Slide Rule

A mechanical pre-cursor of the pocket calculator. Used for complex and scientific calculations, a slide rule consists of three interlocking calibrated strips, which can moved lengthways relative to each other, and a cursor? with an alignment line which is used to align the scales.

The principal scales are calibrated logarithmically. By the skilled manipulation of these strips, multiplication and division can be performed by the mechanical addition and subtraction of logarithms.

Slide rules also had other mathematical functions encoded on other auxiliary scales.