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1 Trésaguet, Pierre Marie Jerome
[br]b. 1716 Nevers, Franced. 1796 France[br]French civil engineer, best known for his system of road construction.[br]Born into a family of engineers, Trésaguet made his career in the Corps des Ponts et Chaussées, becoming Inspector-General of the Corps in 1775. He is best known for his improved method of road construction, which involved the use of carefully placed stones in the base with layers of progressively smaller sizes towards the surface. He also emphasized the importance of good drainage as well as regular maintenance. His system was generally adopted throughout France and in neighbouring European countries.[br]Further ReadingM.Magnusson (ed.), 1990, Chambers Biographical Dictionary, Edinburgh: W. \& R.Chambers.IMcNBiographical history of technology > Trésaguet, Pierre Marie Jerome
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2 Carnot, Nicolas Léonard Sadi
SUBJECT AREA: Steam and internal combustion engines[br]b. 1 June 1796 Paris, Franced. 24 August 1831 Paris, France[br]French laid the foundations for modern thermodynamics through his book Réflexions sur la puissance motrice du feu when he stated that the efficiency of an engine depended on the working substance and the temperature drop between the incoming and outgoing steam.[br]Sadi was the eldest son of Lazare Carnot, who was prominent as one of Napoleon's military and civil advisers. Sadi was born in the Palais du Petit Luxembourg and grew up during the Napoleonic wars. He was tutored by his father until in 1812, at the minimum age of 16, he entered the Ecole Polytechnique to study stress analysis, mechanics, descriptive geometry and chemistry. He organized the students to fight against the allies at Vincennes in 1814. He left the Polytechnique that October and went to the Ecole du Génie at Metz as a student second lieutenant. While there, he wrote several scientific papers, but on the Restoration in 1815 he was regarded with suspicion because of the support his father had given Napoleon. In 1816, on completion of his studies, Sadi became a second lieutenant in the Metz engineering regiment and spent his time in garrison duty, drawing up plans of fortifications. He seized the chance to escape from this dull routine in 1819 through an appointment to the army general staff corps in Paris, where he took leave of absence on half pay and began further courses of study at the Sorbonne, Collège de France, Ecole des Mines and the Conservatoire des Arts et Métiers. He was inter-ested in industrial development, political economy, tax reform and the fine arts.It was not until 1821 that he began to concentrate on the steam-engine, and he soon proposed his early form of the Carnot cycle. He sought to find a general solution to cover all types of steam-engine, and reduced their operation to three basic stages: an isothermal expansion as the steam entered the cylinder; an adiabatic expansion; and an isothermal compression in the condenser. In 1824 he published his Réflexions sur la puissance motrice du feu, which was well received at the time but quickly forgotten. In it he accepted the caloric theory of heat but pointed out the impossibility of perpetual motion. His main contribution to a correct understanding of a heat engine, however, lay in his suggestion that power can be produced only where there exists a temperature difference due "not to an actual consumption of caloric but to its transportation from a warm body to a cold body". He used the analogy of a water-wheel with the water falling around its circumference. He proposed the true Carnot cycle with the addition of a final adiabatic compression in which motive power was con sumed to heat the gas to its original incoming temperature and so closed the cycle. He realized the importance of beginning with the temperature of the fire and not the steam in the boiler. These ideas were not taken up in the study of thermodynartiics until after Sadi's death when B.P.E.Clapeyron discovered his book in 1834.In 1824 Sadi was recalled to military service as a staff captain, but he resigned in 1828 to devote his time to physics and economics. He continued his work on steam-engines and began to develop a kinetic theory of heat. In 1831 he was investigating the physical properties of gases and vapours, especially the relationship between temperature and pressure. In June 1832 he contracted scarlet fever, which was followed by "brain fever". He made a partial recovery, but that August he fell victim to a cholera epidemic to which he quickly succumbed.[br]Bibliography1824, Réflexions sur la puissance motrice du feu; pub. 1960, trans. R.H.Thurston, New York: Dover Publications; pub. 1978, trans. Robert Fox, Paris (full biographical accounts are provided in the introductions of the translated editions).Further ReadingDictionary of Scientific Biography, 1971, Vol. III, New York: C.Scribner's Sons. T.I.Williams (ed.), 1969, A Biographical Dictionary of Scientists, London: A. \& C.Black.Chambers Concise Dictionary of Scientists, 1989, Cambridge.D.S.L.Cardwell, 1971, from Watt to Clausius. The Rise of Thermodynamics in the Early Industrial Age, London: Heinemann (discusses Carnot's theories of heat).RLHBiographical history of technology > Carnot, Nicolas Léonard Sadi
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3 Guericke, Otto von
[br]b. 20 November 1602 Magdeburg, Saxony, Germanyd. 11 May 1686 Hamburg, Germany[br]German engineer and physicist, inventor of the air pump and investigator of the properties of a vacuum.[br]Guericke was born into a patrician family in Magdeburg. He was educated at the University of Leipzig in 1617–20 and at the University of Helmstedt in 1620. He then spent two years studying law at Jena, and in 1622 went to Leiden to study law, mathematics, engineering and especially fortification. He spent most of his life in politics, for he was elected an alderman of Magdeburg in 1626. After the destruction of Magdeburg in 1631, he worked in Brunswick and Erfurt as an engineer for the Swedish government, and then in 1635 for the Electorate of Saxony. He was Mayor of Magdeburg for thirty years, between 1646 and 1676. He was ennobled in 1666 and retired from public office in 168land went to Hamburg. It was through his attendances at international congresses and at princely courts that he took part in the exchange of scientific ideas.From his student days he was concerned with the definition of space and posed three questions: can empty space exist or is space always filled? How can heavenly bodies affect each other across space and how are they moved? Is space, and so also the heavenly bodies, bounded or unbounded? In c. 1647 Guericke made a suction pump for air and tried to exhaust a beer barrel, but he could not stop the leaks. He then tried a copper sphere, which imploded. He developed a series of spectacular demonstrations with his air pump. In 1654 at Rattisbon he used a vertical cylinder with a well-fitting piston connected over pulleys by a rope to fifty men, who could not stop the piston descending when the cylinder was exhausted. More famous were his copper hemispheres which, when exhausted, could not be drawn apart by two teams of eight horses. They were first demonstrated at Magdeburg in 1657 and at the court in Berlin in 1663. Through these experiments he discovered the elasticity of air and began to investigate its density at different heights. He heard of the work of Torricelli in 1653 and by 1660 had succeeded in making barometric forecasts. He published his famous work New Experiments Concerning Empty Space in 1672. Between 1660 and 1663 Guericke constructed a large ball of sulphur that could be rotated on a spindle. He found that, when he pressed his hand on it and it was rotated, it became strongly electrified; he thus unintentionally became the inventor of the first machine to generate static electricity. He attempted to reach a complete physical explanation of the world and the heavens with magnetism as a primary force and evolved an explanation for the rotation of the heavenly bodies.[br]Bibliography1672, Experimenta nova (ut vocantur) Magdeburgica de vacuo spatio (New Experiments Concerning Empty Space).Further ReadingF.W.Hoffmann, 1874, Otto von Guericke (a full biography).T.I.Williams (ed.), 1969, A Biographical Dictionary of Scientists, London: A. \& C.Black (contains a short account of his life).Chambers Concise Dictionary of Scientists, 1989, Cambridge.Dictionary of Scientific Biography, Vol. V, New York.C.Singer (ed.), 1957, A History of Technology, Vols. III and IV, Oxford University Press (includes references to Guericke's inventions).RLH -
4 Torricelli, Evangelista
SUBJECT AREA: Photography, film and optics[br]b. 15 October 1608 Faenza, Italyd. 25 October 1647 Florence, Italy[br]Italian physicist, inventor of the mercury barometer and discoverer of atmospheric pressure.[br]Torricelli was the eldest child of a textile artisan. Between 1625 and 1626 he attended the Jesuit school at Faenza, where he showed such outstanding aptitude in mathematics and philosophy that his uncle was persuaded to send him to Rome to a school run by Benedetto Castelli, a mathematician and engineer and a former pupil of Galileo Galilei. Between 1630 and 1641, Torricelli was possibly Secretary to Giovanni Ciampoli, Galileo's friend and protector. In 1641 Torricelli wrote a treatise, De motugravium, amplifying Galileo's doctrine on the motion of projectiles, and Galileo accepted him as a pupil. On Galileo's death in 1642, he was appointed as mathematician and philosopher to the court of Grand Duke Ferdinando II of Tuscany. He remained in Florence until his early death in 1647, possibly from typhoid fever. He wrote a great number of mathematical papers on conic sections, the cycloid, the logarithmic curve and other subjects, which made him well known.By 1642 Torricelli was producing good lenses for telescopes; he subsequently improved them, and attained near optical perfection. He also constructed a simple microscope with a small glass sphere as a lens. Galileo had looked at problems of raising water with suction pumps, and also with a siphon in 1630. Torricelli brought up the subject again in 1640 and later produced his most important invention, the barometer. He used mercury to fill a glass tube that was sealed at one end and inverted it. He found that the height of mercury in the tube adjusted itself to a well-defined level of about 76 cm (30 in.), higher than the free surface outside. He realized that this must be due to the pressure of the air on the outside surface and predicted that it would fall with increasing altitude. He thus demonstrated the pressure of the atmosphere and the existence of a vacuum on top of the mercury, publishing his findings in 1644. He later noticed that changes in the height of the mercury were related to changes in the weather.[br]Bibliography1641, De motu gravium.Further ReadingT.I.Williams (ed.), 1969, A Biographical Dictionary of Scientists, London: A. \& C.Black.Chambers Concise Dictionary of Scientists, 1989, Cambridge.A Dictionary of Scientific Biography, 1976, Vol. XIII, New York: C.Scribner's Sons.A.Stowers, 1961–2, "Thomas Newcomen's first steam engine 250 years ago and the initial development of steam power", Transactions of the Newcomen Society 34 (provides an account of his mercury barometer).W.E.Knowles Middleton, 1964, The History of the Barometer, Baltimore.RLHBiographical history of technology > Torricelli, Evangelista
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