page_title: William Thomson, 1st Baron Kelvin
section_title: Marine
hierarchical_section_title: William Thomson, 1st Baron Kelvin / Other contributions / Marine
caption_attribution_description: עברית: מצפן ימי של לורד קלווין עם שעון שמש English: Sir Lord Kelvin Mariner's Compass with Sun Dial
context_page_description: William Thomson, 1st Baron Kelvin, OM, GCVO, PC, PRS, FRSE was a British mathematical physicist and engineer who was born in Belfast in 1824. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second laws of thermodynamics, and did much to unify the emerging discipline of physics in its modern form. He worked closely with mathematics professor Hugh Blackburn in his work. He also had a career as an electric telegraph engineer and inventor, which propelled him into the public eye and ensured his wealth, fame and honour. For his work on the transatlantic telegraph project he was knighted in 1866 by Queen Victoria, becoming Sir William Thomson. He had extensive maritime interests and was most noted for his work on the mariner's compass, which previously had limited reliability.
  Absolute temperatures are stated in units of kelvin in his honour. While the existence of a lower limit to temperature was known prior to his work, Kelvin is known for determining its correct value as approximately −273.15 degree Celsius or −459.67 degree Fahrenheit.
context_section_description: Thomson was an enthusiastic yachtsman, his interest in all things relating to the sea perhaps arising from, or fostered by, his experiences on the Agamemnon and the Great Eastern.
  Thomson introduced a method of deep-sea depth sounding, in which a steel piano wire replaces the ordinary hand line. The wire glides so easily to the bottom that "flying soundings" can be taken while the ship is at full speed. A pressure gauge to register the depth of the sinker was added by Thomson.
  About the same time he revived the Sumner method of finding a ship's position, and calculated a set of tables for its ready application. In 1876, he constructed a harmonic analyzer, in which an assembly of disks were used to sum trigonometric series and thus to predict tides. Kelvin mentioned that a similar device could be built to solve differential equations.
  During the 1880s, Thomson worked to perfect the adjustable compass to correct errors arising from magnetic deviation owing to the increased use of iron in naval architecture. Thomson's design was a great improvement on the older instruments, being steadier and less hampered by friction. The deviation due to the ship's magnetism was corrected by movable iron masses at the binnacle. Thomson's innovations involved much detailed work to develop principles identified by George Biddell Airy and others, but contributed little in terms of novel physical thinking. Thomson's energetic lobbying and networking proved effective in gaining acceptance of his instrument by The Admiralty.
   Scientific biographers of Thomson, if they have paid any attention at all to his compass innovations, have generally taken the matter to be a sorry saga of dim-witted naval administrators resisting marvellous innovations from a superlative scientific mind. Writers sympathetic to the Navy, on the other hand, portray Thomson as a man of undoubted talent and enthusiasm, with some genuine knowledge of the sea, who managed to parlay a handful of modest ideas in compass design into a commercial monopoly for his own manufacturing concern, using his reputation as a bludgeon in the law courts to beat down even small claims of originality from others, and persuading the Admiralty and the law to overlook both the deficiencies of his own design and the virtues of his competitors'.
  
  The truth, inevitably, seems to lie somewhere between the two extremes. 
  Charles Babbage had been among the first to suggest that a lighthouse might be made to signal a distinctive number by occultations of its light, but Thomson pointed out the merits of the Morse code for the purpose, and urged that the signals should consist of short and long flashes of the light to represent the dots and dashes.
caption: Kelvin Mariner's Compass
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