 |
slide
rule
 Encyclopędia
Britannica Article |
a device consisting of graduated
scales capable of relative movement, by means of which simple
calculations may be carried out mechanically. Typical slide
rules contain scales for multiplying, dividing, and
extracting square roots, and some also contain scales for
calculating trigonometric
functions and logarithms.
The slide rule remained an essential tool in science
and engineering and was widely used in business and industry until
it was superseded by the portable electronic calculator late in the
20th century.
The logarithmic slide rule is a
compact device for rapidly performing calculations with limited
accuracy. The invention of logarithms in 1614 by the Scottish
mathematician John
Napier and the computation and publication of tables of
logarithms made it possible to effect multiplication and division by
the simpler operations of addition and subtraction. Napier's early
conception of the importance of simplifying mathematical
calculations resulted in his invention of logarithms, and this
invention made possible the slide rule.
|
The first slide
rule
Science
Museum/Science & Society Picture Library
|
|
The English mathematician and inventor Edmund
Gunter (15811626) devised the earliest known logarithmic
rule, known as Gunter's scale or the gunter, which aided
seamen with nautical calculations. In 1632 another English
mathematician, William
Oughtred, designed the first adjustable logarithmic rule;
as shown in the photograph,
it was circular. Oughtred also designed the first linear
slide rule, although the familiar inner sliding
rule was invented by the English instrument-maker Robert Bissaker in 1654. The usefulness of the
slide rule for rapid calculation was recognized,
especially in England, during the 18th century, and the instrument
was made in considerable numbers, with slight modifications.
Improvements in the direction of increased
accuracy were initiated by Matthew
Boulton and James
Watt from about 1779 in connection with calculations in the
design of steam engines at their works at Birmingham, England. In
1814 the English physician Peter
Roget (of Roget's Thesaurus) invented his log-log slide rule for
calculating powers and roots of numbers. The fixed scale, instead of
being divided logarithmically, is divided into lengths that are
proportional to the logarithm of the logarithm of the numbers
indicated on the scale; the sliding scale is divided
logarithmically.
Amédée Mannheim, an officer of the French
artillery, invented in 1859 what may be considered the first of the
modern slide rules. This rule had scales on one
face only. The Mannheim rule, which also brought into
general use a cursor, or indicator, was much used in France, and
after about 1880 it was imported in large numbers into other
countries.
Most important of later improvements was the
arrangement of the scales, trigonometric and log-log, so that they
operate together while maintaining a consistent relationship to the
basic scales. This arrangement gave added speed and flexibility to
the solving of many problemssimple and complex alikebecause it
produced solutions by continuous operation instead of requiring the
user to combine intermediate readings.
 Back
to top |
|
