Glass Manufacture

SUBJECT AREA: Metallurgy

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His family emigrated to Australia when he was 5 years old. He was educated at Wesley College, Melbourne, and attended Queen's College, University of Melbourne, graduating in physics and engineering in 1897. As an 1851 Exhibitioner he then spent three years at St John's College, Cambridge, under Sir Alfred Ewing, where he studied the microstructure of deformed metal crystals and abandoned his original intention of becoming a civil engineer. Rosenhain was the first to observe the slip-bands in metal crystals, and in the Bakerian Lecture delivered jointly by Ewing and Rosenhain to the Royal Society in 1899 it was shown that metals deformed plastically by a mechanism involving shear slip along individual crystal planes. From this conception modern ideas on the plasticity and recrystallization of metals rapidly developed. On leaving Cambridge, Rosenhain joined the Birmingham firm of Chance Brothers, where he worked for six years on optical glass and lighthouse-lens systems. A book, Glass Manufacture, written in 1908, derives from this period, during which he continued his metallurgical researches in the evenings in his home laboratory and published several papers on his work.

In 1906 Rosenhain was appointed Head of the Metallurgical Department of the National Physical Laboratory (NPL), and in 1908 he became the first Superintendent of the new Department of Metallurgy and Metallurgical Chemistry. Many of the techniques he introduced at Teddington were described in his Introduction to Physical Metallurgy, published in 1914. At the outbreak of the First World War, Rosenhain was asked to undertake work in his department on the manufacture of optical glass. This soon made it possible to manufacture optical glass of high quality on an industrial scale in Britain. Much valuable work on refractory materials stemmed from this venture. Rosenhain's early years at the NPL were, however, inseparably linked with his work on light alloys, which between 1912 and the end of the war involved virtually all of the metallurgical staff of the laboratory. The most important end product was the well-known "Y" Alloy (4% copper, 2% nickel and 1.5% magnesium) extensively used for the pistons and cylinder heads of aircraft engines. It was the prototype of the RR series of alloys jointly developed by Rolls Royce and High Duty Alloys. An improved zinc-based die-casting alloy devised by Rosenhain was also used during the war on a large scale for the production of shell fuses.

After the First World War, much attention was devoted to beryllium, which because of its strength, lightness, and stiffness would, it was hoped, become the airframe material of the future. It remained, however, too brittle for practical use. Other investigations dealt with impurities in copper, gases in aluminium alloys, dental alloys, and the constitution of alloys. During this period, Rosenhain's laboratory became internationally known as a centre of excellence for the determination of accurate equilibrium diagrams.

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SUBJECT AREA: Chemical technology, Photography, film and optics

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George's father James was a successful lawyer and merchant, engaging in overseas trade.

A devout but necessarily circumspect Catholic, James sent his sons to the English College at Douai, now in northern France. Leaving there in 1651, George began to learn his father's business and spent some fifteen years in Venice. He took an increasingly important part in it, doubtless dealing in Venice's leading products of lace and glass. By 1666 he was back in England and, perhaps because the supply of Venetian glass was beginning to decline, he started to manufacture glass himself. In 1673 he set up a glassworks in the Savoy in London and succeeded so well that in the following year he petitioned the King for the grant of a patent to make glassware. This was granted on 16 May 1674, stimulating the Glass Sellers' Company to enter into an agreement with Ravenscroft to buy the glassware he produced. Later in 1674 the company allowed Ravenscroft to establish a second glasshouse at Henley-onThames. At first his ware was beset with "crizzling", i.e. numerous fine surface cracks. The Glass Sellers probably urged Ravenscroft to cure this defect, and this he achieved in 1675 by replacing crushed flint with increasing amounts of lead oxide, rising finally to a content of 30 per cent. He thereby obtained a relatively soft, heavy glass with high refractive index and dispersive power. This made it amenable to deep cutting, to produce the brilliant prismatic effects of cut glass. At about the same time, the Duke of Buckingham, a considerable promoter of the glass industry, agreed that Ravenscroft should manage his works at Vauxhall for the making of plate glass for mirrors. Ravenscroft terminated his agreement with the Glass Sellers in 1678, the date of the last evidence of his activities as a maker of crystal glass, and the patent expired in 1681. His new glass had immediately rivalled the best Venetian crystal glass and has been a valued product ever since.

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SUBJECT AREA: Photography, film and optics

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Guinand received little formal education and followed his father's trade of joiner. He specialized in making clock cases, but after learning how to cast metals he took up the more lucrative work of making watch cases. When he was about 20 years old, in a customer's house he caught sight of an English telescope, a rarity in a Swiss mountain village. Intrigued, he obtained permission to examine it. This aroused his interest in optical matters and he began making spectacles and small telescopes.

Achromatic lenses were becoming known, their use being to remove the defect of chromatic aberration or coloured optical images, but there remained defects due to imperfections in the glass itself. Stimulated by offers of prizes by scientific bodies, including the Royal Society of London, for removing these defects, Guinand set out to remedy them. He embarked in 1784 on a long and arduous series of experiments, varying the materials and techniques for making glass. The even more lucrative trade of making bells for repeaters provided the funds for a furnace capable of holding 2 cwt (102 kg) of molten glass. By 1798 or so he had succeeded in making discs of homogeneous glass. He impressed the famous Parisian astronomer de Lalande with them and his glass became well enough known for scientists to visit him. In 1805 Fraunhofer persuaded Guinand to join his optical-instrument works at Benediktheurn, in Bavaria, to make lenses. After nine years, Guinand returned to Brenets with a pension, on condition he made no more glass and disclosed no details of his methods. After two years these conditions had become irksome and he relinquished the pension. On 19 February 1823 Guinand described his discoveries in his classic "Memoir on the making of optical glass, more particularly of glass of high refractive index for use in the production of achromatic lenses", presented to the Société de Physique et d'Histoire Naturelle de Genève. This gives details of his experiments and investigations and discusses a suitable pot-clay stirrer and stirring mechanism for the molten glass, with temperature control, to overcome optical-glass defects such as bubbles, seeds, cords and colours. Guinand was hailed as the man in Europe who had achieved this and has thus rightly been called the founder of the era of optical glassmaking.

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SUBJECT AREA: Agricultural and food technology, Domestic appliances and interiors

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To assist the finances of a coal miner's family, Owens entered a glassworks at Wheeling, Virginia, at the tender age of 10, stoking coal into the "glory hole" or furnace where glass was resoftened at various stages of the hand-forming process. By the age of 15 he had become a glassblower.

In 1888 Owens moved to the glassworks of Edward Drummond Libbey at Toledo, Ohio, where within three months he was appointed Superintendent and, not long after, a branch manager. In 1893 Owens supervised the company's famous exhibit at the World's Columbian Exposition at Chicago. He had by then begun experiments that were to lead to the first automatic bottle-blowing machine. He first used a piston pump to suck molten glass into a mould, and then transferred the gathered glass over another mould into which the bottle was blown by reversing the pump. The first patents were taken out in 1895, followed by others incorporating improvements and culminating in the patent of 8 November 1904 for an essentially perfected machine. Eventually it was capable of producing four bottles a second, thus effecting a revolution in bottle making. Owens, with Libbey and others, set up the Owens Bottle Machine Company in 1903, which Owens himself managed from 1915 to 1919, becoming Vice-President from 1915 until his death. A plant was also established in Manchester in 1905.

Besides this, Owens and Libbey first assisted Irving W.Colburn with his experiments on the continuous drawing of flat sheet glass and then in 1912 bought the patents, forming the Owens-Libbey Sheet Glass Company. In all, Owens was granted forty-five US patents, mainly relating to the manufacture and processing of glass. Owens's undoubted inventive genius was hampered by a lack of scientific knowledge, which he made good by judicious consultation.

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SUBJECT AREA: Photography, film and optics

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The young Eastman was a clerk-bookkeeper in the Rochester Savings Bank when in 1877 he took up photography. Taking lessons in the wet-plate process, he became an enthusiastic amateur photographer. However, the cumbersome equipment and noxious chemicals used in the process proved an obstacle, as he said, "It seemed to be that one ought to be able to carry less than a pack-horse load." Then he came across an account of the new gelatine dry-plate process in the British Journal of Photography of March 1878. He experimented in coating glass plates with the new emulsions, and was soon so successful that he decided to go into commercial manufacture. He devised a machine to simplify the coating of the plates, and travelled to England in July 1879 to patent it. In April 1880 he prepared to begin manufacture in a rented building in Rochester, and contacted the leading American photographic supply house, E. \& H.T.Anthony, offering them an option as agents. A local whip manufacturer, Henry A.Strong, invested $1,000 in the enterprise and the Eastman Dry Plate Company was formed on 1 January 1881. Still working at the Savings Bank, he ran the business in his spare time, and demand grew for the quality product he was producing. The fledgling company survived a near disaster in 1882 when the quality of the emulsions dropped alarmingly. Eastman later discovered this was due to impurities in the gelatine used, and this led him to test all raw materials rigorously for quality. In 1884 the company became a corporation, the Eastman Dry Plate \& Film Company, and a new product was announced. Mindful of his desire to simplify photography, Eastman, with a camera maker, William H.Walker, designed a roll-holder in which the heavy glass plates were replaced by a roll of emulsion-coated paper. The holders were made in sizes suitable for most plate cameras. Eastman designed and patented a coating machine for the large-scale production of the paper film, bringing costs down dramatically, the roll-holders were acclaimed by photographers worldwide, and prizes and medals were awarded, but Eastman was still not satisfied. The next step was to incorporate the roll-holder in a smaller, hand-held camera. His first successful design was launched in June 1888: the Kodak camera. A small box camera, it held enough paper film for 100 circular exposures, and was bought ready-loaded. After the film had been exposed, the camera was returned to Eastman's factory, where the film was removed, processed and printed, and the camera reloaded. This developing and printing service was the most revolutionary part of his invention, since at that time photographers were expected to process their own photographs, which required access to a darkroom and appropriate chemicals. The Kodak camera put photography into the hands of the countless thousands who wanted photographs without complications. Eastman's marketing slogan neatly summed up the advantage: "You Press the Button, We Do the Rest." The Kodak camera was the last product in the design of which Eastman was personally involved. His company was growing rapidly, and he recruited the most talented scientists and technicians available. New products emerged regularly—notably the first commercially produced celluloid roll film for the Kodak cameras in July 1889; this material made possible the introduction of cinematography a few years later. Eastman's philosophy of simplifying photography and reducing its costs continued to influence products: for example, the introduction of the one dollar, or five shilling, Brownie camera in 1900, which put photography in the hands of almost everyone. Over the years the Eastman Kodak Company, as it now was, grew into a giant multinational corporation with manufacturing and marketing organizations throughout the world. Eastman continued to guide the company; he pursued an enlightened policy of employee welfare and profit sharing decades before this was common in industry. He made massive donations to many concerns, notably the Massachusetts Institute of Technology, and supported schemes for the education of black people, dental welfare, calendar reform, music and many other causes, he withdrew from the day-to-day control of the company in 1925, and at last had time for recreation. On 14 March 1932, suffering from a painful terminal cancer and after tidying up his affairs, he shot himself through the heart, leaving a note: "To my friends: My work is done. Why wait?" Although Eastman's technical innovations were made mostly at the beginning of his career, the organization which he founded and guided in its formative years was responsible for many of the major advances in photography over the years.

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SUBJECT AREA: Photography, film and optics

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In 1841, while studying at Cambridge, Sutton became interested in photography and tried out the current processes, daguerreotype, calotype and cyanotype among them. He subsequently settled in Jersey, where he continued his photographic studies. In 1855 he opened a photographic printing works in Jersey, in partnership with L.-D. Blanquart- Evrard, exploiting the latter's process for producing developed positive prints. He started and edited one of the first photographic periodicals, Photographic Notes, in 1856; until its cessation in 1867, his journal presented a fresher view of the world of photography than that given by its London-based rivals. He also drew up the first dictionary of photography in 1858.

In 1859 Sutton designed and patented a wideangle lens in which the space between two meniscus lenses, forming parts of a sphere and sealed in a metal rim, was filled with water; the lens so formed could cover an angle of up to 120 degrees at an aperture of f12. Sutton's design was inspired by observing the images produced by the water-filled sphere of a "snowstorm" souvenir brought home from Paris! Sutton commissioned the London camera-maker Frederick Cox to make the Panoramic camera, demonstrating the first model in January 1860; it took panoramic pictures on curved glass plates 152×381 mm in size. Cox later advertised other models in a total of four sizes. In January 1861 Sutton handed over manufacture to Andrew Ross's son Thomas Ross, who produced much-improved lenses and also cameras in three sizes. Sutton then developed the first single-lens reflex camera design, patenting it on 20 August 1961: a pivoted mirror, placed at 45 degrees inside the camera, reflected the image from the lens onto a ground glass-screen set in the top of the camera for framing and focusing. When ready, the mirror was swung up out of the way to allow light to reach the plate at the back of the camera. The design was manufactured for a few years by Thomas Ross and J.H. Dallmeyer.

In 1861 James Clerk Maxwell asked Sutton to prepare a series of photographs for use in his lecture "On the theory of three primary colours", to be presented at the Royal Institution in London on 17 May 1861. Maxwell required three photographs to be taken through red, green and blue filters, which were to be printed as lantern slides and projected in superimposition through three projectors. If his theory was correct, a colour reproduction of the original subject would be produced. Sutton used liquid filters: ammoniacal copper sulphate for blue, copper chloride for the green and iron sulphocyanide for the red. A fourth exposure was made through lemon-yellow glass, but was not used in the final demonstration. A tartan ribbon in a bow was used as the subject; the wet-collodion process in current use required six seconds for the blue exposure, about twice what would have been needed without the filter. After twelve minutes no trace of image was produced through the green filter, which had to be diluted to a pale green: a twelve-minute exposure then produced a serviceable negative. Eight minutes was enough to record an image through the red filter, although since the process was sensitive only to blue light, nothing at all should have been recorded. In 1961, R.M.Evans of the Kodak Research Laboratory showed that the red liquid transmitted ultraviolet radiation, and by an extraordinary coincidence many natural red dye-stuffs reflect ultraviolet. Thus the red separation was made on the basis of non-visible radiation rather than red, but the net result was correct and the projected images did give an identifiable reproduction of the original. Sutton's photographs enabled Maxwell to establish the validity of his theory and to provide the basis upon which all subsequent methods of colour photography have been founded.

JW / BC

SUBJECT AREA: Metallurgy

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Soon after graduating from the Ecole des Mines at St-Etienne in 1910, Chevenard joined the Société de Commentry Fourchambault et Decazeville at their steelworks at Imphy, where he remained for the whole of his career. Imphy had for some years specialized in the production of nickel steels. From this venture emerged the first austenitic nickel-chromium steel, containing 6 per cent chromium and 22–4 per cent nickel and produced commercially in 1895. Most of the alloys required by Guillaume in his search for the low-expansion alloy Invar were made at Imphy. At the Imphy Research Laboratory, established in 1911, Chevenard conducted research into the development of specialized nickel-based alloys. His first success followed from an observation that some of the ferro-nickels were free from the low-temperature brittleness exhibited by conventional steels. To satisfy the technical requirements of Georges Claude, the French cryogenic pioneer, Chevenard was then able in 1912 to develop an alloy containing 55–60 per cent nickel, 1–3 per cent manganese and 0.2–0.4 per cent carbon. This was ductile down to −190°C, at which temperature carbon steel was very brittle.

By 1916 Elinvar, a nickel-iron-chromium alloy with an elastic modulus that did not vary appreciably with changes in ambient temperature, had been identified. This found extensive use in horology and instrument manufacture, and even for the production of high-quality tuning forks. Another very popular alloy was Platinite, which had the same coefficient of thermal expansion as platinum and soda glass. It was used in considerable quantities by incandescent-lamp manufacturers for lead-in wires. Other materials developed by Chevenard at this stage to satisfy the requirements of the electrical industry included resistance alloys, base-metal thermocouple combinations, magnetically soft high-permeability alloys, and nickel-aluminium permanent magnet steels of very high coercivity which greatly improved the power and reliability of car magnetos. Thermostatic bimetals of all varieties soon became an important branch of manufacture at Imphy.

During the remainder of his career at Imphy, Chevenard brilliantly elaborated the work on nickel-chromium-tungsten alloys to make stronger pressure vessels for the Haber and other chemical processes. Another famous alloy that he developed, ATV, contained 35 per cent nickel and 11 per cent chromium and was free from the problem of stress-induced cracking in steam that had hitherto inhibited the development of high-power steam turbines. Between 1912 and 1917, Chevenard recognized the harmful effects of traces of carbon on this type of alloy, and in the immediate postwar years he found efficient methods of scavenging the residual carbon by controlled additions of reactive metals. This led to the development of a range of stabilized austenitic stainless steels which were free from the problems of intercrystalline corrosion and weld decay that then caused so much difficulty to the manufacturers of chemical plant.

Chevenard soon concluded that only the nickel-chromium system could provide a satisfactory basis for the subsequent development of high-temperature alloys. The first published reference to the strengthening of such materials by additions of aluminium and/or titanium occurs in his UK patent of 1929. This strengthening approach was adopted in the later wartime development in Britain of the Nimonic series of alloys, all of which depended for their high-temperature strength upon the precipitated compound Ni3Al.

In 1936 he was studying the effect of what is now known as "thermal fatigue", which contributes to the eventual failure of both gas and steam turbines. He then published details of equipment for assessing the susceptibility of nickel-chromium alloys to this type of breakdown by a process of repeated quenching. Around this time he began to make systematic use of the thermo-gravimetrie balance for high-temperature oxidation studies.

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SUBJECT AREA: Chemical technology

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Ward is perhaps better described as a "quack" than a medical doctor. His remedies, one containing a dangerous quantity of antimony, were dubious to say the least. A fraudulent attempt to enter Parliament in 1717 forced him to leave the country quickly. After his pardon in 1733, he returned to London and established a successful practice. His medical prowess is immortalized in Hogarth's picture The Harlot's Progress.

Sulphuric acid had been an important chemical for centuries and Ward found that he needed large quantities of it to make his remedies. He set up works to manufacture it at Twickenham, near London, in 1736 and then at Richmond three years later. His process consisted of burning a mixture of saltpetre (nitre; potassium nitrate) and sulphur in the neck of a large glass globe containing a little water. Dilute sulphuric acid was thereby formed, which was concentrated by distillation. Although the method was not new, having been described in the seventeenth century by the German chemist Johann Glauber, Ward was granted a patent for his process in 1749. An important feature was the size of the globes, which had no less than fifty gallons' capacity, which must have entailed considerable skill on the part of the glassblowers. Through the adoption of Ward's process, the price of this essential commodity fell from £2 per pound to only 2 shillings. It provided the best method of manufacture until the advent of the lead-chamber process invented by John Roebuck.

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SUBJECT AREA: Photography, film and optics

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Auguste and his brother Louis Lumière (b. 5 October 1864 Besançon, France; d. 6 June 1948 Bandol, France) developed the photographic plate-making business founded by their father, Charles Antoine Lumière, at Lyons, extending production to roll-film manufacture in 1887. In the summer of 1894 their father brought to the factory a piece of Edison kinetoscope film, and said that they should produce films for the French owners of the new moving-picture machine. To do this, of course, a camera was needed; Louis was chiefly responsible for the design, which used an intermittent claw for driving the film, inspired by a sewing-machine mechanism. The machine was patented on 13 February 1895, and it was shown on 22 March 1895 at the Société d'Encouragement pour l'In-dustrie Nationale in Paris, with a projected film showing workers leaving the Lyons factory. Further demonstrations followed at the Sorbonne, and in Lyons during the Congrès des Sociétés de Photographie in June 1895. The Lumières filmed the delegates returning from an excursion, and showed the film to the Congrès the next day. To bring the Cinématographe, as it was called, to the public, the basement of the Grand Café in the Boulevard des Capuchines in Paris was rented, and on Saturday 28 December 1895 the first regular presentations of projected pictures to a paying public took place. The half-hour shows were an immediate success, and in a few months Lumière Cinématographes were seen throughout the world.

The other principal area of achievement by the Lumière brothers was colour photography. They took up Lippman's method of interference colour photography, developing special grainless emulsions, and early in 1893 demonstrated their results by lighting them with an arc lamp and projecting them on to a screen. In 1895 they patented a method of subtractive colour photography involving printing the colour separations on bichromated gelatine glue sheets, which were then dyed and assembled in register, on paper for prints or bound between glass for transparencies. Their most successful colour process was based upon the colour-mosaic principle. In 1904 they described a process in which microscopic grains of potato starch, dyed red, green and blue, were scattered on a freshly varnished glass plate. When dried the mosaic was coated with varnish and then with a panchromatic emulsion. The plate was exposed with the mosaic towards the lens, and after reversal processing a colour transparency was produced. The process was launched commercially in 1907 under the name Autochrome; it was the first fully practical single-plate colour process to reach the public, remaining on the market until the 1930s, when it was followed by a film version using the same principle.

Auguste and Louis received the Progress Medal of the Royal Photographic Society in 1909 for their work in colour photography. Auguste was also much involved in biological science and, having founded the Clinique Auguste Lumière, spent many of his later years working in the physiological laboratory.

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SUBJECT AREA: Recording

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After arriving in the USA in 1870 and becoming an American citizen, Berliner worked as a dry-goods clerk in Washington, DC, and for a period studied electricity at Cooper Union for the Advancement of Science and Art, New York. He invented an improved microphone and set up his own experimental laboratory in Washington, DC. He developed a microphone for telephone use and sold the rights to the Bell Telephone Company. Subsequently he was put in charge of their laboratory, remaining in that position for eight years. In 1881 Berliner, with his brothers Joseph and Jacob, founded the J.Berliner Telephonfabrik in Hanover, the first factory in Europe specializing in telephone equipment.

Inspired by the development work performed by T.A. Edison and in the Volta Laboratory (see C.S. Tainter), he analysed the existing processes for recording and reproducing sound and in 1887 developed a process for transferring lateral undulations scratched in soot into an etched groove that would make a needle and diaphragm vibrate. Using what may be regarded as a combination of the Phonautograph of Léon Scott de Martinville and the photo-engraving suggested by Charles Cros, in May 1887 he thus demonstrated the practicability of the laterally recorded groove. He termed the apparatus "Gramophone". In November 1887 he applied the principle to a glass disc and obtained an inwardly spiralling, modulated groove in copper and zinc. In March 1888 he took the radical step of scratching the lateral vibrations directly onto a rotating zinc disc, the surface of which was protected, and the subsequent etching created the groove. Using well-known principles of printing-plate manufacture, he developed processes for duplication by making a negative mould from which positive copies could be pressed in a thermoplastic compound. Toy gramophones were manufactured in Germany from 1889 and from 1892–3 Berliner manufactured both records and gramophones in the USA. The gramophones were hand-cranked at first, but from 1896 were based on a new design by E.R. Johnson. In 1897–8 Berliner spread his activities to England and Germany, setting up a European pressing plant in the telephone factory in Hanover, and in 1899 a Canadian company was formed. Various court cases over patents removed Berliner from direct running of the reconstructed companies, but he retained a major economic interest in E.R. Johnson's Victor Talking Machine Company. In later years Berliner became interested in aeronautics, in particular the autogiro principle. Applied acoustics was a continued interest, and a tile for controlling the acoustics of large halls was successfully developed in the 1920s.

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SUBJECT AREA: Architecture and building

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Born Elinor Coade, she never married but adopted, as was customary in business in the eighteenth century, the courtesy title of Mrs. Following the bankruptcy and death of her father, George Coade, in Exeter, Eleanor and her mother (also called Eleanor) moved to London and founded the works at Lambeth, South London, in 1769 that later became famous as the Coade factory. The factory was located at King's Arms Stairs, Narrow Wall. During the eighteenth century, several attempts had been made in other businesses to manufacture a durable, malleable artificial stone that would be acceptable to architects for decorative use. These substances were not very successful, but Coade stone was different. Although stories are legion about the secret formula supposedly used in this artificial stone, modern methods have established the exact formula.

Coade stone was a stoneware ceramic material fired in a kiln. The body was remarkable in that it shrank only 8 per cent in drying and firing: this was achieved by using a combination of china clay, sand, crushed glass and grog (i.e. crushed and ground, previously fired stoneware). The Coade formula thus included a considerable proportion of material that, having been fired once already, was unshrinkable. Mrs Coade's name for the firm, Coade's Lithodipyra Terra-Cotta or Artificial Stone Manufactory (where "Lithodipyra" is a term derived from three Greek words meaning "stone", "twice" and "fire"), made reference to the custom of including such material (such as in Josiah Wedgwood's basalt and jasper ware). The especially low rate of shrinkage rendered the material ideal for making extra-life-size statuary, and large architectural, decorative features to be incorporated into stone buildings.

Coade stone was widely used for such purposes by leading architects in Britain and Ireland from the 1770s until the 1830s, including Robert Adam, Sir Charles Barry, Sir William Chambers, Sir John Soane, John Nash and James Wyatt. Some architects introduced the material abroad, as far as, for example, Charles Bulfinch's United States Bank in Boston, Massachusetts, and Charles Cameron's redecoration for the Empress Catherine of the great palace Tsarkoe Selo (now Pushkin), near St Petersburg. The material so resembles stone that it is often mistaken for it, but it is so hard and resistant to weather that it retains sharpness of detail much longer than the natural substance. The many famous British buildings where Coade stone was used include the Royal Hospital, Chelsea, Carlton House and the Sir John Soane Museum (all of which are located in London), St George's Chapel at Windsor, Alnwick Castle in Northumberland, and Culzean Castle in Ayrshire, Scotland.

Apart from the qualities of the material, the Coade firm established a high reputation for the equally fine quality of its classical statuary. Mrs Coade employed excellent craftsmen such as the sculptor John Bacon (1740–99), whose work was mass-produced by the use of moulds. One famous example which was widely reproduced was the female caryatid from the south porch of the Erechtheion on the acropolis of Athens. A drawing of this had appeared in the second edition of Stuart and Revett's Antiquities of Athens in 1789, and many copies were made from the original Coade model; Soane used them more than once, for example on the Bank of England and his own houses in London.

Eleanor Coade was a remarkable woman, and was important and influential on the neo-classical scene. She had close and amicable relations with leading architects of the day, notably Robert Adam and James Wyatt. The Coade factory was enlarged and altered over the years, but the site was finally cleared during 1949–50 in preparation for the establishment of the 1951 Festival of Britain.

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SUBJECT AREA: Chemical technology, Synthetic materials, Textiles

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The introduction of one type of artificial fibre encouraged chemists to look for more. J.T.Dickson and J.R. Whinfield discovered one such fibre in 1941 when they derived polyester from terephthalic acid and ethylene glycol. Dickson, a 21-year-old Edinburgh graduate, was working under Whinfield at the Calico Printers' Association research laboratory at Broad Oak Print Works in Accrington. He was put onto fibre research: probably in April, but certainly by 5 July 1941, a murky-looking resin had been synthesized, out of which Dickson successfully drew a filament, which was named "Terylene" by its discoverers. Owing to restrictions imposed in Britain during the Second World War, this fibre was developed initially by the DuPont Company in the USA, where it was marketed under the name "Dacron". When Imperial Chemical Industries (ICI) were able to manufacture it in Britain, it acquired the brand name "Terylene" and became very popular. Under the microscope, Terylene appears identical to nylon: longitudinally, it is completely devoid of any structure and the filaments appear as glass rods with a perfectly circular cross-section. The uses of Terylene are similar to those of nylon, but it has two advantages. First, it can be heat-set by exposing the fabric to a temperature about 30°C higher than is likely to be encountered in everyday use, and therefore can be the basis for "easy-care" clothing such as drip-dry shirts. It can be blended with other fibres such as wool, and when pressed at a high temperature the creases are remarkably durable. It is also remarkably resistant to chemicals, which makes it particularly suitable for industrial purposes under conditions where other textile materials would be degraded rapidly. Dickson later worked for ICI.

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SUBJECT AREA: Photography, film and optics

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Edwin Land's career began when, as a Harvard undergraduate in the late 1920s, he became interested in the possibility of developing a polarizing filter in the form of a thin sheet, to replace the crystal and stacked-glass devices then in use, which were expensive, cumbersome and limited in size. He succeeded in creating a material in which minute anisotropic iodine crystals were oriented in line, producing an efficient polarizer that was patented in 1929. After presenting the result of his researches in a Physics Department colloquium at Harvard, he left to form a partnership with George Wheelwright to manufacture the new material, which was seen to have applications as diverse as anti-glare car headlights, sunglasses, and viewing filters for stereoscopic photographs and films. In 1937 he founded the Polaroid Corporation and developed the Vectograph process, in which self-polarized photographic images could be printed, giving a stereoscopic image when viewed through polarizing viewers. Land's most significant invention, the instant picture, was stimulated by his three-year-old daughter. As he took a snapshot of her, she asked why she could not see the picture at once. He began to research the possibility, and on 21 February 1947 he demonstrated a system of one-step photography at a meeting of the Optical Society of America. Using the principle of diffusion transfer of the image, it produced a photograph in one minute. The Polaroid Land camera was launched on 26 November 1948. The original sepia-coloured images were soon replaced by black and white and, in 1963, by Polacolor instant colour film. The original peel-apart "wet" process was superseded in 1972 with the introduction of the SX-70 camera with dry picture units which developed in the light. The instant colour movie system Polavision, introduced in 1978, was less successful and was one of his few commercial failures.

Land died in March 1991, after a career in which he had been honoured by countless scien-tific and academic bodies and had received the Medal of Freedom, the highest civilian honour in America.

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SUBJECT AREA: Photography, film and optics

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Lippershey was a spectacle maker of Middelburg, a contender for the invention of the telescope. It is said that about 1600 two children were playing about his workshop and chanced to place a convex and a concave lens in a line, and noted a great magnification of the nearby church. Lippershey confirmed this and started manufacture of "instruments for seeing at a distance". In 1608 he petitioned the States General of the Netherlands for a patent for thirty years. A committee appointed to look into the matter declared that the device was likely to be of use to the State and suggested the improvement of a binocular arrangement. Other Dutch glass-workers, however, put forward claims to have constructed similar instruments, and, in the confusion, the States General turned down Lippershey's plea and he received no financial reward or patent protection.

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SUBJECT AREA: Metallurgy

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After a private education, Percy went to Paris in 1834 to study medicine and to attend lectures on chemistry by Gay-Lussac and Thenard. After 1838 he studied medicine at Edinburgh, obtaining his MD in 1839. In that year he was appointed Professor of Chemistry at Queen's College, Birmingham, moving to Queen's Hospital at Birmingham in 1843. During his time at Birmingham, Percy became well known for his analysis of blast furnace slags, and was involved in the manufacture of optical glass. On 7 June 1851 Percy was appointed Metallurgical Professor and Teacher at the Museum of Practical Geology established in Jermyn Street, London, and opened in May 1851. In November of 1851, when the Museum became the Government (later Royal) School of Mines, Percy was appointed Lecturer in Metallurgy. In addition to his work at Jermyn Street, Percy lectured on metallurgy to the Advanced Class of Artillery at Woolwich from 1864 until his death, and from 1866 he was Superintendent of Ventilation at the Houses of Parliament. He served from 1861 to 1864 on the Special Committee on Iron set up to examine the performance of armour-plate in relation to its purity, composition and structure.

Percy is best known for his metallurgical text books, published by John Murray. Volume I of Metallurgy, published in 1861, dealt with fuels, fireclays, copper, zinc and brass; Volume II, in 1864, dealt with iron and steel; a volume on lead appeared in 1870, followed by one on fuels and refractories in 1875, and the first volume on gold and silver in 1880. Further projected volumes on iron and steel, noble metals, and on copper, did not materialize. In 1879 Percy resigned from his School of Mines appointment in protest at the proposed move from Jermyn Street to South Kensington. The rapid growth of Percy's metallurgical collection, started in 1839, eventually forced him to move to a larger house. After his death, the collection was bought by the South Kensington (later Science) Museum. Now comprising 3,709 items, it provides a comprehensive if unselective record of nineteenth-century metallurgy, the most interesting specimens being those of the first sodium-reduced aluminium made in Britain and some of the first steel produced by Bessemer in Baxter House. Metallurgy for Percy was a technique of chemical extraction, and he has been criticized for basing his system of metallurgical instruction on this assumption. He stood strangely aloof from new processes of steel making such as that of Gilchrist and Thomas, and tended to neglect early developments in physical metallurgy, but he was the first in Britain to teach metallurgy as a discipline in its own right.

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SUBJECT AREA: Medical technology, Photography, film and optics

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Snellen took his degree in medicine at Utrecht in 1857, and after continued study was appointed Lecturer in Ophthalmology and Surgeon to the Hospital for Diseases of the Eye. In 1877 he succeeded Franciscus Cornelius Donders, an outstanding figure in the development of the understanding of the optics and physiology of vision, as Professor. He held this post until 1899 when he was succeeded by his son.

Although involved in virtually all aspects of the speciality, he particularly laid the basis for the scientific recording of visual acuity with the publication of his Optotypes in 1862. Optotypes were based on the concept of an average standard of vision permitting the discrimination of separate objects which subtended an angle of one minute of arc on the retina. While the concept does not take into account aspects of vision such as perception, it has stood the test of time in terms of practicality, even when abstract figures such as Landolt's rings replace the lines of single letters of the original.

Snellen originated many other advances of a surgical nature, his procedure for eyelid deformity is still practised, and he developed the use of glass in the manufacture of artificial eyes.

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SUBJECT AREA: Photography, film and optics

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Educated at the Polytechnic Institute in Vienna, Voigtländer travelled widely before taking over the family business in 1837. The business had been founded by Voigtländer's grandfather in 1756, and was continued by his father, Johann Friedrich, the inventor of the opera glass, and by the 1830s enjoyed one of the highest reputations in Europe. When Petzval made the calculations for the first purpose-designed photographic objective in 1840, it was inevitable that he should go to Peter Voigtländer for advice. The business went on to manufacture Petzval's lens, which was also fitted to an all-metal camera of totally original design by Voigtländer.

The Petzval lens was an extraordinary commercial success and Voigtländer sold specimens all over the world. Unfortunately Petzval had no formal agreement with Voigtländer and made little financial gain from his design, a fact which was to lead to dispute and separation; the Voigtländer concern continued to prosper, however. To meet the increasing demand for his products, Peter Voigtländer built a new factory in Brunswick and closed the business in Vienna. The closure is seen by at least one commentator as the death blow to Vienna's optical industry, a field in which it was once preeminent. The Voigtländer dynasty continued long after Peter's death and the name enjoyed a reputation for high-quality photographic equipment well into the twentieth century.

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