault which has been closed for the weekend. Time Lock was directed by Gerald Thomas in 1957. Research Time Lock
The Pole Vault is a standard field event for men in the programme of all major athletics championships. Pole vaulting is a jumping contest for height, competitors using a pole to lever their bodies over a bar which is raised according to a fixed progression. Vaulters failing to clear each height within three attempts are eliminated and the winner is the athlete who clears the greatest height. Research Pole Vault
In architecture, back filling refers to the mass of materials used in filling up the space between two walls, or between the inner and outer faces of a wall, or upon the haunches of an arch or vault. Research Back filling
In architecture a barrel vault (Cradle vault, cylindrical vault or wagon vault) is a kind of vault having two parallel abutments, and the same section or profile at all points. It may be rampant, as over a staircase or curved in plan, as around the apse of a church. Research Barrel Vault
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Vera Caslavska
