Papers of the Board of Longitude

Correspondence regarding the effects of magnetic variation on the mariner's compass, the use of magnetic variation to establish longitude and the cause of magnetic variation. The papers include J. Jackson on the cause of magnetism and its effect on the compass; letters from Don Josef de Porras y Ruiz and a minute of the Board relating to these; W. Graham on the cause of annual variation in magnetic variation and two methods of determining longitude; J. Churchman on magnetic variation and finding longitude; J. Newton on a true bearing needle; J. Moore on an instrument for showing the variation of the compass and latitude and longitude; J. Tulloch on finding longitude by the dipping needle and the variation chart; S. Topp on a disturbance in the magnetic needle; J. Miles on the cause of variation in the needle; Lieutenant J.W. Roberts on a magnetic instrument for showing longitude; W. Morrison on a spherical magnet for finding longitude; J. Nicoll on a new mariner's compass to show its own variation; J. Roche on a new compass; W. Casson and J. Minto on their polar compass; J. Bywater on a new variation of the compass, etc.; M. Warren on a theory that the magnetic needle is held on its meridian by the laws of gravity only; T. Yeates on a new variation chart; B. Wood on a magnetic instrument for ascertaining longitude; Captain J. Ross on the variation of the compass; and J. Barlow on a globe showing latitude and longitude.

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