**Edmund Gunter** (1581 – 10
December 1626), English mathematician, of Welsh descent, was
born in Hertfordshire in 1581.
He was
educated at Westminster
School, and in 1599 was elected a student of Christ Church,
Oxford. He took orders, became a preacher in 1614,
and in 1615 proceeded to the degree of bachelor in divinity.
Mathematics, particularly the relationship between mathematics and
the real world, was the one over riding interest throughout his
life.

In 1620 the wealthy but earnest Sir Henry Savile put up money to
fund Oxford University's first twoscience 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] behavior 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."

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 in
Gresham
College, 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 wroteresignedly, "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 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 introduced the words cosine and cotangent,
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 noticed below:

## Gunter's chain

Gunter's interest in geometry led him to develop a method of sea
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 habitually used for the purpose, and is
called

Gunter's chain.

The length of the chain normally used led to the linear measurement
of being called a

chain.

## Gunter's quadrant

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, etc., and other common
problems of the sphere or globe, and also to take the altitude of
an object in degrees.

## Gunter's scale

Gunter's scale or Gunter's rule, generally called the "Gunter" by
seamen, this is a large plane scale, usually long by about 1 1/2
inches broad (600 mm by 40 mm), and engraved with various
scales, or lines. On one side are placed the natural lines (as the
line of chords, the line of

sines,

tangent,

rhumbs, etc), and on the other side the corresponding
artificial or logarithmic ones. By means of this instrument
questions in

navigation,

trigonometry, etc., are solved with the aid of
a pair of compasses. It is a predecessor of the

slide rule, a calculating aid used from
the 1600s 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.

## See also

## External links

## References