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.

Maker unknown.

Measuring cards, two separate cards having formula and procedure for measuring the Radius of the Curve of a rail line.

(1). Light khaki paper on light timber with handwritten formulae and instructions on it in brown.

(2). Light khaki paper on both sides of card with handwritten formulae and instructions on it in black.

Hand written rectangular cards with a diagram indicating the procedure and a scale of the radius (in chains) for different offsets of the 20ft chord to the curve of the rail. The offset is the difference in feet between the centre of the string indicating the chord and the centre of the rail curve marked by that chord. Thus (as can be seen on the top scan) for an offset of 2 1/8th inches the radius of the circle of which the rail curve is an arc is 4.28 chains (a chain is 22 yards or 20.1168m)

Made: 1900 - 1925

2010/1/524

1900 - 1925

10 mm

160 mm