Accession No
2328
Brief Description
Engineer’s slide rule by Routledge, c.1847
Origin
Bolton; England
Maker
Routledge. I.
Class
calculating
Earliest Date
1847
Latest Date
1847
Inscription Date
1847
Material
ivory; metal (nickel-silver, brass)
Dimensions
length closed 317mm; breadth 43mm; thickness 4mm
Special Collection
Provenance
purchased from Sotheby’s, London; Sale of Scientific Instruments, lot 27, 21/10/1977.
Inscription
‘I.ROUTLEDGE ENGINEER BOLTON’ (obverse)
‘J B
Enr. 1847
Manchester ‘ (reverse on hinge)
Description Notes
Ivory folding rule and slide rule with nickel-silver hinge and shoulders, and bindings at tips of limbs. Two metal pins to hold rule together when closed. Letters and figures all stamped.
Obverse: top limb with nickel-silver slider. On the stock, log scale marked ‘A’, divided [1] - 10[0], numbered 1, 2...1[0], 12, 2[0], 3[0]...10[0]. Similar log scales on slider, marked ‘B’ and ‘C’. On the stock, further log scale marked ‘D’, divided 1 - 10, numbered by 1. Reverse of slide has inch scale divided [0] - [12], numbered by 1, subdivided to 1/16. Lower limb has tables of comparison for various substances (e.g. wine gallons, brick, tin, coal etc.) and other tables.
Reverse: inch scale divided [0] - [24], numbered by 1 (except 12), subdivided to 1/8; 0 - 3 subdivided to 1/16. Inner edge of one limb has quarter and half inch scales; inner edge of other limb has three-quarter inch and inch scales.
Outer side of one limb carries decimal foot scale divided [0] - [100], numbered by 10, subdivided to 1. Outer side of other limb carries inch scale divided [0] - [12], numbered by 1, subdivided to 1/12 and 1/10.
Condition good (piece of nickel silver missing around one pin-hole); 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:42264
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