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Edmund Gunter (158110 December 1626), was an English clergyman, mathematician, geometer and
astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...
of Welsh descent. He is best remembered for his mathematical contributions, which include the invention of the Gunter's chain, the Gunter's quadrant, and the Gunter's scale. In 1620, he invented the first successful
analogue device Analog devices are a combination of both analog machine and analog media that can together measure, record, reproduce, receive or broadcast continuous information, for example, the almost infinite number of grades of transparency, voltage, ...
which he developed to calculate logarithmic tangents. He was mentored in mathematics by Reverend Henry Briggs and eventually became a Gresham Professor of Astronomy, from 1619 until his death.


Biography

Gunter was born in Hertfordshire in 1581. He was educated at
Westminster School Westminster School is a Public school (United Kingdom), public school in Westminster, London, England, in the precincts of Westminster Abbey. It descends from a charity school founded by Westminster Benedictines before the Norman Conquest, as do ...
, and in 1599 he matriculated at
Christ Church, Oxford Christ Church (, the temple or house, ''wikt:aedes, ædes'', of Christ, and thus sometimes known as "The House") is a Colleges of the University of Oxford, constituent college of the University of Oxford in England. Founded in 1546 by Henry V ...
. He took orders, became a preacher in 1614, and in 1615 proceeded to the degree of bachelor in
divinity Divinity (from Latin ) refers to the quality, presence, or nature of that which is divine—a term that, before the rise of monotheism, evoked a broad and dynamic field of sacred power. In the ancient world, divinity was not limited to a single ...
. He became rector of St. George's Church in Southwark. Mathematics, particularly the relationship between mathematics and the real world, was the one overriding interest throughout his life. In 1619, Sir Henry Savile put up money to fund Oxford University's first two science faculties, the chairs of astronomy and geometry. Gunter applied to become professor of geometry but Savile was famous for distrusting clever people, and Gunter's behaviour annoyed him intensely. As was his habit, Gunter arrived with his sector and quadrant, and began demonstrating how they could be used to calculate the position of stars or the distance of churches, until Savile could stand it no longer. "Doe you call this reading of Geometric?" he burst out. "This is mere showing of tricks, man!" and, according to a contemporary account, "dismissed him with scorne.""Who invented the calculus? – and other 17th century topics"
, Professor Robin Wilson, lecture transcript,
Gresham College Gresham College is an institution of higher learning located at Barnard's Inn Hall off Holborn in Central London, England that does not accept students or award degrees. It was founded in 1597 under the Will (law), will of Sir Thomas Gresham, ...
, 16 November 2005. Retrieved 7 November 2010.
He was shortly thereafter championed by the far wealthier Earl of Bridgewater, who saw to it that on 6 March 1619 Gunter was appointed professor of
astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
in
Gresham College Gresham College is an institution of higher learning located at Barnard's Inn Hall off Holborn in Central London, England that does not accept students or award degrees. It was founded in 1597 under the Will (law), will of Sir Thomas Gresham, ...
, London. This post he held till his death. With Gunter's name are associated several useful inventions, descriptions of which are given in his treatises on the sector, cross-staff, bow, quadrant and other instruments. He contrived his sector about the year 1606, and wrote a description of it in Latin, but it was more than sixteen years afterwards before he allowed the book to appear in English. In 1620 he published his ''Canon triangulorum''. In 1624 Gunter published a collection of his mathematical works. It was entitled ''The description and use of sector, the cross-staffe, and other instruments for such as are studious of mathematical practise.'' One of the most remarkable things about this book is that it was written, and published, in English not Latin. "I am at the last contented that it should come forth in English," he wrote resignedly, "Not that I think it worthy either of my labour or the publique view, but to satisfy their importunity who not understand the Latin yet were at the charge to buy the instrument." It was a manual not for cloistered university fellows but for sailors and surveyors in real world. There is reason to believe that Gunter was the first to discover (in 1622 or 1625) that the magnetic needle does not retain the same
declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...
in the same place at all times. By desire of James I he published in 1624 ''The Description and Use of His Majesties Dials in Whitehall Garden'', the only one of his works which has not been reprinted. He coined the terms
cosine In mathematics, sine and cosine are trigonometric functions of an angle. The sine and cosine of an acute angle are defined in the context of a right triangle: for the specified angle, its sine is the ratio of the length of the side opposite that ...
and
cotangent In mathematics, the trigonometric functions (also called circular functions, angle functions or goniometric functions) are real functions which relate an angle of a right-angled triangle to ratios of two side lengths. They are widely used in a ...
, and he suggested to Henry Briggs, his friend and colleague, the use of the arithmetical complement (see Briggs ''Arithmetica Logarithmica'', cap. xv). His practical inventions are briefly noted below:


Gunter's chain

Gunter's interest in geometry led him to develop a method of land surveying using triangulation. Linear measurements could be taken between topographical features such as corners of a field, and using triangulation the field or other area could be plotted on a plane, and its area calculated. A chain long, with intermediate measurements indicated, was chosen for the purpose, and is called Gunter's chain. The length of the chain chosen, , being called a
chain A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A ...
gives a unit easily converted to area. Therefore, a parcel of 10 square chains gives 1 acre. The area of any parcel measured in chains will thereby be easily calculated.


Gunter's quadrant

Gunter's quadrant is an instrument made of wood, brass or other substance, containing a kind of stereographic projection of the sphere on the plane of the equinoctial, the eye being supposed to be placed in one of the poles, so that the tropic, ecliptic, and horizon form the arcs of circles, but the hour circles are other curves, drawn by means of several altitudes of the sun for some particular latitude every year. This instrument is used to find the hour of the day, the sun's
azimuth An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point ...
, etc., and other common problems of the sphere or globe, and also to take the altitude of an object in degrees. A rare Gunter quadrant, made by Henry Sutton and dated 1657, can be described as follows: It is a conveniently sized and high-performance instrument that has two pin-hole sights, and the plumb line is inserted at the vertex. The front side is designed as a Gunter quadrant and the rear side as a trigonometric quadrant. The side with the astrolabe has hour lines, a calendar, zodiacs, star positions, astrolabe projections, and a vertical dial. The side with the geometric quadrants features several trigonometric functions, rules, a shadow quadrant, and the chorden line.Ralf Kern: ''Wissenschaftliche Instrumente in ihrer Zeit. Band 2: Vom Compendium zum Einzelinstrument''. Cologne, 2010; p. 205.


Gunter's scale

Gunter's scale or Gunter's rule, generally called the "Gunter" by seamen, is a large plane scale, usually long by about 1½ inches broad (40 mm), engraved with various scales, or lines. On one side are placed the natural lines (as the line of chords, the line of
sine In mathematics, sine and cosine are trigonometric functions of an angle. The sine and cosine of an acute angle are defined in the context of a right triangle: for the specified angle, its sine is the ratio of the length of the side opposite th ...
s,
tangent In geometry, the tangent line (or simply tangent) to a plane curve at a given point is, intuitively, the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points o ...
s, rhumbs, etc.), and on the other side the corresponding artificial or logarithmic ones. By means of this instrument questions in
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navig ...
,
trigonometry Trigonometry () is a branch of mathematics concerned with relationships between angles and side lengths of triangles. In particular, the trigonometric functions relate the angles of a right triangle with ratios of its side lengths. The fiel ...
, etc., are solved with the aid of a pair of compasses. It is a predecessor of the
slide rule A slide rule is a hand-operated mechanical calculator consisting of slidable rulers for conducting mathematical operations such as multiplication, division, exponents, roots, logarithms, and trigonometry. It is one of the simplest analog ...
, a calculating aid used from the 17th century until the 1970s. ''Gunter's line'', or ''line of numbers'' refers to the logarithmically divided scale, like the most common scales used on slide rules for multiplication and division.


Gunter rig

A sail rig which resembles a gaff rig, with the gaff nearly vertical, is called a
Gunter rig Gunter rig is a configuration of sail and spars used in sailing. It is a Fore-and-aft rig, fore and aft sail set abaft (behind) the mast. The lower half of the luff (front) of the sail is attached to the mast, and the upper half is fastened to ...
, or "''sliding gunter"'' from its resemblance to a Gunter's rule.


See also

* Gresham Professor of Astronomy * History of geomagnetism


Notes


References


External links

*
Galileo Project page

Gunter's Quadrant applet
{{DEFAULTSORT:Gunter, Edmund 1581 births 1626 deaths English people of Welsh descent 17th-century English mathematicians People educated at Westminster School, London Alumni of Christ Church, Oxford Fellows of Christ Church, Oxford English scientific instrument makers Academics of Gresham College 17th-century English Anglican priests