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
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, 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 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
"Tachylemme" of C.L.Chambon, c.1876. This instrument shows the daily interest on sums of money at various rates.
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 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
Chuckrum board with 108 small coins.This board was used to count 100 small 'chuckrum' coins rapidly by spreading them over the surface to fill the holes.
Kelvin's harmonic analyser, 1878. The machine was Invented by William Thomson, Lord Kelvin, (1824-1907), a pioneering Irish physicist. The harmonic analyser was designed to analyse graphical records of daily changes in atmospheric temperature and pre
The 'Arithmetical Jewel' publicised by William Pratt in 1619. This instrument combines features of an abacus with those of pen reckoning. Numbers are put in by moving the flags to reveal dots. Sums are then worked out with a pen and paper.