Accession No


Brief Description

Thacher’s cylindrical slide rule, by Keuffel and Esser Company, U.S.A., 1900 (c)


U.S.A.; New York


Keuffel and Esser Company



Earliest Date

Jan. 1, 1881

Latest Date

Dec. 31, 1900

Inscription Date


wood; metal (brass); paper; cloth


length 570mm; breadth 180mm; height 180mm box length 607mm; breadth 227mm; height 187mm

Special Collection


Hutchinson Collection


‘KEUFFEL&ESSER C0 N.Y.’ (stamped into base)
‘Made by Keuffel & Esser Co., New York.’ (on central cylinder)
‘Patented by Edwin Thatcher, C.E. Nov. Ist. 1881.’ (on central scale)
Drawing Materials, Surveying Instruments
Measuring Tapes’ (label in lid of box)

Description Notes

Wooden base with 2 brass standards supporting framework of 20 bars inside which sites a wooden cylinder. Cylinder and bars coated in varnished paper. Cylinder carries scales marked ‘A’ alternating with each other, one divided 100 - 1000 the other divided [105.92] - [1059.2[ both numbered by 1; 100 - 1000 subdivided to 0.1, 1000 upwards subdivided to 1. Lower halves of bars carry scales marked ‘B’ alternating and divided as for ‘A’. Upper part of bars carries scale marked ‘C’ in 2 sections. Left hand parts divided 100 - [316.22] numbered by 1 subdivided to 0.1; right hand parts divided [316.22] - 1000 numbered by 1 subdivided to 0.1.

Magnifying glass set into slide on front of instrument, secured by knurled screw. Instructions pasted to base of instrument.

Mahogany box with brass hinges and hook fasteners. Trade label in lid of box, stamped by Charles Baker (retailer).

Condition good; complete



Patented in 1881 by E. Thacher, this type of slide rule has a scale 40 times as great as an ordinary slide rule of the same length and is accurate for readings of up to four figures.

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.


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