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SUBJECT AREA: Photography, film and optics, Recording, Telecommunications

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He received no formal education, but was brought up by his father, a distinguished teacher and philosopher. He dabbled in diverse subjects (modern and ancient languages, mathematics, drawing) in 1856–60 when he became an instructor at the institute of the Deaf-Mute at Paris. He became a prolific inventor and poet and took part in artistic life in Paris. In the 1867 Exposition Universelle in Paris, Cros contributed a facsimile telegraph; he deposited with the Académie des Sciences a sealed text on photography which was not opened until 1876. In the meantime he published a small text on a general solution of the problem of colour photography which appeared almost simultaneously with a similar publication by Louis Ducos du Hauron and which gave rise to bitter discussions over priority. He deposited a sealed paper on 18 April 1877 concerning his concept of apparatus for recording and reproduction of sound which he called the paléophone. When it was opened on 3 December 1877 it was not known that T.A. Edison was already active in this field: Cros is considered the conceptual founder of reproducible sound, whereas Edison was the first "to reduce to practice", which is one of the US criteria for patentability.

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SUBJECT AREA: Metallurgy

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Darby's father, John, was a farmer who also worked a small forge to produce nails and other ironware needed on the farm. He was brought up in the Society of Friends, or Quakers, and this community remained important throughout his personal and working life. Darby was apprenticed to Jonathan Freeth, a malt-mill maker in Birmingham, and on completion of his apprenticeship in 1699 he took up the trade himself in Bristol. Probably in 1704, he visited Holland to study the casting of brass pots and returned to Bristol with some Dutch workers, setting up a brassworks at Baptist Mills in partnership with others. He tried substituting cast iron for brass in his castings, without success at first, but in 1707 he was granted a patent, "A new way of casting iron pots and other pot-bellied ware in sand without loam or clay". However, his business associates were unwilling to risk further funds in the experiments, so he withdrew his share of the capital and moved to Coalbrookdale in Shropshire. There, iron ore, coal, water-power and transport lay close at hand. He took a lease on an old furnace and began experimenting. The shortage and expense of charcoal, and his knowledge of the use of coke in malting, may well have led him to try using coke to smelt iron ore. The furnace was brought into blast in 1709 and records show that in the same year it was regularly producing iron, using coke instead of charcoal. The process seems to have been operating successfully by 1711 in the production of cast-iron pots and kettles, with some pig-iron destined for Bristol. Darby prospered at Coalbrookdale, employing coke smelting with consistent success, and he sought to extend his activities in the neighbourhood and in other parts of the country. However, ill health prevented him from pursuing these ventures with his previous energy. Coke smelting spread slowly in England and the continent of Europe, but without Darby's technological breakthrough the ever-increasing demand for iron for structures and machines during the Industrial Revolution simply could not have been met; it was thus an essential component of the technological progress that was to come.

Darby's eldest son, Abraham II (1711–63), entered the Coalbrookdale Company partnership in 1734 and largely assumed control of the technical side of managing the furnaces and foundry. He made a number of improvements, notably the installation of a steam engine in 1742 to pump water to an upper level in order to achieve a steady source of water-power to operate the bellows supplying the blast furnaces. When he built the Ketley and Horsehay furnaces in 1755 and 1756, these too were provided with steam engines. Abraham II's son, Abraham III (1750–89), in turn, took over the management of the Coalbrookdale works in 1768 and devoted himself to improving and extending the business. His most notable achievement was the design and construction of the famous Iron Bridge over the river Severn, the world's first iron bridge. The bridge members were cast at Coalbrookdale and the structure was erected during 1779, with a span of 100 ft (30 m) and height above the river of 40 ft (12 m). The bridge still stands, and remains a tribute to the skill and judgement of Darby and his workers.

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SUBJECT AREA: Metallurgy

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Dony trained initially for the Church, and it is not known how he became interested in the production of zinc. Liège, however, was close to extensive deposits of the zinc ore calamine, and brass had been made since Roman times in the region between Liège and Aix-la-Chapelle (now Aachen). William Champion's technique of brass manufacture was known there and was considered to be too complicated and expensive for the routine manufacture of brass. Dony may have learned about earlier processes of manufacturing zinc on the European continent from his friend Professor Villette of Liège University, and about English methods from Henri Delloye, a friend of both Villette and Dony and who visited Birmingham and Bristol on their behalf to study zinc smelting processes and brass manufacture at first hand. By 21 March 1805 Dony had succeeded in extracting zinc from calamine and casting it in ingots. On the basis of this success he applied to the French Republican administration for assistance and in 1806 was assigned by Napoleon the sole mining rights to the calamine deposits of the Vieille Montagne, or Altenberg, near Moresnet, five miles (8 km) from Aachen. With these rights went the obligation of developing an industrially viable method of zinc refining. In 1807 he constructed a small factory at Isle and there, after much effort, he perfected his celebrated horizontal retort process, the "Liège Method". After July 1809 zinc was being produced in abundance, and in January 1810 Dony was granted an Imperial Patent giving him a monopoly of zinc manufacture for fifteen years. He erected a rolling mill at Saint-Léonard and attempted to persuade the Minister of Marine to use zinc sheets rather than copper for the protection of ships. Between 1809 and 1810 Dony reduced the price of zinc in Liège from 8.60 to 2.60 francs per kilo. However, after 1813 he began to encounter financial problems and in 1818 he surrendered his commercial interests to his partner Dominique Mosselman (d. 1837). The horizontal retort process soon rendered obsolete that of William Champion, and variants of the Liège Method were rapidly evolved in Germany, Britain and the USA.

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SUBJECT AREA: Electricity

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After an education at the College of Stanislas, Cannes, Duddell served an apprenticeship with Davy Paxman of Colchester. Studying under Ayrton and Mather at the Central Technical College in South Kensington, he found the facilities for experimental work of exceptional value to him and remained there for some years. In 1897 Duddell produced a galvanometer which was sufficiently responsive to display an alternating-current wave-form. This instrument, with a coil carrying a mirror in the air gap of a powerful electromagnet, had a small periodic time. An oscillating mirror driven by a synchronous motor spread out the deflection on a time-scale. This development became the first commercial oscillograph and brought Duddell into prominence as a first-rate designer of special instruments. The Duddell oscillograph remained in use until after the Second World War, examples being used for recording short-circuit tests on high-power switchgear and other rapidly varying or transient phenomena. His next important work was to collaborate with Professor Marchant at Liverpool University to investigate the characteristics of the electric arc. This led to the suggestion that, coupled to a resonant circuit, the electric arc could form a generator of high-frequency currents. This arrangement was later developed by Poulson for wireless telegraphy. Duddell spent the last years of his life on government research as a member of the Admiralty Board of Inventions and Research and also of the Inventions Board of the Ministry of Munitions.

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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: Chemical technology, Synthetic materials

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Dr Gibson's work towards the discovery of polythene had its origin in a visit in 1925 to Dr A. Michels of Amsterdam University; the latter had made major advances in techniques for studying chemical reactions at very high pressures. After working with Michels for a time, in 1926 Gibson joined Brunner Mond, one of the companies that went on to form the chemical giant Imperial Chemical Industries (ICI). The company supported research into fundamental chemical research that had no immediate commercial application, including the field being cultivated by Michels and Gibson. In 1933 Gibson was joined by another ICI chemist, E.O.Fawcett, who had worked with W.H. Carothers in the USA on polymer chemistry. They were asked to study the effects of high pressure on various reaction systems, including a mixture of benzaldehyde and ethylene. Gibson's notebook for 27 March that year records that after a loss of pressure during which the benzaldehyde was blown out of the reaction tube, a waxy solid was observed in the tube. This is generally recognized as the first recorded observation of polythene. By the following June they had shown that the white, waxy solid was a fairly high molecular weight polymer of ethylene formed at a temperature of 443°K and a pressure of 2,000 bar. However, only small amounts of the material were produced and its significance was not immediately recognized. It was not until two years later that W.P.Perrin and others, also ICI chemists, restarted work on the polymer. They showed that it could be moulded, drawn into threads and cast into tough films. It was a good electrical insulator and almost inert chemically. A British patent for producing polythene was taken out in 1936, and after further development work a production plant began operating in September 1939, just as the Second World War was breaking out. Polythene had arrived in time to make a major contribution to the war effort, for it had the insulating properties required for newly developing work on radar. When peacetime uses became possible, polythene production surged ahead and became the major industry it is today, with a myriad uses in industry and in everyday life.

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SUBJECT AREA: Metallurgy

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Of Dutch descent, Hunstman was apprenticed to a clockmaker at Epworth, Lincolnshire. In 1725 he set up in Doncaster as a maker of clocks, locks and roasting jacks. He made improvements in his tools but found himself hampered by the poor quality of the steel available, then made by the cementation process, which yielded a steel with a non-uniform carbon content. Around 1740, Huntsman moved to Handsworth, now part of Sheffield, and began experimenting by heating varying compositions of fuel and flux with crude steel in a crucible, to obtain a steel of uniform composition. During the years 1745 to 1750 he attained his object, but not without many unsuccessful "heats", as excavations of the site of his works now reveal. Although his steel was far better than that previously available, however, the conservative cutlers of Sheffield rejected it, claiming it was too hard to work; therefore Huntsman exported his product to France, where the cutlers promptly worked it into high-quality knives and razors that were exported to England. The Sheffield cutlers' attempts to prevent Huntsman from exporting his steel proved unsuccessful. Huntsman did not patent his process, preferring to retain his advantage by shrouding his work in secrecy, carrying out his melting at night to escape observation, but a rival cutler, Samuel Walker, gained admittance to Huntsman's works disguised as a tramp seeking food. As a result, Walker was able to make crucible steel at a handsome profit. Huntsman fought back and earned success through the sheer quality of his steel, and had to move to.a larger site at Attercliffe in 1770. Crucible steelmaking remained important through the nineteenth century although, as it was a small-scale process, its application was restricted to engineers' cutting tools and the cutting edges of certain tools.

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SUBJECT AREA: Textiles

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Jacquard was apprenticed at the age of 12 to bookbinding, and later to type-founding and cutlery. His parents, who had some connection with weaving, left him a small property upon their death. He made some experiments with pattern weaving, but lost all his inheritance; after marrying, he returned to type-founding and cutlery. In 1790 he formed the idea for his machine, but it was forgotten amidst the excitement of the French Revolution, in which he fought for the Revolutionists at the defence of Lyons. The machine he completed in 1801 combined earlier inventions and was for weaving net. He was sent to Paris to demonstrate it at the National Exposition and received a bronze medal. In 1804 Napoleon granted him a patent, a pension of 1,500 francs and a premium on each machine sold. This enabled him to study and work at the Conservatoire des Arts et Métiers to perfect his mechanism for pattern weaving. A method of selecting any combination of leashes at each shoot of the weft had to be developed, and Jacquard's mechanism was the outcome of various previous inventions. By taking the cards invented by Falcon in 1728 that were punched with holes like the paper of Bouchon in 1725, to select the needles for each pick, and by placing the apparatus above the loom where Vaucanson had put his mechanism, Jacquard combined the best features of earlier inventions. He was not entirely successful because his invention failed in the way it pressed the card against the needles; later modifications by Breton in 1815 and Skola in 1819 were needed before it functioned reliably. However, the advantage of Jacquard's machine was that each pick could be selected much more quickly than on the earlier draw looms, which meant that John Kay's flying shuttle could be introduced on fine pattern looms because the weaver no longer had to wait for the drawboy to sort out the leashes for the next pick. Robert Kay's drop box could also be used with different coloured wefts. The drawboy could be dispensed with because the foot-pedal operating the Jacquard mechanism could be worked by the weaver. Patterns could be changed quickly by replacing one set of cards with another, but the scope of the pattern was more limited than with the draw loom. Some machines that were brought into use aroused bitter hostility. Jacquard suffered physical violence, barely escaping with his life, and his machines were burnt by weavers at Lyons. However, by 1812 his mechanism began to be generally accepted and had been applied to 11,000 draw-looms in France. In 1819 Jacquard received a gold medal and a Cross of Honour for his invention. His machines reached England c.1816 and still remain the basic way of weaving complicated patterns.

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SUBJECT AREA: Paper and printing, Photography, film and optics

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Klic, sometimes known by the germanized form of his name Karl Klietsch, gained a knowledge of chemistry from his chemist father. However, he inclined towards the arts, preferring to mix paints rather than chemicals, and he trained in art at the Academy of Painting in Prague. His father thought to combine the chemical with the artistic by setting up his son in a photographic studio in Brno, but the arts won and in 1867 Klic moved to Vienna to practise as an illustrator and caricaturist. He also acquired skill as an etcher, and this led him to print works of art reproduced by photography by means of an intaglio process. He perfected the process c.1878 and, through it, Vienna became for a while the world centre for high-quality art reproductions. The prints were made by hand from flat plates, but Klic then proposed that the images should be etched onto power-driven cylinders. He found little support for rotary gravure, or rotogravure, on the European continent, but learning that Storey Brothers, textile printers of Lancaster, England, were working in a similar direction, he went there in 1890 to perfect his idea. Rotogravure printing on textiles began in 1893. They then turned to printing art reproductions on paper by rotogravure and in 1895 formed the Rembrandt Intaglio Printing Company. Their photogra-vures attracted worldwide attention when they appeared in the Magazine of Art. Klic saw photogravure as a small-scale medium for the art lover and not for mass-circulation publications, so he did not patent his invention and thought to control it by secrecy. That had the usual result, however, and knowledge of the process leaked out from Storey's, spreading to other countries in Europe and, from 1903, to the USA. Klic lived on in a modest way in Vienna, his later years troubled by failing sight. He hardly earned the credit for the invention, let alone the fortune reaped by others who used, and still use, photogravure for printing long runs of copy such as newspaper colour supplements.

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SUBJECT AREA: Electricity

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Leclanché was sent to England for his early education. Returning to France, he entered the Central School of Arts and Manufacture, from which he graduated as a chemical engineer in 1860. He spent some years with a railway company in setting up an electrical timing system, and this work led him to electrochemical research. Driven by political pressure into exile, he set up a small laboratory in Brussels to continue the studies of the behaviour of voltaic cells he had started in France. Many workers directed their efforts to constructing a cell with a single electrolyte and a solid insoluble depo-larizer, but it was Leclanché who produced, in 1866, the prototype of a battery that was rugged, cheap and contained no highly corro-sive liquid. With electrodes of carbon and zinc and a solution of ammonium chloride, polarization was prevented by surrounding the positive electrode with manganese dioxide. The Leclanché cell was adopted by the Belgian Government Telegraph Service in 1868 and rapidly came into general use wherever an intermittent current was needed; for example, in telegraph and later in telephone circuits. Carl Gassner in 1888 pioneered successful dry cells based on the Leclanché system, with the zinc anode serving as the container, and c. 1890 commercial production of such cells began.

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SUBJECT AREA: Chemical technology, Weapons and armour

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Alfred's father, Immanuel Nobel, builder, industrialist and inventor, encouraged his sons to follow his example of inventiveness. Alfred's education was interrupted when the family moved to St Petersburg, but was continued privately and was followed by a period of travel. He thus acquired a good knowledge of chemistry and became an excellent linguist.

During the Crimean War, Nobel worked for his father's firm in supplying war materials. The cancellation of agreements with the Russian Government at the end of the war bankrupted the firm, but Alfred and his brother Immanuel continued their interest in explosives, working on improved methods of making nitroglycerine. In 1863 Nobel patented his first major invention, a detonator that introduced the principle of detonation by shock, by using a small charge of nitroglycerine in a metal cap with detonating or fulminating mercury. Two years later Nobel set up the world's first nitroglycerine factory in an isolated area outside Stockholm. This led to several other plants and improved methods for making and handling the explosive. Yet Nobel remained aware of the dangers of liquid nitroglycerine, and after many experiments he was able in 1867 to take out a patent for dynamite, a safe, solid and pliable form of nitroglycerine, mixed with kieselguhr. At last, nitroglycerine, discovered by Sobrero in 1847, had been transformed into a useful explosive; Nobel began to promote a worldwide industry for its manufacture. Dynamite still had disadvantages, and Nobel continued his researches until, in 1875, he achieved blasting gelatin, a colloidal solution of nitrocellulose (gun cotton) in nitroglycerine. In many ways it proved to be the ideal explosive, more powerful than nitroglycerine alone, less sensitive to shock and resistant to moisture. It was variously called Nobel's Extra Dynamite, blasting gelatin and gelignite. It immediately went into production.

Next, Nobel sought a smokeless powder for military purposes, and in 1887 he obtained a nearly smokeless blasting powder using nitroglycerine and nitrocellulose with 10 per cent camphor. Finally, a progressive, smokeless blasting powder was developed in 1896 at his San Remo laboratory.

Nobel's interests went beyond explosives into other areas, such as electrochemistry, optics and biology; his patents amounted to 355 in various countries. However, it was the manufacture of explosives that made him a multimillionaire. At his death he left over £2 million, which he willed to funding awards "to those who during the preceding year, shall have conferred the greatest benefit on mankind".

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SUBJECT AREA: Steam and internal combustion engines

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William was the second son and one of eleven children of Samuel Priestman, who had moved to Hull after retiring as a corn miller in Kirkstall, Leeds, and who in retirement had become a director of the North Eastern Railway Company. The family were strict Quakers, so William was sent to the Quaker School in Bootham, York. He left school at the age of 17 to start an engineering apprenticeship at the Humber Iron Works, but this company failed so the apprenticeship was continued with the North Eastern Railway, Gateshead. In 1869 he joined the hydraulics department of Sir William Armstrong \& Company, Newcastle upon Tyne, but after a year there his father financed him in business at a small, run down works, the Holderness Foundry, Hull. He was soon joined by his brother, Samuel, their main business being the manufacture of dredging equipment (grabs), cranes and winches. In the late 1870s William became interested in internal combustion engines. He took a sublicence to manufacture petrol engines to the patents of Eugène Etève of Paris from the British licensees, Moll and Dando. These engines operated in a similar manner to the non-compression gas engines of Lenoir. Failure to make the two-stroke version of this engine work satisfactorily forced him to pay royalties to Crossley Bros, the British licensees of the Otto four-stroke patents.

Fear of the dangers of petrol as a fuel, reflected by the associated very high insurance premiums, led William to experiment with the use of lamp oil as an engine fuel. His first of many patents was for a vaporizer. This was in 1885, well before Ackroyd Stuart. What distinguished the Priestman engine was the provision of an air pump which pressurized the fuel tank, outlets at the top and bottom of which led to a fuel atomizer injecting continuously into a vaporizing chamber heated by the exhaust gases. A spring-loaded inlet valve connected the chamber to the atmosphere, with the inlet valve proper between the chamber and the working cylinder being camoperated. A plug valve in the fuel line and a butterfly valve at the inlet to the chamber were operated, via a linkage, by the speed governor; this is believed to be the first use of this method of control. It was found that vaporization was only partly achieved, the higher fractions of the fuel condensing on the cylinder walls. A virtue was made of this as it provided vital lubrication. A starting system had to be provided, this comprising a lamp for preheating the vaporizing chamber and a hand pump for pressurizing the fuel tank.

Engines of 2–10 hp (1.5–7.5 kW) were exhibited to the press in 1886; of these, a vertical engine was installed in a tram car and one of the horizontals in a motor dray. In 1888, engines were shown publicly at the Royal Agricultural Show, while in 1890 two-cylinder vertical marine engines were introduced in sizes from 2 to 10 hp (1.5–7.5 kW), and later double-acting ones up to some 60 hp (45 kW). First, clutch and gearbox reversing was used, but reversing propellers were fitted later (Priestman patent of 1892). In the same year a factory was established in Philadelphia, USA, where engines in the range 5–20 hp (3.7–15 kW) were made. Construction was radically different from that of the previous ones, the bosses of the twin flywheels acting as crank discs with the main bearings on the outside.

On independent test in 1892, a Priestman engine achieved a full-load brake thermal efficiency of some 14 per cent, a very creditable figure for a compression ratio limited to under 3:1 by detonation problems. However, efficiency at low loads fell off seriously owing to the throttle governing, and the engines were heavy, complex and expensive compared with the competition.

Decline in sales of dredging equipment and bad debts forced the firm into insolvency in 1895 and receivers took over. A new company was formed, the brothers being excluded. However, they were able to attend board meetings, but to exert no influence. Engine activities ceased in about 1904 after over 1,000 engines had been made. It is probable that the Quaker ethics of the brothers were out of place in a business that was becoming increasingly cut-throat. William spent the rest of his long life serving others.

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SUBJECT AREA: Metallurgy

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The principle of the Sendzimir or planetary rolling mill was first conceived by an English engineer named Picken, but that did not lead to practical development. The principle was taken up independently in the USA by Sendzimir, who put forward his own ideas in 1948 and obtained a patent the same year. By 1952 he had reached agreements with Picken and other workers to license the construction of a plant completely under the control of Sendzimir and his associates. This type of rolling mill was developed primarily for the cold rolling of steel strip. Cold rolling requires higher pressures to be exerted by the rolls, which therefore must be harder than in hot rolling. In the Sendzimir mill the two hard work rolls are backed up by a cluster of heavier rolls of various sizes to prevent distortion of the work rolls. One advantage of this arrangement is that the work rolls can be quite small, so that they can be removed by hand when they need replacement. The Sendzimir mill is in wide use, particularly for rolling stainless steel. The first such mill was installed at Peugeot's in France in 1950, with two sets of planetary rolls for the hot rolling of 16 in. (41 cm) wide steel strip. The second was in the USA in 1951, and a third, larger one followed at Ductile Steels Ltd at Willenhall, Wolverhampton, England, in 1953.

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SUBJECT AREA: Chemical technology

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Spence was first apprenticed to a grocer and then joined his uncle's business. When that failed, he found work in a Dundee gasworks. During his spare time he had been studying chemistry, and in 1834 he established a small chemical works in London, which was none too successful. It was after a move to Burgh, near Carlisle, that his prospects brightened, with an improved method for making alum, a substance much used in the dyeing and textile industries. Spence obtained a patent in 1845 for extracting the substance from alum-containing shale by treating the burned shale and iron pyrites with sulphuric acid. He set up a plant at Pendleton, near Manchester, and enlarged the scale of his operation to become the largest manufacturer of alum in the world. The most profitable product was a crude form of alum known as aluminoferric. This came to be much in demand by the paper industry and in the treatment of sewage, an activity of growing importance in mid-Victorian Britain.

Not all of Spence's ventures met with success; his attempts to exploit the phosphate deposits on the island of Redmonds in the West Indies lost heavily. He was an active citizen of Manchester, with a strongly Nonconformist tendency. He supported the cause against atmospheric pollution, although he himself was successfully prosecuted for pollution from his alum works at Pendleton; that prompted a move to Miles Platting, also near Manchester. In 1900, his firm became part of Laporte Industries Ltd.

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SUBJECT AREA: Civil engineering

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The son of James and Electa Whipple, his father was a farmer and later the owner of a small cotton mil at Hardwick, Massachusetts. In 1817 Squire Whipple moved with his family to Otego County, New York. He helped on the farm and attended the academy at Fairfield, Herkimer County. For a time he taught school pupils, and in 1829 he entered Union College, Schenectady, where he received the degree of AB in 1830; his interest in engineering was probably aroused by the construction of the Erie Canal near his home during his boyhood. He was first employed in a minor capacity in surveys for the Baltimore and Ohio Railroad and for the Erie Canal. In 1836–7 he was resident engineer for a division of the New York and Erie Railroad and was also employed in a number of other railroad and canal surveys, making surveying instruments in the intervals between these appointments; in 1840, he completed a lock for weighing canal boats.

Whipple received his first bridge patent on 24 April 1841; this was for a truss of arched upper chord made of cast and wrought iron. Five years later, he devised a trapezoidal truss which was used in the building of many bridges over the succeeding generation. In 1852–3 Whipple used his truss in an iron railroad bridge of 44.5 m (146 ft) span on the Rensselaer and Saratoga Railroad. He also built a number of bridges with lifting spans.

Whipple's main contribution to bridge engineering was the publication in 1847 of A Work on Bridge Building. In 1869 he issued a continuation of this treatise, and a fourth edition of both was published in 1883.

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SUBJECT AREA: Weapons and armour

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Wilkinson's father Isaac was a farmer turned ironmaster. Soon after 1750, the family acquired Bersham furnace, near Wrexham. This was later in the hands of John and his brother William. By 1763, John had risen to take sole charge of Broseley furnace near Coalbrookdale, Shropshire, and in 1770 he set up a third furnace at Bradley, Staffordshire. By this time he had become one of the country's leading ironmasters, known for the wide range of ware made of cast iron, doubtless the reason for his nickname "Ironmad Wilkinson". He made a cast-iron boat which, to the surprise of many, floated. For his own eventual use, he also made a cast-iron coffin, but did not make sufficient allowance for increasing girth with age! Wilkinson's most notable invention was his cannon-boring machine, patented in 1774. The gun barrel was held rigidly while the cutter head moved forward on a rod inside a hollow boring bar. The machine was easily adapted to bore the cylinders for Boulton \& Watt's steam engines and he became a regular supplier, as only he could bore them with the required accuracy. On the other hand, their second engine was supplied to Wilkinson to power a blowing engine to provide air blast for his Broseley furnace: this was the first use of a Boulton \& Watt engine for a purpose other than pumping. By 1780 he had three further steam engines at work. Wilkinson installed the first Boulton \& Watt engine in France at the Paris waterworks, for which he supplied the iron pipes. Another patent was obtained in 1794 for the invention of the cupola or furnace for melting metal for small castings, although it is now thought that the real inventor was his brother William. Apart from domestic and engineering ironware, Wilkinson was supplier of arms to the American and, illicitly, to the French.

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SUBJECT AREA: Mining and extraction technology

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From an old mining family in the Saxon coalfields, Wolf was aware from his youth of the urgent demand for a miner's lamp which would provide adequate light but not provoke firedamp explosions. While working as an engineer in Zwickau, Wolf spent his spare time conducting experiments for such a lamp. The basic concept of his invention was the principle that dangerous concentrations of methane and air would not explode within a small pipe; this had been established almost seventy years earlier by the English chemist Humphrey Davy. By combining and developing certain devices designed by earlier inventors, in 1883 Wolf produced a prototype with a glass cylinder, a primer fixed inside the lamp and a magnetic lock. Until the successful application of electric light, Wolfs invention was the safest and most popular mining safety lamp. Many earlier inventions had failed to address all the problems of lighting for mines; Davy's lamp, for example, would too quickly become sooty and hot. As Wolfs lamp burned petroleum spirit, at first it was mistrusted outside Saxony, but it successfully passed the safety tests in all the leading coal-producing countries at that time. As well as casting a safe, constant light, the appearance of the cap flame could indicate the concentration of fire-damp in the air, thus providing an additional safety measure. Wolfs first patent was soon followed by many others in several countries, and underwent many developments. In 1884 Heinrich Friemann, a merchant from Eisleben, invested capital in the new company of Friemann and Wolf, which became the leading producer of miners' safety lamps. By 1914 they had manufactured over one million lamps, and the company had branches in major mining districts worldwide.

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