Glass sentence example

glass
  • Could I have a glass of water?
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  • He set a glass of Coke on the counter before her.
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  • It was senseless to look elsewhere, as both had been present when Cynthia placed the small fragment in the cut glass enclosure.
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  • Picking up the glass of orange juice, he took a swallow.
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  • I shook my head and took them all off and made her feel of the two wooden beads and the one glass bead.
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  • I took them off and showed her that the two wooden ones must go on first, then the glass bead.
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  • Let me get you a glass.
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  • She brought him a plate of warm cookies and a glass of milk.
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  • She returned with a bottle and a glass.
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  • Either that or change my eye glass prescription.
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  • Finally, his intent gaze left the glass and found hers.
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  • Daniela refilled the glass without asking, and Deidre drank more.
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  • The glass carafe exploded.
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  • Jackson collected his painting and glass.
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  • He sat down with the bottle, not bothering to use a glass.
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  • She snatched it and swept past him, popping it open as she neared a wall covered in a titanium glass screen.
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  • It is well known that a large plate of glass will have a green tint, owing, as the makers say, to its "body," but a small piece of the same will be colorless.
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  • She stared at her glass.
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  • He smiled and joined us for a glass.
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  • He's run it all summer, Martha said, handing Howie a glass.
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  • I didn't manage to say much before I heard the sound of breaking glass.
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  • She poured the last of the liquor into her glass.
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  • Lydia Larkin continued to stare, then shrugged and began filling her glass.
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  • He found a fifth of whiskey setting on the counter and opened half the cabinet doors before finding a glass.
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  • She refilled he glass.
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  • She cleared her throat, staring into the wine glass.
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  • He swiped a badge to enter what she imagined was the Mecca of all science labs, with rows of stainless steel, machines, computers, and glass.
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  • She waited until the door closed before crossing to the carafe and refilling her glass.
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  • Kris accepted the glass of whiskey but avoided Jade's extended hand.
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  • Completely free, she relaxed and accepted a glass of champagne from one of the wait staff and waded toward the buffet.
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  • Dean rose to pour himself a glass of milk.
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  • Brady watched Angel carefully place the keypad into a wall with several others, then secure them behind a thick shield of titanium glass.
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  • The only thing she had to eat since yesterday noon was a glass of milk in the wee hours of the morning.
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  • The discrepancies produced in this way are, however, very small, if care is taken to minimize the distance between the silver film and the photographic plate and to select a reasonably good piece of glass for the reseau.
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  • The image of the star is set updn the intersections of the lines of the central cross, and the positions of the reseau-lines are read off by estimation to - of a division on the glass scale.
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  • The object glass of the micrometer-microscope is placed midway between the plane of the photographic plate and the plane of the micrometer webs.
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  • Its fundamental principle is that, by a combination of glass scales with a micrometer screw, " the chief part of the distance to be measured is read off on the scale; the fractional part of the scalespace is not estimated but measured by the screw."
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  • In light Kundt's name is widely known for his inquiries in anomalous dispersion, not only in liquids and vapours, but even in metals, which he obtained in very thin films by means of a laborious process of electrolytic deposition upon platinized glass.
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  • The building, chiefly of iron and glass, is flanked by two towers and is visible from far over the metropolis.
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  • He obtains a magic glass cage, yoked with eight griffins, flies through the clouds, and, thanks to enchanters who know the language of birds, gets information as to their manners and customs, and ultimately receives their submission.
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  • That he was capable of better work than is suggested by his average accomplishment is shown by two allegorical poems - the Complaint of the Black Knight and the Temple of Glass (once attributed to Hawes).
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  • Lydgate's most doughty and learned apologist is Dr Schick, whose preface to the Temple of Glass embodies practically all that is known or conjectured concerning this author, including the chronological order of his works.
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  • The import trade shows the largest totals in foodstuffs, wines and liquors, textiles and raw materials for their manufacture, wood and its manufactures, iron and its manufactures, paper and cardboard, glass and ceramic wares.
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  • The market-gardeners of Paris and its vicinity have a high reputation for skill in the forcing of early vegetables under glass.
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  • Glass is manufactured in the departments of Nord (Aniche, &c.), Seine, Loire (Rive-de-Gier) and Meurthe-et-Moselle, Baccarat in the latter department being famous for its table-glass.
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  • It fumes strongly in air, and does not attack glass.
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  • The town has a tribunal of commerce and a communal college, flour-mills, manufactories of earthenware, biscuits, furniture, casks, and glass and brick works; the port has trade in grain, timber, hemp, flax, &c.
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  • Among the industrial establishments of the city are stove and range factories, flour mills, rolling mills, distilleries, breweries, shoe factories, copper refining works, nail and tack factories, glass works and agricultural implement factories.
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  • These vary in form, but essentially they consist of a stem of porcelain, coarse earthenware, glass or other non-conducting substance, protected by an overhanging roof or screen.
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  • In the Korn apparatus the light from a Nernst electric lamp is concentrated to a point by means of a lens on the original picture, which is wound on a glass cylinder in the shape of a transparent photographic film.
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  • A totally reflecting prism placed inside the glass cylinder projects the light which penetrates the film upon a selenium cell situated at the end of the cylinder.
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  • A fine glass siphon tube is suspended with freedom to move in only one degree, and is connected with the signal-coil and moves with it.
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  • He constructed one form of his coherer of a glass tube a few inches long filled with iron borings or brass filings, having contact plates or pins at the end.
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  • The tube is then exhausted of its air, and attached to a bone or glass rod as a holder.
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  • The transformer T has its secondary or high-pressure terminals connected to spark balls S1, which are also connected by a circuit consisting of a large glass plate condenser C, and the primary circuit of an air-core transformer called an oscillation transformer.
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  • In its course it passes through a glass tube wound over with two coils of wire; one of these is an oscillation coil through which the oscillations to be detected pass, and the other is in connexion with a telephone.
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  • If a loop of very fine platinum wire, prepared by the Wollaston process, is included in an exhausted glass bulb like an incandescent lamp, then when electric oscillations are sent through it its resistance is increased.
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  • Down the inner test tube pass four copper strips having platinum wires at their ends sealed through the glass.
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  • This plate is supported by a platinum wire sealed through the glass.
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  • A highly insulated tube contains a little mercury, which is used as a negative electrode, and the tube also has sealed through the glass a platinum wire carrying an iron plate as an anode.
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  • The finest glass is made in Tuscany and Venetia; Venetian glass is often colored and of artistic form.
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  • A vast variety of trinketsin coral, glass, lava, &c.is exported from Italy, or carried away by the annual host of tourists.
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  • The richest, however, of the co-operative societies, though few in number, are those for the production of electricity, for textile industries and for ceramic and glass manufactures.
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  • The most important imports are minerals, including coal and metals (both in pig and wrought); silks, raw, spun and woven; stone, potters earths, earthenware and glass; corn, flour and farinaceous products; cotton, raw, spun and woven; and live stock.
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  • In the south the body is slightly cut by women with small flakes of glass or quartz in zigzag or lineal patterns downwards.
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  • Amber has often been imitated by other resins like copal and kauri, as well as by celluloid and even glass.
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  • The architecture of the department is chiefly displayed in its churches, many of which possess stained glass of the 16th century.
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  • In its simplest form it consists of a tube about twelve inches long containing two glass plates, extending along its whole length and inclined at an angle of 60°.
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  • The eye-end of the tube is closed by a metal plate having a small hole at its centre near the intersection of the glass plates.
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  • The other end is closed by a plate of muffed glass at the distance of distinct vision, and parallel to this is fixed a plate of clear glass.
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  • In the intervening space (the object-box) are contained a number of fragments of brilliantly coloured glass, and as the tube is turned round its axis these fragments alter their positions and give rise to the various patterns.
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  • These images take the place of the coloured fragments of glass, and they are symmetrically multiplied by the mirrors.
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  • The town gives its name to an important coalbasin, and carries on the manufacture of glass.
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  • The city has a considerable trade with the surrounding country, in which large quantities of tobacco and hemp are produced; its manufactures include lumber, brooms, chairs, shoes, hemp twine, canned vegetables and glass bottles.
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  • Sometimes a 30-second glass is used instead of a 28-second one, and the intervals between the knots on the log-line are then made 50 ft.
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  • For speeds over six knots a 14-second glass is employed, and the speed indicated by the log-line is doubled.
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  • When the bunting at the end of the stray line passes his hand, he calls to his assistant to turn the glass, and allows the line to pay out freely.
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  • In a steam vessel running at high speed on an ocean route, with engines working smoothly and uniformly, a careful officer with correct line and glass can obtain very accurate results with the common log.
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  • Pop. (1 9 01) 3799 The church of the Holy Trinity, one of the most noteworthy in Staffordshire, is principally Early English, and has fine stained glass.
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  • Next after cottons come woollens, silk, cloth, chemicals, machinery, paper, furniture, hats, cement, leather, glass and china and other products.
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  • Whatever the pattern adopted for the roof, a sufficient portion of it must be glazed to admit light, and it should be so designed that the ironwork can be easily inspected and painted and the glass readily cleaned.
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  • Gradually, however, the accommodation improved, and by the middle of the 19th century second-class passengers had begun to enjoy " good glass windows and cushions on the seat," the fares they paid being about 2d.
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  • The great reflecting telescope at Dorpat was manufactured by him, and so great was the skill he attained in the making of lenses for achromatic telescopes that, in a letter to Sir David Brewster, he expressed his willingness to furnish an achromatic glass of 18 in.
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  • Manufactures based on the products of mines and quarries (chemicals, glass, clay, stone and metal works) constituted about one-fifth of the whole product.
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  • Parkersburg is the see of a Protestant Episcopal bishop. Oil, coal, natural gas and fire-clay abound in the neighbouring region, and the city is engaged in the refining of oil and the manufacture of pottery, brick and tile, glass, lumber, furniture, flour, steel, and foundry and machine-shop products.
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  • In the Industrial Museum there is (besides collections of various kinds) some good painted glass of the 16th century, taken from the neighbouring Benedictine monastery of Muri (founded 1027, suppressed 1841 - the monks, are now quartered at Gries, near Botzen, in Tirol).
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  • The calorimeter used for solutions is usually cylindrical, and made of glass or a metal which is not, attacked by the reacting substances.
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  • In the older type the combustion chamber (of metal or glass) is sunk in the calorimeter proper, tubes being provided for the entrance and exit of the gaseous substances involved in the action.
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  • The city's manufactures include glass, brick, tile, carriages and wagons, agricultural implements, pianos and organs and cigars.
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  • The principal imports are butter, woollens, timber, cereals, eggs, glass, cottons, preserved meat, wool, sugar and bacon.
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  • They have a passion for fine clothes and ornaments, tricking themselves out with glass trinkets, rings and articles of ivory and horn.
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  • The abbey church contained famous stained glass, and some of this is preserved in the neighbouring church at Morley.
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  • The parish churches of Dronfield, Hathersage (with some notable stained glass), Sandiacre and Tideswell exemplify the Decorated period; the last is a particularly stately and beautiful building, with a lofty and ornate western tower and some good early brasses.
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  • From 1879 to 1888 he was engaged on difficult experimental investigations, which began with an inquiry into the corrections required, owing to the great pressures to which the instruments had been subjected, in the readings of the thermometers employed by the "Challenger" expedition for observing deep-sea temperatures, and which were extended to include the compressibility of water, glass and mercury.
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  • These flew away, leaving their cup at the water's edge, and singing "If that glass either break or fall, Farewell to the luck of Eden Hall."
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  • It is a tradition that, this work not being favourably regarded by the authorities of the Paris Museum, its draughtsman and author were refused closer access to the specimens required, and had to draw and describe them through the glass as they stood on the shelves of the cases.
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  • They hold in their hands books turned upside down, and pretend to read through spectacles in which for glass have been substituted bits of orange-peel."
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  • The pavement consists partly of opus Alexandrinum of red and green porphyry mixed with marbles, partly of tesselated work of glass and marble tesserae.
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  • Like many other arts in Venice, that of glass-making appears to have been imported from Moslem countries, and the influence of Oriental design can be traced in much of the Venetian glass.
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  • The art of making stained xxv11.3 2 a glass windows was not practised by the Venetians; almost the only fine glass in Venice is that in a south transept window in the Dominican church, which, though designed by able Venetian painters, is obviously the work of foreigners.
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  • Similarly, the glass industry has revived.
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  • Other valuable minerals are clay suitable for making pottery, brick and tile (in 1908 the value of the clay working products was $26,622,490) and sand suitable for making glass.
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  • An active trade is carried on with Austria, especially through the Isakovets and Gusyatin custom-houses, corn, cattle, horses, skins, wool, linseed and hemp seed being exported, in exchange for wooden wares, linen, woollen stuffs, cotton, glass and agricultural implements.
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  • Scheele had done, and because he was employing a glass vessel he got "fluor acid air" (silicon fluoride).
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  • It is the chief seat of the glass pearl and imitation jewelry manufacture, and has also an important textile industry, and produces large quantities of hardware, papier mache and other paper goods.
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  • The earliest form of testing instrument employed for this purpose was that of Giuseppe Tagliabue of New York, which consists of a glass cup placed in a copper water bath heated by a spirit lamp. The cup is filled with the oil to be tested, a thermometer placed in it and heat applied, the temperatures being noted at which, on passing a lighted splinter of wood over the surface of the oil, a flash occurs, and after further heating, the oil ignites.
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  • Industry especially attained a high state of development; rich garments were embroidered, and glass, pastes, faience, &c., were manufactured.
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  • It consists of a glass bulb, in which there is a loop of fine wire, and to the bulb is attached a U-tube in which there is some liquid.
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  • But side by side with this literary transmission Berthelot insists that there was another mode of transmission, by means of the knowledge of practical receipts and processes traditional among jewellers, painters, workers in glass and pottery, and other handicraftsmen.
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  • The city's manufactures include glass, brick, tile, foundry and machine-shop products, &c. In 1905 the factory product was valued at $1,888,894, being 51.4% greater than in 1900.
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  • Nursery and market gardening, largely under glass, brickmaking and saw-mills are the chief industries of Cheshunt.
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  • The central tower and the south portal (13th century) are the chief features of its simple exterior; in the interior, the decorative work, notably the chapel-screens and some fine stained glass, is remarkable.
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  • The chief industries include distilleries, breweries, glass works, cigar factories and the ancient linen and cutlery manufactures.
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  • The manufacture of glass, also practised in Egypt, demanded a knowledge of sodium or potassium carbonates; the former occurs as an efflorescence on the shores of certain lakes; the latter was obtained from wood ashes.
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  • The oxidation, which is effected by chromic acid and sulphuric acid, is conducted in a flask provided with a funnel and escape tube, and the carbon dioxide formed is swept by a current of dry air, previously freed from carbon dioxide, through a drying tube to a set of potash bulbs and a tube containing soda-lime; if halogens are present, a small wash bottle containing potassium iodide, and a U tube containing glass wool moistened with silver nitrate on one side and strong sulphuric acid on the other, must be inserted between the flask and the drying tube.
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  • In this method the operation is carried out in a hard glass tube sealed at one end and packed as shown in fig.
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  • Attached to the bulb was a glass rod and then a tube containing iron wire.
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  • The chief article of export is coal from the neighbouring collieries, the other leading exports being ale, whisky, glass and manufactured goods.
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  • The churches of St Etienne and St Jean, both of the Renaissance period with later additions, preserve stained glass of the 16th century.
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  • Instead of drawing these squares upon the map itself, they may be engraved or etched upon glass, or drawn upon transparent celluloid or tracing-paper.
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  • The manufactures include boots and shoes, glass and agricultural implements.
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  • Saw-mills, iron foundries, chemicals, glass and soap works, shipbuilding yards and a cocoanut-oil factory in connexion with the soap-manufacture at Port Sunlight, England,are among the chief industrial establishments.
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  • Coal, oil, natural gas, clay and iron are found in the vicinity, and among the city's manufactures are iron, steel, glass, furniture and pottery.
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  • On the south bank of the river is the township and urban district of Cowpen (pop. 17,879), with collieries and glass works; coal is shipped from this point by river.
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  • Owing to their want of adhesiveness, they are, however, usually mounted on glass as microscopic slides, either in glycerin jelly, Canada balsam or some other suitable medium.
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  • A plan which has been found to answer well is to arrange them in cardboard boxes, either with glass tops or in sliding covers, in drawers - the name being placed outside each box and the specimens gummed into the boxes.
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  • The stained glass both in the cathedral and in other churches of the city is particularly noteworthy; its survival may be traced to the stipulation made by the citizens when surrendering to parliament in the civil wars that it should not be damaged.
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  • The statuary of the lateral portals, the stained glass of the 13th century, and the choir-screen of the Renaissance are all unique from the artistic standpoint.
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  • The abbey church of St Pierre, dating chiefly from the 1 3 th century, contains, besides some fine stained glass, twelve representations of the apostles in enamel, executed about 1 547 by Leonard Limosin.
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  • The game-pies and other delicacies of Chartres are well known, and the industries also include flour-milling, brewing, distilling, iron-founding, leather manufacture, dyeing, and the manufacture of stained glass, billiard requisites, hosiery, &c.
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  • It is very unstable, decomposing into nitrous oxide and water when mixed with copper oxide, lead chromate or even powdered glass.
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  • The imports consist principally of food stuffs, building materials, drinks, sugar, machinery, glass, fats, clothes, wooden and stone wares, and various manufactured goods.
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  • Not far off, similar relics were found at Sobunar, Zlatiste and Debelobrdo; iron and bronze ornaments, vessels and weapons, often of elaborate design, occur in the huts and cemeteries of Glasinac, and in the cemetery of Jezerine, where they are associated with objects in silver, tin, amber, glass, &c. Among the numerous finds made in other districts may be mentioned the discovery, at Vrankamer, near Bihac, of 98 African coins, the oldest of which dates from 300 B.C. Many vestiges of Roman rule survive, such as roads, mines, ruins, tombs, coins, frescoes and inscriptions.
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  • The church of St Martin is ancient, and contains stained glass from Cartmel priory in Furness.
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  • Manufactories of porcelain, glass and earthenware are numerous.
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  • It is questionable whether it is not better, in cold soils and bleak situations, to abandon outdoor peach culture, and to cover the walls with a casing of glass, so that the trees may be under shelter during the uncongenial spring weather.
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  • Wooden and glass copings are also very useful in warding off frosts.
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  • The Myvyrian Archaeology (408-484) gives the three principal bangor (college) institutions as follows: - the bangor of Illtud Farchawg at Caer Worgorn (Wroxeter); that of Emrys (Ambrosius) at Caer Caradawg; bangor wydrin (glass) in the glass isle, Afallach; bangor Illtud, or Llanilltud, or Llantwit major (by corruption), being a fourth.
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  • These crystals have, as a rule, very good crystalline form, but the quartz and felspar are often filled with enclosures of glass.
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  • These crystallites (q.v.) show that the glassy rock has a tendency to crystallize which is inhibited only by the very viscous state of the glass and the rapidity with which it was cooled.
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  • Often bands of spherulites alternate with bands of pure glass, a fact which seems to indicate that the growth of these bodies took place before the rock ceased to flow.
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  • Porphyritic crystals often contract less than the surrounding glass, which accordingly becomes strained, and in polarized light may show a weak double refraction in a limited area surrounding the crystal.
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  • These surround little spherules of glass which are detached when the rock is struck with a hammer.
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  • In mineralogical collections rounded nodules of brown glass, varying from the size of a pea to that of an orange, may often be seen labelled marekanite.
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  • Their behaviour in this respect closely resembles the balls of rapidly cooled, unannealed glass which are called Prince Rupert's drops.
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  • Often this felsitic devitrified glass is so fine-grained that its constituents cannot be directly determined even with the aid of the microscope, but chemical analysis leaves little doubt as to the real nature cf the minerals which have been formed.
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  • Many vitreous rocks show alteration of this type in certain parts where either the glass has been of unstable nature or where agencies of change such as percolating water have had easiest access (as along joints, perlitic cracks and the margins of dikes and sills).
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  • In the same way artificial glass can be devitrified if it be kept at a temperature slightly below the fusing point for some days.
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  • Window glass exposed to alkaline vapours often shows a thin iridescent surface film which is supposed to be due to crystallization; the same change is found in pieces of Roman glass which have been dug out of the ruins of Pompeii.
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  • The chemical composition of typical obsidians is shown by the following analyses Obsidian, when broken, shows a conchoidal fracture, like that of glass, and yields sharp-edged fragments, which have been used in many localities as arrow-points, spear-heads, knives and razors.
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  • By the ancient Greeks and Romans obsidian was worked as a gem-stone; and in consequence of its having been often imitated in glass there arose among collectors of gems in the 18th century the practice of calling all antique pastes "obsidians."
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  • The modern stained glass in the chancel is reckoned amongst the finest in Scotland.
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  • The vats for depositing may be of enamelled iron, slate, glazed earthenware, glass, lead-lined wood, &c. The current densities and potential differences frequently used for some of the commoner metals are given in the following table, taken from M ` Millan's Treatise on Electrometallurgy.
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  • At one time it was used for window panes of houses and the port-holes of Russian men-of-war, being commonly known as "Muscovy glass."
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  • The cathedral contains some fine stained glass, the largest organ in Germany (1856), and a number of interesting old paintings and carvings by Jorg Syrlin the elder, Jorg Syrlin the younger, Burkhard Engelberger, and other masters of the Swabian school.
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  • The tube is made of glass, indiarubber, copper or lead, according to the liquid which is to be transferred.
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  • Among the manufactures are cut glass, stoves and ranges, kitchen furniture, guns, thread-cutting machines, brooms and agricultural implements.
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  • In 1905 the borough ranked fifth among the cities of the United States in the manufacture of glass (plateglass, lamp chimneys and bottles), its product (valued at $1,841,308) being 2.3% of that of the whole country.
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  • It is chiefly used as a pigment and in the manufacture of flint glass.
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  • By fusing litharge with boron trioxide, glasses of a composition varying with the proportions of the mixture are obtained; some of these are used in the manufacture of glass.
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  • A is the upper end of a glass tube, half a metre or so in length, which is clamped in a vertical position.
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  • The wire is supported inside the glass tube A with its upper pole at the same height as the magnetometer needle.
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  • For the practical measurement of field intensity du Bois has used plates of the densest Jena flint glass.
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  • Since Verdet's constant is somewhat uncertain for different batches of glass even of the same quality, each plate should be standardized in a field of known intensity.
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  • A part of one surface of the plate may be silvered, so that the polarized ray, after having once traversed the glass, is reflected back again; the rotation is thus doubled, and moreover, the arrangement is, for certain experiments, more convenient than the other.
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  • The whole was wrapped in several coverings of asbestos and placed in a glass vessel from which the air was partially exhausted, additional precautions being taken to guard against oxidation of the iron.
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  • The temperature of Cutch during the hot season is high, the thermometer frequently rising to roo° or 105° F.; and in the months of April and May clouds of dust and sand, blown about by hurricanes, envelop the houses, the glass windows scarcely affording any protection.
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  • Among other manufactures are butter and cheese, canned fruits and vegetables, glass and earthenware, printing and wrapping paper, furniture, matches, hats, clothing, pharmaceutical products, soaps and - p erfumery, ice, artificial drinks, cigars and cigarettes, fireworks anc candles.
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  • The church of St Martin, dating from the i 5th century, has good stained glass.
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  • Leather-working and the manufacture of stained glass are leading industries.
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  • Clothing, carriages, pottery, glass, paper and furniture are made, and there are numerous minor industries.
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  • Other principal branches of industry are: tobacco manufactories, belonging to the state, tobacco being a government monopoly; iron foundries, mostly in the mining region; agricultural machinery and implements, notably at Budapest; leather manufactures; paper-mills, the largest at Fiume; glass (only the more common sort) and earthenwares; chemicals; wooden products; petroleum-refineries; woollen yarns and cloth manufactories, as well as several establishments of knitting and weaving.
    0
    0
  • In his experiments upon this subject Fraunhofer employed plates of glass dusted over with lycopodium, or studded with small metallic disks of uniform size; and he found that the diameters of the rings were proportional to the length of the waves and inversely as the diameter of the disks.
    0
    0
  • An admissible error of phase of 4X will correspond to an error of IX in a reflecting and 2X in a (glass) refracting surface, the incidence in both cases being perpendicular.
    0
    0
  • In the case of a single lens of glass with the most favourable curvatures, Sf is about equal to a 2 f, so that a 4 must not exceed off.
    0
    0
  • Subsequently he ruled gratings on a layer of gold-leaf attached to glass, or on a layer of grease similarly supported, and again by attacking the glass itself with a diamond point.
    0
    0
  • In an engraved glass grating there is no opaque material present by which light could be absorbed, and the effect depends upon a difference of retardation in passing the alternate parts.
    0
    0
  • Rutherfurd introduced into common use the reflection grating, finding that speculum metal was less trying than glass to the diamond point, upon the permanence of which so much depends.
    0
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  • The earliest is that of Quincke, who coated a glass grating with a chemical silver deposit, subsequently thickened with copper in an electrolytic bath.
    0
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  • A much easier method, applicable to glass originals, is that of photographic reproduction by contact printing.
    0
    0
  • To save the diamond point it might be possible to use something softer than ordinary glass as the material of the plate.
    0
    0
  • The slits may be cut out of tin-plate, and half covered by mica or " microscopic glass," held in position by a little cement.
    0
    0
  • In observing the bands he received them at first upon a screen of finely ground glass, upon which a magnifying lens was focused; but it soon appeared that the ground glass could be dispensed with, the diffraction pattern being viewed in the same way as the image formed by the object-glass of a telescope is viewed through the eye-piece.
    0
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  • In 1845 he established at Paris a special archaeological library, and at the same time a manufactory of painted glass.
    0
    0
  • Sodium uranate, Na2U207, is used as a pigment for painting on glass and porcelain under the name of uranium yellow.
    0
    0
  • Leber experimented with several chemical compounds to find what reaction they had on these cells; by using fine glass tubes sealed at the outer end and containing a chemical substance, and by introducing the open end into the blood vessels he found that the leucocytes were attracted - positive chemiotaxis - by the various compounds of mercury, copper, turpentin, and other substances.
    0
    0
  • But there his stay was equally short, for in 1872 he undertook the duties of engineering manager in the glass manufactories of Messrs Chance Brothers and Company at Birmingham.
    0
    0
  • Moreover, his association with glass manufacture led him to study the refractive indices of different kinds of glass; he further undertook abstruse researches on electrostatic capacity, the phenomena of the residual charge, and other problems arising out of Clerk Maxwell's electro-magnetic theory.
    0
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  • It consisted of a spherical glass vessel opening below by means of a stop-cock and narrow nozzle into the cylinder of an "exhausting syringe," which inclined upwards from the extremity of the nozzle.
    0
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  • A and B are pear-shaped glass vessels connected by a long narrow india-rubber tube, which must be sufficiently strong in the body (or strengthened by a linen coating) to stand an outward pressure of 1 to 2 atmospheres.
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  • At the upper end of A is a glass two-way stop-cock, by turning which the vessel A can either be made to communicate with the vessel to be exhausted, or with the atmosphere, or can be shut off from both when the cock holds an intermediate position.
    0
    0
  • Mile of Warsaw in 1828, who termed it a "hydrostatic air-pump without cylinders, taps, lids or stoppers," this is attained by using, both for the inlet and the outlet, vertical capillary glass tubes, soldered, the former to somewhere near the bottom, the latter to the top of the vessel.
    0
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  • Neisen and others to introduce glass valves in lieu of stop-cocks.
    0
    0
  • If the vertical tube, measuring from the point where the branch comes in, is a few inches greater than the height of the barometer, and the glass and mercury are perfectly clean, the apparatus slowly but surely produces an almost absolute vacuum.
    0
    0
  • The trade is chiefly connected with the produce of the neighbouring coal-mines and that of the numerous important iron and glass works of the district.
    0
    0
  • They pass through a viscous stage in cooling from a state of fluidity; they develop effects of colour when the glass mixtures are fused with certain metallic oxides; they are, when cold, bad conductors both of electricity and heat, they are easily fractured by a blow or shock and show a conchoidal fracture; they are but slightly affected by ordinary solvents, but are readily attacked by hydrofluoric acid.
    0
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  • The structure of glass has been the subject of repeated investigations.
    0
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  • The theory most widely accepted at present is that glass is a quickly solidified solution, in which silica, silicates, borates, phosphates and aluminates may be either solvents or solutes, and metallic oxides and metals may be held either in solution or in suspension.
    0
    0
  • Long experience has fixed the mixtures, so far as ordinary furnace temperatures are concerned, which produce the varieties of glass in common use.
    0
    0
  • The essential materials of which these mixtures are made are, for English flint glass, sand, carbonate of potash and red lead; for plate and sheet glass, sand, carbonate or sulphate of soda.
    0
    0
  • The recent large increase in the number of varieties of glass has been chiefly due to developments in the manufacture of optical glass.
    0
    0
  • In the same way glass can be rendered more or less fusible, and its stability can be increased both in relation to extremes of temperature and to the chemical action of solvents.
    0
    0
  • The fluidity of glass at a high temperature renders possible the processes of ladelling, pouring, casting and stirring.
    0
    0
  • A mass of glass in a viscous state can be rolled with an iron roller like dough; can be rendered hollow by the pressure of the human breath or by compressed air; can be forced by air pressure, or by a mechanically driven plunger, to take the shape and impression of a mould; and can be almost indefinitely extended as solid rod or as hollow tube.
    0
    0
  • So extensible is viscous glass that it can be drawn out into a filament sufficiently fine and elastic to be woven into a fabric.
    0
    0
  • Semi-opacity and opacity are usually produced by the addition to the glass-mixtures of materials which will remain in suspension in the glass, such as oxide of tin, oxide of arsenic, phosphate of lime, cryolite or a mixture of felspar and fluorspar.
    0
    0
  • Little is known about the actual cause of colour in glass beyond the fact that certain materials added to and melted with certain glass-mixtures will in favourable circumstances produce effects of colour.
    0
    0
  • Ferrous oxide produces an olive green or a pale blue according to the glass with which it is mixed.
    0
    0
  • Silver oxide, mixed as a paint and spread on the surface of a piece of glass and heated, gives a permanent yellow stain.
    0
    0
  • Finely divided vegetable charcoal added to a soda-lime glass gives a yellow colour.
    0
    0
  • It has been suggested that the colour is due to sulphur, but the effect can be produced with a glass mixture containing no sulphur, free or combined, and by increasing the proportion of charcoal the intensity of the colour can be increased until it reaches black opacity.
    0
    0
  • Nickel with a potash-lead glass gives a violet colour, and a brown colour with a soda-lime glass.
    0
    0
  • If oxide of copper is added to a glass mixture containing a strong reducing agent, a glass is produced which when first taken from the crucible is colourless but on being reheated develops a deep crimson - ruby colour.
    0
    0
  • A similar glass, if its cooling is greatly retarded, produces throughout its substance minute crystals of metallic copper, and closely resembles the mineral called avanturine.
    0
    0
  • There is also an intermediate stage in which the glass has a rusty red colour by reflected light, and a purpleblue colour by transmitted light.
    0
    0
  • Glass containing gold behaves in almost precisely the same way, but the ruby glass is less crimson than copper ruby glass.
    0
    0
  • C. Maxwell Garnett, who has studied the optical properties of these glasses, has suggested that the changes in colour correspond with changes effected in the structure of the metals as they pass gradually from solution in the glass to a state of crystallization.
    0
    0
  • For this reason chemical agents are added to glass mixtures to remove or neutralize accidental colour.
    0
    0
  • Oxidation may be effected by the addition to the glass mixture of a substance which gives up oxygen at a high temperature, such as manganese dioxide or arsenic trioxide.
    0
    0
  • With the same object, red lead and saltpetre are used in the mixture for potash-lead glass.
    0
    0
  • Manganese dioxide not only acts as a source of oxygen, but develops a pink tint in the glass, which is complementary to and neutralizes the green colour due to ferrous oxide.
    0
    0
  • Glass is a bad conductor of heat.
    0
    0
  • When boiling water is poured into a glass vessel, the vessel frequently breaks, on account of the unequal expansion of the inner and outer layers.
    0
    0
  • If in the process of glass manufacture a glass vessel is suddenly cooled, the constituent particles are unable to arrange themselves and the vessel remains in a state of extreme tension.
    0
    0
  • The surface of the glass was hardened, but the inner layers remained in unstable equilibrium.
    0
    0
  • Electrical furnaces have not as yet been employed for ordinary glass-making on a commercial scale, but the electrical plants which have been erected for melting and moulding quartz suggest the possibility of electric heating being employed for the manufacture of glass.
    0
    0
  • Many forms of apparatus have been tried for ascertaining the temperature of glass furnaces.
    0
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  • Plate and rolled plate glass.
    0
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  • Pressed table glass.
    0
    0
  • Flint glass particularly, which appeared quite satisfactory when viewed in small pieces, was found to be so far from homogeneous as to be useless for lens construction.
    0
    0
  • Guinand, towards the end of the 18th century, by introducing the process of stirring the molten glass by means of a cylinder of fireclay.
    0
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  • In 1848 Bontemps was obliged to leave France for political reasons and came to England, where he initiated the optical glass manufacture at Chance's glass works near Birmingham, and this firm ultimately attained a considerable reputation in the production of optical glass, especially of large disks for telescope objectives.
    0
    0
  • Efforts at improving optical glass had, however, not been confined to the descendants and successors of Guinand and Fraunhofer.
    0
    0
  • Hopkinson, working at Chance's glass works, subsequently made an attempt to produce a titanium silicate glass, but nothing further resulted.
    0
    0
  • The next and most important forward step in the progress of optical glass manufacture was initiated by Ernst Abbe and carried out jointly by him and 0.
    0
    0
  • On the other hand, while in the older crown and flint glasses the relation between refraction and dispersion had been practically fixed, dispersion and refraction increasing regularly with the density of the glass, in some of the new glasses introduced by Abbe and Schott this relation is altered and a relatively low refractive index is accompanied by a relatively high dispersion, while in others a high refractive index is associated with low dispersive power.
    0
    0
  • It must be admitted that, by the aid of certain of these new constituents, glasses can be produced which, as regards purity of colour, freedom from defects and chemical stability are equal or even superior to the best of the " ordinary " glasses, but it is a remarkable fact that when this is the case the optical properties of the new glass do not fall very widely outside the limits set by the older glasses.
    0
    0
  • In practice, however, it is not found that the presence either of a decidedly greenish-yellow colour or of numerous small bubbles interferes at all seriously with the successful use of the lenses for the majority of purposes, so that it is preferable to sacrifice the perfection of the glass in order to secure valuable optical properties.
    0
    0
  • This is probably never completely attained, variations in the sixth significant figure of the refractive index being observed in different parts of single large blocks of the most perfect glass.
    0
    0
  • While such minute and gradual variations are harmless for most optical purposes, sudden variations which generally take the form of striae or veins are fatal defects in all optical glass.
    0
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  • In their coarsest forms such striae are readily visible to the unaided eye, but finer ones escape detection unless special means are taken for rendering them visible; such special means conveniently take the form of an apparatus for examining the glass in a beam of parallel light, when the striae scatter the light and appear as either dark or bright lines according to the position of the eye.
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  • Plate glass of the usual quality, which appears to be perfectly homogeneous when looked at in the ordinary way, is seen to be a mass of fine striae, when a considerable thickness is examined in parallel light.
    0
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  • Plate glass is, nevertheless, considerably used for the cheaper forms of lenses, where the scattering of the light and loss of definition arising from these fine striae is not readily recognized.
    0
    0
  • As a general rule, to which, however, there are important exceptions, both these qualities are found to a greater degree, the lower the refractive index of the glass.
    0
    0
  • Processes of annealing, or very gradual cooling, are intended to relieve these strains, but such processes are only completely effective when the cooling, particularly through those ranges of temperature where the glass is just losing the last traces of plasticity, is extremely gradual, a rate measured in hours per degree Centigrade being required.
    0
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  • The existence of internal strains in glass can be readil y recognized by examination in polarized light, any signs of double refraction indicating the existence of strain.
    0
    0
  • If the glass is very badly annealed, the lenses made from it may fly to pieces during or of ter manufacture, but apart from such extreme cases the optical effects of internal strain are not readily observed except in large optical apparatus.
    0
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  • Very perfectly annealed optical glass is now, however, readily obtainable.
    0
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  • In this table n is the refractive index of the glass for sodium light (the D line of the solar spectrum), while the letters C, F and G' refer to lines in the hydrogen spectrum by which dispersion is now generally specified.
    0
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  • Manufacture of Optical Glass.-In its earlier stages, the process for the production of optical glass closely resembles that used in the production of any other glass of the highest quality.
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  • The raw materials are selected with great care to assure chemical purity, but whereas in most glasses the only impurities to be dreaded are those that are either infusible or produce a colouring effect upon the glass, for optical purposes the admixture of other glass-forming bodies than those which are intended to be present must be avoided on account of their effect in modifying the optical constants of the glass.
    0
    0
  • Fragments of glass of the same composition as that aimed at are generally incorporated to a limited extent with the mixed raw materials to facilitate their fusion.
    0
    0
  • The crucibles or pots used for the production of optical glass very closely resemble those used in the manufacture of flint glass for other purposes; they are " covered " and the molten materials are thus protected from the action of the furnace gases by the interposition of a wall of fireclay, but as crucibles for optical glass are used for only one fusion and are then broken up, they are not made so thick and heavy as those used in flint-glass making, since the latter remain in the furnace for many weeks.
    0
    0
  • The furnace used for the production of optical glass is generally constructed to take one crucible only, so that the heat of the furnace may be accurately adjusted to the requirements of the particular glass under treatment.
    0
    0
  • When a suitable temperature for the fusion of the particular glass in question has been attained, the mixture of raw materials is introduced in comparatively small quantities at a time.
    0
    0
  • In this way the crucible is gradually filled with a mass of molten glass, which is, however, [[Table I]].- Optical Properties.
    0
    0
  • In the next stage of the process, the glass is raised to a high temperature in order to render it sufficiently fluid to allow of the complete elimination of these bubbles; the actual temperature required varies with the chemical composition of the glass, a bright red heat sufficing for the most fusible glasses, while with others the utmost capacity of the best furnaces is required to attain the necessary temperature.
    0
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  • With these latter glasses there is, of course, considerable risk that the partial fusion and consequent contraction of the fireclay of the crucible may result in its destruction and the entire loss of the glass.
    0
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  • The examination of small test-pieces of the glass withdrawn from the crucible by means of an iron rod having shown that the molten mass is free from bubbles, the stirring process may be begun, the object of this manipulation being to render the glass as homogeneous as possible and to secure the absence of veins or striae in the product.
    0
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  • For this purpose a cylinder of fireclay, provided with a square axial hole at the upper end, is heated in a small subsidiary furnace and is then introduced into the molten glass.
    0
    0
  • The men who manipulate the stirring bars are therefore changed at short intervals, while the bars themselves have also to be changed at somewhat longer intervals, as they rapidly become oxidized, and accumulated scale would tend to fall off them, thus contaminating the glass below.
    0
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  • The stirring process is begun when the glass is perfectly fluid at a temperature little short of the highest attained in its fusion, but as the stirring proceeds the glass is allowed to cool gradually and thus becomes more and more viscous until finally the stirring cylinder can scarcely be moved.
    0
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  • When the glass has acquired this degree of consistency it is supposed that no fresh movements can occur within its mass, so that if homogeneity has been attained the glass will preserve it permanently.
    0
    0
  • The stirring is therefore discontinued and the clay cylinder is either left embedded in the glass, or by the exercise of considerable force it may be gradually withdrawn.
    0
    0
  • The crucible with the semi-solid glass which it contains is now allowed to cool considerably in the melting furnace, or it may be removed to another slightly heated furnace.
    0
    0
  • When the glass has cooled so far as to become hard and solid, the furnace is hermetically sealed up and allowed to cool very gradually to the ordinary temperature.
    0
    0
  • If the cooling is very gradual - occupying several weeks - it sometimes happens that the entire contents of a large crucible, weighing perhaps 1000 lb, are found intact as a single mass of glass, but more frequently the mass is found broken up into a number of fragments of various sizes.
    0
    0
  • From the large masses great lenses and mirrors may be produced, while the smaller pieces are used for the production of the disks and slabs of moderate size, in which the optical glass of commerce is usually supplied.
    0
    0
  • In order to allow of the removal of the glass, the cold crucible is broken up and the glass carefully separated from the fragments of fireclay.
    0
    0
  • The pieces of glass are then examined for the detection of the grosser defects, and obviously defective pieces are rejected.
    0
    0
  • As the fractured surfaces of the glass in this condition are unsuitable for delicate examination a good deal of glass that passes this inspection has yet ultimately to be rejected.
    0
    0
  • The next stage in the preparation of the glass is the process of moulding and annealing.
    0
    0
  • Lumps of glass of approximately the right weight are chosen, and are heated to a temperature just sufficient to soften the glass, when the lumps are caused to assume the shape of moulds made of iron or fireclay either by the natural flow of the softened glass under gravity, or by pressure from suitable tools or presses.
    0
    0
  • The glass is, however, by no means ready for delivery, since it has yet to be examined with scrupulous care, and all defective pieces must be rejected entirely or at least the defective part must be cut out and the slab remoulded or ground down to a smaller size.
    0
    0
  • For the purpose of rendering this minute examination possible, opposite plane surfaces of the glass are ground approximately flat and polished, the faces to be polished being so chosen as to allow of a view through the greatest possible thickness of glass; thus in slabs the narrow edges are polished.
    0
    0
  • It will be readily understood from the above account of the process of production that optical glass, relatively to other kinds of glass, is very expensive, the actual price varying from 3s.
    0
    0
  • The price, however, rapidly increases with the total bulk of perfect glass required in one piece, so that large disks of glass suitable for telescope objectives of wide aperture, or blocks for large prisms, become exceedingly costly.
    0
    0
  • The reason for this high cost is to be found partly in the fact that the yield of optically perfect glass even in large and successful meltings rarely exceeds 20% of the total weight of glass melted.
    0
    0
  • Further, all the subsequent processes of cutting, moulding and annealing become increasingly difficult, owing to the greatly increased risk of breakage arising from either external injury or internal strain, as the dimensions of the individual piece of glass increase.
    0
    0
  • Nevertheless, disks of optical glass, both crown and flint, have been produced up to 39 in.
    0
    0
  • Venetian glass is a soda-lime glass; Bohemian glass is a potash-lime glass.
    0
    0
  • The potash-lead glass, which was first used on a commercial scale in England for the manufacture of table-ware, and which is known as " flint " glass or " crystal," is also largely used in France, Germany and the United States.
    0
    0
  • Glass mixtures containing lead are melted in covered, beehive-shaped crucibles holding from 12 to 18 cwt.
    0
    0
  • They have a hooded opening on one side near the top. This opening serves for the introduction of the glass-mixture, for the removal of the melted glass and as a source of heat for the processes of manipulation.
    0
    0
  • Directly work is suspended the glass remaining in the crucibles is ladled into water, drained and dried.
    0
    0
  • It is then mixed with the glass mixture and broken glass (" cullet "), and replaced in the J a 6 FIG.
    0
    0
  • Before work begins the temperature is lowered sufficiently to render the glass viscous.
    0
    0
  • In the viscous state a mass of glass can be coiled upon the heated end of an iron rod, and if the rod is hollow can be blown into a hollow bulb.
    0
    0
  • Across the arms he balances the iron rod to which the glass bulb adheres, and rolling it backwards and forwards with the fingers of his left hand fashions the glass between the blades of his sugar-tongs tool, grasped in his right hand.
    0
    0
  • During the process of manipulation, whether on the chair or whilst the glass is being reheated, the rod must be constantly and gently trundled to prevent the collapse of the bulb or vessel.
    0
    0
  • The old and the new systems of making a wine-glass illustrate almost all the ordinary processes of glass working.
    0
    0
  • Sufficient glass is first " gathered " on the end of a blowing iron to form the bowl of the wine-glass.
    0
    0
  • The mere act of coiling an exact weight of molten glass round the end of a rod 4 ft.
    0
    0
  • The mass of glass is rolled on a polished slab of iron, the " marvor," to solidify it, and it is then slightly hollowed by blowing.
    0
    0
  • The leg is either pulled out from the substance of the base of the bowl, or from a small lump of glass added to the base.
    0
    0
  • The bowl is now severed from its blowing iron and the unfinished wine-glass is supported by its foot, which is attached to the end of a working rod by a metal clip or by a seal of glass.
    0
    0
  • Under the new system the bowl is fashioned by blowing the slightly hollowed mass of glass into a mould.
    0
    0
  • The leg is formed and a small lump of molten glass is attached to its extremity to form the foot.
    0
    0
  • The blowing iron is constantly trundled, and the small lump of glass is squeezed and flattened into the shape of a foot, either between two slabs of wood hinged together, or by pressure against an upright board.
    0
    0
  • The bowl is severed from the blowing iron, and the wine-glass is sent to the annealing oven with a bowl, longer than that of the finished glass, and with a rough fractured edge.
    0
    0
  • When the glass is cold the surplus is removed either by grinding, or by applying heat to a line scratched with a diamond round the bowl.
    0
    0
  • In the manufacture of a wine-glass the ductility of glass is illustrated on a small scale by the process of pulling out the, leg.
    0
    0
  • It is more strikingly illustrated in the manufacture of glass cane and tube.
    0
    0
  • Cane is produced from a solid mass of molten glass, tube from a mass hollowed by blowing.
    0
    0
  • One workman holds the blowing iron with the mass of glass attached to it, and another fixes an iron rod by means of a seal of glass to the extremity of the mass.
    0
    0
  • The diameter of the cane or tube is regulated by the weight of glass carried, and by the distance covered by the two workmen.
    0
    0
  • It is a curious property of viscous glass that whatever form is given to the mass of glass before it is drawn out is retained by the finished cane or tube, however small its section may be.
    0
    0
  • The latter are made by dipping a small mass of molten colourless glass into an iron cup around the inner wall of which short lengths of white cane have been arranged at regular intervals.
    0
    0
  • A vase decorated with these simple or complex canes is produced by embedding short lengths of the cane on the surface of a mass of molten glass and blowing and fashioning the mass into the required shape.
    0
    0
  • Touches of colour may be added to vessels in course of manufacture by means of seals of molten glass, applied like sealing-wax; or by causing vessels to wrap themselves round with threads or coils of coloured glass.
    0
    0
  • By the application of a pointed iron hook, while the glass is still ductile, the parallel coils can be distorted into bends, loops or zigzags.
    0
    0
  • The surface of vessels may be spangled with gold or platinum by rolling the hot glass on metallic leaf, or iridescent, by the deposition of metallic tin, or by the corrosion caused by the chemical action of acid fumes.
    0
    0
  • Cutting and engraving are mechanical processes for producing decorative effects by abrading the surface of the glass when cold.
    0
    0
  • Cutting brings out the brilliancy of glass, which is one of its intrinsic qualities.
    0
    0
  • At the end of the 18th century English cut glass was unrivalled for design and beauty.
    0
    0
  • At the present time cut glass is steadily regaining favour.
    0
    0
  • Engraving is a process of drawing on glass by means of small copper wheels.
    0
    0
  • There are two other processes of marking patterns on glass, but they possess no artistic value.
    0
    0
  • In the " sandblast " process the surface of the glass is exposed to a stream of sharp sand driven by compressed air.
    0
    0
  • In the " etching " process the surface of the glass is etched by the chemical action of hydrofluoric acid, the parts which are not to be attacked being covered with a resinous paint.
    0
    0
  • The glass is first dipped in this protective liquid, and when the paint has set the pattern is scratched through it with a sharp point.
    0
    0
  • The glass is then exposed to the acid.
    0
    0
  • Glass stoppers are fitted to bottles by grinding.
    0
    0
  • The head of the stopper is fastened in a chuck and the peg is ground to the size of the mouth of the bottle by means of sand and water pressed against the glass by bent strips of thin sheet iron.
    0
    0
  • About 1870 the " Jackson " table-glass was made in a light, dull green glass.
    0
    0
  • The dull green was followed successively by amber, white opal, blue opal, straw opal, sea-green, horn colour and various pale tints of soda-lime glass, ranging from yellow to blue.
    0
    0
  • Experiments were also tried with a violet-coloured glass, a violet opal, a transparent black and with glasses shading from red to blue, red to amber and blue to green.
    0
    0
  • In many specimens there were three or more layers of differently coloured glass, and curious effects of blended colour were obtained by cutting through, or partly through, the different layers.
    0
    0
  • The surface of the glass had usually been treated with hydrofluoric acid so as to have a satin-like gloss.
    0
    0
  • The happiest specimens of this glass almost rival the wings of butterflies in the brilliancy of their iridescent colours.
    0
    0
  • The white line of enamel, which is seen in some thermometers behind the bore, is introduced before the mass of glass is pulled out.
    0
    0
  • A flattened cake of viscous glass-enamel is welded on to one side of the mass of glass after it has been hollowed by blowing.
    0
    0
  • The mass, with the enamel attached, is dipped into the crucible and covered with a layer of transparent glass; the whole mass is then pulled out into tube.
    0
    0
  • It has been proved that these variations depend to a great extent on the chemical nature of the glass of which the thermometer is made.
    0
    0
  • The temperature required in the fusion of sheet-glass and of other glasses produced in tank furnaces is much lower than that attained in steel furnaces, and it is consequently pos Since the discovery of the Rntgen rays, experiments have been made to ascertain the effects of the different constituents of glass on the transparency of glass to X-rays.
    0
    0
  • The glass tubes, therefore, from which the X-ray bulbs are to be fashioned, must not contain any of these oxides, whereas the glass used for making the funnel-shaped shields, which direct the rays upon the patient and at the same time protect the hands of the operator from the action of the rays, must contain a large proportion of lead.
    0
    0
  • One method is to form the tube of two layers of glass, one being considerably more expansible than the other.
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  • A certain proportion of soda ash (carbonate of soda) is also used in some works in sheet-glass mixtures, while " decolorizers " (substances intended to remove or reduce the colour of the glass) are also sometimes added, those most generally used being manganese dioxide and arsenic. Another essential ingredient of all glass mixtures containing sulphate of soda is some form of carbon, which is added either as coke, charcoal or anthracite coal; the carbon so introduced aids the reducing substances contained in the atmosphere of the furnace in bringing about the reduction of the sulphate of soda to a condition in which it combines more readily with the silicic acid of the sand.
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  • The proportions in which these ingredients are mixed vary according to the exact quality of glass required and with the form and temperature of the melting furnace employed.
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  • The actual composition, however, of a mixture that will give a glass of this composition cannot be directly calculated from these figures and the known composition of the raw materials, owing to the fact that considerable losses, particularly of alkali, occur during melting.
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  • The glass in process of fusion is contained in a basin or tank built up of large blocks of fire-clay and is heated by one or more powerful gas flames which enter the upper part of the furnace chamber through suitable apertures or " ports."
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  • Thus the dimensions of the largest glass tanks greatly exceed those of the largest steel furnaces; glass furnaces containing up to 250 tons of molten sible to work glass-tanks continuously for many months together; on the other hand, glass is not readily freed from foreign bodies that may become admixed with it, so that the absence of detachable particles is much more essential in glass than in steel melting.
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  • Finally, fluid steel can be run or poured off, since it is perfectly fluid, while glass cannot be thus treated, but is withdrawn from the furnace by means of either a ladle or a gatherer's pipe, and the temperature required for this purpose is much lower than.
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  • In a sheet-glass tank there is therefore a gradient of temperature and a continuous passage of material from the hotter end of the furnace where the raw materials are introduced to the cooler end where the glass, free from bubbles and raw material, is withdrawn by the gatherers.
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  • For the purpose of the removal of the glass, the cooler end of the furnace is provided with a number of suitable openings, provided with movable covers or shades.
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  • When the first ball or " gathering 'T has cooled sufficiently, the whole is again dipped into the molten glass and a further layer adheres to the pipe-end, thus forming a larger ball.
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  • From the hemispherical shape the mass of glass is now gradually blown into the form of a short cylinder, and then the pipe with the adherent mass of glass is handed.
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  • The blower repeatedly heats the lower part of the mass of glass and keeps it distended by blowing while he swings it over a deep trench which is provided next to his working platform.
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  • In this way the glass is extended into the form of a long cylinder closed at the lower end.
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  • The lower end of the cylinder is opened, in the case of small and thin cylinders, by the blower holding his thumb over the mouthpiece of the pipe and simultaneously warming the end of the cylinder in the furnace, the expansion of the imprisoned air and the softening of the glass causing the end of the cylinder to burst open.
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  • The blower then heats the end of the cylinder again and rapidly spins the pipe about its axis; the centrifugal effect is sufficient to spread the soft glass at the end to a radius equal to that of the rest of the cylinder.
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  • In the case of large and thick cylinders, however, another process of opening the ends is generally employed: an assistant attaches a small lump of hot glass to the domed end, and the heat of this added glass softens the cylinder sufficiently to enable the assistant to cut the end open with a pair of shears; subsequently the open end is spun out to the diameter of the whole as described above.
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