by H. K. Higton
© Oxford University Press 2004 All rights reserved
Gunter, Edmund (1581-1626), mathematician, was born in Herefordshire, the son of a Welshman from Gunterstown, Brecknockshire. He was a queen's scholar at Westminster School from where he entered Christ Church, Oxford, matriculating on 25 January 1600. During his time at Oxford his interest in mathematics (already manifested in a fascination with sundials) flourished, and he began to devise his own mathematical instruments. He gained his BA on 12 December 1603 and his MA on 2 July 1606. At about this time he wrote a Latin manuscript on his sector, developed from the earlier instrument of Thomas Hood.
Gunter took holy orders in 1615, being awarded his BD on 23 November. He was established in that year as rector of both St Mary Magdalen, Oxford, and St George's, Southwark. He began to spend time in Gresham College where his friend Henry Briggs was professor of geometry. Briggs had suggested Gunter as the successor to the first Gresham professor of astronomy, but the post was granted to Thomas Williams. Gunter in fact became the third astronomy professor on the resignation of Williams in 1620, and was appointed on 6 March of that year.
The same year Gunter was interviewed by Sir Henry Savile for the new Savilean chair of geometry at Oxford, but was rejected in favour of Henry Briggs. According to Aubrey's account of the event, Gunter appeared to have been turned down for being over-interested in the use of instruments in mathematics (Brief Lives, under 'Sir Henry Savile'). He remained as a Gresham professor until his death.
At Gresham, Gunter devoted most of his time to the development of instruments and to the investigation of the newly discovered logarithms. He devised the first table of logarithms of trigonometrical functions, dubbing them 'artificial sines and tangents'. These were published as Canon triangulorum, or, Table of Artificial Sines and Tangents (1620), in which he also introduced the terms 'cosine' and 'cotangent'. He lectured on much of his logarithmic work at Gresham, where he also considered the use of mathematical instruments in astronomy and navigation.
In 1622 Gunter's investigations at Limehouse, Deptford, of the magnetic variation of the compass needle produced results differing from William Borough's, obtained more than forty years earlier. He assumed an error in Borough's measurements, but this was in fact the first observation of temporal change in magnetic variation, a contribution acknowledged by his successor, Henry Gellibrand, who discovered the phenomenon. In the same year Gunter engraved a new sundial at Whitehall, which carried many different dial plates and supplied a wealth of astronomical data. Prompted by Prince Charles, he wrote an explanation of the dials, published as The Description and Use of his Majesties Dials in White-Hall Garden (1624). The sundial was demolished in 1697.
Easily the most substantial of Gunter's works was The Description and Use of the Sector, the Crosse-Staffe and other such Instruments (1623) which explained instruments which he had designed. Apart from the two mentioned in the title it also included an astronomical quadrant and a 'cross-bow'--an alternative to the backstaff used by sailors for solar altitude measurements. Although this instrument did not become popular the others all did, in one form or another. The Gunter sector was a much more complex instrument than Thomas Hood's. It allowed calculations involving square and cubic proportions, and carried various trigonometrical scales. Moreover it had a scale for use with Mercator's new projection of the sphere, making this projection more manageable for navigators who were only partially mathematically literate. The sector was sold as a navigational instrument throughout the seventeenth century and survived in cases of drawing instruments for nearly three hundred years. The most striking feature of the cross-staff, distancing it from other forms of this instrument, was the inclusion of logarithmic scales. This was the first version of a logarithmic rule, and it was from Gunter's work that logarithmic slide rules were developed, instruments that remained in use until the late twentieth century.
Gunter also invented a surveying chain and is credited by De Morgan (Arithmetical Books, xxv) with introducing the decimal separator. He died on 10 December 1626 at Gresham College and was buried the following day at St Peter-le-Poer, Old Broad Street. Gunter was a firm advocate of the use of instruments in mathematics for easing the work of various mathematical practitioners, notably surveyors and navigators. His instruments were designed with these aims in mind. In particular his work on logarithms, their applications to trigonometry, and their inclusion on instruments greatly simplified the processes of mathematical calculation. His books were popular for many years after his death: an edition of all his works was produced by Samuel Foster in 1636 and this had three more editions, the last in 1680, which had additions by Foster, Henry Bond, and William Leybourn.
H. K. HIGTON
Sources
E. G. R. Taylor, The mathematical practitioners of Tudor and Stuart England (1954)
Wood, Ath. Oxon.
Foster, Alum. Oxon.
E. Gunter, The description and use of the sector, the crosse-staffe and other such instruments (1623)
J. Welch, A list of scholars of St Peter's College, Westminster (1788)
J. Ward, The lives of the professors of Gresham College (1740)
B. Martin, Biographia philosophica (1764)
A. De Morgan, Arithmetical books from the invention of printing to the present time (1847)
Aubrey's Brief lives, ed. O. L. Dick (1949)
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