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glasses

glasses

glasses Sentence Examples

  • I wish everyone wore rose-colored glasses the way you do.

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  • He handed the glasses to the chief and spoke to him in their language.

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  • Maybe you could fill the glasses with tea?

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  • He adjusted his glasses and read.

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  • He adjusted his glasses and read.

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  • Those glasses are only for reading, Fred replied, without looking up.

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  • He studied her over the rim of his reading glasses, and his eyes warmed with a smile.

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  • He needed glasses, but he wouldn't admit it.

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  • She took the glasses from him and downed them one at a time, then handed them back.

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  • The man pulled up his mask enough for Howie to see a mustache and glasses but little else.

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  • He adjusted his glasses and returned to his fishing journal.

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  • Ully said, handing her two glasses of whiskey.

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  • The store manager, a middle-aged woman with glasses, looked up at him in awe.

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  • He now employed himself in making optical glasses, and in engraving on metal, devoting his spare time to the perusal of works on mathematics and optics.

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  • She beamed up at Keaton as he approached with two glasses of iced tea.

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  • They stuck around, pretending to pick up glasses and snack plates while the Dawkins four quarreled, oblivious to their presence.

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  • Fred asked, reaching for his glasses, "some kind of a race?"

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  • Pierre took one of the glasses and emptied it.

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  • Fred asked, reaching for his glasses, "some kind of a race?"

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  • He snatched the whiskey from her hand and placed their glasses on a table.

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  • He was only quite at ease when having poured several glasses of wine mechanically into his large mouth he felt a pleasant warmth in his body, an amiability toward all his fellows, and a readiness to respond superficially to every idea without probing it deeply.

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  • Claire Quincy had donned reading glasses and was scrutinizing the letters as Fred O'Connor followed his notes and explained the information on Annie Quincy he had gathered at the library.

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  • I did the same with the glasses and silverware.

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  • He looked like any normal nerdy American with big glasses and a scrawny frame.

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  • He lowered the glasses and rolled over on his back, gazing up into her face.

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  • The few glasses of wine he had drunk and the conversation with this good-natured man had destroyed the mood of concentrated gloom in which he had spent the last few days and which was essential for the execution of his design.

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  • He leaned back in the chair, tossing his glasses on the table.

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  • He lowered the glasses and met her gaze, a smile playing at the corners of his mouth.

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  • Overly aware of his presence, Deidre stepped outside the kitchen to the breakfast counter and poured two glasses of wine.

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  • Sonya sat down before the glasses, got the right position, and began looking.

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  • Katie sat, irritated to see who followed with a confident stride and two glasses of

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  • He must have mortars, pots, filters, glasses and boxes clean and sweet.

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  • All take glasses; you too, Balaga.

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  • She leaned across him, holding his hat over the glasses as he had shown her.

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  • Of the four crystal glasses engraved with the count's monogram that stood before his plate, Pierre held out one at random and drank with enjoyment, gazing with ever- increasing amiability at the other guests.

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  • It was Roger who introduced first himself, then Charlie, who dipped his paper in acknowledgment, and Harold, who set down the news and looked at Dean over the top of his glasses, curious about the visit.

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  • He positioned his hat so the glasses were shaded.

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  • Signs of the party the night before still remained, from the garbage bags awaiting pickup to one table with two wine glasses still present.

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  • His bright features turned pink beneath his wire-rimmed glasses and straw-colored hair.

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  • Fred poured a full glass of Tequila for Weller but left the other two glasses empty.

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  • They carried their glasses to the overstuffed sofa and sat facing each other.

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  • Jackson collected their glasses and poured their fourth drink.

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  • By this time he had ceased to devote himself to pure mathematics, and in company with his friends Mersenne and Mydorge was deeply interested in the theory of the refraction of light, and in the practical work of grinding glasses of the best shape suitable for optical instruments.

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  • Many substances were used as pigments: Pliny records white lead, cinnabar, verdigris and red oxide of iron; and the preparation of coloured glasses and enamels testifies to the uses to which these and other substances were put.

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  • Jackson collected their glasses and poured their fourth drink.

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  • From behind the crystal decanters and fruit vases, the count kept glancing at his wife and her tall cap with its light-blue ribbons, and busily filled his neighbors' glasses, not neglecting his own.

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  • The band again struck up, the count and countess kissed, and the guests, leaving their seats, went up to "congratulate" the countess, and reached across the table to clink glasses with the count, with the children, and with one another.

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  • When the officers had emptied and smashed their glasses, Kirsten filled others and, in shirt sleeves and breeches, went glass in hand to the soldiers' bonfires and with his long gray mustache, his white chest showing under his open shirt, he stood in a majestic pose in the light of the campfire, waving his uplifted arm.

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  • Bordeaux lowered the glasses and shrugged in a way that was both elegant and masculine.

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  • He pulled his field glasses from the saddlebag and motioned to Cassie.

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  • The scientist.s glasses were missing, his expression growing sorrowful as he looked around at his destroyed lab.

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  • The scientist.s glasses were missing, his expression growing sorrowful as he looked around at his destroyed lab.

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  • The wax candles burned brightly, the silver and crystal gleamed, so did the ladies' toilets and the gold and silver of the men's epaulets; servants in scarlet liveries moved round the table, the clatter of plates, knives, and glasses mingled with the animated hum of several conversations.

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  • On Natasha's table stood two looking glasses which Dunyasha had prepared beforehand.

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  • She sat a long time looking at the receding line of candles reflected in the glasses and expecting (from tales she had heard) to see a coffin, or him, Prince Andrew, in that last dim, indistinctly outlined square.

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  • Bordeaux slung a long leg around his saddle horn and tucked the glasses into his saddlebag.

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  • You want to lend me them glasses, Bordeaux?

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  • Natasha lit the candles, one on each side of one of the looking glasses, and sat down.

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  • I've noticed the guys eyeing you - glasses and all.

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  • Howie immediately began asking who needed more wine though our glasses were full.

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  • He crossed to the wet bar for two glasses, one with red wine and the other with whiskey.

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  • Jackson stood with his glasses and a Cheshire cat grin.

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  • He found her in the kitchen loading clean glasses on trays.

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  • When they returned home, the women were enjoying glasses of wine.

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  • "Put on your glasses, you'll go blind doing that," Dean said, handing Fred his beer and reclaiming his rocker from Mrs. Lincoln, the large black cat that had adopted the pair the prior February.

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  • The drinks arrived in glasses better designed for raising fish than serving alcohol—a sure hit with the traveling salesmen.

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  • He found her in the kitchen loading clean glasses on trays.

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  • Domestic beers are all served in pint glasses and are reasonably priced.

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  • Breakfast over, Bordeaux saddled his horse and pulled the field glasses from his saddlebag.

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  • A bookish man with glasses, wearing a white lab coat, opened the door to the small house.

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  • She wore glasses, a maroon business suit, and an all-business attitude to match.

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  • Kevin, a small man with a quick smile and trendy glasses, smiled as she opened the door.

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  • He found the caterer's boxes and set out collecting all the dishes, glasses and silverware.

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  • Bordeaux studied the dust through a pair of field glasses.

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  • He handed her the glasses.

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  • Oh, and you know what they say: Men don't make passes at girls who wear glasses.

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  • Dean grabbed a bottle of inexpensive merlot and three glasses.

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  • Fred grumbled as he poured three glasses.

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  • As if on cue, the flushed cook returned for her plate, and Daniela ordered the brandy and two glasses.

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  • She withdrew a single sheet of paper from her purse, unfolded it and adjusted her glasses.

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  • Dean put on his reading glasses.

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  • "Toss in Fred, too," he said as the old man returned with a bottle and three glasses.

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  • Rubbing his eyes, he peered at the blurred figures of his clock, (more evidence of the necessity for his glasses).

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  • Approaching from behind, she noticed a bottle of scotch on the table, along with the two glasses.

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  • Sarah handed him his two glasses.

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  • She opened a bottle of Jack Daniels and set out three glasses.

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  • He frowned at her over the rim of his thick glasses.

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  • Dean dutifully paused a few moments until Fred took off his glasses, slammed down the book on a table and said with a broad smile, I knew it!

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  • "Just things," Fred muttered, putting on his glasses.

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  • She reached down behind the desk and brought out a bottle of gin and poured two healthy slugs into water glasses.

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  • With crochet needles in her lap, Mums eyed Carmen over the rim of her reading glasses.

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  • He peered at her over the top of his glasses.

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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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  • Lead silicates are obtained as glasses by fusing litharge with silica; they play a considerable part in the manufacture of the lead glasses.

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  • Such tin-ash, as it is called, is used for the polishing of optical glasses.

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  • It is convenient to treat these glasses as " normal " glasses, but they are in reality mixtures of silicates, and cannot rightly be regarded as definite chemical compounds or represented by definite chemical formulae.

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  • Glasses possessing special qualities have been required, and have been supplied by the introduction of new combinations of materials.

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  • The range of the specific gravity of glasses from 2.5 to 5.0 illustrates the effect of modified compositions.

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  • Glasses are generally transparent but may be translucent or opaque.

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  • Semi-opacity due to crystallization may be induced in many glasses by maintaining them for a long period at a.

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  • 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.

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  • Owing to impurities contained in the materials from which glasses are made, accidental coloration or discoloration is often produced.

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  • Special glasses for thermometers, and other special glasses.

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  • Fraunhofer further initiated the specification of refraction and dispersion in terms of certain lines of the spectrum, and even attempted an investigation of the effect of chemical composition on the relative dispersion produced by glasses in different parts of the spectrum.

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  • As a result a whole series of glasses of novel composition and optical properties were produced.

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  • the production of pairs of glasses of widely differing refraction and dispersion, but having a similar distribution of dispersion in the various regions of the spectrum, was not in the first instance solved.

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  • 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.

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  • The older optical glasses, now generally known as the " ordinary " crown and flint glasses, are all of the nature of pure silicates, the basic constituents being, in the case of crown glasses, lime and soda or lime and potash, or a mixture of both, and in the case of flint glasses, lead and either (or both) soda and potash.

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  • With the exception of the heavier flint (lead) glasses, these can be produced so as to be free both from noticeable colour and from such defects as bubbles, opaque inclusions or " striae," but extreme care in the choice of all the raw materials and in all the manipulations is required to ensure this result.

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  • Further, these glasses, when made from properly proportioned materials, possess a very considerable degree of chemical stability, which is amply sufficient for most optical purposes.

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  • The newer glasses, on the other hand, contain a much wider variety of chemical constituents, the most important being the oxides of barium, magnesium, aluminium and zinc, used either with or without the addition of the bases already named in reference to the older glasses, and - among acid bodies - boric anhydride (B20 3) which replaces the silica of the older glasses to a varying extent.

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  • 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.

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  • On the other hand, the more extreme the optical properties of these new glasses, i.e.

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  • the further they depart from the ratio of refractive index to dispersive power found in the older glasses, the greater the difficulty found in obtaining them of either sufficient purity or stability to be of practical use.

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  • It is, in fact, admitted that some of the glasses, most useful optically, the dense barium crown glasses, which are so widely used in modern photographic lenses, cannot be produced entirely free either from noticeable colour or from numerous small bubbles, while the chemical nature of these glasses is so sensitive that considerable care is required to protect the surfaces of lenses made from them if serious tarnishing is to be avoided.

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  • It is a further striking fact, not unconnected with those just enumerated, that the extreme range of optical properties covered even by the relatively large number of optical glasses now available is in reality very small.

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  • The refractive indices of all glasses at present available lie between 1.46 and 1 90, whereas transparent minerals are known having refractive indices lying considerably outside these limits; at least one of these, fluorite (calcium fluoride), is actually used by opticians in the construction of certain lenses, so that probably progress is to be looked for in a considerable widening of the limits of available optical materials; possibly such progress may lie in the direction of the artificial production of large mineral crystals.

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  • The qualities required in optical glasses have already been partly referred to, but may now be summarized: I.

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  • In Optical Systems. As typical of the range of modern optical glasses Table I.

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  • is given, which constituted the list of optical glasses exhibited by Messrs Chance at the Optical Convention in London in 1905.

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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.

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  • Constancy of composition of the raw materials and their careful and thorough admixture in constant proportions are therefore essential to the production of the required glasses.

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  • 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.

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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.

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  • These glasses may be colourless or coloured.

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  • shows the typical composition of these glasses.

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  • For melting the leadless glasses, open, bowl-shaped crucibles are used, ranging from 12 to 40 in.

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  • 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.

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  • Special glasses have therefore been produced by Tonnelot in France and at the Jena glassworks in Germany expressly for the manufacture of thermometers for accurate physical measurements; the analyses of these are shown in Table III.

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  • 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.

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  • Among the many developments of the Jena Works, not the least important are the glasses made in the form of a tube, from which gas-chimneys, gauge-glasses and chemical apparatus are fashioned, specially adapted to resist sudden changes of temperature.

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  • The composition of these glasses is very similar to that of sheet-glass, but for the ordinary kinds of rolled plate much less scrupulous selection need be made in the choice of raw materials, especially of the sand.

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  • The vessels, especially those in which many differently coloured glasses were incorporated, required prolonged annealing.

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  • On one side of this a lion is engraved, and also a line of cuneiform characters, in which is the name of Sargon, king of Assyria, 722 B.C. Fragments of coloured glasses were also found there, but our materials are too scanty to enable us to form any decided opinion as to the degree of perfection to which the art was carried in Assyria.

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  • The glasses to which the Venetians gave the name " mille fiori " were formed by arranging side by side sections of glass cane, the canes themselves being built up of differently coloured rods of glass, and binding them together by heat.

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  • Imitations of natural stones were made by stirring together in a crucible glasses of different colours, or by incorporating fragments of differently coloured glasses into a mass of molten glass by rolling.

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  • The ground of these cameo glasses is most commonly transparent blue, but sometimes opaque blue, purple or dark brown.

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  • The so-called " Hedwig " glasses may also have originated in Constantinople.

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  • The enamelled Saracenic glasses take the form of flasks, vases, goblets, beakers and mosque lamps.

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  • Many specimens exist of German winged and enamelled glasses of Venetian character.

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  • On tall, roomy, cylindrical glasses they painted portraits of the emperor and electors of Germany, or the imperial eagle bearing on its wings the arms of the states composing the empire.

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  • The earliest-known example of these enamelled glasses bears the date 1553.

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  • of Spain for permission to make glasses, vases and cups of fine crystal, equal to those of Venice, but to be sold at one-third less than Venetian glasses.

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  • The Low Country glasses are closely copied from Venetian models, but generally are heavier and less elegant.

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  • It is the most brilliant and the most colourless of all glasses, and was undoubtedly first perfected in England.

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  • It is probable that flintglass was not invented, but gradually evolved, that potash-lead glasses were in use during the latter part of the 17th century, but that the mixture was not perfected until the middle of the following century.

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  • The most noted are the glasses with stout cylindrical legs (Plate I.

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  • To this type of glass belong many of the Jacobite glasses which commemorate the old or the young Pretender.

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  • Black, green, red, blue and yellow glasses are made, which contain a large proportion of alkali and are readily fusible.

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  • 28 (1893); Albert Hartshorne, Old English Glasses (London); E.

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  • He was well acquainted with the use of magnifying glasses and suggested a kind of telescope for viewing the moon, but does not seem to have thought of applying a lens to the camera.

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  • SPECTACLES, the name given to flat glasses, prisms, spherical or cylindrical lenses, mechanically adjusted to the human eyes, so as to correct defects of vision.

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  • Where, on the other hand, there is no tendency to squinting, care must be taken in selecting spectacles that the distances between the centres of the glasses and the centres of the pupils are quite equal, otherwise squinting, or at any rate great fatigue, of the eyes may be induced.

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  • In higher degrees, where full correction might increase the myopia by inducing a strain of the accommodation, somewhat weaker glasses should be used for near work.

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  • At first glasses may be given of such a strength as to relieve the troublesome symptoms; and the strength may be gradually increased till the total hypermetropia is corrected.

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  • Young adults with slighter forms of hypermetropia need glasses only for near work; elderly people should have one pair of weak glasses for distant and another stronger pair for near vision.

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  • These may be conveniently combined, as in Franklin glasses, where the upper half of the spectacle frame contains a weak lens, and the lower half, through which the eye looks when reading, a stronger one.

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  • Concave glasses were introduced soon afterwards.

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  • Periscopic glasses were introduced by Dr W.

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  • In experiments with magnifying glasses, and through spars, the ordinary effects of magnifying and of alteration of view are sometimes produced; sometimes they are not.

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  • This he mentions " because the glasses in these two sorts are somewhat prismatical, a but mostly those of the first model, which could therefore bear no great charge (magnifying power)."

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  • Glasses can now be made differing considerably both in refractivity and dispersive power.

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  • A specimen of one of these heavy glasses afterwards became historically important as the substance in which Faraday detected the rotation of the plane of polarization of light when the glass was placed in the magnetic field, and also as the substance which was first repelled by the poles of the magnet.

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  • Coloured anti-glare glasses are provided.

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  • The spores should be sown in well-drained pots or seed pans on the surface of a mixture of fibrous sifted peat and small broken crocks or sandstone; this soil should be firmly pressed and well-watered, and the spores scattered over it, and at once covered with propagating glasses or pieces of sheet glass, to prevent water or dry air getting to the surface.

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  • wide covered with lights, and a number of large bell glasses or " cloches."

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  • Plant hyacinths in glasses for windows.

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  • The tea is generally drunk from glasses and while very hot, with a liberal addition of sugar and a flavouring of lemon.

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  • In Morocco and generally throughout North Africa there is a considerable demand for green tea, which is drunk hot out of glasses, the liquor being almost saturated with sugar and strongly flavoured with mint.

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  • Temporary cement for lathe-work, such as the polishing and grinding of jewelry and optical glasses, is compounded thus: - rosin, 4 oz.; whitening previously made redhot, 4 oz.; wax, 4 oz.

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  • Trans., 1758), describing the experiments that led him to the achievement with which his name is specially associated, the discovery of a means of constructing achromatic lenses by the combination of crown and flint glasses.

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  • As a moralist and a guide to the conduct of life - an aspect of Goethe's work which Carlyle, viewing him through the coloured glasses of Fichtean idealism, emphasized and interpreted not always justly - Goethe was a powerful force on German life in years of political and intellectual depression.

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  • William Molyneux, in his Dioptrica Nova (1692), p. 256, declares his opinion that Roger Bacon (who died c. 12 9 4) "did perfectly well understand all kinds of optic glasses, and knew likewise the method of combining them so as to compose some such instrument as our telescope."

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  • Molyneux also cites from Bacon's Epistola ad Parisiensem, " Of the Secrets of Art and Nature," chap. 5: "Glasses or diaphanous bodies may be so formed that the most remote objects may appear just at hand, and the contrary, so that we may read the smallest letters at an incredible distance, and may number things, though never so small, and may make the stars also appear as near as we please."

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  • Giambattista della Porta, in his Magia Naturalis, printed in 558, makes the following remarkable statement: "If you do but know how to join the two (viz.,'the concave and the convex glasses) rightly together, you will see both remote and near objects larger than they otherwise appear, and withal very distinct."

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  • Thomas Digges, in his Stratioticus, p. 359, published in 1579, states that his father, Leonard Digges, "among other curious practices had a method of discovering by perspective glasses set at due angles all objects pretty far distant that the sun shone upon, which lay in the country round about," and that this was by the help of a manuscript book of Roger Bacon of Oxford, who he conceived was the only man besides his father who knew it.

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  • chap. 21) of Leonard Digges 1 (originally published by his son Thomas in 1571, and again in 1591): - "Marvellous are the conclusions that may be performed by glasses concave and convex, of circular and parabolic forms, using for multiplication of beams sometime the aid of glasses transparent, which, by fraction, should unite or dissipate the images or figures presented by the reflection of other."

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  • He then describes the effects of magnification from a combination of lenses or mirrors, adding: - "But of these conclusions I minde not here to intreate, having at large in a volume 2 by itselfe opened the miraculous effects of perspective glasses."

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  • In spite of the improvements in the manufacture of optical glass practically the same crown and flint glasses as used by John Dollond in 1758 for achromatic objectives are still used for all the largest of the modern refracting telescopes.

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  • It has long been known that the spectra of white or solar light yielded by ordinary crown and flint glasses are different: that while two prisms of such glasses may be arranged to give.

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  • These glasses, however, still hold the field, although glasses are now produced whose irrationality of dispersion has been reduced to a very slight amount.

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  • The primary reason for this retention is that nothing approaching the difference in dispersive power between ordinary crown glass and ordinary dense flint glass (a difference of i to 13) has yet been obtained between any pair of the newer glasses.

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  • Consequently, for a certain focal length, much deeper curves must be resorted to if the new glasses are to be employed; this means not only greater difficulties in workmanship, but also greater thickness of glass, which militates against the chance of obtaining large disks quite free from striae and perfect in their state of annealing.

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  • aperture are scarcely possible in most of the newer telescope glasses.

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  • When all is taken into consideration it is scarcely possible to reduce the secondary colour aberration at the focus of such a double object-glass to less than a fourth part of that prevailing at the focus of a double objective of the same aperture and focus, but made of the ordinary crown and flint glasses.

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  • But it can be well illustrated in the case of the older glasses, as the following case will show.

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  • The figures given are the partial dispersions for ordinary crown and ordinary extra dense flint glasses, styled in Messrs Schott's catalogue of optical glasses as o 60 and 0.102 respectively, having refractive indices of 1 5179 and 1.6489 for the D ray respectively, and (µ D -I)/(l F -µc) =60 2 and 33.8 respectively to indicate their dispersive powers (inverted), = v.

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  • Let it be supposed that two positive lenses of equal curvature powers are made out of these two glasses, then in order to represent the combined dispersion of the two together the two 0µ's for each spectral region may be added together to form 0'µ as in the line below, and then, on again expressing the partial z'µ in terms of L'µ (C to F) we get the new figures in the bottom row beneath the asterisks.

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  • Since the curvature powers of the positive lenses are equal, the partial dispersions of the two glasses may be simply added together, and we then have: [0.543 +0.3741 The proportions given on the lower line may now be compared with the corresponding proportional dispersions for borosilicate flint glass 0.658, closely resembling the type 0.164 of Schott's list, viz.: [0.658 (A D = I.546) 50' 11 A slight increase in the relative power of the first lens of 0.543 would bring about a still closer correspondence in the rationality, but with the curves required to produce an object-glass of this type of 6 in.

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  • The fire of Hestia was always kept burning, and, if by any accident it became extinct, only sacred fire produced by friction, or by burning glasses drawing fire from the sun, might be used to rekindle it.

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  • The so-called Renaissance did much; but it did not do the things attributed to it by those who see the "middle ages" through humanist glasses.

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  • In all earlier kinds of glass, however, the dispersive power increased with the refractive index; that is, v decreased as n increased; but some of the Jena glasses by E.

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  • glasses of high refractive index, and achromatic systems from such crown glasses, with flint glasses of lower refractive index, are called the " new achromatts," and were employed by P. Rudolph in the first " anastigmats " (photographic objectives).

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  • If its chromatic effect (d4/4) be greater than that of the same lens, this being made of the more dispersive of the two glasses employed, it is termed " hyper-chromatic."

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  • If a constant of reproduction, for instance the focal length, be made equal for two colours, then it is not the same for other colours, if two different glasses are employed.

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  • Fraunhofer, who defined the colours by means of the dark lines in the solar spectrum; and showed that the ratio of the dispersion of two glasses varied about 20% from the red to the violet (the variation for glass and water is about 50%).

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  • This follows by considering equation (4) for the two pairs of colours ac and bc. Until recently no glasses were known with a proportional degree of absorption; but R.

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  • Fraunhofer prepared glasses which reduced the secondary spectrum; but permanent success was only assured on the introduction of the Jena glasses by E.

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  • In using glasses not having proportional dispersion, the deviation of a third colour can be eliminated by two lenses, if an interval be allowed between them; or by three lenses in contact, which may not all consist of the old glasses.

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  • The most important is the chromatic difference of aberration of the axis point, which is still present to disturb the image, after par-axial rays of different colours are united by an appropriate combination of glasses.

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  • If a collective system be corrected for the axis point for a definite wave-length, then, on account of the greater dispersion in the negative components - the flint glasses; - over-correction will arise for the shorter wavelengths (this being the error of the negative components), and under-correction for the longer wave-lengths (the error of crown glass lenses preponderating in the red).

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  • When the glasses are cool, they may be charged with mercury, of which the first part is rejected.

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  • In a small commonplace book, bearing on the seventh page the date of January 1663/1664, there are several articles on angular sections, and the squaring of curves and " crooked lines that may be squared," several calculations about musical notes, geometrical propositions from Francis Vieta and Frans van Schooten, annotations out of Wallis's Arithmetic of Infinities, together with observations on refraction, on the grinding of " spherical optic glasses," on the errors of lenses and the method of rectifying them, and on the extraction of all kinds of roots, particularly those " in affected powers."

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  • After explaining his discovery of the composition of white light, he proceeds: " When I understood this, I left off my aforesaid Glass works; for I saw, that the perfection of Telescopes was hitherto limited, not so much for want of glasses truly figured according to the prescriptions of Optick Authors (which all men have hitherto imagined), as because that Light itself is a Heterogeneous mixture of differently refrangible Rays.

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  • But these seemed very great difficulties, and I have almost thought them insuperable, when I further considered, that every irregularity in a reflecting superficies makes the rays stray 5 or 6 times more out of their due course, than the like irregularities in a refracting one; so that a much greater curiosity would be here requisite, than in figuring glasses for Refraction.

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  • It has mainly to be considered in connexion with powerful magnifying glasses.

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  • Magnifying glasses are often used for viewing three-dimensional objects.

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  • In magnifying glasses for direct vision the eye must always be considered.

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  • The new glasses produced at Schott's glass works, Jena, possessed in part optical qualities which differed considerably from those of the older kinds of glass.

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  • Schott succeeded, however, in producing glasses which with a comparatively low refraction have a high dispersion, and with a high refraction a low dispersion.

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  • By using these glasses and employing minerals with special optical properties, it is possible to correct objectives so that three colours can be combined, leaving only a quite slight tertiary spectrum, and removing the spherical aberration for two colours.

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  • Abbe overcame this defect by using the so-called compensation ocular, made with Jena glasses.

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  • Abbe's test plate consists of an object carrier on which six cover glasses of exactly determined thickness (between 0.09 mm.

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  • The cover glasses are silvered on their under surfaces, and in the silvering fine lines are drawn; these lines form the test object.

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  • Oil of cloves is used in the silvering of mirror glasses.

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  • I wish everyone wore rose colored glasses the way you do.

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  • He needed glasses, but he wouldn't admit it.

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  • He studied her over the rim of his reading glasses, and his eyes warmed with a smile.

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  • He leaned back in the chair, tossing his glasses on the table.

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  • Bordeaux studied the dust through a pair of field glasses.

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  • Bordeaux lowered the glasses and shrugged in a way that was both elegant and masculine.

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  • He lifted the glasses again, lithely shifting his weight to maintain visual contact as his horse pawed at the sand.

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  • He lowered the glasses and met her gaze, a smile playing at the corners of his mouth.

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  • Bordeaux slung a long leg around his saddle horn and tucked the glasses into his saddlebag.

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  • He pulled his field glasses from the saddlebag and motioned to Cassie.

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  • He handed her the glasses.

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  • Shield the glasses from the sun with my hat like this.

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  • He positioned his hat so the glasses were shaded.

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  • She leaned across him, holding his hat over the glasses as he had shown her.

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  • He lowered the glasses and rolled over on his back, gazing up into her face.

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  • You want to lend me them glasses, Bordeaux?

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  • Breakfast over, Bordeaux saddled his horse and pulled the field glasses from his saddlebag.

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  • He handed the glasses to the chief and spoke to him in their language.

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  • Oh, and you know what they say: Men don't make passes at girls who wear glasses.

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  • I've noticed the guys eyeing you - glasses and all.

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  • Cynthia pushed her glasses up the bridge of her nose with an index finger and cleared her throat of that nauseating lump.

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  • He adjusted his glasses and returned to his fishing journal.

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  • Quinn returned with a tray, glasses, beer and a bottle of wine, looking somewhat apologetic.

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  • The man pulled up his mask enough for Howie to see a mustache and glasses but little else.

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  • Howie immediately began asking who needed more wine though our glasses were full.

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  • Signs of the party the night before still remained, from the garbage bags awaiting pickup to one table with two wine glasses still present.

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  • Dean grabbed a bottle of inexpensive merlot and three glasses.

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  • They stuck around, pretending to pick up glasses and snack plates while the Dawkins four quarreled, oblivious to their presence.

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  • Fred grumbled as he poured three glasses.

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  • A bookish man with glasses, wearing a white lab coat, opened the door to the small house.

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  • She wore glasses, a maroon business suit, and an all-business attitude to match.

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  • It was Roger who introduced first himself, then Charlie, who dipped his paper in acknowledgment, and Harold, who set down the news and looked at Dean over the top of his glasses, curious about the visit.

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  • Overly aware of his presence, Deidre stepped outside the kitchen to the breakfast counter and poured two glasses of wine.

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  • The man behind her was tall with glasses, a brunet ponytail, and a goofy grin.

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  • Katie sat, irritated to see who followed with a confident stride and two glasses of

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  • He snatched the whiskey from her hand and placed their glasses on a table.

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  • Ully said, handing her two glasses of whiskey.

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  • She took the glasses from him and downed them one at a time, then handed them back.

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  • He looked like any normal nerdy American with big glasses and a scrawny frame.

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  • As if on cue, the flushed cook returned for her plate, and Daniela ordered the brandy and two glasses.

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  • His bright features turned pink beneath his wire-rimmed glasses and straw-colored hair.

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  • Kevin, a small man with a quick smile and trendy glasses, smiled as she opened the door.

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  • Claire Quincy had donned reading glasses and was scrutinizing the letters as Fred O'Connor followed his notes and explained the information on Annie Quincy he had gathered at the library.

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  • She withdrew a single sheet of paper from her purse, unfolded it and adjusted her glasses.

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  • Dean put on his reading glasses.

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  • "Toss in Fred, too," he said as the old man returned with a bottle and three glasses.

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  • Fred poured a full glass of Tequila for Weller but left the other two glasses empty.

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  • Rubbing his eyes, he peered at the blurred figures of his clock, (more evidence of the necessity for his glasses).

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  • They carried their glasses to the overstuffed sofa and sat facing each other.

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  • Jackson stood with his glasses and a Cheshire cat grin.

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  • He found the caterer's boxes and set out collecting all the dishes, glasses and silverware.

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  • Approaching from behind, she noticed a bottle of scotch on the table, along with the two glasses.

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  • Sarah handed him his two glasses.

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  • She opened a bottle of Jack Daniels and set out three glasses.

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  • Jackson poured two glasses of blood, using a bottle labeled, 'Elisabeth' for Connor.

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  • When they returned home, the women were enjoying glasses of wine.

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  • He frowned at her over the rim of his thick glasses.

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  • I did the same with the glasses and silverware.

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  • Dean dutifully paused a few moments until Fred took off his glasses, slammed down the book on a table and said with a broad smile, I knew it!

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  • "Put on your glasses, you'll go blind doing that," Dean said, handing Fred his beer and reclaiming his rocker from Mrs. Lincoln, the large black cat that had adopted the pair the prior February.

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  • Those glasses are only for reading, Fred replied, without looking up.

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  • "Just things," Fred muttered, putting on his glasses.

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  • The drinks arrived in glasses better designed for raising fish than serving alcohol—a sure hit with the traveling salesmen.

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  • He clicked off Art Tatum and "Willow Weep For Me" and after pulling out a bot­tle of scotch and two glasses, returned to Fred's room.

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  • She reached down behind the desk and brought out a bottle of gin and poured two healthy slugs into water glasses.

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  • With crochet needles in her lap, Mums eyed Carmen over the rim of her reading glasses.

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  • He peered at her over the top of his glasses.

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  • Maybe you could fill the glasses with tea?

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  • She beamed up at Keaton as he approached with two glasses of iced tea.

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  • The store manager, a middle-aged woman with glasses, looked up at him in awe.

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  • Do you want to spend money on false nostalgia seen through rose-tinted glasses?

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  • buy Czech absinthe, T-shirts, absinthe glasses, ... More information Bargain Coffee Coffee, tea, chocolate delivered to your door.

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  • They offer a selection of strong absinthe drink, T-shirts, glasses, spoons and absinthe drink, T-shirts, glasses, spoons and absinthe e-gift certificates.

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  • anaglyph glasses.

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  • aviator glasses, RX sunglasses, prescription sunglasses, motorcycle goggles and more.

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  • balding man with glasses is sitting opposite my cubicle, he is talking to a younger woman - they both wear white coats.

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  • bifocal glasses can contribute to balance problems for some people.

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  • Fourteen glasses A British diplomat once described how he went to the Caucasus to met some local bigwigs.

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  • bioactive glasses and machinable glass-ceramics are available under a number of trade names.

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  • blarey heard the tinkling of glasses, raucous laughter, and music blaring through loud speakers.

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  • blokes in white coats and glasses peering into test-tubes.

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  • borate glasses.

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  • So now only borderline need glasses but have got a new pair on order.

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  • breakable glasses or crockery in or around the pool.

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  • Additionally, drink at least 8-10 glasses of water each day. * Do consume extra carbohydrate.

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  • Just a quick update: Ben has his eye checkup tomorrow to see how his glasses are getting on.

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  • chinking glasses.

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  • Shake everything with crushed ice, strain into cocktail glasses and sprinkle cinnamon on top.

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  • clinking glasses, is the life.

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  • clink of glasses between the lines.

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  • Essential Vision Tip: 4 Tips to See Better at Night 1. Choose glasses with an anti-reflective coating to reduce glare.

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  • No glasses or hard contact lenses can be worn.

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  • Dwight (the American Gareth) looks down-right creepy with glasses that exactly run across the top of his eyebrows and his hair parting.

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  • All the necessary crockery, cutlery, glasses, utensils, pans etc. Original slate floor.

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  • croissant with cheese and had about 10 glasses of orange and apple juice.

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  • Layer the set jelly, whipped cream and fresh currants in 4 glasses and serve.

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  • It has a bright spacious ambiance, natural pine flooring and furnishings set with silver cutlery and generous crystal wine glasses.

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  • Our current 2 for 1 offer gives you the option of having daytime driving glasses as your free second pair.

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  • decanter of port and two tiny glasses.

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  • diffraction peak in glasses?

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  • Your glasses will be sent direct to your home.

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  • The users wear active stereo LCD shutter glasses, which are controlled by an infra-red emitter.

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  • enamel jug topping up glasses.

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  • excrete 4 glasses urine.

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  • Glasses On Spec - Their site offers prescription eyewear / glasses at reduced prices online or by mail order.

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  • All of the interior fittings, including the glasses, are made of pure, clear ice from the Torne River in northern Sweden.

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  • Had a few too many glasses of wine and far too much cheese fondue which was AMAZING!

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  • They sold the glasses to sixth- formers and staff, and to members of the public at Wymondham's Dickensian evening.

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  • Philip enjoyed himself getting quite frisky, he'd probably been drinking glasses of whiskey.

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  • Vitreous enamel frits The formulation of the development of the specialized glasses known as vitreous enamel frits.

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  • gallon enamel jug topping up glasses.

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  • We drank ginger ale on ice from his parents ' old-fashioned and highball glasses.

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  • Do you know of any famous people who look glamorous in their glasses?

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  • glasses of very welcome apple juice for us.

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  • The populace will be fitted with rose tinted glasses through which to see all the latest policies passed through parliament.

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  • I just need to get an ice crusher, some cocktail glasses and I should have a great time trying out various recipes.

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  • Immediately the Irishman tears into all 10 of the pint glasses, drinking them all back-to-back.

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  • You can even chuck your Ice Shot Glasses in the fireplace and swear in Russian without having to buy replacement glassware.

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  • glassware manufacturers recommend Finish Protector, to keep your glasses looking new for longer!

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  • A fantastic set of six English silver plated goblets / drinking glasses in a very attractive Art Deco style.

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  • Why settle for boring beer glasses when you can sup from a gorgeous goblet.

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  • Dark welding goggles or glasses have to be worn.

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  • guilloche knot with hour glasses on the lozenges.

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  • Are both sexes wearing standard-issue studded belts, asymmetrical punky mullet hairdos, and harsh glasses?

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  • half-moon glasses and winked.

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  • highball glasses?

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  • Ian j, at 1:01 PM I think I've got all but one of my beer fest glasses.

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  • Drinks are served in glasses made out of ice and you sleep in your own private igloo.

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  • intraocular lens has not been inserted, glasses with very thick lenses will be needed.

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  • jenny returns to the dining room with two glasses of wine.

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  • He just roamed the room with a white half gallon enamel jug topping up glasses.

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  • knocked off my glasses, which then smashed on the garage floor.

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  • Whats in designer glasses knockoff sun the too effective then added, door.

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  • lavatory pans and glasses dry without water marks.

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  • Resting only for long tall glasses of fresh lemonade, or big round bowels of chocolate ice cream.

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  • lime around the rim of the 2 chilled glasses.

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  • A waiter brought us a very potent cocktail of something, that smelled of horse liniment and Brian naturally drank both glasses.

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  • litreical experts have recommended that adults consume two liters (eight glasses) of water each day and children approximately half that amount.

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  • Ornate prospect glasses, French lorgnettes and miniature spyglasses became all the rage in pre-Revolutionary France.

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  • There many ways to make a margarita, here's my sunrise special: Recipe: Dip rims of glasses in granulated sugar.

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  • had some martini from the glasses we bought Roz and then set off to the chinese near by.

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  • Host your own martini party in style with some of our distinguished martini party in style with some of our distinguished martini glasses and accessories.

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  • Surprisingly, the study found that not a single person diagnosed as needing glasses ever masturbated.

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  • mohair coat, cap, dark glasses and was smoking a cigar.

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  • The glasses used to manufacture Burle electron multipliers have been specially formulated to produce low background noise.

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  • Anyone who wears glasses or contact lenses but is unable to read standard newsprint is partially sighted.

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  • noveltytuff Online Supplier of low cost fancy dress, wigs, glasses, hats, props and party novelties.

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  • Shop lady: Here you go - here are your glasses with new... er... nubbins.

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  • Glasses will not stop you having nystagmus nor are they a cure.

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  • I have fully qualified opticians working in labs, making the glasses. âI was on GMTV today, arguing with an exec from Specsavers.

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  • To claim vouchers for glasses: ask for the voucher when your optician or hospital optometrist carries out the sight test.

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  • ounce glasses.

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  • overwhelmed with gratitude for the dentures and reading glasses she had received free of charge.

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  • Marks have vanished in basins and lavatory pans and glasses dry without water marks.

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  • petrifyld lady stood petrified with astonishment, peering over her glasses; Tom lay on the floor expiring with laughter.

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  • There was a hunchbacked, goggle-eyed creature behind a desk, with glasses which made his eyes look like a newborn piglet 's.

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  • pinhole glasses are designed to improve any eye problems, especially eye focussing problems.

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  • The easiest way to correct presbyopia is to let the person choose from a selection of glasses of different strengths.

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  • You hear a sound from the doorway, and spin around as a stunning redhead walks in with two glasses of sparkling champagne.

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  • rose-colored glasses, living in a fantasy.

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  • safety glasses at all times.

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  • Useful for tightening those awkward little screws in glasses.

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  • sighted people may need to remove their distance glasses to see money in their hands.

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  • I am registered partially sighted - can I get help with buying my glasses?

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  • But if Mars is taken to mean its natural signification, does that mean that the glasses will be found by a military person?

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  • silicate glasses.

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  • Using red-green glasses, disparity specifies surface slant about the vertical axis.

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  • His glasses were the same, tho, and his face had not changed, still unshaven, still smirking.

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  • striated glasses, Ocular dominance, Sbisa bar, Sensory fusion.

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  • sundae glasses.

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  • takeck took off his glasses and slowly pressed a kiss on each eye.

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  • Glasses were banged down on the tables, half eaten tapas abandoned.

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  • tinted glasses for the rest of his life.

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  • tortoiseshell glasses at the closed door to the boardroom.

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  • He glances down at his Omega Seamaster watch and peers over his Calvin Klein faux tortoiseshell glasses at the closed door to the boardroom.

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  • I managed a full set of six wine glasses at Norfolk this year, but would like the whiskey tumblers to match please.

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  • Glasses have always been a necessity rather than a fashion accessory, and therefore, inevitably, terminally uncool.

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  • Feel somewhat unwell: put down to new glasses - this may be wrong.

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  • For every 2 glasses of wine you drink you will excrete 4 glasses urine.

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  • You can wear glasses or contact lenses and still use a lightbox or a light visor.

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  • To help pay for the glasses, you can receive a voucher, which has a monetary value.

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  • On the next table the wine waiter is topping up glasses.

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  • She went on " His wire-framed glasses lend warmth to his face.

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  • welding goggles or glasses have to be worn.

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  • Books are a celebration and are launched with a few glasses of wine and some welsh cakes.

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  • whiskey glasses by Lifeboat Operations Manager Ian Readman on behalf of his fellow Management Committee.

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  • add some zest to your six to eight glasses a day with a twist of lemon or lime.

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  • To fulfil condition (2) the two microscopes whose object glasses are O l and 0 2 (fig.

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  • By this time he had ceased to devote himself to pure mathematics, and in company with his friends Mersenne and Mydorge was deeply interested in the theory of the refraction of light, and in the practical work of grinding glasses of the best shape suitable for optical instruments.

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  • He must have mortars, pots, filters, glasses and boxes clean and sweet.

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  • He now employed himself in making optical glasses, and in engraving on metal, devoting his spare time to the perusal of works on mathematics and optics.

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  • He was the inventor of the stage-micrometer, and of a form of heliometer; and in 1816 he succeeded in constructing for the microscope achromatic glasses of long focus, consisting of a single lens, the constituent glasses of which were in juxtaposition, but not cemented together.

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  • Many substances were used as pigments: Pliny records white lead, cinnabar, verdigris and red oxide of iron; and the preparation of coloured glasses and enamels testifies to the uses to which these and other substances were put.

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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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  • Lead silicates are obtained as glasses by fusing litharge with silica; they play a considerable part in the manufacture of the lead glasses (see Glass).

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  • Such tin-ash, as it is called, is used for the polishing of optical glasses.

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  • It is convenient to treat these glasses as " normal " glasses, but they are in reality mixtures of silicates, and cannot rightly be regarded as definite chemical compounds or represented by definite chemical formulae.

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  • Glasses possessing special qualities have been required, and have been supplied by the introduction of new combinations of materials.

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  • The range of the specific gravity of glasses from 2.5 to 5.0 illustrates the effect of modified compositions.

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  • Glasses are generally transparent but may be translucent or opaque.

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  • Semi-opacity due to crystallization may be induced in many glasses by maintaining them for a long period at a.

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  • 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.

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  • Owing to impurities contained in the materials from which glasses are made, accidental coloration or discoloration is often produced.

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  • Special glasses for thermometers, and other special glasses.

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  • Fraunhofer further initiated the specification of refraction and dispersion in terms of certain lines of the spectrum, and even attempted an investigation of the effect of chemical composition on the relative dispersion produced by glasses in different parts of the spectrum.

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  • Faraday independently recognized the necessity for mechanical agitation of the molten glass in order to ensure homogeneity, and to facilitate his manipulations he worked with dense lead borate glasses which are very fusible, but have proved too unstable for ordinary optical purposes.

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  • As a result a whole series of glasses of novel composition and optical properties were produced.

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  • the production of pairs of glasses of widely differing refraction and dispersion, but having a similar distribution of dispersion in the various regions of the spectrum, was not in the first instance solved.

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  • 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.

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  • The manufacture of the new varieties of glass, originally known as " Jena " glasses, is now carried out extensively and with a considerable degree of commercial success in France, and also to a less extent in England, but none of the other makers of optical glass has as yet contributed to the progress of the industry to anything like the same extent as the Jena firm.

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  • The older optical glasses, now generally known as the " ordinary " crown and flint glasses, are all of the nature of pure silicates, the basic constituents being, in the case of crown glasses, lime and soda or lime and potash, or a mixture of both, and in the case of flint glasses, lead and either (or both) soda and potash.

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  • With the exception of the heavier flint (lead) glasses, these can be produced so as to be free both from noticeable colour and from such defects as bubbles, opaque inclusions or " striae," but extreme care in the choice of all the raw materials and in all the manipulations is required to ensure this result.

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  • Further, these glasses, when made from properly proportioned materials, possess a very considerable degree of chemical stability, which is amply sufficient for most optical purposes.

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  • The newer glasses, on the other hand, contain a much wider variety of chemical constituents, the most important being the oxides of barium, magnesium, aluminium and zinc, used either with or without the addition of the bases already named in reference to the older glasses, and - among acid bodies - boric anhydride (B20 3) which replaces the silica of the older glasses to a varying extent.

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  • 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.

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  • On the other hand, the more extreme the optical properties of these new glasses, i.e.

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  • the further they depart from the ratio of refractive index to dispersive power found in the older glasses, the greater the difficulty found in obtaining them of either sufficient purity or stability to be of practical use.

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  • It is, in fact, admitted that some of the glasses, most useful optically, the dense barium crown glasses, which are so widely used in modern photographic lenses, cannot be produced entirely free either from noticeable colour or from numerous small bubbles, while the chemical nature of these glasses is so sensitive that considerable care is required to protect the surfaces of lenses made from them if serious tarnishing is to be avoided.

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  • It is a further striking fact, not unconnected with those just enumerated, that the extreme range of optical properties covered even by the relatively large number of optical glasses now available is in reality very small.

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  • The refractive indices of all glasses at present available lie between 1.46 and 1 90, whereas transparent minerals are known having refractive indices lying considerably outside these limits; at least one of these, fluorite (calcium fluoride), is actually used by opticians in the construction of certain lenses, so that probably progress is to be looked for in a considerable widening of the limits of available optical materials; possibly such progress may lie in the direction of the artificial production of large mineral crystals.

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  • The qualities required in optical glasses have already been partly referred to, but may now be summarized: I.

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  • Refraction and Dispersion.-The purely optical properties of refraction and dispersion, although of the greatest importance, cannot be dealt with in any detail here; for an account of the optical properties required in glasses for various forms of lenses see the articles Lens and Aberration: Ii.

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  • In Optical Systems. As typical of the range of modern optical glasses Table I.

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  • is given, which constituted the list of optical glasses exhibited by Messrs Chance at the Optical Convention in London in 1905.

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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.

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  • Constancy of composition of the raw materials and their careful and thorough admixture in constant proportions are therefore essential to the production of the required glasses.

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  • 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.

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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.

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  • These glasses may be colourless or coloured.

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  • shows the typical composition of these glasses.

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  • For melting the leadless glasses, open, bowl-shaped crucibles are used, ranging from 12 to 40 in.

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  • 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.

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  • Special glasses have therefore been produced by Tonnelot in France and at the Jena glassworks in Germany expressly for the manufacture of thermometers for accurate physical measurements; the analyses of these are shown in Table III.

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  • 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 Röntgen rays, experiments have been made to ascertain the effects of the different constituents of glass on the transparency of glass to X-rays.

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  • Among the many developments of the Jena Works, not the least important are the glasses made in the form of a tube, from which gas-chimneys, gauge-glasses and chemical apparatus are fashioned, specially adapted to resist sudden changes of temperature.

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  • The composition of these glasses is very similar to that of sheet-glass, but for the ordinary kinds of rolled plate much less scrupulous selection need be made in the choice of raw materials, especially of the sand.

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  • The vessels, especially those in which many differently coloured glasses were incorporated, required prolonged annealing.

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  • On one side of this a lion is engraved, and also a line of cuneiform characters, in which is the name of Sargon, king of Assyria, 722 B.C. Fragments of coloured glasses were also found there, but our materials are too scanty to enable us to form any decided opinion as to the degree of perfection to which the art was carried in Assyria.

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  • The glasses to which the Venetians gave the name " mille fiori " were formed by arranging side by side sections of glass cane, the canes themselves being built up of differently coloured rods of glass, and binding them together by heat.

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  • Imitations of natural stones were made by stirring together in a crucible glasses of different colours, or by incorporating fragments of differently coloured glasses into a mass of molten glass by rolling.

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  • The ground of these cameo glasses is most commonly transparent blue, but sometimes opaque blue, purple or dark brown.

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  • The so-called " Hedwig " glasses may also have originated in Constantinople.

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  • The enamelled Saracenic glasses take the form of flasks, vases, goblets, beakers and mosque lamps.

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  • The highest perfection with regard both to form and decoration was reached in the 16th century; subsequently the Venetian workmen somewhat abused their skill by giving extravagant forms to vessels, making drinking glasses in the forms of ships, lions, birds, whales and the like.

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  • Many specimens exist of German winged and enamelled glasses of Venetian character.

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  • On tall, roomy, cylindrical glasses they painted portraits of the emperor and electors of Germany, or the imperial eagle bearing on its wings the arms of the states composing the empire.

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  • The earliest-known example of these enamelled glasses bears the date 1553.

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  • of Spain for permission to make glasses, vases and cups of fine crystal, equal to those of Venice, but to be sold at one-third less than Venetian glasses.

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  • The Low Country glasses are closely copied from Venetian models, but generally are heavier and less elegant.

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  • In 1466 the abbess of St Croix of Poitiers received a gross of glasses from the glass-works of La Ferriêre, for the privilege of gathering fern for the manufacture of potash.

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  • It is the most brilliant and the most colourless of all glasses, and was undoubtedly first perfected in England.

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  • It is probable that flintglass was not invented, but gradually evolved, that potash-lead glasses were in use during the latter part of the 17th century, but that the mixture was not perfected until the middle of the following century.

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  • The most noted are the glasses with stout cylindrical legs (Plate I.

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  • To this type of glass belong many of the Jacobite glasses which commemorate the old or the young Pretender.

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  • Black, green, red, blue and yellow glasses are made, which contain a large proportion of alkali and are readily fusible.

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  • 46) states on the authority of the annals of the Han dynasty that the emperor Wu-ti (140 B.C.) had a manufactory of the kind of glass called " lieou-li " (probably a form of opaque glass), that in the beginning of the 3rd century of our era the emperor Tsaou-tsaou received from the West a considerable present of glasses of all colours, and that soon after a glass-maker came into the country who taught the art to the natives.

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  • 28 (1893); Albert Hartshorne, Old English Glasses (London); E.

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  • He was well acquainted with the use of magnifying glasses and suggested a kind of telescope for viewing the moon, but does not seem to have thought of applying a lens to the camera.

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  • SPECTACLES, the name given to flat glasses, prisms, spherical or cylindrical lenses, mechanically adjusted to the human eyes, so as to correct defects of vision.

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  • Where, on the other hand, there is no tendency to squinting, care must be taken in selecting spectacles that the distances between the centres of the glasses and the centres of the pupils are quite equal, otherwise squinting, or at any rate great fatigue, of the eyes may be induced.

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  • In higher degrees, where full correction might increase the myopia by inducing a strain of the accommodation, somewhat weaker glasses should be used for near work.

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  • At first glasses may be given of such a strength as to relieve the troublesome symptoms; and the strength may be gradually increased till the total hypermetropia is corrected.

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  • Young adults with slighter forms of hypermetropia need glasses only for near work; elderly people should have one pair of weak glasses for distant and another stronger pair for near vision.

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  • These may be conveniently combined, as in Franklin glasses, where the upper half of the spectacle frame contains a weak lens, and the lower half, through which the eye looks when reading, a stronger one.

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  • Concave glasses were introduced soon afterwards.

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  • Periscopic glasses were introduced by Dr W.

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  • In experiments with magnifying glasses, and through spars, the ordinary effects of magnifying and of alteration of view are sometimes produced; sometimes they are not.

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  • This he mentions " because the glasses in these two sorts are somewhat prismatical, a but mostly those of the first model, which could therefore bear no great charge (magnifying power)."

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  • Glasses can now be made differing considerably both in refractivity and dispersive power.

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  • A specimen of one of these heavy glasses afterwards became historically important as the substance in which Faraday detected the rotation of the plane of polarization of light when the glass was placed in the magnetic field, and also as the substance which was first repelled by the poles of the magnet.

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  • Coloured anti-glare glasses are provided.

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  • The spores should be sown in well-drained pots or seed pans on the surface of a mixture of fibrous sifted peat and small broken crocks or sandstone; this soil should be firmly pressed and well-watered, and the spores scattered over it, and at once covered with propagating glasses or pieces of sheet glass, to prevent water or dry air getting to the surface.

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  • wide covered with lights, and a number of large bell glasses or " cloches."

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  • Plant hyacinths in glasses for windows.

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  • The tea is generally drunk from glasses and while very hot, with a liberal addition of sugar and a flavouring of lemon.

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  • In Morocco and generally throughout North Africa there is a considerable demand for green tea, which is drunk hot out of glasses, the liquor being almost saturated with sugar and strongly flavoured with mint.

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  • Temporary cement for lathe-work, such as the polishing and grinding of jewelry and optical glasses, is compounded thus: - rosin, 4 oz.; whitening previously made redhot, 4 oz.; wax, 4 oz.

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  • Trans., 1758), describing the experiments that led him to the achievement with which his name is specially associated, the discovery of a means of constructing achromatic lenses by the combination of crown and flint glasses.

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  • Early in 1757 he succeeded in producing refraction without colour by the aid of glass and water lenses, and a few months later he made a successful attempt to get the same result by a combination of glasses of different qualities (see Telescope).

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  • As a moralist and a guide to the conduct of life - an aspect of Goethe's work which Carlyle, viewing him through the coloured glasses of Fichtean idealism, emphasized and interpreted not always justly - Goethe was a powerful force on German life in years of political and intellectual depression.

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  • William Molyneux, in his Dioptrica Nova (1692), p. 256, declares his opinion that Roger Bacon (who died c. 12 9 4) "did perfectly well understand all kinds of optic glasses, and knew likewise the method of combining them so as to compose some such instrument as our telescope."

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  • Molyneux also cites from Bacon's Epistola ad Parisiensem, " Of the Secrets of Art and Nature," chap. 5: "Glasses or diaphanous bodies may be so formed that the most remote objects may appear just at hand, and the contrary, so that we may read the smallest letters at an incredible distance, and may number things, though never so small, and may make the stars also appear as near as we please."

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  • Giambattista della Porta, in his Magia Naturalis, printed in 558, makes the following remarkable statement: "If you do but know how to join the two (viz.,'the concave and the convex glasses) rightly together, you will see both remote and near objects larger than they otherwise appear, and withal very distinct."

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  • Thomas Digges, in his Stratioticus, p. 359, published in 1579, states that his father, Leonard Digges, "among other curious practices had a method of discovering by perspective glasses set at due angles all objects pretty far distant that the sun shone upon, which lay in the country round about," and that this was by the help of a manuscript book of Roger Bacon of Oxford, who he conceived was the only man besides his father who knew it.

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