Edmund Gunter, an English mathematician, born in Hertfordshire about 1581, died in London, Dec. 10,1626. He was educated at Westminster school and at Christchurch college, Oxford, where he gave his attention principally to mathematics, and in 1000 invented the sector. Subsequently he took orders; but his tastes being altogether mathematical, he procured in 1619 the professorship of astronomy in Gresham college, which he filled until his death. His works, consisting of the ('anon Tri-angulorum, "The Sector and Cross Staff," etc, have been several times printed in a collective form, the best edition being that of 1073 (4to, London). His inventive faculty was very usefully exercised in the production of the chain, the logarithmic line, the quadrant, and the scale bearing his name, of which descriptions are subjoined. - Gunter's Chain, the chain employed in land surveying, is 00 feet or 4 rods in length, and is divided into 100 links, which are connected with each other by one, two, or three rings. The length of each link, together with half the length of the rings connecting it with the adjoining links, is 7.92 inches; every 10th link is marked by a tally of brass, for convenience in measuring, and part of the first link at each end is formed into a large ring for the purpose of holding it with the hand.
Ten square chains, or 100,000 square links, make one acre. - Gunter's Link, a logarithmic line, sometimes termed the line of lines or line of numbers, and usually graduated upon scales, sectors, etc, consists simply of logarithms graduated upon a ruler, thus serving to solve problems instrumentally, as logarithms do arithmetically. It is generally divided into 100 parts, every 10th division being numbered from 1 to 10. By means of this line the following problems can be solved : 1. To find the product of two numbers: the space between division 1 and the multiplier is equal to the space between the multiplicand and the product, the distance in each case being laid off in the same direction. 2. To divide one number by another: the extent from the divisor to unity equals that from the dividend to the quotient. 3. To find a fourth proportional to three given numbers: the space between the first two numbers equals the distance from the third number to the required fourth proportional. 4. To find a mean proportional between any two given numbers: one half the distance between the lesser number in the left-hand part of the line, and the greater number in the right-hand part, will extend to the mean proportional sought, if applied forward from the lesser number, or backward from the greater. 5. To extract the square root of a number : one half of the distance between unity and the given number, if laid off from unity, will give the point representing the desired root.
Similarly, the cube root or that of any higher power can be found, by dividing the distance between unity and the given number by the index of the root, the quotient giving the distance between unity and the point representing the root required. - Gunter's Quadrant is usually made of wood or brass, and contains a kind of stereographic projection on the plane of the equinoctial, the eye being supposed in one of the poles. The tropic, ecliptic, and horizon form arcs of circles, but the hour circles are curves, delineated by means of several altitudes of the sun for some particular latitude every year. It can be used for the determination of time, the sun's azimuth, etc, and also for taking altitudes of any object in degrees. - Gunter's Scale, generally termed by seamen the Gunter, is a large plain scale, generally 2 ft. long by about l 1/2 in. broad, and used in solving problems in navigation, trigonometry, etc. On one side of the scale are natural lines, and on the other the artificial or logarithmic ones; the former side contains a scale of inches and tenths, two plain diagonal scales, and various lines relating to trigonometry as performed by natural numbers.