Accession No

4609

Brief Description

universal slide rule with instruction booklet, English, 2/2 20th C

Origin

England

Maker

Unique

Class

calculating

Earliest Date

1950

Latest Date

1960

Inscription Date

Material

paper (card and two others); wood; plastic (three types)

Dimensions

length 170mm; breadth 48mm; thickness 12mm box length 185mm; breadth 54mm; thickness 17mm

Special Collection

Provenance

Purchased on 01/04/1997.

Inscription

‘‘UNIQUE’
UNIVERSAL I.
SLIDE RULE’ (left hand end of slide)
‘U 1/2 UNIQUE SLIDE RULE
UK Price 9/6 inc. insts.’ (end of box)
‘MADE IN
ENGLAND.’ (right hand end of slide)
‘J.O. Lewis’ (in ink on reverse of slide)

Description Notes

Wooden slide rule covered with paper and then clear plastic layer to prevent dirt/wear. Plastic cursor moves along scale; black line for index itself.
Upper part of stock carries log-log scale marked ‘LU’ divided 1.10 - 2.9, numbered 1.10, 1.12, 1.14...1.2, 1.25, 1.3...1.5, 1.6, 1.7...2.5, 2.7, 2.9; sine scale marked ‘S’, divided 35´ - 90˚, numbered 35´, 1, 2...10, 15, 20, 30...60, 90; number scale marked ‘A’ (this scale repeated on slide, marked ‘B’) divided 1 - 100, numbered 1, 1.5, 2, 2.5, 3, π, 3.5, 4, 4.5, 5, 6...10, 15, 20...50, 60...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, 4.5...10; number scale marked ‘C’ (this scale also on lower part of stock, marked ‘D’), divided 1 - 10, numbered 1, 1.1...2, 2.5, 3, π, 3.5, 4, 4.5...10.
Lower part of stock carries tangent scale, marked ‘T’, divided [5˚ 50´] - 45˚, numbered 6, 7...20, 25, 30...45. Log-log scale marked ‘LL’ divided 2.6 - 4[0000], numbered 2.6, 2.8, 3, 4...10, 15, 20, 30, 50, 100, 2[00], 3[00], 4[00], 5[00], 1000, 2[000], 3[000], 4[000], 5[000], 10000, 2[0000], 3[0000], 4[0000]
Underneath the slide is a table for converting fractions to decimals.
On the back of the rule is a table for densities and thermal properties of metals, table for densities of other materials and a third table with ‘useful equivalents’ (conversion between different systems).
Cardboard box mended at the edges with sellotape (possibly not original).

The instruction booklet is titled ‘“Half-Hour” Instructions for the use of British made UNIQUE SLIDE RULES.’ It contains instructions on how to do multiplication, division, squares, square roots, logarithms, reciprical scale etc. 12 pages in thicker paper cover.

Condition good (box poor); complete.

References

Events

Description
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:40355