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The solar compass, an astronomical instrument, was first invented and made by William Austin Burt.〔(Mining and metallurgy, Issues 169-180 By American Institute of Mining and Metallurgical Engineers, p. cccxli Charles S. Burt, the grandson of William Austin Burt )〕 He patented it on February 25, 1836, in the (United States Patent Office as No 9428X ).〔(Solar Compass )〕 It received a medal at the Great Exhibition of 1851.〔Farmer, p. 362〕 The Calumet and Hecla Mine, largest copper mine in the world, was discovered through the use of Burt's solar compass.〔 == History == From the middle of the 19th century until late in the 20th century, the solar compass was widely employed for surveying land. Its original impetus was for use where magnetic compasses were susceptible to iron bearing minerals that made for inaccurate readings. It was then found to be superior to the magnetic compass even when local attraction was not a problem. Its close relative, a solar compass attachment to a surveyor's transit, was still a recommended method of obtaining direction in the 1973 manual of the US Bureau of Land Management.〔http://www.blm.gov/cadastral/Manual/73man/id34.htm〕 Using the location of the sun, or occasionally the moon, with astronomical tables, the solar compass enabled surveyors to run more accurate lines, saving its user valuable time. Burt, a United States Deputy Surveyor, began surveying government lands in Michigan in 1833. While working in Wisconsin, where there were large deposits of iron ore, Burt experienced great difficulty in using his standard vernier scale compass. This motivated him to find a solution that was not dependent on magnetism and would not be influenced by earth's ore materials. With his mechanical abilities, he then devised and built the solar compass. Burt made a model of his instrument in 1835 to test its validity. The instrument was then submitted to a committee at the Franklin Institute in Philadelphia. They examined its principles and merits and ultimately awarded Burt twenty dollars in gold and the John Legacy Medal.〔White, p. 367〕 He improved on his surveying instrument and in 1840 re-submitted it to the Franklin Institute. The instrument was further improved over the years and in 1851 he exhibited that version at the Great Exhibition in London, where he was awarded another prize medal.〔 He then received another medal by jurors of Astronomical Instruments.〔 When Burt's solar compass original patent of 1836 was about to expire, he went to Washington to apply for a renewal in 1850. The land commissioner committee, who consisted of senators from Michigan and other states, recognizing the value of Burt's solar compass in public land surveys, persuaded him to forego renewal and petition congress for suitable advance compensation. Burt did as was suggested to him on the faith he would get paid for his patent of such a valuable instrument. However the compensation indicated did not materialize in Burt's lifetime or at any time thereafter. Since there was no patent on Burt's solar compass after 1850, instrument makers sold "Burt's solar compass" to surveyors.〔Fuller, pp. 175-193 ''William Austin Burt- inventor, by Horace Eldon Burt (Chicago)'' biography〕 In the preface to his '' Key to the Solar Compass and Surveyor's Companion '' published in 1858 by his associate William S. Young, Burt refers to the many requests for such a book on how to use his solar compass. He explains a magnetic compass had problems with the true meridian at different localities. It also had problems from day to day with different readings from that expected as a constant or from previous readings. It was determined that a magnetic compass used as a surveying tool was interfered many times from the local attraction of iron ore. A much better guide for the surveyor than the magnetic needle compass was much needed. Burt’s diligent hard work, persistence and perseverance ultimately paid off in the invention of the Solar or Astronomical Compass.〔Burt, '' Key to the Solar Compass and Surveyor's Companion '' preface〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「solar compass」の詳細全文を読む スポンサード リンク
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