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.

This is an example of a special arrangement of scales to make the calculation tasks of the builder or architect easier. It appears to have been used in the calculations required in the designing of an arch or the roofing structure in a timber building. The scale labelled "Rise of Beam" may refer to the distance above the end supports by which a beam used in making an arch has to rise at the centre of the arch. "Half Beam" may refer to the length of the beam required to span the distance between end supports of the beams used in the arch.

Stephen Jones
March 2008

Slide rule, special purpose, builders, closed frame, single-sided, dual slides, wood, made by G T Cooper & Sons, London, England, early 20th century

Slide rule, special purpose: builders, closed frame, single-sided, dual slides extending beyond the stock, wood with bevelled edges. G.Birks, made by G.T. Cooper & Sons, London.

Scales:
Stock, upper: (blank)
Slide, upper: Half Beam in Feet (2 ½ - 60)
Stock, middle: Rise of Beam in inches (0 - 30)
Slide, lower: Width in Feet (0 - 100)
Stock, lower: Width in Feet (0 - 100)

Mfr: G.T. Cooper & Sons, Ltd, London, S.E 9

Made: 1900 - 1925

on face: scale mnemonics, G.Birks
on reverse: Makers - G.T. Cooper & Sons Ltd - London, S.E 9

2010/1/414

1900 - 1925

70 mm

10 mm