Slide rule scale

Later, multiple scales were provided with the most basic being logarithmic but with others graduated according to the mathematical function required.

A cursor (also called runner or glass) containing one (or more) hairlines[note 2] may be slid along the whole rule so that corresponding readings, front and back, can be taken from the various scales on the body and slider.

[note 3] The form with a single logarithmic scale eventually developed into such instruments as Fuller's cylindrical slide rule.

In about 1622, but not published until 1632, William Oughtred invented linear and circular slide rules which had two logarithmic scales that slid beside each other to perform calculations.

[8][3] Advanced slide rules have many scales and they are often designed with particular types of user in mind, for example electrical engineers or surveyors.