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1 Essen, Louis
SUBJECT AREA: Horology[br]b. 6 September 1908 Nottingham, England[br]English physicist who produced the first practical caesium atomic clock, which was later used to define the second.[br]Louis Essen joined the National Physical Laboratory (NPL) at Teddington in 1927 after graduating from London University. He spent his whole working life at the NPL and retired in 1972; his research there was recognized by the award of a DSc in 1948. At NPL he joined a team working on the development of frequency standards using quartz crystals and he designed a very successful quartz oscillator, which became known as the "Essen ring". He was also involved with radio frequency oscillators. His expertise in these fields was to play a crucial role in the development of the caesium clock. The idea of an atomic clock had been proposed by I.I.Rabbi in 1945, and an instrument was constructed shortly afterwards at the National Bureau of Standards in the USA. However, this device never realized the full potential of the concept, and after seeing it on a visit to the USA Essen was convinced that a more successful instrument could be built at Teddington. Assisted by J.V.L.Parry, he commenced work in the spring of 1953 and by June 1955 the clock was working reliably, with an accuracy that was equivalent to one second in three hundred years. This was significantly more accurate than the astronomical observations that were used at that time to determine the second: in 1967 the second was redefined in terms of the value for the frequency of vibration of caesium atoms that had been obtained with this clock.[br]Principal Honours and DistinctionsFRS 1960. Clockmakers' Company Tompion Gold Medal 1957. Physical Society C.V.Boys Prize 1957. USSR Academy of Science Popov Gold Medal 1959.Bibliography1957, with J.V.L.Parry, "The caesium resonator as a standard of frequency and time", Philosophical Transactions of the Royal Society (Series A) 25:45–69 (the first comprehensive description of the caesium clock).Further ReadingP.Forman, 1985, "Atomichron: the atomic clock from concept to commercial product", Proceedings of the IEEE 75:1,181–204 (an authoritative critical review of the development of the atomic clock).N.Cessons (ed.), 1992, The Making of the Modern World, London: Science Museum, pp.190–1 (contains a short account).See also: Marrison, Warren AlvinDV -
2 Horology
See also: INDEX BY SUBJECT AREA[br]Ctesibius of AlexandriaGrimthorpe, Edmund Beckett, BaronSu SongYi-XingZhang Sixun -
3 Pötsch, Friedrich Hermann
SUBJECT AREA: Mining and extraction technology[br]b. 12 December 1842 Biendorf, near Köthen, Germanyd. 9 June 1902 Dresden, Germany[br]German mine surveyor, inventor of the freezing process for sinking shafts.[br]Pötsch was the son of a forest officer and could not easily attend school, with the consequences that it took him a long time to obtain the scholarly education needed to enable him to begin work on a higher level with the mining administration in the duchy of Anhalt in 1868. Seven years later, he was licensed as a Prussian mining surveyor and in this capacity he worked with the mining inspectorate of Aschersleben. During that time he frequently came across shafts for brown-coal mines which had been sunk down to watery strata but then had to be abandoned. His solution to the problem was to freeze the quicksand with a solution of chloride; this was better than the previous attempts in England to instal cooling coils at the bottom of the shaft. Pötsch's conception implied the construction of ice walls with the means of boreholes and refrigerators. By his method a set of boreholes was driven through the watery strata, the smaller pipes contained within the main bore pipes, providing a channel through which calcium chloride was pumped, returning through the longer pipe until the ground was frozen solid. He obtained a patent in 1883 and many leading international journals reported on the method the same year.In 1884 he established the Internationale Gesselschaft für Schacht-, Brucken-und Tunnelbau in Magdeburg and he also became Director of the Poetsch-Sooy-Smith Freezing Company in New Jersey, which constructed the first freezing shaft in America in 1888.However, Pötsch was successful only for a short period of time and, being a clumsy entrepreneur, he had to dissolve his company in 1894. Unfortunately, his decision to carry out the complete shaft-sinking business did not allow him to concentrate on solving upcoming technical problems of his new process. It was Louis Gebhardt (1861–1924), his former engineer, who took care of development, especially in co-operation with French mining engineers, and thus provided the basis for the freezing process becoming widely used for shaft-sinking in complicated strata ever since.[br]Bibliography1886, Das Gefrierverfahren. Methode für schnelles, sicheres und lotrechtes Abteufen von Schächten im Schwimmsande und uberhaupt im wasserreichen Gebirge; für Herstellung tiefgehender Bruckenpfeiler und für TunnelBauten in rolligem und schwimmendem Gebirge, Freiberg.1889, Geschichtliches über die Entstehung und Herausbildung des Gefrierverfahrens, Magdeburg.1895, Das Gefrierverfahren und das kombinierte Schachtabbohr-und Gefrierverfahren (Patent Pötsch), Freiberg.Further ReadingD.Hoffmann, 1962, AchtJahrzehnte Gefrierverfahren nach Putsch, Essen: Glückauf (the most substantial biography; also covers technological aspects).G.Gach, 1986, In Schacht und Strecke, Essen: Glückauf, pp. 31–53 (provides information on the development of specialized mining companies in Germany originating in the freezing process).WKBiographical history of technology > Pötsch, Friedrich Hermann
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Essen, Louis — ▪ 1998 British physicist (b. Sept. 6, 1908, Nottingham, Nottinghamshire, Eng. d. Aug. 24, 1997, Great Bookham, Surrey, Eng.), built the cesium beam atomic clock, a device that ultimately changed the way time is measured. Atomic clocks… … Universalium
Louis Essen — (segundo por la izquierda). Louis Essen (6 de septiembre de 1908; 24 de agosto de 1997) fue un físico inglés cuyos logros más notables fueron en la medición precisa del tiempo y la determinación de la velocidad de la luz. Se mostró crítico de la… … Wikipedia Español
Louis Essen — (2. von links). Louis Essen (* 6. September 1908; † 24. August 1997) war ein englischer Physiker. Er lieferte wertvolle Beiträge zur präzisen Zeitmessung [1] und zur Bestimmung der … Deutsch Wikipedia
Louis de Tabouillot — oder Anton Carl Ludwig von Tabouillot (* 26. Dezember 1775 in Verdun, Frankreich; † 17. Februar 1813 in Essen, Westfalen) war ein französisch deutscher Gutsbesitzer, königlich preußischer Hauptmann und Bürgermeister („Maire“). Leben Tabouillot… … Deutsch Wikipedia
Louis von Kannengießer — (* 17. April 1852 in Essen; † 30. Oktober 1919 in München) war ein deutscher Kaufmann und Reeder. Inhaltsverzeichnis 1 Leben und Wirken 2 Ehe und Familie 3 Literatur … Deutsch Wikipedia
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Louis Baare — Carl Ludwig Baare, genannt Louis Baare (* 12. Juni 1821 in Minden an der Weser; † 16. Mai 1897 in Bochum) war ein deutscher Wirtschaftspionier und Industrieller.[1][2] Der Kaufmann Baare kam im Alter … Deutsch Wikipedia
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