Accession No
5386
Brief Description
universal slide rule, by Unique, English, 2/4 20th Century
Origin
England
Maker
Unique
Class
calculating
Earliest Date
1955
Latest Date
1983
Inscription Date
Material
wood; paper (card); metal; plastic (celluloid?)
Dimensions
length 300mm; width 36mm; thickness 9mm
Special Collection
Provenance
Donated in 17/02/1999. Used by Denys Bliss, inventor of the segmented skirt (used in Hovercraft).
Inscription
on the slide
“UNIQUE”
UNIVERSAL
SLIDE RULE.
Description Notes
“Unique” universal slide rule in wood, paper and plastic. English first 1/4 - 2/4 20th century. Wooden slide rule covered with paper and then clear plastic layer to prevent dirt/wear.
Upper part of stock carries log-log scale marked divided 1.10 - 2.9, numbered 1.1, 1.11, 1.12, 1.13...1.2, 1.25, 1.3...1.55, 1.6, 1.7...2, 2.1, 2.2...2.9; sine scale divided 35´ - 90˚, numbered 35´, 1, 2...10, 15, 20, 30...60, 90; number scale (this scale repeated on slide) divided 1 - 100, numbered 1, 1.1, 1.2...2, 2.5, 3π, 3.5, ...10, 11, 12...20, 25, 30, 35...100.
Slide carries reciprocal scale divided right to left 1 - 10, numbered 1, 1.1, 1.2...2, 2.5, 3, π, 3.5, 4, 5...10; number scale marked (this scale also on lower part of stock), divided 1 - 10, numbered 1, 1.1...2, 2.5, 3, π, g,3.5, 4, 4.5...10.
Lower part of stock carries tangent scale, marked ‘T’, divided [5 ˚]- 45˚, numbered 6, 7...20, 25, 30...45. Log-log scale divided 2.6 - 5[0000], numbered 2.6, 2.7...3, 4, 4.5...6,7...10, 15...30, 40, 50, 100, 2[00], 3[00], 4[00]... 1000, 2[000], 3[000], 4[000], 5[000], 10000, 2[0000], 3[0000], 4[0000], 5[0000].
On the back of the rule is a table for densities, thermal and ultimate strength of metals, table for permissible bearing pressures, and a table converting fractions to decimals. Finally a table to convert imperial measurements to metric.
Diana Bliss written in blue biro on the back of the slide.
Condition fair - needs attention on upper stock as plastic is coming away from paper.
References
Events
Description
This instrument is a cylindrical slide rule, a variation on the most common type, also shown in this drawer, and described below.
Developed during the seventeenth century, the modern slide rule is based upon the design by William Oughtred (circa 1630). It is one of many calculation devices that is based on the logarithmic scale, a calculation method invented in 1614 by John Napier.
Before the rise of the pocket electronic calculator in the 1970s, the slide rule was the most common tool for calculation used in science and engineering. It was used for multiplication and division, and in some cases also for ‘scientific’ functions like trigonometry, roots and logs, but not usually for addition and subtraction.
A logarithm transforms the operations of multiplication and division to addition and subtraction according to the rules log(xy) = log(x) + log(y) and log(x/y) = log(x) - log(y). The slide rule places movable logarithmic scales side by side so that the logarithms of two numbers can be easily added or subtracted from one another. This much simplifies the alternative process of looking up logs in a table, thus greatly simplifying otherwise challenging multiplications and divisions. To multiply, for example, you place the start of the second scale at the log of the first number you are multiplying, then find the log of the second number you are multiplying on the second scale, and see what number it is next to on the first scale.
FM:45748
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