Accession No
5350
Brief Description
20th century slide rule by Castell. Made in plastic materials
Origin
Maker
Castell
Class
calculating
Earliest Date
1900
Latest Date
1998
Inscription Date
Material
plastic; paper (card)
Dimensions
length of slide rule 300mm, length of case 308mm; width 59mm; depth 23mm
Special Collection
Provenance
Donated on 23/07/1998.
Inscription
beneath slide
[icon]A.W. FABER [icon]CASTELL [icon]111/54 DARMSTADT MADE IN GERMANY
‘W.Johnson & Sons (opticians) LTD. 187 Tottenham Court Road Tel. MUSeum 2855 London, W.’ (label attached to carton)
icon 1 is a set of scales
icon 2 and 3 are multiple arrows in a box
Description Notes
slide rule, 20th century, made in plastic materials by Castell. With its original carton in green. Label attached to carton of sellers ‘W.Johnson & Sons (opticians) LTD. 187 Tottenham Court Road Tel. MUSeum 2855 London, W.’
Plastic cursor moves along scale; black line for index itself.
inch scale at top of stock; 0-10 divided in increments of 1; 0,1,2...10.
log scale 1-1000 divided 1,2,3...10,20,30...100,200,300...1000
log scale 1-100 numbered 1,2,3,π,4,...10,20,...100
Slide has log scale 1-100, numbered 1,2,3,π4,...10,20...100
log scale reading from right to left in red 1-10, numbered 1,1.1,1.2...2,3,π4...10
log scale in black reading left to right 1-10, numbered 1,1.1,1.2...2,3,π4...10
Reciprocal scale divided right to left 1 - 10, numbered 1, 1.1, 1.2...2, 2.5, 3, π, 4,...10;
verso of slide is a scale e to the x
Lower part of stock carries a log scale marked with a ‘D’ 1-10, numbered 1, 1.1, 1.2...2, 2.5, 3, π, 4,...10;
log scale maked ‘P’ ‘1-X2’ but reading right to left 0-0.995, numbered 0,0.2,0.3...0.9,0.91,0.92...0.99, 0.995
Sine scale marked ‘sin’ 5.8˚-90˚ numbered 6,7...20,25,30...40,50...90. This also acts as a cosine scale marked in red ‘cos’ reading from right to left. Below the sine cosine scale is a tangent scale, marked ‘tg’ divided 5.8˚-45˚ numbered 6, 7...20, 25, 30...45. This also acts as a cotangent scale marked in red as ‘ctg’. On its final edge is another inch scale .0-.0 numbered .1,.2....0.
Verso of slide rule are instructions on how to accomplish different calculations.
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.
Cylindrical slide rules allow calculations to be done that would otherwise require a linear slide rule of many times its length.
FM:45687
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