president+of+the+royal+society

SUBJECT AREA: Electricity

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Volta had an early command of English, French and Latin, and also learned to read Dutch and Spanish. After completing studies at the Royal Seminary in Como he was involved in the study of physics, chemistry and electricity. He became a teacher of physics in his native town and in 1779 was appointed Professor of Physics at the University of Pavia, a post he held for forty years.

With a growing international reputation and a wish to keep abreast of the latest developments, in 1777 he began the first of many travels abroad. A journey started in 1781 to Switzerland, Germany, Belgium, Holland, France and England lasted about one year. By 1791 he had been elected to membership of many learned societies, including those in Zurich, Berlin, Berne and Paris. Volta's invention of his pile resulted from a controversy with Luigi Galvani, Professor of Anatomy at the University of Bologna. Galvani discovered that the muscles of frogs' legs contracted when touched with two pieces of different metals and attributed this to a phenomenon of the animal tissue. Volta showed that the excitation was due to a chemical reaction resulting from the contact of the dissimilar metals when moistened. His pile comprised a column of zinc and silver discs, each pair separated by paper moistened with brine, and provided a source of continuous current from a simple and accessible source. The effectiveness of the pile decreased as the paper dried and Volta devised his crown of cups, which had a longer life. In this, pairs of dissimilar metals were placed in each of a number of cups partly filled with an electrolyte such as brine. Volta first announced the results of his experiments with dissimilar metals in 1800 in a letter to Sir Joseph Banks, President of the Royal Society. This letter, published in the Transactions of the Royal Society, has been regarded as one of the most important documents in the history of science. Large batteries were constructed in a number of laboratories soon after Volta's discoveries became known, leading immediately to a series of developments in electrochemistry and eventually in electromagnetism. Volta himself made little further contribution to science. In recognition of his achievement, at a meeting of the International Electrical Congress in Paris in 1881 it was agreed to name the unit of electrical pressure the "volt".

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SUBJECT AREA: Electronics and information technology

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Charles Babbage was the son of a banker, Benjamin Babbage, and was a sickly child who had a rather haphazard education at private schools near Exeter and later at Enfield. Even as a child, he was inordinately fond of algebra, which he taught himself. He was conversant with several advanced mathematical texts, so by the time he entered Trinity College, Cambridge, in 1811, he was ahead of his tutors. In his third year he moved to Peterhouse, whence he graduated in 1814, taking his MA in 1817. He first contributed to the Philosophical Transactions of the Royal Society in 1815, and was elected a fellow of that body in 1816. He was one of the founders of the Astronomical Society in 1820 and served in high office in it.

While he was still at Cambridge, in 1812, he had the first idea of calculating numerical tables by machinery. This was his first difference engine, which worked on the principle of repeatedly adding a common difference. He built a small model of an engine working on this principle between 1820 and 1822, and in July of the latter year he read an enthusiastically received note about it to the Astronomical Society. The following year he was awarded the Society's first gold medal. He submitted details of his invention to Sir Humphry Davy, President of the Royal Society; the Society reported favourably and the Government became interested, and following a meeting with the Chancellor of the Exchequer Babbage was awarded a grant of £1,500. Work proceeded and was carried on for four years under the direction of Joseph Clement.

In 1827 Babbage went abroad for a year on medical advice. There he studied foreign workshops and factories, and in 1832 he published his observations in On the Economy of Machinery and Manufactures. While abroad, he received the news that he had been appointed Lucasian Professor of Mathematics at Cambridge University. He held the Chair until 1839, although he neither resided in College nor gave any lectures. For this he was paid between £80 and £90 a year! Differences arose between Babbage and Clement. Manufacture was moved from Clement's works in Lambeth, London, to new, fireproof buildings specially erected by the Government near Babbage's house in Dorset Square, London. Clement made a large claim for compensation and, when it was refused, withdrew his workers as well as all the special tools he had made up for the job. No work was possible for the next fifteen months, during which Babbage conceived the idea of his "analytical engine". He approached the Government with this, but it was not until eight years later, in 1842, that he received the reply that the expense was considered too great for further backing and that the Government was abandoning the project. This was in spite of the demonstration and perfectly satisfactory operation of a small section of the analytical engine at the International Exhibition of 1862. It is said that the demands made on manufacture in the production of his engines had an appreciable influence in improving the standard of machine tools, whilst similar benefits accrued from his development of a system of notation for the movements of machine elements. His opposition to street organ-grinders was a notable eccentricity; he estimated that a quarter of his mental effort was wasted by the effect of noise on his concentration.

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SUBJECT AREA: Civil engineering, Mechanical, pneumatic and hydraulic engineering, Steam and internal combustion engines

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As a boy, Smeaton showed mechanical ability, making for himself a number of tools and models. This practical skill was backed by a sound education, probably at Leeds Grammar School. At the age of 16 he entered his father's office; he seemed set to follow his father's profession in the law. In 1742 he went to London to continue his legal studies, but he preferred instead, with his father's reluctant permission, to set up as a scientific instrument maker and dealer and opened a shop of his own in 1748. About this time he began attending meetings of the Royal Society and presented several papers on instruments and mechanical subjects, being elected a Fellow in 1753. His interests were turning towards engineering but were informed by scientific principles grounded in careful and accurate observation.

In 1755 the second Eddystone lighthouse, on a reef some 14 miles (23 km) off the English coast at Plymouth, was destroyed by fire. The President of the Royal Society was consulted as to a suitable engineer to undertake the task of constructing a new one, and he unhesitatingly suggested Smeaton. Work began in 1756 and was completed in three years to produce the first great wave-swept stone lighthouse. It was constructed of Portland stone blocks, shaped and pegged both together and to the base rock, and bonded by hydraulic cement, scientifically developed by Smeaton. It withstood the storms of the English Channel for over a century, but by 1876 erosion of the rock had weakened the structure and a replacement had to be built. The upper portion of Smeaton's lighthouse was re-erected on a suitable base on Plymouth Hoe, leaving the original base portion on the reef as a memorial to the engineer.

The Eddystone lighthouse made Smeaton's reputation and from then on he was constantly in demand as a consultant in all kinds of engineering projects. He carried out a number himself, notably the 38 mile (61 km) long Forth and Clyde canal with thirty-nine locks, begun in 1768 but for financial reasons not completed until 1790. In 1774 he took charge of the Ramsgate Harbour works.

On the mechanical side, Smeaton undertook a systematic study of water-and windmills, to determine the design and construction to achieve the greatest power output. This work issued forth as the paper "An experimental enquiry concerning the natural powers of water and wind to turn mills" and exerted a considerable influence on mill design during the early part of the Industrial Revolution. Between 1753 and 1790 Smeaton constructed no fewer than forty-four mills.

Meanwhile, in 1756 he had returned to Austhorpe, which continued to be his home base for the rest of his life. In 1767, as a result of the disappointing performance of an engine he had been involved with at New River Head, Islington, London, Smeaton began his important study of the steam-engine. Smeaton was the first to apply scientific principles to the steam-engine and achieved the most notable improvements in its efficiency since its invention by Newcomen, until its radical overhaul by James Watt. To compare the performance of engines quantitatively, he introduced the concept of "duty", i.e. the weight of water that could be raised 1 ft (30 cm) while burning one bushel (84 lb or 38 kg) of coal. The first engine to embody his improvements was erected at Long Benton colliery in Northumberland in 1772, with a duty of 9.45 million pounds, compared to the best figure obtained previously of 7.44 million pounds. One source of heat loss he attributed to inaccurate boring of the cylinder, which he was able to improve through his close association with Carron Ironworks near Falkirk, Scotland.

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SUBJECT AREA: Chemical technology, Weapons and armour

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His family came from Germany and he was the son of a music master. He first became interested in science at the age of 14, when visiting his mineralogist uncle in Hamburg, and studied chemistry at the Royal Polytechnic Institution in London. In 1845 he became one of the twenty-six founding students, under A.W.von Hofmann, of the Royal College of Chemistry. Such was his aptitude for the subject that within two years he became von Hermann's assistant and demonstrator. In 1851 Abel was appointed Lecturer in Chemistry, succeeding Michael Faraday, at the Royal Military Academy, Woolwich, and it was while there that he wrote his Handbook of Chemistry, which was co-authored by his assistant, Charles Bloxam.

Abel's four years at the Royal Military Academy served to foster his interest in explosives, but it was during his thirty-four years, beginning in 1854, as Ordnance Chemist at the Royal Arsenal and at Woolwich that he consolidated and developed his reputation as one of the international leaders in his field. In 1860 he was elected a Fellow of the Royal Society, but it was his studies during the 1870s into the chemical changes that occur during explosions, and which were the subject of numerous papers, that formed the backbone of his work. It was he who established the means of storing gun-cotton without the danger of spontaneous explosion, but he also developed devices (the Abel Open Test and Close Test) for measuring the flashpoint of petroleum. He also became interested in metal alloys, carrying out much useful work on their composition. A further avenue of research occurred in 1881 when he was appointed a member of the Royal Commission set up to investigate safety in mines after the explosion that year in the Sealham Colliery. His resultant study on dangerous dusts did much to further understanding on the use of explosives underground and to improve the safety record of the coal-mining industry. The achievement for which he is most remembered, however, came in 1889, when, in conjunction with Sir James Dewar, he invented cordite. This stable explosive, made of wood fibre, nitric acid and glycerine, had the vital advantage of being a "smokeless powder", which meant that, unlike the traditional ammunition propellant, gunpowder ("black powder"), the firer's position was not given away when the weapon was discharged. Although much of the preliminary work had been done by the Frenchman Paul Vieille, it was Abel who perfected it, with the result that cordite quickly became the British Army's standard explosive.

Abel married, and was widowed, twice. He had no children, but died heaped in both scientific honours and those from a grateful country.

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SUBJECT AREA: Chemical technology, Synthetic materials, Textiles

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He early showed an aptitude for chemistry and in 1853 entered the Royal College of Chemistry as a student under A.W.von Hofmann, the first Professor at the College. By the end of his first year, he had carried out his first piece of chemical research, on the action of cyanogen chloride on phenylamine, which he published in the Journal of the Chemical Society (1857). He became honorary assistant to von Hofmann in 1857; three years previously he had set up his own chemical laboratory at home, where he had discovered the first of the azo dyes, aminoazonapththalene. In 1856 Perkin began work on the synthesis of quinine by oxidizing a salt of allyl toluidine with potassium dichromate. Substituting aniline, he obtained a dark-coloured precipitate which proved to possess dyeing properties: Perkin had discovered the first aniline dye. Upon receiving favourable reports on the new material from manufacturers of dyestuffs, especially Pullars of Perth, Perkin resigned from the College and turned to the commercial exploitation of his discovery. This proved highly successful. From 1858, the dye was manufactured at his Greenford Green works as "Aniline Purple" or "Tyrian Purple". It was later to be referred to by the French as mauve. Perkin's discovery led to the development of the modern dyestuffs industry, supplanting dyes from the traditional vegetable sources. In 1869, he introduced two new methods for making the red dye alizarin, in place of the process that involved the use of the madder plant (Rubia tinctorum). In spite of German competition, he dominated the British market until the end of 1873. After eighteen years in chemical industry, Perkin retired and devoted himself entirely to the pure chemical research which he had been pursuing since the 1850s. He eventually contributed ninety papers to the Chemical Society and further papers to other bodies, including the Royal Society. For example, in 1867 he published his synthesis of unsaturated organic acids, known as "Perkin's synthesis". Other papers followed, on the structure of "Aniline Purple". In 1881 Perkin drew attention to the magnetic-rotatory power of some of the substances he had been dealing with. From then on, he devoted particular attention to the application of this phenomenon to the determination of chemical structure.

Perkin won wide recognition for his discoveries and other contributions to chemistry.

The half-centenary of his great discovery was celebrated in July 1906 and later that year he received a knighthood.

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SUBJECT AREA: Weapons and armour

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Educated at Westminster College, in 1904 Tizard went to Magdalen College, Oxford, gaining Firsts in mathematics and chemistry. After a period of time in Berlin with Nernst, he joined the Royal Institution in 1909 to study the colour changes of indicators. From 1911 until 1914 he was a tutorial Fellow of Oriel College, Oxford, but with the outbreak of the First World War he joined first the Royal Garrison Artillery, then, in 1915, the newly formed Royal Flying Corps, to work on the development of bomb-sights. Successively in charge of testing aircraft, a lieutenant-colonel in the Ministry of Munitions and Assistant Controller of Research and Experiments for the Royal Air Force, he returned to Oxford in 1919 and the following year became Reader in Chemical Thermodynamics; at this stage he developed the use of toluene as an air-craft-fuel additive.

In 1922 he was appointed an assistant secretary at the government Department of Industrial and Scientific Research, becoming Principal Assistant Secretary in 1922 and its Permanent Director in 1927; during this time he was also a member of the Aeronautical Research Committee, being Chairman of the latter in 1933–43. From 1929 to 1942 he was Rector of Imperial College. In 1932 he was also appointed Chairman of a committee set up to investigate possible national air-defence systems, and it was largely due to his efforts that the radar proposals of Watson-Watt were taken up and an effective system made operational before the outbreak of the Second World War. He was also involved in various other government activities aimed at applying technology to the war effort, including the dam-buster and atomic bombs.

President of Magdalen College in 1942–7, he then returned again to Whitehall, serving as Chairman of the Advisory Council on Scientific Policy and of the Defence Research Policy Committee. Finally, in 1952, he became Pro-Chan-cellor of Southampton University.

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SUBJECT AREA: Electronics and information technology, Telecommunications

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After early education at home and at private school, Eccles won a scholarship to the Royal College of Science (now Imperial College), London, where he gained a First Class BSc in physics in 1898. He then worked as a demonstrator at the college and studied coherers, for which he obtained a DSc in 1901. Increasingly interested in electrical engineering, he joined the Marconi Company in 1899 to work on oscillators at the Poole experimental radio station, but in 1904 he returned to academic life as Professor of Mathematics and Physics and Department Head at South West Polytechnic, Chelsea. There he discovered ways of using the negative resistance of galena-crystal detectors to generate oscillations and gave a mathematical description of the operation of the triode valve. In 1910 he became Reader in Engineering at University College, London, where he published a paper explaining the reflection of radio waves by the ionosphere and designed a 60 MHz short-wave transmitter. From 1916 to 1926 he was Professor of Applied Physics and Electrical Engineering at the Finsbury City \& Guilds College and a private consulting engineer. During the First World War he was a military scientific adviser and Secretary to the Joint Board of Scientific Societies. After the war he made many contributions to electronic-circuit development, many of them (including the Eccles-Jordan "flip-flop" patented in 1918 and used in binary counters) in conjunction with F.W.Jordan, about whom little seems to be known. Illness forced Eccles's premature academic retirement in 1926, but he remained active as a consultant for many years.

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See also: Heaviside, Oliver; Kennelly, Arthur Edwin

SUBJECT AREA: Architecture and building, Civil engineering

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Eaton Hodgkinson's father, a farmer, died when he was 6 years old, but his mother was a resourceful woman who set up a business in Salford and ensured that her son received a sound schooling. Most important for his education, however, was his friendship with the Manchester scientific luminary Dr. Dalton, who instructed him in practical mathematics. These studies led Hodgkinson to devise a new form of cast-iron girder, carefully tested by experiments and which was widely adopted for fire-proof structures in the nineteenth century. Following Dalton, Hodgkinson became an active member of the Manchester Philosophical Society, of which he was elected President in 1848. He also became an active member of the British Association for the Advancement of Science. Hodgkinson's work on cast-iron girders secured him a Fellowship of the Royal Society, and the Royal Medal of the Society, in 1841. It was Hodgkinson also who verified the mathematical value of the pioneering experiments carried out by William Fairbairn for Robert Stephenson's proposed wrought-iron tube structure which, in 1849, became the Britannia Bridge over the Menai Straits. He received a Silver Medal for this work at the Paris Exhibition of 1858. Hodgkinson served as a member of the Royal Commission appointed to enquire into the application of iron to railway structures. In 1847 he was appointed Professor of the Mechanical Principles of Engineering at University College, London, but his health began to fail shortly after. He was elected an Honorary Member of the Institution of Civil Engineers in 1851. Described as "singularly simple and guileless", he was widely admired and respected.

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SUBJECT AREA: Electricity

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With an early bias towards science, Daniell's interest in chemistry was formed when he joined a relative's sugar-refining business. He formed a lifelong friendship with W.T.Brande, Professor of Chemistry at the Royal Institution, and together they revived the journal of the Royal Institution, to which Daniell submitted many of his early papers on chemical subjects. He made many contributions to the science of meteorology and in 1820 invented a hydrometer, which became widely used and gave precision to the measurement of atmospheric moisture. As one of the originators of the Society for Promoting Useful Knowledge, Daniell edited several of its early publications. His work on crystallization established his reputation as a chemist and in 1831 he was appointed the first Professor of Chemistry at King's College, London, where he was largely responsible for establishing its department of applied science. He was also involved in the Chemical Society of London and served as its Vice-President. At King's College he began the research into current electricity with which his name is particularly associated. His investigations into the zinc-copper cell revealed that the rapid decline in power was due to hydrogen gas being liberated at the positive electrode. Daniell's cell, invented in 1836, employed a zinc electrode in dilute sulphuric acid and a copper electrode in a solution of copper sulphate, the electrodes being separated by a porous membrane, typically an unglazed earthenware pot. He was awarded the Copley Medal of the Royal Society for his invention which avoided the "polarization" of the simple cell and provided a further source of current for electrical research and for commercial applications such as electroplating. Although the high internal resistance of the Daniell cell limited the current and the potential was only 1.1 volts, the voltage was so unchanging that it was used as a reference standard until the 1870s, when J. Lattimer Clark devised an even more stable cell.

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SUBJECT AREA: Mechanical, pneumatic and hydraulic engineering

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Osborne Reynolds's father, a clergyman and schoolteacher, had been a Fellow of Queens' College, Cambridge; it was to Queens' that the young Reynolds went to study mathematics, graduating as 7th Wrangler in 1867, and going on in his turn to become a Fellow of the College. Reynolds had developed an interest in practical applications of physics and engineering, and for a short time he entered the office of the London civil engineers Lawson and Mansergh. In 1868 he was appointed to the new Chair of Engineering at Owens College, Manchester, and he remained in this post for thirty-seven years, until he retired in 1905. During this period he presided over a department that grew steadily in size and reputation, and undertook prolonged research projects into phenomena such as lubrication, the laws governing the flow of water in pipes, turbulence and other physical features with practical applications. He was elected a Fellow of the Royal Society in 1877, being nominated Royal Medallist in 1888. In 1883 he became a Member of the Institution of Civil Engineers, and in 1885 he was awarded the Telford Premium of the Institution. He served as Secretary of the Manchester Literary and Philosophical Society from 1874 to 1883, and was appointed President in 1888–9 and Dalton Medallist in 1903. He was President of Section G of the British Association for the History of Science in 1887, and in 1884 he received the degree of LLD from Glasgow University. Among his many students at Owens College was J.J. (later Sir Joseph) Thomson (1856–1940), who entered the college in 1871. Reynolds's collected scientific papers were published in 1900–3.

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SUBJECT AREA: Electricity, Electronics and information technology, Public utilities

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After attending Owens College, Manchester, Hopkinson was admitted to Trinity College, Cambridge, in 1867 to read for the Mathematical Tripos. An appointment in 1872 with the lighthouse department of the Chance Optical Works in Birmingham directed his attention to electrical engineering. His most noteworthy contribution to lighthouse engineering was an optical system to produce flashing lights that distinguished between individual beacons. His extensive researches on the dielectric properties of glass were recognized when he was elected to a Fellowship of the Royal Society at the age of 29. Moving to London in 1877 he became established as a consulting engineer at a time when electricity supply was about to begin on a commercial scale. During the remainder of his life, Hopkinson's researches resulted in fundamental contributions to electrical engineering practice, dynamo design and alternating current machine theory. In making a critical study of the Edison dynamo he developed the principle of the magnetic circuit, a concept also arrived at by Gisbert Kapp around the same time. Hopkinson's improvement of the Edison dynamo by reducing the length of the field magnets almost doubled its output. In 1890, in addition to-his consulting practice, Hopkinson accepted a post as the first Professor of Electrical Engineering and Head of the Siemens laboratory recently established at King's College, London. Although he was not involved in lecturing, the position gave him the necessary facilities and staff and student assistance to continue his researches. Hopkinson was consulted on many proposals for electric traction and electricity supply, including schemes in London, Manchester, Liverpool and Leeds. He also advised Mather and Platt when they were acting as contractors for the locomotives and generating plant for the City and South London tube railway. As early as 1882 he considered that an ideal method of charging for the supply of electricity should be based on a two-part tariff, with a charge related to maximum demand together with a charge for energy supplied. Hopkinson was one the foremost expert witnesses of his day in patent actions and was himself the patentee of over forty inventions, of which the three-wire system of distribution and the series-parallel connection of traction motors were his most successful. Jointly with his brother Edward, John Hopkinson communicated the outcome of his investigations to the Royal Society in a paper entitled "Dynamo Electric Machinery" in 1886. In this he also described the later widely used "back to back" test for determining the characteristics of two identical machines. His interest in electrical machines led him to more fundamental research on magnetic materials, including the phenomenon of recalescence and the disappearance of magnetism at a well-defined temperature. For his work on the magnetic properties of iron, in 1890 he was awarded the Royal Society Royal Medal. He was a member of the Alpine Club and a pioneer of rock climbing in Britain; he died, together with three of his children, in a climbing accident.

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SUBJECT AREA: Medical technology

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Of Quaker stock, his father also being a Fellow of the Royal Society, he studied medicine at University College, London. He qualified, and became a Fellow of the Royal College of Surgeons, in 1852. Wishing to pursue a surgical career, he moved to Edinburgh to study surgery under William Syme, whose daughter he married in 1852, the same year he was appointed Assistant Surgeon to the Edinburgh Royal Infirmary.

Until his appointment as Regius Professor of Surgery at Glasgow University and Glasgow Royal Infirmary in 1861, he was engaged in a wide variety of investigations into the nature of inflammation and the effects of irritants on wounds. Following his move to Glasgow, he became particularly involved in the major problems arising out of the vast increase in the number of surgical procedures brought about by the recent introduction of general anaesthesia. By 1865 his continuing study of wound inflammation and the microbial studies of Pasteur had led him to institute in the operating theatre a regime of surgical antisepsis involving the use of a carbolic acid spray coupled with the sterilization of instruments, the site of operation and the hands of the operator. Increasingly it was appreciated that the air was the least important origin of infection, and by 1887 the antiseptic approach had been superseded by the aseptic.

In 1869 he succeeded Syme in the Chair at Edinburgh and his methods were widely accepted abroad. In 1877 he moved to the Chair of Surgery at King's College Hospital, London, in the hope of encouraging acceptance of his work in the metropolis. As well as developing a variety of new surgical procedures, he was engaged for many years in the development of surgical ligatures, which had always been a potent stimulant of infection. His choice of catgut as a sterilizable, absorbable material paved the way for major developments in this field. The Lister Institute of Preventive Medicine was named in his honour in 1903.

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SUBJECT AREA: Architecture and building

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Born into a High Church and Royalist family, the young Wren early showed outstanding intellectual ability and at Oxford in 1654 was described as "that miracle of a youth". Educated at Westminster School, he went up to Oxford, where he graduated at the age of 19 and obtained his master's degree two years later. From this time onwards his interests were in science, primarily astronomy but also physics, engineering and meteorology. While still at college he developed theories about and experimentally solved some fifty varied problems. At the age of 25 Wren was appointed to the Chair of Astronomy at Gresham College in London, but he soon returned to Oxford as Savilian Professor of Astronomy there. At the same time he became one of the founder members of the Society of Experimental Philosophy at Oxford, which was awarded its Royal Charter soon after the Restoration of 1660; Wren, together with such men as Isaac Newton, Robert Hooke, John Evelyn and Robert Boyle, then found himself a member of the Royal Society.

Wren's architectural career began with the classical chapel that he built, at the request of his uncle, the Bishop of Ely, for Pembroke College, Cambridge (1663). From this time onwards, until he died at the age of 91, he was fully occupied with a wide and taxing variety of architectural problems which he faced in the execution of all the great building schemes of the day. His scientific background and inventive mind stood him in good stead in solving such difficulties with an often unusual approach and concept. Nowhere was this more apparent than in his rebuilding of fifty-one churches in the City of London after the Great Fire, in the construction of the new St Paul's Cathedral and in the grand layout of the Royal Hospital at Greenwich.

The first instance of Wren's approach to constructional problems was in his building of the Sheldonian Theatre in Oxford (1664–9). He based his design upon that of the Roman Theatre of Marcellus (13–11 BC), which he had studied from drawings in Serlio's book of architecture. Wren's reputation as an architect was greatly enhanced by his solution to the roofing problem here. The original theatre in Rome, like all Roman-theatres, was a circular building open to the sky; this would be unsuitable in the climate of Oxford and Wren wished to cover the English counterpart without using supporting columns, which would have obscured the view of the stage. He solved this difficulty mathematically, with the aid of his colleague Dr Wallis, the Professor of Geometry, by means of a timber-trussed roof supporting a painted ceiling which represented the open sky.

The City of London's churches were rebuilt over a period of nearly fifty years; the first to be completed and reopened was St Mary-at-Hill in 1676, and the last St Michael Cornhill in 1722, when Wren was 89. They had to be rebuilt upon the original medieval sites and they illustrate, perhaps more clearly than any other examples of Wren's work, the fertility of his imagination and his ability to solve the most intractable problems of site, limitation of space and variation in style and material. None of the churches is like any other. Of the varied sites, few are level or possess right-angled corners or parallel sides of equal length, and nearly all were hedged in by other, often larger, buildings. Nowhere is his versatility and inventiveness shown more clearly than in his designs for the steeples. There was no English precedent for a classical steeple, though he did draw upon the Dutch examples of the 1630s, because the London examples had been medieval, therefore Roman Catholic and Gothic, churches. Many of Wren's steeples are, therefore, Gothic steeples in classical dress, but many were of the greatest originality and delicate beauty: for example, St Mary-le-Bow in Cheapside; the "wedding cake" St Bride in Fleet Street; and the temple diminuendo concept of Christ Church in Newgate Street.

In St Paul's Cathedral Wren showed his ingenuity in adapting the incongruous Royal Warrant Design of 1675. Among his gradual and successful amendments were the intriguing upper lighting of his two-storey choir and the supporting of the lantern by a brick cone inserted between the inner and outer dome shells. The layout of the Royal Hospital at Greenwich illustrates Wren's qualities as an overall large-scale planner and designer. His terms of reference insisted upon the incorporation of the earlier existing Queen's House, erected by Inigo Jones, and of John Webb's King Charles II block. The Queen's House, in particular, created a difficult problem as its smaller size rendered it out of scale with the newer structures. Wren's solution was to make it the focal centre of a great vista between the main flanking larger buildings; this was a masterstroke.

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SUBJECT AREA: Civil engineering

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Very little is known of his early life, but he was clearly a skilful and gifted engineer who had received comprehensive practical training, for in 1743 he erected the machinery in the world's first water-powered cotton mill at Northampton on the river Nene. In 1748 he invented a weighing machine for use by turnpike trusts for weighing wagons. Until 1757 he remained in Northampton, mainly surveying enclosures and turnpike roads and making agricultural machinery. He also gained a national reputation for building and installing very successful ventilating equipment (invented by Dr Stephen Hales) in hospitals, prisons and ships, including some ventilators of Yeoman's own design in the Houses of Parliament.

Meanwhile he developed an interest in river improvements, and in 1744 he made his first survey of the River Nene between Thrapston and Northampton; he repeated the survey in 1753 and subsequently gave evidence in parliamentary proceedings in 1756. The following year he was in Gloucestershire surveying the line of the Stroudwater Canal, an operation that he repeated in 1776. Also in 1757, he was appointed Surveyor to the River Ivel Navigation in Bedfordshire. In 1761 he was back on the Nene. During 1762–5 he carried out surveys for the Chelmer \& Blackwater Navigation, although the work was not undertaken for another thirty years. In 1765 he reported on land-drainage improvements for the Kentish Sour. It was at this time that he became associated with John Smeaton in a major survey in 1766 of the river Lea for the Lee Navigation Trustees, having already made some surveys with Joseph Nickalls near Waltham Abbey in 1762. Yeoman modified some of Smeaton's proposals and on 1 July 1767 was officially appointed Surveyor to the Lee Navigation Trustees, a post he retained until 1771. He also advised on the work to create the Stort Navigation, and at the official opening on 24 October 1769 he made a formal speech announcing: "Now is Bishops Stortford open to all the ports of the world." Among his other works were: advice on Ferriby Sluice on the River Ancholme (1766); reports on the Forth \& Clyde Canal, the North Level and Wisbech outfall on the Nene, the Coventry Canal, and estimates for the Leeds and Selby Canal (1768–71); estimates for the extension of the Medway Navigation from Tonbridge to Edenbridge (1771); and between 1767 and 1777 he was consulted, with other engineers, by the City of London on problems regarding the Thames.

He joined the Northampton Philosophical Society shortly after its formation in 1743 and was President several times before he moved to London. In 1760 he became a member of the Society for the Encouragement of Arts, Manufactures and Commerce, and in 1763 he was chosen as joint Chairman of the Committee on Mechanics—a position he held until 1778. He was elected a Fellow of the Royal Society on 12 January 1764. On the formation of the Smeatonian Society of Civil Engineers, the forerunner of the present Institution of Civil Engineers, he was elected first President in 1771, remaining as such until his illness in 1780.

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SUBJECT AREA: Photography, film and optics

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Abney began his career as an officer in the Army and was an instructor in chemistry in the Royal Engineers at Chatham, where he made substantial use of photography as a working tool. He retired from the Army in 1877 and joined the Science and Art Department at South Kensington. It was at Abney's suggestion that a collection of photographic equipment and processes was established in the South Kensington Museum (later to become the Science Museum Photography Collection).

Abney undertook significant researches into the nature of gelatine silver halide emulsions at a time when they were being widely adopted by photographers. Perhaps his most important practical innovations were the introduction of hydroquinone as a developing agent in 1880 and silver gelatine citrochloride emulsions for printing-out paper (POP) in 1882. However, Abney was at the forefront of many aspects of photographic research during a period of great innovation and change in photography. He devised new techniques of photomechanical printing and conducted significant researches in the fields of photochemistry and spectral analysis. Abney published throughout his career for both the specialist scientist and the more general photographic practitioner.

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