This slide rule is from the collection of calculating instruments assembled by Assoc. Professor Allan Bromley. His collection provides examples of most forms of calculating devices made from the early 18th to the late 20th centuries. Slide rules constitute a substantial proportion of this collection.

Over the 19th and much of the 20th centuries the slide rule was the primary instrument for calculation used by many people engaged in the trades and in engineering. Although originally invented in the 17th century, and widely used for gauging (or estimating the quantities of certain products such as alcoholic spirits) it took until around 1850 for the slide rule to become generally popular. However for those engaged in estimating (ie, gauging) various quantities of goods in use in the liquor, building and agriculture trades, and for calculating the excise duty to be paid on these goods, numerous kinds of sliding rules with useful scales were developed.

Specialist slide rules of many kinds were developed over the period of their use. In the 20th century many special purpose slide rules were made from various kinds of paper or card, and from light sheet plastics once plastics became a common place in the later part of the century.

France, c. 1890

Lafay cylindrical slide rule, printed paper scales on green metal cylinder with a transparent plastic sleeve and three plastic rings that may be cursors, a red line with a cross hair runs the length of the sliding sleeve, in black card tube container with green metal stoppers at each end, France, 1890

This is a slide rule with a pair of very long scales achieved by aligning them as spirals running around and down the metal cylinder of the rule.

Made: 1885 - 1895

Texts on top end of cylinder, printed in black above scales ' Helice a Calcul (Modèle no.2) A.Lafay NEUVILLE S/Saône (Rhône)'.

Handwriting on a paper tag in the case, ' Lafay Slide Rule/ French c. 1890', reversal ' 3132 / £38'

2010/1/506

1885 - 1895

200 mm

40 mm