Numeric Demonstrator', an elementary teaching aid patented by Ethel Linay in about 1900.. This elementary arithmetical teaching apparatus consists of ten wooden rods with squared paper pasted on them in order to show multiplication visually.
A single surface model made by Alan Bennett in Bedford, 1995. It consists of a sphere with three interlinked loops the equivalent of three interconnected Klein bottles. A Klein bottle has no edges, no outside or inside and cannot be properly construc
Callipers, used for artillery purposes, French, 17th century. Callipers were used to measure the diameter of cannon balls and the bores of cannons. This example also containd scales for artillery calculations
Napier's bones in brass, 17th century. John Napier (1550-1617), inventor of logarithms, also created this popular calculating tool known as Napier's cylindrical 'rods' or 'bones'. Napier's rods reduced muliplication to a sequence of simple additions
Rectangular protractor in brass, engraved "Dollond, London", late 18th century.As well as the usual angular scale the instrument contains a diagonal scale for plotting distances on a map or plan.
A 2 foot boxwood slide rule for navigators, c.1800. 'Sliding Gunters' , or navigator's rules with a slide are comparatively rare, as most navigators preferred to stick with the ordinary 'Gunter' scale based on the combination of trigonometric, logari
A single surface model made by Alan Bennett in Bedford, 1995. It is a toroid Klein bottle with disguised pierce which when cut produces a pair of single-twist Mobius strips. A Klein bottle has no edges, no outside or inside and cannot be properly con
Single surface models made by Alan Bennett in Bedford, 1995. Three toroid single surface vessels, one with the loop inside the torus, one with a narrow loop outside and one with a wider loop outside. All can be cut to produce a pair of single-twist M
Consul' the Educated Monkey. A mathematical toy calculator patented by William Robertson in 1916 and made by the Educational Novelty Company of Dayton, Ohio, USA. When each of the monkey's feet are moved to point at two numbers, the monkey's hands m
Japanese soroban or abacus with 13 columns, each with 5 beads below the bar and one above.This represents an intermediate form between the original Chinese abacus and the modern Japanese type. This arrangement was common from the late 19th century u