Adders
Continuous Band Adders

A collection of adders including a Magic-Brain Calculator, an Exactus Mini-Add, a Troncet Arithmographe, and a Locke Adder.

A handful of adders represented numbers by continuous loops of metal. On some, this loop stretched over a wheel, and had projections representing different digits. On others, holes in the metal allowed one to advance the band with a stylus. The Russian J. Diakoff suggested this as early as 1829, and the idea was adopted by the American journalist Charles Henry Webb in the 1880s.