Henry Gellibrand

English mathematician

Henry Gellibrand (1597-1637) was an English mathematician. He is known for his work on the Earth's magnetic field. He discovered that magnetic declination – the angle of dip of a compass needle – is not constant but changes over time.[1][2] He announced this in 1635, relying on previous observations by others, which had not yet been correctly interpreted.[3]

He was the son of the physician Henry Gellibrand (1568-1615)[4] and Mary Faversham. His four younger brothers were John, Edward, Thomas and Samuel.[5] Samuel Gellibrand became a prominent seventeenth-century London bookseller.[6]

He also devised a method for measuring longitude, based on eclipses.[7] The mathematical tables of Henry Briggs, consisting of logarithms of trigonometric functions, were published by Gellibrand in 1633 as Trigonometria Britannica.

He was Professor at Gresham College, succeeding Edmund Gunter in 1626. He was buried in St Peter le Poer, a London church that was demolished in 1907.[8]

## See also[edit]

* History of geomagnetism
* List of geophysicists

## References[edit]

1. ^ van Helden, Albert; Burr, Elizabeth (1995). "Gellibrand, Henry". The Galileo Project. Rice University. Retrieved 24 October 2011.
2. ^ "Millennium of Geomagnetism".
3. ^ Lloyd Arnold Brown, The Story of Maps (1979), p. 133.
4. ^ "Henry Gellibrand - Biography". Maths History. St Andrews University. Retrieved 26 September 2020.
5. ^ "Gellibrand, Henry". words.fromoldbooks.org. Fromoldbooks.org. Retrieved 26 September 2020.
6. ^ Henry Plomer (1907) A Dictionary of the Booksellers and Printers who Were at Work in England, Scotland and Ireland from 1641 to 1667
7. ^ Michael Hoskin, The Cambridge Concise History of Astronomy (2003), p. 150.
8. ^ "The British Society for the History of Mathematics |".

* O'Connor, John J.; Robertson, Edmund F., "Henry Gellibrand", MacTutor History of Mathematics Archive, University of St Andrews
* Hunter, John Aubrey (2000). "Henry Gellibrand". Brief lives. Selected and edited with introduction, glossary and notes by John Buchanan-Brown. Foreword by Michael. Penguin Books. ISBN 978-0-14-043589-4.

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