On Display

Klein bottles, 1995.

Single surface models made by Alan Bennett in Bedford, 1995. Four small Klein bottles (left to right): i) one loop relating to the single-twist Mobius strip, ii) two loop relating to the three-twist Mobius strip, iii) three loops relating to the five

 
'Magic Brain' calculator, c 1960.

Magic Brain' calculator made by Chadwick in tin and plastic, with stylus and instructions. C.1955. Very similar to the Exaxctus and other stylus calculators of the period, the Magic Brain could add, subtact, and multiply and duivide by repeated addit

 
Exactus stylus-operated adding and subtracting device, 1955-1965.

Exactus stylus-operated adding and subtracting device, with swivelling half plate for add and subtract options, marked "Mini-Add Made in England", c. 1950. The Exactus is one of several simple stylus-operated calculators to have been popular in the

 
Klein bottle, 1995.

A single surface model made by Alan Bennett in Bedford, 1995. It consists of a parallel sided coil with one piercing of the return tube which when theoretically cut gives a pair of 15-twist Mobius strips. A Klein bottle has no edges, no outside or in

 
A stchoty, Russian abacus, early 20th century.

Stchoty (Russian form of Abacus), early 20th century. The stchety has horizontal rows of beads rather than vertical as in the Japanese abacus. It is specifically for counting rubles and kopeks. The lower three rows are for the kopeks. The rest positi

 
Robertson's 'Rapid Calculator', c 1910.

Robertson's Rapid calculator, pat no. 5871,1910. Made by the Robertson Rapid Calculator Company of Glasgow, this was one of several large-scale ready reckoners to be developed in the first decade of the 20th century. This form of ready reckoner place

 
Set of Napier's rods, 1770-1790.

Set of Napier's bones, in wooden case with trade label of "J. Imison, Clock & Watch Maker, Optician, &c., No. 58 Hay-market, London", late 18th century. Napier's bones were invented in 1617 by Lord Napier of Murchiston, the inventor of logarithms, as

 
The 'Tachylemme' ready reckoner, c 1876.

"Tachylemme" of C.L.Chambon, c.1876. This instrument shows the daily interest on sums of money at various rates.

 
Surveyor's sector, early 17th century.

Surveyor's sector, Italian, early 17th century, engraved "Adam Heroldt fecit Romae". The sector was invented independantly by Galileo and Thomas Hook at the end of the 16th century. It primarily measures proportions and can contain lines concerning t

 
Gunner's callipers, early 18th century.

Gunner's callipers by Thomas Wright, early 18th century. The callipers can be used as shown to measure the diameter of cannon balls, or with crossed arms to measure the bore of a cannon. The arms are inscribed with tables containing information relat